JP5560480B2 - Electric vehicle wheel slip control device - Google Patents

Description

  The present invention relates to a wheel slip control device for controlling slip of a drive wheel with respect to a road surface when the drive wheel tends to be locked in an electric vehicle equipped with an electric motor as a driving power source.

2. Description of the Related Art Conventionally, an electric vehicle equipped with an electric motor as a driving power source and a hybrid electric vehicle equipped with an electric motor and an engine as a driving power source are known. Hereinafter, vehicles using at least an electric motor as a driving power source are collectively referred to as an electric vehicle.
In an electric vehicle, the driving torque of the motor operated by the motor is used when driving force is required for acceleration traveling, etc., and when the braking force is required for deceleration traveling etc., the motor is operated by a generator. The kinetic energy of the vehicle is recovered as electric energy while applying the regenerative braking torque to the drive wheels.

  When an automobile using only an engine as a driving power source (hereinafter referred to as a non-electric vehicle) travels at a reduced speed without using a service brake mechanism, the vehicle can be decelerated by the braking force of the engine brake. Also in an electric vehicle, it is possible to perform the same deceleration as in such a non-electric vehicle by applying a regenerative braking torque to the drive wheels by operating the electric generator as described above. At this time, in order to collect as much kinetic energy as electric energy, the regenerative braking torque generated by the motor is set so that the deceleration is somewhat larger than the deceleration caused by engine braking in a non-electric vehicle. It is common that

  For this reason, when traveling on a road having a relatively low road surface friction coefficient, the electric vehicle is used not only when decelerating using the service brake mechanism but also when decelerating without using the service brake mechanism. However, the drive wheels tend to lock more easily than non-electric vehicles. If the driving wheels are locked during the decelerating traveling, the driving wheels slip on the road surface, which causes a problem that the traveling stability of the vehicle is impaired.

  In order to solve such a problem, Patent Document 1 proposes a control device that controls the electric motor when the wheels tend to be locked to prevent the wheels from being locked. The control device of Patent Document 1 corrects or regenerates the regenerative braking torque generated by the electric motor when the driving wheels tend to be locked and the ABS device is activated during deceleration traveling using the service brake mechanism. Switching to torque prevents the drive wheels from locking. The correction amount of the regenerative braking torque at this time is weighted by the deviation dV between the estimated vehicle body speed serving as the reference and the wheel rotational speed of the driving wheel, and the deviation dG between the estimated vehicle body acceleration serving as the reference and the wheel rotational acceleration of the driving wheel, respectively. Then, it is set by adding. The regenerative braking torque correction amount obtained in this way becomes a negative value when the driving wheel tends to be locked, and may become a positive value when the rotational speed of the driving wheel recovers and the braking force becomes insufficient. This is described in Patent Document 1.

JP-A-5-270387

The control device of Patent Document 1 does not set the regenerative braking torque by determining the state of the drive wheel locking tendency, but uses deviations from the respective reference values of the wheel rotation speed and the drive wheel acceleration of the drive wheel, The regenerative braking torque is simply corrected by the correction amount obtained by the above-described calculation. For this reason, it cannot be said that the situation of the actual drive wheel locking tendency is accurately determined, and the regenerative braking torque is generated from the motor or the driving torque is appropriately handled in response to the situation of the driving wheel lock tendency. It cannot be generated. As a result, the control device of Patent Literature 1 may not be able to quickly and accurately suppress the locking of the drive wheels.
When the lock of the drive wheel cannot be suppressed quickly and accurately in this way, the locked drive wheel slips on the traveling road surface, and there is a risk that the traveling stability of the electric vehicle during the decelerating travel may be impaired.

  The present invention has been made in view of such problems, and an object of the present invention is to accurately determine the tendency of the driving wheel to lock and recover when the electric vehicle decelerates, thereby locking the driving wheel. It is an object of the present invention to provide a wheel slip control device which prevents the above.

In order to achieve the above object, the wheel slip control device for an electric vehicle according to the present invention is mounted on an electric vehicle as a driving power source and can transmit driving torque to driving wheels when the motor operates. a regenerative braking torque can be transmitted electric motor to the drive wheels in the case of machine operation, and the wheel speed detecting means for detecting a wheel rotational speed of the driving wheels, if it is determined that there is a tendency that the drive wheel is locked, the set only drive torque as the target output torque of the electric motor, while the motor performs motor operation for applying a driving torque of the electric motor to the drive wheels, if it is determined that the locking tendency of the drive wheel is being resolved, the set only regenerative braking torque as the target output torque of the electric motor, by the generator operate the electric motor to impart the regenerative braking torque of the electric motor to the drive wheel braking And the control means uses a wheel speed change rate, which is a change rate of the wheel rotation speed detected by the wheel speed detection means, and the wheel rotation speed detected by the wheel speed detection means. Based on the obtained slip ratio of the driving wheel, it is determined whether or not the driving wheel has a tendency to lock, and whether or not the driving wheel has a tendency to lock is determined. (Claim 1).

According to the wheel slip control device for an electric vehicle configured as described above, when it is determined that the driving wheel tends to lock based on the wheel speed change rate and the slip rate of the driving wheel, the control means sets the target output torque of the motor. Only the driving torque is set, and the motor is operated to apply the driving torque of the motor to the driving wheels. By applying a driving force to the driving wheels in this way, slipping of the driving wheels with respect to the road surface is suppressed, and locking of the driving wheels is avoided.
On the other hand, if it is determined that the drive wheel lock tendency is being resolved based on the wheel speed change rate and slip rate of the drive wheel, the control means sets only the regenerative braking torque as the target output torque of the motor, The regenerative braking torque of the electric motor is applied to the drive wheels. Thus, by applying a regenerative braking force to the drive wheels, the drive wheels are braked and the electric vehicle is decelerated.

  Further, in the wheel slip control device for an electric vehicle, the control means is configured such that when the wheel speed change rate is a negative value and the slip rate is larger than a predetermined first reference slip rate, After determining that the driving wheel tends to lock, the wheel speed change rate becomes a positive value and the slip rate is larger than the first reference slip rate. When it is smaller than the second reference slip, it is determined that the locking tendency of the driving wheel is being eliminated (Claim 2).

  According to the wheel slip control device for an electric vehicle configured as described above, when the wheel speed change rate of the drive wheel becomes a negative value and the slip rate of the drive wheel becomes larger than the first reference slip rate, the drive wheel is The control means determines that the motor tends to be locked, and the control means operates the motor to apply the drive torque of the motor to the drive wheels.

  When the drive torque of the electric motor is applied to the drive wheels, the wheel speed change rate of the drive wheels is initially a negative value, but changes in a direction in which the absolute value decreases. While the wheel speed change rate of the drive wheel is a negative value, the wheel speed of the drive wheel continues to decrease, and when the drive torque is applied to the drive wheel, the slip ratio of the drive wheel continues to increase. When the drive torque is continuously applied to the drive wheel, the wheel speed change rate of the drive wheel becomes a positive value, and the slip rate of the drive wheel turns in a decreasing direction.

  When the wheel speed change rate of the drive wheel becomes a positive value and the slip rate is smaller than a predetermined second reference slip that is greater than the first reference slip rate, the tendency of the drive wheel to be locked is being resolved. The control means makes the electric motor act as a generator and applies the regenerative braking torque of the electric motor to the drive wheels. Thus, by applying a regenerative braking force to the drive wheels, the drive wheels are braked and the electric vehicle is decelerated.

  Further, in the wheel slip control device for an electric vehicle, the control means is such that the wheel speed change rate is smaller than a predetermined first reference change rate having a negative value, and the slip rate is the first reference slip rate. When it is determined that the driving wheel tends to lock when larger than the rate, the wheel speed change rate has a positive second reference value after determining that the driving wheel tends to lock. When the slip rate is smaller than the second reference slip that is larger than the change rate and larger than the first reference slip rate, it is determined that the drive wheel locking tendency is being resolved ( Claim 3).

  According to the wheel slip control device for an electric vehicle configured as described above, the wheel speed change rate of the drive wheel is smaller than the first reference change rate having a negative value, and the slip rate of the drive wheel is the first rate of change. When it becomes larger than one reference slip ratio, it is determined that the drive wheels tend to lock, and the control means activates the motor to apply the drive torque of the motor to the drive wheels.

  When the drive torque of the electric motor is applied to the drive wheels, the wheel speed change rate of the drive wheels is initially a negative value, but changes in a direction in which the absolute value decreases. While the wheel speed change rate of the drive wheel is a negative value, the wheel speed of the drive wheel continues to decrease, and when the drive torque is applied to the drive wheel, the slip ratio of the drive wheel continues to increase. When the drive torque is continuously applied to the drive wheel, the wheel speed change rate of the drive wheel becomes a positive value, and the slip rate of the drive wheel turns in a decreasing direction.

  When the wheel speed change rate of the drive wheel becomes a value larger than the second reference change rate having a positive value and the slip rate becomes smaller than a predetermined second reference slip greater than the first reference slip rate, the drive wheel The control means activates the electric motor as a generator and applies the regenerative braking torque of the electric motor to the drive wheels. Thus, by applying a regenerative braking force to the drive wheels, the drive wheels are braked and the electric vehicle is decelerated.

  In the wheel slip control device for an electric vehicle, the electric vehicle may be a hybrid electric vehicle having an engine as a driving power source in addition to the electric motor.

  According to the wheel slip control device for an electric vehicle of the present invention, it is determined that the driving wheel tends to lock based on the wheel speed change rate and the slip rate of the driving wheel. Accurately determine that the drive wheels tend to lock, avoiding situations where the drive wheels tend to lock only with a temporary change in speed or slip ratio. can do.

If it is determined that the drive wheels tend to lock, only the drive torque is set as the target output torque of the motor, and the drive torque of the motor that operates the motor is applied to the drive wheels. It becomes possible to eliminate the tendency quickly. Therefore, when the electric vehicle decelerates, it is possible to prevent the driving wheel from slipping due to the locking of the driving wheel quickly and accurately, and to ensure the running stability of the electric vehicle.
Also, not only when the electric vehicle is decelerated using the service brake mechanism, but also when the electric vehicle is decelerated using the auxiliary brake or the regenerative braking torque of the electric motor, the drive wheels tend to lock. In some cases, this can be accurately determined to eliminate the tendency of the drive wheels to lock.

  Similarly, in the wheel slip control device for an electric vehicle according to the present invention, it is determined based on the wheel speed change rate and the slip rate of the driving wheel that the driving wheel lock tendency is being eliminated. This avoids situations in which it is erroneously determined that the driving wheel lock tendency is being resolved only by a temporary change in wheel rotation speed or a temporary change in the slip ratio. It is possible to accurately determine that it is going.

If it is determined that the drive wheel lock tendency is being resolved, only the regenerative braking torque is set as the target output torque of the motor, and the regenerative braking torque of the motor that operates the generator is applied to the drive wheels. Therefore, it is possible to obtain deceleration similar to deceleration by engine braking of a vehicle using only the engine as a power source without causing the drive wheels to be locked.
Also, not only when the electric vehicle is decelerated using the service brake mechanism, but also when the electric vehicle is decelerated using the auxiliary brake or the regenerative braking torque of the electric motor, the tendency to lock the drive wheels is resolved. When this is happening, the electric vehicle can be decelerated well by accurately determining this.

Therefore, in order to recover as much kinetic energy as electric energy when the electric vehicle decelerates, a deceleration slightly larger than the deceleration due to the engine brake of the vehicle using only the engine as a power source is generated. Even when the regenerative braking torque of the electric motor is set, it is possible to collect as much kinetic energy as possible as electric energy while accurately preventing the drive wheels from being locked.
In addition, when the electric vehicle is decelerated using the service brake mechanism, the electric vehicle is decelerated by the regenerative braking force of the electric motor while the driving wheel is properly locked as described above. It is possible to shorten the braking distance while ensuring the running stability.

In addition, since the rotational speed of the driving wheel fluctuates due to unevenness of the road surface on which the electric vehicle runs, the driving wheel does not necessarily tend to lock if the wheel speed change rate of the driving wheel is a negative value. Not necessarily. If the slip ratio of the drive wheel is larger than a predetermined reference value, the drive wheel does not necessarily tend to lock, and the slip of the drive wheel may converge from that state.
Therefore, as in the wheel slip control device for an electric vehicle according to claim 2, the driving speed is changed when the wheel speed change rate of the drive wheel becomes a negative value and the slip rate of the drive wheel becomes larger than the first reference slip rate. By determining that the wheels tend to lock, it is possible to accurately determine that the driving wheels tend to lock.

On the other hand, for the same reason, the tendency of the drive wheels to be locked is not necessarily being eliminated just by changing the wheel speed change rate of the drive wheels to a positive value. If the slip ratio of the drive wheel is merely smaller than the predetermined reference value, the tendency of the drive wheel to lock is not necessarily eliminated, and the slip of the drive wheel may increase from this state.
Therefore, as in the wheel slip control device for an electric vehicle according to claim 2, the wheel speed change rate of the drive wheel becomes a positive value, and the slip rate of the drive wheel is larger than the first reference slip rate. By determining that the driving wheel locking tendency is being eliminated when the slip ratio is smaller than the slip ratio, it is possible to accurately determine that the driving wheel locking tendency is being eliminated.

The wheel speed change rate of the drive wheel is not simply determined as positive or negative, but has a first reference change rate having a negative value and a positive value as in the wheel slip control device for an electric vehicle according to claim 3. When the second reference change rate is used, it can be determined more strictly that the driving wheels tend to lock and that the locking tendency is being eliminated.
That is, in addition to the drive wheel slip rate being greater than the first reference slip rate, the wheel speed change rate of the drive wheel is not only negative, but also below the first reference change rate having a negative value. From this, it is determined that the driving wheel has a locking tendency, so that it is determined more reliably that the driving wheel has a locking tendency. Similarly, in addition to the slip rate of the drive wheel being smaller than the second reference slip rate, the wheel speed change rate of the drive wheel is not only a positive value but also a second reference change rate having a positive value. Since it is not determined that the drive wheel lock tendency is being eliminated, it is more reliably determined that the drive wheel lock tendency is being eliminated.

  When the electric vehicle is a hybrid electric vehicle as in the wheel slip control device for an electric vehicle according to the fourth aspect, the same effect as described above can be obtained.

1 is an overall configuration diagram of a hybrid electric vehicle to which a wheel slip control device according to an embodiment of the present invention is applied. 2 is a flowchart of wheel slip control executed by a vehicle ECU in the hybrid electric vehicle of FIG. 1. It is a graph which shows an example of the condition of the wheel slip control which vehicle ECU performs according to the flowchart of FIG. 2 with the time change of the wheel rotational speed of a drive wheel, and a wheel speed change rate. It is a flowchart which shows the modification of wheel slip control. It is a graph which shows an example of the condition of the wheel slip control performed according to the flowchart of FIG. 4 with the time change of the wheel rotational speed of a driving wheel and a wheel speed change rate.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is an overall configuration diagram of a hybrid electric vehicle 1 to which a wheel slip control device according to an embodiment of the present invention is applied.
The input shaft of the clutch 4 is connected to the output shaft of the engine 2 which is a diesel engine. The output shaft of the clutch 4 is connected to an automatic transmission (hereinafter referred to as a transmission) via a rotating shaft of a permanent magnet type synchronous motor (hereinafter referred to as an electric motor) 6. 8 input shafts are connected. The output shaft of the transmission 8 is connected to the left drive wheel 16 and the right drive wheel 18 via the propeller shaft 10, the differential device 12 and the drive shaft 14, respectively.

  Therefore, when the clutch 4 is connected, both the output shaft of the engine 2 and the rotating shaft of the electric motor 6 can be mechanically connected to the left and right drive wheels 16 and 18 via the transmission 8, and the clutch 4 is When disconnected, only the rotating shaft of the electric motor 6 can be mechanically connected to the left and right drive wheels 16 and 18 via the transmission 8.

The electric motor 6 operates as a motor when the DC power stored in the battery 20 is converted into AC power by the inverter 22 and supplied. The drive torque of the electric motor 6 is transmitted to the left and right drive wheels 16 and 18 after being shifted to an appropriate speed by the transmission 8. Further, when the hybrid electric vehicle 1 is decelerated, the electric motor 6 operates as a generator, and the kinetic energy of the hybrid electric vehicle 1 is transmitted to the electric motor 6 through the transmission 8 and converted into AC power. At this time, the regenerative braking torque generated by the electric motor 6 is transmitted to the left and right drive wheels 16 and 18 via the transmission 8.
The AC power obtained by operating the electric motor 8 as a generator in this way is converted into DC power by the inverter 22 and then charged to the battery 20, and the kinetic energy of the hybrid electric vehicle 1 is recovered as electric energy. It has become so.

  On the other hand, the driving torque of the engine 2 is transmitted to the transmission 8 via the rotating shaft of the electric motor 6 when the clutch 4 is connected, and after being shifted to an appropriate speed, is applied to the left and right driving wheels 16 and 18. It is to be transmitted. Therefore, when the electric motor 6 operates as a motor when the driving torque of the engine 2 is transmitted to the left and right driving wheels 16, 18, the driving torque of the engine 2 and the driving torque of the electric motor 6 are respectively changed to the transmission 8. Is transmitted to the left and right drive wheels 16 and 18. That is, when the clutch 4 is connected, a part of the drive torque to be transmitted to the left and right drive wheels 16 and 18 for driving the hybrid electric vehicle 1 is supplied from the engine 2 and the remaining part is the electric motor 6. Supplied from

  Further, when the charging rate (hereinafter referred to as SOC) of the battery 20 decreases and the battery 20 needs to be charged, the electric motor 6 operates as a generator, and the electric motor 6 is operated using a part of the driving force of the engine 2. Electricity is generated by driving. The AC power thus generated is converted into DC power by the inverter 22 and then charged to the battery 20.

The vehicle ECU 24 (control means) controls the connection / disconnection of the clutch 4 and the gear position of the transmission 8 according to the operation state of the hybrid electric vehicle 1 and the engine 2 and information from the engine ECU 26, the inverter ECU 28, and the battery ECU 30. In addition to performing switching control, integrated control for appropriately operating the engine 2 and the electric motor 6 is performed in accordance with these control states and various operation states such as start, acceleration, and deceleration of the hybrid electric vehicle 1.
In order to perform such control, the vehicle ECU 24 has an accelerator opening sensor 34 that detects the amount of depression of the accelerator pedal 32, and an electric motor that is mounted on the output shaft of the electric motor 6 and detects the rotation speed of the electric motor 6. A rotational speed sensor 36 and an engine rotational speed sensor 38 for detecting the rotational speed of the engine 2 are connected.

  The engine ECU 26 performs various controls necessary for the operation of the engine 2 itself, such as start / stop control of the engine 2, idle control, or regeneration control of an exhaust gas purification device (not shown), and the engine set by the vehicle ECU 24. The fuel injection amount and injection timing of the engine 2 are controlled so that the engine 2 generates the torque required for the engine 2.

  On the other hand, the inverter ECU 28 controls the operation of the electric motor 6 by operating the motor 6 or the electric generator by controlling the inverter 22 based on the torque that should be generated by the electric motor 6 set by the vehicle ECU 24. In addition to receiving an output signal from a temperature sensor (not shown) that detects the temperature of the electric motor 6 and the inverter 22, the temperature of the electric motor 6 is sent to the vehicle ECU 24, and the operating state of the electric motor 6 and the inverter 22 is monitored. The information is sent to the vehicle ECU 24.

The battery ECU 30 detects the temperature of the battery 20, the voltage of the battery 20, the current flowing between the inverter 22 and the battery 20, obtains the SOC of the battery 20 from these detection results, and operates the battery 20. Is monitoring. Then, the obtained SOC and the operating state of the battery 20 are sent to the vehicle ECU 24 together with the detection result.
In the hybrid electric vehicle 1 configured as described above, an outline of control performed mainly by the vehicle ECU 24 when the hybrid electric vehicle 1 is driven is as follows.

  First, when the driver operates a change lever (not shown) from the neutral position to the drive position while the hybrid electric vehicle 1 is stopped and the engine 2 is operating, the vehicle ECU 24 disengages the clutch 4 and at the neutral position. The transmission 8 in the state is switched to a state in which the gear position at the start of start is selected according to the shift map. When the driver depresses the accelerator pedal 32, the vehicle ECU 24 applies the left and right drive wheels 16, 18 to start the hybrid electric vehicle 1 according to the depression amount of the accelerator pedal 32 detected by the accelerator opening sensor 34. The driving torque to be transmitted is obtained, and the output torque of the electric motor 6 is set based on this driving torque and the gear stage being used in the transmission 8.

  The inverter ECU 28 controls the inverter 22 according to the output torque of the electric motor 6 set by the vehicle ECU 24, and the DC power of the battery 20 is converted into AC power by the inverter 22 and supplied to the electric motor 6. The electric motor 6 is actuated by AC power to generate a driving force, and the driving force of the electric motor 6 is transmitted to the left and right driving wheels 16 and 18 via the transmission 8 so that the hybrid electric vehicle 1 is started. To do.

  When the hybrid electric vehicle 1 starts and accelerates and the rotational speed of the electric motor 6 rises to the vicinity of the idle rotational speed of the engine 2, the clutch 4 is connected to transmit the driving force of the engine 2 to the left and right drive wheels 16 and 18. The vehicle ECU 24 obtains the drive torque to be transmitted to the left and right drive wheels 16 and 18 for further acceleration of the hybrid electric vehicle 1 and subsequent travel. Then, this drive torque is appropriately distributed to the output torque of the engine 2 and the output torque of the electric motor 6 according to the gear stage being used in the transmission 8, the operating state of the hybrid electric vehicle 1, and the like, and is distributed to the engine ECU 26 and the inverter ECU 28. At the same time, the transmission 8 and the clutch 4 are controlled as necessary.

The engine ECU 26 and the inverter ECU 28 receive the command of the output torque set by the vehicle ECU 24 and control the engine 2 and the electric motor 6 respectively. When the clutch 4 is connected, the output torque of the engine 2 and the electric motor 6 changes the transmission 8. On the other hand, when the clutch 4 is disengaged, the output torque generated by the electric motor 6 is transmitted to the left and right drive wheels 16 and 18 via the transmission 8, and the hybrid electric The automobile 1 travels.
At this time, the vehicle ECU 24 appropriately controls the shift speed of the transmission 8 according to the driving state of the hybrid electric vehicle 1 and appropriately controls the torque of the engine 2 and the electric motor 6 in accordance with the shift speed change. Thus, the engine ECU 26 and the inverter ECU 28 are instructed and the connection and disconnection of the clutch 4 are controlled.

  On the other hand, when the depression of the accelerator pedal 32 is released while the hybrid electric vehicle 1 is traveling, the vehicle ECU 24 disconnects the clutch 4 and sends a command to the inverter ECU 28 to operate the electric motor 6 as a generator. At this time, the vehicle ECU 24 instructs the inverter ECU 28 to set a regenerative braking torque that is set in advance according to the shift speed selected by the transmission 8 and the rotation speed of the electric motor 6 detected by the electric motor rotation speed sensor 36. Receiving this, the inverter ECU 28 controls the electric motor 6 so as to generate the instructed regenerative braking torque, and the regenerative braking torque generated by the electric motor 6 is transmitted to the left and right drive wheels 16 and 18 via the transmission 8. Is done. At this time, the electric power generated by the electric motor 6 is charged into the battery 20 via the inverter 22. In this way, when the electric motor 6 operates as a generator, the kinetic energy of the hybrid electric vehicle 1 is recovered as electric energy.

  If the clutch 4 is connected when the hybrid electric vehicle 1 travels at a reduced speed, the engine brake torque generated by the engine 2 and the regenerative braking torque of the electric motor 6 operating as a generator as described above cause the transmission 8 to move. To the left and right drive wheels 16 and 18. However, in the present embodiment, the kinetic energy of the hybrid electric vehicle 1 is recovered as much as possible as electric energy. Therefore, when the hybrid electric vehicle 1 travels at a reduced speed, the clutch 4 is disconnected as described above, and the regenerative braking of the electric motor 6 is performed. Only torque is transmitted to the left and right drive wheels 16 and 18. However, in order to prevent overcharging of the battery 20, the clutch 4 may be connected and the engine brake may be used together, or only the engine brake may be used.

  When the clutch 4 is disengaged and only the regenerative braking torque of the electric motor 6 is transmitted to the left and right drive wheels 16 and 18 as described above, it is obtained by engine braking in a vehicle using only the engine as a power source. The regenerative braking torque of the electric motor 6 is set so that a deceleration somewhat larger than the deceleration can be obtained. Thus, in conjunction with the disconnection of the clutch 4 during the deceleration traveling described above, as much kinetic energy as possible of the hybrid electric vehicle 1 during the deceleration traveling is recovered as electric energy.

  By the way, when the hybrid electric vehicle 1 decelerates the hybrid electric vehicle 1 using a service brake mechanism (not shown), either the left and right drive wheels 16, 18 or the left and right driven wheels (not shown) tend to lock. In addition, an ABS device (not shown) for adjusting the braking force by the service brake mechanism to prevent the driving wheels 16 and 18 and the driven wheels from being locked is mounted. The ABS device is controlled by the ABS ECU 40. Hereinafter, the control of the ABS device by the ABS ECU 40 is referred to as ABS control.

  The ABS ECU 40 has a wheel speed sensor (wheel speed detecting means) 42 for detecting the wheel rotation speed of the left drive wheel 16 and the wheel rotation of the right drive wheel 18 in order to obtain information necessary for executing this ABS control. A wheel speed sensor (wheel speed detecting means) 44 for detecting the speed, a wheel speed sensor 46 for detecting a wheel rotational speed of the left driven wheel (not shown), and a wheel rotational speed of the right driven wheel (not shown). Are respectively connected to the wheel speed sensors 48. Further, the ABS ECU 40 exchanges information necessary for the control executed by the both with the vehicle ECU 24.

  Since the ABS control itself executed by the ABS ECU 40 is the same as that widely known conventionally, the detailed description of the control contents is omitted here. As described above, the ABS ECU 40 executes the ABS control when any of the left and right drive wheels 16 and 18 and the left and right driven wheels tends to lock, but information on whether or not the ABS control is being executed is given to the vehicle. It is sent to the ECU 24. Further, the ABS ECU 40 of the present embodiment is not limited to the case of deceleration using the service brake mechanism, and performs ABS control if any of the left and right drive wheels 16 and 18 and the left and right driven wheels tends to lock. It has become. However, when the deceleration is not performed using the service brake mechanism, the braking force by the service brake mechanism cannot be adjusted by the ABS control.

  In order to determine whether any of the left and right driving wheels 16 and 18 and the left and right driven wheels tends to lock, the ABS ECU 40 detects the respective wheels detected by the four wheel speed sensors 42, 44, 46 and 48. Using the rotational speed, the estimated vehicle body speed of the hybrid electric vehicle 1 is calculated by a conventionally known method. The ABS ECU 40 sends the calculated estimated vehicle body speed to the vehicle ECU 24 together with the wheel rotational speeds of the left and right drive wheels 16 and 18 detected by the wheel speed sensors 42 and 44.

  As described above, when the hybrid electric vehicle 1 travels at a reduced speed, the vehicle ECU 24 operates the electric motor 6 as a generator and transmits the regenerative braking torque generated by the electric motor 6 to the left and right drive wheels 16 and 18. Yes. When the friction coefficient of the traveling road surface is low, one of the left and right drive wheels 16 and 18 may be locked by the regenerative braking torque transmitted from the electric motor 6. This is not limited to the case where the hybrid electric vehicle 1 is decelerated using an auxiliary brake mechanism (not shown) such as a service brake mechanism or an exhaust brake, and only the regenerative braking torque is used without using the service brake mechanism or the auxiliary brake mechanism. This may also occur when the hybrid electric vehicle 1 is decelerated.

  When either of the left and right drive wheels 16 and 18 tends to lock, ABS control is performed by the ABS ECU 40 as described above, but the hybrid electric vehicle 1 is operated with regenerative braking torque without using the service brake mechanism. When decelerating, the braking force by the service brake mechanism cannot be adjusted. Even in such a case, in order to appropriately prevent the drive wheels 16 and 18 from being locked, wheel slip control by the vehicle ECU 24 as described in detail below is performed in this embodiment. The wheel slip control by the vehicle ECU 24 is also executed when the hybrid electric vehicle 1 is decelerated using at least one of the service brake mechanism and the auxiliary brake. In this case, the driving wheels 16 and 18 are combined with the ABS control. The lock is prevented.

Below, the wheel slip control performed by vehicle ECU24 is explained in full detail. FIG. 2 is a flowchart of wheel slip control in the present embodiment, and the vehicle ECU 24 executes wheel slip control at a predetermined control cycle according to this flowchart.
In the following, an example of wheel slip control related to the left drive wheel 16 will be described, but the wheel slip control is similarly performed for the right drive wheel 18.

  Wheel slip control by the vehicle ECU 24 is started according to the flowchart of FIG. 2 when a key switch (not shown) of the hybrid electric vehicle 1 is turned on. First, in step S1, the vehicle ECU 24 determines whether or not ABS control by the ABS ECU 40 is being performed. As described above, the ABS control is executed when any of the left and right drive wheels 16 and 18 and the left and right driven wheels tends to lock. When the ABS control is not executed, the vehicle ECU 24 The process proceeds to step S2.

  In step S2, the vehicle ECU 24 sets the value of the flag F1 to zero. The flag F1 indicates whether one of the left and right drive wheels 16 and 18 has been determined to be in a lock tendency in the wheel slip control until the ABS control once started ends. The value is set to 1 when it has been determined that there is a tendency to lock. In step S2, since the ABS control is not yet started, the value of the flag F1 is set to 0, and the vehicle ECU 24 advances the process to step S3.

  When the process proceeds to step S3, the ABS control is not performed, and it is not necessary to perform the process for preventing the drive wheels 16 and 18 from being locked in the wheel slip control. For this reason, in step S3, the vehicle ECU 24 ends the control cycle without giving an instruction to the inverter ECU 28 for controlling the electric motor 6 as wheel slip control in order to prioritize other control. Therefore, unless the ABS control by the ABS ECU 40 is started, the processes of steps S1 to S3 are repeated, and the motor 6 is not controlled by the wheel slip control.

When the hybrid electric vehicle 1 travels at a reduced speed, if any of the left and right drive wheels 16, 18 such as the left drive wheel 16 tends to lock and the ABS control by the ABS ECU 40 is started, the vehicle ECU 24 performs the process in step S1. From step S4, the wheel speed change rate ΔVw, which is the change rate, is calculated from the wheel rotation speed Vw of the drive wheel 16 detected by the wheel speed sensor 42 and sent from the ABS ECU 40. In step S4, the vehicle ECU 24 uses the estimated vehicle body speed Vo calculated by the ABS ECU 40 and the wheel rotation speed Vw of the drive wheel 16 to calculate the slip ratio Sw with respect to the road surface of the drive wheel 16 using the following equation (1).
Sw = (Vo−Vw) / Vo (1)

  Next, the vehicle ECU 24 proceeds with the process to step S5, and determines whether or not the value of the flag F2 is 1. In the wheel slip control, the flag F2 is set to 1 when the electric motor 6 is operating as a motor by a process described later, and is set to 0 when the electric motor 6 is operating as a generator. It has become. Since the initial value of the flag F2 is 0, the vehicle ECU 24 proceeds to step S6 based on the determination in step S5.

In step S6, the vehicle ECU 24 determines whether or not the wheel speed change rate ΔVw of the drive wheel 16 obtained in step S4 is less than the first reference change rate ΔVa. In this embodiment, the value of the first reference change rate ΔVa is set to 0 (m / s ² ), and the determination in step S6 is whether or not the wheel speed change rate ΔVw of the drive wheel 16 has a negative value. It will be determined.

  FIG. 3 is a graph showing an example of the situation of the wheel slip control together with the temporal change of the wheel rotation speed Vw of the drive wheel 16 and the wheel rotation speed change rate ΔVw. In addition, Vo in FIG. 3 is an estimated vehicle body speed. As shown in FIG. 3, as the hybrid electric vehicle 1 travels at a reduced speed, the estimated vehicle speed Vo gradually decreases, and the wheel rotational speed Vw of the drive wheels 16 is greater than the estimated vehicle speed Vo due to slipping on the road surface of the drive wheels 16. Also decreases quickly. If the ABS control by the ABS ECU 40 is started at the time t1, the control of the electric motor 6 by the wheel slip control is not yet performed at this time, and as described above, the electric motor 6 during the decelerating traveling of the hybrid electric vehicle 1 is not performed. The regenerative braking force is in a state of acting on the drive wheel 16.

As shown in FIG. 3, since the wheel speed change rate of the drive wheels 16 has already become a negative value when the ABS control is started, the vehicle ECU 24 advances the process to step S7 based on the determination in step S6.
In step S7, the vehicle ECU 24 determines whether or not the slip ratio Sw of the drive wheels 16 obtained in step S4 is greater than the first reference slip ratio S1. A one-dot chain line in FIG. 3 indicates the wheel rotation speed V1 of the drive wheel 16 when the slip ratio of the drive wheel 16 is set to the first reference slip ratio S1 with respect to the estimated vehicle body speed Vo. Since the wheel rotation speed Vw of the drive wheel 16 is larger than the wheel rotation speed V1 at the beginning of the ABS control, the slip ratio Sw of the drive wheel 16 is smaller than the first reference slip ratio S1. In such a case, the vehicle ECU 24 advances the process to step S10 based on the determination in step S7.

  In step S10, the vehicle ECU 24 determines whether or not the value of the flag F1 is 1. As described above, since the value of the flag F1 has not been changed since the value was set to 0 in step S2, the vehicle ECU 24 proceeds to step S15 based on the determination in step S10.

  In step S15, the vehicle ECU 24 sets the regenerative braking torque Tb as the target output torque Tm of the electric motor 6, and instructs the inverter ECU 28 of the target output torque Tm. The inverter ECU 28 receives an instruction from the vehicle ECU 24, operates the motor 6 as a generator, and controls the motor 6 so that the output torque becomes the target output torque Tm, that is, the regenerative braking torque Tb. The regenerative braking torque output from the electric motor 6 is transmitted to the left and right drive wheels 16 and 18 via the transmission 8.

  In the case of this embodiment, the magnitude of the regenerative braking torque Tb set at this time is determined in the same manner as the regenerative braking torque generated by the electric motor 6 when the hybrid electric vehicle 1 is decelerated. The hybrid electric vehicle 1 is set so as to obtain an appropriate deceleration according to the speed selected in the transmission 8 and the rotational speed of the electric motor 6 detected by the electric motor rotational speed sensor 36. It has become.

  Thus, when the vehicle ECU 24 determines the target output torque Tm of the electric motor 6 in step S15, the vehicle ECU 24 ends the control cycle, and starts the process from step S1 again in the next control cycle. As long as the ABS control by the ABS ECU 40 continues, the vehicle ECU 24 advances the process to step S4, and again calculates the wheel speed change rate ΔVw and the slip rate Sw of the drive wheels 16. Therefore, while the ABS control is being performed, the wheel speed change rate ΔVw and the slip rate Sw of the drive wheels 16 are updated to the latest values in step S4 for each control cycle.

  Further, the vehicle ECU 24 advances the process from step S4 to step S5. Since the value of the flag F2 has not been changed in the series of processes so far, the process further advances to step S6 based on the determination in step S5. Therefore, after the ABS control by the ABS ECU 40 is started, the wheel speed change rate ΔVw of the drive wheel 16 becomes equal to or higher than the first reference change rate ΔVa, that is, it is not a negative value, or the slip rate Sw of the drive wheel 16 is the first. As long as it is not larger than the reference slip ratio S1, the regenerative braking torque Tb is set as the target output torque Tm of the electric motor 6 in step S15 as described above, and the regenerative braking torque output from the electric motor 6 operating as a generator is driven left and right. It is given to the wheels 16 and 18.

  When the regenerative braking torque is continuously applied to the drive wheels 16 and the slip of the drive wheels 16 with respect to the road surface increases, the wheel rotation speed Vw of the drive wheels 16 further decreases and the deviation from the estimated vehicle body speed Vo further increases. Then, when the wheel rotational speed V1 is decreased at time t2 in FIG. 3, the slip ratio Sw of the drive wheels 16 is less than the first reference slip ratio S1. When the process proceeds to step S7 in such a state, the vehicle ECU 24 proceeds to step S8 based on the determination in step S7. In step S8, the vehicle ECU 24 sets both the values of the flags F1 and F2 to 1, and further proceeds to step S9.

  In step S9, the vehicle ECU 24 sets the drive torque Td as the target output torque Tm of the electric motor 6, and instructs the inverter ECU 28 of the target output torque Tm. The inverter ECU 28 receives an instruction from the vehicle ECU 24, operates the electric motor 6 as a motor, and controls the electric motor 6 so that the output torque becomes the target output torque Tm, that is, the driving torque Td. The drive torque output from the electric motor 6 in this way is transmitted to the left and right drive wheels 16 and 18 via the transmission 8. Therefore, the slip with respect to the road surface of the drive wheel 16 that tends to increase is suppressed by the drive torque applied from the electric motor 6.

  As described above, the vehicle ECU 24 determines that the wheel speed change rate ΔVw of the drive wheel 16 is less than the first reference change rate ΔVa, that is, has a negative value, and the slip rate of the drive wheel 16 according to the determinations in steps S6 and S7. When Sw exceeds the first reference slip ratio S1, it is determined that slip with respect to the road surface is increasing and the drive wheels 16 tend to lock, and the electric motor 6 is operated as a motor to drive the drive wheels 16 with drive torque. Is granted.

Since the wheel rotation speed Vw of the driving wheel 16 detected by the wheel speed sensor 42 varies due to road surface unevenness or the like, the wheel speed change rate ΔVw is less than the first reference change rate ΔVa, that is, a negative value. Just having it does not necessarily mean that the drive wheels 16 tend to lock. In addition, just because the slip ratio Sw of the drive wheel 16 is larger than the first reference slip ratio S1, the drive wheel 16 does not necessarily tend to lock, and the slip of the drive wheel 16 may converge from that state. obtain.
Therefore, as described above, the wheel speed change rate ΔVw is simply less than the first reference change rate ΔVa, that is, not only has a negative value, but also when the slip rate Sw exceeds the first reference slip rate S1. By determining that the wheel 16 tends to lock, it is possible to accurately determine that the drive wheel 16 tends to lock.

  Note that the driving torque Td set when it is determined that the driving wheels 16 tend to lock becomes an appropriate magnitude for preventing the driving wheels 16 from being locked by suppressing slipping of the driving wheels 16 with respect to the road surface. Thus, it is determined in advance by experiments or the like, and is set in accordance with the gear stage selected in the transmission 8 and the rotational speed of the electric motor 6 detected by the electric motor rotational speed sensor 36.

Thus, when the drive torque Td is set as the target output torque Tm of the electric motor 6 in step S9, the vehicle ECU 24 ends its control cycle and starts the process from step S1 again in the next control cycle.
If the ABS control by the ABS ECU 40 is continued, the vehicle ECU 24 proceeds from step S1 to step S4 again, calculates the wheel speed change rate ΔVw and the slip rate Sw of the drive wheels 16, and then performs the process in step S5. Proceed.

At this time, since the value of the flag F2 is changed to 1 in step S8 as described above, the vehicle ECU 24 advances the process to step S12 based on the determination in step S5.
In step S12, the vehicle ECU 24 determines whether or not the wheel speed change rate ΔVw of the drive wheels 16 obtained in step S4 exceeds the second reference change rate ΔVb. In the present embodiment, the value of the second reference change rate Vb is also 0 (m / s ² ), the same as the value of the first reference change rate Va, and the determination in step S12 is the wheel speed change rate ΔVw of the drive wheels 16. It is determined whether or not has a positive value.

  As shown in FIG. 3, the wheel rotation speed Vw of the drive wheel 16 decreases gradually due to the application of the drive torque from the electric motor 6 after the time t2 has passed and falls below the wheel rotation speed V1. The wheel speed change rate ΔVw still has a negative value. For this reason, vehicle ECU24 advances a process to step S9 by determination of step S12.

As described above, in step S9, the vehicle ECU 24 operates the electric motor 6 as a motor, and the driving torque output by the electric motor 6 is applied to the driving wheels 16. Accordingly, the slip of the drive wheel 16 with respect to the road surface converges, and the absolute value of the wheel speed change rate ΔVw having a negative value gradually decreases. While the wheel speed change rate ΔVw has a negative value, the process proceeds to step S9 as described above. Therefore, the drive torque of the electric motor 6 that operates as a motor is applied to the drive wheels 16 by the process of step S9. The As a result, as shown in FIG. 3, the wheel speed change rate ΔVw of the drive wheels 16 becomes 0 (m / s ² ) at time t3.

When the wheel speed change rate ΔVw of the drive wheel 16 has a positive value after the time t3 in FIG. 3, the vehicle ECU 24 proceeds to step S13 based on the determination in step S12.
In step S13, the vehicle ECU 24 determines whether or not the slip ratio Sw of the drive wheels 16 obtained in step S4 is lower than the second reference slip ratio S2. In the present embodiment, the second reference slip ratio S2 is larger than the first reference slip ratio S1 used for determination in step S7.

  The wheel rotation speed Vw of the drive wheel 16 starts to increase as described above as slip on the road surface is suppressed by application of drive torque from the electric motor 6, but does not immediately start to increase by application of drive torque. Absent. That is, the wheel rotation speed Vw of the drive wheel 16 starts increasing after a time t2 in FIG. 3 and then increases at a time t3 with a time delay. In the present embodiment, the relationship between the application of the drive torque and the change in the wheel rotation speed Vw is grasped by an experiment or the like in advance, and is determined by the slip rate of the drive wheel 16 when the wheel rotation speed Vw starts to increase from the decrease. A smaller value is used as the second reference slip ratio S2.

  A two-dot chain line in FIG. 3 indicates the wheel rotation speed V2 of the drive wheel 16 when the slip ratio of the drive wheel 16 is set to the second reference slip ratio S2 with respect to the estimated vehicle body speed Vo. Since the second reference slip rate S2 is set as described above, as shown in FIG. 3, initially, the wheel speed change rate ΔVw of the drive wheel 16 has a positive value after the time t3. The wheel rotation speed Vw is smaller than the wheel rotation speed V2, and the slip ratio Sw of the drive wheel 16 is larger than the second reference slip ratio S2. For this reason, if vehicle ECU24 advances a process to step S13 by determination of step S12, vehicle ECU24 will advance a process to step S16 further by determination of step S13.

  In step S <b> 16, the vehicle ECU 24 sets the target output torque Tm of the electric motor 6 to 0 (kg · m), and instructs the inverter ECU 28 about the target output torque Tm. The inverter ECU 28 receives an instruction from the vehicle ECU 24 and controls the electric motor 6 so that the output torque of the electric motor 6 becomes the target output torque Tm, that is, 0 (kg · m). Therefore, the electric motor 6 is in a state where no torque is applied to the drive wheels 6. At this time, the wheel rotational speed Vw of the driving wheel 16 has already turned to an increasing direction as the slip converges on the road surface, and the locking of the driving wheel 16 is in a direction to be suppressed.

Thus, when the target output torque Tm of the electric motor 6 is set in step S16, the vehicle ECU 24 ends the control cycle and starts the process from step S1 again in the next control cycle.
If the ABS control by the ABS ECU 40 is continued, the vehicle ECU 24 proceeds from step S1 to step S4 again, calculates the wheel speed change rate ΔVw and the slip rate Sw of the drive wheels 16, and then performs the process in step S5. Proceed.

Since the value of the flag F2 remains 1, the vehicle ECU 24 proceeds with the process to step S12 based on the determination in step S5. At this time, the wheel rotation speed Vw of the drive wheel 16 turns in the increasing direction as the slip converges on the road surface as described above, and the wheel speed change rate ΔVw of the drive wheel 16 has a positive value. Since it is larger than the 2 reference change rate ΔVb, the vehicle ECU 24 proceeds with the process to step S13 based on the determination in step S12.
Therefore, until the slip rate Sw of the drive wheel 16 decreases and falls below the second reference slip rate S2, the output torque of the motor 6 becomes 0 (kg · m) by the process of step S16, and the motor 6 is driven by the drive wheel 6 In this state, no torque is applied.

As described above, since the wheel rotation speed Vw of the drive wheel 16 turns in the increasing direction as the slip converges on the road surface, the motor 6 does not apply any torque to the drive wheel 6. Continues to increase, and reaches the wheel rotation speed V2 corresponding to the second reference slip ratio S2 at time t4 in FIG.
Therefore, in the period between time t3 and time t4 in FIG. 3, the slip rate Sw of the drive wheels 16 is equal to or greater than the second reference slip rate S2, and the vehicle ECU 24 proceeds to step S16 based on the determination in step S13. Therefore, as described above, during this period, the electric motor 6 does not apply any torque to the drive wheels 6.

  As the wheel rotation speed Vw of the driving wheel 16 increases and exceeds the second reference wheel speed V2 as the slip converges on the road surface, the slip ratio Sw of the driving wheel 16 falls below the second reference slip ratio S2. When the time t4 in FIG. 3 is passed, the vehicle ECU 24 proceeds to step S14 based on the determination in step S13.

  In step S14, the vehicle ECU 24 sets the value of the flag F2 to 0, and then proceeds to step S15. As described above, the vehicle ECU 24 sets the regenerative braking torque Tb as the target output torque Tm of the electric motor 6 in step S15, and instructs the inverter ECU 28 about the target output torque Tm. The inverter ECU 28 receives an instruction from the vehicle ECU 24, operates the motor 6 as a generator, and controls the motor 6 so that the output torque becomes the target output torque Tm, that is, the regenerative braking torque Tb. The regenerative braking torque output from the electric motor 6 is transmitted to the left and right drive wheels 16 and 18 via the transmission 8.

  As described above, the vehicle ECU 24 determines that the wheel speed change rate ΔVw of the drive wheel 16 exceeds the second reference change rate ΔVa, that is, has a positive value and the slip rate Sw of the drive wheel 16 according to the determinations in steps S12 and S13. Is less than the second reference slip ratio S2, it is determined that the slip with respect to the road surface is converging and the locking tendency of the drive wheels 16 is being resolved, and the motor 6 is operated again as a generator, so that the drive wheels 16 Is applied with regenerative braking torque.

Similar to the case where it is determined that the driving wheel 16 tends to lock, the driving wheel 16 does not necessarily have to have a positive value when the wheel speed change rate ΔVw of the driving wheel 16 exceeds the second reference change rate ΔVa. The 16 lock tendency is not necessarily being resolved. In addition, if the slip rate Sw of the drive wheel 16 is less than the second reference slip rate S2, the lock tendency of the drive wheel 16 is not necessarily eliminated, and the slip of the drive wheel 16 increases from that state. There is also a possibility.
Therefore, as described above, the wheel speed change rate ΔVw is not only larger than the second reference change rate ΔVa, that is, has a positive value, and when the slip rate Sw is lower than the second reference slip rate S2, the drive wheel By determining that the lock tendency of 16 is being eliminated, it is possible to accurately determine that the lock tendency of the drive wheels 16 is being eliminated.

When the regenerative braking torque Tb is set as the target output torque Tm of the electric motor 6 in step S15, the vehicle ECU 24 ends the control cycle and starts the process from step S1 again in the next control cycle.
If the ABS control by the ABS ECU 40 is continued, the vehicle ECU 24 proceeds from step S1 to step S4 again, calculates the wheel speed change rate ΔVw and the slip rate Sw of the drive wheels 16, and then performs the process in step S5. Proceed.

At this time, since the value of the flag F2 is changed to 0 again in step S14 as described above, the vehicle ECU 24 advances the process to step S6 based on the determination in step S5. In step S6, the vehicle ECU 24 determines whether or not the wheel speed change rate ΔVw of the drive wheels 16 obtained in step S4 is less than the first reference change rate ΔVa, that is, whether or not it is a negative value.
As shown in FIG. 3, the wheel rotation speed Vw of the drive wheel 16 exceeds the wheel rotation speed V2 after the time t4, and then the degree of increase is moderated by applying the regenerative braking torque from the electric motor 6 described above. However, the wheel speed change rate ΔVw still has a positive value. For this reason, vehicle ECU24 advances a process to step S15 by determination of step S6.

As described above, in step S15, the vehicle ECU 24 operates the electric motor 6 as a generator, and the regenerative braking torque output by the electric motor 6 is applied to the drive wheels 16. Accordingly, the driving wheel 16 receives the braking force, and the wheel speed change rate ΔVw having a positive value gradually decreases. While the wheel speed change rate ΔVw has a positive value, the process proceeds to step S15 as described above. Therefore, the regenerative braking torque of the electric motor 6 that operates as a generator by the process of step S15 is applied to the drive wheels 16. Is granted. As a result, as shown in FIG. 3, the wheel speed change rate ΔVw of the drive wheel 16 becomes 0 (m / s ² ) at time t5, and the wheel speed change rate ΔVw starts to decrease.

When the wheel speed change rate ΔVw of the drive wheel 16 has a negative value after the time t5 in FIG. 3, the vehicle ECU 24 proceeds to step S7 based on the determination in step S6.
In step S7, the vehicle ECU 24 determines whether or not the slip ratio Sw of the drive wheels 16 obtained in step S4 exceeds the first reference slip ratio S1. In the example of FIG. 3, before the wheel rotation speed Vw of the driving wheel 16 starts to decrease at time t5, the wheel rotation speed V1 becomes higher than the rotation speed V1, and the slip ratio Sw of the driving wheel 16 decreases to the first reference slip ratio S1 or less. . Therefore, after time t5, the vehicle ECU 24 proceeds to step S10 according to the determination in step S7.

In step S10, the vehicle ECU 24 determines whether or not the value of the flag F1 is 1. Since the value of the flag F1 has already been set to 1 in the process of step S8, the vehicle ECU 24 determines that the value of the flag F1 is 1 in step S10. The process proceeds to step S11.
In step S11, the same processing as in step S16 described above is performed. That is, the vehicle ECU 24 sets the target output torque Tm of the electric motor 6 to 0 (kg · m), and instructs the inverter ECU 28 of the target output torque Tm. The inverter ECU 28 receives an instruction from the vehicle ECU 24 and controls the electric motor 6 so that the output torque of the electric motor 6 becomes the target output torque Tm, that is, 0 (kg · m). Therefore, the electric motor 6 is in a state where no torque is applied to the drive wheels 6.

Thus, when the target output torque Tm of the electric motor 6 is set in step S16, the vehicle ECU 24 ends the control cycle and starts the process from step S1 again in the next control cycle.
If the ABS control by the ABS ECU 40 is continued, the vehicle ECU 24 proceeds from step S1 to step S4 again, calculates the wheel speed change rate ΔVw and the slip rate Sw of the drive wheels 16, and then performs the process in step S5. Proceed.

Since the value of the flag F2 remains 0, the vehicle ECU 24 advances the process to step S6 based on the determination in step S5. The wheel rotation speed Vw of the drive wheel 16 turns in a decreasing direction at time t5 due to the regenerative braking torque applied until time t5 in FIG. 3, so that the output torque of the electric motor 6 is 0 (kg · m) after time t5. However, the wheel speed change rate ΔVw has a negative value and is smaller than the first reference change rate ΔVa. For this reason, vehicle ECU24 will advance a process to step S7 by determination of step S6.
Therefore, until the slip rate Sw of the drive wheel 16 increases and exceeds the first reference slip rate S1, the output torque of the electric motor 6 is 0 (kg ···) by the process of step S11 proceeding from step S7 through step S10. m), and the electric motor 6 does not apply any torque to the drive wheels 6.

As described above, since the wheel rotation speed Vw of the drive wheel 16 has turned in the decreasing direction, the decrease continues even after the electric motor 6 does not apply any torque to the drive wheel 6. At time t6, the wheel rotational speed V1 corresponding to the first reference slip ratio S1 is reached.
Therefore, in the period between time t5 and time t6 in FIG. 3, the slip ratio Sw of the drive wheels 16 is equal to or less than the first reference slip ratio S1, and the vehicle ECU 24 proceeds to step S11 based on the determination in step S7 and step S10. To proceed. For this reason, as described above, during this period, the electric motor 6 does not apply any torque to the drive wheels 6.

  If the wheel rotation speed Vw of the driving wheel 16 continues to decrease after reaching the wheel rotation speed V1 at time t6 in FIG. 3, the vehicle ECU 24 advances the process to step S8 based on the determination in steps S6 and S7, and sets the flag F1. And the value of F2 is set to 1, the process further proceeds to step S9. That is, the vehicle ECU 24 has the wheel speed change rate ΔVw of the drive wheel 16 smaller than the first reference speed change rate ΔVa, that is, has a negative value, and the slip rate Sw of the drive wheel 16 is larger than the first reference slip rate S1. It is determined that the drive wheels 16 tend to lock, and the drive torque Td is set as the target output torque Tm of the electric motor 6 in step S9. As a result, the drive torque output from the electric motor 6 is applied to the drive wheels 16 as described above, and the drive wheels 16 are prevented from being locked.

  The subsequent processing is as described above, and when it is determined that the drive wheel 16 tends to lock based on the wheel speed change rate ΔVw and the slip rate Sw of the drive wheel 16, the vehicle ECU 24 Operates the motor 6 as a motor, and the driving torque output from the motor 6 is applied to the driving wheel 16 to prevent the driving wheel 16 from being locked. On the other hand, when it is determined that the driving wheel 16 tends to lock, and then it is determined that the locking tendency of the driving wheel 16 is being resolved based on the wheel speed change rate ΔVw and the slip rate Sw of the driving wheel 16. Then, the vehicle ECU 24 operates the electric motor 6 as a generator, and the regenerative braking torque output from the electric motor 6 is applied to the driving wheels 16 so that the driving wheels 16 are appropriately braked.

  When the ABS control by the ABS ECU 40 ends, for example, when the hybrid electric vehicle 1 stops, the vehicle ECU 24 proceeds to step S2 based on the determination in step S1, resets the value of the flag F1 to 0, and then proceeds to step S3. To proceed. In step S3, the vehicle ECU 24 ends the control cycle without giving an instruction to the inverter ECU 28 for controlling the electric motor 6 as wheel slip control in order to prioritize other control as described above. Therefore, the electric motor 6 is controlled by the inverter ECU 28 according to the target output torque set by the vehicle ECU 24 by other control.

  By performing the wheel slip control as described above, not only when the hybrid electric vehicle 1 is decelerated using the service brake mechanism, but also when decelerating with an auxiliary brake mechanism such as an exhaust brake (not shown) Even when the regenerative braking force alone or the combination of the engine brake of the engine 2 and the regenerative braking force of the electric motor 6 is used for deceleration, it is possible to satisfactorily prevent the drive wheels 16 from being locked.

  In particular, when the hybrid electric vehicle 1 is decelerated without using the service brake mechanism, the braking force of the service brake mechanism cannot be adjusted even if the ABS control by the ABS ECU 40 is performed. For this reason, the above-described wheel slip control is extremely useful in that the lock of the drive wheels 16 can be satisfactorily prevented even in such a case.

  By performing the wheel slip control as described above, it is determined that the drive wheel 16 tends to be locked based on the wheel speed change rate ΔVw and the slip rate Sw of the drive wheel 16. It is avoided that the driving wheel 16 tends to be locked by avoiding a situation in which the driving wheel 16 tends to be locked only by a temporary change of Vw or a temporary change of the slip ratio Sw. It can be judged accurately.

  When it is determined that the driving wheel 16 tends to lock, the driving torque of the motor 6 that operates the motor is applied to the driving wheel 16, so that the locking tendency of the driving wheel 16 can be quickly eliminated. It becomes. Therefore, when the hybrid electric vehicle 1 travels at a reduced speed, slippage of the drive wheels 16 due to the lock of the drive wheels 16 can be prevented quickly and accurately, and the traveling stability of the hybrid electric vehicle 1 can be ensured.

  Further, since it is determined that the lock tendency of the drive wheel 16 is being resolved based on the wheel speed change rate ΔVw and the slip rate Sw of the drive wheel 16, a temporary change in the wheel rotation speed Vw of the drive wheel 16 or slip A situation in which it is erroneously determined that the locking tendency of the driving wheel 16 is being resolved only by a temporary change in the rate Sw is avoided, and it is accurately determined that the locking tendency of the driving wheel 16 is being resolved. be able to.

  When it is determined that the tendency to lock the drive wheels 16 is being eliminated, the regenerative braking torque of the electric motor 6 that operates the generator is applied to the drive wheels 16, so that only the engine is used as the power source. It is possible to obtain deceleration similar to deceleration by engine braking of the vehicle without causing the drive wheels 16 to be locked.

  Such wheel slip control is not limited to the case where the electric vehicle is decelerated using the service brake mechanism, but the electric vehicle is decelerated using an auxiliary brake mechanism such as an exhaust brake or a regenerative braking torque of an electric motor. Therefore, when the driving wheel 16 tends to lock, this is accurately determined to prevent the driving wheel 16 from being locked, and when the driving wheel locking tendency is being resolved, The braking distance can be shortened by appropriately determining and appropriately decelerating while ensuring the running stability of the hybrid electric vehicle 1.

  Therefore, as in the present embodiment, when the hybrid electric vehicle 1 is traveling at a reduced speed, in order to collect as much kinetic energy as electric energy as much as possible, it is more than the deceleration by the engine brake of the vehicle using only the engine as a power source. Even when the regenerative braking torque of the electric motor 6 is set so that a somewhat larger deceleration is generated, a relatively large amount of kinetic energy is recovered as electric energy while accurately preventing the drive wheel 16 from being locked. It becomes possible to do.

  In the present embodiment, the wheel slip control executed by the vehicle ECU 24 has been described as an example in which the left drive wheel 16 tends to be locked, but the same wheel slip is also true when the right drive wheel 18 tends to be locked. Control is executed by the vehicle ECU 24, and the same effect can be obtained.

  In the above-described embodiment, when it is determined that the driving wheel 16 tends to lock during the ABS control, the wheel speed change rate ΔVw of the driving wheel 16 is less than the first reference change rate ΔVa, that is, negative. As long as the slip ratio Sw of the drive wheel 16 exceeds the first reference slip ratio S1, the generator 6 is operated as a motor, and the drive torque of the motor 6 is applied to the drive wheel 16. Further, when it is determined that the driving wheel 16 is being given a driving torque in this manner and thus the tendency of the driving wheel 16 to lock is being resolved, the wheel speed change rate ΔVw is greater than the second reference change rate ΔVa. In other words, the generator 6 was operated as a generator and the regenerative braking torque of the motor 6 was applied to the drive wheels 16 as long as it had a positive value and the slip ratio Sw was below the second reference slip ratio S2. And the output torque of the electric motor 6 was set to 0 (kg * m) in the period between the period which gives such drive torque, and the period which gives regenerative braking torque.

  However, once it is determined that the drive wheels 16 tend to lock during execution of the ABS control, the drive wheels 16 and the regenerative braking torque may be alternately applied to the drive wheels 16 without fail. . Wheel slip control in which torque is applied to the drive wheels 16 in this way will be described below as a modification of the above embodiment. The vehicle to which the wheel slip control of this modification is applied is the hybrid electric vehicle 1 configured similarly to the above embodiment, and only the content of the wheel slip control is different from the above embodiment.

FIG. 4 is a flowchart of wheel slip control in the present modification, and the vehicle ECU 24 executes wheel slip control at a predetermined control cycle according to this flowchart.
As in the above-described embodiment, an example of wheel slip control related to the left drive wheel 16 will be described below, but wheel slip control is performed in the same manner for the right drive wheel 18 as well.

  Wheel slip control by the vehicle ECU 24 is started according to the flowchart of FIG. 4 when a key switch (not shown) of the hybrid electric vehicle 1 is turned on. First, in step S101, the vehicle ECU 24 determines whether or not ABS control by the ABS ECU 40 is being performed. Similar to the above-described embodiment, the ABS control is executed when any of the left and right drive wheels 16 and 18 and the left and right driven wheels tend to lock, and when the ABS control is not executed, The vehicle ECU 24 advances the process to step S102.

  In step S102, the vehicle ECU 24 sets the value of the flag F3 to zero. The flag F3 is the same as the flag F2 in the above-described embodiment. In the wheel slip control, the value is set to 1 when the motor 6 is operating as a motor by the processing described later, and the motor 6 is used as a generator. When operating, the value is set to 0. After setting the value of the flag F3 to 0 in step S102, the vehicle ECU 24 advances the process to step S103.

  When the process proceeds to step S103, the ABS control is not performed, and it is not necessary to perform the process for preventing the drive wheels 16 and 18 from being locked in the wheel slip control. For this reason, in step S103, the vehicle ECU 24 terminates the control cycle without giving an instruction to the inverter ECU 28 for controlling the electric motor 6 as the wheel slip control in order to prioritize other control. Therefore, unless the ABS control by the ABS ECU 40 is started, the processes of steps S101 to S103 are repeated, and the motor 6 is not controlled by the wheel slip control.

  When the hybrid electric vehicle 1 travels at a reduced speed, if any of the left and right drive wheels 16, 18, for example, the left drive wheel 16 tends to lock and the ABS control by the ABS ECU 40 is started, the vehicle ECU 24 performs the process in step S 101. From step S104, the wheel speed change rate ΔVw, which is the change rate of the wheel rotation speed Vw of the drive wheel 16, and the slip rate Sw of the drive wheel 16 with respect to the road surface are calculated in the same manner as in the above-described embodiment.

Next, the vehicle ECU 24 proceeds with the process to step S105, and determines whether or not the value of the flag F3 is 1. Since the flag F3 remains 0, the vehicle ECU 24 advances the process to step S106 based on the determination in step S105.
In step S106, the vehicle ECU 24 determines that the wheel speed change rate ΔVw of the drive wheel 16 obtained in step S104 is less than the first reference change rate ΔVa, and the slip rate Sw of the drive wheel 16 obtained in step S104 is the first reference slip. It is determined whether the rate is greater than S1. Also in this modified example, the value of the first reference change rate ΔVa is set to 0 (m / s ² ) as in the above-described embodiment, and the determination in step S106 is a negative value of the wheel speed change rate ΔVw of the drive wheels 16. It is determined whether or not the slip ratio Sw of the drive wheels 16 is greater than the first reference slip ratio S1.

  FIG. 5 is a graph showing an example of the situation of the wheel slip control performed according to the flowchart of FIG. 4 together with the temporal change of the wheel rotation speed Vw and the wheel rotation speed change rate ΔVw of the drive wheel 16. In addition, Vo in FIG. 5 is an estimated vehicle body speed. As shown in FIG. 5, as the hybrid electric vehicle 1 travels at a reduced speed, the estimated vehicle speed Vo gradually decreases, and the wheel rotational speed Vw of the drive wheels 16 is greater than the estimated vehicle speed Vo due to slippage on the road surface of the drive wheels 16. Also decreases quickly. If the ABS control by the ABS ECU 40 is started at time t11, the control of the electric motor 6 by the wheel slip control is not yet performed at this time, and as described above, the electric motor 6 at the time when the hybrid electric vehicle 1 is decelerated is driven. The regenerative braking force is in a state of acting on the drive wheel 16.

  A one-dot chain line in FIG. 5 indicates the wheel rotation speed V1 of the drive wheel 16 when the slip ratio of the drive wheel 16 is set to the first reference slip ratio S1 with respect to the estimated vehicle body speed Vo. As shown in FIG. 5, the wheel speed change rate of the drive wheels 16 is already a negative value when the ABS control is started, but at the beginning of the ABS control, the wheel rotation speed Vw of the drive wheels 16 is started. Is larger than the wheel rotation speed V1, the vehicle ECU 24 advances the process to step S111 based on the determination in step S106.

  In step S111, the vehicle ECU 24 sets the regenerative braking torque Tb as the target output torque Tm of the electric motor 6, and instructs the inverter ECU 28 about the target output torque Tm. The inverter ECU 28 receives an instruction from the vehicle ECU 24, operates the motor 6 as a generator, and controls the motor 6 so that the output torque becomes the target output torque Tm, that is, the regenerative braking torque Tb. The regenerative braking torque output from the electric motor 6 is transmitted to the left and right drive wheels 16 and 18 via the transmission 8.

  In this modification as well, as in the above-described embodiment, the magnitude of the regenerative braking torque Tb set at this time is the same as the regenerative braking torque generated by the electric motor 6 when the hybrid electric vehicle 1 is decelerated. The hybrid electric vehicle 1 can obtain an appropriate deceleration according to the speed selected in the transmission 8 and the rotational speed of the electric motor 6 detected by the electric motor rotational speed sensor 36. It is set to be.

  Thus, when the vehicle ECU 24 determines the target output torque Tm of the electric motor 6 in step S111, the vehicle ECU 24 ends the control cycle, and starts the process from step S101 again in the next control cycle. As long as the ABS control by the ABS ECU 40 continues, the vehicle ECU 24 advances the process to step S104, and calculates the wheel speed change rate ΔVw and the slip rate Sw of the drive wheels 16 again. Therefore, while the ABS control is being performed, the wheel speed change rate ΔVw and the slip rate Sw of the drive wheels 16 are updated to the latest values in step S104 every control cycle.

  Further, the vehicle ECU 24 proceeds from step S104 to step S105, and determines the value of the flag F3. Since the value of the flag F3 has not been changed in the process so far, the vehicle ECU 24 further proceeds to step S106 based on the determination in step S105. Therefore, after the ABS control by the ABS ECU 40 is started, the wheel speed change rate ΔVw of the drive wheel 16 is less than the first reference change rate ΔVa, that is, a negative value, and the slip rate Sw of the drive wheel 16 is the first reference slip. As long as the ratio does not exceed S1, the regenerative braking torque Tb is set as the target output torque Tm of the electric motor 6 in step S111 as described above, and the regenerative braking torque output from the electric motor 6 is applied to the drive wheels 16. .

  When the regenerative braking torque is continuously applied to the drive wheels 16 and the slip of the drive wheels 16 with respect to the road surface increases, the wheel rotation speed Vw of the drive wheels 16 further decreases and the deviation from the estimated vehicle body speed Vo further increases. When the time t12 in FIG. 5 has passed and the wheel rotational speed V1 is not reached, the slip ratio Sw of the drive wheels 16 has fallen below the first reference slip ratio S1. At this time, since the wheel speed change rate ΔVw of the drive wheels 16 is less than the first reference change rate ΔVa, that is, a negative value, when the process proceeds to step S106, the vehicle ECU 24 proceeds to step S107 according to the determination in step S106. Proceed. In step S107, the vehicle ECU 24 sets both the values of the flags F3 to 1, and further proceeds to step S108.

  In step S108, the vehicle ECU 24 sets the drive torque Td as the target output torque Tm of the electric motor 6, and instructs the inverter ECU 28 of the target output torque Td. The inverter ECU 28 receives an instruction from the vehicle ECU 24, operates the electric motor 6 as a motor, and controls the electric motor 6 so that the output torque becomes the target output torque Tm, that is, the driving torque Td. The drive torque output from the electric motor 6 in this way is transmitted to the left and right drive wheels 16 and 18 via the transmission 8. Therefore, the slip with respect to the road surface of the drive wheel 16 that tends to increase is suppressed by the drive torque applied from the electric motor 6.

  Thus, the vehicle ECU 24 determines that the wheel speed change rate ΔVw of the drive wheel 16 is less than the first reference change rate ΔVa, that is, has a negative value, and the slip rate Sw of the drive wheel 16 is the first reference value, as determined in step S106. When the slip ratio S1 is exceeded, it is determined that slip with respect to the road surface is increasing and the drive wheels 16 tend to be locked, and the electric motor 6 is operated as a motor to apply drive torque to the drive wheels 16.

  Thus, not only the wheel speed change rate ΔVw is less than the first reference change rate ΔVa, that is, not only has a negative value, but also when the slip rate Sw exceeds the first reference slip rate S1, the drive wheels 16 The reason for determining that there is a tendency to lock is for the same reason as in the above-described embodiment.

That is, since the wheel rotation speed Vw of the driving wheel 16 detected by the wheel speed sensor 42 varies due to road surface unevenness or the like, the wheel speed change rate ΔVw is less than the first reference change rate ΔVa, that is, negative Just having a value does not necessarily mean that the drive wheel 16 tends to lock. In addition, just because the slip ratio Sw of the drive wheel 16 is larger than the first reference slip ratio S1, the drive wheel 16 does not necessarily tend to lock, and the slip of the drive wheel 16 may converge from that state. Because you get.
Therefore, also in the present modification, it can be accurately determined that the drive wheels 16 tend to lock based on both the wheel speed change rate ΔVw and the slip rate Sw.

  Note that the driving torque Td set when it is determined that the driving wheel 16 tends to be locked, as in the above-described embodiment, prevents the driving wheel 16 from being locked by suppressing slipping of the driving wheel 16 with respect to the road surface. In order to obtain an appropriate size, it is determined in advance by experiments or the like, and is set according to the gear stage selected in the transmission 8 and the rotation speed of the motor 6 detected by the motor rotation speed sensor 36. It has come to be.

Thus, when the target output torque Tm of the electric motor 6 is set in step S108, the vehicle ECU 24 ends the control cycle, and starts the process from step S101 again in the next control cycle.
If the ABS control by the ABS ECU 40 continues, the vehicle ECU 24 proceeds from step S101 to step S104 again, calculates the wheel speed change rate ΔVw and the slip rate Sw of the drive wheels 16, and then performs the process in step S105. Proceed.

At this time, since the value of the flag F3 is changed to 1 in step S107 as described above, the vehicle ECU 24 advances the process to step S109 based on the determination in step S105. In step S109, the vehicle ECU 24 determines that the wheel speed change rate ΔVw of the drive wheel 16 obtained in step S104 exceeds the second reference change rate ΔVb, and the slip rate Sw of the drive wheel 16 obtained in step S104 is the second reference slip rate. Judgment is made as to whether or not the value is below S2. Also in this modified example, the value of the second reference change rate Vb is set to 0 (m / s ² ) as in the above-described embodiment, and the determination in step S109 is that the wheel speed change rate ΔVw of the drive wheels 16 is positive. It is determined whether or not the slip ratio Sw of the drive wheel 16 is lower than the second reference slip ratio S2.

  As described above, after the process proceeds from step S107 to step S108 according to the determination in step S106 and the driving torque of the electric motor 6 is applied to the driving wheel 16, the wheel speed change rate ΔVw of the driving wheel 16 remains for a while. The state where the reference change rate ΔVa is below 1, that is, the state having a negative value continues. That is, the drive torque is applied to the drive wheels 16 by the process of step S108 after the time t12 in FIG. 5, but the wheel rotation speed Vw of the drive wheels 16 does not immediately start increasing due to the application of the drive torque. The wheel speed change rate ΔVw of the drive wheel 16 still has a negative value. For this reason, vehicle ECU24 advances a process to step S108 by determination of step S109.

In step S108, the vehicle ECU 24 sets the drive torque Td as the target output torque Tm of the electric motor 6 as described above, and instructs the inverter ECU 28 about the target output torque Tm. Accordingly, the drive torque of the electric motor 6 is continuously applied to the drive wheels 16. In this way, the drive torque is continuously applied to the drive wheels 16 so that slip of the drive wheels 16 with respect to the road surface is suppressed. As the drive wheel 16 slip is suppressed, as shown in FIG. 5, the wheel rotation speed Vw of the drive wheel 16 gradually decreases after the time t12 and falls below the wheel rotation speed V1. And starts increasing at time t13. . Corresponding to such a change in the wheel rotational speed Vw, the absolute value of the wheel speed change rate ΔVw, which had a negative value after the hybrid electric vehicle 1 started decelerating, gradually decreases, and becomes 0 at time t13. (M / s ² ).

The two-dot chain line in FIG. 5 indicates the wheel rotation speed V2 of the drive wheel 16 when the slip ratio of the drive wheel 16 is set to the second reference slip ratio S2 with respect to the estimated vehicle body speed Vo. Also in this modified example, the second reference slip rate S2 is larger than the first reference slip rate S1 used for determination in step S106, as in the above-described embodiment.
The wheel rotation speed Vw of the drive wheel 16 starts to increase as described above as slip on the road surface is suppressed by application of drive torque from the electric motor 6, but does not immediately start to increase by application of drive torque. Absent. That is, the wheel rotation speed Vw of the drive wheel 16 starts to increase at time t13 with a time delay from the start of application of drive torque after time t12 in FIG. Therefore, in the present modification as well, as in the above-described embodiment, the relationship between the application of the drive torque and the change in the wheel rotation speed Vw is grasped by an experiment or the like in advance, and the wheel rotation speed Vw turns from a decrease to an increase. A value somewhat smaller than the slip ratio of the driving wheel 16 is used as the second reference slip ratio S2.

  Accordingly, as shown in FIG. 5, when the wheel speed change rate ΔVw of the drive wheel 16 has a positive value after the time t13, the wheel rotation speed Vw corresponds to the second reference slip ratio S2. It is smaller than the wheel rotation speed V2 and reaches the wheel rotation speed V2 at time t14. Therefore, until the time t14, the slip ratio Sw of the drive wheel 16 is larger than the second reference slip ratio S2, and therefore, during the period between the time t12 and the time t14, the vehicle ECU 24 proceeds to step S108 according to the determination in step S109. As a result, the application of the drive torque to the drive wheels 16 continues. Thus, when the drive torque of the electric motor 6 is applied to the drive wheels 16, the slip of the drive wheels 16 with respect to the road surface quickly converges.

  Thus, when the wheel rotation speed Vw of the drive wheel 16 exceeds the wheel rotation speed V2 after time t14 in FIG. 5 as the slip of the drive wheel 16 converges due to the continuous application of the drive torque, the drive wheel 16 Slip ratio Sw becomes smaller than the second reference slip ratio S2. At this time, since the wheel speed change rate ΔVw of the drive wheels 16 already has a positive value, the vehicle ECU 24 proceeds with the process to step S110 according to the determination in step S109.

  In step S110, the vehicle ECU 24 sets the value of the flag F3 to 0, and then proceeds to step S111. As described above, in step S111, the vehicle ECU 24 sets the regenerative braking torque Tb as the target output torque Tm of the electric motor 6, and instructs the inverter ECU 28 of the target output torque Tm. The inverter ECU 28 receives an instruction from the vehicle ECU 24, operates the motor 6 as a generator, and controls the motor 6 so that the output torque becomes the target output torque Tm, that is, the regenerative braking torque Tb. The regenerative braking torque output from the electric motor 6 is transmitted to the left and right drive wheels 16 and 18 via the transmission 8.

  Thus, the vehicle ECU 24 determines that the wheel speed change rate ΔVw of the drive wheel 16 exceeds the second reference change rate ΔVa, that is, has a positive value, and the slip rate Sw of the drive wheel 16 is the second reference slip, as determined in step S109. When the ratio is lower than the rate S2, it is determined that slip on the road surface is converging and the tendency of the drive wheels 16 to be locked is resolved, the motor 6 is operated again as a generator, and the drive wheels 16 are supplied with regenerative braking torque. Give.

Thus, not only the wheel speed change rate ΔVw exceeds the second reference change rate ΔVb, that is, has a positive value, but also when the slip rate Sw falls below the second reference slip rate S2, the drive wheel 16 is locked. The determination that the tendency is being resolved is based on the same reason as in the above-described embodiment.
That is, since the wheel rotational speed Vw of the driving wheel 16 detected by the wheel speed sensor 42 varies due to road surface unevenness or the like, the wheel speed change rate ΔVw exceeds the second reference change rate ΔVa, that is, a positive value. However, the tendency to lock the drive wheels 16 is not necessarily being eliminated. Further, if the slip ratio Sw of the drive wheel 16 is smaller than the second reference slip ratio S2, the lock tendency of the drive wheel 16 is not necessarily eliminated, and the slip of the drive wheel 16 increases from that state. It is also possible.
Therefore, also in this modification, it is possible to accurately determine that the lock tendency of the drive wheels 16 is being resolved based on both the wheel speed change rate ΔVw and the slip rate Sw.

When the regenerative braking torque Tb is set as the target output torque Tm of the electric motor 6 in step S111, the vehicle ECU 24 ends the control cycle and starts the process from step S101 again in the next control cycle.
If the ABS control by the ABS ECU 40 continues, the vehicle ECU 24 proceeds from step S101 to step S104 again, calculates the wheel speed change rate ΔVw and the slip rate Sw of the drive wheels 16, and then performs the process in step S105. Proceed.

  At this time, since the value of the flag F3 is changed to 0 again in step S110 as described above, the vehicle ECU 24 advances the process to step S106 based on the determination in step S105. As described above, in step S106, the vehicle ECU 24 determines that the wheel speed change rate ΔVw of the drive wheel 16 obtained in step S104 is less than the first reference change rate ΔVa, that is, a negative value, and the slip rate Sw of the drive wheel 16 Is determined to exceed the first reference slip ratio S1.

  As described above, after the process proceeds from step S110 to step S111 according to the determination in step S109 and the regenerative braking torque of the electric motor 6 is applied to the drive wheels 16, the wheel speed change rate ΔVw of the drive wheels 16 remains for a while. A state where the second reference change rate ΔVb is exceeded, that is, a state having a positive value continues. That is, the regenerative braking torque is applied to the drive wheels 16 by the process of step S111 after the time t14 in FIG. 5, but the wheel rotation speed Vw of the drive wheels 16 immediately starts to decrease due to the application of the regenerative braking torque. The wheel speed change rate ΔVw of the drive wheel 16 still has a positive value. For this reason, vehicle ECU24 advances a process to step S111 by determination of step S106.

In step S111, the vehicle ECU 24 sets the regenerative braking torque Tb as the target output torque Tm of the electric motor 6 as described above, and instructs the inverter ECU 28 about the target output torque Tm. Therefore, the regenerative braking torque of the electric motor 6 is continuously applied to the drive wheels 16. As the regenerative braking torque is continuously applied to the drive wheels 16 in this way, as shown in FIG. 5, the wheel rotation speed Vw of the drive wheels 16 exceeds the wheel rotation speed V2 after the time t14, and then gradually. The degree of increase becomes gradual and starts decreasing at time t15. With such a change in the wheel rotation speed Vw, the wheel speed change rate ΔVw that had a positive value at the time t14 gradually decreases, and becomes 0 (m / s ² ) at the time t15.

  By continuously applying the regenerative braking torque to the drive wheels 16, the wheel speed change rate ΔVw of the drive wheels 16 has a negative value after the time t15. Similarly, at time t15, the wheel rotation speed Vw of the drive wheel 16 is greater than the wheel rotation speed V1 corresponding to the first reference slip ratio S1, and the slip ratio Sw of the drive wheel 16 is the first reference slip ratio S1. Smaller than. Therefore, even if the wheel speed change rate ΔVw of the drive wheel 16 becomes a negative value after the time t15, the vehicle ECU 24 continues to perform step S106 while the slip rate Sw of the drive wheel 16 is smaller than the first reference slip rate S1. With this determination, the process proceeds to step S111, and the regenerative braking torque of the generator 6 is applied to the drive wheels 16 as described above.

  As the regenerative braking torque is continuously applied in this way, when the wheel rotational speed Vw of the driving wheel 16 further decreases after reaching the wheel rotational speed V1 at time t16 in FIG. It becomes larger than 1 standard slip ratio S1. Therefore, in the period between time t14 and time t16 in FIG. 5, the vehicle ECU 24 proceeds to step S111 based on the determination in step S106, and the application of the regenerative braking torque to the drive wheels 16 is continued.

When the wheel rotation speed Vw of the drive wheel 16 becomes lower than the wheel rotation speed V1 after the time t16 in FIG. 5, the wheel speed change rate ΔVw of the drive wheel 16 already has a negative value. The vehicle ECU 24 advances the process to step S107 by determining in step S106 that the drive wheels 16 tend to lock as described above.
In step S107, the vehicle ECU 24 sets the value of the flag F3 to 1 as described above, and then proceeds to step S108, sets the drive torque Td as the target output torque Tm of the electric motor 6, and outputs the target output to the inverter ECU 28. Instruct the torque Tm.

  When the process proceeds to step S108 and the driving torque of the electric motor 6 is applied to the drive wheels 16, the vehicle ECU 24 ends the control cycle and starts the process again from step S101 in the next control cycle. The contents of are as described above. In other words, as long as the ABS control by the ABS ECU 40 is being executed, if it is determined in step S106 that the drive wheels 16 tend to be locked, the electric motor is not processed until it is determined in step S109 that the lock tendency of the drive wheels 16 is being eliminated. A driving torque of 6 is applied to the driving wheel 16. If it is determined in step S109 that the driving wheel 16 is being locked, the regenerative braking torque of the motor 6 is applied to the driving wheel 16 until it is determined in step S106 that the driving wheel 16 tends to lock. Is done.

  As in the above-described embodiment, when the ABS control by the ABS ECU 40 ends, for example, when the hybrid electric vehicle 1 stops, the vehicle ECU 24 advances the process to step S102 based on the determination in step S101, and sets the value of the flag F3 to 0. After resetting, the process proceeds to step S103. In step S103, the vehicle ECU 24 does not give an instruction to the inverter ECU 28 for controlling the electric motor 6 as wheel slip control so as to give priority to other control as described above, and ends the control cycle. Therefore, the electric motor 6 is controlled by the inverter ECU 28 according to the target output torque set by the vehicle ECU 24 by other control.

  By performing the wheel slip control as described above, not only when the hybrid electric vehicle 1 is decelerated using the service brake mechanism but also by an auxiliary brake mechanism such as an exhaust brake (not shown) as in the above-described embodiment. Even when the vehicle is decelerated, or when only the regenerative braking force of the electric motor 6 is used, or when the engine 2 is braked in combination with the regenerative braking force of the electric motor 6, the drive wheel 16 is prevented from being locked and the hybrid electric vehicle is prevented. 1 running stability can be ensured.

  Then, since it is determined that the drive wheel 16 tends to lock based on the wheel speed change rate ΔVw and the slip rate Sw of the drive wheel 16, a temporary change in the wheel rotation speed Vw of the drive wheel 16 or a slip rate Sw Thus, it is possible to avoid a situation in which it is erroneously determined that the driving wheel 16 tends to lock only by a temporary change of the above, and to accurately determine that the driving wheel 16 tends to lock.

  Further, since it is determined that the lock tendency of the drive wheel 16 is being resolved based on the wheel speed change rate ΔVw and the slip rate Sw of the drive wheel 16, a temporary change in the wheel rotation speed Vw of the drive wheel 16 or slip A situation in which it is erroneously determined that the locking tendency of the driving wheel 16 is being resolved only by a temporary change in the rate Sw is avoided, and it is accurately determined that the locking tendency of the driving wheel 16 is being resolved. be able to.

The wheel slip control executed by the vehicle ECU 24 in this modification has been described by taking an example in which the left drive wheel 16 tends to be locked, but the same wheel slip is also applied to the case where the right drive wheel 18 tends to be locked. Control is executed by the vehicle ECU 24, and the same effect can be obtained.
This is the end of the description of the wheel slip control device for an electric vehicle according to one embodiment of the present invention and its modification, but the present invention is not limited to the above-described embodiment or modification.

For example, in the embodiment and the modified example, the first reference change rate ΔVa and the driving wheel 16 (or driving wheel 18) used when it is determined that the driving wheel 16 (or driving wheel 18) tends to lock. The second reference rate of change ΔVb used when determining that the lock tendency of the two is being eliminated was set to 0 (m / s ² ). However, both may be different values, the first reference change rate ΔVa may be a negative predetermined value, and the second reference change rate ΔVb may be a positive predetermined value.

By doing so, it is possible to more strictly determine that the driving wheel 16 (or the driving wheel 18) tends to lock and that the locking tendency of the driving wheel 16 (or the driving wheel 18) is being eliminated.
That is, in addition to the slip rate Sw of the drive wheel 16 (or drive wheel 18) being greater than the first reference slip rate S1, the wheel speed change rate ΔVw of the drive wheel 16 (or drive wheel 18) is only a negative value. Instead, since the driving wheel 16 (or driving wheel 18) is determined to be in a locking tendency after falling below the first reference change rate having a negative value, the driving wheel 16 (or driving wheel 18) is in a locking tendency. It is determined more reliably that there is.

Similarly, the slip rate Sw of the drive wheel 16 (or drive wheel 18) is smaller than the second reference slip rate S2, and the wheel speed change rate ΔVw of the drive wheel 16 (or drive wheel 18) is a positive value. In addition, since it is not determined that the locking tendency of the driving wheel 16 (or the driving wheel 18) is being eliminated until the second reference change rate having a positive value is reached, the driving wheel 16 (or the driving wheel 18) is not determined. It is determined with more certainty that the tendency to lock is being resolved.
As described above, when the first reference change rate ΔVa is set to a negative predetermined value and the second reference change rate ΔVb is set to a positive predetermined value, the wheel speed change rate of the drive wheels 16 (or the drive wheels 18) is particularly large. This is effective when there is a possibility that minute fluctuations are repeated in the vicinity of 0 (m / s ² ).

  Further, in the above embodiment, after determining that the driving wheel 16 (or the driving wheel 18) tends to lock, the driving wheel 16 (or the driving wheel 18) is interposed with a state in which no torque is output from the electric motor 6. ) And a state in which the regenerative braking torque is applied to the drive wheels 16 (or the drive wheels 18) are alternately repeated. On the other hand, in the above modification, after determining that the drive wheel 16 (or the drive wheel 18) tends to lock, the drive wheel 16 ( Alternatively, the state in which drive torque is applied to the drive wheels 18) and the state in which regenerative braking torque is applied to the drive wheels 16 (or drive wheels 18) are alternately repeated.

  Instead of such two types of control, only when switching from the state in which drive torque is applied to the drive wheel 16 (or drive wheel 18) to the state in which regenerative braking torque is applied to the drive wheel 16 (or drive wheel 18). Between the state where no torque is output from the electric motor 6 and the state where the regenerative braking torque is applied to the driving wheel 16 (or the driving wheel 18), the state where the driving torque is applied to the driving wheel 16 (or the driving wheel 18). In the case of switching, the switching may be performed directly without interposing a state in which no torque is output from the electric motor 6.

  In order to perform such control, for example, in the flowchart of FIG. 2, step S10 is omitted, and in step S7, the slip ratio Sw of the drive wheels 16 (or drive wheels 18) is equal to or less than the first reference slip ratio S1. When it determines, vehicle ECU24 should just make a process advance to step S15. In this case, the flag F1 is not necessary, and the processing in step S2 and step S11 is also unnecessary.

  Moreover, in the said embodiment and modification, although the value of the drive torque Td set as target output torque of the electric motor 6 and the regenerative braking torque Tb was changed according to the output rotation speed of the electric motor 6, these, The value can be set in various ways. That is, for example, at least one of them may be a fixed value, set by taking into account parameters other than the output rotational speed of the motor 6, or the deviation of the slip ratio of the drive wheel 16 (or drive wheel 18) from the target slip ratio. It may be calculated by PID control based on it.

Further, in the above embodiment and the modification, on the assumption that the ABS control is performed, the drive wheel or the regenerative braking torque is supplied from the electric motor 6 according to the lock state of the drive wheel 16 (or the drive wheel 18). However, the present invention can be applied to a hybrid electric vehicle and an electric vehicle that do not have an ABS device.
In this case, instead of determining whether or not the ABS control is being executed in step S1 in the flowchart of FIG. 2 or step S101 in the flowchart of FIG. 4, for example, whether or not the vehicle is traveling at a reduced speed. The determination may be performed. That is, a process similar to the process performed when it is determined that the ABS control is being executed may be performed when it is determined that the vehicle is decelerating.

  In the above-described embodiment and modification, the present invention is applied to the hybrid electric vehicle 1 having an electric motor and an engine as a driving power source. However, the electric vehicle having only the electric motor as a driving power source. In this case, the present invention can be similarly applied.

DESCRIPTION OF SYMBOLS 1 Hybrid electric vehicle 6 Electric motor 16, 18 Drive wheel 24 Vehicle ECU (control means)
42, 44 Wheel speed sensor (wheel speed detection means)

Claims (4)

An electric motor that is mounted on an electric vehicle as a driving power source and can transmit driving torque to the driving wheels when the motor is operated, and can transmit regenerative braking torque to the driving wheels when the generator is operated; ,
Wheel speed detection means for detecting the wheel rotation speed of the drive wheel;
If it is determined that the driving wheel tends to lock, only the driving torque is set as the target output torque of the electric motor, and the electric motor is operated by the motor to apply the driving torque of the electric motor to the driving wheel. When it is determined that the wheel locking tendency is being resolved, only the regenerative braking torque is set as the target output torque of the motor, and the motor is operated as a generator to apply the regenerative braking torque of the motor to the drive wheels. Means and
The control means is the driving wheel obtained by using the wheel speed change rate which is the change rate of the wheel rotation speed detected by the wheel speed detection means and the wheel rotation speed detected by the wheel speed detection means. The wheel of the electric vehicle is characterized in that it is determined whether or not the driving wheel tends to lock based on the slip ratio and whether or not the locking tendency of the driving wheel is being resolved. Slip control device.   The control means determines that the drive wheel tends to lock when the wheel speed change rate is a negative value and the slip rate is greater than a predetermined first reference slip rate, while the drive After determining that the wheel has a tendency to lock, when the wheel speed change rate becomes a positive value and the slip rate is smaller than a predetermined second reference slip rate larger than the first reference slip rate, 2. The wheel slip control device for an electric vehicle according to claim 1, wherein it is determined that the lock tendency of the drive wheel is being eliminated.   The control means locks the drive wheel when the wheel speed change rate is smaller than a predetermined first reference change rate having a negative value and the slip rate is higher than the first reference slip rate. After determining that the driving wheels tend to lock, the wheel speed change rate is greater than a predetermined second reference change rate having a positive value, and the slip rate is determined. 2. The wheel slip control for an electric vehicle according to claim 1, wherein when it is smaller than a second reference slip ratio that is greater than the first reference slip ratio, it is determined that the drive wheel lock tendency is being eliminated. apparatus.   2. The wheel slip control device for an electric vehicle according to claim 1, wherein the electric vehicle is a hybrid electric vehicle in which an engine is mounted as a driving power source in addition to the electric motor.

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