JP2007223421A - Controller of hybrid electric vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To generate appropriate deceleration torque while increasing the efficiency of energy recovery during vehicle deceleration without increasing the size of an electric motor. <P>SOLUTION: The driving force of an engine 2 and the driving force of an electric motor 6 can be transmitted to the driving wheels 16 of the vehicle via a transmission 8. Also, the engine 2 and the transmission 8 can be mechanically connected to and disconnected from each other by a clutch 4. When upper limit deceleration torque Tu, i.e., the deceleration torque that the electric motor 6 can generate, is equal to or greater than the required deceleration torque Tr, i.e., the deceleration torque that should be generated from the engine 2 and the electric motor 6, the clutch 4 is disconnected and the electric motor 6 is controlled to generate the required deceleration torque Tr. When the upper limit deceleration torque Tu is less than the required deceleration torque Tr, the clutch 4 is connected and the engine 2 and the electric motor 6 are controlled so that the sum total of the deceleration torque of the engine 2 and the deceleration torque of the electric motor 6 becomes equal to the required deceleration torque Tr. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a control device for a hybrid electric vehicle, and more particularly to a control device for a hybrid electric vehicle capable of transmitting an engine driving force and an electric motor driving force to driving wheels of a vehicle.

Conventionally, a so-called parallel type hybrid electric vehicle has been developed and put into practical use in which an engine and an electric motor are mounted on a vehicle and the driving force of the engine and the driving force of the electric motor can be transmitted to the driving wheels of the vehicle, respectively.
As such a parallel type hybrid electric vehicle, a hybrid in which a clutch for mechanically connecting and disconnecting an engine and an automatic transmission is provided, and a rotating shaft of an electric motor is connected between an output shaft of the clutch and an input shaft of the automatic transmission. An electric vehicle is proposed by, for example, Patent Document 1.

In a hybrid electric vehicle as disclosed in Patent Document 1, the clutch is disengaged when starting the vehicle, the motor is operated by supplying power from the battery, and the vehicle is started only by the driving force of the motor. When traveling, a clutch is connected, and the driving force of the engine is transmitted to the drive wheels via the transmission.
In addition, when the vehicle is decelerated, the electric motor is operated to generate a regenerative braking force, and the regenerative braking energy is converted into electric power to charge the battery.

  By the way, when the accelerator pedal is released and the hybrid electric vehicle is decelerating in a state where the vehicle brake is not activated, a similar vehicle using only the engine as the power source performs the same deceleration. It is desirable to control the electric motor and the engine so that the obtained deceleration can be almost the same as the obtained deceleration. This control prevents the driver from feeling uncomfortable and prevents a decrease in driving feeling. can do.

Thus, for example, Patent Document 2 proposes a control apparatus for a hybrid electric vehicle that controls an engine and an electric motor so as to obtain a desired vehicle deceleration.
The hybrid electric vehicle of Patent Document 2 has a configuration in which an electric motor is arranged between a torque converter and an engine, and an output shaft of the engine and a rotating shaft of the electric motor are connected.
JP-A-5-176405 JP 2000-224713 A

In the configuration of the hybrid electric vehicle of Patent Document 2, the drive shaft of the engine and the rotation shaft of the electric motor are connected, and a part of the rotational energy of the drive wheels during vehicle deceleration is always consumed on the engine side. Therefore, there is a problem that the energy recovery efficiency is lowered accordingly.
Further, in order to eliminate the generation of deceleration torque by the engine and improve the energy recovery efficiency when the vehicle decelerates, the fuel must be supplied to bring the engine into an operating state, and the fuel is required to improve the energy recovery efficiency. There is a problem that the fuel consumption is worsened.

  On the other hand, as disclosed in Patent Document 1, a clutch that mechanically connects and disconnects an engine and an automatic transmission is provided, and a hybrid electric motor in which a rotating shaft of an electric motor is connected between an output shaft of the clutch and an input shaft of the automatic transmission. In an automobile, since the vehicle can be decelerated only by the regenerative braking torque of the electric motor, it is possible to improve the energy recovery efficiency during vehicle deceleration. However, the deceleration torque obtained by the electric motor tends to decrease as the rotational speed increases due to the characteristics of the electric motor. If an attempt is made to obtain sufficient deceleration torque from the electric motor even at a high rotational speed, the electric motor becomes larger and the vehicle weight increases. Inconvenience, and the mounting space on the vehicle increases.

  The present invention has been made in view of such problems, and an object of the present invention is to generate an appropriate deceleration torque without increasing the size of the motor while improving the energy recovery efficiency during vehicle deceleration. An object of the present invention is to provide a control device for a hybrid electric vehicle.

  In order to achieve the above object, a control apparatus for a hybrid electric vehicle according to the present invention can transmit the driving force of an engine and the driving force of an electric motor to driving wheels of a vehicle via a transmission, In a control apparatus for a hybrid electric vehicle that can be mechanically connected to and disconnected from the machine by means of a clutch, a rotational speed detecting means that detects the rotational speed of the electric motor, and the rotational speed detecting means that is detected when the vehicle is decelerated. The upper limit deceleration torque, which is a deceleration torque that can be generated by the electric motor, and the required deceleration torque, which is a deceleration torque that should be generated from the engine and the electric motor, are set according to the number of rotations. When the above is satisfied, the motor is controlled so as to generate the required deceleration torque by disengaging the clutch, while the upper limit Control means for controlling the engine and the electric motor so that a sum of a deceleration torque of the engine and a deceleration torque of the motor becomes the required deceleration torque by connecting the clutch when a speed torque is smaller than the required deceleration torque; (Claim 1).

  According to the hybrid electric vehicle control apparatus configured as described above, when the vehicle decelerates, the required deceleration torque, which is a deceleration torque to be generated from the engine and the electric motor, according to the rotational speed of the electric motor detected by the rotational speed detection means, The upper limit deceleration torque that can be generated by the motor is set, and when the upper limit deceleration torque is equal to or greater than the required deceleration torque, the motor is controlled to generate the requested deceleration torque by disconnecting the clutch, while the upper limit deceleration torque is When the torque is smaller than the required deceleration torque, the engine and the motor are controlled such that the clutch is connected and the sum of the engine deceleration torque and the motor deceleration torque is equal to the required deceleration torque.

  In the hybrid electric vehicle control device, when the upper limit deceleration torque is smaller than the required deceleration torque, the control means stops the fuel supply to the engine and the fuel from the requested deceleration torque to the engine. The electric motor is controlled so that the electric motor generates a deceleration torque obtained by subtracting a deceleration torque generated by the engine when the supply is stopped (Claim 2).

  According to the hybrid electric vehicle control apparatus configured as described above, when the upper limit deceleration torque is smaller than the required deceleration torque, the clutch is connected and the fuel supply to the engine is stopped, and the engine deceleration torque at this time is reduced. By controlling the electric motor so that the electric motor generates a deceleration torque reduced from the required deceleration torque, the engine deceleration torque and the motor deceleration torque are transmitted to the drive wheels via the transmission.

  Further, in the hybrid electric vehicle control apparatus as described above, the transmission is an automatic transmission that is downshifted in response to a decrease in the traveling speed of the vehicle when the vehicle is decelerated. When the rotational speed detected by the rotational speed detection means is higher than a predetermined rotational speed that is higher than the fluctuation range of the rotational speed of the electric motor when the vehicle decelerates while traveling on a flat road, While setting the requested deceleration torque larger than the upper limit deceleration torque, setting the requested deceleration torque that is less than or equal to the upper limit deceleration torque when the number of revolutions detected by the revolution number detection means is less than or equal to the predetermined revolution number. It is characterized (Claim 3).

  According to the hybrid electric vehicle control apparatus configured as described above, the transmission is shifted down in accordance with a decrease in the traveling speed of the vehicle when the vehicle is decelerated, but such a shift is performed while the vehicle is traveling on a flat road. When the rotational speed of the motor is higher than a predetermined rotational speed that is higher than the fluctuation range of the rotational speed of the motor when the vehicle is decelerated with down, the upper limit deceleration torque is smaller than the required deceleration torque, while the motor The upper limit deceleration torque is equal to or greater than the required deceleration torque when the rotation speed is equal to or lower than the predetermined rotation speed. As a result, the clutch is engaged when the rotation speed of the electric motor is higher than the predetermined rotation speed, and the clutch is disengaged when the rotation speed of the electric motor is equal to or less than the predetermined rotation speed.

  According to the control apparatus for a hybrid electric vehicle of the present invention, when the upper limit deceleration torque that can be generated by the electric motor is equal to or higher than the required deceleration torque that is the deceleration torque that should be generated from the engine and the electric motor, the clutch is disconnected and the required deceleration torque is By controlling the electric motor to generate the engine, it becomes possible to decelerate the vehicle properly and to recover the maximum energy by regenerative braking of the electric motor without using the engine deceleration torque. Can be improved.

At this time, since it is not necessary to supply fuel to the engine in order to cancel the deceleration torque of the engine, fuel efficiency is not deteriorated.
On the other hand, when the upper limit deceleration torque is smaller than the required deceleration torque, the engine and the motor are controlled so that the sum of the engine deceleration torque and the motor deceleration torque is equal to the required deceleration torque by connecting the clutch. The vehicle can be decelerated appropriately. Therefore, it is not necessary to mount an electric motor whose upper limit deceleration torque is always equal to or greater than the required deceleration torque, and the electric motor can be downsized to reduce the vehicle weight and mounting space.

  According to the hybrid electric vehicle control device of the second aspect, when the upper limit deceleration torque is smaller than the required deceleration torque, the deceleration torque generated by the engine due to the stop of the fuel supply is driven via the transmission by the clutch connection. The motor is controlled so that the motor generates a deceleration torque obtained by subtracting the engine deceleration torque from the requested deceleration torque at this time, and the motor deceleration torque is transmitted to the drive wheels via the transmission. The

As a result, the vehicle can be appropriately decelerated by transmitting the deceleration torque corresponding to the required deceleration torque to the drive wheels. In addition, since the fuel supply to the engine is stopped, unnecessary fuel supply is not performed when the vehicle decelerates, and fuel consumption can be improved.
Furthermore, according to the control apparatus for a hybrid electric vehicle according to claim 3, the predetermined rotational speed is higher than the fluctuation range of the rotational speed of the electric motor when the vehicle decelerates with downshifting while the vehicle is traveling on a flat road. When the rotational speed of the electric motor is higher, the clutch is in a connected state, and when the rotational speed of the electric motor is equal to or lower than the predetermined rotational speed, the clutch is in a disconnected state. In general, the frequency that the vehicle travels on a flat road is higher than the frequency that the vehicle travels on a non-flat road surface, and the range in which the rotation speed of the motor fluctuates when the vehicle decelerates in such a traveling state is However, in such a normal rotation range when the vehicle is decelerated, the clutch remains disengaged.

  Accordingly, it is possible to suppress a decrease in durability due to wear of the clutch due to repeated operation of the clutch during vehicle deceleration, and a decrease in driving feeling due to an increase in vibration and noise. In addition, to reduce the torque shock when the clutch is connected, if fuel is supplied to the engine so that the engine speed matches the motor speed, the fuel efficiency can be improved by reducing the clutch connection frequency. Can do.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a main part configuration diagram of a control device for a hybrid electric vehicle 1 according to a first embodiment of the present invention. An input shaft of a clutch 4 is connected to an output shaft of a diesel engine (hereinafter referred to as an engine) 2, and the output shaft of the clutch 4 is moved forward via a rotating shaft of a permanent magnet type synchronous motor (hereinafter referred to as an electric motor) 6. An input shaft of an automatic transmission (hereinafter referred to as “transmission”) 8 having five speeds (hereinafter simply referred to as “shift speed”) is connected. The output shaft of the transmission 8 is connected to the left and right drive wheels 16 via a propeller shaft 10, a differential device 12 and a drive shaft 14.

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 drive wheels 16 via the transmission 8, and the clutch 4 is disconnected. Only the rotating shaft of the electric motor 6 can be mechanically connected to the drive wheels 16 via the transmission 8.
The electric motor 6 operates as a motor when the DC power stored in the battery 18 is converted into AC power by the inverter 20 and supplied thereto, and after the driving torque is shifted to an appropriate speed by the transmission 8, the driving wheel is driven. 16 is transmitted. Further, when the vehicle is decelerated, the electric motor 6 operates as a generator, and the kinetic energy generated by the rotation of the drive wheels 16 is transmitted to the electric motor 6 through the transmission 8 and converted into AC power, thereby generating deceleration torque due to regenerative braking. To do. Then, the AC power is converted into DC power by the inverter 20, and then charged in the battery 18. The kinetic energy generated by the rotation of the drive wheels 16 is recovered as electric energy.

  On the other hand, the drive 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 is transmitted to the drive wheels 16 after being shifted to an appropriate speed. It has become. Therefore, when the electric motor 6 operates as a motor when the driving torque of the engine 2 is transmitted to the driving wheels 16, the driving torque of the engine 2 and the driving torque of the electric motor 6 are transmitted to the driving wheels 16, respectively. It will be. That is, a part of the drive torque to be transmitted to the drive wheels 16 for driving the vehicle is supplied from the engine 2 and the remaining part is supplied from the electric motor 6.

When the charging rate (hereinafter referred to as SOC) of the battery 18 decreases and the battery 18 needs to be charged, the electric motor 6 operates as a generator, and the electric motor 6 is turned on using a part of the driving force of the engine 2. Power generation is performed by driving, and the generated AC power is converted into DC power by the inverter 20 and then the battery 18 is charged.
The vehicle ECU 22 (control means) performs connection / disconnection control of the clutch 4 and gear stage switching control of the transmission 8 in accordance with the operation state of the vehicle and the engine 2 and information from the engine ECU 24, the inverter ECU 26, and the battery ECU 28. At the same time, integrated control for appropriately driving the engine 2 and the electric motor 6 is performed in accordance with these control states and various driving states such as start, acceleration, and deceleration of the vehicle.

  When the vehicle ECU 22 performs such control, the accelerator opening sensor 32 that detects the depression amount of the accelerator pedal 30, the vehicle speed sensor 34 that detects the traveling speed of the vehicle, and the rotation that detects the rotation speed of the electric motor 6. Based on the detection result of the number sensor (rotational speed detection means) 36, the total drive torque required for traveling of the vehicle and the total deceleration torque to be generated by the engine 2 and the electric motor 6 when the vehicle is decelerated are calculated. From the total deceleration torque, the torque generated by the engine 2 and the torque generated by the electric motor 6 are set.

The engine ECU 24 performs various controls necessary for the operation of the engine 2 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 22 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 26 controls the operation of the motor 6 by operating the motor 6 or the generator by controlling the inverter 20 based on the torque that should be generated by the motor 6 set by the vehicle ECU 22.

The battery ECU 28 detects the temperature of the battery 18, the voltage of the battery 18, the current flowing between the inverter 20 and the battery 18, etc., and obtains the SOC of the battery 18 from these detection results. It is sent to the vehicle ECU 22 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 22 in order to drive the vehicle is as follows.

  First, when the vehicle is stopped and the engine 2 is stopped, and the change lever (not shown) is in the neutral position, the driver performs an operation of starting the engine 2 with a starter switch (not shown). Then, the vehicle ECU 22 confirms that the mechanical connection between the electric motor 6 and the drive wheel 16 is cut off and the clutch 4 is connected with the transmission 8 in the neutral position, and then the engine 2 is connected to the inverter ECU 26. In addition to instructing the driving torque of the electric motor 6 necessary for starting the engine 2, the engine ECU 24 is instructed to operate the engine 2.

Based on an instruction from the vehicle ECU 22, the inverter ECU 26 operates the motor 6 to generate drive torque, cranks the engine 2, and the engine ECU 24 starts supplying fuel to the engine 2, thereby starting the engine 2. . After the start of the engine 2 is completed, the engine 2 performs idle operation.
After the engine 2 is started in this manner, when the vehicle is in a stopped state, the engine 2 is in an idle operation state. When the driver operates the change lever to the drive position or the like, the clutch 4 is disengaged, and when the accelerator pedal 30 is further depressed, the vehicle is started according to the depression amount of the accelerator pedal 30 detected by the accelerator opening sensor 32. The vehicle ECU 22 sets the driving torque of the electric motor 6 necessary for this.

  The inverter ECU 26 controls the inverter 20 according to the torque set by the vehicle ECU 22, and the DC power of the battery 18 is converted into AC power by the inverter 20 and supplied to the electric motor 6. The electric motor 6 is actuated by AC power to generate a driving torque, and the driving torque of the electric motor 6 is transmitted to the driving wheels 16 through the transmission 8 so that the vehicle starts.

  When the vehicle 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 vehicle ECU 22 connects the clutch 4, and further increases the total driving torque necessary for further acceleration of the vehicle and subsequent travel. This is obtained based on the depression amount of the accelerator pedal 30 detected by the accelerator opening sensor 32 and the traveling speed of the vehicle detected by the vehicle speed sensor 34. The total drive torque is appropriately distributed to the engine 2 side and the electric motor 6 side according to the driving state of the vehicle, the torque to be generated by the engine 2 is instructed to the engine ECU 24, and the drive torque to be generated by the electric motor 6 is determined. The inverter ECU 26 is instructed.

  The engine ECU 24 and the inverter ECU 26 receive the driving torque set by the vehicle ECU 22 and control the engine 2 and the electric motor 6, respectively. The driving torque generated by the engine 2 and the electric motor 6 is transmitted to the driving wheels 16 via the transmission 8. The vehicle runs. Further, at this time, the vehicle ECU 22 appropriately changes the gear position of the transmission 8 according to the driving state of the vehicle such as the depression amount of the accelerator pedal 30 detected by the accelerator opening sensor 32 and the traveling speed detected by the vehicle speed sensor 34. In addition to switching control, the engine ECU 24 and the inverter ECU 26 are instructed to appropriately control the torque of the engine 2 and the electric motor 6 in accordance with the shift speed change.

Next, the case of decelerating the vehicle will be described below.
When the depression of the accelerator pedal 30 is released, the vehicle ECU 22 executes a control routine for decelerating traveling at a predetermined control cycle according to the flowchart shown in FIG.
In the first step S1, the rotation speed of the electric motor 6 detected by the rotation speed sensor 36 is read, and in the next step S2, the required deceleration torque Tr corresponding to the rotation speed of the electric motor 6 read in step S1 is set. The required deceleration torque Tr is a total deceleration torque that should be generated from the engine 2 and the electric motor 6 during deceleration of the vehicle, and corresponds to the rotational speed of the electric motor 6 as a deceleration torque necessary for obtaining an appropriate deceleration for the vehicle. Thus, it is preset and stored in the vehicle ECU 22. The relationship between the rotational speed of the electric motor 6 and the required deceleration torque Tr is shown by a solid line in the upper graph of FIG. 3, and the required deceleration torque Tr increases as the rotational speed of the electric motor 6 increases. Yes.

  In the next step S3, an upper limit deceleration torque Tu corresponding to the rotation speed of the electric motor 6 read in step S1 is set. This upper limit deceleration torque Tu is an upper limit value of the deceleration torque that can be generated by the electric motor 6 determined by the specifications of the electric motor 6, and is preset according to the rotation speed of the electric motor 6 and stored in the vehicle ECU 22. The relationship between the rotational speed of the electric motor 6 and the upper limit deceleration torque Tu is shown by a two-dot chain line in the upper graph of FIG. 3. The upper limit deceleration torque Tu has a constant value on the low rotation side, while On the rotation side, it gradually decreases as the number of rotations of the electric motor 6 increases.

As shown in FIG. 3, the required deceleration torque Tr is equal to the upper limit deceleration torque Tu when the rotation speed of the electric motor 6 is Nx (predetermined rotation speed), and is smaller than the upper limit deceleration torque Tu in a region lower than Nx, and from Nx It is set to be larger than the upper limit deceleration torque Tu in the high region.
After setting the required deceleration torque Tr and the upper limit deceleration torque Tu according to the rotational speed of the electric motor 6 in steps S2 and S3, in step S4, it is determined whether or not the upper limit deceleration torque Tu is greater than or equal to the required deceleration torque Tr. judge.

If it is determined in step S4 that the upper limit deceleration torque Tu is equal to or greater than the required deceleration torque Tr, the process proceeds to step S5, the clutch 4 is disconnected, and then the process proceeds to step S6. The electric motor 6 is controlled by instructing the inverter ECU 26 so as to be equal to the required deceleration torque Tr set in step S2.
In this case, since the upper limit deceleration torque Tu, which is the upper limit value of the deceleration torque that can be generated by the electric motor 6, is equal to or greater than the required deceleration torque Tr, a deceleration torque equal to the required deceleration torque Tr is generated only by the electric motor 6 in this way. By decelerating the vehicle, the kinetic energy of the drive wheels 16 is recovered to the maximum while generating an appropriate deceleration in the vehicle, thereby increasing the energy recovery efficiency.

When the control cycle is completed in this manner, the process is performed again from step S1 in the next control cycle. After the rotation speed of the electric motor 6 detected by the rotation speed sensor 36 is read in step S1, the motor rotation is detected in steps S2 and S3. A required deceleration torque Tr and an upper limit deceleration torque Tu corresponding to the rotational speed are set.
In step S4, it is determined again whether the upper limit deceleration torque Tu is equal to or greater than the required deceleration torque Tr. If the upper limit deceleration torque Tu is still greater than the required deceleration torque Tr, the clutch 4 is continuously disengaged as described above. The vehicle is decelerated with the deceleration torque of the electric motor 6 as it is.

In this way, when the upper limit deceleration torque Tu is equal to or greater than the required deceleration torque Tr, the clutch 4 is disengaged and the required deceleration torque Tr is obtained only by the deceleration torque of the electric motor 6. Therefore, the electric motor 6 at the time of vehicle deceleration is obtained. It is possible to recover the energy by the maximum and improve the energy efficiency.
On the other hand, if it is determined in step S4 that the upper limit deceleration torque Tu is less than the required deceleration torque Tr, the routine proceeds to step S7 where the clutch 4 is connected.

  When the clutch 4 is connected, if the rotational speed of the engine 2 and the rotational speed of the electric motor 6 are greatly different, a large torque shock occurs. Therefore, when the clutch 4 is connected in step S7, the vehicle ECU 22 The engine ECU 24 is instructed to increase the rotational speed of the engine 2 above the idle rotational speed so as to substantially match the rotational speed of the electric motor 6, and the engine ECU 24 increases the fuel supply amount of the engine 2 in accordance with this to increase the rotational speed of the engine 2. And the rotational speed of the motor 6 is adjusted.

When the process proceeds to step S8 after the clutch 4 is connected in step S7, the vehicle ECU 22 instructs the engine ECU 24 to stop the fuel supply to the engine 2, and the engine ECU 24 stops the fuel supply to the engine 2 accordingly.
Next, in step S9, the deceleration torque Tm to be generated by the electric motor 6 is set by subtracting the deceleration torque Te generated by the engine 2 due to the stop of fuel supply in step S8 from the required deceleration torque Tr set in step S2. To do.

  Here, the deceleration torque Te generated by the engine 2 due to the stop of the fuel supply changes according to the change in the rotational speed of the engine 2, but the engine 2 rotates with the electric motor 6 via the clutch 4. It changes according to the rotation speed of the electric motor 6. The relationship between the deceleration torque Te of the engine 2 and the rotation speed of the electric motor 6 at this time is as shown by a one-dot chain line in the upper graph of FIG. 3. The deceleration torque Te of the engine 2 and the upper limit deceleration torque of the electric motor 6 The sum with Tu is not less than the required deceleration torque Tr.

Accordingly, the deceleration torque Tm of the electric motor 6 set in step S9 is equal to or lower than the upper limit deceleration torque Tu corresponding to the rotational speed at that time, and is a deceleration torque that can be generated by the electric motor 6.
When the process proceeds to the next step S10, the vehicle ECU 22 instructs the inverter ECU 26 to generate the deceleration torque Tm set as described above in step S9, and the inverter ECU 26 controls the motor 6 according to this.

As a result, the deceleration torque Te from the engine 2 and the deceleration torque Tm from the electric motor 6 are shifted by the transmission 8 and then transmitted to the drive wheels 16 to decelerate the vehicle. At this time, since the sum of the deceleration torque Te from the engine 2 and the deceleration torque Tm from the electric motor 6 is equal to the required deceleration torque Tr, the vehicle decelerates with an appropriate deceleration.
When the control cycle is completed in this way, in the next control cycle, the processing is performed again from step S1, and the required deceleration torque Tr and the upper limit deceleration torque Tu corresponding to the rotation speed of the electric motor 6 read in step S1 are obtained in steps S2 and S3. Set with.

In step S4, it is determined again whether or not the upper limit deceleration torque Tu is greater than or equal to the required deceleration torque Tr. If the upper limit deceleration torque Tu is still less than the required deceleration torque Tr, the clutch 4 remains connected. As described above, the vehicle is decelerated by the deceleration torque of both the engine 2 and the electric motor 6.
As described above, when the requested deceleration torque Tr is larger than the upper limit deceleration torque Tu that is a deceleration torque that can be generated by the electric motor 6, the clutch 4 is connected to reduce the deceleration torque of the engine 2 and the deceleration torque of the electric motor 6. In addition, since the required deceleration torque Tr is obtained, it is not necessary to increase the size of the electric motor 6 so that the required deceleration torque Tr can always be obtained only by the electric motor 6, and the vehicle weight and the mounting space of the electric motor 6 are reduced. be able to.

  When the deceleration torque from the engine 2 and the deceleration torque from the electric motor 6 are used in combination, the fuel supply to the engine 2 is stopped, and the deceleration torque Tm obtained by subtracting the deceleration torque Te of the engine 2 at that time from the required deceleration torque Tr Is generated in the electric motor 6, so that fuel consumption is not wasted when the vehicle is decelerated using the engine 2 together, and fuel consumption can be improved.

On the other hand, if it is determined in step S4 that the upper limit deceleration torque Tu is greater than or equal to the required deceleration torque Tr, the process proceeds to step S5 as described above, and after the clutch 4 is disconnected, the required deceleration torque is determined only by the deceleration torque of the electric motor 6. The electric motor 6 is controlled so that Tr is obtained, and the vehicle decelerates.
When the depression of the accelerator pedal 30 is released while the vehicle is traveling, the vehicle is decelerated as described above. The vehicle ECU 22 uses the vehicle speed sensor 34 according to a preset shift-down shift map. The gears of the transmission 8 are sequentially shifted down in accordance with the detected decrease in travel speed.

  In the lower graph of FIG. 3, when the vehicle is traveling on a substantially flat road, the change in the traveling speed of the vehicle when the vehicle is decelerating in this way and the rotation speed of the electric motor 6 associated therewith are shown. The change is indicated by a solid line. In the lower graph of FIG. 3, the alternate long and short dash line indicates the relationship between the traveling speed at each shift stage of the transmission 8 and the rotation speed of the electric motor 6, and these straight lines are hereinafter referred to as shift lines. Further, in the shift map for downshifting, the gear position of the transmission 8 is set to the fourth speed when the traveling speed detected by the vehicle speed sensor 34 is decreased from the fifth speed to the fourth speed when the vehicle speed is decreased to V4. Is shifted down from 3rd speed to 2nd speed when lowered to V2 and from 2nd speed to 1st speed when lowered to V1.

  In FIG. 3, it is assumed that the maximum value of the practical traveling speed of the vehicle is V5, and the vehicle decelerates by depressing the accelerator pedal 30 while traveling on a substantially flat road with the shift speed being 5th. If it shifts to, the rotational speed of the electric motor 6 moves in a decreasing direction along the solid line along the fifth speed shift line as the traveling speed decreases. When the traveling speed decreases and reaches V4, the vehicle ECU 22 shifts down the transmission 8 from the fifth speed to the fourth speed, and accordingly, the rotational speed of the motor 6 is changed to the fifth speed as shown by a solid line in FIG. Shift from the first shift line to the fourth shift line and increase.

  If the vehicle continues to decelerate after the downshift to the fourth speed, the rotational speed of the electric motor 6 moves in a decreasing direction along the solid line on the shift line corresponding to the fourth speed. When the traveling speed further decreases and reaches V3, the vehicle ECU 22 shifts down the transmission 8 from the fourth speed to the third speed, and accordingly, the rotational speed of the motor 6 is 4 as shown by a solid line in FIG. The shift shifts from the speed shift line to the speed shift line of the third speed and increases.

  Furthermore, when the vehicle continues to decelerate after the downshift to the third speed, the rotational speed of the electric motor 6 moves in a decreasing direction along the solid line on the shift line corresponding to the third speed. When the traveling speed further decreases and reaches V2, the vehicle ECU 22 shifts down the transmission 8 from the third speed to the second speed, and accordingly, the rotational speed of the motor 6 is 3 as shown by a solid line in FIG. It shifts from the high speed shift line to the second speed shift line and increases.

  When the vehicle continues to decelerate after the downshift to the second speed, the rotational speed of the electric motor 6 moves along the solid line in the decreasing direction on the shift line corresponding to the second speed. When the traveling speed further decreases and reaches V1, the vehicle ECU 22 shifts down the transmission 8 from the second speed to the first speed, and accordingly, the rotational speed of the motor 6 is 2 as shown by a solid line in FIG. It shifts and increases from the speed shift line to the first speed shift line.

As described above, when the vehicle travels on a substantially flat road and shifts to decelerating travel, the rotational speed of the electric motor 6 gradually decreases as the travel speed decreases while repeating the increase / decrease associated with the downshift. However, the fluctuation region of the rotational speed of the electric motor 6 at this time is Nr or less when the traveling speed is V5.
In general, since the frequency with which the vehicle travels on a substantially flat road is higher than the frequency with which the vehicle travels on a non-flat road surface, the region below this rotational speed Nr is the normal rotational region for vehicle deceleration travel. Thus, the rotational speed of the electric motor 6 exceeds this Nr only when it is necessary to travel while decelerating at a relatively high speed, such as during downhill.

  Here, Nr, which is the upper limit rotational speed of such a normal rotational range, is lower than the rotational speed Nx at which the upper limit deceleration torque Tm becomes equal to the required deceleration torque Tr as shown in FIG. Accordingly, since the upper limit deceleration torque Tu is always greater than the required deceleration torque Tr in the normal rotation range, the required deceleration torque Tr can be obtained only by the deceleration torque generated by the regenerative braking of the electric motor 6 while the clutch 4 is kept disconnected. it can.

For this reason, by reducing the frequency of operation of the clutch 4 when the vehicle is decelerated, a decrease in durability due to wear of the clutch 4 and a decrease in driving feeling due to an increase in vibration and noise associated with frequent operation of the clutch 4 are suppressed. In addition, it is possible to improve the fuel efficiency by reducing the frequency of adjusting the rotational speed of the engine 2 when the clutch 4 is connected.
In the present embodiment, the rotation speed Nx at which the upper limit deceleration torque Tu and the required deceleration torque Tr are equal is made higher than Nr, which is the upper limit rotation speed in the normal rotation range, and therefore, in the vicinity of the rotation speed Nx as shown in FIG. The required deceleration torque Tr is corrected to a small value. That is, the rate of increase in the required deceleration torque Tr with respect to the increase in the rotational speed of the electric motor 6 is lowered in the vicinity of the rotational speed Nx. By doing in this way, the rotation speed area | region of the electric motor 6 which can generate | occur | produce a request | requirement deceleration torque only with the electric motor 6 can be set still wider.

However, the method for making the rotational speed Nx higher than Nr is not limited to this. For example, the speed ratio of the transmission 8 may be adjusted, or the upper limit deceleration torque Tu may be changed.
Although the description of the control apparatus for a hybrid electric vehicle according to one embodiment of the present invention is finished above, the present invention is not limited to the above embodiment.

For example, in the above embodiment, when the deceleration torque of the engine 2 is used together, the fuel supply to the engine 2 is stopped. In addition to this, an exhaust rake device is provided in the exhaust passage of the engine 2, and this exhaust brake device A larger deceleration torque may be obtained by operating the.
In the above-described embodiment, the upper limit deceleration torque Tu and the required deceleration torque Tr are set according to the rotation speed of the electric motor 6 detected by the rotation speed sensor 36, but instead of the rotation speed of the electric motor 6, It is also possible to detect the rotational speed that changes in accordance with the change in the rotational speed, for example, the output rotational speed of the transmission 8, and convert it into the rotational speed of the electric motor 6 for use.

In the above embodiment, the engine 2 is a diesel engine, but the engine type is not limited to this, and a gasoline engine or the like may be used.
Moreover, in the said embodiment, although the electric motor 6 was made into the permanent magnet type | mold synchronous motor, the form of an electric motor is not restricted to this, What is necessary is just to be able to operate a motor and a generator.
Further, in the above embodiment, the transmission 8 is an automatic transmission having five forward shift stages, but the number of forward shift stages and the transmission type are not limited to this, and a continuously variable transmission or manual transmission is not limited thereto. It may be a transmission of the type.

1 is an overall configuration diagram of a control apparatus for a hybrid electric vehicle according to an embodiment of the present invention. FIG. 3 is a flowchart of a control routine at the time of decelerating that is executed in the control apparatus for the hybrid electric vehicle of FIG. It is a figure which shows the change of the rotation speed of the electric motor accompanying the fall of the running speed at the time of vehicle deceleration, and the relationship between the upper limit deceleration torque used by the control apparatus of the hybrid electric vehicle of FIG. 1, a request | requirement deceleration torque, and the deceleration torque of an engine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hybrid electric vehicle 2 Engine 4 Clutch 6 Electric motor 8 Transmission (automatic transmission)
16 Drive wheels 22 Vehicle ECU (control means)
36 Rotational speed sensor (Rotational speed detection means)

Claims (3)

In the hybrid electric vehicle, the engine driving force and the motor driving force can be transmitted to the driving wheel of the vehicle via a transmission, and the engine and the transmission can be mechanically connected and disconnected by a clutch. In the control device,
A rotational speed detection means for detecting the rotational speed of the electric motor;
When the vehicle decelerates, an upper limit deceleration torque that is a deceleration torque that can be generated by the electric motor and a required deceleration torque that is a deceleration torque that should be generated from the engine and the electric motor according to the rotation speed detected by the rotation speed detecting means. When the upper limit deceleration torque is equal to or greater than the required deceleration torque, the clutch is disengaged to control the electric motor to generate the required deceleration torque, while the upper limit deceleration torque is greater than the required deceleration torque. And control means for controlling the engine and the electric motor so that the sum of the engine deceleration torque and the motor deceleration torque becomes the required deceleration torque when the clutch is small. Control device for hybrid electric vehicle.   The control means stops the fuel supply to the engine when the upper limit deceleration torque is smaller than the required deceleration torque, and generates a deceleration torque generated by the engine when the fuel supply to the engine is stopped from the requested deceleration torque. 2. The control apparatus for a hybrid electric vehicle according to claim 1, wherein the electric motor is controlled such that the motor generates a reduced deceleration torque. The transmission is an automatic transmission that is downshifted in response to a decrease in the traveling speed of the vehicle when the vehicle is decelerated,
The control means is configured such that the rotational speed detected by the rotational speed detection means is higher than a predetermined rotational speed that is higher than a fluctuation range of the rotational speed of the electric motor when the vehicle decelerates while traveling on a flat road. When the engine speed is high, the requested deceleration torque larger than the upper limit deceleration torque is set. On the other hand, when the rotational speed detected by the rotational speed detection means is equal to or smaller than the predetermined rotational speed, the required deceleration torque that is equal to or smaller than the upper limit deceleration torque is set. The control device for a hybrid electric vehicle according to claim 1, wherein the control device is set.

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