JP6071066B2 - Control device for automatic engine stop vehicle - Google Patents

Description

  The present invention relates to a control device for an engine automatic stop vehicle.

  In Patent Document 1, in a vehicle that automatically stops an engine when a stop condition is satisfied during traveling, a clutch is engaged when the engine rotation speed is equal to or higher than a rotation speed that can be restarted by fuel injection without using a starter. There has been disclosed a control device that restarts the engine by fuel injection when a condition for restarting the engine is satisfied.

  In this device, the time required for starting is shortened by restarting the engine with the clutch engaged, and the lag for the driver's acceleration request is shortened.

JP 2012-72740 A

  However, if the engine is restarted with the clutch engaged, the vehicle may be pushed forward and the driver may feel uncomfortable if the driving force at the time of restarting is large. Therefore, it is conceivable to suppress the pushing out of the vehicle within an allowable range by reducing the torque capacity of the clutch to slip, but in this case, since the frequency of the clutch slipping increases, the durability of the clutch is increased. There is a problem of lowering.

  The present invention has been made in view of such a technical problem, and an object of the present invention is to improve the durability of the clutch while suppressing the vehicle from being pushed out when the engine is restarted.

  According to an aspect of the present invention, a control device for an engine automatic stop vehicle is provided.

  The engine automatic stop vehicle includes an engine, a starting device that starts the engine, a transmission that shifts the rotation of the engine and transmits it to driving wheels, a clutch that is provided between the engine and the driving wheels, Is provided.

  When the engine stop condition is satisfied while the vehicle is running, the engine automatic stop vehicle automatically stops the engine, and when the condition for restarting the engine is satisfied, when the rotation speed of the engine is equal to or higher than the self-rotating speed, The engine is restarted by fuel injection with the clutch engaged, and the engine is restarted by the starter device with the clutch open when the engine speed is lower than the self-rotating speed. .

  When the engine is restarted by the fuel injection, the control device determines whether the driving force at the time of restarting the engine is equal to or higher than the allowable driving force based on the vehicle speed and the transmission gear ratio.

  Further, when the control device determines that the driving force at the time of restarting the engine is equal to or greater than the allowable driving force, the torque capacity of the clutch when the engine is restarted by the fuel injection is not pushed out of the vehicle. Change to less than the allowable torque capacity.

  According to the above aspect, only when the driving force at the time of engine restart is larger than the allowable driving force, the torque capacity of the clutch is changed to be equal to or less than the torque capacity at which the vehicle is allowed to be pushed out. Can be reduced. Therefore, it is possible to improve the durability of the clutch while suppressing the vehicle from being pushed out when the engine is restarted.

1 is a schematic configuration diagram of a vehicle to which a control device according to an embodiment of the present invention is applied. It is a flowchart of the engine restart control which a control apparatus performs. It is a map which shows the driving force with respect to a vehicle speed and a gear ratio when an engine speed is constant. It is a time chart which shows the mode of the engine restart by fuel injection.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a schematic configuration diagram of a vehicle to which a control device according to an embodiment of the present invention is applied.

  The vehicle 1 includes an engine 2 as a power source, a starter 3 as a starting device, a torque converter 4 with a lock-up clutch, a belt-type continuously variable transmission (hereinafter referred to as CVT) 5, and an output rotation of the CVT 5. Is provided with a final speed reduction device 6 that decelerates the motor, left and right drive wheels 7, a hydraulic control circuit 8, and a controller 9. The output rotation of the engine 2 is transmitted to the drive wheels 7 via the torque converter 4, the CVT 5 and the final reduction gear 6.

  The CVT 5 includes a continuously variable transmission mechanism (hereinafter referred to as a variator) 10 and a forward / reverse switching mechanism 20.

  The variator 10 includes a primary pulley 11 provided on the input shaft, a secondary pulley 12 provided on the output shaft, and a V belt 13 wound around the pulleys 11 and 12. Each of the pulleys 11 and 12 includes a fixed conical plate, a movable conical plate that is disposed with a sheave surface facing the fixed conical plate and forms a V-groove between the fixed conical plate, and the movable conical plate. And a hydraulic cylinder that displaces the movable conical plate in the axial direction. When the hydraulic pressure supplied from the hydraulic control circuit 8 to the hydraulic cylinder is adjusted, the width of the V groove changes, the contact radius between the V belt 13 and each pulley 11, 12 changes, and the speed change ratio of the variator 10 changes steplessly. To do. In the variator 10, the input shaft is connected to the turbine output shaft of the torque converter 4, and the output rotation of the torque converter 4 is shifted and transmitted from the output shaft to the forward / reverse switching mechanism 20.

  The forward / reverse switching mechanism 20 is a forward clutch 21 that is a frictional engagement element for transmitting the rotation transmitted from the variator 10 in the forward (forward) direction, and a frictional engagement element for transmitting in the reverse (reverse) direction. A reverse brake 22 is provided. When hydraulic pressure is supplied from the hydraulic control circuit 8 and the forward clutch 21 is connected, the output rotation from the variator 10 is transmitted to the final reduction device 6 in the forward direction, and when the reverse brake 22 is connected, the output is decelerated in the reverse direction. Communicated.

  The hydraulic control circuit 8 includes a plurality of flow paths and a plurality of hydraulic control valves. Based on the control signal from the controller 9, the hydraulic control circuit 8 controls a plurality of hydraulic control valves to switch the hydraulic pressure supply path, and prepares the necessary hydraulic pressure from the hydraulic pressure generated by an oil pump (not shown). Supply to each part of CVT5. As a result, the variator 10 is shifted, and the forward clutch 21 and the reverse brake 22 are engaged / released.

  The controller 9 is a controller that controls the engine 2 and the CVT 5 in an integrated manner. The controller 9 includes an output signal of an accelerator opening sensor 31 that detects an accelerator opening APO that is an operation amount of an accelerator pedal, an output signal of a rotation speed sensor 32 that detects a rotation speed of a primary pulley 11 of the variator 10, and a variator 10. The output signal of the rotation speed sensor 33 for detecting the rotation speed of the secondary pulley 12, the output signal of the vehicle speed sensor 34 for detecting the vehicle speed, the output signal of the brake switch 35 for detecting ON / OFF of the brake, and the like are input. The controller 9 performs various calculations based on various input signals and performs various controls of the engine 2 and the CVT 5.

  Further, the controller 9 performs coast stop control described below in order to suppress fuel consumption.

  The coast stop control is used when the driver is coasting without operating the accelerator pedal, even when the vehicle is traveling, in a so-called coast driving state (including a state where the brake pedal is operated). This is a control for suppressing fuel consumption by stopping injection.

In the present embodiment, the controller 9 determines the following conditions when executing the coast stop control.
a: The foot is released from the accelerator pedal (accelerator opening APO = 0)
b: The brake pedal is depressed (brake switch ON)
c: Vehicle speed is lower than a predetermined low vehicle speed (for example, 15 km / h)

  The controller 9 determines that the coast stop condition is satisfied when all of these conditions a to c are satisfied, stops the fuel supply, and automatically stops the engine 2.

  Further, the controller 9 restarts the engine 2 when the engine restart condition is satisfied during the coast stop. The restart condition is, for example, when the brake switch is turned off.

  Here, when the rotational speed of the engine 2 when the engine restart condition is satisfied is equal to or higher than the self-sustainable rotational speed, the starter 3 performs cranking by performing fuel injection with the forward clutch 21 engaged. The engine 2 can be started without performing it. That is, the self-sustainable rotation speed is a rotation speed at which the engine 2 can be started by so-called pushing by performing fuel injection with the forward clutch 21 engaged. According to this, since the engine 2 can be restarted with the forward clutch 21 engaged, the time required for starting can be shortened, and the lag for the driver's acceleration request can be shortened.

  On the other hand, if the rotational speed of the engine 2 when the restart condition is satisfied is smaller than the self-rotating speed, the engine 2 cannot be started unless cranking is performed by the starter 3. Therefore, in this case, the forward clutch 21 is disengaged and cranking is performed by the starter 3 to start the engine 2.

  By the way, as described above, when the engine 2 is restarted by fuel injection while the forward clutch 21 is engaged, if the driving force at the time of restarting the engine is large, the vehicle 1 is pushed forward and the driver feels uncomfortable. May give. Therefore, it is conceivable to suppress the pushing of the vehicle 1 within an allowable range by lowering the torque capacity of the forward clutch 21 to slip, but in this case, the frequency with which the forward clutch 21 slips increases. Therefore, there is a problem that the durability of the forward clutch 21 is lowered.

  Therefore, the controller 9 performs the engine restart control described below when restarting the engine 2 during the coast stop, thereby suppressing the vehicle 1 from being pushed out at the time of restart, and the forward clutch 21. The durability is improved.

  Hereinafter, the control performed by the controller 9 will be described in detail according to the flowchart of FIG.

  FIG. 2 is a flowchart of the engine restart control performed by the controller 9.

  First, in S1, the controller 9 determines whether the engine 2 is stopped based on signals input from various sensors.

  If the controller 9 determines that the engine 2 is stopped, the process proceeds to S2. If it is determined that the engine 2 is not stopped, the determination process of S1 is repeated.

  In S2, the controller 9 determines whether the engine restart condition is satisfied. The engine restart condition is, for example, when the brake switch is turned off as described above, but when the driver operates the steering, or when the battery voltage becomes a predetermined value or less, the engine restart is performed. It can also be assumed that the condition is satisfied.

  If the controller 9 determines that the engine restart condition is satisfied, the process proceeds to S3. If it is determined that the engine restart condition is not satisfied, the determination process of S2 is repeated.

  In S3, the controller 9 determines whether the rotational speed of the engine 2 when the restart condition is satisfied is equal to or higher than the self-sustainable rotational speed. Note that the self-rotating speed is set in advance through experiments or the like.

  If the controller 9 determines that the rotational speed of the engine 2 when the restart condition is satisfied is equal to or higher than the self-sustainable rotational speed, the process proceeds to S4 in order to restart the engine 2 by fuel injection. If it is determined that the rotational speed of the engine 2 when the restart condition is satisfied is smaller than the self-sustainable rotational speed, the process proceeds to S5 in order to restart the engine 2 by the starter 3.

  In S <b> 5, the controller 9 releases the forward clutch 21 and performs cranking by the starter 3. Then, after the engine 2 is started, the forward clutch 21 is engaged, and the engine restart control is terminated.

  In S4, the controller 9 refers to the map of FIG. 3 and determines whether or not the driving force at the time of engine restart is greater than or equal to the allowable driving force. FIG. 3 is a map showing the driving force with respect to the vehicle speed and the gear ratio of the variator 10 when the engine rotation speed is constant.

  In the map of FIG. 3, the region of low vehicle speed and gear ratio Low delimited by the broken line is a region where the driving force at the time of engine restart is larger than the allowable driving force. The allowable driving force is a driving force at the time of engine restart that is a threshold value as to whether or not the pushing-out of the vehicle 1 falls within the allowable range, and is obtained in advance through experiments or the like. A dotted arrow indicates an example of shifting of the variator 10 and is a trajectory when shifting according to the coast line.

  Here, the driving force when the engine is restarted increases as the engine intake air density increases and the engine negative pressure decreases. That is, the higher the engine intake air density and the lower the engine negative pressure, the larger the broken line area in the direction of the solid arrow in FIG. 3. The lower the engine intake air density and the higher the engine negative pressure. As shown, the broken line area is reduced in the direction opposite to the solid arrow in FIG.

  Specifically, the controller 9 refers to the map of FIG. 3, and the intersection position of the vehicle speed and the gear ratio falls within the broken line area based on the vehicle speed, the gear ratio, the engine intake air density, and the engine negative pressure. To determine. When the intersection position between the vehicle speed and the gear ratio falls within the broken line area, the controller 9 determines that the driving force at the time of engine restart is equal to or greater than the allowable driving force, and the process proceeds to S6. If the intersection position between the vehicle speed and the gear ratio does not fall within the broken line area, it is determined that the driving force at the time of engine restart is smaller than the allowable driving force, and the process proceeds to S7.

  Note that the engine intake air density and the engine negative pressure are not indispensable elements for the above determination, but by using these, the influence of the atmospheric pressure, the temperature, and the engine negative pressure can be suppressed, and the determination accuracy can be improved. . Therefore, for example, only one of the engine intake air density and the engine negative pressure may be used for the determination.

  In S6, the controller 9 changes the torque capacity of the forward clutch 21 to be equal to or less than the torque capacity at which the vehicle 1 is allowed to be pushed, starts the engine 2 by fuel injection, and ends the engine restart control. The torque capacity in which the vehicle 1 is allowed to be pushed out is a torque capacity in which the driving force transmitted to the drive wheels 7 becomes smaller than the allowable driving force when the forward clutch 21 slips.

  According to this, since the engine 2 is restarted with the forward clutch 21 engaged, the lag with respect to the driver's acceleration request can be shortened compared to when the engine 2 is restarted by the starter 3, and the engine Pushing of the vehicle 1 at the start can be suppressed within an allowable range.

  In S7, the controller 9 starts the engine 2 by fuel injection with the forward clutch 21 completely engaged, and ends the engine restart control.

  In this case, since the driving force at the time of restarting the engine is smaller than the allowable driving force, even if the engine 2 is restarted by fuel injection while the forward clutch 21 is completely engaged, the vehicle 1 is not pushed out. Within acceptable range. Moreover, since the forward clutch 21 is not slipped, the durability of the forward clutch 21 can be improved. In addition, since the engine 2 is restarted with the forward clutch 21 fully engaged, the lag with respect to the driver's acceleration request is less than when the engine 2 is restarted by reducing the torque capacity of the forward clutch 21. It can be further shortened.

  Thus, in the engine restart control performed by the controller 9, the torque capacity of the forward clutch 21 is only allowed to be pushed out of the vehicle 1 only when the driving force at the time of engine restart is larger than the allowable driving force. Since the capacity is changed to less than the capacity, the frequency with which the forward clutch 21 slips can be reduced. Therefore, it is possible to improve the durability of the forward clutch 21 while suppressing the vehicle 1 from being pushed out when the engine is restarted.

  Next, the operation of this embodiment will be described with reference to FIG.

  FIG. 4 is a time chart showing a state of engine restart by fuel injection. The first half of the time chart shows a case where the torque capacity of the forward clutch 21 is reduced and the engine 2 is restarted, and the second half of the time chart is a case where the engine 2 is restarted with the forward clutch 21 completely engaged. Indicates.

  First, the case where the torque capacity of the forward clutch 21 is reduced and the engine 2 is restarted will be described.

  When the coast stop control is started at time t1, the lockup clutch of the torque converter 4 is released, and the variator 10 is shifted to the low side. As the vehicle speed decreases, the rotational speed of the engine 2 decreases.

  When the brake switch is turned off at time t2 and the restart condition is satisfied, the hydraulic pressure supplied from the hydraulic control circuit 8 to the forward clutch 21 is reduced to reduce the torque capacity, and the engine 2 is restarted by fuel injection.

  After the engine 2 is started, the driving force increases as the rotational speed of the engine 2 increases. At time t3, the forward clutch 21 starts to slip, and a difference occurs between the rotational speed of the secondary pulley 12 and the output rotational speed of the CVT 5. As a result, the driving force exceeding the torque capacity of the forward clutch 21 is not transmitted to the drive wheels 7.

  From time t3 to time t5, the torque capacity of the forward clutch 21 is increased and the forward clutch 21 is completely engaged.

  As the torque capacity of the forward clutch 21 is increased, the driving force transmitted to the drive wheels 7 increases, and the acceleration G of the vehicle 1 becomes maximum at time t4. At this time, the torque capacity of the forward clutch 21 is gradually increased by gradually increasing the hydraulic pressure supplied from the hydraulic control circuit 8 to the forward clutch 21. Accordingly, since the driving force is gradually transmitted to the drive wheels 7, the acceleration G at time t4 is equal to or less than the allowable acceleration G at which the pushing of the vehicle 1 is within the allowable range.

  Next, the case where the engine 2 is restarted with the forward clutch 21 completely engaged will be described.

  When the coast stop control is started at time t6, the lockup clutch of the torque converter 4 is released, and the variator 10 is shifted to the Low side. As the vehicle speed decreases, the rotational speed of the engine 2 decreases.

  When the brake switch is turned off at time t7 and the restart condition is satisfied, the engine 2 is restarted by fuel injection while the forward clutch 21 is completely engaged.

  In this case, since the vehicle speed at time t7 is high, the driving force at the time of engine restart does not enter the region indicated by the broken line in FIG. For this reason, even if the engine 2 is restarted without reducing the torque capacity of the forward clutch 21 and slipping, the maximum value of the acceleration G applied to the vehicle 1 becomes the allowable acceleration G or less (time t8). That is, the pushing out of the vehicle 1 is within the allowable range.

  As described above, according to the present embodiment, the torque capacity of the forward clutch 21 is allowed to be pushed out of the vehicle 1 only when the driving force at the time of engine restart is larger than the allowable driving force. Since the frequency is changed to the following, the frequency with which the forward clutch 21 slips can be reduced. Therefore, it is possible to improve the durability of the forward clutch 21 while suppressing the vehicle 1 from being pushed out when the engine is restarted.

  In addition, it is determined whether the driving force at the time of engine restart exceeds the allowable driving force based on the vehicle speed, gear ratio, engine intake air density, and engine negative pressure. Can be suppressed, and the determination accuracy can be improved.

  As mentioned above, although embodiment of this invention was described, the said embodiment showed only a part of application example of this invention, and is not the meaning which limits the technical scope of this invention to the specific example of said embodiment. .

  In the above-described embodiment, the frictional engagement element that is engaged / released when the engine is restarted is the forward clutch 21 of the forward / reverse switching mechanism 20 disposed on the downstream side of the variator 10 in the power transmission path. The frictional engagement element may be disposed upstream of the variator 10, and may be disposed, for example, between the torque converter 4 and the variator 10.

  Moreover, in the said embodiment, although the transmission is CVT5, a stepped transmission may be sufficient, for example.

1 vehicle 2 engine 3 starter (starting device)
5 Belt type continuously variable transmission (CVT, transmission)
10 Continuously variable transmission mechanism (transmission)
21 Forward clutch (clutch)
9 Controller (control device, driving force judging means, torque capacity changing means)

Claims (2)

An engine, a starting device that starts the engine, a transmission that shifts the rotation of the engine and transmits the rotation to driving wheels, and a clutch that is provided between the engine and the driving wheels. When the engine stop condition is satisfied, the engine is automatically stopped and the engine restart condition is satisfied. When the engine speed is equal to or higher than the self-rotating speed, the fuel injection is performed with the clutch engaged. The engine is restarted by the engine, and when the rotational speed of the engine is smaller than the self-sustainable rotational speed, the engine automatic stop vehicle control device restarts the engine by the starting device with the clutch released. And
When restarting the engine by the fuel injection, based on the vehicle speed and the gear ratio of the transmission, driving force determination means for determining whether the driving force at the time of restarting the engine is greater than or equal to an allowable driving force;
If the driving force determining means determines that the driving force at the time of restarting the engine is greater than or equal to the allowable driving force, the torque capacity of the clutch when the engine is restarted by the fuel injection is pushed out of the vehicle. Torque capacity changing means for changing the torque capacity to an allowable torque capacity or less,
A control apparatus for an engine automatic stop vehicle. The engine automatic stop vehicle control device according to claim 1,
The driving force determining means determines whether the driving force when the engine is restarted is equal to or greater than the allowable driving force based on at least one of the engine intake air density and the engine negative pressure in addition to the vehicle speed and the speed ratio. To
A control apparatus for an engine automatic stop vehicle.

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