JP7707956B2 - Vehicle control device - Google Patents

Description

The present invention relates to a vehicle control device.

The vehicle described in Patent Document 1 includes an internal combustion engine, a motor generator, a clutch, and a control device. The internal combustion engine and the motor generator are the driving sources of the vehicle. The internal combustion engine includes a crankshaft. The motor generator includes an output shaft. The clutch is interposed between the crankshaft of the internal combustion engine and the output shaft of the motor generator. The control device can control the engaged and disengaged states of the clutch. When the clutch is engaged, the torque of the internal combustion engine can be transmitted to the output shaft of the motor generator. On the other hand, when the clutch is disengaged, the torque of the internal combustion engine is not transmitted to the output shaft of the motor generator.

JP 2020-111276 A

In the vehicle described in Patent Document 1, the engine speed of the internal combustion engine may drop when the clutch is engaged. When the engine speed drops to near zero, the force that moves the piston toward top dead center is no longer able to resist the pressure of the gas compressed during the compression stroke. At this time, the piston is unable to get past the compression top dead center and is pushed back toward the bottom dead center. In other words, the crankshaft of the internal combustion engine rotates slightly in the reverse direction. If ignition occurs in a cylinder while the crankshaft is rotating in the reverse direction in this way and unburned fuel remains in the cylinder, the crankshaft will rotate significantly in the reverse direction as the fuel burns.

In order to solve the above problems, the present invention is applied to a vehicle that includes an internal combustion engine having a crankshaft, a motor generator having an output shaft that is part of the path of transmission of driving force from the crankshaft to the drive wheels, a clutch interposed between the crankshaft and the output shaft, a first rotation sensor capable of detecting an engine speed, which is the rotation speed of the crankshaft, and a second rotation sensor capable of detecting an MG speed, which is the rotation speed of the motor generator, and the clutch is switchable between an engaged state in which torque can be transmitted between the crankshaft and the output shaft and an open state in which torque cannot be transmitted between the crankshaft and the output shaft, and is a control device that controls the internal combustion engine and the clutch, and when the clutch is engaged during operation of the internal combustion engine, and the engine speed is equal to or lower than a predetermined specified speed that is lower than an idle speed, and the absolute value of the difference between the engine speed and the MG speed is equal to or lower than a predetermined differential speed, the control device changes the clutch to a released state and stops fuel injection and ignition in the internal combustion engine.

According to the above configuration, when the clutch is engaged and there is a possibility that the piston will not be able to overcome the top dead center of compression, the drive of the internal combustion engine is stopped. In other words, when there is a situation in which a phenomenon such as the crankshaft rotating slightly in reverse may occur, the drive of the internal combustion engine is stopped before such a phenomenon occurs. Therefore, it is difficult for a situation to occur in which fuel burns while the crankshaft is rotating slightly in reverse. In addition, the clutch is changed to a released state in conjunction with the drive of the internal combustion engine being stopped. Therefore, the torque of the motor generator is not used to idle the internal combustion engine.

FIG. 1 is a schematic diagram of a vehicle. FIG. 2 is a flowchart of the engine stop control executed by the vehicle control device.

Hereinafter, an embodiment of a vehicle control device will be described with reference to the drawings.
[Vehicle drive system configuration]
1, a vehicle 500 includes an internal combustion engine 10, a transmission unit 20, left and right drive wheels 30, and a differential 40. The internal combustion engine 10 is a drive source for traveling. The internal combustion engine 10 has a crankshaft 11 as an output shaft.

The transmission unit 20 is located on the power transmission path from the internal combustion engine 10 to each drive wheel 30. The transmission unit 20 includes a motor generator 21, a clutch 22, a torque converter 23, an automatic transmission 24, an oil pump 25, and a hydraulic section 26.

The motor generator 21 has a stator and a rotor. The rotor rotates relative to the stator. The motor generator 21 is a so-called three-phase AC motor. The motor generator 21 has an output shaft 21A. The output shaft 21A rotates integrally with the rotor. The output shaft 21A is connected to the crankshaft 11 via the clutch 22. In other words, the output shaft 21A is part of the transmission path of the driving force from the crankshaft 11 to the drive wheels 30.

The motor generator 21 is connected to the battery 21C of the vehicle 500 via the inverter 21B of the vehicle 500. The motor generator 21 functions as an electric motor and a generator. When the motor generator 21 functions as an electric motor, it can apply torque to the crankshaft 11 using electric power from the battery 21C. When the motor generator 21 functions as a generator, it supplies electric power to the battery 21C.

The clutch 22 is interposed between the crankshaft 11 and the output shaft 21A of the motor generator 21. The clutch 22 can be switched between an engaged state and a disengaged state by hydraulic pressure. When the clutch 22 is in an engaged state, torque can be transmitted between the crankshaft 11 and the output shaft 21A. When the clutch 22 is in a disengaged state, torque cannot be transmitted between the crankshaft 11 and the output shaft 21A.

The torque converter 23 has a lock-up clutch 23A, an input shaft 23B, and an output shaft 23C. The input shaft 23B is connected to the output shaft 21A of the motor generator 21 on the side opposite to the clutch 22. The lock-up clutch 23A is interposed between the input shaft 23B and the output shaft 23C. The lock-up clutch 23A can be switched between an engaged state and a disengaged state by hydraulic pressure. When the lock-up clutch 23A is in an engaged state, the input shaft 23B and the output shaft 23C rotate integrally. When the lock-up clutch 23A is in an engaged state, the torque converter 23 changes the speed of the torque input to the input shaft 23B and outputs it from the output shaft 23C.

The automatic transmission 24 is connected to the output shaft 23C of the torque converter 23. In other words, the automatic transmission 24 is connected to the crankshaft 11 via the torque converter 23. Although not shown, the automatic transmission 24 has multiple gear mechanisms and multiple engagement elements. The engagement elements of the automatic transmission 24 are, for example, a clutch mechanism and a brake mechanism. Each engagement element of the automatic transmission 24 can be switched between an engaged state and a disengaged state by hydraulic pressure. By switching the engaged state and disengaged state of each engagement element, the automatic transmission 24 can change gears.

The oil pump 25 is an electric pump. The oil pressure generated by the oil pump 25 is supplied to the transmission unit 20. Specifically, the oil pressure generated by the oil pump 25 is supplied to the clutch 22, the torque converter 23, the lock-up clutch 23A, and the automatic transmission 24.

The hydraulic section 26 has hydraulic circuits for the clutch 22, the torque converter 23, the lock-up clutch 23A, and the automatic transmission 24, and various hydraulic control valves for controlling the operating hydraulic pressures of these. By controlling the hydraulic section 26, for example, the clutch 22 is switched between an engaged state and a released state. Note that the hydraulic circuits and hydraulic control valves of the hydraulic section 26 are not shown in FIG. 1.

The differential 40 is connected to the automatic transmission 24 and each of the drive wheels 30. That is, the differential 40 is interposed between the transmission unit 20 and each of the drive wheels 30. The differential 40 distributes the torque output from the transmission unit 20 to the left and right drive wheels 30. The differential 40 allows a difference in rotational speed to occur between the left and right drive wheels 30.

The vehicle 500 is equipped with a first rotation sensor 51 and a second rotation sensor 52. The first rotation sensor 51 is located near the crankshaft 11. The first rotation sensor 51 detects the angular position of the crankshaft 11 as a crank angle CA. The second rotation sensor 52 is attached to the stator of the motor generator 21. The second rotation sensor 52 detects the angular position of the output shaft 21A of the motor generator 21 as a motor angle MA.

[Regarding the control device]
The vehicle 500 includes a control device 100. The control device 100 acquires a signal related to the crank angle CA output by the first rotation sensor 51. The control device 100 also calculates an engine speed NE, which is the number of revolutions per unit time of the crankshaft 11, based on the signal related to the crank angle CA. The control device 100 acquires a signal related to the motor angle MA output by the second rotation sensor 52. The control device 100 also calculates an MG speed NM1, which is the number of revolutions per unit time of the output shaft 21A, based on the signal related to the motor angle MA. Note that when the clutch 22 is in an engaged state, the values of the engine speed NE and the MG speed NM1 are approximately the same.

The control device 100 controls the internal combustion engine 10. The control device 100 controls fuel injection and ignition in the internal combustion engine 10. In other words, the control device 100 controls the driving and stopping of the internal combustion engine 10.

The control device 100 also controls the clutch 22. Specifically, the control device 100 switches the clutch 22 between an engaged state and a released state by controlling the hydraulic unit 26. By controlling the hydraulic unit 26, the control device 100 can switch the gear position of the automatic transmission 24 and the engaged state and released state of the lock-up clutch 23A.

[Regarding engine stop control executed by the control device]
The following describes the engine stop control executed by the control device 100. The control device 100 repeatedly executes the engine stop control while the internal combustion engine 10 is in operation.

As shown in FIG. 2, when the control device 100 executes engine stop control, it first executes the process of step S11. In step S11, the control device 100 determines whether the clutch 22 is engaged. If the clutch 22 is released (S11: NO), the control device 100 ends the engine stop control. On the other hand, if the clutch 22 is engaged (S11: YES), the process of the control device 100 proceeds to step S12.

In step S12, the control device 100 calculates the engine speed NE based on the detection value of the first rotation sensor 51. The control device 100 then determines whether the engine speed NE is equal to or lower than a specified speed RR. The specified speed RR is preset as the minimum speed at which the internal combustion engine 10 can continue to operate autonomously, i.e., a speed lower than the idle speed. An example of the specified speed RR is 250 rpm. If the determination in step S12 is negative (S12: NO), the control device 100 ends the engine stop control. On the other hand, if the determination in step S12 is positive (S12: YES), the processing of the control device 100 proceeds to step S13.

In step S13, the control device 100 calculates the MG rotation speed NM1 based on the detection value of the second rotation sensor 52. The control device 100 then determines whether the absolute value of the difference between the engine rotation speed NE and the MG rotation speed NM1 is equal to or less than the differential rotation speed DR. The differential rotation speed DR is the maximum rotation speed at which the rotation speed of the crankshaft 11 and the rotation speed of the motor generator 21 can be considered to be linked. An example of the differential rotation speed DR is 100 rpm. If the determination in step S13 is negative (S13: NO), the control device 100 ends the engine stop control. On the other hand, if the determination in step S13 is positive (S13: YES), the processing of the control device 100 proceeds to step S14.

In step S14, the control device 100 controls the hydraulic unit 26 to change the clutch 22 from an engaged state to a released state. After that, the processing of the control device 100 proceeds to step S15.

In step S15, the control device 100 stops fuel injection and ignition in the internal combustion engine 10. That is, the control device 100 stops the operation of the internal combustion engine 10. Then, the control device 100 ends the engine stop control.

[Operation of this embodiment]
While the vehicle 500 is traveling, resistance that stops the rotation of the drive wheels 30 may be received due to the influence of the road surface, etc. The resistance received by the drive wheels 30 is transmitted to the power transmission path. Therefore, when the clutch 22 is in an engaged state, if resistance that stops the rotation of the drive wheels 30 acts, the rotation speed of the crankshaft 11 decreases. That is, the engine speed NE decreases. If the engine speed NE becomes smaller than the specified rotation speed RR, the force that moves the piston of the internal combustion engine 10 to the top dead center may not be able to resist the pressure of the gas compressed in the compression stroke. At this time, the piston cannot get over the compression top dead center and is pushed back toward the bottom dead center. That is, the crankshaft 11 of the internal combustion engine 10 rotates slightly in the reverse direction. Even in such a state, if the internal combustion engine 10 continues to be driven, fuel injection and ignition will continue in the internal combustion engine 10. If fuel injection and ignition were to be performed in the internal combustion engine 10 while the crankshaft 11 was rotating in the reverse direction, the crankshaft 11 would rotate significantly in the reverse direction as the fuel was burned.

[Effects of this embodiment]
(1) According to the above embodiment, when the clutch 22 is engaged and the engine speed NE is equal to or lower than the specified speed RR, the internal combustion engine 10 is stopped. The engine speed NE being equal to or lower than the specified speed RR is a situation in which a phenomenon may occur in the near future in which the piston cannot overcome the compression top dead center and is pushed back toward the bottom dead center. In other words, the engine speed NE being equal to or lower than the specified speed RR is a situation immediately before the engine speed NE becomes zero. That is, in the above embodiment, the internal combustion engine 10 is stopped before the phenomenon of the piston being pushed back toward the bottom dead center occurs. Therefore, it is difficult for a situation to occur in which fuel burns while the crankshaft 11 is slightly rotating in the reverse direction. In addition, the clutch 22 is changed to the released state in accordance with the stopping of the internal combustion engine 10. Therefore, the torque of the motor generator 21 is not used to idle the internal combustion engine 10.

(2) Even if the clutch 22 is engaged, if the difference between the engine speed NE and the MG speed NM1 is greater than the differential speed DR, there is a possibility that an abnormality has occurred in the detection of the crank angle CA. That is, there is a possibility that a malfunction has occurred in the first rotation sensor 51. In the above embodiment, if the absolute value of the difference between the engine speed NE and the MG speed NM1 is greater than the differential speed DR, the control device 100 ends the engine stop control. That is, if there is a possibility that a malfunction has occurred in the first rotation sensor 51, the clutch 22 is not released and the internal combustion engine 10 is not stopped. Therefore, the above-mentioned processing of steps S14 and S15 is not executed unnecessarily due to a malfunction of the first rotation sensor 51.

[Example of change]
The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined and implemented within a range that does not cause technical contradiction.

The overall configuration of the vehicle 500 is not limited to the example of the above embodiment. The vehicle 500 only needs to include an internal combustion engine 10, a motor generator 21, a clutch 22, a first rotation sensor 51, a second rotation sensor 52, and a control device 100.

- In the above embodiment, the value of the specified rotation speed RR is an example. The specified rotation speed RR may be greater than or less than 250 rpm. However, the specified rotation speed RR is a value for detecting the state in which the engine speed NE is about to become zero. Therefore, the specified rotation speed RR needs to be set to a value smaller than the idle speed.

In the above embodiment, the value of the rotational speed difference DR is an example. The rotational speed difference DR may be greater than or less than 100 rpm.
In the above embodiment, in step S13, instead of the MG speed NM1, the absolute value of the difference between another speed and the engine speed NE may be calculated. In this case, the speed of a shaft that rotates in synchronization with the crankshaft 11 can be used as the "other speed". For example, the internal combustion engine 10 is equipped with a camshaft for driving an intake valve and an exhaust valve. This camshaft is connected to the crankshaft 11 via a sprocket and a chain wound around the sprocket. In other words, the speed of the camshaft is normally synchronized with the crankshaft 11. Therefore, when the absolute value of the difference between the engine speed NE and the speed of the camshaft is equal to or smaller than the differential speed RR, the processes of steps S14 and S15 may be performed. In this modification, the same effect as that of (2) above can be obtained.

The technical ideas that can be derived from the above-described embodiments and modifications will be described below.
an internal combustion engine having a crankshaft; a motor generator having an output shaft which is a part of a transmission path of a driving force from the crankshaft to a driving wheel; a clutch interposed between the crankshaft and the output shaft; a camshaft which rotates in synchronization with the rotation of the crankshaft and opens and closes an intake valve or an exhaust valve of the internal combustion engine; a first rotation sensor capable of detecting an engine rotation speed which is the rotation speed of the crankshaft; and a second rotation sensor capable of detecting a cam rotation speed which is the rotation speed of the camshaft, a control device that is applied to a vehicle in which a state in which a torque transmission is switchable between an engaged state and an open state in which torque transmission is impossible between the crankshaft and the output shaft, and that controls the internal combustion engine and the clutch, wherein, when the clutch is in an engaged state while the internal combustion engine is running, and the engine speed is equal to or lower than a predetermined specified speed that is lower than an idle speed, and the absolute value of the difference between the engine speed and the cam speed is equal to or lower than a predetermined differential speed, the control device for a vehicle changes the clutch to a released state and stops fuel injection and ignition in the internal combustion engine.

DR...Differential rotation speed NE...Engine rotation speed NM1...MG rotation speed RR...Regulated rotation speed 10...Internal combustion engine 11...Crankshaft 21...Motor generator 22...Clutch 30...Drive wheel 51...First rotation sensor 52...Second rotation sensor 100...Control device 500...Vehicle

Claims (1)

an internal combustion engine having a crankshaft;
a motor generator having an output shaft which is a part of a transmission path of a driving force from the crankshaft to a driving wheel;
a clutch interposed between the crankshaft and the output shaft;
a first rotation sensor capable of detecting an engine speed, which is the rotation speed of the crankshaft;
a second rotation sensor capable of detecting an MG rotation speed, which is the rotation speed of the motor generator;
The clutch is applied to a vehicle that is switchable between an engaged state in which torque can be transmitted between the crankshaft and the output shaft and a disengaged state in which torque cannot be transmitted between the crankshaft and the output shaft,
A control device for controlling the internal combustion engine and the clutch,
When the internal combustion engine is in an engaged state, and the engine speed is equal to or lower than a predetermined specified speed that is lower than an idle speed, and an absolute value of a difference between the engine speed and the MG speed is equal to or lower than a predetermined differential speed, the clutch is changed to a disengaged state, and fuel injection and ignition in the internal combustion engine are stopped ;
When the absolute value is greater than the differential rotation speed, the clutch is maintained in an engaged state, and the internal combustion engine continues to be driven.
Vehicle control device.