Hybrid vehicle control device

Abstract

To provide a control device of a hybrid vehicle that can determine whether or not an internal combustion engine has stalled out or not.SOLUTION: A control device of a hybrid vehicle, which has an internal combustion engine, a motor and a clutch provided between the internal combustion engine and the motor, is provided with a cranking control part that controls cranking of the internal combustion engine by the motor, a clutch control part that controls engagement pressure of the clutch, and a determining part that determines whether the internal combustion engine has stalled out or not on the basis of a rotation speed of the internal combustion engine, after decreasing the engagement pressure of the clutch, after the cranking is executed.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a control device for a hybrid vehicle.

Background Art

[0002] Some hybrid vehicles include an internal combustion engine (engine), a motor provided in a power transmission path between the engine and the wheels, and a clutch provided in the power transmission path between the engine and the motor. When starting the engine is requested, the clutch is slipped and the motor is used to crank the engine, and then the clutch is engaged to start the engine (for example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to reduce the shock at engine start, the clutch may be temporarily released. When appropriate combustion is not occurring in the engine, the engine speed may decrease after the clutch is released, and the engine may stall. Accordingly, an object of the present invention is to provide a control device for a hybrid vehicle that can determine whether or not the internal combustion engine has stalled.

Means for Solving the Problems

[0005] A control device for a hybrid vehicle, comprising an internal combustion engine, a motor, and a clutch provided between the internal combustion engine and the motor, the control device including a cranking control unit configured to control cranking of the internal combustion engine by the motor, a clutch control unit configured to control an engagement pressure of the clutch, and a determination unit configured to determine whether or not the internal combustion engine has stalled based on a rotational speed of the internal combustion engine after the cranking is performed and after the engagement pressure of the clutch is decreased. The determination unit the aforesaid the peak rotational speed during cranking the difference obtained by subtracting the rotational speed of the internal combustion engine after the engagement pressure has decreased from the aforesaid as a first difference, and the aforesaid the rotational speed of the motor subtracting the rotational speed of the internal combustion engine after the engagement pressure has decreased from the aforesaid as a second difference, and when the first difference is less than a first threshold value or the second difference is less than a second threshold value, the determination unit determines that combustion in the internal combustion engine is normal, and when the first difference is greater than or equal to the first threshold value and the second difference is greater than or equal to the second threshold value, the determination unit determines that the internal combustion engine has stalled. This can be achieved by a control device for a hybrid vehicle.

Advantages of the Invention

[0006] A control device for a hybrid vehicle capable of determining whether or not an internal combustion engine has stalled can be provided.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0008] (Hybrid Vehicle) FIG. 1 is a schematic diagram illustrating a hybrid vehicle 1. The hybrid vehicle 1 is equipped with an engine 10 (internal combustion engine) and a motor 15 as power sources. In the hybrid vehicle 1, a K0 clutch 14, a motor 15, a torque converter 18, and an automatic transmission 19 are sequentially provided in the power transmission path from the engine 10 to the wheels 13. The engine 10 is, for example, a V-type 6-cylinder engine and has six cylinders #1 to #6. The engine 10 may be, for example, a V-type engine or an in-line engine. The engine 10 may be a gasoline engine or a diesel engine. The number of cylinders of the engine 10 may be plural, such as 4 or 6, or may be 1. The K0 clutch 14, the motor 15, the torque converter 18, and the automatic transmission 19 are provided in the transmission unit 11. The transmission unit 11 and the left and right wheels 13 are drivingly connected via a differential gear 12.

[0009] The K0 clutch 14 is provided between the engine 10 and the motor 15 on the same power transmission path. The K0 clutch 14 can be switched to any of a released state, a slip state, and an engaged state according to the supply of hydraulic pressure. Specifically, when the K0 clutch 14 is in the released state, it becomes the slip state or the engaged state by hydraulic pressure supply, and the power transmission between the engine 10 and the motor 15 is connected. Also, the K0 clutch 14 becomes the released state according to the stop of hydraulic pressure supply, and cuts off the power transmission between the engine 10 and the motor 15. Note that the slip state is a state in which the engaging element on the engine 10 side and the engaging element on the motor 15 side of the K0 clutch 14 are in sliding contact with a predetermined rotational speed difference. The engaged state is a state in which both engaging elements of the K0 clutch 14 are connected and the engine 10 and the motor 15 have the same rotational speed. The released state is a state in which both engaging elements of the K0 clutch 14 are separated.

[0010] The motor 15 is connected to the battery 16 via the inverter 17. The motor 15 functions as a motor that generates the driving force of the vehicle in response to the power supply from the battery 16, while also functioning as a generator that generates electric power for charging the battery 16 in response to the power transmission from the engine 10 or the wheels 13. The electric power exchanged between the motor 15 and the battery 16 is adjusted by the inverter 17.

[0011] The inverter 17 is controlled by the ECU 50 described later, and converts the DC voltage from the battery 16 into an AC voltage, or converts the AC voltage from the motor 15 into a DC voltage. In the case of the power running operation where the motor 15 outputs torque, the inverter 17 converts the DC voltage of the battery 16 into an AC voltage and adjusts the power supplied to the motor 15. In the case of the regenerative operation where the motor 15 generates electricity, the inverter 17 converts the AC voltage from the motor 15 into a DC voltage and adjusts the power supplied to the battery 16.

[0012] The torque converter 18 is a fluid coupling having a torque amplification function. The automatic transmission 19 is a stepped automatic transmission that switches the gear ratio in multiple steps by switching the gear stages. The automatic transmission 19 is provided between the motor 15 and the wheels 13 on the power transmission path. The motor 15 and the automatic transmission 19 are connected via the torque converter 18. The torque converter 18 is provided with a lock-up clutch 20 that is supplied with hydraulic pressure and engages to directly connect the motor 15 and the automatic transmission 19.

[0013] The transmission unit 11 is further provided with an oil pump 21 and a hydraulic control mechanism 22. The hydraulic pressure generated by the oil pump 21 is supplied to the K0 clutch 14, the torque converter 18, the automatic transmission 19, and the lock-up clutch 20 via the hydraulic control mechanism 22. The hydraulic control mechanism 22 is provided with respective hydraulic circuits for the K0 clutch 14, the torque converter 18, the automatic transmission 19, and the lock-up clutch 20, and various hydraulic control valves for controlling their operating hydraulic pressures.

[0014] The hybrid vehicle 1 is provided with an ECU (Electronic Control Unit) 50 as a control device. The ECU 50 is an electronic control unit including an arithmetic processing circuit that performs various arithmetic processes related to the running control of the vehicle, and a memory in which control programs and data are stored. The ECU 50 is an example of a control device for a hybrid vehicle, and functions as a cranking control unit, a clutch control unit, and a determination unit.

[0015] The ECU 50 controls the driving of the engine 10 and the motor 15. For example, the ECU 50 controls the throttle opening, ignition timing, and fuel injection amount of the engine 10 to control the torque and rotational speed of the engine 10. Further, the ECU 50 performs drive control of the K0 clutch 14, the lock-up clutch 20, and the automatic transmission 19 through control of the hydraulic control mechanism 22. The ECU 50 controls the hydraulic pressure applied to the K0 clutch 14 using the hydraulic control mechanism 22, and changes the state of the K0 clutch 14 to control the cranking torque transmitted from the motor 15 to the engine 10.

[0016] The ECU 50 controls the inverter 17 to adjust the amount of power transfer between the motor 15 and the battery 16, thereby controlling the rotational speed and torque of the motor 15. Although details will be described later, the ECU 50 controls the power supplied from the motor 15 to the battery 16 by the inverter 17 so that the motor braking torque in regenerative operation becomes the target value.

[0017] Signals from the ignition switch 71, the crank angle sensor 72, the motor rotational speed sensor 73, the air flow meter 74, and the accelerator opening sensor 75 are input to the ECU 50. The crank angle sensor 72 detects the rotational speed of the crankshaft of the engine 10. The motor rotational speed sensor 73 detects the rotational speed of the output shaft of the motor 15. The air flow meter 74 detects the intake air amount of the engine 10. The accelerator opening sensor 75 detects the accelerator pedal opening, which is the amount of depression of the driver's accelerator pedal.

[0018] The ECU 50 drives the hybrid vehicle in either a motor mode or a hybrid mode. In the motor mode, the ECU 50 disengages the K0 clutch 14 and drives by the power of the motor 15. In the hybrid mode, the ECU 50 engages the K0 clutch 14 and drives by at least the power of the engine 10. Note that in the hybrid mode, it includes a mode of driving only by the power of the engine 10 and a mode of driving with both the engine 10 and the motor 15 as power sources by powering the motor 15.

[0019] The switching of the driving mode is performed based on the required driving force of the vehicle obtained from the vehicle speed and the accelerator opening degree, the state of charge of the battery 16, etc. For example, when the required driving force is relatively small and the SOC (State Of Charge) indicating the remaining charge amount of the battery 16 is relatively high, the motor mode with the engine 10 stopped is selected to improve fuel efficiency. When the required driving force is relatively large or the SOC of the battery 16 is relatively low, a hybrid mode with at least the engine 10 driven is selected.

[0020] In the hybrid mode, when a predetermined stop condition is satisfied, the ECU 50 automatically stops the engine 10, and when a predetermined restart condition is satisfied, the ECU 50 executes intermittent operation control to restart the automatically stopped engine 10. For example, in the hybrid mode, when the accelerator opening degree becomes zero, the ECU 50 automatically stops the engine 10 as if the automatic stop condition is satisfied. Also, when the accelerator opening degree becomes larger than zero, the ECU 50 automatically restarts the engine 10 as if the restart condition is satisfied. When automatically stopping the engine 10, the ECU 50 disengages the K0 clutch 14 and stops fuel injection. When automatically restarting the engine 10, the ECU 50 cranks the engine 10 by the motor 15 via the K0 clutch 14 and starts fuel injection and ignition.

[0021] After the engine is started, the K0 clutch 14 is engaged, and the rotational speed of the engine 10 becomes equal to the rotational speed of the motor 15 (synchronization). When the rotational speed of the engine 10 increases during startup, there is a risk of shock. To suppress the shock, after cranking, the hydraulic pressure of the K0 clutch 14 is decreased, for example, the K0 clutch 14 is temporarily disengaged. However, when combustion in the engine 10 is not performed properly, after the K0 clutch 14 is disengaged, the rotational speed of the engine 10 decreases. There is also a risk that the engine 10 stalls and the startup fails.

[0022] Figure 2 is a flowchart exemplifying the processing executed by the ECU 50. The ECU 50 performs cranking by the motor 15 (step S10). After the cranking is performed, the ECU 50 determines whether the K0 clutch 14 is temporarily disengaged (step S12). In the case of a negative determination (No), the processing ends.

[0023] In the case of an affirmative determination (Yes), the ECU 50 determines whether the difference Nep - Ne between the engine rotational speed Nep at the peak and the rotational speed Ne of the engine 10 is less than a predetermined amount ΔNeth1 (step S14). Negative In the case of a determination, the ECU 50 determines whether the difference Nem - Ne between the rotational speed Ne of the engine 10 and the rotational speed Nem of the motor 15 is less than a predetermined amount ΔNeth2 (step S16). In step S16 Negative In the case of a determination, the ECU 50 determines that combustion is not performed properly in the engine 10 and that it has stalled (step S18). In either one of steps S14 and S16 Positive In the case of a determination, the ECU 50 determines that combustion is being performed normally in the engine 10 (step S20).

[0024] Figure 3 is a time chart exemplifying the rotational speed and the hydraulic pressure. The horizontal axis represents time. The upper part represents the rotational speed of the engine 10 (engine rotational speed) and the rotational speed of the motor 15 (motor rotational speed). The lower part represents the hydraulic pressure of the K0 clutch 14.

[0025] At time t1, the hydraulic pressure of the K0 clutch 14 is increased to engage the K0 clutch 14. Cranking is performed by the motor 15, and the rotational speed of the engine 10 begins to increase. The rotational speed Ne of the engine 10 reaches the peak value Nep. At time t2, the hydraulic pressure of the K0 clutch 14 is decreased to temporarily disengage the K0 clutch 14 (step S12 in FIG. 2). The rotational speed Ne of the engine 10 decreases from Nep.

[0026] The dotted line in FIG. 3 shows an example where the engine 10 stalls. The engine rotational speed Ne continues to decrease and moves away from the motor rotational speed Nem. The difference Nep - Ne between the peak value Nep and the engine rotational speed Ne, and the difference Nem - Ne between the motor rotational speed Nem and the engine rotational speed Ne increase. When Nep - Ne is equal to or greater than Neth1 and Nem - Ne is equal to or greater than Neth2, the ECU 50 determines that the engine 10 has stalled (step S18 in FIG. 2).

[0027] The solid line in FIG. 3 shows an example where the combustion of the engine 10 is normal. In response to the disengagement of the K0 clutch 14, the engine rotational speed Ne temporarily decreases. Since combustion occurs in the engine 10, the engine rotational speed Ne increases again and synchronizes with the motor rotational speed Nem. The difference Nep - Ne between the peak value Nep and the engine rotational speed Ne, and the difference Nem - Ne between the motor rotational speed Nem and the engine rotational speed Ne decrease. When Nep - Ne is less than Neth1 or Nem - Ne is less than Neth2, the ECU 50 determines that the combustion in the engine 10 is normal (step S20 in FIG. 2).

[0028] According to the present embodiment, after cranking the engine 10, the engagement pressure of the K0 clutch 14 decreases, and for example, the K0 clutch 14 is in a disengaged state. The ECU 50 determines whether or not the engine 10 has stalled based on the engine rotational speed Ne.

[0029] When the difference Nep - Ne between the engine speed Ne and the peak speed Nep after cranking and the release of the K0 clutch 14 is ΔNeth1 or more, and the difference Nem - Ne between the engine speed Ne and the motor speed Nem is ΔNeth2 or more, the ECU 50 determines that there is an engine stall (step S18 in FIG. 2). It is possible to detect that combustion is not being properly performed, the engine speed Ne has decreased due to the release of the K0 clutch 14, and the engine 10 has stalled.

[0030] When Nep - Ne is less than ΔNeth1, or Nem - Ne is less than ΔNeth2, the ECU 50 determines that combustion is being normally performed in the engine 10 (step S20). The engine speed Ne synchronizes with the motor speed Nem. Since the K0 clutch 14 is temporarily released after cranking, the shock caused by engine starting can be suppressed.

[0031] In the above example, the hybrid vehicle 1 is controlled by a single ECU 50. The embodiment is not limited to this, and for example, the above control may be executed by a plurality of ECUs such as an engine ECU that controls the engine 10, a motor ECU that controls the motor 15, and a clutch ECU that controls the K0 clutch 14.

[0032] Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

Explanation of Reference Numerals

[0033] 1 Hybrid vehicle 10 Engine 11 Transmission unit 12 Differential gear 13 Wheel 14 K0 clutch 15 Motor 16 Battery 17 Inverter 18 Torque converter 19 Automatic Transmission 20 Lock-up Clutch 21 Oil Pump 22 Hydraulic Control Mechanism 50 ECU 71 Ignition Switch 72 Crank Angle Sensor 73 Motor Rotation Speed Sensor 74 Air Flow Meter 75 Accelerator Opening Sensor

Claims

【Claim 1】 A control device for a hybrid vehicle, comprising: an internal combustion engine, a motor, and a clutch provided between the internal combustion engine and the motor, a cranking control unit configured to control cranking of the internal combustion engine by the motor, a clutch control unit configured to control an engagement pressure of the clutch, and a determination unit configured to determine whether or not the internal combustion engine has stalled based on a rotational speed of the internal combustion engine after the engagement pressure of the clutch has been decreased after the cranking is performed, wherein the determination unit obtains a first difference, which is a difference obtained by subtracting a rotational speed of the internal combustion engine after the engagement pressure has been decreased from a peak rotational speed during the cranking, and a second difference, which is a difference obtained by subtracting the rotational speed of the internal combustion engine after the engagement pressure has been decreased from a rotational speed of the motor, and when the first difference is less than a first threshold value or the second difference is less than a second threshold value, the determination unit determines that combustion in the internal combustion engine is normal, and when the first difference is greater than or equal to the first threshold value and the second difference is greater than or equal to the second threshold value, the determination unit determines that the internal combustion engine has stalled.

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