Hybrid vehicle control device

Abstract

To provide a control device of a hybrid vehicle that can suppress an internal combustion engine from stalling out and start the internal combustion engine.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 first starting control part that starts the internal combustion engine while performing cranking of the internal combustion engine by the motor; a second starting control part that starts the internal combustion engine without performing the cranking of the internal combustion engine by the motor; and a setting part that sets a threshold for a rotation speed of the internal combustion engine, in accordance with a vehicle speed of the hybrid vehicle. When the rotation speed of the internal combustion engine is less than the threshold, the first starting control part starts the internal combustion engine, and when the rotation speed of the internal combustion engine is above the threshold, the second starting control part starts the internal combustion engine.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] Some hybrid vehicles include an internal combustion 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 a request is made to start the engine, the clutch is slipped to crank the engine using the motor, and the clutch is engaged to start the engine (for example, see Patent Document 1, etc.). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-111276 A Summary of the Invention [Problem to be solved by the invention]

[0004] As described above, the internal combustion engine may be started by cranking. The internal combustion engine may also be started by supplying and burning fuel without cranking. Air is introduced into the internal combustion engine for combustion. However, there is a risk that the rotation speed of the internal combustion engine may decrease before the air is introduced, resulting in engine stall. Therefore, the object of the present invention is to provide a control device for a hybrid vehicle that can suppress engine stall and start the internal combustion engine. [Means for solving the problem]

[0005] The above object is to provide a control device for a hybrid vehicle having an internal combustion engine, a motor, and a clutch provided between the internal combustion engine and the motor, the control device including a first start control unit that starts the internal combustion engine by cranking the motor, a second start control unit that starts the internal combustion engine without cranking the motor, and a setting unit that sets a threshold value for the rotation speed of the internal combustion engine in accordance with a vehicle speed of the hybrid vehicle. A throttle control unit that controls a throttle valve of the internal combustion engine; When the rotation speed of the internal combustion engine is less than the threshold value, the first start control unit starts the internal combustion engine, and when the rotation speed of the internal combustion engine is equal to or greater than the threshold value, the second start control unit starts the internal combustion engine. When the vehicle speed of the hybrid vehicle is equal to or higher than a predetermined speed, the throttle control unit opens the throttle valve, and when the vehicle speed of the hybrid vehicle is equal to or higher than the predetermined speed, the setting unit sets the threshold to a first value, and when the vehicle speed of the hybrid vehicle is lower than the predetermined speed, the setting unit sets the threshold to a second value larger than the first value. This can be achieved by a control device for a hybrid vehicle. Effect of the Invention

[0007] It is possible to provide a control device for a hybrid vehicle that is capable of suppressing engine stalls and starting the internal combustion engine. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram illustrating a hybrid vehicle. [Diagram 2] FIG. 2 is a schematic diagram of the engine. [Diagram 3] FIG. 3 is a flowchart illustrating a process executed by the ECU. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] (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 driving sources. In the hybrid vehicle 1, a K0 clutch 14, a motor 15, a torque converter 18, and an automatic transmission 19 are provided in this order in a power transmission path from the engine 10 to the wheels 13. The engine 10 is, for example, a V-type six-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 in the engine 10 may be a plurality of cylinders, for example, four or six, or may be one. The K0 clutch 14, the motor 15, the torque converter 18, and the automatic transmission 19 are provided in a transmission unit 11. The transmission unit 11 and the left and right wheels 13 are drivingly connected via a differential gear 12.

[0010] The K0 clutch 14 is provided between the engine 10 and the motor 15 on the power transmission path. The K0 clutch 14 is switched to any one of a released state, a slip state, and an engaged state according to the supply of hydraulic pressure. In detail, when the K0 clutch 14 is in the released state, the K0 clutch 14 is switched to a slip state or an engaged state by the supply of hydraulic pressure, and the power transmission between the engine 10 and the motor 15 is connected. In addition, the K0 clutch 14 is switched to a released state according to the stop of the hydraulic pressure supply, and the power transmission between the engine 10 and the motor 15 is interrupted. The slip state is a state in which the engagement element of the K0 clutch 14 on the engine 10 side and the engagement element on the motor 15 side are in sliding contact with each other with a predetermined difference in rotation speed. The engaged state is a state in which both engagement elements of the K0 clutch 14 are connected and the engine 10 and the motor 15 have the same rotation speed. The released state is a state in which both engagement elements of the K0 clutch 14 are separated.

[0011] The motor 15 is connected to the battery 16 via an inverter 17. The motor 15 functions as a motor that generates driving force for the vehicle in response to power supplied from the battery 16, and also functions as a generator that generates electric power to charge the battery 16 in response to power transmission from the engine 10 and the wheels 13. The electric power exchanged between the motor 15 and the battery 16 is adjusted by the inverter 17.

[0012] 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 powering operation in which 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 regenerative operation in which the motor 15 generates power, the inverter 17 converts the AC voltage from the motor 15 into a DC voltage and adjusts the power supplied to the battery 16.

[0013] The torque converter 18 is a fluid coupling having a torque amplifying function. The automatic transmission 19 is a stepped automatic transmission that switches the gear ratio in multiple stages by switching the gear stage. 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 enters an engaged state to directly connect the motor 15 and the automatic transmission 19.

[0014] 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 hydraulic circuits for each of 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 the operating hydraulic pressures thereof.

[0015] 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 a calculation processing circuit that performs various calculation processes related to vehicle driving control, and a memory that stores control programs and data. The ECU 50 is an example of a control device for a hybrid vehicle, and functions as a first start control unit and a second start control unit that start the engine 10, a setting unit that sets a threshold value for the rotation speed of the engine 10, and a throttle control unit that controls the opening degree of the throttle valve 40.

[0016] The ECU 50 controls the operation of the engine 10 and the motor 15. For example, the ECU 50 controls the torque and rotation speed of the engine 10 by controlling the throttle opening, ignition timing, and fuel injection amount of the engine 10. The ECU 50 also controls the operation 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, thereby controlling the cranking torque transmitted from the motor 15 to the engine 10.

[0017] The ECU 50 controls the inverter 17 to adjust the amount of power exchanged between the motor 15 and the battery 16, thereby controlling the rotation speed and torque of the motor 15. As will be described in detail later, the ECU 50 also controls the power supplied by the inverter 17 from the motor 15 to the battery 16 so that the motor braking torque during regenerative operation becomes a target value.

[0018] The ECU 50 receives signals from an ignition switch 71, a crank angle sensor 72, a motor revolution speed sensor 73, an airflow meter 74, an accelerator opening sensor 75, and a vehicle speed sensor 76. The crank angle sensor 72 detects the rotation speed of the crankshaft 33 of the engine 10. The motor revolution speed sensor 73 detects the rotation speed of the output shaft of the motor 15. The airflow meter 74 detects the amount of intake air of the engine 10. The accelerator opening sensor 75 detects the accelerator pedal opening, which is the amount of depression of the accelerator pedal by the driver. The vehicle speed sensor 76 detects the speed of the hybrid vehicle 1 (vehicle speed).

[0019] The ECU 50 runs the hybrid vehicle in either a motor mode or a hybrid mode. In the motor mode, the ECU 50 releases the K0 clutch 14 and runs the vehicle using the power of the motor 15. In the hybrid mode, the ECU 50 engages the K0 clutch 14 and runs the vehicle using at least the power of the engine 10. The hybrid mode includes a mode in which the vehicle runs using only the power of the engine 10, and a mode in which the motor 15 is powered and the vehicle runs using both the engine 10 and the motor 15 as power sources.

[0020] The driving mode is switched based on the vehicle's required driving force calculated from the vehicle speed and accelerator opening, and the state of charge of the battery 16. For example, when the required driving force is relatively small and the SOC (State Of Charge) indicating the remaining charge of the battery 16 is relatively high, the motor mode in which the engine 10 is 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, the hybrid mode in which at least the engine 10 is driven is selected.

[0021] In the hybrid mode, the ECU 50 executes intermittent operation control to automatically stop the engine 10 when a predetermined stop condition is satisfied, and to restart the automatically stopped engine 10 when a predetermined restart condition is satisfied. For example, in the hybrid mode, when the accelerator opening becomes zero, the ECU 50 automatically stops the engine 10 assuming that the automatic stop condition is satisfied. In addition, in the hybrid mode, when the accelerator opening becomes greater than zero, the ECU 50 automatically restarts the engine 10 assuming that the restart condition is satisfied. When automatically stopping the engine 10, the ECU 50 releases the K0 clutch 14 to stop fuel injection. When automatically restarting the engine 10, the ECU 50 cranks the engine 10 by the motor 15 via the K0 clutch 14 to start fuel injection and ignition, and then engages the K0 clutch 14. In addition, the ECU 50 can also start the engine 10 without cranking. The engine 10 is started by supplying fuel into the cylinders of the engine 10 and combusting the mixture of fuel and air.

[0022] During coasting rotation after combustion in the engine 10 has stopped, the ECU 50 temporarily increases the opening of the throttle valve 40, and then decreases the opening (stop position control). By opening the throttle valve 40 during coasting rotation, air is introduced into the cylinder. By increasing the compression torque, the stop position of the engine 10 is set to a desired position. By using the stop position control, the cranking torque required of the motor 15 when restarting the engine 10 can be reduced.

[0023] (engine) 2 is a schematic diagram of the engine 10, showing one cylinder #1 among the multiple cylinders of the engine 10. The engine 10 has a piston 31, a connecting rod 32, a crankshaft 33, an intake passage 35, an intake valve 36, an exhaust passage 37, and an exhaust valve 38. An air-fuel mixture is burned inside the cylinder. The piston 31 is accommodated in the cylinder #1 so as to be capable of reciprocating, and is connected to the crankshaft 33, which is the output shaft of the engine 10, via the connecting rod 32. The connecting rod 32 and the crankshaft 33 convert the reciprocating motion of the piston 31 into the rotational motion of the crankshaft 33.

[0024] The intake passage 35 is connected to an intake port 35p of cylinder #1 via an intake valve 36. The exhaust passage 37 is connected to an exhaust port 37p of cylinder #1 via an exhaust valve 38. The intake passage 35 is provided with the above-mentioned air flow meter 74 and a throttle valve 40 that adjusts the amount of intake air. The exhaust passage 37 is provided with a catalyst 43 for purifying exhaust gas.

[0025] Cylinder #1 is provided with an in-cylinder injection valve 41. The in-cylinder injection valve 41 injects fuel directly into cylinder #1. In addition to or instead of the in-cylinder injection valve 41, a port injection valve that injects fuel toward an intake port may be provided. Cylinder #1 is provided with an ignition device 42 that ignites a mixture of intake air introduced through the intake passage 35 and fuel injected by the in-cylinder injection valve 41 by spark discharge. The other cylinders of engine 10 have a similar configuration.

[0026] The ECU 50 starts the engine 10 with or without cranking. When cranking is not performed, the engine 10 is started by supplying fuel to the engine 10 and burning it. In order to burn the fuel, it is important that air is introduced into the cylinder. It takes time for air to be introduced after the engine 10 is stopped. The rotation speed continues to decrease even while air is being introduced.

[0027] If the engine speed is low when a request to start the engine 10 is made, the engine speed may drop, causing the engine 10 to stall. To prevent the engine 10 from stalling, cranking is performed to start the engine 10. On the other hand, if the engine speed is high, it takes a long time for the engine 10 to stall. Air can be introduced during this time to start the engine 10 without cranking.

[0028] 3 is a flowchart illustrating the process executed by the ECU 50. The engine 10 is in a fuel cut (F / C) state. The ECU 50 determines whether the rotation speed Ne of the engine 10 is less than a predetermined value Neth1 (step S10). If the determination is negative (No), the ECU 50 returns the engine 10 from the fuel cut (F / C return, step S12). After step S12, the process ends.

[0029] If the determination in step S10 is positive (Yes), the ECU 50 determines whether the vehicle speed V of the hybrid vehicle 1 is equal to or greater than a predetermined value Vth (step S14). If the determination is negative, the ECU 50 sets the threshold value Neth2 for the rotation speed to Neth2A (second value) (step S16). The stop position control described below is not performed. If the determination in step S14 is positive, the ECU 50 sets the threshold value Neth2 to Neth2B (first value) (step S18). Neth2B is smaller than Neth2A. Furthermore, the ECU 50 performs starting position control and temporarily opens the throttle valve 40 (step S19).

[0030] After step S16 or S19, the ECU 50 determines whether the rotation speed Ne is equal to or greater than the threshold value Neth2 (step S20). If the determination is negative, the ECU 50 starts the engine 10 with cranking (step S22). If the determination is positive, the ECU 50 starts the engine 10 without cranking (step S24). After step S22 or S24, the process ends.

[0031] According to this embodiment, the ECU 50 starts the engine 10. To start the engine 10, air is introduced into the engine 10. The rotation speed decreases while air is being introduced into the engine 10. The ECU 50 sets a threshold value Neth2 according to the vehicle speed. When the rotation speed Ne is less than Neth2, the ECU 50 starts the engine 10 by cranking (step S22). On the other hand, when the rotation speed Ne is equal to or greater than Neth2, the ECU 50 starts the engine 10 without cranking. When the rotation speed Ne is high, such as equal to or greater than Neth2, the engine is less likely to stall while air is being introduced. It is possible to suppress stalling and start the engine 10.

[0032] When the vehicle speed V is less than a predetermined speed Vth, the ECU 50 sets the threshold value Neth2 to Neth2A (step S16). When the rotation speed Ne is equal to or greater than Neth2A, the ECU 50 starts the engine 10 without cranking. Because the rotation speed is high, the engine is unlikely to stall before a sufficient amount of air for combustion is introduced. Therefore, the engine 10 can be started without cranking. When the rotation speed Ne is less than Neth2A, the ECU 50 cranks the engine 10 to start it. By cranking, the engine can be prevented from stalling.

[0033] When the vehicle speed V is equal to or higher than Vth, the ECU 50 opens the throttle valve 40 (step S19), so that air is introduced into the engine 10 before a start request is made. This allows a sufficient amount of air for combustion to be quickly secured. Therefore, the ECU 50 sets the threshold value Neth2 to Neth2B, which is smaller than Neth2A. Even if the threshold value Neth2B is smaller than Neth2A, the time until air can be introduced is short, so that engine stall is unlikely to occur. Engine stall is suppressed, and the engine 10 can be started without cranking (step S24). When the rotation speed Ne falls to, for example, less than Neth2B, cranking may be performed to start the engine 10 (step S22).

[0034] In the above example, the hybrid vehicle 1 is controlled by a single ECU 50. However, the embodiment is not limited to this, and 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.

[0035] Although a preferred embodiment of the present invention has been described in detail above, the present invention is not limited to such a specific embodiment, and various modifications and variations are possible within the scope of the gist of the present invention described in the claims. [Explanation of symbols]

[0036] 1 Hybrid vehicles 10 Engine 11. Gear unit 12 Differential gear 13 wheels 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 31 Piston 32 Connecting rod 33 Crankshaft 35 Intake passage 35p Intake port 36 Intake valve 37 Exhaust passage 37p Exhaust port 38 Exhaust valve 40 Throttle valve 41 In-cylinder injection valve 42 Ignition system 43 Catalyst 50 ECU 71 Ignition switch 72 Crank angle sensor 73 Motor speed sensor 74 Air flow meter 75 Accelerator opening sensor 76 Vehicle speed sensor

Claims

[Claim 1] A control device for a hybrid vehicle having an internal combustion engine, a motor, and a clutch provided between the internal combustion engine and the motor, A first start control unit that starts the internal combustion engine by performing cranking using the motor; A second start control unit that starts the internal combustion engine without cranking by the motor; a setting unit that sets a threshold value for a rotation speed of the internal combustion engine in accordance with a vehicle speed of the hybrid vehicle; a throttle control unit that controls a throttle valve of the internal combustion engine, When the rotation speed of the internal combustion engine is less than the threshold value, the first start control unit starts the internal combustion engine, When the rotation speed of the internal combustion engine is equal to or greater than the threshold value, the second start control unit starts the internal combustion engine, When the vehicle speed of the hybrid vehicle is equal to or higher than a predetermined speed, the throttle control unit opens the throttle valve, When the vehicle speed of the hybrid vehicle is equal to or higher than the predetermined speed, the setting unit sets the threshold value to a first value, A control device for a hybrid vehicle, wherein, when a vehicle speed of the hybrid vehicle is less than the predetermined speed, the setting unit sets the threshold value to a second value that is greater than the first value.

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