Control device for a hybrid vehicle

Abstract

This invention relates to a control device for a hybrid vehicle. The control device for a hybrid vehicle including an internal combustion engine, a motor, and a clutch disposed between the internal combustion engine and the motor includes: a first starting control unit that starts the internal combustion engine without causing the motor to perform crank starting; and a second starting control unit that starts the internal combustion engine by causing the motor to perform crank starting. After the first starting control unit performs starting control of the internal combustion engine, the second starting control unit starts the internal combustion engine when the crankshaft of the internal combustion engine has stopped for a predetermined time or longer, or when the crankshaft rotates in the direction opposite to the direction of crank starting.

Description

Technical Field

[0001] This invention relates to a control device for hybrid vehicles. Background Technology

[0002] Some hybrid vehicles are equipped with an internal combustion engine (engine), a motor in the power transmission path between the engine and the wheels, and a clutch in the power transmission path between the engine and the motor (e.g., Japanese Unexamined Patent Application Publication No. 2020-111276). Summary of the Invention

[0003] When an engine start request is made, it is possible to start the engine simply by burning fuel in the engine without using the motor to start the engine crankshaft. However, for example, starting may fail when the engine speed is low at the time of the start request. This invention provides a control device for hybrid vehicles that prevents this failure when starting the internal combustion engine.

[0004] One aspect of this disclosure is a control device for a hybrid vehicle, the hybrid vehicle including an internal combustion engine, a motor, and a clutch disposed between the internal combustion engine and the motor. The control device includes: a first starting control unit configured to start the internal combustion engine without causing the motor to perform crank starting; and a second starting control unit configured to start the internal combustion engine by causing the motor to perform crank starting. The second starting control unit is configured to start the internal combustion engine after the first starting control unit performs starting control of the internal combustion engine, when the crankshaft of the internal combustion engine has stopped for a predetermined time or longer, or when the crankshaft rotates in a direction opposite to the direction of crank starting.

[0005] In this respect, the control device may include a position acquisition unit configured to acquire the position of the crankshaft. The position acquisition unit may reset the position of the crankshaft when the crankshaft rotates in the opposite direction.

[0006] It is possible to provide a control device for hybrid vehicles that can prevent failure when starting the internal combustion engine. Attached Figure Description

[0007] Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, wherein similar symbols denote similar elements, and wherein:

[0008] Figure 1 It is a schematic diagram illustrating a hybrid vehicle;

[0009] Figure 2It is a rough configuration diagram of the engine; and

[0010] Figure 3 This is a flowchart illustrating the processes performed by the ECU. Detailed Implementation

[0011] Hybrid vehicles

[0012] Figure 1 This 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 its drive sources. Along the power transmission path from the engine 10 to the wheels 13, the hybrid vehicle 1 is arranged in the following order: a K0 clutch 14, a motor 15, a torque converter 18, and an automatic transmission 19. The engine 10 can be, for example, a V6 engine with six cylinders #1 to #6. The engine 10 can be, for example, a V-type engine or an inline engine. The engine 10 can be a gasoline engine or a diesel engine. The engine 10 can have multiple cylinders, such as four or six, or it can have only one. The K0 clutch 14, motor 15, torque converter 18, and automatic transmission 19 are housed in a transmission unit 11. The transmission unit 11 and the left and right wheels 13 are driven together via differential gears 12.

[0013] The K0 clutch 14 is disposed between the engine 10 and the motor 15 on the same power transmission path. The state of the K0 clutch 14 is switched to one of three states—released, slipping, and engaged—depending on the hydraulic supply. Specifically, when the K0 clutch 14 is in the released state, the hydraulic supply puts it in either the slipping or engaged state, and power transmission between the engine 10 and the motor 15 is connected. Furthermore, when the hydraulic supply stops, the K0 clutch 14 returns to the released state, and power transmission between the engine 10 and the motor 15 is cut off. The slipping state is a state in which the engaging elements of the K0 clutch 14 on the engine 10 side and the engaging elements on the motor 15 side slide into contact with each other with a predetermined difference in rotational speed. The engaged state is a state in which the two 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 the two engaging elements of the K0 clutch 14 are separated from each other.

[0014] Motor 15 is connected to battery 16 via inverter 17. Motor 15 functions as a motor that generates driving force for the vehicle in response to power supplied from battery 16, and also functions as a generator that generates power to charge battery 16 in response to power transmission from engine 10 and wheels 13. The power transmitted between motor 15 and battery 16 is regulated by inverter 17.

[0015] Inverter 17 is controlled by ECU 50 as described below, and either converts DC voltage from battery 16 to AC voltage, or converts AC voltage from motor 15 to DC voltage. In the case of power operation where motor 15 outputs torque, inverter 17 converts DC voltage from battery 16 to AC voltage to regulate the power supplied to motor 15. In the case of regenerative operation where motor 15 generates power, inverter 17 converts AC voltage from motor 15 to DC voltage to regulate the power supplied to battery 16.

[0016] The torque converter 18 is a fluid connector with torque amplification function. The automatic transmission 19 is a stepped automatic transmission that switches gear ratios in multiple stages by switching gear stages. The automatic transmission 19 is positioned between the motor 15 and the wheels 13 in 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, which receives hydraulic pressure and is engaged to directly connect the motor 15 and the automatic transmission 19.

[0017] The transmission unit 11 is further provided with an oil pump 21 and a hydraulic control mechanism 22. Hydraulic pressure generated by the oil pump 21 is supplied via the hydraulic control mechanism 22 to the K0 clutch 14, torque converter 18, automatic transmission 19, and lock-up clutch 20, respectively. The hydraulic control mechanism 22 is provided with hydraulic circuits for each of the K0 clutch 14, torque converter 18, automatic transmission 19, and lock-up clutch 20, and various hydraulic control valves for controlling their hydraulic pressure.

[0018] The hybrid vehicle 1 is equipped with an electronic control unit (ECU) 50 as a control device. The ECU 50 is an electronic control unit that includes arithmetic processing circuitry that performs various arithmetic operations related to vehicle driving control, and a memory that stores programs and data for control therein. The ECU 50 is an example of a control device for a hybrid vehicle. Functionally, the ECU 50 serves as a first starting control unit for starting the engine 10 without cranking the motor 15, a second starting control unit for starting the engine 10 by cranking, and a unit for acquiring the crank angle position, which is the position of the crankshaft 33 detected by the crank angle sensor 72.

[0019] ECU 50 controls the drive of engine 10 and motor 15. For example, ECU 50 controls the torque and speed of engine 10 by controlling the throttle opening, ignition timing, and fuel injection quantity of engine 10. Furthermore, ECU 50 controls the drive of K0 clutch 14, lock-up clutch 20, and automatic transmission 19 via hydraulic control mechanism 22. ECU 50 controls the hydraulic pressure applied to K0 clutch 14 using hydraulic control mechanism 22 and changes the state of K0 clutch 14 to control the crankshaft starting torque transmitted from motor 15 to engine 10.

[0020] The ECU 50 controls the rotational speed and torque of the motor 15 by controlling the inverter 17 to regulate the electrical force exchanged between the motor 15 and the battery 16. Furthermore, as will be described in detail below, the ECU 50 controls the power supplied from the motor 15 to the battery 16 via the inverter 17 so that the motor braking torque during regenerative operation reaches a target value.

[0021] Signals from the ignition switch 71, crank angle sensor 72, motor speed sensor 73, air flow meter 74, and accelerator pedal opening sensor 75 are input to the ECU 50. The crank angle sensor 72 detects the rotational speed of the crankshaft 33 of the engine 10. The crankshaft 33 has, for example, a plurality of protrusions (not shown) arranged along the direction of rotation, and a portion of a recess in which no protrusions are provided. The crank angle sensor 72 is, for example, an electromagnetic sensor, and detects the crank angle based on the voltage change caused by the rotation of the crankshaft 33. The motor speed sensor 73 detects the rotational speed of the output shaft of the motor 15. The air flow meter 74 detects the intake air volume of the engine 10. The accelerator pedal opening sensor 75 detects the opening degree of the accelerator pedal, which is the amount by which the driver depresses the accelerator pedal.

[0022] ECU 50 drives the hybrid vehicle in either motor mode or hybrid mode. In motor mode, ECU 50 releases clutch 14 and drives the hybrid vehicle using power from motor 15. In hybrid mode, ECU 50 engages clutch 14 and drives the hybrid vehicle using at least power from engine 10. Hybrid modes include a mode in which the hybrid vehicle uses only power from engine 10, and a mode in which motor 15 is driven by power and the hybrid vehicle uses both engine 10 and motor 15 as power sources.

[0023] The driving mode is switched based on the vehicle's required driving force obtained from vehicle speed and accelerator opening, the state of charge of battery 16, etc. For example, when the required driving force is relatively low and the state of charge (SOC) of battery 16 is relatively high, a motor mode in which engine 10 is stopped is selected to improve fuel efficiency. When the required driving force is relatively high or the SOC of battery 16 is relatively low, a hybrid mode in which at least engine 10 is driven is selected.

[0024] In the hybrid mode, the ECU 50 performs intermittent operation control to automatically stop the engine 10 when a predetermined stop condition is met and restart the automatically stopped engine 10 when a predetermined restart condition is met. For example, when the accelerator opening becomes zero in hybrid mode, the ECU 50 considers the automatic stop condition met and thus automatically stops the engine 10. Furthermore, when the accelerator opening becomes greater than zero, the ECU 50 considers the restart condition met and thus automatically restarts the engine 10. When the engine 10 automatically stops, the ECU 50 releases the K0 clutch 14 to stop fuel injection. When the engine 10 automatically restarts, the ECU 50 starts the engine 10 via the crankshaft of the motor 15 through the K0 clutch 14 to initiate fuel injection and ignition, and then engages the K0 clutch 14.

[0025] engine

[0026] Figure 2 This is a schematic diagram of the configuration of engine 10, showing one of the multiple cylinders of engine 10, cylinder #1. Engine 10 has a piston 31, connecting rod 32, crankshaft 33, intake passage 35, intake valve 36, exhaust passage 37, and exhaust valve 38. An air-fuel mixture is burned inside the cylinder. Piston 31 is housed in cylinder #1 for reciprocating motion and is connected via connecting rod 32 to crankshaft 33, which is the output shaft of engine 10. Connecting rod 32 and crankshaft 33 convert the reciprocating motion of piston 31 into rotational motion of crankshaft 33.

[0027] The intake passage 35 is connected to the intake port 35p of cylinder #1 via the intake valve 36. The exhaust passage 37 is connected to the exhaust port 37p of cylinder #1 via the exhaust valve 38. The intake passage 35 is equipped with the air flow meter 74 described above and a throttle valve 40 for regulating the intake air volume. The exhaust passage 37 is equipped with a catalyst 43 to purify the exhaust gases.

[0028] Cylinder #1 is equipped with an in-cylinder injection valve 41. The in-cylinder injection valve 41 injects fuel directly into cylinder #1. In addition to, or as an alternative to, the in-cylinder injection valve 41, a port injection valve that injects fuel toward the intake port can be provided. Cylinder #1 is equipped with an ignition device 42, which ignites the mixture of intake air introduced through intake passage 35 and fuel injected by the in-cylinder injection valve 41 by spark discharge. The other cylinders of the engine 10 have a similar configuration.

[0029] Figure 3 This is a flowchart illustrating the process of starting engine 10, executed by ECU 50. Controls exist for starting engine 10 without cranking the motor 15 and for starting engine 10 via cranking. Figure 3 In the process, firstly, ECU 50 controls the starting of engine 10 without cranking (step S10). When the engine speed of 10 is high at the start of starting control, starting without cranking is likely to be successful. On the other hand, when the speed of rotation is low, starting is likely to fail.

[0030] The ECU 50 determines whether the crankshaft 33 has stopped for a predetermined time or longer (step S12). In the affirmative case (yes), the engine 10 has failed to start. Then, the ECU 50 executes step S18 as described below. In the negative case (no), the ECU 50 obtains the crank angle from the crank angle sensor 72 and determines whether the crankshaft 33 is rotating in the opposite direction (step S14). When a negative determination is made in both steps S12 and S14, the engine 10 has been successfully started without cranking, and the process ends.

[0031] For example, when ignition is performed with the piston 31 on the delayed side of top dead center (TDC), the crankshaft 33 rotates in the opposite direction (as determined affirmatively in step S14). In this case, the ECU 50 resets the crank position. The ECU 50 sets the crank angle obtained from the crank angle sensor 72 to an initial value and, for example, re-detects the crank angle based on the position of the notch on the crankshaft 33.

[0032] After the affirmative determination in step S12 or S16, the ECU 50 starts the engine 10 by cranking the starter (step S18). The hydraulic pressure of the K0 clutch 14 increases, and torque is transmitted from the motor 15 to the engine 10 via the K0 clutch 14, thus rotating the crankshaft 33. This completes the process.

[0033] According to this embodiment, the ECU 50 performs engine 10 starting control without cranking (step S10). Engine 10 may fail to start, and the crankshaft 33 may stop, or the crankshaft 33 may rotate in the opposite direction (steps S12 and S14). When starting without cranking fails, the ECU 50 performs starting control accompanied by cranking to start the engine 10 (step S18). By attempting to start independently without cranking and starting by cranking when it fails, starting failures can be prevented.

[0034] When starting fails, crankshaft 33 may rotate in the opposite direction to the intended direction (step S14). Due to the reverse rotation, there may be a difference between the actual position of crankshaft 33 (actual crank angle) and the crank angle obtained by ECU 50. ECU 50 is able to obtain the accurate crank angle by resetting the crank angle.

[0035] In the example described above, the hybrid vehicle 1 is controlled by a single ECU 50. The embodiments are not limited to this, and the control described above can be performed by multiple ECUs such as an engine ECU for controlling the engine 10, a motor ECU for controlling the motor 15, and a clutch ECU for controlling the K0 clutch 14.

[0036] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to these specific embodiments, and various modifications and changes can be made within the scope of the spirit of the invention as described in the claims.

Claims

1. A control device for a hybrid vehicle that includes 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 configured to start the internal combustion engine without causing the motor to perform a cranking, and a second start control unit configured to start the internal combustion engine by causing the motor to perform a cranking, wherein the second start control unit is configured to start the internal combustion engine when a crankshaft of the internal combustion engine has stopped for a predetermined time or more or when the crankshaft is rotating in a direction opposite to a direction of the cranking after the first start control unit performs start control of the internal combustion engine, wherein the control device further includes: a position acquisition unit configured to acquire a position of the crankshaft, wherein the position acquisition unit is configured to reset the position of the crankshaft when the crankshaft is rotating in a reverse direction to eliminate a difference between an actual position of the crankshaft and the position of the crankshaft acquired by the position acquisition unit due to the rotation of the crankshaft in the reverse direction.

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