Hybrid vehicle

Abstract

To provide a hybrid vehicle suppressing stall of an engine.SOLUTION: A power transmission device is provided with an engine, a filter for collecting exhaust particulates from the engine, a motor provided on a power transmission path between the engine and drive wheels, a torque converter having a lockup clutch provided on the power transmission path between the motor and the drive wheels, a battery, and a control device, wherein the control device includes a regeneration control unit for executing auxiliary regeneration control for assisting the rotation of the engine by the motor while executing regeneration of the filter by fuel cut by releasing the lockup clutch, a judgment unit for judging whether the upper limit value of the discharge power of the battery during execution of the auxiliary regeneration control has dropped to a threshold value at which it becomes difficult for the motor to assist the rotation of the engine by the auxiliary regeneration control, and a stop unit for stopping the auxiliary regeneration control when the judgment unit makes an affirmative judgment.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to hybrid vehicles. [Background technology]

[0002] BACKGROUND ART Auxiliary regeneration control is known in which the lockup clutch is released to perform filter regeneration by cutting fuel in the engine, while assisting engine rotation with a motor (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2024-066865 Summary of the Invention [Problem to be solved by the invention]

[0004] If the upper limit of the discharge power of the battery that supplies power to the motor decreases while auxiliary regeneration control is being performed, the engine speed may decrease due to an insufficient power being supplied to the motor, which may result in the engine stalling.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a hybrid vehicle in which engine stalling is suppressed. [Means for solving the problem]

[0006] The above object can be achieved by a hybrid vehicle comprising an engine, a filter that collects exhaust particulates from the engine, a motor provided on a power transmission path between the engine and drive wheels, a torque converter having a lock-up clutch provided on the power transmission path between the motor and the drive wheels, a battery that supplies power to the motor, and a control device, wherein the control device includes a regeneration control unit that performs auxiliary regeneration control to assist the rotation of the engine by the motor while releasing the lock-up clutch and performing regeneration of the filter by cutting fuel in the engine, a determination unit that determines whether or not an upper limit value of discharge power of the battery during execution of the auxiliary regeneration control has fallen to a threshold value at which it becomes difficult for the motor to assist the rotation of the engine under the auxiliary regeneration control, and a cancellation unit that cancels the auxiliary regeneration control when the determination unit makes a positive determination. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a hybrid vehicle in which engine stalling is suppressed. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of a hybrid vehicle. [Figure 2] FIG. 1 is a schematic configuration diagram of an engine. [Figure 3] 10 is a flowchart illustrating a GPF regeneration process. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Hybrid vehicle configuration] FIG. 1 is a schematic diagram of a hybrid vehicle 1. The hybrid vehicle 1 is equipped with an engine 10 and a motor 15 as a power source for traveling. The engine 10 is a gasoline engine having multiple cylinders, but may also be a diesel engine. A transmission unit 11 is provided on a power transmission path from the engine 10 to drive wheels 13. The transmission unit 11 and the left and right drive wheels 13 are drivingly connected via a differential 12.

[0010] The transmission unit 11 is provided with a K0 clutch 14 and a motor 15. The motor 15 is provided on a power transmission path from the engine 10 to the drive wheels 13.

[0011] The K0 clutch 14 is provided between the engine 10 and the motor 15 in the power transmission path. The K0 clutch 14 is engaged when supplied with hydraulic pressure, connecting the power transmission between the engine 10 and the motor 15. The K0 clutch 14 is released when the hydraulic pressure supply is stopped, cutting off the power transmission between the engine 10 and the motor 15. The K0 clutch 14 is in a slip state from when torque transmission begins until it is fully engaged.

[0012] The motor 15 is connected to the battery 16 via an inverter 17. The battery 16 is a rechargeable secondary battery such as a nickel-metal hydride battery or a lithium-ion battery. The motor 15 functions as a motor that generates driving force for the vehicle in response to power supplied from the battery 16. The motor 15 also functions as a generator that generates electric power to charge the battery 16 in response to power transmitted from the engine 10 and the drive wheels 13. The electric power exchanged between the motor 15 and the battery 16 is adjusted by the inverter 17.

[0013] The transmission unit 11 is provided with a torque converter 18 and an automatic transmission 19. The torque converter 18 is a fluid coupling with a torque amplification function. The automatic transmission 19 is a stepped transmission that switches the gear ratio in multiple stages. The torque converter 18 is provided on the power transmission path between the motor 15 and the drive wheels 13. The automatic transmission 19 is provided on the power transmission path between the torque converter 18 and the drive wheels 13. The torque converter 18 is provided with a lock-up clutch (hereinafter referred to as an LU clutch) 20 that receives a supply of hydraulic pressure and engages to directly connect the motor 15 and the automatic transmission 19.

[0014] The LU clutch 20 is engaged when hydraulic pressure is supplied, connecting the power transmission between the motor 15 and the drive wheels 13. The LU clutch 20 is released when the hydraulic pressure supply is stopped. The LU clutch 20 is in a slip state from the released state to the engaged state.

[0015] 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 LU 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 LU clutch 20, and various hydraulic control valves for controlling the operating hydraulic pressures thereof.

[0016] The hybrid vehicle 1 is provided with an ECU (Electronic Control Unit) 50 as a control device for the hybrid vehicle. The ECU 50 is an electronic control unit that includes a processing circuit that performs various arithmetic 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, and functionally realizes a regeneration control unit, a determination unit, and a cancellation unit, which will be described in detail later.

[0017] The ECU 50 is connected to an ignition switch 61, a crank angle sensor 62, an air flow meter 63, air-fuel ratio sensors 64 and 65, a water temperature sensor 66, a SOC (State Of Charge) sensor 67, a battery temperature sensor 68, and a battery voltage sensor 69. The ignition switch 61 detects whether the ignition is on or off. The crank angle sensor 62 detects the rotation speed of the crankshaft of the engine 10. The air flow meter 63 detects the amount of intake air introduced into the engine 10. The air-fuel ratio sensors 64 and 65 detect the air-fuel ratio of the exhaust gas from the engine 10. The water temperature sensor 66 detects the temperature of the coolant that cools the engine 10. The SOC sensor 67 detects the charge amount of the battery 16. The battery temperature sensor 68 detects the temperature of the battery 16. The battery voltage sensor 69 detects the voltage of the battery 16.

[0018] The ECU 50 controls the operation of the engine 10 and the motor 15. Specifically, the ECU 50 controls the inverter 17 to adjust the amount of electric power exchanged between the motor 15 and the battery 16, thereby controlling the torque of the motor 15. The ECU 50 controls the operation of the K0 clutch 14, the LU clutch 20, and the automatic transmission 19 through the control of the hydraulic control mechanism 22.

[0019] The ECU 50 drives the hybrid vehicle 1 in either a motor driving mode or a hybrid driving mode. In the motor driving mode, the ECU 50 disengages the K0 clutch 14 to rotate the drive wheels 13 using the power of the motor 15. In the hybrid driving mode, the ECU 50 engages the K0 clutch 14 to rotate the drive wheels 13 using the power of at least one of the engine 10 and the motor 15. For example, when the required driving force for the hybrid vehicle 1 exceeds a driving force threshold, the mode is switched from the motor driving mode to the hybrid driving mode. Furthermore, when the charge amount of the battery 16 falls below a power threshold, the mode is switched from the motor driving mode to the hybrid driving mode.

[0020] [Engine outline] 2 is a schematic diagram of the engine 10. The engine 10 includes a cylinder block 30, a cylinder head 32, a piston 33, a connecting rod 34, a crankshaft 35, an intake passage 36, an intake valve 36v, an exhaust passage 37, and an exhaust valve 37v.

[0021] A cylindrical bore 31 is provided in the cylinder block 30. A piston 33 is housed in the bore 31 so as to be able to reciprocate. A combustion chamber C is defined by the wall surface of the bore 31, the lower surface of the cylinder head 32, and the top surface of the piston 33. The volume of the combustion chamber C increases and decreases as the piston 33 reciprocates.

[0022] The engine 10 is connected to a crankshaft 35, which is the output shaft of the engine 10, via a connecting rod 34. The connecting rod 34 and the crankshaft 35 convert the reciprocating motion of the piston 33 into the rotational motion of the crankshaft 35. The engine 10 is provided with the crank angle sensor 62 described above.

[0023] The intake passage 36 is connected to the combustion chamber C via an intake valve 36v. The exhaust passage 37 is connected to the combustion chamber C via an exhaust valve 37v. The intake passage 36 is provided with the air flow meter 63 described above.

[0024] The cylinder block 30 is provided with an in-cylinder injection valve 41D that injects fuel directly into the combustion chamber C. The intake passage 36 is provided with a port injection valve 41P that injects fuel toward the intake port. The cylinder head 32 is provided with an ignition plug 42 that ignites the mixture of intake air and fuel introduced into the combustion chamber C. Note that only one of the in-cylinder injection valve 41D and the port injection valve 41P may be provided.

[0025] The exhaust passage 37 is provided with a three-way catalyst 43 and a GPF (Gasoline Particulate Filter) 44. The three-way catalyst 43 contains catalytic metal, has oxygen storage capacity, and purifies NOx, HC, and CO. The GPF 44 is a porous ceramic structure that captures exhaust fine particles (hereinafter referred to as PM (Particulate Matter)) in the exhaust gas. The GPF 44 is an example of a filter. Note that, for example, if the engine 10 is a diesel engine, a DPF (Diesel Particulate Filter) is provided instead of the GPF 44.

[0026] An air-fuel ratio sensor 64 is provided between the three-way catalyst 43 and the GPF 44. The air-fuel ratio sensor 64 detects the air-fuel ratio of the exhaust gas discharged from the three-way catalyst 43. An air-fuel ratio sensor 65 is provided downstream of the GPF 44. The air-fuel ratio sensor 65 detects the air-fuel ratio of the exhaust gas discharged from the GPF 44.

[0027] The ECU 50 controls the operation of the engine 10 by controlling the opening of the throttle valve 40, the fuel injection amount of the in-cylinder injection valve 41D and the port injection valve 41P, the ignition timing of the spark plug 42, etc. based on the detection signals of the above-mentioned sensors.

[0028] The ECU 50 estimates the amount of PM accumulated in the GPF 44, and when the amount of PM accumulated exceeds a predetermined value, requests regeneration control of the GPF 44. The method for estimating the amount of PM accumulated may be, for example, based on the driving history of the engine 10 since the completion of the previous regeneration control, the pressure difference across the GPF 44, or other known methods. In regeneration control, oxygen is supplied to the GPF 44 by cutting fuel to burn the accumulated PM.

[0029] [GPF recycling process] 3 is a flowchart illustrating the GPF regeneration process. This process is repeatedly executed while the ignition is on. The ECU 50 determines whether or not a regeneration request has been made (step S1). If the result in step S1 is No, this control ends.

[0030] If the answer is Yes in step S1, the ECU 50 determines whether the LU clutch 20 is disengageable (step S2). Specifically, the ECU 50 determines that the LU clutch 20 is disengageable if the temperature of the hydraulic oil is below a predetermined value. The predetermined value is set to the lowest temperature that does not interfere with the engagement of the LU clutch 20. This is because if the temperature of the hydraulic oil is below the predetermined value, the viscosity of the hydraulic oil becomes too high, which reduces the responsiveness and controllability of the LU clutch 20.

[0031] If the answer is No in step S2, the ECU 50 engages the LU clutch 20 and executes regeneration control by fuel cut (step S3). With the LU clutch 20 engaged, power is transmitted from the drive wheels 13 to the engine 10 even during fuel cut, suppressing a decrease in the rotation speed of the engine 10. This allows the GPF 44 to be regenerated while preventing the engine 10 from stalling.

[0032] If the answer is Yes in step S2, the ECU 50 determines whether or not the motor 15 can assist the rotation of the engine 10 (step S4). Specifically, it is determined whether or not the motor 15 can assist the rotation of the engine 10 so that the engine 10 does not stall when a fuel cut is executed with the LU clutch 20 in the released state.

[0033] For example, if at least one of the following conditions is met: the temperature of battery 16 is below a predetermined value, the voltage of battery 16 is below a predetermined value, or the charge amount of battery 16 is below a predetermined value, the determination in step S4 is No. If the determination in step S4 is No, this control ends. This is because if the temperature of battery 16 is below a predetermined value or the charge amount of battery 16 is below a predetermined value, there is a risk of a decrease in the power supplied from battery 16 to motor 15. Furthermore, if the voltage of battery 16 is below a predetermined value and the motor 15 is used to assist the rotation of engine 10, there is a risk of deterioration of battery 16 progressing.

[0034] If the answer to step S4 is Yes, the ECU 50 executes assisted regeneration control, which is regeneration control by fuel cutoff, while assisting the rotation of the engine 10 with the motor 15 while the LU clutch 20 is in a disengaged state (step S5). This makes it possible to prevent the engine 10 from stalling, while suppressing a decrease in engine rotation, and ensure time for fuel cutoff. In this way, the GPF 44 can be regenerated even when the LU clutch 20 cannot be engaged, thereby suppressing a decrease in regeneration frequency. Step S5 is an example of processing executed by the regeneration control unit.

[0035] During auxiliary regeneration control, the ECU 50 controls the output torque of the motor 15 to the minimum torque that the engine 10 can output in a combustion state. The minimum torque that the engine 10 can output in a combustion state is the minimum indicated torque within the range in which misfire does not occur. Therefore, the total torque output by the engine 10 and motor 15 during execution of auxiliary regeneration control is the minimum torque minus the friction torque of the engine 10 and the torque of the accessories. In other words, during execution of auxiliary regeneration control by fuel cut, the motor 15 simulates a state in which the engine 10 is operating at minimum torque with the LU clutch 20 in a disengaged state. Therefore, when auxiliary regeneration control is executed in, for example, hybrid driving mode, it is possible to prevent the driver from noticing that the driving power source has switched from the engine 10 to the motor 15. The minimum torque of the engine 10 is stored in advance in the ROM of the ECU 50 based on the results of experiments and simulations.

[0036] Next, the ECU 50 determines whether the upper limit of the discharge power of the battery 16 has fallen below a threshold value during execution of the auxiliary regeneration control (step S6). The threshold value is set to the discharge power of the battery 16 at which it becomes difficult for the motor 15 to assist the rotation of the engine 10 under the auxiliary regeneration control. The upper limit of the discharge power of the battery 16 is calculated by the ECU 50 based on, for example, the temperature and charge amount of the battery 16. If the determination is No in step S6, that is, if the upper limit of the discharge power of the battery 16 is greater than the threshold value, it is determined that the motor 15 can continue to assist the rotation of the engine 10 based on the power from the battery 16, and the auxiliary regeneration control is continued. Step S6 is an example of processing executed by the determination unit.

[0037] If the answer is Yes in step S6, it is determined that the power supplied from the battery 16 to the motor 15 has decreased, making it difficult for the motor 15 to assist the rotation of the engine 10. Therefore, the ECU 50 stops the auxiliary regeneration control (step S7). Specifically, the ECU 50 immediately returns the engine 10 from the fuel cut and stops the motor 15 from assisting the rotation of the engine 10, thereby stopping the regeneration of the GPF 44. Since fuel injection of the engine 10 is started, the rotation speed of the engine 10 increases and stalling of the engine 10 is suppressed. Furthermore, by stopping the motor 15 from assisting the rotation of the engine 10, a decrease in the charge amount of the battery 16 is suppressed.

[0038] As described above, by suspending the auxiliary regeneration control when the upper limit value of the discharge power of the battery 16 falls below the threshold value while the auxiliary regeneration control is being executed, stalling of the engine 10 is suppressed. Step S7 is an example of processing executed by the suspension unit.

[0039] Although the 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 variations are possible within the scope of the gist of the present invention as defined in the claims. [Explanation of symbols]

[0040] 1 Hybrid vehicle 10 Engine 15 Motor 16 Battery 18 Torque converter 20 Lock-up clutch 44 GPF (filter) 50 ECU (control unit, regeneration control unit, judgment unit, cancellation unit)

Claims

[Claim 1] The engine and a filter for collecting exhaust particulates from the engine; a motor provided on a power transmission path between the engine and drive wheels; a torque converter having a lock-up clutch provided on the power transmission path between the motor and the drive wheels; a battery for supplying power to the motor; a control device; The control device a regeneration control unit that performs auxiliary regeneration control to assist the rotation of the engine by the motor while disengaging the lock-up clutch to regenerate the filter by cutting fuel in the engine; and a determination unit that determines whether or not an upper limit value of discharge power of the battery has decreased to a threshold value at which it becomes difficult for the motor to assist the rotation of the engine under the auxiliary regeneration control; a stop unit that stops the auxiliary regeneration control when the determination unit makes a positive determination. Hybrid vehicle.

Images