Hybrid vehicles

Abstract

To provide a hybrid vehicle with improved responsiveness in recovering from fuel cut-off. [Solution] The system comprises an engine, a filter for collecting exhaust particulate matter from the engine, a motor provided on a power transmission path between the engine and the drive wheels, a torque converter having a lock-up clutch provided on the power transmission path between the motor and the drive wheels, and a control device, wherein the control device includes a determination unit that determines whether there is a request to return from fuel cut-off in the engine based on accelerator input while performing auxiliary regeneration control in which the motor assists the rotation of the engine while releasing the lock-up clutch to regenerate the filter by cutting off fuel in the engine, and an auxiliary return control unit that, if the determination unit makes an affirmative determination, restarts fuel injection in the engine with the lock-up clutch released and assists the rotation of the engine with the motor.

Description

Technical Field

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

Background Art

[0002] There is known auxiliary regeneration control that releases the lock-up clutch of a torque converter and performs regeneration of a filter by fuel cut in an engine while assisting the rotation of the engine by a motor (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When there is a return request from a fuel cut based on accelerator on during the execution of auxiliary regeneration control, return control is executed to resume fuel injection in the engine and increase the engine speed. However, since a motor is connected to the engine, it takes time for the engine speed to increase, and there is a risk that the responsiveness of the return from the fuel cut will decrease.

[0005] Therefore, an object of the present invention is to provide a hybrid vehicle with improved responsiveness of return from a fuel cut.

Means for Solving the Problems

[0006] The above objective can be achieved by a hybrid vehicle comprising: an engine; a filter for collecting exhaust particulate matter from the engine; a motor provided on a power transmission path between the engine and the drive wheels; a torque converter having a lock-up clutch, provided on the power transmission path between the motor and the drive wheels; and a control device, wherein the control device is performing auxiliary regeneration control, which involves releasing the lock-up clutch to regenerate the filter by cutting fuel in the engine while assisting the rotation of the engine with the motor, and includes a determination unit that determines whether or not there is a request to return from fuel cut in the engine based on accelerator input; and, if the determination unit makes an affirmative determination, an auxiliary return control unit that restarts fuel injection of the engine with the lock-up clutch released and assists the rotation of the engine with the motor.

[0007] The auxiliary return control unit may perform the auxiliary return control by controlling the engine and motor so that the sum of the torque of the engine and the torque of the motor becomes the required torque calculated based on the accelerator opening.

[0008] The auxiliary recovery control unit may terminate the auxiliary recovery control if the difference between the requested torque and the engine torque during the execution of the auxiliary recovery control falls below a threshold. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a hybrid vehicle with improved responsiveness in recovering from fuel cut-off. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram of a hybrid vehicle. [Figure 2] This is a schematic diagram of the engine's configuration. [Figure 3] This flowchart illustrates the control process for recovering from fuel cut-off. [Figure 4]This is a timing chart illustrating auxiliary recovery control. [Modes for carrying out the invention]

[0011] [Overall configuration of a hybrid vehicle] Figure 1 is a schematic diagram of the hybrid vehicle 1. The hybrid vehicle 1 is equipped with an engine 10 and a motor 15 as the power source for driving. The engine 10 is a gasoline engine with multiple cylinders, but it may also be a diesel engine. A transmission unit 11 is provided in the power transmission path from the engine 10 to the drive wheels 13. The transmission unit 11 and the left and right drive wheels 13 are driven together via a differential gear 12.

[0012] The transmission unit 11 is equipped with a K0 clutch 14 and a motor 15. The motor 15 is located on the power transmission path from the engine 10 to the drive wheels 13.

[0013] The K0 clutch 14 is located between the engine 10 and the motor 15 in the power transmission path. The K0 clutch 14 engages when hydraulic pressure is supplied, connecting the power transmission between the engine 10 and the motor 15. The K0 clutch 14 disengages when the hydraulic pressure supply is stopped, interrupting the power transmission between the engine 10 and the motor 15. The K0 clutch 14 also slips from the start of torque transmission until it is fully engaged.

[0014] 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. Furthermore, the motor 15 also functions as a generator that generates electricity to charge the battery 16 in response to power transmission from the engine 10 and the drive wheels 13. The power exchanged between the motor 15 and the battery 16 is regulated by the inverter 17.

[0015] The transmission unit 11 is equipped 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 multi-stage transmission that switches the gear ratio in multiple stages. The torque converter 18 is installed between the motor 15 and the drive wheels 13 on the power transmission path. The turbine shaft 18a of the torque converter 18 is connected to the input shaft of the automatic transmission 19. The turbine shaft 18a corresponds to the output shaft of the torque converter 18. The automatic transmission 19 is installed between the torque converter 18 and the drive wheels 13 on the power transmission path. The torque converter 18 is equipped with a lock-up clutch (hereinafter referred to as LU clutch) 20 that receives hydraulic pressure, engages with it, and directly connects the motor 15 and the automatic transmission 19.

[0016] The LU clutch 20 engages when hydraulic pressure is supplied, connecting the power transmission between the motor 15 and the drive wheels 13. The LU clutch 20 disengages when the hydraulic pressure supply is stopped. The LU clutch 20 also slips from disengagement until it engages again.

[0017] The transmission unit 11 is further equipped 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, torque converter 18, automatic transmission 19, and LU clutch 20 via the hydraulic control mechanism 22. The hydraulic control mechanism 22 is equipped with hydraulic circuits for the K0 clutch 14, torque converter 18, automatic transmission 19, and LU clutch 20, as well as various hydraulic control valves for controlling their operating hydraulic pressures.

[0018] The hybrid vehicle 1 is equipped with an ECU (Electronic Control Unit) 50 as its control device. The ECU 50 is an electronic control unit comprising an arithmetic processing circuit that performs various calculations 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 implements the determination unit and auxiliary return control unit, which will be described in more detail later.

[0019] The ECU 50 is connected with 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 an accelerator opening sensor 69. The ignition switch 61 detects the on / off state of the ignition. The crank angle sensor 62 detects the rotational speed of the crankshaft of the engine 10. The air flow meter 63 detects the intake air volume introduced into the engine 10. The air-fuel ratio sensors 64 and 65 detect the air-fuel ratio of the exhaust of the engine 10. The water temperature sensor 66 detects the temperature of the cooling water 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 accelerator opening sensor 69 detects the accelerator opening which is the opening of the accelerator pedal operated by the driver.

[0020] The ECU 50 controls the driving of the engine 10 and the motor 15. Specifically, the ECU 50 controls the inverter 17 to adjust the amount of power transfer between the motor 15 and the battery 16, thereby performing torque control of the motor 15. The ECU 50 performs drive control of the K0 clutch 14, the LU clutch 20, and the automatic transmission 19 through the control of the hydraulic control mechanism 22.

[0021] The ECU 50 drives the hybrid vehicle 1 in either the motor driving mode or the hybrid driving mode. In the motor driving mode, the ECU 50 releases the K0 clutch 14 and rotates the drive wheels 13 with the power of the motor 15. In the hybrid driving mode, the ECU 50 engages the K0 clutch 14 and rotates the drive wheels 13 with 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 is equal to or greater than the driving force threshold value, the mode is switched from the motor driving mode to the hybrid driving mode. Also, when the charge amount of the battery 16 is equal to or less than the power threshold value, the mode is switched from the motor driving mode to the hybrid driving mode.

[0022] [Schematic Configuration of Engine] Figure 2 is a schematic configuration diagram of the engine 10. The engine 10 has 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.

[0023] The cylinder block 30 is provided with a cylindrical bore 31. The piston 33 is reciprocally accommodated within the bore 31. The 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 due to the reciprocating motion of the piston 33.

[0024] The crankshaft 35, which is the output shaft of the engine 10, is connected via the 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 above-described crank angle sensor 62.

[0025] The intake passage 36 is connected to the combustion chamber C via the intake valve 36v. The exhaust passage 37 is connected to the combustion chamber C via the exhaust valve 37v. The above-described air flow meter 63 is provided in the intake passage 36.

[0026] The cylinder block 30 is provided with an in-cylinder injection valve 41D that directly injects fuel 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 a spark plug 42 that ignites the air-fuel mixture 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.

[0027] The exhaust passage 37 is equipped with a three-way catalytic converter 43 and a GPF (Gasoline Particulate Filter) 44. The three-way catalytic converter 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 particulate matter (hereinafter referred to as PM (Particulate Matter)) in the exhaust gas. The GPF 44 is an example of a filter. For example, if the engine 10 is a diesel engine, a DPF (Diesel Particulate Filter) is provided instead of the GPF 44.

[0028] An air-fuel ratio sensor 64 is provided between the three-way catalytic converter 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 catalytic converter 43. Downstream of the GPF 44, an air-fuel ratio sensor 65 is provided. The air-fuel ratio sensor 65 detects the air-fuel ratio of the exhaust gas discharged from the GPF 44.

[0029] The ECU 50 controls the operation of the engine 10 by controlling the opening degree of the throttle valve 40, the fuel injection amount of the in-cylinder injection valve 41D and the port injection valve 41P, and the ignition timing of the spark plug 42, based on the detection signals from the aforementioned sensors.

[0030] The ECU 50 estimates the amount of PM (particulate matter) accumulated in the GPF 44, and requests regeneration control of the GPF 44 if the amount of PM exceeds a predetermined value. The method for estimating the amount of PM accumulation may be, for example, based on the driving history of the engine 10 since the completion of the previous regeneration control or the differential pressure before and after the GPF 44, or it may be estimated by other known methods. In the regeneration control, oxygen is supplied to the GPF 44 to burn off the accumulated PM by executing a fuel cut.

[0031] The ECU 50 performs auxiliary regeneration control when predetermined conditions are met. The auxiliary regeneration control is a control that regenerates the GPF 44 by cutting off fuel while the LU clutch 20 is disengaged and the motor 15 assists in the rotation of the engine 10. This prevents the engine 10 from stalling and suppresses a decrease in the rotation of the engine 10, allowing the regeneration of the GPF 44 to continue. The predetermined conditions are, for example, when there is a request for GPF 44 regeneration, the hydraulic oil temperature is below a predetermined value, and the temperature, voltage, and charge level of the battery 16 are above a predetermined value.

[0032] [Fuel cut-off recovery control] Figure 3 is a flowchart illustrating the control process for recovering from fuel cut-off. This control is executed repeatedly while the ignition is on. The ECU 50 determines whether or not there is a request to recover from fuel cut-off (step S1). If the answer in step S1 is No, this control is terminated.

[0033] If the answer in step S1 is Yes, the ECU 50 determines whether or not auxiliary regeneration control is being performed (step S2). If the answer in step S2 is Yes, the ECU 50 determines whether or not there is a load operation request for the engine 10 (step S3). A load operation request means that there is no idle operation request. In other words, if there is a load operation request, it indicates that the auxiliary regeneration control was not performed during idle operation. If the answer in step S2 or S3 is No, the ECU 50 performs a known normal recovery control (step S4).

[0034] If the answer in steps S2 and S3 is Yes, the ECU 50 determines whether or not it is a request to recover from fuel cut based on accelerator input (step S5). A request to recover from fuel cut based on accelerator input is a request to recover from fuel cut when the driver operates the accelerator (requests acceleration), and is also called a forced recovery request. A request to recover from fuel cut that is not a forced recovery request is a spontaneous recovery request. A spontaneous recovery request is a request to recover from fuel cut when the engine speed falls below the recovery speed without accelerator input. Steps S1, S2, and S5 are examples of processes executed by the determination unit.

[0035] If the answer in step S5 is Yes, i.e., if there is a request to recover from fuel cut based on accelerator input, the ECU 50 performs auxiliary recovery control (step S6a). In auxiliary recovery control, the LU clutch 20 is released and fuel injection to the engine 10 is restarted, and the motor 15 assists in the rotation of the engine 10. In auxiliary recovery control, the engine 10 and motor 15 are controlled so that the sum of the engine torque and motor torque becomes the required torque required for auxiliary recovery control. Specifically, the progression of engine torque during auxiliary recovery control is estimated, and the torque obtained by subtracting the engine torque from the required torque is calculated as the motor torque. The ECU 50 controls the motor 15 to output the calculated motor torque. The required torque is calculated based on the accelerator opening, and the larger the accelerator opening, the greater the required torque. The progression of engine torque during auxiliary recovery control is known in advance by the ECU 50. Step S6a is an example of the processing performed by the auxiliary recovery control unit.

[0036] Next, the ECU 50 determines whether the termination condition for the auxiliary recovery control has been met (step S7a). The termination condition, as will be described in detail later, is considered to have been met when the difference between the requested torque and the engine torque falls below a threshold, or when a predetermined time has elapsed since the start of the auxiliary recovery control. Therefore, if the determination in step S7a is Yes, the auxiliary recovery control is terminated. If the determination in step S7a is No, step S6a is continued.

[0037] In the case of step S5No, i.e., in the case of a spontaneous return request, the ECU 50 performs the same auxiliary return control (step S6b). However, when there is a spontaneous return request, the requested torque is lower than when there is a return request based on accelerator pedal activation as described above. In other respects, it is the same as the auxiliary return control performed in step S6a. Step S6b is an example of the processing performed by the auxiliary return control unit.

[0038] Next, the ECU 50 determines whether the termination conditions for the auxiliary recovery control have been met (step S7b). The termination conditions for the auxiliary recovery control when a natural recovery request is made are the same as the termination conditions for the auxiliary recovery control when a forced recovery request is made, but they may be different. For example, the threshold value and predetermined time used to determine whether the termination conditions have been met may be different.

[0039] Figure 4 is a timing chart illustrating auxiliary return control. Figure 4 shows the transitions of turbine speed, motor speed, required torque, engine torque, and total torque. Total torque is the sum of engine torque and motor torque. Therefore, in Figure 4, the torque obtained by subtracting engine torque from total torque corresponds to motor torque. Also, because the K0 clutch 14 is engaged, the motor speed matches the engine speed. Furthermore, the motor speed and total torque are shown for both this embodiment and a comparative example. The comparative example, unlike this embodiment, shows return control in a case where the motor 15 does not assist in the rotation of the engine 10. The turbine speed is shown for this embodiment.

[0040] During auxiliary regeneration control, the LU clutch 20 is in a disengaged state, so the motor speed is lower than the turbine speed, and the engine torque is zero, so the total torque is equal to the motor torque (time t0). When a recovery request is made, the requested torque increases, and in the comparative example, the engine torque begins to rise, but the motor torque begins to fall to zero, so the total torque begins to fall (time t1). In contrast, in this embodiment, the motor torque also begins to rise as the engine torque rises, so the total torque rises earlier (time t1). Therefore, the total torque in this embodiment reaches the requested torque before the total torque in the comparative example reaches the requested torque (time t2). Therefore, the motor speed also becomes equal to or greater than the turbine speed earlier in this embodiment than in the comparative example (time t3). Consequently, the turbine speed rises earlier in this embodiment than in the comparative example.

[0041] Thus, the auxiliary recovery control allows for an earlier increase in engine speed, improving the responsiveness of recovery from fuel cut-off. For example, in cases where there is a recovery request based on accelerator input, the responsiveness to the driver's acceleration request is improved, resulting in improved drivability. Furthermore, if the motor 15 starts driving when the recovery control in the comparative example is completed, there is a risk of torque shock due to the torque of the motor 15. In the auxiliary recovery control, since the motor 15 is already driving, by continuing to use the motor 15 when the auxiliary recovery control is completed, smooth driving can be continued due to the torque of the engine 10 and the motor 15.

[0042] Although embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims. [Explanation of Symbols]

[0043] 1. Hybrid vehicle 10 Engines 15 Motor 18 Torque Converter 20 Lock-up clutch 44 GPF (Filter) 50 ECU (Control Unit, Judgment Unit, Auxiliary Return Control Unit)

Claims

1. The engine and A filter for collecting exhaust particulate matter from the engine, A motor is provided on the power transmission path between the engine and the drive wheels, A torque converter having a lock-up clutch is provided on the power transmission path between the motor and the drive wheel, A control device is provided, The control device is A determination unit determines whether or not there is a request to return from fuel cut-off in the engine based on accelerator input while auxiliary regeneration control is being performed, which involves releasing the lock-up clutch and performing regeneration of the filter by cutting off fuel in the engine while assisting the rotation of the engine with the motor, A hybrid vehicle comprising: an auxiliary return control unit that, in the case of a positive determination by the determination unit, restarts fuel injection of the engine with the lock-up clutch in the released state and performs auxiliary return control to assist the rotation of the engine with the motor.

2. The hybrid vehicle according to claim 1, wherein the auxiliary return control unit performs the auxiliary return control by controlling the engine and the motor such that the sum of the torque of the engine and the torque of the motor becomes a required torque calculated based on the accelerator opening.

3. The hybrid vehicle according to claim 2, wherein the auxiliary return control unit terminates the auxiliary return control when the difference between the requested torque and the engine torque during the execution of the auxiliary return control falls below a threshold.

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