Hybrid vehicles

Abstract

To provide a hybrid vehicle in which the decrease in the frequency of filter regeneration is suppressed. [Solution] The system comprises a catalyst for purifying exhaust gas from the engine, a filter disposed downstream of the catalyst for collecting exhaust particulate matter, a motor provided between the engine and the drive wheels, a torque converter provided between the motor and the drive wheels and having a lock-up clutch, a battery, and a control device. The control device performs auxiliary regeneration control by releasing the lock-up clutch and performing fuel cut-off to regenerate the filter while assisting the rotation of the engine with the motor when the lock-up clutch is not engaged and the upper limit of the battery's discharge power is greater than a threshold, and when the lock-up clutch is not engaged and the upper limit of the discharge power is less than or equal to the threshold, it performs lean regeneration control by releasing the lock-up clutch and operating the engine at a lean air-fuel ratio.

Description

Technical Field

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

Background Art

[0002] When the lock-up clutch of a torque converter cannot be engaged, there is known an auxiliary regeneration control in which the lock-up clutch is released and the rotation of the engine is assisted by a motor while performing regeneration of a filter by fuel cut in the engine (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] If the above-described auxiliary regeneration control is executed even when the upper limit value of the discharge power of the battery is low, there is a possibility that the assistance of the rotation of the engine by the motor cannot be continued for a desired time. In this case, the engine speed drops below the recovery speed and fuel injection is restarted. Thus, the regeneration of the filter stops before sufficient oxygen is supplied to the filter, and the regeneration frequency of the filter may decrease.

[0005] Therefore, an object of the present invention is to provide a hybrid vehicle in which a decrease in the regeneration frequency of a filter is suppressed.

Means for Solving the Problems

[0006] The above objective can be achieved by a hybrid vehicle comprising: an engine; a catalyst for purifying exhaust gases from the engine; a filter disposed downstream of the catalyst 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 provided on the power transmission path between the motor and the drive wheels and having a lock-up clutch; a battery for supplying power to the motor; and a control device, wherein the control device includes an auxiliary regeneration control unit that, when the lock-up clutch is not engaged and the upper limit of the battery's discharge power is greater than a threshold, releases the lock-up clutch to perform auxiliary regeneration control, thereby assisting the rotation of the engine by the motor while regenerating the filter by cutting fuel in the engine; and a lean regeneration control unit that, when the lock-up clutch is not engaged and the upper limit of the battery's discharge power is less than or equal to the threshold, releases the lock-up clutch to perform lean regeneration control, thereby regenerating the filter by operating the engine at a lean air-fuel ratio. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a hybrid vehicle in which the decrease in the frequency of filter regeneration is suppressed. [Brief explanation of the drawing]

[0008] [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 is a flowchart illustrating the GPF regeneration process. [Figure 4] This is an example diagram of a map that defines thresholds. [Modes for carrying out the invention]

[0009] [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 12.

[0010] 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.

[0011] 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.

[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. 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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 first determination unit, the second determination unit, and the regeneration control unit, which will be described in more detail later.

[0017] 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 a turbine rotation speed sensor 69. The ignition switch 61 detects the on / off state of the ignition. 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 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 turbine rotation speed sensor 69 detects the rotation speed of the turbine shaft 18a of the torque converter 18.

[0018] 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.

[0019] 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 disengages 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.

[0020] [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.

[0021] 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.

[0022] 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 above-described crank angle sensor 62 is provided in the engine 10.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] [GPF playback processing] Figure 3 is a flowchart illustrating the GPF regeneration process. This process is executed repeatedly while the ignition is on. The ECU 50 determines whether or not there is a regeneration request (step S1). If the answer in step S1 is No, this control is terminated.

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

[0031] If the answer in step S2 is No, the ECU 50 engages the LU clutch 20 and performs regeneration control by cutting off fuel (step S3). When the LU clutch 20 is engaged, power is transmitted from the drive wheels 13 to the engine 10 even during fuel cut-off, suppressing a decrease in the engine speed of the engine 10. This prevents the engine 10 from stalling while regenerating the GPF 44.

[0032] If the answer in step S2 is Yes, the ECU 50 sets a threshold value based on the turbine rotation speed of the torque converter 18 (step S4). The threshold value is used for comparison with the upper limit of the discharge power of the battery 16, which will be described later. Figure 4 is an example of a map that defines the threshold value according to the turbine rotation speed. As shown in Figure 4, the higher the turbine rotation speed, the lower the threshold value is set. The ECU 50 sets the threshold value by referring to the map in Figure 4. Next, the ECU 50 determines whether the upper limit of the discharge power of the battery 16 is greater than the threshold value (step S5). 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.

[0033] If the answer in step S5 is Yes, the ECU 50 performs auxiliary regeneration control, which is regeneration control of the GPF 44 by cutting off fuel, while the motor 15 assists the rotation of the engine 10 with the LU clutch 20 disengaged (step S6). This prevents the engine 10 from stalling and suppresses the decrease in the rotation of the engine 10, thereby ensuring sufficient time for fuel cut. In this way, the GPF 44 can be regenerated even when the LU clutch 20 is unable to engage, thus suppressing a decrease in the regeneration frequency. Step S6 is an example of the process performed by the auxiliary regeneration control unit.

[0034] In auxiliary regeneration control, the ECU 50 controls the output torque of the motor 15 to the minimum torque that the engine 10 can output while in combustion mode. The minimum torque that the engine 10 can output while in combustion mode is the minimum value of the indicated torque within the range where misfires do not occur. Therefore, the total torque output by the engine 10 and motor 15 during the execution of auxiliary regeneration control is the torque obtained by subtracting the friction torque of the engine 10 and the auxiliary torque from the above minimum torque. In other words, during the execution of auxiliary regeneration control by fuel cut, the motor 15 simulates a state in which the LU clutch 20 is disengaged and the engine 10 is operating at minimum torque. Therefore, for example, when auxiliary regeneration control is executed in hybrid driving mode, it is possible to avoid the driver 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 the ROM of the ECU 50 in advance based on experimental and simulation results.

[0035] If the answer in step S5 is No, the ECU 50 performs lean regeneration control to regenerate the GPF 44 by operating the engine 10 at a lean air-fuel ratio with the LU clutch 20 disengaged (step S7). By controlling the target air-fuel ratio of the engine 10 to a lean air-fuel ratio greater than the stoichiometric air-fuel ratio, excess oxygen is created during combustion in the combustion chamber C, and the excess oxygen is supplied to the GPF 44 to burn off the PM accumulated in the GPF 44. In this way, lean regeneration control is performed even when the upper limit of the discharge power of the battery 16 is below the threshold, so a decrease in the regeneration frequency is suppressed. Step S7 is an example of the processing performed by the lean regeneration control unit.

[0036] As described above, the threshold is set based on the map in Figure 4. As shown in Figure 4, when the turbine rotation speed is relatively low, the threshold is set to a high value. In order to perform auxiliary regeneration control in this state, a high upper limit for the discharge power of the battery 16 is required. Conversely, when the turbine rotation speed is relatively high, the threshold is set to a low value. Therefore, in order to perform auxiliary regeneration control in this state, a high upper limit for the discharge power of the battery 16 is not required. This is because even if the upper limit for the discharge power of the battery 16 is low and the rotation speed of the motor 15 is insufficient, torque is transmitted from the turbine side to increase the rotation speed of the engine 10 and the motor 15 because the turbine rotation speed is high. In other words, the rotation of the turbine assists the rotation of the engine 10 and the motor 15.

[0037] 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]

[0038] 1. Hybrid vehicle 10 Engines 15 Motor 16 batteries 18 Torque Converter 18a Turbine shaft 20 Lock-up clutch 43 Three-way catalyst (catalyst) 44 GPF (Filter) 50 ECU (Control Unit, Auxiliary Regeneration Control Unit, Lean Regeneration Control Unit)

Claims

[Claim 1] The engine and A catalyst for purifying exhaust gas from the aforementioned engine, A filter positioned downstream of the catalyst and used to collect 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 battery that supplies power to the motor, A control device is provided, The control device is An auxiliary regeneration control unit, which, when the lock-up clutch is unable to engage and the upper limit of the battery's discharge power is greater than a threshold, releases the lock-up clutch and performs auxiliary regeneration control to assist the rotation of the engine by the motor while simultaneously performing fuel cut-off in the engine to regenerate the filter, and A hybrid vehicle comprising: a lean regeneration control unit that performs lean regeneration control to regenerate the filter by releasing the lock-up clutch and operating the engine at a lean air-fuel ratio when the lock-up clutch is unable to engage and the upper limit of the battery's discharge power is below the threshold; and a lean regeneration control unit that operates the engine at a lean air-fuel ratio.

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