Hybrid vehicle control device

Abstract

To provide a control device of a hybrid vehicle that can suppresses shock from occurring and hesitation from occurring when returning from fuel cut based on accelerator-on operation.SOLUTION: A control device of a hybrid vehicle, which is equipped with a damper mechanism, a motor, a transmission and a differential gear in this order from an engine side to a driving wheel side, comprises: a return control part that when returning the engine from fuel-cut on the basis of accelerator-on operation, switches total output torque of the engine and the motor from negative torque to positive torque to perform first backlash control to the differential gear, and switches output torque of the engine from negative torque to positive torque after the first backlash control to perform second backlash control to the damper mechanism; and a setting part that sets a period of time during which the first backlash control is executed, longer as a gear stage established in the transmission is lower.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] Techniques related to eliminating backlash in a differential gear are known (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 returning the engine from fuel cut based on accelerator on, it is conceivable to execute backlash elimination control of a damper device or a differential. If the execution period of the backlash elimination control is short, there is a risk of increasing shock to the vehicle. On the other hand, if the execution period of the backlash elimination control is long, although the shock can be suppressed, there is a risk of a decrease in the responsiveness of the return from fuel cut and the occurrence of hesitation.

[0005] Therefore, an object of the present invention is to provide a control device for a hybrid vehicle that suppresses the occurrence of shock and the occurrence of hesitation when returning from fuel cut based on accelerator on.

Means for Solving the Problems

[0006] In a control device for a hybrid vehicle including a damper mechanism, a motor, a transmission, and a differential gear, in that order from the engine side to the drive wheel side, when the engine is caused to resume from fuel cut based on an accelerator on, the total output torque of the engine and the motor is changed from negative torque to positive torque to perform first backlash elimination control on the differential gear, and after the first backlash elimination control, the output torque of the engine is changed from negative torque to positive torque to perform second backlash elimination control on the damper mechanism. The object can be achieved by a control device for a hybrid vehicle including a return control unit and a setting unit that sets a longer execution period for the first backlash elimination control as the gear stage established in the transmission is lower.

Advantages of the Invention

[0007] According to the present invention, it is possible to provide a control device for a hybrid vehicle that suppresses the occurrence of shock and hesitation during return from fuel cut based on an accelerator on.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0009] [Schematic Configuration of Hybrid Vehicle] FIG. 1 is a schematic configuration diagram of a hybrid vehicle 1. In the hybrid vehicle 1, a damper device 10, a K0 clutch 14, a motor 15, a wet clutch 18, and a transmission 19 are sequentially provided in the power transmission path from the engine 9 to the drive wheels 13. The engine 9 and the motor 15 are mounted as the driving power sources of the hybrid vehicle 1. The engine 9 is, for example, a V-type 6-cylinder gasoline engine, but the number of cylinders is not limited to this, and it may be an in-line gasoline engine or a diesel engine. The damper device 10, the K0 clutch 14, the motor 15, the wet clutch 18, and the transmission 19 are provided in the transmission unit 11. The transmission unit 11 and the left and right drive wheels 13 are drivingly connected via a differential gear 12.

[0010] The damper device 10 is provided between the engine 9 and the K0 clutch 14 on the power transmission path. The damper device 10 is a dual flywheel damper and includes a plurality of coil springs that attenuate torsional vibration. The damper device 10 absorbs the rotational fluctuations of the engine 9.

[0011] The K0 clutch 14 is provided between the engine 9 and the motor 15 on the same power transmission path. The K0 clutch 14 receives hydraulic pressure supply from the released state and enters the engaged state, connecting the power transmission between the engine 9 and the motor 15. The K0 clutch 14 enters the released state in response to the stop of hydraulic pressure supply, blocking the power transmission between the engine 9 and the motor 15. The engaged state means a state in which both engaging elements of the K0 clutch 14 are connected and the engine 9 and the motor 15 have the same rotational speed. The released state means a state in which both engaging elements of the K0 clutch 14 are separated.

[0012] The motor 15 is connected to the battery 16 via the inverter 17. The motor 15 functions as a motor that generates driving force for the vehicle in response to power supply from the battery 16, and also functions as a generator that generates electric power for charging the battery 16 in response to power transmission from the engine 9 or the drive wheels 13. The electric power exchanged between the motor 15 and the battery 16 is adjusted by the inverter 17.

[0013] The inverter 17 is controlled by an ECU (Electronic Control Unit) 100 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 a power running operation where 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 a regenerative operation where the motor 15 generates electricity, the inverter 17 converts the AC voltage from the motor 15 into a DC voltage and adjusts the power supplied to the battery 16.

[0014] The transmission 19 is a stepped automatic transmission that switches the gear ratio in multiple steps by switching the gear stage, but is not limited to this and may be a continuously variable transmission. The transmission 19 in this embodiment has its gear stage switched between the first speed as the lowest speed stage and the sixth speed as the highest speed stage. The transmission 19 is provided between the motor 15 and the drive wheels 13 on the power transmission path. A wet clutch 18 that is supplied with hydraulic pressure and engages to directly connect the motor 15 and the transmission 19 is provided.

[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 wet clutch 18, and the transmission 19 via the hydraulic control mechanism 22, respectively. The hydraulic control mechanism 22 is provided with respective hydraulic circuits for the K0 clutch 14, the wet clutch 18, and the transmission 19, and various hydraulic control valves for controlling their operating hydraulic pressures. Note that, instead of the wet clutch 18, a torque converter equipped with a lock-up clutch may be provided.

[0016] The hybrid vehicle 1 is provided with an ECU 100 as a control device for the vehicle. The ECU 100 is an electronic control unit including an arithmetic processing circuit that performs various arithmetic processes related to the running control of the vehicle, and a memory in which control programs and data are stored. The ECU 100 functionally realizes a return control unit and a setting unit, which will be described in detail later.

[0017] The ECU 100 controls the driving of the engine 9 and the motor 15. Specifically, the ECU 100 controls the throttle opening degree, ignition timing, and fuel injection amount of the engine 9 to control the torque and rotational speed of the engine 9. The ECU 100 controls the inverter 17 to adjust the amount of power transfer between the motor 15 and the battery 16, thereby controlling the rotational speed and torque of the motor 15. Also, the ECU 100 performs drive control of the K0 clutch 14, the wet clutch 18, and the transmission 19 through the control of the hydraulic control mechanism 22.

[0018] Signals from the ignition switch 71, the crank angle sensor 72, the motor rotational speed sensor 73, the accelerator opening sensor 74, and the gear position sensor 75 are input to the ECU 100. The crank angle sensor 72 detects the rotational speed of the crankshaft of the engine 9, that is, the engine rotational speed. The motor rotational speed sensor 73 detects the rotational speed of the output shaft of the motor 15. The accelerator opening sensor 74 detects the opening degree of the accelerator pedal. The gear position sensor 75 detects the gear position established in the transmission 19.

[0019] The ECU 100 drives the hybrid vehicle in either an electric driving mode (hereinafter referred to as the BEV (Battery Electric Vehicle) mode) or a hybrid driving mode (hereinafter referred to as the HEV (Hybrid Electric Vehicle) mode). In the BEV mode, the ECU 100 releases the K0 clutch 14 and runs by the power of the motor 15. In the HEV mode, the ECU 100 switches the K0 clutch 14 to the engaged state and runs by the power of at least the engine 9. Note that the HEV mode includes a mode of running by the power of only the engine 9 and a mode of running with both the engine 9 and the motor 15 as power sources by powering the motor 15.

[0020] The switching of the driving mode is performed based on the required driving force of the vehicle obtained from the vehicle speed and the accelerator opening, the SOC (State Of Charge) indicating the power storage amount of the battery 16, and the like. For example, when the required driving force is relatively small and the SOC is relatively high, the BEV mode is selected. When the required driving force is relatively large or the SOC of the battery 16 is relatively low, the HEV mode is selected.

[0021] When the ECU 100 detects that the accelerator is off during traveling in the HEV mode, it executes a fuel cut to stop the fuel supply to the engine 9. As a result, the hybrid vehicle 1 decelerates. When the driver depresses the accelerator pedal during the fuel cut and the accelerator on is detected, the ECU 100 resumes the fuel supply to the engine 9 and drives the engine 9 in accordance with the driver's request. In addition, when the engine speed drops below the return speed while the accelerator opening remains at 0 or below the threshold during the fuel cut, the ECU 100 resumes the fuel supply to the engine 9 and drives the engine 9 in order to avoid engine stalling.

[0022] When returning from the fuel cut based on the above-described accelerator on, the power transmission path is switched from the drive wheel 13 side to the motor 15 and the engine 9 side, and then from the engine 9 and the motor 15 side to the drive wheel 13 side. At this time, for example, in the differential gear 12, the gear on the transmission 19 side shifts from a state of being driven by the gear on the drive wheel 13 side to a state of driving the gear on the drive wheel 13 side. Similarly, in the damper device 10, the rotating element on the engine 9 side shifts from a state of being driven by the rotating element on the K0 clutch 14 side to a state of driving the rotating element on the K0 clutch 14 side. When such a power transmission path is switched, there is a possibility that a shock may occur in the hybrid vehicle 1. In order to suppress such a shock, the ECU 100 executes backlash elimination control when returning from the fuel cut based on the accelerator on.

[0023] In the backlash suppression control, the total torque of the engine 9 and the motor 15 is limited to a torque lower than the required torque for the hybrid vehicle 1 based on the accelerator opening. Thereby, the occurrence of the shock described above can be suppressed. It is possible to suppress the shock that occurs when returning from fuel cut.

[0024] FIG. 2 is a timing chart showing an example of backlash suppression control when returning from fuel cut based on the accelerator being turned on. FIG. 2 shows the transition of the accelerator state, the fuel cut request, the motor torque, the engine torque, and the total torque of the engine 9 and the motor 15. In FIG. 2, the total torque is shown by a solid line, the engine torque is shown by a dotted line, and the motor torque is shown by a dashed-dotted line.

[0025] When the fuel cut request is on, the engine torque is a negative torque so that the total torque becomes a negative torque in the direction opposite to the rotation direction, and the motor torque is a positive torque which is a torque in the rotation direction. When the accelerator being turned on is detected, the fuel cut request is switched off, the fuel supply to the engine 9 is restarted, and the motor torque increases (at time t1). Here, the motor torque increases from time t1 to a predetermined value and is maintained constant. On the other hand, the engine torque is maintained at a value lower than 0 from time t1 to time t2. During this period, since the combustion of the engine 9 is in an unstable state, the engine torque does not immediately increase. Also, between time t1 and time t2, the motor torque increases so that the total torque changes from a negative torque to a positive torque. Thereby, the backlash of the differential gear 12 occurs. Therefore, the period from time t1 to time t2 corresponds to the first backlash suppression period in which the backlash suppression control of the differential gear 12 is executed.

[0026] When the combustion state of the engine 9 stabilizes at time t2, the engine torque begins to increase. At time t3, the rate of increase of the engine torque is suppressed, and the engine torque changes from negative torque to positive torque. As a result, the backlash elimination control of the damper device 10 is executed. Therefore, the period from time t3 to time t4 corresponds to the second backlash elimination period during which the backlash elimination control of the damper device 10 is executed. The second backlash elimination period is set to a period during which no shock occurs due to backlash in the damper device 10 based on experimental results and the like. After time t4, the engine torque increases so that the total torque becomes the required torque based on the accelerator opening.

[0027] As described above, the first backlash elimination period is a period during which the backlash elimination control of the differential gear 12 is performed by increasing the motor torque instead of increasing the engine torque during the period when the combustion of the engine 9 is unstable. For example, if the first backlash elimination period is set uniformly regardless of the gear position, there may be the following problems. When the gear position is in the low speed range, the first backlash elimination period may be too short to increase the motor torque gently, and there is a risk of shock occurring during the backlash elimination of the differential gear 12. When the gear position is in the high speed range, it is necessary to increase the motor torque significantly from the viewpoint of ensuring equal output because the gear ratio is small. In this case, there is a risk of hesitation because the motor torque is limited to be below the upper limit value during the first backlash elimination period and the desired motor torque cannot be ensured. Therefore, the ECU 100 sets the first backlash elimination period longer as the gear position is lower as follows.

[0028] [Fuel cut return control] FIG. 3 is a flowchart showing an example of the fuel cut return control executed by the ECU 100. This control is repeatedly executed at a predetermined cycle with the ignition on. The ECU 100 determines whether or not the accelerator has been turned on during the fuel cut of the engine 9 based on the accelerator opening sensor 74 (step S1). If the answer in step S1 is No, this control is terminated.

[0029] If the answer is Yes in step S1, the ECU 100 acquires the gear stage established in the transmission 19 based on the gear stage sensor 75 (step S2). Next, the ECU 100 refers to the map in FIG. 4 based on the acquired gear stage and sets the first backlash period (step S3). FIG. 4 is an example of a map defining the relationship between the gear stage and the first backlash period. As shown in FIG. 4, the lower the gear stage established in the transmission 19, the longer the first backlash period is set. Step S3 is an example of the process executed by the setting unit.

[0030] Next, the ECU 100 executes the return control from fuel cut (step S4). Specifically, the ECU 100 executes the first backlash control according to the above-described execution period, and then executes the second backlash control. Thereby, it is possible to suppress the occurrence of shock due to the backlash of the differential gear 12 when the gear stage is a low speed stage. Further, when the gear stage is a high speed stage, it is possible to suppress the occurrence of hesitation and ensure the responsiveness of the return from fuel cut. Step S4 is an example of the process executed by the return control unit.

[0031] In the map shown in FIG. 4, the same execution period of the first backlash is set for some adjacent gear stages, but it is not limited to this. That is, as long as the first backlash period is set longer as the gear stage is lower, the first backlash periods may be the same for some adjacent gear stages, or the first backlash periods may be different for all gear stages.

[0032] Further, when the gear stage is the first speed which is the lowest speed stage, the occurrence of shock may be suppressed by setting the first backlash period to be longer than the second backlash period. Further, when the gear stage is the sixth speed which is the highest speed stage, the occurrence of hesitation may be suppressed by setting the first backlash period to be shorter than the second backlash period.

[0033] As described above, the embodiments of the present invention have been described in detail, but the present invention is not limited to such specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

Description of Symbols

[0034] 1 Hybrid vehicle 9 Engine 10 Damper device 12 Differential gear 13 Driving wheel 15 Motor 19 Transmission 100 ECU (Hybrid vehicle control device, return control unit, setting unit)

Claims

【Claim 1】 In a control device for a hybrid vehicle including, in order from the engine side to the drive wheel side, a damper mechanism, a motor, a transmission, and a differential gear, when the engine is caused to resume from fuel cut based on an accelerator on, a total output torque of the engine and the motor is changed from a negative torque to a positive torque to perform first backlash elimination control on the differential gear, and after the first backlash elimination control, an output torque of the engine is changed from a negative torque to a positive torque to perform second backlash elimination control on the damper mechanism; a return control unit; a setting unit configured to set a longer execution period of the first backlash elimination control as a gear stage established in the transmission is lower. A control device for a hybrid vehicle comprising the same.

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