JP7708026B2 - Hybrid vehicle control device - Google Patents

Description

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

Technology for eliminating backlash in differential gears is known (see, for example, Patent Document 1).

JP 2018-115757 A

When the engine is returned from a fuel cut based on the accelerator being pressed, it is possible to execute backlash elimination control for the damper device or differential. If the backlash elimination control is executed for a short period of time, there is a risk that the shock to the vehicle will increase. On the other hand, if the backlash elimination control is executed for a long period of time, the shock can be suppressed, but the responsiveness of the return from the fuel cut may decrease, and hesitation may occur.

The present invention aims to provide a control device for a hybrid vehicle that suppresses the occurrence of shock and hesitation when returning from a fuel cut due to accelerator depression.

The above object can be achieved by a control device for a hybrid vehicle that includes, in order from the engine side to the drive wheel side, a damper mechanism, a motor, a transmission, and a differential gear, and includes a return control unit that, when returning the engine from a fuel cut based on accelerator ON, converts the total output torque of the engine and the motor from negative torque to positive torque to perform a first backlash eliminating control on the differential gear, and after the first backlash eliminating control, converts the output torque of the engine from negative torque to positive torque to perform a second backlash eliminating control on the damper mechanism, and a setting unit that sets the execution period of the first backlash eliminating control to be longer the lower the gear stage established in the transmission.

The present invention provides a control device for a hybrid vehicle that suppresses the occurrence of shock and hesitation when returning from a fuel cut due to accelerator depression.

FIG. 1 is a schematic diagram of a hybrid vehicle. FIG. 2 is a timing chart showing an example of backlash elimination control when returning from a fuel cut based on accelerator depression. FIG. 3 is a flowchart showing an example of the control executed by the ECU. FIG. 4 is an example of a map that defines the relationship between the gear and the first backlash eliminating period.

[General configuration of hybrid vehicle]
1 is a schematic 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 provided in this order in a power transmission path from an engine 9 to drive wheels 13. The engine 9 and the motor 15 are mounted as a driving power source 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 thereto, and 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 a transmission unit 11. The transmission unit 11 and the left and right drive wheels 13 are drivingly connected via a differential gear 12.

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 multiple coil springs that damp torsional vibrations. The damper device 10 absorbs rotational fluctuations of the engine 9.

The K0 clutch 14 is provided between the engine 9 and the motor 15 on the power transmission path. The K0 clutch 14 switches from a released state to an engaged state when it receives a supply of hydraulic pressure, connecting the power transmission between the engine 9 and the motor 15. The K0 clutch 14 switches to a released state when the hydraulic pressure supply is stopped, cutting off the power transmission between the engine 9 and the motor 15. The engaged state is a state in which both engagement elements of the K0 clutch 14 are connected and the engine 9 and the motor 15 have the same rotation speed. The released state is a state in which both engagement elements of the K0 clutch 14 are separated.

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 supplied from the battery 16, and also functions as a generator that generates power to charge the battery 16 in response to power transmission from the engine 9 and the drive wheels 13. The power exchanged between the motor 15 and the battery 16 is adjusted by the inverter 17.

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 powered operation in which 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 regenerative operation in which the motor 15 generates power, the inverter 17 converts the AC voltage from the motor 15 into a DC voltage and adjusts the power supplied to the battery 16.

The transmission 19 is a stepped automatic transmission that changes the gear ratio in multiple stages by changing the gear stage, but is not limited to this and may be a continuously variable automatic transmission. In this embodiment, the transmission 19 changes gear stages between the first gear, which is the lowest gear stage, and the sixth gear, which is the highest gear stage. The transmission 19 is provided between the motor 15 and the drive wheels 13 on the power transmission path. A wet clutch 18 is provided that receives hydraulic pressure and enters an engaged state to directly connect the motor 15 and the transmission 19.

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. The hydraulic control mechanism 22 is provided with 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 a torque converter equipped with a lock-up clutch may be provided instead of the wet clutch 18.

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 that includes a calculation processing circuit that performs various calculation processes related to the vehicle's driving control, and a memory that stores control programs and data. The ECU 100 functionally realizes a return control unit and a setting unit, which will be described in detail later.

The ECU 100 controls the operation of the engine 9 and the motor 15. Specifically, the ECU 100 controls the torque and rotation speed of the engine 9 by controlling the throttle opening, ignition timing, and fuel injection amount of the engine 9. The ECU 100 controls the rotation speed and torque of the motor 15 by controlling the inverter 17 to adjust the amount of power exchanged between the motor 15 and the battery 16. The ECU 100 also controls the operation of the K0 clutch 14, the wet clutch 18, and the transmission 19 through the control of the hydraulic control mechanism 22.

Signals are input to the ECU 100 from an ignition switch 71, a crank angle sensor 72, a motor revolution speed sensor 73, an accelerator opening sensor 74, and a gear stage sensor 75. The crank angle sensor 72 detects the revolution speed of the crankshaft of the engine 9, i.e., the engine revolution speed. The motor revolution speed sensor 73 detects the rotation speed of the output shaft of the motor 15. The accelerator opening sensor 74 detects the opening of the accelerator pedal. The gear stage sensor 75 detects the gear stage established in the transmission 19.

The ECU 100 drives the hybrid vehicle in either an electric driving mode (hereinafter referred to as BEV (Battery Electric Vehicle) mode) or a hybrid driving mode (hereinafter referred to as HEV (Hybrid Electric Vehicle) mode). In the BEV mode, the ECU 100 releases the K0 clutch 14 and drives the vehicle using the power of the motor 15. In the HEV mode, the ECU 100 switches the K0 clutch 14 to an engaged state and drives the vehicle using at least the power of the engine 9. The HEV mode includes a mode in which the vehicle runs using only the power of the engine 9, and a mode in which the motor 15 is powered and the vehicle runs using both the engine 9 and the motor 15 as power sources.

The driving mode is switched based on the vehicle's required driving force, which is calculated from the vehicle speed and accelerator opening, and the SOC (State of Charge), which indicates the amount of charge stored in the battery 16. 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.

When the ECU 100 detects that the accelerator is off while driving in HEV mode, it executes a fuel cut to stop the fuel supply to the engine 9. This causes the hybrid vehicle 1 to decelerate. When the driver depresses the accelerator pedal during fuel cut and the accelerator is detected as on, the ECU 100 resumes the fuel supply to the engine 9 and drives the engine 9 in accordance with the driver's request. Note that if the engine speed drops to or below the return speed while the accelerator opening is at zero or below the threshold during fuel cut, the ECU 100 resumes the fuel supply to the engine 9 to drive the engine 9 in order to avoid the engine stalling.

When returning from the fuel cut based on the accelerator on described above, the power transmission path is switched from the drive wheels 13 side to the motor 15 and engine 9 side to the engine 9 and motor 15 side to the drive wheels 13 side. At this time, for example, in the differential gear 12, the gear on the transmission 19 side transitions from a state in which it was driven by the gear on the drive wheels 13 side to a state in which it drives the gear on the drive wheels 13 side. Similarly, in the damper device 10, the rotating element on the engine 9 side transitions from a state in which it was driven by the rotating element on the K0 clutch 14 side to a state in which it drives the rotating element on the K0 clutch 14 side. When such a power transmission path is switched, a shock may occur in the hybrid vehicle 1. In order to suppress such a shock, the ECU 100 executes backlash reduction control when returning from the fuel cut based on the accelerator on.

In the backlash elimination control, the total torque of the engine 9 and the motor 15 is limited to a torque lower than the torque required for the hybrid vehicle 1 based on the accelerator opening degree, thereby making it possible to suppress the occurrence of the above-mentioned shock.
This can suppress the shock that occurs when recovering from a fuel cut.

Figure 2 is a timing chart showing an example of backlash elimination control when returning from a fuel cut based on accelerator on. Figure 2 shows the accelerator state, fuel cut request, motor torque, engine torque, and the transition of the total torque of the engine 9 and motor 15. In Figure 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 line.

When the fuel cut request is on, the engine torque is negative and the motor torque is positive, so that the total torque is negative in the direction opposite to the direction of rotation. When the accelerator is detected, the fuel cut request is switched off, fuel supply to the engine 9 is resumed, and the motor torque increases (time t1). Here, the motor torque increases from time t1 to a predetermined value and is maintained constant. In contrast, the engine torque is maintained at a value lower than 0 from time t1 to time t2. During this period, the combustion of the engine 9 is unstable, so the engine torque does not increase immediately. In addition, between time t1 and time t2, the motor torque increases so that the total torque changes from negative to positive. This eliminates backlash in the differential gear 12. Therefore, the period from time t1 to time t2 corresponds to the first backlash elimination period in which backlash elimination control of the differential gear 12 is executed.

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. This causes the damper device 10 to execute the backlash elimination control. Therefore, the period from time t3 to time t4 corresponds to a second backlash elimination period during which the damper device 10 executes the backlash elimination control. The second backlash elimination period is set based on experimental results, etc., to a period during which no shock due to backlash elimination occurs in the damper device 10. After time t4, the engine torque increases so that the total torque becomes the required torque based on the accelerator opening.

As described above, the first backlash elimination period is a period during which backlash elimination control of the differential gear 12 is performed by increasing the motor torque instead of increasing the engine torque during a 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 stage, the following problems may occur. When the gear stage is a low gear stage, the first backlash elimination period is too short, so the motor torque cannot be increased gradually, and shocks may occur when the backlash of the differential gear 12 is eliminated. When the gear stage is a high gear stage, the gear ratio is small, so it is necessary to increase the motor torque significantly in order to ensure output. In this case, the motor torque is limited to an upper limit value or less during the first backlash elimination period, and the desired motor torque cannot be secured, so hesitation may occur. Therefore, the ECU 100 sets the first backlash elimination period to be longer the lower the gear stage, as follows.

[Recovery control from fuel cut]
3 is a flow chart showing an example of fuel cut return control executed by the ECU 100. This control is repeatedly executed at a predetermined cycle while the ignition is on. The ECU 100 judges whether the accelerator is turned on during fuel cut of the engine 9 based on the accelerator opening sensor 74 (step S1). If the answer is No in step S1, this control is terminated.

If step S1 is Yes, 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 sets a first backlash elimination period by referring to the map in FIG. 4 based on the acquired gear stage (step S3). FIG. 4 is an example of a map that specifies the relationship between the gear stage and the first backlash elimination period. As shown in FIG. 4, the first backlash elimination period is set longer the lower the gear stage established in the transmission 19. Step S3 is an example of processing executed by the setting unit.

Next, the ECU 100 executes the return control from the fuel cut (step S4). Specifically, the ECU 100 executes the first backlash elimination control according to the execution period described above, and then executes the second backlash elimination control. This makes it possible to suppress the occurrence of shocks due to backlash elimination in the differential gear 12 when the gear is in a low gear. Also, when the gear is in a high gear, it is possible to suppress the occurrence of hesitation and ensure responsiveness in returning from the fuel cut. Step S4 is an example of processing executed by the return control unit.

In the map shown in FIG. 4, the same first backlash elimination execution period is set for several adjacent gears, but this is not limited to the above. In other words, as long as the first backlash elimination period is set longer for lower gears, the first backlash elimination period may be the same for several adjacent gears, or the first backlash elimination period may be different for all gears.

In addition, when the gear is in the lowest gear, 1st speed, the first backlash elimination period may be set to be longer than the second backlash elimination period to suppress the occurrence of shock.In addition, when the gear is in the highest gear, 6th speed, the first backlash elimination period may be set to be shorter than the second backlash elimination period to suppress the occurrence of hesitation.

Although the 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 variations are possible within the scope of the gist of the present invention as described in the claims.

REFERENCE SIGNS LIST 1 Hybrid vehicle 9 Engine 10 Damper device 12 Differential gear 13 Drive wheels 15 Motor 19 Transmission 100 ECU (hybrid vehicle control device, return control unit, setting unit)

Claims (1)

A control device for a hybrid vehicle including, in order from an engine side to a drive wheel side, a damper mechanism, a motor, a transmission, and a differential gear,
a recovery control unit that, when recovering the engine from a fuel cut based on an accelerator ON, performs a first backlash eliminating control on the differential gear by converting a total output torque of the engine and the motor from negative torque to positive torque, and performs a second backlash eliminating control on the damper mechanism by converting the output torque of the engine from negative torque to positive torque after the first backlash eliminating control;
A control device for a hybrid vehicle comprising: a setting unit that sets an execution period of the first backlash eliminating control to be longer as the gear stage established in the transmission is lower.