JP7690889B2 - Vehicle control device - Google Patents

Description

The present invention relates to a vehicle control device.

A technology is known that controls the stopping position of an internal combustion engine by temporarily increasing the throttle opening during inertial rotation when combustion has stopped during automatic stopping of the internal combustion engine (see, for example, Patent Document 1).

JP 2020-147276 A

In the above-mentioned stop position control, there is a risk that the accuracy of the stop position of the internal combustion engine will decrease because it is not possible to fill the desired cylinder with only the desired amount of intake air due to variations in the control accuracy of the throttle opening and deterioration of the throttle valve over time.

The present invention aims to provide a vehicle control device that suppresses deterioration in the accuracy of the stopping position of an internal combustion engine.

The above object can be achieved by a control device for a hybrid vehicle having an internal combustion engine as a driving power source, the control device including: a control unit that executes stop position control of the internal combustion engine by switching the throttle opening from a first opening to a second opening greater than the first opening and switching the throttle opening from the second opening to a third opening smaller than the second opening during inertial rotation in which combustion has stopped when the internal combustion engine is automatically stopped; an acquisition unit that acquires an intake manifold pressure, which is the pressure in the intake passage downstream of the throttle valve, at the timing when the intake valve of any cylinder is closed after the throttle opening is switched to the third opening during execution of the stop position control; and an adjustment unit that maintains the second opening when the intake manifold pressure is within an allowable range with respect to a target value, reduces the second opening compared to when the intake manifold pressure is within the allowable range when the intake manifold pressure is higher than the allowable range, and increases the second opening compared to when the intake manifold pressure is within the allowable range when the intake manifold pressure is lower than the allowable range.

The present invention provides a vehicle control device that suppresses deterioration in the accuracy of the stopping position of an internal combustion engine.

FIG. 1 is a schematic diagram of a hybrid vehicle. FIG. 2 is a schematic diagram of the engine. FIG. 3 is a timing chart showing an example of the stop position control. FIG. 4 is a flowchart showing an example of the throttle opening adjustment control executed by the ECU.

[General configuration of hybrid vehicle]
1 is a schematic diagram of a hybrid vehicle 1. In the hybrid vehicle 1, a K0 clutch 14, a motor 15, a torque converter 18, and a transmission 19 are provided in this order in a power transmission path from an engine 10 to drive wheels 13. The engine 10 and the motor 15 are mounted as a driving power source for the hybrid vehicle 1. The engine 10 is, for example, a V6 gasoline engine, but the number of cylinders is not limited thereto, and may be an in-line gasoline engine or a diesel engine. The K0 clutch 14, the motor 15, the torque converter 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 12.

The K0 clutch 14 is provided between the engine 10 and the motor 15 on the power transmission path. The K0 clutch 14 receives a supply of hydraulic pressure from a released state and enters an engaged state, connecting the power transmission between the engine 10 and the motor 15. The K0 clutch 14 enters a released state in response to the cessation of the hydraulic pressure supply and cuts off the power transmission between the engine 10 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 10 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 10 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 the ECU 100 described below, and converts the DC voltage from the battery 16 to an AC voltage, or converts the AC voltage from the motor 15 to a DC voltage. In the case of power running in which the motor 15 outputs torque, the inverter 17 converts the DC voltage of the battery 16 to an AC voltage and adjusts the power supplied to the motor 15. In the case of regenerative running in which the motor 15 generates power, the inverter 17 converts the AC voltage from the motor 15 to a DC voltage and adjusts the power supplied to the battery 16.

The torque converter 18 is a fluid coupling with a torque amplification function. The transmission 19 is a stepped automatic transmission that switches 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. The transmission 19 is provided between the motor 15 and the drive wheels 13 on the power transmission path. The motor 15 and the transmission 19 are connected via the torque converter 18. The torque converter 18 is provided with a lock-up clutch 20 that receives a supply of 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 torque converter 18, the transmission 19, and the lock-up clutch 20 via the hydraulic control mechanism 22. The hydraulic control mechanism 22 is provided with hydraulic circuits for the K0 clutch 14, the torque converter 18, the transmission 19, and the lock-up clutch 20, and various hydraulic control valves for controlling their operating hydraulic pressures. A wet clutch may be provided instead of the torque converter 18.

The hybrid vehicle 1 is provided with an ECU (Electronic Control Unit) 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 is an example of a vehicle control device, and functionally realizes a control unit, an acquisition unit, and an adjustment unit, which will be described in detail later.

The ECU 100 controls the operation of the engine 10 and the motor 15. Specifically, the ECU 100 controls the torque and rotation speed of the engine 10 by controlling the throttle opening, ignition timing, and fuel injection amount of the engine 10. 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 lock-up clutch 20, and the transmission 19 through the control of the hydraulic control mechanism 22.

The ECU 100 receives signals from an ignition switch 71, a crank angle sensor 72, a motor speed sensor 73, an accelerator opening sensor 74, an air flow meter 75, a pressure sensor 76, and a water temperature sensor 77. The crank angle sensor 72 detects the rotation speed of the crankshaft of the engine 10. The motor speed sensor 73 detects the rotation speed of the output shaft of the motor 15. The accelerator opening sensor 74 detects the accelerator pedal opening, which is the amount of depression of the accelerator pedal by the driver. The air flow meter 75 detects the amount of intake air of the engine 10. The pressure sensor 76 detects the pressure in the intake passage 37 downstream of the throttle valve 40 (described later) (hereinafter referred to as the intake manifold pressure). The water temperature sensor 77 detects the temperature of the cooling water of the engine 10.

The ECU 100 runs the hybrid vehicle in either the motor mode or the hybrid mode. In the motor mode, the ECU 100 releases the K0 clutch 14 and runs the vehicle using the power of the motor 15. In the hybrid mode, the ECU 100 switches the K0 clutch 14 to an engaged state and runs the vehicle using at least the power of the engine 10. The hybrid mode includes a mode in which the vehicle runs using only the power of the engine 10, and a mode in which the motor 15 is powered and the vehicle runs using both the engine 10 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 state of charge of the battery 16. For example, when the required driving force is relatively small and the SOC (State of Charge), which indicates the amount of charge stored in the battery 16, is relatively high, the motor mode, in which the engine 10 is stopped, is selected to improve fuel efficiency. When the required driving force is relatively large or the SOC of the battery 16 is relatively low, the hybrid mode, in which the engine 10 is driven, is selected.

The ECU 100 executes intermittent operation control to automatically stop the engine 10 when a predetermined stop condition is satisfied, and to restart the automatically stopped engine 10 when a predetermined restart condition is satisfied. For example, when the accelerator opening becomes zero in the hybrid mode, the ECU 100 automatically stops the engine 10 as the automatic stop condition is satisfied. Also, when the accelerator opening becomes greater than zero, the ECU 100 automatically restarts the engine 10 as the restart condition is satisfied. In the case of automatic stop, the ECU 100 releases the K0 clutch 14 to stop combustion. In the case of automatic restart, the ECU 100 cranks the engine 10 by the motor 15 via the K0 clutch 14 to start combustion, and then engages the K0 clutch 14. Also, when the engine 10 is automatically stopped and combustion is stopped during coasting, if the accelerator opening increases again and the restart condition is satisfied, combustion starts and the K0 clutch 14 is engaged.

[General configuration of engine]
Fig. 2 is a schematic diagram of the engine 10. The engine 10 has cylinders 30, pistons 31, connecting rods 32, a crankshaft 33, an intake passage 35, an intake valve 36, an exhaust passage 37, and an exhaust valve 38. Only one of the multiple cylinders 30 of the engine 10 is shown in Fig. 2. An air-fuel mixture is burned in the cylinder 30. A piston 31 is accommodated in each cylinder 30 so as to be capable of reciprocating, and is connected to a crankshaft 33, which is an output shaft of the engine 10, via a connecting rod 32. The connecting rod 32 converts the reciprocating motion of the piston 31 into the rotational motion of the crankshaft 33.

The intake passage 35 is connected to the intake port of each cylinder 30 via an intake valve 36. The exhaust passage 37 is connected to the exhaust port of each cylinder 30 via an exhaust valve 38. The intake passage 35 is provided with an air flow meter 75, a pressure sensor 76, and a throttle valve 40 that adjusts the amount of intake air. The exhaust passage 37 is provided with a catalyst 43 for purifying exhaust gas.

Each cylinder 30 is provided with an in-cylinder injection valve 41. The in-cylinder injection valve 41 injects fuel directly into the cylinder 30. Note that instead of or in addition to the in-cylinder injection valve 41, a port injection valve that injects fuel toward the intake port may be provided. Each cylinder 30 is provided with an ignition device 42 that ignites a mixture of the intake air introduced through the intake passage 35 and the fuel injected by the in-cylinder injection valve 41 by spark discharge.

[Engine stop position control]
When the engine 10 is automatically stopped, a stop position control is executed to control the stop position of the engine 10 by temporarily increasing the throttle opening. By setting the stop position of the engine 10 to a desired stop position, the cranking torque of the engine 10 required of the motor 15 when restarting the engine 10 can be reduced. Therefore, for example, when restarting the engine 10 while traveling in the motor mode, the portion of the output torque of the motor 15 consumed for cranking torque is suppressed. This makes it possible to secure the torque consumed for traveling of the hybrid vehicle 1 out of the output torque of the motor 15, and to secure an operating range in which the hybrid vehicle 1 can travel in the motor mode, thereby improving fuel efficiency.

Figure 3 is a timing chart showing an example of the stop position control of the engine 10. Figure 3 shows the transition of the engine speed [rpm], the throttle opening [deg], and the intake manifold pressure [kPa]. The combustion of the engine 10 is stopped, and the throttle opening is controlled to the first opening A1 (hereinafter referred to as the opening A1) to reduce the engine speed (time t1). The opening A1 is a value close to 0 and may be 0. Next, at a predetermined timing, the throttle opening is switched from the opening A1 to the second opening A2 (hereinafter referred to as the opening A2) (time t2), and the throttle opening is maintained at the opening A2 for a predetermined time. The opening A2 is a value closer to the maximum opening than 0. Next, the throttle opening is switched from the opening A2 to the third opening A3 (hereinafter referred to as the opening A3) (time t3). The opening A3 is a value close to 0 and may be 0. This temporary increase in the throttle opening introduces intake air into the intake passage 35 downstream of the throttle valve 40, and the intake manifold pressure increases to the target intake manifold pressure (time t4). The target intake manifold pressure is a target value of the intake manifold pressure suitable for stopping the engine 10.

Next, the intake valve 36 of the cylinder 30 on the intake stroke closes, filling the cylinder 30 with some of the intake air introduced downstream of the throttle valve 40 (time t5). The intake valve 36 of the cylinder 30 on the intake stroke closes, filling the cylinder 30 with some of the intake air (time t6). After that, the piston 31 of the cylinder 30 that was first filled with intake air is in the expansion stroke, and the piston 31 of the cylinder 30 that was next filled with intake air is in the compression stroke, and the rotation of the engine 10 stops (time t7). After that, the intake manifold pressure returns to atmospheric pressure (time t8).

In this way, the engine 10 stops at a position where the compression reaction forces of the intake air filled in the two cylinders 30 are balanced. This allows the engine 10 to start combustion in the cylinder 30 where the piston 31 stopped during the compression stroke when restarting the engine 10, ensuring restartability. Stop position control is an example of a process executed by the control unit.

[Throttle opening control]
4 is a flow chart showing an example of the throttle opening adjustment 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 or not the stop position control of the engine 10 is being executed (step S1). If the answer is No in step S1, this control ends.

If the answer is Yes in step S1, the ECU 100 acquires the intake manifold pressure for each cylinder 30 at the timing when the intake valve 36 of each cylinder 30 is closed (step S2). The higher the intake manifold pressure is at the timing when the intake valve 36 is closed, the greater the intake air charge amount in the cylinder 30 having that intake valve 36. Therefore, by grasping the intake manifold pressure at the timing when the intake valve 36 of each cylinder 30 is closed, it is possible to grasp the intake air charge amount of each cylinder 30 during execution of the stop position control.

Next, the ECU 100 determines whether the stop position control has ended, i.e., whether the rotation of the engine 10 has stopped (step S3). If the answer is No in step S3, step S2 continues. That is, since the engine 10 in this embodiment is a six-cylinder engine, the ECU 100 always acquires and updates the intake manifold pressure for all six cylinders while the stop position control is being executed. Step S2 is an example of a process executed by the acquisition unit.

If the answer is Yes in step S3, the ECU 100 determines whether the maximum value of the acquired intake manifold pressures for the six cylinders is higher than the target intake manifold pressure and whether the maximum value is higher than a predetermined value compared to the target intake manifold pressure (step S4). The maximum value of the intake manifold pressure means the maximum amount of intake air charged in each cylinder 30. The predetermined value in step S4 is the upper limit of the allowable range that does not affect the accuracy of the stopping position of the engine 10 when the maximum value is higher than the intake manifold pressure. If the answer is Yes in step S4, the ECU 100 assumes that the above-mentioned maximum value is too high compared to the target intake manifold pressure, and adds "1" to the HI counter value and subtracts "1" from the LO counter value (step S5).

If the answer is No in step S4, it is determined whether the above-mentioned maximum value is lower than the target intake manifold pressure and whether the maximum value is lower than a predetermined value compared to the target intake manifold pressure (step S6). The predetermined value in step S6 is the upper limit of the allowable range that does not affect the accuracy of the stopping position of the engine 10 when the maximum value is lower than the intake manifold pressure. If the answer is Yes in step S6, the maximum value is deemed to be too low compared to the target intake manifold pressure, and the ECU 100 subtracts "1" from the HI counter value and adds "1" to the LO counter value (step S7). If the answer is No in step S6, this control is terminated. That is, in steps S4 and S6, it is determined whether the maximum value is outside the allowable range for the target intake manifold pressure.

Next, the ECU 100 judges whether the HI counter value is equal to or greater than a predetermined value (step S8). If the answer is Yes in step S8, the ECU 100 learns the opening obtained by subtracting a predetermined small opening ΔA2 from the opening A2 as a new opening A2 (step S9). If the answer is No in step S8, the ECU 100 judges whether the LO counter value is equal to or greater than a predetermined value (step S10). If the answer is Yes in step S10, the ECU 100 learns the opening obtained by adding the small opening ΔA2 to the opening A2 as a new opening A2 (step S11). Steps S9 and S11 are an example of a process executed by the adjustment unit. Note that the small opening ΔA2 when decreasing the opening A2 and the small opening ΔA2 when increasing the opening A2 may be the same opening or different openings. If the answer is No in step S10, the control is terminated. That is, if the answer is No in step S10, the opening degree A2 is assumed to be set to an appropriate opening degree, so the opening degree A2 is maintained at the current opening degree and no adjustment is made. Similarly, if the answer is No in step S6, the opening degree A2 is assumed to be an appropriate opening degree and no adjustment is made.

As described above, if the maximum value of the intake manifold pressure at the timing when the intake valve 36 is closed is within an allowable range for the target intake manifold pressure, the opening degree A2 is maintained at the current opening degree, and if the maximum value is too high for the target intake manifold pressure, the opening degree A2 is adjusted to the decreasing side, and if it is too low, the opening degree A2 is adjusted to the increasing side. This makes it possible to adjust the opening degree A2 in response to variations in the control accuracy of the throttle opening degree and aging of the throttle valve 40, and to fill the desired cylinder with the desired amount of intake air. As a result, it is possible to suppress deterioration in the accuracy of the stop position of the engine 10.

In the above embodiment, the intake manifold pressure is acquired for each cylinder 30 when the intake valve 36 is closed during execution of the stop position control, and the maximum value of the acquired intake manifold pressure is compared with the target intake manifold pressure. Here, the intake manifold pressure increases with a delay after the throttle opening is switched from the opening A2 to the opening A3. Therefore, the maximum value of the acquired intake manifold pressure is the intake manifold pressure after the throttle opening is switched to the opening A3. Therefore, instead of the maximum value described above, for example, the intake manifold pressure at the timing when the intake valve 36 closes for the first time after the throttle opening is switched to the opening A3 may be compared with the target intake manifold pressure. Also, the intake manifold pressure at the timing when the intake valve 36 closes for the second time after the throttle opening is switched to the opening A3 may be compared with the target intake manifold pressure. Also, the intake manifold pressure at the timing when the intake valve 36 closes after the throttle opening is switched to the opening A3 may be acquired for each cylinder, and the maximum value of the acquired intake manifold pressure may be compared with the target intake manifold pressure.

The respective predetermined values in steps S4 and S6 may be the same or different. The increments and decrements for each counter value in steps S5 and S7 are all the same value, but are not limited to this and may be partially or entirely different. The respective predetermined values in steps S8 and S10 may be the same or different.

In the above embodiment, a hybrid vehicle is controlled by a single ECU 100, but this is not limited to the above. For example, the above-mentioned control may be performed by multiple ECUs, such as an engine ECU that controls the engine 10, a motor ECU that controls the motor 15, and a clutch ECU that controls the K0 clutch 14.

In the above embodiment, the hybrid vehicle 1 has been described as an example, but the invention is not limited to this. For example, the stop position control of this embodiment can also be applied to an engine vehicle that is provided with only an engine as a driving power source and in which the engine is automatically stopped and automatically restarted by an idling stop function.

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.

1 Hybrid vehicle (vehicle)
10. Engine (internal combustion engine)
15 Motor 40 Throttle valve 100 ECU (control unit, acquisition unit, adjustment unit)

Claims (1)

In a control device for a vehicle equipped with an internal combustion engine as a driving power source,
a control unit that executes a stop position control of the internal combustion engine by switching a throttle opening from a first opening to a second opening larger than the first opening and switching the throttle opening from the second opening to a third opening smaller than the second opening during inertial rotation in which combustion has stopped upon automatic stop of the internal combustion engine;
an acquisition unit that acquires an intake manifold pressure that is a pressure in an intake passage downstream of a throttle valve at a timing when an intake valve of any cylinder is closed after the throttle valve opening is switched to the third opening during execution of the stop position control;
and an adjustment unit that maintains the second opening degree when the intake manifold pressure is within an acceptable range with respect to a target value, reduces the second opening degree when the intake manifold pressure is higher than the acceptable range, compared to when the intake manifold pressure is within the acceptable range, and increases the second opening degree when the intake manifold pressure is lower than the acceptable range, compared to when the intake manifold pressure is within the acceptable range.

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