JP7652089B2 - 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, the throttle opening is set to a default value. This means that it is not possible to respond to various requirements, and it may be difficult to apply the stop position control to some vehicles, resulting in low versatility.

The present invention aims to provide a vehicle control device that can perform stop position control with improved versatility.

The above object can be achieved by a control device for a vehicle equipped with an internal combustion engine as a driving power source, the control device comprising: a control unit that executes stop position control of the internal combustion engine by temporarily switching the throttle opening from a first opening to a second opening larger than the first opening and then reducing it below the second opening during inertial rotation in which combustion has stopped upon automatic stopping of the internal combustion engine; an acquisition unit that acquires the rotation speed of the internal combustion engine and the temperature of the internal combustion engine while the stop position control is being executed; and a setting unit that sets the first opening to a larger value the higher the rotation speed of the internal combustion engine and sets the first opening to a larger value the lower the temperature of the internal combustion engine.

The above object can also be achieved by a control device for a 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 temporarily switching a throttle opening from a first opening to a second opening larger than the first opening and then reducing the throttle opening below the second opening during inertial rotation in which combustion has stopped upon automatic stop of the internal combustion engine; an acquisition unit that acquires the internal combustion engine speed before the throttle opening is switched from the first opening to the second opening during execution of the stop position control, an intake manifold pressure that is the pressure in the intake passage downstream of a throttle valve, and a target intake manifold pressure that is a target value of the intake manifold pressure by switching the throttle opening to the second opening; and a setting unit that sets the second opening to a larger value as the internal combustion engine speed is higher, sets the second opening to a larger value as the differential pressure obtained by subtracting the intake manifold pressure from the target intake manifold pressure is larger, and sets the second opening to a larger value as the target intake manifold pressure is higher.

The present invention provides a vehicle control device that can perform stop position control with improved versatility.

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 control in the stop position control executed by the ECU. FIG. 5A is a map that defines the relationship between engine speed and opening degree A1, FIG. 5B is a map that defines the relationship between engine speed and opening degree A2, and FIG. 5C is a map that defines the relationship between target intake manifold pressure and opening degree A2 when the differential pressure is constant.

[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 of 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 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 when the hydraulic pressure supply is stopped, cutting 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 powering operation 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 operation 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 a setting 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 35 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 engine 10 stops rotating (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 combustion to start in the cylinder 30 where the piston 31 stopped during the compression stroke when the engine 10 is restarted, 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 throttle opening control in the stop position 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 step S1 is Yes, ECU 100 determines whether there is a request to switch the throttle opening to opening A2 (step S2). If step S2 is No, ECU 100 acquires the engine speed and the coolant temperature from crank angle sensor 72 and water temperature sensor 77 (step S3). Step S3 is an example of a process executed by the acquisition unit. Next, ECU 100 sets the throttle opening to opening A1 based on the engine speed and the coolant temperature, which will be described in detail later (step S4). Step S4 is an example of a process executed by the setting unit.

If the answer is Yes in step S2, the ECU 100 acquires the engine speed and the intake manifold pressure from the crank angle sensor 72 and the pressure sensor 76, and further acquires the target intake manifold pressure (step S5). Step S5 is an example of a process executed by the acquisition unit. Next, the ECU 100 sets the throttle opening to the opening A2 based on the engine speed, the intake manifold pressure, and the target intake manifold pressure, which will be described in detail later (step S6). Step S6 is an example of a process executed by the setting unit. Next, the ECU 100 determines whether a predetermined time has elapsed since the throttle opening was switched to the opening A2 (step S7). If the answer is No in step S7, the throttle opening is maintained at the opening A2. Thus, while the throttle opening is maintained at the opening A2, step S6 is not executed. This is because the time during which the throttle opening is maintained at the opening A2 in order to fill only two cylinders 30 with intake air is short, and it is difficult to feedback control the throttle opening based on the intake manifold pressure and the target intake manifold pressure during this period.

If the answer is Yes in step S7, the ECU 100 sets the throttle opening to A3 (step S8). In this manner, the throttle opening is controlled during the stop position control.

[How to set the opening degree]
Next, a method for setting the opening degree A1 will be described. The ECU 100 sets the opening degree A1 by referring to the map of FIG. 5A. FIG. 5A is a map that specifies the relationship between the engine speed and the opening degree A1. The horizontal axis indicates the engine speed [rpm], and the vertical axis indicates the opening degree A1 [deg]. As shown in FIG. 5A, the higher the engine speed, the larger the opening degree A1 is set. When the throttle opening is small, the higher the engine speed, the easier it is for the intake manifold pressure to decrease. If the intake manifold pressure is too low, lubricating oil may be sucked into the combustion chamber through the gap between the piston ring and the bore wall surface, and the consumption of lubricating oil may increase. Also, if the intake manifold pressure is too low, when the engine 10 is restarted while the throttle opening degree is set to the opening degree A1, the intake amount may be insufficient, and the restartability of the engine 10 may be reduced. In order to prevent the intake manifold pressure from becoming too low, taking into account such consumption of lubricating oil and the restartability of the engine 10, the opening degree A1 is set to a larger value as the engine speed increases.

Figure 5A also shows the cases when the coolant is low and high. The lower the coolant temperature, the larger the opening A1 is set. If the engine 10 is restarted while the throttle opening is set to opening A1 when the coolant temperature is low, fuel atomization is not promoted, ignition is reduced, and the amount of fuel adhering to the wall surface inside the cylinder 30 increases, which may reduce restartability. In consideration of this restartability of the engine 10, the opening A1 is set to a larger value as the coolant temperature decreases, thereby ensuring the intake volume at the time of restart and increasing the fuel injection volume accordingly, thereby ensuring restartability.

Since the opening degree A1 is set in the above manner, the stop position control of this embodiment can be applied to vehicles that require low lubricant consumption, or vehicles that require high acceleration performance even when restarting while the throttle opening degree is set to opening degree A1. In this way, the versatility of the stop position control of this embodiment is improved. In the above map, the opening degree A1 is defined linearly with respect to the engine speed, but this is not limited to this and it may be defined curvedly. Furthermore, the use of such a map is not limited to the setting of the opening degree A1, and the opening degree A1 may be calculated, for example, by an arithmetic formula with the engine speed and the coolant temperature as arguments.

Next, a method for setting the opening degree A2 will be described. The ECU 100 sets the opening degree A2 by referring to the maps of FIG. 5B and FIG. 5C. FIG. 5B is a map that specifies the relationship between the engine speed and the opening degree A2. The higher the engine speed, the larger the opening degree A2 is set. FIG. 5B also shows cases where the differential pressure between the target intake manifold pressure and the intake manifold pressure is large and small. Here, the intake manifold pressure is the intake manifold pressure detected by the pressure sensor 76 before the throttle opening is switched to the opening degree A2 when there is a request to switch the throttle opening to the opening degree A2, as described above. As shown in FIG. 5B, the larger the differential pressure is, the larger the opening degree A2 is calculated to be. When the throttle opening is constant, the larger the differential pressure is, the longer it takes for the intake manifold pressure to reach the target intake manifold pressure, and there is a risk that the intake air cannot be sufficiently filled into the cylinder, resulting in a decrease in the accuracy of the stop position. For this reason, taking into consideration the accuracy of the stop position, the larger the differential pressure is, the larger the opening degree A2 is set to be.

Figure 5C is a map that specifies the relationship between the target intake manifold pressure and the opening degree A2 when the differential pressure is constant. The higher the target intake manifold pressure, the larger the opening degree A2 is set. The higher the target intake manifold pressure, the closer the target intake manifold pressure is to atmospheric pressure. Even when the differential pressure is the same, the closer the intake manifold pressure is to the target intake manifold pressure, the slower the rate of increase becomes, and it takes time to reach the target intake manifold pressure, which may result in insufficient intake air being filled into the cylinder and reducing the accuracy of the stop position. For this reason, in consideration of the accuracy of the stop position, the higher the target intake manifold pressure, the larger the opening degree A2 is set. Since the opening degree A2 is set as described above, the stop position control of this embodiment can be applied to vehicles in which the cranking torque at the time of restarting the engine 10 is desired to be reduced as much as possible, or to vehicles in which the cranking torque is desired to be a constant value. In this way, the stop position control of this embodiment has improved versatility.

In the above map, the opening degree A2 is defined linearly with respect to the engine speed and the target intake manifold pressure, but this is not limited to this and may be defined as a curve. Furthermore, the use of such a map is not limited to when setting the opening degree A2, and the opening degree A2 may be calculated, for example, by an arithmetic expression using the engine speed, the target intake manifold pressure, and the intake manifold pressure as arguments. As described above, the opening degrees A1 and A2 can be set to meet various requirements.

The opening degree A3 only needs to be small enough to maintain the intake manifold pressure, which has increased due to an increase in the throttle opening degree, at the target intake manifold pressure. For example, the opening degree A3 may be the same value as the opening degree A1, may be a different value, or may be a fixed value.

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, setting unit)

Claims (2)

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 temporarily switching a throttle opening from a first opening to a second opening larger than the first opening and then decreasing the throttle opening to a value lower 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 a rotation speed of the internal combustion engine and a temperature of the internal combustion engine during execution of the stop position control;
a setting unit that sets the first opening degree to a larger value as the rotation speed of the internal combustion engine is higher and sets the first opening degree to a larger value as the temperature of the internal combustion engine is lower. 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 temporarily switching a throttle opening from a first opening to a second opening larger than the first opening and then decreasing the throttle opening to a value lower 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 a rotation speed of the internal combustion engine before the throttle opening is switched from the first opening to the second opening during execution of the stop position control, an intake manifold pressure that is a pressure in an intake passage downstream of a throttle valve, and a target intake manifold pressure that is a target value of the intake manifold pressure by switching the throttle opening to the second opening;
a setting unit that sets the second opening to a larger value as the rotation speed of the internal combustion engine is higher, that sets the second opening to a larger value as the differential pressure obtained by subtracting the intake manifold pressure from the target intake manifold pressure is larger, and that sets the second opening to a larger value as the target intake manifold pressure is higher.

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