JP6756198B2 - Vehicle control method and vehicle control device - Google Patents

Description

The present invention relates to a vehicle control method and a vehicle control device that automatically stop the engine during traveling and contribute to improvement of fuel efficiency.

Patent Document 1 discloses a technique for automatically stopping an engine when a predetermined condition is satisfied during traveling. In this publication, when the brake is operated using the negative pressure, the negative pressure cannot be obtained while the engine is stopped. Therefore, the negative pressure pump is operated to secure the negative pressure, or the accumulator stores the negative pressure. By doing so, the braking system is operating.

Japanese Unexamined Patent Publication No. 7-266932

However, the technique of Patent Document 1 has a problem that a negative pressure pump and an accumulator must be provided, which causes an increase in cost.
An object of the present invention is to provide a vehicle control method capable of ensuring braking force without using an actuator for ensuring negative pressure even if the engine is automatically stopped during traveling.

In order to achieve the above object, in the vehicle control method of the present invention, while the engine is automatically stopped, an engine restart process is performed in which the engine is cranked and fuel injection is restarted in accordance with the driver's brake pedal operation. when it is determined that it can not restart the engine ends the engine restart process, while the brake pedal operation is, it was decided to continue the cranking of the engine.

Therefore, the negative pressure of the engine can be secured by cranking, and the braking force can be secured without providing an actuator or the like.

It is a system diagram of the vehicle to which the engine automatic stop control of Example 1 was applied. It is a control block diagram which performs the engine automatic stop control of Example 1. FIG. It is a flowchart which shows the cranking process after the engine restart of Example 1. FIG. It is a flowchart which shows the engine restart determination process of Example 1.

[Example 1]
FIG. 1 is a system diagram of a vehicle to which the automatic engine stop control of the first embodiment is applied. In the vehicle, the rotation output from the engine 1 which is an internal combustion engine is input to the belt-type continuously variable transmission 3 via the clutch 2. The rotation shifted by the belt-type continuously variable transmission 3 is transmitted to the drive wheels 10 via the final gear or the like. The engine 1 includes a starter generator 11 (hereinafter, referred to as SSG 11) that functions as a starter motor and also a generator, a battery 12 that transmits and receives electric power between the SSG 11, and intake air of the engine 1. It has a throttle valve 13 for controlling the amount. An oil pump 4 is provided on the output shaft of the engine 1, and the belt-type continuously variable transmission 3 is controlled by the hydraulic pressure of the oil pump 4. An electric oil pump or the like may be provided, and the present invention is not particularly limited.

A master back 6 that assists the brake pedal operating force by using the negative pressure of the engine 1 is connected to the brake pedal 5. The master back 6 is connected to the cylinder chamber side of the throttle valve 13 of the engine 1 by a pipe, and supplies the negative pressure generated by the piston movement of the engine 1 to the master back 6. A master cylinder 7 that supplies wheel cylinder pressure is connected to the master back 6. The master cylinder 7 is connected to the wheel cylinder 9 of each wheel via a brake control unit 8 that performs anti-lock brake control, vehicle behavior stabilization control, and the like. The brake control unit 8 has a pump motor and various solenoid valves, and is configured to be able to drive the pump motor and supply brake fluid pressure to the wheel cylinder 9 regardless of the driver's brake pedal operation state. ..

FIG. 2 is a control block diagram for performing automatic engine stop control according to the first embodiment. The vehicle is provided with an automatic transmission control unit C1 (hereinafter, also referred to as ATCU) that controls the engaged state of the clutch 2 and the shifting state of the belt-type continuously variable transmission 3, the operating state of the engine 1, and the passenger compartment. It has an engine control unit C2 (hereinafter, also referred to as an ECU) that controls the lighting state of the warning lamp 30, and an SSG control unit C3 (hereinafter, also referred to as SSGCU) that controls the operating state of the SSG11.

The vehicle includes a turbine sensor 21 that detects the turbine rotation speed (hereinafter, also referred to as Nt), which is the engine-side rotation speed of the clutch 2, and a vehicle speed sensor 22 that detects the vehicle speed (hereinafter, also referred to as VSP). An accelerator opening sensor 23 that detects the accelerator pedal opening (hereinafter, also referred to as APO), a brake switch 24 that detects whether or not the brake pedal 5 is depressed, and an engine rotation speed that detects the engine speed Ne. It has a sensor 25 and an SOC sensor 26 that detects the charging state SOC of the battery 12. In addition to the above sensors, a crank angle sensor that detects the engine crank angle, a cam angle sensor that detects the cam shaft rotation angle, a hydraulic sensor that detects various control hydraulic voltages supplied to the belt-type stepless transmission 3, and SSG11. It further has a current sensor for detecting a current value, a voltage sensor for detecting a voltage value of SSG11, and the like.

The detection signals of various sensors are supplied to each control unit. Each control unit is connected by a CAN communication line so that control information can be transmitted and received to each other. Therefore, among the various sensors, for example, the accelerator opening sensor 23 and the engine speed sensor 25 may be transmitted to the ECU and supplied from the ECU to another control unit, and is not particularly limited.

Next, the engine automatic stop control will be described. The ECU has an engine automatic stop control unit that automatically stops the engine 1 when a predetermined condition is satisfied while the ignition switch is on. Specifically, when the VSP is equal to or higher than the predetermined vehicle speed representing a relatively high vehicle speed, the APO is equal to or lower than the predetermined value representing 0, and the brake switch 24 is OFF, the clutch 2 is released and the fuel injection is stopped. .. As a result, when it is determined that the driver desires coasting, the engine friction is reduced to secure the coasting distance, and the fuel injection to the engine 1 is stopped to improve the fuel efficiency. In other words, when the engine automatic stop control is performed, the engine speed becomes zero. Therefore, when the engine restart request is made, the SSG 11 performs engine cranking, and then restarts fuel injection and ignites.

On the other hand, in a general vehicle having a clutch 2, only fuel injection is stopped without releasing the clutch 2. As a result, the rotation of the drive wheels 10 is transmitted to the engine 1 to suppress a decrease in the engine speed. Then, as the VSP decreases, Ne decreases, and when the fuel injection recover speed is reached, the fuel injection is restarted, so that the engine is restarted without cranking. That is, in a general vehicle, cranking is not required when restarting fuel injection, which is different from the automatic engine stop control of the first embodiment.

When the engine automatic stop command is output by the engine automatic stop control, the engine 1 is stopped and the engine is in an inertial running state. At this time, in the vehicle braking system, a booster assist that assists the brake pedal pedaling force is provided by the master back 6 that uses the negative pressure of the engine 1. Therefore, when the engine 1 is stopped, negative pressure cannot be generated. Therefore, if the driver repeatedly operates the brake pedal 5 while the engine 1 is stopped, the negative pressure may be insufficient to provide sufficient boosting assistance. is there. Therefore, in the automatic engine stop control, after the engine is automatically stopped, the driver operates the brake pedal 5, specifically, when the brake switch 24 is turned on, the engine restart process is performed. The engine restart process is to make the SSG11 function as a starter motor to perform cranking, raise Ne to a predetermined number of revolutions, restart fuel injection, and start ignition to make the engine 1 capable of autonomous rotation. It is a process.

Here, even if the engine restart process is performed, the engine 1 may not necessarily restart. If the driver repeatedly depresses the brake pedal 5 in this state, the negative pressure may be insufficient. Therefore, in the first embodiment, if the engine 1 does not restart even if the engine restart process is performed, the cranking process for continuing the cranking is performed to secure the negative pressure.

FIG. 3 is a flowchart showing a cranking process after restarting the engine according to the first embodiment. This flow is a process performed after the engine is automatically stopped by the engine automatic stop control, and when the brake switch 24 is turned on, the engine restart process is automatically performed.
In step S1, it is determined whether or not the brake switch 24 is ON, and if it is ON, the process proceeds to step S2, and otherwise, this control flow is terminated.
In step S2, an engine restart determination process for determining whether or not the engine 1 has been restarted by the engine restart process is performed. Details will be described later.
In step S3, it is determined whether or not the engine 1 is operating, and when it is determined that the engine is operating, this control flow is terminated and the brake operation is performed by boosting assistance using normal negative pressure. Is done. On the other hand, when it is determined that the engine cannot be started, the process proceeds to step S4.

In step S4, it is determined whether or not the VSP is the predetermined vehicle speed VSP1 or more, and if it is determined that the VSP is VSP1 or more, the process proceeds to step S5, and if not, the process proceeds to step S6. Here, VSP1 represents a vehicle speed at which the engine 1 can be sufficiently cranked by the inertia of the vehicle when the clutch 2 is engaged. This value is a value determined in advance for each vehicle type in consideration of inertia and the like.
In step S5, the clutch 2 is engaged, and the engine 1 is forcibly cranked by the inertial torque of the vehicle transmitted from the drive wheels 10 to secure the negative pressure.

In step S6, it is determined whether or not the SOC is a predetermined value SOC1 or more, and if it is SOC1 or more, the process proceeds to step S7, and if not, the process proceeds to step S8. Here, SOC1 represents a charge amount capable of supplying driving energy of SSG11 which is a negative pressure sufficient for decelerating the vehicle by cranking. This value is appropriately set according to engine friction, vehicle inertia, deceleration required by the driver, and the like. This arithmetic processing is performed in parallel not only in the ECU but also in the SSGCU, and each arithmetic result is shared. Therefore, the determination can be made with higher accuracy than the case where the determination is made by one control unit. ..
In step S7, the engine 1 is forcibly cranked by the SSG 11 to secure a negative pressure.

In step S8, the warning lamp 30 is turned on and a warning is displayed to the driver. That is, it becomes difficult to secure the negative pressure, and there is a possibility that the braking force assisted by the boosting force cannot be generated according to the driver's operation of the brake pedal.

In step S9, it is determined whether or not the vehicle is decelerating, and if the vehicle is decelerating, the process proceeds to step S10 to end the control flow. This is because it can be stopped if it is decelerating. On the other hand, when the vehicle is not decelerating, the process proceeds to step S11. Whether or not the vehicle is decelerating may be determined by using, for example, a differential value of the vehicle speed, or using a G sensor or the like (not shown). Further, the threshold value for determining whether or not the vehicle is decelerating may be a preset value or may be set according to the driver's brake pedal operation amount.
In step S11, the vehicle is stopped by using the electric brake by the brake control unit 8. Specifically, the pump motor of the brake control unit 8 is driven, the solenoid valve is shut off so that the pump discharge pressure does not flow to the master cylinder 7 side, and the pump discharge pressure is supplied to the wheel cylinder 9 side. As a result, a braking force is generated to stop the vehicle.

FIG. 4 is a flowchart showing the engine restart determination process of the first embodiment. This control process is a process performed in step S2 of the cranking process shown in FIG. 3, and is calculated in parallel in the ATCU.
In step S21, it is determined whether or not there is an engine restart request, and if there is an engine restart request, the process proceeds to step S22, and if not, this step is repeated.
In step S22, the fastening hydraulic pressure L / Up required for engaging the clutch 2 is confirmed.
In step S23, a predetermined turbine speed required at restart is calculated based on the fastening hydraulic pressure L / Up. Since the oil pump 4 discharges hydraulic pressure according to the turbine rotation speed, it is determined that the engine has been restarted if the turbine rotation speed corresponding to the oil pump discharge pressure required for engaging the clutch 2 is obtained. Because there is no problem.
In step S24, the turbine speed Nt is detected.
In step S25, it is determined whether or not Nt is larger than the predetermined turbine speed, and if it is larger than the predetermined turbine speed, the process proceeds to step S26 to determine that the engine 1 has been operated. On the other hand, when the turbine speed is equal to or lower than the predetermined turbine speed, the process proceeds to step S27, the engine restart fails, and it is determined that the engine 1 cannot be started.

Next, the action will be described. First, when the brake switch 24 is turned on during the automatic engine stop control, the engine restart process is executed. At this time, the engine start determination can be performed more accurately by determining in detail whether or not the engine 1 has restarted in the ATCU.
When the engine restart fails, it is first determined whether or not the VSP is VSP1 or higher, and when it is determined that the VSP is VSP1 or higher, the clutch 2 is engaged. As a result, cranking can be reliably performed. Next, when VSP is less than VSP1 and SOC is SOC1 or more, cranking is forcibly performed by SSG11. As a result, negative pressure can be secured and stable braking force can be secured. If the SOC is less than SOC 1, the negative pressure cannot be secured, so the brake control unit 8 operates the electric brake to stop the vehicle. As a result, the vehicle can be stopped stably even when the engine cannot be restarted after the automatic engine stop control is performed.

As described above, in Example 1, the following effects can be obtained.
(1) It has a master back 6 that assists the brake pedal operating force by using the negative pressure of the engine 1, and releases the clutch 2 between the engine 1 and the drive wheels 10 during running to automatically stop the engine 1. In the vehicle control method, when the engine 1 is automatically stopped, the engine 1 is restarted according to the driver's brake pedal operation, it is determined whether or not the engine 1 can be restarted, and the engine 1 cannot be restarted. When the determination is made, the cranking of the engine 1 is continued.
Therefore, the negative pressure of the engine 1 can be secured by cranking, and the braking force can be secured without providing an actuator or the like.

(2) When VSP is VSP1 or higher, the clutch 2 is engaged and cranking is continued. Therefore, cranking can be performed using the inertial torque of the vehicle, and negative pressure can be secured.
(3) When the SOC (storage amount) of the battery 12 that supplies power to the SSG 11 (starter motor) is SOC 1 (predetermined value) or more, the SSG 11 is driven to continue cranking. Therefore, cranking can be performed using battery power, and negative pressure can be secured.

(4) The wheel has a brake control unit 8 (brake fluid pressure generator) that generates a braking force, and when a predetermined deceleration cannot be obtained by cranking, the brake control unit 8 generates a braking force.
Therefore, the vehicle can be reliably stopped even when negative pressure cannot be obtained.
(5) Whether or not the engine 1 has been restarted is determined by both the ECU (controller that controls the engine) and ATCU (controller that controls the clutch). Therefore, the engine restart determination can be made with higher accuracy, and the braking force can be stably secured.

[Other Examples]
Although the present invention has been described above based on the examples, the specific configuration may be another configuration. For example, in the first embodiment, when the engine restart determination is performed, the determination based on the turbine speed is performed in the ATCU. For example, in the SSGCU, the torque at the time of cranking the SSG11 changes from the power running torque to the regenerative torque. It may be determined whether or not it has been done. If the engine 1 rotates independently, the SSG 11 is driven by the engine 1, so that a more accurate engine restart determination can be made. Further, in the ECU, the engine start determination may be made based on the crank angle detected by the crank angle sensor and the cam angle. Further, in the ATCU, an engine start determination may be made based on whether or not various hydraulic pressures are appropriately supplied by using a hydraulic pressure sensor or the like provided in the hydraulic pressure circuit.

In this way, when the engine restart determination is executed in parallel in the plurality of control units and it is determined that the engine 1 cannot be started in any one of them, it is determined that the engine 1 cannot be started. May be good. As a result, it is possible to shift to the control for securing the negative pressure and the control for generating the brake fluid pressure when the negative pressure cannot be secured, and the vehicle can be stopped stably.

In the first embodiment, an example in which the belt type continuously variable transmission 3 is adopted as the transmission is shown, but a transmission of another type may be used. Further, the clutch 2 of the first embodiment may be a lockup clutch provided in the torque converter or a start clutch in the transmission. Further, in the first embodiment, SSG is shown as a starter motor, but a starter motor having only a function as a starter may be used, or both may be provided.

1 Engine 2 Clutch 3 Belt type continuously variable transmission 4 Oil pump 5 Brake pedal 6 Master back 7 Master cylinder 8 Brake control unit 9 Wheel cylinder 10 Drive wheel 11 Motor generator (SSG)
12 Battery 13 Throttle bulb 30 Warning lamp C1 Automatic transmission control unit (ATCU)
C2 engine control unit (ECU)
C3 SSG control unit (SSGCU)

Claims (7)

It has a master back that assists the brake pedal operating force using the negative pressure of the engine, and when a predetermined condition is met during driving, the clutch between the engine and the drive wheels is released to automatically activate the engine. In the control method of the stopped vehicle
While the engine is automatically stopped, an engine restart process is performed in which the engine is cranked and fuel injection is restarted in accordance with the driver's brake pedal operation.
Judging whether the engine could be restarted,
A vehicle control method, characterized in that when it is determined that the engine cannot be restarted, the engine restart process is terminated and cranking of the engine is continued while the brake pedal is being operated. In the vehicle control method according to claim 1,
A vehicle control method, characterized in that when the vehicle speed is equal to or higher than a predetermined vehicle speed, the clutch is engaged to continue the cranking. In the vehicle control method according to claim 1 or 2.
A vehicle control method, characterized in that when the amount of electricity stored in a battery that supplies electric power to a starter motor is equal to or greater than a predetermined value, the starter motor is driven to continue the cranking. In the vehicle control method according to any one of claims 1 to 3,
It has a brake fluid pressure generator that generates braking force on the wheels.
A vehicle control method, characterized in that a braking force is generated by the brake fluid pressure generator when a predetermined deceleration cannot be obtained by the cranking. In the vehicle control method according to any one of claims 1 to 4.
A vehicle control method, wherein determining whether or not the engine has been restarted is performed by both a controller that controls the engine and a controller that controls the clutch. In the vehicle control method according to claim 3,
A vehicle control method, wherein determining whether or not the engine has been restarted is performed by each of a controller that controls the engine, a controller that controls the clutch, and a controller that controls the starter motor. A master back that uses the negative pressure of the engine to assist the brake pedal operating force,
A first control unit that automatically stops the engine by releasing the clutch between the engine and the drive wheels during traveling.
While the engine is automatically stopped, a second control unit that performs an engine restart process that cranks the engine and restarts fuel injection according to the driver's brake pedal operation.
It is determined whether or not the engine can be restarted, and when it is determined that the engine cannot be restarted, the engine restart process is terminated and the engine is cranked while the brake pedal is being operated. With the third control unit that continues,
A vehicle control device characterized by being equipped with.

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