JP7020842B2 - Brake control device - Google Patents

Description

The present invention relates to a brake control device that performs brake hold control that automatically holds a braking force when the vehicle stops.

When the vehicle is stopped by the brake operation while the vehicle is running, the braking force is maintained as it is in the vehicle that performs the brake hold control. The vehicle remains stationary even when the brake pedal is released. By operating the brake pedal, the wheel cylinder hydraulic pressure of the wheel cylinders of each wheel increases according to the brake hydraulic pressure generated from the master cylinder, and braking force is generated. When the brake control device that performs brake hold control closes the valve provided between the master cylinder and the wheel cylinder, the wheel cylinder hydraulic pressure is held and the braking force is held.

If the idle stop system is installed, the engine will stop when the vehicle is stopped. In the idle stop system, the engine restarts when a predetermined operation is performed during the idle stop. For example, when you take your foot off the brake pedal, the engine restarts. When the engine restarts, driving force is generated and the vehicle tries to start. Patent Document 1 describes that in a vehicle provided with an idle stop system, the engine is not restarted even if the operation of the brake pedal is released during the brake hold. In this case, no driving force is generated in the vehicle.

Japanese Unexamined Patent Publication No. 2015-11803

After a certain period of time has passed since the engine was stopped by idle stop, the engine restarts without performing a predetermined operation. During this fixed period of time, the brake fluid gradually leaks from the valve. The wheel cylinder hydraulic pressure gradually decreases, and the braking force also decreases. Here, when the engine is restarted after a certain period of time, a driving force is generated by the creep torque. If the driving force exceeds the braking force during the brake hold, the driver may unintentionally start moving the vehicle.

In view of the above, it is an object of the present invention to provide a brake control device capable of suppressing unintended movement of a vehicle when a brake hold and an idle stop are operating at the same time.

The brake control device of the present invention performs brake hold control that automatically holds the braking force when the vehicle equipped with the idle stop system stops, and the engine restart condition is set while the engine is stopped and the brake hold is in progress. If so, the wheel cylinder hydraulic pressure is increased according to the wheel cylinder hydraulic pressure difference between the wheel cylinder hydraulic pressure at that time and the wheel cylinder hydraulic pressure required to stop the movement due to the creep torque when the engine is restarted. Allow the engine to restart.

As a result, the braking force of the brake can be increased at the timing when the idle stop is released. Therefore, since the braking force is higher than the driving force generated when the engine is restarted, the movement of the vehicle can be suppressed.

The brake control device is a wheel cylinder fluid consisting of the wheel cylinder hydraulic pressure when the engine is stopped and the engine restart conditions are met during the brake hold, and the wheel cylinder hydraulic pressure required to stop movement due to creep torque when the engine is started. The pressure increase obtained from the pressure difference is corrected according to the gradient in the front-rear direction of the vehicle, and the wheel cylinder hydraulic pressure is increased.

As a result, the braking force of the brake can be increased according to the condition of the slope when the vehicle is stopped. Therefore, when the vehicle is stopped on a slope, the movement of the vehicle can be suppressed even if the engine is restarted.

The brake control device prohibits idle stop if the wheel cylinder hydraulic pressure after the maximum duration of the brake hold is lower than the wheel cylinder hydraulic pressure required to stop movement by creep torque when the engine is restarted.

If there is a risk that the vehicle will move when the engine is restarted, the vehicle will not move because the engine will not be restarted by prohibiting idle stop.

If the wheel cylinder hydraulic pressure after the maximum duration of the brake hold is lower than the wheel cylinder hydraulic pressure required to stop movement due to creep torque when the engine is restarted, the brake control device will stop the engine and during the brake hold. Exclude steering operation and air conditioner operation from the engine restart conditions in.

As a result, even if the driver performs an unintended operation during the idle stop system, the engine does not restart, so that it is possible to prevent the vehicle from starting to move unknowingly.

According to the present invention, it is possible to suppress the driver's unintended movement of the vehicle during the brake hold. In particular, when idle stop and brake hold are performed at the same time, the braking force is higher than when idle stop is not performed, so that the vehicle is prevented from moving even if the engine restarts and the driving force is generated. can.

Configuration diagram of the brake system according to the embodiment of the present invention Block diagram of brake control device and engine control device The figure which shows the time change of the wheel cylinder hydraulic pressure and the engine speed of 1st Embodiment Flowchart of idle stop control and brake hold control The figure which shows the time change of the wheel cylinder hydraulic pressure and the engine speed of 2nd Embodiment Flowchart of idle stop control and brake hold control

The vehicle according to the embodiment of the present invention includes a brake system that automatically holds a braking force when the vehicle stops. It also has an idle stop system that stops the engine when the vehicle stops.

As shown in FIG. 1, the brake system that operates the hydraulic brake includes a brake booster 2 that amplifies the pedaling force on the brake pedal 1, a master cylinder 3 that generates a brake hydraulic pressure according to the operation of the brake pedal 1, and a brake hydraulic pressure. A wheel cylinder 4 that generates a brake fluid pressure to operate the brake, and a hydraulic pressure control actuator 5 that supplies the brake hydraulic pressure from the master cylinder 3 to each wheel cylinder 4 are provided. The actuator 5 has a normally open opening / closing valve 6 that opens / closes a pipeline to the wheel cylinder 4. The brake system includes a brake control device (brake ECU) 7 that performs brake hold control.

As shown in FIG. 2, when the brake hold switch 10 for starting the brake hold is provided and the brake hold switch 10 is turned on, the brake control device 7 performs the brake hold control. A vehicle speed sensor 11 for detecting the vehicle speed, a pressure sensor 12 for detecting the brake fluid pressure of the master cylinder 3, and an inclination sensor 13 for detecting the slope of the road surface are connected to the brake control device 7, respectively. Then, the brake control device 7 controls the on-off valve 6 and the pressurizing motor 14 that drives the pump that increases the wheel cylinder hydraulic pressure in order to maintain the wheel cylinder hydraulic pressure.

When the brake hold switch 10 is turned on, the brake control device 7 detects that the vehicle has stopped due to the operation of the brake, that is, the vehicle speed has become 0, determines that the operating conditions for the brake hold have been satisfied, and opens and closes the vehicle. Close the valve 6. When the on-off valve 6 is closed, the wheel cylinder hydraulic pressure is held at a predetermined pressure, and brake hold is performed. As a result, even if the foot is taken off from the brake pedal 1, the braking force is maintained and the vehicle is stopped.

When the accelerator pedal 15 is depressed to turn on the accelerator while the brake hold is operating, the brake control device 7 releases the brake hold. The on-off valve 6 is opened, the wheel cylinder hydraulic pressure is reduced, the braking force is reduced, and the vehicle starts. Further, when the predetermined duration elapses, the brake control device 7 releases the brake hold.

The idle stop system includes an engine control device (engine ECU) 20 that performs idle stop control. The engine control device 20 and the brake control device 7 can communicate with each other. When the idle stop switch 21 is turned on, the engine control device 20 performs idle stop control. The engine control device 20 stops the engine 22 when a predetermined operating condition is satisfied. A detection unit 23 is provided to detect the current state of the plurality of operating conditions. The engine control device 20 determines whether or not a predetermined operating condition is satisfied based on the current state information detected by the detection unit 23. When a predetermined operating condition such as the brake pedal 1 being depressed or the access pedal 15 not being depressed is satisfied, the engine control device 20 stops the engine 22 before or when the vehicle is stopped. When the brake hold switch 10 is on, the brake hold is performed at the same time.

During the idle stop, the engine 22 is restarted when a predetermined restart condition is satisfied. The engine control device 20 determines whether or not the predetermined restart condition is satisfied based on the current state information detected by the detection unit 23. When a predetermined restart condition such as the accelerator pedal 15 being stepped on or the steering operation being performed is satisfied, the brake control device 20 restarts the engine 22. Further, when the predetermined duration (3 minutes) has elapsed, the engine control device 20 restarts the engine 22.

When the engine 22 is restarted, the number of revolutions of the engine 22 is increased by cranking, and a driving force due to creep torque is generated. As the number of revolutions of the engine 22 increases, the driving force increases and the vehicle tries to start. When idle stop and brake hold are performed at the same time, if the braking force exceeds the driving force, the movement of the vehicle is blocked.

By the way, when time elapses from the start of the brake hold, the brake fluid leaks from the open / close valve 6, so that the wheel cylinder hydraulic pressure gradually decreases and the braking force decreases. Therefore, as a first embodiment, as shown in FIG. 3, when the engine 22 is stopped and the restart condition of the engine 22 is satisfied during the brake hold, the brake control device 7 has a wheel cylinder hydraulic pressure at that time. The wheel cylinder hydraulic pressure is increased according to the hydraulic pressure difference between the engine and the wheel cylinder hydraulic pressure required to stop the movement due to the creep torque when the engine is restarted. The hydraulic pressure of the wheel cylinder after the pressure increase becomes higher than the predetermined pressure when only the brake hold is performed without performing the idle stop. Then, the brake control device 7 permits the restart of the engine 22 after the pressure increase is completed.

The brake control device 7 calculates the wheel cylinder hydraulic pressure that has decreased with the passage of time when the restart condition is satisfied. For example, the wheel cylinder hydraulic pressure is estimated from the brake fluid pressure detected by the pressure sensor 12. Alternatively, the wheel cylinder hydraulic pressure may be detected directly. Further, the brake control device 7 estimates the wheel cylinder hydraulic pressure required to stop the movement due to the creep torque when the engine 22 is restarted. The creep torque is estimated from the torque converter capacity, engine speed, and gear ratio. Then, the wheel cylinder hydraulic pressure for countering the driving force due to this creep torque is calculated. The wheel cylinder hydraulic pressure required to stop the movement calculated in this way is higher than the wheel cylinder hydraulic pressure that has decreased over time.

Then, the brake control device 7 calculates the hydraulic pressure difference between the latter wheel cylinder hydraulic pressure and the former wheel cylinder hydraulic pressure so that the braking force required to counter the driving force at the time of restart can be obtained. The pressurizing motor 14 is driven so as to increase the pressure by this hydraulic pressure difference, and the wheel cylinder hydraulic pressure is increased. As a result, the minimum required pressure increase is performed, so that the power consumption required for the pressure increase can be reduced.

The timing for increasing the hydraulic pressure in the wheel cylinder is set to the timing when the idle stop is released and before the engine 22 is restarted. If cranking is performed at the time of restart, the voltage drop of the battery may occur and the pressurizing motor 14 may not be driven. Therefore, the engine 22 is restarted after increasing the wheel cylinder hydraulic pressure to increase the braking force. That is, the brake control device 7 permits the restart of the engine 22 after the pressure increase is completed. By increasing the wheel cylinder hydraulic pressure first in this way, a high braking force can be reliably maintained when the engine 22 is restarted.

As shown in FIG. 4, the engine control device 20 checks whether the idle stop operating condition is satisfied based on the current state information from the detection unit 23. Similarly, the brake control device 7 also checks whether the operating condition of the brake hold is satisfied. When each operating condition is satisfied, the engine control device 20 stops the engine 22. The brake control device 7 performs a brake hold.

The engine control device 20 checks whether the restart condition is satisfied based on the current state information from the detection unit 23. When the restart conditions are not met, idle stop and brake hold continue. When the engine control device 20 determines that the restart condition of the engine 22 is satisfied, the engine control device 20 notifies the brake control device 7 of this. The brake control device 7 drives the pressurizing motor 15 accordingly. The hydraulic pressure of the wheel cylinder increases, and the braking force increases. The brake control device 7 notifies the engine control device 20 that the pressure increase has been completed. The engine control device 20 restarts the engine 22. At this time, the braking force is larger than the driving force, so the vehicle does not move.

When the driver steps on the access pedal 15 to start the vehicle, the restart condition of the engine 22 is satisfied and the brake hold is released. The brake control device 7 controls the on-off valve 6 in order to reduce the hydraulic pressure of the wheel cylinder. The on-off valve 6 is opened, the braking force is reduced, the driving force of the engine 22 exceeds the braking force, and the vehicle starts to move.

In this way, by increasing the braking force in preparation for restarting the engine 22, even if the engine 22 is restarted, the braking force of the brake is higher than the force trying to move the vehicle, so that the vehicle starts to move. do not have. Therefore, it is possible to suppress the unintended movement of the vehicle by the driver.

In the brake control device of the second embodiment, when the brake hold is started when the idle stop is performed, the braking force of the brake is applied according to the stop state of the vehicle when the brake hold is performed without the idle stop. By making it higher than the power, the braking force of the brake is increased against the force trying to move the vehicle. As a force for moving the vehicle, in addition to the driving force generated by the creep torque at the time of restarting the engine 22, the driving force is generated in the direction in which the vehicle is lowered due to the slope of the road surface.

Therefore, the brake control device 7 determines the wheel cylinder hydraulic pressure at the time when the engine 22 is stopped and the engine restart conditions are satisfied during the brake hold, and the wheel cylinder hydraulic pressure required to stop the movement due to the creep torque at the time of starting the engine. The pressure increase obtained from the hydraulic pressure difference is corrected according to the gradient in the front-rear direction of the vehicle, and the wheel cylinder hydraulic pressure is increased. The larger the gradient, the larger the pressure increase.

The timing for increasing the wheel cylinder hydraulic pressure is when the brake hold is started. The driving force due to the gradient is generated from the time when the vehicle stops. Therefore, it is preferable to increase the wheel cylinder hydraulic pressure when starting the brake hold. The wheel cylinder hydraulic pressure may be increased when the restart condition of the engine 22 is satisfied, and the engine 22 may be restarted after the pressure increase is completed.

As shown in FIG. 5, the difference between the braking force that opposes the driving force generated when the engine is restarted and the braking force that decreases with the passage of time is the braking force that opposes the driving force generated according to the gradient. Is added, and the braking force is increased. The brake control device 7 corrects the wheel cylinder hydraulic pressure by multiplying the increase in braking force against the driving force at restart + the decrease in braking force by a coefficient according to the gradient, and obtains the increased pressure. calculate. The brake control device 7 drives the pressurizing motor 14 according to the calculated boosting amount to boost the wheel cylinder hydraulic pressure. The pressure increase of the wheel cylinder hydraulic pressure is set in advance according to the gradient, and a hydraulic pressure map for the gradient is created. The brake control device refers to the hydraulic pressure map and determines the boosted amount of the wheel cylinder hydraulic pressure according to the gradient. As a result, it is possible to increase the pressure to the minimum necessary, so that the power consumption required for increasing the pressure can be reduced.

As shown in FIG. 6, the engine control device 20 checks whether the idle stop operating condition is satisfied based on the current state information from the detection unit 23. Similarly, the brake control device 7 also checks whether the operating condition of the brake hold is satisfied. When each operating condition is satisfied, the engine control device 20 stops the engine 22. The brake control device 7 determines the stop state of the vehicle based on the output of the tilt sensor 13. When the vehicle is stopped at a gradient of 0, the braking force that opposes the driving force generated by the gradient is 0. When the vehicle is stopped at a slope, the brake control device 7 increases the wheel cylinder hydraulic pressure including a preset pressure booster according to the slope to increase the braking force and perform brake hold.

The engine control device 20 checks whether the restart condition is satisfied based on the current state information from the detection unit 23. When the restart conditions are not met, idle stop and brake hold continue. When the engine control device 20 determines that the restart condition of the engine 22 is satisfied, the engine control device 20 restarts the engine 22. At the same time, the brake control device 7 releases the brake hold. The on-off valve 6 is opened, the wheel cylinder hydraulic pressure is reduced, and the braking force is reduced. When the driving force of the engine 22 exceeds the braking force, the vehicle starts to move.

In this way, when the vehicle is in a situation where it is easy to move, by increasing the braking force in advance, even if the engine 22 of the vehicle stopped at a slope is restarted, the force to move the vehicle is increased. However, the braking force of the brake is high, so the vehicle does not start moving. Therefore, it is possible to suppress the unintended movement of the vehicle by the driver.

The brake control device of the third embodiment regulates the operation of the idle stop when the vehicle stops. That is, if the wheel cylinder hydraulic pressure after the lapse of the maximum duration of the brake hold is lower than the wheel cylinder hydraulic pressure required to stop the movement due to the creep torque when the engine is restarted, idle stop is prohibited.

When the vehicle stops, the brake control device 7 estimates the wheel cylinder hydraulic pressure after the lapse of the maximum duration of the brake hold, that is, the wheel cylinder hydraulic pressure after decompression. In addition, the wheel cylinder hydraulic pressure is estimated according to the braking force that opposes the driving force due to the creep torque. Then, the brake control device 7 compares the hydraulic pressure of each wheel cylinder.

When the wheel cylinder hydraulic pressure after depressurization is lower than the wheel cylinder hydraulic pressure required to stop the movement, the brake control device 7 instructs the engine control device 20 not to perform idle stop. The engine control device 20 does not perform idle stop even if the operating conditions for idle stop are satisfied. Further, when the wheel cylinder hydraulic pressure after depressurization is equal to or higher than the wheel cylinder hydraulic pressure required to stop the movement, the brake control device 7 permits idle stop and instructs the engine control device 20 to start idle stop. .. The engine control device 20 stops the engine 22.

By prohibiting idle stop when the brake hold is performed in this way, the engine 22 remains in operation during the brake hold. Therefore, the engine 22 is not restarted, and the driving force for moving the vehicle is not generated. Therefore, unintended movement of the vehicle can be suppressed.

In the brake control device 7 of the fourth embodiment, it is prohibited to release the idle stop when an unintended operation is performed. That is, the brake control device 7 stops the engine 22 when the wheel cylinder hydraulic pressure after the lapse of the maximum duration of the brake hold is lower than the wheel cylinder hydraulic pressure required to stop the movement due to the creep torque when the engine 22 is restarted. However, steering operation and air conditioner operation are excluded from the engine restart conditions during brake hold.

When the steering operation is performed during the idle stop, or when the air conditioner is operated such as the air conditioner switch is turned on or the defroster switch is turned on, the brake control device 7 prohibits the restart of the engine 22. Instruct the control device 20. The engine control device 20 does not restart the engine 22 according to the instruction.

Further, when the wheel cylinder hydraulic pressure after depressurization is equal to or higher than the wheel cylinder hydraulic pressure required to stop the movement, the brake control device 7 is operated by the steering operation or the air conditioner, when the engine 22 is operated. Is allowed to restart, and nothing is instructed to the engine control device 20. The engine control device 20 determines that the restart condition is satisfied, and restarts the engine 22.

In this way, even if an unintended operation such as the driver accidentally touching the steering during the idle stop is performed, the engine 22 does not restart, so that the driving force for moving the vehicle is not generated. Therefore, unintended movement of the vehicle can be suppressed.

It should be noted that the present invention is not limited to the above embodiment, and it goes without saying that many modifications and changes can be made to the above embodiment within the scope of the present invention.

1 Brake pedal 3 Master cylinder 4 Wheel cylinder 6 Open / close valve 7 Brake control device 14 Pressurization motor 15 Accelerator pedal 20 Engine control device 22 Engine

Claims (1)

It is a brake control device that performs brake hold control that automatically holds the braking force when the vehicle equipped with the idle stop system stops, and the engine stops when the brake hold is started and the engine is during the brake hold. The boosted pressure obtained from the difference in wheel cylinder hydraulic pressure between the wheel cylinder hydraulic pressure when the restart conditions are met and the wheel cylinder hydraulic pressure required to stop the movement due to creep torque when starting the engine is used as the gradient in the front-rear direction of the vehicle. A brake control device characterized in that the wheel cylinder hydraulic pressure is increased according to the correction.

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