JP7370940B2 - Vehicle brake fluid pressure control device - Google Patents

Description

The present invention relates to a vehicle brake fluid pressure control device.

Conventionally, a vehicle brake fluid pressure control device that executes stop-holding control to maintain brake fluid pressure when the vehicle is stopped, for example, reduces the brake fluid pressure when a yaw rate is applied to the vehicle during the stopping-holding control. is known (see Patent Document 1). With this technology, when a vehicle stopped on a slope with a low μ road such as an icy road rotates and slides down, the brake fluid pressure that was maintained decreases, and the wheels are unlocked and the driver can operate the vehicle. It is now possible to rebuild the vehicle.

Special Publication No. 2006-528579

However, if the brake fluid pressure is reduced based only on the yaw rate during the holding control when stopped as in the past, for example, if the yaw rate is applied to a vehicle stopped on a turntable in a multi-level parking lot due to the rotation of the turntable, There was a risk that the brake fluid pressure would drop against the driver's intention.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a brake fluid pressure control device for a vehicle that can suppress a decrease in brake fluid pressure that is contrary to the driver's intention during stop-time holding control.

In order to solve the above-mentioned problems, a vehicle brake fluid pressure control device according to the present invention is a vehicle brake fluid pressure control device that can perform stop-time holding control to maintain brake fluid pressure when it is determined that the vehicle has stopped. The vehicle speed at the time of the brake input was equal to or higher than the specified speed value, the absolute value of the wheel deceleration after the brake input was equal to or higher than the specified deceleration value, and the vehicle was If the first condition including that the amount of lateral behavior of the vehicle is equal to or greater than a specified value is met, the stop-time holding control may be canceled even if there is no operation of an operating member for operating the vehicle. It is characterized by

According to this configuration, when the first condition is satisfied, the vehicle stop holding control is canceled without operating the operating member, so the vehicle stopping holding control can be canceled quickly. Furthermore, when a vehicle is stopped at a turntable, it is generally unlikely that the vehicle will come to a sudden stop from a high speed. Therefore, by setting the speed regulation value and deceleration regulation value to values larger than those that can be assumed when entering such a turntable, even if the vehicle experiences lateral movement on the turntable, the driver It is possible to suppress an unintended drop in brake fluid pressure.

Further, during the stop-time holding control, the first condition or a second condition including that the amount of lateral behavior of the vehicle is equal to or greater than the specified value, and that the operation member is operated. If the condition is satisfied, the vehicle stop holding control may be canceled.

According to this, even if the amount of behavior exceeds the specified value during the holding control when stopped, the holding control during stopping will not be canceled unless the operating member is operated. Even if the vehicle exhibits a lateral movement amount, it is possible to suppress a drop in brake fluid pressure that is contrary to the driver's intention. Additionally, if the vehicle rolls and slides down during stop hold control on a slope with a low μ road surface such as an icy road, the amount of lateral movement will occur in the vehicle, and the driver will perform an operation to right the vehicle. By operating the member, the hold-at-stop control is canceled and the brake fluid pressure is lowered, allowing the vehicle to be rebuilt.

Further, the vehicle brake fluid pressure control device is capable of executing wheel lock suppression control that suppresses the wheels from locking when the vehicle body speed is equal to or higher than a predetermined speed, and the speed regulation value is set to the predetermined speed. It may be set to a value less than

In a low speed range where the wheel lock suppression control is not executed, even if the vehicle is stopped due to erroneous intervention by the vehicle hold control, the vehicle will be reset as long as the first condition is met. It can be carried out.

Further, the vehicle speed to be compared with the speed regulation value may be updated every time the brake is input.

According to the present invention, it is possible to suppress a decrease in brake fluid pressure that is contrary to the driver's intention during the vehicle stop holding control.

1 is a configuration diagram of a vehicle equipped with a vehicle brake fluid pressure control device according to an embodiment of the present invention. FIG. 2 is a brake fluid pressure circuit diagram of a vehicle brake fluid pressure control device. FIG. 3 is a block configuration diagram of a control section. It is a flowchart which shows the judgment process whether the 1st condition is satisfied. It is a flowchart which shows the judgment process whether a 2nd condition is satisfied. It is a flowchart which shows the process for canceling hold|maintenance control at the time of a stop. 6 are time charts (a) to (h) showing changes in various parameters when the vehicle stop holding control is canceled under the first condition; FIG. 9 are time charts (a) to (g) illustrating changes in various parameters when the vehicle stop holding control is canceled under the second condition.

Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.
As shown in FIG. 1, the vehicle brake fluid pressure control device 100 is for appropriately controlling the braking force (brake fluid pressure) applied to each wheel W of the vehicle CR. The hydraulic pressure unit 10 is mainly provided with a hydraulic pressure unit 10 provided with various components such as the hydraulic pressure unit 10, and a control section 20 for appropriately controlling the various components within the hydraulic pressure unit 10.

The control unit 20 includes a wheel speed sensor 91 that detects the wheel speed of the wheels W, a steering angle sensor 92 that detects the steering angle of the steering ST as an example of an operation member, and a lateral sensor that detects the acceleration acting in the lateral direction of the vehicle CR. An acceleration sensor 93, a yaw rate sensor 94 that detects the turning angular velocity (yaw rate) of the vehicle CR as a lateral behavior amount of the vehicle CR, and an acceleration sensor 95 that detects the longitudinal acceleration of the vehicle CR are connected. The detection results of each sensor 91 to 95 are output to the control section 20.

The control unit 20 includes, for example, a CPU, a RAM, a ROM, and an input/output circuit, and includes a wheel speed sensor 91, a steering angle sensor 92, a lateral acceleration sensor 93, a yaw rate sensor 94, an acceleration sensor 95, and a pressure sensor 8 (described later). Control is executed by performing various arithmetic operations based on input from the computer (see FIG. 2) and programs and data stored in the ROM. Additionally, the wheel cylinder H is equipped with a hydraulic fluid that converts the brake fluid pressure generated by the master cylinder MC and the vehicle brake fluid pressure control device 100 into operating force for the wheel brakes FR, FL, RR, and RL provided on each wheel W. These hydraulic pressure devices are each connected to the hydraulic pressure unit 10 of the vehicle brake hydraulic pressure control device 100 via piping.

As shown in FIG. 2, the hydraulic unit 10 of the vehicle brake hydraulic pressure control device 100 includes a master cylinder MC, which is a hydraulic pressure source that generates brake hydraulic pressure according to the pedal force applied by the driver to the brake pedal BP; It is arranged between the wheel brakes FR, FL, RR, and RL. The hydraulic unit 10 includes a pump body 10a, which is a base body having an oil passage through which brake fluid flows, and a plurality of inlet valves 1, outlet valves 2, etc. arranged on the oil passage. Two output ports M1 and M2 of the master cylinder MC are connected to an inlet port 121 of the pump body 10a, and an outlet port 122 of the pump body 10a is connected to each wheel brake FR, FL, RR, and RL. Under normal conditions, the oil passage from the inlet port 121 to the outlet port 122 in the pump body 10a is connected, so that the depression force of the brake pedal BP is transmitted to each wheel brake FL, RR, RL, and FR. It looks like this.

Here, the oil passage starting from the output port M1 leads to the wheel brake FL on the left side of the front wheel and the wheel brake RR on the right side of the rear wheel, and the oil passage starting from the output port M2 leads to the wheel brake FR on the right side of the front wheel and the wheel brake FR on the right side of the rear wheel. It leads to the wheel brake RL. In addition, below, the oil path starting from output port M1 is called a "first system," and the oil path starting from output port M2 is called a "second system."

The hydraulic unit 10 is provided with two control valve means V corresponding to each wheel brake FL, RR in its first system, and similarly, two control valve means V are provided in its second system corresponding to each wheel brake RL, FR. Two control valve means V are provided. Further, this hydraulic pressure unit 10 is provided with a reservoir 3, a pump 4, an orifice 5a, a pressure regulating valve (regulator) R, and a suction valve 7 for each of the first system and the second system. Further, the hydraulic unit 10 is provided with a common motor 9 for driving the pump 4 of the first system and the pump 4 of the second system. This motor 9 is a motor whose rotation speed can be controlled, and in this embodiment, the rotation speed is controlled by duty control. Further, in this embodiment, the pressure sensor 8 is provided only in the second system.

Note that in the following, the oil passages from the output ports M1 and M2 of the master cylinder MC to the respective pressure regulating valves R are referred to as "output hydraulic pressure passages A1", and the oil passages from the pressure regulating valves R of the first system to the wheel brakes FL and RR are referred to as "output hydraulic pressure passages A1". The oil passages from the pressure regulating valve R of the second system to the wheel brakes RL and FR are respectively referred to as "wheel hydraulic pressure passages B". Further, the oil passage from the output hydraulic pressure passage A1 to the pump 4 is referred to as the "suction hydraulic pressure passage C", the oil passage from the pump 4 to the wheel hydraulic pressure passage B is referred to as the "discharge hydraulic pressure passage D", and further, The oil passage from the wheel hydraulic pressure passage B to the suction hydraulic pressure passage C is referred to as an "open passage E."

The control valve means V is a valve that controls the flow of hydraulic pressure from the master cylinder MC or the pump 4 to the wheel brakes FL, RR, RL, FR (specifically, the wheel cylinder H), and controls the pressure of the wheel cylinder H. It can be increased, maintained or decreased. Therefore, the control valve means V includes an inlet valve 1, an outlet valve 2, and a check valve 1a.

The inlet valve 1 is a normally open proportional solenoid valve provided between each wheel brake FL, RR, RL, FR and the master cylinder MC, that is, in the wheel hydraulic pressure path B. Therefore, the differential pressure between the upstream and downstream sides of the inlet valve 1 can be adjusted depending on the value of the drive current flowing through the inlet valve 1.

The outlet valve 2 is a normally closed electromagnetic valve interposed between each wheel brake FL, RR, RL, FR and each reservoir 3, that is, between the wheel hydraulic pressure path B and the open path E. The outlet valve 2 is normally closed, but when the wheels W are about to lock, the outlet valve 2 is opened by the control unit 20 to reduce the brake fluid pressure acting on each wheel brake FL, FR, RL, and RR. Drain into each reservoir 3.

Check valve 1a is connected to each inlet valve 1 in parallel. This check valve 1a is a valve that only allows the brake fluid to flow from each wheel brake FL, FR, RL, RR side to the master cylinder MC side, and when the input from the brake pedal BP is released, the inlet Even when the valve 1 is closed, brake fluid is allowed to flow from the wheel brakes FL, FR, RL, and RR to the master cylinder MC.

The reservoir 3 is provided in the open path E and has a function of temporarily storing brake fluid that is released when each outlet valve 2 is opened. Further, a check valve 3a is interposed between the reservoir 3 and the pump 4 to allow the brake fluid to flow only from the reservoir 3 side to the pump 4 side.

The pump 4 is interposed between a suction hydraulic pressure path C leading to the output hydraulic pressure path A1 and a discharge hydraulic pressure path D leading to the wheel hydraulic pressure path B, and sucks brake fluid stored in the reservoir 3. It has a function of discharging the liquid to the discharge hydraulic pressure path D. As a result, the brake fluid absorbed by the reservoir 3 can be returned to the master cylinder MC, and brake fluid pressure is generated regardless of whether or not the brake pedal BP is operated, and the brake fluid is applied to the wheel brakes FL, RR, RL, and FR. Can generate braking force.
Note that the amount of brake fluid discharged by the pump 4 depends on the rotation speed (duty ratio) of the motor 9. That is, as the rotational speed (duty ratio) of the motor 9 increases, the amount of brake fluid discharged by the pump 4 also increases.

The orifice 5a attenuates pressure pulsations in the brake fluid discharged from the pump 4.

The pressure regulating valve R normally allows the flow of brake fluid from the output hydraulic pressure path A1 to the wheel hydraulic pressure path B, and when increasing the pressure on the wheel cylinder H side by the brake fluid pressure generated by the pump 4, the pressure regulating valve R allows the flow of brake fluid from the output hydraulic pressure path A1 to the wheel hydraulic pressure path B. It has a function of regulating the pressure on the wheel hydraulic pressure path B and the wheel cylinder H side to a set value or less while blocking the flow, and is comprised of a switching valve 6 and a check valve 6a.

The switching valve 6 is a normally open proportional solenoid valve interposed between the output hydraulic pressure path A1 leading to the master cylinder MC and the wheel hydraulic pressure path B leading to each wheel brake FL, FR, RL, and RR. . Although details are not shown, the valve body of the switching valve 6 is biased in the valve closing direction by an electromagnetic force according to the applied current, so that the pressure in the wheel hydraulic pressure path B is higher than the pressure in the output hydraulic pressure path A1. When the brake fluid becomes higher than a predetermined value (this predetermined value is determined by the applied current), the brake fluid escapes from the wheel hydraulic pressure path B toward the output hydraulic pressure path A1, causing the brake fluid on the wheel hydraulic pressure path B side to The pressure is adjusted to a predetermined pressure. That is, by arbitrarily changing the valve closing force according to the value of the drive current input to the switching valve 6 (instruction current value), the differential pressure upstream and downstream of the switching valve 6 is adjusted, and the wheel hydraulic pressure path is adjusted. The pressure of B can be adjusted to below a set value.

The check valve 6a is connected to each switching valve 6 in parallel. This check valve 6a is a one-way valve that allows brake fluid to flow from the output hydraulic pressure path A1 to the wheel hydraulic pressure path B.

The suction valve 7 is a normally closed electromagnetic valve provided in the suction hydraulic pressure path C, and switches between opening and closing the suction hydraulic pressure path C. The suction valve 7 is opened under the control of the control unit 20, for example, when the pump 4 pressurizes the hydraulic pressure in each of the wheel brakes FL, FR, RL, and RR.

The pressure sensor 8 detects the brake hydraulic pressure in the output hydraulic pressure path A1, and the detection result is input to the control section 20.

Next, details of the control section 20 will be explained.
As shown in FIG. 3, the control unit 20 controls the control valve means V, the pressure regulating valve R (switching valve 6), and the suction valve 7 in the hydraulic unit 10 based on the signals input from the sensors 91 to 95, 8. The opening/closing operation of the motor 9 and the operation of the motor 9 are controlled to control the operation of each wheel brake FL, RR, RL, and FR. The control section 20 includes a behavior determination means 21 , an operation determination means 22 , a hydraulic pressure control means 23 , a valve drive section 24 , a motor drive section 25 , and a storage section 26 .

The behavior determining means 21 has a function of determining whether the absolute value of the yaw rate Y (hereinafter also simply referred to as "yaw rate Y") output from the yaw rate sensor 94 is equal to or greater than a specified value Yth. When the behavior determining means 21 determines that the yaw rate Y is equal to or greater than the specified value Yth, it outputs a yaw rate generation signal indicating this to the hydraulic pressure controlling means 23.

The operation determining means 22 determines whether or not the steering ST has been operated by determining whether the steering angle θ (absolute value) output from the steering angle sensor 92 is greater than or equal to the specified steering angle value θth. It has the function of When the operation determination means 22 determines that an operation has been performed, it outputs an operation signal indicating this to the hydraulic pressure control means 23.

Note that the specified value Yth and the specified steering angle value θth described above may be appropriately set through experiments, simulations, and the like.

The hydraulic pressure control means 23 operates based on the signals inputted from each sensor 91 to 95, 8, for example, in a known sideslip prevention control mode, traction control mode, stop hold control, wheel lock prevention control, etc. In order to control the brake fluid pressure in different control modes, it has a function of instructing the valve drive unit 24 and motor drive unit 25 to operate various valves and drive the motor 9. Here, the holding control when the vehicle is stopped is a mode in which the brake fluid pressure is maintained when the vehicle is stopped. A mode in which the brake fluid pressure is maintained at a higher fluid pressure (the fluid pressure increased by the pump 4) than the brake fluid pressure corresponding to the depression force of the brake pedal BP. Note that various control modes are stored in the storage section 26.

Wheel lock suppression control is control for suppressing the wheels W from locking when the wheels W tend to lock. The hydraulic pressure control means 23 determines whether the brake hydraulic pressure of each wheel W should be in a reduced pressure state, an increased pressure state, or a maintained state based on the wheel acceleration estimated from the wheel speed and the amount of slip, and controls the valve. It has a function of outputting to the drive section 140. The hydraulic pressure control means 23 determines that the wheels W tend to lock when the slip amount is larger than a predetermined threshold value and the wheel acceleration is 0 or less, and determines to reduce the brake fluid pressure. . Further, the hydraulic pressure control means 23 determines to maintain the brake hydraulic pressure when the wheel acceleration is greater than 0, and the slip amount is equal to or less than a predetermined threshold value, and the wheel acceleration is equal to or less than 0. In this case, it is decided to increase the brake fluid pressure.

When the hydraulic pressure control means 23 determines that the wheels W tend to lock when the vehicle speed is equal to or higher than a predetermined speed, the hydraulic pressure control means 23 executes (starts) wheel lock suppression control. Note that, when the vehicle speed is less than a predetermined speed, the hydraulic pressure control means 23 does not perform the wheel lock suppression control even if the above-mentioned conditions (conditions for determining the lock tendency of the wheels W) are met.

Further, the hydraulic pressure control means 23 determines whether or not the vehicle CR is in a skid state (sideslip state) during the stop state holding control based on the signals output from the behavior determination means 21 and the operation determination means 22. It has skid determining means 23a. Specifically, the skid determination means 23a determines that the vehicle body speed Vb at the time of the brake input was equal to or higher than the speed regulation value Vth, that the absolute value Aw of the wheel deceleration after the brake input became equal to or higher than the deceleration regulation value Ath, If the first condition, including that the yaw rate Y is equal to or higher than the specified value Yth, is satisfied during the hold control when stopped, the first flag F1 is set to 1, which indicates that a skid has occurred due to the fulfillment of the first condition. It has the function of

Specifically, when the driver depresses the brake pedal BP, the skid determining means 23a stores the vehicle body speed Vb at the time of brake input in the storage unit 26, and determines the maximum value among the absolute values Aw of wheel decelerations after the brake input. The value Awmax is stored in the storage unit 26. Then, the skid determining means 23a compares the vehicle body speed Vb and the maximum value Awmax of wheel deceleration stored in the storage unit 26 with respective threshold values (Vth, Ath) during the stop state holding control, and the behavior determining means 21 By determining whether a yaw rate generation signal is output from , it is determined whether the first condition is satisfied.

Note that the vehicle body speed Vb at the time of brake input, which is compared with the speed regulation value Vth, is updated every time the brake is input. Further, the maximum value Awmax of wheel deceleration after brake input, which is compared with the deceleration specified value Ath, is reset to 0 every time the brake is input.

The vehicle speed Vb may be, for example, the maximum wheel speed among the wheel speeds detected by each wheel speed sensor 91, or may be the average value of the wheel speeds of the four wheels. Further, the wheel deceleration can be calculated based on the wheel speed detected by the wheel speed sensor 91, for example. Then, the skid determining means 23a stores the maximum value Awmax of the wheel decelerations of the four wheels in the storage unit 26 after the brake input, and in determining the first condition, which of the maximum values Awmax of the respective wheel decelerations It may be determined whether or not the deceleration has become equal to or greater than the deceleration specified value Ath.

Further, the specified speed value Vth and the specified deceleration value Ath are set to values larger than the maximum speed and maximum deceleration that can be assumed when the vehicle CR approaches the turntable. The speed regulation value Vth can be set to a value less than a predetermined speed that constitutes one of the starting conditions for the wheel lock suppression control described above, and can be set to a value of 10 km/h or more, for example.

Further, the skid determination means 23a determines that during the stop state holding control, if a second condition including that the yaw rate Y is equal to or greater than the specified value Yth and that the steering ST has been operated is satisfied, It has a function of setting a second flag F2, which indicates that a skid has occurred, to 1 when a second condition is met.

The hydraulic pressure control means 23 has a function of determining whether or not the vehicle CR has stopped, and when determining that the vehicle CR has stopped, starting the holding control when the vehicle is stopped. Here, any method may be used to determine whether or not the vehicle CR has stopped. For example, the vehicle body speed calculated based on the signal from the wheel speed sensor 91 is set to a predetermined value V1 (see FIG. 7). (See a)) A method of determining whether or not the vehicle CR is stopped by determining whether or not the following conditions are met.

Furthermore, when the first flag F1 or the second flag F2 is 1 during the stop-time holding control, the hydraulic pressure control means 23 cancels the stop-time holding control regardless of whether a known release condition is satisfied. It is configured as follows. In other words, the hydraulic pressure control means 23 is configured to cancel the vehicle stop retention control if the first condition or the second condition is satisfied during the vehicle vehicle retention control. In particular, the hydraulic pressure control means 23 is configured to cancel the stop-hold control even if the stop-hold control switch or the steering wheel ST is not operated when the first condition is satisfied during the stop-hold control. It is composed of

Here, the stationary hold control switch is a switch for determining whether or not the control unit 20 can execute the stationary hold control. When the stop-time holding control switch is ON, the control unit 20 executes the stop-time holding control when the start condition for the stop-time holding control is satisfied. In addition, when the vehicle stop hold control switch is OFF, the control unit 20 does not execute the vehicle stop hold control even if the start condition for the vehicle stop hold control is satisfied. Further, the control unit 20 cancels the stop-time holding control when the stop-time holding control switch is turned from ON to OFF during the stop-time holding control.

Note that known release conditions include, for example, that a start operation is performed with the shift position in "D" or "R".

The valve drive unit 24 is a part that controls the control valve unit V, the pressure regulating valve R, and the suction valve 7 based on instructions from the hydraulic pressure control unit 23. Therefore, the valve drive section 24 includes a control valve means drive section 24a, a pressure regulating valve drive section 24b, and a suction valve drive section 24c.

The control valve means driving section 24a controls the inlet valve 1 and the outlet valve 2 based on instructions from the hydraulic pressure control means 23 to increase, maintain, or reduce the pressure. Specifically, when the pressure in the wheel cylinder H is to be increased, no current is applied to both the inlet valve 1 and the outlet valve 2. When the pressure in the wheel cylinder H should be reduced, a signal is sent to both the inlet valve 1 and the outlet valve 2 to close the inlet valve 1 and open the outlet valve 2, thereby reducing the brake fluid in the wheel cylinder H. flows out from the outlet valve 2. Further, when maintaining the pressure in the wheel cylinder H, a signal is sent to the inlet valve 1 and no current is applied to the outlet valve 2, thereby closing both the inlet valve 1 and the outlet valve 2.

The pressure regulating valve drive unit 24b does not apply current to the pressure regulating valve R under normal conditions. When a drive instruction is received from the hydraulic pressure control means 23, current is supplied to the pressure regulating valve R by duty control in accordance with this instruction. When a current is supplied to the pressure regulating valve R, a pressure difference corresponding to this current is formed between the master cylinder MC side and the control valve means V (wheel cylinder H) side of the pressure regulating valve R. As a result, the hydraulic pressure in the discharge hydraulic pressure path D between the pressure regulating valve R and the control valve means V is adjusted.

The suction valve drive unit 24c does not apply current to the suction valve 7 under normal conditions. When an instruction is received from the hydraulic pressure control means 23, a signal is output to the suction valve 7 in accordance with this instruction. As a result, the suction valve 7 opens and brake fluid is sucked into the pump 4 from the master cylinder MC.

The motor drive unit 25 determines the rotation speed of the motor 9 based on instructions from the hydraulic pressure control means 23 and drives the motor 9. That is, the motor drive section 25 drives the motor 9 by controlling the rotation speed, and in this embodiment, the rotation speed is controlled by duty control.

Next, the operation of the control section 20 will be explained with reference to FIGS. 4 to 6.
The control unit 20 always repeatedly executes the skid determination process shown in FIGS. 4 and 5 and the process for canceling the stop-time holding control shown in FIG. 6.

In the process shown in FIG. 4, the control unit 20 first determines whether or not braking is being performed (S1). Here, whether or not braking is in progress may be determined based on a signal from the pressure sensor 8, or based on a signal from a sensor that detects the operation amount of the brake pedal BP (not shown). You may.

If it is determined in step S1 that the vehicle is not braking (No), the control unit 20 ends this control. If it is determined that the brake is being applied in step S1 (Yes), it is determined whether or not the timing is when the brake is switched from OFF to ON (S2). Note that the determination in step S2 may be made based on the signal from the pressure sensor 8 or the like, similar to the determination in step S1.

If it is determined in step S2 that it is the timing when the brake is switched ON (Yes), the control unit 20 updates the vehicle body speed at that time as the vehicle body speed Vb at the time of brake input, and stores it in the storage unit 26. Store it (S3). After step S3, the control unit 20 resets the maximum value Awmax of wheel deceleration to 0 (S4).

If it is determined in step S2 that it is not the timing when the brake is switched on (No), the control unit 20 determines whether the absolute value Aw of the wheel deceleration exceeds the maximum value Awmax (S5). If it is determined in step S5 that Aw>Awmax (Yes), the control unit 20 updates the absolute value Aw of the wheel deceleration at that time as the maximum value Awmax (S6).

After Steps S4 and S6, or when the determination is No in Step S5, the control unit 20 determines whether or not the vehicle is under vehicle stop holding control (S7). If it is determined in step S7 that the vehicle is under stop-holding control (Yes), the control unit 20 determines whether the yaw rate Y applied to the vehicle CR is equal to or greater than the specified value Yth (S8).

If it is determined in step S8 that Y≧Yth (Yes), the control unit 20 determines whether the vehicle body speed Vb at the time of brake input is equal to or higher than the specified speed value Vth (S9). If it is determined in step S9 that Vb≧Vth (Yes), the control unit 20 determines whether the maximum value Awmax of wheel deceleration is greater than or equal to the specified deceleration value Ath (S10).

If it is determined in step S10 that Awmax≧Ath (Yes), the control unit 20 determines that the first condition is satisfied, sets the first flag F1 to 1 (S11), and starts this control. finish.

Further, if the control unit 20 determines No in any of steps S7 to S10, it sets the first flag F1 to 0 (S12) and ends this control.

In the process shown in FIG. 5, the control unit 20 first determines whether or not the vehicle is under vehicle stop holding control (S21). If it is determined in step S21 that the vehicle is under stop-holding control (Yes), the control unit 20 determines whether the yaw rate Y applied to the vehicle CR is equal to or greater than the specified value Yth (S22).

If it is determined in step S22 that Y≧Yth (Yes), the control unit 20 determines whether the steering angle θ of the steering ST is equal to or greater than the specified steering angle value θth (S23).

If it is determined in step S23 that θ≧θth (Yes), the control unit 20 determines that the second condition is satisfied, sets the second flag F2 to 1 (S24), and starts this control. finish.

Furthermore, if the control unit 20 determines No in any of steps S21 to S23, it sets the second flag F2 to 0 (S25) and ends this control.

In the process shown in FIG. 6, the control unit 20 first determines whether or not the vehicle is under stop control (S31). If it is determined in step S31 that the vehicle is not in the vehicle stop state holding control (No), the control unit 20 ends this control.

If it is determined in step S31 that the vehicle is under the vehicle stop holding control (Yes), the control unit 20 determines whether the first flag F1 is 1 (S32). If it is determined in step S32 that F1 is not 1 (No), the control unit 20 determines whether the second flag F2 is 1 (S33). If it is determined in step S33 that F2 is not 1 (No), the control unit 20 determines whether other cancellation conditions are satisfied (S34).

If the control unit 20 determines that the first flag F1 is 1 in step S32 (Yes), if it determines that the second flag F2 is 1 in step S33 (Yes), or if the control unit 20 determines that the first flag F1 is 1 in step S34, If it is determined that the cancellation condition is satisfied (Yes), the vehicle stop holding control is canceled (S35), and this control is ended. Further, if the control unit 20 determines that the other release conditions are not satisfied in step S34 (No), the control unit 20 ends the present control without canceling the hold control when the vehicle is stopped. In other words, in this case, the vehicle stop holding control is continued.

Next, control when the first condition or the second condition is satisfied during the vehicle stop holding control will be described with reference to FIGS. 7 and 8. Note that the maximum values Awmax of the yaw rate, steering angle, and wheel deceleration in FIGS. 7 and 8 are illustrated as absolute values for convenience. Further, the vehicle body speed is illustrated as a value estimated from the wheel speed. First, with reference to FIG. 7, a description will be given of control when the first condition is satisfied during the vehicle stop holding control.

As shown in FIGS. 7(a), (b), and (g), when the driver depresses the brake pedal BP while the vehicle CR is traveling at a vehicle speed V2 (time t1), the inside of the wheel cylinder H As the brake fluid pressure gradually increases, the vehicle speed gradually decreases. At this time, the control unit 20 updates the vehicle body speed Vb at the time of brake input to the vehicle body speed V2 and stores it in the storage unit 26.

When the vehicle speed decreases to a predetermined value V1 (time t2), it is determined that the vehicle CR should stop, and, for example, the stop-time holding control is executed using the brake fluid pressure P1 at that time (see FIG. 7(h)). Since wheel deceleration occurs after the brake is input, the control unit 20 stores the maximum value Awmax of the wheel deceleration after the brake input in the storage unit 26 while updating it as needed.

Then, when the control unit 20 starts the holding control during stopping (time t2), the control unit 20 sets the vehicle body speed Vb at the time of brake input and the maximum value Awmax of the wheel deceleration after the brake input stored in the storage unit 26 to respective threshold values (Vth , Ath). In the example of FIG. 7, it is assumed that the vehicle body speed Vb is equal to or greater than the specified speed value Vth, and the maximum value Awmax of wheel deceleration is equal to or greater than the specified deceleration value Ath.

If the vehicle speed Vb at the time of brake input is high to some extent and a large wheel deceleration occurs after brake input, even though it is determined that the vehicle CR has stopped, the vehicle CR may actually be rotating. While doing so, you may skid. Note that such a phenomenon may occur even on flat ground, for example, when the road surface is a low μ road surface such as an icy road.

In this case, as shown in FIG. 7(c), since a yaw rate Y higher than the specified value Yth occurs in the vehicle CR (time t3), as shown in FIG. 7(f) and (h), at this point When the first condition is satisfied, the first flag F1 becomes 1, and the hold control when the vehicle is stopped is canceled. As a result, after time t3, the brake fluid pressure decreases, the wheels are unlocked, and the grip force of the wheels W is restored, making it possible to maneuver the vehicle CR. Therefore, when the driver performs a steering operation to correct the attitude of the vehicle CR (time t4), the attitude of the vehicle CR can be corrected by the driver's operation.

Next, with reference to FIG. 8, a description will be given of control when the second condition is satisfied during the vehicle stop holding control.

As shown in FIGS. 8(a), (b), and (f), when the driver depresses the brake pedal BP (time t11) while the vehicle CR is traveling at a vehicle speed V2, the inside of the wheel cylinder H As the brake fluid pressure gradually increases, the vehicle speed gradually decreases. When the vehicle speed decreases to a predetermined value V1 (time t12), it is determined that the vehicle CR should stop, and, for example, the stop-time holding control is executed using the brake fluid pressure P1 at that time (see FIG. 8(g)).

When the road surface is a low μ road surface such as an icy road, even if the road surface is flat, after the control unit 20 determines that the vehicle CR has stopped, the vehicle CR does not actually stop but continues to rotate and slide. Sometimes.

When such a phenomenon occurs, as shown in FIGS. 8(c) and 8(g), a yaw rate Y occurs during the stop hold control (times t12 to t14), and the yaw rate Y exceeds the specified value Yth. Sometimes (time t13). In this case, the driver performs a steering operation to correct the attitude of the vehicle CR. As a result of this steering operation, as shown in FIG. 8(d), when the steering angle θ exceeds the specified steering angle value θth (time t14), as shown in FIGS. 8(e) and (g), at this point When the two conditions are met, the second flag F2 becomes 1, and the stop-time holding control is canceled.

As a result, as shown in FIG. 8(b), the brake fluid pressure held by the stop-time holding control decreases, so that the locked state of the wheels W is released as shown in FIG. 8(a). (Time t15). Therefore, the grip force of the wheels W is restored and the vehicle CR becomes maneuverable, so that the attitude of the vehicle CR can be repositioned by the driver's operation.

According to the above, the following effects can be obtained in this embodiment.
When the first condition is met, the vehicle stop holding control is canceled without operating the steering wheel ST, so the vehicle stopping holding control can be canceled quickly. Furthermore, when the vehicle CR is stopped on the turntable, it is usually unlikely that the vehicle will come to a sudden stop from a high speed. Therefore, by setting the specified speed value Vth and the specified deceleration value Ath to values larger than the values that can be assumed when approaching the turntable, even if the yaw rate Y occurs in the vehicle CR on the turntable, the driver It is possible to suppress an unintended drop in brake fluid pressure.

Even if the yaw rate Y becomes equal to or higher than the specified value Yth during the stop state holding control, the stop state holding control will not be canceled unless the steering wheel ST is operated. Even if yaw rate Y occurs, it is possible to suppress a drop in brake fluid pressure that is contrary to the driver's intention. Additionally, if the vehicle CR slides down while rotating during stop hold control on a slope with a low μ road surface such as an icy road, a yaw rate Y occurs in the vehicle CR, and the driver attempts to right the vehicle by turning the steering wheel ST. By operating the brake, the hold-at-stop control is canceled and the brake fluid pressure is lowered, so that the vehicle CR can be rebuilt.

When approaching the turntable, it is common sense to run the vehicle CR at a speed of less than 10 km/h, so setting the speed regulation value Vth to a value of 10 km/h or more suppresses misjudgments at the turntable. can do.

By setting the speed regulation value Vth to a value less than a predetermined speed that constitutes one of the start conditions for wheel lock suppression control, it is possible to prevent erroneous intervention of the stop hold control in a low speed range where wheel lock suppression control is not executed. Even when the wheels W are locked, if the first condition is satisfied, the hold control during stopping is canceled, so that the vehicle CR can be rebuilt.

Note that the present invention is not limited to the embodiments described above, and can be utilized in various forms as exemplified below.

In the embodiment, the absolute value Aw (maximum value Awmax) of the vehicle body speed Vb and wheel deceleration stored in the storage unit 26 was compared with the respective threshold values (Vth, Ath) during the stop state holding control, but the present invention is not limited to this. For example, when the brake is input, it may be determined whether the vehicle speed Vb is equal to or higher than the speed regulation value Vth, and if Vb≧Vth, a speed condition flag indicating this may be set. Similarly, after applying the brake, it is determined whether the absolute value Aw of the wheel deceleration is equal to or greater than the specified deceleration value Ath, and if Aw≧Ath, a deceleration condition flag indicating this is set. good. In this case, the conditions for the vehicle speed and wheel deceleration may be determined by determining whether each flag is set during the vehicle stop holding control.

In the embodiment, the yaw rate is exemplified as the lateral behavior amount of the vehicle, but the present invention is not limited thereto, and may be, for example, lateral acceleration detected by a lateral acceleration sensor. However, when the yaw rate is employed as the behavior quantity as in the embodiment, the sideslip state (skid state) of the vehicle can be satisfactorily determined based on the yaw rate.

In the above-mentioned embodiment, the stop-hold control switch and the steering ST are illustrated as operating members, but the present invention is not limited thereto, and the operating member may be, for example, a brake or an accelerator.

In the embodiment described above, the pressure reduction control (pressure reduction control when canceling the holding control when stopped) was performed by controlling the pressure regulating valve R, but the present invention is not limited to this, and for example, the master control is performed by driving the motor. When brake fluid pressure is maintained or reduced by an electric booster that moves a piston in a cylinder, the electric booster may be controlled to perform the stop-time holding control or release thereof according to the present invention.

The elements described in the embodiments and modifications described above may be implemented in any combination.

100 Vehicle brake fluid pressure control device Ath Deceleration specified value Awmax Maximum value CR Vehicle ST Steering Vb Vehicle speed Vth Speed specified value Y Yaw rate Yth specified value

Claims (4)

A brake fluid pressure control device for a vehicle that is capable of performing stop-time retention control that maintains brake fluid pressure when it is determined that the vehicle has stopped,
The vehicle speed at the time of the brake input was equal to or higher than the specified speed value, the absolute value of the wheel deceleration after the brake input was equal to or higher than the specified deceleration value, and the lateral direction of the vehicle was If the first condition including that the amount of behavior is equal to or greater than a specified value is satisfied, the stop-time holding control is canceled even if there is no operation of an operating member for operating the vehicle. Vehicle brake fluid pressure control device. During the stop holding control, the first condition or the second condition, which includes that the amount of lateral behavior of the vehicle is equal to or greater than the specified value, and that the operation member is operated, is satisfied. 2. The brake fluid pressure control device for a vehicle according to claim 1, wherein the brake fluid pressure control device for a vehicle cancels the holding control when the vehicle is stopped. When the vehicle speed is equal to or higher than a predetermined speed, it is possible to perform wheel lock suppression control that suppresses the wheels from locking;
3. The vehicle brake fluid pressure control device according to claim 1, wherein the speed regulation value is set to a value less than the predetermined speed. 4. The vehicle brake fluid pressure control device according to claim 1, wherein the vehicle speed to be compared with the speed regulation value is updated each time a brake is applied.

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