JP2003154926A - Brake fluid pressure control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a brake fluid pressure control device capable of preventing a vehicle from moving when an operator releases a brake pedal and prepares to depress an accelerator pedal to re-start the vehicle, from the state of being temporarily stopped by a brake operation utilizing the holding control of an ABS, i.e., allowing a hill hold control. SOLUTION: An automatic vehicle with an idle stop function comprises a hill hold control means. The hill hold control means maintains a braking force when the brake pedal B/P is released and the accelerator pedal is depressed by eliminating a bypass circuit bypassing the pressure boosting control valve 5 and a one-way valve installed in the bypass circuit and maintaining the fluid pressure of a wheel cylinder W/C by closing a pressure boosting control valve 5 for a specified time when the initial stage of release of the operation of the brake pedal B/P is detected after the start of control of an idle stop control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake fluid pressure control provided with an antilock brake system (ABS) capable of performing wheel lock prevention control during braking (this control is referred to as ABS control in this specification). The present invention relates to an apparatus, and more particularly, to an improved technique of so-called hill hold control for preventing movement of a vehicle when changing the brake pedal from a stopped state of the vehicle.

[0002]

2. Description of the Related Art Conventionally, as a brake fluid pressure control device capable of executing ABS control, one described in Japanese Patent Laid-Open No. 5-58260 is known. This conventional brake hydraulic pressure control device includes a master cylinder that generates hydraulic pressure in response to a driver's braking operation, a wheel cylinder that generates a braking force at each wheel, and a brake circuit that connects the master cylinder and each wheel cylinder. The normally open pressure increasing control valve which is installed in the middle of each wheel and controls each wheel cylinder pressure, and is interposed between each pressure increasing control valve and each wheel cylinder in the brake circuit and between the master cylinder. A recirculation circuit, a normally closed decompression control valve provided in the recirculation circuit, a reservoir interposed between the decompression control valve in the recirculation circuit and the master cylinder for temporarily storing the hydraulic fluid flowing out from the wheel cylinder, and the recirculation A hydraulic pump that is interposed between the reservoir and the master cylinder in the circuit to recirculate the working fluid stored in the reservoir to the master cylinder side. When, it was equipped with one-way valve that allows only the flow of hydraulic fluid from the wheel cylinder to the master cylinder direction being interposed in a bypass circuit for bypassing the pressure increase control valve, as the main components.

[0003]

However, in a vehicle equipped with a conventional brake fluid pressure control device capable of ABS control, the vehicle is temporarily stopped by a brake operation on a sloped surface such as in the middle of a steep uphill. When the driver depresses the brake pedal to the accelerator pedal in order to restart the vehicle, the vehicle may move backward. As a solution to this problem, it is conceivable to use ABS holding control to temporarily hold the brake fluid pressure at the time of stepping to maintain the braking force and prevent the vehicle from reversing. However, conventional ABS
As described above, since the one-way valve that allows only the flow of the hydraulic fluid from the wheel cylinder to the master cylinder is installed in the bypass circuit that bypasses the pressure increase control valve that is closed by the holding control as described above, the brake When the brake pedal is not operated, the one-way valve is opened due to the differential pressure, and the high-pressure wheel cylinder fluid pressure flows toward the low-pressure (atmospheric pressure) master cylinder. Cylinder hydraulic pressure cannot be maintained.

The present invention has been made by paying attention to the above-mentioned conventional problems, and utilizes the ABS holding control to drive the vehicle from a state in which the vehicle is temporarily stopped by a brake operation for restarting. An object of the present invention is to provide a brake fluid pressure control device capable of so-called hill hold control, which prevents the vehicle from moving when a person changes the brake pedal to the accelerator pedal.

[0005]

In order to achieve the above-mentioned object, a brake fluid pressure control device according to claim 1 of the present invention comprises:
A master cylinder that generates a hydraulic pressure in response to a driver's brake operation, a wheel cylinder that generates a braking force at each wheel by the introduced hydraulic pressure, and a brake cylinder that connects the master cylinder and each wheel cylinder in the middle. A normally open pressure increasing control valve for opening and closing the brake circuit, and a return circuit interposed between the pressure increasing control valve and each wheel cylinder in the brake circuit and between the master cylinder. A normally closed pressure reducing control valve provided in the reflux circuit for opening and closing the reflux circuit, and a hydraulic fluid flowing out from the wheel cylinder interposed between the pressure reducing control valve and the master cylinder in the reflux circuit. Is stored between the reservoir and the master cylinder in the reflux circuit, and the working fluid stored in the reservoir is stored in the master cylinder. To the hydraulic pump, a vehicle stop state detecting means for detecting the stop state of the vehicle, a brake operation release detecting means for detecting the release of the brake operation by the driver at an initial stage, and a vehicle by the vehicle stop state detecting means. When the initial stage of brake operation release is detected by the brake operation release detecting means after the stop state is detected, the brake pedal is closed by closing the pressure increase control valve for a predetermined time to maintain the wheel cylinder hydraulic pressure. To a braking force maintaining control means for maintaining the braking force when the accelerator pedal is depressed.

A brake fluid pressure control device according to a second aspect is
2. The brake fluid pressure control device according to claim 1, wherein when the pressure increase control valve is opened due to the termination of the control by the braking force maintenance control means, the pressure reducing control valve is opened for a predetermined time to bring the wheel cylinder fluid pressure to the reflux circuit side. Also, the means provided with a containment prevention means for discharging the above.

The brake fluid pressure control device according to claim 3 is
The brake fluid pressure control device according to claim 1 or 2, further comprising a fluid pressure sensor that detects a master cylinder fluid pressure generated in the master cylinder, and the brake operation release detection means is detected by the fluid pressure sensor. The means for detecting the release of the brake operation due to the decrease in the master cylinder hydraulic pressure is adopted in the initial stage.

[0008]

In the brake fluid pressure control device according to the first aspect of the present invention, when the brake operation release detecting means detects the initial stage of releasing the brake operation after the vehicle stop state detecting means detects the vehicle stop state. In the braking force maintenance control means, control is performed to maintain the braking force at the time of switching from the brake pedal to the accelerator pedal by closing the pressure increase control valve for a predetermined time to maintain the wheel cylinder hydraulic pressure, As a result, when the driver depresses the brake pedal to the accelerator pedal to restart the vehicle from the state in which the vehicle is temporarily stopped by the brake operation, it is possible to maintain the braking force by the vehicle moving. Can be prevented by.

In the brake fluid pressure control device according to the second aspect of the present invention, in the containment prevention means, when the pressure increase control valve is opened due to the termination of the control by the braking force maintenance control means, the pressure reduction control valve is opened for a predetermined time and the wheel cylinder fluid is closed. By discharging the pressure to the recirculation circuit side as well, it is possible to quickly and reliably reduce the hydraulic pressure in the wheel cylinders when the braking force maintenance control is completed. The brake drag can be reliably prevented.

In the brake fluid pressure control device according to the third aspect of the invention, the brake operation release detecting means detects the release of the brake operation at the initial stage due to the decrease in the master cylinder fluid pressure detected by the fluid pressure sensor. With this, the pressure increasing control valve can be closed at the optimum timing in the braking force maintaining control means.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. First, the overall configuration of the embodiment of the present invention will be described with reference to the hydraulic circuit diagram of FIG. In the figure, W / C indicates a wheel cylinder, and reference symbols (FL), (RR), (FR), and (RL) following the reference symbol W / C indicating the wheel cylinder are wheel cylinders, respectively. It shows the arrangement of W / C,
(FL) is the left front wheel, (RR) is the right rear wheel, (FR) is the right front wheel, (RL) is the left rear wheel (By the way, the front stage (F) is the front wheel side, (R) is the rear) (Wheel side, rear (R) shows the right side, (L) shows the left side). In the following description, if the wheel cylinders W / C do not indicate a specific one, reference numerals (FL), (RR),
(FR) and (RL) are omitted in the description. Further, the symbols (FL), (RR), (FR), (RL), and
The terms (F) and (R) in the preceding stage are also used in the same meaning for the pressure increase control valve 5 and the pressure reduction control valve 6 which will be described later.

In the figure, M / C is a master cylinder 2
It is a tandem type master cylinder of the system. The master cylinder M / C generates two systems of brake fluid pressure in conjunction with depression of the brake pedal B / P, and one of the two systems of brake fluid pressure constitutes a brake circuit. Wheel cylinders W / C (FR) and W / C for the left front wheel and the right rear wheel via the first channel circuit 1
(RL) and one of the brake fluid pressures is
The right front wheel and the left rear wheel side wheel cylinder W / C (F
L) and W / C (RR), the master cylinder M / C corresponds to the master cylinder in the claims. The master cylinder M / C has a reservoir tank R / T for storing hydraulic fluid.
Is provided.

In describing the configuration below, the configurations of both channel circuits 1 and 2 are substantially the same. Therefore, the configuration of the first channel circuit 1 will be described, and the same configuration will be described for both channel circuits 1 and 2. The same reference numerals are given and the description of the configuration of the second channel circuit 2 is omitted. The first channel circuit 1 includes a front wheel branch circuit 1 that extends from a branch portion 1a to a wheel cylinder W / C (FR) for the right front wheel.
f and a rear wheel branch circuit 1r that reaches the wheel cylinder W / C (RL) of the left rear wheel.

On the branch circuits 1f, 1r side, pressure increasing control valves 5 (FR), 5 constituting a hydraulic pressure control valve for reducing, maintaining and increasing the brake hydraulic pressure of each wheel cylinder W / C.
(RL) and pressure reducing control valves 6 (FR) and 6 (RL) are provided. That is, the pressure increase control valve 5 is provided in the middle of each of the branch circuits 1f and 1r, and when not in operation, the branch circuits 1f and 1r are brought into communication with each other by a spring force, and when in operation, the branch circuits 1f and 1r are shut off. Always open 2
It is composed of an electromagnetic switching valve in the port 2 position. Further, the pressure reducing control valve 6 includes the branch circuits 1f,
The wheel cylinder W / C side of the 1r pressure increase control valve 5 (hereinafter, the side relatively close to the master cylinder M / C in each channel circuit 1 and 2 is referred to as upstream, and the side close to the wheel cylinder W / C is referred to as upstream. It is provided in the middle of a discharge circuit (reflux circuit) 4k branched from branch points 1e and 1e provided on the downstream side) to reach the reservoir 7, and cuts off the discharge circuit 4k when not operating and discharges the discharge circuit 4k when operating. It is composed of a normally closed 2-port 2-position electromagnetic switching valve that communicates.

Further, the reservoir 7 is connected to a suction side circuit (reflux circuit) 4g connected to the suction side of the hydraulic pump 4 having a suction valve 4a and a discharge valve 4b. A discharge side circuit (reflux circuit) 4c communicating with the master cylinder is connected to the discharge side of the hydraulic pump 4, and an orifice 4d is provided in the discharge side circuit 4c. As described above, in the embodiment of the present invention, the pressure increase control valve 5
The configuration is different from the conventional example in that a pressure increasing control valve bypass circuit having a check valve that allows only the flow from the downstream side to the upstream side is bypassed while bypassing the.

The pressure increasing control valve 5 and the pressure reducing control valve 6
Is opened / closed as necessary in order to reduce / maintain / increase the brake fluid pressure. Then, during the ABS control, the hydraulic pump 4 is driven. That is, the hydraulic pressure pump 4, the pressure increase control valve 5, and the pressure reduction control valve 6 constitute an ABS unit. That is, the content of the ABS control will be briefly described. When the wheel lock occurs when each wheel cylinder W / C performs the braking operation, the pressure increase control valve 5 is closed and the pressure reduction control valve 6 is opened. For example, the brake fluid pressure of the wheel cylinder W / C is drained to the reservoir 7 and reduced in pressure, the braking force is weakened, and the wheel lock can be released. Also, from this state, the pressure increase control valve 5 and the pressure reduction control valve 6 are released. When the valve is closed, the brake fluid pressure of the wheel cylinder W / C is held, and the wheel lock release state can be maintained. Further, the pressure increase control valve 5 is opened and the pressure reduction control valve 6 is closed. For example, the hydraulic fluid in the reservoir 7 supplied upstream of the pressure increase control valve 5 by the operation of the hydraulic pump 4 is supplied to the wheel cylinders W / C to increase the braking force. Prevent Natteri so that the maximum braking force can be obtained in circumference.

Next, the contents of the hill hold control in the brake fluid pressure control apparatus according to the embodiment of the present invention will be described with reference to FIGS. 2 and 3 by taking an automatic vehicle equipped with an idle stop function as an example. That is, in an automatic vehicle having an idle stop function, the engine is stopped by the idle stop when the vehicle is stopped. Therefore, especially when the vehicle is stopped on an uphill road, the brake pedal B / P
When the vehicle is changed over from the accelerator pedal to the accelerator pedal, the vehicle is likely to retreat. Therefore, the demand for hill hold control (braking force maintaining control) is particularly increasing.

FIG. 2 is a flow chart showing the contents of hill hold control, and FIG. 3 is the same time chart. From the idle stop standby state of step S101 in FIG.
First, in step S102, the master cylinder hydraulic pressure M
By determining whether or not P exceeds the idle stop permission hydraulic pressure threshold value POs, it is determined whether or not the master cylinder hydraulic pressure capable of preventing the vehicle from jumping out is generated at the time of restart after the idle stop, NO (MP ≦ P
If Yes (MP> POs), the process returns to step S101, and if YES (MP> POs), the process proceeds to step S103.

In step S103, it is determined whether the idle stop start flag is set to 1. This idle stop start flag is set to 1 when the wheel speed is 0, the brake switch is ON, and the battery voltage is normal, for example. Then, when this determination is NO (flag = 0), the idle stop cannot be permitted, so the process returns to step S101, and Y
If ES (flag = 1), the process proceeds to step S104 to reset the engine ON flag to 0, and then proceeds to step S105 to perform idle stop. That is, the engine is turned off to gain fuel efficiency.

In a succeeding step S106, it is determined whether or not the master cylinder hydraulic pressure MP has become less than the idle stop release hydraulic pressure threshold value PNs to confirm that the driver has begun to release the brake pedal B / P. If NO (MP ≧ POs), the brake is still in operation and the idle stop is released (engine ON).
Therefore, the determination in step S106 is repeated, and when YES (MP <PNs), the process proceeds to step S107 for starting the brake operation release.

In step S107, hill hold control is started. That is, the pressure increase control valve 5 is energized and closed to disconnect the wheel cylinder W / C and the master cylinder M / C in the branch circuits 1f and 1r. The hydraulic pressure in C is maintained at a hydraulic pressure in a substantially braking state. Therefore, in this state, even if the brake pedal B / P is completely released, the vehicle is prevented from moving (backing). Therefore, in the following step S108, the idle stop cancellation flag is set to 1, and then the process proceeds to step S109.

In step S109, the pressure increase control valve 5
Is operated to determine whether or not the valve has been closed, it is determined whether or not the engine start permission state has been reached.
When it is O, this step S109 is repeated and YES.
When the engine start permission state is reached, step S1
Proceed to 10 to end the hill hold control. That is, by releasing the power supply to the pressure increase control valve 5 and opening the valve,
Hydraulic pressure of wheel cylinder W / C is changed to master cylinder M / C
Is discharged to the side to release the braking force, and in the subsequent step S111, the engine ON flag is set to 1 to restart the engine, and then in the subsequent step S112.
In, containment prevention control is performed. That is, in this containment prevention control, the depressurization control valve 6 is energized to open for a predetermined time, so that the hydraulic pressure of the wheel cylinder W / C is discharged to the side of the discharge circuit 4k (recirculation circuit) in which the reservoir 7 is interposed. The hydraulic pressure of the wheel cylinders W / C can be promptly and reliably reduced, and therefore, the drag of the brake due to the containment of the brake hydraulic pressure can be reliably prevented.

As described above, in the brake fluid pressure control device according to the embodiment of the present invention, in the automatic vehicle having the idle stop function, the initial release stage of the brake pedal B / P operation is detected after the idle stop control is started. When the pressure is increased, the pressure increasing control valve 5 is closed for a predetermined time to maintain the hydraulic pressure of the wheel cylinders W / C to maintain the braking force when the brake pedal B / P is changed over to the accelerator pedal. As a result, the driver changes the brake pedal B / P to the accelerator pedal to restart the vehicle from a state where the vehicle is temporarily stopped by operating the brake pedal B / P on an uphill road. The effect of being able to prevent the vehicle from reversing when maintaining the vehicle by the action of maintaining the braking force is obtained.

When the pressure increase control valve 5 is opened by the end of the hill hold control described above, the pressure reduction control valve 6 is opened for a predetermined time to discharge the hydraulic pressure of the wheel cylinders W / C.
By discharging the fluid to the k side as well, the hydraulic pressure in the wheel cylinders W / C can be reduced quickly and reliably, so that the drag of the brake due to the containment of the brake hydraulic pressure can be reliably prevented. The effect is obtained.

Further, since the release of the brake pedal B / P operation is detected in the initial stage due to the decrease in the hydraulic pressure of the master cylinder M / C detected by the hydraulic pressure sensor, the pressure increase control is performed at the optimum timing. The valve 5 can now be closed.

Since the hill hold control can be executed only by controlling the opening / closing of the pressure increase control valve 5, the ABS
The cost can be reduced by sharing with. Further, as compared with the conventional brake fluid pressure control device, the bypass circuit bypassing the pressure increase control valve 5 and the one-way valve interposed in the bypass circuit can be omitted, so that the cost can be further reduced.

Further, without driving the motor M,
Since the hill hold control can be executed, the sound vibration problem does not occur, and the durability of the motor M can be improved, the size of the motor M can be reduced, and the work amount can be reduced. Further, in the hill hold control, as compared with the case where the wheel cylinder hydraulic pressure is increased by driving the motor M,
It is better to close the boost control valve 5 and maintain the brake fluid pressure.
Since there is no time lag in the wheel cylinder pressure increase time, it is excellent in that it can completely prevent the vehicle from moving backward.

Although the embodiments of the present invention have been described above with reference to the drawings, the specific configurations are not limited to the embodiments of the present invention. For example, in the embodiment of the invention, 2
Although the two hydraulic pumps 4 and 4 are configured to be operated by the single motor M, the first channel circuit 1 and the second channel circuit 2 may be configured to be operated by different motors.

Further, in the embodiment of the invention, an example in which the present invention is applied to an automatic vehicle having an idle stop function has been shown, but the present invention can also be applied to a vehicle not having an idle stop function. Furthermore, the present invention can be applied to a manual vehicle. Also,
In the embodiment of the invention, it is confirmed whether or not the driver has begun to release his / her foot from the brake pedal B / P by determining whether or not the master cylinder hydraulic pressure MP has become less than the idle stop release hydraulic pressure threshold value PNs. However, the signal from the brake switch can also be used.

In order to prevent the brake fluid pressure from being contained, the pressure reducing control valve 6 is energized and opened for a predetermined time, whereby the fluid pressure of the wheel cylinder W / C is stored in the reservoir 7.
When the fluid is also discharged to the side of the discharge circuit 4k (recirculation circuit) in which is installed, the hydraulic pump 4 is driven to discharge the hydraulic fluid in the reservoir 7 to the master cylinder side, so that the reservoir 7 is filled with the hydraulic fluid. Can be prevented. Further, by providing the hydraulic pressure sensor that detects the wheel cylinder hydraulic pressure, it becomes possible to execute the containment prevention control only when necessary.

[0031]

As described above, the present invention claims 1.
The brake fluid pressure control device described is a normally open pressure increasing control valve which is interposed in the middle of a brake circuit connecting a master cylinder and each wheel cylinder to open and close the brake circuit, and each of the brake circuits. A recirculation circuit interposed between the pressure increase control valve and each wheel cylinder and between the master cylinder, a normally closed decompression control valve provided in the recirculation circuit for opening and closing the recirculation circuit, A reservoir that is interposed between the pressure reducing control valve and the master cylinder in the reflux circuit and temporarily stores the hydraulic fluid flowing out from the wheel cylinder; and a reservoir that is interposed between the reservoir in the reflux circuit and the master cylinder. A hydraulic pump that circulates the stored hydraulic fluid to the master cylinder side, vehicle stop state detection means that detects the stop state of the vehicle, and brake operation by the driver. The brake operation release detecting means for detecting the release in the initial stage, and when the brake operation release initial stage is detected by the brake operation release detecting means after the vehicle stop state is detected by the vehicle stop state detecting means, A braking force maintaining control means for maintaining the braking force at the time of switching from the brake pedal to the accelerator pedal by maintaining the wheel cylinder hydraulic pressure by closing the pressure increase control valve for a predetermined time. Thus, when the driver steps on the accelerator pedal from the brake pedal to restart the vehicle from the state in which the vehicle is temporarily stopped by the brake operation, it is possible to maintain the braking force by the vehicle moving. The effect is that it can be prevented by.

Further, since the braking force maintaining control can be executed only by controlling the opening / closing of the pressure increasing control valve, the cost can be reduced by sharing it with the ABS. Also,
Compared to the conventional brake fluid pressure control device, the bypass circuit bypassing the pressure increase control valve and the one-way valve interposed in the bypass circuit can be omitted, so that the cost can be further reduced.

The brake fluid pressure control device according to claim 2 is
2. The brake fluid pressure control device according to claim 1, wherein when the pressure increase control valve is opened due to the termination of the control by the braking force maintenance control means, the pressure reducing control valve is opened for a predetermined time to bring the wheel cylinder fluid pressure to the reflux circuit side. By adopting a means that also includes a containment prevention device that discharges the liquid, the hydraulic pressure in the wheel cylinders can be quickly and reliably reduced when the braking force maintenance control is completed. It will be possible to reliably prevent the brake drag due to the containment of the.

The brake fluid pressure control device according to claim 3 is
The brake fluid pressure control device according to claim 1 or 2, further comprising a fluid pressure sensor that detects a master cylinder fluid pressure generated in the master cylinder, and the brake operation release detection means is detected by the fluid pressure sensor. By adopting the means configured to detect the release of the brake operation at the initial stage due to the decrease of the master cylinder hydraulic pressure, the pressure increasing control valve can be closed at the optimum timing in the braking force maintaining control means. Become.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram showing a brake fluid pressure control device according to an embodiment of the invention.

FIG. 2 is a flowchart showing the contents of hill hold control in the brake fluid pressure control device according to the embodiment of the invention.

FIG. 3 is a time chart showing the contents of hill hold control in the brake fluid pressure control device according to the embodiment of the invention.

[Explanation of symbols]

W / C wheel cylinder M / C master cylinder B / P brake pedal M motor P1 connection port P2 connection port P3 connection port P4 connection port P5 connection port P6 connection port 1st channel circuit (brake circuit) 1a Branch part 1b Fork 1e branch point 1f Front wheel branch circuit 1r Rear wheel branch circuit 2 Second channel circuit (brake circuit) 4 hydraulic pump 4a Suction valve 4b discharge valve 4c Discharge side circuit (reflux circuit) 4d orifice 4g suction side circuit (reflux circuit) 4h intake valve 4j Branch 4k discharge circuit (reflux circuit) 5 Booster control valve 6 Pressure reducing control valve 7 Reservoir

Claims (3)

[Claims] 1. A master cylinder that generates a hydraulic pressure in response to a driver's brake operation, a wheel cylinder that generates a braking force at each wheel by an introduced hydraulic pressure, and a brake circuit that connects the master cylinder and each wheel cylinder. A normally open pressure-increasing control valve that is provided in the middle of the brake circuit to open and close the brake circuit; and an intermediate pressure-increasing control valve in the brake circuit between each pressure-increasing control valve and each wheel cylinder and between the master cylinder. A recirculation circuit, a normally closed decompression control valve provided in the recirculation circuit for opening and closing the recirculation circuit, and a wheel cylinder interposed between the decompression control valve in the recirculation circuit and the master cylinder. Reservoir for temporarily storing the hydraulic fluid flowing out from the reservoir, and the hydraulic fluid stored in the reservoir that is interposed between the reservoir and the master cylinder in the reflux circuit. Hydraulic pump that recirculates the vehicle to the master cylinder side, vehicle stop state detection means that detects the stop state of the vehicle, brake operation release detection means that detects the release of brake operation by the driver at the initial stage, and the vehicle stop state When the brake operation release detection means detects the brake operation release initial stage after the detection means detects the vehicle stopped state, the pressure increase control valve is closed for a predetermined time to maintain the wheel cylinder hydraulic pressure. Therefore, a braking fluid pressure control device is provided, which includes a braking force maintenance control unit that maintains the braking force when the brake pedal is changed over to the accelerator pedal. 2. A containment preventing means for opening the pressure reducing control valve for a predetermined time to discharge the wheel cylinder hydraulic pressure to the recirculation circuit side when the pressure increasing control valve is opened due to the termination of the control by the braking force maintaining control means. The brake fluid pressure control device according to claim 1, further comprising: 3. A hydraulic pressure sensor for detecting a master cylinder hydraulic pressure generated in the master cylinder, wherein the brake operation release detecting means detects a brake operation due to a decrease in the master cylinder hydraulic pressure detected by the hydraulic pressure sensor. The brake fluid pressure control device according to claim 1 or 2, wherein the release is detected at an initial stage.