JPH06115415A - Brake control device - Google Patents

Abstract

PURPOSE:To carry out the fail decision whether the wheel cylinder pressure obtained naturally to the given brake depressing force is generated or not in a brake control device to control the hydraulic pressure to the wheel cylinder by a hydraulic control valve of a proportional valve type which receives a thrust by a master cylinder pressure in the pressure increasing direction, and a thrust by a solenoid in the pressure decreasing direction. CONSTITUTION:A controller 15 to calculate a wheel cylinder pressure inference value Pw1 to be fed to a wheel cylinder 4 from a master cylinder pressure measured value Pm and a solenoid current Is fed to a solenoid 5b, and to decide the fail condition by comparing a wheel cylinder pressure inference value Pw and the wheel cylinder pressure measured value Pw1, has been provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake control device for controlling a braking force with a high degree of freedom.

[0002]

2. Description of the Related Art Conventionally, as a brake control device for controlling a hydraulic pressure to a wheel cylinder by a proportional valve type hydraulic control valve having a spool which receives a thrust force by a master cylinder pressure in a pressure increasing direction and a thrust force by a solenoid in a pressure reducing direction. For example, an apparatus described in Japanese Patent Application Laid-Open No. 4-87867 (Japanese Patent Application No. 2-201010) is known.

[0003]

However, in the above-mentioned conventional brake control device, it is detected whether or not the wheel cylinder pressure that should be obtained for a given brake pedal force is generated, that is, the failure judgment. It was not disclosed how to do.

Japanese Patent Laid-Open No. 2-193753 discloses a device which detects a hydraulic pressure increase state with respect to an opening time of a two-position solenoid valve used in a brake control device to make a failure judgment. Since the one using the valve controls the hydraulic pressure directly by the given electric current value, the hydraulic pressure cannot be detected by the opening time of the valve as in this known example. Not applicable.

The present invention has been made in view of the above problems, and is a proportional valve type hydraulic control having a spool that receives thrust by a master cylinder pressure in a pressure increasing direction and thrust by a solenoid in a pressure reducing direction. A first object of the present invention is to make a fail determination as to whether or not a wheel cylinder pressure that should be naturally obtained for a given brake pedal force is generated in a brake control device that controls hydraulic pressure to a wheel cylinder by a valve.

In addition to the above first problem, a second problem is to reduce the number of detecting means for obtaining the master cylinder pressure which is the fail judgment input information.

In a brake control device for controlling hydraulic pressure to a wheel cylinder by a proportional valve type hydraulic control valve having a spool that receives thrust by a master cylinder pressure in a pressure increasing direction and thrust by a solenoid in a pressure reducing direction, The third problem is to make a fail determination as to whether or not a change in the wheel cylinder pressure that should be obtained with respect to the change in the current supplied to the solenoid occurs regardless of the change.

[0008]

In order to solve the first problem, in the brake control device according to the first aspect, the wheel cylinder is supplied to the wheel cylinder from the master cylinder pressure value and the current value supplied to the solenoid. Estimate the pressure,
A fail judgment means for judging the fail state by comparing the estimated wheel cylinder pressure value and the measured wheel cylinder pressure value is provided.

That is, a master cylinder for generating a master cylinder pressure corresponding to a pedaling force applied to a brake pedal, a hydraulic pressure source, a wheel cylinder for braking each wheel with an output hydraulic pressure from the hydraulic pressure source, and the hydraulic pressure source. A hydraulic control valve that is provided between the wheel cylinder and controls the output hydraulic pressure from the hydraulic pressure source to a control pressure according to the master cylinder pressure, and the control pressure by switching the oil passage provided in the hydraulic control valve. Supply spool in the direction of increasing / decreasing and reducing control pressure in the direction of receiving control pressure as feedback pressure and receiving the force of master cylinder pressure in the direction of increasing control pressure, and in the direction of reducing control pressure to this spool A master cylinder pressure that detects the master cylinder pressure in a brake control device that has a solenoid that applies thrust corresponding to the current Output means, wheel cylinder pressure estimation means for estimating the wheel cylinder pressure supplied to the wheel cylinder from the master cylinder pressure value detected by the detection means and current value supplied to the solenoid, and wheel for actually measuring the wheel cylinder pressure. Cylinder pressure measuring means and fail judging means for judging the fail state by comparing the estimated value estimated by the estimating means and the measured value measured by the measuring means are provided.

A second aspect of the present invention is provided to solve the second problem.
In the described brake control device, the switching means for selectively switching is provided, and the means for obtaining the master cylinder pressure information and the wheel cylinder pressure information only by the wheel cylinder pressure measuring means is used.

That is, in the brake control device according to claim 1, a first position for connecting a master cylinder oil passage communicating with the master cylinder with a wheel cylinder oil passage communicating with the wheel cylinder, and an output port of the hydraulic control valve. A switching means for selectively switching between an output oil passage communicating with the wheel cylinder oil passage and a second position for communicating the wheel cylinder oil passage, and the wheel cylinder pressure measuring means is provided in the wheel cylinder oil passage, The value measured by the wheel cylinder pressure measuring means in the position 1 is the master cylinder pressure, and the value measured by the wheel cylinder pressure measuring means in the condition that the switching means is in the second position is the wheel cylinder. It is pressure.

In order to solve the third problem, a third aspect is provided.
The described brake control device is provided with the fail determination means for determining the failure based on the amount of change in the wheel cylinder pressure that occurs when the current supplied to the solenoid is changed by a predetermined amount.

That is, a master cylinder for generating a master cylinder pressure corresponding to a pedaling force applied to a brake pedal, a hydraulic pressure source, a wheel cylinder for braking each wheel with an output hydraulic pressure from the hydraulic pressure source, and the hydraulic pressure source. A hydraulic control valve that is provided between the wheel cylinder and controls the output hydraulic pressure from the hydraulic pressure source to a control pressure according to the master cylinder pressure, and the control pressure by switching the oil passage provided in the hydraulic control valve. Supply spool in the direction of increasing / decreasing and reducing control pressure in the direction of receiving control pressure as feedback pressure and receiving the force of master cylinder pressure in the direction of increasing control pressure, and in the direction of reducing control pressure to this spool In a brake control device having a solenoid that gives a thrust corresponding to the current, the current supplied to the solenoid is changed by a predetermined amount. A predetermined pressure change detecting means for outputting a signal by detecting that the wheel cylinder pressure has changed by the amount of wheel cylinder pressure change that occurs occasionally, and a fail for judging a failure based on the output state from the detecting means corresponding to the supply current. The judgment means is provided.

[0014]

The operation of the present invention will be described.

At the time of fail determination, the master cylinder pressure detecting means detects the master cylinder pressure, and the wheel cylinder pressure estimating means detects the master cylinder pressure value detected by the master cylinder pressure detecting means and the current supplied to the solenoid of the hydraulic control valve. The wheel cylinder pressure supplied to the wheel cylinder is estimated from the value and the value.

On the other hand, the wheel cylinder pressure measuring means measures the wheel cylinder pressure supplied to the wheel cylinder.

Then, the fail judging means judges whether or not it is in the fail state by comparing the estimated value estimated by the wheel cylinder pressure estimating means with the measured value actually measured by the wheel cylinder pressure measuring means.

The operation of the invention according to claim 2 will be described.

In making the fail judgment, the wheel cylinder pressure measuring means actually measures the switching means in the first position in which the master cylinder oil passage communicating with the master cylinder and the wheel cylinder oil passage communicating with the wheel cylinder are in communication with each other. This value is used as the master cylinder pressure actual measurement value.

Further, the value measured by the wheel cylinder pressure measuring means is the measured value of the wheel cylinder pressure in the second position where the output oil passage communicating with the output port of the hydraulic control valve is communicated with the wheel cylinder oil passage. To be done.

The operation of the invention according to claim 3 will be described.

At the time of fail determination, the predetermined pressure change detection means detects that the wheel cylinder pressure has changed by the amount of change in the wheel cylinder pressure that occurs when the current supplied to the solenoid is changed by a predetermined amount, and outputs a signal. .

Then, the fail judgment means judges the failure by comparing the output state from the predetermined pressure change detection means corresponding to the supply current to the solenoid changed by the predetermined amount.

[0024]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) First, the structure will be described.

FIG. 1 is an overall system diagram showing a brake control device of a first embodiment corresponding to the present invention described in claims 1 and 2.

In FIG. 1, 1 is a brake pedal, 2 is a master cylinder, 3 is an oil pressure source, 4 is a wheel cylinder,
5 is a hydraulic control valve, 6 is a fail-safe valve, 7 is an electromagnetic switching valve, 8 is a pilot switching valve (corresponding to switching means), 9
Is a master cylinder pressure oil passage, 10 is a supply pressure oil passage, 11 is a control pressure oil passage, 12 is a wheel cylinder pressure oil passage, and 13 is TC.
S pressure oil passage, 14 drain oil passage, 15 controller,
Reference numeral 16 is a wheel cylinder pressure sensor (corresponding to wheel cylinder pressure measuring means), and 17 is an alarm lamp.

The hydraulic pressure source 3 is composed of an oil pump 3a, a check valve 3b and an accumulator 3c.

The hydraulic control valve 5 increases or decreases the control pressure by switching the oil passage and reduces the control pressure, receives the control pressure as feedback pressure, and increases the control pressure (left direction in the drawing). It has a spool 5a that receives a force due to the master cylinder pressure, and a solenoid 5b that applies a thrust force proportional to the supply current to the spool 5a in the direction of reducing the control pressure (rightward in the drawing).

Sensors (not shown) necessary for ABS control, TCS control, etc. are connected to the controller 15 as input sensors.

Next, the operation will be described.

First, the operation during normal braking, the operation during ABS operation, and the operation during TCS operation are described in Japanese Patent Application Laid-Open No. 4-87867, which has been disclosed in the prior art, and therefore the description thereof is omitted here. To do.

(B) Operation of hydraulic control valve 5 FIG. 2 shows the relationship between the master cylinder pressure Pm and the wheel cylinder pressure Pw (= control pressure Pc) when the solenoid current IS is used as a parameter.

As can be seen from the characteristics shown in FIG. 2, in the present hydraulic system, if the two values of the solenoid current IS, the master cylinder pressure Pm and the wheel cylinder pressure Pw are known, the other one can be calculated.

At the time of normal braking by the boosting action, the solenoid current IS is IS = IS0, and as shown in FIG.
The relationship between the master cylinder pressure Pm and the wheel cylinder pressure Pw is a straight line passing through the zero point. When the wheel cylinder pressure Pw is reduced during ABS operation or the like, pressure reduction control is achieved by making the solenoid current IS larger than IS0, and when the wheel cylinder pressure Pw is increased during ABS operation or the like. Solenoid current I
The pressure increase control is achieved by setting S to IS0 or less (for example, IS1 or IS2).

Further, even when the brake pedal 1 is not depressed (master cylinder pressure Pm = 0), the solenoid current I
Wheel cylinder pressure Pw by setting S to Is0 or less
Occurs.

(B) Fail judgment operation FIG. 3 is a flow chart showing the flow of the fail judgment processing performed by the controller 15 when the ignition is turned on. The failure judgment operation will be described below with reference to this flow chart.

In step 30, the master cylinder pressure actual measurement value Pm1 is read by the sensor signal from the wheel cylinder pressure sensor 16. In other words, immediately after the ignition is turned on with the fail-safe valve 6 turned off,
The pilot switching valve 8 is at the position shown in FIG. 1, and the master cylinder pressure oil passage 9 and the wheel cylinder pressure oil passage 12 communicate with each other (corresponding to master cylinder pressure detection means).

At step 31, a command for turning on the fail-safe valve 6 is output. As a result, the hydraulic pressure from the supply pressure oil passage 10 acts on the pilot switching valve 8, the pilot switching valve 8 switches, and the master cylinder pressure oil passage 9
And the wheel cylinder pressure oil passage 12 are disconnected, and instead the control pressure oil passage 11 and the wheel cylinder pressure oil passage 12 are communicated.

In step 32, IS1 (<IS0) is applied to the solenoid 5b as the solenoid current IS. By applying this solenoid current, as shown in FIG. 2, the wheel cylinder pressure Pw is generated regardless of whether or not the master cylinder pressure Pm is generated.

In step 33, the wheel cylinder pressure measured value Pw1 is read by the sensor signal from the wheel cylinder pressure sensor 16. That is, the pilot switching valve 8
Is at a position where the control pressure oil passage 11 and the wheel cylinder pressure oil passage 12 communicate with each other (corresponding to wheel cylinder pressure measuring means).

In step 34, the wheel cylinder pressure estimated value Pw1 ^* is calculated from the master cylinder pressure actual measurement value Pm1 and the Pw-IS characteristic shown in FIG. For example, when the measured master cylinder pressure value Pm1 is Pm1 = 0 and the solenoid current IS = IS1, the estimated wheel cylinder pressure value is Pw1 ^* from FIG.
Is estimated (corresponding to wheel cylinder pressure estimation means).

In step 35, a deviation ε which is an absolute value obtained by subtracting Pw1 ^* from the wheel cylinder pressure estimated value Pw1 is calculated.

In step 36, it is judged whether the deviation ε obtained in step 35 is less than the set deviation B (corresponding to fail-safe judgment means).

When it is judged at step 36 that ε <B, the routine proceeds to step 37, where the system operation is started. When it is judged at step 36 that ε ≧ B, the routine proceeds to step 38 where the fail safe valve 6 is operated. Is turned off, and the fail-safe operation of turning on the alarm lamp 17 is executed.

When the fail-safe operation for turning off the fail-safe valve 6 is executed, the system is operated as shown in FIG.
In this state, the boosting function using the hydraulic control valve 5, the ABS function, the TCS function, etc. cannot be performed, but the master cylinder pressure generated according to the pedal depression force becomes the wheel cylinder pressure as it is and braking is performed. Reserved.
Next, the effect will be described.

(1) The hydraulic pressure to the wheel cylinders 4 is controlled by the proportional valve type hydraulic control valve 5 having the spool 5a which receives the thrust force by the master cylinder pressure Pm in the pressure increasing direction and the thrust force by the solenoid 5b in the pressure reducing direction. In the brake control device, the wheel cylinder pressure estimated value Pw1 supplied to the wheel cylinder 4 from the master cylinder pressure actual measurement value Pm1 and the solenoid current IS to the solenoid 5b.
^{Since *} is a device for performing a fail judgment process for judging the fail state by comparing the estimated wheel cylinder pressure value Pw1 ^* with the measured wheel cylinder pressure value Pw1, the wheel that should be naturally obtained for a given brake pedal force. It is possible to make a fail determination as to whether or not cylinder pressure is generated.

(2) The first position connecting the master cylinder pressure oil passage 9 and the wheel cylinder pressure oil passage 12 and the control pressure oil passage 1
1 and a second position communicating with the wheel cylinder pressure oil passage 12 are selectively provided with a pilot switching valve 8, and the wheel cylinder pressure sensor 1 is provided in the wheel cylinder pressure oil passage 12.
Since 6 is provided, it is possible to reduce the number of detecting means for obtaining the master cylinder pressure, which is the fail determination input information.

(Second Embodiment) Next, a second embodiment having a different fail judgment action will be described. Since the system configuration and other functions are the same as those in the first embodiment, the description thereof will be omitted.

FIG. 5 is a flow chart showing the flow of the fail judgment processing performed by the controller 15 when the ignition is turned on. The fail judgment operation will be described below with reference to this flow chart.

In step 50, a command to turn on the fail-safe valve 6 is output. As a result, the hydraulic pressure from the input pressure oil passage 10 acts on the pilot switching valve 8, the pilot switching valve 8 switches, and the master cylinder pressure oil passage 9
And the wheel cylinder pressure oil passage 12 are disconnected, and instead the control pressure oil passage 11 and the wheel cylinder pressure oil passage 12 are communicated.

In step 51, the solenoid 5b is applied with a current that changes stepwise as IS1.fwdarw.IS2.fwdarw.IS1 as the solenoid current Is. By this stepwise application of the solenoid current, as shown in FIG. 2, a wheel cylinder pressure Pw that changes regardless of whether or not the master cylinder pressure Pm is generated appears.

In step 52, the wheel cylinder pressure actual measurement value Pw1 corresponding to the solenoid current IS1 and the wheel cylinder pressure actual measurement value Pw2 corresponding to the solenoid current IS2 are read by the sensor signal from the wheel cylinder pressure sensor 16, and Pw1 and Pw2 are read. The actual measured value ΔPw of the amount of change in the cylinder pressure of the wheel is calculated from the difference between the measured value and the difference (corresponding to a predetermined pressure change detecting means).

At step 53, the solenoid current IS1,
An estimated wheel cylinder pressure change amount .DELTA.Pw ^* is calculated from IS2 and the Pw-IS characteristic shown in FIG. For example, when the master cylinder pressure Pm is Pm = 1, Pw1 ^* and I
It is estimated by the difference from Pw2 ^{* at} S2.

In step 54, a change amount deviation Δε which is an absolute value obtained by subtracting the wheel cylinder pressure change amount estimated value ΔPw ^* from the wheel cylinder pressure change amount measured value ΔPw is calculated.

In step 55, it is judged whether or not the change amount deviation Δε obtained in step 54 is less than the set change amount deviation A (corresponding to fail-safe judging means).

When it is judged at step 55 that Δε <A, the routine proceeds to step 56, where the operation of the system is started. When it is judged at step 55 that Δε ≧ A, the routine proceeds to step 57 and the fail safe valve 6 is started. O
The FF is set, and the fail-safe operation of turning on the alarm lamp 17 is executed.

When the fail-safe operation for turning off the fail-safe valve 6 is executed, the system is operated as shown in FIG.
In this state, the boosting function using the hydraulic control valve 5, the ABS function, the TCS function, etc. cannot be performed, but the master cylinder pressure generated according to the pedal depression force becomes the wheel cylinder pressure as it is and braking is performed. Reserved.
Next, the effect will be described.

(3) The hydraulic pressure to the wheel cylinders 4 is controlled by the proportional valve type hydraulic control valve 5 having the spool 5a that receives the thrust force by the master cylinder pressure Pm in the pressure increasing direction and the thrust force by the solenoid 5b in the pressure reducing direction. In the brake control device, the fail judgment process is performed by comparing the measured value ΔPw of the wheel cylinder pressure change amount generated when the supply current to the solenoid 5b is changed from IS1 to IS2 by a predetermined amount and the estimated value ΔPw ^*. Since it is a device that does so, the solenoid 5
It is possible to make a fail determination as to whether or not a change in the wheel cylinder pressure that should be obtained should occur with respect to the change in the current supplied to b.

In the second embodiment, as shown in FIG.
Since the slope of the Pw characteristic is constant regardless of the master cylinder pressure, it holds even if the master cylinder pressure changes.
Further, even if there is some variation in the slope of Pw / IS when the master cylinder pressure is different, it is possible to check the failure multiple times within the set time and to make the final failure determination based on the result, thereby improving the accuracy of the failure determination. You can

(Third Embodiment) Next, a third embodiment in which pressure switches SW1, SW2 and SW3 are provided in place of the master cylinder pressure sensor 16 will be described.

In the third embodiment, as shown in FIG. 7, P ₁ , P ₂ and P ₃ are respectively provided in the wheel cylinder oil passages 12.
The pressure switch SW1, SW2, SW3 that outputs a signal to the controller 15 is turned on when the pressure (P ₁ <P ₂ <P ₃ ) is set. Depending on which of these SW1, SW2, SW3 is ON, the actual Detect wheel cylinder pressure (eg SW
If 1, SW2 are SW3 is OFF at ON, the wheel cylinder pressure is between P ₂ of P _3), like the first embodiment, the fail determination with Pw-IS characteristics of the hydraulic control valve 5 Do.

Therefore, in the third embodiment, since the device using the pressure switches SW1, SW2, SW3 is used, the device cost can be reduced as compared with the case where the pressure sensor is used.

(Fourth Embodiment) Next, a fourth embodiment in which a part of the hydraulic control circuit of the first embodiment is modified will be described.

In the fourth embodiment, two fail safe valves are provided: a first fail safe valve 6a provided in the input oil passage 10 and a second fail safe valve 6b provided at the end of the drain oil passage 14. Is provided to switch both valves 6a and 6b to the oil passage closed / closed position when the ignition is turned off and when the controller 15 determines a failure.

Further, the pilot switching valve 18 is provided in the master cylinder pressure oil passage 9 and serves as a valve for switching only communication / interruption between the master cylinder 2 and the wheel cylinder 4 and for detecting the master cylinder pressure. A sensor 19 is provided.

Since the other structures are the same as those of the first embodiment shown in FIG. 1, the corresponding structures are designated by the same reference numerals and the description thereof will be omitted.

Therefore, in the fourth embodiment, the oil passage is closed by both valves 6a and 6b as shown in FIG. 8 when a failure is judged, so that the first seal 5c and the second seal in the hydraulic control valve 5 are closed. Even if 5d is damaged, hydraulic oil does not leak, and the manual valve can be operated reliably.

Incidentally, this second fail-safe valve 6b
May be a pilot switching valve that switches to the communication side using the output pressure of the first fail-safe valve 6a as the pilot pressure.

Although the embodiment has been described above with reference to the drawings, the specific structure is not limited to this embodiment.

For example, the fail determination may be made by the controller only when the vehicle speed sensor (not shown) detects zero vehicle speed.

Also, an example has been shown in which the driver is notified of the failure by lighting the alarm lamp when the failure is determined, but an alarm sound may be used to warn the driver.

[0073]

According to the present invention as set forth in claim 1, a wheel cylinder is provided by a proportional valve type hydraulic control valve having a spool which receives thrust by a master cylinder pressure in a pressure increasing direction and thrust by a solenoid in a pressure reducing direction. In the brake control device that controls the hydraulic pressure to the wheel cylinder, the wheel cylinder pressure supplied to the wheel cylinder is estimated from the master cylinder pressure value and the current value supplied to the solenoid, and the estimated wheel cylinder pressure value and the measured wheel cylinder pressure value are Since the fail judging means for judging the fail state by comparison is provided, it is possible to make a fail judgment as to whether or not the wheel cylinder pressure that should be naturally obtained with respect to the applied brake pedal force is generated.

According to the second aspect of the present invention, in the brake control device according to the first aspect, the switching means for selectively switching is provided, and the master cylinder pressure information and the wheel cylinder pressure information are obtained only by the wheel cylinder pressure measuring means. In addition to the above effect, there is an effect that it is possible to reduce the number of detecting means for obtaining the master cylinder pressure which is the fail judgment input information.

According to the third aspect of the present invention, the hydraulic control valve of the proportional valve type having the spool for receiving the thrust by the master cylinder pressure in the pressure increasing direction and the thrust by the solenoid in the pressure reducing direction is applied to the wheel cylinder. In the brake control device that controls the hydraulic pressure, the fail judgment means is provided to judge the failure based on the amount of change in the wheel cylinder pressure that occurs when the current supplied to the solenoid is changed by a predetermined amount. The effect is that it is possible to make a fail determination as to whether or not a wheel cylinder pressure change that should be obtained with respect to a current change occurs.

[Brief description of drawings]

FIG. 1 is an overall system diagram showing a brake control device according to a first embodiment of the present invention.

FIG. 2 is a master cylinder pressure-wheel cylinder pressure characteristic diagram in which the solenoid current of the hydraulic control device of the first embodiment device is used as a parameter.

FIG. 3 is a flowchart showing a fail determination process performed by the controller of the first embodiment device.

FIG. 4 is a solenoid current-wheel cylinder pressure characteristic diagram used for obtaining an estimated wheel cylinder pressure value in the fail determination process of the first embodiment device.

FIG. 5 is a flowchart showing a fail determination process performed by the controller of the second embodiment device.

FIG. 6 is a solenoid current-wheel cylinder pressure characteristic diagram used for obtaining a wheel cylinder pressure change amount estimated value in a fail determination process of the second embodiment device.

FIG. 7 is an overall system diagram showing a brake control device according to a third embodiment of the present invention.

FIG. 8 is an overall system diagram showing a brake control device according to a fourth embodiment of the present invention.

[Explanation of symbols]

1 brake pedal 2 master cylinder 3 hydraulic power source 4 wheel cylinder 5 hydraulic control valve 5a spool 5b solenoid 6 fail-safe valve 7 electromagnetic switching valve 8 pilot switching valve (switching means) 15 controller 16 wheel cylinder pressure sensor (master cylinder pressure detecting means, Wheel cylinder pressure measurement means)

Claims (3)

[Claims] 1. A master cylinder for generating a master cylinder pressure according to a pedaling force applied to a brake pedal, a hydraulic pressure source, a wheel cylinder for braking each wheel by an output hydraulic pressure from the hydraulic pressure source, and the hydraulic pressure source. A hydraulic control valve that is provided between the wheel cylinder and controls the output hydraulic pressure from the hydraulic pressure source to a control pressure that corresponds to the master cylinder pressure, and that is provided in the hydraulic control valve. A spool that receives control force as feedback pressure in the direction of increasing / decreasing and reducing the control pressure and receives the force of the master cylinder pressure in the direction of increasing the control pressure, and supplies the spool in the direction of reducing the control pressure. A master cylinder pressure detection that detects the master cylinder pressure in a brake control device that has a solenoid that gives thrust according to the current Stage, wheel cylinder pressure estimating means for estimating the wheel cylinder pressure supplied to the wheel cylinder from the master cylinder pressure value detected by the detecting means and the current value supplied to the solenoid, and the wheel cylinder for actually measuring the wheel cylinder pressure. A brake control device comprising: a pressure measuring unit; and a fail determining unit that determines a fail state by comparing an estimated value estimated by the estimating unit with an actual measured value measured by the actual measuring unit. 2. A first position for communicating a master cylinder oil passage communicating with the master cylinder with a wheel cylinder oil passage communicating with the wheel cylinder; an output oil passage communicating with an output port of the hydraulic control valve; and the wheel cylinder oil. A second position for communicating with the passage is provided with a switching means for selectively switching between, and the wheel cylinder oil pressure passage is provided with the wheel cylinder pressure measuring means so that the switching means is at the first position. A value measured by means is the master cylinder pressure, and a value measured by the wheel cylinder pressure measuring means is the wheel cylinder pressure when the switching means is in the second position. The brake control device according to 1. 3. A master cylinder for generating a master cylinder pressure according to a pedaling force applied to a brake pedal, a hydraulic pressure source, a wheel cylinder for braking each wheel with an output hydraulic pressure from the hydraulic pressure source, and the hydraulic pressure source. A hydraulic control valve that is provided between the wheel cylinder and controls the output hydraulic pressure from the hydraulic source to a control pressure that corresponds to the master cylinder pressure, and that is provided in the hydraulic control valve that controls the control pressure by switching the oil passage. A spool that receives the control pressure as feedback pressure in the direction of increasing / decreasing and reducing the control pressure and receives the force of the master cylinder pressure in the direction of increasing the control pressure, and supplies the spool in the direction of reducing the control pressure. In a brake control device having a solenoid that gives a thrust corresponding to the current, when the current supplied to the solenoid is changed by a predetermined amount. A predetermined pressure change detecting means for detecting a change in the wheel cylinder pressure by the generated change amount of the wheel cylinder pressure and outputting a signal, and a fail judgment for judging a failure based on an output state from the detecting means corresponding to the supply current. And a brake control device.