JPH01122764A - Device for controlling brake at time of vehicle stop - Google Patents

Abstract

PURPOSE:To reduce substantially the longitudinal vibration of a body by controlling brake fluid pressure to be reduced tentatively at the time of reduction start in brake pressure preferable just before the body is brought to a stop by braking. CONSTITUTION:A brake control device includes a brake pressure regulating means M1 controlling the brake pressure for wheel cylinders to be reduced or increased. In this case, a pressure reducing time control means M3 is provided, which computes the time TD of reduction start in brake pressure just before a body is brought to a stop based on the speed of the body detected by a body speed detecting means M2. In addition, a pressure reducing time computing means M4 is provided, which computes a pressure reducing time DELTAT2 to be controlled in reducing pressure since the time of reduction start in pressure based on the speed of the body. And then, when it has come to the time TD of reduction start in pressure, a pressure reducing signal is outputted to the brake pressure control means M1 by a control means M5, and concurrently the control is performed in such a way that a pressure increasing signal is outputted after the pressure reducing time has elapsed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a brake control device for a vehicle such as an automobile, and particularly to a brake control device when a vehicle body is stopped, which is suitable for controlling brake oil pressure immediately before the vehicle body stops.

[Conventional technology]

When a vehicle is stopped by braking at -i, a characteristic vibration in the longitudinal direction of the vehicle body is generated when the vehicle is stopped, which may cause discomfort to the occupants. This vibration is a combination of pitching vibration of the vehicle body, so-called rocking motion, and longitudinal vibration of the vehicle body having a period of several Hz. Among these, pitching vibration is related to the characteristics of the vehicle's suspension spring and shock absorber, so conventionally, devices have been devised to increase the damping force of the shock absorber during vehicle braking to reduce the occurrence of pitching vibration. There is.

(Problems to be Solved by the Invention) According to the above-mentioned conventional device, pitching vibration when the vehicle body is stopped can be reduced to some extent. However, since it is impossible to reduce the vibration in the longitudinal direction of the vehicle body, the occupant may feel uncomfortable ride due to this vibration.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problems, that is, to appropriately reduce vibrations in the longitudinal direction of the vehicle body that occur when the vehicle body is stopped.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention, as shown in FIG.
Ml); a vehicle speed detection means (M2) for detecting the vehicle speed; and a brake pressure reduction start timing T immediately before the vehicle stops, based on the vehicle speed. a depressurization time calculation means (M3) for calculating the decompression time, based on the vehicle speed, a depressurization time calculation means (M4) for calculating T2 from the depressurization start time to the depressurization time to be controlled for decompression, and the depressurization start time TD. control means (M
5).

The present invention was made with the focus on the fact that longitudinal vibration of the vehicle body can be significantly reduced by temporarily reducing the brake fluid pressure at a suitable time to start brake pressure reduction immediately before the vehicle body stops due to braking.

[Effect] Next, the principle of operation of the device of the present invention will be explained.

Generally, wheels are mounted so as to be vertically displaceable relative to a vehicle body using suspension springs and absorbers in order to absorb road surface irregularities.

On the other hand, although we tend to think that it has high rigidity against movement in the longitudinal direction, in reality, it is caused by bending of the rubber bushings attached to the rotating part of the suspension link or other link components. Displacements in the directions are also possible. Furthermore, during braking, the wheels themselves undergo deflection and deformation due to the braking force.

First, we will discuss the generation mechanism of longitudinal vibration immediately after braking stops.

When braking, a force equivalent to the braking force acts between the wheels and the vehicle body. This force causes relative displacement between the wheels and the vehicle body. If the spring constant of the wheel's longitudinal stiffness is K, then
This displacement causes the suspension system to change to %χ2 (χ:
Then, when the vehicle comes to a stop, the potential energy is converted into kinetic energy of the vehicle, which causes longitudinal vibration of the vehicle body.

One possible way to reduce this vibration is to increase the rigidity of the wheels in the longitudinal direction. However, since the longitudinal stiffness is closely related to the impact transmitted to the vehicle body when passing over a bump, etc., increasing the longitudinal rigidity unnecessarily causes the problem that the shock transmitted to the vehicle body also increases significantly.

Taking these points into consideration, the present invention instantly lowers the brake pressure immediately before the vehicle stops, thereby setting the wheels in a free state and dissipating the energy accumulated in the suspension system through wheel vibration, thereby reducing the vehicle body. This is intended to suppress the occurrence of longitudinal vibrations. That is, when the vehicle is stopped, the vehicle body vibrates back and forth due to the compliance of the suspension system, with the grounding point of the wheels as a fixed point. However, if the brake oil pressure is reduced at the same time as the vehicle stops, the wheels can move freely back and forth. In this situation, the mass of the car body is very large compared to the mass of the wheels, so the car body does not vibrate, but the wheels vibrate, the energy stored in the suspension system is released, and the vibration of the car body is reduced. suppressed.

Next, an example of a simulation that is the basis of the above-mentioned control will be explained with reference to it.

Figure 2 shows the vibration state of the vehicle body when it is stopped, determined by simulation calculations. FIG. 1(a) shows the conventional case, and shows the vehicle body position P0 and vehicle body longitudinal acceleration G0 when stopped at a constant deceleration (deceleration acceleration -0.3G). From this, it can be seen that after the stop time T, longitudinal vibrations occur for several cycles. On the other hand, FIG. 1 et al.) show the case where the present invention is applied. That is, an example of a simulation result is shown in which the brake pressure B is reduced for a pressure reduction time ΔT2 at the pressure reduction start time TS immediately before the vehicle body stops, and then the brake pressure B is increased again.

From this, it can be seen that the longitudinal acceleration G of the vehicle body quickly becomes zero, and the vibration (PI) is significantly reduced.

Also, looking at this vehicle body stopping position P (Figure 2 (b)), the final stopping position is approximately 1011111 times lower than in the conventional case where brake pressure is not controlled (Figure 2 (a)). It is moving in the forward direction. However, the point at which the vehicle body is displaced most forward, P OH* PIN, is a difference of about 2[ll11], and the braking distance does not substantially increase.

In the simulation example shown in FIG. 2, pressure reduction is started approximately 0.7 seconds before the estimated vehicle speed stop time.

This is because there is a delay in response to pressure reduction.

As described above, the present invention can significantly reduce the longitudinal vibration of the vehicle body, so-called rocking back, by reducing the brake pressure all at once at the time M To when the brake pressure starts to decrease immediately before the vehicle body stops. .

〔Effect of the invention〕

Therefore, the present invention can significantly reduce vibrations in the longitudinal direction of the vehicle body that occur after the vehicle body has stopped due to sudden braking, etc., and can improve the feeling during braking.

〔Example〕

Next, embodiments of the present invention will be described based on the drawings.

FIG. 3 shows a first embodiment of the brake system according to the present invention, and FR, FL, RR, and RL indicate the right front wheel, the left front wheel, the right rear wheel, and the left rear wheel, respectively.

Reference numerals 2 to 5 are wheel brake cylinders provided on each wheel. 6 is a proportioning valve that adjusts the oil pressure of the rear wheels, 1 is a master cylinder, 7 is a brake pedal, and 8 is a stop lamp switch, and each of the above elements is a configuration that is installed in a normal vehicle.

The following are constituent elements of the present invention, and are denoted by reference numeral 100.
100' is a flow path switching valve for controlling the oil pressure of the front wheel and rear wheel cylinders, respectively, and 101, 101'
is a reservoir for temporarily storing brake oil, 102, 102'
is a check valve. These constitute brake pressure adjusting means. Further, 300 is a front and rear wheel speed sensor, and 200 is an electronic control circuit (ECU) that drives the switching valves 100 and 100' based on a signal from the wheel speed sensor 300.

The operation of this embodiment will be explained based on the above diagram.

In the illustrated state, the hydraulic pressure of the master cylinder 1 generated by depressing the brake pedal 7 is directly applied to each wheel cylinder 2.3.4.5 to effect braking. On the other hand, the wheel speed sensor 300 momentarily sends a pulse signal or voltage at a frequency proportional to the wheel speed to the ECU 200.
Output to.

The ECU 200 calculates vehicle speed, deceleration acceleration, etc. from the signal. ECU 200 calculates an estimated vehicle stop time from the obtained vehicle speed and deceleration acceleration. On the other hand, EC
U200 stores in advance data indicating how many m5ec before the estimated vehicle stop time TS to start reducing the brake pressure with respect to vehicle deceleration. ECU20
0 calculates the depressurization start time and depressurization holding time based on these data from time to time, and when the time is reached, the switching valve 100. Outputs a signal that drives too'.

This drive signal causes the valves 100, 100' to
Switched to side position, wheel cylinders 2, 3, 4
．． The brake fluid in 5 flows into the reservoir 101.101' and the cylinder pressure is reduced. When the reduced pressure holding time has elapsed, the valves 101 and 101' return to their previous positions (positions A in the figure), and the pressure of the master cylinder 1 is applied to the wheel cylinder again, increasing the brake pressure.

Next, the estimated vehicle body stop time (TS) and decompression start time (T
o ) time difference (: I & positive pressure pre-pressure time) ΔT.

A method of setting the depressurization holding time ΔTt will be described. Generally, the vehicle body deceleration acceleration and the brake pressure are in an approximately proportional relationship, and when the vehicle body deceleration acceleration is small, the brake pressure is low, so it does not take much time to reduce the pressure. Conversely, when the deceleration acceleration is large, the brake oil pressure is high, so it takes time to reduce the pressure. Therefore, the time difference ΔTS needs to be changed depending on the magnitude of the deceleration acceleration. Therefore, E.C.U.
200 calculates the deceleration acceleration from the pulse frequency or voltage generated by the wheel speed sensor 300, and determines the time difference ΔT1. The reduced pressure holding time ΔT2 is similarly set to be long when the deceleration acceleration is large, and short when the deceleration acceleration is small. Here, the above time difference ΔTS and reduced pressure holding time ΔT2
To describe the approximate time of ΔT1. Both ΔT2 are approximately 0.2 seconds at the longest, and are set so as not to exceed this even in the case of large deceleration and acceleration.

Next, the above-mentioned calculation flowchart is shown in FIG. Fourth
The figure is a flowchart of the processing procedure executed by the microcomputer within the ECU 200.

First, in step S1, a brake signal from the stop lamp switch 8 is read, and in step S2, a wheel speed signal from the wheel speed sensor 300 is read. Next, in step S3, the slip rate is calculated from the wheel speed sensor signals of the front wheels and the rear wheels by a known method, and it is determined whether or not this slip rate is larger than an appropriate range. When it is larger, slip rate control is performed in step S4. ``This slip rate control is executed by a known method, for example, by calculating the wheel speeds and wheel decelerations of the front wheels and rear wheels, creating an approximate vehicle body speed, and using these to judge the vehicle condition and road surface condition, A control signal is output to the pulps 100 and 100' so that the front and rear wheels have appropriate slip ratios. The pulps 100 and 100' control switching between positions A and B to appropriately adjust the brake pressure of the wheel cylinder by increasing or decreasing the pressure.

On the other hand, when it is determined in step S3 that the slip ratio is not large, that is, when the wheels are not in a slip (locked) state, control from step S5 onwards is executed. Here, when the wheels are not in the locked state, there is a one-to-one correspondence between the wheel speed and the vehicle body speed, so the following calculation is performed by regarding the wheel speed as the vehicle body speed.

First, in step S5, the vehicle body deceleration α is calculated from the rate of change of the wheel (body) speed ■. In step S6, an estimated vehicle stop time T is determined based on the vehicle speed V and the vehicle deceleration α.

time ΔT8, and time ΔT before depressurization.

is calculated from a preset map or calculation formula. Next, in step S7, the decompression start time TD is determined from the current time.
The waiting time ΔTD (ΔTS=ΔT.

-ΔTS) and the reduced pressure holding time ΔT2.

Next, in step S8, the waiting time ΔTD and the ECU2
40 calculations - calculation cycle time Δ of the time required for a cycle
Comparison with Tc is made and ΔTD>ΔT.

In this case, the process returns to step S1 and the above procedure is executed. This is to perform control based on the latest data possible. On the other hand, if ΔTS<TS, EC
The U200 measures time by ΔTD in step S9, and after a period of ΔTS, outputs a pressure reduction signal for performing pressure reduction for a pressure reduction holding time ΔT2 in step SIO, thereby reducing the brake hydraulic pressure. After outputting a pressure reduction signal for a pre-calculated pressure reduction holding time ΔT2, the control is stopped for ΔT1 in step Sll, and then returns to the start.

Here, the reason why the control stop period of ΔTS is provided is to improve the stability of the control. This is because if the starting state is returned immediately after the end of depressurization, if there is even a slight amount of vehicle speed remaining at that point, depressurization may be performed again, which may extend the braking distance. This control stop time ΔTS
The preferred time is 0°5 to 5 seconds.

In addition to the method described above, the decompression start time can be determined by determining the decompression start vehicle speed ■ from the vehicle deceleration α. The process may be such that the pressure reduction is started when the vehicle speed (2) reaches the vehicle speed vD. Further, instead of finding the vehicle body deceleration α from the wheel speed, an accelerometer may be installed and its output may be used instead.

Next, another embodiment of the flow path switching valve will be described.

FIG. 5 is an example in which a 3-point, 3-position valve is used as the flow path switching valve. At valve position A, the brake system becomes a normal brake system, and the master cylinder (MC) and wheel cylinder (W-C) are in communication. At the same position B,
Oil in the wheel cylinder (W-C) flows into the reservoir 101 and is depressurized. Further, at the same level Hc, the communication between the wheel cylinder (W-C), the master cylinder (MC), and the reservoir 101 is cut off, and the pressure of the wheel cylinder (W-C) is maintained constant.

Moreover, the one shown in FIG. 6 uses two 2-point/2-position valves to enable operation of the flow path switching valve, so the pulp 100-a is connected to the master cylinder (M・C) and the wheel cylinder. Open and close the flow path between (W and C). Same valve 100-
b is provided between the wheel cylinder (W-C) and the reservoir 101, and opens and closes this flow path. When reducing the wheel cylinder pressure, first the valve 100-a is switched to position B, then the valve 100-b is switched to position B, and the pressure is reduced. On the other hand, when increasing the pressure, first return the valve 100-b to position A, then return the valve 100-a to position A, and connect the master cylinder (MC) and wheel cylinder (W-C). The pressure in the wheel cylinder (W-C) is increased.

In the hydraulic control circuit described above, when the wheel cylinder pressure is increased again after being reduced, the pressure is increased using the pressure of the master cylinder, so the driver must depress the brake pedal one step.

FIG. 7 shows an embodiment in which this pressure increase is performed by a pump without depending on the master cylinder pressure. In Figure 7, 1
03 is a hydraulic pump, which is installed between the reservoir 101 and the wheel cylinder (W-C), and after the pressure of the wheel cylinder (W-C) is reduced, by operating this pump 103, water flows into the reservoir 101. Pressure is increased by pumping oil to the wheel cylinder (W-C).

In addition, in the case of pressure increase by this pump 103, the valve 10
Needless to say, 0-a is switched to position B, and 1oo-b is switched to position A. As the pump 103, various types such as an electromagnetic solenoid type, a piezoelectric type, and a motor type can be used.

FIG. 9 shows an operation time chart of the hydraulic circuit shown in FIG. 7. In addition, the valve 100'-a is a mode switching valve,
100-b will be designated as a pressure reducing valve.

Next, another example of the pressure increasing method is shown in FIG. In this embodiment, the pressure is increased by applying a hydraulic pressure separate from the brake system to the piston 101' of the reservoir, and by force-feeding the brake oil accumulated in the reservoir to the wheel cylinder. be. In the embodiment, hydraulic pressure from a power steering system is used. 1000 in the figure
1 is a hydraulic pump for power steering, 1001 is a power steering gear box, and 1004 is an oil sump. Reference numerals 1002 and 1003 constitute components of the present invention. Reference numeral 1002 is a two-position valve which normally assumes the valve position indicated by A in the figure. 1003 is a relief valve. Increasing the wheel oil pressure according to this embodiment is performed in the following process. First, a certain amount of brake oil flows into the reservoir 101' due to the pressure reduction operation. Next, the valve 100
2 takes position B, the hydraulic system indicated by P in the figure receives the hydraulic pressure (approximately 30
~35 atm) is generated. This oil pressure is applied to the reservoir 101'
Since the oil pressure is guided to the hydraulic chamber 101'-3 of the piston 101'-2, the hydraulic pressure causes the piston 101'-
1 pressure-feeds the brake fluid in the reservoir toward the wheel cylinder, increasing the pressure. In this case, of course the valve 10
0-a takes position B, and 100-b takes position B. According to this pressure increase method, there is no need to press the brake pedal during pressure increase, resulting in a good feeling.

It goes without saying that the valve configuration of the brake pressure regulating means for controlling the oil pressure of the wheel cylinder may be other than that shown in this figure as long as it can operate in the same manner as described above.

The system shown in Fig. 3 is one in which the present invention is applied to a brake system for a rear-wheel drive vehicle which has two hydraulic systems, mainly for the front and rear wheels. The hydraulic system is equipped with a hydraulic control device.

Although it is preferable to control the brake pressure for both the front and rear wheels in this way, considerable effects can be obtained even if the brake system is controlled only for the front wheels or only for the rear wheels.

Next, an example of application to a front wheel drive vehicle is shown in FIG. 1O.

In the case of a front-wheel drive vehicle, a so-called cross-piped brake system is generally used as shown in the figure. In this case, a brake pressure regulating device 50, 60 shown in FIG. 3, FIG. 5, FIG. 6, or FIG. 7 is installed in each system.

In this case as well, in order to increase the vibration reduction effect when the vehicle body is stopped, it is preferable to control both systems simultaneously, but the effect can be obtained even if only one system is controlled. In this case, since only one brake pressure regulating device is required, there is an advantage that the cost is low.

In the above-described embodiment, the brake pressure is once reduced at an appropriate pressure reduction start time TD immediately before the vehicle stops to reduce vibrations in the longitudinal direction of the vehicle. In order to increase the vibration reduction effect, it is preferable to reduce the pressure rapidly, but if the speed of pressure reduction is too high, high-frequency vibrations will occur in the suspension system, giving the driver a sense of discomfort. may be given. This is an uncomfortable feeling caused by the sudden change in wheel braking force. This vibration can be prevented by appropriately controlling the rate of pressure reduction.

For example, by providing a throttle with an appropriate throttle diameter in the middle of the conduit between the wheel cylinder and the reservoir, it is possible to prevent the rate of pressure reduction from becoming excessive. Further, for example, in the hydraulic circuit shown in FIG. 6, the reduced pressure pulp 100-b
By intermittently driving (pulse pressure reduction) with an appropriate duty ratio, the pressure reduction speed can be adjusted arbitrarily. FIG. 10 shows the relationship between the drive of the valve 100-b and the brake oil pressure at this time, and (A) shows the relationship between the drive of the valve 100-b and the brake oil pressure.
B) shows the case without pulse decompression.

FIG. 12 shows another embodiment of a reservoir that smoothly performs pressure reduction and prevents the above-mentioned discomfort.

In FIG. 12, 2000 is a reservoir housing, 3
000 is a reservoir piston, 4000 is a return spring, and 3002 is a sealing O-ring. 5000 is an oil reservoir chamber, and brake oil flows into the chamber 5000 from an inlet 2001 when the pressure is reduced. A needle 3001 is installed in the piston 3000 with a portion thereof fitting into the inlet 2001. At the initial stage of pressure reduction, the brake oil flows into the oil reservoir chamber through the fitting gap 2002 at the inlet to the needle flow, so that pressure reduction is performed slowly. Once the pressure has been reduced to a certain extent, the needle moves down as the piston moves, increasing the speed of pressure reduction. Therefore, sudden pressure reduction is prevented, and the above-mentioned discomfort can be eliminated.

Further, FIG. 13 shows the measurement results of vehicle body longitudinal vibration when the brake control according to the above embodiment is performed (solid line c) and when it is not performed (dotted line 2).

As shown in FIG. 13, it can be seen that vibrations generated in the vehicle body can be significantly reduced by appropriately reducing the brake pressure immediately before the vehicle body stops.

In addition, in the above embodiment, when the wheels are not in the locked state, there is a correspondence between the wheel speed and the vehicle body speed, so the wheel speed from the wheel speed sensor is used as the vehicle body speed. Alternatively, an ultrasonic sensor or the like may be emitted onto the road surface, and the actual vehicle speed may be detected from the reflected waves or light.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing the configuration of the present invention, Fig. 2 is a waveform diagram showing a simulation example to explain the present invention in detail, and Fig. 3 is a hydraulic and electrical circuit diagram showing an embodiment of the present invention. , FIG. 4 is a flowchart showing the processing procedure executed by the electronic control circuit (ECU 200) shown in FIG. 3, and FIGS. 5 and 6 are partial hydraulic circuit diagrams showing other embodiments of the switching valve.
7 and 8 are partial hydraulic circuit diagrams showing other embodiments of the present invention, FIG. 9 is a timing chart for explaining the operation of the hydraulic circuit in FIG. 7, and FIG. 10 is another embodiment of the present invention. A hydraulic and electrical circuit diagram showing an example, Fig. 11 is a waveform diagram to explain the operation of pulse reduction, Fig. 12 is a sectional view showing an embodiment of the reservoir, and Fig. 13 is a waveform diagram showing the effect of one embodiment. be. ■...Master cylinder, 2, 3.4.5...Wheel cylinder, 7...Brake pedal, 8...Stop lamp switch, 100,100'...Switching valve (brake pressure adjustment means) , 300...Wheel speed sensor. Representative Patent Attorney Takashi Okabe (a) -C

Claims (10)

[Claims] (1) A brake pressure adjusting means capable of decreasing or increasing the brake pressure of a wheel cylinder that adjusts a control force to the wheels; a vehicle speed detecting means for detecting vehicle speed; a pressure reduction time calculation means for calculating a pressure reduction start time T_D of brake pressure immediately before stopping; a pressure reduction time calculation means for calculating a pressure reduction time ΔT_2 for which pressure reduction control is to be performed from the pressure reduction start time based on the vehicle body speed; A brake control device when a vehicle body is stopped, comprising: a control means for outputting a pressure reduction signal to the brake pressure control means when a start time T_D has been reached, and a control means for outputting a pressure increase signal to the brake pressure control means after the elapse of the pressure reduction time. (2) The control means includes a slip control means for controlling brake pressure according to the slip situation of the wheels, and when the slip control means is not controlling, the vehicle body speed detection means detects the wheel speed as the vehicle body speed. A brake control device when a vehicle body is stopped according to claim 1. (3) The depressurization timing calculation means calculates the estimated vehicle stop timing T_S from the vehicle speed and the vehicle deceleration determined from the vehicle speed, and also calculates the pre-depressurization drop time ΔT_1 based on the vehicle deceleration. The depressurization start time T_D is calculated from the vehicle body stop time T_S and the pre-depressurization drop time ΔT_1 (T_D=T_S−ΔT_
1) A brake control device when a vehicle body is stopped according to claim 2, characterized in that: (4) The control means determines a vehicle speed V_D at the start of pressure reduction based on the vehicle deceleration, sets a time when the vehicle speed reaches the vehicle speed V_D at the start of pressure reduction as a pressure reduction start time T_D, and performs control to output a pressure reduction signal. The brake control device when the vehicle body is stopped according to claim 3, wherein the brake control device performs the following: (5) The pre-depressurization time ΔT_1 and the depressurization time ΔT
When the vehicle body is stopped according to claim 3, _2 is corrected based on the magnitude of the vehicle body deceleration, and is corrected to increase as the vehicle body deceleration increases. brake control device. (6) Brake control when the vehicle body is stopped according to claim 1, wherein the brake oil pressure adjusting means is provided in at least one of a plurality of brake systems extending from a master cylinder to a wheel cylinder. Device. (7) After outputting the pressure reduction signal, the control means:
When the vehicle body is stopped according to claim 1, a control stop period is set in which the output of the decompression signal is stopped for a predetermined time regardless of the subsequent vehicle speed and vehicle deceleration. Brake control device. (8) The brake pressure adjusting means controls the pressure reduction speed by intermittently driving a solenoid valve involved in pressure reduction, the brake when the vehicle body is stopped according to claim 1. Control device. (9) Hydraulic pressure generating means, which is composed of a flow path cutoff valve installed between the gear box and the reservoir tank of the power steering hydraulic system and a regulator valve attached to the cutoff valve, and generates a constant oil pressure by closing the cutoff valve. 2. The brake control device according to claim 1, further comprising pressure increasing means for increasing the pressure after decreasing the pressure by applying the hydraulic pressure to the back surface of the brake oil reservoir piston. (10) In the reservoir that temporarily stores brake oil during depressurization, by providing a needle on the reservoir piston that fits into the brake oil inlet with an appropriate clearance, the amount of brake oil that flows into the reservoir when depressurization starts. The brake control device according to claim 1, further comprising a reservoir that controls the initial pressure reduction speed by limiting the pressure reduction speed.