JPH0229009Y2 - - Google Patents

Description

[Detailed description of the invention] [Subject of the invention and its field of application] The invention is installed in the middle of the hydraulic circuit from the brake master cylinder of the vehicle to the rear brake cylinder, and is designed to reduce vehicle deceleration when braking the vehicle. When the vehicle deceleration exceeds a predetermined value, the brake master cylinder and rear brake cylinder are communicated to make the rear brake cylinder fluid pressure the same as the brake master cylinder fluid pressure, and when the vehicle deceleration exceeds a predetermined value, the brake master cylinder and rear brake cylinder communicate with each other. Particularly related to a brake fluid pressure control device for a vehicle that controls the pressure of the rear brake cylinder to be lower than the brake master cylinder fluid pressure by communicating and disconnecting the cylinder in response to the brake master cylinder fluid pressure and the rear brake cylinder fluid pressure. , relates to a vehicle brake fluid pressure control device in which the distance of the inertia-responsive valve body from the valve seat changes in magnitude according to the rise and fall of the brake master cylinder fluid pressure when the vehicle deceleration is below a predetermined value. .

[Prior art]

As a conventional device of this kind, Japanese Patent Application Laid-Open No. 52-84371
There is one described in the publication No. 1 and shown in Fig. 5.
This conventional device 10 includes a brake master cylinder connection port 11a and a rear brake cylinder connection port 11.
a hydraulically responsive piston 15 having both ends fitted into the inner hole 11c of the body 11 to form liquid chambers 12 and 13 and an air chamber 14 within the body; A spring 16 is installed and urges the hydraulically responsive piston 15 to the right in the drawing.
, a spherical inertia-responsive valve body 18 installed in a liquid chamber 17 that communicates with the liquid chamber 13 through a communication passage 11d of the body 11, and a spring 1 caused by the liquid pressure in the liquid chamber 17.
Piston 20 is slidably displaced to the right against 9.
is the main component. The body 11 is fixed to the vehicle in such a manner that the axis of its inner hole points in the longitudinal direction of the vehicle and forms a predetermined angle θ with respect to the horizontal line LL. When the vehicle is not braking, the hydraulic pressure-responsive piston 15 and the piston 20 are held in the illustrated positions by springs 16 and 19, respectively, and both the connection ports 11a and 11b are connected to the liquid chamber 13, the communication passage 11d, the liquid chamber 17, and the inertia-responsive valve body 18. Valve seat 1 of body 11
The gap between 1e and the liquid chamber 12 communicate with each other.
Therefore, when braking the vehicle, the rear brake cylinder fluid pressure
PW starts to rise at the same value as brake master cylinder hydraulic pressure PM (see Figure 6). When the brake master cylinder hydraulic pressure PM reaches point A in Figure 6,
The hydraulic response piston 15 slides against the spring 16, and the protrusion 15a of the hydraulic response piston 15
is displaced to a position that does not prevent the inertia-responsive valve body 18 from seating on the valve seat 11e. In the subsequent process of increasing the brake master cylinder hydraulic pressure PM, if the vehicle is in a lightly loaded state, the vehicle deceleration will exceed a predetermined value at point B in FIG. It moves and seats on the valve seat 11e, and both connection ports 11a, 1
1e is cut off, and the hydraulic response piston 1
5 has been displaced to a position where its left end is in contact with the body 11 during the period from point A to point B in FIG. The rise in hydraulic pressure from point B to point C in FIG. 6 is due to the time it takes for the inertia-responsive valve body 18 to roll from its rest position in contact with the piston 20 and sit on the valve seat 11e. . As the brake master cylinder hydraulic pressure PM further increases from point C in FIG. 6, a balanced state between the leftward thrust force and the rightward thrust force on the hydraulic response piston 15 occurs up to point D in FIG. During this period, the rear wheel brake cylinder hydraulic pressure PW does not increase, and the subsequent increase in brake master cylinder hydraulic pressure causes the hydraulic pressure response piston 15 to increase.
slides to the right, and the protrusion 15a finally comes into contact with the inertia-responsive valve body 18, causing it to separate from the valve seat 11e. As a result, a well-known proportioning valve operation is performed, and the rear wheel brake cylinder hydraulic pressure increases. It rises as shown by D-E in Fig. 6.

Furthermore, if the brake master cylinder hydraulic pressure PM is increased from point A in Figure 6 while the vehicle is in a constant volume state, the vehicle deceleration will exceed the predetermined value at point F in Figure 6, but the brake master cylinder fluid will During the period when the pressure PM exceeds point C and reaches point F, the piston 20 slides to the right in FIG. It rolls so that it increases. Therefore, the inertia-responsive valve body 1
8 from the valve seat 11e is larger than when the load is light, so the inertia-responsive valve body 18
Since the time from the start of rolling to seat on the valve seat 11e to the time when the valve seat 11e seats on the valve seat 11e is longer than when the valve is lightly loaded, the time from the point F to the point G in FIG.
8 is seated on the valve seat 11e) is larger than the amount of increase in hydraulic pressure from point B to point C. In the process of increasing the brake master cylinder hydraulic pressure PM after this, the same operation as in the case of the light load described above is performed, and the rear wheel brake cylinder hydraulic pressure PW increases as shown in Fig. 6.
It rises like E.

[Problems with conventional technology and their surgical resolution]

However, in the conventional device as described above, the distance between the inertia-responsive valve element 18 and the valve seat 11e is changed by changing the rest position of the inertia-responsive valve element 18 using the piston 20 that responds to hydraulic pressure PM. , when the piston 20 slides against the spring 19, there is a time delay until the inertia-responsive valve element 18 starts rolling toward the piston 20 due to the inertia of the inertia-response valve element 18, and due to vehicle deceleration. The force that causes the inertia-responsive valve body 18 to roll toward the piston 20 side is small, and the inertia-response valve body 18
The differential pressure generated by the brake fluid flowing through the gap between the brake fluid and the valve seat 11e prevents the inertia-responsive valve element 18 from rolling toward the piston 20 and moves the inertia-response valve element 18 toward the valve seat 11e. Since it works to make the above-mentioned gap smaller, when the brake pedal is depressed rapidly, the inertia-responsive valve body 18 does not sufficiently follow the sliding displacement of the piston 20, and the piston 20
Since the inertia-responsive valve body 18 that has started rolling toward the 0 side begins to roll in the opposite direction before it comes into contact with the piston 20, the intended operation is not performed, and the control characteristics of the device are therefore unstable. .

In addition, in the pressure range where the rear wheel brake cylinder hydraulic pressure is adjusted to a lower pressure than the brake master cylinder hydraulic pressure, the area of action of the hydraulic pressure PM, PW and the spring force on the hydraulic responsive piston are constant, and the control characteristics are as follows: Even if the brake fluid pressure increases, the rear brake cylinder fluid pressure does not increase in sections C-D, G-H, and the rear brake cylinder fluid pressure remains constant relative to the brake master cylinder fluid pressure as the brake master cylinder fluid pressure increases. The brake master cylinder hydraulic pressure and the rear brake cylinder hydraulic pressure are If the ideal distribution line between the Generally, priority is given to the control characteristics when the load is light, so the control characteristics when the load is constant are far below the ideal distribution line, resulting in insufficient braking force.

[Technical issues]

As described above, the present invention changes the distance of the inertia-responsive valve element from the valve seat in accordance with the level of brake master cylinder hydraulic pressure when the vehicle deceleration is below a predetermined value. By changing the configuration, we have made the control characteristics more stable than conventional ones, and the spring that biases the hydraulic pressure-responsive piston in the pressure range that adjusts the rear wheel brake cylinder hydraulic pressure to a lower pressure than the brake master cylinder hydraulic pressure. By increasing the force as the hydraulic pressure exceeds a predetermined hydraulic pressure, a control characteristic line that controls the rate of increase in the rear wheel brake cylinder hydraulic pressure to be smaller than the rate of increase in the brake master cylinder hydraulic pressure is set to a predetermined pressure reduction ratio. By having a low section, an intermediate section with a smaller decompression ratio, and a section with a high predetermined decompression ratio, it is possible to control when the vehicle is lightly loaded in a vehicle where the ideal distribution line during light and constant loads is significantly different. The aim is to reduce the lack of braking during constant volume compared to the conventional method without impairing the characteristics.

[Technical means and their effects]

The configuration of the present invention according to this problem consists of the following ~.

a body having a brake master cylinder connection port and a rear brake cylinder connection port; one end thereof and the other end having a smaller diameter than the body are fitted into an inner hole of the body; a first liquid chamber that is exposed and communicates with the brake master cylinder connection port; an air chamber with the other end surface exposed; and an annular valve portion between both ends of which is exposed and communicated with the rear wheel brake cylinder connection port. a second liquid chamber, which communicates with the second liquid chamber through an inner hole of a first annular valve seat member that is supported by the body and cooperates with the annular valve portion, and also communicates with the brake master cylinder connection port. A hydraulic responsive piston, which is divided into an annular third liquid chamber and further has a communication passage therein, which is open at one end surface and communicates between the first liquid chamber and the second liquid chamber.

A spring is installed in the third liquid chamber and biases the hydraulic pressure responsive piston toward the first liquid chamber so that the annular valve portion is separated from the first annular valve seat member.

The third liquid chamber has a large diameter part and a small diameter part that are disposed in the third liquid chamber and slidably fit into the inner hole of the body in a liquid-tight manner, and is moved in a direction to increase the force of the spring by liquid pressure. Hydraulic response sleeve.

a second annular valve seat disposed within the first liquid chamber, and fixed to one end of the hydraulic pressure responsive piston; the second annular valve seat assumes a rest position in contact with a stopper provided on the body when vehicle deceleration is below a predetermined value; a spherical inertia-responsive valve body that is separated from the member and rolls when the vehicle deceleration exceeds a predetermined value to contact the second annular valve seat member and cut off communication between the communication passage and the first liquid chamber; .

The circular area of the piston between one end of the hydraulic responsive piston and the body is subtracted from the circular area of the seal diameter between the annular valve portion of the hydraulic responsive piston and the first annular valve seat member. The area is larger than the circular area of the seal diameter between the other end of the hydraulically responsive piston and the body.

The set load of the spring is such that when the load is light, the hydraulic pressure-responsive piston is held at or near its rest position when the hydraulic pressure is lower than the first predetermined pressure at which the vehicle deceleration of the predetermined value occurs, and when the load is constant, the The hydraulic pressure responsive piston is set to slide in a state lower than a second predetermined hydraulic pressure at which a predetermined value of vehicle deceleration occurs.

A third valve in which the hydraulic pressure applied to the brake master cylinder connection port is higher than the first predetermined hydraulic pressure.
When the predetermined hydraulic pressure is abnormal, the hydraulic pressure responsive sleeve moves against the spring, and when the hydraulic pressure reaches a fourth predetermined hydraulic pressure higher than the third predetermined hydraulic pressure, the hydraulic pressure is increased. The diameters of the large diameter portion and the small diameter portion of the hydraulic response sleeve are set so that the response sleeve contacts the body and is prevented from moving.

[Operations and effects of technical means]

In a device having such a configuration, the rest position of the inertia-responsive valve element is fixed, and the second annular valve seat member, which is the valve seat of the inertia-response valve element, is displaced together with the hydraulic pressure-responsive piston, so that the inertia-response valve element is moved. The distance from the valve seat is changed. The sliding displacement of the hydraulic pressure-responsive piston is much faster and more reliable than the piston displacement following movement of the inertia-responsive valve body in conventional devices, and the sliding displacement of the hydraulic pressure-responsive piston causes the inertia-responsive valve body and the second annular The gap between the valve seat members is expanded,
As the brake fluid flows through this gap, the differential pressure that tends to move the inertia-responsive valve element toward the second annular valve seat member decreases, so the distance between the inertia-response valve element and the valve seat decreases. It is less affected by the pedal depression speed, and the control performance of the device is more stable than that of conventional devices.

In addition, in the device of the present invention, when braking under a light load, the inertia-responsive valve element comes into contact with the second annular valve seat member based on the increase in brake master cylinder hydraulic pressure. After that, as the brake master cylinder hydraulic pressure further increases, the hydraulic pressure-responsive piston moves against the spring toward the third liquid chamber, brings its annular valve portion into contact with the first annular valve seat member, and the well-known The proportioning valve action is created to adjust the rear wheel brake cylinder hydraulic pressure to a value that is reduced at a predetermined pressure reduction ratio as the brake master cylinder hydraulic pressure increases, and then the brake master cylinder hydraulic pressure is reduced to a third predetermined hydraulic pressure. When the hydraulic pressure exceeds the pressure, the hydraulic pressure responsive sleeve starts to move and increases the force of the spring in response to the rise in hydraulic pressure, resulting in a smaller pressure reduction ratio and the rear brake cylinder hydraulic pressure is equal to the brake master cylinder hydraulic pressure. As it rises, it rises at a higher rate of rise than before, and after the movement of the hydraulic pressure responsive sleeve is stopped by the body, the rear wheel brake cylinder hydraulic pressure again increases to the brake master cylinder hydraulic pressure at a predetermined pressure reduction ratio. It increases accordingly. On the other hand, since one of the latter two of these three pressure reduction ratio lines appears at constant load, it is possible to compensate for the lack of braking force at constant load even in vehicles where the ideal distribution during constant load and light load are significantly different. be able to.

In addition, in the device of the present invention, after the inertia-responsive valve element is seated on the second annular valve seat, communication and disconnection between the two connection ports is achieved between the hydraulic-response piston and the first annular valve, which are almost unaffected by vehicle vibration. Since this is done with the seat member,
Compared to the conventional device which performs the above-mentioned communication and cutoff using an inertia-responsive valve body, the communication and cutoff operations are more reliable, and the control characteristics are also stabilized in this respect.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 4.

In FIG. 1, a body 11 of a brake hydraulic pressure control device 10 has a main body 11A and plugs 11B and 11C as main components, and has a brake master cylinder connection port 11a and a rear wheel brake cylinder connection port 11b. The hydraulic pressure-responsive piston 15 inside the body 11 has one end 15b and the other end 15c with a smaller diameter than the inner hole 15 of the body 11.
c, and the interior of the body 11 is divided into a first liquid chamber 17, a second liquid chamber 12, a third liquid chamber 13, and an air chamber 14. The second fluid chamber 12 communicates with the rear wheel brake cylinder connection port 11b, the third fluid chamber 13 communicates with the brake master cylinder connection port 11a, and the first fluid chamber 17 communicates with the rear wheel brake cylinder connection port 11b.
It communicates with the brake master cylinder connection port 11a through a communication passage 11d. The hydraulically responsive piston 15 has an annular valve portion 15d between its both ends, and this annular valve portion 15d is accommodated in the second fluid chamber 12 so that the hydraulically responsive piston 15 moves leftward in FIG. The second liquid chamber 12 and the third liquid chamber 13 are seated on the first annular valve seat member 21 supported by the body 11 by sliding, and are opened through the inner hole of the first annular valve seat member 21.
cut off communication between The spring 16 in the third liquid chamber 13 has its right end connected to the flange portion 15e of the hydraulic pressure responsive piston 15, and its left end connected to the third liquid chamber 13.
It is received by the inner peripheral flange 22a of the stepped hydraulic response sleeve 22 installed therein, and urges the hydraulic response piston 15 to the right. Note that the hydraulic response sleeve 22 is disposed within the third liquid chamber 13, has a large diameter portion and a small diameter portion that are slidably fitted in the inner hole 11c of the main body 11A in a liquid-tight manner, and The spring 16 is moved in a direction where the force of the spring 16 is strengthened by the liquid pressure in the liquid chamber 13. Hydraulic pressure responsive piston 1
5 slides in the right direction, as shown in the figure, the annular valve portion 15d
is restricted by the right end thereof coming into contact with the stepped portion 11e of the body 11, and this position is the rest position. The hydraulic response sleeve 22 has a groove 22b at its left end, is movable between the plug 11B and the shoulder 11f of the main body 11A, and does not come into contact with the hydraulic response piston 15. ing.

The hydraulic pressure-responsive piston 15 includes an axial hole and a radial hole, and has a communication passage 15f that communicates the first liquid chamber 17 with the second liquid chamber 12. This communication path 15f
The right end is open to the right end surface of the hydraulic pressure responsive piston 15, and the right end surface of the hydraulic responsive piston 15 has a second opening.
An annular valve seat member 23 is fixed so as to surround the opening of the communication passage 15f. A spherical inertia-responsive valve body 18 is accommodated in the first liquid chamber 17 . body 11
has both left and right ends pointing in the longitudinal direction of the vehicle, and the inner hole 1
The 1C axis is fixed to the vehicle at an angle of θ with respect to the horizontal axis LL. Therefore, for example, when the vehicle is stopped, the inertia-responsive valve body 18
When the vehicle deceleration exceeds a predetermined value set by θ, the second annular valve seat member 23
roll towards.

In Figure 1, 24, 25, 26, 27, 40, 4
1 is a sealing member, 28 is a retaining ring for the plug 11B, and 29 is a dust cover. Also, 30
is the brake pedal, 31 is the brake booster, 3
2 is a tandem type brake master cylinder, 33
is the left front wheel brake cylinder, 34 is the right front wheel brake cylinder, 35 is the left rear wheel brake cylinder, 3
6 is the right rear wheel brake cylinder, 37, 38 and 3
9 is a brake pipe, and 42 is an air chamber.

FIG. 2 is a diagram showing the control characteristics of the brake hydraulic pressure control device 10 as described above. In Figure 2, the dashed-dotted line a is the ideal distribution line when the load is light, and the dashed-dotted line b
is the ideal distribution line at constant volume. Point B on the solid line indicates the hydraulic pressure value when the vehicle deceleration exceeds a predetermined value when the load is light, and point F indicates the hydraulic pressure value when the vehicle deceleration exceeds the predetermined value when the load is constant. There is. In addition, the C-E line follows the following equation (1) obtained from the balance equation of the left and right thrust forces that the hydraulic responsive piston 15 receives from the spring 16 and the hydraulic pressures PM and PW.

PW=[1-(AS/AV-AL)]・PM+(FP/
AV−AL) ...(1) PW: Rear brake cylinder hydraulic pressure PM: Brake master cylinder hydraulic pressure AS: Circular area that is the seal diameter between the end 15c of the hydraulic response piston 15 and the body 11, AV
-Smaller than AL, larger than AB-AC AV: Annular valve portion 15d of hydraulic pressure responsive piston 15
AL: Circular area corresponding to the seal diameter between the end 15b of the hydraulic pressure responsive piston 15 and the body 11 FP: Circular area corresponding to the seal diameter between the annular valve portion 15d and the first annular valve seat member 21
The load on the spring 16 when the piston is seated on the hydraulic pressure-responsive piston 1.
The value is set to hold 5 in the rest position,
At point B, the hydraulic response piston 15 is connected to the spring 16.
It is also possible to set it so that it is slightly displaced against the force.

The line E-I in FIG. 2 is the following (2) obtained from the balance equation of the left and right thrust force on the hydraulically responsive piston 15 while the hydraulically responsive sleeve 22 is moving.
In addition, the line I-J follows the equation obtained from the balance equation of the left and right thrust forces on the hydraulically responsive piston 15 when the movement of the hydraulically responsive sleeve 22 is stopped by the shoulder 11f of the body. So, this formula is the above formula (1), where FP is FP+
This corresponds to the formula changed to ΔFP.

PW {[1-(AS/AV-AL)]+[(AB-AC)/
(AV-AL)〕}・PM AB: Circular area that is the seal diameter between the large diameter part of the hydraulic response sleeve 22 and the body AC: The seal diameter between the small diameter part of the hydraulic response sleeve 22 and the body Circle area AC<AB−AC Next, the operation of the one shown in Fig. 1 will be explained. When the brake pedal 30 is depressed to brake the vehicle,
The brake master cylinder 32 is operated by the brake booster 31, and the brake master cylinder 3
Brake fluid flows from one pressure chamber of 2 to the front brake cylinders 33, 34 via the brake pipe 37.
and from the other pressure chamber to the rear wheel brake cylinders 35, 3 via the brake pipe 38 and the brake fluid pressure control device 10-brake pipe 39.
6, and the braking operation begins.

The brake fluid pressure-fed from the brake pipe 38 to the brake master cylinder connection port 11a flows between the third fluid chamber 13 and the first annular valve seat member 2 until the brake master cylinder fluid pressure PM exceeds point B in FIG.
1 inner hole - flows through the second liquid chamber 12 to the rear wheel brake cylinder connection port 11b, and also flows through the communication path 11d
It flows through - the first liquid chamber 17 - the communication path 15f - the second liquid chamber 12 to the rear brake cylinder connection port 11b.

Here, assuming that the vehicle is lightly loaded, when the brake master cylinder hydraulic pressure PM exceeds point B in FIG. At point C, the hydraulic piston 15 seats on the second annular valve seat member 23 and blocks the first fluid chamber 17 and the communication path 15f, and as the brake master cylinder hydraulic pressure increases thereafter, the hydraulic piston 15 moves to the inertia-responsive valve body 18.
By moving in unison with the first annular valve seat member 21, a well-known proportioning valve operation is performed, and the rear wheel brake cylinder hydraulic pressure PW is
is the second brake master cylinder hydraulic pressure PM.
Adjustments are made as shown by O-C-E in the figure. When the hydraulic pressure PM further increases from point E in FIG. 2, the hydraulic responsive sleeve 22 moves to the right in FIG.
Until the line of contact with 1f, the hydraulic pressure PW is adjusted to the hydraulic pressure PM as shown by the line E-I in Fig. 2, and when the hydraulic pressure PM further increases from the point I, the line I-
Adjusted as indicated by J.

Further, assuming that the vehicle is in a constant volume state, the inertia-responsive valve body 18 begins to roll to be seated on the second annular valve seat member 23 at point F in FIG. On the other hand, the hydraulic response piston 15 has been slid to a position where its left end 15c (in FIG. 1) is in contact with the plug 11B before reaching point F in FIG. Due to the displacement, the distance of the inertia-responsive valve body 18 from the second annular valve seat member 23 near point F is larger than when the load is light. Therefore, the inertia-responsive valve body 18 is seated on the second annular valve seat member 23.
The difference between point F and point C is greater than the difference between point C and point B. Brake master cylinder fluid pressure after this
When PM increases, the rear brake cylinder hydraulic pressure PW does not increase until the point H where the thrust force balance on the hydraulic pressure responsive piston 15 occurs, and from the point H it increases like H-I-J.

When the brake pedal 30 that has been depressed is released, the inertia-responsive valve 18 separates from the second annular valve seat member 23 when the brake master cylinder hydraulic pressure PM becomes lower than the rear wheel brake cylinder hydraulic pressure PW. , rear brake cylinders 35, 36
The brake fluid in the cylinder returns to the brake master cylinder through the communication hole 15f, which lowers the rear wheel brake cylinder hydraulic pressure, and the spring 16 causes the annular valve portion 15d of the hydraulic pressure-responsive piston 15 to move toward the first annular valve seat member 21. When it is separated from the valve seat member 21, it also returns through the inner hole of the first annular valve seat member 21.

The embodiment shown in FIG. 3 is similar to the air chamber 4 of the embodiment shown in FIG.
A spring 43 is additionally installed inside the sleeve 2 so that the spring 43 urges the hydraulic pressure responsive sleeve 22 in a direction opposite to the hydraulic pressure. The spring 43 acts to shift point I toward point E in FIG. 2, and can reverse the height relationship between point I and point H. FIG. 4 shows the control characteristics of this embodiment, and the height relationship between the H point and the I point is reversed from that in FIG. 2.

Although the embodiment described above is used for a two-system brake system divided into a front wheel brake system and a rear wheel brake system, it can also be used for the well-known digonile type two-system brake system and other systems.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a brake system including an embodiment of the present invention, FIG. 2 is a diagram showing control characteristics of the brake fluid pressure control device of FIG. 1, and FIG. 3 is a diagram showing another embodiment. FIG. 4 is a diagram showing the control characteristics of the device shown in FIG. 3, FIG. 5 is a sectional view showing the conventional device, and FIG. 6 is a diagram showing the control characteristics of the conventional device. 10...braking fluid pressure control device, 11...body,
12...Second liquid chamber, 13...Third liquid chamber, 15...
Hydraulic pressure responsive piston, 16... Spring, 17...
...First liquid chamber, 18...Inertia responsive valve body, 21... First annular valve seat member, 22... Hydraulic pressure responsive sleeve, 2
3...Second annular valve seat member.

Claims (1)

[Scope of Claim for Utility Model Registration] A body having a brake master cylinder connection port and a rear brake cylinder connection port, one end of which and the other end with a diameter smaller than this are fitted into an inner hole of the body. , a first liquid chamber having one end surface exposed in the body and communicating with the brake master cylinder connection port, an air chamber having the other end surface exposed, and an annular valve portion between both ends thereof being exposed and the rear an annular second fluid chamber communicating with a wheel brake cylinder connection port; and communicating with the second fluid chamber through an inner hole of a first annular valve member supported by the body and cooperating with the annular valve portion; an annular third fluid chamber communicating with the brake master cylinder connection port;
a hydraulically responsive piston having a communication passage therein for communicating a fluid chamber and the second fluid chamber; a spring that urges the first liquid chamber to move away from the member; and a large diameter portion that is installed in the third liquid chamber and is slidably fitted into the inner hole of the body in a liquid-tight manner. and a hydraulic responsive sleeve, which has a small diameter portion and moves in a direction to increase the force of the spring due to hydraulic pressure, and is installed in the first liquid chamber and is provided in the body when the vehicle deceleration is below a predetermined value. It occupies a rest position in contact with a stopper and is separated from a second annular valve seat member fixed to one end of the hydraulic pressure responsive piston, and when the vehicle deceleration exceeds a predetermined value, it rolls and closes the second annular valve. a spherical inertia-responsive valve body that contacts the seat member and blocks communication between the communication passage and the first liquid chamber; The area obtained by subtracting the circular area of the seal diameter between one end of the hydraulic pressure responsive piston and the body from the circular area of the seal diameter is less than the circular area of the seal diameter between the other end of the hydraulic responsive piston and the body. The set load of the spring maintains the hydraulic responsive piston at or near its rest position when the hydraulic pressure is lower than the first predetermined pressure that causes the vehicle deceleration of the predetermined value when the load is light, and when the load is constant. The hydraulic pressure-responsive piston is set to slide in a state lower than a second predetermined hydraulic pressure at which the predetermined value of vehicle deceleration occurs, and the hydraulic pressure applied to the brake master cylinder connection port is When the hydraulic pressure is higher than the third predetermined hydraulic pressure, which is higher than the first predetermined hydraulic pressure, the hydraulic pressure-responsive sleeve moves against the spring, and when the hydraulic pressure is higher than the third predetermined hydraulic pressure, A vehicle in which the diameters of the large diameter portion and the small diameter portion of the hydraulic responsive sleeve are set such that when the hydraulic pressure reaches a predetermined hydraulic pressure, the hydraulic responsive sleeve comes into contact with the body and is prevented from moving. Brake hydraulic pressure control device.