Four-piston brake fluid pressure controller with diaphragm

Details Four-piston brake fluid pressure controller with diaphragm Four-piston brake fluid pressure controller with diaphragm

1998-04-06

2001-03-06

Graham, Matthew C. (Department: 3613)

Fluid-pressure and analogous brake systems

Speed-controlled

Having a valve system responsive to a wheel lock signal

C303S116100

Reexamination Certificate

active

06196642

ABSTRACT:

This application claims the benefit of Japanese Patent Application Nos. Hei. 9-114607 and Hei. 9-114612, both filed on May 2, 1997, which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a brake fluid pressure controller having an automatic braking function such as anti-lock control, traction control and yawing moment control, and more particularly, to a structure for sealing a piston in a control valve used in an anti-lock automobile brake.
2. Discussion of the Related Art
A well-known conventional brake fluid pressure controller has a brake fluid passage changed over by pressure generated in a master cylinder, and in which the hydraulic pressure from a hydraulic pressure source is transmitted to a hydraulic pressure transmitter in order to boost the hydraulic pressure. Such a conventional brake fluid pressure controller is disclosed in Japanese Examined Patent Publication No. 61-53265.
FIG. 7
shows a conventional hydraulic brake system of the Japanese Examined Patent Publication No. 61-53265. When a driver presses a brake pedal
301
, hydraulic pressure is generated in a master cylinder
302
. The hydraulic pressure is transmitted to a modulator cylinder
303
via branch pipes
304
a,
306
a.
Therefore, the hydraulic pressure acts on base portions of pistons
307
,
308
, so that the pistons
307
,
308
can be displaced to the left in
FIG. 7
, and a hole
311
of the piston
308
is closed by a conic end portion
310
of a shut-off valve
309
. At the same time, a passage
312
is closed, and servo hydraulic pressure is generated in a hydraulic chamber
313
.
The servo hydraulic pressure generated in the hydraulic chamber
313
displaces the shut-off valve
309
and resists a force generated by a return spring
314
. As a result, pressurized hydraulic fluid flows into a distributing chamber
315
. The pressurized hydraulic fluid then flows from the distributing chamber
315
into hydraulic chambers
317
of both servo cylinders through a passage
316
. Hydraulic pressure generated in the hydraulic chambers
317
displaces a servo piston
318
. Due to the displacement of the servo piston
318
, a stem
319
is displaced to the right in FIG.
7
. As a result, end flanges
320
of each stem
319
engages each auxiliary piston
321
. Therefore, a hole
322
of each auxiliary piston
321
is closed.
The hydraulic fluid in each hydraulic chamber
323
is pressurized by a thrust given by each servo piston
318
. Therefore, the hydraulic pressure in each hydraulic chamber
323
transmitted from the master cylinder
302
is proportionally increased. Accordingly, each auxiliary piston
321
is given a force of servo, and the brake can be operated. As a result, the force a driver needs to apply to the brake pedal
301
can be reduced.
However, the following problems may be encountered in the conventional brake fluid pressure controller. The conventional brake fluid pressure controller does not have an automatic braking function. Further, since the same bulkhead seal is shared by the pistons
307
and
308
, it is difficult to effect an automatic braking operation in which the pistons
307
and
308
are effectively utilized. Further, adding an automatic braking function to the conventional brake fluid pressure controller makes the entire brake structure complicated.
Moreover, a piston arranged in a modulator of a brake booster, such as described above, includes hydraulic chambers formed on both sides of the piston that are sealed by a sealing member, such as an O-ring, attached to an outer circumference of the piston. Therefore, when the piston moves in the cylinder, a sliding resistance is generated between the sealing member and an inner circumferential surface of the cylinder. When a contact pressure between the sealing member and the inner circumferential surface of the cylinder is increased to improve the sealing effect, the sliding resistance is also increased when the piston moves in the cylinder. To overcome the sliding resistance, a high hydraulic pressure is needed in order to operate the piston. When the hydraulic pressure is increased, a loss occurs in the hydraulic pressure over time, and the response of the brake deteriorates. Further, when wheel cylinder pressure is generated, the driver must press the brake pedal
301
harder. Hysteresis occurs due to the sliding resistance of the sealing member when a pressurized state is shifted to a depressurized state. As a result, control characteristics of the brake deteriorate.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a brake fluid pressure controller that substantially obviates one or more of the problems and limitations of the related art.
One object of the present invention is to provide a diaphragm arranged on an end surface of a piston, wherein both hydraulic chambers provided on the right and left of the piston are sealed from each other by the diaphragm.
Additional features and advantages of the present invention will be set forth in the description which follows, and will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure and process particularly pointed out in the written description as well as in the appended claims.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, in accordance with a first aspect of the present invention there is provided a brake fluid pressure controller of a brake having a master cylinder and wheel cylinders including a control valve having a pilot piston, wherein pressure generated in the master cylinder acts on the pilot piston to control pressure generated in a pressure source, and wherein the generated pressure is applied to the wheel cylinders, and changeover valves for applying the pressure on the pilot piston.
In another aspect of the present invention, there is provided a brake fluid pressure controller including a diaphragm slidably arranged on a front end surface of a piston in a cylinder, wherein a circumference of the diaphragm is secured to the cylinder via a flexible portion of the diaphragm, wherein a hydraulic chamber formed in the cylinder and sectioned by an end surface of the piston is sealed by the diaphragm.
In another aspect of the present invention, there is provided a brake fluid pressure controller of a brake having a tandem master cylinder and a wheel cylinder including a control valve connected to a hydraulic pressure source for feeding hydraulic pressure of the hydraulic pressure source to the wheel cylinder while the hydraulic pressure is being controlled by moving a spool piston in response to hydraulic pressure generated in the tandem master cylinder, the spool piston being positioned in the control valve, and a diaphragm on an end surface of the spool piston for changing over a passage, wherein the spool piston is slidably arranged in a cylinder of the control valve, wherein an outer circumference of the diaphragm is secured in a main body of the control valve via a flexible portion of the diaphragm.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.


REFERENCES:
patent: 4660899 (1987-04-01), Ando et al.
patent: 4872731 (1989-10-01), Nakamura
patent: 5123717 (1992-06-01), Willmann
patent: 5171073 (1992-12-01), Matsuda et al.
patent: 5330254 (1994-07-01), Ravndal et al.
patent: 4126120 (1993-02-01), None
patent: 61-53265 (1986-11-01), None

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