US 5,174,635 A · Hydraulic braking pressure control system for rear wheel brake

Abstract

In a hydraulic braking pressure control system for a rear wheel brake wherein a control piston normally works to provide a hydraulic braking pressure control by cooperation with a cut-off valve interposed between an input chamber leading to a master cylinder and an output chamber leading to a wheel cylinder of the brake, the cut-off valve has a valve seat piston whose pressure-receiving area facing the output chamber is larger than the pressure-receiving area facing the output chamber. This ensures that opening and closing of the cut-off valve can be repeated in accordance with the output pressure from the master cylinder, so that the output pressure from the master cylinder can be reduced and applied to the brake wheel cylinder. When the control hydraulic pressure is lost, the control piston and sleeve can be moved in a direction to increase the volume of the output chamber thereby to close the lock valve and tightly close a control chamber between the control piston and sleeve, while restraining by a stopper the movement of the cut-off valve following in a closing direction of the control piston and sleeve. This makes it possible to insure a hydraulic braking pressure applied to the brake wheel cylinder.

Drawings

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Drawings

Claims3

Dependent claims

A hydraulic braking pressure control system for a rear wheel brake, comprising:

an output chamber defined in a housing to lead to a rear wheel brake cylinder;
a control chamber defined in the housing and connected to a control hydraulic pressure source and a reservoir through a switchover valve means which is operable to selectively connect and disconnect said control hydraulic pressure source and said reservoir to said control chamber;
a control piston being provided to have opposite end faces thereof facing the output chamber and the control chamber, respectively;
a partition wall provided in the housing for partitioning said output chamber and an input chamber which is defined in the housing to lead to a master cylinder;
and a cut-off valve interposed between said input and output chambers and movable to a closed position in response to movement of the control piston toward the control chamber, wherein said system further includes:
a sleeve slidably received in said housing with a back of the sleeve facing a pilot chamber leading to said control hydraulic pressure source and with a front end of the sleeve facing said output chamber, said control piston being slidably received in the sleeve and having a front end facing the output chamber and a rear end facing the control chamber defined between the control piston and the sleeve;
and
a lock valve interposed between the control chamber and the switchover valve means, said lock valve being movable to a closed position in response to movement of the sleeve in a direction to reduce a volume of the pilot chamber;
wherein said cut-off valve includes:
a valve seat piston formed into a stepped cylinder shape with a pressure-receiving area thereof facing said input chamber being smaller than a pressure-receiving area thereof facing said output chamber, said valve seat piston being slidably received in said partition wall with an end of the valve seat piston closer to the output chamber operatively connected to the front end of said sleeve, said valve seat piston having a valve seat at an end closer to the input chamber;
a spring interposed between said housing and said valve seat piston to provide an operative connection of said valve seat piston with the front end of said sleeve;
a valve member disposed in the input chamber and biased by a further spring in a direction to seat on the valve seat;
a rod for transmitting an operation of said control piston to said valve member;
and
a stopper fixedly disposed in the housing to restrict the maximum amount of movement of said valve member in the seating direction to a position at which the valve member is moved away from the valve seat upon the maximum movement of the valve seat piston permitted in response to the movement of said sleeve toward the pilot chamber.

12 more elements

Dependencies are inferred from the claim text.

Description8,161 words

Summary1,488 words

#1. Field of the Invention

#The field of the present invention is hydraulic braking pressure control systems for rear wheel brake, of a type comprising an output chamber defined in a housing to lead to a rear wheel brake cylinder, a control chamber defined in the housing and capable of being connected to a control hydraulic pressure source and a reservoir through a switchover valve means capable of switching the communication and interruption, a control piston being provided to have opposite end faces thereof facing the output chamber and the control chamber, respectively, a partition wall provided in the housing for partitioning the output chamber and an input chamber which is defined in the housing to lead to a master cylinder, and a cut-off valve interposed between the input and output chambers and adapted to be closed in response to movement of the control piston toward the control chamber.

#2. Description of the Prior Art

Brief description of the drawings9 figures

#FIGS. 1 to 3 illustrate a first embodiment of the present invention, wherein

#FIG. 1 is a diagram of a hydraulic braking pressure circuit for a vehicle;

#FIG. 2 is a longitudinal sectional view of a hydraulic braking pressure control system for a rear wheel brake; and

Detailed description6,523 words

#The present invention will now be described by way of a first embodiment in connection with FIGS. 1 to 3.

#Referring first to FIG. 1, brake cylinders C.sub.FL, C.sub.FR, C.sub.RL and C.sub.RR are mounted on front and rear, left and right wheels of a vehicle for exhibiting a braking force, respectively. A hydraulic braking pressure output passage 2 is connected to one output port 1a in a tandem type master cylinder 1, while a hydraulic braking pressure output passage 3 is connected to another output port 1b. A hydraulic braking pressure control system M.sub.FR for a right front wheel brake and a hydraulic braking pressure control system M.sub.RL for a left rear wheel brake are interposed between the hydraulic braking pressure output passage 2 and the right front brake cylinder C.sub.FR and the left rear brake cylinder C.sub.RL, respectively. A hydraulic braking pressure control system M.sub.FL for a left front wheel brake and a hydraulic braking pressure control system M.sub.RR for right rear wheel brake are interposed between the hydraulic braking pressure output passage 3 and the left front brake wheel cylinder C.sub.FL and the right rear brake cylinder C.sub.RR, respectively.

#The left and right front wheel brake hydraulic braking pressure control systems M.sub.FL and M.sub.FR are capable of transmitting a hydraulic braking pressure delivered from the output ports 1a and 1b of the master cylinder 1 in response to depression of a brake pedal 4 to the left and right front brake cylinders C.sub.FL and C.sub.FR during a normal braking, and are capable of controlling the hydraulic braking pressure applied to the brake cylinders C.sub.FL, C.sub.FR in response to the operation of switchover valve means V.sub.FL and V.sub.FR which are provided in correspondence to the left and right front wheel brake hydraulic braking pressure control systems M.sub.FL and M.sub.FR, respectively, during an anti-lock control. The left and right rear brake hydraulic braking pressure control systems M.sub.RL and M.sub.RR are capable of reducing and transmitting a hydraulic braking pressure delivered from the output ports 1a and 1b of the master cylinder 1 in response to depression of the brake pedal 4 to the left and right rear brake cylinders C.sub.RL and C.sub.RR during the normal braking, and are capable of controlling the hydraulic braking pressure applied to the brake cylinders C.sub.RL and C.sub.RR in response to the operation of a switchover valve mean V.sub.R common to the hydraulic braking pressure control systems M.sub.RL and M.sub.RR during the anti-lock control.

Facts

Application

07/763,011Filed 20 Sep 1991

Priority

JP 2-25473125 Sep 1990

Granted

29 Dec 1992

Term ended

20 Sep 2011

Estimated · how

Pre-1995 term; greater of 17 years from grant or 20 years from filing when eligible. Maintenance-fee lapses, terminal disclaimers and statutory extensions have not been checked. The continuity chain may be incomplete; this is not an enforceability determination.

Classification4 codes

B60T 8/266
Characterised by producing differential braking between front and rear wheels: using valves or actuators with external control means
B60T 8/265
Using valves with stepped characteristics: for hydraulic brake systems
B60T 8/4225
Debooster systems: having a fluid actuated expansion unit
B60T
Vehicle brake control systems or parts thereof

Description8,161 words

Summary1,488 words

#1. Field of the Invention

#2. Description of the Prior Art

Brief description of the drawings9 figures

#FIGS. 1 to 3 illustrate a first embodiment of the present invention, wherein

#FIG. 1 is a diagram of a hydraulic braking pressure circuit for a vehicle;

#FIG. 2 is a longitudinal sectional view of a hydraulic braking pressure control system for a rear wheel brake; and

Detailed description6,523 words

#The present invention will now be described by way of a first embodiment in connection with FIGS. 1 to 3.

Hydraulic braking pressure control system for rear wheel brake

Life of this patent

Hydraulic braking pressure control system for rear wheel brake

Life of this patent

Life of this patent

Abstract

Drawings

Drawings

Claims3

Description8,161 words

Drawings

Classification4 codes

Life of this patent

Description8,161 words