Electromagnetic valve and hydraulic circuit

Details Electromagnetic valve and hydraulic circuit Electromagnetic valve and hydraulic circuit

2000-08-08

2002-04-02

Rodriguez, Pam (Department: 3613)

Fluid-pressure and analogous brake systems

Speed-controlled

Having a valve system responsive to a wheel lock signal

C303S115400, C303S116100, C137S627500, C251S129150

Reexamination Certificate

active

06364431

ABSTRACT:

CROSS REFERENCE TO RELATED APPLICATION
This application is based on Japanese Patent Application No. Hei 11-241468 filed on Aug. 27, 1999, the content of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention:
The present invention relates to an electromagnetic valve for a vehicular brake apparatus and a hydraulic circuit thereof.
2. Description of Related Art:
Conventionally, in a vehicular brake system, a pump is used for practicing several kinds of control methods such as a trace control (VSC), a traction control (TRC) and a brake assist control. The pump pressurizes a brake fluid from a master reservoir and supplies the pressurized brake fluid to a wheel cylinder. Additionally, a normally close type electromagnetic valve is used between the pump and the master reservoir for opening and closing a passage therebetween. For instance,
FIG. 7
shows this kind of valve. A valve has a movable member
102
having a plunger
100
and a ball
101
which are welded integrally. Normally, a spring
103
pushes the movable member
102
in a direction A. Therefore, a fluid communication between a suction side of the pump and the master reservoir is closed by pressing the ball
101
on a seat surface
105
of a seat member
104
. When a coil
106
is energized, the movable member
102
is attracted in a direction B, opens the connection.
However, in a case that a large pulsation is generated in a pressure P
2
, a pressure difference is generated between a front end and a rear end of the plunger
100
. Therefore, the movable member
102
occasionally moves in direction B even though the coil
106
is not energized.
Such an unnecessary movement of the movable member
102
causes an unnecessary opening and lowers a controllability of the system.
SUMMARY OF THE INVENTION
The present invention addresses these drawbacks by providing an improved electromagnetic valve and a hydraulic circuit.
It is therefore an object of this invention to provide an electromagnetic valve for avoiding an unnecessary and undesired opening even if a pressure pulsation is generated.
It is a further object of this invention to provide a small electromagnetic valve.
It is another object of this invention to provide a hydraulic circuit having an electromagnetic valve in which an unnecessary and undesired opening is avoided even if a pressure pulsation is generated.
According to a first aspect of the present invention, a plunger and a movable member are made as independent members. The plunger is separated from the movable member to permit a free movement of the movable member between the plunger and the seat member. Therefore, if the plunger moves undesirably, the movable member can keep a closing condition in response to a pressure difference between a plunger side and a valve seat side.
The electromagnetic valve may apply to a hydraulic circuit, such as a brake fluid circuit for a vehicle. In this case, the electromagnetic valve is disposed between a suction side of a pump and a reservoir for supplying a brake fluid.


REFERENCES:
patent: 4312380 (1982-01-01), Leiber et al.
patent: 5316378 (1994-05-01), Maehara
patent: 5335984 (1994-08-01), Alaze et al.
patent: 5542755 (1996-08-01), Staib et al.
patent: 5683151 (1997-11-01), Friedow et al.
patent: 5718489 (1998-02-01), Megerle et al.
patent: 6065816 (2000-05-01), Nakazawa
patent: 6206486 (2001-03-01), Sakai et al.
patent: 6209970 (2001-04-01), Kamiya et al.

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