Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1995-04-28
1996-09-17
Ballato, Josie
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
25112902, 25112914, F16K 3106
Patent
active
055561756
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a solenoid valve, and more particularly, to a solenoid valve which is particularly effective for brake-pressure control of an anti-lock brake system (ABS) for vehicle use.
2. Description of the Related Art
In brake-pressure control according to an ABS, as shown in FIG. 3, when rotation of a tire shows a tendency to lock, hydraulic pressure in a wheel cylinder is reduced by opening a reducing solenoid valve 102, and when the rotation of the tire resumes, the hydraulic pressure in the wheel cylinder is increased in a step-like fashion by opening a pressure increasing solenoid valve 101 for a few milliseconds periodically responsive to a pulse driving signal. If the cross-sectional area of the pressure increasing solenoid valve 101 is large, since an amount of the pressure increase per pulse signal becomes large, hydraulic pulsation increases and the tire easily reaches a lock-up state. Conventionally, in order to prevent the above problems and to increase a suitable amount of the hydraulic pressure in the brake-pressure control, a control orifice inside the pressure increasing solenoid valve 101 has been provided.
However, the control orifice increases the passage resistance between a master cylinder (M/C) and wheel cylinder (W/C) during normal braking operations, and thereby it causes a problem in which a long time delay until the braking operations take effect is introduced and it lowers the quality of the brake feeling. In an attempt to provide a device solving the above problems, Japanese Unexamined Patent Publication No. 64-49779. teaches that during normal braking operations, a hydraulic pressure valve is maintained in a wide-open state by holding a movable member with a permanent magnetic holding device. During brake-pressure control by the ABS, the movable member is separated from the holding device by means of electromagnetic power. After that, when the brake fluid flows through an inflow area installed a globe-shaped sealing member, a suction effect is created on the sealing member. Furthermore, when the brake fluid flows through holes formed in a sealing support member, a pressure difference is created between upper and bottom surfaces of the movable member, and a suction effect is created on the bottom surface of the movable member. Due to the suction effects, the valve does not open completely but moves within a narrow range. Therefore, it is possible to improve controllability of the brake fluid pressure and prevent time delay of the normal braking operations.
However, the above device is required to provide the permanent magnetic holding device not to create the suction effect on the bottom surface of the movable member during the normal brake operations. Also, additional electromagnetic power is required to remove the movable member from the holding device. Therefore, use of the device makes construction of the solenoid valve complex and increases its size.
SUMMARY OF THE INVENTION
The present invention is made in light of the foregoing problems, and it is an object of the present invention to provide a solenoid valve which has a simple structure without adding unnecessary components, which can prevent time delay of normal braking operations by enlarging the cross-sectional area of a oil pressure control valve during normal braking operations, and which can improve controllability of the ABS by making the cross-sectional area small during brake-pressure control by the ABS.
For attaining the above object, a solenoid valve according to the present invention is constructed so that a negative pressure is formed when fluid flows through an area between a seat member with a tapered surface and a communication interruption member which has a spherical face and which is pressed by a moving member which moves responsive to electromagnetic power, and the negative pressure attracts the communication interruption member toward the tapered face, characterized in that the communication interruption member and the mov
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Hayakawa Hideyuki
Imaeda Makoto
Imoto Yuzo
Kondoh Masuhiro
Takeda Kenji
Ballato Josie
Nippondenso Co. Ltd.
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