Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
1999-11-29
2001-12-25
Schwartz, Christopher P. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
C303S113100
Reexamination Certificate
active
06332655
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application is based upon and claims priority from Japanese Patent Applications No. Hei 10-340096 filed Nov. 30, 1998 and No. Hei 11-260604 filed Sep. 14, 1999, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electromagnetic valve for brake hydraulic pressure control valve and a brake control system having the same for vehicle, in particular, applicable to an ABS actuator for controlling vehicle wheel lock by increasing and decreasing hydraulic pressure.
2. Description of Related Art
The ABS actuator for an anti-skid control is provided with a hydraulic circuit composing fluid conduits and various control valves in which the control valves are operative for increasing/decreasing hydraulic pressure to be applied to wheel cylinders by controlling a communicating/interrupting state of each of the fluid conduits.
There is a pressure-increase control valve (normally open state valve), as one of the various control valves, for controlling the communicating/interrupting state of the fluid conduit connecting a master cylinder and each of the wheel cylinders.
The pressure-increase control valve is under a communicating state during a normal braking operation (not during the anti-skid control) and, thus, operative for allowing brake fluid to flow from a master cylinder side to a wheel cylinder side.
The pressure-increase control valve is turned to an interrupting state at a pressure-hold timing or a pressure-decrease timing during the anti-skid control in order to inhibit brake fluid to flow from the master cylinder side to the wheel cylinder side and switched to the communicating state at a pressure-increase timing during the anti-skid control in order to allow brake fluid to flow from the master cylinder side to the wheel cylinder side.
However, the conventional pressure-increase control valve has a problem that, when switched to the communicating state at a pressure-increase timing during the anti-skid control, large amount of brake fluid flows instantaneously because the diameter of the valve hole is defined to be large enough to allow brake fluid to flow during the normal braking operation. The instantaneous large amount brake fluid flow generates a hydraulic shock wave leading to a large pulsating pressure vibration that causes noises.
SUMMARY OF THE INVENTION
The present invention is made in light of the foregoing problem, and it is an object of the present invention to provide an electromagnetic valve for brake fluid control, for example, a pressure increase control valve, having a distinctive feature that the instantaneous large amount brake fluid flow may be restricted when brake fluid pressure is controlled, in particular, at a pressure-increase timing during the anti-skid control.
Further, it is another object of the present invention to provide an electromagnetic valve applicable to a so-called “normally-open” or “normally closed” state valve.
To achieve the above objects, the electromagnetic valve comprises first and second communication paths connecting an inlet and an outlet for brake fluid flow in parallel to each other, one of the first and second communication paths having a throttle for partly restricting brake fluid flow, a first plunger being provided with first valve for interrupting/communicating the first communication path and, further, provided with a penetration hole extending to the second communication path, a second plunger being provided with second valve movable in or through the penetration hole for interrupting/communicating the second communication path, a spring generating a spring biasing force in a direction that the first and second plungers move away from each other, and a coil member arranged around outer circumferences of the first and second plungers for generating an electromagnetic attracting force, when energized, to have the first and second plungers come close to each other against the spring biasing force.
The electromagnetic valve above mentioned may be controlled. at any one of three operating states representing a fully-open state that both the first and second communication paths are communicated, a half-open state that the one of the first and second communication paths having the throttle is communicated and the other one of the first and second communication paths is interrupted and a fully-closed state that both the first and second communication paths are interrupted.
At pressure-increase timing, the electromagnetic valve is controlled at the half-open state so as to allow brake fluid flow through the throttle so that brake fluid flow may be limited, compared with brake fluid flow at the fully-open state. As a result, the pulsating pressure vibration due to instantaneous large amount brake fluid flow can be prevented.
To achieve the above objects, a first spring is disposed between the first and second plungers arranged in series for generating a first spring biasing force against the first and second plungers in a direction that the first and second plungers move away from each other. Therefore, when the coil member is energized, the first valve may be operative for moving from an upstream side of brake fluid flow to a downstream side thereof to communicate or interrupt the first communication path and the second valve may be operative for moving from an downstream side of brake fluid flow to a upstream side thereof to communicate or interrupt the second communication path. As a modification, in addition to the first spring, a second spring may be disposed between the first plunger and a first seat valve provided with the first communication path for generating a second spring biasing force against the first plunger in a direction that the first plunger comes close to the second plunger. As the first spring biasing force is larger than the second spring biasing force so that a sum of the first and second spring biasing forces may act in a direction that the first and second plungers move away from each other, the first and second valves are operative respectively as mentioned above when the coil member is energized.
Furthermore, it is a further object to provide an electromagnetic valve having a simple and compact construction by which the electromagnetic valve is not only accurately operative but also assembled or manufactured at low cost.
To achieve the above object, an area of the first valve to receive brake fluid pressure on an upstream side thereof is defined to be large enough to generate a pressure biasing force due to brake fluid pressure difference between the upstream side of the first valve and a downstream side thereof that is larger than the first spring biasing force or the sum of the first and second spring biasing forces at the half-open state. As a result, once the half-open state has been established by generating the magnetic attracting force that is larger than the first spring biasing force or the sum of the first and second spring biasing forces at the half-open state, the half-open state may be maintained even if the magnetic attracting force is removed, that is, without current supply to the coil member.
Further, a second seat valve having the second communication path, the throttle and a second valve seat is integrated into the first valve as one body. Thus, the number of component parts may be minimized.
Furthermore, the coil member comprises a coil, a yoke surrounding an outer circumference of the coil, a cylindrical shaped sleeve made of non-magnetic material in which the first and second plungers are slidably housed, and a ring member made of magnetic material disposed between the yoke and the first seat valve without intervening the sleeve. As a result, a magnetic efficiency may be improved because the magnetic circuit for generating the magnetic attracting force passes only one time through the non-magnetic sleeve.
As another aspect of the present invention, the coil member may have a cylindrical shaped sleeve made of basically magnetic material in pla
Kamiya Masahiko
Majima Yozo
Denso Corporation
Pillsbury & Winthrop LLP
Schwartz Christopher P.
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