Fluid handling – Systems – Multi-way valve unit
Reexamination Certificate
1999-11-09
2001-03-20
Michalsky, Gerald A. (Department: 3753)
Fluid handling
Systems
Multi-way valve unit
C251S129020, C251S129080
Reexamination Certificate
active
06202697
ABSTRACT:
TECHNICAL FIELD
This invention relates to a proportional pressure control valve used in a power steering, transmission or brake system for automobiles.
BACKGROUND ART
A proportional pressure control valve is known in which a spool is moved to a position corresponding to a magnetic force for changeover of connection of a load port to a high pressure source port and a low pressure source port and for adjustment of degree of opening of variable throttles for communication of the load port with the high pressure source port and the low pressure source port, thereby controlling the pressure at the load port (hereinafter referred to as “load pressure”), e.g. from unexamined Japanese patent publication 1-261581 or unexamined Japanese utility model publication 7-6579.
In the control valve of the former publication, the spool is biased from both sides by springs to keep a neutral position, and the load pressure is applied to one end of the spool, and a thrust produced by a proportional solenoid is applied to its other end. Also, in order to case a plunger (actuating element) of the proportional solenoid to follow the spool, it is pressed against the other end of the spool by a spring.
On the other hand, in the fluid pressure control valve of the latter publication, in a normal state, an output port is in communication with a drain port. When a plunger (actuating element) of a pressure-increasing solenoid is attracted by an electromagnet, the spool connected to the plunger moves in such a direction that the output fluid pressure increases. Also, a reaction force piston for applying a returning force to the spool using the output fluid pressure is inserted in one end of the spool on the side where the pressure-increasing solenoid is provided, and further the plunger of the pressure-increasing solenoid is supported by a bush for guiding its movement.
The control valve of the former publication needs three springs, so that the structure is complicated and the cost is high due to increase in the number of parts.
Also, in the fluid pressure control valve of the latter publication, since the reaction force piston inserted in the spool is provided on the same side as the plunger (actuating element) of the pressure-increasing solenoid fitted on the spool, it is necessary to form a hole (oil path) in the plunger at the portion where the magnetic flux density of the plunger portion becomes high so that no pressure difference is produced between both ends of the plunger. Thus, the volume of the portion in question decreases. This results in the loss of power of the electromagnet.
Also, in either control valve, because the plunger of the soleniod is supported by a bush which serves as a slide guide, the slide resistance of the plunger adds to the slide resistance of the spool, thus affecting the movement of the spool unfavorably.
Further, in either control valve, because the reaction force produced by the reaction force piston (referred to as “slide pin” in the former publication 1-2615819) is applied to the spool in such a direction against the spool driving force from the solenoid, extra power is needed for the electromagnet, so that the power consumption increases.
An object of this invention is to solve these problems.
DISCLOSURE OF THE INVENTION
The proportional pressure control valve of this invention comprises.
a casing formed with a spool guide hole, a high pressure source port, a low pressure source port and a load port, the ports each opening in the spool guide hole at intermediate portions, and first and second low-pressure pressure chambers communicating with the low pressure source port;
a spool liquid-tightly and slidably inserted in the spool guide hole with one end thereof protruding into the first low-pressure pressure chamber and the other end into the second low-pressure pressure chamber and having a load pressure chamber in communication with the load port;
a reaction force piston slidably inserted in the spool with one end thereof protruding into the load pressure chamber in the spool, and the other end thereof protruding into the second low-pressure pressure chamber and abutting the casing;
a spring for biassing the spool toward the second low-pressure pressure chamber; and
an electromagnet having an actuating element provided in the first low-pressure pressure chamber for pulling the spool against the force of the spring;
the high pressure source port, the low pressure source port and the load port being positioned such that the load port does not communicate with the low pressure source port and the load port communicates with the high pressure source port when the spool is at an extreme end biassed by the spring,
wherein the spool is moved to a position determined by the magnetic attraction force of the electromagnet to change over the communication between the load port and the high pressure source port and the low pressure source port and adjust the degree of opening of a variable throttle through which the load port communicates with the high pressure source port or the low pressure source port.
In this proportional pressure control valve, if the actuating element of the electromagnet is formed integrally with the spool, or a separate actuating element is fixed to the spool through a fixed connecting portion, it is possible to omit a slide guide for the actuating element and thus to form a gap larger than a gap designed as a slide clearance between the actuating element and members arranged around the actuating element (which are below-described sleeve and part of a lid) is formed therebetween. If the gap around the actuating element is larger than the slide clearance, the actuator and the members provided therearound will not contact with each other, thus preventing decrease in control accuracy and response. Also, by omitting the slide guide, manufacture is easier.
In this invention, since the spool is biased toward the second low-pressure pressure chamber by a single spring together with the actuating element of the electromagnet, the number of parts decreases and the structure becomes simple.
Also, because the reaction force piston is provided near the second low-pressure pressure chamber, it is possible to reduce the loss of force of the electromagnet by forming a hole as an oil path in the actuating element of the electromagnet in e.g. a core portion where magnetic flux scarcely passes.
Further, because the reaction force piston is provided near the second low-pressure pressure chamber, the direction in which the spool is pushed by the load pressure and the direction in which the spool is pulled by the electromagnet coincide with each other, so that the force of the electromagnet can be saved.
Although the control valve will function normally even if a structure in which the actuating element of the electromagnet is made separate and pressed against the spool by a spring is employed (when the actuating element is pulled by the force of the electromagnet, the spool follows the actuating element under the load pressure). But by forming the actuating element integral with the spool, it is possible to simplify manufacture and make it easier for the spool to move by omitting the slide guide of the actuating element.
REFERENCES:
patent: 5036885 (1991-08-01), Miura
patent: 5186093 (1993-02-01), Kervagoret
patent: 5571248 (1996-11-01), Seetharaman et al.
patent: 5577534 (1996-11-01), Ward
patent: 5894860 (1999-04-01), Baldauf et al.
patent: 1-261581 (1989-10-01), None
patent: 7-6579 (1995-01-01), None
English language abstract of JP 1-261581.
Hashida Koichi
Oyama Hitoshi
Greenblum & Bernstein P.L.C.
Michalsky Gerald A.
Sumitomo Electric Industries Inc.
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