GB2199910A

GB2199910A - Fluid pressure control valve

Info

Publication number: GB2199910A
Application number: GB08711504A
Authority: GB
Inventors: Ichiro Ishiwata; Keiji Nakagawa
Original assignee: Nabco Ltd
Current assignee: Nabco Ltd
Priority date: 1987-01-19
Filing date: 1987-05-15
Publication date: 1988-07-20
Anticipated expiration: 2007-05-15
Also published as: GB8711504D0; GB2199910B

Abstract

A proportioning or other fluid pressure control valve includes a housing (1) with an internal bore (2) within which a plunger (14) is movably disposed inlets (31) to an inlet chamber (B) defined therein around one part of the plunger (14) and an outlet chamber (A) spaced relatively along the plunger (14), the plunger also having a passage (21) by which the outlet chamber (A) communicates with the inlet chamber (B). A valve (24) is disposed in the passage and openable and closable in response to plunger movement in the housing (1), a spring (19) biassing the plunger (14) in a direction to open the valve (24). The housing (1) has a cylindrical body (3) with one open end closed by a cover member (4) (or 3a). A spring seat (18) is disposed in the cylindrical body (3) in engagement with the cover member (4). The preloading or biassing spring (19) acts between the spring seat (18) and the plunger (14). The spring seat (18) is force-fitted in the internal bore (2) of the housing (1) or in the cover member (4) (or 3a). <IMAGE>

Description

FLUID PRESSURE CONTROL VALVE The present invention relates to a fluid pressure control valve for use in a braking system of an automobile or the like.

A known fluid pressure control valve is disclosed in Japanese Laid-Open Utility Model Publication No.

59(1984)-63064.

It has a valve body defining inlet and outlet chambers communicating with each other through a passage, a valve device disposed in the passage and capable of shutting off the communication between the inlet and outlet chambers,and a plunger for selectively opening and closing the valve device. The plunger is moved in a direction to close the valve device against the bias of a preloading spring when the pressure in the inlet and outlet chambers reaches a prescribed pressure level.

One end of the preloading spring engages the plunger through a spring seat and the other end engages a cover member of the body through another spring seat. The other spring seat held against the cover member has an outside diameter smaller than the inside diameter of the inlet chamber, is fitted over the plunger, and is only pressed against the cover member under the force of the spring. Therefore,this other cover end) spring seat tends to become tilted and compressed when assembled.

When this happens, the plunger becomes inclined, due to a localized load imposed by the preloading spring,resulting in a sluggish movement of, or scratches imparted by, the plunger as it slides. The fluid pressure control valve may then fail to operate properly.

The present invention sets out to provide a fluid pressure control valve in which a spring seat, bearing one end of a preloading spring, can be mounted in place easily and reliably in a proper posture.

The present invention consists in a fluid pressure control valve comprising: an elongate hollow housing with a plunger movable along an internal bore thereof, the housing defining with the plunger an inlet chamber and an outlet chamber with an intercommunicating passage; a valve device disposed in said passage and openable and closable in response to movement of said plunger in relation to said housing; and a spring disposed in said housing for biassing said plunger in a direction to open said valve device; said housing comprising a hollow cylindrical body with a cover member closing an otherwise open end thereof: and a spring seat being held within said cylindrical body and engaging said cover member, whereby said spring acts between the said spring seat and the plunger.

Since the spring seat which engages one end of the preloading spring is held, i.e. held against the peripheral surface of the internal bore of the housing or held in position by the cover member, it does not tilt when assembled in position. It can therefore always be mounted properly in position,and no malfunction which would otherwise result from improper posture of the spring seat in the housing will take place.

In the accompanying drawings preferred embodiments of the present invention are shown by way of illustrative example.

Figure 1 is a longitudinal cross-section of an embodiment of a fluid pressure control valve according to the present invention; Figure 2 is a cross-section along line Il-I I of Figure 1; and Figure 3 is a fragmentary longitudinal cross-section of another embodiment of a fluid pressure control valve according to the present invention.

Figure 1 shows a valve body or housing 1 comprising a cylindrical member 3 having an internal bore 2 with one end open and a cover member 4 closing the open end. The internal bore 2 is stepped to have a smallest-diameter bore portion 6 near the closed end 5, an intermediate diameter bore portion 7, and a largest-diameter bore portion 8 having a diameter slightly larger than that of the intermediate portion 7 and being open at one end.

The cover member 4 fits in the open bore portion 8 and has a stepped recess 11 composed of a recess portion 9 opening into the internal bore 2 and a recess portion 10 at the bottom of the recess portion 9 with an air vent passage 12 defined through the bottom of portion 10. A sealing member 13 is fitted in the recess portion 9 in the cover member 4.

Slidably housed in the internal bore 2 is a plunger 14 with a stepped shape including a larger-diameter portion 15 near one end thereof, being slidably fitted in the smallest-diameter bore portion 6 with a sealing member 16 therebetween. The opposite end 17 of the plunger 14 is slidably inserted in the recess portion 10 of the cover member 4 through the sealing member 13. The plunger 14 is normally biassed towards the smallest-diameter bore portion 6 by spring 19 around the plunger 14. This spring has one end supported by the cover member 4 via a spring seat 18 and an opposite end supported by the plunger 14 via a spring seat 20. The plunger 14 defines an outlet chamber A in the smallest-diameter bore portion 6, an inlet chamber B in the intermediate hole portion 7, and a non-pressure chamber C in the recess portion 10.Outer peripheral edge of the spring seat 18 is held in sliding contact with the inner peripheral surface of the open portion 8.

The spring seat 18 is fitted into the open bore portion 8 to locate by a step X between the open bore portion 8 and the intermediate diameter bore portion 7, and engages an end surface of the cover member 4. As shown in Figure 2, the spring seat 18 has a polygonal shape including three angularly spaced arcuate periphral surfaces a. b, c held against the inner peripheral surface of the open bore portion 8.

The plunger 14 has a passage 21 defined therein and providing communication between the inlet and outlet chambers B, A. The passage 21 comprises a diametrical through passageway 22 opening into the inlet chamber B and an axial passageway 22 opening into the outlet chamber A. A valve device 24 has a valve member 25 operatively disposed in the passageway 23 for selectively shutting off communication between the inlet and outlet chambers B. A. Valve member 25 is normally biassed by a valve spring 28 to seat on seat 27 (having a hole 27a and attached to the plunger 14 at the end of the passageway 23) thereby pressing stem 26 against the closed end 5 of the internal bore 2.

The valve housing 1 has an outlet 30 communicating with the outlet chamber A and an inlet 32 communicating with the inlet chamber B. The outlet chamber 30 is connected to a wheel brake cylinder of an automobile (not shown) through a suitable pipe. and the inlet 32 is connected by a pipe to the pressure chamber of a master cylinder for generating a brakig fluid pressure.

The fluid pressure control valve may be fixedly inserted in an appropriate bore such as a bore in a brake master cylinder parallel to the cylinder bore itself.

Operation of the fluid pressure control valve constructed as shown in Figures 1 and 2 will be described below.

When the brake is not actuated, i.e. no fluid pressure is present in the pressure chamber of the brake master cylinder, the components of the fluid pressure control valve are in the illustrated position, and the valve device 24 is open with the valve member 25 unseated and off the seat member 27.

If the driver operates the brake master cylinder by depressing the brake pedal, fluid pressure is generated by the brake master cylinder. While the generated fluid pressure is low, it is transmitted though the inlet 31 into the inlet chamber B, and then passes through the passageway 22, 23, the hole 17a, and the outlet chamber A, from which the fluid pressure is transmitted, without being subjected to a pressure reduction, through the outlet 30 and the pipe to the brake cylinder.

Thereafter, when the fluid pressure generated is increased to the extent that the pressure acting on the differential area between the pressure-bearing area S1 of the plunger 14 (with respect to the inlet chamber B) and the pressure-bearing area S2 of the plunger 14 (with respect to the outlet chamber A) reaches a prescribed level, then the plunger 14 is moved to the right (Figure 1) until the seat member 27 seats on the valve member 25, whereupon the valve device 24 is closed. The pressure in the outlet chamber A is then controlled so as to be reduced at a given ratio in the well-known manner.

As described above, the spring seat 18 is of such a size that its outer arcuate surfaces a, b, c are held against the inner peripheral surface of the open portion 8 of the internal bore 2. During assembly. the spring seat 18 may be inserted into the open bore portion 8 while being guided by the inner peripheral surface of the bore and so can be mounted, without being tilted, in a proper posture.

Since spring seat 18 is of a polygonal profile, it can be inserted into the open bore portion 8 with a relatively small force. Gaps G are defined between the polygonal spring seat 18 and the inner peripheral surface of the open bore portion 8. The gaps G serve as air vent passages when the plunger 14 is moved to compress the preloading spring 19 until it is held closely against the spring seat 18.

Figure 3 fragmentarily shows a fluid pressure control valve according to another embodiment of the present invention. In this embodiment, spring seat 18 is lightly forced into place and held by a cover member 3A which closes the open bore portion 8 of a cylindrical member 3. The cover member 3A has a stepped recess 11 composed of a recess portion 9, a recess portion 10 in the bottom of the recess portion 9 and an an air vent passage 12 defined through the bottom of the recess portion 10. The cover member 3A also has a recess 9b defined in the distal end 9a of the recess portion 9, the recess 9b having a diameter larger than that of the recess portion 9. The spring seat 18 is forced into the recess 9b.

In each of the above embodiments, the recess 11 is defined in the cover member 4, 3A. However, the recess 11 may be defined in the cylindrical member.

Preferred embodiments have been shown and described but it should be understood that many changes and modifications may be made without departing from the scope of the invention.

Claims

Claims.

1. A fluid pressure control valve comprising: an elongate hollow housing with a plunger movable along an internal bore thereof, the housing defining with the plunger an inlet chamber and an outlet chamber with an intercommunicating passage; a valve device disposed in said passage and openable and closable in response to movement of said plunger in relation to said housing; and a spring disposed in said housing for biassing said plunger in a direction to open said valve device: said housing comprising a hollow cylindrical body with a cover member closing an otherwise open end thereof; and a spring seat being held within said cylindrical body and engaging said cover member, whereby said spring acts between the said spring seat and the plunger.

2.A fluid pressure control valve as claimed in claim 1, wherein said spring seat is force-fitted in the internal bore of the housing.

3.A fluid pressure control valve as claimed in claim 2, wherein said internal bore comprises a first portion.

and a second portion having a diameter larger than that of said first portion, a step being defined between said first and second portions and said spring seat being positioned between said step and said cover member.

4. A fluid pressure control valve as claimed in claim 2 or 3 wherein said spring seat has at least one arcuate outer peripheral edge held against an inner peripheral surface of said internal bore.

5. A fluid pressure control valve as claimed in claim 1, wherein said cover member has a recess in which said spring seat is force-fitted.

6. A fluid pressure control valve as claimed in claim 1 and substantially as herein described with reference to the accompanying drawings.