Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
1999-08-24
2001-08-28
Schwartz, Christopher P. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
Reexamination Certificate
active
06280005
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to anti-lock brake relief solenoid valves, and more particularly to methods and structure for controlling hydraulic fluid flow rate through anti-lock brake relief solenoid valves.
BACKGROUND OF THE INVENTION
Anti-lock brake systems include solenoid-actuated relief valves that relieve the hydraulic pressure applied to the brakes when the wheels start to skid, i.e., to lock. By relieving the hydraulic braking pressure, the wheels are permitted to roll while nonetheless being slowed by the brakes, which significantly promotes control of the vehicle relative to what is experienced when the brakes lock.
Typically, an anti-lock relief valve includes a ball that is attached to a solenoid plunger. The relief valve also includes a valve seat that receives the ball. To relieve pressure in the hydraulic lines, the solenoid is actuated to move the ball away from the seat, thereby opening a relief passageway through which hydraulic fluid can flow back to a brake fluid reservoir.
The rate of hydraulic fluid flow through the relief passageway must be established to be sufficiently high to quickly alleviate skidding, but not so high as to cease braking altogether or to cause braking instability. Because the relief passageway itself must be kept sufficiently large to provide an adequate seating surface for the ball at one end of the passageway, conventional relief valves establish the rate of fluid flow by press-fitting an orifice cup into the relief passageway, with the orifice cup being formed with an orifice that is configured to establish the desired fluid flow rate.
As recognized herein, however, several disadvantages attend the use of orifice cups. For example, the orifice cup can be unintentionally deformed during the press-fitting process, degrading the performance of the cup. Furthermore, contaminants can enter the hydraulic system during press-fitting. Moreover, occasionally hydraulic fluid can leak between the sides of the orifice cup and the passageway into which it is press-fit. Still further, once installed only the size of the orifice can be easily inspected, not the entire cup. And, the press-fit process is difficult to monitor for installation errors. Apart from the above problems, requiring an orifice cup that is separate from the valve body adds to the number of components and, hence, to the cost of the relief valve. Having recognized these drawbacks, the present invention has provided the below-disclosed solutions to one or more of the prior art deficiencies.
SUMMARY OF THE INVENTION
A relief valve for an anti-lock brake system includes a valve body that is formed with a relief passageway. The relief passageway terminates at a valve opening that is circumscribed by a valve seat. Per the present invention, the valve body is integrally formed with an orifice in the relief passageway, and the orifice is smaller than the valve opening. A solenoid-actuated valve element is movable between a pressure hold configuration, wherein the valve element contacts the valve seat to prevent fluid flow through the relief passageway, and a pressure relief configuration, wherein the valve element is distanced from the valve seat to permit fluid flow through the passageway.
Preferably, the orifice defines a diameter and the valve body defines a length, and the ratio of the length to the diameter (L/D ratio) is established based on a predetermined vehicle type. The LID ratio can be, e.g., between seven (7) and twenty (20).
As disclosed in greater detail below, the anti-lock brake system includes a hydraulic fluid line and a valve housing disposed in the line, and the valve body is disposed in the valve housing. In one preferred embodiment, the valve element is a ball. To move the ball, a solenoid plunger is attached to the ball and the plunger is controlled by a solenoid which is actuated by an anti-lock brake system (ABS) processor.
In another aspect, a method is disclosed for forming a relief valve for an anti-lock brake system (ABS). The method includes establishing an orifice diameter and a valve seat opening diameter larger than the orifice diameter, and establishing a valve body length bearing a predetermined relationship to the orifice diameter. Moreover, the method includes forming a relief valve body having the valve body length and an orifice having the orifice diameter. The relief valve body is then assembled into an ABS system.
In still another aspect, a relief valve system for an ABS system includes a hydraulic fluid line, a valve housing disposed in the line, and a valve body disposed in the valve housing. The valve body is formed with an open valve seat and a relief passageway extends away from the seat. An orifice is in the valve body to establish a predetermined rate of fluid flow through the relief passageway.
The details of the present invention, both as to its structure and operation, can best be understood in reference to the accompanying drawings, in which like reference numerals refer to like parts, and in which:
REFERENCES:
patent: 5556175 (1996-09-01), Hayakawa et al.
patent: 5725289 (1998-03-01), Mueller et al.
patent: 5810330 (1998-09-01), Eith et al.
patent: 5865213 (1999-02-01), Scheffel et al.
patent: 5879060 (1999-03-01), Megerle et al.
Anderson Daniel H.
Nawman Rick Lee
Pepper Sterling Charles
Quinnette Denise Ann
Delphi Technologies Inc.
Dobrowitsky Margaret A.
Schwartz Christopher P.
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