Control valve seal

Details Control valve seal Control valve seal

1998-10-09

2001-01-09

Lopez, F. Daniel (Department: 3745)

Motors: expansible chamber type

Constantly applied motive fluid with controlled venting

Fluid vented through working member

C091S37600A

Reexamination Certificate

active

06170381

ABSTRACT:

This invention relates to a seal of a control valve for a brake booster wherein a structural relationship with a seat modifies turbulence created upon the restriction in the flow of fluid from an inlet port to an outlet port to attenuate the development of undesirable audible noise.
BACKGROUND OF THE INVENTION
The structural components in hydraulic brake boosters, such as illustrated in U.S. Pat. No. 4,961,846, are designed to permit fluid under pressure in a fluid supply system to continually flow from an inlet port through a power piston to an outlet port when in an inactive or rest position. In actuation position, an input force applied to a control valve moves the control valve toward a valve seat in the power piston to restrict the flow of fluid present in an inlet chamber and create a fluid pressure differential across the power piston. After overcoming a return spring, the pressure differential acts on and moves the power piston to develop an output force. When the control valve is in the rest position, fluid freely flows through the power piston and creates essentially a broad band non-resonance sound. This broad band non-resonance sound is combined with noises produced by the engine and other components in a vehicle and is accepted as a total overall operational sound of the vehicle. When the flow of fluid through the power piston is restricted, a corresponding resonant frequency is created by the flow of fluid to the outlet port which is manifested as an undesirable noise or audible resonant sound.
SUMMARY OF THE INVENTION
In evaluating the development of undesirable noise or audible sounds in such brake boosters, it was concluded that such noise was generated by turbulence in the fluid caused when restricting the flow of fluid past a valve seat. Such turbulence develops a frequency in the fluid which locks on to a corresponding resonance frequency in the brake booster and creates an undesirable audible sound. In the present invention, a valve seal is designed to attenuate the development of turbulence in the flow of fluid by shifting its frequency to attenuate or prevent the locking on to with the resonant frequency of the brake booster.
According to the present invention, the fluid power apparatus has a housing with a bore therein which is divided by a power piston into an inlet chamber and an outlet chamber. The power piston has a passageway therethrough for connecting the inlet chamber with the outlet chamber. A valve is located in the passageway for controlling the flow of a fluid under pressure from a source through the power piston. The valve including a valve seal, a valve spring and an input rod. The valve spring urges the valve seal into engagement with the input rod to define a working chamber within the passageway. Fluid under pressure flows from the inlet chamber to the outlet chamber after passing between the valve seal and a valve seat located in the working chamber. When the control valve is in the rest position, fluid freely flows past the valve seat and creates a first turbulence therein to produces a first resonance frequency that is manifested as an acceptable audible sound. When the input rod is moved by an operator to effect a brake application, the valve seal is moved toward the valve seat to restrict the flow of fluid from the working chamber. The restriction in the flow of fluid across the valve seat causes a corresponding increase in the fluid pressure present in the working and inlet chambers. The increase in fluid pressure acts on the power piston to create an output force. The decrease in the flow of fluid from the working chamber creates a change in the turbulence in the fluid which produces a corresponding variable frequency noise or sound. The valve seal which is characterized by a of a cylindrical body with a labyrinth ring located on a face for modifying the level of the turbulence in the fluid flowing past the valve seat such that the audible sound of a resulting variable resonance frequency resonance of the fluid is within an acceptable audible range.
An advantage of a brake booster using this invention resides in its operation within an audible accepted noise range.
A further advantage of the brake boosters of this invention is provided through the use of a valve seal having a face with a labyrinth ring which compensates for a pressure drop across a valve seat to attenuate turbulent noise energy in the fluid communicated to an outlet chamber of the brake booster and as a result an acceptable sound level of operation.


REFERENCES:
patent: 5339722 (1994-08-01), Mauro et al.

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