Fluid handling – Systems – Multi-way valve unit
Reexamination Certificate
1999-05-18
2001-01-09
Michalsky, Gerald A. (Department: 3753)
Fluid handling
Systems
Multi-way valve unit
C251S129060
Reexamination Certificate
active
06170526
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to hydraulic valves, and, more specifically, to the control of a hydraulic valve by a piezoelectric actuated poppet valve.
BACKGROUND ART
Piezoelectric materials respond to exposure to an electrical field by deforming in a manner that varies directly with the applied potential difference. The direction of deformation, namely an increase or a decrease in length, is dependent on the polarity of the electrical field and the arrangement of the piezoelectric material. Generally, a piezoelectric element is formed by stacking a series of discs of the piezoelectric material wherein the discs are interweaved with electrodes to enable the discs to be exposed to an electrical field.
Piezoelectric elements have the advantage of being able to sustain very high cycle frequencies and to respond nearly instantaneously to a change in the electrical field. By way of example, a piezoelectric element formed of a properly oriented stack of discs can respond to a negative polarity by expanding along a longitudinal axis of the stack of discs within microseconds. For example, a stack of discs approximately 150 mm long will expand approximately 75 &mgr;m.
In a typical hydraulic control system, a hydraulic valve includes an internal spool having at either end of it a control volume. High hydraulic pressure is metered into each of the control volumes at each end of the spool. Movement of the spool is used to control the output of the hydraulic valve. Movement of the spool within the hydraulic valve is often accomplished by modulation of a pilot pressure, which is also fed into each control volume at each end of the spool. The pilot pressure is under a lower pressure than the high hydraulic pressure. Thus, movement of the spool within the hydraulic valve can be accomplished by small changes in the pilot pressure at either end of the spool. Typically, operator input is used to regulate the pilot pressure to either end of the spool in order to effect movement of the spool within the valve which in turn causes movement of, for example, a machine implement.
One disadvantage with current hydraulic valves is their response time to operator input. It would be advantageous to have a hydraulic valve that responded nearly instantaneously to operator inputs. The very rapid response time of piezoelectric materials makes them ideal candidates for incorporation into a hydraulic control valve system.
The present invention is directed to overcoming one or more of the problems set forth above.
DISCLOSURE OF THE INVENTION
In one aspect of this invention, a piezoelectric valve is disclosed. The piezoelectric valve includes a valve body having a first end opposite a second end, first multiple passages in fluid communication with a first chamber adjacent the first end and second multiple passages in fluid communication with a second chamber adjacent the second end, an interior space defined between the first chamber and the second chamber, a poppet valve received within the interior space in a fluid tight fit and slideable within the interior space, the poppet valve having a first end opposite a second end, a piezoelectric actuator contacting the poppet valve, the piezoelectric actuator sliding the poppet valve within the interior space when the piezoelectric actuator is actuated, a spring biasing the second end of the poppet valve into a valve seat when the piezoelectric actuator is not actuated and permitting fluid flow through the first multiple passages and the first chamber, thereby establishing a first fluid flow path through the valve body, the spring preventing fluid flow through the second multiple passages and the second chamber, and actuation of the piezoelectric actuator moving the poppet valve away from the valve seat and compressing the spring to permit fluid flow through the second multiple passages and the second chamber thereby establishing a second flow path through the valve body and preventing fluid flow through the first flow path.
In another aspect of this invention, a method for controlling flow of fluid through a valve body is disclosed. The method includes the steps of providing a valve body having a first chamber and a second chamber with an interior space defined between the first and second chambers, providing first multiple passages through the valve body and in fluid communication with the first chamber and second multiple passages through the valve body and in fluid communication with the second chamber, positioning a poppet valve within the interior space in a slideable and fluid-tight fit, positioning a piezoelectric actuator to contact the poppet valve, biasing the poppet valve in a first direction when the piezoelectric actuator is not actuated, thereby permitting fluid flow through the first multiple passages while preventing fluid flow through the second multiple passages, and actuating the piezoelectric actuator to move the poppet valve in a second direction opposite the first direction to thereby permitting fluid flow through the second multiple passages while preventing fluid flow through the first multiple passages.
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patent: 5740969 (1998-04-01), Hoffman et al.
patent: 5779149 (1998-07-01), Hayes, Jr.
patent: 3006231 (1981-08-01), None
patent: 62-159878 (1987-07-01), None
patent: 5-272656 (1993-10-01), None
Caterpillar Inc.
Howard & Howard
Michalsky Gerald A.
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