Microvalve device suitable for controlling a variable displacement compressor

1 . A control valve for a variable displacement compressor having a piston having a displacement within a compression chamber, the compression chamber admitting a gas from a suction area at a suction pressure and discharging the gas to a discharge area at a discharge pressure, a gas-filled crankcase chamber having a crankcase pressure, the displacement of the piston varying according to the crankcase pressure, the control valve controlling the crankcase pressure, the control valve comprising:

a discharge pressure valve portion for controlling gas communication between the discharge area and the crankcase chamber;

a reference chamber isolated from the crankcase chamber having a reference pressure, the reference pressure established by a flow of the gas from the discharge area to the reference chamber or by a flow of the gas from the reference chamber to the suction area;

a pressure sensitive member having a suction pressure receiving area in communication with the gas at the suction area and a reference pressure receiving area in communication with the gas in said reference chamber, said pressure sensitive member moving in response to a differential pressure between the reference pressure and the suction pressure;

a member that couples movement of said pressure sensitive member to said discharge valve portion for controlling gas communication between the discharge area and the crankcase chamber; and

a microvalve device for controlling at least one of the flow of the gas from the discharge area to the reference chamber and the flow of the gas from the reference chamber to the suction area in response to electrical signals, thereby establishing the reference pressure.

2 . A control valve according to claim 1 , further comprising a micromachined pressure sensor in gas communication with the reference chamber, wherein the pressure sensor produces an electrical signal related to the reference pressure, said pressure sensor being integrally formed with the microvalve device.

3 . A control valve according to claim 1 , wherein the reference chamber is a closed space formed by rigid walls, the reference pressure receiving area of the pressure sensitive member, and a plug upon which the microvalve device is mounted.

4 . The control valve according to claim 1 wherein the microvalve device comprises a thermally actuated microvalve.

5 . The control valve according to claim 1 wherein the microvalve device comprises a micro spool valve.

6 . The control valve according to claim 5 wherein the micro spool valve includes a pilot portion and a pilot operated spool portion.

7 . The control valve according to claim 1 wherein the microvalve device comprises:

a 2-way pilot operated microvalve; and

a 4-way pilot microvalve for controlling the 2-way pilot operated microvalve.

8 . The control valve according to claim 7 wherein the 4-way pilot microvalve comprises:

a body having an intermediate plate layer with a cavity formed therein, said body defining an inlet connection, an outlet connection, and first and second load connections in fluid communication with said cavity;

a moveable microvalve element disposed in said cavity moveable between a first position and a second position, said moveable element being operable to allow fluid communication between said inlet connection and said first load connection and between said outlet connection and said second load connection when said moveable element is in said first position and being operable to allow fluid communication between said inlet connection and said second load connection and between said outlet connection and said first load connection when said moveable element is in said second position; and

a microvalve actuator operable to move said moveable element between said first position and said second position.

9 . The control valve according to claim 7 wherein the 2-way pilot operated microvalve comprises:

a multilayer plate valve body having an intermediate plate layer with a cavity formed therein, said body defining an inlet connection and an outlet connection in fluid communication with said cavity;

a moveable microvalve element disposed in said cavity moveable between a first position and a second position, said moveable element being operable to allow fluid communication between said inlet connection and said outlet connection when said moveable element is in said first position and being operable to block fluid communication between said inlet connection and said outlet connection when said moveable element is in said second position; and

a feedback port formed in the moveable element operable to regulate the pressure on an end of the moveable element relative to the movement of said moveable element between said first position and said second position.

10 . The 2-way pilot operated microvalve of claim 9 wherein the moveable microvalve element comprises a spool blocking portion defining a recessed portion, said recessed portion slidably engaging a spool beam attached to layers of said multilayer plate valve body adjacent to said intermediate plate layer.