Compressor having capacity modulation system

1. A compressor comprising:

a housing defining a suction pressure region;

a first scroll member supported within said housing and including a first end plate defining a capacity modulation passage and having a first spiral wrap extending from said first end plate;

a second scroll member supported within said housing and including a second end plate having a second spiral wrap extending therefrom and meshingly engaged with said first spiral wrap to form a suction pocket, a first intermediate compression pocket and a discharge pocket, said capacity modulation passage being in communication with said first intermediate compression pocket;

a piston supported on said first scroll member and partially defining a modulation control chamber;

a control valve in communication with said modulation control chamber and with first and second pressure sources, said control valve selectively providing communication between said modulation control chamber and one of said first and second pressure sources to displace said piston between a closed position and an open position, said piston isolating said capacity modulation passage from communication with said suction pressure region when in the closed position and providing communication between said capacity modulation passage and said suction pressure region when in the open position; and

a seal engaged with said first scroll member, said seal and said first scroll member at least partially defining a biasing chamber in communication with a second intermediate compression pocket formed by said first and second spiral wraps, said control valve being in communication with said biasing chamber and said biasing chamber forming said first pressure source.

2. The compressor of claim 1 , wherein said control valve is in communication with said suction pressure region and said suction pressure region forms said second pressure source.

3. The compressor of claim 1 , wherein said piston includes an annular body at a location axially between said first end plate and said seal.

4. The compressor of claim 3 , wherein said piston is spaced axially from said seal and at least a portion of said seal overlaps said piston in a radial direction.

5. The compressor of claim 3 , wherein said first end plate defines a biasing passage extending from said second intermediate compression pocket to said biasing chamber and located radially inward relative to an inner radial surface of said annular body of said piston.

6. The compressor of claim 1 , wherein said piston is displaceable axially outward relative to said first end plate to provide the open and closed positions.

7. The compressor of claim 1 , wherein said piston includes an annular body.

8. The compressor of claim 7 , wherein said first scroll member defines a hub extending from said first end plate and through an inner circumferential wall of said piston, said hub surrounding a discharge passage in said first end plate in communication with said discharge pocket.

9. The compressor of claim 1 , wherein said piston is forced against said first end plate to isolate said capacity modulation passage from communication with said suction pressure region when in the closed position and being offset from said first end plate to provide communication between said capacity modulation passage and said suction pressure region when in the open position.

10. The compressor of claim 1 , wherein said control valve is operable in a pulse width modulation capacity mode to operate the compressor at an intermediate capacity between full capacity and zero capacity.

11. The compressor of claim 1 , wherein said piston includes an end surface facing said biasing chamber and pressurized fluid within said biasing chamber biases said piston to the closed position.

12. The compressor of claim 11 , wherein a portion of said piston is in communication with said biasing chamber when said piston is in the open position and when said piston is in the closed position.

13. A compressor comprising:

a housing defining a suction pressure region;

a first scroll member supported within said housing and including a first end plate defining a capacity modulation passage and a biasing passage and having a first spiral wrap extending from said first end plate;

a second scroll member supported within said housing and including a second end plate having a second spiral wrap extending therefrom and meshingly engaged with said first spiral wrap to form a suction pocket, a first intermediate compression pocket, a second intermediate compression pocket and a discharge pocket, said capacity modulation passage being in communication with said first intermediate compression pocket and said biasing passage being in communication with said second intermediate compression pocket;

a seal engaged with said first scroll member, said seal and said first scroll member at least partially defining a biasing chamber in communication with said second intermediate compression pocket via said biasing passage;

a piston supported on said first scroll member and partially defining a modulation control chamber; and

a control valve in communication with said modulation control chamber and with said suction pressure region and said biasing chamber, said control valve selectively providing communication between said modulation control chamber and one of said suction pressure region and said biasing chamber to displace said piston between a closed position and an open position, said piston isolating said capacity modulation passage from communication with said suction pressure region when in the closed position and providing communication between said capacity modulation passage and said suction pressure region when in the open position.

14. The compressor of claim 13 , wherein said piston includes an end surface facing said biasing chamber, pressurized fluid within said biasing chamber biasing said piston to the closed position.

15. A compressor comprising:

a housing defining a suction pressure region;

a first scroll member supported within said housing and including a first end plate defining a capacity modulation passage and a biasing passage and having a first spiral wrap extending from said first end plate;

a second scroll member supported within said housing and including a second end plate having a second spiral wrap extending therefrom and meshingly engaged with said first spiral wrap to form a suction pocket, a first intermediate compression pocket, a second intermediate compression pocket and a discharge pocket, said capacity modulation passage being in communication with said first intermediate compression pocket and said biasing passage being in communication with said second intermediate compression pocket;

a seal engaged with said first scroll member, said seal and said first scroll member at least partially defining a biasing chamber in communication with said second intermediate compression pocket via said biasing passage;

a piston supported on said first scroll member and partially defining a modulation control chamber, said piston including an end surface facing and in communication with said biasing chamber; and

a control valve in communication with said modulation control chamber and with first and second pressure sources and selectively providing communication between said modulation control chamber and one of said first and second pressure sources to displace said piston between a closed position and an open position, said piston isolating said capacity modulation passage from communication with said suction pressure region when in the closed position and providing communication between said capacity modulation passage and said suction pressure region when in the open position.

16. The compressor of claim 15 , wherein a portion of said piston is in communication with said biasing chamber when said piston is in the open position and when said piston is in the closed position.

17. The compressor of claim 15 , wherein said control valve is operable in a pulse width modulation capacity mode to operate the compressor at an intermediate capacity between full capacity and zero capacity.

18. The compressor of claim 15 , wherein one of said first and second pressure sources includes said suction pressure region of the compressor.

19. A compressor comprising:

a housing defining a suction pressure region;

a first scroll member supported within said housing and including a first end plate defining a capacity modulation passage and having a first spiral wrap extending from said first end plate;

a second scroll member supported within said housing and including a second end plate having a second spiral wrap extending therefrom and meshingly engaged with said first spiral wrap to form a suction pocket, a first intermediate compression pocket and a discharge pocket, said capacity modulation passage being in communication with said first intermediate compression pocket;

a piston supported on said first scroll member and partially defining a modulation control chamber;

a control valve in communication with said modulation control chamber and with first and second pressure sources, said control valve selectively providing communication between said modulation control chamber and one of said first and second pressure sources to displace said piston between a closed position and an open position, said piston isolating said capacity modulation passage from communication with said suction pressure region when in the closed position and providing communication between said capacity modulation passage and said suction pressure region when in the open position; and

a seal engaged with said first scroll member, said seal and said first scroll member at least partially defining a biasing chamber in communication with a second intermediate compression pocket formed by said first and second spiral wraps, said piston including an end surface facing said biasing chamber and pressurized fluid within said biasing chamber biasing said piston to the closed position.