Compressor having capacity modulation system

1. A compressor comprising:

a housing;

a first scroll member supported within said housing and including a first end plate, a first spiral wrap extending from a first side of said first end plate, and a first passage extending from said first side of said first end plate to a second side of said first end plate generally opposite said first side;

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 series of compression pockets operating at an intermediate fluid pressure between a suction pressure and a discharge pressure, said first passage being in communication with one of said compression pockets; and

a modulation plate overlying said second side of said first scroll member and secured within said housing for radial displacement between first and second positions, said modulation plate isolating said first passage from communication with a suction pressure region of the compressor when in the first position and providing communication between said first passage and said suction pressure region when in the second position.

2. The compressor of claim 1 , wherein said modulation plate slides along said second side of said first end plate during displacement from the first position to the second position.

3. The compressor of claim 1 , wherein said modulation plate is pivotally coupled within said housing to a structure that is fixed relative to said first scroll member.

4. The compressor of claim 3 , wherein said modulation plate is pivotally coupled to said first scroll member.

5. The compressor of claim 3 , further comprising an actuation mechanism engaged with said modulation plate to displace said modulation plate between the first and second positions.

6. The compressor of claim 1 , wherein said first scroll member defines a first recess housing said modulation plate therein and being in communication with said first passage and said suction pressure region.

7. The compressor of claim 6 , further comprising a seal assembly engaged with said housing and isolating said suction pressure region of the compressor from a discharge pressure region of the compressor, said seal assembly and said first scroll member defining a second recess.

8. The compressor of claim 7 , wherein said first recess is isolated from said second recess.

9. The compressor of claim 7 , wherein said first recess is located axially between said second side of said first end plate and said second recess.

10. The compressor of claim 1 , wherein said modulation plate includes an aperture in communication with said first passage when said modulation plate is in the first position.

11. The compressor of claim 10 , wherein said modulation plate includes first and second surfaces generally opposite one another, said first surface having a recess extending therein and defining a first radial surface area, said aperture extending through said first and second surfaces providing communication between said recess and said first passage when said modulation plate is in the first position, said second surface defining a second radial surface area exposed to said first passage when said modulation plate is in the first position, said second radial surface area being approximately equal to said first radial surface area.

12. The compressor of claim 11 , wherein said recess includes a seal to prevent communication between said suction pressure region and said recess when said modulation plate is in the first position.

13. The compressor of claim 12 , further comprising a spring disposed within said recess of said modulation plate to axially bias said seal against said first scroll member.

14. The compressor of claim 1 , wherein said first passage has a generally arcuate shape having an angular extent of at least 20 degrees.

15. A compressor comprising:

a housing,

a first scroll member supported within said housing and including a first end plate, a first spiral wrap extending from a first side of said first end plate, and a first passage extending from said first side of said first end plate to a second side of said first end plate generally opposite said first side;

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 series of compression pockets operating at an intermediate fluid pressure between a suction pressure and a discharge pressure, said first passage being in communication with one of said compression pockets;

a seal assembly engaged with said housing and said first scroll member and defining an axial biasing chamber in communication with a first of said compression pockets; and

a modulation plate overlying said second side of said first scroll member and located axially between said axial biasing chamber and said compression pockets and within an outer perimeter of said axial biasing chamber, said modulation plate secured within said housing for radial displacement between first and second positions, said modulation plate isolating said first passage from communication with a suction pressure region of the compressor when in the first position and providing communication between said first passage and said suction pressure region when in the second position.

16. The compressor of claim 15 , wherein said modulation plate includes an annular body defining a central opening and said first scroll member includes an annular hub extending through said central opening.

17. The compressor of claim 16 , wherein said modulation plate includes a pivot mount having a pivot pin extending therethrough and pivotally coupling said modulation plate within said housing to a structure that is fixed relative to said first scroll member.

18. The compressor of claim 17 , further comprising an actuation mechanism, said modulation plate including an arm extending radially outward from said annular body and coupled to said actuation mechanism.

19. The compressor of claim 18 , wherein said actuation mechanism pivots said modulation plate about said pivot pin.

20. The compressor of claim 19 , wherein said modulation plate slides along said second side of said first end plate during displacement from the first position to the second position.

21. The compressor of claim 15 , wherein said modulation plate includes an aperture in communication with said first passage when said modulation plate is in the first position.

22. The compressor of claim 21 , wherein said modulation plate includes first and second surfaces generally opposite one another, said first surface having a recess extending therein and defining a first radial surface area, said aperture extending through said first and second surfaces providing communication between said recess and said first passage when said modulation plate is in the first position, said second surface defining a second radial surface area exposed to said first passage when said modulation plate is in the first position, said second radial surface area being approximately equal to said first radial surface area.

23. The compressor of claim 22 , wherein said recess includes a seal to prevent communication between said suction pressure region and said recess when said modulation plate is in the first position.

24. The compressor of claim 23 , further comprising a spring disposed within said recess of said modulation plate to axially bias said seal against said first scroll member.