Rotary expansible chamber devices – Working member has planetary or planetating movement – Helical working member – e.g. – scroll
Reexamination Certificate
1998-12-21
2001-03-20
Denion, Thomas (Department: 3748)
Rotary expansible chamber devices
Working member has planetary or planetating movement
Helical working member, e.g., scroll
C418S055100, C418S055200, C418S055500, C418S057000
Reexamination Certificate
active
06203299
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a scroll compressor wherein the volume of the compressor may be changed upon system demand, and wherein the back pressure force is also adjusted.
Scroll compressors provide efficient compression of the refrigerant and thus are becoming popular. On the other hand, scroll compressors do present many design challenges.
Essentially, scroll compressors are formed of two interfitting generally spiral wraps, with one of the wraps orbiting relative to the other. Compression chambers are formed on inner and outer surfaces of the wraps, and close during the orbiting movement of the orbiting scroll member. The compression chambers decrease in size as the orbiting scroll continues its orbital movement, and the refrigerant is compressed.
One challenge with the design of a scroll compressor is providing the ability to vary the output mass of the scroll compressor. This “modulation” of the output volume is desirable for many refrigerant compression applications. In general, proposed modulation schemes to date have concentrated on the mass changes.
However, with mass changes other aspects of the compressor need to be adjusted. In particular, scroll compressors often rely upon a back pressure force from a compressed gas delivered to a rear face of one of the scroll members. The purpose of the back pressure force is to resist a separating force generated from the entrapped fluid between the scroll members. However, with mass changes, the necessary back pressure force also changes. The prior art has not addressed this issue.
SUMMARY OF THE INVENTION
In a disclosed embodiment of this invention, the back pressure chamber provided to maintain the scroll wraps in contact is controlled depending upon whether the compression chambers are modulated. When the mass of gas being compressed is reduced, a separating force tending to separate the fixed and orbiting scrolls is also reduced. As known, scroll compressors are provided with a back pressure chamber wherein a portion of the compressed fluid is tapped to provide a force in opposition to the separating force.
The present invention discloses an embodiment for controlling the amount of gas in the back pressure chamber to in turn control the back pressure force such that when the capacity is reduced, the force in the back pressure chamber is also reduced. In one embodiment this is achieved by providing two distinct back pressure chambers. In a first embodiment a vane blocks flow to one of the two chambers when the volume is reduced. In this way, the back pressure force is reduced to accommodate the reduced separating force from the compression chambers.
In a second embodiment, a separate tap leads from certain of the compression chambers to each of the two back pressure chambers. Thus, when certain of the compression chambers are not provided with compressed fluid pressurized fluid is not tapped into its back pressure chamber. Thus, there will be no force from the non-compression chambers. The back pressure force is correspondingly thus reduced whenever the mass of the scroll compressor is reduced.
In a disclosed embodiment of this invention, modulation is achieved by a modulation member selectively biased to a restriction position wherein it blocks flow of suction fluid to at least some compression chambers between the orbiting and non-orbiting scroll wraps. In a preferred embodiment, the restriction member completely blocks flow to certain of the chambers. It should be understood that the invention could be incorporated into other modulation schemes.
These and other features of the present invention can be best understood from the following specification and drawings, the Following of which is a brief description.
REFERENCES:
patent: 4431388 (1984-02-01), Eber et al.
patent: 4696627 (1987-09-01), Asano et al.
patent: 5256044 (1993-10-01), Nieter et al.
patent: 5447420 (1995-09-01), Caillat et al.
patent: 5645408 (1997-07-01), Fujio et al.
patent: 0249684 (1985-12-01), None
patent: 0106388 (1988-05-01), None
patent: 0294584 (1990-12-01), None
patent: 403172592 (1991-07-01), None
patent: 405149270 (1993-06-01), None
Fields Gene Michael
Hill Joe T.
Lyons Terry L.
Milliff Tracy
Williams John R.
Carlson & Gaskey & Olds
Denion Thomas
Scroll Technologies
Trieu Theresa
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