Scroll compressor with slanted back pressure seal

Details Scroll compressor with slanted back pressure seal Scroll compressor with slanted back pressure seal

1999-10-13

2001-01-09

Denion, Thomas (Department: 3748)

Rotary expansible chamber devices

Working member has planetary or planetating movement

Helical working member, e.g., scroll

C418S055400, C418S057000

Reexamination Certificate

active

06171088

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to an improved seal design for use in defining the back pressure chamber in a scroll compressor.
Scroll compressors are becoming increasingly popular in refrigerant compression applications. In a scroll compressor, a first scroll member has a base and a generally spiral wrap extending from the base. A second scroll member is driven to orbit relative to the first scroll member and has a base and a generally spiral wrap interfitting with the spiral wrap of the first scroll member. The wraps interfit to define compression chambers. As the second scroll member orbits relative to the first, the size of the compression chambers is reduced, and an entrapped refrigerant is compressed.
There are many challenges for the scroll compressor designer. In one main challenge, the compressed refrigerant creates a force, tending to separate the two scroll members away from each other. The sealing of the compression chambers is achieved by having the wraps in contact with the base of the opposed scroll member. As the two scroll members are forced away from each other by this “separating” force, this sealing contact might be lost, and the efficiency of the compressor could drop.
To combat this separating force, scroll compressor designers have tapped a portion of the entrapped refrigerant to a chamber behind one of the two scroll member bases. The entrapped refrigerant creates a force tending to hold the two scroll members together. This so-called “back chamber” is utilized in most modem scroll compressors. One known “back chamber” is defined outwardly of the base of the second scroll member. An inner seal and an outer seal define a chamber between the base of the second scroll member and a forward face of a crankcase which supports the second scroll member. These seals have typically been generally C-shaped with an internal C-shaped leaf spring biasing the outer ends of the seal into contact with the base of the second scroll member, and with a base of a groove which receives the seal. The seals are effective in defining the back pressure chamber, and sealing against leakage.
However, during certain operational conditions, the forces on the seals are not as expected. In particular, as an example, during reverse rotation the pressure forces in the compressor change rapidly and dramatically. In some cases, the lips of the C-shaped seal can be forced together. With the prior art C-shaped seals with an internal C-shaped leaf spring, the springs have sometimes been damaged when forced together.
So called APS seals are known which have a slanted internal coil spring. However, this type spring has not been used to define a back pressure chamber behind the orbiting scroll base plate. It would be desirable to design a seal which has a better survivability during such occurrences.
SUMMARY OF THE INVENTION
In a disclosed embodiment of this invention, a seal for a scroll compressor back pressure chamber is generally C-shaped and has an inner and outer lip. A coil spring is captured between the lips. The coils are slanted relative to a circumferential direction of the scroll compressor. That is, the coils are slanted such that they do not define planes which are parallel to a central circumferential axis of the coil spring. Of course, this would be true of any coil spring due to the helix angle. However, in the inventive coil springs, it is preferred that the slant angle be less than 80° when measured from the central axis. While coil springs may have been suggested for use in scroll compressors back pressure chambers in the past, the coil springs have typically been standard coil springs which have coils which are not slanted, and which would have an angle approaching 90°.
The present invention utilizing the slanted coil springs, develops a seal which is better able to withstand the crushing force during non-standard operation, such as reverse rotation.
In a preferred embodiment, ends of the seal have their coils interfitted to secure the spring together.
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.


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patent: 63-106388 (1988-05-01), None
patent: 1-177483 (1989-07-01), None

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