Rotary expansible chamber devices – Working member has planetary or planetating movement – Helical working member – e.g. – scroll
Reexamination Certificate
1998-10-21
2001-02-27
Denion, Thomas (Department: 3748)
Rotary expansible chamber devices
Working member has planetary or planetating movement
Helical working member, e.g., scroll
C029S888022
Reexamination Certificate
active
06193484
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a scroll compressor wherein the housing components are force-fit into the housing cylinder.
Scroll compressors are becoming widely utilized in refrigerant compression applications. In a typical scroll compressor, a pair of scroll members each have a base with a generally spiral wrap extending from the base. One of the two scroll members orbits relative to the other, and the wraps interfit to define compression chambers.
A scroll compressor is typically assembled by preparing a modular “pump unit” which includes the two scroll members and a crank case which supports the orbiting scroll. The pump unit is inserted as a modular preassembled unit into a cylindrical housing. A shaft is then inserted into the pump unit, and supported in a lower bearing.
In the past, pump units have been secured to the cylinders by many different methods. As one example, the pump unit has been welded to the cylinder. Other examples include various bolting arrangements, etc. Similarly, the lower bearing has typically been welded to the cylinder.
These known assemblies have been rather expensive and time consuming. One proposed method has been to force-fit the components into the cylinder. However, the known crankcases and the known lower bearings have been non-continuous at their outer periphery. When these known non-continuous members have been force-fit into the housing, there has thus been force-fit connections at less than the full inner circumference of the housing.
The non-full inner circumference interference fits have caused the shell to take the shape of the inner object, which causes other assembly problems.
Known equations for calculating the holding strength of an interference connection show that a non-continuous member has a much lower holding strength than a generally continuous force-fit member.
In addition, the overall surface contact area between the two members to be held together by an interference fit also effects the holding force. The structure in the prior art compressors which was in contact with the housing have not extended for a long distance, and thus have had relatively small holding areas. Again, this has resulted in undesirably low holding strength.
In the prior art non-continuous force-fit connections, there has not been sufficient holding strength to be practically reliable as the only means of holding the parts. However, these known formulas have never been applied to the concept of interference housing components into scroll compressor cylinders.
In addition, with the prior art, the outer housing did not yield beyond its plastic deformation point. Instead, the housing was able to flow around the spaced contact areas. This also effected the holding force.
SUMMARY OF THE INVENTION
In a disclosed embodiment of this invention, a portion of the pump unit of a scroll compressor is formed to have a generally cylindrical outer surface of a diameter slightly larger than the inner diameter of the cylinder which is to receive the pump unit. This pump unit may then be interference-fit into the cylinder. Since the cylindrical outer diameter portion is generally continuous, the interference-fit holding force is at a maximum. Also, the amount of interference causes the outer cylinder material to yield. Therefore, the holding force will not be diminished until the internal pressure is high enough to cause the outer cylinder material to yield.
Similarly, the lower bearing is formed with a cylindrical portion which is interference-fit into the cylinder housing.
In a preferred embodiment, the generally cylindrical portion extends at least 315°, more preferably 350°, and most preferably over the entire 360° about the central axis of the compressor. These ranges define the term “generally” as used in this application and its claims.
Applicant has found that with these cylindrical components, there is sufficient holding force, and the relatively simple method of force-fit assembly may be utilized.
In a preferred embodiment of this invention, it is the crankcase which is the portion of the pump unit having the generally cylindrical outer peripheral portion to be force-fit into the cylinder housing.
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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Hahn Gregory W.
Hugenroth Jason J.
Carlson & Gaskey & Olds
Denion Thomas
Scroll Technologies
Trieu Theresa
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