Rotary expansible chamber devices – Working member has planetary or planetating movement – Helical working member – e.g. – scroll
Utility Patent
1998-12-16
2001-01-02
Denion, Thomas (Department: 3748)
Rotary expansible chamber devices
Working member has planetary or planetating movement
Helical working member, e.g., scroll
C418S055600, C418S057000
Utility Patent
active
06168404
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to scroll compressors which include fixed and orbiting scroll members and, more particularly, to a valve which regulates a pressure intermediate suction and discharge pressures to maintain sealing axial engagement between the orbiting scroll member and the fixed scroll member.
2. Description of the Related Art
A typical scroll compressor comprises two facing scroll members, each having an involute wrap wherein the respective wraps interfit to define a plurality of closed compression pockets. When one of the scroll members is orbited relative to the other member, the pockets decrease in volume as they travel between a radially outer suction port and a radially inner discharge port. The pockets thereby convey and compress a fluid, typically a refrigerant, contained therein.
During compressor operation, the pressure of the compressed refrigerant tends to force the scroll members axially apart. Axial separation of the scroll members causes the closed pockets to leak at the interface between the wrap tips of one scroll member and the face of the other scroll member. Such leakage reduces the operating efficiency of the compressor and, in extreme cases, may result in the inability of the compressor to operate.
Efforts to counteract the separating force applied to the scroll members during compressor operation, and thereby minimize the aforementioned leakage, have resulted in the development of a variety of axial compliance mechanisms. For example, it is known to axially preload the scroll members toward each other with a force sufficient to resist the dynamic separating force. One approach is to assure close manufacturing tolerances for the component parts and have a thrust bearing interface between the fixed and orbiting scroll members for conveying axial forces between the members. The most common approach is to feed back compressed refrigerant gas to urge the two scroll members together.
Typically, the axial compliance forces bias the tips of the scroll compressor wraps against the inner surface of the opposite scroll and/or may bias sliding surfaces on the outer perimeter of the two scroll members into mutual engagement. Frictional forces are created at these areas of contact as the moveable scroll is orbited about the fixed scroll. Excessive frictional forces generated by the axial compliance mechanism can increase the power required to operate the scroll compressor and have an abrasive effect on the engagement surfaces. The abrasive effects created by the axial compliance forces can damage or lead to wearing of the wrap tips and interior surfaces, or faces, of the two scrolls when excessive axial compliance forces are borne by these surfaces and thereby negatively impact the sealing ability and longevity of the wrap tips.
Some prior art scroll compressors provide passageways in the orbiting scroll member plate through which a portion of the compression chamber formed by the interfitting scroll wraps, in which refrigerant is at intermediate pressure, is in direct fluid communication with an intermediate pressure chamber formed in part by the side of orbiting scroll member opposite that on which scroll wraps are disposed. The refrigerant gas in the intermediate pressure chamber exerts an axial sealing force between the orbiting and fixed scroll members. However, under certain operating conditions such arrangements can create intermediate pressures greater than discharge pressure, forcing the fixed and orbiting scroll members together too tightly, resulting in compressor inefficiency. A method of regulating the pressure of a fluid, which may be gas or liquid, which biases the fixed and orbiting scroll members into consistent and proper sealing engagement under varying compressor operating conditions is needed.
SUMMARY OF THE INVENTION
The present invention provides a pressure regulation valve for regulating the pressure of a fluid to bias the orbiting scroll member into consistent, proper sealing engagement with the fixed scroll member under varying operating conditions. The regulation of this axial compliance pressure by the inventive valve reduces frictional power losses and maintains the tips and interior surfaces of the fixed and orbiting scrolls at fixed relative axial positions.
A scroll compressor assembly according to the present invention thus includes a first scroll device having a first involute wrap element projecting from a first substantially planar surface and a second scroll device having a second involute wrap element projecting from a second substantially planar surface, the first and second scroll devices adapted for mutual engagement with the first involute wrap element projecting toward the second surface and the second involute wrap element projecting toward the first surface. The first surface is positioned substantially parallel with the second surface and the second scroll device further has a third surface facing oppositely the second surface. Relative orbiting motion of the first and second surfaces compresses fluids between the involute wrap elements. A first source of a first fluid under a pressure intermediate suction pressure and discharge pressure is located between the first and second scroll wrap elements. A frame partly defines a chamber containing a quantity of a second fluid under pressure. A valve is provided in fluid communication with the first source of the first fluid and a second source of the second fluid substantially at the discharge pressure. The chamber and the second source are out of communication in a first valve position, and are in communication in a second valve position. The valve is activated by the fluid pressure of the first source. Through this arrangement, the first and second scroll wrap elements are thus maintained in controlled axial sealing engagement against the second and first surfaces, respectively.
The present invention also provides a scroll compressor assembly having a first scroll member having a first involute wrap element projecting from a first substantially planar surface, a second scroll member having a second involute wrap element projecting from a second substantially planar surface and a third surface opposite its second surface. The first and second scroll members are adapted for mutual engagement with the first involute wrap element projecting toward the second surface and the second involute wrap element projecting toward the first surface, the first and second surfaces positioned substantially parallel relative to each other and relative orbiting of the scroll members compresses fluids between their involute wrap elements. The compressor assembly also includes a first source of a first fluid under a pressure between suction pressure and discharge pressure, and a frame which partly defines a chamber which contains a quantity of a second fluid under pressure. Means are provided for automatically controlling the axial compliance forces between said first and second scroll devices. Thus present invention thus maintains the first and second scroll members in controlled axial sealing engagement.
An advantage of the present invention is that by utilizing the pressure regulation valve to control the pressure of the axial compliance medium, which may be gas or liquid, the wrap tips do not bear excessive axial compliance forces. With the axial compliance force controlled, the orbiting and fixed scroll members are axially forced together by the axial compliance medium, or allowed to be axially forced apart by the gas pressures between the scroll wraps, to such a degree that the frictional contact between the wrap tip/scroll plate interface is properly maintained, providing an appropriate balance between frictional losses and sealing effectiveness. The controlled axial compliance force allows the wrap tips to wear-in properly against its scroll plate interface and the orbiting and fixed scroll members to achieve proper and substantially constant relationships relative to one another.
REFERENCES:
patent: Re. 35216 (
Baker & Daniels
Denion Thomas
Tecumseh Products Company
Trieu Theresa
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