US20090060767A1

US20090060767A1 - Axial compliance

Info

Publication number: US20090060767A1
Application number: US11/847,464
Authority: US
Inventors: Carlos Zamudio
Original assignee: Individual
Current assignee: Danfoss Scroll Technologies LLC
Priority date: 2007-08-30
Filing date: 2007-08-30
Publication date: 2009-03-05
Also published as: GB0814752D0; CN101377197A; GB2452379A

Abstract

A scroll compressor has its back pressure chamber defined by two seals. The two seals are on different planes. Locating the seals on two distinct planes allows a more direct connection for a tap through a compression chamber and the back pressure chamber. In addition, the volume of the back pressure chamber can be made significantly larger, reducing resistance at start-up of the scroll compressor.

Description

BACKGROUND OF THE INVENTION

This application relates to a scroll compressor wherein a back pressure chamber is defined by inner and outer seals, with the seals on different planes. The formation of a tap for the back pressure chamber is simplified, and there is also less resistance at startup.
Scroll compressors are becoming widely utilized 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 has a base and a generally spiral wrap extending from its base. The wraps interfit to define compression chambers, and one of the two scroll members is caused to orbit relative to the other. As the scroll member orbits, the size of the compression chambers decreases and an entrapped refrigerant is compressed.
Generally, at least one of the two scroll members is allowed to move axially away from the other. As compression occurs a separating force is created which tends to drive the two scroll members apart. To address the separating force, scroll compressor designers have typically provided a “back pressure chamber.”
A back pressure chamber typically includes a sealed chamber into which compressed refrigerant is tapped. This compressed refrigerant works in opposition to the previously mentioned separating force, causing the two scroll members to be held in contact with each other.
In the prior art, the back pressure chamber has typically been formed by two radially spaced seals which are mounted in seal recesses in a face of a crankcase. The prior art back pressure chamber has required that a tap from an intermediate compression chamber to the back pressure chamber go through a plurality of drilled holes. This has resulted in some difficulty in machining the tap.
In addition, due to seal location in a crankcase seal face, and the part geometry (crankcase and orbiting scroll), the prior art back chamber pressure volume is limited to a relatively small volume. Thus, at startup of the compressor, the back pressure chamber fills quickly driving the scroll members into contact, and causing resistance to the orbiting movement from a point relatively soon after startup. This raises challenges under differential pressures for an electric motor that drives the scroll member to orbit.

SUMMARY OF THE INVENTION

In the disclosed embodiment of this invention, one of the two seals for defining the back pressure chamber is at a surface which is spaced away from the plane which receives the other seal. In this manner, the seals may be spaced radially further from each other such that a more direct path from the compression chamber to the back pressure chamber can be utilized, and a simple drilled hole can provide the tap.
Further, the radially innermost of the seals can be spaced axially from the radially outermost of the seals to define a relatively large volume back pressure chamber. Thus, it will take a relatively longer time for the back pressure chamber to fill, and for the scroll members to be brought in contact with each other at startup. In this manner, resistance to movement of the scroll member at startup is significantly reduced. This new arrangement also provides greater flexibility to tailor back chamber volume for optimized starting versus compression ramp-up.
The seals may be in the crankcase or in the orbital scroll.
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.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a prior art scroll compressor.

FIG. 1B shows a detail of the prior art.

FIG. 2 shows the inventive scroll compressor.

FIG. 3 shows a second embodiment.

FIG. 4 shows a third embodiment.

FIG. 5 shows a fourth embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A prior art scroll compressor 20 is illustrated in FIG. 1. As known, a crankcase 22 is fixed to a non-orbiting scroll member 24. Non-orbiting scroll member 24 has a base 26 and a generally spiral wrap 28 extending from its base. An orbiting scroll member 29 has a base 30 and a generally spiral wrap 32 extending from its base. The orbiting scroll member 29 is supported on the crankcase 22. The wraps of the orbiting scroll and non-orbiting scroll interfit to define compression chambers such as 42. A boss 44 extends rearwardly away from the base 30 and receives a driveshaft 46 through an intermediate slider block 48. As known, the orbiting scroll member is caused to orbit relative to the non-orbiting scroll member. As this occurs, the size of the compression chambers 42 is decreased to compress an entrapped refrigerant.
A separating force is created in the compression chambers as the refrigerant is compressed. To address this separating force, a back pressure chamber 34 is provided. A radially outer seal 36 and a radially inner seal 38 are mounted within recesses in a face of the crankcase 22. Refrigerant is tapped through a tap 40 from an intermediate pressure compression chamber 42. As shown in FIG. 1B, the tap 40 typically includes three sub portions 40A, 40B and 40C. This is necessary since a compression chamber of significantly high pressure tends to be more radially centered, and the crankcase face which receives the innermost seal is not sufficiently centered. Typically, the crossing path 40B must be drilled from an outer surface of the orbiting scroll and then plugged. The creation of this three-part path is somewhat complex.
In addition, as can be appreciated, the back pressure chamber 34 is very small in volume. At startup, refrigerant sufficient to fill the back pressure chamber 34 is quickly directed through the tap 40 increasing the back chamber pressure and pushing the orbiting scroll member 29 into contact with the non-orbiting scroll 24. At this point, the motor 100 rotating the driveshaft 46 is still starting up, and it is somewhat difficult for it to overcome the compressive resistance. Therefore, a relatively high torque exists to begin compressing refrigerant. This situation is worst when discharge pressure is significantly higher than suction pressure.
FIG. 2 shows a scroll compressor 50 which is modified to address the concerns mentioned above. Scroll compressor 50 modifies the boss 52 such that it has an outwardly extending flange 54. Flange 54 defines an enlarged chamber 56 between a lower surface 60 of the crankcase 22 and an upper surface 62. Lower surface 60 receives a seal 58, while upper surface 62 receives a seal 64. In this manner, the radially inner seal 58 may be positioned more radially inwardly than in the prior art. Thus, the tap 66 can extend directly through the base of the orbiting scroll member. Forming the tap 66 is much simpler than forming the tap 40. In addition, the volume of the chamber 56 is much larger than the volume of the prior art back pressure chamber 34. A longer period of time is required after startup for the back pressure chamber 56 to pressurize and push the orbiting scroll member 51 into contact with the non-orbiting scroll member 24. The volume that controls this start-up torque can be adjusted by several methods, including, as an example, thickening of flange 54 or boss 52 or adding additional boss to upper surface 62. Thus, the start-up torque resistance on the motor is reduced until the motor is rotating at a significantly higher speed.
An embodiment 150 is shown in FIG. 3, wherein the radially inner seal 156 is in the hub 154 of the orbiting scroll 152. The radially outer seal 64 remains in the crankcase. Of course, the two seal locations could be reversed, with the radially outer seal in the orbiting scroll and the radially inner seal in the crankcase.
FIG. 4 shows another embodiment 250 wherein the orbiting scroll 252 has the hub 254 receiving the radially inner seal 258. The base of the orbiting scroll 252 receives the radially outer seal 256.
FIG. 5 shows another embodiment 300 wherein the orbiting scroll 302 includes a hub 305 with a separate member 308 that contacts the radially inner seal 306. The radially outer seal 304 sits in the crankcase in this embodiment. In this embodiment, the formation of the orbiting scroll is simplified in that the hub need not have the radially outwardly extending lowermost portion, but can instead receive a separate component to provide that function.
Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.

Claims

1. A scroll compressor comprising:

a first scroll member having a base and a generally spiral wrap extending from its base;

a second scroll member having a base and a generally spiral wrap extending from its base, said second scroll member having a boss extending in an opposed direction from said base relative to said wrap, and a driveshaft causing orbiting motion of the scroll members relative to each other;

a housing supporting said second scroll member, said housing having a first surface adjacent to said base of said second scroll member, and a radially outer seal sealing at said first surface, said second scroll member being adjacent to a second surface of said housing on a plane spaced from said first surface and said base of said second scroll member, a radially inner seal at said second surface, and said inner and outer seals defining a back pressure chamber; and

a tap extending from a compression chamber through said base of said second scroll member and into said back pressure chamber.

2. The scroll compressor as recited in claim 1, wherein said tap extends directly through said base along a single direction.

3. The scroll compressor as recited in claim 1, wherein said boss extends axially away from said base and then has a surface which is adjacent to said second surface.

4. The scroll compressor as recited in claim 3, wherein said surface is formed integrally with said boss.

5. The scroll compressor as recited in claim 3, wherein said surface is formed as a separate part from said boss.

6. The scroll compressor as recited in claim 1, wherein said radially inner and said radially outer seals are both received in recesses in said housing.

7. The scroll compressor as recited in claim 1, wherein said radially inner and said radially outer seals are both received in said recesses in said second scroll member.

8. The scroll compressor as recited in claim 1, wherein one of said radially inner seal and said radially outer seal is received in a recess in said housing, and the other of said radially inner seal and said radially outer seal is received in a recess in said second scroll member.

9. A scroll compressor comprising:

a second scroll member having a base and a generally spiral wrap extending from its base, said second scroll member having a boss extending in an opposed direction from said base relative to said wrap, said second scroll member receiving a driveshaft within said boss, and said driveshaft causing said second scroll member to orbit relative to said first scroll member;

a crankcase supporting said second scroll member, said crankcase having a first surface in contact with said base of said second scroll member, and receiving a radially outer seal, said second scroll member contacting a second surface of said crankcase on a plane spaced from a contact plane between said first surface and said base of said second scroll member, said second surface receiving a radially inner seal, and said inner and outer seals defining a back pressure chamber, said boss extends axially away from said base and then has a radially outwardly extending lip which contacts said second surface; and

a tap extending from said one of said compression chambers along a single direction through said base of said second scroll member and into said back pressure chamber.