Cantilever mount orbiting scroll with shaft adjustment

Abstract

A scroll compressor of the type having a cantilever mounted shaft is provided with a carbon crankcase bearing. Further, the bearing mounting the eccentric pin within the orbiting scroll is also formed of a carbon material. The bearing mounting the lower end of the shaft is further formed of the carbon material. The carbon bearing insures that the shaft will be quickly worn away should there be shaft misalignment.

Description

BACKGROUND OF THE INVENTION

The invention relates to a scroll compressor, wherein the bearings for mounting the drive shaft are formed of a material that will cause wear to the shaft when the shaft becomes misaligned.

Scroll compressors are becoming widely utilized in many compression applications. Essentially, a scroll compressor includes a first scroll which orbits relative to a second scroll. Both members have a base and a generally spiral wrap extending from the bases. The two wraps interfit to define compression chambers. When the orbiting scroll orbits, the size of the chambers decreases to compress an entrapped refrigerant.

Scroll compressors are very popular because they are efficient. However, they present many design challenges in that there are a number of forces on the compressor components. One problem that occurs in the scroll compressor relates to the mounting of the shaft. A shaft drives the orbiting scroll through an electric motor. The shaft is mounted in an upper bearing and a lower bearing. An eccentric pin from the shaft is received in a slider block mounted in an upper bearing in the first scroll.

In the past, the three bearings have sometimes been misaligned. One type of scroll compressor shaft is cantilevered in the upper bearing. When bearing misalignment occurs with this type compressor, the shaft moves to an angle which is non-parallel to the central axis of the bearings. When this happens, there is contact between the edges of the bearings, and the outer surface of the shaft and slider block. There is the edge loading between the shaft and slider block, and the bearings at the edges that are in contact. Seizure of the shaft can result, and there is also inadequate lubricant flow to the contact area.

Scroll compressors have sometimes utilized carbon containing bearings to mount the shaft. However, this type of bearing has only been utilized in a male mounted scroll compressor shaft, which does not have the cantilevered shaft. In this type of scroll compressor, there is no danger of edge loading.

SUMMARY OF THE INVENTION

In a disclosed embodiment of this invention, a shaft for driving an orbiting scroll extends through a bearing in a crankcase. A portion of the shaft extends entirely through the bearing, and another portion of the shaft is mounted in a lower bearing. That is, the shaft is cantilevered in the upper bearing. The bearing mounted in the crankcase contains hard carbon in a resin matrix. When shaft misalignment occurs, the bearing edges contact the shaft. However, rather than seizing as in the prior art, the bearing will cause removal of the material in the shaft at the area of the contact. Eventually, grooves will be formed in the shaft at the contact areas. The grooves prevent seizure and also insure adequate lubrication. The grooves also promote full-film hydrodynamic lubrication in the edge loaded region.

More preferably, there are three bearings mounting the shaft. A first bearing is placed between the slider block and the orbiting scroll. The second bearing is the above-mentioned bearing mounted in the crankcase for cantilever mounting the shaft. The third bearing mounts the opposed end of the shaft on a remote side of the motor. Preferably, at least one, and most preferably all three of these bearings are formed of the material mentioned above.

The same benefit would not occur in the prior art which has utilized these carbon bearings, in that those types of compressors did not have the problem.

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 is a cross-sectional view through an inventive scroll compressor of the type which benefits from the present invention.

FIG. 2 is a cross-sectional view through an inventive bearing.

FIG. 3 is a cross-sectional view through the area shown by line 3 in FIG. 2.

FIG. 4 shows a problem encountered by this type of compressor.

FIG. 5 shows the inventive bearing solving the FIG. 4 problem.

FIG. 6 shows a second embodiment invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

A compressor 20 shown in FIG. 1 incorporates a fixed, or non-orbiting scroll member 22, and an orbiting scroll member 23. The orbiting scroll member 23 has a lower mount portion 24 received on a crank pin 26. A slider block connects the pin 26 to the portion 24. The crank pin 26 is associated with a shaft 25, which is driven by a motor 27. The shaft 25 is mounted in a crankcase 28 at a bearing mount portion 30 by a bearing 32. The other end of the shaft 25 is mounted in a lower bearing 34. Notably, the compressor 20 is of the sort wherein the crank pin 26 on the shaft 25 extends through the bearing 32 and the crankcase 28, and is thus cantilever mounted in the bearing 32.

As shown in FIG. 2, the bearing 32 incorporates an outer liner portion 36 formed of a steel material, and an inner portion 38 formed of a composite resin material.

As shown in FIG. 3, the composite material includes a graphite and heat resistance resin complex layer 40 incorporating a plurality of lead bronze porous sintering layer particles 42. The layer 40 includes hard carbon particles deposited into a resin base. The use of the graphite carbon composite bearing provides benefits which will be described below. The bearing is available from Taiho Kogyo, Ltd., under their trade name "Carbon Composite bi-Metal Bearings CB100G."

In one embodiment, the steel backing 36 extended for 1.35 mm and the total thickness was 1.7 mm. Thus, the layer 38 is relatively thin compared to the layer 36.

The structure of the bearing forms no portion of this invention, it is the use of such a bearing in the particular application which is inventive.

The problem to be addressed by this invention is shown for example in FIG. 4. As shown in FIG. 4, a central axis of the bearings 32 and 34 has been misaligned. This can happen during assembly of the compressor. The amount of misalignment is exaggerated in FIG. 4 to show the fact of misalignment. Also, the structure of the pin 26 is simplified in FIGS. 4 and 5.

When misalignment occurs, the cantilever mounted pin 26 extends beyond the bearing 32, and a contact edge point 44 exists between the bearing 32 and the shaft outer periphery 25. In addition, another contact edge point 45 is also created. In the prior art, this contact is sometimes led to seizing of the shaft, and will often result in inadequate lubricant supply to the contact areas.

As shown in FIG. 5, the inventive compressor with the carbon particles embedded in the outer layer will instead result in the shaft being quickly worn away such as at 46 and 48 to prevent edge contact. This will ensure flow of lubricant between the shaft and the edges 44 and 45 of the bearing 32. Thus, the bearing material provides an unexpected benefit when utilized in a cantilever mounted scroll compressor. The prior art provided no such benefit, and included no such problem. Thus, the use of this type of bearing in the particular disclosed application provides unexpected benefits.

FIG. 6 shows another embodiment 50 wherein a bearing 52, of similar composition to bearing 32, is mounted in the lower bearing mount 34. As shown, an edge 55 of the shaft 25 contacts the bearing 52 when the shaft 25 is misaligned. Further, portion 54 of the shaft contacts an end of the bearing 52. The bearing material 52 will cause wear at portions 54 and 55 on the shaft 25, similar to the wear described above.

A bearing 56, of similar composition to bearing 32, is mounted between the slider block 29 and the orbiting scroll 23. As can be seen, there will be wear surfaces 58 and 60 which will wear the slider block to accommodate any misalignment. As can be appreciated, the combination of the three bearing 56, 32 and 52 serve to accommodate any misalignment between the three bearings by forming wear into the shaft to modify the shaft to the particular location of the three bearings.

A preferred embodiment of this invention has been disclosed; however, a worker of ordinary skill in the 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 said base;

a second scroll member having a base and a generally spiral wrap extending from said base, said wraps of said first and second scroll members interfitting to define compression chambers, said first scroll member having a mount portion extending away from said second scroll member to receive a drive shaft;

a crankcase mounted beneath said first scroll member, and on a side opposed from said second scroll member;

a shaft having an eccentric pin extending through said crankcase, and into a slider block mounted in said mount portion of said first scroll member, a first bearing received between said slider block and said mount portion, and an electric motor driving said shaft;

a second bearing mounted in said crankcase and surrounding said shaft, said pin of said shaft extending through said second bearing and into said mount portion of said first scroll member;

a third bearing mounted at an opposed end of said shaft and on a remote side of said motor from said first bearing; and

at least one of said first, second and third bearings having a material composition including carbon particles deposited into a resin.

2. A scroll compressor as recited in claim 1, wherein said material results in said shaft being worn away at edges of said one of said first, second and third bearing should said shaft be misaligned in any of said first, second and third bearings.

3. A scroll compressor as recited in claim 1, wherein each of said first, second and third bearings is formed of said material composition including carbon particles deposited into a resin.

4. A scroll compressor as recited in claim 1, wherein said first bearing is formed of said material composition.

5. A scroll compressor as recited in claim 1, wherein said second bearing is formed of said material composition.

6. A scroll compressor as recited in claim 1, wherein said third bearing is formed of said material composition.

7. A method of operating a scroll compressor comprising the steps of:

1) providing a scroll compressor including a first and second scroll member, each having a base and a generally spiral wrap extending from said base, said wraps of said first and second scroll members interfitting to define compression chambers, said first scroll member having a mount portion extending away from said second scroll member, a shaft including a mount pin extending into a slider block mounted in said mount portion of said first scroll member, a first bearing between said slider block and said mount position, said shaft mounted to be driven by an electric motor, said shaft having said mount pin extending into said slider block, and said mount portion of said first scroll member at one end of said motor, a portion of said shaft intermediate said motor and said pin being mounted in a second bearing in a crankcase, said mount pin extending entirely through said second bearing such that said mount pin is cantilever mounted within said second bearing, said shaft being mounted at an opposed end of said motor in a third bearing, and one of said first, second and third bearing being formed of an outer metal portion and an inner portion including a carbon material deposited into a resin layer;

2) driving said first scroll member to orbit relative to said second member by driving said shaft with said electric motor; and

3) wearing portions of at least one of said shaft and said slider block which are in contact with edges of said one bearing should said first, second and third bearings be misaligned relative to each other, said carbon material causing said portions to be quickly worn away.

8. A method as recited in claim 7, wherein said first bearing is formed of said carbon material.

9. A method as recited in claim 7, wherein said second bearing is formed of said carbon material.

10. A method as set forth in claim 7, wherein said third bearing is formed of said carbon material.