US20030059319A1

US20030059319A1 - Shaft axial compliance mechanism

Info

Publication number: US20030059319A1
Application number: US09/964,241
Authority: US
Inventors: David Haller; Robin Skinner
Original assignee: Tecumseh Products Co
Current assignee: Tecumseh Products Co
Priority date: 2001-09-26
Filing date: 2001-09-26
Publication date: 2003-03-27
Also published as: CA2401636A1

Abstract

A hermetic compressor assembly including a compressor housing has a motor and a compression mechanism mounted therein, operatively coupled by a drive shaft having a substantially horizontal axis of rotation. A bearing housing is connected to the motor and receives a portion of the drive shaft having a bearing assembly affixed thereto. A retaining element is received in a groove formed in the bearing housing and is in abutting contact with the bearing assembly to prevent relative movement of the drive shaft in both directions along the axis of rotation.

Description

BACKGROUND OF THE INVENTION

The present invention relates to hermetic compressors and particularly to those having substantially horizontal drive shafts.

Conventionally, hermetic compressors include a hermetically sealed housing having a compression mechanism and an electric motor disposed therein. The compression mechanism and motor are operatively coupled by a drive shaft. A substantially horizontal hermetic compressor is one in which the shaft axis of rotation and thus the drive shaft are nearly horizontal. Electrical power is provided to the motor through a hermetic terminal assembly to induce rotation of the drive shaft which in turn induces rotation of the compression mechanism. As the compression mechanism operates, refrigerant fluid is compressed therein to a discharge pressure and is exhausted as refrigerant gas to a refrigeration system.

Particularly with horizontal compressors, the weight of the drive shaft and the rotor does not urge the drive shaft along its axis of rotation into a position in which the drive shaft is in abutting relationship with a thrust bearing surface. During operation of the compressor, the rotation of the rotor, drive shaft, and compression mechanism may generate oscillating axial movement of the drive shaft. Such back and forth oscillation of the drive shaft is often accompanied by objectionable noise, such as knocking.

One method of biasing the rotor and drive shaft in one direction along the longitudinal shaft axis of rotation is by using the solenoid effect of the motor. The stator and the rotor of the motor are offset by a specific distance, and upon energization of the stator, the rotor is urged in a direction along the longitudinal shaft axis of rotation to allow alignment of its laminae with those of the stator. The rotor exerts an axial force on the drive shaft, moving the drive shaft into engagement with a thrust bearing surface to maintain axial compliance of the drive shaft during compressor operation. When using the solenoid effect of the motor to bias the rotor and the drive shafts, axial positioning of the rotor and the stator must be closely toleranced.

An additional method which may be used to prevent axial oscillations of the drive shaft includes constructing the compressor to have close tolerances and selective fits. By constructing the compressor in such a manner, the available space in which the drive shaft may move is limited, thus limiting axial movement of the drive shaft. Therefore, the amount of noise produced by oscillating axial movement of the drive shaft is reduced.

A problem with these methods of providing axial compliance of a horizontal drive shaft is that gauging and selective assembly of compressor components is labor intensive. Further, manufacturing processes for compressor components having close tolerances are more difficult and thus more expensive.

Further means for limiting axial movement of the drive shaft is described in pending U.S. patent application Ser. No. 09/849,541, assigned to the assignee of the present invention, the disclosure of which is expressly incorporated herein by reference. Those means include providing a circumferential groove near one end of the shaft. A bore is provided in the outboard bearing supporting one end of the drive shaft, aligning with the circumferential groove. A retaining element is positioned in both the bore and shaft circumferential groove such that a portion of the retaining element is located within each of the bore and the groove. The retaining element thereby prevents relative axial movement of the drive shaft.

A problem with such means for limiting axial movement of the drive shaft is that complex machining of the drive shaft and outboard bearing to receive a retaining element is labor intensive and requires additional steps in the manufacturing process, thus increasing manufacturing costs.

It is desired to provide a shaft axial compliance mechanism for a substantially horizontal hermetic compressor which simplifies machining and assembly of the compressor components to prevent objectionable noise created by oscillating axial movement of the drive shaft.

SUMMARY OF THE INVENTION

The present invention provides a shaft compliance mechanism for a substantially horizontal hermetic compressor to prevent objectionable noise created by oscillating axial movement of the drive shaft.

The substantially horizontal compressor of the present invention includes a housing having a motor and a compression mechanism located therein, and operatively coupled by a drive shaft. A bearing housing is affixed to the motor and includes a collar in which one end of the drive shaft is rotatably supported. A bearing assembly is shrink fitted onto an end of the drive shaft. The bearing/drive shaft assembly is inserted into a cavity defined in the collar of the bearing housing. The bearing housing is further provided with a circumferential groove in which a retaining element such as an annular snap ring is positioned to maintain the axial position of the bearing assembly, and thus the drive shaft within the bearing housing. The retaining element prevents oscillating axial movement of the drive shaft, and thus reduces objectionable noise created by such movement.

The present invention provides a hermetic compressor assembly including a compressor housing having a compression mechanism and a motor disposed therein. A drive shaft having an axis of rotation operatively couples the compression mechanism and the motor. A bearing housing is connected to the motor. A bearing assembly is affixed to the drive shaft with the bearing assembly and the drive shaft being received in the bearing housing. A retaining element connected to the bearing housing is in abutting contact with the bearing assembly to prevent relative movement of the drive shaft in both directions along the axis of rotation.

The present invention further provides a hermetic compressor assembly having a compressor housing in which a compression mechanism and motor are disposed. The compression mechanism and motor are operatively coupled by a drive shaft having an axis of rotation. A bearing assembly is affixed to the drive shaft, the bearing assembly and the drive shaft being received in a bearing housing connected to the motor. A circumferential groove is formed in the bearing housing and a retaining element received therein. The retaining element is in abutting contact with the bearing assembly to prevent relative movement of the drive shaft in both directions along the axis of rotation.

The present invention also provides a hermetic compressor assembly including a compressor housing in which a compression mechanism and a motor are disposed. A drive shaft having an axis of rotation operatively couples the compression mechanism and the motor. A bearing housing is connected to the motor. Further provided are shaft axial compliance means engaging the drive shaft and the bearing housing to prevent relative movement of the drive shaft in both directions along the shaft axis of rotation.

The present invention provides a method of preventing oscillating axial movement of a drive shaft in a hermetic compressor. The method includes attaching a bearing housing to a motor of the compressor; affixing a bearing assembly to one end of a drive shaft; positioning the bearing assembly and drive shaft in the bearing housing; and engaging a circumferential groove formed in the bearing housing with a retaining element, the retaining element in abutting contact with the bearing assembly, to prevent relative movement of the drive shaft.

An advantage of the present invention is that the tolerances of the compressor may be looser and selective component assembly is not required to provide axial compliance of the horizontal drive shaft. Further, complex machining and assembly of parts is eliminated, allowing for axial compliance of the drive shaft with minimal increases in cost and labor.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of the embodiment of the invention taken in conjunction with the accompanying drawings, wherein: [0017]
FIG. 1 is a sectional side view of a compressor assembly in accordance with the present invention; and [0018]
FIG. 2 is a fragmentary sectional view of the compressor assembly of FIG. 1.[0019]
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate an embodiment of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. [0020]

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, [0021] hermetic compressor assembly 20 includes housing 22 having end portions 24 and 26 with central portion 28 located therebetween. Housing portions 24, 26, and 28 are hermetically sealed at 30 by any suitable process including welding, brazing, or the like. Compressor 20 is arranged substantially horizontally and is supported by mounting bracket 32 and stand 34 located at opposite ends of compressor housing 22. One end of compressor 20 may be slightly higher than the other to influence the flow of oil in oil sump 35 located within compressor housing 22 toward oil pick-up tube 92.
Located within [0022] housing 22 is electric motor 36 including stator 38 and rotor 40. Located centrally in rotor 40 is aperture 42 in which drive shaft 44 is shrink fitted. End 46 of drive shaft 44 is rotatably supported in collar 48 of bearing housing 50. Bearing housing 50 includes substantially cylindrical portion 52 with a plurality of radially extending arms 54 extending between cylindrical portion 52 and collar 48. Edge 56 of cylindrical portion 52 is affixed to motor 36 by any suitable method including fasteners such as bolts.
Operatively coupled to end [0023] 58 of drive shaft 44 is compression mechanism 60 which is illustrated as being a scroll-type compression mechanism. However, the present invention may be suitably adapted to any other type of compressor, such as, e.g., a rotary compressor. The general operation of a scroll compressor is described in U.S. Pat. Nos. 5,306,126 and 6,139,294, the disclosures of which are hereby expressly incorporated herein by reference. The general operation of a rotary compressor is described in U.S. Pat. No. 5,222,885, the disclosure of which is hereby expressly incorporated herein by reference. Each of these references is assigned to the assignee of the present invention.
[0024] Scroll compression mechanism 60 includes fixed scroll member 62, orbiting scroll member 64, and main bearing frame member 66. Fixed scroll member 62 is secured to main bearing frame member 66 by any suitable method including mounting bolts. Fixed scroll member 62 includes flat plate 72 having scroll wrap 74 extending approximately perpendicularly therefrom. Orbiting scroll member 64 is fixedly mounted to roller 68 which is secured to offset crank pin 70 formed at end 58 of drive shaft 44. Orbiting scroll member 64 includes flat plate 76 having scroll wrap 78 extending approximately perpendicularly therefrom which intermeshes with scroll wrap 74 when assembled with fixed scroll member 62. Further, back surface 80 of flat plate 76 engages main bearing frame member 66 at thrust bearing surface member 82 while the compressor is in a de-energized or inoperative state.
Bearings are provided between interfacing surfaces of [0025] drive shaft 44, scroll compression mechanism 60, main bearing frame member 66, and roller 68. Specifically, bearing 84 is located between the outer surface of roller 68 and surface 86 of orbiting scroll member 64 and bearing 88 is positioned between interfacing surfaces of roller 68 and crank pin 70. Bearing 90 is located between main bearing frame member 66 and drive shaft 44. During compressor operation, oil is provided to compression mechanism 60 and bearings 84, 88, and 90 from oil sump 35. Oil pick-up tube 92 is secured to plate 94 which is attached to collar 48 via fastener 96 and extends into oil sump 35 (FIGS. 1 and 2). Oil pump assembly 98 is attached to end 46 of drive shaft 44 for rotation therewith and causes lubricating oil to travel along oil pickup tube 92 as drive shaft 44 rotates. From oil pick-up tube 92, oil flows into oil passageway 100 longitudinally extending through drive shaft 44 to a plurality of passageways (not shown) radially extending from oil passageway 100 to supply compression mechanism 60, and bearings 84, 88, and 90 with oil.
During compressor operation, [0026] motor 36 is energized which induces rotation of rotor 40 and thus drive shaft 44. Cylindrical roller 68 surrounding offset crank pin 70 rotates with drive shaft 44 to generate rotation of orbiting scroll member 64 with respect to fixed scroll member 62. A biasing force acts upon orbiting scroll member 64 to move it axially toward fixed scroll member 62 so that tips 102 and 104 of scroll wraps 74 and 78 sealingly engage scroll member flat plates 76 and 72, respectively, to define a plurality of compression chambers 106.
Refrigerant fluid at suction pressure is drawn into [0027] compression chambers 106 from a refrigeration system (not shown). As orbiting scroll member 64 is rotated with respect to fixed scroll member 62, refrigerant fluid captured within compression chambers 106 is compressed to discharge pressure. The refrigerant fluid progresses radially inwardly toward discharge port 108 located in fixed scroll member 62. A refrigerant gas flows through discharge port 108 into discharge chamber 110 which occupies the interior of compressor housing 22. The discharge pressure fluid is then exhausted through discharge tube 112 back into the refrigerant system.
During compressor operation, rotation of [0028] drive shaft 44 and compression mechanism 60 may produce axial movement of drive shaft 44. In a substantially vertically oriented compressor, gravity acts along the longitudinal axis of rotation of the drive shaft and the rotor to maintain seating of the drive shaft with respect to an outboard bearing, for example. In a substantially horizontally arranged compressor 20, gravity does not influence axial movement of drive shaft 44. Oscillating axial movement of drive shaft 44 produces objectionable noise, such as knocking, during compressor operation. In order to counteract these movements of drive shaft 44, a shaft axial compliance mechanism in accordance with the present invention is provided.
Referring to FIGS. 1 and 2, end [0029] 46 of drive shaft 44 is rotatably supported in collar 48 of bearing housing 50. Both drive shaft 46 and bearing housing 50 are engaged by shaft axial compliance mechanism 114 which prevents relative movement of drive shaft 44 in both directions along shaft axis of rotation 45. Shaft axial compliance mechanism 114 includes bearing assembly 116, circumferential groove 118 located in collar 48, and retaining element 120.
[0030] Collar 48 includes first portion 122 and second portion 124 extending in opposite directions, perpendicularly to radially extending arms 54. First collar portion 122 is provided with cavity 126 which is concentric with aperture 128 extending through second collar portion 124. End 46 of drive shaft 44 is received in aperture 128 and shaft axial compliance mechanism 114 is located in cavity 126.
[0031] Bearing assembly 116 of shaft axial compliance mechanism 114 is affixed to drive shaft 44 near end 46 to rotatably support drive shaft 44 in cavity 126. Bearing assembly 116 is an annular, single row ball bearing assembly including inner race 130, outer race 132, and ball bearings 134. Inner and outer races 130 and 132 are each provided with semicircular groove 136 which align to receive a plurality of ball bearings 134. Bearing assembly 116 is shrink fitted onto end 46 of drive shaft 44 at drive shaft stepped portion 138.
[0032] Drive shaft 44, having bearing assembly 116 affixed thereto, is received in cavity 126 located in collar 48 with opposite axial ends 140, 142 of outer race 132 in abutting contact with both collar 48 and retaining element 120. Bearing housing 50 is provided with annular surface 144 on which outer race 132 of bearing assembly 116 is seated with end 140 contacting surface 144. Circumferential groove 118 is formed in first collar portion 122 a distance away from surface 144 approximately equal to the axial distance between ends 140, 142 of outer race 132. Retaining element 120 is positioned within groove 118, extending inwardly to cover a portion of outer race 132 and with lower surface 146 of retaining element 120 in abutting contact end 142 of outer race 132. Retaining element 120 may be any suitable element including an annular snap ring, for example, constructed from any suitable material able to withstand forces acting on element 120 by bearing assembly 116 created during compressor operation when drive shaft 44 attempts to oscillate axially along shaft axis of rotation 45. Retaining element 120 thus maintains the seated position of bearing assembly 116 and prevents axial movement of drive shaft 44 along shaft axis of rotation 45.
In assembly, bearing [0033] assembly 116 is heated so that the diameter of bearing assembly 116 increases to receive stepped portion 138 of drive shaft 44. Bearing assembly 116 is then allowed to cool to provide a shrink fit between inner race 130 and drive shaft 44. Drive shaft 44, having bearing assembly 116 secured thereto, is then received in cavity 126 of collar 48 with axial end 140 being seated against surface 144 formed in first collar portion 122 of collar 48. Retaining element or snap ring 120 is inserted into circumferential groove 118 in contact with axial end 142 of outer race 132.
During compressor operation, retaining [0034] element 120 maintains the seated position of bearing assembly 116 and thus prevents axial oscillating movement of drive shaft 44. Shaft axial compliance mechanism 114 therefore provides a simple, inexpensive device for eliminating oscillating axial movement of drive shaft 44 and objectionable noise, such as knocking, associated therewith in substantially horizontally oriented compressor 20.
While this invention has been described as having an exemplary design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims. [0035]

Claims

What is claimed is:

1. A hermetic compressor assembly, comprising:

a compressor housing;

a compression mechanism disposed in said housing;

a motor disposed in said housing;

a drive shaft operatively coupling said compression mechanism and said motor, and an axis of rotation;

a bearing housing connected to said motor;

a bearing assembly affixed to said drive shaft, said bearing assembly and said drive shaft received in said bearing housing; and

a retaining element connected to said bearing housing in abutting contact with said bearing assembly, whereby relative movement of said drive shaft in both directions along said axis of rotation is prevented.

2. The compressor of claim 1, wherein said bearing housing further comprises a circumferential groove, a portion of said retaining element received in said groove.

3. The compressor of claim 1, wherein said bearing assembly is shrink fitted onto an end of said drive shaft.

4. The compressor of claim 1, wherein said bearing assembly further comprises an inner race, an outer race, and at least one ball bearing located between said inner and outer races.

5. The compressor of claim 4, wherein said bearing housing further comprises an annular surface, said bearing assembly seated against said surface.

6. The compressor of claim 5, wherein said outer race further comprises two ends, one of said ends in abutting contact with said annular surface, and one of said ends in abutting contact with said retaining element.

7. The compressor of claim 1, wherein said retaining element is a snap ring.

8. A hermetic compressor assembly, comprising:

a compressor housing;

a compression mechanism disposed in said housing;

a motor disposed in said housing;

a bearing housing connected to said motor;

a bearing assembly affixed to said drive shaft, said bearing assembly and said drive shaft received in said bearing housing;

a circumferential groove formed in said bearing housing; and

a retaining element received in said circumferential groove, said retaining element in abutting contact with said bearing assembly, whereby relative movement of said drive shaft in both directions along said axis of rotation is prevented.

9. The compressor of claim 8, wherein said bearing assembly is shrink fitted onto an end of said drive shaft.

10. The compressor of claim 8, wherein said bearing assembly further comprises an inner race, an outer race, and at least one ball bearing located between said inner and outer races.

11. The compressor of claim 10, wherein said bearing housing further comprises an annular surface, said bearing assembly seated against said surface.

12. The compressor of claim 11, wherein said outer race further comprises two ends, one of said ends in abutting contact with said annular surface, and one of said ends in abutting contact with said retaining element.

13. The compressor of claim 8, wherein said retaining element is a snap ring.

14. A hermetic compressor assembly, comprising:

a compressor housing;

a compression mechanism disposed in said housing;

a motor disposed in said housing;

a bearing housing connected to said motor; and

shaft axial compliance means engaging said drive shaft and said bearing housing, whereby relative movement of said drive shaft in both directions along said shaft axis of rotation is prevented.

15. The compressor of claim 14, wherein said shaft axial compliance means includes a bearing assembly affixed to said drive shaft, said bearing assembly and said drive shaft received in said bearing housing.

16. The compressor of claim 15, wherein said shaft axial compliance means includes a circumferential groove formed in said bearing housing, a retaining element received in said groove, said retaining element in abutting contact with said bearing assembly.

17. The compressor of claim 15, wherein said bearing assembly is shrink fitted onto an end of said drive shaft.

18. The compressor of claim 16, wherein said bearing assembly further comprises two ends, one of said ends in abutting contact with said bearing housing, and one of said ends in abutting contact with said retaining element.

19. The compressor of claim 16, wherein said retaining element is a snap ring.

20. A method of preventing oscillating axial movement of a drive shaft in a hermetic compressor comprising:

attaching a bearing housing to a motor of the compressor;

affixing a bearing assembly to one end of a drive shaft;

positioning the bearing assembly and drive shaft in the bearing housing; and

engaging a circumferential groove formed in the bearing housing with a retaining element, the retaining element in abutting contact with the bearing assembly, whereby relative movement of the drive shaft is prevented.