Refrigeration compressor

Abstract: A refrigeration motor compressor assembly (24) has a housing (14) including a lubricant sump in the bottom thereof into which the lower end of the drive shaft and associated rotor extend. A shield (12) is provided which is positioned by the drive shaft (26) and extends above the oil level (38) in the sump in surrounding spaced relationship to the lower end of the rotor (22). As the rotor (22) rotates within the shield (12), lubricant contained therein is thrown out of the surrounding shield (12) and a close fit between the shield (12) and the shaft (26) restricts return flow of lubricant into the area occupied by the rotating rotor (22).

Description: The present invention relates generally to refrigeration compressors and more specifically to such compressors incorporating shields for reducing the lubricating oil level in the area surrounding the rotating rotor. Typical refrigeration compressors incorporate a lubricant sump in the lower or bottom portion of the housing into which the drive shaft extends so as to pump lubricant therefrom to the various portions requiring lubrication. In addition, the lubricant also often acts to aid in removal of heat from the various components. In order to insure sufficient lubricating oil is contained within the sump to assure adequate lubrication and/or cooling of the moving parts while also minimizing the overall height of the housing, it is sometimes necessary that the oil level extend above the rotating lower end of the rotor. However, the higher viscosity of the oil as compared to refrigerant gas creates an increased drag on rotation of the rotor resulting in increased power consumption. This problem is further aggravated in scroll type compressors which typically employ a counterweight secured to the lower end of the rotor. US-A-4621993 discloses a compressor having a plate member secured to the compressor shell to allow flow of lubricant only from its upper side to its lower side. This prevents foaming of the lubricant in the sump from emptying the sump of lubricant, which can cause damage to the bearings of the compressor. The plate member does not restrict lubricant flow to the rotor, nor does the end of the rotor extend below the normal upper level of lubricant in the sump. According to the present invention there is provided a refrigeration compressor comprising: an outer shell; a sump disposed in the bottom of said shell containing a supply of lubricant; compressor means within said shell; and a motor disposed within said shell for driving said compressor means, said motor including a stator and a rotor secured to a shaft drivingly connected to said compressor means, said shaft extending downwardly from a lower end of said rotor; characterised in that the lower end of said rotor extends below the normal upper level of said lubricant and that the compressor further comprises shield means said shield means comprising first and second portions, said second portion cooperating with said shaft to position said shield means and said first portion extending radially outwardly from said second portion adjacent to said lower end of said rotor to restrict lubricant flow to the rotating lower end of said rotor whereby to reduce power consumption of the motor. Thus, the oil induced drag on the rotor, and resulting increased power consumption of the motor may be greatly reduced. In one embodiment, a rotation inhibiting projection is provided on the shield while in another embodiment the shield is allowed to rotate with the drive shaft although the speed of rotation thereof will be substantially less than that of the drive shaft due to the drag exerted thereon by the lubricant. In both embodiments, however, the power consumption of the motor is greatly reduced thus resulting in significant improvement in the operating efficiency of the compressor. Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a section view of a refrigeration compressor of the scroll type incorporating a shield surrounding the lower end of the motor rotor in accordance with the present invention, the section being taken along a radial plane extending along the axis of rotation of the drive shaft; Fig. 2 is a section view of the compressor of Fig. 1, the section being taken along line 2-2 thereof; Fig. 3 is a perspective view of the shield shown in Figs. 1 and 2; and Fig. 4 is a fragmentary section view similar to Fig. 1 but showing only a portion of the oil sump and an alternative embodiment of the shield, all in accordance with the present invention. Referring now to the drawings and more specifically to Figure 1, there is shown a hermetic refrigeration compressor 10 incorporating a shield 12 all in accordance with the present invention. Compressor 10 comprises an outer shell or housing 14 within the lower portion of which is disposed an electric motor 16 including a stator 20 and a rotor 22. Motor 16 is operative to drive a compressor assembly 24 disposed in the upper portion of shell 14 via a drive shaft 26 extending therebetween and to which rotor 22 is secured adjacent the lower end. As shown, compressor assembly 24 is of the scroll type and incorporates an upper fixed scroll member 28 and a lower scroll member 30 which is driven by drive shaft 26 in orbiting motion relative to the fixed scroll member 28. Drive shaft 26 is rotatably supported within shell 14 by means of upper and lower bearing assemblies 32 and 34 respectively each of which are fixedly secured to shell 14. Compressor 10 is described in greater detail in presently pending application Serial No. 899,003 filed August 22, 1986 entitled "Scroll Type Machine With Axially Compliant Mounting" assigned to the same assignee as the present application, the disclosure of which is hereby incorporated by reference. The lower portion of shell 14 defines a lubricant sump 36 containing a supply of oil for lubrication of the various components of compressor 10 as well as augmenting cooling thereof. In order to both minimize the overall height of compressor 10 as well as to assure an adequate supply of lubricant is contained within the sump, oil level 38 extends above the lower ends of the end turns 40 of stator 20 and both a counterweight 42 and the lower end portion 44 of rotor 22 to which counterweight 42 is secured. Shield 12 is preferably formed as a one piece structure from a suitable polymeric composition such as a nylon material for example. It should be noted that other materials may be utilized so long as they are able to resist degradation from both the oil and refrigerant utilized in the system as well as the heat generated during operation of compressor 10. It should also be noted that the use of a dielectric non-magnetic material is believed preferable due to the proximity of the shield to the motor rotor and stator and the desire to avoid any interference with the operation thereof. As best seen with reference to Figures 1 and 3, shield 12 incorporates a first generally cylindrically shaped portion 46 open at the upper end thereof and positioned in surrounding relationship to lower end portion 44 of rotor 22 and associated counterweight 42. Cylindrical portion 46 extends axially upwardly between rotor 22 and the end turns 40 of stator 20 to a height just slightly above maximum normal oil level 38. A lower hollow generally cylindrically shaped portion 48 extends axially downwardly therefrom in relatively closely spaced relationship to shaft 26 and includes an annular radially inwardly extending flange portion 50 which is received within a reduced diameter portion 51 of shaft 26. A radially extending annular flange portion 52 extends between and interconnects cylindrical portions 46 and 48. In order to restrict rotation of shield 12, a generally flat flange portion 54 is integrally formed on shield 12 extending axially downwardly from the lower surface of flange portion 52 and generally radially outwardly from cylindrical portion 48. Leg 56 extends axially downwardly from flange portion 54 and is received between a pair of support legs 58, 60 forming a part of lower bearing assembly 34 and cooperates therewith to restrict rotational movement of shield 12. In operation, the rotational movement of the lower end portion 44 of rotor 22 and the associated counterweight 42 will operate to throw oil which has accumulated within the hollow shield 12 radially outwardly and over the top edge of shield 12 through the open spaces in the stator end turns as well as between shield 12 and these end turns and into sump 36 thereby lowering the oil level in the area surrounding the rotating rotor. Because the lower cylindrical portion 48 of shield 12 is closely fitted to the shaft 26, only a very small amount of oil will flow upwardly therebetween. Further, once a substantial amount of the oil within shield 12 has been expelled, shield 12 will become buoyant and float upwardly in the oil sump. As this occurs, flange portion 50 will move into engagement with the annular shoulder 62 on crankshaft 26 thus limiting further axial movement so as to thereby prevent shield 12 from moving upwardly into engagement with the spinning rotor 22. This engagement will also operate to establish a further restriction or seal against oil flow into the interior of shield 12. Thus, shield 12 will operate to effectively reduce the drag on rotor rotation due to its partial immersion into the oil in the lubricant sump and thereby eliminate the resulting power consumption. In this regard, it should be noted that the clearance between cylindrical portion 48 and shaft 26 is sufficient to avoid any excessive wear or drag on shield 12 but yet small enough to enable shaft 26 to effectively maintain shield 12 and particularly upper cylindrical portion 46 thereof in the desired substantially coaxial position with respect to rotor 22 so as to avoid the possibility of contact therebetween. When compressor 10 is de-energized, shield 12 will slowly settle axially downwardly as lubricating oil gradually flows back into the interior thereof until such time as it comes to rest on lower bearing assembly 34 as shown in Figure 1. Referring now to Figure 4, a modified embodiment of a shield 64 in accordance with the present invention is shown in operative relationship to a motor assembly 66 and associated drive shaft 68 of a refrigeration compressor 70. Shield 64 is virtually identical to shield 12 with the exception that flange portion 54 and associated leg 56 have been deleted therefrom. Accordingly, corresponding portions of shield 64 have been indicated by like numbers primed. Because shield 64 does not incorporate any means to prevent relative rotation thereof, the viscous drag resulting from the oil disposed between cylindrical portion 48' and shaft 66 will result in rotational movement thereof. However, this rotation will be substantially slower than the speed of rotation of drive shaft 66 because of the viscous drag exerted on shield 64 by the oil within sump 36'. Hence, it is believed only a slight stirring of the oil within sump 36' will occur as shield 64 is allowed to rotate which stirring may be beneficial to aid in cooling of the lower end turns of stator 20'. Thus, as may now be appreciated, substantial improvements in operating efficiency are achieved by incorporation of either shield 12 or 64 due to the reduced motor power consumption. These longlasting benefits are achieved at a relatively low cost as shields 12 and 64 may be easily and inexpensively formed in any suitable manner such as injection molding or the like and further enable the overall height of the motor compressor to be kept to a minimum.

Claims: A refrigeration compressor comprising: an outer shell (14, 14'); a sump (36, 36') disposed in the bottom of said shell containing a supply of lubricant; compressor means (10) within said shell; and a motor (16) disposed within said shell for driving said compressor means, said motor including a stator (20) and a rotor (22) secured to a shaft (26, 66) drivingly connected to said compressor means (10), said shaft (26, 66) extending downwardly from a lower end (44, 44') of said rotor (22); characterised in that the lower end (44, 44') of said rotor (22) extends below the normal upper level of said lubricant and that the compressor further comprises shield means (12, 64), said shield means comprising first (46, 46') and second (48, 48') portions, said second portion cooperating with said shaft to position said shield means and said first portion extending radially outwardly from said second portion adjacent to said lower end (44, 44') of said rotor (22) to restrict lubricant flow to the rotating lower end (44, 44') of said rotor (22) whereby to reduce power consumption of the motor. A refrigeration compressor as claimed in claim 1, wherein said first portion (46, 46') of said shield means (12, 64) surrounds said lower end (44, 44') of said rotor (22). A refrigeration compressor as claimed in claim 1 or claim 2, wherein said second portion (48, 48') is positioned in closely spaced relationship with said shaft (26, 66). A refrigeration compressor as claimed in any of the preceding claims, wherein said second portion (48, 48') includes flange means (50, 50') cooperating with means (62, 62') on said shaft (26, 66) to limit axial movement of said shield means (12, 64). A refrigeration compressor as claimed in any of the preceding claims, wherein said first portion (46, 46') extends between said rotor (22) and said stator (20). A refrigeration compressor as claimed in any of the preceding claims, wherein said shield means (12) includes means (54, 56) to restrict rotational movement of said shield means. A refrigeration compressor as claimed in claim 6, further comprising lower bearing means (34) for rotatably supporting said shaft (26, 66) and wherein said rotation restricting means (54, 56) comprise a flange portion cooperating with said lower bearing means. A refrigeration compressor as claimed in claim 7, wherein said shield means (12) is supported by said lower bearing means (34) when said compressor is not operating and by said lubricant when said compressor is operating. A refrigeration compressor as claimed in any of the preceding claims, wherein said compressor means (10) includes first and second interleaved scroll members (28, 30) supported for relative orbital movement therebetween so as to define moving fluid pockets of changing volume. A refrigeration compressor as claimed in claim 1, wherein said first portion (46, 46') of said shield means (12, 64) encloses an area surrounding said lower end (44, 44') of said rotor (22). A refrigeration compressor as claimed in any of the preceding claims, wherein said shield means (12, 64) is integrally formed from a polymeric composition. A refrigeration compressor as claimed in any of the preceding claims, wherein said shield means (12, 64) is formed from a dielectric material. A refrigeration compressor as claimed in any of the preceding claims, wherein said second portion (48, 48') of said shield means (12, 64) includes a hollow portion, said lower end (44, 44') of said rotor (22) projecting into said hollow portion. A refrigeration compressor as claimed in any of the preceding claims, wherein said motor (16) further includes a counterweight (42) disposed within said sump below the normal upper level of said lubricant and rotatable with said shaft (26, 66) and rotor (22) and wherein said shield means (12, 64) encloses an area surrounding said counterweight and extends above the normal upper level of said lubricant, said counterweight being operative to expel lubricant from said area enclosed by said shield means during rotation. A refrigeration compressor as claimed in any of claims 1 to 13, wherein said rotor is operative to expel lubricant from an area between said lower end of said rotor and said shield means during rotation of the rotor. A refrigeration compressor as claimed in claim 15, wherein a counterweight (42) is provided on said lower end (44, 44') of said rotor (22) above said first portion (46, 46') of said shield means (12, 64), said counterweight being operative to expel lubricant from the area between said lower end of said rotor and said first portion of said shield means (12, 64) during rotation of the rotor.

Inventors: ELSON JOHN PAUL, ELSON, JOHN PAUL
Applicants: COPELAND CORP, COPELAND CORPORATION
Application year: 1989
Main classification: F04C18
IPC codes: F04B39, F04C29, F04C18, F25B31