Hermetic compressor lubrication system

Abstract: A compressor assembly (20) including a housing (22) having an oil sump (54) containing a liquid lubricant, a compressor mechanism (36) disposed within the housing, a vertical, rotatable shaft (30, 30') associated with the compressor mechanism and provided with a conduit (58', 62) having a downwardly directed open end (68, 73) extending beneath the surface level (56) of the lubricant and through which oil is conveyed to the compressor mechanism, whereby the lubricant is drawn into the conduit open end, and a guard (70, 70') in surrounding relationship with, and having an aperture (72, 72') disposed beneath and proximate to, the conduit open end, the guard fixed relative to the housing, the sump in fluid communication with the conduit through the aperture.

Description: The present invention relates to lubrication systems for hermetic compressors and in particular vertically oriented hermetic compressors having a pick-up tube or shaft end which extends into the oil contained in a sump. Hermetic compressors having hollow shafts or pick-up tubes which extend into the oil contained in a sump are used for drawing lubricant from the sump and providing it to moving parts of the compressor assembly. JP61-011479 and US 3,388,855 relate to covers or shields for lubricant pick-up tubes that are stationary relative to the pick-up tube and fastened either to the compressor housing or to the lower end of the motor-compressor unit. Often these tubes or shafts are provided with a paddle for pumping the oil through the shaft or tube. A problem experienced with pick-up tubes or shafts is that on their rotation they tend to create vortices around the end of the shaft or tube which extends into the oil. These vortices hinder the performance of oil delivery into the tube or shaft. A way of preventing the formation of these vortices is desirable. The present invention provides an oil inlet guard disposed about the end of a rotating oil pickup tube or shaft provided with an oil passage opening. The guard is fixed such that it does not rotate and is provided with a central oil aperture through which oil flows from the sump into the rotating shaft or pick-up tube. The guard smooths the oil which flows into the pickup tube or shaft, eliminating flow-disrupting vortices and thereby increasing the oil pick-up performance of the shaft or tube. The present invention provides a compressor assembly including a housing having an oil sump in which is contained a liquid lubricant, a compressor mechanism disposed within the housing, a vertical, rotatable shaft associated with the compressor mechanism and provided with a conduit having an downwardly directed open end which extends beneath the surface level of the lubricant in the sump and through which oil is conveyed to the compressor mechanism, and a guard in surrounding relationship with the conduit open end and having an aperture disposed beneath and proximal to it, the guard fixed relative to the housing, the sump in fluid communication with the conduit through the guard aperture. 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 embodiments of the invention taken in conjunction with the accompanying drawings, wherein: Fig. 1 is a sectional side view of a hermetic compressor according to a first embodiment of the present invention; Fig. 2 is an enlarged fragmentary sectional side view of a portion of the compressor shown in Fig. 1, showing the pick-up tube and guard in greater detail; Fig. 3 is a fragmentary sectional side view of a portion of a compressor according to a second embodiment of the present invention, showing the pick-up tube and guard; Fig. 4 is a fragmentary sectional perspective view of the compressor portion shown in Fig. 2, also showing an alternative vent configuration; and Fig. 5 is a fragmentary sectional perspective view of the compressor portion shown in Fig. 3, also showing an alternative vent configuration. Corresponding reference characters indicate corresponding parts throughout the several views. Although the drawings represent embodiments of the present invention, the drawings are not necessarily to scale and certain features may be exaggerated in order to better illustrate and explain the present invention. The exemplification set out herein illustrates one embodiment of the invention, and such exemplification is not to be construed as limiting the scope of the invention in any manner. The embodiment disclosed below is not intended to be exhaustive or limit the invention to the precise form disclosed in the following detailed description. Referring to Fig. 1, there is shown a first embodiment of a compressor according to the present invention. Vertically-oriented compressor assembly 20 is of the rotary type, although it is to be understood that the present invention is adaptable to other types of vertical compressors such as, for example, scroll compressors, rotary vane compressors and reciprocating piston compressors. Compressor assembly 20 comprises outer shell 22 and has, disposed within shell 22 motor assembly 24 having stator 26 and rotor 28. Rotor 28 is provided with shaft 30 having axial bore 32 extending therethrough. Shaft 30 is journalled in main bearing 34 which comprises in part compressor mechanism 36. Compressor mechanism 36 is of the rotary type having cylinder block 38 disposed between axial surface 40 of bearing 34 and axial surface 42 of outboard bearing 44. Cylinder block 38 is provided with cylindrical cavity 46 in which is disposed eccentric 48 attached to or integral with shaft 30. Disposed about and rotatable relative to eccentric 48 is cylindrical piston 50 which moves about cavity 46 in an epicyclic fashion. A vane (not shown) is biased by a spring (not shown) against the outer surface of piston 50, the vane reciprocating in a slot (not shown) provided therefor in cylinder block 38. Discharge and suction ports (not shown) are disposed on opposite sides of the vane and allow refrigerant to enter and exit a compression chamber of compressor mechanism 36 in the known way. Refrigerant enters compressor mechanism 36 through via a suction tube (not shown) and exits compressor assembly 20 through discharge tube 52, compressor assembly 20 being of the type in which the entire interior of shell 22 is at discharge pressure. Disposed in the bottommost portion of shell 22 is lubricant sump 54 containing a quantity of oil having surface level 56. As best seen in Fig. 2, shaft 30 has portion 58 radially supported in journal 60 of outboard bearing 44 and provided with pick-up tube 62 which is interference-fitted into a pump receiving portion 64 of shaft bore 32. Within bore portion 64 is disposed helical paddle 66 which serves as a pump for helping to convey lubricant from sump 54 through shaft bore 32. Paddle 66 may be retained in bore portion 64 by means of clip 65. Pick-up tube 62 extends below surface level 56 of the lubricant in sump 54 and its tip 68 is provided with axial opening 69 (Fig. 2) through which oil is received into shaft bore 32. Alternatively, as shown in the second embodiment of Fig. 3, shaft portion 58' itself extends below oil surface level 56, with shaft 30' not provided with a pick-up tube such as pick-up tube 62. As seen in Fig. 3, paddle 66 is provided in shaft bore portion 64', and may be retained therein by means of clip 65 or, as shown, by snap ring 67. Further, shaft 30 or 30' may not be provided with paddle 66 at all, instead relying on alternative pump means (not shown) for helping to convey lubricant from sump 54 through shaft bore 32. Affixed to the bottommost end of outboard bearing 44 is guard 70 which encloses oil pick up tube tip 68 and, as shown, may be somewhat hemispherically or domed shaped. Guard 70 is provided with aperture 72 which is downwardly directed and in close proximity with tip 68 of pick-up tube 62. The inside surface of guard 70 near its aperture 72 is contoured such that it surrounds the open end of tip 68. The vertical clearance between the bottommost portion of tip 68, in which oil inlet aperture 69 is provided, and the inside surface of guard 70 therebeneath is preferably approximately 0,508 mm to 0,762 mm (0.020 to 0.030 inch), indicated as distance A in Fig. 2. Guard 70 is provided with cylindrical portion 74 which is interference-fitted into counterbore 76 provided in outboard bearing 44. Provided in guard 70 near cylindrical portion 74 and below counterbore 76 is at least one vent 78 which allows air to escape the interior of guard 70 during oil filling. As shown in Fig. 2, vent 78 may be formed by providing hole 80 in the surface of guard 70 or, as shown in Fig. 4, vent 78 may be formed by providing axially elongate notch 82 in cylindrical portion 74 of guard 70. Similarly, as shown in Fig. 3, the second embodiment of the present invention has, affixed to the bottommost end of outboard bearing 44', guard 70' which encloses tip 73 of shaft 30' and may also be somewhat hemispherically or domed shaped and provided with downwardly directed aperture 72'. The inside surface of guard 70' near its aperture 72' is contoured such that it surrounds shaft tip 73. The vertical clearance between tip 73 the inside surface of guard 70' therebeneath is preferably approximately 0,508 mm to 0,762 mm (0.020 to 0.030 inch), indicated as distance A' in Fig. 3. Aperture 72' is in close proximity to tip 73 of shaft 30, which may be contoured to approximate the inner surface configuration of guard 70'. The clearance between shaft tip 73 and the inside, adjacent surface of guard 70' is likewise preferably approximately 0,508 mm to 0,762 mm (0.020 to 0.030 inch). Guard 70' is provided with cylindrical portion 74' which is interference-fitted to annular shoulder 75 provided in outboard bearing 44'. To allow air to escape the interior of guard 70' during oil filling, at least one vent 78' is provided in guard 70' near cylindrical portion 74' and below shoulder 75. As shown in Fig. 3, vent 78' may be formed by providing hole 80' in the surface of guard 70' or, as shown in Fig. 5, vent 78' may be formed by providing axially elongate notch 82' in cylindrical portion 74' of guard 70'. Guard 70, 70' may be made of plastic or stamped sheet metal. As indicated above, in the shown embodiments guards 70, 70' are interference-fitted to bearings 44, 44', but may alternatively be adhered, welded or brazed thereto. Apertures 72, 72' (Figs. 2, 3) axial pickup tube opening 69 (Fig. 2) and/or shaft bore portion diameter 64' (Fig. 3) are appropriately sized to accommodate the compressor size and type, and the amount of oil required for proper lubrication. Referring to the first embodiment of Figs. 1, 2 and 4, in operation, as shaft 30 and pick-up tube 62 rotate within fixed outboard bearing 44 and guard 70 affixed thereto, oil from sump 54 enters guard aperture 72 and flows immediately into pick-up tube guard opening 69. The oil outside of guard 70 is generally still, and does not have vortices which may disrupt the flow of lubricant through guard opening 72, and thus into pick-up tube opening 69. While it may be that vortices are created adjacent the outer surfaces of pick-up tube 62 inside of guard 70, these vortices do not appreciably affect the flow of oil from sump 54 through openings 72, 69 into shaft bore 32. As can be readily visualized with reference to Figs. 3 and 5, the second embodiment of the present invention operates in the same way to prevent the formation of vortices within the oil sump which disrupt the flow of lubricant into the shaft bore.

Claims: A compressor assembly (20) comprising a housing (22) having an oil sump (54), said sump containing a liquid lubricant; a compressor mechanism (36) disposed within said housing; and a vertical, rotatable shaft (30, 30') associated with said compressor mechanism and provided with a conduit (58', 62) having an open end (68, 73) through which oil is conveyed to said compressor mechanism, wherein said conduit open end is downwardly directed, said conduit open end extending beneath the surface level (56) of said liquid lubricant, whereby said lubricant is drawn into said conduit open end; a guard (70, 70') in surrounding relationship with said conduit open end and having an aperture (72, 72') disposed beneath and proximal said conduit open end, said guard fixed relative to said housing, said sump in fluid communication with said conduit through said aperture characterized in that said guard is provided with a vent (78, 78'), said vent fluidly communicating the interior of said guard and said sump. The compressor of Claim 1, characterized in that said vent is defined by a hole (80, 80') in said guard. The compressor of Claim 1, characterized in that said vent is defined by a notch (82, 82') in said guard. The compressor of Claim 1, characterized in that said bearing has a generally cylindrical inner surface and said guard comprises a generally cylindrical outer surface, said inner and said outer surfaces interference-fitted together. The compressor of Claim 1, characterized in that said bearing has a generally cylindrical outer surface and said guard comprises a generally cylindrical inner surface, said inner and said outer surfaces interference-fitted together.

Inventors: HURLEY DAVID C, HURLEY, DAVID C.
Applicants: TECUMSEH PRODUCTS CO, TECUMSEH PRODUCTS COMPANY
Application year: 1999
Main classification: F04C29
IPC codes: F04B39, F04C29, F16N7