Maschine with reverse rotation protection

Abstract: A scroll compressor incorporating a fluid brake for resisting and impeding objectionable reverse movement of the orbiting scroll member. The brake includes a one-way clutch interconnecting a drive shaft and a paddle disposed in the compressor oil sump, and optionally a rotor shield for controlling oil flow around the lower end of the motor rotor.

Description: The present invention relates generally to scroll type compressors and more specifically to scroll type compressors incorporating a fluid brake operative to resist and impede reverse movement of the orbiting scroll member. It aslo relates to rotary compressors and other powered work producing apparatus. Scroll type machines are becoming more and more popular for use as compressors in both refrigeration as well as air conditioning applications due primarily to their capability for extremely efficient operation. Generally, these machines incorporate a pair of intermeshed spiral wraps, one of which is caused to orbit relative to the other so as to define one or more moving chambers which progressively decrease in size as they travel from an outer suction port toward a center discharge port. An electric motor is provided with operates to drive the orbiting scroll member via a suitable drive shaft affixed to the motor rotor. In a hermetic compressor, the bottom of the hermetic shell normally contains an oil sump for lubricating and cooling purposes. Because scroll compressors depend upon a seal created between opposed flank surfaces of the wraps to define successive chambers for compression, suction and discharge valves are generally not required. However, when such compressors are shut down, either intentionally as a result of the demand being satisfied or unintentionally as a result of a power interruption or other problem, there is a strong tendency for the gas in the pressurized chambers and/or backflow of compressed gas from the discharge chamber to effect a reverse orbital movement of the orbiting scroll member and associated drive shaft. This reverse movement often generates objectionable noise or rumble. Further, in machines employing a single phase drive motor, it is possible for the compressor to begin running in the reverse direction should a momentary power failure be experienced. This reverse operation may result in overheating of the compressor and/or other damage to the apparatus. Additionally, in some situations, such as a blocked condenser fan, it is possible for the discharge pressure to increase sufficiently to stall the drive motor and effect a reverse rotation thereof. As the orbiting scroll rotates in the reverse direction, the discharge pressure will decrease to a point where the motor again is able to overcome this pressure head and rotate the scroll member in the "forward" direction. However, the discharge pressure will now increase to a point where the cycle is repeated. Such cycling may also result in damage to the compressor and/or associated apparatus. U.S. Letters Patent No. 4,998,864, on which the preambles of the independent claims are based, discloses a scroll compressor in which the drive shaft is connected to a rigid structure by a one-way clutch to prevent reverse rotation. According to one aspect of the present invention there is provided a scroll compressor comprising: (a) a housing having an oil sump in a lower portion thereof; (b) scroll compressor means disposed in said housing; (c) motor means including a drive shaft coupled to said compressor means for operatively driving same; and (d) one-way drive means for permitting free rotation of said drive shaft in one direction; characterised in that said compressor further comprises a paddle disposed in said oil sump for rotation therein, and said one way drive means operatively connects said drive shaft to said paddle, whereby undesirable rotation of said drive shaft in the opposite direction causes said paddle to be driven by said drive shaft to resist and impede said undesirable rotation. According to a further aspect of the present invention there is provided a powered work producing apparatus having directional drive control, comprising: (a) a housing having an oil sump in a lower portion thereof; (b) a powered mechanism for performing work disposed in said housing; (c) motor means including a drive shaft coupled to said mechanism for operatively driving same; (d) one-way drive means for permitting free rotation of said drive shaft in one direction; characterised in that the apparatus further comprises a paddle disposed in said oil sump for rotation therein, and said one-way drive means operatively connects said drive shaft to said paddle, whereby undesirable rotation of said drive shaft in the opposite direction causes said paddle to be driven by said drive shaft to resist and impede said undesirable rotation. The powered work producing apparatus of the further aspect of the present invention may be a rotary compressor whose powered mechanism is a rotary compressor means. The hereinafter described and illustrated embodiments of apparatus overcome the problems of prior art compressors (discussed above) by incorporating one-way drive means, such as a one-way clutch, coupled between the drive shaft and a paddle disposed in the compressor oil sump. When the drive shaft is rotating in the desired direction the clutch is inoperative to drive the paddle but when rotation reverses the drive shaft rotates the paddle in the sump so that it acts like a fluid brake to resist and impede movement of the orbiting scroll member in a reverse direction, thereby eliminating the objectionable noise generated upon shut down of the compressor. Further, this fluid brake operates to resist damage to the motor and/or compressor resulting from a reversing of single phase motors as well as resisting the cyclical reversing resulting from a blocked or failed condenser fan. The brake is passive in that it does not create any load during normal operation of the compressor. Relative to the arrangement disclosed in US Patent No. 4,998,864 braking with the present design is much gentler, thereby significantly increasing the life of the one-way clutch mechanism. Several embodiments of the novel anti-reverse rotation mechanism are hereinafter described and illustrated, and in addition there are illustrated versions of the apparatus which also incorporate an integral circular rotor shield of the type generally disclosed in assignees's copending application Serial No. 591,442, filed October 1, 1990 entitled Counterweight Shield for Refrigeration Compressor. Such a shield is useful in reducing the oil level in the area surrounding the rotating motor rotor during operation. 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 relatively high 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 compressors because they typically employ a counterweight secured to the lower end of the rotor. The present shield incorporates a generally flat circular disk or flange positioned in close proximity to the lower end of the rotor which serves to reduce return flow of oil to the area of the rotating rotor and/or counterweight but still enables some circulation thereof, which thereby increases the circulation of oil across the adjacent motor stator end turns. In operation, it has been found that this improved shield has resulted in improved cooling of the stator end turns without any substantial effect on the overall operating efficiency of the compressor. Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims taken in conjunction with the accompanying drawings. Figure 1 is a vertical sectional view through the center of a scroll type refrigeration compressor incorporating a fluid brake in accordance with the present invention; Figure 2 is a horizontal sectional view taken generally line 2-2 in Figure 1; Figure 3 is an enlarged view of the one-way clutch mechanism of the invention illustrated in Figure 1, looking radially outwardly in a direction through the plane of the drawing, and showing the mechanism in driving mode; Figure 4 is an enlarged sectional view taken generally along line 4-4 in Figure 3; Figure 5 is a vertical sectional view taken generally along line 5-5 in Figure 2; Figure 6 is a view similar to Figure 2 illustrating a three-bladed version of the paddle of the fluid brake of the present invention; Figure 7 is a view similar to Figure 6 but showing a fluid brake utilizing curved paddle blades; Figure 8 is a view illustrating in transverse section a variation of the fluid brake blades of Figure 2 in which they are provided with a curvature in cross-section; Figure 9 is a fragmentary sectional view similar to Figure 1 illustrating an alternative mounting technique for the fluid brake of the present invention and also incorporating a more distinct motor rotor shield; and Figure 10 is a view similar to Figure 9 showing yet another mounting technique. Referring now to the drawings and in particular to Figure 1, a compressor 10 is shown which comprises a generally cylindrical hermetic shell 12 having welded at the upper end thereof a cap 14 at the lower end thereof a base 16 having a plurality of mounting feet (not shown) integrally formed therewith. Cap 14 is provided with a refrigerant discharge fitting 18 which may have the usual discharge valve therein (not shown). Other major elements affixed to the shell include a transversely extending partition 22 which is welded about its periphery at the same point that cap 14 is welded to shell 12, a main bearing housing 24 which is suitably secured to shell 12 and a lower bearing housing 26 also having a plurality of radially outwardly extending legs each of which is also suitably secured to shell 12. A motor stator 28 which is generally square in cross-section but with the corners rounded off is press fitted into shell 12. The flats between the rounded corners on the stator provide passageways between the stator and shell, which facilitate the return flow of lubricant from the top of the shell to the bottom. A drive shaft or crankshaft 30 having an eccentric crank pin 32 at the upper end thereof is rotatably journaled in a bearing 34 in main bearing housing 24 and a second bearing 36 in lower bearing housing 26. Crankshaft 30 has at the lower end a relatively large diameter concentric bore 38 which communicates with a radially outwardly inclined smaller diameter bore 40 extending upwardly therefrom to the top of the crankshaft. Disposed within bore 38 is a stirrer 42. The lower portion of the interior shell 12 defines an oil sump 43 which is filled with lubricating oil to a level slightly above the lower end of rotor 46, and bore 38 acts as a pump to pump lubricating fluid up the crankshaft 30 and into passageway 40 and ultimately to all of the various portions of the compressor which require lubrication. Crankshaft 30 is rotatively driven by an electric motor including stator 28, windings 44 passing therethrough and a rotor 46 press fitted on the crankshaft 30 and having upper and lower counterweights 48 and 50, respectively. The upper surface of main bearing housing 24 is provided with a flat thrust bearing surface 53 on which is disposed an orbiting scroll 54 having the usual spiral vane or wrap 56 on the upper surface thereof. Projecting downwardly from the lower surface of orbiting scroll 54 is a cylindrical hub having a journal bearing 58 therein and in which is rotatively disposed a drive bushing 60 having an inner bore 62 in which crank pin 32 is drivingly disposed. Crank pin 32 has a flat on one surface which drivingly engages a flat surface (not shown) formed in a portion of bore 62 to provide a radially compliant driving arrangement, such as shown in assignee's U.S. Letters Patent 4,877,382, the disclosure of which is hereby incorporated herein by reference. An Oldham coupling 63 is also provided positioned between and keyed to orbiting scroll 54 and bearing housing 24 to prevent rotational movement of orbiting scroll member 54. Oldham coupling 63 is preferably of the type disclosed in assignee's copending application Serial No. 591,443, entitled "Oldham Coupling For Scroll Compressor" filed October 1, 1990. A non-orbiting scroll member 64 is also provided having a wrap 66 positioned in meshing engagement with wrap 56 of scroll 54. Non-orbiting scroll 64 has a centrally disposed discharge passage 75 which communicates with an upwardly open recess 77 which in turn is in fluid communication with a discharge muffler chamber 79 defined by cap 14 and partition 22. An annular recess 81 is also formed in non-orbiting scroll 64 within which is disposed a seal assembly 83. Recesses 77 and 81 and seal assembly 83 cooperate to define axial pressure biasing chambers which receive pressurized fluid being compressed by wraps 56 and 66 so as to exert an axial biasing force on non-orbiting scroll member 64 to thereby urge the tips of respective wraps 56, 66 into sealing engagement with the opposed end plate surfaces. Seal assembly 83 is preferably of the type described in greater detail in assignee's copending application Serial No. 591,454, filed October 1, 1990, entitled "Scroll Machine with Floating Seal". Scroll member 64 is designed to be mounted to bearing housing 24 in a suitable manner such as disclosed in the aforementioned U.S. Patent No. 4,877,382 or as disclosed in assignee's copending application Serial No. 591,444 filed October 1, 1990 and entitled "Non-Orbiting Scroll Mounting Arrangement For Scroll Machine". The fluid clutch of the present invention comprises a paddle 84, which can be an aluminum casting, having two diametrically opposite relatively flat blades 86 integrally formed with a hub 88, and having a hardened insert 90 embedded therein which defines a center bore 92 into which is press fit a one-way clutch assembly 94. Shaft 30 is disposed in bore 92 and paddle 84 is supported on shaft by a washer 96 which is supported by a snap ring 98 disposed in an annular groove 100 in shaft 30. Upward movement of the paddle on shaft 30 is limited by a shoulder 99 on the latter. Blades 86 are disposed below the normal level of oil in the sump, indicated at 102, between the lower end of winding 44 and lower bearing housing 26. As can be best seen in Figure 5, hub 88 has a relatively short integral horizontal flange 103 extending radially outwardly from the upper periphery thereof between blades 86, which can act as a rotor shield of the type described in the aforementioned application Serial No. 591,442. As best seen with reference to Figures 1, 3 and 4, clutch assembly 94 includes an outer housing 104, formed of steel or the like, within which are disposed a plurality of circumferentially spaced roller pins 106 rotatably supported within axially extending cavities defined by housing 104, which is channel-shaped in cross-section, and a plastic retainer 108 comprising spaced annular end portions 110 and integral axially extending portions 112 disposed between each roller 106. Each of the cavities is substantially identical, extending over the full length of each pin 106, and includes a rear wall 114 formed in housing 104 which tapers in a circumferential direction from one end wherein it is positioned at a maximum radial distance from the axis of rotation of shaft 30 to the opposite end wherein it is positioned at a minimum radial distance therefrom. At the maximum radial distance location the distance between shaft 30 and wall 114 will be equal to or slightly greater than the diameter of each pin 106 and at the minimum radial distance location it is less than the diameter of each pin. A generally C-shaped leaf spring 116 is also disposed within each cavity which operates to urge each pin 106 toward the radially shallower end thereof. Each spring 116 is supported by a radial projection 118 on each portion 112 of retainer 108. Thus, as best shown in Figure 4, rotation of shaft 30 in a clockwise direction looking downwardly will act to move each pin 106 against its spring 116 and into an area of its cavity wherein pin 106 may rotate freely under action of shaft 30, with no drive forces being transmitted from the shaft to the paddle. However, should the direction of rotation of shaft 26 be reversed, the action of springs 116 and shaft 30 will cause each pin 106 to move into a shallower area of its cavity and thereby exert a wedging action between wall 114 and the outer surface of shaft 30 thereby causing shaft 30 to operatively drive paddle 84. The very high viscous friction between blades 86 and the oil in the sump provides a substantial drag force (torque) on shaft 30 thereby quickly stopping the reverse rotation thereof, which in turn quickly impedes movement of the orbiting scroll member 30 in a reverse direction. In a presently preferred embodiment, it has been found that a Torrington Model RC-162110-FS, or equivalent, clutch assembly has provided satisfactory performance. Variations of the paddle are illustrated in Figures 6 through 8. For example, in Figure 6 there is illustrated a paddle which is in all respects identical to paddle 84 except that it has three relatively flat blades 200 rather than merely two blades. In Figure 7 there is illustrated a three bladed patent similar to that of Figure 6 except that in the Figure 7 version each blade 300 is slightly curved in the plane shown to thereby alter the braking characteristics of the device. In Figure 8 there is illustrated a paddle which can have any number of blades but which instead of being flat in cross-section is curved in the manner shown at 350. In Figures 9 and 10 there are illustrated two additional alternative embodiments of the paddle in which the paddle is formed from a polymeric material, such as glass filled nylon, and in which the paddle is affixed to the shaft by integral fingers. With reference to Figure 9, there is illustrated a paddle 400 having two or more relatively flat plates 402 integrally formed with a hub 404 having extending outwardly from the upper periphery thereof a generally circular flange 406 which can act as a rotor shield as described above. Paddle 400 is provided with a steel insert 90 and a one-way clutch assembly 94 in the same manner and for the same function as in the preceding embodiments. Note that Figure 9 is not a 180 degree section and that on the right-hand portion the section line passes through the paddle, whereas in the left-hand portion the section line passes through a non-blade portion of the paddle. Extending downwardly and inwardly from the center of hub 404 are a plurality (e.g., eight or more) integrally formed resilient fingers 408 which are disposed in a groove 410 in shaft 30. The interaction of fingers 408 and groove 410 serves to axially locate the paddle on the shaft. The variant of Figure 10 is very similar to that of Figure 9 except that the paddle, indicated at 500, comprises a plurality of upwardly extending fingers 502 disposed in a groove on shaft 30 for the purpose of retaining the paddle in axial position. In addition, flange 406, which acts as the rotor shield, has a slightly different configuration than that in the preceding embodiment; however, it is intended to function in substantially the same manner, which is the manner disclosed and described in the aforementioned application Serial No. 591,442.

Claims: A scroll compressor (10) comprising: (a) a housing (12) having an oil sump (43) in a lower portion thereof; (b) scroll compressor means (54,64) disposed in said housing; (c) motor means (28,44,46) including a drive shaft (30) coupled to said compressor means for operatively driving same; and (d) one-way drive means (94) for permitting free rotation of said drive shaft (30) in one direction; characterised in that said compressor further comprises a paddle (84) disposed in said oil sump (43) for rotation therein, and said one way drive means (94) operatively connects said drive shaft (30) to said paddle (84), whereby undesirable rotation of said drive shaft (30) in the opposite direction causes said paddle to be driven by said drive shaft to resist and impede said undesirable rotation. A scroll compressor as claimed in claim 1, wherein said one-way drive means (94) is a one-way clutch. A scroll compressor as claimed in claim 1 or claim 2, wherein said drive means (94) is positioned in surrounding relationship to said drive shaft. A scroll compressor as claimed in any one of the preceding claims, wherein said paddle (84) has a plurality of blades (86,200,300,350) disposed in said oil sump (43). A scroll compressor as claimed in claim 4, wherein said paddle (84) has two blades (86) disposed in said oil sump (43). A scroll compressor as claimed in claim 4, wherein said paddle (84) has more than two blades (200,300) disposed in said oil sump (43). A scroll compressor as claimed in claim 4, wherein said blades (300) are curved in the plane of movement thereof. A scroll compressor as claimed in claim 4, wherein said blades (350) are curved in cross-section. A scroll compressor as claimed in any one of the preceding claims, further comprising a relatively hard metal insert (90) centrally disposed in said paddle (84) and defining a bore (92) coincident with the axis of rotation of said paddle. A scroll compressor as claimed in claim 9, wherein said one-way drive means (94) is mounted in said bore (92). A scroll compressor as claimed in any one of the preceding claims, wherein said paddle (84) is formed of aluminium. A scroll compressor as claimed in any one of claims 1 to 10, wherein said paddle (84) is formed of a polymeric material. A scroll compressor as claimed in any one of the preceding claims, wherein said drive means (94) is non-rotatively affixed to said paddle (84). A scroll compressor as claimed in any one of the preceding claims, wherein the paddle (84) is supported on an annular shoulder on said drive shaft (30). A scroll compressor as claimed in claim 14, wherein said annular shoulder is defined by a washer (96) surrounding said drive shaft (30). A scroll compressor as claimed in claim 15, wherein said washer (96) is supported on said drive shaft (30) by snap ring means (98). A scroll compressor as claimed in claim 14, wherein said shoulder is defined by an annular groove (410) on said drive shaft (30). A scroll compressor as claimed in claim 17, further comprising a plurality of fingers (408,502) on said paddle (84) disposed in said groove (410) to retain said paddle against axial movement with respect to said drive shaft (30). A scroll compressor as claimed in claim 18, wherein said fingers (408,502) are integrally formed with said paddle (84). A scroll compressor as claimed in claim 18 or 19, wherein said fingers (502) extend upwardly from said paddle (84). A scroll compressor as claimed in claim 18 or 19, wherein said fingers (408) extend downwardly from said paddle (84). A powered work producing apparatus having directional drive control, comprising: (a) a housing (12) having an oil sump (43) in a lower portion thereof; (b) a powered mechanism (54,64) for performing work disposed in said housing; (c) motor means (28,44,46) including a drive shaft (30) coupled to said mechanism for operatively driving same; (d) one-way drive means (94) for permitting free rotation of said drive shaft (30) in one direction; characterised in that the apparatus further comprises a paddle (84) disposed in said oil sump (43) for rotation therein, and said one-way drive means (94) operatively connects said drive shaft (30) to said paddle (84), whereby undesirable rotation of said drive shaft in the opposite direction causes said paddle to be driven by said drive shaft to resist and impede said undesirable rotation. A powered work producing apparatus as claimed in claim 22, wherein said apparatus is a rotary compressor and said powered mechanism is a rotary compressor means (54,64). An apparatus as claimed in claim 23, further comprising a rotor, a counterweight (50) on the lower end of said rotor, and a shield (103,406) on said paddle (84) for controlling oil flow around the lower end of said rotor and said drive shaft.

Inventors: MONNIER KENNETH JOSEPH, MONNIER, KENNETH JOSEPH
Applicants: COPELAND CORP, COPELAND CORPORATION
Application year: 1992
Main classification: F04C29
IPC codes: F04C28, F04C29, F04C18