SCROLL TYPE COMPRESSOR

Abstract: This invention discloses a oil separating mechanism of a hermetically sealed scroll type compressor in which an inner chamber of a housing (10) is kept at discharge pressure. The compressor includes a drive shaft (13) supported by a plain bearing (14) in an inner block member (40). The drive shaft is operatively linked to an orbiting scroll (30) which orbits within a stationary scroll (20). A rotation preventing device (34) prevents rotation of the orbiting scroll. The drive shaft includes an axial bore (131) extending from an open end and terminating within the inner block member. A radial bore (132) is provided near the terminal end of the axial bore and leads to a discharge chamber (60) of the compressor. A helical groove (134) is formed in the exterior surface of the supported portion of the drive shaft. The helical groove is linked to the axial bore through a radial hole (133) formed through the supported portion of the drive shaft. A large part of mists of lubricating oil are separated from refrigerant gas atmosphere by sticking on a portion of the exterior surface of the drive shaft where the radial bores exists by collision of discharged refrigerant gas therewith.

Description: A hermetically sealed scroll type compressor is disclosed in JP-A-61-87994 and shown in Figure 1 of the accompanying drawings. As shown a hermetically sealed housing includes an inner chamber 1 which is maintained at discharge pressure. A compression mechanism, including interfitting scrolls 2 and 3 and the forward end of the drive mechanism including a drive shaft 130, is isolated from the inner chamber 1 behind a partition 110. Channel 5 links intermediate pocket 6 of the interfitting scrolls 2 and 3 with chamber 7. Refrigerant gas flows through an inlet port 850 and is compressed inwardly by the scrolls 2 and 3 towards a central pocket 700, and is discharged to a discharge chamber 500 through a hole 240 and flows to external elements of the refrigeration system through an outlet port 860, before returning to the compressor again. Some of the discharged refrigerant gas also flows to the inner chamber 1. Mists of lubricating oil are mixed in the discharged refrigerant gas so that if the discharged refrigerant gas flows to an element of the external refrigeration system without separation of the lubricating oil from the refrigerant gas atmosphere, the refrigerating efficiency of the refrigeration system is reduced. To overcome the above-mentioned problem, JP-A-57-69991 and JP-A-61-205386 disclose an oil separating member within the compressor casing. In these applications, separating the oil mist from refrigerant gas atmosphere is obtained by causing the oil mist to stick to a surface of an oil separating member by collision of discharged refrigerant gas with the oil separating member. The separated oil on the surface of the oil separating member produces drops by repeated collision and the drops are collected in a bottom of the compressor casing. The collected oil in the bottom of the compressor casing is supplied to a frictional portion of the compressor by virtue of a pressure difference in the compressor casing as shown in the above-mentioned JP-A-205386. However, disposing the oil separating member within the compressor casing causes an inner structure of the compressor assembly of the compressor to be complicated. As a result, manufacturing cost of the compressor is high. It is a primary object of this invention to provide a simplified oil separating mechanism for use in a hermetically sealed scroll type compressor in which an inner chamber of the hermetically sealed housing is maintained at discharge pressure. According to the invention, scroll type compressor comprising a hermetically sealed housing; a fixed scroll disposed within the housing, the fixed scroll having a first end plate and a first spiral element extending therefrom; an orbiting scroll having a second end plate from which a second spiral element extends, the first and second spiral elements interfitting at an angular and radial offset to form a plurality of line contacts which define at least one pair of sealed off fluid pockets; a drive mechanism operatively connected to the orbiting scroll to effect orbital motion of the orbiting scroll; and a rotation preventing means for preventing rotation of the orbiting scroll during motion whereby the volume of the fluid pockets changes to compress fluid in the pockets; the drive mechanism including a drive shaft rotatably supported within an inner block member, the inner block member being fixed to the housing, and the first end plate of the fixed scroll and the inner block member cooperatively dividing the housing into a discharge chamber and a suction chamber in which the first and second spiral elements exist; is characterised by a bearing disposed between an interior surface of the inner block member and an exterior surface of the drive shaft; by the drive shaft having an axial bore, at least one radial bore linking the axial bore to the discharge chamber and at least one radial hole extending through its exterior surface to the axial bore; and by a helical groove formed on the exterior surface of the drive shaft and linked to the radial hole. In operation, a large part of the mists of lubricating oil are separated from the refrigerant gas atmosphere and stick on a portion of the exterior surface of the drive shaft where the radial bores exist by collision of the discharged refrigerant gas therewith, and is available for lubricating the bearing. In the accompanying drawings:- Figure 1 is a vertical longitudinal section of a hermetically sealed scroll type compressor in accordance with the prior art; and, Figure 2 is a vertical longitudinal section of a hermetically sealed scroll type compressor in accordance with the present invention. For purpose of explanation only, the left side of Figure 2 will be refered to as the forward end or front and the right side of Figure 2 will be refered to as the rearward end. The compressor includes a heremetically sealed casing 10, fixed and orbiting scrolls 20, 30, an inner block member 40 and a motor 50. Fixed scroll 20 includes circular end plate 21 and a spiral element or wrap 22 extending from one end (rearward) surface thereof. The inner block member 40 is disposed within the casing 10. A first annular wall axially projects from a forward peripheral surface of inner block member 40. A forward end surface of first annular wall 41 and a rearward peripheral surface of circular end plate 21 of fixed scroll 20 are fixed by a plurality of screws 26. Second annular wall 42 axilly projects from a rearward peripheral surface of inner block member 40 and is fixedly disposed at an inner side wall casing 10. Stator 51 of motor 50 is firmly held by second annular wall 42 and ring member 43 these which are screwed on a plurality of bolts 44. Axial annular projection 45 extends from a central region of the rearward end surface of inner block member 40. Drive shaft 13 is rotatably supported within axial annular projection 45 through fixed plain bearing 14. Drive shaft 13 extends through the center of inner block member 40 and is supported within it through fixed plain bearing 14. Orbiting scroll 30 is disposed in forward side of inner block member 40 and includes circular end plate 31 and spiral element or wrap 32 extending from one end (forward) surface of circular end plate 31. Sprial element 22 of fixed scroll 20 and spiral element 32 of orbiting sroll 30 interfit at an angular and radial offset to form a plurality of line contacts which define at least one pair of sealed off fluid pockets 71. Annular projection 33 axially projects from the rearward end surface of circular end plate 31 opposite spiral element 32. Rotation preventing device 34 is disposed between a rearward peripheral surface of circular end plate 31 and the forward surface of inner block member 40 to prevent rotation of orbiting scroll 30 during orbital motion. O-ring seal 23 is disposed between an inner peripheral surface of first annular wall 41 and a part of exterior peripheral surface of circular end plate 21 to seal the mating surface of first annular wall 41 and circular end plate 21. Circular end plate 21 of fixed scroll 20 and inner block member 40 cooperatively divide casing 10 into discharge chamber 60 and suction chamber 70 in which spiral elements 22, 32 exist. Hole 25 is formed at a central portion of circular end plate 21 to discharge compressed gas to discharge chamber 60. Motor 50 also includes rotor 52 fixedly secured to an exterior peripheral surface of drive shaft 13. Pin member 15 is integral with and axially projects from the forward end surface of drive shaft 13 and is radially offset from the axis of drive shaft 13. Bushing 16 is rotatably disposed within annular projection 33 and is supported through bearing 35. Pin member 15 is inserted in hole 17 of bushing 16 which is offset from the center of bushing 16. Shaft seal mechanism 18 is disposed within cavity 46 formed at a central portion of the forward end surface of inner block member 40 to prevent leakage of refrigerant gas from discharge chamber 60 to suction chamber 70 due to the rotation of drive shaft 13. Balance weight 36 is attached at a rearward end surface of bushing 16 to average the torque of drive shaft 13 during rotation. Suction gas inlet pipe 80 radially penetrates through casing 10 and first annular wall 41, and opens to suction chamber 70. O-Ring seal 81 is disposed at an outer peripheral surface of inlet pipe 80 to seal the mating surface of inlet pipe 80 and first annular wall 41. Seal elements 221 and 321 are disposed at an end surface of spiral elements 22 and 32 respectively. Drive shaft 13 is provided with axial bore 131 and a plurality of riadial bores 132. Axial bore 131 extends from an opening at a rearward end of drive shaft 13, that is, the end opposite pin member 16, to a closed end rearward of pin member 16. The plurality of radial bores 132 link axial bore 131 near its closed end to discharge chamber 60 through a plurality of communication holes 47 formed in axial annular projection 45 and corresponding holes 141 in fixed plain bearing 14. Discharge gas outlet pipe 90 is inserted through the rear end of casing 10 and faces the opening of axial bore 131. Annular projection 91 axially projects from an inner surface of the rear end of casing 10 and links discharge gas outlet pipe 90 to the rearward end of drive shaft 13. The rearward end of drive shaft 13 is rotatably disposed within an inner forward portion of annular projection 91 through bearing 92. A pair of radial holes 133 linking to axial bore 131 are formed through drive shaft 13. Helical groove 134 is formed on the exterior surface of drive shaft 13 and is linked to radial holes 133. Wires 110 extends from stator 51 and pass through hermetic seal base 120 for connection with an electrical power source (not shown). Hermetic seal base 120 is hermetically secured to casing 10 about hole 121 which is formed at the side wall of casing 10. For example, base 120 may be welded or brazed to casing 10 to provide the hermetic seal therebetween. Conduit 140 is radially formed in inner block member 40. Lubricant oil collected in an inner bottom portion of casing 10 (a lowerward in Figure 2) is lead into suction chamber 70 through orifice tube 141 fixedly inserted to conduit 140 in virtue of pressure difference between suction chamber pressure and discharge chamber pressure. Filter element 142 is attached at a lower end of orifice tube 141 immersing in the collected lubricant oil. In operation, stator 51 generates a magnetic field causing rotation of rotor 52, thereby rotating drive shaft 13. This rotation is converted to orbital motion of orbiting scroll 30 through bushing 16; rotational motion is prevented by rotation preventing device 34. Refrigerant gas introduced into suction chamber 70 through suction gas inlet pipe 80 is taken into the outer sealed fluid pockets 71 between fixed scroll 20 and orbiting scroll 30, and moves inwardly towards the centre of spiral elements 22, 32 due to the orbital motion of orbiting scroll 30. As the refrigerant moves towards the central pocket, it undergoes a resultant volume reduction and compression, and is discharged to discharge chamber 60 through hole 25 and a one way valve (not shown). Cavity 60a locating between the inner side wall of casing 10 and first annular wall 41 leads discharged gas to hollow portion 61 as a part of discharge chamber 60 locating in a rearward side of inner block member 40. Discharge gas in hollow portion 61 then flows to an external fluid circuit (not shown) via communication holes 47, holes 141, radial bores 32, axial bore 131, annular projection 91 and discharge gas outlet pipe 90. The separating oil mechanism of the present invention operates as follows. Compressed refrigerant gas including numberless mists of lubricating oil is discharged to discharge chamber 60, and flows into axial bore 131 through cavity 60a, hollow portion 61, communication holes 47, holes 141 and radial bores 132, and then flows toward discharge gas outlet pipe 90. A large part of mists of lubricating oil are separated from refrigerant gas atmosphere to stick the oil mists to exterior surface of a portion of drive shaft 13 where radial bores 132 are formed by colliding discharged refrigerant gas therewith. A part of the sticked oil mist of the exterior surface of the portion of drive shaft 13 gets into a gap between plain bearing 14 and the exterior surface of drive shaft 13 to lubricate therebetween. Furthermore, a part of oil in the gap is led to helical groove 134 through one of radial holes 133 (left side one in Figure 2) to effecrtively lubricate between plain bearing 14 and the exterior surface of drive shaft 13 and is led out the gap through another of radial holes 133 (right side one in Figure 2). Another part of the sticked oil mist on the exterior surface of the portion of drive shaft 13 drops to be collected in a bottom of casing 10 along an inner peripheral wall of holes 141 and communication holes 47. The collected oil in the bottom of casing 10 is supplied to suction chamber 70 to lubricate the frictional portions therein by virtue of pressure difference in casing 10.

Claims: 1. A scroll type compressor comprising a hermetically sealed housing (10); a fixed scroll (20) disposed within the housing, the fixed scroll having a first end plate (21) and a first spiral element (22) extending therefrom; an orbiting scroll (30) having a second end plate (31) from which a second spiral element (32) extends, the first and second spiral elements interfitting at an angular and radial offset to form a plurality of line contacts which define at least one pair of sealed off fluid pockets (71); a drive mechanism (51,52,13) operatively connected to the orbiting scroll to effect orbital motion of the orbiting scroll; and a rotation preventing means (34) for preventing rotation of the orbiting scroll during motion whereby the volume of the fluid pockets changes to compress fluid in the pockets; the drive mechanism including a drive shaft (13) rotatably supported within an inner block member (40), the inner block member being fixed to the housing, and the first end plate (21) of the fixed scroll and the inner block member cooperatively dividing the housing into a discharge chamber (60) and a suction chamber (70) in which the first and second spiral elements (22,32) exist; characterised by a bearing (14) disposed between an interior surface of the inner block member (40) and an exterior surface of the drive shaft (13); by the drive shaft having an axial bore (131), at least one radial bore (132) linking the axial bore to the discharge chamber (60) and at least one radial hole (133) extending through its exterior surface to the axial bore; and by a helical groove (134) formed on the exterior surface of the drive shaft and linked to the radial hole. 2. A compressor according to claim 1, wherein the bearing (14) is a plain bearing. 3. A compressor according to claim 1 or claim 2, wherein the inner block member (40) comprises an axial annular projection (45), the bearing (14) being disposed between an interior surface of the axial annular projection and an exterior surface of the drive shaft. 4. A compressor according to any one of the preceding claims, wherein the axial bore (131) of the drive shaft (13) extends from an opening at one end of the drive shaft to a closed end near an opposite end of the drive shaft. 5. A compressore according to claim 4, wherein the housing (10) is provided with a refrigerant gas outlet port (90) extending therethrough and connected to the opening at the one end of the axial bore. 6. A compressor according to claim 5, further comprising an annular projection (91) axially projecting from an inner surface of the housing and linking the discharge gas outlet pipe to the one end of the drive shaft. 7. A compressor according to any one of claims 4 to 6, wherein the radial bore (132) links the axial bore (131) near its closed end to the discharge chamber (60). 8. A compressor according to any one of the preceding claims, further comprising at least one communication hole (47) linking the discharge chamber (60) to the axial bore (131) and formed through the inner block member (40) and the bearing (14). 9. A compressor according to any one of the preceding claims, further comprising a shaft seal mechanism (18) disposed within a cavity (46) formed at a central portion of a side of the inner block member facing the suction chamber to prevent leakage of refrigerant gas from the discharge chamber to the suction chamber due to the rotation of the drive shaft. 10. A compressor according to any one of the preceding claims, further comprising a suction gas inlet pipe (80) radially penetrating the housing (10) and the inner block member (40), and opening into the suction chamber (70). 11. A compressor according to any one of the preceding claims, further comprising a conduit (140) formed in the inner block member (40) to supply lubricating oil to the suction chamber (70) from the discharge chamber (60) by virtue of pressure difference in the housing.

Inventors: KIKUCHI, KAZUTO
Applicants: SANDEN CORPORATION
Application year: 1989
Main classification: F04C29
IPC codes: F04C18, F04C29