AXIAL SEALING MECHANISM FOR A SCROLL TYPE COMPRESSOR

Abstract: This invention discloses an axial sealing mechanism for axially sealing an orbiting scroll (20) and a fixed scroll (10) of a scroll type compressor. The compressor includes a driving mechanism (54) for driving the orbiting scroll in an orbital motion and a block member (30) fixedly attached to the housing of the scroll compressor to support the driving mechanism. The block member and the fixed scroll define an intermediate chamber (40) in which the orbiting scroll is disposed. The intermediate chamber is divided into a first (41) and second chamber (42) by an end plate (21) of the orbiting scroll. A first conduit (71a, 71b), which is sized to produce a pressure throttling effect, links the second chamber (42) and the discharge chamber of the compressor to increase the pressure in the intermediate chamber. A second conduit (81a, 81b), which also is sized to produce a pressure throttling effect, links the second chamber (42) to the suction cham­ ber (80) of the compressor. During operation of the compressor, the second chamber is maintained at an intermediate pressure without pressure fluctuation due to the pressure of the first and second conduits. This intermediate pressure provides a constant urging force against the orbiting scroll to urge it against the fixed scroll to obtain a good axial seal between both scrolls without decreasing the durability of the driving mechanism and the rota­ tion preventing mechanism.

Description: This invention relates to a scroll type compressor, and more particularly, to an axial sealing mechanism for the scroll members of a scroll type compressor. A conventional scroll type compressor with an axial sealing mechanism for axially sealing the scroll members is illustrated in Figure 1. The axial sealing mechanism shown in Figure 1 is similar to the axial sealing mechanism described in U.S. Patent No. 4,475,874. The scroll type compressor includes fixed scroll 10 having circular end plate 11 from which spiral element 12 extends, and orbiting scroll 20 having circular end plate 21 from which spiral element 22 extends. Block member 30 is attached to circular end plate 11 by a plurality of fastening members, such as bolts 31, to define chamber 40 in which orbiting scroll 20 is disposed. Spiral elements 12 and 22 are interfitted at an angular and radial offset to make a plurality of line contacts to define at least one pair of sealed-off fluid pockets. Driving mechanism 50 includes drive shaft 51 rotatably supported in bore 31 which is centrally formed in block member 30. Bushing 53 is integrated at one end of drive shaft 51. Immediately below bushing 53, bearing 511 is disposed between an outer peripheral surface of drive shaft 51 and an inner peripheral surface of bore 31. Circular boss 23 projects from an end surface of circular end plate 21 opposite spiral element 22 of orbiting scroll 20 and is rotatably inserted into circular depression 531 of bushing 53 through bearing 231. The center of circular boss 23 is radially offset from the center of drive shaft 51. Thereby, orbiting scroll 20 orbits when drive shaft 51 rotates. Circular end plate 21 of orbiting scroll 20 divides chamber 40 into first chamber 41 in which spiral elements 12 and 22 are disposed and second chamber 42 in which Oldham coupling 60 and one end of driving mechanism 50 are disposed. Below bearing 511, a mechanical seal (not shown) is mounted in block member 30 through drive shaft 51 extends. The mechanical seal is used for preventing the fluid communication between second chamber 42 with the outside second chamber. Discharge port 70 is formed at a central portion of circular end plate 11 to discharge the compressed fluid from a central fluid pocket. Suction port 80 is formed at a peripheral portion of circular end plate 11 to supply suction fluid to the outermost fluid pockets. A pair of apertures 90 which are sized to produce a pressure throttling effect are formed at a middle portion of circular end plate 21 of orbiting scroll 20 to link second chamber 42 to a pair of intermediately compressed fluid pockets 41a. During operation of the compressor, since the pressure in intermediate fluid pockets 41a facing aperture 90 fluctuates within a defined range, thus, even in a stable operating condition of the compressor, the pressure in second chamber 42, which is connected with intermediate fluid pockets 41a by apertures 90, is an average pressure which is related to the range of pressures in intermediate fluid pockets 41a. Accordingly, the axial sealing force applied against orbiting scroll 20 to urge it against fixed scroll 10 is a function of the average intermediate pressure in second chamber 42. One of the disadvantage of the above prior art axial sealing mechanism is that, since second chamber 42 admits the intermediately compressed fluid from intermediate fluid pocket 41a in which pressure fluctuates within a range of pressures, the pressure in second chamber 42 also fluctuates thereby varying the axial sealing force applied to the orbiting scroll. This occurs even in the stable operating condition of the compressor. As a result, Oldham coupling 60 and driving mechanism 50 intermittently receive an undesirable thrust force which is generated by the reaction force to the compressed fluid in all the fluid pockets. This reduces the durability of the compressor. Another disadvantage of the above prior art axial sealing mechanism is that machining process for forming aperture 90 in circular end plate 21 must by very precise, which increases manufacturing cost and may lead to reduced operating efficiency in the event precise tolerances are not observed. Another disadvantage of the above prior art axial sealing mechanism is to have to provide the mechanical seal, which increases manufacturing cost. It is a primary object of this invention to provide an axial sealing mechanism for a pair of scroll members of a scroll type compressor in which a constant axial force is generated. Another object of the present invention is to provide an axial sealing mechanism for a scroll type compressor which is easy and inexpensive to manufacture and does not require high precision machining. JP-A-60-228787 discloses a scroll type compressor including a housing, a fixed scroll having a first end plate from which a first spiral element extends, an orbiting scroll having a second end plate from which a second spiral element extends, a block member mounted in the housing in a fixed position relative to the first end plate to define an intermediate chamber in which the orbiting scroll is disposed, the first spiral element and the second spiral element interfitting at an angular and radial offset to make a plurality of line contacts to define at least one pair of sealed-off fluid pockets, a discharge space within the housing which receives compressed fluid discharged from a central fluid pocket defined by the first and second spiral elements, a suction space within the housing which receives suction fluid and passes the suction fluid to the radial outermost fluid pockets defined by the first and second spiral elements, a driving mechanism to effect the orbital motion of the orbiting scroll, and a rotation preventing mechanism for preventing the rotation of the orbiting scroll during its orbital motion whereby the volume of the fluid pockets changes, the driving mechanism including a drive shaft rotatably supported in a bore formed at the block member, the second end plate of the orbiting scroll dividing the intermediate chamber into a first chamber in which the first and second spiral elements are disposed and a second chamber in which the rotation-preventing mechanism and a portion of the driving mechanism are disposed, the housing comprising an hermetically sealed casing member, the casing member including an inner space in which compressed fluid from the central fluid pocket is discharged, the inner space including the discharge space, a first throttled conduit linking the inner space and the second chamber, a second throttled conduit linking the second chamber to the suction space; and, according to a first aspect of the invention, such a compressor is characterised in that the first and second throttled conduits are arranged to pass a flow of fluid to, through and from the second chamber to establish a substantially constant intermediate pressure in the second chamber to thereby apply a substantially constant axial sealing force between the orbiting and fixed scroll; and in that the first throttled conduit is formed between an outer peripheral surface of the drive shaft and an inner peripheral surface of the bore. Alternatively the inner space may include the suction space in which case the second conduit will be formed between the drive shaft and bore. Thus, a second aspect of the invention provides a scroll type compressor including a housing, a fixed scroll having a first end plate from which a first spiral element extends, an orbiting scroll having a second end plate from which a second spiral element extends, a block member mounted in the housing in a fixed position relative to the first end plate to define an intermediate chamber in which the orbiting scroll is disposed, the first spiral element and the second spiral element interfitting at an angular and radial offset to make a plurality of line contacts to define at least one pair of sealed-off fluid pockets, a discharge space within the housing which receives compressed fluid discharged from a central fluid pocket defined by the first and second spiral elements, a suction space within the housing which receives suction fluid and passes the suction fluid to the radial outermost fluid pockets defined by the first and second spiral elements, a driving mechanism to effect the orbital motion of the orbiting scroll, and a rotation preventing mechanism for preventing the rotation of the orbiting scroll during its orbital motion whereby the volume of the fluid pockets changes, the driving mechanism including a drive shaft rotatably supported in a bore formed at the block member, the second end plate of the orbiting scroll dividing the intermediate chamber into a first chamber in which the first and second spiral elements are disposed and a second chamber in which the rotation-preventing mechanism and a portion of the driving mechanism are disposed, the housing comprising an hermetically sealed casing member, the casing member including an inner space in which suction fluid from the suction port is circulated, the inner space including the suction space, a first throttled conduit linking the discharge space and the second chamber, a second throttled conduit linking the second chamber and the inner space, the first and second throttled conduits being arranged to pass a flow of compressed fluid to, through and from the second chamber to establish a substantially constant intermediate pressure in the second chamber to thereby apply a substantially constant axial sealing force between the orbiting and fixed scroll, and the second throttling conduit being formed between an outer peripheral surface of the drive shaft and an inner peripheral surface of the bore. In the accompanying drawings: Figure 1 is a vertical sectional view of a conventional scroll type compressor. Figure 2 is a vertical sectional view of a scroll type compressor in accordance with a first embodiment of the present invention. Figure 3 is a vertical sectional view of a scroll type compressor in accordance with a second embodiment of the present invention. Figure 4 is an enlarged cross-sectional view taken along line 4-4 of Figures 2 and 3. Figure 5 is an enlarged partial vertical sectional view of a scroll type compressor in accordance with the modified first and second embodiments of the present invention. Figure 6 is an enlarged cross-sectional view taken along line 6-6 of Figure 5. A first embodiment of the present invention is illustrated in Figure 2. The same numerals are used in Figure 2 to denote the corresponding elements shown in Figure 1, and the substantial explanation thereof is omitted. The scroll type compressor 100 includes hermetically sealed casing 110 comprising cup-shaped portion 111 and plate-shaped portion 112 of which periphery is hermetically connected to an opening end of cup-shaped portion 111 by, for example, brazing. Casing 110 houses fixed scroll 10, orbiting scroll 20, block member 30, driving mechanism 50 and Oldham coupling 60 therein. Fixed scroll 10 includes circular end plate 11 from which spiral element 12 extends. Orbiting scroll 20 includes circular end plate 21 from which spiral element 22 extends. Block member 30 is firmly secured to an inner peripheral wall of cup-shaped portion 111 adjacent to the opening end by forcible insertion, and is attached to circular end plate 11 by a plurality of fastening members, such as bolts (not shown), to define chamber 40 in which orbiting scroll 20 is disposed. Spiral elements 12 and 22 are interfitted at an angular and radial offset to make a plurality of line contacts to define at least one pair of sealed-off fluid pockets. Driving mechanism 50, which includes rotatably supported drive shaft 51, is connected to orbiting scroll 20 to effect the orbital motion of orbiting scroll 20. Oldham coupling 60 is disposed between circular end plate 21 and block member 30 to prevent the rotation of orbiting scroll 20 during its orbital motion. Circular end plate 21 of orbiting scroll 20 divides chamber 40 into first chamber 41 in which spiral elements 12 and 22 are disposed and second chamber 42 in which Oldham coupling 60 and one end of driving mechanism 50 are disposed. Discharge port 70 is formed at a central portion of circular end plate 11 to discharge the compressed fluid from a central fluid pocket. Drive shaft 51 is rotatably supported in bore 31 which is centrally formed in block member 30. One end of drive shaft 51 is fixedly attached to bushing 53, which is disposed within second chamber 42. First and second plain bearings 52a and 52b axially away each other by a certain interval are disposed between an outer peripheral surface of drive shaft 51 and an inner peripheral surface of bore 31. First plain bearing 52a includes flange portion 521a which faces a bottom surface of bushing 53. Annular space 512 is formed between the outer peripheral surface of drive shaft 51 and the inner peripheral surface of bore 31 at the certain interval defined by first and second plain bearings 52a and 52b. Circular boss 23 projects from an end surface of circular end plate 21 opposite spiral element 22 of orbiting scroll 20 and is rotatably inserted into circular depression 531 of bushing 53 through bearing 231. The center of circular boss 23 is radially offset from the center of drive shaft 51. Casing 110 further houses motor 54 for rotating drive shaft 51. Motor 54 includes ring-shaped stator 54a and ring-shaped rotor 54b. Stator 54a is firmly secured to the inner peripheral wall of cup-shaped portion 111 by forcible insertion and rotor 54b is firmly secured to drive shaft 51 by forcible insertion. Hole 511 is formed in drive shaft 51 to supply lubricating oil 55 collected in the bottom of cup-shaped portion 111 to a gap between the outer peripheral surface of drive shaft 51 and an inner peripheral surface of plain bearings 52a and 52b. One end of radial inlet port 83, which is hermetically sealed to cup-shaped portion 111, is connected to suction port 80 which is formed at a peripheral portion of circular end plate 11 to supply suction fluid to the outermost fluid pockets. One end of radial outlet port 73, which also is hermetically sealed to cup-shaped portion 111, is connected to inner space 101 of casing 110. With reference to Figure 4 additionally, axial grooves 71a and 71b (only axial groove 71a is shown in Figure 4) are formed at an inner peripheral surface of first and second plain bearings 52a and 52b, respectively. Grooves 71a and 71b are covered by the outer peripheral surface of drive shaft 51, thereby substantially forming conduits or apertures 71a and 71b. Radial groove 71c is formed at a top end surface of flange portion 521a, and is covered by the bottom end surface of bushing 53. One end of conduit 71a is connected to one end of groove 71c of which another end opens to second chamber 42, and another end of conduit 71a opens to annular space 512. One end of conduit 71b opens to annular space 512, and another end of conduit 71b opens to inner space 101 of casing 110. These apertures 71a and 71b are sized to produce a pressure throttling effect as further described below. But, annular space 512 and groove 71c are sized to substantially produce no pressure throttling effect. These apertures 71a and 71b form aperture 71. Accordingly, aperture 71, annular space 512 and groove 71c link inner space 101 of casing 110 to second chamber 42. Conduit or aperture 81, which is formed in block member 30, includes first conduit or aperture 81a and second conduit or aperture 81b. These first and second apertures 81a and 81b also are sized to produce a pressure throttling effect as further described below. First aperture 81a extends radially in block member 30 from an outer peripheral surface of block member 30 to an inner peripheral surface of block member 30 which partially defines second chamber 42. Second aperture 81b extends axially in block member 30 to connect first aperture 81a to suction port 80. Plug 82 is fixedly attached to the outer peripheral surface of block member 30 to close the outer radial end of first aperture 81a. Accordingly, aperture 81 links suction port 81 to second chamber 42. In operation, as arrows 91 in Figure 2 indicate, suction gas entering suction port 80 from another element in the refrigerating circuit, such as an evaporator (not shown), flows through inlet port 83 into the outermost fluid pockets of the scroll elements. The suction gas is compressed by virtue of the orbital motion of orbiting scroll 20 and then is discharged through discharge port 70. In this type of hermetic scroll compressor, which is generally called a high pressure type hermetic scroll compressor, the discharged refrigerant gas fills inner space 101 of casing 100 except chamber 40. Only a small portion of the discharged refrigerant gas flows into second chamber 42 through aperture 71, annular space 512 and groove 71c at a reduced pressure due to the throttling effect of aperture 71. Most of the discharged refrigerant gas flows to another element of the refrigerating circuit, such as a condenser (not shown), through outlet port 73. The refrigerant gas which flows into second chamber 42 through aperture 71, annular space 512 and aperture 71c flows into suction port 80 through aperture 81 at a pressure which is further reduced due to the throttling effect of aperture 81. This refrigerant gas merges with the suction gas. As a result, the pressure in second chamber 42 which urges orbiting scroll 20 to fixed scroll 10 is maintained at a value which is smaller than the discharge pressure and larger than the suction pressure, that is, an intermediate pressure. In particular, in the stable operating condition of the compressor, the pressure in second chamber 42 is maintained at an intermediate pressure with no fluctuation since both the discharge and suction pressures are maintained constant. Accordingly, a good axial seal between orbiting scroll 20 and fixed scroll 10 is maintained without reducing durability of Oldham coupling 60 and driving mechanism 50. Furthermore, the desired axial sealing pressure (the intermediate pressure) in second chamber 42 can be obtained by selecting the appropriate sectional area of apertures 71 and 81. Reduction of the compression capability of the compressor from the discharge gas blown through aperture 71, annular space 512, groove 71c, second chamber 42 and aperture 81 is minimal by virtue of the throttling effect of apertures 71 and 82. Figure 3 illustrates a second embodiment of the present invention. In Figure 3, the same numerals are used to denote the corresponding elements shown in Figure 2 and the essential explanation thereof is omitted. In this embodiment, one end of radial inlet port 831, which is hermetically sealed to casing 110 of scroll type compressor 200, opens into inner space 101 of casing 110 adjacent suction port 80. One end of axial outlet port 731, which is hermetically sealed to casing 110, is connected to discharge port 70. Conduit or aperture 711, which is formed in circular end plate 11 of fixed scroll 10, includes first conduit or aperture 711a and second conduit or aperture 711b. These apertures 711a and 711b are sized to produce a pressure throttling effect. First aperture 711a extends radially in circular end plate 11 from an outer peripheral surface of circular end plate 11 to an inner peripheral wall of discharge port 70. Second aperture 711b extends axially in circular end plate 11 from first aperture 71a to second chamber 42. Plug 720 is fixedly attached to the outer peripheral surface of circular end plate 11 to close the outer radial end of first aperture 711a. Accordingly, aperture 711 links discharge port 70 to second chamber 42. Conduits or apertures 811a, 811b are formed at first and second plain bearings 52a and 52b, respectively by the same manner as described in the first embodiment of the present invention. Apertures 811a and 811b form aperture 811. Accordingly, aperture 811, annular space 512 and groove 71c link inner space 101 of casing 110 to second chamber 42. During operation of the compressor, as arrows 92 in Figure 3 indicate, suction gas entering suction port 80 from another element in the refrigerating circuit, such as an evaporator (not shown), flows through inlet port 831 into the outermost fluid pockets of the scroll elements. The suction gas is compressed by virtue of the orbital motion of orbiting scroll 20 and then is discharged through discharge port 70. In this type of hermetic scroll compressor, which is generally called a low pressure type hermetic scroll compressor, a portion of the suction gas flows into and fills inner space 101 of casing 110 except chamber 40. Only a small portion of the discharged refrigerant gas flows into second chamber 42 through aperture 711 at a reduced pressure. Most of the discharged refrigerant gas flows to another element of the refrigerating circuit, such as a condenser (not shown), through outlet port 731. The refrigerant gas which flows into second chamber 42 through aperture 711 flows into inner space 101 of casing 100 through aperture 811, annular space 512 and groove 71c at a pressure which is further reduced due to the throttling effect of aperture 811. This refrigerant gas merges with the suction gas. The effect obtained by apertures 711 and 811 is similar to the effect of apertures 71 and 81 shown in Figure 2 so that the explanation thereof is omitted. Figures 5 and 6 illustrate the sectional views of a scroll type compressor in accordance with the modified first and second embodiments of the present invention. With reference to Figures 5 and 6, axial grooves 513a and 513b (only groove 513a is shown in Figure 6) are formed at the outer peripheral surface of drive shaft 51. Axial groove 513a extends along first plain bearing 52a so as to link annular space 512 to radial groove 532 which is formed at the bottom end surface of bushing 53 and opens to second chamber 42. Axial groove 513b extends along second plain bearing 52b so as to link annular space 512 to inner space 101 of the casing. Grooves 513a and 513b are covered by the inner peripheral surface of each of plain bearings 52a and 52b, respectively, thereby substantially forming conduits or apertures 513a and 513b. These apertures 513a and 513b are sized to produce a pressure throttling effect. Apertures 513a and 513b, annular space 512 and radial groove 532 link inner space 101 of the casing to second chamber 42. As pointed out previously, one of the advantages of this invention is that the machining process for forming the apertures need not be precise. Accordingly, improved axial sealing of the scroll elements can be achieved by a simple, easy to manufacture construction which does not adversely affect the overall operation of the scroll compressors.

Claims: A scroll type compressor including a housing, a fixed scroll (10) having a first end plate (11) from which a first spiral element (12) extends, an orbiting scroll (20) having a second end plate (21) from which a second spiral element (22) extends, a block member (30) mounted in the housing in a fixed position relative to the first end plate to define an intermediate chamber (40) in which the orbiting scroll is disposed, the first spiral element and the second spiral element interfitting at an angular and radial offset to make a plurality of line contacts to define at least one pair of sealed-off fluid pockets, a discharge space (70) within the housing which receives compressed fluid discharged from a central fluid pocket defined by the first and second spiral elements, a suction space (80) within the housing which receives suction fluid and passes the suction fluid to the radial outermost fluid pockets defined by the first and second spiral elements, a driving mechanism to effect the orbital motion of the orbiting scroll, and a rotation preventing mechanism (60) for preventing the rotation of the orbiting scroll during its orbital motion whereby the volume of the fluid pockets changes, the driving mechanism including a drive shaft (51) rotatably supported in a bore (31) formed at the block member, the second end plate of the orbiting scroll dividing the intermediate chamber (40) into a first chamber (41) in which the first and second spiral elements are disposed and a second chamber (42) in which the rotation-preventing mechanism and a portion of the driving mechanism are disposed, the housing comprising an hermetically sealed casing member, the casing member (110) including an inner space (101) in which compressed fluid from the central fluid pocket is discharged, the inner space including the discharge space, a first throttled conduit (71) linking the inner space and the second chamber, a second throttled conduit (81) linking the second chamber to the suction space; characterised in that the first and second throttled conduits are arranged to pass a flow of fluid to, through and from the second chamber to establish a substantially constant intermediate pressure in the second chamber to thereby apply a substantially constant axial sealing force between the orbiting and fixed scroll; and in that the first throttled conduit (71) is formed between an outer peripheral surface of the drive shaft (51) and an inner peripheral surface of the bore (31). A compressor according to claim 1 further comprising at least one plain bearing (52) disposed between the outer peripheral surface of the drive shaft (51) and the inner peripheral surface of the bore (31). A compressor according to claim 2, wherein the first throttled conduit (71) is a groove formed at the plain bearing. A compressor according to claim 1 or claim 2, wherein the first throttled conduit (71) is a groove (513) formed at the outer peripheral surface of the drive shaft. A scroll type compressor including a housing, a fixed scroll (10) having a first end plate (11) from which a first spiral element (12) extends, an orbiting scroll (20) having a second end plate (21) from which a second spiral element (22) extends, a block member (30) mounted in the housing in a fixed position relative to the first end plate to define an intermediate chamber (40) in which the orbiting scroll is disposed, the first spiral element and the second spiral element interfitting at an angular and radial offset to make a plurality of line contacts to define at least one pair of sealed-off fluid pockets, a discharge space (70) within the housing which receives compressed fluid discharged from a central fluid pocket defined by the first and second spiral elements, a suction space (80) within the housing which receives suction fluid and passes the suction fluid to the radial outermost fluid pockets defined by the first and second spiral elements, a driving mechanism to effect the orbital motion of the orbiting scroll, and a rotation preventing mechanism (60) for preventing the rotation of the orbiting scroll during its orbital motion whereby the volume of the fluid pockets changes, the driving mechanism including a drive shaft (51) rotatably supported in a bore (31) formed at the block member, the second end plate of the orbiting scroll dividing the intermediate chamber (40) into a first chamber (41) in which the first and second spiral elements are disposed and a second chamber (42) in which the rotation-preventing mechanism and a portion of the driving mechanism are disposed, the housing comprising an hermetically sealed casing member, the casing member including an inner space (101) in which suction fluid from the suction port is circulated, the inner space including the suction space, a first throttled conduit (711) linking the discharge space and the second chamber, a second throttled conduit (811) linking the second chamber and the inner space, the first and second throttled conduits being arranged to pass a flow of compressed fluid to, through and from the second chamber to establish a substantially constant intermediate pressure in the second chamber to thereby apply a substantially constant axial sealing force between the orbiting and fixed scroll, and the second throttling conduit being formed between an outer peripheral surface of the drive shaft (51) and an inner peripheral surface of the bore (31). A compressor according to claim 5, further comprising at least one plain bearing (52) disposed between the outer peripheral surface of the drive shaft (51) and the inner peripheral surface of the bore. A compressor according to claim 6, wherein the second throttled conduit (811) is a groove formed the plain bearing. A compressor according to claim 5 or claim 6, wherein the second throttled conduit (81) is a groove (513) formed at the outer peripheral surface of the drive shaft.

Inventors: KIKUCHI, KAZUTO, KIKUCHI, KAZUTO, C/O SANDEN CORPORATION
Applicants: SANDEN CORPORATION
Application year: 1990
Main classification: F04C27
IPC codes: F04C18, F04C27