SCROLL TYPE COMPRESSOR

Abstract: A scroll type compressor includes a housing (10) having an inner chamber and fluid inlet and outlet ports connected to the inner chamber. A fixed scroll (13) is mounted within the housing and has a circular end plate (131) from which a first sprial element (132) extends. An orbiting scroll (14) is also mounted within the housing for orbital motion with respect to the fixed scroll, and includes a circular end plate (141) from which a second spiral element (142) extends. The fixed scroll and the orbiting scroll are maintained angularly and radially offset from each other so that the spiral elements interfit to form a plurality of line contacts between their spiral curved surfaces which seal-off and defined at least one pair of fluid pockets. The orbital movement of the orbiting scroll relative to the fixed scroll shifts the line contacts along the spiral curved surfaces of the spiral elements which changes the volume of the fluid pockets. The end plate (131) of the fixed scroll partitions the inner chamber of the housing into a suction chamber (18) and a discharge chamber (19). A sealing structure (30) is disposed between the inner peripheral wall (12) of the housing and the outer peripheral surface of the end plate of the fixed scroll. The sealing structure includes an annular cut-out portion formed in the outer peripheral of the end plate of the fixed scroll, an annular shoulder formed in the inner peripheral wall of the housing and an O-ring element disposed between the annular cut-out portion and the annular ridge.

Description: This invention relates to a scroll type refrigerant compressor, and more particularly, to a sealing structure for insulating the suction chamber and the discharge chamber of the compressor casing. Scroll type refrigerant compressors are well known in the prior art. For example, Japanese Patent Application Publication No. 56-156492 discloses such a compressor which includes two scrolls, each having a circular end plate and an involute spiral element. The scrolls are maintained angularly and radially offset from each other so that the spiral elements interfit to form a plurality of line contacts between their spiral curved surfaces to thereby seal off and define at least one pair of fluid pockets. The relative orbital motion of the two scrolls shifts the line contacts along the spiral curved surfaces and, as a result, the volume of the fluid pockets decreases with compression. Referring to Figure 1, a scroll type refrigerant compressor 1 in accordance with the prior art is shown. Compressor 1 includes a compressor housing 10 having a front end plate 11 and a cup shaped casing 12, which is attached to the rearwardly facing surface of front end plate 11 to define an inner chamber between the inner wall of casing 12 and the surface of front end plate 11. Disposed within the inner chamber of cup shaped casing 12 are a fixed scroll 13 having a circular end plate 131 from which a spiral element 132 extends, an orbiting scroll 14 having a circular end plate 141 from which a spiral element 142 extends, a driving mechanism 15 and a rotation preventing/thrust bearing device 16. A drive shaft 151 penetrates an opening 111 in front end plate 11 and is rotatably supported by front end plate 11 through a bearing 17. Driving mechanism 15 is operatively coupled to drive shaft 151, and is connected to orbiting scroll 14 to effect orbiral movement of the orbiting scroll during rotation of the drive shaft. Rotation of orbiting scroll 14 is prevented by rotation preventing/ thrust bearing device 16. Scrolls 13 and 14 are maintained angularly and radially offset from each other so that spiral elements 132, 142 interfit to form a plurality of line contacts between their spiral curved surfaces which seal-off and define at least one pair of fluid pockets. The orbital movement of orbiting scroll 14 relative to fixed scroll 13 shifts the line contacts along the spiral curved surfaces of spiral elements 132, 142 which changes the volume of the fluid pockets. Circular end plate 131 of fixed scroll 13 partitions the inner chamber of cup shaped casing 12 into a suction chamber 18 and a discharge chamber 19. A sealing structure 20 (Figure 2) is formed in the outer peripheral wall of circular end plate 131 to isolate suction chamber 18 and discharge chamber 19. The sealing structure 20 includes a circumferential groove 21 formed in the outer peripheral surface of circular end plate 131 and an O-ring seal element 22 disposed in the circumferential groove 21. Formation of circumferential groove 21 is accomplished by a cutting process, comprising seven steps, shown in Figures 3a through 3g in which circular end plate 131 is mounted for rotation proximate a surface cutting tool. In a first step, shown in Figure 3a, the outer peripheral surface 131a of circular end plate 131 and the outer circumferential portion 131e of the surface of circular end plate 131 are cut by a surface cutting tool 201 which is attached to a numerical controlled lathe (not shown). In steps 2-4, shown in Figures 3b through 3d, respectively, outer peripheral surface 131a of circular end plate 131 is cut by a groove cutting tool 202. Typically, groove cutting tool 202 will have a vertical sectional view similar to that of circumferential groove 21, i.e., the groove cutting tool 202 is used as a forming tool. The final steps in the process are shown in Figures 3e through 3g, in which the corners of circumferential groove 21 are rounded by groove cutting tool 202. There are a number of problems associated with this technique for forming a circumferential groove in the outer peripheral surface of the circular end plate. One problem is that the tip of the groove cutting tool is easily broken, which destroys its utility as a forming tool. It is also difficult to precisely control the dimensions of the groove to within a certain standard because of sticking residual material left at the tip of the groove cutting tool and within the groove itself during the cutting operation. In addition, the process is time-consuming and requires a plurality of cutting tools. EP-A-0106288 discloses a scroll type fluid compressor including a housing having a fluid inlet port and a fluid outlet port, a fixed scroll fixedly disposed within the housing and having an end plate from which a first spiral element extends, an orbiting scroll having an end plate from which a second spiral element extends, an inner chamber of the housing being partitioned into a front chamber and a rear chamber, a sealing structure for isolating the front and rear chambers formed between the outer peripheral surface of the plate of the fixed scroll and the inner peripheral wall of the housing, the scrolls being maintained angularly and radially offset from each other so that the first and second spiral elements interfit to form a plurality of line contacts between their spiral surfaces to thereby seal off and define at least one pair of fluid pockets, a driving mechanism operatively connected to the orbiting scroll to effect orbital motion of the orbiting scroll, and rotation preventing means for preventing rotation of the orbiting scroll so that the motion of the orbiting scroll relative to the fixed scroll shifts the line contacts along the spiral surfaces of the spiral elements to thereby change the volume of the fluid pockets, one of the chambers being associated with the fluid outlet port to receive compressed fluid from a centrally located fluid pocket formed by the scrolls during orbital motion, and, according to the invention, such a compressor is characterised in that the sealing structure includes an annular cut-out portions formed at the intersection of the outer peripheral surface and an axial end surface of the end plate of the fixed scroll, an annular shoulder formed in the inner peripheral wall of the housing and an O-ring seal element disposed between the annular cut-out portion and the annular shoulder. CH-A-640607 discloses a screw pump having a seal positioned in engagement with a flange. In the accompanying drawings: Figure 1 is a vertical longitudinal sectional view of a scroll type compressor in accordance with the prior art. Figure 2 is a partial sectional fragmentary schematic view which shows a sealing structure in accordance with the prior art. Figures 3a through 3g are partial sectional fragmentary schematic illustrations which show the cutting process used in forming the circumferential groove in accordance with the prior art. Figure 4 is a vertical longitudinal sectional view of a scroll type compressor in accordance with one embodiment of the present invention. Figure 5 is a partial sectional fragmentary schematic view which shows a sealing structure in accordance with one embodiment of the present invention. Figure 6a and 6b are partial sectional fragmentary schematic illustrations which show the cutting process used to form the sealing structure of Figure 5. Figure 7 is a partial sectional fragmentary schematic view which shows a sealing structure in accordance with a second embodiment of the present invention. Figure 8 is a partial sectional fragmentary schematic view which shows a sealing structure in accordance with a third embodiment of the present invention. Figure 9 is a partial sectional fragmentary schematic view which shows a sealing structure in accordance with a fourth embodiment of the present invention. Referring to Figure 4, a scroll type refrigerant compressor 1 in accordance with one embodiment of the present invention is shown. Compressor 1 includes a compressor housing 10 having a front end plate 11 and a cup shaped casing 12, which is attached to an end surface of front plate 11 to define an inner chamber between the inner wall of casing 12 and the rearwardly facing surface of front end plate 11. Disposed within the inner chamber of cup shaped casing 12 are a fixed scroll 13 having a circular end plate 131 from which a spiral element 132 extends, an orbiting scroll 14 having a circular end plate 141 from which a spiral element 142 extends, a driving mechanism 15 and a rotation preventing/thrust bearing device 16. Fixed scroll 13 is fixed to the rear end plate of cup shaped casing 12 by screws 133. Scrolls 13 and 14 are maintained angularly and radially offset from each other so that spiral elements 132, 142 interfit to form a plurality of line contacts between their spiral curved surfaces which define at least one pair of sealed off fluid pockets 51. The circular end plate 141 of the orbiting scroll 14 is provided with a boss 143 projecting annularly from the surface of end plate 141 opposite the surface from which spiral element 142 extends. A drive shaft 151 penetrates an opening 111 of front end plate 11 and is rotatably supported by front end plate 11 through a bearing 17 and a sleeve 171. Drive shaft 151 is operatively connected at one end with driving mechanism 15 which includes a disk shaped rotor 152 formed at the inner end of drive shaft 151, a driving pin (not shown) attached to the disk shaped rotor 152 eccentrically, and a bushing 153 connected to the driving pin. Bushing 153 is connected to orbiting scroll 14 through a bearing 154 which is disposed on the inner wall of boss 143. As drive shaft 151 is rotated, bushing 153 also tends to rotate eccentrically. However, rotation of orbiting scroll 14 is prevented by rotation preventing/thrust bearing device 16 so that orbiting scroll 14 exhibits orbital motion. The orbital movement of orbiting scroll 14 relative to fixed scroll 13 shifts the line contacts along the spiral curved surfaces of spiral elements 132, 142 which changes the volume of the fluid pockets with compression of the fluid. The compressed fluid is then discharged to a discharge chamber, described below, through a hole 52 formed in circular end plate 131 of fixed scroll 13. Circular end plate 131 of fixed scroll 13 partitions the inner chamber of cup shaped casing 12 into a suction chamber 18 and a discharge chamber 19. A sealing structure 30, for isolating suction chamber 18 and discharge chamber 19, is formed between the outer peripheral surface of circular end plate 131 and the inner peripheral wall of cup shapes casing 12. Referring to Figure 5, sealing structure 30 includes an annular cut-out portion 31, having an L-shaped sectional side view, formed in the outer peripheral surface of circular end plate 131, an annular ridge 32 formed in the inner peripheral wall of cup shaped casing 12 and an O-ring seal element 33 disposed between annular cut-out portion 31 and annular ridge 32. The formation of annular ridge 32 is accomplished by a cutting process in which cup shaped casing 12 is mounted for rotation proximate a cutting tool, which is attached to a numerical controlled lathe. During rotation of casing 12, the cutting tool is controlled to move in an longitudinal direction along the inner surface of the casing and to cut away a portion of the peripheral surface of the inner wall of the casing. As a result of the cutting operation, the inner wall of at least a portion of discharge chamber 19 is thicker, by "h" in Figure 5, than the inner wall of suction chamber 18 so that annular ridge 32 is formed. In accordance with the invention, annular ridge 32 is positioned at a distance from circular end plate 131 so that a gap, having width "t" in Figure 5, is created between the rearwardly facing surface of circular end plate 131 and the surface of annular ridge 32 when fixed scroll 13 is fixedly secured to cup shaped casing 12. This gap prevents circular end plate 131 from contacting annular ridge 32 during operation of the compressor, and thus protects the scroll from damage. Referring to Figures 6a and 6b, the formation of annular cut-out portion 31 is accomplished by a cutting process in which circular end plate 131 is mounted for rotation proximate a surface cutting tool 201, which is attached to a numerical controlled lathe (not shown). In a first steps, shown in Figure 6a, cutting tool 201 is positioned to cut the outer circumferential portion 131e of the opposite surface of circular end plate 131. Then, as part of a continuous movement, cutting tool 201 is repositioned to cut the outer peripheral surface of circular end plate 131 to thereby from annular cut-out portion 31 and a projection 34, located at the upper portion of the outer peripheral surface of circular end plate 131, as shown in Figure 5. In the second step, shown in Figure 6b, cutting tool 201 is repositioned, again as part of a continous movement, to cut away a corner 35 formed by the lateral surface of annular cut-out portion 31 and the outer peripheral surface of projection 34. Referring to Figure 7, a sealing structure 30 in accordance with a second embodiment of the present invention is shown. In this embodiment, the longitudinal surface 31a of annular cut-out portion 31 is slanted, and gradually extends toward the inner wall of casing 12. Referring to Figure 8, a sealing structure 30 in accordance with a third embodiment of the present invention is shown. In this embodiment, the lower (relative to Figure 8) part of the longitudinal surface 31b of annular cut-out portion 31 is slanted, and gradually extends toward the inner wall of casing 12. Referring to Figure 9, a sealing structure 30 in accordance with a fourth embodiment of the present invention is shown. In this embodiment, both annular cut-out portion 31 and annular ridge 32 are located on the suction chamber side of circular end plate 131. Sealing structure 30, thus, comprises annular cut-out portion 31 formed at the upper (relative to Figure 9) part of the outer peripheral surface of circular end plate 131, and annular ridge 32 is formed in the inner surface of suction chamber 18. The annular cut-out portion 31 shown in each of Figures 7 and 8 is formed using the same two-steps cutting process described above with respect to Figure 6a and 6b, except that the blade angle of the cutting tool used in the process will be different depending upon the configuration of cut-out portion 31.

Claims: 1. A scroll type fluid compressor including a housing (10) having a fluid inlet port and a fluid outlet port, a fixed scroll (13) fixedly disposed within the housing and having an end plate (131) from which a first spiral element (132) extends, an orbiting scroll (14) having an end plate (141) from which a second spiral element (142) extends, an inner chamber of the housing being partitioned into a front chamber (18) and a rear chamber (19), a sealing structure (30) for isolating the front and rear chambers formed between the outer peripheral surface of the plate (131) of the fixed scroll and the inner peripheral wall of the housing, the scrolls being maintained angularly and radially offset from each other so that the first and second spiral elements interfit to form a plurality of line contacts between their spiral surfaces to thereby seal off and define at least one pair of fluid pockets, a driving mechanism (15) operatively connected to the orbiting scroll to effect orbital motion of the orbiting scroll, and rotation preventing means (16) for preventing rotation of the orbiting scroll so that the motion of the orbiting scroll relative to the fixed scroll shifts the line contacts along the spiral surfaces of the spiral elements to thereby change the volume of the fluid pockets, one of the chambers being associated with the fluid outlet port to receive compressed fluid from a centrally located fluid pocket formed by the scrolls during orbital motion, characterised in that the sealing structure includes an annular cut-out portions (31) formed at the intersection of the outer peripheral surface and an axial end surface of the end plate of the fixed scroll, an annular shoulder (32) formed in the inner peripheral wall (12) of the housing and an O-ring seal element (33) disposed between the annular cut-out portion and the annular shoulder. 2. A compressor according to claim 1, wherein the annular cut-out portion is formed in the rear chamber side of the outer peripheral surface of the end plate of the fixed scroll and the annular shoulder is formed in the rear chamber side of the inner peripheral wall of the housing (Figs 4-8). 3. A compressor according to claim 1, wherein the annular cut-out portion is formed in the front chamber side of the outer peripheral surface of the end plate of the fixed scroll and the annular shoulder is formed in the front chamber side of the inner peripheral wall of the housing (Fig 9). 4. A compressor according to any one of the preceding claims, wherein the annular ridge is located in the inner wall (12) of the housing at a distance (t) from the circular end plate (131) of the fixed scroll to create a gap between the surface of the end plate and the surface of the annular shoulder (32) when the fixed scroll is fixedly disposed in the housing. 5. A compressor according to any one of the preceding claims, wherein the annular cut-out portion (31) comprises an axially inclined surface (Fig 7).

Inventors: KIMURA, YOSHIO, OCHIAI, YOSHIHIRO, YAGUCHI, MASASHI
Applicants: SANDEN CORPORATION
Application year: 1988
Main classification: F04C18
IPC codes: F04C18, F04C27