SCROLL TYPE COMPRESSOR WITH VARIABLE DISPLACEMENT MECHANISM

Abstract: A scroll type compressor with a variable displacement mechanism is disclosed which includes a housing (10) with an inner chamber and fluid inlet and outlet ports connected to the inner chamber. A fixed scroll (21), which is mounted within the housing, has an end plate (211) from which a first spiral wrap (212) extends. An orbiting scroll (22) also is mounted within the housing for orbital motion with respect to the fixed scroll. The orbiting scroll has an end plate (221) from which a second spiral wrap (222) extends. The first and second wraps interfit to define at least one pair of sealed off fluid pockets. The end plate (211) of the fixed scroll partitions the inner chamber of the housing into a suction chamber (271) and rear chamber (28). The rear chamber includes an intermediate pressure (282) chamber which communicates with the sealed off fluid pockets through a pair of circular holes (214,215 not shown) formed at the end plate of the fixed scroll. A control mechanism (36) controls fluid communication between the intermediate pressure chamber (282) and the suction chamber (271). A plurality of seal elements (240a,240b,240c) located along the axial end of the second wrap (222) are spaced by the certain portions which are positioned so as to cross over the circular holes (214,215) during orbital motion of the orbiting scroll. Thereby, even when the diameter of the circular holes are enlarged to prevent the undesirable pressure drop at the circular holes in the compressor high rotational speed, damage of the seal elements can be prevented.

Description: The present invention relates to a scroll type compressor. More particularly, the present invention relates to a scroll type compressor with a variable displacement mechanism. Scroll type fluid displacement apparatus are well known in the prior art. For example, U.S. Pat. No. 801, 182 issued to Cruex discloses such an apparatus which includes two scrolls, each having a circular end plate and a spiroidal or involute spiral element. The scrolls are maintained angularly and radially offset so that both 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 increases or decreases, dependent on the direction to the orbital motion. Thus, a scroll type fluid displacement apparatus may be used to compress, expand or pump fluids. When conventional scroll type compressors are used in automobile air conditioners, these compressors usually are driven by the automobile engine through an electromagnetic clutch. In such automobile air conditioners, thermal control of a passenger compartment, or control of the air conditioner, is generally accomplished by intermittent operation of the compressor through the electromagnetic clutch because capacity control mechanisms usually are not provided for the compressors of such air conditioners. Though the energy required for maintaining the passenger compartment at the desired temperature usually is not large once the desired temperature is first achieved, a relatively large load is required to drive the compressor, et least during initial intermittent operation of the compressor, and to a lesser extent upon each subsequent actuation of the compressor. This intermittent operation wastefully consumes large amounts of energy. Recently, it was recognized that it is desirable to provide a scroll type compressor with a displacement or volume adjusting mechanism to control the compression ratio as operation demands. Mechanisms to control the compression ratio generally have used a pair of holes through the end plate of one of the scrolls, with the pair of holes providing controlled communication to a chamber which is located on the opposite side to the spiral element with respect to the end plate. For example, in U.S. Pat. No. 4,904,164 issued on Feb. 27, 1990 to Atsushi Mabe et al., the pair of circular holes provide controlled communication to an intermediate pressure chamber. In the compressor disclosed in the patent, an axial tip seal element is disposed in the groove which is located along the axial end of each of the spiral elements in order to sufficiently maintain the axial sealing between the axial end surface of the spiral elements and the inner surface of the end plates. The intermediately compressed fluid which flows from the sealed off pockets to the intermediate pressure chamber through the pair of circular holes controllably flows back to the suction chamber via a communication channel formed at the end plate in response to operation of a communication control mechanism. Thereby, pressure in the intermediate pressure chamber varies from the suction pressure to the certain pressure which can prevent the communication between the sealed off fluid pockets and the intermediate pressure chamber so that the compression ratio of the compressor is controlled in the range from the maximum value, i.e., 100 % to the predetermined minimum value, e.g., 30 %. However, when the compressor operates in a high rotational speed while the compression ratio is adjusted to the predetermined minimum value, the minimum value of compression ratio is undesirably increased because that the value of the pressure drop at the pair of circular holes becomes not negligible due to extreme increase in flow rate of the fluid which passes through the pair of circular holes. Accordingly, controllability of the displacement adjusting mechanism becomes decreased, in particular, in operation of the compressor in the high rotational speed. In order to resolve the above drawback, a radius of the pair of circular holes can be enlarged within the value, which is slightly smaller than thickness of the spiral elements, so as to reduce the pressure drop at the pair of circular holes to the negligible value. However, when a certain portion of the axial end of the spiral element of one of the scrolls passes over the circular hole in a situation when the diameter of the circular hole is enlarged, a certain portion of the axial tip seal element locating on the circular hole during relative orbital motion of the scrolls easily tends to bend toward the opening of the circular hole because of increase in lack of support caused by an enlargement of the blank which is defined by the circular hole. As a result, the certain portion of the axial tip seal element easily tends to be bitten by an edge of the axial end of the spiral element and an edge of the circular hole. Thereby, the axial tip seal element is damaged, such as cutting thereof, so that the function of the compression mechanism of the compressor becomes decreased. EP-A-49480 discloses a scroll type compressor without displacement adjusting means but with a discontinuous seal element. The discontinuous seal prevents concentrated wear of the seal due to back pressure acting on it. Accordingly, it is a primary object of the present invention in a scroll type compressor to prevent decrease in controllability of a displacement adjusting mechanism in any rotational speed of the compressor without damage of an axial tip seal element. A scroll type compressor according to the present invention is defined in claim 1. Various additional advantages and features of novelty which characterize the invention are further pointed out in the claims that follow. However, for a better understanding of the invention and its advantages, reference should be made to the accompanying drawings and descriptive matter which illustrate and describe preferred embodiment of the invention. Figure 1 is a vertical longitudinal sectional view of a scroll type compressor with a variable displacement mechanism in accordance with one embodiment of this invention. Figure 2 is a schematic horizontal perspective view of the scroll type compressor of Figure 1, viewing from the right side in Figure 1. Referring to Figure 1, a scroll type compressor according to one embodiment of this invention is shown. The scroll type compressor includes a compressor housing 10 having a front end plate 11 and a cup-shaped casing 12 which is attached to front end plate 11. An opening 111 is formed in the center of the front end plate 11 and a drive shaft 13 is disposed in the opening 111. An annular projection 112 is formed in a rear surface of the front end plate 11. An annular projection 112 faces cup-shaped casing the 12 and is concentric with opening the 111. An outer peripheral surface of the projection 112 extends into an inner wall of an opening 121 of the cup-shaped casing 12. The opening 121 of the cup-shaped casing 12 is covered by the front end plate 11. An O-ring 14 is placed between the outer peripheral surface of the annular projection 112 and an inner wall of the opening 121 of the cup-shaped casing 12 to seal the mating surface of the front end plate 11 and the cup-shaped casing 12. An annular sleeve 16 longitudinally projects from a front end surface of the front end palte 11, surrounds the drive shaft 13, and defines a shaft seal cavity 161. The drive shaft 13 is rotatably supported by an annular sleeve 16 through a bearing 17 located within the front end of sleeve 16. The drive shaft 13 has a disk-shaped rotor 131 at its inner end which is rotatably supported by the front end plate 11 through a bearing 15 located within the opening 111 of the front end plate 11. A shaft seal assembly 18 is coupled to the drive shaft 13 within the shaft seal cavity 161 of annular sleeve 16. A pulley 201 is rotatably supported by a ball bearing 19 which is carried on the outer peripheral surface of the annular sleeve 16. An electromagnetic coil 202 is fixed about the outer surface of the annular sleeve 16 by a support plate 204. An armature plate 203 is elastically supported on the outer end of the drive shaft 13. The pulley 201, the electromagnetic coil 202 and the armature plate 203 form an electromagnetic clutch 20. In operation, the drive shaft 13 driven by an external power source, for example, the engine of an automobile, through a rotation transmitting device such as the electromagnetic clutch 20. A fixed scroll 21, an orbiting scroll 22 and a rotation preventing/thrust bearing mechanism 24 for the orbiting scroll 22 are disposed in the interior of the housing 10. The fixed scroll 21 includes a circular end plate 211 and a spiral element 212 affixed to or extending from one end surface of the circular end plate 211. The fixed scroll 21 is fixed within the inner chamber of the cup-shaped casing 12 by screws (not shown) screwed into the end plate 211 from the outside of the cup-shaped casing 12. An O-ring 123 is disposed between an outer peripheral surface of the circular end plate 211 and an inner peripheral wall of the cup-shaped casing 12. Therefore, the circular end plate 211 of the fixed scroll 21 insulatingly partitions the inner chamber of the cup-shaped casing 12 into two chambers, a front chamber 27 and a rear chamber 28. The spiral element 212 of the fixed scroll 21 is located within the front chamber 27. A wall 122 longitudinally projects from the inner end surface of the cup-shaped casing 12 to device the rear chamber 28 into a discharge chamber 281 and an intermediate pressure chamber 282. The end surface of wall 122 contacts the rear end surface of the circular end plate 211. The orbiting scroll 22, which is located in the front chamber 27, includes a circular end plate 221 and a spiral element 222 extending from one end surface of the circular end plate 221. The spiral element 222 of the orbiting scroll 22 and the spiral element 212 of the fixed scroll 21 interfit at an angular offset of approximately 180° and a predetermined radial offset, to form sealed spaces between the spiral element 212 and 222. The orbiting scroll 22 is rotatably supported by a bushing 23, which is eccentrically connected to the inner end of a disc-shaped portion 131, through a radial needle bearing 30. While the orbiting scroll 22 orbits, rotation of the orbiting scroll 22 is prevented by a rotation preventing/thrust bearing mechanism 24 which is placed between the rear end surface of the front end plate 11 and the circular end plate 221 of the orbiting scroll 22. The compressor housing 10 is provided with an inlet port 31 and an outlet port 32 for connecting the compressor to an external refrigeration circuit. Refrigeration fluid from the external circuit is introduced into a suction chamber 271 through the inlet port 31 and flows into sealed formed between the spiral elements 212 and 222 through open spaces between the spiral elements. The sealed spaces between the spiral elements sequentially open and close during the orbital motion of the orbiting scroll 22. When these spaces are open, fluid to be compressed flows into these spaces but no compression occurs. When these spaces are closed, no additional fluid flows into these spaces and compression begins. Since the location of the outer terminal ends of the spiral elements 212 and 222 is at a final involute angle, location of the spaces is directly related to the final involute angle. Furthermore, refrigeration fluid in the sealed space is moved radially inwardly and is compressed by the orbital motion of the orbiting scroll 22. Compressed refrigeration fluid at a center sealed space 272 is discharged to the discharge chamber 281 past a valve plate 231 of spring material through a discharge port 213 which is formed at the center of the circular end plate 211. When the valve plate 231 is pushed by virtue of pressure difference, a valve retainer 231a receives the valve plate 231 to prevent excessive bending of the valve plate 231. Excessive bending of the valve plate 231 can cause damage to the valve plate 231. Referring to figure 2 additionally, a pair of circular holes 214 and 215 are formed in the circular end plate 211 of fixed scroll 21 and are generally symmetrically placed so that an axial end surface of the spiral element 222 of the orbiting scroll 22 generally simultaneously crosses over both holes. The holes 214, 215 communicate between an intermediate sealed space 273 and an intermediate pressure chamber 282. A radius of each of the holes 214, 215 is designed so as to be slightly smaller than thickness of the spiral elements. The circular hole 214 opens along the inner side wall of the spiral element 212. The circular hole 215 opens along the outer side wall of the spiral element 212. Therefore, for instance, when the outer wall of the spiral element 222 of the orbiting scroll 22 contacts the inner wall of the spiral element 212 of the fixed scroll 21 at the location of the circular hole 214, a part of the circular hole 214 formed at the circualr end palte 211 of the fixed scroll 21 can be entirely covered by the axial end of the spiral element 222 of the orbiting scroll 22 by means of deeply cutting out the circular hole 214 into the inner wall of the spiral element 212 of the fixed scroll 21. The circular hole 215 can be formed as well. A pair of valve plates (only one valve plate is shown in Figure 1 as valve plate 341) are attached by fasteners (not shown) to the rear end surface of the circular end plate 211. The valve plate 341 and the other valve plate are made of spring material so that the bias of the valve plate 341 and the other valve plate push them against a rear end opening of the hole 214 and the other hole to close hole. A pair of valve retainers (only one valve retainer is shown in Figure 1 as valve retainer 341a) which are associated with the valve plates function as well as a valve retainer 231a. The circular end plate 211 of the fixed scroll 21 also has a communicating channel 29 formed at an outer side portion of the terminal end of the spiral element 212. The communicating channel 29 is provided for communication between the suction chamber 271 and the intermediate pressure chamber 282. A control mechanism 36 controls fluid communication between the suction chamber 271 and the intermediate pressure chamber 282. A detail of the control mechanism 36 is described in U.S. '164 patent, which is considered in the section of the description of the prior art of this specification, so that an explanation thereof is omitted. An axial tip seal element 230 is disposed in a groove 213 which is located along the axial end of the spiral element 212 of the fixed scroll 21. A plurality of axial tip seal elements 240a, 240b and 240c are disposed in a plurality of grooves 223a, 223b, 223c, which are located along the axial end of the spiral element 222 of the orbiting scroll 22 in series, respectively. As illustrated in Figure 2, the axial tip seal elements 240a and 240b define a first spaced portion 241 at the axial end of the spiral element 222 of the orbiting scroll 22. The axial tip seal elements 240b and 240c define a second spaced portion 242 at the axial end of the spiral element 222 of the orbiting scroll 22. Therefore, the first and second spaced portions 241 and 242 are provided with no groove and no axial tip seal element. The first and second spaced portions 241 and 242 are positioned so as to cross over the circular holes 214 and 215 respectively during the orbital motion of the orbiting scroll 22. Accordingly, even when the diameters of the circular holes 214 and 215 are enlarged in order to prevent the undesirable pressure drop at the circular holes 214 and 215 in operation of the compressor in the high rotational speed, a bite of the axial tip seal element between the edge of the axial end of the spiral element 212 of the orbiting scroll 22 and the edge of the circular holes 214 and 215 can be prevented, thereby preventing damage of the axial tip seal element, such as cutting thereof. Therefore, controllability of the displacement adjusting mechanism of the compressor can effectively function in any compressor rotational speed without damage of the axial tip seal element. Though the axial tip seal element 204a, 204b and 204c define the first and second spaced portions 241 and 242 the axial sealing between the axial end surface of the spiral element 222 of the orbiting scroll 22 and the inner surface of the circular end plate 211 of the fixed scroll 21 can be negligibly spoiled. This invention has been described in detail in connection with the illustrated preferred embodiment. This embodiment, however, is merely for example only and the invention is not restricted thereto. It will be easily understood by those skilled in the art that other variations and modifications can be easily made within the scope of this invention, as defined by the appended claims.

Claims: A scroll type fluid compressor including a housing (10) having a fluid inlet port (31) and a fluid outlet port (32), a fixed scroll (21) fixedly disposed within said housing (10) and having an end plate (211) from which a first spiral wrap (212) extends into the interior of said housing (10), an orbiting scroll (22) having an end plate (221) from which a second spiral wrap (222) extends, said first and second wraps (221, 222) 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, displacement adjusting means including at least one pair of holes (214, 215) formed through said end plate (211) of one of said scrolls (21) to form a first fluid channel between the at least one pair of sealed off fluid pockets and the opposite side of said end plate (211) of said one scroll (21) from its respective wrap (212), characterized by at least three seal elements (240a, 240b, 240c) located along the axial end surface of at least of the wrap (222) of the other of said scrolls (22) in series, said at least three seal elements (240a, 240b, 240c) defining at least two spaced portions therebetween, said at least two spaced portions being positioned so as to cross over said at least one pair of holes (214, 215) during relative orbital motion of said scrolls (21, 22). A scroll type compressor according to claim 1, comprising a driving mechanism operatively connected to said orbiting scroll (22) to effect the orbital motion of said orbiting scroll (22), rotation preventing means (24) for preventing the rotation of said orbiting scroll (22) during orbital motion whereby the volume of the fluid pockets changes during orbital motion to compress the fluid in the pockets and the compressed fluid from a central fluid pocket (272) formed by said scrolls (21, 22) is discharged through an outlet aperture formed in one of said end plates (211, 221). A scroll type compressor according to claim 1 or 2, wherein said at least one pair of holes (214, 215) are circular. A scroll type compressor according to one of claims 1 to 3, said circular end plate (211) of said fixed scroll (21) dividing the interior of said housing (10) into a front chamber (27) and a rear chamber (28), said front chamber (27) communicating with said fluid inlet port (31), and said rear chamber (28) being divided into a discharge chamber (281) which communicates between said fluid outlet port (32) and the central fluid pocket (272), and an intermediate pressure chamber (282), said first fluid channel being formed between the fluid pockets and said intermediate pressure chamber (282), a communication channel formed through said end plate (211) of said fixed scroll (21) to form a second fluid channel between said intermediate pressure chamber (282) and said front chamber (27).

Inventors: MABE, ATSUSHI, MATSUDAIRA, YASUYUKI, Mabe, Atsushi, c/o Sanden Corporation, Matsudaira, Yasuyuki, c/o Sanden Corporation
Applicants: SANDEN CORPORATION
Application year: 1991
Main classification: F04C27
IPC codes: F04C18, F04C27