AU634895B2 - Scroll type compressor with variable displacement mechanism - Google Patents

Description

1 634895 S F Ref: 185347

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

6g S @59 Sn *c C Name and Address of Applicant: Actual Inventor(s): Address for Service: Invention Title: eo* Sanden Corporation Kotobuki-cho, Isesaki-shi Gunma 372

JAPAN

Yasuyuki Matsudaira and Atsushi Mabe Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia Scroll Type Compressor With Variable Displacement Mechanism ol e The following statement is a full description of this invention, including the best method of performing it known to me/us:- 5845/5 SCROLL TYPE COMPRESSOR WITH VARIABLE DISPLACEMENT MECHANISM BACKGROUND OF THE INVENTION Field Of The Invention 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.

Description Of The Prior Art 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 i to thereby seal off and define at least one pair of fluid pockets. The relative orbital motion of the two scrolls shifts the S: 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 auto- S mobile air conditioners, these compressors usually are driven by the automobile engine through an electromagnetic (;lu7ch. 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, at 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 #co oi 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, S 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, 100 to the predetermined minimum value, 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 S of circular holes can be enlarged within the value, which is •e o S 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.

SUMMARY OF THE INVENTION 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 i includes a housing having an inlet port and an outlet port. A fixed scroll is disposed within the housing and has a circular end plate from which a first spiral element extends. An orbiting o scroll having a circular end plate from which a second spiral element extends is placed on a drive shaft. The two spiral elements interfit at an angular and radial offset to form a plurality of line contacts and to define at least one pair of fluid pockets within the interior of the housing.

The housing includes mechanisms for driving the orbiting scroll and for preventing rotation of the orbiting scroll. A driving mechanism is operatively connected to the orbiting scroll to effect orbital motion of the orbiting scroll and to change the volume of the fluid pockets during orbital motion. A rotation preventing mechanism prevents rotation of the orbiting scroll.

The circular end plate of the fixed scroll divides the interior of the housing into a front chamber and a rear chamber.

The front chamber communicates with the inlet port. The rear chamber is divided into a discharge chamber which communicates with the outlet port and a central fluid pocket formed by both scrolls, and an intermediate pressure chamber. At least one pair of circular holes are formed through the circular end plate of the fixed scroll to form a first fluid channel between the fluid pockets and the intermediate pressure chamber. A communicating channel formed through the circular end plate of the fixed scroll provides a second fluid channel between the intermediate pressure chamber and the front chamber. A communication control mechanism controls the communication of the second fluid channel.

At least three seal elements locate along the axial end S surface of the second spiral element of the orbiting scroll in series. The at least three seal elements define at least two spaced portions therebetween. The at least two spaced portions are positioned so as to cross over the at least one pair of circular holes during relative orbital motion of the scrolls.

Various additional advantages and features of novelty which o 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.

BRIEF DESCRIPTION OF THE DRAWINGS 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.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 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 front end plate 11 and drive shaft 13 is disposed in opening 11. An annular projection 112 is formed in a rear surface of front end plate 11. Annular projection 112 faces cup-shaped casing 12 and oloo•2 is concentric with opening 111. An outer peripheral surface of projection 112 extends into an inner wall of opening 121 of cupshaped casing 12. Opening 121 of cup-shaped casing 12 is covered by front end plate 11. An 0-ring 14 is placed between the outer o• peripheral surface of annular projection 112 and an inner wall of S" opening 121 of cup-shaped casing 12 to seal the mating surface of front end plate 11 and cup-shaped casing 12.

S• An annular sleeve 16 longitudinally projects from a front end surface of front end plate 11, surrounds drive shaft 13, and defines a shaft seal cavity 161.

Drive shaft 13 is rotatably supported by annular sleeve 16 through a bearing 17 located within the front end of sleeve 16.

Drive shaft 13 has a disk-shaped rotor 131 at its inner end which is rotatably supported by front end plate 11 through a bearing located within opening 111 of front end plate 11. A shaft seal assembly 18 is coupled to drive shaft 13 within 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 annular sleeve 16. An electromagnetic coil 202 is fixed about the outer surface of annular sleeve 16 by a support plate 204. An armature plate 203 is elastically supported on the outer end of drive shaft 13. Pulley 201, electromagnetic coil 202 and armature plate 203 form an electromagnetic clutch 20. In operation, d-ive shaft 13 driven by an external power source, for example, the engine of an automobile, through a rotation transmitting device such as electromagnetic clutch A fixed scroll 21, an orbiting scroll 22 and a rotation preventing/thrust bearing mechanism 24 for orbiting scroll 22 are *f Soe disposed in the interior of housing g Fixed scroll 21 includes a circular end plate 211 and spiral element 212 affixed to or extending from one end surface of circular end plate 211. Fixed scroll 21 is fixed within the inner chamber of cup-shaped casing 12 by screws (not shown) screwed into end plate 211 from the outside of cup-shaped casing 12. An 0-ring 123 is disposed between an outer peripheral surface of circular end plate 211 and an inner peripheral wall of cup-shaped casing 12. Therefore, circular end plate 211 of fixed scroll 21 insulatingly partitions te inner chamber of cup-shaped casing 12 into two chambers, a front chamber 27 and a rear chamber 28. Spiral element 212 of fixed scroll 21 is located within front chamber 27.

A wall 122 longitudinally projects from the inner end surface of cup-shaped casing 12 to divide 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 circular end plate 211.

Orbiting scroll 22, which is located in front chamber 27, includes a circular end plate 221 and a spiral element 222 extending from one eid surface of circular end plate 221. Spiral element 222 of orbiting scroll 22 and spiral element 212 of fixed scroll 21 interfit at an angular offset of approximately 180 and a predetermined radial offset, form sealed spaces between spiral element 212 and 222. Orbiting scroll 22 is rotatably supported busing 23, which is eccentrically connected to the inner end of disc-shaped portion 131, through a :r^dial needle bearing While orbiting scroll 22 orbits, rotation of orbiting scroll 22 is prevented by a rotation preventing/thrust bearing mechanism 24 which is placed between the rear end surface of front end plate 11 and circular end plate 221 of orbiting scroll 22.

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 inlet port 31 and flows into sealed spaces formed between 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 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 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 orbiting scroll 22. Compressed refrigeration fluid at center sealed space 272 is discharged to discharge chamber 281 past valve plate 231 of spring material through discharge port 213 which is formed at the center of circular end plate 211. When valve plat- 231 is pushed by virtue of a pressure difference, valve retainer 231a receives valve plate 231 to prevent excessive bending of valve plate 231. Excessive bending of valve S plate 23i can cause damage to valve plate 231.

Raferring to Figure 2 additionally, a pair of circular holes 214 and 215 are formed in circular end plate 211 of fixed scroll 21 and are generally symmetrically placed so that an axial end Ssurface of spiral element 222 of orbiting scroll 22 generally simultaneously crosses over both holes. Holes 214, 215 communicate between intermediate sealed space 273 and intermediate pressure chamber 282. A radius of each of holes 214, 215 is designed so as to be slightly smaller than thickness of the spiral elements. Circular hole 214 opens along the inner side wall of spiral element 212. Circular hole 215 opens along the outer side wall of spiral element 212. Therefore, for instance, when the outer wall of spiral element 222 of orbiting scroll 22 contacts the inner wall of spiral element 212 of fixed scroll 21 at the location of the circular hole 214 a part of circular hole 214 formed at circular end plate 211 of fixed scroll 21 can be entirely covered by the axial end of spiral element 222 of orbiting scroll 22 by means of deeply cutting out circular hole 214 into the inner wall of spiral element 212 of fixed scroll 21. 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 circular end plate 211. Valve plate 341 and the other valve plate are made of spring material so that the bias of valve plate 341 and the other valve plate push them against a rear end opening of hole 214 and the other hole to close each 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 valve retainer 231a.

.oeooi S"Circular end plate 211 of fixed scroll 21 also has communicating channel 29 formed at an outer side portion of the terminal end of spiral element 212. The communicating channel 29 is provided for communication between a suction chamber 271 and intermediate pressure chamber 282. A control mechanism 36 controls fluid communication between suction chamber 271 and intermediate pressure chamber 282. A detail of 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.

Axial tip seal element 230 is disposed in groove 213 which is located along the axial end of spiral element 212 of fixed scroll 21. A plurality of axial tip seal elements 240a, 240b and 240c are disposed in a plurality of grooves 223a, 223b and 223c, which are located along the axial end of spiral element 222 of orbiting scroll 22 in series, respectively. As illustrated in Figure 2, axial tip seal elements 240a and 240b define first spaced portion 241 at the axial end of spiral element 222 of orbiting scroll 22. Axial tip seal elements 240b and 240c define second spaced portion 242 at the axial end of spiral element 222 of orbiting scroll 22. Therefore, first and second spaced portions 241 and 242 are provided with no groove and no axial tip seal element. First and second spaced portions 241 and 242 are positioned so as to cross over circular holes 214 and 215 respectively during the orbital motion of orbiting scroll 22.

Accordingly', even when the diameter of circular holes 214 S and 215 are enlarged in order to prevent the undesirable pressure drop at circular holes 214 and 215 in operation of the compressor in the high rotational speed, a bite of the axial lip seal element between the edge of the axial end of spiral element 212 of orbiting scroll 22 and the edge of 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 effec-, tively function in any compressor rotational speed without damage S of the axial tip seal element.

Though axial tip seal element 204a, 240b and 240c define first and second spaced portions 241 and 242, the axial sealing between the axial end surface of spiral element 222 of orbiting scroll 22 and the inner surface of circular end plate 211 of 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.

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Claims (3)

1. 2. A scroll type compressor according to claim 1 wherein the holes of said at least one pair of holes are circular.
2. 3. A scroll type compressor according to claim 1, said end plate said fixed scroll being circular and dividing the interior of said 30 housing into a front chamber and a rear chamber, said front chamber communicating with said fluid inlet port, and said rear chamber being divided into a discharge chamber which communicates between said fluid outlet port and the central fluid pocket, and an intermediate pressure chamber, said first pair of fluid channels being formed between the fluid S• 35 pockets and said intermediate pressure chamber, a communication channel formed through said end plate of said fixed scroll to form a second fluid •channel between said intermediate pressure chamber and said front chamber. v -13 ,LF/1782h
3. 4. A scroll type compressor according to claim 3 wherein the holes of said at least one pair of holes are circular. A scroll type compressor substantially as hereinbefore described with reference to the accompanying drawings. DATED this TWENTY-SECOND day of DECEMBER 1992 Sanden Corporation Patent Attorneys for the Applicant SPRUSON FERGUSON r c o 14 A"i tLF/1782h ABSTRACT OF THE DISCLOSURE 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 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 (10) for orbital motion with respect to the fixed scroll The orbiting scroll (22) has an end plate (221) from which a second spiral wrap (222) extends. The first and second wraps (212,222) interfit to define at least one pair of sealed off fluid pockets. The end plate (211) of the fixed scroll (21) partitions the inner chamber of the housing (10) into a suction chamber (27) and rear chamber The rear chamber (28) includes an intermediate press-ure chamber (282) which communicates with the sealed off fluid pockets through a pair of circular holes (214,215) formed at the end plate (211) of the fixed scroll A control mechanism controls fluid communication between the intermediate pressure chamber (282) and the suction chamber A plurality of seal elements (230) located along the axial end of the second wrap (212) are spaced by the certain portions which are positioned so as to cross over the circular holes (214,215) during orbitl motion of the orbiting scroll Thereby, even when the diameter of the circular holes (214,215) are enlarged to prevent the undesirable pressure drop at the circular holes (214,215) in the compressor high rotational speed, damage of the seal elements (230) can be prevented. Fig. 1