CA2046245C - Scroll type compressor with variable displacement mechanism - Google Patents

Abstract

A scroll type compressor with a variable displacement mechanism is disclosed which includes a housing 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 from which a first spiral wrap extends. An orbiting scroll also is mounted within the housing for orbital motion with respect to the fixed scroll. The orbiting scroll has an end plate from which a second spiral wrap extends. The first and second wraps interfit to define at least one pair of sealed off fluid pockets. The end plate of the fixed scroll partitions the inner chamber of the housing into a suction chamber and rear chamber. The rear chamber includes an intermediate pressure chamber which communicates with the sealed off fluid pockets through a pair of circular holes formed at the end plate of the fixed scroll. A control mechanism controls fluid communication between the intermediate pressure chamber and the suction chamber. A plurality of seal elements are sequentially located along the axial end of the second wrap such that the spaces between the seal elements cross over the circular holes during orbital motion of the orbiting scroll. Thereby, the diameter of the circular holes may be enlarged to prevent constriction of the flow of fluid through the holes during high rotational operation of the compressor, without increasing the possibility of damaging the seal elements due to the seal elements being sandwiched between the spiral wrap and the holes.

Description

CA 0204624~ l997-l2-24 SCROLL TYPE COMPRESSOR WITH VARL~BLE
DISPLACEMENT MECHANISM
BACKGROUND OF THE INVENTION
Field of the Invention The present invention relates to a scroll type compressor, and in particular, to a scroll type co~ ressor with a variable displacement mech~ni~m Description of the Prior Art Scroll type fluid displacement apparatuses are known int he prior art.
For example, U.S. Patent No. 801,182 to Cruex 10 discloses a scroll apparatus which inrl~ldes two scrolls, each having a circular end plate and a spiroidal or involute spiral element extending from the end plates. The scrolls are m~int~ined ~n~ rly 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 increased or decreases, depending upon the direction of the orbital motion.
Thus, a scroll type fluid displacement apparatus may be used to compress, expand or pump fluids.
When conventional scroll type coll~lessors are used in automobile air conditioners, these compressors usually are driven by the automobile engine through an electromagnetic clutch. In such automobile air conditioners, when capacity control mech~ni~m~ are not provided for the colllplessors, thermal control of the passenger compartment or control of the air conditioner is generally accomplished by intermittent operation of the compressor through engagement of the electromagnetic clutch. Although the energy required for m~int~ining the passenger colllpalllllent at the desired temperature may not be large once the desired temperature is initially achieved, a relatively large D~1:31828 ~ CA 0204624~ 1997-12-24 force is required to drive the co~ ressor during the initial intermittent operation thereof, and to a lesser extent, upon each subsequent actuation of the compressor. This intermittent operation consumes large amounts of energy.
It is known to provide a scroll type compressor with a displacement or volume adjusting mech~ni~m to control the col~ression ratio as operation demands. For example, as disclosed in U.S. Patent No. 4,904,164 issued on February 27, 1990, to Atsushi Mabe et al., A variable di$placement mech~ni.~m for controlling the 10 compression ratio includes a pair of holes formed through the end plate of one of the scrolls. The pair of holes provides fluid communication between intermediate fluid pockets formed between the spiral elements and located on one side of the end plate, and an intermediate pressure chamber which is located on the opposite side of the end plate. Flow of the fluid through the 15 holes is controlled by valve plates which cover the holes. The intermediate pressure chamber is linked by a communication channel with the suction chamber. The opening and closing of the communication channel is controlled by a valve control meçh~ni~m in response to the suction pressure. The compressor also includes an axial tip seal element disposed in a groove formed 20 along the axial end of each of the spiral elements. The tip seals m~int~in the axial sealing between the axial end surface of the spiral element of each scrolland the inner surface of the end plate of the other scroll.
During compressor operation, at high suction pressure, the communication channel is closed by the valve control m~rh~nicm Fluid 25 compressed to the intermediate pressure level corresponding to the intermediate fluid pockets, flows into the intermediate pressure chamber and raises the pressure therein until it is equal to the pressure in the intermediate D~1:31828 CA 0204624~ l997-l2-24 pockets, thereby c~-lcing the valve plates to close the holes and prevent further flow. In this situation, since no further fluid may escape from the fluid pockets before being forced into the discharge chamber, the displacement volume or compression ratio of the colllpressor is m~Yimllm When the suction pressure is reduced, for example, as the demand on the system decreases, the communication ch~nn~l is opened by the valve control mech~ni~m, linking the intermediate pressure chamber with the suction chamber and thereby reducing the pressure in the intermediate pressure chamber. Accordingly, the valve plates are opened, and fluid flows from the 10 intermediate fluid pockets to the intermediate pressure chamber thought the pair of circular holes, and back to the suction chamber through the communication channel. In this situation, since a portion of the fluid escapes from the fluid pockets before being forced into the discharge chamber, the displacement volume is minimllm The pressure in the intermediate pressure chamber is varied in a range from the suction pressure to the predetermined intermediate pressure which ~revell~s communication between the sealed-off fluid pockets and the intermediate pressure chamber. This variance is controlled in accordance with the opening and closing of the link between the interme~ ted pressure 20 chamber and suction chamber, which is itself dependent upon the suction pressure. Thus, the compression ratio of the compressor, which depends upon whether the fluid in the pockets escapes back to the suction chamber, is controlled in a range from the m~ximllm value, that is, 100~o, to a predetermined minim~lm value, for example, 305to, generally in dependence 25 upon the suction ~res~ule.
However, if the compressor is operating at a high rotational speed while the compression ratio is being adjusted to equal the minimllm value, that is, D~1:31828 CA 0204624~ l997-l2-24 when the co,lul,ul~ication channel is opened, the obtainable minimllm value of the compression ratio is undesirably increased above the predetermined minim~lm value since the pressure drop of the fluid as it flows through the pairof circular holes is not negligible due to the extreme increase in flow rate of 5 the fluid as it passes through the pair of circular holes. In other words, theflow of fluid though the holes is restricted by the size of the holes, which is not large enough to accommodate the sudden increase in flow rate when the communication channel is opened, c?~llcing a greater than desired quantity of fluid to remain in the fluid pockets and be col,l~ressed. Accordingly, the 10 effectiveness of the displacement control provided by the displacement adjusting mech~ni~m is ~limini~hed, particularly during operation of the compressor at high rotational speeds.
In order to resolve the above~ -c~e~l drawback, the radius of the pair of circular holes can be enlarged so as to be slightly smaller than the thickness 15 of the spiral elements. Thus, the pressure drop through the pair of circular holes may be reduced to a negligible value. However, during orbital motion, certain portions of the tip seal on one of the spiral elements will repeatedly pass over the circular holes. These portions of the tip seal will tend to be bent into the circular holes due to the plessùre differential and the fact that the 20 support provided behind the tip seal is reduced when enlarged holes are used.As a result, these portions of the axial tip seal element tend to be sandwiched between the edge of the axial end of the spiral element and an edge of the circular hole c~llsin~ damage thereto, for example, the tip seal may be cut.
Damaged tip seals reduce the efficiency of the compressor and possibly impair 25 proper functioning, altogether.

DC01:31828 CA 0204624~ 1997-12-24 SUMMARY OF THE INVENTION
The present invention is directed to a scroll type fluid compressor including a housing having a fluid inlet port and a fluid outlet port. A fixed scroll is fixedly disposed within the housing and has an end plate from which 5 a first spiral wrap extends into the interior of the housing. An orbiting scroll has an end plate from which a second spiral wrap extends. The first and second wraps interfit at an ~n~ r and radial offset to form a plurality of line contacts which define at least one sealed-off fluid pocket. The co~ ressor further includes an outlet aperture formed through the end plate of one of the 10 scrolls. A driving meçh~ni~m is operatively connected to the orbiting scroll to effect the orbital motion of the orbiting scroll whereby the volume of the fluidpockets change during orbital motion to conl~less the fluid in the pockets with the compressed fluid discharged though the outlet aperture. A displacement adjusting means includes at least one hole formed through the end plate of one 15 of the scrolls to form a first fluid channel between the at least one sealed-off fluid pocket and the opposite side of the end plate of the one scroll. A
plurality of seal elements are sequentially disposed along the axial end surfaceof the wrap of the other of the scrolls, with the plurality of seal elements defining at least one spaced portion therebetween on the axial end surface.
20 The spaced portion is positioned so as to cross over the hole during relative orbital motion of the scrolls.
In a further embodiment the colllpressor in~h~des two fluid pockets and two holes forming the first fluid channel. The plurality of seal elements includes three seal elements defining two spaced portions on the axial end 25 surface, with each spaced portion positioned to cross over the holes.

DC01:31828 CA 0204624~ l997-l2-24 In a further embodiment the holes and fluid pockets are positioned in pairs such that the spaced portions simlllt~neously cross over the holes during relative orbital motion of the scrolls.
Accordingly, since no portion of the tip seals of the orbiting scroll 5 crosses over the holes, the diameter of the holes may be enlarged in order to prevent the undesirable constriction of flow therethrough, without increasing the possibility of d~m~ging the tip seal. Therefore, the present invention has the advantage of allowing the displacement adjusting mech~ni~m to more effectively control the compression ratio at any rotational speed, without 10 increasing the possibility that the tip seal element will be damaged.
Various additional advantages and features of novelty which characterize the invention are further pointed out in the claims that follow.
However, for a better underst~n~ling 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 longit~ltlin~l sectional view of a scroll type compressor with a variable displacement mech~ni~m in accordance with a preferred embodiment of this invention.
Figure 2 is a schematic horizontal perspective view of the scroll type compressor of Figure 1, as viewed from the right side in Figure 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to Figure 1, a scroll type co~ ressor according to the present invention is shown. The scroll type co~ ressor in~ ldes compressor housing 10 having front end plate 11 and cup-shaped casing 12 attached to front end plate 11. Opening 111 is formed through the center of front end plate 11 and drive shaft 13 is disposed in opening 111. Annular projection 112 projects D~1:31828 CA 0204624~ l997-l2-24 .

rearwardly from front end plate 11. Annular projection 112 faces cup-shaped casing 12 and is concentric with opening 111. An outer peripheral surface of projection 112 extends into opening 121 of cup-shaped casing 12. Opening 121 of cup-shaped casing 12 is covered by front end plate 11. O-ring 14 is disposed 5 between the outer peripheral surface of ~nn~ r projection 112 and an inner wall of opening 121 of cup-shaped casing 12 to seal the mating surface of front end plate 11 and cup-shaped casing 12.
Annular sleeve 16 longitlltlin~lly projects from the front end surface of front end plate 11, and defines shaft seal cavity 161. Drive shaft 13 is disposed 10 though sleeve 16 which surrounds and rotatably supports drive shaft 13 through bearing 17 located within the front end of sleeve 16. Drive shaft 13 inclll~les disk-shaped rotor 131 formed on its inner end. Rotor 131 is rotatably supported in opening 111 of front end plate 11 though bearing 15. Shaft seal assembly 18 is coupled to drive shaft 13 within shaft seal cavity 161 of ~nnlll~r 15 sleeve 16.
Pulley 201 is rotatably supported by ball bearing 19 which is disposed about the outer peripheral surface of ~nn~ r sleeve 16. Electromagnetic coil 202 is fixed about the outer surface of ~nmll~r sleeve 16 by support plate 204.
Coil 202 is disposed within the inner and outer surfaces of pulley 201. Support 20 plate 204 is fixed to sleeve 16 by a snap ring, and supports coil 202 so as to allow pulley 201 to freely rotate with respect thereto. Armature plate 203 is elastically supported on the outer end of drive shaft 13 in a known manner.
Pulley 201, electromagnetic coil 202 and armature plate 203 form electromagnetic clutch 20. When a current is provided to coil 202, plate 203 25 is attracted into contact with the axial surface of pulley 201, and rotational motion is transferred from pulley 201 to drive shaft 13. In operation, drive shaft 13 is driven by an external power source, for exarnple, the engine of an D~1:31828 CA 0204624~ l997-l2-24 automobile, through a rotation tra~ llilling device such as electromagnetic clutch 20.
Fixed scroll 21, orbiting scroll 22 and rotation preventing/thrust bearing mech~ni~m 24 are disposed in the interior of housing 10. Fixed scroll 21 5 includes circular end plate 211 and spiral element 212 affixed to or integrally 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. Circular end plate 211 of fixed scroll 21 in~nl~tingly partitions the inner chamber of 10 cup-shaped casing 12 into two chambers, front charnber 27 and rear chamber 28. Front chamber 27 inclllcles suction chamber 271. O-ring 123 is disposed between an outer peripheral surface of circular end plate 211 and an inner peripheral wall of cup-shaped casing 12 to increase the in~ul~tion between front chamber 27 and rear chamber 28. Spiral element 212 of fixed scroll 21 15 is located within front chamber 27. Front chamber 27 is linked to an element of an external fluid circuit such as an air-conditioning system through inlet opening 31 formed through casing 12.
Wall 122 longitu(lin~lly projects from the inner rear end surface of cup-shaped casing 12 and divides rear chamber 28 into discharge chamber 281 and 20 intermediate pressure chamber 282. The axial end surface of wall 122 contracts the rear end surface of circular end plate 211. Discharge chamber 281 is linked to an external element of the air conditioning system through outlet 32 formed through the rear end surface of casing 12.
Orbiting scroll 22 is located in front chamber 27 and includes circular 25 end plate 221 and spiral element 222 extending from one end surface of circular end plate 221. Spiral element 222 of orbiting scroll 22 and spiral element 212 of fixed scroll 21 interfit at an ~n~ r offset of appr- xi~ tely 180~

D~1:31828 CA 0204624~ l997-l2-24 and a predetermined radial offset to form sealed spaces or fluid pockets between spiral element 212 and 222. Bushing 23 is supported on a pin which projects from the rear end of disc-shaped portion 131 of drive shaft 13. The pin is offset from the axis of drive shaft 13 such that bushing 23 is eccentric 5 with respect to drive shaft 13. Orbiting scroll 22 is supported on bushing 23 through radial needle bearing 30. Rotation of drive shaft 13 is converted into orbiting motion of orbiting scroll 22 through the projecting pin and bushing 23.Rotation of orbiting scroll 22 is prevented by convenlional rotation preventing/thrust bearing m~rh~ni~m 24 which is disposed between ~nmll~r 10 projection 112 of front end plate 11 and circular end plate 221 of orbiting scroll 22.
A plurality of line contacts are formed between the walls of the spiral elements to form the fluid pockets between the scrolls. As the orbiting scroll orbits with respect to the fixed scroll, the line contacts move along the spiral15 elements, casing the volume of the fluid pockets to be decreased, and the pockets to moved until they open into central fluid pocket 272. Central fluid pocket 272 also undergoes co,lll)ression as well.
Refrigeration fluid from the external fluid circuit is introduced into suction chamber 271 through inlet port 31 and flows into the outer fluid 20 pockets formed between spiral elements 212 and 222 through open spaces between the spiral elements. The outer fluid pockets between the spiral elements sequentially open and close during the orbital motion of orbiting scroll ~. When the outer fluid pockets are open, fluid to be compressed flows into the pockets but no compression occurs. When the pockets are closed, no 25 additional fluid flows into the pockets and colllpression begins. Since the location of the outer terminal ends of spiral elements 212 and 222 is at a finalinvolute angle, the location of the pockets is directly related to the final DC01:31828 CA 0204624~ l997-l2-24 involute angle. As orbiting motion contin~les, the refrigeration fluid in the sealed pockets is moved along the walls of the spiral elements and is compressed as the volume of the pockets is decreased.
The compressed refrigeration fluid llltim~tely flows into central pocket 5 272 and is discharged into discharge chamber 281 through discharge aperture or port 213 which is formed at the center of circular end plate 211. Valve plate 231 of spring material is disposed on discharge port 231 and the compressed fluid is pushed pass valve plate 231 by virtue of a pressure difference between the central pocket and the discharge ch~mber. Damage or 10 deformation of valve plate 231 is prevented by valve retainer 231a which receives valve plate 231 to prevent excessive bending thereo~
Referring to Figure 2, 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 surface of spiral element 222 of orbiting scroll 22 15 generally simultaneously crosses over both holes. Holes 214, 215 communicate between intermediated fluid pockets 273 and intermediate pressure chamber 282. The radius of each of holes 214, 215 is designed so as to be slightly smaller than the thickness of the spiral elements. Circular hole 214 opens along the inner side wall of spiral element 212. Circular hole 215 opens along 20 the outer side wall of spiral element 212. Both circular hole are formed by deeply cutting the holes into the wall of spiral element 212 of fixed scroll 21.Therefore, when the radially outer wall of spiral element 222 of orbiting scroll22 contacts the radially inner wall of spiral element 212 of fixed scroll 21 at the location of circular holes 214, the circular hole is entirely covered by the axial 25 end of spiral element 222 of orbiting scroll 22. Similarly, hole 215 is covered as well since the inner wall of element 2~ contacts the outer wall of element 212.

D~1:31828 . CA 0204624~ 1997-12-24 A pair of valve plates 341 (only one valve plate is shown in Figure 1) are attached by fasteners (not shown) to the rear end surface of circular end plate 211. Valve plates 341 are made of spring material so that the bias of valve plate 34 pushes them against a rear end opening of holes 214 and 215 to 5 close each hole. A pair of valve retainers 341a (only one valve retainer is shown in figure 1) are associated with the valve plates and function to prevent excessive bending or deforrnation as discussed with respect to valve retainer 231a.
Circular end plate 211 of fixed scroll 21 also includes communicating 10 channel 29 formed at an outer side portion of the terminal end of spiral element 212. Communication ch~nnel 29 provides communication between suction chamber 271 and irltermediate pressure chamber 282. Control mesh~ni~m 36 controls fluid co~w,ication between suction chamber 271 and intermediate pressure chamber 282, and thus between the intermediate fluid 15 pockets and the suction chamber, to vary the compression ratio of the compressor as discussed above with reference to aforementioned U.S. Patent No. 4,904,164.
A complete description of the operation of control mech~ni~m 36 also is providedin the '164 patent.
Axial tip seal element 230 is disposed in groove 213 which is formed to 20 extend 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, respectively, which are sequentially located along the axial end of spiral element 222 of orbiting scroll 22. As illustrated in Figure 2, first spaced portion 241 is defined between axial tip seal elements 25 240a and 240b on the axial end of spiral element 222 of orbiting scroll 22.
Second spaced portion 242 is defined between axial tip seal elements 240b and 240c on the axial end of spiral element 222 of orbiting scroll 22. The axial DC01:31828 CA 0204624~ l997-l2-24 surface of spiral element 222 is not provided with a groove at the location of first and second spaced portions 241 and 242. First and second spaced portions 241 and 242 are located so as to cross over circular holes 214 and 215, respectively, during the orbital motion of orbiting scroll 22.
Accordingly, since no portion of the tip seals of the orbiting scroll cross over the circular holes, the diameter of circular holes 214 and 215 may be enlarged in order to prevent the undesirable constriction of flow therethrough and corresponding pressure drop during operation of the compressor at high rotational speeds, without experiencing the drawback of having the axial tip 10 seal element becoming sandwiched between the edge of the axial end of spiral element 222 and the edge of circular holes 214 and 215. Thus, the possibility of ~l~m~ging the axial tip seal elements, such as by cutting thereof, is precluded. Therefore, the effectiveness of the displacement adjusting meçh~ni~m in controlling the col"pression ratio at any rotational speed is 15 increased without increasing the possibility that the tip seal element will be damaged. In fact, the provision of spaced portions 241 and 242 reduces the chance of damage even if the circular holes are not enlarged. Finally, the effectiveness of the sealing between the axial end surface of spiral element 222or orbiting scroll 22 and the inner surface of circular end plate 211 of fixed 20 scroll 21 which is provided by the use of axial tip seal elements 204a, 240b and 240c is only negligibly decreased as compared with the use of only one tip seal.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 25 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.

D~1:31828

Claims (8)

1. In a scroll type fluid compressor including a housing having a fluid inlet port and fluid outlet prot, a fixed scroll fixedly disposed within said housing and having an end plate from which a first spiral wrap extends into the interior of said housing, an orbiting scroll having an end plate from which a second spiral wrap extends, said first and second wraps interfitting at an angular and radial offset to form a plurality of line contacts which define at least one sealed-off fluid pocket, an outlet aperture formed through the end plate of one of said scrolls, a driving mechanism operatively connected to said orbiting scroll to effect the orbital motion of said orbiting scroll whereby thevolume of the fluid pocket changes during orbital motion to compress the fluid in the pocket with the compressed fluid discharged through said outlet aperture, a displacement adjusting means including at least one hole formed through the end plate of said one of said scrolls to form a first fluid channel between said at least one sealed-off fluid pocket and the opposite side of said end plate of said one of said scrolls, the improvement comprising:
a plurality of seal elements sequentially disposed along the axial end surface of the wrap of the other of said scrolls, said plurality of seal elements defining at least one spaced portion therebetween on said axial end surface, said at least one spaced portion positioned so as to cross over said at least one hole during relative orbital motion of said scrolls.

2. The compressor recited in claim 1, said at least one fluid pocket comprising two fluid pockets, said at least one hole comprising two holes forming said first fluid channel, said plurality of seal elements comprising three seal elements defining two spaced portions on said axial end surface, each spaced portion positioned to cross over one of said holes.

3. The compressor recited in claim 2, said holes and said fluid pockets positioned in pairs such that said spaced portions simultaneously cross over said holes during relative orbital motion of said scrolls.

4. The compressor recited in claim 2, said end plate of said fixed scroll dividing the interior of said housing into a front chamber and a rear chamber, said front chamber communicating with said fluid inlet port, and said rear chamber divided into a discharge chamber which communicates with said fluid pockets through said aperture and said fluid outlet port, and into an intermediate pressure chamber, said first fluid channel linking the fluid pockets and said intermediate pressure chamber, and a communication channel formed through said end plate of said fixed scroll to form a second fluid channel having a control mechanism between said intermediate pressure chamber and said front chamber.

5. The compressor recited in claim 4, said holes comprising circular holes.

6. The compressor recited in claim 2 further comprising a suction chamber formed on the same side of said end plate of said one scroll as said spiral wrap of said one scroll and an intermediate pressure chamber formed on the opposite side of said end plate of said one scroll, said first fluid channel linking said intermediate pressure chamber with said at least one fluid pocket, said displacement adjusting means further comprising a suction responsive valve means for controlling the communication link between said intermediate pressure chamber and said suction chamber.

7. The compressor recited in claim 1 further comprising rotation preventing means for preventing the rotation of said orbiting scroll around a longitudinal axis of said driving mechanism during orbital motion.

8. The scroll type compressor recited in claim 1, said hole comprising a circular hole.