Wear-resisting means for scroll-type fluid-displacement apparatuses

This invention relates to scroll type fluid displacement apparatus.

Scroll type apparatus are well known in the prior art. For example U.S. Patent No. 801,182 discloses a scroll type apparatus including two scroll members each having a circular end plate and a spiroidal or involute spiral element. These scroll members are maintained angularly and radially offset so that both spiral elements interfit to make a plurality of line contacts between both spiral curved surfaces, thereby sealing off and defining at least one pair of fluid pockets. The relative orbital motion of the two scroll members shifts the line contacts along the spiral curved surfaces to change the volume of the fluid pockets. Since the volume of the fluid pockets increases or decreases, dependent on the direction of the orbiting motion, the scroll type apparatus is applicable to compress, expand or pump fluids.

In comparison with conventional compressors of the piston type, the scroll type compressor has certain advantages, such as fewer parts and continuous compression of fluid. However, one of the problems with scroll type compressors is the ineffective sealing of the fluid pockets. Axial and radial sealing of the fluid pockets must be maintained in a scroll type compressor in order to achieve efficient operation. The fluid pockets are defined by the line contacts between the interfitting two spiral elements and the axial contacts between the axial end surface of one spiral element and the inner end surface of the end plate supporting the other spiral element.

Various techniques have been used in the prior art to resolve the sealing problem, in particular, the axial sealing problem. In U.S. Patent No. 3,334,635, a seal element is mounted on the axial end surface of each spiral element. The end surface of each spiral element facing the end plate of the other scroll member is provided with a groove along the spiral. The seal element is placed within each of the grooves together with an axial force urging means, such as a spring. The axial force urging the seal element toward the facing end surface of the end plate to thereby effect the axial sealing.

Because the seal element inthe above patent is urged toward the facing end surface of the end plate by a spring or other axial force urging mechanism, over a period of time, abrasions occur between the end surface of the seal element and the end plate of the scroll member, especially when light weight alloys, such as aluminum alloys, are used as material of the spiral element. These abrasions cause the occurrence of wear dust, which, in turn, not only creates damages on the parts of the apparatus, for example, the surface of the scroll members and the gearings, but also adversely affects the operation of the filter and expansion valve for the refrigerant circuit. When the end plate wears due to abrasion, the seal elements are also damaged, and the axial contact between the end surface of spiral element and the inner end surface of the end plate becomes imperfect, thereby reducing compressor efficiency.

It is an object of this invention to provide a scroll type fluid displacement apparatus, particularly a scroll type fluid compressor wherein the axial contact and axial sealing between the spiral element and the end plate is improved.

It is still another object of this invention to provide a scroll type fluid displacement apparatus having an axial sealing device which prevents wear or damages to the scroll member.

According to the present invention there is provided a scroll type fluid displacement apparatus including a pair of scroll members each having an end plate and a spiral wrap extending from one side of said end plate, said spiral wraps interfitting at an angular and radial offset to make a plurality of line contacts between the spiral curved surfaces which define fluid pockets, and drive means operatively connected to one of said scroll member for orbiting said one scroll member relative to the other scroll member while preventing rotation of said one scroll member to thereby change the volume of the fluid pockets, wherein an anti-wear plate is disposed on an end surface of said end plate of at least one of said scroll members, said anti-wear plate facing the axial end surface of said spiral wrap of the other of said scroll members to prevent wear and maintain axial sealing.

According to the invention there is also provided a scroll type fluid displacement apparatus comprising:

• a housing having a fluid inlet port and fluid outlet port;
• a fixed scroll member fixedly disposed relative to said housing and having an end plate from which a first spiral wrap extends into the interior of said housing;
• an orbiting scroll member having an end plate from which a second spiral wrap extends, said first and second spiral wraps interfitting at an angular and radial offset to make a plurality of line contacts defining at least one pair of sealed off fluid pockets, said fixed and orbiting scroll members being formed of aluminum and at least one of said scroll members having a hardened. surface;
• a driving mechanism including a drive shaft rotatably supported by said housing to effect the orbital motion of said orbiting scroll member by the rotation of said drive shaft to thereby change the volume of said fluid pockets; and
• an anti-wear plate mounted on said end plate of at least the other of said scroll members, said anti-wear plate facing the hardened axial end surface of said spiral wrap of said one scroll member to prevent wear and maintain axial sealing.

One embodiment of the invention is a scroll type fluid displacement apparatus which includes a pair of scroll members, each comprising an end plate and a spiral wrap extending from one side of the end plate. Both spiral wraps interfit to make a plurality of line contacts between the spiral curved surfaces of the spiral wraps. These spiral wraps are angularly and radially offset. A driving mechanism includes a drive shaft which is rotatably supported by a housing and operatively connected to one of the scroll members to cause the one scroll member to undergo orbital motion relative to the other scroll member, while preventing rotation of the one orbiting scroll member. The relative motion of the scroll members changes the volume of the fluid pockets.

In order to. effectively change the volume of the fluid pockets, the fluid displacement apparatus must provide axial and radial sealing between the scroll members. However, since the scroll members benerally the axial sealing is more critical and involute shape seal elements are used on the end surfaces of both spiral wraps which are formed of an aluminum alloy to reduce the weight of the apparatus, the softness of the aluminum alloy results in considerable abrasion and wear between the scroll member and axial seal element over a period of time. To minimize wear, while at the same time achieving effective axial sealing, the present invention provides an involute plate formed of a hard material such as hardened steel between the axial end surface of the spiral wrap of the orbiting scroll member and the circular end plate' of the fixed scroll member. This involute palte covers only the area of the surface of the circular end plate of the fixed scroll member where the spiral wrap makes axial contact during the orbital motion of the orbiting scroll member to thereby prevent excessive wear and abrasion. A similar involute plate could be placed on the circular end plate of the orbiting scroll member to prevent excessive wear between the circular end plate of the orbiting scroll member and the axial end surface of the spiral wrap of the fixed scroll member.

In another aspect of this invention, where both scroll members are formed of aluminium alloy, the rubbing or contact surface of one of the scroll members is hardened by covering it with a hard material and the other scroll member is provided with an involute plate as described above. As a result, a tight fit and seal is achieved between the scroll members, particularly after the intial wear, and further wear or damage of the scroll members is prevented.

In yet another aspect of this invention, an elastic spring member or an elastic sheet is disposed between the inner end surface of the circular end plate and the involute plate. This elastic spring member is to vary its thickness on necessity. Thus, if an error is made in the dimensions of a spiral element in manufacturing process of the scroll member, axial sealing is still secured between the axial end surface of the spiral element with or without sealing element on it, and the end surface of the circular end plate because the elastic spring member compensates for this error. Furthermore, wear or damage to the scroll member is prevented.

Further objects, features and other aspects of this invention will be understood from the following detailed description of the preferred embodiment of this invention. The following detailed description of a preferred embodiment of the invention relates to a fluid displacement apparatus of the compressor type. The principles of the invention are equally applicable to other types of fluid displacement apparatus.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which:-

• Fig. 1 is a vertical sectional view of a compressor according to one embodiment of this invention;
• Fig. 2 is an exploded perspective view of a driving mechanism for the orbiting scroll member of the compressor of Fig. 1;
• Fig. 3 is a sectional view taken along a line 3-3 in Fig. 1;
• Fig. 4 is a perspective view of a rotation preventing mechanism for the compressor of Fig. 1;
• Fig. 5(a) is a front view of a fixed scroll member and Fig. 5(b) is a front of an involute anti-wear member;
• Fig. 6 is a vertical sectional view of compressor according to another embodiment of this invention;
• Fig. 7 is a vertical sectional ..view of part of another embodiment of this invention; and
• Fig. 8 is a diagrammatic sectional view illustrating the spiral elements of the fixed and orbiting scroll members.

Referring to Fig. 1, a fluid displacement apparatus according to the present invention is shown which consists of a refrigerant compressor 1. The compressor 1 includes a compressor housing 10 formed by a cylindrical housing 11, a front end plate 12 and a rear end plate 13. A drive shaft 15 is rotatably supported in an opening in front end plate 12 by a bearing, such as a ball bearing 14. Front end plate 12 has a sleeve portion 16 projecting from the front surface thereof to surround drive shaft 15 and define a shaft seal cavity. A shaft seal assembly 17 is assembled on drive shaft 15 within the shaft seal cavity. A pulley 19 is rotatably supported by bearing 18 on the outer surface of sleeve portion 16. An electromagnetic annular coil 20 is mounted within an annular cavity in the outer part of sleeve portion 16. An armature plate 21 is supported on the end of drive shaft 15 which extends from sleeve portion 16. The pulley 19, magnetic coil 20 and armature plate 21 form a magnetic clutch. Thus, drive shaft 15 is driven by an external power source, such as an engine of a vehicle through a rotational force transmitting device, such as a magnetic clutch.

Front end plate 12, which is fixed to the front end of cylindrical housing 11 by a bolt (not shown), covers an opening in the front end of cylindrical housing 11. An 0-ring 22 seals this opening. Rear end plate 13 has an annular projection 23 on its inner surface to partition suction chamber 24 from discharge chamber 25. Rear end plate 13 also has a fluid inlet port 26 and a fluid outlet port (not shown) which are connected to the suction and discharge chamber 24 and 25, respectively. Rear end plate 13 is fixed to rear end of cylindrical housing 11 by bolts and nuts 27. Circular end palte 281 of fixed scroll member 28, which is also fixed to housing 11 by bolts and nuts 27, is located between cylindrical housing 11 and rear end plate 13. Gaskets 2 and 3 prevent fluid leakage past the outer perimeter. of circular end plate 281 and between discharge chamber 25 and suction chamber 24.

Fixed scroll member 28 includes circular end plate 281 and a wrap or spiral element 282 extending from one side of circular end plate 281. An opening in the rear end of cylindrical hbusing 11 is covered by circular end plate 281. Spiral element 282 is disposed in inner chamber 29 of cylindrical housing 11. Circular end plate 281 has one hole or suction port 283 which communicates between suction chamber 24 and inner chamber 29 of cylinderical housing 11 and another hole or discharge port 284 at a position near the center of spiral element 282 which is connected to discharge chamber 25.

An orbiting scroll member 30 is also disposed in inner chamber 29. Orbiting scroll emmber 30 compresses circular end plate 301 and wrap or spiral element 302 extending from one side of circular end plate 301, Both spiral elements 282 and 302 interfit at an angular offset of 180° and at a predetermined radial offset to make a plurality of line contacts to define at least one pair of sealed off fluid pockets 'between the spiral element 282 and 302. Each of the spiral elements 282 and 302 has a groove in its axial end surface and a seal element 285, 304 is disposed in the groove for preventing fluid leakage between the end surface of each circular end plate and the axial end surface of each spiral element.

Orbiting scroll member 30 is connected to a driving mechanism, including drive shaft 15, and to a rotation preventing mechanism. These last two mechanism effect orbital motion of orbiting scroll member 30 at a circular radius R_o to thereby compress fluid passing through the compressor. The raius R_o generally is given by the following formule:

• [(pitch of spiral element) - 2(wall thickness of spiral element)J X 1/2

As shown in Fig. 8, the pitch (P) of the spiral elements can be define by 2πrg, where rg is the involute generating circle radius. The radius of orbital motion R_o is also illustrated in Fig. 8 as the locus of an arbitrary point Q on orbiting scroll member 30. The spiral leement 302 is radially offset from spiral element 282 of fixed scroll member 28 by the distance R_o. Thus, orbiting scroll member 30 undergoes orbital motion of a radius R_o upon rotation of drive shaft 15. As the orbiting scroll member 30 orbits, the line contacts between spiral elements 282 and 302 moves toward the center of the spiral elements along the surfaces of the spiral elements. The fluid pockets, which are defined by spiral elements 282 and 302, also move to the center with a consequent reduction in volume and compression of the fluid in the pockets. The fluid or refrigerant gas, which is introduced into chamber 29 from an external fluid circuit through inlet port 26, suction chamber 24 and hole 283, is drawn into fluid pockets formed between spiral elements 282 and 302. As orbiting scroll member .30 orbits, fluid in the fluid pockets is compressed and the compressed fluid is discharged into discharge chamber 25 through hole 284 at the center of the spiral elements. The fluid then is discharged through an outlet port to an external fluid circuit, for example, a cooling circuit.

Referring to Figs. 1, 2 and 3, a driving mechanism for orbiting scroll member 30 will be described. Drive shaft 15, which is rotatably supported by front end plate 12 through ball bearing 14, has a disk portion 151 at its inner end. Disk 151 is rotatably supported by cylindrical housing 11 through bearing 31 at an opening in the front end of cylindrical housing 11. Ball bearing 31 fits between coolar 152 on disk.151 and collar 111 at the opening of cylindrical housing 11. An inner ring of ball bearing 14 fits against stepped portion 153 of drive shaft 15 and an outer_ring fits against shoulder portion 121 of front end plate 12. Therefore, ball bearings 14 and 31 permit the drive shaft to undergo rotation while preventing axial motion.

A crank pin or drive pin 154 axailly projects from an end surface of disk 151 at a position which is radially offset from the center of drive shaft 15. Circular plate 301 of orgiting scroll member 30 has a tubular boss 303 axially projecting from the end surface opposite the surface from which spiral element 302 extends. A discoid or short axial bushing 33 fits into boss 303 and is rotatably supported therein by a bearing such as a needle bearing 34. Bushing 33 has a balance weight 331 which is radially connected to bushing 33 along a front surface thereof. An eccentric hole 332 is formed in bushing 33 at a position radially offset from center of bushing 33. Drive pin 154 fits into eccentric hole 332 together with bearing 32. As a result, bushing 33, which is driven by the rotation of drive pin 154,. rotates within bearing 34.

The relative positions of drive shaft center Os, center Oc of bushing 33 and center Od of hole 332 and drive pin 154 'are shown in Fig. 3. In the position shown in Fig. 3, the distance between Os and Oc is the radius R. of orbital motion. When drive pin 154 is placed in eccentric hole 332, center Od of drive pin is on the opposite side of line Ll from shaft center Os. Line Ll passes through bushing center Oc and is perpendicular to line L2 passing through both Oc and Os. Direction A is the direction of rotation of drive shaft 15.

In this construction of a driving mechanism, bushing center Oc swings about the center Od of drive pin 154 at a radius E2, as shown in Fig. 3. The swing of center Oc is illustrated as are Oc'-Oc" in Fig.3. When drive shaft 15 rotates, a drive force is exerted at center Od to the left, and a reaction force of gas compression occurs _'at center Oc to the right, both forces being parallel to line Ll. As a result of the moment generated by these forces, the moment art Od-Oc swings outwardly and spiral element 302 of orbiting scroll member 30. is forced toward spiral element 282 to fixed scroll member 28 so that the line contacts between spiral elements 282 and 302 necessarily orbit with the center Os of drive shaft 15. During the orbit of the orbiting scroll member, orbiting scroll member 30 does not rotate because of the operation of a rotation preventing/thrust bearing mechanism, which is described more fully hereinafter. The orbiting scroll member 30 orbits while maintaining its angular orientation. The fluid pockets move because of orbital motion of the orbition scroll member 30 to thereby compress the fluid in these fluid pockets.

When the fluid in teh. fluid pockets is compressed by orbital motion of orbiting scroll member 30, a reaction force is caused by the compression of the fluid which acts on spiral element 302. The reaction force gives rise to a force which acts on the line contact between spiral elements 302 and 282 to urge spiral element,302 into engagement with spiral element 282 to seal the fluid pockets. In addition, since bushing center Oc can swing around center Od of drive pin 154, if the pitch or wall thickness of a spiral element has a dimentional error due to manufacturing inaccuracy or wear, the distance Oc-Os varies in accordance with the error. Orbiting scroll member 30 thereby moves smoothly along the line contacts between the spiral elements.

If bushing 33 does not have balance weight 331-, a centrifugal force caused by the orbiting motion of orbiting parts, i.e., orbiting scroll member 30, bearing means 34 and bushing 33, is added to the curging force of spiral element 302 acting on spiral element 282, In this event, the contact force between the spiral elements 282 and 302 would increase as shaft speed increases, which would increase the friction force between spiral elements 302 and 282 and increase wearing of both spiral elements as well as increase the mechanical friction loss.

When bushing 33 is provided with a properly designed balance weight 331, the centrifugal force can be cancelled by the centrifagal force of the balance weight. The mass of balance weight 331 is selected so that the centrifugal force is equal in magnitude to the total centrifugal force of the orbiting parts and it is positioned so that the centrifagal forces are in the opposite direction.. As a result, wear of both spiral elements will be decreased, the sealing force between the spiral elements will be attained through the mechanism explained above and the orbiting scroll member will move smoothly.

Referring to Fig. 4 and Fig. 1, a rotation preventing/thrust bearing device 37 is shown which is integral with a thrust bearing device. Rotation preventing/thrust bearing device 37 surrounds boss 303 and includes fixed ring 371 and Oldham ring 372. Fixed ring 371 is attached to stepped portion 112 of the inner surface of cylindrical housing 11 by pin 373. Fixed ring 371 is provided iwht a pair of keyways 371a and 371b in an axial end surface facing orbiting scroll member 30. Oldham ring 371 is positioned between fixed 371 and circular plate 301 or orbiting scroll member 30. Oldham ring 372 includes a pair of keys 372a and 372b facing fixed ring 371; these keys are received in keyways 371a and 371b. Therefore, Oldham ring 372 can slide in a radial direction on keys 372a and 372b within keyways 371a and 371b. Olaham ring 372 has a pair of keys 372c and 372d on its opposite surface. Keys 372c and 372d are located along a radial line perpendicular to the radial line on which keys 372a and 372b are located. Circular plate 301 of orbiting scroll member 30 has a pair of keyways (in Fig.4 only one keyway 301a is shown; the other keyway is located diamerically opposite keyway 301a) on the surface facing Oldham ring 392 for receiving keys 372c and 372d. Therefore, orbiting scroll member 30 can slide in a radial direction on keys 372c. 372d within the keyways of circular plate 301.

Accordingly, orbiting scroll member 30 slides in two perpendicular directions on Oldham ring 372. The ring 372 prevents rotation of orbiting scroll member 30, but permits the orbiting scroll member to move in two perpendicular radial direction, which results in a freedoms of orbital motion of the orbiting scroll member with radius R_o.

Oldham ring 372 also has a plurality of holes 38. Bearing elements, such as balls 39 each having a diameter greater than the thickness of Oldham ring 372, are placed in holes 38. Balls 39 contact and roll on the surfaces of fixed ring 371 and circular plate 301. Therefore, the thrust load from orbiting scroll member 30 is supported by fixed ring 371 through balls 39.

Both spiral elements 282 and 302 of the scroll members, as shown in Fig. 1, have a groove on the axial end surface and seal elements 285 and 304 for providing a seal between the end surface of each circular end plate and the axial end surface of each spiral element. An involute plate 40, which is formed of hard meral, such as hardened steel, is fitted to the end surface of circular end plate 281 facing orbiting scroll member'30. A screw 41 can be used to prevent the touch of involute plate from flapping, as shown in Fig. 5. The involute plate is necessary because, in the embodiment shown in Fig. 1, both scroll members 28 and 30 are formed of aluminum alloy to reduce the weight of the compressor. However, because aluminum alloy is soft, considerable abrasion occrus between the contact surfaces formed by aluminum parts and sealing element 304. Thus, use of involute plate 40 minimizes the abrasion and reduces wear.

Similarly, to minimize abrasion and reduce wear, the rubbing surfaces of orbiting scroll member 30, that is the end surface of circular palte 301 facing fixed scroll member 28 and all surfaces of spiral element 302 are surface hardened. Fixed scroll member 28, which is also formed of aluminum alloy, is not surface hardened. As a result, the rubbing surface between spiral elements 282 and 302 will fit tightly after intial wearing. Subsequent wearing is minimized and the resulting seal between the rubbing surfaces is secured.

The axial contact between circular end plate 301 of orbiting scroll member 30, which is surface hardened, and seal element 285 also must be tightly fitted and sealed. By hardening the surface of circular end plate 301, and making hardness seal element 285 lower than the hardened surface of circular end plate 301, wear of damage to circular end palte 301 is prevented while a tight fit and sealing is achieved.

The other axial contact between circular end plate 281 and the end surface of seal element 302, is effectively sealed while preventing wear. of damage to circular end plate 281. The circular end plate 281 is covered by involute plate 40 in those areas of the end surface of circular end plate 281. As a result, .seal element 304 on spiral element 302 does not directly contact the end surface of circular end plate 281. Since seal element 304 and involute plate 40 are made of different material of different hardness, a tight fit and seal occurs after initial wearing.

Referring to 'Fig. 6, another embodiment is shown which is directed to a modification of the axial sealing between the axial end surface of the spiral elements and the end surfaces of the circular end plates. In this embodiment, the seal element described in connection with Fig. 1 is not used. Similar parts in Fig. 6 are represented by the same reference numerals as the embodiment shown in Fig. 1.

Orbiting scroll member 30 of Fig. 6 is operatively connected to the drive mechanism, fixed scroll member 28 is fastened to cylindrical housing 11 of housing 10 by bolts and nuts 29, and these bolts and nuts 29 also fasten rear end plate 13 to cylindrical housing 11, in the same manner as in Fig. 1. As shown in Fig. 7 (a), the surfaces of circular end plate 301 and spiral element 302 of orbiting scroll member 30 are coated with a hard material. An involute plate 40, which is formed of hard metal such as steel, is placed'to the end surface of circular plate 281 of fixed scroll, menber 28 facing orbiting scroll member 30. The involute plate 40 covers the contact surface between the extended portion of the spiral element 302 and the circular end plate 281 in the same manner as in the forst embodiment. In addition, an elastic plate 41, for example a rubber plate, is disposed between involute plate 40 and the end surface of circular end plate 281. The thickness of elastic plate 41 varies in response to relative position of orbiting scroll member 30 against involute plate 40. Therefore, if a manufacturing error exists with the axial dimentions of the spiral element, elastic plate 41 compensates for this error by changing its thickness. As a result, the axial sealing between the axial end surface of the spiral element and the end surface of the circular end plate is secured without wear or damage to the scroll member.

When assembling the compressor, a perfect adjustment for minimum axial clearance between the end surface of fixed spiral element 282 and the end surface of the circular end plate 301 should be done by selecting the thickness of gasket 3 which is used as a shim since the thickness of the elastic plate 41 is determined to give a preload to the orbiting spiral end surface through involute plate 40, axial seal between the end surface of orbiting spiral element 302 and the involute plate 40 is secured. Even though the thickness of gasket is properly selected in the initial state, the axial location of the orbiting scroll member 30 may be changed relative to the housing 11 once the thrust race and thrust balls settle due to a continuous gas load of compression. Then the tight seal between the end surface of fixed spiral element 282 and the circular end plate 301 is lost, while the other axial seal is maintained by the preloading fruction of the elastic plate 41. A seal element 285 at the end surface of the fixed spiral element 282 may be necessary to overcome this problem, as shown in Fig. 7 (a). Another set of involute plate 40 and elastic plate 41 applied on the orbiting scroll member 30 is an alternative of the seal element 285 as shown in Fig. 7(b).

As shown in Fig. 7(c), the construction of Fig.7(a) can be modified by placing another seal element 304 in a groove on the axial end surface of spiral element 302 to further prevent fluid leakage between spiral element 302 and circular end plate 281.

With the latter comstruction of the axial sealing between the axial end surface of the spiral element-302 and the end surface.of the circular end plate 281, involute plate 40 of hard anti-wear material, (as best shown in Fig. 5(b)) is disposed on the end surface of at least one scroll member.

The invention has been described in detail in connection with the preferred embodiments, but these are examples only and this 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.