EP0075053B1

EP0075053B1 - Wear-resisting means for scroll-type fluid-displacement apparatuses

Info

Publication number: EP0075053B1
Application number: EP81304364A
Authority: EP
Inventors: Takayuki Iimori; Kiyoshi Terauchi
Original assignee: Sanden Corp
Current assignee: Sanden Corp
Priority date: 1981-09-22
Filing date: 1981-09-22
Publication date: 1986-12-17
Also published as: EP0075053A1; DE3175720D1

Description

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 the 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 in the 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.
Our earlier EP-A-0 061 065 discloses a scroll type fluid displacement apparatus in which an anti-wear plate is disposed between an axial end surface of each spiral element and an inner surface of the end plate of the other scroll member. EP-A-0 061 065 was published after the date of filing of the present application but claims a priority date which is earlier than that date of filing.
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 flud 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 first scroll member having a first end plate and a first spiral wrap extending from an inner surface of said first end plate, a second scroll member having a second end plate and a second spiral wrap extending from, an inner surface of said second end plate, said first spiral wrap and said second spiral wrap interfitting at an angular and radial offset to make a plurality of axial contacts between the axial end surface of said first spiral wrap and said second spiral wrap and said first end plate and line contacts between the spiral curved surfaces, which together define fluid pockets, an anti-wear plate disposed between the axial end surface of said second spiral wrap and the adjacent first end plate to prevent the wearing of said first end plate and to maintain axial sealing of the fluid pockets, and drive means operatively connected to one of said first and second scroll members 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 said first and second scroll members are formed of aluminum or aluminum alloy, said second scroll member has a hardened surface, and an elastic member is disposed between said anti-wear plate and the end surface of said first end plate of said first scroll member.
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 contracts 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, axial sealing of scroll members is generally more critical and seal elements of involute shape are used on the end surfaces of both spiral wraps. The scroll members are formed of an aluminum alloy to reduce the weight of the apparatus and the softness of the aluminum alloy results in considerable abrasion and wear between the scroll member and the axial seal element over a period of time. To minimize wear, while at the same time achieving effective axial sealing, an involute plate formed of hard material such as hardened steel is provided 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 plate covers only the area of the surface of the circular end plate of the fixed scroll member with which the spiral wrap of the orbiting scroll member makes axial contact during the orbital motion of the orbiting scroll member, thereby to 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.
Since both scroll members are formed of aluminum 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 initial wear, and further wear or damage of the scroll members is prevented.
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;
Figs. 6(a), (b) and (c) are vertical sectional views of parts of another embodiments of this invention; and
Fig. 7 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 plate 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 housing 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 portion 283 which communicates between suction chamber 24 and inner chamber 29 of cylindrical 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 member 30 comprises 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.
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. to thereby compress fluid passing through the compressor. The radius R_o generally is given by the following formula:

[(pitch of spiral element) - 2(wall. thickness of spiral element)]x1/2

As shown in Fig. 7, the pitch (P) of the spiral elements can be defined by 2nrg, where rg is the involute generating circle radius. The radius of orbital motion R. is also illustrated in Fig. 7 as the locus of an arbitrary point Q on orbiting scroll member 30. The spiral element 302 is radially offset from spiral element 282 of fixed scroll member 28 by the distance R.. Thus, orbiting scroll member 30 undergoes orbital motion of a radius R. 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 comprssed 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 collar 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 axiai motion.
A crank pin or drive pin 154 axially 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 orbiting 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_o 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 L1 from shaft center Os. Line L1 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 L1. 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 the 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 dimensional 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 urging 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 centrifugal 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 centrifugal forces are in the opposite direction. As a result, wear of both spiral elements will be descreased, the sealing force between the spiral elements wlll 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 with a pair of keyways 371 a and 371 b 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 371 a and 371 b. Therefore, Oldham ring 372 can slide in a radial direction on keys 372a and 372b within keyways 371a and 371 b. Oldham 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 diametrically 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 directions, which results in a freedom 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 ai 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.
As shown in Figure 1, the surfaces of circular end plate 301 and spiral element 302 of orbiting scroll member 30 are coated with a hard material 305. An involute plate 40, which is formed of hard metal.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 edge of the involute plate from flapping, as shown in Figs. 5(a) and (b). The involute plate 40 covers the contact surfaces between the extended portion of the spiral element 302 and the circular end plate 281. 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 occurs between the contact surfaces formed by aluminum parts and material 305. Thus, use of involute plate 40 minimizes the abrasion and reduces wear.
In addition, as shown in Fig. 1, 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 dimensions 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.
As described above, the rubbing surfaces of orbiting scroll member 30, that is the end surface of circular plate 301 facing fixed scroll member 28 and all surfaces of spiral element 302 are surface hardened by coating with a hard material, as shown at 305. This minimizes abrasion and reduces wear. 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 initial wearing. Subsequent wearing is minimized and the resulting seal between the rubbing surfaces is secured.
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 plate 301 is lost, while the other axial seal is maintained by the preloading function of the elastic plate 41. A seal element 285 in a groove in an axial end surface of the fixed spiral element 282 may be necessary to overcome this problem, as shown in Fig. 6(a).
By hardening the surface of circular end plate 301, and making the hardness of seal element 285 lower than the hardness of the hardened surface of circular end plate 301, wear or damage to circular end plate 301 is prevented while a tight fit and sealing is achieved.
Another embodiment having an involute plate 40 and an elastic plate 41 applied to the orbiting scroll member 30, as an alternative to the seal element 285 of Fig. 6(a), is shown in Fig. 6(b).
As shown in Fig. 6(c), the construction of Fig. 6(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. The axial contact between circular end plate 281 and the end surface of seal element 302, is then effectively sealed while preventing wear or 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, 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.
With the latter construction 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.

Claims

1. A scroll type fluid displacement apparatus including a first scroll member (28) having a first end plate (281) and a first spiral wrap (282) extending from an inner surface of said first end plate (281), a second scroll member (30) having a second end plate (301) and a second spiral wrap (302) extending from an inner surface of said second end plate (301), said first spiral wrap (282) and said second spiral wrap (302) interfitting at an angular and radial offset to make a plurality of axial contacts between the axial end surface of said first spiral wrap (282) and said second end plate (301) and between the axial end surface of said second spiral wrap (302) and said first end plate (281) and line contacts between the spiral curved surfaces, which together define fluid pockets, an anti-wear plate (40) disposed between the axial end surface of said second spiral wrap (302) and the adjacent first end plate (281) to prevent the wearing of said first end plate (281) and to maintain axial sealing of the fluid pockets, and drive means operatively connected to one of said first and second scroll members (28, 30) 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 said first and second scroll members (28, 30) are formed of aluminium or aluminum alloy, said second scroll member (30) has a hardened surface (305), and an elastic member (41) is disposed between said anti-wear plate (40) and the inner surface of said first end plate (281) of said first scroll member (28).

2. An apparatus as claimed in claim 1, wherein another anti-wear plate (40) and an elastic member (41) are disposed between the axial end surface of said first spiral wrap (282) of said first scroll member (28) and the facing area of said hardened surface layer (305) of said second scroll member (30).

3. An apparatus as claimed in claim 1, wherein said first scroll member (28) has a seal element (285) at an axial end surface of said first spiral wrap (282) thereof to thereby seal a gap between said first spiral wrap axial end surface of said first scroll member (28) and said hardened surface layer (305) of said second scroll member (30).

4. An apparatus as claimed in claim 3, wherein another seal element (304) is disposed in an axial end hardened surface of said second spiral wrap (302) of said second scroll member (30).