Improvements in scroll type fluid compressor units

This invention relates to scroll type fluid compressor units.

A scroll type apparatus has been well known in the prior art as disclosed in, for example, U.S. Patent No. 801,182, and others, which comprises two scroll members each having an end plate and a spiroidal or involute spiral element. These scroll members are so maintained angularly and radially offset that their spiral elements interfit to make a plurality of line contacts between their spiral curved surfaces, thereby to seal off and define at least one fluid pocket. The relative orbital motion of these scroll members shifts the line contacts along the spiral curved surfaces and, therefore, the volume of the fluid pocket increases or decreases in dependence on the direction of the orbital motion. Therefore, a scroll type apparatus is suitable for handling fluids or for compressing, expanding or pumping them.

In comparison with conventional compressors of a piston type, a scroll type compressor has some advantages such as less number of parts, continuous compression of fluid and others. But, there have been several problems; primarily sealing of the fluid pocket, wearing of the spiral elements, and inlet and outlet porting.

Although there have been many patents, for example, U.S. Patents Nos. 3,884,599, 3,924,977, 3,994,633, 3,994,635, and 3,994,636 in order to resolve these and other problems, the resultant compressor is complicated in construction and in production. Specifically, the problems of wearing of the scroll members and of friction between the scroll members are not resolved sufficiently.

Since a compressor of this type is compact and relatively light, it is advantageously used for a refrigerant compressor of an air conditioning system for an automobile. In such applications, since the compressor is desirably light, the scroll members and other parts can be made of aluminium or aluminium alloy. If the scroll members are made of aluminium or an aluminium alloy, the sealing of the fluid pockets becomes insufficient owing to wearing.

According to the present invention there is provided a scroll type fluid compressor unit including a compressor housing having a fluid inlet port and a fluid outlet port, a fixed scroll member fixedly disposed within said compressor housing and having first end plate means to which first wrap means are affixed, and an orbiting scroll member orbitally disposed within said compressor housing and having second end plate means to which second wrap means are affixed, said first and second wrap means interfitting, being at a predetermined angular relationship, and having a plurality of line contacts so as to define at least one sealed off fluid pocket which moves with reduction in volume thereof upon orbital motion of said orbiting scroll member, thereby to compress the fluid in the pocket, wherein said fixed and orbiting scroll members are each formed of aluminium or an aluminium alloy, and at least one of the fixed and orbiting members has at least the surface of its wrap means and the end surface of its end plate means on which said wrap means are affixed formed of a material having anti-wearing properties.

One embodiment of the invention is an improved compressor unit of the scroll type which has excellent sealing and anti-wearing properties. The dimensional accuracy of the scroll members is readily secured. Friction between the scroll members is reduced.

One embodiment of the invention is a scroll type fluid compressor unit which includes a compressor housing having a fluid inlet port and a fluid outlet port. Within the housing, a fixed scroll member fixedly disposed which comprises first plate means to which first wrap means are affixed. An orbiting scroll member is orbitally disposed within the housing and comprises second end plate means to which second wrap means are affixed. The first and second wrap means interfit at a predetermined angular relationship to make a plurality of line contacts to define at least one sealed off fluid pocket. The fluid pocket moves with reduction of volume thereof by the orbital motion of the orbiting scroll member. The fluid in the pocket is thereby compressed. The first and second scroll members are made of aluminium or an aluminium alloy. One of the scroll members is treated by surface hardening the entire surface of its wrap means and the end surface of its end plate means on which the wrap means are affixed.

In order to effect the surface hardening, copper plating, anodic oxidation coating or hard chromium plating may be employed.

In a further embodiment of the invention, at least one -of scroll members is made of a high silicon aluminium alloy. The entire surface of the scroll member has an anti-wearing property because many silicon crystals are dispersed in the surface. Therefore, a surface hardening treatment is not necessary.

In a further embodiment of the invention, one of scroll members is coated with a polytetrafluoroethylene coating. The other scroll member is treated by the surface hardening, as above described. Alternatively, if the other scroll member is made of a high silicon aluminium alloy, such a surface hardening treatment is not necessary.

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

• Fig. 1 shows a vertical sectional view of a compressor unit of a scroll type according to an embodiment of this invention;
• Fig. 2 is a cross-sectional view taken along line II-II in Fig. 1;
• Figs. 3a-3d are schematic views for illustrating movement of interfitting spiral elements to compress fluid; and
• Fig. 4 is a vertical sectional view of another embodiment of this invention.

Referring to Fig. 1, a refrigerant compressor unit 10 of an embodiment shown includes a compressor housing comprising a front end plate 11, a rear end plate 12 and a cylindrical body 13 connecting between those end plates. Rear end plate 12 is shown formed integral with the cylindrical body and is provided with a fluid inlet port 14 and a fluid outlet port 15 formed therethrough. A drive shaft 17 is rotatably supported by a radial needle bearing 16 in front end plate 11. Front end plate 11 has a sleeve portion 18 projecting on the front surface thereof and surrounding drive shaft 17 to define a shaft seal cavity 181. Within the shaft seal cavity, a shaft seal assembly 19 is assembled on drive shaft 17. A pulley 20 is rotatably mounted on sleeve portion 18 and is connected with drive shaft 17 to transmit an external drive power source (not shovm) to drive shaft 17 through belt means (not shown) wound around pulley 20. A disk rotor 21 is fixedly mounted on an inner end of drive shaft 17 and is born on the inner surface of front end plate 11 through a thrust needle bearing 22 which is disposed concentric with drive shaft 17. Disk rotor 21 is provided with a drive pin 23 projecting on the rear surface thereof. Drive pin 23 is radially offset from drive shaft 17 by a predetermined length.

Reference numerals 24 and 25 represent a pair of interfitting orbiting and fixed scroll members. Orbiting scroll member 24 includes an end circular plate 241 and a wrap means or spiral element 242 affixed onto one end surface of the end plate. End plate 241 is provided with a boss 243 projecting on the other end surface thereof. Drive pin 23 is fitted into boss 243 with a radial needle bearing 26 therebetween, so that orbiting scroll member 24 is rotatably supported on drive pin 23.

A hollow member 27 having a radial flange 271 is fitted onto boss 243 non-rotatably by means of key and keyway connection. Radial flange 271 is supported on the rear end surface of disk rotor 21 by a thrust needle bearing 28 which is disposed concentric with drive pin 23. The axial length of hollow member 27 is equal to, or more than, the axial length of boss 243, so that the thrust load from orbiting scroll member 24 is supported on front end plate 11 through disk rotor 21. Therefore, the rotation of drive shaft 17 effects the orbital motion of orbiting scroll member 24 together with hollow member 27. Namely, orbiting scroll member 24 moves along a circle of a radius of the length between drive shaft 17 and drive pin 23.

Means 29 for preventing orbiting scroll member 24 from rotating during the orbital motion is disposed between end plate 241 of orbiting scroll member 24 and radial flange 271 of hollow member 27.

Referring to Fig. 2 in addition to Fig. 1, hollow member 27 comprises a cylindrical portion 272 having. a rectangular outer contour, on which a rectangular slider member 291 is fitted slidable in a radial direction. Rectangular slider member 291 has a rectangular hole with one pair of parallel sides equal to one pair of parallel sides of the outer rectangle of cylindrical portion 272 and with the other pair of parallel sides longer than the other pair of sides of rectangular cylindrical portion 272 by at least twice length between drive shaft 27 and drive pin 23. Accordingly, slider member 291 is slidable on hollow member 27 in a radial direction along the longer parallel sides of the rectangular hole. Slider member 291 is also fitted into a ring like member 292 which is non-rotatably fixed on the inner surface of cylindrical body 13 of the compressor housing by key and keyway connection (shown at 293 in Fig. 2). The central hole of ring like member 292 is a rectangular hole with one pair of parallel sides equal to one pair of parallel sides of the outer rectangle of slider member 291 and with the other pair of parallel sides longer than the other parallel sides of the same outer rectangle by at least twice length between drive shaft 17 and drive pin 23, so that slider member 291 may be slidable within ring like member 292 in a radial direction perpendicular to the slide direction of it on hollow member 27.

Accordingly, hollow member 27 is permitted to move in two radial directions perpendicular to one another and, therefore, moves along a circle as a result of movement in the two radial directions but is prevented fr,om rotation. Therefore, the eccentric movement of drive pin 23 by the rotation of drive shaft 17 effects the orbital motion of orbiting scroll member 24 together with hollow member 27 without rotation.

In another construction of ring like member 292, the ring like member has a central hole permitting hollow member to axially pass therethrough and is formed with a depression in an end surface for receiving and slidably guide slider member 291. This construction of the ring like member permits the ring like member itself to be thin.

The other fixed scroll member 25 also comprises an end circular plate 251 and a wrap means or spiral element 252 affixed on one end surface of the end plate. End plate 251 is provided with a hole or a discharge port 253 formed at a position corresponding to the center of the spiral elements, and with an annular projection 254 on the rear end surface around discharge port 253.

Rear end plate 12 is provided with an annular projection 121 on the inner surface thereof around outlet port 15. The outer radius of annular projection 121 is selected slightly shorter than the inner radius of annular projection 254. Annular projection 121 is cut away along the outer edge of the projecting end to define an annular recess 122. An annular elastic material, for example, a rubber ring 30 is fitted into annular recess 122 and is compressedly held between interfitted annular projections 121 and 254, so that fixed scroll member 25 is elastically supported on annular projection 121 of the rear end plate. Rubber ring 30 serves as a seal for sealing off a chamber 31 defined by annular projections 121 and 254 from the interior space 131 of the compressor housing. Chamber 31 connects between outlet port 15 and discharge port of fixed scroll member 25.

End plate 251 of fixed scroll member 25 is formed with a plurality of cut away portions 255 at its rear peripheral edge. A plurality of projections 132 are formed on the inner surface of cylindrical body 13 of the compressor housing and are mated i₄to_'cut away portions 255, so that fixed scroll member 25 is non-rotatably disposed within the compressor housing. Gaps 32 is maintained between the inner wall of cylindrical body 13 and the peripheral end of fixed scroll member 25, and, therefore, a chamber portion 33 surrounding annular projections 121 and 254 does not form a sealed off chamber within interior space 131 of the compressor housing. Chamber portion 33 communicates with inlet port 14.

In operation, when drive shaft 17 is rotated by an external drive power source (not shown) through pulley 20, drive pin 23 moves eccentrically to effect the orbital motion of orbiting scroll member 24. The rotation of orbiting scroll member 24 is prevented by rotation preventing means 29. The orbital motion of orbiting scroll member 24 compresses the fluid introduced into interior space 131 through inlet port 14, chamber portion 33, and gaps 32, and the compressed gas is discharged-from outlet port 15 through discharge port 253 and chamber 31.

Referring to Figs. 3a-3d, the introduced fluid is taken into fluid pockets 1 and 2 (which are shown at dotted regions) which are defined by line contacts between orbiting spiral element 242 and fixed spiral element 252, as shown in Fig. 3a. The line contacts shift by the orbital motion of orbiting spiral element 242 and, therefore, fluid pockets 1 and 2 angularly and radially move toward the center of spiral elements and decrease their volume, as shown in.Figs. 3b-3d. Therefore, the fluid in each pocket is compressed. When orbiting scroll member moves over 360⁰ to the status shown in Fig. 3a, fluid is again taken into new formed fluid pockets 1 and 2, while old pockets connected together to form a reduced pocket and the already taken and compressed fluid is discharged from the pocket through discharge port 253.

In the arrangement as above described, since fixed scroll member 25 is axially urged toward orbiting scroll member 24 by the restoring force of compressed rubber ring 30, sealing between end plate 241 of orbiting scroll member 24 and the axial end of fixed spiral element 252, and between end plate 251 of fixed scroll member 25 and the axial end of orbiting spiral element 242 is secured. And the sealing is reinforced by a fluid pressure discharged into chamber 31. The axial load for securing the sealing is supported on disk rotor 21 through orbiting scroll member 24, hollow member 27 having radial flange 271, and thrust bearing 28, and is further supported through disk rotor 21 and thrust bearing 22 on front end plate 11 which is secured onto the front end of cylindrical body 13 of compressor housing. Therefore, any deflection of moving parts is prevented during operation of the compressor, so that the vibration of compressor and abnormal wearing of each parts may be prevented. Since disk rotor 21 fixedly mounted on drive shaft 17 is supported through thrust bearing 22 on front end plate 11, drive shaft 17 is securely and non-vibratingly supported by the use of a single needle bearing as a radial bearing.

In the arrangement of the compressor as above described, assembling operation of the compressor is very simple; annular elastic material 30, fixed and orbiting scroll members 25 and 24, rotation preventing means 29, hollow member 27, bearings 26 and 28, and a pre- assembly of drive pin 23, disk rotor 21, bearings 16 and 22, drive shaft 17 and front end plate 11, are inserted in this order into cylindrical body 13 having rear end plate 12, and the compressor is completed by securing front end plate 11 onto cylindrical body 13 by bolt means 34.

The above described compressor arrangement is proposed in a copending patent application by the same applicant filed on September 3, 1979 under Application No. 79301808.6.

Considering sealing of fluid pockets in the compressor as above described, the radial sealing force at each line contact between fixed and orbiting spiral elements 252 and 242 is determined by the radius of the orbital motion of orbiting scroll member 24 or the offset length between drive shaft 17 and drive pin 23, and the pitch and thickness of each of fixed and orbiting spiral elements 252 and 242. In practical use, the distance between drive shaft 17 and drive pin 23 is preferably selected slightly larger than the half of the dimensional difference between the pitch of each spiral element and the total dimension..of thickness of fixed and orbiting spiral elements. This arrangement is permitted by the fact that fixed scroll member 25 is radially movably supported by compressed rubber ring 30. The sufficient radial sealing is established, even at the initial use of the compressor as assembled.

The reasonable radial sealing is completed after contact surfaces of both spiral elements wear by friction during use to get to fit to one another.

According to this invention, both scroll members 24 and 25 are made of aluminum or aluminum alloy by forging, casting or die casting, to make the compressor unit light.

In case of forging, for example, aluminum alloy of No. 6051, in JIS (Japanese Industrial Standards) H 4140, which comprises by weight 0.40-0.8 % Si, up to 0.7 % Fe, 0.15-0.40 % Cu, up to 0.15 % Mn, 0.8-1.2 % Mg, 0.04-0.35 % Cr, up to 0.25 % Zn, up to 0.15 % Ti, and the balance essentially A1, is preferably used.

In case of casting, aluminum alloy of AC2A by JIS, H 5202 which comprises 3.5-4.5 % Cu, 4.0-5.0 % Si, up to 0.2 % Mg, up to 0.5 % Zn, up to 0.8 % Fe, up to 0.5 % Mn, up to 0.2 % Ti and the balance of Al, is preferably used.

In case of die casting, aluminum alloy of ADC 10 in JIS H 5302 (which comprises 2.0-4.0 % Cu, 7.5-9.5 % Si, up to 0.3 % Mg, up to 1.0 % Zn, up to 1.3 % Fe, up to 0.5 % Mn, up to 0.5 % Ni, up to 0.3 % Sn and the balance of Al), or ADC 12 in JIS H 5302 (which comprises 1.5-3.5 % Cu, 9.6-12.0 % Si, up to 0.3 % Mg, up to 1.0 % Zn, up to 1.3 % Fe, up to 0.5 % Mn, up to 0.5 % Ni, up to 0.3 % Sn and the balance of Al) is preferably used.

Since aluminum and aluminum alloy tend to wear by friction, the sealing of fluid pockets becomes imperfect by the use of the compressor.

Therefore, at least one of scroll members of aluminum or aluminum alloy is treated by surface hardening at its at least surface area in slidingly contact with one another, in this invention.

In the embodiment of Figs. 1 and 2, orbiting scroll member 24 is treated by surface hardening as shown at 35.

As the surface hardening treatment, hard chromium plating, copper plating, and anodic oxidation coating can be selectively used. Since these treatments are well known per se in the prior art of aluminum and aluminum alloy surface treating technique, the description as to the concrete processes for producing such surface hardened coatings on to aluminum or aluminum alloy scroll members is omitted for the purpose of simplification of the description.

The existence of surface hardened coating 35, such as plated hard chromium coating, plated copper coating, or anodic oxidation coating on orbiting scroll member 24, establishes a reduced friction at contact portions between both scroll members 24 and 25. Therefore, not only orbiting scroll member 24 but also fixed scroll member 25 are protected from wearing due to sliding contact therebetween, so that the sealing of fluid pockets is maintained during long use.

Furthermore, since the thickness of the coating can be controlled in above described surface hardening treatments, as is well known, the dimensional accuracy of orbiting scroll member 24 can be readily obtained.

Such a surface hardening treatment may be performed onto not orbiting scroll member 24 but fixed scroll member 25. The application onto both scroll members is also preferable.

If at least one of scroll members is made of high silicon aluminum alloy or anti-wearing aluminum alloy including high silicon such as about 12-25 wt%, such surface hardening treatment is not necessary. The dimensional accuracy is obtained by machining. The machined surface is subjected by exposure of many silicon crystals, so that the surface has an anti-wearing property.

Anti-wearing aluminum alloy like this is known as disclosed in U.S. Patent No. 3,514,286.

If the above mentioned surface hardening treatment is not applied onto one of scroll members, a polytetrafluoro- ethylene coating may be used onto the scroll member as shown in Fig. 4.

Referring to Fig. 4, fixed scroll member 25 is coated by a surface hardening coating 36 similar to the coating 35 in Fig. 1, and orbiting scroll member 24 is coated by a polytetrafluoroethylene coating 37.

It is natural that the surface hardening coating and the polytetrafluoroethylene coating are applied onto orbiting scroll member 24 and fixed scroll member 25, respectively.

The employment of the surface hardening coating and the polytetrafluoroethylene coating further reduces the contacting friction between both scroll members. Thus, the sealing of fluid pockets can be maintained during a longer time period.

If the anti-wearing aluminum alloy as above described is used for at least one of scroll members, the surface hardening coating is not necessary.

As above described, a scroll type compressor. unit is obtained according to this invention, which is light and wherein the sealing of fluid pockets between both scroll members is maintained for a long time use. Furthermore, since scroll members are made light, dynamic unbalance is reduced. Moreover, the dimensional accuracy of scroll members can be readily obtained so that the sealing of fluid pockets is further secured.

This invention has been described in connection with preferred embodiments, but these are merely for example only and this invention is not restricted thereto. It will be easily understood by those skilled in the art that the other variations and modifications can be easily made within the scope of this invention.