Scroll type compressor

0001This invention relates to a scroll type compressor, and more particularly, to an axial sealing mechanism between a pair of scroll members of the scroll type compressor.

0002In Japanese Patent Application Pubblication JP-A-60 224987 and US-A-4,475,874, an axial sealing mechanism for a pair of scroll members of a scroll type compressor is disclosed.

0003Referring to Figure 1 of the accompanying drawings, the above-mentioned scroll type compressor includes fixed scroll 10 having circular end plate 11 from which spiral element 12 extends and orbiting scroll 20 having circular end plate 21 from which spiral element 22 extends. Block member 30 is attached to circular end plate 11 by a plurality of fastening member, such as bolts 31, to define chamber 40 in which orbiting scroll 20 is disposed. Spiral elements 12 and 22 are interfitted at an angular and radial offset to make a plurality of line contacts to define at least one pair of sealed-off pockets. Driving mechanism 50 including rotatably supported drive shaft 51 is connected to orbiting scroll 20 to effect the orbital motion of orbiting scroll 20. Oldham coupling 60 is disposed between circular end plate 21 and block member 30 to prevent the rotation of orbiting scroll 20 during its orbital motion. Circular end plate 21 of orbiting scroll 20 divides chamber 40 into first chamber 41 in which spiral elements 12 and 22 exists and second chamber 42 in which Oldham coupling 60 and one end of driving mechanism 50 exists. Discharge port 70 is formed at a central portion of circular end plate 11 to discharge the compressed fluid from a central merged fluid pocket. Suction port 80 is formed at a peripheral portion of circular end plate 11 for the entry of fluid into the radially outermost fluid pockets. A pair of apertures 90 having throttling effect are formed at a middle portion of circular end plate 21 of orbiting scroll 20 to link second chamber 42 to a pair of intermediately compressed fluid pockets 41a respectively.

0004During operation of the compressor, while intermediate fluid pockets 41a faces aperture 90, pressure in intermediate fluid pockets 41a is changed in some range. However, in a stable condition of operation of the compressor, pressure in second chamber 42 is maintained an average pressure of the range by throttling effect of aperture 90. Accordingly, orbiting scroll 20 is urged to fixed scroll 10 in virtue of averaged intermediate pressure in second chamber 42 to obtain a good axial seal therebetween.

0005However, in above prior art, second chamber 42 admits the intermediately compressed fluid from intermediate fluid pocket 41a in which pressure changes in the some range. Therefore, fluctuation of pressure in second chamber 42 cannot be avoided, even in the stable condition of operation of the compressor. In result, Oldham coupling 60 end driving mechanism 50 intermittently undesirably receive a thrust force which is generated by a reaction force of compressed fluid in all of fluid pockets, thereby durability of the compressor is reduced. Furthermore, a machining process for forming aperture 90 at circular end plate 21 is required to be precise.

0006It is a primary object of this invention to provide an improved axial sealing mechanism for a pair of scroll members of the scroll type compressor.

0007According to the invention, a scroll type compressor including a fixed scroll having a first end plate from which a first wrap or spiral element extends, an orbiting scroll having a second end plate from which a second wrap or spiral element extends, a block member attached to the first end plate to define a chamber in which the orbiting scroll is disposed, the first wrap and second wrap interfitting at an angular and radial offset to make a plurality of line contacts to define at least one pair of sealed-off fluid pockets, a first hollow portion for admitting discharged compressive fluid from a central merged-fluid pocket defined in the compressor, a second hollow portion for admitting suction fluid to be sucked into radial outermost fluid pockets defined within the compressor, a driving mechanism including a rotatable drive shaft connected to the orbiting scroll to effect the orbital motion of the orbiting scroll, and rotation-preventing mechanism for preventing the rotation of the orbiting scroll during its orbital motion, whereby the volumes of the fluid pockets change, the second end plate dividing the chamber into a first chamber in which the first and second wraps are located and a second chamber in which the rotation-preventing mechanism and one end of the drive shaft are located, (as disclosed in US-A-4475874) is characterised by a first permanently open bleed passage for linking the second chamber to the first hollow portion, and a second permanently open bleed passage for linking the second chamber to the second hollow portion, whereby there is a continuous bleed of fluid through the second chamber, and the second end plate is subjected in the second chamber to a substantially constant pressure which is intermediate the suction and discharge pressures.

0008In the drawings:- <ul id="ul0001" list-style="none"><li>Figure 1 is a vertical sectional view of the scroll type compressor in accordance with a prior art.</li><li>Figure 2 is a vertical sectional view of the scroll type compressor in accordance with a first embodiment of the invention.</li><li>Figure 3 is a vertical sectional view of the scroll type compressor in accordance with a second embodiment of the invention.</li><li>Figure 4 is a vertical sectional view of the scroll type compressor in accordance with a third embodiment of the invention.</li></ul>

0009A first embodiment of the present invention applied to a scroll type compressor for use a refrigerant circuit is illustrated in Figure 2, in which the same numerals are used to denote the corresponding elements shown in Figure 1 and the explanation of those elements is omitted. In Figure 2, the bolts used as fastening members for fixedly attaching block member 30 to circular end plate 11 are not shown. In this embodiment, drive shaft 51 rotatably penetrates hole 31 which is centrally formed in block member 30 through plain bearing 52 disposed between an outer peripheral surface of drive shaft 51 and an inner peripheral surface of hole 31. One end of drive shaft 51 is fixedly attached to bushing 53 disposed within second chamber 42. Circular boss 23 projecting from an end surface surface opposite to spiral element 22 is rotatably inserted into a circular depression 531 of which center is radially off set from a center of drive shaft 51 through bearing 231.

0010Passage 71 having a throttling effect includes first passage 71a and second passage 71b. First passage 71a is radially formed in circular end plate 11 to radially penetrate from an outer peripheral surface of circular end plate 11 to an inner peripheral wall of discharge port 70. Second passage 71b is axially formed at circular end plate 11 to connect first passage 71a to second chamber 42. Plug member 72 is fixedly attached to the outer peripheral surface of circular end plate 11 to close an outer radial end of first passage 71a. Accordingly, passage 71 links discharge port 70 to second chamber 42.

0011Passage 81 having a throttling effect includes third passage 81a and fourth passage 81b. Third passage 81a is radially formed at block member 30 to radially penetrate from an outer peripheral surface of block member 30 to an inner peripheral surface of block member 30. Fourth passage 81b is axially formed at block member 30 to connect third passage 81a to second chamber 42. Plug member 82 is fixedly attached to the outer peripheral surface of block member 30 to close an outer radial end of third passage 81a. Accordingly, passage 81 links suction port 80 to second chamber 42.

0012During operation of the compressor, a part of discharged refrigerant gas in discharge port 70 flows into second chamber 42 through passage 71 with pressure reduction by virtue of throttling effect of passage 71. Then refrigerant gas in second chamber 42 flows into suction port 80 through aperture 81 with pressure reduction by virtue of throttling effect of passage 81. As a result, pressure in second chamber urging orbiting scroll 20 to fixed scroll 10 is maintained at some value which is smaller than discharge pressure and larger than suction pressure, that is, an intermediate pressure. Particularly, in the stable condition of operation of the compressor, pressure in second chamber 42 is maintained an intermediate pressure with no pressure fluctuation due to both discharge and suction pressure being maintained constant. Accordingly, a good axial seal between orbiting scroll 20 and fixed scroll 10 is maintained without reducing durability of Oldham coupling 60 and driving mechanism 50. Furthermore, pressure in second chamber 42 can be selected by changing a diameter of both passages 71 and 81. Still furthermore, reduction of compression ability of the compressor due to blown-by discharge gas through passage 71, second chamber 42 and passage 81 can be largely decreased by virtue of the throttling effect of both passages 71 and 81.

0013Figure 3 illustrates a second embodiment of the present invention applied to a hermetic type scroll compressor for use in a refrigerating circuit. In Figure 3, the same numerals are used to denote the corresponding elements shown in Figure 2 and the explanation of those elements is omitted. In this embodiment, above-mentioned elements, such as, fixed scroll 10, orbiting scroll 20, block member 30, driving mechanism 50 and Oldham coupling 60 are housed in hermetically sealed casing 100. Casing 100 further houses motor 54 for rotating drive shaft 51. Motor 54 includes ring-shaped stator 54a and ring-shaped rotor 54b. Stator 54a is firmly secured to an inner peripheral wall of casing 100 by forcible insertion. Rotor 54b is firmly secured to drive shaft 51 also by forcible insertion. Hole 511 is formed in drive shaft 51 to lead a lubricating oil 55 collected in a bottom of casing 100 to a gap between an outer peripheral surface of drive shaft 51 and an inner peripheral surface of plain bearing 52.

0014One end of inlet port 83 which radially penetrates casing 100 is hermetically sealed and connected to suction port 80. One end of outlet port 73, which also radially penetrates and is hermetically sealed to casing 100, is open to inner space 101 of casing 100. Passage 711 having a throttling effect is formed in block member 30 to connect second chamber 42 to inner space 101 of casing 100. Passage 811 having a throttling effect is also formed in block member 30 to connect suction port 80 to second chamber 42. Passage 811 includes passages 811a and 811b which are radially and axially formed at block member 30 respectively.

0015In operation, as arrows 91 indicate, suction gas in suction port 80 flowing from one element of a refrigerating circuit, such as an evaporator (not shown), through inlet port 83 is taken into the outermost fluid pockets and compressed by virtue of the orbital motion of orbiting scroll 20 and then discharged through discharge port 70. The discharged refrigerant gas fills inner space 101 of casing 100 except chamber 40, therefore this type of hermetic scroll compressor is generally called a high pressure type hermetic scroll compressor. Then a small part of the discharged refrigerant gas flows into second chamber 42 through passage 711 with pressure reduction. On the other hand, a greater part of the discharged refrigerant gas flows to another element of the refrigerating circuit, such as a condenser (not shown), through outlet port 73. Pressure decreased refrigerant gas in second chamber 42 flows into suction port 80 through passage 811 with further pressure reduction and merges into the suction gas. The effect obtained by a cooperation of both passages 711 and 811 is similar to the effect of the cooperation of the passages 71 and 81 described in the first embodiment so that the explanation thereof is omitted.

0016Figure 4 illustrates a third embodiment of the present invention also applied to a hermetic type scroll compressor for use in a refrigerating circuit. In Figure 4, the same numerals are used to denote the corresponding elements shown in Figure 3 and the explanation of those elements is omitted. In this embodiment, one end of inlet port 83' which radially penetrates and is hermetically sealed to casing 100 is opened to inner space 101 of casing 100 with being adjacent to suction port 80. One end of outlet port 73', which axially penetrates casing 100, is hermetically sealed and connected to discharge port 70. Passage 712 having throttling effect is formed in circular end plate 11 to connect discharge port 70 to second chamber 42. Passage 712 includes passages 712a and 712b which are radially and axially formed in circular end plate 11 respectively. Passage 812 having throttling effect is formed in block member 30 to connect second chamber 42 to inner space 101 of casing 100.

0017In operation, as arrows 92 indicate, suction gas in suction port 80 flowing from a element of a refrigerating circuit, such as an evaporator (not shown), through inlet port 83' is taken into the outermost fluid pockets and compressed by virtue of the orbital motion of orbiting scroll 20 and then discharged through discharge port 70. A part of suction gas flows into, and fills inner space 101 of casing 100 except chamber 40, therefore,this type of hermetic scroll compressor is generally called a low pressure type hermetic scroll compressor. Then, a small part of the discharged refrigerant gas flows into second chamber 42 through passage 712 with pressure reduction. On the other hand, a greater part of discharged refrigerant gas flows to another element of the refrigerating circuit, such as a condenser (not shown), through outlet port 73'. Pressure decreased refrigerant gas in second chamber 42 flows into inner space 101 of casing 100 through passage 812 with pressure reduction and merges into the suction gas. The effect obtained by a cooperation of both passages 712 and 812 is similar to the effect of a cooperation of passages 71 and 72 shown in Figure 2 so that the explanation thereof is omitted.

0018In the second and third embodiments, the invention is applied to a hermetic type scroll compressor, but these embodiments could be adapted for use in an open type scroll compressor.

0019Furthermore, a machining process for forming the passages does not require to be precise.