SCROLL TYPE FLUID DISPLACEMENT APPARATUS WITH IMPROVED FIXED CONSTRUCTION OF FIXED SCROLL

Abstract: The scroll type displacement apparatus includes a compressor housing (2), an orbiting scroll (7) and a fixed scroll (6) each has an end plate (61,71,171) and a spiral element (62,72). The both spiral elements interfit at angular and radial offset to make a plurality of line contacts between the spiral curved sur­ faces to define fluid pockets. A drive mechanism is operatively connected to the orbiting scroll for orbiting the orbiting scroll relative to the fixed scroll while preventing rotation of the orbiting scroll to thereby change the volume of the fluid pockets. A plurality of first holes (171a,171b) are formed through the end plate (171) of the fixed scroll for fixing thereof on the inner end surface of the projecting portions. A plurality of projecting portions (451) are formed on an inner end surface of the housing (2) to extended toward the fixed scroll, and second threaded hole (451a) are formed on projecting portions (451), respectively. A bolt (18) is screwed into the second holes through the first holes to fixed the fixed scroll on the housing.

Description: This invention relates to a scroll type fluid displacement apparatus, and more particularly, to an improved fixed construction for a fixed scroll of scroll type fluid compressor. Scroll type fluid displacement apparatus are well-known in the prior art. For example, US-A-4 547 138 discloses the basic construction of a scroll type fluid apparatus. These apparatus include two scrolls each having a circular end plate and a spiroidal or involute spiral element. The scrolls are maintained at an angular and radial offset so that both spiral elements interfit to form a plurality of line contacts between their curved surfaces to thereby seal off and define at least one pair of fluid pockets. The relative orbital motion of the two scrolls shifts the line contacts along the spiral curved surfaces and, as a result, the volume of the fluid pockets increases or decreases, dependent on the direction of the orbital motion. Thus, a scroll type fluid displacement apparatus may be used to compress, expand, or pump fluids. Referring to Fig. 1 showing a similar conventional scroll type fluid compressor 1, such compressor includes a compressor housing 2 having a front end plate 3 and a cup-shaped casing 4 fixed on one end surface of front end plate 3 by bolts 5. A fixed scroll 6 and an orbiting scroll 7 are placed in the compressor housing 2. Fixed scroll 6 includes an end plate 61, a spiral element 62 which is formed on one end surface of end plate 61, and a projecting portion 63 which is formed on the other end surface of end plate 61. Projecting portion 63, which includes a divided wall 631 and a plurality of shank portions 632, is fixed on the inner wall surface of a bottom portion 41, which includes a divided wall 411 and a shank portion 412, of cup shaped casing 4 by bolts 8, which penetrates through holes 412a and 632a formed therein. End plate 61 of fixed scroll 6, which is secured to cup-shaped casing 4, divides the interior of cup-shaped casing 4 into a discharge chamber 42 and a suction chamber 43 due to the sealing between the outer surface of end plate 61 and the inner surface of cup-shaped casing 4 through seal ring 9. Orbiting scroll 7 includes an end plate 71, a spiral element 72 which is formed on one end surface of end plate 71, and a tubular boss 73 which is formed on the other end surface of end plate 71. Spiral element 72 interfits spiral element 62 of fixed scroll 6 at angular and radial offset to form a plurality of line contacts to seal off fluid pockets in a manner known in the art. Orbiting scroll 7 is coupled to a drive shaft 10 which is rotatably supported within front end plate 3 through a radial bearing 31. Since the drive mechanism which drives orbiting scroll 7 without rotation is known in the art, for examples, U.S. Patent Nos. 4,439,118 and 4,547,138, the detailed explanation of this drive mechanism is omitted. When orbiting scroll 7 is undergo the orbital motion, the fluid, which flows into suction chamber 43 from suction port 11 formed on cup-shaped casing 4, is taken into the fluid pockets formed between spiral elements 62 and 72. The fluid is gradually compressed and moved toward the center of the spiral elements. Compressed fluid at the center of the spiral elements moves to discharge chamber 42 through a discharge hole 611 formed through end plate 61 of fixed scroll 6. The compressed fluid is discharged to the outside of compressor housing 2 through discharge post 12 formed on cup-shaped casing 4. In the above compressor, it is needed to form a threaded hole 632a in shank portion 632 of projecting portion 63 to screwed bolt 8 thereby an axial certain length of hole 632a should be required. Therefore, the axial length of shank portion 632 is desigined to be larger than the required dimension which is needed to define a suitable discharge chamber, and the axial length of compressor 1 becomes longer. In addition, a seal ring 13 is disposed between the outer surface of cap-shaped casing 4 and bolt 8 to prevent leakage of the discharged gas for discharge chamber 42 to the outside. However, when the discharged gas pressure is becoming high, it can not be avoided for gas to leak from discharge chamber 42 to the outside through a small gap adjacent seal ring 13 although the volume of the gas leaking is very little. Referring to Fig. 2, the rear end surface of a fixed scroll of a conventional scroll type fluid compressor is shown. Fixed scroll 6 is originally made by casting and the rear end surface of end plate 61 and the axial end surface of projecting portion 63 are formed in the form of plane by cutting. However, since the surrounding area 612 of projecting portion 63 including dividing wall 631 and shank portion 632 can not be finished by cutting, a casting surface still remains on the surface of surrounding area 612 thereof. Therefore, a valve retainer 14 to limit the opening volume of valve plate 15 can not be fixed on the casing outer surface of surrounding area 612. Because of this, valve retainer 14 is needed to be extended to the cutted surface adjacent the outer surface of end plate 61 so as to be securedly fixed therein by bolt 16. It is a primary object of this invention to provide a scroll type fluid compressor with a fixed construction of a fixed scroll of which the axial length can be relatively short. It is another object of this invention to provide a scroll type fluid compressor with a fixed construction of a fixed scroll which can be prevented from leakage of fluid to the outside. It is a further object of this invention to provide a scroll type fluid compressor which is simple in construction for fixing the fixed scroll. The scroll type displacement apparatus according to the present invention includes a compressor housing which has a plurality of projecting portions on an inner surface thereof. An orbiting scroll and a fixed scroll each has an end plate and a spiral element which extends from one side of the end plate. The spiral element interfit at angular and radial offset to make a plurality of line contacts between the spiral curved surfaces, which define fluid pockets. A drive mechanism is operatively connected to the orbiting scroll for orbiting the orbiting scroll relative to the fixed scroll while preventing rotation of the orbiting scroll to thereby change the volume of the fluid pockets. A plurality of first holes are formed through the end plate of the fixed scroll for fixing thereof on the inner end surface of the projecting portions. A plurality of second threaded holes are formed in projecting portions, respectively. A plurality of bolts are screwed into the second threaded holes through the first holes. Further objects, features and other aspects of this invention will be understood from the following detailed description of preferred embodiments of this invention with reference to the annexed drawings. Fig. 1 is a cross-sectional view of a conventional scroll type fluid compressor. Fig. 2 is a plane view of a fixed scroll in Fig. 1. Fig. 3 is a partly cross-sectional view of a scroll type fluid compressor in accordance with one embodiment of this invention. Fig. 4 is plane view of a fixed scroll in Fig. 3. Referring to Fig. 3, the fixed construction of a fixed scroll in accordance with one embodiment of this invention is shown. The description of the same parts and constructions of the compressor shown in Fig. 1 is omitted to simplify the specification and the same numerals are used accorded to each parts and constructions thereof. An annular shaped portion wall 45 is axially extended from the inner surface of the bottom portion of cup-shaped casing 2 to surround a discharge hole 171c on fixed scroll 17. A plurality of shank portion 451 are formed on partition wall 45 equiangularly placed. The partition wall is not always needed to be formed, if a pluratlity of shank portion 451 are equiangularly formed on the inner surface of bottom portion of casing 2. A threaded hole 451a is formed on each shank portion 451. The fixed scroll 17 comprises a circular end plate 171 and a spiral element 172 axially extending from one end surface of end plate 171. A plurality of penetrating holes 171b are formed thourgh end plate 171 to be aligned with threaded hole 451a of partition wall 45. One end opening portion of penetrating hole 171b which faces the same side as spiral element 172 extends is formed in a concave portion 171a. The dimension of concave portion 171a, such as diameter and depth, is formed to be larger than that of the head portion of bolts 18. The width of end plate 171 is formed larger than that in convention so that end plate 171 can prevent decreasing of strength thereof by forming concaves 171a. The fixed scroll 17 is fixed on the inner end surface of bottom portion of cup-shaped casing 4 by said bolts 18 which are screwed into threaded holes 451a through hole 171b of end plate 171. A bottom end plate 19 is disposed on the end surface of end plate 171 to cover the surface of end plate 171 defined between spiral element 172, therefore, the opening space of concave portion 171a is covered by bottom plate 19. As explained above, the rear end surface of end plate 171 which faces discharge chamber 42 is formed as flat surface, as shown in Fig. 4. Therefore, the finishing of the rear surface by cutting is easily operated, and a fixed position of valve retainer 14 which is fixed on the rear surface of end plate 171 by bolt 16 is freely selected in accordance with the configuration of discharge valve 15 and valve retainer 14.

Claims: 1. A scroll type displacement apparatus including a compressor housing (2), an orbiting scroll (7) and a fixed scroll (6) each having an end plate (61, 71, 171) and a spiral element (62, 72) extending from one side of said end plate, said spiral elements interfitting each other with an angular and radial offset to make a plurality of line contacts to define fluid pockets, and drive means operatively connected to said orbiting scroll for orbiting said orbiting scroll relative to said fixed scroll while preventing rotation of said orbiting scroll to thereby change the volume of said fluid pockets, a plurality of projecting portions (451) being formed on the inner end surface of the housing (2) and extending toward said fixed scroll (6), characterized by a plurality of first holes (171a, 171b) formed through said end plate (171) of said fixed scroll (6) for fixing said scroll (6) to the inner end surface of said projecting portions (451), second holes (451a) formed in said projecting portions (451), respectively, and bolts (18) screwed into said second holes through said first holes (171a, 171b), thereby fixing the scroll so that it is fixedly disposed on said housing (2). 2. The scroll type displacement apparatus of claim 1, wherein said first and second holes (171a, 171b; 451a) are disposed to be equiangularly spaced respectively. 3. The scroll type displacement apparatus of claim 1 or 2, wherein said first holes (171a, 171b) are formed to have two-stepped inner diameters. 4. The scroll type displacement apparatus of one of claims 1 to 3, wherein said projecting portions (451) are connected with one another by an annular partition wall.

Inventors: HASEGAWA, MASATO
Applicants: SANDEN CORPORATION
Application year: 1988
Main classification: F04C18
IPC codes: F04C18