Scroll type fluid machine

Abstract: Object: In a scroll type fluid machine in which a swivel scroll (14) is driven by a drive bush (101) engaged with a drive shaft bearing portion of said swivel scroll (14) and an eccentric drive pin (25) provided eccentrically on a drive shaft (7), a concentrated surface fatigue caused on the surface of the drive bush (101) is avoided and an elongation of the life of the drive bush (101) is attained. Construction: A rotatable cylindrical ring (102) is provided on the outer circumference of the drive bush (101).

Description: BACKGROUND OF THE INVENTION: Field of the Invention: The present invention relates to a scroll type fluid machine as defined in the preamble portion of claim 1, to be used as a compressor, an expander, etc. Description of the Prior Art: Fig. 4 is a longitudinal sectional view of a scroll type compressor in the prior art. A similar scroll type compressor disclosing the features of the preamble portion of claim 1 is known from DE-A-43 38 771. In the figure, numeral 1 designates a hermetic housing consisting of a cup-like body 2, a front end plate 4 fixed thereto by bolts 3 and a cylindrical element 6 fixed thereto by bolts 5. A rotating shaft 7, passing through said cylindrical element 6, is supported rotatably by the hermetic housing 1 via bearings 8, 9. Within the housing 1, there are provided a stationary scroll 10 and a swivel scroll 14. The stationary scroll 10 has an end plate 11 and a spiral wrap 12 provided standingly on its inner surface, said end plate 11 being tied to the cup-like body 2 by bolts 13 so as to be fixed within the housing 1. By the outer circumferential surface of the end plate 11 and the inner circumferential surface of the cap-like body 2 being sealingly contacted, the inside of the housing 1 is partitioned so as to form a discharge cavity 31 on the outer side of the end plate 11 and a suction chamber 28 on the inner side of the end plate 11. Further, at the center of the end plate 11, a discharge port 29 is dug so that opening and closing thereof is made by a discharge valve 30. The swivel scroll 14 has an end plate 15 and a spiral wrap 16 provided standingly on its inner surface, said spiral wrap 16 having a substantially same shape as the spiral wrap 12 of the stationary scroll 10. The swivel scroll 14 and the stationary scroll 10 are engaged with each other eccentrically by a length of a revolutional swivel radius and with a deviation of angle of 180 degrees, as shown in the figure. Thus, a tip seal 17 provided buriedly on the tip surface of the spiral wrap 12 being sealingly contacted to the inner surface of the end plate 15, and a tip seal 18 provided buriedly on the tip surface of the spiral wrap 16 being sealingly contacted to the inner surface of the end plate 11, the side surfaces of spiral wraps 12, 16 make line contact with each other at a plurality of places, thereby a plurality of compression chambers 19a, 19b, being nearly in a point symmetry to each other around the centers of the spirals, are formed. Within a cylindrical boss 20 provided projectingly at the central portion of the outer surface of the end plate 15, a drive bush 21 is inserted rotatably via s swivel bearing 23, and within a slide groove 24 dug in said drive bush 21, an eccentric drive pin 25 provided eccentrically and projectingly at the inner end of the rotating shaft 7 is inserted slidably. Said drive bush 21 is fitted with a balance weight 27 for balancing dynamic unbalances caused by revolutional swivel motions of the swivel scroll. Between the circumferential edge of the outer surface of the end plate 15 and the inner surface of the front end plate 4, a thrust plate 36 and an Oldham coupling 26 are interposed. Incidentally, numeral 37 designates a balance weight fixed to the rotating shaft 7. Thus, upon the rotating shaft 7 being rotated, the swivel scroll 14 is driven via a swivel drive mechanism consisting of the eccentric drive pin 25, the drive bush 21, boss 20, etc. and the swivel scroll 14, being prevented from rotating by a rotation preventing mechanism or the Oldham coupling 26, does revolutional swivel motions on a circular track having a revolutional swivel radius, i.e. a radius being the eccentricity amount between the rotating shaft 7 and the eccentric drive pin 25. Then, the line contact portions of the side surfaces of the spiral wraps 12, 16 move gradually to the direction of the spiral centers, and as a result, the compression chambers 19a, 19b move, with volume thereof being reduced, to the direction of the spiral centers. Accompanying therewith, a gas flown into the suction chamber 28 through a suction port (not shown in the figure) is taken into each compression chamber 19a, 19b from openings of the outer finish ends of the spiral wraps 12, 16. While being compressed, the gas comes in a central chamber 22 and, passing through the discharge port 29 and pushingly opening the discharge valve 30, it is discharged into the discharge cavity 31 and flown out through a discharge port (not shown in the figure). In the meanwhile, a thrust load acts on the end plate 15 of the swivel scroll 14 by a compressed gas within the compression chambers 19a, 19b and this thrust load is supported by the inner surface of the front end plate 4 via the thrust plate 36. Fig. 3 is an explanatory drawing of gas pressures acting on the swivel scroll 14. A gas pressure F P acting on the swivel scroll 14 is a combined force of a component force F T and a component force F R . Because of a geometrical dimensional relationship, F T is far larger than F R (F T » F R ) and the direction of the gas pressure F P acts, as shown in Fig. 3, always nearly in a rectangular direction to the contacting direction of the spiral wrap 16 of the swivel scroll 14 and the spiral wrap 12 of the stationary scroll 10. Because this load acts on the drive bush 21, out of the swivel drive mechanism to drive the swivel scroll 14, at a certain definite position all through the operation time, there occurs a surface fatigue concentratedly at one position of the drive bush, hence there are such shortcomings that a flaking occurs and the life of the drive bush 21 is damaged. SUMMARY OF THE INVENTION: It is therefore an object of the present invention to dissolve the above-mentioned shortcomings in the prior art, aiming at avoiding a concentrated surface fatigue caused on the surface of a drive bush so as to remarkably elongate the life thereof. The present invention which dissolves the above-mentioned shortcomings relates to a scroll type fluid machine in which a swivel scroll is driven by a drive bush engaged with a drive shaft bearing portion of the swivel scroll and an eccentric drive pin provided eccentrically on a drive shaft, having the following feature or features: (1) On the outer circumference of the drive bush, a rotatable cylindrical ring is provided. (2) In the scroll type fluid machine mentioned in (1) above, a step is provided at one end of the drive bush and a stopper plate is provided at the other end thereof so that a movement of the cylindrical ring is regulated. (3) In the scroll type fluid machine mentioned in (1) above, a self-lubricating high molecular compound coating is applied to one surface either of the outer circumference of the drive bush or of the inner circumference of the cylindrical ring. (4) In the scroll type fluid machine mentioned in (1) above, a path to supply a lubricating oil to the sliding portion between the drive bush and the cylindrical ring is dug within the eccentric drive pin and the drive bush. According to the present invention constructed as above, as the surface of the drive bush moves even if a load acting on the drive bush from the swivel scroll via a swivel bearing is always concentrated at one position in principle, the concentrated surface fatigue on the surface of the drive bush can be avoided and a remarkable elongation of the life of the drive bush can be attained. In the scroll type fluid machine in which the step and the stopper are provided, coming out of the cylindrical ring is prevented. In the scroll type fluid machine in which the self-lubricating high molecular compound coating is applied, the movement of the cylindrical ring becomes smooth and the concentrated surface fatigue can be avoided. In the scroll type fluid machine in which a path to supply a lubricating oil to the sliding portion between the drive bush and the cylindrical ring is dug, as the mutual movement of the drive bush and the cylindrical ring becomes facilitated, the concentrated surface fatigue can be avoided. BRIEF DESCRIPTION OF THE DRAWINGS: In the accompanying drawings: Fig. 1 is a longitudinal sectional view of a main portion of a scroll type compressor of a first preferred embodiment according to the present invention. Fig. 2 is a longitudinal sectional view of a main portion of a scroll type compressor of a second preferred embodiment according to the present invention. Fig. 3 is an explanatory drawing of gas pressures acting on a swivel scroll. Fig. 4 is a longitudinal sectional view of a scroll type compressor in the prior art. DESCRIPTION OF THE PREFERRED EMBODIMENTS: Fig. 1 is a longitudinal sectional view of a main portion of a scroll type compressor of a first preferred embodiment according to the present invention. In the figure, numeral 25 designates an eccentric drive pin provided eccentrically to a rotating shaft 7 and inserted in a drive bush 101. At one end of the drive bush 101, a balance weight 27 is fitted. In this preferred embodiment, on the outer circumference of the drive bush 101, a step 105 is provided, and a rotatable cylindrical ring 102 is fitted there. On the shaft end side, a stopper plate 103 is provided so that coming out of the cylindrical ring 102 is prevented. The stopper plate 103 is fixed by a snap ring 104 fitted in a groove of the end portion of the eccentric drive pin 25. Further, on the outer circumferential surface of the drive bush or on the inner circumferential surface of the cylindrical ring, a self-lubricating high molecular compound coating of a small friction coefficient, for example, a coating of polyamide-imide group resin etc. is applied. The other portions than those mentioned here are same as those in the prior art. In the preferred embodiment constructed as above, as the surface of the drive bush moves even if a load acting on the drive bush from the swivel scroll via a swivel bearing is always concentrated at one position in principle, a concentrated surface fatigue caused on the surface of the drive bush can be avoided and a remarkable elongation of the life of the drive bush can be attained. Fig. 2 is a longitudinal sectional view of a main portion of a scroll type compressor of a second preferred embodiment according to the present invention. In the figure, numeral 110 designates a suction path provided in parallel with a rotating shaft 7 within a larger diameter portion of the rotating shaft 7 and an eccentric drive pin 25, numeral 111 designates a radial directional path connecting to the suction path 110, provided in a radial direction within the eccentric drive pin 25 and a drive bush 101, and numeral 112 designates a groove connecting to the outside end of the radial directional path 111, provided in parallel with a rotating shaft 7 on the outer circumference of the drive bush 101. The direction of the radial directional path 111 is same as that of the eccentricity of the eccentric drive pin 25. The other portions than those mentioned here are same as those in the first preferred embodiment. In the construction mentioned above, by an action of a centrifugal force of the radial directional path 111, gas and oil contained in the gas enter from the suction path 110 and are supplied into between the drive bush 101 and a cylindrical ring 102 through the radial directional path 111. The gas and the oil colliding with the cylindrical ring 102, the oil content sticks on the inner surface of the cylindrical ring 102 to work for lubrication and the gas content comes out from the groove 112 on the outer circumference of the drive bush 101. Thus, without a choke in the flow of oil, the oil supply between the drive bush and the cylindrical ring is ensured. Thereby, the mutual movement of the drive bush and the cylindrical ring is made smooth and an elongation of the life of the drive bush can be attained. In a scroll type fluid machine according to the present invention, as a rotatable cylindrical ring is provided on the outer circumference of a drive bush, or as a step is provided on one end of the drive bush and a stopper plate is provided on the other end thereof so that the movement of the cylindrical ring is regulated, or further as a self-lubricating high molecular compound coating is applied either on the outer circumferential surface of the drive bush or on the inner circumferential surface of the cylindrical ring, or further as a lubricating oil is supplied into the sliding portion between the drive bush and the cylindrical ring, a concentrated surface fatigue caused on the surface of the drive bush is avoided and a remarkable elongation of the life of the drive bush can be attained.

Claims: A scroll type fluid machine in which a swivel scroll (14) is driven by a drive bush (101) engaged with a drive shaft bearing portion of said swivel scroll (14) and an eccentric pin (25) provided eccentrically on a drive shaft (7), characterized in that a rotatable cylindrical ring (102) is provided on the outer circumference of said drive bush (101), between the bearing portion mounted to the swivel scroll and the drive bush. A scroll type fluid machine as claimed in Claim 1, characterized in that a step (105) is provided at one end of the drive bush (101) and a stopper plate (103) is provided at the other end thereof so that a movement of the cylindrical ring (102) is regulated. A scroll type fluid machine as claimed in claim 1 or 2, characterized in that a self-lubricating high molecular compound coating is applied to one surface either of the outer circumference of the drive bush (101) or of the inner circumference of the cylindrical ring (102). A scroll type fluid machine as claimed in claim 1 or 2, characterized in that a path (110,111) to supply a lubricating oil to the sliding portion between the drive bush (101) and the cylindrical ring (102) is provided within the eccentric drive pin (25) and the drive bush (101).

Inventors: SHIGEOKA TETSUO, TAKAHASHI KAZUAKI, TOMATSU KATSUHISA, SHIGEOKA, TETSUO, TAKAHASHI, KAZUAKI, TOMATSU, KATSUHISA, Shigeoka, Tetsuo, c/o Nagoya Res., Mitsubishi, Takahashi, Kazuaki, c/o Churyo Eng. K.K., Tomatsu, Katsuhisa, c/o Nagoya Res., Mitsubishi
Applicants: MITSUBISHI HEAVY IND LTD, MITSUBISHI JUKOGYO KABUSHIKI KAISHA
Application year: 1996
Main classification: F04C18
IPC codes: F04C29