Abstract:
A scroll compressor has a scroll mechanism disposed in a closed container and driven by a motor through a crank shaft rotatably supported at two points by first and second bearings disposed adjacent the opposite ends of the motor. The bearing which is remote from the scroll mechanism comprises a sliding bearing. The first end of the crank shaft remote from the scroll mechanism has a peripheral surface disposed in sliding engagement with the sliding bearing and formed therein with a lubricant supply groove communicated with an axial lubricant supply hole formed in the crank shaft and having a closed end adjacent the first end of the crank shaft and opened in an end face of a crank pin section thereof. The sliding bearing is communicated with a lubricant reservoir formed by a lower part of the container. The lubricant in the reservoir is subjected to the pressure of a compressed fluid discharged from the scroll mechanism and is forcibly fed into the lubricant supply groove through the sliding bearing.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a lubricant supply system for a scroll fluid machine such as a compressor, an expander or a liquid pump. 
     A scroll compressor of the type in which a drive shaft is supported at both sides of an electric motor is disclosed in Japanese Patent Unexamined Publication No. 62-135676. In this known scroll compressor, the bearing mounted on a lower suspension structure of the compressor to support the lower portion of the drive shaft is lubricated with a part of lubricant which is suctioned by a pumping action effected by rotation of the drive shaft from a lubricant reservoir through a lubricant passage bore and then supplied to the bearing via lubricant supply holes formed in an inner race of the bearing past a passage hole and a peripheral groove. The remainder of the lubricant is supplied to the other bearing and other portions requiring lubrication. 
     Thus, in this lubricant supply system, the smoothness of the flow of the lubricant tends to be impaired due to the fact that a part of the lubricant is supplied to the bearing provided on the lower structure while the remainder is fed to the other bearing and other portions. 
     In addition, the lubricant supply system is required to have a complicated structure in order to distribute the lubricant to the bearings at rates which are optimum for the respective bearings. 
     Furthermore, this known lubricant supply system may fail to create the necessary supply pressure when the pumping effect is too low due to a low rotation speed of the drive shaft, particularly in the case where the operation speed of the rotary compressor is controlled by an inverter. 
     SUMMARY OF THE INVENTION 
     Accordingly, an object of the present invention is to provide a scroll compressor having a bearing lubricating system which is simple in construction but yet capable of ensuring optimum lubrication of the bearings. 
     Another object of the present invention is to provide a scroll compressor which can reliably and stably supply lubricant to a bearing which supports the end of the drive shaft remote from the scroll mechanism. 
     To these ends, according to the present invention, a scroll fluid machine is provided which includes a scroll mechanism disposed in a closed space and including a stationary scroll member and an orbiting scroll member cooperating with the stationary scroll member to define therebetween a scroll space, an electric motor disposed in the closed space, a drive shaft including a first portion axially extending through the rotor of the electric motor and fixed to the rotor and a second portion having a crank section drivingly connected to the orbiting scroll member to transmit the rotation of the rotor thereto. Bearing means are provided including a first bearing supporting supports the free end of the first portion of the drive shaft and a second bearing supporting a portion of the drive shaft between the first and second portions thereof. The first bearing comprises a sliding bearing, with the first portion of the drive shaft having peripheral surface slidingly contacting the sliding bearing. The peripheral surface includes a lubricant supply groove formed therein and opening at its one end in the end surface of the free end of the drive shaft and terminating at its other end in the peripheral surface. The drive shaft further includes an axial lubricant supply formed hole and a radial lubricant hole providing a communication between the lubricant supply groove and the axial lubricant supply hole. The axial lubricant supply hole is closed at the end adjacent the end surface of the drive shaft but opened in the end surface of the crank section. The scroll fluid machine further includes lubricant supply means for supplying a pressurized lubricant to the lubricant supply groove. 
     In a preferred embodiment of the present invention, the scroll mechanism is a compression mechanism for compressing a gaseous fluid. The compression mechanism, the drive shaft and the electric motor are arranged such that their longitudinal axes extend horizontally, with the bottom of the closed space forming a lubricant reservoir for the lubricant while the upper portion of the closed space communicates with a discharge port of the compression mechanism so that the pressure of the pressurized fluid discharged form the discharge Port of the compression mechanism acts on the lubricant in the lubricant reservoir. The scroll fluid machine further includes Passage means provided for communication between the lubricant reservoir and the lubricant supply groove. Consequently, the pressure of the pressurized fluid acting on the lubricant in the lubricant reservoir forces the lubricant into the oil supply groove through the passage means. 
     The above and other objects, features and advantages of the present invention will become more clear from the following description of the preferred embodiment with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an axial sectional view of a scroll compressor embodying the present invention; 
     FIG. 2 is a fragmentary enlarged sectional view of the compressor shown in FIG. 1 showing a sliding bearing incorporated therein; 
     FIG. 3 is a cross-sectional view of the sliding bearing taken along the line III--III in FIG. 2; and 
     FIG. 4 is a cross-sectional view of the scroll compressor taken along the line IV--IV in FIG. 1. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The compressor shown in FIG. 1 is a refrigerant compressor for compressing a refrigerant gas in, for example, an air conditioning system. The compressor has a substantially cylindrical closed container 1 composed of a cylindrical casing 1a and end caps 1a and 1b which close both open ends of the casing 1a. The container 1 accommodates a scroll compression mechanism 2, an electric motor 3 and a drive shaft 7 which is a crankshaft interconnecting the scroll compression mechanism 2 and the electric motor 3 such that the axes of the compression mechanism 2, the drive shaft 7 and the electric motor 3 extend horizontally. The lower end portion of the closed space inside the container 1 serves as a lubricant reservoir 4. 
     The compression mechanism 2 has an orbiting scroll member 5, a stationary scroll member 6 and a mechanism 9 for preventing the orbiting scroll member from rotating about its own axis. The orbiting scroll member 5 has a flat end plate 5a and a spiral wrap 5b on one surface of the end plate 5a. Similarly, the stationary scroll member 6 has an end plate 6a and a spiral wrap 6b on one surface of the end pate 6a. Both scroll members 5 and 6 are assembled together such that their wraps 5b and 6b mesh each other such that wrap spaces are formed between both scroll members 5 and 6 in a manner known. The drive shaft 7 has a crank pin section 7a on one end thereof. The crank pin section 7a is received in a bearing 5c which is provided on the surface of the end plate 5a of the orbiting scroll member 5 opposite to the wrap 5b. A pressure equalizer hole 5d is formed in the plate 5a so as to provide a communication between a wrap space in compression phase and a back-pressure chamber 8c which will be described later. 
     The stationary scroll member 6 is disposed in one 1b of the caps of the container 1. A suction port 6c is formed in a peripheral region of the end plate 6a outside the wrap 6b, while a discharge port 6d is formed in the central region of the end plate 6a. A suction port piece 1e, extending through and welded to the cap 1b, is connected to the suction port 6c . 
     Referring specifically to FIGS. 1 and 4, a frame 8 has a generally cylindrical form and is received in the casing 1a of the container 1 in close contact with the inner peripheral surface of the casing 1a. More specifically, one end 8d of the frame 8, which is the left end as viewed in FIG. 1, has a generally circular form with a notched portion which forms a passage 8h to be described later. The stationary scroll member 6 is fixed to the end surface of this circular end 8d of the frame 8 by means of bolts. The peripheral surface 8d&#39; of the circular end 8d of the frame 8 closely contacts with the inner peripheral surface of the casing 1a of the container 1 so as to divide the space inside the container 1 into a chamber or a space 1b-1 adjacent the cap 1b and a chamber or a space 1c-1 adjacent the cap 1c. The discharge port 6d opens to the space 1b-1. 
     The other end of the frame 8, i.e., the right end as viewed in FIG. 1, has four radial projections 8e which are arranged at a constant circumferential pitch thereby forming a spider. The outer ends of the radial projections 8e of the spider closely contact with the inner peripheral surface of the casing 1a. A hat-shaped motor cover 10, forming a part of the frame 8, is fixed by bolts to the axially outer end surface 8i of the spider 8e. The motor cover 10 is disposed adjacent the space 1c-1. 
     The frame 8 has a cylindrical peripheral wall 8f of a diameter smaller than that of the inner peripheral surface of the casing 1a. The peripheral wall 8f is disposed between the spider 8e and the first-mentioned end 8d of the frame 8 and cooperates with the casing 1a to define therebetween an annular chamber 1a-1 which communicates with the aforementioned space 1c-1 through arcuate passages 8e-1 defined by the projections 8e of the spider and the casing 1a of the container 1. The annular chamber 1a-1 communicates at its lower portion with the space 1b-1 through a communication hole 8k formed in a lower region of the left end portion 8d of the frame 8. The casing 1a of the container 1 is provided with an outlet port 1i which communicates with the aforementioned annular chamber 1a-1. 
     The left end portion 8d of the frame 8 is recessed at its central region so as to receive the orbiting scroll member 5. The mechanism 9 for preventing the orbiting scroll member 5 from rotating about its own axis is disposed between the rear surface of the orbiting scroll 5 and the frame 8. A seat 8b is provided on the peripheral edge of the recess and supports the orbiting scroll member 5 in such a manner as to allow the orbiting scroll member 5 to make an orbiting movement relative to the stationary scroll member 6. The back-pressure chamber 8c is formed between the bottom 8m of the recess and the orbiting scroll member 5. The pressure in the back-pressure chamber 8c is maintained at an intermediate level equal to that of the refrigerant gas in a scroll space which is in midst of the compression phase. The pressure in the back-pressure chamber 8c acts on the rear side of the orbiting scroll member 5 so as to urge the same towards the stationary scroll member 6 with a proper force. 
     A bearing 8a is secured to the central portion of the bottom wall 8m. The axially outer end of the bearing 8a is exposed to the back-pressure chamber 8c. A sliding bearing 8a&#39;, axially aligned with the bearing 8a, is formed on the center of the frame 8. 
     The electric motor 3 includes a stator 3a which fits on the inner peripheral surface of the peripheral wall 8f of the frame 8. The electric motor 3 also has a rotor 3b which is disposed radially inwardly of the stator 3a and fixed to the drive shaft 7. The drive shaft 7 extends axially through the rotor 3b and has a free end 7-1 projecting from one end surface of the rotor 3a  towards the motor cover 10. This free end 7-1 of the drive shaft 7 is rotatably supported by a sliding bearing 10a formed in the center of the motor cover 10. The other end of the drive shaft 7 is formed by the crank pin section 7a mentioned before. Thus, the drive shaft 7 is also supported by the bearings 8a and 8a&#39; at two points between the crank pin section 7a and the free end 7-1. 
     Referring now to FIGS. 2 and 3, an axial lubricant supply groove 7b is formed in a peripheral surface 7-1a of the free end 7-1 of the drive shaft 7, which peripheral surface slidingly contacts with the sliding bearing 10a mentioned before. The lubricant supply groove 7b opens at its one end in the end surface of the free end 7-1 of the drive shaft 7, while the other end of the lubricant supply groove 7b terminates within a region of the peripheral surface 7-1a. The drive shaft 7 is also provided with an axial lubricant supply hole 7c, a first radial lubricant supply hole 7d providing a communication between the lubricant supply groove 7b and the axial lubricant supply hole 7c, and a second radial oil supply hole 7f through which the axial lubricant supply hole 7c is communicated with the sliding bearing 8a&#39;. As will be seen from FIG. 1, the lubricant supply hole 7c opens in the end surface of the crank pin section 7a. The other end of this hole 7c, adjacent to the sliding bearing 10a, is closed by a screw 7e. 
     The sliding bearing 10a is received in a hole or recess 10-1 formed in the axially inner surface of the motor cover 10. A lubricant chamber 10-2 is formed between the bottom of the recess 10-1 and the end surface of the free end 7-1 of the drive shaft 7. An axial lubricant supply hole 10c formed in the bottom of the hole 10-1 communicates with the lubricant chamber 10-2. The motor cover 10 further has a pipe bore 10b communicating at its upper end with the lubricant hole 10c and connected at its lower end to the upper end of a lubricant pipe 11, the lower end of which opens in the lubricant reservoir 4 disposed in the bottom portion of the chamber 1c-1. 
     Referring again to FIG. 1, the motor cover 10 is further provided with a through-hole 10d for passing lead wires 3c through which the electric motor 3 is supplied with electric power. A lead-line protecting bushing 12 is secured to the peripheral edge of this through-hole 10d. A chamber 10e is formed between the motor cover 10 and the electric motor 3. The motor cover 10 further has a communication hole 10g which provides a communication between a lower part of the chamber 10e and the lubricant reservoir 4 on the bottom of the chamber 1c-1, and a pair of openings 10f through which the chamber 10e is communicated at its upper portion with the upper portion of the space 1c-1, as shown in FIG. 4. 
     A balance weight 3d is attached to the end of the rotor 3b of the electric motor 3 adjacent the sliding bearing 10a, while blades 3e are attached to the other end of the rotor 3b. The end of the rotor 3b carrying the blades 3e is exposed to a chamber 8g formed in the peripheral wall 8f of the frame 8 and communicating with the passage 8h formed in the frame 8. 
     Power terminals 1f connected to the leads 3c and terminal covers 1g and 1h are attached to the cap 1c of the container 1. Legs 1d are attached to the lower portions of both caps 1b and 1c. 
     As the electric motor 3 starts to operate, the drive shaft 7 rotates to cause the crank pin section 7a to revolve about the axis of the crank shaft 7, which in turn causes the orbiting scroll member 5 to make an orbiting movement. Meanwhile, the rotation of the orbiting scroll member 5 about its own axis is prevented by the mechanism 9. Consequently, the scroll space defined by the wraps 5b and 6b and end plates 5a and 6a of both scroll members 5 and 6 is progressively moved towards the center while decreasing its volume, so that the gas suctioned through the suction port 6c is compressed and discharged into the space 1b-1 through the discharge port 6d. 
     The discharged gas collides with the cap 1b so that lubricant content is separated from the gas. The gas is then introduced into the chamber 8g through the passage 8h formed in the frame 8. The gas is then diffused and cooled by the blades 3e provided on the rotor 8b and cools the electric motor 3 while flowing therethrough. The gas then flows into the space 1c-1 through the chamber 10e and the openings 10f in the motor cover 10 and further into the upper portion of the space 1a-1 through the passage 8e-1. The gas is finally discharged from the space 1a-1 to the exterior of the container 1 through the outlet port 1i. 
     During the operation of the compression mechanism 2, the gas compressed between both scroll members 5 and 6 produces a separating force which tends to urge both scroll members 5 and 6 away from each other. In order to prevent such a tendency, a part of the gas in the scroll chamber in its compression phase, compressed to an intermediate pressure level between the suction and discharge pressures, is introduced through the pressure equalizer hole 5d into the back-pressure chamber 8c so as to produce a force which acts to urge the orbiting scroll member 5 towards the stationary scroll member against the above-mentioned separating force. 
     Therefore, the bearing 5c of the orbiting scroll member 5 and the end surface of the bearing 8a&#39; in the frame 8 adjacent to the back-pressure chamber 8c receive the intermediate pressure level, whereas the lubricant in the lubricant reservoir 4 receives the discharge pressure. Consequently, the lubricant is fed by the pressure differential between the discharge pressure and the intermediate pressure from the reservoir 4 to the end of the lubricant supply hole 7c adjacent the crank section 7a of the drive shaft 7 via the lubricant supply pipe 11 connected to the motor cover 10 and the lubricant supply hole 10c. As a result, the lubricant supply groove 7b, the lubricant supply hole 7d and the axial lubricant supply hole 7c are all filled with the lubricant, so that the sliding bearing 10a is supplied with the lubricant stably and without fail. 
     The lubricant in the axial lubricant supply hole 7c is further supplied therefrom to the bearings 8a and 8a&#39; through the radial lubricant hole 7f. The bearing 5c is lubricated by the lubricant fed through the axial lubricant hole 7c. 
     Although the supply of the lubricant has been described as being effected satisfactorily by the pressure differential alone, it will be obvious to those in the art that the lubricant supply system of the invention can employ another suitable means such as an oil pump.