Patent Publication Number: US-6210137-B1

Title: Scroll fluid machine

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a scroll fluid machine suitable for use in an air compressor, a vacuum pump, etc. 
     A generally known scroll fluid machine has a casing and a fixed scroll member provided in the casing. The fixed scroll member has a spiral wrap portion standing on an end plate. A driving shaft is rotatably provided in the casing. An orbiting scroll member is orbitably provided on the distal end of the driving shaft in the casing. The orbiting scroll member has a spiral wrap portion standing on an end plate so as to overlap the wrap portion of the fixed scroll member to define a plurality of compression chambers. 
     In this type of known scroll fluid machine, the driving shaft is externally driven to rotate, causing the orbiting scroll member to perform an orbiting motion with a predetermined eccentricity with respect to the fixed scroll member, thereby sucking a fluid, e.g. air, from a suction opening provided at the outer periphery of the fixed scroll member, and successively compressing the fluid in the compression chambers formed between the wrap portions of the fixed and orbiting scroll members. Finally, the compressed fluid is discharged to the outside from a discharge opening provided in the center of the fixed scroll member. 
     In another known scroll fluid machine, a lubrication pump is provided between the casing and the outer periphery of the end plate of the orbiting scroll member. The lubrication pump operates in response to the orbiting motion of the orbiting scroll member to lubricate the driving shaft, the orbiting scroll member, etc. That is, a lubricant contained in the casing is led to the area between the casing and the outer periphery of the end plate of the orbiting scroll member by the lubrication pump and thus supplied to the driving shaft, the orbiting scroll member, etc. 
     Incidentally, in the above-described known scroll fluid machine, the lubrication pump is provided between the inner periphery of the casing and the outer periphery of the end plate of the orbiting scroll member. Consequently, the lubrication pump is placed near the sliding contact surfaces of the orbiting and fixed scroll members, and it is likely that the lubricant pressurized by the lubrication pump will enter the area between the sliding contact surfaces of the orbiting and fixed scroll members. 
     Therefore, the prior art involves the danger that the high-pressure lubricant, which has been pressurized in the pump chamber of the lubrication pump, may enter the area between the sliding contact surfaces of the fixed and orbiting scroll members and leak into the compression chambers. If the lubricant leaks into the compression chambers, it is difficult to discharge a clean compressed fluid to the outside. Thus, if there is likelihood that the lubricant may leak, the apparatus cannot be improved in performance and reliability. 
     In view of the above-described problems with the prior art, an object of the present invention is to provide a scroll fluid machine designed to be capable of preventing the entry of the lubricant from the lubrication pump into the compression chambers and of discharging a clean compressed fluid at all times and also capable of efficiently lubricating the driving shaft, etc. and hence improving the apparatus in performance, reliability and so forth. 
     SUMMARY OF THE INVENTION 
     The present invention is applicable to a scroll fluid machine including a casing and a fixed scroll member provided in the casing. The fixed scroll member has a spiral wrap portion standing on an end plate. A driving shaft is rotatably provided in the casing. An orbiting scroll member is orbitably provided at the distal end of the driving shaft through an orbiting bearing in the casing. The orbiting scroll member has a spiral wrap portion standing on an end plate so as to overlap the wrap portion of the fixed scroll member to define a plurality of compression chambers. A thrust bearing is provided in the casing so as to come in sliding contact with the rear side of the orbiting scroll member to bear a thrust load acting on the orbiting scroll member. 
     An arrangement adopted by the present invention is characterized by a lubrication pump provided between the rear side of the orbiting scroll member and the thrust bearing. The lubrication pump has a pump chamber defined between a sliding contact surface on the rear side of the orbiting scroll member and a sliding contact surface of the thrust bearing. The lubrication pump operates in response to the motion of the orbiting scroll member. A lubricant suction passage is provided in the thrust bearing to lead a lubricant contained in the casing into the pump chamber of the lubrication pump. A discharge passage is provided in the orbiting scroll member to deliver the lubricant sucked into the pump chamber of the lubrication pump to lubricating points. 
     With the above-described arrangement, as the orbiting scroll member orbits, the lubrication pump operates in response to the motion of the orbiting scroll member, causing the lubricant contained in the casing to be led into the pump chamber through the suction passage provided in the thrust bearing. The lubricant led into the pump chamber is delivered to lubricating points, for example, the driving shaft and the orbiting bearing, by the lubrication pump through the discharge passage provided in the orbiting scroll member to cool and lubricate the driving shaft, the orbiting bearing, etc. While flowing through the discharge passage, the lubricant from the lubrication pump cools the whole orbiting scroll member. 
     The pump chamber of the lubrication pump is provided between the sliding contact surface on the rear side of the orbiting scroll member and the sliding contact surface of the thrust bearing. That is, the pump chamber is provided on the side of the end plate of the orbiting scroll member remote from the compression chambers. Therefore, the pump chamber can be isolated from the compression chambers. Thus, the lubricant pressurized in the pump chamber of the lubrication pump can be prevented from leaking to the compression chamber side. 
     In the present invention, the lubrication pump may be arranged as follows. An orbiting member accommodating recess is provided in either one of the sliding contact surface on the rear side of the orbiting scroll member and the sliding contact surface of the thrust bearing to define a pump chamber between the orbiting member accommodating recess and the other of the sliding contact surfaces. An orbiting member projects from the other of the sliding contact surfaces into the orbiting member accommodating recess. The orbiting member performs a relative orbiting motion along the peripheral wall surface of the orbiting member accommodating recess in response to the motion of the orbiting scroll member. A movable partition is provided in the orbiting member accommodating recess so as to be movable relative to the orbiting member accommodating recess. The movable partition cooperates with the orbiting member to divide the pump chamber into a suction chamber and a discharge chamber in the orbiting member accommodating recess. A partition driving mechanism drives the movable partition to perform relative movement in the orbiting member accommodating recess in response to the motion of the orbiting member. 
     In the above-described arrangement, as the orbiting scroll member orbits, the orbiting member, which projects from the other of the sliding contact surfaces, performs a relative orbiting motion in the orbiting member accommodating recess, which is provided in the one of the sliding contact surfaces, along the peripheral wall surface thereof. In addition, the movable partition is driven by the partition driving mechanism to perform relative movement in the orbiting member accommodating recess in response to the motion of the orbiting member. At this time, the pump chamber in the orbiting member accommodating recess is divided into the suction chamber and the discharge chamber by the orbiting member and the movable partition. Therefore, the lubricant from the suction passage can be sucked into the suction chamber, and while doing so, it can be delivered from the discharge chamber to the discharge passage. 
     In the present invention, the partition driving mechanism may be arranged as follows. A cavity is provided in the one of the sliding contact surfaces at a distance from the orbiting member accommodating recess. A guide groove is formed in the one of the sliding contact surfaces between the cavity and the orbiting member accommodating recess. The guide groove is contiguous at both longitudinal ends thereof with the cavity and the orbiting member accommodating recess. A driving projection projects from the other of the sliding contact surfaces into the cavity. The driving projection performs a relative orbiting motion in the cavity in response to the motion of the orbiting scroll member. The movable partition is a slide plate slidably held between the orbiting member and the driving projection. The slide plate is slidable longitudinally along the guide groove. 
     In the above-described arrangement, as the orbiting scroll member orbits, the driving projection, which projects from the other of the sliding contact surfaces, can perform a relative orbiting motion in the cavity as in the case of the orbiting member. At this time, the slide plate slides longitudinally along the guide groove by following the motion of the orbiting member and the driving projection in a state where both ends of the slide plate are in sliding contact with the orbiting member and the driving projection. Consequently, the suction and discharge chambers, which are defined in the orbiting member accommodating recess by the orbiting member and the slide plate, expand or contract in response to the motion of the orbiting member. Thus, the lubricant sucked into the suction chamber can be delivered from the discharge chamber. 
     In the present invention, the sliding contact surfaces of the orbiting member and the driving projection that are in sliding contact with the slide plate may be plane surfaces which are parallel to each other. Thus, when the orbiting scroll member orbits, the orbiting member and the driving projection, which are each integrally provided on the orbiting scroll member, can be guided relatively along the slide plate. In addition, the slide plate slides longitudinally along the guide groove. Therefore, it is possible to construct a rotation preventing mechanism for preventing rotation of the orbiting scroll member by the orbiting member, the driving projection, the slide plate and the guide groove. 
     In the present invention, the one of the sliding contact surfaces may be provided with a lubricant reservoir constantly communicating with the orbiting member accommodating recess and the discharge passage. With this arrangement, as the orbiting scroll member orbits, the lubricant sucked into the orbiting member accommodating recess can be smoothly delivered from the lubricant reservoir to the discharge passage. 
     In the present invention, the discharge passage may be arranged to extend through the rear side portion of the orbiting scroll member and to open in a boss portion accommodating the orbiting bearing. Thus, the lubricant from the discharge passage can be supplied to the orbiting bearing. 
     In the present invention, the driving shaft may be provided with a balance weight projecting radially from the outer periphery of the driving shaft to obtain a rotational balance of the driving shaft with respect to the orbiting scroll member. The driving shaft may be further provided with a lubricant supply passage opening at one end thereof at a distal end of the driving shaft to communicate with the discharge passage. The other end of the lubricant supply passage opens at the outer peripheral surface of the driving shaft on the rear side of the boss portion. 
     With the above-described arrangement, the lubricant from the discharge passage can be supplied to the orbiting bearing, and the lubricant can also be supplied to the rear side of the orbiting scroll member from the outer peripheral surface of the driving shaft through the lubricant supply passage. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a longitudinal sectional view taken along the line I—I in FIG. 2, showing a scroll air compressor according to an embodiment of the present invention. 
     FIG. 2 is a front view as seen in the direction of the arrow II—II in FIG. 1, showing an orbiting scroll member, a thrust bearing, etc. with a fixed scroll member removed. 
     FIG. 3 is a fragmentary enlarged sectional view of the orbiting scroll member, the thrust bearing, a lubrication pump, etc. in FIG.  1 . 
     FIG. 4 is an enlarged sectional view as seen in the direction of the arrow IV—IV in FIG. 2, showing the orbiting scroll member, the thrust bearing, the lubrication pump, etc. 
     FIG. 5 is a sectional view as seen in the direction of the arrow V—V in FIG. 3, showing the thrust bearing, an Oldham&#39;s ring, the lubrication pump, etc. 
     FIG. 6 is a sectional view as seen in the direction of the arrow VI—VI in FIG. 3, showing the orbiting scroll member, the Oldham&#39;s ring, the lubrication pump, etc. 
     FIG. 7 is a front view as seen in the direction of the arrow VII—VII in FIG. 1, showing only the thrust bearing. 
     FIG. 8 is a rear view as seen in the direction of the arrow VIII—VIII in FIG. 1, showing only the orbiting scroll member. 
     FIG. 9 is a fragmentary enlarged sectional view of the lubrication pump in FIG.  6 . 
     FIG. 10 is a diagram showing the operation of the lubrication pump in the embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A scroll fluid machine according to an embodiment of the present invention will be described below in detail with reference to the accompanying drawings. In the embodiment, the present invention is applied to a scroll air compressor as an example of scroll fluid machines. 
     FIGS. 1 to  10  show an embodiment of the present invention. Referring to the figures, a closed-end cylindrical casing  1  forms an outer frame of a scroll air compressor. The casing  1  has an annular bottom portion  1 A. A cylindrical portion  1 B extends from the outer periphery of the bottom portion  1 A toward a fixed scroll member  3  (described later). A bearing portion  1 C projects from the center of the bottom portion  1 A toward the fixed scroll member  3 . A lubricant  2  is contained in the casing  1 . 
     The fixed scroll member  3  is secured to the distal end of the casing  1 . As shown in FIG. 1, the fixed scroll member  3  has an end plate  3 A formed in an approximately disk-like shape. The end plate  3 A is positioned so that the center thereof is coincident with the axis of a driving shaft  4  (described later). A spiral wrap portion  3 B is provided on the obverse side of the end plate  3 A. A cylindrical portion  3 C projects axially from the outer peripheral edge of the end plate  3 A so as to surround the wrap portion  3 B. A flange portion  3 D projects radially outward from the outer periphery of the cylindrical portion  3 C and abuts on a thrust bearing  13  (described later). 
     The driving shaft  4  is rotatably supported by bearings  5  and  6  in the casing  1 . The proximal end of the driving shaft  4  is connected to a driving source (not shown). The distal end portion of the driving shaft  4  extends into the casing  1  to form a crank  4 A. The axis of the crank  4 A is displaced with respect to the axis of the driving shaft  4  by a dimension δ. 
     A balance weight  7  is provided on the outer periphery of the driving shaft  4  between the bearing portion  1 C of the casing  1  and a boss portion  8 C of an orbiting scroll member  8  (described later). The balance weight  7  projects radially outward from the driving shaft  4  to obtain a rotational balance of the driving shaft  4  with respect to the orbiting scroll member  8 . 
     The orbiting scroll member  8  is orbitably provided in the casing  1  in opposing relation to the fixed scroll member  3 . As shown in FIG. 1, the orbiting scroll member  8  has an end plate  8 A formed in the shape of a disk. A spiral wrap portion  8 B extends axially from the obverse side of the end plate  8 A. 
     The orbiting scroll member  8  further has a boss portion  8 C projecting from the center of the rear side of the end plate  8 A. The orbiting scroll member  8  is orbitably attached to the crank  4 A of the driving shaft  4  through an orbiting bearing  9  accommodated in the boss portion  8 C. The obverse side of the end plate  8 A is adapted to come in sliding contact with the flange portion  3 D of the fixed scroll member  3 . The rear (reverse) side of the end plate  8 A forms a sliding contact surface  8 D adapted to come in sliding contact with a thrust bearing  13  (described later). 
     The orbiting scroll member  8  is positioned so that the wrap portion  8 B overlaps the wrap portion  3 B of the fixed scroll member  3  with an offset angle of 180 degrees, for example. Thus, a plurality of compression chambers  10  are defined between the two wrap portions  3 B and  8 B. During the operation of the scroll air compressor, air is sucked into the outermost compression chamber  10  from a suction opening  11  provided in an outer peripheral portion of the fixed scroll member  3 , and the sucked air is successively compressed in the compression chambers  10  during the orbiting motion of the orbiting scroll member  8 . Finally, the compressed air is discharged from the central compression chamber  10  to the outside through a discharge opening  12  provided in the center of the fixed scroll member  3 . 
     An annular thrust bearing  13  is provided at the distal end of the cylindrical portion  1 B of the casing  1 . An annular cut portion  13 A is formed on the inner periphery of the thrust bearing  13 . The end plate  8 A of the orbiting scroll member  8  is slidably mounted in the cut portion  13 A. The cut portion  13 A of the thrust bearing  13  has an annular sliding contact surface  13 B adapted to come in sliding contact with the end plate  8 A. The sliding contact surface  13 B bears a thrust load acting on the orbiting scroll member  8  through contact with the end plate  8 A. 
     Referring to FIG. 5, a pair of guide projections  14  project radially inward from the inner periphery of the thrust bearing  13 . The guide projections  14  slidably guide an Oldham&#39;s ring  16  (described later) leftward or rightward as viewed in FIG.  5 . 
     Referring to FIG. 6, Oldham&#39;s ring guide grooves  15  are provided on the rear side of the end plate  8 A of the orbiting scroll member  8 . The guide grooves  15  slidably guide the Oldham&#39;s ring  16  upward or downward as viewed in FIG.  6 . 
     The Oldham&#39;s ring  16  is slidably provided between the orbiting scroll member  8  and the thrust bearing  13 . The Oldham&#39;s ring  16  is guided in two orthogonal axis directions by the guide projections  14  and the guide grooves  15 . The Oldham&#39;s ring  16  constitutes a rotation preventing mechanism for preventing rotation of the orbiting scroll member  8  in combination with the guide projections  14  and the guide grooves  15 . 
     A lubrication pump  21  is provided between the respective sliding contact surfaces  8 D and  13 B of the orbiting scroll member  8  and the thrust bearing  13 . The lubrication pump  21  comprises an orbiting member accommodating recess  22 , an orbiting member  24 , a slide plate  25  and a slide plate driving mechanism  28  (described later). The lubrication pump  21  operates in response to the motion of the orbiting scroll member  8  to discharge the lubricant  2  sucked into a pump chamber  23  (described later) to various lubricating points, i.e. the driving shaft  4 , the bearings  5  and  6 , the orbiting scroll member  8 , and the orbiting bearing  9 . 
     The orbiting member accommodating recess  22  is provided in the sliding contact surface  13 B of the thrust bearing  13 . As shown in FIG. 9, the orbiting member accommodating recess  22  is a closed-end circular hole with a peripheral wall surface  22 A to define a pump chamber  23  between itself and the sliding contact surface  8 D of the orbiting scroll member  8 . The orbiting member  24  is orbitably accommodated in the pump chamber  23  formed by the orbiting member accommodating recess  22 . 
     The orbiting member  24  projects from the rear side of the end plate  8 A of the orbiting scroll member  8 . The orbiting member  24  is a circular projection projecting from the end plate  8 A of the orbiting scroll member  8  into the orbiting member accommodating recess  22 . The projecting end surface of the orbiting member  24  is substantially in sliding contact with the bottom surface of the orbiting member accommodating recess  22 . The orbiting member  24  has a sliding contact surface  24 A formed on the outer periphery thereof. The sliding contact surface  24 A is a plane surface extending in a direction perpendicular to the lengthwise direction of a guide groove  31  (described later). That is, the sliding contact surface  24 A extends in the X-axis direction in FIG.  9 . The sliding contact surface  24 A is in sliding contact with the slide plate  25 . 
     The orbiting member  24  is placed in the orbiting member accommodating recess  22  in a decentered position. The outer peripheral surface of the orbiting member  24  is substantially in sliding contact with the peripheral wall surface  22 A. Consequently, the orbiting member  24  moves in response to the motion of the orbiting scroll member  8 , performing an orbiting motion in the orbiting member accommodating recess  22  along the peripheral wall surface  22 A. It should be noted that the X- and Y-axis directions in FIG. 9 are at an angle of approximately 45 degrees to the guide projections  14  and the guide grooves  15 . 
     The slide plate  25  is movably provided in the orbiting member accommodating recess  22  to serve as a movable partition. The slide plate  25  is a rectangular flat plate member and provided in a guide groove  31  (described later) so as to be slidable in the Y-axis direction in FIG.  9 . Both ends of the slide plate  25  in the lengthwise direction thereof are in sliding contact with the sliding contact surface  24 A of the orbiting member  24  and a sliding contact surface  30 A of a driving projection  30  (described later), respectively. 
     Consequently, as the orbiting scroll member  8  orbits, as shown in FIG. 10, the slide plate  25  is caused to move in the orbiting member accommodating recess  22  by a slide plate driving mechanism  28  (described later) in response to the motion of the orbiting member  24 . The slide plate  25  divides the pump chamber  23  into a suction chamber  26  and a discharge chamber  27  in cooperation with the orbiting member  24 . 
     The slide plate driving mechanism  28  is a partition moving mechanism for moving the slide plate  25  in the orbiting member accommodating recess  22  in response to the motion of the orbiting member  24 . The slide plate driving mechanism  28  comprises a cavity  29 , a driving projection  30  and a guide groove  31  (described later). 
     The cavity  29  is provided in the sliding contact surface  13 B of the thrust bearing  13  at a distance from the orbiting member accommodating recess  22 . The cavity  29  has an approximately rectangular shape. The driving projection  30  is accommodated in the cavity  29 . 
     The driving projection  30  projects from the rear side of the end plate  8 A of the orbiting scroll member  8 . As shown in FIG. 9, the driving projection  30  is a rectangular projection projecting from the end plate  8 A into the cavity  29 . The driving projection  30  has a sliding contact surface  30 A that is a plane surface facing the sliding contact surface  24 A of the orbiting member  24  in the Y-axis direction and extending parallel to the X-axis direction. The sliding contact surface  30 A is in sliding contact with the slide plate  25 . 
     Consequently, as the orbiting scroll member  8  orbits, the driving projection  30  performs an orbiting motion together with the orbiting member  24 , causing the slide plate  25  to slide in the Y-axis direction along the guide groove  31  in such a state that the slide plate  25  is held between the driving projection  30  and the orbiting member  24 . The driving projection  30  further constitutes another rotation preventing mechanism for preventing rotation of the orbiting scroll member  8  in combination with the orbiting member  24  and the slide plate  25  for the reason stated later. 
     The slide plate guide groove  31  is provided in the sliding contact surface  13 B of the thrust bearing  13  to extend between the orbiting member accommodating recess  22  and the cavity  29 . The guide groove  31  is an elongate groove extending in the Y-axis direction in FIG.  9 . The guide groove  31  is contiguous at both ends thereof with the orbiting member accommodating recess  22  and the cavity  29 . The guide groove  31  slidably guides the slide plate  25  in the Y-axis direction. 
     A lubricant reservoir  32  is provided in the sliding contact surface  13 B of the thrust bearing  13  at a position between the orbiting member accommodating recess  22  and the cavity  29 . The lubricant reservoir  32  is a circular hole that opens in the sliding contact surface  13 B of the thrust bearing  13  and is contiguous with the orbiting member accommodating recess  22 . As shown in FIG. 10, the lubricant reservoir  32  is provided at a position where it communicates with both the orbiting member accommodating recess  22  and a discharge passage  34  at all times during the orbiting cycle of the orbiting scroll member  8 . Accordingly, the lubricant reservoir  32  can deliver the lubricant  2  from the discharge chamber  27  to the discharge passage  34  at all times. 
     A suction passage  33  is formed in the thrust bearing  13 . One end of the suction passage  33  opens into the casing  1  at a lower portion of the thrust bearing  13 . The other end of the suction passage  33  opens on the bottom surface of the orbiting member accommodating recess  22  at a position within the suction chamber  26 . The suction passage  33  leads the lubricant  2  contained in the casing  1  into the suction chamber  26  by the operation of the lubrication pump  21 . 
     The discharge passage  34  is formed in the end plate  8 A of the orbiting scroll member  8 . The discharge passage  34  extends through the rear side of the orbiting scroll member  8  and opens at one end thereof into the lubricant reservoir  32 . The other end of the discharge passage  34  opens into the boss portion  8 C. The discharge passage  34  is arranged such that the lubricant  2  discharged from the discharge chamber  27  and stored in the lubricant reservoir  32  is delivered from the rear side of the end plate  8 A of the orbiting scroll member  8  to the driving shaft  4 , the orbiting bearing  9 , etc., and that while flowing through the discharge passage  34 , the lubricant  2  cools the whole orbiting scroll member  8 . 
     A lubricant supply passage  35  is formed in the driving shaft  4 . The lubricant supply passage  35  axially extends through the driving shaft  4 . One end of the lubricant supply passage  35  opens into the boss portion  8 C of the orbiting scroll member  8  to communicate with the discharge passage  34 . The other end of the lubricant supply passage  35  bends radially and opens into the bearing portion  1 C of the casing  1  to supply the lubricant  2  from the discharge passage  34  to the bearings  5  and  6 . Moreover, while flowing through the lubricant supply passage  35 , the lubricant  2  cools the whole driving shaft  4 . 
     In addition, the lubricant supply passage  35  has a portion extending radially from an intermediate part thereof and opening into the casing  1  between the bearing portion  1 C of the casing  1  and the boss portion  8 C of the orbiting scroll member  8  to return a part of the lubricant  2  from the discharge passage  34  into the casing  1 . 
     A seal member  36  is fitted between the respective sliding contact surfaces of the fixed and orbiting scroll members  3  and  8 . The seal member  36  prevents the lubricant  2  from entering the area between the two sliding contact surfaces. 
     The scroll air compressor according to the embodiment has the above-described arrangement. Next, the operation of the scroll air compressor will be described. 
     As the driving shaft  4  is rotated by an electric motor, the orbiting scroll member  8  performs a circular (orbiting) motion with an orbiting radius δ about the driving shaft  4 . 
     Consequently, the compression chambers  10 , which are defined between the wrap portion  3 B of the fixed scroll member  3  and the wrap portion  8 B of the orbiting scroll member  8 , are continuously contracted. Thus, the outside air sucked in from the suction opening  11  of the fixed scroll member  3  is successively compressed in the compression chambers  10 , and the compressed air is discharged from the discharge opening  12  of the fixed scroll member  3  and stored in an external air tank or the like (not shown). 
     When the orbiting scroll member  8  is orbiting in this way, the Oldham&#39;s ring  16  slides along the guide projections  14  of the thrust bearing  13 , and the Oldham&#39;s ring  16  and the orbiting scroll member  8  are displaced relative to each other along the guide grooves  15  provided on the orbiting scroll member  8 . Thus, rotational torque acting on the orbiting scroll member  8 , which is transmitted through the driving shaft  4 , is borne between the Oldham&#39;s ring  16  and the guide projections  14  and the guide grooves  15 , thereby preventing the orbiting scroll member  8  from rotating on its own axis while allowing it to perform an orbiting motion with an orbiting radius δ. 
     Next, the operation of the lubrication pump  21  will be described with reference to FIG.  10 . As the orbiting scroll member  8  orbits, the orbiting member  24  and the driving projection  30 , which are integral with the orbiting scroll member  8 , perform orbiting motions clockwise in the orbiting member accommodating recess  22  and the cavity  29 , respectively, as shown sequentially in parts (a), (b), (c) and (d) of FIG.  10 . At this time, the slide plate  25  follows the motions of the orbiting member  24  and the driving projection  30  in a state where both ends of the slide plate  25  are in sliding contact with the orbiting member  24  and the driving projection  30 . Thus, the slide plate  25  slides along the guide groove  31 . 
     Consequently, in the pump chamber  23 , which is defined between the orbiting member accommodating recess  22  and the orbiting scroll member  8 , the volume of the suction chamber  26  continuously increases in response to the motion of the slide plate  25  as shown sequentially in parts (a), (b), (c) and (d) of FIG.  10 . Thus, a suction stroke is performed during which the lubricant  2  in the casing  1  is sucked into the suction chamber  26  through the suction passage  33 . 
     On the other hand, the volume of the discharge chamber  27  continuously decreases in response to the motion of the slide plate  25  as shown sequentially in parts (a), (b), (c) and (d) of FIG.  10 . Thus, a discharge stroke is performed during which the lubricant  2  in the discharge chamber  27  is discharged from the lubricant reservoir  32  to the discharge passage  34 . 
     When the orbiting member  24  reaches the position shown in part (d) of FIG. 10, the volume of the suction chamber  26  reaches a maximum, and thus the suction stroke is completed. On the other hand, the volume of the discharge chamber  27  reaches a minimum, and thus the lubricant discharge stroke is completed. During the period that the orbiting member  24  returns to the position in part (a) from the position in part (d) of FIG. 10, the opening of the suction passage  33  is closed by the orbiting member  24 . Then, the subsequent cycle starts. 
     Thus, in this embodiment, even if there are variations in the level of the lubricant  2 , because the inlet of the suction passage  33  is located sufficiently low, the lubricant  2  in the casing  1  can be stably delivered from the discharge passage  34  to the driving shaft  4  by the lubrication pump  21  to lubricate and cool the orbiting bearing  9 . In addition, the lubricant  2  from the discharge passage  34  can be stably supplied to the bearings  5  and  6  in the bearing portion  1 C through the lubricant supply passage  35  to lubricate and cool the bearings  5  and  6 . While flowing through the discharge passage  34  and the lubricant supply passage  35 , the lubricant  2  also cools the orbiting scroll member  8  and the driving shaft  4 . Thus, the whole apparatus can be efficiently cooled. 
     Further, because the lubricant reservoir  32  and the discharge passage  34  are constantly kept in communication with each other, it is possible to suppress variations in pressure of the lubricant  2  in the lubricant reservoir  32  and the discharge chamber  27  and hence possible to suppress displacement of the orbiting scroll member  8  in the thrust direction which may be caused by the variations in pressure. 
     In this embodiment, the lubrication pump  21  has the pump chamber  23 , which includes the suction chamber  26  and the discharge chamber  27 , and the pump chamber  23  is provided between the sliding contact surfaces  8 D and  13 B of the orbiting scroll member  8  and the thrust bearing  13 . That is, the pump chamber  23  is provided on the side of the end plate  8 A of the orbiting scroll member  8  remote from the compression chambers  10 . Thus, the pump chamber  23  can be isolated from the compression chambers  10 . 
     Accordingly, there is no likelihood that the high pressure of the lubricant  2  pressurized in the pump chamber  23  will act on the outer periphery-side sliding contact surfaces of the fixed and orbiting scroll members  3  and  8  as stated in regard to the prior art. Therefore, it is possible to prevent occurrence of the problem that the lubricant  2  entering the area between the sliding contact surfaces  8 D and  13 B leaks into the compression chambers  10  through the seal member  36 . Thus, it is possible to discharge clean compressed air from the discharge opening  12  to the outside at all times, and hence the apparatus can be improved in performance, reliability and so forth. 
     In addition, the sliding contact surface  13 B of the thrust bearing  13  is provided with the lubricant reservoir  32  constantly communicating with the orbiting member accommodating recess  22  and the discharge passage  34 . Therefore, while the opening of the discharge passage  34  is orbiting in response to the motion of the orbiting scroll member  8  as shown by the chain line in FIG. 10, the lubricant  2  from the discharge chamber  27  can be smoothly delivered to the discharge passage  34  at all times. Accordingly, the efficiency of delivery of the lubricant  2  by the lubrication pump  21  can be increased, and thus the pump performance can be improved. 
     The orbiting member  24  and the driving projection  30 , which are each integrally provided on the orbiting scroll member  8 , are positioned so that their respective sliding contact surfaces  24 A and  30 A, which are in sliding contact with the slide plate  25 , extend perpendicularly to the Y-axis direction and parallel to each other. Therefore, the orbiting member  24  and the driving projection  30  can slide in the X-axis direction relative to the slide plate  25 . 
     In this case, the slide plate  25  slides in the Y-axis direction along the guide groove  31  provided on the thrust bearing  13 , as stated above, and therefore, the direction of the sliding contact surfaces of the orbiting member  24  and the slide plate  25  is maintained in a direction perpendicular to the Y-axis. Thus, the orbiting member  24 , the slide plate  25 , the driving projection  30  and the guide groove  31  constitute another rotation preventing mechanism for preventing rotation of the orbiting scroll member  8 . Accordingly, rotational torque from the orbiting scroll member  8  that is added to the rotation preventing mechanism comprising the Oldham&#39;s ring  16 , etc. can be reduced by the above-described rotation preventing mechanism, and thus the durability, lifetime, etc. of the Oldham&#39;s ring  16  can be increased. 
     Furthermore, because the slide plate  25  is held between the orbiting member  24  and the driving projection  30 , the slide plate  25  can slide along the guide groove  31  in response to the motion of the orbiting member  24  and driving projection  30 . Accordingly, it is possible to eliminate such a problem that the slide plate  25  moves in the orbiting member accommodating recess  22  in retard of the motion of the orbiting member  24 . Thus, the follow-up performance of the slide plate  25  with respect to the orbiting member  24  is improved. Consequently, the pump performance of the lubrication pump  21  can be further improved. 
     Although in the foregoing embodiment the orbiting member  24  is provided on the sliding contact surface  8 D of the orbiting scroll member  8  and the orbiting member accommodating recess  22  is provided on the sliding contact surface  13 B of the thrust bearing  13 , the arrangement may be such that the orbiting member accommodating recess is provided on the sliding contact surface  8 D of the orbiting scroll member  8  and the orbiting member is provided on the sliding contact surface  13 B of the thrust bearing  13 . 
     Although in the foregoing embodiment the present invention has been described with regard to a scroll air compressor as an example of scroll fluid machines, the present invention is not necessarily limited to the scroll air compressor, but may also be widely applied to other scroll fluid machines, e.g. vacuum pumps, refrigerant compressors, etc.