Patent Publication Number: US-7713038-B2

Title: Scroll fluid machine

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a scroll fluid machine such as a scroll compressor or a scroll vacuum pump. 
   A scroll fluid machine comprises a driving shaft driven by an electric motor and comprising an eccentric axial portion at one end; an orbiting scroll rotatably mounted around the eccentric axial portion via a bearing and having an orbiting wrap on an orbiting end plate; and a fixed scroll having a fixed wrap on a fixed end plate. The orbiting wrap engages with the fixed wrap to form a sealed chamber. A self-rotation-preventing device is provided to prevent the orbiting scroll from rotating on its own axis. 
   The orbiting scroll is eccentrically revolved with the eccentric axial portion of the driving shaft and self-rotation-preventing device. The sealed chamber is gradually decreased in volume toward the center to allow fluid sucked from the outer circumference to be compressed, or is gradually increased away from the center to allow fluid sucked from the center to be decompressed and discharged from the outer circumference. 
   In such a scroll fluid machine, thermal load increases with compression and expansion. Especially, heat significantly affects a rotary part or a bearing rotatably supporting the eccentric axial portion of the orbiting scroll. JP63-43427Y2 discloses that an axial fan is provided in the housing of the scroll fluid machine to allow external air taken in from the inlet to blow into the rear surface of the sealed or compression chamber and to be discharged from the outlet to the housing. 
   The scroll fluid machine can transfer external air sucked from the inlet to the rear surface of the sealed chamber and a bearing for the driving shaft close to the rear wall of the housing, but it cannot flow air to a bearing for the eccentric axial portion which cannot effectively be cooled. 
   SUMMARY OF THE INVENTION 
   In view of the disadvantages in the prior art, it is an object of the present invention to provide a scroll fluid machine in which a bearing of an eccentric axial portion of a driving shaft can be cooled effectively. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features and advantages of the invention will become more apparent from the following description with respect to embodiments as shown in accompanying drawings wherein: 
       FIG. 1  is a vertical sectional view of a scroll fluid machine according to the present invention. 
       FIG. 2  is an enlarged vertical sectional view taken along the line II-II in  FIG. 1 . 
       FIG. 3  is a vertical sectional view of another embodiment of the present invention and similar to  FIG. 2 . 
       FIG. 4  is a vertical sectional view of further embodiment of the present invention and similar to  FIG. 2 . 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   The left side in  FIG. 2  is deemed as “the front”, and the right side is as “the rear”. 
   A scroll fluid machine  1  comprises a housing  2  having a cylindrical bearing  2   a  in the center; a driving shaft  4  rotatably mounted to the bearing  2   a  via a ball bearing  3 ; an orbiting scroll  7  rotatably mounted to an eccentric axial portion  4   a  at the front end of the driving shaft  4  and comprising an orbiting end plate  6  having an orbiting wrap  7   a  on the front face; a fixed scroll  8  having a fixed wrap  8   a  on the rear surface of a fixed end plate (not shown) to engage with the orbiting wrap  7   a ; and three crank pins  9  or self-rotation-preventing devices for preventing the orbiting scroll  7  from rotating on its own axis. When the orbiting scroll  7  is revolved with rotation of the driving shaft  4 , a sealed chamber is formed between the orbiting wrap  7   a  and the fixed wrap  8   a  so that a gas sucked from an inlet (not shown) is compressed and discharged from an outlet (not shown). A bearing  5  of the eccentric axial portion  4   a  is provided in a cylindrical bearing portion  7   b  at the center of the orbiting scroll  7 . 
   The crank pins  9  as self-rotation-preventing devices are circumferentially spaced at an angle of 120 degrees between the orbiting scroll  7  and housing  2 . The front end of the crank pin  9  is pivotally mounted to a bearing portion (not shown) of the orbiting scroll  7  via a ball bearing (not shown), and the rear end is pivotally mounted in a cylindrical boss  2   d  of the inner wall of the housing  2  via a ball bearing  10 . 
   The rear end of the driving shaft  4  is mounted to an electric motor (not shown) and a cooling fan  11  is mounted on the outer circumference of the driving shaft  4  which projects rearward from the bearing portion  2   a  of the housing  2 . The cooling fan  11  rotates with the driving shaft  4  to generate cooling wind rearward. 
   Four intake ports  2   b  for introducing external air are formed on the outer circumference of the housing  2  and three discharge ports  2   c  for discharging air taken in the housing  2  from the intake port  2   b.    
   With rotation of the cooling fan  11  with the driving shaft  4 , when cooling wind is blown rearward, a gas is sucked into the housing  2  via the discharge port  2   c . Owing to negative pressure in the housing  2 , external air is introduced from the intake port  2   b  to allow inside of the housing  2  to be cooled with flowing air. 
   In the housing  2 , ribs  12  project axially from the front surface of a vertical rear wall  16  of the housing  2  so that air taken in the housing  2  from the intake port  2   b  is directed toward the bearing  5  of the eccentric axial portion  4   a . The ribs  12  reinforce the bearing  2   d  of the crank pin  9  and prevent the bearing portion  2   d  from being deformed. 
   The ribs  12  are disposed in the vicinity of the intake port  2   b  and surround the discharge port  2   c . The ribs  12  extend concentrically with the bearing  2   a  from the inner vertical rear wall  16  of the housing  2  to surround the bearing  5  for the eccentric axial portion  4   a  and extend circumferentially to connect circumferentially-adjacent bosses  2   d  to each other. 
   As shown by an arrow in  FIG. 2 , air taken in the housing  2  from the intake port  2   b  moves along the boss  2   d  of the crank pin  9  toward the center and then moves over the rib  12  to the bearing portion  7   b  of the eccentric axial portion  4   a . Air moves rearward along the outer circumference of the bearing portion  7   b . Heated air is discharged from the discharge port  2   c  to the outside. Thus, the eccentric axial portion  4   b , the bearing  5  and their surroundings are cooled effectively. 
   The ribs  12  connect the circumferentially adjacent bosses  2   d  of the crank pin  9  to each other to reinforce the boss  2   d  to increase rigidity. Thus, the axis of the crank pin  9  is prevented from tilting, or a gap between the bosses  2  is prevented from varying owing to heat and load produced with revolution of the orbiting scroll  7 . 
   As shown by two-dotted lines in  FIG. 2 , the surface of the rib  12  which faces the intake port  2   b  may be inclined to allow air to flow more positively toward the bearing  5 . The rib  12  extends and is inclined from an internal corner  17  between the circumferential wall  15  and the vertical wall  16 . 
   In  FIG. 3 , the guide plate  13  may be formed separately from the housing  2  and may be mounted on the lower surface of the circumferential wall  15  with a bolt  18  in the vicinity of the end of the intake port  2   b  in the housing  2  so that the guide surface for air is more inclined toward the bearing  5 . Accordingly, the guide plate  13  can be adjusted in a direction or inclination through the intake port  2   b  of the housing  2  from the outside. 
   In  FIG. 4 , an intake port  2   d  in the circumferential wall  15  of the housing  2  is inclined or curved toward the eccentric axial portion  4   a  of the driving shaft  4  and the bearing  5  in the housing  2 . Air can be transferred in a desired direction without a guide in the housing  2 . 
   The foregoing merely relates to embodiments of the invention. Various changes and modifications may be made by those skilled in the art without departing from the scope of claims.