Patent Publication Number: US-6336798-B1

Title: Rotation preventing mechanism for scroll-type fluid displacement apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a rotation preventing mechanism for a scroll-type fluid displacement apparatus. 
     2. Description of Related Art 
     Scroll-type fluid displacement apparatus are known in the art. For example, Japanese Patent Application No. 10-44821 describes the construction of the scroll-type fluid displacement apparatus shown in FIG.  1 . 
     The scroll-type fluid displacement apparatus includes two scroll members—an orbiting scroll and a fixed scroll, each having an end plate, and a spiroidal or involute spiral wrap element extending from one side of each end plate. The scroll members are maintained at an angular and radial offset, so that both spiral elements interfit to form a plurality of line contacts between their spiral curved surfaces to thereby seal off and define at least one pair of fluid pockets. The relative orbital motion of the two scroll members shifts the line contacts along the spiral curved surfaces and, as a result, changes the volume of the fluid pockets. The volume of the fluid pockets increases or decreases depending on the direction of orbital motion. Thus, this scroll-type apparatus is able to compress, expand, or pump fluids. 
     Referring to FIG. 1, at least a pair of fluid pockets  103  are formed between fixed scroll  101  and orbiting scroll  102 . When orbiting scroll  102  is driven with an orbital motion relative to fixed scroll  101 , fluid pockets  103  are moved to the center with a consequent reduction in volume, and refrigerant gas confined within fluid pockets  103  is compressed. Ball coupling  115 , which prevents orbiting scroll  102  from rotating and transfers thrust load from orbiting scroll  102  to front housing  106 , includes first race  116 , ball rolling grooves  116   a , second race  117 , ball rolling grooves  117   a , balls  118 . First race  116 , which is ring-shaped and is fixed to orbiting scroll  102 , includes a plurality of ball rolling grooves  116   a  formed on a circumference thereof at an angular interval. Second race  117 , which is ring-shaped and is fixed to front housing  106 , includes a plurality of ball rolling grooves  117   a  formed on a circumference thereof at an angular interval. A plurality of balls  118  are positioned between ball rolling grooves  116   a  and ball rolling grooves  117   a . An interior circular portion of first race  116  contacts an interior circular portion of an end plate of orbiting scroll  102 , and a clearance is created between an exterior circular portion of the end plate of orbiting scroll  102  and an exterior circular portion of first race  116 . An exterior circular portion of second race  117  contacts an exterior circular portion of an end surface of front housing  106 , and a clearance is created between an interior circular portion of front housing  106  and an interior circular portion of second race  117 . 
     In this known compressor, front housing  106  and rear housing  104  are assembled, such that first race  116  and second race  117  are elastically deformed like a coned disk spring, which is a circular plate spring having a hole in the center portion. Therefore, elasticity is created between first race  116  and second race  117 , and a connecting force toward the x-axis is generated between fixed scroll  101  and orbiting scroll  102 . As a result, a spacer, which is inserted between front housing  106  and rear housing  104  to generate an appropriate force between fixed scroll  101  and orbiting scroll  102 , may be no longer required, and the number of parts of the compressor may be reduced. 
     In this known compressor, however, first race  116  and second race  117  are supported like cantilever. Therefore, when the thrust load, which is transferred from orbiting scroll  102  to front housing  106  through ball coupling  115 , increases, the amount of elastic deformation of first race  116  and second race  117  may become excessive. As a result, rolling of balls  118  may lose stability, and the orbiting motion of orbiting scroll  102  may become unstable. Therefore, in this known compressor, the efficiency of compression may be reduced, and wear may occur because a clearance between a top end of a spiral wall of fixed scroll  101  and a top end of a spiral wall of orbiting scroll  102  may increase or decrease. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a scroll-type fluid displacement apparatus which includes fewer parts than known configurations, and maintains stability of the orbital motion of an orbiting scroll during high thrust load. 
     In an embodiment, a ball coupling component for use in a scroll-type fluid displacement apparatus comprises a first race and a second race and a plurality of balls. The first race is fixed to a second side of an end plate of an orbiting scroll. The second race is fixed to an end surface of a front housing, which opposes the second side of the end plate of the orbiting scroll. The balls are positioned between a plurality of ball rolling grooves formed on a circumference of the first race at an angular interval and a plurality of ball rolling grooves formed on a circumference of the second race. An interior circular portion and an exterior circular portion of the first race is connected to the second side of the end plate of the orbiting scroll. A clearance is created between the ball rolling grooves of the first race and the end plate of the orbiting scroll. An interior circular portion and an exterior circular portion of the second race is connected to the end surface of the front housing. A clearance is created between the ball rolling grooves of the second race and the end surface of the front housing. 
     In another embodiment, a scroll-type fluid displacement apparatus comprises a rear housing and a front housing, a fixed scroll and an orbiting scroll, a driving mechanism, and a ball coupling. The rear housing has an open end and an inlet port and outlet port. A front housing closes the opening of the rear housing. The fixed scroll has a first end plate and a spiral element formed on and extending from a first side of the first end plate. The fixed scroll is attached to the rear housing. The orbiting scroll has a second end plate and a spiral element formed on and extending from a first side of the second end plate. Each of the spiral elements interfits at an angular and a radial offset to form a plurality of line contacts defining at least one pair of sealed-off fluid pockets. A driving mechanism includes a drive shaft rotatably supported by the front housing to effect the orbital motion of the orbiting scroll by rotation of the drive shaft to thereby change the volume of the fluid pockets. A disk-shaped eccentric bushing is rotatably connected to a crank pin on a disk, which is formed integrally with the drive shaft. A radial bearing is fitted into an annular boss formed on the second side of the end plate of the orbiting scroll and receives the disk-shaped eccentric bushing. A ball coupling includes an first race fixed to the second side of the end plate of the orbiting scroll and a second race fixed to an end surface of the front housing and a plurality of balls. The first race and the second race face each other. The balls are positioned between a plurality of all rolling grooves formed on a circumference of the first race at an angular interval and a plurality of ball rolling grooves formed on a circumference of the second race at an angular interval. An interior circular portion and an exterior circular portion of the first race are connected to the second side of the end plate of the orbiting scroll. A clearance is created between the ball rolling grooves of the first race and the second side of the end plate of the orbiting scroll. An interior circular portion and an exterior circular portion of the second race are connected to the end surface of the front housing. A clearance is created between the ball rolling grooves of the second race and the end surface of the front housing. 
     The structure for the scroll-type fluid displacement apparatus according to this invention may no longer require a spacer, which is inserted between the front housing and the rear housing to generate an appropriate force between the fixed scroll and the orbiting scroll, and the number of the parts of the scroll-type fluid apparatus may be reduced. Further, the structure for the scroll-type fluid displacement apparatus according to this invention may permit stable movement of the orbiting scroll in an orbital motion. 
     Other objects, features, and advantages will be apparent to persons of ordinary skill in the art from the following detailed description of the invention and the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention may be more readily understood with reference to the following drawings, in which: 
     FIG. 1 is a longitudinal, cross-sectional view of a known scroll-type fluid displacement apparatus; 
     FIG. 2 is a longitudinal, cross-sectional view of a scroll-type fluid displacement apparatus in accordance with an embodiment of the present invention; 
     FIG. 3 is a cross-sectional view taken along the line III—III of FIG. 2; 
     FIG. 4 is a cross-sectional view taken along the line IV—IV of FIG. 2; 
     FIG. 5 is a cross-sectional view taken along the line V—V of FIG. 2; 
     FIG. 6 is a cross-sectional view taken along the line VI—VI of FIG. 2; 
     FIGS. 7 a-b  depict other embodiments of the scroll-type fluid displacement apparatus, which relate to the depiction of FIG. 4; and 
     FIGS. 8 a-b  depict other embodiments of the scroll-type fluid displacement apparatus, which relate to the depiction of FIG.  6 . 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to FIG. 2, scroll-type compressor includes housing  50  and fixed scroll  1  and orbiting scroll  2 . Housing  50  comprises cup-shaped rear housing  4  and front housing  6 . 
     Fixed scroll  1  is located in rear housing  4 . Fixed scroll  1  is secured to rear housing  4  by a plurality of bolts  40 . Discharge chamber  5  is formed in rear housing  4  behind fixed scroll  1 . Fixed scroll  1  includes disk-shaped first end plate  1   a  and first spiral element  1   b . First spiral element  1   b  has discharge port  30 , which is formed through first end plate  1   a  at a position near the center of first spiral element  1   b . First spiral element  1   b  extends from the first end surface of first end plate  1   a , which is opposite side of discharge chamber  5 . First end plate  1   a  of fixed scroll  1  divides the inner chamber of rear housing  4  into suction chamber  19  and discharge chamber  5 . An inlet port (not shown) is formed on rear housing  4 , and communicates with suction chamber  19 . An outlet port (not shown) is formed on rear housing  4 , and communicates with discharge chamber  5 . 
     Orbiting scroll  2  is located in rear housing  4 . Orbiting scroll  2  includes disk-shaped second end plate  20  and second spiral element  21 , which extends from the first end surface of second end plate  20 , and annular boss  2   a , which is formed on and axially projects from the second end surface of second end plate  20 . First spiral element  1   a  of fixed scroll  1  and second spiral element  21  of orbiting scroll  2  interfit at an angular offset of about 180 degrees and a predetermined radial offset. At least a pair of fluid pockets  3  are defined between fixed scroll  1  and orbiting scroll  2 . 
     Front housing  6  is secured to rear housing  4  from the side of orbiting scroll  2  by a plurality of bolts  19 . Crank chamber  7  is formed in front housing  6  behind orbiting scroll  2 . 
     Drive shaft  8  is disposed on a central axis of front housing  6  and rear housing  4  (i.e., the x-axis), and located in crank chamber  7 . Drive shaft  8  is rotatably supported by front housing  6  through radial bearing  9 . One end of drive shaft  8  projects from front housing  6 . Electromagnetic clutch  10  is rotatably supported by front housing  6  through radial bearing  11 . Crank pin  12  is connected eccentrically to another end of drive shaft  8 . Crank pin  12  is inserted into annular boss  2   a  of orbiting scroll  2 , and is inserted into a disk-shaped eccentric bushing  13 . Eccentric bushing  13  is rotatably disposed in the annular boss  2   a  through radial bearing  14 . 
     Ball coupling  15 , which prevents orbiting scroll  2  from rotating and transfers thrust load from orbiting scroll  2  to front housing  6 , comprises first race  16  and second race  17  and a plurality of balls  18 . Ball coupling  15  is disposed between second end plate  20  of orbiting scroll  2  and an end surface of front housing  6 . As shown in FIGS. 2 and 3, ball coupling  15  has ring-shaped first race  16 , which is secured to the second surface of second end plate  20  of orbiting scroll  2  by a plurality of screws. A plurality of ball rolling grooves  16   a  are formed on a circumference of first race  16  at an angular interval. An interior circular portion and an exterior circular portion of first race  16  are connected to the second surface of second end plate  20  of orbiting scroll  2 . As shown in FIGS. 2 and 4, a plurality of circular-shaped recess portions  2   b , whose diameters are larger than that of ball rolling grooves  16   a , are formed on the second surface of second end plate  20  of orbiting scroll  2 . Recess portions  2   b  correspond to a plurality of ball rolling grooves  16   a  of first race  16 . Referring again to FIG. 2, a clearance is created between one surface of first race  16  and the second surface of second end plate  20  of orbiting scroll  2 . 
     As shown in FIGS. 2 and 5, ball coupling  15  has ring-shaped second race  17 , which is secured to an end surface of front housing  6  by a plurality of screws. A plurality of ball rolling grooves  17   a  are formed on a circumference of second race  17  at an angular interval. An interior circular portion and an exterior circular portion of second race  17  are connected to the end surface of front housing  6 . As shown in FIGS. 2 and 6, a plurality of circular-shaped recess portions  6   a , whose diameters are larger than those of ball rolling grooves  17   a , are formed on the end surface of front housing  6  corresponding to a plurality of ball rolling grooves  17   a  of second race  17 . Referring again to FIG. 2, a clearance is created between a first surface of second race  17  and the end surface of front housing  6 . 
     As shown in FIG. 2, ball coupling  15  has a plurality of balls  18 , which are engaged between ball rolling grooves  16   a  of first race  16  and ball rolling grooves  17   a  of second race  17 . 
     The rotation of orbiting scroll  2  is prevented by a rotation preventing mechanism, i.e., ball coupling  15 , which is disposed between the second surface of second end plate  20  of orbiting scroll  2  and the end surface of front housing  6  and around annular boss  2   a  of orbiting scroll  2 . 
     When a driving force is transferred from an external driving source (e.g. an engine of a vehicle) via electromagnetic clutch  10 , drive shaft  8  is rotated, and orbiting scroll  2 , which is supported by crank pin  12 , is driven in an orbital motion around the x-axis by the rotation of drive shaft  8 . Ball coupling  15  prevents the rotation of orbiting scroll  2  with respect to fixed scroll  1 . When orbiting scroll  2  is driven in an orbital motion, fluid pockets  3 , which are defined between first spiral element  1   b  of fixed scroll  1  and second spiral element  21  of orbiting scroll  2 , move from the outer or peripheral portions of spiral elements to the center part of the spiral elements. Refrigerant gas, which enters suction chamber  19  through an inlet port (not shown), flows into one of fluid pockets  3 . When fluid pockets  3  move from the outer portions of the spiral element to the center part of the spiral element, the volume of fluid pockets  3  is reduced, and refrigerant gas in fluid pockets  3  is compressed. Compressed refrigerant gas confined within fluid pockets  3  moves to discharge port  30 , displaces a reed valve  31 , and is discharged through discharge port  30  into discharge chamber  5 . Finally, the compressed refrigerant gas is discharged into an external refrigerant circuit (not shown) through an outlet port (not shown). 
     In this invention of a scroll-type fluid displacement apparatus, front housing  6  and rear housing  4  are assembled, such that an adjacent portion of ball rolling grooves  16   a  of first race  16  is elastically deformed toward inside of a circular-shaped recess portions  2   b  of second end plate  20  of orbiting scroll  2  and an adjacent portion of ball rolling grooves  17   a  of second race  17  is elastically deformed toward inside of a circular-shaped recess portions  6   a  of the end surface of front housing  6 . Therefore, elasticity is created between first race  16  and second race  17 , and a connecting force toward the x-axis is generated between fixed scroll  1  and orbiting scroll  2 . As a result, a spacer, which is inserted between front housing  6  and rear housing  4  to generate an appropriate force between fixed scroll  1  and orbiting scroll  2 , may no longer be required, and the number of parts of the compressor may be reduced. 
     An interior circular portion and an exterior circular portion of first race  16  are connected to the second surface of second end plate  20  of orbiting scroll  2 . An interior circular portion and an exterior circle portion of second race  17  are connected to the end surface of front housing  6 . Both first race  16  and second race  17  are supported at interior circular and exterior circular portions thereof. Therefore, when the thrust load, which is transferred from orbiting scroll  2  to front housing  6  through ball coupling  15 , is increased, the amount of elastic deformation of first race  16  and second race  17  may not be excessive. As a result, rolling of balls  18  may maintain stability, and orbiting scroll  2  may stably move in an orbital motion, when the thrust load is high. 
     In above-described apparatus, a plurality of a circular-shaped recess portions  2   b  are formed on the second surface of second end plate  20  of orbiting scroll  2  corresponding to a plurality of ball rolling, grooves  16   a  of first race  16 , and a plurality of circular-shaped recess portions  6   a  are formed on the end surface of front housing  6  corresponding to a plurality of ball rolling grooves  17   a  of second race  17 . However, as shown in FIGS. 7 a-b , forming a single, circular-shaped recess portion  2   c  or  2   d  on the second surface of second end plate  20  of orbiting scroll  2  corresponding to a plurality of ball rolling grooves  16   a  of first race  16  is within scope of the present invention. Similarly, as shown in FIGS. 8 a-b , forming a single, circular-shaped recess portion  6   b  or  6   c  on the end surface of front housing  6  corresponding to a plurality of ball rolling grooves  17   a  of second race  17  is within scope of the present invention. 
     As described above, with respect to embodiments of the present invention of a scroll-type fluid apparatus, front housing  6  and rear housing  4  are assembled, such that an adjacent portion of ball rolling grooves  16   a  of first race  16  is elastically deformed toward inside of single circular-shaped recess portions  2   c  or  2   d  of the second surface of end plate  20  of orbiting scroll  2  and an adjacent portion of ball rolling grooves  17   a  of second race  17  is elastically deformed toward inside of single circular-shaped recess portions  6   b  or  6   c  of the end surface of front housing  6 . Therefore, elasticity is created between first race  16  and second race  17 , and a connecting force toward the x-axis is generated between fixed scroll  1  and orbiting scroll  2 . As a result, a spacer, which is inserted between front housing  6  and rear housing  4 , may be no longer required, and the number of parts of the scroll-type fluid apparatus may be reduced. 
     An interior circular portion and an exterior circular portion of first race  16  are connected to the second surface of end plate  20  of orbiting scroll  2 . An interior circular portion and an exterior circular portion of second race  17  are connected to the end surface of front housing  6 . Both first race  16  and second race  17  are supported at interior circular and exterior circular portion thereof. Therefore, when the thrust load, which is transferred from orbiting scroll  2  to front housing  6  through ball coupling  15 , is increased, the amount of elastic deformation of first race  16  and second race  17  may not be excessive. As a result, rolling of balls  18  may maintain stability, and orbiting scroll  2  may stably move in an orbital motion. 
     Although the present invention has been described in connection with preferred embodiments, the invention is not limited thereto. It will be understood by those skilled in the art that variations and modifications may be made within the scope and spirit of this invention, as defined by the following claims.