Abstract:
The reversing of the direction of rotation of the motor of a fixed vane rotary compressor reverses the direction of rotation of the rolling piston. The rolling piston through viscous friction or frictional torque frictionally engages a reversing disk and causes the reversing disk to move between two positions depending upon the direction of rotation of the rolling piston. The reversing disk has a slot therein which forms the suction inlet and is moved by rotation of the reversing disk so as to be in fluid communication with the plenum which is serving as the suction plenum at that time.

Description:
BACKGROUND OF THE INVENTION 
     In heat pump applications, the switchover from the heating to the cooling mode, and vice versa, reverses the direction of flow for the refrigerant such that the coils serving as the condenser and evaporator, respectively, reverse functions. Where the compressor operates in a single direction, the change in the direction of the flow is generally achieved through a valving arrangement located externally of the compressor. If the compressor itself is reversible, it can be selectively run in either direction to, thereby, achieve the desired direction of flow. The simple reversal of the motor and, thereby, the compressor is not, in and of itself, sufficient to produce a compressor with satisfactory performance in both directions. This unequal performance in both directions is due to the switching between high and low side compressor operation, the change in the cooling requirements and the cooling flow, flow volumes, the reversal of porting function and direction of opening/closing, etc. 
     In a fixed vane or rolling piston type of compressor, a cylindrical rolling piston is in linear rolling contact with the cylindrical wall of the piston chamber. The rolling piston is moved by an eccentric located on the crankshaft and has a rolling contact with the wall of the piston chamber and defines therewith a crescent shaped chamber extending for almost 360°. A vane is radially movable and engages the rolling piston so as to divide the crescent shaped chamber into a suction chamber and a discharge chamber with their relative instantaneous volumes depending upon the location of the linear contact between the rolling piston and the wall of the piston chamber. 
     SUMMARY OF THE INVENTION 
     In a rotary hermetic compressor of the fixed vane or rolling piston type driven by a reversible motor, the reversing of the motor direction causes the shifting of the port controlling structure. Specifically, a suction port formed in a reversing disk is moved, due to viscous friction through the hydrodynamic oil film separating the disk and the rolling piston, between two positions according to the direction of motor rotation. At each of these two extreme positions the suction port provides a path for suction gas between a plenum and the cylinder suction volume while a second plenum becomes the discharge plenum for the compression volume. The two plenums reverse functions when the motor is reversed. Discharge chamber pressure is used to bias the reversing disk into a metal-to-metal seal with the crankcase. 
     It is an object of this invention to provide a mechanism and method to enable a reversible fixed vane compressor to efficiently deliver flow in either direction when the direction of motor rotation is reversed. 
     It is an additional object to provide a compressor that can be reversed simply by reversing the direction of motor rotation. 
     It is another object of this invention to reduce the clearance between the reversing disk and the bottom surface of the cylinder. 
     It is an additional object to provide a reversible hermetic compressor having all of the reversing structure within the shell. 
     It is a further object of this invention to provide a single suction port which is movable responsive to the direction of motor rotation. These objects, and others as will become apparent hereinafter, are accomplished by the present invention. 
     Basically, the reversal of the direction of rotation of a motor driving a fixed vane or rolling piston compressor reverses the operation of the compressor and thereby the direction of fluid flow. A reversing disk is located beneath the rolling piston and is movable between two positions, depending upon the direction of rotation of the motor, due to viscous frictional forces produced by the moving rolling piston through the oil seal. The reversing disk contains a slot which extends for a radial distance greater than that of the overlying cylinder wall and thereby serves as a suction inlet. In the two positions of the disk, the slot is respectively located on opposite sides of the vane and is in fluid communication with the respective plenums located on either side of the vane. As the vane reciprocates in response to the eccentric movement of the rolling piston, the vane and disk coact to cyclically establish a fluid path to bleed fluid from the discharge chamber to bias the disk into sealing engagement with the crankcase. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a fuller understanding of the present invention, reference should now be made to the following detailed description, thereof, taken in conjunction with the accompanying drawings wherein: 
     FIG. 1 is a vertical sectional view taken along line I--I of FIG. 2; 
     FIG. 2 is a sectional view taken along line II--II of FIG. 1; 
     FIG. 3 is a sectional view taken along line III--III of FIG. 1; 
     FIG. 4 is a sectional view of the vane taken essentially along line II--II of FIG. 1; 
     FIG. 5 corresponds to FIG. 2 but with the direction of rotation reversed; 
     FIG. 6 corresponds to FIG. 3 but with the direction of rotation reversed; 
     FIG. 7 is a partial sectional view taken along line VII--VII of FIG. 5; and 
     FIG. 8 is an isometric view of the reversing disk and vane structure. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the Figures, the numeral 10 generally designates a hermetic motor-compressor unit having a shell 12. Fluid communication with the interior of shell 12 is via lines 14 and 15, respectively. Within shell 12 is a reversible electric motor 16 including a stator 17 and a rotor 18. Motor 16 can be a conventional reversible electric motor for use in a hermetic compressor. Crankshaft 20 includes an eccentric 21 and is operatively connected to the rotor 18 so as to be rotated therewith, as is conventional. In addition to the crankshaft 20, the compressor 22 includes an upper bearing cap 24 and a lower bearing cap 26 with crankcase 28 located therebetween. 
     As is best shown in FIG. 2, crankcase 28 defines cylindrical piston chamber 30 and plenums 31 and 32. Crankcase 28 further defines a radially extending vane slot 34 and chamber 35. Vane 36 is reciprocably located in vane slot 34 and chamber 35 and is in essentially fluid tight contact with the walls of slot 34 to prevent leakage across the vane 36. Rolling piston 40 is driven by eccentric 21 so as to roll about the circumference of piston chamber 30 making line contact therewith. Vane 36 is biased into contact with rolling piston 40 by springs 38 and 39. Located beneath rolling piston 40 and a portion of the crankcase 28 and received within a corresponding recess in lower bearing cap 26 is reversing disk 50. The upper face of reversing disk 50 has a pair of arcuate slots 51 and 52 formed therein which serve as part of the rotational limiting structure and the suction inlet, respectively. The lower face of the reversing disk 50 has a circumferential groove 53 formed therein which is in fluid communication with the upper face via circumferentially spaced passages 54 and 55. An annular groove 56 is formed in the lower portion of reversing disk 50 and receives 0-ring 58 therein. A pin 60 is fixedly received in crankcase 28 and extends into slot 51. 
     Plenums 31 and 32 each contain a discharge valve 61 and 62, respectively, having valve stops 63 and 64, respectively. Preferably valves 61 and 62 and stops 63 and 64 are configured to control passages 28a and b which are each plural in number. As illustrated, passages 28a and b are each made up of three openings so that valves 61 and 62 and stops 63 and 64 are &#34;E&#34; shaped to cover each of the openings with a respective one of the &#34;arms&#34; of the &#34;E&#34;. Line 15 connects directly with plenum 32. Line 14 fluidly connects with plenum 31 via the interior of shell 12 and passage 25 extending through upper bearing cap 24. As best shown in FIG. 4, on either side of vane 36 is a radially extending groove 36a and b, respectively, which is in fluid communication with a corresponding axially extending groove 37a and b, respectively. At the lower end of crankshaft 20 is located an oil pickup tube 66 and an oil galley 68 extends along the axis of crankshaft 20, with radial bearing oil feed holes 68a, as is conventional. 
     In operation, the coaction of the rolling piston 40 and vane 36 is similar to that of a cam and cam follower with the rotation of rolling piston due to eccentric 21 producing reciprocating movement of the vane 36 as rolling piston 40 rolls along the wall of piston chamber 30. Referring now specifically to FIGS. 1-3, the hermetic compressor unit 10 is operating as a low side compressor with line 14 serving as the suction line and line 15 serving as the discharge line. The rotation of the crankshaft and its eccentric 21 is counterclockwise as shown by the arrow in FIG. 2. Refrigerant is drawn into shell 12 via line 14 and passes over and cools the structure of motor 16 before passing via passage 25 into plenum 31 which is serving as the suction plenum. From plenum 31 the refrigerant passes into portion 30a of piston chamber 30 via slot 52 in reversing disk 50. While portion 30a of piston chamber 30 remains in fluid communication with suction plenum 31 it will be the suction chamber. Once fluid communication with suction plenum 31 is cut off, the trapped volume, as in the case of portion 30b of piston chamber 30, becomes the discharge chamber. The discharge chamber 30b is in fluid communication with discharge plenum 32 via passages 28b under the control of normally closed discharge valve 62. Refrigerant entering discharge plenum 32 is discharged from the compressor via line 15. In rotating, viscous friction in the oil seal between rolling piston 40 and reversing disk 50 would cause continuous movement of disk 50 but for the presence of pin 60 which coacts with slot 51 to limit movement of disk 50 to the angular extent of slot 51 when going in either direction. When the direction of rotation is reversed, the fluid pressure causing the metal-to-metal seal between disk 50 and crankcase 28 must be relieved before the viscous friction is sufficient to move the disk to the other limiting postion. 
     As noted above, vane 36 reciprocates due to the rotation of the eccentric 21 and thereby rolling piston 40. Referring specifically to FIGS. 1 and 2, it will be noted that outward movement of vane 36 from the illustrated position will establish fluid communication between the current illustrated discharge chamber 30b and circumferential groove 53 via groove 36b, groove 37b and passage 55. Chamber 30a will be in the same fluid communication via a corresponding fluid path defined by grooves 36a, 37a and passage 54 when it is the discharge chamber. The exact moment of the discharge stroke when this fluid communication takes place will be determined by the specific compressor design, but basically it cyclically places groove 53 at essentially discharge pressure to establish a sealing bias of reversing disk 50 against crankcase 28. O-ring 58 acts to prevent leakage from groove 53 as does the interruption of fluid communication between groove 37b and passage 55. 
     If the motor 16 is reversed so that rotation of the crankshaft and its eccentric 21 is clockwise as shown by the arrow in FIG. 5, rotation of rolling piston 40 by the eccentric 21 will tend to cause disk 50 to move clockwise from the FIGS. 2 and 3 position to the FIGS. 5 and 6 position due to viscous friction. However, the metal-to-metal contact between disk 50 and crankcase 28 initially prevents this so that disk 50 initially remains in the FIGS. 2 and 3 position. The illustrated chamber 30b becomes the suction chamber upon reversal of the motor to a clockwise rotation but, until disk 50 is moved to the FIGS. 5 and 6 positions slot 52 is not in the proper position to serve as the suction inlet and chamber 30b is therefore at a vacuum. The reciprocation of vane 36 cyclically continues to establish the fluid path defined by grooves 36b, 37b and passage 55 but the pressure differential causes the bleeding of pressurized fluid from groove 53 to chamber 30b. When the fluid pressure in groove 53 drops sufficiently to cause the release of the metal-to-metal seal between disk 50 and crankcase 28, the viscous friction or frictional torque generated between rolling piston 40 and disk 50 is sufficient to turn the disk 50 in the direction of movement of rolling piston 40 to the FIGS. 5 and 6 position which is limited by pin 60 engaging the end of slot 51. In the FIGS. 5 and 6 position, slot 52 is properly placed to serve as the suction inlet and chamber 30b is properly supplied. In the FIGS. 5 and 6 position reciprocation of vane 36 cyclically establishes fluid communication between the discharge chamber and groove 53 via grooves 36a, 37a and passage 54 to establish the metal-to-metal seal between crankcase 28 and disk 50 as previously described. 
     Referring now specifically to FIGS. 5-7, the hermetic compressor unit 10 is operating as a high side compressor with line 15 serving as the suction line and line 14 serving as the discharge line. Refrigerant is drawn into plenum 32, which is acting as the suction plenum, via line 15. Refrigerant discharged from the piston chamber 30 into the plenum 31, which is acting as the discharge plenum, passes via passage 25 into the interior of shell 12 where it passes over the structure of motor 16 before passing from the compressor unit 10 via line 14. More specifically, as shown in FIG. 7, slot 52 provides free fluid communication between suction plenum 32 and piston chamber 30b which is acting as the suction chamber and will continue to be the suction chamber as long as it remains in fluid communication with suction plenum 32. Once fluid communication with suction plenum 32 is cut off, the trapped volume, as in the case of portion 30a of piston chamber 30, becomes the discharge chamber. The discharge chamber 30a is in fluid communication with discharge plenum 31 via passages 28a under the control of normally closed discharge valve 61. 
     As in the low side operation described above, movement of vane 36 will cyclically establish fluid communication between the current illustrated discharge chamber, 30a, and circumferential groove 53 via groove 36a, groove 37a and passage 54. Chamber 30b will be in the same fluid communication when it is the discharge chamber. Discharge pressure acting in groove 53 establishes a sealing bias of reversing disk 50 against crankcase 28 as previously described. This sealing bias will be reduced/eliminated upon reversal of motor direction, as described above, to permit movement of the disk 50 by rolling piston 40. 
     From the foregoing description it should be clear that the same inlet structure is used for both directions of operation which avoids the problems of different volumetric flows in the suction and discharge lines. Similarly, identical discharge valves are used in each direction of operation. The repositioning of the inlet structure is responsive to a viscous friction force produced by the rolling piston which is the structure directly driven by the motor, and is therefore the initial compressor structure which is reversed by reversing the direction of rotation of the motor. 
     Although a preferred embodiment of the present invention has been illustrated and described, other changes will occur to those skilled in the art. It is, therefore, intended that the present invention is to be limited only by the scope of the appended claims.