Patent Publication Number: US-8967984-B2

Title: Rotary compressor

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims priority under 35 U.S.C. §119 to Korean Application No. 10-2009-0129188, filed in Korea on Dec. 22, 2009, whose entire disclosure is hereby incorporated by reference. 
     BACKGROUND 
     1. Field 
     This relates to a rotary compressor, and in particular, to a twin rotary compressor having a plurality of compression spaces. 
     2. Background 
     In general, refrigerant compressors are used in refrigerators or air conditioners using a vapor compression refrigeration cycle (hereinafter, referred to as ‘refrigeration cycle’). A constant speed type compressor may be driven at a substantially constant speed, while an inverter type compressor may be operated at selectively controlled rotational speeds. 
     A refrigerant compressor, in which a driving motor and a compression device operated by the driving motor are installed in an inner space of a hermetic casing, is called a hermetic compressor, and may be used in various home and/or commercial applications. A refrigerant compressor, in which the driving motor is separately installed outside the casing, is called an open compressor. Refrigerant compressors may be further classified into a reciprocal type, a scroll type, a rotary type and others based on a mechanism employed for compressing a refrigerant. 
     The rotary compressor may employ a rolling piston which is eccentrically rotated in a compression space of a cylinder, and a vane, which partitions the compression space of the cylinder into a suction chamber and a discharge chamber. Such a compressor may benefit from an enhanced capacity or a variable capacity. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments will be described in detail with reference to the following drawings in which like reference numerals refer to like elements wherein: 
         FIG. 1  is a schematic view of a refrigeration cycle including a two-stage type rotary compressor in accordance with an embodiment as broadly described herein; 
         FIGS. 2 and 3  are longitudinal views showing of the two-stage type rotary compressor shown in  FIG. 1 ; 
         FIG. 4  is a graph of compressor efficiency with respect to a height of a cylinder of the two-stage rotary compressor shown in  FIG. 2 ; 
         FIG. 5  is a graph of compressor efficiency with respect to a ratio of a refrigerant suction pipe to a connection pipe in the two-stage rotary compressor shown in  FIG. 2 ; and 
         FIG. 6  is a longitudinal sectional view of another embodiment of a two-stage rotary compressor as broadly described herein. 
     
    
    
     DETAILED DESCRIPTION 
     A twin rotary compressor may include a plurality of cylinders that may be selectively operated to provide increased and/or variable capacity. Such a twin rotary compressor may be further classified into a capacity-variable type compressor in which a plurality of cylinders may be operated independent of each other to independently compress refrigerant, and a two-stage type in which a plurality of cylinders communicate with each other to sequentially compress refrigerant. Such a twin rotary compressor may have upper and lower cylinders, which may have the same capacity or different capacities. For example, if both cylinders have the same inner diameter and the same capacity, the upper and lower cylinders may have the same height. If both cylinders have the same inner diameter and different capacities, the upper and lower cylinders may have different heights. 
     In such a two-stage type rotary compressor, a refrigerant suction pipe is typically connected to the lower cylinder, and so a height of the lower cylinder may be greater than that of the upper cylinder to accommodate the connection of the suction pipe thereto. That is, if the refrigerant suction pipe is connected to the lower cylinder, the height of the lower cylinder may be greater than at least an outer diameter of the refrigerant suction pipe. In order for the cylinder to have sufficient rigidity to preclude deformation thereof upon insertion of the refrigerant suction pipe, the cylinder may have a predetermined thickness in the vicinity of an inlet through which the refrigerant suction pipe is received. Therefore, the overall height of the lower cylinder may be at least as much as a value obtained by adding the outer diameter of the refrigerant suction pipe and additional thicknesses thereof at both upper and lower ends of the refrigerant suction pipe to ensure sufficient strength. However, as the height of the lower cylinder is greater, a contact area between a rolling piston and a vane in the lower cylinder may be increased, thus increasing refrigerant leakage between the rolling piston and the vane and losses in compression efficiency and capacity. 
     As shown in  FIG. 1 , a refrigeration cycle may include a compressor  1 , a condenser  2 , an expansion valve  3 , an evaporator  4  and a phase separator  5 . Refrigerant compressed in the compressor  1  may be introduced into the condenser  2 , where it is heat-exchanged with ambient air and condensed. The condensed refrigerant may pass through the expansion valve  3  and is then divided into gas refrigerant and liquid refrigerant by the phase separator  5 . The liquid refrigerant is then introduced into the evaporator  4  and evaporated through heat-exchange, and introduced into an accumulator  6  in a gas state. This refrigerant then flows from the accumulator  6  into a first compression device of the compressor  1  via a refrigerant suction pipe  11 . 
     The gas refrigerant divided by the phase separator  5  may be introduced into the compressor  1  via an injection pipe  13 . An intermediate pressure refrigerant compressed in the first compression device of the compressor  1  and refrigerant introduced via the injection pipe  13  may then flow into a second compression device of the compressor  1  to be compressed into a high pressure refrigerant, thereby being discharged into the condenser  2  via a refrigerant discharge pipe  12 . 
     As shown in  FIGS. 2 and 3 , in a configuration of the two-stage type rotary compressor  1  according to the one exemplary embodiment, a driving motor  102  may be installed in an inner space of the hermetic casing  101  to generate a driving force, and a first compression device  110  and a second compression device  120  may be positioned below the driving motor  102 , with a middle plate  130  positioned therebetween such that the first compression device  110  may define a low pressure side and the second compression device  120  may define a high pressure side. The refrigerant suction pipe  11  may be installed at and inserted into the hermetic casing  101 , and connected to an inlet of the first compression device  110  via the middle plate  130 . The refrigerant discharge pipe  12  may be installed at a top of the hermetic casing  101 , and may be connected to the inner space of the hermetic casing  101  so as to discharge a refrigerant into the condenser  2 . 
     The driving motor  102  may include a stator  103  secured to an inner circumferential surface of the hermetic casing  101 , a rotor  104  rotatably installed in the stator  103 , and a crankshaft  105  coupled to the center of the rotor  104  so as to transfer a rotating force to each of the compression device  110  and  120 . In certain embodiments, the stator  103  may be formed by laminating a plurality of annular steel plates and winding a coil C on the laminated steel plates. In certain embodiments, the rotor  104  may be formed by laminating a plurality of annular steel plates. 
     The crankshaft  105  may include a shaft portion  106  having a bar-like shape with a predetermined length, and being integrally fixed through a center of the rotor  104 , and first and second eccentric portions  107  and  108  that protrude eccentrically from a lower part of the shaft portion  106  in a radial direction so as to be rotatably coupled to first and second rolling pistons  112  and  122 , respectively. 
     An oil passage may extend from a lower to an upper end of the shaft portion  106 , and an oil feeder  109  may be coupled to a lower end of the oil passage. 
     The first eccentric portion  107  and the second eccentric portion  108  may be formed such that a suction process and a discharge process of the first compression device  110  have a phase difference of about 180° with respect to those of the second compression device  120 . The first eccentric portion  107  and the second eccentric portion  108  may each have a size, i.e., widths and heights, that allow them to be housed within a first cylinder  111  and a second cylinder  121 , respectively. At least one of the first and second eccentric portions  107  and  108  may include a balance hole  107   a  and  108   a  for reducing a weight thereof. 
     The first compression device  110  and the second compression device  120  may be laminated, positioning the middle plate  130  therebetween, in the order of the first compression device  110 , the middle plate  130  and the second compression device  120 , beginning at the lower end. Alternatively, they may be laminated in the order of the second compression device  120 , the middle plate  130  and the first compression device  110 . 
     The first compression device  110  may include the first cylinder  111  having a first compression space V 1 , the first rolling piston  112  that orbits in the first cylinder  111  and is rotatably coupled to the first eccentric portion  107 , a first vane  113  coupled to the first cylinder  111  so as to be linearly movable and contact an outer circumferential surface of the first rolling piston  112 , and a first vane spring  114  that elastically supports a rear end of the first vane  113 . 
     A height H 1  of the first cylinder  111  may be substantially the same as a height H 2  of the second cylinder  121 . Further, as the refrigerant suction pipe  11  is connected to the middle plate  130  and the connection pipe  14  is connected to the second cylinder  121 , the height H 1  of the first cylinder  111  may be less than the height H 2  of the second cylinder  121 . 
     The first cylinder  111  may include a suction port  115  formed at one edge of its inner circumferential surface to be connected to the refrigerant suction pipe  11 , a first vane slot  116  formed at one side of the suction port  115  in a circumferential direction such that the first vane  113  may slide therein, and a first discharge guide groove formed at another side of the first vane slot  116  so as to be connected to a first outlet  141 . 
     The second compression device  120  may include the second cylinder  121  having a second compression space V 2 , the second rolling piston  122  that orbits in the second cylinder  121  and is rotatably coupled to the second eccentric portion  108 , a second vane  123  coupled to the second cylinder  121  so as to be linearly movable and selectively contact an outer circumferential surface of the second rolling piston  122 , and a second vane spring  124  that elastically supports a rear end of the second vane  123 . 
     The second cylinder  121  may include a second inlet  125  formed at one side thereof to be connected to the first cylinder  111  via the connection pipe  14 , a second vane slot  126  formed at one side of the second inlet  125  such that the second vane  123  may slide therein, and a second discharge guide groove formed at another side of the second vane slot  126  to be connected to a second outlet  151 . 
     The middle plate  130  may have a ring shape, and include a first inlet  131  formed at one side of its outer circumferential surface so as to be connected to the refrigerant suction pipe  11 . The first inlet  131  may be recessed from an outer circumferential surface of the middle plate  130  by a predetermined depth. A communication hole  132  may be formed at a middle portion of the first inlet  131 , or at an inner end of the first inlet  131  in an axial direction, or at an inclination angle so as to communicate with the suction port  115  of the first cylinder  111 . Therefore, the middle plate  130  may be formed such that the first inlet  131  has a diameter long enough to communicate with the refrigerant suction pipe  11 . The middle plate  130  may have a predetermined thickness in the vicinity of the first inlet  131  so as to ensure reliability thereof. 
     Irrespective of the order of laminating the first and second compression devices  110  and  120 , a lower bearing  140  and an upper bearing  150  may be installed at lower and upper ends of the laminated compression devices so as to support the crankshaft  105  in an axial direction and simultaneously define the first and second compression spaces V 1  and V 2 , respectively, together with the cylinders  111  and  121 . 
     The lower bearing  140  may include the first outlet  141  formed at one side thereof such that refrigerant that has undergone first-stage compression in the first cylinder  111  is discharged therethrough, and a first discharge valve  142  installed at an end of the first outlet  141 . A storage space  143  may be formed at one side surface of the lower bearing  140 , namely, at a surface opposite the bearing surface. The storage space  143  may be covered with a cover plate  144  coupled to the lower bearing  140 . A communication hole  145  may be formed at one side of the storage space  143  to allow a refrigerant discharged into the storage space  143  to be introduced into the second cylinder  121  via the connection pipe  14 . 
     The upper bearing  150  may include the second outlet  151  formed at one side thereof to discharge refrigerant that has undergone second-stage compression in the second cylinder  121  therethrough, and a second discharge valve  152  installed at an end of the second outlet  151 . A muffler  153  for housing the second discharge valve  152  may be installed at one side surface of the upper bearing  150 , for example, at a surface opposite the bearing surface. 
     Operation of a twin rotary compressor as embodied and broadly described herein will now be discussed. 
     When the rotor  104  rotates in response to power supplied to the stator  103  of the driving motor  102 , the crankshaft  105  rotates together with the rotor  103  so as to transfer a rotating force of the driving motor  102  to both the first and second compression devices  110  and  120 . The first rolling piston  112  and the first vane  113  and the second rolling piston  122  and the second vane  123 , which are respectively disposed in the first and second compression devices  110  and  120 , perform an eccentric rotation in the first compression space V 1  and the second compression space V 2 , respectively, thereby compressing refrigerant with a phase difference of approximately 180° therebetween. 
     For instance, when a suction process is initiated in the first compression space V 1 , refrigerant is introduced into the first compression space V 1  of the first cylinder  111  sequentially through the accumulator  6 , the refrigerant suction pipe  11 , the first inlet  131  and the communication hole  132  of the middle plate  130  and the suction port  115  of the first cylinder  111 , thereby undergoing first-stage compression. The first-stage compressed refrigerant is then discharged into the storage space  143  of the lower bearing  140  via the first outlet  141 . 
     During the compression process in the first compression space V 1 , a suction process is initiated in the second compression space V 2 , which has a phase difference of approximately 180° from the first compression space V 1 . Accordingly, the refrigerant, which has been first-stage compressed in the first cylinder  111  and discharged into the storage space  143  of the lower bearing  140  is introduced into the second compression space V 2  of the second cylinder  121  via the connection pipe  14 . The refrigerant introduced in the second compression space V 2  is then second-stage compressed in the second compression space V 2  of the second cylinder  120 , and discharged into the inner space of the hermetic casing  101  via the second outlet  151  and the muffler  153 , thereby being discharged into the refrigeration cycle via the refrigerant discharge pipe  12 . This series of processes may be repeated. 
     As the refrigerant suction pipe  11  is connected to the middle plate  130 , the refrigerant suction pipe  11  does not necessarily have to be connected directly to the first cylinder  111 , so the height H 1  of the first cylinder  111  may be reduced. Consequently, a contact area between the first rolling piston  112  and the first vane  113  may be reduced, which allows reduction of refrigerant leakage from the first compression space V 1 , and improves performance of the compressor. 
     Referring to  FIGS. 2 and 3 , the connection pipe  14  may have one end connected to the communication hole  145  of the lower bearing  140  through the hermetic casing  101 , and another end inserted in the second inlet  125  of the second cylinder  121  through the hermetic casing  101 . A diameter of the connection pipe  14  may be less than a diameter of the refrigerant suction pipe  11 . 
     For example, to enhance performance of the compressor, the connection pipe  14  may have a diameter D 1  greater than 0.5 times a diameter D 2  of the refrigerant suction pipe  11  and less than 0.3 times thereof. As shown in  FIGS. 4 and 5 , if the diameter D 1  of the connection pipe  14  is less than or equal to 0.5 times of the diameter D 2  of the refrigerant suction pipe  11 , the refrigerant, which is first-stage compressed in the first compression space V 1  to be discharged into the storage space  143 , may not flow fast enough toward the second compression space V 2  due to flow resistance, thereby lowering performance of the compressor. On the other hand, if the diameter D 1  of the connection pipe  14  greater than or equal to 3.0 times the diameter D 2  of the refrigerant suction pipe  11 , the diameter of the connection pipe  14  also increases that much. Accordingly, the height H 2  of the second cylinder  121  drastically increases, causing further refrigerant leakage between the second rolling piston  122  and the second vane  123 , and lowering performance of the compressor. 
     This embodiment illustrates that the height of the first cylinder  111  may be less than the height of the second cylinder  121 . Alternatively, the first and second cylinders  111  and  121  may have substantially the same height. In this case, the diameter of the connection pipe  14  may less than the diameter D 2  of the refrigerant suction pipe  11 , so as to enhance performance of the compressor. 
     The first and second cylinders  111  and  121 , as aforesaid, may be connected to each other via the connection pipe  14 , and the connection pipe  14  may be connected thereto via the outside of the hermetic casing  101 . Alternatively, as shown in  FIG. 6 , the first and second cylinders  111  and  121  may communicate with each other via an internal passage F, which sequentially penetrates through the lower bearing  140 , the first cylinder  111 , the middle plate  130  and the second cylinder  121 , causing a refrigerant discharged into the storage space  143  to flow into the second compression space V 2 . In these cases, the injection pipe  13  may be connected to the connection pipe  14  or the internal passage F, and the compression efficiency of the compressor may be enhanced. Also, even in this case, a diameter of the internal passage F may be greater than 0.5 times the diameter D 2  of the refrigerant suction pipe  11  and less than 0.3 times thereof. 
     A twin rotary compressor is provided that is capable of enhancing efficiency of the compressor by decreasing a refrigerant leakage out of a cylinder in view of reducing a height of the cylinder. 
     A twin rotary compressor as embodied and broadly described herein may include a hermetic casing, a crankshaft installed in the hermetic casing and having first and second eccentric portions, a first cylinder installed in the hermetic casing and having a first rolling piston coupled to the first eccentric portion, a second cylinder installed in the hermetic casing and having a second rolling piston coupled to the second eccentric portion, an upper bearing and a lower bearing installed at one side surfaces of the first cylinder and the second cylinder, respectively, to define a first compression space and a second compression space, and a middle plate interposing between the first cylinder and the second cylinder and configured to partition the first compression space of the first cylinder and the second compression space of the second cylinder, wherein the middle plate comprises an inlet connected with a refrigerant suction pipe, the inlet is communicated with the first compression space of the first cylinder, an outlet of the first compression space of the first cylinder is connected to the second compression space of the second cylinder, and an outlet of the second compression space of the second cylinder is communicated with an inner space of the hermetic casing. 
     In a twin rotary compressor as embodied and broadly described herein, as a refrigerant suction pipe is connected to a middle plate interposed between a first cylinder and a second cylinder to thus reduce a height of the first cylinder, heights of a first rolling piston and a first vane can be lowered, which allows a contact area between the first rolling piston and the first vane to be decreased so as to reduce a refrigerant leakage from a first compression space of the first cylinder, resulting in improvement of compression efficiency of the compressor. 
     Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments. 
     Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.