Patent Publication Number: US-2022228587-A1

Title: Rotary compressor

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     Pursuant to 35 U.S.C. § 119(a), this application claims the benefit of the earlier filing date and the right of priority to Korean Patent Application No. 10-2021-0006830, filed on Jan. 18, 2021, the contents of which are incorporated by reference herein in their entirety. 
     BACKGROUND 
     1. Field 
     A vane rotary compressor in which a vane is coupled to a roller is disclosed herein. 
     2. Background 
     Rotary compressors may be divided into two types, namely, a type in which a vane is slidably inserted into a cylinder to come in contact with a roller, and a type in which a vane is slidably inserted into a roller to come in contact with a cylinder. Generally, the former is referred to as a roller eccentric rotary compressor (hereinafter, a “rotary compressor”), and the latter is referred to as a vane concentric rotary compressor (hereinafter, a “vane rotary compressor”). 
     As for the rotary compressor, a vane inserted into a cylinder is pulled out toward a roller by elastic force or back pressure to come into contact with an outer circumferential surface of the roller. On the other hand, as for the vane rotary compressor, a vane inserted into a roller rotates together with the roller and is pulled out toward a cylinder by centrifugal force and back pressure to come into contact with an inner circumferential surface of the cylinder. 
     A rotary compressor independently forms as many compression chambers as the number of vanes per revolution of a roller, and each compression chamber simultaneously performs suction, compression, and discharge strokes. On the other hand, a vane rotary compressor continuously forms an many compression chambers as the number of vanes per revolution of a roller, and each compression chamber sequentially performs suction, compression, and discharge strokes. Accordingly, the vane rotary compressor has a higher compression ratio than the rotary compressor. Therefore, the vane rotary compressor is more suitable for high pressure refrigerants, such as R32, R410a, and CO 2 , which have low ozone depletion potential (ODP) and global warming index (GWP). 
     Such a vane rotary compressor is disclosed in U.S. Patent Application No. 2015/0064042 A1 (hereinafter, “Patent Document 1”), which is hereby incorporated by reference. The vane rotary compressor disclosed in Patent Document 1 is a low-pressure type in which a suctioned refrigerant is filled in an inner space of a motor chamber but has a structure in which a plurality of vanes is slidably inserted into a rotating roller, which is a feature of the vane rotary compressor. 
     In the vane rotary compressor disclosed in Patent Document 1, an inner circumferential surface of a cylinder defining a compression space is formed as a plurality of curves. For example, the inner circumferential surface of the cylinder disclosed in Patent Document 1 may be formed in an asymmetric elliptical shape eccentric with respect to an axial center of a rotational shaft. Accordingly, the inner circumferential surface of the cylinder has a proximal portion which is closest to the axial center and a remote portion which is farthest away from the axial center, and the proximal portion and the remote portion are connected by curved surfaces having different aspect ratios. 
     An outer circumferential surface of the roller has a circular shape with a constant curvature such that the roller is disposed concentrically with respect to the axial center of the rotational shaft. The plurality of vane slots is recessed into the outer circumferential surface of the roller by a predetermined depth and disposed at equal intervals along the outer circumferential surface of the roller. 
     When the inner circumferential surface of the cylinder is formed in the asymmetric elliptical shape biased in a specific direction, an inflection point may be generated on the inner circumferential surface of the cylinder at a point at which two ellipses having different aspect ratios meet. The largest inflection point may occur at a portion defining the distal portion. Accordingly, as a length of the vane pulled out from the vane slot of the roller becomes the greatest (longest) around the inflection point or both sides including the inflection point when the roller rotates, the loudest impulse sound due to collision between the vane and the cylinder is generated. The impulse sound may occur periodically due to the equally spaced vanes, causing noise of the compressor to be increased. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments will be described in detail with reference to the following drawings in which like reference numerals refer to like elements, and wherein: 
         FIG. 1  is a longitudinal cross-sectional view of a vane rotary compressor according to an embodiment; 
         FIG. 2  is an assembled perspective view of a compression unit of  FIG. 1 ; 
         FIG. 3  is an exploded perspective view of the compression unit of  FIG. 2 ; 
         FIG. 4  is a planar view illustrating a portion of the compression unit in  FIG. 3 ; 
         FIG. 5  is a schematic view illustrating an example of intervals between vane slots according to an embodiment; 
         FIG. 6  is a graph showing comparison of compressor efficiency according to maximum variable angles in the embodiment of  FIG. 5 ; 
         FIG. 7  is a graph showing comparison between vane slots disposed at unequal intervals according to embodiments and vane slots disposed at equal intervals; 
         FIG. 8  is a perspective view of a vane according to an embodiment; 
         FIG. 9  is a planar view illustrating a state in which the vane of  FIG. 8  is inserted into a vane slot; 
         FIG. 10  is a planar view of a chamfer portion according to an embodiment; 
         FIG. 11  is a planar view illustrating an example in which unequally spaced vane slots are employed in a cylinder having a symmetric elliptical shape according to an embodiment; 
         FIG. 12  is a planar view illustrating an example in which unequally spaced vane slots are employed in a cylinder having a circular shape according to an embodiment; and 
         FIG. 13  is a planer view of a roller in which examples of vane slots are employed according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Description will now be given of a vane rotary compressor according to embodiments disclosed herein, with reference to the accompanying drawings. For reference, vane slots of a roller according to embodiments may also be applied to a vane rotary compressor in which a vane is slidably inserted into a roller. They may be equally applied when vane slots are formed in an inclined manner as described herein, as well as when vane slots are formed radially. In addition, the vane slots of the roller according to embodiments may also be applicable regardless of a shape of an inner circumferential surface of a cylinder. For example, they may be equally applied to a cylinder having an inner circumferential surface with an asymmetric or symmetric elliptical shape, and a cylinder having an inner circumferential surface with a circular shape. Hereinafter, description will be mainly given of an example in which vane slots are obliquely or inclinedly formed in a roller and an inner circumferential surface of a cylinder has an asymmetric elliptical shape. 
       FIG. 1  is a longitudinal cross-sectional view of a vane rotary compressor according to an embodiment.  FIG. 2  is an assembled perspective view of a compression unit of  FIG. 1 .  FIG. 3  is an exploded perspective view of the compression unit of  FIG. 2 .  FIG. 4  is a planar view illustrating a portion of the compression unit in  FIG. 3 . 
     Referring to  FIG. 1 , a vane rotary compressor according to this embodiment may include a casing  110 , a drive motor  120 , and a compression unit  130 . The drive motor  120  may be installed in an upper inner space of the casing  110 , and the compression unit  130  may be installed in a lower inner space of the casing  110 . The drive motor  120  and the compression unit  130  may be connected through a rotational shaft  123 . 
     The casing  110  which defines an outer appearance of the compressor may be classified as a vertical type and a horizontal type according to a compressor installation method. In the vertical type casing, the drive motor  120  and the compression unit  130  are disposed at upper and lower sides in an axial direction, respectively. As for the horizontal type casing, the drive motor  120  and the compression unit  130  are disposed at left and right sides, respectively. The casing according to this embodiment may be the vertical type. 
     The casing  110  may include an intermediate shell  111  having a cylindrical shape, a lower shell  112  that covers a lower end of the intermediate shell  111 , and an upper shell  113  that covers an upper end of the intermediate shell  111 . The drive motor  120  and the compression unit  130  may be inserted into the intermediate shell  111  to be fixedly coupled thereto, and a suction pipe  115  may be formed through the intermediate shell  111  to be directly connected to the compression unit  130 . 
     The lower shell  112  may be sealed and coupled to the lower end of the intermediate shell  111 , and an oil storage space  110   b  in which oil to be supplied to the compression unit  130  is stored may be formed below the compression unit  130 . The upper shell  113  may be sealed and coupled to the upper end of the intermediate shell  111 , and an oil separation space  110   c  may be formed above the drive motor  120  to separate oil from refrigerant discharged from the compression unit  130 . 
     The drive motor  120  which constitutes a motor unit provides power to cause the compression unit  130  to be driven. The drive motor  120  may include a stator  121 , a rotor  122 , and the rotational shaft  123 . 
     The stator  121  may be fixedly inserted into the casing  110 . The stator  121  may be fixed to an inner circumferential surface of the cylindrical casing  110  in a shrink-fitting manner, for example. For example, the stator  121  may be press-fitted into an inner circumferential surface of the intermediate shell  111 . 
     The rotor  122  may be rotatably inserted into the stator  121 , and the rotational shaft  123  may be press-fitted into a center of rotation (or a rotation or rotational center) of the rotor  122 . Accordingly, the rotational shaft  123  may rotate concentrically together with the rotor  122 . 
     An oil flow path  125  having a hollow hole shape may be formed in a central portion of the rotational shaft  123 , and oil passage holes  126   a  and  126   b  may be formed through a middle portion of the oil flow path  125  toward an outer circumferential surface of the rotational shaft  123 . The oil passage holes  126   a  and  126   b  may include first oil passage hole  126   a  belonging to a range of a main bearing portion  1312  to be described hereinafter and a second oil passage hole  126   b  belonging to a range of a sub bearing portion  1322 . Each of the first oil passage hole  126   a  and the second oil passage hole  126   b  may be provided as one hole or as a plurality of holes. In this embodiment, each of the first and second oil passage holes is provided as a plurality. 
     An oil pump  127  may be installed at a middle or lower end of the oil flow path  125 . A gear pump, a viscous pump, or a centrifugal pump may be used for the oil pump  127 . This embodiment illustrates a case in which a centrifugal pump is employed. Accordingly, when the rotational shaft  123  rotates, oil filled in the oil storage space  110   b  is pumped by the oil pump  127  and is suctioned along the oil flow path  125 , so as to be introduced to a sub bearing surface  1322   a  of the sub bearing portion  1322  through the second oil passage hole  126   b  and to a main bearing surface  1312   a  of the main bearing portion  1312  through the first oil passage hole  126   a . This will be described hereinafter. 
     The compression unit  130  may include a main bearing  131 , a sub bearing  132 , a cylinder  133 , a roller  134 , and a plurality of vanes  135  ( 1351 ,  1352 , and  1353 ). The main bearing  131  and the sub bearing  132  are respectively provided at upper and lower portions of the cylinder  133  to define a compression space V together with the cylinder  133 , the roller  134  is rotatably installed in the compression space V, and the vanes  135  ( 1351 ,  1352 , and  1353 ) are slidably inserted into the roller  134  to divide the compression space V into a plurality of compression chambers. 
     Referring to  FIGS. 1 to 3 , the main bearing  131  may be fixedly installed at the intermediate shell  111  of the casing  110 . For example, the main bearing  131  may be inserted into the intermediate shell  111  and welded thereto. 
     The main bearing  131  may be coupled to an upper end of the cylinder  133  in a close contact manner. Accordingly, the main bearing  131  defines an upper surface of the compression space V, and supports an upper surface of the roller  134  in the axial direction and at the same time supports an upper portion of the rotational shaft  123  in a radial direction. 
     The main bearing  131  may include a main plate portion  1311  and main bearing portion  1312 . The main plate portion  1311  covers an upper portion of the cylinder  133  to be coupled thereto, and the main bearing portion  1312  axially extends from a center of the main plate portion  1311  toward the drive motor  120  so as to support the upper portion of the rotational shaft  123 . 
     The main plate portion  1311  may have a disk shape, and an outer circumferential surface of the main plate portion  1311  may be fixed to the inner circumferential surface of the intermediate shell  111  in a close contact manner. One or more discharge ports  1313  ( 1313   a ,  1313   b ,  1313   c ) may be defined in the main plate portion  1311 , and a plurality of discharge valves  1361   a ,  1361   b , and  1361   c  configured to open and close the respective discharge ports  1313   a ,  1313   b , and  1313   c  may be installed on an upper surface of the main plate portion  1311 , and a discharge muffler  137  having a discharge space (no reference numeral) may be provided at an upper portion of the main plate portion  1311  to accommodate the discharge ports  1313   a ,  1313   b  and  1313   c , and the discharge valves  1361   a ,  1361   b , and  1361   c . Accordingly, refrigerant compressed in the compression unit  130  may be discharged to an inner space  110   a  of the casing  100  through the discharge ports  1313   a ,  1313   b  and  1313   c , and the discharge muffler  137  and may then be discharged to a discharge pipe  116 . As a result, the inner space  110   a  of the casing  110  may be maintained at a high pressure forming a discharge pressure. 
     The main bearing portion  1312  may be formed in the shape of a hollow bush, and an oil groove (not shown) may be formed on main bearing surface  1312   a  which is an inner circumferential surface of the main bearing portion  1312 . The oil groove may extend linearly or diagonally between upper and lower ends of the main bearing portion  1312  to communicate with a second main back pressure pocket  1315   b  through a second main bearing protrusion  1316   b  described hereinafter. 
     The first main back pressure pocket  1315   a  and the second main back pressure pocket  1315   b  may be formed at a lower surface of the main plate portion  1311  facing the upper surface of the roller  134 . The first main back pressure pocket  1315   a  and the second main back pressure pocket  1315   b  each having an arcuate shape may be disposed at a predetermined interval in a circumferential direction. The first main back pressure pocket  1315   a  and the second main back pressure pocket  1315   b  may each have an inner circumferential surface with a circular shape, but may each have an outer circumferential surface with an oval or elliptical shape in consideration of vane slots to be described hereinafter. 
     The first main back pressure pocket  1315   a  and the second main back pressure pocket  1315   b  may be formed within an outer diameter range of the roller  134 . Accordingly, the first main back pressure pocket  1315   a  and the second main back pressure pocket  1315   b  may be separated from the compression space V. However, the first main back pressure pocket  1315   a  and the second main back pressure pocket  1315   b  may slightly communicate with each other through a gap between the lower surface of the main plate portion  1311  and the upper surface of the roller  134  facing each other unless a separate sealing member is provided therebetween. 
     The first main back pressure pocket  1315   a  forms a pressure lower than a pressure formed in the second main back pressure pocket  1315   b , for example, an intermediate pressure between a suction pressure and a discharge pressure. Oil (refrigerant oil) may pass through a fine or tiny passage between a first main bearing protrusion  1316   a  described hereinafter and the upper surface of the roller  134  to be introduced into the main back pressure pocket  1315   a . The first main back pressure pocket  1315   a  may be formed in a range of a compression chamber forming an intermediate pressure of the compression space V. This may allow the first main back pressure pocket  1315   a  to maintain the intermediate pressure. 
     Oil flowing into the main bearing surface  1312   a  of the main bearing  1312  described hereinafter through the first oil passage hole  126   a  may be introduced into the second main back pressure pocket  1315   b  through a main communication flow path (not shown). The second main back pressure pocket  1315   b  may be formed in a range of a compression chamber forming a discharge pressure of the compression space V. This may allow the second main back pressure pocket  1315   b  to maintain the discharge pressure. 
     In addition, the first main bearing protrusion  1316   a  and the second main bearing protrusion  1316   b  may be formed on inner circumferential sides of the first main back pressure pocket  1315   a  and the second main back pressure pocket  1315   b , respectively, extending from the main bearing surface  1312   a  of the main bearing portion  1312 . Accordingly, the inner circumferential sides of the first main back pressure pocket  1315   a  and the second main back pressure pocket  1315   b  may be separated from the main bearing surface  1312   a , and an area that supports the rotational shaft  123  may be increased. 
     The first main bearing protrusion  1316   a  and the second main bearing protrusion  1316   b  may have a same height or different heights. For example, when the first main bearing protrusion  1316   a  and the second main bearing protrusion  1316   b  have the same height, an oil communication groove (not shown) or an oil communication hole (not shown) may be formed on an end surface of the second main bearing protrusion  1316   b  to allow inner and outer circumferential surfaces of the second main bearing protrusion  1316   b  to communicate with each other. Accordingly, high-pressure oil (refrigerant oil) flowing into the main bearing surface  1312   a  may be introduced into the second main back pressure pocket  1315   b  through the oil communication groove (not shown) or the oil communication hole (not shown). 
     On the other hand, when the first main bearing protrusion  1316   a  and the second main bearing protrusion  1316   b  have different heights, the height of the second main bearing protrusion  1316   b  may be lower than the height of the first main bearing protrusion  1316   a . Accordingly, high-pressure oil (refrigerant oil) flowing into the main bearing surface  1312   a  may be introduced into the second main back pressure pocket  1315   b  by passing over the second main bearing protrusion  1316   b.    
     Referring to  FIGS. 1 to 3 , the sub bearing  132  may be coupled to a lower end of the cylinder  133  in a close contact manner. Accordingly, the sub bearing  132  defines a lower surface of the compression space V, and supports a lower surface of the roller  134  in the axial direction and at the same time supports a lower portion of the rotational shaft  123  in the radial direction. 
     The sub bearing  132  may include a sub plate portion  1321  and sub bearing portion  1322 . The sub plate portion  1321  may cover a lower portion of the cylinder  133  to be coupled to thereto, and the sub bearing portion  1322  may axially extend from a center of the sub plate portion  1321  toward the lower shell  112  so as to support the lower portion of the rotational shaft  123 . 
     The sub plate portion  1321  may have a disk shape like the main plate portion  1311 , and an outer circumferential surface of the sub plate portion  1321  may be spaced apart from the inner circumferential surface of the intermediate shell  111 . The sub bearing portion  1322  may be formed in the shape of a hollow bush, and an oil groove (not shown) may be formed on sub bearing surface  1322   a  which is an inner circumferential surface of the sub bearing portion  1322 . The oil groove may extend linearly or diagonally between upper and lower ends of the sub bearing portion  1322  to communicate with a second sub back pressure pocket  1325   b  through a second sub bearing protrusion  1326   b  described hereinafter. The first sub back pressure pocket  1325   a  and the second sub back pressure pocket  1325   b  may be formed on a lower surface of the sub plate portion  1321  facing the lower surface of the roller  134 . 
     The first sub back pressure pocket  1325   a  and the first main back pressure pocket  1315   a  may be symmetric with respect to the roller  134 , and the second sub back pressure pocket  1325   b  and the second main back pressure pocket  1315   b  may be symmetric with respect to the roller  134 . For example, the first sub back pressure pocket  1325   a  and the first main back pressure pocket  1315   a  may be symmetric to each other, and the second sub back pressure pocket  1325   b  and the second main back pressure pocket  1315   b  may be symmetric to each other. Accordingly, a first sub bearing protrusion  1326   a  may be formed on an inner circumferential side of the first sub back pressure pocket  1325   a , and the second sub bearing protrusion  1326   b  may be formed on an inner circumferential side of the second sub back pressure pocket  1325   b.    
     Descriptions of the first sub back pressure pocket  1325   a  and the second sub back pressure pocket  1325   b , and the first sub bearing protrusion  1326   a  and the second sub bearing protrusion  1326   b  may be the same as descriptions of the first main back pressure pocket  1315   b  and the second main back pressure pocket  1315   b , and the first main bearing protrusion  1316   a  and the second main bearing protrusion  1316   b , and repetitive description has been omitted. 
     Although not illustrated in the drawings, back pressure pockets [( 1315   a ,  1315   b ) ( 1325   a ,  1325   b )] may be provided only at any one of the main bearing  131  and the sub bearing  132 . 
     The discharge port  1313  may be formed in the main bearing  131  as described above. However, the discharge port may be defined in the sub bearing  132 , defined in each of the main bearing  131  and the sub bearing  132 , or formed by penetrating between inner and outer circumferential surfaces of the cylinder  133 . This embodiment describes an example in which the discharge ports are defined in the main bearing. 
     In addition, one discharge port  1313  may be provided. However, in this embodiment, a plurality of discharge ports  1313   a ,  1313   b , and  1313   c  is formed at predetermined intervals along a compression proceeding direction (or a rotational direction of the roller). 
     In the case of the vane rotary compressor, the roller  134 , in general, is eccentrically disposed with respect to the compression space V, such that a proximate point P 1  at which an outer circumferential surface  1341  of the roller  134  and an inner circumferential surface  1331  of the cylinder  133  are almost in contact is generated, and the discharge port  1313  is formed near the proximate point P 1 . As the compression space V gets closer to the proximate point P 1 , a gap (or distance) between the inner circumferential surface  1331  of the cylinder  133  and the outer circumferential surface  1341  of the roller  134  becomes smaller (or narrower), making it difficult to secure the area of the discharge port. 
     Thus, as in this embodiment, the discharge port  1313  may be divided into a plurality of discharge ports  1313   a ,  1313   b , and  1313   c  formed along the rotational direction of the roller  134  (or the compression proceeding direction). In addition, each of the plurality of discharge ports  1313   a ,  1313   b , and  1313   c  may be provided as one, or a pair (a set of two). 
     For example, the discharge port  1313  according to this embodiment may be configured such that first discharge port  1313   a , second discharge port  1313   b , and third discharge port  1313   c  are arranged in the order of proximity to a proximal portion  1331   a  based on the rotational direction of the roller  134 . A distance between the first discharge port  1313   a  and the second discharge port  1313   b  and/or a distance between the second discharge port  1313   b  and the third discharge port  1313   c  may be approximately similar to a distance between a preceding vane and a following vane, namely, a circumferential length of each compression chamber. 
     For example, the distance between the first discharge port  1313   a  and the second discharge port  1313   b , which is a first distance, and the distance between the second discharge port  1313   b  and the third discharge port  1313   c , which is a second distance, may be equal. The first distance and the second distance may be substantially equal to a circumferential length of a first compression chamber V 1 , a circumferential length of a second compression chamber V 2 , and a circumferential length of a third compression chamber V 3 . Accordingly, the first discharge port  1313   a  may communicate with the first compression chamber V 1 , the second discharge port  1313   b  may communicate with the compression chamber V 2 , and the third discharge port  1313   c  may communicate with the third compression chamber V 3 , rather than providing communication between a plurality of discharge ports  1313  and one compression chamber or between one discharge port  1313  and a plurality of compression chambers. 
     However, when vane slots  1342   a ,  1342   b , and  1342   c  described hereinafter are disposed at unequal or irregular intervals, the compression chambers V 1 , V 2 , and V 3  may have different circumferential lengths, such that one compression chamber may communicate with a plurality of discharge ports, or a plurality of compression chambers may communicate with one discharge port. This will be described hereinafter together with the vane slots. 
     In addition, a discharge groove  1314  may extend from the discharge port  1313  according to this embodiment. The discharge groove  1314  may extend in an arcuate shape along the compression proceeding direction (the rotational direction of the roller). Accordingly, refrigerant, which is not discharged from a preceding compression chamber, may be guided to a discharge port  1313  communicating with a following compression chamber through the discharge groove  1314 , so as to be discharged together with refrigerant compressed in the following compression chamber. As a result, residual refrigerant in the compression space V may be minimized to thereby suppress over compression or excessive compression. Thus, efficiency of the compressor may be increased. 
     The discharge groove  1314  may extend from the last discharge port, for example, the third discharge port  1313 . In the vane rotary compressor, as the compression space V is divided into a suction chamber and a discharge chamber with the proximal portion (proximate point)  1331   a  interposed therebetween, the discharge port  1313  cannot overlap the proximate point P 1  located at the proximal portion  1331   a  in consideration of sealing between the suction chamber and the discharge chamber. Accordingly, a refrigerant remaining space S by which the inner circumferential surface  1331  of the cylinder  133  and the outer circumferential surface  1341  of the roller  134  are spaced apart is formed between the proximate point P 1  and the discharge port  1313  along the circumferential direction, and refrigerant which is not discharged through the last discharge port  1313  remains in the refrigerant remaining space S. This residual refrigerant may increase pressure of the last compression chamber to thereby cause a decrease in compression efficiency due to over compression. 
     However, as in this embodiment, when the discharge groove  1314  extends from the last discharge port  1313  to the refrigerant remaining space S, refrigerant remaining in the refrigerant remaining space S may be discharged additionally by flowing back to the last discharge port  1313  through the discharge groove  1314 , thereby suppressing a decrease in compression efficiency due to over compression in the last compression chamber. 
     Although not illustrated in the drawings, a residual refrigerant discharge hole may be defined in the refrigerant remaining space in addition to the discharge groove. The residual refrigerant discharge hole may have a smaller inner diameter than the discharge port. Unlike the discharge port, the residual refrigerant discharge hole may be configured to remain open at all times, rather than being opened and closed by the discharge valve. 
     In addition, the plurality of discharge ports  1313   a ,  1313   b , and  1313   c  may be opened and closed by the discharge valves  1361   a ,  1361   b , and  1361   c , respectively. Each of the discharge valves  1361   a ,  1361   b , and  1361   c  may be implemented as a cantilever type reed valve having one end defining a fixed end and another end defining a free end. These discharge valves  1361   a ,  1361   b , and  1361   c  are widely known in the conventional rotary compressor, and thus, detailed description thereof has been omitted. 
     Referring to  FIGS. 1 to 4 , the cylinder  133  according to this embodiment may be in close contact with a lower surface of the main bearing  131  and coupled to the main bearing  131  by, for example, a bolt together with the sub bearing  132 . Accordingly, the cylinder  133  may be fixedly coupled to the casing  110  by the main bearing  131 . 
     The cylinder  133  may be formed in an annular shape having compression space V at its center, and the inner circumferential surface  1331  of the cylinder  133  defining the compression space V may have an elliptical shape. The inner circumferential surface  1331  of the cylinder  133  defining the compression space V may be eccentric with respect to a rotational center (or center of rotation) Or of the roller  134  defining an axial center (no numeral reference). The inner circumferential surface  1331  of the cylinder  133  will be described hereinafter. 
     The cylinder  133  may be provided with a suction port  1332  communicating with the compression space V. The suction port  1332  may be formed by penetrating from an outer circumferential surface of the cylinder  133  to the inner circumferential surface  1331  of the cylinder  133 . The outer circumferential surface of the cylinder  133  at which the suction port  1332  is formed may be in close contact with an inner circumferential surface of the casing  110 , allowing the suction pipe  115  formed through the casing  110  to be directly connected thereto. Accordingly, refrigerant may be directly suctioned into the compression space V through the suction port  1332 . 
     In addition, the suction port  1332  may be formed at one side in the circumferential direction with respect to the proximate point P 1  described hereinafter, namely, at an opposite side of the discharge port  1313  in the circumferential direction based on the proximate point P 1 . Accordingly, the suction port  1332  and the discharge port  1313  may be separated in the circumferential direction with respect to the proximate point P 1 . 
     The inner circumferential surface  1331  of the cylinder  133  according to this embodiment may have an elliptical shape. A plurality of ellipses may be combined to form an asymmetric elliptical shape biased or concentrated in a specific direction. 
     The inner circumferential surface  1331  of the cylinder  133  may include the proximal portion  1331   a , a distal (or remote) portion  1331   b , and a curved portion  1331   c . The proximal portion  1331   a  is a portion which is closest to the outer circumferential surface (or the rotational center of the roller)  1341  of the roller  134 , the distal portion  1331   b  is a portion which is farthest away from the outer circumferential surface  1341  of the roller  134 , and the curved portion  1331   c  is a portion connecting the proximal portion  1331   a  and the distal portion  1331   b.    
     The proximal portion  1331   a  may also be defined as the proximate point P 1 , and the suction port  1332  and the discharge port  1313  may be provided at both sides with respect to the proximal portion  1331   a . For example, the suction port  1332  may be formed at one or a first side in the circumferential direction with respect to the proximal portion  1331   a , and the discharge port  1313  may be formed at another or a second side in the circumferential direction with respect to the proximal portion  1331   a.    
     The distal portion  1331   b  may extend in a specific direction to be formed convexly. For example, the distal portion  1331   b  is a portion at which two ellipses having largest aspect ratios meet. Accordingly, an inflection point P 2  on the distal portion  1331   b  has a greatest curvature change compared to inflection points on other portions of the inner circumferential surface  1331  of the cylinder  133 . Hereinafter, an inflection point may be referred to as the inflection point P 2  on the distal portion  1331   b . The inflection point P 2  in a broader sense may be understood as the distal portion  1331   b  including the inflection point P 2 . 
     The curved portion  1331   c  may be formed as a plurality of elliptical surfaces having different aspect ratios and disposed asymmetrically with respect to a first center line CL 1  and a second center line CL 2 . Hereinafter, the first center line CL 1  may be referred to as a virtual line that passes through the rotational center Or of the roller  134  and the proximate point P 1 , and the second center line CL 2  may be referred to as a virtual line that passes through the rotational center Or of the roller  134  and is orthogonal to the first center line CL 1 . 
     For example, based on the compression proceeding direction (rotational direction of the roller), the curved portion  1331   c  may include a first curved portion  1331   c   1  which is from the proximal portion (more precisely, the proximate point)  1331   a  to the distal portion (more precisely, the inflection point)  1331   b , a second curved portion  1331   c   2  which is from the distal portion  1331   b  to the first center line CL 1 , a third curved portion  1331   c   3  which is from the first center line CL 1  to the second center line CL 2 , and a fourth curved portion  1331   c   4  which is from the second center line CL 2  to the proximal portion, that is, the first center line,  1331   a.    
     The first curved portion  1331   a   1  may have the largest aspect ratio. Accordingly, an inflection point between the first curved portion  1331   c   1  and the second curved portion  1331   c   2 , which is the inflection point P 2 , may have a larger curvature change than an inflection point between the second curved portion  1331   c   2  and the third curved portion  1331   c   3 , an inflection point between the third curved portion  1331   c   3  and the fourth curved portion  1331   c   4 , and an inflection point between the fourth curved portion  1331   c   4  and the first curved portion  1331   c   1 . Therefore, as described above, the largest inflection point P 2  may be formed between the first curved portion  1331   c   1  and the second curved portion  1331   c   2 , namely, at the distal portion  1331   b.    
     Referring to  FIGS. 1 to 4 , the roller  134  may be rotatably disposed in the compression space V of the cylinder  133 , and the plurality of vanes  1351 ,  1352 , and  1353  described hereinafter may be inserted into the roller  134  at predetermined intervals in the circumferential direction. The compression space V may be divided into a plurality of compression chambers as many as the number of vanes  1351 ,  1352 , and  1353 . This embodiment describes an example in which three vanes  1351 ,  1352 , and  1353  are provided and the compression space V is divided into three compression chambers. 
     The outer circumneutral surface  1341  of the roller  134  according to this embodiment may have a circular shape, and the rotational shaft  123  may be coupled to the rotational center Or of the roller  134 . Accordingly, the rotational center Or of the roller  134  is located on a same axis as an axial center (no reference numeral) of the rotational shaft  123 , and the roller  134  rotates concentrically with the rotational shaft  123 . 
     However, as described above, as the inner circumferential surface  1331  of the cylinder  133  is formed in the asymmetric elliptical shape biased in a specific direction, the rotational center Or of the roller  134  may be disposed eccentric with respect to a geometrical center of an inner space of the cylinder  133 , that is, the compression space, namely, an outer diameter center (a center of an outer diameter) Oc of the cylinder  133 . Accordingly, one side of the outer circumferential surface  1341  of the roller  134  is almost in contact with the inner circumferential surface  1331  of the cylinder  133 , more precisely, the proximal portion  1331   a  to thereby form the proximate point P 1 . 
     The proximate point P 1  may be defined in the proximal portion  1331   a  as described above. Accordingly, the first center line CL 1  passing through the proximate point P 1  may correspond to a minor axis of an elliptic curve defining the inner circumferential surface  1331  of the cylinder  133 . 
     A plurality of vane slots  1342   a ,  1342   b , and  1342   c  may be defined in the outer circumferential surface  1341  of the roller  134  along the circumneutral direction at appropriate locations, and the plurality of vanes  1351 ,  1352 , and  1353  to be described hereinafter may be slidably inserted into the plurality of vane slots  1342   a ,  1342   b , and  1342   c , respectively. 
     The plurality of vane slots  1342   a ,  1342   b , and  1342   c  may be defined as a first vane slot  1342   a , a second vane slot  1342   b , and a third vane slot  1342   c  along the compression proceeding direction (rotational direction of the roller), and the first vane slot  1342   a , the second vane slot  1342   b , and the third vane slot  1342   c  may be identical. Each of the plurality of vane slots  1342   a ,  1342   b , and  1342   c  may be inclined by a predetermined angle with respect to the radial direction to thereby secure sufficient lengths for the vanes  1351 ,  1352 , and  1353 . 
     As the inner circumferential surface  1331  of the cylinder  133  is formed in the asymmetric elliptical shape, separation of the vanes  1351 ,  1352 , and  1353  from the respective vane slots  1342   a ,  1342   b , and  1342   c  may be suppressed even when a distance between the outer circumferential surface  1341  of the roller  134  and the inner circumferential surface  1331  of the cylinder  133  increases, thereby increasing a degree of design freedom for the inner circumferential surface  1331  of the cylinder  133 . 
     A direction in which the vanes  1351 ,  1352  and  1353  are tilted may be an opposite direction to the rotational direction of the roller  134 . That is, front surface of the vanes  1351 ,  1352 , and  1353  in contact with the inner circumferential surface  1331  of the cylinder  133  may be tilted in the rotational direction of the roller  134 , which allows a compression start angle to be formed ahead in the rotational direction of the roller  134  so that compression may start quickly. 
     Back pressure chambers  1343   a ,  1343   b , and  1343   c  may be formed at inner ends of the vane slots  1342   a ,  1342   b , and  1342   c , respectively, in a communicating manner. Oil (or refrigerant) with the discharge pressure or intermediate pressure may be accommodated in the back pressure chambers  1343   a ,  1343   b , and  1343   c  to introduce the oil at or to rear sides of the vanes  1351 ,  1352 , and  1353 , namely, vane rear end portions  1351   c ,  1352   c , and  1353   c , such that each of the vanes  1351 ,  1352 , and  1353  may be pushed toward the inner circumferential surface  1331  of the cylinder  133  by pressure of the oil (or refrigerant) filled in the back pressure chambers  1343   a ,  1343   b , and  1343   c . For the sake of convenience, a direction toward the cylinder with respect to a motion direction of the vane will be referred to as a front side, and an opposite direction will be referred to as a rear side. 
     The back pressure chambers  1343   a ,  13343   b , and  1343   c  may be hermetically sealed by the main bearing  131  and the sub bearing  132 . The back pressure chambers  1343   a ,  1343   b , and  1343   c  may independently communicate with the back pressure pockets [( 1315   a ,  1315   b ) ( 1325   a ,  1325   b )], or the back pressure chambers  1343   a ,  13343   b , and  1343   c  may communicate to each other through the back pressure pockets [( 1315   a ,  1315   b ) ( 1325   a ,  1325   b )]. 
     Referring to  FIGS. 1 to 3 , the plurality of vanes  1351 ,  1352 , and  1353  according to this embodiment may be slidably inserted into the respective vane slots  1342   a ,  1342   b , and  1342   c . Accordingly, the plurality of vanes  1351 ,  1352 , and  1353  may have substantially a same shape as the vane slots  1342   a ,  1342   b , and  1342   c , respectively. 
     For example, when the plurality of vanes  1351 ,  1352 , and  1353  is referred to as a first vane  1351 , a second vane  1352 , and a third vane  1353  along the rotational direction of the roller  134 , the first vane  1351  may be inserted into the first vane slot  1342   a , the second vane  1352  may be inserted into the second vane slot  1342   b , and the third vane  1353  may be inserted into the third vane slot  1342   c . The plurality of vanes  1351 ,  1352 , and  1353  may have substantially the same shape. More specifically, the plurality of vanes  1351 ,  1352 , and  1353  may include vane bodies  1351   a ,  1352   a  and  1353   a , vane front end portions (or front surfaces)  1351   b ,  1352   b  and  1353   b , and vane rear end portions (or rear surfaces)  1351   c ,  1352   c  and  1353   c , respectively. The vane front end portions  1351   b ,  1352   b , and  1353   b  may be understood as surfaces in contact with the inner circumferential surface  1331  of the cylinder  133 , and the vane rear end portions  1351   c ,  1352   c , and  1353   c  may be understood as surfaces facing the back pressure chambers  1343   a ,  1343   b , and  1343   c.    
     Each of the vane bodies  1351   a ,  1352   a , and  1353   a  may be formed in a substantially cuboid shape. Accordingly, the vane bodies  1351   a ,  1352   a , and  1353   a  may smoothly slide along lengthwise (or longitudinal) directions of the vane slots  1342   a ,  1342   b , and  1342   c , respectively. 
     The vane front end portions  1351   b ,  1352   b , and  1353   b  may be curved to be in line contact with the inner circumferential surface  1331  of the cylinder  133 . The vane rear end portions  1351   c ,  1352   c , and  1353   c  may be flat to be inserted into the back pressure chambers  1342   a ,  1342   b ,  1342   c  to thereby evenly receive a back pressure. 
     The vane front end portions  1351   b ,  1352   b , and  1353   b  may be formed by curvedly chamfering an edge on a downstream side located opposite to the rotational direction of the roller  134  of both edges in the circumferential direction. However, in some cases, both edges of each of the vane front end portions  1351   b ,  1352   b , and  1353   b  may be curvedly chamfered to form a semicircle, or formed in a substantially right angle without being chamfered. 
     In addition, the vane rear end portions  1351   c ,  1352   c , and  1353   c  may be formed flat to be orthogonal to lengthwise directions of the vanes  1351 ,  1352 , and  1353 , respectively. However, as in this embodiment, one edge of each of the vane rear end portions  1351   c ,  1352   c , and  1353   c  may be chamfered to have an inclined surface or a stepped surface. This will be described hereinafter. 
     In the vane rotary compressor having the hybrid cylinder, when power is applied to the drive motor  120 , the rotor  122  of the drive motor  120  and the rotational shaft  123  coupled to the rotor  122  rotate together, causing the roller  134  coupled to the rotational shaft  123  or integrally formed therewith to rotate together with the rotational shaft  123 . Then, the vanes  1351 ,  1352 , and  1353  are drawn (or pulled) out from or inserted into the respective vane slots  1342   a ,  1342   b , and  1342   c  by a centrifugal force generated when the roller  134  rotates and back pressures of the back pressure chambers  1343   a ,  1343   b , and  1343   c  provided at the rear side of the vanes  1351 ,  1352 , and  1353 . Accordingly, the vane front end portions  1351   b ,  1352   b , and  1353   b  are brought into contact with the inner circumferential surface  1331  of the cylinder  133 . 
     The compression space V of the cylinder  133  is divided by the plurality of vanes  1351 ,  1352 , and  1353  into the plurality of compression chambers (including a suction chamber or a discharge chamber) V 1 , V 2 , and V 3  as many as the number of vanes  1351 ,  1352 , and  1353 . A volume of each compression chamber V 1 , V 2 , and V 3  changes according to a shape of the inner circumferential surface  1331  of the cylinder  133  and eccentricity of the roller  134  while moving in response to rotation of the roller  134 . Refrigerant introduced into each of the compression chambers V 1 , V 2 , and V 3  flows along the roller  134  and the vanes  1351 ,  1352 , and  1353 , is compressed, and is then discharged into the inner space of the casing  110 . Such series of processes are repeated. 
     At this time, the plurality of vanes  1351 ,  1352 , and  1353  are drawn out from the vane slots  1342   a ,  1342   b , and  1342   c  of the roller  134 , respectively, and the vane front end portions  1351   b ,  1352   b , and  1353   b  defining the front surfaces of the respective vanes  1351 ,  1352 , and  1353  are brought into contact with the inner circumferential surface  1331  of the cylinder  133 . However, as the vanes  1351 ,  1352 , and  1353  are supported by unstable oil pressures of the back pressure chambers  1343   a  and  1343   b , and  1343   c , abnormal noise in a specific band is generated in a specific area of the inner circumferential surface  1331  of the cylinder  133 . 
     When the inner circumferential surface of the cylinder  133  is formed in the asymmetric elliptical shape biased in a specific direction, the largest inflection point (the inflection point P 2 ) is formed at the distal portion  1331   b  which is farthest away from the rotational center Or of the roller  134 , and the vane front end portions  1351   b ,  1352   b , and  1353   b  passing through the inflection point P 2  sequentially collide with the inner circumferential surface  1331  of the cylinder  133  to thereby periodically generate a strong impulse sound. Due to the periodicity of the impulse sound, noise in a specific (frequency) band increases to thereby increase noise of the compressor. By appropriately adjusting intervals (or distances) of the vane slots or the vanes respectively inserted into the vane slots as in this embodiment, the periodicity of the impulse sound may be reduced. As a result, noise of the compressor may be reduced. 
       FIG. 5  is a schematic view illustrating intervals between vane slots according to an embodiment.  FIG. 6  is a graph showing comparison of compressor efficiency according to maximum variable angles in embodiment of  FIG. 5 . 
     Referring to  FIG. 5 , the plurality of vane slots  1342   a ,  1342   b , and  1342   c  according to this embodiment may be inclined with respect to the radial direction as described above. The plurality of vane slots  1342   a ,  1342   b , and  1342   c  may be formed such that at least a portion (one or two) of angles θ 1 , θ 2 , and θ 3  respectively formed between two adjacent virtual lines, of virtual lines CL 41 , CL 42 , and CL 43  respectively connecting entry points P 31 , P 32 , and P 33  of the respective vane slots  1342   a ,  1342   b , and  1342   c  located on the outer circumferential surface and the rotational center Or of the roller  134 , is different. Accordingly, the plurality of vane slots  1342   a ,  1342   b , and  1342   c  adjacent to one another may be disposed at unequal intervals. 
     For example, when three vane slots  1342   a ,  1342   b , and  1342   c  are formed along the circumferential direction, the angles θ 1 , θ 2 , and θ 3  respectively formed between two adjacent vane slots may vary. For the sake of convenience, an angle between the first vane slot  1342   a  and the second vane slot  1342   b  will be referred to as a first angle θ 1 , an angle between the second vane slot  1342   b  and the third vane slot  1342   c  will be referred to as a second angle θ 2 , and an angle between the third vane slot  1342   c  and the first vane slot  1342   a  will be referred to as a third angle θ 3 . 
     The first angle θ 1  may be greater or less than the second angle θ 2 , and greater or less than the third angle θ 3 . The second angle θ 2  may be greater or less than the third angle θ 3 . 
     The first angle θ 1 , the second angle θ 2 , and the third angle θ 3  may be different from one another. However, in some cases, one angle may be different from the rest. This embodiment illustrates an example in which the first angle θ 1 , the second angle θ 2 , and the third angle θ 3  are different from each other. 
     The number of the angles (first angle θ 1 , second angle θ 2 , third angle θ 1 ) may be determined by the number of vane slots ( 1342   a ,  1342   b ,  1342   c ), namely, the number of vanes ( 1351 ,  1352 ,  1353 ) respectively inserted into the vane slots ( 1342   a ,  1342   b ,  1342   c ). 
     For example, if three vane slots  1342   a ,  1342   b , and  1342   c  are provided, three vanes  1351 ,  1352 , and  1353  may be provided, and the three vanes  1351 ,  1352 , and  1353  may be deposed at unequal intervals in the circumferential direction. Accordingly, vanes adjacent to each other pass through any one crank angle, for example, the inflection point P 2  at a different time interval. Then, the periodicity of impulse sound, due to collision with the inner circumferential surface  1331  of the cylinder  133  when the vanes  1351 ,  1352 , and  1353  pass through the inflection point P 2 , may be reduced, allowing noise in a specific band to be reduced. 
     The plurality of vane slots  1342   a ,  1342   b , and  1342   c  may be inclined with respect to the radial direction, disposed at the unequal intervals, and have longitudinal centers CL 31 , CL 32 , and CL 33  that intersect the virtual lines CL 41 , CL 42 , and CL 43 , respectively, at the same angle. 
     In other words, an inclination angle α 1  of the vane slot  1342   a , an inclination angle α 2  of the vane slot  1342   b , and an inclination angle α 3  of the vane slot  1342   c  may be equal to one another. Accordingly, the plurality of vane slots  1342   a ,  1342   b , and  1342   c  may be disposed at the unequal intervals, and the center of gravity of the roller including the vanes may be maintained almost nearly the same as the rotational center Or of the roller  134 . Thus, an eccentric load due to the unequally spaced vane slots may be suppressed. 
     However, the inclination angles α 1 , α 2 , and α 3  of the plurality of vane slots  1342   a ,  1342   b , and  1342   c  are not necessarily equal. For example, among the inclination angles α 1 , α 2 , and α 3  of the plurality of vane slots  1342   a ,  1342   b , and  1342   c , at least one of the inclination angles α 1 , α 2 , and α 3  may be different. However, even in this case, the center of gravity of the roller including the vanes should be maintained almost nearly the same as the rotational center Or of the roller  134  in order to suppress the eccentric load caused by the unequally spaced vane slots. 
     In terms of compressor efficiency, the plurality of vane slots  1342   a ,  1342   b , and  1342   c  may be formed such that an interval (angle) between two vane slots adjacent to each other in the circumferential direction is disposed within an appropriate range. For example, if the interval between two adjacent vane slots is too small, the effect of reducing the periodicity of impulse sound may be decreased, whereas if the interval between two adjacent vane slots is too large, a volume difference between chambers may be increased to thereby reduce compressor efficiency. Accordingly, an interval between two adjacent vanes, namely, each of the angles θ 1 , θ 2 , and θ 3  may be formed in a range that can minimize a decrease in compressor efficiency and reduce the periodicity of impulse sound, that is, a maximum variable angle is formed to satisfy a specific range. 
     In other words, the interval between two vane slots, namely, the angles θ 1 , θ 2 , and θ 3  between each of two adjacent vane slots may be defined by the following [Equation 1]. 
       θ i ′=θ i +Δθ×Sin( m×θ   i )  [Equation 1]
 
     where, θ i ′ denotes a rearrangement angle of vane slots, θ i  denotes an equal interval angle, Δθ denotes a maximum variable angle, and m denotes the order (or sequence) of vanes. The maximum variable angle (Δθ) may be defined as 2 to 10°. As can be seen from  FIG. 6 , the compressor efficiency may be the highest at 0° when the interval between the vane slots  1342   a ,  1342   b , and  1342   c  is 0°, and the compressor efficiency may decrease with an increase in the interval between the vane slots  1342   a ,  1342   b , and  1342   c . However, it can be seen that the compressor efficiency gradually decreases up to approximately 10°, and then drops rapidly after reaching 10°. Therefore, the maximum variable angle (Δθ) may be in the range of 2 to 10°. 
     When applying [Equation 1] to the embodiment of  FIG. 5 , and setting the maximum variable angle (Δθ) to 6°, the first angle may be approximately 125.2°, the second angle may be 114.8°, and the third angle may be 120.0°. When the intervals between the vanes (or vane slots)  1351 ,  1352 , and  1353  are different from each other, a time difference occurs between the vanes  1351 ,  1352 , and  1353  when passing through the inflection point P 2 . Then, the periodicity of impulse sound generated at the inflection point P 2  may be reduced to thereby reduce the compressor noise in overall. In particular, as noise in a specific band is reduced, the compressor noise may be further reduced. 
       FIG. 7  is a graph showing comparison between vane slots disposed at unequal intervals according to embodiments and vane slots disposed at equal intervals. Referring to  FIG. 7 , it can be seen that noise of a vane rotary compressor (dot hatching) in which unequally spaced vane slots  1342   a ,  1342   b , and  1342   c  according to embodiments are employed exhibits lower noise in overall than a vane rotary compressor (slash hatching) in which equally spaced vane slots are employed. 
     In particular, it can be seen that a sharp pure tone (impulse sound at the inflection point is significantly included) in the 3 to 4 kHz band, which is the main noise band range, was reduced by about 5 dB, and noise was reduced by about 2.5 dB in terms of the overall noise level below 10 kHz. This is a component evaluation for a flange sample with a thick compressor outer wall. Therefore, when applied to an actual compressor with a relatively thin outer wall, a greater effect of noise reduction may be expected. 
     Hereinafter, another embodiment of a vane will be described. 
     That is, in previous embodiment, the vane rear end portion defining the rear surface of the vane is formed as a flat surface orthogonal to the lengthwise direction of the vane. However, in some cases, a chamfer (or chamfered) portion may be formed at one edge of the vane rear end portion. 
       FIG. 8  is a perspective view of a vane according to another embodiment.  FIG. 9  is a planar view illustrating a state in which the vane of  FIG. 8  is inserted into a vane slot.  FIG. 10  is a planar view of a chamfer portion according to an embodiment. 
     Referring to  FIGS. 8 and 9 , vanes  1351 ,  1352 , and  1353  according to this embodiment may be formed similar to the vanes  1351 ,  1352 , and  1353  described in the previous embodiment. However, the vanes  1351 ,  1352 , and  1353  according to this embodiment may have chamfer portions  1351   d ,  1352   d , and  1353   d , respectively. Each of the chamfer portions  1351   d ,  1352   d , and  1353   d  may be formed on one edge at a side in the compression proceeding direction (rotational direction of the roller) of two edges of the respective vane rear end portions  1351   c ,  1352   c , and  1353   c.    
     The chamfer portions  1351   d ,  1352   d , and  1353   d  may be formed in an inclined manner, as shown in  FIG. 9 , or formed in a stepped manner although not shown. Accordingly, each of the vanes  1351 ,  1352 , and  1353  receives a plurality of components of force by oil (or refrigerant) accommodated in the back pressure chambers  1343   a ,  1343   b , and  1343   c . That is, the vanes  1351 ,  1352 , and  1353  not only receive a first pressure at the vane rear end portions  1351   c ,  1352   c , and  1353   c  in the lengthwise direction thereof, but also receive a second pressure at the chamfer portions  1351   d ,  1352   d , and  1353   d  in a direction intersecting the lengthwise direction. The second pressure acts in a direction opposite to a direction in which the vanes  1351 ,  1352 , and  1353  rotate. 
     Then, even when a side (or lateral) gap is generated between the vane ( 1351 ,  1352 ,  1353 ) and the vane slot ( 1342   a ,  1342   b ,  1342   c ) into which the vane is inserted, the vane ( 1351 ,  1352 ,  1353 ) may be supported by being pressed against an inner surface of the vane slot ( 1342   a ,  1342   b ,  1342   c ) by the second pressure. Accordingly, trembling or shaking of the vanes  1351 ,  1352 , and  1353  generated as the vanes  1351 ,  1352 , and  1353  are inserted into and pulled out (or enter and exit) from the respective vane slots  1342   a ,  1342   b , and  1342   c  may be suppressed to thereby reduce noise of the vanes  1351 ,  1352 , and  1353  caused by the shaking. As a result, noise of the compressor may be further reduced. 
     The chamfer portions  1351   d ,  1352   d , and  1353   d  may each have a cross-sectional area A 2  in a widthwise direction that is less than or equal to a cross-sectional area A 1  of each of the vane rear end portions  1351   c ,  1352   c , and  1353   c  in a widthwise direction. Alternatively, the cross-sectional area A 2  of each of the chamfer portions  1351   d ,  1352   d , and  1353   d  in the widthwise direction may be greater than or equal to the cross-sectional area A 1  of each of the vane rear end portions  1351   c ,  1352   c , and  1353   c  in the widthwise direction. The cross-sectional area A 2  of each of the chamfer portions  1351   d ,  1352   d , and  1353   d  in the widthwise direction may be a cross-sectional area excluding the cross-sectional area A 1  of each of the rear end portions  1351   c ,  1352   c , and  1353   c  in the widthwise direction of a cross-sectional area of each of the vane bodies  1351   a ,  1352   a , and  1353   a  in the widthwise direction. 
     The cross-sectional areas A 2  of the chamfer portions  1351   d ,  1352   d , and  1353   d  in the widthwise direction may be selectively determined according to dimensions of the vane rotary compressor or a type of refrigerant. For example, referring to  FIG. 9 , in the case of a compressor operating at a low speed, the cross-sectional area A 2  of the chamfer portion ( 1351   d ,  1352   d ,  1353   d ) in the widthwise direction may be less than or equal to the cross-sectional area A 1  of the vane rear end portion ( 1351   c ,  1352   c ,  1353   c ). That is, a centrifugal force applied to the vanes  1351 ,  1352 , and  1353  in the compressor operating at the low speed is reduced compared to a compressor operating at a high speed. Accordingly, it may be advantageous to reduce the second pressure acting in a direction that intersects the centrifugal force of each of the vanes  1351 ,  1352 , and  1353 . 
     The vanes  1351 ,  1352 , and  1353  according to this embodiment may be formed such that the cross-sectional areas A 2  of the chamfer portions  1351   d ,  1352   d , and  1353   d  are less than or equal to the cross-sectional areas A 1  of the vane rear end portions  1351   c ,  1352   c , and  1353   c . As the vane rear end portions  1351   c ,  1352   c , and  1353   c  of the vanes  1351 ,  1352 , and  1353  are formed larger, the first pressure is greatly applied even when the vanes  1351 ,  1352 , and  1353  receive a small centrifugal force due to low-speed rotation of the roller  134 . This may allow the vanes  1351 ,  1352 , and  1353  to be in close contact with the inner circumferential surface  1331  of the cylinder  133  to thereby effectively seal between compression chambers even during low-speed operation. As a result, shaking of the vanes may be reduced to thereby reduce the noise of the compressor. Further, compression loss may be reduced to thereby increase the efficiency of the compressor. 
     This may be equally applicable to a compressor using a high-pressure refrigerant. That is, when the high-pressure refrigerant is used, a pressure difference between compression chambers is greater than when a low-pressure refrigerant is used. Accordingly, a relatively high pressure may be required to allow the vanes  1351 ,  1352 , and  1353  to be in close contact with the cylinder  133  for suppressing leakage between the compression chambers. Therefore, even in this case, the cross-sectional areas A 2  of the chamfer portions  1351   d ,  1352   d , and  1353   d  may be greater than or equal to the cross-sectional areas A 1  of the vane rear end portions  1351   c ,  1352   c , and  1353   c , so as to allow the vanes  1351 ,  1352 , and  1353  to be in close contact with the cylinder  133  to thereby effectively reduce leakage between the compression chambers. As a result, shaking of the vanes  1351 ,  1352 , and  1353  may be reduced, compressor noise and compression loss may be reduced. This may lead to an increase in efficiency of the compressor. 
     On the other hand, referring to  FIG. 10 , in the case of a compressor operating at a high speed, a cross-sectional area A 2 ′ of each of chamfer portions  1351   d ,  1352   d , and  1353   d  in a widthwise direction may be greater than or equal to a cross-sectional area A 1 ′ of each of vane rear end portions  1351   c ,  1352   c , and  1353   c  in the widthwise direction. That is, during the high-speed operation, as the vanes  1351 ,  1352 , and  1353  receive a strong centrifugal force, the cross-sectional areas of the chamfer portions  1351   d ,  1352   d , and  1353   d  in the widthwise direction may be greater than or equal to the cross-sectional areas of the vane rear end portions  1351   c ,  1352   c , and  1353   c  in the widthwise direction so that the second pressure acting in a direction intersecting the centrifugal force may be widely applied as possible. This may result in suppressing excessive contact of the vanes  1351 ,  1352 , and  1353  with the cylinder  133  to thereby reduce noise of the compressor as well as motor loss. 
     This may be equally applicable to a compressor using a low-pressure refrigerant. That is, when the low-pressure refrigerant is used, a pressure difference between compression chambers is less (smaller) than when a high-pressure refrigerant is used. Even when the vanes  1351 ,  1352 , and  1353  are brought into close contact with the cylinder  133  by a relatively low pressure, leakage between the compression chambers may be suppressed. Accordingly, the cross-sectional area A 2 ′ of each of the chamfer portions  1351   d ,  1352   d , and  1353   d  may be greater than or equal to the cross-sectional area A 1 ′ of each of the vane rear end portions  1351   c ,  1352   c , and  1353   c  to reduce noise of the compressor. Thus, shaking of the vanes  1351 ,  1352 , and  1353  may be reduced to thereby reduce noise of the compressor. Further, motor loss may be reduced to thereby increase the efficiency of the compressor. 
     Although not illustrated in the drawings, the chamfer portion formed at the vane rear end portion may be equally applied to an example in which one vane is provided. Even in this case, as the basic configuration and effect of the chamfer portion is the same as those of the embodiment having the plurality of vanes, detailed description thereof has been omitted. 
     The unequally spaced vane slots according to this embodiment may also be applied to a cylinder having an inner circumferential surface with a symmetric elliptical shape. 
       FIG. 11  is a planar view illustrating an example in which unequally spaced vane slots are employed in cylinder having a symmetric elliptical shape according to an embodiment. Referring to  FIG. 11 , inner circumferential surface  1331  of cylinder  133  according to this embodiment may be formed such that a plurality of ellipses are symmetrical to each other based on one center line, for example, a second center line CL 2 . For example, the inner circumferential surface  1331  of the cylinder  133  may extend lengthwise to one side, and the extended portion may be symmetrical with respect to the second center line CL 2 . 
     Even in this case, rotational center Or of roller  134  may be located on a same axis as an axial center (no reference numeral) of rotational shaft  123 , but may be eccentric with respect to outer diameter center Oc of the cylinder  133 . Like the previous embodiment, the inner circumferential surface  1331  of the cylinder  133  of this embodiment may have proximal portion  1331   a , distal portion  1331   b  and curved portion  1331   c , and proximate point P 1  and inflection point P 2  may be formed at the proximal portion  1331   a  and the distal portion  1331   b , respectively. 
     Even when the inner circumferential surface  1331  of the cylinder  133  is formed in the symmetric elliptical shape, configurations and effects of components except for the cylinder  133 , such as vane slots  1342   a ,  1342   b , and  1342   c  of the roller  134 , and vanes  1351 ,  1352 , and  1353  are the same as those of the previous embodiment. Therefore, repetitive description thereof has been omitted. 
     Unequally spaced vane slots according to this embodiment may also be applied to a case in which the inner circumferential surface of the cylinder is formed in a circular shape having a constant curvature. 
       FIG. 12  is a planar view illustrating an example in which unequally spaced vane slots are employed in a cylinder having a circular shape according to an embodiment. Referring to  FIG. 12 , cylinder  133  according to this embodiment may have inner circumferential surface  1331  with a circular shape. For example, the inner circumferential surface  1331  of the cylinder  133  may have a constant (or same) curvature in the circumferential direction. 
     Even in this case, configurations and effects of components except for the cylinder  133 , such as vane slots  1342   a ,  1342   b , and  1342   c  of roller  134  and vanes  1351 ,  1352 , and  1353  are similar to those of the previous embodiments. Therefore, repetitive description has been omitted. 
     When the inner circumferential surface  1331  of the cylinder  133  is formed in the circular shape as in this embodiment, an inflection point is not formed on the inner circumneutral surface  1331  of the cylinder  133 . However, even in this case, the vanes  1351 ,  1352 , and  1353  are in close contact with the inner circumferential surface  1331  of the cylinder  133  by being pressed by oil (or refrigerant) accommodated in back pressure chambers  1343   a ,  1343   b , and  1343   c , and pressures of the back pressure chambers  1343   a ,  1343   b , and  1343   c  that press the vanes  1351 ,  1352 , and  1353  toward the inner circumferential surface  1331  of the cylinder  133  are not uniform. As a result, the vanes  1351 ,  1352 , and  1353  may generate noise while slightly trembling with respect to the cylinder  133 . This phenomenon may regularly occur at a specific crank angle, causing periodicity of noise. 
     However, as the vane slots  1342   a ,  1342   b , and  1342   c  according to this embodiment are formed at unequal intervals, the periodicity of noise between the cylinder  133  and the vanes  1351 ,  1352 , and  1353  slidably inserted into the respective vane slots  1342   a ,  1342   b , and  1342  may be reduced. Accordingly, the overall noise may be reduced and the effect of noise reduction in a specific band may be improved. 
     Hereinafter, a roller according to another embodiment will be described. That is, in the examples described above, the vane slots defined in the roller are formed in the inclined manner. However, in some cases, a plurality of vane slots may be formed in the radial direction. Even in this case, intervals between the vane slots, namely, intervals between the vanes may be unequal. 
       FIG. 13  is a planer view of a roller in which vane slots according to an embodiment are employed. Referring to  FIG. 13 , roller  134  according to this embodiment may have a circular shape to be coupled to rotational shaft  123  or integrally formed with the rotational shaft  123 . The roller  134  may be provided with a plurality of vane slots  1342   a ,  1342   b , and  1342   c  formed along the circumferential direction. 
     Vanes  1351 ,  1352 , and  1353  are slidably inserted the vane slots  1342   a ,  1342   b , and  1342   c , respectively. The vanes  1351 ,  1352 , and  1353  may be drawn out of the respective vane slots  1342   a ,  1342   b , and  1342   c  to be brought into close contact with inner circumferential surface  1331  of cylinder  133 . The basic structure and operating effects of the vane rotary compressor including the roller  134  and the vanes  1351 ,  1352 , and  1353  are substantially the same as those of the previous embodiments, and thus, repetitive description thereof has been omitted. 
     However, in this embodiment, the plurality of vane slots  1342   a ,  1342   b , and  1342   c  may be formed in the radial direction based on rotational center Or of the roller  134 . That is, in the previous embodiments, the plurality of vane slots  1342   a ,  1342   b , and  1342   c  are inclined with respect to the radial direction. In this embodiment, however, the plurality of vane slots  1342   a ,  1342   b  and  1342   c  may be disposed in the radial direction with respect to the rotational center Or of the roller  134 . 
     The plurality of vane slots  1342   a ,  1342   b , and  1342   c  may be disposed at predetermined intervals in the circumferential direction, and the intervals between the vane slots  1342   a ,  1342   b , and  1342   c , namely, the intervals between the vanes  1351 ,  1352 , and  1353  may be unequal as in the embodiments described above. The intervals between the vane slots  1342   a ,  1342   b , and  1342   c  or the vanes  1351 ,  1352 , and  1353  may be determined according to [Equation 1] described above. Accordingly, the periodicity of noise may be reduced to thereby lower the overall noise. Further, the effect of noise reduction in a specific band may be improved. 
     Although not illustrated in the drawings, the cylinder  133  may be a symmetrical ellipse or a true circle having an inner circumferential surface with a constant curvature in addition to the asymmetrical ellipse. 
     Embodiments disclosed herein provide a rotary compressor that can reduce noise of the compressor. Embodiments disclosed herein also provide a rotary compressor that can reduce noise of the compressor by reducing periodicity of the noise. 
     Embodiments disclosed herein further provide a rotary compressor that can reduce periodicity of noise by allowing vanes to pass through a specific crank angle at irregular (or different) time intervals. Embodiments disclosed herein furthermore provide a rotary compressor that can reduce shaking or trembling noise of a vane slidably inserted into a vane slot of a roller. 
     Embodiments disclosed herein provide a rotary compressor that can disperse pressure directed toward a cylinder so as to allow a vane to be in close contact with a side surface of a vane slot. Embodiments disclosed herein also provide a rotary compressor that can increase the compression efficiency and the effect of noise reduction by adjusting force that causes a vane to come in close contact with a side surface of a vane slot according to the condition of a compressor. 
     Embodiments disclosed herein provide a rotary compressor that may include a plurality of vane slots formed along an outer circumferential surface of a roller, and a plurality of vanes slidably inserted into the plurality of vane slots, respectively. Embodiments disclosed herein may include one or more of the following. For example, the plurality of vanes may be formed such that intervals between each of two adjacent vanes are different from each other. Accordingly, compressor noise may be reduced to thereby reduce periodicity of the noise. 
     Embodiments disclosed herein provide a rotary compressor that may include a vane slot formed along an outer circumferential surface of a roller, and a vane slidably inserted into the vane slot. Embodiments disclosed herein may include one or more of the following. For example, a chamfer portion may be formed at one edge of the vane to be inclined or stepped with respect to a lengthwise direction of the vane. With this configuration, a force that causes the vane to come in contact with a side surface of the vane slot may be generated to thereby reduce shaking of the vane. As a result, noise of the compressor may be reduced. 
     A cylinder may have an inner circumferential surface with an annular shape to form a compression space. A roller may be rotatably inserted into the compression space of the cylinder, and a plurality of vane slots may be disposed at predetermined intervals along an outer circumferential surface of the roller. A plurality of vanes may be slidably inserted into the plurality of vane slots, respectively, and the plurality of vanes may divide the compression space into a plurality of compression chambers while rotating together with the roller. At least one of the plurality of vane slots may be unequally spaced in a circumferential direction. Accordingly, periodicity of the vanes passing through a specific crank angle becomes non-uniform, thereby reducing periodicity of noise. As a result, a sharp pure tone at a specific frequency may be alleviated to thereby reduce noise of the compressor. 
     The outer circumferential surface of the roller may have a circular shape with a constant diameter in the circumferential direction, and the plurality of vane slots may be formed such that at least one of angles between two adjacent virtual lines, of virtual lines respectively connecting an entry point thereof in contact with the outer circumferential surface of the roller and a rotational center of the roller, is different. Accordingly, the plurality of vane slots may be disposed at unequal intervals along the circumferential direction. 
     The plurality of vane slots may be formed such that longitudinal center lines thereof intersect the virtual lines, respectively, at a predetermined inclination angle. Thus, periodicity of noise may be reduced even when the plurality of vane slots are inclined with respect to a radial direction. 
     The plurality of vane slots may have a same inclination angle. Accordingly, the vane slots may be disposed at equal intervals while being inclined with respect to the radial direction, allowing an eccentric load of the roller including the vanes to be suppressed. 
     At least one of the plurality of vane slots may have a different inclination angle. Accordingly, the vane slots may be disposed at unequal intervals while being inclined with respect to the radial direction. 
     The plurality of vane slots may be formed such that longitudinal center lines thereof are formed in a radial direction with respect to a rotational center of the roller. Accordingly, the vane slots may be formed in the radial direction and disposed at unequal intervals. 
     The outer circumferential surface of the roller may have a circular shape with a constant diameter in the circumferential direction, and angles between virtual lines respectively passing through entry points of the plurality of vane slots in contact with the outer circumferential surface of the roller and a rotational center of the roller may satisfy the following formula: θi′=θi+Δθ×Sin (m×θi), where θi denotes an equal interval angle, θi′ denotes a rearrangement angle of the vane slots, Δθ denotes a maximum variable angle, and m denotes the order of the vanes. Thus, the plurality of vane slots may be disposed at unequal intervals, and the intervals may be optimized. 
     The maximum variable angle Δθ in the formula may be 2 to 10°. Accordingly, the plurality of vane slots may be disposed at unequal intervals to thereby reduce compressor noise while maintaining compression efficiency. 
     Each of the plurality of vanes may include a vane front end portion in contact with the inner circumferential surface of the cylinder, and a vane rear end portion disposed at an end surface opposite to the vane front end portion to receive pressure, and a chamfer portion may be formed at the vane rear end portion. This allows the vanes to be brought into close contact with side surfaces of the vane slots to thereby reduce shaking of the vanes. As a result, noise of the compressor may be reduced. 
     The chamfer portion may be formed at an edge disposed in a rotational direction of the roller in an inclined or stepped manner. By using pressure generated at rear sides of the vanes, the vanes may be brought into contact with side surfaces of the vane slots in an easier manner. 
     A cross-sectional area of the chamfer portion in a widthwise direction may be less than or equal to a cross-sectional area of the vane rear end portion in the widthwise direction. Accordingly, shaking of the vanes during low-speed operation or when using high-pressure refrigerant may be reduced. As a result, noise of the compressor may be reduced. In addition, adhesion to the cylinder may be increased to thereby reduce compression loss. 
     A cross-sectional area of the chamfer portion in a widthwise direction may be greater than or equal to a cross-sectional area of the vane rear end portion in the widthwise direction. Accordingly, shaking of the vanes during high-speed operation or when using low-pressure refrigerant may be reduced. As a result, noise of the compressor noise may be reduced. In addition, adhesion to the cylinder may be reduced to thereby reduce friction loss. 
     The inner circumferential surface of the cylinder may have an asymmetric elliptical shape. With this configuration, even when the inner circumferential surface of the cylinder is asymmetric, periodicity of noise may be reduced to thereby lower noise of the compressor. 
     The inner circumferential surface of the cylinder may have a symmetric elliptical shape. With this configuration, even when the inner circumferential surface of the cylinder is symmetric, periodicity of noise may be reduced to thereby lower noise of the compressor. 
     The inner circumferential surface of the cylinder may have a circular shape with a constant curvature. With this configuration, even when the inner circumferential surface of the cylinder has the circular shape, periodicity of noise may be reduced to thereby lower noise of the compressor. 
     Embodiments disclosed herein provide a rotary compressor that may include a cylinder having an inner circumferential surface with an annular shape to form a compression space, a roller rotatably inserted into the compression space of the cylinder and provided with one or more vane slots disposed at a predetermined interval along a circumferential surface thereof, and a vane slidably inserted into the vane slot and drawn out from the vane slot to divide the compression space into a plurality of compression chambers while rotating together with the roller. The vane may include a vane front end portion in contact with the inner circumferential surface of the cylinder, and a vane rear end portion disposed at an end surface opposite to the vane front end portion to receive pressure. A chamfer portion for pressing the vane toward an inner surface of the vane slot may be formed on an edge, of edges of the vane rear end portion in a circumferential direction, disposed in a rotational direction of the roller. This may allow the vane to be in close contact with a side surface of the vane slot. As a result, shaking of the vane may be reduced to thereby reduce noise of the compressor. 
     Although not illustrated in the drawings, embodiments disclosed herein are not necessarily limited to three vane slots. 
     It will be understood that when an element or layer is referred to as being “on” another element or layer, the element or layer can be directly on another element or layer or intervening elements or layers. In contrast, when an element is referred to as being “directly on” another element or layer, there are no intervening elements or layers present. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     It will be understood that, although the terms first, second, third, etc., may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another region, layer or section. Thus, a first element, component, region, layer or section could be termed a second element, component, region, layer or section without departing from the teachings of the present invention. 
     Spatially relative terms, such as “lower”, “upper” and the like, may be used herein for ease of description to describe the relationship of one element or feature to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation, in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “lower” relative to other elements or features would then be oriented “upper” relative to the other elements or features. Thus, the exemplary term “lower” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     Embodiments are described herein with reference to cross-section illustrations that are schematic illustrations of idealized embodiments (and intermediate structures). As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     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. 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.