Patent Publication Number: US-11378079-B2

Title: Rotary vane compressor with a step in the bearing adjacent the rail groove

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims priority under 35 U.S.C. § 119 to Korean Application No. 10-2020-0037805, filed in Korea on Mar. 27, 2020, whose entire disclosure(s) is/are hereby incorporated by reference. 
     BACKGROUND 
     1. Field 
     A rotary compressor, and more particularly, a vane rotary compressor in which a compression chamber is formed while a vane protrudes on a rotating rotor to be in contact with an inner circumferential surface of a cylinder is disclosed herein. 
     2. Background 
     In general, a compressor refers to a device that receives power from a power generating device, such as a motor or a turbine, to compress a working fluid, such as air or refrigerant. More specifically, the compressor is widely applied to home appliances, in particular, a steam compression type refrigeration cycle (hereinafter, referred to as a ‘refrigeration cycle’). 
     The compressor may be classified into a reciprocating compressor, a rotary compressor, and a scroll compressor according to a method of compressing a refrigerant. The rotary compressor may be classified into a method in which a vane is slidably inserted into a cylinder to be in contact with a roller and a method in which the vane is slidably inserted into the roller to be in contact with the cylinder. In general the former is referred to as a “rotary compressor”, while the latter is referred to as a “vane rotary compressor”. 
     In the rotary compressor, the vane inserted into the cylinder is drawn out toward the roller by an elastic force or back pressure to be in contact with an outer circumferential surface of the roller. In contrast, in the vane rotary compressor, the vane inserted into the roller is drawn out by a centrifugal force and the back pressure while rotating together with the roller to be in contact with an inner circumferential surface of the cylinder. 
     In the rotary compressor, compression chambers as many as the vanes per rotation of the roller are independently formed and respective compression chambers simultaneously perform suction, compression, and discharge strokes. In contrast, in the vane rotary compressor, compression chambers as many as the vanes per rotation of the roller are continuously formed and respective compression chambers sequentially perform suction, compression, and discharge strokes. 
     In the vane rotary compressor, in general, as a front end surface of the vane slides while being in contact with the inner circumferential surface of the cylinder while a plurality of vanes rotates together, friction loss increases compared with a general rotary compressor. Further, in the vane rotary compressor, the inner circumferential surface of the cylinder has a circular shape, but in recent years, a vane rotary compressor (hereinafter, referred to as a “hybrid rotary compressor”) has been introduced, which includes a so-called “hybrid cylinder” in which the inner circumferential surface of the cylinder has an oval shape or a shape in which an ellipse and a circle are combined to reduce friction loss and increase compression efficiency. 
     In the hybrid rotary compressor, a position where a contact point for dividing a region where the refrigerant enters and the compression stroke starts due to a characteristic in which the inner circumferential surface of the cylinder has an asymmetric shape and a region where the discharge stroke of the compressed refrigerant is performed is formed exerts a significant influence on efficiency of the compressor. In particular, in a structure in which an inlet and an outlet are sequentially formed adjacent to each other in a direction opposite to a rotational direction of the roller in order to achieve a high compression ratio by increasing a compression path as much as possible, the position of the contact point exerts a large influence on the efficiency of the compressor. However, compression efficiency is reduced by contact of the vane and the cylinder and a reliability problem occurs due to abrasion. 
    
    
     
       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 rotary compressor according to an embodiment; 
         FIG. 2  is a cross-sectional view, taken along line II-II′ of  FIG. 1 ; 
         FIGS. 3 and 4  are exploded perspective views of a rotary compressor according to an embodiment; 
         FIG. 5  is a longitudinal cross-sectional view of some components of a rotary compressor according to an embodiment; 
         FIG. 6  is a plan view of some components of a rotary compressor according to an embodiment; 
         FIG. 7  is a bottom view of some components of a rotary compressor according to an embodiment; 
         FIGS. 8 to 10  are operation diagrams of a rotary compressor according to an embodiment; and 
         FIG. 11  is a graph showing a load applied to a pin with rotation of a rotary compressor according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, embodiments will be described with reference to the accompanying drawings. The same or similar components are denoted by the same or similar reference numerals, and repetitive description thereof has been omitted. 
     In describing embodiments, it should be understood that, when it is described that a component is “connected to” or “accesses” another component, the component may be directly connected to or access the other component or a third component may be present therebetween. Further, in describing an embodiment, a detailed description of related known technologies will be omitted if it is determined that the description makes the gist of the embodiment unclear. Further, it is to be understood that the accompanying drawings are just used for easily understanding embodiments and a technical spirit is not limited by the accompanying drawings and all changes, equivalents, or substitutes included in the spirit and the technical scope are included. Meanwhile, the term “disclosure” may be replaced with terms such as document, specification, description, etc. 
       FIG. 1  is a longitudinal cross-sectional view of a rotary compressor according to an embodiment.  FIG. 2  is a cross-sectional view, taken along line II-II″ of  FIG. 1 .  FIGS. 3 and 4  are exploded perspective views of a rotary compressor according to an embodiment.  FIG. 5  is a longitudinal cross-sectional view of some components of a rotary compressor according to an embodiment.  FIG. 6  is a plan view of some components of a rotary compressor according to an embodiment.  FIG. 7  is a bottom view of some components of a rotary compressor according to an embodiment.  FIGS. 8 to 10  are operation diagrams of a rotary compressor according to an embodiment.  FIG. 11  is a graph showing a load applied to a pin with rotation of a rotary compressor according to an embodiment. 
     Referring to  FIGS. 1 to 11 , a rotary compressor  100  according to an embodiment may include a casing  110 , a drive motor  120 , and compression units  131 ,  132 ,  133 , and  134 , but other additional components are not excluded. The casing  110  may form an exterior of the rotary compressor  100 . The casing  110  may be formed in a cylindrical shape. The casing  110  may be divided into a vertical type or a horizontal type according to an installation mode of the rotary compressor  100 . The vertical type may be a structure in which the drive motor  120  and the compression units  131 ,  132 ,  133 , and  134  are disposed on or at both upper and lower sides in an axial direction and the horizontal type may be a structure in which the drive motor  120  and the compression units  131 ,  132 ,  133 , and  134  are disposed on or at both left and right or lateral sides. The drive motor  120 , a rotational shaft  123 , and the compression units  131 ,  132 ,  133 , and  134  may be disposed in the casing  110 . The casing  110  may include an upper shell  110   a , an intermediate shell  110   b , and a lower shell  110   c . The upper shell  110   a , the intermediate shell  110   b , and the lower shell  110   c  may seal an inner space S. 
     The drive motor  120  may be disposed in the casing  110 . The drive motor  120  may be disposed inside the casing  110 . The compression units  131 ,  132 ,  133 , and  134  mechanically connected by the rotational shaft  123  may be installed on or at one side of the drive motor  120 . 
     The drive motor  120  may provide power for compressing a refrigerant. The drive motor  120  may include a stator  121 , a rotor  122 , and the rotational shaft  123 . 
     The stator  121  may be disposed in the casing  110 . The stator  121  may be disposed inside the casing  110 . The stator  121  may be fixed inside the casing  110 . The stator  121  may be mounted on an inner circumferential surface of the cylindrical casing  110  by a method, such as shrink fit, for example. For example, the stator  121  may be fixedly installed on an inner circumferential surface of the intermediate shell  110   b.    
     The rotor  122  may be separated from the stator  121 . The rotor  122  may be disposed on or at an inner side of the stator  121 . The rotational shaft  123  may be disposed at a center of the rotor  122 . The rotational shaft  123  may be, for example, press-fit and coupled to the center of the rotor  122 . 
     When power is applied to the stator  121 , the rotor  122  may rotate according to an interaction of the stator  121  and the rotor  122 . As a result, the rotational shaft  123  coupled to the rotor  122  may rotate concentrically with the rotor  122 . 
     An oil path  125  may be formed at the center of the rotational shaft  123 . The oil path  125  may extend in the axial direction. In a middle of the oil path  125 , oil through holes  126   a  and  126   b  may be formed through an outer circumferential surface of the rotational shaft  123 . 
     The oil through holes  126   a  and  126   b  may include a first oil through hole  126   a  which belongs to or is formed in a range of a first bearing  1311  and a second oil through hole  126   b  which belongs to or is formed in a range of a second bearing  1321 . One first oil through hole  126   a  and one second oil through hole  126   b  may be formed, respectively, or a plurality of each may be formed. 
     An oil feeder  150  may be disposed in the middle or on or at a bottom of the oil path  125 . When the rotational shaft  123  rotates, oil filled in a lower portion of the casing  110  may be pumped by the oil feeder  150 . As a result, the oil may rise along the oil path  125 , and may be supplied to a sub bearing surface  1321   a  through the second oil through hole  126   b  and supplied to a main bearing surface  1311   a  through the first oil through hole  126   a.    
     The first oil through hole  126   a  may be formed to overlap with a first oil groove  1311   b . The second oil through hole  126   b  may be formed to overlap with a second oil groove  1321   b . In other words, the oil supplied to the main bearing surface  1311   a  of main bearing  131  and the sub bearing surface  1321   a  of sub bearing  132  through the first oil through hole  126   a  and the second oil through hole  126   b  may rapidly flow into a main-side second pocket  1313   b  and a sub-side second pocket  1323   b.    
     The compression units  131 ,  132 ,  133 , and  134  may include main bearing  131  installed on or at both sides in the axial direction, a cylinder  133  in which compression space  410  is formed by the sub bearing  132 , and a rotor  134  rotatably disposed inside the cylinder  133 . 
     Referring to  FIGS. 1 and 2 , the main bearing  131  and the sub bearing  132  may be disposed in the casing  110 . The main bearing  131  and the sub bearing  132  may be fixed to the casing  110 . The main bearing  131  and the sub bearing  132  may be separated from each other along the rotational shaft  123 . The main bearing  131  and the sub bearing  132  may be separated from each other in the axial direction. In one embodiment, the axial direction may mean a vertical direction based on  FIG. 1 . 
     The main bearing  131  and the sub bearing  132  may support the rotational shaft  123  in a radial direction. The main bearing  131  and the sub bearing  132  may support the cylinder  133  and the rotor  134  in the axial direction. The main bearing  131  and the sub bearing  132  may include bearings  1311  and  1321  that support the rotational shaft  123  in the radial direction and flanges  1312  and  1322  that extend on or from the bearings  1311  and  1321  in the radial direction. More specifically, the main bearing  131  may include first bearing  1311  that supports the rotational shaft  123  in the radial direction and first flange  1312  that extends on or from the first bearing  1311  in the radial direction and the sub bearing  132  may include second bearing  1321  that supports the rotational shaft  123  in the radial direction and second flange  1322  that extends on or from the second bearing  1321  in the radial direction. 
     Each of the first bearing  1311  and the second bearing  1321  may be formed in a bush shape. The first flange  1312  and the second flange  1322  may be formed in a disc shape. The first oil groove  1311   b  may be formed on the main bearing surface  1311   a  which is a radial inner circumferential surface of the first bearing  1311 . The second oil groove  1321   b  may be formed on the sub bearing surface  1321   a  which is a radial inner circumferential surface of the second bearing  1321 . The first oil groove  1311   b  may be formed as a straight line or a diagonal line between upper and lower ends of the first bearing  1311 . The second oil groove  1321   b  may be formed as a straight line or a diagonal line between the upper and lower ends of the second bearing  1321 . 
     A first communication path  1315  may be formed in the first oil groove  1311   b . A second communication path  1325  may be formed in the second oil groove  1321   b . The first communication path  1315  and the second communication path  1325  may guide the oil which flows to the main bearing surface  1311   a  and the sub bearing surface  1321   a  to a main-side back pressure pocket  1313  and a sub-side back pressure pocket  1323 . 
     The main-side back pressure pocket  1313  may be formed in the first flange  1312 . The sub-side back pressure pocket  1323  may be formed in the second flange  1322 . The main-side back pressure pocket  1313  may include main-side first pocket  1313   a  and main-side second pocket  1313   b . The sub-side back pressure pocket  1323  may include sub-side first pocket  1323   a  and sub-side second pocket  1323   b.    
     The main-side first pocket  1313   a  and the main-side second pocket  1313   b  may be formed at a predetermined interval in a circumferential direction. The sub-side first pocket  1323   a  and the sub-side second pocket  1323   b  may be formed at a predetermined interval in the circumferential direction. 
     The main-side first pocket  1313   a  may form a lower pressure than the main-side second pocket  1313   b , for example, an intermediate pressure between a suction pressure and a discharge pressure. The sub-side first pocket  1323   a  may form a lower pressure than the sub-side second pocket  1323   b , for example, an intermediate pressure between the suction pressure and the discharge pressure. The pressure of the main-side first pocket  1313   a  and the pressure of the sub-side first pocket  1323   a  may correspond to each other. 
     While the oil flows into the main-side first pocket  1313   a  through a minute passage between a main-side first bearing protrusion  1314   a  and a top  134   a  of the rotor  134 , the main-side first pocket  1313   a  is depressurized, and as a result, the intermediate pressure may be formed. While the oil flows into the sub-side first pocket  1323   a  through a minute passage between a sub-side first bearing protrusion  1324   a  and a bottom  134   b  of the rotor  134 , the sub-side first pocket  1323   a  is depressurized, and as a result, the intermediate pressure may be formed. 
     As the oil which flows to the main bearing surface  1311   a  through the first oil through hole  126   a  flows into the main-side second pocket  1313   b  through the first communication path  1315 , the main-side second pocket  1313   b  may be maintained at the discharge pressure or at a pressure similar to the discharge pressure. As the oil which flows to the sub bearing surface  1321   a  through the second oil through hole  126   b  flows into the sub-side second pocket  1323   b  through the second communication path  1325 , the sub-side second pocket  1323   b  may be maintained at a discharge pressure or at a pressure similar to the discharge pressure. 
     In the cylinder  133 , an inner circumferential surface forming the compression space  410  may be formed in a circular shape. In contrast, the inner circumferential surface of the cylinder  133  may be formed in a symmetrical elliptical shape having a pair of long axis and short axis or an asymmetrical elliptical shape having several pairs of long axes and short axes. An outer circumferential surface of the cylinder  133  may be formed in the circular shape, but if the outer circumferential surface of the cylinder  133  may be fixed to the inner circumferential surface of the casing  110 , the outer circumferential surface of the cylinder  133  is not limited thereto and may be variously changed. The cylinder  133  may be fastened to the main bearing  131  or the sub bearing  132  fixed to the casing  110  with a bolt, for example. 
     An empty space may be formed at a center of the cylinder  133  so as to form the compression space  410  including the inner circumferential surface. The empty space may be sealed by the main bearing  131  and the sub bearing  132  to form the compression space  410 . The rotor  134 , the outer circumferential surface of which may be formed in the circular shape, may be rotatably disposed in the compression space  410 . 
     An inlet  1331  and an outlet  1332  may be formed at both circumferential sides around a contact point P where inner circumferential surface  133   a  of the cylinder  133  and outer circumferential surface  134   c  of the rotor  134  are almost in contact with each other on the inner circumferential surface  133   a  of the cylinder  133 . The inlet  1331  and the outlet  1332  may be separated from each other. In other words, the inlet  1331  may be formed at a front flow side based on a compression path (a rotational direction) and the outlet  1332  may be formed at a rear flow side in a direction in which the refrigerant is compressed. 
     A suction pipe  113  that penetrates the casing  110  may be directly connected to the inlet  1331 . The outlet  1332  may be indirectly connected to a discharge pipe  114  which communicates with internal space S of the casing  110  and is through-coupled to the casing  110 . As a result, the refrigerant may be directly suctioned into the compression space  410  through the inlet  1331  and the compressed refrigerant may be discharged to the internal space S of the casing  110  through the outlet  1332  and then discharged to the discharge pipe  114 . Accordingly, the internal space S of the casing  110  may be maintained at a high-pressure state having the discharge pressure. 
     More specifically, high-pressure refrigerant discharged from the outlet  1332  may stay in the internal space S adjacent to the compression units  131 ,  132 ,  133 , and  134 . As the main bearing  131  is fixed to the inner circumferential surface of the casing  110 , the main bearing  131  may border upper and lower sides of the internal space S. In this case, the high-pressure refrigerant which stays in the internal space S may rise through discharge path  1316  and may be discharged to the outside through the discharge pipe  114  provided at an upper side of the casing  110 . 
     The discharge path  1316  may penetrate the first flange  1312  of the main bearing  131  in the axial direction. The discharge path  1316  may secure a sufficient path area so as to prevent path resistance from being generated. More specifically, the discharge path  1316  may be formed to extend in the circumferential direction in a region which does not overlap with the cylinder  133  in the axial direction. In other words, the discharge path  1316  may be formed to have an arc shape. 
     Further, the discharge path  1316  may be constituted by a plurality of holes separated from each other in the circumferential direction. As such, as a maximum path area is secured, the path resistance may be reduced when the high-pressure refrigerant moves to the discharge pipe  114  provided at the upper side of the casing  110 . 
     Further, a separate suction valve is not installed in the inlet  1331 , while a discharge valve  1335  that opens and closes the outlet  1332  may be disposed in the outlet  1332 . The discharge valve  1335  may include a lead type valve one end of which is fixed and the other end of which is a free end. Alternatively, the discharge valve  1335  may be variously changed as necessary, and may be a piston valve, for another example. 
     When the discharge valve  1335  is formed by the lead type valve, a discharge groove (not illustrated) may be formed on the outer circumferential surface of the cylinder  133  so that the discharge valve  1335  may be mounted. As a result, a length of the outlet  1332  may be reduced to a minimum, thereby reducing a dead volume. At least a portion of a valve groove may be formed in a triangular shape so as to secure a flat valve seat surface as illustrated in  FIG. 2 . In one embodiment, it is described as an example that one outlet  1332  is provided; however, embodiments are not limited thereto and a plurality of the outlet  1332  may be provided along a compression path (compression progress direction). 
     The rotor  134  may be disposed in the cylinder  133 . The rotor  134  may be disposed in the compression space  410  of the cylinder  133 . The outer circumferential surface  134   c  of the rotor  134  may be formed in a circular shape. The rotational shaft  134  may be disposed at a center of the rotor  123 . The rotational shaft  123  may be integrally coupled to the center of the rotor  134 . Therefore, the rotor  134  may have a center Or which coincides with a shaft center Os of the rotational shaft  123  and may rotate concentrically with the rotational shaft  123  around the center Or of the rotor  134 . 
     The center Or of the rotor  134  may be eccentric with respect to a center Oc of the cylinder  133 , that is, the center Oc of an internal space of the cylinder  133 . One side of the outer circumferential surface  134   c  of the rotor  134  may be almost in contact with the inner circumferential surface  133   a  of the cylinder  133 . The outer circumferential surface  134   c  of the rotor  134  is not actually in contact with the inner circumferential surface  133   a  of the cylinder  133 , but the outer circumferential surface  134   c  of the rotor  134  and the inner circumferential surface  133   a  of the cylinder  133  are separated from each other and should be adjacent to each other enough to limit leakage of the high-pressure refrigerant in a discharge pressure region to a suction pressure region through a gap between the outer circumferential surface  134   c  of the rotor  134  and the inner circumferential surface  133   a  of the cylinder  133  without occurrence of friction damage. A point of the cylinder  133  almost contacting one side of the rotor  134  may be regarded as contact point P. 
     At least one vane slot  1341   a ,  1341   b , or  1341   c  may be formed at an appropriate location in the circumferential direction of the outer circumferential surface  134   c  of the rotor  134 . The vane slots  1341   a ,  1341   b , and  1341   c  may include a first vane slot  1341   a , a second vane slot  1341   b , and a third vane slot  1341   c . In one embodiment, it is described as an example that three vane slots  1341   a ,  1341   b , and  1341   c  are formed; however, embodiments are not limited thereto and the vane slots may be variously changed according to the number of vanes  1351 ,  1352 , and  1353 . 
     First to third vanes  1351 ,  1352 , and  1353  may be slidably coupled to the first to third vane slots  1341   a ,  1341   b , and  1341   c , respectively. Each of the first to third vane slots  1341   a ,  1341   b , and  1341   c  may be formed toward the radial direction based on the center Or of the rotor  134 . In other words, each of straight lines extending from the first to third vane slots  1341   a ,  1341   b , and  1341   c , respectively, may pass through the center Or of the rotor  134 . 
     First to third back pressure chambers  1342   a ,  1342   b , and  1342   c  may be formed on inner ends of the first to third vane slots  1341   a ,  1341   b , and  1341   c , respectively, in which each of the first to third vanes  1351 ,  1352 , and  1353  allows the oil or refrigerant to flow into a rear side to add each of the first to third vanes  1351 ,  1352 , and  1353  in the inner circumferential surface of the cylinder  133 . The first to third back pressure chambers  1342   a ,  1342   b , and  1342   c  may be sealed by the main bearing  131  and the sub bearing  132 . Each of the first to third back pressure chambers  1342   a ,  1342   b , and  1342   c  may independently communicate with back pressure pockets  1313  and  1323 . Alternatively, the first to third back pressure chambers  1342   a ,  1342   b , and  1342   c  may communicate with each other by the back pressure pockets  1313  and  1323 . 
     The back pressure pockets  1313  and  1323  may be formed in the main bearing  131  and the sub bearing  132 , respectively, as illustrated in  FIG. 1 . Alternatively, the back pressure pockets  1313  and  1323  may be formed only on either the main bearing  131  or the sub bearing  132 . In one embodiment, it is described as an example that the back pressure pockets  1313  and  1323  are formed in both the main bearing  131  and the sub bearing  132 . The back pressure pockets  1313  and  1323  may include main-side back pressure pocket  1313  formed in the main bearing  131  and sub-side back pressure pocket  1323  formed in the sub bearing  132 . 
     The main-side back pressure pocket  1313  may include main-side first pocket  1313   a  and main-side second pocket  1313   b . The main-side second pocket  1313   b  may have a higher pressure than the main-side first pocket  1313   a . The sub-side back pressure pocket  1323  may include sub-side first pocket  1323   a  and sub-side second pocket  1323   b . The sub-side second pocket  1323   b  may have a higher pressure than the sub-side first pocket  1323   a . Therefore, the main-side first pocket  1313   a  and the sub-side first pocket  1323   a  may communicate with a vane chamber to which a vane located relatively upstream (before a discharge stroke in a suction stroke) among the vanes  1351 ,  1352 , and  1353  belongs and the main-side second pocket  1313   b  and the sub-side second pocket  1323   b  may communicate with a vane chamber to which a vane located relatively downstream (before the suction stroke in the discharge stroke) belongs among the vanes  1351 ,  1352 , and  1353 . 
     Among the first to third vanes  1351 ,  1352 , and  1353 , a vane closest to the contact point P based on a compression progress direction may be referred to as “first vane  1351 ” and subsequent vanes may be sequentially referred to as “second vane  1352 ” and “third vane  1353 ”. In this case, there may be a spacing as large as a same circumferential angle between the first vane  1351  and the second vane  1352 , between the second vane  1352  and the third vane  1353 , and between the third vane  1353  and the first vane  1351 . 
     When a compression chamber formed by the first vane  1351  and the second vane  1352  is referred to as a “first compression chamber V 1 ”, a compression chamber formed by the second vane  1352  and the third vane  1353  is referred to as a “second compression chamber V 2 ”, and a compression chamber constituted by the third vane  1353  and the first vane  1351  is referred to as a “third compression chamber V 3 ”, all the compression chambers V 1 , V 2 , and V 3  have a same volume at a same crank angle. The first compression chamber V 1  may be referred to as a “suction chamber” and the third compression chamber V 3  may be referred to as a “discharge chamber”. 
     Each of the first to third vanes  1351 ,  1352 , and  1353  may be formed in a substantially rectangular parallelepiped shape. A surface among both longitudinal ends of each of the first to third vanes  1351 ,  1352 , and  1353 , which is in contact with the inner circumferential surface  133   a  of the cylinder  133 , may be referred to as a “front end surface” and a surface facing each of the first to third back pressure chambers  1342   a ,  1342   b , and  1342   c  may be referred to as a “rear end surface”. 
     The front end surface of each of the first to third vanes  1351 ,  1352 , and  1353  may be formed in a curved surface shape so as to be in line contact with the inner circumferential surface  133   a  of the cylinder  133 . The rear end surfaces of the first to third vanes  1351 ,  1352 , and  1353  may be inserted into the first to third back pressure chambers  1342   a ,  1342   b , and  1342   c , respectively, to be formed flat to evenly receive a back pressure. 
     In the rotary compressor  100 , when power is applied to the drive motor  120  and the rotor  122  and the rotational shaft  123  rotate, the rotor  134  rotates together with the rotational shaft  123 . In this case, the first to third vanes  1351 ,  1352 , and  1353  may be drawn out from the first to third vane slots  1341   a ,  1341   b , and  1341   c , respectively, by a centrifugal force generated by rotation of the rotor  134  and the respective back pressures of the first to third back pressure chambers  1342   a ,  1342   b , and  1342   c  disposed at rear sides of the first to third back pressure chambers  1342   a ,  1342   b , and  1342   c , respectively. Therefore, the front end surface of each of the first to third vanes  1351 ,  1352 , and  1353  is in contact with the inner circumferential surface  133   a  of the cylinder  133 . 
     In one embodiment, a case in which the front end surface of each of the first to third vanes  1351 ,  1352 , and  1353  is in contact with the inner circumferential surface  133   a  of the cylinder  133  may mean that the front end surface of each of the first to third vanes  1351 ,  1352 , and  1353  is in direct contact with the inner circumferential surface  133   a  of the cylinder  133  and that the front end surface of each of the first to third vanes  1351 ,  1352 , and  1353  is adjacent to the inner circumferential surface  133   a  of the cylinder  133  enough to be in direct contact with the inner circumferential surface  133   a  of the cylinder  133 . The compression space  410  of the cylinder  133  may form compression chambers V 1 , V 2 , and V 3  (including the suction chamber and the discharge chamber) by the first to third vanes  1351 ,  1352 , and  1353  and while each of the compression chambers V 1 , V 2 , and V 3  moves with the rotation of the rotor  134 , a volume of each of the compression chambers V 1 , V 2 , and V 3  may be varied by eccentricity of the rotor  134 . Therefore, refrigerant filled in each of the compression chambers V 1 , V 2 , and V 3  may be suctioned, compressed, and discharged while moving along the rotor  134  and the vanes  1351 ,  1352 , and  1353 . 
     The first to third vanes  1351 ,  1352 , and  1353  may include upper pins  1351   a ,  1352   a , and  1353   a  and lower pins  1351   b ,  1352   b , and  1353   b , respectively. The upper pins  1351   a ,  1352   a , and  1353   a  may include a first upper pin  1351   a  formed on a top of the first vane  1351 , a second upper pin  1352   a  formed on a top of the second vane  1352 , and a third upper pin  1353   a  formed on a top of the third vane  1353 . The lower pins  1351   b ,  1352   b , and  1353   b  may include a first lower pin  1351   b  formed on a bottom of the first vane  1351 , a second lower pin  1352   b  formed on a bottom of the second vane  1352 , and a third lower pin  1353   b  formed on a bottom of the third vane  1353 . 
     The bottom of the main bearing  131  may include a first rail groove  1317  into which the upper pins  1351   a ,  1352   a , and  1353   a  may be inserted. The first rail groove  1317  may be formed in a circular band shape. The first rail groove  1317  may be disposed adjacent to the rotational shaft  123 . As the first to third upper pins  1351   a ,  1352   a , and  1353   a  of the respective first to third vanes  1351 ,  1352 , and  1353  are inserted into the first rail groove  1317  to guide positions of the first to third vanes  1351 ,  1352 , and  1353 , compression efficiency may be enhanced by preventing direct contact between the vanes  1351 ,  1352 , and  1353  and the cylinder  133  and deterioration in reliability by abrasion of a product may be prevented. 
     The bottom of the main bearing  131  may include a first step portion or step  1318  disposed adjacent to the first rail groove  1317 . The first step portion  1318  may be disposed between the bottom of the main bearing  131  and the first rail groove  1317 . An outermost side of the first step portion  1318  may be disposed inside an outer surface of the rotor  134 . An innermost side of the first step portion  1318  may be disposed outside the rotational shaft  123 . Therefore, the first step portion  1318  may reduce the pressure of the compression space  410  by increasing an area of the compression space  410  to reduce a load applied to the first to third upper pins  1351   a ,  1352   a , and  1353   a , thereby preventing damage to the component. 
     Further, the first step portion  1318  may be disposed adjacent to the inlet  1331 . Further, a width of the first step portion  1318  may become larger or increase as the first step portion  1318  is closer to the inlet  1331 . More specifically, referring to  FIGS. 3, 4, 6, and 7 , a cross section of the first step portion  1318  may be formed in a half moon shape, the first step portion  1318  may be disposed closer to the inlet  1331  than to the outlet  1332 , and the width of the first step portion  1318  may become larger or increase as the first step portion  1318  is closer to the inlet  1331 . Therefore, efficiency of reducing the load applied to the first to third upper pins  1351   a ,  1352   a , and  1353   a  may be enhanced. 
     The top of the sub bearing  132  may include a second rail groove  1327  into which the lower pins  1351   b ,  1352   b , and  1353   b  may be inserted. The second rail groove  1327  may be formed in a circular band shape. The second rail groove  1327  may be disposed adjacent to the rotational shaft  123 . As the first to third lower pins  1351   b ,  1352   b , and  1353   b  of the respective first to third vanes  1351 ,  1352 , and  1353  are inserted into the second rail groove  1327  to guide positions of the first to third vanes  1351 ,  1352 , and  1353 , the compression efficiency may be enhanced by preventing direct contact between the vanes  1351 ,  1352 , and  1353  and the cylinder  133  and deterioration in reliability by the abrasion of the product may be prevented. 
     The first rail groove  1317  and the second rail groove  1327  may be formed in shapes corresponding to each other. The first rail groove  1317  and the second rail groove  1327  may overlap with each other in the axial direction. Therefore, efficiency of guiding the positions of the first to third vanes  1351 ,  1352 , and  1353  may be enhanced. 
     The sub bearing  132  may include a second step portion or step  1328  disposed adjacent to the second rail groove  1327 . The second step portion  1328  may be disposed between the top of the sub bearing  132  and the second rail groove  1327 . An outermost side of the second step portion  1328  may be disposed inside the outer surface of the rotor  134 . An innermost side of the second step portion  1328  may be disposed outside the rotational shaft  123 . Therefore, the second step portion  1328  may reduce the pressure of the compression space  410  by increasing the area of the compression space  410  to reduce a load applied to the first to third lower pins  1351   b ,  1352   b , and  1353   b , thereby preventing damage to components. 
     Further, the second step portion  1328  may be disposed adjacent to the inlet  1331 . A width of the second step portion  1328  may become larger or increase as the second step portion  1328  is closer to the inlet  1331 . More specifically, referring to  FIGS. 3, 4, 6, and 7 , a cross section of the second step portion  1328  may be formed in a half moon shape, the second step portion  1328  may be disposed closer to the inlet  1331  than to the outlet  1332 , and a width of the second step portion  1328  may become larger or increase as the second step portion  1328  is closer to the inlet  1331 . Therefore, efficiency of reducing the load applied to the first to third lower pins  1351   b ,  1352   b , and  1353   b  may be enhanced. 
     The first step portion  1318  and the second step portion  1328  may be formed in shapes corresponding to each other. The first step portion  1318  and the second step portion  1328  may overlap with each other in the axial direction. Therefore, the efficiency of reducing the load applied to the first to third lower pins  1351   b ,  1352   b , and  1353   b  may be enhanced. 
     In one embodiment, it is described as an example that each of the number of vanes  1351 ,  1352 , and  1353 , the number of vane slots  1341   a ,  1341   b , and  1341   c , and the number of back pressure chambers  1342   a ,  1342   b , and  1342   c  is three, but each of the number of vanes  1351 ,  1352 , and  1353 , the number of vane slots  1341   a ,  1341   b , and  1341   c , and the number of back pressure chambers  1342   a ,  1342   b , and  1342   c  may be variously changed. 
     Further, in one embodiment, it is described as an example that the upper pins  1351   a ,  1352   a , and  1353   a  and the lower pins  1351   b ,  1352   b , and  1353   b  are all formed on the vanes  1351 ,  1352 , and  1353 ; however, only the upper pins  1351   a ,  1352   a , and  1353   a  may be formed or only the lower pins  1351   b ,  1352   b , and  1353   b  may be formed. 
     A process in which refrigerant is suctioned, compressed, and discharged in the cylinder  133  according to an embodiment will be described with reference to  FIGS. 8 to 10 . 
     Referring to  FIG. 8 , until the first vane  1351  passes through the inlet  1331  and the second vane  1352  reaches a suction completion time, the volume of the first compression chamber V 1  continuously increases. In this case, the refrigerant may continuously flow into the first compression chamber V 1  from the inlet  1331 . 
     The first back pressure chamber  1342   a  disposed at a rear side of the first vane  1351  may be exposed to each of the main-side first pocket  1313   a  of the main-side back pressure pocket  1313  and the main-side second pocket  1313   b  of the main-side back pressure pocket  1313  disposed at a rear side of the second vane  1352 . As a result, the intermediate pressure may be formed in the first back pressure chamber  1342   a  and the first vane  1351  may be pressurized by the intermediate pressure to be in close contact with the inner circumferential surface  133   a  of the cylinder  133  and a discharge pressure or a pressure close to the discharge pressure is formed in the second back pressure chamber  1342   b  and the second vane  1352  may be pressurized by the discharge pressure to be in close contact with the inner circumferential surface  133   a  of the cylinder  133 . 
     Referring to  FIG. 9 , when the second vane  1352  performs the compression stroke after the suction completion time (or compression start time), the first compression chamber V 1  becomes a sealing state to move toward the outlet together with the rotor  134 . In such a process, the volume of the first compression chamber V 1  may continuously decrease and the refrigerant of the first compression chamber V 1  may be gradually compressed. 
     Referring to  FIG. 10 , when the first vane  1351  passes through the outlet  1332  and the second vane  1352  does not reach the outlet  1332 , the discharge valve  1335  may be opened by the pressure of the first compression chamber V 1  while the first compression chamber V 1  communicates with the outlet  1332 . In this case, refrigerant of the first compression chamber V 1  may be discharged to an internal space of the casing  110  through the outlet  1332 . 
     In this case, the first back pressure chamber  1342   a  of the first vane  1351  may be just before entering the main-side first pocket  1313   a , which is an intermediate pressure region, by passing through the main-side second pocket  1313   b , which is the discharge pressure region. Accordingly, the back pressured formed in the first back pressure chamber  1342   a  of the first vane  1351  may be lowered from the discharge pressure to the intermediate pressure. In contrast, the second back pressure chamber  1342   b  of the second vane  1352  may be located in the main-side second pocket  1313   b , which is the discharge pressure region, and the back pressure corresponding to the discharge pressure may be formed in the second back pressure chamber  1342   b.    
     As a result, the intermediate pressure between the suction pressure and the discharge pressure may be formed on a rear end portion of the first vane  1351  located in the main-side first pocket  1313   a  and the discharge pressure (actually, a pressure slightly lower than the discharge pressure) may be formed on the rear end portion of the second vane  1352  located in the main-side second pocket  1313   b . In particular, as the main-side second pocket  1313   b  is in direct communication with the oil path  125  through the first oil through hole  126   a  and the first communication path  1315 , the pressure of the second back pressure chamber  1342   b  which communicates with the main-side second pocket  1313   b  may be prevented from increasing to the discharge pressure or more. As a result, the intermediate pressure lower than the discharge pressure is formed in the main-side first pocket  1313   a  to increase mechanical efficiency between the cylinder  133  and the vanes  1351 ,  1352 , and  1353 . Further, as the discharge pressure or the pressure slightly lower than the discharge pressure is formed in the main-side second pocket  1313   b , the vanes  1351 ,  1352 , and  1353  are disposed adjacent to the cylinder  133  to increase mechanical efficiency while suppressing leakage between the compression chambers. 
     Referring to  FIG. 11 , it can be seen that the pressure applied to the upper pins  1351   a ,  1352   a , and  1353   a  and/or the lower pins  1351   b ,  1352   b , and  1353   b  of the vanes  1351 ,  1352 , and  1353  is lowered in the rotary compressor  100  according to an embodiment. An upper graph may mean a pressure applied to applied to the upper pins  1351   a ,  1352   a , and  1353   a  and/or the lower pins  1351   b ,  1352   b , and  1353   b  of the vanes  1351 ,  1352 , and  1353  in a conventional rotary compressor and a lower graph may mean a pressure applied to the upper pins  1351   a ,  1352   a , and  1353   a  and/or the lower pins  1351   b ,  1352   b , and  1353   b  of the vanes  1351 ,  1352 , and  1353  in rotary compressor  100  according to an embodiment. In other words, the load applied to the upper pins  1351   a ,  1352   a , and  1353   a  and/or the lower pins  1351   b ,  1352   b , and  1353   b  is reduced, thereby preventing damage to components. 
     Certain embodiments or other embodiments described above are not mutually exclusive or distinct from each other. The certain embodiments or other embodiments described above may be used in combination or combined with each other in configuration or function. 
     For example, it is meant that a configuration “A” described in a specific embodiment and/or the drawings and a configuration “B” described in another embodiment and the drawings may be combined with each other. Namely, although the combination between the configurations is not directly described, the combination is possible except in the case where it is described that the combination is impossible. 
     The aforementioned detailed description should not be construed as restrictive in all terms and should be exemplarily considered. The scope should be determined by rational construing of the appended claims and all modifications within an equivalent scope are included in the scope. 
     According to embodiments disclosed herein, it is possible to provide a rotary compressor capable of enhancing compression efficiency by preventing contact between a vane and a cylinder. Further, according to embodiments disclosed herein, it is possible to provide a rotary compressor capable of preventing reliability from being deteriorated due to abrasion by preventing contact between the vane and the cylinder. Furthermore, according to embodiments disclosed herein, it is possible to provide a rotary compressor capable of preventing damage to a product by reducing a load applied to a pin of the vane. 
     Embodiments disclosed herein provide a rotary compressor capable of enhancing compression efficiency by preventing contact between a vane and a cylinder. Embodiments disclosed herein also provide a rotary compressor capable of preventing reliability from being deteriorated due to abrasion by preventing contact between the vane and the cylinder. Embodiments disclosed herein also provide a rotary compressor capable of preventing damage to a product by reducing a load applied to a pin of the vane. 
     Embodiments disclosed herein provide a rotary compressor that may include a rotational shaft; first and second bearings supporting the rotational shaft in a radial direction; a cylinder disposed between the first bearing and the second bearing, and forming a compression space; a rotor forming a contact point disposed in the compression space and having a predetermined gap with the cylinder, and coupled to the rotational shaft to compress refrigerant according to rotation; and at least one vane slidably inserted into the rotor, and contacting an inner circumferential surface of the cylinder to separate the compression space into a plurality of regions. Each of the at least one vane may include an upper pin extending upward, and a lower pin extending downward. A bottom of the first bearing may include a first rail groove into which the upper pin may be inserted, and a first step portion or step disposed adjacent to the first rail groove, and a top of the second bearing may include a second rail groove into which the lower pin may be inserted, and a second step portion or step disposed adjacent to the second rail groove. 
     Therefore, compression efficiency may be enhanced by preventing contact between the vane and the cylinder. Further, deterioration in reliability by abrasion may be prevented by preventing the contact between the vane and the cylinder. Moreover, damage to a product may be prevented by reducing a load applied to the pin of the vane. 
     The first step portion may be disposed between the bottom of the first bearing and the first rail groove, and the second step portion may be disposed between the top of the second bearing and the second rail groove. Further, outermost sides of the first and second step portions may be disposed inside an outer surface of the rotor, and innermost sides of the first and second step portions may be disposed outside the rotational shaft. 
     The cylinder may include an inlet through which the refrigerant may be suctioned into one region of the compression space, and an outlet disposed on or at a position spaced apart from the inlet in a direction opposite to a rotational direction of the compressor and through which compressed refrigerant may be discharged, and the contact point may be disposed on or at a predetermined position between the inlet and the outlet. 
     The first step portion and the second step portion may be disposed adjacent to the inlet. Further, widths of the first step portion and the second step portion may become larger as the first and second step portions are closer to the inlet. Furthermore, the first step portion and the second step portion may overlap with each other in an axial direction. Also, a straight line passing through the at least one vane in a direction perpendicular to the rotational shaft may pass through a center of the rotor. 
     Embodiments disclosed herein provide a rotary compressor that may include a rotational shaft; first and second bearings supporting the rotational shaft in a radial direction; a cylinder disposed between the first bearing and the second bearing, and forming a compression space; a rotor forming a contact point disposed in the compression space and having a predetermined gap with the cylinder and coupled to the rotational shaft to compress refrigerant according to rotation; and at least one vane slidably inserted into the rotor and contacting an inner circumferential surface of the cylinder to separate the compression space into a plurality of regions. Each of the at least one vane may include an upper pin extending upward, and a bottom of the first bearing may include a rail groove into which the upper pin may be inserted and a step portion or step disposed adjacent to the rail groove. 
     Therefore, compression efficiency may be enhanced by preventing contact between the vane and the cylinder. Further, deterioration in reliability by abrasion may be prevented by preventing contact between the vane and the cylinder. Moreover, damage to a product may be prevented by reducing a load applied to the pin of the vane. 
     The step portion may be disposed between the bottom of the first bearing and the rail groove. Further, an outermost side of the step portion may be disposed inside an outer surface of the rotor, and an outermost side of the step portion may be disposed outside the rotational shaft. 
     The cylinder may include an inlet through which the refrigerant may be suctioned into one region of the compression space, and an outlet disposed on a position spaced apart from the inlet in a direction opposite to a rotational direction of the compressor and through which compressed refrigerant may be discharged. The contact point may be disposed on or at a predetermined position between the inlet and the outlet. 
     The step portion may be disposed adjacent to the inlet. A width of the step portion may become larger or increase as the step portion is closer to the inlet. 
     Embodiments disclosed herein provide a rotary compressor that may include a rotational shaft; first and second bearings supporting the rotational shaft in a radial direction; a cylinder disposed between the first bearing and the second bearing, and forming a compression space; a rotor forming a contact point disposed in the compression space and having a predetermined gap with the cylinder and coupled to the rotational shaft to compress refrigerant according to rotation; and at least one vane slidably inserted into the rotor and contacting an inner circumferential surface of the cylinder to separate the compression space into a plurality of regions. Each of the at least one vane may include a lower pin extending downward, and a top of the second bearing may include a rail groove into which the lower pin may be inserted and a step portion or step disposed adjacent to the rail groove. 
     Therefore, compression efficiency may be enhanced by preventing contact between the vane and the cylinder. Further, deterioration in reliability by abrasion may be prevented by preventing the contact between the vane and the cylinder. Moreover, damage to a product may be prevented by reducing a load applied to the pin of the vane. 
     The step portion may be disposed between the top of the second bearing and the rail groove. Further, an outermost side of the step portion may be disposed inside an outer surface of the rotor, and an outermost side of the step portion may be disposed outside the rotational shaft. 
     The cylinder may include an inlet through which the refrigerant may be suctioned into one region of the compression space, and an outlet disposed on or at a position spaced apart from the inlet in a direction opposite to a rotational direction of the compressor and through which compressed refrigerant may be discharged. The contact point may be disposed on or at a predetermined position between the inlet and the outlet. 
     The step portion may be disposed adjacent to the inlet. Further, a width of the step portion may become larger or increase as the step portion is closer to the inlet. 
     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 of the disclosure are described herein with reference to cross-section illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of the disclosure. 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 of the disclosure 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.