Patent Publication Number: US-9429156-B2

Title: Compressor

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims priority to Korean Application No. 10-2012-0157218, filed in Korea on Dec. 28, 2012, which is herein expressly incorporated by reference in its entirety. 
     BACKGROUND 
     1. Field 
     A compressor is disclosed herein. 
     2. Background 
     In general, a compressor is applicable to a vapor compression type refrigeration cycle (hereinafter, abbreviated as a “refrigeration cycle”), such as a refrigerator, or air conditioner. For a refrigerant compressor, there has been introduced a constant speed compressor, which is driven at a predetermined speed, or an inverter type compressor, in which a rotation speed is controlled. 
     A compressor can be divided into a hermetic type compressor, in which an electric motor drive, which is a typical electric motor, and a compression unit or device operated by the electric drive are provided together at an inner space of a sealed casing, and an open type compressor in which an electric motor is separately provided outside of the casing. The hermetic compressor is mostly used for household or commercial refrigeration equipment. 
     The hermetic compressor may be divided into a single hermetic compressor and a multiple hermetic compressor according to a number of cylinders. The single hermetic compressor is provided with one cylinder having one compression space within the casing, whereas the multiple hermetic compressor is provided with a plurality of cylinders each having a compression space, respectively, within the casing. 
     The multiple hermetic compressor may be divided into a 1-suction, 2-discharge type and a 1-suction, 1-discharge type according to the refrigerant compression mode. The 1-suction, 1-discharge type is a compressor in which an accumulator is connected to a first cylinder among a plurality of cylinders through a first suction passage, and a second cylinder is connected to a discharge side of the first cylinder connected to the accumulator through a second suction passage, and thus, refrigerant is compressed by two stages and then discharged to an inner space of the casing. In contrast, the 1-suction, 2-discharge type is a compressor in which a plurality of cylinders are branched and connected to one suction pipe and refrigerant is compressed in the plurality of cylinders, respectively, and discharged to an inner space of the casing. 
       FIG. 1  is a longitudinal cross-sectional view of a related art 1-suction, 2-discharge type rotary compressor. As illustrated in the related art 1-suction, 2-discharge type rotary compressor, a motor drive  2  is provided within the casing  1 , and a compressor unit or device  3  is provided at a lower side of the motor drive  2 . The motor drive  2  and compressor unit  3  are mechanically connected through a crank shaft  23 . Reference numerals  21  and  22  denote a stator and a rotor, respectively. 
     For the compressor unit  3 , a main bearing  31  and a sub bearing  32  are fixed to the casing  1  at regular intervals to support the crank shaft  23 , and a first cylinder  34  and a second cylinder  35  separated by an intermediate plate  33  are provided between the main bearing  31  and sub bearing  32 . An inlet port  33   a  connected to a suction pipe  11  is formed at or in the intermediate plate  33 , and a first suction groove  33   b  and a second suction groove  33   c  that communicate with each compression space (V 1 , V 2 ) of the first cylinder  34  and second cylinder  35  are formed at an end of the inlet port  33   a.    
     A first eccentric portion  23   a  and a second eccentric portion  23   b  are formed on the crank shaft  23  along an axial direction with a distance of about 180° therebetween, and a first rolling piston  36  and a second rolling piston  37  to compress refrigerant are coupled to an outer circumferential surface of the first eccentric portion  23   a  and the second eccentric portion  23   b , respectively. A first vane (not shown) and a second vane (not shown) welded to the first rolling piston  36  and the second rolling piston  37 , respectively, to divide first compression space (V 1 ) and second compression space (V 2 ) into a suction chamber and a compression chamber, respectively, are coupled to the first cylinder  34  and the second cylinder  35 . Reference numerals  5 ,  12 ,  31   a  and  32   a  denote an accumulator, a discharge pipe, and discharge ports, respectively. 
     According to the foregoing related art 1-suction, 2-discharge type rotary compressor, when power is applied to the motor drive  2  to rotate the rotor  22  and the crank shaft  23  of the motor drive  2 , refrigerant is alternately inhaled into the first cylinder  34  and the second cylinder  35  while the first rolling piston  36  and the second rolling piston  37  revolve. The refrigerant is subjected to a series of processes of being discharged into an inner space of the casing  1  through the discharge ports  31   a ,  32   a  provided in the main bearing  31  and the sub bearing  32 , respectively, while being compressed by the first vane of the first rolling piston  36  and the second vane of the second rolling piston  37 . 
     However, according to the foregoing 1-suction, 2-discharge type rotary compressor, the first eccentric portion  23   a  and the second eccentric portion  23   b  are eccentrically formed at regular intervals with respect to an axial center in a lengthwise direction of the crank shaft  23 , and thus, a moment due to an eccentric load is increased, thereby causing a problem of increasing vibration and friction loss of the compressor. Further, each vane is welded to each rolling piston  36 ,  37  to divide the suction chamber and the compression chamber, but according to operating conditions, refrigerant leakage is generated between each vane and each rolling piston  36 ,  37  while they are separated from each other, thereby reducing compressor efficiency. 
     Taking this into consideration, a 1-cylinder, 2-compression chamber type rotary compressor having two compression spaces in one cylinder has been introduced as disclosed in Korean Patent Registration No. 10-0812934.  FIG. 2  is a longitudinal cross-sectional view of a related art 1-cylinder, 2-compression chamber type rotary compressor, and  FIG. 3  is a transverse cross-sectional view of a cylinder and a piston in the 1-cylinder, 2-compression chamber type compressor of  FIG. 2 , taken along line “III-III” of  FIG. 2 . 
     As illustrated in  FIG. 2 , for a 1-cylinder, 2-compression chamber type rotary compressor (hereinafter, abbreviated as a “1-cylinder, 2-compression chamber compressor”) according to the related art, a first compression space (V 1 ) and a second compression space (V 2 ) are formed at an outer side and an inner side of the piston  44 , respectively. Further, the piston  44  is fixedly coupled to an upper housing  41  and casing  1 , and the cylinder  43  is coupled in a sliding manner, between the upper housing  41  and lower housing  42 , to eccentric portion  23   c  of crank shaft  23  so as to be revolved with respect to the piston  44 . 
     A long hole-shaped inlet port  41   a  is formed at one side of the upper housing  41  to communicate with each suction chamber of the first compression space (V 1 ) and the second compression space (V 2 ), and a first discharge port  41   b  and a second discharge port  41   c  are formed at the other side of the upper housing  41  to communicate with each compression chamber of the first compression space (V 1 ) and the second compression chamber V 2  and the discharge space (S 2 ). 
     As illustrated in  FIG. 3 , the cylinder  43  may include an outer cylinder portion  45  that forms the first compression space (V 1 ), an inner cylinder portion  46  that forms the second compression space (V 2 ), and a vane portion  47  that connects the outer cylinder portion  45  and the inner cylinder portion  46  to divide the suction chamber and the compression chamber. The outer cylinder portion  45  and the inner cylinder portion  46  are formed in a ring shape, and the vane portion  47  is formed in a vertically raised flat plate shape. 
     An inner diameter of the outer cylinder portion  45  is formed to be greater than an outer diameter of the piston  44 , and an outer diameter of the inner cylinder portion  46  is formed to be less than an inner diameter of the piston  44 , and thus, an inner circumferential surface of the outer cylinder portion  45  is brought into contact with an outer circumferential surface of the piston  44  at one point, and an outer circumferential surface of the inner cylinder portion  46  is brought into contact with an inner circumferential surface of the piston  44  at one point, thereby forming the first compression space (V 1 ) and the second compression space (V 2 ), respectively. 
     The piston  44  is formed in a ring shape, and a bush groove  49  is formed to allow the vane portion  47  of the cylinder  43  to be inserted thereinto in a sliding manner, and a rolling bush  48  is provided at or in the bush groove  45  to allow the piston  44  to make a turning movement. The rolling bush  48  is disposed such that flat surfaces of a semicircular suction side bush  48   a  and a discharge side bush  48   b  are brought into contact with the vane portion  47  at both sides thereof. 
     On the drawing, unexplained reference numerals  43   a  and  44   a  are lateral inlet ports. 
     According to the foregoing related art 1-cylinder, 2-compression chamber compressor, the cylinder  43  coupled to the crank shaft  23  makes a turning movement with respect to the piston  44  to alternately inhale refrigerant into the first compression space (V 1 ) and the second compression space (V 2 ), and the inhaled refrigerant is compressed by the outer cylinder portion  45 , the inner cylinder portion  46 , and the vane portion  47 , and thus, alternately discharged into an inner space of the casing  1  through the first discharge port  41   b  and the second discharge port  41   c.    
     As a result, the first compression space (V 1 ) and the second compression space (V 2 ) may be disposed adjacent to each other on the same plane, thereby reducing moment and friction loss. In addition, the vane portion  47 , which divides the suction chamber and compression chamber, may be integrally coupled to the outer cylinder portion  45  and the inner cylinder portion  46 , thereby enhancing sealability of the compression space. 
     However, according to the foregoing related art 1-cylinder, 2-compression chamber compressor, the piston  44  is fixed, but the relatively heavy cylinder  43  is rotated, and thus, a high power loss results with respect to the same cooling power and a large bearing area, thereby increasing concerns of refrigerant leakage. 
     Further, according to the related art 1-cylinder, 2-compression chamber compressor, part of an outer circumferential surface of the cylinder  43  may be closely adhered to an inner circumferential surface of the upper housing  41 , and thus, a diameter of the upper housing  41  should be increased to change a volume of the cylinder  43  according to turning movement, and consequently, the casing  1  itself should be changed in an increasing manner, thereby causing a problem in which volume control of the compressor is not so easy. 
     Furthermore, according to the related art 1-cylinder, 2-compression chamber compressor, the first discharge port  41   b  and the second discharge port  41   c  may be formed to extend in the same direction, and thus, refrigerant being discharged first may lead to a so-called pulsation phenomenon, thereby aggravating vibration noise of the compressor. 
    
    
     
       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 related art 1-suction, 2-discharge type rotary compressor; 
         FIG. 2  is a longitudinal cross-sectional view of a related art 1-cylinder 2-compression chamber type rotary compressor; 
         FIG. 3  is a transverse cross-sectional view of a cylinder and a piston, taken along line “III-III” of  FIG. 2 ; 
         FIG. 4  is a longitudinal cross-sectional view of a 1-cylinder, 2-compression chamber type rotary compressor according to an embodiment; 
         FIG. 5  is an exploded perspective view of a compression device in the compressor of  FIG. 4 ; 
         FIG. 6  is a cross-sectional view, taken along line “VI-VI” of  FIG. 4 ; 
         FIG. 7  is a longitudinal cross-sectional view of the compression device, taken along line “VII-VII” of  FIG. 6 ; 
         FIGS. 8 and 9  are a longitudinal cross-sectional view and a plan view of fastening structure of a cylinder in the compressor of  FIG. 4 ; 
         FIG. 10  is a perspective view of an oil passage that guides oil to a bush groove in the compressor of  FIG. 4 ; 
         FIG. 11  is a plan view illustrating a standard of the oil passage in  FIG. 10 ; 
         FIG. 12  is a plan view illustrating an oil passage according to another embodiment; 
         FIGS. 13A-13D  are transverse cross-sectional views illustrating a compression process of an outer compression space and an inner compression space in the compressor according to embodiments; 
         FIG. 14  is a perspective view of a rolling piston in a compressor according to another embodiment; 
         FIG. 15  is a perspective view of the rolling piston of  FIG. 14 ; 
         FIG. 16  is a longitudinal cross-sectional view of a rolling piston and in a compressor according to another embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, a compressor according to embodiments will be described in detail with reference to the accompanying drawings. Where possible, like reference numerals have been used to indicate like elements, and repetitive disclosure has been omitted. 
       FIG. 4  is a longitudinal cross-sectional view of a 1-cylinder, 2-compression chamber type rotary compressor according to an embodiment,  FIG. 5  is an exploded perspective view of a compression device in the compressor of  FIG. 4 .  FIG. 6  is a cross-sectional view, taken along line “VI-VI” of  FIG. 4 .  FIG. 7  is a longitudinal cross-sectional view of the compression device, taken along line “VII-VII” of  FIG. 6 .  FIGS. 8 and 9  are a longitudinal cross-sectional view and a plan view illustrating fastening structure of a cylinder in the compressor of  FIG. 4 . 
     As illustrated in the drawings, according to a 1-cylinder, 2-compression chamber type rotary compressor in accordance with an embodiment, a motor drive  2  that generates a driving force may be provided in an inner space of casing  1 , and a compression device  100  having two compression spaces (V 1 , V 2 ) in one cylinder may be provided at a lower side of the motor drive  2 . 
     The motor drive  2  may include a stator  21  fixed and installed on an inner circumferential surface of the casing  1 , a rotor  22  rotatably inserted into an inner side of the  21 , and a crank shaft  23  coupled to a center of the rotor  22  to transmit a rotational force to a rolling piston  140 , which will be described hereinbelow. The stator  21  may be formed in such a manner that a lamination laminated with a ring-shaped steel plate is shrink-fitted to be fixed and coupled to the casing  1 , and a coil (C) may be wound around the lamination. The rotor  22  may be formed in such a manner that a permanent magnet (not shown) is inserted into the lamination laminated with the ring-shaped steel plate. The crank shaft  23  may be formed in a rod shape having a predetermined length and formed with an eccentric portion  23   c  that eccentrically protrudes in a radial direction at a lower end portion thereof to which the rolling piston  140  may be eccentrically coupled. 
     The compression unit or device  100  may include an upper bearing plate (hereinafter, referred to as an “upper bearing”)  110  and a lower bearing plate (hereinafter, referred to as an “lower bearing”)  120  provided at predetermined intervals in an axial direction to support the crank shaft  23 , a cylinder  130  provided between the upper bearing  110  and the lower bearing  120  to form a compression space (V), and the rolling piston  140  coupled to the crank shaft  23  to compress the refrigerant of the compression space (V) while making a turning movement in the cylinder  130 . The upper bearing  110  may be adhered to an inner circumferential surface of the casing  1  in, for example, a welded and coupled manner, and the lower bearing  120  may be fastened to the upper bearing  110  along with the cylinder  130  by, for example, a bolt. 
     A first discharge port  112   a  that communicates with first compression space (V 1 ), which will be described hereinbelow, may be formed on the upper bearing  110 , and a second discharge port  122   a  that communicates with second compression space (V 2 ), which will be described later, may be formed on the lower bearing  120 . A discharge cover  150  may be coupled to the upper bearing  110  to accommodate the first discharge port  112   a , and a lower chamber  160  may be coupled to the lower bearing  120  to accommodate the second discharge port  122   a . A discharge passage (F) sequentially passing through the lower bearing  120 , the cylinder  130 , and the upper bearing  110  may be formed to communicate an inner space of the lower chamber  160  with an inner space of the discharge cover  150 . 
     The upper bearing  110  and the lower bearing  120  may each be formed in a ring shape, and axle receiving portions  111 ,  121  having axle holes  111   a ,  121   a , respectively, may be formed at a center thereof. 
     An inner diameter (D 1 ) of the axle hole  111   a  of the upper bearing  110  may be formed to be greater than an inner diameter (D 2 ) of the axle hole  121   a  of the lower bearing  120 . In other words, the crank shaft  23  may be formed in such a manner that a diameter at a portion brought into contact with the upper bearing  110  may be greater than a diameter at a portion brought into contact with the lower bearing  120  so as to mostly support the upper bearing  110  close to a center of an eccentric load. Accordingly, the second discharge port  122   a  located at a relatively inner side between the first discharge port  112   a  and the second discharge port  122   a  may be formed on the lower bearing  120  not to intrude into the axle receiving portion  121  of the lower bearing  120 . 
     If the rolling piston  140  is turned upside down such that a driving transmission portion  142  comes in contact with the lower bearing  120  and accordingly the first discharge port  112   a  is closer to the crankshaft  23  than the second discharge port  122   a  of the lower bearing  120 , the first discharge port  112   a  may intrude into the axis receiving portion  111  of the upper bearing  110  having a relative large outer diameter, thereby lowering bearing strength of the axis receiving portion  111  of the upper bearing  110 . By considering this, in order to compensate for the bearing strength as much as the intrusion of the first discharge port  112   a , the axis receiving portion  111  of the upper bearing  110  should be lengthened, which may cause an increase a size of the compressor. 
     As illustrated in  FIGS. 5 and 6 , the cylinder  130  may include an outer cylinder portion  131  formed in a ring shape, an inner cylinder portion  132  disposed at a predetermined interval therefrom to form a compression space (V) at an inner side of the outer cylinder portion  131 , and a vane portion  133  configured to divide the first compression space (V 1 ) and the second compression space (V 2 ) into a suction chamber and a compression chamber, respectively, while at the same time connecting the outer cylinder portion  131  and the inner cylinder portion  132  in a radial direction. The vane portion  133  may be formed between a first inlet port  131   b , which will be described hereinbelow, and the first discharge port  112   a.    
     An outer circumferential surface of the outer cylinder portion  131  may be pressed onto an inner circumferential surface of the casing  1  in, for example, a welded and coupled manner, but an outer diameter of the outer cylinder portion  131  may be formed to be less than an inner diameter of the casing  1  and fastened between the upper bearing  110  and the lower bearing  120  by, for example, a bolt (B 1 ), thereby preventing thermal deformation of the cylinder  130 . However, in order to adhere a portion of the outer cylinder portion  131  to the inner circumferential surface of the casing  1 , a protruded fixing portion  131   a  thereof may be formed in a circular arc shape, and the first inlet port  131   b , which may pass through the protruded fixing portion  131   a  in a radial direction to communicate with the first compression space (V 1 ) may be formed thereon. Refrigerant suction pipe  11  connected to accumulator  5  may be inserted and coupled to the first inlet port  131   b.    
     Further, an upper surface and a lower surface of the outer cylinder portion  131  may be adhered to the upper bearing  110  and the lower bearing  120 , respectively, and a plurality of fastening holes  131   c  may be formed at regular intervals along a circumferential direction. Furthermore, a plurality of discharge guide holes  131   d  that form a discharge passage (F) may be formed between the plurality of fastening holes  131   c.    
     An axle hole  132   a  may be formed in the inner cylinder portion  132  to which the crank shaft  23  may be rotatably coupled to a central portion thereof. A center of the inner cylinder portion  132  may be formed to correspond to a rotational center of the crank shaft  23 . 
     The inner cylinder portion  132  may be formed in such a manner that a height (H 2 ) thereof is lower than a height (H 1 ) of the outer cylinder portion  131 . In other words, a lower surface of the inner cylinder portion  132  may be formed in a same plane as a lower surface of the outer cylinder portion  131  to be brought into contact with the lower bearing  120 , whereas an upper surface thereof may be formed with a height at which the drive transmission portion  142  of the rolling piston  140 , which will be described hereinbelow, may be inserted between the upper bearing  110  and the upper surface thereof. 
     The cylinder  130  may be fastened to fastening hole  112   b  of the upper bearing  110  and fastening hole  122   b  of the lower bearing  120  through the fastening hole  131   c  formed on the outer cylinder portion  131  of the cylinder  130 . However, as illustrated in  FIGS. 8 and 9 , a fastening groove  132   b  may be formed on the inner cylinder portion  132  so as to be fastened to another fastening hole  122   c  of the lower bearing  120  through a bolt (B 2 ). As a result, it may be possible to prevent the inner cylinder portion  132  from being deformed by a pressure of refrigerant compressed in the second compression space (V 2 ). In this case, a plurality of fastening grooves  132   b  may be formed along a circumferential direction of the inner cylinder portion  132 , but when the vane portion  133  is located at the center as illustrated in  FIG. 9 , they may be formed at the inlet side having a relatively high tolerance margin. As a result, a friction loss with the rolling piston  140  may be reduced even when the deformation of the inner cylinder portion  132  is generated during a bolt fastening process to fix the inner cylinder portion  132 , thereby minimizing performance of the compressor from being deteriorated. 
     As illustrated in  FIGS. 5 through 7 , the vane portion  133  may have a predetermined thickness to connect between an inner circumferential surface of the outer cylinder portion  131  and an outer circumferential surface of the inner cylinder portion  132 , as described above, and formed in a vertically raised plate shape. 
     Further, a stepped portion  133   a  may be formed on an upper surface of the vane portion  133  in such a manner that the drive transmission portion  142  of the rolling piston  140 , which will be described hereinbelow, may be placed on part of the inner cylinder portion  132  and the vane portion  133  in a covering manner. Accordingly, when a portion from the outer connecting end  133   b  to the stepped portion  133   a  is referred to as a first vane portion  135  and a portion from the inner connecting end  133   c  to the stepped portion  133   a  is referred to as a second vane portion  136 , a height of the first vane portion  135  in an axial direction may be formed with the same height as a height (H 1 ) of the outer cylinder portion  131  in the axial direction, and a height of the second vane portion  136  in the axial direction may be formed with the same height as a height (H 2 ) of the inner cylinder portion  132  in the axial direction. 
     Further, as illustrated in  FIG. 11 , a length (L 1 ) of the first vane portion  135  in a radial direction may be formed to be no greater than or substantially the same as an inner diameter of a bush groove  145  (or outer diameter of the rolling bush  170 ), which will be described hereinbelow, thereby preventing a gap from being generated between an inner circumferential surface of the outer cylinder portion  131  and an outer circumferential surface of the rolling piston  140  (or an outer circumferential surface of the rolling bush  170 ). 
     The rolling piston  140  may include a piston portion  141  disposed between the outer cylinder portion  131  and the inner cylinder portion  132 , and a drive transmission portion  142  that extends from an upper end inner circumferential surface of the piston portion  141  and coupled to an eccentric portion  23   c  of the crank shaft  23  as illustrated in  FIGS. 5 through 7 . 
     The rolling piston  140  may include a piston portion  141  disposed between the outer cylinder portion  131  and the inner cylinder portion  132 , and the drive transmission portion  142 , which may extend from an upper end inner circumferential surface of the piston portion  141  and be coupled to the eccentric portion  23   c  of the crank shaft  23 , as illustrated in  FIGS. 5 through 7 . 
     The piston portion  141  may be formed in a ring shape having a substantially rectangular cross section, and an outer diameter of the piston portion  141  may be formed to be less than an inner diameter of the outer cylinder portion  131  to form the first compression space (V 1 ) at an outer side of the piston portion  141 , and an inner diameter of the piston portion  141  may be formed to be greater than an outer diameter of the inner cylinder portion  132  to form the second compression space (V 2 ) at an inner side of the piston portion  141 . Further, a second inlet port  141   a  that passes through an inner circumferential surface of the piston portion  141  may be formed to communicate the first inlet port  131   b  with the second compression space (V 2 ) may be formed, and the bush groove  145  may be formed between one side of the second inlet port  141   a , namely, the second inlet port  141   a  and the second discharge port  122   a  formed on the lower bearing  120  in such a manner that the vane portion  133  passes through the rolling piston  140 , which will be described hereinbelow, therebetween and is slidably inserted thereinto. 
     The bush groove  145  may be formed in a substantially circular shape, but an outer open surface  145   a  and an inner open surface  145   b  with a non-continuous surface on an outer circumferential surface and an inner circumferential surface of the piston portion  141  may be formed in such a manner that the vane portion  133  may pass through and be coupled to the bush groove  145  in a radial direction. The bush groove  145  may be formed in a substantially circular shape, but a portion thereof may be brought into contact with the outer circumferential surface and the inner circumferential surface of the piston portion  141  to have a non-continuous surface. The vane portion  133  may be inserted into the bush groove  145  in a radial direction, and an inlet side bush  171  and a discharge side bush  172  of rolling bush  170  may be inserted and rotatably coupled to both left and right sides of the vane portion  133 , respectively. A flat surface of the rolling bush  170  may be slidably brought into contact with both lateral surfaces of the vane portion  133 , respectively, and a round surface thereof may be slidably brought into contact with a main surface of the bush groove  145 . 
     The drive transmission portion  142  may be formed as a ring-shaped plate shape having an eccentric portion hole  142   a  to be coupled to the eccentric portion  23   a  of the crank shaft  23 . Further, a stepped back pressure groove  142   b  having a predetermined depth and area may be formed to form a back pressure space while at the same time reducing a friction area with a bearing surface of the upper bearing  110 , around the eccentric portion hole  142   a  of the drive transmission portion  142 , namely, on an upper surface of the drive transmission portion  142 . Though not shown in the drawings, the back pressure groove may be formed on a bearing surface  112   c  of the upper bearing  110  in an axial direction. 
     Further, as illustrated in  FIGS. 10 and 11 , an oil passage  142   c  connected to an inner circumferential surface of the bush groove  145  (or an outer circumferential surface of the piston portion  141 ) at the stepped groove  142   b  to guide a portion of the oil to flow into the stepped groove  142   b  or eccentric portion hole  142   a  between the bush groove  145  and the rolling bush  170  may be formed thereon. As a result, a portion of the oil sucked up through the crank shaft  23  and flowing into the stepped groove  142   b  around the eccentric portion hole  142   a  may flow into the bush groove  145  through the oil passage  142   c , and the oil may lubricate between the bush groove  145  and the rolling bush  170  or between the rolling bush  170  and the vane portion  133 , thereby reducing a friction loss between the rolling piston  140  and the rolling bush  170 , as well as the vane portion  133  during the turning movement of the rolling piston  140 . 
     As illustrated in  FIG. 11 , a width (L 2 ) of the oil passage  142   c  may be formed not to be greater than a thickness (L 3 ) of the vane portion  133 . When the width (L 2 ) of the oil passage  142   c  is greater than the thickness (L 3 ) of the vane portion  133 , a kind of surface discontinuity may be generated with respect to the rolling bush  170  during the turning movement of the rolling piston  140 , thereby increasing abrasion or pressure. Accordingly, in order to minimize the surface discontinuity, the width (L 2 ) of the oil passage  142   c  may be formed not to be greater than the thickness (L 3 ) of the vane portion  133 . 
     The oil passage  142   c  may be formed with a groove having a predetermined depth on an upper surface of the drive transmission portion  142 , as illustrated in  FIG. 10 , but may be also formed as a hole that passes through the bush groove  145  on an inner circumferential surface of the eccentric portion hole  142   a . Even in this case, the diameter of the oil passage  142   c  may be formed to be less than the thickness (L 3 ) of the vane portion  133 . 
     On the drawing, unexplained reference numerals  133   d  is sliding surface,  181  and  182  are first and second discharge valves, respectively. 
     Operation of a 1-cylinder, 2-compression chamber type rotary compressor having the foregoing configuration according to embodiments will be described as follows. 
     When power is applied to coil (C) of the motor drive  2  to rotate the rotor  22  along with the crank shaft  23 , the rolling piston  140  coupled to the eccentric portion  23   c  of the crank shaft  23  may be supported by the upper bearing  110  and the lower bearing  120  and at the same time guided by the vane portion  133  to alternately form the first compression space (V 1 ) and the second compression space (V 2 ) while making a turning movement between the outer cylinder portion  131  and the inner cylinder portion  132 . More specifically, when the rolling piston  140  allows the first inlet port  131   b  of the outer cylinder portion  131  to be open, refrigerant may be inhaled into the suction chamber of the first compression space (V 1 ) and compressed while being moved in the direction of the compression chamber of the first compression space (V 1 ) by the turning movement of the rolling piston  140 , as illustrated in  FIGS. 13A and 13B , and the refrigerant allows the first discharge valve  181  to be open and is discharged into an inner space of the discharge cover  150  through the first discharge port  112   a , as illustrated in  FIGS. 13C and 13D . At this time, an upper surface of the vane portion  133  is formed in a stepped manner, but the suction chamber and the compression chamber of the second compression space (V 2 ) may be blocked by the rolling bush  170 , thereby preventing leakage of refrigerant. 
     In contrast, when the rolling piston  140  allows the second inlet port  141   a  to be open, refrigerant is inhaled into the suction chamber of the second compression space (V 2 ) through the first inlet port  131   b  and the second inlet port  141   a  and is compressed while being moved in the direction of the compression chamber of the second compression space (V 2 ) by the rolling piston  140 , as illustrated in  FIGS. 13C and 13D , and the refrigerant allows the second discharge valve  182  to be open and is discharged into the lower chamber  160  through the second discharge port  122   a , and the refrigerant is moved to an inner space of the discharge cover  150  through the discharge passage (F) and exhausted into an inner space of the casing  1 , as illustrated in  FIGS. 13A and 13B , so as to repeat a series of processes. 
     According to a 1-cylinder, 2-compression chamber type rotary compressor having the foregoing configuration in accordance with embodiments, the cylinder  130  may be fixed and the rolling piston  140  may perform a turning movement at an inner side of the cylinder  130 , and thus, it may be possible to obtain a low power loss with respect to the same cooling power and a small bearing area compared to the rotating movement of a relatively heavy and large cylinder, thereby reducing concerns of refrigerant leakage. Further, according to embodiments, the cylinder  130  may be fixed and the rolling piston  140  may make a turning movement whereas the protruded fixing portion  131   a  may be formed at one side on an outer circumferential surface of the outer cylinder portion  131  to form a free space (S) between an inner circumferential surface of the casing  1  and an outer circumferential surface of the cylinder  130 , and thus, a diameter of the cylinder  130  may be increased using the free space (S), thereby easily changing a capacity of the cylinder  130  in an expanded manner. 
     Furthermore, according to embodiments, the first discharge port  112   a  and the second discharge port  122   a  may be formed in opposite directions to each other, and thus, refrigerant being discharged may be absorbed with each other to reduce a pulsation phenomenon, thereby reducing vibration noise of the compressor. 
     In this manner, according to a 1-cylinder, 2-compression chamber type rotary compressor in accordance with embodiments, a cylinder having an outer cylinder portion and an inner cylinder portion may be fixed, and a rolling piston may perform a turning movement at an inner side of the cylinder, and thus, it may be possible to obtain a low power loss with respect to the same cooling power and a small bearing area compared to the rotating movement of a relatively heavy and large cylinder, thereby reducing concerns of refrigerant leakage. Further, the cylinder may be fixed and the rolling piston may make a turning movement whereas the protruded fixing portion may be formed at one side on an outer circumferential surface of the outer cylinder portion to form a free space between an inner circumferential surface of the casing and an outer circumferential surface of the cylinder, and thus, the diameter of the cylinder may be increased using the free space, thereby easily changing the capacity of the cylinder in an expanded manner. 
     Further, the first discharge port, which communicates with the outer compression space, and the second discharge port, which communicates with the inner compression space, may be formed in opposite directions to each other and thus refrigerant being discharged may be absorbed with each other to reduce a pulsation phenomenon, thereby reducing the vibration noise of the compressor. 
     A 1-cylinder, 2-compression chamber type rotary compressor according to another embodiment will be described hereinbelow. According to the previous embodiment, the drive transmission portion  142  of the rolling piston  140  may be integrally formed with the piston portion  141 , but according to this embodiment, the piston portion  141  and the drive transmission portion  142  may be fabricated in a separate manner and then fastened with, for example, a bolt, as illustrated in  FIGS. 14 and 15 . In this case, an outer diameter of the piston portion  141  may be formed to be the same as an outer diameter of the drive transmission portion  142 , and thus, the drive transmission portion  142  may be placed on an upper surface of the piston portion  141  so as to be fastened with, for example, a bolt, but as illustrated in  FIGS. 14 and 15 , a ring-shaped mounting groove  141   b  may be formed in a stepped manner into which the drive transmission portion  142  may be inserted and placed on an upper surface of the piston portion  141 . Reference numerals  141   c  and  142   d  denote a fastening groove and a fastening hole, respectively. Even in this case, the second inlet port  141   a  and bush groove  145  may be formed on the piston portion  141  with the same standard as the previous embodiment. 
     The basic configuration and working effects thereof for a 1-cylinder, 2-compression chamber type rotary compressor having a rolling piston according to embodiments may be substantially the same as the previous embodiments, and thus, detailed description thereof has been omitted. However, according to this embodiment, the piston portion and drive transmission portion of the rolling piston may be separately fabricated and assembled, and thus, fabrication of the rolling piston may be relatively facilitated, as well as friction loss and leakage loss due to machining error may be suppressed, thereby enhancing performance of the compressor. 
     On the other hand, a 1-cylinder, 2-compression chamber type rotary compressor having the foregoing configuration according to still another embodiment will be described hereinbelow. According to this embodiment, the drive transmission portion of the rolling piston may be formed to extend from an upper end of the piston portion, but according to this embodiment, as illustrated in  FIG. 16 , the drive transmission portion  142  of the rolling piston  140  may be formed to extend from a lower end of the piston portion  141 . The basic configuration and working effects thereof according to this embodiment may be substantially the same as the foregoing embodiments. 
     However, according to this embodiment, the drive transmission portion  142  may be formed to extend from a lower end of the piston portion  141 , and thus, a first discharge port  122   d  may be formed on the lower bearing  120 , and a second discharge port  112   d  on the upper bearing  110 , respectively. Further, in this case, when the second discharge port  112   d  is formed in a vertical direction, the second discharge port  112   d  may interfere with an outer circumferential surface of the axle receiving portion  111  of the upper bearing  110  to intrude into part of the outer circumferential surface of the axle receiving portion  111  of the upper bearing  110 , and thus, as illustrated in  FIG. 16 , the second discharge port  112   d  may be formed to be inclined out from the axle receiving portion  111  of the upper bearing  110 . 
     According to a 1-cylinder, 2-compression chamber type rotary compressor having the foregoing embodiment, the drive transmission portion  142  may be formed at a lower end of the piston portion  141 , thereby reducing a friction loss between the rolling piston  140  and the lower bearing  120 . In other words, as illustrated in the previous embodiment, when the drive transmission portion  142  is formed to extend from an upper end of the piston portion  141 , a lower surface of the piston portion  141  may receive an entire weight of the rolling piston  140 , but the lower surface of the piston portion  141  should secure an adequate sealing area and as a result, a stepped groove cannot be formed on a lower surface of the piston portion  141 . 
     Accordingly, in the previous embodiments, it may be difficult to reduce a friction loss between the lower surface of the piston portion  141  and the lower bearing  120 , but as illustrated in the foregoing embodiment, when the drive transmission portion  142  is formed at a lower end of the piston portion  141 , the stepped groove  142   b  may be formed on a lower surface of the drive transmission portion  142 , thereby reducing friction loss while the rolling piston  140  rises by a back pressure of oil that flows into the stepped groove  142   b  without increasing a friction area. 
     Embodiments disclosed herein provide a compressor having a low power loss with respect to the same cooling power and a small bearing area capable of reducing a weight of a rotating body, thereby reducing refrigerant leakage. 
     Embodiments disclosed herein further provide a compressor capable of easily changing a capacity of a cylinder in an expanded manner. 
     Embodiments disclosed herein also provide a compressor in which refrigerant discharged from each compression space is absorbed with each other to reduce a pulsation phenomenon, thereby reducing vibration noise. 
     Embodiments disclosed herein provide a compressor that may include a casing; a crank shaft configured to transmit a rotational force of a motor drive provided within the casing; a plurality of bearing plates configured to support the crank shaft; a cylinder fixed and coupled between the bearing plates to form a compression space; and a rolling piston eccentrically coupled to the crank shaft to divide the compression space into an outer compression space and an inner compression space while making a turning movement with respect to the cylinder. The cylinder may include an outer cylinder portion; an inner cylinder portion separated from an inner side of the outer cylinder portion by a predetermined distance to form a compression space; and a vane portion configured to connect between an inner circumferential surface of the outer cylinder portion and an outer circumferential surface of the inner cylinder portion, to which the rolling piston is slidably inserted and coupled. 
     Further, embodiments disclosed herein provide a compressor that may include a cylinder having an outer cylinder portion and an inner cylinder portion formed in a ring shape with a predetermined distance in a radial direction, and a vane portion that connects between the outer cylinder portion and inner cylinder portion; and a rolling piston having a piston portion slidably coupled to the vane portion between the outer cylinder portion and inner cylinder portion to divide a compression space between the outer cylinder portion and inner cylinder portion into an outer compression space and an inner compression space, and a drive transmission portion extended from the piston portion and eccentrically coupled with respect to an axial center of the crank shaft. A height of the inner cylinder portion may be formed to be less than that of the outer cylinder portion to cover one lateral surface thereof by the drive transmission portion of the rolling piston. 
     Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments. 
     Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.