Abstract:
Disclosed herein is a rotary compressor capable of maintaining the overall dynamic balance and providing low vibration and low noise even at high speed operation and capable of improving efficiency by providing a communication passage to communicate operation chambers, which are provided inside each of the plurality of cylinders for compressing a refrigerant, to each other. The rotary-type compressor includes a housing, a drive motor provided inside the housing to generate power and having a stator and a rotor, and a compression unit that receives power from the drive motor and compresses the refrigerant. The compression unit includes a plurality of cylinders in which an operation chamber to compress the refrigerant is provided. The operation chambers provided in each of the plurality of cylinders are provided to have different volumes, and a balancer provided to maintain dynamic balance is provided only in the lower side of the rotor.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) AND CLAIM OF PRIORITY 
       [0001]    The present application claims priority under 35 U.S.C. §365 to International Patent Application No. PCT/KR2015/009479 filed Sep. 9, 2015, entitled “ROTATING-TYPE COMPRESSOR”. International Application PCT/KR2015/009479 claims priority under 35 U.S.C. §365 to Japanese Patent Application Nos. 2014-253125, and 2015-006936, filed Dec. 15, 2014, and Jan. 16, 2015, respectively in the Japanese Intellectual Property Office; and Korean Patent Application No. 10-2015-0092654 filed in the Korean Intellectual Property Office on Jun. 30, 2015, the entire contents of each are incorporated herein by reference into the present disclosure as if fully set forth herein. 
     
    
     TECHNICAL FIELD 
       [0002]    Embodiments disclosed herein relate to a rotary-type compressor used in an air conditioner or the like. 
       BACKGROUND 
       [0003]    Generally, a compressor is a machine that receives power from an electric motor or a turbine or other power generating device to compress air, refrigerant or various other operating gases to increase the pressure. It is widely used in household appliances such as refrigerators and air conditioners or throughout the industry. 
         [0004]    The compressor includes a reciprocating-type compressor in which a compression space in which a working gas is sucked and discharged between a piston and a cylinder is formed and the piston reciprocates linearly in the cylinder to compress the refrigerant, a rotary-type compressor in which a compression space in which a working gas is sucked and discharged between a rolling piston that rotates eccentrically and a cylinder is formed and the rolling piston eccentrically rotates along the inner wall of the cylinder to compress the refrigerant, and a scroll-type compressor in which a compression space in which a working gas is sucked and discharged between an orbiting scroll and a fixed scroll is formed and the orbiting scroll rotates along the fixed scroll to compress the refrigerant. 
         [0005]    The rotary-type compressor having a plurality of cylinders maintains the static balance by making the displacement volume of the compressor uniform, and maintains the dynamic balance by installing a balancer at the upper and lower portions of the rotor. 
         [0006]    However, there is a problem that a rotary shaft is deformed by the high-speed operation due to the expansion of the operation range of the compressor, and vibration and noise are generated due to the deflection of the rotary shaft. The deflection of the rotary shaft is mainly generated by the balancer provided in the upper side of the rotor. 
       SUMMARY 
       [0007]    It is an aspect of the present disclosure to provide a rotary-type compressor capable of maintaining a dynamic balance as a whole and capable of allowing low vibration and low noise even at high speed operation. 
         [0008]    It is another aspect of the present disclosure to provide a rotary-type compressor including a communication passage to communicate operation chambers, which are provided inside each of the plurality of cylinders for compressing a refrigerant, with each other to improve efficiency. 
         [0009]    In accordance with an aspect of the present disclosure, a rotary-type compressor includes a housing, a drive motor provided inside the housing to generate power, and provided with a stator and a rotor and a compression unit to receive power from the drive motor to compress the refrigerant, the compression unit having a plurality of cylinders, each of which is provided with an operation chamber to compress the refrigerant therein. The operation chambers provided in each of the plurality of cylinders are configured to have different volumes, and a balancer to maintain dynamic balance is provided only in the lower side of the rotor. 
         [0010]    The drive motor may include a rotary shaft to transmit rotation force of the rotor to the compression unit, and the cylinder may include a first cylinder provided in the lower side of the drive motor in the axial direction of the rotary shaft and a second cylinder provided between the drive motor and the first cylinder. 
         [0011]    The volume of the operation chamber provided in the first cylinder may be larger than the volume of the operation chamber provided in the second cylinder. 
         [0012]    The rotary shaft may include a shaft body to which the rotor is fixed, a first eccentric shaft disposed in the first cylinder so as to be eccentric from a central axis of the shaft body, and a second eccentric shaft disposed in the second cylinder to be eccentric with a phase difference of 180 degrees with the first eccentric shaft in the circumferential direction of the rotary shaft. 
         [0013]    The compression unit may include a first piston inserted into the first eccentric shaft to rotate together with the rotary shaft, and a second piston inserted into the second eccentric shaft to rotate together with the rotary shaft. 
         [0014]    If a mass obtained by adding a mass of the first eccentric shaft to a mass of the first piston is defined by m1, an eccentricity amount of the first eccentric shaft is defined by r1, and a distance from the lower end of the rotary shaft to the central axis of the first eccentric shaft is defined by L1, and if a mass obtained by adding a mass of the second eccentric shaft to a mass of the second piston is defined by m2, an eccentricity amount of the second eccentric shaft is defined by r2, and a distance from the lower end of the rotary shaft to the central axis of the second eccentric shaft is defined by L2, and if a mass of the balancer is defined by m3, a distance between the center of the balancer and the central axis of the rotary shaft is defined by r3, and a distance from the lower end of the rotary shaft to the center of the balancer is defined by L3, the following expression may be satisfied. 
         [0000]      ( m 2× r 2× L 2− m 1× r 1× L 1)× m 1× r 1× L 1/( m 2× r 2× L 2)≦ m 3× r 3× L 3≦ m 2× r 2× L 2− m 1× r 1× L 1
 
         [0015]    The first cylinder and the second cylinder may be each provided with a suction passage through which the refrigerant is sucked from the outside of the first cylinder and the second cylinder to the inside thereof, and a suction pipe to guide the refrigerant is inserted into the suction passage. 
         [0016]    The suction passage may include a first suction passage provided in the first cylinder and a second suction passage provided in the second cylinder, and a communication passage communicating the first suction passage with the second suction passage may be provided between the first suction passage and the second suction passage. 
         [0017]    The communication passage may communicate the first suction passage with the second suction passage in the downstream of the suction pipe. 
         [0018]    The operation chamber may include a first operation chamber provided in the first cylinder and a second operation chamber provided in the second cylinder, wherein the first operation chamber and the second operation chamber may communicate with each other through the first suction passage, the communication passage, and the second suction passage. 
         [0019]    when the volume change and the suction flow rate of a first suction chamber provided in the first operation chamber are large, a large amount of refrigerant maybe sucked through the first suction passage than the second suction passage, and when the volume change and the suction flow rate of a second suction chamber provided in the second operation chamber are large, a large amount of refrigerant may be sucked through the second suction passage than the first suction passage. 
         [0020]    If a cross-sectional area of the suction pipe is defined by S (mm2), an displacement volume of the operation chamber is defined by V (cm3), an rotation speed of the drive motor is defined by N (rps), and if an evaluation value H is defined by a formula H=(V/S)×N, the evaluation value H may be in the range of 0.5≦H≦12. 
         [0021]    The cross-sectional S (mm2) of the suction pipe may be set to a value obtained by the formula S=V×Nr/3.5 when a rated rotation speed of the drive motor is Nr (rps). 
         [0022]    In accordance with another aspect of the present disclosure, a rotary-type compressor includes a housing, a drive motor provided inside the housing to generate power, and provided with a stator and a rotor and a compression unit that receives power from the drive motor and compresses the refrigerant. The compression unit includes a first cylinder provided under the drive motor and having a first operation chamber to compress the refrigerant therein, a second cylinder provided between the drive motor and the first cylinder and having a second operation chamber to compress the refrigerant therein, a first suction passage provided so that the refrigerant is sucked from the outside of the first cylinder to the first operation chamber, a second suction passage provided so that the refrigerant is sucked from the outside of the second cylinder to the second operation chamber and a communication passage communicating the first suction passage with the second suction passage. 
         [0023]    The communication passage may include a first through hole provided in the first cylinder, a second through hole provided in the second cylinder, and a through hole communicating the first through hole and the second through hole. 
         [0024]    The first operation chamber and the second operation chamber may communicate with each other through the first suction passage, the communication passage, and the second suction passage. 
         [0025]    In accordance with another aspect of the present disclosure, a rotary-type compressor includes a housing, a drive motor provided inside the housing to generate power, and provided with a stator and a rotor and a compression unit that receives power from the drive motor and compresses the refrigerant. The compression unit includes a plurality of cylinders having operation chambers to compress the refrigerant, a plurality of suction passages provided in each of the plurality of cylinders to suck the refrigerant from the outside of the plurality of cylinders into the operation chambers and a plurality of suction pipes inserted into the plurality of suction passages to induce suction of the refrigerant. If a cross-sectional area of the suction pipe is defined by S (mm2), a displacement volume of the operation chamber is defined by V (cm3), a rotation speed of the drive motor is defined by N (rps), and if an evaluation value H is defined by a formula H=(V/S)×N, the evaluation value H is in the range of 0.5≦H≦12. 
         [0026]    In accordance with one aspect of the present disclosure, it may be possible to maintain the overall dynamic balance and to achieve low vibration and low noise even at high speed operation. 
         [0027]    In addition, the friction loss can be reduced by reducing the deflection of the rotating shaft and thus the efficiency can be improved. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]    For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts: 
           [0029]      FIG. 1  is an axial cross-sectional view of a rotary-type compressor according to an embodiment of the present disclosure. 
           [0030]      FIG. 2  is a cross-sectional view taken along line II-II of  FIG. 1 . 
           [0031]      FIG. 3  is a view for explaining a balance according to an embodiment of the present disclosure. 
           [0032]      FIG. 4  is a graph showing the relationship between the dynamic balance and the amount of deflection at point A in  FIG. 3  during high-speed operation according to an embodiment of the present disclosure. 
           [0033]      FIG. 5A  is a view showing a state in which refrigerant gas is sucked into a first suction chamber according to an embodiment of the present disclosure. 
           [0034]      FIG. 5B  is a view showing a state in which refrigerant gas is sucked into a second suction chamber according to an embodiment of the present disclosure. 
           [0035]      FIG. 6  is a graph showing the relationship between the evaluation value H and the efficiency improvement ratio according to an embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0036]    Hereinafter, exemplary embodiments according to the present disclosure will be described in detail with reference to the accompanying drawings. 
         [0037]      FIG. 1  is an axial cross-sectional view of a rotary-type compressor according to an embodiment of the present disclosure.  FIG. 2  is a cross-sectional view taken along line II-II of  FIG. 1 . 
         [0038]    A rotary-type compressor  1  is a compressor used in a refrigerant circuit such as an air conditioner. 
         [0039]    The rotary-type compressor  1  includes a compression unit  10  for compressing a refrigerant, a drive motor  20  for driving the compression unit  10  and a housing  30  for accommodating the compression unit  10  and the drive motor  20 . The rotary-type compressor  1  according to the present embodiment is a vertical-type compressor in which the axial direction of the rotary shaft  23 , which will be described later, of the drive motor  20  is arranged in the gravity direction. 
         [0040]    Hereinafter, the axial direction of the rotary shaft  23  will be referred to as “vertical direction”, and the upper side may be referred to as “upper side” and the lower side may be referred to as “lower side” with reference to  FIG. 1 . 
         [0041]    First, the drive motor  20  will be described. 
         [0042]    The drive motor  20  is fixed to the housing  30  above the compression unit  10 . 
         [0043]    The drive motor  20  includes a stator  21 , a rotor  22  and a rotary shaft  23  supporting the rotor  22  and rotating with respect to the housing  30 . 
         [0044]    The stator  21  has a stator main body  211  and a coil  212  wound on the stator main body  211 . 
         [0045]    The stator main body  211  is a laminated body in which a plurality of electromagnetic steel plates is stacked, and the approximate shape of the stator main body  211  is a cylindrical shape. 
         [0046]    A diameter of an outer circumferential surface of the stator main body  211  is formed to be larger than a diameter of an inner circumferential surface of a central housing  31  of the housing  30 , and the stator main body  211  is fitted in the central housing  31  in an interference fit. As a method of fitting the stator main body  211  into the central housing  31 , a shrinkage fit or a press fit may be exemplified. 
         [0047]    The stator main body  211  has a plurality of teeth (not shown) in the circumferential direction at a portion on the inner side facing the outer periphery of the rotor  22 . The coil  212  is disposed in a notch (not shown) between adjacent tooth. 
         [0048]    The rotor  22  is a laminated body in which a plurality of ring-shaped electromagnetic steel plates is stacked, and is generally cylindrical shape. A diameter of an inner peripheral surface of the rotor  22  is formed to be smaller than a diameter of an outer peripheral surface of the rotary shaft  23 , and the rotor  22  is fitted in the rotary shaft  23  in an interference fit. As a method of fitting the rotary shaft  23  into the rotor  22 , a press fitting can be exemplified. The rotor  22  is fixed to the rotary shaft  23  and rotates together with the rotary shaft  23 . A diameter of an outer circumferential surface of the rotor  22  is smaller than a diameter of an inner circumferential surface of the stator main body  211  of the stator  21 , and a clearance is formed between the rotor  22  and the stator  21 . 
         [0049]    The rotor  22  has a compression unit side balancer  221  on the surface facing the compressing unit  10  in the axial direction. 
         [0050]    The rotary shaft  23  has a shaft main body  230  to which the rotor  22  is fitted and a first eccentric shaft  231  and a second eccentric shaft  232  which are provided at a lower portion of the shaft body  230 , the first eccentric shaft  231  and the second eccentric shaft  232  each has an axis eccentric from the shaft central axis of the shaft body  230 . The first eccentric shaft  231  is disposed so as to have a phase difference of 180 degrees with the second eccentric shaft  232  in the circumferential direction of the rotary shaft  23 . 
         [0051]    The shaft main body  230  is rotatably supported by a main bearing  140  which will be described later and a lower end portion of the shaft main body  230  is rotatably supported by a sub bearing  150  which will be described later. 
         [0052]    Next, the housing  30  will be described. 
         [0053]    The housing  30  has a cylindrical central housing  31  arranged at the center in the vertical direction, an upper housing  32  for covering the upper opening of the central housing  31  and a lower housing  33  for covering the lower opening of the central housing  31 . 
         [0054]    The housing  30  includes a discharge unit  34  for discharging a high-pressure refrigerant gas compressed by the compression unit  10  to an outside of the housing  30 , and a suction unit  35  for sucking the refrigerant gas from the outside of the housing  30 . 
         [0055]    The stator  21  of the drive motor  20  and the main bearing  140  are fixed to the central housing  31 . The suction unit  35  is formed by inserting a first suction pipe  36  and a second suction pipe  37 , which will be described later, into a through hole formed in the central housing  31 . 
         [0056]    The upper housing  32  is formed in a convex bowl shape. 
         [0057]    The discharge unit  34  is formed by inserting a tube into a through hole formed in the top portion of the upper housing  32 . 
         [0058]    The lower housing  33  is formed in a concave bowl shape. 
         [0059]    The upper housing  32  and the lower housing  33  are fixed to the central housing  31 . 
         [0060]    Next, the compression unit  10  will be described. 
         [0061]    The compression unit  10  includes a first cylinder  110 , a second cylinder  120 , and a disk-shaped partition  130  partitioning the first cylinder  110  and the second cylinder  120  each other. 
         [0062]    The compression unit  10  includes the main bearing  140  disposed above the second cylinder  120  to cover the second cylinder  120  and rotatably supporting the rotation shaft  23 . 
         [0063]    The compression unit  10  includes the sub bearing  150  disposed below the first cylinder  110  to cover the first cylinder  110  and rotatably supporting the rotation shaft  23 . The main bearing  140  is fixed to the central housing  31  of the housing  30  by welding or the like. The sub bearing  150  is fixed to the main bearing  140  by a fastening member such as a bolt. 
         [0064]    The compression unit  10  includes a first cover  161  which forms a first discharge chamber  161   a  together with the sub bearing  150  and a second cover  162  which forms a second discharge chamber  162   a  together with the main bearing  140 . 
         [0065]    The compression unit  10  includes a first operation chamber  11  formed by the first cylinder  110 , the partition  130  and the sub bearing  150 , and a second operation chamber  12  formed by the second cylinder  120 , the partition  130  and the main bearing  140 . 
         [0066]    The compression unit  10  is provided with a first piston  111  which is fitted in the first eccentric shaft  231  of the rotary shaft  23  and rotates together with the rotary shaft  23  in the first operation chamber  11 , and a first vane  112  (see  FIG. 2 ) elastically supported by a spring so as to be in constant contact with the first piston  111 . 
         [0067]    The first operation chamber  11  is partitioned into a first suction chamber  11   a  (see  FIG. 2 ) and a first compression chamber  11   b  (see  FIG. 2 ) by the first piston  111  and the first vane  112 . 
         [0068]    The compression unit  10  is provided with a second piston  121  which is fitted in the second eccentric shaft  232  of the rotary shaft  23  and rotates together with the rotary shaft  23  in the second operation chamber  12  and a second vane (not shown) elastically supported by a spring so as to be in constant contact with the second piston  121 . The second operation chamber  12  is partitioned into a second suction chamber  12   a  (see  FIG. 5B ) and a second compression chamber (not shown) by the second piston  121  and the second vane (not shown), similar to the first operation chamber  11 . 
         [0069]    The first cylinder  110  is formed with a first suction passage  113  which penetrates the first cylinder  110  in the direction (radial direction) perpendicular to the axial direction of the rotary shaft  23  so as to communicate the first suction chamber  11   a  with the outside of the first cylinder  110 . The first cylinder  110  is formed with a first discharge gas passage  114  penetrating the first cylinder  110  in the axial direction of the rotary shaft  23  outside the first operation chamber  11 . 
         [0070]    The second cylinder  120  is formed with a second suction passage  123  which penetrates the second cylinder  120  in the direction (radial direction) perpendicular to the axial direction of the rotary shaft  23  so as to communicate the second suction chamber  12   a  with the outside of the second cylinder  120 . The second cylinder  120  is formed with a second discharge gas passage  124  penetrating the second cylinder  120  in the axial direction of the rotary shaft  23  outside the second operation chamber  12 . 
         [0071]    The compression unit  10  has a first suction pipe  36  having one end inserted into the first suction passage  113  and the other end connected to an accumulator, and a second suction pipe  37  having one end inserted into the second suction passage  123  and the other end connected to the accumulator. 
         [0072]    The compression unit  10  according to the present embodiment has a communication passage  135  to communicate the first suction passage  113  with the second suction passage  123 . 
         [0073]    The communication passage  135  has an axial partitioning through hole  131  formed in the partition  130 , a first through hole  115  formed in the first cylinder  110  to communicate the first suction passage  113  with the through hole  131 , and a second through hole  125  formed in the second cylinder  120  to communicate the second suction passage  123  with the through hole  131 . 
         [0074]    In the compression unit  10  according to the present embodiment, the displacement volume V2 of the second operation chamber  12  of the second cylinder  120  close to the motor  20  in the axial direction is larger than the displacement volume V1 of the first operation chamber  11  of the first cylinder  110  far from the motor  20 . 
         [0075]    The displacement volume V1 of the first operation chamber  11  is approximately the volume of the space surrounded by an inner peripheral surface of the first cylinder  110  and an outer peripheral surface of the first piston  111 . The displacement volume V2 of the second operation chamber  12  is approximately the volume of the space surrounded by an inner peripheral surface of the second cylinder  120  and an outer peripheral surface of the second piston  121 . 
         [0076]    In order to make the displacement volume V2 of the second operation chamber  12  larger than the displacement volume V1 of the first operation chamber  11 , in the compression unit  10  according to the present embodiment, as shown in  FIG. 1 , a cross-sectional area of the first operation chamber  11  and a cross-sectional area of the second operation chamber  12  in the direction perpendicular to the axial direction, are the same and a size of the first operation chamber  11  and a size of the second operation chamber  12  are different from each other in the axial direction. That is, a length (thickness) in the axial direction of the second cylinder  120  and the second piston  121  is larger than a length (thickness) in the axial direction of the first cylinder  110  and the second piston  121 . 
         [0077]    Therefore, a balancer is not provided on a surface opposite to the surface facing the compression unit  10  of the rotor  22 , which is a major cause of the deflection of the rotary shaft  23 , thereby realizing low vibration and low noise. 
         [0078]    The mass of the compression unit side balancer  221  of the rotary-type compressor  1  configured as described above according to this embodiment is set as follows. 
         [0079]      FIG. 3  is a view for explaining the balancer. 
         [0080]    A mass obtained by adding a mass of the first eccentric shaft  231  to a mass of the first piston  111  is defined by m1, an eccentricity amount of the first eccentric shaft  231  is defined by r1, and a distance from a distal end  23   a  of the rotary shaft  23  to the central axis of the first eccentric shaft  231  is defined by L1. A mass obtained by adding a mass of the second eccentric shaft  232  to a mass of the second piston  121  is defined by m2, an eccentricity amount of the second eccentric shaft  232  is defined by r2, and a distance from the distal end  23   a  of the rotary shaft  23  to the central axis of the second eccentric shaft  232  is defined by L2. a mass of the compression unit side balancer  221  is defined by m3, a distance between the center of the compression unit side balancer  221  and the central axis of the rotary shaft  23  is defined by r3, and a distance from the distal end  23   a  of the rotary shaft  23  to the center of the compression unit side balancer  221  is defined by L3, the following formula is satisfied. 
         [0081]    In this case, a dynamic balance of the rotary-type compressor  1  according to a second embodiment is expressed by the following equation (1). 
         [0000]        m 2× r 2× L 2− m 1× r 1× L 1= m 3× r 3× L 3  (1)
 
         [0082]    Even if the mass or the like of the compression unit side balancer  221  is set so that the dynamic balance is balanced, the axis of the rotor  22  is displaced due to slight deflection of the rotary shaft  23  due to manufacturing variation or the like, and thus the dynamic balance may become unbalanced. 
         [0083]    Therefore, it is needed to minimize the deflection of the rotary shaft  23  particularly during high-speed operation. 
         [0084]      FIG. 4  is a graph showing the relationship between the dynamic balance and the amount of deflection at a point A in  FIG. 3  during high-speed operation. 
         [0085]    The point A in  FIG. 3  is an end portion of the rotor  22  opposite to the compression unit  10  in the axial direction, and is the outermost portion in the rotation radial direction. In  FIG. 4 , when the right side of the central axis of the rotary shaft  23  in  FIG. 3  is positive and the left side of the central axis of the rotary shaft  23  is negative, the vertical axis represents the amount of deflection of the rotary shaft  23  at the point A, and the horizontal axis represents dynamic balance. 
         [0086]    As shown in  FIG. 4 , as the dynamic balance shifts toward the positive side from zero, that is when the equation (1) is satisfied (a point B shown in  FIG. 4 ), the amount of deflection of the point A gradually decreases and becomes zero. Further, as the dynamic balance shifts toward the positive side than the point at which the amount of deflection of the point A becomes zero, the amount of deflection of the point A gradually increases. 
         [0087]    Because the amount of deflection of the rotary shaft  23  becomes larger as the values of m2×r2×L2 and m1×r1×L1 become larger, it can be seen that the amount of deflection of the rotary shaft  23  is reduced by setting the mass of the compression unit side balancer  221  to the value of the equation (2), which is obtained by dividing the left side of the expression (3) by the values of m2×r2×L2 and m1×r1×L1. 
         [0000]        m 3× r 3× L 3=( m 2× r 2× L 2− m 1× r 1× L 1)× m 1× r 1× L 1/( m 2× r 2× L 2)  (2)
 
         [0088]    The amount of deflection of the rotary shaft  23  when the mass of the compression unit side balancer  221  satisfies the equation (2) is a point C shown in  FIG. 4 . 
         [0089]    In view of the above, in the rotary-type compressor  1  according to the present embodiment, the mass of the compression unit side balancer  221  is set to satisfy the following expression (3). 
         [0000]      ( m 2× r 2× L 2− m 1× r 1× L 1)× m 1× r 1× L 1/( m 2× r 2× L 2)
 
         [0000]      ≦ m 3× r 3× L 3≦ m 2× r 2× L 2− m 1× r 1× L 1  (3)
 
         [0090]    In the rotary-type compressor  1  according to the present embodiment configured as described above, the balancer in the upper side of the rotor  22  which is a major cause of the deflection of the rotary shaft  23  is removed and the displacement volume of the respective compression chambers is formed to be unbalanced so as to balance the overall dynamic balance and realize the low vibration and the low noise during the high-speed operation. Further, the deflection of the rotary shaft  23  is reduced, and the friction loss can be reduced, so that the efficiency can be improved. 
         [0091]    The rotary-type compressor  1  configured as above operates as follows. 
         [0092]    When the rotary shaft  23  is driven by the drive motor  20 , the first piston  111  and the second piston  121  rotate at a phase difference of 180 degrees with respect to each other as the first eccentric shaft  231  and the second eccentric shaft  232  rotate. By the eccentric rotation of the first piston  111  and the second piston  121 , the first suction chamber  11   a  and the second suction chamber  12   a  and the first compression chamber  11   b  and the second compression chamber (not shown) in the first operation chamber  11  and the second operation chamber  12  are repeatedly reduced and expanded. 
         [0093]    When the first suction chamber  11   a  and the second suction chamber  12   a  are expanded, the refrigerant gas supplied from the refrigeration cycle through the first suction pipe  36  and the second suction pipe  37  is sucked through the first suction passage  113  and the second suction passage  123 . The suction operation will be described later in detail. 
         [0094]    The refrigerant gas sucked into the first suction chamber  11   a  is compressed by reducing the first compression chamber  11   b  and the refrigerant gas is discharged to the first discharge chamber  161   a  when the pressure becomes a predetermined discharge pressure. The refrigerant gas sucked into the second suction chamber  12   a  is compressed by reducing the second compression chamber (not shown), and the refrigerant gas is discharged to the second discharge chamber  162   a  when the pressure becomes a predetermined discharge pressure. 
         [0095]    The refrigerant gas is alternately compressed by the first and second operation chambers  11  and  12  and discharged into the housing  30  through the first discharge chamber  161   a  and the second discharge chamber  162   a . The refrigerant gas discharged to the housing  30  is discharged to the refrigeration cycle through the discharge unit  34 . 
         [0096]    The suction operation will be described in detail. 
         [0097]      FIG. 5A  is a view showing a state in which the refrigerant gas is sucked into the first suction chamber  11   a , and  FIG. 5B  is a view showing a state in which the refrigerant gas is sucked into the second suction chamber  12   a.    
         [0098]    In the rotary-type compressor  1  according to the present embodiment, the first suction chamber  11   a  and the second suction chamber  12   a  communicate with each other through the first suction passage  113 , the communication passage  135  and the second suction passage  123 . The first suction chamber  11   a  communicates with the second suction pipe  37  through the first suction passage  113 , the communication passage  135  and the second suction passage  123 . The second suction chamber  12   a  communicates with the first suction pipe  36  through the second suction passage  123 , the communication passage  135  and the first suction passage  113 . 
         [0099]    According to this configuration, when the volume change of the first suction chamber  11   a  is large and the suction flow rate is large, the refrigerant gas mainly flows from the first suction pipe  36  to the first suction chamber  11   a  through the first suction passage  113 . When the volume change of the first suction chamber  11   a  is large and the suction flow rate is large, the refrigerant gas is also sucked into the first suction chamber  11   a  from the second suction pipe  37  through the second suction passage  123 , the communication passage  135  and the first suction passage  113  (See  FIG. 5A ). 
         [0100]    At this time, the volume change of the second suction chamber  12   a  is small because the phase is shifted by 180 degrees, and the suction flow rate of the second suction chamber  12   a  is small. 
         [0101]    When the volume change of the second suction chamber  12   a  is large and the suction flow rate is large, the refrigerant gas mainly flows from the second suction pipe  37  to the second suction chamber  12   a  through the second suction passage  123 . When the volume change of the second suction chamber  12   a  is large and the suction flow rate is large, the refrigerant gas is also sucked into the second suction chamber  12   a  from the first suction pipe  36  through the first suction passage  113 , the communication passage  135  and the second suction passage  123  (See  FIG. 5B ). 
         [0102]    At this time, the volume change of the first suction chamber  11   a  is small because the phase is shifted by 180 degrees, and the suction flow rate of the first suction chamber  11   a  is small. 
         [0103]    In the rotary-type compressor  1  according to the present embodiment, the phase of the maximum value of the suction flow rate of the first suction chamber  11   a  and the phase of the maximum value of the suction flow rate of the second suction chamber  12   a  are 180 degrees shifted from each other although the volume change is large and the change in the suction flow rate during a single rotation is large. 
         [0104]    In the rotary-type compressor  1  according to the present embodiment, the first suction passage  113  connected to the first suction chamber  11   a  and the second suction passage  123  connected to the second suction chamber  12   a  communicate with each other through the communication passage  135 . Therefore, one of the first suction chamber  11   a  and the second suction chamber can suck the refrigerant gas from both the first suction pipe  36  and the second suction pipe  37 , and the suction loss due to the flow resistance in the first suction pipe  36  and the second suction pipe  37  is reduced. 
         [0105]    However, a pressure pulsation occurs in the first suction passage  113  and the second suction passage  123  due to the volume change of the first suction chamber  11   a  and the second suction chamber  12   a . Therefore, if there is a communication passage  135  for communicating the first suction passage  113  with the second suction passage  123 , one of the first suction chamber  11   a  and the second suction chamber  12   a  may be influenced by the pressure pulsation of the other suction chamber, and the suction may become unstable or the suction flow rate may be lowered. As a result, the efficiency may be lowered. 
         [0106]    Taking these points into account, it is possible to define an evaluation value H by the following expression (4) and the specification of the rotary-type compressor  1  may be set based on the evaluation value H. 
         [0000]        H =( V/S )× N   (4)
 
         [0107]    S is a cross-sectional area (mm2) (see  FIG. 5A ) of the first suction pipe  36  and the second suction pipe  37 , and N is a rotation per second (rps) of the drive motor  20 . V is the displacement volume (cm3) of each operation chamber of the compression unit  10 . In the present embodiment, although the displacement volume V2 of the second operation chamber  12  is larger than the displacement volume V1 of the first operation chamber  11 , in the expression (4), the displacement volume V1 of the first operation chamber  11  and the displacement volume V2 of the second operation chamber  12  are equal to each other. 
         [0108]      FIG. 6  is a graph showing the relationship between the evaluation value H and the efficiency improvement ratio (%). 
         [0109]    As shown in  FIG. 6 , it is derived that the efficiency of the rotary-type compressor  1  is improved (100% or more) when the range of the evaluation value H is 0.5≦H≦12. 
         [0110]    When the evaluation value H is less than 0.5 (for example, when the N is small), since the suction loss is small in the suction of the refrigerant gas, the efficiency improvement effect is small even if the communication passage  135  is provided. 
         [0111]    Meanwhile, when the evaluation value H is larger than 12 (for example, the N is large), the switching of the flow direction of the refrigerant gas flowing through the communication passage  135  is not performed smoothly even if the communication passage  135  is provided, and thus the effect of reducing the suction loss is reduced and the efficiency improvement effect is small. 
         [0112]    Therefore, the rotary-type compressor  1  according to the present embodiment is set such that the range of the evaluation value H is 0.5≦H≦12. 
         [0113]    The low-speed rotation speed Nmin (rps), the high-speed rotation speed Nmax (rps), and the cylinder volume (displacement volume) V (cm3) of each cylinder (operation chamber) of the compression unit  10  are determined in accordance with the specification of the rotary-type compressor  1 . Therefore, the cross-sectional area S (mm2) of the first suction pipe  36  and the second suction pipe  37  is set so that the following expression (5) is satisfied. 
         [0000]      ( V ×min)/0.5≦ S ≦( V ×max)/12  (5)
 
         [0114]    For example, when the rated rotation speed of the rotary-type compressor  1  is Nr (rps), the cross-sectional area S (mm2) of the first suction pipe  36  and the second suction pipe  37  may be set (S=V×Nr/3.5) so that the evaluation value H is 3.5 where the efficiency improvement rate is maximized shown in  FIG. 6 . 
         [0115]    In the rotary-type compressor  1  according to the present embodiment, the evaluation values H1 and H2 are set to the following equations (6) and (7), and the ranges of the evaluation values H1 and H2 are set to satisfy 0.5≦H1≦12 and 0.5≦H2≦12. 
         [0000]        H 1=( V 1/ S )× N   (6)
 
         [0000]        H 2=( V 2/ S )× N   (7)
 
         [0116]    The low-speed rotation speed Nmin (rps), the high-speed rotation speed Nmax (rps), and the displacement volume V1, and V2 (cm3) of each cylinder (operation chamber) of the compression unit  10  are determined in accordance with the specification of the rotary-type compressor  1  according to the present embodiment. Therefore, the cross-sectional area S (mm2) of the first suction pipe  36  and the second suction pipe  37  is set so that the following expressions (8), and (9) are satisfied. 
         [0000]      ( V 1× N min)/0.5≦ S ≦( V 1× N max)/12  (8)
 
         [0000]      ( V 2× N min)/0.5≦ S ≦( V 2× N max)/12  (9)
 
         [0117]    For example, when the rated rotation speed of the rotary-type compressor  1  is Nr (rps), the cross-sectional area S (mm2) of the first suction pipe  36  and the second suction pipe  37  may be set (S=V1×Nr/3.5 or S=V2×Nr/3.5, or V2×Nr/3.5≦S≦V1×Nr/3.5) so that the evaluation value H is 3.5 where the efficiency improvement rate is maximized shown in  FIG. 6 . 
         [0118]    The rotary-type compressor  1  configured as described above has the communication passage  135  that communicates the first suction passage  113  with the second suction passage  123 , and the range of the evaluation value H determined from the equation (4) is set so as to satisfy 0.5≦H≦12, so that the efficiency is high. In other words, the efficiency of the rotary-type compressor  1  can be increased by setting the range of the evaluation value H to satisfy 0.5≦H≦12 and forming the communication passage  135  communicating with the first suction pipe  36  and the second suction pipe  37 . 
         [0119]    When the displacement volume V2 of the compression unit  10  is larger than the displacement volume V1, there is a possibility that the suction loss of the first suction chamber  11   a  with a small volume change becomes large. However the rotary-type compressor  1  according to the second embodiment includes the communication passage  135  communicating with the first suction pipe  36  and the second suction pipe  37  and the range of the evaluation value H is set so as to satisfy 0.5≦H≦12, thereby increasing the efficiency. 
         [0120]    Although a few embodiments of the present disclosure have been shown and described, it would be appreciated by those skilled in the art that various changes may be made in these embodiments without departing from the spirit and scope of the disclosure as defined in the claims.