Patent Publication Number: US-9890786-B2

Title: Rotary compressor having vane that has diamond-like carbon layer

Description:
CROSS-REFERENCE 
     This application is the U.S. National Phase under 35 U.S.C. § 371 of International Application No. PCT/JP2014/051981, filed Jan. 29, 2014, which claims the benefit of Japanese Application No. 2013-205825, filed Sep. 30, 2013, the entire contents of each are hereby incorporated by reference. 
     TECHNICAL FIELD 
     The present invention relates to a rotary compressor that is used in an air conditioner or a refrigerating machine. 
     BACKGROUND ART 
     In the related art, a compressor (rotary compressor) which is provided in a refrigeration cycle and compresses and circulates a fluorocarbon refrigerant which does not contain chlorine is disclosed, in which, of sliding members which configure a compressing mechanism, a base member of a blade (vane) is made of a ferrous metal, a chromium nitride layer is formed on a surface of the base member, an iron nitride layer which contains chromium nitride is formed as a joint layer between the base member and the chromium nitride layer, and a roller (annular piston) as a counterpart member is formed of Ni—Cr—Mo cast iron (for example, see PTL 1). 
     CITATION LIST 
     Patent Literature 
     PTL 1: JP-A-7-217568 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, when an air conditioner using the rotary compressor in the related art described above is used as a heater at a low outside temperature, the air conditioner is operated under operation conditions of low inlet pressure of a refrigerant, a high compression ratio, and a high discharge temperature. In a case where the rotary compressor is operated with a discharge temperature above 115° C., a problem arises in that abnormal wear of the annular piston made of the Ni—Cr—Mo cast iron occurs. 
     The present invention is performed by taking the above problems into account and has an object to achieve a rotary compressor in which abnormal wear of the annular piston does not occur even in a case where a refrigerant discharge temperature of the rotary compressor exceeds 115° C. during operation. 
     Solution to Problem 
     In order to solve the above problems and to achieve the object, a rotary compressor of the present invention includes a compressor housing, a compressing unit, and a motor. The compressor housing is a vertically-positioned airtight compressor housing having an upper section in which a discharge portion of a refrigerant is provided and a lower section in which an inlet unit of the refrigerant is provided on a side surface thereof. The compressing unit is disposed in the lower section of the compressor housing and includes an annular cylinder, an end plate which has a bearing unit and a discharge valve unit and closes an end portion of the cylinder, an annular piston which is fit in an eccentric portion of a rotation shaft supported in the bearing unit, performs an orbital motion inside the cylinder along a cylinder inner wall of the cylinder, and forms an operation chamber together with the cylinder inner wall, and a vane which protrudes from the inside of a vane groove of the cylinder to the inside of the operation chamber, comes into contact with the annular piston, and partitions the operation chamber into an inlet chamber and a compression chamber and the compressing unit performs suction of the refrigerant via the inlet unit and discharges the refrigerant from the discharge portion via the inside of the compressor housing. The motor is disposed in the upper section of the compressor housing and drives the compressing unit via the rotation shaft. Further, the vane is formed of steel and has a diamond-like carbon layer formed on a sliding surface with respect to the annular piston. The annular piston is formed of Ni—Cr—Mo cast iron to which 0.15 wt % to 0.45 wt % of phosphorus is added or the annular piston is formed of cast iron or steel and has an iron nitride layer formed on an outer circumferential surface thereof. 
     Advantageous Effects of Invention 
     According to the present invention, the effect that abnormal wear of the annular piston does not occur even in a case where a refrigerant discharge temperature of a rotary compressor exceeds 115° C. during operation is achieved. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a vertical cross-sectional view illustrating an example of a rotary compressor according to the present invention. 
         FIG. 2  is a horizontal cross-sectional view of first and second compressing units according to the example when viewed from above. 
         FIG. 3  is a partial cross-sectional view illustrating a sliding portion of first and second annular pistons and first and second vanes of Example 1. 
         FIG. 4  is a partial cross-sectional view illustrating a sliding portion of first and second annular pistons and first and second vanes of Example 2. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, an example of a rotary compressor according to the present invention will be described in detail based on the drawings. The invention is not limited to the example. 
     Example 1 
       FIG. 1  is a vertical cross-sectional view illustrating an example of a rotary compressor according to the present invention.  FIG. 2  is a horizontal cross-sectional view of first and second compressing units according to the example when viewed from above. 
     As illustrated in  FIG. 1 , a rotary compressor  1  of the example includes a compressing unit  12  that is disposed in the lower section of a vertically-positioned airtight compressor housing  10  which has a cylindrical shape and a motor  11  that is disposed in the upper section of the compressor housing  10  and drives the compressing unit  12  via a rotation shaft  15 . 
     A stator  111  of the motor  11  is formed in a cylindrical shape and is shrink-fitted and fixed in the inner circumferential surface of the compressor housing  10 . A rotor  112  of the motor  11  is disposed inside the cylindrical stator  111  and is shrink-fitted and fixed to the rotation shaft  15  that mechanically connects the motor  11  with the compressing unit  12 . 
     The compressing unit  12  includes a first compressing unit  12 S and a second compressing unit  12 T that is disposed in parallel with the first compressing unit  12 S and is stacked on the first compressing unit  12 S. As illustrated in  FIG. 2 , the first and second compressing units  12 S and  12 T include annular first and second cylinders  121 S and  121 T in which first and second inlet holes  135 S and  135 T that are radially disposed and first and second vane grooves  128 S and  128 T are provided in first and second side-flared portions  122 S and  122 T. 
     As illustrated in  FIG. 2 , circular first and second cylinder inner walls  123 S and  123 T are formed in the first and second cylinders  121 S and  121 T so as to be concentric with the rotation shaft  15  of the motor  11 . First and second annular pistons  125 S and  125 T which have an outer diameter smaller than an inner diameter of the cylinder are provided inside the first and second cylinder inner walls  123 S and  123 T, respectively. In this manner, first and second operation chambers  130 S and  130 T which suck in, compress, and discharge a refrigerant gas are formed between the first and second cylinder inner walls  123 S and  123 T and the first and second annular pistons  125 S and  125 T. 
     The first and second vane grooves  128 S and  128 T are formed over the entire cylinder height of the first and second cylinders  121 S and  121 T in a radial direction from the first and second cylinder inner walls  123 S and  123 T. In addition, first and second vanes  127 S and  127 T, each of which has a plate shape, are slidably fit in the first and second vane grooves  128 S and  128 T. 
     As illustrated in  FIG. 2 , first and second spring bores  124 S and  124 T are formed in a deep portion of the first and second vane grooves  128 S and  128 T such that communication from the outer circumferential portions of the first and second cylinders  121 S and  121 T to the first and second vane grooves  128 S and  128 T is performed. First and second vane springs (not illustrated) which press the back surface of the first and second vanes  127 S and  127 T are inserted into the first and second spring bores  124 S and  124 T. 
     When the rotary compressor  1  is started, the first and second vanes  127 S and  127 T protrude from the inside of the first and second vane grooves  128 S and  128 T to the inside of the first and second operation chambers  130 S and  130 T due to bounces of the first and second vane springs. This allows ends of the vanes to come into contact with the outer circumferential surfaces of the first and second annular pistons  125 S and  125 T and the first and second vanes  127 S and  127 T to partition the first and second operation chambers  130 S and  130 T into first and second inlet chambers  131 S and  131 T and first and second compression chambers  133 S and  133 T. 
     In addition, the refrigerant gas compressed in the compressor housing  10  is guided into the first and second cylinders  121 S and  121 T by communicating the deep portion of the first and second vane grooves  128 S and  128 T with the inside of the compressor housing  10  via an opening R illustrated in  FIG. 1 . First and second pressure guiding-in paths  129 S and  129 T which cause back pressures to be applied by the pressure of the refrigerant gas are formed in the first and second vanes  127 S and  127 T. 
     The first and second inlet holes  135 S and  135 T which cause the first and second inlet chambers  131 S and  131 T to communicate with the outside are provided in the first and second cylinders  121 S and  121 T such that a refrigerant is sucked into the first and second inlet chambers  131 S and  131 T from the outside. 
     In addition, as illustrated in  FIG. 1 , an intermediate partition plate  140  is disposed between the first cylinder  121 S and the second cylinder  121 T and partitions and closes the first operation chamber  130 S (refer to  FIG. 2 ) of the first cylinder  121 S from the second operation chamber  130 T (refer to  FIG. 2 ) of the second cylinder  121 T. A lower end plate  160 S is disposed on a lower end portion of the first cylinder  121 S and closes the first operation chamber  130 S of the first cylinder  121 S. In addition, an upper end plate  160 T is disposed on an upper end portion of the second cylinder  121 T and closes the second operation chamber  130 T of the second cylinder  121 T. 
     A sub-bearing unit  161 S is formed on the lower end plate  160 S and a sub-shaft unit  151  of the rotation shaft  15  is rotatably supported in the sub-bearing unit  161 S. A main-bearing unit  161 T is formed on the upper end plate  160 T and a main-shaft unit  153  of the rotation shaft  15  is rotatably supported in the main-bearing unit  161 T. 
     The rotation shaft  15  includes a first eccentric portion  152 S and a second eccentric portion  152 T which are eccentric by a 180° phase shift from each other. The first eccentric portion  152 S is rotatably fit in the first annular piston  125 S of the first compressing unit  12 S. The second eccentric portion  152 T is rotatably fit in the second annular piston  125 T of the second compressing unit  12 T. 
     When the rotation shaft  15  rotates, the first and second annular pistons  125 S and  125 T make orbital motions inside the first and second cylinders  121 S and  121 T along the first and second cylinder inner walls  123 S and  123 T in a counterclockwise direction in  FIG. 2 . Accordingly, the first and second vanes  127 S and  127 T perform reciprocal motions. The motions of the first and second annular pistons  125 S and  125 T and the first and second vanes  127 S and  127 T cause volumes of the first and second inlet chambers  131 S and  131 T and the first and second compression chambers  133 S and  133 T to be continually changed. In this manner, the compressing unit  12  continually sucks in, compresses, and discharges the refrigerant gas. 
     As illustrated in  FIG. 1 , a lower muffler cover  170 S is disposed on the lower side of the lower end plate  160 S and a lower muffler chamber  180 S is formed between the lower end plate  160 S and the lower muffler cover  170 S. The first compressing unit  12 S opens to the lower muffler chamber  180 S. That is, a first outlet  190 S (refer to  FIG. 2 ) through which the first compression chamber  133 S of the first cylinder  121 S communicates with the lower muffler chamber  180 S is provided in the vicinity of the first vane  127 S of the lower end plate  160 S. A first discharge valve  200 S which prevents the compressed refrigerant gas from flowing backward is disposed in the first outlet  190 S. 
     The lower muffler chamber  180 S is a single annular chamber. The lower muffler chamber  180 S is a part of a communication path through which a discharge side of the first compressing unit  12 S communicates with the inside of the upper muffler chamber  180 T by passing through a refrigerant path  136  (refer to  FIG. 2 ) which penetrates the lower end plate  160 S, the first cylinder  121 S, the intermediate partition plate  140 , the second cylinder  121 T and the upper end plate  160 T. The lower muffler chamber  180 S causes pressure pulsation of the discharged refrigerant gas to be reduced. A first discharge valve cover  201 S which controls an amount of flexural valve opening of the first discharge valve  200 S is stacked on the first discharge valve  200 S and is fixed to the first discharge valve  200 S using a rivet. The first outlet  190 S, the first discharge valve  200 S, and the first discharge valve cover  201 S configure a first discharge valve unit of the lower end plate  160 S. 
     As illustrated in  FIG. 1 , an upper muffler cover  170 T is disposed on the upper side of the upper end plate  160 T and the upper muffler chamber  180 T is formed between the upper end plate  160 T and the upper muffler cover  170 T. A second outlet  190 T (refer to  FIG. 2 ) through which the second compression chamber  133 T of the second cylinder  121 T communicates with the upper muffler chamber  180 T is provided in the vicinity of the second vane  127 T of the upper end plate  160 T. A reed valve type second discharge valve  200 T which prevents the compressed refrigerant gas from flowing backward is disposed in the second outlet  190 T. In addition, a second discharge valve cover  201 T which controls an amount of flexural valve opening of the second discharge valve  200 T is stacked on the second discharge valve  200 T and is fixed using a rivet with the second discharge valve  200 T. The upper muffler chamber  180 T causes pressure pulsation of discharged refrigerant to be reduced. The second outlet  190 T, the second discharge valve  200 T, and the second discharge valve cover  201 T configure a second discharge valve unit of the upper end plate  160 T. 
     The first cylinder  121 S, the lower end plate  160 S, the lower muffler cover  170 S, the second cylinder  121 T, the upper end plate  160 T, the upper muffler cover  170 T, and the intermediate partition plate  140  are integrally fastened using a plurality of penetrating bolts  175  or the like. The outer circumferential portion of the upper end plate  160 T of the compressing unit  12  which is integrally fastened using the penetrating bolts  175  or the like is firmly fixed to the compressor housing  10  through spot welding. This allows the compressing unit  12  to be fixed to the compressor housing  10 . 
     First and second through holes  101  and  102  are provided in the outer-side wall of the cylindrical compressor housing  10  at an interval in an axial direction in this order from a lower section thereof so as to communicate with first and second inlet pipes  104  and  105 , respectively. In addition, outside the compressor housing  10 , an accumulator  25  which is formed of a separate airtight cylindrical container is held by an accumulator holder  252  and an accumulator band  253 . 
     A system connecting pipe  255  which is connected to an evaporator in a refrigeration cycle is connected at the center of the top portion of the accumulator  25 . First and second low-pressure communication tubes  31 S and  31 T, each of which has one end extending toward the upward side inside the accumulator  25 , and which have the other ends connected to one ends of the first and second inlet pipes  104  and  105 , are connected to a bottom through hole  257  provided in the bottom of the accumulator  25 . 
     The first and second low-pressure communication tubes  31 S and  31 T which guide a low pressure refrigerant in the refrigeration cycle to the first and second compressing units  12 S and  12 T via the accumulator  25  are connected to the first and second inlet holes  135 S and  135 T (refer to  FIG. 2 ) of the first and second cylinders  121 S and  121 T via the first and second inlet pipes  104  and  105  as an inlet unit. That is, the first and second inlet holes  135 S and  135 T are connected to the evaporator of the refrigeration cycle in parallel. 
     A discharge pipe  107  as a discharge portion which is connected to the refrigeration cycle and discharges a high pressure refrigerant gas to a side of a condenser in the refrigeration cycle is connected to the top portion of the compressor housing  10 . That is, the first and second outlets  190 S and  190 T are connected to the condenser in the refrigeration cycle. 
     Lubricant oil is sealed in the compressor housing  10  substantially to the elevation of the second cylinder  121 T. In addition, the lubricant oil is sucked up from a lubricating pipe  16  attached to the lower end portion of the rotation shaft  15 , using a pump blade (not illustrated) which is inserted into the lower section of the rotation shaft  15 . The lubricant oil circulates through the compressing unit  12 . This allows sliding components to be lubricated and the lubricant oil to seal a fine gap in the compressing unit  12 . 
     Next, a characteristic configuration of the rotary compressor of the example will be described with reference to  FIG. 3 .  FIG. 3  is a partial cross-sectional view illustrating a sliding portion of the first and second annular pistons and the first and second vanes of Example 1. As illustrated in  FIG. 3 , the first and second vanes  127 S and  127 T of Example 1 have base members, respectively, which are made of steel such as high-speed tool steel (SKH) or stainless steel (SUS). In addition, diamond-like carbon layers (DLC layers)  127 SD and  127 TD are formed on sliding surfaces (end surfaces) with respect to the first and second annular pistons  125 S and  125 T, respectively. It is possible to form the DLC layers  127 SD and  127 TD using an ionized deposition method which is a plasma process under high vacuum. The diamond-like carbon layers (DLC layers)  127 SD and  127 TD have a diamond bond (SP3: high hardness substance) and a graphite bond (SP2: low hardness and low friction substance). A ratio of a diamond bond (SP3)/a graphite bond (SP2) of the DLC layers  127 SD and  127 TD described above is 6 to 10 and micro-Vickers hardness thereof is HmV of 1500 or higher. 
     Even though wear-resistance is improved by the DLC layer, insufficient adhesion between the DLC layer and the base member results in peeling-off of the DLC layer. Hence, between the DLC layer and the base member, a DLC layer of which a ratio of SP3/SP2 is 5 or less or either a CrN layer or a nitride layer is formed as a joint layer. When the joint layer is formed, the hardness changes by small degrees between the DLC layer, the joint layer, and the base member and thus, it is possible to improve adhesion of the DLC layer to the base member. 
     The first and second annular pistons  125 S and  125 T of Example 1 are formed using, as a material, Ni—Cr—Mo cast iron to which 0.15 wt % to 0.45 wt % of phosphorus (P) is added. When phosphorus is added to cast iron, a large amount of very hard steadite (P+Fe+C) is generated and wear-resistance is improved. However, since the great amount of steadite results in deterioration of machinability, the upper limit of an amount of phosphorus to be added is set to 0.45 wt %. 
     In addition, the base members of the first and second annular pistons  125 S and  125 T may be formed of cast iron or steel and iron nitride layers  125 SN and  125 TN (refer to  FIG. 3 ) may be formed on outer circumferential surfaces of the pistons. A nitriding treatment is performed on the first and second annular pistons  125 S and  125 T and thereby, wear-resistance is improved. The nitriding treatment as ion nitriding is performed only on the outer circumferential surfaces. The nitriding treatment is not performed on inner circumferential surfaces of the first and second annular pistons  125 S and  125 T and abnormal wear of the first and second eccentric portions  152 S and  152 T of the rotation shaft  15  which slide on the inner circumferential surfaces is prevented. 
     Example 2 
     Next, a characteristic configuration of the rotary compressor of Example 2 will be described with reference to  FIG. 4 .  FIG. 4  is a partial cross-sectional view illustrating a sliding portion of first and second annular pistons and first and second vanes of Example 2. As illustrated in  FIG. 4 , the first and second vanes  127 S and  127 T of Example 2 have base members, respectively, which are made of steel such as high-speed tool steel (SKH) or stainless steel (SUS). In addition, DLC layers  127 SD 1  and  127 TD 1  having HmV of 1500 or higher are formed as under layers on sliding surfaces (end surfaces) with respect to the first and second annular pistons  125 S and  125 T. Further, DLC layers  127 SD 2  and  127 TD 2  having HmV of 1200 or lower are formed as fitness layers on the outer sides of the DLC layers  127 SD 1  and  127 TD 1  as the under layers. 
     The DLC layers  127 SD 2  and  127 TD 2  having HmV of 1200 or lower as the fitness layers have the diamond bond (SP3) and the graphite bond (SP2) and a metal or other elements such as tungsten (W), silicon (Si), or nitrogen (n) is added thereto. In this manner, the hardness is further decreased than the under layers and the fitness layer becomes a soft layer, wear of the soft layer due to sliding causes a fine protrusion to be removed or one-side contact not to occur, surface pressure during the sliding is decreased, and seizing or abnormal wear is prevented. 
     In addition, a ratio of SP3/SP2 of the DLC layers  127 SD 1  and  127 TD 1  having HmV of 1500 or higher as the under layers is 6 to 10. The ratio of SP3/SP2 of the DLC layers  127 SD 2  and  127 TD 2  having HmV of 1200 or lower as the fitness layers is 5 or less and the DLC layers  127 SD 2  and  127 TD 2  may be the soft layers having hardness lower than the under layers. 
     Even though wear-resistance is improved by the DLC layer, insufficient adhesion between the DLC layer and the base member results in peeling-off of the DLC layer. Hence, between the DLC layer and the base member, a DLC layer of which a ratio of SP3/SP2 is 5 or less or either a CrN layer or a nitride layer is formed as a joint layer. In this manner, it is possible to improve adhesion of the DLC layer to the base member. 
     The first and second annular pistons  125 S and  125 T of Example 2 are formed using, as a material, Ni—Cr—Mo cast iron or Ni—Cr—Mo cast iron to which 0.15 wt % to 0.45 wt % of phosphorus (P) is added. In addition, the base members of the first and second annular pistons  125 S and  125 T may be formed of cast iron or steel and iron nitride layers  125 SN and  125 TN (refer to  FIG. 4 ) may be formed on outer circumferential surfaces of the pistons. The nitriding treatment as ion nitriding is performed only on the outer circumferential surfaces. The nitriding treatment is not performed on inner circumferential surfaces of the first and second annular pistons  125 S and  125 T and abnormal wear of the first and second eccentric portions  152 S and  152 T of the rotation shaft  15  which slide on the inner circumferential surfaces is prevented. 
     The first and second vanes  127 S and  127 T of Example 1 or Example 2 which have the sliding surfaces on which the DLC layers are provided and the first and second annular pistons  125 S and  125 T of Example 1 or Example 2 are combined to be used and thereby, abnormal wear of the first and second annular pistons  125 S and  125 T does not occur even in a case where a refrigerant discharge temperature of the rotary compressor  1  exceeds 115° C. during operation. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1  rotary compressor 
               10  compressor housing 
               11  motor 
               12  compressing unit 
               15  rotation shaft 
               16  lubricating pipe 
               25  accumulator 
               31 S first low-pressure communication tube 
               31 T second low-pressure communication tube 
               101  first through hole 
               102  second through hole 
               104  first inlet pipe 
               105  second inlet pipe 
               107  discharge pipe (discharge portion) 
               111  stator 
               112  rotor 
               12 S first compressing unit 
               12 T second compressing unit 
               121 S first cylinder (cylinder) 
               121 T second cylinder (cylinder) 
               122 S first side-flared portion 
               122 T second side-flared portion 
               123 S first cylinder inner wall (cylinder inner wall) 
               123 T second cylinder inner wall (cylinder inner wall) 
               124 S first spring bore 
               124 T second spring bore 
               125 S first annular piston (annular piston) 
               125 T second annular piston (annular piston) 
               125 SN,  125 TN iron nitride layer 
               127 S first vane (vane) 
               127 T second vane (vane) 
               127 SD,  127 TD diamond-like carbon layer (DLC layer) 
               127 SD 1 ,  127 TD 1  under layer (DLC layer) 
               127 SD 2 ,  127 TD 2  fitness layer (DLC layer) 
               128 S first vane groove (vane groove) 
               128 T second vane groove (vane groove) 
               129 S first pressure guiding-in path 
               129 T second pressure guiding-in path 
               130 S first operation chamber (operation chamber) 
               130 T second operation chamber (operation chamber) 
               131 S first inlet chamber (inlet chamber) 
               131 T second inlet chamber (inlet chamber) 
               133 S first compression chamber (compression chamber) 
               133 T second compression chamber (compression chamber) 
               135 S first inlet hole (inlet hole) 
               135 T second inlet hole (inlet hole) 
               136  refrigerant path 
               140  intermediate partition plate 
               151  sub-shaft unit 
               152 S first eccentric portion (eccentric portion) 
               152 T second eccentric portion (eccentric portion) 
               153  main-shaft unit 
               160 S lower end plate (end plate) 
               160 T upper end plate (end plate) 
               161 S sub-bearing unit 
               161 T main-bearing unit 
               170 S lower muffler cover 
               170 T upper muffler cover 
               175  penetrating bolt 
               180 S lower muffler chamber 
               180 T upper muffler chamber 
               190 S first outlet (outlet) 
               190 T second outlet (outlet) 
               200 S first discharge valve 
               200 T second discharge valve 
               201 S first discharge valve cover 
               201 T second discharge valve cover 
               252  accumulator holder 
               253  accumulator band 
               255  system connecting pipe 
             R opening