Patent Publication Number: US-2022235770-A1

Title: Rotary compressor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation of International Application No. PCT/JP2020/038201 filed on Oct. 8, 2020, which claims priority to Japanese Patent Application No. 2019-188530, filed on Oct. 15, 2019. The entire disclosures of these applications are incorporated by reference herein. 
    
    
     BACKGROUND 
     Technical Field 
     The present disclosure relates to a rotary compressor. 
     Background Art 
     Conventionally a rotary compressor has a bottom portion that reserves lubricating oil lubricating a compression mechanism and a motor bearing. This lubricating oil reaches an upper high-pressure space provided above the rotary compressor. JP 2018-061420 A discloses a rotary compressor including a motor having a motor stator provided with nine concave portions. 
     SUMMARY 
     A rotary compressor according to a first aspect of the present disclosure includes a compression mechanism, a casing having a cylindrical portion and covering the compression mechanism, a motor stator and a motor rotor. The motor stator includes stacked steel plates obtained by stacking a plurality of steel plates, teeth, and slots. The stacked steel plates are fixed to an inner surface of the cylindrical portion. A number of the teeth and a number of the slots is nine. The motor rotor is configured to rotate a crankshaft that is configured to drive the compression mechanism. The stacked steel plates have first to ninth areas provided radially outside the nine teeth, first concave portions provided respectively in five of the first to ninth areas, and a second concave portion provided in at least one of four areas other than the five areas including the first concave portions. The five first concave portions and an inner circumferential surface of the cylindrical portion form five first passages allowing communication between a first side and a second side of the motor stator. The second concave portion and the inner circumferential surface of the cylindrical portion form at least one second passage allowing communication between the first side and the second side of the motor stator. Each of the first passages has a sectional area larger than a sectional area of the second passage. No passage having a sectional area larger than the sectional area of the first passage is formed in the four areas other than the five areas where the first passages are located. Three or more areas including the first concave portions are not continuous in the first area to the ninth area. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a longitudinal sectional view of a rotary compressor  10  according to an embodiment of the present disclosure. 
         FIG. 2  is a plan view of a casing  20  and a core  44  according to the embodiment of the present disclosure. 
         FIG. 3  is plan view of the casing  20  and the core  44  according to the embodiment of the present disclosure. 
         FIG. 4  is a graph indicating a relation among the number of first passages  101 , a sound level, and oil run out quantity. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENT(S) 
     Described hereinafter with reference to the drawings is a rotary compressor  10  according to an embodiment of the present disclosure. The following embodiment specifically exemplifies the present disclosure and is not intended to limit the technical scope of the present disclosure. 
     (1) ENTIRE CONFIGURATION 
     The rotary compressor  10  is applied to a vapor compression refrigeration apparatus or the like. The rotary compressor  10  according to the present embodiment is mounted on an outdoor unit of an air conditioner exemplifying the refrigeration apparatus, and constitutes part of a refrigerant circuit of the air conditioner. 
       FIG. 1  is a longitudinal sectional view of the rotary compressor  10  according to the embodiment of the present disclosure.  FIG. 1  includes bold arrows indicating a flow of a refrigerant. The rotary compressor  10  includes a compression mechanism  30 , a casing  20 , a motor stator  41 , a motor rotor  42 , and a crankshaft  50 . The motor stator  41  has a cylindrical shape and is provided on an outer circumference of the motor rotor  42 . The motor stator  41  and the motor rotor  42  magnetically interact to rotate the motor rotor  42  and the crankshaft  50  about a rotation center  44   c . The motor stator  41  and the motor rotor  42  constitute a motor  40 . 
     (2) DETAILED CONFIGURATIONS 
     (2-1) Casing  20   
     The casing  20  principally accommodates the compression mechanism  30 , the motor stator  41 , the motor rotor  42 , and the crankshaft  50 . A suction pipe  60  and a discharge pipe  70  penetrate the casing  20  and are fixed to the casing  20  to secure airtightness of the casing  20 . 
     The casing  20  has a cylindrical portion  21  having a cylindrical shape with opened upper and lower ends, and an upper lid  22   a  and a lower lid  22   b  provided at the upper end and the lower end of the cylindrical portion  21 , each having a bowl shape, and closing the opened upper and lower ends of the cylindrical portion  21 . The cylindrical portion  21  is fixed to the upper lid  22   a  and the lower lid  22   b  by welding to secure airtightness. 
     The casing  20  has a lower portion provided with an oil reservoir  92 . The oil reservoir  92  reserves lubricating oil lubricating the compression mechanism  30  and the like. 
     (2-2) Compression Mechanism  30   
     The compression mechanism  30  principally includes a piston  31 , a front head  32 , a cylinder  33 , a rear head  34 , and a muffler  35 . The front head  32 , the cylinder  33 , and the rear head  34  are fixed to one another by fastening or the like. 
     The compression mechanism  30  sucks and compresses low-pressure refrigerant gas, and discharges high-pressure refrigerant gas. The casing  20  has an internal space that corresponds to a space provided above the compression mechanism  30  and serves as a high-pressure space receiving refrigerant gas compressed by the compression mechanism  30 . This high-pressure space includes a lower high-pressure space  90  provided below the motor  40  and an upper high-pressure space  91  provided above the motor  40 . 
     The compression mechanism  30  includes a compression chamber  36  surrounded with the front head  32 , the cylinder  33 , and the rear head  34 . The piston  31  is disposed in the compression chamber  36 . The compression chamber  36  includes a suction chamber and a discharge chamber zoned by the piston  31 . The suction chamber communicates with the suction pipe  60 . The discharge chamber communicates with the lower high-pressure space  90  via a muffler space  93  to be described later. 
     The crankshaft  50  includes an eccentric shaft portion  51  fitted into the piston  31 . When the crankshaft  50  rotates, the piston  31  turns about an eccentric shaft. Turn of the piston  31  causes periodical change in capacity of the suction chamber and the discharge chamber. 
     The front head  32  includes an upper bearing  32   a  supporting the crankshaft  50 . The upper bearing  32   a  extends upward from a center of an upper surface of the front head  32 . The front head  32  includes a discharge port configured to discharge, into the muffler space  93 , a refrigerant in the compression chamber  36 . 
     The cylinder  33  is a cylindrical member interposed between the front head  32  and the rear head  34 . The cylinder  33  has an upper surface covered with the front head  32 . The cylinder  33  has a lower surface covered with the rear head  34 . 
     The rear head  34  includes a lower bearing  34   a  supporting the crankshaft  50 . The lower bearing  34   a  extends downward from a center of a lower surface of the rear head  34 . 
     The muffler  35  is fixed to the upper surface of the front head  32 . The muffler  35  constitutes the muffler space  93  provided to reduce noise generated when a refrigerant is discharged from the discharge port of the front head  32 . The muffler space  93  is surrounded with the muffler  35  and the front head  32 . The muffler  35  has a hole allowing communication between the muffler space  93  and the lower high-pressure space  90 . 
     (2-3) Crankshaft  50   
     The crankshaft  50  has an axis  50   a  extending in a vertical direction. The crankshaft  50  rotates about the axis  50   a . The crankshaft  50  includes the eccentric shaft portion  51 . The eccentric shaft portion  51  of the crankshaft  50  is fitted into the piston  31  of the compression mechanism  30 . The crankshaft  50  has an upper portion coupled to the motor rotor  42 . 
     (2-4) Motor  40   
     The motor  40  is disposed above the compression mechanism  30 . The motor  40  principally includes the motor stator  41  and the motor rotor  42 . The motor stator  41  has a substantially cylindrical shape and is fixed to the cylindrical portion  21  of the casing  20 . The motor rotor  42  has a columnar shape and is disposed inside the motor stator  41 . The motor stator  41  and the motor rotor  42  interpose a gap  43 . 
     (2-4-1) Motor Stator  41   
     The motor stator  41  principally includes a core  44 , an insulator  45 , and a coil  46 . The core  44  is fixed to an inner circumferential surface of the cylindrical portion  21  by shrink fitting or the like. The core  44  is constituted by stacked steel plates  80  obtained by stacking electromagnetic steel. The insulator  45  is attached to both vertical end surfaces of the core  44 . The insulator  45  is made of a resin. 
     As depicted in  FIG. 2 , the core  44  includes an annular portion  44   a  and nine teeth  44   b . The annular portion  44   a  has a substantially cylindrical shape. The core  44  is disposed such that the rotation center  44   c  extends in the vertical direction. The nine teeth  44   b  project from an inner circumferential surface  44   e  of the annular portion  44   a  in a radially inward direction of the annular portion  44   a . The nine teeth  44   b  are disposed at equal intervals along a circumference of the annular portion  44   a . Hereinafter, nine spaces each provided between adjacent two of the nine teeth  44   b  along the circumference of the annular portion  44   a  will be called slots  44   d . The coil  46  is constituted by a lead wire wound around the nine teeth  44   b  and the insulator  45 . 
       FIG. 2  depicts first to ninth areas A 441  to A 449  provided radially outside the nine teeth  44   b . Any five of these first to ninth areas A 441  to A 449  are each provided with a first concave portion  81 . The first concave portions  81  according to the present embodiment are provided in the first area A 441 , the third area A 443 , the fourth area A 444 , the sixth area A 446 , and the eighth area A 448 . 
     The first concave portions  81  are cut-away sections provided in a vertical direction of the motor stator  41 . The five first concave portions  81  and an inner circumferential surface  21   a  of the cylindrical portion  21  constitute five first passages  101  allowing communication between a first side and a second side of the motor stator  41 . 
     There is further provided a second concave portion  82  in at least one of four areas other than the five areas including the first concave portions  81  among the areas provided radially outside the nine teeth  44   b . The second concave portion  82  according to the present embodiment is provided in each of the second area A 442 , the fifth area A 445 , and the ninth area A 449 . There is further provided at least one second passage  102  that is constituted by the second concave portion  82  and the inner circumferential surface  21   a  of the cylindrical portion  21  and allows communication between the first side and the second side of the motor stator  41 . 
     The first passages  101  and the second passage  102  are provided with a plurality of convex portions  83  made of weld bead. 
     The seventh area A 447  is closed in the present embodiment. 
     (2-4-1-1) First Passages  101   
     The first passages  101  are provided in any five of the first to ninth areas A 441  to A 449  provided radially outside the nine teeth  44   b.    
     The first passages  101  are used to return, to the oil reservoir  92 , lubricating oil separated from a refrigerant by centrifugal force of a refrigerant flow in the upper high-pressure space  91  and adhering to an inner circumferential surface of the casing  20 . 
     The five first passages  101  provided at the motor stator  41  are evenly disposed in the first to ninth areas A 441  to A 449 . For example, the first passages  101  are provided respectively in the first area A 441 , the third area A 443 , the fourth area A 444 , the sixth area A 446 , and the eighth area A 448 . Even disposition of the first passages  101  in this manner inhibits unbalanced stress at the motor stator  41  when the motor  40  is fixed to the casing  20  by shrink fitting or the like. 
     (24-1-2) Second Passage  102   
     The second passage  102  is provided in at least one of four areas other than the five areas including the first passages  101  among the areas provided radially outside the nine teeth  44   b.    
     The second passage  102  is used to return, to the oil reservoir  92 , the lubricating oil separated from the refrigerant by the centrifugal force of the refrigerant flow in the upper high-pressure space  91  and adhering to the inner circumferential surface of the casing  20 . 
     (24-2) Motor Rotor  42   
     The motor rotor  42  includes a rotor core  47 , an upper plate  48 , and a lower plate  49 . The rotor core  47  is constituted by a plurality of vertically stacked metal plates. The rotor core  47  includes an embedded magnet. The upper plate  48  is a metal plate covering an upper end surface of the rotor core  47 . The lower plate  49  is a metal plate covering a lower end surface of the rotor core  47 . 
     (3) OPERATION OF COMPRESSOR 
     When the motor  40  is driven by electric power supplied from an external power source, the eccentric shaft portion  51  of the crankshaft  50  coupled to the motor rotor  42  eccentrically rotates about the axis  50   a . Rotation of the crankshaft  50  causes rotation, about the axis  50   a  in the compression chamber  36 , of the piston  31  provided with the eccentric shaft portion  51  fitted therein. Rotation of the piston  31  leads to periodical change in capacity of the suction chamber and the discharge chamber in the compression chamber  36 . 
     In the rotary compressor  10 , low-pressure refrigerant gas is sucked from an accumulator (not depicted) into the suction chamber of the compression chamber  36  through the suction pipe  60 . The suction chamber is reduced in capacity by rotation of the piston  31 . The refrigerant gas in the suction chamber is accordingly compressed, and the suction chamber turns into the discharge chamber filled with high-pressure refrigerant gas. The high-pressure refrigerant gas is discharged from the discharge chamber into the muffler space  93  via the discharge port, and is discharged from the muffler space  93  into the lower high-pressure space  90 . 
     The refrigerant gas discharged into the lower high-pressure space  90  passes through the gap  43  between the motor stator  41  and the motor rotor  42 , the first passages  101 , and the second passage  102 , and flows into the upper high-pressure space  91 . The refrigerant gas in the upper high-pressure space  91  passes through the discharge pipe  70  and is supplied to the refrigerant circuit disposed outside the casing  20 . 
     (4) RELATION AMONG THE NUMBER OF FIRST PASSAGES  101 , SOUND LEVEL, AND OIL RUN OUT LEVEL 
     Described next is a relation among the number of first passages  101  provided at the motor stator  41 , a level of sound generated from the rotary compressor  10 , and an oil run out level. Terms “sound level” and “oil run out level” will be defined in (4-1) and (4-2) below. 
     (4-1) Sound Level 
     The sound level according to the present disclosure indicates amplitude of pressure by discharge pulsation in the upper high-pressure space  91  in the casing  20  of the rotary compressor  10 . 
     In the rotary compressor  10 , the internal space of the casing  20  has discharge pulsation generated by a refrigerant discharged from the compression mechanism  30 . Discharge pulsation indicates pressure variation in a discharge space caused by a compressed refrigerant periodically flowing from the compression mechanism  30  into the discharge space. When such discharge pulsation propagates outside the compressor via the discharge pipe  70 , the outdoor unit vibrates. This causes noise generated from the outdoor unit. 
     (4-2) Oil Run Out Level 
     The oil run out level according to the present disclosure indicates quantity of lubricating oil discharged outside the compressor due to running out of oil. Running out of oil indicates a phenomenon that lubricating oil is exhausted outside the compressor along with a high-pressure refrigerant discharged from the compressor. 
     Normally, lubricating oil reserved in the oil reservoir  92  of the casing  20  is principally supplied to a slide portion of the compression mechanism  30 . The lubricating oil supplied to the slide portion of the compression mechanism  30  flows into the compression chamber  36 . The lubricating oil is mixed into a refrigerant gas in the compression chamber  36 . Accordingly, high-pressure refrigerant gas discharged from the compression mechanism contains the lubricating oil. Part of the lubricating oil contained in the high-pressure refrigerant gas is separated from the high-pressure refrigerant gas by centrifugal force of a refrigerant flow in the upper high-pressure space  91  of the motor  40  and adheres to the inner circumferential surface  21   a  of the cylindrical portion  21 . The lubricating oil adhering to the inner circumferential surface  21   a  of the cylindrical portion  21  drops along the inner circumferential surface  21   a  of the cylindrical portion  21  to a level of an upper surface of the motor stator  41  in the motor  40 . The lubricating oil then passes through the first passages  101  and the second passage  102  at the core  44  to drop. The lubricating oil passing through the first passages  101  and the second passage  102  eventually returns to the oil reservoir  92 . In a case where the lubricating oil does not return to the oil reservoir  92  in the above manner but is exhausted outside the compressor, the lubricating oil is short and the rotary compressor is deteriorated in reliability. 
     (4-3) 
       FIG. 4  is a graph indicating the relation among the number of first passages  101 , the sound level, and the oil run out level. The sound level and the oil run out level are each assumed herein to have a reference state (100%) where there are provided nine first passages  101 . 
     According to  FIG. 3 , the sound level is highest when there are provided nine first passages  101 , and decreases as the number of first passages  101  decreases. In other words, noise is largest when there are provided nine first passages  101 , and is reduced as the number of first passages  101  decreases. 
     For example, assuming that the sound level is 100% when there are provided nine first passages  101 , the sound level decreases to 92% when the number of first passages  101  is decreased to five. The sound level decreases to 89% when the number of first passages  101  is decreased to four. 
     Meanwhile, the oil run out level does not have significant change between the case where there are provided nine first passages  101  and the case where there are provided five first passages  101 . In other words, provision of at least five first passages  101  will lead to sufficient inhibition of oil run out. However, assuming that the oil run out level is 100% when there are provided nine first passages  101 , the oil run out level increases to 500% when the number of first passages  101  is decreased to four. 
     Accordingly, the sound level decreases as the number of first passages  101  decreases, but the oil run out level rapidly increases when the number of first passages  101  is four or less. In view of noise reduction and inhibition of running out of oil, it will be desired to provide five first passages  101 . 
     (5) CHARACTERISTICS 
     (5-1) 
     A rotary compressor including a nine-slot motor having nine teeth and nine slots provided at a core portion of a motor stator conventionally has nine concave portions respectively disposed radially outside the teeth of the motor stator. The nine concave portions and an inner circumferential surface of a cylindrical portion of a casing constitute nine passages allowing communication between a first side and a second side of the motor stator. The nine passages are used to return, to an oil reservoir, lubricating oil separated in an upper high-pressure space. In other words, the nine passages enable inhibition of running out of oil. 
     Meanwhile, an internal space of the casing of the rotary compressor has discharge pulsation generated by a refrigerant discharged from a compression mechanism. Discharge pulsation indicates pressure variation in a discharge space caused by a compressed refrigerant periodically flowing from the compression mechanism into the discharge space. When pressure variation caused by the discharge pulsation propagates outside the compressor via a discharge pipe, an outdoor unit vibrates. This causes noise generated from the outdoor unit. In the rotary compressor including the nine-slot motor having the nine teeth and the nine slots provided at the core portion of the motor stator, discharge pulsation reaches the upper high-pressure space via the nine passages and propagates outside the compressor via the discharge pipe. 
     In order to reduce such noise generated from the outdoor unit, the rotary compressor conventionally includes a soundproof material wound therearound to inhibit vibration propagation in the entire compressor. In contrast, the present disclosure achieves noise reduction by inhibiting vibration propagation inside the compressor. 
     (5-2) 
     Discharge pulsation by a refrigerant periodically discharged from the compression mechanism typically propagates pressure variation to a lower high-pressure space, the passages allowing communication between the first side and the second side of the motor stator, the upper high-pressure space, and the discharge pipe in the mentioned order. 
     In the rotary compressor  10  according to the present embodiment, assuming that the motor stator  41  has the first to ninth areas A 441  to A 449  as the areas provided radially outside the nine teeth  44   b , the motor stator  41  has the first concave portions  81  provided respectively in five of the first to ninth areas A 441  to A 449 . The motor stator  41  further has the second concave portion  82  in at least one of four areas other than the areas including the first concave portions  81 . 
     The five first concave portions  81  and the inner circumferential surface  21   a  of the cylindrical portion  21  constitute the five first passages  101  allowing communication between the first side and the second side of the motor stator  41 . There is further provided at least one second passage  102  that is constituted by the at least one second concave portion  82  and the inner circumferential surface  21   a  of the cylindrical portion  21  and allows communication between the first side and the second side of the motor stator  41 . 
     As described above, discharge pulsation passes through the passages allowing communication between the first side and the second side of the motor stator to propagate pressure variation. 
     In the configuration according to the present disclosure, the motor stator  41  is provided with the five first passages  101  and the at least one second passage  102 . In comparison to the case where the motor stator has nine passages allowing communication between the first side and the second side, the configuration according to the present disclosure is decreased in the number of passages or is reduced in sectional area of the passages. 
     This increases flow path resistance in the case where discharge pulsation passes through the five first passages  101  and the at least one second passage  102  at the motor stator  41 . 
     This increases pressure loss caused when the discharge pulsation passes through the five first passages  101  and the at least one second passage  102  at the motor stator  41 , to inhibit propagation of pressure variation caused by the discharge pulsation. 
     Pressure variation propagating to the upper high-pressure space  91  is decreased in amplitude in this manner, to also decrease pressure variation propagating outside the compressor via the discharge pipe  70  and inhibit noise generated from the outdoor unit. 
     (5-3) 
     At least one second passage  102  is provided in any of four areas other than the five areas including the first passages  101 . The second passage  102  has a sectional area S 2  smaller than a first sectional area S 1  of the first passages  101 . Specifically, the sectional area S 2  of the second passage  102  corresponds to 10% to 25% of the sectional area S 1  of the first passages  101 . A second maximum depth D 2  as a maximum value of a radial length of the second passage  102  is smaller than a first maximum depth D 1  as a maximum value of a radial length of the first passages  101 . Specifically, the second maximum depth D 2  corresponds to 10% to 45% of the first maximum depth D 1 . 
     (5-4) 
     Assuming that one of the first passages  101  has a first end and a second end as both circumferential ends along the inner circumferential surface  21   a  of the cylindrical portion, a first straight line connecting the rotation center  44   c  of the crankshaft  50  and the first end and a second straight line connecting the rotation center of the crankshaft  50  and the second end form an angle having 15 to 35 degrees. The five first passages  101  can thus be provided continuously as in an exemplary case where the first passages are provided respectively in the first area A 441 , the second area A 442 , the third area A 443 , the fourth area A 444 , and the fifth area A 445 . 
     The five first passages  101  provided at the motor stator  41  are desired to be evenly disposed in the first to ninth areas A 441  to A 449 . The first passages  101  are evenly disposed to inhibit unbalanced stress at the motor stator  41  when the motor  40  is fixed to the casing  20  by shrink fitting or the like. 
     In a case where the five first passages  101  are disposed collectively in areas positioned on one side with respect to the vertical direction, the motor stator  41  has unbalanced stress. In such a case, the inner circumferential surface  44   e  of the annular portion  44   a  is pushed outward by stress on the side with larger stress of the motor stator  41 , leading to deformation of an inner diameter portion of the motor stator  41  and unevenness at the gap  43  to cause noise. 
     The five first passages  101  according to the present embodiment are thus provided respectively in the first area A 441 , the third area A 443 , the fourth area A 444 , the sixth area A 446 , and the eighth area A 448  as depicted in  FIG. 2 . 
     (6) MODIFICATION EXAMPLES 
     The embodiment described above provides an exemplary case, while the above embodiment is not intended to limit contents of the present disclosure and the contents of the present disclosure are not limited to the above embodiment. The contents of the present disclosure obviously include also aspects obtained through appropriate modification without departing from the purpose of the present disclosure. 
     (6-1) Modification Example A 
     The above embodiment exemplifies the case where the five first passages  101  provided evenly at the motor stator  41  are disposed respectively in the first area A 441 , the third area A 443 , the fourth area A 444 , the sixth area A 446 , and the eighth area A 448 . 
     However, provision of the five first passages  101  at the motor stator  41  achieves noise reduction through inhibition of vibration propagation inside the compressor. Accordingly, the first passages  101  may alternatively be provided unevenly as in an exemplary case where the first passages  101  are disposed respectively in the first area A 441 , the second area A 442 , the third area A 443 , the fourth area A 444 , and the fifth area A 445 . 
     (6-2) Modification Example B 
     The above embodiment exemplifies the case where the compressor is configured as the rotary compressor. However, the embodiment of the present disclosure should not be limited to the rotary compressor, and is also applicable to a swing compressor. 
     The embodiment of the present disclosure has been described above. Various modifications to modes and details should be available without departing from the object and the scope of the present disclosure recited in the claims.