Patent Publication Number: US-11028848-B2

Title: Scroll compressor having a fitted bushing and weight arrangement

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a U.S. national stage application of PCT/JP2016/060380 filed on Mar. 30, 2016, the contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to a scroll compressor having a slider. 
     BACKGROUND ART 
     In a conventional scroll compressor, a fixed scroll having a spiral vane and an orbiting scroll having a spiral vane are combined to form a plurality of compression chambers, and refrigerant or other medium is compressed by the rotation of the orbiting scroll. To reduce the scroll pressing load caused by the spiral vane during the rotation of the orbiting scroll, some scroll compressors of this type are configured to have a bushing, in which a slider and a balance weight to offset or cancel the centrifugal force generated by the orbiting scroll are joined together, at the upper end portion of a crank shaft (for example, see Patent Literature 1). 
     Furthermore, there is a bushing in which a slider has a flange portion on the outer circumference of the lower end portion thereof, a balance weight has a holding portion on the inner circumference thereof, and the slider and the balance weight are positioned relative to each other at the contact surfaces of the flange portion and the holding portion and are fixed together by shrink fitting (for example, see Patent Literature 2). 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2015-165105 
     Patent Literature 2: Japanese Patent No. 3858762 
     SUMMARY OF INVENTION 
     Technical Problem 
     In Patent Literature 1, because the outer circumferential surface of the slider has a straight structure, when the balance weight is fixed at a predetermined position on the outer circumferential surface of the slider by shrink fitting, the balance weight has to be positioned in the axial direction by using a jig or other tool. 
     In Patent Literature 2, although there is no need to position the balance weight in the axial direction by using a jig or other tool because the slider has the flange portion on the outer circumferential surface of the lower end thereof, since the slider is inserted into the center hole in the balance weight when shrink fitting is performed, the positioning process is not easy. 
     The present invention has been made to overcome the above-described problems, and an object thereof is to provide a scroll compressor and a refrigeration cycle device in which the positioning between a slider and a balance weight is easy. 
     Solution to Problem 
     A scroll compressor according to an embodiment of the present invention includes: a compression mechanism unit that includes a fixed scroll and an orbiting scroll; a crank shaft that causes the orbiting scroll to orbit about the fixed scroll; a slider that is provided between the orbiting scroll and the crank shaft and that includes a tubular portion and a flange portion projecting from an outer circumferential surface between one end and an other end of the tubular portion; and a balance weight that is fitted to the slider and that includes a ring-like portion having a portion of an inner surface facing the flange portion, a weight portion having an inner surface facing the tubular portion closer to the one end than the flange portion, and a projection projecting from an inner circumferential surface of the ring-like portion and having an inner surface facing the tubular portion closer to the other end than the flange portion. 
     Advantageous Effects of Invention 
     According to the present invention, it is possible to provide a scroll compressor and a refrigeration cycle device in which the positioning between a slider and a balance weight is easy. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic vertical sectional view of a scroll compressor according to Embodiment 1 of the present invention. 
         FIG. 2  shows a bushing of the scroll compressor according to Embodiment 1 of the present invention, as viewed from one end. 
         FIG. 3  is a sectional view of the bushing of the scroll compressor according to Embodiment 1 of the present invention, taken along line A-A′ in  FIG. 2 , as viewed in the direction indicated by the arrows. 
         FIG. 4  is a sectional view showing the structure of a bushing of a scroll compressor according to Embodiment 2 of the present invention. 
         FIG. 5  is a sectional view showing the structure of a bushing of a scroll compressor according to Embodiment 3 of the present invention. 
         FIG. 6  shows a bushing of a scroll compressor according to Embodiment 4 of the present invention, as viewed from one end. 
         FIG. 7  is a sectional view showing the structure of the bushing of the scroll compressor according to Embodiment 4 of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     An embodiment of the present invention will be described below with reference to the drawings. Note that, in the figures, the same or equivalent portions are denoted by the same reference signs, and the descriptions thereof will be omitted or simplified where appropriate. Furthermore, the shapes, sizes, arrangements, and other properties of the configurations shown in the figures may be appropriately modified within the scope of the present invention. 
     Embodiment 1 
     Embodiment 1 will be described below.  FIG. 1  is a schematic vertical sectional view of a scroll compressor according to Embodiment 1. Note that the compressor in  FIG. 1  is what is called a vertical scroll compressor that is used in a state in which the central axis of a crank shaft (described below) is substantially perpendicular to the ground. In the descriptions below, to refer to positions in the vertical direction in, for example,  FIG. 1  showing the scroll compressor, the terminologies, one end side U and the other end side L, may be used. Where any referent is said to be on the one end side U relative to a subject being compared, that may mean the referent is located upper in the vertical direction than the compared subject. Similarly, where any referent is said to be on the other end side L relative to a subject being compared, that may mean the referent is located lower in the vertical direction than the compared subject. The other end side is, in other words, the ground side. The referent and the compared subject may be within the extremities of an element as a whole. 
     The scroll compressor includes a shell  1 , a main frame  2 , a compression mechanism unit  3 , a driving mechanism unit  4 , a sub frame  5 , a crank shaft  6 , a bushing  7 , and a power supply unit  8 . 
     The shell  1  is a tubular housing that is a part made of a conducting material, such as metal, and has closed ends. The shell  1  includes a middle shell  11 , a lower shell  12 , and an upper shell  13 . The middle shell  11  is cylindrical and has a suction pipe  111  in a side wall thereof. The suction pipe  111  is a pipe through which refrigerant is introduced into the shell  1  and communicates with the inner space of the middle shell  11 . The lower shell  12  is a substantially hemispherical bottom body, and a portion of the side wall thereof is joined to the lower end portion of the middle shell  11  by welding or other method to close the opening of the middle shell  11  at the bottom. The upper shell  13  is a substantially hemispherical lid body, and a portion of the side wall thereof is joined to the upper end portion of the middle shell  11  by welding or other method to close the opening of the middle shell  11  at the top. The upper shell  13  has a discharge pipe  131  at the top. The discharge pipe  131  is a pipe through which the refrigerant is discharged to the outside of the shell  1 . The discharge pipe  131  communicates with the inner space of the middle shell  11 . Note that the shell  1  is supported by a fixing base  121  having a plurality of screw holes, and, by screwing screws into the screw holes, the scroll compressor can be fixed to another part, such as a housing of an outdoor unit. 
     The main frame  2  is a metal support part and is disposed inside the shell  1 . The main frame  2  includes a body unit  21  and a main bearing unit  22 . The body unit  21  is securely fixed to and supported by the inner circumferential surface of the upper part of the middle shell  11  by shrink fitting, welding, or other method and has, inside thereof, an accommodating space  211  extending in the longitudinal direction of the shell  1 . The accommodating space  211  is open on the one end side U thereof and has steps inside such that the space narrows toward the other end side L. A thrust surface  212  is formed on a portion of the step portions. The main bearing unit  22  is formed to be continuous with the other end side L of the body unit  21  and has a through-hole  221  inside thereof. The through-hole  221  penetrates in the top-bottom direction of the main bearing unit  22 , and the one end side U thereof communicates with the accommodating space  211 . 
     The compression mechanism unit  3  is a compression mechanism that compresses refrigerant. In Embodiment 1, the compression mechanism unit  3  is a scroll compression mechanism that includes a fixed scroll  31  and an orbiting scroll  32 . The fixed scroll  31  includes a first substrate  311  and a first spiral body  312 . The first substrate  311  has a disc shape, and the outer end portion of the first substrate  311  is in contact with the surface of the body unit  21  on the one end side U of the body unit  21  and is fixed to the main frame  2  with screws or other fasteners. The first spiral body  312  projects from the surface of the first substrate  311  on the other end side L and forms a spiral vane, and the distal end thereof is oriented toward the other end side L. The orbiting scroll  32  includes a second substrate  321 , a second spiral body  322 , and a tubular portion  323 . The second substrate  321  has a disc shape and is disposed in the accommodating space  211  such that the outer circumferential surface thereof on the other end side L slides on the thrust surface  212  of the main frame  2 . The second spiral body  322  projects from the surface on the one end side U of the second substrate  321  and forms a spiral vane, and the distal end thereof is oriented toward the one end side U. The tubular portion  323  is a cylindrical boss that is projecting from substantially the center of the surface of the second substrate  321  on the other end side L. Furthermore, an Oldham ring  33  is provided between the main frame  2  and the second substrate  321  of the orbiting scroll  32 . The Oldham ring  33  has a pair of projections on each side of the ring, and the projections are accommodated in corresponding grooves formed in the main frame  2  and grooves formed in the second substrate  321 . With this configuration, the Oldham ring  33  prevents the rotation of the orbiting scroll  32  when the orbiting scroll  32  revolves due to the rotation of the crank shaft  6 . 
     By meshing the first spiral body  312  of the fixed scroll  31  and the second spiral body  322  of the orbiting scroll  32  together, a compression space  34  is formed. The compression space  34  is a space of a volume narrowing from the outside toward the inside in the radial direction. As a result of the refrigerant being taken in from the outside and the orbiting scroll  32  revolving, the refrigerant is compressed. The compression space  34  communicates with a discharge port  313 , which is formed at the central portion of the first substrate  311  of the fixed scroll  31  to penetrate in the top-bottom direction, and the compressed refrigerant is discharged from the discharge port  313 . A discharge valve  35  that opens and closes the discharge port  313  in a predetermined manner and prevents backflow of the refrigerant, and a muffler  36  that has a discharge hole  361  and covers the discharge port  313  and the discharge valve  35  are fixed to the surface on the one end side U of the fixed scroll  31  with screws or other fasteners. 
     The refrigerant includes, for example, halogenated hydrocarbons having a carbon-carbon double bond in the composition, halogenated hydrocarbons having no carbon-carbon double bond in the composition, hydrocarbons, and mixtures containing them. The halogenated hydrocarbons having a carbon-carbon double bond include HFO refrigerant and fluorocarbon-based low-GWP refrigerant, whose ozone depletion potentials are zero, and the examples include tetrafluoropropenes, such as HFO1234yf, HFO1234ze, and HFO1243zf, which have the chemical formula C3H2F4. The tetrafluoropropenes have a double bond in their chemical formulae, are easy to be decomposed in the air, have low (4 to 6) global warming potentials (GWP) and thus are environment-friendly, but have lower densities than existing refrigerants, such as R410A. Examples of the halogenated hydrocarbons having no carbon-carbon double bond include refrigerants in which R32 (difluoromethane), R41, or other component having the chemical formula CH2F2 is mixed. Examples of the hydrocarbons include propane, propylene, or other component, which are natural refrigerants. Examples of the mixtures include mixed refrigerants in which R32, R41, or other component is mixed in HFO1234yf, HFO1234ze, HFO1243zf, or other component. 
     The driving mechanism unit  4  is provided on the other end side L of the main frame  2  inside the shell  1 . The driving mechanism unit  4  includes a stator  41  and a rotor  42 . The stator  41  is a stationary part that has an annular shape formed by, for example, winding a winding wire around an iron core, which is formed by stacking a plurality of electromagnetic steel plates, with an insulating layer therebetween. The outer circumferential surface of the stator  41  is securely fixed to and supported by the inside of the middle shell  11  by shrink fitting or other method. The rotor  42  is a cylindrical rotating part that has a permanent magnet inside an iron core, which is formed by stacking a plurality of electromagnetic steel plates, and has a through-hole penetrating in the top-bottom direction at the center thereof. The rotor  42  is disposed in the inner space of the stator  41 . 
     The sub frame  5  is a support part made of metal and is provided on the other end side L of the driving mechanism unit  4  inside of the shell  1 . The sub frame  5  is securely fixed to and supported by the inner circumferential surface of the lower part of the middle shell  11  by shrink fitting, welding, or other method. The sub frame  5  includes an auxiliary bearing unit  51  and an oil pump  52 . The auxiliary bearing unit  51  is a ball bearing provided on the upper side of the central portion of the sub frame  5  and has a through-hole penetrating in the top-bottom direction at the center. The oil pump  52  is provided on the lower side of the central portion of the sub frame  5  and is disposed such that at least a portion thereof is immersed in lubricant (not shown) accommodated in a lubricant reservoir  122  formed inside the lower shell  12  of the shell  1 . 
     The crank shaft  6  is a long, bar-like metal part provided inside the shell  1 . The crank shaft  6  includes a main shaft unit  61  and an eccentric shaft unit  62  and has a lubricant passage hole  63 . The outer surface of the main shaft unit  61  is in contact with and fixed to the through-hole in the rotor  42 . The main shaft unit  61  is disposed such that the portion corresponding to the rotor  42  is positioned in the inner space of the stator  41  and such that the central axis thereof is aligned with the central axis of the middle shell  11 . The eccentric shaft unit  62  is provided at the one end side U relative to the main shaft unit  61  such that the central axis thereof is eccentric relative to the central axis of the main shaft unit  61 . The lubricant passage hole  63  is provided inside the main shaft unit  61  and the eccentric shaft unit  62  to penetrate in the top-bottom direction. A portion on the one end side U of the crank shaft  6 , which is the eccentric shaft unit  62 , is inserted into and fixed to the tubular portion  323 , and the crank shaft  6  is inserted into and fixed to the auxiliary bearing unit  51  of the sub frame  5  at the other end side L. With this configuration, the crank shaft  6  is positioned inside the main bearing unit  22  of the main frame  2 , and a predetermined space is maintained between the outer surface of the rotor  42  and the inner surface of the stator  41 . 
     The bushing  7  is a doughnut-shaped mechanical part and is fixed to the eccentric shaft unit  62  of the crank shaft  6 . The bushing  7  includes a slider  71  and a balance weight  72 . The slider  71  is a tubular metal part that is made of, for example, iron and is inserted into each of the eccentric shaft unit  62  and the tubular portion  323  to connect the orbiting scroll  32  and the crank shaft  6 . The balance weight  72  is a doughnut-shaped metal part that is made of, for example, iron and is fitted into the slider  71 . 
     The power supply unit  8  is a power supply part that supplies power to the scroll compressor and is formed on the outer circumferential surface of the middle shell  11  of the shell  1 . The power supply unit  8  includes a cover  81 , a power supply terminal  82 , and a wire  83 . The cover  81  is a cover part that has a bottom and an opening. The power supply terminal  82  is a metal part having one end provided inside the cover  81  and the other end provided inside the shell  1 . The wire  83  has one end connected to the power supply terminal  82  and the other end connected to the stator  41 . 
     The bushing  7  will be described in detail with reference to  FIGS. 2 and 3 .  FIG. 2  shows the bushing of the scroll compressor according to Embodiment 1 of the present invention, as viewed from one end.  FIG. 3  is a sectional view of the bushing of the scroll compressor according to Embodiment 1 of the present invention, taken along line A-A′ in  FIG. 2 , as viewed in the direction indicated by the arrows. 
     The bushing  7  is formed of the slider  71  and the balance weight  72  disposed on the outer circumference thereof. The slider  71  includes a tubular portion, which includes a first tubular portion  711  and a second tubular portion  712 , and a flange portion  713 . The first tubular portion  711  is a cylinder positioned on the one end side U of the slider  71 , and the second tubular portion  712  is a cylinder provided on the other end side L of the first tubular portion  711  to be continuous with the first tubular portion  711 . The thickness T 2  of the second tubular portion is larger than the thickness T 1  of the first tubular portion  711 . Furthermore, because the inside diameters of the first tubular portion  711  and the second tubular portion  712  are the same as each other, the outside diameter D 3  of the second tubular portion  712  is larger than the outside diameter D 1  of the first tubular portion  711 . The flange portion  713  is a flange formed on the outer surface on the one end side U of the second tubular portion  712 . In other words, the flange portion  713  is projecting from the outer circumferential surface between one end and the other end of the tubular portions  711  and  712 . The outside diameter D 2  of the flange portion  713  is larger than the outside diameter D 3  of the second tubular portion  712 . Furthermore, the relationship between the thickness T 3  of the flange portion  713  and the thickness T 4  of the second tubular portion  712  is T 3 ≤T 4 /2. 
     The balance weight  72  includes a ring-like portion  721 , a weight portion  722 , and a projection  723 . The ring-like portion  721  is a ring part positioned on the other end side L of the balance weight  72 , and a portion of the inner surface of the ring-like portion  721  faces the flange portion  713 . The weight portion  722  is formed on at least a portion of the ring-like portion  721  to project upwardly toward the second substrate  321  of the orbiting scroll  32  and is disposed such that the inner surface thereof faces the first tubular portion  711 , which is a part of the tubular portion on the one end side U relative to the flange portion  713 . The weight portion  722  is provided in a space formed by the main frame  2 , the second substrate  321 , and the tubular portion  323 . The projection  723  is formed on the inner surface of the ring-like portion  721  on the other end side L to project toward the center and is disposed such that the inner surface thereof faces the second tubular portion  712 , which is another part of the tubular portion on the other end side L relative to the flange portion  713 . In other words, the projection  723  forms a step in the inside of the ring-like portion  721  of the projection  723 . The meaning of the word “face” includes, besides a state in which two objects face each other with a space therebetween, a state in which they are in contact with each other without a space therebetween, a state in which they are in contact with each other without a space therebetween. 
     In the slider  71  and the balance weight  72 , the outer surface of the second tubular portion  712  and the inner surface of the projection  723  are fitted together by shrink fitting with the surface, on the other end side L, of the flange portion  713 , and the surface, on the one end side U, of the projection  723  being in contact with each other. Furthermore, a gap  73  is provided between the outer surface of the flange portion  713  and the inner surface, on the one end side U, of the ring-like portion  721 . 
     How to fit the slider  71  and the balance weight  72  together will be described. First, the balance weight  72  is expanded by heating, and then, the second tubular portion  712  and the flange portion  713  of the slider  71  are inserted into the inner space of the ring-like portion  721  from the one end side U of the balance weight  72 . At this time, the surface, on the other end side L, of the flange portion  713  and the surface, on the one end side U of the projection  723  are brought into contact with each other to position the slider  71  and the balance weight  72 . Then, the balance weight  72  is contracted by cooling to fit (shrink-fit) the outer surface of the second tubular portion  712  and the inner surface of the projection  723  together. Once the shrink fitting is done, there is no problem if the surface, on the other end side L, of the flange portion  713  and the surface, on the one end side U, of the projection  723 , which have been in contact with each other, are separated by a small gap. Note that, in Embodiment 1, the gap  73  is provided between the flange portion  713  and the one end side U of the ring-like portion  721 , so, the flange portion  713  and the ring-like portion  721  are not fitted together. The gap  73  can be used when the surface, on the other surface side, of the flange portion  713  of the slider  71  and the surface, on the one end side U, of the ring-like portion  721  of the balance weight  72  are brought into contact with each other or when the second tubular portion  712  and the projection  723  are fitted together in the shrink-fitting process. 
     As has been described, in the process of shrink-fitting the slider  71  and the balance weight  72  together, only the second tubular portion  712  and the flange portion  713  of the slider  71  are inserted into the inner space of the balance weight  72 , and the first tubular portion  711  does not pass through the inner space of the balance weight  72 . When, as disclosed in Patent Literature 2, the tubular portion of the slider is also inserted into the hole in the balance weight, the outer circumferential surface of the tubular portion could be damaged during the process. Because the outer circumferential surface of the slider is required to be precise, such damage could significantly lower the reliability and decreases the shrink-fitting yield and the working efficiency. In Embodiment 1, because the outer surface of the first tubular portion  711  is not damaged, it is possible to improve the reliability, as well as improving the shrink-fitting yield and the working efficiency. Furthermore, because the positioning can be done by bringing the surface, on the other end side L, of the flange portion  713  and the surface, on the one end side U, of the projection  723  into contact with each other; it is possible to improve the working efficiency during the shrink fitting. Specifically, because the slider  71  and the balance weight  72  can be easily positioned, the fitting process is simplified. 
     Furthermore, during shrink fitting, the slider  71  is subjected to a stress that tends to deform and contract the one end side U of a portion to be shrink-fitted radially inward. Hence, the slider as disclosed in Patent Literature 1 tends to be deformed by shrink fitting. In particular, because the centrifugal force of the balance weight increases with an increase in the amount of force cancelled by the balance weight, the shrink-fitting force needs to be increased, which will increase deformation of the slider caused by shrink fitting. In contrast, in Embodiment 1, the thickness of the one end side U of the portion to be shrink-fitted, that is, the boundary between the second tubular portion  712  and the other end side L of the flange portion  713 , is larger than the thickness of the first tubular portion  711 . Hence, it is possible to minimize deformation of the slider  71 . Note that, it is more preferable that the slider  71  to be used be subjected to quenching or tempering for increased rigidity and be subjected to surface treatment, such as nitriding, manganese phosphate treatment, or diamond-like carbon (DLC) treatment, for increased sliding property. Doing so makes the fitting process easy. Furthermore, because the second tubular portion  712  of the slider  71  has a larger thickness and thus has higher rigidity than the first tubular portion  711 , the amount of deformation can be reduced even if it is subjected to a load during shrink fitting. 
     The operation of the scroll compressor will be described. When power is supplied to the power supply terminal  82  of the power supply unit  8 , torques are generated in the stator  41  and the rotor  42 , rotating the crank shaft  6 . The rotation of the crank shaft  6  is transmitted to the orbiting scroll  32  via the bushing  7 , and the orbiting scroll  32  eccentrically revolves, while being inhibited from rotating by the Oldham ring  33 , with the surface of the second substrate  321  on the other end side L sliding on the thrust surface  212 . At this time, the lubricant accumulated in the lubricant reservoir  122  is sucked by the oil pump  52 , is distributed, via the lubricant passage hole  63  in the crank shaft  6 , to driving portions that need to be lubricated, such as the interface between the main bearing unit  22  and the main shaft unit  61 , the interface between the thrust surface  212  and the second substrate  321 , and the interface between the fixed scroll  31  and the orbiting scroll  32 , and then returns to the lubricant reservoir  122  through a lubricant discharge hole (not shown) provided in the main frame  2 . 
     Meanwhile, the refrigerant taken into the shell  1  from the suction pipe  111  passes through the refrigerant path provided in the main frame  2  and is taken into the compression space  34 . Then, the refrigerant is reduced in volume and is compressed as it moves from the outer circumferential portion toward the center in accordance with the eccentric revolution of the orbiting scroll  32 . During the eccentric revolution of the orbiting scroll  32 , the orbiting scroll  32  moves in the radial direction together with the bushing  7  due to the centrifugal force of its own, bringing the second spiral body  322  and the first spiral body  312  into tight contact with each other. Thus, leakage of the refrigerant from the high-pressure side to the low-pressure side in the compression space  34  is prevented, and efficient compression is performed. The compressed refrigerant is discharged from the discharge port  313  in the fixed scroll  31  against the discharge valve  35  and is discharged to the outside of the shell  1  through the discharge hole  361  in the muffler  36  and the discharge pipe  131 . 
     The weight portion  722  provided in the balance weight  72  of the bushing  7  cancels out the centrifugal force caused by the orbiting movement of the orbiting scroll  32 . Meanwhile, when the crank shaft  6  rotates, the balance weight  72  is subjected to centrifugal force and thus is subjected to a clockwise moment that tilts the balance weight  72  outward. However, because the moment is brought into contact at the surface, on the other end side L, of the flange portion  713  of the slider  71  and the surface, on the one end side U, of the projection  723  of the balance weight  72 , it is possible to receive the moment with the contact surfaces, and thus, to minimize deformation of the slider  71  caused by separation of the slider  71  and the balance weight  72  and by the moment. Although it is difficult to increase the thickness T 4  of the second tubular portion  712  due to the limited space in which the bushing  7  is disposed, the thickness T 3  of the flange portion  713  with the thickness T 4  of the second tubular portion  712  may be changed according to the purpose. For example, in a specification in which the moment applied to the balance weight  72  is small, the dimension of the shrink-fitted portion may be increased for higher fitting strength by setting the thickness T 3  of the flange portion  713  to be smaller than half the thickness T 4  of the second tubular portion  712 . 
     Furthermore, when a refrigeration cycle device having a compressor, a condenser, an expansion valve, and an evaporator performs compression similar to conventional compression using a refrigerant, such as HFO1234yf, having a lower density than existing refrigerants, such as R410A, the speed of the eccentric revolution of the orbiting scroll  32  needs to be increased, which increases the centrifugal force applied to the balance weight  72 . However, as described above, because the influence of the moment caused by the centrifugal force can be canceled out by the flange portion  713  and the projection  723 , highly reliable operation is possible even with a refrigerant such as HFO1234yf. 
     In Embodiment 1, the scroll compressor includes: the compression mechanism unit  3  that includes the fixed scroll  31  and the orbiting scroll  32 ; the crank shaft  6  that causes the orbiting scroll  32  to orbit about the fixed scroll  31 ; the slider  71  that is provided between the orbiting scroll  32  and the crank shaft  6  and that has the tubular portions  711  and  712  and the flange portion  713  projecting from the outer circumferential surface between one end and the other end of the tubular portions  711  and  712 ; and the balance weight  72  that is fitted to the slider  71  and that includes the ring-like portion  721  having a portion of the inner surface facing the flange portion  713 , the weight portion  722  having an inner surface facing the tubular portion  711  or  712  closer to the one end side U than the flange portion  713 , and the projection  723  projecting from the inner circumferential surface of the ring-like portion  721  and having the inner surface facing the tubular portion  711  or  712  closer to the other end side L than the flange portion  713 . Accordingly, in the process of shrink-fitting the slider  71  and the balance weight  72  together, the flange portion  713  and the projection  723  can be brought into contact with each other, and thus, positioning is easy. Furthermore, it is possible to minimize deformation of the slider  71  when the moment is applied to the balance weight  72 . Furthermore, the outer surface of the tubular portions  711  and  712  will not be damaged, improving the reliability. 
     Furthermore, the outer surface of the second tubular portion  712 , which is the tubular portion closer to the other end side L than the flange portion  713 , and the inner surface of the projection  723  are fitted together, and the gap  73  is provided between the outer surface of the flange portion  713  and a portion of the inner surface of the ring-like portion  721 . Accordingly, highly reliable positioning and fitting are possible. 
     Furthermore, the tubular portion of the slider  71  includes the first tubular portion  711  and the second tubular portion  712  on one side of the first tubular portion  711 , the flange portion  713  is provided on the second tubular portion  712 , at a portion close to the first tubular portion  711 , the thickness T 2  of the second tubular portion  712  is larger than the thickness T 1  of the first tubular portion  711 , and the outside diameter D 2  of the second tubular portion  712  is larger than the outside diameter D 1  of the first tubular portion  711 . Accordingly, it is possible to improve the rigidity of the second tubular portion  712 , which is to be fitted by shrink fitting, and hence, to minimize deformation. 
     Furthermore, refrigerant including HFO1234yf is supplied to the compression mechanism unit  3 . Although the speed of the eccentric revolution of the orbiting scroll  32  needs to be increased when compression similar to conventional compression is to be performed with low-density refrigerant, such as HFO1234yf, it is possible to perform highly reliable operation even at a high speed. 
     Embodiment 2 
       FIG. 4  is a sectional view showing the structure of a bushing of a scroll compressor according to Embodiment 2 of the present invention. In  FIG. 4 , portions having the same configurations as those of the compressor in  FIGS. 1 to 3  are denoted by the same reference signs, and the descriptions thereof will be omitted. 
     As shown in  FIG. 4 , in Embodiment 2, the thickness T 2  (the outside diameter D 3 ) of a second tubular portion  712 A of a slider  71 A is equal to the thickness T 1  (the outside diameter D 1 ) of the first tubular portion  711 . The structure of a balance weight  72 A is the same as that in Embodiment 1. Embodiment 2 provides the same advantages as those in Embodiment 1 and makes the production of the slider  71 A easier than that in Embodiment 1. 
     Embodiment 3 
       FIG. 5  is a sectional view showing the structure of a bushing of a scroll compressor according to Embodiment 3 of the present invention. 
     As shown in  FIG. 5 , in Embodiment 3, the outer circumferential surface of the flange portion  713  of a slider  71 B and the one end side U of the ring-like portion  721  of a balance weight  72 B are fitted together, and a space  73 B is provided between the outer circumferential surface of the second tubular portion  712  and the inner circumferential surface of the projection  723 . In Embodiment 3, the rigidity against the shrink-fitting force is further increased, minimizing deformation, and it is possible to obtain the same advantages as those obtained in Embodiment 1. 
     Embodiment 4 
       FIG. 6  shows the structure of a bushing of a scroll compressor according to Embodiment 4 of the present invention, and  FIG. 7  is a sectional view showing the structure of the bushing of the scroll compressor according to Embodiment 4 of the present invention. 
     As shown in  FIGS. 6 and 7 , in Embodiment 4, a flange portion  713 C of a slider  71 C is formed on a portion of the outer circumferential surface of the second tubular portion  712 , and a projection  723 C of a balance weight  72 C is formed on a portion of the inner circumferential surface of the ring-like portion  721 . Furthermore, the area in which the flange portion  713 C and the projection  723 C are formed is formed in association with the portion in which a weight portion  722 C is formed. 
     More specifically, the weight portion  722 C has a C shape in which θ 1 , which is the angle that satisfies θ 1 &lt;360°, where θ 1  is an angle defined by the center O′ of the arc of the weight portion  722 C, and both ends of the weight portion  722 C. The flange portion  713 C has a C shape in which θ 2 , which is the angle that satisfies θ 1 ≤θ 2 &lt; 360 ° where θ 2  is an angle defined by the center O′ of the arc of the flange portion  713 C and the both end portions of the flange portion  713 C. The weight portion  722 C is disposed such that the angle θ 1  is included in the angle θ 2  of the flange portion  713 C, that is, such that the C-shaped portion of the flange portion  713 C and the C-shaped portion of the weight portion  722 C face each other. For example, the angle θ 1  is 220°, and the angle θ 2  is 240°. It is more preferable that the angle θ 1  and the angle θ 2  be between 180° and 270°. In Embodiment 4, because the area in which the flange portion  713 C is formed corresponds to the weight portion  722 C, which is formed in the area where the centrifugal force of the orbiting scroll  32  can be cancelled out, it is possible to receive the moment applied to the weight portion  722 C with contact surfaces and to increase the shrink fitting area in a portion where the flange portion  713 C is not formed. 
     Note that the present invention is not limited to the invention according to the above-described embodiments and can be appropriately modified within the scope not departing from the spirit thereof. For example, although vertical scroll compressors have been described in the above-described embodiments, the present invention can also be applied to horizontal scroll compressors. Furthermore, low-pressure shell scroll compressors have been described in the above-described embodiments, the present invention can also be applied to high-pressure shell scroll compressors. 
     REFERENCE SIGNS LIST 
       1  shell  11  middle shell  111  suction pipe  12  lower shell  121  fixing base  13  upper shell  131  discharge pipe  2  main frame  21  body unit  211  accommodating space  212  thrust surface  22  main bearing unit  221  through-hole  3  compression mechanism unit  31  fixed scroll  311  first substrate  312  first spiral body  32  orbiting scroll  321  second substrate  322  second spiral body  323  tubular portion  33  Oldham ring  34  compression space  35  discharge valve  36  muffler  361  discharge hole  4  driving mechanism unit stator  42  rotor  5  sub frame  51  auxiliary bearing unit  52  oil pump  6  crank shaft  61  main shaft unit  62  eccentric shaft unit  63  lubricant passage hole  7  bushing  71  slider  711  first tubular portion  712  second tubular portion  713  flange portion  72  balance weight  721  ring-like portion  722  weight portion  723  projection  73  gap  8  power supply unit  81  cover  82  power supply terminal  83  wire U one end L the other end