Patent Publication Number: US-2013243635-A1

Title: Scroll-type fluid machine

Description:
TECHNICAL FIELD 
     The present invention relates to a scroll-type fluid machine in which a sealed chamber confining a fluid is formed by a pair of fixed scroll and rotary scroll meshed together. 
     BACKGROUND ART 
     A scroll compressor, in which a compression chamber is formed by a pair of fixed scroll and rotary scroll meshed together, includes a wall erected on one side face of an end plate of the rotary scroll and a boss part protruding from the other side face. 
     A bush part of a crankshaft is inserted in a rotary bearing inserted in the boss part, and the bush part is rotatably supported by the rotary bearing. The rotary scroll is caused to revolve, via the rotary bearing and the boss part, by rotation of the crankshaft around an axis. Since an axis of the bush part is eccentric to the axis of the crankshaft, the rotary scroll makes orbital motion. 
     On the other hand, a technique is disclosed in Patent Literature 1 in which use of the rotary bearing is avoided by adopting a drive bush made of polyimide resin and directly fitting the drive bush into the boss. 
     CITATION LIST 
     Patent Literature 
     {PTL 1} 
     
         
         Japanese Unexamined Patent Application, Publication No. Hei 11-132170 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     In the scroll compressor, different metallic materials are usually used for the boss part and the rotary bearing. Accordingly, there is a risk that, when inserting the rotary bearing into the boss part, a gap is generated between the boss part and the rotary bearing at high temperatures due to a difference in thermal expansion coefficients. 
     For this reason, when inserting and fixing the rotary bearing into the boss part at low temperatures, the rotary bearing has been conventionally inserted (press-fitted) into the boss part while applying pressure thereto so as not to generate a gap at the time of temperature rise. However, this creates a problem that, during press-fitting, an open side of the boss part is deformed to open outward and the end plate of the rotary scroll is deformed accordingly. As a result, contact portions of the wall bodies of the fixed scroll and the rotary scroll are brought into point contact, instead of line contact, causing a refrigerant to leak into an adjacent compression chamber during revolution. In some cases, a tip of the boss part is swaged in addition to press-fitting of the rotary bearing to prevent the rotary bearing from coming off. 
     In other cases, the rotary bearing is prevented from coming off by inserting a snap ring in a groove provided on the inner face of the boss part. In this case, deformation of the rotary scroll caused by press-fitting and swaging can be prevented, but a gap is generated between the boss part and the rotary bearing during a temperature rise due to the difference in thermal expansion coefficients. This leads to a problem that the boss part and the rotary bearing partially come into contact with each other and develop surface damage (fretting) by being subjected to vibration, repeated stress, and the like. 
     The present invention has been made in view of these circumstances, and an object thereof is to provide a scroll-type fluid machine which can reduce deformation of the rotary scroll caused when fixing the bearing into the boss part. 
     Solution to Problem 
     To solve the above problems, the scroll-type fluid machine of the present invention adopts the following solutions. 
     That is, the scroll-type fluid machine according to the present invention is a scroll-type fluid machine in which a sealed chamber confining a fluid is formed by a fixed scroll and a rotary scroll meshed together, each of the scrolls having a spiral wall erected on one side face of an end plate. The scroll-type fluid machine includes: a metallic boss part protruding from the other side face of the end plate of the rotary scroll; a metallic bearing inserted into the boss part; a crankshaft rotating around an axis and including a bush part inserted in the bearing and rotatably supported by the bearing; and an insert member disposed between the boss part and the bearing and having a thermal expansion coefficient greater than those of the boss part and the bearing. 
     According to the present invention, the rotary scroll is provided with the wall erected on the one side face of the end plate, and the boss part protruding from the other side face, and the bush part is inserted in the bearing, which is inserted in the boss part, so that the bush part is rotatably supported by the bearing. By rotation of the crankshaft having the bush part around the axis, the rotary scroll is caused to revolve via the bearing and the boss part. When the axis of the bush part is eccentric to the axis of the crankshaft, the rotary scroll makes orbital motion. 
     In the present invention, the insert member is disposed between the boss part and the bearing. Since the insert member has the thermal expansion coefficient greater than those of the metallic boss part and bearing, the boss part and the bearing are securely fixed by the insert member at high temperatures. It is therefore not necessary to press-fit the bearing into the boss part at low temperatures in expectation of the difference in expansion occurring at high temperatures, and deformation of the rotary scroll caused when press-fitting the bearing into the boss part can be reduced or prevented. 
     As the insert member is made of, for example, synthetic resin or synthetic rubber, it is also possible to reduce noise and vibration during revolution of the rotary scroll. 
     In the present invention, the insert member may have a ring shape and be disposed along the inner face of the boss part. 
     According to the present invention, since the ring-shaped insert member is disposed along the inner face of the boss part, the metallic boss part and bearing do not come into contact with each other. Thus, it is possible to reduce or prevent surface damage (fretting) caused, when the insert member is not provided, by the boss part and the bearing partially coming into contact and being subjected to vibration, repeated stress, and the like. 
     Advantageous Effects of Invention 
     According to the present invention, deformation of the rotary scroll caused when fixing the bearing into the boss part can be reduced. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a longitudinal cross-sectional view of a scroll compressor according to an embodiment of the present invention. 
         FIG. 2  is a longitudinal cross-sectional view illustrating a boss part, a rotary bearing, and an insert member according to the embodiment. 
         FIG. 3  is a perspective view illustrating the insert member according to the embodiment. 
         FIG. 4  is a partially enlarged longitudinal cross-sectional view illustrating the boss part, the rotary bearing, and the insert member according to the embodiment. 
         FIG. 5  is a longitudinal cross-sectional view illustrating a modification of the boss part, the rotary bearing, and the insert member according to the embodiment. 
         FIG. 6  is a perspective view illustrating a modification of the insert member according to the embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, an embodiment according to the present invention will be described with reference to the drawings. 
       FIG. 1  is a longitudinal cross-sectional view illustrating a scroll compressor  1  according to the embodiment of the present invention. The scroll compressor  1  includes a housing  2  constituting an outer shell. The housing  2  is constituted by integrally fastening and fixing a front housing  3  and a rear housing  4  by a bolt  5 . The front housing  3  and the rear housing  4  have fastening flanges  3 A and  4 A integrally formed at regular intervals at multiple places, for example, at four places on a circumference. By fastening these flanges  3 A and  4 A to each other by the bolt  5 , the front housing  3  and the rear housing  4  are integrally coupled. 
     A crankshaft  6  is supported freely rotatably around its axis L via a main bearing  7  and a sub-bearing  8  inside the front housing  3 . One end side of the crankshaft  6  (the left side in  FIG. 1 ) forms a small-diameter shaft part  6 A, and the small-diameter shaft part  6 A passes through the front housing  3  to protrude toward the left side in  FIG. 1 . A protruding portion of the small-diameter shaft part  6 A is provided, as well known, with an electromagnetic clutch, a pulley, or the like (not shown) for receiving power, and the power is transmitted from a drive source such as an engine via a V-belt, etc. A mechanical seal (lip seal)  9  is disposed between the main bearing  7  and the sub-bearing  8  to air-tightly seal between the inside of the housing  2  and the atmosphere. 
     The other end side of the crankshaft  6  (the right side in  FIG. 1 ) is provided with a large-diameter shaft part  6 B, and the large-diameter shaft part  6 B has a crank pin  6 C integrally formed in a state of being eccentric to the axis L of the crankshaft  6  by a predetermined dimension. The crankshaft  6  is freely rotatably supported by the large-diameter shaft part  6 B and the small-diameter shaft part  6 A being supported by the front housing  3  via the main bearing  7  and the sub-bearing  8 . A rotary scroll  15  to be described later is coupled to the crank pin  6 C via a drive bush  10 , a cylinder ring (floating bush)  11 , and a rotary bearing  12 , and the rotary scroll  15  is configured to be driven to revolve by the rotation of the crankshaft  6 . 
     The drive bush  10  includes a balance weight  10 A integrally formed for removing an unbalanced load generated when the rotary scroll  15  is driven to revolve, and is configured to revolve together with the rotary scroll  15  being driven to revolve. Further, the drive bush  10  is provided with a crank pin hole  10 B for fitting the crank pin  6 C at a position eccentric to the center thereof. Thus, the drive bush  10  fitted with the crank pin  6 C and the rotary scroll  15  are caused to revolve around the crank pin  6 C upon receiving gas compression reaction force, constituting a known driven crank mechanism with a variable revolution radius of the rotary scroll  15 . 
     Further, the housing  2  has incorporated therein a scroll compression mechanism  13  constituted of a pair of fixed scroll  14  and rotary scroll  15 . The fixed scroll  14  is constituted of a fixed end plate  14 A and a fixed spiral lap  14 B (wall) erected on the fixed end plate  14 A, and the rotary scroll  15  is constituted of a revolving end plate  15 A and a revolving spiral lap  15 B (wall) erected on the revolving end plate  15 A. 
     These fixed scroll  14  and rotary scroll  15  have their centers separated from each other by the revolution radius, are engaged with phases of the respective spiral laps  14 B and  15 B shifted by 180 degrees, and are installed so as to have a slight clearance (several tens to several hundreds of micrometers) at room temperature in a lap height direction between a tooth tip face and a tooth bottom face of the spiral laps  14 B and  15 B. Thus, as shown in  FIG. 1 , the both scrolls  14  and  15  are configured so that a plurality of pairs of compression chambers  16  formed therebetween by being partitioned by each end plate  14 A and  15 A and each spiral lap  14 B and  15 B are point-symmetric with respect to a scroll center, and the rotary scroll  15  can smoothly revolve around the fixed scroll  14 . 
     The compression chambers  16  have a height in a rotation axis direction which is larger on an outer circumferential side than on an inner circumferential side of each spiral lap  14 B and  15 B, thereby constituting the scroll compression mechanism  13  capable of compressing gas three-dimensionally in both a circumferential direction and a height direction of each spiral lap  14 B and  15 B. The spiral laps  14 B and  15 B of the fixed scroll  14  and rotary scroll  15  may have incorporated therein tip seals  17  and  18 , respectively, which seal a tip clearance formed between the tooth tip face and the tooth bottom face of the mating scroll, fitted to a seal groove provided on each tooth tip face. 
     The fixed scroll  14  is fixedly installed on the inner face of the rear housing  4  via a bolt  27 . As described above, the rotary scroll  15  has the boss part  15 C, which is provided on a back face of the revolving end plate  15 A, coupled to the crank pin  6 C, which is provided on one end side of the crankshaft  6 , via the drive bush  10 , the cylinder ring (floating bush)  11 , and the rotary bearing  12 , and is configured to be driven to revolve. 
     Further, the rotary scroll  15  has the back face of the revolving end plate  15 A supported by a thrust receiving surface  3 B of the front housing  3 , and is configured to be driven to revolve around the fixed scroll  14  while being prevented from rotating on its own axis through a rotation preventing mechanism  19  provided between the thrust receiving surface  3 B and the back face of the revolving end plate  15 A. The rotation preventing mechanism  19  of the present embodiment is the pin-ring type rotation preventing mechanism  19 , in which a rotation preventing pin  19 B which is incorporated in a pin hole provided in the front housing  3  is freely slidably fitted to an inner circumferential face of the rotation preventing ring  19 A which is incorporated in a ring hole provided in the revolving end plate  15 A of the rotary scroll  15 . 
     The fixed scroll  14  has a discharge port  14 C for discharging compressed refrigerant gas opened at a central portion of the fixed end plate  14 A, and the discharge port  14 C has installed therein a discharge reed valve  21  mounted to the fixed end plate  14 A via a retainer  20 . Further, a seal material  22  such as an O-ring is inserted on the back face side of the fixed end plate  14 A so as to be in close contact with the inner face of the rear housing  4 , thereby forming a discharge chamber  23  divided from the inner space of the housing  2  between the back face of the fixed end plate and the inner face of the rear housing  4 . Thus, the inner space of the housing  2  except for the discharge chamber  23  is configured to function as a suction chamber  24 . 
     The refrigerant gas returning from a refrigeration cycle through a suction port  25  provided in the front housing  3  is sucked into the suction chamber  24 , and the refrigerant gas is sucked through this suction chamber  24  into the compression chamber  16 . A seal material  26  such as an O-ring is interposed between joining faces of the front housing  3  and the rear housing  4  so as to air-tightly seal the suction chamber  24  formed inside of the housing  2  against the atmosphere. 
     Note that the scroll compressor  1  uses lubricant oil for smoothly moving a sliding part inside thereof. The lubricant oil coexists with the refrigerant in a predetermined ratio, and is sucked into the fixed scroll  14  and the rotary scroll  15  together with the refrigerant. This lubricant oil is capable of sealing a minute clearance by adhering to inner wall faces of the fixed scroll  14  and the rotary scroll  15 . In the case of application in air conditioning, an oil film thickness of the lubricant oil adhering to the inner wall faces is approximately 5 μm in a thin part, approximately 100 μm in a thick part, and approximately 40 μm on average. 
     The lubricant oil is discharged from the scroll compressor  1  to, for example, a refrigerant pipe constituting a refrigeration circuit, passes through each component of the refrigeration circuit, returns to the scroll compressor  1 , and is sucked into the scroll compressor  1 . Note that some refrigeration circuits are provided with an oil separator for separating the lubricant oil and the refrigerant installed on the discharge side of the scroll compressor  1 , and the oil separator is capable of returning the separated lubricant oil into the scroll compressor  1 . 
     Next, a description will be given of a joining portion between the boss part  15 C and the rotary bearing  12  with reference to  FIGS. 2 to 4 . In this embodiment, an insert member  31  is disposed in a gap formed between the boss part  15 C and the rotary bearing  12 . 
     The boss part  15 C has a ring shape and is made of metal, for example, aluminum, and protrudes from the back face of the revolving end plate  15 A. The insert member  31  and the rotary bearing  12  are inserted into the boss part  15 C. 
     The rotary bearing  12  is a metallic, for example, steel needle bearing. An outer diameter of the rotary bearing  12  is smaller than an inner diameter of the boss part  15 C. As shown in  FIG. 2 , the rotary bearing  12  is constituted of an outer ring  28 , a plurality of needle rollers  29 , and a holder  30 . The outer ring  28  is of a substantially hollow cylindrical shape, and for example, has a collar part, which is bent at an approximately right angle toward the inside, formed on both ends in the axis L direction of the crankshaft  6 . The holder  30  holds the plurality of needle rollers  29  at almost equal intervals in the circumferential direction, and is mounted to the inside of the outer ring  28 . 
     As shown in  FIG. 3 , the insert member  31  has a ring shape. The insert member  31  has a thermal expansion coefficient greater than those of the metallic boss part  15 C and rotary bearing  12 , and is made of synthetic resin, for example, nylon 66, or synthetic rubber. In the example shown in  FIGS. 1 and 2 , two insert members  31  are disposed between the boss part  15 C and the rotary bearing  12 . 
     The insert member  31  is first installed on the inner face of the boss part  15 C at room temperature, and thereafter the rotary bearing  12  is inserted into the insert member  31 . The boss part  15 C may have a groove portion formed on the inner face to prevent displacement of the insert member  31 . Further, one end side  31   a  of the insert member  31  may be round-chamfered or corner-chamfered as shown in  FIG. 4 . This shape allows the rotary bearing  12  to be smoothly inserted into the insert member  31 . Note that the other end side  31   b  may be chamfered, or have a right-angled shape as it is as shown in  FIG. 4 . 
     It is preferable that the insert member  31  and the rotary bearing  12  are securely fixed to the boss part  15 C, that is, to the rotary scroll  15  at room temperature. According to the present embodiment, since the insert member  31  has the thermal expansion coefficient greater than those of the metallic boss part  15 C and rotary bearing  12 , even if each member expands at high temperatures at which the scroll compressor  1  is operating, the rotary bearing  12  is securely fixed to the boss part  15 C by the insert member  31 . 
     Supposing, for example, that the rotary scroll  15  and the boss part  15 C are made of aluminum and the rotary bearing  12  is made of steel, linear thermal expansion coefficients are 22.0×10 −6 /° C. and 12.5×10 −6 /° C., respectively, and the outer diameter of the rotary bearing  12  is 36 mm, if the temperature rises by 80° C., a difference of 27 μm is produced, generating a gap between the boss part  15 C and the rotary bearing  12 . For this reason, the inner diameter of the boss part  15 C has been set smaller at room temperature, and the rotary bearing  12  has been press-fitted into the boss part  15 C in the conventional practice. 
     On the other hand, in this embodiment, when supposing that the insert member  31  is, for example, made of nylon 66 and has a linear thermal expansion coefficient of 10×10 −5 /° C., since the thermal expansion coefficient is greater compared with that of the boss part  15 C and the rotary bearing  12 , the rotary bearing  12  is securely fixed to the boss part  15 C by the insert member  31 . It is preferable that the thickness, material, and the like of the insert member  31  are set or selected such that a gap generated between the boss part  15 C and the rotary bearing  12  at high temperatures, and an expansion difference of the insert member  31  when the temperature shifts from room temperature to a high temperature are equal. 
     INDUSTRIAL APPLICABILITY 
     Thus, according to the present embodiment, it is not necessary, during manufacturing, etc. of the scroll compressor  1  at low temperatures, to press-fit the rotary bearing  12  into the boss part  15 C in expectation of a difference in expansion occurring at high temperatures, and deformation of the rotary scroll  15  caused when press-fitting the rotary bearing  12  into the boss part  15 C can be prevented. As a result, it is also possible to prevent performance degradation of the scroll compressor  1  due to deformation during press-fitting. 
     Further, since the insert member  31  has a ring shape and is evenly disposed between the boss part  15 C and the rotary bearing  12 , the metallic boss part  15 C and rotary bearing  12  do not come into contact with each other. It is therefore possible to prevent surface damage (fretting) which has been conventionally caused, when the insert member  31  is not provided, on the contact portion between the boss part  15 C and the rotary bearing  12  by being subjected to vibration, repeated stress, and the like. Note that the shape of the insert member  31  is not limited to the ring shape, and other shapes may be used as long as the boss part  15 C and the rotary bearing  12  do not come into contact with each other. 
     Further, as the insert member  31  is made of, for example, synthetic resin or synthetic rubber, it is also possible to reduce noise and vibration during revolution of the rotary scroll  15 . 
     Note that it is not necessary to form a groove for fixing the insert member  31  to the outer face of the outer ring  28 , as long as the boss part  15 C and the rotary bearing  12  can be securely fixed by the insert member  31 . For example, the present embodiment can be applied even where the outer ring is thin like in the case of the needle bearing, that is, even where no groove can be formed on the outer face of the outer ring unlike the outer ring of a ball bearing, etc. 
     Further, the insert member of the present invention is not limited to the insert member  31  described above. For example, the insert member may be sheet-shaped, like the insert member  32  shown in  FIGS. 5 and 6 , and a wider member than the example shown in  FIGS. 1 to 4 , or may be an O-ring made of NBR. When the insert member  31  or the insert member  32  is made of nylon, a slit  33  may be provided as shown in  FIGS. 5 and 6 . Although it is difficult to insert the insert members  31  and  32  made of nylon into the boss part  15 C due to the relative hardness, providing the slit  33  allows the insert members  31  and  32  to be smoothly installed into the boss part  15 C. 
     Note that in the above embodiment, it has been described that the insert members  31  and  32  are disposed between the boss part  15 C and the rotary bearing  12 , and that the boss part  15 C and the rotary bearing  12  do not come into contact with each other. However, the present invention is not limited to this example. The rotary bearing  12  may be inserted into the boss part  15 C while compressing the insert members  31  and  32  with a press-fitting allowance for the fitting between the boss part  15 C and the rotary bearing  12  set to 0 or a value smaller than a conventional allowance. In this case, the boss part  15 C and the rotary bearing  12  partially come into contact with each other at low temperatures, for example, at room temperature. Even by such an insertion method, it is possible to suppress deformation caused when press-fitting the rotary bearing  12  into the boss part  15 C, and also to reduce noise and vibration during revolution of the rotary scroll. 
     Moreover, in the above embodiment, description has been given of the case where the cylinder ring (floating bush)  11  is provided to the crankshaft  6  on the outside of the drive bush  10 . However, the present invention is not limited to this example. For example, the present invention can also be applied to a case where no cylinder ring  11  is provided and the drive bush  10  is directly inserted into the rotary bearing  12 . Further, in the above embodiment, description has been given of the case where the present invention is applied to the scroll compressor, but it can be applied to a scroll expander as well. 
     REFERENCE SIGNS LIST 
     
         
           6  crankshaft 
           10  drive bush 
           11  cylinder ring (floating bush) (bush part) 
           12  rotary bearing (bearing) 
           14  fixed scroll 
           15  rotary scroll 
           15 A revolving end plate 
           15 B spiral lap (wall) 
           15 C boss part 
           28  outer ring 
           29  roller 
           30  holder 
           31 ,  32  insert member 
           33  slit