Patent Publication Number: US-10330098-B2

Title: Scroll compressor with controlled pressing force

Description:
TECHNICAL FIELD 
     The present invention relates to a scroll compressor. 
     BACKGROUND ART 
     A scroll compressor used in a vehicle air conditioner includes a fixed scroll and an orbiting scroll. Each of the fixed scroll and the orbiting scroll is configured of a spiral wrap that is integrally formed on one surface of a disc-like end plate. The fixed scroll and the orbiting scroll face each other while the respective wraps are engaged with each other, to cause the orbiting scroll to revolve relative to the fixed scroll. Then, a compression space formed between the respective wraps is reduced in capacity while the compression space is caused to move from the outer periphery side to the inner periphery side, thereby resulting in compression of a refrigerant. Note that the mechanism that relates to the compression of the refrigerant and includes the fixed scroll and the orbiting scroll is also referred to as a scroll compression mechanism. 
     During operation of the scroll compressor, the orbiting scroll and the fixed scroll each receive force, in a direction separating from each other, from the compressed refrigerant, and the orbiting scroll accordingly moves in an axial direction. As a result, a gap is formed between a front end surface (a tooth top) of the wrap of each scroll and the end plate on the opposite side, and the refrigerant is leaked from the gap, which may deteriorate performance of the compressor. 
     Therefore, for example, as disclosed in Patent Literature 1, it has been proposed that, to prevent the orbiting scroll from moving during the operation of the compressor, the compressed refrigerant is applied to the rear surface of the orbiting scroll to cause the orbiting scroll to float, thereby controlling the front end surface of the wrap to be constantly brought into contact with the end plate on the opposite side. Note that the control is also referred to as orbiting back-pressure control. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Patent No. 3893487 
     Patent Literature 2: Japanese Patent Laid-Open No. 8-86287 
     Patent Literature 3: Japanese Patent Laid-Open No. 8-159051 
     SUMMARY OF INVENTION 
     Technical Problem 
     When the orbiting scroll is floated, however, a thrust load from the orbiting scroll is received by a tooth top of the wrap. Thus, when the pressure applied as the back pressure becomes excessively large, pressing force of the tooth top of the wrap with respect to the end plate on the opposite side also becomes excessively large, which may cause the tooth top of the wrap to seize to the end plate or to be damaged. 
     The present invention is made based on such problems, and an object of the present invention is to provide a scroll compressor that makes it possible to avoid occurrence of excessive pressing force on a tooth top of a wrap while adopting orbiting back-pressure control. 
     Solution to Problem 
     A scroll compressor of the present invention made for such a purpose includes: a scroll compression mechanism; a back-pressure application mechanism; a floating amount restriction mechanism; and a housing that houses the scroll compression mechanism, the back-pressure application mechanism, and the floating amount restriction mechanism. 
     The scroll compression mechanism according to the present invention includes an orbiting scroll, a fixed scroll that faces the orbiting scroll to form a compression chamber compressing refrigerant gas, and a thrust plate supporting a load of the orbiting scroll in a thrust direction. 
     The back-pressure application mechanism applies, as back pressure, the refrigerant gas compressed by the scroll compression mechanism to a rear surface of the thrust plate. 
     The floating amount restriction mechanism restricts an amount of floating of the thrust plate caused by the back pressure. 
     In the scroll compressor according to the present invention, the back-pressure application mechanism applies, as the back pressure, the refrigerant gas compressed by the scroll compression mechanism to the rear surface of the thrust plate. This causes the thrust plate to float, thereby causing the orbiting scroll to float. Then, the scroll compressor according to the present invention restricts the amount of floating of the orbiting scroll through the restriction of the amount of floating of the thrust plate by the floating amount restriction mechanism. Therefore, it is possible to avoid occurrence of excessive pressing force on the tooth top of the wrap. 
     In the scroll compressor according to the present invention, the floating amount restriction mechanism may include a restriction pin that has a shaft part and a head part, and locks the thrust plate to the head part to restrict the amount of floating. The shaft part passes through the thrust plate and has a front end part fixed to the housing. The head part is continuous to the shaft part and has a diameter larger than a diameter of the shaft part. The head part may be locked to a step of a restriction hole that passes through the thrust plate and into which the restriction pin is inserted. 
     A pin-ring rotation preventing mechanism that prevents rotation of the orbiting scroll may be provided as the restriction pin, and the rotation preventing pin may function as the restriction pin. 
     In the scroll compressor according to the present invention, the floating amount restriction mechanism restricts the amount of floating through locking of a peripheral edge of the thrust plate to an inner circumferential wall of the housing. 
     In the scroll compressor according to the present invention, an abradable coating may be preferably provided on a front end surface of one or both of the wrap provided in the orbiting scroll and the wrap provided in the fixed scroll. Providing the abradable coating makes it possible to relax the dimensional tolerance required for members relating to the floating amount restriction of the orbiting scroll. 
     Advantageous Effects of Invention 
     The present invention provides the scroll compressor that makes it possible to avoid occurrence of excessive pressing force on the tooth top of the wrap while adopting the orbiting back-pressure control. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a vertical cross-sectional view of a scroll compressor according to a first embodiment. 
         FIG. 2  is a diagram of a front housing of the scroll compressor as viewed from a front side thereof. 
         FIGS. 3A to 3C  are diagrams illustrating a floating amount restriction mechanism according to the first embodiment, where  FIG. 3A  is a diagram illustrating a restriction pin and a restriction hole formed on a thrust plate,  FIG. 3B  is a diagram illustrating a state in which a floating amount of the thrust plate is zero, and  FIG. 3C  is a diagram illustrating a state in which the floating amount of the thrust plate is the maximum. 
         FIG. 4  is a vertical cross-sectional view of a scroll compressor according to a second embodiment. 
         FIGS. 5A to 5C  are diagrams illustrating a floating amount restriction mechanism according to the second embodiment, where  FIG. 5A  is a diagram illustrating a restriction pin and a restriction hole formed on a thrust plate,  FIG. 5B  is a diagram illustrating a state in which a floating amount of the thrust plate is zero, and  FIG. 5C  is a diagram illustrating a state in which the floating amount of the thrust plate is the maximum. 
         FIG. 6  is a vertical cross-sectional view of a scroll compressor according to a third embodiment. 
         FIGS. 7A and 7B  are diagrams illustrating a floating amount restriction mechanism according to the third embodiment, where  FIG. 7A  is a diagram illustrating a state in which a floating amount of a thrust plate is zero, and  FIG. 7B  is a diagram illustrating a state in which the floating amount of the thrust plate is the maximum. 
         FIG. 8  is a perspective view of an orbiting scroll. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The present invention is described in detail below based on some embodiments illustrated in accompanying drawings. 
     First Embodiment 
     As illustrated in  FIG. 1 , a horizontal scroll compressor (hereinafter, a compressor)  1  according to the present embodiment includes, as main components: a housing  11 ; a scroll compression mechanism (hereinafter, a compression mechanism)  12  that is disposed inside the housing  11  and compresses refrigerant gas taken in the housing  11 ; and a main shaft  13  that drives the compression mechanism  12 . The compressor  1  compresses a refrigerant and provides the compressed refrigerant to, for example, a refrigerant circuit of a vehicle air conditioner. 
     The compressor  1  has a configuration that makes it possible to avoid occurrence of excessive pressing force on a tooth top of a wrap while adopting orbiting back-pressure control. In the following, the configuration of the compressor  1  is described. 
     [Housing  11 ] 
     The housing  11  includes a front housing  14  and a rear housing  15 . Tightening flanges are provided on a plurality of positions on a circumference of each of the front housing  14  and the rear housing  15 , and are integrally tightened and fixed by fasting members  9 . 
     The compression mechanism  12  described below is housed in a housing space that is formed by combination of the front housing  14  and the rear housing  15 . Note that, in the compressor  1 , side on which the front housing  14  is provided is referred to as front, and side on which the rear housing  15  is provided is referred to as rear. 
     [Compression Mechanism  12 ] 
     The compression mechanism  12  includes a fixed scroll  20  that is fixed to the housing  11 , and an orbiting scroll  30  that revolves relative to the fixed scroll  20 . Further, an inside of the housing  11  is partitioned into a low pressure chamber  10 A and a high pressure chamber  10 B by the compression mechanism  12 . 
     The fixed scroll  20  is provided such that a center axis thereof is coincident with a center axis L of the main shaft  13 , and forms a compression chamber PR together with the orbiting scroll  30 . 
     The fixed scroll  20  includes a fixed end plate  21  supported by the rear housing  15 , and a spiral wrap  22  that stands from one of surfaces of the fixed end plate  21 . 
     A discharge port  23  that passes through in an axial direction is provided on a center part of the fixed end plate  21 . The high pressure/high temperature refrigerant gas that has been compressed in the compression chamber PR flows into the high pressure chamber  10 B through the discharge port  23 . The refrigerant gas contains a lubricant oil that lubricates a sliding surface and a bearing of the fixed scroll  20  and the orbiting scroll  30 . 
     A chip seal  28  is provided on a front end surface of the wrap  22  in order to secure sealability between the front end surface of the wrap  22  and an orbiting end plate  31  of the orbiting scroll  30  on the opposite side facing the front end surface. The chip seal  28  is slid while being brought into contact with the orbiting end plate  31  of the orbiting scroll  30  through the lubricant oil, thereby sealing a gap that is formed between the front end surface of the wrap  22  and the orbiting end plate  31 . The gap necessary for formation of an oil film of the lubricant oil is formed between the front end surface and the orbiting end plate  31 . 
     An abradable coating may be formed, as a sealing member, on the front end surface of the wrap  22 . 
     The abradable coating is worn when being brought into contact with the orbiting end plate  31  of the orbiting scroll  30  on the opposite side. This makes it possible to maintain the gap between the front end surface of the wrap  22  and the orbiting end plate  31  at the minimum level. In addition, it is possible to relax the dimensional tolerance required for a member relating to the floating amount restriction of the orbiting scroll  30  by a wearing amount of the abradable coating. Examples of the member relating to the floating amount restriction may include the restriction pin  60  described later, and a thrust plate  19  that has a restriction hole  65  into which the restriction pin  60  is inserted. 
     The material of the abradable coating is not limited, and may be selected from metal materials, resin materials, and ceramic materials. The abradable coating may also be provided on a wrap  32  of the orbiting scroll  30 . 
     The orbiting scroll  30  includes the disc-like orbiting end plate  31  and the spiral wrap  32  that stands from one of surfaces of the orbiting end plate  31 . 
     A boss  27  is provided on a rear surface of the orbiting end plate  31  of the orbiting scroll  30 , and an eccentric bushing  17  is assembled to the boss  27  through a bearing. An eccentric pin  18  is fitted to the inside of the eccentric bushing  17 . This couples the orbiting scroll  30  with the main shaft  13  while being eccentric from the shaft center of the main shaft  13 . Accordingly, when the main shaft  13  rotates, the orbiting scroll  30  revolves at an orbiting radius that is an eccentric distance from the shaft center of the main shaft  13 . 
     To prevent rotation of the orbiting scroll  30  while allowing revolution of the orbiting scroll  30 , an Oldham&#39;s coupling not illustrated and a pin-ring rotation preventing mechanism are provided between the orbiting scroll  30  and the main shaft  13 . The rotation preventing mechanism is provided on each of four positions illustrated by P 1  in  FIG. 2 , and the configuration thereof is described in a second embodiment. 
     A chip seal  38  is provided on the front end surface of the wrap  32  as with the front end surface of the wrap  22 , and an oil film of a lubricant oil is formed between the chip seal  38  and the fixed end plate  21 . 
     The fixed scroll  20  and the orbiting scroll  30  are assembled to be eccentric from each other by a predetermined amount and to have a small gap in a wrap height direction between the front end surfaces and bottom surfaces of the respective wraps  22  and  32  that are engaged with each other with a phase shifted by 180 degrees. As a result, as illustrated in  FIG. 1 , the pair of compression chambers PR that are formed by the end plates  21  and  31  and the wraps  22  and  32  are formed, symmetrically to the scroll center, between the scrolls  20  and  30 . Each of the compression chambers PR gradually moves toward an inner circumference along with the revolution of the orbiting scroll  30  while decreasing the volume of the compression chamber PR. Then, the refrigerant gas is compressed at the maximum level at the center part of the spiral. 
     The compression mechanism  12  decreases the capacity of the compression space that is formed between the scrolls  20  and  30 , in the wrap height direction at the middle of the spiral, and is called a 3D scroll (R). Therefore, the height of the wrap is made lower on the inner peripheral side than that on the outer peripheral side on both of the fixed scroll  20  and the orbiting scroll  30 . In addition, the end plate on the opposite side facing the stepped warp is made project toward the inner surface of the end plate on the inner peripheral side rather than the outer peripheral side. 
     As illustrated in  FIG. 8 , a step part  32 C is provided between an inner circumferential wrap  32 A and an outer circumferential wrap  32 B of the orbiting scroll  30 . In the step part  32 C, the outer circumferential wrap  32 B stands up from the inner circumferential wrap  32 A, and the outer circumferential wrap  32 B has a height higher than that of the inner circumferential wrap  32 A. In contrast, the end plate  31  includes an inner circumferential bottom part  31 A and an outer circumferential bottom part  31 B, and a step part  31 C is provided therebetween, which causes the inner circumferential bottom part  31 A to be higher in height than the outer circumferential bottom part  31 B. 
     Note that the fixed scroll  20  also has a structure similar to the structure of the orbiting scroll. 
     Further, although the example of one step is illustrated in this case, two or more steps may be provided. 
     [Thrust Plate  19 ] 
     The annular thrust plate  19  is provided in front of the orbiting scroll  30  to be close to and to face the orbiting end plate  31 . 
     The thrust plate  19  is formed of a wear resident material, is disposed between the orbiting end plate  31  and the front housing  14  that faces the orbiting end plate  31 , and supports the thrust load from the orbiting scroll  30 . The thrust plate  19  functions as a thrust sliding bearing relative to the orbiting scroll  30 , and the orbiting scroll  30  slides on the thrust plate  19  during operation of the compressor  1 . 
     The thrust plate  19  according to the present embodiment has a function of applying back pressure to the orbiting scroll  30 , in addition to a function as the thrust sliding bearing as mentioned above. Movement of the thrust plate  19  in a circumferential direction is constrained; however, forward movement of the thrust plate  19  is not constrained in order to achieve back-pressure application function, and the thrust plate  19  can float from the front housing  14 . 
     [Back-Pressure Application Mechanism] 
     The scroll compressor  1  has the following configuration in order to apply back pressure to the orbiting scroll  30  through the thrust plate  19 . 
     As illustrated in  FIG. 2 , an inner sealing body  46  and an outer sealing body  47  are provided between the thrust plate  19  and the front housing  14  with a distance therebetween in a radial direction. Each of the inner sealing body  46  and the outer sealing body  47  is formed of an elastic material. Further, an annular concave part  44  is provided between the inner sealing body  46  and the outer sealing body  47  along the circumferential direction of the front housing  14  (the thrust plate  19 ). 
     Further, as illustrated in  FIG. 1 , a communication passage  43  that communicates with the concave part  44  is annularly provided in the front housing  14 . The concave part  44  and the communication passage  43  are together referred to as a pressure pocket  45 . The communication passage  43  and the high pressure chamber  10 B are communicated with each other by a high-pressure side flow path  41  that has an opening area A 1 . The high-pressure refrigerant gas discharged to the high pressure chamber  10 B flows into the pressure pocket  45  through the high-pressure side flow path  41 . 
     Note that, in the present embodiment, providing the inner sealing body  46  as close as possible to the center, except for the position P 1  where the rotation preventing mechanism is provided and the position P 2  where the floating amount restriction mechanism is provided, increases the opening area of the concave part  44 . This makes it possible to secure the back pressure to be applied to the orbiting scroll  30 . 
     The communication passage  43  communicates with an end of a low-pressure side flow path  42  having an opening area A 2 , and the other end of the low-pressure side flow path  42  communicates with the low pressure chamber  10 A. Accordingly, the high pressure/high temperature refrigerant gas that has flowed from the high-pressure side flow path  41  into the pressure pocket  45  passes through the pressure pocket  45 , and then flows into the low pressure chamber  10 A through the low-pressure side flow path  42 . Note that the refrigerant gas contains a lubricant oil, and the low-pressure side flow path  42  mainly functions as a passage returning the lubricant oil to the low pressure chamber  10 A. 
     The opening area A 2  of the low-pressure side flow path  42  is set to be smaller than the opening area A 1  of the high-pressure side flow path  41  (A 2 &lt;A 1 ). Therefore, the amount of the refrigerant gas that flows from the pressure pocket  45  to the low pressure chamber  10 A is smaller than the amount of the refrigerant gas that flows from the high-pressure side flow path  41  into the pressure pocket  45 . 
     [Floating Amount Restriction Mechanism] 
     The compressor  1  includes a mechanism restricting the floating amount of the orbiting scroll  30 . As described below, the mechanism restricts the floating amount of the thrust plate  19  that receives the pressure of the refrigerant gas to float the orbiting scroll  30 , thereby restricting the floating amount of the orbiting scroll  30 . 
     As illustrated in  FIG. 1  and  FIGS. 3A to 3C , the mechanism includes a restriction pin  60  that passes through the thrust plate  19  and has a front end fixed to the front housing  14 . As illustrated in  FIG. 3A , the restriction pin  60  includes, as components, a shaft part  61  and a head part  62  continuous with the shaft part  61 . The head part  62  has a diameter larger than that of the shaft part  61 . A cylindrical air gap  35  is provided on the orbiting end plate  31  at a position corresponding to the restriction pin  60 . 
     As illustrated in  FIG. 3A , the thrust plate  19  has a restriction hole  65  that passes through front and rear of the thrust plate  19  and into which the restriction pin  60  is inserted. The restriction hole  65  includes a small-diameter part  66  and a large-diameter part  67 . The small-diameter part  66  has a diameter corresponding to the shaft part  61  of the restriction pin  60 , and the large-diameter part  67  has a diameter corresponding to the head part  62  of the restriction pin  60 . 
     As illustrated in  FIG. 3B  and  FIG. 3C , the restriction pin  60  is inserted into the restriction hole  65  of the thrust plate  19 , and the front end part of the restriction pin  60  is fixed to the front housing  14 . Here,  FIG. 3B  is a diagram illustrating a state in which the thrust plate  19  does not float (the floating amount is zero) because the thrust plate  19  does not receive the back pressure.  FIG. 3C  is a diagram illustrating a state in which the back pressure is applied to the thrust plate  19  and the floating amount of the thrust plate  19  accordingly becomes the maximum. As illustrated in  FIG. 3B  and  FIG. 3C , when receiving the back pressure, the thrust plate  19  floats; however, the head part  62  of the restriction pin  60  is locked to a step that is a boundary between the small-diameter part  66  and the large-diameter part  67 , which restricts floating of the thrust plate  19  beyond the locked position. As mentioned above, the floating of the orbiting scroll  30  follows the floating of the thrust plate  19 . Therefore, restricting the floating amount of the thrust plate  19  makes it possible to restrict the floating amount of the orbiting scroll  30 . 
     In the present embodiment, as illustrated in  FIG. 3B , a front surface  19 S of the thrust plate  19  and a top surface  62 S of the head part  62  of the restriction pin  60  may preferably form the same plane in the state where the floating amount of the thrust plate  19  is zero. This allows for specification of the floating amount of the thrust plate  19  by a value that is obtained by subtracting a thickness t of the head part  62  from a depth d of the large-diameter part  67 , which facilitates control of the floating amount of the orbiting scroll  30 . 
     Further, although one floating amount restriction mechanism configured of the pair of the restriction pin  60  and the restriction hole  65  is illustrated in  FIGS. 3A, 3B, and 3C , two or more floating amount restriction mechanism may be provided in the present embodiment. For example, the floating amount restriction mechanism may be provided on each of positions denoted by P 2  in  FIG. 2 . Note that, in  FIG. 2 , two positions P 2  are symmetrical to each other. 
     [Operation of Compressor  1 ] 
     Next, the operation of the compressor  1  including the above-described configuration is described. 
     When a drive source is driven and the compressor  1  is accordingly driven, the main shaft  13  rotates, and the orbiting scroll  30  revolves relative to the fixed scroll  20  along with the rotation of the main shaft  13 . As a result, the refrigerant gas is compressed in the compression chamber PR between the orbiting scroll  30  and the fixed scroll  20 , and the refrigerant gas that has been introduced from an unillustrated suction pipe to the low pressure chamber  10 A inside the housing  11  is sucked into a space between the orbiting scroll  30  and the fixed scroll  20 . Then, the refrigerant gas that has been compressed in the compression chamber PR and put into the high temperature/high pressure state is discharged to the high pressure chamber  10 B through the discharge port  23  of the fixed end plate  21 . 
     Then, the discharged high pressure/high temperature refrigerant gas is discharged to the outside through an unillustrated discharge port. The suction, compression, and discharge of the refrigerant are sequentially performed in this manner. 
     A portion of the refrigerant gas discharged to the high pressure chamber  10 B flows into the pressure pocket  45  through the high-pressure side flow path  41 . The pressure pocket  45  is sealed by the thrust plate  19 , the inner/outer sealing bodies  46  and  47 , and the front housing  14 , except for a connection part with the high-pressure side flow path  41  and the low-pressure side flow path  42 . The high-pressure refrigerant gas that has flowed into the pressure pocket  45  applies, to the orbiting scroll  30  through the thrust plate  19 , back pressure that presses the orbiting scroll  30  toward the fixed scroll  20 , in the process of flowing inside the pressure pocket  45  along the circumferential direction, as described later. Since the opening area A 2  of the low-pressure side flow path  42  is smaller than the opening area A 1  of the high-pressure side flow path  41 , predetermined pressure is loaded to the pressure pocket  45 . The force pressing the orbiting scroll  30  depends on the pressure of the refrigerant gas discharged to the high pressure chamber  10 B. 
     The refrigerant gas that has passed through the pressure pocket  45  is sucked from the low-pressure side flow path  42  into the low pressure chamber  10 A, whereas the lubricant oil contained in the refrigerant gas is returned to the low pressure chamber  10 A. 
     Hereinbefore, the case in which the refrigerant gas flows into the pressure pocket  45  is described; however, the lubricant oil contained in the refrigerant gas may flow into the pressure pocket  45 . 
     In this case, an oil separation chamber is provided on the high pressure chamber  10 B side, and the high-pressure side flow path  41  is provided on a bottom of the oil separation chamber. 
     The lubricant oil separated by the oil separation chamber flows to the bottom of the oil separation chamber by its own weight, and then flows into the pressure pocket  45  through the high-pressure side flow path  41 . Pressure is applied to the lubricant oil from the refrigerant gas in the high pressure chamber  10 B. Thus, the pressing force of the lubricant oil to the thrust plate  19  depends on the pressure of the refrigerant gas discharged from the compression chamber PR. The lubricant oil is returned to the low pressure chamber  10 A through the low-pressure side flow path  42 . 
     [Effects] 
     Next, action and effects of the compressor  1  having the above-described configuration are described. 
     The compressor  1  restricts the floating amount of the orbiting scroll  30  with use of the floating amount restriction mechanism that is configured of the restriction pin  60  and the restriction hole  65 , during the high performance operation. This prevents the front end surfaces of the wraps  22  and  32  from being pressed against the end plates  31  and  21  on the respective counter sides by excessive force. Therefore, the compressor  1  makes it possible to secure reliability with respect to failure such as seizure of the tooth tops of the respective wraps  32  and  22 , while performing the back-pressure control. 
     Further, the compressor  1  achieves restriction of the floating amount of the orbiting scroll  30  through restriction of the floating amount of the thrust plate  19 . For example, a floating amount restriction mechanism similar to that of the present embodiment may be provided on the orbiting scroll  30 ; however, failure such as galling and seizure may occur between the orbiting scroll  30  and the restriction pin  60  due to sliding that inevitably occurs therebetween along with the orbiting motion of the orbiting scroll  30 . In contrast, in the case where the mechanism is provided in the thrust plate  19  as with the present embodiment, it is possible to secure reliability with respect to the failure because the thrust plate  19  does not perform motion other than floating. 
     Further, in the compressor  1 , the rotation preventing mechanism prevents the thrust plate  19  from being inclined when the thrust plate  19  floats, thereby contributing to stable floating of the thrust plate  19 . 
     Second Embodiment 
     Next, a compressor  2  according to a second embodiment is described based on  FIG. 4  and  FIGS. 5A, 5B , and  5 C. 
     In the second embodiment, a pin that is originally provided in the scroll compressor  2  to prevent rotation of the orbiting scroll  30  is replaced with the restriction pin  60  of the floating amount restriction mechanism. Since the compressor  2  has a configuration similar to that of the compressor  1  except for the above-described pin, the components same as those used in the first embodiment are denoted by the reference numerals in  FIG. 4  and  FIGS. 5A, 5B, and 5C  same as those in  FIG. 1  to  FIGS. 3A, 3B, and 3C , and the compressor  2  is described below while focusing on differences with the compressor  1 . 
     The compressor  2  includes a rotation preventing mechanism that prevents rotation of the orbiting scroll  30 . The rotation preventing mechanism is provided at a position denoted by P 1  in  FIG. 2 , and a pin-ring rotation preventing mechanism is adopted in the present embodiment. 
     As illustrated in  FIG. 5 , the rotation preventing mechanism includes the restriction pin (a rotation preventing pin)  60  fixed to the front housing  14 , and a rotation preventing ring  68  provided in the orbiting scroll  30 . 
     The restriction pin  60  is different from that of the first embodiment in that the restriction pin  60  of the present embodiment includes a rotation preventing pin part  63  in addition to the shaft part  61  and the head part  62  as illustrated in  FIG. 5A . 
     As illustrated in  FIG. 5B , the thrust plate  19  includes the restriction hole  65  that passes through the front and rear of the thrust plate  19  and into which the restriction pin  60  is inserted. The restriction hole  65  is configured of the small-diameter part  66  and the large-diameter part  67 , as with the first embodiment. 
     The rotation preventing ring  68  is fitted to the cylindrical air gap  35  that is formed on a thrust surface on the rear surface side of the orbiting end plate  31  of the orbiting scroll  30 . 
     As illustrated in  FIG. 5B  and  FIG. 5C , the restriction pin  60  is inserted into the restriction hole  65  of the thrust plate  19 , and the front end side thereof is fixed to the front housing  14 . The rotation preventing pin part  63  is provided to project from the surface of the thrust plate  19  to the inside of the air gap  35 . 
     As with the first embodiment,  FIG. 5B  is a diagram illustrating the state in which the floating amount of the thrust plate  19  is zero, and  FIG. 5C  is a diagram illustrating the state in which the floating amount of the thrust plate  19  is the maximum. As illustrated in  FIGS. 5B and 5C , the head part  62  of the restriction pin  60  is locked to the step that is the boundary between the small-diameter part  66  and the large-diameter part  67 , which restricts the floating amount of the orbiting scroll  30 . In this process, the rotation preventing pin part  63  of the restriction pin  60  revolves along an inner wall surface of the rotation preventing ring  68 , thereby preventing the rotation of the orbiting scroll  30 . Accordingly, the orbiting scroll  30  may revolve relative to the fixed scroll  20 . 
     [Effects] 
     The compressor  2  includes the action and effects similar to those of the compressor  1  according to the first embodiment and exhibits the following effects as well. 
     It is unnecessary for the compressor  2  to include a dedicated restriction pin for restriction of the floating amount because the compressor  2  uses the rotation preventing pin provided in the scroll compressor to restrict the floating amount of the orbiting scroll  30 . Accordingly, the number of components of the compressor  2  may be reduced as compared with the first embodiment, which contributes to cost reduction. 
     Further, since the part where the dedicated restriction pin  60  passes through the thrust plate  19  cannot receive the back pressure, the area of the thrust plate  19  receiving the back pressure is decreased when the dedicated restriction pin  60  is provided. In contrast, using the rotation preventing pin as with the compressor  2  eliminates reduction of the back-pressure area by the dedicated restriction pin  60 . This makes it possible to expand the back-pressure area as compared with the first embodiment. 
     Third Embodiment 
     Next, a compressor  3  according to a third embodiment is described based on  FIG. 6  and  FIGS. 7A and 7B . 
     In the third embodiment, the thrust plate  19  is locked to the housing to restrict the floating amount of the orbiting scroll  30  through the thrust plate  19 . Although the compressor  3  includes a configuration necessary therefor, the basic configuration of the compressor  3  as the scroll compressor is similar to that of the compressor  1 . Therefore, the components same as those of the compressor  1  are denoted by the reference numerals in  FIG. 6  and  FIGS. 7A and 7B  same as those in  FIG. 1  to  FIGS. 3A, 3B, and 3C , and the compressor  3  is described below while focusing on differences with the compressor  1 . 
     As illustrated in  FIG. 6  and  FIGS. 7A and 7B , in the compressor  3 , the diameter of the thrust plate  19  is expanded up to an extent interfering the inner wall surface of the front housing  14 . On the other hand, a restriction groove  69  that recedes from the inner wall surface in the thickness direction is provided in a region, of the front housing  14 , corresponding to the floating range of the thrust plate  19 . The restriction groove  69  is formed in a ring shape continuously to the circumferential direction of the inner wall surface. The peripheral edge part of the thrust plate  19  is inserted into the restriction groove  69 , which restricts the floating amount of the thrust plate  19 . 
     Here,  FIG. 7A  is a diagram illustrating the state in which the floating amount of the thrust plate  19  is zero, and  FIG. 7B  is a diagram illustrating the state in which the floating amount of the thrust plate  19  is the maximum. 
     As illustrated in  FIGS. 7A and 7B , when receiving the back pressure, the thrust plate  19  floats; however, the peripheral edge of the thrust plate  19  is locked to an upper wall of the restriction groove  69 , which restricts floating of the thrust plate  19  up to the locked position. In this way, the compressor  3  causes the thrust plate  19  and the front housing  14  to lock to each other, thereby restricting the floating amount of the orbiting scroll  30 . 
     In this case, the dimension (the depth) receded from the inner wall surface and the dimension (the width) in the axial direction of the restriction groove  69  are optional as long as the restriction groove  69  achieves the restriction of the floating amount mentioned above. 
     Moreover, it is assumed that the restriction groove  69  is formed continuously to the entire region in the circumferential direction and the entire peripheral edge of the thrust plate  19  is inserted into the restriction groove  69 . The restriction groove  69 , however, may be optionally provided intermittently in the circumferential direction, and the expanded part of the diameter of the thrust plate  19  that is to be inserted into the restriction groove  69  may be optionally provided intermittently according to the restriction groove  69 , as long as the restriction of the floating amount mentioned above is achieved. 
     [Effects] 
     The compressor  3  has the effects similar to those of the compressor  1  according to the first embodiment and exhibits the following effects as well. 
     The compressor  3  causes the thrust plate  19  and the front housing  14  to lock to each other, thereby restricting the floating amount of the orbiting scroll  30 . Therefore, it is unnecessary for the compressor  3  to include the dedicated restriction pin for restriction of the floating amount. This makes it possible to achieve cost reduction by the reduction of the number of components, as compared with the first embodiment. 
     Further, since it is unnecessary for the compressor  3  to include the dedicated restriction pin  60 , it is possible to expand the back-pressure area as with the second embodiment, as compared with the first embodiment. 
     Moreover, since the compressor  3  locks the entire peripheral edge of the thrust plate  19  by the restriction groove  69 , it is possible to reduce variation of the floating amount in the circumferential direction when the floating amount of the thrust plate  19  becomes the maximum. This makes it possible to prevent the orbiting scroll  30  from being inclined in the axial direction and to secure stable floating when the orbiting scroll  30  floats through the thrust plate  19 . Furthermore, the peripheral edge of the thrust plate  19  is locked to the restriction groove  69 , which exerts a function of preventing the thrust plate  19  from rotating in the circumferential direction. 
     In the third embodiment in which the thrust plate  19  is locked to the housing, formation of the restriction groove  69  with high accuracy is important for strictly controlling the floating amount of the orbiting scroll  30 . Since the restriction groove  69  described above is located on the bottom of the front housing  14  as illustrated in  FIG. 6 , it is difficult to perform mechanical processing of the restriction groove  69  with high accuracy. Thus, as illustrated in  FIG. 6 , the housing is divided into two members different from each other at a boundary CL corresponding to the restriction groove  69 , which facilitates the processing of the restriction groove  69 . In this case, a part that corresponds to the front housing  14  located on right side of the boundary CL in the drawing and the fixed scroll  20  are integrally formed. Then, the integrated structure is abutted on a part that corresponds to the front housing  14  located on left side of the boundary CL in the drawing, at the boundary CL. When the third embodiment is applied to this three-piece scroll compressor, it is possible to easily form the restriction groove  69  with high accuracy. 
     Although the preferred embodiments of the present invention are described hereinbefore, the configurations described in the above-described embodiments may be selected or may be appropriately modified without departing from the scope of the present invention. 
     It is sufficient for the present invention to include the part that presses the orbiting scroll  30 . Therefore, although the concave part  44  is provided on the front housing  14  in the present embodiment, the concave part  44  may be provided in the thrust plate  19 . 
     The front surface side of the orbiting end plate  31 , however, may have a complicated form in relation to the peripheral members. Therefore, providing the thrust plate  19  makes it possible to form the concave part  44  on the same plane. This allows for pressing of the orbiting scroll with uniform force. 
     REFERENCE SIGNS LIST 
     
         
           1 ,  2 ,  3  Scroll compressor (compressor) 
           9  Fasting member 
           10 A Low pressure chamber 
           10 B High pressure chamber 
           11  Housing 
           12  Compression mechanism 
           13  Main shaft 
           14  Front housing 
           15  Rear housing 
           17  Eccentric bushing 
           18  Eccentric pin 
           19  Thrust plate 
           19 S Front surface 
           20  Fixed scroll 
           21  Fixed end plate 
           22  Wrap 
           23  Discharge port 
           27  Boss 
           28  Chip seal 
           30  Orbiting scroll 
           31  Orbiting end plate 
           31 A Inner circumferential bottom part 
           31 B Outer circumferential bottom part 
           31 C Step part 
           32  Wrap 
           32 A Inner circumferential wrap 
           32 B Outer circumferential wrap 
           32 C Step part 
           35  Air gap 
           38  Chip seal 
           41  High-pressure side flow path 
           42  Low-pressure side flow path 
           43  Communication passage 
           44  Concave part 
           45  Pressure pocket 
           46  Inner sealing body 
           47  Outer sealing body 
           60  Restriction pin 
           61  Shaft part 
           62  Head part 
           62 S Top surface 
           63  Rotation preventing pin part 
           65  Restriction hole 
           66  Small-diameter part 
           67  Large-diameter part 
           68  Rotation preventing ring 
           69  Restriction groove