Abstract:
Variable displacement compressor is provided with a displacement control valve ( 2 ) that can change an opening degree of supplying passage ( 44, 46 ) between a valve seat (VS) and a valve body (VB), thereby changing the pressure in a crank chamber ( 9 ). The displacement control valve ( 2 ) is accommodated within a control valve chamber ( 5   c ) in a rear housing ( 5 ) and fixed in place by means of a circlip ( 50 ). A cutout ( 50   g ) is formed between the displacement control valve ( 2 ) and the circlip ( 50 ) and/or between the circlip ( 50 ) and the rear housing ( 5 ). A clearance (C) formed by the cutout ( 50   g ) and the like inhibits the transmission of vibrations caused by impacts between the valve seat (VS) and the valve body (VB). This makes the variable displacement compressor quiet, reduces costs by obviating the need for additional components, and results in excellent durability.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a displacement control valve. 
       BACKGROUND ART 
       [0002]    A conventional variable displacement compressor includes a suction chamber, crank chamber, discharge chamber, and control valve chamber that are arranged in a housing. A displacement control valve is accommodated in the control valve chamber by way of an O-ring, and the displacement control valve is fixed by a circlip. A valve seat and a valve body are arranged in a passage that connects the discharge chamber and the crank chamber and extends through the displacement control valve. The displacement control valve, for example, changes an opening degree of the passage between the valve seat and the valve body through pulse width modulation (PWM) control to change the pressure of the crank chamber. 
         [0003]    The variable displacement compressor is employed in an air conditioning device of a vehicle. For example, when the opening degree of the passage is increased by the PWM control during acceleration of the vehicle, high pressure refrigerant gas can easily be supplied from the discharge chamber to the crank chamber thereby decreasing displacement. On the other hand, when the opening degree of the passage is decreased by the PWM control during deceleration of the vehicle, the supply of high pressure refrigerant gas from the discharge chamber to the crank chamber is restricted thereby increasing displacement. In this manner, the variable displacement compressor can vary displacement in accordance with the vehicle speed and the like. 
         [0004]    In the variable displacement compressor, for example, depending on an input signal of the PWM control, small impacts may repetitively occur between the valve seat and valve body. The vibration caused by the impacts is transmitted to a case of the displacement control valve. Although the vibration is not transmitted to the housing of the variable displacement compressor through the O-ring, the vibration is transmitted to the housing of the variable displacement compressor through the circlip. As a result, the variable displacement compressor and components and the like of a refrigerant circuit, which is connected to the variable displacement compressor, produce abnormal noise. This tendency becomes strong especially when the input signal (frequency) is small. 
         [0005]    Like the variable displacement compressor disclosed in patent document 1, the circlip may be made of a vibration absorbing alloy. In such a case, the circlip suppresses vibration and restricts the transmission of vibration thereby realizing quietness. 
       PRIOR ART DOCUMENT 
     Patent Document 
       [0000]    
       
         Patent Document 1: Japanese Laid-Open Patent Publication No. 2007-71114 
       
     
       DISCLOSURE OF THE INVENTION 
     Problems to be Solved by the Invention 
       [0007]    However, the variable displacement compressor of the prior art described above uses a circlip that is made of a special vibration absorbing alloy. This raises costs. 
         [0008]    Thus, as shown in  FIGS. 15 and 16 , a displacement control valve  90  and a conventional circlip  91  may be arranged to sandwich a rubber sheet  92 . In the drawings, reference character  93  denotes a housing of a variable displacement compressor, and reference character  90   a  denotes a cover located at a rear end of the displacement control valve  90 . A terminal and the like formed in the cover  90   a  to supply power to a coil is not shown in the drawings. In this case, the sheet  92  absorbs vibration and restricts the transmission of the vibration to the circlip  91  and the housing  93  for the quietness. 
         [0009]    However, even in this compressor, the sheet  92  adds to the number of assembling steps and increases the component price thereby inevitably raising costs. Further, the sheet  92  may deteriorate when the compressor is used for a long period. This may adversely affect the quietness and the sealing between the housing  93  and the displacement control valve  90 . 
         [0010]    It is an object of the present invention to provide a variable displacement compressor that can realize quietness and have superior durability, while lowering costs by eliminating the need for additional components. 
       Means for Solving the Problem 
       [0011]    One aspect of the present invention is a variable displacement compressor including a housing including a suction chamber, a crank chamber, a discharge chamber, and a control valve chamber. A displacement control valve is accommodated in the control valve chamber and fixed to the housing by a circlip, which is engaged with an engagement groove of the housing. The displacement control valve includes a valve seat and a valve body arranged in a passage connecting the discharge chamber and the crank chamber or a passage connecting the crank chamber and the suction chamber. The valve body is accommodated in a valve case. An external signal is input to a coil to change an opening degree of the passage between the valve seat and the valve body so that pressure of the crank chamber can be changed. The coil is protected by a cover. Vibration generated by impact between the valve seat and the valve body is transmitted through a path extending from the valve seat via the valve case and the circlip to the housing. At least one of the circlip, the cover, and the engagement groove includes a cutout or a recess in the path. A clearance defined by the cutout or the recess forms a means for suppressing transmission of the vibration. 
         [0012]    In a first embodiment, the circlip includes a C-shaped engagement portion, which engages with the engagement groove, and a wide portion, which is formed at two ends of the engagement portion and has a fitting hole into which pliers is fitted. The engagement portion includes the cutout formed in a widthwise direction to avoid contact with the displacement control valve. The vibration transmitting suppressing means is the clearance defined by the cutout. 
         [0013]    In a further embodiment, the circlip includes an opposing surface that opposes the displacement control valve. The displacement control valve includes an end surface that opposes the opposing surface. The end surface includes the recess that avoids contact with the opposing surface. The vibration transmitting suppressing means is the clearance defined by the recess. 
         [0014]    In a further embodiment, the circlip includes an opposing surface that opposes the displacement control valve. The displacement control valve includes an end surface that opposes the opposing surface. The opposing surface includes the recess that avoids contact with the end surface. The vibration transmitting suppressing means is the clearance defined by the recess. 
         [0015]    In a further embodiment, the engagement groove is defined by a first engagement surface and a second engagement surface that are spaced apart by an equal distance in a circumferential direction. The circlip includes a first surface and a second surface spaced apart by an equal distance in the circumferential direction to engage with the engagement groove. At least one of the first surface and the second surface includes a recess for avoiding contact with the first engagement surface and the second engagement surface. The vibration transmitting suppressing means is the clearance defined by the recess. 
         [0016]    In a further embodiment, the engagement groove is defined by a first engagement surface and a second engagement surface that are spaced apart by an equal distance in a circumferential direction. The circlip includes a first surface and a second surface spaced apart by an equal distance in the circumferential direction to engage with the engagement groove. At least one of the first engagement surface and the second engagement surface includes the recess so that the distance between the first engagement surface and the second engagement surface is greater than the thickness of the circlip to avoid contact with the first surface and the second surface. The vibration transmitting suppressing means is the clearance defined by the recess. 
         [0017]    In a further embodiment, the vibration transmitting suppressing means is a means for attenuating vibration transmitted in at least either one of between the displacement control valve and the circlip and between the circlip and the housing. 
         [0018]    In a further embodiment, the cover is sealed by an O-ring, and the vibration attenuating means is the recess formed in a circumference of the cover closer to an opening of the control valve chamber than the O-ring. 
         [0019]    In a further embodiment, the engagement groove is defined by a first engagement surface and a second engagement surface spaced apart by an equal distance in a circumferential direction. The circlip is elastically deformable. The distance between the first engagement surface and the second engagement surface of the engagement groove is greater than the thickness of the circlip so that the circlip elastically deforms to obtain the clearance between the first engagement surface and the second engagement surface. The vibration attenuating means is the clearance. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  is a cross-sectional view of a variable displacement compressor according to first to eighth embodiments. 
           [0021]      FIG. 2  is a cross-sectional view of a displacement control valve according to the first to eighth embodiments. 
           [0022]      FIG. 3  is an enlarged cross-sectional view showing the main part of the variable displacement compressor in the first embodiment. 
           [0023]      FIG. 4  is a cross-sectional view taken along line IV-IV in  FIG. 3 . 
           [0024]      FIG. 5  is a plan view showing a circlip of the variable displacement compressor in the second embodiment. 
           [0025]      FIG. 6  is a cross-sectional view of the compressor in the second embodiment corresponding to  FIG. 4 . 
           [0026]      FIG. 7  is an enlarged cross-sectional view showing the main part of the variable displacement compressor in the third embodiment. 
           [0027]      FIG. 8  is a bottom view of the displacement control valve in the compressor of the third embodiment. 
           [0028]      FIG. 9  is a cross-sectional view taken along line IX-IX in  FIG. 7 . 
           [0029]      FIG. 10  is an enlarged cross-sectional view showing the main part of the variable displacement compressor in the fourth embodiment. 
           [0030]      FIG. 11  is an enlarged cross-sectional view showing the main part of the variable displacement compressor in the fifth embodiment. 
           [0031]      FIG. 12  is an enlarged cross-sectional view showing the main part of the variable displacement compressor in the sixth embodiment. 
           [0032]      FIG. 13  is an enlarged cross-sectional view showing the main part of the variable displacement compressor in the seventh embodiment. 
           [0033]      FIG. 14  is an enlarged cross-sectional view showing the main part of the variable displacement compressor in the eighth embodiment. 
           [0034]      FIG. 15  is an enlarged cross-sectional view showing the main part of a variable displacement compressor in a comparative example. 
           [0035]      FIG. 16  is a cross-sectional view of the compressor in the comparative example of  FIG. 15  taken alone line XIV-XIV in  FIG. 15 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0036]    First to eighth embodiments of the present invention will now be described with reference to the drawings. 
       First Embodiment 
       [0037]    As shown in  FIG. 1 , a variable displacement compressor according to a first embodiment is provided with a cylinder block  1  including a plurality of cylinder bores  1   a . The cylinder bores  1   a  are concentrically arranged at equal angular intervals and extend parallel to one another in the cylinder block  1 . The cylinder block  1  is held between a front housing  3  and a rear housing  5  and fastened in this state. A crank chamber  9  is defined in the cylinder block  1  and the front housing  3 . 
         [0038]    The front housing  3  includes a shaft hole  3   a , and the cylinder block  1  includes a shaft hole  1   b . The shaft holes  3   a  and  1   b  rotatably receive a drive shaft  11  with a shaft seal  9   a  and bearings  9   b  and  9   c . A pulley  13  is arranged on the front housing  3  by way of a bearing  3   b , and the pulley  13  is fixed to the drive shaft  11 . A belt  13   c , which is driven by an engine or a motor of a vehicle, runs about the pulley  13 . An electromagnetic clutch may be used instead of the pulley  13 . 
         [0039]    In the crank chamber  9 , a lug plate  15  is press-fitted to the drive shaft  11 , and bearings  9   d  and  9   e  are arranged between the lug plate  15  and the front housing  3 . A swash plate  17  is fitted to the drive shaft  11 . A spring  19 , which decreases a tilt angle of the swash plate  17  about the drive shaft  11 , is arranged between the lug plate  15  and the swash plate  17 . In the crank chamber  9 , a circlip  11   a  is fixed to the drive shaft  11 , and a return spring  21  is arranged to the circlip  11   a  facing toward the swash plate  17 . A link mechanism  23 , which supports the swash plate  17  in a tiltable manner, couples the lug plate  15  and the swash plate  17 . In the present specification, the term circlip is analogous to snap ring. 
         [0040]    Each cylinder bore  1   a  accommodates a piston  25  that is movable back and forth. Shoes  27   a  and  27   b , which form a pair, are arranged between each piston  25  and the swash plate  17 . The pairs of the shoes  27   a  and  27   b  convert the wobbling movement of the swash plate  17  into a reciprocating movement of the pistons  25 . 
         [0041]    A valve unit  29  is arranged between the cylinder block  1  and the rear housing  5 . A compression chamber  31  is formed between the piston  25  of each cylinder bore  1   a  and the valve unit  29 . The valve unit  29  draws refrigerant from a suction chamber  5   a  into the compression chamber  31  when the piston  25  is in the suction stroke, encloses the refrigerant in the compression chamber  31  when the piston  25  is in the compression stroke, and discharges the refrigerant in the compression chamber  31  to a discharge chamber  5   b  when the piston  25  is in the discharge stroke. 
         [0042]    The rear housing  5  includes the suction chamber  5   a , which is located inward in the radial direction, and the discharge chamber  5   b , which is annular and located outward in the radial direction. A bleeding passage  42  connects the crank chamber  9  and the suction chamber  5   a . Supplying passages  44  and  46  connect the crank chamber  9  and the discharge chamber  5   b . The rear housing  5  includes a control valve chamber  5   c  defined by a cylindrical cavity. The control valve chamber  5   c  accommodates a displacement control valve  2 , which is in communication with the suction chamber  5   a  through a pressure detection passage  48  and which is in communication with the supplying passages  44  and  46 . 
         [0043]    As shown in  FIG. 2 , the displacement control valve  2  includes a first case  4  and a second case  10  that form a valve case, which serves as a shell. An upper end portion of the first case  4  defines a detection chamber  4   a , and a lower end portion of the first case  4  defines a valve chamber  4   b . A side surface of the first case  4  includes a suction port  4   c  that opens the detection chamber  4   a  to the exterior. The suction port  4   c , which is in communication with the suction chamber  5   a  (refer to  FIG. 1 ) through the pressure detection passage  48 , is supplied with suction pressure Ps. The detection chamber  4   a  may be formed to supply the detection chamber  4   a  with flow rate differential pressure. An adjustment screw  6  is fastened to the upper end of the first case  4 , and the detection chamber  4   a  is defined by the first case  4  and the adjustment screw  6 . 
         [0044]    A tubular fixed steel core  8  is fixed to the lower end of the first case  4 . The first case  4  and the fixed steel core  8  define the valve chamber  4   b . The side surface of the first case  4  includes a crank port  4   d  that opens the valve chamber  4   b  to the exterior. The crank port  4   d  is in communication with the crank chamber  9  (refer to  FIG. 1 ) through the supplying passage  44  and is supplied with crank chamber pressure Pc. 
         [0045]    The first case  4  also includes a shaft hole  4   e , which extends in the axial direction. The shaft hole  4   e  communicates the detection chamber  4   a  and the valve chamber  4   b . The side surface of the first case  4  includes a discharge port  4   f  that opens the shaft hole  4   e  to the exterior and extends in the radial direction. The discharge port  4   f  is in communication with the discharge chamber  5   b  (refer to  FIG. 1 ) through the supplying passage  46  and is supplied with discharge pressure Pd. 
         [0046]    The second case  10 , which is tubular, is fixed to the lower end of the first case  4 , and a coil  12  is fixed around the fixed steel core  8  in the second case  10 . An input signal for the PWM control, which is an external signal, is input to the coil  12  through a terminal (not shown). In the present embodiment, the side at which the coil  12  is arranged is referred to as the lower end side, and the opposite side is referred to as the upper end side. 
         [0047]    A shaft hole  8   a  extends through the fixed steel core  8  coaxially with the shaft hole  4   e . A movable steel core  14  is located at a lower side of the fixed steel core  8 . A rod  16 , which is fixed to an upper end of the movable steel core  14 , extends upward through the shaft hole  8   a , the valve chamber  4   b , and the shaft hole  4   e  and into the detection chamber  4   a.    
         [0048]    A bellows  18  is accommodated in the detection chamber  4   a . The bellows  18  includes an upper end fixed to the adjustment screw  6  and a lower end fixed to the rod  16 . The lower end of the bellows  18  is urged upward by a spring  20 , which is arranged between the bellows  18  and the first case  4 . 
         [0049]    The upper part of the rod  16  includes a small diameter portion  16   a  that extends over the shaft hole  4   e  and the valve chamber  4   b . The portion above the small diameter portion  16   a  of the rod  16  has a diameter that is sufficient for sealing the shaft hole  4   e  while allowing for movement of the rod  16 , and the small diameter portion  16   a  has a smaller diameter than this upper portion. 
         [0050]    A valve seat VS extends around the shaft hole  4   e  of the valve chamber  4   b . The rod  16  includes a valve body VB, which faces the valve seat VS, below the small diameter portion  16   a . A spring washer  24  is fixed to the rod  16  in the valve chamber  4   b , and a push spring  26  is arranged between the spring washer  24  and the first case  4 . In the present embodiment, the valve seat VS is formed integrally with the first case  4 , and the rod including the valve body VB extends through the first case  4  and the second case  10 . 
         [0051]    A flange  28  is fixed to the lower end of the second case  10 , and a cover  30  is fixed to the lower end of the flange  28  to conceal the movable steel core  14 . The cover  30  is made of resin such as nylon in which glass fiber is dispersed. Part of the coil  12  is insert molded to the cover  30  in a state connected to the terminal (not shown). The cover  30  prevents lubricating oil and the like from collecting on the coil  12  and the terminal. 
         [0052]    As shown in  FIG. 3 , a wall surface of the control valve chamber  5   c  in the rear housing  5  includes an engagement groove  40  for engagement with a circlip  50 . The engagement groove  40  is annular and has a uniform depth from the wall surface of the control valve chamber  5   c . The engagement groove  40  includes a first engagement surface  40   a , which is located at an inner far side, and a second engagement surface  40   b , which is located at an outer side. The first engagement surface  40   a  has a tapered shape, the second engagement surface  40   b  is orthogonal to an axis of the control valve chamber  5   c , and the first engagement surface  40   a  and the second engagement surface  40   b  are spaced apart by an equal distance in the circumferential direction. 
         [0053]    The displacement control valve  2  is accommodated in the control valve chamber  5   c  of the compressor by way of five O-rings  2   a  to  2   e . The O-rings  2   a  to  2   d  seal passages from one another that are in communication with the displacement control valve  2 . The O-ring  2   e  functions to seal and prevent the entrance of refrigerant from the exterior and absorb vibration transmitted in the radial direction of the displacement control valve  2 . The circlip  50  is engaged with the engagement groove  40 . The circlip  50  uses a widely-circulated material, for example, carbon steel (S-C material), spring steel (SK material), and stainless steel (SUS material). In this state, each of the O-rings  2   a  to  2   e  is forced against the wall surface of the control valve chamber  5   c . Thus, the cover  30  of the displacement control valve  2  is in contact with the circlip  50 . 
         [0054]    As shown in  FIG. 4 , the circlip  50  includes a C-shaped engagement portion  50   a , which engages the engagement groove  40 , wide portions  50   b  and  50   c  formed on the two ends of the engagement portion  50   a , and a wide portion  50   d  formed at the middle of the engagement portion  50   a  and projecting inward in the radial direction opposing the wide portions  50   b  and  50   c . Fitting holes  50   e ,  50   f , which a pliers is fitted to reduce the diameter, extend through the wide portions  50   b  and  50   c.    
         [0055]    The circlip  50  shown in  FIG. 4  differs from the conventional circlip  91  shown in  FIG. 16  in that the engagement portion  50   a  is narrow excluding the wide portions  50   b  to  50   d . More specifically, the engagement portion  50   a  includes a cutout  50   g , which avoids contact with the cover  30  of the displacement control valve  2 , defined at an inner side of the C-shaped main body. The cutout  50   g  defines a clearance C that serves as a vibration transmitting suppressing means and a contact area reducing means. That is, the cutout  50   g  reduces the contact area between the cover  30  and the circlip  91  and lowers the rigidity of the cover  30 . This decreases the spring constant and shifts the resonance frequency to a low frequency thereby lowering the peak frequency and suppressing the transmission of vibration. 
         [0056]    As shown in  FIG. 3 , the circlip  50  includes a first surface  50   h , which faces the first engagement surface  40   a  and the cover  30 , and a second surface  50   i , which faces the second engagement surface  40   b . The first surface  50   h  and the second surface  50   i  engage the first engagement surface  40   a  and the second engagement surface  40   b , respectively. The first surface  50   h  and the second surface  50   i  are parallel. The first surface  50   h , which is an opposing surface opposing the cover  30 , can contact the cover  30  at the locations of the wide portions  50   b  to  50   d  but cannot contact the cover  30  at the location of the engagement portion  50   a . Thus, the parts of the first surface  50   h  at the wide portions  50   b  to  50   d  serves as contact surfaces that come into contact with the cover  30 . The cover  30  includes a surface  30   a  that contacts the first surface  50   h  or the second surface  50   i  where the wide portions  50   b  to  50   d  are located. 
         [0057]    In a vehicle air conditioner, the above compressor has the discharge chamber  5   b , which is shown in  FIG. 1 , connected to a condenser. The condenser is connected by an expansion valve to an evaporator, and the evaporator is connected to the suction chamber  5   a . When the drive shaft  11  is driven and rotated by an engine or the like, the refrigerant in the suction chamber  5   a  is compressed in the compression chambers  31  and discharged to the discharge chamber  5   b  with a displacement corresponding to the tilt angle of the swash plate  17 . 
         [0058]    During this operation, for example, when the vehicle is accelerated and the PWM control increases the opening degree between the valve seat VS and the valve body VB shown in  FIG. 2 , high pressure refrigerant gas is easily supplied in from the discharge chamber  5   b  to the crank chamber  9  through the discharge port  4   f , the shaft hole  4   e , the valve chamber  4   b , and the crank port  4   d . This decreases the displacement. On the other hand, when the speed of the vehicle is constant and the PWM control decreases the opening degree between the valve seat VS and the valve body VB, the supply of high pressure refrigerant gas from the discharge chamber  5   b  to the crank chamber  9  is restricted. This increases the displacement. Thus, in the compressor, the displacement is varied in accordance with the vehicle speed and the like. 
         [0059]    In this compressor, an input signal of the PWM control is transmitted to the coil  12  and transmitted by the rod  16  to the valve body VB. Thus, when the opening degree of the valve seat VS and the valve body VB is small, the valve body VB impacts the valve seat VS a number of times. The vibration generated by the impact of the valve seat VS and the valve body VB in the displacement control valve  2  is transmitted over a path extending through the case  10  from the valve seat VS to the rear housing  5 . 
         [0060]    However, in this compressor, the clearance C formed by the cutout  50   g  shown in  FIGS. 3 and 4  is arranged in the path and suppresses the transmission of the vibration generated by the impact of the valve seat VS and the valve body VB. This restricts the transmission of the vibration to the rear housing  5  and accomplishes noise reduction. 
         [0061]    This compressor does not employ a sheet, which is an additional member that increases the number of assembling steps and increases the cost of components. Further, the circlip  50  is made of a typical SUS. Thus, the compressor lowers cost. In particular, in the compressor, the rear housing  5  includes the engagement groove  40 , which is normal, and only the shape of the circlip  50  is special. Thus, costs are subtly increased. The compressor does not employ a rubber sheet that may deteriorate when used over a long period. Thus, quietness and sealing can be achieved over a long period. 
         [0062]    Accordingly, the compressor reduces noise, lowers cost, and has superior durability. 
       Second Embodiment 
       [0063]    A compressor of a second embodiment employs a circlip  51  shown in  FIGS. 5  and.  6 . In the circlip  51 , an engagement portion  51   a  includes a small diameter portion  51   b  and a large diameter portion  51   c  that are successively bent. Fitting holes  51   f  and  51   g  used to reduce the diameter are formed in wide portions  51   d  and  51   e . The parts of the small diameter portion  51   b  bent toward the large diameter portion  51   c  forms a cutout  51   h  that avoids contact with the cover  30  of the displacement control valve  2 . The clearance C formed by the cutout  51   h  serves as the vibration transmitting suppressing means and the contact area reducing means. That is, the cutout  50   h  reduces contact between the cover  30  and the circlip  51  and suppresses the transmission of vibration. Otherwise, the structure is the same as the first embodiment. 
         [0064]    The second embodiment has the same advantages as the first embodiment. 
       Third Embodiment 
       [0065]    As shown in  FIGS. 7 to 9 , a compressor of a third embodiment employs a novel cover  31  while employing the conventional circlip  91  shown in  FIG. 15  and  FIG. 16 . As shown in  FIG. 8 , recesses  31   b  and  31   c  are arranged at two opposite sides of a surface  31   a  of the cover  31  facing the circlip  91 . The recesses  31   b  and  31   c  avoid contact between the cover  31  and the circlip  91 . A clearance C formed by the two recesses  31   b  and  31   c  serves as the vibration transmitting suppressing means and the contact area reducing means. That is, the recesses  31   b  and  31   c  reducing the contact area between the cover  31  and the circlip  91  and suppress the transmission of vibration. Otherwise, the structure is the same as the first embodiment. 
         [0066]    The third embodiment also has the same advantages as the first embodiment. In particular, in the compressor of the third embodiment, the conventional circlip  91  is employed, and only the shape of the cover  31  of the displacement control valve  2  is special. Thus, costs are subtly increased. 
       Fourth Embodiment 
       [0067]    As shown in  FIG. 10 , a compressor of a fourth embodiment employs a novel circlip  52  while employing the conventional cover  30  and the engagement groove  40  shown in  FIGS. 1 to 4 . A plurality of recesses  52   b  are arranged in a circumferential direction in a surface  52   a , which comes into contact with the cover  30 , at one side of the circlip  52 . The recesses  52   b  avoid contact between the cover  30  and the circlip  52 . A clearance C formed by each recess  52   b  serves as the vibration transmitting suppressing means and the contact area reducing means. That is, the recesses  52   b  reduce the contact area between the cover  30  and the circlip  52  and between the circlip  52  and the rear housing  5 . This suppresses the transmission of vibration. Otherwise, the structure is the same as the first embodiment. 
         [0068]    The fourth embodiment also has the same advantages as the first embodiment. In particular, in the compressor of the fourth embodiment, the conventional displacement control valve  2  is employed, and only the shape of the circlip  52  is special. Thus, costs are subtly increased. 
       Fifth Embodiment 
       [0069]    As shown in  FIG. 11 , in a compressor of a fifth embodiment, a circlip  53  has a second surface  53   a  facing the second engagement surface  40   b  of the engagement groove  40  on the side opposite to the surface that comes into contact with the cover  30 . A plurality of recesses  53   b  are arranged in the circumferential direction in the second surface  53   a . The recesses  53   b  avoid contact between the circlip  53  and the rear housing  5 . A clearance C formed by each recess  53   b  serves as the vibration transmitting suppressing means and the contact area reducing means. That is, the recesses  53   b  reduce the contact area between the circlip  53  and the rear housing  5  and suppresse the transmission of vibration. Otherwise, the structure is the same as the fourth embodiment. 
         [0070]    The fifth embodiment also has the same advantages as the fourth embodiment. 
       Sixth Embodiment 
       [0071]    As shown in  FIG. 12 , a compressor of a sixth embodiment employs a novel engagement groove  41  while employing the conventional cover  30  shown in  FIGS. 1 to 4  and the conventional circlip  91  shown in  FIGS. 15 and 16 . The engagement groove  41  is defined by a first engagement surface  41   a , which is located at the inner side (upper end side) of the control valve chamber  5   c , and a second engagement surface  41   b , which is located at the open side (lower end side). A plurality of recesses  41   c  are arranged in the circumferential direction in the second engagement surface  41   b . In the portion where the recesses  41   c  are arranged, the distance between the first engagement surface  41   a  and the second engagement surface  41   b  is greater than the thickness of the circlip  91 . The recesses  41   c  avoid contact between the circlip  91  and the rear housing  5 . A clearance C formed by each recess  41   c  serves as the vibration transmitting suppressing means and the contact area reducing means. That is, the recesses  41   c  reduce the contact area between the circlip  91  and the rear housing  5  and suppress the transmission of the vibration. Otherwise, the structure is the same as the first embodiment. 
         [0072]    The sixth embodiment has the same advantages as the first embodiment. In particular, in the compressor of the sixth embodiment, only the shape of the engagement groove  41  is special. Thus, costs are subtly increased. 
       Seventh Embodiment 
       [0073]    As shown in  FIG. 13 , a compressor of a seventh embodiment employs a novel cover  32  while employing the conventional engagement groove  40  shown in  FIGS. 1 to 4  and the conventional circlip  91  shown in  FIGS. 15 and 16 . The circumferential part of the cover  32  includes a clearance  32   a  extending in the circumferential direction and arranged closer to the opening of the control valve chamber  5   c  than the O-ring  2   e . The clearance  32   a , which is formed by a recess, serves as the vibration transmitting suppressing means and the vibration attenuating means. That is, when the cover  32 , which defines the clearance, transmits vibration, the clearance  32   a  deforms and attenuates the vibration. This suppresses the transmission of vibration between the cover  32  and the circlip  91 . A contact surface  32   b  of the cover  32  contacts the circlip  91 . Otherwise, the structure is the same as the first embodiment. 
         [0074]    The seventh embodiment has the same advantages as the first embodiment. In particular, in the compressor of the seventh embodiment, the clearance  32   a  attenuates the vibration transmitted from the displacement control valve  2  to the circlip  91 . In this case, only the shape of the cover  32  for the displacement control valve  2  is special. Thus, costs are subtly increased. 
       Eighth Embodiment 
       [0075]    As shown in  FIG. 14 , a compressor of an eighth embodiment employs a new circlip  54  while employing the conventional engagement groove  40  and cover  30  shown in  FIGS. 1 to 4 . The circlip  54  has a thickness that is less than that of the conventional circlip  91 , smaller than the distance between the first engagement surface  40   a  and the second engagement surface  40   b  of the engagement groove  40 , and allows for elastic deformation to obtain clearances  54   a  and  54   b  between the engagement surfaces  40   a  and  40   b . The clearances  54   a  and  54   b  serve as the vibration transmitting suppressing means and the vibration attenuating means. That is, the clearances  54   a  and  54   b  attenuate the vibration transmitted in at least either one of between the cover  32  and the circlip  91  and between the circlip  91  and the rear housing  5 . This suppresses the transmission of the vibration between the components. Otherwise, the structure is the same as the first embodiment. 
         [0076]    The eighth embodiment has the same advantages as the first embodiment. In particular, the compressor of the eighth embodiment is only required to employ the circlip  54  that is elastically deformable in the thicknesswise direction. Thus, costs are subtly increased. 
         [0077]    The present invention has been described through the first to eighth embodiments. However, the present invention is not limited to the first to eighth embodiments, which may be modified within the scope of the invention. 
         [0078]    For instance, the displacement control valve  2  may include a bleeding passage  42  that connects the crank chamber  9  and the suction chamber  5   a  of the variable displacement compressor.