Patent Publication Number: US-2018051682-A1

Title: Wobble Plate Type Variable Displacement Compressor

Description:
TECHNICAL FIELD 
     The present invention relates to a wobble plate type variable displacement compressor in which a piston is reciprocated by a wobble plate which swings along with the rotation of a rotating main shaft, and specifically, relates to a wobble plate type variable displacement compressor used in a refrigerant circulating device for a vehicle air conditioning system, and the like. 
     BACKGROUND ART 
     As this type of wobble plate type variable displacement compressor, a compressor disclosed in Patent Document 1 has been proposed. In the wobble plate type variable displacement compressor disclosed in Patent Document 1, a piston support is swung along with rotation of a swash plate synchronously rotating with a main shaft of which a front end side and a rear end side are rotatably supported by a housing via bearings, to thereby reciprocate the piston in a cylinder bore. Furthermore, by providing a rotation preventing mechanism of the piston support on a middle portion of the main shaft, and devising a structure of the rotation preventing mechanism, the whirling vibration of the main shaft occurring when the compressor is driven and noise occurring therefrom are reduced. 
     REFERENCE DOCUMENT LIST 
     Patent Document 
     Patent Document 1: JP H05-99137 A 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     In the rotation preventing mechanism of the wobble plate type variable displacement compressor disclosed in Patent Document 1, onto the outer periphery of a swash plate sleeve which is installed so as to be movable in an axial direction with respect to a main shaft and rotatable integrally with the main shaft, a support sleeve is externally fitted to be rotatable relative to the swash plate sleeve, and the support sleeve is supported in the guide hole of a cylinder block (constituting a part of the housing) to be movable only in the axial direction of the main shaft. That is, the main shaft is supported on the inner peripheral surface of the support sleeve via the swash plate sleeve, and the support sleeve is supported in the guide hole of the cylinder block. However, since the supporting portion of the support sleeve which supports the main shaft and the supported portion of the support sleeve which is supported in the guide hole of the cylinder block do not overlap in the axial direction of the main shaft, with respect to the whirling vibration of the main shaft occurring when the compressor is driven, the support sleeve is supported by a cantilever structure, and thus, the effect of reducing the whirling vibration of the main shaft is insufficient. 
     The present invention has been made by focusing on the abovementioned problem, and it is an object of the invention to provide a wobble plate type variable displacement compressor which is able to sufficiently reduce the whirling vibration of the rotating main shaft by modifying the mounting structure of the rotation preventing mechanism. 
     Means for Solving the Problems 
     Thus, a wobble plate type variable displacement compressor of the present invention includes: a rotating main shaft of which a front end side and a rear end side are rotatably supported by a housing; a swash plate which synchronously rotates with the rotating main shaft and is inclinable with respect to the rotating main shaft; a wobble plate which swings along with the rotation of the swash plate with respect to the rotating main shaft to thereby reciprocate a piston in a cylinder bore; a wobble plate rotation preventing mechanism disposed at a middle portion of the rotating main shaft and prevents the wobble plate from rotating at the time of rotating the rotating main shaft. In the wobble plate type variable displacement compressor, an inclination angle of the swash plate with respect to the rotating main shaft is varied to thereby control a stroke amount of the piston. The wobble plate rotation preventing mechanism includes: a guide member which has a first support portion of which an outer peripheral surface is supported on an inner peripheral surface of a guide hole in the housing to be movable in an axial direction of the rotating main shaft and prevented from rotating around the rotating main shaft; and a connecting mechanism which connects the wobble plate to the guide member so that the wobble plate is swingable with respect to the guide member and rotation preventing force of the guide member is transmitted. The guide member further includes a second support portion of which an inner peripheral surface supports the rotating main shaft. The first support portion and the second support portion are arranged to overlap in the axial direction of the rotating main shaft. 
     Effects of the Invention 
     According to the wobble plate type variable displacement compressor of the present invention, it is possible to reduce the whirling vibration of the main shaft occurring when the compressor is driven. Thus, it is possible to improve the contact state of each part of the wobble plate rotation preventing mechanism and reduce the abnormal wear of the wobble plate rotation preventing mechanism, so that the durability of the wobble plate type variable displacement compressor is improved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view illustrating a configuration example of a wobble plate type variable displacement compressor according to an embodiment of the present invention. 
         FIG. 2  is a sectional view illustrating the wobble plate type variable displacement compressor of  FIG. 1  in another operating state. 
         FIG. 3  is an exploded perspective view illustrating a main part including a wobble plate rotation preventing mechanism of the wobble plate type variable displacement compressor of  FIG. 1 . 
         FIGS. 4A and 4B  are a view illustrating an example of the wobble plate rotation preventing mechanism of the wobble plate type variable displacement compressor of  FIG. 1 ,  FIG. 4A  being a partial sectional view and  FIG. 4B  being a partial front view. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, an embodiment of the present invention is explained with reference to the accompanying drawings. 
     A configuration example of an embodiment of a wobble plate type variable displacement compressor according to the present invention will be described with reference to  FIGS. 1 to 4A and 4B . 
       FIG. 1  is a configuration example of a wobble plate type variable displacement compressor according to the present embodiment, and shows the operating state when the discharge displacement is maximum and when the inclination angle of a swash plate is maximum.  FIG. 2  shows the operating state of the wobble plate type variable displacement compressor of  FIG. 1  when the discharge displacement is minimum and when the inclination angle of the swash plate is minimum.  FIG. 3  is an exploded perspective view illustrating a main part including the wobble plate rotation preventing mechanism of the wobble plate type variable displacement compressor of  FIG. 1 .  FIGS. 4A and 4B  show an example of a wobble plate rotation preventing mechanism of the wobble plate type variable displacement compressor of  FIG. 1 . 
     In the wobble plate type variable displacement compressor  1 , the inclination angle of the swash plate which synchronously rotates with the rotating main shaft is varied with respect to the rotational main shaft, to change the wobble width of the wobble plate which swings along with rotation of the swash plate with respect to the rotational main shaft, to control a stroke amount of a piston, so that a refrigerant discharge displacement from a cylinder bore is varied. 
     In the wobble plate type variable displacement compressor  1  of  FIG. 1 , a housing is made up of a cylinder block  2  disposed at a middle portion, a front housing  3  disposed on a front side of the cylinder block  2 , and a rear housing  4  disposed on a rear side of the cylinder block  2 . A rotating main shaft  5  to which a rotational driving force is input from outside is provided to penetrate from the front housing  3  to a portion of the cylinder block  2 . The front end portion of the rotating main shaft  5  is rotatably supported on the front housing  3  via a bearing  33  (radial bearing), and a rear end portion of the rotating main shaft  5  is rotatably supported on a fixed wall inside the cylinder block  2  via a bearing  22  (thrust bearing). To the rotating main shaft  5 , a rotor  6  is fixed to be rotatable integrally therewith, and a thrust bearing  32  is interposed between the rotor  6  and the front housing  3 . To the rotor  6 , a swash plate  8  is connected via a hinge mechanism  7  so as to be inclined with respect to the rotating main shaft  5  and synchronously rotatable with the rotating main shaft  5 . A piston  10  is inserted into each cylinder bore  9  arranged in an inner peripheral edge portion of the cylinder block  2  so as to be reciprocated, and the piston  10  is connected to a wobble plate  12  via a connecting rod  11 . A thrust bearing  31  is interposed between the wobble plate  12  and the swash plate  8 . The wobble plate  12  swings along with rotation of the swash plate  8  to reciprocate the piston  10  via the connecting rod  11 . Along with the reciprocation of the piston  10 , a fluid (for example, refrigerant gas) to be compressed is drawn from a suction chamber  13  formed in an inner peripheral edge portion of the rear housing  4  into the cylinder bore  9  through a suction hole  15  (a suction valve is not shown in the drawing) formed in a valve plate  14 , and the drawn fluid is compressed. The compressed fluid is discharged into a discharge chamber  17  formed in an inner central portion of the rear housing  4  through a discharge hole  16  (discharge valve not shown in the drawing), and thereafter, the discharged fluid is sent to an external circuit. 
     The wobble plate  12  swings in a state in which a wobble plate rotation preventing mechanism  21  disposed at a middle portion of the rotating main shaft  5 , prevents the wobble plate  12  from rotating. Hereinafter, the wobble plate rotation preventing mechanism  21  will be explained. 
     The wobble plate rotation preventing mechanism  21  is movable in an axial direction of the rotating main shaft  5 , and an inner ring rotation preventing mechanism described later prevents the wobble plate rotation preventing mechanism  21  from rotating around the rotating main shaft  5 . The wobble plate rotation preventing mechanism  21  includes an inner ring  27  as a guide member and a connecting mechanism which connects the wobble plate  12  to the inner ring  27 . The inner ring  27  has a first support portion  52  of which an outer peripheral surface is supported by an inner peripheral surface of a guide hole  2 A of the cylinder block  2  so as to be movable in the axial direction of the rotating main shaft  5  and prevented from rotating therearound, and a second support portion  53  of which an inner peripheral surface supports the rotating main shaft  5  via a plain bearing  51  mounted on the inner peripheral surface. Furthermore, the connecting mechanism is configured as a so-called constant velocity universal joint. The connecting mechanism includes a plurality of guide grooves  26  formed on the inner ring  27  for guiding balls provided for power transmission, an outer ring  30  which has a plurality of guide grooves  28  for guiding the balls at positions facing the respective guide grooves  26  of the inner ring  27  and which functions as a supporting member which fixedly supports the wobble plate  12  on an outer peripheral portion of the outer ring  30  and rotatably supports the swash plate  8  on an outer peripheral portion of the outer ring  30  via a bearing  29  (radial bearing), a plurality of balls  25  held by the guide grooves  26 ,  28  facing each other and formed in the inner ring  27  and the outer ring  30 , respectively, and performing power transmission by being compressed between the guide grooves  26 ,  28 , and a sleeve  24  which supports the rotating main shaft  5  via a bearing  23  (radial bearing) and is provided so as to be rotatable relative to the rotating main shaft  5  and be movable in the axial direction thereof, the sleeve  24  swingably supporting the outer ring  30  and being engaged with the inner ring  27  to be movable in the axial direction together therewith on the rotating main shaft  5 . The outer ring  30  is swingable about the sleeve  24  relative to the inner ring  27  through spherical surface contact between the balls  25  and the guide grooves  26 ,  28  facing each other. Furthermore, a rotation preventing force from the side of the inner ring  27  is transmitted to the side of the outer ring  30  through the spherical surface contact between the balls  25  and the guide grooves  26 ,  28 . 
     The abovementioned inner ring rotation preventing mechanism is configured by an abutting structure in which the guide hole  2 A of the cylinder block  2  is abutted against the outer peripheral surface of the inner ring  27  when the rotating main shaft  5  rotates. Specifically, the outer peripheral surface of the inner ring  27  has three peripheral surfaces formed in a substantially triangular shape of which each angle formed by adjacent peripheral surfaces is 60 degrees. Furthermore, the guide hole  2 A of the cylinder block  2  is also has three peripheral surfaces formed in a substantially triangular shape of which each angle formed by adjacent peripheral surfaces is 60 degrees so as to correspond to the outer peripheral surface of the inner ring  27 . At the time of rotating the inner ring  27  along with rotation of a rotating main shaft  5  with respect to the cylinder block  2 , each edge portion of peripheral surfaces of the inner ring  27  is abutted against each peripheral surface of the guide hole  2 A of the cylinder block  2  to prevent the inner ring  27  from rotating. 
     The inner ring rotation preventing mechanism in the wobble plate rotation preventing mechanism  21  of the present embodiment is not limited to the abovementioned abutting structure, but may be a general rotation restricting mechanism such as a key or a spline. 
       FIGS. 4A and 4B  show a state in which the relative angle between the inner and outer rings  27 ,  30  is zero in the wobble plate rotation preventing mechanism  21 . As shown in  FIG. 4A , the guide grooves  26 ,  28  formed on the inner ring  27  and the outer ring  30  of the wobble plate rotation preventing mechanism  21  are disposed to be inclined at relative angles (relative angles within a range of 30 to 60 degrees) relative to the center axis of the rotating main shaft  5 . The guide groove  26  formed on the inner ring  27  (an axis of the guide groove  26  is indicated by symbol  42 ) and the guide groove  28  formed on the outer ring  30  (an axis of the guide groove  28  is indicated by symbol  43 ), which form one ball guide  41  and face each other, are disposed so as to be symmetrically formed relative to a plane  44  which is perpendicular to the rotating main shaft  5  and passes through the wobble center of the wobble plate  12 , in a state in which the relative angle between the axis of the inner ring  27  and the axis of the outer ring  30  is zero. The ball  25  is regulated and supported on the intersection of the axis  42  of the guide groove  26  and the axis  43  of the guide groove  28 . Furthermore, as shown in  FIG. 4B , a structure can be employed in which two ball guides adjacent to each other among a plurality of the ball guides  41  of the wobble plate rotation preventing mechanism  21  are referred to be a pair of ball guides, and the respective ball guides  41  in the pair of ball guides  45 , in other words, axes  46  of the guide grooves formed on the inner and outer rings in this portion, are disposed in parallel to each other. In such a structure, as aforementioned, since the play in the rotational direction in the wobble plate rotation preventing mechanism portion is schematically decided by a relation between the distance between the bottoms of the pair of guide grooves provided on the inner and outer rings  27 ,  30  and the diameter of the balls, setting and management of a clearance are facilitated to thereby suppress the play so that the play is small by setting a proper clearance. The plurality of balls  25  are supported in the compression direction between the guide grooves  26 ,  28  facing each other through the respective balls, and perform power transmission. Since the ball  25  is held by the guide grooves  26 ,  28  facing each other so as to be embraced and comes into contact with both guide grooves  26 ,  28 , a sufficiently large contact area between the ball  25  and the respective guide grooves  26 ,  28  may be ensured to reduce the contact surface pressure, so that a structure is remarkably advantageous in reliability, vibration and quiet performance. Furthermore, it is also possible to make the diameter of the balls  25  small, so that it is possible to reduce the size of the entire wobble plate rotation preventing mechanism  21 . 
     Furthermore, the load applied to the ball  25 , which is provided as a moment about the rotating main shaft  5 , is generated as a normal reaction of an actual contact surface. The smaller inclination of a normal line of the contact surface relative to the direction of the moment is, the smaller the contact load becomes, and by a structure in which the pair of ball guides  45  disposed in parallel as described above are disposed symmetrically relative to a plane including a center axis  5   a  of the rotating main shaft  5 , in other words, by a structure in which the axes  46  of two sets of guide grooves formed on the inner and outer rings  27 ,  30  are disposed symmetrically relative to the plane including the center axis  5   a  of the rotating main shaft  5 , the mechanism is made as a wobble plate rotation preventing mechanism which does not select the rotational direction, and it is possible to minimize the ball contact load. 
     In the abovementioned wobble plate rotation preventing mechanism  21 , the inner ring  27  including the first support portion  52  of which the outer peripheral surface is supported by the inner peripheral surface of the guide hole  2 A of the cylinder block  2 , further includes the second support portion  53  of which the inner peripheral surface supports the rotating main shaft  5 . The first support portion  52  and the second support portion  53  of the inner ring  27  are arranged to overlap in the axial direction of the rotating main shaft  5 , and the wobble plate rotation preventing mechanism  21  has a function of reducing the whirling vibration of the rotating main shaft  5 . Specifically, in this embodiment, assuming that the inclination angle of the swash plate  8  perpendicular to the rotating main shaft  5  is 0°, within a range from a minimum inclination angle of the swash plate  8  shown in  FIG. 2  to a maximum inclination angle of the swash plate  8  regulated by being abutted against the rotor  6  as shown in  FIG. 1 , the first support portion  52  and the second support portion  53  are arranged to overlap in the axial direction of the rotating main shaft  5 . However, the present invention is not limited to this. The first support portion  52  and the second support portion  53  may overlap at least at the minimum inclination angle of the swash plate  8  and may not overlap when the swash plate  8  has the maximum inclination angle, for example. 
     In the wobble plate type variable displacement compressor  1  according to the present embodiment, since the first support portion  52  and the second support portion  53  are arranged to overlap in the axial direction of the rotating main shaft  5 , a supporting structure of the middle portion of the rotating main shaft  5  is not a cantilever structure as in the prior art. Thus, it is possible to effectively reduce the whirling vibration of the rotating main shaft  5  occurring when the compressor is driven. Therefore, the rotating main shaft  5  is smoothly rotated, to improve contact state of each part of the wobble plate rotation preventing mechanism  21  and reduce abnormal wear of the wobble plate rotation preventing mechanism  21  and the like. As a result, it is possible to improve durability of the wobble plate type variable displacement compressor  1 . Furthermore, in the present embodiment, the rotating main shaft  5  is also supported by the sleeve  24 , and thus, it is possible to further effectively reduce the whirling vibration of the rotating main shaft  5  to improve the durability of the wobble plate type variable displacement compressor  1 . 
     In the present embodiment, as the connecting mechanism which connects the wobble plate  12  to the inner ring  27 , by using the constant velocity universal joint, the rotation speed to be transmitted does not vary even when the inclination angle changes; however, the present invention is not limited to this. For example, by using a universal joint, the rotation speed to be transmitted can be varied when the inclination angle changes. 
     Furthermore, in the present embodiment, the bearing  23  is interposed between the sleeve  24  and the rotating main shaft  5 ; however, the bearing  23  may be omitted and the rotating main shaft  5  may be directly supported by the sleeve  24 . 
     Moreover, in the present embodiment, the plain bearing  51  is interposed between the inner ring  27  and the rotating main shaft  5 ; however, the plain bearing  51  may be omitted and the rotating main shaft  5  may be directly supported on the inner peripheral surface of the inner ring  27 . 
     There may be a case in which the inner ring  27  is formed by assembling a plurality of divided members, for example, two divided members. In this case, the plurality of divided members (two divided members, for example) is arranged between the rotating main shaft and the guide hole to support the rotating main shaft on inner surfaces of each divided member. The inner surfaces of each divided member, that is, a surface facing the rotating main shaft is also included in the “inner peripheral surface”. 
     REFERENCE SYMBOL LIST 
     
         
           1  wobble plate type variable displacement compressor 
           2  cylinder block 
           2 A guide hole 
           5  rotating main shaft 
           6  rotor 
           8  swash plate 
           9  cylinder bore 
           10  piston 
           12  wobble plate 
           21  wobble plate rotation preventing mechanism 
           22 ,  33  radial bearing 
           24  sleeve 
           25  ball 
           26  guide groove (inner ring side) 
           27  inner ring 
           28  guide groove (outer ring side) 
           30  outer ring 
           51  plain bearing 
           52  first support portion 
           53  second support portion