Abstract:
In a swash plate type compressor, a swash plate ( 22 ) is fixed to a boss ( 21 ) by means of rivets ( 35 ). The swash plate is coupled to a plurality of pistons ( 24 ) via shoes ( 25 ). When a main shaft ( 16 ) is rotated to rotate a rotor ( 18 ), a rotational motion of the rotor is transmitted to the boss via a hinge mechanism ( 19 ) which changes an inclination of the swash plate. Accordingly, the boss is rotated to rotate the swash plate at the inclination to cause the pistons to make reciprocating motions in cylinders ( 26 ) via the shoes for performing a compressing operation.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a swash plate type compressor for use in, for example, an automobile air conditioner. 
     In a swash plate type compressor, a swash plate is mounted on a shaft which is rotated by an automobile engine. Pistons are indirectly coupled to the swash plate. When the swash plate is rotated together with the shaft, the pistons make reciprocating motions to compress fluid. 
     In a swash plate type compressor of a variable displacement type, a swash plate boss (which will be abbreviated hereinunder a boss) is coupled to a shaft via a rotor and a hinge mechanism at a variable inclination relative to the shaft. A swash plate is fixed to the boss. In this case, since pistons have a stroke corresponding to the inclination of the swash plate, the displacement of the compressor can be set variable. 
     In the conventional techniques, fixation of the swash plate relative to the boss has been carried out using a screw. However, since the swash plate type compressor generates various vibrations, there has been a problem of causing loosening of the screw. The loosening of the screw may cause separation of the swash plate from the boss, leading to breakage of the compressor. On the other hand, when welding is used for the fixation, welded portions should be made of the same material and further an influence of heat should be considered, so that it is disadvantageous in view of cost and quality. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a swash plate type compressor wherein fixation of a swash plate is carried out reliably and inexpensively. 
     Other objects of the present invention will become clear as the description proceeds. 
     The present invention pays attention to fixation by a rivet rather than fixation by a screw which has been long used as a fixing means for fixation against vibration. It has been confirmed through experiments that use of the rivet is excellent for fixation against vibration. 
     According to an aspect of the present invention, there is provided a swash plate type compressor which comprises a rotated member subjected to a rotation motion, a swash member, a plurality of rivets fixing the swash member to the rotated member, a piston, and shoe means interposed between the swash member and the piston for moving the piston in response to movement of the swash member to perform a compression operation. 
     According to another aspect of the present invention, there is provided a swash plate type compressor, wherein a swash plate fixed to a boss is coupled to a plurality of pistons via shoes and, when a main shaft is rotated to rotate a rotor, a rotational motion of the rotor is transmitted to the boss via a hinge mechanism which changes an inclination of the swash plate, so that the boss is rotated to rotate the swash plate at the inclination to cause the pistons to make reciprocating motions in cylinders via the shoes for performing a compressing operation. The swash plate type compressor is characterized in that the swash plate is fixed to the boss by a plurality of rivets. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a longitudinal sectional view of a conventional swash plate type compressor; 
     FIG. 2 is a longitudinal sectional view of a swash plate type compressor according to a first preferred embodiment of the present invention; 
     FIG. 3 is a sectional view showing a main part of a swash plate type compressor according to a modification of the first preferred embodiment; 
     FIG. 4 is a longitudinal sectional view of a swash plate type compressor according to a second preferred embodiment of the present invention; and 
     FIG. 5 is a plan view of a combination of a boss, a swash plate, and a fixing plate which are included in each of the compressors of FIGS.  2  and  4 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1, a conventional swash plate type compressor will be first explained for facilitating understanding of the present invention. The shown swash plate type compressor is of a variable displacement type and is used in an automobile air conditioner. The swash plate type compressor comprises a tubular casing  1 , a front housing  12  closing one axial end of the casing  1 , and a cylinder head  14  attached to the other axial end of the casing  1  via a valve plate assembly  13  interposed therebetween. A cylinder block  15  is integrally provided in the casing  1 . A main shaft  16  extends at the center of the casing  1  and is supported by the front housing  12  and the cylinder block  15  so as to be rotatable. The shaft  16  is rotated with an automobile engine in the manner known in the art. 
     A crank chamber  17  is defined between the front housing  12  and the cylinder block  15 . In the crank chamber  17 , a rotor  18  is fixedly mounted on the shaft  16 . A boss  21  is coupled to the rotor  18  via a hinge mechanism  19 . The boss  21  is formed with a tubular portion  21   a . An annular swash plate  22  is fitted over the tubular portion  21   a  and fixed to the boss  21  by means of an annular fixing screw  23 . The hinge mechanism  19  allows an inclination of the swash plate  22  relative to an axis of the shaft  16  to be variable. The swash plate  22  is rotated together with the rotor  18 . 
     A plurality of pistons  24  are coupled to the swash plate  22  at peripheral portions thereof via shoes  25 , respectively. The pistons  24  are received in corresponding cylinder bores  26 , formed in the cylinder block  15 , so as to be slidable in an axial direction. When the swash plate  22  rotates, the pistons  24  make reciprocating motions in the corresponding cylinder bores  26  with a stroke determined according to the inclination of the swash plate  22 . 
     The cylinder head  14  is formed at its peripheral portion with a suction chamber  27  and at its center with a discharge chamber  28 . A known refrigeration circuit (not shown) is connected between the suction chamber  27  and the discharge chamber  28 . 
     The valve plate assembly  13  is provided with suction holes  31  and discharge holes  32  for allowing the respective cylinder bores  26  to communicate with the suction chamber  27  and the discharge chamber  28 , and further provided with corresponding valve mechanisms (not shown). 
     When the shaft  16  rotates, the rotor  18  rotates. The rotation of the rotor  18  is transmitted to the boss  21  via the hinge mechanism  19 , so that the boss  21  and the swash plate  22  rotate in response to the rotation of the shaft  16 . When the swash plate  22  rotates at an inclination relative to the shaft  16 , the pistons  24  make reciprocating motions in the corresponding cylinder bores  26 . Following the reciprocating motions of the pistons  24 , refrigerant gas in the refrigeration circuit is sucked into the cylinder bores  26  via the suction chamber  27  and the suction holes  31  and then discharged into the discharge chamber  28  via the discharge holes  32  so as to be supplied to the refrigeration circuit. 
     The effective cylinder displacement is determined by the inclination of the swash plate  22 . FIG. 1 shows a state of the maximum inclination of the swash plate  22 , wherein the stroke of each piston  24  is maximum so that the effective cylinder displacement is also maximum. By means of the hinge mechanism  19 , the inclination of the boss  21 , i.e. the swash plate  22 , can be changed. 
     Referring now to FIG. 2, a swash plate type compressor according to the first preferred embodiment of the present invention will be described hereinbelow. Similar portions are designated by like reference numerals. 
     The swash plate type compressor includes an annular fixing plate  34 , behind the swash plate  22 , fitted over a tubular portion  33  of the boss  21 , and a plurality of rivets  35  fixing the fixing plate  34  and the swash plate  22  relative to the boss  21 . The fixing plate  34  is made of a mild steel. The rivets  35  are made of a carbon steel. It is preferable that the rivets  35  are made of a cold-rolled carbon steel. A combination of the shaft  16 , the rotor  18 , the hinge mechanism  19 , and the boss  21  is referred to as a rotated member. 
     The swash plate  22  is of a ring shape and fitted outside the tubular portion  33  of the boss  21  to be superposed on the boss  21  in a predetermined direction. The fixing plate  34  is superposed on the swash plate  22  in the predetermined direction. A combination of the swash plate  22  and the fixing plate  34  is referred to as a swash member. 
     The boss  21 , the swash plate  22 , and the fixing plate  34  are formed with rivet holes  21   a ,  22   a , and  34   a , respectively. Each of the rivets  35  extends in a predetermined direction through the rivet holes  21   a ,  22   a , and  34   a  and has heads  35   a  and  35   b  engaged with the fixing plate  34  and the boss  21  in the predetermined direction, respectively. The fixing plate  34  has a plurality of concave portions  36  each of which receives the head  35   a  of each of the rivets  35 . In other words, the fixing plate  34  is formed with the concave portions  36  for preventing the heads  35   a  of the rivets  35  from projecting, so as not to interfere with the movement of the swash plate  22  and not to increase an axial length of the assembly. 
     Fixation by the rivets  35  can be easily carried out by a known technique and can be securely maintained without being loosened even being subjected to vibration. 
     Since recent swash plate type compressors are long in running duration favored by improvement in performance thereof, it is not necessary to change the swash plate  22 . Therefore, there will be raised no practical problem even if the swash plate  22  is fixed to the boss  21  by the rivets  35 . 
     Referring now to FIG. 3, a modification of the foregoing first preferred embodiment will be described. In the modification, the concave portion  36  extends into the swash plate  22  through the fixing plate  34 . In this case, a length of a portion fixed by the rivets  35 , for example, the sum of lengths of the boss  21 , the swash plate  22  and the fixing plate  34 , can be reduced. 
     Referring now to FIG. 4, a swash plate type compressor according to the second preferred embodiment of the present invention will be described. Similar portions are designated by like reference numerals. 
     In the swash plate type compressor, the swash plate  22  is fixed to the boss  21  directly by the rivets  35 . For facilitating the direct fixation by the rivets  35 , the swash plate  22  is integrally formed with a tubular portion  37  corresponding to the fixing plate  34 . This means that the swash plate  22  and the fixing plate  34  are formed integral with each other. In this case, the swash plate  22  is referred to as a swash member alone. With this arrangement, the number of the parts can be reduced. 
     Referring to FIG. 5, the description is made as regards a modification of a combination of the boss  21 , the swash plate  22 , and the fixing plate  34 . As shown in the modification, it is preferable that use is made of three rivets  35  arranged at positions which have an angle of 120° therebetween. 
     According to each of the foregoing preferred embodiments, since the rivets are used as fixing means in the swash plate type compressor which is frequently subjected to vibration, the fixed portion is prevented from loosening so that the secure fixation can be ensured. The fixation by the rivets can be quickly carried out and is far less inexpensive as compared with the conventional fixation by the screw, thereby leading to large reduction in production cost of the compressor. 
     While the present invention has thus far been described in connection with a few embodiments thereof, it will readily be possible for those skilled in the art to put this invention into practice in various other manners. For example, for eliminating projecting portions of the rivets, concave portions may be provided corresponding to both heads of the rivets.