Patent Publication Number: US-6988875-B2

Title: Lubricating structure in fixed displacement piston type compressor

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a lubricating structure in a fixed displacement piston type compressor with a rotary valve that introduces fluid from a suction pressure region into a compression chamber in accordance with its rotation. 
   A piston type compressor disclosed in Unexamined Japanese Patent Publication No. 7-63165 employs a rotary valve for introducing refrigerant into a compression chamber defined in a cylinder bore. A double-headed piston in the compressor reciprocates by the rotation of a swash plate. In this fixed displacement swash plate type compressor, a rotary shaft itself functions as the rotary valve. In comparison to a flapper suction valve that opens and closes a suction port for introducing refrigerant into the compression chamber, a rotary valve improves volumetric efficiency. 
   The refrigerant containing lubricant oil in the compression chamber leaks through a gap between the piston and the inner circumferential surface of the cylinder bore into a crank chamber that accommodates the swash plate. An unwanted feature is that the refrigerant leaked into the crank chamber flows out to a suction pressure region along the circumferential surface of the rotary shaft. As a result, the lubricant oil in the crank chamber also flows out to the suction pressure region. Meanwhile, a shoe slides on the swash plate in the crank chamber to transmit the power of the swash plate to the piston so that the sliding portion needs to be lubricated. However, since the lubricant oil together with the refrigerant in the crank chamber flows out to the suction pressure region along the circumferential surface of the rotary shaft, the crank chamber cannot ensure the sufficient amount of lubricant oil. Therefore, it is desired that lubricating performance is improved in a fixed displacement piston type compressor with a rotary valve. 
   SUMMARY OF THE INVENTION 
   In accordance with the present invention, a lubricating structure in a fixed displacement piston type compressor has a housing, a rotary shaft, a cam, a piston and a rotary body. The housing defines a cam chamber, a plurality of cylinder bores and a suction pressure region. The rotary shaft is rotatably supported by the housing. The cam is located in the cam chamber and is connected to the rotary shaft. The piston is located in each of the cylinder bores and engages the cam to reciprocate in accordance with rotation of the rotary shaft through the cam. The rotary valve is connected to the rotary shaft and includes an introducing passage and a supply passage that interconnects the introducing passage and the suction pressure region. The introducing passage introduces fluid into the cylinder bores through the supply passage. The rotary body is connected to the rotary shaft and includes a communication passage that interconnects the cam chamber and the suction pressure region. 
   Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. The invention together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which: 
       FIG. 1A  is a longitudinal cross-sectional view of a fixed displacement double-headed piston type compressor according to a first preferred embodiment of the present invention; 
       FIG. 1B  is a cross-sectional view that is taken along the line I—I in  FIG. 1A ; 
       FIG. 2  is a cross-sectional view that is taken along the line II—II in  FIG. 1A ; 
       FIG. 3  is a cross-sectional view that is taken along the line III—III in  FIG. 1A ; 
       FIG. 4  is a longitudinal cross-sectional view of a fixed displacement double-headed piston type compressor according to a second preferred embodiment of the present invention; 
       FIG. 5  is a cross-sectional view that is taken along the line IV—IV in  FIG. 4 ; 
       FIG. 6  is a cross-sectional view that is taken along the line V—V in  FIG. 4 ; and 
       FIG. 7  is a longitudinal cross-sectional view of a fixed displacement double-headed piston type compressor according to an alternative embodiment. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   A first preferred embodiment of the present invention will now be described in reference to  FIGS. 1A through 3 . 
   Now referring to  FIG. 1A , a diagram illustrates a longitudinal cross-sectional view of a fixed displacement double-headed piston type compressor according to the first preferred embodiment of the present invention. The front side and the rear side of the compressor respectively correspond to the left side and the right side in the drawing. A housing of the compressor includes a pair of front and rear cylinder blocks  11 ,  12 , a front housing  13  and a rear housing  14 . The front cylinder block  11  is connected to the rear cylinder block  12 . The front housing  13  is connected to the front cylinder block  11 . The rear housing  14  is connected to the rear cylinder block  12 . A discharge chamber or a discharge pressure region  131  is defined in the front housing  13 . A discharge chamber or a discharge pressure region  141  and a suction chamber or a suction pressure region  142  are defined in the rear housing  14 . 
   A valve port plate  15 , a valve plate  16  and a retainer plate  17  are interposed between the front cylinder block  11  and the front housing  13 . A valve port plate  18 , a valve plate  19  and a retainer plate  20  are interposed between the rear cylinder block  12  and the rear housing  14 . Discharge ports  151  and  181  are respectively formed in the valve port plates  15  and  18 . Discharge valves  161  and  191  are respectively formed in the valve plates  16  and  19  to open and close the respective discharge ports  151  and  181 . Retainer  171  and  201  are respectively formed in the retainer plate  17  and  20  to regulate the respective opening degrees of the discharge valves  161  and  191 . 
   A rotary shaft  21  is rotatably supported by the front and rear cylinder blocks  11 ,  12  and is inserted into shaft holes  111  and  121  that extend through the front and rear cylinder blocks  11 ,  12 . Namely, the rotary shaft  21  is directly supported by the front and rear cylinder blocks  11 ,  12  through the respective shaft holes  111  and  121 . A shaft seal member  22  is interposed between the front housing  13  and the rotary shaft  21 . A swash plate or a cam  23  is secured to the rotary shaft  21  and is located in a crank chamber or a cam chamber  24  that is defined between the front and rear cylinder blocks  11 ,  12 . A thrust bearing  25  is interposed between a rear end surface of the cylinder block  11  and an annular proximal portion  231  of the swash plate  23 . A thrust bearing  26  is interposed between a front end surface of the cylinder block  12  and the annular proximal portion  231  of the swash plate  23 . The thrust bearings  25  and  26  sandwich the swash plate  23  to regulate a position of the rotary shaft  21  in a direction of an axis  213  of the rotary shaft  21 . 
   A plurality of front cylinder bores  27  (only one front cylinder bore  27  is shown in the drawing) is formed in the front cylinder block  11 . Similarly, a plurality of rear cylinder bores  28  (only one rear cylinder bore  28  is shown in the drawing) is formed in the rear cylinder block  12 . Front and rear heads of a double-headed piston  29  are respectively located in the pair of cylinder bores  27 ,  28 . The double-headed piston  29  engages the swash plate  23  through a pair of shoes. The swash plate  23  integrally rotates with the rotary shaft  21  and transmits the power of the swash plate  23  to the doubled-headed piston  29  through the shoes  30  so that the double-headed piston  29  reciprocates in the pair of cylinder bores  27 ,  28 . Compression chambers  271  and  281  are defined in the respective cylinder bores  27  and  28 . 
   Sealing portions  112  and  122  are respectively provided at the inner circumferential surfaces of the shaft holes  111  and  121 . The sealing portions  112  and  122  are smaller in diameter than the rest of the inner circumferential surfaces of the shaft holes  111  and  121 . In other words, the rotary shaft  21  is directly supported by the cylinder blocks  11  and  12  through the respective sealing portions  112  and  122 . A supply passage  211  is formed in the rotary shaft  21 . The supply passage  211  extends to the rear end of the rotary shaft  21  and communicates with the suction chamber  142  in the rear housing  14 . Introducing passages  31  and  32  are formed in the rotary shaft  21  so as to communicate with the suction chamber  142  through the supply passage  211 . 
   A suction passage  33  is formed in the front cylinder block  11  so as to interconnect the cylinder bore  27  and the shaft hole  111 . An inlet  331  of the suction passage  33  opens on the sealing portion  112 . Similarly, a suction passage  34  is formed in the rear cylinder block  12  so as to interconnect the cylinder bore  28  and the shaft hole  121 . An inlet  341  of the suction passage  34  opens on the sealing portion  122 . As the rotary shaft  21  rotates, an outlet  311  of the introducing passage  31  intermittently communicates with the inlet  331  of the suction passage  33 . Likewise, as the rotary shaft  21  rotates, an outlet  321  of the introducing passage  32  intermittently communicates with the inlet  341  of the suction passage  34 . 
   When the front cylinder bore  27  is in a suction cycle, that is, when the double-headed piston  29  moves from the left side to the right side in  FIG. 1A , the outlet  311  communicates with the inlet  331  of suction passage  33 . As a result, refrigerant in the supply passage  211  is introduced into the compression chamber  271  through the introducing passage  31  and the suction passage  33 . When the front cylinder bore  27  is in a discharge cycle, that is, when the double-headed piston  29  moves from the right side to the left side in  FIG. 1A , the outlet  311  is disconnected from the inlet  331  of the suction passage  33 . As a result, refrigerant in the compression chamber  271  is discharged to the discharge chamber  131  through the discharge port  151  by pushing the discharge valve  161 . The refrigerant discharged to the discharge chamber  131  flows out to an external refrigerant circuit, which is not shown in the drawing. 
   Similarly, when the rear cylinder bore  28  is in a suction cycle, that is, when the double-headed piston  29  moves from the right side to the left side in FIG.  1 A, the outlet  321  communicates with the inlet  341  of suction passage  34 . As a result, refrigerant in the supply passage  211  of the rotary shaft  21  is introduced into the compression chamber  281  through the introducing passage  32  and the suction passage  34 . When the rear cylinder bore  28  is in a discharge cycle, that is, when the double-headed piston  29  moves from the left side to the right side in  FIG. 1A , the outlet  321  is disconnected from the inlet  341  of the suction passage  34 . As a result, refrigerant in the compression chamber  281  is discharged to the discharge chamber  141  through the discharge port  181  by pushing the discharge valve  191 . The refrigerant discharged to the discharge chamber  141  flows out to the external refrigerant circuit. The refrigerant flowing out to the external refrigerant circuit returns to the suction chamber  142 . 
   Rotary valves  35  and  36  are integrated with the rotary shaft  21  and are surrounded by the sealing portions  112  and  122 . A communication passage  37  includes a communication hole  212  and the supply passage  211  and interconnects the crank chamber  24  and the suction chamber  142 . The communication hole  212  is formed in the circumferential surface of the rotary shaft  21  to face the thrust bearing  25 . The communication hole  212  interconnects the supply passage  211  and the crank chamber  24 . 
   Now referring to  FIG. 1B , a diagram illustrates a cross-sectional view that is taken along the line I—I in FIG.  1 A. The communication hole  212  is located near the thrust bearing  25  and extends substantially in a radial direction of the rotary shaft  21 . As the rotary shaft  21  rotates, the communication hole  212  orbits along the inner circumference of the thrust bearing  25 . As a result, the communication hole  212  contributes to lubricating substantially the entire portion of the thrust bearing  25 . 
   Now referring to  FIG. 2 , a diagram illustrates a cross-sectional view that is taken along the line II—II in FIG.  1 A. The plurality of front cylinder bores  27  is formed in the front cylinder block  11  and is aligned around the rotary shaft  21 . Each of the front cylinder bores  27  accommodates the double-headed piston  29  and communicates with the suction passage  33 . Meanwhile, the rotary shaft  21  includes the supply passage  211  and the introducing passage  31  that communicates with the supply passage  211 . As the rotary shaft  21  rotates, the introducing passage  31  intermittently communicates with the suction passage  33  for introducing the refrigerant into the front cylinder bore  27 . Thus, the rotary shaft  21  functions as the rotary valve  35 . 
   Now referring to  FIG. 3 , a diagram illustrates a cross-sectional view that is taken along the line III—III in FIG.  1 A. The plurality of rear cylinder bores  28  is formed in the rear cylinder block  12  and is aligned around the rotary shaft  21 . Each of the rear cylinder bores  28  accommodates the double-headed piston  29  and communicates with the suction passage  34 . Meanwhile, the rotary shaft  21  includes the supply passage  211  and the introducing passage  32  that communicates with the supply passage  211 . As the rotary shaft  21  rotates, the introducing passage  32  intermittently communicates with the suction passage  34  for introducing the refrigerant into the rear cylinder bore  28 . Thus, the rotary shaft  21  functions as the rotary valve  36 . 
   According to the first preferred embodiment, the following advantageous effects are obtained. 
   (1-1) The part of refrigerant in the compression chambers  271  and  281  respectively leaks through a gap between the inner circumferential surfaces of the cylinder bores  27 ,  28  and the outer circumferential surface of the double-headed piston  29 . The lubricant oil in the refrigerant also leaks from the compression chambers  271 ,  281  to the crank chamber  24 . Meanwhile, the communication hole  212  orbits around the axis  213  of the rotary shaft  21  as the rotary shaft  21  rotates. The gaseous refrigerant in the crank chamber  24  mainly flows out to the supply passage  211  through the communication hole  212 . On the other hand, the liquid lubricant oil in the refrigerant substantially does not enter into the orbiting communication hole  212 . Therefore, the part of lubricant oil in the refrigerant is separated from the gaseous refrigerant that flows out to the supply passage  211 . The separated lubricant oil contributes to lubricating a required lubricating portion, such as a sliding portion between the swash plate  23  and the shoe  30 , in the crank chamber  24 , thus improving lubricating performance in the compressor. 
   According to an experiment, the amount of lubricant oil in the crank chamber  24  is approximately 10 ml in a conventional compressor when the compressor is running. On the other hand, the amount of lubricant oil in the crank chamber  24  is increased to approximately 60 ml in a compressor with the communication hole  212  when the compressor is running. 
   (1-2) The supply passage  211  sends the refrigerant to the introducing passages  31 ,  32  of the respective rotary valve  35 ,  36  and constitutes a portion of the communication passage  37 . A new formed passage for communication is to only form the communication hole  212 . Accordingly, It is simple for forming the communication passage  37 .
 
(1-3) The communication hole  212  of the communication passage  37  is located near the thrust bearing  25 , and the gaseous refrigerant flows from the crank chamber  24  to the communication passage  37 . The flow of refrigerant guides the lubricant oil toward the thrust bearing  25 . The part of guided lubricant oil contributes to lubricating the thrust bearing  25 .
 
(1-4) The rotary valves  35 ,  36  are integrated with the rotary shaft  21  in the first preferred embodiment. In comparison to a structure that separately includes rotary valves from a rotary shaft, the number of components is reduced and an assembling process of the compressor is simple in the first preferred embodiment.
 
   A second preferred embodiment of the present invention will now be described in reference to  FIGS. 4 through 6 . The same reference numerals denote the identical components to those in the first preferred embodiment. 
   Now referring to  FIG. 4 , a diagram illustrates a longitudinal cross-sectional view of a fixed displacement double-headed piston type compressor according to the second preferred embodiment of the present invention. Rotary valves  39  and  40  are secured to a rotary shaft  38 . A pair of thrust bearings  43  and  44  regulates a position of the rotary shaft  38  in a direction of an axis  381  of the rotary shaft  38 . Introducing passages  41 ,  42  formed in the respective rotary valves  39 ,  40  communicate with the crank chamber  24 . An outlet  411  of the introducing passage  41  intermittently communicates with the inlet of the suction passage  33  as the rotary valve  39  rotates. Likewise, an outlet  421  of the introducing passage  42  intermittently communicates with the inlet of the suction passage  34  as the rotary valve  40  rotates. The refrigerant in a suction chamber  132  defined in the front housing  13  is introduced into the compression chamber  271  in a suction cycle through a supply passage  45 , the introducing passage  41  and the suction passage  33 . Similarly, the refrigerant in the suction chamber  142  defined in the rear housing  14  is introduced into the compression chamber  281  in a suction cycle through a supply passage  46 , the introducing passage  42  and the suction passage  34 . 
   Communication passages  391  and  401  are respectively formed in the inner circumferential surface of the rotary valves  39  and  40  and extend substantially in the direction of the axis  381  of the rotary shaft  38 . The communication passage  391  interconnects the suction chamber or the suction pressure region  132  and the crank chamber  24 . Similarly, the communication passage  401  interconnects the suction chamber or the suction pressure region  142  and the crank chamber  24 . The crank chamber  24  communicates with the suction chambers or the suction pressure regions  132 ,  142  only through the respective communication passages  391 ,  401  and the respective supply passages  45 ,  46 . The communication passages  391 ,  401  are formed in the respective rotary valves or the rotary bodies  39 ,  40  that integrally rotate with the rotary shaft  38  and function as well as the communication passage  37  in the first preferred embodiment. 
   Now referring to  FIG. 5 , a diagram illustrates a cross-sectional view that is taken along the line IV—IV in FIG.  4 . The plurality of front cylinder bores  27  is formed in the front cylinder block  11  and is aligned around the rotary shaft  38 . Each of the front cylinder bores  27  accommodates the double-headed piston  29  and communicates with the suction passage  33 . Meanwhile, the rotary valve  39  is connected to the rotary shaft  38  so as to rotate integrally with. The rotary valve  39  includes the supply passage  45  and the introducing passage  41  that communicates with the supply passage  45 . As the rotary shaft  38  rotates, the introducing passage  41  intermittently communicates with the suction passage  33  for introducing the refrigerant into the front cylinder bore  27 , and the communication passage  391  orbits around the axis  381  of the rotary shaft  38 . 
   Now referring to  FIG. 6 , a diagram illustrates a cross-sectional view that is taken along the line V—V in FIG.  4 . The plurality of rear cylinder bores  28  is formed in the rear cylinder block  12  and is aligned around the rotary shaft  38 . Each of the rear cylinder bores  28  accommodates the double-headed piston  29  and communicates with the suction passage  34 . Meanwhile, the rotary valve  40  is connected to the rotary shaft  38  so as to rotate integrally with. The rotary valve  40  includes the supply passage  46  and the introducing passage  42  that communicates with the supply passage  46 . As the rotary shaft  38  rotates, the introducing passage  42  intermittently communicates with the suction passage  34  for introducing the refrigerant into the rear cylinder bore  28 , and the communication passage  401  orbits around the axis  381  of the rotary shaft  38 . 
   According to the second preferred embodiment, the advantageous effect as well as the paragraph (1-1) in the first preferred embodiment is obtained. 
   The present invention is not limited to the above-described embodiments, but may be modified into the following alternative embodiments. 
   In alternative embodiments to the above first preferred embodiment, referring to  FIG. 7 , a second communication hole  213  that is substantially identical to the communication hole  212  is formed in a portion of the outer circumferential surface of the rotary shaft  21  in such a manner that the second communication hole  213  faces the thrust bearing  26 . Thus, lubricating performance is improved on the thrust bearing  26 . 
   In alternative embodiments to the above preferred embodiments, a fixed displacement single-headed piston type compressor is employed. 
   In alternative embodiments to the above preferred embodiments, a piston type compressor that has a cam in a predetermined shape other than a swash plate is employed. 
   Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein but may be modified within the scope of the appended claims.