Piston for compressor and method of manufacturing the same

Abstract

A piston for a compressor has a head portion, a neck portion, a receiving wall for receiving reactive force and a first guide wall. The receiving wall extends from a drive shaft side of the head portion towards the neck portion; is disposed on a preceding side in a rotating direction of a cam plate; and has an outer circumferential surface that slides over the inner circumferential surface of the cylinder bore. The first guide wall extends from the drive shaft side of the head portion towards the neck portion; is disposed on a following side in the rotating direction of the cam plate; and has an outer circumferential surface that slides relative to the inner circumferential surface of the cylinder bore. A recess is formed in the outer circumferential surface of the first guide wall.

What is claimed is:  
     
         1 . A piston in use for a compressor, the compressor including a drive shaft having a central axis and a cam plate rotatably supported by the drive shaft, the cam plate converting rotating movement of the drive shaft into reciprocating movement of the piston, the piston having a central axis, the piston comprising: 
 a head portion slidably fitted in a cylinder bore;    a neck portion connected to the head portion, the neck portion being engaged with the cam plate, the cam plate being rotated in a direction defined as a cam plate rotating direction;    a receiving wall for receiving side force extending from the drive shaft side of the head portion towards the neck portion, the receiving wall being disposed on a preceding side in the cam plate rotating direction, the receiving wall having an outer circumferential surface that slides over the inner circumferential surface of the cylinder bore; and    a first guide wall extending from the drive shaft side of the head portion towards the neck portion, the first guide wall being disposed on a following side that is opposite to the preceding side with respect to a hypothetical plane including the central axes of the drive shaft and the piston, the first guide wall having an outer circumferential surface that is continuous with the receiving wall and slides over the inner circumferential surface of the cylinder bore, a recess being formed in the outer circumferential surface of the first guide wall.    
     
     
         2 . The piston according to  claim 1 , wherein the recess is formed in such manner that the outer circumferential surface of the first guide wall is frame-shaped.  
     
     
         3 . The piston according to  claim 2 , wherein the shape of the frame is a triangular shape.  
     
     
         4 . The piston according to  claim 2 , wherein the shape of the frame is a square shape.  
     
     
         5 . The piston according to  claim 1 , wherein an intersectional point between the hypothetical plane and a circumferential surface of the head portion that is further from the central axis of the cam plate is designated as 12 o'clock when the piston is viewed from a side where the cam plate rotating direction is clockwise, the outer circumferential surface of the receiving wall extending substantially in a range of 3 o'clock to 6 o'clock, the outer circumferential surface of the first guide wall extending substantially in a range of 6 o'clock to 9 o'clock.  
     
     
         6 . The piston according to  claim 1  further comprising a rib located between the upper side of the head portion and the neck portion for connecting the head portion and the neck portion.  
     
     
         7 . The piston according to  claim 6  further comprising an interrupting wall, wherein a space is surrounded by the head portion, the neck portion, the receiving wall, the first guide wall and the rib, the interrupting wall dividing the space into a preceding side and a following side of the cam plate rotating direction.  
     
     
         8 . The piston according to  claim 6 , wherein a space is surrounded by the head portion, the neck portion, the receiving wall, the first guide wall and the rib and is open along the cam plate rotating direction.  
     
     
         9 . The piston according to  claim 1 , wherein the first guide wall has a support portion connecting the receiving wall so as to form the recess, the support portion supporting the first guide wall.  
     
     
         10 . The piston according to  claim 1 , wherein the first guide wall has a plurality of support portions connecting the receiving wall so as to form a plurality of recesses, the support portions supporting the first guide wall, a plurality of the recesses being formed in such manner that the outer circumferential surface of the first guide wall is frame-shaped.  
     
     
         11 . The piston according to  claim 1 , wherein the compressor is a variable displacement compressor that changes a stroke volume of the piston.  
     
     
         12 . The piston according to  claim 1 , wherein a through hole is formed on the receiving wall.  
     
     
         13 . The piston according to  claim 1 , wherein a groove is formed on the outer circumferential surface of the first guide wall.  
     
     
         14 . The piston according to  claim 1  further comprising a second guide wall extending from the upper side of the head portion towards the neck portion for guiding the piston.  
     
     
         15 . A piston in use for a compressor, the compressor including a drive shaft having a central axis and a cam plate rotatably supported by the drive shaft, the cam plate converting rotating movement of the drive shaft into reciprocating movement of the piston, the piston having a central axis, the piston comprising: 
 a head portion slidably fitted in a cylinder bore;    a neck portion connected to the head portion, the neck portion being engaged with the cam plate, the cam plate being rotated in a direction defined as a cam plate rotating direction;    a receiving wall for receiving side force extending from the drive shaft side of the head portion towards the neck portion, the receiving wall being disposed on a preceding side in the cam plate rotating direction, the receiving wall having an outer circumferential surface that slides over the inner circumferential surface of the cylinder bore, when the piston is viewed from a side where the cam plate rotating direction is clockwise, a hypothetical plane including the central axes of the drive shaft and the piston, an intersectional point between the hypothetical plane and a circumferential surface of the head portion that is further from the central axis of the cam plate being designated as 12 o'clock, the outer circumferential surface of the receiving wall extending substantially in a range of 3 o'clock to 6 o'clock; and    a first guide wall extending from the drive shaft side of the head portion towards the neck portion, the first guide wall being disposed on a following side that is opposite to the preceding side with respect to the hypothetical plane, the first guide wall having an outer circumferential surface that is continuous with the receiving wall and slides over the inner circumferential surface of the cylinder bore, the outer circumferential surface of the first guide wall extending substantially in a range of 6 o'clock to 9 o'clock, a recess being formed in the outer circumferential surface of the first guide wall, the first guide wall having a support portion connecting the receiving wall so as to form the recess, the support portion supporting the first guide wall.    
     
     
         16 . The piston according to  claim 15 , wherein the supporting portion is parallel to a hypothetical line passing through 3 o'clock and 9 o'clock.  
     
     
         17 . A compressor comprising: 
 a housing having a cylinder bore, the cylinder bore having an inner circumferential surface;    a drive shaft supported by the housing, the drive shaft having a central axis;    a cam plate supported by the drive shaft, the cam plate being rotated in a direction defined as a cam plate rotating direction; and    a piston having a central axis, the piston including; 
 a head portion slidably fitted in the cylinder bore,  
 a neck portion connected to the head portion, the neck portion being engaged with the cam plate for converting the rotating movement of the cam plate into reciprocating movement of the piston,  
 a receiving wall for receiving side force extending from the drive shaft side of the head portion towards the neck portion, the receiving wall being disposed on a preceding side in the cam plate rotating direction, the receiving wall having an outer circumferential surface that slides over the inner circumferential surface of the cylinder bore, and  
 a first guide wall extending from the drive shaft side of the head portion towards the neck portion, the first guide wall being disposed on a following side that is opposite to the preceding side with respect to a hypothetical plane including the central axes of the drive shaft and the piston, the first guide wall having an outer circumferential surface that is continuous with the receiving wall and slides over the inner circumferential surface of the cylinder bore, a recess being formed in the outer circumferential surface of the first guide wall.  
   
     
     
         18 . The compressor according to  claim 17 , wherein the recess is formed in such manner that the outer circumferential surface of the first guide wall is frame-shaped.  
     
     
         19 . The compressor according to  claim 17 , wherein the shape of the frame is a triangular shape.  
     
     
         20 . The compressor according to  claim 17 , wherein an intersectional point between the hypothetical plane and a circumferential surface of the head portion that is further from the central axis of the cam plate is designated as 12 o'clock when the piston is viewed from a side where the cam plate rotating direction is clockwise, the outer circumferential surface of the receiving wall extending substantially in a range of 3 o'clock to 6 o'clock, the outer circumferential surface of the guide wall extending substantially in a range of 6 o'clock to 9 o'clock.  
     
     
         21 . The compressor according to  claim 17  further comprising a rib located between the upper side of the head portion and the neck portion for connecting the head portion and the neck portion.  
     
     
         22 . The compressor according to  claim 21  further comprising an interrupting wall, wherein a space is surrounded by the head portion, the neck portion, the receiving wall, the first guide wall and the rib, the interrupting wall dividing the space into a preceding side and a following side of the cam plate rotating direction.  
     
     
         23 . The compressor according to  claim 21 , wherein a space is surrounded by the head portion, the neck portion, the receiving wall, the first guide wall and the rib and is open along the cam plate rotating direction.  
     
     
         24 . The compressor according to  claim 17 , wherein the first guide wall has a support portion connecting the receiving wall so as to form the recess, the support portion supporting the first guide wall.  
     
     
         25 . The compressor according to  claim 17 , wherein the first guide wall has a plurality of support portions connecting the receiving wall so as to form a plurality of recesses, the support portions supporting the first guide wall, a plurality of the recesses being formed in such manner that the outer circumferential surface of the first guide wall is frame-shaped.  
     
     
         26 . The compressor according to  claim 17 , wherein the compressor is a variable displacement compressor that changes a stroke volume of the piston.  
     
     
         27 . The compressor according to  claim 17 , wherein the piston further comprises a second guide wall extending from the upper side of the head portion towards the neck portion for guiding the piston.  
     
     
         28 . A method of providing a piston blank that includes two piston components in use for a compressor including a drive shaft having a central axis, a cam plate rotated in a predetermined direction and a piston having a central axis, a head portion, a neck portion connected to the head portion, a receiving wall for receiving side force extending from the drive shaft side of the head portion towards the neck portion and disposed on a preceding side in the predetermined direction, and a guide wall extending from the drive shaft side of the head portion towards the neck portion and disposed on a following side that is opposite to the preceding side with respect to a hypothetical plane including the central axes of the drive shaft and the piston, the guide wall having an outer circumferential surface that is continuous with the receiving wall, the guide wall having a support portion connecting to the receiving wall, a recess being formed in the outer circumferential surface of the guide wall, one of the piston components having a first predetermined recess, the other piston component having a second predetermined recess, the method comprising the steps of: 
 setting a first core in a first mold for forming the first predetermined recess such that the first core moves in a direction in which the first and second molds are separated;  
 further setting a second core in a second mold for forming the second predetermined recess that is open to a substantially opposite side of the first predetermined recess;  
 forming the piston blank in the first and second molds by one of die-casting and forging;  
 moving the first core relative to the first mold in order to break adhesion among the receiving wall, the guide wall and the first core; and  
 separating the first mold from the second mold.  
 
     
     
         29 . The method according to  claim 28 , wherein the first mold is a fixed mold, the second mold being a movable mold.