Shoe for use in swash plate type compressor and method of forming the same

Abstract

A shoe in a swash plate type compressor has a spherical engaging surface that engages with a piston, and a plane engaging surface that is substantially a plane and engages with a swash plate. The plane engaging surface includes a substantially planar sliding surface, a substantially radially extending peripheral surface and a connecting surface. The sliding surface is formed near a center of the plane engaging surface and slides over the swash plate. The peripheral surface is formed near a periphery of the plane engaging surface, is formed at a distance from the sliding surface away from the surface of the swash plate so as to form an inwardly-directed step in the plane engaging surface, and is connected to the spherical engaging surface at its outer periphery. The connecting surface connects the sliding surface to the peripheral surface.

What is claimed is:  
     
         1 . A shoe in a swash plate type compressor including a swash plate and a piston, the shoe being interposed between the swash plate and the piston, the shoe comprising: 
 a spherical engaging surface for engaging with the piston; and    a plane engaging surface being substantially a plane, the plane engaging surface engaging with the swash plate, the plane engaging surface comprising: 
 a substantially planar sliding surface formed near a center of the plane engaging surface, the sliding surface sliding over a surface of the swash plate;  
 a substantially radially extending peripheral surface formed near a periphery of the plane engaging surface, the peripheral surface being formed at a distance from the extended sliding surface away from the surface of the swash plate so as to form an inwardly-directed step in the plane engaging surface, the peripheral surface being connected to the spherical engaging surface at its outer periphery; and  
 a connecting surface connecting the sliding surface to the peripheral surface.  
   
     
     
         2 . The shoe according to  claim 1 , wherein a distance between the peripheral surface and the extended sliding surface of the shoe ranges from 0.02 mm to 0.5 mm.  
     
     
         3 . The shoe according to  claim 2 , wherein the distance between the peripheral surface and the extended sliding surface is 0.05 mm or above.  
     
     
         4 . The shoe according to  claim 3 , wherein the distance between the peripheral surface and the extended sliding surface is 0.1 mm or above.  
     
     
         5 . The shoe according to  claim 4 , wherein the distance between the peripheral surface and the extended sliding surface is 0.15 mm or above.  
     
     
         6 . The shoe according to  claim 2 , wherein the distance between the peripheral surface and the extended sliding surface is 0.3 mm or below.  
     
     
         7 . The shoe according to  claim 6 , wherein the distance between the peripheral surface and the extended sliding surface is 0.25 mm or below.  
     
     
         8 . The shoe according to  claim 1 , wherein the peripheral surface is substantially parallel to the sliding surface.  
     
     
         9 . The shoe according to  claim 1 , wherein the peripheral surface is inclined with respect to the sliding surface, an angle between the peripheral surface and the extended sliding surface is 10° or below.  
     
     
         10 . The shoe according to  claim 1 , wherein the connecting surface further comprises: 
 a chamfered surface forming a side surface of a truncated cone, a diameter of the chamfered surface near the peripheral surface being larger than that of the chamfered surface near the sliding surface; and    a rounded corner connecting the chamfered surface to the sliding surface.    
     
     
         11 . The shoe according to  claim 10 , wherein the connecting surface further comprising another rounded corner that connects the chamfered surface to the peripheral surface.  
     
     
         12 . The shoe according to  claim 1 , wherein the spherical engaging surface further comprises a spherical sliding surface that is substantially a part of sphere surface and slides over a surface of the piston, and a peripheral rounded surface that connects the spherical sliding surface to the peripheral surface.  
     
     
         13 . The shoe according to  claim 1  further comprising a base member made of metal.  
     
     
         14 . The shoe according to  claim 13 , wherein the metal is aluminum series alloy.  
     
     
         15 . The shoe according to  claim 14 , wherein the surface of the base member is coated with metal plating layer.  
     
     
         16 . The shoe according to  claim 13 , wherein the metal is iron series alloy.  
     
     
         17 . The shoe according to  claim 16 , wherein the iron series alloy includes high carbon chromium bearing steel.  
     
     
         18 . The shoe according to  claim 13 , wherein the metal includes magnesium.  
     
     
         19 . The shoe according to  claim 1  further comprising a base member made of resin.  
     
     
         20 . A swash plate type compressor comprising: 
 a housing;    a drive shaft rotatably supported by the housing;    a swash plate operatively connected to the drive shaft;    a piston accommodated in the housing, the piston being operatively connected to the swash plate; and    a pair of shoes interposed between the swash plate and the piston, each of the shoes including: 
 a spherical engaging surface for engaging with the piston; and  
 a plane engaging surface being a substantially plane, the plane engaging surface engaging with the swash plate, the plane engaging surface comprising: 
 a substantially planar sliding surface formed near a center of the plane engaging surface, the sliding surface sliding over a surface of the swash plate;  
 a substantially radially extending peripheral surface formed near a periphery of the plane engaging surface, the peripheral surface being formed at a distance from the extended sliding surface away from the surface of the swash plate so as to form an inwardly-directed step in the plane engaging surface, the peripheral surface being connected to the spherical engaging surface at its outer periphery; and  
 a connecting surface connecting the sliding surface to the peripheral surface.  
 
   
     
     
         21 . The swash plate type compressor according to  claim 20 , wherein the connecting surface further comprises: 
 a chamfered surface forming a side surface of a truncated cone, a diameter of the chamfered surface near the peripheral surface being larger than that of the chamfered surface near the sliding surface; and    a rounded corner connecting the chamfered surface to the sliding surface.    
     
     
         22 . A method of forming a shoe that is interposed between a swash plate and a piston in a swash plate type compressor, the shoe including a spherical engaging surface and a plane engaging surface that is substantially a plane, the plane engaging surface having a substantially planar sliding surface that is formed near a center of the plane engaging surface and has a predetermined outer diameter, a substantially radially extending peripheral surface that is formed near a periphery of the plane engaging surface and is formed at a distance from the extended sliding surface so as to form an inwardly-directed step in the plane engaging surface, and a connecting surface that connects the sliding surface to the peripheral surface, the method comprising the steps of: 
 preparing a blank piece having a predetermined outer diameter that is smaller than that of the planar sliding surface;    preparing a pair of dies including a first die for molding the spherical engaging surface and a second die for molding the plane engaging surface;    setting the blank piece in the pair of the dies; and    closing the pair of the dies for forging the shoe.    
     
     
         23 . The method according to  claim 22 , wherein the first preparing step further includes preparing the blank piece from a blank by forging.  
     
     
         24 . The method according to  claim 22 , wherein the first preparing step further includes preparing the blank piece with a cylindrical shape.  
     
     
         25 . The method according to  claim 22 , wherein the first preparing step further includes preparing the blank piece with a spherical shape.  
     
     
         26 . A shoe manufactured by a method according to  claim 22 .  
     
     
         27 . A shoe in a swash plate type compressor including a swash plate and a piston, the shoe being interposed between the swash plate and the piston, the shoe comprising: 
 a spherical engaging surface for engaging with the piston; and    a plane engaging surface being substantially a plane, the plane engaging surface engaging with the swash plate, the plane engaging surface comprising: 
 a substantially planar sliding surface formed near a center of the plane engaging surface, the sliding surface sliding over a surface of the swash plate;  
 a peripheral surface formed near a periphery of the plane engaging surface, the peripheral surface being formed at a distance from the extended sliding surface away from the surface of the swash plate so as to form an inwardly-directed step in the plane engaging surface, the peripheral surface being substantially parallel with the sliding surface such that the peripheral surface is oriented at an angle, with respect to the extended sliding surface of the shoe, of from about 0 degree to about 10 degrees; and  
 a connecting surface connecting the sliding surface to the peripheral surface.  
   
     
     
         28 . A set of dies for molding a shoe that is interposed between a swash plate and a piston in a swash plate type compressor, the shoe including a spherical engaging surface for engaging with the piston and a plane engaging surface for engaging with the swash plate, the plane engaging surface having a substantially planar sliding surface that is formed near a center of the plane engaging surface, a substantially radially extending peripheral surface that is formed near a periphery of the plane engaging surface and is formed at a distance from the extended sliding surface so as to form an inwardly-directed step in the plane engaging surface and a connecting surface that connects the sliding surface to the peripheral surface, the set of dies comprising: 
 a first die having a spherical molding surface for molding the spherical engaging surface; and    a second die having a plane molding surface for molding the plane engaging surface, the plane molding surface including: 
 a first molding surface formed near a center of the plane molding surface for molding the sliding surface;  
 a second molding surface formed near a periphery of the plane molding surface for molding the peripheral surface; and  
 a third molding surface connecting the first molding surface to the second molding surface for molding the connecting surface.