Method of manufacturing a crank shaft for a hermetic reciprocal compressor

Abstract

A method of manufacturing a crank shaft for a hermetic reciprocal compressor including the steps of providing a main shaft and a crank portion eccentric for a predetermined degree from the main shaft that are separately formed. The main shaft and the crank portion are joined through laser welding. The main shaft is a hollow pipe and the crank portion is made by sintering. The main shaft and the crank portion are connected, and an end portion of the main shaft is inserted into an annular groove formed at a main shaft connection side of the crank portion. Accordingly, the main shaft is a drawn steel pipe, and the crank portion is formed by sintering, thus the crank shaft becomes lighter and no post-process is needed. Therefore, the manufacturing process is remarkably reduced, and the crank shaft manufactured at a lower production cost.

What is claimed is:  
     
         1 . A crank shaft for a hermetic reciprocal compressor, 
 wherein the crank shaft includes a main shaft connected with a rotor of the hermetic reciprocal compressor; and    a crank portion eccentric to a predetermined degree with respect to the main shaft connected with a connecting rod, and    the main shaft and the crank portion being joined to each other through laser welding, after the main shaft is formed as a hollow pipe, and the crank portion is formed by sinter molding.    
     
     
         2 . The crank shaft of  claim 1 , wherein material of the hollow pipe and the sintering molded product is a metallic alloy including less than 0.5% carbon.  
     
     
         3 . The crank shaft of  claim 1 , wherein the hollow pipe is a carbon steel pipe for use in a machine or an automobile.  
     
     
         4 . The crank shaft of  claim 1 , wherein an annular groove for embracing an end portion of the main shaft is disposed at a connection side of the main shaft of the crank portion, and the crank portion and the main shaft are connected with each other by the end portion of the main shaft being inserted into the annular groove.  
     
     
         5 . The crank shaft of  claim 4 , wherein the annular groove is formed so that the main shaft can transition-fit relative to the annular groove.  
     
     
         6 . A method for manufacturing a crank shaft for a hermetic reciprocal compressor, comprising the steps of: 
 providing a crank shaft including a main shaft for connection with a rotor of the hermetic reciprocal compressor; and    connecting a connecting rod to a crank portion of the crank shaft so as to be eccentric to a predetermined degree with respect to the main shaft,    forming the main shaft as a hollow pipe;    and forming the crank portion by sinter molding; and    laser welding the main shaft and the crank portion.    
     
     
         7 . The method of  claim 6 , wherein the hollow pipe and the sinter molded product further comprises a metallic alloy material including less than 0.5% carbon.  
     
     
         8 . The method of  claim 6 , wherein the hollow pipe is comprises a carbon steel pipe for use in a machine or an automobile.  
     
     
         9 . The method of  claim 6 , wherein an annular groove for embracing an end portion of the main shaft is formed at a connection side of the main shaft of the crank portion; and 
 the crank portion and the main shaft are connected with each other so that the end portion of the main shaft is inserted into the annular groove before the laser welding step.    
     
     
         10 . The method of  claim 6 , wherein the annular groove is formed so that the main shaft can transition-fit relative to the annular groove.  
     
     
         11 . A method of manufacturing a crank shaft for a hermetic reciprocal compressor having a main shaft and a crank portion eccentric to a predetermined degree from the main shaft, comprising the steps of: 
 preparing the main shaft by drawing and cutting a carbon steel hollow pipe of a predetermined length, and forming at least one oil passage in the hollow carbon steel pipe;    preparing the crank portion by forming a molded product having an eccentric shaft and a weight balancer by sintering a metallic alloy powder,    forming at least one oil passage in the molded product, and forming an annular groove in one side of the molded product at a predetermined depth;    connecting the main shaft and the crank portion by inserting an end portion of the main shaft into the annular groove of the crank portion;    joining the main shaft and the crank portion by laser welding the main shaft to the crank portion where the two intersect;    forming an oxide coating for increasing corrosion and abrasion resistance of the joined crank shaft; and    final clean cutting.