Method for manufacturing cylinder block

Abstract

A method of manufacturing a cylinder block including a semicircular bearing section that rotatably supports a crankshaft is provided. The method of manufacturing a cylinder block includes pressure-injecting molten metal into a cavity formed inside a metal mold, and sliding a pressure pin disposed in the metal mold after the pressure-injecting of the molten metal and thereby applying a pressure to the molten metal injected in the cavity, in which in the applying of the pressure to the molten metal, the pressure pin is slid toward an area where the bearing section is formed, a tip of the pressure pin protruding in an arc shape so as to conform to a shape of the bearing section.

What is claimed is: 
     
         1 . A method for manufacturing a cylinder block comprising a semicircular bearing section that rotatably supports a crankshaft, the method comprising:
 pressure-injecting molten metal into a cavity formed inside a metal mold; and   sliding a pressure pin disposed in the metal mold after the pressure-injecting of the molten metal and thereby applying a pressure to the molten metal injected in the cavity, wherein   in the applying of the pressure to the molten metal, the pressure pin is slid toward an area where the bearing section is formed, a tip of the pressure pin protruding in an arc shape so as to conform to a shape of the bearing section.   
     
     
         2 . The method for manufacturing a cylinder block according to  claim 1 , wherein the tip of the pressure pin is formed in a semicircular shape. 
     
     
         3 . The method for manufacturing a cylinder block according to  claim 1 , wherein
 the tip of the pressure pin is formed in an arc shape shorter than a semicircle, and   in the pressure-injecting of the molten metal, no recess is formed in a boundary between the metal mold and the pressure pin.   
     
     
         4 . The method for manufacturing a cylinder block according to  claim 3 , wherein
 notches are formed on both edges of the tip of the pressure pin, which are in contact with the metal mold, and   in the pressure-injecting of the molten metal, the boundary between the metal mold and the pressure pin is flat without any difference in level formed therein.