Drain Bolt Mounting Structure

Abstract

A drain bolt mounting structure comprises a bottomed hole formed on an outer surface of an oil pan to extend continuously with a drain hole of the oil pan, a female thread formed on an inner peripheral surface of the drain hole; a drain bolt including a shaft portion having a male thread threadingly engageable with the female thread of the drain hole and a head portion formed at one end portion of the shaft portion; a press-in member formed of a second metal containing aluminum which has a higher standard electrode potential than a first metal forming the oil pan, the press-in member being configured to be pressed into the bottomed hole; and a crushing member configured to be crushed between the press-in member and the head portion of the drain bolt.

1 . A drain bolt mounting structure for sealably closing a drain hole provided on an oil pan formed of a first metal containing magnesium, in a fluid-tight state, the drain bolt mounting structure comprising:
 a bottomed hole formed on an outer surface of the oil pan to extend continuously with the drain hole, an end portion of the drain hole being open in a part of a bottom surface of the bottomed hole;   a female thread formed on an inner peripheral surface of the drain hole;   a drain bolt including a shaft portion having a male thread threadingly engageable with the female thread of the drain hole and a head portion formed at one end portion of the shaft portion to protrude in a radial direction of the shaft portion;   a press-in member formed of a second metal containing aluminum which has a higher standard electrode potential than the first metal and having a first hole into which the shaft portion of the drain bolt is inserted, the press-in member being configured to be pressed into the bottomed hole such that an outer peripheral surface of the press-in member is tightly fitted to an inner peripheral surface of the bottomed hole; and   a crushing member having a second hole into which the shaft portion of the drain bolt is inserted, the crushing member being configured to be crushed between the press-in member and the head portion of the drain bolt.   
     
     
         2 . The drain bolt mounting structure according to  claim 1 , wherein at least a surface of the crushing member which is opposite to the press-in member is formed of a third metal containing aluminum which has a lower hardness than a surface of the press-in member which is opposite to the crushing member. 
     
     
         3 . The drain bolt mounting structure according to  claim 2 , wherein at least the surface of the press-in member which is opposite to the crushing member is a surface subjected to a hardening treatment. 
     
     
         4 . The drain bolt mounting structure according to  claim 1 , wherein an O-ring is provided between the bottom surface of the bottomed hole and the press-in member and around the shaft portion.