Method for producing an aluminum piston for an internal combustion engine

Abstract

A method for producing an aluminum piston for an internal combustion engine, which piston is designed as a round skirt piston. In the region of the radially outer end faces of the piston pin bosses the piston skirt has skirt recesses extending in the direction of the piston axis. In order to be able, when using the piston, to produce skirt recesses that have any shape a piston blank is produced in a forging process using a forging die, which piston blank has inner faces that are complementary to the outer shape of the piston having skirt recesses and not-recessed regions of the piston skirt, and the piston blank can then be further machined to produce the aluminum piston.

1 . Method for the production of an aluminum piston ( 1 ) for an internal combustion engine, which is configured as a round-skirt piston, having a piston crown ( 2 ), having a ring belt ( 4 ) and having a piston skirt ( 5 ) that follows the ring belt ( 4 ) in the direction facing away from the piston crown, which skirt has two pin bosses ( 6 ,  6 ′) that lie opposite one another, wherein the piston skirt ( 5 ) has skirt recesses ( 9 ,  9 ′) that extend in the direction of the piston axis ( 10 ), in the region of the radially outer face surfaces ( 8 ,  8 ′) of the pin bosses ( 6 ,  6 ′),
 comprising the following method steps:
 production of a piston blank using the forging method, using a mandrel for forming the piston interior and a forging die for forming the outer shape of the piston ( 1 ), wherein the outer shape of the piston skirt ( 5 ), with the skirt recesses ( 9 ,  9 ′) and the non-recessed regions ( 11 ,  11 ′) of the piston skirt ( 5 ), which is complementary to the inner surface of the forging die, is formed in, 
 final machining of the piston blank for the production of the piston ( 1 ), using a drilling machine for the production of the pin bores ( 7 ,  7 ′) and using a lathe for production of the grooves of the ring belt ( 4 ). 
 
 
     
     
         2 . Method according to  claim 1 , wherein the skirt recesses ( 9 ,  9 ′) are produced with a depth between 0.5 mm and 2 mm. 
     
     
         3 . Method according to  claim 2 , wherein transition regions ( 12   a ) are formed in between the skirt recesses ( 9 ,  9 ′) and the non-recessed regions ( 11 ,  11 ′) of the piston skirt ( 5 ), which regions have an edge ( 18 ,  19 ) that reaches over the entire height ( 14 ) of the skirt recess ( 9 ,  9 ′), in each instance, as compared with the skirt recesses ( 9 ,  9 ′) and as compared with the non-recessed regions ( 11 ,  11 ′), and have a flat surface between the edges ( 18 ,  19 ). 
     
     
         4 . Method according to  claim 2 , wherein transition regions ( 12   b ) are formed in between the skirt recesses ( 9 ,  9 ′) and the non-recessed regions ( 11 ,  11 ′) of the piston skirt ( 5 ), which regions connect the skirt recesses ( 9 ,  9 ′) with the non-recessed regions ( 11 ,  11 ′) of the piston skirt ( 5 ), continuously and without edges. 
     
     
         5 . Method according to  claim 3 , wherein during forging of the piston blank, the transition regions ( 12   a ,  12   b ) are structured in such a manner that they come to lie parallel to the piston axis ( 10 ). 
     
     
         6 . Method according to  claim 3 , wherein during forging of the piston blank, the transition regions ( 12   a ,  12   b ) are structured in such a manner that they narrow conically toward one another in the direction of the piston crown ( 2 ). 
     
     
         7 . Method according to  claim 3 , wherein during forging of the piston blank, the transition regions ( 12   a ,  12   b ) are structured in such a manner that they narrow conically toward one another in the direction of the end ( 15 ) of the piston skirt ( 5 ) that faces away from the piston crown.