The present invention relates to a piston made of a light metal for internal combustion engines, having bearing bushings for the piston pin inserted into piston pin bores, by means of which the piston is in driven connection with the connecting rod of the engine.
The bearing shells of known light metal pistons, such as described in German Patent DE 39 32 563 A1, are sections turned on a lathe, which were cut off a pressed pipe. At times, a permanent fixed seating of the bearing bushings in the piston pin bore has been shown to be problematic.
Based on the foregoing, the present invention is based on the object of improving the secure seating of bearing bushings in the piston pin bore.
In accordance with the present invention, this is achieved in connection with a light metal piston of the type described at the outset in that the bearing bushings is a shell wrapped from a rolled strip-or band-shaped metal material, which has a butt-joint at the joint which is closed in the pressed-in state, and in that an orientation in the first drawing direction of the metallurgical grain areas is formed in the circumferential direction.
By means of the present invention it was noted that loosening effects no longer appear in the bearing bushings when employing a wrapped bearing bushings of the type described above. With wrapped bushings with an orientation in the first drawing direction of the metallurgical grain areas in the circumferential direction, the permanency of the secure seating is considerably increased. The orientation in the first drawing direction of the metallurgical grain areas is achieved in accordance with the present invention in that during the production of the bearing bushings the strip-or band shaped metal material is oriented in such a way that the circumferential direction of the bearing bushings to be produced coincides with the milling direction of the alloy material.
It has furthermore been shown to be particularly advantageous if the bushings is oriented in the piston pin bore in such a way that, viewed in the linear direction of the piston pin the gap at the joint is arranged in the half of the piston pin bore facing the shaft end of the piston, preferably in the segment between 130 and 180 degrees, in particular between 130 and 150 degrees. Moreover, it has been shown to be advantageous if the butt-joint at the joint is located on the counter-pressure side (GDS) of the piston.
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