Abstract: The invention relates to a soluble and essentially annular casting core (2) for forming a cooling channel that transitions into two areas (14, 15) which are approximately parallel to the piston axis (16) and are facing away from the piston head (3), via a respective bending of the core (17, 18) in the shape of a quadrant, wherein the second area (14) transitions into a part of the casting core (2) that forms the feed opening (12) of the cooling channel, and the first area (15) transitions into a part of the casting core (2) that forms the discharge opening (13) of the cooling channel. The two areas (14, 15) of the casting core (2) are disposed at a distance from one another, which corresponds at a maximum to two times the cross-sectional diameter of one of the two areas (14, 15). As a result, the throughflow of the cooling oil traversing the cooling channel is accelerated and the cooling of the piston improved.

Abstract: A soluble casting core for forming a cooling channel in a piston has a formed-on part for forming an oil supply opening and a formed-on part for forming an oil drain opening. In order to improve the mechanical strength of the piston, the oil supply opening and the oil drain opening lie in a different pin boss support of the pin bosses of the piston. A third formed-on part, which lies in the circumferential direction and is configured in oblong manner, is disposed between the first formed-on part and the end of the casting core, which part has a shape that narrows conically towards the end of the casting core and forms a continuation of the cooling channel, which narrows conically towards the end of the cooling channel.