Light metal trunk piston for internal combustion engines

Light metal trunk piston for internal combustion engines with a piston head containing the piston ring grooves and, immediately below the lowest ring groove, a piston skirt having the following properties:

• (a) the piston head has a longitudinal axis X which is the axis for its axial generatrices,
• (b) the piston skirt on a counter-pressure side is separated from the piston head by a transverse slot,
• (c) inside the piston skirt, at a top end thereof, there is at least one control strip, the material of which has a lower heat expansion coefficient than the light metal of the piston, characterized by the features:
• (d) the control strip disposed at an upper end of the piston skirt is confined to that half of the skirt which is towards the counter-pressure side,
• (e) when the piston is in a cold state, the generatrix on the counter-pressure side extends in such a way that at least in a middle third of the skirt height its distance from the longitudinal axis X diminishes steadily towards an end of the skirt and is substantially rectilinear in this height range,
• (f) wherein further on that half of the skirt which is on the pressure side and at a bottom end thereof, there is a second control strip, the material of which has a lower heat expansion coefficient than the light metal of the piston,
• (g) in a region of the second control strip, when the piston is in the cold state, a distance between the skirt generatrices on the pressure side and the longitudinal axis of the piston is at the greatest.