Patent ID: 9328823
Filing Date: 2016-05-03
CPC Classification: F02F,F16J

Claim Text:
1. A steel piston comprising: a cooling channel free of any flash; an upper piston part having a circle-shaped upper outer wall and an upper inner wall formed inward from the upper outer wall with a predetermined distance therebetween, the upper outer wall having one or more concave grooves, and the upper inner wall having two concave grooves; and a lower piston part having a circle-shaped lower outer wall and a lower inner wall formed inward from the lower outer wall at a predetermined distance from each other when the lower outer wall and the lower inner wall are coupled with the upper piston part, wherein an inner circumference surface of an upper end of lower outer wall is carved to a predetermined depth to form a first stepped portion between the inner circumference and an outer circumference surface of the upper end of the lower outer wall, and inner and outer circumference surfaces of an upper end of the lower inner wall are carved to a predetermined depth, and the lower inner wall having a protrusion formed at a middle location of the upper end of the lower inner wall so that the lower inner wall forms second stepped portions on both of two opposite sides of the protrusion, the protrusion being positioned within the upper inner wall.