Sliding members and piston for internal combustion engine

DETAILED DESCRIPTION The present invention provides sliding members having a sliding surface and which slide with respect to each other in a sliding direction, the sliding surface of at least one of the sliding members comprising: a protrusion extending along a direction intersecting the sliding direction; and fine dimples provided on a surface of the protrusion.
The protrusion preferably extends in a direction perpendicular or approximately perpendicular to the sliding direction.
The present invention further provides a piston comprising: a piston body; a skirt portion provided on a side surface of the piston body; a protrusion provided on at least the skirt portion and extending along the outer circumference thereof; and fine dimples provided on a surface of the protrusion.
The functions of the invention will be explained with reference to pistons in FIG.
1A and other figures.
FIG.
1A shows a surface of a skirt portion of a piston without dimples, which is shown by a computer generated illustration, and shows protrusions extending along the outer circumference of the piston body.
FIG.
1A shows the state of the outer circumference of the piston body after machining.
The protrusion is formed between recesses having a circular cross section.
The machining can be performed such that the outer circumference of the piston body is cut by a bite when relatively feeding the piston body in the axial direction thereof.
In this case, the protrusion spirals along the axial direction.
When initial wear occurs on the piston, the edge portion of the protrusion is worn away so as to be approximately trapezoidal in cross section as shown FIG.
1B.
The trapezoidal portion consists of a sliding surface and edge E formed at the peripheral portions thereof, and the edge E inhibits the lubricating oil accumulated in the recesses from being supplyed to the sliding surface which requires lubrication.
FIGS.
2A and 2B show a cross section of the protrusion shown in FIGS.
1A and 1B, wherein FIG.
2A shows a status after machining and FIG