Reciprocating piston engine

A reciprocating piston engine provided with a piston reciprocating in a cylinder and a crank mechanism, the reciprocating piston engine comprising:

• a first member having a first sliding surface;
• and
• a second member which has a second sliding surface opposed to the first sliding surface with a gap provided between the first sliding surface and the second sliding surface and moves relative to the first member in a predetermined sliding direction during reciprocation of the piston,
• wherein
• the second sliding surface has a projecting-shape portion projecting toward the first sliding surface in a section along the sliding direction,
• the projecting-shape portion includes an apical portion which is a most projecting part, and a bottom edge portion which is arranged at least on a downstream side of the apical portion in the sliding direction and is at a position most spaced apart from the first sliding surface, and
• when in the projecting-shape portion, the gap at the apical portion is assumed to be a minimum gap h1 and the gap at the bottom edge portion is assumed to be a maximum gap h2, the minimum gap h1 and the maximum gap h2 are set to be within the following range in a state where the first member and the second member are at room temperature:
• h1=0.5 μm to 40 μm;
• and
• h2/h1=1.5 to 5.0.