Abstract: A squish surface having the shape of a plane surface orthogonal to the axis of a piston is formed on the intake side of the piston top surface. A squish area is formed between the squish surface and a plane surface-shaped squish surface on the cylinder head side, and at the same time, a squish guide surface is formed in the piston top surface so as to be continuously ridged from the squish surface toward the vicinity of a spark plug.

Abstract: A squish surface having the shape of a plane surface orthogonal to the axis of a piston is formed on the intake side of the piston top surface. A squish area is formed between the squish surface and a plane surface-shaped squish surface on the cylinder head side, and at the same time, a squish guide surface is formed in the piston top surface so as to be continuously ridged from the squish surface toward the vicinity of a spark plug.

Abstract: In the control of the slip in a slip clutch device for joining and separating an input shaft and an output shaft, the improvement comprises detecting a slip in the clutch, calculating a time change in the said slip and calculating a slip deviation between a preset target slip and the said slip, and feedback-controlling the engaging force of the clutch in proportion to the quantity of the time change in the said slip, obtained from these calculations, and the slip deviation so that the slip in the clutch is caused to get near to the target slip.According to the slip clutch device control method of this invention, the hunting in slip can be prevented from being caused even when the .mu.-v characteristics of a clutch facing is worsened, and a shock applied upon the clutch at the start of its operation can be reduced in a large extent.