Abstract: This invention provides a piston in which the moving piston unit can be prevented from rotating with respect the base piston unit, while suppressing the increase of the sliding resistance the piston has with respect to the cylinder. The circumferential wall of the moving piston unit has a pair of skirt parts opposing each other across a piston boss and a pair of side-wall parts coupling the skirt parts and each having an outer circumferential surface concaved toward the central axis X1 of the piston. The side-wall parts have a penetration part each, which penetrates the side-wall part and extends in the directions the moving piston unit reciprocates with respect to the base piston unit. The base piston unit has rotation preventing projections that project perpendicular to the central axis of the piston and are inserted into the penetration parts.

Abstract: This invention provides a piston in which the moving piston unit can be prevented from rotating with respect the base piston unit, while suppressing the increase of the sliding resistance the piston has with respect to the cylinder. The circumferential wall of the moving piston unit has a pair of skirt parts opposing each other across a piston boss and a pair of side-wall parts coupling the skirt parts and each having an outer circumferential surface concaved toward the central axis X1 of the piston. The side-wall parts have a penetration part each, which penetrates the side-wall part and extends in the directions the moving piston unit reciprocates with respect to the base piston unit. The base piston unit has rotation preventing projections that project perpendicular to the central axis of the piston and are inserted into the penetration parts.

Abstract: The variable valve gear for an internal combustion engine includes a cam lobe that is rotatably supported by a cam drive shaft, and a variable valve mechanism that includes a drive arm fixed adjacent to one end of the cam lobe in the cam drive shaft, an eccentric shaft member that is swivelably supported at a position opposite to the cam lobe with respect to the drive arm in the cam drive shaft, has an outer circumferential surface eccentric to an axis of the cam drive shaft, and is adjustable in eccentricity, and an intermediate rotary member that is rotatably supported through a bearing member around the eccentric shaft member, and is connected to the drive arm, wherein the drive arm includes an end face that overlaps with an end face of the bearing member, when projecting along the axis of the cam drive shaft, and the end face of the drive arm is protruding further than the end face of the cam lobe toward the bearing member.

Abstract: The variable valve gear for an internal combustion engine includes a cam lobe that is rotatably supported by a cam drive shaft, and a variable valve mechanism that includes a drive arm fixed adjacent to one end of the cam lobe in the cam drive shaft, an eccentric shaft member that is swivelably supported at a position opposite to the cam lobe with respect to the drive arm in the cam drive shaft, has an outer circumferential surface eccentric to an axis of the cam drive shaft, and is adjustable in eccentricity, and an intermediate rotary member that is rotatably supported through a bearing member around the eccentric shaft member, and is connected to the drive arm, wherein the drive arm includes an end face that overlaps with an end face of the bearing member, when projecting along the axis of the cam drive shaft, and the end face of the drive arm is protruding further than the end face of the cam lobe toward the bearing member.

Abstract: A variable valve-operating system for an internal combustion engine, comprising a cylinder head having an intake or exhaust valve, a camshaft rotatably supported by the cylinder head, a cam body rotatably fitted around the camshaft and including a cam lobe having an outer peripheral surface for driving the valve and a boss protruding radially from the cam body, and a valve open period-varying mechanism supported on the camshaft and including an intermediate rotating member having a center of rotation offset from the camshaft, the mechanism transmits rotation of the camshaft to the boss of the cam body through the intermediate rotating member and also permits the valve open period of the valve to be varied through adjustment of the eccentric phase angle of the intermediate rotating member, wherein at least a part of the boss is so positioned as to overlap with the profile of a nose of the cam lobe when viewed in the axial direction of the cam body.