Abstract: In a piston actuation system of a V-type internal combustion engine with two cylinder banks having at least one pair of cylinders, a piston pin, an upper link, a lower link, and a control link are mechanically linked to each other for each cylinder bank. When changing a compression ratio of the engine, ends of the control links of the two cylinder banks are moved in synchronism. The lower links of the two cylinder banks are coaxially rotatably fitted on the outer periphery of the same crankpin whose axis is eccentric to the axis of the crankshaft.

Abstract: A paired counterweights of a crankshaft have projected inner surfaces which protrude toward each other defining a given space therebetween. A plurality of links are arranged to convert a reciprocating motion of a piston to a rotational motion of the crankshaft. One of the links is pivotally connected to other links through link connecting portions and swingably disposed on a crank pin of the crankshaft so that upon rotation of the crankshaft, a peripheral portion of the link passes through the given space. At least one of the link connecting portions is placed within an imaginary circle which would be described by a radially innermost part of the projected inner surfaces of the paired counterweights when the paired counterweights turn about an axis of the crank pin.

Abstract: A variable compression-ratio, multiple-link type reciprocating internal combustion engine has at least three links, namely an upper link, a lower link and a third link, for each engine cylinder. The upper link is connected to a piston pin, the lower link connects the upper link to a crank pin, and the third link is pivoted at one end to a body of the engine and connected at its other end to either of the upper and lower links to permit oscillating motion of the third link on the engine body.

Abstract: An internal combustion engine is constructed to include a variable compression ratio mechanism. The mechanism has the following structure. An upper link has one end pivotally connected to a piston pin of a piston of the engine. A lower link is pivotally disposed on a crank pin of a crankshaft of the engine and has one part pivotally connected to the other end of the upper link. A control shaft extends substantially in parallel with the crankshaft. A control link has an end pivotally connected to the other part of the lower link. The other end of the control link is connected to the control shaft through an eccentric bearing structure, so that rotation of the control shaft about its axis induces a pivoting of the lower link about the crank pin varying the stroke of the piston.

Abstract: A variable compression ratio mechanism of a reciprocating engine includes at least an upper link connected at one end to a piston pin and a lower link connecting the other end of the upper link to a crankpin. At top dead center, when, of hypothetical connecting points between the upper and lower links, to be able to be supposed on both sides of a line segment connecting a piston-pin center and a crankpin center, a first one of the connecting points has a smaller inclination angle measured in the same direction as a direction of rotation of the crankshaft from an axial line of reciprocating motion of the piston-pin center and formed between a line segment connecting the piston-pin center and the first connecting point as compared to the second connecting point, the first connecting point is selected as an actual connecting point.

Abstract: A variable compression-ratio, multiple-link type reciprocating internal combustion engine has at least three links, namely an upper link, a lower link and a third link, for each engine cylinder. The upper link is connected to a piston pin, the lower link connects the upper link to a crank pin, and the third link is pivoted at one end to a body of the engine and connected at its other end to either of the upper and lower links to permit oscillating motion of the third link on the engine body.

Abstract: A piston of an internal combustion engine, comprises a skirt portion in sliding-contact with a cylinder wall, an inner crown-plus-boss portion having a crown portion and piston-pin boss portions, and a stay portion interconnecting the skirt portion and the inner crown-plus-boss portion at a lower portion of the piston. Also provided is an annular partition groove through which a rim of the skirt portion and the inner crown-plus-boss portion are partitioned all around the circumference of the upper portion of the piston. A thermal-expansion absorption ring is tightly fitted into the annular partition groove in a gas tight-fashion. The top face of the inner crown-plus-boss portion, the flat face of the rim of the skirt portion, and the top wall of the thermal-expansion absorption ring serve as a piston crown.

Abstract: In an engine cylinder block, a water jacket base wall is formed between a lower end of a water jacket outer wall and an intermediate part of a cylinder wall. A head bolt boss is formed in the water jacket outer wall for screwing in a head bolt. A thin part is formed in an intermediate part of the water jacket base wall. The rigidity of the water jacket base wall thereby falls, a force in the axial direction of the head bolt due to tightening of the head bolt or input of combustion pressure is absorbed by deformation of the water jacket base wall, and deformation of the cylinder wall is suppressed.

Abstract: An integral cast flywheel comprises a circular center flange portion, an annular mass portion concentric with the center flange portion, and an annular plate portion concentrically interposed between the center flange portion and the mass portion. Between the plate portion and the mass portion, there is defined an annular cavity which has an annular opening directed radially inward. The annular cavity is concentric with the center flange portion.