Abstract: A variable compression ratio internal combustion engine is equipped with a variable compression ratio mechanism configured to change an engine compression ratio in accordance with a rotational position of a control shaft, and a housing that accommodates therein a drive motor for changing and holding the rotational position of the control shaft. A reference position of the control shaft is learned in a state where a position of maximum rotation of the control shaft in a first rotational direction has been mechanically restricted by bringing a first movable part, which operates in conjunction with the control shaft, into abutted-engagement with a first stopper provided outside of an engine body. Subsequently, a maximum conversion angle range of the control shaft is learned in a state where a position of maximum rotation of the control shaft in a second rotational direction has been mechanically restricted by a second stopper.

Abstract: An internal combustion engine includes: a variable compression ratio mechanism arranged to vary an engine compression ratio in accordance with a rotation position of a control shaft; an actuator arranged to vary the rotation position of the control shaft; an arm portion extending from the control shaft in a radially outward direction; a lever arranged to link the actuator and the arm portion; a link pin which penetrates the lever and the arm portion, and which rotatably links the lever and the arm portion; and a wall portion which confronts an end surface of the link pin irrespective of the rotation position of the control shaft, and which retains the link pin to the lever or the arm portion.

Abstract: An internal combustion engine includes: a variable compression ratio mechanism arranged to vary an engine compression ratio in accordance with a rotation position of a control shaft; an actuator arranged to vary the rotation positon of the control shaft; an arm portion extending from the control shaft in a radially outward direction; a lever arranged to link the actuator and the arm portion; a link pin which penetrates the lever and the arm portion, and which rotatably links the lever and the arm portion; and a wall portion which confronts an end surface of the link pin irrespective of the rotation position of the control shaft, and which retains the link pin to the lever or the arm portion.

Abstract: A variable compression ratio internal combustion engine is equipped with a variable compression ratio mechanism configured to change an engine compression ratio in accordance with a rotational position of a control shaft, and a housing that accommodates therein a drive motor for changing and holding the rotational position of the control shaft. A reference position of the control shaft is learned in a state where a position of maximum rotation of the control shaft in a first rotational direction has been mechanically restricted by bringing a first movable part, which operates in conjunction with the control shaft, into abutted-engagement with a first stopper provided outside of an engine body. Subsequently, a maximum conversion angle range of the control shaft is learned in a state where a position of maximum rotation of the control shaft in a second rotational direction has been mechanically restricted by a second stopper.

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.