Abstract: An internal combustion engine includes a piston adapted to reciprocate in a cylinder. The piston includes a first portion, a second portion, and a third portion. The first portion of the piston forms a crown surface of the piston, the second portion of the piston forms a piston ring groove of the piston with the piston ring groove arranged and configured to receive a piston ring, and the third portion of the piston forms a crankcase side surface of the piston with the crankcase side surface facing a crankcase of the engine. The second portion of the piston is formed of a material having a higher thermal conductivity than a material forming the first portion of the piston and a material forming a third portion of the piston.

Abstract: A lower link for a piston crank mechanism of an internal combustion engine includes an upper section, a lower section, and a crank pin bearing section disposed between the upper section and the lower section, and mounted on a crank pin of a crank shaft. One of the upper section and the lower section is formed with a bolt inserting hole. The other of the upper section and the lower section is formed with an internal thread portion including an open end. One of the bolts passes through the bolt inserting hole, is screwed into the internal thread portion, and includes an end bared from the open end which is formed in a surface perpendicular to a bolt center axis. The other of the upper section and the lower section includes a recessed portion formed in the surface to divert a stress transmitting path.

Abstract: An internal combustion engine includes a piston reciprocating in a cylinder; a crankshaft; and a multilink piston-crank mechanism linking the piston with the crankshaft. The multilink piston-crank mechanism includes an upper link having a first end connected with the piston by a piston pin; a lower link mounted rotatably on a crankpin of the crankshaft and having a first end connected with a second end of the upper link by a first connection pin; a control link having a first end connected with a second end of the lower link by a second connection pin; a control shaft connected movably with a second end of the control link and configured to rotate in synchronization with the crankshaft and at a half rotational speed of the crankshaft; and a phase adjusting section configured to variably adjust a phase of rotation of the control shaft relative to the crankshaft in accordance with an operating condition of the engine.

Abstract: A link mechanism usable for a variable compression ratio mechanism of an internal combustion engine includes first and second links pivotally connected by a pin inserted through cylindrical first and second pin boss portions of the first and second links. Each of the first and second pin boss portions includes a circumferentially extending first narrow section, and a circumferentially extending first wide section having an axial wall thickness greater than the axial wall thickness of the first narrow section. The wide sections of the first and second pin boss portions are overlapped in an region extending in the axial direction of the pin.

Abstract: An engine having a cylinder, a piston slideably received in the cylinder, a crankshaft connected to the piston, and a multi-link piston crank mechanism. The multi-link piston crank mechanism controls movement of the piston such that an acceleration of the piston at top dead center is less than an acceleration of the piston at bottom dead center. A determining device determines an operating condition of the engine. A combustion mode control device controls the engine to operate at an air-fuel ratio leaner than a stoichiometric air-fuel ratio when the determining device determines that the operating condition of the engine is in a predetermined operating region.

Abstract: A multi-link piston crank mechanism for an internal combustion engine, including a crankshaft having a crank pin, and crank webs connected with each other through the crank pin. A pair of thrust surfaces are formed on the crank webs so as to be opposed in a direction of a center axis of the crank pin. A first link pivotally supported on the crank pin is coupled to a second link through a connection pin located in a space between the thrust surfaces. The connection pin is moveable about the crank pin to form a circular trace along which the thrust surfaces extend. The end surfaces of the connection pin and the thrust surfaces come into mutual contact to prevent the connection pin from falling out of the space between the thrust surfaces.

Abstract: In an internal combustion engine, a piston reciprocating in a cylinder and a crankshaft are linked with each other by a piston-crank linking mechanism. The crankshaft includes a counterweight. When the piston is located in the proximity of a bottom dead center, an outermost portion of the counterweight crosses an imaginary extension line extended from a piston pin in an axial direction of the piston pin.

Abstract: A V-type 8-cylinder four cycle internal combustion engine has a bank angle of 90 deg. and employs a double link type piston-crank mechanism for transmitting the force of each piston to a crankshaft. The double link type piston-crank mechanism comprises an upper link that has one end pivotally connected to the piston, a lower link that is rotatably supported by a crank pin of the crankshaft and has one end pivotally connected to the other end of the upper link, and a control link that has one end pivotally connected to the other end of the lower link and the other end pivotally connected to a cylinder block. Preferably, the crankshaft is of a single plane type in which all of the four throws are in a common plane.

Abstract: A variable compression ratio mechanism that changes the compression ratio according to the rotation angle of a control shaft, wherein a stopper is provided at the highest compression ratio side for regulating the rotation of said control shaft. Then, the output detected by a compression ratio sensor for detecting the rotation angle of said control shaft when said stopper is in an abutted state is read and an adjustment value is learned in order to revise the sensor output based on said detected output.

Abstract: An internal combustion engine includes a piston (2) and a crankshaft (33). The crankshaft (33) includes: a journal (33A) as a rotation center; a crank pin (33B) that is located eccentrically with respect to the journal (33A) and rotates integrally with the journal (33A), the crank pin (33b) connecting the piston (2) to the crankshaft (33); and a counter weight (33C) that is located eccentrically with respect to the journal (33A) in a direction opposite to the crank pin (33) and rotates uniformly with the journal (33A). A cutout (11) through which the counter weight (33C) passes is formed in a wall (1) of a cylinder bore that accommodates the piston (2) so as to be free to move reciprocally along the wall (1). As a result, the bottom dead center position of the piston can be lowered, and the overall height of the engine can be decreased.

Abstract: An internal combustion engine includes a piston reciprocating in a cylinder; a crankshaft; and a multilink piston-crank mechanism linking the piston with the crankshaft. The multilink piston-crank mechanism includes an upper link having a first end connected with the piston by a piston pin; a lower link mounted rotatably on a crankpin of the crankshaft and having a first end connected with a second end of the upper link by a first connection pin; a control link having a first end connected with a second end of the lower link by a second connection pin; a control shaft connected movably with a second end of the control link and configured to rotate in synchronization with the crankshaft and at a half rotational speed of the crankshaft; and a phase adjusting section configured to variably adjust a phase of rotation of the control shaft relative to the crankshaft in accordance with an operating condition of the engine.

Abstract: A lower link for an engine piston crank mechanism includes first and second half members joined by bolts to form a crankpin bearing portion. The first half member includes a first pin boss portion to connect the lower link with a first link which is one of an upper link connected with a piston and a control link having one end mounted swingably on the engine. The second half member includes a second pin boss portion to connect the lower link with a second link which is the other of the upper link and the control link, and an internally threaded portion into which one bolt is screwed. The second half member further includes a load transfer portion which is made greater in rigidity than the internally threaded portion.

Abstract: A lower link of a double link type piston crank mechanism comprises a crank pin bearing housing portion that is adapted to receive a crank pin of a crankshaft and defines a first contour, an upper pin receiving bore portion that is adapted to receive an upper pin of an upper link and defines a second contour, a control pin receiving bore portion that is adapted to receive a control pin of a control link and defines a third contour, and a given portion that has therein an internally threaded bore formed in one of upper and lower half-parts of the lower link and a bored portion formed in the other of the upper and lower half-parts of the lower link, the given portion defining a fourth contour. The upper and lower half-parts are coupled by a bolt that passes through the bored portion and is engaged with the internally threaded bore.

Abstract: An engine having a cylinder, a piston slideably received in the cylinder, a crankshaft connected to the piston, and a multi-link piston crank mechanism. The multi-link piston crank mechanism controls movement of the piston such that an acceleration of the piston at top dead center is less than an acceleration of the piston at bottom dead center. A determining device determines an operating condition of the engine. A combustion mode control device controls the engine to operate at an air-fuel ratio leaner than a stoichiometric air-fuel ratio when the determining device determines that the operating condition of the engine is in a predetermined operating region.

Abstract: A V-type 8-cylinder four cycle internal combustion engine has a bank angle of 90 deg. and employs a double link type piston-crank mechanism for transmitting the force of each piston to a crankshaft. The double link type piston-crank mechanism comprises an upper link that has one end pivotally connected to the piston, a lower link that is rotatably supported by a crank pin of the crankshaft and has one end pivotally connected to the other end of the upper link, and a control link that has one end pivotally connected to the other end of the lower link and the other end pivotally connected to a cylinder block. Preferably, the crankshaft is of a single plane type in which all of the four throws are in a common plane.

Abstract: A reciprocating engine with a variable compression ratio mechanism is disclosed. A lubrication system of the engine is improved by controlling an oil pressure according to a compression ratio setting. The lubrication system includes various combinations of control valves and oil passages. The oil relief passage is opened at a high compression ratio setting applied to a low engine load range and is otherwise closed at a low compression ratio setting applied to a high engine load range.

Abstract: In an internal combustion engine, a piston reciprocating in a cylinder and a crankshaft are linked with each other by a piston-crank linking mechanism. The crankshaft includes a counterweight. When the piston is located in the proximity of a bottom dead center, an outermost portion of the counterweight crosses an imaginary extension line extended from a piston pin in an axial direction of the piston pin.

Abstract: A link mechanism of an engine includes: an upper link having a first end connected to a piston pin of a piston; a lower link connected to the upper link via an upper pin having a center, the lower link being connected to a crank pin of a crank shaft; a control shaft extending substantially in parallel with the crank shaft, the control shaft having a rotational center; and a control link including: a first end swingably connected to the control shaft, and a second end connected to the lower link. In a process of the center of the upper pin moving nearer to the axial line of the piston pin, the center of the control pin moves in the upward direction, thus inclining the lower link and allowing the center of the upper pin and the center of the piston pin to move in the downward direction.

Abstract: A multi-link piston crank mechanism for an internal combustion engine, including a crankshaft having a crank pin, and crank webs connected with each other through the crank pin. A pair of thrust surfaces are formed on the crank webs so as to be opposed in a direction of a center axis of the crank pin. A first link pivotally supported on the crank pin is coupled to a second link through a connection pin located in a space between the thrust surfaces. The connection pin is moveable about the crank pin to form a circular trace along which the thrust surfaces extend. The end surfaces of the connection pin and the thrust surfaces come into mutual contact to prevent the connection pin from falling out of the space between the thrust surfaces.

Abstract: A lower link of a double link type piston crank mechanism comprises a crank pin bearing housing portion that is adapted to receive a crank pin of a crankshaft and defines a first contour, an upper pin receiving bore portion that is adapted to receive an upper pin of an upper link and defines a second contour, a control pin receiving bore portion that is adapted to receive a control pin of a control link and defines a third contour, and a given portion that has therein an internally threaded bore formed in one of upper and lower half-parts of the lower link and a bored portion formed in the other of the upper and lower half-parts of the lower link, the given portion defining a fourth contour. The upper and lower half-parts are coupled by a bolt that passes through the bored portion and is engaged with the internally threaded bore.