Abstract: A lower link (13) is formed such that outer circumferential sides of both end portions of a crankpin through-hole (21) are stiffer than a center portion of the crankpin through-hole (21), i.e. a bifurcation portion of a bifurcated shape thereof. The both end portions of the crankpin through-hole (21) are formed such that inner circumferential surfaces (22a) of the both end portions are curved at a predetermined curvature in an axial direction of a crankshaft with no load input on the lower link (13). Moreover, the center portion of the crankpin through-hole (21) is formed such that an inner circumferential surface (22b) thereof is located inward of the inner circumferential surfaces (22a) of the both end portions and is straight in the axial direction of the crankshaft with no load input on the lower link (13).

Abstract: A multi-link piston crank mechanism includes a crank pin bearing portion including a crank pin bearing central portion that is disposed at a center thereof in an axial direction of a crank shaft. The crank pin bearing central portion at a portion positioned on the first end side of the lower link is thicker in a radial direction of the crank pin than a portion positioned on the second end side of the lower link. The second control link end portion is thicker along a radial direction of the second through hole than the second upper link end portion along a radial direction of the first through hole.

Abstract: When the compression ratio of a variable compression ratio internal combustion engine (10) is set at a low compression ratio, a lubricating oil ejected from a lower link oil passage (25) is reflected by an upper link (11) at the piston top dead center, and supplied to a cylinder inside wall surface on the side on which a control link (15) is located in a view as viewed in the axial direction of the crank shaft. When the compression ratio of the variable compression ratio internal combustion engine (10) is set at a high compression ratio, the lubricating oil ejected from lower link oil passage (25) is reflected by upper link (11) at the piston top dead center, and supplied to the back side of the piston crown.

Abstract: A multi-link piston crank mechanism includes a crank pin bearing portion including a crank pin bearing central portion that is disposed at a center thereof in an axial direction of a crank shaft. The crank pin bearing central portion at a portion positioned on the first end side of the lower link is thicker in a radial direction of the crank pin than a portion positioned on the second end side of the lower link. The second control link end portion is thicker along a radial direction of the second through hole than the second upper link end portion along a radial direction of the first through hole.

Abstract: An opening on one end side of a pin-boss oil passage opens to the inner circumferential surface of a pin boss part of an upper link, while an opening on the other end side thereof opens to the outer circumferential surface of the pin boss part of the upper link. A lower-link oil passage has a one-end-side opening structured to open to a pin-boss-facing surface of the lower link facing the outer circumferential surface of the pin boss part of the upper link and its other-end-side opening structured to open to a crankpin bearing surface. The lower-link oil passage is configured to point, at a prescribed crankangle, to a specified end edge of end edges of the other-end-side opening of the pin-boss oil passage, the specified end edge facing one end side of the upper link.

Abstract: When the compression ratio of a variable compression ratio internal combustion engine (10) is set at a low compression ratio, a lubricating oil ejected from a lower link oil passage (25) is reflected by an upper link (11) at the piston top dead center, and supplied to a cylinder inside wall surface on the side on which a control link (15) is located in a view as viewed in the axial direction of the crank shaft. When the compression ratio of the variable compression ratio internal combustion engine (10) is set at a high compression ratio, the lubricating oil ejected from lower link oil passage (25) is reflected by upper link (11) at the piston top dead center, and supplied to the back side of the piston crown.

Abstract: A lower link (13) is formed such that outer circumferential sides of both end portions of a crankpin through-hole (21) are stiffer than a center portion of the crankpin through-hole (21), i.e. a bifurcation portion of a bifurcated shape thereof. The both end portions of the crankpin through-hole (21) are formed such that inner circumferential surfaces (22a) of the both end portions are curved at a predetermined curvature in an axial direction of a crankshaft with no load input on the lower link (13). Moreover, the center portion of the crankpin through-hole (21) is formed such that an inner circumferential surface (22b) thereof is located inward of the inner circumferential surfaces (22a) of the both end portions and is straight in the axial direction of the crankshaft with no load input on the lower link (13).

Abstract: An opening on one end side of a pin-boss oil passage opens to the inner circumferential surface of a pin boss part of an upper link, while an opening on the other end side thereof opens to the outer circumferential surface of the pin boss part of the upper link. A lower-link oil passage has a one-end-side opening structured to open to a pin-boss-facing surface of the lower link facing the outer circumferential surface of the pin boss part of the upper link and its other-end-side opening structured to open to a crankpin bearing surface. The lower-link oil passage is configured to point, at a prescribed crankangle, to a specified end edge of end edges of the other-end-side opening of the pin-boss oil passage, the specified end edge facing one end side of the upper link.

Abstract: Joining surfaces (2a, 2b) of a pair of conductive joining members (1a, 1b) to be joined to each other are caused to face each other, and while one of the joining members (1a, 1b) is slid relative to the other of the joining members (1a, 1b), a current is passed from one of the joining members (1a, 1b) to the other of the joining members (1a, 1b) so as to cause resistance heating. Abrasion, plastic flow, and material diffusion therefore occur in high surface-pressure sections of the joining surfaces (2a, 2b), and the joining surfaces (2a, 2b) are joined together while current concentration locations are varied from moment to moment.

Abstract: In a reciprocating piston engine employing a variable compression ratio mechanism linked to a reciprocating piston for variably adjusting a geometrical compression ratio by varying at least a piston top dead center position, so that the top dead center position obtained at a low geometrical compression ratio is set to be lower than that at a high geometrical compression ratio, responsively to a controlled variable, a controller is configured to set a target compression ratio to a high value at low engine load operation, and to a relatively low value at high engine load operation. A substantially entire area of a crown of the piston, defining a part of a wall surface of a combustion chamber, is formed of a non-metallic material having a higher heat-insulating and heat-reserving property as compared to a base structural material of each of the combustion chamber and the piston.

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 crankshaft mechanism is disclosed that takes advantage of component makeup and orientation to cancel out inertial force. A crankshaft of the crankshaft mechanism includes at least one counterweight that is arranged in combination with the rest of the mechanism to cancel out the inertial force particularly at a timing in front of a bottom dead center of a piston where the inertial force becomes a maximum.

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: 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 the control shaft. Then, the output detected by a compression ratio sensor for detecting the rotation angle of the control shaft when the stopper is in an abutted state is read. An adjustment value is learned in order to revise the sensor output based on the detected output.

Abstract: In a reciprocating piston engine employing a variable compression ratio mechanism configured to be linked to a reciprocating piston for variably adjusting a geometrical compression ratio by varying at least a top dead center position of the piston responsively to a controlled variable, a controller is configured to control the variable compression ratio mechanism depending on an engine operating condition. A part of a wall surface of a combustion chamber is formed of a non-metallic material having a higher heat-insulating and heat-reserving property as compared to a base structural material of each of the combustion chamber and the piston.

Abstract: A piston crank mechanism has an upper link coupled to a piston by a piston pin, a lower link having a crankpin journal, wherein the crankpin journal is coupled to a crankpin of a crankshaft and is coupled to the upper link by an upper pin, and a control link is coupled to an eccentric cam of a control shaft that is supported by an engine block and coupled to a control pin boss by a control pin. The crankpin journal of the lower link is arranged and dimensioned relative to the upper pin such that a projection area defined by projecting the width of the upper pin along a direction line passing through a center of the piston pin and a center of the upper pin does not obscure an area defined by the crankpin during operation of the crankshaft as viewed in an axial direction of the crankpin.

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 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: A piston crank mechanism has an upper link coupled to a piston by a piston pin, a lower link having a crankpin journal, wherein the crankpin journal is coupled to a crankpin of a crankshaft and is coupled to the upper link by an upper pin, and a control link is coupled to an eccentric cam of a control shaft that is supported by an engine block and coupled to a control pin boss by a control pin. The crankpin journal of the lower link is arranged and dimensioned relative to the upper pin such that a projection area defined by projecting the width of the upper pin along a direction line passing through a center of the piston pin and a center of the upper pin does not obscure an area defined by the crankpin during operation of the crankshaft as viewed in an axial direction of the crankpin.

Abstract: A crankshaft mechanism is disclosed that takes advantage of component makeup and orientation to cancel out inertial force. A crankshaft of the crankshaft mechanism includes at least one counterweight that is arranged in combination with the rest of the mechanism to cancel out the inertial force particularly at a timing in front of a bottom dead center of a piston where the inertial force becomes a maximum.