Abstract: An upper oil pan assembly is attached to the lower portion of a cylinder block. An opening is formed on a side wall of the upper oil pan assembly. The variable compression ratio mechanism changes a top dead center position of a piston in accordance with the rotational position of a control shaft to thereby change the compression ratio. The control shaft is rotationally driven by an actuator. At least a portion of the actuator is fixed to a main bearing cap in a state in which at least a portion thereof is positioned on the outer side of an upper oil pan assembly.

Abstract: An upper oil pan assembly is attached to the lower portion of a cylinder block. An opening is formed on a side wall of the upper oil pan assembly. The variable compression ratio mechanism changes a top dead center position of a piston in accordance with the rotational position of a control shaft to thereby change the compression ratio. The control shaft is rotationally driven by an actuator. At least a portion of the actuator is fixed to a main bearing cap in a state in which at least a portion thereof is positioned on the outer side of an upper oil pan assembly.

Abstract: A bearing structure has a crankshaft rotatably supported by a crankshaft bearing part, formed of a cylinder block of an internal combustion engine and a first bearing cap, through a bearing metal, a second shaft rotatably supported by a second shaft bearing part formed of the first bearing cap and a second bearing cap, wherein the bearing metal has a bearing metal planar portion for rotatably supporting the crankshaft with an entire inner peripheral surface of the bearing metal, the inner peripheral surface at which the bearing metal planar portion is formed, a bearing metal oil groove portion formed with an oil groove formed to extend circumferentially in an inner peripheral surface of the bearing metal, the inner peripheral surface at which the bearing metal oil groove portion is formed, a first oil hole opening at the oil groove, and a second oil hole opening at the oil groove.

Abstract: A bearing structure has a crankshaft rotatably supported by a crankshaft bearing part, formed of a cylinder block of an internal combustion engine and a first bearing cap, through a bearing metal, a second shaft rotatably supported by a second shaft bearing part formed of the first bearing cap and a second bearing cap, wherein the bearing metal has a bearing metal planar portion for rotatably supporting the crankshaft with an entire inner peripheral surface of the bearing metal, the inner peripheral surface at which the bearing metal planar portion is formed, a bearing metal oil groove portion formed with an oil groove formed to extend circumferentially in an inner peripheral surface of the bearing metal, the inner peripheral surface at which the bearing metal oil groove portion is formed, a first oil hole opening at the oil groove, and a second oil hole opening at the oil groove.

Abstract: In a flywheel in which narrow portions to be engaged with a coil spring included in the flywheel are formed of recessed portions made by recessing the surface of a flywheel cover, the portions of a sensor plate welded to the front cover, which confront with the recessed portions are made more fragile than adjacent portions of the sensor plate. With this configuration, when the front cover is deformed, stress applied to welded portions adjacent to the recessed portions can be suppressed since the fragile portions are easily deformed. Accordingly, even if the recessed portions are formed to the surface of a flywheel cover, stress can be prevented from being concentrated on the coupling portions of the flywheel cover and the sensor plate.

Abstract: An internal combustion engine connecting rod is designed with bolts having a minimum required strength. A strength safety factor Sfa is calculated based on an axial strength limit load FX of the bolt and the maximum load FB to be born by the bolt due to a piston inertia force (Sfa=FX/FB) acting on the connecting rod. A mating surface separation safety factor Sfb is calculated based on the tensile load (FB?FC) resulting from the piston inertia force and the load FE carried by the bolts at a mating surface separation limit, i.e., the maximum bolt load FE at which the connecting rod main body and the cap remain in contact without separating (Sfb=FE/(FB?FC)). The mating surface separation safety factor Sfb of the connecting rod is set to be equal to or larger than the strength safety factor Sfa of the bolts (Sfb?Sfa).

Abstract: In a flywheel in which narrow portions to be engaged with a coil spring included in the flywheel are formed of recessed portions made by recessing the surface of a flywheel cover, the portions of a sensor plate welded to the front cover, which confront with the recessed portions are made more fragile than adjacent portions of the sensor plate. With this configuration, when the front cover is deformed, stress applied to welded portions adjacent to the recessed portions can be suppressed since the fragile portions are easily deformed. Accordingly, even if the recessed portions are formed to the surface of a flywheel cover, stress can be prevented from being concentrated on the coupling portions of the flywheel cover and the sensor plate.

Abstract: An internal combustion engine connecting rod is designed with bolts having a minimum required strength. A strength safety factor Sfa is calculated based on an axial strength limit load FX of the bolt and the maximum load FB to be born by the bolt due to a piston inertia force (Sfa=FX/FB) acting on the connecting rod. A mating surface separation safety factor Sfb is calculated based on the tensile load (FB?FC) resulting from the piston inertia force and the load FE carried by the bolts at a mating surface separation limit, i.e., the maximum bolt load FE at which the connecting rod main body and the cap remain in contact without separating (Sfb=FE/(FB?FC)). The mating surface separation safety factor Sfb of the connecting rod is set to be equal to or larger than the strength safety factor Sfa of the bolts (Sfb?Sfa).