In an internal combustion engine, a breather chamber can be formed without increasing the number of component parts. The internal combustion engine (1) comprises an engine block (30) defining a cylinder (2); a case member (19) fastened to a lower part of the engine block to define a crank chamber (4) jointly with the engine block; and a bearing member (50) fastened to the engine block in the crank chamber to rotatably support a crankshaft; wherein the engine block is provided with a central recess (134) formed in a part thereof to which the bearing member is fastened, a blow-by gas inlet passage (112, 116, 121) communicating the central recess with the crank chamber, and a blow-by gas return passage (122, 118) forming a part of a passage communicating the central recess with an intake device, the central recess and the bearing member jointly defining a central breather chamber.

An engine includes an output shaft, a cylinder head, a cylinder block, and a plurality of head bolts. The cylinder block includes three or more cylinder parts, a plurality of connecting portions, a plurality of output shaft supporting parts, and a plurality of head bolt holes. A side wall face of at least one cylinder part includes a first rib. The first rib diagonally extends from the connecting portion toward a head bolt hole base.

A half thrust bearing for a crankshaft includes a back metal layer defining a first surface and a second surface, and a bearing alloy layer on the first surface to form a slide surface, and thrust relieves formed adjacent to both circumferential end surfaces and having a thrust relief surface consisting of the bearing alloy layer. Each circumferential end surface of the back metal layer includes an exposed end surface adjacent to the second surface, and a transition surface adjacent to the first surface. The bearing alloy layer further includes an extension portion covering the transition surface and having extension end surface adjacent to the exposed end surface, the extension end surface and the exposed end surface extending at least partly in the same plane.

A lubricating oil supply structure includes: a shaft; a bearing supporting the shaft and having an oil supply port, through which lubricating oil is supplied to between the shaft and the bearing, and an oil introduction port, through which the lubricating oil is introduced; a first oil passage, connected to the oil supply port, distributing the lubricating oil from an oil pump toward the oil supply port; a second oil passage, connected to the oil introduction port, supplying the lubricating oil introduced through the oil introduction port to a supply destination; a connection oil passage, formed by a gap between the bearing and the shaft, connecting between the first oil passage and the second oil passage, and a throttle portion, formed on a part of the connection oil passage, suppressing a flow of the lubricating oil from the oil supply port toward the oil introduction port.

A shaft assembly may include two or more Poka-Yoke bearing caps, each Poka-Yoke bearing cap having a pair of reference bores offset from a central axis of the bearing cap by differing offset distances, and each bearing cap defining a semi-circular recess that is positioned so as to align in use a central axis of the semi-cylindrical recess in the bearing cap with an axis of rotation of a shaft rotatably supported by the bearing cap. The differing offsets of the reference bores prevent the bearing cap from being assembled in a reversed orientation. To ensure that each bearing cap can only be fitted in one position, a centre spacing between the first and second reference bores of each bearing cap is different to the centre spacing used for other bearing caps used to support a single shaft.

An internal combustion engine includes a crankshaft that has a journal linked to a bearing and is rotatably supported on the crankcase, a power transmission gear fixed to an extremity of the crankshaft that has a smaller diameter than a diameter of the journal and projects outward of the crankcase, a to-be-detected body that is fixed on an outer periphery of a collar member disposed between the bearing and the power transmission gear and is relatively non-rotatably supported on the crankshaft, and a detection sensor that is made to face a trajectory of the to-be-detected body and detects movement of the to-be-detected body to generate a pulse signal. This provides a structure for disposing a to-be-detected body that enables any increase in the dimensions of an internal combustion engine to be avoided.

An internal combustion engine includes: a crankshaft supported via a bearing; a balancer drive gear; a balancer shaft; and a one-way clutch mechanism that transmits to the crankshaft a drive force to start the internal combustion engine. In the internal combustion engine, the bearing includes an oil seal built therein, the oil seal sealing a crank chamber of the crankcase. The one-way clutch mechanism includes a case fixed to the crankshaft and a starter driven gear provided relatively rotatably with respect to the case and driven by the drive force. The starter driven gear includes a thrust bearing portion that abuts on the balancer drive gear in an axial direction of the crankshaft.

A bearing cap according to one embodiment of this disclosure includes: a concave part that supports a crankshaft of an internal combustion engine; first bosses that are disposed one on each side of the concave part and each have a first bolt hole; and second bosses that are disposed one on each side of a bearing cap main body having the concave part and the first bosses so as to flank the bearing cap main body and each have a second bolt hole. The bearing cap is fixed to a first member of the internal combustion engine by first bolts inserted into the first bolt holes, and to a second member of the internal combustion engine by second bolts inserted into the second bolt holes. At least the pair of second bosses have higher rigidity than a frame.

A cylinder block assembly includes a cylinder block having cylinders and a plurality of crank caps fixed to the cylinder block. The crank caps are arranged such that one of the crank caps is disposed on each of both sides of each of the cylinders in the alignment direction and among the plurality of crank caps arranged in line, each of a center crank cap located at a center position and two side crank caps respectively located at both ends has a hole or a groove in such a manner as to be more easily deformable than intermediate crank caps each of which is located between the center crank cap and one of the side crank caps when a load is received from the crankshaft.

A structural frame is provided. The structural frame includes a bottom surface, first and second cylinder block sidewall engaging surfaces, the first and second cylinder block sidewall engaging surfaces positioned above the bottom surface at a height that is above a centerline of a crankshaft support included in a cylinder block when the structural frame is coupled to the cylinder block.