Abstract: In an engine, an oil level sensor (47) provided in a bottom part of an oil pan (15) storing engine oil so as to stand vertically upright is placed between a mutually parallel pair of balancer shafts (27, 28) housed in a balancer housing (21) provided between a lower face of a cylinder block and the oil pan (15). This not only enables the oil level sensor (47) to be placed compactly by utilizing effectively dead space formed between the pair of balancer shafts (27, 28), but also enables agitation of engine oil to be suppressed by the pair of balancer shafts (27, 28) and any degradation in detection precision due to engine oil splashing over the oil level sensor (47) to be prevented.

Abstract: In an engine, an oil level sensor (47) provided in a bottom part of an oil pan (15) storing engine oil so as to stand vertically upright is placed between a mutually parallel pair of balancer shafts (27, 28) housed in a balancer housing (21) provided between a lower face of a cylinder block and the oil pan (15). This not only enables the oil level sensor (47) to be placed compactly by utilizing effectively dead space formed between the pair of balancer shafts (27, 28), but also enables agitation of engine oil to be suppressed by the pair of balancer shafts (27, 28) and any degradation in detection precision due to engine oil splashing over the oil level sensor (47) to be prevented.

Abstract: Oil passages 12 for lubricating and cooling a piston pin 10 are provided in such a manner as to each open to an oil ring groove 5 of a piston 1 and to a piston inner side surface 2b of a piston pin supporting part 2 at portions in the vicinity of an upper end of a piston-pin hole 2a through the piston pin supporting part 2. The oil passages 12 are provided diagonally relative to an axis of the piston-pin hole 2a.

Abstract: A recessed portion 15 for removing a circlip 13 is formed in such a manner as to coincide in location with a broached groove 12 formed in a piston bore 2a for relieving the compression deformation of a piston pin 10 that would be caused by a thrust load.

Abstract: An engine has two balancer shafts supported on two bearing bushings which are made of the same material and mounted to a balancer holder. Lubricating oil passages for supplying oil to the bearing bushings are defined offset upwards from the centers O of the bearing bushings and by a distance .delta.. Each of the bearing bushings has two oil bores having a center angle .theta. other than 180.degree.. The two oil bores in the bearing bushing of one balancer shaft communicate with the lubricating oil passage, and one of the oil bores in the bearing bushing of another balancer shaft communicates with the lubricating oil passage, while the other oil bore of that another balancer shaft is closed to keep out of the lubricating oil passage. Thus, downstream ends of the lubricating oil passages for supplying the oil to the bearing bushings of the plurality of rotary shafts can be closed without use of a special closing member such as a blind plug.

Abstract: An engine having a lower block made of an aluminum-based material and having a bearing cap mounted therein in a cast-in manner abutting against front and rear sidewalls of a cylinder block of the engine and coupled to the cylinder block by a bolt, and a pump body is coupled to a lower surface of the lower block by bolts. The pump body also serves as a balancer shaft supporting member, and a journal portion of a balancer shaft is supported on the balancer shaft supporting member. Thus, the rigidity of supporting of the balancer shaft on the balancer shaft supporting member can be enhanced without an increase in size of the balancer shaft supporting member of the engine.

Abstract: An oil passage structure in an engine includes a first oil passage and a second oil passage. The second oil passage has a hydraulic pressure which is different from that in the first oil passage. The first and second oil passages are provided in engine body in an arrangement where they intersect each other when viewed in projection onto a plane parallel to an axis of the first oil passage. In order to enable the space for disposition of both the oil passages to be reduced to a necessary minimum to provide a reduction in size of the engine body, a cylindrical partition member having annular seal members mounted on its outer surface at opposite ends is fitted into the first oil passage. Thus, an annular intermediate chamber is defined between the outer surface of the partition member and an inner surface of the first oil passage and is sealed at its opposite ends by the seal members.