Abstract: An internal combustion engine having its cylinders tilted at an angle of less an than 90 degrees relative to a vertical axis is provided with a oil drain mechanism for drainign excess oil that collects when the engine stops. For this purpose, an oil drain hole, which communicates with an interior of the piston body to drain the lubricating oil, is formed in the inner wall of an oil ring groove in such a way as to be located below the center line of the piston body. Both ends of the oil drain hole are set lower than the lowest portion of a piston head. Therefore, it is possible to prevent lubricating oil from entering the combustion chamber when the engine stops, without providing a whirl-stop on piston rings.

Abstract: A composite oil-ring comprising an oil control ring disposed on a lower surface of an oil-ring groove, a seal ring disposed on the oil control ring and having substantially no oil path in the radial direction thereof, and a spring seal ring disposed between an upper surface of the oil-ring groove and the seal ring which is constituted as a Belleville spring structure having abutted end portions with no gap in the circumferential direction. The spring seal ring presses upwards against the upper surface of the oil-ring groove and presses downwards against the seal ring, the seal ring is pressed against the oil control ring, and the oil control ring is pressed against the lower surface of the oil-ring groove, by the spring force of the spring seal ring. Both the spring seal ring and seal ring have substantially no oil path in the radially outer direction.

Abstract: A steel having good wear resistance which contains 0.55-1.10% of C, up to 2.0% of Si, up to 2.0% of Mn, 12.0-25.0% of Cr and particularly suitable as a material for piston rings or rocker arms. Further addition of 0.05-1.10% of Al to the above steel gives a steel improved in properties for spheroidization of carbides and uniformization of carbide particle size, leading to further enhancement of wear resistance. If required 0.20-2.0% of Ni may be added to the steels, whereby corrosion resistance, toughness and hardenability are improved. An addition of at least one of 0.2-3.0% of Mo, 0.1-1.5% of V and 0.05-0.70% of Nb to the steels improves high-temperature strength and surface hardness. The steel is surface treated by gas nitriding of the like in a surface area for sliding contact with an opponent member.

Abstract: A steel having good wear resistance which contains 0.55-1.10% of C, up to 2.0% of Si, up to 2.0% of Mn, 12.0-25.0% of Cr and particularly suitable as a material for piston rings or rocker arms. Further addition of 0.05-1.10% of Al to the above steel gives a steel improved in properties for spheroidization of carbides and uniformization of carbide particle size, leading to further enhancement of wear resistance. If required 0.20-2.0% of Ni may be added to the steels, whereby corrosion resistance, toughness and hardenability are improved. An addition of at least one of 0.2-3.0% of Mo, 0.1-1.5% of V and 0.05-0.70% of Nb to the steels improves high-temperature strength and surface hardness. The steel is surface treated by gas nitriding of the like in a surface area for sliding contact with an opponent member.

Abstract: A piston and piston-ring assembly includes a piston and piston-rings located in piston-ring grooves formed in the piston. Such a kind of surface hardening treatment as is accompanied by an increase in surface roughness, such as alumite treatment, is applied to at least a lower groove surface of a top piston-ring groove. On the other hand, a resin with an excellent adhesive property is coated on a portion of a surface of the piston-ring opposing the hardened surface of the piston-ring groove. The heat resistive property of the assembly is improved by the surface hardening treatment without being accompanied by an increase in blowby gas amount and oil consumption because resin removed from the piston ring fills the valleys of the rugged hardened surface of the piston-ring groove.

Abstract: A three-piece oil-ring comprises a pair of side rails and an expander disposed between the side rails. The expander extends in a circumferential direction and has waves in a radial direction. At both sides of radially inner portions of the expander side rail engaging portions protrude in an axial direction and extend in a circumferential direction. A slot in the expander is provided between the paired side rail engaging portions. The slot may have a rib at a longitudinally central portion of the slot. Due to the slot and the rib, the oil-ring can have an appropriate rigidity, thereby decreasing oil consumption.

Abstract: A light metal alloy cast piston comprises a thermal strut provided in the shoulder portion of the piston skirt. The thermal strut is composed of a fiber reinforced metal portion containing high tensile strength fibers integrally molded in the matrix metal. The piston is shaped in such a manner that the inner periphery of the thermal strut is exposed toward the inside of the piston skirt, except for the regions at the piston pin bosses, to avoid the presence of non-reinforced metal a the inside of the thermal strut. This arrangement prevents the formation of cracks along the inner periphery of the thermal strut.

Abstract: An oil-ring comprising a pair of side rails and an expander disposed between the side rails. The expander extends in a circumferential direction and has waves in a radial direction. At both sides of radially inner portions of the expander, side rail engaging portions protrude in an axial direction. The side rail engaging portions are formed as paired side rail engaging sections within one pitch of the waves, by defining a slit extending in the axial direction at a central portion of one side rail engaging portion. Due to the division from one side rail engaging portion to paired side rail engaging sections, the rigidity of each side rail engaging portion can be weakened appropriately, and each side rail can follow against the cylinder bore surface satisfactorily, thereby decreasing oil consumption.

Abstract: A light metal alloy cast piston including a thermal strut (32, 48, 52) arranged in a shoulder portion of the piston skirt. The thermal strut is composed of an annular fiber-reinforced metal portion in which high-tensile-strength reinforcing fibers are integrally molded. The reinforcing fibers include first fibers (34), such as carbon fibers, having a coefficient of linear expansion substantially smaller than that of the matrix metal alloy, and second fibers (36), such as silicon carbide fibers and alumina fibers, having a flexural or bending strength larger than that of the first fibers. The first fibers primarily serve to restrain thermal expansion of the piston skirt and the second fibers, having a larger bending strength, act to protect the first fibers from excessive bending forces. In a preferred embodiment, the first fibers are located in the inner region of the thermal strut and the second fibers are arranged in the outer region.

Abstract: A three-piece oil-ring with a pair of side rails and an expander disposed between the side rails. The expander extends in a circumferential direction and has waves in a radial direction. Flat portions are located at radially inner portions of the expander. At a plurality of the flat portions protrusions extend radially inward. The protrusions contact a bottom surface of an oil-ring groove of a piston and prevents overlapping of the ends of the expander. The protrusion may be provided with holes at both sides thereof and a wire may be passed through the holes to prevent overlapping of the ends of the expander.

Abstract: A composite oil-ring comprises a pair of rail rings and an expander-spacer ring. The expander-spacer ring is laterally extending U-shaped in cross section providing rail supporting legs and an inwardly open channel between the legs of the U. The expander-spacer ring is integrally formed with a plurality of axially extending rail engaging portions circumferentially spaced at the inner periphery of each of the legs, and has a plurality of slots extending radially cut from the inner peripheries of the legs. Also, the rail engaging portions may have circumferential central portions with the same curvature as that of the rail rings and circumferential end portions with a smaller curvature than that of the rail rings. Such structure reduces the abrasion of the composite oil-ring and prevents an independent movement of the rail rings.

Abstract: A helically-shaped intake port comprising a helical portion formed around an intake valve, and a substantially straight inlet passage portion tangentially connected to the helical portion. A bypass passage is branched off from the inlet passage portion and connected to the helical portion. The slide valve, actuated by lubricating oil, is arranged in the bypass passage. The slide valve is opened when the amount of air fed into the cylinder of an engine is increased beyond a predetermined value.

Abstract: A combustion chamber is formed between a cylinder head, which has a central recess and planar surfaces on each side of it, and a juxtaposed piston, which has a central recess and planar surfaces on each side of it. Inlet and outlet ports are formed in the head with the axes of the ports on one side of a phantom plane that includes the axis of the cylinder. The juxtaposed planar regions of the cylinder head and piston define a first squish area between those planar portions on the same side of the phantom plane as the axes of the ports, and a second squish area, which is smaller than the first, between those planar surfaces of the head and piston on the other side of the phantom plane. A spark plug is mounted in the head so that its igniting tip is on the other side of the phantom plane from the axes of the ports but is close to the axis of the cylinder bore and to the planar region in which the squish areas are formed.

Abstract: A bearing structure for a cam shaft has a first journal-receiving cavity of a semi-circular cross section provided in an upper face of a cylinder head, and a second journal-receiving cavity of a semi-circular section provided in a lower face of a bearing cap. The bearing cap is mounted on the cylinder head with the two faces joining together. A groove is provided in at least one of the two joining faces to extend across that face and to communicate at one end thereof with the internal space of the cylinder head so as to collect or intercept oil leaking out through a clearance left between the two adjacent faces.

Abstract: A timing belt tensioner for an internal combustion engine comprising a base plate pivotally mounted about one end of the base plate to the front of the engine, a first arcuous slot formed in the base plate and extending along an arc having its center of curvature at the pivot axis of the base plate, a cylindrical tensioner bearing holder disposed on the base plate, a tensioner bearing rotatably coupled to the bearing holder, a second arcuous slot in the bearing holder corresponding to the first arcuous slot in the base plate, and a bolt extending through the first and second arcuous slot for fixing the position of the timing belt tensioner on the engine.