Abstract: An internal combustion engine includes an engine main body defining a cylinder bore, a piston received in the cylinder bore, and a crankshaft rotatably supported by the engine main body and connected with the piston via a connecting rod, the piston including a skirt. The cylinder bore includes a first region defined as a range along the cylinder axial line on a side of a top dead center from a first piston position, and a second region defined as a range along the cylinder axial line on a side of the bottom dead center from a second piston position closer to the bottom dead center than the first piston position, and a connection region positioned between the first and second regions. A diameter of the cylinder bore is smaller in the first region than in the second region, and the connection region connects the first and second regions smoothly.

Abstract: An internal combustion engine includes an engine main body defining a cylinder bore, a piston received in the cylinder bore, and a crankshaft rotatably supported by the engine main body and connected with the piston via a connecting rod, the piston including a skirt. The cylinder bore includes a first region defined as a range along the cylinder axial line on a side of a top dead center from a first piston position, and a second region defined as a range along the cylinder axial line on a side of the bottom dead center from a second piston position closer to the bottom dead center than the first piston position, and a connection region positioned between the first and second regions. A diameter of the cylinder bore is smaller in the first region than in the second region, and the connection region connects the first and second regions smoothly.

Abstract: Provided is an oil ring (13) for a piston assembly that can minimize the frictional resistance without impairing the oil control function such as the scraping of lubricating oil from the cylinder wall surface by the oil ring. The oil ring consists of an upper side rail (16), a lower side rail (17) and an annular expander (18) interposed between the two side rails, and is received in an oil ring groove (8) with a prescribed vertical clearance (20) that permits tilting of the side rails. An outer peripheral surface (16E, 17E) of each side rail is provided with a radially inward slant. Therefore, during the upward stroke of the piston, the upper side rail tilts in the radially outward direction so that the effective slant angle of the outer peripheral surface of the upper side ring is adjusted to an optimum value.

Abstract: Provided is an oil ring (13) for a piston assembly that can minimize the frictional resistance without impairing the oil control function such as the scraping of lubricating oil from the cylinder wall surface by the oil ring. The oil ring consists of an upper side rail (16), a lower side rail (17) and an annular expander (18) interposed between the two side rails, and is received in an oil ring groove (8) with a prescribed vertical clearance (20) that permits tilting of the side rails. An outer peripheral surface (16E, 17E) of each side rail is provided with a radially inward slant. Therefore, during the upward stroke of the piston, the upper side rail tilts in the radially outward direction so that the effective slant angle of the outer peripheral surface of the upper side ring is adjusted to an optimum value.

Abstract: Provided is an oil ring (13) that can minimize the frictional resistance without impairing the oil control function such as the scraping of lubricating oil from the cylinder wall surface by the oil ring. The oil ring consists of an upper side rail (16), a lower side rail (17) and an annular expander (18) interposed between the two side rails, and is received in an oil ring groove (8) with a prescribed vertical clearance (20) that permits tilting of the side rails. An outer peripheral surface (16E, 17E) of each side rail is provided with a radially inward slant. Therefore, during the upward stroke of the piston, the upper side rail tilts in the radially outward direction so that the effective slant angle of the outer peripheral surface of the upper side ring is adjusted to an optimum value.

Abstract: A fuel cell stack is provided with a plurality of stacked separators. This fuel cell stack includes: terminals that extend from the separators; packing in which are formed a plurality of through holes through which the terminals are inserted; a packing casing that has a packing housing concave portion that envelops side surfaces of the packing and supports a bottom surface of the packing, and has through holes through which the terminals are inserted; and a connector housing that has a pressing surface that presses a top surface of the packing. Mountain-shaped protruding portions whose apex portions are formed by circumferential edges of apertures of the respective through holes are provided on the top surface of the packing, and the pressing surfaces of the connector housing are formed in a configuration that conforms to the side surfaces of the protruding portions. Internal surfaces of the through holes in the packing are in contact without a gap in between with external surfaces of the terminals.

Abstract: A fuel cell stack is provided with a plurality of stacked separators. This fuel cell stack includes: terminals that extend from the separators; packing in which are formed a plurality of through holes through which the terminals are inserted; a packing casing that has a packing housing concave portion that envelops side surfaces of the packing and supports a bottom surface of the packing, and has through holes through which the terminals are inserted; and a connector housing that has a pressing surface that presses a top surface of the packing. Mountain-shaped protruding portions whose apex portions are formed by circumferential edges of apertures of the respective through holes are provided on the top surface of the packing, and the pressing surfaces of the connector housing are formed in a configuration that conforms to the side surfaces of the protruding portions. Internal surfaces of the through holes in the packing are in contact without a gap in between with external surfaces of the terminals.

Abstract: A cylindrical support portion is provided on a wafer pump case to surround a rotary shaft, and a cylindrically formed power transmitting rotary wheel surrounding the support portion is integrally coupled to an outer end of the rotary shaft which protrudes outwardly from the support portion. A bearing means is interposed between an inner surface of the power transmitting rotary wheel and an outer surface of the support portion. A plurality of sealing members disposed concentrically with the bearing means are interposed between the rotary shaft and an inner surface of the cylindrical support portion at a location axially outwardly spaced from the mechanical seal, and a grease is filled between the sealing members. The water pump structure not only improves the sealing property of the sealing members by providing the sealing members at a location in which the deflection of the rotary shaft is smallest, but also increases the retaining property for the grease between the plurality of sealing members.