Abstract: A valve operation control system for an internal combustion engine in which hydraulic pressure applied to a valve operation mode changing mechanism is controlled by hydraulic pressure control means that is formed from a holder mounted on a cylinder head, a spool valve formed by slidably housing a spool valve body in a valve body, and an electromagnetic open/close valve for controlling hydraulic pressure of a pilot hydraulic chamber, wherein the holder (109) is formed by integrally connecting a housed portion (109a) and a projecting portion (109b) by means of a connection portion (109c), the housed portion (109a) being housed between the cylinder head (22R) and a head cover, the projecting portion (109b) projecting outside the cylinder head (22R) and the head cover and having the electromagnetic open/close valve (113, 114) mounted thereon, a seal face (116) with the head cover is formed on the connection portion (109c), and the valve body (110) is provided so as to be connected to the housed portion (109a) whi

Abstract: A valve operation control system for an internal combustion engine in which hydraulic pressure applied to a valve operation mode changing mechanism is controlled by hydraulic pressure control means that is formed from a holder mounted on a cylinder head, a spool valve formed by slidably housing a spool valve body in a valve body, and an electromagnetic open/close valve for controlling hydraulic pressure of a pilot hydraulic chamber, wherein the holder (109) is formed by integrally connecting a housed portion (109a) and a projecting portion (109b) by means of a connection portion (109c), the housed portion (109a) being housed between the cylinder head (22R) and a head cover, the projecting portion (109b) projecting outside the cylinder head (22R) and the head cover and having the electromagnetic open/close valve (113, 114) mounted thereon, a seal face (116) with the head cover is formed on the connection portion (109c), and the valve body (110) is provided so as to be connected to the housed portion (109a) whi

Abstract: A casing accommodating therein a pair of balance shafts below the cylinder block comprises an upper casing and a lower casing that can vertically be split, and an oil pump body is molded integrally with one of the upper and lower casings. In addition, one end of each of the two casings is inserted into the oil pump body for support therein, and the two balance shafts are each supported on a bearing provided between the two casings in such a manner as to be split into two halves at an intermediate portion or the other end thereof. With this construction, the oil pump body can be molded together with the casing, thereby making it possible to reduce the number of components used and man hours for assembling. In addition, since the bearings can be split into two halves, when compared with other portions of the balance shafts, the journal portion can be thinned, thereby making it possible not only to reduce the sliding friction but also to make the casing smaller in size and lighter in weight.

Abstract: A balancing device for a reciprocating engine is provided which is improved so as not to disturb the compactification of an engine. There is provided a balancing device for a reciprocating engine comprising two balance shafts 10L, 10R gear connected to each other, a chain/sprocket mechanism 9, 11, 12 for coupling at least one 10L of the balance shafts with a crankshaft 1 in an interlocking fashion, a chain tensioner 14 for automatically adjusting the tension of the chain 12 and a pump receiving portion 22 integrally provided in a balance shaft holder 16 for supporting the balance shafts for receiving a rotor 21B of a lubricating oil pump 21, the balancing device being characterized in that the rotor of the lubricating oil pump is directly connected to the other balance shaft 10R, and that the chain tensioner is disposed on an shaft end side of the other balance shaft.

Abstract: A cylinder head structure for a multiple cylinder engine, comprising, at least for each of its cylinders (1) located at either longitudinal end of its cylinder bank: a combustion chamber (13) defined by the cylinder and a piston received therein; an intake passage (18) communicated with an intake manifold (20) at its one end and with said combustion chamber at its other end; and exhaust passage (19) communicated with an exhaust manifold (21) at its one end and with said combustion chamber at its other end; at least one of said intake passage and said exhaust passage being curved toward a longitudinally central part of said cylinder bank as it extends from its other end to its one end. Hence, the size and weight of the intake manifold and/or the exhaust manifold can be reduced.

Abstract: In a valve operating system for an internal combustion engine that includes a valve operation mode changing mechanism capable of changing at least one of either the lift amount of opening of an engine valve openably and closably carried in an engine body or the opening or closing timing in accordance with a variation in hydraulic pressure supplied to the changing mechanism. A selector valve is provided and includes a valve element slidably received in a housing attached to the engine body to change the supply of hydraulic pressure to the valve operation mode changing mechanism. The housing of the selector valve is provided with a working oil chamber which receives an oil pressure for driving, toward a position to supply a higher hydraulic pressure to the valve operation mode changing mechanism, a valve element biased toward a position to supply a lower hydraulic pressure to the valve operation mode changing mechanism.

Abstract: A lubricant supplying system for a DOHC type multicylinder internal combustion engine comprising a plurality of cylinders arranged in series in a cylinder block, a pair of cam shafts parallel to each other and rotatably supported by a cylinder head and cam holders fixed to the cylinder head at opposite sides of the respective cylinders along the cylinder arranging direction, a plurality of cams including low speed cams corresponding to intake and exhaust valves of the respective cylinders and fixed to the cam shafts, a plurality of rocker arms in slidable contact with the respective cams corresponding to the intake and exhaust valves of the respective cylinders, and a connection switching mechanism for switching connection and disconnection of the rocker arms in response to a hydraulic pressure to vary the operating states of the valves responsive to the operating state of the engine, wherein a hydraulic pressure supply passage independent from an oil supply passage for supplying a hydraulic pressure to the c