Abstract: For the purpose of improving the fuel efficiency by lean combustion and enhancing the fuel efficiency improvement effects by performing compression ignition efficiently in some cylinders, a multi-cylinder spark ignition engine is constructed such that exhaust gas, that is exhausted from preceding cylinders 2A, 2D on the exhaust stroke side among pairs of cylinders whose exhaust stroke and intake stroke overlap in a low load, low rotational speed region, is directly introduced through an inter-cylinder gas passage 22 into following cylinders 2B, 2C on the intake stroke side and only gas exhausted from the following cylinders 2B, 2C is fed to an exhaust passage 20, which is provided with a three-way catalyst 24.

Abstract: In a pair of preceding and following cylinders whose exhaust and intake strokes overlap each other, intake air supplied to the preceding cylinder (2A, 2D) is supercharged by a turbocharger (23) to produce combustion at a “lean” air-fuel ratio in the preceding cylinder (2A, 2D), and burned gas discharged from the preceding cylinder (2A, 2D) is introduced into the following cylinder (2B, 2C) through an intercylinder gas channel (22). Combustion in the following cylinder (2B, 2C) is made at an air-fuel ratio equal to or smaller than the stoichiometric air-fuel ratio by supplying fuel to the burned gas of a “lean” air-fuel ratio introduced from the preceding cylinder (2A, 2D), and gas discharged from the following cylinder (2B, 2C) is led to an exhaust passage (20) provided with a three-way catalyst (30).

Abstract: The invention is intended to provide good emission-cleaning performance by use of a three-way catalyst alone, without the need for a lean NOx catalyst, while ensuring a fuel economy improvement effect of lean burn operation, and to improve fuel economy up to high-load operating ranges while maintaining desired engine output performance by use of a supercharger. In a pair of preceding and following cylinders whose exhaust and intake strokes overlap each other, intake air supplied to the preceding cylinder (2A, 2D) is supercharged by a turbocharger (23) to produce combustion at a “lean” air-fuel ratio in the preceding cylinder (2A, 2D), and burned gas discharged from the preceding cylinder (2A, 2D) is introduced into the following cylinder (2B, 2C) through an intercylinder gas channel (22).

Abstract: In a partial load range of the engine, control of the flowing state of sucked and discharged gas is executed between a pair of cylinders, an exhaust stroke of one of the cylinders overlapping with an intake stroke of the other, so that burnt gas discharged from preceding cylinders 2A, 2D on the exhaust-stroke side is introduced, in a state where it has been discharged, through an inter-cylindrical gas passage 22 into following cylinders 2B, 2C on the intake stroke side. In a higher load range than the partial load range, control is executed so that a fresh-air introducing valve 18 disposed in a fresh-air introduction passage of the following cylinders 2B, 2C is opened, both the burnt gas and fresh air are introduced into the following cylinders 2B, 2C, and fuel is supplied to conduct combustion in the following cylinders 2B, 2C.

Abstract: A control device for a multicylinder spark-ignition engine includes a flow path switching unit for switching intake and exhaust flow paths between a two-cylinder interconnect configuration and an independent cylinder configuration and an air-fuel ratio control unit. In a low-load, low-speed operating range, the flow path switching unit switches the engine to the two-cylinder interconnect configuration, and the air-fuel ratio control unit produces a lean mixture having an air-fuel ratio larger than the stoichiometric air-fuel ratio by a specific amount in preceding cylinders by injecting fuel thereinto and an air-fuel ratio approximately equal to the stoichiometric air-fuel ratio in following cylinders by supplying fuel together with burned gas of a lean mixture state discharged from the preceding cylinders into the following cylinders to perform combustion in special operation mode.

Abstract: A valve driving device including a tappet assembly adapted to slide in a tappet guide hole to drive a valve and including a high-speed center tappet and low-speed side tappet; and a high-speed center cam and a low-speed side cam provided corresponding to the center tappet and the side tappet. A depression is formed which is depressed from a base circle to roughly the same profile as a shaft section of the camshaft so that the cam portion over a predetermined angle range where a cam nose section is not formed in the centrally located center cam is smaller than the base circles of the outside located side cams in profile.

Abstract: For the purpose of improving the fuel efficiency by lean combustion and enhancing the fuel efficiency improvement effects by performing compression ignition efficiently in some cylinders, a multi-cylinder spark ignition engine is constructed such that exhaust gas, that is exhausted from preceding cylinders 2A, 2D on the exhaust stroke side among pairs of cylinders whose exhaust stroke and intake stroke overlap in a low load, low rotational speed region, is directly introduced through an inter-cylinder gas passage 22 into following cylinders 2B, 2C on the intake stroke side and only gas exhausted from the following cylinders 2B, 2C is fed to an exhaust passage 20, which is provided with a three-way catalyst 24.

Abstract: A valve driving device including a tappet assembly adapted to slide in a tappet guide hole to drive a valve and including a high-speed center tappet and low-speed side tappet; and a high-speed center cam and a low-speed side cam provided corresponding to the center tappet and the side tappet. A depression is formed which is depressed from a base circle to roughly the same profile as a shaft section of the camshaft so that the cam portion over a predetermined angle range where a cam nose section is not formed in the centrally located center cam is smaller than the base circles of the outside located side cams in profile.

Abstract: A control device for a multicylinder spark-ignition engine includes a flow path switching unit for switching intake and exhaust flow paths between a two-cylinder interconnect configuration and an independent cylinder configuration and an air-fuel ratio control unit. In a low-load, low-speed operating range, the flow path switching unit switches the engine to the two-cylinder interconnect configuration, and the air-fuel ratio control unit produces a lean mixture having an air-fuel ratio larger than the stoichiometric air-fuel ratio by a specific amount in preceding cylinders by injecting fuel thereinto and an air-fuel ratio approximately equal to the stoichiometric air-fuel ratio in following cylinders by supplying fuel together with burned gas of a lean mixture state discharged from the preceding cylinders into the following cylinders to perform combustion in special operation mode.

Abstract: In a partial load range of the engine, control of the flowing state of sucked and discharged gas is executed between a pair of cylinders, an exhaust stroke of one of the cylinders overlapping with an intake stroke of the other, so that burnt gas discharged from preceding cylinders 2A, 2D on the exhaust-stroke side is introduced, in a state where it has been discharged, through an inter-cylindrical gas passage 22 into following cylinders 2B, 2C on the intake stroke side. In a higher load range than the partial load range, control is executed so that a fresh-air introducing valve 18 disposed in a fresh-air introduction passage of the following cylinders 2B, 2C is opened, both the burnt gas and fresh air are introduced into the following cylinders 2B, 2C, and fuel is supplied to conduct combustion in the following cylinders 2B, 2C.

Abstract: A valve drive mechanism includes a tappet assembly which comprises a center tappet, a pair of side tappets between which the center tappet is interposed so as to move relatively to the side tappets, and a locking/unlocking mechanism operative to mechanically couple the center tappet to both of the side tappets and to uncouple the center tappet from both of the side tappets so as to selectively transmit rotation of a high lift center cam and low lift side cams to twin valves such as twin intake valves and twin exhaust valves per cylinder. Locking/unlocking of the center tappet and each side tappet is performed in a position which is in a vertical plane including a center axis of each side tappet and intersecting perpendicularly to an axial direction of a camshaft and is offset from the center axis of the side tappet.

Abstract: A valve drive mechanism includes a generally cylindrically shaped tappet assembly (24) comprising a center tappet (41 ) and a side tappet (42). The center tappet (41 ) has a circular-arcuate side walls (41c) formed with vertical side shrouds (41d) at opposite sides of each side wall (41c) which overlap and slide contact with opposite end guide walls (42h) of the side tappet (42), respectively. When the tappet assembly (24) is in an unlocked state so as to transmit rotation of the side cams (25, 27), the vertical side shroud (41d) of the center tappet (41 ) slide on the vertical side walls (42h) of the side tappet 42 so as thereby to guide slide movement of the center tappet (41) relative to the side tappet (42).

Abstract: A valve drive mechanism includes a generally cylindrically shaped tappet assembly (24) comprising a center tappet (41 ) and a side tappet (42). The center tappet (41 ) has a circular-arcuate side walls (41c) formed with vertical side shrouds (41d) at opposite sides of each side wall (41c) which overlap and slide contact with opposite end guide walls (42h) of the side tappet (42), respectively. When the tappet assembly (24) is in an unlocked state so as to transmit rotation of the side cams (25, 27), the vertical side shroud (41d) of the center tappet (41 ) slide on the vertical side walls (42h) of the side tappet 42 so as thereby to guide slide movement of the center tappet (41 ) relative to the side tappet (42).

Abstract: A valve drive mechanism includes a tappet assembly which comprises a center tappet, a pair of side tappets between which the center tappet is interposed so as to move relatively to the side tappets, and a locking/unlocking mechanism operative to mechanically couple the center tappet to both of the side tappets and to uncouple the center tappet from both of the side tappets so as to selectively transmit rotation of a high lift center cam and low lift side cams to twin valves such as twin intake valves and twin exhaust valves per cylinder. Locking/unlocking of the center tappet and each side tappet is performed in a position which is in a vertical plane including a center axis of each side tappet and intersecting perpendicularly to an axial direction of a camshaft and is offset from the center axis of the side tappet.

Abstract: In a V-type internal combustion engine having a pair of upwardly diverging cylinder banks and an auxiliary unit disposed at an upper portion in a space defined between the cylinder banks, a suction arrangement includes intake ports provided at an inner side of the respective cylinder banks, inclined inwardly by a predetermined angle with respect to respective clyinder axes, and extending upwardly in a generally vertical direction so as not to interfere with the auxiliary unit, and cylinder communicating portions connected to upper portions of the intake ports in communication with the respective cylinders to permit the introduction of the intake gas thereto.