A balance weight includes a main weight portion extending over a range defined by a circular-arc circumferential edge centered at a rotational shaft hole side and a pair of virtual end surfaces located on the circular-arc circumferential edge on both sides of the rotational shaft hole, a pair of extension weight portions extending from the pair of virtual end surfaces to an opposite circular-arc side of the rotational shaft hole from the circular-arc circumferential edge, the rotational shaft hole provided at the main weight portion so as to be located on a central side of the circular-arc circumferential edge, a crank shaft attachment protrusion, a crank shaft hole provided at the crank shaft attachment protrusion radially eccentrically with respect to the rotational shaft hole, and a pair of spaces formed between positions on both sides of the crank shaft attachment protrusion and the pair of extension weight portions, respectively.

An engine is described having a crankcase, a liner and a head assembly. The crankcase is split along a plane defining a two part crankcase, where fluid passages are passing through only one of the crankcase portions, so as to not require crossing the split line. A connecting rod also includes a tapered end, and the piston has a complementary carrier receiving the connecting rod.

An engine is described having a crankcase, a liner and a head assembly. The crankcase is split along a plane defining a two part crankcase, where fluid passages are passing through only one of the crankcase portions, so as to not require crossing the split line. A connecting rod also includes a tapered end, and the piston has a complementary carrier receiving the connecting rod.

In a vehicle power unit having an internal combustion engine, a pair of power transmission gears for transmitting rotation of a crank shaft to a balancer shaft is arranged between a crankcase and a crankcase cover, and a fluid pump is provided on a power transmission gear shaft supporting a power transmission gear, by which the backlash between the crank shaft and the balancer shaft is reduced and the friction and the noise of the gears are restrained while achieving downsizing of the gears of the crank shaft and the balancer, weight reduction and downsizing of the power unit.

A balancer device includes a housing fixed to an internal combustion engine, a roller bearing disposed in the housing, a balancer shaft rotatably supported in the housing by the roller bearing, a balancer weight integrally mounted on the balancer shaft and rotatably accommodated in an weight accommodation room of the housing, an introduction part that introduces a lubricating oil from the outside to the inside of the weight accommodation room, and a discharge part that provides communication between the inside and the outside of the weight accommodation room and discharges the lubricating oil from the inside of the weight accommodation room, wherein herein the roller bearing is arranged to face the weight accommodation room.

An engine assembly having a cover for catching oil splatted by crankshaft gear and a balance shaft gear is provided. The crankshaft gear is mechanically coupled to the balance shaft gear. The balance shaft gear may be partially submerged in a pool of oil formed at the bottom of the crankcase housing. The cover includes a first cover portion having a back wall and a pair of side walls extending along a top portion and a bottom portion. The top portion covers a respective portion of a circumferential edge of the crankshaft gear. The bottom portion a respective portion of a circumferential edge of the balance shaft gear. Accordingly, oil splattered by the crankshaft gear and the balance shaft gear is caught by the cover, reducing oil entrainment and increasing oil pumping efficiency. Further, the cover helps prevent oil mist from escaping the system so as to reduce oil consumption.

A balancer apparatus equipped with an oil pump includes a pump housing including a pump containing chamber provided therein, a pump forming member contained in the pump containing chamber and configured to discharge oil introduced from an intake portion from a discharge portion to an oil passage of the internal combustion engine when a rotational force is transmitted thereto, a control oil chamber provided between the pump containing chamber and the pump forming member in a radial direction with respect to a rotational axis of the pump forming member and configured to change a hydraulic pressure of the oil to be discharged from the pump forming member with the aid of the oil introduced therein after being discharged from the discharge portion, passing through an oil passage of the internal combustion engine, and being subjected to a pressure adjustment, and a balancer housing including a bearing retainer portion configured to transmit the rotational force from the internal combustion engine to the pump forming member. The bearing retainer portion supports a balancer shaft disposed along the rotational axis of the pump forming member. The balancer housing is attached to the pump housing in a direction of the rotational axis of the pump forming member. The balancer apparatus equipped with the oil pump further includes a plurality of oil passage opening portions formed together on one side surface of the balancer housing and each connected to an oil passage connected to a main oil gallery of the internal combustion engine. The plurality of oil passage opening portions includes a discharge oil passage opening portion of a discharge oil passage connecting the discharge portion and the main oil gallery of the internal combustion engine to each other, a feedback oil passage opening portion of a feedback oil passage connecting the main oil gallery of the internal combustion engine and the control oil chamber to each other, and a bearing oil passage opening portion of a bearing oil passage connecting the main oil gallery of the internal combustion engine and the bearing retainer portion to each other.

A power transmitting device includes a first rotor and a second rotor rotatably disposed coaxially with a rotational central axis and in facing relation to each other, a single arc spring that is elastically deformable to a large extent and has a small modulus of elasticity, the arc spring being interposed between the first rotor and the second rotor for urging the first rotor and the second rotor to opposite sides in a ration direction, a first pressing protrusion projecting from the first rotor and a second pressing protrusion projecting from the second rotor, the first pressing protrusion and the second pressing protrusion being disposed in relative positions on superposed rotation trajectories, and a rubber member that is elastically deformable to a small extent and has a large modulus of elasticity, the rubber member being interposed between the first pressing protrusion and the second pressing protrusion with gaps therebetween.

A power transmitting device includes a first rotor and a second rotor rotatably disposed coaxially with a rotational central axis and in facing relation to each other, a single arc spring that is elastically deformable to a large extent and has a small modulus of elasticity, the arc spring being interposed between the first rotor and the second rotor for urging the first rotor and the second rotor to opposite sides in a ration direction, a first pressing protrusion projecting from the first rotor and a second pressing protrusion projecting from the second rotor, the first pressing protrusion and the second pressing protrusion being disposed in relative positions on superposed rotation trajectories, and a rubber member that is elastically deformable to a small extent and has a large modulus of elasticity, the rubber member being interposed between the first pressing protrusion and the second pressing protrusion with gaps therebetween.

A balance shaft includes an unbalanced shaft (3) comprising a bearing journal (8, 9), the periphery of which is merely partially cylindrical. The cylindrical partial periphery (10) of the bearing journal is oriented toward the shaft imbalance. The balance shaft also includes a needle roller cage assembly (15); and a bearing ring (13), which extends around the bearing journal, lies against the cylindrical partial periphery and forms the inner raceway of the needle roller cage assembly. The cage (27) of the needle roller cage assembly is designed to run on the end faces of the bearing ring axially on both sides by means of radially inwardly extending projections.