There is provided a balancer device for an internal combustion engine that suppresses lubricating oil from failing onto a reduction gear and a pump drive gear provided to drive and rotate an oil pump and thereby suppresses an increase in resistance against rotation between the reduction gear and the pump drive gear. The balancer device for the internal combustion engine includes a lower side housing on which a balancer drive gear, a first balancer shaft including a first balance weight, a first gear, a second gear, a second balancer shaft including a second balance weight, and the reduction gear are mounted. The balancer device also includes an upper side housing formed in such a shape that covers the balancer drive gear, the first balancer shaft including the first balance weight, the first gear, the second gear, the second balancer shaft including the second balance weight, the reduction gear, and the pump drive gear from above in the state that the oil pump is assembled with the upper side housing such that the pump drive gear is meshed with the reduction gear. The upper side housing is assembled with the lower side housing. The balancer device further includes an exposure opening formed in the upper side housing such that only the balancer drive gear is exposed from the upper side housing to be meshed with an engine-side gear.

A balance shaft structure includes a balance shaft including a balance weight, a driven gear to rotate the balance shaft by being engaged with a drive gear, a scissors mechanism, whose position in an axial direction is regulated, including a scissors gear to reduce backlash between the drive gear and the driven gear and an axially urging member to urge the scissors gear toward the driven gear in the axial direction, a first regulating portion to regulate an axially inner position of the scissors mechanism, and a second regulating portion fixed to the balance shaft on a side close to the shaft end part of the balance shaft beyond the first regulating portion and configured to regulate an axially outer position of the scissors mechanism.

A force and moment canceling reciprocating mechanism for a power-driven tool may include a transmission including an input gear assembly and an output gear assembly, coupled to a reciprocating mechanism. The input gear assembly may include a first input gear coaxially aligned with a second input gear. The output gear assembly may include a first output gear coaxially arranged with a second output gear. The reciprocating mechanism may be coupled to the output gear assembly, to convert rotational motion to linear motion, for output to an output accessory of the tool. One or both of the first and second input gears may include counterweights, or counterweight masses, and one or both of the first and second output gears may include counterweights, or counterweight masses. The counterweighting of the input and output gear assemblies may provide for the cancelation of forces and moments generated by the operation of the motor and the transmission, and the reciprocal motion of the reciprocating mechanism.

An object of the present invention is to improve design flexibility of a balancer apparatus. A balancer apparatus includes a balancer shaft, a balancer housing, and an oil pump including an oil pump housing formed separately from the balancer housing and attached to the balancer housing. The balancer housing includes an upper housing and a lower housing formed separately from the upper housing. The lower housing includes first to third bosses configured to fasten the oil pump to the lower housing. The first and second bosses protrude downward on one end side of an axial direction of the balancer shaft. The third boss is disposed on an upper side with respect to the first and second bosses. The first and second bosses are disposed so as to be spaced apart from each other in a direction orthogonal to the axial direction in such a manner that a recessed portion is formed therebetween. The oil pump includes an intake portion having an opening portion. The intake portion is disposed at least partially in the recessed portion.

Variable counterweight apparatuses, systems and methods. The variable counterweight system includes at least one rotatable actuator, a first variable counterweight assembly, and a second variable counterweight assembly. The first variable counterweight assembly is rotatably coupled to the rotatable actuator to rotate about a first axis. The first variable counterweight assembly is configured to geometrically reconfigure so as to change a first variable counterweight assembly center of gravity position with respect to the first variable counterweight assembly. The second variable counterweight assembly is rotatably coupled to the rotatable actuator to rotate about a second axis. The second variable counterweight assembly is configured to geometrically reconfigure so as to change a second variable counterweight assembly center of gravity position with respect to the second variable counterweight assembly.

A piston internal combustion engine with generator has two cylinders and cylinder heads and pistons with connecting rods and two crankshafts which are connected by gears with a ratio of 1:1 (with opposite direction of rotation). The first crankshaft with the gear is mounted parallel to the second crankshaft with the second gear in one engine case such, that the gears engage. The first crankshaft is coupled to the first generator rotor and the second crankshaft is coupled to the second generator rotor or the flywheel. The moment of inertia of the first crankshaft assembly with the first gear and the first generator rotor is equal to the moment of inertia of the second crankshaft assembly with the second gear and the second generator rotor or flywheel. The cylinders with the pistons and are positioned perpendicularly to the plane of symmetry between the crankshafts, with the axes of the pair of cylinders lying in a plane with the both pistons being at the top dead center simultaneously.

Provided is a balancer device for an internal combustion engine capable of effectively decreasing gear rattle between gears of a drive mechanism. A balancer drive gear and a balancer driven gear are arranged on a second end side of a drive-side balancer shaft and a second end side of a driven-side balancer shaft, respectively, and an oil pump is arranged on a first end side of the driven-side balancer shaft via the drive mechanism.

Balancer device has upper and lower housings 3 and 4 having therein an accommodation section 10, a pair of drive and driven side shafts 5 and 6 which are rotatably supported by four plain bearings 11 to 14 provided in the accommodation section and to which a rotation force is transmitted from a crankshaft, and arc band-shaped thrust receiving portions 32a and 33a which thrust flange portions of drive and driven gears 8 and 9 provided at the drive and driven side shafts respectively can contact from a thrust direction. First and second oil storing grooves 34 and 35, groove passages 36 and 37 and vertical groove passages 38a to 39b are formed at the thrust receiving portions on a gravity direction lower side with respect to a meshing portion of the both gears. With this configuration, it is possible to suppress occurrence of abrasion of the thrust receiving portion.

A four-stroke internal combustion engine including variable compression ratio comprises a crankcase including a crankshaft having a crankpin and being supported by the crankcase and rotatable with respect thereto about a crankshaft axis, a connecting rod including a big end and a small end, a crank member being rotatably mounted on the crankpin, and comprising at least a bearing portion which is eccentrically disposed with respect to the crankpin, a crank member drive system for rotating the crank member at a rotation frequency with respect to the crankcase which is half of that of the crankshaft, and a control system for operating the engine with repetitive cycles, wherein the compression ratio in the compression stroke is changed. The control system is configured to interrupt the repetitive cycles by rotating the crankshaft an additional single revolution between two successive combustion strokes for switching between a high and low compression ratio.

A single-shaft dual expansion internal combustion engine includes an engine block, a cylinder head and a crankshaft. First and second power pistons are moveable in first and second power cylinders and are connected to first and second crankpins of the crankshaft. An expander piston is moveable in an expander cylinder and is connected via a multi-link connecting rod assembly to a third crankpin of the crankshaft. A first balance shaft is arranged in a first longitudinal opening in the engine block, and a second balance shaft is arranged in a second longitudinal opening in the engine block. The first and second balance shafts have first and second counterweight portions, respectively, and the crankshaft has a third counterweight portion causing an imbalance in the crankshaft.