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.

When each of the crank arms is divided by the crank arm centerline-into a right arm portion and a left arm portion, an area moment of inertia of one of the right and the left arm portions that is in a side that is subjected to the maximum load is greater than an area moment of inertia of the other arm portion that is in a side opposite to the side that is subjected to the maximum load, and, the area moment of inertia of the arm portion that is in the side opposite to the side that is subjected to the maximum load is greater than the area moment of inertia of the arm portion that is in the side that is subjected to the maximum load.

A forged crankshaft assembly for an engine, and a method of manufacturing the same, has a forged crankshaft and a removable counterweight to provide access for core drilling or milling a cavity. The forged crankshaft has a pin bearing journal, a main bearing journal, a first crank arm supporting the pin bearing journal, a second crank arm supporting the pin bearing journal and connecting the pin bearing journal and the main bearing journal, and at least one milled crank arm cavity formed within at least a portion of the second crank arm. The removable counterweight extends radially outward from the first crank arm, wherein the crank arm cavity is configured to be accessible to a core drill or mill cutter only when the removable counterweight is removed from the first crank arm and inaccessible to the core drill or mill cutter when the removable counterweight is coupled to the first crank arm.

An engine system has a balance gear coupled to a balance shaft. The balance gear is formed by a disc having first and second opposite sides extending radially outwardly to a circumferential edge defining a series of teeth, with a first sector of the disc having a first aperture therethrough, and a second opposite sector of the disc having a second aperture therethrough. A damper is positioned within the second aperture and extends across the disc. The damper has a container enclosing a plurality of particles therein. Opposed ends of the container are outboard of the first and second sides of the disc. A method of forming the balance gear is also provided.

A full, one-piece, wrap around bumper for a crankshaft pendulum is disclosed. The pendulum includes two halves. Continuous, mirror-image bumper-receiving channels are formed in each pendulum half. When the two halves are attached, the bumper is captured between therebetween and is retained by a crush fit. Each pendulum half includes an elevated central area and a pair of recessed areas with each recessed area formed on one side of the elevated area. Side walls are formed at the intersections of the elevated area and the recessed areas. A base wall is formed along the lower edge of the elevated area. The continuous channel in each half is formed along portions of the side walls and along the entire length of the base wall. The elongated, one-piece bumper wraps around the side walls and the base wall and extends from the elevated area beyond the side and base walls.

A bumper clip having rubber or elastomeric bumpers for use with a pendulum assembly for attachment to the crankshaft of an internal combustion engine is disclosed. The bumper clip is has particular application for use with pendulum carriers that are formed from stamped steel. By using the stamped steel carrier, more room is created to provide a more robust bumper. The pendulum carrier bumper clip can be either two separate, L-shaped clips or a single U-shaped clip. If the pendulum carrier bumper clip includes two separate clips, each clip includes a bumper surface to which the bumper is attached and an attachment leg for attachment of the clip to the pendulum carrier and to the crankshaft by a fastener such as a bolt. The bumper surface has a channel through which the pendulum carrier passes, thus dividing the bumper surface into two surfaces. A bumper is attached to each surface.

An engine assembly has a damper rotationally coupled to a crankshaft. The damper has first and second spokes connecting a hub to an inertial weight, with the inertial weight circumferentially surrounding and spaced apart from the hub. Each of the spokes has an airfoil section. The first spoke is oriented with a positive angle of attack and the second spoke is oriented with one of a negative angle of attack and a zero angle of attack. A crankshaft damper is provided by a member having first and second spokes extending radially outwardly from a huh to an outer rim supporting an inertial weight. A chord associated with the first spoke is oriented at a first angle of attack relative to a rotational plane of the member. A chord associated with the second spoke is oriented at a second angle of attack relative to the rotational plane.

A forged crankshaft assembly for an engine, and a method of manufacturing the same, has a forged crankshaft and a removable counterweight to provide access for core drilling or milling a cavity. The forged crankshaft has a pin bearing journal, a main bearing journal, a first crank arm supporting the pin bearing journal, a second crank arm supporting the pin bearing journal and connecting the pin bearing journal and the main bearing journal, and at least one milled crank arm cavity formed within at least a portion of the second crank arm. The removable counterweight extends radially outward from the first crank arm, wherein the crank arm cavity is configured to be accessible to a core drill or mill cutter only when the removable counterweight is removed from the first crank arm and inaccessible to the core drill or mill cutter when the removable counterweight is coupled to the first crank arm.

An engine trigger wheel is disclosed having a central annular portion and a cylindrical rim portion defining a number of trigger teeth, wherein the central annular and cylindrical rim portions are pressed from a single piece of metal. A number of balance apertures are formed in the central annular portion to move a center of mass of the trigger wheel away from an axis of rotation. The engine trigger wheel when fastened to one end of a crankshaft of an engine provides both an indication of the angular position of the crankshaft and a counterweight function.

A crankshaft includes journals serving as a central axis of rotation, crank pins decentered from the journals, and crank arms connecting the journals and the crank pins. Some or all of the crank arms have counterweights integrated therewith. At least one of the crank arms has a recess in a crank pin facing surface. The crank arm includes ribs formed respectively in two side portions of the recess along a periphery of the crank arm.