A torsional vibration damper that a torsional vibration damper having a planetary gear unit, and a manufacturing method of the torsional vibration damper for limiting damages on gears of the planetary gear unit due to dimension errors. In the planetary gear unit, at least one of a sun gear, a ring gear, and a set of planetary gears is/are formed by a press forming method. The gear formed by the press forming method is engaged with the remaining gears in such a manner that a thinner portion of each tooth is individually engaged with a thicker portion of the adjacent teeth of the remaining gears.

A pulley structure may include: a tubular outer rotating body having a belt looped thereon; an inner rotating body which is disposed radially inside the outer rotating body and which is rotatable relative to the outer rotating body; and a torsional coil spring which is arranged in a spring accommodating space formed between the outer rotating body and the inner rotating body. At least in a state in which the pulley structure has not been operated even once, grease containing a rust inhibitor is applied to an opposing surface of the inner rotating body opposing an inner peripheral surface of the torsional coil spring.

A torque transmitting shaft includes a first member and a second member. The first member extends along an axis and has an inner surface extending between a first end and a second end. The inner surface defines a plurality of first engagement elements disposed proximate the first end. The second member extends along the second axis and has a first end portion and an intermediate portion extending from the first end portion. An end of the intermediate portion is fixedly attached to the second end. The first end portion has a first spline portion and each member of the first spline portion is received within corresponding engagement elements of the plurality of first engagement elements.

A torque transmitting shaft includes a first member and a second member. The first member extends along an axis and has an inner surface extending between a first end and a second end. The inner surface defines a plurality of first engagement elements disposed proximate the first end. The second member extends along the second axis and has a first end portion and an intermediate portion extending from the first end portion. An end of the intermediate portion is fixedly attached to the second end. The first end portion has a first spline portion and each member of the first spline portion is received within corresponding engagement elements of the plurality of first engagement elements.

A belt pulley decoupler (1) for the transfer of torque between the belt of a belt drive and a shaft (2) in drive connection therewith, includes: a hub (5) to be fastened to the shaft, a belt pulley (3) rotatably mounted on the hub, and two helical torsion springs (18, 19) which transfer the torque between the belt pulley and the hub and are connected in parallel.

A pulley structure includes: a cylindrical outer rotation body; an inner rotation body; and a torsion coil spring. The torsion coil spring includes: one end region which is in contact with one rotation body; the other end region which is in contact with the other rotation body; and a middle region. The other rotation body includes: a first contact surface; a facing surface; an inclined surface; and a second contact surface. The facing surface includes a constraining surface connected to the inclined surface. The constraining surface is configured to be capable of constraining the other end region of the torsion coil spring before press fitting so as to prevent a displacement of an axis of the torsion coil spring before the press fitting with respect to an axis of the other rotation body.

The present invention relates to a pulley structure (1) equipped with an outer rotating body (2), an inner rotating body (3), and a coil spring (4) provided between the outer rotating body (2) and the inner rotating body (3). The coil spring (4) is configured so as to undergo torsional deformation in a diameter-expanding or a diameter-contracting direction, thereby engaging the outer rotating body (2) and the inner rotating body (3) and transmitting torque, and to undergo torsional deformation in the direction opposite the direction in which torque is transmitted, thereby entering a disengaged state in which the coil spring slides with the outer rotating body (2) or the inner rotating body (3), thus interrupting the transmission of torque. The number of windings of the coil spring (4) is in a range between [M-0.125] and M (both inclusive), where M is a natural number.

A torsional vibration damper whose vibration damping performance will not be reduced in a high speed range. In the torsional vibration damper, a planetary gear is oscillated within a first oscillating range when a torsional torque is smaller than a reference torque, and within a second oscillating range when the torsional torque is greater than the reference torque. Each backlash between the pinion gear and at least one of a sun gear and a ring gear within the second oscillating range is individually wider than each backlash between the pinion gear and the sun gear and each backlash between the pinion gear and the ring gear within the first oscillating range.

A torque transmitting shaft includes a first member and a second member. The first member extends along an axis and has an inner surface extending between a first end and a second end. The inner surface defines a plurality of first engagement elements disposed proximate the first end. The second member extends along the second axis and has a first end portion and an intermediate portion extending from the first end portion. The first end portion has a first spline portion and each member of the first spline portion is received within corresponding engagement elements of the plurality of first engagement elements.

In an aspect, an isolation device is provided for a belt and a component shaft in an engine. The device includes a hub, a pulley, an isolation spring and a damping member that is fixed rotationally relative to the hub and is engageable frictionally with the pulley. Torque transmission through the spring below a selected non-zero torque, irrespective of hub load on the pulley, drives a change in radius of the helical coils of the spring that is sufficiently small that the spring avoids pressing the damping member against the pulley. Torque transmission through the spring above the selected non-zero torque, irrespective of hub load on the pulley, drives a change in radius of the helical coils that is sufficiently large that the isolation spring applies a radial force to press the damping member against the pulley so as to generate frictional damping.