To provide a sprocket that reduces the influence of tension fluctuations concurrent with load torque variations to suppress noise and vibration, and that prevents an increase in tension fluctuations, noise, and vibration even when the chain tension is low and the load torque is small, and in regions where engagement between the chain and sprocket is free of the influence of tension. The sprocket has a plurality of seating points for the chain when the chain sits under no load set between adjacent pairs of the teeth such that their radial positions change in a circumferentially continuous manner. The radial positions of the seating points under no load have a variation pattern in which the radial positions increase and decrease depending on circumferential positions of the seating points.

To provide a sprocket that reduces the influence of tension fluctuations concurrent with load torque variations to suppress noise and vibration, and that prevents an increase in tension fluctuations, noise, and vibration even when the chain tension is low and the load torque is small, and in regions where engagement between the chain and sprocket is free of the influence of tension. The sprocket has a plurality of seating points for the chain when the chain sits under no load set between adjacent pairs of the teeth such that their radial positions change in a circumferentially continuous manner. The radial positions of the seating points under no load have a variation pattern in which the radial positions increase and decrease depending on circumferential positions of the seating points.

To provide a sprocket that reduces the influence of tension fluctuations concurrent with load torque changes to suppress noise and vibration and that allows for a weight reduction while retaining high strength as well as enables high productivity, and a drive mechanism that uses this sprocket. Sprocket teeth are configured by providing a cushioning layer on tooth faces of tooth portions of a sprocket base body made of a high-rigidity material. The sprocket teeth include the cushioning layer that varies in thickness.

To provide a sprocket that reduces the influence of tension fluctuations concurrent with load torque changes to suppress noise and vibration and that allows for a weight reduction while retaining high strength as well as enables high productivity, and a drive mechanism that uses this sprocket. Sprocket teeth are configured by providing a cushioning layer on tooth faces of tooth portions of a sprocket base body made of a high-rigidity material. The sprocket teeth include the cushioning layer that varies in thickness.

An input gear, an output gear, an input-side intermediate gear, and an output-side intermediate gear are helical gears. The output gear and the output-side intermediate gear have a larger module than the input gear and the input-side intermediate gear. The input gear and the input-side intermediate gear have a larger twisting angle than the output gear and the output-side intermediate gear. The output gear and the output-side intermediate gear have a larger effective tooth length than the input gear and the input-side intermediate gear.

In a wobble removal shaft coupling device including a wobble removal gear having an internal gear with a first central axial line and an external gear meshing with the wobble removal gear and having a second central axial line. The first and second central axial lines are in parallel with and offset from each other, and the external gear teeth are identical in number to the internal gear teeth of the wobble removal gear. At least one of the two sets of the gear teeth are resiliently deformable in a circumferential and/or radial direction so as to allow the two gears to be meshing with each other while permitting an eccentric wobbling movement of the external gear relative to the internal gear without requiring a play or a sliding engagement. The wobble removal shaft coupling device can be incorporated in a hypocycloid reduction gear device.

In a wobble removal shaft coupling device including a wobble removal gear having an internal gear with a first central axial line and an external gear meshing with the wobble removal gear and having a second central axial line. The first and second central axial lines are in parallel with and offset from each other, and the external gear teeth are identical in number to the internal gear teeth of the wobble removal gear. At least one of the two sets of the gear teeth are resiliently deformable in a circumferential and/or radial direction so as to allow the two gears to be meshing with each other while permitting an eccentric wobbling movement of the external gear relative to the internal gear without requiring a play or a sliding engagement. The wobble removal shaft coupling device can be incorporated in a hypocycloid reduction gear device.

Gear pairing of a transmission with a first gear and with a second gear engaged with the first gear, whereby the first gear, in comparison to the second gear, is manufactured from a material that is less elastic or less soft, and whereby the first gear and the second gear have different normal target base pitches.

A worm speed reducer includes a worm and a worm wheel meshed with the worm. The worm wheel has teeth with a modulus of elasticity of 6000 Pa or more. The difference obtained by subtracting the pressure angle on the pitch circle of the worm wheel from the pressure angle on the pitch circle of the worm is set in the range of 0.5° to 1°.

A worm speed reducer includes a worm and a worm wheel meshed with the worm. The worm wheel has teeth with a modulus of elasticity of 6000 Pa or more. The difference obtained by subtracting the pressure angle on the pitch circle of the worm wheel from the pressure angle on the pitch circle of the worm is set in the range of 0.5° to 1°.