A drive device includes: a motor; and a power transmission device that transmits power of the motor to a wheel. Further, in the power transmission device has a meshing portion in which a meshing tooth that is formed on an input-side rotation member and a meshing tooth that is formed on an output-side rotation member mesh with each other on a power transmission path between the motor and the wheel, the meshing tooth has a driving-side teeth surface that makes contact for transmission of power from the motor to the wheel and a non-driving-side teeth surface that makes contact for transmission of power from the wheel to the motor, and in the meshing tooth, a tooth root of the driving-side teeth surface has a higher breaking strength than a tooth root of the non-driving-side teeth surface.

The present invention relates to a power transmission device, which includes: a worm shaft; a Janggu (slim waist drum)-shaped worm which is provided on the worm shaft, and has a diameter-reduced part whose outer diameter is increased toward both ends from a center thereof in an axial direction of the worm shaft, wherein the diameter-reduced part has spiral worm teeth formed thereon; a first transmission shaft disposed in parallel to the worm shaft at an interval; and a first transmission gear which is provided on the first transmission shaft, and includes first gear teeth having tooth shapes conjugated with the worm teeth of the Janggu-shaped worm and are continuously formed in a spiral shape on an outer circumferential surface thereof, thus to rotate by threadedly engaging with the worm teeth of the Janggu-shaped worm.

A vehicle drive device uses a parallel shaft gear reducer (30) in which a gear is composed of helical gear, as a speed reducer part (B) that decelerates and outputs a rotation of an electric motor part (A). In the vehicle drive device, of meshing parts of the gears formed in the speed reducer part (B), two gears form a meshing part in which the amount of misalignment that occurs between the tooth surfaces of the two gears meshing with each other is different during driving and during coasting of a vehicle. A first tooth surface (S1) meshing with a mating tooth surface during driving is subjected to tooth surface modification, and a second tooth surface (S2) meshing with a mating tooth surface during coasting is subjected to tooth surface modification of an amount different from an amount of the tooth surface modification to the first tooth surface (S1).

A speed reduction mechanism and a motor equipped with the speed reduction mechanism are provided. A pinion gear is provided with one spiral engagement projected part, and a helical gear is provided with a plurality of engagement recessed parts with which the engagement projected part is engaged. The engagement projected part and the engagement recessed part are formed so that their cross-sectional shapes along a direction orthogonal to an axial direction of the pinion gear are in arc shapes. A shape of helical teeth and a shape of the engagement recessed part are determined based on a shape of the engagement projected part provided on a spiral tooth.

A transmission mechanism has a set of two composite sprockets, each having pinion sprockets (210) supported movably in a radial direction with respect to a rotation shaft 1 that inputs or outputs power and a movement mechanism radially moving the pinion sprockets (210) in synchronization with each other while maintaining equidistance of the pinion sprocket (210) from a shaft center (C.sub.1) of the rotation shaft 1, and a chain wound around the two composite sprockets. Transmission ratio is changed by changing a circumcircle radius that is a radius of a circle encircling and circumscribing all the pinion sprockets (210). The pinion sprocket (210) is formed into a sector gear shape having a teeth portion (212) that is arranged along a circumference of a minimum radius circumcircle (A.sub.1) and meshes with the chain. With this configuration, torque can surely be transmitted.

A gear mechanism (6) for a rolling mill drive includes at least one involute cylindrical gear tooth system between at least two intermeshing gear wheels (3) with asymmetrical gearing. The normal pressure angle of the load-bearing tooth flanks (5) of the gear wheels (3) is greater than 20° and less than or equal to 30°, and the normal pressure angle of the trailing flanks (4) of the gear wheels is greater than or equal to 14° and less than 22°. A rolling mill drive has a gear mechanism (6) of this type, and the gear mechanism (6) is used as a rolling mill gear mechanism.

A speed reduction mechanism and a motor equipped with the speed reduction mechanism are provided. A pinion gear is provided with one spiral engagement projected part, and a helical gear is provided with a plurality of engagement recessed parts with which the engagement projected part is engaged. The engagement projected part and the engagement recessed part are formed so that their cross-sectional shapes along a direction orthogonal to an axial direction of the pinion gear are in arc shapes. A shape of helical teeth and a shape of the engagement recessed part are determined based on a shape of the engagement projected part provided on a spiral tooth.

The gear mechanism includes a gear shaped to have a bottom land, a first tooth flank connected to the bottom land, a second tooth flank connected to the bottom land, a first tooth face connected to the first tooth flank, and a second tooth face connected to the second tooth flank. The bottom land is curved, a radius of curvature of the first tooth flank is greater than a radius of curvature of the second tooth flank, and parts of the first tooth flank and the second tooth flank connected to connection points with the bottom land are curved such that a distance of each of the parts from a shaft center of the gear decreases toward the connection points and that a gradient of each of the parts decreases toward the connection points.

A gear train includes a first gear having teeth meshed with teeth of a second gear. Each tooth of the first gear includes a coast side and a drive side opposed to the coast side. The drive side has a pressure angle that is greater than that of the coast side. The gear train can be part of a powertrain system for a rotorcraft, and can replace a traditional gear train in a retrofit or new build. The first gear is a planet gear and the second gear is a ring gear wherein the planet gear and ring gear are in a planetary gear train configuration.

A drive device includes: a motor; and a power transmission device that transmits power of the motor to a wheel. Further, in the power transmission device has a meshing portion in which a meshing tooth that is formed on an input-side rotation member and a meshing tooth that is formed on an output-side rotation member mesh with each other on a power transmission path between the motor and the wheel, the meshing tooth has a driving-side teeth surface that makes contact for transmission of power from the motor to the wheel and a non-driving-side teeth surface that makes contact for transmission of power from the wheel to the motor, and in the meshing tooth, a tooth root of the driving-side teeth surface has a higher breaking strength than a tooth root of the non-driving-side teeth surface.