A gear transmission system (20) comprising at least a first cylindrical gear (21) and a second cylindrical gear (22). Each of the first and the second cylindrical gears (21, 22) comprise a plurality of teeth (23, 26). The teeth (23) of the first cylindrical gear (21) having a first tooth flank (24) for contacting a first tooth flank (27) of the teeth (26) of the second cylindrical gear (22) according to a predefined first contact line (30). The first tooth flanks (24, 27) of the teeth (23, 26) of each of the first and second cylindrical gears (21, 22) have a tooth shape and tooth properties determined by the predefined first contact line (30).

A helical gear and a machining method thereof. Each tooth of the helical gear includes a tooth surface profile, the tooth surface profile includes a series of peaks and a series of valleys, the series of peaks or the series of valleys form a ripple direction, and the helical gear forms a meshing line during meshing, and the helical gear includes a predetermined noise sound pressure level threshold, which is characterized in that an angle between the ripple direction and the meshing line is selected so that an actual noise sound pressure level of the helical gear is less than the predetermined noise sound pressure level threshold, and a difference between the actual noise sound pressure level and the predetermined noise sound pressure level threshold increases with an increase of the angle.

Provided is a herringbone planetary gear transmission device with a constant meshing characteristics constructed tooth pair, which relates to the technical field of gear transmission. The transmission device includes a sun gear with a constructed tooth pair, a planetary gear with a constructed tooth pair and an internal gear with a constructed tooth pair based on conjugate curves. Normal tooth profiles of the gears with a constructed tooth pair in the present disclosure are all the same combined curve and can be machined by using the same cutter. A common normal at an inflection point or a tangent point of the curve passes through a pitch point of a meshing gear pair, and a sliding ratio of the meshing gear pair is adjusted according to an adjusted position of the inflection point or the tangent point. A contact ratio of the meshing gear pair is designed as an integer.

A rotary element for a rotary transmission has a helical radial projection disposed about a rotary axis thereof, the helical radial projection having leading and trailing edges of different diameter. A helical peripheral surface between the leading and trailing edges has a radial profile which is inclined to a tangent to the envelope and preferably has an elliptic profile in a radial plane. In use with another such rotary element having a helical radial projection of opposite handedness in a rotary transmission, a point (P) of rolling contact of the helical peripheral surface with a helical peripheral surface of the other such rotary element helically traverses the helical peripheral surfaces of both rotary elements to positively transmit rotary drive between them without interdigitation of their respective helical radial projections and the associated sliding friction between them as arising in a gear transmission.

The present disclosure provides a parabolic tooth trace gear mechanism with a combined tooth profile of an end face circular arc and a parabola, which belongs to the field of gear transmission. The parabolic tooth trace gear mechanism with the combined tooth profile of the end face circular arc and the parabola includes a small wheel and a big wheel geared externally with parallel axes, tooth surfaces of the small wheel and the big wheel both have a parabolic tooth trace structure, and both are formed by the motion of a combined tooth profile curve of an end face along a contact point, contact lines are all parabolas after being unfolded along a cylindrical surface, and the parabola is determined by a meshing line parameter equation and basic design parameters such as a coincidence degree, the number of teeth, a transmission ratio and the like. When correctly installed, at least one pair of gear teeth of the small wheel and the big wheel, implement pure rolling meshing contact at a node. The small wheel and the big wheel rotate when being driven by a driver to implement transmission between two shafts. The parabolic tooth trace gear mechanism with the combined tooth profile of the end face circular arc and the parabola according to the present disclosure has the advantages of a low frictional wear, a high transmission efficiency, a large single-stage transmission ratio, a strong bearing capacity and the like, and can be widely applied to a transmission system design of mechanical equipment.

Provided is an internal meshing cylindrical gear pair with a constant meshing characteristics constructed tooth pair. The internal meshing cylindrical gear pair with a constructed tooth pair includes an external cylindrical gear with a constructed tooth pair and an internal cylindrical gear with a constructed tooth pair based on conjugate curves. In the present disclosure, normal tooth profile curves of the external cylindrical gear with a constructed tooth pair and the internal cylindrical gear with a constructed tooth pair are continuous combined curves with the same curve shape, which facilitates machining by the same cutter. A common normal at an inflection point or a tangent point of the continuous combined curve passes through a pitch point of the gear pair, and a position of the inflection point or the tangent point can be adjusted as required, so as to adjust a sliding ratio of the gear pair.