Patent attributes
A planetary gear device configured by combining a plurality of planetary gear mechanisms includes first and second planetary gear mechanisms sharing a carrier, wherein each planetary gear mechanism is composed of an internal gear Ik (k is an integer equal to or larger than 2) and a planetary gear Pk which is engaged with the internal gear Ik and revolves in a circumferential direction of the internal gear, the planetary gear Pk of each planetary gear mechanism is composed of a spur gear in the form of an external gear, the planetary gears Pk of the planetary gear mechanisms share a central axis or have central axes integrally connected to integrally rotate on a common rotation central axis line or are integrated with each other to integrally rotate on the common rotation central axis line in order to configure the entire planetary gear device as a two-stage gear mechanism, the planetary gear device is configured such that the number of teeth zp1 of a first planetary gear constituting the first planetary gear mechanism and the number of teeth zp2 of a second planetary gear constituting the second planetary gear mechanism are different from each other, the number of teeth on the internal gear I1 is zi1, and the number of teeth on the internal gear I2 is zi2, an addendum modification coefficient of the first planetary gear is xp1, an addendum modification coefficient of an internal gear which is engaged with the first planetary gear and constitutes the first planetary gear mechanism is xi1, an addendum modification coefficient of the second planetary gear is xp2, an addendum modification coefficient of an internal gear which is engaged with the second planetary gear and constitutes the second planetary gear mechanism is xi2, a power transmission efficiency of the planetary gear device having the addendum modification coefficients xp1, xi1, xp2, and xi2 is η, an addendum modification coefficient of the internal gear I1 is xi1, and an addendum modification coefficient of the internal gear I2 is xi2, and the addendum modification coefficients have relationships in which values selected from combinations of the addendum modification coefficients which maximize or submaximize the power transmission efficiency η within an allowable range of design specifications given in advance are combined.
