Speed-varying device and wind turbine generator system

A wind turbine generator system generating electricity by driving a generator positioned in a rotor head and coupled via a drive-train to the rotor head which wind turbine rotor blades are attached thereto and integrally rotate therewith, said wind turbine generator system comprising:

• a speed-increasing device provided with the drive-train and arranged at a front end of the rotor head,
• wherein the speed-increasing device includes
• an input shaft, an output shaft and a plurality of speed-increasing shafts arranged in a circumferential direction;
• parallel gears including
• an input gear provided on the input shaft;
• a plurality of output gears provided on the output shaft that are coupled to each other via the plurality of speed-increasing shafts;
• input shaft-side gears arranged at one end of the speed-increasing shafts;
• and
• output shaft-side gears arranged at the other end of the speed-increasing shafts,
• wherein
• the number of teeth of the input shaft-side gears are different from that of the output shaft-side gears,
• the output shaft-side gears are engaged with the plurality of output gears alternately in the circumferential direction, and
• the output shaft-side gears are arranged so as to be shifted from one another in an axial direction of the output shaft.