Multi-spindle synchronous drive unit and gear cutting machine employing the same

A multi-spindle synchronous drive unit for synchronously driving a plurality of spindles, comprising:

• a plurality of motors for respectively driving said spindles;
• a plurality of encoders for respectively detecting rotational positions of said plurality of motors and for respectively outputting corresponding detection signals;
• a plurality of phase locked loop control means for respectively controlling a driving of said plurality of motors and for respectively receiving as feedback signals the detection signals respectively output by said plurality of encoders;
• a reference pulse oscillator for outputting a pulse signal;
• and
• a plurality of multipliers for respectively multiplying the pulse signal by multiplication factors corresponding to rotational speed ratios of said spindles, and for respectively outputting corresponding speed command pulse signals to said phase locked loop control means.