To eliminate heating of a liquid transmitting drive force and drag.

This driving gear, comprising a first servomotor 10a, first hydraulic pump 20a connected thereto, and an actuator 4 connected capable of communication therewith, is provided with a second servomotor 10b and a motor-operable second hydraulic pump 20b connected thereto also connected capable of communication with also the actuator 4, to generate and control drag by the servomotor 10b and the hydraulic pump 20b when a hydraulic cylinder 4 is driven by the servomotor 10a and the hydraulic pump 20a. Pressure energy in a re-circulation side is converted into mechanical energy by motor action of the hydraulic pump 20b, further converted into electric energy and thermal energy by the servomotor 10b, to be taken away from a liquid.