Auxiliary drive device

An auxiliary drive device that drives auxiliary drive wheels of a four-wheel-drive vehicle including main drive wheels and the auxiliary drive wheels, the device comprising:

• a drive unit that has an electric motor that generates a drive force that matches a supplied current;
• a meshing clutch that has a first meshing member including first meshing teeth and a second meshing member including second meshing teeth, and that allows and blocks torque transfer between the electric motor and the auxiliary drive wheels;
• an actuator that causes the first meshing teeth and the second meshing teeth to be meshed with each other by moving the second meshing member in an axial direction with respect to the first meshing member;
• and
• a control unit that controls the electric motor and the actuator, wherein:
• the actuator moves the second meshing member among a separation position, at which the first meshing teeth and the second meshing teeth are arranged side by side in the axial direction at a predetermined distance away from each other, an abutment position, at which distal end portions of the first meshing teeth and distal end portions of the second meshing teeth possibly abut against each other, and a meshing position, at which the first meshing teeth and the second meshing teeth are meshed with each other;
• and
• the control unit makes a current supplied to the electric motor when the second meshing member is located between the abutment position and the meshing position smaller than a current required to maintain a rotational speed of the electric motor when the control unit controls the actuator so as to move the second meshing member from the separation position to the meshing position by way of the abutment position.