Patent ID: 8308612

Claim:
A drive unit that drives a power transmission apparatus in a vehicle provided with an internal combustion engine capable of being automatically stopped and automatically started and the power transmission apparatus having a friction engagement element and being capable of establishing a connection and breaking the connection between an output shaft of the internal combustion engine and a shaft on an axle side by switching an engagement state of the friction engagement element, the drive unit comprising: a solenoid device that includes: a solenoid section having a movable portion that abuts on a case to arrive at an initial state when de-energized; a pump section axially sliding in association with a movement of the movable portion by an electromagnetic force of the solenoid section and pumping a hydraulic fluid by reciprocation; and an elastic member biasing the pump section in a direction counter to the electromagnetic force of the solenoid section; and a control unit that controls the solenoid device so that a current applied to the solenoid section is repeatedly increased and decreased between an upper limit value and a lower limit value that is greater than 0, wherein: the solenoid device includes a valve element that adjusts a fluid pressure from a fluid pressure source, the pump section pumps the hydraulic fluid by reciprocation of the valve element sliding in association with the movement of the movable portion, and the control unit is a unit that, when the internal combustion engine is automatically stopped, repeatedly increases and decreases the current applied to the solenoid section between an upper limit value and a lower limit value that is set to a first predetermined current in preparation for causing the solenoid device to function as a pump while the solenoid device adjusts and supplies the fluid pressure from the fluid pressure source to the friction engagement element, and thereafter repeatedly increases and decreases the current applied to the solenoid section between the upper limit value and a lower limit value that is set to a second predetermined current smaller than the first predetermined current and greater than 0.