Patent attributes
A drive unit comprises an electric motor, a drive unit casing 2 accommodating therein the electric motor, an inverter 3 that controls the electric motor, and a flow passage of a refrigerant that cools the inverter. The inverter defines a space R between it and a heat sink 5 integral with a substrate of the inverter, and is mounted to the drive unit casing, the space being communicated to the flow passage of the refrigerant. The heat sink comprises fins 56 that cross the space R, and abuts against the drive unit casing in a state of low thermal conduction. Thereby, the heat sink is effectively cooled by heat exchange with a cooling refrigerant in wide areas. Also, the fins contact with the drive unit casing in a state of low thermal conduction via a heat insulation material, etc., whereby direct heat conduction is avoided and efficient cooling is enabled while temperature gradient conformed to heat-resistant temperatures of the inverter and the electric motor is maintained.
