| 摘要 |
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 is compartmented by separation means 8 into a first chamber R1 facing the heat sink and a second chamber R2 facing the drive unit casing, and is communicated to the flow passage of the refrigerant, and the heat sink comprises heat-sink-side fins 56 extending into the first chamber and apart from the separation means. Thereby, temperature gradient can be provided between the both chambers, and effective cooling of the heat sink and the drive unit casing can be made possible with less flow rate of the refrigerant as compared with the case where the entire space comprising a single layer is cooled by the refrigerant according to the heat-resistant temperature of the inverter.
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