In a direct current circuit 11 for supplying electric power from an electrical storage device 10 to the heater 20, there is provided a changeover switch 23 for switching between continuity and cutoff. 蓄電装置10からヒータ20に電力を供給する直流回路11に、導通と遮断を切り換える切り換えスイッチ23を設ける。 - 特許庁