FREEZER FOR VEHICLE

PURPOSE:To optimize freezing cycle and to charge a battery with high efficiency by means of the recovery power of an expansion machine, by a method wherein a generator is disposed coaxially with the expansion machine, and the exciting current of the generator is controlled based on a superheat at the outlet of a vaporizer. CONSTITUTION:By means of a detecting signal from a superheat detecting part 2, a control part 25 decides whether a refrigerant flow rate is excessively high or low. When the degree of superheat is too high, the exciting current of an exciting part 21 of a generator 8 is decreased, load torque is decreased, through increase of the number of revolutions of an expansion machine 6, a refrigerant flow rate is increased, and cooling capacity is increased. When it is too low, an exciting current is increased, and cooling capacity is decreased. Meanwhile, the expansion machine 6 recovers a power, and is rotated at the number of revolutions matching a proper refrigerant flow rate. The generator 8 generates a voltage determined by the number of revolutions and the exciting current. The generated voltage is adjusted to a specified charge voltage through a rectifier 26 and a varying load 29, and is fed to a battery 27 for charging. This constitution enables execution of high-efficiency charge by means of a recovery power.