Controllable drive unit with combustion engine and generator

In a controllable drive unit operating device including

• an internal combustion engine (VM) able to rotate at an rpm and including an rpm actuator (DR, DRS) for controlling the rpm of the engine,
• a refrigerator (AM) and a direct drive mechanically coupling the engine to the refrigerator,
• a control unit including
• thermostat means for maintaining an internal temperature of the refrigerator at a predetermined set point value (SW),
• the improvement comprising:
• (a) refrigerator internal temperature setting input means coupled to the control unit;
• (b) a sensor of a refrigerator external temperature, the sensor being coupled to the control unit;
• (c) a tachometer (DM) disposed on the engine for measuring an engine speed, the tachometer being coupled to the control unit;
• (d) the control unit including means for accepting
• the refrigerator internal temperature setting,
• the external temperature, and
• the engine speed measured by the tachometer,
• and for determining therefrom an optimal value of the engine rpm according to values of an output characteristic function stored in a memory device (ST) of the control unit;
• and
• (e) means for causing the rpm actuator to adjust the rpm toward the optimal value determined by the control unit.