Engine rotational speed control apparatus

A rotational speed control apparatus for an engine, the engine configured to drive a compressor that compresses a cooling medium for air conditioning, the rotational speed control apparatus comprising:

• an electronic control unit configured to:
• (a) correct a torque of the engine through feedback in accordance with a deviation between a rotational speed during idle operation and a target rotational speed;
• (b) (i) calculate a load torque of the compressor, and (ii) correct the calculated load torque through feedback in accordance with a deviation between the rotational speed of the engine and the target rotational speed and correct a required value of the torque of the engine in accordance with the corrected load torque, in a predetermined period from a start of a changeover between a driven state of the compressor and a stopped state of the compressor, the start of the changeover being during idling stability of the engine;
• wherein a first period of the changeover from the stopped state of the compressor to the driven state of the compressor is set longer than a second period of the changeover from the driven state of the compressor to the stopped state of the compressor,
• the first period of changeover comprises a convergence of the load torque to a stable value through an increase from 0,
• the second period of changeover comprises a convergence of the load torque to 0 through a decrease, and
• the electronic control unit is further configured to determine if there is a possibility of a liquid pool of cooling medium in a crank chamber of the compressor based on an outside air temperature and an elapsed time from a last stoppage of the compressor, and if the electronic control unit determines that the possibility of the liquid pool of cooling medium in the crank chamber of the compressor exists, then the first period of the changeover from the stopped state of the compressor to the driven state of the compressor is longer than when the electronic control unit determines that there is no possibility of the liquid pool of cooling medium being in the crank chamber of the compressor,
• wherein when the outside air temperature is lower than a predetermined value and the elapsed time is longer than a predetermined value, the electronic control unit determines that the possibility of the liquid pool of cooling medium in the crank chamber of the compressor exists.