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 that is configured to:
• (a) correct a torque of the engine based on a required value of the torque of the engine through feedback in accordance with a deviation between a rotational speed of the engine during idle operation and a target rotational speed;
• (b) (i) calculate a load torque of the compressor, and (ii) correct the calculated value of the load torque through feedback using a deviation between the rotational speed of the engine and the target rotational speed and correct the required value of the torque of the engine in accordance with the corrected value of the calculated value of the load torque, as a changeover transition period control, in a changeover transition period between a driven state of the compressor and a stopped state of the compressor;
• and
• (c) set an execution period of the changeover transition period control such that the execution period in a changeover transition period from the stopped state of the compressor to the driven state of the compressor is longer than an execution period of the changeover transition period control in a changeover transition period from the driven state of the compressor to the stopped state of the compressor, wherein
• the electronic control unit is configured to set the execution period of the changeover transition period control in the changeover transition period from the stopped state of the compressor to the driven state of the compressor, such that the execution period in a case where there is a possibility of a liquid pool being formed inside the compressor is longer than the execution period in a case where there is no possibility of the liquid pool being formed inside the compressor.