Liquid-feed-type gas compressor

A liquid-feed-type gas compressor comprising:

• an electric motor;
• a compressor main body that is driven by the electric motor and compresses gas while supplying liquid to working chambers;
• a suction throttle valve disposed on an intake side of the compressor main body;
• a separator that separates the liquid from the compressed gas delivered from the compressor main body;
• a liquid supply system that supplies the liquid separated by the separator to the working chambers of the compressor main body;
• a cooling fan;
• a liquid cooler that is disposed in the liquid supply system and cools the liquid by using cooling air generated by the cooling fan;
• a delivery-side pressure sensor that senses a delivery-side pressure of the compressor main body;
• and
• a controller that controls the electric motor, the suction throttle valve, and the cooling fan, wherein
• the controller is configured to:
• control the suction throttle valve to make switching from load operation to no-load operation when the delivery-side pressure sensed by the delivery-side pressure sensor has risen to a predetermined upper-limit value during driving of the electric motor;
• and
• stop the electric motor when continuation time of the no-load operation has reached a predetermined value and then restart the electric motor and control the suction throttle valve to make switching to the load operation when the delivery-side pressure sensed by the delivery-side pressure sensor has lowered to a predetermined lower-limit value, and
• the controller is configured to:
• stop the cooling fan when the continuation time of the no-load operation has reached the predetermined value and the electric motor stops;
• predict a return timing at which the delivery-side pressure of the compressor main body lowers to the predetermined lower-limit value and the electric motor restarts, on a basis of a sensing history of the delivery-side pressure sensor during the stop of the electric motor or the no-load operation, and predict a delivery-side temperature of the compressor main body at the return timing in a case of stopping the cooling fan until the return timing;
• and
• continue the stop of the cooling fan when the predicted delivery-side temperature is equal to or lower than a predetermined acceptable value, and restart the cooling fan antecedently to the electric motor when the predicted delivery-side temperature exceeds the predetermined acceptable value.