Air compressor

An air compressor comprising:

• a tank part that stores compressed air to be supplied to a pneumatic tool;
• a compressed-air generation part for generating the compressed air and supplying the compressed air to the tank part;
• a drive part with a motor for driving the compressed-air generation part;
• a pressure sensor for detecting an air pressure inside the tank part;
• and
• a control circuit part for controlling the motor of the drive part based on a detection signal from the pressure sensor,
• wherein the control circuit part:
• stops operating the motor when a detected pressure indicating the air pressure in the tank part acquired from the detection signal is higher than a maximum set pressure value,
• sets, as restart set pressure values, a first restart set pressure value and a second restart set pressure value lower than the first restart set pressure value,
• operates the motor at a first predetermined revolving speed if a pressure drop rate calculated based on the detected pressure is greater than a set pressure drop rate and when the detected pressure drops from the maximum set pressure value to or below the first restart set pressure value,
• operates the motor at a second predetermined revolving speed that is lower than the first predetermined revolving speed if the pressure drop rate is less than the set pressure drop rate and when the detected pressure drops from the maximum set pressure value to or below the second restart set pressure value, and
• forcibly operates the motor at the first predetermined set revolving speed independent of the pressure drop rate, when the detected pressure becomes equal to or less than a minimum set pressure value, independent of the operation of the motor, and does so until the detected pressure reaches the maximum set pressure value.