Ink jet printer and ink supply method of ink jet printer

An ink jet printer comprising:

• an installation case in which a first tank communicating with an atmosphere is to be installed;
• a second tank having a sensor configured to output a signal in response to a position of a liquid surface of ink in the second tank, the sensor outputs a first signal in a case that the liquid surface of the ink is detected by the sensor to be below a lower fill position and a second signal in a case that the liquid surface of the ink is detected by the sensor to be at an upper fill position;
• a head communicating with the second tank, where the second tank and the first tank are upstream of the head;
• a first channel having one end to be communicated with the first tank installed in the installation case and a second end communicating with the second tank;
• a second channel having one end communicating with an upper part inside the second tank and a second end to be communicated with the first tank installed in the installation case, where the one end of the second channel is positioned at the upper fill position;
• a pump which is disposed in the second channel;
• and
• a controller electrically connected to the pump and the sensor, and configured to control the pump to move air or ink at least from the one end of the second channel to the second end of the second channel in response to receipt of the first signal from the sensor until a receipt of the second signal, whereby ink is moved from the first tank to the second tank via the first channel,
• wherein the air is moved in a case that the liquid surface of the ink is below the lower fill position and the ink is moved in a case that the liquid surface of the ink is at the upper fill position, whereby the ink is returned to the first tank;
• and
• wherein the controller is configured to stop controlling the pump to move the air or ink at least from the one end of the second channel to the second end of the second channel in response to receipt of the second signal from the sensor which stops movement of the ink from the first tank to the second tank via the first channel.