Patent ID: 7766466

Claim:
A printing apparatus comprising: a carriage mounted with an ink jet printing head for ejecting ink and a sub tank for storing ink to be supplied to the printing head, wherein the sub tank includes an ink supply opening which communicates with an interior of the sub tank; a main tank provided on the printing apparatus, wherein the main tank stores ink to be supplied to the sub tank, and wherein the ink supply opening is configured to connect with the main ink tank so as to allow ink to be supplied from the main tank to the sub tank; a gas-liquid separation member provided at a boundary portion between the interior of the sub tank and an exhaust path, wherein the gas-liquid separation member permits gas to pass through the gas-liquid separation member and blocks liquid from passing through the gas-liquid separation member, and wherein a defoaming point is defined at a position of the gas-liquid separation member through which air in a portion of the sub tank is exhausted, the portion being finally filled with ink; a negative pressure generating unit for aspirating air in the sub tank through the exhaust path and the gas-liquid separation member so as to supply ink from the main tank to the sub tank through the ink supply opening; and a control unit for controlling the negative pressure generating unit so as to change the position of the defoaming point, wherein in order to change the position of the defoaming point the control unit changes a suction rate of the negative pressure generating unit depending on the number of times ink has been supplied from the main tank to the sub tank.