Inkjet printing apparatus and ink filling method

An inkjet printing apparatus comprising:

• a detachable inktank which contains ink;
• a subtank which contains the ink supplied from the inktank;
• a printhead configured to discharge the ink supplied from the subtank;
• an ink supply path which connects the subtank to the printhead;
• a supply unit configured to include a valve, whose volume is variable, being arranged on the ink supply path, and configured to supply the ink from the inktank to the subtank by varying the volume of the valve;
• a suction unit configured to perform a suction operation of sucking the ink from the printhead by driving a suction pump;
• a first detection unit configured to detect whether an amount of the ink contained in the inktank is or is not less than a first threshold value;
• a second detection unit configured to detect whether an amount of the ink contained in the subtank is or is not less than a second threshold value;
• and
• a control unit configured to control the suction unit to perform the suction operation in a case in which the first detection unit detects that the amount of ink contained in the inktank is less than the first threshold value and the second detection unit detects that the amount of ink contained in the subtank is not less than the second threshold value.