Patent ID: 7575312

Claim:
A method of injecting ink into an ink cartridge, comprising steps of: providing an ink cartridge including: a lower section ink chamber; an upper section ink chamber; an ink supply port adapted to supply ink to a recording head; a communication flow passage connecting a lower portion of the lower section ink chamber and a lower portion of the upper section ink chamber to each other; a flow passage connecting the upper section ink chamber and the ink supply port to each other; an opening communicating with the lower section ink chamber; and a differential pressure valve disposed in the flow passage, wherein the ink cartridge is arranged such that the ink in the upper section ink chamber is discharged from the ink supply port through the differential valve, and the ink in the lower section ink chamber is moved to the upper section ink chamber through the communication flow passage in accordance with consumption of the ink in the upper section ink chamber, reducing pressure in the ink cartridge through the ink supply port; injecting ink into the upper section ink chamber through the communication flow passage while the reducing pressure is performed; and injecting the ink into the lower section ink chamber through the opening such that air is present in the lower section ink chamber.