Patent ID: 7963643

Claim:
An inkjet recording apparatus, comprising: a casing; an inkjet head which is arranged in the casing and forms an image on a recording medium by ejecting ink while moving to scan the recording medium in a main scanning direction, and moving the recording medium in a sub scanning direction that is substantially perpendicular to the main scanning direction; an ink cartridge which has an ink accommodating unit which accommodates ink to be supplied to the inkjet head and is removably installed into the casing via a front face side of the casing and disposed in a position whereby a central position of the ink accommodating unit is situated below the inkjet head in the vertical direction, at a distance of not less than 10 mm and not more 50 mm from the inkjet head in the vertical direction; an ink supply channel which is provided between the ink cartridge and the inkjet head; a coupling unit which is provided in at an end portion of a scanning region of the inkjet head, and couples and separates the inkjet head with and from the ink supply channel; a negative pressure maintaining unit which includes an ink supply port which has a first opening and closing member, couples with the coupling unit, and is connected to an ink flow channel inside the inkjet head; and a pressure determination device which determines an internal pressure of the negative pressure maintaining unit, wherein the negative pressure maintaining unit couples with the ink supply channel and maintains an internal pressure of the inkjet head at a liquid head pressure differential between the inkjet head and the ink cartridge during supply of the ink to the inkjet head, and seals an interior of the inkjet head by closing the first opening and closing member when the inkjet head is carrying out printing; the inkjet head and the ink supply channel is coupled and separated in accordance with the determined internal pressure of the negative pressure maintaining unit; the negative pressure maintaining unit includes a sub tank having a plastic film that deforms according to internal pressure of the sub tank; and the pressure determination device includes a sensor detecting deformation of the plastic film.