Ink jet recording apparatus, sub-tank unit adapted thereto, and ink droplet ejection capability recovery method

An ink jet recording apparatus, comprising:

• a sub-tank unit, mounted on a carriage, for supplying ink to an ink jet record head;
• and
• an ink replenishment unit that is connected to a main tank installed in a housing by a conduit and that is connectable to and disconnectable from said sub-tank unit, wherein said sub-tank unit comprises a single container divided into a plurality of chambers by a wall or walls;
• said sub-tank unit has, for each of the chambers, an ink injection port and an exhaust port communicating with a respective ink storage chamber through self-seal type valve means, and a valve mechanism for opening and closing the ink injection port or the exhaust port based on a liquid level of ink, wherein ink is supplied to the respective ink storage chamber by negative pressure produced by sucking air through the exhaust port.

An ink jet recording apparatus comprising:

• a sub-tank unit provided with a record head;
• and
• a main tank capable of replenishing said sub-tank unit with ink,
• wherein an ink storage chamber and the record head of said sub-tank unit are connected through backflow prevention means for enabling ink to flow into the record head from the ink storage chamber, and
• wherein an ink replenishment unit for replenishing said sub-tank unit with ink from the main tank by reducing pressure in the ink storage chamber by negative pressure generation means is provided.

A sub-tank unit for an ink jet recording apparatus, adapted to be mounted on a carriage, to be connectable to and disconnectable from a main tank installed in a housing side by a conduit, to receive ink supplied from an ink replenishment unit in an ink storage chamber and to supply ink to an ink jet record head, said sub-tank unit comprising:

• ink flow passage means for guiding the ink supplied from the main tank into the ink storage chamber, and
• negative pressure generation means for supplying the ink to the record head,
• wherein the ink flow passage means and the negative pressure generation means are located in the ink storage chamber,
• wherein an ink flow-out port of said ink flow passage means and an ink flow-in port of said negative pressure generation means are arranged to face each other through such a gap as to allow air bubbles to be moved upward.