Patent ID: 8162454

Claim:
An ink jet recording apparatus comprising: a recording head for recording by discharging ink; a main tank configured to contain ink to be supplied to the recording head; and a sub tank configured to store the ink supplied from the main tank and capable of supplying the ink to the recording head, wherein the sub tank has an ink supply path for supplying ink from the main tank and an air introducing path for introducing air into the main tank, wherein a length of the air introducing path is shorter than that of the ink supply path and a flow path resistance of the air introducing path is smaller than that of the ink supply path, wherein the air introducing path has: an air introducing pin provided at a side of the main tank and a first cross-sectional area; and a thick tube part provided at a side of the sub tank and a second cross-sectional area greater than the first cross-section area, and wherein the following formula is satisfied, H>M+R where pressure by a vertical water head difference of the thick tube part is (H), the flow path resistance of the air introducing pin is (R) and a meniscus of the air introducing pin is (M).