Patent ID: 8721060

Claim:
A liquid circulation system which is mounted on a droplet ejection device, comprising: a droplet ejection head which is formed with a common flow passage communicated with a plurality of nozzles from which the droplets are ejected; a liquid filling container which is filled with liquid that is supplied to the droplet ejection head; a first flow passage through which the liquid is supplied from the liquid filling container to one end part of the common flow passage; a second flow passage through which the liquid is returned from an other end part of the common flow passage to the liquid filling container; a differential pressure generating means structured to pressurize the liquid on one end part side in the common flow passage and depressurize the liquid on an other end part side in the common flow passage; a pressurization regulator which is disposed between the differential pressure generating means and the one end part of the common flow passage and is structured to maintain the liquid at the one end part in the common flow passage to be a first pressure; and a differential pressure regulator which is disposed between the differential pressure generating means and the other end part of the common flow passage and is structured to maintain a differential pressure between both end parts in the common flow passage to be a second pressure, wherein the differential pressure generating means pressurizes the liquid on the one end part side in the common flow passage by a pressurization bellows for pressurizing the liquid and a first tube pump for sending the liquid to a liquid droplet ejection head side, the differential pressure generating means depressurizes the liquid on the other end part side in the common flow passage by a pressure reduction bellows for depressurizing the liquid and a second tube pump for sending the liquid to a liquid filling container side, and a height difference is provided between the droplet ejection head and the liquid filling container so that a liquid pressure at the other end part in the common flow passage is lower than a liquid pressure at the one end part in the common flow passage.