Patent ID: 8602537
Filing Date: 2013-12-10
Classification: B41J

Abstract:
1. An image forming apparatus comprising: a recording head having, disposed in a nozzle surface of the recording head, nozzles from which liquid droplets are ejected; a liquid tank that stores a liquid to be supplied to the recording head; a first flow path through which the liquid is supplied to the recording head; a second flow path in communication with the liquid tank; a pressure regulation unit having a flow path that connects the first flow path with the second flow path; a third flow path that bypasses the pressure regulation unit to connect the second flow path or the liquid tank with the first flow path; and a liquid supply unit provided in the third flow path; wherein the pressure regulation unit wherein the liquid tank is configured to be open to atmosphere, and the liquid tank and the recording head are disposed relative to each other such that a surface of the liquid stored in the liquid tank open to the atmosphere is located at a position that is lower than the nozzle surface of the recording head so as to cause the recording head to generate a negative pressure due to a water head difference between the nozzle surface of the recording head and the surface of the liquid inside the liquid tank, the fluid resistance inside the pressure regulation unit is changed in accordance with a change in the water head difference between the nozzle surface of the recording head and the surface of the liquid inside the liquid tank due to a change in the liquid surface inside the liquid tank, the liquid supply unit disposed in the third flow path supplies the liquid in a direction from the liquid tank toward the recording head, such that a remaining liquid of the liquid supplied from the liquid supply unit to the recording head flows back in a direction from the recording head towards the liquid tank inside the pressure regulation unit to generate a circulation flow that passes through the third flow path and returns to the liquid supply unit, a pressure in accordance with the fluid resistance of the pressure regulation unit is generated in a state in which the liquid supplied by the liquid supply unit flows in the direction from the liquid tank toward the recording head inside the pressure regulation unit, and when a negative pressure of the recording head is increased due to an increase in the water head difference between the nozzle surface of the recording head and the liquid surface of the liquid tank, caused by a decrease in the remaining amount of liquid inside the liquid tank, the increase in the negative pressure of the recording head is cancelled by increasing the fluid resistance to increase the pressure generated by the circulation flow to generate a high positive pressure inside the pressure regulation unit.