Patent ID: 8562090

Claim:
A method for controlling an image forming apparatus including a liquid droplet discharge head having a nozzle configured to discharge a droplet of liquid; a sub-tank configured to temporarily store the liquid supplied to the liquid droplet discharge head; a main tank configured to store the liquid; a liquid sending pump capable of sending the liquid from the main tank to the sub-tank by forward sending and sending the liquid from the sub-tank to the main tank by reverse sending; and a pressure sensing unit configured to sense a pressure in the sub-tank, wherein the pressure sensing unit includes a negative pressure lever configured to perform a pressure sensing function to sense the pressure in the sub-tank on a basis of a sensing result of the position sensing unit and to be displaced in accordance with an amount of the liquid stored in the sub-tank, the negative pressure lever including plural leading end parts parallel to each other, indicating different positional information from each other and separated by a specific separation distance interposed therebetween, and a position sensing unit configured to detect a displacement of the negative pressure lever as positional information, and the method comprising: before sending the liquid by the forward sending or the reverse sending by the liquid sending pump to achieve a target negative pressure value of a pressure in the sub-tank, performing a determination of whether the pressure sensing function of the pressure sensing unit is normal by sending the liquid by the liquid sending pump with the pressure in the sub-tank being at a negative pressure in a range in which a meniscus of the liquid formed in the nozzle is maintained; and when it is determined that the pressure sensing function is abnormal, controlling not to send the liquid by the liquid sending pump to achieve the target negative pressure value of the pressure in the sub-tank, wherein a displacement amount, detected by the position sensing unit, of at least one of the plural leading end parts is employed in the determination of whether the pressure sensing function is normal, wherein a displacement amount, detected by the position sensing unit, of at least another of the plural leading end parts is employed in the determination of whether the target negative pressure value has been achieved, and wherein the separation distance interposed between the leading end parts corresponds to a displacement amount when the liquid in the sub-tank is discharged by a predetermined volume.