Patent ID: 8540329

Claim:
A liquid ejection apparatus comprising: a tank which stores a recording liquid; a recording liquid ejection head which includes an internal passage having an inflow opening and an outflow opening and a plurality of individual recording liquid passages respectively connecting outlets of the internal passage with ejection openings from which the recording liquid is ejected; a supply passage which connects the inflow opening with the tank; a return passage which connects the outflow opening with the tank; a valve which adjusts a flow rate of the recording liquid on the return passage; a pump which operates to supply the recording liquid from the tank to the internal passage via the supply passage; a pump control unit which controls the pump; a valve control unit which controls the valve; a detecting unit which detects an operating state of the pump; and a calculating unit which calculates the viscosity of the recording liquid, wherein: while the valve control unit controls the valve and the pump control unit controls the pump so that the recording liquid in the tank circulates by serially passing through the supply passage, the internal passage, and the return passage, the calculating unit calculates the viscosity of the recording liquid based on the operating state of the pump detected by the detecting unit, and after the calculating unit calculates the viscosity of the recording liquid, the pump control unit controls, based on the calculated viscosity of the recording liquid, the pump so that circulation purging is carried out to circulate the recording liquid to serially pass through the supply passage, the internal passage, and the return passage, in such a way as to achieve a condition that a flow rate per unit of time of the recording liquid supplied by the pump is higher than a circulation flow rate per unit of time of the recording liquid when the calculating unit calculates the viscosity of the recording liquid but is within a range with which no recording liquid leaks through the ejection openings.