Patent ID: 7600845

Claim:
An inspection device for a piezoelectric head that includes a pressure chamber filled with liquid, a liquid supply channel that supplies the liquid to the pressure chamber, a nozzle at which droplets are jetted from the pressure chamber, and a piezoelectric element that applies pressure to the pressure chamber, the inspection device comprising: a detection component that, when the piezoelectric element is driven on the basis of a predetermined detection signal, outputs a signal corresponding to behavior of an acoustic vibration system of the piezoelectric head; and a judgment component that, on the basis of the detection signal and the signal outputted by the detection component, judges for a cause of defective ejections at the piezoelectric head; wherein the detection component calculates a rate of volume change of the piezoelectric element on the basis of the signal corresponding to behavior of the acoustic vibration system, on the basis of an equation of state that represents the acoustic vibration system of the piezoelectric head, calculates, from the detection signal and the calculated rate of volume change, time series data of at least one of flow speed and flow amount of droplets that are jetted from the nozzle, and judges for a cause of defective ejections at the piezoelectric head on the basis of a frequency characteristic of the calculated time series data; wherein the equation of state is the following equation: P = M ⁢ ⁢ ⅆ 2 ⁢ x ⅆ t 2 + R ⁢ ⁢ ⅆ x ⅆ t 2 + Kx in which: given that volume changes of the piezoelectric element, the pressure chamber, the liquid supply channel and the nozzle are designated x 0 , x 1 , x 2 and x 3 , respectively, with the relationship x 0 =x 1 +x 2 +x 3 , x is a state vector constituted with x 0 and any two of the variables x 1 , x 2 and x 3 ; M is an inertia matrix of the piezoelectric element, liquid supply channel, pressure chamber and nozzle of the acoustic vibration system, R is a viscosity matrix of the same and K is a rigidity matrix of the same; and P is a pressure vector that the piezoelectric element applies to the pressure chamber when voltage is applied to a switching element of a bridge circuit of the detection component.