Driving device provided with piezoelectric element deterioration detection circuit and deterioration detection method

A driving device comprising:

• a piezoelectric element;
• a first resistor connected in series with the piezoelectric element;
• a voltage supply unit for supplying a DC voltage across the series connection circuit formed by the piezoelectric element and the first resistor;
• a measuring unit for measuring a voltage of the first resistor, and
• a control unit for controlling the voltage supply unit and the measuring unit;
• wherein
• the resistance value of the first resistor is smaller than an insulation resistance value of the piezoelectric element,
• the measuring unit measures the voltage of the first resistor, in a state where a predetermined voltage is supplied from the voltage supply unit,
• the control unit calculates a resistance value of the piezoelectric element from the voltage value obtained by the measurement of the measuring unit and determines whether or not deterioration has occurred in the piezoelectric element, based on the calculated resistance value,
• the measuring unit measures the voltage of the first resistor for a plurality of times, in a state where the predetermined voltage is supplied from the voltage supply unit, and
• the control unit conducts repeatedly a process of calculating the resistance value of the piezoelectric element from each of a plurality of voltage values obtained by a plurality of measurements, and a process of calculating a representative value of the plurality of calculated resistance values of the piezoelectric element, calculates a slope of the plurality of calculated representative values, and determines whether or not deterioration has occurred in the piezoelectric element by comparing the slope with a predetermined threshold value.

A deterioration detection method of a piezoelectric element in the driving device including the piezoelectric element, a first resistor connected in series with the piezoelectric element, a voltage supply unit for supplying a DC voltage, and a measuring unit for measuring the voltage, comprising:

• a step of supplying, by the voltage supply unit, a predetermined DC voltage across the series connection circuit of the piezoelectric element and the first resistor,
• a measurement step of measuring a voltage of the first resistor by the measuring unit, in a state of supplying the predetermined DC voltage,
• a calculation step of calculating a resistance value of the piezoelectric element from the voltage value obtained by the measurement step, and
• a step of determining whether or not deterioration has occurred in the piezoelectric element, based on the resistance value calculated by the calculation step.