Patent ID: 7862230

Claim:
A method for operating an internal combustion engine with an actuating device that includes a piezoelectric actuator, and a temperature sensor, that detects a temperature outside the actuating device, and a charge sensor, whose measuring signal is representative of an electrical charge which is applied to the piezoelectric actuator, and a voltage sensor, whose measuring signal is representative of an electrical voltage that is dropped across the piezoelectric actuator, the method comprising the steps of: when a specified first condition is met, which is met at the earliest after a time period that exceeds a specified engine stop period, detecting a measuring signal of the temperature sensor and a piezoelectric temperature value on the basis of the measuring signal of the temperature sensor, determining a temperature-capacitance characteristic value of the piezoelectric actuator by means of a specified mapping on the basis of the piezoelectric temperature value, determining a measured capacitance characteristic value by means of a detected charge value and a voltage value corresponding to the measuring signal of the temperature sensor of the piezoelectric actuator, determining a first correction capacitance characteristic on the basis of the measured capacitance characteristic value and the temperature-capacitance characteristic value, independently of the specified first condition detecting the charge value and the voltage value of the piezoelectric actuator and depending on the detected charge and voltage value, determining the measured capacitance characteristic value, determining the piezoelectric temperature value on the basis of the measured capacitance characteristic value and the first correction capacitance characteristic value by means of the inverse mapping with respect to the temperature and the capacitance characteristic value.