Patent ID: 8483933
Filing Date: 2013-07-09
Classification: F02D,F02M

Abstract:
1. A method for operating a fuel injector having a piezoelectric actuator for driving a valve needle coupled to the actuator, the method comprising: analyzing a trigger voltage of the piezoelectric actuator to infer an operating state of the fuel injector; and analyzing at least one of (a) a second time derivative of the trigger voltage and (b) a variable depending on the second time derivative of the trigger voltage, wherein the trigger voltage is sampled at a fixed sampling frequency, and the variable depending on the second time derivative of the trigger voltage is formed from the sampling values thereby obtained, and wherein at least one of an inflection point, an extreme, and a maximum of at least one of (a) the second time derivative of the trigger voltage and (b) the variable depending on the second time derivative of the trigger voltage is regulated to a constant instant with regard to a start of triggering.