Patent ID: 7681555

Claim:
A controller for controlling the operation of a fuel injector having a piezoelectric actuator, the actuator being operable by an application of a voltage drive profile across the actuator, the controller comprising: inputs for receiving data relating to one or more engine parameters; a processor for determining a voltage drive profile for controlling the actuator in dependence upon the one or more engine parameters, the voltage drive profile being arranged to comprise a first pilot injection event, a second pilot injection event, a main injection event, an activating voltage component to initiate the second pilot injection event and a deactivating voltage component to terminate the second pilot injection event, the activating and deactivating voltage components being separated by a time interval T ON ; and outputs for outputting the voltage drive profile as determined by the processor to the actuator, wherein the processor is arranged to set the time interval T ON greater than or equal to a predetermined pressure wave time period (T P ) of a pressure wave cycle within the injector.