Patent ID: 7886720

Claim:
A method for operating a fuel pump having a variable delivery rate in order to feed fuel from a fuel container to an internal combustion engine, the method comprising the steps of: feeding electrical energy in the form of pulses periodically to the fuel pump, controlling a pulse width as a function of the fuel requirement of the internal combustion engine, and controlling the frequency of the pulses in such a way that an inaudible frequency is set when there is a low delivery rate of the fuel pump but not when there is a relatively high delivery rate, wherein controlling the pulse width and the frequency of the pulses includes transitioning between a plurality of integral operational states, each corresponding to a predefined range of fuel requirement values, including at least: a first state corresponding to a first range of fuel requirement values, wherein the pulses have a first frequency and a first pulse width; a second state corresponding to a second range of fuel requirement values, wherein the pulses have the same first frequency but a second pulse width different than the first pulse width; and a third state corresponding to a third range of fuel requirement values, wherein the pulses have a second frequency different than the first frequency, and a third pulse width different than both the first and second pulse widths.