Abstract: A controller for controlling the operation of a fuel injector having a piezoelectric actuator which is operable by the application of a voltage drive profile across the actuator, the controller comprising inputs for receiving data relating to one or more engine parameters and 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 is arranged to comprise an activating voltage component to initiate an injection event and a deactivating voltage component to terminate the injection event, the activating and deactivating voltage components being separated by a time interval TON. The controller further receives 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 TON greater than or equal to a predetermined pressure wave time period (TP) of a pressure wave cycle within the injector.

Abstract: A method of operating a fuel injector including a piezoelectric actuator having a stack of piezoelectric elements, comprises applying a discharge current (IDISCHARGE) to the actuator for a discharge period so to discharge the stack from a first differential voltage level across the stack to a second, lower differential voltage level across the stack so as to initiate an injection event, and applying a charge current (ICHARGE) to the actuator for a charge period (T3 to T4?) so as to charge the stack from the second differential voltage level to a third differential voltage level so as to terminate the injection event. The method includes determining at least one engine parameter (e.g. common rail pressure) of the injection event prior to applying the charge current (ICHARGE) to the actuator and selecting the third differential voltage level in dependence on the at least one engine parameter.

Abstract: A controller for controlling the operation of a fuel injector having a piezoelectric actuator which is operable by the application of a voltage drive profile across the actuator, the controller comprising inputs for receiving data relating to one or more engine parameters and 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 is arranged to comprise an activating voltage component to initiate an injection event and a deactivating voltage component to terminate the injection event, the activating and deactivating voltage components being separated by a time interval TON. The controller further receives 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 TON greater than or equal to a predetermined pressure wave time period (TP) of a pressure wave cycle within the injector.

Abstract: A method of assembling a piezoelectric actuator arrangement comprises providing a piezoelectric element having first and second ends and arranging the piezoelectric element within a sleeve member such that the inner surface of the sleeve member defines, together with the outer surface of the piezoelectric element, a chamber for receiving a first filler material. The first filler material is injected into the chamber and a heating effect is applied to the sleeve member such that the sleeve member deforms to seal against the first filler material.

Abstract: A method of assembling a piezoelectric actuator arrangement (10) comprises the steps of providing a piezoelectric element (12) having first and second ends and arranging the piezoelectric element (12) within a sleeve member (20) such that the inner surface of the sleeve member (20) defines, together with the outer surface of the piezoelectric element (12), a chamber (24) for receiving a first filler material (30). The first filler material (30) is injected into the chamber (24) and a heating effect is applied to the sleeve member (20) such that the sleeve member (20) deforms to seal against the first filler material (30).

Abstract: An actuator arrangement comprising a piezoelectric element formed from a piezoelectric material, a first end of the piezoelectric element cooperating with an input piston member slidable within a bore. A surface associated with the input piston member defines, in part, a control chamber for fluid, fluid pressure within the control chamber acting on a surface associated with an output piston member. The fluid within the control chamber is substantially incompressible such that, in use, movement of the input piston member is transmitted to the output piston member, the piezoelectric element being arranged within a second chamber for fluid such that fluid pressure within the second chamber exerts a force on at least a part of the surface of the piezoelectric element which serves to oppose the load exerted on the piezoelectric element due to fluid pressure within the control chamber, thereby suppressing distortions in the piezoelectric material.

Abstract: A method is provided for detecting injection events in a piezoelectric actuated fuel injector. The method comprises the steps of: (a) providing a piezoelectric element for actuating the injector valve; (b) applying a voltage to the piezoelectric element, thereby actuating the injector valve; and (c) monitoring at least one of the voltage or current associated with the piezoelectric element, wherein changes in voltage or current are indicative of injection events in the fuel injector.

Abstract: A piezoelectrically actuable fuel injector comprising an accumulator volume within which a piezoelectric stack is arranged, the accumulator volume being arranged to receive fuel from a source of pressurized fuel, in use. The piezoelectric stack carrying an end member which engages a surface associated with a piston member so as to apply a retracting force to the piston member upon a reduction in the axial length of the piezoelectric stack, the piston member being operable to control fuel pressure within a control chamber. A volume is defined between the end member and the surface associated with the piston member. The volume is provided with a vent arrangement to permit fuel within the volume to flow to a low pressure drain.