Abstract: Provided are barrier coatings and methods for applying barrier coatings to piezoelectric actuators that are intended for use in automotive fuel injectors. The barrier coatings are characterised by the presence of at least one organic layer, and additionally metal and/or non-metallic inorganic layers. The barrier coatings described show advantage in resisting permeation by liquid fuel, water and other contaminants.

Abstract: A method of poling a ferroelectric sample suitable for use in a fuel injector of an internal combustion engine, the method comprising providing a ferroelectric sample having a stack of ferroelectric layers, wherein adjacent layers are separated by internal electrodes, forming a first group and a second group of electrodes; applying a multiaxial pressure to the ferroelectric sample; reducing the bonding strength between each pair of adjacent ferroelectric layers and internal electrodes; and generating a first electric field between the first and second group of electrodes to pole each ferroelectric layer in a first poling direction.

Abstract: The invention provides an encapsulating arrangement for an electrical component comprising first and second insulating layers and an electrically charged conductive layer, preferably in the form of a metal foil, intermediate the first and second insulating layers, and arranged to prevent the passage of ionic species across the encapsulating arrangement. The encapsulating arrangement of the invention has particular application to piezoelectric actuator arrangements for fuel injectors of internal combustion engines.

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 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: The invention provides a piezoelectric actuator having a stack body comprising a plurality of piezoelectric elements, each element having a positive and negative electrode pair which are electrically isolated from one another by the piezoelectric elements, the electrode pairs being arranged in groups of one or more electrode pairs, each group having a conducting arrangement in electrical connection therewith. The piezoelectric actuator further comprises a distribution electrode arrangement for connecting the conducting arrangement to a power supply, in use, wherein the distribution electrode arrangement includes a fuse arrangement. In the event of a short circuit between electrodes of a pair within one of the groups, the fuse arrangement breaks the electrical connection between the power supply and the conducting arrangement.

Abstract: The invention provides a piezoelectric actuator having a stack body comprising a plurality of piezoelectric elements, each element having a positive and negative electrode pair which are electrically isolated from one another by the piezoelectric elements, the electrode pairs being arranged in groups of one or more electrode pairs, each group having a conducting arrangement in electrical connection therewith. The piezoelectric actuator further comprises a distribution electrode arrangement for connecting the conducting arrangement to a power supply, in use, wherein the distribution electrode arrangement includes a fuse arrangement. In the event of a short circuit between electrodes of a pair within one of the groups, the fuse arrangement breaks the electrical connection between the power supply and the conducting arrangement.

Abstract: A method of assembling a fuel injector (8) comprising a fuel injector body having an accumulator volume (22) defined therein is described. The method comprises: providing an encapsulated actuator arrangement (29a) having a piezoelectric actuator stack (29) and electrical connector means (34,36), wherein the stack (29) is encapsulated in a sleeve member (30); providing a volume of sealing material (42) in the region of the electrical connector means (34,36); locating the encapsulated actuator arrangement (29a) in the accumulator volume (22); applying heat indirectly to the volume of sealing material (42) so as to soften the volume of sealing material; and applying pressure to the encapsulated actuator arrangement (29a) such that the volume of sealing material (42) deforms to form a substantially fluid-tight seal (38) between the encapsulated actuator arrangement (29a) and the accumulator volume (22) in the region of the electrical connector means (34,36).