Abstract: A casing for encapsulation of an electrical component, for example a piezoelectric actuator, comprising an outer layer of a semipermeable material and an inner layer comprising a chemically active, hydrophilic substance that chemically combines with water to form a compound.

Abstract: A piezoelectric actuator comprising a stack of piezoelectric layers formed from a piezoelectric material, a plurality of internal electrodes disposed throughout the stack to define active regions of the piezoelectric material therebetween which are responsive to a voltage applied across two or more groups of the internal electrodes in use, an insulating arrangement which at least partially covers at least one surface of the stack to define a piezoelectric/insulator interface, and two or more side electrodes to connect with the two or more groups of the internal electrodes.

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; and generating an electric field between the first and second group of electrodes to pole the ferroelectric sample. The multiaxial pressure is ideally applied by means of a fluid, and the fluid may be an dielectric fluid or fuel.

Abstract: Piezoelectric actuators of the type comprising a stack of layers of ferroelectric material and intervening electrodes which extend only part-way across the adjacent ferroelectric layers suffer differential remanent stress when electric fields are applied across the layers. To overcome this, a tensile stress is applied to the actuator along an axis substantially perpendicular to the layers of piezoelectric material in the actuator, which tensile stress is sufficient to mechanically align the dipoles, thus giving rise to a remanent strain which is uniform throughout the actuator. The actuator is advantageously heated while the tensile stress is applied, so as to increase the difference between the tensile strength of the material and the applied tensile stress. An alternative arrangement involves subjecting the actuator to a multidirectional stress and reducing the stress along the axis substantially perpendicular to the layers of piezoelectric material in the actuator.

Abstract: A casing for encapsulation of an electrical component, for example a piezoelectric actuator, comprising an outer layer of a semipermeable material and an inner layer comprising a chemically active, hydrophilic substance that chemically combines with water to form a compound.

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 piezoelectric actuator comprising a stack of piezoelectric layers formed from a piezoelectric material, a plurality of internal electrodes disposed throughout the stack to define active regions of the piezoelectric material therebetween which are responsive to a voltage applied across two or more groups of the internal electrodes in use, an insulating arrangement which at least partially covers at least one surface of the stack to define a piezoelectric/insulator interface, and two or more side electrodes to connect with the two or more groups of the internal electrodes.