Delphi Technologies Holding S.arl

Delphi Technologies, Inc.

Delphi Technologies Holdings Sarl

Christopher Andrew Goat

Michael Peter Cooke

Martin Paul Hardy

Russell Harmon Bosch

Andrew John Hargreaves

Gordon M Reid

Jean-Francois Berlemont

Simon R Panteny

Russell Bosch

Joachim c/o Delphi Tech Centre-Luxembourg Kiefer

A piezoelectric actuator comprises a co-fired stack of piezoelectric elements formed from a piezoelectric material and a plurality of positive internal electrodes interdigitated with a plurality of negative internal electrodes throughout the stack to define active regions of the piezoelectric material which are responsive to a voltage applied across the internal electrodes, in use. An external positive electrode connects with the positive internal electrodes and an external negative electrode connects with the negative internal electrodes. The actuator is characterized in that the stack further comprises means for deliberately creating artificial cracks within the stack at a location at which the artificial cracks do not give rise to a short circuit between the internal electrodes but serve to relieve stresses within the piezoelectric material.

Piezoelectric actuator

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.

Casing for an electrical component

A method for manufacturing a piezoelectric actuator, the method comprising: co-extruding alternating strips of a high permittivity material and a low permittivity material to form a green tape comprising said alternating strips of said high permittivity material and said low permittivity material; cutting said green tape to form a plurality of sheets, each sheet comprising a high permittivity region and at least two low permittivity regions adjacent to the high permittivity region; applying at least one conductive region to each one of two or more of the sheets to overly the high permittivity region and to leave exposed at least one low permittivity region; and stacking a plurality of sheets to form an actuator stack comprising adjacent sheets, wherein the or each conductive region on each sheet is offset with respect to a conductive region on a different sheet within the actuator stack.

Method for manufacturing a piezoelectric actuator

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. At least one bridging arrangement extends through the insulating arrangement and comprises a conductive material, so as to provide a connection between a side electrode and an internal electrode, wherein at least one first surface, defined by an interface between the conductive material and the insulating arrangement, and at least one second surface, defined by an internal boundary of a piezoelectric layer, are substantially continuous with one another in the vicinity of the piezoelectric/insulator interface.

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.

Method of poling ferroelectric materials

A piezoelectric actuator for use in a fuel injection system of an internal combustion engine, the actuator comprising a stack of ferroelectric layers; an encapsulation for protecting the stack from the ingress of liquid; and oxygenation means for providing oxygen to the ferroelectric layers, the means positioned between the encapsulation and stack. The oxygenation means is preferably impregnated in a fabric which forms a layer between the encapsulation and the stack.

Ferroelectric Durability

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. The entire process is performed on completed actuators. Under suitable temperature and load conditions no tensile margin fractures form and electrode tip discontinuity is reduced.

Reducing stress gradients within piezoelectric actuators

An actuator arrangement comprising a piezoelectric actuator having a body section, a shroud which enshrouds at least part of the body section of the actuator, and at least one constrictive member disposed externally with respect to the shroud. The constrictive member applies a constrictive force to the shroud to maintain a seal between the shroud and the underlying body section of the actuator.

Actuator arrangement

A method of operating a fuel injector including a piezoelectric actuator having a stack of piezoelectric elements, comprises applying a discharge current (I) 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 (I) to the actuator for a charge period (Tto T') 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 (I) to the actuator and selecting the third differential voltage level in dependence on the at least one engine parameter.

System and method for operating a piezoelectric fuel injector

A method of producing an actuator includes shaping a block of ferroelectric material to provide an active element of the actuator. The element includes a stack of ferroelectric layers with adjacent layers separated by electrodes arranged parallel to end faces of the element. The method includes applying a primary electrode to the end faces, immersing the element and the primary electrode within a dielectric fluid, applying a primary poling voltage to the primary electrode so as to polarize the element in a first polarization direction, applying a secondary external electrode to side faces of the element, and applying a secondary poling voltage to the secondary electrode to polarize alternate layers along the first polarization direction and the other layers along a second, oppositely-directed polarization axis. The method may also include applying a conductive film to the end faces and/or applying heat to help evaporate the dielectric fluid.

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Offham, United Kingdom

Christopher Andrew Goat