Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
1999-08-06
2001-10-23
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S365000, C310S363000
Reexamination Certificate
active
06307306
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is directed to a piezo actuator that comprises an electrically conductive contact lug for electrical contacting of an electrode. An employment of such a piezo actuator is also recited.
A piezo actuator is usually constructed of a plurality of piezo elements arranged to form a stack-shaped actuator member. Each piezo element is composed of a piezo ceramic layer that is provided with a metallic electrode at both sides. When an electrical voltage is applied to these electrodes, then the piezo ceramic layer reacts with a lattice distortion. As a result thereof, the piezo element expands and contracts and, thus, the actuator member expands and contracts in a direction that is determined by the arrangement of the piezo ceramic layer and of the electrodes of a piezo element. A usable modification of an expansion of a stack-shaped actuator member occurs according to an extent of the expansion and contraction.
German reference DE 197 15 488 discloses such a piezo actuator. The piezo actuator has an actuator member with a multi-layer structure comprising at least one stack of alternating electrode and piezo ceramic layers. One electrode layer serves neighboring piezo ceramic layer as electrode. To that end, an electrical contacting of the electrode layers ensues in an alternating polarity. The alternating polarity is achieved with the assistance of two metallization strips that are laterally applied to the actuator member. A metallization strip extends over a height that derives from electrically active layers of the actuator member stacked on top of one another. One of the metallization strips is electrically conductively connected to each second electrode layer and is insulated from each first electrode layer lying therebetween. By contrast thereto, the second metallization strip is insulated from every second electrode layer and electrically conductively connected to each first electrode layer.
In order to ensure the electrical contacting of every individual electrode layer, a voltage supply to a metallization strip in the known piezo actuator ensues via a strip-shaped, electrically conductive contact lug in the form of a plastic film laminated with copper. The contact lug is thereby soldered to a metallization strip via one of its edges. The contact lug likewise extends over the entire height of the electrically active layer of the actuator member. An outside edge of the contact lug pointing away from the actuator member is connected to a rigid electrical terminal element. A crack in a metallization strip that potentially occurs is electrically bridged with the assistance of the contact lug. As a result thereof, the piezo actuator exhibits a high plurality of cycles and, thus, a high service life. One cycle comprises a one-time expansion and contraction of the piezo actuator or, respectively, of the actuator member in a specific direction.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a piezo actuator that comprises an even more improved electrical contacting compared to a known piezo actuator and, thus, exhibits an even greater number of cycles and longer service life.
For achieving the object, a piezo actuator comprises an actuator member for an expansion and contraction in a specific direction and at least one electrically conductive contact lug secured to the actuator member that has a dimension or an expanse in the specific direction with an improvement of the contact lug having means for adapting the expanse or the dimension of the lug to a change of dimension or size of the actuator member due to the expansion and contraction.
Corresponding to the extent of the expansion and contraction of the actuator member during a cycle, a change in an expanse of the actuator member in the specific direction occurs. The expanse comprises, for example, a height of the actuator member. Due to this change, a mechanical stress can occur in the contact lug that is secured to the actuator member.
These mechanical stresses are particularly great, for example, when a crack due to a polarization of the piezo actuator has arisen (polarization crack) in a region of the metallization strips in which the actuator member is piezo electrically inactive. A relatively great change of a dimension of the actuator member occurs at such a crack during the expansion and contraction. High mechanical stresses in the contact lug occur due to these great changes, particularly when the contact lug is rigidly connected to a rigid electrical terminal element.
The underlying idea of the invention is to reduce this mechanical stress in the contact lug. This succeeds in that the expanse or dimension of the contact lug during operation of the actuator member is automatically adapted to the constantly changing expanse or size of the actuator member. The adaptation thereby particularly ensues in a contacting region of the contact lug in which the contact lug is secured to the actuator member.
The adaptation in view of the mechanical stress in the contact lug can ensue at a maximum, minimum or medium extent of the expansion and contraction of the actuator member. This is dependent on the application and on the means that is utilized therefor.
In a particular development, the piezo actuator is characterized in that the actuator member comprises a surface at which at least one electrode is arranged, the contact lug is electrically connected to the electrode and is secured to at least two points of the surface, a spacing between the points is dependent on the expansion and contraction, the contact lug comprises the means at least between the two points and the means comprises a deformation material.
The points are preferably a component part of a planar surface and are arranged successively along the direction defined by the expansion and contraction. The points, however, can also be arranged deviating from this direction. The surface can likewise be fashioned arcuate or in some other way.
In particular, there are a plurality of points at which the contact lug is secured to the actuator member. In this way, for example, the contact lug is secured to the actuator member along an entire edge of the contact lug. In particular, the plurality of points at the surface is aligned along the direction of the expansion and contraction of the actuator member.
The spacing between two points is dependent on an electrical voltage that is applied to the electrodes of the actuator member and, thus, on the expansion and contraction of the actuator member. Due to the variable spacing from one point to another, the contact lug has a means, particularly between the points, that is suitable for adapting the expanse of the contact lug to the extent of the expansion and contraction.
The means or, respectively, the entire contact lug is, for example, a metallic leaf spring that is mechanically secured to a few points of the surface of the actuator member along an edge of the leaf spring. The points are arranged deviating from the direction in which the actuator member expands and contracts. Given expansion and contraction of the actuator member, the leaf spring bends as a result thereof. The expanse of the leaf spring in the direction in question is adapted to the extent of the expansion and contraction. The electrodes of the actuator member to be contacted are only electrically connected to the leaf spring by a touch contact. The electrodes are arranged such at the surface that the electrical contact remains preserved when the leaf spring bends.
In a particular development of the invention, the means comprises a deformation material that can be elastically and/or plastically deformed. This property is preferably not limited to the direction determined by the expansion and contraction of the actuator member. A movement within the contact lug in this direction simultaneously leads to a tensile force that can extend in any direction and over the entire contact lug. It is therefore especially advantageous when the means is deformable with respect to every spatial direction
Bast Ulrich
Cramer Dieter
Kainz Gerald
Lubitz Karl
Schuh Carsten
Medley Peter
Ramirez Nestor
Schiff & Hardin & Waite
Siemens Aktiengesellschaft
LandOfFree
Piezo actuator with improved electrical contacting and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Piezo actuator with improved electrical contacting and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Piezo actuator with improved electrical contacting and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2562545