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EP-4739059-A1 - CONVERTING ELEMENT AND VIBRONIC SENSOR

EP4739059A1EP 4739059 A1EP4739059 A1EP 4739059A1EP-4739059-A1

Abstract

The invention refers to a converting element (2) for converting between mechanical vibrations and electric signals. There are various piezoelectric elements (3) arranged in a stack and a connector (4) being a wire. At the outside (5) of the stack are grooves (6) between adjacent piezoelectric elements (3). The connector (4) is located within the grooves (6) which are filled with an electrically conductive filling material (7). The connector (4) is connected to the stack via a sintering process. The connector (4) comprises inner segments (8) located within the grooves (6) and outer segments (9) located outside of the grooves (6). The outer segments (9) are located at the outside (5) of the stack. The invention further covers a vibronic sensor with a converting element (2).

Inventors

  • BAUER, HARALD
  • Dötsch, Michael
  • WIMBERGER, PETER
  • MANGEOT, CHARLES
  • Feidenhans'l, Nikolaj Agentoft
  • LOU-MOELLER, Rasmus
  • Bloch, Henrik
  • MIGNANELLI, Laura

Assignees

  • Endress+Hauser SE+Co. KG
  • CTS Corporation Advanced Materials and Solutions

Dates

Publication Date
20260506
Application Date
20241029

Claims (20)

  1. Converting element (2) for converting between mechanical vibrations and electric signals, wherein the converting element (2) comprises various piezoelectric elements (3) arranged in a stack, wherein the converting element (2) further comprises at least one connector (4), wherein the connector (4) is a wire, wherein the stack of piezoelectric elements (3) comprises at its outside (5) grooves (6) between adjacent piezoelectric elements (3), wherein the connector (4) is located partially within the grooves (6), wherein at least grooves (6) in which the connector (4) is located are filled with an electrically conductive filling material (7), wherein the connector (4) is connected to the stack of piezoelectric elements (3), wherein the connector (4) comprises inner segments (8) that are located within the grooves (6) and outer segments (9) that are located outside of the grooves (6), and wherein the outer segments (9) are located at the outside (5) of the stack of piezoelectric elements (3).
  2. Converting element (2) according to claim 1, wherein the piezoelectric elements (3) of the stack of piezoelectric elements (3) are essentially identical in their dimensions and/or their material.
  3. Converting element (2) according to claim 1 or 2, wherein the grooves (6) have a form of a straight cut with a given length and/or a given depth.
  4. Converting element (2) according to one of claims 1 to 3, wherein the various piezoelectric elements (3) are connected to each other via a sintering process, and wherein between adjacent piezoelectric elements (3), at least a layer of a sintering component (10) - preferably comprising silver - is located.
  5. Converting element (2) according to one of claims 1 to 4, wherein the filling material (7) comprises a low temperature sintering silver.
  6. Converting element (2) according to one of claims 1 to 5, wherein the piezoelectric elements (3) are polarized, wherein the piezoelectric elements (3) are such arranged within the stack of piezoelectric elements (3) that they form two sub-stacks (11, 12), wherein in each sub-stack (11, 12) of the two sub-stacks (11, 12) the piezoelectric elements (3) are such arranged that sides of the piezoelectric elements (3) with same polarization are in contact with another, wherein at least one isolator ceramic (18) is located between the front sides of the two sub-stacks (11, 12) being aligned with each other, and wherein the front sides of the two sub-stacks (11, 12) being aligned with each other have same polarizations.
  7. Converting element (2) according to claim 6, wherein the isolator ceramic (18) is made with a piezoelectric ceramic, and wherein the piezoelectric ceramic is preferably the material of the piezoelectric elements (3) of the stack of piezoelectric elements (3).
  8. Converting element (2) according to claim 6 or 7, wherein at least a region (14) of the outside (5) of the stack of piezoelectric elements (3) comprising at least the grooves (6) between the front sides of the two sub-stacks (11, 12) being aligned with each other and the isolator ceramic (18) is covered by a barrier (15) preferably comprising a layer of glass.
  9. Converting element (2) according to one of claims 6 to 8, wherein the converting element (2) comprises two connectors (4), and wherein each of the two connectors (4) is associated to one sub-stack of the two sub-stacks (11, 12).
  10. Converting element (2) according to one of claims 1 to 9, wherein the stack of piezoelectric elements (3) comprises at its outside (5) grooves (6) between each pair of adjacent piezoelectric elements (3).
  11. Converting element (2) according to one of claims 1 to 10, wherein a number of grooves (6) of the stack of piezoelectric elements (3) is greater than a number of grooves (6) in which a connector (4) is located.
  12. Converting element (2) according to one of claims 1 to 11, wherein the outside (5) of the stack of piezoelectric elements (3) is covered by a electrically isolating protection (13) preferably being a resin.
  13. Converting element (2) according to one of claims 1 to 12, wherein at least one line of isolation (16) is located in such a way on top of at least a part of the outer segments (9) of the connector (4) that the line of isolation (16) acts as a strain relief of the connector (4).
  14. Converting element (2) according to claim 13, wherein the at least one line of isolation (16) - preferably comprising a layer of glass - runs essentially along the longitudinal axis (17) of the stack of piezoelectric elements (3).
  15. Converting element (2) according to claim 13 or 14, wherein two lines of isolation (16) are located on top of at least a part of the outer segments (9) of the connector (4), and wherein the two lines of isolation (16) run essentially parallel.
  16. Converting element (2) according to claim 14 or 15 and claim 8, wherein the two lines of isolation (16) and the barrier (15) form the capital letter H.
  17. Converting element (2) according to one of claims 1 to 16, wherein at least one isolator ceramic (18) is located at each of two front sides of the stack of piezoelectric elements (3).
  18. Converting element (2) according to one of claims 1 to 17, wherein the converting element (2) comprises a first side (21) and a second side (22), wherein the converting element (2) comprises at least two connectors (4), wherein the first side (21) and the second side (22) comprise grooves (6), and wherein one of the at least two connectors (4) is located partially within the grooves (6) of the first side and another of the at least two connectors (4) is located partially within the grooves (6) of the second side (22).
  19. Vibronic sensor for determining and/or monitoring at least one process variable, with at least one vibrating element (1) and with a converting element (2) for converting between mechanical vibrations and electric signals, wherein the converting element (2) is embodied according to one of the claims 1 to 18.
  20. Vibronic sensor according to claim 19, wherein the vibronic sensor further comprises an electronic unit (23), wherein the electronic unit (23) is embodied to receive electric signals from the converting element (2) and to submit electric signals to the converting element (2), wherein the converting element (2) is such embodied that the piezoelectric elements (3) form two sub-stacks (11, 12), wherein the converting element (2) comprises a first side (21) and a second side (22), wherein the converting element (2) comprises four connectors (4), wherein two connectors (4) are associated to each sub-stack (11, 12) and are located at different sides (21, 22) of the converting element (2), and wherein the electronic unit (23) receives the electric signals from the converting element (2) and submits signals to the converting element (2) via the four connectors (4) is such a way that connectors (4) located at a same side (21, 22) of the converting element (2) carry electric signals of different polarity.

Description

The invention relates to a converting element. The invention further relates to a vibronic sensor with a converting element. The vibronic sensor serves for determining or monitoring at least one process variable, e.g. level, density or viscosity of a medium. The medium for example being a fluid, a liquid, a gas or a bulk solid. Vibronic sensors are widely used in process and/or automation technology. The sensors comprise at least one mechanically oscillatable unit (also called vibrating element), such as, for example, a single tine, a fork or a membrane. The vibrating element is excited during operation by means of an exciter/receiving unit (also: driver or converting element) such that mechanical oscillations are executed. The exciter/receiving unit is frequently an electromechanical transducer unit in most cases comprising piezoelectric elements. The piezoelectric elements are usually disks arranged in a stack. A design of a converting element suitable especially for the operation under higher temperatures is given by US 6,710,517 B2. Described is a stack of piezoelectric elements in the form of disks with grooves at their respective front side. Within these grooves - and due to the location within the stack - is a connector arranged that serves for the electric connection of the stack. The production of such a stack is rather cumbersome as it has to be built level by level. An object of the invention is to provide a converting element with piezoelectric elements that can be used at higher temperature and that also addresses the topic of the electric connection. The object is achieved by a converting element for converting between mechanical vibrations and electric signals, wherein the converting element comprises various piezoelectric elements arranged in a stack, wherein the converting element further comprises at least one connector, wherein the connector is a wire, wherein the stack of piezoelectric elements comprises at its outside grooves between adjacent piezoelectric elements, wherein the connector is located partially within the grooves, wherein at least grooves in which the connector is located are filled with an electrically conductive filling material, wherein the connector is connected to the stack of piezoelectric elements, wherein the connector comprises inner segments that are located within the grooves and outer segments that are located outside of the grooves, and wherein the outer segments are located at the outside of the stack of piezoelectric elements. The piezoelectric elements are electrically connected by at least one connector. The connector is arranged within grooves at the outside and, thus, at the rim of the piezoelectric elements. The grooves are deep enough so that the connector reaches at least one of the electrodes that are usually provided at the front sides of the piezoelectric elements. Within the stack, the electrodes of adjacent piezoelectric elements face each other and have the same polarity. In an embodiment, each groove reaches into both piezoelectric elements between which the groove is located. In an embodiment, the front sides of the piezoelectric elements are completely covered by their respective electrodes. Hence, the grooves between neighboring piezoelectric elements allow the part of connector within them to reach the electrodes of both adjacent piezoelectric elements. The connector is partially within the grooves and partially outside of the stack of piezoelectric elements. Thus, the connector just has to be put into contact with the grooves at the outside. This facilitates the production. For the fixation of the connector to the stack of piezoelectric elements, for example, a sintering process or a bonding process is performed. In an alternative way or additionally, a high temperature resistant adhesive is used for connecting the connector to the stack, e.g. for the bonding process. Prefarably, no soldering or welding process has to be performed. Hence, the connector which is a wire remains flexible. This is, e.g., necessary for the further handling of the converting element. In an embodiment of the converting element, the piezoelectric elements of the stack of piezoelectric elements are essentially identical in their dimensions and/or their material. In this embodiment, the ceramic components that are polarized and, thus, used as piezoelectric elements are identical with regard to their dimension and/or to their material, This embodiment facilitates the production of the converting element. The piezoelectric elements have preferably a form of a disk with a diameter between 5 mm and 10 mm. The ground area of the piezoelectric elements has in an embodiment the form of a circle or of a square. In embodiment, the disks of the piezoelectric elements have closed surface or have a hole. According to an embodiment of the converting element, the grooves have a form of a straight cut with a given length and/or a given depth. The size of the groove is at least dep