DE102019218254A1 - Piezoceramic as a raised structure that is defined by a trench with a variable wall slope - Google Patents

Abstract

A device is shown with a piezoceramic as the elevation structure, the elevation structure being defined by a trench, the elevation structure having a wall with a variable wall slope.

Description

The invention relates to a piezoceramic, in particular a piezocomposite ceramic, which is produced by means of additive manufacturing.

Piezoceramics are used, for example, in (underwater) sound receivers in order to receive underwater noises, for example sonar signals, and to convert them into an electrical signal. Piezocomposite ceramic elements were created in order to obtain the broadest possible / sensitive receiver possible. These are made from a plate made of a piezoceramic, i.e. a piezoceramic material. The plate (semi-finished product) is typically produced by means of a sintering process. At least one trench is formed, in particular cut or ground, in the plate. The trenches are then filled with a filler material, in particular a plastic, in order to obtain the piezocomposite ceramic. The trenches filled with plastic then form a matrix in the plate. However, the shaping of the trenches in the plate is limited to straight, one-dimensional cuts, so that only straight edges can be formed without changes in direction in the cutting direction. These can be vertical or oblique cuts. However, the cuts must not include any change of direction during the cut, as otherwise the saw blade can no longer be guided out of the piezoceramic, i.e. the cut trench. The number of possible structures is therefore limited by the manufacturing process, which also limits the sensitivity / bandwidth of the piezoceramic.

The task is therefore to create an improved concept for piezoceramics, in particular piezocomposite ceramics.

The object is achieved by the subject matter of the independent claims. Further advantageous embodiments are the subject of the dependent claims.

Exemplary embodiments show a device with a piezoceramic as the elevation structure, the elevation structure being defined by a trench. The elevation structure also has a wall with a variable wall slope. A slope that is not constant, that is to say changes over an expansion (in particular height) of the wall, is referred to as a variable wall slope. In other words, the wall has a first slope in a first section of the wall and a second slope in a second section of the wall. In particular, the sections are arranged one above the other, in the viewing direction from a base point of the elevation structure. In particular, the first and second sections of the wall are not to be understood as two walls that are adjacent to one another. A discontinuous transition from one wall to the other wall, that is to say an edge in colloquial terms, can be viewed as a feature of two walls that are adjacent to one another. Furthermore, two walls adjoining one another are arranged next to one another in the viewing direction from the base point of the elevation structure. The trench is also referred to as the free space or matrix space. The piezoceramic is a component that has a piezoceramic material. The piezoceramic has the elevation structure and can, e.g., to simplify the manufacturing process, have a base element on which the elevation structure is arranged. The piezoceramic, i.e. in particular the elevation structure, is advantageously produced by means of a 3D printer.

The trench can be filled with a filler material such as a plastic. A polyurethane or an epoxy can be used as the plastic. For filling, the plastic can be liquefied and harden in the trench. After the filling material has been introduced, the base element can be removed so that the raised structure remains in the filling material as a piezoceramic. The piezoceramic and the filling material form a piezocomposite ceramic. The trench can be selected such that it completely encloses the raised structure. The elevation structure is then designed like a tower. The variable wall slope refers to the fact that the slope of the wall of the elevation structure is not constant. Advantageously, instead of one elevation structure, a plurality of elevation structures can also be formed, which are enclosed by the filler material, so that the filler material forms a matrix structure with the elevation structures.

The idea is to use additive manufacturing, for example printing with a 3D printer, of the elevation structure (i.e. the piezoceramic) to obtain greater variability in the shape of the elevation structure. While sawing processes for wafers, with which the elevation structure is typically produced, are limited to the contour of the saw blade, piezoceramics produced by means of additive manufacturing are free in the shape of the elevation structure. An elevation structure with a variable wall slope can, for example, have a greater sensitivity than an elevation structure with a constant wall slope without a change of direction. Examples of advantageous forms of the elevation structure are the S-shape or the fly-shape. An elevation structure is referred to as a fly shape, which has a taper at a distance from the base point of the elevation structure and a highest point of the elevation structure.

The piezoceramic can have a base element, with the raised structure rising from the base element starting from the base of the elevation structure. A carrier on which the raised structures are arranged is understood as a basic element. During the manufacture of the piezoceramic, the carrier can be manufactured in one piece with the elevation structure (s) and accordingly consist of the same material as the elevation structure (s). If the piezoceramic is filled with the filling material after production, the raised structure (s) are fixed in their predetermined place by means of the base element. After the filling, the carrier can then be separated from the piezocomposite ceramic, ie the matrix structure made up of the elevation structure (s) and the filling material.

Thereafter, the manufactured piezocomposite ceramic can be applied to another carrier for further use. A large number of piezocomposite ceramics can be arranged on a correspondingly shaped carrier to form an arbitrarily shaped, for example (part) spherical or (part) circular, sound transducer, e.g. hydrophone. This carrier typically has a material different from the piezoceramic.

In exemplary embodiments, the piezoceramic also has a further elevation structure, the further elevation structure differing from the elevation structure. However, the same applies to the rest of the survey structure as described for the survey structure. However, the further elevation structure can have the fly shape, for example, while the elevation structure has the S-shape. Furthermore, both the elevation structure and the further elevation structure can have the same shape, while a strength (or thickness) of the elevation structure, a wall slope of the trench or an orientation of the elevation structure, if it is not symmetrical in all directions, differ. Furthermore, the further elevation structure is arranged at a distance from the elevation structure. In particular, the elevation structure is separated from the further elevation structure by means of the trench.

Furthermore, a piezocomposite ceramic with a plurality of elevation structures is shown, each of which has a piezoceramic material, the elevation structure having a wall with a variable wall slope. The elevation structures are at least partially enclosed with a filler material.

Furthermore, a sound transducer for converting underwater sound waves into an electrical signal is shown, which has the device described for converting the underwater sound waves.

Furthermore, a method for producing an intermediate product of a piezocomposite ceramic is disclosed with the following steps: additive manufacturing of a piezoceramic as a raised structure which is defined by a trench, introduction of a filler material into the trench in order to obtain an intermediate product of the piezocomposite ceramic. One method of additive manufacturing is 3D printing. The additive manufacturing can take place by means of a powder of a piezoceramic material. Additive manufacturing makes it possible to create elevation structures of any shape. In particular, a wall slope of the elevation structure, and thus also of the trench, can have a variable wall slope. The limitations associated with the sawing process for wafers are thus eliminated. Typically, a large number of elevation structures are manufactured simultaneously using additive manufacturing. These can be (mechanically) connected to one another by a common basic element. After the filling material has been introduced (and hardened), the common base element can then be removed in order to form the piezocomposite ceramic. The connection of the basic elements to one another is then carried out by the filling material. In exemplary embodiments, the filler material is a plastic. This can be liquefied and introduced into the trench, where it then hardens and completely or at least partially fills the trench. The trench can form a matrix. The piezoceramic, i.e. in particular the elevation structures with the filled trench or the matrix, is also referred to as piezocomposite ceramic.

• 1: eine schematische Seitenansicht einer Piezokeramik mit drei Erhebungsstrukturen, die durch einen Graben mit einer variablen Wandsteigung definiert sind;
• 2: eine schematische Draufsicht der Piezokeramik aus 1; und
• 3: eine schematische Darstellung eines Schallwandlers in einer seitlichen Schnittdarstellung.

Preferred exemplary embodiments of the present invention are explained below with reference to the accompanying drawings. Show it:

• 1 : a schematic side view of a piezoceramic with three elevation structures which are defined by a trench with a variable wall slope;
• 2 : a schematic plan view of the piezoceramic 1 ; and
• 3rd : a schematic representation of a sound transducer in a lateral sectional view.

Before exemplary embodiments of the present invention are explained in more detail below with reference to the drawings, it is pointed out that identical, functionally identical or identically acting elements, objects and / or structures in the different figures are provided with the same reference numerals, so that those shown in different exemplary embodiments Description of these elements is interchangeable or can be applied to one another.

1 shows a schematic side view of a device 20th of the page, 2 from above in plan view. The device initially comprises only one piezoceramic as elevation structures 24a, 24b and 24c. The survey structures 24 , also known as chopsticks, are passed through a ditch 26th limited. Interface between elevation structure 24a and trench 26th forms a wall 28a and a wall 28b of the elevation structure 24a. The same applies to the further elevation structures 24b, 24c. The walls 28a, 28b have a variable wall slope. In the case of the elevation structure 24a, the wall is S-shaped. The elevation structures 24b, 24c have a taper at a distance from a base point of the elevation structure and a highest point of the elevation structure. The shape of the elevation structures 24b, 24c is also referred to as a fly shape. The base of the elevation structure is located at the transition between elevation structure 24a, 24b, 24c and a base element 30th . The basic element 30th can also have the piezoceramic material. The device 20th can therefore be viewed as an intermediate product for the manufacture of a piezo composite ceramic.

The highest point of the elevation structure is located in the thickness direction at the opposite end of the base point. At the highest point of the elevation structure and at the base point, electrodes for contacting the piezocomposite ceramic can be arranged. If the basic element 30th is designed to be electrically conductive, the electrode can also be arranged on the base element instead of at the base.

The trenches are used to preserve the piezocomposite ceramic 26th filled and the basic element 30th removed, especially cut off. Are the trenches 26th filled, and the basic element made of piezoceramic removed, the piezocomposite ceramic can be placed on a (further) basic element as a carrier (cf. 3rd ). In order to set a resonance frequency, the height of the piezocomposite ceramic can also be adjusted, for example by grinding.

The ditch 26th can also be filled, in particular encapsulated, by means of a filler material, for example a plastic (cf. 3rd ). After the casting, the basic element is removed, in particular cut off. The device 20th (with cast trenches and removed base element) is then referred to as piezocomposite ceramic. Typically the device 20th an array of the elevation structures. The individual elevation structures are then typically of the same type, ie have the same shape. However, a mixture of different types of elevation structures or different sizes of elevation structures as in 1 and 2 shown to be used advantageously. Thus, a piezocomposite ceramic can have elevation structures with different resonance frequencies, so that a frequency response of the piezocomposite ceramic can be individually adapted, in particular smoothed.

3rd shows a schematic representation of a sound transducer 32 , for example a sound transmitter or a hydrophone. The transducer 32 has a plurality of the devices 20a, 20b, 20c, 20d. The device 20a has the base element 30a on which the raised structures 24a, 24'a, 24''a are arranged. The devices 20b, 20c and 20d are constructed accordingly. The filling material is between the elevation structures 34 arranged. If elevation structures are arranged on two adjacent piezoceramics, this is due to the schematic representation and the associated inaccuracy in the drawing. Instead of using different basic elements, the piezocomposite ceramics can also be arranged on a common basic element. The basic element is designed, for example, to reflect hard sound waves or to absorb interference waves.

The sound transducer can have any shape, for example spherical, hemispherical, linear. For better illustration, only a small number of the survey structures shown were shown. A density of the elevation structures of the piezocomposite ceramic is, for example, more than 10 elevation structures per square centimeter, more than 50 elevation structures per square centimeter or more than 99 elevation structures per square centimeter.

Each piezoceramic can have its own contact. The output signal of the sound transducer can, however, be a sum signal of the individual contacts.

In order to emit sound waves, the same voltage can also be applied to the contacts, i.e. the same voltage curve over time.

Although some aspects have been described in connection with a device, it goes without saying that these aspects also represent a description of the corresponding method, so that a block or a component of a device is also to be understood as a corresponding method step or as a feature of a method step. Analogously to this, aspects that have been described in connection with or as a method step also represent a description of a corresponding block or details or features of a corresponding device.

The embodiments described above are merely illustrative of the principles of the present invention. It is to be understood that modifications and variations of the arrangements and details described herein will be apparent to other skilled persons. It is therefore intended that the invention be limited only by the scope of protection of the following patent claims and not by the specific details presented herein with reference to the description and explanation of the exemplary embodiments.

List of reference symbols

20th

contraption

24

Survey structure

26th

dig

28

wall

30th

Basic element

32

Transducer

34

filling material

Claims (14)

Device with the following features: a piezoceramic as an elevation structure, the elevation structure being defined by a trench, the elevation structure having a wall with a variable wall slope. Device according to Claim 1 , wherein the trench is filled with a filler material. Device according to one of the preceding claims, wherein the trench is selected in such a way that it completely encloses the elevation structure. Device according to one of the preceding claims, wherein the device has a base element, the elevation structure rising from the base element starting from a base point of the elevation structure. Device according to one of the preceding claims, wherein the elevation structure forms an S-shape. Device according to one of the preceding claims, wherein the elevation structure has a taper at a distance from a base point of the elevation structure and a highest point of the elevation structure. Device according to one of the preceding claims, wherein the piezoceramic has a further elevation structure, wherein the further elevation structure differs in its shape from the elevation structure. Device according to one of the preceding claims, wherein the wall has a first slope in a first section of the wall and has a second slope in a second section of the wall. Piezo composite ceramics with the following features: a plurality of bump structures each comprising a piezoceramic material; a filler material which at least partially encloses the elevation structures; wherein the elevation structure has a wall with a variable wall slope. Sound transducer for converting underwater sound waves into an electrical signal, the sound transducer comprising the device according to one of the Claims 1 to 8th or the pieozocomposite ceramic according to Claim 9 having. Process for the production of an intermediate product of a piezocomposite ceramic with the following steps: Additive manufacturing of a piezoceramic as a raised structure that is defined by a trench, Introducing a filler material into the trench in order to obtain an intermediate product of the piezocomposite ceramic. Procedure according to Claim 11 , wherein the filling material is a plastic. Method according to one of the Claims 11 or 12th , wherein the trench has a variable wall slope. Method according to one of the Claims 11 to 13th , with removal of a basic element from the elevation structure in order to preserve the piezocomposite ceramic.

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