Electroacoustic transducer

Abstract

According to the invention, the electroacoustic transducer (1) has a plurality of piezoelectric elements (2) which are arranged in a holder (3) in recesses in which the piezoelectric element (2) is held positively in the circumferential direction. Furthermore, holding means which positively engage over the piezo elements (2) at their end faces (9) and thus hold them are provided. After wiring, this structure is then embedded in a hardening plastic potting compound (4).

Description

Title: Electroacoustic Transducer Description

[0001] The invention relates to an electroacoustic transducer having the features specified in the preamble of claim 1.

[0002] Electroacoustic transducers of the aforementioned type are used in particular for generating shock waves for medical and other applications. Such a transducer consists of a large number of piezoelectric elements arranged side by side, e.g., in a dome shape, in one or more planes, thus forming a self-focusing transducer. Numerous transducer configurations are known, which, for example, are linear, ring-shaped, point-shaped, or non-focusing.

[0003] It is state of the art to glue the piezoelectric elements to the inside of a metal dome, whereby the metal dome forms the support for the later transducer and simultaneously establishes the electrical connection on one side of the piezoelectric elements, whereas wiring takes place on the other side and the piezoelectric elements are subsequently embedded in a potting compound.

[0004] In this respect, a design such as that described in DE 102010055836 B4, which is considered prior art, is more advantageous. In this so-called carrier-less design, the carrier essentially serves assembly purposes, i.e., it holds the piezoelectric elements before the potting compound, which forms the actual carrier, is applied. The flat holder (referred to there as the carrier), which accommodates the piezoelectric elements, contains through- through-holes are provided, into which a piezo element is inserted, which is clamped in the through-holes or held in a form-fitting manner on the carrier between two shrink tubing sections which are attached to the piezo element.

[0005] This arrangement has the disadvantage that inserting and aligning the piezoelectric elements within the flat holder is labor-intensive. Furthermore, the alignment of the piezoelectric elements within the holder can be inaccurate, which should be avoided.

[0006] Against this background, the invention is based on the objective of designing a generic electroacoustic transducer in such a way as to avoid the aforementioned disadvantages.

[0007] This problem is solved according to the invention by an electroacoustic transducer with the features listed in claim 1. Advantageous embodiments of the invention will become apparent from the dependent claims, the following description, and the drawings.

[0008] The electroacoustic transducer according to the invention comprises a plurality of piezoelectric elements arranged in one or more holders, wherein recesses or retaining elements are provided on the holder side, each of which positively surrounds a piezoelectric element at least partially. According to the invention, the one or more holders have retaining means which positively hold the piezoelectric elements at their end faces.

[0009] The basic idea of ​​the present invention is to not only fully enclose the piezoelectric elements in a form-fitting manner through the holder(s). Not only should the piezoelectric elements be accommodated, but retaining means should also be provided that hold the piezoelectric elements securely at their end faces, thus ensuring a defined position relative to the holder and therefore proper positioning within the transducer. It is particularly advantageous to provide the retaining means on the holder side, as the holder itself then defines the positioning of the piezoelectric elements, eliminating the need for any further preparation on the part of the piezoelectric elements. The holder is therefore solely responsible for the defined arrangement of the piezoelectric elements; piezoelectric elements can thus be inserted into the holder without any preparation or adjustment. After inserting the piezoelectric elements into the holder, the following steps are then taken:The electrical contacts on the end faces are made in the holders, for example by soldering with suitable connecting wires, after which the potting can take place to create a self-supporting, typically (frameless) transducer. The holder(s) primarily serve to fix the piezoelectric elements during manufacturing.

[0010] According to a further development of the invention, it is particularly advantageous if the retaining means have arms that preferably engage the end faces of the piezoelectric elements in a form-fitting manner. Each retaining means has at least one such retaining arm. These retaining arms are particularly advantageous because, with a suitable slim and elastic design, they facilitate the simple insertion of the piezoelectric elements into the respective holder, while simultaneously securing the respective piezoelectric element in the holder in a defined position in all directions after this process. Furthermore, these retaining arms provide sufficient clearance not only during installation but also during electrical connection, e.g., when soldering the connecting wires to the end faces.

[0011] In an advantageous embodiment of the invention, at least one pair of retaining arms is provided for each piezoelectric element, with one arm encompassing one end face and another arm encompassing the other end face. Such a pair of retaining arms is advantageously arranged parallel to the longitudinal axis of a piezoelectric element. If the holder is a substantially planar element with recesses or retaining elements, these retaining arms advantageously extend substantially perpendicular to the planar holder or to the retaining elements forming it. Advantageously, the retaining arms of a pair of retaining arms are aligned with each other; however, they can also be arranged offset from each other.

[0012] At least one of the retaining arms of such a pair can also be slightly inclined to facilitate the insertion of the piezoelectric element into the holder. According to an advantageous embodiment, at least one of the retaining arms of a pair of retaining arms is spring-elastic, so that it can deflect laterally outwards and be tensioned to allow the insertion of the piezoelectric element into the holder, thus enabling the piezoelectric element to be freely inserted into the recess of the holder or into the retaining element of the holder in the direction of the longitudinal axis of the piezoelectric element.The piezoelectric element is advanced until one end face of the piezoelectric element is axially engaged with the end of one arm of the holding arm pair, and the other holding arm then returns to its original position after insertion of the piezoelectric element by springing back, in which its end positively engages the other end face of the piezoelectric element and thus the piezoelectric element is positively locked in the holder in all directions.

[0013] In order to insert a piezoelectric element into the holder by simple axial insertion and simultaneously secure it positively in this holder, it is advantageous if the retaining arm is designed to be spring-elastic. The portion of the holder that overlaps the end face of the piezoelectric element has an inclined contact surface. When the piezoelectric element is inserted axially into the holder, aligned with the recess or the retaining element, this inclined contact surface causes the overlapping portion of the retaining arm to be spring-loaded outwards relative to the recess until the piezoelectric element is in its intended position within the holder. The retaining arm then springs back, and its end face engages the piezoelectric element, thus securing it axially. This arrangement is particularly advantageous for automated but also for simple manual installation.

[0014] Advantageously, a piezoelectric element is secured in the holder by two or more, preferably three, pairs of retaining arms evenly distributed around its circumference. Such an arrangement allows, on the one hand, easy axial insertion of the piezoelectric element into the holder and, on the other hand, guarantees a precise fit within the holder as well as free access to the end faces for contacting.

[0015] Advantageously, a piezoelectric element is completely covered with an insulating sleeve, preferably a heat-shrink tube. Such an insulating sleeve increases the dielectric strength and, unlike in the prior art, can be attached and fixed to the piezoelectric element before it is mounted in the holder.

[0016] Cylindrical piezoelectric elements, which have a circular cross-section, are advantageously used. However, piezoelectric elements with a polygonal cross-section can also be used. the end faces should preferably be flat and arranged transversely to the longitudinal axis.

[0017] The holder(s) are advantageously designed as plastic components. Particularly when producing smaller quantities, it is beneficial to manufacture these components using 3D printing. A holder is typically understood to be a flat component with recesses for receiving the piezoelectric elements. Alternatively, the holder can be formed by a grid-like, flat structure, with the grid portions surrounding a piezoelectric element forming a retaining element. The retaining arms are then advantageously attached to this retaining element.

[0018] From both a mounting and connection perspective, it is advantageous if the electrical connections of the piezoelectric elements are located on their end faces. This also results in a comparatively high dielectric strength, both without and further improved with the use of an insulating sleeve.

[0019] To complete the electroacoustic transducer, the holder(s) with the integrated piezoelectric elements are embedded in a hardening compound, preferably plastic. The holder(s) also serve to position the piezoelectric elements relative to each other, but after the surrounding plastic has hardened, they generally no longer have a load-bearing function. However, in an advantageous embodiment according to the invention, the holder(s) can form a kind of reinforcement for the composite material within the hardening compound, thereby improving the service life of the electroacoustic transducer thus formed.

[0020] To apply the potting compound, the module(s) already equipped with piezoelectric elements and wired are arranged in a mold, which can also be advantageously produced using 3D printing. This mold can either be removed after the compound has cured or become part of the final transducer. The mold and holder are expediently designed and coordinated so that they interlock securely and can be mounted in the position they will occupy after the compound has cured.

[0021] The invention is described in more detail below using an exemplary embodiment. The figures show: Fig. 1 shows a section of a holder with piezo elements arranged therein in a sectional view, Fig. 2 shows the arrangement of the fully assembled holder section within the electroacoustic transducer in sectional view. Fig. 3 shows an alternative arrangement of support arm pairs in an enlarged top view and Fig. 4 shows a preferred embodiment of a pair of retaining arms on the support as depicted in Figure 1.

[0022] Fig. 2 shows a section of a self-supporting transducer dome of a piezoelectric shock wave source, as described, for example, in DE 10 2010 055 836 B4 with reference to Fig. 1 or 5. This is a self-focusing electroacoustic transducer 1. which is composed of a multitude of piezoelectric elements 2 arranged in a holder 3 and connected by a hardening potting compound 4 to form a self-supporting structure. In the illustrated embodiment, the piezoelectric elements 2 have a cylindrical shape and are arranged in recesses 5 of the planar holder 3, which is essentially transverse to the longitudinal axes 8 of the piezoelectric elements 2. The holder 3 follows the dome shape, so that all piezoelectric elements 2 are arranged at the same distance from a focal point not visible in the drawing.

[0023] The holder 3 essentially serves to hold the piezoelectric elements 2 in their designated position before they are encased with the potting compound 4. The recesses 5 are designed and arranged to accommodate the piezoelectric elements 2 with minimal play, ensuring both easy assembly and a secure, form-fitting fit.

[0024] In the area of ​​the recesses 5, the holder 3 has retaining means, specifically, in the embodiment shown in Figures 1 and 2, in the form of retaining arm pairs 6, 6 and guide arm pairs 7, 7. Each arm pair 6, 6; 7, 7 extends from the edge of a recess 5 to one side of the flat holder 3 essentially in a direction parallel to the longitudinal axis 8 of a piezoelectric element 2. The guide arms 7 extend only to near the end faces of the piezoelectric elements 2; a guide arm pair 7, 7 is thus shorter than the extent of a piezoelectric element 2 in the direction of its longitudinal axis 8. The retaining arm pairs 6, 6, on the other hand, extend beyond the end faces 9 of a piezoelectric element 2 and, with their ends 10, overlap the end faces of a piezoelectric element 2, thereby securing it axially to the holder 3 in a form-fitting manner.

[0025] Each retaining arm 6 is designed at its free end such that it projects slightly beyond the end face 9 of the associated piezoelectric element 2, thus holding the piezoelectric element 2 in a positive-locking manner in the axial direction. Each retaining arm 6 is designed such that its end 10 can spring radially outward relative to the associated piezoelectric element 2, allowing the piezoelectric element 2 to be guided past this end 10, inserted through the recess 5, and advanced until it abuts the end 10 of the opposite retaining arm 6. The other retaining arm 6 then automatically returns to its original position due to spring force, so that the piezoelectric element 2 is positively locked in the axial direction by the two ends 10 of the retaining arm pair 6, 6.

[0026] In principle, the arrangement of a pair of retaining arms 6, 6 on a recess 5 or a corresponding circumferential retaining element of the holder 3 is sufficient to ensure a defined position of the piezoelectric element 2 in relation to the holder 3. However, it is advantageous to provide at least one pair of guide arms 7, 7 or another pair of retaining arms 6, 6.

[0027] In the embodiment according to Fig. 3, three pairs of retaining arms 6, 6a are provided, which are arranged symmetrically around the recess 5 and whose ends 10 and 10a each overlap the end faces 9 of the piezoelectric element 2. This design allows for secure positioning and also ensures that the end-face contacts 11 are easily accessible and can thus be soldered to the connecting wires 12, which are to be made after the piezoelectric elements 2 have been inserted into the recesses 5 of the holder 3, before the potting compound 4 encloses the assembly.

[0028] Figure 4 shows a side view of a pair of retaining arms 6, 6a from Figure 3, in which the end 10a of one retaining arm 6a (the upper end in Figure 4) is provided with a contact surface 13 which runs obliquely to the longitudinal axis of the retaining arm 6, which is arranged such that when a piezo element 2 is inserted, it hits the contact surface 13 and when further moved in the direction of its longitudinal axis 8, this contact surface 13 is pushed radially outwards, i.e. springily towards the retaining arm 6a. Therefore, no separate handle is needed to spring back the retaining arm 6a when inserting the piezo element 2; instead, this happens automatically through the feed force of the piezo element 2 in the direction of its longitudinal axis 8, just as this end 10a springs back after the piezo element 2 has passed through, thus holding the piezo element 2 positively between the ends 10 and 10a.

[0029] In order to avoid exerting lateral forces on the piezo element when inserting it into the holder 3, it is advantageous to arrange these retaining arms 6a with the contact surfaces 13 at their ends 10a point-symmetrically around the axis 8, as shown in Figure 3. Reference symbol list 1 electroacoustic transducer 2 pierceable elements 3 holders 4 potting compounds 5 exceptions 6 Support arm 6a Holding arm with contact surface 6, 6 pair of retaining arms 7 Guide arm 7.7 Guide arm pair 8 Longitudinal axis of 2 9 end faces of 2 10 End of 6 10a End of 6a 1 1 Contacts 12 wires 13 Approach area

Claims

Claims 1. Electroacoustic transducer (1 ) with a plurality of piezo elements (2) arranged in one or more holders (3), wherein recesses (5) or retaining elements are provided in the one holder (3) or the several holders (3) which each surround a piezo element (2) in a form-fitting manner at least partially, characterized in that the one or the several holders (3) have retaining means which hold the piezo elements at their end faces in a form-fitting manner.

2. Electroacoustic transducer according to claim 1, characterized in that the holding means have holding arms (6, 7) which preferably engage the end faces (9) of the piezo elements (2) in a form-fitting manner.

3. Electroacoustic transducer according to claim 2, characterized in that at least one pair of retaining arms (6, 6) is provided for each piezo element (2), with one arm (6) that covers one end face and with another arm (6) that covers the other end face.

4. Electroacoustic transducer according to claim 3, characterized in that at least one of the retaining arms (6, 6a) of a retaining arm pair (6, 6) is designed to be spring-elastic such that when a piezo element (2) is inserted into the holder (3) the part (10, 10a) of the retaining arm (6, 6a) that overlaps the end face can be springily pivoted out.

5. Electroacoustic transducer according to claim 4, characterized in that the spring-elastic retaining arm (6a) has an inclined starting surface (13) on its part (10a) which overlaps the end face of the piezo element (2).

6. Electroacoustic transducer according to one of the preceding claims, characterized in that a piezoelectric element (2) is fixed in the holder (3) with two or more, preferably three, retaining arm pairs (6, 6a).

7. Electroacoustic transducer according to one of the preceding claims, characterized in that the piezo elements (2) are circumferentially covered with an insulating tube, preferably a heat shrink tube.

8. Electroacoustic transducer according to one of the preceding claims, characterized in that the piezo elements (2) have a circular or polygonal cross-section and preferably flat end faces (9) arranged transversely to the longitudinal axis (8).

9. Electroacoustic transducer according to one of the preceding claims, characterized in that the one or more holders (3) are preferably formed by a plastic component which is manufactured by 3D printing.

10. Electroacoustic transducer according to one of the preceding claims, characterized in that the piezo elements (2) are electrically connected at the end face.

1. Electroacoustic transducer according to one of the preceding claims, characterized in that the one or more holders (3) with the piezo elements (2) arranged therein are embedded in a hardening mass (4), in particular plastic.

Images