DE102009046143A1 - Method for manufacturing ultrasonic converter utilized in e.g. ultrasonic flow meter in exhaust gas system of internal combustion engine of commercial vehicle, involves connecting housing part with sealing element during molding process - Google Patents

Abstract

The method involves accommodating a converter core (116) with an electric-acoustic converter element (118) in a housing (112), and sealing a radiation opening (128) of the housing against fluid medium (126) with a sealing element (134). A housing part is produced by a plastic molding process, and the sealing element is inserted into a molding cavity of a molding tool. The molding tool is filled with plastic material, and the housing part is connected with the sealing element during the molding process. An independent claim is also included for an ultrasonic converter comprising a sealing element for sealing a radiation opening of a housing.

Description

State of the art

From the prior art, a plurality of ultrasonic transducers for use in fluid media is known. In the context of the present invention, an ultrasound transducer is understood to mean an element which is able to emit ultrasonic signals into the fluid medium and / or to receive ultrasound signals from the fluid medium. Such ultrasonic transducers generally comprise a transducer core with at least one electrically-acoustic transducer element, ie an element which is able to convert electrical signals into acoustic signals (for example ultrasound signals) or vice versa. For example, these electrical-acoustic transducer elements may be electrical transducer elements, in particular piezo-ceramic transducer elements. Furthermore, the transducer cores may comprise impedance matching bodies, that is, one or more bodies whose acoustic impedance is between those of the electro-acoustic transducer element and that of the fluid medium to enable an improvement in the acoustic coupling of signals between the electro-acoustic and fluid media. Furthermore, the transducer cores may include additional elements, such as thermal matching bodies and / or adhesive layers. Such ultrasonic transducers are basically made, for example EP 0 766 071 A1 or off DE 42 30 773 C1 known.

The transducer cores are usually introduced into a housing which is intended to protect the transducer core, for example, against mechanical and / or chemical influences from the outside. In many cases, the housing has a radiation opening towards the fluid medium. In order to prevent the penetration of aggressive media into the interior of the housing and a possible possible damage or interference of the converter core, this opening must be sealed in the rule. An example of such a seal is a sealing foil. A difficulty of these seals, however, is that the sealing element must be connected to the rest of the housing. This connection can be done for example by means of an adhesive process. Alternatively, the sealing element can also be designed as a coating, which is applied to the front of the emission opening. However, these conventional processes for fixing the sealing element are often difficult to reproduce in practice and do not meet the high robustness requirements, especially in the automotive industry. In addition, the known methods are in many cases technically complex and thus sometimes associated with considerable costs.

Disclosure of the invention

Therefore, a method for producing an ultrasonic transducer for use in a fluid medium and an ultrasonic transducer for use in a fluid medium are proposed, which at least largely avoid the disadvantages of known ultrasonic transducers and methods. The ultrasonic transducers can be used in particular in ultrasonic flow meters (Ultrasonic Flow Meter, UFM). Examples of such ultrasonic flow meters are flow meters for the motor vehicle sector, in particular for use in the intake tract and / or exhaust tract of motor vehicle internal combustion engines, in particular in the commercial vehicle sector. Alternative applications are sensors for gases or liquids, for example in process engineering, applications in process control, applications as distance sensors, as level sensors or as flow sensors in the chemical and pharmaceutical industries, applications in medical technology, for example for respiratory gas monitoring or applications in power engineering, for example as Heat meters in power plants or in the household.

The ultrasonic transducer has a housing, in which at least one transducer core is accommodated with at least one electrically-acoustic transducer element. With regard to the possible embodiments of the converter core, reference may be made largely to the prior art described above. Thus, in principle, the converter cores known from the prior art can also be used in the context of the present invention. In the context of the present invention, a housing is to be understood as meaning an element which at least partially gives the ultrasound transducer an outer shape and which protects an interior of the ultrasound transducer at least largely from mechanical influences and preferably also from chemical and optionally electromagnetic influences. The housing may for example be wholly or partly made of a plastic material. Alternatively or additionally, other materials can be used. Since the method described below is based essentially on the use of a plastic molding process, basically at least one housing part should be wholly or partially made of a plastic material.

The housing is designed such that at least one emission opening of the housing is sealed off from the fluid medium with at least one sealing element. In this case, an emission opening is to be understood as meaning an opening which assigns the fluid medium, via which ultrasound signals are emitted from the converter core to the fluid medium and / or taken up from the fluid medium can be. For example, the emission opening may comprise a round housing opening and / or a polygonal housing opening into which, preferably centrically, an emission surface of the converter core is introduced.

Under a sealing element is to be understood an element which prevents at least largely penetration of the fluid medium in an interior of the housing in which the transducer core is received. In particular, penetration of moisture and / or aggressive media can be prevented in this way. In addition, a pressure load of the interior can be at least reduced. It is particularly preferred if the sealing element, as explained in more detail below, comprises at least one sealing film, which spans the emission opening at least partially, preferably completely. Under a sealing film is to be understood a film element, which has the said sealing properties of the sealing element and which has flexible properties. The lateral extent of the sealing film should exceed its thickness by at least a factor of 10, preferably by at least a factor of 100 and more preferably by a factor of 1000 or more.

In the method according to the invention, a plastic molding process is used to produce at least one housing part of the housing. For example, this plastic molding process may be an injection molding process. Alternatively or additionally, however, other, known in the art plastic molding processes can be used, for example, casting processes, transfer molding processes or the like. In the plastic molding process, the sealing element is inserted into a mold cavity of a forming tool. In this case, a cavity of the tool is to be understood as a cavity of the mold which, at least in part, determines the outer shape of the manufactured component after the plastic molding process. A tool can also include several mold cavities. The sealing element can be completely introduced into the mold cavity or only partially, so that, for example, parts of the sealing element can be arranged outside of the mold cavity. Again alternatively, the sealing element can also be inserted into a plurality of mold cavities.

After insertion, the mold cavity is at least partially filled with at least one plastic material. As stated above, this can be done for example by means of an injection molding process. Other methods are possible. During this filling, the plastic material gets in contact at least in places with the sealing element inserted in the mold cavity. Accordingly, the housing part of the housing is connected to the sealing element during the plastic molding process, for example during curing. This compound can be done in particular directly Lind directly and without intermediate elements. In particular, in the plastic molding process, the sealing element and the housing part can be non-positively and / or positively connected with each other.

According to the method described above, an ultrasonic transducer is proposed for use in a fluid medium, which can be produced by a method according to the above description or according to one of the method variants described below. The ultrasonic transducer comprises a housing with at least one housing part, wherein the housing part is connected in a plastic molding process directly non-positively and / or materially connected to a sealing opening of the housing sealing sealing element.

For example, the proposed method and proposed ultrasonic transducer may include a transducer core having a piezoceramic and an impedance matching body. As a sealing element, as shown above, in particular a sealing film can be used. The at least one housing part may for example be a plastic carrier part, for example with a frame shape, a ring shape or a cup shape. Various embodiments will be described in more detail below. The plastic carrier member may act as or serve as part of the entire converter housing. By means of the proposed method, a direct frictional and / or cohesive connection between the sealing film and the plastic carrier part can be produced. This connection can be realized in particular by an injection molding process for the plastic material with the sealing film as an insert. Due to the direct frictional connection, a dense transition between the transducer core as an ultrasonic coupling body and the housing, in particular the plastic housing part, for example, the plastic frame given. In particular, the use of an injection molding process or another injection process is reproducible even in mass production, and is more robust and less expensive to implement than conventional adhesive processes. The use of a plastic housing part as a plastic carrier part allows a specific embodiment of the interfaces to other components of the ultrasonic transducer and / or the installation environment of the ultrasonic transducer.

If a sealing film is used, this sealing film can in particular have a total thickness of less than 100 .mu.m, preferably of less than 50 microns, and more preferably less than 20 microns. The sealing film can also be configured as a multi-layer sealing film, wherein different layers, for example, can fulfill different functions. For example, at least one layer can ensure mechanical stability, while at least one further layer can provide increased impermeability, for example to moisture. The sealing film may be a thermoplastic material or a thermosetting material, in particular one or more of the following materials: polyimide, in particular Kapton ^®; a fluorinated polymer, especially a polytetrafluoroethylene (PTFE), ^Teflon® ; a polyvinyl fluoride (PVF); a polyetheretherketone (PEEK); a polymethylmethacrylate (PMMA); a polyamide-imide (PAI); a liquid crystal polymer (LCP); a polyethersulfone (PES); a polysulfone (PSU); a polyethylene naphthalate (PEN); a polyphenylene sulfide (PPS); a fluorinated ethylene-propylene (FEP); a metallic, plastic or ceramic coating; an adhesive layer. Combinations of these materials and / or other materials are possible.

In the plastic molding process, in particular a part of the plastic material can be arranged on a side facing away from the fluid medium side of the sealing element and another part of the plastic material on a side facing the fluid medium side of the sealing element. This can be realized in different ways. For example, the plastic material can reach through the sealing element, in particular the sealing film, during the plastic molding process. For this purpose, the sealing element can for example have a plurality of openings through which the plastic material can pass in the plastic molding process. Alternatively or additionally, in the plastic molding process, a part of the plastic material can encompass an edge of the sealing element in time. Overall, different types of connection between the sealing element and the housing part can be realized in this way, which partially represent mixed forms of a cohesive and a positive and / or non-positive connection. In addition to the connection between the sealing element and the housing part produced by the injection process, transition regions between the sealing element and the housing part can be subsequently sealed with an adhesive. This is particularly advantageous if there is a risk that forms a creepage path for aggressive media between the sealing element and the housing part. This can occur in particular when the sealing element has a surface against which the housing plastic builds up a low adhesion.

The housing part may in particular comprise one or more of the following housing parts: a housing sleeve; a housing ring, a housing frame. The housing part can make up the entire housing or can only make up a part of this housing and be connectable to other housing parts. The connection with other housing parts can be made by various methods, for example cohesive methods such as bonding methods and / or other connection methods, such as laser welding and / or ultrasonic welding or similar joining techniques.

The converter core or a part of the converter core may in particular be in direct or indirect contact with the sealing element. Thus, the converter core or a part of the converter core can be connected to the sealing element, in particular the sealing film, in particular before or after the plastic molding process. For this connection, in particular a cohesive connection method can be used, for example an adhesive method. For example, before or after the shaping process, an impedance matching body can be glued onto the sealing film. If this is done before the molding process, for example, a shaping tool can be used to accommodate the transducer core or a part of the transducer core, in particular with a tolerance compensation. For example, a tool can be used which has a punch for tolerance compensation. Preferably, the electrical-acoustic transducer element is applied only after the plastic molding process in order not to expose the electro-acoustic transducer element to the high temperatures occurring in conventional plastic molding processes.

After the plastic molding process, the sealing element can be subjected to further process steps in which the final shape of the sealing element is influenced. Thus, in particular after the plastic molding process, at least one region of the sealing element, in particular an edge region, can be removed. Various embodiments of such removal will be described below. The sealing element may alternatively or additionally also be influenced during the shaping process in its shape. For example, the sealing element in the forming tool can be subjected to a deep-drawing process. The shaping tool can be shaped accordingly and for example tempered accordingly.

After the plastic molding process, further process steps can follow. For example, according to the plastic Shaping process at least one damping element can be introduced in an interior of the housing. For example, this at least one damping element comprise at least one damping mass. This damping mass can be introduced for example in a casting process, in particular in the form of a Dämpfungsvergusses. Alternatively or additionally, inserts can also be used. Furthermore, the damping element may comprise at least one decoupling element. The damping element can be at least partially produced by a liquid silicone rubber process (Liquid Silicone Rubber, LSR).

The method may include further method steps beyond the method steps described above. For example, the sealing element may be subjected to at least one activation step before the plastic molding process, for example, before or even after insertion into the forming tool. In particular, this activation step may serve the purpose of improving adhesion between the housing part and the sealing element and / or facilitating subsequent application of the transducer core to the sealing element. This activation step may in particular comprise a plasma treatment and / or a corona treatment. Other activations are alternatively or additionally possible, for example chemical activations.

Brief description of the drawings

Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description.

Show it:

1 a schematic structure of a conventional ultrasonic transducer sectional view;

2 to 7 Method steps of a first embodiment of an inventive method for producing an ultrasonic transducer;

8th to 12 to the process step according to 7 alternative additional process steps;

13 to 15 to the method steps according to the 2 and 3 alternative process steps; and

16 to 18 further to the method step according to 3 alternative process steps.

embodiments

In 1 is a basic structure of a possible ultrasonic transducer as a basis for the invention described below 110 shown in a sectional view from the side. The ultrasonic transducer 110 includes a housing 112 , For example in the form of a housing sleeve. In an interior 114 of the housing 112 is a converter core 116 introduced, the an electric-acoustic transducer element 118 , and optionally an impedance matching body 120 and, further optionally, one between the impedance matching body 120 and the electro-acoustic transducer element 118 introduced leveling layer 122 and / or gluing. The electric-acoustic transducer element 188 may include, for example, a piezoceramic. This can be done via the leveling layer 122 or the bond with the impedance matching body 120 be connected, which a Schallkopplung with over a radiating surface 124 with a fluid medium 126 facilitated. The radiating surface 124 of the converter core 116 is in a radiation opening 128 of the housing 112 recorded, which from a margin 130 of the housing 112 is surrounded annularly. To after the transmission, the ringing of the electric-acoustic transducer element 118 , For example, the piezoelectric element, time limit, is the ultrasonic transducer 110 in his interior 114 , For example, within the housing sleeve 112 wholly or partly with a damping mass 132 filled. To improve the resistance to chemicals, moisture or aggressive media, the ultrasonic transducer 110 on the side of the emission opening 128 with a sealing element 134 , in particular in the form of a coating or a sealing film 136 be provided. In some ultrasonic transducers 110 According to the prior art, between the damping mass 132 and the housing 112 In addition, an additional decoupling material are used.

Basically, as a connection technology between sealing film 136 and housing 112 , in particular the housing sleeve, adhesive method can be used. However, these are not necessarily optimal in terms of mass production and robustness. In the case of a coating as a sealing element 134 In principle, methods are known in which the coating, for example, as a paint or in a vacuum process (for example, Parylene) directly frictionally on the ultrasonic transducer 110 is applied. However, this procedure leads to a mechanically less robust sealing layer, in particular in transition areas between different materials such as the impedance matching body 120 , the damping or decoupling and the housing 112 , At this Transition areas can exert strong shear forces on the coating during thermomechanical loading so that it can rupture.

These disadvantages are in a method according to the invention for producing an ultrasonic transducer 110 avoided, which is described below in different variants of the method. In principle, an ultrasonic transducer 110 according to 1 or other ultrasonic transducers 110 ,

In the 2 to 7 a first embodiment of a manufacturing method according to the invention is shown. 2 shows a schematic diagram of a forming tool 138 , For example, an injection mold with at least one mold cavity 140 , The sealing foil 136 thus becomes the forming tool 138 in that at least a portion of the sealing film 136 in the area of mold cavities 140 is arranged. The mold nests 140 later determine the shape of the case 112 or a housing part produced in this method step 142 of the housing 112 (see for example 4 ). In an in 3 illustrated method step is a plastic material 144 in the form of a plastic mass, for example at high pressure and high temperature, in the mold cavity 140 injected so that the plastic material 144 to the sealing film 136 annetzt and enters into a firm connection with this. In 4 is shown a demolding, in which two tool parts 146 . 148 be ascended.

After demolding in 4 can the protruding sealing foil 136 be further processed. For one thing, as in 4 by the reference number 150 is designated, a supernatant of the sealing film 136 outside the emission opening 128 remain. Alternatively, the sealing film 136 also be completely or partially removed, for example by punching or laser machining. This can be done in different places. For example, removal can be done on the edge 152 of the housing 112 take place or, alternatively, in Anspritzbereich 154 of the plastic material 144 so that the sealing film 136 not completely to the edge 152 the housing sleeve 112 sufficient. Again alternatively or additionally, the unneeded foil area may also be removed elsewhere within the overall process sequence.

Subsequently, as in 6 is shown, the converter core 116 on the sealing foil 136 be applied. This can also be done step by step, for example by first of all the impedance matching body 120 on the sealing foil 136 is adhered, followed by the electro-acoustic transducer element 118 , optionally with the leveling layer 122 or adhesive layer. Alternatively, an application as a common assembly is possible. The converter core 116 is before or after application to the sealing film 136 through electrical contacts 156 contacted. The contacting takes place before or after the bonding.

Anschießend can, as in 7 is shown, a damping mass 132 , For example, in the form of a Dämpfungsvergusses be introduced. For example, it is possible to use silicone, polyurethane and / or epoxides for this purpose, in which case solid or hollow fillers or gas inclusions can optionally be mixed in.

Alternatively or in addition to a complete or partial introduction of the converter core 116 after injection molding of the housing part 142 can also have one already with the converter core 116 or parts of the converter core 116 equipped sealing foil 136 for example, one already with an impedance matching body 120 equipped sealing foil 136 into the forming tool 138 be inserted. This is in the 5A and 5B shown. Here is one already with the matching body 120 and optionally the leveling layer 122 equipped sealing foil 136 in the forming tool 138 inserted. Either the impedance matching body can 120 previously on the sealing film 136 glued or the firm connection between impedance matching body 120 and sealing film 136 will be set up during the spraying process. A tolerance compensation, for example, by an additional stamp 158 from underneath ( 5A ) or from above ( 5B ), so that such a stamp 158 For example, part of the tool part 148 and / or the tool part 146 can be.

Alternative to the simple damping mass 132 according to the in 7 illustrated embodiment, the damping mass 132 be designed more complex or multi-part. Thus, as an alternative or in addition to the damping encapsulation, it is also possible to use another substance or another component (see reference numeral 160 in 10 ) are used to improve structure-borne sound decoupling. These can be introduced for example as moldings, in a casting process or for large-scale production particularly advantageous in a further injection process. One possibility for this is provided by a so-called LSR process (LSR: liquid silicone rubber, liquid silicone rubber). The injected substance, in particular the LSR, can optionally be filled with gas bubbles or gas-filled plastic hollow spheres. A corresponding tool design of the necessary shaping tool 138 is in 8th (before injection) or in 9 (during or after injection), whereas 10 a demolding process after the injection shows. The required forming tool 38 can be completely or partially identical to the component forming tool for the manufacture of the housing part 142 be. Alternatively or additionally, however, shaping tools can also be used. After injecting the raw mass of the structure-borne sound decoupling 160 in 9 and demolding according to 10 then, in turn, optionally further elements of the converter core 116 be applied, for example, the electric-acoustic transducer element 118 , This is in 11 shown. Also the electrical contacts 156 can be applied. Subsequently, the ultrasonic transducer 110 , as in 12 shown with damping mass 132 be poured out.

Another method variant which can also be used in one of the methods described above is that in the forming tool 138 for the housing part 142 , For example, the transducer sleeve, not only in one of the tool parts 146 . 148 cavities 150 to provide in the form of moldings, but in both tool parts 146 . 148 , and the sealing film 136 between both tool parts 146 . 148 contribute. This process variant is in 3 shown. Here, both the upper tool part 146 as well as the lower tool part 148 corresponding formations in the form of mold cavities 140 on, which thus above and below the inserted sealing film 136 are arranged. Will a sealing film 136 inserted, which in the same position one or more perforations 162 has, as in 14 exemplified, then through these perforations 162 during the injection process plastic material 144 pass through and the sealing film 136 thereby fix positively. This is in 15 shown. The perforation 162 can be in the form of holes or slits or other contours that improve the fit. These contours can be, for example, by laser processing, punching, cutting, etching processes or other processes in the sealing film 136 be generated.

Alternatively, the sealing film 136 , with or without perforations 162 or similar contouring, at the lateral edge are also completely or partially encapsulated. This is in 16 shown. Again, both have the upper tool part 146 as well as the lower tool part 148 corresponding mold nests 140 but which are fluidly interconnected. This encapsulation of the edges of the sealing film 136 has the advantage that the film edge completely with plastic material 144 is enclosed, allowing potential creepage paths for aggressive media along the sealing film 136 can be largely suppressed.

Particularly advantageous is the combination of in 15 shown perforation 162 or other positive contouring and lateral encapsulation, as in 17 is shown. In this case, the sealing film 136 simultaneously non-positive and positive fit with the housing part 142 connected, and at the same time, the entire film edge of plastic material 144 enclosed.

18 finally shows a variant in which the housing part 142 in the form of a plastic carrier not as in the previous variants rather a sleeve it housing 112 corresponds, but actually has an annular frame shape. The housing part 142 is in this case as a frame-shaped frame 164 configured in the method of the sealing film 136 is stretched. Optionally, in turn, the Umspritzungsvarianten and / or injection variants according to one or more of 13 to 17 be used, optionally with a perforation 162 the sealing film 136 , The frame 164 can then with other components of the ultrasonic transducer 110 , in particular of the housing 112 , and / or the installation location for the ultrasonic transducer 110 be connected, for example, by gluing, laser welding, ultrasonic welding or the like. Also in this case can a stamp 158 Compensate for tolerances, as indicated by the arrow in 18 is symbolized, and / or it can, as variously described above, the converter core 116 in whole or in part, in particular the impedance matching body 120 , already miteingelegt, which is not shown in the figures.

In all in the 2 to 18 variants shown, as usual in injection molding, Auswerfergeometrien in the forming tool 138 integrated to improve demolding. The forming tool 138 can simultaneously be designed so that the sealing film 136 when approaching the forming tool 138 deep-drawn at the same time.

Another variant of the method consists in the use of a multilayer sealing film 136 , For example, thermosets can be combined with thermoplastics. It is conceivable, for example, a combination of a polyimide carrier film, which even at a thickness of less than 10 microns still has a relatively high thermal and mechanical stability, but it has weaknesses with respect to a Wasserdampfpermeation. As a further layer, a material which is as water vapor impermeable as possible can be used, for example ^Teflon® or fluorinated ethylene-propylene (FEP). In the case of air or other gases as a fluid medium 126 (Measuring medium) should be the total thickness of the sealing film 136 usually be significantly smaller than 100 microns, preferably less than 25 microns and optimally less than 10 microns, so as not to hinder an acoustic coupling too much. In the case of liquids as a fluid medium 126 can also tend to slightly thicker film thicknesses for the sealing film 136 be used.

Except polyimide and Teflon ^® come for the sealing film 136 or their constituents other substances in question. For example, let Kapton ^® JP (thermoformable polyimide), standard Kapton ^® or Kapton ^® HN (not suitable for deep drawing), Kapton ^® E (polyimide having a small thermal expansion coefficient of about 16 ppm / ° K), Kapton ^® EKJ (self-adhesive film with polyimide glue), PVF (polyvinyl fluoride, for example Tedlar ^® ES), PEEK, PMMA, PAI, LCP, PES, PSU, PPS, other plastics or metallic coatings. The sealing foil 136 may also include an adhesive coating, for example, a bond to the impedance matching body 120 to enable.

The injection molding process or, more generally, the plastic molding process can be a plasma or corona treatment of the sealing film 136 or other components of the ultrasonic transducer or another type of activation.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 0766071 A1 [0001]
• DE 4230773 C1 [0001]

Claims (11)

Method for producing an ultrasonic transducer ( 110 ) for use in a fluid medium ( 126 ), wherein the ultrasonic transducer ( 110 ) a housing ( 112 ), wherein in the housing ( 112 ) at least one transducer core ( 116 ) with at least one electrical-acoustic transducer element ( 118 ), wherein at least one emission opening ( 128 ) of the housing ( 112 ) relative to the fluid medium ( 126 ) with at least one sealing element ( 134 ) is sealed, wherein for the production of at least one housing part ( 142 ) of the housing ( 112 ) a plastic molding process is used, wherein the sealing element ( 134 ) in a mold nest ( 140 ) of a forming tool ( 138 ) and the mold nest ( 140 ) at least partially with at least one plastic material ( 144 ) is filled, wherein the housing part ( 142 ) of the housing ( 112 ) during the plastic molding process with the sealing element ( 134 ) is connected. Method according to the preceding claim, wherein in the plastic molding process the sealing element ( 134 ) and the housing part ( 142 ) are positively connected to each other and / or positively. Method according to one of the preceding claims, wherein the sealing element ( 134 ) a sealing film ( 136 ). Method according to one of the preceding claims, wherein in the plastic molding process a part of the plastic material ( 144 ) on a fluid medium ( 126 ) facing away from the sealing element ( 134 ) and another part of the plastic material ( 144 ) on a fluid medium ( 126 ) facing side of the sealing element ( 134 ). Method according to the preceding claim, wherein the sealing element ( 134 ) a plurality of openings ( 162 ), through which in the plastic molding process the plastic material ( 144 ) can pass through. Method according to one of the two preceding claims, wherein in the plastic molding process, a part of the plastic material ( 144 ) an edge of the sealing element ( 134 ) engages laterally. Method according to one of the preceding claims, wherein the transducer core ( 116 ) or part of the converter core ( 116 ) before or after the plastic molding process with the sealing element ( 134 ), in particular by a cohesive connection. Method according to one of the preceding claims, wherein after the plastic molding process at least a portion of the sealing element ( 134 ), in particular a border area, is removed. Method according to one of the preceding claims, wherein the sealing element ( 134 ) in the forming tool ( 138 ) is further subjected to a deep drawing process. Method according to one of the preceding claims, wherein the sealing element ( 134 ) is subjected to at least one activation step before the plastic molding process, in particular a plasma treatment and / or a corona treatment. Ultrasonic transducer ( 110 ) for use in a fluid medium ( 126 ), producible according to a method according to one of the preceding claims, wherein the ultrasonic transducer ( 110 ) a housing ( 112 ) with at least one housing part ( 142 ), wherein the housing part ( 142 ) in a plastic molding process directly frictionally and / or cohesively with a an emitting aperture ( 128 ) of the housing ( 112 ) sealing sealing element ( 134 ) connected is.

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