WO2023117374A1

WO2023117374A1 - Ultrasonic transducer with a housing

Info

Publication number: WO2023117374A1
Application number: PCT/EP2022/084250
Authority: WO
Inventors: Mikel Gorostiaga Altuna; Amira HEDHILI; Martina KREUZBICHLER; Peter LUKAN; Abdelouahid Zakriti; Philipp Seebacher; Michael PIROLT; Stefan SAX; Mehrdad SHAYGANPOOR
Original assignee: Tdk Electronics Ag
Priority date: 2021-12-20
Filing date: 2022-12-02
Publication date: 2023-06-29
Also published as: DE102021133906A1

Abstract

The present invention relates to an ultrasonic transducer (1) with a housing which comprises a plastics material, the housing comprising a base (2) and a housing wall, the housing wall comprising a first section (3), which is adjacent to the base (2), and a second section (4), the first and the second section (4) having different dimensions, wherein a transition section (5) is provided between the first and the second section (4), and wherein a surface normal which is perpendicular to the outer side of the housing wall in the transition section (5) is oblique with respect to a surface normal which is perpendicular on the base (2), and is oblique with respect to a surface normal which is perpendicular to the outer side of the housing wall in the first section and to the outer side of the housing wall in the second section (4). A transducer element (6) is arranged here on the base (2), the transducer element being designed to excite the base (2) into a vibration with a frequency in the ultrasound range. The present invention further relates to a method for producing a corresponding housing by injection moulding.

Description

Ultrasonic transducer with housing

The present invention relates to an ultrasonic transducer with a housing and a method for its production.

Known ultrasonic transducers for the frequency range from 40 to 80 kHz usually have aluminum housings. A section of the housing usually forms the diaphragm, which can vibrate at an ultrasonic frequency. Furthermore, the housing serves as a carrier for the transducer element and as a resonance body. The vibration of the membrane can be transmitted to the rest of the housing in an undesired manner. Also, as a rule, mechanical damping is necessary through direct contact of the membrane with a damping element, since small distances can no longer be measured by ultrasound if the membrane is not sufficiently damped. On the other hand, excessive damping leads to a lack of sensitivity of the sensor, so that large distances in particular can no longer be measured.

A corresponding ultrasonic transducer with an aluminum housing is known, for example, from WO 2020245064 A2.

One aim of the present invention is to provide an improved ultrasonic transducer and a method for its production.

An ultrasonic transducer is provided with a housing that includes a plastic material.

The housing includes a floor and a housing wall. An outside of the housing wall includes a first section, which is bottom contiguous and a second portion which is preferably not bottom contiguous . The second section follows a housing opening.

The first and second sections have different dimensions. In particular, the first and the second section can have different dimensions in a direction perpendicular to a surface normal of the floor or have parallel to the ground.

A transition section is also provided between the first and the second section. The housing thus comprises in this order the base, the adjoining first section of the housing wall, the transition section of the housing wall adjoining the first section and the second section of the housing wall adjoining the transition section, as well as the housing opening adjoining the second section. In a direction parallel to the floor, the first section, the transition section and the second section preferably have different dimensions. The sections can also have different dimensions in a direction perpendicular to the ground.

The transition section preferably follows directly on the first section and the second section preferably follows directly on the transition section. This means that the housing wall preferably has no further sections apart from the three sections mentioned.

A surface normal that is perpendicular to the outside of the housing wall in the transition section is also oblique to a surface normal that is perpendicular to the floor. Furthermore, the surface normal, which is perpendicular to the The outside of the housing wall in the transition section is inclined to a surface normal that is perpendicular to the outside of the housing wall in the first section. Furthermore, the surface normal, which is perpendicular to the outside of the housing wall in the transition section, is oblique to a surface normal, which is perpendicular to the outside of the housing wall in the second section.

A transducer element is disposed on the floor and is configured to excite the floor to vibrate at a frequency in the ultrasonic range.

The surface normal that is perpendicular to the outside of the housing wall in the transition section is therefore oblique to a surface normal that is perpendicular to the floor, oblique to a surface normal that is perpendicular to the outside of the housing wall in the first section, and oblique to a surface normal that is perpendicular to the outside of the housing wall in the second section.

In particular, in relation to a sectional plane of the housing, the surface normal that is perpendicular to the outside of the housing wall in the transition section is inclined to a surface normal that is perpendicular to the floor, oblique to a surface normal that is perpendicular to the outside of the housing wall in the first section, and oblique to a surface normal that is perpendicular to the outside of the housing wall in the second section. All surface normals mentioned here are therefore in one plane, namely in the same sectional plane of the housing.

In one embodiment, each surface normal that is perpendicular to the outside of the transition section is oblique to any surface normal that is perpendicular to the ground.

In a preferred embodiment, each surface normal that is perpendicular to the outside of the transition section is also oblique to each surface normal that is perpendicular to the outside of the first section.

In a further preferred embodiment, each surface normal that is perpendicular to the outside of the transition section is also oblique to each surface normal that is perpendicular to the outside of the second section.

Preferably, each surface normal that is perpendicular to the outside of the transition section is oblique to each surface normal that is perpendicular to the bottom or the outside of the first section or the outside of the second section.

Here and in the following, the term oblique is understood to mean a position that is neither vertical nor parallel.

The bottom of the housing can preferably be designed as a membrane which vibrates at an ultrasonic frequency when excited by a transducer element or by external vibrations. For this purpose, the base is very thin, in particular thinner than the housing wall.

The described housing with a transition section has the advantage that vibrations of the floor are hardly transmitted or are only transmitted in a damped manner to the rest of the housing, in particular to the second section of the housing wall. This effect is through the geometric shape of the housing, the shape of the transition section and a suitable material for the housing.

In particular, the appropriate selection of a plastic fes with appropriate elasticity and damping properties enables the setting of a desired sensitivity or Dampening of floor vibrations, which determines the minimum and maximum measurable distance. If the damping of floor vibrations is too high, the maximum measurable distance decreases, if the damping is too low, the minimum measurable distance increases.

Furthermore, the housing described has a high level of stability, in particular with respect to mechanical pressure on the outside of the housing wall. Thus, the housing described is particularly suitable to be installed in automated assembly processes, in the course of which pressure is exerted on the outside of the housing wall, for example by gripping arms.

In particular, the use of a suitable plastic material enables the housing to have a versatile, variable shape that is adapted to the assembly and application conditions and can then be produced, for example, in an injection molding process.

According to one embodiment, a surface normal that is perpendicular to the outside of the housing wall in the transition section and a surface normal that is perpendicular to the floor form an angle of between 1° and 89°, preferably between 5° and 85° and even more preferably between 10° and 80° in. The same preferably applies to an angle between a surface normal that is perpendicular to the outside of the housing wall in the transition section, and a surface normal that is perpendicular to the outside of the housing wall in the first section, and also for an angle between a surface normal that is perpendicular to the outside of the housing wall in the transition section, and a surface normal that is perpendicular to the outside of the Housing wall in the second section is .

Such an inclined position of the outside of the housing wall in the transition section dampens vibration in the housing between the first and the second section of the housing wall. Furthermore, this increases the stability of the housing against pressure on the outside of the housing wall.

If the housing wall forms a flat inclined surface in the transition section, any surface normal of this surface is preferably inclined to a surface normal of the base, preferably at an angle between 1° and 89°, more preferably at an angle between 5° and 85° and even more preferably in an angle between 10° and 80°.

According to one embodiment, the outside of the housing wall is curved in the transition section. The housing wall can have both a concave and a convex outward curvature or both. The housing wall in the transition section can also include one or more curved and planar sections.

In particular, a curved section can be provided adjacent to the first section and a flat section can be provided adjacent to the second section.

Alternatively or additionally, oblique and curved sections can also be arranged next to one another, each of which is attached to the first and second section or just one of them

connect sections .

With an outside of the housing wall designed in this way in the transition section, the vibration behavior of the housing can be adjusted in a targeted manner and in particular the vibration behavior of individual housing sections can be adapted to the requirements desired for this. In particular, a damping of vibrations in the housing between the first and the second section of the housing wall can be achieved, so that at least in desired sections of the second section of the housing wall only little or no vibration occurs. In other sections of the housing wall, including the second section, the vibrations can be more pronounced. Furthermore, this increases the stability of the housing against pressure on the outside of the housing wall, in particular during assembly of the housing.

According to one embodiment, the plastic material has a quality factor Q as a measure of the damping between 10 and 100, preferably between 10 and 65. More preferably, the quality factor Q is between 25 and 50. The quality factor is a measure of the attenuation or the energy loss of a system capable of oscillations. A high quality of a system means that the system is weakly damped. The desired figure of merit can be obtained by appropriate choice of plastic material for the housing. A base made of a plastic material with the selected quality factor Q can be sufficiently excited and dampened to vibrate when used as an ultrasonic transducer. In particular, the housing can consist of the plastic material. The entire housing, including the bottom and the housing wall, can be made of the plastic material. The plastic material can have homogeneous properties over the entire housing. Differences in the damping or the mechanical stability, in particular the stability against external pressure, between individual sections of the housing are preferably not achieved in the present housing by different compositions of the housing material but by the suitably designed housing shape.

According to one embodiment, the plastic material has an E module of at least 1 GPa. The plastic material preferably has an E module of at least 10 GPa. A floor made of the plastic material with the selected modulus of elasticity can be sufficiently excited and dampened to vibrate when used as an ultrasonic transducer.

According to one embodiment, the transition section is shaped in such a way that vibration of the first section is damped in the second section.

According to one embodiment, the bottom has a round shape and the first section has a cylindrical or conical shape. The base preferably has a circular shape and the first section has a circular cylindrical shape or a conical shape with a circular base area. The base here forms the base of the cylinder or the cone, with cone being a synonym for a truncated cone.

In the case of a conical shape, this preferably deviates only slightly from a cylindrical shape. So the jacket surface of the cone has only a slight slope for example a maximum of 10°, preferably a maximum of 5° in relation to the surface normal of the floor.

In particular, a conical shape of the section is advantageous, for example, to increase the stability of the housing against external pressure.

According to one embodiment, the second section has larger dimensions parallel to the bottom than the first section. In the transition section, the housing then widens from the dimension of the first section to the dimension of the second section.

The transition in the dimensions of the sections makes it possible to adjust the vibration behavior of the housing wall and in particular dampen vibrations in the housing wall or in desired sections of the housing wall.

A wider dimension of the second section also makes it possible to embed a printed circuit board with evaluation electronics of the ultrasonic transducer directly in the second section.

According to one embodiment, an inner space of the housing has a conical shape in a lower portion adjacent to the bottom. The shape of the interior of the housing and an outside of the housing wall, which delimits the housing on the outside, do not have to be the same. In particular, an inside of the housing wall, which delimits the interior of the housing, and the outside of the housing wall can have different slopes. In particular, the lower section can be formed in the section of the housing in which the first section is formed on an outside of the housing wall. However, the lower section of the interior space can also be formed in a section of the housing in which the transition section or the second section is formed on the outside of the housing wall.

An inner side of the housing is preferably beveled at an angle of between 0.5° and 45°, preferably between 0.5° and 5°, particularly preferably 2° relative to a cylinder jacket surface perpendicular to the base.

Such a pronounced conical shape of the interior of the housing increases its mechanical stability and enables the insertion of a preformed absorption element without it slipping through to the floor.

According to one embodiment, the contour of the second portion widens in the direction towards the ground. This increases the mechanical stability of the housing and leads to the adjustment of different vibrations and in particular to the damping of vibrations in sections of the housing wall. In particular, a larger difference in the dimensions between the first and the second section must then be bridged via the transition section, for example by the transition section being formed or curved further outwards, which further increases the damping in the housing wall due to its shape.

According to one embodiment, the second section of the housing wall and the first section of the housing wall have different geometric shapes. This enables precise adjustment of the vibration behavior in the housing wall and in particular better damping of vibrations in individual sections of the housing wall. In particular, a difference in the geometric shape between the first and the second section must then be bridged via the transition section, which increases a damping effect in the housing wall due to its shape. The different geometric shapes ensure that the transition section has an irregular shape. As a result, vibrations are transmitted differently across the transition section at different sections, so that the vibrations are damped in individual sections of the second section and amplified in other sections.

According to one embodiment, an outer side of the second section has a rectangular outline.

According to a preferred embodiment, an interior space of the housing also has a rectangular outline shape in an upper section that adjoins the housing opening. The outlines are preferably square.

In particular, the upper section can be formed in the section of the housing in which the second section is formed on an outside of the housing wall. However, the upper section of the interior can also be formed in a section of the housing in which the transition section or the first section is formed on the outside of the housing wall. The transition section can then comprise a curved section which is directly adjacent to the first section and extends to the corners of the rectangular shape of the second section. Furthermore, the transition section may include planar sloping sections that border on the side edges of the rectangular outline shape of the second section. Such a shape is advantageous in terms of stability of the housing and damping in the transition section.

A rectangular shape also means, in particular, a rectangular shape with rounded corners. Rounding the corners improves the handling of the case.

In addition to the advantages of the shape of the second section that have already been explained, this makes it possible to insert a rectangular printed circuit board with evaluation electronics directly into the second section. A rectangular PCB is easier to manufacture than a round PCB. In addition, the production of a round printed circuit board involves a considerable loss of material. A lot of material has to be discarded in the case of round printed circuit boards, especially when cutting out from a wafer. A material-saving process is cheaper and more sustainable.

According to a further embodiment, the second section has a round outline, in particular a cylindrical or conical shape. According to one embodiment, an interior of the housing also has a cylindrical or conical shape in the upper section. Such a shape also enables round printed circuit boards to be installed directly in the housing. A round housing shape is still easy to manufacture. The outer outline of The second section of the housing wall and the inner contour of the upper section in the interior of the housing can also be shaped differently.

According to one embodiment, the transducer element can be a piezoelectric element, for example in the form of a disc. The piezoelectric element contains a piezoelectric material, for example a piezoelectric ceramic. Furthermore, the transducer element preferably comprises two electrodes which rest, for example, on different sides of the piezoelectric ceramic in order to pick up an electrical signal or build up an electrical voltage in the ceramic. The piezoelectric element is preferably glued to the inside of the floor.

According to one embodiment, a printed circuit board is arranged in the upper portion of the interior of the housing, the printed circuit board being designed as a cover covering the housing opening which is opposite to the bottom.

The housing can therefore have the shape of a pot, which has a bottom and a housing wall and a housing opening opposite the bottom. The housing opening is preferably closed by a cover. The cover can be the printed circuit board mentioned, on which the evaluation electronics and control electronics of the ultrasonic transducer can be partially or completely arranged. The electronics are preferably attached to the inside of the printed circuit board in the interior of the housing and are thus protected from external influences. According to one embodiment, the printed circuit board is bonded to corresponding contact surfaces in the interior of the housing by means of an elastic adhesive on a number of separate contact surfaces on the printed circuit board. The use of an elastic adhesive reduces or eliminates any possible transmission of vibrations in the housing to the cover, which can also disrupt the electronics in particular. completely avoided.

According to one embodiment, at least a part or the entire upper section of the interior of the housing is below the printed circuit board or between an optional absorption element and the printed circuit board filled with a filler. The filler is preferably introduced in pasty form through the housing opening and then hardened. The filler preferably comprises a plastic material or synthetic resin. The filler is preferably elastic. The filler can also include any other suitable material.

In one embodiment, the circuit board as a cover does not end flush with the surrounding housing wall, but is arranged sunken in the interior of the housing. The remaining space in the housing, outside of the interior enclosed by the base and circuit board, is preferably partially filled with the filler. The filler then preferably covers almost the entire printed circuit board, apart from a section of the printed circuit board on which electrical contact to the outside is provided. The printed circuit board is thus additionally fixed in the housing and in front of the outside

protected from influences. In a preferred embodiment, the printed circuit board rests in particular on contact surfaces in the interior of the housing where the vibrations in the housing are minimal (so-called vibration nodes) in order to prevent the vibrations from being transmitted to the printed circuit board.

According to one embodiment, a step is formed in the upper section of the interior of the housing, on which the printed circuit board rests and on which the contact surfaces of the housing are provided. For example, the step may have a rectangular outline or a circular outline.

Preferably, the outline of the step resembles that of the interior space in the upper portion.

According to an exemplary embodiment, the contact surfaces of the housing are pronounced at corners or in the middle between two corners of the step. The vibrations in the housing are then preferably minimal at these points.

The transducer element and the circuit board or. in particular the evaluation electronics of the printed circuit board are electrically contacted. In particular, at least two contacts are preferably provided in order to contact two differently polarized electrodes of the converter element.

According to one embodiment, the printed circuit board and the converter element are electrically contacted via conductive traces on the inside of the housing.

In particular, it can be imprinted or sputtered

Traces of an electrically conductive material such as a

Metal, preferably copper, or an electrically conductive trade plastic . An electrically conductive plastic contains electrically conductive particles, for example metal particles that include copper.

Alternatively, the tracks can also be formed within the housing wall in one embodiment, so that only contact points of the tracks for contacting the evaluation electronics and the converter element on the inside of the housing, i.e. in particular on the inside of the housing wall and the bottom, are exposed.

Such a design means that there is no longer any need for contacting by wires in the interior of the housing, the installation of which is complex and laborious.

In one embodiment, the conductive traces are contacted to electrical contacts on the printed circuit board by means of a conductive adhesive. In particular, this concerns the contacts of the evaluation electronics on the printed circuit board. The conductive adhesive is preferably also elastic, so that transmission of vibrations from the housing to the printed circuit board is avoided.

With such a configuration of the contact via the tracks and the electrically conductive adhesive, the ultrasonic transducer can be assembled simply by placing the printed circuit board as a cover, without having to take any further steps to make contact between the printed circuit board and the transducer element.

According to one embodiment, the plastic material is electrically insulating. Thus the traces can be applied directly to the plastic material or pronounced in this become . A suitable method for forming the tracks in the case of a housing consisting of an electrically insulating base material would be laser direct structuring (LDS).

In one embodiment, the tracks terminate in multiple contact pads on the ground. The transducer element is preferably glued to the floor at a section provided for this purpose by means of a non-conductive adhesive.

In one embodiment, the electrodes of the transducer element contact the electrically conductive traces. In this embodiment, the tracks preferably reach down to the floor and the transducer element rests on the tracks.

In particular, the transducer element can be glued to the floor in such a way that the transducer element and in particular its electrodes rest directly on the tracks and are preferably electrically contacted with them.

In a preferred embodiment, contact between the electrodes of the transducer element and the traces is made via a conductive adhesive. Alternatively, the contact can also be made using a non-conductive adhesive if the surface roughness of the traces or the electrodes of the transducer element is sufficiently large that an electrical

Contact, in particular contact by direct contact, between the traces and the electrodes of the transducer element sets. In one embodiment, the tracks can also end next to the transducer element and the transducer element cannot fly onto the tracks. In this embodiment, electrical contact between the electrodes of the transducer element and the traces is preferably made via the conductive adhesive.

According to one embodiment, an electrically conductive coating for electromagnetic shielding is applied to the outside of the housing, ie in particular to the outside of the housing wall and the base.

In a further embodiment, the housing comprises a material which is not electrically insulating or the plastic material is electrically conductive. In this embodiment, on an inside of the housing wall or of the floor on which the electrically conductive traces are applied, an electrically insulating layer is arranged between the housing wall and the traces. For example, an insulating layer of Parylene C can be provided.

A housing wall made of an electrically conductive material has the advantage that the housing wall shields the electronics arranged in the housing against interfering electromagnetic influences from the outside (EMC/EMI protection z).

In a further embodiment, in particular if the housing is not electrically conductive, an electrically conductive coating is applied to the outside of the housing, which preferably completely covers the outside of the housing. Such a coating shields the electronics and electrically conductive traces arranged in the housing against interfering electromagnetic influences and in particular against electrical induction from the outside (EMC/EMI protection z).

In particular, the electrically conductive coating can contain a metallic material such as copper. The coating can be applied evenly and thinly. The coating can be applied, for example, by sputtering, but also, for example, in the form of a paint that includes electrically conductive particles.

In one embodiment, for ground contacting of the coating, an electrically conductive via, ie through contacting, can be provided between the coating on the outside of the housing and one of the tracks on the inside of the housing.

In particular, in one embodiment, the via can be stamped out in a through-hole in the housing wall.

The through-hole can be a borehole in the housing wall that is specially made for this purpose. The electrically conductive coating can then also be arranged on a surface in the bore and can extend up to the electrically conductive track on the inside of the housing wall. In particular, the track and the coating can have the same material and form a continuously connected coated area.

In a further embodiment, the via can be formed in a groove in an outer edge of the housing wall surrounding the housing opening, instead of in a through hole be . Analogous to the through-hole, the groove can be a bore, but not in the center of the housing wall, but rather on an outer edge of the housing wall.

The groove ensures that the electrically conductive coating or the trace or its electrical connection is exposed at an outer edge of the housing wall so that, for example, an unintentional short circuit with an electrical contact in the vicinity of the housing is avoided.

In a further embodiment, the electrically conductive coating and one of the tracks are electrically contacted via the printed circuit board. In this

In one embodiment, the conductive coating and the track only make electrical contact when the cover is closed, ie the printed circuit board is placed on the housing. A coated groove or a coated through-hole can in particular be provided again for contacting between the electronics on the printed circuit board and the outer coating.

In one embodiment, a cylindrical or conical preformed absorption element is arranged at a distance from the floor in the interior of the housing. The preformed absorption element can easily be inserted into the housing when the ultrasonic transducer is connected.

The absorption element absorbs sound and ultrasonic waves and preferably prevents, in particular, sound or ultrasonic propagation in the interior of the housing, but preferably does not dampen the mechanical vibrations or Vibrations in the housing wall. Therewith the absorption element also enables the measurement of distances at short distances with the aid of the ultrasonic transducer.

According to one embodiment, a cavity is provided between the preformed absorption element and the floor. In particular, the cavity is a gap containing only air. The cavity prevents vibrations of the floor from being dampened by undesired direct contact of the absorption element with the floor. Rather, the cavity should be so wide that even with maximum vibration of the floor during operation of the ultrasonic transducer, the floor does not come into contact with the absorption element.

Additionally or alternatively, the distance between the floor and the absorption element is preferably measured in such a way that destructive interference of the acoustic waves occurs between the two opposite surfaces of the floor and the absorption element.

On the other hand, direct mechanical damping of the floor is not necessary due to the advantageously selected plastic material as described and the described shape of the housing.

In particular, in one embodiment, the absorption element is a foamed-on plastic element. The plastic element includes, for example, a urethane derivative such as polyurethane or a silicone. With a suitable choice, such a foamed-on plastic has the necessary material properties in order to dampen the vibrations, in particular sound vibrations, as completely as possible. Such an absorption element is also easy to prefabricate and can be brought into the desired required shape easily and without post-processing.

According to one embodiment, a radial dimension of the absorption element is greater than a radial extension of the interior of the housing in the area of the bottom. In particular, this prevents the absorption element from slipping through to the bottom of the housing.

In particular, the absorption element and/or the lower section of the interior of the housing can be shaped conically, so that a radial dimension of the absorption element is greater than that of the interior only in the region of the bottom.

Furthermore, a method for producing a housing of an ultrasonic transducer from a plastic is disclosed.

The method can be used in particular to produce the housing and ultrasonic transducer described above.

In one step, the method includes the production of the housing by injection molding.

The housing may include all of the features and components previously described.

In particular, the housing comprises a base and a housing wall, the housing wall comprising a first section, which adjoins the base, and a second section. The first and second sections have different dimensions, with a transition section being provided between the first and second sections. A surface normal perpendicular to the outside of the Housing wall is in the transition section, is oblique to a surface normal, which is perpendicular to the ground, and oblique to a surface normal, which is perpendicular to the outside of the housing wall in the first and to the outside of the housing wall in the second section.

According to one embodiment of the method, the conductive traces are formed in an interior space of the housing by means of direct laser structuring, the conductive traces being designed to electrically connect a transducer element on the bottom to a printed circuit board that forms a cover of the housing.

In addition to the LDS process, other methods for generating the conductive traces are also possible, such as e.g. B. Sputtering, metal printing, in particular by means of metallic inserts, or another method using metallic inserts or a laser-induced graphene process (LIG process).

In the LDS process, an electrically conductive track is defined by a laser beam that writes a layout of the track directly onto the plastic material of the package. A special LDS additive is added to the plastic material for this purpose. Areas on which tracks are provided are then exposed to the laser beam and the added LDS additive activated. In a subsequent metallization in a copper bath, copper layers are formed on the activated areas that are adhesive and have sharp contours. Different layers can be built up one after the other, for example made of nickel, gold, silver or solder, which then form the tracks. Exemplary embodiments are described below with reference to figures. The present invention is not limited to the exemplary embodiments shown.

The figures show:

Figure 1: Perspective view from diagonally above a first embodiment of a housing of an ultrasonic transducer.

FIG. 2: Perspective view obliquely from below of the first exemplary embodiment of the housing of the ultrasonic transducer with surface normals drawn in.

FIG. 3: Side view in cross section of the housing of the first exemplary embodiment of the ultrasonic transducer.

FIG. 4: Side view in cross section of the first exemplary embodiment of the ultrasonic transducer.

FIG. 5: View of the first exemplary embodiment of the ultrasonic transducer obliquely from above. Shown are the case and two conductive traces.

Figure 6: Simulation of the vibration of the housing.

FIG. 7: Perspective view of a further exemplary embodiment of the housing with a metallic layer for shielding and drilling.

Figure 8: Cross section through the housing with metallic layer for shielding and drilling. FIG. 9: Cross section through another housing with a metallic layer for shielding and a channel.

Similar or apparently identical elements in the figures are provided with the same reference symbols. The figures and the proportions in the figures are not true to scale.

FIGS. 1, 2 and 3 show different views of a housing of a first embodiment of an ultrasonic transducer 1. Figures 1 and 2 show perspective views obliquely from above and. obliquely below, Figure 3 is a side view in cross section. FIG. 4 shows a side view of the ultrasonic transducer including the housing and other described components of the ultrasonic transducer.

The ultrasonic transducer 1 comprises a housing which is closed off on its underside by a base 2 . In the exemplary embodiment, the bottom 2 has a circular shape. The housing further comprises a housing wall and a housing opening opposite the base. A first section 3 of a housing wall adjoins the base 2 at the top.

The direction away from the floor and toward the housing opening is defined as "top".

The outside of the first section 3 can have a cylinder or cone shape. In the present exemplary embodiment, the outside of the first section has a conical shape. The angle of inclination of the cone shape in relation to the lateral surface of a flat cylinder is 0.5° to 5°, preferably 2°. The angle can also be lower or be chosen larger. The diameter of the cone shape is smallest adjacent to the bottom 2 and then increases towards the top.

A lower section 31 also encloses a cone-shaped cavity in the interior of the housing. The slope of the inside of the housing wall in the lower section 31 can differ from the slope of the outside in the first section 3 . The slope is preferably 0.5° to 45°, more preferably 0.5° to 5°, more preferably 2° relative to a surface normal of the inside of the bottom 2 .

The housing wall further comprises a second section 4 which is arranged above the first section 3 and remote from the bottom 2 . The second section 4 can have different outline shapes. In the present exemplary embodiment, the outer contour of the second section 4 is rectangular and preferably square. This also means, in particular, a rectangular or square shape with rounded corners, as is also shown in the figures. The dimensions of the second section 4 parallel to the bottom 2 are larger than the dimensions of the first section 3 .

A transition section 5 of the housing wall is provided between the first section 3 and the second section 4 . The transition section preferably follows directly on the first section and the second section preferably follows directly on the transition section. This means that the housing wall preferably has no further sections apart from the three sections mentioned.

The outside of the transition section 5 can be curved or flat. The outside of the transition section is in particular not parallel or perpendicular to the bottom and not parallel or perpendicular to one of the outer sides of the first or second section, but rather inclined to the bottom and to said outer sides, as illustrated for example in FIG.

"Oblique" in turn means that a surface normal FN5, which is perpendicular to the outside of the transition section 5, is not parallel and not perpendicular to a surface normal FN2, which is perpendicular to the floor 2. Likewise, a surface normal FN5, which perpendicular to the outside of the transition section 5, not parallel and not perpendicular to a surface normal FN3, which is perpendicular to the outside of the first section 3, and not perpendicular to a surface normal FN 4, which is perpendicular to the outside of the second section 4.

Rather, the outside of the transition section forms a transition between the outside of the first section 3 and the outside of the second section 4 . A surface normal FN5, which is perpendicular to the outside of the housing wall in the transition region 5, preferably has an angle of between 10 and 80 degrees with respect to a surface normal FN2 of the base 2 of the housing. Likewise, a surface normal FN5, which is perpendicular to the outside of the housing wall in the transition region 5, preferably at an angle of between 10 and 80 degrees to a surface normal FN3, which is perpendicular to the outside of the first section 3, and to a surface normal FN4, which is perpendicular to the Outside of the second section 4 is on. In the embodiment shown, the outside of the housing wall has a transition section 5 with the following configuration. The transition section 5 extends from the outside of the first section 3 to the outside of the second section 4 . In this case, the transition section 5 is noticeably curved towards the corners of the rectangularly shaped outline of the second section 4 . The curvature decreases between the corners. In a crest line between the corners, the transition section 5 is not curved at all, but runs flat from an outer edge of the first section 3 to an outer edge of the second section 4 . The differences in the curvature of the transition section 5 are caused by a different height of the second section 4 . The outer edges of the second section 4 are between the corners in the direction of the first section or. of the bottom 2 bent.

The different height of the second section 4 leads to an irregular shape of the transition section 5, as a result of which a vibration in the housing is only transmitted to a small extent between the first and second sections 3 and 4, ie the vibration is damped in the transition section 5.

The interior of the housing also has a rectangular outline in an upper portion 41 adjacent the housing opening. A stage 4A is also provided within the housing. In the interior of the housing, the lower section 31 with a circular inner outline directly adjoins the upper section 41 with a rectangular inner outline.

In particular, the upper portion 41 is pronounced in the portion of the housing in which on an outside of the Housing wall of the second section 4 is pronounced.

In particular, the lower section 31 is also formed in the section of the housing in which the first section 3 is formed on an outside of the housing wall. However, the upper section 41 and the lower section 31 of the interior space are also formed in a section of the housing in which the transition section 5 is formed on the outside of the housing wall.

The bottom 2 of the housing is designed as a membrane which vibrates at an ultrasonic frequency when excited by a transducer element 6 or by external vibrations. For this purpose, the base 2 is very thin, in particular thinner than the housing wall.

The entire housing including base 2 and housing wall is made in one piece and from the same material. The housing is an injection molded part made of plastic.

The plastic has vibration and sound-damping properties. A plastic with a high modulus of elasticity of more than 1 GPa, preferably more than 10 GPa, is selected for this. The ratio of density p to modulus of elasticity E of the plastic and in particular the factor (p) ³ /E should be as small as possible. Preferably the factor (p) ³ /E is less than 0.35, more preferably less than 0.1, even more preferably less than 0.01. Furthermore, the plastic has a quality factor Q as a measure of the damping between 10 and 100, preferably between 10 and 65.

Another preferred selection criterion for the plastic is that its mechanical properties in one Application temperature range of -40 ° C and + 85 ° C remain constant. Even more preferably, the mechanical properties remain constant in an application temperature range of -55°C and +150°C.

The transducer element 6 is preferably a piezoelectric element. The piezoelectric element preferably comprises a piezoelectric ceramic material. The piezoelectric element can be disc-shaped. Two electrodes, one electrode each on one of the surfaces, are preferably arranged on two opposite surfaces of the disk-shaped piezoelectric element. The piezoelectric element can be controlled electrically via the electrodes and can, in particular, be subjected to an electrical voltage, or an electrical signal, in particular an electrical voltage, can be tapped from the piezoelectric element.

In the exemplary embodiment, the piezoelectric element is disc-shaped and is glued to the inside of the base 2 . The piezoelectric element can also be applied to the floor 2 in a material-locking manner in some other way.

Furthermore, the ultrasonic transducer 1 includes a preformed absorption element 7 which is arranged in the interior of the housing. The preformed absorption element consists of a foamed plastic.

The absorption element 7 has a cylindrical or conical shape. In particular, the absorption element has a larger dimension in a radial direction than the lower portion 31 of the inner space close to the floor 2. so that the absorption element in the lower section 31 of the

Interior of the housing is pinched and does not slip through to the bottom 2. Thus a cavity 7A is formed between the bottom 2 and the absorption element 7 . The cavity 7A prevents feedback between the bottom 2 and the absorption element 7 . In particular, the absorption element 7 does not dampen the oscillations or vibrations of the floor 2 since the floor 2 is not in contact with the absorption element 7 . Rather, the absorption element 7 serves to dampen ultrasonic waves in the interior of the housing, in particular so that the ultrasonic waves do not interfere with downstream evaluation electronics.

The evaluation electronics are mounted on a printed circuit board 8 which at the same time forms the cover of the housing. For this purpose, the printed circuit board 8 is placed on the step 4A in the second section, so that it covers the housing opening in the second section. In order to dampen vibrations from the housing and, if possible, not to transfer them to the circuit board, the circuit board 8 is only on selected contact surfaces on corresponding contact surfaces of the housing or. level 4A glued on . The corresponding contact surfaces of the housing are in particular points in the housing at which vibration is maximally damped due to the housing structure described. Such locations are in particular the corners 4B or the midpoints between the corners 4B of the rectangular outline of the second housing section 4 .

A simulation of vibrations in the housing of the ultrasonic transducer 1 is shown in FIG. For this purpose, the floor 2 is excited to a defined vibration. The oscillations are transmitted in the form of vibrations throughout the housing. Strong vibration occurs in particular on the floor 2 .

The simulation shown clearly shows that there are hardly any vibrations at the corners 4B of the rectangular second section 4 of the housing wall, while stronger vibrations occur in sections 4C between the corners 4B. In housings of other shapes, however, smaller vibrations can also occur in the sections 4G between the corners 4B.

Vibrations of the floor 2 in particular, which propagate from there via the housing, are strongly damped at these points.

The cavity between the preformed absorption element 7 and the circuit board 8 or. In the exemplary embodiment, the remaining cavity above the circuit board 8 in the housing is filled with a filler 12 , preferably with an elastic plastic or a synthetic resin. The filler 12 preferably only hardens after it has been introduced into the cavity, so that the cavity is filled as completely as possible.

In one exemplary embodiment, the printed circuit board 8 as a cover is not flush with the surrounding housing wall, but is lowered in the upper section 41 of the interior of the housing. The remaining, unused space in the housing, outside of the interior enclosed by base 2 and circuit board 8 , is preferably also filled with filler 12 . The filler 12 then preferably covers almost the entire printed circuit board, except for a section of the printed circuit board on which an external electrical contact 13 is provided. The printed circuit board 8 is thus additionally fixed in the housing and protected from external influences. Both in the first and in the second section, the outside of the housing wall has a slight incline, as also shown in FIG. In this case, an incline means, in particular, an incline relative to a surface normal FN 2 on the surface of the floor 2 . The bevel and the transition section 5 described contribute to the mechanical stability of the housing in relation to a force applied to this outside from the outside.

In particular, the housing shaped as described is stable with respect to a uniform force applied from two sides on the outside, for example of a gripping frame during assembly or a clamp for fastening the housing.

For contacting between the converter element 6 and the printed circuit board 8, electrically conductive traces 9 are applied to the inside of the housing wall, as shown in FIG. At least two tracks 9 are provided for contacting two differently polarized electrodes of the transducer element 6 . The traces 9 extend in particular up to the stage 4A on which the printed circuit board 8 is applied. The tracks 9 extend at most to a surface of an upper side of the case formed parallel to the bottom 2 around the case opening. In particular, the tracks 9 do not extend to the outside of the housing wall.

The traces 9 can be both a metal coating that is applied to the inside of the housing wall and electrically conductive traces 9 inside the housing wall itself, ie not on the Surface, ie the inside or outside, the housing wall act.

With the exception of any traces 9 formed in the housing wall, the housing wall is not electrically conductive in the exemplary embodiment, but can also be electrically conductive in other exemplary embodiments. In the latter case, an electrically insulating layer is applied to the inside of the housing wall or at least between the electrically conductive traces 9 and the housing wall. The insulating layer can, for example, comprise a plastic, such as Parylene C in particular.

The electrically conductive traces 9 end in a number of contact areas on the floor 2 . In the exemplary embodiment, the transducer element 6 is glued to the floor 2 . The transducer element 6 is preferably glued to the base 2 at a section provided for this purpose using a non-conductive adhesive, while the electrodes of the transducer element 6 contact the electrically conductive traces 9 on its sides. In this exemplary embodiment, the tracks 9 preferably reach down to the floor 2 so that the converter element 6 can be glued to the floor in such a way that the electrodes of the converter element 6 rest directly on the tracks 9 .

In another embodiment, the contact between the transducer element 6, in particular its electrodes, and the electrically conductive traces 9 is established via a conductive adhesive. Alternatively, the contact can also be made using a non-conductive adhesive if the surface roughness of the tracks 9 is so large that direct contact between the tracks can occur through the adhesive layer the tracks 9 and the electrodes of the transducer element 6 sets.

The tracks 9 can also already end next to the transducer element 6, so that the transducer element 6 does not fly onto the tracks 9. In this embodiment, the electrical contact between the electrodes of the transducer element 6 and the traces 9 is made via the conductive adhesive.

The electrically conductive traces 9 can be applied in particular by sputtering or by imprinting a metallic layer or by laser direct structuring (LDS). The traces contain a metallic, electrically conductive material such as copper. So that the tracks 9 can be structured using the LDS process, the housing preferably does not contain any carbon fibers.

In the LDS process, the electrically conductive track 9 is defined by a laser beam, which writes a layout of the track 9 directly onto the injection-molded plastic of the housing.

A special LDS additive is added to the plastic for this purpose. Areas on which tracks 9 are provided are then exposed to the laser beam, thereby activating the added LDS additive. In a subsequent metallization in a copper bath, copper layers are formed on the activated areas that are adhesive and have sharp contours. In this way, different layers, for example made of nickel, gold, silver or solder, can be built up one after the other, which then form the tracks 9 . Various other embodiments of the housing of the ultrasonic transducer with a metallic layer for electromagnetic shielding (EMI/EMC shielding) of the housing are shown in the further FIGS.

If the housing is not electrically conductive, an electrically conductive layer 10 must be applied to the outside of the housing, ie in particular the housing wall and the base 2, for electromagnetic shielding. The layer 10 can be applied, for example, by painting, physical or chemical vapor deposition (CVD) or sputtering. The layer can, for example, comprise a metal or a conductive plastic, ie generally a plastic with a conductive additive. The layer 10 preferably covers the entire outside of the housing.

The required ground contact of the layer 10 is produced, for example, by a through-hole, such as a bore 11A (FIG. 8), or by a groove 11B (FIG. 9) in the housing wall. The electrically conductive layer 10 is also applied in the bore 11A or the groove 11B, so that the electrically conductive layer 10 is in contact with one of the electrically conductive traces 9 on the inside of the housing.

Alternatively, the electrically conductive layer 10 can be in contact with the printed circuit board 8 and can be contacted with the electrically conductive tracks 9 via this. In this case, the necessary ground contact of the layer 10 is produced via the printed circuit board 8 . In this last example, however, the circuit board is in one case, in which the cover with the circuit board is removed from the housing, not electrically contacted.

List of Reference Characters

1 ultrasonic transducer

2 floor

3 first section

31 lower section

4 second section

41 upper section

4A level

4B corner

4C section between two corners

5 transition section

6 transducer element

7 absorption element

7A cavity

8 circuit board

9 lanes

10 electrically conductive layer

11A bore

11B gutter

12 filler f

13 electrical contact

FN2 surface normal to ground

FN3 surface normal to first section

FN4 surface normal to second section

FN5 surface normal to the transition section

Claims

Expectations

1. Ultrasonic transducer (1) with a housing which has a plastic material, the housing comprising a base (2) and a housing wall, an outer side of the housing wall having a first section (3) which adjoins the base (2), and a second section (4) which adjoins a housing opening, wherein the first and the second section (4) have different dimensions, wherein a transition section (5) is provided between the first and the second section (4) and wherein a Surface normal (FN5) that is perpendicular to an outside of the housing wall in the transition section (5), oblique to a surface normal (FN2) that is perpendicular to the bottom (2), and the surface normal (FN5) that is perpendicular to the outside of the housing wall in the transition section (5) is inclined to a surface normal (FN3) which is perpendicular to an outside of the housing wall in the first section (3), and wherein the surface normal (FN5) which is perpendicular to the outside of the housing wall in the transition section ( 5) is inclined to a surface normal (FN4) which is perpendicular to an outside of the housing wall in the second section (4), and wherein a transducer element (6) is arranged on the floor (2) which is designed to Floor (2) to stimulate a vibration with a frequency in the ultrasonic range.

2. Ultrasonic transducer (1) according to claim 1, wherein the surface normal (FN5), which is perpendicular to the outside of the housing wall in the transition section (5), and the surface normal (FN2), which is perpendicular to the bottom (2), an angle between Include 1° and 89°.

3. Ultrasonic transducer (1) according to claim 1 or 2, wherein the outside of the housing wall is curved in the transition section (5).

4. Ultrasonic transducer (1) according to any one of claims 1 to 3, wherein the plastic material has a quality factor Q between 10 and 100.

5. Ultrasonic transducer (1) according to any one of claims 1 to 4, wherein the plastic material has a modulus of elasticity of at least 1 GPa or preferably at least 10 GPa.

6. Ultrasonic transducer (1) according to any one of claims 1 to 5, wherein the transition section (5) is shaped such that vibration of the first section (3) is damped in the second section (4).

7. Ultrasonic transducer (1) according to any one of claims 1 to 6, wherein the bottom (2) has a round shape and the first section (3) has a cylindrical or conical shape.

8. Ultrasonic transducer (1) according to any one of claims 1 to 7, wherein the second section (4) parallel to the bottom (2) has larger dimensions than the first section (3).

9. Ultrasonic transducer (1) according to any one of claims 1 to 8, wherein an interior of the housing in a lower portion

(31) adjacent to the bottom (2) has a conical shape.

10. Ultrasonic transducer (1) according to any one of claims 1 to 9, wherein the outline of the second portion (4) widens towards the bottom (2).

11. Ultrasonic transducer (1) according to any one of claims 1 to

10, wherein the second section (4) and the first section (3) have different geometric shapes.

12. Ultrasonic transducer (1) according to any one of claims 1 to

11, wherein an outer side of the second section (4) has a rectangular or round outline shape.

13. Ultrasonic transducer (1) according to any one of claims 1 to

12, wherein the transducer element (6) is a piezoelectric element.

14. Ultrasonic transducer (1) according to any one of claims 1 to

13, wherein a printed circuit board (8) is arranged in an upper portion (41) of the interior of the housing, the printed circuit board (8) being designed as a cover covering the housing opening which faces the bottom (2).

15. Ultrasonic transducer (1) according to claim 14, wherein the printed circuit board (8) is bonded by means of an elastic adhesive to a plurality of separate contact surfaces of the printed circuit board (8) with corresponding contact surfaces in the interior of the housing.

16. Ultrasonic transducer (1) according to claim 15, wherein a step (4A) is formed in the upper section (41) of the interior of the housing, on which the printed circuit board (8) rests, and wherein the contact surfaces of the housing on the step (4A ) are provided.

17. Ultrasonic transducer (1) according to claim 16, wherein the contact surfaces of the housing at the corners (4B) or in the Center between two corners (4B) of the stage (4A) are pronounced.

18. Ultrasonic transducer (1) according to any one of claims 14 to 17, wherein the printed circuit board (8) and the transducer element (6) are electrically contacted via conductive traces (9) on an inside of the housing.

19. Ultrasonic transducer (1) according to claim 18, wherein the conductive tracks (9) are contacted by means of a conductive adhesive with electrical contacts on the printed circuit board (8).

20. Ultrasonic transducer (1) according to claim 18, wherein the conductive traces (9) are connected to electrical contacts on the circuit board (8) by means of a non-electrically conductive adhesive and the surface roughness of the traces (9) or of electrodes of the transducer element (6) is sufficiently large that electrical contact is established between the tracks (9) and the transducer element (6) through the adhesive.

21. Ultrasonic transducer (1) according to any one of claims 18 to

20, wherein the conductive traces (9) extend to the ground (2) and the transducer element (6) on the traces (9) is located.

22. Ultrasonic transducer (1) according to any one of claims 18 to 20, wherein the transducer element (6) does not fly on the tracks (9).

23. Ultrasonic transducer (1) according to any one of claims 14 to 22, wherein part of the upper portion (41) of the interior is filled with a filler (12).

24. Ultrasonic transducer (1) according to claim 23, wherein the circuit board (8) does not end flush with the surrounding housing wall, but is arranged lowered in the interior (41) of the housing and part of the remaining space in the housing, outside of the floor (2nd ) And printed circuit board (8) enclosed interior, with the filler (12) is filled.

25. Ultrasonic transducer (1) according to any one of claims 1 to

24, the plastic material being electrically insulating.

26. Ultrasonic transducer (1) according to any one of claims 1 to

25, wherein an electrically conductive coating (10) for electromagnetic shielding is applied to an outside of the housing.

27. Ultrasonic transducer (1) according to claim 26, wherein the electrically conductive coating (10) completely covers the outside.

28. Ultrasonic transducer (1) according to claim 18 and claim 26, wherein an electrically conductive via between the coating

(10) on the outside and one of the tracks (9) on the inside.

29. Ultrasonic transducer (1) according to claim 28, wherein the via is formed in a through hole (11A) in a wall of the housing.

30. Ultrasonic transducer (1) according to claim 28, wherein the via is formed in a groove (11B) in an outer edge of the housing wall surrounding the housing opening.

31. Ultrasonic transducer (1) according to claim 18 and claim 26, wherein the electrically conductive coating (10) and one of the tracks (9) on the printed circuit board (8) are electrically contacted.

32. Ultrasonic transducer (1) according to any one of claims 1 to 31, wherein a cylindrical or conical preformed absorption element (7) is arranged at a distance from the bottom (2) in the interior of the housing.

33. Ultrasonic transducer (1) according to claim 32, wherein a cavity (7A) is provided between the preformed absorption element (7) and the base (2).

34. Ultrasonic transducer (1) according to claim 32 or 33, wherein the absorption element (7) is a foamed plastic element which has, for example, urethane or silicone.

35. Ultrasonic transducer (1) according to any one of claims 32 to 34, wherein a radial dimension of the absorption element (7) is greater than a radial extent of the interior of the housing in the region of the bottom (2).

36. A method for producing a housing of a

Ultrasonic transducer (1) having the steps:

- Manufacture of a housing in an injection molding process, the housing comprising a base (2) and a housing wall, an outer side of the housing wall having a first section (3) which adjoins the base (2) and a second section (4) which adjoins a housing opening, wherein the first and the second section (4) have different dimensions, with a transition section (5) between the first and the second section (4) is provided and wherein a surface normal

(FN5), which is perpendicular to an outside of the housing wall in the transition section (5), obliquely to a surface normal

(FN2) that is perpendicular to the floor (2), and the surface normal (FN5) that is perpendicular to the outside of the housing wall in the transition section (5) is oblique to a surface normal (FN3) that is perpendicular to an outside of the housing wall in the first section (3), and wherein the surface normal (FN5) which is perpendicular to the outside of the housing wall in the transition section (5) is inclined to a surface normal (FN4) which is perpendicular to an outside of the housing wall in the second section (4) stands, and

- Attaching a transducer element, which is designed to excite the floor (2) to vibrate at a frequency in the ultrasonic range, on an inside of the floor.

37. The method according to claim 36, wherein conductive traces (9) are formed in an interior of the housing, wherein the conductive traces (9) are designed to the transducer element (6) on the bottom (2) with a printed circuit board (8) that forms a cover of the housing to connect electrically.

38. The method according to claim 37, wherein the conductive traces (9) are formed by means of laser direct structuring, sputtering, metal printing or a laser-induced graphene process.