Ultrasonic Transducer and Method for Producing an Ultrasonic Transducer

Abstract

In an embodiment an ultrasonic transducer includes a container having an opening, a base and a wall, a piezoelectric disk arranged within the container on the base, a cover closing the container and an electronics system integrated in the cover, wherein the electronics system makes electrical contact with the piezoelectric disk and is configured to control and to read the piezoelectric disk.

Claims

1.-41. (canceled)

42. An ultrasonic transducer comprising: a container having an opening, a base and a wall; a piezoelectric disk arranged within the container on the base; a cover closing the container; and an electronics system integrated in the cover, wherein the electronics system makes electrical contact with the piezoelectric disk and is configured to control and to read the piezoelectric disk.

43. The ultrasonic transducer according to claim 42, further comprising a damping element arranged between the base and the cover, wherein the damping element fills the container.

44. The ultrasonic transducer according to claim 42, wherein the cover is fixed by way of a re-closeable fastening mechanism.

45. The ultrasonic transducer according to claim 42, wherein the cover is arranged in the container at a distance from the opening of the container.

46. The ultrasonic transducer according to claim 42, wherein the cover comprises at least two recesses.

47. The ultrasonic transducer according to claim 46, wherein a passage for a wire is formed at least in one of the recesses, and wherein the piezoelectric disk is electrically connected to the electronics system by the wire.

48. The ultrasonic transducer according to claim 42, wherein the container comprises a step along the opening in the wall.

49. The ultrasonic transducer according to claim 42, wherein the electronics system comprises a digital I/O interface on an outer side of the cover.

50. The ultrasonic transducer according to claim 42, wherein the electronics system comprises pins on an outer side of the cover.

51. The ultrasonic transducer according to claim 42, wherein the base is thinner than 1 mm.

52. The ultrasonic transducer according to claim 42, wherein a thickness of the wall is at least 1.5 times a thickness of the base.

53. The ultrasonic transducer according to claim 42, wherein the container consists of an electrically conductive material.

54. The ultrasonic transducer according to claim 42, wherein an inner surface of the container is partially roughened and/or smoothed.

55. The ultrasonic transducer according to claim 42, wherein the container is anodized.

56. The ultrasonic transducer according to claim 42, wherein an inner surface of the container is anodized and an outer surface is untreated, or wherein the inner surface of the container and the outer surface of the container is anodized, or wherein the outer surface of the container is anodized and the inner surface is untreated.

57. The ultrasonic transducer according to claim 56, wherein the inner surface of the container comprises an anodization layer, and wherein the anodization layer comprises an aperture.

58. The ultrasonic transducer according to claim 57, wherein an electrical connection from the piezoelectric disk and/or the electronics system to a reference potential is formed via the aperture.

59. The ultrasonic transducer according to claim 42, wherein an inner surface of the container comprises a conductive layer.

60. The ultrasonic transducer according to claim 42, wherein a portion of the base has a greater wall thickness than a base area adjacent to the piezoelectric disk.

61. The ultrasonic transducer according to claim 42, wherein an area of the container that runs parallel to the base and does not overlap with the base has a greater wall thickness than a base area adjacent to the piezoelectric disk.

62. The ultrasonic transducer according to claim 61, wherein the container comprises an adhesive material on an outer surface of the areas that have a greater wall thickness.

63. The ultrasonic transducer according to claim 42, further comprising vibration-damping components arranged on an outer surface of the container.

64. The ultrasonic transducer according to claim 42, wherein the cover is a printed circuit board.

65. The ultrasonic transducer according to claim 64, wherein the printed circuit board is flexible.

66. The ultrasonic transducer according to claim 64, wherein the printed circuit board is potted in a plastic compound.

67. The ultrasonic transducer according to claim 64, wherein the printed circuit board comprises electrical components, and wherein the electrical components are arranged on an area of the printed circuit board that faces the piezoelectric disk.

68. The ultrasonic transducer according to claim 64, wherein the printed circuit board comprises an integrated circuit with a charge pump.

69. The ultrasonic transducer according to claim 64, wherein the printed circuit board comprises an analog ground line and a digital ground line, and wherein the analog ground line and the digital ground line are configured such that electromagnetic interaction between the digital ground line and the analog ground line is suppressed.

70. The ultrasonic transducer according to claim 69, wherein an analog ground line and a digital ground line are arranged on opposite sides of an integrated circuit.

71. The ultrasonic transducer according to claim 42, wherein the piezoelectric disk is a temperature sensor.

72. The ultrasonic transducer according to claim 71, wherein the ultrasonic transducer is configured to compensate for a temperature dependence of measured distances on account of the temperature dependence of a speed of sound on basis of measurement values from the temperature sensor.

73. The ultrasonic transducer according to claim 42, wherein the ultrasonic transducer comprises a temperature sensor.

74. The ultrasonic transducer according to claim 73, wherein the temperature sensor comprises an NTC sensor or a PTC sensor.

75. The ultrasonic transducer according to claim 73, wherein the temperature sensor is arranged in an interior of the container.

76. The ultrasonic transducer according to claim 42, wherein the container is produced by an impact extrusion process.

77. A device comprising: the ultrasonic transducer according to claim 42, wherein the device is configured to measure a distance of the device from an object on basis of a signal ascertained by the ultrasonic transducer.

78. A method for producing an ultrasonic transducer, the method comprising: producing a container having an opening, a base and a wall; fastening a piezoelectric disk on the base of the container; and closing the container with a cover comprising an integrated electronics system, wherein the electronics system makes electrical contact with the piezoelectric disk and is configured to control and to read the piezoelectric disk.

79. The method according to claim 78, wherein the container is produced by an impact extrusion process.

80. The method according to claim 78, further comprising, before closing the container, arranging a first silicone ring on a bearing area of the container facing away from the base, wherein closing the container comprises arranging the cover on the first silicone ring.

81. The method according to claim 80, further comprising arranging a second silicone ring on a side of the cover facing away from the base, wherein the cover is fixed between the first and second silicone rings.

82. The method according to claim 80, wherein the electronics system makes electrical contact with the piezoelectric disk via a wire which is soldered to the electronics system.

83. The method according to claim 82, wherein the cover comprises at least one recess in which the wire is arranged, and wherein closing the container comprises pushing the cover onto the container with a translational movement and subsequently soldering the wire to the electronics system.

84. The method according to claim 78, further comprising filling a cavity between the cover and the base with a liquid filler material, and curing the liquid filler material to form a damping element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0061] The invention will be described in more detail below with reference to schematic illustrations.

[0062] FIG. 1 shows an exploded view of an ultrasonic transducer;

[0063] FIG. 2 shows a plan view of a bottom side of a cover;

[0064] FIG. 3 shows a cross section through an assembled ultrasonic transducer;

[0065] FIG. 4 shows an alternative embodiment of a container in which a temperature sensor is arranged;

[0066] FIG. 5 shows an exploded view of a further embodiment of an ultrasonic transducer;

[0067] FIG. 6 shows a cross section through a further embodiment of an assembled ultrasonic transducer; and

[0068] FIG. 7 shows a perspective view of an assembled ultrasonic transducer.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0069] FIG. 1 shows an exploded view of an ultrasonic transducer 1. A container 2, which comprises an opening, a base 3 and a circular wall, is constructed from two cylindrical parts, a lower part and an upper part. The lower part has a smaller radius than the upper part and is closed at a lower round base area by way of the base 3, which also serves as a diaphragm. The lower part is open at the top. The entire container 2 is formed from one piece and the upper part is therefore connected to the lower part via a connecting area which runs parallel to the base 3. The upper part is likewise open at the top.

[0070] In the interior of the container 2, a piezoelectric disk 5 is fixed to the base 3 by way of an adhesive layer 13 or an adhesive disk. A damping element 8 is arranged above said piezoelectric disk and is matched to the shape of the container 2 and completely fills it. The piezoelectric disk 5 is connected to an electronics system 7 via wires 14. Said electronics system is arranged on a side of a cover 6 that faces inward. The cover 6 itself is a printed circuit board 12 and comprises a digital I/O interface 9 on a side that faces outward.

[0071] The digital I/O interface 9 not only implements communication to the outside but also supplies electricity to the electronics system 7 and the piezoelectric disk 5. The arrangement of the digital I/O interface 9 on the cover 6 renders possible a compact design of the ultrasonic transducer 1 and a simple contact-connection since no further connections have to be considered. In contrast to analog interfaces, a digital I/O interface 9 has a high tolerance to interference signals which can originate, for example, from nearby electric motors. For example, the interface can also be implemented byway of an FFC connector. This provides, via its eight contacts, a debug interface which provides a large number of reading options which may be advantageous, in particular, for developers and in relatively complex applications. As a particularly simple alternative, a 2- or 3-wire interface can be used as the interface. These are the most cost-effective interfaces from amongst the alternatives mentioned above. In addition, simple pin headers, which are provided with two to eight pins, are possible as the interface for the ultrasonic transducer 1.

[0072] The cover 6 is a printed circuit board 12 which comprises, on an outer side, ground areas and, on an inner side, the electronics system 7 in the form of electrical components. The cover 6 is preferably shaped such that it does not touch the walls of the container 2. The conductor tracks on the printed circuit board 12 can be adjusted in order to arrange the electrical components, for example, in a space-saving or geometrically advantageous manner with respect to the shape of the container 2.

[0073] Owing to the arrangement of the electronics system 7 on the inner side of the cover 6, the electrical components, if the container 2 consists of an electrically conductive material, are protected against external electromagnetic interference signals.

[0074] Furthermore, the uneven surface, which is caused by the electrical components, facilitates scattering of ultrasound which propagates from the piezoelectric disk 5 to the cover 6, and therefore the wrong way around. A further advantage of the arrangement of the electronics system 7 on the inner side of the cover 6 is that the electronics system 7 is protected against mechanical or chemical damage which can result from environmental influences.

[0075] Since the printed circuit board 12 is flexible and/or is potted in a plastic compound, ultrasound which propagates from the piezoelectric disk 5 to the cover 6 can be damped and therefore further propagation of vibrations and associated phantom signals can be suppressed. Installation of a flexible printed circuit board 12 as the cover 6 may be easier to carry out than for rigid covers 6. The plastic compound is used for filling possible cracks and holes in the printed circuit board 12 and a possible gap between the cover 6 and the container 2. Therefore, the container 2 can be sealed and the propagation of the ultrasound waves can be suppressed even better. If a cover 6 which is smaller than the container 2 is used, a tight closure, which even reduces transmission of vibrations between the cover 6 and the wall 4, can nevertheless be implemented by way of the plastic compound. The plastic compound used may be, for example, a silicone or a soft resin.

[0076] The cover 6 can be fixed in the container 2 by way of a re-closeable fastening mechanism. The fastening mechanism may be, for example, a snap-in mechanism which releasably fixes the cover 6 in one position. As a result, the cover 6 can be opened and the electrical components or contact-connections of the electronics system 7 on the inner side of the cover 6 can be inspected. If the cross section of the cover 6 corresponds to the inside cross section of the container 2, it is advantageous to position an elastic ring 22, which may be composed of silicone for example, beneath the cover 6. In this way, a slight clearance can be permitted when the cover 6 is opened, said clearance making the opening process easier.

[0077] FIG. 2 shows an exemplary embodiment for an outline shape and for a layout of the conductor tracks of a cover 6. The cover 6, together with the electronics system 7, can be covered by a protective layer on the outer and the inner side of the cover 6 in order to protect the lines, the electronics system 7 and the contact-connections against moisture, corrosion and possible short circuits. The protective layer may be, for example, a lacquer or a potting compound.

[0078] The cover 6 has three recesses 15 at the edge, wherein two of the three recesses 15 are situated on opposite sides of the cover 6. The opposite recesses 15 allow the cover 6 to be able to be handled more easily when it is inserted into the container 2. For example, the recesses 15 in the cover 6, which recesses can likewise comprise an electrical connection between the outer and the inner side, allow simpler contact-connection between the wires 14 and the electronics system 7. For example, owing to the recesses 15, it may be possible to push the cover 6 against the wires 14 with a translational movement. The cover 6 can be further moved to a certain extent via the recesses 15 for simple contact-connection, which is implemented by way of a soldering process for example, in order to in this way create a certain amount of flexibility for making contact with the cover 6 by means of the wires 14. As an alternative, the wires 14 would have to be threaded through small holes in the cover, as a result of which assembly of the ultrasonic transducer would be made more difficult.

[0079] Advantageous mounting of the cover 6 is performed as follows. Firstly, on the container 2, a bearing area and adjacent side faces of the cover are covered with a damping material, for example silicone, and this is cured if necessary. The cover 6 is then arranged in the container 2 and an electrical contact-connection is established between the piezoelectric disk 5 and the electronics system 7 via the wire 14. Once electrical contact is made with the cover 6, it is pushed to its final position. A further layer of damping material, such as silicone for example, is then adhesively applied along the outer circumference of the cover 6, this fastening the cover 6 in its position. Subsequently, the container can be filled with a liquid damping material.

[0080] Furthermore, the container 2 can also be filled with a liquid filler material through a recess 15 in the closed state. This ensures that a positive connection can be formed between the damping element 8 and the cover 6 as well as the electronics system 7 since air pockets between the cover 6 and the damping element 8 are avoided since the liquid filler material completely fills the container 2. This ensures that the electronics system 7 on the cover 6 is even better protected by the positive damping element 8 and the cover 6 is damped with respect to vibrations. In particular, transmission of vibrations from the container 2 to the cover 6 can be suppressed owing to the damping of the cover 6 by the damping element 8, and therefore no acoustic side lobes, which may corrupt the distance measurement, can form. Since more than one recess 15 is made in the cover 6, continuous and uniform pressure equalization can take place during the filling process. This prevents bubbles and air pockets which may otherwise readily occur during the filling process. Instead, a homogeneous positive damping element 8, without macroscopic air bubbles, is formed in the container 2.

[0081] A passage 16 for a wire 14 has been formed in two of the three recesses 15. The piezoelectric disk 5 can be electrically connected to the electronics system 7 in the cover 6 owing to said passages. The electrical connection between the wire 14 and the electronics system 7 is stabilized owing to the passage 16. In one embodiment, the container 2 can be filled with a liquid filler material such that the liquid filler material covers the recesses 15 and therefore also the passage 16 and the contact-connection between the wire 14 and the electronics system 7. Owing to the coating composed of liquid filler material, which subsequently dries, the contact-connection between the wire 14 and the electronics system 7 is protected against external influences. Furthermore, the cover 6, after mounting, can be coated on the outer side with a protective layer and sealed by way of a film or foil or a closure in order to protect the ultrasonic transducer 1 and the electronics system 7 from the surrounding area.

[0082] In the layout of the conductor tracks that is shown in FIG. 2, an integrated circuit 17 is arranged in the center. The integrated circuit 17 has a charge pump with which the operating voltage required by the piezoelectric disk 5, which operating voltage is higher than a supply voltage of the circuit of between 5 and 12 V, can be generated. As an alternative, transformers could be used for generating higher voltages, but these have a large physical size. Charge pumps tend to generate a low offset voltage on the ground line. Rapid oscillations on the ground lines, which rapid oscillations can form, for example, on a digital ground line 19 on account of the rapid switching times of the integrated circuit 17, can parasitically propagate onto an analog ground line 18 and therefore cause interference in the signal processing and the distance measurement. Since the digital and the analog ground line 18, 19 are configured such that they do not influence each other, interference in the distance measurement is suppressed. This has been achieved with the layout that is shown in FIG. 2.

[0083] Firstly, an electromagnetic decoupling of the digital ground line 19 is achieved by way of the analog ground line 18 and the digital ground line 19 being arranged on opposite sides of the integrated circuit 17. In the layout from FIG. 2, the digital ground line 19 is arranged at the bottom right corner of the integrated circuit 17 and forms a ground area there, whereas the analog ground line 18 is formed merely by a short conductor track at the top left corner of the integrated circuit 17. Therefore, a physical distance between the digital and the analog ground line 18, 19 is prescribed, and therefore electromagnetic interaction between the ground lines is avoided and no undesired interference occurs.

[0084] The damping element 8, which is arranged between the cover 6 and the base 3 and fills the entire container 2, primarily serves to damp the ultrasound and the vibrations that originate from the piezoelectric disk 5. Therefore, the most important property for the damping element 8 is the damping constant, in particular for typical ultrasound frequencies of between 50 kHz and 100 kHz, where the damping constant should be as large as possible. Rubbers or foams have suitable damping properties. Foams composed of plastics, such as silicone for example, which comprise gas pockets are expressly suitable as materials for the damping element 8. These can be positioned into the container 2 as solids or poured into the container 2 as liquids, where the liquid compound, such as two-component silicone for example, cures and positively fills the container 2. In addition to damping the ultrasound waves, the damping element 8 also further mechanically stabilizes the container 2, so that the container 2 withstands a greater external pressure.

[0085] An adhesive material 10 is arranged on an outer surface of the connecting area between the upper and the lower part of the container 2. The adhesive material 10 is preferably composed of a foam-like, soft material that damps vibrations. Owing to the use of the adhesive material 10, installation of the ultrasonic transducer 1 is simplified since the ultrasonic transducer 1 merely has to be placed in a target position, so that the adhesive material 10 adheres to a fastening. A foam-like material reduces transmission of vibrations from the ultrasonic transducer 1 to the fastening. Said fastening may be, for example, a double-sided adhesive tape which has a foam-like core. This adhesive tape can already be applied to the intended area by way of one side of the adhesive tape, wherein a second adhesive side of the adhesive tape can remain covered by a protective film or foil until the ultrasonic transducer 1 is finally mounted into an application.

[0086] A vibration-damping component 11 is arranged along an outer surface of the wall 4 of the lower part of the container 2. The vibration-damping component 11 damps the ultrasound and vibrations with respect to an undesired propagation direction perpendicular to the base 3. The vibration-damping component 11 is preferably composed of a foam-like material which is preferably also electrically conductive in order to increase the electromagnetic compatibility of the ultrasonic transducer 1. However, it is also possible to use a non-conductive material, such as silicone for example.

[0087] FIG. 3 shows the cross section through an assembled ultrasonic transducer 1. The wall 4 of the lower part of the container 2 is clad with a vibration-damping component 11 from the outside and the connecting area between the lower and the upper part of the container 2 is provided with adhesive material 10 from the outside. A piezoelectric disk 5 is arranged on the base 3 in the interior of the container 2 and is electrically contact-connected to the electronics system 7 via wires 14 through the damping element 8, which fills the entire container 2.

[0088] The connecting area between the upper and the lower part of the container 2 is thicker than the rest of the container 2. These reinforced connecting areas are designed to be used as bearing areas on a fastening, a frame or a carrying structure in an application. The base 3, which is also used as a diaphragm, is thinner than 1 mm. On the one hand, the base 3 has to be elastic enough to not severely impede the deflection movements of the piezoelectric disk 5. On the other hand, the base 3 has to have a certain degree of stability, so that it is not damaged in the event of an external action of force, such as when sprayed with water for cleaning purposes for example. An advantageous compromise has been found with a thickness of the base 3 of less than 1 mm and more than 0.2 mm. The walls are at least 1.5 times as thick as the base 3, but if possible should be more than 3 times the thickness of the base 3. Such a large wall thickness is suitable for reducing the transmission of vibrations from the base 3 or the diaphragm to the connecting area between the upper and the lower part of the container 2. Since the connecting area may be a bearing area for the ultrasonic transducer 1 to form a fastening, vibrations and deflections should be avoided precisely at these connecting areas. Otherwise, vibrations may be transmitted to an adjacent fastening which belongs to the application. The transmitted vibrations may in turn be reflected and therefore incorrectly detected as a measurement signal in the ultrasonic transducer 1 in the form of a phantom signal. A wall thickness of at least 1.5 times the thickness of the diaphragm reduces the transmission of vibrations from the base 3 to other parts of the container 2 and in this way prevents the problem.

[0089] In a further embodiment of the container 2 that is shown in FIG. 4, the container 2 has a step along the opening in the wall 4. This step is used as a bearing area for the cover 6, so that the cover 6 can be easily arranged in the container 2. The cover 6 can be connected to the container 2 in a fixed and vibration-damped manner by way of a silicone or foam layer being used between the cover 6 and the container 2 as a composite material. A further layer of silicone or foam can be placed on or in the edge between the embedded cover 6 and the container 2 in order to render the ultrasonic transducer 1 even more water resistant.

[0090] All the corners of the container 2 are rounded with a small radius. This is due to the production method for the container 2 which can be produced using an impact extrusion process. Here, an aluminum slug is pressed between an inner punch and an outer die to form the container 2. In order to easily release the container 2 from the stamping tool, it is advantageous to avoid sharp edges and corners and instead to establish rounded portions at corners.

[0091] FIG. 4 furthermore shows a temperature sensor 20 which is arranged on an inner surface of the container 2, on the base 3. Since the speed of sound in a medium is temperature-dependent, a distance measurement by the ultrasonic transducer 1, which distance measurement is based on the propagation time of a sound pulse, will also depend on the ambient temperature. The linear correction formula for the speed of sound in air can read c.sub.air=(331.3+0.606*ν)m/s, where ν is the air temperature in ° C. In order to render possible a correct distance measurement by the ultrasonic transducer 1, this correction term is taken into account in the distance measurement. Therefore, a correct distance measurement can be implemented in the range of from −40 to 85° C.

[0092] Owing to the arrangement of the temperature sensor 20 in the interior of the container 2, the temperature sensor is protected against external hazards. Owing to the direct contact with the container 2, the temperature sensor 20 is in good thermal contact with the surrounding area since the wall thickness of the container 2 is low. A container 2 composed of metal may be advantageous, in particular, in combination with a temperature sensor 20 since metal exhibits excellent thermal conductivity. Moreover, waste heat is produced by the electronics system 7 which is integrated in the cover 6, as a result of which a temperature measurement in the vicinity of the cover 6 may be corrupted. An arrangement of the temperature sensor 20 on the base 3 of the container 2 is therefore particularly useful since the wall thickness of the container 2 at the base 3 is particularly low and the electronics system 7 and the temperature sensor 20 are at the greatest possible distance. Therefore, precise temperature measurement is rendered possible since the temperature sensor 20 is in good thermal contact with the surrounding area at the base and the temperature measurement is not changed by generation of heat by the electronics system 7.

[0093] The temperature sensor 20 may be, for example, an NTC sensor or a PTC sensor. Both types of sensor have a high degree of measurement accuracy and robustness together with a low level of energy consumption. Both types of temperature sensor 20 can be integrated into electrical circuits without problems, and therefore are suitable for use in the ultrasonic transducer 1. In a particularly advantageous embodiment, the piezoelectric disk 5 is used as a temperature sensor 20. Since the piezoelectric disk 5 is composed of a piezoelectric material which is arranged between two electrodes, it forms a capacitance between the electrodes. This capacitance changes depending on the ambient temperature since the piezoelectric material expands in the event of a positive change in temperature and contracts in the event of a negative change in temperature. On the basis of this, the distance between the electrodes, and therefore also the capacitance of the piezoelectric disk 5, is also changed depending on the ambient temperature. Therefore, by way of reading the capacitance of the piezoelectric disk 5, using the electronics system 7 integrated in the cover 6, conclusions can be drawn about the ambient temperature and consequently the distance measurement by the ultrasonic transducer 1 can be corrected on the basis of the ambient temperature.

[0094] The container 2 is ideally produced from an electrically conductive material since the electromagnetic compatibility of the ultrasonic transducer 1 is increased in this way. In particular, the piezoelectric disk 5 and the electronics system 7 arranged on the inner side of the cover 6 can be shielded from external electromagnetic interference signals owing to the use of conductive materials in the container 2. A large number of electric motors, which may adversely affect the ultrasonic transducer 1, are often installed in small and also narrow applications, such as drones or autonomous robots for example. Metals such as Al, Cu, Sn, Fe and steel, but also alloys, are appropriate conductive materials for the container 2. The function of the base 3 as a diaphragm requires a relatively high degree of flexibility. On account of this, conductive materials with a low modulus of elasticity, such as Al and Sn, are extremely suitable.

[0095] The container 2 can additionally be optimized by way of the inner surface being partially roughened and/or smoothed. Roughening a surface results in materials adhering to this surface more strongly. However, ultrasound is also scattered to a greater extent over a rough, uneven surface. Smoothing the surface reduces adhesion to the surface, but incident ultrasound scatters less. Therefore, it is expedient to roughen the surface of the base 3 adjacent to the piezoelectric disk 5 so that it holds better by means of the adhesive layer 13. Furthermore, the remaining area of the base 3 in the interior of the container 2 is smoothed, so that a damping element 8 does not adhere to these areas and the deflection of the piezoelectric disk 5 is not excessively impeded by the damping element 8. The inner surface of the container 2 can optionally likewise be roughened in order to scatter the ultrasound over this surface to a greater extent. Suitable roughening methods are, for example, a sandblasting or etching process, and grinding or coating processes are suitable for smoothing the surface.

[0096] Furthermore, an outer surface of the base 3 can be coated, anodized or lacquered. Firstly, possible irregularities on the surface, which may cause interference in the distance measurement, are eliminated as a result. Secondly, the area can be matched to a possible application since the color or the surface material can be configured to match the surrounding area, so that the ultrasonic transducer 1 does not stand out. It is also possible to anodize the entire outer surface of the container 2. The outer surface of the container 2 is subject to particularly intense environmental influences, such as salt spray from road traffic. Owing to anodization of the outer surface, the container 2 is protected against corrosion.

[0097] Anodization of the inner surface of the container 2 may also be desirable in order to shield the container 2 from chemical reactions, for example due to a solvent in the damping element 8 or the adhesive in the adhesive layer 13. For optimum protection, the container 2 can be anodized both on the outer surface and also on the inner surface.

[0098] One disadvantage of anodization of the inner surface of the container 2 is that electrical contact can no longer be made with the container 2 and therefore said container can no longer be readily used for electrical connection, for example to a reference potential such as ground. Therefore, it is advantageous to additionally apply a conductive layer to the inner surface of the container 2.

[0099] As an alternative or in addition to this, the anodized inner surface of the container 2 can comprise specific apertures in the anodization in at least one point. In other words, apertures in the electrically non-conductive anodization layer of the inner surface can be provided in a targeted manner. These apertures can render possible an electrically conductive contact-connection with the container 2. For example, electrical contact can be made with the container 2 by way of an additionally applied conductive layer via the at least one aperture. As an alternative, electrical contact can be made with the container 2 via a solder contact made in the aperture.

[0100] By way of introducing an additional conductive layer, the specific aperture in the anodization or a combination thereof, electrical connection of installed electronic components, such as the piezoelectric disk 5, the temperature sensor 20 or the electronics system 7, to a reference potential can be carried out and the electromagnetic compatibility of the ultrasonic transducer 1 and the electromagnetic shielding of the electronics system 7 in the container 2 can be achieved similarly as well or equally as well as in the case of a container 2 that is not anodized on the inner surfaces.

[0101] FIG. 5 shows an exploded view of a further embodiment of the ultrasonic transducer 1, similarly to the exploded view shown in FIG. 1. In contrast to FIG. 1, the cover 6 is arranged between two silicone rings 22 in this embodiment. The silicone rings 22 serve primarily to mechanically decouple the cover 6 from the container 2, but also as a seal in order to prevent a potting compound from entering the interior of the container 2. The damping element 8 has, on a surface that faces the cover 6, recesses in which the electronics system 7, which protrudes out of the cover 6, can be accommodated. In this embodiment, three pins 21 are provided as the electrical connection for the ultrasonic transducer.

[0102] FIG. 6 shows a cross section through the embodiment of the ultrasonic transducer 1 shown in FIG. 5, wherein the illustration is similar to the illustration of FIG. 3. The shape of the container 2 corresponds to the shape of the container 2 from FIG. 4. The cover 6 is arranged at a distance from the opening of the container 2 and therefore in the container 2. In this way, the electronics system 7 is protected against mechanical and electromagnetic loads in the cover 6. A potting compound can be introduced into the intermediate space between the cover 6, the opening and the wall of the container 2, said potting compound fixing the cover 6 in a vibration-damping manner in the container 2 and providing protection. Owing to the silicone ring 22 between the cover 6 and the damping element 8, the potting compound is not in direct contact with the damping element 8.

[0103] FIG. 7 shows a perspective view of the embodiment of the ultrasonic transducer 1 shown in FIG. 5 and FIG. 6. The three pins 21 are rigidly connected to one another by way of a connecting piece 23. The pins 21 are each bent at an end that rests on the cover 6 and are arranged such that they provide a stable stand in the form of a tripod. Each of the three pins 21 is situated on an electrically conductive contact area 24 which can be considered to be part of the electronics system 7 in the cover 6. The three pins 21 can respectively be used as a connection for the supply voltage, as a connection to a reference potential or as an I/O connection 9. Since the cover 6 is at a distance from the opening of the container 2, a potting compound applied to the cover 6 can be used for fixing the pins 21 on the cover 6. The three pins 21 are designed such that they can be simultaneously used as an electronic connection and for mechanically fastening the ultrasonic transducer.

[0104] Although the invention has been illustrated and described in detail by means of the preferred embodiment examples, the present invention is not restricted by the disclosed examples and other variations may be derived by the skilled person without exceeding the scope of protection of the invention.