DE102018128513B4 - Ultrasonic sensor with laser-welded cover and labeling - Google Patents

Abstract

Ultrasonic sensor (10) with a pot-like housing (12) that absorbs light with a first wavelength, a membrane for coupling or decoupling ultrasonic signals on a front side of the housing (12), control and evaluation electronics in an interior space (14) of the housing (12) is arranged, and a cover (16) made of a material which is transparent to light having the first wavelength and absorbing light having a second wavelength, characterized in that the cover (16) at its has a peripheral edge (20) facing the interior (14), a gap (22) being formed between the housing (12) and the edge (20).

Description

The present invention relates to a method for producing an ultrasonic sensor, comprising the steps of providing a pot-like housing that absorbs light with a first wavelength, arranging a membrane for coupling and decoupling ultrasonic signals on a front side of the housing, arranging a control and evaluation electronics in an interior of the housing, arranging a cover made of a material that is transparent to light with the first wavelength on a rear side of the pot-like housing, closing the pot-like housing with the cover by laser welding with a first laser with the first wavelength the lid.

The present invention also relates to an ultrasonic sensor with a pot-like housing that absorbs light with a first wavelength, a membrane for coupling and decoupling ultrasonic signals on a front side of the housing, control and evaluation electronics in an interior of the housing is arranged, and a cover made of a material that is transparent to light with the first wavelength, wherein the ultrasonic sensor is made according to the above method.

Ultrasonic sensors are used in the prior art for distance measurement for various types of driving assistance systems in vehicles. Ultrasonic sensors are very popular because of their efficiency and low costs. Current vehicles are practically all equipped with ultrasonic sensors in the front and/or rear area of the vehicle.

The ultrasonic sensors typically include a pot-like housing that is designed with a membrane for coupling and decoupling of ultrasonic signals on a front side. An electronic control and evaluation system is arranged in an interior of the housing, which controls a piezo element, which is coupled to the membrane, and receives ultrasonic signals coupled into the piezo element from the membrane.

In order to ensure the function of the ultrasonic sensor, it is necessary to protect the interior of the housing against the ingress of dirt and moisture. Initially, the ultrasonic sensors were realized with open housings, which were cast with a synthetic resin, for example. However, this was found to be disadvantageous because the synthetic resin is heavy and increases the cost of the ultrasonic sensor. Therefore, the housing was closed with a cover that protects the interior against the ingress of dirt and moisture. The protective effect of the cover depends on the reliability of the attachment of the cover to the housing.

Fastening by laser welding has proven itself for fastening the cover to the housing. The cover is welded onto the housing using a laser transmission process with a first wavelength. For this purpose, the cover must be transparent for this first wavelength of the laser radiation, so that the laser beams can pass through the cover. The housing itself absorbs light of the first wavelength, so that the laser beam can heat up the housing in the contact area with the cover. The housing melts in the contact area with the cover, so that the housing reliably connects to the cover when it cools down. Such lids are typically optically white or transparent.

Additionally, it may be desirable to label the lid. Various methods are known in the prior art for this purpose. This typically includes a separate process step, which makes the manufacturing process for the ultrasonic sensor very complex.

In this context, for example, from the DE 195 10 493 A1 a workpiece, in particular a housing for an electrical switch, and a method for its production are known. The workpiece consists of at least two workpiece parts made of a thermoplastic material and welded to one another by laser beams along a joining zone, the two workpiece parts having different transmission and absorption coefficients for the spectrum of the laser beams, at least in some areas. One of the first workpiece parts is designed to be at least partially transmissive for the laser beams in the area from a first coupling zone, in which the laser beams hit the first workpiece part, to the joining zone, as a result of which some of the laser beams penetrate the first workpiece part and at a second coupling zone into the second Workpiece part can penetrate. The second workpiece part is designed to be at least partially absorbing for the laser beams in the area of the joining zone on the second coupling zone.

the DE 10 2010 024 205 A1 relates to an ultrasonic sensor, in particular for a vehicle, with a pot-shaped housing and a cover by which the rear of the housing is covered, the cover being a film.

In addition, the DE 10 2013 022 061 A1 a method for manufacturing an ultrasonic sensor for a motor vehicle, in which for the Ultra sound sensor, a membrane for emitting ultrasonic signals in a transmission direction and a sensor housing can be provided in and/or on which the membrane is attached. The sensor housing has a front side pointing in the transmission direction of the membrane and a rear side pointing in a rearward direction opposite to the transmission direction. The front of the sensor housing is designed with a front opening for the membrane. The front side of the sensor housing is connected to a cap formed from a foil, with which the front opening of the sensor housing is covered in the transmission direction. The membrane is introduced at least in regions into a receptacle in the cap, and a front side of the membrane pointing in the transmission direction is connected to a bottom of the receptacle in the cap.

the DE 10 2015 113 994 A1 relates to a method for producing a membrane of an ultrasonic sensor for a motor vehicle, in which a floor body is produced. An essentially hollow-cylindrical jacket body is produced. The base body and the jacket body are connected to one another to form the membrane, with the membrane being essentially pot-shaped. The base body is reshaped in an edge area in such a way that the base body and the casing body are connected to one another in a form-fitting and/or force-fitting manner.

From the DE 10 2006 011 155 A1 an ultrasonic sensor for a vehicle with a housing is known. A transducer element for generating ultrasonic vibrations is attached to the bottom of the housing. A first damping element for vibration damping of the floor is arranged in the housing. A cover with a second damping element is provided for closing the housing, with the cover having a continuous tapering of the cover thickness in the region of the second damping element.

the DE 10 2013 211 409 A1 relates to a distance sensor for a motor vehicle, the housing of which is designed to be attached to a bumper of the motor vehicle. At the same time, the housing is designed to accommodate or attach a crash or acceleration sensor of an airbag device.

From the DE 10 2005 025 147 A1 a method for laser welding a cover of a fuel injector and a method for laser inscribing the cover is known.

Proceeding from the prior art mentioned above, the invention is therefore based on the object of specifying a method for producing an ultrasonic sensor and an ultrasonic sensor produced in particular with the method, each of the type mentioned above, which enable high reliability of the ultrasonic sensor.

The object is achieved according to the invention by the features of the independent claims. Advantageous refinements of the invention are specified in the dependent claims.

According to the invention, a method for producing an ultrasonic sensor is thus specified, comprising the steps of providing a pot-like housing that absorbs light with a first wavelength, arranging a membrane for coupling and decoupling ultrasonic signals on a front side of the housing, arranging a control and evaluation electronics in an interior of the housing, arranging a cover made of a material that is transparent to light with the first wavelength and absorbing light with a second wavelength on a rear side of the pot-like housing, closing the pot-like housing with the cover by laser welding a first laser with the first wavelength through the lid, and writing on the outside of the lid with a second laser with the second wavelength.

Also according to the invention is an ultrasonic sensor with a pot-like housing that absorbs light with a first wavelength, a membrane for coupling in and out of ultrasonic signals on a front side of the housing, control and evaluation electronics that are arranged in an interior of the housing , and a cover made of a material which is transparent to light having the first wavelength and absorbing light having a second wavelength. In particular, the ultrasonic sensor can be produced according to the above method.

The basic idea of the present invention is therefore to enable simple production of the ultrasonic sensor and simple labeling by using a material for the rear cover that is transparent to the wavelength of the welding laser but absorbs to the wavelength of an additional inscription laser. Due to the corresponding design of the cover together with the design of the housing, the ultrasonic sensor can be closed by laser welding, i.e. the cover is attached to the rear of the housing by laser welding, and the cover can also be laser inscribed. Due to the design and installation of typical ultrasonic sensors, the lid is the preferred location for labeling.

The pot-like housing is open at the back and is closed there by the lid. The cover is attached to the housing using a so-called laser transmission process with the first wavelength. Since the cover is transparent to this first wavelength of the laser radiation, the laser beams can pass through the cover and heat the housing, which absorbs the light of the first wavelength, in the area of contact with the cover. The housing melts in the contact area with the cover, so that the housing cools down after being irradiated with the first laser and reliably connects to the cover when it cools down.

The pot-like housing is therefore absorbent for light with the first wavelength in order to enable the material to be melted by the laser radiation with the first wavelength without being melted itself. The material of the housing is melted or at least partially melted in the connection area with the cover. As a result, the pot-like housing can be reliably closed with the lid. The cover can be welded to the housing all around, for example. Alternatively, the cover can be welded to the housing only at certain points or in sections, for example.

The membrane is arranged on the front of the ultrasonic sensor. This corresponds to a bottom of the pot-like housing. A piezo element is typically arranged on the diaphragm. The control and evaluation electronics control the piezo element in order to deflect the membrane and emit ultrasonic pulses. In addition, vibrations in the ambient air are conducted via the membrane into the piezo element and recorded. The control and evaluation electronics receive corresponding signals from the piezo element and output them.

The ultrasonic sensor is typically used in a driving support system of a vehicle to detect surroundings of the vehicle. The driving assistance system usually includes a plurality of ultrasonic sensors. The driving support system can evaluate the signals from the ultrasonic sensors individually or in combination in order to record the surroundings of the vehicle.

The cover of the housing is also referred to as the rear cover of the housing. Correspondingly, the side of the housing on which the membrane is arranged is defined as the front side.

The lid is inscribed on its outside with the second laser with the second wavelength. Laser light of the second wavelength thus does not penetrate the cover, but causes local heating of the cover on its surface, as a result of which the inscription is produced. Lettering details are given below.

In principle, the method can be carried out with only one laser, which emits light with different wavelengths corresponding to the first and second wavelength. One laser can thus be used both as the first and as the second laser.

In an advantageous embodiment of the invention, the first wavelength is longer than the second wavelength, i.e. the light with the longer wavelength passes through the cover and melts the housing in the contact area with the cover. The laser light with the shorter wavelength is used to label the lid.

In an advantageous embodiment of the invention, arranging a cover made of a material that is transparent to light with the first wavelength and absorbs light with a second wavelength on a rear side of the pot-like housing includes providing the cover made of a material that is suitable for light of the first wavelength of at least 900 nm, for example 980 nm, 1032 nm or 1064 nm. Corresponding materials are known in principle as such and can therefore be used easily. In addition, corresponding first lasers with wavelengths of at least 900 nm, for example 980 nm, 1032 nm or 1064 nm, are known in principle as such and are therefore easily available.

In an advantageous embodiment of the invention, arranging a cover made of a material that is transparent to light with the first wavelength and absorbs light with a second wavelength on a rear side of the pot-like housing includes providing the cover made of a material that is suitable for light of the second wavelength of less than 700 nm, for example about 530 nm, in particular 532 nm. Corresponding materials are known in principle as such and can therefore be used easily. In addition, corresponding second lasers with wavelengths of less than 700 nm, for example approximately 530 nm, in particular 532 nm, are known in principle as such and are therefore easily available.

In principle, it is preferred that the material of the cover has wavelength ranges for the first or second wavelength. Typically, corresponding materials have properties in which wavelengths above a limit wavelength or a limit wavelength range as first wavelength are suitable, while wavelengths below the cut-off wavelength or the cut-off wavelength range are suitable as the second wavelength. Corresponding lasers for processing are therefore not limited to individual wavelengths, but can have different wavelengths from the corresponding areas as the first or second wavelength.

In an advantageous embodiment of the invention, arranging a cover made of a material that is transparent to light with the first wavelength and absorbs light with a second wavelength on a rear side of the pot-like housing includes providing the cover made of one of the materials BASF Ultradur LUX B4300G4 sw. 15092 -PBTGF20, laser-transparent black, BASF Ultradur LUX B4300G6 sw. 15092 - PBTGF30, laser-transparent black or BASF Ultradur B4300G6 HR sw. 15092 - PBTGF30 HR, laser-transparent black.
The materials with the designations BASF Ultradur LUX B4300G4 sw. 15092 - PBTGF20, laser-transparent black and BASF Ultradur LUX B4300G6 sw. 15092 - PBTGF30, laser-transparent black are laser-transparent types with high laser transparency for wavelengths greater than 900 nm. The material with the designation BASF Ultradur B4300G6 HR sw. 15092 - PBTGF30 HR, laser-transparent black, is a hydrolysis-stabilized, laser-transparent type with acceptable laser transparency for wavelengths greater than 900 nm. All materials mentioned are highly absorbent for wavelengths smaller than 700 nm. The materials mentioned have properties that allow both the attachment of the cover to the housing by laser welding and the laser inscription of the cover.

In an advantageous embodiment of the invention, arranging a cover made of a material that is transparent for light with the first wavelength and absorbs light with a second wavelength on a rear side of the pot-like housing includes providing the cover made of a plastic material with the addition of laser-sensitive additives , for example color pigments or glass fibers. By adding the laser-sensitive additives, it can be ensured that the inscription can be produced with a contour sharpness and a contrast that meet the requirements for machine-readable inscriptions. The plastic material itself can, for example, have only a low absorption for the second wavelength. The absorption is then ensured by the laser-sensitive additives.

In an advantageous embodiment of the invention, arranging a cover made of a material that is transparent to light with the first wavelength and absorbs light with a second wavelength on a rear side of the pot-like housing includes injection molding of the cover from a thermoplastic material. Injection molding enables the lid to be easily manufactured in a desired shape. A suitable mold must be provided.

In an advantageous embodiment of the invention, arranging a cover made of a material that is transparent to light with the first wavelength and absorbs light with a second wavelength on a rear side of the pot-like housing includes providing the cover as a film cover. The use of a film cover allows a particularly light cover to be produced and thus a particularly light ultrasonic sensor. The film cover has a low material thickness and is therefore low in weight.

In an advantageous embodiment of the invention, the labeling of the cover includes labeling by means of a color change, for example by carbonization or material foaming, by means of photochemical processes, for example photoreduction or fading, or by engraving, for example by local material evaporation. The various lettering methods can be used to create different types of lettering. Depending on the type of inscription, different resolutions can sometimes be achieved.

In an advantageous embodiment of the invention, arranging a cover made of a material that is transparent for light with the first wavelength and absorbs light with a second wavelength on a rear side of the pot-like housing includes providing the cover with an outer surface with low reflectivity for the light of the first and second wavelength. The low reflectivity means, on the one hand, that the light of the first wavelength passes through the cover to the greatest possible extent and the housing can melt in the area where it connects to the cover, and on the other hand that the light of the second wavelength penetrates the cover to the greatest possible extent heated outside. Reflections of the laser beams cannot contribute to the corresponding heating and therefore represent losses that must be avoided.

In an advantageous embodiment of the invention, arranging a cover made of a material that is transparent to light with the first wavelength and absorbs light with a second wavelength on a rear side of the pot-like housing includes a positive, material or non-positive connection of the cover a functional layer. The lid with the functional layer can implement extended functions. The cover can be made of a non-electrically conductive plastic material, for example, which forms a mechanical structure, and the functional layer can be made, for example, as a thin metal foil that forms a shield against electromagnetic radiation. In order to ensure reliable welding of the cover to the housing, the functional layer is preferably recessed in the contact area with the housing, ie in the area in which the cover is welded to the housing. In principle, several functional layers can also be connected to the cover.

In an advantageous embodiment of the invention, the cover has at least one reinforcing rib on its inside facing the interior. The at least one reinforcement rib stabilizes the cover and thus makes it easier to handle the cover during assembly on the housing. In addition, the cover can be produced with a small material thickness by a corresponding reinforcement by the at least one reinforcement rib, whereby the weight of the ultrasonic sensor is reduced overall and/or the internal or usable volume for the electronics is increased.

According to the invention, the cover has a peripheral edge on its inner side facing the interior space, with a gap being formed between the housing and the edge. The rim can facilitate positioning of the lid on the back of the case. In addition, the edge can form a barrier for material escaping during laser welding. Impairment or contamination, in particular of the control and evaluation electronics, but also of the membrane for coupling or decoupling the ultrasonic signals can thus be avoided. The edge can be designed, for example, as a circumferential embossing or web that prevents liquid welding material from getting into an interior space of the ultrasonic sensor.

The invention is explained in more detail below with reference to the attached drawing based on preferred embodiments. The features shown can represent an aspect of the invention both individually and in combination. Features of different exemplary embodiments can be transferred from one exemplary embodiment to another.

• 1 eine Schnittdarstellung eines Ausschnitts eines Ultraschallsensors gemäß einer ersten, bevorzugten Ausführungsform im Verbindungsbereich von Gehäuse und Deckel in einer seitlichen Ansicht,
• 2 eine Schnittdarstellung eines Ausschnitts eines Ultraschallsensors gemäß einer zweiten Ausführungsform im Verbindungsbereich von Gehäuse und Deckel mit einer Beschriftung auf dem Deckel in einer Ansicht von schräg unten,
• 3 eine Schnittdarstellung eines Ausschnitts des Ultraschallsensors aus 2 im Verbindungsbereich von Gehäuse und Deckel mit einer Beschriftung auf dem Deckel in einer Ansicht von schräg oben, und
• 4 eine Darstellung des Deckels des Ultraschallsensors aus 2 in einer Ansicht von schräg unten.

It shows

• 1 a sectional view of a section of an ultrasonic sensor according to a first, preferred embodiment in the connection area of the housing and cover in a side view,
• 2 a sectional view of a section of an ultrasonic sensor according to a second embodiment in the connection area of the housing and cover with an inscription on the cover in a view obliquely from below,
• 3 a sectional view of a section of the ultrasonic sensor 2 in the connection area of the housing and cover with an inscription on the cover in an oblique view from above, and
• 4 a representation of the cover of the ultrasonic sensor 2 in an oblique view from below.

the 1 shows a partial view of an ultrasonic sensor 10 according to a first preferred embodiment of the invention.

Ultrasonic sensor 10 includes a pot-like housing 12 with a membrane (not shown here) for coupling or decoupling ultrasonic signals on a front side of housing 12. A piezo element (also not shown here) is arranged on the membrane. Ultrasonic sensor 10 also includes a 1 control and evaluation electronics, not shown, which are arranged in an interior space 14 of the housing 12 . The control and evaluation electronics control the piezo element in order to deflect the membrane and generate ultrasonic pulses. In addition, vibrations in the ambient air are conducted via the membrane into the piezo element and recorded. The control and evaluation electronics receive corresponding signals from the piezo element and output them. The signals from the piezo element are output to a control unit, for example.

The ultrasonic sensor 10 of the first exemplary embodiment is used here, for example, in a driving support system of a vehicle in order to detect surroundings of the vehicle. The driving support system includes a plurality of these ultrasonic sensors 10 and the control unit connected to the ultrasonic sensors 10 to receive the signals from the ultrasonic sensors 10 . The driving support system can evaluate the signals from the ultrasonic sensors 10 individually or in combination in order to detect the surroundings of the vehicle.

The ultrasonic sensor 10 also includes a cover 16 which is arranged on a rear side 18 of the pot-like housing 12 and closes it. The side of the case is similar 12, on which the membrane is arranged, is defined as the front side.

The cover 16 is positively, materially or non-positively connected to a functional layer not shown individually. In this exemplary embodiment, the cover 16 is made of plastic, that is to say an electrically non-conductive material, and forms a mechanical structure. The cover 16 is produced from a thermoplastic material by injection molding. In this exemplary embodiment, the functional layer is in the form of a thin metal foil, which forms a shield against incoming and outgoing electromagnetic radiation. The functional layer is cut out in the contact area with the housing 12 . In an alternative embodiment, several functional layers are connected to the cover 16 .

In addition, the cover 16 has, on its inner side facing the interior 14 , a peripheral edge 20 which runs inside the housing 12 . A gap 22 is formed between the housing 12 and the rim 20 . In this exemplary embodiment, the edge 20 is designed as a circumferential web.

The cover 16 is attached to the housing 12 using a so-called laser transmission process. For this purpose, the pot-like housing 12 is made of a plastic material that absorbs light with a first wavelength. The first wavelength here is a wavelength greater than 900 nm. The cover 16 is made of a material that is transparent to light at the first wavelength and absorbs light at a second wavelength. In this exemplary embodiment, the second wavelength is a wavelength less than 700 nm. Such materials are available, for example, under the trade names BASF Ultradur LUX B4300G4 sw. 15092 - PBTGF20, laser-transparent black, BASF Ultradur LUX B4300G6 sw. 15092 - PBTGF30, laser-transparent black or BASF Ultradur B4300G6 HR sw. 15092 - PBTGF30 HR, laser-transparent black known. The materials with the designations BASF Ultradur LUX B4300G4 sw. 15092 -PBTGF20, laser-transparent black and BASF Ultradur LUX B4300G6 sw. 15092 - PBTGF30, laser-transparent black are laser-transparent types with high laser transparency for wavelengths greater than 900 nm. The material with the designation BASF Ultradur B4300G6 HR sw. 15092 - PBTGF30 HR, laser-transparent black, is a hydrolysis-stabilized, laser-transparent type with acceptable laser transparency for wavelengths greater than 900 nm. All materials mentioned are highly absorbent for wavelengths smaller than 700 nm.

The materials BASF Ultradur LUX B4300G4 sw. 15092 - PBTGF20, laser-transparent black, BASF Ultradur LUX B4300G6 sw. 15092 - PBTGF30, laser-transparent black or BASF Ultradur B4300G6 HR sw. 15092 - PBTGF30 HR, laser-transparent black correspond to wavelengths of 1064 nm, for example , 1032 nm or 980 nm have particularly good transparency. In addition, the materials have a particularly low transparency for light with the second wavelength of, for example, approximately 530 nm, in particular 532 nm. This low transparency of the cover 16 for the laser light with the second wavelength is achieved by adding laser-sensitive additives, for example color pigments or glass fibers, to a plastic material as a basis. When the cover 16 is produced, it is processed in such a way that its outer surface has a low reflectivity for the light of the first and second wavelength.

When sealing the pot-like housing 12 with the cover 16 by laser welding with the first wavelength, laser radiation with said first wavelength is emitted from a first laser 24 through the cover 16 onto the housing 12 in the contact area with the cover 16 . The first wavelength laser radiation passes through the cover 16 and impinges on the housing 12 which absorbs the first wavelength laser radiation. As a result, the housing 12 melts in the area of contact with the cover 16, as a result of which a melted layer 26 is formed. This is made possible because the functional layer is cut out in the contact area with the housing 12 .

In this state, the edge 20 forms a barrier for the melting layer 26 and prevents material from escaping from the gap 22 .

When the molten layer 26 cools down, the molten material of the housing 12 reliably connects to the cover 16, as a result of which the ultrasonic sensor 10 is closed. In this exemplary embodiment, the cover 16 is welded to the housing 12 all around. Alternatively, the lid 16 can be welded to the housing 12 only at certain points or in sections.

Finally, the cover 16 is inscribed on its outside with a second laser 28 with the second wavelength. A corresponding inscription 30 can be implemented as a QR code, for example, as shown in 2 is shown. The laser light with the second wavelength does not penetrate the cover 16, but causes local heating of the cover 16 at the latter Surface through which the lettering is made. The cover 16 is inscribed by means of a color change, for example by carbonization or material foaming, by means of photochemical processes, for example photoreduction or fading, or by engraving, for example by local material evaporation.

the 2 until 4 relate to an ultrasonic sensor 10 according to a second embodiment of the invention. The ultrasonic sensor 10 of the second embodiment largely corresponds to the ultrasonic sensor 10 of the first embodiment, so that the differences between the ultrasonic sensor 10 of the second embodiment and the ultrasonic sensor 10 of the first embodiment are essentially described below. Details of the ultrasonic sensor 10 of the second embodiment correspond to those of the ultrasonic sensor 10 of the first embodiment unless otherwise described.

Ultrasonic sensor 10 of the second embodiment includes a pot-like housing 12 with a membrane, not shown here, for coupling in and out of ultrasonic signals on a front side of housing 12. A piezoelectric element is arranged on the membrane. The ultrasonic sensor 10 also includes control and evaluation electronics, which are arranged in an interior 14 of the housing 12 in order to control the piezo element and to generate ultrasonic pulses. In addition, vibrations in the ambient air are conducted via the membrane into the piezo element and recorded and then received and output by the control and evaluation electronics.

The ultrasonic sensor 10 also includes a cover 16 which is arranged on a rear side 18 of the pot-like housing 12 and closes it. The cover 16 is positively, materially or non-positively connected to a functional layer not shown individually. In this exemplary embodiment, the cover 16 is made of plastic and forms a mechanical structure. In this exemplary embodiment, the functional layer is in the form of a thin metal foil, which forms a shield against incoming and outgoing electromagnetic radiation. The functional layer is cut out in the contact area with the housing 12 . In an alternative embodiment, several functional layers are connected to the cover 16 . In addition, the cover 16 has a plurality of reinforcing ribs 32 on its inner side facing the interior space 14, such as in FIG 4 can be seen.

In addition, the cover 16 has a peripheral edge 20 on its inner side facing the interior space 14 , a gap 22 being formed between the housing 12 and the edge 20 . In this exemplary embodiment, the edge 20 is designed as a circumferential web. In addition, the cover 16 has an outer circumferential closing edge 34 on its inner side facing the interior space 14 . A gap 22 is also formed between the housing 12 and the closing edge 34 . The cover 16 is made of a thermoplastic material by injection molding.

The cover 16 is attached to the housing 12 with a so-called laser transmission process in accordance with the ultrasonic sensor 10 of the first embodiment. Correspondingly, the pot-like housing 12 is made of a plastic material which is absorbing for light with a first wavelength. The cover 16 is made of a material that is transparent to light having the first wavelength and is absorptive to light having a second wavelength.

Here, the first wavelength is, for example, 1064 nm, 1032 nm or 980 nm, while the second wavelength is, for example, approximately 530 nm, in particular 532 nm. In addition, the cover 16 has a low reflectivity for the light of the first and second wavelength on its outer surface.

When sealing the pot-like housing 12 with the cover 16 by laser welding with the first wavelength, laser radiation with said first wavelength is directed through the cover 16 onto the housing 12 in the contact area with the cover 16 by a first laser 24 . The first wavelength laser radiation passes through the cover 16 and impinges on the housing 12 which absorbs the first wavelength laser radiation. As a result, the housing 12 melts in the area of contact with the cover 16, as a result of which a melted layer 26 is formed. This is made possible because the functional layer is cut out in the contact area with the housing 12 .

In this state, both the rim 20 and the closing edge 34 each form a barrier for the melted layer 26 and prevent material from escaping from the melted layer 26 via the gap 22 into the interior 14 of the ultrasonic sensor 10 or into an exterior of the ultrasonic sensor 10 .

When the molten layer 26 cools down, the molten material of the housing 12 reliably connects to the cover 16, as a result of which the ultrasonic sensor 10 is closed. In this exemplary embodiment, the cover 16 is welded to the housing 12 all around. Alternatively, the lid 16 can be welded to the housing 12 only at certain points or in sections.

Finally, the cover 16 is lasered on its outside with a second laser 28 with the second wavelength with an in 2 labeled label 30 shown. The laser light with the second wavelength thus does not penetrate the cover 16, but causes local heating of the cover 16 on its surface, as a result of which the inscription is produced. The cover 16 is inscribed by means of a color change, for example by carbonization or material foaming, by means of photochemical processes, for example photoreduction or fading, or by engraving, for example by local material evaporation.

Reference List

10

ultrasonic sensor

12

pot-like housing

14

inner space

16

lid

18

back

20

edge

22

gap

24

first laser

26

enamel layer

28

second laser

30

labeling

32

reinforcing rib

34

finishing edge

Claims (12)

Ultrasonic sensor (10) with a pot-like housing (12) which absorbs light with a first wavelength, a membrane for coupling and decoupling ultrasonic signals on a front side of the housing (12), control and evaluation electronics in a Interior (14) of the housing (12) is arranged, and a cover (16) made of a material which is transparent to light having the first wavelength and absorbing light having a second wavelength, characterized in that the cover (16) on has a peripheral edge (20) on its inner side facing the interior (14), a gap (22) being formed between the housing (12) and the edge (20). Ultrasonic sensor (10) after claim 1 , characterized in that the cover (16) has at least one reinforcing rib (32) on its interior (14) facing the inside. Ultrasonic sensor (10) after claim 1 or 2 , characterized in that the first wavelength is greater than the second wavelength. Ultrasonic sensor (10) according to any one of the preceding Claims 1 until 3 , characterized in that the material of the cover (16) for light with the first wavelength of at least 900 nm, for example 980 nm, 1032 nm or 1064 nm is transparent. Ultrasonic sensor (10) according to one of the preceding claims, characterized in that the material of the cover (16) absorbs light with the second wavelength of less than 700 nm, for example approximately 530 nm, in particular 532 nm. Ultrasonic sensor (10) according to one of the preceding claims, characterized in that the material of the cover (16) comprises a plastic material with the addition of laser-sensitive additives, for example color pigments or glass fibres. Ultrasonic sensor (10) according to one of the preceding claims, characterized in that the cover (16) is produced from a thermoplastic material by injection molding. Ultrasonic sensor (10) according to one of the preceding claims, characterized in that the cover (16) is a film cover. Ultrasonic sensor (10) according to one of the preceding claims, characterized in that the cover (16) has an outer surface with low reflectivity for the light of the first and second wavelength. Method for producing an ultrasonic sensor (10) according to one of Claims 1 until 9 , comprising the steps of providing the pot-like housing (12), which absorbs light with the first wavelength, arranging the membrane for coupling or decoupling ultrasonic signals on the front of the housing (12), arranging the control and evaluation electronics in the Interior (14) of the housing (12), arranging the cover (16) made of the material that is transparent to light with the first wavelength and absorbing light with the second wavelength on a rear side (18) of the pot-like housing (12) , Closing the pot-like housing (12) with the cover (16) by laser welding with a first laser (24) with the first wavelength through the lid (16), and inscribing the lid (16) on its outside with a second laser (28) with the second wavelength. procedure after claim 10 , characterized in that the labeling of the cover (16) includes labeling by means of a color change, for example by carbonization or material foaming, by means of photochemical processes, for example photoreduction or fading, or by engraving, for example by local material evaporation. procedure after claim 10 or 11 , characterized in that arranging a cover (16) made of a material which is transparent to light having the first wavelength and absorbing light having a second wavelength, on a rear side of the pot-like housing (12) a molded, material or non-positively connecting the cover (16) to a functional layer.

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