Ultrasonic sensor for motor vehicle, motor vehicle and method for manufacturing ultrasonic sensor

Abstract

An ultrasonic sensor (100) for a motor vehicle (1) comprises: a plastic housing (2); a membrane canister (7) inserted into an opening (12) in the plastic housing (2) and having an ultrasonic membrane (8); an acoustic transducer element (25) for inducing and sensing vibrations of the ultrasonic membrane (8), the acoustic transducer element being internally mounted on the ultrasonic membrane (8); a circuit board (16) which is arranged in the interior (14) of the plastic housing (2) and on which a drive circuit (19) for controlling the acoustic transducer elements (25) is mounted; two contact pins (20, 21) for electrically contacting the drive circuit (19) with the acoustic transducer element (25), the circuit board (16) being pressed against the contact pins (20, 21) such that the ends (35) of the contact pins (20, 21) pass through the circuit board (16); and a metal cover (40) which, together with the circuit board (16), surrounds and shields the ends (35) of the contact pins (20, 21) passing through the circuit board (16) on all sides.

Description

Technical Field

[0001] The present invention relates to an ultrasonic sensor for a motor vehicle and a motor vehicle. Background Art

[0002] Modern motor vehicles are equipped with ultrasonic sensors that allow the environment of the motor vehicle to be measured by sending and receiving ultrasonic signals. The information about the vehicle environment obtained in this way can be evaluated by a driver assistance system in order to generate warnings for the driver and to enable autonomous parking or partial or fully autonomous driving.

[0003] An ultrasonic sensor typically has a plastic housing with an opening into which a membrane can is inserted. A transducer element for inducing and sensing the vibration of the ultrasonic membrane is arranged internally on the ultrasonic membrane of the membrane can. In addition, a printed circuit board is arranged inside the plastic housing, on which a drive circuit for activating the transducer element is mounted. Contact pins are used to bring the drive circuit into contact with the transducer element. In particular, the unamplified signal on the conduction path from the transducer element via the contact pins to the drive circuit is particularly vulnerable to electromagnetic interference.

[0004] A shielding plate is typically arranged on the upper side of the printed circuit board (the side remote from the transducer element) to shield electromagnetic interference. For example, the shielding plate substantially covers the entire printed circuit board or at least the entire area of the drive circuit components mounted on the lower side of the printed circuit board. The entire device is then cast with a synthetic resin.

[0005] However, it is desirable to dispense with casting because this results in an additional weight of up to 20 g, which changes the stress characteristics of the ultrasonic sensor, thereby increasing the risk of breakage of the component parts. Without casting, it is not possible to securely mount a freely arranged large-area shielding plate inside the plastic housing. The shielding plate will start to vibrate and shift under the influence of the ultrasonic waves. This is why the shielding plate is also dispensed with, and downstream signal processing and maintaining a minimum distance during installation are relied upon to avoid electromagnetic interference.

[0006] However, in some installation cases, such as in the bumper of a motor vehicle, the EMC immunity is still not satisfactory.

[0007] WO 2017 / 097496 discloses that the membrane of the transducer element can be connected to ground.

[0008] US 2019 / 0388936 A1 discloses a membrane can for an ultrasonic transducer. The membrane can is provided with a metal coating. A piezoelectric element mounted internally on the membrane is electrically connected to the metal coating. The membrane can thus performs an electrical function, in particular electrical grounding for improving EMC protection.

[0009] US 2006 / 0229785 A1 discloses a pedestrian protection system, in which a plurality of ceramic sensors are attached to a carrier film. The carrier film has a continuous metallization layer or a metal protection layer for EMC shielding of the plurality of ceramic sensors. Summary of the Invention

[0010] In this context, the object of the present invention is to improve the EMC immunity of ultrasonic sensors.

[0011] According to a first aspect, to achieve this object, an ultrasonic sensor for a motor vehicle is proposed, which has: a plastic housing, a membrane can inserted into an opening of the plastic housing and having an ultrasonic film, an acoustic transducer element for inducing and sensing vibrations of the ultrasonic film, the acoustic transducer element being mounted on the ultrasonic film from the inside, a printed circuit board arranged inside the plastic housing, on which a drive circuit for activating the acoustic transducer element is mounted; two contact pins for electrically contacting the drive circuit with the acoustic transducer element, wherein the printed circuit board is pressed against the contact pins such that the ends of the contact pins pass through the printed circuit board; and a metal cover, which together with the printed circuit board surrounds and shields the ends of the contact pins passing through the printed circuit board on all sides.

[0012] The inventors have recognized that the contact pins passing through the printed circuit board play a decisive role as antennas for electrical interference. However, pressing the printed circuit board against the ends of the contact pins such that they penetrate the printed circuit board is desirable and advantageous because in this case, a simple manufacturing method and a more stable and higher-quality connection between the contact pins and the printed circuit board can be achieved compared to the case where the contact pins are only soldered to the printed circuit board from one side. According to the proposed ultrasonic sensor, the contact pins passing through the printed circuit board are now shielded by a metal cover. Thus, the field entry of the electric field can be advantageously dissipated before it can be coupled into the capacitance formed by the contact pins that extend substantially parallel to each other. Thus, the EMC immunity of the ultrasonic sensor to the electric field can be advantageously improved. Thus, no damage will be caused even when the contact pins form a high capacitance. Thus, the contact pins can now be arranged very closely side by side. The inductance formed by the contact pins can thus be advantageously kept low. Thus, the EMC immunity of the ultrasonic sensor to the magnetic field can also be advantageously improved. Overall, the EMC immunity of the ultrasonic sensor can thus be advantageously improved.

[0013] The membrane can having the ultrasonic film can be integrally formed. That is to say, the membrane can can be an element in the form of a can. The bottom surface of the can form can be made thinner than the wall of the can form. In this case, the bottom surface in particular forms the ultrasonic film.

[0014] The contact pin can be pressed into the plastic housing so that it can be firmly installed against vibrations in the housing. The contact pin can be pressed into the plastic housing before the printed circuit board is pressed against the end of the contact pin.

[0015] For example, when the printed circuit board is pressed against the end of the contact pin, the end of the contact pin is pressed into a through plating (also known as a via) having a metallized (e.g., tin-plated) inner surface, whereby the contact pin can contact the drive circuit. Thus, a reliable electrical contact between the contact pin and the drive circuit can be provided.

[0016] For example, the acoustic transducer element is a piezoelectric element. Activation of the acoustic transducer element particularly includes sending an activation signal to the acoustic transducer element and then receiving the received signal from the acoustic transducer element.

[0017] This end of the respective contact pin passing through the printed circuit board can also be referred to as the "upper end". At the lower end opposite the upper end, the contact pin can be in direct contact with the acoustic transducer element, for example, welded thereto. The contact pin can also be in indirect contact with the acoustic transducer element. For example, a loose fine wire can be used to connect the lower end of a respective contact pin to the acoustic transducer element. The area between the acoustic transducer element and the lower end of the contact pin can be backfilled with foam, and the loose fine wire extends in this area. Thus, additional sound decoupling can be achieved.

[0018] "Surrounding on all sides together with the printed circuit board" is understood to particularly mean that the space in which the upper end of the contact pin is arranged is bounded in each spatial direction either by an area of the metal cover or by an area of the printed circuit board.

[0019] The metal cover is particularly a grounded metal cover. "Grounded" is understood to particularly mean at least a non-high-impedance connection to ground. "Non-high-impedance" is understood to particularly mean a resistance to ground of less than 1000 ohms, preferably less than 800 ohms, and particularly preferably less than 600 ohms.

[0020] According to one embodiment, the drive circuit includes one or more electronic components that are mounted outside the metal cover on the printed circuit board, on the same side of the printed circuit board as the metal cover.

[0021] The components are arranged outside the metal cover and are thus not shielded by it. However, the metal cover shields the end of the contact pin where an electrical interference field is most likely to couple. Thus, advantageously, the metal cover is small and can be firmly mounted on the printed circuit board against vibrations. Thus, advantageously, the interior of the cast plastic housing can be dispensed with.

[0022] According to this embodiment, one side of the printed circuit board on which the metal cover is arranged, the end of the contact pin passing through the printed circuit board, and the electronic component can also be referred to as the upper side. The other side of the printed circuit board on which the remaining part of the contact pin is arranged and which contacts the acoustic transducer element can also be referred to as the lower side.

[0023] For example, the electronic component can include a capacitor, a coil, a transistor, an operational amplifier, a processor, an ASIC, etc.

[0024] According to another embodiment, the interior in the plastic housing is at least not cast on the same side of the printed circuit board as the metal cover.

[0025] In particular, the interior can be an open space on the upper side of the printed circuit board, that is to say, a non-backfilled space, as long as it is not occupied by the metal cover or components.

[0026] Therefore, the weight of the ultrasonic sensor can be reduced, the ultrasonic sensor can be less rigid, and advantageously, there may be fewer material fractures. However, at the same time, the metal cover provides excellent electric field attenuation.

[0027] According to another embodiment, the printed circuit board is mounted upright on a protrusion of the plastic housing.

[0028] Mounting upright on the housing protrusion advantageously provides stability and vibration resistance.

[0029] The protrusion of the plastic housing is in particular a protrusion protruding inward. The protrusion can be annular or circumferential. The protrusion can in particular be formed near the membrane can, where the main part of the plastic housing narrows to an opening into which the membrane can is inserted. Mounting upright on such a protrusion is particularly only possible by arranging the components advantageously on the upper side of the printed circuit board. Specifically, this can in turn be made possible by the metal cover providing shielding against the electric interference field, which shielding could not be provided by traditional solutions in the case of components arranged on the upper side.

[0030] According to another embodiment, the metal cover has four walls extending perpendicular to the printed circuit board and a wall extending parallel to the printed circuit board and above the end of the contact pin.

[0031] In other words, the metal cover is in particular a cover in the shape of a cuboid or a cube. Advantageously, such a cover can be manufactured particularly easily. In addition, it can be firmly fastened to the printed circuit board against vibration, particularly advantageously at the three edges where it stands upright on the printed circuit board, and can be advantageously very rigid.

[0032] According to another embodiment, the outer wall of the metal cover is arranged at the boundary of the printed circuit board, and a tab continuously formed with the outer wall extends towards the membrane can beyond the boundary of the printed circuit board.

[0033] Therefore, advantageously, a part of the contact pins on the lower side of the printed circuit board between the printed circuit board and the membrane can also be shielded by the tab, and the shielding effect can be further improved.

[0034] "Arranged at the boundary" can particularly mean that the outer wall is arranged such that the tab extending from the outer wall towards the membrane contacts the boundary of the printed circuit board.

[0035] In particular, the tab and the outer wall can be integrally formed. The metal cover can be formed as a single piece as a whole, where the tab and the outer wall are parts of the single-piece metal cover. The outer wall can be one of the walls extending perpendicular to the printed circuit board.

[0036] The tab extends at least in the direction towards the membrane. Particularly preferably, the tab advantageously extends up to the membrane or is flush with the membrane.

[0037] According to another embodiment, the tab extends parallel to the plane formed by the two contact pins and is as wide as or wider than the distance between the two contact pins.

[0038] Therefore, the capacitance formed by the two contact pins is advantageously shielded by the tab in the portion of the contact pins extending along the tab.

[0039] According to another embodiment, the metal cover contacts the printed circuit board and is grounded.

[0040] Therefore, the grounding of the metal cover can be advantageously provided through the conductor traces of the printed circuit board. In addition to the two contact pins for contacting the acoustic transducer element, the printed circuit board can be pressed onto another contact pin that connects the inside of the plastic housing to the outside of the plastic housing. In this way, the vehicle ground for grounding the metal cover can be introduced into the ultrasonic sensor and to the metal cover.

[0041] According to another embodiment, the metal cover contacts the printed circuit board through a spring pin continuously formed with one of the walls of the metal cover, and the spring pin is pressed into the through plating of the printed circuit board.

[0042] Therefore, when assembling the ultrasonic sensor, the metal cover can be advantageously pressed into the through plating of the printed circuit board in a particularly simple manner, and then the spring pin presents a stable fit due to the restoring force after pressing. Thus, the entire metal cover can be advantageously mounted on the printed circuit board in a simple, vibration-resistant and stable manner.

[0043] Preferably, more than one wall of the metal cover is provided with a corresponding spring pin; particularly preferably, at least three of the four walls extending perpendicular to the printed circuit board (which stand upright on the printed circuit board) are provided with corresponding spring pins.

[0044] The spring pin can in particular be integrally formed with the metal cover.

[0045] The through-plating can also be referred to as a via or a through-hole. In particular, it can have a metallized inner surface, for example tinned, which is connected to ground and which comes into contact with the spring pin if the spring pin is pressed into the through-plating.

[0046] According to another embodiment, the spring pin is formed as an eyelet surrounding an elongated hole.

[0047] Thus, the spring pin can be formed integrally with the rest of the metal cover particularly simply, for example by stamping from a metal sheet.

[0048] According to another embodiment, the metal cover is made of a copper or brass sheet with a sheet thickness between 0.2 and 0.4 mm, preferably 0.3 mm.

[0049] Thus, eddy currents within the operating range of the ultrasonic sensor are optimally attenuated while the required material costs are minimal. Thus, the penetration depth of eddy currents with a frequency of 50 kHz in copper is approximately 0.3 mm.

[0050] According to another embodiment, the metal cover is stamped and folded integrally from a copper or brass sheet.

[0051] Thus, a simple and inexpensive manufacturing method is possible.

[0052] According to another embodiment, the membrane can is a metal membrane can which is not connected to ground with a high impedance.

[0053] Thus, the membrane can is grounded and can also advantageously have a shielding effect against electromagnetic interference fields. In a particularly preferred embodiment, in which the metal cover also has a tab extending up to the membrane can, thus, by the interaction of the metal membrane can, the metal cover and its walls and its tabs, the entire current path of the unamplified original signal from the metal element via the contact pin up to the transducer element of the drive circuit can be shielded against electrical interference fields.

[0054] For example, the membrane can can be made of aluminum. As an alternative thereto, the membrane can can be made of a non-metallic material and can have at least one metal coating; such a membrane can can also be considered a metal membrane can in the sense of this embodiment.

[0055] "Grounded" is understood in particular to mean at least a non-high-impedance connection to ground. "Non-high-impedance" is understood in particular to mean a ground resistance of less than 1000 ohms, preferably less than 800 ohms, particularly preferably less than 600 ohms.

[0056] According to another aspect, a motor vehicle having an ultrasonic sensor according to the first aspect or one of the embodiments of the first aspect is proposed.

[0057] For example, the motor vehicle can be a car or a passenger vehicle or a truck.

[0058] According to a third aspect, a method for manufacturing an ultrasonic sensor is described. The method includes: pressing two contact pins into a plastic housing; inserting a membrane can having an ultrasonic membrane and a transducer element for inducing and sensing vibrations of the ultrasonic membrane into an opening of the plastic housing, the transducer element being mounted on the ultrasonic membrane from the inside; bringing the contact pins into contact with the transducer element; pressing a printed circuit board on which a drive circuit for activating the transducer element is mounted onto an end portion of the contact pin such that the end portion passes through the printed circuit board; manufacturing a metal cover by stamping a blank from a copper or metal sheet and folding the blank; and mounting the metal cover onto the printed circuit board such that the metal cover surrounds and shields, together with the printed circuit board, the end portion of the contact pin passing through the printed circuit board on all sides.

[0059] The embodiments and features described for the proposed ultrasonic sensor apply correspondingly to the proposed motor vehicle and the proposed manufacturing method.

[0060] Other possible embodiments of the present invention also include combinations of features or embodiments not explicitly mentioned above or below with respect to the exemplary embodiments. In such cases, the person skilled in the art will also add individual aspects as improvements or additions to the corresponding basic forms of the present invention.

[0061] Further advantageous configurations and aspects of the present invention are the subject matter of the dependent claims and the exemplary embodiments of the present invention described below. The present invention will be explained in more detail below with reference to the drawings based on preferred embodiments. Description of the Drawings

[0062] Figure 1 An ultrasonic sensor according to an exemplary embodiment is shown;

[0063] Figure 2 A motor vehicle according to an exemplary embodiment is shown;

[0064] Figures 3A to 3D Possible electric interference fields are shown;

[0065] Figure 4 The cross-section A-A of an ultrasonic sensor according to a first exemplary embodiment is shown Figure 1 in;

[0066] Figure 5 is shown Figure 4 the cross-section B-B in;

[0067] Figure 6 The cross-section A-A of an ultrasonic sensor according to a second exemplary embodiment is shown Figure 1 in;

[0068] Figure 7 shows Figure 6 and 8 section B-B in

[0069] Figure 8 shows Figure 6 and 7 section C-C in

[0070] Figure 9 shows a blank workpiece according to a second exemplary embodiment; and

[0071] Figure 10 shows a manufacturing method according to a third exemplary embodiment.

[0072] Unless otherwise specified, identical or functionally identical elements in the figures have the same reference numerals. Detailed Description

[0073] Figure 1 shows an ultrasonic sensor 100 according to an exemplary embodiment. The ultrasonic sensor has a housing 2 made of plastic and a metal diaphragm can 7 with an ultrasonic diaphragm 8, and the diaphragm can 7 is inserted into an opening ( Figure 1 not shown) of the housing 2. The housing has a main body 3, a retaining ring 4, a cover 5, and an extension part 6. The retaining ring 4 holds the diaphragm can 7 on the main body 3 of the housing 2. After components described in more detail below are installed inside the housing 2, the cover 5 is placed on the main body 3. For example, the retaining ring 4, the cover 2, and the extension part 6 can be connected to the main body 3 by ultrasonic welding.

[0074] The ultrasonic sensor 100 is designed to emit ultrasonic signals by activating the ultrasonic diaphragm 8, wherein the central direction of the emitted ultrasonic signal lobe is aligned with the axial direction 13 of the diaphragm can 7. In this case, the ultrasonic diaphragm 8 serves as a "speaker". The ultrasonic sensor 100 is also designed to receive ultrasonic signals reflected, for example, from the environment of the motor vehicle 1 ( Figure 2 ). In this case, the ultrasonic diaphragm 8 serves as a "microphone". The signal for activating the ultrasonic diaphragm 8 and the received signal transmitted from the ultrasonic diaphragm 8 are led out of the housing 2 of the ultrasonic sensor 100 by signal lines (not shown) through the extension part 6.

[0075] Figure 2 shows a motor vehicle 1 according to an exemplary embodiment. The motor vehicle 1 has a plurality of ultrasonic sensors 100. A first ultrasonic sensor 101 is arranged in the front bumper 52 of the motor vehicle 1. Three ultrasonic sensors 102, 103, 104 are arranged in the side beam 9 of the motor vehicle 1. The ultrasonic sensor 105 is arranged in the rear bumper 10 of the motor vehicle 1.

[0076] Furthermore, a line 11 of a local instrument network LIN is arranged in the front bumper 52 of the motor vehicle 1, for example in the immediate vicinity of the ultrasonic sensor 101. LIN is a simple standard for data-driven onboard vehicle electrical systems, for example for rain sensors, wiper motors, sprinklers, etc. The signal of LIN is rectangular, with a stroke of 12 V and a slew rate of 2 V / µs. The operating frequency of LIN is 19 kHz. This harmonic oscillation is three times higher, namely 57 kHz, and is therefore within the range that the ultrasonic sensor 101 also transmits and receives acoustic ultrasonic signals. As will be described later with reference to Figure 4 and Figure 5 Explanation: the electrical signal is transmitted by the acoustic transducer element 25 ( Figure 5 ) is generated within the ultrasonic sensor 101, and this electrical signal corresponds to the acoustic ultrasonic signal. Therefore, the electric field generated by the line 11 of the LIN represents a potential interference field for the ultrasonic sensor 101. For example, the ultrasonic sensor 101 may falsely send a signal that an ultrasonic echo has been received, even though in fact only the interference field from the signal on the line 11 has interfered with the ultrasonic sensor 101. This is called a "phantom echo".

[0077] This problem is particularly evident in the front bumper 52 of the motor vehicle 1 , since it may not be feasible here to maintain the required minimum distance between the ultrasonic sensor 101 and the line 11 due to the limited space.

[0078] exist Figure 3A -D shows a possible relative spatial arrangement of the ultrasonic sensor 101 and the line 11. The field line trajectory of the electric interference field is indicated by arrows. Figure 3A As shown in FIG. 1 -D , the electric interference field acts on the ultrasonic sensor 101 mainly from the left and from above.

[0079] Figure 4 The ultrasonic sensor 100 in the configuration according to the first exemplary embodiment is shown. Figure 1 Section AA in Figure 5 Shows Figure 4 Section BB in. The following reference Figure 4 and Figure 5 The directional indications "downwards / downwardly" and the position indications "at the bottom / below" in the following text refer to Figure 5 Downward along the axial direction 13 or into Figure 4 In the following the directional indications "upwards / upwardly" and the position indications "above" refer to Figure 5 in the direction opposite to the axial direction 13 or Figure 4 The direction away from the plane of the page.

[0080] like Figure 5As shown, the membrane can 7 is placed on the edge 11 of the bottom-open main body 3. The retaining ring 4 is placed on the membrane can 7 and the main body 3. Thus, the membrane can 7 is inserted into the opening 12 of the housing 2 formed by the main body 3 and the retaining ring 4.

[0081] The printed circuit board 16 is arranged in the interior 14 of the housing 2. The electronic components 17, 18 of the drive circuit 19 are arranged on the printed circuit board 16. The drive circuit 19 may also include conductor tracks (not shown) that extend on or in the printed circuit board 16.

[0082] A plurality of first contact pins 20, 21 are pressed into the main body 3 of the housing 2. In addition, a plurality of second contact pins 22, 23, 24 are pressed into the main body 3 and the extension part 5 of the housing 6.

[0083] The first contact pins 20, 21 are used to contact the piezoelectric element 25 arranged inside the ultrasonic membrane 8 with the drive circuit 19. The lower ends of the first contact pins 19, 20 are indirectly in contact with the piezoelectric element 25 through the respective unstressed loose thin wires 26. The lower region 28 of the interior 14 can be backfilled with foam in the region of the loose wires 26. Thus, a favorable vibration decoupling is achieved between the ultrasonic membrane 8 having the piezoelectric element 25 on the one hand and the housing 3 and the printed circuit board 16 on the other hand.

[0084] The second contact pins 22, 23, 24 are used to contact the drive circuit 19 through a line (not shown), which is led out from the ultrasonic sensor 100 through the extension part 6 and can be connected, for example, to the control device (not shown) of the motor vehicle 1 ( Figure 2 )

[0085] The printed circuit board 16 has a plurality of through-platings 29 - 33. The printed circuit board is pressed onto the upper ends 35, 36 of the contact pins 20 - 24 such that the upper ends 35, 36 of the contact pins 20 - 24 pass through the through-platings 29 - 33 of the printed circuit board 16. In this way, the contact pins 20 - 24 are in contact with the drive circuit 19. At the same time, this provides a tight fit for the printed circuit board 16 on the contact pins 20 - 24.

[0086] In addition, the printed circuit board 16 is particularly preferably mounted upright on the inwardly projecting protrusion 15 on the circumference of the housing 2. Thus, being mounted on the protrusion 15 arranged far below enables the components 17, 18 of the drive circuit 19 to be arranged on the upper side of the printed circuit board 16, that is to say, on the same side as the upper ends 35, 36 of the contact pins 20 - 24 passing through the printed circuit board 16. Therefore, advantageously, the printed circuit board 16 is stably and firmly pressed and assembled in the housing 2, especially firmly against vibration.

[0087] During operation, the drive circuit 19 is powered by the motor vehicle 1 ( Figure 2) The not-shown control device is activated via contact pins 22, 23, 24 and not-shown lines. The drive circuit generates a suitable electrical activation signal for the piezoelectric element 25 and transmits it to the piezoelectric element 25 via contact pins 20, 21 and the loose thin wire 26. In response to the activation signal, the piezoelectric element 25 induces vibrations in the ultrasonic membrane 8 of the membrane tank 7, thereby transmitting an acoustic ultrasonic signal in the axial direction 13. If this ultrasonic signal is reflected back to the ultrasonic membrane 8 in the environment of the motor vehicle 1 ( Figure 2 ), vibrations are caused in the ultrasonic membrane. The piezoelectric element 25 senses the vibrations of the ultrasonic membrane 8 and sends an electrical reception signal indicating the received ultrasonic signal to the drive circuit 19 via the loose thin wire 26 and contact pins 20, 21. The drive circuit 19 amplifies the received signal and sends it to the not-shown control device of the motor vehicle 1 ( Figure 2 ) via contact pins 22, 23, 24 and not-shown lines. The not-shown control device can utilize the time-of-flight difference between the transmitted ultrasonic signal and the received reflected ultrasonic signal to determine, for example, the distance to an obstacle in the environment of the motor vehicle 1 ( Figure 2 ).

[0088] It should be noted here that the unamplified and thus very weak electrical reception signal is transmitted from the piezoelectric element 25 to the drive circuit 19 via contact pins 20, 21 and thin wires 26, 27. This reception signal is particularly vulnerable to electrical and magnetic interference fields.

[0089] Therefore, the distance between contact pins 20 and 21 is chosen to be small, as Figure 4 shown. The distance between the two contact pins 20, 21 is not greater than 5 mm, for example, preferably not greater than 3 mm, and particularly preferably not greater than 1 mm. In this way, the inductance of the coil formed by contact pins 20, 21, the printed circuit board 16 and the piezoelectric element 25 is low, and a magnetic interference field can be coupled in through this coil.

[0090] Furthermore, the membrane tank 7 is formed of metal or provided with a metal coating and thus shields the loose thin wire 26 from electrical interference fields. Particularly preferably, the membrane tank 7 is also directly or at least connected to ground with a low impedance, for example with a resistance of 600 ohms to 800 ohms, and in any case with a resistance less than 1000 ohms, in order to be able to deploy this shielding effect in the best possible way. For this purpose, for example, not-shown lines extending in the body 3 can be used, which connect the membrane tank 2 to one of the second contact pins 22 - 24.

[0091] The first contact pins 20, 21 are also well shielded in their tracks, on the one hand by the membrane tank 7 and on the other hand by the printed circuit board 16.

[0092] However, the inventors have recognized that an electrical interference field couples from the piezoelectric element 25 into the signal path up to the drive circuit 19, in particular at the upwardly protruding upper ends 35 of the first contact pins 20, 21 that have passed through the printed circuit board 16.

[0093] Therefore, according to the first exemplary embodiment, a metal cover 40 is arranged on the printed circuit board 16 such that it surrounds and shields the upper ends 35 of the first contact pins 20, 21 together with the printed circuit board 16 on all sides.

[0094] Experiments have shown that, correspondingly, the interference from Figures 3A-3D the illustrated electric field is significantly reduced. This effect is particularly evident in the Figure 3B and Figure 3D illustrated configurations, where the electrical interference field acts on the ultrasonic sensors 100, 101 from above.

[0095] However, the metal cover 40 neither surrounds and shields the upper ends 36 of the second contact pins 22 - 24 nor the components 17, 18 of the drive circuit 19. Most of the unillustrated conductor traces on the printed circuit board 16 are also not covered by the metal cover 40. Therefore, the metal cover 40 can be advantageously designed to be small in size and light in weight. Thus, the metal cover 40 can be firmly mounted on the printed circuit board 16 in an anti-vibration manner using simple means and in a manner comparable to other components 17, 18, and in the process, hardly increases the weight of the ultrasonic sensor 100. In particular, with such a small metal cover 40, it is particularly advantageous that it is not necessary to cast the interior 14 of the ultrasonic sensor 100 in order to achieve anti-vibration.

[0096] The metal cover 40 can in particular be made of copper or brass sheet. The sheet thickness is preferably designed such that the penetration depth of the expected electrical interference field is substantially completely absorbed into the sheet, but the sheet does not become unnecessarily thick. In the case of LIN as the interference source discussed with reference to Figure 2 a plate thickness of 0.3 mm is sufficient. The sheet thickness is preferably at least 0.2 mm and at most 0.4 mm.

[0097] Figure 6 shows a cross-section A - A of the ultrasonic sensor 100 according to the second exemplary embodiment in Figure 1 , Figure 7 shows Figure 6 and Figure 8 a cross-section B - B in Figure 8 shows Figure 6 and Figure 7 a cross-section C - C in Figures 6 to 8 . The following refers to Figures 6 to 8 . Features of the second exemplary embodiment that are equivalent to those of the first exemplary embodiment will not be described in detail. The second exemplary embodiment differs from the first exemplary embodiment as follows:

[0098] The printed circuit board 16 is not flush with the inner surface 37 of the body 3 along its entire circumference. In the Figure 6 and 7 left part of, opposite to the extension 6 of the housing 2, a recess 38 is formed in the printed circuit board 16. A metal cover 40 is arranged at the boundary 39 of the printed circuit board 16, which boundary adjoins the recess 38 and projects slightly into the recess 38.

[0099] The printed circuit board 16 is mounted upright on the annular protruding projection 15 of the body 3 of the housing 2, and the annular protruding projection 15 also has a recess 47 in the region of the recess 38 of the printed circuit board 16.

[0100] According to the second exemplary embodiment, in the part arranged above the printed circuit board 16, the metal cover 40 has a cubic or cuboid shape, with four vertical walls 41, 42, 43, 44 extending perpendicular to the printed circuit board and a horizontal wall 45 extending parallel to the printed circuit board 16 above the ends 35 of the first contact pins 20, 21. In this case, the outer vertical wall 41 is arranged near the boundary 39 of the printed circuit board 16 above the recess 38. In particular, as Figure 7 shown, a tab 46 continuously formed with the outer vertical wall 41 extends from the lower end of the vertical wall 41 through the recess 38 of the printed circuit board 16, passes through the boundary 39 of the printed circuit board 16, and extends downward through the recess 47 in the inward protruding projection 15 of the housing 2 towards the membrane can 7. As Figure 7 and 8 shown, the tab 46 extends parallel to the plane formed by the first contact pins 20, 21. As can be seen from Figure 8 , the tab 46 is only slightly wider than the distance between the first contact pins 20, 21, and the first contact pins 20, 21 themselves extend parallel to each other towards the membrane can 7. In particular, the tab 46 is not wider than the outer wall 41 and is preferably narrower than the outer wall 41, which represents an elongation of the outer wall 41.

[0101] According to the second exemplary embodiment, the tab 46 extending towards the membrane can 7 can also advantageously be used to shield the vertical portions of the first contact pins 20, 21 between the printed circuit board 16 and the membrane can 7 from the entry of an electric interference field, especially from Figure 7 the left side (see Figure 3A and Figure 3C ).

[0102] As Figure 7As shown, the inner vertical wall 42 arranged opposite to the outer vertical wall 41 also has a spring pin 48. The spring pin 48 is pressed into another through plating 34 of the printed circuit board 16 and is stably held in the through plating 34 by the spring force (restoring force) of the spring pin 48. The through plating 34 may have a tinned inner surface that is grounded. Thus, the metal cover 40 is in contact with and grounded to the printed circuit board 16 through the spring pin 48 of the inner vertical wall 42.

[0103] Figure 9 Shown is a blank 50 according to a second exemplary embodiment. The blank 50 is a shape stamped from a copper or brass sheet having a thickness between 0.2 and 0.4 mm, preferably 0.3 mm. If the blank 49 is folded along the dotted fold line, for example, folded backward in the plane of the sheet, this forms the metal cover 40 ( Figures 6-8 ) having four vertical walls 41 - 44, a horizontal wall 45, a tab 46 adjacent and continuous with the outer vertical wall 41, and a spring pin 48.

[0104] The spring pin 48 is specifically formed as, for example, an eyelet 51 that surrounds an elongated hole 49. The wall thickness of the eyelet is, for example, 0.3 mm, and the elongated hole 49 is, for example, a 1 - mm hole. If the spring pin 48 is pressed into the through plating 34 ( Figure 7 ), the elongated hole 49 is compressed and exerts a restoring force that acts outwardly in the through plating 34 ( Figure 7 ) perpendicular to the inner surface of the through plating 34 ( Figure 7 ) and fixes the metal cover 40 ( Figure 7 ) to the printed circuit board 16 ( Figure 7 ).

[0105] Figure 10 Shown is a manufacturing method for manufacturing an ultrasonic sensor 100 according to a third exemplary embodiment. Also refer to Figures 4 to 10 .

[0106] In step S1, the first contact pins 20, 21 and the second contact pins 22 - 24 are pressed into a body 3 made of plastic (pressed into the housing 2).

[0107] In step S2, the membrane can 7 is inserted into the opening 12 of the housing 2, and the transducer element 25 is assembled internally on the ultrasonic membrane 8 of the membrane can 7. For example, as shown in Figure 7 and 8 , the membrane can 7 can be placed on the edge 11 of the body 3, and the retaining ring 4 can be slipped over the membrane can 7 and the body 3. The retaining ring can then be connected to the membrane can 7 and the body 3 by, for example, ultrasonic welding.

[0108] In step S3, the first contact pins 20, 21 come into contact with the transducer element 25. For this purpose, for example, the first contact pins 20, 21 are soldered to the loose fine wires 26, 27, and the loose fine wires 26, 27 are soldered to the sound transducer element 25.

[0109] In step S4, the printed circuit board 16 on which the drive circuit 19 is mounted is pressed onto the upper ends 35, 36 of the contact pins 20 - 24 such that the ends 35, 36 pass through the printed circuit board 16.

[0110] In step S5, the Figure 9 shown blank 50 is punched out from a copper or metal sheet and folded along the dotted fold line, thereby obtaining the metal cover 40.

[0111] In step S6, the metal cover 40 is mounted on the printed circuit board 16 such that the metal cover 40 surrounds and shields the upper ends 35 of the first contact pins 20, 21 passing through the printed circuit board 16 on all sides. For the mounting, in particular, the spring pins 48 are pressed into, for example, the through - plating 34 of the printed circuit board 16, so that the metal cover 40 is fixed on the printed circuit board 16, in contact with it and grounded.

[0112] Subsequently, the cover 5 can be placed on the body 3 and connected to it by ultrasonic welding.

[0113] Thereby, the ultrasonic sensor 100 according to the third exemplary embodiment is obtained.

[0114] Thus, the ultrasonic sensor 100 according to the exemplary embodiment can be manufactured particularly simply, can have a vibration - stable structure, in which the vibration - resistant mounting of the printed circuit board 16 and the vibration - resistant assembly of the metal cover 40 do not require casting the interior 14 of the plastic housing 2, can be light and fracture - proof, and due to the parallel - extending first contact pins 20, 21 and the metal cover 40 that at least shields the ends 35 of the first contact pins 20, 21 passing through the printed circuit board 16, can have good EMC immunity.

[0115] Although the present invention has been described based on the exemplary embodiments, it can be modified in various ways. The features disclosed for different exemplary embodiments can be combined with each other in any suitable way as long as this does not result in any contradiction.

[0116] The retaining ring 4 is not an essential feature of the present invention, and the membrane can 7 can also be directly inserted into the opening of the body 3 of the housing 2.

[0117] The loose fine wires 26, 27 are not necessary. The contact pins 20, 21 can also come into contact with the piezoelectric element 25 in another way, for example, directly.

[0118] In the drawings, three second contact pins 22 - 24 are shown, but it is also possible to use only two or more than three second contact pins 22 - 24 for external connection.

[0119] The metal cover 40 does not necessarily need to have the shape of a cube or cuboid with five walls, especially in the first embodiment, and the same is true in the second embodiment. For example, it can also be formed in the shape of a hemisphere.

[0120] In the second exemplary embodiment, the tab 46 does not need to extend near the membrane can 7, as Figure 7 shown. To achieve the desired additional shielding effect of the tab 46, it is sufficient if the tab extends at least slightly from the lower side of the printed circuit board 16 in the direction of the membrane can 7. However, according to an advantageous development, the tab 46 can also extend completely up to the membrane can 7 and contact it. In this way, the membrane can 7 can be advantageously grounded simply via the tab 46 of the metal cover 40.

[0121] Only one spring pin 48 mounted to the inner wall 42 has been described. However, it should be understood that corresponding spring pins 48 can be formed on one or more of the inner wall 42, side walls 43, 44, and outer wall 41 and can be pressed into the corresponding viewing plating 34 of the printed circuit board 16. If there are multiple spring pins 48, the metal cover 40 can be more reliably mounted and fixed to the printed circuit board 16.

[0122] List of reference numerals

[0123] 1 Motor vehicle

[0124] 2 Housing

[0125] 3 Body

[0126] 4 Retaining ring

[0127] 5 Cover

[0128] 6 Extension

[0129] 7 Membrane can

[0130] 8 Ultrasonic membrane

[0131] 9 Side beam

[0132] 10 Rear bumper

[0133] 11 Edge

[0134] 12 Opening in the housing

[0135] 13 Axial direction

[0136] 14 Interior

[0137] 15 Protrusion of the housing

[0138] 16 Printed circuit board

[0139] 17, 18 Components

[0140] 19 Driving circuit

[0141] 20, 21 Contact pins, First contact pins

[0142] 22 - 24 Contact pins, Second contact pins

[0143] 25 Piezoelectric element, Acoustic transducer element

[0144] 26, 27 Loose thin wires

[0145] 28 Lower region

[0146] 29 - 34 Through - plating

[0147] 35, 36 Upper ends

[0148] 37 Inner surface of the main body

[0149] 38 Recess of the printed circuit board

[0150] 39 Boundary of the printed circuit board

[0151] 40 Metal cover

[0152] 41 Outer vertical wall

[0153] 42 Inner vertical wall

[0154] 43, 44 Side vertical walls

[0155] 45 Horizontal wall

[0156] 46 Tab

[0157] 47 Recess for protruding protrusion

[0158] 48 Spring pin

[0159] 49 Elongated hole

[0160] 50 Stamped metal sheet, Blank

[0161] 51 Hole

[0162] 52 Front bumper

[0163] 100 - 105 Ultrasonic sensors

[0164] S1 - S6 Method steps

Claims

1. An ultrasonic sensor (100) for a motor vehicle (1), having: a plastic housing (2), a membrane canister (7) which is inserted into an opening (12) of the plastic housing (2) and has an ultrasonic membrane (8), an acoustic transducer element (25) for inducing and sensing vibrations of the ultrasonic membrane (8), which is mounted on the ultrasonic membrane (8) from the inside, a printed circuit board (16) arranged in the interior (14) of the plastic housing (2), on which a drive circuit (19) for activating the acoustic transducer element (25) is mounted, two contact pins (20, 21) for electrically contacting the drive circuit (19) with the acoustic transducer element (25), wherein the printed circuit board (16) is pressed onto the contact pins (20, 21) such that the ends (35) of the contact pins (20, 21) pass through the printed circuit board (16), and a metal cover (40) which, together with the printed circuit board (16), surrounds and shields the ends (35) of the contact pins (20, 21) passing through the printed circuit board (16) on all sides.

2. The ultrasonic sensor according to claim 1, characterized in that the drive circuit (19) includes one or more electronic components (17, 18) which are mounted outside the metal cover (40) on the printed circuit board (16), on the same side of the printed circuit board (16) as the metal cover (40).

3. The ultrasonic sensor according to claim 2, characterized in that the interior (14) in the plastic housing (2) is not cast at least on the same side of the printed circuit board (16) as the metal cover (40).

4. The ultrasonic sensor according to claim 2 or 3, characterized in that the printed circuit board (16) is mounted upright on a projection (15) of the plastic housing (2).

5. The ultrasonic sensor according to any one of the preceding claims, characterized in that the metal cover (40) has four walls (41 - 44) extending perpendicular to the printed circuit board (16) and a wall (45) parallel to the printed circuit board (16) and extending above the ends (35) of the contact pins (20, 21).

6. The ultrasonic sensor according to any one of the preceding claims, characterized in that the outer wall (41) of the metal cover (40) is arranged at the boundary (39) of the printed circuit board (16), and a tab (46) formed continuously with the outer wall (41) extends beyond the boundary (39) of the printed circuit board (16) towards the membrane canister (7).

7. The ultrasonic sensor according to claim 6, characterized in that the tab (46) extends parallel to the plane formed by the two contact pins (20, 21) and is as wide or wider than the distance between the two contact pins (20, 21).

8. The ultrasonic sensor according to any one of the preceding claims, characterized in that the metal cover (40) is in contact with the printed circuit board (16) and is grounded.

9. The ultrasonic sensor according to claim 8, characterized in that The metal housing (40) is in contact with the printed circuit board by means of spring pins (48) formed continuously with one of the walls (42) of the metal housing (40), and the spring pins are pressed into the through-plating (34) of the printed circuit board (16).

10. The ultrasonic sensor according to claim 9, characterized in that the spring pins (48) are formed as eyes (51) surrounding an elongated hole (49).

11. The ultrasonic sensor according to any one of the preceding claims, characterized in that the metal housing (40) is made of a copper or brass sheet, the sheet thickness being between 0.2 and 0.4 mm, preferably 0.3 mm.

12. The ultrasonic sensor according to claim 11, characterized in that the metal housing (40) is stamped and folded from the copper or brass sheet in one piece.

13. The ultrasonic sensor according to any one of the preceding claims, characterized in that the membrane can (7) is a metal membrane can (7) which is not connected to ground with a high impedance.

14. A motor vehicle (1) having an ultrasonic sensor (100, 101 - 105) according to any one of the preceding claims.

15. A method for manufacturing an ultrasonic sensor (100), comprising: - pressing (S1) two contact pins (20, 21) into a plastic housing (2); - inserting (S2) a membrane can (7) having an ultrasonic membrane (8) and a transducer element (25) for inducing and sensing vibrations of the ultrasonic membrane (8) into an opening (12) of the plastic housing (2), the transducer element being mounted on the ultrasonic membrane (8) from the inside; - bringing the contact pins (20, 21) into contact with the transducer element (25) (S3); - pressing (S4) a printed circuit board (16) on which a drive circuit (19) for activating the transducer element (25) is mounted onto the ends (35) of the contact pins (20, 21) such that the ends (35) pass through the printed circuit board (16); - manufacturing (S5) a metal housing (40) by stamping a blank (50) from a copper or metal sheet and folding the blank (50); - mounting (S6) the metal housing (40) onto the printed circuit board (16) such that the metal housing (40) surrounds and shields the ends (35) of the contact pins (20, 21) passing through the printed circuit board (16) together with the printed circuit board (16) on all sides.

Images