Ultrasonic sensor for a motor vehicle, motor vehicle, and method for producing an ultrasonic sensor

Abstract

An ultrasonic sensor (100) for a motor vehicle (1) comprises: a plastics housing (2); a diaphragm cup (7) that is inserted into an opening (12) in the plastics housing (2) and has an ultrasonic diaphragm (8); a sound transducer element (25) for inducing and sensing vibration of the ultrasonic diaphragm (8), which sound transducer element is mounted on the ultrasonic diaphragm (8) from the inside; a circuit board (16) which is disposed in the interior (14) of the plastics housing (2) and on which a driver circuit (19) for controlling the sound transducer element (25) is mounted; two contact pins (20, 21) for bringing the driver circuit (19) into electrical contact with the sound transducer element (25), the circuit board (16) being pressed onto the contact pins (20, 21) such that ends (35) of the contact pins (20, 21) pass through the circuit board (16); and a metal hood (40) which, together with the circuit board (16), surrounds and shields on all sides the ends (35) of the contact pins (20, 21) passing through the circuit board (16).

Description

[0001] ULTRASONIC SENSOR FOR A MOTOR VEHICLE, MOTOR VEHICLE AND

[0002] MANUFACTURING METHOD FOR AN ULTRASOUND SENSOR

[0003] The present invention relates to an ultrasonic sensor for a motor vehicle and a motor vehicle.

[0004] Modern motor vehicles are equipped with ultrasonic sensors that allow the measurement of the vehicle's surroundings by transmitting and receiving an ultrasonic signal. The information about the vehicle's surroundings obtained in this way can be evaluated by a driver assistance system to generate warnings for the driver, enable autonomous parking, or partially or fully autonomous driving.

[0005] An ultrasonic sensor typically has a plastic housing with an opening into which a diaphragm cup is inserted. A transducer element for exciting and detecting vibrations of the ultrasonic diaphragm is arranged on the inside of the diaphragm cup. A circuit board is also located inside the plastic housing, on which a driver circuit for controlling the transducer element is mounted. Contact pins are used to connect the driver circuit to the transducer element. Unamplified signals on the conduction path from the transducer element via the contact pins to the driver circuit are particularly susceptible to electromagnetic interference.

[0006] Traditionally, to shield against electromagnetic interference, a shielding plate was arranged on the top side of the circuit board (a side facing away from the sound transducer element). This shielding plate essentially covered the entire circuit board or at least the entire area of ​​the driver circuit components mounted, for example, on the underside of the circuit board. The entire assembly was then potted with a synthetic resin. However, it is desirable to forgo potting, as it adds up to 20 g of weight, changes the stress characteristics of the ultrasonic sensor, and thus increases the risk of component breakage. Without potting, it is not possible to securely mount a large-area shielding plate freely arranged inside the plastic housing. The shielding plate would vibrate under the influence of the ultrasound and become loose.For this reason, the shielding plate is omitted and relies on downstream signal processing and compliance with minimum distances during installation to deal with electromagnetic interference.

[0007] However, in certain installation situations, such as in the bumper of a motor vehicle, the EMC immunity is not yet satisfactory.

[0008] WO 2017 / 097496 discloses that a membrane of a sound transducer element can be connected to a ground.

[0009] US 2019 / 0388936 A1 discloses a diaphragm cup for an ultrasonic transducer. The diaphragm cup is provided with a metallic coating. A piezo element attached to the inside of the diaphragm is electrically connected to the metallic coating. The diaphragm cup thus implements electrical functionality, in particular an electrical ground to improve EMC protection.

[0010] US 2006 / 0229785 A1 discloses a pedestrian protection system in which a plurality of ceramic sensors are applied to a carrier film. The carrier film has a continuous metallization layer or metallic protective layer for EMC shielding of the multiple ceramic sensors.

[0011] Against this background, one object of the present invention is to improve the EMC immunity of an ultrasonic sensor.According to a first aspect, to achieve the object, an ultrasonic sensor for a motor vehicle is proposed, which comprises: a plastic housing, a diaphragm cup with an ultrasonic diaphragm inserted into an opening in the plastic housing, a sound transducer element attached to the ultrasonic diaphragm from the inside for exciting and detecting vibrations of the ultrasonic diaphragm, a printed circuit board arranged in the interior of the plastic housing, on which a driver circuit for controlling the sound transducer element is mounted, two contact pins for electrically contacting the driver circuit with the sound transducer element, wherein the printed circuit board is pressed onto the contact pins in such a way that ends of the contact pins pass through the printed circuit board, and a metallic hood which, together with the printed circuit board, surrounds and shields on all sides the ends of the contact pins passing through the printed circuit board.

[0012] The inventors recognized that the contact pins penetrating the circuit board play a crucial role as antennas for electrical interference. However, pressing the circuit board onto the ends of the contact pins so that they penetrate the circuit board is desirable and advantageous, as this allows for a simpler manufacturing process and a more stable and higher-quality connection between the contact pins and the circuit board than in a case where the contact pins are soldered to the circuit board from only one side. According to the proposed ultrasonic sensor, the contact pins penetrating the circuit board are now shielded by the metallic hood. This advantageously allows for the field input of an electric field to be diverted before it can couple into the capacitance formed by the contact pins, which run essentially parallel to one another.This advantageously improves the ultrasonic sensor's immunity to electric fields. This also eliminates the risk of high capacitance in the contact pins. Therefore, it is now possible to arrange the contact pins very closely together.

[0013] This advantageously minimizes the inductance generated by the contact pins. Accordingly, the ultrasonic sensor's immunity to magnetic fields can also be advantageously improved. Overall, the ultrasonic sensor's EMC immunity can be advantageously improved. The diaphragm cup with the ultrasonic diaphragm can be formed as a single piece. This means that the diaphragm cup can be a cup-shaped element. A base surface of the cup can be thinner than the walls of the cup. In this case, the base surface, in particular, forms the ultrasonic diaphragm.

[0014] The contact pins can be pressed into the plastic housing, thus ensuring vibration-proof installation. The contact pins can be pressed into the plastic housing before the circuit board is pressed onto the ends of the contact pins.

[0015] The contact pins can be connected to the driver circuit, for example, by pressing the ends of the contact pins into a through-hole, also known as a via, with a metallized, for example, tinned, inner surface when the circuit board is pressed onto the ends of the contact pins. Accordingly, a reliable electrical connection between the contact pins and the driver circuit can be provided.

[0016] The sound transducer element is, for example, a piezo element. Controlling the sound transducer element comprises, in particular, sending a control signal to the sound transducer element and subsequently receiving a receive signal from the sound transducer element.

[0017] The end of each contact pin that penetrates the circuit board can also be referred to as the "upper end." At a lower end opposite the upper end, the contact pins can be directly connected to the sound transducer element, for example, by soldering. The contact pins can also be indirectly connected to the sound transducer element. For example, a loose fine wire can be used to connect a lower end of each of the contact pins to the sound transducer element. An area between the sound transducer element and the lower end of the contact pin, where the loose fine wire runs, can be filled with foam. This allows for additional sound decoupling.

[0018] The term "surrounded on all sides by the printed circuit board" means in particular that a space in which the upper ends of the contact pins are arranged is limited in every spatial direction either by a surface of the metallic hood or by a surface of the printed circuit board.

[0019] The metallic hood is, in particular, a grounded metallic hood. "Grounded" is understood to mean, in particular, a connection to a ground that is at least not high-resistance. "Not high-resistance" is understood to mean, in particular, 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 driver circuit comprises one or more electronic components mounted on the circuit board on the same side of the circuit board as the metallic hood, outside the metallic hood.

[0021] The components are located outside the metal cover and are therefore not shielded by it. However, the metal cover shields the ends of the contact pins, where electrical interference is most likely to couple. The metal cover is therefore advantageously small and can be mounted on the circuit board in a vibration-resistant manner. This advantageously eliminates the need for encapsulation of the interior of the plastic housing.

[0022] The side of the circuit board on which the metallic hood, the ends of the contact pins that penetrate the circuit board, and, according to the present embodiment, also the electronic components are arranged, can also be referred to as the top side. The other side of the circuit board, on which the remaining sections of the contact pins are arranged and contact the sound transducer element, can also be referred to as the bottom side. The electronic components can be, for example, a capacitor, a coil, a transistor, an operational amplifier, a processor, an ASIC, and the like.

[0023] According to a further embodiment, an interior space in the plastic housing is not encapsulated at least on the same side of the circuit board as the metallic hood.

[0024] The interior space can be, in particular, a free space, i.e. an unfilled space, on the top side of the printed circuit board, as long as it is not occupied by the metallic cover or the components.

[0025] Accordingly, the weight of the ultrasonic sensor can be reduced, the ultrasonic sensor can be less rigid, and material fractures are advantageously less likely. At the same time, the metallic cover still provides excellent damping against electric fields.

[0026] According to a further embodiment, the circuit board is mounted on a projection of the plastic housing.

[0027] The bearing on the projection of the housing advantageously offers stability and vibration resistance.

[0028] The projection of the plastic housing is, in particular, an inwardly projecting projection. The projection can be annular or circumferential. The projection can, in particular, be formed near the diaphragm cup, where a main section of the plastic housing narrows to the opening into which the diaphragm cup is inserted. A seated mounting on such a projection can, in particular, only be made possible by advantageously arranging the components on the top side of the circuit board. This, in turn, can be made possible in particular by the metallic cover providing shielding against electrical interference fields, which could not previously be provided with conventional solutions for components arranged on the top side.

[0029] According to a further embodiment, the metallic hood has four walls running perpendicular to the circuit board and one wall running parallel to the circuit board and over the ends of the contact pins.

[0030] In other words, the metallic cover is, in particular, a cuboid or cube-shaped cover. Such a cover is particularly easy to manufacture. It can also be attached to the circuit board at three edges, where it is perpendicular to the board, in a vibration-resistant manner, and can advantageously exhibit high rigidity.

[0031] According to a further embodiment, an outer wall of the metallic hood is arranged at an edge of the circuit board, and a tab formed continuously with the outer wall runs past the edge of the circuit board towards the membrane pot.

[0032] Thus, a section of the contact pins on the underside of the circuit board between the circuit board and the membrane pot can also be advantageously shielded by the tab and the shielding effect can be further improved.

[0033] "Arranged at an edge" may in particular mean that the outer wall is arranged such that the tab extending from the outer wall to the diaphragm cup touches the edge of the circuit board.

[0034] The tab and the outer wall can, in particular, be formed as a single piece. The metallic hood can be formed as a single piece, with the tab and the outer wall being sections of the single-piece metallic hood. The outer wall can be one of the walls running perpendicular to the circuit board. The tab extends at least in one direction toward the diaphragm cup. Particularly preferably, the tab extends as far as the diaphragm cup or to a level of the diaphragm cup.

[0035] According to a further embodiment, the tab runs parallel to a plane formed by the two contact pins and is as wide as or wider than a distance between the two contact pins.

[0036] Thus, a capacitance formed by the two contact pins in a section of the contact pins that runs along the tab is advantageously shielded by the tab.

[0037] According to a further embodiment, the metallic hood is contacted with the circuit board and grounded.

[0038] Accordingly, grounding of the metallic cover can advantageously be provided via a conductor track of the circuit board. In addition to the two contact pins used to contact the sound transducer element, the circuit board can be pressed onto additional contact pins that connect the interior of the plastic housing to an exterior of the plastic housing. In this way, a vehicle ground can be routed into the ultrasonic sensor and to the metallic cover for grounding the metallic cover.

[0039] According to a further embodiment, the metallic hood is contacted with the printed circuit board by means of a spring pin formed continuously with one of the walls of the metallic hood, which spring pin is pressed into a through-hole of the printed circuit board.

[0040] It is therefore advantageously possible to press the metal cover into the through-holes of the circuit board in a particularly simple manner during assembly of the ultrasonic sensor, whereupon the spring pin assumes a stable seat due to the restoring force after pressing in. Thus, the entire metal cover can be advantageously mounted on the circuit board in a simple, vibration-resistant and stable manner.

[0041] Preferably, more than one wall of the metallic hood is provided with a respective spring pin; particularly preferably, at least three of the four walls extending perpendicular to the circuit board and perpendicular to the circuit board are provided with a respective spring pin.

[0042] The spring pin can in particular be formed in one piece with the metallic hood.

[0043] The through-hole plating can also be referred to as a contact hole or via. It can, in particular, have a metallized, for example, tinned, inner surface that is grounded and in contact with the spring pin when it is pressed into the through-hole plating.

[0044] According to a further embodiment, the spring pin is designed as an eyelet enclosing an elongated hole.

[0045] Accordingly, the spring pin can be particularly easily formed in one piece with the rest of the metal hood, for example by punching from a metallic sheet.

[0046] According to a further embodiment, the metallic hood is made of copper or brass sheet with a sheet thickness between 0.2 and 0.4 mm, preferably 0.3 mm.

[0047] Accordingly, electrical eddy currents with a frequency within the operating range of the ultrasonic sensor are optimally dampened while using the minimum amount of material required. For example, the penetration depth of an electrical eddy current with a frequency of 50 kHz in copper is approximately 0.3 mm. According to another embodiment, the metallic cap is stamped and folded in one piece from the copper or brass sheet.

[0048] Accordingly, a simple and cost-effective manufacturing process is possible.

[0049] According to a further embodiment, the diaphragm pot is a metallic diaphragm pot that is not connected to ground with high resistance.

[0050] Accordingly, the diaphragm cup is grounded and can advantageously also provide a shielding effect against electromagnetic interference fields. In a particularly preferred embodiment, in which the metallic cap also has the tab extending to the diaphragm cup, an entire current path of the not yet amplified raw signals of the sound transducer element, from the metallic element via the contact pins to the driver circuit, can be shielded against electrical interference fields through the interaction of the metallic diaphragm cup, the metallic cap, and their walls and tab.

[0051] The diaphragm cup can be made of aluminum, for example. Alternatively, the diaphragm cup can be made of a non-metallic material and have at least one metallic coating; such a diaphragm cup is also considered a metallic diaphragm cup within the meaning of the present embodiment.

[0052] "Grounded" is understood in particular to mean a connection to a ground that is at least not high-resistance. "Non-high-resistance" is understood in particular to mean a resistance to ground of less than 1000 ohms, preferably less than 800 ohms, and most preferably less than 600 ohms.

[0053] According to a further aspect, a motor vehicle with an ultrasonic sensor according to the first aspect or one of the embodiments of the first aspect is proposed. The motor vehicle can be, for example, an automobile or a passenger car or even a truck.

[0054] According to a third aspect, a method for producing an ultrasonic sensor is provided.The method comprises: pressing two contact pins into a plastic housing; inserting a membrane cup with an ultrasonic membrane and a sound transducer element attached to the ultrasonic membrane from the inside for exciting and detecting vibrations of the ultrasonic membrane into an opening in the plastic housing; contacting the contact pins with the sound transducer element; pressing a circuit board, on which a driver circuit for controlling the sound transducer element is mounted, onto the ends of the contact pins in such a way that the ends pass through the circuit board; producing a metallic hood by punching out a blank from a copper or metal sheet and folding the blank; and mounting the metallic hood on the circuit board in such a way that the metallic hood, together with the circuit board, surrounds and shields the ends of the contact pins passing through the circuit board on all sides.

[0055] The embodiments and features described for the proposed ultrasonic sensor apply accordingly to the proposed motor vehicle and the proposed manufacturing method.

[0056] Further possible implementations of the invention also include combinations of features or embodiments described above or below with respect to the exemplary embodiments that are not explicitly mentioned. In this case, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the invention.

[0057] Further advantageous embodiments and aspects of the invention are the subject of the dependent claims and the exemplary embodiments of the invention described below. The invention will be explained in more detail below using preferred embodiments with reference to the accompanying figures. Fig. 1 shows an ultrasonic sensor according to exemplary embodiments;

[0058] Fig. 2 shows a motor vehicle according to embodiments;

[0059] Fig. 3A-D show possible electrical interference fields;

[0060] Fig. 4 shows a section AA in Fig. 1 of an ultrasonic sensor according to a first embodiment;

[0061] Fig. 5 shows a section BB in Fig. 4;

[0062] Fig. 6 shows a section AA in Fig. 1 of an ultrasonic sensor according to a second

[0063] Example of implementation;

[0064] Fig. 7 shows a section BB in Figs. 6, 8;

[0065] Fig. 8 shows a section CC in Figs. 6, 7;

[0066] Fig. 9 shows a blank according to the second embodiment; and

[0067] Fig. 10 shows a manufacturing method according to a third embodiment.

[0068] In the figures, identical or functionally equivalent elements have been given the same reference numerals unless otherwise stated.

[0069] Fig. 1 shows an ultrasonic sensor 100 according to exemplary embodiments. The ultrasonic sensor has a housing 2 made of plastic and a metallic diaphragm cup 7 with an ultrasonic diaphragm 8 inserted into an opening in the housing 2 (not shown in Fig. 1). The housing has a body 3, a collar ring 4, a cover 5, and an extension section 6. The collar ring 4 holds the diaphragm cup 7 to the body 3 of the housing 2. The cover 5 is placed onto the body 3 after the components described in more detail below have been assembled in an interior of the housing 2. The collar ring 4, the cover 2, and the extension section 6 can be joined to the body 3, for example, by ultrasonic welding.

[0070] The ultrasonic sensor 100 is configured to emit ultrasonic signals by controlling the ultrasonic membrane 8, wherein a central direction of an emitted ultrasonic signal beam coincides with an axial direction 13 of the membrane cup 7. The ultrasonic membrane 8 serves as a "loudspeaker." The ultrasonic sensor 100 is further configured to receive ultrasonic signals reflected, for example, from the surroundings of a motor vehicle 1 (Fig. 2). The ultrasonic membrane 8 serves as a "microphone." Signals for controlling the ultrasonic membrane 8 as well as received signals supplied by the ultrasonic membrane 8 are routed out of the housing 2 of the ultrasonic sensor 100 via signal lines (not shown) through the extension section 6.

[0071] Fig. 2 shows a motor vehicle 1 according to exemplary embodiments. The motor vehicle 1 has several ultrasonic sensors 100. A first ultrasonic sensor 101 is arranged in a front bumper 52 of the motor vehicle 1. Three ultrasonic sensors 102, 103, 104 are arranged in a side sill 9 of the motor vehicle 1. An ultrasonic sensor 105 is arranged in a rear bumper 10 of the motor vehicle 1.

[0072] In the front bumper 52 of the motor vehicle 1, for example, a line 11 of a Local Instrumentation Network (LIN) is also arranged in the immediate vicinity of the ultrasonic sensor 101. LIN is a simple standard for data-based vehicle electrical systems and is used, for example, for rain sensors, wiper motors, spray devices, and the like. The signals of a LIN are rectangular with a swing of 12 V and a slew rate of 2 V / ps. A LIN operates at a frequency of 19 kHz. A harmonic of this is three times this, i.e., 57 kHz, and thus in a range in which the ultrasonic sensor 101 also transmits and receives acoustic ultrasonic signals. Within the ultrasonic sensor 101, as explained later with reference to Fig. 4 and Fig. 5, a sound transducer element 25 (Fig. 5) generates electrical signals that correspond to the acoustic ultrasonic signals.Thus, electric fields generated by line 11 of the LIN represent potential interference fields for ultrasonic sensor 101. For example, ultrasonic sensor 101 could falsely signal the reception of an ultrasonic echo, even though in fact only an interference field from a signal on line 11 was interfering with ultrasonic sensor 101. These are referred to as "ghost echoes." This problem is particularly pronounced in the front bumper 52 of motor vehicle 1, since a required minimum distance between ultrasonic sensor 101 and line 11 may not be maintained due to limited space.

[0073] Figs. 3A-D show possible relative spatial arrangements of ultrasonic sensor 101 and line 11. Arrows indicate the path of field lines of an electric interference field. As can be seen in Figs. 3A-D, the electric interference field acts primarily from the left and from above on ultrasonic sensor 101.

[0074] Fig. 4 shows a section AA in Fig. 1 of the ultrasonic sensor 100 in a configuration according to a first exemplary embodiment, and Fig. 5 shows a section BB in Fig. 4. Reference is made below to Fig. 4 and Fig. 5. A direction indication "downward" and a location indication "down" refer hereinafter to a direction along the axial direction 13 downward in Fig. 5 or into the plane of the page in Fig. 4. A direction indication "upward" and a location indication "up" refer hereinafter to a direction opposite the axial direction 13 upward in Fig. 5 or out of the plane of the page in Fig. 4.

[0075] As can be seen in Fig. 5, the diaphragm cup 7 is placed on an edge 11 of the downwardly open body 3. The collar ring 4 is placed on the diaphragm cup 7 and the body 3. Accordingly, the diaphragm cup 7 is inserted into an opening 12 of the housing 2 formed by the body 3 and the collar ring 4.

[0076] A printed circuit board 16 is arranged in an interior space 14 of the housing 2. Electronic components 17, 18 of a driver circuit 19 are arranged on the printed circuit board 16. The driver circuit 19 may further comprise conductor tracks (not shown) that run on or in the printed circuit board 16.

[0077] A plurality of first contact pins 20, 21 are pressed into the body 3 of the housing 2. Furthermore, a plurality of second contact pins 22, 23, 24 are pressed into the body 3 and the extension section 5 of the housing 6. The first contact pins 20, 21 serve to contact the driver circuit 19 with a piezo element 25 arranged on an inner side of the ultrasonic membrane 8. Lower ends of the first contact pins 19, 20 are indirectly contacted with the piezo element 25 via respective loose, non-stressed fine wires 26. A lower region 28 of the interior 14 in the region of the loose wires 26 can be filled with foam. This achieves advantageous vibration decoupling between the ultrasonic membrane 8 with the piezo element 25 on the one hand, and the housing 3 and the circuit board 16 on the other.

[0078] The second contact pins 22, 23, 24 serve to contact the driver circuit 19 with lines (not shown) which lead out of the ultrasonic sensor 100 through the extension section 6 and can be connected, for example, to a control unit (not shown) of the motor vehicle 1 (Fig. 2).

[0079] The circuit board 16 has several vias 29-33. The circuit board is pressed onto the upper ends 35, 36 of the contact pins 20-24, so that the upper ends 35, 36 of the contact pins 20-24 pass through the vias 29-33 of the circuit board 16. In this way, the contact pins 20-24 are connected to the driver circuit 19. At the same time, this ensures a tight fit of the circuit board 16 on the contact pins 20-24.

[0080] Furthermore, the circuit board 16 is particularly preferably mounted on a circumferential and inwardly projecting projection 15 of the housing 2. Supporting the projection 15, which is located far below, is made possible by the fact that the components 17, 18 of the driver circuit 19 are arranged on the top side of the circuit board 16, i.e., on the same side as the upper ends 35, 36 of the contact pins 20-24 that penetrate the circuit board 16. Thus, the circuit board 16 is advantageously pressed and mounted in the housing 2 in a stable and secure manner, particularly vibration-resistant.

[0081] During operation, the driver circuit 19 is controlled via the contact pins 22, 23, 24 and the lines not shown by the control unit (not shown) of the motor vehicle 1 (Fig. 2). The driver circuit generates a suitable electrical control signal for the piezo element 25 and transmits this to the piezo element 25 via the contact pins 20, 21 and the loose fine wires 26. In response to the control signal, the piezo element 25 excites the ultrasonic membrane 8 of the membrane cup 7 to vibrate, thereby emitting an acoustic ultrasonic signal in the axial direction 13. When this ultrasonic signal is reflected back to the ultrasonic membrane 8 in the environment of the motor vehicle 1 (Fig. 2), the membrane is excited to vibrate.The piezo element 25 detects the vibrations of the ultrasonic membrane 8 and transmits an electrical reception signal, indicative of the received ultrasonic signal, via the loose fine wires 26 and the contact pins 20, 21 to the driver circuit 19. The driver circuit 19 amplifies the reception signal and transmits it via the contact pins 22, 23, 24 and the lines not shown to the control unit (not shown) of the motor vehicle 1 (Fig. 2). The control unit (not shown) can, for example, determine a distance to an obstacle in the vicinity of the motor vehicle 1 (Fig. 2) based on a propagation time difference between the transmission of the ultrasonic signal and the reception of the reflected ultrasonic signal.

[0082] It should be noted that an un-amplified and therefore very weak electrical reception signal is transmitted from the piezo element 25 to the driver circuit 19 via the contact pins 20, 21 and the fine wires 26, 27. This reception signal is particularly susceptible to electrical and magnetic interference.

[0083] The distance between the contact pins 20 and 21 is therefore chosen to be close, as shown in Fig. 4. The distance between the two contact pins 20, 21 is, for example, no more than 5 mm, preferably no more than 3 mm, particularly preferably no more than 1 mm. In this way, the inductance of a coil formed by the contact pins 20, 21, the circuit board 16, and the piezo element 25, through which a magnetic interference field could couple, is low.

[0084] Furthermore, the diaphragm cup 7 is made of metal or provided with a metallic coating and thus shields the loose fine wires 26 from electrical interference fields. Particularly preferably, the diaphragm cup 7 is also directly grounded or at least not with a high resistance, for example, with a resistance of 600 ohms to 800 ohms, and in any case with a resistance of less than 1000 ohms, in order to best achieve this shielding effect. For this purpose, a cable (not shown) running within the body 3 can be used, for example, to connect the diaphragm cup 2 to one of the second contact pins 22-24.

[0085] The first contact pins 20, 21 are also comparatively well shielded in their course by the membrane pot 7 on the one hand and by the printed circuit board 16 on the other hand.

[0086] However, the inventors have recognized that electrical interference fields couple into the signal path from the piezo element 25 to the driver circuit 19, in particular at the upper ends 35 of the first contact pins 20, 21 which pass through the circuit board 16 and project upwards.

[0087] Therefore, according to the first embodiment, a metallic hood 40 is arranged on the circuit board 16 in such a way that, together with the circuit board 16, it surrounds and shields the upper ends 35 of the first contact pins 20, 21 on all sides.

[0088] Experiments have shown that this significantly reduces the interference of the electric fields shown in Figs. 3A-3D. This effect is particularly pronounced in the configurations shown in Figs. 3B and 3D, in which the electric interference field acts on the ultrasonic sensor 100, 101 from above.

[0089] However, the metallic cover 40 neither surrounds nor shields the upper ends 36 of the second contact pins 22-24 nor the components 17, 18 of the driver circuit 19. The majority of the conductor tracks (not shown) on the circuit board 16 are also not covered by the metallic cover 40. Accordingly, the metallic cover 40 can advantageously be designed with a small size and low weight. The metallic cover 40 can thus be mounted on the circuit board 16 in a vibration-resistant manner using simple means, comparable to other components 17, 18, and hardly contributes to an increase in the weight of the ultrasonic sensor 100. In particular, with such a small metallic cover 40, it is particularly advantageous that no encapsulation of the interior 14 of the ultrasonic sensor 100 is required to achieve vibration resistance.

[0090] The metallic hood 40 can be made, in particular, from a copper or brass sheet. The sheet thickness is preferably such that the penetration depth of an expected electrical interference field is essentially completely absorbed by the sheet, but the sheet does not become unnecessarily thick. In the case of the LIN as the interference source discussed with reference to Fig. 2, a sheet thickness of 0.3 mm is sufficient. Preferably, the sheet thickness is at least 0.2 and at most 0.4 mm.

[0091] Fig. 6 shows a section AA in Fig. 1 of an ultrasonic sensor 100 according to a second embodiment, Fig. 7 shows a section BB in Figs. 6, 8, and Fig. 8 shows a section CC in Figs. 6, 7. Reference is made below to Figs. 6 to 8. Features of the second embodiment that are similar to the features of the first embodiment will not be described in detail again. The second embodiment differs from the first embodiment as follows:

[0092] The printed circuit board 16 does not lie flush against an inner surface 37 of the body 3 along its entire circumference. In a section on the left in Fig. 6, 7, which is arranged opposite the extension section 6 of the housing 2, a recess 38 is formed in the printed circuit board 16. The metallic hood 40 is arranged on an edge 39 of the printed circuit board 16, which borders the recess 38, and protrudes slightly into the recess 38.

[0093] The annular, projecting projection 15 of the body 3 of the housing 2, on which the printed circuit board 16 is mounted, also has a recess 47 in a region of the recess 38 of the printed circuit board 16. According to the second exemplary embodiment, the metallic hood 40 has a cube or cuboid shape in a section arranged above the printed circuit board 16, with four vertical walls 41, 42, 43, 44 running perpendicular to the printed circuit board 16 and a horizontal wall 45 running parallel to the printed circuit board 16 above the ends 35 of the first contact pins 20, 21. An outer vertical wall 41 is arranged close to the edge 39 of the printed circuit board 16 above the recess 38. As can be seen particularly in Fig.7, a tab 46, which is continuous with the outer vertical wall 41, runs from a lower end of the vertical wall 41 through the recess 38 of the circuit board 16, past the edge 39 of the circuit board 16 and through the recess 47 in the inwardly projecting projection 15 of the housing 2 downwards towards the diaphragm pot 7. The tab 46 runs, as can be seen in Fig. 7, 8, parallel to a plane formed by the first contact pins 20, 21. The tab 46 is, as can be seen in Fig. 8, only slightly wider than a distance between the first contact pins 20, 21, which in turn run parallel to one another towards the diaphragm pot 7. In particular, the tab 46 is not wider than, and preferably narrower than, the outer wall 41, of which it represents an extension.

[0094] With the tab 46 extending towards the diaphragm cup 7 according to the second embodiment, a vertical section of the first contact pins 20, 21 between the circuit board 16 and the diaphragm cup 7 can also advantageously be shielded against electrical interference field inputs, in particular from the left in Fig. 7 (cf. Fig. 3A and Fig. 3C).

[0095] As shown in Fig. 7, an inner vertical wall 42, which is arranged opposite the outer vertical wall 41, also has a spring pin 48. The spring pin 48 is pressed into another via 34 of the circuit board 16 and is held securely in the via 34 by a spring force (restoring force) of the spring pin 48. The via 34 can have a tinned inner surface that is connected to ground. Accordingly, the metallic hood 40 is contacted and grounded to the circuit board 16 via the spring pin 48 of the inner vertical wall 42. Fig. 9 shows a blank 50 according to the second embodiment. The blank 50 is a shape punched out of a copper or brass sheet with a thickness between 0.2 and 0.4 mm, preferably 0.3 mm. If the blank 49 is folded along the dot-dashed fold lines, for example, backwards in the plane of the sheet, the metallic hood 40 is produced (Fig.6-8) with the four vertical walls 41-44, the horizontal wall 45, the tab 46, which is continuously connected to the outer vertical wall 41, and the spring pin 48.

[0096] The spring pin 48 is designed, for example, as an eyelet 51 enclosing an elongated hole 49. The eyelet has, for example, a wall thickness of 0.3 mm, and the elongated hole 49 is, for example, a 1 mm bore. When the spring pin 48 is pressed into the through-hole 34 (Fig. 7), the elongated hole 49 is compressed and exerts a restoring force that acts outward in the through-hole 34 (Fig. 7) perpendicular to an inner surface of the through-hole 34 (Fig. 7) and fixes the metallic hood 40 (Fig. 7) to the circuit board 16 (Fig. 7).

[0097] Fig. 10 illustrates a manufacturing method of the ultrasonic sensor 100 according to a third embodiment. Reference is also made to Figs. 4 to 10.

[0098] In step S1, the first contact pins 20, 21 and the second contact pins 22-24 are pressed into the plastic body 3 (into the housing 2).

[0099] In step S2, the diaphragm cup 7, to whose ultrasonic diaphragm 8 the sound transducer element 25 is attached from the inside, is inserted into an opening 12 of the housing 2. For example, the diaphragm cup 7 can be placed on an edge 11 of the body 3, as shown in Fig. 7, 8, and the collar ring 4 can be thrown over the diaphragm cup 7 and the body 3. The collar ring can then be joined to the diaphragm cup 7 and the body 3, for example by ultrasonic welding. In step S3, the first contact pins 20, 21 are contacted with the sound 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.

[0100] In step S4, the circuit board 16 on which the driver circuit 19 is mounted is pressed onto the upper ends 35, 36 of the contact pins 20-24 in such a way that the ends 35, 36 pass through the circuit board 16.

[0101] In step S5, the blank 50 shown in Fig. 9 is punched out of a copper or metal sheet and folded along the dash-dotted fold lines, thus obtaining the metallic hood 40.

[0102] In step S6, the metallic hood 40 is mounted on the circuit board 16 in such a way that the metallic hood 40 completely surrounds and shields the upper ends 35 of the first contact pins 20, 21 that extend through the circuit board 16. For assembly, for example, the spring pin 48 is pressed into the through-hole 34 of the circuit board 16, thereby securing the metallic hood 40 to the circuit board 16, contacting it, and grounding it.

[0103] The lid 5 can then be placed on the body 3 and joined to it by ultrasonic welding.

[0104] Thus, an ultrasonic sensor 100 according to the third embodiment is obtained.

[0105] An ultrasonic sensor 100 according to embodiments can thus be particularly easy to manufacture, have a vibration-stable construction with vibration-resistant mounting of the circuit board 16 and vibration-resistant attachment of the metallic cover 40, require no encapsulation of an interior space 14 of the plastic housing 2, be lightweight and shatter-proof, and have excellent EMC immunity thanks to the parallel first contact pins 20, 21 and the metallic cover 40 shielding at least the ends 35 of the first contact pins 20, 21 that penetrate through the circuit board 16.

[0106] Although the present invention has been described using exemplary embodiments, it is susceptible to numerous modifications. Features disclosed for different embodiments may be combined in any suitable manner, provided that no contradictions arise.

[0107] The collar ring 4 is not a necessary feature of the invention, and the diaphragm cup 7 can also be inserted directly into an opening of the body 3 of the housing 2.

[0108] The loose fine wires 26, 27 are not necessary. The contact pins 20, 21 can also be connected to the piezo element 25 in other ways, for example, directly.

[0109] In the figures, three second contact pins 22-24 are shown, but only two or more than three second contact pins 22-24 can be used for external connection.

[0110] The metallic hood 40, particularly in the first, but also in the second embodiment, does not necessarily need to have a cube or cuboid shape with five walls. It can also be hemispherical, for example.

[0111] In the second exemplary embodiment, the tab 46 does not need to extend close to the diaphragm cup 7, as shown in Fig. 7. To achieve the desired additional shielding effect of the tab 46, it is sufficient if the tab extends from the underside of the circuit board 16 at least a short distance toward the diaphragm cup 7. On the other hand, according to an advantageous further development, the tab 46 can also extend all the way to the diaphragm cup 7 and contact it. In this way, the diaphragm cup 7 can advantageously be easily grounded via the tab 46 of the metallic hood 40. Only one spring pin 48 attached to the inner wall 42 has been described. However, it is understood that a respective spring pin 48 can be formed on one or more of the inner wall 42, the side walls 43, 44, and the outer wall 41 and can be pressed into respective vias 34 of the circuit board 16.If several spring pins 48 are present, the metallic hood 40 can be mounted and fixed on the circuit board 16 even more reliably.

[0112] LIST OF REFERENCE SYMBOLS

[0113] 1 motor vehicle

[0114] 2 housings

[0115] 3 Corpus

[0116] 4 coupling ring

[0117] 5 lids

[0118] 6 Extension section

[0119] 7 diaphragm pot

[0120] 8 Ultrasonic membrane

[0121] 9 side skirts

[0122] 10 rear bumper

[0123] 11 edge

[0124] 12 Opening in the housing

[0125] 13 Axial direction

[0126] 14 Interior

[0127] 15 Housing projection

[0128] 16 circuit board

[0129] 17, 18 Component

[0130] 19 Driver circuit

[0131] 20, 21 contact pin, first contact pin

[0132] 22-24 contact pin, second contact pin

[0133] 25 Piezo element, sound transducer element

[0134] 26, 27 loose fine wire

[0135] 28 lower area

[0136] 29-34 vias

[0137] 35, 36 upper ends

[0138] 37 Body inner surface

[0139] 38 Circuit board recess

[0140] 39 Edge of the circuit board 40 metallic cover

[0141] 41 outer vertical wall

[0142] 42 inner vertical wall

[0143] 43, 44 lateral vertical wall 45 horizontal wall

[0144] 46 tab

[0145] 47 Recess of the projecting projection

[0146] 48 spring pin

[0147] 49 Slotted hole 50 Punched metal sheet, blank

[0148] 51 eyelet

[0149] 52 front bumper

[0150] 100-105 Ultrasonic sensor

[0151] S1 -S6 process steps

Claims

PATENT CLAIMS 1 . Ultrasonic sensor (100) for a motor vehicle (1), comprising: a plastic housing (2), a membrane cup (7) with an ultrasonic membrane (8) inserted into an opening (12) of the plastic housing (2), a sound transducer element (25) attached to the ultrasonic membrane (8) from the inside for exciting and detecting vibrations of the ultrasonic membrane (8), a printed circuit board (16) arranged in the interior (14) of the plastic housing (2), on which printed circuit board a driver circuit (19) for controlling the sound transducer element (25) is mounted, two contact pins (20, 21) for electrically contacting the driver circuit (19) with the sound transducer element (25), wherein the printed circuit board (16) is pressed onto the contact pins (20, 21) in such a way that ends (35) of the contact pins (20, 21) pass through the printed circuit board (16), and a metallic hood (40) which, together with the printed circuit board (16), the ends (35) of the contact pins (20,21 ) surrounds and shields on all sides., 2. Ultrasonic sensor according to claim 1, characterized in that the driver circuit (19) comprises one or more electronic components (17, 18) which are mounted on the same side of the circuit board (16) as the metallic hood (40) outside the metallic hood (40) on the circuit board (16).

3. Ultrasonic sensor according to claim 2, characterized in that an interior space (14) in the plastic housing (2) is not encapsulated at least on the same side of the circuit board (16) as the metallic hood (40).

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

5. Ultrasonic sensor according to one of the preceding claims, characterized in that the metallic hood (40) has four walls (41-44) running perpendicular to the circuit board (16) and one wall (45) running parallel to the circuit board (16) and over the ends (35) of the contact pins (20, 21).

6. Ultrasonic sensor according to one of the preceding claims, characterized in that an outer wall (41) of the metallic hood (40) is arranged at an edge (39) of the printed circuit board (16) and a tab (46) formed continuously with the outer wall (41) runs past the edge (39) of the printed circuit board (16) towards the diaphragm pot (7).

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

8. Ultrasonic sensor according to one of the preceding claims, characterized in that the metallic hood (40) is contacted with the circuit board (16) and grounded.

9. Ultrasonic sensor according to claim 8, characterized in that the metallic hood (40) is contacted with the circuit board by means of a spring pin (48) which is formed continuously with one of the walls (42) of the metallic hood (40) and which is pressed into a through-plating (34) of the circuit board (16).

10. Ultrasonic sensor according to claim 9, characterized in that the spring pin (48) is designed as an eyelet (51) enclosing an elongated hole (49). 11 . Ultrasonic sensor according to one of the preceding claims, characterized in that the metallic hood (40) is made of copper or brass sheet with a sheet thickness between 0.2 and 0.4 mm, preferably 0.3 mm.

12. Ultrasonic sensor according to claim 11, characterized in that the metallic Hood (40) is punched and folded in one piece from the copper or brass sheet.

13. Ultrasonic sensor according to one of the preceding claims, characterized in that the diaphragm pot (7) is a metallic diaphragm pot (7) which is not connected to ground with high resistance.

14. Motor vehicle (1) with an ultrasonic sensor (100, 101 -105) according to 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 pot (7) with an ultrasonic membrane (8) and a sound transducer element (25) attached to the ultrasonic membrane (8) from the inside for exciting and detecting vibrations of the ultrasonic membrane (8) into an opening (12) of the plastic housing (2); Contacting (S3) the contact pins (20, 21) with the sound transducer element (25); Pressing (S4) a printed circuit board (16), on which a driver circuit (19) for controlling the sound transducer element (25) is mounted, onto ends (35) of the contact pins (20, 21) in such a way that the ends (35) pass through the printed circuit board (16); Producing (S5) a metallic hood (40) by punching out a blank (50) from a copper or metal sheet and folding the blank (50); Mounting (S6) the metallic hood (40) on the printed circuit board (16) in such a way that the metallic hood (40), together with the printed circuit board (16), surrounds and shields on all sides the ends (35) of the contact pins (20, 21) passing through the printed circuit board (16).

Images