Radar system, having internal welding points, for detecting the surroundings

Abstract

The invention relates to a radar system for detecting the surroundings, wherein the radar system comprises a front housing part (4) through which the radar waves pass, a rear housing part (5) and a printed circuit board (1), and additionally can comprise at least one waveguide antenna (2) between the front housing part (4) and the printed circuit board (1), and the two housing parts are welded to one another, for which purpose the two housing parts can advantageously at least partially consist of plastic and laser welding can be used, characterised in that the two housing parts are welded not just at their edge (8.1) but also at least at one point (8.2) in the internal region, for which purpose there is at least one structure for example in the shape of a dome (5.5, 4.3) which projects into or through the printed circuit board (1) and / or optionally can project into or through the antenna (2).

Description

[0001] 202405369

[0002] 1

[0003] Radar system for environmental sensing with internal weld points

[0004] The invention relates to a radar system for environmental sensing in motor vehicle applications. According to the invention, the radar system has internal weld points.

[0005] State of the art

[0006] Motor vehicles are increasingly equipped with driver assistance systems that use sensors to perceive the surroundings and derive automatic vehicle reactions from the detected traffic situation and / or instruct the driver, in particular by issuing warnings. A distinction is made between comfort and safety functions.

[0007] In current vehicle development, FSRA (Full Speed ​​Range Adaptive Cruise Control) plays an important role as a comfort feature. The vehicle regulates its own speed to the driver's desired speed, provided the traffic situation allows it; otherwise, the vehicle's speed is automatically adjusted to the traffic situation.

[0008] Safety features now come in a wide variety of forms. One group consists of functions for reducing braking or stopping distance in emergency situations, up to and including autonomous emergency braking. Another group comprises lane change functions: These warn the driver or intervene in the steering if the driver intends to make a dangerous lane change, i.e., if a vehicle in the adjacent lane is either in the blind spot (referred to as BSD - "Blind Spot Detection") or is approaching rapidly from behind (LCA - "Lane Change Assist").

[0009] Nowadays, the driver is no longer just assisted, but the driver's task is increasingly performed autonomously by the vehicle, i.e., the driver is increasingly replaced; this is referred to as autonomous driving.

[0010] Radar sensors are used for systems of the type described above, often in combination with sensors from other technologies, such as camera sensors. 202405369

[0011] 2

[0012] Radar sensors have the advantage, among others, of operating reliably even in poor weather conditions and being able to directly measure not only the distance to objects but also their radial relative velocity via the Doppler effect. Transmission frequencies of 77 GHz and 79 GHz are typically used.

[0013] Due to the increasing functional scope of such systems, the requirements are constantly increasing, especially regarding the detection range and resolution in azimuth and elevation - therefore, significantly larger antennas are needed; radar systems with high resolution are often referred to as imaging radars.

[0014] From DE 10 2018 203 106 A1, a basic design of a radar sensor of this type is known, in which a waveguide antenna made of plastic and a high-frequency component with at least one element for direct transmission or reception are used, wherein the waveguide antenna and the high-frequency component are located on opposite sides of the circuit board and the coupling between the high-frequency component and the waveguide antenna takes place through the circuit board, e.g. via a simple hole in the circuit board. DE 10 2020 211 254 A1 describes how the antenna can be implemented cost-effectively by a single, single-layer molded part, which is connected to the circuit board, in particular by soldering.

[0015] Especially with large antennas and thus large sensors, it is challenging to achieve sufficient dimensional accuracy, mechanical robustness and stability, particularly if, for performance reasons, the front housing cover is made of thin plastic and, for cost reasons, the rear housing half is also to be made at least partially of plastic.

[0016] Problem, solution and advantages of the invention

[0017] The object of the invention is to propose, in contrast to the prior art, a simple, robust and high-performance design which allows the simple implementation of even large radar sensors.

[0018] This problem is fundamentally solved by a radar system according to claim 1. Advantageous embodiments of the invention are claimed in the dependent claims. 202405369

[0019] 3

[0020] The advantages of the invention arise from the fact that high performance and a robust sensor design can be achieved without incurring significant additional costs or effort.

[0021] The radar system according to the invention for environmental sensing comprises a front housing part through which the radar waves are irradiated, a rear housing part, and a circuit board. It can additionally include or comprise at least one waveguide antenna between the front housing part and the circuit board. The two housing parts are welded together, for which purpose the two housing parts advantageously comprise or consist at least partially of plastic, and laser welding can be employed. The system is characterized in that the two housing parts are welded not only at their edges but also at least at one point in the inner area. For this purpose, there is at least one structure, for example in the form of a dome, which projects into or through the circuit board and / or optionally can project into or through the antenna. Preferably, the structure comprises a first section (e.g.,a small dome) that is connected to the front housing part and a second section (e.g. a larger, longer dome) that is connected to the rear housing part, wherein the one point in the inner area where the housing parts are welded is provided at the location where the two sections touch or contact each other.

[0022] Advantageously, the front housing part can have at least one structure in its inner area which, after welding, rests on the circuit board and / or antenna, thus creating a defined distance between the front housing part in the area of ​​this structure and the circuit board and / or antenna.

[0023] In an advantageous embodiment of the invention, at least one of the two housing parts may have at least one planar area in its inner region which, after welding, rests on the circuit board and / or components on this and / or the antenna itself or on a thermal paste located on these, thereby enabling good heat dissipation.

[0024] Advantageously, the rear housing part, the circuit board and / or the antenna or a combination thereof can be significantly stiffer and more dimensionally stable than the front housing part, and thus, through one or more welds in the internal area and through the bearing of the front housing part on the circuit board 202405369

[0025] 4 and / or antenna in the welded state, unevenness of the front housing part should be at least partially avoided.

[0026] Furthermore, the material displaced during welding can lead to a local positive fit between the antenna and the at least one housing part structure used for welding, which advantageously achieves a lateral fixation of the antenna in a defined position.

[0027] Advantageously, structures are provided on the front and rear housing parts that project into the same, in particular, hole-shaped recess of the antenna, and after welding these structures, the material displaced to the side during welding leads to a local positive fit between the antenna and these housing part structures, which advantageously achieves a lateral fixation of the antenna in a defined position.

[0028] Advantageously, after welding, the circuit board rests on structures on the rear housing part, and the circuit board and / or antenna also rests on structures and / or surfaces on the front housing part. This, in combination with the at least one weld in the inner area, results in a positionally stable arrangement, so that, particularly over its lifetime and / or in the event of strong mechanical shock, displacement of the circuit board and / or antenna or tearing of a thermal connection located between the circuit board or a component on it and the housing or antenna can be avoided.

[0029] Furthermore, welding prevents pressure from being applied to the front part of the housing, which would then press onto sensitive components in the sensor.

[0030] Advantageously, welding prevents the front housing part from bending due to an internal elastic element between the front housing part and a waveguide antenna.

[0031] Furthermore, a structure of a housing part that protrudes into or through the antenna can be used not only for welding but also for positioning the antenna.

[0032] Advantageously, the surfaces and / or points to be welded on the two housing parts are melted by a laser beam, and then the two housing parts are pressed together in this state. 202405369

[0033] 5

[0034] Brief description of the drawings

[0035] Fig. 1 shows a cross-sectional view of a radar sensor structure with a weld according to the invention in the inner area, wherein the antenna is formed by soldering a molded part to the circuit board.

[0036] Fig. 2 shows a cross-sectional view of a radar sensor structure with a welding according to the invention in the inner area, wherein the antenna is formed from a separate two-layer part.

[0037] Examples of implementation

[0038] Fig. 1 shows a cross-section through a radar system with a circuit board 1 and a molded part 2 soldered onto it, which, in conjunction with the circuit board, forms a waveguide antenna with several individual antennas for transmitting and receiving. Waveguides 3 provide the feed lines to the individual antennas; three walls of these waveguides are formed by slot-shaped recesses in the underside of the molded part, and the fourth wall by a metallized surface of the circuit board 1. A front housing half 4 made of plastic is located above the antenna, through which the radar beams are transmitted and received. Furthermore, there is a rear housing half 5, which consists of an outer plastic part 5.1 and an inner metal part 5.2; the metal part 5.2 can be connected to the plastic part 5.1.1 is injection-molded or connected to it, in particular by hot riveting, and serves on the one hand for electromagnetic shielding and on the other hand for dissipating and distributing the heat generated by the radar chip 6, wherein the thermal connection between radar chip 6 and metal part 5.2 is realized by a thermal paste 7. The radar chip 6 contains the electrical high-frequency components for generating and receiving the radar waves as well as the digital components for signal processing and generating the sensor's output signals (which can be a description of the environment or control signals for a vehicle function); the radar chip consumes most of the power in the sensor and is therefore the main heat source. On the underside of the radar chip 6 are radiating and receiving elements 6.1, which are each connected by a hole 1.1 in 202405369.

[0039] 6 of the circuit board with metallized side walls 1.2 are connected to the waveguides 3 formed by the molded part and circuit board.

[0040] The circuit board is connected to the rear housing half 5 by metal pins embedded in the housing half, so-called press fits 5.3; on the one hand, they serve to fix the circuit board 1 by means of their clamping effect, on the other hand, some of the pins represent the electrical connection between the circuit board and the connector 5.4 integrated in the rear housing part 5.

[0041] During the production of the radar sensor, the two housing halves 4 and 5 are joined together by laser welding. For this process, the edges of both halves are continuously melted superficially by a laser, and then pressed together in this state; this creates the bonded connection 8.1. Other methods, such as ultrasonic welding, can also be used instead of laser welding.

[0042] For good performance, it is important that the antenna and the front housing half maintain a defined and constant distance from each other. To minimize losses due to radar attenuation and reflections, the front of the housing half should be thin, preferably half a radar wavelength in the plastic material, which is approximately 1.1 mm. These two requirements for the front housing half (i.e., a flat shape for a constant distance to the antenna and a thin profile of only about 1.1 mm) are particularly difficult to meet for larger radar sensors, since the dimensional accuracy of a plastic molded part decreases with increasing thickness and size, both during production (by injection molding) and over its service life. Therefore, structures 4.1 of defined height are provided, over which the front housing half 4 rests on the antenna; according to the invention, this contact is ensured by the inclusion of weld points 8.2 inside the sensor.In the example shown, these welding points are achieved by having domes 5.5 in the lower housing half, which protrude through the circuit board 1 and the antenna molding 2, and are welded to the front housing part 4 near the supports 4.1 - for this purpose, during sensor production, the end face of the dome and the opposite part of the front housing half are also melted (i.e., in addition to the surrounding edge of the housing halves), so that after pressing the two housing halves together, a materially interlocking 202405369 is also formed there.

[0043] 7

[0044] Connection 8.2 exists. In the example according to Fig. 1, the welding points 8.2 (or more precisely the small welding surfaces) are realized inside an, for example, annular support surface, wherein there is a small recess 4.2 in the corresponding surface of the front housing part between the support and welding area, which can accommodate the material displaced to the side during welding (this displaced material is not shown in the picture).

[0045] There can also be contact points (or small areas) of the front housing half 4 that do not rest on the antenna, but on the front side of the circuit board. Furthermore, there can also be contact points from the rear housing surface 5 on the underside of the circuit board; advantageously, these are located approximately in line with the contact points of the front housing half on the antenna or circuit board to prevent possible stress on the circuit board 1 during welding and thus also after the welding process – Fig. 1 shows corresponding contact structures 5.6 of the rear housing half, which simultaneously form the base of the dome 5.5 for welding. These contact structures 5.6 on the rear housing half (their contact is ensured by the compression during welding and the sufficient elasticity of the housing halves and the circuit board to compensate for the mechanical tolerances) realize a defined distance between rear housing half 5 and circuit board 1 and thus also a defined distance between radar chip 6 and rear housing half (since contact points are close to the radar chip); this allows for the realization of the thinnest possible layer of thermal paste 7 and thus an optimal thermal connection of the radar chip to the metal part 5.2 of the rear housing half.

[0046] The approach using support structures in combination with internal welding points of the two housing halves offers further advantages besides achieving defined distances, which can be even more relevant. An important and often critical test for radar sensors is that a sensor dropped from 1 meter onto a concrete floor must not exhibit any internal damage (such an event can occur if a sensor is dropped from the person installing it in a vehicle). Without sufficiently rigid fixation of the circuit board, the hard impact upon impact with the ground could cause it to partially or completely detach from the press-fit connectors 5.3. Even fixation via clamping or elastic elements in the central area of ​​the front housing half could not reliably prevent such detachment, as very high forces can occur and the front 202405369

[0047] 8 of the front housing half is itself elastic due to its small thickness. In the design according to the invention, the detachment of the circuit board from the press-fits is prevented by the combination of internal weld points, contact points, and the relatively rigid rear housing part (due to its metallic component), resulting in a very rigid positioning of the circuit board. Furthermore, in the design according to the invention, the thermal paste, which hardens over time, cannot tear or crack, which could otherwise occur with such a hard impact or even over time (because parts deform), thus rendering the thermal paste ineffective and potentially leading to overheating of the radar chip 6.

[0048] Another problem with conventional radar sensor designs can arise from the fact that installing the sensor in the vehicle (especially when done by clipping it in) can exert high forces on the front of the front housing half. Since this front is thin and therefore quite elastic, it can be pressed, particularly with large sensors, all the way to the antenna or electronic components mounted next to the antenna on the top of the circuit board, which can lead to damage. This can no longer occur with the rigid design according to the invention.

[0049] Figure 1 shows a sensor with a radar chip; such sensors, typically with four individual transmitting and receiving antennas, have limited angular accuracy and resolution, which are sufficient for current driver assistance functions. Autonomous driving, in particular, requires significantly higher environmental sensing performance, necessitating considerably larger antennas with many more individual transmitting and receiving antennas – such radars are referred to as imaging radars. They typically contain several radar chips and, optionally, an additional processing chip; the overall antenna can be composed of several smaller antennas. Due to their significantly increased size, the advantages of the design according to the invention become even more apparent.Then several internal welds are used, which are distributed over the sensor; this also avoids unevenness on the front of the front housing half, which would otherwise occur due to its small thickness (the rear housing half is stiffer and significantly more dimensionally stable, i.e. flatter, especially due to its metal part, which then affects the front housing half 202405369.

[0050] 9 transmits). In such imaging radars, individual antennas are often primarily located in the outer areas (i.e., towards the edges) in order to achieve the largest possible apertures; the inner area is then without individual antennas, so that the front housing half can project downwards over a step and be thermally coupled to the circuit board over a flat area, either directly or via a thin layer of thermal paste, using the inventive approach (there could also be an additional internal metal part in this area of ​​the front housing half).

[0051] Previously, the antenna was implemented by soldering a molded part onto the circuit board. DE 102018 203 106 A1 describes an antenna consisting of several surface metallized plastic layers, wherein the feed lines to the antennas are implemented by internal waveguides formed by slot-shaped recesses in joined layers. As shown in a cross-sectional view in Fig. 2, the two-layer antenna 2 rests on the circuit board 1. For positioning the antenna, it has small pins 2.1 that project into holes 1.3 in the circuit board. According to the prior art, an elastic element, e.g., in the form of a spring, is used between the front housing half and the antenna to fix it in place, pressing the antenna against the circuit board and holding it thereon. Instead, in the inventive proposal according to Fig.2. The antenna 2 is fixed to the circuit board 1 using the approach described above: Firstly, there are two support structures 4.1 on the front housing half, and secondly, between the two housing halves, there are two welded, material-locking connections 8.2, each formed by a small dome 4.3 on the front housing half 4 and a longer dome 5.5 on the rear housing half 5. The two domes project into a hole in the antenna from the front and rear, respectively. The material 9 displaced laterally during welding is forced between the domes and the antenna, thus creating a positive fit between the domes and the antenna; this also creates a positive fit between the antenna and the housing parts, so that the antenna is also fixed laterally. This ensures that the antenna does not shift laterally during the drop test described above (from 1 m onto a concrete floor).Without this inventive construction, it could even happen during the drop test that the small pins 2.1 used for the lateral positioning of the antenna break off - due to allowances for tolerances, these pins always have some play in relation to the associated 202405369.

[0052] 10

[0053] Holes 1 .3 in the circuit board, so that in the event of a lateral impact the antenna can first move over this gap, building up energy and then the pins can hit the side wall of the circuit board holes and thus break off - also because the plastic material used for the antenna is often less break-resistant than a glass fiber reinforced material used for housing parts.

[0054] The described lateral positive fit between the antenna and the housing parts could also be achieved without the short dome 4.3 on the front housing half 4; the long dome 5.5 from the rear housing half would then protrude completely through the antenna, and on the front of the antenna there would be a small recess around the hole, e.g. in the form of a chamfer, which could accommodate the material displaced to the side.

[0055] It should be noted that the small pins 2.1 and associated holes 1 .3 used for positioning in the circuit board could in principle also be omitted, since the domes 5.5 on the rear half of the housing already achieve positioning (which is generally somewhat less precise, since from a functional point of view the positioning of the antenna to the circuit board with its waveguide holes 1.1 is relevant).

[0056] If, in addition to the internally welded connection, an additional elastic element, e.g. in the form of a spring, is used for vertical fixing or clamping of the antenna onto the circuit board, the welds prevent the upper housing half from bending due to the force of the elastic element.

[0057] It should be noted that it can be advantageous if there are chamfers for joining the sensor parts to the domes and / or antenna components.

[0058] For tolerance reasons (i.e., to compensate for more tolerances), a deeper melting may be necessary for the inner welds than for the surrounding edge; therefore, it can be advantageous to first melt the surrounding edge and then the structures / areas for inner welding - i.e., immediately before joining the two housing halves.

[0059] So far, welding of plastic surfaces has been assumed. Since plastic can also be welded to metal, a completely metal rear housing half is also conceivable.

[0060] Finally, it should be noted that the holes required for the domes in the antenna are identical to those required during antenna and sensor production.

[0061] 11

[0062] Holes (especially for handling) can be used, meaning no additional holes are needed.

[0063] Although we have always referred to two halves of the case, the case can of course consist of more than two parts, so the term "half" should then be understood metaphorically, i.e., in the sense of "part". Furthermore, the dividing line between the two halves of the case may not be exactly in the middle, but—as also shown in the images—off-center.

Claims

202405369 12 Claims 1. Radar system for environmental sensing, wherein the radar system comprises a front housing part (4) through which the radar waves are irradiated, a rear housing part (5) and a circuit board (1), and may additionally comprise at least one waveguide antenna (2) between the front housing part (4) and the circuit board (1), and wherein the two housing parts are welded together, wherein the two housing parts (4, 5) may at least partially comprise plastic and laser welding may be used, characterized in that the two housing parts (4, 5) are welded not only at their edge (8.1) but also at least at one location (8.2) in the inner area, for which at least one structure, for example in the form of a dome (5.5, 4.3), is provided which projects into or through the circuit board (1) and / or into or through the antenna (2).

2. Radar system according to claim 1, wherein in the front housing part (4) there is at least one structure (4.1) in its inner area which, after welding, rests on the circuit board (1) and / or antenna (2) and thus realizes a defined distance between the front housing part (4) in the area of ​​this structure and the circuit board (1) and / or antenna (2).

3. Radar system according to one of the above claims, wherein in at least one of the two housing parts (4, 5) there is at least one planar area in its inner region which, after welding, rests on the circuit board (1) and / or components on it and / or the antenna (2) itself or on a thermal paste (7) located thereon, thereby enabling good heat dissipation.

4. Radar system according to one of the above claims, in which the rear housing part (5), the circuit board (1) and / or the antenna (2) or a combination thereof is significantly stiffer and dimensionally more stable than the front housing part (4) and is thus reinforced by one or more welds (8.2) in the inner area and by bearings of the front housing part on the circuit board (1) and / or antenna 202405369 13 (2) in the welded state, irregularities of the front housing part (4) are at least partially avoided.

5. Radar system according to one of the above claims, characterized in that the material (9) displaced during welding leads to a local positive locking between antenna (2) and the at least one housing part structure used for welding, which advantageously achieves a lateral fixation of the antenna (2) in a defined position.

6. Radar system according to claim 5, in which there are structures (5.5, 4.3) on the front and rear housing parts (3, 4) which project into the same, in particular, hole-shaped recess of the antenna (2), and after welding these structures, the material (9) displaced laterally during welding leads to a local positive locking between the antenna (2) and these housing part structures, which advantageously achieves a lateral fixation of the antenna (2) in a defined position.

7. Radar system according to one of the above claims, in which, after welding, the circuit board (1) rests on structures (5.6) on the rear housing part (5) and the circuit board and / or antenna (2) also rests on structures (4.1) and / or surfaces on the front housing part (4), and this in combination with the at least one weld (8.2) in the inner area leads to a positionally stable arrangement, so that, in particular over its lifetime and / or in the event of strong mechanical shock, a displacement of the circuit board (1) and / or antenna (2) or a tearing of a thermal interface (7) located between the circuit board (1) or a component on it and the housing or antenna (2) can be avoided.

8. Radar system according to one of the above claims, in which the welding (8.2) prevents the front housing part (4) from bending due to an internal elastic element between the front housing part (4) and a waveguide antenna. 202405369 14 9. Radar system according to one of the above claims, in which the structure (5.5, 4.3) of a housing part (4, 5) projecting into or through the antenna is used not only for welding but also for positioning the antenna (2).

10. Radar system according to one of the above claims, characterized in that first the surfaces and / or points to be welded on the two housing parts (4, 5) are melted by a laser beam and then the two housing parts (4, 5) are pressed together in this state.

Images