Method for producing radar sensor covers

Abstract

The invention relates to a method for producing radar sensor covers, comprising the steps of: a) characterising a plurality of differently coloured plastics materials on the basis of at least their dielectric constants; b) selecting one of the plastics materials and determining an optimal thickness of the radar sensor cover to be produced in at least one radar transmission range; c) processing the selected plastics material in a manufacturing method using a mould (10), in which the thickness of the radar sensor cover produced can be adjusted to the optimal thickness, for producing the radar sensor cover.

Description

[0001] Description

[0002] Process for manufacturing radar sensor covers

[0003] The invention relates to a method for producing radar sensor covers, in particular for motor vehicles

[0004] Radar sensor covers are used in motor vehicles to cover and visually conceal radar devices on the visible side. These can be short-range or long-range radar systems operating in the 76 / 77 GHz range and hidden behind bumper fascias, radomes, or other visible components of the vehicle. The radar sensor cover should ensure a customer-friendly appearance that, if possible, matches the rest of the vehicle's color and appearance, while also offering low effective transmission losses.

[0005] Radar sensor covers are known to be designed to accommodate multiples of half the wavelength in the material (depending on the dielectric constant) to ensure optimal radar transparency. Different materials have different dielectric constants, which results in different cover thicknesses depending on the material used. Due to the differences in the refractive index of the different materials, each radome must be redesigned to a different thickness. This typically means a new tool for each radome variant. Additional coatings on the components lead to reduced radar transparency.

[0006] Against this background, the object of the invention is to provide a way to improve and cost-effectively manufacture radar sensor covers with high radar transparency. This object is achieved by a method for producing radar sensor covers according to claim 1. Further advantageous embodiments emerge from the subclaims and the following description.

[0007] A method for producing radar sensor covers is specified, comprising the steps of: a) characterizing a plurality of plastic materials of different colors based on at least their dielectric constants, b) selecting one of the plastic materials and determining an optimal thickness of the radar sensor cover to be produced in at least one radar transmission range, c) processing the selected plastic material in a manufacturing process with a molding tool, in which the thickness of the radar sensor cover produced can be adapted to the optimal thickness, to produce the radar sensor cover.

[0008] In other words, in the first step, materials—preferably from one plastic class—but with different colors are characterized, and their dielectric constants are determined. The relationship between the thickness of the radar sensor cover and the reflection and transmission coefficients can be determined, for example, under idealized conditions using conduction theory. From this, an optimal thickness for the component can be determined that maximizes radar transparency. In the next step, a manufacturing process is proposed in which the component thickness can be easily adjusted, e.g., using tool inserts of different thicknesses.

[0009] In one embodiment, steps a) to c) are repeated several times, and an optional step bb) is provided between step b) and step c), in which the mold is modified to adapt to the optimal thickness determined in step b). Several identical radar sensor covers can be produced one after the other in the mold. If, for example, different colors are desired and this changes the optimal thickness of the radar sensor cover, the mold is modified accordingly so that sensor covers with the "new" optimal thickness are subsequently manufactured. This allows optimally adapted sensor covers with different colors to be obtained from a single tool with a short lead time.

[0010] The manufacturing process for processing the selected plastic material is preferably an injection molding process. In this process, plasticized plastic material is injected into the mold and fills the cavity of the mold, which essentially has the shape of the radar sensor cover to be manufactured.

[0011] The mold can be equipped with a movable separating frame. This ensures complete closure of the mold without creating visible dipping edges at the component edge.

[0012] In one embodiment, the manufacturing process is injection-compression molding. In this process, a melt cake of a specified volume or mass is compressed in the mold to the final dimension, thereby achieving particularly tight component tolerances and good homogeneity of the radar sensor cover.

[0013] Furthermore, the mold can have different tool inserts, which allow the thickness of the manufactured radar sensor cover to be varied. The thickness is adjusted at least in one radar transmission area. The radar transmission area is the area of ​​the radar sensor cover through which the radar radiation is to pass. For example, by using pressure plates of different thicknesses, the distance between the cavity walls in the radar transmission area can be adjusted to an optimum corresponding to the plastic material (a multiple of half the wavelength in the material).

[0014] The radar sensor cover can be formed entirely from the plastic material selected in step b). In an alternative embodiment, in step c), a semi-finished product is inserted into the tool and over-molded with the selected plastic material. The semi-finished product can, for example, be a standardized component that is the same for all color variants. The semi-finished product can, for example, have additional functions, such as component heating. The semi-finished product can, for example, be a pre-molded part that was formed in a previous injection molding process. The thickness of the semi-finished product and its radar transmission properties are also taken into account in this embodiment to determine the optimal thickness of the radar sensor cover in the radar transmission range.

[0015] The plastic materials have different colors. They are preferably available as solid-colored plastics. This can include, for example, different shades and different opacities. The plastic materials are preferably unfilled plastics, which may optionally contain talc as an additional component. Plastic materials without conductive additives or conductive fillers are preferably used. The plastic materials may contain a proportion of recycled plastic. In one embodiment, it is provided that the majority of plastic materials all belong to the same plastic class. For example, PP, EPDM, PC, PC-ABS can be considered as plastic classes. Depending on their composition, the plastic materials differ at least in their dielectric constant. This is related to the optimal thickness of the plastic material - determined from the perspective of radar transparency.Depending on the desired color, a plastic material is selected from the wide range of characterized plastic materials.

[0016] The radar sensor cover can be, for example, a radome or a plastic visible component of a motor vehicle, such as a bumper cover, an outer headlight lens, a mirror cap, etc.

[0017] Further advantages, features, and details of the invention will become apparent from the following description, which describes embodiments of the invention in detail with reference to the drawings. The features mentioned in the claims and in the description may be essential to the invention individually or in any combination. Where the term "may" is used in this application, it refers to both the technical possibility and the actual technical implementation.

[0018] The following examples are explained with reference to the accompanying drawings, which show schematically:

[0019] Figure 1 shows an exemplary process flow

[0020] Figures 2 and 3 show an exemplary mold for carrying out the method

[0021] Figures 4A, 4B and 4C show exemplary sensor covers.

[0022] Figure 1 shows an exemplary process sequence for the production of radar sensor covers. In step a), a plurality of plastic materials of different colors are first characterized based on at least their dielectric constants. In step b), one of the plastic materials is selected; this will be used to produce the radar sensor cover. The optimal thickness of the radar sensor cover to be produced is then determined in at least one radar transmission range. With the optimal thickness, the radar sensor cover has the best possible radar transmission. The process uses a mold in which the thickness of the produced sensor cover can be adapted to the optimal thickness. In step bb), the mold is modified to adapt to the optimal thickness determined in step b).For example, mold inserts can be changed, changing the thickness of the mold cavity and thus the thickness of the radar sensor cover, at least in the radar transmission range. Step bb) can be omitted if no adjustment to the mold is necessary. In step c), the selected plastic material is injected into the mold and cooled to produce the radar sensor cover 100. The mold 10 is then opened, and the radar sensor cover is removed from the mold using the ejector assembly 18. The process is then repeated to produce additional radar sensor covers.

[0023] Figures 2 and 3 show an exemplary mold 10 in the form of an injection mold for use in the method. The mold 10 has two mold halves 11, 12, each mounted on a clamping plate 13, 14. A movable separation frame 15, which is movable via hydraulic cylinders 19, is adjusted in its end position (see Figure 3) by means of spacers 16 so that the mold 10 can be closed to the desired extent. Different optimal thicknesses can be achieved with this mold 10 using different spacers 16. In the closed state, the mold halves 11, 12 enclose a cavity 17 in which the radar sensor cover 100 is formed.To produce radar sensor covers, the closed cavity 17 is filled with the plastic material (see Figure 3), then, for example, the sensor covers 100 and 100A shown in Figures 4A and 4B are produced with different thicknesses D, D1 in the radar transmission area 110. In an alternative embodiment, before the injection molding process, a semi-finished product 120 in the form of a pre-molded part is inserted into the mold 10 and over-molded with the plastic material, whereby the radar sensor cover 100B shown in Figure 4C is produced.

[0024] List of reference symbols a), b), bb), c) Process steps

[0025] D, D1 thickness

[0026] 10 mold tool

[0027] 11 , 12 tool halves

[0028] 13, 14 clamping plate

[0029] 15 separation frames

[0030] 16 spacer

[0031] 17 Cavity

[0032] 100, 100A, 100B radar sensor cover

[0033] 120 semi-finished products

Claims

Patent claims 1 . A method for producing radar sensor covers, comprising the steps of: a) characterizing a plurality of plastic materials of different colors based on at least their dielectric constants, b) selecting one of the plastic materials and determining an optimal thickness of the radar sensor cover to be produced in at least one radar transmission range, c) processing the selected plastic material in a manufacturing process with a molding tool (10), in which the thickness of the radar sensor cover produced can be adapted to the optimal thickness, to produce the radar sensor cover.

2. Method according to claim 1, wherein steps a) to c) are repeated several times and furthermore an optional step bb) is provided between step b) and step c), in which the mold is converted to adapt to the optimal thickness determined in step b).

3. Method according to one of claims 1 or 2, wherein the manufacturing process is an injection molding process.

4. Method according to one of claims 1 or 2, wherein the manufacturing process is injection-compression molding.

5. Method according to claim 4, wherein the molding tool (10) has a movably mounted separating frame (15).

6. Method according to one of the preceding claims, wherein the molding tool (10) has different tool inserts by means of which the thickness of the radar sensor cover (100, 100A, 100B) produced can be varied.

7. Method according to one of the preceding claims, in which in step c) a pre-molded part (120) is inserted into the mold and over-molded with the selected plastic material.

8. A method according to any one of the preceding claims, wherein the plurality of plastic materials all belong to the same plastic class.

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