Patent Application
20130141269
The invention relates to a device for fastening a sensor assembly on a motor vehicle, especially a radar sensor having at least one detection zone in the sensor direction according to the preamble of Patent claim 1.
WO 2006/005546 A1 discloses a generic device for fastening a sensor assembly, especially a radar sensor, which device is a moulded part arranged behind a bumper of a motor vehicle by means of a collar surrounding at least part of said sensor assembly, wherein said collar consists of a material that absorbs radar radiation. In addition to its electrical shielding effect, said collar largely prevents dirt, moisture and particles from accumulating on the sensor assembly. Furthermore, said known collar can be made of a flexible material in order to reduce or absorb mechanical stress on the sensor assembly, which may occur during normal and intended use as well as in case of a less severe collision, and to prevent mechanical vibrations from being transferred. Moreover, said known collar can be placed immediately next to the bumper and may even serve as a sensor holder.
It has shown, however, that said known device for fastening a radar sensor assembly, i.e. by means of a collar, does not provide optimum protection of said sensor assembly.
The object of this invention is therefore to improve a device for fastening a sensor assembly behind an add-on part of a motor vehicle of the type described in the opening paragraph in such a manner as to achieve optimal mechanical protection of said sensor assembly.
The aforesaid object is achieved by means of a device having the features set out in Patent claim 1.
According to said claim, the invention proposes that
The aforesaid solution according to the invention ensures that the sensor assembly will not be affected by dirt between the sensor assembly and the motor vehicle add-on part, which also improves signal quality. The solid structure of the moulded part also serves to achieve a mechanical protective function for the sensor assembly against vibration and shock.
In addition to said mechanical protective function of the moulded part, additional further functions can be provided in a simple manner by means of said moulded part. In this case, the moulded part serves as a carrier matrix for additional components.
For instance, according to a further development of the invention, a transmission beam generated by the sensor assembly is shaped by means of optical lens elements that are arranged in said moulded part.
Furthermore, according to another further development of the invention, the moulded part comprises absorber elements outside the detection zone, which absorb parasitic portions of a transmission beam generated by the sensor assembly.
Moreover, according to yet another embodiment of the invention, the sensor assembly has a primary radiation zone for a transmission beam it generates, and secondary radiation zones are generated due to reflection on at least one reflector element arranged in the moulded part.
Finally, according to one embodiment of the invention, a waveguide structure extending from the sensor assembly to the motor vehicle add-on part is integrated in the moulded part, which waveguide structure can be designed to be resonant and auto-calibrated over a defined length, thus allowing any blockage caused by dirt to be detected.
According to an advantageous further development of the invention, the moulded part can be elastically deformed and has mechanical dampening properties, i.e. is designed with a vibration-dampening or energy-absorbing material property. This serves to substantially improve, i.e. reduce, vibrations and shock affecting the sensor assembly, in particular mechanical stress on the sensor assembly exerted by the add-on part.
According to a further development of the invention, it is particularly advantageous if the free surface of the moulded part is hydrophobic to prevent liquids, moisture, ice or snow from accumulating on said moulded part, which would affect the performance of the sensor assembly.
The sensor assembly can easily be fastened by means of an advantageous embodiment of the invention according to which a clip or snap-in mechanism is provided to connect the moulded part to said sensor assembly.
The moulded part and the sensor assembly can be fastened on the body of the motor vehicle by means of a mechanical device.
The motor vehicle add-on part, in particular the bumper, is able to transmit the sensor signals in the detection zone of the sensor assembly.
Said device according to the invention is particularly suitable as a radar sensor assembly for motor vehicle applications.
The invention will be explained in more detail below, with reference to the single
Said
In order to fasten the radar sensor 1, an elastic and solid moulded part 3 is provided, which e.g. is made of foamed plastic and only slightly dampens radar radiation. Said moulded part 3 has a pocket-shaped recess 3b whose inner contour is adapted to the shape of the radar sensor assembly 1. As a result, said radar sensor 1 is enclosed almost completely, i.e. in the x direction (direction of travel) as well as in the y direction. In the rearward direction, a snap-in projection 3c is formed on the circumferential edge of the pocket-shaped recess 3b, so that the radar sensor 1 can be snap-fitted in said recess 3b, allowing for easy mounting. In addition, another fastening device (not shown) is provided in order to connect the radar sensor 1 to the body structure.
The surface 3a of the moulded part 3 facing the add-on part is designed so as to be complementary to the opposite inner surface 2a of the bumper 2, so that the two surfaces 3a and 3b lie flat against each other. As a result, dirt, ice or snow are prevented from accumulating between the moulded part 3 and the bumper 2.
The close fit between the moulded part 3 and the bumper 2 prevents local vibrations of the bumper 2 from being transferred to said moulded part, thus protecting the radar sensor 1 from mechanical impact caused by the bumper 2, so that a high signal quality of the radar sensor 1 is achieved due to minimizing vibrations in the bumper 2.
In case the moulded part 3 is made of a foamed plastic, the bulk factor is adjusted such that transmission is minimally reduced by just a few decibels in the direction of propagation (x direction) of the radar beams. This requirement is for example met by foams on a polyethylene or polyurethane base.
The free surface 4 of the moulded part 3 is designed to be hydrophobic, e.g. as a liquid- and moisture-repellent coating.
Those parts of the moulded part 3 that enclose the radar sensor 1 on the side, i.e. in the y direction, contain absorbent additives in the form of graphite particles or ferromagnetic absorbent materials as absorbers 5, which e.g. are manufactured by a two-component injection moulding method. As a result, parasitic radiation that is frequently caused by surface waves and/or leakage radiation on antenna elements of the radar sensor 1 is effectively absorbed. Such a shielding in fact helps to significantly reduce the incidence of side lobes in the antenna pattern as well as the probability of false detection of objects by the radar sensor 1.
In the detection zone of the radar sensor 1, the moulded part 3 contains optical lens elements 6 for shaping the beam(s) in the near and far range, which lens elements 6 consist of a dielectric material. Another option for beam shaping in the near and far range and absorbing surface waves and leakage radiation is the incorporation of local periodic structures in the form of material geometries (Photonic Band Gaps (PBG), Electromagnetic Band Gap (EBG), Frequency Selective Surfaces (FFS)).
Furthermore, a waveguide structure 8 extending from the radar sensor 1 to the bumper 2 of the motor vehicle can be integrated in the moulded part 3. The current state of the bumper 2 (e.g. if covered with dirt, ice/snow, etc.) can then be approximately determined by analyzing the conductive properties (e.g. amplitudes and phase relations) of the conductive structure. The determined state parameters serve to detect any blockage of the sensor and to auto-calibrate sensor parameters such as transmission performance, noise behaviour, etc. In this way, degradation effects of the sensor can be detected and recalibrated during the sensor's service life.
Furthermore, reflector elements 7 incorporated in the moulded part 3 during injection moulding additionally help to shape the beam(s) and to generate additional antenna lobes. Said reflector elements 7 can also be integrated in the moulded part 3 for calibration purposes.
The device according to the invention for fastening the radar sensor by means of a moulded part provides reliable protection against dirt, prevents foreign matter from accumulating between the radar sensor and the bumper of the motor vehicle and serves a protective function against vibrations and shock. In addition, the performance and characteristics (directivity) of the antenna are optimized by means of functional elements that are incorporated in said moulded part, such as absorber elements, optical lens elements, waveguide structures and reflector elements.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2010 034 073.1 | Aug 2010 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/DE2011/001592 | 8/12/2011 | WO | 00 | 2/11/2013 |
