Patent Application
20240117949
This nonprovisional application claims priority under 35 U.S.C. § 119(a) to German Patent Application No. 10 2022 126 304.5, which was filed in Germany on Oct. 11, 2022, and which is herein incorporated by reference.
The invention relates to a Fresnel projection lens for a headlight of a motor vehicle, to a headlight for a motor vehicle, and to a motor vehicle.
In order to meet legal requirements, a headlight must fulfill the so-called overhead sign values in the low beam mode. This requirement serves to ensure that, for example, highway signs mounted above the roadway can be safely recognized and read by the driver.
The light intensities to be achieved at the corresponding measuring points are comparatively low. These measuring points are at large, positive vertical angles. The requirement of having to satisfy these measuring points is somewhat at odds with the main requirement for a low beam, namely, the condition that no or hardly any light should be emitted into the traffic area above a horizontal boundary, the so-called cut-off line. Basically, the entire headlight is designed for this.
Previously used technical measures to provide the overhead sign values include, for example, subsequently introducing grooves or notches or circumferential beads with a refractive effect into a projection lens that was initially calculated and manufactured as a perfectly imaging collimating lens. This means an additional process step in the production. Often, this measure adversely affects the appearance of the Fresnel projection lens. For example, a slight thickening (bead) running horizontally around the Fresnel projection lens may be perceived as annoying by customers.
An alternative measure used so far to achieve the overhead sign values is to introduce additional reflective elements into the headlight optics, which, for example, deflect a small part of the light coming from the primary optics toward high vertical angles. Such technical measures have disadvantages similar to the insertion of grooves or notches or the application of beads.
With the above measures, the geometry that provides the desired effect must be found and determined in optimization loops. This refers to both the lighting design and the manufacturing implementation of the specified geometry.
It is therefore an object of the present invention to at least partially overcome at least one of the above-described disadvantages in headlights of a motor vehicle. In particular, it is an object of the invention to provide a Fresnel projection lens for a headlight of a motor vehicle, a headlight for a motor vehicle, as well as a motor vehicle with optimized integration of the overhead sign values, without impairing the collimation effect of the lens.
The foregoing object is achieved in an exemplary embodiment by a Fresnel projection lens, by a headlight, and by a vehicle. In this regard, features and details that are described in relation to the safety system of the invention also apply, of course, in relation to the method of the invention or in relation to the vehicle of the invention, and conversely in each case, so that with regard to the disclosure, reference is or can always be made mutually to the individual aspects of the invention.
According to the invention, a Fresnel projection lens is provided for a headlight of a motor vehicle having a light entry surface, wherein the light entry surface has a smooth or substantially smooth surface, and having a light exit surface, wherein the light exit surface has a plurality of adjacent, in particular annular, flanks, wherein one flank each comprises a bottom, an effective facet, and an interfering facet arranged at a first pitch angle to the effective facet, wherein the effective facet and the interfering facet form a cut edge opposite to the bottom, wherein a pass-through area is provided on at least one of the flanks, wherein the pass-through area is angled to the effective facet.
A Fresnel projection lens designed in this way enables the light from a light source to pass through directly or substantially directly without being refracted or only slightly refracted. As a result, areas, in particular the overhead sign areas limited by the overhead sign values, outside a light cone of the low beam can be illuminated with a low light intensity. At the same time, the use of the pass-through areas of the main headlight reduces the glare in the low beam function.
The flanks can have a triangular or substantially triangular cross section. In this case, the bottom of the flank can have a curvature.
The flanks are designed in such a way that the light from a light source is refracted to a large extent via the effective facet and only a small part of the light is refracted via the interfering facet. It is advantageous for a Fresnel projection lens in this regard if the adjacent flanks differ at least slightly in their geometry. The first pitch angle, therefore, the angle between the effective facet and the interfering facet, must be designed in such a way that the effective facets of the flanks have a common refractive power. Accordingly, the pitch angles of the respective adjacent flanks differ from each other.
The different first pitch angles have the result that a parallel or substantially parallel beam path forms starting from a light source after passage of the individual effective facets, therefore, after refraction of the light at the effective facets.
This has the result that the Fresnel projection lens can be made flatter, so that material can be saved. Further, steps can be saved in the manufacturing process, because the subsequent introduction of grooves or recesses into the Fresnel projection lens or the placement of additional elements on or within the optics can be dispensed with.
It is particularly advantageous if the flanks and thus also the pass-through area are formed annular. This makes Fresnel projection lenses easier to design and manufacture.
The pass-through area can be arranged at a second pitch angle to the effective facet, wherein the second pitch angle is different from the first pitch angle.
The second pitch angle can be designed or calculated in such a way that the light is refracted only slightly, in particular not at all, during the passage of light. This enables the illumination of defined areas outside the defined light cone. These defined areas are specified by the overhead sign values. These areas must be illuminated at least in such a way that, for example, road signs can be read in the dark without blinding oncoming traffic.
The pass-through areas of a flank can be formed circumferential.
The circling of the pass-through area can ensure continuous illumination of the legally specified overhead sign values.
In order to create sufficient light passage through the pass-through areas, without blinding traffic, it is advantageous if the height of the pass-through areas corresponds to 40% to 95%, preferably 50% to 90%, of the height of the flank.
In this case, the height of the flank can be understood as the distance between the bottom of the flank and the cut edge of the effective facet and the interfering facet. The height of the pass-through area is the distance between the bottom of the flank and the pass-through area.
Further, it is conceivable that a maximum of 15%, preferably a maximum of 12%, further preferably 10%, of the flanks have a pass-through area.
A low light intensity is sufficient to achieve the overhead sign values or to meet the legal requirements. The other flanks in this regard generate the low beam or the generally well illuminated area.
At least two flanks can have a pass-through area. Sufficient illumination of the areas specified by the overhead sign values can be achieved thereby.
Further, it is conceivable that a maximum of five flanks, preferably a maximum of four flanks, further preferably a maximum of three flanks, have a pass-through area.
Here, the number of flanks with a pass-through area depends on the desired and/or legally specified intensity of the passing light in the area of the overhead sign values.
Within the scope of the invention, it is conceivable that the flanks with pass-through areas are arranged adjacent and/or alternating.
In the present context, alternating can mean that at least one flank without a pass-through area may be provided between two flanks with a pass-through area. Depending on the number, it is conceivable that two flanks with a pass-through area are adjacent and a third (or even fourth) flank is arranged alternately. The arrangement of the flanks with a pass-through area positively influences the size of the overhead sign area next to the light cone and its intensity.
It is particularly advantageous for the accuracy of the lower intensity areas, therefore, the overhead sign areas, if the second pitch angle of adjacent and/or alternating flanks with a pass-through area differs from one another.
The flanks with pass-through areas can be arranged in an aspherical region of the Fresnel projection lens. This makes it possible to minimize the number of flanks with pass-through areas.
The Fresnel projection lens can be cast, in particular injection molded.
The Fresnel projection lenses can be manufactured more easily by casting. Here, the subsequent introduction of grooves or recesses into the Fresnel projection lens or the placement of additional elements on or within the optics can be dispensed with.
Advantageously, the Fresnel projection lens can have a plastic, in particular polymethyl methacrylate or polycarbonate. These can be easy to cast, preferably injection molded, wherein at the same time the production can be made cost-effective.
Alternatively, it is also conceivable to fabricate the Fresnel projection lens from glass. This allows a higher precision of the light passage across the pass-through area and/or the effective facet.
The Fresnel projection lens can be concave and/or convex. By this it is understood that the Fresnel projection lens can also be bi-convex, plano-convex, concave-convex, convex-concave, plano-concave, or bi-concave. The focal points of the Fresnel projection lens can be easily adapted thereby to customer-specific requirements.
The above object is further achieved by a headlight for a motor vehicle, having a housing and having a light unit with at least one light source, wherein the headlight, in particular the light unit, has a Fresnel projection lens described above.
The above object is further achieved by a motor vehicle having an above-described headlight.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes, combinations, and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:
A Fresnel projection lens 1 for a headlight 2 of a motor vehicle 3 is shown in
Pass-through area 11 is arranged here at a second pitch angle β to effective facet 8. The second pitch angle β between effective facet 8 and pass-through area 11 differs from the first pitch angle α between effective facet 8 and interfering facet 9.
In the example according to
The height HDF of pass-through area 11 or pass-through areas 11 corresponds to 40% to 95% of the height HF of flank 6. Here, the height HF of flank 6 is the distance between bottom 7 of flank 6 and cut edge 10 of effective facet 8 and interfering facet 9. The height HDF of pass-through area 11 is the distance between bottom 7 of flank 6 and pass-through area 11.
To ensure the anti-glare function, therefore, to ensure that most of the light is refracted, in a Fresnel projection lens 1 according to
In this context, when designing Fresnel projection lens 1 to achieve the overhead sign values, it has proven advantageous if at least two flanks 6 have a pass-through area 11.
Regardless of the size of Fresnel projection lens 1, however, care should be taken that a maximum of five flanks 6 have a pass-through area 11, wherein three flanks 6 turned out to be optimal.
Depending on the size of Fresnel projection lens 1 and the number of pass-through areas 11 in the overhead sign area, flanks 6 with pass-through areas 11 may be arranged adjacent and/or alternating.
In the example according to
In this case, the second pitch angle β of adjacent flanks 6 with pass-through areas 11 differs from each other. This also applies to the case when they are arranged alternately, therefore, with a flank 6 without a pass-through area 11.
Furthermore, flanks 6 with pass-through areas 11 are arranged in an aspherical region of the concave-convex Fresnel projection lens 1.
Fresnel projection lens 1 according to
The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2022 126 304.5 | Oct 2022 | DE | national |
