HEADLIGHTS FOR MOTOR VEHICLES

Description

[0001] The invention relates to a motor vehicle headlight according to the preamble of claim 1.

[0002] Furthermore, the invention relates to a motor vehicle with at least one such, preferably two such vehicle headlights.

[0003] Motor vehicle headlights use light imaging systems containing lenses. These lenses focus parallel sunlight incident from outside and direct it to focal points on a motor vehicle headlight element. Depending on the position of the sun relative to the motor vehicle headlight, the vehicle inclination, or the nature of the motor vehicle headlight element material, the energy input of the sunlight, measured by the irradiance in W / m², can be too high at the motor vehicle headlight element and lead to the melting of the motor vehicle headlight elements. As a result, at the very least, the surfaces of the motor vehicle headlight elements are damaged and unsightly; in addition, mechanical instabilities of the motor vehicle headlight elements and / or outgassing can occur. In this case, this is referred to as the magnifying glass effect.

[0004] Motor vehicle headlights of the type mentioned above are known in the prior art. Among them, some motor vehicle headlights are already known that offer a solution for mitigating the magnifying glass effect. For example, DE 19803986 A1 discloses the use of optical deflection means on the outer surface of the lens, which are intended to substantially prevent light from penetrating the interior of the lens. These optical deflection means are often achieved by sandblasting or granite blasting the lens surface and usually require an additional element that prevents the light generated by the light source arranged in the headlight from striking the roughened outer surface of the lens. This solution effectively reduces the numerical aperture of the lens and can impair the light distributions produced by the motor vehicle headlight.

[0005] Furthermore, the application of a surface structure to the entrance side of a lens is known from DE 29912504 U1. Similar to the above-mentioned solution, this surface structure becomes a disadvantage when it comes to generating legally prescribed light distributions.

[0006] Furthermore, JP 2014063604 A discloses a motor vehicle headlight comprising a light source having a light-emitting surface and an aspherical lens, wherein the lens projects light emitted by the light source arranged in the motor vehicle headlight in front of the motor vehicle headlight in the form of a low-beam distribution. The lens has a region 8 that is not illuminated by the light emitted by the light source and onto which sunlight falls. This region is used exclusively to reduce the magnifying glass effect by diffusely scattering the sunlight. A disadvantage of this approach is the reduction of the refractive region of the lens, and it can only be used for low-beam modules. Furthermore, the effect achieved with this region depends significantly on the position of the sun.

[0007] Another approach, in which the relevant vehicle headlight element is protected by a special metal layer, is known from DE 102012101434 A1. The application of an additional reflective metal layer or the insertion of a corresponding additional, e.g. heat-resistant, headlight element into the light imaging system often represents a technically difficult problem to solve due to space constraints. The following disadvantages can arise individually or in combination: Increased costs due to additional work steps and headlight elements; impairment of the mechanical integrity of one of the headlight elements, e.g. a lens holder; fixing of the additional headlight element; creation of undesirable scattered light in the vehicle headlight; change in the design desired by the customer; dependence of the vapor deposition option on the geometry of the headlight element concerned.Other motor vehicle headlights are known from WO 2015 / 031925 A1 or WO 2014 / 027020 A1.

[0008] The described disadvantages of the prior art are to be eliminated. Therefore, the object of this invention is to provide a headlight for motor vehicles in which, on the one hand, the energy input into a focal point is distributed over a larger area of ​​a vehicle headlight element surface, and, on the other hand, the light distribution generated by the lighting device arranged in the vehicle headlight is substantially unchanged. This reduces magnifying glass effects, allows the use of materials with lower thermal resistance, and, on the other hand, complies with legal regulations regarding light distributions.

[0009] This object is achieved with a motor vehicle headlight as described above having the features of the characterising part of claim 1.

[0010] In one of the preferred embodiments, the lighting device arranged in the motor vehicle headlight comprises one, two or more light sources which emit / emit the light to generate the predetermined light distribution, wherein preferably a reflector, in particular an ellipsoidal free-form reflector, and / or an auxiliary optical system, preferably an imaging lens arrangement, and / or a diaphragm is assigned to the light source(s).

[0011] It is expedient that the light source(s) is / are designed as an HID lamp, i.e., a xenon gas discharge lamp, for example according to standard ECE-R99, and / or one, two or more LEDs, which may have the same or different designs, and / or an incandescent lamp, for example a filament lamp according to standard ECE-R37.

[0012] The light incident from outside can be imagined as a plurality of parallel light beams. When they hit a region of a conventional lens, many of these light beams are refracted to a focal point. This creates a surface area with a high irradiance. Through the presence of an inventive optical structure, which can be applied, for example, to one of the lens surfaces, each light beam is refracted to a different focal point, i.e., defocused.

[0013] It has proven to be expedient to distribute the optical structural elements over at least one, preferably exactly one defined basic structure of at least one, preferably exactly one, element of the light imaging system.

[0014] To facilitate the manufacturing process of such optical structures, it is advantageous to use the basic structure with certain geometric properties.

[0015] For this reason, in one of the preferred embodiments, it is ensured that the basic structure is designed as a two-dimensional grid and consists of one, two or more defined grid cells.

[0016] Furthermore, it is useful that the two-dimensional grid essentially forms a structured grid with regular cell geometry.

[0017] Furthermore, it is conceivable for the grid cells to be formed as regular polygons. In a particularly advantageous embodiment, at least one, preferably exactly one, structural element is arranged on each grid cell.

[0018] In order to avoid the diffraction of the incident light at the optical structure and the subsequent interference effects after the optical structure, the geometric dimensions of the grating cells and the structural elements should be carefully selected.

[0019] In one of the preferred embodiments, it is provided that the optical structural elements are designed substantially identically.

[0020] The design of the individual structural elements is of great importance for reducing the magnifying glass effect.

[0021] According to the invention, the optical structural elements have a central elevation in their center.

[0022] According to the invention, the height of the central elevation is 25 micrometers.

[0023] In general, the invention provides that the central elevation is described by a function graph of a continuous real and non-negative function defined on a grid cell. The function graph represents a two-dimensional surface.

[0024] It can also be provided that the function is designed as a piecewise linear function.

[0025] It is also advantageous that the function is designed in such a way that the function graph is essentially rotationally symmetrical with respect to a vertical axis passing through the center of the grid cell.

[0026] In a particularly advantageous embodiment, it is provided that a vertical section of the function graph along a horizontal line passing through the center of the grid cell has a piecewise linear function, wherein this function has at least five linear sections and the extension of the second linear section and the third linear section enclose an angle of rise.

[0027] Furthermore, it is provided according to the invention that the optical structural elements have a base area whose extent is 1.0 millimeters.

[0028] In order to discuss the reduction of the magnifying glass effect in more detail, the refracted modified light beams must be considered. According to the invention, the first modified light beam is incident on a first headlight element and illuminates a first modified luminous point, and the second modified light beam is incident on a second headlight element and illuminates a second modified luminous point. It is particularly advantageous that the size of the first modified luminous point and / or the second modified luminous point, for example, a diameter of the luminous point, is related to the dimensions of the central elevation, for example, a first angle of ascent and / or a second angle of ascent, a plateau diameter, and / or a height of the central elevation.

[0029] It is provided according to the invention that the size, for example a diameter, of the first modified luminous point and / or of the second modified luminous point is larger than the size, for example a diameter, of an unmodified luminous point.

[0030] According to the invention, the maximum irradiance within the first modified luminous point and / or within the second modified luminous point is lower than the irradiance within the unmodified luminous point.

[0031] It should be noted here that the optical structure can be mounted in many locations within the vehicle headlight. The exact position of the optical structure depends on the specific design of the vehicle headlight. In addition to legal regulations, another requirement must be met regarding the positioning of the optical structure: The structure must be illuminated by externally incident light (in the case of sunlight, regardless of the sun's altitude).

[0032] It has proven to be expedient to arrange the optical structure on at least one, preferably exactly one, surface of a light imaging system element which is designed in the form of a projection lens and / or imaging lens.

[0033] According to the invention, the optical structure is arranged on an entrance surface and / or an exit surface of a light imaging system element which is designed in the form of a projection lens and / or imaging lens.

[0034] The present invention is illustrated in more detail below using preferred, non-limiting embodiments with reference to the drawings. It shows: Fig. 1 a schematic representation of the inner and outer magnifying glass effect in a vehicle headlight according to the state of the art, Fig. 2 a schematic representation of the inner and outer magnifying glass effect in a vehicle headlight with an optical structure according to the invention, Fig. 3 an unmodified and a modified luminous point on a headlight element produced in a vehicle headlight, each without and with an optical structure according to the invention, Fig. 4 a lens with an optical structure in a three-dimensional view, a section of the lens in an enlarged view, and further a further enlarged section of the already enlarged section, Fig. 5 a light point expansion by a single structural element according to the invention in the case of parallel incident light, Fig. 6 a plan view of an optical structure distributed over a hexagonal basic structure, which consists of structural elements with round central elevations, Fig. 7 a perspective view of a section of an optical structure, and Fig. 8 a side section of a rotationally symmetric structural element, which section is designed as a function graph of a piecewise linear one-dimensional real function.

[0035] First, the reference to the Fig. 1 which schematically shows a conventional vehicle headlight with its most important elements in side section. Therein, a lighting device 200, a first motor vehicle headlight element, e.g. a cover, a holder or a design element 204, which can be designed, for example, as a cover separating functional units in the headlight, a second motor vehicle headlight element, e.g. a lens holder, a primary optics holder, a circuit board, for example a printed circuit board / circuit carrier 205 in the form of a PCB (Printed Circuit Board), on which, for example, LEDs are mounted, a light imaging system, which for the sake of simplicity is shown here in the form of a typical imaging lens 210, and a cover plate 220.

[0036] The incident light beam, "sunlight," is refracted and reflected several times upon entering the vehicle headlight. Of particular interest are the light rays that, after repeated refraction and / or reflection, strike vehicle headlight elements, often made of plastic, such as various holders, designs, or circuit boards 204, 205. These usually arise from refraction and / or reflection at the entrance surface 211 of an optical element, for example, an imaging or projection lens. The passing beam then falls directly onto a vehicle headlight element (internal magnifying glass effect), for example, onto a plastic holder. The reflected beam only strikes a vehicle headlight element after further refraction at the exit surface of an optical element, e.g., an imaging or projection lens 212 (external magnifying glass effect).

[0037] A strong focus of the refracted and / or reflected light beam results in a high irradiance at a luminous spot 305 on the surface 205 of the automotive headlight element, which can far exceed the damage limit of the material. For example, the irradiance can reach a value of 75,000 W / m², which exceeds the damage limit of approximately 62,000 W / m² of a special plastic material used in automotive headlights, "PBT-GF30 black," and causes rapid melting of the automotive headlight element.

[0038] To reduce the irradiance, an optical structure is used that defocuses the refracted and / or reflected light beam. Fig. 2 shows an imaging lens 210 with an optical structure 215 applied to the exit surface of the lens. Due to the special shape of the structural elements 502, the focal point position is shifted in space. This creates a different, larger luminous spot 350 on one of the motor vehicle headlight elements 204, 205, as shown schematically in Fig. 3 Although neither of the two luminous dots forms an exact luminous dot, it is quite conceivable to qualitatively represent the size of both luminous dots by their diameters d and D, respectively. The larger the diameter of a luminous dot, the smaller the maximum irradiance value.

[0039] Fig. 4 shows a perspective view of an enlarged section of an optical structure arranged on the exit surface 215 of a lens, which is applied to a hexagonal basic structure, and an even larger section with a structural element 502. The structural element has a central elevation in the form of a truncated cone of a certain height h.

[0040] A "smearing" of the point by the truncated cone-shaped central elevation of the structural element 502 is in Fig. 5 The left image shows a scatter pattern of a structural element 502 without a central elevation (h=0). The illuminated area is a point with a diameter. The radiant flux per unit area (radiant flux density) is large. The central elevation causes the illuminated area to expand (right image in Fig. 5 ). This reduces the radiant flux density. The total incident radiant energy is redistributed over a larger area; in other words, the original light beam is "defocused," creating defocused light beams LB1.

[0041] In Fig. 6 An embodiment of an optical structure is shown in plan view. The basic structure 500 consists of hexagonal grid cells 501. The structural elements have a rotationally symmetric central elevation. Fig. 7 It can be seen that this central elevation is formed as a straight truncated cone with a top surface 506 and a lateral surface 507 and is arranged on a base surface 505. When light is incident perpendicular to the base surface 505, it is refracted at the lateral surfaces and leads to the blurring of the luminous spot on a motor vehicle headlight element.

[0042] The degree of smearing depends on the geometric properties of the central elevation of the optical structural element 502. For the above-mentioned example of a truncated cone-shaped central elevation, these properties are Fig. 8 summarized. The Fig. 8 shows a vertical section of the structural element 502 along a horizontal line AA passing through the center 510 of the grid cell 501 ( Fig. 6 und 7 ). The section through the center 510 of the structural element 502 can be described by a graph of a piecewise linear function. In Fig. 8 The function has five linear sections 601, 602, 603, 604, 605. The blurring of the luminous dot depends on the length P of the central linear section 603, which is equal to the diameter of the cover surface 506, the length of the second section 602 and the fourth section 604, and the angle of rise α of the second linear section 602.

[0043] The invention has been described with reference to a hexagonal basic structure and a substantially flat, rotationally symmetrical central elevation, for which the invention is particularly advantageous.

[0044] In principle, however, the invention can also be used with non-hexagonal basic structures and with differently designed central elevations.

Claims

1. Motor vehicle headlamp, which comprises an at least partially transparent cover lens (220), in particular in the visible spectral range, at least one lighting device (200), at least one light imaging system (210) associated with the lighting device (200), which images light emitted by at least one light source into an area in front of the lighting device in the form of a predetermined light distribution, wherein at least one optical structure (215) is provided in the motor vehicle headlamp, which optical structure (215) comprises one, two or more optical structural elements (502) and is arranged in the motor vehicle headlamp in such a way that at least some of the light, in particular sunlight, incident on the motor vehicle headlamp from outside in parallel is incident on the optical structure (215) and is scattered by the optical structure when it passes through the optical structure and when it is reflected, wherein the structural elements (502) have a light-scattering effect and are designed such that each structural element (502) modifies a light beam passing through the structural element to form a first modified light beam (LB1) and modifies a light beam reflected by the structural element (502) to form a second modified light beam (LB2), the predetermined light distribution by the optical structure (215) remaining essentially unchanged, wherein the first modified light beam is incident on a first headlamp element (205) and illuminates a first modified light spot (350) and the second modified light beam is incident on a second headlamp element (204) and illuminates a second modified light spot, and wherein a size, for example a diameter (D), of the first modified light spot (350) and of the second modified light spot is greater than a size, for example a diameter (d), of an unmodified light spot (305), the maximum irradiance within the first modified light spot (350) and within the second modified light spot (450) being less than the irradiance within the unmodified light spot (305), and wherein the optical structure (215) is arranged on an entrance surface (211) and / or an exit surface (212) of a light imaging system element which is designed in the form of a projection lens and / or imaging lens (210), and wherein the optical structural elements (502) have a base surface, and the optical structural elements (502) have a central elevation (506) in their center, and wherein the central elevation (506) is described by a function graph of a continuous real and non-negative function defined on a grid cell (501), characterized in that the extension of the base area is 1.0 millimetre and the central elevation has a height (h) of 25 micrometres.

2. Motor vehicle headlamp according to claim 1, wherein the lighting device (200) comprises one, two or more light sources, wherein preferably a reflector, in particular an ellipsoidal free-form reflector, and / or an optical attachment, preferably an imaging lens arrangement, and / or a diaphragm is associated with the at least one light source.

3. Motor vehicle headlamp according to claim 1 or 2, wherein the at least one light source is designed as an HID lamp, preferably an HID lamp according to standard ECE-R99, and / or one, two or more LEDs and / or an incandescent lamp, for example a filament lamp according to ECE-R37.

4. Motor vehicle headlamp according to one of claims 1 to 3, wherein the optical structural elements (502) are distributed over at least one, preferably exactly one, defined basic structure (500) of at least one, preferably exactly one, light imaging system element, wherein the basic structure (500) is designed, for example, as a two-dimensional grid (503) and consists of one, two or more defined grid cells (501), wherein the two-dimensional grid (503) preferably essentially forms a structured grid with regular cell geometry and / or the grid cells (501) are formed, for example, as regular polygons, wherein at least one, in particular exactly one, structural element (502) is preferably arranged on each grid cell (501).

5. Motor vehicle headlamp according to one of claims 1 to 4, wherein the optical structural elements (502) are essentially identical.

6. Motor vehicle headlamp according to one of claims 1 to 5, wherein the size of the first modified light spot (350) and / or the second modified light spot, for example a diameter of the light spot, is related to the dimensions of the central elevation, for example to a first angle of rise (α) and / or to a second angle of rise, a plateau diameter (P) and / or a height of the central elevation (h).

7. Motor vehicle headlamp according to any one of claims 1 to 6, wherein the real and non-negative function is formed such that the function graph is substantially rotationally symmetric with respect to a vertical axis passing through a center point (510) of the grid cell (501),and whereina vertical section of the function graph along a horizontal line (AA) running through the center point (510) of the grid cell (501) has a piecewise linear function, wherein this function has at least five linear sections (601, 602, 603, 604, 605) and the extension of the second linear section (602) and the third linear section (603) include an angle of approach (α).

8. Motor vehicle with at least one, preferably two motor vehicle headlights according to any one of claims 1 to 7.