CAR HEADLIGHTS
Patent Information
- Application Number
- AT2021769897T
- Authority / Receiving Office
- AT · AT
- Patent Type
- Patents
- Current Assignee / Owner
- Priority Date
- 2020-09-23
- Filing Date
- 2021-08-23
- Publication Date
- 2026-03-15
- Estimated Expiration
- 2041-08-23
AI Technical Summary
Conventional methods for defrosting motor vehicle headlights without a cover plate are complex, expensive, and inefficient, particularly when the projection lens is exposed to moisture and ice, leading to light obstruction in wintry conditions.
A projection module with a heating element featuring a transparent, electrically insulating carrier film and conductor tracks applied to or embedded within the projection lens, which can be easily integrated during production, allowing for efficient defrosting by heating the lens directly.
The solution provides a simple, cost-effective, and efficient method to prevent ice and snow accumulation on the projection lens, ensuring uninterrupted light emission even in harsh weather conditions with minimal light loss and increased durability.
Abstract
Description
[0001] Projection module of a motor vehicle headlight and motor vehicle headlight with such a projection module
[0002] The present invention relates to a projection module for a headlight of a motor vehicle. The projection module comprises a light source for emitting light, a primary optics system for bundling, shaping, and / or redirecting the light emitted by the light source, and a secondary optics system in the form of a projection lens, which images an intermediate image of an intermediate image plane, which is arranged in the beam path between the primary optics system and the secondary optics system, in a light exit direction of the projection module in a foreground in front of the motor vehicle as the resulting light distribution of the projection module. The projection module has a heating element for heating the projection lens.
[0003] The invention also relates to a method for producing a projection lens of a projection module of a motor vehicle headlight that can be heated by means of a heating element. The invention further relates to a motor vehicle headlight. The headlight comprises a housing with a light passage opening arranged in a light exit direction of the headlight.
[0004] A projection module and a motor vehicle headlight of the aforementioned type are known, for example, from JP 2007-242 291 A. There, it is proposed to arrange a planar heating element for heating a cover plate of the headlight, which closes a light passage opening of the headlight housing, at any location in the headlight, except on the cover plate itself. In the exemplary embodiment shown in Fig. 4, the heating element is arranged on an outer surface of a projection lens, so that the heat generated by the heating element radiates towards the cover plate and heats it. The planar heating element is applied to the outer surface of the projection lens by means of a coating process, e.g., vacuum vapor deposition or sputter deposition using ITO (indium tin oxide). The planar heating element therefore has no discrete conductor tracks, but rather emits heat across its entire surface when supplied with current.Contact points of the flat heating element are applied, for example, using a conductive paint.
[0005] The described projection module has the disadvantage that applying and contacting the heating element is very complex and expensive. Therefore, the described process has not yet been and will not be adopted for large-scale production in the future. Although the cited prior art is almost 15 years old, conventional heating of the inside of the cover plate of a motor vehicle headlight using a heated air flow is still used in practice. Either waste heat from electrical or electronic components or heat generated by separate heating elements inside the headlight housing is used to heat the air flow.
[0006] However, these common and practical methods for defrosting headlights reach their limits in headlights that do not have a cover plate. In these newer headlights, the projection module is located in the light passage opening of the headlight housing and the projection lens forms the outer edge of the headlight in the direction of light emission. Because the cover plate is missing, moisture (e.g. raindrops, fog, misting, etc.) and ice (e.g. snow, icing, hail, hoarfrost, etc.) settle on the outside of the projection lens in such headlights. This effect is further aggravated by the fact that the outer surface of the projection lens of such headlights is often located in a recess in which moisture and ice can settle particularly easily.
[0007] Based on the described prior art, the present invention is based on the object of proposing a simple and cost-effective, yet efficient way of defrosting projection lenses of light modules of motor vehicle headlights, in particular when the headlights do not have a cover plate for closing the light passage opening of a headlight housing.
[0008] To achieve this object, a projection module having the features of claim 1 is proposed. In particular, starting from the projection module of the type mentioned at the outset, it is proposed that the heating element comprises a transparent film made of an electrically insulating material and conductor tracks applied thereto or embedded therein, which are connected to an electrical energy source via a switching element, wherein the heating element is applied at least to a partial area of a light entry and / or light exit surface of the projection lens of the projection module or is at least incorporated into a part of the projection lens itself, so that the heating element heats the projection lens when the current flow through the conductor tracks is switched on.
[0009] The present invention can be implemented particularly easily and cost-effectively. Advance production and stocking of a large number of heating elements is readily possible. The finished heating element then only needs to be applied to an outer surface of the projection lens or projection module during production of the projection lens or projection module, or it needs to be inserted into the lens and electrically contacted. The transparent film is preferably flexible enough to be able to adapt to a curvature or slight curvature of the outer surface of the projection lens. In this context, it is proposed that the projection lens preferably be designed as a cylindrical lens. This has a light exit surface with a greater curvature around a cylinder axis and a significantly lesser curvature around an axis running perpendicular to the cylinder axis. The curvature around the axis running perpendicular to the cylinder axis is preferably very small, in particular almost zero.Thus, the light-emitting surface of the lens is flat or nearly flat in a cross-sectional plane encompassing the cylinder axis. When the projection module is installed in the motor vehicle in operational condition, the cylinder axis runs essentially vertically, i.e., approximately perpendicular to the roadway on which the vehicle is stationary or traveling. A cylindrical lens is generally a lens with two cylindrical surfaces. For the purposes of the present invention, however, lenses with toric surfaces (i.e., lenses whose surface emerges from a torus) are also referred to as cylindrical lenses.
[0010] A further advantage of the invention is the small number of parts required for the manufacture and contacting of the heating element, as well as the simple mounting of the heating element on or in the projection lens.
[0011] The transparent carrier film is preferably made of a plastic, e.g., a transparent polycarbonate (PC). The plastic used should be UV- and / or heat-resistant and—at least if the heating element is applied to an outer surface of the projection lens—weather- and / or acid-resistant. The resistance of the plastic ensures that it does not become brittle or hard, crack, or discolor over its lifetime due to UV radiation and weathering. For example, Makrofol® UV 244 from Covestro AG, Leverkusen, Germany, could be used as the material for the carrier film. The film has a thickness in the range of 100–600 μm, preferably in the range of 200–500 μm, and most preferably in the range of approximately 350 μm.
[0012] The conductor tracks can be printed conductors, e.g. made of copper, on the transparent carrier film. Preferably, however, the conductor tracks are formed by heating wires which heat up when current flows and transfer heat to the projection lens, thus thawing it. The heating wires are preferably made of a metal, e.g. copper. They preferably have a circular cross-sectional area. However, other cross-sectional areas (e.g. oval or rectangular) are also conceivable. Without electrical insulation, the heating wires have a diameter in the range of 10-100 pm, preferably in the range of 30-70 pm, and most preferably in the range of 40-55 pm. Insulation can be applied to the wires, at least in sections, e.g. in the form of insulating varnish or plastic insulation. With the insulation, the diameter of the heating wires increases by approximately 20-30% or by approximately 10-20 pm.A heating wire with a diameter of 44 pm without insulation and 56 pm with insulation is particularly preferred. The small diameter of the heating wires, when evenly distributed on or within the projection lens, results in negligible light losses. In particular, the light losses are in the range of <1%. There is also no risk of uncontrolled scattering, refraction, or diffraction of the light passing through the lens due to the heating wires.
[0013] It is conceivable to apply several separate conductor tracks to the carrier film or to incorporate them into the film. The conductor tracks can run parallel to one another or concentrically, for example. The ends of the individual conductor tracks can be led together to a switching element or an electrical energy source. However, it is preferred that a single conductor track be applied to the carrier film in several meandering loops or be incorporated into it. The loops of the conductor track can run parallel to one another or concentrically, for example. The ends of the conductor track can be led to a contacting element, which can be part of the heating element. The contacting element can be connected to a switching element or an electrical energy source.
[0014] The heating element can be applied and secured to an outer surface of the projection lens, for example, by means of adhesion or an adhesive. The adhesive is preferably transparent and heat-resistant when cured. UV, weather, and acid resistance of the adhesive would also be advantageous. The heating element's carrier film preferably has an adhesive layer on one side, via which the heating element can be attached to the outer surface of the projection lens.
[0015] However, it is particularly preferred if the heating element is inserted into an injection mold during production of the projection lens using an injection molding process (so-called molding), and then the lens material (e.g., glass or transparent plastic, e.g., PC, PMMA, etc.) is injected into the mold onto the heating element. The injected hot lens material preferably bonds with the material of the carrier film and, after curing, ensures a permanent connection between the heating element and the projection lens. Preferably, a material bond, in particular a fused bond, is created between the transparent film and the projection lens.
[0016] Alternatively, the heating element can also be inserted between two parts of the projection lens during production of the projection lens using a so-called co-molding process. The heating element can be inserted into the projection lens, for example, during production of the projection lens in several steps, as is known, for example, from DE 10 2010 033 902 A1. The content of this document is hereby incorporated in its entirety into the subject matter of the present application. In particular, a first part of the projection lens can be manufactured using an injection molding tool in a first process cycle. The heating element is then placed on top of the first part in the injection molding tool and, in a subsequent process cycle, overmolded again with the lens material to produce another part of the projection lens. The two parts of the lens and the transparent film also bond to one another and form a permanent connection after curing.On the finished projection lens, the various parts or the transparent film of the inserted heating element can no longer be seen with the naked eye.
[0017] The object is also achieved by a motor vehicle headlight with the features of claim 18. In particular, starting from the headlight of the type mentioned at the outset, it is proposed that the headlight have a projection module according to the invention in the housing. It is particularly preferred if the light passage opening of the headlight housing is not closed by a cover plate and if the projection module, in particular the projection lens, is sealed off from the housing all around the light exit direction of the headlight. The advantages of the heatable projection lens of the light module according to the invention are particularly evident in headlights without a cover plate, where the outer surface of the projection lens forms the outward closure of the projection module or headlight in the light exit direction of the headlight.Direct and immediate heating of the projection lens ensures particularly efficient defrosting of the projection lens and a particularly fast response.
[0018] To seal the projection module or projection lens from the headlight housing, a waterproof, elastic material, such as plastic or rubber, is preferably used. Sufficient flexibility of the sealing material allows movement of the projection module or projection lens relative to the headlight housing, for example, to implement a basic vertical adjustment, headlight range adjustment, and / or dynamic cornering lights. Alternatively, headlight range adjustment and / or dynamic cornering lights can also be implemented purely electrically by using a semiconductor light source array, such as an LED array, as the light source of the light module, and specifically controlling the semiconductor light sources to switch them on, off, or dim them.
[0019] According to an advantageous development of the invention, it is proposed that the light source comprises at least one semiconductor light source, in particular at least one LED, preferably a multi-chip LED. Several LED semiconductor light sources can be arranged next to and above one another in a matrix-like manner, thus forming an LED array. The light emitted by semiconductor light sources often does not contain enough thermal energy (IR radiation components) to ensure warming of the projection lens or the cover plate and defrosting of the light module or headlight without additional heating. The present invention now enables particularly efficient and simple defrosting of a projection lens of a projection module of a motor vehicle headlight, even if the light module has a semiconductor light source whose radiation has only a very low IR component.
[0020] According to a preferred embodiment of the invention, the conductor tracks of the heating element are routed outward on a contact side of the transparent carrier film. This allows the heating element to be connected quickly and securely to the switching element or the electrical power source in a particularly simple manner. Contact surfaces can be formed at the conductor track ends on the contact side, further simplifying contacting.
[0021] According to another advantageous development of the invention, it is proposed that an electrical circuit board be attached to the transparent film on the contacting side, and that contact areas of the circuit board be in contact with the conductor tracks of the heating element. The circuit board can be flexible or rigid. The conductor track ends on the contacting side of the carrier film are thus in electrical contact with contact areas of the circuit board. The electrical contact can be realized, for example, via conductor tracks formed on the circuit board in a conventional manner.
[0022] The circuit board can be attached to the transparent carrier film on the contacting side in any manner, in particular by gluing, lamination, welding, in particular laser welding, etc. Electrical contacting of the conductor tracks of the heating element and conductor tracks of the circuit board can also be carried out in any manner, e.g. by soldering, in particular ultrasonic soldering, welding, gluing, etc.
[0023] The contact areas can, for example, have contact pads applied to the circuit board, which further simplify contacting. The contact pads can be bonded to the circuit board using self-adhesive contact pads, e.g., made of copper, and contacted with the ends of the conductor tracks on the carrier film. The contact pads can be bonded around the circuit board so that the flanged contact pads are bonded to the top and bottom of the circuit board. This allows the heating element to be contacted simultaneously from the top and bottom of the circuit board, enabling particularly reliable and secure contacting.
[0024] Furthermore, it is conceivable that contact surfaces could be applied directly to the carrier foil, for example, to simplify contacting. The contact surfaces could be bonded to the carrier foil using self-adhesive contact pads, e.g., made of copper, and contacted with the conductor tracks. The contact pads can be bonded around the carrier foil so that the flanged contact pads are bonded to the top and bottom of the carrier foil. This allows the heating element to be contacted simultaneously from the top and bottom of the carrier foil, enabling particularly reliable and secure contacting.
[0025] According to a further preferred embodiment of the invention, it is proposed that the heating element has a contacting element which is in contact with the conductor tracks of the heating element and via which the conductor tracks are connected to the switching element or the electrical energy source. The contacting element can be designed as a plug element. The plug element can be fastened on a contacting side of the transparent carrier film directly to the film or on a circuit board which is fastened on a contacting side to the transparent carrier film. The plug element can be designed as a plug or as a socket. It can mechanically engage with a corresponding plug element (socket or plug), whereby an electrical connection is automatically established between the plug elements. The plug element can be fastened directly to the carrier film or the circuit board.Alternatively, the plug element can also be attached indirectly to the carrier film or the circuit board via wires. In the latter case, the plug element is movable relative to the carrier film and / or the circuit board and can be positioned and aligned as desired for contacting the switching element or the electrical energy source. Alternatively, the contacting element can have contact surfaces that are in contact with the conductor tracks of the heating element. The contact surfaces are applied to a contact side of the transparent carrier film or to an electrical circuit board that is attached to a contact side of the carrier film. The contact surfaces can be glued to the carrier film, for example, using self-adhesive contact pads, e.g. made of copper, and contact can be made with the conductor track ends.The contact pads can be glued around the carrier foil so that the flanged contact pads are glued to the top and bottom of the carrier foil. This allows the heating element to be contacted simultaneously from the top and bottom of the carrier foil, enabling particularly reliable and secure contact.
[0026] The electrical contact between the contact surfaces and the switching element or the electrical energy source can be made using spring contact pins, for example. By applying force to the contact head of the pin, it is compressed to the installation dimension. Maintaining the electrical contact between the pin head and the contact surface is ensured by a spring built into the pin. The spring contact pins can be installed or inserted in a lens carrier, which positions and holds the projection lens in the light module, for example, in suitable grooves. A circumferential pin collar with a slightly larger diameter than the pin body can be provided as a stop for the end position. This stop ensures that there is counterhold when the pin is compressed and that the pin cannot escape backward.When mounting the projection lens with the heating element in the lens carrier of the projection module according to the invention, the heating element can be automatically contacted via the spring contact pins.
[0027] Finally, it is proposed that an opaque diaphragm element is arranged on an outer side of the projection lens, which conceals areas of the heating element outside the conductor tracks, in particular contact areas via which the conductor tracks are connected to the switching element or to the electrical energy source. From the outside, the diaphragm element has, for example, a reflective or dark appearance. The diaphragm element can be a separate element that is attached from the outside to the light exit surface of the projection lens, for example by means of gluing, welding, clamping, locking, clipping, etc. It would also be conceivable for the diaphragm element to be designed as an opaque layer that is applied from the outside to the light exit surface of the projection lens. It would also be conceivable for the separate diaphragm element to be incorporated into the projection lens itself. This can be done, for example, as part of a manufacturing process for the projection lens in several steps, as is the case, for example, withfrom DE 10 2010 033 902 A1. The content of this document is hereby incorporated in its entirety into the subject matter of the present application. In particular, in a first process step, a first part of the projection lens can be injection-molded. The aperture element is applied to the first part and, in at least one further process step, material for at least one further part of the projection lens is then over-molded. In addition to the aperture element, the heating element can also be incorporated into the projection lens or applied to the light entry surface of the lens. The decisive factor is that the aperture element is arranged outside the heating element in order to shield the covered part of the heating element from being viewed from the outside. Instead of being an opaque element, it would also be conceivable for the aperture element to be partially transparent, for example in the manner of a frosted glass pane or similar.
[0028] Further features and advantages of the present invention are explained in more detail below with reference to the figures. It should be noted that individual features of the exemplary embodiments shown in the figures may each be essential to the invention on their own, even if this is not expressly mentioned in the following description. Furthermore, any combination of features of the various exemplary embodiments may also be essential to the invention, even if this combination is not expressly mentioned in the following description. They show:
[0029] Figure 1 shows a light module of a motor vehicle headlight according to the invention;
[0030] Figure 2 shows a heating element for use in a light module of a motor vehicle headlight; Figure 3 shows the heating element from Figure 2 in a plan view, in a cross-section A-A and in a detailed view X;
[0031] Figure 4 shows a circuit board as part of a heating element;
[0032] Figure 5 shows a heating element from Figures 2 and 3 with a printed circuit board made of
[0033] Fig. 4 in a view from below;
[0034] Figure 6 shows the heating element with the circuit board attached to it from Fig. 5 in a view from above;
[0035] Figure 7 shows the heating element with the circuit board from Figure 5 attached thereto, applied to an inner surface of a projection lens of a light module of a motor vehicle headlight in a sectional view;
[0036] Figure 8 shows the heating element with circuit board applied to a projection lens in an internal view;
[0037] Figure 9 shows a heating element for use in a light module of a motor vehicle headlight;
[0038] Figure 10 shows the heating element from Fig. 9 in a section with contact surfaces for electrical contacting of conductor tracks of the heating element;
[0039] Figure 11 shows a heating element for use in a light module of a motor vehicle headlight with a plug element in a contacting area;
[0040] Figure 12 shows the heating element from Fig. 11 in a section with a plug element for electrically contacting conductor tracks of the heating element;
[0041] Figure 13 shows a heating element from Figure 9 with a circuit board attached to it; Figure 14 shows a section of the heating element from Figure 13;
[0042] Figure 15 shows the heating element from Fig. 13 with the plug element attached to the circuit board;
[0043] Figure 16 shows a heating element in a plan view, in a cross-section AA and in a detailed view X;
[0044] Figure 17 shows the heating element from Figure 16 with a circuit board with a plug element attached to it in a contacting area;
[0045] Figure 18 shows the heating element from Figure 16 with a plug element attached directly to a carrier foil in a contacting area;
[0046] Figure 19 shows a projection lens of a projection module of a motor vehicle headlight with a heating element integrated into the lens in a horizontal section;
[0047] Figure 20 shows the projection lens from Fig. 19 in a vertical section;
[0048] Figure 21 shows an injection mold for producing a projection lens according to Fig. 19 in a first process step;
[0049] Figure 22 shows an injection mold for producing a projection lens according to Fig. 19 in a subsequent process step;
[0050] Figure 23 shows a finished projection lens in a transparent view from the outside;
[0051] Figure 24 shows a finished projection lens in an external view with a diaphragm element applied to the outer surface; Figure 25 shows another example of a heating element for use in a light module of a motor vehicle headlight;
[0052] Figure 26 shows a section of the heating element from Fig. 25 with contact area in a view from above;
[0053] Figure 27 shows the section from Fig. 26 in a perspective view obliquely from above;
[0054] Figure 28 shows the section from Fig. 26 in a perspective view obliquely from below;
[0055] Figure 29 shows a comparison of the contact areas of the heating elements from Figures 11 and 12 and Figures 25 to 28;
[0056] Figure 30 shows an example of a spring contact pin in unloaded length for contacting the contact area of the heating element from Figures 25 to 28;
[0057] Figure 31 shows the spring contact pin from Fig. 30 in compressed length;
[0058] Figure 32 shows an example of contacting the heating element from Figs. 25 to
[0059] 28 with two spring contact pins and a plug element;
[0060] Figure 33 shows a lens carrier with integrated spring contact pins and plug element according to Fig. 32 in an external view;
[0061] Figure 34 shows the lens carrier from Fig. 33 in a section in a view from the inside;
[0062] Figure 35 shows the lens carrier from Figure 33 in an external view with the projection lens to be inserted; Figure 36 shows the lens carrier from Figure 33 in a section in an internal view with the projection lens to be inserted;
[0063] Figure 37 shows the lens carrier from Fig. 33 in a section in a view from the inside with the projection lens inserted; and
[0064] Figure 38 shows the lens carrier from Fig. 37 in cross section with the projection lens inserted.
[0065] An example of a projection module according to the invention for a headlight of a motor vehicle is shown in Fig. 1 and is designated in its entirety by the reference numeral 2. The projection module 2 comprises a light source for emitting light, which is arranged inside the projection module 2 in Fig. 1 and is therefore not visible. The light source preferably comprises at least one semiconductor light source, for example an LED or a laser diode, particularly preferably a semiconductor light source array. Furthermore, the projection optics 2 comprise primary optics for bundling, shaping and / or redirecting the light emitted by the light source. The primary optics are also not visible in Fig. 1. They can comprise one or more reflectors or lenses.However, it can also comprise one or more auxiliary optics which focus the light emitted by the light source by means of refraction at the light entry and / or exit surface of the auxiliary optics and / or by means of total internal reflection at interfaces of the auxiliary optics. In addition, the projection module 2 comprises a secondary optics 4 in the form of a projection lens which images an intermediate image of an intermediate image plane, which is arranged in the beam path between the primary optics and the secondary optics 4, in a light exit direction 6 of the projection module 2 in a foreground in front of the motor vehicle as the resulting light distribution of the projection module 2. The projection lens is preferably designed as a cylindrical lens, wherein a light exit surface of the lens 4 has a greater curvature around a cylinder axis 60 and a lesser curvature around an axis running transversely to the cylinder axis 60.When the projection module 2 is installed in the motor vehicle in an operational state, the cylinder axis 60 runs in a substantially vertical direction. The projection module 2 is preferably arranged in a headlight housing which has a light passage opening in the light exit direction 6, through which the light passing through the projection lens 4 is projected onto the roadway in front of the motor vehicle. The headlight housing preferably does not have a transparent cover plate which closes the light passage opening. Rather, the projection lens 4 forms the outward closure of the headlight in the light exit direction 6. The projection lens 4 has a heating element for heating the projection lens 4. The design of the heating element for use in the projection module 2 according to the invention and the manufacture of the projection lens 4 with such a heating element are explained in more detail below.
[0066] In order to propose a simple and cost-effective, yet efficient way of defrosting the projection lens 4 of a projection module 2 of a motor vehicle headlight, particularly when the headlight does not have a cover plate for closing the light passage opening, it is proposed that the heating element 8 have a transparent carrier film 10 made of an electrically insulating material and conductor tracks 12 applied thereto or embedded therein, which are connected to an electrical energy source 16 via a switching element 14. The energy source 16 can be, for example, a vehicle battery of the motor vehicle. A current flow through the conductor tracks 12 can be enabled or interrupted via the switching element 14. The switching element 14 can be controlled manually, for example by the driver of the motor vehicle, or automatically, for example depending on the outside temperature or a temperature of the light module 2 or the projection lens 4.
[0067] The heating element 8 is applied to at least a partial area of a light entry and / or light exit surface of the projection lens 4 of the projection module 2 or at least incorporated into a portion of the projection lens 4 itself. When the current flow through the conductor tracks 12 is switched on, the heating element 8 heats the projection lens 4 and ensures efficient defrosting. In headlights and light modules 2 of headlights without a cover plate, there is a risk that the projection lens 4 may be at least partially covered by snowfall and ice formation in winter weather, thereby completely or partially blocking the light, or that the illumination of the roadway may no longer be complete or may even fail completely.Some headlights are equipped with washer systems that spray antifreeze onto the cover or lens 4 of a light module 2, thus completely or partially preventing them from becoming clogged with snow and / or ice. However, the use of washer systems is complex and expensive, and their efficiency is not always guaranteed, especially at very low outside temperatures.
[0068] To ensure that the light projected onto the road surface of a headlight without a cover lens is largely unaffected even in winter weather, the exposed projection lens 4 must be kept free of snow and ice. One way to achieve this is to heat the lens 4 and maintain it at a sufficiently high temperature so that ice and snow melt and / or cannot settle.
[0069] In light modules 2 with semiconductor light sources that emit light with a low IR component, the temperatures at the outer lenses 4 in the case of a headlight without a cover plate are usually not high enough to prevent ice and snow from accumulating on the lens 4. However, with targeted means arranged directly on or in the projection lens 4, it is possible to increase the temperature at the lenses 4 sufficiently to prevent snow and ice from accumulating. By heating the lens 4, it is ensured that no or only a small amount of precipitation such as snow and ice accumulates on the outer surface of the lens, preventing too little light from being projected onto the roadway.
[0070] Essentially, a heatable projection lens 4 can be obtained by inserting a carrier film 10 with an integrated or applied heating wire 12 into an injection mold and overmolding it with transparent material (e.g. plastic, in particular PC), from which the lens 4 is made. Fig. 3 shows a heating element 8 in which the heating wire 12 is applied to the carrier film 10. However, since the carrier film 10 is thicker than the diameter of the heating wire 12, the heating wire 12 can also be easily integrated into the film 10. In particular, the heating wire 12 can be welded into the carrier film 10 by means of ultrasonic welding. By applying a voltage to the exposed ends 18 of the heating wire 12, the latter heats up. The resulting heat 20 radiates in all directions and will also heat the surrounding material of the lens 4, ultimately leading to heating of the outer surface of the lens.If the temperature is sufficient, ice and snow are prevented from sticking to the heated surface.
[0071] The carrier film 10 is preferably made of transparent plastic, e.g., PC, into which a thin heating wire 12 of the order of 50 μm is inserted. This wire 12 has a plastic sheath or another type of electrical insulation. The individual tracks or loops of the welded-in wire 12 should, if possible, cover a sufficiently large area on the film 10 to heat the optically effective surface of the lens 4 as evenly as possible and over the largest possible area. With a uniform distribution of the tracks or loops of the wire 12 on or in the projection lens 4 and the small diameter of the wire 12, very little light loss occurs, <1%, which is negligible from a lighting technology perspective.
[0072] Various options are conceivable for contacting the heating element 8 with the switching element 14 and / or the energy source 16. In the example in Fig. 5, the film 10 is attached, e.g., glued, to a circuit board 22. The adhesive connection is designated by reference numeral 26 in Fig. 5. The circuit board 22 can be flexible or rigid. The circuit board 22 can be provided with a plug element 24, which facilitates contacting with the switching element 14 and / or the energy source 16. The insulation-free wire ends 18 are bonded / soldered to the circuit board 22. Conductor tracks 28 are applied to the circuit board 22 and form an electrical connection from the wire ends 18 to contacts 30 of the plug element 24. This structure consisting of the carrier foil 10, the heating wire 12, the attached circuit board 22 with the plug element 24 forms the heating element 8 (see Fig. 6).
[0073] This heating element 8 can be inserted into a plastic injection molding tool and overmolded or encapsulated with the material for manufacturing the projection lens 4. The finished lens 4 with the heating element 8 attached is shown in Figs. 7 and 8. The projection lens 4 and the carrier film 10 are preferably made of the same material, e.g., PC. The overmolded or encapsulated injection molding creates a permanent, material-locking connection between the heating element 8 and the lens 4 after curing. This results in an optical lens 4 with an integrated heating element 8 that can be attached to a light module 2. This allows for particularly quick and easy production of the heatable projection lens 4, as well as assembly and electrical contacting of the lens 4 or the heating element 8 in the light module 2.With active heating, the lens surface oriented in the direction of travel can be warmed up and ice and snow are prevented from clogging this light-emitting surface.
[0074] The material of the heating wire 12, the geometric dimensions of the wire 12 such as diameter and length, the specific electrical resistance of the wire 12 as well as the applied voltage and the current flowing through it influence the achievable heating power of the heating element 8. These parameters of the heating wire 12 can be selected individually from case to case.
[0075] Heating element 8 can be heated by voltage or current control or regulation to avoid overheating, which could impair the optical properties of lens 4 or damage the lens material. Electrical and / or electronic components required for control and / or regulation can be provided on circuit board 22. These components include, for example, a temperature sensor and / or a microprocessor.
[0076] Alternatively, a plug-in element 24 can also be attached directly to the carrier film 10 (see Figs. 11 and 12). In this case, the heating wires 12 can be provided with copper pads 32 at their ends 18. The copper pads 32 can, for example, be self-adhesively adhered to the film 10 and connected to the insulation-free wire ends 18, for example by means of a low-temperature soldering process. The contacts 30 of the plug-in element 24 are connected to the copper pads 32, for example by soldering (see Fig. 12). The heating element 8 is then overmolded or encapsulated during the production of the projection lens 4 in an injection molding process (molding or co-molding) as described above. The advantage of this design is that, by omitting a separate circuit board 22, a smaller installation space is required.
[0077] Another alternative for applying an electrical voltage to the wires 12 of the heating element 8 can be achieved by means of a flexible circuit board 22 (see Figs. 13 to 15). For this purpose, a flexible circuit board 22 is attached to a contact side of the transparent film 10 with the integrated heating wires 12, for example by lamination or adhesive bonding 26. The insulation-free wire ends 18 are then soldered onto the circuit board 22 onto contact surfaces 32 provided for this purpose. The circuit board 22 has conductor tracks 28 which connect the contact surfaces 32 to the contacts 30 of the plug element 24. Instead of the single plug element 24 shown in Fig. 15, several plug elements can also be attached to the circuit board 22 and contacted with the wire ends 18. The advantage of this design is that the flexible circuit board 22 can be folded, thus reducing the length of the heating element 8.This enables a compact design of the overmolded or molded lens 4 with the integrated heating element 8.
[0078] In the previous embodiments, the current-carrying conductor tracks 12 of the heating element 8 are designed as heating wires that are applied to the carrier film 10 or incorporated therein. Instead of these heating wires 12, however, printed strands 12a can alternatively serve as current-carrying tracks (cf. Figs. 16 to 18). These can be printed onto the transparent film 10, for example, using a screen printing process or by means of pad printing or inkjet printing. When using an electrically conductive printing ink or paste, the printed strands 12a can be used as current-carrying tracks and, similar to the heating wires 12, can be used to heat the projection lens 4 when voltage is applied.
[0079] In this design, the dimensions of the printed conductor strands 12a are particularly important. These must be capable of offering a correspondingly low resistance (depending on the material used and the cross-sectional area of the strands 12a) in order to be applied to the film 10 easily and cost-effectively, while also being able to provide the desired thermal output. To keep light losses as low as possible, the conductor strands 12a should be as narrow as possible. A width of the strands 12a in the order of approximately 0.5 mm would still be acceptable. The light losses would then be in the range of approximately 5%. This light loss can be compensated for by increasing the current supplied to the light source of the light module 2.In order to apply a thickness (or height) of ink / paste that results in a cross-sectional area sufficient for the calculated resistance, the thickness should be greater than that of conventional screen printing, i.e. a thickness of >50 pm should be achieved.
[0080] The electrical contacting possibilities of the carrier foil 10 with printed strands 12a as conductor tracks essentially correspond to those of the designs described above with carrier foil 10 and heating wires 12 (cf. Figs. 17 and 18).
[0081] The flat heating elements 8 described above were applied to one side (inside or outside) of a projection lens 4 using an injection molding process (see Fig. 7). Another possible embodiment would be to incorporate the heating element 8 into the projection lens 4 itself by overmolding it on the inside and outside with the material of the lens 4 (see Figs. 19 to 22).
[0082] This can be achieved in a multi-stage injection molding process. In a simple case, the process is designed in two stages. In a first stage, as described above, the carrier film 10 with integrated conductor tracks 12 is overmolded with a layer of the material 4.1, for example plastic, in particular PC, from which the projection lens 4 is made (cf. Fig. 21). Subsequently, in a second stage, lens material 4.2 is injection-molded onto the still free side of the carrier film 10 (cf. Fig. 22). The heating element 8 is encapsulated with the lens material in an injection mold, as shown in Figs. 21 and 22. A first tool side is designated W1, a second tool side W2.
[0083] For the production of the projection lens 4 which can be heated by means of the heating element 8, it is particularly preferably proposed that the heating element 8 in the form of the transparent film 10 made of an electrically insulating material and conductor tracks 12, 12a applied thereto or embedded therein is applied at least to a partial area of a light entry and / or light exit surface of the projection lens 4 of the projection module 2 or at least introduced into a part of the projection lens 4 itself. For the introduction of the heating element 8 into the lens 4, it is proposed that firstly a first part 4.1 of the projection lens 4 is manufactured by means of an injection molding tool W, the heating element 8 is placed in the injection molding tool W, if present on the first part 4.1 of the projection lens 4, and a further part 4.2 of the projection lens 4 is manufactured on the heating element 8 by means of the injection molding tool W.
[0084] Between the first stage (Fig. 21) and the second stage (Fig. 22), a first tool insert WE1 is preferably exchanged for a second tool insert WE2. The second tool insert WE2 provides a recess 34 for molding the second part 4.2 of the lens 4. The finished projection lens 4 encloses the heating element 8 and leaves only the plug element 24 free to supply voltage to the heating element 8 or the conductor tracks 12, 12a.
[0085] Fig. 23 shows a view of the finished projection lens 4 provided with the integrated heating element 8, opposite the light exit direction 6, i.e. from the outside. The outer transparent first part 4.1 of the lens 4 and behind it the heating element 8 with all its components 10, 12, 18, 22 can be clearly seen. The contact area of the heating element 8 (with the circuit board 22, the conductor tracks 28, the contact surfaces 32 and the plug element 24) as well as a manufacturing-related edge of the projection lens 4 can be covered by means of a cover element 36 (a cover, a frame or design part) (cf. Fig. 24). The cover element 36 can be opaque or partially transparent. An opaque cover element 36 has, for example, a silver or black color. The aperture element 36 may be a separate element that is attached to the outer surface of the lens 4, for example by gluing or welding.It would also be conceivable for the aperture element 36 to be applied as a colored layer to the outer surface of the lens 4, for example, by spraying or dipping. Finally, it would also be conceivable for the aperture element 36 to be applied as one of several components of the lens 4 as part of the multi-stage manufacturing process using the injection molding method. To this end, the aperture element 36 can first be inserted into the injection molding tool and overmolded with a first layer 4.1 of the material of the lens 4. Subsequently, the heating element 8 is placed on the first layer 4.1 and overmolded with a second layer 4.2.
[0086] A further possibility for contacting the heating element 8 is described below with reference to Figs. 25 to 29. In this embodiment, a plug element 24 directly on the carrier film 10 is omitted. While in the previously described embodiments, a plug connection was made using a plug element 24 (socket housing and pin housing) directly on the film 10, in this embodiment, the electrical contact to the switching element 14 and / or the energy source 16 is established by placing contact pins (cf. Figs. 30 to 32) on contact pads (cf. Figs. 26 to 28) that are applied directly to the film 10. The advantages lie in the simple and cost-effective production of the heating element 8 and in the simple but reliable integration (mechanical fastening and electrical contact) of the projection lens 4 into the projection module 2. In addition, this embodiment requires particularly few parts and less space in the light module 2.This enables a weight reduction and opens up new styling possibilities for the light module 2. Fig. 25 shows the plastic carrier film 10 described above with the applied or integrated conductor tracks 12 (e.g., heating wires or printed strands). The ends 18 of the conductor tracks 12 are guided to the lateral edge on a contacting side of the film 10. Fig. 26 shows contact pads 38, which can consist of a copper foil, for example. The contact pads 38 can be self-adhesive, so that simple attachment to the carrier film 10 and contacting with the conductor tracks 12 or their ends 18 in the contacting area of the film 10 is possible. The wire ends 18 can be soldered to the contact pads 38. Laterally projecting sections 38a of the contact pads 38 can be folded backwards and attached to the back of the carrier film 10 (see Figs. 26 to 28).The folded contact pads 38, with their contact surfaces on the front and back of the film 10, provide a suitable surface for an electrical contact connection. Compared to the previously described embodiments, this results in a significantly narrower contact area 40, since in the previous embodiments the plug element 24 takes up a relatively large amount of space (see Fig. 29). In particular, the contact area 40 is reduced to approximately 35% of the previous value (e.g., only 7 mm instead of the previous 20 mm).
[0087] The electrical contacting of the contact pads 38 can be achieved by means of spring contact pins 42. By applying a force F (compressive force) to a contact head 44 of the pin 42, the contact head is compressed by (length 11 - length 12) to an installation dimension. Fig. 30 shows the unloaded (original) length of the pin 42 and Fig. 31 shows the compressed length (final length when assembled). The establishment and maintenance of contact between the pin head 44 and the contact pad 38 is ensured by a spring element installed inside the pin 42. The diameter of the contact surface on the pin head 44 or of the entire pin 42 as well as the pin lengths can be designed as desired or selected from existing standard dimensions from suitable suppliers. The contact forces or the spring forces F can also be designed for a specific application or selected from standard designs. Here, for example,a diameter D of the pin 42 of 1.5 mm and a contact area of 1.767 mm. 2 (U ■ (d / 2) 2) is proposed. For the present application, contact pins 42 with attached cables 46 could be used, which are already brought together in a connector housing 24a (see Fig. 32). During further assembly, the pins 42 are inserted into suitable grooves 48 in a lens carrier 50 and fastened therein (see Fig. 33). The lens carrier 50 serves to fasten the projection lens 4 in the projection module 2. A pin collar 52 with a slightly larger diameter than the pin body serves as a stop for the end position. This stop 52 ensures that when the pin 42 is pressed together, a counter-hold is provided and the pin 42 cannot escape backwards. By connecting it with cables 46, the connector 24a can be fastened to the lens carrier 50 at any desired distance from the lens 4, e.g. by means of a clip connection (see Fig. 34).To secure the lateral position of the contact pins 42 in the grooves 48, a cover 54 could be clipped on (see Figs. 34 and 36). Other fastening options, with or without additional fastening or securing parts, are also conceivable.
[0088] In a subsequent step, the projection lens 4 with the integrated heating element 8 can be applied to the lens carrier 50 (cf. Fig. 35). The projection lens can have a sealing base 56 which, when placed on the lens carrier 50, enters a sealing channel 58 formed on the lens carrier 50. The sealing channel 58 can be filled in advance with an adhesive or a sealing compound (e.g., butyl). The sealing base 56 can run over the entire circumference of the lens 4. At least in this case, the sealing channel 58 would then also run over the entire circumference of the lens 4. By pressing the sealing base 56 into the sealing channel 58 and after the adhesive or sealing compound has hardened, the projection lens 4 is almost permanently attached to the lens carrier 50. Alternatively, the lens 4 can also be attached to the lens carrier 50 in another way, e.g., by means of a retaining spring, laser welding, or the like.
[0089] In this installed position, the lens 4 compresses the spring contact pins 42 to a predetermined final dimension. This creates a permanent spring-loaded contact between the contact pads 38 located on the inside of the lens 4 and the contact surfaces 44 of the pin heads, enabling electrical contact with the heating element 8 integrated into the lens 4. Contacting occurs automatically when the lens 4 is mounted on the lens carrier 50. This allows the contacts 38 to be placed even in difficult or inaccessible areas.
Claims
27 Claims 1. Projection module (2) of a headlight of a motor vehicle, comprising a light source for emitting light, a primary optic for focusing, shaping and / or deflecting the light emitted by the light source, and a secondary optic in the form of a projection lens, which projects an intermediate image of an intermediate image plane, which is arranged in the beam path between the primary optic and the secondary optic (4), in a light emission direction (6) of the projection module (2) in a foreground in front of the motor vehicle as the resulting light distribution of the projection module (2), wherein the projection module (2) has a heating element (8) for heating the projection lens (4), characterized in that the heating element (8) has a transparent film (10) made of an electrically insulating material and conductive traces (12) applied to or embedded therein, which are connected to an electrical energy source (16) via a switching element (14),wherein the heating element (8) is applied to at least a partial area of a light entry and / or light exit surface of the projection lens (4) of the projection module (2) or is at least incorporated into a part of the projection lens (4) itself, such that the heating element (8) heats the projection lens (4) when current is switched on through the conductor tracks (12).
2. Projection module (2) according to claim 1 , characterized in that the projection lens (4) in the light emission direction (6) forms the outer termination of the projection module (2).
3. Projection module (2) according to claim 1 or 2, characterized in that the heating element (8) is applied to the light entry and / or light exit surface of the projection lens (4) or is incorporated into the projection lens (4) itself as part of an injection molding process or a co-molding process during the manufacture of the projection lens (4).
4. Projection module (2) according to one of the preceding claims, characterized in that the light source comprises at least one semiconductor light source, in particular at least one LED, preferably a multi-chip LED.
5. Projection module (2) according to one of the preceding claims, characterized in that the projection lens (4) is made of a plastic, in particular of polycarbonate.
6. Projection module (2) according to one of the preceding claims, characterized in that the transparent film (10) is made of a plastic, in particular of polycarbonate.
7. Projection module (2) according to one of the preceding claims, characterized in that the projection lens (4) has the shape of a cylindrical lens, with a greater curvature of a light-exiting surface of the lens (4) about a cylinder axis (60) and a lesser curvature of the light-exiting surface about an axis extending transversely to the cylinder axis (60).
8. Projection module (2) according to claim 7, characterized in that, when the projection module (2) is installed in the motor vehicle in an operational state, the cylinder axis (60) runs in a substantially vertical direction.
9. Projection module (2) according to one of the preceding claims, characterized in that the conductor tracks (12) of the heating element (8) are led outwards on a contacting side of the transparent film (10).
10. Projection module (2) according to claim 9, characterized in that an electrical circuit board (22) is attached to the transparent film (10) on the contacting side and contacting areas (28; 40) of the circuit board (22) are contacted with the conductor tracks (12) of the heating element (8).
11. Projection module (2) according to one of the preceding claims, characterized in that the heating element (8) has a contacting element which is in contact with the conductor tracks (12) of the heating element (8) and via which the conductor tracks (12) are connected to the switching element (14) or to the electrical energy source (16).
12. Projection module (2) according to claims 10 and 11, characterized in that the contacting element is designed as a plug element (24) which is attached to the circuit board (22).
13. Projection module (2) according to claim 11, characterized in that the contacting element has contacting surfaces (38; 32) which are contacted with the conductor tracks (12) of the heating element (8), wherein the contacting surfaces (38) are applied to the transparent film (10) on a contacting side of the transparent film (10) or the contacting surfaces (32) are applied to an electrical circuit board (22) which is attached to the transparent film (10) on a contacting side of the transparent film (10).
14. Projection module (2) according to one of the preceding claims, characterized in that an aperture element (36) is arranged on an outer side of the projection lens (4), which covers areas of the heating element (8) outside the conductor tracks (12), in particular a contact area (40) via which the conductor tracks (12) are connected to the switching element (14) or to the electrical energy source (16).
15. Method for manufacturing a projection lens (4) of a projection module (2) of a headlight of a motor vehicle which can be heated by means of a heating element (8), characterized in that the heating element (8) in the form of a transparent film (10) made of an electrically insulating material and conductor tracks (12) applied to or embedded therein is applied at least to a partial area of a light entry and / or light exit surface of the projection lens (4) of the projection module (2) or is at least incorporated into a part of the projection lens (4) itself.
16. Method according to claim 15, characterized in that optionally a first part (4.1 ) of the projection lens (4) is first manufactured by means of an injection molding tool (W), the heating element (8) is placed in the injection molding tool (W), if present, on the first part (4.1 ) of the projection lens (4), and on the heating element (8) either a further part (4.2) of the projection lens (4) or the entire projection lens (4) is manufactured by means of the injection molding tool (4).
17. Method according to claim 15 or 16, characterized in that the projection lens (4) is made of a material which, during the manufacture of the projection lens (4), can form a fusion bond with the material of the transparent film (10) of the heating element (8), in particular made of the same material as the transparent film (10) of the heating element (8).
18. Headlight of a motor vehicle, comprising a housing with a light transmission opening arranged in a light emission direction (6) of the headlight, characterized in that the headlight has a projection module (2) in the housing according to one of claims 1 to 14.
19. Headlight according to claim 18, characterized in that the light transmission opening of the housing is not closed by a cover plate and that the projection module (2), in particular the projection lens (4), is sealed around the light emission direction (6) of the headlight against the housing.