CAR HEADLIGHTS

Description

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

[0002] A projection module and a motor vehicle headlight of the type mentioned are known, for example, from JP 2007-242 291 A. There, it is proposed to arrange a flat heating element for heating a cover lens of the headlight, which closes a light-transmitting opening of the headlight housing, at any point in the headlight except on the cover lens itself. In the exemplary embodiment of the Fig. 4The heating element is positioned on the outer surface of a projection lens, so that the heat generated by the heating element radiates towards the cover plate and heats it. The flat heating element is applied to the outer surface of the projection lens using a coating process, such as vacuum deposition or sputter deposition using ITO (indium tin oxide). The flat heating element therefore has no discrete conductive traces, but rather emits heat across its entire surface when current is applied. Contact points of the flat heating element are created, for example, using a conductive paint.

[0003] The described projection module has the disadvantage that applying and contacting the heating element is very complex and expensive. Therefore, the described method has not, and will not, become established in mass production in the future. Although the cited state of the art is almost 15 years old, conventional heating of the inside of a vehicle headlight lens using a heated airflow is still used in practice. This airflow is heated either by waste heat from electrical or electronic components or by heat generated by separate heating elements inside the headlight housing.

[0004] These common methods for defrosting headlights, which are used in practice, reach their limits with headlights that lack a cover lens. In these newer headlight designs, the projection module is located in the light-transmitting opening of the headlight housing, and the projection lens forms the outer edge of the headlight in the direction of light emission. Since the cover lens is missing, moisture (e.g., raindrops, fog, condensation, etc.) and ice (e.g., snow, icing, hail, frost, etc.) accumulate on the outer surface of the projection lens in such headlights. This effect is further intensified by the fact that the outer surface of the projection lens in such headlights is often located in a recess where moisture and ice can accumulate particularly easily. Further headlights for motor vehicles known from the prior art are disclosed in EP 2 315 494 A1 and US 2020 / 032974 A1.

[0005] Based on the described prior art, the present invention aims to propose a simple and cost-effective, yet efficient way to defrost projection lenses of light modules of motor vehicle headlights, especially when the headlights do not have a cover plate to close the light transmission opening of a headlight housing.

[0006] To solve this problem, a headlight with the features of claim 1 is proposed. In particular, starting from the headlight of the type mentioned above, it is proposed that the heating element comprises a transparent film made of an electrically insulating material and conductive traces applied to or embedded therein, and that the light-transmitting opening of the housing is not closed by a cover plate, and that the projection module, in particular the projection lens, is sealed around the light-emitting direction of the headlight against the housing. The present invention can be implemented particularly easily and cost-effectively. Prefabrication and the stockpiling of a large number of heating elements are readily possible.The finished heating element then only needs to be applied to an outer surface of the projection lens or projection module during its manufacture, or inserted into the lens and electrically connected. The transparent film is preferably flexible enough to conform to any 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 lens has a light-emitting surface with a greater curvature around a cylinder axis and a significantly smaller curvature around an axis perpendicular to the cylinder axis. The curvature around the axis 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 vehicle in a ready-to-use state, the cylinder axis runs in a substantially vertical direction, i.e., approximately perpendicular to the road surface on which the vehicle is stationary or driving. Generally, lenses with two cylindrical surfaces are referred to as cylindrical lenses. However, for the purposes of the present invention, lenses with toric surfaces (i.e., lenses whose surface is formed by a torus) are also referred to as cylindrical lenses.

[0007] Another 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.

[0008] 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 mounted on an outer surface of the projection lens—weather and / or acid resistant. The plastic's resistance ensures that it does not become brittle or hard, develop cracks, or discolor over its service life due to UV radiation and weathering. For example, Makrofol® UV 244 from Covestro AG, Leverkusen, Germany, could be used as the carrier film material. 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.

[0009] The conductive traces can be printed onto the transparent carrier film, for example, made of copper. Preferably, however, the conductive traces are formed by heating wires, which heat up when current flows and transfer heat to the projection lens, thus defrosting it. The heating wires are preferably made of a metal, for example, 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 µm, preferably in the range of 30–70 µm, and most preferably in the range of 40–55 µm. Insulation can be applied to the wires, at least partially, for example, in the form of an insulating varnish or plastic insulation. With the insulation, the diameter of the heating wires increases by about 20–30% or by about 10–20 µm.A heating wire with a diameter of 44 µm without insulation and 56 µm 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 loss. In particular, the light loss is less than 1%. Furthermore, uncontrolled scattering, refraction, or diffraction of the light passing through the lens is not a concern with these heating wires.

[0010] It is conceivable to apply or integrate several separate conductor tracks onto the carrier film. The conductor tracks can, for example, run parallel to each other or concentrically. The ends of the individual conductor tracks can be connected to a switching element or an electrical power source. Preferably, however, a single conductor track is applied to or integrated into the carrier film in several meandering loops. The loops of the conductor track can, for example, run parallel to each other or concentrically. The ends of the conductor track can be connected to a contact element, which can be part of the heating element. The contact element can be connected to a switching element or an electrical power source.

[0011] The heating element can be applied and attached to an outer surface of the projection lens, for example, by adhesion or by means of an adhesive. The adhesive is preferably transparent and heat-resistant in its cured state. UV, weather, and acid resistance of the adhesive would also be advantageous. Preferably, the carrier film of the heating element has an adhesive layer on one side, which allows the heating element to be attached to the outer surface of the projection lens.

[0012] It is particularly preferred, however, if the heating element is placed in an injection mold during the manufacture of the projection lens using an injection molding process (so-called molding), and then the lens material (e.g., glass or transparent plastic, such as 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, creates a permanent bond between the heating element and the projection lens. Preferably, a metallurgical bond, in particular a fusion bond, is formed between the transparent film and the projection lens.

[0013] Alternatively, the heating element can also be integrated between two parts of the projection lens during its manufacture using a so-called co-molding process. The integration of the heating element into the projection lens can, for example, be carried out in several steps during the lens manufacturing process, as is known, for instance, from DE 10 2010 033 902 A1. The entire contents of this document are hereby incorporated into the present application. In particular, in a first process step, a first part of the projection lens can be manufactured using an injection mold. The heating element is then placed in the injection mold onto the first part and, in a further process step, overmolded with the lens material to manufacture another part of the projection lens. The two parts of the lens and the transparent film also bond together and, after curing, form an inseparable connection.The various parts or the transparent film of the integrated heating element are no longer visible to the naked eye on the finished projection lens.

[0014] According to the invention, the light-transmitting opening of the headlight housing is not closed by a cover plate, and the projection module, in particular the projection lens, is sealed all around the light-emitting direction of the headlight against the housing. The advantages of the heated projection lens of the headlight according to the invention become apparent in headlights without a cover plate, where the outer surface of the projection lens in the light-emitting direction of the headlight forms the outer boundary of the projection module or headlight. Direct and immediate heating of the projection lens ensures particularly efficient defrosting of the projection lens and a particularly rapid response time.

[0015] A waterproof, elastic material, such as plastic or rubber, is preferably used to seal the projection module or lens against the headlight housing. Sufficient flexibility of the sealing material allows movement of the projection module or lens relative to the headlight housing, for example, to implement a vertical basic setting, 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 for the light module and selectively controlling the semiconductor light sources to switch them on, off, or dim them.

[0016] According to an advantageous embodiment 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 side by side and one above the other in a matrix-like configuration, thus forming an LED array. The light emitted by semiconductor light sources often does not contain enough thermal energy (IR radiation components) to warm the projection lens or cover plate and defrost the light module or headlight without additional heating. With the present invention, a particularly efficient and simple defrosting of a projection lens of a projection module of a motor vehicle headlight is now possible, even if the light module has a semiconductor light source whose radiation has only a very low IR component.

[0017] According to a preferred embodiment of the invention, it is proposed that the conductive traces of the heating element are led outwards on a contact side of the transparent carrier film. This allows the heating element to be connected to the switching element or the electrical power source in a particularly simple, quick, and secure manner. Contact surfaces can be formed at the ends of the conductive traces on the contact side, which further simplifies the connection.

[0018] According to another advantageous embodiment of the invention, it is proposed that an electrical circuit board is attached to the transparent film on the contact side, and that contact areas of the circuit board are contacted with the conductor tracks of the heating element. The circuit board can be flexible or rigid. The conductor track ends on the contact side of the carrier film are thus in electrical contact with contact areas of the circuit board. The electrical contact can, for example, be realized via conductor tracks that are formed on the circuit board in a manner known per se.

[0019] The printed circuit board can be attached to the transparent carrier film on the contact side in any way, in particular by gluing, laminating, welding, especially laser welding, etc. Electrical contacting of the conductor tracks of the heating element and of conductor tracks of the printed circuit board can also be carried out in any way, e.g. by soldering, in particular ultrasonic soldering, welding, gluing, etc.

[0020] The contact areas can, for example, have contact pads applied to the circuit board, which further simplifies the contacting process. These contact pads can be attached to the circuit board using self-adhesive pads, such as those made of copper, and connected to the conductor ends of the carrier film. The contact pads can be glued around the circuit board so that the crimped contact pads are adhered to both the top and bottom surfaces. This allows the heating element to be contacted simultaneously from both sides of the circuit board, resulting in a particularly reliable and secure connection.

[0021] Furthermore, it is conceivable that contact surfaces could be applied directly to the carrier film, simplifying the contacting process. These contact surfaces could be attached to the carrier film using self-adhesive contact pads, for example, made of copper, and then connected to the conductive traces. The contact pads could be wrapped around the carrier film so that the crimped contact pads are adhered to both the top and bottom surfaces. This allows the heating element to be contacted simultaneously from both sides of the carrier film, resulting in a particularly reliable and secure connection.

[0022] According to a further preferred embodiment of the invention, it is proposed that the heating element has a contacting element that is in contact with the conductive traces of the heating element and through which the conductive traces are connected to the switching element or the electrical power source. The contacting element can be designed as a connector element. The connector element can be attached directly to the transparent carrier film on one contacting side or to a printed circuit board that is attached to the transparent carrier film on one contacting side. The connector element can be designed as a plug or a socket. It can engage mechanically with a corresponding connector element (socket or plug), thereby automatically establishing an electrical connection between the connector elements. The connector element can be attached directly to the carrier film or the printed circuit board.Alternatively, the connector element can also be attached indirectly to the carrier film or the circuit board via wires. In the latter case, the connector element is movable relative to the carrier film and / or the circuit board and can be positioned and oriented as desired for contact with the switching element or the electrical power source.

[0023] Alternatively, the contacting element can have contact pads that connect to the conductive traces of the heating element. These contact pads are located on one contact side of the transparent carrier film or on an electrical circuit board that is attached to the carrier film on one contact side. The contact pads can be attached to the carrier film, for example, using self-adhesive contact pads made of copper, and connected to the conductive trace ends. The contact pads can be wrapped around the carrier film so that the crimped contact pads are adhered to both the top and bottom surfaces. This allows the heating element to be contacted simultaneously from both sides of the carrier film, resulting in a particularly reliable and secure connection.

[0024] The electrical contact between the contact surfaces and the switching element or electrical power source can be achieved, for example, via spring-loaded contact pins. Applying force to the contact head of the pin compresses it to its installation dimension. A spring inside the pin ensures that the electrical contact between the pin head and the contact surface is maintained. The spring-loaded contact pins can be installed or inserted into suitable grooves in a lens holder, which positions and holds the projection lens in the light module. A circumferential pin collar, with a slightly larger diameter than the pin body, can be provided as a stop at the end position. This stop ensures that there is counter-pressure when the pin is compressed, preventing it from slipping backward.When the projection lens is mounted 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.

[0025] Finally, it is proposed that an opaque aperture element be arranged on the outer surface of the projection lens, concealing areas of the heating element outside the conductor tracks, particularly contact areas through which the conductor tracks are connected to the switching element or the electrical power source. The aperture element has, for example, a reflective or dark appearance from the outside. The aperture element can be a separate component attached to the light-emitting surface of the projection lens from the outside, for example by gluing, welding, clamping, snapping, clipping, etc. It would also be conceivable that the aperture element is designed as an opaque layer applied to the light-emitting surface of the projection lens from the outside. It would also be conceivable that the separate aperture element is integrated into the projection lens itself. This could be achieved, for example, as part of a multi-step manufacturing process for the projection lens, as is the case, for example, with...as is known from DE 10 2010 033 902 A1. In particular, a first part of the projection lens can be injection molded in a first process step. The aperture element is applied to the first part and overmolded with material for at least one further part of the projection lens in at least one further process step. In addition to the aperture element, the heating element can also be incorporated into the projection lens or applied to the light entrance surface of the lens. Crucially, the aperture element is arranged outside the heating element to prevent an external view of the covered part of the heating element. Instead of being an opaque element, it would also be conceivable for the aperture element to be semi-transparent, e.g., like a frosted glass pane or similar.

[0026] 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 embodiments shown in the figures may each be essential to the invention even on their own, even if this is not expressly mentioned in the following description. Furthermore, any combination of features of the various embodiments may also be essential to the invention, even if this combination is not expressly mentioned in the following description. The invention is limited only by the accompanying claims. The figures show: Figure 1: A light module of a motor vehicle headlight according to the invention; Figure 2: A heating element for use in a light module of a motor vehicle headlight; Figure 3: The heating element made of Fig. 2in a top view, in a cross-section AA and in a detail view X; Figure 4 a printed circuit board as part of a heating element; Figure 5 a heating element made of Fig. 2 and 3 with attached circuit board made of Fig. 4 in a view from below; Figure 6 the heating element with circuit board attached to it made of Fig. 5 in a top view; Figure 7 the heating element with circuit board attached to it made of Fig. 5 Figure 8 shows the heating element with circuit board applied to an inner surface of a projection lens of a light module of a motor vehicle headlight in a sectional view; Figure 9 shows a heating element for use in a light module of a motor vehicle headlight; Figure 10 shows the heating element made of Fig. 9Figure 11 shows a heating element for use in a light module of a motor vehicle headlight with a connector element in a contact area; Figure 12 shows the heating element made of Fig. 11 in the section with a plug element for electrical contacting conductor tracks of the heating element; Figure 13 a heating element made of Fig. 9 with attached circuit board; Figure 14 shows a section of the heating element. Fig. 13 Figure 15 shows the heating element. Fig. 13 with connector element attached to the circuit board; Figure 16 a heating element in a top view, in a cross-section AA and in a detail view X; Figure 17 the heating element made of Fig. 16 with attached circuit board with connector element in a contact area; Figure 18 the heating element made of Fig. 16with a connector element attached directly to a carrier film in a contact area; Figure 19 a projection lens of a projection module of a motor vehicle headlight with a heating element integrated into the lens in a horizontal section; Figure 20 the projection lens made of Fig. 19 in a vertical section; Figure 21 an injection mold for the production of a projection lens according to Fig. 19 in a first process step; Figure 22 an injection mold for the production of a projection lens according to Fig. 19 in a subsequent process step; Figure 23 a finished projection lens in a transparent view from the outside; Figure 24 a finished projection lens in an external view with an aperture element applied to the outer surface; Figure 25 another example of a heating element for use in a light module of a motor vehicle headlight; Figure 26 a section of the heating element made of Fig. 25with contact area in a top view; Figure 27 the section from Fig. 26 in a perspective view from a slightly elevated angle; Figure 28 the section from Fig. 26 in a perspective view from a low angle; Figure 29 shows a comparison of the contact areas of the heating elements from the Figs. 11 and 12 as well as the Figs. 25 to 28 Figure 30 shows an example of a spring contact pin in unloaded length for contacting the contact area of ​​the heating element from the Figs. 25 to 28 Figure 31 shows the spring contact pin made of Fig. 30 in compressed length; Figure 32 an example of contacting the heating element from the Figs. 25 to 28 with two spring contact pins and a plug element; Figure 33 a lens carrier with integrated spring contact pins and plug element according to Fig. 32 in an external view; Figure 34 the lens carrier made of Fig. 33 in the excerpt in an interior view; Figure 35 the lens carrier made of Fig. 33in an external view with the projection lens to be inserted; Figure 36 the lens carrier made of Fig. 33 in the section in an internal view with the projection lens to be inserted; Figure 37 the lens carrier made of Fig. 33 in the section in an interior view with the projection lens inserted; and Figure 38 the lens carrier made of Fig. 37 Cross-section with projection lens inserted.

[0027] An example of a projection module of a headlight according to the invention for a motor vehicle is shown in Fig. 1 shown and designated in its entirety by reference symbol 2. The projection module 2 comprises a light source for emitting light, which is shown in Fig. 1The projection module 2 is arranged inside the projection module and is therefore not visible. The light source preferably comprises at least one semiconductor light source, e.g., an LED or a laser diode, and more preferably a semiconductor light source array. Furthermore, the projection optics 2 comprise a primary optic for focusing, shaping, and / or deflecting the light emitted by the light source. The primary optic is arranged in Fig. 1also not visible. It can comprise one or more reflectors or lenses. It can also comprise one or more auxiliary optics that focus the light emitted by the light source by means of refraction at the light entry and / or light exit surface of the auxiliary optics and / or by means of total internal reflection at interfaces of the auxiliary optics. Furthermore, the projection module 2 comprises a secondary optic 4 in the form of a projection lens, which projects an intermediate image of an intermediate image plane, arranged in the beam path between the primary optics and the secondary optic 4, in a light exit direction 6 of the projection module 2 in a foreground in front of the vehicle as the resulting light distribution of the projection module 2.The projection lens is preferably designed as a cylindrical lens, wherein a light-exiting surface of the lens 4 has a greater curvature about a cylinder axis 60 and a lesser curvature about an axis extending transversely to the cylinder axis 60. When the projection module 2 is installed in the motor vehicle in its operational state, the cylinder axis 60 runs in a substantially vertical direction.

[0028] The projection module 2 is arranged in a headlight housing which has a light-transmitting opening in the direction of light emission 6, through which the light passing through the projection lens 4 is projected onto the road surface in front of the vehicle. The headlight housing does not have a transparent cover that closes the light-transmitting opening. Rather, the projection lens 4 forms the outer termination of the headlight in the direction of light emission 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, as well as the manufacture of the projection lens 4 with such a heating element, are explained in more detail below.

[0029] To propose a simple and cost-effective, yet efficient method for defrosting the projection lens 4 of a projection module 2 of a motor vehicle headlight when the headlight lacks a cover to close the light transmission opening, it is proposed that the heating element 8 have a transparent carrier film 10 made of an electrically insulating material and conductive traces 12 applied to or embedded in it, which are connected to an electrical power source 16 via a switching element 14. The power source 16 could, for example, be the vehicle battery. The switching element 14 can enable or interrupt the flow of current through the conductive traces 12. The switching element 14 can be controlled manually, for example by the driver of the motor vehicle, or automatically, for example depending on the ambient temperature or a temperature of the light module 2 or the projection lens 4.

[0030] The heating element 8 is applied to at least a portion of a light entry and / or light exit surface of the projection lens 4 of the projection module 2, or at least integrated into a portion of the projection lens 4 itself. When current flows through the conductor tracks 12, the heating element 8 heats the projection lens 4 and ensures efficient defrosting.

[0031] With headlights and light modules 2 of headlights without a cover lens, there is a risk that the projection lens 4 will be at least partially covered by snowfall and ice formation in winter weather conditions, thereby blocking the light completely or partially, or preventing the road from being fully illuminated or even eliminating it entirely. Some headlights are equipped with washers that spray the cover lens or the lens 4 of a light module 2 with antifreeze, thus preventing them from becoming partially or completely clogged with snow and / or ice. However, the use of washers is complex and expensive, and their efficiency is not always guaranteed, especially at very low ambient temperatures.

[0032] To ensure that the light projected onto the road from a headlight without a cover lens remains largely unaffected by winter weather conditions, the exposed projection lens 4 must be kept free of snow and ice. One way to achieve this is to heat lens 4 and maintain it at a sufficiently high temperature so that ice and snow melt and / or cannot adhere to it.

[0033] In light modules 2 with semiconductor light sources that emit light with a low IR component, the temperatures at the outer lenses 4 are usually not high enough in the case of a headlight without a cover 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 the accumulation of snow and ice. By warming the lens 4, little or no precipitation such as snow and ice adheres to the outer lens surface, thus preventing insufficient light from being projected onto the road.

[0034] Essentially, a heated projection lens 4 can be obtained by placing 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, especially PC) from which the lens 4 is manufactured. Fig. 3A heating element 8 is shown in which the heating wire 12 is applied to the carrier film 10. However, since the carrier film 10 has a greater thickness 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 ultrasonic welding. By applying a voltage to the exposed ends 18 of the heating wire 12, it heats up. The resulting heat 20 radiates in all directions and will also warm the surrounding material of the lens 4 and ultimately lead to a warming of the lens's outer surface. With sufficient heating, ice and snow are prevented from adhering to the heated surface.

[0035] The carrier film 10 preferably consists of transparent plastic, e.g., PC, into which a thin heating wire 12 of approximately 50 µm diameter is embedded. This wire 12 has a plastic sheath or another type of electrical insulation. The individual tracks or loops of the embedded wire 12 should, if possible, cover a sufficiently large area on the film 10 to heat the optically effective area of ​​the lens 4 as uniformly 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 low light loss of <1% occurs, which is negligible from a photometric point of view.

[0036] Several possibilities are conceivable for contacting the heating element 8 with the switching element 14 and / or the energy source 16. In the example of the Fig. 5The foil 10 is attached to a circuit board 22, e.g. by gluing. The adhesive bond is in Fig. 5 Designated with reference numeral 26. The circuit board 22 can be flexible or rigid. The circuit board 22 can be provided with a connector element 24, which facilitates contact with the switching element 14 and / or the power source 16. The uninsulated wire ends 18 are bonded / soldered to the circuit board 22. Conductive traces 28 are applied to the circuit board 22, which form an electrical connection from the wire ends 18 to contacts 30 of the connector element 24. This assembly, consisting of the carrier film 10, the heating wire 12, the attached circuit board 22 with the connector element 24, forms the heating element 8 (see figure). Fig. 6 ).

[0037] This heating element 8 can be inserted into a plastic injection mold and overmolded or encased with the material for manufacturing the projection lens 4. The finished lens 4 with the attached heating element 8 is in the Figs. 7 and 8The projection lens 4 and the carrier film 10 are preferably made of the same material, e.g., PC. After curing, overmolding or overmolding creates a permanent, bonded connection between the heating element 8 and the lens 4. This results in an optical lens 4 with an integrated heating element 8, which can be attached to a light module 2. Both the manufacturing of the heated projection lens 4 and the assembly and electrical contacting of the lens 4 or the heating element 8 in the light module 2 can be carried out particularly quickly and easily. Active heating warms the lens surface oriented in the direction of travel and prevents ice and snow from clogging this light-emitting surface.

[0038] The material of the heating wire 12, its geometric dimensions (e.g., diameter and length), its specific electrical resistance, as well as the applied voltage and current flowing through it, all influence the achievable heating power of the heating element 8. These parameters of the heating wire 12 can be individually selected for each application.

[0039] The heating element 8 can be heated by means of voltage or current control or regulation to prevent overheating, which could impair the optical properties of the lens 4 or damage the lens material. Electrical and / or electronic components required for control and / or regulation can be provided on the circuit board 22. These components include, for example, a temperature sensor and / or a microprocessor.

[0040] Alternatively, a plug-in element 24 can also be attached directly to the carrier film 10 (see below). 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-adhesive and attached to the foil 10, and connected to the uninsulated wire ends 18, for example, by means of a low-temperature soldering process. The contacts 30 of the connector element 24 are connected to the copper pads 32, for example, by soldering (see figure). Fig. 12 Subsequently, the heating element 8 is overmolded or co-molded as part of the manufacturing process of the projection lens 4 using an injection molding process as described above. The advantage of this design is that, by eliminating the need for a separate circuit board 22, a smaller installation space is required.

[0041] Another alternative for applying an electrical voltage to the wires 12 of the heating element 8 can be done using a flexible circuit board 22 (see figure). Figs. 13 to 15 For this purpose, a flexible printed circuit board 22 is attached to a contact side of the transparent film 10 with the integrated heating wires 12, e.g. by laminating or gluing 26. The uninsulated wire ends 18 are then soldered onto the printed circuit board 22 on designated contact pads 32. The printed circuit board 22 has conductive traces 28 which connect the contact pads 32 to the contacts 30 of the connector element 24. Instead of the in Fig. 15In addition to the single connector element 24 shown, several connector 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 required length of the heating element 8. This enables a compact design of the overmolded or overmolded lens 4 with the integrated heating element 8.

[0042] In previous embodiments, the current-carrying conductors 12 of the heating element 8 are designed as heating wires that are applied to or embedded in the carrier film 10. However, instead of these heating wires 12, printed strands 12a can alternatively serve as current-carrying conductors (see Figure 1). Figs. 16 to 18These can be printed onto the transparent film 10, for example, using a screen printing process, pad printing, or inkjet printing. If an electrically conductive printing ink or paste is used, 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 a voltage is applied.

[0043] In this design, the dimensions of the printed conductor strands 12a are of particular importance. These strands must offer a sufficiently low resistance (depending on the material used and the cross-sectional area of ​​the strands 12a) to allow for simple and cost-effective application to the film 10 and to provide the desired heat output. To minimize light loss, the conductor strands 12a should be as narrow as possible. A strand width of approximately 0.5 mm would be acceptable. The light loss would then be around 5%. This loss can be compensated for by increasing the current to the light source of the light module 2.To apply a thickness (or height) of ink / paste sufficient to create a cross-sectional area adequate for the calculated resistance, the thickness should be greater than that of standard screen printing, i.e., a thickness of >50 µm should be achieved.

[0044] The electrical contacting possibilities of the carrier film 10 with printed strands 12a as conductor tracks correspond essentially to those of the versions described at the beginning with carrier film 10 and heating wires 12 (cf. Figs. 17 and 18 ).

[0045] The above-described flat heating elements 8 have been attached to one side (inside or outside) of a projection lens 4 using an injection molding process (see Figure 1). Fig. 7 ). Another possible embodiment would be to integrate 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 (cf. Figs. 19 to 22 ).

[0046] 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 conductive tracks 12 is overmolded with a layer of material 4.1, e.g., plastic, in particular PC, from which the projection lens 4 is made (see Figure 4). Fig. 21 ). Subsequently, in a second step, lens material 4.2 is injected onto the still free side of the carrier film 10 (see below). Fig. 22 The overmolding of the heating element 8 with the lens material takes place in an injection mold, as is used in the Figs. 21 and 22 The first tool side is labelled W1, the second tool side W2.

[0047] It is particularly preferred that, for the manufacture of the projection lens 4 which can be heated by means of the heating element 8, the heating element 8, in the form of a transparent film 10 made of an electrically insulating material and with conductive traces 12, 12a applied to or embedded therein, be applied to at least a portion of a light entry and / or light exit surface of the projection lens 4 of the projection module 2, or at least be incorporated into a portion of the projection lens 4 itself. For the incorporation of the heating element 8 into the lens 4, it is proposed that First, a first part 4.1 of the projection lens 4 is manufactured using an injection mold W, the heating element 8 is placed in the injection mold W, if present, on the first part 4.1 of the projection lens 4, and another part 4.2 of the projection lens 4 is manufactured on the heating element 8 using the injection mold W.

[0048] Between the first stage ( Fig. 21 ) and the second stage ( Fig. 22 Preferably, a first tool insert WE1 is replaced by a second tool insert WE2. The second tool insert WE2 provides a recess 34 for injection molding the second part 4.2 of the lens 4. The finished projection lens 4 encloses the heating element 8 and leaves only the connector element 24 exposed to supply voltage to the heating element 8 and / or the conductor tracks 12, 12a.

[0049] Fig. 23 Figure 1 shows a view of the finished projection lens 4, equipped with the integrated heating element 8, viewed from the outside, opposite to the direction of light emission 6. 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 are clearly visible.

[0050] The contact area of ​​the heating element 8 (with the circuit board 22, the conductor tracks 28, the contact surfaces 32 and the connector element 24) as well as a manufacturing-related edge of the projection lens 4 can be covered by means of a diaphragm element 36 (a cover, a frame or design part) (see Fig. 24The aperture element 36 can be opaque or semi-transparent. An opaque aperture element 36, for example, is silver or black. The aperture element 36 can be a separate component that is attached to the outer surface of the lens 4, for example, by gluing or welding. It would also be conceivable that the aperture element 36 is applied to the outer surface of the lens 4 as a layer of paint, for example, by spraying or dipping. Finally, it would also be conceivable that the aperture element 36 is applied as one of several components of the lens 4 as part of the multi-stage manufacturing process using injection molding. For this purpose, the aperture element 36 can first be placed in the injection mold and overmolded with a first layer 4.1 of the lens 4 material. Subsequently, the heating element 8 is placed on the first layer 4.1 and overmolded with a second layer 4.2.

[0051] The following will be based on the Figs. 25 to 29Another possibility for contacting the heating element 8 is described. In this embodiment, a connector element 24 directly on the carrier film 10 is omitted. While in the previously described embodiments a plug connection was made directly on the film 10 using a connector element 24 (socket housing and pin housing), in this embodiment the electrical contact to the switching element 14 and / or the power source 16 is made by placing contact pins (see Figure 1). Figs. 30 to 32 ) on contact pads (see below) Figs. 26 to 28) manufactured, which are applied directly to the film 10. The advantages lie in the simple and cost-effective manufacturing of the heating element 8 as well as in the simple but reliable integration (mechanical fastening and electrical contacting) of the projection lens 4 into the projection module 2. In addition, this design requires significantly fewer parts and less space in the light module 2. This allows for a reduction in weight and opens up new styling possibilities for the light module 2.

[0052] Fig. 25 Figure 1 shows the plastic carrier film 10 described above, with the applied or integrated conductive traces 12 (e.g., heating wires or printed strands). The ends 18 of the conductive traces 12 are guided to the lateral edge on a contact side of the film 10. Fig. 26Figure 3 shows contact pads 38, which can, for example, consist of a copper foil. The contact pads 38 can be self-adhesive, allowing for easy attachment to the carrier film 10 and contact with the conductor tracks 12 or their ends 18 in the contact area of ​​the film 10. The wire ends 18 can be soldered to the contact pads 38. Laterally protruding sections 38a of the contact pads 38 can be folded backward and attached to the back of the carrier film 10 (see Figure 3). 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 embodiments described so far, this results in a significantly narrower contact area 40, since in the previous embodiments the connector element 24 occupied a relatively large amount of space (see Figure 1). Fig. 29In particular, the contact area 40 is reduced to approximately 35% of its previous value (e.g., from 20 mm to only 7 mm).

[0053] The electrical contact of the contact pads 38 can be effected by means of spring contact pins 42. By applying a force F (pressure force) to a contact head 44 of the pin 42, it is compressed by (length I1 - length I2) to an installation dimension. Fig. 30 is the unloaded (original) length of the pin 42 and in Fig. 31The compressed length (final length when assembled) is shown. 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 freely designed or selected from existing standard dimensions from suitable suppliers. The contact forces or spring forces F can also be application-specific or selected from standard versions. Here, for example, a pin diameter D of 1.5 mm and a contact area of ​​1.767 mm² are proposed.

[0054] For the present application, contact pins 42 with attached cable 46 could be used, which are already joined together in a connector housing 24a (see figure). Fig. 32During further assembly, the pins 42 are inserted into suitable grooves 48 in a lens carrier 50 and secured therein (see figure). Fig. 33 The lens carrier 50 serves to mount 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 compressed, there is a counter-support, and the pin 42 cannot move backward. By connecting cables 46, the connector 24a can be attached to the lens carrier 50 at any distance from the lens 4, e.g., by means of a clip connection (see figure). Fig. 34 ). A cover 54 could be clipped on to secure the contact pins 42 in the grooves 48 from the side (see figure). Fig. 34 and 36 Other fastening options, with or without an additional fastening or securing component, are also conceivable.

[0055] In a subsequent step, the projection lens 4 with the integrated heating element 8 can be applied to the lens carrier 50 (see figure). 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 pre-filled with an adhesive or sealant (e.g., butyl). The sealing base 56 can extend over the entire circumference of the lens 4. In this case, the sealing channel 58 would also extend over the entire circumference of the lens 4. By pressing the sealing base 56 into the sealing channel 58 and after the adhesive or sealant has cured, 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 other ways, e.g., by means of a retaining spring, laser welding, or similar methods.

[0056] 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. This contact is established automatically when the lens 4 is mounted on the lens carrier 50. This allows the contacts 38 to be positioned even in areas that are difficult or impossible to access.

Claims

1. Headlamp for a motor vehicle, comprising a housing with a light transmission opening arranged in a light emission direction (6) of the headlamp, wherein the headlamp has a projection module (2) in the housing, which comprises a light source for emitting light, primary optics for focusing, shaping and / or deflecting the light emitted by the light source, and a secondary optics (4) 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 optics and the secondary optics (4), in a light emission direction (6) of the projection module (2) in an front area in front of the motor vehicle as resulting light distribution of the projection module (2), wherein the projection module (2) comprises a heating element (8) for heating the projection lens (4), which is connected to an electrical power 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 incorporated into at least part of the projection lens (4) itself, so that the heating element (8) heats the projection lens (4) when the current flow through the conductor tracks (12) is switched on, characterised in that the heating element (8) has a transparent film (10) made of an electrically insulating material and conductor tracks (12) applied thereto or embedded therein, and in that the light transmission opening of the housing is not closed by a cover plate and the projection module (2), in particular the projection lens (4), is sealed around the light emission direction (6) of the headlamp in respect to the housing.

2. Headlamp according to claim 1, characterised in that the projection lens (4) forms the outer edge of the projection module (2) in the light emission direction (6).

3. Headlamp according to claim 1 or 2, characterised in that the heating element (8) is applied to the light entry and / or light exit surface of the projection lens (4) or incorporated into the projection lens (4) itself as part of an injection moulding process or a co-moulding process during the manufacture of the projection lens (4).

4. Headlamp according to one of the preceding claims, characterised in that the light source comprises at least one semiconductor light source, in particular at least one LED, preferably a multi-chip LED.

5. Headlamp according to one of the preceding claims, characterised in that the transparent film (10) is made of a plastic, in particular polycarbonate.

6. Headlamp according to one of the preceding claims, characterised in that the projection lens (4) has the shape of a cylindrical lens, with a stronger curvature of a light exit surface of the lens (4) about a cylinder axis (60) and a lesser curvature of the light exit surface about an axis extending transversely to the cylinder axis (60), wherein, in particular when the projection module (2) is installed in the motor vehicle in an operational state, the cylinder axis (60) extends in a substantially vertical direction.

7. Headlamp according to one of the preceding claims, characterised in that the conductor tracks (12) of the heating element (8) are led outwards on a contact side of the transparent film (10), wherein, in particular, an electrical circuit board (22) is attached to the transparent film (10) on the contact side and contact areas (28; 40) of the circuit board (22) are in contact with the conductor tracks (12) of the heating element (8).

8. Headlamp according to one of the preceding claims, characterised 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 power source (16), wherein, in particular, the contacting element is designed as a plug element (24) which is fastened to the circuit board (22).

9. Headlamp according to claim 8, characterised in that the contacting element has contacting surfaces (38; 32) which are in contact 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).

10. Headlamp according to one of the preceding claims, characterised in that on an outer side of the projection lens (4) a bezel element (36) is arranged, 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 power source (16).