WO2008006483A1 - Heating device for a mirror glass - Google Patents

Abstract

The invention relates to a mirror, especially an outside rear view mirror for a motor vehicle, said mirror comprising a carrier plate (1) which is back-moulded with the rear side (7) of an intermediate layer by means of injection moulding. To this end, the intermediate layer (3) consists of a back-mouldable nonwoven material. A heating device in the form of a strip conductor (2) consisting of a resistance material is applied to the front side (8) of the intermediate layer (3) by means of a thermal injection method according to DIN EN 657.

Description

 Heating device for a mirror glass

The invention relates to a heating device for a mirror glass of a mirror, in particular an exterior mirror for a motor vehicle, according to the preamble of claim 1 and a method for producing a support plate for a mirror glass.

EP 0 732 865 B1 discloses a heating device which is formed by carbon fibers which are connected to one another in a conductive manner via a binder. An adhesive layer is used to apply a mirror glass to a support plate for the mirror glass.

Further, it is known to apply a heater directly to the mirror glass of a mirror directly by a screen printing method or the like. However, as is apparent from FR 2 628 041 A1, the reflection layer is then attached to the outside of the mirror glass, with increased risk of damage to the reflection layer. In addition, the conductive paste is to be baked at a temperature of about 670 ° in the known method, resulting in problems in compliance with the bending accuracy can result in spherical and aspherical mirror glasses.

In addition, it is known, for example from DE 10 2004 002 979 A1, to form the rear reflection layer on a mirror glass directly as a heating layer. However, it is problematic to evenly distribute the current flow in the thin reflection layer and make the contact.

DE 42 23 590 A1 shows a mirror in which on the front of the mirror glass, a transparent heating device is attached as an ITO layer, which is covered by a protective layer, which is attached for example by sputtering or plasma deposition. In this arrangement, the known problems in the contacting of thin layers. In addition, the ITO layer is very sensitive to damage, which can lead to local overheating (hot spots).

Furthermore, FR 2 618 396 A1 describes a carrier foil for a mirror glass, with a heating device applied by screen printing. On the front side of the heating device facing the mirror glass, a secure connection between the mirror glass and the carrier film is established via a double-sided adhesive tape. In addition, this will seal the heater.

Further, it is generally known to produce a resistance heating for a mirror glass in the form of a laminated copper foil in the photo-etching process and then to secure the copper foil with a double-sided adhesive tape on the support plate.

The object of the invention is to provide a heating device for a mirror glass of a mirror, in particular an exterior mirror of a motor vehicle, which is inexpensive to produce and can be connected in a simple manner with the support plate of the mirror glass.

This object is achieved by a heating device with the features of claim 1. Claim 8 describes a mirror with a carrier plate according to the invention. Claim 9 relates to a method for producing a carrier plate for a mirror glass.

The core idea of the invention according to claim 1 or 9 is to provide an intermediate layer of a back-sprayable nonwoven material, on the front side thereof by a thermal spraying method according to DIN EN 657 a heating device is applied. The intermediate layer can in turn be connected in a simple and cost-effective manner directly to the carrier plate by the plastic material of the carrier plate is sprayed onto the back of the intermediate layer. Thus, the connection of the intermediate layer with the carrier plate does not take place in a separate operation, but directly in the production of the carrier plate itself.

According to DIN EN 657, the term "thermal spraying process" covers all processes in which spray additives are supplied inside or outside a spray gun and heated to the plastic or molten state and then thrown onto the prepared surface, wherein the surface is not melted. The particles, which are thrown onto the surface to be coated by means of compressed air, heating gas, cold gas, arc, plasma, etc., with high kinetic energy, cling mechanically to the surface as they impact. The particles which are subsequently fed further onto the surface in turn become entangled in the previously applied particle layer. The result is a layer of resistance material, which is in intimate connection with the intermediate layer.

The resistance material is in this case in wire, powder or granular form in a specially designed "burner" (in the manner of a spray gun) fed, the material melted and then the molten particles by one of the energy sources mentioned in Table 1 of DIN EN 657 high kinetic energy are thrown onto the surface to be coated.

In contrast to the known production of a resistance heating from a laminated copper foil in the photo-etching process, which is subsequently fixed with a double-sided adhesive tape to the carrier plate, the operation of gluing the "heating foil" to the carrier layer is omitted in the case of an intermediate layer according to the invention. Rather, the intermediate layer is back-injected with the previously applied on its front heater on its back directly with the plastic material of the support plate. This reduces the assembly effort. Also, an increase in the reliability of the heater is achieved. In difference to the known sticking of the "heating foil" on the support plate, the production can be automated.

As a nonwoven material for the intermediate layer, all materials that are hinterspritzbar with a plastic material, so enter into an intimate connection with the plastic material in the injection mold. In a special way, a mineral fiber fleece, in particular a glass fiber fleece, is suitable for this purpose.

In principle, all processes mentioned in the structure of the thermal spray processes of DIN EN 657 in Annex A are suitable for the production of heating devices according to the invention. However, as a particularly suitable manufacturing method, the arc spraying method is proposed. With the arc spraying process, a solid connection of the resistance material with the nonwoven material is achieved, at the same time comparatively low cost for the application of the resistance material. The energy generated by the arc spraying process, with which the particles are applied to the intermediate layer, is completely sufficient for the connection of the resistance material with the intermediate layer. Thus, the use of expensive processes, such as high-speed wire flame spraying, which operates at higher kinetic energies, can be dispensed with.

In the arc spraying process, an arc is used between two wire-shaped spray additives of the same or different composition to melt the wire tip. With one or more gas jets, usually compressed air, the molten material is atomized and thrown onto the prepared surface of the intermediate layer.

To improve the properties of the applied resistance path, the inert gas arc spraying method can be used. In this method, a lower porosity and a reduced oxidation in the layer of the deposited resistance material is achieved. By a second gas flow in a protective body or by a protective gas jacket around the arc and the spray jet around an ingress of air is prevented in the hot gas and particle flow. To increase the density of the resistance material can In addition, the speed of the spray jet can be increased. As a result, the contact time of the particles of the resistance material is reduced with the Zerstäuber- and inert gas.

As resistance material ferrous metals, non-ferrous metals, conductive plastics, cermets (sintered ceramic metals), etc. can be processed. Also, special alloys with selected specific resistive resistance can be processed.

The order of the resistance material can be carried out continuously along the desired course of the conductor track. In a preferred embodiment of the invention, a mask is used to accelerate the application of material, covering those areas of the intermediate layer to which no resistance material is to be applied, so that the order of the resistance material can be made flat. The free spaces of the mask in this case correspond to the course of the conductor track. The mask is preferably coated with an antiblocking agent. The clean detachment of the mask from the intermediate layer achieved hereby ensures sharply defined boundaries of the conductor track. In addition, the mask can be easily cleaned and thus used several times.

In addition to the inventive application of the resistance material of the conductor track on the intermediate layer and the periphery of the heater can be sprayed by a thermal spray process according to DIN EN 657 to the intermediate layer. This may be, for example, the power supply for the conductor track, which is formed by a highly conductive material. In an analogous manner, insulating materials can also be applied to the intermediate layer by means of a thermal spraying process according to DIN EN 657.

As is apparent from claim 8, the electrical insulation of the heater relative to the reflective layer of the mirror glass by an adhesive or an insulating varnish. The adhesive or insulating paint here has a double function, namely on the one hand the electrical insulation and on the other hand the connection of the mirror glass with the intermediate layer and thus with the support plate. About the adhesive or the insulating varnish is compared to mechanical stress gen and environmental influences sensitive reflection layer of the mirror glass protected.

According to claim 9, the carrier plate is produced by an injection molding process, with a thermoplastic or thermosetting plastic. In this case, the intermediate layer already provided with the conductor track on its front side is inserted into an injection mold in such a way that the rear side of the intermediate layer can be back-injected directly with the plastic material.

The connection between the end sections of the conductor track and electrical contacts for connecting the supply voltage for the heating device is preferably carried out by a soldering method, before inserting the intermediate layer in the injection mold.

The term "mirror glass" is used in connection with the present invention not only for mineral glass, but also for all conceivable other transparent substrates, for example of thermoplastic or thermosetting materials.

All information on DIN EN 657 refers to the issue of June 2005.

Advantageous embodiments of the invention are the subject of the dependent claims.

A possible embodiment of the invention is illustrated in the drawing and will be explained in more detail below. It shows:

1 shows a carrier plate according to the invention with a heater carrying intermediate layer in plan view,

Fig. 2 is a sectional view taken along the section line A-A of Fig. 1 and

3 is a graphical overview of the thermal spraying method according to DIN EN 657. A carrier plate 1 for a mirror, not shown in detail, in particular an outside mirror for a motor vehicle, has an intermediate layer 3 on the front side of a mirror glass, not shown. The intermediate layer 3 is part of a heating device and is provided on its front side 8 with a meandering conductor 2. The ends 6 of the conductor 2 are led out on one side of the intermediate layer 3 and soldered with angled contacts 4.

The carrier plate 1 consists of a plastic material and is produced by injection molding. Webs 5 on the back of the support plate 1 increase the mechanical rigidity of the support plate 1. As a material for the support plate 1 are all types of plastics that can be processed by injection molding.

The intermediate layer 3 consists of a back-spun nonwoven material, preferably a glass fiber fleece, which is inserted into the injection mold so that the rear side 7 of the intermediate layer 3 is back-injected directly with the plastic material of the carrier plate 1.

To clarify the structure of support plate 1 and intermediate layer 3, the intermediate layer 3 is shown at a distance from the support plate 1 in the sectional view of FIG. In fact, however, the material of the carrier plate 1 is sprayed directly onto the rear side 7 of the intermediate layer 3, so that the carrier plate 1 and the intermediate layer 3 are firmly bonded to one another.

The conductor 2 is meandered in a plurality of loops on the front side 8 of the intermediate layer 3 is sprayed. Among other things, the available area of the carrier plate 1 plays a role in the selection of the resistance material. The following table gives a selection of possible resistance materials, their specific electrical resistance and the required total length of the conductor 2. It is assumed here, for example, of a cross-sectional area of the conductor 2 of 0.2 mm ² and a desired resistance of 6 ohms to reach at a vehicle electrical system voltage of 12 volts, a heating current of 2 amps and thus an electrical power of 24 watts.

The heater (trace 2) and its heating power are to be designed so that a fast and uniform defrosting of the mirror of fog and / or ice is achieved.

Notwithstanding the illustrated embodiment, two or more separate heating circuits may be provided with electrically separate interconnects 2 and contacts 4.

Fig. 3 shows an overview of the thermal spraying method according to DIN EN 657 according to Annex A of DIN EN 657, divided according to the energy sources used. In principle, all of the thermal spraying methods cited in the overview are suitable for applying the resistance material to the intermediate layer 3. As practical experiments have shown, arc spraying provides a sufficiently solid connection between conductor 2 and intermediate layer 3, with a low porosity of the resistance material. This is the arc spraying a very economical method for applying the resistance material to the intermediate layer 3 is available.

Claims

Heating device for a mirror glass patent claims 1. heating device for a mirror glass of a mirror, which is arranged between the mirror glass and a support plate for receiving the mirror glass, characterized in that the heating means comprises an intermediate layer (3) of a back-spun nonwoven material, on the at least one conductor track (2) of a Resistance material is applied by a thermal spray method according to DIN EN 657. 2. Heating device according to claim 1, characterized in that the intermediate layer (3) is formed by a mineral fiber fleece, preferably a glass fiber fleece. 3. Heating device according to claim 1 or 2, characterized in that the thermal spraying process is an arc spraying process. 4. Heating device according to one of the preceding claims, characterized in that the resistance material is formed by a ferrous metal, a non-ferrous metal, a conductive plastic or a ceramic metal. 5. Heating device according to one of the preceding claims, characterized in that the intermediate layer (3) is covered before the application of the resistance material with a mask through which the areas in which no resistance material is to be applied, are covered. 6. Heating device according to one of the preceding claims, characterized in that the conductor track (2) extends meandering. 7. Heating device according to one of the preceding claims, characterized in that the carrier plate (1) consists of a plastic material and is produced by injection molding. 8. Mirror with a heating device according to one of the preceding claims, with a mirror glass with a rear reflection layer, characterized in that the mirror glass is applied by an adhesive method or an insulating varnish on the intermediate layer (3). 9. A method for producing a support plate for a mirror glass, comprising a heater for the mirror glass, characterized by the following steps: Applying at least one printed conductor (2) made of a resistance material by a thermal spraying method according to DIN EN 657 to the front side (8) of an intermediate layer (3) made of a back-sprayable non-woven material, Inserting the intermediate layer (3) in an injection mold and back injection of the back (7) of the intermediate layer (3) with a plastic material which forms the support plate (1). 10. The method according to claim 9, characterized in that after the application of the conductor track (2) and before inserting the intermediate layer (3) in the injection mold, the end portions (6) of the conductor track (2) by a soldering electrically conductive contacts (4 ) are connected, which serve to supply power to the conductor track (2).