METHOD FOR MANUFACTURING A HEATING DEVICE, AND HEATING DEVICE

Abstract

A method for manufacturing a heating device having a carrier and at least one heating conductor applied thereto has the steps: provision of a carrier having a heating conductor side, wherein the carrier consists of aluminum, generation of an anodized layer on the heating conductor side, wherein the anodized layer is applied directly to the carrier and/or its heating conductor side, application of the at least one heating conductor above the anodized layer in a thick-film method. Advantageously, the anodized layer can be manufactured as a hard anodized layer. An additional insulation layer and/or a thickening layer can also be applied to the anodized layer.

Claims

1. A method for manufacturing a heating device, wherein said heating device has a carrier and at least one heating conductor applied to said carrier, wherein said method has the steps: provision of a carrier having a heating conductor side, wherein said carrier consists of aluminum, generation of an anodized layer on said heating conductor side, wherein said anodized layer is generated directly on said carrier and/or said heating conductor side, application of said at least one heating conductor above or onto said anodized layer.

2. The method according to claim 1, wherein an additional insulation layer is applied to said anodized layer.

3. The method according to claim 2, wherein said additional insulation layer is generated and applied by thermal spraying as an aluminum oxide layer.

4. The method according to claim 1, wherein said anodized layer is generated and applied in a galvanic method and to do so said carrier is moved at least with said heating conductor side into a galvanic bath, wherein said galvanic bath has an acid electrolyte, wherein said acid electrolyte has a temperature of less than 20 C.

5. The method according to claim 4, wherein said anodized layer is generated as a hard anodized layer by means of a relatively high current density.

6. The method according to claim 5, wherein said current density is greater than 20 mA/cm.sup.2 or greater than 30 mA/cm.sup.2.

7. The method according to claim 4, wherein said temperature of said galvanic bath is between 0 C. and 15 C.

8. The method according to claim 1, wherein said anodized layer is applied with a thickness between 20 m and 150 m.

9. The method according to claim 1, wherein said carrier consists of an aluminum alloy Al 99.5 or AlMg.sub.3.

10. The method according to claim 1, wherein a thickening layer is applied to said anodized layer as a high-temperature-resistant thickening layer, wherein said heating conductors are applied directly onto said thickening laver.

11. The method according to claim 2, wherein a thickening layer is applied to said additional insulation layer as a high-temperature-resistant thickening layer, wherein said heating conductors are applied directly onto said thickening layer.

12. The method according to claim 10, wherein said thickening layer has a thickness between 10 m and 100 m.

13. The method according to claim 1, wherein said at least one heating conductor is applied above said anodized layer in a thin-film method or in a thick-film method.

14. A heating device with a carrier and at least one heating conductor applied thereto that has been manufactured with a method according to claim 1, wherein said heating device has: said carrier with a heating conductor side, wherein said carrier consists of aluminum, an anodized layer on said heating conductor side, wherein said anodized layer is generated directly on said carrier or onto said heating conductor side, at least one said heating conductor above said anodized layer.

15. The heating device according to claim 14, wherein an additional insulation layer is applied to said anodized layer.

16. The heating device according to claim 15, wherein said additional insulation layer is applied directly onto said anodized layer.

17. The heating device according to claim 15, wherein said additional insulation layer is generated and applied by thermal spraying as an aluminum oxide layer.

18. The heating device according to claim 14, wherein said carrier consists of an aluminum alloy Al 99.5 or of AlMg.sub.3.

19. The heating device according to claim 14, wherein a thickening layer is applied to said anodized layer as a high-temperature-resistant thickening layer.

20. The heating device according to claim 15, wherein a thickening layer is applied to said additional insulation layer.

21. The heating device according to claim 19, wherein said heating conductors are applied directly to said thickening layer.

22. The heating device according to claim 19, wherein said thickening layer has a thickness between 10 m and 100 m.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Examples of the invention are shown schematically in the drawings and are explained in more detail in the following. The drawings show in:

[0021] FIG. 1 a plan view onto a heating device in accordance with the invention with an anodized layer on a carrier of aluminum, to which a heating conductor is applied,

[0022] FIG. 2 a sectional view through a heating device similar to FIG. 1, showing the anodized layer on top of the carrier and an additional thickening layer between the anodized layer and the heating conductor,

[0023] FIG. 3 a schematic view of a method for manufacturing the anodized layer in a galvanic bath,

[0024] FIG. 4 a schematic view of a method for application of an additional insulation layer to the anodized layer by thermal spraying and

[0025] FIG. 5 a further possible method step with application of a thickening layer to the anodized layer or the additional insulation layer by means of a spraying device.

DETAILED DESCRIPTION OF THE EXAMPLES

[0026] FIG. 1 shows a plan view onto a heating device 11 in accordance with the invention. The heating device 11 has a carrier 13, advantageously consisting of a pure or ultrapure aluminum alloy, for example Al99.5 or AlMg3. The carrier 13 is flat and rectangular, but may also have any other shape.

[0027] An anodized layer 16 shown hatched is applied to the carrier 13 and/or its upward-facing heating conductor side over the full surface. It insulates the carrier 13 and/or its heating conductor side in the same way as an electrical insulation layer. A heating conductor 21 can then be applied directly to this anodized layer 16, advantageously as a thick-film heating conductor using a standard method, in particular a screen printing method. The heating conductor 21 has a meandering form and can be electrically connected by means of two contact fields 22a and 22b in known manner. This corresponds of course to the known prior art. The anodized layer 16 thus provides sufficient electrical insulation between the heating conductor 21 and the contact fields 22a and 22b on the one hand and the metallic carrier 13 on the other. The anodized layer can also have a thickness as stated at the outset, for example around 50 m.

[0028] FIG. 2 shows a sectional view through a somewhat modified heating device 111. Here too a flat carrier 113 made from an aforementioned aluminum alloy is provided, for example with a thickness of 0.5 mm to 5 mm. An anodized layer 116 is generated on an upward-facing heating conductor side 114 of the carrier 113 as electrical insulation. This anodized layer 116 however not only builds up on the heating conductor side and/or upper side of the carrier 113, but also effectively penetrates into this upper side with a penetration depth 117, shown hatched. This can be several micrometers thick and be up to half the thickness of the anodized layer 116. The anodized layer 116 consists in known manner of aluminum oxide, and during its growth the aluminum on the upper side and/or heating conductor side 114 is converted into aluminum oxide and hence into the anodized layer 116 itself.

[0029] A thickening layer 119 as explained at the outset is applied to the anodized layer 116. This is advantageously a sol-gel layer which is also high-temperature-resistant like the anodized layer 116 itself. It can be generated in the aforementioned manner, and can consist for example of a mixture of aluminum oxide and titanium dioxide, or alternatively of chromium oxide, zirconium oxide or magnesium oxide. Its thickness can be lower than that of the anodized layer 116, for example only half as thick, i.e. around 50 m.

[0030] A heating conductor 121 is in turn applied as previously described to the thickening layer 119, advantageously once again by means of a screen printing method as a thick-film heating conductor.

[0031] FIG. 3 shows how an anodized layer in accordance with the invention can be applied to a tubular carrier 213. To do so, the tubular carrier 213 is completely immersed in a container 24 with a galvanic bath 25 therein, advantageously of aqueous sulfuric acid. The galvanic bath 25 can be kept at an advantageously low temperature, for example at 5 C. constant, by means of a cooling device 27 having cooling coils 28. A voltage source 31 is connected on one side to an electrode 30 in the galvanic bath 25 and on the other side to the carrier 213 in electrically conductive manner. It can thus be achieved by applying such a voltage that a current density of around 40 mA/cm2 to 60 mA/cm2 is applied or a corresponding current flows. In a period from 30 mins to 60 mins, an anodized layer then grows as a hard anodized layer on the carrier 213, in this case on the inside and outside, or wherever the carrier 213 is immersed into the galvanic bath 25. This galvanization process is known and can be easily implemented. By suitable masking of at least part of the surface of the carrier 213, growth of an anodized layer there can be prevented.

[0032] FIG. 4 shows an alternative method for applying an additional insulation layer to a rectangular carrier 13 according to FIG. 1 and/or to its hard anodized layer or normal anodized layer by means of thermal spraying. A plasma spraying device 33 is provided that applies aluminum oxide as plasma 35 in known manner to the heating conductor side 14. To do so, the plasma spraying device 33 can be moved accordingly over the carrier 13, or alternatively the carrier 13 can be moved relative to the plasma spraying device 33. The aluminum oxide of the plasma 35 hitting the heating conductor side 14 grows there as an additional insulation layer.

[0033] FIG. 5 shows how a sol-gel sealant 38 is sprayed by means of a spraying device 37 onto an anodized layer 116, corresponding to the heating device 111 of FIG. 2b. It forms a previously described thickening layer 119 on the anodized layer 16. It can fill possible pores or cracks in the anodized layer 116 and hence effect a dependable electrical insulation of the electrically conductive aluminum carrier 113. Furthermore, it forms in simple manner an additional electrically insulating layer and thus additionally improves the electrical insulation of the aluminum carrier 113, in particular against the heating conductor 121.