Method for manufacturing a contact plate for a heating element, as well as contact plate and heating element

Abstract

Method for manufacturing a contact plate (3) for a heating element, wherein the contact plate (3) is manufactured from a strip of aluminium by in the strip compartments (7) for receiving ceramic heating resistors (2) are formed on a front side by forming, characterized in that the front and back of the strip are provided with an anodized layer (4), the anodized layer (4) in the compartments (7) of the strip is removed by means of a laser, and The front and back of an end section of the strip are not provided with the anodized layer (4).

Description

[0001] The invention relates to a method for manufacturing a contact plate for a heating element, as well as a contact plate and a heating element with such a contact plate. A method with the features specified in the preamble of claim 1 is known from DE 10 2009 039 099 A1.

[0002] Heating elements are used for auxiliary heating systems in automobiles. In such heating devices, sheet metal fins can be attached to the heating elements as heat sinks. Heating elements can also be integrally designed with heat sinks, as is known, for example, from DE 10 2009 013 927 A1.

[0003] In some heating elements, the heating resistors are held within the housing by an electrically insulating frame and electrically contacted by a contact plate that protrudes from the housing. The contact plate is electrically insulated from the housing by an insulating plate.

[0004] From DE 10 2013 111 811 A1, a heating element is known in which the contact plate has projections that define compartments for ceramic heating resistors. Furthermore, the back of this contact plate is covered by an anodized layer, which electrically insulates the contact plate from the housing. In this way, a frame and an insulating plate can be omitted, thus simplifying the construction of the heating element and saving costs.

[0005] Anodizing aluminum transforms the surface into an oxide layer, thus creating an electrical insulating layer. The anodizing of aluminum sheets is sometimes also referred to as electrolytic oxidation, anodic oxidation, or anodizing.

[0006] The familiar contact plate is made from an aluminum strip, the front of which is covered by a protective layer during anodizing, for example, wax, lacquer, or a plastic film. To easily distinguish the anodized back of the strip from the electrically conductive front, which later contacts the heating resistors, the anodized back is colored.

[0007] The object of the present invention is to show a way in which a contact plate for a heating rod can be manufactured with less effort.

[0008] This problem is solved by a method having the features specified in claim 1. Advantageous embodiments of the invention are the subject of dependent claims.

[0009] According to the invention, during the manufacture of the contact plate, an aluminum strip is coated with an electrically insulating anodized layer on both its front side, which later makes electrical contact with the heating resistors, and its back side. In the area of ​​the recesses, which are defined by projections and designed to accommodate the heating resistors, the anodized layer is then removed. The effort involved in removing the anodized layer is significantly less than the effort involved in anodizing only one side and covering the other. The anodized layer can be removed from the recesses, for example, by laser or by grinding.

[0010] Preferably, the aluminum strip is first formed to create protrusions that define the compartments for the ceramic heating elements, and then anodized. However, it is also possible to anodize the aluminum strip first and then create the protrusions.

[0011] The protrusions for positioning the heating elements can be created, for example, by embossing them into the contact plate, perhaps as bumps. Another possibility is to cut tabs out of the contact plate and bend them to create protrusions. The protrusions can also be formed by bending over opposing edge sections of the contact plate, such as the longitudinal edges.

[0012] In a method according to the invention, the entire surface of the aluminum strip could be provided with an anodized layer. However, according to the invention, the front and back sides of an end section of the aluminum strip remain uncoated. This end section can then be advantageously used for electrically connecting the heating element without having to remove the anodized layer in this area through a further processing step.

[0013] As a general rule, the higher the operating voltage of the heating element, the greater the thickness of the anodized layer must be. For operating voltages of 12 volts, such as those supplied by the electrical system of a motor vehicle, an anodized layer with a thickness of at least 10 µm may suffice. Preferably, the anodized layer is at least 20 µm thick.

[0014] Further details and advantages of the invention are explained using an exemplary embodiment with reference to the accompanying drawings. These show: Fig. 1 a schematic longitudinal section of a heating element; Fig. 2 an isometric view of a contact plate with a heating resistor; Fig. 3 a top view of the contact plate; Fig. 4 a sectional view along the section line AA of Fig. 3; and Fig. 5 a section view along the section line BB of Fig. 3.

[0015] The in Fig. A heating element, schematically depicted in a sectional view, has a metal housing 1. The housing 1 is preferably a tube, for example, a square tube. One or more ceramic heating elements 2 are arranged in the housing 1. The heating elements 2 are preferably PTC heating elements, for example, based on barium titanate. The heating elements 2 are in contact with the front face of a contact plate 3, which projects from the housing 1. The contact plate 3 has an anodized back surface. The anodized layer 4 on the back surface provides electrical insulation of the contact plate 3 from the housing 1.

[0016] The heating resistors 2 are electrically contacted by the housing 1 on the side facing away from the contact plate 3. During operation, a heating current flows through the contact plate 3, the heating resistors 2, and the housing 1. The contact plate 3 is an aluminum sheet, for example, made of technically pure aluminum or an aluminum-based alloy, such as AlMg3. The housing 1 can also be made of aluminum.

[0017] After inserting the contact plate 3 and the heating resistors 2, the housing 1 can be pressed together to improve the thermal coupling of the heating resistors 2 to the housing 1.

[0018] The anodized layer 4 can have a thickness of more than 20 µm, for example 30 µm or more.

[0019] The in the Fig. The contact plate 3 shown in Figures 2 to 4 has projections 5, 6 on its front surface for positioning the heating resistors 2. These projections 5, 6 define compartments 7 in which the heating resistors 2 are seated; for example, the heating resistors 2 can be clamped in the compartments 7 between the projections 5, 6. The contact plate 3 was coated on its front and back surfaces with an anodized layer 4, which was subsequently removed from the front surface in the area of ​​the compartments 7, for example, by irradiation with intense laser light. Between the compartments 7, the front surface of the contact plate 3 is covered by the anodized layer 4.

[0020] One end section of the contact plate 3 is also free of the anodized layer 4, so that this end section can be used for electrically connecting the heating rod.

[0021] Some of the protrusions that define compartments for the heating resistors 2 can be tabs cut out of the contact plate 3 and positioned. For example, a U-shaped cut can be made in the contact plate 3, and the tab bounded by the U-shaped cut line can be positioned. Such protrusions are found in the Fig. 5 and Fig. 6 with the reference number 5.

[0022] Additionally, protrusions for positioning the heating resistors 2 can also be formed by bent edge sections of the contact plate 3. In the Fig. 5 and Fig.These projections are marked with the reference number 6. The heating resistors 2 can be clamped between the bent sections on the longitudinal edge of the contact plate 3. For this purpose, it is advantageous if the edge sections 6 are bent in an S-shape, so that the edge sections rest against the heating resistors 2 with a bend and the longitudinal edge of the contact plate 3 faces away from the heating resistors 2. In this way, the risk of damage to the heating resistors 2 by clamping forces of the contact plate 3 can be reduced.

Claims

[1] Method for producing a contact sheet (3) for a heating rod, wherein the contact sheet (3) is produced from a strip of aluminum by in which strips are formed by forming on a front side compartments (7) for receiving ceramic heating resistors (2), characterized by , that the front and back of the strip are provided with an anodized layer (4), the anodized layer (4) in the compartments (7) of the strip is removed by means of a laser, and The front and back of an end section of the strip are not provided with the anodized layer (4). [2] Method according to claim 1, characterized by that the compartments are defined by projections (5, 6), at least some of the projections being tabs cut out of the strip and bent out. [3] Method according to one of the preceding claims, characterized bythat the compartments are defined by projections (5, 6), at least some of the projections being bent edge sections of the strip. [4] Method according to one of the preceding claims, characterized by that the strip clamps the ceramic heating resistors (2) in the compartments. [5] Method for producing a heating rod, wherein a contact sheet is produced according to one of the preceding claims, ceramic heating resistors (2) are placed in the compartments (7) of the contact sheet (3) and covered by a contact element. [6] Method according to claim 5, characterized by that the contact element is part of a housing (1), preferably a housing wall.

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