Coolable resistor, braking resistor, and method for producing a coolable resistor

Abstract

A coolable resistor (W) is disclosed. The coolable resistor has a cooling element (1), through which a coolant can flow, and at least one resistor element (2, 2'), which is applied flat to a surface of the cooling element (1), the resistor element (2, 2') and the cooling element (1) being designed to be connected by means of a non-heat-generating connection method.

Description

[0001] DESCRIPTION

[0002] Coolable resistor, brake resistor, and method for producing a coolable resistor

[0003] The present application relates to a coolable resistor and a method for manufacturing a coolable resistor, wherein the coolable resistor is in particular a resistor for use as a braking resistor.

[0004] In the field of drive technology, particularly in commercial vehicles, excess braking energy can be converted into braking resistors. For example, the vehicle's kinetic energy is converted into electrical energy by a regenerative brake (in generator mode for drive motors). If this energy cannot be used elsewhere, such as being stored in a fully charged battery, it is converted into a liquid-cooled braking resistor. The resistor then acts as a consumer, converting electrical energy into heat. This heat must then be dissipated to prevent the braking resistor from overheating.

[0005] Document DE 10 2021 202 037 A1 discloses a liquid-cooled braking resistor, which is constructed from several shaped sheets. The shaped sheets have a first side and a second side, and two shaped sheets are joined together at their edges by means of beads, for example by welding, to form a cooling element. Each shaped sheet has a pre-printed insulation and an electrically conductive device, namely a resistive layer, on one side, which is then baked on.

[0006] The fundamental problem is that firing the resistive layer of a resistance element, applied to the molded sheets via screen printing, requires a relatively large amount of heat, as the molded sheets themselves must also be heated accordingly, which increases production costs. Furthermore, the workflow, which involves prior printing of the electrically conductive device or resistance element onto the molded sheets to form a cooling element, can sometimes present additional, various problems.

[0007] If the sheet metal parts are welded before the resistance element is printed on, the problem may arise that the flatness accuracy required for screen printing cannot be achieved due to distortion during welding.

[0008] Otherwise, if the sheet metal components are welded after the resistance element has been printed on them, there is a risk that deformation of the elements forming the cooling element may occur during welding, potentially damaging the resistance element through cracking. Additionally, there is a risk that the resistance element could be damaged by excessive heat.

[0009] The object underlying the invention is therefore to eliminate the aforementioned disadvantages and to provide a coolable resistor that can be manufactured with lower energy consumption and lower manufacturing costs in the required quality.

[0010] The problem is solved by a coolable resistor according to claim 1, a braking resistor according to claim 10 and a method for manufacturing the coolable resistor according to claim 11.

[0011] According to one aspect of the invention, a coolable resistor comprises: a cooling element having a channel in which a coolant can flow, and at least one resistance element which can be applied over a surface of the cooling element, wherein the resistance element and the cooling element are connected by means of a non-heat-generating joining method.

[0012] The cooling element, through which the coolant flows, dissipates heat generated in the resistance element, which is mounted on a surface of the cooling element, by the electric current flowing through it. By manufacturing the resistance element as a separate component beforehand and connecting it to the cooling element using a non-heat-generating joining method, the risk of damage to the resistance element from heat input, such as the formation of cracks due to thermal stresses, is eliminated, thus ensuring the required quality.

[0013] According to an advantageous embodiment of the coolable resistor, the cooling element has several, in particular plate-shaped, wall elements, wherein at least one of the wall elements has a surface structure with a recess, and the wall elements are connected to one another in such a way that the recess forms a channel between the wall elements. In the case of the plate-shaped wall element, the recess is located on a surface, i.e., not on an end face of the plate.

[0014] In a further advantageous embodiment of the coolable resistor, the several wall elements are connected to each other by means of a material-bonded joining process, in particular by welding, or are formed in one piece.

[0015] According to an advantageous embodiment of the coolable resistor, the at least one resistive element has a carrier plate onto which a resistive layer is directly applied, wherein the resistive element optionally has an insulating layer for electrical insulation between the carrier plate and the resistive layer, and the resistive layer is then indirectly applied to the carrier plate.

[0016] In a further advantageous embodiment, the at least one resistance element is connected to the cooling element by means of rivets.

[0017] In a preferred embodiment, the at least one resistance element is connected to the cooling element by means of a thermally conductive connecting element. In a preferred embodiment, the connecting element includes an adhesive.

[0018] According to another aspect of the invention, a braking resistor for reducing braking energy converted into electrical energy is provided with a coolable resistor according to the invention.

[0019] According to another aspect of the invention, a method for producing a coolable resistor is provided comprising the steps of: providing a cooling element through which a coolant can flow; providing a resistance element that can be applied over a surface of the cooling element; applying the resistance element to the surface of the cooling element and connecting the cooling element and the resistance element by means of a non-heat-generating joining method.

[0020] In an advantageous embodiment of the method, the cooling element is produced by welding together several, in particular plate-shaped, elements, so that a channel is formed between them in which the coolant can flow.

[0021] In an advantageous further development of the method, the resistance element is produced by printing a resistance layer onto a carrier plate before being applied to the cooling element (1).

[0022] According to an advantageous further development of the method, an insulating layer for electrical insulation is applied between the resistance layer and the cooling element.

[0023] According to an advantageous further development of the method, the joining of the resistance element and the cooling element is carried out using a thermally conductive adhesive.

[0024] The invention is described below using embodiments with reference to the figure. In particular, it shows

[0025] Fig. 1 shows a coolable resistor according to the invention.

[0026] Fig. 1 shows a coolable resistor W that can be used as a braking resistor. The braking resistor serves to dissipate braking energy converted into electrical energy. The electrical energy is thereby converted into heat, which is then dissipated via a coolant.

[0027] The coolable resistor W comprises a cooling element 1 through which the coolant flows, as well as two resistance elements 2, 2'. In alternative embodiments, the coolable resistor W comprises only a single resistance element 2, 2' or more than two resistance elements 2, 2'.

[0028] The cooling element 1 in turn has two wall elements 3, 3'. Each of the two wall elements 3, 3' has a surface structure with a recess 4, 4', and the two wall elements 3, 3' are connected to each other such that a channel 5 is provided between the wall elements 3, 3' through the recesses 4, 4', in which the coolant can flow. In the illustrated embodiment, the wall elements 3, 3' are plate-shaped, so-called cooling plates; in an alternative embodiment, they can also be, for example, pipe-section-shaped.

[0029] The two elements 3, 3' are joined to each other by means of a material-bonded joining process, namely welding. Alternatively, the two elements 3, 3' can also be joined to each other by means of another material-bonded joining process, for example, soldering. In another alternative embodiment, the cooling element 1 is made of more than two elements or a single component, for example, a rectangular tube, with the channel 5.

[0030] The resistive elements 2, 2' each have a carrier plate 6, 6' onto which a resistive layer 7, 7' made of silver-containing, such as silver-palladium, or copper-containing materials is applied. The resistive layer 7, 7' is applied to the carrier plate 6, 6' by means of a screen printing process. In an alternative embodiment, the resistive layer 7, 7' can also be applied by means of another process, for example, spray or plasma spraying. The carrier plate 6, 6' is made of steel, and an electrically insulating layer 8, 8' is applied between the carrier plate 6, 6' and the resistive layer 7, 7', also by means of the screen printing process or, alternatively, by the spray process. This insulating layer 8, 8' consists of a single layer applied to the carrier plate 6, 6', but can alternatively consist of several layers. If the carrier plate 6, 6' is not made of steel orSince the insulating layer 8, 8' is made of a conductive material rather than an electrically insulating material, it can be omitted in this alternative embodiment. Optionally, the resistive layer is covered with a coating, for example, a lacquer.

[0031] The wall elements 3, 3' have a significantly greater thickness than the support plate 6, 6', so that the mass to be heated when firing a resistance layer 7, 7' applied directly to the wall elements 3, 3' would be significantly larger and thus a greater amount of energy would be required.

[0032] The resistive elements 2, 2' are connected to the cooling element 1 by means of a thermally conductive connecting element 9, 9' using a non-heat-generating joining method. This non-heat-generating joining method has the characteristic that no specific heat is generated by the process, or that no or only minimal heat input is required to establish a connection between the resistive elements 2, 2' and the cooling element 1, so that the components to be joined are not damaged or altered to such an extent that their function is no longer guaranteed. In the present embodiment, the connecting element 9, 9' includes an adhesive. In an alternative embodiment, the resistive elements 2, 2' can, for example, be attached to the cooling element 1 by rivets.

[0033] The resistive elements 2, 2' are applied to a flat surface of the cooling element 1 to enable heat transfer from the resistive elements 2, 2' to the cooling element 1. In an alternative embodiment, the surface of the cooling element 1 can also be curved, in which case the resistive elements 2, 2' must also have a curved surface to be applied in a flat manner.

[0034] In the production of the coolable resistor W, the cooling element 1 and the resistance elements 2, 2' are first provided.

[0035] The resistance elements 2, 2' are then applied over a flat surface to the cooling element 1 and the cooling element 1 and the resistance elements 2, 2' are connected to each other using the non-heat-generating joining method.

[0036] The cooling element 1, if it consists of several elements, here the plate-shaped wall elements 3, 3', is joined together by a material-bonded process, here by welding. The two plate-shaped elements 3, 3' are welded together in such a way that the channel 5 is formed by the recesses 4, 4', thus allowing the coolant to flow through the cooling element 1. In an alternative embodiment, the channel 5 is formed only within one of the wall elements 3, 3'.

[0037] The resistive elements 2, 2' are manufactured as separate components by applying the resistive layer 7, 7' to the carrier plate 6, 6' using the screen printing process. Alternatively, the resistive layer 7, 7' is applied to the carrier plate 6, 6' using a different method, namely spray or plasma spraying.

[0038] If the substrate 6, 6', as in this embodiment, is made of a conductive material, the electrically insulating layer 8, 8' is applied to the substrate 6, 6', either by a screen printing process or, alternatively, by spraying, before the resistive layer 7, 7' is indirectly applied to the substrate. However, if the substrate 6, 6' material itself is electrically insulating, the resistive layer 7, 7' can be applied directly to the substrate 6, 6'. Following the application of the resistive layer 7, 7' and, if applicable, the insulating layer 8, 8' to the substrate 6, 6', the resistive layer 7, 7' is cured.

[0039] By applying the resistive layer 7, 7' and the insulating layer 8, 8' to the substrate 6, 6' to form separate resistive elements 2, 2' instead of applying them to the wall elements 3, 3' of the cooling element 1, a high degree of planarity of the substrate 6, 6', which is advantageous for the printing process, can be achieved. Furthermore, it is not necessary to apply a larger amount of energy to fire the layers, since only a smaller mass of the substrate 6, 6' needs to be heated. Thus, it is possible to save energy during the manufacturing process.

[0040] The application of the resistance elements 2, 2', and in particular their connection, is carried out using the connecting element 9, 9' in a non-heat-generating joining process. By connecting the resistance elements 2, 2' to the cooling element 1 using this non-heat-generating joining process, the risk of damage to the resistance elements 2, 2' due to heat input, for example, through the formation of cracks due to thermal stresses, is eliminated. Furthermore, unlike applying the layers to the cooling element 1 by screen printing, it is not necessary to ensure a very high degree of flatness accuracy for the wall elements 3, 3', which in turn simplifies the production process and reduces costs.

[0041] Although the present invention has been described with reference to certain features and embodiments, it is obvious that various modifications and combinations can be made to it without departing from the invention as defined in the appended claims. Accordingly, the description and the drawings are to be regarded merely as an illustration of the invention as defined by the appended claims and are intended to cover all modifications, variations, combinations, or equivalents that fall within the scope of the present invention. LIST OF REFERENCE MARKS

[0042] 1 cooling element

[0043] 2.2' Resistance element 3.3' Wall element

[0044] 4.4' Depth

[0045] 5-channel

[0046] 6, 6' carrier plate

[0047] 7, 7' Resistance layer 8, 8' Insulation layer

[0048] 9, 9' Connecting element

[0049] W coolable resistor

Claims

PATENT CLAIMS 1. Coolable resistor (W) comprising: a cooling element (1) having a channel (5) in which a coolant can flow, and at least one resistance element (2, 2') designed to be able to generate heat and which can be applied over a surface of the cooling element (1), wherein the resistance element (2, 2') and the cooling element (1) are connected by means of a non-heat-generating joining method.

2. Coolable resistor (W) according to claim 1, wherein the cooling element (1) has several, in particular plate-shaped, wall elements (3, 3'), wherein at least one of the wall elements (3, 3') has a surface structure with a recess (4, 4'), and the wall elements (3, 3') are connected to each other in such a way that the channel (5) between the wall elements (3, 3') is formed by the recess (4, 4').

3. Coolable resistor (W) according to claim 2, wherein the multiple wall elements (3, 3') are connected to each other by means of a material-bonded joining process or are formed in one piece.

4. Coolable resistor (W) according to claim 3, wherein the multiple wall elements (3, 3') are connected to each other by welding.

5. Coolable resistor (W) according to one of the preceding claims, wherein the at least one resistive element (2, 2') has a carrier plate (6, 6') onto which a resistive layer (7, 7') is applied directly or indirectly.

6. Coolable resistor (W) according to claim 5, wherein the at least one resistive element (2, 2') between the carrier plate (6, 6') and the resistive layer (7, 7') has an insulating layer (8, 8') for electrical insulation.

7. Coolable resistor (W) according to one of the preceding claims, wherein the at least one resistor element (2, 2) is connected to the by means of rivets. Cooling element (1) is connected.

8. Coolable resistor (W) according to one of the preceding claims, wherein the at least one resistance element (2, 2') is cooled by means of a thermally conductive The connecting element (9, 9') is connected to the cooling element (1).

9. Coolable resistor (W) according to claim 8, wherein the connecting element (9, 9') comprises an adhesive.

10. Braking resistor for dissipating braking energy converted into electrical energy, comprising a coolable resistor (W) according to one of the preceding claims.

11. Method for producing a coolable resistor (W) comprising the steps of: providing a cooling element (1) through which a coolant flows; providing a resistance element (2, 2') which is placed on a surface of the Cooling element (1) can be applied over a surface; and Applying the resistance element (2, 2') to the surface of the cooling element (1 ) and joining the cooling element (1 ) and the resistance element (2, 2') using a non-heat-generating joining method.

12. Method according to claim 11, wherein the cooling element (1) is produced by welding together several, in particular plate-shaped, wall elements (3, 3'), such that a channel (5) is formed between them in which the coolant can flow.

13. Method according to one of claims 11 or 12, wherein The resistive element (2, 2') is produced by printing a resistive layer (7, 7') onto a carrier plate (6, 6') before being applied to the cooling element (1).

14. Method according to claim 13, wherein an insulating layer (8, 8') is applied between the resistive layer (7, 7') and the cooling element (1).

15. Method according to any one of claims 11 to 14 wherein the joining of the resistance element (2, 2') and the cooling element (1 ) is carried out by means of a thermally conductive adhesive.

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