EP2009648A1 - Heating and/or cooling device with multiple layers - Google Patents

Abstract

A surface of electroconductive material (18) is applied. The resulting layer (14) is initially not in the desired form. Partial local removal (24) produces an electrically conducting, resistive layer (26) of the desired form. An independent claim is included for a heating and/or cooling unit made as described.

Description

The invention initially relates to a method for producing an electrically conductive resistance layer, in which an electrically conductive material is applied by means of thermal spraying on a non-conductive substrate.

Such a method is from the DE 198 10 848 A1 known. In this a heating element is described, which is produced by applying band-shaped layers of an electrically conductive and a resistance-forming material on surfaces of a substrate by means of arc sputtering or by plasma spraying. In order to achieve the desired shape of the electrically conductive layer, a release liner is previously applied to the substrate by means of a printing process. The separating layer is made of such a material that in those places of the Substrate on which the separation layer is present, the electrically conductive material does not adhere.

The known method has the disadvantage that it is relatively complicated and therefore the parts with the electrically conductive resistance layers are relatively expensive. In addition, only more or less flat parts can be provided with an electrically conductive layer with the known method.

The present invention therefore has the object of developing a method of the type mentioned so that the production of an electrically conductive layer on a substrate easier and cheaper possible and also complex shaped objects can be provided with such an electrically conductive resistance layer.

This object is achieved in a method of the type mentioned above in that the electrically conductive material is applied in such a way that a resulting material layer initially has substantially no desired shape and then the material layer is partially removed in such a way that an electrically conductive resistance layer arises, which has essentially the desired shape.

In the method according to the invention, no special pre-treatment is required to obtain the desired shape of the electrically conductive resistance layer. Instead, first the electrically conductive material of which the resistance layer is made, is applied flat and generally uniformly on the non-conductive substrate. The application by means of thermal spraying ensures a high adhesion of the electrical conductive material on the non-conductive substrate. In addition, a variety of materials can be applied quickly and very evenly in this way on the non-conductive substrate.

Thereafter, the applied electrically conductive material is removed at certain points by means of a suitable device. As a result, a complex shaping of the electrically conductive layer is made possible in only two steps.

Advantageous developments of the invention are specified in subclaims.

First, it is proposed that the partial removal of the material layer takes place by means of laser radiation or by means of a water jet or by means of a powder sandblast.

When using laser radiation, the material is heated so much that it evaporates. The use of a laser beam has the advantage that with him very quickly very high energies can be coupled into the electrically conductive material, so that it evaporates immediately. This instantaneous evaporation of the electrically conductive material ensures that only comparatively little heat is coupled into the substrate present under the electrically conductive material. This is therefore not damaged in the method according to the invention. The evaporation has the advantage over incineration that essentially no residues remain in the evaporated areas on the substrate and so their insulation is very good.

By a corresponding optics of the device, which the Laser beam emits, this can be directed in almost any way on the workpiece to be produced. Thus, on the one hand, arbitrarily complex contours can be evaporated out of the sprayed-on electrically conductive material, so that correspondingly complexly contoured electrical resistance layers can be produced. On the other hand, however, also such workpieces can be processed, which are themselves three-dimensionally complex. In a total of only two steps, an electrically conductive resistance layer with complex geometry can thus be produced.

When using a water jet, no thermal energy is coupled into the workpiece at all. This is particularly advantageous in the processing of heat-sensitive plastics. The same applies to the use of powder sandblasting.

In another particularly preferred development of the method according to the invention, it is proposed that the electrical resistance of the electrically conductive resistance layer is detected at least indirectly during the area-wise removal of the material layer. In this way, a precise quality control is already possible directly during the production of the electrically conductive layer.

In a further development, it is proposed that an actual value of the electrical resistance of the electrically conductive resistance layer is compared with a desired value and the electrical resistance of the electrically conductive layer is changed by removal of additional electrically conductive material in regions such that the difference between the actual value and the desired value is reduced. This has the advantage that already during production the electrically conductive layer deviations from a desired resistance can be compensated.

Such deviations may, for example, be caused by the fact that different amounts of the electrically conductive material reach the substrate during spraying of the thermally conductive material so that the resulting electrically conductive layer has a different thickness at one point than at another location. With the method proposed here, deviations of the actual value of the electrical resistance of the electrically conductive layer from the desired value can be compensated for with an accuracy of +/- 1%. The partial removal of additional electrically conductive material may include a shortening or lengthening of the electrically conductive layer and / or the variation of the width of the electrically conductive layer.

It is again particularly advantageous if the detection of the actual value of the electrical resistance of the electrically conductive resistance layer and the reduction of the difference between the actual value and the desired value take place in parallel. This is possible since the electrical resistance of the electrically conductive layer can already be measured during the processing of the electrically conductive layer by means of laser radiation. If this method according to the invention is used, time and thus money can be saved in the production of the electrically conductive resistance layer.

In one embodiment of the method according to the invention, it is also proposed that the material layer is removed in such a way that a desired melting point in the sense of a fuse is produced at at least one point of the electrically conductive layer. Such integrated fuse increases the safety when using the electrically conductive resistance layer. In this case, the fuse can be integrated into the electrically conductive resistance layer virtually without additional costs and additional time.

It is also advantageous if the material layer is removed in such a way that the electrically conductive resistance layer is at least partially meandering. This allows the formation of the longest electrically conductive resistive layer on a small area.

It is also proposed that, after the removal of the electrically conductive material in regions and the completion of the electrically conductive resistance layer, a nonconductive intermediate layer is applied thereto, then an electrically conductive material is applied by means of thermal spraying to the nonconductive intermediate layer in such a way that a resulting therefrom Material layer initially essentially has no desired shape, and then by means of laser radiation, the material layer is partially removed in such a way that a second electrically conductive layer is formed, which has the desired shape. According to the invention, it is thus possible to arrange several layers one above the other. It should be expressly pointed out at this point that the inventive method is applicable not only for the formation of two superposed electrically conductive resistance layers, but for any number of superimposed resistive layers.

The electrically conductive material preferably comprises bismuth, tellurium, germanium, silicon and / or Gallium arsenide. These materials have proved to be particularly favorable for the application by means of thermal spraying and the subsequent processing by means of laser radiation. In addition, with these materials, the relevant known technical effects can be realized.

Plasma spraying, high-speed flame spraying, arc spraying, autogenous spraying, laser spraying or cold gas spraying has proved to be advantageous for the application of the electrically conductive material to the substrate.

It is also proposed that the electrically conductive material is applied in this way and the material layer is partially removed in such a way and comprises such a material that an electrical heating or an electrical cooling layer is formed. In the production of an electrical cooling layer, the "Peltier effect" is advantageously utilized.

In an advantageous embodiment, it is also proposed that the local electrical resistance of the electrically conductive resistance layer is adjusted by a local heat treatment. By heating locally oxides can be registered in the layer, which has an effect on the local electrical conductivity of the material. This allows a special precise and fine adjustment of the electrical resistance.

In addition, it is favorable if the electrically conductive resistance layer is sealed. This has advantages in particular with a porous substrate (for example metal with Al 2 O 3 intermediate layer). Sealing reduces the risk of electrical breakdown due to Humidity, especially at high voltage. As a material for sealing silicone, polyimide, or water glass, the latter on sodium or potassium-based. The application can be done by dipping, spraying, brushing, etc. The seal of the seal is best when the sealant layer is applied under vacuum.

As a non-conductive substrate is also glass or glass ceramic in question. Then the electrical resistance layer can be applied permanently, especially by plasma spraying. The good insulating effect of glass makes grounding in the operation of the resistive layer superfluous. Also possible is the use of special high-temperature glass, such as Ceranglas (R).

The invention also relates to a heating and / or cooling device with a non-conductive substrate and an applied to the substrate by thermal spraying electrically conductive resistance layer.

The production costs for such a heating and / or cooling device can be reduced if the resistance layer comprises an electrically conductive material initially applied by thermal spraying, which was then removed in regions by means of laser radiation and thus brought into a desired shape.

The following are particularly preferred

Figur 1

eine perspektivische Darstellung eines Rohres, auf welches ein elektrisch leitendes Material aufgespritzt wird;

Figur 2

das Rohr von Fig. 1, dessen elektrisch leitende Materialschicht mittels Laserstrahlung bearbeitet wird;

Figur 3

eine Seitenansicht des Rohres von Fig. 2 nach der Bearbeitung;

Figur 4

eine Draufsicht auf ein plattenförmiges Teil mit einer mäanderförmigen elektrisch leitenden Widerstandsschicht;

Figur 5

zwei Diagramme, wobei im einen Diagramm der zeitliche Verlauf des elektrischen Widerstands und im anderen Diagramm der zeitliche Verlauf der Länge der elektrisch leitenden Widerstandsschicht von Fig. 4 während ihrer Herstellung dargestellt sind; und

Figur 6

einen Schnitt durch ein plattenförmiges Teil mit zwei übereinander angeordneten elektrisch leitenden Widerstandsschichten.

Embodiments of the invention with reference to the accompanying drawings explained in detail. In the drawing show:

FIG. 1

a perspective view of a tube, on which an electrically conductive material is injected;

FIG. 2

the pipe of Fig. 1 whose electrically conductive material layer is processed by means of laser radiation;

FIG. 3

a side view of the tube of Fig. 2 after processing;

FIG. 4

a plan view of a plate-shaped part with a meandering electrically conductive resistance layer;

FIG. 5

two diagrams, wherein in one diagram, the time course of the electrical resistance and in the other diagram, the time course of the length of the electrically conductive resistance layer of Fig. 4 are shown during their manufacture; and

FIG. 6

a section through a plate-shaped part with two superimposed electrically conductive resistance layers.

In the Figures 1 and 2 shows the production of a tubular water heater: In this case, an electrically conductive material layer 14 is applied to a tube 12 made of a high-temperature resistant and an electrical insulator material ( Fig. 1 ). The application takes place in the present exemplary embodiment by means of a device 16, with which germanium particles 18 are sprayed onto the tube 12. The application is carried out by cold gas spraying (also "gas-dynamic Powder coatings called ").

In this injection process, the unmelted germanium particles are accelerated to speeds of about 300 - 1,200 m / s and sprayed onto the tube 12. Upon impact with the tube 12, the germanium particles 18 and also the surface of the tube 12 deform. The impact breaks up surface oxides on the surface of the tube 12. Micro-friction due to the impact increases the temperature at the contact surface and leads to micro-welds.

The acceleration of the germanium particles 18 takes place by means of a delivery gas, the temperature of which can be slightly increased. However, since the germanium powder 18 in no case reaches its melting temperature, the temperatures arising at the surface of the tube 12 are relatively moderate, so that, for example, a comparatively inexpensive plastic material for the tube 12 can be used.

In other embodiments, not shown, plasma spraying, high-speed flame spraying, arc spraying, autogenous spraying or laser spraying for applying the electrically conductive material to the substrate can also be used instead of the cold gas spraying. Instead of germanium, bismuth, tellurium, silicon and / or gallium arsenide are also suitable, depending on the desired technical effect.

The coating of the tube 12 with the germanium particles 18 is carried out initially so that gradually the entire surface of the tube 12 is covered with the germanium material layer 14 (see. Fig.1 ). However, this material layer 14 does not yet have the desired shape: To produce a tubular water heater can, an electrically conductive resistance layer must be made, which extends in the manner of a spiral in the circumferential direction around the tube 12. This will, as out Fig. 2 It can be seen, by means of a laser device 20, a laser beam 22 directed to the still "shapeless" material layer 14, that a spirally around the tube 12 extending portion 24 is created in which the sprayed electrically conductive material 14 is no longer present.

This happens because the material of the material layer 14 at the location where the laser beam 22 strikes the layer 14 is suddenly heated so strongly that it evaporates. The laser device 20 on the one hand and a device, not shown in the figure, with which the tube 12 is held, are thereby moved so that a continuous working process by the laser device 20 is possible.

How out Fig. 3 As can be seen, thereby extending from one axial end of the tube 12 to the other and extending spirally extending in the circumferential direction electrically conductive resistance layer 26 is provided. The tube 12 and the electrically conductive resistance layer 26 form a total of an electric water heater 28th

• Zunächst ist an dem in Fig. 4 oberen Ende die Materialschicht 14, aus der die elektrisch leitende Widerstandsschicht 26 hergestellt ist, so abgedampft worden, dass die Leiterbahn 26 eine Querschnittsverengung aufweist. Hierdurch wird eine Schmelzsicherung 30 geschaffen, durch welche der Betrieb der Heizplatte 28 abgesichert wird.

FIG. 4 shows in plan view a flat heating plate 28. This consists of a non-visible in this plan view non-conductive ground, on the analogous to that in the FIGS. 1 and 2 described first, a sheet-like material layer 14 has been applied, were subsequently evaporated from the areas 24 by means of a laser beam (for illustrative purposes, only one area 24 provided with reference numerals). This resulted a meandering from one end to the other end of the plate 28 extending electrically conductive resistance layer 26. However, this has two peculiarities:

• First, at the in Fig. 4 upper end of the material layer 14, from which the electrically conductive resistance layer 26 is made, has been evaporated so that the conductor track 26 has a cross-sectional constriction. As a result, a fuse 30 is provided, through which the operation of the heating plate 28 is secured.

• An Endbereiche 32 und 34 der elektrisch leitenden Widerstandsschicht 26 wird während des Abdampfens der Bereiche 24 eine elektrische Spannung angelegt, so dass während dieses Abdampfens der elektrische Widerstand der elektrisch leitenden Schicht 26 kontinuierlich gemessen werden kann. Mit dem Laserstrahl wird dabei die Materialschicht 14 nur in zunächst sehr schmalen Bereichen 24 abgedampft. Die in Fig. 4 horizontal verlaufenden abgedampften Bereiche 24 verlaufen also zunächst nur von einem in Fig. 4 gestrichelt dargestellten Rand 36 bis zu dem darüber liegenden horizontalen Rand 38 der elektrisch leitenden Widerstandsschicht 26 (auch hier ist aus Darstellungsgründen nur in einem Bereich 24 das entsprechende Bezugszeichen eingetragen). Darüber hinaus wird die Materialschicht 14 zunächst vom Laserstrahl so bearbeitet, dass der in Fig. 4 untere elektrische Endbereich 34 relativ breit ist. Dies ist ebenfalls durch eine gestrichelte Linie mit dem Bezugszeichen 40 dargestellt.

A second special feature is that the heating power or the heat flux density of the electrically conductive resistive layer was corrected during its production so that it corresponds to the desired heat output and the desired heat flux density with very high precision. This happens in the following way:

• At the end regions 32 and 34 of the electrically conductive resistance layer 26, an electrical voltage is applied during the evaporation of the regions 24, so that the electrical resistance of the electrically conductive layer 26 can be continuously measured during this evaporation. With the laser beam while the material layer 14 is evaporated only in initially very narrow regions 24. In the Fig. 4 horizontally extending evaporated areas 24 thus initially run only from one in Fig. 4 Dashed edge 36 shown up to the overlying horizontal edge 38 of the electrically conductive resistance layer 26 (here, too, for representation reasons, only in a region 24, the corresponding reference number entered). Furthermore the material layer 14 is first processed by the laser beam so that the in Fig. 4 lower electrical end region 34 is relatively wide. This is also shown by a dashed line by the reference numeral 40.

In the present embodiment, it is found during the evaporation of the regions 24 from the material layer 14 by resistance measurement of the resulting layer 26, that the actual electrical resistance WIST (see. Fig. 5 ) of the electrically conductive resistance layer 26 is less than the desired per se electrical resistance WSOLL. The in Fig. 4 The lower connecting region 34 of the electrically conductive resistance layer 26 is therefore processed by the laser beam so that its width decreases, so that additional material is evaporated. As a result, the electrically conductive resistance layer 26 extends by a dimension d1 (cf. Fig. 4 and 5 ) and, as a result, the actual electrical resistance WIST increases until it approximately corresponds to the desired resistance WSOLL. The final position of the boundary line of the lower electrical connection 34 carries in Fig. 4 the reference numeral 42.

In order to adjust the heat flow density, the in Fig. 4 horizontal evaporated areas 24 enlarged. The final boundary, in which the electrically conductive resistance layer 26 has the desired heat flow density contributes Fig. 4 the reference numeral 44 (for illustrative purposes, this reference numeral is also entered only at a vaporized area 24).

• Zunächst wird wie bei den obigen Ausführungsbeispielen ein elektrisch leitendes Material auf einen plattenförmigen Träger 12 aufgebracht. Die,Aufbringung erfolgt dabei flächig durch thermisches Spritzen in einer Art und Weise, dass die hieraus entstehende Materialschicht zunächst im Wesentlichen noch keine gewünschte Form aufweist. Anschließend wird mittels Laserstrahlung die Materialschicht bereichsweise (Bezugszeichen 24a) derart abgedampft, dass eine elektrisch leitende Widerstandsschicht 26a erzeugt wird, welche die gewünschte Form aufweist.

In Fig. 6 a plate-shaped heater is shown in section. Unlike the ones described above Embodiments, it includes not only an electrically conductive resistance layer, but two electrically conductive resistance layers 26a and 26b. Between these an electrically non-conductive intermediate layer 46 is present. The production of this electric heating plate 28 takes place as follows:

• First, as in the above embodiments, an electrically conductive material is applied to a plate-shaped carrier 12. The, application takes place surface by thermal spraying in such a way that the resulting material layer initially has substantially no desired shape. Subsequently, the material layer is partially evaporated by laser radiation (reference numeral 24a) in such a way that an electrically conductive resistance layer 26a is produced, which has the desired shape.

On the finished electrically conductive resistance layer 26a, the electrically insulating intermediate layer 46 is applied in the further course of the manufacturing process. Then the process described above is repeated, i. H. again electrically conductive material is applied by means of thermal spraying onto the non-conductive intermediate layer 46 in such a way that a second material layer formed therefrom substantially does not yet have the desired shape. This is then processed by laser radiation and partially evaporated (reference numeral 24b) such that a second electrically conductive resistance layer (26b) is formed in the desired shape.

In an embodiment not shown, the material of the electrically conductive layer is selected such that instead of an electrical heating layer, an electrical cooling layer is formed.

In another embodiment, not shown, the temperature of the heating layer is monitored by a ceramic switch. This is understood to mean a non-mechanical switch which has an element whose conductivity depends to a considerable extent on its temperature. Alternatively, a bimetal switch can be used.

Claims (16)

A multi-layer heating and / or cooling device (28) applied by thermal spraying, said layers comprising a nonconductive substrate (12), an electrically conductive resistive layer (26; 26a; 26b) and an electrical insulating layer (46) characterized in that the electrically conductive resistive layer (26; 26a; 26b) is applied to the nonconductive substrate (12) and comprises an electrically conductive material (14) initially by plasma spraying, high velocity flame spraying, arc spraying, autogenous spraying, laser spraying or cold gas spraying is applied and then partially removed so that a desired shape is formed, and the electrical insulating layer (46) on the electrically conductive resistance layer (26; 26a, 26b) is applied. Heating and / or cooling device (28) according to claim 1, characterized in that it comprises a plurality of electrically conductive resistance layers (26; 26a; 26b) separated by a corresponding plurality of non-conductive intermediate layers (46). Heating and / or cooling device (28) according to one of claims 1 or 2, characterized in that the desired shape is locally adapted to provide desired electrical properties along the mold. Heating and / or cooling device (28) according to any one of the preceding claims, characterized in that the non-conductive substrate (12) is a glass material is. Heating and / or cooling device (28) according to one of the preceding claims, characterized in that the electrically conductive resistance layer (26; 26a; 26b) consists of a material containing bismuth, tellurium, germanium, silicon and / or gallium arsenide. Heating and / or cooling device (28) according to one of the preceding claims, characterized in that the regions of the electrically conductive material (14) have been removed by means of a laser and / or by means of a water jet and / or by means of a powder sandblast. Heating and / or cooling device (28) according to any one of the preceding claims, characterized in that during the removal of the electrically conductive material (14) to obtain the desired shape, an actual electrical resistance (WIST) of the mold is determined. Heating and / or cooling device (28) according to claim 7, characterized in that the actual electrical resistance (WIST) of the mold has been compared with a nominal resistance (WSOLL) and certain areas of the electrically conductive material (14) have been removed, to reduce the difference between the actual electrical resistance (WIST) and the nominal electrical resistance (WIST). Heating and / or cooling device (28) according to claim 8, characterized in that the determination of the electrical actual resistance (WIST) of the mold and the Removing the material to reduce the difference between the actual electrical resistance (WIST) and the nominal electrical resistance (WSOLL) was performed in parallel. Heating and / or cooling device (28) according to any one of the preceding claims, characterized in that at least one of the layers has been applied under vacuum. Heating and / or cooling device (28) according to one of the preceding claims, characterized in that the areas of the electrically conductive material (14) have been removed by a laser so that no residues remain where removed, so that the insulating effect is improved. Heating and / or cooling device (28) according to any one of the preceding claims, characterized in that by a micro friction due to impact during the thermal spraying, the temperature increases and leads to a micro-welding of the thermally sprayed particles. Heating and / or cooling device (28) according to one of the preceding claims, characterized in that the size of the region (24) of the removed electrically conductive resistance layer (26; 26a; 26b) is increased in order to set a heat flux density. Heating and / or cooling device (28) according to one of the preceding claims, characterized in that the temperature of the electrically conductive resistance layer (26; 26a; 26b) is monitored by a ceramic switch. Heating and / or cooling device (28) according to one of the preceding claims, characterized in that a thickness of the resulting electrically conductive resistance layer (26; 26a; 26b) differs from one location to another. Heating and / or cooling device (28) according to any one of the preceding claims, characterized in that at least a portion of the electrically conductive resistance layer comprises a desired melting point in the sense of a fuse.

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