Apparatus for a heating device for a vehicle

An apparatus for a heating device for a vehicle comprises a layer stack which, in a stacking direction, has a heating conductor layer, an electrically conductive layer which forms a contact region, wherein a contour in a projection in the stacking direction of the electrically conductive layer is prespecified, in order to prevent a hotspot on the electrically conductive layer, by at least one of a prespecified width of a front side of the electrically conductive layer which faces a central region of the heating conductor layer, a prespecified distance from a joint of the heating conductor layer, and a prespecified curvature of the contour.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national phase application filed under 35 U.S.C. § 371 of International Application No. PCT/EP2016/076150, filed Oct. 28, 2016, designating the United States, which claims priority from German Patent Application 10 2015 119 252.7, filed Nov. 9, 2015, which are hereby incorporated herein by reference in their entirety for all purposes.

FIELD

The invention relates to an apparatus for a heating device for a vehicle, in particular for an electrical heating device.

BACKGROUND

Heating devices are used in motor vehicles in order to heat the interior of the motor vehicle. In this respect, use is also made of electrical resistance heating devices. These comprise a heating conductor layer which heats up when an electrical voltage is applied. To this end, the heating conductor layer has to be electrically connected to a voltage source during operation.

It is desirable to specify an apparatus for a heating device for a vehicle which allows for reliable operation.

According to one embodiment of the invention, an apparatus for a heating device for a vehicle has a layer stack. The layer stack has a heating conductor layer. The layer stack has, in a stacking direction, an electrically conductive layer on the heating conductor layer. The electrically conductive layer forms a contact region, in particular a contact region for the heating conductor layer for the purpose of connection to a voltage source. A contour of the electrically conductive layer in a projection in the stacking direction is prespecified, in order to prevent a hotspot on the electrically conductive layer. The contour is prespecified by at least one of:

a prespecified width of a front side of the electrically conductive layer. The front side faces a central region of the heating conductor layer;

a prespecified distance from a joint of the heating conductor layer; and

a prespecified curvature of the contour.

The width, the distance and/or the curvature are prespecified such that a sufficiently low current density is achieved at the contact region during operation even with a current flow of, for example, 10 amperes or more, for example up to 20 amperes or up to 30 amperes. Therefore, it is possible to keep temperatures which occur on the electrically conductive layer below a prespecified maximum value during operation. The prespecified maximum value is, for example, 250° C. According to further embodiments, the prespecified maximum value is, for example 200° C. or 195° C.

SUMMARY

In particular, the width, the distance and the curvature are prespecified depending on one another such that the maximum value for the temperature is not exceeded or is not exceeded for a relatively long period of time during operation. Therefore, it is possible to prevent hotspots by means of the prespecification for the contour. Preventing a hotspot means, in particular, that the temperatures remain below the maximum value for the temperature during operation in the immediately adjacent regions of the electrically conductive layer.

By way of example, the width is prespecified to be as large as possible but preferably only wide enough that the prespecified distance is still maintained. The curvature is, for example, prespecified depending on the width and prespecified distance. The width and the curvature are prespecified, in particular, such that the contact region extends in the direction of a conductor track of the heating conductor layer.

Since the contour of the electrically conductive layer is prespecified by the width, the distance and/or the curvature, it is possible to prevent a hotspot at which temperatures occur which are so large that they can have an adverse effect on the reliable operation of the heating device.

According to embodiments, in the projection in the stacking direction along the front side, the prespecified curvature is prespecified by means of two prespecified radii, which are different from one another, for the front side. Therefore, it is possible, in particular, to form a region of the front side, which region is central in the projection, with a relatively large radius. By way of example, the central region of the front side approximates a straight line. The two side regions have a relatively small radius, and therefore are more severely curved. As a result, the contact region is routed in the direction of the conductor track of the heating conductor layer. The contact region is formed such that it has a projecting region in the direction of a current flow which flows from the contact region to the heating conductor layer during operation. As a result, it is possible that the field lines of the electrical field which is produced during operation are concentrated as little as possible and therefore a low current density is realized.

According to embodiments, the the front side has, in the projection in the stacking direction, a straight section. In particular, the straight section is arranged in a central region of the front side. According to embodiments, the curved regions which have one or more prespecified radii are provided on either side of the straight section.

According to further embodiments, the front side has a concave section and a convex section. In this way, it is possible to extend the contact region in the direction of the conductor track of the heating conductor layer and still maintain a sufficiently large distance from the joint.

According to further embodiments, in the projection in the stacking direction, a width of the electrically conductive layer tapers, starting from the width of the front side, at least in a subregion of the electrically conductive layer. The width of the front side in the projection is, for example, greater than a maximum width of the remainder of the electrically conductive layer. The electrically conductive layer is, in the projection in the direction of the current flow which occurs during operation, wider than in the upstream direction. Therefore, it is possible to realize a sufficiently low current density.

According to further embodiments, the apparatus has a conduction strip which is composed of an electrically conductive material. The apparatus has a connection which connects the electrically conductive layer and the conduction strip to one another in order to form electrical and/or mechanical contact with the electrically conductive layer by means of the conduction strip. The conduction strip serves, for example, as an electrical and/or mechanical contact interface to the electrically conductive layer. It is possible to apply a voltage to the electrically conductive layer and therefore the heating conductor layer by means of the conduction strip. The conduction strip can be connected to a power supply system of the motor vehicle by means of further lines for example. By way of example, the connection of the conduction strip to the electrically conductive layer is a welding connection. According to embodiments, the conduction strip is welded to the electrically conductive layer. The conduction strip comprises, for example, copper or is formed from a copper alloy.

According to embodiments, the distance from the joint is prespecified depending on a width of a conductor track of the heating conductor layer transverse to the stacking direction. In particular, the width of the conductor track is prespecified in order to realize a reliable heating output during operation. Depending on the width of the conductor track, the distance from the joint is prespecified such that hotspots are prevented during operation.

According to further embodiments, an area of the electrically conductive layer, which area is averted from the heating conductor layer, is larger than a contact area in which the conduction strip is in contact with the electrically conductive layer. The contact region which is formed by the electrically conductive layer is larger than the region of the conduction strip which forms the common contact area with the heating conductor layer. This makes a further contribution to hotspots being prevented during operation.

According to embodiments, the electrically conductive layer is a thermally sprayed electrically conductive layer. In particular, the electrically conductive layer comprises copper. By way of example, the electrically conductive layer is a thermally sprayed copper layer.

According to embodiments, the heating conductor layer is a thermally sprayed heating conductor layer. A simple option for producing the electrically conductive layer and/or the heating conductor layer is realized in this way.

Owing to the apparatus, it is possible to form the contact region for the heating conductor layer such that a sufficiently high current flow is possible during operation and no hotspots or virtually no hotspots occur in the process.

Further advantages, features and developments will become apparent from the following examples which are explained in connection with the figures.

DETAILED DESCRIPTION

FIG. 1shows a schematic plan view of an apparatus100. In particular,FIG. 1shows a projection of the apparatus100on the x-y plane. The apparatus100is, in particular, part of a heating device for a motor vehicle. The heating device is an electrical heating device which generates heat when a voltage is applied during operation.

The apparatus100has a layer stack101. The layer stack101has a heating conductor layer102. The heating conductor layer102is formed from a material which heats up when an electrical voltage is applied. The heating conductor layer102is produced, in particular, by means of thermal spraying. According to further exemplary embodiments, the heating conductor layer is produced by means of another method which is suitable for applying the conductive material for the heating conductor layer to further layers128(FIG. 2) of the layer stack102. The heating conductor layer102comprises, in particular, nickel and chromium (NiCr).

An electrically conductive layer103is applied to a portion of a surface117of the heating conductor layer102. The electrically conductive layer103is applied, in particular, in two or more subregions of the surface117in order to form contact regions for the heating conductor layer102.

The electrically conductive layer103is applied, in particular, by means of a thermal spraying process, in particular by means of atmospheric plasma spraying. According to further exemplary embodiments, the electrically conductive layer103is applied by means of another production method. The electrically conductive layer103comprises copper or a copper alloy. According to further exemplary embodiments, another sufficiently highly electrically conductive material is used for the electrically conductive layer103.

A conduction strip104is applied in a cohesive manner to the electrically conductive layer103. The conduction strip104is connected to the electrically conductive layer103by means of a welding connection109in particular. Other types of connection are also possible, for example a soldering connection.

As shown inFIG. 2, in order to form the welding connection, a laser beam108of a laser118is emitted such that the connection109is formed.

As is likewise shown inFIG. 2, the electrically conductive layer103is arranged on the surface117of the heating conductor layer102in a stacking direction105. A longitudinal direction106extends transverse to the stacking direction105.

The electrically conductive layer103has a front side113which extends, in cross section, in the direction of the stacking direction105and transverse to the longitudinal direction106. The front side113faces a central region114of the heating conductor layer102. The central region114along the longitudinal direction106is arranged between two outer edges132and133.

The central region114is arranged along the longitudinal direction106approximately in the center of the surface117. A main propagation direction of the front side113runs along the y direction in the coordinate system ofFIG. 1. The front side113is that side of the electrically conductive layer103which faces the closer outer edge132. The front side113faces the further outer edge133which is situated further away. The two outer edges132and133each run substantially in the y direction.

A surface115of the electrically conductive layer103is averted from the surface117of the heating conductor layer102and extends transverse to the stacking direction105. A contact area107at which the electrically conductive layer103and the conduction strip104are in contact with one another is formed at the surface115. The surface115of the electrically conductive layer103is larger than the contact area107.

FIG. 3shows the apparatus100, in which the welding connection109is formed, in cross section.

As explained in more detail in connection withFIGS. 4 to 8, the electrically conductive layer103has, in a projection in the stacking direction105, a prespecified contour110, in particular of one of the contact regions which are formed by means of the electrically conductive layer.FIGS. 4 to 8each show the projection of the apparatus100in the stacking direction105on the x-y plane.

FIG. 4shows a detail of a plan view of the apparatus100. The apparatus100according toFIG. 4has a central contact region129which is formed by means of the electrically conductive layer103. The apparatus100has two further contact regions130which are likewise each formed by means of the electrically conductive layer103. According to further embodiments, more or fewer contact regions, but at least two contact regions129and130, are provided, so that a heating circuit of the heating conductor layer102can be connected to a positive pole and a negative pole of a voltage source.

The apparatus100according toFIG. 4has two heating circuits which are each connected to the contact region129and one of the further contact regions130. It is also possible for more than two heating circuits to be provided. In this case, more than two further contact regions130are accordingly provided.

In particular, the contour110of the contact region129is prespecified. According to embodiments, the contour of the further contact regions130is designed differently to the contour110of the contact region129.

The contour110of the contact region129is prespecified by means of a width112on the front side113. In addition, the contour110is prespecified by a radius121which prespecifies a curvature of the contour110, in particular a transition to a side111. The side111runs along the longitudinal direction106transverse to the front side113. In addition, the contour110is prespecified by means of a distance116of the contact region129from a joint119. The joint119divides the heating conductor layer102into a plurality of conductor tracks127. If a plurality of joints119are arranged adjacent to the contact region129, such as for example inFIG. 4three joints119in the upper region which forms part of the first heating circuit, a distance116a,116band116cbetween the contact region129and the respective joint119is prespecified in each case. The distance116is, in particular, the distance between the outer edge of the joint119, which outer edge faces the contact region119, and the outer edge of the contact region129, which outer edge faces the joint119.

The contact region129has a width126. The width126tapers, starting from the front side113, along the side111in a subregion125. Therefore, the contact region129widens along the longitudinal direction106. The width112of the front side113is greater than the width126of the contact region129at an end of the subregion125which faces the front side113. Therefore, it is possible for the contour110to follow a profile of the two direct joints119in the region of the front side113, which joints run, beginning at the outer edge132, in the direction of the outer edge133directly next to the contact region129and have a curved profile. These two joints119run such that a region of the heating conductor layer102which is arranged between these two joints119is widened in the region of the front side113in the direction of the conductor tracks127.

By way of example, the contact region129is of narrower design at its end which is averted from the central region114than at its end which faces the central region114. This is prespecified, for example, by the radius121and the width112.

The contour110which is determined, in particular, by the width112, the radius121and the distance116is prespecified such that so-called hotspots are prevented during operation as current flows through the contact region129into the heating conductor layer102. The contour110is prespecified such that a maximum temperature remains below a prespecified maximum value during operation, in particular at the contact region129and the immediately adjacent regions of the heating conductor layer102. Therefore, it is possible to keep the temperature below 220° C., for example below 210° C., in particular below 200° C., even in the case of high-voltage applications in the motor vehicle sector of, for example, up to 100 V, and a current flow of up to amperes. Therefore, reliable operation of the heating device is possible and material weakening phenomena can be prevented.

As shown inFIG. 5, according to exemplary embodiments, the contour110, in particular in the region of the front side113, is prespecified by the radius121and a further radius120. In particular, the further radius120which defines a central region of the front side113is larger than the radius121which defines the two side regions at the transition to the sides111. By way of example, the further radius120is 11 mm and the radius121is 0.5 mm.

According to further embodiments, a straight section122is provided in the central region of the front side113(FIGS. 4 and 8). The size of the further radius120and the size of the radius121is in each case prespecified, in particular, depending on the width112of the front side113. The width112is in turn prespecified by the installation space for the heating device or the heating conductor layer102or the contact region129.

The width112and also the radius121, the further radius120and the straight section122which is provided between the curved regions according to embodiments are prespecified such that the contact region129extends in the direction of the respectively associated conductor tracks127on both sides of the front side113which form the transition to the side111. Therefore, the contact region129is formed such that its contour follows a current flow which is directed from the contact area107, through the electrically conductive layer103, to the heating conductor layer102, in particular to the two heating circuits of the heating conductor layer102, during operation. In this case, the contour110is prespecified such that the field lines in the contact region129are not concentrated as far as possible, but rather are uniformly distributed as far as possible. Therefore, a low current density is realized at the contact region129.

FIG. 6shows a further exemplary embodiment of the contour110of the contact region129. In this embodiment, the width126of the contact region130is unchanged and equal to the width112of the front side113.

The front side113has a convex section124transverse to the longitudinal direction106and to the stacking direction105, a concave section123which adjoins said convex section, and a further convex section124.

Owing to this curvature in the front side113, the contact region129is expanded in the direction of the conductor tracks127. The convex sections124are each curved in the direction of the current flow which occurs during operation, as a result of which the current density remains low and therefore a hotspot is prevented. The two convex sections124are in the form of projecting regions in the direction of the conductor tracks127. According to exemplary embodiments, the convex sections124each have at least the two radii120and121which are different from one another.

Therefore, the curvature respectively changes along the convex section124. According to further embodiments, the convex sections124each have a single radius121. Therefore, the respective curvature does not change along the convex section124.

According to exemplary embodiments, the concave section123has at least two radii which are different from one another. Therefore, the curvature changes along the concave section123. According to further embodiments, the concave section123has a single radius. Therefore, the curvature does not change along the concave section123.

FIG. 7shows a further embodiment for the contour110of the contact region129. Comparably to the embodiment ofFIG. 6, the front side113has two convex sections124and the concave section123which is arranged between the two convex sections124. In contrast toFIG. 6, the width112of the front side113according to the embodiment ofFIG. 7is wider than the width126of the contact region126in the section which faces the outer edge132. In addition, the side111is longer along the longitudinal direction than inFIG. 6. Therefore, it is possible to route the contact region129closer to the conductor tracks127. The contact area107remains unchanged. Therefore, the contact region129is routed to the conductor tracks127in the direction of the current flow which occurs during operation.

FIG. 8shows a further embodiment of the contour110for the contact region129. The contour110ofFIG. 8corresponds substantially to the contour as illustrated inFIG. 7. In contrast toFIG. 7, according to the exemplary embodiment ofFIG. 8, the straight section122between the two convex sections124is arranged on the front side113. In connection with the contour110according toFIG. 8too, according to exemplary embodiments, the convex sections124each have at least the two radii120and121which are different from one another. Therefore, the respective curvature changes along the convex section124. Therefore, the contour110has a changing curvature at the transition from the straight section122to the sides111. According to further embodiments, the convex sections124each have a single radius121. Therefore, the respective curvature along the convex section124does not change.

Therefore, it is possible, for example, to achieve a maximum temperature at the contact pad of less than 205° C., in particular less than 200° C., for example less than 196° C., at a thickness of the heating conductor layer102of 20 μm in stacking direction105, a thickness of the contact region129of 40 μm in stacking direction105, an applied voltage of 400 V to the contact region129, an applied voltage of 0 V to the contact region130and also an average temperature at the heating conductor layer102of 150° C. During operation, the hottest region is, for example, on the heating conductor layer102directly at the convex section124of the contact region129. In this region, the prespecified configuration of the contour110, with corresponding matching of the width112, the radii120and121and also the distances116a,116band116cmeans that the maximum temperature is at most 60° C. higher than the average temperature in the heating conductor layer102. This is achieved since the contour110is prespecified such that as uniform as possible a profile of the field lines of the current flow is achieved and hotspots are prevented as a result. According to exemplary embodiments, the lowest maximum temperature is achieved at the contact region129when the second radius121is as small as possible. By way of example, the radius121is 0.5 mm. This results in the smallest maximum temperature for a radius120of 11 mm.

In addition to the radii of curvature120and121, the width112of the front side113also plays a role. At a relatively small radius121, the front side113is wider and as a result the field line concentration is weaker. Therefore, less heat is generated owing to a lower current density. Therefore, a maximum temperature of below 195.1° C. is made possible, in particular at the contour110, as illustrated inFIG. 8. At a radius121of 1 mm, a maximum temperature of below 201° C. is made possible, for example, at a radius120of 11 mm.

The width113, the radius121and/or the radius120and also the distance116are prespecified depending on one another. Along the longitudinal direction106, the contact region has, in the projection in stacking direction105, at least the subregion125in which the width126of the contact region129is increased in size in relation to the width112. In addition, the transition between the front side113and the two sides111is curved, in particular rounded, in each case. The relative dimensions in relation to one another can vary, but are always prespecified such that the effect of the low current density and therefore the prevention of hotspots is achieved. A large number of configurations of the contour110which are different from one another are possible, said configurations each always being prespecified by means of the the width113, the curvature, in particular of the front side113at the transition to the sides111, and the distance116and being designed such that a hotspot is prevented during operation. The result of the low current density and the accompanying prevention of hotspots can be achieved, for example, by various modifications depending on the width131of the conductor track127by the width112of the front side113first being ascertained, the radii120and121being ascertained depending on said width, and the distance116being ascertained depending on said radii.