Electric heating device and electric heating system

Abstract

The present invention relates to an electric heating device (2) comprising an electric heating element (22) with a layered structure (34) comprising heating elements (23), in particular PTC elements (24), electrically conductive contact layers (20; 30; 300) on both sides thereof, and preferably electrical insulating layers (18; 32) which cover the contact layers (20; 30; 300) externally, wherein the layered structure (34) is clamped between contact surfaces of heat-emitting elements. In the electric heating device (2) according to the invention, at least one of the contact layers (300) forms partially separated contact segments (310), each of which is electrically conductively connected to one of the heating elements (23).

Description

[0001] The present invention relates to an electric heating device and an electric heating apparatus.

[0002] Electric heating devices, particularly in motor vehicles, the development of which is also the preferred embodiment of the present invention, typically have multiple heating elements, for example in the form of PTC elements, which are electrically connected via electrical contact layers. Such heating elements, especially PTC elements, are subject to dimensional variations due to manufacturing processes.

[0003] In the electric heating devices known from EP 2 607 121 A1, PTC elements are arranged on both sides between contact plates, which form specific contact layer configurations within the meaning of the present invention. These contact layers are in direct electrical contact with the PTC elements. Depending on the operating voltage, it may be necessary to electrically insulate the energized layers of the heating device from the heat-emitting surfaces of the heat-emitting elements. For this purpose, EP 2 607 121 A1 discloses providing insulating layers between the contact layers and these contact surfaces.

[0004] The present invention aims to provide improved contacting of the individual heating elements provided in one plane of the layered structure.

[0005] To solve this problem, the present invention provides an electric heating device according to claim 1 and an electric heating device according to claim 8.

[0006] In the solution according to the invention, at least one of the contacting layers has contacting segments that are partially separated from one another and each of which is electrically connected to one of the heating elements.

[0007] The present invention is based on the idea that individual contact segments are provided for individual heating elements arranged next to one another in a plane, usually relatively close to one another. These contact segments are movable within limits out of the plane formed by the initially flat contact layer and can thus compensate for dimensional fluctuations in the thickness of the individual heating elements. Preferably, a separate contact segment is provided for each individual heating element. This makes it possible to optimally connect each of the adjacent heating elements electrically via the contact layer, while still supplying power to them with a single element.

[0008] While both contact layers can be adapted as described above, it is usually sufficient to compensate for certain dimensional fluctuations by providing the contact layer designed according to the invention only on one side of the heating elements and placing the heating elements on the opposite side against a completely flat contact layer, for example, against a flat sheet of metal supported against a flat contact surface, possibly with an insulating layer interposed. Electrically isolated contact elements assigned to different heating circuits can also be provided there.

[0009] The contacting layer forming the contacting segments can be formed by a uniform sheet metal element having slots for forming the contacting segments. In the case of cuboid-shaped heating elements, the slots are preferably aligned at right angles or parallel to one another. Each individual contacting segment is preferably cut free from adjacent surfaces of the sheet metal element by at least two slots extending at right angles to one another. The slots usually run parallel to the side edges of the heating elements. The slots are preferably located in an area between adjacent heating elements. The heating elements can be provided in a conventional manner in a positioning frame which forms receptacles for receiving the individual heating elements or for receiving a plurality of heating elements. The slots are usually provided at the level of webs of the positioning frame which define the individual receptacles.This ensures that the slots are aligned with the webs. The slots can be wider than the webs, allowing them to elastically compress between the webs. However, the positioning frame is typically dimensioned so that the heating elements extend beyond the positioning frame, regardless of their respective manufacturing tolerances. This eliminates the need for the contact segments to actually penetrate the positioning frame's receptacle.

[0010] In cuboid heating elements, the slots are arranged at right angles or parallel to each other and are shaped according to the contours of the respective heating elements. The slots are usually located between the individual heating elements.

[0011] The heat-emitting elements can be formed by corrugated fin layers, which are arranged, for example, in a frame in which a layered structure of electric heating devices and corrugated fin layers can be clamped (cf. EP 2 607 121 A1). However, the contact surfaces can also be formed by surfaces that delimit one or more heating chambers. An example of surfaces delimiting a single heating chamber are heating fins that protrude into a single heating chamber, as is known from EP 3 334 243 A1. In such a configuration, the electric heating device is held prestressed by a wedge element between the heat-emitting surfaces.

[0012] Preferably, an elastic preloading device is provided between the electric heating device and at least one of the contact surfaces. The elastic preloading device allows a certain degree of mobility of the contact segments to compensate for the manufacturing-related thickness tolerances of the heating elements without losing the desired direct contact. Thus, the thickness of the preloading device, which is preferably formed from a compressible material, depends on the expected thickness tolerances of the heating elements.

[0013] A plastic film, particularly a silicone film, has proven to be a suitable elastic prestressing device, also with regard to good heat dissipation. The corresponding film typically has a base area that at least covers the heat-dissipating base area of ​​the electric heating device. The film preferably has a thickness of no more than 0.8 mm; more preferably no more than 0.45 mm, and most preferably no more than 0.30 mm. The corresponding film preferably has a Shore A hardness of between 25 and 70.

[0014] It has been shown that such a foil can not only store certain prestresses and pass them on to the electric heating device, so that it is applied flatly on both sides to the heat-coupling surfaces for heat extraction. Rather, such a foil can also compensate for certain tolerances that regularly occur on the side of PTC elements, which are the preferred design of the heating elements in the present invention. The PTC elements are usually distributed flatly relative to a surface that couples out the heat. This surface usually only forms a support surface for the PTC elements, but not their direct contact surface. The PTC elements are usually ceramic cuboid-shaped components that are provided with a metallization on opposite sides, usually on the opposite main side surfaces, for current introduction.

[0015] The heating device according to the invention is preferably advantageously provided together with a control device of the electric heating device in a housing comprising a housing base part and a housing cover. The housing base part has a usually flat housing base that defines the housing and usually extends essentially parallel to the housing cover. These components of the housing are usually made of a metallic material; in any case, the materials have good electromagnetic shielding properties. Also suitable are plastic housings with a shielding device incorporated therein or surrounding or shielding the housing, for example, formed by a wire mesh.This design principle offers the best possible EMC protection, so that the electric heating device of the present invention can be arranged in close proximity to electrical or electronic components, for example, in a motor vehicle, without the operation of the electric heating device disturbing these other components. The electric heating device of the present invention is particularly suitable for operation with a high-voltage current, such as that used for drives in electric vehicles. According to the present invention, a high-voltage current is considered to be, in particular, a current with more than 400 volts, possibly more than 700 volts.

[0016] Below, details of a specific design are presented, in which a fluid housing is accommodated within the housing, which is adapted for the passage of the medium to be heated. This fluid housing is typically self-contained and has only predetermined inlets and outlets through which the medium is introduced into and discharged from the fluid housing.

[0017] This fluid housing is thermally coupled to the electrical heating device. This is understood in particular to mean a thermally conductive connection of the fluid housing to the electrical heating device. To ensure the most effective heat dissipation possible, the fluid housing is usually made of a material with good thermal conductivity, generally a metal, for example aluminum or an aluminum alloy. To electrically insulate the fluid housing from the electrical heating device, an insulating layer can be provided between the fluid housing and the electrical heating device. This insulating layer can be formed, for example, by a plastic film, a ceramic plate, or a coated plate, or a combination of the above, for example, by a ceramic plate covered with a plastic film or sandwiched between the two.

[0018] According to a preferred development of the present invention, the electrical heating device is thermally coupled to a housing base of the housing base part, which housing base defines a first heating chamber. Here, too, an insulating layer as described above can be provided between the electrical heating device and the housing base. The electrical heating device is then preferably provided between the fluid housing and the housing base, generally as a flat component extending parallel to the housing base and parallel to the fluid housing, which is preferably also flat. To improve heat dissipation, the electrical heating device bears against the housing base and the fluid housing under prestress.

[0019] The previously described structure is provided in reverse order on the side opposite the housing base, and thus between the electric heating device and the fluid housing. An at least thermally symmetrical or nearly thermally symmetrical design of the layers on both sides of the electric heating device is preferred in order to achieve the most equal heat dissipation possible toward the fluid housing on the one hand and the housing base on the other.

[0020] The aforementioned first heating chamber and a second heating chamber delimited by the fluid housing and defined by the latter are also preferably designed almost identically in that the same flow conditions and the same heat transfer values ​​to the medium to be heated are achieved on both sides.

[0021] As can be seen from the above description, the present invention proposes an electric heating device comprising a plurality of parallel layers, wherein both a fluid housing which at least partially conducts the medium for heating and the control device are accommodated in the housing. The housing has a housing base part which forms the bottom and thus a contact surface for the electric heating device inside the housing. On the side opposite the housing bottom, a housing cover extends parallel to it and forms the first heating chamber. This usually extends parallel to and with a comparable geometric design to the second heating chamber which is formed within the fluid housing. This results in approximately comparable heat extraction on both sides of the electric heating device.The PTC elements, which preferably form the heating elements, are accordingly cooled uniformly on both sides. These layers can be prestressed by screwing the fluid housing against the housing base. Within a plane containing the contacting layer, the contacting segments can be movable within limits. This makes it possible to compensate for tolerances locally and for a single heating element, in particular a PTC element. This movement is tracked by the insulating foil, which preferably forms the prestressing device and against which the contacting layer rests.

[0022] All electronic components of the electric heating device are provided within the housing and shielded accordingly, so that the electric heating device according to the present invention can be operated in the vehicle with good EMC protection.

[0023] Further details and advantages of the present invention will become apparent from the following description of an embodiment in conjunction with the drawings, in which: Fig. 1: an exploded perspective view of an embodiment of the present invention; Fig. 2: a perspective exploded view of the housing base part and the heating chamber cover of the embodiment according to Fig. 1; Fig. 3: a perspective exploded view of the fluid housing of the embodiment according to Fig. 1; Fig. 4: a perspective top view of the housing base part partially equipped with components of the embodiment according to Fig. 1; Fig. 5: Sectional view of the embodiment along the Fig. 4 drawn line VV and Fig. 6 a perspective top view approximately according to Fig. 1 to the second contact layer 30 shown there with the positioning frame 26.

[0024] Fig. 1 shows an electric heating device 2 with a housing base part 4 which is arranged at its Fig. 1 lower side to form a first heating chamber 6.1 with a heating chamber cover 8 - see Fig. 2. Reference numeral 10 denotes a fluid housing, which is accommodated in a receiving space 12 formed by the housing base part 4. In this receiving space 12, which is bounded on the underside by a base 14 and on the edge by a circumferential wall 16 extending from the base 14, and between the base 14 and the fluid housing 10, there is a first insulating layer 18, which can be placed against the base 14, a first contact layer 20, and a heating device 22 with a plurality of heating elements 23, here in the form of PTC elements 24, and a positioning frame 26 with receptacles 28 for receiving the PTC elements 24.

[0025] On the side of the heating device 22 opposite the first contacting layer 20, a second contacting layer 30 is provided, on the side of which, opposite the heating device 22, a second insulating layer 32 is arranged. The PTC elements thus bear electrically conductively against the contacting layers 20, 30 and are supplied with current via them. The PTC elements 24 are ceramic cuboid-shaped components that are provided with metallization on opposite main side surfaces for current introduction. The main side surface is the surface of the cuboid with the largest areal extent. The main side surfaces are connected to one another by edge surfaces that specify the height of the PTC elements and have no metallization. The main side surfaces are generally each larger by a factor of 5 than one of the edge surfaces, preferably than the sum of all edge surfaces.

[0026] The second insulating layer 32 is formed as a prestressing device 33 by a silicone film which is able to absorb certain compressions by elastic deformation and thus to apply the electrical heating device 22 between the housing base part 10 and the housing bottom 14 under prestress against the housing base part 10 and the housing bottom 14.

[0027] The layering of the first insulating layer 18, the first contacting layer 20, the heating device 21, the second contacting layer 30 and the second insulating layer 32 is also referred to below as layered structure 34.

[0028] On the side of the fluid housing 10 facing away from this layered structure 34, in the embodiment shown, a transistor insulation 40 is located between a circuit board 38 forming a control device 36 and the fluid housing 10. Reference number 42 designates a housing cover which is used to form a Fig. 5, which is designated by reference numeral 44, is connected to the housing base part 4. The housing base part 4 and the housing cover 42, and possibly other housing parts, are designed to be shielded, i.e., made of metal and / or provided with separate shielding inside, outside, or in the walls of the respective housing part, which may conceivably be made of plastic. Aluminum is preferred as the metallic material, or, with regard to corrosion resistance, stainless steel.

[0029] On the underside of the housing base part 4 opposite this housing cover 42, Fig. 1 shows a power connector 46 and a control connector 48. These two connectors 46, 48 are sealed to the housing base part 4 and have various male electrical plug contacts that are sealed through the respective housings of the connectors 46, 48 and plugged into the circuit board 38 and electrically connected via this plug contact to conductor tracks of the circuit board 38. Details will be given below in connection with Fig. 4. For plug-in contact, the circuit board has 38 female contact receptacles, which are described in EP 2 236 330 A1.

[0030] Inlet and outlet ports 50, 52 are also provided on the underside for connecting pipes or hoses carrying the fluid to be heated. Reference numeral 53 denotes Fig. 1 below the fluid housing 10, which in this case is formed by two sealing rings 54, which are explained in more detail below. Reference numeral 56 denotes screws for securing the fluid housing 10 relative to the housing base part 4 with the layered structure 34 interposed. Through this screw connection, the layers of the layered structure 34 are applied under prestress against the fluid housing 10 and the base 14 of the housing base part 4.

[0031] The Fig. Figure 2 shows an exploded view of the housing base part 4 and the heating chamber cover 8 shown at a distance therefrom, revealing the interior of the first heating chamber 6.1. The nozzles 50, 52 are clearly formed by separate components that align with two holes within the heating chamber cover 8, which is formed from a flat sheet metal. One of these holes forms an inlet 58 and the other an outlet 60. The nozzles 50, 52 can be welded or glued to the heating chamber cover 8.

[0032] Reference numeral 62 denotes a distributor arranged in a plane HE containing the first heating chamber 6.1. The distributor 62 has an inlet distributor section 64 and an outlet distributor section 66, each provided separately from one another and covered by the heating chamber cover 8. The respective distributor sections 64, 66 are provided symmetrically to a longitudinal axis L of the housing base part 4 and are assigned an inlet branch 68 and an outlet branch 70, respectively, of the first heating chamber 6.1. In plan view, the distributor sections 64, 66 each have an approximately triangular base area. Each distributor section 64, 66 merges into the respective branch 68, 70 via an overflow edge 72. The overflow edge 72 lies in the vertical direction between a first heating chamber floor 74 of the first heating chamber 6.1 and an opposite cover surface of the first heating chamber 6.1 formed by the heating chamber cover 8.

[0033] Flow guide ribs 76 protrude from this first heating chamber base 74 to guide the flow, against which the heating chamber cover 8 rests in a fluid-tight manner.

[0034] The inlet 58 and the outlet 60 are each arranged such that they partially cover the first heating chamber 6.1 and partially cover the respective distributor section 64, 66. The overflow edge 72 extends approximately centrally through the bore forming the inlet 58 and the outlet 60, respectively.

[0035] Details of the second heating chamber 6.2 are Fig. 3. The fluid housing 10 is formed by a fluid housing base part 78 and a fluid housing cover 80 welded thereto. The second heating chamber 6.2 also has flow-guiding ribs 76. On the periphery of the fluid housing 10, several fastening eyes 82 are provided, through which the screws 56 are passed in order to connect the fluid housing 10 to the housing base 14 with the interposition of the electric heating device 22. Fig. 4, threads formed on the housing base 14 are marked with reference numeral 83.

[0036] In Fig. 4, reference numeral 84 denotes a first inlet channel section and reference numeral 86 denotes a first outlet channel section. These channel sections 84, 86 are formed on and through the housing base part 4. The Fig. 3 shows second inlet and outlet channel sections 88, 90 formed integrally on the fluid housing base part 78.

[0037] As in particular Fig. 5, the second channel sections 88, 90 are designed as spigot ends 92, which each engage a socket end 94 formed by the first channel sections 84, 86, wherein the sealing arrangement 53 is provided therebetween and bears in the axial and radial direction against a bearing shoulder 96 provided on the respective spigot end 92.

[0038] The spigot end 92 and the socket end 94 have an axial length such that electric heating devices 22 of different thicknesses can be arranged between the fluid housing 10 and the housing base 14 without compromising the tightness between the housing base part 4 and the fluid housing 10. As a result, an inlet flow connection ES formed by the inlet channel sections 84, 86 can be varied in length transversely to the plane E containing the electric heating device 22. The same applies to an outlet flow connection designated by reference symbol AS.

[0039] The fluid flow introduced into the electric heating device 2 through the inlet 58 is divided into two partial flows in the region of the distributor 62. The first partial flow T1 flows over the overflow edge 72 into the first heating chamber 6.1, whereas the second partial flow T2 passes through the inlet flow connection ES, flows through the second heating chamber 6.2, first through the inlet branch 68 and then through the outlet branch 70, and finally passes through the outlet flow connection AS, is combined with the first partial flow T1 in the region of the distributor 62, and the fluid flow resulting from the combination of these two partial flows T1, T2 is discharged through the outlet.

[0040] Reference number 280 is in Fig. 5, a contact surface is identified, which is formed by the fluid housing 10 as the first heat-emitting element 282. Reference numeral 290 denotes a second contact surface, which points to the inner surface of the housing base 14 as the further heat-emitting element 292. The electric heating device 22 is held clamped between these contact surfaces 280, 290 due to the clamping force of the screws 56, which compress the second insulating layer, acting as a pretensioning device 33, which can compensate for certain compensating movements of the contacting segments 310, so that these contacting segments 310 each rest securely and electrically conductively against the surface of the heating elements 23 and energize them.

[0041] Fig. 4 also illustrates the electrical connection concept for the printed circuit board 38. Contact tabs 202 of male plug contacts 204 protrude into a mounting plane of the printed circuit board 38, which is recognizable by support 200 for the printed circuit board 38. These contact tabs are exposed at the free ends of the plugs (only the power connector 46 is shown) or at the free ends of connection lugs 206 for the negative contacts or at the free ends of connection lugs 208 of the positive contact. Even after assembly, the connection lugs 206, 208 project beyond the fluid housing 10, which is arranged below the mounting plane of the printed circuit board 38. The printed circuit board 38 can be plug-connected to all contact tabs 202 by simply lowering it toward the housing base 14, i.e., in a direction orthogonal to the planar extension of the housing base 14.The assembled circuit board 38 rests on the supports 200 and is fixed relative to the housing base part 2 by screws (not shown) which engage in threads of the supports 200.

[0042] In Fig. 6, the second contact layer is identified by reference numeral 300. Apart from that, identical components are identified by the same reference numerals as in the previous description.

[0043] The second contact layer 300 is evidently formed by a single sheet metal part from which the terminal lug 208 was formed by punching and bending. The second contact layer 300 has a central bore 302 through which a screw 56 passes through the center of the fluid housing 10 and is screwed with a central thread 83, which is Fig. 4, the second insulating layer 32 is shown projecting above. The collar surrounding this thread 83 also serves to position the fluid housing 10 during assembly. A cross-shaped pattern of slots 304, 306 is formed on both sides of the central bore 203. These slots are arranged at right angles or parallel to each other and intersect at intersection points 308.

[0044] The Fig.6, the positioning frame designated by reference numeral 260 has longitudinal webs 264 and transverse webs 266, which form receptacles 28 for the heating elements 23. The grid formed by the longitudinal and transverse webs 264, 266 determines the position and orientation of the slots 304, 306. In other words, a longitudinal web 264 of the positioning frame 260 is located aligned below each longitudinal slot 304, and a transverse web 266 of the corresponding positioning frame 260 is located below each transverse slot 306. The respective slots 304, 306 form contact segments 310, which are connected to the remaining sheet metal of the contact layer 300 either at two edge sides of an imaginary cuboid, corresponding to the cuboid-shaped configuration of the heating elements 23, or at only one longitudinal edge. According to the arrangement of a total of twelve heating elements 23 in two groups of six each, twelve contacting segments are provided.Each contact segment 310 accordingly rests electrically conductively against one of the heating elements 23. As mentioned, the heating elements 23 in the illustrated embodiment consist of PTC elements 24, which are provided with a metallization on their surfaces that are electrically contacted with the contact layers 20, 30; 300. Due to the slots, the contact segments 310 can pivot within limits out of the plane of the sheet metal and thus compensate for dimensional deviations in the height of the heating elements 23. List of reference symbols 2 electric heaters 4 Housing base part 6.1 first heating chamber 6.2 second heating chamber 8 heating chamber lids 10 fluid housings 12 Recording room 14 Case back 16 surrounding wall 18 first insulation layer 20 first contact situation 22 Heating device 23 Heating element 24 PTC elements 26 Position frames 28 recordings 30 second contact layer 32 second insulation layer 33 Pre-tensioning device 34 layered structure 36 Control device 38 circuit board 40 Transistor Isolation 42 Housing cover 44 housings 46 power connectors 48 control plugs 50 inlet nozzles 52 outlet nozzles 53 Sealing arrangement 54 sealing rings 56 screw 58 Entrance 60 outlet 62 distributors 64 Inlet manifold section 66 Outlet manifold section 68 Inlet branch 70 outlet branch 72 overflow edge 74 first heating chamber floor 76 Flow guide rib 78 Fluid housing base part 80 Fluid housing cover 82 Mounting eye 83 threads 84 first inlet channel section 86 first exhaust duct section 88 second inlet channel section 90 second exhaust duct section 92 top executives 94 socket end 96 Investment shoulder 200 supports 202 contact tongues 204 male plug contact 206 terminal lugs minus contact 208 Connection lug plus contact 260 Position frames 264 Longitudinal web 266 crossbar 280 investment area 282 first heat-emitting element 290 second investment area 292 additional heat-emitting element 300 second contact layer 302 medium bore 304 longitudinal slot 306 cross slot 308 crossing point 310 Contacting segment AS outlet flow connection ES inlet flow connection E level containing the electric heating device HE level containing the first heating chamber L Longitudinal axis T1 first partial flow T2 second partial flow QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 2 607 121 A1 [0003, 0011] EP 3 334 243 A1

[0011] EP 2 236 330 A1

[0029]

Claims

[1] Electric heating device (2) comprising an electric heating device (22) with a layered structure (34) comprising heating elements (23), in particular PTC elements (24), contact layers (20; 30; 300) lying electrically conductively on both sides thereof and preferably electrical insulating layers (18; 32) covering the contact layers (20; 30; 300) on the outside, wherein the layered structure (34) is clamped between contact surfaces of heat-emitting elements, characterized by that at least one of the contacting layers (300) forms contacting segments (310) which are partially separated from one another and which each bear electrically conductively against one of the heating elements (23). [2] Electric heating device (2) according to claim 1, characterized by that the contacting layer (300) is formed by a uniform sheet metal element into which slots (304; 306) are introduced to form the contacting segments (310). [3] Electric heating device (2) according to claim 2, characterized by that the heating elements (23) are cuboid-shaped and that the slots (304; 306) are aligned at right angles or parallel to one another. [4] Electric heating device (2) according to one of the preceding claims, characterized by that the electric heating device (22) is held clamped against the contact surfaces of the heat-emitting elements (282; 292) by an elastic pretensioning device (33), the elastic pretensioning device (33) being arranged between the electric heating device (22) and one of the contact surfaces (280). [5] Electric heating device (2) according to one of the preceding claims, characterized by that the electric heating device (22) is thermally conductively coupled to a first heating chamber (6.1) and a second heating chamber (6.1) and is held prestressed between two flat housing parts (14; 10) delimiting the heating chambers. [6] Electric heating device (2) according to one of the preceding claims, characterized by a housing base part (4) with a housing bottom (14) which delimits a first heating chamber and against which one of the electrical insulating layers (18) rests, and which accommodates a fluid housing (10) forming the second heating chamber (6.2), against which the other of the electrical insulating layers (32) rests. [7] Electric heating device (2) according to claim 6, characterized by that a control device (36) is arranged in the housing base part (4) and that at least one of the contacting layers (30) forms a connection lug (208) which is electrically connected to the control device (36). [8] Electric heating device (22) with a layered structure (34) comprising heating elements (23), in particular PTC elements (24), contact layers (20; 30; 300) lying electrically conductively on both sides thereof and preferably electrical insulating layers (18; 32) covering the contact layers (20; 30; 300) on the outside, characterized by that at least one of the contacting layers (30) forms contacting segments (310) which are partially separated from one another and which each bear electrically conductively against one of the heating elements (23). [9] Electric heating device (22) according to claim 8, characterized by that the contacting layer (30) is formed by a uniform sheet metal element into which slots (304; 306) are introduced to form the contacting segments (310). [10] Electric heating device (22) according to claim 9, characterized bythat the heating elements (23) are cuboid-shaped and are accommodated in a positioning frame (260) which forms receptacles (28) for the heating elements (23) which are delimited by webs (264; 266), and that the slots (304; 306) are aligned with the webs (264; 266).

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