Electric heating device

Abstract

The present invention relates to an improved electric heating device (2) with regard to thermal performance, comprising a housing (4) and a layered structure (14) in the housing (4), wherein the layered structure (14) comprises at least one heat-generating layer (18) formed by an electric heating device (24) and at least one heat-emitting layer (16), which is thermally connected to the heat-generating layer (18) and is formed by a meanderingly bent sheet metal strip (30) which forms heating fins (32) extending substantially perpendicular to the heat-generating layer (18), wherein two adjacent heating fins (32) are connected to each other via a bending region (34) which is thermally conductive towards the heat-generating layer (18), the bending region (34) forming a flattened heat dissipation surface (38).

Description

[0001] The present invention relates to an electric heating device comprising a housing and a layered structure within the housing. The layered structure includes at least one heat-generating layer and at least one heat-emitting layer. The at least one heat-generating layer is generally formed by an electric heating element.

[0002] Such an electric heating device is known, for example, from EP 2 298 582 A1.

[0003] The heat-emitting layer is formed by a meandering sheet metal strip. After meandering bending, this sheet metal strip has heating fins extending essentially perpendicular to the heat-generating layer. The heating fins accordingly bridge the gap between the heat-generating layer and an opposing layer of the layered structure. In the present invention, this opposing layer can also be formed by a sheet metal strip that separates another heat-emitting layer from the heat-emitting layer directly adjacent to the heat-generating layer and forms a contact surface for the two adjacent corrugated fin layers. However, the opposing surface can also be the contact surface of another heat-generating layer.

[0004] Due to the meandering bending of the sheet metal strip, each layer of corrugated fins has bending zones. These zones form the contact with the adjacent layer. In the prior art, the individual heating fins of the corrugated fin layer are connected to each other by simply bent bending zones. Since as many heating fins as possible are to be arranged in a narrow space along the length of the individual layers, this results in a bend with a relatively small radius. Thus, in the prior art, the bending zone only contacts the heat-generating layer along a line. In a cross-sectional view of the layered structure, the bending zone contacts the heat-generating layer at specific points. The linear shape results from the width of the sheet metal strip forming the corrugated fin layer.

[0005] The present invention addresses the problem of providing a device of the type mentioned at the outset with improved thermal performance.

[0006] To solve this problem, the present invention proposes to provide the bending area with a flattened heat dissipation surface.

[0007] By flattening the surface, the heat extraction area between adjacent heating fins is increased, resulting in improved heat transfer between the heat-generating layer and the heat-emitting layer, and thus improved thermal performance of the electric heating device.

[0008] The flattened heat dissipation surface can be formed by a modified forming process of the sheet metal strip. Alternatively, the flattened heat dissipation surface can be produced by post-processing the corrugated rib layer and its bending area, particularly by grinding or similar post-processing, in which the initially strictly convex bending area is flattened, resulting in a substantially flat heat dissipation surface that can rest against the regularly flat outer surface of the heat-generating layer.

[0009] The present invention represents an improvement over the prior art. In the previously discussed prior art, adjacent heating fins intersect at a point that determines the height of the heat-generating layer and accordingly defines the area where the corrugated fin layer rests against the heat-emitting layer.

[0010] According to a preferred embodiment of the present invention, the bending area can comprise a first bending point and a second bending point. These two bending points are arranged at a distance from each other in the longitudinal direction of the heat-generating layer and are thermally conductive towards the heat-generating layer. Thus, a bending area does not only have, as in the prior art, a single bending point produced by bending, where the two heating fins intersect at a point or line and which rests against the heat-generating layer as a convex elevation. Rather, at least two, optionally three or more of these elevations are realized in a single bending area.

[0011] With regard to providing defined contact surfaces between the heat-emitting layer and the heat-generating layer, a concave recess is preferably provided between the first and second bends. The bends are typically strictly convex. Accordingly, a concave area (from the perspective of the contact surface of the heat-generating layer) is located between the two bends, ensuring that the convex bends bear against the heat-generating layer in a predefined manner.

[0012] It is understood that the previously described possibilities for increasing the heat dissipation area can be provided on opposite sides with respect to the vertical direction of the wave fin layers. According to the present proposal, the increase in the heat dissipation area results solely from the modification of the meanderingly bent sheet metal strip forming the wave fin layers. The heat-generating layer can be bonded or soldered to the heat-emitting layer. This type of connection may lead to an increased, thermally conductive contact between the wave fin layer and the heat-generating layer. However, the heat dissipation area according to the invention is formed solely by the meanderingly bent sheet metal strip. Thus, solder or adhesive are not to be included in the consideration of the increased heat dissipation area.

[0013] As already known from EP 2 298 582 A1 or EP 1 564 503 A1, the layered structure is preferably thermally conductive within the housing due to the preload force of an elastic element. This elastic element preferably extends as a spring element over the entire length of the layered structure and preloads the layers of the layered structure against each other. Thus, in this preferred embodiment, no material bond between the individual layers is required, in particular no bonding or soldering of the corrugated rib layer to the heat-generating layer.

[0014] The housing can be a frame-shaped housing that forms opposing housing openings, allowing the passage of a medium to be heated, and between which the layered structure is essentially exposed.

[0015] The heat-generating layer can have contact plates arranged parallel to each other in a manner known per se, which serve as conductor elements for contacting an electrical heating element. Typically, a plurality of electrical heating elements are arranged one behind the other in the longitudinal direction of the layered structure. The electrical heating elements are preferably formed by PTC elements. The individual electrical heating elements can be held by a positioning frame between the two contact plates, resulting in a predetermined distribution of the individual heating elements in the longitudinal direction of the layered structure.

[0016] Further details and advantages of the present invention will become apparent from the following description of an exemplary embodiment in conjunction with the drawing shown therein: Fig. 1 a cross-sectional view of an embodiment of an electric heating device; Fig. 2 a detail II according to Fig. 1 in enlarged view; Fig. 3A the bending range of a conventional heat-emitting layer and Fig. 3B the bending area of ​​a second embodiment of the present invention.

[0017] The Fig. Figure 1 shows a cross-sectional view of an electric heating device 2 with a housing 4, which is formed as a plastic frame with longitudinal beams 6 and transverse beams 8. Adjacent to the one in Fig. 1 longitudinal beam 8 shown and parallel to it extends an elastic pretensioning device 10 with a spring element 12 as an elastic element which can first be inserted into the housing 4 without tension in the manner described in EP 2 298 582 A1 and can be tensioned in it by relative movement.

[0018] Reference numeral 14 designates a layered structure comprising several heat-emitting layers 16, which accommodate heat-generating layers 18 between them. In this case, the heat-generating layers 18 comprise two contact plates 20 extending parallel to each other and PTC elements 22 arranged between them, which are arranged one behind the other in the longitudinal direction L and form heating elements according to the present invention. The two contact plates 20 and the PTC elements 22 form an electrical heating device 24.

[0019] The Fig. Figure 2 shows an enlarged detail of the heat-emitting layer 16. This heat-emitting layer 16 consists of a meanderingly bent sheet metal strip 30, which forms a plurality of heating fins 32 extending perpendicular to the longitudinal direction L. These heating fins 32 are formed by bending the uniform sheet metal strip 30. The bending process creates the corresponding bending regions 34 at the respective ends in the vertical direction H. In this case, the corresponding bending regions 34 begin with a convex curvature 36 extending from the heating fin 32.

[0020] In the exemplary embodiment according to Fig. 2. At the end of this convex curve 36 and between the heating fins 32 forming the respective curves 36, a basically linear heat dissipation surface 38 is formed, specifically at the front convex end of each individual convex curve 36. Between the two heat dissipation surfaces 38, the connection between adjacent heating fins 32, formed by bending the sheet metal strip 30, has a concave recess 40. The concave recess 40 and the convex curves 36 are each formed with an identical bending radius. In this case, this radius is 0.5. The extension of the bending area 34 in the longitudinal direction L is approximately 2 mm.

[0021] The convex curvatures 36 form a first bending point 42 and a second bending point 44, which are enclosed between the concave depression 40 and transition into the heating fins 32 on the outside.

[0022] How Fig. 2 mediated, the adjacent bending areas 34 lie directly against each other. The outer surfaces of heating fins 32 forming different bending areas 34 accordingly touch directly in the bending area 34 or slightly outside the bending area 34 in the vertical direction H.

[0023] In each bending area 34, the heat extraction surface 38 is enlarged compared to the conventional design due to flattening.

[0024] The conventional setup is in Fig. Figure 3A illustrates this. Here, the bending area 50 forms a single convex tip 52, with which the corresponding heat-emitting layer 16 rests against the associated heat-emitting surface.

[0025] Fig. Figure 3B illustrates an alternative embodiment of the present invention. In this embodiment, the tip 52 is flattened by mechanical processing, for example, abrasive processing, compared to the prior art. Accordingly, the bending area 34 in this embodiment of the invention forms a flat heat dissipation surface 38, which, compared to the heat dissipation surface 54 in the prior art, Fig. 3A is significantly enlarged, at least by a factor of 5.

[0026] The area is at least 4 times larger, preferably at least 5 times larger, than the heat extraction area formed by the tip 52. This is more likely to be seen in the cross-sectional view according to Fig. 3A point-like and accordingly linear over the entire width of the sheet metal strip 30.

[0027] It is understood that the exemplary embodiment according to Fig. 2 also with the design according to variant according to Fig. 3B can be combined to further increase the heat extraction area 38 of the heat-emitting layer 16. In addition, besides the two bending points 42, 44 shown, according to Fig. 3B third or fourth bending points of a single bending area 34 may be formed. Reference symbol list 2 Electric heating device 4 cases 6 Longitudinal beam 8 crossbeam 10 elastic prestressing device 12 spring element 14-layered structure 16 heat-emitting positions 18 heat-generating location 20 contact plates 22 PTC elements 24 electric heating device 30 strips of sheet metal 32 heating fins 34 Bending range 36 convex curvature 38 Heat extraction area 40 concave recesses 42 first bending point 44 second bending point 50 bending range 52 peak 54 Heat extraction area L Longitudinal direction H Altitude QUOTES INCLUDED IN THE DESCRIPTION

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

[0000] EP 2 298 582 A1 [0002, 0013, 0017] EP 1 564 503 A1

[0013]

Claims

[1] Electric heating device (2) with a housing (4) and a layered structure (14) in the housing (4), wherein the layered structure (14) comprises at least one heat-generating layer (18) formed by an electric heating device (24) and at least one heat-emitting layer (16) which is thermally connected to the heat-generating layer (18) and is formed by a meanderingly bent sheet metal strip (30) which forms heating fins (32) extending substantially perpendicular to the heat-generating layer (18), wherein two adjacent heating fins (32) are connected to each other via a bending section (34) which is thermally conductive towards the heat-generating layer (18), characterized by , that the bending area (34) forms a flattened heat extraction surface (38). [2] Electric heating device (2) according to claim 1, characterized by , that the bending area (34) is flattened by post-processing of the sheet metal strip (30). [3] Electric heating device (2) according to claim 1 or 2, characterized by , that the bending area (34) comprises a first bending point (42) and a second bending point (44), wherein the first and the second bending point (42; 44) are located at a distance from each other in the longitudinal direction of the heat-generating layer (18) and are thermally conductive against the heat-generating layer (18). [4] Electric heating device (2) according to claim 3, characterized by , that a concave recess (40) is provided between the first bending point (42) and the second bending point (44). [5] Electric heating device (2) according to any one of the preceding claims, characterized by , that adjacent bending areas (34) are directly adjacent to each other. [6] Electric heating device (2) according to any one of the preceding claims, characterized by , that the sheet metal strip (30) has a thickness of between 0.1 and 0.5 mm. [7] Electric heating device (2) according to any one of the preceding claims, characterized by, that the layers (16, 18) of the layered structure (14) are thermally conductive against each other by the prestressing force of an elastic element (12). [8] Electric heating device (2) according to any one of the preceding claims, characterized by , that adjacent bending areas (34) are directly adjacent to each other. [9] Electric heating device (2) according to any one of the preceding claims, characterized by , that the heat-generating layer (18) comprises contact plates (20) arranged parallel to each other and electrical heating elements, in particular PTC elements (22), arranged between them and electrically contacted therewith.

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