Electric heating device

Abstract

The invention relates to an electric heating device (2) comprising at least one PTC element (4) having a first main face (6) and a second main face (8) opposite the first main face (6), characterized in that the electric heating device (2) further comprises two metal plates (12), the at least one PTC element (4) being positioned between the metal plates (12) and each metal plate (12) covering the at least one PTC element (4), each metal plate (12) is provided with an insulating coating (18) on the first side (14) thereof facing the at least one PTC element (4), which insulating coating covers the at least one PTC element (4), an electrically conductive layer (20) is formed between the insulating coating (18) and the at least one PTC element (4), which electrically conductive layer rests on a main surface (6, 8) of the at least one PTC element (4), and wherein the insulating coating (18) and the at least one PTC element (4) are electrically conductive. A medium to be heated can flow through a second side (16) of the metal plate (12), which is in each case opposite the first side (14).

Description

Technical Field

[0001] The invention relates to an electric heating device having at least one PTC element, which is designed to be flat. Background Art

[0002] Electric heating devices for heating media are known, which include at least one PTC element, i.e. an element made of a material with a positive temperature coefficient. For example, EP1872986A1 discloses an electric heating device, in which a plurality of PTC elements are respectively held in a kind of bag, which extends into a circulation chamber through which the medium to be heated can flow. Such electric heating devices are designed respectively according to the required heating power. In this case, the scalability, i.e. the adaptation to different, especially greater, heating requirements is usually very complicated. In addition, the known system consists of a relatively large number of components. Summary of the invention

[0003] The problem underlying the invention is to provide an electric heating device which is easy to expand and consists of few components.

[0004] In order to solve this problem, an electric heating device is proposed, which includes at least one PTC element and two metal plates, wherein the at least one PTC element has a first main surface and a second main surface opposite to the first main surface, the at least one PTC element is positioned between the two metal plates, and each metal plate covers at least one PTC element, and each metal plate is provided with an insulating coating covering the at least one PTC element on its first side facing the at least one PTC element, wherein a conductive layer is respectively constructed between the insulating coating and the at least one PTC element, and the conductive layer is abutted against the main surface of the at least one PTC element, wherein the second sides of the metal plates opposite to the first sides can be passed by the medium to be heated.

[0005] In order to operate the PTC element with good efficiency, it is necessary to conduct the heat generated by the PTC element to the main surface of the PTC element as well as possible. The PTC element is usually and preferably also constructed as a cuboid in the present invention. The main surface is the surface of the cuboid with the largest plane extension. These main surfaces are usually and preferably also connected to each other by the surrounding edge of the PTC element in the present invention, and the PTC element usually has an edge side extending at right angles to the plane of the main surface. The area of ​​each main surface is usually at least 5 times larger than the area of ​​one of the edge sides.

[0006] At least one PTC element is made of a material having a positive temperature coefficient (PTC). In the present invention, the PTC element is usually a sintered ceramic stone, and the PTC element is provided with a metallization portion on its main surface for introducing a power supply current into the PTC element.

[0007] Although the invention also explicitly relates to an electric heating device with a single PTC element, it is preferred to use a plurality of PTC elements. These PTC elements are preferably arranged in a row or in a matrix in a flat manner in a plane with multiple rows and columns of PTC elements. This ensures that the electric heating device has good scalability, because multiple or even all PTC elements can always be contact-connected via a common metal plate, an insulating coating and a conductive coating. Thus, even with a large number of PTC elements, the structure is very simple and the contact connection can be easily established.

[0008] One or more PTC elements are electrically contacted via a conductive layer on each main surface, and power supply currents of different polarities are applied during operation, so that the PTC elements generate heat. The electrically insulating coating of the metal plate electrically insulates the conductive layer from the metal plate. In order to achieve good electrical contact connection to the PTC element, the conductive layer covers the main surface of the PTC element or multiple PTC elements, and the electrically insulating layer in turn covers the conductive layer, thereby achieving electrical insulation between the conductive layer and the metal plate. In the present case, covering is understood to mean that the covering layer extends above the metal plate parallel to the plane defined by the layer or the corresponding main surface. The electrically insulating coating is preferably made of aluminum oxide or enamel. Due to the structure with only a few layers, only a small amount of heat is transferred between the heat generating part and the medium flowing through or passing the metal plate during operation. In this case, this design can ensure that the medium directly wets the metal plate. The medium is preferably a liquid and includes water. At the same time, the structure of the electric heating device is simple and easy to expand, because the heating power can be achieved by adapting the number of PTC elements.

[0009] According to a preferred embodiment, the insulating coating is produced by a printing method or a sputtering deposition method. A printing method is particularly understood to be a screen printing method. A sputtering deposition method is a physical vapor deposition method in which a coating is deposited from the vapor phase onto the metal plate. Both methods can easily form a sufficiently electrically insulating coating on the metal plate.

[0010] According to a preferred design, the conductive layer is applied as a coating on the insulating coating. The conductive layer particularly includes a metal layer. The conductive layer is preferably applied by sputtering deposition or screen printing. By designing the conductive layer as a coating on the electrically insulating coating, these layers can be formed on a metal plate, and then these layers can be easily assembled into an electric heating device together with (one or more) PTC elements, in particular, the coated metal plate is bonded to at least one PTC element. Alternatively or additionally, the coated metal plate can be pressed toward at least one PTC element via a screw-on connector. Thus, a simple structure and efficient manufacturing are achieved. The metal used as the conductive layer is preferably aluminum and / or copper, particularly in a paste-like carrier material. Alternatively, the conductive layer is introduced between the insulating coating and the PTC element as a contact sheet, thereby eliminating the need to apply the conductive coating to the insulating coating. Here, the contact sheet is preferably bonded to the PTC element or the coated metal sheet.

[0011] According to a preferred design, the metal plate, the conductive layer and at least the PTC element are bonded together. Alternatively or additionally, the metal plate, the conductive layer and the at least one PTC element are clamped to each other by at least one screw connection. In order to achieve good heat transfer, it is necessary to press the metal plate, the insulating layer and the conductive layer to each other and to press the main surface of at least one PTC element to each other. The conductive layer must also be closely attached to the main surface of at least one PTC element so that the electrical contact connection to the PTC element can be achieved. Preferably, the adhesive is applied very thinly only between the individual elements to produce a sufficient degree of adhesion to keep the electric heating device together, while the heat transfer between the elements will not be significantly hindered. It is also possible to construct a corresponding adhesive in an existing cavity between the elements, in particular between adjacent PTC elements and between the edge side of the PTC element and the edge of the electric heating device, so as to increase the air distance and creepage distance between the elements. Preferably, one or more screw connections are formed between the metal plates, and the clamping of the elements of the electric heating device is achieved by the screw connection. The embodiment of the element clamping of the electric heating device by means of at least one screw connection has the advantage that no further heat transfer due to the adhesive can take place between the respective main surface of the at least one PTC element and the medium to be heated.

[0012] According to a preferred design, the flow-guiding structure is constructed on the second side of at least one metal plate. The flow-guiding structure is preferably constructed integrally with the metal plate. Alternatively or additionally, the flow-guiding structure is abutted against the second side of at least one metal plate. The flow-guiding structure is preferably connected to the metal plate of the adjacent electric heating device or is constructed integrally with the metal plate. Through the flow-guiding structure, a flow channel for the medium to be heated in the form of one or more flow channels is formed. The flow-guiding structure can be designed to: generate at least one straight flow channel above the metal plate, generate at least one flow channel with at least one straight segment, or generate at least one tortuous flow channel.

[0013] The electric heating device preferably comprises at least two PTC elements, wherein each metal plate is assigned to or provided to at least two PTC elements. Through the structure according to the present invention, it is achieved that a plurality of PTC elements are combined flatly, preferably in rows or in the form of a matrix with rows and columns to form an electric heating device, and a metal plate having an electrical insulation layer and a conductive layer as described above is arranged on each main surface of the PTC element. Thus, an easily expandable electric heating device is obtained, and its heating power can be expanded by the number of PTC elements. In addition, the corresponding electric heating device is simply composed of only a few elements. This simplifies the manufacture of the electric heating device.

[0014] Preferably, the conductive layer is electrically connected to the main surface of the PTC element via at least one contact arch. The contact arch is preferably formed as a deformation portion of the contact sheet forming the conductive layer, as a coating on the contact sheet forming the conductive layer, or as an area with a thickened coating. The contact arch is preferably constructed in a dome or dome shape. Preferably, multiple contact arches are constructed on each main surface of the PTC element. The electrical contact connection of at least one PTC element can be achieved in a simple manner through the contact arch. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Other details and advantages of the present invention can be obtained from the following description of the embodiments in conjunction with the accompanying drawings. In the drawings:

[0016] Figure 1 A first embodiment of an electric heating device is shown in cross-section;

[0017] Figure 2 A second embodiment of the electric heating device is shown in cross-section;

[0018] Figure 3 A third embodiment of the electric heating device is shown in cross-section;

[0019] Figure 4 A first example of a flow guide structure according to the first, second or third embodiment in an electric heating device is shown; and

[0020] Figure 5 A second example of the flow guide structure according to the first or second embodiment in the electric heating device is shown. DETAILED DESCRIPTION

[0021] Figure 1 A first embodiment of an electric heating device 2 according to the invention is shown. The electric heating device 2 comprises a plurality of PTC elements 4, which are arranged in a flat row. Each PTC element 4 has a metallized first main surface 6 and a metallized second main surface 8, which are connected to each other via an edge side 10 and are opposite to each other. In this case, each main surface 6, 8 of each PTC element 4 is at least 5 times larger than each edge side 10. For the sake of clarity, the edge side 10 is only partially provided with reference numerals.

[0022] The electric heating device 2 further comprises two metal plates 12, each of which has a first side 14 facing the PTC element 4 and an opposite second side 16 facing away from the PTC element 4. Here, the size of the metal plates 12 is designed so that the metal plates cover all the PTC elements 4 of the electric heating device 2, so that the PTC elements 4 are positioned between the metal plates 12 and the metal plates 12 extend beyond the corresponding PTC elements 4 at the edge side. Therefore, the extension of the main surface 6, 8 of each metal plate 12 parallel to each PTC element 4 (here all PTC elements 4) is greater than the extension of the one or more PTC elements 4.

[0023] On the first side 14, respectively, an insulating coating 18 is applied by sputtering deposition or printing, which consists of a dielectric material (preferably including aluminum oxide and / or enamel). Here, the surface of the insulating coating 18 covers the surface of the main surface 6, 8 of the PTC element 4 facing the first side 14 of the metal plate 12. In the case of only one PTC element 4, the surface of the insulating coating 18 covers the surface of the main surface 6, 8 of the PTC element 4 facing the first side 14 of the metal plate 12.

[0024] Conductive layers 20 are respectively constructed between the insulating coating 18 and the respective main surfaces 6, 8 of the PTC element 4. In this embodiment, these conductive layers 20 are designed as contact strips 22. The conductive layers 20 contact and connect the respective main surfaces 6, 8 of all PTC elements 4 and cover these main surfaces. During operation, currents of different polarities are supplied to the main surfaces 6, 8 of the PTC element 4 through the conductive layers 20 and heat is generated.

[0025] The conductive layer 20 is connected to a power electronic device (not shown here), through which the PTC element 4 is controlled. The heat generated in the PTC element 4 is dissipated to the medium through the metal plate 12, and the medium is guided through the second side 16 of the metal plate 12 and flows through the metal plate. The medium is preferably a liquid, in particular water. In this example, the different elements of the electric heating device 2 are bonded to each other by means of an adhesive 24. As a result, the metal plate 12 with the electrically insulating coating 18 and the conductive layer 20 is pressed toward the PTC element 4, so that the conductive layer 20 is in contact with the corresponding main surfaces 6, 8 of the PTC element 4, and the PTC element is preferably constructed in a metallized manner.

[0026] The electric heating device 2 has a simple structure and is expandable. This means that the number of PTC elements 4 in the electric heating device 2 can be adapted to the required heating power. As shown here, multiple elements 4 in a row can be used in the electric heating device 2, but there are also occasions such as two or more rows of PTC elements 4. The electric heating device 2 can be easily manufactured from a few elements, and the PTC elements 4 can be easily contact-connected.

[0027] Figure 2 A second embodiment of the electric heating device 2 is shown. In order to avoid repetition, only the differences from the first embodiment are listed here, and the other parts refer to the above description of the first embodiment. Unlike the first embodiment, in the second embodiment, no contact sheet is used, but a metal layer 26 is used as the conductive layer 20. Preferably, the metal layer is applied to the electrically insulating coating 18 by a spraying method, a sputtering deposition method or a separation method. The power supply current is supplied to the PTC element 4 during operation through this metal layer 26.

[0028] Furthermore, the electric heating device 2 is not glued as in the first exemplary embodiment, but the metal plates 12 are connected to one another by screw connections 28 , so that the metal plates 12 together with the electrically insulating layer 18 and the electrically conductive layer 20 are pressed against the respective main surfaces 6 , 8 of the PTC element 4 .

[0029] Figure 3The third embodiment of the electric heating device 2 is shown. In order to avoid repetition, only the differences from the first and second embodiments are listed here, and the other parts refer to the above description of the first and second embodiments. In the third embodiment, an adhesive 24 is constructed in a partial area between the conductive layer 20 and the PTC element 4, wherein the conductive layer can be designed as a contact sheet 22 and a metal layer 26, and the adhesive fixes the composite of the metal plate 12, the electrical insulation layer 18 and the conductive layer 20 on the PTC element 4. Although only one PTC element 4 is shown here, there can be multiple PTC elements 4 aligned in a plane, as in the first or second embodiment. A contact bulge 44 is constructed between adjacent adhesives 24, and electrical contact is established between the conductive layer 20 and the metallized surface of the main surface 6, 8 of the PTC element 4 via the contact bulge. The contact bulge 44 preferably has a convex shape and is preferably in the shape of a dome or a dome. Here, the contact bulge 44 can be designed as a region of a correspondingly thicker metal coating 26 or as a bulge of the contact sheet 22. A corresponding metallic coating on the contact strip 22 can also form the contact curvature 44 .

[0030] Figure 4 and Figure 5 Two examples of flow guide structures 30 are shown in cross-section. Figure 4 1 shows a metal plate 12 of an electric heating device 2 according to the first or second embodiment described above, for example. The metal plate 12 is structureless, i.e. substantially smooth. A flow guide structure 30 is attached to the second side 16 of the metal plate 12, which is formed integrally with a matching plate 32. The matching plate 32 is preferably also the metal plate 12 of the adjacent electric heating device. Alternatively, the matching plate 32, which together with the flow guide structure 30 and the metal plate 12 defines at least one flow channel 42 for the medium, can be designed as a metal plate, a ceramic plate or a synthetic material plate. Figure 4 The flow path in the cross section shown is provided as an arrow with reference numeral 34. The flow path in Figure 4 In the figure, the fluid is first guided from the right in front of the first flow-guiding structure 36 shown on the right, then after passing the first flow-guiding structure 36, guided through the opening 38, and then guided again from right to left behind the second flow-guiding structure 40. A single fluid channel 42 or a plurality of fluid channels 42 can be configured on the second side 16 of each metal plate 12. The flow channel 42 can extend straight, curved or meandering.

[0031] Figure 5A second example of a flow-guiding structure 30 is shown in a sectional view. In contrast to the first example, the metal plate 12 here has a flow-guiding structure 30 which is molded onto the metal plate 12 and is made of the same material as the metal plate 12. The flow-guiding structure 30 rests on a counter plate 32. In this example, the counter plate 32 is substantially smooth. The counter plate 32 is preferably the metal plate 12 of the adjacent electric heating device. Alternatively, the counter plate 32 is a plate made of metal or ceramic material and / or synthetic material. The fluid channel 42 is formed by the metal plate 12, the flow-guiding structure 30 and the counter plate 32. In addition, reference is made to the corresponding Figure 4 of the first example to avoid repetition.

[0032] Reference numerals list

[0033] 2 Electric heating device

[0034] 4 PTC components

[0035] 6 First main surface

[0036] 8 Second main surface

[0037] 10 Edge side

[0038] 12 Metal Plate

[0039] 14 First side

[0040] 16 Second side

[0041] 18 Electrical insulation coating

[0042] 20 Conductive layer

[0043] 22 Contact piece

[0044] 24 Adhesive

[0045] 26 Metal Layer

[0046] 28 Screw the connector together

[0047] 30 diversion structure

[0048] 32 Pairing Board

[0049] 34 Flow Path

[0050] 36. First diversion structure

[0051] 38 Opening

[0052] 40 Second diversion structure

[0053] 42 Fluid Channels

[0054] 44 Contact arch

Claims

1. An electric heating device (2), comprising at least one PTC element (4) and two metal plates (12), wherein the at least one PTC element has a first main surface (6) and a second main surface (8) opposite to the first main surface (6), wherein: The at least one PTC element (4) is positioned between metal plates (12), and each metal plate (12) covers the at least one PTC element (4), characterized in that each metal plate (12) is provided with an insulating coating (18) on its first side (14) facing the at least one PTC element (4), the insulating coating covering the at least one PTC element (4), wherein a conductive layer (20) is respectively constructed between the insulating coating (18) and the at least one PTC element (4), the conductive layer being in contact with the main surface (6, 8) of the at least one PTC element (4), wherein a second side (16) of the metal plate (12) opposite to the first side (14) can be flowed through by a medium to be heated.

2. The electric heating device (2) according to claim 1, characterized in that: The insulating coating (18) is produced by a printing method or a sputtering deposition method.

3. The electric heating device (2) according to claim 1 or 2, characterized in that: The conductive layer (20) is applied as a coating (26) on the insulating coating (18).

4. The electric heating device (2) according to claim 1 or 2, characterized in that: The conductive layer (20) is introduced as a contact piece (22) between the insulating coating (18) and the at least one PTC element (4).

5. The electric heating device (2) according to any one of the preceding claims, characterized in that The metal plate (12), the conductive layer (20) and the at least one PTC element (4) are bonded together.

6. The electric heating device (2) according to any one of the preceding claims, characterized in that The metal plate (12), the conductive layer (20) and the at least one PTC element (4) are clamped to one another by at least one screw connection (28).

7. The electric heating device (2) according to any one of the preceding claims, characterized in that A flow-guiding structure (30, 36, 40) is formed on a second side (16) of at least one metal plate (12).

8. The electric heating device (2) according to any one of the preceding claims, characterized in that The flow-guiding structure (30, 36, 40) abuts against a second side (16) of at least one metal plate (12).

9. The electric heating device (2) according to any one of the preceding claims, characterized in that At least two PTC elements (4) are configured, wherein a metal plate (12) is respectively assigned to the at least two PTC elements (4).

10. The electric heating device (2) according to any one of the preceding claims, characterized in that The electrically conductive layer (20) is electrically connected to the main surfaces (6, 8) of the PTC element (4) via at least one contact protrusion (44).

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