Electric heating device and method for its manufacture

Abstract

The present invention relates to an electric heating device (2), particularly for a motor vehicle, comprising a housing (6) that is at least partially electrically conductive and has a circumferential groove (36) on its end face, and a sheet metal cover (34) that closes the housing (6), wherein an adhesive (50) is introduced into the groove (36), and the cover (34) has a circumferential rim (38) that engages in the groove (36) such that the rim of the cover (38) is immersed in the adhesive (50) all the way around. The sealing and fastening of the cover (34) relative to the housing (6) is improved by the fact that the rim (38) is in contact with a surface (42) that laterally delimits the groove (36) and is arranged at a distance from the opposite surface (44) of the groove (36).

Description

[0001] The present invention relates to an electric heating device, in particular for a motor vehicle, with a housing that is at least partially electrically conductive, a circumferential groove being provided on the front face of which is a cover made of sheet metal, which closes the housing, wherein an adhesive is introduced into the groove, and the cover has a circumferential rim that engages in the groove in such a way that the rim of the cover is immersed in the adhesive all around.

[0002] An electric heating device known from DE 10 2022 127 107 A1 is considered to be of the generic type. This prior art discloses an electric heating device with a housing that is at least partially electrically conductive and a sheet metal cover that closes the housing. The cover has a surface that covers the housing, from which the circumferential edge extends at essentially right angles. The groove formed by the housing has projections on opposing surfaces that bound the groove. These projections are corrugated and alternate with each other, so that crests on one side correspond to troughs on the other. This improves the connection between the cover and the housing. In particular, it ensures reliable metallic contact between the cover and the housing.

[0003] The present invention relates in particular to an electric heating device in which the housing comprises a circulation chamber with inlet and outlet openings for a fluid to be heated, a heating element thermally connected to the circulation chamber, a connection chamber in which the heating element is electrically connected, and a partition wall, wherein the partition wall separates the circulation chamber from the connection chamber in a fluid-tight manner. The heating element can be a PTC heating element with a PTC element for heating a medium in the circulation chamber. Alternatively, the heating element can also be a thick-film heating element.

[0004] In the electrical heating device according to the invention, for example, several PTC heating elements are housed within the casing. Typically, several PTC heating elements are electrically connected in the connection chamber, optionally grouped into heating circuits. A circuit board can be provided in the connection chamber for this purpose, assigning different PTC heating elements to different heating circuits. Furthermore, a populated circuit board can be provided in the connection chamber, which is a central component of a control unit that typically controls the multiple PTC heating elements to appropriately adjust the power output of the electrical heating device.

[0005] These details are known from DE 20 2020 000 689 U1.

[0006] The features mentioned above can also be preferred features of the electrical heating device according to the invention.

[0007] With electric heating devices, a particular problem arises when the heating element is switched on: electromagnetic waves can interfere with other components in the vicinity. These components can include, for example, electronic components or on-board entertainment components in a vehicle. Therefore, it is known to design the housing to be at least partially electrically conductive for shielding purposes. In particular, the connection chamber and the control device located therein are housed in a metallic casing. Parts of the casing surrounding or defining the circulation chamber can be made of a non-conductive material. Plastic is preferred for its reduced weight.

[0008] The requirements for an electric heating device in a motor vehicle, in particular, include several additional considerations. The electric heating device must not only be as lightweight as possible, but its electrical components must also be reliably protected from the environment. This is especially important for electric heating devices used in electric vehicles, which are typically operated at high voltage. Moisture and / or dirt, which can penetrate, for example, the connection chamber, can impair the desired electrical insulation of individual components. Dirty or moist surfaces can promote the formation of leakage currents.

[0009] The present invention addresses the problem of providing an electric heating device that enables the best possible sealing of the housing while reliably shielding the electrical components housed within it. The proposed design must be implementable in a process-reliable manner.

[0010] To solve this problem, the present invention provides an electric heating device of the type mentioned above, in which the edge is contacted with a surface that laterally delimits the groove and is arranged at a distance from an opposite surface of the groove.

[0011] A circumferential groove, in this context, refers to a groove that extends around the entire circumference. It is not essential that the groove has the same depth across its entire perimeter. An adhesive is applied to the groove, creating a seal around the lid. The lid has a circumferential rim that engages with the groove, ensuring that the entire edge of the lid is immersed in the adhesive. This results in a completely fluid-tight seal around the lid within the groove. A suitable adhesive is one that cures but remains elastic even after curing. For example, a silicone adhesive can be used.

[0012] The adhesive not only serves to hold the lid in place. It also acts as a sealant, preventing the passage of dirt and / or moisture in the groove area by ensuring that the surrounding edge engages with the adhesive.

[0013] In contrast to the solution known from DE 10 2022 127 107 A1, a certain gap remains between the opposing surfaces, which may preferably be formed by the outer surface of the groove, and between the groove and the edge over the entire length of the groove. This gap is generally filled with adhesive, thus ensuring a secure seal of the cover in the groove. The gap typically results in a circumferential groove filled with adhesive between the opposing surface and the edge. It is understood that adhesive will also be provided below the edge, i.e., between the base of the groove and the end face of the edge. The opposing surface is preferably straight in sections. Only the basic alignment of the corners of the housing that deflect the groove form areas where the opposing surface is not straight.

[0014] The lid is preferably made of sheet metal. This wording indicates that the lid material has a wall thickness predetermined by the sheet metal material. The lid is preferably produced by stamping and bending or other forming processes such that a circumferential rim projects from the otherwise essentially flat covering surface of the lid at a substantially right angle. The lid thus forms a covering surface that is regularly bounded on the outside by this rim.

[0015] Since the edge is in contact with the surface that laterally delimits the groove, this contact creates an electrical connection and thus reliable EMC protection. As is known per se from DE 10 2022 127 107 A1, the surface contacted with the edge can be corrugated, such that the crests of the corrugations preferably bear directly against the edge, causing deformation, and troughs are provided between them, leaving a gap between themselves and the surface that laterally delimits the groove. This surface that laterally delimits the groove is usually completely surrounded by the edge. It is preferably the inner surface of the groove, which faces the inside of the housing.

[0016] The wave troughs can also be filled with adhesive, which improves the material bond of the edge within the groove and the sealing.

[0017] Preferably, the wave crests cause plastic deformation of the edge to increase strength and / or ensure electrical contact.

[0018] The present invention proposes further measures to make the manufacturing process more reliable. In this process, the adhesive is preferably metered volumetrically into the groove so that when the edge is subsequently immersed in the groove, the adhesive is reliably covered and thus secured. The edge is then inserted into the groove and immersed in the adhesive bath. The adhesive is displaced towards the groove opening and thus vertically. By carefully shaping the height of the edges defining the groove, it is possible to prevent the upwardly displaced adhesive from entering the housing. The inner edge is preferably higher than the outer edge. Any adhesive displaced beyond the groove will accordingly flow over the outer edge and outwards, thus preventing it from entering the housing.Furthermore, the inner rim can form a contact area that acts as a stop surface for the lid when the rim is inserted into the groove, thus limiting the depth to which the rim penetrates the groove. Preferably, the lid rests against this contact area after assembly.

[0019] Further details and advantages of the present invention will become apparent from the following description of an exemplary embodiment in conjunction with the drawing. The drawing shows: Fig. 1 a perspective exploded view of an embodiment of an electric heating device; Fig. 2 a longitudinal sectional view of a PTC heating device of the heating unit according to Fig. 1; Fig. 3 a perspective side view of a schematically represented housing with a lid; Fig. 4. A longitudinal section view through the groove and the edge of the lid for the example shown. Fig. 3 and Fig. 5 a cross-sectional view through the groove and the edge of the lid for the example according to Fig. 3.

[0020] The Fig. Figure 1 shows an embodiment of an electric heating device 2 with a multi-part heater housing comprising a lower housing part 4 made of plastic and an upper housing part 6 formed in one piece from metal by means of die casting.

[0021] The lower housing part 4 is trough-shaped and encloses a heating chamber 8, forming inlet and outlet ports 10 that communicate with the heating chamber 8. These inlet and outlet ports 10 are molded as a single piece with the lower housing part 4 by injection molding. Several heating elements 12 are shown between the upper housing part 6 and the lower housing part 4.

[0022] How Fig. As illustrated in Figure 2, these heating devices 12 each have at least one PTC element 14, against which contact elements 16.1; 16.2 bear, forming contact tongues 18 that project beyond a metallic housing 20. The PTC element 14 is held in a frame 22 and between the contact elements 16.1; 16.2. Insulating layers 26 are provided between the metallic housing 20 and a heating cell 24 formed by the two contact elements 16.1; 16.2 and the PTC element 14.

[0023] The heating devices 12 are held by plug connections in a designated receptacle 28 of a partition 30 of the upper housing part 6 and are electrically connected and controlled in a connection chamber 29 of a control unit 32. Details of this embodiment are described in EP 3 334 242 A1, which originates from the applicant.

[0024] In the Fig. 1 and Fig. Reference numeral 34 designates a cover that is sealed and electrically conductively connected to the housing upper part 6. This component, hereinafter also referred to as housing 6, is in Fig. Figure 3 shows a perspective side view. The housing 6 is clearly shown with a circumferential groove 36, the course of which corresponds to the geometry of an edge 38 of the cover 34, which projects from a covering surface 40 formed by the cover 34. The design of the groove 36 results in particular from the Fig. 4 and Fig. 5.

[0025] Reference numeral 42 designates a surface of the groove 36 that laterally delimits it on the outside. Reference numeral 44 designates the opposite inner surface of the groove 36 on its inside. These two surfaces, also referred to as inner surface 42 and outer surface 44 respectively, extend from a groove base 46. Fig. Figure 4 illustrates that the outer surface 44 runs in a straight line and at a distance from the edge 38. The straight course of the outer surface 44 is only interrupted at the corners 6.1 of the rectangular housing 6 in the top view.

[0026] Thus, a constant film of adhesive 50 is formed between the edge 38 and the outer surface 44. How Fig. As further illustrated in Figure 4, the inner surface 42 is corrugated. It has troughs 52 and crests 54. The crests 54 are in direct contact with the rim 38. When the rim is inserted into the groove 36, the adhesive 50 is scraped off by the crests 54. The crests 54 plastically deform the rim 38 section by section, thereby creating increased strength of the mechanical connection between the cover 34 and the housing 6. Fig. 4 Furthermore, the adhesive 50 is also located in the wave troughs 52. Since the surface sections contacting the edge 38 are formed by the inner surface 42, this inner surface is clamped all around by the edge 38, which further improves the strength.

[0027] Further details of the Nut 36 are provided with reference to Fig. 5 discussed below, whereby the height of the groove 36, in the sense of the present description, is to be understood as the extension of the groove 36 from the groove base 46 upwards to the open end of the groove 36. A in Fig. The inner edge 5, marked with reference numeral 56, is generally higher than an outer edge 58, from which the outer surface 44 extends. The inner edge 56 has an intermediate area 60 and a contact area 62 offset inwards, which in this case is designed as a circumferential ridge.

[0028] Since the outer edge 58 is set downwards relative to the inner edge 56, any excess adhesive displaced when the edge 38 is inserted into the groove 36 is channeled outwards. This makes the bonding of the cover 34 more reliable. There is no risk of the adhesive 50 penetrating the interior of the housing 6, which is sealed by the cover 34. Reference symbol list 2 Heating device 4 Housing lower part 6. Housing top 6.1 Corners 8 Heating chamber 10 inlet and outlet ports 12 heating units 14 PTC elements 16 Contact element 16.1 lower contact element 16.2 upper contact element 18 Contact tongue 20 cases 22 frames 24 heating cell 26 Insulation layer 28 recording 29 Connection chamber 30 partition wall 32 Control unit 34 lids 36 Nut 38 Edge of the lid 40 Coverage area 42 interior surface 44 outdoor area 46 Groove 50 glue sticks 52 wave troughs 54 wave crests 56 inner edge 58 outer edge 60 Intermediate range 62 Contact area 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] DE 10 2022 127 107 A1 [0002, 0013, 0015] DE 20 2020 000 689 U1

[0005] EP 3 334 242 A1

[0023]

Claims

Electric heating device (2), in particular for a motor vehicle, with a housing (6) that is at least partially electrically conductive, on the end face of which a circumferential groove (36) is provided, and a cover (34) made of sheet metal that closes the housing (6), wherein an adhesive (50) is introduced into the groove (36), and the cover (34) has a circumferential rim (38) that engages in the groove (36) such that the rim of the cover (38) is immersed circumferentially in the adhesive (50), characterized in that the rim (38) is in contact with a surface (42) that laterally delimits the groove (36) and is arranged at a distance from the opposite surface (44) of the groove (36). Electric heating device according to claim 1, characterized in that the surface (42) contacted by the edge (38) is corrugated, wherein the troughs (52) of the corrugations leave a space between themselves and the edge (38) and the crests (54) lie directly against the edge (38). Electric heating device according to claim 2, characterized in that the wave troughs (52) are filled with adhesive (50). Electric heating device according to claim 2 or 3, characterized in that the opposite surface (44) between the corners (6.1) deflecting the longitudinal direction of the groove (36) is designed to run in a straight line. Electric heating device according to one of claims 2 to 4, characterized in that the edge (38) is plastically deformed by the wave crests (54). Electric heating device according to one of the preceding claims, characterized in that the surface of the groove (36) interacting with the edge (38) is the inner surface (42) of the groove (36) lying within the edge (38). Electric heating device according to claim 6, characterized in that the outer surface (44) provided opposite the inner surface (42) is spaced completely away from the edge (38). Electric heating device according to one of the preceding claims, characterized in that an inner edge (56) of the groove (36) which limits the groove (36) internally has a greater height than the opposite outer edge (58) of the groove (36). Electric heating device according to claim 8, characterized in that the inner edge (56) forms a contact area (62) that contacts a covering surface (40) of the lid (34) and an intermediate area (60) provided between the contact area (62) and the groove (36) and offset in the height direction relative to it in the direction towards a groove base (46). Electric heating device according to claim 9, characterized in that the intermediate area (60) has a greater height than the outer edge (58).

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