Electric heater

Abstract

Electric heating device, in particular for a motor vehicle, with a heating block (38) forming opposing surfaces for an inlet (44) and an outlet (40) for air to be heated, with at least one heat-generating layer with at least one PTC element (54) and heat-emitting layers (2) lying on both sides against the heat-generating layer, wherein one of the heat-emitting layers (2) forms the surface for the inlet (44) and the other of the heat-emitting layers (2) forms the surface for the outlet (40), and the heat-generating layer is arranged between the heat-emitting layers (2), and wherein the heat-emitting layers (2) are each formed by a stamped sheet metal (4) which forms a contact surface (20) for contacting the PTC element (54), characterized in that from the contact surface (20) on both sides, parallel to formed plane (E1) extending heat transfer fins (10).

Description

[0001] The present invention relates to an electric heating device according to the preamble of claim 1. Such an electric heating device is known, for example, from WO 2008 / 122 362 A1. Further prior art is known from DE 10 2007 062 302 A1, DE 42 25 990 C1, US 2015 / 0 343 883 A1, US 2004 / 0 252 986 A1, EP 2 017 103 A1, and EP 2 873 296 B1. EP 2 873 296 B1 relates to a high-voltage application in which the heat-generating layer is electrically insulated from the heat-dissipating layers.

[0002] In the prior art described above, the heating block is usually located in a frame as a layered structure in which the heat-generating layer, preferably several heat-generating layers, are arranged parallel to one another transversely to the direction of passage of the air through the heating block.

[0003] The heat-generating layer comprises contact plates that rest on opposite surfaces of the PTC element to energize the PTC element. On the opposite side relative to the PTC element, the heat-dissipating layers rest on the contact plates. In a high-voltage electric heating device that can be operated with high voltage, the heat-dissipating layer rests on the associated contact plate with at least one insulating layer interposed.

[0004] The structure described above has been widely adopted, but it still leaves room for improvement.

[0005] The present invention aims to provide an electric heating device of the type mentioned at the outset which can be manufactured economically and more easily and leaves open the possibility of constructing the electric heating device with fewer parts.

[0006] To achieve the above object, the present invention provides an electric heating device having the features of claim 1.

[0007] In this electric heating device, one of the heat-emitting layers forms the area for the inlet of the air to be heated, and the other of the heat-emitting layers forms the area for the outlet of the air to be heated. In other words, one of the heat-emitting layers is located at the front and the other at the back of the heating block. The air enters one heat-emitting layer and exits the other heat-emitting layer. The heat-emitting layer for the air inlet usually does not form any surface area on the opposite surface of the heating block to the air outlet. The same applies to the layer provided at the outlet. This does not take up any surface area of ​​the heating block in the area formed by the heating block for the air inlet.

[0008] The two surfaces are typically arranged one behind the other in the direction of air flow. The heat-generating layer is positioned between the heat-dissipating layers. Accordingly, in the direction of air flow, the first heat-dissipating layer is located at the inlet. This is followed in the direction of air flow by the PTC element(s). Further downstream of the PTC element is the other, second heat-dissipating layer.

[0009] While the electric heating device known from EP 2 017 103 A1 comprises heat-generating layers which form both the inlet surface and the outlet surface of the heating block, in the present invention the surface formed for the inlet and outlet of the air to be heated through the heating block is formed by only one of the heat-generating layers.

[0010] The present invention thus creates a completely new design principle for the construction of an electric heating device, in particular an air heater for a motor vehicle. Such an air heater is typically installed in an HVAC system and is located upstream or downstream of a conventional heat exchanger for air conditioning the vehicle interior.

[0011] According to the present invention, the heat-dissipating layers are each formed by a stamped sheet metal. Each of the heat-dissipating layers is preferably formed from a single stamped sheet metal. The stamping of the sheet metal is carried out in such a way that heat transfer fins are created, which are usually arranged parallel to the air flowing through the heating block, i.e., extend essentially at right angles to the inlet and outlet surfaces of the heating block. According to the present invention, however, the stamping of the sheet metal is carried out in such a way that, after this processing, the sheet metal forms a contact surface for contacting the PTC element. This contact can be a thermally conductive and electrical contact.However, it can also simply be a thermally conductive contact if, as is indicated by a preferred development of the present invention, the PTC element rests thermally conductively against the heat-emitting layers with an electrical insulating layer interposed. In this case, a conductor track is located between the insulating layer and the PTC element, which is electrically contacted with the PTC element in order to supply it with current. Insulation is usually located on opposite outer sides of associated contact plates, so that both heat-emitting layers associated with the PTC element are electrically insulated from the heat-generating layer arranged between them. According to the present invention, heat transfer fins protrude from the contact surface on both sides, extending parallel to a plane formed by the contact surface.Thus, the contact surface in the width direction of a heat-generating layer is usually located centrally to the length and width of the heat-generating layer.

[0012] The sheet metal forming the heat-dissipating layer is preferably bent in a meandering manner, such that the contact surface for the PTC element is formed by several, preferably parallel, webs of the sheet metal. Heat transfer fins extend from these webs in the flow direction of the air to be heated. The sheet metal is typically considerably wider than the contact surface. Adjacent to the contact surface, these heat transfer fins allow air to pass through the heating block from the inlet surface to the outlet surface. The sheet metal is typically processed only by punching and bending to form the heat transfer fins on the one hand and the contact surface for the PTC element on the other.

[0013] To simplify orientation, the direction in which the air to be heated passes through the heating block is referred to as the height direction. In this direction, the heating block has a height that is formed by the individual thicknesses of the two heat-emitting layers and the heat-generating layer. Any contact plates for supplying current to the PTC element and any insulating layers on the outside are to be assigned to the heat-generating layer. The heating block has a length and width extension at right angles to this height extension. The width extension is the direction of the heating block which has a smaller dimension in the corresponding plane transverse to the direction in which the air passes through than the lengthwise direction. The inlet and outlet directions also lie in the plane containing the width and lengthwise directions or parallel to them.The exit surface of the heating block, which is usually cuboid-shaped, usually has parallel inlet and outlet surfaces. The heat transfer fins project beyond the contact surface on both sides in the width direction. Furthermore, a plurality of heat transfer fins and webs are usually provided one behind the other in the longitudinal direction, with each of the webs forming a contact surface or a portion thereof for a PTC element, or multiple contact surfaces for multiple PTC elements.

[0014] To increase the stability of the heat-dissipating layer and to position it in a frame that may be provided, a preferred embodiment of the present invention proposes that the heat transfer fins be connected to one another at their opposite free ends by a connecting web extending parallel to the webs. This connecting web is usually located with its outer surface in the plane containing the contact surface. In other words, the connecting web is preferably shaped like the web that completely or partially forms the contact surface. It has the same direction of extension and height. The web and the connecting webs prevent the passage of air through the heat-dissipating layer at this point. This is only possible between these web-shaped elements.Here, the heat transfer fins can also be made air-permeable through punching or provided with projections or roughness to enable improved heat transfer.

[0015] The connecting webs are preferably provided with a notch on the outside. This allows air to pass between the inner peripheral surface of a frame opening defined by the frame and the outer surface of the heat-dissipating layer, even when the heat-dissipating elements are arranged at the edge of a frame. This results in a certain degree of cooling between the edge of the heat-dissipating layers and the frame.

[0016] The two heat-emitting layers are preferably glued together with the PTC element interposed. This results in a structural unit consisting of the two heat-generating layers and the PTC element. It is understood that an electrically conductive adhesive is used here, or the adhesive bond is designed in such a way that the direct contact of the PTC element with the heat-emitting layers is not completely prevented by the adhesive bond, so that the PTC elements can be directly energized via the heat-emitting layers. An adhesive bond is also possible with a highly insulating design, in which the contact surface is, for example, covered with an electrically insulating layer, to the inside of which a contact plate is glued, which in turn is connected to the PTC element, preferably via an electrically conductive adhesive.An electrically conductive adhesive is created, for example, by a plastic adhesive into which electrically conductive particles are incorporated.

[0017] To facilitate installation of the electric heating device, the heating block is preferably housed in a plastic frame in a manner known per se. The plastic frame forms opposing frame openings, in each of which a plurality of heat-emitting layers extending parallel to one another are exposed. This makes it possible to create an electric heating device with a higher heat output. If heat-emitting layers that are each identically designed are used in such a configuration, the manufacturing costs can be reduced. In this case, all heat-emitting layers of the electric heating device are preferably identical. The heat-emitting layers are preferably placed next to one another with the interposition of the PTC element(s) in such a way that air guide channels formed between the structures of the heat-emitting layers merge seamlessly into one another.The air ducts of the opposing heat-dissipating elements are preferably aligned accordingly. This prevents excessive pressure losses of the air passing through the heat-dissipating layers. Alternatively, a certain offset of the associated heat-dissipating layers can be set when joining these layers with the PTC element(s) interposed to achieve a certain turbulence, which improves heat transfer at the interface to the heat-dissipating layer.

[0018] The frame preferably forms a projection which is encompassed by the two heat-emitting elements to form-fit the heating block to the frame. This engagement is completed by gluing the second heat-emitting layer to the layer below it in the direction of air flow. For this purpose, the heat-emitting layers preferably have connecting segments which, as flat sheet metal segments, overlap the projection on the outside and thus secure the heating block to the frame in a form-fitting manner. The connecting segments usually extend parallel to the contact surface for contracting the PTC element. The connecting segments are preferably flat. The connecting segments preferably lie in a plane which defines the air inlet or outlet surface or is only slightly offset forwards or backwards in the direction of flow.

[0019] The connecting segments are typically formed from the stamped sheet metal, i.e., formed integrally with the sheet metal forming the heat-dissipating layer. The connecting segments are connected to a connecting plate, which forms at least one connecting lug. These connecting plates are used to establish electrical contact with the heating block.

[0020] The heat-dissipating layers are preferably provided with electrical connection lugs. These electrical connection lugs serve to electrically contact the heating block. They can be exposed within the aforementioned plastic frame or protrude beyond it. It is also conceivable to establish the electrical connection entirely without a plastic frame.

[0021] The connecting plate discussed here accordingly represents a separate connecting lug element, which can be connected to the heat-generating layer by clamping, welding, flanging, soldering, gluing or crimping.

[0022] For this purpose, the connecting segment preferably has a bore arranged off-center relative to a central longitudinal axis of the heat-generating element. The bore is sufficiently large to guide a tool against the opposite inner surface of the connecting segment of the respective other heat-generating layer in order to apply and install the connecting plate. A clinching tool or a welding stud, for example, can be passed through the bore.

[0023] The terminal lugs can be connected directly to a power cable. The terminal lugs can also be connected to the power supply via a control unit that is provided as a structural unit with the electric heating device, preferably arranged in a control housing that is connected to the plastic frame and formed entirely or partially by the plastic frame.

[0024] 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 a perspective side view of a heat-emitting element; Fig. 2 that in Fig. 1 drawn detail A in an enlarged view; Fig. 3 an enlarged perspective view of a connection-side end of the heat-emitting element according to the Fig. 1 and Fig. 2; Fig. 4 a perspective view corresponding Fig. 3 for the outer surface of the heat-emitting layer; Fig. 5 a plan view of a sheet metal strip undergoing stand processing and forming heat-emitting parts prior to bending; Fig. 6 a perspective end view of a heating block formed from the heat-emitting elements according to the Fig. 1 to 3; Fig. 7 a perspective top view of a layer of the heating block forming the air outlet according to Fig. 4 with PTC elements applied; Fig. 8 a representation according to Fig. 5 after applying a plastic frame; Fig. 9 a view according to the Fig. 5 and Fig. 6 after application of the layer forming the air inlet; Fig. 10 a perspective side view of a ground connection to the heating block according to the Fig. 4 and Fig. 7 forming connecting plate and Fig. 11 a plan view of parts of the heating block and the frame of the embodiment.

[0025] The Fig. 1 to 3 illustrate an embodiment of a sheet metal part 4 punched to form a heat-dissipating layer 2. The punched sheet metal part 4 has a connection region 6 and a heat-dissipating region 8.

[0026] The heat dissipation region 8 has a plurality of heat transfer fins 10, which are connected to one another via webs 12 and connecting webs 14 located in a first plane E1, on the one hand, and via bends 16 located in a second plane E2, on the other hand. The planes E1 and E2 are spaced apart from one another by the extent of the heat transfer fins 10. The heat transfer fins 10 extend in the direction of passage of the air to be heated.

[0027] The webs 12 lie on a central longitudinal axis 16 of the heat-dissipating layer 2 and form an approximately continuous contact surface 20 located in the first plane E1. The connecting webs 14 are provided at the opposite ends of the heat transfer fins 10. The ends referred to here are those ends located in the first plane E1. This is the direction of extension of the heat transfer fins 10 parallel to the planes E1 and E2, respectively. Fig. 3, the connecting webs 14 have a notch 22 opening outwards.

[0028] The bend 16 is designed such that two heat transfer fins 10 extending from adjacent connecting webs 14 or webs 12 essentially abut one another. This has the advantage that the contact surface 20, as formed by the webs 12, is essentially continuous.

[0029] By a previous punching process, whose punching pattern is made up of Fig. 5, large openings are formed between the connecting webs 14 and the webs 12 in the still flat sheet 4, which in Fig. 5 are marked with reference numeral 24. In between, small openings marked with reference numeral 26 are formed, which, after bending of the sheet 4, are located in the second plane E2, which is the visible plane according to Fig. 4. This punching process allows the air to be heated to not only pass through the large openings 24, but also into the gap between the almost adjacent heat transfer fins 10 extending from the bend 16. This creates a relatively large air transfer surface, with the narrow gap between the heat transfer fins 10 extending from the bend 16 enabling greater heat transfer through boundary layer turbulence.

[0030] In Fig. 5 also shows parallel bending lines 28 around which the initially flat material of the sheet 4 is bent in order to form the Fig. 1 to 4 to produce the heat-emitting layer 2.

[0031] The connection area 6 is formed by a connection segment 30 of the sheet metal 4, which extends in the second plane E2 and runs linearly within this plane. The connection segment 30 is provided with a bore 32 arranged eccentrically to the central longitudinal axis 18.

[0032] How Fig. As illustrated in Figure 2, the heat-emitting layers 2 in the first plane E1 form locking projections 34, which are formed by punching the sheet metal in the region of the last web 12, particularly the last connecting webs 14. These locking projections 34 can cooperate with an associated recess in a plastic frame 36 to attach a heating block 38 to the plastic frame 36 (see Figure 2). Fig. 9, Fig. 11). Alternatively, the plastic frame 36 can also have a web-shaped projection, which is provided centrally on the frame in the direction of air passage and is positively encompassed by the locking projections 34 of the mutually applied layers 2. A similar fastening is selected on the connection side, which is described below with reference to the Fig. 8 and Fig. 9 will be explained in more detail.

[0033] Fig. Figure 6 shows the heating block 38 after joining three heat-emitting layers to form an air outlet surface 40 with three identical heat-emitting layers to form an air inlet surface 44. The heating block 38 is provided with connecting plates for the electrical connection of the heating block 38. The connecting plate designated by reference numeral 46 serves as the ground connection and is connected to all three heat-emitting layers 2 via their connecting segments 30. The corresponding connecting plate 46 is shown separately in Fig. 10. It has three connection plate bores 49 corresponding to the bore 32 and is basically L-shaped in cross-section. The narrower leg of the L-shaped cross-sectional design is projected over by two electrical connection lugs 50, which are cut free by punching and bent out by bending over the plane containing the narrow webs of the L-shaped profile. The longer of the L-shaped legs with the connection plate bores 48 is placed on the inside against the three connection segments 30 of the heat-dissipating layers 2 and connected thereto. For this purpose, a tool, for example a welding stud, reaches through the bores 32 of the other heat-dissipating layers in order to weld the connection plate 46 to the three heat-dissipating layers 2.

[0034] In a corresponding manner, the connecting plates designated by reference numeral 52 for connecting the positive pole are each connected to the connecting segments 30 of the other heat-dissipating layers. These connecting plates 52 have no holes and are significantly shorter than the connecting plate 46. The connecting plates 52 are each assigned to only one connecting segment 30 of a single heat-dissipating layer. Their longer leg of the L-shaped profile also rests flat against the inside of the associated connecting segment 30.

[0035] The following describes the production of the Fig. 6 shown heating block 38 including the plastic frame 36 with reference to the Fig. 7 to 9 explained.

[0036] First, the three heat-emitting layers 2 can be connected to each other via the connecting plate 46. This creates a unit that Fig. 7. PTC elements 54 are glued to the contact surfaces 20 at a distance from one another in the longitudinal direction. In this case, the PTC elements 54 are contacted via the heat-emitting layers 2. Accordingly, the PTC elements 54 are provided on the heat-emitting layers 2 with an electrically conductive adhesive. Fig. 7 accordingly illustrates the ground connection of the PTC elements 54. In the embodiment shown, the heat-emitting layers are current-carrying.

[0037] The plastic frame 36 is then placed over the three heat-dissipating layers 2. The plastic frame 36 has a box-shaped projection 56, which serves as a connector housing and is adapted to guide a mating connector housing. The box-shaped projection 56 accommodates the electrical connection lugs 50, 53. However, in the longitudinal direction of the heat-dissipating layers 2, the connection segments 30 project beyond the projection 56. The same applies to the other heat-dissipating layers, which are Fig. 9, after the PTC elements 54 have been bonded to the contact surfaces 20 formed by these heat-emitting layers 52. Thus, the connecting segments 30 of the heat-emitting layers 2 engage around the projection 56, so that the plastic frame 36 is positively connected to the heating block 38. For example, the connecting plates 52 for the positive connection lugs 52 can now be inserted through the interior of the projection 56 and connected to the corresponding connecting segments 30 in the manner described above.

[0038] Fig. Figure 11 shows the effect of the notches 22, which allow air to pass between the outer surface of the outer heat-dissipating layers 2 and the inner peripheral surface of the plastic frame 36. This also ensures sufficient cooling so that the plastic frame 36 cannot overheat. List of reference symbols 2 heat-emitting layer 4 sheet metal 6 Connection area 8 Heat dissipation area 10 heat transfer fin 12 jetty 14 Connecting bridge 16 Bend 18 Central longitudinal axis 20 contact surface 22 Notch 24 major breakthrough 26 small opening 28 Bending line 30 connection segment 32 bore 34 Locking projection 36 plastic frames 38 heating block 40 air outlet area 44 Air inlet area 46 connecting plate 48 connection plate hole 50 electrical connection lugs 52 connecting plate 53 Connection lug 54 PTC element 56 lead E1 first level E2 second level

Claims

[1] Electric heating device, in particular for a motor vehicle, with a heating block (38) forming opposing surfaces for an inlet (44) and an outlet (40) for air to be heated, with at least one heat-generating layer with at least one PTC element (54) and heat-emitting layers (2) lying on both sides of the heat-generating layer, wherein one of the heat-emitting layers (2) forms the surface for the inlet (44) and the other of the heat-emitting layers (2) forms the surface for the outlet (40), and the heat-generating layer is arranged between the heat-emitting layers (2), and wherein the heat-emitting layers (2) are each formed by a stamped sheet metal (4) which forms a contact surface (20) for contacting the PTC element (54), characterized by that heat transfer fins (10) extend from the contact surface (20) on both sides parallel to a plane (E1) formed by the contact surface (20). [2] Electric heating device according to claim 1, characterized by that the sheet (4) is bent in a meandering manner and the contact surface (20) is formed by a plurality of webs (12) of the sheet (4), from each of which the heat transfer fins (10) extend, which extend in the flow direction of the air to be heated. [3] Electric heating device according to claim 1 or 2, characterized by that the heat transfer fins (10) are each connected to one another at their opposite free ends by a connecting web (14) extending parallel to the webs (12). [4] Electric heating device according to claim 3, characterized by that the connecting webs (14) are provided with a notch (22) on the outside. [5] Electric heating device according to one of the preceding claims, characterized by that the PTC element (54) is electrically conductively bonded to the heat-emitting layers (2). [6] Electric heating device according to one of claims 1 to 4, characterized by that the PTC element (54) lies in thermally conductive contact with the heat-emitting layers (2) with an electrical insulating layer interposed therebetween. [7] Electric heating device according to one of the preceding claims, characterized by that the heating block (38) is accommodated in a plastic frame (36), that the plastic frame (36) forms mutually opposite frame openings, in each of which a plurality of heat-emitting layers (2) extending parallel to one another are exposed, and at least one projection (56) which is encompassed by the two heat-emitting layers (2) for the positive fixing of the heating block (38) to the plastic frame (36). [8] Electric heating device according to one of the preceding claims, characterized by that the heat-emitting layers (2) each have identically designed heat-emitting elements. [9] Electric heating device according to one of the preceding claims, characterized by a connection segment (30) formed by the punched sheet metal (4) which is connected to a connection plate (46, 52) forming at least one electrical connection lug (50, 53). [10] Electric heating device according to claim 9, characterized by that the connecting segment (30) has a bore (32) arranged off-center to a central longitudinal axis (18) of the heat-emitting layer (2).

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