ELECTRIC HEATING DEVICE

Description

[0001] The present invention relates to an electric heating device having an inlet and outlet opening for a housing forming a fluid to be heated, which housing encloses a layered structure comprising at least one PTC element which is electrically conductively connected to terminals of different polarity, and heat-emitting elements which are thermally conductively connected to the PTC element on both sides.

[0002] Such an electric heating device is known, for example, from EP 2 607 121 A1 of the present applicant. In this known solution, the PTC element is electrically connected via a contact plate, which in turn is connected to a contact pin to form a connection. Other generic electric heating devices, particularly for a motor vehicle, are known from EP 2 299 201 A1 or EP 2 242 327 A1.

[0003] EP 0 243 077 A2 discloses an electric heating device for a motor vehicle with conductor tracks designed as contact plates, which clamp PTC elements between them on their inner surface and are contacted with corrugated fin elements on their outer surface. Each of the corrugated fin elements consists of a meandering, bent sheet metal strip. To increase heat transfer to the air to be heated, the sheet metal strips have perforations bent out of the plane by punching and bending the sheet metal, each of which forms air passages through the sheet metal material. A similar concept for increasing the heat transfer surface of a corrugated fin layer made of bent sheet metal material is known from US 2014 / 012 4494 A1.

[0004] The present invention aims to provide an electric heating device which is able to dissipate the heat generated by the PTC elements in an improved manner while being as simple as possible in design.

[0005] In these known electric heating devices, the heat-dissipating elements extend as ribs between heat-generating layers of the layered structure, which are formed by the PTC element(s) arranged one behind the other in a plane and the conductor tracks provided for supplying current to the elements. The heat-dissipating elements consist of meandering, bent sheet metal strips that rest directly against the heat-generating layer or with an insulating layer (cf. EP 2 873 296 A2) interposed.

[0006] Effective heat dissipation is crucial for the effectiveness of the electric heating device of the aforementioned type. Therefore, the skilled person strives to minimize thermal resistance between the heat-generating layer and the heat-dissipating elements, which are typically located on both sides of the heat-generating layer.

[0007] In view of this, the present invention proposes an electric heating device according to claim 1, in which the heat-emitting element is formed from a flat area of ​​heat-conducting material provided with perforations in the form of a wire mesh or expanded metal. According to the invention, this flat structure has the same perforations over its entire surface extent. The flat structure in the form of the wire mesh can comprise heat-conducting fibers and is preferably formed as a woven fabric made of the heat-conducting fibers. The flat structure is preferably formed as a mesh made exclusively of wire. The wire is preferably a metallic wire. The wire mesh preferably has alternating intersecting "warp and weft threads" like a simple woven fabric.

[0008] However, a punched sheet, for example expanded metal or perforated sheet, can also be used as a flat structure not according to the invention. If a perforated sheet is used, it is preferable to bend the edges of the punched holes out of the plane of the perforated sheet in order to form projections protruding from the actual sheet plane, against which the medium to be heated is swirled as it passes over the heat-emitting element, thereby improving heat transfer between the heat-conducting element and the medium to be heated. A perforated sheet is a sheet provided with a regular grid of holes. The grid extends at least predominantly, if not completely, over the entire surface of the sheet. The perforated sheet is preferably a perforated plate in accordance with DIN 4185-2 or DIN 24021, whereby the plate is generally made of copper or aluminum. The same applies to the material of the expanded metal.

[0009] The housing forming the inlet and outlet openings for the medium to be heated is preferably made of plastic. It encloses the layered structure and forms the inlet and outlet openings, which are preferably arranged in mutually parallel planes. The housing is preferably a frame-shaped housing, which leaves the entire layered structure free within the frame-shaped housing, so that the medium to be heated can pass over the layered structure. In this preferred embodiment, the housing preferably closely surrounds the layered structure, so that the medium to be heated and passing through the frame-shaped housing must necessarily pass over the layered structure and is thus inevitably heated.

[0010] The orientation of the inlet and outlet openings relative to the layered structure is preferably such that the medium to be heated passes through the layered structure in a direction substantially perpendicular to the layers of the layered structure.

[0011] This layered structure can comprise conductor elements, for example, in the form of contact plates that accommodate at least one PTC element between them. Such conductor elements can form the aforementioned terminals for electrically connecting the PTC elements to the power current, as well as conductor tracks that contact the PTC element. Such conductor elements can be formed from a stamped sheet metal. The conductor elements can each have contact tongues cut free by stamping to form the terminals, or they can be formed as a single piece.

[0012] The heat-dissipating elements can be placed directly against the PTC element or with the conductor element interposed. It is also possible to place the heat-dissipating element with an insulating layer interposed, thus indirectly against the conductor element. The heat-dissipating element can be formed exclusively from the wire mesh.

[0013] A plate-shaped support is preferred, which is provided between the heat-emitting element and the PTC element and against which the heat-emitting element rests in a heat-conducting manner. Such a plate-shaped support essentially forms the base area of ​​the heat-generating layer. This heat-generating layer can be formed exclusively by a PTC element and / or several PTC elements arranged one behind the other in the corresponding layer plane, and the electrical conductor elements provided for them. The heat-generating layer can also comprise a positioning frame made of an electrically insulating material, which accommodates and positions the PTC element(s).

[0014] The aforementioned plate-shaped support can be designed with the heat-emitting element as a pre-assembled unit, for example, welded, flanged, or glued, so that the plate-shaped support can be handled together with the heat-emitting element as an intermediate product during assembly of the electric heating device. The conductor element can also be provided between the plate-shaped support and the PTC element. Thus, the conductor element is located between the heat-emitting element and the PTC element in the heat dissipation direction. In this case, the PTC element bears directly or indirectly against the heat-emitting element with a heat-emitting main side surface. In a direct contact, the conductor element usually does not cover the main side surface of the PTC element, or at most only slightly.Instead of an insulating layer, the heat-emitting element can also be placed against and connected to an electrically non-insulating sheet. This sheet forms the contact surface directly to the PTC element or the conductor element placed on top of the PTC element.

[0015] According to a preferred development of the present invention, the heat-emitting element also forms electrically conductive conductor tracks adjacent to the PTC element. In this case, specifically curved segments of the heat-emitting element are designed as heating fins that best transfer and dissipate heat from the PTC element to the medium to be heated, whereas other segments of the wire mesh are electrically conductively connected to the PTC element in order to supply current to it. According to a preferred development of the present invention, each of the heat-emitting elements is formed from at least one track of wire mesh. The wire mesh is preferably bent for this purpose, so that various functional elements are formed from the flat structure through plastic deformation. Details of this are explained in the following specific description of the invention.

[0016] Further details and advantages will become apparent from the following description of exemplary embodiments in conjunction with the drawings, which show: Fig. 1 is a perspective side view of an embodiment of an electric heating device not according to the invention; Fig. 2 is a side view of a housing bottom part with a heating block of the Fig. 1 shown non-inventive embodiment; Fig. 3 is a perspective side view in an exploded view of the essential components of an embodiment of a heat-generating element; Fig. 4 is a perspective side view of a non-inventive first variant of an embodiment of a heat-emitting element; Fig. 5 is a perspective side view of a non-inventive second variant of an embodiment of a heat-emitting element; Fig. 6 is a perspective side view of a third variant of an embodiment of a heat-emitting element according to the invention; Fig. 7 is a perspective side view of a non-inventive fourth variant of an embodiment of a heat-emitting element; Fig. 8 is an enlarged perspective side view of detail VIII in Figur 7 ; Fig. 9 is a perspective side view of a fifth variant of an embodiment of a heat-dissipating element not according to the invention; Fig. 10 is a perspective side view of a sixth variant of an embodiment of a heat-dissipating element not according to the invention; Fig. 11 is a perspective side view of a seventh variant of an embodiment of a heat-dissipating element not according to the invention; and Fig. 12 is a perspective top view of an embodiment made of wire mesh.

[0017] The Fig. 1 shows a perspective side view of a non-inventive embodiment of the electric heating device with a frame-shaped housing 2, consisting of a lower housing part 4 and an upper housing part 6. Both housing parts 4, 6 are positively connected to one another and accommodate a heating block 8 as a layered structure, which consists of several heat-generating elements 10 and heat-emitting elements 12 arranged in parallel layers to one another.

[0018] The heat-emitting elements 12 consist of an initially flat and bent wire mesh 14, the exact design of which will be explained in more detail in variants below.

[0019] The plastic housing 2 has two opposite frame openings, of which Fig. 1 Only the frame opening 16 formed by the upper housing part 6 is visible, forming the inlet or inlet openings for the medium to be heated. The medium to be heated is air in this case. The exemplary embodiment is an air heater.

[0020] The Fig. 2 shows details of the heating block 8 and its housing, particularly in the lower housing part 4, and shows the lower housing part 4 in a top view with the upper housing part removed. The heat-emitting elements 12 are only partially shown at the respective front ends of the lower housing part 4. Accordingly, the illustration in Fig. 2 also a view of a frame opening 18 formed by the lower housing part 4.

[0021] Again Fig. 3 As can be seen, a plurality of PTC elements 30 are received at predetermined locations in a positioning frame 28 made of an insulating material (in this case plastic) and positioned by this material. In this case, a receptacle 32 is cut out in the positioning frame 28 for each individual PTC element 30, which receptacle encloses and thus secures this PTC element 30. On both sides of the respective PTC elements 30, which are arranged next to one another in a plane, there are metal strips 34, 36 which form electrical conductors for supplying current to the PTC heating elements 30 and through which the heat generated by the PTC heating elements is conducted to the heat-emitting elements 12 by means of heat transfer. These heat-emitting elements 12 lie directly against the metal strips 34, 36.

[0022] Further details of the embodiment are described in EP 2 025 541 A1.

[0023] The following description of various embodiments of the heat-emitting element 12 according to the present invention is based on a basic structure of the electric heating device as discussed above. The description refers to a sheet metal strip 34, against which the heat-emitting element 12 bears in the embodiment discussed here. As is clear from the general description, an insulating layer (not shown here) can also be provided between the heat-emitting element and the contact sheet.

[0024] In the figures discussed below, the sheet metal strip, or where this is missing, the PTC element, is shown in its longitudinal direction with straight edges. The longitudinal direction corresponds to a main direction of extension of each individual layer of the layered structure. The longitudinal direction extends transversely to the flow direction of the fluid to be heated. Its flow direction is indicated by arrow F. The flow direction F passes through the inlet and outlet openings 16, 18 and thus the housing 2 at right angles.

[0025] The Fig. 4 shows a non-inventive embodiment of the heat-dissipating element 13, as is generally known from the prior art. The heat-dissipating element 12 has main side surfaces 40 that extend parallel to the fluid flow F to be heated and substantially transversely to the layers of the layer structure and accordingly act like heating fins 41. The main side surfaces 40 are connected to one another by webs 42, which also extend in the direction of extension of the fluid flow F, but are substantially parallel to the layers of the layer structure and accordingly parallel to main side surfaces of the PTC element, which are identified by reference numeral 44 and extend parallel to the top and bottom sides of the respective sheet metal strip 34. Curved transitions are provided between the webs 42 and the main side surfaces 40.The webs 42 extend in two parallel planes, which are the planes of the layer structure, with the lower plane E1 coinciding with the surface plane of the sheet metal strip 34, and the other plane E2 being provided at a distance therefrom that corresponds to the transverse extent of the heating fins 41. The webs 42 are arranged next to one another in a direction transverse to the passage direction F of the medium to be heated.

[0026] The fluid to be heated can pass through the meandering, curved path of the wire mesh in a conventional manner, ie, pass past the main side walls 40 to extract heat. Due to the uneven surface of the wire mesh, however, the air flow is also swirled, which leads to improved heat transfer from the heat-emitting element 12 to the air to be heated.

[0027] Even with the Fig. 5 In the non-inventive embodiment shown, the main side surfaces 40 of the meandering curved path are arranged via webs 46 in two discrete planes E1, E2 lying parallel to a heat-emitting main side surface 44 of the PTC element. However, these webs 46 are arranged one behind the other in the direction of passage F of the medium to be heated. Such a configuration is in principle also possible with the specific shape of the meandering curved path according to Fig. 4 possible (see flow direction F2 there). Improved heat dissipation through turbulence is achieved in particular by the fact that the fluid flow F to be heated must pass through the main side surfaces 44 and is thus swirled when passing through the main side surfaces 40. This effect is achieved regardless of whether the curved path is strictly rectangular, as is the case Fig. 5 in which the webs 46 extend at right angles from the main side surfaces 40, or a rounded transition between the main side surfaces 40 and the webs 42 is selected, as is basically the case in Fig. 4 is clarified.

[0028] Even with the Fig. 6 In the exemplary embodiment according to the invention shown, the heat-dissipating element is formed from a meandering curved path, so that several main side surfaces 48 are connected to one another via several webs 50. These webs 50 lie in two discrete planes E3, E4, which run parallel to the inlet and outlet openings 16, 18 of the housing 2. Accordingly, the fluid flow F of the medium to be heated passes through the webs 56 and passes essentially parallel to the main side surfaces 48. Here, too, due to the non-uniformly smooth surface of the heat-dissipating element 12, turbulence occurs on the surface and thus improved heat dissipation. This is particularly evident in the specific embodiment according to Fig. 6 , in which the fluid to be heated has to pass through several webs 50 when entering the heat-emitting element 12 and is thereby swirled.

[0029] This turbulence also leads to a disturbance of those air layers that pass between the main side surfaces 48 without having to pass through a web 50.

[0030] The Fig. 7 shows a further non-inventive embodiment of a heat-emitting element of the present invention, which is formed by bending a flat structure provided with perforations in the form of a wire mesh. However, this flat structure is not bent in a meandering manner in the present case. Rather, the structure has two main side surfaces 52 extending essentially at right angles to the direction of passage F of the fluid to be heated, and which are connected to one another via a single web 54 extending parallel to the layers of the layer structure. The web 54 is located on the side opposite the PTC element 30. This results in a Fig. 7 heat-dissipating fin designated by reference numeral 56. Opposite the web 54, the fin 56 can be open. The main side surfaces 52 extend parallel to the inlet and outlet openings 16, 18 of the housing 2. The web 54, however, extends parallel to the passage direction F. The rib 56 further has, on the side opposite the web 54, two fastening segments 58 extending parallel to the web 54, which are formed by bending the flat structure / wire mesh and can be glued to the sheet metal strip 34 to ensure good heat transfer, see enlarged detail in Fig. 8 .

[0031] The Fig. 9 shows several fins 56 provided one after the other in the direction of passage F of the fluid to be heated, each of which is designed like the Fig. 7 und 8 described rib 56 and are attached to the sheet metal strip 34. This embodiment is also not the subject of the invention. By attaching them to the sheet metal strip 34, the ribs 56 can be handled together with the sheet metal strip as a preassembled unit. The ribs 56 can be soldered or glued to the sheet metal strip 34.

[0032] The above mentioned with reference to the Fig. 7 und 9 The described type of fastening between the heat-dissipating element 12 and the associated sheet metal strip 34 also applies to the other exemplary embodiments. A further sheet metal strip may also be provided, which serves solely for contacting and / or pre-assembling the curved flat structure and can rest against the sheet metal strip 34 or 36 directly or with an insulating layer interposed.

[0033] The Fig. 10 shows an alternative embodiment not according to the invention, in which the heat-emitting element comprises a plurality of hollow cylinders 60. These hollow cylinders are formed by bending the flat structure and form a cavity 62 that extends perpendicular to the layers of the layer structure 34 and along a passage direction F. Accordingly, the hollow cylinders 60 stand on the associated sheet metal strip. Fig. 10 shows rectangular hollow cylinders 60. It is understood that the illustrated basic shape is only an example. The hollow cylinders 60 can have any desired base area, including oval, round, or polygonal shapes. Several hollow cylinders 60 are arranged side by side in one plane of the layered structure, transverse to the flow direction F of the fluid to be heated.

[0034] The Fig. 11 shows a modification of the embodiment according to Fig. 5 . This illustrates Fig. 11 only a single rib 70 with two main side surfaces 44, which are connected to each other by a single web 46. Of course, several heating ribs can be used as in Fig. 5 be provided one behind the other in the direction of passage F of the fluid to be heated. Fastening segments 72 are formed by bending, extending transversely to the main extension direction of the rib 70. These fastening segments 72 are directly connected to the main side surface 74 of the PTC element 30. In this exemplary embodiment, the current is supplied directly through the heat-emitting element 12. For this purpose, the element can have a connection lug formed by punching the flat structure for introducing the power current. In the case of a wire mesh, the connection lug can also be punched out of a sheet material and connected to the wire mesh by soldering.

[0035] The previously discussed embodiments each provide improved heat dissipation, since the air passing over the heat-emitting elements 12 is swirled on the non-smooth surface of the heat-emitting element 12, resulting in improved heat transfer.

[0036] The Figur 12 shows an example of a flat structure 80 in the form of a wire mesh from which the previously discussed design of heat-emitting elements 12 can be bent. List of reference symbols

[0037] 2 Housing 4 Housing base 6 Housing top 8 Heating block 10 Heat-generating element 12 Heat-emitting element 14 Contact tongue 15 Slot 16 Frame opening / inlet opening 18 Frame opening / outlet opening 28 Positioning frame 30 PTC element 32 Receptacle for PTC heating element 34 Sheet metal strip 36 Sheet metal strip 40 Main side surface of the heat-emitting element 41 Heating fins 42 Web 44 Main side surface of the PTC element 46 Web 48 Main side surface of the heat-emitting element 50 Web 52 Main side surface of the heat-emitting element 54 Web 56 Rib 58 Mounting segment 60 Hollow cylinder 62 Cavity 70 Rib 72 Mounting segment 74 Main side surface of the PTC element 80flat structure / wire mesh E1first level E2second level E3first level E4second level FDirection of passage of the fluid to be heated

Claims

1. Electric heating device, in particular for a motor vehicle having an inlet and outlet opening (16, 18) for a housing (2) which forms a medium to be heated and which encloses a layered structure (8) comprising at least one PTC element (30) which is electrically conductively connected to connections of different polarity, and which comprises heat-emitting elements (12) heat conductively connected on both sides to the PTC element (30), characterized in that the heat-emitting elements (12) include a panel element (80) provided with perforations in form of a mesh wire or an expanded metal or a perforated sheet and made of heat-conducting material, that the panel element (80) has perforations throughout its entire extent, that the heat-emitting element (12) is formed from a meandering bent sheet and has main side surfaces (48), which are connected to each other by webs (46, 50), that the webs (46, 50) are located at two discrete planes (E3, E4), which run parallel to the inlet and outlet openings (16, 18) of the housing (2) and branch off at right angles from the main side surfaces (40) and that the heat-emitting element (12) abuts the PTC element (30) in a heat-conducting manner with an intermediate layer of a plate-shaped carrier (34).

2. Electric heating device according to claim 1, characterized in that the heat-emitting element (12) is formed from the panel element (80) provided with perforations.

3. Electric heating device according to one of the preceding claims, characterized in that the panel element forms the heat-emitting element (12) and a conducting element which electrically conductively abuts the PTC element (30).

4. Electric heating device according to one of the preceding claims, characterized in that the housing (2) is frame-shaped and forms on opposite sides the inlet and outlet openings (16; 18) between which the layered structure (8) is exposed.

5. Electric heating device according to one of the preceding claims, characterized in that each of the heat-emitting elements (12) is formed of at least one track of the perforated panel element (80) of heat-conducting material which is meanderingly bent.

6. Electric heating device according to claim 5, <b>characterized in that the main side surfaces (40) of the meanderingly bent track are connected to one another via webs (42, 46) which are arranged in two planes (E1; E2) lying parallel to a heat-emitting main side surface of the PTC element.

7. Electric heating device according to claim 6, characterized in that the webs (42) are arranged side by side in a direction transverse to a direction of penetration (F) of the medium to be heated.

8. Electric heating device according to claim 6, characterized in that the webs (46) are arranged one behind the other in the direction of penetration (F) of the medium to be heated.

9. Electric heating device according to claim 5, <b>characterized in that the main side surfaces of the meandering bent track are connected to one another via webs (50) which are arranged in two planes (E3; E4) lying parallel to the inlet or outlet opening (16; 18).

10. Electric heating device according to one of claims 1 to 4, characterized in that each of the heat-emitting elements (12) comprises at least one path of the perforated panel element of heat-conducting material bent as a heat-emitting rib (56) comprising at least two main side surfaces (52) extending substantially parallel to the inlet and outlet openings, respectively, and a web (54) connecting the main side surfaces on a side opposite the PTC element (30).

11. Electric heating device according to claim 10, characterized in that a plurality of ribs (56) are arranged one behind the other in the direction of penetration (F) of the medium to be heated.

12. Electric heating device according to one of the preceding claims, characterized in that the conducting element is formed by at least one bent segment of the heat-emitting element which abuts at least partially against the PTC element.