DE102018212012A1 - Heat generating element and process for its manufacture - Google Patents

Abstract

The invention relates to a heat-generating contact plate (6) with a PTC element (2) and an electrically conductive contact thereon for energizing the PTC element (2). For permanent and secure contact between the contact plate and the PTC element and the easy handling of the heat-generating element in the course of production, it is proposed according to the invention to provide at least one of the contact plates (6) with retaining tabs (12), which with the interposition of an insulating layer Grip the PTC element (2) for the prestressing contact of the contact plate (6) against the PTC element (2) in a form-fitting manner.

Description

The present invention relates to a heat-generating element with a PTC element and electrically conductive contact plates thereon for energizing the PTC element.

Such heat-generating elements are used in various areas of technology. The present invention relates in particular to a heat-generating element for use in motor vehicles. Here, heat-generating elements of the type mentioned at the outset are used as auxiliary heaters to compensate for insufficient heating of air introduced into the passenger compartment by the heat exchanger, which is connected to the cooling water of the engine, or in an electric vehicle in a heater for heating the Interior and for defrosting the windshield. This also applies to the heat-generating element according to the invention.

In a motor vehicle, the heat-generating elements are exposed to special conditions. A considerable temperature spectrum must be taken into account in the design. Vehicles can be used in very hot regions or in very cold regions. In addition, all components in a motor vehicle are exposed to considerable vibration. Finally, the motor vehicle manufacturers place special demands on the fatigue strength that the components have to meet under the conditions mentioned.

Furthermore, there are requirements for economical production. Heat-generating elements for heating a motor vehicle must be economically produced and easy to handle.

In view of this, it is known to add the above-mentioned components of a heat-generating element to a structural unit, which can be handled as a unit during the assembly of the heat-generating element and the installation. For example, is out EP 2 190 256 A1 a heat-generating element is known in which the PTC element is glued to the contact plates lying thereon on both sides. Such a solution is indeed suitable for handling the components. However, it cannot be assumed that the adhesive connection is so permanent that the PTC element and the contact plates adjoining it are adequately connected to one another so that good electrical and heat-conducting contact can be ensured over the lifetime of the electrical heating device of the motor vehicle.

On the other hand, it is from the EP 2 298 582 A1 respectively. EP 1 564 503 A1 the present applicant known to first mount the contact plates and the PTC element attached thereto in a heater and then to produce the electrical contact by applying an external spring force by inserting a spring into the frame receiving the heat-generating element, which the elements of electric heating device biased against each other, so that there is also good electrical contact between the PTC element and the contact plates and good heat dissipation of the heat generated by the PTC element.

In high-voltage applications, it is generally necessary to cover the heat-generating element on the outside with an insulating layer, so that the heat-emitting surfaces of the electrical heating device do not lie directly on the contact plate in an electrically conductive manner. Such a solution is out, for example EP 1 768 457 A1 known.

The aforementioned prior art can be generic in each case. It still leaves nothing to be desired regarding the permanent and safe contact between the contact plate and the PTC element and the easy handling of the heat-generating element in the course of production.

In view of this, the present invention proposes a heat generating element having the features of claim 1. The heat-generating element according to the invention has, in a manner known per se, at least one PTC element and electrically conductive contact plates adjoining it for energizing the PTC element. The contact plates are usually on opposite side surfaces of the PTC element. They are electrically isolated from one another and assigned to different polarities. The PTC element usually has a rectangular shape, with a main side surface, i. H. the area with the largest base area is generally used to dissipate the heat generated by the PTC element. Here, the contact plate usually lies with its contact surface on the PTC element. In the context of the invention, however, it is also conceivable to place the contact plate on an end face which connects the two main side faces of the PTC element to one another and which is usually not used for heat extraction. The contact plate can just as well rest on the main side surface as on an end surface.

In the embodiment according to the invention, at least one of the contact plates has retaining tabs, which are usually on opposite longitudinal sides of the contact surface of the contact plate protrude to form-fit around the PTC element. The gripping takes place with the interposition of an insulating layer, so that the mechanical fastening of the contact plate to the PTC element caused by the form-fitting wrap is not at the same time also a current-conducting contact of the holding tab on the PTC element. Thus, the retaining tab usually rests on the surface of the PTC element which is opposite the surface of the PTC element which is in contact with the contact plate for energization. Thus, the PTC element is braced against the contact surface of the contact plate designed for electrical contacting due to the positive engagement by the retaining tab. The retaining tab holds the PTC element under tension against the contact plate for energizing the PTC element.

The contact plate has a plurality of retaining tabs, which means that at least two retaining tabs lie opposite one another in order to place opposite longitudinal sides of the PTC element against it and to press the PTC element against the contact plate.

The holding tabs are usually made in one piece by stamping and bending from a sheet metal material, so that the contact surface of the contact sheet provided for contacting and the holding tabs are formed on a one-piece piece of sheet metal. This reduces the manufacturing costs.

The retaining tabs encompassing the PTC element do not only effect a preassembly of the components of the heat-generating element. Rather, due to the permanent elastic prestressing of the contact surface of the contact plate against the PTC element, an advantageous contact is obtained even during operation.

The quality of this contacting and also of the connection between the contact plate and the PTC element can be increased in that the PTC element is encompassed by the retaining tabs. In the case of a rectangular PTC element, at least one retaining tab is provided on all edges of the PTC element. In the case of a round PTC element, retaining tabs are provided with a pitch of not more than 30 ° from one another. As a result, extensive pretensioning of the contact surface of the contact plate against the PTC element is promoted.

With a view to the best possible contacting of the PTC element on both sides, it is proposed according to a preferred development of the present invention that each of the contact plates is provided with a plurality of retaining tabs and that the retaining tabs of the respective contact plates alternately encompass the PTC element along its longitudinal edge. The contact sheets usually grip around the PTC element at least on opposite longitudinal edges. Here, too, both contact plates can encompass the PTC element. The retaining tabs are provided alternately, so that two contact tabs of a first contact plate receive a retaining tab of a second contact plate between them. This results in a solid bracing of the PTC element against both contact surfaces of the respective contact plates. The cohesion of the pre-assembled components is also improved.

According to a preferred development of the present invention, the insulating layer is formed by an insulating plate. This insulating plate can be, for example, a ceramic plate made of aluminum oxide or titanium nitride. The insulating plate has sufficient strength so that the force applied by the elastic contact of the retaining tabs can be transferred back from the insulating plate without the insulating plate being mechanically damaged. Those elements which have good thermal conductivity are preferably considered as the insulating plate. This basically applies to ceramic materials. The insulating plate usually extends over the entire main side surface of the PTC element, i. H. it covers the main side surface of the PTC element and the contact surface which is usually provided with the same dimensions and is formed by the contact plate. The insulating plate preferably projects over the edge of the PTC element. This offers the possibility of providing the holding tabs with a greater physical extension, so that the spring travel provided by the holding tab is increased, which has a favorable effect on the resulting spring force. This measure also increases the clearance or creepage distance.

The holding tab usually has a free end which is bent at a right angle, so that a contact section extends parallel to the surface of the insulating layer or insulating plate and a holding section extends at right angles from the contact section and surrounds the insulating layer or plate so that it borders relatively is prepositioned to the PTC element in the latitude and / or longitude direction. The configuration then ensures that the insulating layer fixed over the holding tabs is arranged centrally over the PTC element and the contact surface.

According to a preferred development of the present invention, the contact plate has cut-out contact tabs from the sheet metal material forming the contact plate, which are bent in the direction of the PTC element in order to form contacts abutting the PTC element. On the one hand, this results in an elastically pre-stressed Contact plate formed against the surface of the PTC element to be contacted. This measure leads to an improved elastic pretension due to the engagement of the retaining tabs. Because not only the elasticity of the retaining tabs, but also the elasticity of the contact tabs apply elastic prestress and accordingly improve the contacting of the PTC element on the one hand and the mounting of the components of the heat-generating element on the other. The discrete contacts have the further advantage that electrical contacting can be effected in a predetermined manner. For the design of the spring tongues and their arrangement, for example, on the EP 2 637 475 directed. The configuration and arrangement of the spring tongues described there can also be used for the present invention.

For the best possible heat extraction of the heat generated by the PTC element, it is proposed according to a preferred development of the present invention to provide a thermally conductive compound between the PTC element and the contact plate. The mass does not necessarily have to be electrically conductive if the aforementioned spring tongues are provided for the defined contacting of the contact plate. The thermally conductive mass fills the gap between the contact surface of the PTC element facing the PTC element and the contact tongues, so that there is a good heat-conducting connection between the contact plate and the PTC element. Of course, an electrically and thermally conductive compound can be used. For example, a plastic compound filled with electrically conductive particles, for example silicone, can be used. A heat-curable two-component silicone compound is preferred, which is filled with said filler components made of metal or ceramic. The thermally conductive composition can also extend between the contact plate and the insulating layer, in order to also ensure good decoupling of the heat generated by the PTC element on the heat conducting path behind the contact plate.

In particular for high-voltage applications, it is proposed according to a preferred development of the present invention to completely surround the PTC element with a frame made of an insulating material, leaving a heat-emitting surface formed by the insulating layer free. In this embodiment, the outer surface of the heat-generating element is formed by the heat-emitting surfaces of the two insulating layers, which cover the PTC element and the contact plates in a heat-conducting manner and for this purpose are regularly connected to one of the main side surfaces of the PTC element. The edge of the insulating layers is surrounded by the insulating material and is regularly embedded in it. This insulating material forms a frame that completely surrounds the PTC element. The insulating material is sealingly connected to the heat-emitting surface, so that the heat-generating element according to this development is also suitable for direct use in a liquid heater in which the heat-emitting surfaces of the insulating layers are exposed. This frame made of insulating material is usually only surmounted by connecting lugs or contact tongues which are provided for the electrical contacting of the PTC element in the manner of male plug contact elements. For details of the further training discussed here, reference is made to E 3 334 242 A1.

The present invention also provides a method for producing a heat-generating element. In this process, contact sheets with retaining tabs molded onto them are first produced by stamping and bending sheet metal material. The manufacture is usually carried out by machining a uniform piece of sheet metal, so that the retaining tabs are formed in one piece on the contact sheet. The contact plates are then placed on opposite sides of a PTC element, so that the retaining tabs projecting over the PTC element on one side cross over and the retaining tabs of the one contact plate projecting over the PTC element between their free ends and the other contact plate, a receptacle for one Form insulation layer. The insulating layer is then introduced into this receptacle under elastic prestressing of the holding tabs and is placed against the other contact plate.

This methodical procedure creates a uniform heat-generating element that can be further processed as a pre-assembled unit. Preferably, before the contact plates are placed on the surface of the PTC element, a thermally conductive composition is liquidly applied to said surface, which mass is displaced when the contact plates are pressed against the PTC element, so that the contact plates are electrically conductive, but without any remaining air pockets, are good heat conductors against the Apply PTC element. The contact plates preferably have spring tongues which bear against the PTC element under elastic pretension and accordingly cause selective contacts. When the contact plate is pressed against the PTC element, the heat-conductive mass can preferably penetrate through openings provided on the contact plate, in order to get into a gap between the contact plate and the insulating layer and also to fill any space there, displacing air. As an alternative or in addition, additional heat-conductive compound can be applied to this rear side of the contact plate facing away from the PTC element. This can be done before and / or after the contact plate is applied to the PTC element.

The heat-conductive mass is preferably an adhesive mass that hardens, so that the good heat-conducting connection is also provided by the heat-conductive mass. Due to the tabs, the insulating layer and the contact plate are spring-loaded against the PTC element. The components are assembled into a preassembled unit, so that this preassembled unit can later be handled as a unit, for example for molding around the frame or for installing the heat-generating element in an electrical heating device.

• 1 eine perspektivische Draufsicht auf ein Ausführungsbeispiel vor dem Auflegen der Isolierschicht;
• 2 eine perspektivische Draufsicht auf das Ausführungsbeispiel nach 1 mit der Isolierschicht;
• 3 eine Längsschnittansicht entlang der Linie II-II gemäß der Darstellung in 2;
• 4 eine Ansicht gemäß 3 für einen Randbereich des Ausführungsbeispiels in vergrößerter Darstellung und
• 5 eine perspektivische Stirnseitenansicht eines wärmeerzeugenden Elementes nach Umspritzen eines isolierenden Rahmens.

Further details and advantages of the present invention can be found in the following description of an exemplary embodiment in conjunction with the drawing. It shows:

• 1 a top perspective view of an embodiment before placing the insulating layer;
• 2 a top perspective view of the embodiment 1 with the insulating layer;
• 3 a longitudinal sectional view along the line II-II as shown in 2 ;
• 4 a view according to 3 for an edge area of the embodiment in an enlarged view and
• 5 a perspective end view of a heat-generating element after extrusion coating an insulating frame.

The 1 and 2 show the essential components of a heat generating element of the present invention with a PTC element 2 which with its main side surfaces 4 electrically conductive with a contact plate 6 connected is. For this purpose, the contact plate 6 several in one piece by stamping and bending on the contact plate 6 trained spring tongues 8th on. These spring tongues 8th are in the 2 and 3 than from one through the contact plate 6 formed contact area 10 segments of the contact plate lifted out by punching and bending 6 recognizable, the more punctiform or linear than the full area on the PTC element 2 issue.

In the 1 to 3 are also holding tabs 12 recognizable by stamping and bending in one piece on the contact plate 6 are formed and those with the dimensions of the main side surface 4 trained contact areas 10 of the contact plate 6 overtop. The holding tabs 12 have one in 4 with reference numerals 14 marked connecting section, from the plane of the contact surface 10 of a contact plate 6.1 to the contact area 10 of the other contact plate 6.2 there is a turn. The connecting section 14 accordingly extends in the height direction of the PTC element 2 , The connecting section protrudes at an angle of between 35 and 60 ° to the outside and to the opposite side. The connecting section 14 merges into a holding section that is parallel to the height direction of the PTC element 2 is aligned and in a system section bent inwards at right angles thereto 18 transforms.

How from 2 can be seen, protrude from opposite edges of the contact surface 10 retaining tabs 12 from. Any contact sheet 6 also forms an electrical connection lug cut free by punching and bending 20 from, which serves the plug contact of the embodiment shown and the other components of the PTC element 2 clearly towered over. Between the two connecting lugs 20 are through the contact plate 6 positioning stops 21 educated. Also on the opposite side there is a positioning stop formed by stamping and bending the sheet metal material forming the contact sheet for each contact sheet 21 , This is how the insulation layer is 22 positively enclosed on all sides via the contact plate 6 formed contact area 10 ,

The embodiment also has ceramic insulating plates that are an embodiment of an insulating layer 22 formed. Like that 2 to 4 can be seen, this insulating layer protrudes 22 the PTC element 2 edge. The insulation layer 22 accordingly has a larger footprint than the contact area 10 whose dimensions are the main side surface 4 of the PTC element 2 equivalent. The insulating layer projects beyond this main side surface and the contact surface by at least 0.5 to 2 cm.

The through the plant section 18 and the holder section 16 formed free ends of the opposite spring tongues 8th form a recording 24 for the insulating layer 22 out.

How in particular 2 mediated, the retaining tabs of the contact plates are alternately along the longitudinal edges of the PTC element 2 intended. So they belong with reference numerals 12.2 marked holding tabs to the in 1 upper contact surface of the other contact plate 6.2 where on the other hand those with reference numerals 12.1 marked holding tabs to the lower and thus the one contact plate 6.1 belong. So are the retaining tabs 12.1 of a contact plate 6.1 between two retaining tabs 12.2 of the other contact plate 6.2 intended.

According to the enlarged view 4 is also an insulating and with reference numerals 26 labeled well thermally conductive mass to be found, both in the gap between the contact surface 10 and the main face 4 extends, as well as in the gap between one of the contact surface 18 provided opposite and through the contact plate 6 formed contact surface 28 for the insulating layer 22 and this insulating layer itself.

Between the main side surface 4 and the contact area 10 fills this mass 26 a gap from the elastic contact of the spring tongues 8th against the main side surface 4 is released. This results in spite of the elastic arrangement of the spring tongues 8th a good heat-conducting connection between the PTC element 2 and the contact plate 6 , The same applies due to the insulating mass provided on the opposite side for the heat-conducting connection between the contact plate 6 and the insulating layer 22 ,

The mass 26 can be a hardening, in particular thermosetting, plastic compound, for example a two-component silicone, to which a filler made of ceramic and / or metallic powder can be added.

To produce the exemplary embodiment shown, the contact plates are first 6 prepared by punching and bending. Here we do not only the contact surface 10 cut free, but also the retaining tabs 12 formed, and essentially in a geometric shape, as in 4 can be seen. After that, go to the main side panel 4 of the PTC element 12 and / or the contact surface 10 of the contact plate 6 the mass 26 applied. The PTC element 2 is against the contact surfaces 10 of the two contacts 6.1 and 6.2 created. Then the insulating layer 22 in the recording 24 brought in. The free ends of the retaining tabs 12 pushed outwards. The free ends can have a funnel-like configuration, with the progressing insertion movement of the insulating layer 22 to be pushed outwards. Alternatively, the free ends of the retaining tabs can be used 12 also be pushed outwards by an outer holding device, so that the recording 24 for inserting the insulating layer 22 is kept clear at the top.

Before applying the insulating layer 22 can on this and / or outside on the contact plate 6 the mass 26 be applied. After applying the insulation layer 22 in the recording 24 hold the elastic tabs that reflect back inwards 12 the insulating layer 22 widthwise in position. In addition, there is an elastic prestress due to the abutment of the abutment sections 18 against the outer surface of the insulating layer 22 , so that together with the contact surface 10 under elastic tension against the main side surface 4 of the PTC element 2 is created. How 4 the plant section is located 18 on an edge 30 the insulating layer 22 the PTC element 2 overlaps on the edge.

The 5 shows this with reference to the 1-4 Embodiment described after extensive encasing with an insulating material, the one with reference numerals 32 marked frame. The frame surrounds the PTC element 2 fully extensive. Only the connecting lugs 20 tower over the frame 32 outside. The frame 32 forms opposite frame openings 34 in which the major part of the outer surface of the insulating layer 22 as a heat-emitting surface 36 exposed. The frame 32 forming insulating material is, for example, a silicone. The insulating material forming the frame is usually fluid-tight against the heat-emitting surface 36 the insulating layer 22 so that the heat-emitting surface 36 can be directly illuminated by a gaseous or liquid fluid to be heated, without fear that the fluid will reach the current-carrying tracks within the frame 32 arrives. The frame 32 forms at its from the connecting flags 20 protruding side sealing lips 38 for sealing insertion in a connector receptacle of a heater housing, as in EP 3 334 242 A1 is described.

As the 1 and 5 to illustrate the connection lugs 20 at the same height. They are by bending inwards opposite the contact surface 10 added. This also results in a stop for the PTC element when it bears against the respective contact surface 10 ,

LIST OF REFERENCE NUMBERS

2

PTC element

4

Major side surface

6

contact sheet

8th

spring tongue

10

contact area

12

retaining tab

14

connecting portion

16

holding section

18

contact section

20

terminal lug

21

positioning

22

insulating

24

admission

26

Dimensions

28

contact surface

30

edge

32

frame

34

frame opening

36

heat-emitting surface

38

sealing lip

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• EP 2190256 A1 [0005]
• EP 2298582 A1 [0006]
• EP 1564503 A1 [0006]
• EP 1768457 A1 [0007]
• EP 2637475 [0018]
• EP 3334242 A1 [0036]

Claims (9)

Heat-generating element with a PTC element (2) and electrically conductive contact plates (6) thereon for energizing the PTC element (2), characterized in that at least one of the contact plates (6) is provided with retaining tabs (12) which are located under Intermediate layer of an insulating layer, grip the PTC element (2) for the prestressing contact of the contact plate (6) against the PTC element (2) in a form-fitting manner. Heat generating heating element after Claim 1 , characterized in that the PTC element (2) is circumferentially encompassed by retaining tabs (12). Heat generating element after Claim 1 or 2 , characterized in that each of the contact plates (6) is provided with a plurality of holding tabs (12) and that the holding tabs (12) of the respective contact plates (6.1; 6.2) alternately encompass the PTC element (2) along its longitudinal edge. Heat-generating element according to one of the preceding claims, characterized in that the insulating layer (22) is formed by an insulating plate which is encompassed by the retaining tab (12) of the contact plate (6). Heat generating element after Claim 4 , characterized in that the edges (30) of the insulating plate (22) encompassed by the retaining tabs (12) project beyond the edge of the PTC element (2). Heat-generating element according to one of the preceding claims, characterized in that the contact plate (6) has spring tongues (8) cut out of the sheet metal material forming the contact plate, which tongues for forming contacts on the PTC element (2) in the direction of the PTC element. Element (2) are bent. Heat-generating element according to one of the preceding claims, characterized in that a thermally conductive mass (26) is provided between the PTC element (2) and the contact plate (6) and / or the insulating layer (22). Heat-generating element according to one of the preceding claims, characterized in that the PTC element (2) is completely surrounded by a frame (32) made of an insulating material, leaving a heat-dissipating surface (36) formed by the insulating layer (22) free. A method for producing a heat-generating element, in which contact plates (6) with holding tabs (12) are produced by punching and bending sheet metal material, the contact plates (6) are placed on opposite sides of a PTC element (2), so that the one Cross over the PTC element (2) projecting retaining tabs (12) and the PTC element (2) projecting retaining tabs (12.1) of one contact plate (6.1) between their free ends and the other contact plate (6.2) a receptacle (24) form for an insulation layer (22) and the insulation layer is introduced into the receptacle (24) under elastic prestressing of the retaining tabs (12) and is placed against the other contact plate (6.3).

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