WO2009027217A1

WO2009027217A1 - Flexible heating module and method for the production thereof

Info

Publication number: WO2009027217A1
Application number: PCT/EP2008/060544
Authority: WO
Inventors: Jan Ihle; Werner Kahr; Helmut Pölzl
Original assignee: Epcos Ag
Priority date: 2007-08-27
Filing date: 2008-08-11
Publication date: 2009-03-05
Also published as: DE102007040408A1

Abstract

The invention relates to a flexible heating module having a positioning frame (1) comprising cavities (2). PTC heating elements (3) are incorporated in the cavities (2), said elements being attached in the cavities (2) by planar electric conductors (4) that are glued onto the positioning frame (1). For this purpose the heating modules have a lower resistance tolerance than the PTC heating elements (2).

Description

description

Flexible heating module and method of manufacture

From the document DE 8309023 Ul a flexible heating element in tape form is known, which consists of electrically conductive granules of PTC material and an organic insulating plastic as a binder.

An object to be solved is to specify a heating module which is flexible and in which PTC heating elements with defined dimensions are used.

This object is achieved by a heating module according to claim 1.

Furthermore, the object is achieved by a method for producing heating modules according to claim 34.

The flexible heating module comprises an electrically non-conductive positioning frame. The positioning frame has several cavities. The cavities are preferably used for receiving PTC heating elements. The PTC heating elements are fixed in the cavities by means of at least one planar electrical conductor. The flat electrical conductor is applied on at least one side on the positioning frame. The electrical conductor thus seals each individual cavity of the positioning frame completely to the outside. The arranged in the cavities PTC heating elements are thus protected against environmental and pollutant effects. If the dew point is undershot, the PTC heating elements are thus protected against corrosion of the ceramic and the metallization. In a preferred embodiment, the electrical conductor is glued to a flat surface of the positioning frame.

The cavities in a preferred embodiment have the shape of a rectangle. The PTC heating elements are preferably formed in this embodiment as a cuboid.

In a further embodiment, the cavities may also have the shape of a circular opening. The heating elements accordingly have the shape of a round disc.

The circumference of the rectangular PTC heating elements or the diameter of the round PTC heating elements is preferably slightly smaller than the circumference of the rectangular cavities or the diameter of the circular cavities in the positioning frame. This creates a free space between the PTC heating elements and the edge of the cavities. Due to this lateral clearance, the heating module has a voltage-reduced structure. The PTC heating elements are thus not clamped in the cavities of the positioning frame in the lateral direction. The PTC heating elements are therefore subjected to the greatest possible flexibility of the heating module, lower mechanical stresses within the cavities. In the event that the heating module is bent mechanically or due to temperature, it is further ensured that the PTC heating elements are held by the planar electrical conductors. In a fixed connection between the flat electrical conductor and the PTC heating elements arise when bending or Twisting the heating module Tensions that could lead to cracks at the joints.

In the production of PTC heating elements by the sintering results in a normal distribution (Gaussian curve) for the electrical resistance of the PTC heating elements. The width of this curve (6 sigma) is divided into resistance classes. From these resistance classes PTC heating elements are selected, which are used to populate the cavities of the positioning frame. Due to the number of resistance classes of the PTC heating elements results in a minimum assembly, which corresponds to the number of filled cavities of the heating module. In the manufacture of the PTC heating elements usually a resistance tolerance of about +/- 40% is achieved. However, such large tolerance values are not sufficient for the heating modules. In order to achieve the required tolerance requirements with respect to the resistance values for heating modules of approximately +/- 10% (or +/- 25%), the heating module is equipped with selected PTC heating elements in a defined manner. In the case of the minimum assembly, one PTC heating element is selected from each resistance class. With a higher number of filled cavities, the PTC heating elements are selected according to the normal distribution. In this embodiment, therefore, PTC heating elements which have a smaller deviation from their desired value are used in larger numbers in the heating module than PTC heating elements which have a greater deviation from their nominal value. Thus, the resistance of the heating module has a lower deviation from a predetermined setpoint than the deviation of the individual PTC heating elements from their setpoint.

Preferably, PTC heating elements are selected that have a resistance that is both larger and smaller - A -

than the setpoint. By equipping the heating module with PTC heating elements, which have a high resistance tolerance, a resistance tolerance is achieved for the heating module, which is smaller than the resistance tolerance of the individual PTC heating elements.

The positioning frame is preferably formed of a flexible and temperature-resistant material. For this purpose, preferably silicone or other temperature-resistant, flexible, electrically insulating plastics, which are suitable for a temperature range of about -50 ⁰ C to 200 ⁰ C.

The positioning frame preferably has a region with a flat surface on the upper side and the lower side.

The positioning frame has a glued planar electrical conductor which completely covers the cavities, so that the PTC heating elements located in the cavities are preferably completely sealed to the outside.

The thickness of the positioning frame in the region of the cavities preferably corresponds to the thickness of the PTC heating elements located in the cavities of the positioning frame.

The thickness of the positioning frame preferably has the height of the PTC heating elements. As a result, the heating module on the top and bottom on an approximately flat surface.

In a preferred embodiment, the heating module has a surface-mounted electrical conductor adhered to the positioning frame, which covers the positioning frame except for a narrow edge region. In a preferred embodiment, this planar electrical conductor is a foil. The film is preferably made of metal or has on the side facing the cavities on a metallic surface which is electrically conductive. The film has good conductivity for current and temperature.

In a further embodiment, this planar electrical conductor can also be a thin sheet metal in strip form.

The positioning frame preferably has on both sides in the edge region a longitudinally extending narrow guide web. The guide web is preferably designed such that its height corresponds approximately to the thickness of the planar electrical conductor fastened to the positioning frame. The total height of the positioning frame then results from the thickness of the PTC heating elements and twice the thickness of the planar electrical conductors which are applied to the positioning frame.

In a preferred embodiment, the positioning frame in the region of the flat surfaces is temperature-resistant connected to the planar conductor. The planar conductor is preferably glued only to the positioning frame, so that the PTC heating elements are held and contacted only by clamping by means of the flat conductor applied on both sides.

The PTC heating elements preferably have full-area electrical contacts on two sides. The PTC heating elements are due to the bonding of the planar electrical conductors Covered with the positioning frame on all sides to the outside and completely sealed.

Preferably, the PTC heating element is clamped in the cavity of the positioning frame between the two flat electrical conductors. The glued on the top and bottom of the positioning frame planar electrical conductors thus allowing a stress-free mechanical attachment of the PTC heating elements in the cavities of the positioning frame. Due to the flexible contacting, cracks can be avoided when bending the heating module. Flexible heating modules with brazed joints used to fix the PTC heating elements may crack. By clamping between the flat electrical conductors thus secure contact with the greatest possible flexibility of the heating modules is given.

In a further embodiment, in which a lesser value is placed on the service life of the heating module, the PTC heating element can also be connected to the planar electrical conductor by means of an adhesive connection.

In a further embodiment, the connection can also be made via a solder joint. It is also possible for the PTC heating element to be fastened or contacted between the planar electrical conductors on the positioning frame with a combination of clamping, soldering and / or adhesive connections.

The PTC heating elements are electrically contacted on both sides with the surface-mounted electrical conductor glued to the positioning frame. In a preferred embodiment the electrical contacting takes place on both sides over the entire surface of the PTC heating elements.

In a preferred embodiment, the planar electrical conductor has an electrical connection contact at one end. The terminal contact is formed in a preferred embodiment as part of the electrical conductor. The terminal contact thus forms the first end of the planar electrical conductor. In a further embodiment, the terminal contact may be formed as a terminal lug or plug contact. The connection contact is preferably used to supply the heating module with electricity.

When manufacturing a flexible heating module, several PTC heating elements are introduced into the cavities of a positioning frame. These are then fastened by means of applied on both sides of the positioning frame planar conductors.

The planar electrical conductor is then preferably glued to the positioning frame.

The attachment of the PTC heating elements in the cavities of the positioning frame is preferably carried out by a clamping between the two applied flat electrical conductors. In a further embodiment, the attachment can also be effected by a solder or adhesive connection. It is also possible to use a combination of clamped, soldered or glued joints.

To equip the heating module with PTC heating elements, the resistance of each individual PTC Heating element measured. The measured resistances are divided into resistance classes based on the measurement results.

The number of resistance classes thus results in a minimum population of PTC heating elements in the positioning frame. By a defined equipping of the heating module with PTC heating elements with known resistance values, a heating module can be produced which has a lower resistance tolerance than the resistance tolerance of the PTC heating elements used. Thus, all PTC heating elements having a resistance within the tolerance limits can be used for the placement of the heating modules.

Due to the previous division of the PTC heating elements into resistance classes and the resulting assembly of the heating modules with PTC heating elements, the heating modules have a lower tolerance than the PTC heating elements used with each other. With a minimum configuration, a PTC heating element is selected for each resistance class. The parallel connection of the PTC heating elements thus results in an average value for the total resistance, which, viewed over a larger number of heating modules, lies within lower tolerance limits than the resistance values of the individual PTC heating elements. If more cavities are equipped with PTC heating elements than are necessary for a minimum configuration, then the PTC heating elements are selected in accordance with the Gaussian distribution of the resistance classes. Thus, the mean deviation of the resistance values, the PTC heating elements of a heating module, compared to a predetermined setpoint above the deviation of the heating module from the setpoint of the heating module. The heating module described has the particular advantage that flexible connection of the PTC heating elements in the positioning frame takes place by means of a clamping connection. Due to the clamp connection, a flexible electrical contact is possible, which avoids stress cracks, which would lead to a reduced service life. The contacting by a clamping connection ensures a thermo-mechanical stress compensation.

In special applications, in which lower life requirements are sufficient, instead of the Klemmkontaktierung adhesive or solder joints can be used, as well as combinations of solder, adhesive joint and Klemmkontaktierung are possible.

The described objects will be explained in more detail with reference to the following figures and exemplary embodiments.

The drawings described below are not to be considered as true to scale. Rather, for better representation, individual dimensions can be enlarged, reduced or distorted.

Elements which are identical or which assume the same function are designated by the same reference numerals.

FIG. 1 shows a schematic exploded view of the heating module in a three-dimensional representation.

FIG. 2 shows a schematic view of the positioning frame from the front. FIG. 3 shows a schematic view of the positioning frame from above.

Figure 4 shows a schematic view of the positioning frame from the side.

Figure 5 shows a schematic view of the attachment of the PTC heating elements in the positioning frame.

FIG. 1 shows a three-dimensional exploded view of the heating module. The positioning frame 1 of the heating module has a plurality of cavities 2 which, preferably uniformly, are distributed over the entire length of the positioning frame 1. The cavities 2 serve to receive a plurality of PTC heating elements 3. The cavities 2 preferably have a rectangular shape. The PTC heating elements 3 preferably also have a rectangular shape. In a further embodiment, not shown, the PTC heating elements may also have a round shape, wherein the cavities in this embodiment, adapted to the PTC heating elements, also have a round shape.

The circumference of the PTC heating elements is preferably slightly less than the circumference of the cavity. The PTC heating elements 3 thus have no contact with the edge region of the cavities 2, so that the PTC heating elements 3 are movable within the cavity 2 in the lateral direction. On the positioning frame 1, planar electrical conductors 4 are applied on both sides. The sheet-like electrical conductors 4 are preferably applied to the planar surfaces of the positioning frame 1 via a bond. The positioning frame 1 has on both sides a narrow web 5, which serves to guide the flat electrical conductor 4. The width of the flat electrical conductor 4 corresponds approximately to the width of the free planar surface of the positioning frame 1 between the webs arranged on both sides 5. The height H2 of the web 5 corresponds approximately to the thickness D2 of the applied planar electrical conductor 4th

FIG. 2 shows a front view of the positioning frame 1. The positioning frame 1 has a narrow web 5 on both sides at the edge. The thickness Dl of the positioning frame 1 corresponds approximately to the height Hl of the arranged in the cavities 2 of the positioning frame 1 PTC heating elements 3. The total height of the positioning frame 1 corresponds approximately to the height Hl of the PTC heating elements 3 plus twice approximately the thickness D2 of The height H2 of the web 5 should preferably be so high that an insulation of the planar electrical conductor 4 is ensured to the sides, and the height is sufficient for the guidance of the flat electrical conductor 4 at the same time. Preferably, the height of the webs 5 is kept as low as possible, so that the heating module can be flowed around by air, which heats up to the heating module.

In Figure 3, the positioning frame 1 is shown in a view from above. The cavities 2 are distributed uniformly over the entire length of the positioning frame 1. The positioning frame has a narrow web 5 on both sides of the edge. The length of the positioning frame 1, or the number of cavities 2, results from the number of PTC heating elements in the cavities 2, or the required minimum assembly of the heating module. The PTC heating elements have a normal distribution for the electrical resistance. The width of this curve is divided into resistance classes. The size of the Minimal assembly of the positioning frame 1, or the number of filled cavities 2, corresponds to the number of resistance classes.

In Figure 4, the positioning frame 1 is shown from the side. The cavities 2 are distributed uniformly over the entire length of the positioning frame 1.

FIG. 5 shows a schematic illustration of the heating module in cross section. The thickness Dl of the positioning frame 1 preferably corresponds approximately to the height Hl of the PTC heating element 3 in the cavity 2. On the positioning frame 1, a flat electrical conductor 4 is applied which has a thickness D2. The height H2 of the web 5, which is arranged laterally on the positioning frame 1, corresponds approximately to the thickness D2 of the planar electrical conductor 4.

Although only a limited number of possible developments of the invention could be described in the embodiments, the invention is not limited to these. It is possible in principle to use other defined forms of PTC heating elements and corresponding shapes of the cavities. The invention is not limited to the number of schematically illustrated elements.

The description of the objects and methods disclosed herein is not limited to the individual specific embodiments. Rather, the features of the individual embodiments - as far as technically reasonable - can be combined with each other. LIST OF REFERENCE NUMBERS

1 positioning frame

2 cavity

3 PTC heating element

4 flat electrical conductors

5 footbridge

Dl Thickness of the positioning frame (1)

Hl height of PTC heating elements (3)

D2 thickness of the planar electrical conductor (4)

H2 height of the bridge (6)

Claims

claims

1. A flexible heating module, comprising an electrically non-conductive positioning frame (1) having a plurality of cavities (2), a plurality of PTC heating elements (3) arranged in the cavities (2), wherein the PTC heating elements (3) by means of at least one planar electrical conductor (4) are fixed, which is applied to the positioning frame (1), wherein the planar electrical conductor (4) and the

Positioning frame (1) are connected to each other such that each individual cavity (2) is sealed moisture-proof and the PTC heating elements (3) within the cavities (2) are freely movable in the lateral direction.

2. Flexible heating module according to claim 1, wherein the electrical conductor (4) is adhered to at least one of the planar surfaces of the positioning frame (1).

3. Flexible heating module according to claim 1 or 2, wherein the positioning frame (1) on the top and bottom each have a flat electrical conductor (4).

4. Flexible heating module according to one of claims 1 to 3, wherein the cavities (2) have the shape of a rectangle.

5. Flexible heating module according to claim 4, wherein the PTC heating element (3) has the shape of a cuboid.

6. Flexible heating module according to one of claims 1 to 3, wherein the cavities (2) have the shape of a circle.

7. Flexible heating module according to claim 6, wherein the PTC heating element (3) has the shape of a round disc.

8. Flexible heating module according to one of the preceding claims, in which the average deviation of the resistance values of the PTC heating elements (3) of a heating module, compared to a predetermined setpoint has a greater value than the deviation of the heating module from the setpoint of the heating module.

9. Flexible heating module according to one of the preceding claims, wherein the heating module with PTC heating elements

(3), wherein the PTC heating elements (3) have resistance values which are both greater and smaller than their nominal value.

10. Flexible heating module according to one of the preceding claims, wherein the positioning frame (1) is temperature-resistant.

11. Flexible heating module according to one of the preceding claims, wherein the positioning frame (1) is flexible.

12. Flexible heating module according to one of the preceding claims, wherein the positioning frame (1) consists of silicone.

13. Flexible heating module according to one of the preceding claims, wherein the positioning frame (1) has a flat surface on both sides.

14. Flexible heating module according to one of the preceding claims, wherein the positioning frame (1) in the region of the cavities (2) has a thickness (Dl), the height

(Hl) of the PTC heating element (3) corresponds.

15. Flexible heating module according to one of the preceding claims, wherein the positioning frame (1) on both sides except for a narrow edge region each having a planar electrical conductor (4).

16. Flexible heating module according to one of the preceding claims, wherein the cavities (2) are covered by a flat electrical conductor (4).

17. Flexible heating module according to one of the preceding claims, wherein the planar electrical conductor (4) is a film.

18. A flexible heating module according to one of the preceding claims, wherein the film has a good conductivity for current and temperature.

19. Flexible heating module according to one of the preceding claims, wherein the film consists of metal.

20. Flexible heating module according to one of the preceding claims, wherein the planar electrical conductor (4) is a thin sheet metal strip.

21. Flexible heating module according to one of the preceding claims, in which the positioning frame (1) has on both sides in the longitudinal direction a web (5) which has a height (H2) which is at least equal to the thickness (D2). which on the positioning frame (2) fixed flat electrical conductor (4) corresponds.

22. Flexible heating module according to one of the preceding claims, wherein the positioning frame (1) with the flat electrical conductor (4) on both sides in the region of the flat surfaces of the positioning frame (1) is adhesively bonded temperature-resistant.

23. Flexible heating module according to one of the preceding claims, wherein the PTC heating element (3) on two sides full-surface electrical contacts.

24. Flexible heating module according to one of the preceding claims, wherein the PTC heating element (3) on both sides with the on the positioning frame (1) applied electrical flat conductors (4) is electrically connected

25. Flexible heating module according to one of the preceding claims, wherein the PTC heating element (3) is completely sealed by an all-round cover to the outside.

26. Flexible heating module according to one of the preceding claims, wherein the PTC heating element (3) in the cavity (2) of the positioning frame (1) by means of the flat electrical conductor (4) is clamped.

27. Flexible heating module according to one of the preceding claims, wherein the attachment of the PTC heating element

(3) has taken place in the cavity (2) of the positioning frame (1) by means of an adhesive connection.

28. A flexible heating module according to any one of the preceding claims, wherein the attachment of the PTC heating element

(3) has taken place in the cavity (2) of the positioning frame (1) by means of a solder joint.

29. A flexible heating module according to one of the preceding claims, wherein the attachment of the PTC heating element

(3) in the cavity (2) of the positioning frame (1) by means of a combination of clamping, soldering and adhesive connection.

30. Flexible heating module according to one of the preceding claims, wherein the electrical conductor (4) has an electrical connection contact at one end.

31. Flexible heating module according to one of the preceding claims, wherein the terminal contact at the end of the electrical conductor (4) is formed as part of the electrical conductor (4).

32. Flexible heating module according to one of the preceding claims, wherein the connection contact at the end of the electrical conductor (4) is a connection lug.

33. Flexible heating module according to one of the preceding claims, wherein the terminal contact at the end of the electrical conductor (4) is a plug contact.

34. Method for producing a flexible heating module, wherein first in the cavities (2) of a flat positioning frame (1) a plurality of PTC heating elements (3) are introduced.

35. The method of claim 34, wherein the PTC heating elements

(3) then be attached by means of both sides on the flat positioning frame (1) applied flat electrical conductors (4).

36. The method according to any one of claims 34 to 35, wherein the planar electrical conductor (4) is glued to the flat surfaces of the positioning frame (1).

37. The method according to any one of claims 34 to 36, wherein the fixing of the PTC heating elements (3) in the cavities (2) of the positioning frame (1) by means of a clamping between the planar electrical conductors (4).

38. The method according to any one of claims 34 to 36, wherein the fixing of the PTC heating elements (3) in the cavities (2) of the positioning frame (1) by means of an adhesive bond to the planar electrical conductors (4).

39. The method according to any one of claims 34 to 36, wherein the fixing of the PTC heating elements (3) in the cavities (2) of the positioning frame (1) by means of a soldered connection to the flat electrical conductors (4).

40. The method according to any one of claims 34 to 36, wherein the fixing of the PTC heating elements (3) in the cavities (2) of the positioning frame (1) by means of a combination of clamping, adhesive and soldered connection between the planar electrical conductors ( 4).

41. The method according to any one of claims 34 to 40, wherein before the placement of the positioning frame (1) with the PTC Heating elements (3) the resistance of the PTC heating elements (3) is measured and the PTC heating elements (3) are divided into resistance classes based on the measured values.

42. The method according to any one of claims 34 to 41, wherein the minimum assembly of the positioning frame (1) corresponds to the number of resistance classes of the PTC heating elements (3).