EP0939579B1 - Electric planar heating element with a quasi homogeneous heating area and bonding area - Google Patents

Description

The invention relates to a flexible surface heating element with electrically conductive contact and heating conductors, both the contact conductors as well as the heating conductors each with each other touch.

In known heating elements, e.g. according to DE 41 42 774 (I.G. GmbH), these heating conductors are parallel or substantially parallel, and each heat conductor contributes to a certain extent to the total heating power. If this heating conductor fails interruption out, so is a more or less broad segment of the Heating element fail. These failures are caused by strong ones mechanical loads on the entire surface or through punctiform loading by kneeling or standing on the seat Area of contact manager presents a similar situation Are there one or more parallel to each other Contact conductor destroyed, so there is a balancing flow between the contact leaders.

This compensating current inevitably flows through the heating conductors, which interconnect the parallel contact conductors, which causes undesirable heating. This effect can also in other known heating elements made of tissue surfaces, such as in DE 42 33 118 using the example of a carbon heating mat described, occur. Another method is described by the DE 31 17 247, in which the surrounding textile material between the parallel heating conductors and contact conductors is metallized and so a connection between the individual Heating conductors and contact conductors is created.

In this process, the conductive properties of the metallization insufficient and unstable under mechanical bending stress, so that this technique is for producing durable, flexible Heating elements can not be used.

Object of the present invention is one under operating conditions electrically (quasi) homogeneous surface heating element with improved consistency of current density to develop, despite Breakthroughs, recesses or punched holes in the heating field has largely uniform heating.

This object is achieved by the in the claims indicated features shown.

In contrast to the existing surface heating elements The invention is based on the following principle:

Both the heating conductor 1 and the contact conductors 3, 4 are so in the surface of the heating element, that this in as possible touch short distances. This can be done by that each heating conductor 1 and contact conductor 3, 4 of the surface heating element mirror image and phase-shifted to the other conductors is arranged and the respective adjacent conductor in touched as short distances (Fig. 1a, 1b).

A preferred embodiment is the multiple overlap the heating conductor 1, wherein the deflection or amplitude the heating conductor 1 is so large that each conductor several adjacent Head overlaps and touches (Fig. 2).

By this type of introduction arises in the heating field 2, 5 also after the punching of air passage openings a quasi homogeneous, covered by heating conductors surface, which also has a Directional conductivity towards both Side lying contact conductors shows. This will flow to the Break points or at the hole edges lower equalizing currents than in a version with identical conductivities in all directions, resulting in much lower thermal loads of Perforated edges leads, without being as in DE 41 42 774 whole segments fail.

In the case of a conductor break, the current flow along the Heating conductor unchanged by the contact of adjacent conductors maintained and then in two sections Disintegrated heating element 1 by short bridging the break point continue to be powered. An interruption of individual heating conductors 1 does not lead to the failure of one as described above whole heating segment, but will affect the immediate Restrict area of interruption. The heating conductor segments For example, in Fig. 1b are designated 2a, 2b.

In the area of the contact conductors 3, 4 causes the multiple contact the conductor at a short distance a quasi resistance homogeneous Contact strips. This will be orthogonal to the main direction the contact strip achieves high electrical conductivities, the hardly any additional in case of failure of individual contact parts and generate unwanted heating in the contact field.

As a further advantage of the invention, this provides a improved conductivity of the contact track or the contact strip and thus less heat on the contact strip one.

This advantage of low power loss and heat dissipation in particular compared to known heating element techniques where the contact strip in the trench or in the foam body of a Car seat accommodated and so thermally isolated. The Danger of local overheating is therefore also at break points Minimized in the trench of the passenger car seat.

Bild 3

Ausschnitt einer Heizmatte gemäß DE 42 33 118 A1;

Bild 4

Teilansicht eines Flächenheizelementes mit netzartiger Ausbildung des Grundmaterials;

Bild 5

Ausschnitt aus einem erfindungsgemäßen Flächenheizelement;

Bild 6 - 8

Defekte Sitzheizungen mit jeweils unterschiedlichen Heizelementen analog zu den Bildern 3 - 5.

In the following, the advantages of the invention are illustrated in a comparison with the prior art. Show it:

picture 3

Section of a heating mat according to DE 42 33 118 A1;

Picture 4

Partial view of a Flächenheizelementes with reticulate formation of the base material;

Picture 5

Section of a surface heating element according to the invention;

Picture 6 - 8

Defective seat heaters, each with different heating elements analogous to the pictures 3 - 5.

The heating mat shown as a detail in Figure 3 consists of net-like heating conductors 6 and contact conductors 7, 8. In the heating surface between the contact conductors 7, 8 there is a hole 9. This hole is intended to illustrate two different situations namely the flow of current in a punched to Improvement of air circulation or if greater damage or a break has occurred.

With the blackening 10, 11 is the increased current flow in the side area of the hole 9 symbolizes, whereby in picture 3 of a constant conductance for all directions of the heating conductor network is assumed. This means that both the horizontal and the the vertical heating conductors each have the same conductance, so that when an interruption of the heating a local overheating due to the compensation current threatens. This danger will be reinforced if several holes are next to each other, because then the current density between the holes the permissible Values far exceeds.

In figure 4 is the typical case of a wavy laying of the heat conductor 12, 13, 14 in a woven base material 15th shown, wherein the integration of the heating conductors at the nodes he follows.

In an interruption of the middle heat conductor 13 of the Power distributed to the remaining heating conductors 12 and 14, so that Here, too, an increased current density lead to overheating can. In segment-like division of a Sitzheizfläche is then not just the segment affected by the power interruption but fail the entire Sitzheizfläche. The transfer the currents on the heating element is done by a not here illustrated contact conductor rail and the contact conductor 8a, the the ends of the heating conductors connected in parallel 12 - 14 connect.

In Figure 5 is now an inventive Heizleiterfeld with quasi Homogeneous current density in the range of holes, punched or the like. Also by the multiple overlapping the heating conductor 16 may occur in the region of the hole 17 Line breaks no significant concentration of Current density in the edge areas cause, since the heating surface 18th has a directional conductivity. This is located in Current direction from the contact conductors 19 to the contact conductors 20, so that only small equalizing currents in the region of the hole 17th flow.

Figure 6 illustrates the situation with a seat heater, the is provided with a heating conductor network according to Figure 3. At a sharp bends as in the ditch 21, 22 can break at the Lines occur. After that, the current density in the trench increases a lot strong, so that a total failure of the heating element as shown 6 is to be feared.

According to Figure 7 is a seat heater with wavy heating conductors shown as a parallel circuit. The heating conductors point Break points 23, 24, 25, which increased the current density at cause the neighboring lines. A power interruption at one Fracture 26 of the contact leads to a complete Failure of the whole segment.

The above comparisons were made on the basis of thermographic Investigations carried out. The investigations prove that surprising advantages due to a directional conductivity in connection with a multiple contact over several adjacent heating conductors are effected across.

Claims (6)

1. A flexible surface heating element with electrically conducting contact and heater conductors, wherein both the contact conductors (4), (4) and the heating conductors contact one another,
   characterised in that the heating surface (2) comprises a direction-dependent conductivity in the direction of the contact conductors (3), (4) positioned on the two sides.
2. A flexible surface heating element according to claim 1,
   characterised in that both the contact conductors (3), (4) and the heating conductors (1) contact one another, wherein the angle of deflection of the individual heating conductor lines is such that each conductor overlaps with and contacts a plurality of adjoining conductors.
3. A surface heating element according to claim 1 or 2,
   characterised in that in the case of an interruption of both individual heating conductors (1) and contact conductors (3), (4), the power flow along the heating and contact conductors is maintained in a substantially unchanged way via the multiple contact between adjoining conductors.
4. A surface heating element according to any one of claims 1 to 3,
   characterised in that both the heating conductors (1) and the contact conductors (3), (4) are incorporated into a textile knitted material, wherein, in the region of the contact conductors (3), (4), as a result of the contact between the contact conductors, there is obtained a quasi homogeneous contact strip which, even if individual contacting parts are interrupted, comprises a high degree of conductivity directed orthogonally relative to the main direction of the contact strip.
5. A surface heating element according to any one of the preceding claims,
   characterised in that the heating conductors (1) consist of carbon fibre or high-grade steel filaments.
6. A surface heating element according to any one of claims 1, 3, 4 and 5,
   characterised in that individual periodically placed heating conductors (1) are arranged mirror-image-like in the heating field (5) and so as to be dephased relative to the remaining heating conductors and
   that at least two heating segments (2a), (2b) are differently placed segment-wise, so that different surface heating output values are achieved.

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