HEATING CONDUCTIVE WIRE-LIKE ELEMENT

Abstract

The invention provides a heating conductive wire-like element comprising a core made from synthetic fibers a plurality of heating conductive wires around said core. The core is twisted in a predetermined direction X and the plurality of heating conductive wires are wound in a predetermined direction Y. The predetermined direction X is different from the predetermined direction Y. A predetermined number of said heating conductive wires are individually covered with a non- electrically conductive material.

Claims

1. A heating conductive wire-like element, comprising a core made from synthetic fibers, being twisted in a predetermined direction X a plurality of heating conductive wires around said core, being wound in a predetermined direction Y, wherein said predetermined direction X is different from said predetermined direction Y, and wherein a predetermined number of said heating conductive wires are individually covered with a non-electrically conductive material.

2. The heating conductive wire-like element according to claim 1, wherein said predetermined direction X is S-direction and said predetermined direction Y is Z-direction.

3. The heating conductive wire-like element according to claim 1, wherein said predetermined direction X is Z-direction and said predetermined direction Y is S-direction.

4. The heating conductive wire-like element according to claim 1, wherein the pitch length of the twisted core is in a range from 2 to 25 mm, preferably from 2 to 20 mm, more preferably from 2 to 15 mm, and most preferably from 5 to 15 mm.

5. The heating conductive wire-like element according to claim 1, wherein said plurality of heating conductive wires are made from copper or copper alloy.

6. The heating conductive wire-like element according to claim 1, wherein said heating conductive wires are in a state of being paralleled together.

7. The heating conductive wire-like element according to claim 1, wherein said plurality of heating conductive wires are covering at least 50% of the surface of said core.

8. The heating conductive wire-like element according to claim 1, wherein said plurality of heating conductive wires are covering 100% of the surface of said core.

9. The heating conductive wire-like element according to claim 1, wherein said predetermined number of said heating conductive wires are individually lacquered with a resin.

10. The heating conductive wire-like element according to claim 1, wherein said predetermined number of said heating conductive wires are individually wrapped with one or more non-electrically conductive filaments or individually wrapped with non-electrically conductive fibers or individually wrapped with one or more non-electrically conductive tapes.

11. The heating conductive wire-like element according to claim 1, wherein an insulation jacket layer is formed on an outer periphery of the heating conductive wires.

12. The heating conductive wire-like element according to claim 1, wherein the electrical resistance of said heating conductive wire-like element is in a range of 0.2 to 1000 Ohm/meter.

13. The heating conductive wire-like element according to claim 1, wherein the diameter of the heating conductive wire-like element is in a range of 0.1 to 1 millimeter.

14. A method of producing a heating conductive wire-like element, comprising the steps of (a) pre-twisting a core made from synthetic fibers in a predetermined direction X, preferably said pre-twisted core having a pitch length in a range of 2 to 25 mm, (b) winding a plurality of heating conductive wires around said pre-twisted core in a predetermined direction Y, preferably with a pitch of 0.1 to 10 mm, wherein said predetermined direction X is different from said predetermined direction Y, and a predetermined number of said heating conductive wires are individually covered with a non-electrically conductive material.

15. The method of producing a heating conductive wire-like element according to claim 14, wherein said plurality of heating conductive wires are in a state of being paralleled together.

Description

BRIEF DESCRIPTION OF FIGURES IN THE DRAWINGS

[0021] FIG. 1 shows an example of the cross-section of a heating conductive wire-like element according to the invention.

[0022] FIG. 2 shows an example of a longitudinal view of a heating conductive wire-like element according to the invention.

[0023] FIG. 3 shows another example of a longitudinal view of a heating cable according to the invention.

MODE(S) FOR CARRYING OUT THE INVENTION

[0024] FIG. 1 shows the cross-section of a heating conductive wire-like element 10, that can be used as heating cable in the vehicle seat heating.

[0025] The configuration of the heating conductive wire-like element is illustrated in FIG. 1. A core strand 12 formed of fiber multi-filament bundle having an external diameter of 0.15 mm is provided. The core material is an aromatic polyester produced by the polycondensation of 4-hydroxybenzoic acid and 6-hydroxynaphthalene-2-carboxylic acid, e.g. commercially available Vectran®. The parallel non-twisted core is first pre-twisted at 300 twist/m in S- direction. Ten conductive wires 14, which are formed of a tin-containing copper alloy wire having a diameter of 0.12 mm, are spirally wound at 200 twist/m in a Z-direction around an outer periphery of the core strand 12 in a state of being paralleled together. The conductive wires 14 are individually lacquered with a non-electrically conductive material, e.g. a silicone resin with a thickness of about 8 pm by applying an alkyd silicone varnish and drying it. A heating conductive wire-like element 10 is formed by winding the conductive wires 14 around the core 12 with a gap 16 between two adjacent turns. As an example, the gap has a size similar to the diameter of the conductive wire. Then an extrusion covering of a polyamide 12 resin with a thickness of 0.25 mm is formed on the outer periphery of the wound conductive wires 14 as an insulation jacket layer 18. The heating conductive wire-like element 10 as described above has a finished cross-section of 0.12 mm.sup.2 and an electrical resistance of about 0.5 Ohm/m.

[0026] In this embodiment, as shown in FIG. 2, the core 22 of the heating conductive wire-like element 20 is not fully covered. The conductive wires 24 is covering about 90 percent of the surface of the core. In a folding endurance test, the flex life of the heating conductive wire-like element 20 of this embodiment is about 40,000.

[0027] A similar sample is made for comparison, which has the same configuration except the core is made from parallel multi-filaments but not twisted. The flex life of the heating conductive wire-like element with parallel non-twisted fiber core is about 22,000.

[0028] As a second embodiment, the core (not visible in FIG. 3) is fully covered.

[0029] As shown in FIG. 3, the conductive wires 34 are fully covering the surface of the core. There were eleven conductive wires 34 in a parallel state winding around the core without distance between two adjacent turns. The flex life of this heating conductive wire-like element 30 of this second embodiment is comparable to the first embodiment but the heating conductive wire-like element with fully covered conductive wires has higher electrical conductivity.

[0030] The invention conductive wire-like element has significantly higher flex life.

[0031] A 45% higher flex life was obtained than the comparable conductive wire-like element without a twisted but parallel synthetic fibre core. The higher flex life is beneficial for dynamic applications, e.g. for vehicle seat heating. The experiments have shown that the vehicle seat heating that include the above heating conductive wire-like element have efficient hot-spot prevention and excellent flex life.

[0032] Elements and features of the different embodiments and examples can be combined while staying within the content and scope of the invention.