Electric cable

Abstract

An electric cable, in particular a data cable, has a transmission core which is surrounded by a shield and concentrically surrounded by a sheath that includes an outer layer made of an electrically insulating plastic material and a second layer underneath that is made of a semiconducting material. The semiconducting material primary purpose is to divert interference currents.

Claims

1. An electric cable, comprising: a transmission core having at least one core pair and said at least one core pair having no pair shielding configuration; a shielding configuration surrounding said transmission core; a cable sheath surrounding said transmission core in a concentric manner, said cable sheath having a first outer layer of an electrically insulating synthetic material and a second layer of a semi-conductive material disposed below said first outer layer; an intermediate sheath disposed between said transmission core and said second layer formed of said semi-conductive material so that there is a minimum spacing between said second layer and said transmission core, the minimum spacing being at least 0.5 mm.

2. The electric cable according to claim 1, wherein said second layer is provided together with said first outer layer by means of a co-extrusion process.

3. The electric cable according claim 1, wherein said second layer of said semi-conductive material has a wall thickness in a range from 0.05 to 1.2 mm.

4. The electric cable according to claim 1, wherein said intermediate sheath is a conductive layer that lies against said second layer in an electrically contacting manner.

5. The electric cable according to claim 4, wherein said conductive layer is configured as a foil.

6. The electric cable according to claim 1, wherein said shielding configuration is formed exclusively by said second layer.

7. The electric cable according to claim 1, wherein the electric cable is connected at at least one end to an electric component, wherein said shielding configuration is not contacted in an electrical manner to the electric component.

8. The electric cable according to claim 1, wherein said semi-conductive material has a specific resistance being greater than 1 Ohm*mm.sup.2/m.

9. The electric cable according to claim 8, wherein the specific resistance is less than 1,000 Ohm*mm.sup.2/m.

10. The electric cable according to claim 1, wherein said semi-conductive material is a conductive synthetic material.

11. The electric cable according to claim 1, wherein said semi-conductive material is formed by an insulating synthetic material having conductive particles embedded therein.

12. The electric cable according to claim 1, wherein said semi-conductive material does not contain any metal particles and/or does not contain any magnetic particles.

13. The electric cable according to claim 1, wherein: the electric cable is a data cable; and said transmission core is formed by precisely one said core pair being directly surrounded by said intermediate sheath, said intermediate sheath being applied by means of an extrusion process.

14. The electric cable according to claim 1, wherein the spacing with respect to said transmission core is at least 0.5 mm and at most 1.5 mm.

15. The electric cable according to claim 1, wherein said intermediate sheath is configured from a solid insulating material.

16. The electric cable according to claim 1, wherein: the electric cable is configured as a symmetrical data cable; and said transmission core is formed for transmitting a symmetrical data signal.

17. The electric cable according to claim 1, wherein said at least one core pair is one of two core pairs without any shielding between said two core pairs.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) FIG. 1 is a diagrammatic, cross-sectional view of an electric cable in accordance with a first embodiment variant according to the invention;

(2) FIG. 2 is a cross-sectional view of the electric cable in accordance with a second embodiment variant;

(3) FIG. 3 is a cross-sectional view of the electric cable in accordance with a third embodiment variant having an intermediate sheath; and

(4) FIG. 4 is an illustration of the electric cable of the first embodiment variant as shown in FIG. 1 in a partial sectional view and connected to a component.

DETAILED DESCRIPTION OF THE INVENTION

(5) Like functioning parts are each provided with the like reference numeral in the figures.

(6) Referring now to the figures of the drawings in detail and first, particularly to FIGS. 1-3 thereof, there is shown cables 2 that are configured in the exemplary embodiment in each case as data cables and contain a central transmission core 4 that is surrounded by a cable sheath 6. In all variants, the cable sheath 6 contains an outer first layer 8 of an electric insulating synthetic material and also a second layer 10 of a semi-conductive material that is arranged directly below the outer first layer. The cable sheath 6 in the exemplary embodiments illustrated in FIGS. 1 and 2 lies directly against the transmission core 4. The cable sheath 6 is in particular a cable sheath 6 that is provided by an extrusion process. The two layers 8, 10 are provided in particular by a co-extrusion process. The cable sheath 6 is applied to the transmission core 4 as a type of tube extrusion.

(7) The cable 2 in accordance with the embodiment variant illustrated in FIG. 1 is configured as a symmetrical data cable having in the exemplary embodiment preferably 2 core pairs. A respective core pair 12 is used during the data transmission of a symmetrical data signal for transmitting on the one hand the signal and on the other hand the inverted signal. In particular, the respective core pair 12 is a twisted core pair. A respective core 14 is formed by a central conductor 16 that is surrounded by an insulating sheath 18 as a core sheath.

(8) In the case of the embodiment variant in accordance with FIG. 1, the cable sheath 6 contains in addition also a conductive layer 20 that is formed in particular by a foil, in particular a conventional shield foil. This is in particular an aluminum-coated synthetic material foil. The metal face is oriented toward the second layer 10 and contacts the second layer in an electrically conductive manner. The conductive layer 20 is omitted in an alternative variant.

(9) In contrast thereto, in the case of the embodiment variant in accordance with FIG. 2, the cable is a coaxial cable in which the transmission core 4 is formed by an inner conductor 22, a dielectric 24 of insulating synthetic material that directly surrounds the inner conductor and also an outer conductor 26 that lies directly against the dielectric 24. The outer conductor 26 simultaneously defines a shield layer 28. This shield layer 28 contains in the exemplary embodiment a multi-layer construction having a braid 30 and a shield foil 32. The shield foil 32 is preferably arranged on the outer face but it may as an alternative also be arranged on the inner face facing the braid 30. It is also in this case of importance that the shield layer 28 is in electrical contact with the second semi-conductive layer 10. The second semi-conductive layer 10 surrounds the shield layer 28 directly and is in particular configured as a sheath that is applied by an extrusion process.

(10) In the event that external interference fields occur in the high frequency range, in particular in the range from 1 to 5000 MHz, the high frequency interference fields penetrate the cable sheath 6 and pass through the cable sheath. As a result of the conductivity of the second layer 10, the high frequency interference fields are greatly damped in this second layer 10, in other words their energy is at least in part, preferably completely converted into heat in the second layer 10.

(11) In the case of the embodiment variant in accordance with FIG. 1, portions of the external inference field that pass through the second layer 10 impinge on the conductive layer 20, by way of example on the shield layer 28 in the case of the embodiment variant shown in FIG. 2. In the case of said embodiment, interference currents are generated that propagate in the longitudinal direction of the cable 2. As a result of the skin effect, said interference currents dissipate at the outer face of the conductive layer 20 or rather of the shield layer 28 and as a result of the immediate vicinity pass into the second layer 10 where they are further damped.

(12) As a result of the particular construction of the cable sheath 6, a shielding effect is in general improved by the shielding damping process. Any interference fields that are introduced are converted into heat in the second layer 10.

(13) Third-party cross-talk is also avoided as a result. The currents that are impressed in the conductive layer as a result of the electromagnetic coupling cause the electromagnetic field to be attenuated toward the outside and as a consequence cause a reduction in the coupling over into adjacent cables (third party cross-talk).

(14) This applies in particular also for the embodiment variant shown in FIG. 3. The cable 2 contains as a transmission core only one core pair 12 that is in particular twisted and is surrounded directly by an intermediate sheath 40. In this case, the intermediate sheath is a synthetic material sheath that is applied in particular by an extrusion process and forms a dielectric 24.

(15) The intermediate sheath 40 is in turn surrounded directly by the second semi-conductive layer 10 that is finally surrounded by the outer sheath 8. The latter provides the electrical insulation, the protection against environmental influences or also acts as a spacer element. In an alternative variant, it is also possible to provide a conductive layer 20.

(16) In particular in the case of low-cost applications, preferably in the automotive industry, the construction described here having the intermediate sheath 10 is used for the purpose of replacing conventional unshielded cables, in particular data cables, in particular unshielded symmetrical data cables, with a cable 2 (symmetrical data cable) that is provided with a cable sheath 6 of this type. Simultaneously, however, the conventional components for the unshielded data cable and also the conventional process steps are retained. In particular, a shielding contact is not provided in a connection region to a component 34. The respective shield of the cable 2 is therefore not directly connected in an electrical manner to the component 34as is otherwise usualto a reference potential, in particular to a ground potential.

(17) This concept is illustrated in FIG. 4. It is apparent in FIG. 4 that the cable 2 by way of example in accordance with FIG. 1 or FIG. 3 is inserted into the component 34, which is merely greatly simplified in the illustration, through an inlet opening. The cable sheath 6 is by way of example inserted simultaneously through the opening. The opening is usually sealed, by way of example by means of a seal ring, a grommet or by circumferential webs that are pressed into the cable sheath 6. The component 34 is by way of example a plug connector that is used to connect to a consumer. As an alternative thereto, the component 34 is directly a consumer. In both cases, the cable 2 is inserted through the opening of a housing.

(18) The individual cores 14 are not covered by the cable sheath 6 within the component 34 and also the insulation is removed from the respective conductor 16 of the respective core 14 and connected to one end at a contact element 36. These are by way of example contact bushes or contact pins that are configured by way of example as crimp contacts. As an alternative thereto, it is also possible to provide a screw contact arrangement.