EP3369099A1

EP3369099A1 - Electric cable

Info

Publication number: EP3369099A1
Application number: EP16798654.6A
Authority: EP
Inventors: Erwin Köppendörfer; Rainer PÖHMERER
Original assignee: Leoni Kabel GmbH
Current assignee: Leoni Kabel GmbH
Priority date: 2015-10-28
Filing date: 2016-10-27
Publication date: 2018-09-05
Anticipated expiration: 2036-10-27
Also published as: EP3369099B1; US20180233254A1; US10325698B2; CN108352222A; WO2017072265A1

Abstract

Electric cable (2), in particular data cable, comprising a transmission core (4) which is surrounded by a shield (20) and concentrically surrounded by a sheath (6) that includes an outer layer (8) made of an electrically insulating plastic material and a second layer (10) underneath that is made of a semiconducting material. The semiconducting layer improves the shielding effect.

Description

description

Electrical line

The invention relates to an electrical line, in particular a data line with a transmission core surrounded by a shield, wherein the transmission core is surrounded concentrically by a line jacket.

Electrical cables often have a shield. Especially with data lines this shield serves to shield against external interference on the signal transmission within the transmission core. At the same time, such a shield also serves to shield it from the outside, so that no interference fields are emitted by the transmission core into the environment. Shielding of this kind is required especially for power transmission lines, especially for high-voltage cables, for example.

The shield is regularly formed as an electrically conductive element surrounding the lead core. There are a variety of screen options available, such as film screens, braided shields (C-screens) or helical screens (D-umbrellas) or combinations thereof. For the effectiveness of the shielding, it is necessary that the shield has a high conductivity and in a connection region, ie where the electrical line with an electrical component such as a plug or an electrical device is connected, with a reference potential, for example ground potential electrically contacted. This is associated with the assembly with an increased effort. A screen which is not contacted with the reference potential, or not optimally, shows only a poor shielding effect or even leads to additional disturbing influences in comparison to an unshielded line. In the case of cables which are subjected to frequent bending cycle stresses, a compromise between good shielding effect and low rigidity must furthermore be chosen.

In the case of data lines, so-called unshielded data lines are known in addition to shielded lines. Frequently twisted pairs of wires are provided without shielding, which are used for a symmetrical data transmission (so-called unshielded twisted pair, UTP). Such unshielded data lines are used especially in low-cost applications, for example, in the automotive sector and in those applications in which no excessive demands on the data transmission quality and in particular speed (frequency of the transmitted data signals) are provided.

Frequently, symmetrical data lines are used for symmetric data transmission. In this case, a signal is transmitted via a first wire and the inverted signal is transmitted via a second wire and both signals are evaluated together. Two wires form a respective wire pair for a symmetrical data transmission.

In the future, more and more data transmission systems are required, especially for single-pair data lines without shielding. By limiting e.g. on a pair and the elimination of the shielding both space, weight and line costs are reduced. The same applies in a similar way to the plug and the assembly process. Especially in the automotive sector such transmission systems are desired, since the space is limited and improved by weight saving both the handling and the Kraftstoffbzw. Energy requirement while driving can be reduced.

However, in a cable channel or in a vehicle electrical system, a large number of lines are packed tightly directly against each other. Due to the short distances, an interference signal from one line (aggressor / transmitter) to the other line (victim receiver) is coupled over (so-called alien crosstalk). Proceeding from this, the object of the invention to provide an electrical cable with a shield, which is inexpensive to manufacture and at the same time achieves an improved compared to the conventional lines shielding effect.

The object is achieved according to the invention by an electrical line having the feature of claim 1. The electrical line has a transmission core, which is surrounded by a shield. The transmission core as a whole is surrounded concentrically by a cable jacket. The cable jacket itself is now formed in two layers and has an outer layer of an electrically insulating plastic, as well as a second layer disposed thereunder of a semiconductive material.

This embodiment is fundamentally based on the consideration that interference currents caused by external interference fields are conducted away via the shielding in the longitudinal direction of the line. Conventionally, reliable shielding of the interference currents and, in particular, good contacting of the shield with reference potential, for example, with ground potential in the region of a connection (plug or device), are required for effective shielding effect.

The particular advantage of the measure presented here with the second layer of a semiconductive material is now that instead of such a dissipation of the interference currents they are at least partially attenuated already within the second layer due to their low conductivity. The energy of the interference currents is therefore consumed at least partially and preferably completely in the second position. This therefore forms a "swamp" for interference fields, in particular external RF interference fields.

In addition, the outer, conventional insulating layer is used for insulation from the environment.

Due to the second semiconductive layer, therefore, overall the shielding effectiveness is improved over conventional unshielded lines. At the same time is one to apply such second layer of semiconductive material inexpensively and in a simple manner.

Specifically, the second layer is applied by extrusion, in particular by Schlauchextru- sion on the transfer core or on a core surrounding the shield layer.

Furthermore, the semiconductive jacket has a wall thickness which is constant in particular around the circumference of the transmission core. The wall thickness is suitably in the range between 0.05 mm to 1, 2 mm and in particular in the range of 0.1 mm to 0.3 mm. Specifically, a wall thickness of 0.2 mm is selected in the case of, for example, an extruded semiconductive jacket.

As an alternative or in addition to the extruded sheath, the semiconductive sheath has a foil and / or a nonwoven which has been applied in particular and / or individual wires which have a correspondingly low conductivity, in particular in the manner of a winding. When using a film or a nonwoven, the wall thickness is typically slightly below the previously specified 0.2 mm. In the case of a film, for example, a suitably slotted film, in particular metal-clad plastic film, is used. Through the slots, the low conductivity is set.

Preferably, furthermore, the outer layer of the insulating plastic is applied by extrusion. The two layers are applied in particular by coextrusion.

As an alternative to the extrusion of the second layer, this is applied by banding, for example. In any case, the cable jacket and the second layer extend continuously over the entire length of the line.

The outer layer is, in particular, an outer jacket of the electrical line, which is not surrounded concentrically by any further jacket. Several such electrical lines can be combined to form a cable or a bundle of cables.

The transmission core is generally an electrical transmission core, which is preferably designed for data transmission or alternatively for transmission of electrical power.

Under semiconductive material is generally understood herein a material whose conductivity is significantly lower than that of metals, as is the case with conventional shield layers. Specifically, the conductivity is at least a factor of 10, preferably at least a factor of 100 or 1000 to a factor of 10 ⁶ lower than the conductivity of pure copper (each at 20 ° C).

According to a preferred embodiment, the cable jacket has a conductive layer below the second layer, ie in the direction of the transfer core, which contacts the second layer in an electrically contacting manner.

This embodiment is based on the consideration that, especially in the case of higher-frequency interference fields, these can penetrate the cable jacket and also the second layer, so that they are only partially attenuated in the second position. These portions of the interference then apply to the conductive layer and generate in this interference currents. Due to the skin effect, these run on the outside of the conductive layer and therefore penetrate again into the second layer and are further attenuated there. Overall, the energy introduced via the interference fields is thereby used up as completely as possible in the second position.

This conductive layer is suitably designed as a cost-effective to produce and applied film. If this is referred to as a conductive layer, this is generally understood to mean a conductivity in the range of metals. The conductive film is typically a conventional screen film, which is often used as a metal-laminated plastic film, especially an aluminum-clad plastic film or also as a copper foil. is forming. The aluminum layer can be applied on one or both sides of the carrier film. The total thickness of such a film is typically in the range between 20 to 100 μηπ, wherein the thickness of the at least one metal layer is at least about 7m or at least 10 μηι and for example up to 30 or even up to 50 μηι. Such comparatively thin metal layers in the range of 7 to 20 μηι are sufficient for the intended application here.

According to a preferred embodiment, in addition to the cable jacket, i. in particular, in addition to the second layer and the conductive layer, no further shielding layer provided. Such an electrical line therefore consists of the transfer core, a possibly surrounding this film as a conductive layer, the second layer of semiconductive material and the outer insulating layer.

Such a line is used in particular as a replacement for previously unshielded data lines, for example unshielded twisted data lines (UTP lines). The shield effect of the extruded second layer of semiconductive material and the concomitant damping of unwanted spurious currents, a significant improvement in data transmission is achieved.

Due to the damping of the interference currents in the second layer, the parasitic energy introduced is preferably consumed reliably within the second position. In general, the particular advantage is achieved that for the desired shielding effect - unlike conventional umbrellas - no contacting of the shield in the connection area is required.

In an expedient embodiment, therefore, even in the assembled state, ie when an electrical component is connected at one end to the end of the electrical line, the shielding is not contacted electrically, that is, for example, not connected to a ground potential. The shielding in this case may be due to the second layer, if necessary in combination with the underlying layer. formed the conductive layer. This has the decisive advantage that the cost of assembly is kept low and that in particular recourse is made to conventional (connection) components, which are also used for conventional, unshielded cables. All process steps, components, such as plugs, etc., can be retained unchanged (in comparison to previous unshielded cables), while at the same time significantly improving the shielding effect.

The components are in particular contact or even directly to consumers who are directly connected to the line. In general, therefore, in this particular embodiment, a shield contact in the area of the components and thus a decided connection concept for the shield is dispensed with.

In particular, these data lines are symmetrical data lines with at least one core pair, via which a symmetrical signal is transmitted during operation. This is in particular a twisted wire pair. In addition, quadrilaterals, such as, for example, the so-called Sternvierer stranded network, are used as the transmission core.

As an alternative to this low-cost application without shielding contact, the cable jacket with the semiconductive second layer is used in conventional, shielded lines, in particular in the coax line. Specifically, in this case, the transfer core is at least surrounded by a shield layer, around which then applied to the line jacket, in particular extruded. This shielding layer is connected in the assembled state, in particular via a shield contact in the region of the component and connected to reference potential. Such a shield layer forms in particular an outer conductor of a coaxial line.

The shield layer is a conventional, also multi-layer shield layer, which can be used, for example, as a screen braiding (C screen) as a wire Wraps educated screen (D-screen or Wendelschirm) is formed. In addition, also foil shields or a combination of these screen types are used for a multilayer construction.

Even with such a conventional shielded line is achieved with the special cable jacket structure with the semiconductive second layer an improved shielding effect due to the attenuation of the interference currents in the second layer. Again, the effect described above is exploited that interference currents due to the higher-frequency fields and the skin effect spread on the outside of the shield layer and are thus attenuated by the second layer.

In the first variant with the transmission core of one or more wire pairs without dedicated (in the assembled state with reference potential connected) shielding the shielding of the line is formed exclusively by the cable jacket, namely only the second semiconductive layer or possibly also in interaction with the conductive layer , In the second variant with the additional shielding layer, the (total) shielding is formed by the second layer of the cable jacket (possibly with the additional conductive layer) in combination with the shielding layer.

The specific resistance of the semiconductive material is generally preferably greater than 1 ohm ^* mm ² / m and preferably greater than 10 ohm ^* mm ² / m. The specific resistance is typically at least two orders of magnitude higher, for example compared to the specific resistance of copper (based on an ambient temperature of 20 ° C.). Furthermore, the specific resistance is preferably less than 1000 ohms ^* mm ² / m and in particular less than 100 ohms ^* mm ² / m. Thus, the specific resistance is well below the resistance of typical insulating materials. Specifically, therefore, the specific resistance is in the range between 10 to 100 ohms ^* mm ² / m. This ensures good damping. The semiconductive material is, for example, a conductive plastic, ie a plastic with intrinsic conductivity.

Alternatively, the low conductivity is formed by an insulating plastic with conductive particles embedded therein. The particles are in particular carbon or soot particles, or else carbon nanoparticles. These are so-called nanoflocs as well as nanotubes etc. understood. By the carbon particles, the desired conductivity is achieved. The proportion of particles is selected such that the above desired conductivity or the desired specific resistance is set. Depending on the particle and the desired specific resistance, the degree of filling of the particles is for example in the range between 8 and 55% by volume and in particular in the range between 10 and 40% by volume based on the total volume of the second semiconductive layer.

Preferably no metal particles and / or no magnetic, in particular no ferromagnetic or magnetizable particles are used for the semiconductive material. Such comparatively hard metal particles would lead to tool wear during extrusion. Therefore, these particles are dispensed with.

The semiconductive second layer is arranged in a first variant directly around the transmission core formed by the wires. It is designed in particular in the manner of a (extruded) tube.

In a preferred alternative, an intermediate sheath is arranged between the transfer core, which preferably has exactly one core pair or else several wire pairs, and the semiconductive sheath, so that the semiconductive sheath has a (minimum) distance to the core pair. This is preferably at least about 0.5 mm and is in particular at most 1, 5 mm. Distance here means the smallest distance to a respective core. The intermediate casing itself expediently consists of a particularly solid insulating material, such as polypropylene. The intermediate jacket therefore forms a suitable dielectric, which has a positive effect on the transmission of the particular symmetrical signal.

On the outside, the data line is surrounded by another outer jacket made of an insulating material. This can be a solid coat or a foamed coat. It can also be provided spacer elements, so that adjacent data lines are kept at a defined distance from each other.

Such a data line therefore preferably has a total (single) pair of wires, wherein the core pair is formed by two wires, consisting of a conductor, in particular a stranded conductor of stranded individual strands of a conductive material, in particular copper, a copper alloy or aluminum, stranded one another Aluminum alloy, etc. The conductor is surrounded by a core insulation. The conductor typically has a diameter in the range of 0.3 mm to a maximum of 1.2 mm, preferably in a range of 0.3 mm to 0.9 mm. The diameter of the wire is typically in the range between 0.7 mm to 2.5 mm. The two wires are stranded together and surrounded by the intermediate sheath. This typically has a diameter which corresponds to 2 times the core diameter plus the minimum wall thickness of the intermediate sheath of preferably 0.5 mm.

For small conductor diameters (0.3 mm) and correspondingly small core diameter (0.7 mm), therefore, the diameter of the intermediate sheath is about 2.4 mm. This is then surrounded by the semiconductive jacket, which has a wall thickness of about 0.2 mm, so that an outer diameter of this semiconductive jacket is preferably about 3 mm. Finally, this is still surrounded by an outer sheath, which in turn has a wall thickness of, for example, 0.5 mm to 1, 5 mm. As already stated, the line according to a first embodiment variant is a symmetrical data line, in which the transmission core is formed by at least one wire pair for the transmission of a symmetrical data signal. In this case, the transfer core is preferably formed by at least one stranded pair or else by a plurality of stranded pairs or else a quad stranding etc. According to a first embodiment variant, a respective pair may be surrounded by a pair shielding. Alternatively, no pair shielding is provided. Preferably, no shielding contact is made in the connection region to a component in this symmetrical data line.

Alternatively, the electrical line is designed as a coaxial line with an inner conductor, with a dielectric surrounding the inner conductor made of plastic material and with an outer conductor, which is formed by the aforementioned shield layer. To the outer conductor then the cable jacket is attached, wherein the second layer is applied to the shielding layer.

Finally, according to a further embodiment variant, the electrical line is designed as a supply line for supplying a load with electrical power in the range of, for example, at least several 10 W or 100 W or even in the KW range. The transmission core may in this case have a plurality of power cores with an insulated conductor with a sufficiently large conductor cross-section. The conductor cross section is designed, for example, for the transmission of currents in the ampere range.

Embodiments of the invention will be explained in more detail with reference to FIGS. These show each in schematic representations:

1 shows a cross-sectional view of the electrical line according to a first

Variant,

2 shows a cross-sectional view of the electrical line according to a second

Variant, 3 shows a cross-sectional view of the electrical line according to a third embodiment variant with an intermediate jacket as well

4 shows the electrical line of the first embodiment of FIG. 1 in a partially sectioned view and connected to a component.

In the figures, equivalent parts are each provided with the same reference numerals.

In the exemplary embodiment, the lines 2 shown in FIGS. 1 to 3 are each designed as data lines and have a central transmission core 4, which is surrounded by a line jacket 6. In all variants, the cable jacket 6 has an outer first layer 8 made of an electrically insulating plastic and a second layer 10, which is arranged directly underneath, made of a semiconductive material. The cable jacket 6 is located in the embodiments of Figures 1 and 2 directly on the transfer core 4. Specifically, the cable jacket 6 is a cable jacket 6 formed by extrusion. The two layers 8, 10 are specially formed by co-extrusion. The cable jacket 6 is applied to the transfer core 4 in the manner of a tube extrusion.

The line 2 according to the embodiment of Figure 1 is formed as a symmetrical data line with in the embodiment preferably 2 pairs of wires. A respective pair of wires 12 is used in the data transmission of a symmetrical data signal for transmitting on the one hand the signal and on the other hand the inverted signal. Specifically, the respective pair of wires 12 is a twisted wire pair. A respective core 14 is formed by a central conductor 16, which is surrounded by an insulating jacket 18 as a core jacket.

In the embodiment according to FIG 1, the cable jacket 6 additionally has a conductive layer 20 which is formed in particular by a film, especially a conventional screen foil. It is specifically an aluminum-laminated plastic film. The metal side is in the direction of the second Layer 10 orientates and contacts these electrically conductive. In an alternative variant, this conductive layer 20 is dispensed with.

In contrast thereto, the embodiment according to FIG. 2 is a coaxial line, in which the transfer core 4 is formed by an inner conductor 22, a dielectric 24 which is immediately surrounding it made of insulating plastic material and by an outer conductor 26 directly adjacent to the dielectric 24 , The outer conductor 26 defines at the same time a shield layer 28. In the exemplary embodiment, this shield layer 28 has a multilayer construction with a braid 30 and a shielding foil 32. The shielding film 32 is preferably arranged on the outside, but may alternatively also be arranged on the inside to the mesh 30. Here again, it is important that the shield layer 28 is in electrical contact with the second semiconductive layer 10. The second semiconductive layer 10 surrounds the shield layer 28 directly and is designed in particular as an extruded jacket.

When external interference fields occur in the high-frequency range, especially in the range from 1 to 5000 MHz, these high-frequency interference fields penetrate into the cable jacket 6 and penetrate it. Due to the conductivity of the second layer 10, the high-frequency interference fields are strongly attenuated in this second layer 10, d. H. their energy is at least partially, preferably completely converted into heat in the second layer 10.

Shares of the external interference field, which penetrate through the second layer 10, then apply in the case of the embodiment according to FIG. 1 to the conductive layer 20 or to the shield layer 28 in the embodiment variant of FIG. In this then interference currents are generated which propagate in the longitudinal direction of the line 2. Due to the skin effect, these spread on the outer side of the conductive layer 20 and the shield layer 28 and reach due to the immediate vicinity in the second layer 10 and are further attenuated there. Due to the special construction of the cable jacket 6, therefore, an improved screening effect is generally achieved by a screen damping. Applied interference energy is converted into heat in the second layer 10.

This also avoids alien crosstalk. The impressed in the conductive layer by electromagnetic coupling currents lead to a weakening of the electromagnetic field to the outside and thereby to a lower overcoupling in adjacent lines (alien crosstalk).

This is especially true for the embodiment of Figure 3. The line 2 has as a transfer core only one particular twisted pair of wires 12, which is surrounded directly by an intermediate casing 40. This is a particularly extruded plastic jacket which forms a dielectric 24.

The intermediate jacket 40 is in turn directly surrounded by the second semiconductive layer 10, which is finally surrounded by the outer jacket 8. The latter is used for electrical insulation, protection against environmental influences or as a spacer. In an alternative variant, a conductive layer 20 may be formed.

Especially in low-cost applications, preferably in the automotive sector, the structure described here with the intermediate jacket 10 is used to conventional unshielded lines, especially data lines, in particular unshielded balanced data lines by a provided with such a cable jacket 6 line 2 (symmetrical data line) replace. At the same time, however, the conventional components for the unshielded data line as well as the conventional process steps are retained. In particular, no shielding contact takes place in a connection region to a component 34. The respective shield of the line 2 is therefore not electrically connected to the component 34 - as usual - with a reference potential, in particular ground potential. This concept is illustrated in FIG 4. From this it can be seen that the line 2 is introduced, for example according to FIG 1 or FIG 3 in the only greatly simplified component 34 shown through an inlet opening. In this case, the cable jacket 6 is guided, for example, through the opening. The opening is usually sealed, for example by a sealing ring, a nozzle or by circumferential webs which are pressed into the cable jacket 6. The component 34 is, for example, a plug which serves for connection to a consumer. Alternatively, component 34 is directly a consumer. In both cases, the conduit 2 is passed through the opening of a housing.

The individual wires 14 are freed from the cable jacket 6 within the component 34 and also the respective conductor 1 6 of the respective core 14 is stripped and connected at the end to a contact element 36. These are, for example, contactbooks or contact pins, for example as

Crimp contacts are formed. Alternatively, a screw can be made.

Claims

claims

1 . Electrical line, in particular data line, with a transmission core surrounded by a shield, which is surrounded concentrically by a cable jacket which has an outer layer of an electrically insulating plastic and a second layer of a semiconductive material arranged thereunder.

2. Electrical line according to the preceding claim, wherein the second layer are formed by extrusion, in particular together with the outer layer by coextrusion.

3. Data cable according to one of the preceding claims, wherein the second semiconductive layer has a wall thickness in the range of 0.05 to 1, 2mm, in particular in the range of 0.1 mm to 0.3 mm.

4. Electrical line according to one of the preceding claims, wherein the cable jacket below the second layer has a conductive layer which bears against the second layer in an electrically contacting manner.

5. Electrical line according to the preceding claim, wherein the conductive layer is formed as a film.

An electrical lead according to any one of the preceding claims, wherein the conductive sheath forms the sole shield of the transmission core.

An electrical lead as claimed in any one of the preceding claims connected to an electrical component at at least one end, wherein the shield is not electrically contacted to the component.

8. Electrical line according to one of claims 1 to 4, wherein in addition to the cable jacket at least one shielding layer is arranged around the transfer core.

9. Electrical line according to one of the preceding claims, wherein the resistivity of the semiconductive material is greater than 1

Ohm ^* mm ² / m and preferably greater than 10 ohm ^* mm ² / m.

An electrical lead as claimed in any preceding claim, wherein the resistivity is less than 1000 ohms ^* mm ² / m, and more preferably less than 100 ohms ^* mm ² / m.

1 1. An electrical lead according to any one of the preceding claims, wherein the semiconductive material is a conductive plastic

12. Electrical line according to one of the preceding claims, wherein the semiconductive material is formed by an insulating plastic with conductive particles embedded therein, in particular carbon particles, such as soot particles or carbon nanoparticles.

13. Electrical line according to one of the preceding claims, wherein the semiconductive material has no metal particles and / or no magnetic, in particular no ferromagnetic or magnetizable particles.

14. Data cable according to one of the preceding claims, wherein between the transfer core, which is preferably formed by exactly one wire pair or a plurality of wire pairs, and the semiconductive jacket an intermediate sheath is arranged, so that the semiconductive sheath to the transfer core has a (minimum) distance.

15. Data cable according to the preceding claim, wherein the distance to the transfer core, in particular to a respective core is at least about 0.5 mm, and preferably at most 1, 5mm.

16. Data cable according to one of the two preceding claims, wherein the intermediate jacket consists of a preferably solid insulating material, such as polypropylene.

17. Electrical line according to one of the preceding claims, which is designed as a symmetrical data line, wherein the transmission core is formed by at least one pair of wires for the transmission of a symmetrical data signal.

18. Electrical line according to one of claims 1 to 13, which is designed as a coaxial line with an inner conductor, a surrounding dielectric and an outer conductor, wherein the outer conductor of the cable jacket is arranged.

19. Electrical line according to one of claims 1 to 16, which is designed as a supply line for supplying a consumer with electrical power and in which the transmission core is formed as a conductor or has a plurality of power cores.