EP2721696B1 - Wire for sliding contacts and sliding contacts - Google Patents

Description

The invention relates to a wire for making a sliding contact. The invention also relates to a sliding contact with such a wire.

Finally, the invention relates to a potentiometric sensor, potentiometer, slider, position sensor, rotary switch, electric motor, generator, wind turbine, slip ring system, actuator or current collector with such a sliding contact.

Wires for sliding contacts and sliding contacts themselves have a wide range of applications when electricity is to be transmitted to moving parts. Sheathed wires with an inner core are also made from a first metal. or a first metallic alloy. and a jacket or a coating made of a second metal or a second metallic alloy is used. Such sheathed wires are used, for example, as sliding contacts in slip-ring transmission systems. These are used to transmit signal and power currents in rotating systems, such as wind turbines or robot arms.

Sliding contacts are for example from the DE 40 20 700 A1 known. The DE 199 13 246 A1 discloses a grinder for the transmission of electrical signals, which is designed as a multi-wire grinder. The large number of contacts is intended to ensure continuous electrical contact. From the EP 0 054 380 A2 a brush contact with a slip ring is known as a sliding contact, which consists of a large number of individual wires. The tendency in slip ring systems is towards the transmission of higher currents. At the same time, a reduction in expensive precious metals is increasingly being sought.

From the DE 10 2004 028 838 A1 a sliding contact with a base body made of a wire is known, in which a sliding contact body is arranged at one end of the wire. In this way, it is possible to choose an inexpensive, resilient material, such as stainless steel, for the base body of the contact, while the part transmitting the energy, as a sliding contact body, can consist of another material optimized for energy transmission. The advantage here is that expensive precious metal can be saved, since the entire spring contact does not have to be made from a precious metal or a precious metal alloy. The disadvantage here is the greater effort required to produce such a sliding contact compared to using a simple wire.

The JP 2000 243139 A describes a rigid wire-like conductor made of a composite material. An inner core of the conductor consists of a copper alloy, with 0.01 to 0.03% by weight of one or two elements from the group Sn, In, Cr, Zr, Fe and P being alloyed to form pure copper. Alternatively, a copper alloy is used for the inner core, which is produced by alloying 1 to 20 wt.% Ag or Nb or an alloy thereof to form pure copper. An outer layer of the conductor consists of copper with a zirconium content of 0.01 to 0.3% by weight. The conductor produced in this way should have good flexural strength and tensile strength combined with high conductivity.

A material that is preferably used for the construction of wires for sliding contacts is copper-beryllium alloys, in particular CuBe ₂ , which are popular because of their good elastic properties. It is also known to use sheathed wires which have a core made of a copper-beryllium alloy and a sheath made of a noble metal or a noble metal alloy. These sheathed wires have good spring properties due to the hardened CuBe ₂ core. The contact resistance and the corrosion resistance of these sheathed wires are also very good due to a sheath that is typically high in gold.

The disadvantage here is that the copper-beryllium alloy has poor electrical conductivity compared to pure copper. As a result, the current-carrying capacity of such a wire or of a coated wire with a core made of a copper-beryllium alloy is comparatively low. To transmit higher currents, either the diameter of the wires or the number of wires must be increased. Both measures are associated with significant additional costs due to the higher use of precious metals in the jacket or the coating. Beryllium and beryllium alloys such as CuBe ₂ are also increasingly being avoided because of their environmental pollution.

The object of the invention is therefore to overcome the disadvantages of the prior art. In particular, a wire and a sliding contact with such a wire should be provided which has a higher conductivity but at the same time still has sufficiently good elastic properties that are necessary for a sliding contact. A wire that does not contain environmentally harmful beryllium would be particularly preferred. Furthermore would be it is advantageous if the production costs of such a wire and thus of a sliding contact established with such a wire could be reduced.

The object of the invention is achieved in that at least one inner core of the wire consists of a copper-silver alloy, the wire comprising a coating made of a noble metal alloy.

Due to its electrical and mechanical properties, the copper-silver alloy enables a thin, highly conductive spring contact to be built up.

The coating ensures that the surface of the wire does not oxidize and thus a low contact resistance of such a wire to a mating contact is guaranteed in the long term. With the core of the wire made of a copper-silver alloy, there is the surprising combinatorial effect that a smaller amount of precious metal can be used to coat the wire due to the better electrical conductivity of the copper-silver core. This saves costs when building the wire.

It can be provided that the inner core extends along the entire length of the wire.

According to the invention it can also be provided that the wire is an elastic wire with a round or an angular cross section.

Wires are easy to obtain. If the wire has a round cross section, it has a symmetrical elasticity, so that a mating contact of a sliding contact that is established with such a wire can also be uneven.

Particularly advantageous wires according to the invention are characterized in that the copper-silver alloy has up to 30% by weight of silver, preferably 1 to 25% by weight of silver, particularly preferably 5 to 15% by weight of silver, very particularly preferred 10 wt% silver.

In these mixtures, the mechanical and electrical properties are particularly well suited for building up wires according to the invention. This applies in particular to the electrical conductivity of the copper-silver alloy (Cu-Ag alloy) and the elastic properties, that is, above all, the modulus of elasticity of the Cu-Ag alloy. The wires are then particularly well suited for sliding contacts according to the invention. The proportion of silver is given here in percent by weight (% by weight).

It can also be provided that the copper-silver alloy contains small admixtures of other elements with a proportion below 4% by weight, in particular Zr and / or Cr, preferably with a proportion of below 1% by weight, particularly preferably with a proportion of less than 0.1% by weight.

A small addition of chromium (Cr) but also of zirconium (Zr) can, for example, simplify the application of a gold alloy as a coating, or ensure that a gold alloy adheres better to the surface of the wire.

According to a further embodiment of the invention it can be provided that the wire is elongated and has a cross section between 0.1 mm and 4 mm.

It can further be provided that the wire has a thickness of 0.1 mm to 3 mm, preferably a thickness of 0.15 mm to 2 mm.

According to a further embodiment of the invention, it can be provided that the wire is a wound endless wire or has a length of 10 mm to 300 mm, preferably a length of 20 mm to 180 mm, particularly preferably a length of 30 mm to 100 mm mm has.

Wires with a length between 10 mm and 300 mm are particularly easy to install in sliding contacts according to the invention. By providing wires of suitable length, manual cutting of an endless wire is avoided. Therefore, cut wires for sliding contacts are particularly preferred.

A very particularly preferred embodiment of the invention provides that the noble metal alloy of the coating comprises a gold alloy, preferably the gold alloy comprises silver, copper and / or palladium, very particularly preferably the coating of an alloy with 70 wt. % Gold, 20% by weight silver and 10% by weight copper and / or palladium.

The Cu-Ag core is particularly good and easy to coat with the specified gold alloys. The durability of such a coating on the Cu-Ag alloy is particularly good, especially in the case of silver-containing gold alloys.

It can also be provided that the coated wire comprises a chromium-containing intermediate layer between the core and the coating.

This further improves the durability of the coating on the core.

In the case of wires according to the invention with a coating, it can be provided that the coating is a galvanic coating, preferably with a layer thickness of 0.1 μm to 20 μm, particularly preferably with a layer thickness of 0.5 μm to 2 μm.

Alternatively, it can be provided that the coating is a mechanically applied jacket coating so that the wire is a jacket wire, preferably with a layer thickness of 5 µm to 50 µm, particularly preferably with a layer thickness of 10 µm to 25 µm.

Coated wires can also be characterized in that the coating is a cylinder jacket that extends around the cylindrical core of the wire.

It can also be provided that the coating of the wire is applied to the base body by roll cladding, sputtering or electroplating.

The object of the invention is also achieved by a sliding contact with at least one such wire, with a mating contact being provided, on whose conductive surface at least one of the wires rests, the spring force of the wire on the conductive surface of the mating contact creating an electrical contact between the wire and causes the mating contact and the mating contact is movable against the wire, so that the surface of the wire slides over the mating contact when the mating contact moves.

It can be provided that the mating contact is rotatably mounted and the conductive surface of the mating contact is at least partially rotationally symmetrical.

It can furthermore be provided that the sliding contact is a multi-wire wiper with a large number of wires that are electrically contacted with one another.

Multi-wire grinders are particularly suitable because they can cope with the failure of individual contacts and adapt well to the profile of a mating contact.

It can also be provided that the sliding contact is designed in such a way that at least one of the wires rests with its coating on the mating contact.

The object of the invention is also achieved by a potentiometric sensor, potentiometer, slider, position sensor, rotary switch, electric motor, generator, wind turbine, slip ring system, actuator or current collector with such a sliding contact. The object of the invention is finally also achieved by a potentiometric sensor, a potentiometer, a slide control, a position sensor, a rotary switch, an electric motor, a generator, a wind turbine, a slip ring system, an actuator or a current collector with such a wire as a sliding contact.

The wires and sliding contacts according to the invention can be used particularly effectively in such components.

The invention is based on the surprising finding that the material used, namely the copper-silver alloy, is a highly conductive material that allows the transmission of higher currents with a constant cross-section, or the transmission of constant currents with a smaller cross-section, and the alloy at the same time has suitable mechanical properties, such as elasticity, to form a spring contact.

If the wire is designed as a sheathed wire or as a coated wire that includes a core made of such a copper-silver alloy, the constant cross-section with higher currents or the smaller cross-section with constant currents results in the surprising combinatorial advantage that the jacket or the coating, which is usually made up of expensive precious metals, has a smaller cross-section and therefore less of the expensive jacket material or the coating has to be consumed to produce such a jacket wire or coated wire. This leads to a significant reduction in costs in the production of such a sheathed wire or coated wire, in particular in the case of thicker coatings such as sheathed wires. This is associated with a corresponding saving in precious metals, especially with a clad wire.

Due to the significantly higher electrical conductivity of Cu-Ag materials compared to CuBe ₂ , the use of a wire made of a Cu-Ag alloy or a coated wire or a sheathed wire with a Cu-Ag core enables the transmission of considerably higher electrical currents constant wire cross-section. Conversely, a wire with a smaller cross-section can be used to transmit comparable currents.

By replacing CuBe ₂ with Cu-Ag for wires for sliding contacts, the market demand for beryllium-free products can be met. Beryllium is in Suspected of having harmful effects on the environment, so there is a need for beryllium-free products.

Wires according to the invention based on Cu-Ag can be used in sliding contacts according to the invention such as slip ring transmission systems. Such slip ring transmitters are mainly used for the transmission of electrical signals and electrical power in wind energy systems. In general, slip ring assemblies are used wherever electrical currents are to be transmitted between rotating and static parts, such as in robot arms.

Figur 1:

eine schematische Seitenansicht eines erfindungsgemäßen Schleifkontakts;

Figur 2:

eine schematische perspektivische Ansicht eines erfindungsgemäßen Drahts und

Figur 3:

eine schematische Ansicht eines alternativen erfindungsgemäßen Schleifkontakts.

In the following, exemplary embodiments of the invention are explained with the aid of three schematically illustrated figures, without, however, restricting the invention. It shows:

Figure 1:

a schematic side view of a sliding contact according to the invention;

Figure 2:

a schematic perspective view of a wire according to the invention and

Figure 3:

a schematic view of an alternative sliding contact according to the invention.

Figure 1 shows a schematic side view of a sliding contact 1, which is constructed with a wire 2 according to the invention. The wire 2 comprises a core made of a copper-silver alloy and is coated on its outer jacket surface with a gold alloy. The copper-silver alloy conducts the current and ensures sufficient elasticity of the wire 2.

The wire 2 is fixed on a device 4 with a fixation 3. The device 4 can be any type of installation, for example the mast of a wind power plant or a part which is permanently connected to the mast of a wind power plant. A suspension 5 is arranged on the device 4 and is firmly connected to the device 4. In the suspension 5, a roller 6 is rotatably mounted about an axis 7 as a counter contact to the wire 2. The roller 6 has a conductive surface and is cylindrical in shape. The axis 7 is at the same time the axis of symmetry of the cylindrical roller 6. The roller 6 is connected to the device 4 via the suspension 5 in a non-electrically conductive manner.

The wire 2 is fixed relative to the roller 6 in such a way that it is pressed onto the roller 6. As a result, the wire 2 is elastically deformed. When the roller 6 rotates in the suspension 5, the surface of the wire 2 slides over the conductive cylinder jacket of the roller 6. The continuous contact that the wire 2 creates with the rotating roller 6 allows electricity be transferred from the wire 2 to the roller 6 or vice versa. The contact with the surface of the roller 6 is maintained by the spring force of the wire 2.

An electrical line 8 is connected to the wire 2, with which current can be conducted to further components (not shown) or from other components to the wire 2.

The wire 2, which has a core made of a copper-silver alloy, can have a smaller diameter than conventional wires for conventional sliding contacts in order to transmit the same current. Such a wire 2 is therefore less expensive to manufacture and uses fewer resources. The wire 2 can be produced easily and does not cause any problems with disposal or recycling. Finally, the wire 2 also manages completely without beryllium, which meets newer environmental requirements.

A wire can be used as the wire 2, as shown in FIG Figure 2 and is described below.

Figure 2 FIG. 11 shows a schematic perspective view of a wire 12 according to the invention for sliding contacts, as shown for example in FIG Figures 1 and 3 are shown. The wire 12 shown is a sheathed wire 12 with a core 19 made of a copper-silver alloy. The sheathed wire 12 is round in cross section. The round surface of the core 19 is surrounded by a jacket 20 which forms a cylindrical coating of the core 19. The jacket 20 consists of a gold alloy which consists of more than 50% by weight of gold. The jacket 20 is mechanically applied to the core 19. Alternatively, the wire 12 can also be coated with a thin layer of such a gold alloy.

The coating 20 can be applied to the copper-silver core 19 of the wire 12 by roll cladding, by sputtering or by electroplating. In order to achieve better durability of the coating 20 on the core 19 of the wire 12, an intermediate layer (not shown) can be provided between the core 19 and the coating 20. The intermediate layer can be, for example, a chromium alloy which is applied to the core 19 by electroplating or by means of gas phase deposition.

Figure 3 shows a schematic view of an alternative sliding contact 21 according to the invention. The sliding contact 21 is constructed with a multiplicity of wires 22 according to the invention and thus forms a multi-wire wiper or a brush contact. The wires 22 are held by a fixation 23. The fixation 23 positions the wires 22 such that they are held at a distance from a metallic rail 26 which is smaller than the part of the length of the wires 22 which protrude from the fixation 23.

As a result, the wires 22 are pressed onto the metallic rail 26 and are elastically deformed in the process. As a result of the spring force of the wires 22, they are always pressed onto the rail 26, which forms the mating contact with the wires 22. The wires 22 of the sliding contact 21 are electrically contacted via a line 28. A current can be transmitted from the rail 26 via the wires 22. When the wires 22 move over the rail 26, current can thus always be transmitted from the rail 26 to the wires 22.

The wires 22 comprise a copper-silver alloy and can therefore be made smaller than wires for conventional sliding contacts. As a result, on the one hand, less material is used and, on the other hand, smaller structures can be realized. This is advantageous with increasing miniaturization of many components. The sliding contact 21 shown can be used, for example, in a model railway, as in FIG Figure 3 shown to be realized.

As wires 22, in particular wires as shown in FIG Figure 2 and are explained in the description for this purpose.

It has been found that copper-silver alloys with up to 25% by weight silver and the remainder of copper are particularly well suited to construct a wire 2, 12, 22 according to the invention for a sliding contact 1, 21 according to the invention. In addition, the alloy may contain small amounts (less than 4% by weight) of other metals. Suitable small admixtures can be, for example, chromium or zirconium.

The features of the invention disclosed in the above description and in the claims, figures and exemplary embodiments can be essential both individually and in any combination for the implementation of the invention in its various embodiments.

List of reference symbols

1, 21

Sliding contact

2, 12, 22

wire

3, 23

Fixation

4th

contraption

5

suspension

6

Roller / mating contact

7th

Hub / axle

8, 28

management

19th

core

20th

coat

26th

Rail / mating contact

Claims (15)

1. Wire for producing a sliding contact (1, 21), at least an inner core (19) of the wire (2, 12, 22) consists of a copper-silver alloy, characterized in that
   the wire (2, 12, 22) comprises a coating (20) made of a noble metal alloy.
2. Wire (2, 12, 22) according to claim 1, characterized in that,
   the inner core (1) extends along the entire length the wire (2, 12, 22).
3. Wire (2, 12, 22) according to claim 1, characterized in that,
   the copper-silver alloy contains up to 30% by weight silver, preferably 1 to 25% by weight silver, particular preferably 5 to 15% by weight silver, very particular preferably 10% by weight silver.
4. Wire (2, 12, 22) according to claim 1, 2 or 3, characterized in that,
   the copper-silver alloy contains small admixtures of other elements with their fraction being less than 4% by weight, and the small admixtures of other elements are Zr and/or Cr, preferably with their fraction being less than 1% by weight, particular preferably with their fraction being less than 0.1% by weight.
5. Wire (2, 12, 22) according to any one of the preceding claims, characterized in that,
   the thickness of the wire (2, 12, 22) is 0.1 mm to 3 mm, preferably the thickness of the wire (2, 12, 22) is 0.15 mm to 2 mm.
6. Wire (2, 12, 22) according to any one of the preceding claims, characterized in that,
   the wire (2, 12, 22) is reeled-up continuous wire or has a length of 10 mm to 300 mm, preferably has a length of 20 mm to 180 mm, particular preferably has a length of 30 mm to 100 mm.
7. Wire (2, 12, 22) according to any one of the preceding claims, characterized in that,
   the noble metal alloy of the coating (20) comprises a gold alloy, preferably the gold alloy comprising silver, copper and/or palladium, particular preferably the coating is made of an alloy containing 70% by weight gold, 20% by weight silver, and 10% by weight copper and/or palladium.
8. Wire (2, 12, 22) according to any one of the preceding claims, characterized in that,
   the coating (20) is an electroplated coating (20), preferably having a thickness of 0.1 µm to 20 µm, particular preferably having a thickness of 0.5 µm to 2 µm.
9. Wire (2, 12, 22) according to any one of the preceding claims, characterized in that,
   the coating (20) is a jacket coating (20) applied mechanically such that the wire (2, 12, 22) is a jacked wire (12), wherein preferably the coating (20) is of a thickness of 5 µm to 50 µm, particular preferably the coating (20) is of a thickness of 10 µm to 25 µm.
10. Wire (2, 12, 22) according to any one of the preceding claims, characterized in that,
    the coating (20) is a cylinder jacket that extends around the cylindrical core (19) of the wire (2, 12, 22).
11. Sliding contact (1, 21) having at least one wire (2, 12, 22) according to any one of preceding claims, characterized in that,
    a counter-contact (6, 26) is provided which conductive surface has at least one of the wires (2, 12, 22) touch against it, whereby the spring force of the wire (2, 12, 22) acting on the conductive surface of the counter-contact (6, 26) effects electrical contacting between the wire (2, 12, 22) and the counter contact (6, 26) and the counter contact (6, 26) is mobile with respect to the wire (2, 12, 22) such that the surface of the wire (2, 12, 22) slides over the counter-contact (6, 26) when the counter-contact (6, 26) moves.
12. Sliding contact (1,21) according to claim 11, characterized in that,
    the counter-contact (6) is supported against the wire (2, 12, 22) like in a bearing such that it can rotate and at least part of the conductive surface of the counter-contact (6) is rotationally-symmetrical.
13. Sliding contact (1, 21) according to claim 11 or 12, characterized in that,
    the counter-contact (6) is a multi-wire wiper contact (21) having a multitude of wires (2, 12, 22) that are electrically contacted to each other.
14. Sliding contact (1, 21) according to any one of claims 11, 12 or 13 having at least one wire (2, 12, 22) according to any one of claims 1 to 10, characterized in that,
    the sliding contact (1, 21) is designed appropriately such that at least one of the wires (2, 12, 22) touches, by its coating (20), against the counter-contact (6, 26).
15. Potentiometric sensor, potentiometer, sliding dolly regulator, position sensor, rotary switch, electrical motor, generator, wind turbine, slip ring system, actuator or current collector having a sliding contact (1, 21) according to any one of claims 11 to 14.

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