EP3389059A1 - Winding wire and use of same - Google Patents

Abstract

The invention relates to a winding wire, in particular one as they are used for the coils of electric motors. The invention is characterized in that the conventional system for the production of winding wire coils for electric motors can be practically taken over, but two or more process steps can be omitted, because a small amount of commercially available slip additive formulation at least for the top layer of insulating coating of the winding wire is added. The invention also relates to the use of a winding wire for producing a coil for an electric motor.

Description

The invention relates to a winding wire, in particular one as they are used for the coils of electric motors.

Coils for electric motors are made of copper wires by winding method. The electrical insulation of the individual wires with each other is ensured by an insulating wire enamel, for example based on polyamide-imide. After winding, the coils are usually still applied with a impregnating resin to fix the position of the individual wires.

When winding the coils, it is an essential goal to wrap them as tight and compact as possible. The reason for this is, on the one hand, the greatest possible weight distribution, but also the accommodation of as many turns as possible in a small space. For this reason, the wires are wound on a winding form and pulled under high tensile force into a grooved laminated core.

In addition, in the case of defective packing of the winding wires, the impregnation behavior is influenced such that out of the cavities which result between the individual wires, the impregnating resin runs out before curing and as a result the mechanical adhesion of the individual wires is also insufficient. This can cause vibration-related problems during later operation of the engine.

A disadvantage of the previously known winding wire with wire insulation, however, is a poor lubricity, so that without the application of an additional wax layer - for example, paraffin - the tensile force for introducing the wires or copper mass would have to be increased in the groove.

On the other hand, however, it is disadvantageous to the wax and / or paraffin that a disturbing abrasion results in the winding, which in turn requires a high cleaning effort.

The object of the present invention is therefore to provide an insulated winding wire with improved sliding properties, which overcomes the disadvantages of the prior art.

This object is solved by the subject matter of the present invention as disclosed in the specification and the claims.

The subject of the present invention is therefore a winding wire made of an electrically conductive material, comprising at least one layer of an insulating coating, characterized in that a formulation for producing the insulating coating is added at least one lubricant additive, the sliding and / or leveling properties of insulating coating on the surface improved. In addition, the invention relates to the use of an insulating coated according to the invention winding wire for producing a winding wire coil for an electric motor.

General knowledge of the invention is that a small addition of a commercially available lubricant additive in the formulation for producing the at least one layer of an insulating paint material to improve the sliding and / or leveling properties of the insulating paint material whose sliding friction coefficient so greatly reduced that the addition of Lubricant such as wax can be dispensed with when winding the winding wires to form a coil for an electric motor.

According to an advantageous embodiment of the invention, the insulating coating comprises at least one, but preferably several layers of an insulating paint material.

It is altogether particularly preferred that the concentration of the slip additive increases radially outwards, that is, for example, lower, that is to say metal-wire-closer layers, no lubricant additive is added at all, whereas in outer, surface-closer layers Additive is added. It is particularly preferred that the uppermost and outermost layer of insulating paint material is mixed with slip additive.

It is provided that the distribution of the slip additive in the position is inhomogeneous, in particular so that it follows a concentration gradient that reaches its maximum on the surface of the layer.

According to an advantageous embodiment of the invention, the insulating coating comprises a plurality of layers of one or more different lacquers.

According to an advantageous embodiment, at least the uppermost layer of the coating is added a lubricant additive which improves the sliding and / or leveling properties.

According to an advantageous embodiment of the invention, the distribution of the slip additive in the paint coating is inhomogeneous, such that the slip additive is enriched on the surface of the layer of insulating paint material. In particular, it is advantageous if the distribution of the slip additive in the position follows a concentration gradient which reaches a maximum at the surface.

Since a suitable slip additive usually accumulates on the paint surface and / or also improves the flow properties of the paint, the surface roughness and / or surface waviness is reduced and thus also produces an improved surface topography of the insulating paint.

The improved surface topography in turn leads to improved windability of the wires regardless of whether the surface is additionally lubricious or not.

The surface is lubricated, for example, by the "lubricating film" described below. It is particularly advantageous in the present invention that lubricity and surface topography are improved in one go.

The term "course" refers to the property of paints, unevenness, which have arisen during the application, for example by spray mist, to compensate automatically after the application. The course of a lacquer and / or a coating material is highly dependent on its flow behavior, its surface tension, the application parameters and the drying conditions. If the course is insufficient, surface defects occur, such as a pronounced structure, dents and / or craters on the paint surface. Good coatings, on the other hand, create even, smooth surfaces with low coefficients of sliding friction.

According to an advantageous embodiment, at least one polysiloxane, in particular an organically modified siloxane, is added as slip additive. Alternatively or additionally, a compound from the class of polyacrylates may be added as a slip additive in the insulating paint.

As polysiloxanes, in particular the following have proven useful: Polyethersiloxane and / or organically modified siloxanes having a high content of polydimethylsiloxane segments, which show particularly low interactions both with each other and with other substances.

Organically modified siloxanes or polysiloxanes are derived, for example, from low molecular weight polydimethylsiloxanes by replacing individual methyl groups with various organic side chains. For example, polyethers are used as organic side chains.

Organically modified polysiloxanes minimize surface irregularities and give the paint a particularly smooth surface. During the venting / evaporating and / or drying process, the organically modified polysiloxanes accumulate continuously on the surface. It forms a film that allows the pasting of a solid. This creates a kind of hydrodynamic lubrication and the sliding resistance is significantly reduced.

For example, a slip additive can produce a hydrodynamic lubricant film by accumulating on the paint surface. For example, this lubricating film is comparable to a very thin liquid film.

In solvent-containing formulations, slip additives prove to be particularly effective, because they are transported to the surface during evaporation of the solvent, ie during drying of the paint with the solvent.

As slip additive, for example, a commercial lubricant and / or flow control agent is added, for example one with a molecular weight in the range of 500 to 25,000 g / mol, in particular one with a molecular weight in the range of 1000 to 15,000 g / mol, in particular one with a Molar mass in the range of 5,000 to 10,000 g / mol.

Due to their high molecular weight, the preferred polymeric slip additives are relatively immobile in the interface and form a bulky resistor on the surface, contrary to the flow of material that usually arises, for example, not only from the substrate to the surface of the paint when evaporating the solvent, but also transversely to it, in particular by gaps, which leave behind for example a evaporated solvent molecule. The flow of material along the surface is but one of the causes of drying the paint, which is why the original smoothness, the freshly applied, even wet and still uncrosslinked, that is not cured lacquer, disappears during drying and a surface roughness, which is visually recognizable by a matting of the lacquer, is formed. Due to the large bulky lubricant additive molecules, which preferentially also crosslink with the molecules of the paint, so unevenness on the surface is avoided and favors a smooth, lubricious surface. Nevertheless, the surface energy of the dried paint is retained and is not reduced, which is why the wetting of a subsequent layer is not critical.

As paint base for the formulation in which the at least one slip additive is introduced, for example, a crosslinking curing, in particular a radiation and / or temperature-curing paint, in particular a conventionally already customary for this application paint used. In this case, crosslinking of the slip additive (s) may well take place with the paint base formulation.

Preference is given to using a lacquer base conventionally used as a wire enamel polymer, in particular, for example, polyamide-imide and / or polyester-imide, as well as any mixtures and / or blends thereof.

In the formulation, the lubricity additive may, for example, in an amount in the range of 0.01 wt% to 2.5 wt%, in particular from 0.1 wt% to 1.0 wt%, particularly preferably from 0.15 wt% to 0.5% by weight of the dry matter of the individual paint layer may be present.

In the present case, the term "dry mass" refers to the mass of the lacquer layer after removal of the solvent.

The sliding friction is reduced to less than 20% of the value of the standard wire compared to the coated winding wire without lubricant additive and without lubricant.

Example of the coating of a winding wire:

The wire enamel is applied to the winding wire in up to 12 layers, for example in the form of two different lacquers, which are applied alternately.

This is done according to the prior art, for example, by pulling the wire through paint baths in which - for example, solvent-containing - formulation is present and subsequent thermal consolidation. For the effect of the improved sliding properties, it is only necessary to provide the last coating layer, so the top, with the corresponding lubricant additive.

• Integraler Gleitreibungskoeffizient über Fläche A und Fahrstrecke s: $$\bar{\mathrm{\mu }}={\mathbf{F}}_{\mathrm{R}}/{\mathbf{F}}_{\mathrm{G}}$$
  

For the determination of the sliding properties of painted surfaces, a laboratory setup consisting of a motorized traverse and a fine balance was created. The coefficient of sliding friction between a corresponding wire-coated copper plate and a wire-coated Si wafer was used according to the method described in US Pat FIG. 1 structure shown and according to the formula:

• Integral coefficient of sliding friction over area A and distance s: $$\tilde{\mathrm{\mu }}={\mathbf{F}}_{\mathrm{R}}/{\mathbf{F}}_{\mathrm{G}}$$
  

In the FIG. 1 It can be seen how a mass 1 is held with a weight F _G = mg via a spring balance 2 at a fixed point 3 horizontal right. The table 4 on which the mass 1 is on the contact interface 5 is pulled to the left, while the sliding friction 6 wants to keep the mass 1 against this direction. The resistance to be overcome is determined via the fine balance 2.

The fine scale indicates the force that must be expended to bring the mass 1 on the surface of the contact interface 5 to slide.

In FIG. 2 are the reduced sliding friction coefficients of wire enamel samples with sliding additive addition shown. The value 1 on the far left in the graph was a sample coated with wax, in particular polyethylene glycol. The slip additive 2 proved to be particularly advantageous because it not only provides the lowest coefficients of friction, but also has no appreciable concentration dependence with respect to the reduction in sliding friction. Thus, added to this lubricant additive added in very small amounts, the same effect as other lubricious additives in larger amounts added. The sample was the slip additive available under the trade name Glide 415®.

In order to investigate the wettability of the paint surface offset with slip additive according to a preferred embodiment of the invention, wetting results of two conventional standard impregnating resins on a paint coated winding wire surface coated according to the invention with slip additive were shown. In both standard impregnating resins, the sliding additive slightly increases the contact angle. In no case can it be assumed that this will influence the impregnating resin filling of cavities, ie the spaces between the wires, of the winding wire coils.

In FIG. 3 the corresponding results are shown, as reference sample again a wire enamel without sliding additive was taken, which is to be seen as "value 1" far left in the diagram. Here it is quite clear that the paraffin-coated surface is much harder to wet than that according to the invention with slip-additive-added wire enamel.

In FIG. 4 Finally, the results of shear tests of 2x2 mm quartz glass cubes on with sliding additive staggered wire enamel surfaces. The reference value herein refers to a paraffin-free surface, so the reference values should be slightly lower. At the in FIG. 4 The graphs shown show that the values are slightly reduced by the sliding-additive staggered coating in both investigated standard impregnating resins.

By the possibility presented here for the first time of the sliding friction coefficient reduction by adding amounts as low as 1% by weight slip additive for paint formulation in the manufacture of electric motors with winding wire coils, it is possible to add superficial lubricants such as waxes and / or paraffins to dispense with the winding of the wires.

In particular, so the sliding friction can be reduced to less than 20%, which equals the construction of higher-torque motors in the same space or of the same torque motors in a smaller space, in any case, an increase in power density in electric motors. In addition, the efficiency is increased by the invention, since higher wire fillings in the groove are possible, finally, a reduction of the asymmetry of windings and / or a reduction of the failure rate by wire damage during retraction due to high pull-in forces are possible.

The here presented for the first time isolated winding wire with lubricant additive can be used without changing the manufacturing processes, the lubricant or paraffin in the production can be omitted, reducing the pull-in forces increases the life of the corresponding devices and finally, the process times for producing the coils for the electric motors be shortened because the application and removal of the lubricant is eliminated and also higher winding speeds can be realized.

The invention is characterized in that the conventional system for the production of winding wire coils for electric motors can be practically adopted, but two or more process steps can be omitted, because a small amount of commercially available lubricant additive of the formulation at least for the uppermost layer of the insulating coating of the wires is added. The invention also relates to the use of a winding wire for producing a coil for an electric motor.

Claims (10)

Winding wire of an electrically conductive material, at least one layer of an insulating coating having , characterized in that a formulation for producing this layer of insulating coating is added at least one slip additive to reduce the coefficient of friction. A winding wire according to claim 1, wherein the insulating coating comprises at least one layer of an insulating varnish with or without lubricant additive additive. Winding wire according to one of the preceding Claims 1 or 2, in which the sliding additive is distributed inhomogeneously within the at least one layer of the insulating coating, in particular following a concentration gradient which reaches its maximum at the surface of the layer. Winding wire according to one of the preceding claims, wherein at least two layers of different paint material are provided. Winding wire according to one of the preceding claims, wherein as lubricating additive, an organically modified siloxane and / or an acrylate are added to the formulation. A winding wire according to any one of the preceding claims, wherein the slip additive is added in an amount of up to 2.5% by weight, based on the dry weight of the insulating paint material of the respective layer. A winding wire according to any one of the preceding claims, wherein the base of the insulating paint material comprises a polyester-imide and / or a polyamide-imide. A winding wire according to any preceding claim, wherein the formulation is for producing the insulating coating contains a solvent which is removed after drying and / or curing of the paint. A winding wire according to any one of the preceding claims, wherein the molecular weight of the slip additive is in the range of 500 g / mol to 25,000 g / mol. Use of a winding wire according to one of Claims 1 to 9 for producing a winding wire coil for an electric motor.

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