DE602005003798T2 - Brushes for electric motors operated at a high temperature - Google Patents

Abstract

The unit has copper particles obtained from a mixture of electrolytic copper, atomized copper and crushed copper, and a mixture of natural graphite, organic binder e.g. bakelite resin, and molybdenum disulphide. The weight percent of the copper particles is comprised between 20 and 60 percentage. Additional metal e.g. zinc carbonate, is added with material in the form of metallic particles. Independent claims are also included for the following: (A) a fabricating method of a sliding contact unit (B) a fabricating method of an electric motor operating under low voltage.

Description

TECHNICAL PART

The The invention relates to a brush for electric motors, especially for those that serve devices on board a motor vehicle to drive (forced ventilation (independent, direct on the radiator attached fans) and other fans, power generators, auxiliary drives, etc.), for the an increased performance is sought.

STATE OF THE ART

Such electric motors are operated at low voltage and high current. Because of this high current intensity, the brushes with which these motors are equipped must ensure an electrical sliding contact at elevated temperature, which is typically above 100 ° C or even 200 ° C, and at the same time have a current density greater than 15 A / cm ² , The operating conditions of the electric motors incorporated in motor vehicles concerned by the invention are completely different from those of the starters.

The starters not affected by the invention are to work several hundred thousand times for a few milliseconds at a current density of over 500 A / cm ² . In the patent application US2003 / 0135993 brushes are described, which are designed for such operating conditions. Although they are exposed to very high stress, but are operated by the cumulative time very little and therefore only slightly heated in the short period in which they are operated.

In contrast, engines, such as those installed in the engine compartment of motor vehicles, always exposed to higher temperatures forced ventilation constantly, ie as long as the engine, in operation. They are operated at a lower current density, which is typically below 50 A / cm ² , but are subject to Joule effect heating and must be maintained at elevated temperatures throughout the life of the motor vehicle, ie for several thousand hours, typically over 2,000 hours above 100 ° C or even over 200 ° C.

by virtue of The ever more demanding operating conditions for the brushes need these adapted to withstand not only the increased stress, but also a higher one Have life.

Brushes for on board electric motors installed by motor vehicles (forced ventilators, electricity generators, Fans, etc.) generally consist of a mixture of Copper particles and graphoid particles.

The Copper particles can be of different origin: electrolytic copper (by electrolytic Deposition on a copper-derived copper, the anode of pure copper and the electrolyte typically from a mixture from copper sulfate, sulfuric acid and additives), atomized copper (molten and under the action of a strong jet of gas or liquid in the form of fine droplets sprayed copper) or crushed copper (ground, atomized copper in the form of fine Fins).

The Graphoids are made of different types of graphite - in general Natural graphites - and organic binders. The mixture thus formed is heat treated and subsequently ground to obtain the graphoid particles.

These base materials (copper and graphoid particles) are generally conductive abrasives, typically carbides, z. As silicon carbide or coke, and solid lubricants - typically molybdenum bisulfide (MOS ₂ ) is added. The type and mass fraction of each of these ingredients are determined depending on the desired application. The material resulting from this mixture generally has an electrical resistance which must not deteriorate over time so as not to affect the performance expected of the electric motor in question (see US-A-2003/0135993 ).

If however, an engine at elevated Temperatures is operated, for. B. in a forced ventilation, at the ambient temperature during its operation often over 100 ° C, can the temperature of the brush up to 200 ° C or above go up and an increase the electrical resistance of the material and increased oxidation of the material Copper can be determined. These probably related Cause phenomena accelerated wear of the brushes and a performance or speed loss of the engine.

PROBLEM

The Applicant thus wishes to develop a method by which to provide a material for the brushes of an electric motor having better wear resistance when the engine is operated at a temperature above 100 ° C and typically around 150 ° C, and at the same time the engine is given the opportunity to have a largely consistent performance throughout its life. The cumulative service life of the engines in question may be between a few hours (windows, Windscreen wiper) up to more than 2,000 hours (forced ventilation) are.

SCOPE OF THE INVENTION

A first object of the invention is a sliding contact part, which has an electric current with increased. Density - typically above 15 A / cm ² and below 50 A / cm ² - and consists of copper particles and a crushed mixture of graphite particles - preferably natural graphite particles - and organic binders derived graphoid particles, characterized in that for conducting said stream over at least 2,000 hours at a temperature above 100 ° C - typically at about 150 ° C - said contact portion contains copper particles whose mass fraction is between 20% and 60%, and particles in the form of a metal or a compound of this metal, an additional metal which belongs to the group consisting of the elements zinc, manganese and tin.

The sliding contact member capable of conducting an electric current is a current-conducting friction member such as an electric motor. B. the brush of an electric motor. The current density conducted via this contact part can be more than 15 A / cm ² . The intended application concerns the small motor-mounted electric motors for forced ventilators, ventilators, power generators, etc., which are operated with a current whose intensity - typically below 50 A / cm ² - less than that required to operate a starter - typically exceeds 100 A / cm ² - Amperage is. On the other hand, however, the average value of the density of the current supplied to the motors is steadily increasing in order to meet the ever higher performance requirements, which were previously in the range below one kilowatt. Such motors must be fed without interruption, which in turn is associated with an ever higher operating temperature.

Typically, the following conditions are set for testing the fatigue life of the material making up the brushes of electric motors: The brush must conduct a current at a density of 25 A / cm ² for 2000 hours at an ambient temperature in the engine around 150 ° C.

According to the invention, a relatively high mass fraction of copper is preferably selected, which is typically around 30% and between 20% and 60%, preferably between 20% and 30%. The material formed from the mixture has a low resistivity (resistance AG or "Against Grain", ie perpendicular to the longitudinal direction of the grain), but above 200 μΩcm (2 10 ^-6 Ωm), but typically below 10,000 μΩcm (10 ^-4 Ωm ), preferably below 5,000 μΩcm (5 10 ^-5 Ωm) after 2,000 hours of operation at 150 ° C

The copper particles may be formed by mixing particles of different origin (electrolytic copper, sputtered copper, crushed copper) whose bulk density is typically between 0.3 g / cm ³ and 4 g / cm ³ . Preference is given to using electrolytic copper whose density is between 0.6 g / cm ³ and 0.9 g / cm ³ , or a mixture of particles of electrolytic copper (65 to 100% by weight) and crushed copper (bulk density between 0.9 g / cm ³ and 1.2 g / cm ³ ) (0 to 35% by weight).

The Graphoid particles are preferably made of natural graphites and organic Binders, preferably phenolic, or based on of polyamides or polyethylene terephthalate. The solid lubricant, typically molybdenum sulphide, can be found in the composition of Be included in graphoids.

Of the Blend Copper + Graphoid will be a conductive abrasive, preferably a mixture of coke and silicon carbide and an additional metal accompanied that belongs to the group, made of metals and alloys based on zinc, manganese and tin exist.

This additional Metal becomes the material in the form of a compound of this metal attached, the is preferably unstable at the firing temperature of the mixture. Thus, zinc is preferably an oxide, a carbonate or a sulfate selected. The proportion by weight of said additional metal is preferably between 0.1% and 20%, and preferably between 0.5% and 10%. The Applicant noted that due to the presence of this additional metal by limiting the oxidation of the copper a deterioration the brush delayed can be.

• a) eine Mischung aus Kupferpartikeln, Graphoidpartikeln und Partikeln hergestellt wird, die ein zusätzliches Metall in Form von Metall oder einer Verbindung des besagten Metalls enthalten, das zu der aus den Elementen Zink, Mangan und Zinn gebildeten Gruppe gehört, wobei der Massenanteil der Kupferpartikel zwischen 20% und 60%, der Massenanteil der Graphoid-Partikel zwischen 45% und 75% und der Massenanteil des Zusatzmetalls bzw. der Verbindung desselben zwischen 0,5% und 20% betragen,
• b) die derart gemischten Partikel auf eine Einbrenntemperatur zwischen 250°C und 700°C, vorzugsweise zwischen 250°C und 450°C, typischerweise auf ungefähr 400°C gebracht werden, und zwar über eine Dauer zwischen 0,5 und 10 Stunden, typischerweise ungefähr 4 Stunden, in einer reduzierenden Atmosphäre, die zwischen 5% und 50% Wasserstoff enthält, wobei die Ergänzung durch Stickstoff oder ein Neutralgas erfolgt, typischerweise eine Mischung aus 40% Wasserstoff und 60% Stickstoff.

The invention further relates to a manufacturing method of a sliding contact member capable of conducting a high-density electric current, typically higher than 15 A / cm ² and lower than 50 A / cm ² , comprising copper particles and graphoid particles resulting from the crushing of a Blend of graphite particles and organic binders, characterized in that

• a) a mixture of copper particles, graphoid particles and particles is prepared containing an additional metal in the form of metal or a compound of said metal, which belongs to the group consisting of the elements zinc, manganese and tin, wherein the mass fraction of the copper particles between 20% and 60%, the mass fraction of graphoid particles between 45% and 75% and the mass fraction of the additive metal or the compound thereof between 0.5% and 20%,
• b) the particles thus mixed are brought to a stoving temperature between 250 ° C and 700 ° C, preferably between 250 ° C and 450 ° C, typically to about 400 ° C, over a period between 0.5 and 10 hours, typically about 4 hours, in a reducing atmosphere containing between 5% and 50% hydrogen supplemented by nitrogen or a neutral gas, typically a mixture of 40% hydrogen and 60% nitrogen.

The Graphoid in turn comes from the mixture of graphite, preferably Natural graphite and organic, preferably phenolic binder, typically a bakelite resin, as well as solid lubricants, typically Molybdenum bisulfide, wherein the whole preferably by stirring was mixed in a humid environment, then the solvent evaporated and the powder is ground and sieved, so that one gets a grain size that corresponds to a sieve passage, which is smaller than 630 microns and preferably between 90 and 355 μm is.

Of the Mixture may also be a conductive abrasive before firing be added, such as one of silicon carbide and coke, wherein the mass fraction is typically from 0.05% to 1%.

The thus achieved mixture is at a baking temperature between 250 ° C and 700 ° C, preferably between 250 ° C and 450 ° C, typically, with an accuracy of about 10 degrees, brought to about 400 ° C become, over one Duration between 0.5 and 10 hours, typically about 4 hours, in a reducing atmosphere, which contains between 5% and 50% hydrogen, the supplement being Nitrogen or a neutral gas occurs, typically a mixture of 40% hydrogen and 60% nitrogen.

The invention further relates to the use of a sliding contact part comprising copper particles and graphoid particles, wherein the mass fraction of the copper particles is between 20% and 60%, said contact part also containing particles containing an additional metal in the form of metal or a compound of the metal belonging to the group consisting of the elements zinc, manganese and tin, characterized in that said part is used as a brush for a DC electric motor of equipment in a motor vehicle such as a motor vehicle. A forced air fan, a window regulator, a windscreen wiper or power generator is used and operates at an electrical voltage which is 60 volts or less, said part conducting an electric current having a density higher than 15 A / cm ² and is lower than 50 A / cm ² , and is capable of conducting said current for more than 2,000 hours at a room temperature higher than 100 ° C, typically at about 150 ° C.

• a) das Ausführen eines Gestells, auf dem ein Induktor befestigt ist,
• b) das Ausführen eines Ankers, der mit einem Kollektor verbunden ist, der sich um eine Achse dreht, wobei der Anker Leitungsdrähte umfasst, die mit den Lamellen des besagten Kollektors verbunden sind,
• c) das Zusammensetzen des Induktors und des Ankers und
• d) das Befestigen von elektrischen Gleitkontakten auf einem Element, das mit dem Gestell verbunden ist, wobei die elektrischen Gleitkontakte imstande sind, mit einer Stromversorgungsquelle bei einer Spannung, die 60 Volt oder weniger beträgt, verbunden zu werden, und zur Herstellung der elektrischen Verbindung mit den Wicklungen des Ankers gegen die Oberfläche des Kollektors gedrückt werden, so dass sie während der Drehbewegung des Läufers nacheinander mit jeder der Lamellen des Kollektors in Berührung gesetzt werden, dadurch gekennzeichnet, dass zum Betreiben des besagten Motors über mindestens 2.000 Stunden bei einer höher als 100°C liegenden Raumtemperatur, typischerweise bei ungefähr 150°C, und mit einer Stromdichte, die zwischen 15 A/cm² und 50 A/cm² beträgt, elektrische Gleitkontakte verwendet werden, die Kupferpartikel, deren Massenanteil zwischen 20% und 60% beträgt, Graphoid- Partikel, die aus dem Zermahlen einer Mischung aus Graphitpartikeln und organischen Bindemitteln stammen, und ebenfalls Partikel eines Metalls in Form von Metall oder einer Verbindung des besagten Metalls enthalten, das zu der aus den Elementen Zink, Mangan und Zinn gebildeten Gruppe gehört.

The invention further relates to a manufacturing method of a collector motor, typically a DC motor, comprising:

• a) carrying out a rack on which an inductor is mounted,
• b) carrying out an armature connected to a collector rotating about an axis, said armature including lead wires connected to the fins of said collector,
• c) assembling the inductor and the armature and
• d) attaching electrical sliding contacts on a member connected to the frame, the sliding electrical contacts being capable of being connected to a power source at a voltage of 60 volts or less and for establishing electrical connection with the windings of the armature are pressed against the surface of the collector so that they are contacted successively with each of the fins of the collector during the rotation of the rotor, characterized in that for operating said motor for at least 2,000 hours at a higher than 100 ° C, typically at about 150 ° C, and with a current density of between 15 A / cm ² and 50 A / cm ² , electrical sliding contacts are used, the copper particles whose mass fraction is between 20% and 60%, Graphoid particles resulting from the grinding of a mixture of graphite particles and organic bin and particles of a metal in the form of metal or a compound of said metal belonging to the group formed by the elements zinc, manganese and tin.

The The following examples describe some nuances according to the invention and show the suitability of the brushes made with these shades, the To better withstand wear and oxidation.

PICTURES

In 1a is the micrograph of a brush made of a non-inventive material, which was used for 620 hours at 150 ° C: The copper particles show strong traces of oxidation. In 1b are the in the micrograph of 1a recognizable areas shown schematically.

In 2a is the microsection of a brush made of a material represented by the 1 similar, but according to the invention particles of an additional metal are added. In 2 B are the in the micrograph of 2a recognizable areas shown schematically. This brush was also used for 620 hours at 150 ° C: The copper particles show no significant traces of oxidation.

In 3 the results of the measurements are summarized in a common graph. It shows the increase of the specific resistance AG over time depending on the respective brush material.

EXAMPLES

Example 1: Oxidation Traces in Copper for Two Material Varieties: One without Zinc, the Other with 2% Zinc Carbonate ( 1 and 2 ).

• 34 Gewichtsprozent Kupfer (Mischung aus Elektrolytkupfer mit geringer Rohdichte und eingestampftem Kupfer)
• 2% Zinkcarbonat
• 2% Molybdenbisulfid MoS₂
• 0,4% Schleifmittel (Mischung aus Koks und Siliciumcarbid)
• 61,6% Graphoid.

For this purpose, a powder (grade X1) was prepared with the following constituents:

• 34% by weight of copper (mixture of low-density electrolytic copper and evaporated copper)
• 2% zinc carbonate
• 2% molybdenum bisulfide MoS ₂
• 0.4% abrasive (mixture of coke and silicon carbide)
• 61.6% graphoid.

The graphoid consisted of a premix of 86% natural graphite, 5% MoS ₂ and 9% bakelite resin. After mixing in a humid environment, the solvent was evaporated, and then the powder was ground and sieved to obtain a grain size between 90 and 355 μm.

To the Comparison with a non-inventive type of material was the Type of material X2 with the same constituents and in the same quantities in the mixture as stated above, but prepared without zinc carbonate. This type of material X2 corresponds to that of the applicant usually before this invention for engines offered by forced ventilation has been.

From the material types X1 and X2 brushes were then made, which were fired at 400 ° C under 40% H ₂ and 60% N ₂ .

Subsequently, long-term tests were carried out for 620 hours at 150 ° C and 25 A / cm ² on two brush series (material grade X1 and material grade X2). Representative micrographs were made of each of these two lots. They are in 1 and 2 shown. These are the areas occupied by the copper particles 10 and 10 ' with more or less strong traces of oxidation and the areas occupied by graphite particles consisting of graphite particles and binder 20 recognizable. The areas 10 ' in which the copper is not oxidized, are significantly lighter than the graphoid areas 20 while the areas 10 with oxidized copper only little contrast to the graphoid areas 20 exhibit. Thus, the difference between the areas of high oxidation of copper in the material grade X2 (areas 10 in 1a ) and the areas of low oxidation of the copper (areas 10 ' in 2a ) recognizable.

EXAMPLE 2 Measurement of Specific Resistivity of Brushes of Different Varieties of Material in the Hot Cabinet at 155 ° C and 25 A / cm ² ( 3 )

The Contains material grade Y1 48% copper and 0% zinc.

The Contains material type Y2 52% copper and 3% zinc carbonate.

The Contains material grade Y3 48% copper and 1% zinc carbonate.

Out Each type of material was measured on several specimens of the specific Resistance over longer Time made.

Out 3 For example, the influence of the zinc added in the form of zinc carbonate on the retention of resistivity during the life of the brush can be seen.

Of the specific resistance AG of the material type Y1, which contains no zinc increases Relatively fast over time: Exceeds 155 ° C after 500 hours of operation he value of 10,000 μΩmm.

ever after test piece the specific resistance of the material grade Y3, which contains 1% zinc carbonate, decreases less fast too. Here we are on the border of the frame The desired characteristics of the invention, because of individual specimens (eg at Y3.1) the resistivity increases too fast, so not guaranteed is that the specific resistance of this type of material after 2,000 Operating hours at 150 ° C does not exceed the value of 10,000 μΩmm.

Of the specific resistance of the material type Y2, the 3% zinc carbonate contains is in contrast much more time constant, so he also after 2,000 hours of use at 150 ° C the value of 10,000 μΩmm with certainty does not exceed.

Then there was also a matter prepared as Y4 containing 50% copper and 2% zinc carbonate, and made appropriate measurements on the brushes made from them. Their results also met expectations.

Claims (13)

A sliding contact member for conducting an electric current having a density comprised between 15 A / cm ² and 50 A / cm ² , comprising copper particles, graphoid particles derived from grinding a mixture of graphite particles, preferably natural graphite, and organic binders, characterized for passing said current for at least 2000 hours at a temperature higher than 100 ° C, typically at about 150 ° C, said contact part contains copper particles whose mass fraction is between 20% and 60% and also contains particles containing manganese in Form of metal or a compound. Sliding contact part according to claim 1, wherein the mass fraction the copper particle is between 20% and 30%. Sliding contact part according to claim 1 or 2, wherein the Copper particles Electrolytic copper particles or a mixture of electrolytic copper (100 to 65% by weight) and of steamed Copper (0 to 35 weight percent) are. Sliding contact part according to one of claims 1 to 3, wherein the graphoid particles of a mixture of natural graphites and organic binders, typically phenolic or on Basis of polyamides or polyethylene terephthalate, come. Sliding contact part according to one of claims 1 to 4, which also contains particles of a conductive abrasive, typically a mixture of coke and silicon carbide. Sliding contact part according to one of claims 1 to 5, wherein said manganese is in the composition in a mass fraction is present, which is between 0.5 and 20%, preferably between 1 and 10%. Gleitkontaktteil according to one of claims 1 to 6, characterized in that it is a brush for an electric motor, which is at a voltage of 60 volts or less, for at least 2000 hours at a higher than 100 ° C lying room temperature, typically at 150 ° C, with its specific electrical resistance AG remaining over 2000 hours at a temperature of 150 ° C at between 200 μΩcm and 10000 μΩcm (at between 2 10 ^-6 Ωm and 10 ^-4 Ωm). A method of manufacturing a sliding contact member capable of conducting a high density electrical current, typically greater than 15 A / cm ² and less than 50 A / cm ² , comprising copper particles and graphoid particles resulting from the grinding of a mixture of graphite particles and organic Binders, characterized in that: a) a mixture of copper particles, graphoid particles and particles is carried out containing manganese in the form of metal or a compound of said metal, wherein the mass fraction of the copper particles is between 20% and 60%, wherein the Mass fraction of graphoid particles is between 45% and 75%, and wherein the mass fraction of manganese or its compound is between 0.5% and 20%. b) the thus-mixed particles are brought to a baking temperature of 250 ° C to 450 ° C, typically to about 400 ° C, over a period of 0.5 to 10 hours, typically about 4 hours, in a reducing atmosphere containing between 5% and 50% hydrogen supplemented by nitrogen or a neutral gas, typically a mixture of 40% hydrogen and 60% nitrogen. Manufacturing method of a sliding contact after Claim 8, wherein said manganese is the material in the form of metal particles or in the form of a compound of said metal, preferably at the baking temperature of the mixture is unstable, added becomes. Manufacturing method of a sliding contact after Claim 8 or 9, wherein said graphoid of a mixture of graphites, preferably natural graphites, organic binders, preferably phenolic, typically a bakelite resin, and solid lubricants, typically molybdenum disulfide, emerges, the whole preferably mixed by stirring in a humid environment was, the solvent evaporated and the powder is ground and sieved, so that one receives a sieve passage, which is lower than 630 μm, preferably between 90 and 355 μm. Manufacturing method of a sliding contact after one of the claims 8 to 10, wherein the mixture prior to baking a conductive abrasive is added, such as one of silicon carbide and coke, wherein the mass fraction is typically from 0.05% to 1%. A method of manufacturing a collector motor, typically a DC motor, comprising: a) carrying out a rack on which an inductor is mounted, b) carrying out an armature connected to a collector Tor, which rotates about an axis, wherein the armature comprises lead wires which are connected to the fins of said collector, c) the assembly of the inductor and the armature and d) the fixing of electrical sliding contacts on a member which with connected to the frame, wherein the sliding electrical contacts are capable of being connected to a power supply source at a voltage of 60 volts or less and being kept pressed against the surface of the collector so as to be engaged during the rotation of the rotor being sequentially contacted with each of the fins of the collector, characterized in that for operating said motor for at least 2000 hours at a room temperature higher than 100 ° C, typically at about 150 ° C, and at a current density of between 15 A / cm ² and 50 A / cm ² , electrical sliding contacts are used, the copper particles l, whose mass fraction is between 20% and 60%, graphoid particles derived from grinding a mixture of graphite particles and organic binders, and also containing particles containing manganese in the form of metal or a compound. Use of a sliding contact part comprising copper particles and graphoid particles, wherein the mass fraction of the copper particles is between 20% and 60%, said contact part also containing particles containing an additional metal in the form of metal or a compound of the metal which is the manganese characterized in that said part is used as a brush for a DC electric motor operating at an electrical voltage of 60 volts or less, said part conducting an electric current with a density higher than 15 A / cm ² and less than 50 A / cm ² , and is capable of conducting said current for more than 2000 hours at a temperature higher than 100 ° C, typically at about 150 ° C.