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WO2025247657A1 - Procédé de production d'une brosse électrique - Google Patents

Procédé de production d'une brosse électrique

Info

Publication number
WO2025247657A1
WO2025247657A1 PCT/EP2025/063385 EP2025063385W WO2025247657A1 WO 2025247657 A1 WO2025247657 A1 WO 2025247657A1 EP 2025063385 W EP2025063385 W EP 2025063385W WO 2025247657 A1 WO2025247657 A1 WO 2025247657A1
Authority
WO
WIPO (PCT)
Prior art keywords
graphene
composite material
electric brush
copper powder
copper
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/EP2025/063385
Other languages
English (en)
Inventor
Jian Qin
Su Zhao
Andreas FRIBERG
Srinidhi Sampath
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ABB Schweiz AG
Original Assignee
ABB Schweiz AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by ABB Schweiz AG filed Critical ABB Schweiz AG
Publication of WO2025247657A1 publication Critical patent/WO2025247657A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/04—Making non-ferrous alloys by powder metallurgy
    • C22C1/05—Mixtures of metal powder with non-metallic powder
    • C22C1/059—Making alloys comprising less than 5% by weight of dispersed reinforcing phases
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/12—Both compacting and sintering
    • B22F3/14—Both compacting and sintering simultaneously
    • B22F3/15—Hot isostatic pressing
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/04—Making non-ferrous alloys by powder metallurgy
    • C22C1/0425—Copper-based alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/10—Alloys containing non-metals
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C26/00—Alloys containing diamond or cubic or wurtzitic boron nitride, fullerenes or carbon nanotubes
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C32/00—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ
    • C22C32/0084—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ carbon or graphite as the main non-metallic constituent
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01R—ELECTRICALLY-CONDUCTIVE CONNECTIONS; STRUCTURAL ASSOCIATIONS OF A PLURALITY OF MUTUALLY-INSULATED ELECTRICAL CONNECTING ELEMENTS; COUPLING DEVICES; CURRENT COLLECTORS
    • H01R39/00—Rotary current collectors, distributors or interrupters
    • H01R39/02—Details for dynamo electric machines
    • H01R39/18—Contacts for co-operation with commutator or slip-ring, e.g. contact brush
    • H01R39/20—Contacts for co-operation with commutator or slip-ring, e.g. contact brush characterised by the material thereof
    • H01R39/22—Contacts for co-operation with commutator or slip-ring, e.g. contact brush characterised by the material thereof incorporating lubricating or polishing ingredient
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01R—ELECTRICALLY-CONDUCTIVE CONNECTIONS; STRUCTURAL ASSOCIATIONS OF A PLURALITY OF MUTUALLY-INSULATED ELECTRICAL CONNECTING ELEMENTS; COUPLING DEVICES; CURRENT COLLECTORS
    • H01R43/00—Apparatus or processes specially adapted for manufacturing, assembling, maintaining, or repairing of line connectors or current collectors or for joining electric conductors
    • H01R43/12—Manufacture of brushes

Definitions

  • the present disclosure generally relates to a composite material for an electric brush configured to transmit electric current between a stationary part and its moving counterpart.
  • Electric brushes are used for conducting current to or from the rotating shaft of electrical machines.
  • a rotating contacting component such as a slip ring or a commutator, is fixedly attached to the rotating shaft.
  • the rotating contacting component typically made of copper, bronze or stainless steel, is thus in contact with the stationary part via the electric brush, the latter being e.g. made of carbon and graphite or a metal-graphite blend.
  • the electric brush is pressed to the surface of the rotating contacting component by a spring to ensure good electrical contact.
  • the graphite in the electric brush has two functions. The first is to provide sufficient conductivity to transfer the needed current to or from the rotating contacting component, and the second is to act as a solid lubricant to provide low friction to keep the rotating contacting component intact.
  • a common practice to prolong the lifetime of electric brushes is to limit the contact pressure between the electric brush and rotating contacting component to a very low level, for example 20-25 kPa. Because the contact resistance is inversely proportional to the contact pressure, the electrical losses at the contact region are relatively high. Another limitation of the commercial graphite containing electrical brushes is that the frictional performance is sensitive to humidity which limits the application to less humid environments.
  • a general object of the present disclosure is to provide a method for producing an electric brush that solves or at least mitigates the problems of the prior art.
  • a method of producing an electric brush configured to transmit electric current between a stationary part and its moving counterpart, the method comprising: producing a composite material, including: a) mixing 85 to 99 wt% copper powder having a particle size of 10-500 pm with 0.5 to 5 wt% graphene to obtain a material mixture, the weight percentages being based on the composite material as a whole; and b) subjecting the material mixture to hot isostatic pressing at a temperature of between 650 and 950 °C and under a pressure of 1500 to 2000 bar for at least 1 hour to form the composite material.
  • the method further comprises: shaping the composite material as an electric brush.
  • the step of shaping the composite material as an electric brush may be performed in step b), or subsequent to step b).
  • the composite material exhibits advantageous tribological properties including low friction and high wear resistance in comparison with the known electric brushes such as e.g. commercial graphite containing electrical brushes.
  • the electric brush produced by the first aspect of the disclosure exhibits well-balanced properties related to conducting electricity effectively while also resisting deterioration from friction and minimizing the material loss due to wear. This contributes to a more reliable and efficient operation of the device in which the electric brush is used.
  • the electric brush produced by the first aspect of the present disclosure exhibits advantageous tribological properties in comparison with an electric brush produced by conventional sintering, or even spark plasma sintering.
  • electric brush produced by the first aspect of the present disclosure may exhibit a compact density over 90% relative to the theoretical density of pure copper, and a higher hardness compared to an electric brush produced by conventional sintering, or even spark plasma sintering. Due to the improved properties of the electric brush produced by the first aspect of the present disclosure, the contact pressure between the electric brush and the moving counterpart can be increased, leading to reduced contact resistance and voltage drop, and thereby also reduced electrical loss during use.
  • the amount of copper powder and graphene may be adapted such that the copper powder and the graphene in the material mixture amount to at least 92 wt%, or at least 95 wt%, or at least 97 wt%, or at least 99 wt% such as at least 99.5 wt% of the composite material. Any remaining part may e.g. stem from ceramic nanoparticles and/or one or more additives, as described later.
  • the copper powder is, or is comprised in, a copper-based compound powder (e.g.
  • any remaining part may stem from the ceramic nanoparticles and/or the one or more additives.
  • the material mixture comprises: 85 to 99 wt% of the copper powder and 0.5 to 5 wt% of the graphene, wherein the amount of copper powder is adapted such that the copper powder and the graphene amount to at least 92 wt%, or at least 95 wt%, or at least 97 wt%, or at least 99 wt% such as at least 99.5 wt% of the composite material.
  • the composite material thus provides low friction, good electrical conductivity and additionally less wear which leads to an extended lifetime of the electric brush. Reduced voltage drop and contact resistance also opens up the possibility to increase the current carrying capacity. Unlike the graphite containing commercial brushes which are sensitive to humidity change, the present composite material is more robust and maybe operated at a broad humidity and temperature range.
  • the electric brush produced by the first aspect of the present disclosure may consist of the composite material, i.e. the whole electric brush may be made out of the composite material.
  • the electric brush may comprise a support to which the composite material is attached, e.g. as a composite material layer.
  • the electric brush produced by the first aspect of the present disclosure comprises a contacting surface configured to be in contact with the moving counterpart during use. Therefore, the composite material may be referred to as a composite contacting material.
  • graphene is used collectively for carbon atoms in a 2D- honeycomb lattice in the form of mono-layer sheets, bi-layer sheets, few (3-5 layers) layer sheets, or nano-platelets having a thickness of at most 50 nm, e.g., within the range of 1 to 50 nm.
  • the graphene maybe referred to as 2D material.
  • the graphene may be pure graphene or reduced graphene oxide (rGO).
  • the graphene is preferably pure graphene. However, certain advantages for using rGO over pure graphene exists.
  • rGO refers to graphene oxide with an oxygen content below 4%, offering a partially restored sp 2 -bonded carbon network, thus fulfilling the same, or essentially the same functional role as pure graphene in the present composite material, e.g. in providing electrical conductivity and contributing to the lubricating effect.
  • the use of rGO is advantageous in that it retains key electrical and structural properties of graphene while being more economically favourable, thus enabling broader industrial applicability. Accordingly, in at least some embodiments, the term “graphene” as used herein encompasses rGO, unless otherwise explicitly specified.
  • Hot isostatic pressing typically comprises the following additional steps: placing the material mixture in a holder, e.g. a metal capsule, and placing the holder with the material mixture in a HIP furnace having an inert atmosphere (e.g. a He-atmosphere). Thereafter, the previously mentioned step b) is performed. Finally, the holder (e.g. the metal capsule) is machined away and the composite material is shaped as an electric brush (e.g. during the machining step). Step b) may e.g. be performed for at least 2 hours, such as e.g. between i and 3 hours. During hot isostatic pressing, the material mixture is subjected to the same pressure in all directions compared to a uniaxial sintering process.
  • a holder e.g. a metal capsule
  • the mixing in step a) includes dry-mixing the copper powder with the graphene.
  • the dispersity of the graphene in the material mixture may be improved, resulting in advantageous tribological properties of the composite material.
  • the drymixing can be performed in a high-speed shaker, for example, with adequate results.
  • Other mixing methods such as ball milling may also be employed.
  • step a) excludes ball milling.
  • the mixing in step a) is a mechanical mixing.
  • the content of graphene in the material mixture is in a range of 1 to 3 wt%. It has been found that this ranges of graphene provides an advantageous trade-off between cost, and lubrication and wear resistance properties, while accounting for the risk of graphene turning into graphite.
  • the weight percentage is based on the composite material as a whole.
  • the content of copper powder in the material mixture is between 90 and 99 wt%.
  • the composite material produced in step b) comprises: 90 to 99 wt% copper and 1 to 3 wt% of graphene. These ranges of copper and graphene provides an advantageous trade-off between cost, and lubrication and wear resistance properties.
  • the weight percentage is based on the composite material as a whole.
  • the content of the copper powder in the material mixture is between 92 or 95 and 99 wt%, the weight percentages being based on the composite material as a whole.
  • the particle size of the copper powder used in step a) is typically referring to the average particles size. That is, the copper powder used in step a) typically has a particle size of 10-500 pm. According to one embodiment the copper powder has a particle size of at least 15 pm, such as at least 30 pm, at least 50 pm, at least 100 pm, or at least 200 pm, and a particle size of at most 500 pm, such as at most 450 pm, at most 400 pm, at most 350 pm, or at most 300 pm.
  • the particle size of the copper powder maybe determined with quasi spherical morphology.
  • the particle size of the copper powder may be referred to as the grain size of the copper powder.
  • the average size of the copper powder may be determined using an electron microscope according to know methods.
  • the size of the copper powder may be determined by Transmission Electron Microscopy (TEM), Dynamic Light Scattering (DLS) or Scanning Electron Microscopy (SEM).
  • TEM Transmission Electron Microscopy
  • DLS Dynamic Light Scattering
  • SEM Scanning Electron Microscopy
  • the copper powder is in the form of bronze powder.
  • the bronze powder typically comprises at least 85 wt% copper.
  • the composite material produced in step b) may comprise, or consists of, the bronze and the graphene, and possibly one or more additives (as described later).
  • graphene is graphene nanoplatelets.
  • Graphene nanoplatelets is a low-cost material which suffices for the purpose of making the composite material. Typically, the graphene nanoplatelets are visible under electron microscope in the composite material.
  • the graphene is in the form of graphene particles each having a surface area in a range of 100-750 m 2 /g.
  • the graphene maybe graphene nanoplatelets each having a surface area in a range of 100-750 m 2 /g.
  • the graphene particles may be graphene nanopowder, or graphene flakes.
  • the surface area of the graphene particles may e.g. be measured using the Brunauer- Emmett-Teller (BET) method.
  • step a) involves mixing a first sub-set of the copper powder having a first average particle size with a second sub-set of the copper powder having a second average particle size, wherein the first and second average particle size differ from each other by at least 50 pm.
  • the density of the composite material of the electric brush may be increased.
  • the first and second average particle size differ from each other by at least 75 pm, or at least 100 pm, such as e.g. 150 pm.
  • the first average particle size is between 50 and 100 pm
  • the second average particle size is between 200 and 300 pm. That is, as the material mixture comprises copper powder of at least two sub-sets having distinctly different average particles sizes differing by at least 50 pm, the copper powder may be more densely packed.
  • the dispersity of the graphene in the material mixture may be improved, resulting in advantageous tribological properties of the composite material of the electric brush.
  • the size or average particle size of the copper powder may be determined by TEM, DLS or SEM.
  • the respective weight of the first sub-set of the copper powder and the second sub-set of the copper powder may e.g. be approximately the same, or differ by at most 10%, or at most 20% or at most 50% .
  • the first sub-set of the copper powder and the second sub-set of the copper powder may e.g. amount to at least 50 wt% of the total copper powder, or at least 75 wt% of the total copper powder, or at least 90 wt% of the total copper powder, or at least 99 wt% (or all of) the copper powder.
  • the composite material has a density of at least 85% of the theoretical density of pure copper.
  • the composite material of the electric brush has a density of at least 90% of the theoretical density of pure copper, or of at least 95% of the theoretical density of pure copper.
  • Samples of composite material produced by the method according to the first aspect of the disclosure have shown to have a compact density between 80 to 99% of the theoretical density of pure copper.
  • the density of the composite material may e.g. be determined according to the Archimedes’ principle using water as the immersion medium, in accordance with ISO 3369 (e.g. ISO 3369:2006) or equivalent recognized standards. The density maybe calculated based on the measured mass of the sample in air and its apparent mass when immersed in water. The measured density may then be compared to the theoretical density of pure copper (8.96 g/cm 3 ) to express the compactness as a relative percentage.
  • the composite material has a Vickers Hardness of at least 65 HV for a theoretical density of at least 90 % of pure copper.
  • the composite material of the electric brush may exhibit a higher hardness compared to a composite material produced by conventional sintering, an even an electric brush produced by spark plasma sintering.
  • the composite material has a Vickers Hardness of at least 70 HV, or at least 75 HV, or at least 80 HV for a theoretical density of at least 90 % of pure copper.
  • the contact resistance of the composite material is below 20 mohm for a contact load of 10 N, and/or is below 5 mohm for a contact load of 40 N, using the contact resistance method as defined herein.
  • the contact resistance of the composite material is below 20 mohm for a contact load of 10 N, and/or is below 5 mohm for a contact load of 40 N, using the contact resistance method as defined herein.
  • the contact resistance method is defined later in the text.
  • the contact resistance of the composite material is below 10 mohm for a contact load of 10 N, and/ or is below 3 mohm for a contact load of 40 N, using the contact resistance method as defined herein. According to one embodiment, the contact resistance of the composite material is below 1 mohm for a contact load of above 60 N, and/or below 0.4 mohm for a contact load of 100 N or above.
  • the method further comprises that step a) in addition to mixing the copper powder with the graphene, involves mixing 0.5 to 3 wt%, preferably 0.5 to 1 wt%, of ceramic nanoparticles having a size of between 5 to 100 nm and/or 0.1 to 5 wt% of one or more additives, with the copper powder and the graphene to obtain the material mixture.
  • the composite material produced in step b) may exhibit advantageous tribological properties in comparison with an electric brush comprising a copper- graphene composite material without the ceramic nanoparticles.
  • the advantageous tribological properties may include low friction and high wear resistance. Due to the low wear nature of the copper- graphene-ceramic nanoparticles composite material, the contact pressure between the electric brush and the moving counterpart may be further increased, leading to reduced contact resistance and voltage drop, and thereby also reduced electrical loss during use.
  • the mixing of the ceramic nanoparticles with the copper powder and the graphene is included in the previously described dry-mixing.
  • the material mixture comprises: 92 to 99 wt% copper powder; 0.5 to 5 wt% of graphene; 0.5 to 3 wt% of ceramic nanoparticles having a size of between 5 to 100 nm; wherein the weight percentages are based on the composite material as a whole.
  • the material mixture comprises: 85 to 99 wt% of the copper powder; 0.5 to 5 wt% of the graphene; and 0.5 to 3 wt% of the ceramic nanoparticles, wherein the amount of copper powder is adapted such that the copper powder, the graphene and the ceramic nanoparticles amount to at least 95 wt%, or at least 97 wt%, or at least 99 wt% such as at least 99.5 wt% of the composite material. Any remaining part may e.g. stem from the one or more additives.
  • the composite material produced in step b) comprises, or consists of, 92 to 99 wt% of a copper-based compound (such as bronze as previously described), 0.5 to 5 wt% of graphene; and optionally 0.5 to 3 wt% of ceramic nanoparticles having a size of between 5 to 100 nm and possibly one or more additives.
  • the copperbased compound may e.g. be bronze and comprise at least 85 wt% copper, or it may be pure copper (e.g. at least 99 wt% copper).
  • the copper-based compound may e.g. comprise between 5 to 12 wt% tin, and optionally small amounts of Al, P, Mn Ni, Fe Zn, Sb or S.
  • the composite material consists of the copper-based compound, the graphene, optionally the ceramic nanoparticles and possibly the one or more additives previously described.
  • the ceramic nanoparticles are selected from the group consisting of aluminium oxide, silicon oxide, yttrium oxide, silicon carbide and tungsten carbide. Such ceramic nanoparticles may improve the strength of the composite material at the same time showing excellent dry lubricating properties and good electrical conductivity.
  • the ceramic nanoparticle is aluminium oxide.
  • the ceramic nanoparticles are selected from the group consisting of aluminium oxide, silicon oxide, yttrium oxide and silicon carbide.
  • the size of the ceramic nanoparticles is referring to the average size, or average diameter of the nanoparticles.
  • the average size may e.g. be determined using an electron microscope according to know methods.
  • the size of the ceramic nanoparticles may be determined by Transmission Electron Microscopy (TEM), Dynamic Light Scattering (DLS) or Scanning Electron Microscopy (SEM).
  • TEM Transmission Electron Microscopy
  • DLS Dynamic Light Scattering
  • SEM Scanning Electron Microscopy
  • BET Brunauer- Emmett-Teller
  • the size determination of the ceramic nanoparticles is typically performed on dry particles.
  • the DLS is typically performed for the hydrodynamic particle size.
  • the ceramic nanoparticles have a size of between 5 to 50 nm.
  • the ceramic nanoparticle is aluminium oxide having an average particle size of below 50 nm, but above 5 nm.
  • the composite material comprises: a) 85 to 99 wt% copper; b) 1 to 3 wt% of graphene; c) 0.5 to 3 wt% of ceramic nanoparticles being aluminium oxide having a size of between 5 to 100 nm or between 5 to 50 nm; or a) 85 to 99 wt% copper; b) 0.5 to 5 wt% of graphene; c) 0.5 to 1 wt% of ceramic nanoparticles being aluminon oxide having a size of between 5 to 100 nm or between 5 to 50 nm.
  • the amount of the copper in the composite material maybe at least: 90, or 92, or 95, or 98.5 or 99 wt%.
  • the material mixture comprises: at least 92 wt% of the copper powder; 1 to 3 wt% or 0.5 to 5 wt% of the graphene; and 0.5 to 1 wt% or 0.5 to 3 wt% of the ceramic nanoparticles.
  • the material mixture may comprise 92 to 98.5 wt % of the copper powder; 1 to 3 wt% of the graphene; and 0.5 to 1 wt% of the ceramic nanoparticles.
  • the ceramic nanoparticles have a mean aspect ratio of between 1 and 3, preferably between 1 and 2. It has been found that such aspect ratio of the ceramic nanoparticles is preferable for the composite material. For example, the dispersity of the ceramic nanoparticles in the copper powder and graphene is improved, resulting in advantageous tribological properties of the composite material. Stated differently, a majority, e.g. at least 90 wt%, of the ceramic nanoparticles have an aspect ratio of between 1 and 3, preferably between 1 and 2.
  • the ceramic nanoparticles may be spherical, or near spherical, e.g. such that a majority, e.g.
  • the ceramic nanoparticles have an aspect ratio of between 1 and 1.5.
  • the ceramic nanoparticles are not formed as whiskers (e.g. 90 wt% of the ceramic nanoparticles do not have an aspect ratio of between 3 and 7).
  • the aspect ratio refers to the ratio of the longest to the shortest axis of a particle (or ratio of the longest edge by the shortest edge of the particle), and may e.g. be determined using an electron microscope according to know methods, such as measured by electron microscopy techniques such as SEM or TEM.
  • the one or more additives which may be included in the material mixture may include a stabilizer and/or a binder. According to one embodiment the one or more additives consist of the stabilizer and the binder.
  • additives as used herein may refer to materials added in minor amounts (such as 0.1 to 5 wt%) to facilitate processing or stability. Specifically, additives may include stabilizers to prevent oxidation during processing, and/ or binders to enhance sintering.
  • the composite material consists of the copper and the graphene, and at least one of the ceramic nanoparticles and the one or more additives.
  • the composite material may consist of a sintered copper, graphene, ceramic nanoparticles mixture including the one or more additives.
  • the composite material consists of, or consists essentially of, the copper (or bronze), the graphene, the ceramic nanoparticles selected from aluminium oxide, silicon oxide, yttrium oxide, or silicon carbide, and optionally one or more additives, such as a stabilizer and/or binder. For example, no other constituents are intentionally included in the composite material apart from trace impurities.
  • the mixing in step a) excludes wet-mixing the copper powder with the graphene.
  • the electric brush is free of graphite.
  • the electric brush is free of nickel and/or free of chromium.
  • the composite material is nickel-free and/or chromium-free and/or graphite-free.
  • the absence of graphite combined with HIP processing results in superior mechanical strength and/or contact resistance stability.
  • the method further comprises that step b) is the only sintering step performed for producing the composite material of the electric brush.
  • step b) is the only sintering step performed for producing the composite material of the electric brush.
  • an electric brush configured to transmit electric current between a stationary part and its moving counterpart, the electric brush being produced by the method of the first aspect of the disclosure.
  • an electric motor or generator comprising a stationary part and a moving counterpart, and an electric brush of the second aspect of the disclosure, wherein the electric brush is configured to transmit electric current between the stationary part and the moving counterpart.
  • the electric brush typically forms part of the stationary part of the motor or generator, and the moving counterpart may form part of a rotating shaft.
  • the motor or generator may e.g. be a wind turbine generator such as a doubly fed wind turbine generator, a slip ring modular motor, a (large) synchronous motor, and a non-magnet based brushed synchronous motor.
  • the motor or generator may e.g. be a stationary motor or generator, or may be used in moving applications, such as e.g. in electric vehicles (EVs).
  • EVs electric vehicles
  • the moving counterpart is a slip ring or a commutator.
  • Fig. 1 is a side view of an electric motor comprising an electric brush configured to transmit electric current between a stationary part of the motor and its moving counterpart according to one example;
  • Fig. 2 is a flowchart of a method of producing an electric brush according to one example
  • Fig. 3 is a graph showing contact resistance vs contact force for various samples of electric brushes
  • Fig. 4 is a graph showing normalized volume wear rate vs current for various samples of electric brushes
  • Fig. 5 is a graph showing Vickers hardness vs theoretical density for various samples of electric brushes.
  • Fig. 6 shows two SEM images of composite material produced using hot isostatic pressing according to one example.
  • Fig. 1 depicts an electric motor 1 comprising a stationary part io and a moving counterpart 20.
  • the moving counterpart 20 comprises a rotating shaft 22 and a plurality of slip rings 24 mounted in a support 26.
  • the support 26 is attached to the shaft 22.
  • the stationary part 10 comprises a plurality of associated electric brushes 12.
  • the electric brushes 12 are in Fig. 1 mounted to a holder 14, and are pushed against the slip rings 24 by means of a force member 16, such as one or more mechanical springs.
  • the force maybe higher than 25 kPa, such as 30 kPa or higher than 30 kPa, for example equal to or higher than 35 kPa or equal to or higher than 40 kPa, such as equal to or higher than 45 kPa.
  • the force maybe equal to or higher than 100 MPa, for example equal to or higher than 250 MPa.
  • each electric brush 12 is arranged in mechanical and electrical contact with a respective slip ring 24.
  • the electric brushes 12 are arranged stationarily and the slip rings 24 are rotated concurrently with rotation of the shaft 22.
  • the electric brushes 12 are pressed radially inwards towards its associated slip ring 24 by means of the force member 16.
  • the electric brushes 12 are configured to transmit electric current between the stationary part 10 and the moving counterpart 20 via the slip rings 24.
  • the electric brushes 12 are configured to transmit electric current from the stationary part 10 to the moving counterpart 20 via the slip rings 24.
  • the electric motor 1 maybe operated in reverse, and thus function as a generator.
  • the method generally comprises producing a composite material, which is shaped or formed as an electric brush.
  • step a), or a first step, S10 copper powder is mixed with graphene to obtain a material mixture.
  • a material mixture 85 or 90 to 99 wt% copper powder having a particle size of 10-500 pm is mixed with 0.5 to 5 wt% graphene to obtain the material mixture, the weight percentages being based on the composite material as a whole.
  • the mixing in the first step S10 is preferably dry-mixing, and preferably mechanical mixing.
  • the material mixture is achieved by vigorously mixing, e.g. using a high-speed shaker.
  • the shaking speed maybe 700 rpm and the mixing time may be 150 seconds.
  • the mixing time may vary depending on the amount of material mixed.
  • the mixing in the first step S10 may exclude wetmixing the copper powder with the graphene.
  • the average particles size of the copper powder maybe between 30 and 200 pm, such as between 40 or 50 pm and 100 or 150 pm.
  • the content of graphene in the material mixture is preferably in a range of 1 to 3 wt%.
  • the graphene which is a 2D material, maybe in the form of graphene particles each having a surface area in a range of 100-750 m 2 /g.
  • the graphene is preferably in the form of graphene nanoplates.
  • the first step Sio may comprise the sub-step S15 of mixing a first sub-set of the copper powder having a first average particle size with a second sub-set of the copper powder having a second average particle size, wherein the first and second average particle size differ from each other by at least 50 pm.
  • copper powder, and other components of the material mixture may be more densely packed.
  • the first step Sio additionally includes mixing 0.5 to 3 wt%, preferably 0.5 to 1 wt%, of ceramic nanoparticles having a size of between 5 to 100 nm and/or 0.1 to 5 wt% of one or more additives, with the copper powder and the graphene to obtain the material mixture.
  • the weight percentages are here based on the composite material as a whole.
  • the ceramic nanoparticles are preferably selected from the group consisting of aluminium oxide, silicon oxide, yttrium oxide, silicon carbide and tungsten carbide.
  • the ceramic nanoparticles may be defined by an aspect ratio of between 1 and 3, preferably between 1 and 2.
  • the ceramic nanoparticles may be spherical, or near spherical having an aspect ratio of between 1 and 1.5.
  • a step b), or a second step, S20 occurring subsequent to the first step Sio, the material mixture (with or without the ceramic nanoparticles and/ or the one or more additives) is subjected to hot isostatic pressing (HIP) at a temperature of between 650 and 950 °C and under a pressure of 1500 to 2000 bar for at least 1 hour to form the composite material.
  • HIP hot isostatic pressing
  • the material mixture is placed in a holder, typically a metal capsule, whereafter the holder with the material mixture is subjected to the hot isostatic pressing, typically for between 1 and 3 hours.
  • the sintering is typically performed in a HIP furnace with inert atmosphere (e.g. a He-atmosphere).
  • the holder e.g. the metal capsule
  • the sintering of the second step S20 is preferably the only sintering step performed to obtain the composite material or the electric brush.
  • the composite material may be shaped as an electric brush during the second step S20, or it may be shaped as an electric brush in a third step S30 after the second step S20.
  • the electric brush thus obtained is composed of the composite material obtained according to the method.
  • the composite material may consist of the copper and the graphene, and optionally at least one of the ceramic nanoparticles and the one or more additives.
  • each one of the electric brushes 12 may be produced by the method described with reference to Fig. 1.
  • each one of the electric brushes 12 may be made of a composite material comprising: a) 85 or 90 to 99 wt% copper; and b) 0.5 to 5 wt% of graphene, e.g. 1 to 3 wt% graphene, and/or c) 0.5 to 3 wt% of ceramic nanoparticles having a size of between 5 to 100 nm; and/or d) 0.1 to 5 wt% of one or more additives, wherein the weight percentages are based on the composite material as a whole, here being the electric brush 12 as a whole.
  • the composite material of each electric brush 12 is a sintered composite material which consists of the previously described material mixture.
  • the composite material of the electric brush 12 is, during use, arranged in contact with the moving counterpart 20 and the slip rings 24 as previously described.
  • the electric brush 12 is preferably free of nickel, chromium and/or graphite.
  • each sample correspond to the previously described electric brush.
  • the samples were prepared by mixing copper powder with graphene powder.
  • the graphene powder was graphene nanoplatelets, and the copper powder had an average particle size of 75 pm.
  • the mixing was dry-mixing.
  • a paint shaker model SK35 from Fast & Fluid was used.
  • the copper-graphene powder mixture was then sintered by hot isostatic pressing (Quintus Technologies, HIP QIH9 with graphite furnace) into a composite material to be used as an electric brush.
  • hot isostatic pressing Quintus Technologies, HIP QIH9 with graphite furnace
  • the copper-graphene powder mixture was placed in a holder, here a metal capsule (tube-shaped), whereafter the holder with the copper-graphene powder mixture was placed in a HIP furnace with inert atmosphere (He- atmosphere) and subjected to hot isostatic pressing (1800 bar) under elevated temperature (740 °C) for approximately 3 hours.
  • He- atmosphere inert atmosphere
  • hot isostatic pressing (1800 bar) under elevated temperature (740 °C) for approximately 3 hours.
  • the holder was machined away and the composite material shaped into an electric brush.
  • a first sample (IE1) was prepared by dry-mixing 99 wt% copper powder with 1 wt% graphene powder using hot isostatic pressing as previously described
  • a second sample (IE2) was prepared by dry-mixing 97 wt% copper powder with 3 wt% graphene powder using hot isostatic pressing as previously described.
  • the contact resistance vs contact force was evaluated for the first and second samples, together with a comparison with an electrographite brush (CEi) and a graphite-copper brush (CE2) not produced by hot isostatic pressing.
  • the contact resistance of IE1 is below 20 mohm for a contact load of 10 N, below 8 mohm for a contact load of 20 N, below 3 mohm for a contact load of 30 N, below 2 mohm for a contact load of 40 N, and even below 1 mohm for a contact load of 50 N.
  • the contact resistance of IE2 is below 10 mohm for a contact load of 10 N, below 4 mohm for a contact load of 20 N, below 3 mohm for a contact load of 30 N, and below 2 mohm for a contact load of 40 N and 50 N. This is vastly better performance as compared to CEi and CE2, for which the contact resistance is above 20 mohm for all contact loads 0-50 N. Thus, for both of IE1-IE2, the contact resistance is below 20 mohm for a contact load of 10 N, and is below 6 mohm for a contact load of 40 N. For higher contact forces, both IE1-IE2 exhibit a contact resistance of below 1 mohm for a contact load of above 60 N, and even below 0.4 mohm for a contact load of 100 N.
  • the normalized wear rate vs current was evaluated for IE2 of example 1, a comparative sample (CE3) prepared by dry-mixing 99 wt% copper powder with 1 wt% graphene powder using spark plasma sintering (SPS), and the graphite-copper brush (CE2) not produced by hot isostatic pressing of example 1.
  • a comparative sample CE3 prepared by dry-mixing 99 wt% copper powder with 1 wt% graphene powder using spark plasma sintering (SPS), and the graphite-copper brush (CE2) not produced by hot isostatic pressing of example 1.
  • SPS spark plasma sintering
  • CE2 graphite-copper brush
  • the normalized wear rate is below 1 mitf/km for all measured currents 0-30 A, as compared to CE3 exhibiting a normalized wear rate of over 1 mitf/km, and even over 10 mm3/km, for all measured currents except that of 6 A.
  • the wear rate is significantly reduced, by more than one order of magnitude (mm3/km), owing to the hot isostatic pressing.
  • the Vickers hardness was evaluated for the previously described samples IE1, IE2 and CEi, together with and an additional comparative sample (CE4) prepared by dry-mixing 97 wt% copper powder with 3 wt% graphene powder using spark plasma sintering (SPS).
  • the samples prepared by spark plasma sintering method both showed lower hardness values compared to their corresponding inventive samples prepared by hot isostatic pressing (IE1 and IE2) at the same graphene loading (1 wt% or 3 wt%).
  • the densities were at least 90 % of the theoretical density of pure copper.
  • Both IE2 and IE2 exhibit a Vickers hardness of above 65 HV, even above 70 HV or above 75 HV.
  • the Coefficient of Friction (COF) is below 0.3 as measured by a standard pin-on-disk tribology test (using stainless steel or bronze counterface).
  • FIG. 6 two SEM images are shown for a composite material produced using hot isostatic pressing as previously described and comprising 99 wt% copper and 1 wt% graphene (left) and 97 wt% copper and 3 wt% graphene.
  • the copper-graphene composite material produced through hot isostatic pressing retains the structure of graphene material and is almost free from aggregation.
  • the homogenous distribution of graphene flakes at the grain boundary revealed in Fig. 6 is believed to contribute to the increased strength of the composite material produced by hot isostatic pressing. That is, the increased strength could be partially due to grain-boundary strengthening of graphene sheets that are distributed around the grain boundary, serving as a barrier for dislocations.
  • the contact resistances were measured between a corresponding flat surface of the sample materials against an Ag contact pin having a half spherical tip with a diameter of 10 mm.
  • a microohmmeter MR 300 C-A from Schuetz-Messtechnik was used for the contact resistance measurements.
  • the method used was a 4-point probe measurement method. Certain contact forces were applied during the CR measurement with a spring load measured by a load cell from Nobel Elektronik.
  • the contact resistance was measured by the 4- point probe technique involving four equally spaced probes around the contact region.
  • a DC current was applied between the outer two probes and a voltmeter measured the voltage difference between the two inner probes.
  • the contact force between the contact surfaces (between flat surface of the sample and the half spherical tip of the Ag contact pin having a diameter of 10 mm) was manipulated with a screw connected to a spring load and monitored with force measuring transducer.
  • the sample was prepared in a test rig including a stationary part and a moving counterpart.
  • the sample was used an electric brush contacting the moving counterpart during rotation of the latter.
  • the applied power/ contact pressure of the sample relative to the moving counterpart was 6-8 N.
  • the current was varied from o to 26 A.
  • the normalized wear rate was measured by weight loss of the sample after a certain traveling distance of the moving counterpart (i.e. the product of circumference of the moving counterpart, the rpm and the time).
  • the wear rate of the electric brush depends on many parameters, such as contact pressure, electrical load, speed of the moving counterpart, state of the collector, ambient conditions etc.
  • the above method for the different samples and ensuring that the conditions and parameters are corresponding, comparison between the wear rates of the samples can be achieved.

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Abstract

L'invention concerne un procédé de production d'une brosse électrique conçue pour transmettre un courant électrique entre une partie fixe et sa contrepartie mobile, le procédé comprenant : la production d'un matériau composite, consistant à : a) mélanger entre 85 et 99 % en poids de poudre de cuivre ayant une taille de particule comprise entre 10 et 500 µm avec entre 0,5 et 5 % en poids de graphène pour obtenir un mélange de matériaux, les pourcentages en poids étant basés sur le matériau composite dans son ensemble ; et b) soumettre le mélange de matériaux à un pressage isostatique à chaud à une température comprise entre 650 et 950 °C et sous une pression comprise entre 1 500 et 2 000 bars pendant au moins 1 heure pour former le matériau composite. Le procédé consiste en outre à façonner le matériau composite en brosse électrique.
PCT/EP2025/063385 2024-05-29 2025-05-15 Procédé de production d'une brosse électrique Pending WO2025247657A1 (fr)

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EP24178906.4 2024-05-29

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5168620A (en) * 1990-11-15 1992-12-08 Westinghouse Electric Corp. Shunt attachment and method for interfacing current collection systems
CN108512006A (zh) * 2017-02-24 2018-09-07 上海新池能源科技有限公司 一种铜-石墨-石墨烯电刷及其制备方法
CN109004380A (zh) * 2018-07-18 2018-12-14 上海电机学院 一种动车组轴端接地装置用碳刷材料及其制备方法
CN111979438A (zh) * 2020-08-25 2020-11-24 西北有色金属研究院 一种改善石墨烯铜基复合材料界面结合强度的方法

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5168620A (en) * 1990-11-15 1992-12-08 Westinghouse Electric Corp. Shunt attachment and method for interfacing current collection systems
CN108512006A (zh) * 2017-02-24 2018-09-07 上海新池能源科技有限公司 一种铜-石墨-石墨烯电刷及其制备方法
CN109004380A (zh) * 2018-07-18 2018-12-14 上海电机学院 一种动车组轴端接地装置用碳刷材料及其制备方法
CN111979438A (zh) * 2020-08-25 2020-11-24 西北有色金属研究院 一种改善石墨烯铜基复合材料界面结合强度的方法

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