KR102506927B1 - Carbon brush and producing method for the same - Google Patents

Abstract

A carbon brush according to an embodiment of the present invention includes graphite and glass carbon, and the weight ratio of glass carbon increases from the center to the surface in the width direction of the cross section.
A method for manufacturing a carbon brush according to an embodiment of the present invention includes preparing a mixture including graphite and a liquid binder; Molding the mixture to produce a molded article; and heat-treating the molding.

Description

Carbon brush and its manufacturing method {CARBON BRUSH AND PRODUCING METHOD FOR THE SAME}

It relates to a carbon brush and a manufacturing method thereof. Specifically, it relates to a carbon brush with improved durability and a manufacturing method thereof.

A carbon brush is a device that supplies power to electric motors or generators. Since the carbon brush continuously causes contact friction during operation of the device, consumption of the carbon brush occurs due to friction and electrical consumption. As such, the consumption of the carbon brush has an absolute effect on the durability of the device.

In general, the carbon brush has a low friction coefficient and a low mechanical wear rate, an improved mechanical durability, and excellent arc generation suppression characteristics. In addition, as the consumption by the arc is reduced, the electrical lifetime is improved.

Currently used carbon brush materials can be largely classified into electrical graphite, graphite, metal graphite, and resin-bonded graphite. The electric graphitic carbon brush means that a brush formed by mixing materials such as graphite, coke, and binder is graphitized at a high temperature to improve electrical characteristics. Graphite means that raw materials composed of graphite powder, binder, and additives are heated and molded. The metal graphite brush means that it is manufactured by mixing graphite with an electrically conductive material such as copper, silver, or iron to improve electrical properties. Resin-bonded graphite means that the graphite powder is molded by bonding with a resin-based binder such as epoxy without a high-temperature carbonization process.

Metal graphite, electric graphite, and graphite brushes need to use a binder to form particles, and the binder is mainly composed of phenol, epoxy, amine-based resins, and materials such as PVA and PEG. After compression processing using a binder, the binder undergoes a carbonization process through heat treatment. At this time, the binder forms an amorphous carbon phase rather than a graphite phase, and since such a carbon phase has a high friction coefficient and almost no conductivity, the physical properties of the brush is the main cause of the drop in

Conventionally, attempts have been made to solve arc durability and conductivity through a multi-layered brush in which the concentration of metal graphite is different for each layer, or a structure in which the surface of the brush is coated with metal. However, this method requires the addition of a number of processes, and the process is complicated and inefficient. In addition, when applied as a brush used for a slip ring, there is a problem in that the advantage for durability is lost.

One embodiment of the present invention is to provide a carbon brush and a manufacturing method thereof. Specifically, it is to provide a carbon brush with reduced mechanical and electrical wear and a manufacturing method thereof.

A carbon brush according to an embodiment of the present invention includes graphite and glass carbon, and the weight ratio of glass carbon increases from the center to the surface in the width direction of the cross section.

The carbon brush includes, in the width direction of the cross section, a center portion from the center to 10% of the total width length and a surface portion from the surface to 10% of the total width length, and the center portion contains 10% by weight or less of glass carbon, The surface portion may include 30 wt % or more of glass carbon.

The carbon brush may further include an interposition portion between the center portion and the surface portion, and the interposition portion may include more than 10 wt % and less than 30 wt % of glass carbon.

It may further include 5 to 20% by weight of a catalytic metal.

The Shore hardness of the central portion may be 21 to 23, and the Shore hardness of the surface portion may be 26 to 30.

A method for manufacturing a carbon brush according to an embodiment of the present invention includes preparing a mixture including graphite and a liquid binder; Molding the mixture to produce a molded article; and heat-treating the molding.

The preparing of the mixture may include kneading graphite and a liquid binder to form a lumpy kneaded product; It may include; preparing a mixed powder by pulverizing the kneaded material.

In the step of preparing the mixture, a mixture may be prepared by mixing 90 to 99% by weight of graphite and 1 to 10% by weight of a liquid binder.

In the step of preparing the mixture, a solid binder may be further mixed, and 90 to 99% by weight of graphite, 0.5 to 5% by weight of a liquid binder, and 0.5 to 5% by weight of a solid binder may be mixed.

The liquid binder may include at least one of a phenol resin and polyacrylonitrile.

In the step of preparing the mixture, a catalyst metal may be further mixed, and 75 to 90% by weight of graphite, 0.5 to 5% by weight of a liquid binder, and 5 to 20% by weight of a catalyst metal may be mixed.

The step of preparing a molding by molding the mixture may be performed at a pressure of 30 t/cm ² to 50 t/cm ² and a temperature of 10 to 250°C.

The heat treatment of the molding may be performed at a temperature of 1000 to 2000 °C.

The heat treatment of the molding may be performed in an inert gas atmosphere.

The heat treatment of the molding may be performed in an atmosphere containing 0.1 to 10 vol% of hydrogen gas and 90 to 99.9 vol% of inert gas.

According to an embodiment of the present invention, the strength of the surface of the carbon brush is improved, and the wear of the central part occurs first, thereby stabilizing the contact surface with the commutator (or slip ring), and suppressing mechanical and electrical wear as a whole. , it is possible to provide a carbon brush with improved durability.

According to one embodiment of the present invention, it is possible to provide a method for manufacturing a carbon brush with improved durability.

1 is a view schematically showing a cross section of a carbon brush according to an embodiment of the present invention.
2 is a view schematically showing a cross section of a carbon brush according to an embodiment of the present invention.
3 is a diagram schematically showing a cross section of a rotary electric device to which a carbon brush according to an embodiment of the present invention is applied.
4 is a diagram schematically showing a cross section of a conventional rotary electric machine to which a carbon brush is applied.

Advantages and features of the present invention, and methods of achieving them, will become clear with reference to the detailed description of the following embodiments taken in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and can be implemented in various different forms, only these embodiments are intended to complete the disclosure of the present invention, and are common in the art to which the present invention belongs. It is provided to fully inform the knowledgeable person of the scope of the invention, and the invention is only defined by the scope of the claims. Like reference numbers designate like elements throughout the specification.

When a part is referred to as being “on” or “on” another part, it may be directly on or on the other part or may be followed by another part therebetween. In contrast, when a part is said to be “directly on” another part, there is no intervening part between them.

Thus, in some embodiments, well-known techniques are not described in detail in order to avoid obscuring the interpretation of the present invention. Unless otherwise defined, all terms (including technical and scientific terms) used in this specification may be used in a meaning commonly understood by those of ordinary skill in the art to which the present invention belongs. In the entire specification, when a certain part is said to "include" a certain component, it means that it may further include other components without excluding other components unless otherwise stated. In addition, singular forms also include plural forms unless specifically stated in the text.

1 schematically shows a cross section of a carbon brush 100 according to an embodiment of the present invention. The carbon brush 100 of FIG. 1 is merely for illustrating the present invention, and the present invention is not limited thereto.

As shown in FIG. 1, the carbon brush 100 according to an embodiment of the present invention includes graphite and glassy carbon, and in the width direction (x direction) of the cross section, from the center to the surface, the glassy The weight ratio of carbon is increased. In FIG. 1, the weight of glass carbon is expressed as the intensity of black. That is, from the center to the surface, the weight ratio of glass carbon increases, and the intensity of black color gradually increases.

Graphite can be natural graphite or synthetic graphite.

Glassy carbon is a carbon material obtained by heat-treating a thermosetting resin in an inert atmosphere. Glassy carbon is surrounded by graphite nanoribbons. Because of this, glassy carbon has been assumed to have similar properties to graphite. Recently, however, research results suggesting that the crystal structure of glassy carbon is the same as fullerene. Therefore, it can be said that it is difficult to say that it is a specific type of crystal structure. Glassy carbon has very unique properties different from ceramic materials as well as general carbon materials, such as superior thermal conductivity and electrical conductivity compared to general ceramic products, high elasticity compared to graphite, and similar mechanical properties to glass. is a material with Glassy carbon has a higher resistance value than graphite and is denser than graphite. In addition, since it is free from corrosion, corrosion of metal inclusions included in the brush can be suppressed. In addition, glassy carbon has a very high thermal conductivity, and thus has excellent heat dissipation characteristics.

In one embodiment of the present invention, the weight ratio of the glass carbon is increased from the center to the surface in the width direction of the cross section by using the properties of the glass carbon. Conversely, going from the center to the surface, the weight fraction of graphite decreases.

2 schematically shows a cross section of a carbon brush 100 according to an embodiment of the present invention.

As shown in FIG. 2, the carbon brush 100 has a center portion 10 from the center to 10% of the total width length and a surface portion from the surface to 10% of the total width length in the width direction (x direction) of the cross section. (30).

As described above, since the carbon brush 100 according to an embodiment of the present invention is configured such that the weight ratio of glass carbon increases from the center to the surface in the width direction of the cross section, the central portion 10 and the surface portion ( 30) have different weight ratios of glass carbon.

Specifically, the center part 10 contains 10% by weight or less of glass carbon, and the surface part 30 contains 30% by weight or more of glass carbon. Ingredients other than glassy carbon are graphite. That is, graphite is included as the remainder.

When the central portion 10 includes too much glassy carbon, the difference in hardness from the surface portion is relatively small, reducing the contact stabilization effect and causing excessive wear of the counterpart material. More specifically, the center portion 10 may include 0.1 to 8% by weight of glassy carbon.

When the surface portion 30 contains too little glassy carbon, the hardness and abrasion resistance of the surface portion 30 decrease, making it impossible to achieve the desired stability of the contact surface with the commutator. More specifically, the surface portion 10 may include 50 to 95 wt% of glass carbon.

The glassy carbon content of the central portion 10 and the surface portion 30 means the average content of the entire central portion 10 and the surface portion 30, and in detail, the center portion 10 and the surface portion 30 also have a center It is configured so that the weight ratio of glass carbon increases in the direction of the surface.

As shown in FIG. 2 , an intervening portion 20 is formed between the central portion 10 and the surface portion 30 . The intervening portion 20 may include glassy carbon in an amount greater than 10 wt % and less than 30 wt %. When the intervening portion 20 contains too little glassy carbon, mechanical strength is too low, which can be a problem. When the intervening portion 20 includes too much glassy carbon, the graphite content is relatively low, which may cause problems in terms of electrical characteristics and lubricity. The glassy carbon content of the intervening portion 20 means the average content of the entire intervening portion 20, and in detail, the weight ratio of the glassy carbon increases in the direction from the center to the surface within the intervening portion 20. It consists of More specifically, the intervening portion 20 may include 15 wt % to 25 wt % of glassy carbon.

As such, by varying the mechanical strength of the central part 10, the intervening part 20, and the surface part 30, wear of the central part 10, which has relatively low hardness, occurs preferentially, and the contact surface with the commutator (or slip ring) This is stabilized, and mechanical wear and electrical wear can be suppressed. Specifically, the Shore hardness of the central portion 10 may be 21 to 23, and the Shore hardness of the surface portion 30 may be 26 to 30. However, shore hardness is a value measured according to ISO868.

The carbon brush may further include a catalytic metal. The catalytic metal may be iron, copper, or oxides thereof. When the catalyst metal is further included, it may further include 1 to 10% by weight.

3 is a diagram schematically showing a cross section of a rotary electric machine to which a carbon brush 100 according to an embodiment of the present invention is applied. As shown in FIG. 3 , the rotary electric machine includes a carbon brush 100 , a commutator 110 and a brush holder 120 .

Since the description of the carbon brush 100 has been described above, duplicate descriptions will be omitted. The commutator 110 has a cylindrical shape with a circular cross section, and is disposed so as to contact the commutator 110 in the width direction of the carbon brush 100 . The brush holder 120 is configured in a cup shape, and the opening faces the commutator 110 and is disposed so as to contain the carbon brush 100.

As shown in FIG. 3, the carbon brush 100 moves in the direction of both arrows due to the occurrence of vibration or flow. At this time, since the hardness of the surface portion 30 of the carbon brush 100 is higher than that of the central portion 10, wear of the central portion 10 occurs preferentially. As a result, the contact surface with the commutator 110 is stabilized, and mechanical wear and electrical wear are suppressed.

4 is a diagram schematically showing a cross section of a conventional rotary electric machine to which a carbon brush is applied. Unlike one embodiment of the present invention, the content of the conventional carbon brush is constant throughout the carbon brush. As a result, when the carbon brush moves in the direction of both arrows due to vibration or flow, force is concentrated on the surface portion and mechanical wear is accelerated, or a gap between the carbon brush and the commutator is widened, causing electricity consumption by an arc.

As described above, according to one embodiment of the present invention, the strength of the surface portion 30 of the carbon brush 100 is improved, and the wear of the central portion 10 occurs relatively preferentially, thereby stabilizing the contact surface with the commutator 110 , Overall mechanical and electrical wear is suppressed, and durability is improved.

A method for manufacturing a carbon brush according to an embodiment of the present invention includes preparing a mixture including graphite and a liquid binder (S10); Molding the mixture to prepare a molding (S20); and heat-treating the molding (S30).

In one embodiment of the present invention, a liquid binder is used as a binder for a carbon brush. For this reason, when molding by applying pressure in step S20 or the like, the concentration of the liquid binder increases from the center of the brush to the surface due to flow and capillarity caused by the pressure. Thereafter, by heat treatment in step S30, the liquid binder is carbonized to be carbonized into glass carbon. In the carbon brush 100 manufactured through this, the weight ratio of glass carbon increases from the center to the surface. Since the specific configuration and effects of the weight ratio of glass carbon are the same as those described above, overlapping descriptions will be omitted. Hereinafter, each step is described in detail.

First, in step S10, a mixture including graphite and a liquid binder is prepared. Step (S10) is more specifically a step of kneading a liquid binder to form a kneaded product in a lumpy state; and preparing a mixed powder by pulverizing the kneaded material.

In step S10, a mixture may be prepared by mixing 90 to 99% by weight of graphite and 1 to 10% by weight of a liquid binder. When the liquid binder is excessively insufficient, a problem in that the content of glassy carbon in the surface portion 30 is lowered, and the binding properties of graphite may be deteriorated. If the amount of the liquid binder is too large, the amount of graphite is relatively reduced, and electrical properties of the carbon brush 100 may deteriorate.

In step S10, a mixture may be prepared by further mixing a solid binder (ie, a powder type binder) in addition to a liquid binder as a binder. When only the liquid binder is included, when strong pressure is applied in step S20, which will be described later, the concentration of the binder in the central portion 10 is lowered, so that a desired level of hardness may not be obtained. In this case, it can be solved by properly mixing the solid binder further. Specifically, 90 to 99% by weight of graphite, 0.5 to 5% by weight of a liquid binder, and 0.5 to 5% by weight of a solid binder may be mixed. If too much solid binder is included, a problem may occur in which a difference in hardness between the center and the surface is not properly generated. The solid binder may be a polymer resin or pitch.

The liquid binder may include at least one of a phenol resin and polyacrylonitrile. Since the phenolic resin and polyacrylonitrile contain a large number of aromatic benzene rings, conversion efficiency to glass carbon is excellent.

In the step of preparing the mixture, a catalyst metal may be further mixed, and 80 to 95% by weight of graphite, 0.5 to 5% by weight of a liquid binder, and 1 to 10% by weight of a catalyst metal may be mixed. Graphite, a liquid binder, a solid binder, and a catalyst metal may be mixed. In this case, 80 to 95% by weight of graphite, 0.5 to 5% by weight of a liquid binder, 0.5 to 5% by weight of a solid binder, and 1 to 10% by weight of a catalyst metal 10% by weight can be mixed.

In step S10, graphite and a liquid or solid binder as well as other additives may be further added. Specifically, metal powder, a solid lubricant or an abrasive may be further added.

Next, in step S20, a molded article is prepared by shaping the mixture.

In step (S20), it may be performed at a pressure of 30 t/cm ² to 50 t/cm ² and a temperature of 10 to 250°C. If the pressure is too low, a problem of poor molding may occur. If the pressure is too high, the concentration of the binder in the central portion 10 is low, and a desired level of hardness may not be obtained. In addition, if the temperature is too low, the flow of the binder is reduced, which may cause a springback problem. If the temperature is too high, carbonization of the binder proceeds, which may cause problems.

Next, in step S30, a carbon brush is manufactured by heat-treating the molding. In step S30, the binder in the molding is carbonized and converted into glass carbon. Since a concentration gradient in which the concentration of the binder increases from the center to the surface is formed due to the pressurization in step S20, the weight ratio of glass carbon in the finally manufactured carbon brush 100 increases from the center to the surface. .

Step (S30) may be performed at a temperature of 1000 to 2000 ℃. If the temperature is too low, the binder may not be smoothly converted into glass carbon. Higher temperatures do not improve the effect, only production costs increase with higher temperatures.

Step S30 may be performed in an inert gas atmosphere. At this time, if oxygen is included, combustion of carbon occurs. The inert gas means argon (Ar) or nitrogen (N ₂ ) gas.

Step S30 may be performed in an atmosphere containing hydrogen gas so that the binder is smoothly converted into glass carbon. Specifically, it may be performed in an atmosphere containing 0.1 to 10% by volume of hydrogen gas and 90 to 99.9% by volume of an inert gas. If too much hydrogen gas is included, the mechanical properties of the brush may deteriorate due to excessive erosion caused by the hydrogen gas.

Preferred examples and comparative examples of the present invention are described below. However, the following example is only a preferred embodiment of the present invention, but the present invention is not limited to the following example.

Example 1

99 g of graphite, 0.8 g of liquid phenol resin, and 0.2 g of water were kneaded at a temperature of 70 DEG C for 4 hours to obtain 99.7 g of a powdery kneaded product.

The powdery kneaded material was re-ground to prepare a mixed powder having a particle size of 10 to 50 μm.

The mixed powder was put into a molding machine and pressurized at 23° C. with a pressure of 30 t/cm ² to obtain a molded article having a size of 1 cm x 0.5 cm x 3 cm. A carbon brush was prepared by heat-treating the molding at 1800° C. for 12 hours in an inert atmosphere containing 3 vol% hydrogen.

Density, resistivity, flexural strength, shore hardness, durability consumption rate, and weight increase rate after being left at high temperature and high humidity were measured and are shown in Table 1 below.

Shore hardness was measured according to ISO868. The central part has a hardness of up to 1 mm from the center in the width direction, and the surface part has a hardness of up to 1 mm from the surface in the width direction.

The durability consumption rate was measured by attaching it to a 1kW capacity automotive motor, applying a load of 25Nm, repeating 1 second ON and 3 seconds OFF 200,000 times, and then measuring the consumed weight. In Comparative Example 1, the consumed weight was set as 100, and the relative value was displayed.

The weight increase rate after leaving at high temperature and high humidity was measured by measuring the increased weight after leaving for 24 hours at a temperature of 85 °C and a humidity of 85 °C.

Example 2

82 g of graphite, 17 g of copper powder, 0.8 g of a liquid phenol resin, and 0.2 g of water were kneaded at a temperature of 70° C. for 4 hours. During the kneading process, volatile substances were removed to obtain 99.7 g of a powdery kneaded product.

The powdery kneaded material was re-ground to prepare a mixed powder having a particle size of 10 to 50 μm.

The mixed powder was put into a molding machine and pressurized at 23° C. with a pressure of 30 t/cm ² to obtain a molded article having a size of 1 cm x 0.5 cm x 3 cm. A carbon brush was prepared by heat-treating the molding at 1800° C. for 12 hours in an inert atmosphere containing 3 vol% hydrogen.

Density, resistivity, flexural strength, shore hardness, durability consumption rate, and weight increase rate after being left at high temperature and high humidity were measured and are shown in Table 1 below.

Comparative Example 1

It was prepared in the same manner as in Example 1, except that the heat treatment temperature was carried out at 600 ° C.

Density, resistivity, flexural strength, shore hardness, durability consumption rate, and weight increase rate after being left at high temperature and high humidity were measured and are shown in Table 1 below.

Comparative Example 2

It was prepared in the same manner as in Example 2, except that the heat treatment temperature was carried out at 600 ° C.

Density, resistivity, bending strength, Shore hardness, and endurance test limits were measured and shown in Table 1 below.

Comparative Example 3

The layer surface of 82 g of graphite, 17 g of copper powder, 0.8 g of liquid phenolic resin, and 0.2 g of water is surrounded by a material with a high graphite content of 90 g of graphite, 9 g of copper, 0.8 g of liquid phenolic resin, and 0.2 g of water. It was prepared in the same manner as in Comparative Example 2 except that it was made.

Density, resistivity, bending strength, Shore hardness, and endurance test limits were measured and shown in Table 1 below.

Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Density (g/cm ³ ) 1.77 2.30 1.82 2.31 2.13 Resistivity (μΩ cm) 4275 720 10426 318 824 Bending strength (kgf/cm ² ) 273 215 141 135 127 Shore Hardness (HSc) center 23 24 20 23 23 surface area 27 28 20 23 20 durability consumption rate 37 52 100 121 88 Weight increase rate after leaving high temperature and high humidity (%) 0.7 1.2 1.9 1.7 1.7

As shown in Table 1, in the case of the embodiment in which the hardness of the center and the surface are different, it can be seen that the durability consumption rate is significantly reduced. On the other hand, Comparative Example 1 and Comparative Example 2, in which the hardness of the center and surface portions are the same, can be confirmed to increase the durability consumption rate. This is analyzed as the cause of accelerated mechanical wear due to pressure concentration occurring during motor operation. In addition, it can be confirmed that the examples have excellent mechanical properties and electrical properties compared to the comparative examples.

The present invention is not limited to the above embodiments, but can be manufactured in a variety of different forms, and those skilled in the art to which the present invention pertains may take other specific forms without changing the technical spirit or essential features of the present invention. It will be understood that it can be implemented as. Therefore, the embodiments described above should be understood as illustrative in all respects and not limiting.

100: carbon brush 10: center
20: intervening portion 30: surface portion
110: commutator 120: brush holder

Claims (15)

including graphite and glassy carbon;
A carbon brush in which the weight ratio of glass carbon increases from the center to the surface in the width direction of the cross section. According to claim 1,
The carbon brush includes a center portion extending from the center to 10% of the total width length and a surface portion extending from the surface to 10% of the total width length in the width direction of the cross section, and the center portion contains 10% by weight or less of glass carbon. And, the surface portion of the carbon brush contains 30% by weight or more of glassy carbon. According to claim 2,
The carbon brush of claim 1 , wherein the carbon brush further includes an intervening portion between the central portion and the surface portion, and wherein the interposing portion includes more than 10% by weight and less than 30% by weight of glass carbon. According to claim 2,
The shore hardness of the central portion is 21 to 23, and the shore hardness of the surface portion is 26 to 30 carbon brush. According to claim 1,
A carbon brush further comprising 5 to 20% by weight of a catalyst metal. A method for producing the carbon brush according to any one of claims 1 to 5,
preparing a mixture comprising graphite and a liquid binder;
molding the mixture to produce a molded article; and
Including the step of heat-treating the molding,
The step of molding the mixture to produce a molded product is performed at a pressure of 30 to 50 t / cm ² and a temperature of 10 to 250 ° C. Method for producing a carbon brush. According to claim 6,
Preparing the mixture
kneading graphite and a liquid binder to form a lumpy kneaded product; and
preparing a mixed powder by pulverizing the kneaded material;
Method for manufacturing a carbon brush comprising a. According to claim 6,
Preparing the mixture
A method for producing a carbon brush by mixing 90 to 99% by weight of graphite and 1 to 10% by weight of a liquid binder to prepare a mixture. According to claim 6,
Preparing the mixture
A method for producing a carbon brush in which a solid binder is further mixed, and 90 to 99% by weight of graphite, 0.5 to 5% by weight of a liquid binder, and 0.5 to 5% by weight of a solid binder are mixed. According to claim 6,
Preparing the mixture
A method for producing a carbon brush in which a catalyst metal is further mixed, and 75 to 90% by weight of graphite, 0.5 to 5% by weight of a liquid binder, and 5 to 20% by weight of a catalyst metal are mixed. According to claim 6,
The method of manufacturing a carbon brush, wherein the liquid binder includes at least one of a phenol resin and polyacrylonitrile. delete According to claim 6,
The step of heat-treating the molding is a method of manufacturing a carbon brush performed at a temperature of 1000 to 2000 ° C. According to claim 6,
The method of manufacturing a carbon brush in which the heat treatment of the molding is performed in an inert gas atmosphere. According to claim 6,
The heat treatment of the molding is performed in an atmosphere containing 0.1 to 10% by volume of hydrogen gas and 90 to 99.9% by volume of an inert gas.

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