Metallic graphite brush

Abstract

By making the porosity of the opposing surface and the sliding surface different, it is possible to improve the ride comfort and ensure stability of friction and wear, thereby providing a long-lasting metal graphite brush. [Solution] The metal graphite brush 1 has a sliding surface 2 that contacts the commutator and an opposing surface 3 that faces the sliding surface, and contains graphite and metal powder, and is characterized in that the porosity of the region including the opposing surface is higher than the porosity of the region including the sliding surface.

Description

Technical Field

[0001] The present invention relates to a metallic graphite brush used in electric machines such as electric motors and generators, and more particularly to a metallic graphite brush having excellent riding comfort and stability of friction and wear.

Background Art

[0002] Since a metallic graphite brush is a member having a function of supplying electric current from a stationary part to a rotating part of a rotating electric machine by sliding contact, it is required to have conductivity, slidability, and wear resistance. As shown in Patent Document 1, this metallic graphite brush is manufactured by mixing metal particles for ensuring conductivity, graphite particles for ensuring slidability and wear resistance, and a binder for binding the metal particles and the graphite particles, followed by molding and firing.

[0003] By the way, since the metallic graphite brush as described above has a large elastic modulus, under high-speed rotation of a rotating electric machine, due to the influence of the unevenness of the rotating part or the vibration of the rotating electric machine itself, the metallic graphite brush jumps, and there is a problem that sparks are generated between the commutator and the brush contact part, and the brush wear increases. The sparks generated at the commutator and the brush contact part are affected by the riding comfort of the brush. Generally, in order to improve the riding comfort, it is effective to reduce the elastic modulus.

[0004] In Patent Document 2, it is proposed to make the metallic graphite brush porous in order to reduce the elastic modulus and improve the riding comfort. Specifically, a metallic graphite brush has been proposed in which the pore volume of pores having a pore diameter of 5 to 300 μm occupies 20% to 70% of the total pore volume in the measurement of the pore size distribution by a mercury porosimeter, and these pores of 5 to 300 μm are dispersed in the brush structure.

[0005] However, reducing the elastic modulus lowers the hardness of the metal graphite brush, leading to increased wear of the metal graphite brush during rotational sliding. This increased wear of the metal graphite brush causes it to wear down, resulting in a thicker adhesion film on the commutator, which tends to stick to the brush and prevent the formation of a uniform adhesion film, leading to the generation of sparks.

[0006] To address these issues, the present inventors have proposed in Patent Document 3 a metal graphite brush containing graphite and metal powder, wherein the metal graphite brush has elongated pores on at least the sliding surface, and the open porosity is 15% to 40%. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 2775902 [Patent Document 2] Japanese Patent Application Publication No. 2-197238 [Patent Document 3] Japanese Patent Publication No. 2024-89637 [Disclosure of the Invention] [Problems that the invention aims to solve]

[0008] Incidentally, the metal graphite brush described in Patent Document 3 can form a uniform adhesive film while maintaining a low elastic modulus, thereby ensuring improved seating performance and stability against frictional wear, and resulting in a long-lasting metal graphite brush. However, in the metal graphite brush described in Patent Document 3, at least elongated pores are present on the sliding surface, and the open porosity of these pores is formed to be between 15% and 40%. These open pores are formed uniformly, and the metal graphite brush as a whole has a predetermined porosity (the pores are formed as closed pores inside the brush, and become open pores when they appear on the sliding surface, hence the term porosity. In other words, there are no parts of the brush with different porosities). Therefore, the elastic modulus of the metal graphite brush as a whole also has a predetermined elastic modulus (there are no parts with different elastic moduli). As a result, this metal graphite brush had the problem that when the brush vibration reached its natural frequency, it would resonate, worsening the ride quality.

[0009] To solve this problem, the inventors of the present invention diligently researched how to improve riding comfort by creating areas with different elastic moduli in the metal graphite brush by making the porosity of the opposing surface side and the sliding surface side different, thereby dispersing the natural vibrations, and came up with the present invention.

[0010] This invention was made to solve the above problems, and by making the porosity of the opposing surface and the sliding surface different, it is possible to ensure improved seating performance and stability of friction and wear, and to provide a long-life metal graphite brush. [Means for solving the problem]

[0011] The metal graphite brush according to the present invention, which was made to solve the above-mentioned problems, has a sliding surface that contacts a commutator and an opposing surface that faces the sliding surface, contains graphite and metal powder, and has pores formed on it, characterized in that the porosity of the region including the opposing surface is higher than the porosity of the region including the sliding surface. This configuration ensures improved rideability and stable friction and wear, resulting in a long-lasting metal graphite brush.

[0012] Here, it is desirable that the open porosity of the opposing surface is 40% or less, and that the open porosity of the opposing surface is higher than that of the sliding surface.

[0013] Here, it is desirable that the open porosity of the opposing surface is 1.3 times or more and 1.6 times or less than the open porosity of the sliding surface.

[0014] In addition, the method for manufacturing a metal graphite brush according to the present invention, which has been made to solve the above problem, is a method for manufacturing an electric brush of the metal graphite brush. It includes a step of filling at least a raw material powder composed of graphite and metal powder into a stepped mold in which the outer shape on the opposing surface side facing the sliding surface is formed larger than the outer shape on the sliding surface side, and press-molding.

[0015] Thus, by press-molding at least a raw material powder composed of graphite and metal powder using a stepped mold in which the outer shape on the opposing surface side facing the sliding surface is formed larger than the outer shape on the sliding surface side, a metal graphite brush having different open pore rates between the opposing surface and the sliding surface can be obtained.

Advantages of the Invention

[0016] According to the present invention, improvement in riding comfort and stability of friction and wear can be ensured, and a long-life metal graphite brush can be obtained.

Brief Description of the Drawings

[0017] [Figure 1] FIG. 1 is a schematic perspective view showing an embodiment of a metal graphite brush according to the present invention. [Figure 2] FIG. 2 is a schematic cross-sectional view showing a state in which an adhesion film formed by open pores of a metal graphite brush according to the present invention on the surface of a commutator is peeled off. [Figure 3] FIG. 3 is a process diagram showing a process for manufacturing an embodiment of a metal graphite brush according to the present invention. [Figure 4] FIG. 4 is a diagram showing an example of a molding process of a metal graphite brush according to the present invention. [Figure 5] FIG. 5 is a diagram showing another example of a molding process of a metal graphite brush according to the present invention.

Modes for Carrying Out the Invention

[0018] Embodiments of a metal graphite brush and a method for manufacturing a metal graphite brush according to the present invention will be described. These embodiments are examples of the present invention and the present invention is not limited to these embodiments.

[0019] (Metallic graphite brush) The metal graphite brush according to the present invention is a metal graphite brush 1 that contains graphite and metal powder and has pores formed thereon, and as shown in Figure 1, has a sliding surface 2 that contacts a commutator and an opposing surface 3 that faces the sliding surface 2. In this metal graphite brush 1, the open porosity of the opposing surface 3 is higher than that of the sliding surface 2. The open pores are closed pores inside the metal graphite brush 1, and become open pores when they appear on the sliding surface. Therefore, the fact that the open porosity of the opposing surface 3 and the open porosity of the sliding surface 2 are different means that the porosity of the opposing surface and the porosity of the sliding surface are different, and that there are parts of the metal graphite brush with different porosity. Because there are areas with different porosity in a metal graphite brush, there are also areas with different elastic moduli in the metal graphite brush. As a result, the natural vibrations of the metal graphite brush are dispersed, and even when the vibration of the metal graphite brush reaches its natural vibration level, it does not become a large vibration, thus suppressing deterioration of ride comfort.

[0020] Furthermore, it is preferable that the open porosity of the opposing surface 3 is 40% or less, and that the open porosity of the opposing surface 3 is higher than that of the sliding surface 2. That is, the open porosity of the sliding surface 2 is lower than that of the opposing surface 3, and is preferably 40% or less. In this way, because the open porosity of the sliding surface 2 is 40% or less, the amount of wear of the metal graphite brush during rotational sliding wear is suppressed.

[0021] Preferably, the open porosity of the opposing surface 3 is formed to be 1.3 times or more and 1.6 times or less than the open porosity of the sliding surface 2. By having an open porosity of the opposing surface 3 that is 1.3 to 1.6 times that of the sliding surface 2, the rideability can be improved by dispersing the natural frequencies of an integrated electric brush having different elastic moduli.

[0022] Furthermore, this metal graphite brush 1 is divided into a region 1A including the sliding surface 2 and a region 1B including the opposing surface 3. The length X of region 1A and the length Y of region 1B of this metal graphite brush 1 are formed in a ratio of X:Y = 7-8:3-2. In this way, the natural frequencies can be dispersed by having the ratio X:Y = 7-8:3-2.

[0023] Furthermore, the metal graphite brush 1 according to the present invention is characterized in that the open porosity (porosity) of region 1B including the opposing surface 3 is set to 40% or less, and the open porosity (porosity) of region 1B including the opposing surface 3 is higher than the porosity of region 1A including the sliding surface 2. Thus, in the metal graphite brush 1 according to the present invention, the open porosity (porosity) of the region 1B on the opposing surface 3 side and the open porosity (porosity) of the region 1A on the sliding surface side are different, and this metal graphite brush 1 has parts with different open porosity (porosity).

[0024] Due to the presence of these areas with different open porosity (porosity), the elastic modulus of region 1A and region 1B of the metal graphite brush 1 are different. As a result, compared to the case where the entire metal graphite brush 1 has a single specific elastic modulus, region 1A and region 1B each have specific elastic moduli. Therefore, the natural vibrations are dispersed, and even when the vibration of the metal graphite brush 1 reaches its natural vibration, it does not become a large vibration, and the deterioration of seating stability is suppressed.

[0025] Furthermore, as described above, the open porosity (porosity) of region 1B including the opposing surface 3 is set to 40% or less, and since the open porosity (porosity) of region 1B including the opposing surface 3 is higher than the porosity of region 1A including the sliding surface 2, the porosity of the sliding surface 2 is also set to 40% or less. In addition, it is preferable that the open porosity (porosity) of this sliding surface 2 be 12% or more. Here, the sliding surface 2 of the metal graphite brush 1 refers to the surface of the brush that contacts the commutator, and also includes the surface that comes into contact with the commutator and is newly exposed due to wear.

[0026] As shown in Figure 2, when the commutator 5 and the metal graphite brush 1 slide relative to each other, the edges 4a of the pores 4 in the sliding direction can be brought into contact with the adhesion film 6 formed on the commutator surface, and the adhesion film 6 can be efficiently peeled off by these edges 4a. The edges 4a of these pores 4 actively peel off the adhering film 6, promoting the formation of a new film and enabling stable sliding wear characteristics.

[0027] Furthermore, the pores 4 on the sliding surface may be elliptical or rectangular in shape when viewed from above. Note that this elliptical shape includes not only geometric ellipses but also oval shapes that are generally rounded, and the shape may have defects or imperfections. Similarly, the rectangular shape includes not only geometric rectangles but also elongated rectangles where the vertical and horizontal directions are not straight lines, and the shape may have defects or imperfections.

[0028] Preferably, closed pores are formed inside the metal graphite brush 1, although these are not shown in the figure. That is, when the sliding surface of the metal graphite brush wears down, the pores are exposed (developed) from the inside. The porosity of the closed air inside this metal graphite brush 1 is also formed to be between 12% and 40%. Therefore, since the pores that are exposed (emerge) from inside the brush are also pores, they can come into wider contact with the adhering film compared to circular pores, and the adhering film can be efficiently peeled off.

[0029] As described above, the open porosity of the pores formed on the sliding surface of the metal graphite brush is preferably 12% to 40%. By having an open porosity of 12% to 40% of the pores formed on the sliding surface, wear due to deterioration of the brush's mechanical strength is not significantly worsened, and sparks can be suppressed. Furthermore, even if the pores inside the brush are exposed due to wear, it is preferable that the open porosity ratio be between 12% and 40%.

[0030] As mentioned above, it is desirable that the open porosity of the pores formed on the opposing surface 3 of the metal graphite brush 1 be 40% or less. By having an open porosity of 40% or less of the pores formed on the opposing surface 3, the mechanical strength of the brush will not deteriorate. Furthermore, the porosity formed on the opposing surface 3 of the metal graphite brush is called the open porosity of the opposing surface.

[0031] Furthermore, the density of the metal graphite brush having the pores described above is 2.44 g / cm³. 3 ~3.13 g / cm³ 3 It is desirable that this be the case. Here, the density of region 1B including the opposing surface 3 is different from the density of region 1A including the sliding surface 2, and the density of region 1A including the sliding surface 2 is formed to be greater than the density of region 1B including the opposing surface 3. In other words, the porosity of region 1B, which includes the opposing surface 3, increases, and as a result of pores being formed in the material, the density of region 1B, which includes the opposing surface, decreases.

[0032] Furthermore, the elastic modulus of the metal graphite brush having the aforementioned pores is preferably 3 to 29 GPa. Here, the elastic modulus of region 1B, which includes the opposing surface 3, is different from the elastic modulus of region 1A, which includes the sliding surface 2, and the elastic modulus of region 1A, which includes the sliding surface 2, is formed to be greater than the elastic modulus of region 1B, which includes the opposing surface. In other words, the porosity of region 1B including the opposing surface 3 increases, and the elastic modulus of region 1B including the opposing surface 3 decreases.

[0033] Incidentally, the metal powder used in this metal graphite brush can include, for example, copper, silver, aluminum, tin, lead, manganese, iron, and nickel, but copper and silver are particularly preferred. When copper or silver is used, its excellent conductivity can be taken advantage of. Alternatively, electrolytic copper powder may be used because it has excellent conductivity as a metal powder and its resistivity and strength can be easily adjusted. Furthermore, the electrolytic copper powder used has a particle size of 40 to 50 μm (or 300 mesh pass).

[0034] Furthermore, examples of graphite (graphite powder) used in this metal graphite brush include natural graphite powder such as flake graphite and clay graphite, and artificial graphite such as carbon black and coke powder. However, it is particularly preferable to use natural graphite powder or deashed graphite powder from which the "ash" component contained as an impurity in natural graphite has been removed. When natural graphite powder is used, it has superior lubricity compared to artificial graphite, which can improve sliding properties and contribute to extending the lifespan of the metallic graphite brush.

[0035] (Method of manufacturing a metallic graphite brush) To manufacture this metal graphite brush, as shown in Figure 3, graphite powder is mixed with a binder, dried, crushed, and granulated (S1-S4). Preferably, the graphite powder has a particle size of 20 μm to 1000 μm (or 15 mesh pass), and more preferably, a particle size of 50 μm to 300 μm is used. By having the particle size of the graphite powder within the above range, stable brush strength and resistivity physical properties can be obtained.

[0036] The amount of graphite powder added is 20-80% by weight. This amount allows for a balance between good sliding properties due to the graphite and brush resistance. The amount added here is a percentage of the total brush weight.

[0037] Furthermore, it is desirable to use thermosetting resins such as phenolic resins and epoxy resins, or thermoplastic resins such as PVA (polyvinyl alcohol), as binders added to the aforementioned graphite powder. These binders are dissolved in alcohol and added to the graphite powder. Furthermore, the amount of binder added should be such that sufficient bonding strength can be obtained by heat treatment after molding. Preferably, the amount of binder added is 1 to 30% by weight relative to the weight of the graphite powder. Then, a binder (phenolic resin or polyvinyl alcohol (PVA)) was added to the specified graphite powder and kneaded (S2).

[0038] The kneaded mixture is then dried (S3), crushed in a pulverizer, and sieved to obtain the desired granulated powder (S4). The particle size of the granulated powder is preferably 20 μm to 1000 μm (or 15 mesh pass), and more preferably 50 μm to 300 μm. Furthermore, metal powder is added to the granulated powder and mixed in a mixer to obtain a mixed powder (S5, S6). The amount of metal powder added is preferably 20 to 80% by weight relative to the total weight of the granulated powder and the metal powder.

[0039] Then, as described above, a binder is added to the graphite powder and granulated to obtain graphite granulated powder having a predetermined particle size, and electrolytic copper powder is added as a metal powder (S5) and mixed (S6). Furthermore, when adding electrolytic copper powder, a solid lubricant may also be added. As a solid lubricant, one or more of the following may be used: molybdenum disulfide (MoS2), tungsten disulfide (WS2), or boron nitride (BN), due to their excellent lubricity at high temperatures.

[0040] Furthermore, the mixed powder was molded using a uniaxial press to produce a brush molded body. As shown in Figure 4(a), stepped molds M1 and M2 with different sizes for regions 1A and 1B were used. Then, the mixed powder P is filled into the mold, and the molds M1 and M2 are raised and lowered to form the product as shown in Figure 4(b). The molding pressure is, for example, 1 to 4 tons / cm². 2 It is preferable to mold it using (S7). In this case, the sliding surface side (step dimension T1 side) becomes denser, while the opposing surface side (step dimension T2 side) becomes less dense compared to the sliding surface side. As a result, the open porosity (porosity) is higher on the opposing surface side (step dimension T2 side), where the structure is less dense, and thus differs between the sliding surface side (step dimension T1 side) and the opposing surface side (step dimension T2 side). Subsequently, it is preferable to perform the heat treatment (firing temperature) at a temperature of 400°C or higher and 900°C or lower (S8). After the heat treatment, as shown in Figure 4(c), the stepped portions 1a and 1b of the metal graphite brush 1 are removed, thereby producing the metal graphite brush 1 as shown in Figure 4(d) (S9).

[0041] Furthermore, the molding machine shown in Figure 5 can also be used. That is, using molds M1 and M2, which have a stepped portion formed on one side, only the stepped portion 1b of the metal graphite brush 1 may be formed. By removing this stepped portion 1b, the metal graphite brush 1 is manufactured as shown in Figure 5(d). [Examples]

[0042] (Example 1) 10% by weight of liquid phenolic resin was added to 100% by weight of deashed graphite powder and kneaded in a kneader. The kneaded mixture was crushed and sieved to obtain granulated powder with a particle size of 50 to 300 μm (or 50 mesh pass). The graphite powder used had a particle size of 50 μm to 300 μm. Then, 41.6% by weight of electrolytic copper powder and 3.4% by weight of molybdenum disulfide (MoS2) were added to 55% by weight of granulated powder and mixed by dry process to obtain a mixed powder. Electrolytic copper powder with a particle size of 40 to 50 μm (or 300 mesh pass) was used.

[0043] The resulting mixed powder is placed in a mold, at a rate of 1 ton / cm². 2 The material was then pressed using a uniaxial press to obtain the desired brush shape. The resulting molded body was fired at 800°C in an inert atmosphere for 2 hours to obtain a brush. The shape of this brush is shown in Figure 4(c), with a thickness T1 of 25 mm and a thickness T2 of 33 mm. The particle sizes of graphite powder, granulated powder, and electrolytic copper powder were measured by laser diffraction and scattering. The obtained brushes were evaluated for open porosity according to JIS-R1634 "Method for measuring density and open porosity of sintered fine ceramics". The open porosity (porosity) of region 1A was 16%, and the open porosity (porosity) of region 1B was 24.7%. Furthermore, density and elastic modulus were determined based on the physical property measurement method for test specimens (conform to the JCAS-10 test method for electric machinery brushes). The density (bulk specific gravity) was calculated as weight W (g) / volume V (cm³). 3 The elastic modulus was determined from the following. Furthermore, the elastic modulus was determined by the resonance method using a test piece with a width of 15 mm, a length of 60 mm, and a thickness of 3 mm, based on the JIS Fine Ceramics Standard. The results are shown in Table 1.

[0044] Furthermore, the amount of wear on the obtained brushes was evaluated using a sliding wear testing machine. The evaluation conditions were a peripheral speed of 10 m / s and a pressing pressure of 200 g / cm². 2 Under the conditions of a rotating electric machine made of Cu-Ag alloy, a metallic graphite brush was run for 1000 hours, and the amount of brush wear per unit time before and after evaluation was calculated and compared. The results are shown in Table 1.

[0045] (Example 2) 100% by weight of natural graphite powder was mixed with 5% by weight of PVA and kneaded in a kneader. The kneaded mixture was crushed and sieved to obtain granulated powder with a particle size of 50 to 300 μm (or 50 mesh pass). The graphite powder used had a particle size of 50 μm to 300 μm. Then, 61.2% by weight of electrolytic copper powder was added to 38.8% by weight of granulated powder and mixed by dry process to obtain a mixed powder. Molybdenum disulfide (MoS2) was not added. Electrolytic copper powder with a particle size of 40 to 50 μm (or 300 mesh pass) was used. Subsequently, a brush was fabricated in the same manner as in Example 1. This brush had the shape shown in Figure 4(c), with a thickness T1 of 27 mm and a thickness T2 of 43 mm. The evaluation was then carried out in the same manner as in Example 1. As a result of the evaluation of open porosity, the open porosity of region 1A was 24.4%, and the open porosity of region 1B was 36.4%.

[0046] Then, the density and elastic modulus of the obtained brushes were determined, and the amount of wear was evaluated using a sliding wear testing machine, in the same manner as in Example 1. The results are shown in Table 1.

[0047] (Example 3) 10% by weight of liquid phenolic resin was added to 100% by weight of deashed graphite powder and kneaded in a kneader. The kneaded mixture was crushed and sieved to obtain granulated powder with a particle size of 50 to 300 μm (or 50 mesh pass). The graphite powder used had a particle size of 50 μm to 300 μm. Then, 41.6% by weight of electrolytic copper powder and 3.4% by weight of molybdenum disulfide (MoS2) were added to 55% by weight of granulated powder and mixed by dry process to obtain a mixed powder. Electrolytic copper powder with a particle size of 40 to 50 μm (or 300 mesh pass) was used. Subsequently, a brush was fabricated in the same manner as in Example 1. This brush had the shape shown in Figure 4(c), with a thickness T1 of 30 mm and a thickness T2 of 46 mm. In order to achieve the same product thickness of 29 mm as Comparative Example 1, the metal graphite brush 1 was processed as shown in Figure 4(d) by removing the stepped portions 1a and 1b of the metal graphite brush 1, as shown in Figure 4(c).

[0048] The evaluation was then carried out in the same manner as in Example 1. As a result of the evaluation of open porosity, the open porosity of region 1A was 20.3%, and the open porosity of region 1B was 31.3%.

[0049] Then, the density and elastic modulus of the obtained brushes were determined, and the amount of wear was evaluated using a sliding wear testing machine, in the same manner as in Example 1. The results are shown in Table 1.

[0050] (Example 4) 100% by weight of natural graphite powder was mixed with 5% by weight of PVA and kneaded in a kneader. The kneaded mixture was crushed and sieved to obtain granulated powder with a particle size of 50 to 300 μm (or 50 mesh pass). The graphite powder used had a particle size of 50 μm to 300 μm. Then, 61.2% by weight of electrolytic copper powder was added to 38.8% by weight of granulated powder and mixed by dry process to obtain a mixed powder. Molybdenum disulfide (MoS2) was not added. Electrolytic copper powder with a particle size of 40 to 50 μm (or 300 mesh pass) was used. Subsequently, a brush was fabricated in the same manner as in Example 1. This brush had the shape shown in Figure 4(c), with a thickness T1 of 36 mm and a thickness T2 of 52 mm. In order to achieve the same product thickness of 35 mm as in Comparative Example 2, the metal graphite brush 1 was processed as shown in Figure 4(d) by removing the stepped portions 1a and 1b of the metal graphite brush 1, as shown in Figure 4(c). The samples were then evaluated in the same manner as in Example 1. The open porosity was evaluated, and the open porosity of region 1A was 30.4%, while the open porosity of region 1B was 39.6%.

[0051] Then, the density and elastic modulus of the obtained brushes were determined, and the amount of wear was evaluated using a sliding wear testing machine, in the same manner as in Example 1. The results are shown in Table 1.

[0052] (Comparative Example 1) Using the same mixed powder as in Example 1, molding was performed using a general molding machine. The resulting mixed powder is placed in a mold, at a rate of 1 ton / cm². 2 The material was then pressed using a uniaxial press to obtain the desired brush shape. The resulting molded body was fired at 800°C in an inert atmosphere for 2 hours to obtain a brush. This brush was formed in a rectangular parallelepiped shape without any stepped shape, and its thickness T1 was 29 mm. Then, as in Example 1, the open porosity was evaluated, and the result was 20.3%. Then, the density and elastic modulus of the obtained brushes were determined, and the amount of wear was evaluated using a sliding wear testing machine, in the same manner as in Example 1. The results are shown in Table 1.

[0053] (Comparative Example 2) Using the same powder mixture as in Example 2, molding was performed using a general-purpose molding machine. The resulting mixed powder is placed in a mold, at a rate of 1 ton / cm². 2 The material was then pressed using a uniaxial press to obtain the desired brush shape. The resulting molded body was fired at 800°C in an inert atmosphere for 2 hours to obtain a brush. This brush was formed in a rectangular parallelepiped shape without any stepped shape, and was formed to a thickness of 35 mm. Then, as in Example 1, the open porosity was evaluated, and the result was 30.4%. Then, the density and elastic modulus of the obtained brushes were determined, and the amount of wear was evaluated using a sliding wear testing machine, in the same manner as in Example 1. The results are shown in Table 1.

[0054] [Table 1]

[0055] As shown in Examples 1 and 2 above, the open porosity of the opposing surface (porosity of the opposing surface) and the open porosity of the sliding surface (porosity of the sliding surface) are different, and the resulting difference in elastic modulus causes the natural vibration of the brush to be dispersed, which suppresses deterioration of seating performance and leads to a reduction in wear. [Explanation of Symbols]

[0056] 1. Metal graphite brush 2. Sliding surface 3 Opposing surfaces 4 Stomata 4a Pore edge 5 Commutator 6. Adhesion membrane

Claims

1. A metal graphite brush having a sliding surface that contacts a commutator and a facing surface that faces the sliding surface, containing graphite and metal powder, and having pores formed therein, A metallic graphite brush characterized in that the porosity of the region including the opposing surface is higher than the porosity of the region including the sliding surface.

2. The metal graphite brush according to claim 1, characterized in that the open porosity of the opposing surface is 40% or less, and the open porosity of the opposing surface is higher than the open porosity of the sliding surface.

3. The metal graphite brush according to claim 2, characterized in that the open porosity of the opposing surface is 1.3 times or more and 1.6 times or less than the open porosity of the sliding surface.

4. A method for manufacturing an electrobrush of a metal graphite brush according to any one of claims 1 to 3, In a stepped mold, the outer shape of the opposing surface facing the sliding surface is formed to be larger than the outer shape of the sliding surface, The raw material powder consists of at least graphite and metal powder, The press molding process, A method for manufacturing a metallic graphite brush, characterized by including the following:

Images