JP4883374B2 - Method for producing metal graphite brush material for motor - Google Patents

Description

  The present invention relates to a method for producing a metal graphite brush material used for a motor.

  2. Description of the Related Art Conventionally, as a brush material used for a motor with a brush, a metal graphite brush material for a motor (for example, see Patent Document 1) in which graphite particles and copper particles are mixed using a bonding solvent and fired is known.

  As an example of a method for producing a metallic graphite brush material for motors, a natural resin particle is kneaded using a phenol resin solution as a binder, granulated into a predetermined shape, and then a current passed through the brush to the obtained graphite particle. An amount of copper powder corresponding to the density and a required amount of solid lubricant are mixed, and then the mixed powder is formed into a predetermined shape. And the obtained molded object is baked in the non-oxidizing atmosphere which interrupted | blocked oxygen. By such a manufacturing method, the phenol resin formed as a film on the surface of the graphite particles is carbonized to become amorphous carbon, and the graphite particles are bonded. In the process of reduction firing, oxygen atoms and hydrogen atoms constituting the phenol resin solution are sublimated as carbon dioxide and water vapor, so that a large number of pores are formed on the surface and inside of the sintered body.

  Generally, in a motor using a metal graphite brush, the metal graphite brush is in sliding contact with the commutator, and power is supplied from the brush to the commutator or from the commutator to the brush. When the coil wound around the core provided in the rotor is connected to the commutator and the coil is energized, the rotor is attracted to the permanent magnet disposed opposite the rotor inside the housing. Rotates by force and repulsive force.

  Since the motor with a metal graphite brush operates on the above-mentioned operating principle, the problem that the metal graphite brush is worn on the sliding contact surface with the commutator due to the sliding contact between the metal graphite brush and the commutator when the motor is driven. Various studies have been made so far in order to suppress the wear of the metallic graphite brush when the motor is driven.

  As this kind of technology, focusing on the wear of metal graphite brushes due to the electrical wear of spark discharge in addition to the mechanical wear due to sliding contact with the commutator, the surfaces of the graphite particles contacted each other. A metallic graphite brush material carrying a group of copper particles (see, for example, Patent Document 2) has been proposed. This metal graphite brush material can suppress spark discharge and wear due to spark discharge by forming on the surface of the graphite particle a conductive path through which charges induced from the graphite particle are conducted. Furthermore, according to this metal graphite brush material, the quantity of electric charges released from the copper fine particles can be reduced by making the copper fine particles, thereby reducing the electrical energy of the spark discharge and generating the spark discharge. The electrical noise level at the time can also be reduced.

Such a metal graphite brush material is obtained by applying a solution of a copper complex to the surface of the graphite particles, forming a coating film on the surface of the graphite particles, and forming the molded body by forming the graphite particles. The molded body can be produced by firing in an oxygen-containing atmosphere and further heat-treating in a reducing atmosphere.
JP 2001-298913 A JP 2005-12957 A

  However, since graphite particles are generally hydrophobic, when preparing a metal graphite brush material carrying a group of copper particles in contact with each other on the surface of the graphite particles, the conventional copper complex solution is used as the graphite particles. In the manufacturing method of the metal graphite brush material to apply | coat, there existed a problem that the solution of a copper complex did not adhere easily to the surface of a graphite particle. For this reason, it becomes difficult to form a coating film uniformly on the surface of the graphite particles, and copper particles may be formed loosely on the surface of the graphite particles.

  On the other hand, attempts have been made to modify the surface of graphite particles to hydrophilicity that is compatible with the solution of the copper complex, but the effect is not effective because the formation density of the copper particles varies depending on the degree of modification. It was enough. That is, when the modification of the graphite particles is partial, the copper particles are formed only in the modified part, and the formation density of the copper particles on the surface of the graphite particles is lowered. For this reason, there has been a problem that the degree of reduction of the energy of the spark discharge is reduced, and the degree of reduction of electrical noise accompanying the spark discharge and the degree of reduction of the abrasive wear of the metal graphite brush are reduced.

  The present invention has been devised in view of the above problems, and an object of the present invention is to provide a method for producing a metallic graphite brush material for motors capable of uniformly forming copper particles on the surface of graphite particles. .

  In order to achieve the above object, the first feature means of the method for producing a metallic graphite brush for motors according to the present invention includes an attaching step of bringing the copper complex into contact by bringing a solution having a copper complex into contact with graphite particles, A heat treatment step of decomposing the copper complex by forming a copper particle on the surface of the graphite particle by heat-treating the graphite particle to which the copper complex is attached in an oxygen-containing atmosphere, and the graphite particle having the copper particle formed thereon A forming step of forming a formed body by molding, and a reduction in which the formed body is fired in a reducing atmosphere to form a sintered body and the copper oxide generated on the surface layer of the copper particles in the heat treatment step is reduced to copper And a baking step, and in the attaching step, the solution contains an organometallic compound having a hydrolyzable group or a hydroxyl group and an organic functional group having an unshared electron pair.

  That is, according to this means, in the adhesion step, the organometallic compound is added to the copper complex solution by adding an organometallic compound having a hydrolyzable group or a hydroxyl group and an organic functional group having an unshared electron pair. The following two effects are brought about. One function is due to the organic functional group. The organic functional group dissociates the hydrophobic functional group bonded to the graphite particle by the oxidation action of the lone pair, and coordinates or van der Waals force on the graphite particle. The organometallic compound is bound by such as. Another function is due to the hydrolyzable group or hydroxyl group, and the hydrolyzable group or hydroxyl group hydrophilizes the surface of the graphite particles. By these actions, the copper complex can be uniformly attached to the surface of the graphite particles, and the copper particles can be uniformly formed on the surface of the graphite particles by heat-treating the graphite particles in the heat treatment step.

  Therefore, in the metal graphite brush using the metal graphite brush material according to the present invention, the damage of the metal graphite brush and the damage of the commutator are reduced, so that the amount of wear can be reduced. In addition, the electrical energy of the spark discharge can be reduced, and the electrical noise level when the spark discharge occurs can be reduced.

  The 2nd characteristic means of the manufacturing method of the metallic graphite brush material for motors which concerns on this invention exists in the point whose said organometallic compound is a silane compound.

  That is, according to this means, by using a silane compound as the organometallic compound, a preferred embodiment of a method for producing a metallic graphite brush material for motors capable of uniformly forming copper particles on the surface of graphite particles. Provided.

  The 3rd characteristic means of the manufacturing method of the metallic graphite brush material for motors which concerns on this invention is that the said hydrolysable group is an alkoxy group.

  That is, according to this means, the organometallic compound can be easily cross-linked with each other by applying an alkoxy group as the hydrolyzable group and causing a hydrolysis reaction or a condensation reaction. As a result, the number of unshared electron pairs that are binding sites with the graphite particles can be increased, and the binding force between the organometallic compound and the graphite particles can be increased. Since the crosslinked organometallic compound is hydrophilic, the surface of the graphite particles is covered with a hydrophilic substance when the organometallic compound is crosslinked, thereby promoting the hydrophilicity of the surface of the graphite particles. be able to.

  The 4th characteristic means of the manufacturing method of the metallic graphite brush material for motors which concerns on this invention exists in the point in which the said organic functional group has at least 1 sort (s) of hetero atom among an oxygen atom, a nitrogen atom, and a sulfur atom.

  That is, according to this means, copper particles can be uniformly formed on the surface of graphite particles by using an organometallic compound having at least one hetero atom among oxygen, nitrogen and sulfur atoms as an organic functional group. A preferred embodiment of a method for producing a metallic graphite brush material for a motor that can be used is provided.

  The fifth characteristic means of the method for producing a metallic graphite brush material for motors according to the present invention is that the organic functional group has a heterocyclic group.

  That is, according to this means, the heterocyclic group is bonded to the graphite particles by coordination or van der Waals force and complexed with copper ions, so that the adhesion of the graphite particles to the copper complex can be improved. .

  The 6th characteristic means of the manufacturing method of the metallic graphite brush material for motors which concerns on this invention exists in the point whose said heterocyclic group is an imidazole group.

  That is, according to this means, there is a preferred embodiment of a method for producing a metallic graphite brush material for motors that can uniformly form copper particles on the surface of graphite particles by applying an imidazole group as a heterocyclic group. Provided.

  The seventh characteristic means of the method for producing a metallic graphite brush material for motors according to the present invention is that the solution further contains an ether type nonionic surfactant.

  In other words, according to this means, by adding an ether type nonionic surfactant to the solution, the non-shared electron pair possessed by the oxygen atom of the ether type nonionic surfactant is bonded to the hydrophobic functional group. The surface of the graphite particle can be hydrophilized by oxidizing and dissociating the group and bonding an ether type nonionic surfactant to the graphite particle by coordination or van der Waals force. Therefore, by adding an ether type nonionic surfactant together with an organic metal compound having a hydrolyzable group or a hydroxyl group and an organic functional group having a lone pair to the solution brought into contact with the graphite particle, The hydrophilicity of the surface can be increased and the copper complex can be uniformly attached to the surface of the graphite particles.

  The method for producing a metallic graphite brush material for a motor according to the present invention includes an adhesion step in which a solution having a copper complex is brought into contact with graphite particles to adhere the copper complex, and the graphite particles to which the copper complex is adhered contain oxygen. A heat treatment step in which the copper complex is decomposed by heat treatment in an atmosphere to form copper particles on the surface of the graphite particles; and a molding step in which the graphite particles on which the copper particles are formed are formed to form a compact. And firing the molded body in a reducing atmosphere to form a sintered body, and including a reduction firing process for reducing the copper oxide generated on the surface layer of the copper particles in the heat treatment process to copper, in the adhesion process, The solution contains an organometallic compound having a hydrolyzable group or a hydroxyl group and an organic functional group having an unshared electron pair.

  In general, graphite particles have a crystal structure in which carbon atoms are covalently bonded in a ring shape in a layered manner by van der Waals force. The carbon atoms at the ends of the crystallites of such graphite particles include -H , ═O, —COOH and other functional groups are bonded. For this reason, the graphite particles become hydrophobic and have water repellency so that the contact angle with water is 86 degrees. The present inventor has paid attention to the fact that the functional group bonded to the carbon atom of the graphite particle can be dissociated from the graphite particle by oxidation. And, when attaching the copper complex to the surface of the graphite particles, by contacting with a solution having a copper complex and an organometallic compound comprising a hydrolyzable group or an organic functional group having a hydroxyl group and an unshared electron pair, It was found that the copper complex can be uniformly attached to the surface of the graphite particles. That is, the organometallic compound dissociates the functional group from the surface of the graphite particle by the oxidation action of the lone pair of the organic functional group, and binds to the graphite particle by coordination or van der Waals force. The surface of the graphite particles can be made hydrophilic by the action of a hydrolyzable group or a hydroxyl group.

  According to this method, the copper complex can be uniformly attached to the surface of the graphite particles in the attaching step. For this reason, copper particles can be uniformly formed on the surface of the graphite particles by heat-treating the graphite particles in a heat treatment step.

  Generally, there are very few contact points on the sliding contact surface between the metal graphite brush and the commutator. For this reason, air is the medium for most of the sliding contact surfaces of both. As a result, most of the sliding surface becomes a minute air gap, so when a potential is applied to the metal graphite brush, a high electric field is induced in the metal graphite brush, and the valence electrons of the graphite particles are formed. Π electrons are excited. The excited π electrons move all at once to the relatively low-potential copper particles present near the graphite particles. Since copper particles cannot accumulate π electrons that have moved, they emit π electrons all at once. This phenomenon is a spark discharge phenomenon. And by this spark discharge, the copper particle used as the nucleus of a spark discharge locally sublimes, and destruction in a brush occurs. In addition, some spark discharges reach the commutator, and the spark that reaches the commutator locally sublimes the commutator surface and changes the surface state of the commutator. Happens.

  Therefore, in the metal graphite brush using the metal graphite brush material according to the present invention, the number of π electrons emitted from the graphite particles and accumulated on the copper particles by forming the copper particles in the metal graphite brush material at a high density. Is dispersed and reduced according to the size of the copper particles and the quantity of the copper particles. By this phenomenon, the energy of the spark discharge emitted from one copper particle is reduced. Thus, damage to the metal graphite brush and commutator can be reduced, and the amount of wear of the metal graphite brush can be reduced. Further, since the energy of the spark discharge can be reduced, the electric noise associated with the spark discharge is also reduced according to the size of the copper particles and the quantity of the copper particles, and the countermeasure against the electric noise accompanying the spark discharge becomes unnecessary.

  As shown in FIG. 1, the metal graphite brush material for motors can be manufactured through an adhesion step S <b> 1, a heat treatment step S <b> 2, a molding step S <b> 3, and a reduction firing step S <b> 4. Hereinafter, each process of the manufacturing method of the metallic graphite brush material for motors concerning this invention is explained in full detail.

(Adhesion process S1)
The attachment step S1 is a step of attaching a copper complex to the graphite particles. Specifically, by bringing a solution containing a copper complex and an organometallic compound having a hydrolyzable group or a hydroxyl group and an organic functional group having an unshared electron pair into contact with the graphite particles, the graphite complex is brought into contact with the graphite complex. To attach. The method for bringing the graphite particles into contact with the solution is not particularly limited, and conventionally known methods such as dipping, coating, spraying, and the like can be applied.

  The copper complex to be attached to the graphite particles is not particularly limited. For example, it is preferable to use a carboxylic acid copper complex that is easily synthesized, easily dissolved in an organic solvent, and thermally decomposed at a relatively low temperature. The carboxylic acid copper complex can be prepared by a liquid phase reaction between a copper compound and a carboxylic acid. Examples of the copper compound include copper chloride, copper sulfate, and copper carbonate. Examples of the carboxylic acid include linear saturated monocarboxylic acids such as butanoic acid and octanoic acid, linear saturated dicarboxylic acids, and linear saturated monocarboxylic acids. And chain unsaturated monocarboxylic acid, chain unsaturated dicarboxylic acid, aromatic carboxylic acid and the like. Among these, a linear saturated monocarboxylic acid copper complex using a linear saturated monocarboxylic acid as a carboxylic acid is particularly preferable. Since the linear saturated monocarboxylic acid copper complex has a thermal decomposition temperature as low as 150 ° C. or lower compared with other carboxylic acid copper complexes, the copper particles are formed at a relatively low temperature of 300 to 350 ° C. in the heat treatment step S2. Can do. Thus, by using a linear saturated monocarboxylic acid copper complex as a copper complex, it can be thermally decomposed at a particularly low temperature among other carboxylic acid copper complexes. As a result, the heat treatment in the heat treatment step S2 can be performed in a temperature region in which growth to copper particles can be suppressed. As a solvent for dissolving the copper complex, water, methanol, ethanol, 1-propanol, 1-butanol and the like can be used.

  Examples of the organometallic compound having a hydrolyzable group or a hydroxyl group and an organic functional group having an unshared electron pair include silane compounds, titanium compounds, aluminum compounds, and the like, and are not particularly limited. Among them, silane compounds are relatively inexpensive. It is particularly preferable because it is easy to handle.

  As long as the organic functional group has an unshared electron pair, the number of unshared electron pairs is not limited, and for example, an organic functional group having a hetero atom such as an oxygen atom, a nitrogen atom, or a sulfur atom can be used. In addition, the organic functional group preferably has a heterocyclic group, and this heterocyclic group binds to the graphite particles by coordination or van der Waals force and also forms a complex with copper ions. Can be improved. The heterocyclic group is not particularly limited, and examples thereof include a pyrrole group, a furan group, a thiophene group, an imidazole group, an oxazole group, a thiazole group, a pyridine group, a pyrimidine group, a pyrazine group, and a piperazine group.

  The hydrolyzable group can be arbitrarily selected as long as it is a hydrolyzable functional group such as an alkoxy group such as a methoxy group, an ethoxy group, or a methoxyethoxy group, a halogen group, an acetoxy group, or an acyloxy group. For example, an alkoxy group can easily crosslink organic metal compounds with each other by a hydrolysis reaction or a condensation reaction. This is preferable because the number of unshared electron pairs that are bonding sites with the graphite particles can be increased, and the bonding force between the organometallic compound and the graphite particles can be increased. Further, the crosslinked organometallic compound is hydrophilic, and the surface of the graphite particles is covered with a hydrophilic substance when the organometallic compound is crosslinked, which is preferable from the viewpoint of hydrophilizing the surface of the graphite particles. .

  As an organometallic compound having a hydrolyzable group or a hydroxyl group and an organic functional group having an unshared electron pair, as shown in Chemical Formula 1 and Chemical Formula 2, an imidazole group and a silyl group are converted into a methylene chain, an oxygen atom, and a nitrogen atom. For example, conventionally known silane coupling agents are exemplified as shown in Chemical Formula 3 and imidazole silane compounds bonded by the like.

In the imidazole silane compound, in R ^{1 and} R 2, R ^{1 to} R ⁶ are conventionally known functional groups such as hydrogen, an alkyl group, and an alkoxy group, and at least one of R ^{4 to} R ⁶ is an alkoxy group or the like. It is a hydrolyzable group or a hydroxyl group. As such an imidazole silane compound, those in which two or three of R ^{4 to} R ⁶ have a dialkoxysilyl group or trialkoxysilyl group, which is an alkoxy group such as a methoxy group or an ethoxy group, are preferable. For example, when an imidazolesilane compound having a trialkoxysilyl group is used, as shown in FIG. 2, the imidazolesilane compounds form a network based on silanol bonds, and the imidazole group forms a complex with copper ions while forming a graphite. By bonding to the particles by coordination or van der Waals force, the adhesion of the graphite particles to the copper complex can be improved. Further, the imidazolesilane compound preferably has a secondary hydroxyl group as shown in Chemical Formula 2. Such a hydroxyl group can further enhance the hydrophilicity of the imidazolesilane compound, and can further strengthen the cross-linked structure by hydrogen bonding of the hydroxyl group. In addition, the thermal decomposition temperature of such an imidazole silane compound is 300-350 degreeC, and since copper brings about the catalytic action of a thermal decomposition reaction when it contains copper, a thermal decomposition temperature will be 300 degrees C or less. For this reason, the imidazole silane compound is thermally decomposed in the heat treatment step S2, and a low molecular weight substance obtained by thermally decomposing the imidazole silane compound after producing the metal graphite brush material does not adversely affect.

  In the attaching step S1, the solution brought into contact with the graphite particles can further contain an ether type nonionic surfactant. The ether type nonionic surfactant has an oxygen atom, dissociates the functional group from the surface of the graphite particle by the oxidation action of the unshared electron pair of the oxygen atom, and also converts the functional group into the graphite particle as shown in FIG. The surface of the graphite particles can be hydrophilized by binding an ether type nonionic surfactant by coordination or van der Waals force. For this reason, graphite particles can be obtained by containing an ether type nonionic surfactant together with an organometallic compound having a hydrolyzable group or a hydroxyl group and an organic functional group having an unshared electron pair in a solution to be brought into contact with the graphite particles. The hydrophilicity of the surface of can be further increased. As a result, the copper complex can be uniformly attached to the wider surface of the graphite particles. In addition, when the organometallic compound and the ether type nonionic surfactant are added to the solution, they may be added simultaneously or stepwise. When these compounds are added stepwise to the solution, the order of addition is not particularly limited, but after adding one to the solution and thoroughly blending the solution and the graphite particles, the other may be added. For example, when an ether type nonionic surfactant is first added to the solution, the ether type nonionic surfactant is bonded to the surface of the graphite particles, and then the added organometallic compound is bonded to the surface of the graphite particles. Since it reacts with the nonionic surfactant, the hydrophilicity of the surface of the graphite particles can be increased.

  For example, when a solution containing an imidazole silane compound having an alkoxy group and an ether type nonionic surfactant is used, each of the solutions not only binds to graphite particles, but also the alkoxy silyl group of the imidazole silane compound and the ether type non-ionic surfactant. By reacting with the polyether chain of the ionic surfactant, it is possible to synergistically enhance the adhesion of the graphite particles to the copper complex.

  The ether type nonionic surfactant is not particularly limited, but a conventionally known ether type nonionic surfactant such as polyoxyalkylene alkyl ether type nonionic surfactant as shown in Chemical Formula 4 or Chemical Formula 5 is applied. Can do. When a polyoxyalkylene alkyl ether type nonionic surfactant is used, the average added mole number of alkylene oxide added per mole of the polyoxyalkylene alkyl ether type nonionic surfactant is preferably 5 or more, It is more preferably 7 or more, and further preferably 10 or more. That is, as the average added mole number of alkylene oxide increases, the number of unshared electron pairs possessed by the polyoxyalkylene alkyl ether type nonionic surfactant increases, so that the oxidation action increases. This makes it easier to dissociate the functional group bonded to the graphite particles and to make the graphite particles hydrophilic. Moreover, since the hydrophilicity of nonionic surfactant itself increases so that there are many average addition mole numbers of alkylene oxide, it becomes easy to melt | dissolve with respect to the solvent which melt | dissolves a copper complex.

  Moreover, in the polyoxyalkylene alkyl ether type nonionic surfactant, the solubility in a solvent such as 1-butanol decreases as the average number of added moles of alkylene oxide increases. For this reason, when using a polyoxyalkylene alkyl ether type nonionic surfactant having a large average number of added moles of alkylene oxide, the temperature of the solution is increased to improve the solubility in a solvent such as 1-butanol. It is preferable to do. For example, in order to dissolve a polyoxyalkylene alkyl ether type nonionic surfactant having an average addition mole number of alkylene oxide of 20 in a solvent, the temperature may be raised to about 50 ° C. In this case, 1-butanol has a boiling point of 117 ° C. and can be preferably applied as a solvent. On the other hand, when a polyoxyalkylene alkyl ether type nonionic surfactant solution is used at room temperature, the average addition mole of alkylene oxide is considered from the viewpoint of the oxidizing power for the functional group bonded to the graphite particles and the solubility in the solvent. The number is preferably 5 to 15, and more preferably 7 to 12. As the polyoxyalkylene alkyl ether type nonionic surfactant, for example, a polyoxyethylene alkyl ether type nonionic surfactant, a polyoxypropylene alkyl ether type nonionic surfactant and the like can be selected.

(Heat treatment step S2)
The heat treatment step S2 is a step of heat-treating the graphite particles to which the copper complex is attached in an oxygen-containing atmosphere. By this step, the copper complex is thermally decomposed to form copper particles on the surface of the graphite particles. The oxygen-containing atmosphere can be arbitrarily selected from an air atmosphere, an oxygen-rich atmosphere, an oxygen atmosphere, and the like, and is not particularly limited.

In this heat treatment step S2, the copper complex adhering to the surface of the graphite particles is thermally decomposed at 150 ° C. or lower, and the copper atoms are separated. And the isolate | separated copper atom turns into a copper molecule, and it grows to a copper particle by further heating up. On the other hand, if the heat treatment temperature becomes too high, the degree of growth that grows to copper particles becomes excessive, and the copper particles that have grown too much form a discontinuous network structure in which regions where no copper particles are present are partially scattered. . Thus, if the growth of the copper particles proceeds too much, the area where the copper is lost increases, and the copper particles have a dotted island structure. From such a viewpoint, the heat treatment temperature is preferably 300 to 500 ° C. In particular, in order to suppress the growth of copper particles and form copper particles at a higher density on the surface of graphite particles, it is preferable that the temperature is closer to 300 ° C. Thereby, the π electrons emitted from the graphite particles and accumulated in the copper particles are further dispersed, and the number of π electrons emitted from the copper particles is further reduced, so that the energy at the time of spark discharge is further reduced. Therefore, heat treatment at 300 ° C. is particularly preferable. In addition, the heat treatment time is not particularly limited. For example, when heat treatment is performed at 300 ° C., about 2 hours is preferable because the growth to copper particles at 300 ° C. is sufficiently advanced.
In this heat treatment step S2, heat treatment is performed in an oxygen-containing atmosphere in order to thermally decompose the copper complex. For this reason, the surface of the copper particles formed on the surface of the graphite particles is oxidized, and copper oxide is generated on the surface layer of the copper particles.

(Molding step S3)
The forming step S3 is a step of forming a molded body by forming graphite particles having copper particles formed on the surface, and a conventionally known method can be adopted. For example, a graphite particle compression molded body can be formed by filling graphite particles formed on the surface of copper particles into a box-shaped container and pressurizing them with a predetermined pressure (for example, 100 Pa). In addition, when forming the molded object of a graphite particle, a binder can be mixed. By attaching a binder to the graphite particles formed on the surface of the copper particles, the graphite particles can be bonded to each other in the reduction firing step S4 described later. Examples of the binder include modified phenolic resin, glycerin and the like. Such a binder can be dissolved in a solvent such as methanol and attached as a solution to the graphite particles by coating or the like.

(Reduction firing step S4)
The reduction firing step S4 is a step of firing the molded body in a reducing atmosphere. By this step, a sintered body is formed, and the copper oxide generated in the surface layer of the copper particles in the heat treatment step S2 is reduced to copper. Although it does not specifically limit as reducing atmosphere, For example, 50-95 vol. % Nitrogen gas and 5-50 vol. A mixed gas atmosphere with% hydrogen gas can be employed. In particular, 90 vol. % Nitrogen gas and 10 vol. A reducing atmosphere consisting of 1% hydrogen gas is preferable from the viewpoint of reducing the copper oxide to copper and reducing the safety of the reduction treatment. The reduction firing can be performed at about 150 to 500 ° C., but the firing temperature is equal to or lower than the heat treatment temperature in the heat treatment step S2 in order to suppress the growth of the copper particles formed on the surface of the graphite particles in this step. Is preferable, for example, 300 ° C., which is equivalent to the heat treatment temperature, is more preferable. The heat treatment time is preferably about 10 minutes to 5 hours.

  Examples of the method for producing a metallic graphite brush material for motors will be described below and the present invention will be described in more detail. However, the present invention is not limited to these examples.

Example 1
Copper octoate was dissolved in 1-butanol so as to be a saturated solution, an imidazolesilane compound having a trimethoxysilyl group represented by Chemical Formula 2 was added at a rate of 2 wt%, and the mixture was stirred for 10 minutes. A container containing graphite particles was immersed in this solution, vibrated up and down, left and right in the solution for about 1 hour, and further rotated clockwise and counterclockwise. Thereafter, the container containing the graphite particles was pulled out of the solution, heated in the air atmosphere from room temperature to 150 ° C. at a rate of 5 ° C./min, held at 150 ° C. for 1 hour, and then up to 300 ° C. The temperature was raised at a rate of minutes and held at 300 ° C. for 5 hours to form a group of copper particles on the surface of the graphite particles.

(Example 2)
To the saturated solution of copper octoate using 1-butanol as a solvent, the imidazole silane compound used in Example 1 was added in a proportion of 2 wt%, and the polyoxyethylene shown in Chemical Formula 4 was used as an ether type nonionic surfactant. This was performed in the same manner as in Example 1 except that an alkyl ether type nonionic surfactant (m + n = 12 to 14) having an average addition mole number x of ethylene oxide of 12 was added at a rate of 5 wt%. .

(Example 3)
The ether type nonionic surfactant used in Example 2 was added to a saturated solution of copper octoate using 1-butanol as a solvent at a ratio of 5 wt%, and the mixture was stirred for 10 minutes. A container containing graphite particles was immersed in this solution, vibrated up and down, left and right in the solution for about 1 hour, and further rotated clockwise and counterclockwise. Subsequently, the imidazolesilane compound used in Examples 1 and 2 was added at a rate of 2 wt%, and the container containing the graphite particles was rotated in various directions for about 1 hour. Thereafter, the container containing the graphite particles was pulled up from the solution, and the same treatment as in Example 1 was performed.

  The formation state of the copper particles in each example was observed with a scanning electron microscope (SEM) at a magnification of 5000 times. Further, the treated graphite particles were compression molded to form a compact, and reduced and fired to produce a metal graphite brush material. As a result of calculating the copper content constituting the obtained metal graphite brush material from the chemical formula of the copper complex and the adhesion amount of the copper complex, the mixing ratio of copper in each example corresponds to 45 wt%. there were. The electric resistance of the metal graphite brush material of each example was measured by a four-probe method. The results are shown in Table 1. The electric resistance of the metal graphite brush material prepared by mixing 45 wt% of electrolytic copper powder with graphite particles based on the conventional manufacturing method is 15E-3 Ω · cm, and the metal graphite brush material of any of the examples The electrical resistance was lower than the conventional one.

  Moreover, the graphite particles produced in Examples 1 to 3 were filled in a box-shaped container and molded by pressurizing with a pressure of 100 Pa, and then 90 vol. % Nitrogen gas and 10 vol. Firing was performed at 300 ° C. for 5 hours in a reducing atmosphere consisting of% hydrogen gas. The metal graphite brush material thus manufactured was attached to a motor, and the wear amount and electric noise level of the metal graphite brush were measured. The metal graphite brush is formed into a size of 4.5 mm × 9.0 mm, the load on the commutator of the metal graphite brush is 78.5 kPa, the motor rotation speed is 3.6 m / s, and the metal graphite brush A current of 10 A was passed between the commutator and the motor to rotate the motor. The motor was rotated continuously for 500 hours at an ambient temperature of 100 ° C. As a comparative example, a metal graphite brush produced by mixing 45 wt% of electrolytic copper powder with graphite particles based on a conventional manufacturing method was used. The electric noise level was determined with reference to 1 for the metal graphite brush of the comparative example. As a result, as shown in Table 2, in any of Examples 1 to 3, the amount of wear was greatly reduced and the electric noise was also reduced as compared with the comparative example.

  As described above, the metal graphite brush using the metal graphite brush material produced by the manufacturing method according to the present invention is formed with a high density of fine copper particles as a group structure on the surface. It was confirmed that a synergistic effect of suppressing spark discharge and electric noise was obtained.

  The metal graphite brush material produced by the manufacturing method according to the present invention is a metal graphite brush used for a motor for driving a water pump for cooling a vehicle engine, a motor for rotating a cooling fan, a motor for driving an oil pump for the engine, etc. Can be applied to.

The figure which shows the manufacturing process of the metal graphite brush material for motors Schematic diagram showing the binding state of imidazole silane compound to graphite particles Schematic diagram showing the binding state of ether type nonionic surfactant to graphite particles

Claims (7)

An adhesion step in which a solution having a copper complex is brought into contact with graphite particles to attach the copper complex;
A heat treatment step of decomposing the copper complex by heat-treating the graphite particles to which the copper complex is adhered in an oxygen-containing atmosphere, and forming copper particles on the surface of the graphite particles;
Forming step of forming the graphite particles forming the copper particles to form a molded body;
The molded body is fired in a reducing atmosphere to form a sintered body, and includes a reduction firing step of reducing the copper oxide generated on the surface layer of the copper particles in the heat treatment step to copper,
The manufacturing method of the metallic graphite brush material for motors in which the said attachment process is made to contain the organometallic compound provided with the organic functional group which has an organic functional group which has a hydrolysable group or a hydroxyl group, and a lone pair in the said solution.   The method for producing a metallic graphite brush material for motors according to claim 1, wherein the organometallic compound is a silane compound.   The method for producing a metallic graphite brush material for a motor according to claim 1, wherein the hydrolyzable group is an alkoxy group.   The method for producing a metallic graphite brush material for a motor according to claim 1, wherein the organic functional group has at least one hetero atom among an oxygen atom, a nitrogen atom, and a sulfur atom.   The method for producing a metallic graphite brush material for a motor according to claim 1, wherein the organic functional group has a heterocyclic group.   The method for producing a metallic graphite brush material for a motor according to claim 5, wherein the heterocyclic group is an imidazole group.   The method for producing a metallic graphite brush material for motors according to any one of claims 1 to 6, wherein the solution further contains an ether type nonionic surfactant.

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