JP2007172867A - Method of manufacturing brush - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a long-lived brush with less electric loss, which does not generate variation of filling density between powder for forming a low resistivity layer and powder for forming a high resistivity layer, and is easy to control characteristics and thicknesses of respective layers. <P>SOLUTION: The method of manufacturing the brush which forms a sliding surface for contacting with a commutator by the low resistivity layer 3 and the high resistivity layer 2, buries and forms a lead wire 1 in the powder for the low resistivity layer to fix the lead wire 1 and form the low resistivity layer 3, and then, forms the high resistivity layer 2 on its upper surface. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a brush used in a DC motor or the like.

Recent DC motors have been made smaller and lighter by increasing speed and current density.
However, this type of electric motor has a large decrease in rectification performance, output characteristics, etc., and a large amount of brush wear, resulting in short durability. In order to solve these problems, there is a limit to improving the performance of the brush material, so the brush structure is devised.

As an example, as shown in Patent Documents 1 and 2, etc., a brush having a multilayer structure having a low resistance layer and a high resistance layer in which the mixing ratio of graphite and metal contained in the brush is adjusted is used. It has become.
Japanese Patent Publication No. 06-0666147 Japanese Patent Publication No. 06-007505

However, since the multi-layered brush shown above is integrally molded after the powder molding die is filled with the low resistance layer molding powder and the high resistance layer molding powder in layers, the low resistance layer is formed during molding. The powder at the boundary between the molding powder and the high-resistance layer molding powder was mixed, resulting in variations in the packing density between the powders, making it difficult to control the characteristics and thickness of each layer. .
In addition, the multi-layered brush described above has a problem that it is quickly worn and has a large electrical loss, particularly a large increase in voltage drop in the lead wire embedded portion.

  In the present invention, there is no variation in the packing density between the low resistance layer molding powder and the high resistance layer molding powder, the characteristics and the thickness of each layer can be easily controlled, and the long service life is achieved. A method of manufacturing a brush with low electrical loss is provided.

The present invention relates to a method of manufacturing a brush in which a sliding surface that is in contact with a commutator is formed of a low resistance layer and a high resistance layer, and a lead wire is embedded in a powder for a low resistance layer or a brush piece for a low resistance layer. In addition, the present invention relates to a method for manufacturing a brush, characterized in that a high resistance layer is formed on an upper surface of a low resistance layer formed by pressurizing and fixing a lead wire.
The present invention also relates to a method for producing a brush, wherein the high resistance layer is a molded body adhered to the low resistance layer or formed by molding a powder for the high resistance layer on the low resistance layer.

  The brush obtained by the production method of the present invention does not cause variations in the packing density of the low resistance layer molding powder and the high resistance layer molding powder, and controls the characteristics and the thickness of each layer. Is easy to use, has a long service life and low electrical loss, and is extremely suitable industrially.

The brush according to the present invention includes a lead wire, a low resistance layer, and a high resistance layer. The low resistance layer is formed first, and then the high resistance layer is formed.
In the present invention, the method for forming the high resistance layer is not particularly limited. For example, a brush piece to be the high resistance layer is prepared in advance and then adhered to the low resistance layer or used for the high resistance layer. There is a method in which powder is formed on a low resistance layer.

  The resistivity in the high resistance layer and the low resistance layer is not limited as long as the relationship of high resistance layer> low resistance layer is satisfied. To satisfy these resistivity relationships, for example, high resistance The resistivity of the layer is preferably about 2 to 20 times that of the low resistance layer, more preferably about 4 to 16 times, and even more preferably about 8 to 12 times.

  The resistivity is set in accordance with the required characteristics of the rotating electrical machine to be used, but generally has a value of about 0.1 to 30 μΩ · m. In order to achieve the above-mentioned resistivity, the amount of metal contained in a brush mainly composed of graphite is adjusted and appropriately selected. Examples of the metal contained in the brush include powders of copper, silver, and the like.

  In the present invention, when the low resistance layer and the high resistance layer are bonded, as an adhesive used for bonding, an adhesive having conductivity, for example, an epoxy resin containing metal powder such as silver, copper, and palladium is used. Is preferred.

  In the present invention, when the low resistance layer and the high resistance layer are bonded, a protrusion is formed on one of the bonding surfaces of the low resistance layer and the high resistance layer, and a recess is formed on the other, and the protrusion and the recess are fitted together. Adhesive strength is preferable because the adhesive strength is excellent.

Examples of the present invention will be described below.
Example 1
80% by weight of natural graphite powder having an average particle size of 50 μm (trade name CB-150, manufactured by Nippon Graphite Industry Co., Ltd.) and 20% by weight of resol type phenol resin (trade name VP11N, manufactured by Hitachi Chemical Co., Ltd.) Then, it was dried at 65 ° C. for 16 hours and then pulverized to obtain a resin-treated graphite powder having an average particle size of 150 μm.

  Next, 45% by weight of this resin-treated graphite powder and 55% by weight of electrolytic copper powder having an average particle size of 35 μm (trade name CE-25, manufactured by Fukuda Metal Foil Industry Co., Ltd.) are mixed to form a low resistance layer forming powder. Got the body. On the other hand, 65% by weight of the resin-treated graphite powder obtained above and 35% by weight of the electrolytic copper powder used above were mixed to obtain a high resistance layer molding powder.

  The high resistance layer molding powder obtained above is filled in a mold, molded with a molding press at a pressure of 392 MPa, then heated to 700 ° C. in 3 hours in a reducing atmosphere, and sintered at 700 ° C. for 1 hour. Then, a high resistance layer brush piece having a size of 16 × 15 × 2 mm provided with a lead wire insertion hole was obtained by machining into a predetermined shape.

  On the other hand, the low resistance layer molding powder obtained above is filled in a mold, molded with a molding press at a pressure of 392 MPa, then heated to 700 ° C. in a reducing atmosphere in 3 hours, and then at 700 ° C. for 1 hour. Sintering was then performed to obtain a low resistance layer brush piece having a size of 16 × 15 × 5 mm provided with a recess for embedding the lower end of the lead wire by machining into a predetermined shape.

  Next, as shown in FIG. 1, after inserting the tip of the lead wire 1 into a recess provided in the low resistance layer brush piece, the lead wire 1 is filled with silver-plated copper powder (not shown). Then, the lead wire 1 was embedded, and further, the silver plating copper powder was pressurized by a stamping operation, and the lead wire 1 was fixed to the low resistance layer brush piece.

  Thereafter, the exposed portion of the lead wire 1 fixed to the low resistance layer brush piece is inserted into the lead wire insertion hole provided in the high resistance layer brush piece obtained above, and then the high resistance layer brush. Adhering the two pieces and the low resistance layer brush pieces using an epoxy resin adhesive (trade name MP200V1 manufactured by Hitachi Chemical Co., Ltd.) and silver paste mixed into a paste. The resin was cured to obtain a brush having the high resistance layer 2 and the low resistance layer 3.

When the resistivity of the obtained brush was measured, the high resistance layer 2 was 3.5 μΩ · m, and the low resistance layer 3 was 0.2 μΩ · m.
The resistivity is measured by molding each powder independently under the same conditions as described above, sintering, and machining to prepare a test piece having a size of 5 × 5 × 20 mm, and a current of 1 A in the direction of 20 mm. The voltage drop between 10 mm when flowing was measured and calculated by the following formula. Here, in the test specimen for measurement, the 20 mm direction was set to the direction perpendicular to the molding pressure.

Example 2
A process similar to that of Example 1 was performed except that a protrusion was formed on the high resistance layer, while a recess for fitting the protrusion was formed on the low resistance layer, and the protrusion and the recess were fitted and bonded. I got a brush.

Comparative Example 1
The high-resistance layer molding powder and the low-resistance layer molding powder obtained in Example 1 were separately filled in predetermined positions of the mold, and lead wires were further installed at predetermined positions. After integrally molding at a pressure of 392 MPa, the temperature is raised to 700 ° C. in 3 hours in a reducing atmosphere, sintered at 700 ° C. for 1 hour, and then machined into a predetermined shape, as shown in FIG. A brush having a high resistance layer 2 and a low resistance layer 3 of 16 × 15 × 7 mm was obtained.

When the surface of the obtained brush was cut across the high resistance layer 2 and the low resistance layer 3 and observed, the boundary between the high resistance layer 2 and the low resistance layer 3 could not be clearly confirmed. There was variation in the packing density between the powders.

  Next, immediately after the manufacture of the brushes obtained in Examples 1 and 2 and the brush obtained in Comparative Example 1 (at 0 hour), the voltage drop value of the lead wire embedded portion, the temperature was 80 ° C., and the humidity was 90%. The change with time in the voltage drop value of the lead wire embedded portion after the time was examined. The result is shown in FIG. 3, and the value at 0 hours in FIG. 3 is a value immediately after production. Note that the voltage drop value of the lead wire embedded portion is a value obtained by measuring the voltage drop between CD when a current of 200 A is passed between AB as shown in FIG.

As shown in FIG. 3, it is clear that the voltage drop value of the lead wire embedded portion is reduced in the brushes obtained in Examples 1 and 2 according to the present invention as compared with the brush obtained in Comparative Example 1. It is.
Separately from the above, the wear amounts of the brushes obtained in Examples 1 and 2 and the brush obtained in Comparative Example 1 were measured. As a result, the wear amount of the brush obtained in Example 1 is 1.4 mm, the wear amount of the brush obtained in Example 2 is 1.6 mm, and the wear amount of the brush obtained in Comparative Example 1 is 1.5 mm. The brushes obtained in Examples 1 and 2 had almost the same amount of wear as the brush obtained in Comparative Example 1.

  The amount of wear of the brush is a 1.8 liter diesel engine equipped with a 1.4 kW starter motor with a brush attached. The operation of turning on for 2 seconds and turning off for 28 seconds is one cycle, and this operation is performed for 10,000 cycles. (Test) It was determined from the difference between the size of the brush before and the size of the brush after 10,000 cycles.

1 is a cross-sectional view of a brush obtained in Example 1. FIG. 6 is a cross-sectional view of a brush obtained in Comparative Example 1. FIG. It is a graph which shows the relationship between leaving time and the voltage drop of a lead wire embedding part. It is the schematic which shows the measuring method of the voltage drop of a lead wire embedding part.

Explanation of symbols

1 Lead wire 2 High resistance layer 3 Low resistance layer 4 Adhesive

Claims (2)

  In a method of manufacturing a brush in which the sliding surface that contacts the commutator is formed of a low resistance layer and a high resistance layer, a lead wire is embedded in the powder for the low resistance layer or the brush piece for the low resistance layer and pressed. And forming a low resistance layer by fixing the lead wire, and then forming a high resistance layer on the upper surface. 2. The method for producing a brush according to claim 1, wherein the high resistance layer is a molded body which is adhered to the low resistance layer or formed by molding a powder on the low resistance layer.

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