JP2006320067A - Process of metal graphite brush - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reliable process of a metal graphite brush which suppresses increase in the specific resistance of the brush in hot humid atmosphere without increasing brush abrasion. <P>SOLUTION: This is a process of a metal graphite brush, in which metal or alloy that is larger in ionization tendency than copper is added to the composites of copper and graphite, in a metal graphite brush which contains a metallic sulfide solid lubricant, with its chief components copper and graphite, and these are baked at a temperature of 350-500°C after mixing and molding. Especially, it is to be desired that the obtained metallic graphite brush should contain 1-5 wt.% metallic sulfide solid lubricants, and that the metal or alloy that is larger in ionization tendency than copper should be one or more kinds out of manganese, iron, nickel, zinc, and tin. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a metallic graphite brush for use in a rotating electrical machine used for a generator, an electric motor, etc., particularly for an automobile electric motor.

Recent DC motors for rotating electrical machines are required to reduce lead used as lubricants and oxidation inhibitors in the past due to environmental requirements.
By reducing the lead, the specific resistance increases in high temperature and high humidity. Especially, brushes used in starter motors for automobiles may cause a problem of breakage due to the large amount of heat generated when a large current is applied. There is.

As a measure for improving the above, there is a method of blending a copper-zinc alloy instead of lead as described in Patent Document 1 to suppress a change in specific resistance at high temperature and high humidity.
JP 2000-221607 A

  However, the metal graphite brush as described above may have poor lubricity and increase brush wear.

  The present invention provides a highly reliable method for producing a metal-graphite brush that suppresses an increase in specific resistance of a brush in high temperature and high humidity without increasing brush wear.

The present invention is a metal graphite brush comprising copper and graphite as main components and containing a metal sulfide solid lubricant, and further adding a metal or alloy having a higher ionization tendency to copper to the composition, and mixing and molding them. Then, it is related with the manufacturing method of the metal graphite brush characterized by baking at the temperature of 350-500 degreeC.
The present invention also relates to the above-described method for producing a metal graphite brush, wherein the metal sulfide solid lubricant is contained in an amount of 1 to 5% by weight with respect to the obtained metal graphite brush.
Furthermore, this invention relates to the manufacturing method of the said metal graphite brush whose metal or alloy whose ionization tendency is larger than copper is 1 or more types of manganese, iron, nickel, zinc, and tin.

  The metallic graphite brush obtained by the production method of the present invention suppresses an increase in specific resistance of the brush in high temperature and high humidity without increasing brush wear, is excellent in safety, and is extremely suitable industrially.

  In the present invention, the addition amount of the metal or alloy having a higher ionization tendency than copper is preferably 0.05 to 2% by weight, more preferably 0.05 to 1.5% by weight, and further 0.05 to 1% by weight. preferable.

As the metal or alloy having a higher ionization tendency than copper, it is preferable to use a metal such as manganese, iron, nickel, zinc, or tin, or an alloy in which two or more of these are mixed.
There is no particular limitation on the particle size of a metal or alloy having a higher ionization tendency than copper, but it is usually preferable to use a particle having an average particle size of about 0.1 to 100 μm.

  Moreover, in this invention, it is preferable to use the electrolytic copper powder whose average particle diameter is 75 micrometers or less for the copper used as the main component of a metal graphite brush from the point of an output improvement and a mechanical strength improvement. On the other hand, it is preferable to use natural graphite having developed crystals and good lubricity. Although there is no restriction | limiting in particular about the particle size of graphite, It is preferable to use the thing of the particle diameter whose average particle diameter is about 30-200 micrometers normally.

As a component other than the above, it is preferable to blend a metal sulfide solid lubricant such as molybdenum disulfide and tungsten disulfide from the viewpoint of lubricity.
The content of the metal sulfide solid lubricant is preferably 1 to 5% by weight, and more preferably 2 to 4% by weight with respect to the obtained metal graphite brush.

The particle size of the metal sulfide solid lubricant is not particularly limited, and it is usually preferable to use a particle size having an average particle size of about 0.5 to 50 μm.
The average particle diameter can be determined by a method defined by a general particle size distribution measurement method using a laser diffraction method.

  The metallic graphite brush is uniformly mixed with a blender with the above components, then molded with a molding press at a pressure of 200 to 600 MPa, and then sintered in a reducing atmosphere containing hydrogen to have a predetermined shape, Obtained by machining to dimensions.

  The maximum sintering temperature is 350 to 500 ° C., preferably 400 to 500 ° C., more preferably 450 to 500 ° C. If it is less than 350 ° C., there is a problem in lubricity, and 500 ° C. If it exceeds, the effect of suppressing the increase in specific resistance is small.

Comparative Example 1
80% by weight of natural graphite powder (trade name CB-150, manufactured by Nippon Graphite Industry Co., Ltd.) having an average particle size of 35 μm and 20% by weight of phenol resin (trade name VP-11N, manufactured by Hitachi Chemical Co., Ltd.) After mixing, a resin-treated graphite having a particle size of 300 μm or less was obtained by curing at 70 ° C. for 10 hours to form granules.

  Next, 42% by weight of this resin-treated graphite, 55% by weight of electrolytic copper powder having a mean particle size of 35 μm (trade name CE-25, manufactured by Fukuda Metal Foil Powder Co., Ltd.) and molybdenum disulfide 3 having a mean particle size of 5 μm The weight% was weighed and mixed for 50 minutes to obtain a mixed powder in which all components were uniformly dispersed.

  Thereafter, the obtained mixed powder was molded at a pressure of 392 MPa with a copper stranded wire pigtail molding press, heated to 700 ° C. in a reducing atmosphere containing hydrogen in 3 hours, and held at 700 ° C. for 1 hour. Sintered. Next, the obtained sintered body was machined into a predetermined shape and size to obtain a metal graphite brush.

Example 1
42% by weight of resin-treated graphite obtained in Comparative Example 1, 53% by weight of electrolytic copper powder (trade name CE-25, manufactured by Fukuda Metal Foil Powder Co., Ltd.) having an average particle size of 35 μm, and two particles having an average particle size of 5 μm 3% by weight of molybdenum sulfide and 2% by weight of zinc having an average particle size of 30 μm were weighed and mixed for 30 minutes to obtain a mixed powder in which all components were uniformly dispersed.
Hereinafter, a metal graphite brush was obtained through the same process as Comparative Example 1 except that the sintering temperature was 500 ° C.

Example 2
42% by weight of resin-treated graphite obtained in Comparative Example 1, 54.95% by weight of electrolytic copper powder (trade name CE-25, manufactured by Fukuda Metal Foil Powder Co., Ltd.) having an average particle size of 35 μm, and 5 μm in average particle size 3% by weight of molybdenum disulfide and 0.05% by weight of zinc having an average particle size of 30 μm were weighed and mixed for 30 minutes to obtain a mixed powder in which all components were uniformly dispersed.
Hereinafter, a metal graphite brush was obtained through the same process as Comparative Example 1 except that the sintering temperature was 500 ° C.

  Next, the resistivity, weight and temperature of the metallic graphite brush obtained in Examples 1 and 2 and Comparative Example 1 were left in an atmosphere of 80 ° C. and 95% humidity for 100 hours, and the specific resistance after 100 hours was measured. Examined. The results are shown in Table 1.

  The resistivity was measured by machining each metal graphite brush obtained above to produce a 3 × 6 × 12 mm test piece, and a current of 2 A was passed in the direction of 12 mm between 5 mm. The voltage drop was measured and calculated by the following formula. Here, the test specimen for measurement was set to a 12 mm direction molding pressure perpendicular direction.

但し、Ｓは断面積（ｍ^２）、Ｖは電圧降下、Ｉは電流及びＬは電圧降下測定スパンである。

However, S is a cross-sectional area (m ² ), V is a voltage drop, I is a current, and L is a voltage drop measurement span.

As shown in Table 1, in the metal graphite brushes of Examples 1 and 2, the resistivity after leaving at a temperature of 80 ° C. and a humidity of 95% was almost the same as that before leaving, but the metal of Comparative Example 1 It was confirmed that the resistivity after leaving the graphite brush at a temperature of 80 ° C. and a humidity of 95% increased by about 4 times the resistivity before leaving.

Claims (3)

  .   2. The method for producing a metal graphite brush according to claim 1, wherein the metal sulfide solid lubricant is contained in an amount of 1 to 5% by weight based on the obtained metal graphite brush. The method for producing a metallic graphite brush according to claim 1 or 2, wherein the metal or alloy having a higher ionization tendency than copper is one or more of manganese, iron, nickel, zinc and tin.