RU2061285C1 - Method for manufacturing electrical machine brushes - Google Patents

Abstract

FIELD: electrical engineering; brushes for machines operating under unfavourable commutation conditions, under heavy vibration and shock loads, such as traction motors. SUBSTANCE: pills and binders of prepared composition are additionally pelletized at 250-320 C prior to compression, cooled down, and crushed; content of particles in powder, mass percent: particle size smaller than 63 mcm - 15-80; particles measuring 63-250 mcm - 19-55; those measuring more than 250 mcm - 1-30; proportion of components in compressed composition, respectively, mass percent: wood filler - 3-61; carbon filler - 3-55; bonder - 36-42. EFFECT: improved quality of brushes. 1 tbl

Description

 The invention relates to electrical engineering and relates to methods for manufacturing brushes for electric machines operating in difficult switching conditions, in the presence of significant vibration and shock loads, for example, traction electric motors of electric locomotives.

A known method of manufacturing brushes for electric machines based on carbon and wood fillers, as well as a binder, in which the carbon filler and the binder are compositionally combined into granules of a certain fractional composition, and particles of wood filler in a ratio of 4: 100 are mixed with granules, then the composition is pressed and subjected heat treatment [1]
Brushes made by a known method have disadvantages associated with the manifestation of the negative effect of brushes on the collector (covering collector copper) due to the high microhardness of the brush material.

A known method of manufacturing brushes for electric machines from press compositions in which 5-40 wt. wood filler and 60-95 wt. carbon filler compositionally combined into granules, and the ratio of the particle size of the carbon filler to the particle size of the wood filler in the granule is in the range of 0.8-1.2. First, in the known method prepare compositionally combined granules, and then they are mixed with a binder [2]
The disadvantages of this method are the complexity of the technological cycle due to the separate preparation of granules and a binder, which complicates the mechanization of the process and leads to low stability of the characteristics of the brushes and to the deterioration of the contact properties of the brushes.

The proposed method allows to eliminate the noted drawbacks and lies in the fact that in the method of manufacturing brushes for electric machines from a press composition containing carbon and wood fillers and a binder, comprising a composite combination of fillers into granules, mixing them with a binder, pressing, heat treatment and impregnation, the combined composition formed granules and binder prior to compression is further granulated at a temperature of 250-320 ^{° C,} cooled and subjected to grinding, the contents portion (Wt.) To press powder is
size less than 63 microns 15-80
size 63-250 microns 19-55
more than 250 microns in size 1-30, and the ratio of components in the press composition is selected, respectively, wt.

wood filler 3-61
carbon filler 3-55
Binder 36-42.

Research has established that at temperatures granulation lower than 250 ^{° C,} for example in a screw mixer, there is no formation of granules, and at temperatures above 320 ^C. complicated work mixer and obtaining granules of the tight adhesion of the pellets to the heated parts of the mixer, followed by coking of granules and stopping the granulation process.

 The content of particles in the press powder after grinding the chilled granules depends mainly on the type of grinding equipment and is selected for specific operating conditions of electric machines.

 When the content of particles in the press powder and the ratio of the components in the press composition exceeding the specified limits, the characteristics of the brushes when working on electric machines deteriorate.

PRI me R. For the preparation of the press composition, carbon filler (carbon black PM805E GOST 7885-85), wood filler (wood coniferous flour grade 180 GOST 16362-86) and a solid binder (high-temperature coal tar pitch brand "T" TU FEO.054.992) are used. Fillers taken in various ratios (options 1-5) are combined into granules and mixed with a binder simultaneously in a CBM 40/2 type vibratory mill for 45-60 minutes. Then half of the press composition is molded into blocks at a specific pressure of 1000 kgf / cm ² with an apparent density of 1.20-1.22 g / cm ³ . Blocks calcined at 1200 ^{° C} in a box furnace, graphitizable at 2800 ^{° C,} made from a semifinished blank, which is subjected to impregnation with furfuryl alcohol and reinforce brush (embodiments 1-5). The other half molding composition is subjected to further granulation in a screw mixer CH-100 at temperatures of 250-320 ^{° C,} cooled and subjected to grinding in a hammer-mill MM 300 (embodiment 6). The particle content (wt.) In the press powder is
size less than 63 microns 15
size 63-250 microns 55
size over 250 microns 30
Part of the powder ground on DM-300 is ground in a SM2 SM-493A mill (option 7). The particle content (wt.) In the press powder is
size less than 63 microns 80
size 63-250 microns 19
size over 250 microns 1
Blocks are pressed from the press powder at a specific pressure of 1200 kgf / cm ² , with an apparent density of 1.34-1.36 g / cm ³ (option 7), 1.30-1.32 g / cm ³ (option 8). Blocks calcined at 1200 ^{° C} and graphitizable at 2800 ° ^C. From the semifinished product is manufactured preforms which are impregnated with furfuryl alcohol (embodiment 8) and a mixture of furfuryl alcohol with fospoliolom (variant 7).

 The manufactured brushes of options 1–8 were tested on a UK installation (coefficient of friction) and on traction electric motors AL4846eT of electric locomotives ChS2T (average wear of brushes, condition of the collector). The test results are presented in the table.

As follows from the presented results, the application of the proposed method allows to realize the following advantages in comparison with known methods:
the coefficient of friction of brushes on the collector is reduced by 10-30%;
the wear of brushes on electric machines decreases 1.1-2.0 times;
collector condition improves, covering and darkening of collectors is eliminated;
reduced costs for materials for the manufacture of brushes through the use of wood filler obtained from waste wood.

Claims (1)

A method of manufacturing brushes for electric machines from a press composition containing carbon and wood fillers and a binder, comprising combining the fillers into granules, mixing them with a binder, pressing, heat treatment and impregnation, characterized in that the composite granules and binder formed before pressing are additionally granules and binder prior to compression is further granulated at 250 320 ^o C, cooled and milled, the particle size of the content in the powder press It is by weight. Less than 63 microns 15 80
63 250 μm 19 55
Over 250 μm 1 30
and the ratio of components in the press composition is, wt. Wood filler 3 61
Carbon filler 3 55
Binder 36 42

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