RU2166817C1 - Compound for manufacturing electrical machine brushes - Google Patents

Abstract

FIELD: brushes for electrical machines including those used in railway and municipal transport. SUBSTANCE: compound incorporates coaltar pitch, furnace and thermal black, pitch coke, and phenol-formaldehyde resin, proportion of ingredients being as follows, mass percent: coal-tar pitch - 36-38; furnace black - 21-23.5; thermal black - 25-29.5; pitch coke - 5-6; phenol-formaldehyde resin - 3-4. EFFECT: improved environmental friendliness of manufacture and improved quality of brushes. 2 tbl, 2 ex

Description

 The invention relates to electrical engineering and relates to compositions for the manufacture of brushes for electric machines, for example brushes for engines of railway and public transport.

 A known composition for the manufacture of brushes containing carbon black (soot) and a binder - coal tar pitch in an amount of 60 - 65 wt.% In relation to the filler (ed. Certificate. USSR N 122801, MKI H 01 R 43/12).

 The composition provides the formation of the structure of soot aggregates and interconnecting filiform pores, which, in turn, leads to good commutation of the brushes during their testing and operation on electric machines. The specified structure is formed in the process of joint vibration grinding of raw materials.

 The disadvantage of the composition is the instability of the physical and mechanical characteristics of the material.

 Also known is a composition for the manufacture of brushes containing carbon black (furnace soot), coal tar pitch and phenol-formaldehyde resin in an amount of 2 wt.% To pitch. ("On the properties of carbon-graphite materials based on modified pitch" Chuparova L.D., Nazina G.A., Suslina V.I., Konstantinova D.S. - Non-ferrous metals, 1986, N 11, pp. 47-49 - prototype ) The introduction of phenol-formaldehyde resin increases the strength characteristics of the material.

 Brushes made from this composition are wear resistant and commute well.

 The disadvantage of this composition is the instability (dispersion) of wear of the brushes mounted on the engine, which affects the operation of the traction motor itself during operation.

 In addition, the fine grinding of raw materials, which is used in the manufacture of this composition, leads to environmental degradation due to the increased dust content in the production room. The composition of dust includes a carcinogenic component - pitch.

 The technical result of the invention is to improve the ecology of the production of brushes and their operational properties by reducing the spread of wear of the brushes and improve commuting properties.

The technical result is achieved by the fact that the known composition for the manufacture of brushes for electric machines, containing coal tar pitch, furnace soot and phenol-formaldehyde resin, additionally contains pitch coke and thermal soot in the following ratio of components, wt.%:
Coal tar pitch - 36 - 38
Furnace soot - 21 - 23.5
Thermal soot - 25 - 29.5
Pitch coke - 5 - 6
Phenol formaldehyde resin - 3 - 4
The industrial applicability of the proposed technical solution is undeniable, since the main consumers of electric machine brushes made using the proposed technical solution are city and rail transport (trolleybuses, trams, electric trains).

 The brushes provide not only the necessary mileage of the vehicle, but also improve the technical condition of the engine, the quality of its tuning in switching terms, the conditions of its operation.

 The invention consists in the following. Based on the joint vibration grinding in the ball vibratory mills of the filler and the binder, a whole class of brushes has been created that ensure the operation of traction engines in urban and railway transport.

Material competitively with the brushes of the same purpose, issued by the world's largest firms: Morganayt, La Karbon, Hoffman & ^Co et al.

 The main disadvantage of brushes is the instability of the electrophysical and wear characteristics of brushes in one set mounted on the engine.

 This leads to the following consequences: uneven wear of the brushes occurs, in connection with which the pressure on the unevenly worn brushes changes, due to which there is a violation of the current distribution between parallel connected brushes and under some of them arcing occurs. This ultimately leads to a noticeable disruption of the brush-collector assembly. ("The study of the dependence of the wear of EG-61 brand brushes on operating conditions" B. V. Sizov, G. I. Krylov. Proceedings of the All-Union Scientific Research and Design Institute of Electric Coal Products: Issue 3. M .: Energy, 1975 pg. 229-234). The instability of the properties is due to the fact that the structure of the brush material formed by the joint vibration grinding of raw materials can vary in the same volume from porous to soot aggregates, from soot aggregates to monolithic, which significantly affects the wear resistance of the brushes. ("Carbon materials A.S. Fialkov. M.: Energy, 1979, p. 74).

 The formation of the structure of the brush material, which has the advantages of a material obtained by vibration grinding, but devoid of the main drawback, namely, a significant dispersion of electrophysical and wear indicators, is an urgent task.

 This problem is solved by introducing into the composition containing coal tar pitch, furnace soot and phenol-formaldehyde resin, in addition coke pitch and thermal soot. In this case, the operation of vibration grinding from the technological process is excluded, which leads to improved ecology.

 The coke pitch fraction (-07) added to the composition restores the adsorption capacity of the filler to that value which is characterized by vibro-crushed filler (Table 1). Adsorption capacity was evaluated by potentiometric titration, which is based on the adsorption of iron ions from solutions of the redox system of 2 and 3 valence iron (method NIIEI).

 The structure of soot aggregates obtained by vibration grinding is characterized by filiform pores uniformly distributed in the material. This makes it possible to uniformly impregnate the material.

 For the formation of similar filiform pores in the proposed composition, formed without prior vibration grinding of raw materials, thermal soot is introduced. The shrinkage of the material based on furnace black and binder and on the basis of thermal black and binder differs by 15-20% during firing and graphitization, due to this difference, filiform pores are formed.

 The following are specific examples of the manufacture of the composition.

Example 1 (prototype). Carbon black (furnace soot) of the PM-16E grade (TU 3831515-04-92), coal tar pitch with a softening temperature of 120 ^o C, sieved through a screen with a mesh size of 50x50 mm and phenol-formaldehyde resin (TU 6-05-1370-90) in ratio (wt.%): 59.9: 38.9: 1.2 was loaded into a vibratory mill M400. Raw materials were subjected to joint grinding for 40 min at a vibration mill vibration amplitude A = 5.0 mm. The mixture was unloaded, plasticized on two-pair rollers at a temperature of 220 ^o C. The resulting mass was crushed on a DM-300 crusher, sieved through 025 mesh, averaged in a 400 L Z-shaped mixer. Blocks of 115x75x30 mm in size were pressed from the press powder at a pressure of 100 ± 5% MPa. The blocks were fired in a tunnel furnace at a final temperature of 1200 + 20 ^o C, then they were subjected to graphitization at a temperature of 2800 ^o C. Billets were cut from graphitized blocks, in which hardness and electrical resistivity were determined (GOST 30262-95).

 The preforms were impregnated, and the amount of impregnation introduced (in wt.%) Was determined by weighing, after which brushes were made that were tested on a bench-mounted traction motor NB-418K according to the FEO 005 897 method. The test results obtained in Example 1 are given in Table 2.

Example 2. Carbon black (furnace soot) grade PM-16E (TU 3831515-04-92) and thermal carbon black grade T-900 ((GOST 7885-86) in the amount of 23.4 wt.% And 29.5 wt.% respectively loaded into a Z-shaped mixer. Added crushed and sieved through a grid 07 coke pitch (TU 14-7-80-86) in the amount of 5.9 wt.%. Powders were mixed for 20 minutes, Then the binder was loaded into the mixer: crushed and sieved through a 07 mesh coal tar pitch with a softening point of 65 ^o C (GOST 10200-83) in an amount of 37.5 wt.% and sieved through a 01 mesh phenol-formaldehyde resins TFP 011L (TU6-05-1370-90) in an amount of 3.7 wt.%.

The raw materials were mixed for 45 minutes. The mixture was unloaded, plasticized on a twin-screw mixer at a temperature of 125 - 140 ^o C. The resulting mass was ground on a crusher DM-300, sieved through a mesh 045, averaged in 400 l of a Z-shaped mixer. Blocks of 115x75x30 mm in size were pressed from the press powder at a pressure of 100 ± 5% MPa. The blocks were fired in a tunnel furnace at a final temperature of 1200 ± 20 ^o C, then they were subjected to graphitization at a temperature of 2800 ^° C. Billets were cut from graphitized blocks, in which hardness and electrical resistivity were determined (GOST 30262-95).

 The obtained preforms were impregnated and the amount of impregnation introduced (by weight%) was determined by weighing, after which brushes were made that were tested on a bench-type traction motor NB-418 K using the FEO method 005 897. The test results obtained in example 2 are given in table 2 .

Example 3
Carbon black (furnace soot) of the PM-16E grade (TU 3831515-04-92) and thermal carbon black of the T-900 brand ((GOST 7885-86) in the amount of 23.3 wt.% And 28.9 wt.%, Respectively, were loaded into Z-shaped mixer: 5.8 wt.% Coke pitch (TU 14-7-80-86), crushed and sieved through a wire mesh 07, was added. Powders were mixed for 20 minutes, then binders were loaded into the mixer: crushed and sieved through the net 07 coal tar pitch with a softening temperature of 65 ^o C (GOST 10200-83) in the amount of 38.0 wt.% and sieved through the grid 01 phenol-formaldehyde resin SFP 011L ( TU6-05-1370-90) in an amount of 4.0 wt.%.

The raw materials were mixed for 45 minutes. The mixture was unloaded, plasticized on a twin-screw mixer at a temperature of 125 - 140 ^o C. The resulting mass was ground on a crusher DM-300, sieved through a mesh 045, averaged in 400 l of a Z-shaped mixer. Blocks of 115x75x30 mm in size were pressed from the press powder at a pressure of 100 ± 5% MPa. The blocks were fired in a tunnel furnace at a final temperature of 1200 ± 20 ^o C, then they were subjected to graphitization at a temperature of 2800 ^o C. Billets were cut from graphitized blocks, in which hardness and electrical resistivity were determined (GOST 30262-95).

 The obtained blanks were impregnated and the amount of impregnation introduced (in wt.%) Was determined by weighing, and then brushes were made that were tested on a bench-mounted traction motor NB-418 K using the FEO method 005 897. The test results obtained in example 3 are given in table 2 .

 As follows from the analysis of the data obtained, presented in table 2, brushes made from the proposed composition are characterized by a much smaller variation in values according to electrophysical indicators (in hardness and electrical resistivity) and, which is especially important when operating brushes, in wear in the brush set: coefficient the variations are 3-4 times lower than for brushes made from a known composition. The obtained characteristics guarantee a significantly more stable operation of the brush-collector assembly, which is also manifested in the commuting properties of brushes: the commutation index is higher for brushes made from the proposed composition. At the same time, the activation of raw materials, i.e. vibration grinding.

This leads to a decrease in dust content in the production room by 2.5 times (8-9 mg / m ³ - the content of carbon dust in the air according to the known technology; 3 - 4 mg / m ³ - the content of carbon dust in the air when using the new technology. MPC - 6 mg / m ³ ).

Claims (1)

Composition for the manufacture of brushes for electric machines, containing coal tar pitch, furnace soot and phenol-formaldehyde resin, characterized in that it additionally contains pitch coke and thermal soot in the following ratio of components, wt.%:
Coal tar pitch - 36 - 38
Furnace soot - 21-23.5
Thermal soot - 25 - 29.5
Pitch coke - 5-6
Phenol formaldehyde resin - 3 - 4

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