JPS5826156B2 - Manufacturing method of electric brush material - Google Patents

Description

Detailed Description of the Invention Normally, electric brushes are required to have good rectification properties, low wear resistance, and no damage to the commutator surface, etc. A variety of material improvement studies are being carried out in line with the objectives.

However, with the recent development of electrical equipment, no one has been developed that completely satisfies the harsh operating conditions associated with it, and attempts to improve damage to the commutator surface from the material standpoint have not been sufficient. do not have.

When an electric brush operates normally, a uniform, chocolate-colored thin film of cuprous oxide is formed on the commutator surface, but if this film is damaged by roughening or cutting, it can cause creaks at the sliding interface. This causes phenomena such as noise and copper picking on the electric brush surface, resulting in spark generation and poor rectification.

Commutator damage can occur for a variety of reasons, but the most common cause is the abrasion resistance of the electric brush itself.

Conventionally, it has been known that the abrasion resistance of an electric brush depends on the ash content of its constituent materials, but there has been no detailed study of the correlation between the two.

In view of the above circumstances, the inventors conducted various studies on the relationship between ash content and abrasion resistance for electric brush materials made of natural graphite and synthetic resin binders, which have good rectification properties and abrasion resistance. As a result, it was discovered that the abrasion resistance of electric brushes significantly differs when the ash content of natural graphite used as a raw material reaches 0605φ, leading to the present invention.

That is, the present invention is characterized in that high-purity natural graphite powder with an ash content of 0.05% or less is kneaded with a synthetic resin binder, the mixed material is pulverized, and then subjected to pressure molding and heat treatment.

Normally, commercially available natural graphite has 1 to 2
Although it contains a large amount of ash, the present invention reduces this to 0.05.
A highly purified product with an ash content of 1% or less is selected and used as a raw material.

The form of graphite is preferably phosphor-like graphite and is preferably provided as a fine powder with a particle size of 250 mesh or less.

As the powder particle size increases, the mechanical strength of the resulting material decreases.

As the synthetic resin binder, initial condensates such as novolac type phenol resin, resol type phenol resin, urea resin, epoxy resin, polyimide resin, furan resin, etc. are suitable, and novolak type phenol resin initial condensate is particularly suitable. .

High-purity natural graphite powder with an ash content of 0.05% or less and a synthetic resin binder are mixed, and an appropriate organic solvent is added as needed and thoroughly kneaded.

The synthetic resin binder is blended in an amount of 30 to 60 parts by weight, preferably 40 to 50 parts by weight, based on 100 parts by weight of the raw natural graphite powder.

The kneaded material is sometimes subjected to roll treatment and then finely ground.

In this case, the pulverized particle size is desirably adjusted to 200 mesh or less.

The pulverized fine powder is then filled into a mold of a predetermined shape, and pressure molded at room temperature.

The molding pressure is preferably 2 tons A4 or more; if the pressure is too small, the mechanical strength of the resulting material will not improve.

The molded body is placed in a heater such as a hot air drying oven and heat-treated until the synthetic resin binder is completely cured.

The heat treatment temperature is preferably in the range of 120 to 180°C; at higher temperatures, the molded product may develop cracks, and at lower temperatures of less than 120°C, it takes a long time to harden.

The electric brush material obtained in this way has a specific resistance of 800
0~1000010000p Bending strength 400kg/cr
In addition to having good rectification properties and mechanical properties of A or better, it also has a remarkable effect of improving wear resistance compared to electric brush materials produced by conventional methods.

Therefore, damage to the commutator surface during use is effectively prevented and normal and smooth operation is ensured.

Hereinafter, the present invention will be explained based on examples.

Example Commonly used phosphor-like graphite powder with a particle size of 250 mesh or less (ash content 1.5%) is treated with high purity to obtain 0.0
The ash content was adjusted to be 1%, 0.05%, 0.08%, 0.1%, 0.25%, and 0.65%.

Novolak type phenol formaldehyde resin initial condensate (particle size 250
45 parts by weight (less than mesh) were blended and thoroughly kneaded at room temperature for 2 hours.

The kneaded material had a partially agglomerated form.

The mixed material is crushed into a fine powder of 200 mesh or less using a pulverizer (after pulverizing, the length is 280 rran, the width is 110 rran,
Filled into a mild steel mold with a height of 80 Mn, 2.5 ton
Pressure molding was carried out at room temperature by applying a pressure of /crA.

As a result, the length is 280 rrvn, the width is 110y++m,
A brick-like block body with a thickness of 30rrtIrL was formed.

The obtained block molded body was dried in a hot air drying oven (150
The resin binder was completely cured by heat treatment at a temperature of .degree. C. for 60 hours.

At this time, both the outer surface and the inner core of the block molded body (no cracks were observed and the structure was uniform).

Table I shows a comparison of the general physical properties measured for each electric brush material manufactured in this manner and the sliding test results of the electric brush manufactured from the material.

In addition, as an example of a conventional material, a product similarly manufactured using phosphorescent graphite powder (ash content 1.5%) that is not subjected to high purity treatment (results of measurements made using this method are also included).

For the sliding test, commutator: copper simulated commutator, current density: DC 2
．． 5A/crA, rotation speed: 3000r, p, m, peripheral speed: 39? ? Z/sec, electric brush pressure 600'? /
Performed under the conditions of ctfL, sliding time: 500 hr,
The degree of damage to the commutator surface was determined based on the level of vibration noise, the condition of the coating on the commutator surface, the condition of the electric brush sliding surface, and the wear resistance.

If the electric brush material does not have wear resistance (it exhibits a normal sliding condition with no cracking or vibration noise (squeak), a homogeneous chocolate-colored thin layer is formed on the entire surface of the commutator surface after the test,
Furthermore, the sliding surface of the electric brush forms a mirror surface with no evidence of copper picking.

The overall wear resistance is determined semi-quantitatively by the extent of the area of the copper powder adhered to the electric brush sliding surface Q.

Claims (1)

[Claims] 1. A method for producing an electric brush material, which comprises kneading high-purity natural graphite powder with an ash content of 0.05φ or less with a synthetic resin binder, pulverizing the kneaded material, and then subjecting it to pressure molding and heat treatment.