JPH0666147B2 - Brush for signal transmission - Google Patents

Description

The present invention relates to the provision of a brush suitable for signal transmission.

It goes without saying that contact electric wires such as insulating trolleys are widely used for power supply to mobile devices, but recently, cases of using this kind of electric wires for signal transmission are increasing.

As is well known, this type of contact electric wire supplies electric power to a mobile device by sliding a brush while pressing a brush on an exposed conductor surface continuous in the length direction.

For such brushes, a metal graphite material generally called a carbon brush is adopted, and in order to reduce wear as much as possible, a solid lubricant (molybdenum disulfide, tungsten disulfide) is added to improve lubricity. It had been.

However, the addition of this solid lubricant increases the contact resistance of the brush with respect to the conductor to be slid, and this is not a serious problem for power with a large voltage and current, but it does occur for signals with a small voltage and current. Solid lubricants are harmful substances for proper signal transmission.

In view of the conventional problems, as a brush for signal transmission,
A metallic graphite material that does not contain a solid lubricant has been used.

[Problems to be solved by the invention]

Signal transmission, which has been targeted in the past, is a random system that handles electromagnetic relay level signals, the frequency of operation of the device is low, and it operates by sending signals only when necessary, and therefore wear is reduced. Therefore, the above-mentioned metal graphite material without solid lubricant can be used.

However, distant monitoring and control devices using semiconductors are often adopted for recent mobile devices, and most of them are cyclic transmission systems, and generally those that constantly scan the monitoring items and send the information. It has become.

In the case of the cyclic signal transmission method, the signal transmission / reception unit is made contactless by a semiconductor, and the signal is sequentially and repeatedly carried out at a high speed.

With such a high frequency of use, in the metal graphite material without such a lubricant, a large amount of abrasion powder is generated due to an increase in the sliding amount of the brush with respect to the sliding conductor, and most of the abrasion powder is metal. It is an oxide, and when it adheres to and accumulates on the sliding surface and is caught in the sliding portion of the brush, it may increase the contact resistance and cause a voltage drop, or may be accompanied by an instantaneous disconnection.

The voltage drop caused by such a contact resistance is small, and it is not a serious problem in the case of power for which both voltage and current are large, but noise is generated in the case of a signal handling a weak current at a low voltage of about 12 V and several mA. It may cause a malfunction of the device, which is further amplified by a momentary disconnection.

When power is supplied, the metal oxide can be destroyed by the arc generated by high voltage and current, but low voltage,
In the case of signal transmission of electric current, such metal oxide destruction is not performed, and as it is, abrasion powder harmful to transmission still remains, and correct signal transmission cannot be performed.

In the conventional current collecting brush, in order to suppress the adhered substances on the sliding surface to a certain amount or less, chrome, iron,
Others have added self-polishing properties by adding hard metal substances, but the contact resistance to the sliding conductor of the brush is increased by the fact that the sliding surface is damaged by such hard metal substances. It was difficult to use for signal transmission.

In view of the present situation, the present invention has a contact resistance reduced by suppressing the use of a lubricant that is harmful at low voltage and current, and can easily remove the abrasion powder that is inevitably generated in the sliding process, and thus the signal It does not provide the optimum brush for transmission.

[Means for solving problems]

As a result of the inventors' earnest research on a signal transmission brush that solves the above problems and achieves the object, it is composed of a metal graphite containing no solid lubricant, and the metal graphite contains copper 7
9 to 89% by weight, tin 7 to 13% by weight, lead 2 to 5% by weight, carbon 1 to 7% by weight, and silicon carbide powder in an amount of 0.1% by weight to 1% by weight. It was found that the one added in the ratio of is effective.

The metallic graphite material contains copper, tin, lead and carbon,
Copper is used to ensure conductivity, tin is used to adjust the curing, and lead and carbon are used to provide the minimum necessary lubricity.

The preferred composition is as shown below.

Copper: 79 to 89% by weight Tin: 7 to 13% by weight Lead: 2 to 5% by weight Carbon: 1 to 7% by weight The silicon carbide powder to be added functions as an abrasive, and a preferable addition amount is 0.1 to 10. It is 1% by weight. That is, when the amount is less than 0.1% by weight, the polishing effect is not remarkable, and when the amount is more than 1% by weight, the brush itself becomes very hard, which is not easy to process and may be damaged by a light impact. This is because the tap hole may break when tapping is applied to attach the lead wire.

[Action]

The silicon carbide powder after molding is in a dry state and mixes with the wear powder appropriately during the wear process that occurs during sliding on the sliding conductor, which enhances the peelability of the wear powder from the sliding conductor and allows the brush to travel. This facilitates scattering from the sliding surface.

Moreover, since the powder of silicon carbide acts as an abrasive grain of the grindstone,
Not only does it help oxides that adhere to the sliding surface to peel off and fall off, but it is also polished so as to maintain a fresh conductor surface.

Further, since silicon carbide is a powder, the surface to be slid is hardly roughened.

〔Example〕

 A preferred embodiment will be described below.

Copper, tin, lead, carbon and silicon carbide were blended in the following formulation, and the obtained mixed powder body was embossed, and then a brush having a predetermined shape was manufactured.

Copper: 84% by weight Tin: 10% by weight Lead: 3% by weight Carbon: 2.5% by weight Silicon carbide: 0.5% by weight Sliding under the following conditions in order to confirm the performance of the brush having the above composition. The test was conducted and no noise was found in the transmitted signal.

Sliding conductor: Trolley wire whose sliding surface is electrolytic copper Signal voltage: 12v Signal current: 10mA Sliding speed: 60m / min Sliding distance: 50m 15,000 times reciprocating under the above test conditions, solid lubricant (two Molybdenum sulfide,
We also tested a brush made of metallic graphite material added with (tungsten disulfide) and a brush made of metallic graphite without the solid lubricant, but in many cases, noise was often found in the transmission signal. It was

〔The invention's effect〕

As is clear from the above description, according to the brush for signal transmission of the present invention, the contact resistance is small and the abrasion powder unavoidably generated by sliding is efficiently removed, and the low voltage,
Even though it is an electric current, it can wipe out the generation of noise, and since the added silicon carbide is in a very small amount and can be manufactured in the same manner as a conventional brush,
The actual profit is quite large, such as contributing to mass production and being economical.

Claims (1)

[Claims] 1. A metal graphite containing no solid lubricant, wherein the metal graphite contains 79 to 89% by weight of copper and 7% of tin.
-13% by weight, 2-5% by weight of lead, 1-7% by weight of carbon, and 0.1% by weight of silicon carbide powder.
A brush for signal transmission, characterized in that the brush is added in an amount of 1% by weight or less.