RU81921U1 - CONTACT DETAIL - Google Patents

Abstract

A contact part made of a layered composite based on graphite, characterized in that the base is made in the form of a spatial body, a layer of pyrolytic carbon with a thickness of 100-150 microns is deposited on the surface of the substrate, an additional metal layer with a thickness of 50-100 microns is deposited on non-contacting surfaces, and as applied metal, for example, copper, nickel, silver are used.

Description

The utility model relates to electrical engineering, primarily for the manufacture of electrical contacts for switching low currents. It can be used in electromechanical relays, which require high reliability and resource.

A distinctive feature of the conditions in which low-voltage devices operate is a high frequency of contact operation at significant shock loads, high power of electric switching current, and high chemical and mechanical pollution of the working environment. Very modern requirements are imposed on modern materials from which contact details are made. Contact materials should have significant hardness and strength, and low deformability at high temperatures, a slight tendency to weld and adhere, high resistance to oxidation and electrical erosion, and at the same time good thermal conductivity and electrical conductivity.

Known contact details made of graphite with the addition of silver in a ratio of 35-40% of the mass. silver, the rest is graphite. (Powder metallurgy. Materials, technology, properties, applications: Handbook / Under the editorship of I.M. Fedorchenko. -Kiev: Naukova Dumka, 1985, p. 422).

The disadvantage of such contacts is the significant likelihood of welding to the reciprocal contacts due to the rather high concentration in the composition of the metal component (silver), as well as the high cost of contact details.

These disadvantages are eliminated by contact inserts known from the patent for a trolley bus contact insert made in the form of a plate of pressed powder graphite composite material with a working part corresponding to the contact wire profile, made in two layers, with the top layer having a working surface corresponding to the contact wire profile , made of composite material based on graphite and is 65-70% of the insert volume, and the bottom layer is made of composite material on the base ove graphite with a metal additive in the form of powder with particle size not exceeding 150 microns, and 30-35% by volume of the insert (RF application №97109406, publ. 1999 YG).

Graphite, which is part of the material, protects the parts in the sliding contact from sticking of metal and welding under the action of adhesion forces, especially at elevated temperatures and sparks slipping. However, contact inserts made of such a material have increased oxidizability and insufficient electrical conductivity due to the high content of graphite.

To eliminate these drawbacks (increasing the resistance of contact to oxidation and increasing electrical conductivity), a contact part made of a layered composite based on graphite is proposed, the base being made in the form of a spatial body, a layer of pyrolytic carbon with a thickness of 100-150 μm is deposited on the surface, additionally a non-contacting surface is coated with a metal layer 50-100 μm thick, and, for example, copper, nickel, silver are used as the deposited metal.

The presence of a metal component in the contact zone increases the electrical conductivity of the contact parts, the graphite base reduces the likelihood of setting (welding) with the reciprocal contact part, which leads to a decrease in wear rate on the one hand

both contacting surfaces of the parts, on the other - to reduce the likelihood of false signals when the relay is turned on. In addition, the inventive contact part ensures the achievement of an additional result, which consists in reducing the cost of manufacturing a contact part due to a significant reduction in the content of expensive silver.

The design of the claimed contact details is illustrated by illustrative material, where the numbers indicate the following positions: 1 - graphite base, 2 - contact surface with pyrolytically deposited carbon; 3 - non-contacting surfaces with a deposited metal coating.

Contact details are made as follows.

Example 1. The basis of the contact details of the required spatial shape (tablet, cylinder, prism, etc.) is machined from structural graphite grade MPG7 taking into account allowances for the subsequent application of conductive layers. Then the preform is placed in the reactor and pyrolytic carbon, for example from methane, is deposited on the surface of the part at a temperature of 900-1200 ° C for 50-100 hours. After carbon is deposited, non-contacting surfaces are additionally coated with, for example, galvanic deposition, a metal coating 50-70 μm thick. As the metal used, for example, copper, nickel or silver. In this case, the contacting surface of the part is shielded.

Example 2. A graphite base is obtained by molding a mixture of synthetic graphite with a particle size of 10-80 microns with the addition of coal tar pitch and a binder (for example, pulverbakelite). Then the resulting base is subjected to calcination at a temperature of 850-950 ° C for 4.5 hours.

Coating with pyrolytic carbon and applying a metal layer is carried out analogously to example 1. Contact-parts obtained by such methods are mounted on contact springs, installed in an NMSh1 relay and tested. The test results of the claimed contact details are presented in the table in comparison with the contact detail of the prototype containing 40% by weight of silver, the rest is carbon.

Comparative Test Results

Parameter Prototype The inventive contact part made in different ways Note Example 1 Example 2 The number of metal components in the material of construction, wt.% 35-40 5-7 5-7 Electrical resistance, mOhm 0.9 1,1 1,5 : Depreciation after 500 thousand commutations of a direct current paired with a silver contact, microns 155 90 one hundred Switching current parameters: 24 V, 2 A, positive wire on the tested contact The number of failures (weldings) per 1000 switching paired with a silver contact 6 no no Short-circuit test of a capacitor with a capacity of 10,000 uF charged with a voltage of 24 V

Claims (1)

A contact part made of a layered composite based on graphite, characterized in that the base is made in the form of a spatial body, a layer of pyrolytic carbon with a thickness of 100-150 microns is deposited on the surface of the substrate, an additional metal layer with a thickness of 50-100 microns is deposited on non-contacting surfaces, and as applied metal, for example, copper, nickel, silver are used.