DE2836045A1 - Polyimide and poly:aryl sulphide esp. polyphenylene sulphide binder - for electric circuit contact body contg. carbon and opt. metal powder - Google Patents

Abstract

In a contact body for use in an electric circuit and consisting of C, binder and opt. metal powder mixt., the binder consists of a mixt. of polyimide, (I), with an aromatic polymer, (II), in which the aromatic rings are linked directly by a C-C bond or by a heteroatom or heteroatom grouping. Pref. (II) is a polyaryl sulphide having formula ....Ar-S-Ar-S-Ar.... (where Ar is an aromatic ring system the H atoms of which may be partly replaced by alkyl), esp. polyphenylene sulphide (IIa). The use of a (I)/(IIa) mixt. as binder in contact body mfr., esp. C brushes and sliding rings, is claimed. The addn. of (I) increases contact body service life, and reduces sliding partner abrasion. E.g. the addn. of 5 pts. wt. (I) to a mixt. of 100 pts. wt. graphite and 10 pts. wt. (IIa) lowered C brush abrasion from 1.5 - 0.9 mm/100 hrs. and sliding ring abrasion from 0.8-1.5 - to 0.1-0.2 mm/1000 hrs. at 15000 rpm and >=70 degrees C.

Description

State of the art

The invention is based on a contact body of the type Main claim. It is known, carbon brushes and slip rings as representatives of such To produce contact bodies on the basis of carbon, since such pairings, Especially when using metal-free carbon brushes, a very good electrical one Behavior and good wear resistance, so that such pairings function largely maintenance-free and trouble-free. However, these contact bodies have the disadvantage that they once have too low a mechanical strength and that on the other hand, it is awkward to attach the contact connections to these contact bodies, which leads to high manufacturing costs of such contact bodies.

Such contact bodies, e.g. carbon brushes and slip rings, are generally made by having the constituents - graphite, coke, optionally Metal powder and binder - mixed in the desired ratio, the powder or Granules are compressed in the die to the desired shape and then through a suitable heat treatment including the bond between the components the hardening or coking of the binder, is brought about.

It is advantageous if the compression in the die at room temperature made and the electrical connection cable can be pressed in at the same time.

The following requirements must be placed on the binding agent: 1. At room temperature it should be in a powdery state with good flowability.

2. Above a defined and sufficiently high melting point it should soften quickly and then have the lowest possible viscosity.

9. In the molten state it should contain the carbon as well, if applicable wet the metal powder very well, which contributes to a high mechanical strength 4. It should be easy to crosslink exhibit by heat treatment in air.

5. It should have a favorable wear behavior when used as a Promote pairing of carbon brush and slip ring.

A binder is already known that meets these requirements as far as possible Fulfills. This involves using compounds from the group the monovalent aromatic polymers, preferably from the group of polyaryl sulfides as a binder for such contact bodies. It has proven to be particularly suitable the polyphenylene sulfide proved. Although considerable successes with this binder could be achieved in terms of service life, it is a constant requirement the user of such contact bodies, the service life or the service life of such Body, even under increased demands, to continue to increase. In addition, must also in the case of an application as a sliding contact, the wear of the sliding partner be reduced.

Advantages of the Invention The contact body according to the invention with the characterizing features of the main claim has the advantage that the The service life of these contact bodies compared to those that do not contain polyimide is clear could be increased.

Another advantage is that the wear and tear of the sliding partner could be significantly reduced. Overall, the running behavior, e.g. in electrical machines, are significantly improved.

The measures listed in the subclaims are advantageous Developments and improvements of the contact body specified in the main claim possible.

It is particularly advantageous to limit the polyimide surcharges to 0.5 to 10 Weight - with a grain size (75 to be determined.

The optimal setting must be for each application and for each Polyimide type can be made separately.

Description of the Invention The invention is set forth below with reference to it an example will be explained in more detail. 100 parts by weight of natural graphite are included 10 parts by weight of polyphenylene sulfide and 5 parts by weight of polyimide of the polyimide type 2080 "from Upjohn, finely ground and thoroughly mixed.

The grain size of the binder components should be less than 75 μm. The mixture is in a press die, the inner shape of the contact body to be produced corresponds, filled and pressed at a pressure of 4 t / cm2. After removing of the compact from the press die, the compact is approx.

1 hour at a temperature of about 350 ° C under protective gas, e.g. nitrogen or town gas, a mixture consisting essentially of hydrogen, Ethane and carbon monoxide are made sintered. After cooling down, the finished one lies Contact body before. As a result of the relatively low sintering temperature it is possible to press in or press on the contact connections in the same operation.

Instead of 100 parts by weight of natural graphite, for example 42 parts by weight of natural graphite and 55 parts by weight of powdered copper are used so that you do not have a metal-free contact body, but one with a corresponding copper content. The manufacturing conditions are the same as described above became. Here too you can the contact connections are directly pressed in or pressed on.

Comparison values for speed change test (nmax = 15000 rpm, ambient temperature > 70 ° C) on three-phase generator brushes with and without polyimide addition: with PI without PI brush wear 0.9 1.5 (mm / 100 hours) ring wear 0.1-0.2 0.8-1.5 (mm / 1000 Hours.)

Claims (5)

Claims X contact body, which is made of a mixture of carbon, Binder and optionally metal powder, for use in an electrical Circuit, characterized in that a polyimide and a compound from the Group of monovalent aromatic polymers, these are polymers in which aromatic Nuclei through a C-G bond or through a heteroatom or a heteroatom grouping are directly linked to one another, contains as a binder. 2. Contact body according to claim 1, characterized in that it as a binder polyimide and a polyarylsulfide of the general formula ... Ar - 5 - Ar - 5 - Ar ... contains, where Ar represents an aromatic ring system, the H atoms of which can be partially replaced by alkyl radicals. 3. Contact body according to claim 2, characterized in that it is as Binder contains a polyimide and polyphenylene sulfide. 4. Contact body according to claim 3, characterized in that it 2 up to 10 parts by weight of polyimide and 0.5 to 50 parts by weight of polyphenylene sulfide contains to 100 parts by weight of coal as a binder. 5. Use of a mixture of polyimide and polyphenylene sulfide as a binder in the manufacture of contact bodies, especially carbon brushes or slip rings made from a mixture of carbon, binder and optionally Metal powder can be produced.