CN1028267C

CN1028267C - Carbon brush for miniature motors and method of making same

Info

Publication number: CN1028267C
Application number: CN 91101674
Authority: CN
Inventors: 涩谷功
Original assignee: Mabuchi Motor Co Ltd
Current assignee: Mabuchi Motor Co Ltd
Priority date: 1990-03-07
Filing date: 1991-03-16
Publication date: 1995-04-19
Anticipated expiration: 2006-03-16
Also published as: CN1054855A

Abstract

A carbon brush for miniature motors comprising a stator using a permanent magnet as the field, and a rotor on which a rotor winding is wound, and having a commutator for feeding current to the rotor winding and brushes, formed by bonding graphite powder, for making sliding contact with the commutator; the brush being a metal-plated graphite brush formed by adding 0.1 wt. % to 12.0 wt. % of a fibrous material of particle sizes less than 40 microns and lengths less than 50 microns to metal-plated graphite powder formed by coating graphite powder with a metallic layer, and pressure-forming and sintering a mixture of the metal-plated graphite powder and the fibrous material; the graphite powder containing less than 0.05 wt. % of ashes, and the method of making the same.

Description

Carbon brush for miniature motors and method of making same

The present invention relates generally to have the carbon brush of the micromachine of permanent-magnetic field, particularly the black lead brush of coating metal.The generative process of the black lead brush of this coating metal is: earlier at plating add fiber material in the powdered graphite of the formed coating metal of powdered graphite of metal level, give the mixture extrusion forming of the powdered graphite of coating metal and fiber material then and make its sintering.

So far, made a large amount of micromachine carbon brush already, its production process is, be about in purity 98% or 99.5% the powdered graphite and add binding material, grind this solidified mixture and it is sieved, in the metallization powder, mix soil and the conductance of screening mixture, give the mixture extrusion forming that draws thus then and make its sintering needing to obtain.

Again, use binding material for exempting, a kind of what is called " black lead brush of plating coating copper " has been well-known.The production process of the black lead brush of this plating coating copper is: earlier purity is about 99% powdered graphite particle plating coating copper, then the powdered graphite of plating coating copper is not added binding material and extrusion forming and make it sintering.

In above-mentioned any situation, in powdered graphite, contain such as SiO often ₂, Al ₂O ₃, Fe ₂O ₃, MnO, MgO and TiO and so on granular size be 1 to 500 micron dust.

Fig. 7 illustrates main by SiO contained in the powdered graphite ₂The micrograph of the particle structure of the dust that constitutes.Bright this dust of this micro-diagram has different granular sizes, even has big particle.

During motor rotation, when dust enters between carbon brush and the commutator, contain particle and rectification characteristic is degenerated greater than the carbon brush of 50 microns dust, under opposite extreme situations, cause motor to damage.

In order to address this problem the method that the applicant proposed to use the micromachine carbon brush of the manufacture method manufacturing that comprises process for purifying process (powdered graphite is purified to dust content and is lower than 0.05 weight %) for a long time and made this carbon brush.

Show that in test extrusion forming and sintering and the micromachine carbon brush (Japanese patent application 103201/1989) made are having superiority aspect machinery noise and the improvement rectification characteristic reducing then for the powdered graphite elder generation coating metal that purifies with above-mentioned process for purifying process, but it is easy to be subjected to heavy wear, shown in Fig. 3 (Test No. 1), this will be described below.

In order to improve resistance to wear, the applicant proposes a kind of carbon brush and manufacture method (Japanese patent application 103201/1989) thereof of micromachine, adds oxide in the powdered graphite that has wherein purified in purification process; Also propose a kind of carbon brush and manufacture method (Japanese patent application 247114/1989) thereof of micromachine, wherein add conductive material in an identical manner.

Showed above-mentionedly in these tests, the carbon brush that adds oxide or conductive material has still improved its resistance to wear, but their shape stability is very poor.

The present invention attempts to address these problems, for reaching this purpose, micromachine carbon brush of the present invention is to use dust content to be purified to be lower than the powdered graphite of 0.05 weight % and adds in this powdered graphite that 0.1 weight % forms to the fiber material of 12.0 weight % (have granular size less than 40 microns, length less than 50 microns).

Fig. 1 (A) illustrates the schematic diagram that embodies micromachine carbon brush principle of the present invention;

Fig. 1 (B) illustrates the flow diagram that helps to explain manufacture method of the present invention;

Fig. 2 illustrates the overview diagram of the purification stove that is used for purification process of the present invention;

Fig. 3 illustrates and helps to explain the form that concerns between additive types and the wear intensity.

Fig. 4 illustrates and helps to explain among the present invention the form that concerns between the quantity of adding fiber material and the wear intensity;

Fig. 5 illustrates particle structure and the micrograph of dosing the glass fibre in the carbon brush of the present invention;

Fig. 6 illustrates the flow diagram that helps to explain another embodiment of the present invention;

Fig. 7 illustrates main by SiO contained in the powdered graphite ₂The micrograph of the particle structure of the dust that constitutes.

Fig. 1 illustrates schematic diagram of the present invention, and wherein Fig. 1 (A) illustrates the schematic diagram of the explanation principle of the invention, and Fig. 1 (B) is a process drawing.

In Fig. 1 (A), label 1 expression commutator, label 2 expression commutator segments, label 3 expression rotors, label 4 expression carbon brush, label 5 expression carbon brush elastomeric elements.

In Fig. 1 (B), label 20 expressions are purified to and for example are about 99% powdered graphite; Label 21 expressions purification process of the present invention; Label 22 expression fiber material blending processes, wherein add the fiber material (glass fibre, alumina fiber, silica fibre, Zirconium oxide fibre, carbon fiber, beard etc.) of 0.1 weight % to 12.0 weight %, its granular size less than 40 microns, its length less than 50 microns; Label 23 expression metal-plated processes; Label 25 expression sintering processes.

Carbon brush 4 by conductivity, 5 clampings of carbon brush elastomeric element and

commutator segment

2,2 and 2 sliding contacts.Carbon brush 4 is sintered into has chock plug and the inverted T-shape shape of being supported by carbon brush elastomeric element 5, shown in the carbon brush perspective view of the figure A-1 of Fig. 1 (A).The lower surface of example T word shape form slightly bending with sliding contact commutator segment 2.

Shown in Fig. 1 (B), the manufacture process of carbon brush is to carry out: purification process 21, fiber material blending process 22, metal-plated process 23, extrusion forming process 24, in the sintering process 25 of powdered graphite 20.

The graphite carbon brush of the plating coating copper of making by plating coating copper on powdered graphite is for known.The invention is characterized in: powdered graphite is purified to its dust content and is lower than 0.05 weight % in purification process 21, and this just makes the dust content of the carbon brush of having produced 4 be lower than 0.05 weight %.That is to say that carbon brush of the present invention has good rectification characteristic owing to the dust content of carbon brush is extremely low.

In fiber material blending process 22, add the above-mentioned fiber material of 0.1 weight % to 12.0 weight %, its granular size helps to improve shape stability and abrasion resistance less than 40 microns, length less than 50 microns.

In the metal-plated process 23 shown in Fig. 1 (B), extrusion forming process 24 and sintering process 25, respective process processing much at one in execution and the prior art.

Fig. 2 is illustrated in the overview diagram of the purification stove that uses in the purification process of the present invention.Number in the figure 20 expression powdered graphites, label 30 expressions purify stove, label 31 indication transformers, label 32 expression halide torches, label 33 expression heaters.

In purification process 21, utilize such as CCl ₄Or CCl ₂f ₂And so on halogen dissociant (this material discharges easily halogen when high temperature in the inert gas such as nitrogen or argon gas) dust is got rid of from powdered graphite 20.That is to say that the halogen air inlet pipe 32 in the time of in powdered graphite 20 is packed purification stove 30 in stove just places among the powdered graphite 20.When furnace temperature being elevated to be about 1800 ℃ along with heater 33, CCl saturated in inert gas supplies with through halogen air inlet pipe 32.In this state, suppose in purifying stove, to take place following chemical reaction:

When temperature further is elevated to 1900 ℃, CCl ₄By Cl ₂F ₂Substitute, and more than 2500 ℃ the time, purified treatment continues more than 4 hours.In cooling procedure subsequently, keep to inject inert gas such as nitrogen or argon gas to prevent dust content and oppositely spread and to get rid of halogen.

The graphite purity that obtains in purification process surpasses 99.95%, and its dust content is lower than 0.05 weight %.

The applicant uses following method to make the black lead brush of plating coating copper, except purification process, all can improve the purity of the graphite that uses in the black lead brush of coating metal, and motor (comprising these brushes) is tested.

(1) physical purification:

Use floatation to make graphite and dust separation according to the difference of the Surface Physical Chemistry character of solid particle.The granular size that the physical purification process is handled is about 300 microns.The fact that can utilize graphite available air bubble to separate is injected powdered graphite in the mixture of oil and air bubble, collects by graphite granule is attached on the floating air bubble.In this process, available purity is not less than 98% but be lower than 99.5%, that is to say, contains 0.5% to 2.0% dust in this powdered graphite.

(2) chemical purification:

The dust content of powdered graphite is dissolved in the bronsted lowry acids and bases bronsted lowry solution of high concentration and with this solution heating (to 160 ° to 170 ℃), also pressurization (to 5 to 6 atmospheric pressure).This processing is commonly referred to " hot pressing ".This process mainly comprises following reaction.

By such chemical treatment, available purity is not less than 99% and be lower than 99.9%, still residually in powdered graphite is not less than 0.05% and near 1.0% impurity.

Fig. 3 is illustrated in the result who tests on the carbon brush.These carbon brush comprise: brush, its interior brush, non-additive brush and brush of the present invention that adds electric conducting material of adding oxide in it.All carbon brush all mention, have that the manufacture method of purification process makes by this specification beginning, make its dust content be lower than 0.05 weight % to purify powdered graphite.No. 1 test representative is to the test result of additive-free carbon brush, and No. 2 test representatives are to having added conductive material (SiO ₂) test result of carbon brush of subparticle, No. 3 test representatives are to the test result of the carbon brush that added conductive material (TiC) subparticle, and No. 4 test representatives are to the test result of the carbon brush of the present invention that added fiber material (glass fibre).Fig. 3 illustrates 10 carbon brush, and wherein each is all reaching most the test result that operation test in 80 hours is drawn corresponding to No. 1 to No. 4 test.SiO ₂With the addition of TiC respectively be 1.0 weight %, the granular size of selecting is all less than 40 microns.And under the situation of No. 4 tests, added 1.0 weight % glass fibres, its granular size all less than 40 microns, length less than 50 microns.The carbon brush that " service time when motor damages " hurdle among Fig. 3 shows No. 1 to No. 4 test experience continuously reaches 80 hours test.As in " wear intensity " hurdle shown in when the EOT that reaches 80 hours, aspect wear intensity in significant difference, that is, No. 1 the test wear intensity the most serious, No. 2 and No. 3 tests make moderate progress, and the wear intensity of No. 4 tests (carbon brush of the present invention) is improved significantly.

Again, these tests that the applicant carried out have also pointed out the addition of wear intensity and fiber material that confidential relation is arranged.The relation of wear intensity and fiber material (glass fibre) addition as shown in Figure 4.Its granular size of the glass fibre that in test, adds in the employed carbon brush all less than 40 microns, its length all less than 50 microns.Test result shown in Fig. 4 shows that they have all experienced and have reached 80 hours operation corresponding to the test of carrying out on each of 10 carbon brush of each Test No..Time when " X " mark is represented the carbon brush damage.

Can find out obviously that from Fig. 4 the addition of glass fibre must remain on 0.1 weight %(1 number test) to 12.0 weight %(7 numbers the test) scope in, with degree of reducing wear.In other words, be 15.0 weight %(8 numbers tests at addition) situation under, all carbon brush all are unable to undergo to reach 80 hours operation, and damage when average service time is 64 hours.

Fig. 5 is illustrated in the particle structure micrograph of the glass fibre that adds during the manufacture process of carbon brush of the present invention.As can be conspicuous from micrograph, the particle of the glass fibre that the present invention uses all be uniform on shape and size.As mentioned above, the granular size of this glass fibre all less than 40 microns, its length all less than 50 microns.

The carbon brush made from the manufacture method shown in Fig. 1 (B) of the present invention has been described in front.Yet the present invention is not the restriction that is subjected to it.The order of the manufacture process shown in Fig. 1 (B) also can be purification process 21 → coating metal process 23 → fiber material blending process 22 → extrusion forming process 24 → sintering process 25.In this case, it is identical to obtain the resulting effect of carbon brush made with processing method shown in Fig. 1 (B).

Below, the another kind of manufacture method of carbon brush of the present invention is described with reference to Fig. 6.Number in the figure 26 expression binder-treatment processes, the powdered graphite that purifies through purification process solidifies with binding agent in this process, label 27 expressions are ground and screening process, and the graphite material with adhesive cures grinds and screens in grinding and screening process in binder-treatment process 26.Other label is corresponding to identical label among Fig. 1 (B).

In Fig. 6, powdered graphite 20 is to purify in purification process 21.The powdered graphite 20 that has purified is used adhesive cures in binder-treatment process 26.The graphite material that solidifies grinds and screens in grinding and screening process 27.

Then, in fiber material blending process 22, add granular size less than 40 microns, length less than 50 microns, 0.1 weight % is to the fiber material of 12.0 weight %, and with grind and the graphite material blending of screening.Make graphite material experience extrusion forming process 24 and sintering process 25 produce carbon brush 4 then.Fiber material blending process 22 at Fig. 6 also can combine with binder-treatment process 26, that is the powdered graphite after purifying in purification process 21 experiences binder-treatment after can admixing at the interpolation fiber material and with powdered graphite.

The another kind of manufacture method of carbon brush of the present invention has been described with reference to Fig. 6 above.Carbon brush with manufacture method manufacturing shown in Figure 6 can reach identical with the resulting effect of manufacture method manufacturing carbon brush shown in Fig. 1 (B).

As mentioned above, the present invention can make in the powdered graphite contained dust as impurity less than 0.05 weight % by purifying powdered graphite; In powdered graphite, add granular size less than 40 microns, length less than 50 microns 0.1 weight % fiber material to 12.0 weight %, a kind of the have shape stability of improvement and wear-resistant carbon brush are provided.

Claims

1, the carbon brush that a kind of micromachine is used, this micromachine comprises: a rotor that utilizes permanent magnet to twine a rotor winding on it as the stator in magnetic field and, and has one in order to commutator from electric current to above-mentioned rotor winding that present with form by the bonding powdered graphite, in order to produce the carbon brush of sliding contact with above-mentioned commutator, it is characterized in that, described carbon brush is by forming to powdered graphite coating layer of metal layer, described powdered graphite be included in granular size less than 40 microns and length less than 50 microns, 0.1 weight % is in the fiber material of 12.0 weight %, described powdered graphite dust burdening is less than 0.05 weight %, and this coating metal black lead brush is to be had the powdered graphite extrusion forming of metal layer and sintered into by described.

2, the carbon brush that a kind of micromachine is used, this micromachine comprises: a rotor that utilizes permanent magnet to twine a rotor winding on it as the stator in magnetic field and, and has one in order to commutator from electric current to above-mentioned rotor winding that present with form by the bonding powdered graphite, in order to produce the carbon brush of sliding contact with above-mentioned commutator, it is characterized in that described carbon brush has and is purified to above-mentioned powdered graphite and contains as the dust of impurity less than the granular size in the powdered graphite of 0.05 weight % less than 40 microns and length less than 50 microns, 0.1 weight % is to the fiber material of 12.0 weight %; And described carbon brush is by the mixture extrusion forming of above-mentioned powdered graphite and above-mentioned fiber material and sinters into.

3, the carbon brush used of micromachine according to claim 1 and 2 is characterized in that described fiber material is glass fibre, alumina fiber, silica fibre at least, and the material of more than one in Zirconium oxide fibre, carbon fiber, the beard is made.