【発明の詳細な説明】[Detailed description of the invention]
［産業上の利用分野］
この発明は、モーターや発電機等の回転電機に
使用する電刷子に関し、特にその耐摩耗特性の改
善に関する。
［従来技術］
天然質黒鉛は普通、スリランカ産やマダガスカ
ル産等の多量の灰分を含んだ原鉱石を微粉砕し、
浮遊選鉱法で精製して市販されている。このよう
な市販の天然質黒鉛は、通常0.7〜2.0重量％程度
の灰分を含んでいる。そして電刷子に天然質黒鉛
を用いる場合、灰分量0.6〜１重量％程度のもの
が一般に使用されている。以下％は重量％を現
す。
更に天然質黒鉛の純度を高める場合、浮遊選鉱
後に化学的に処理し灰分を除去すれば、灰分0.2
〜0.5％程度の高純度の天然質黒鉛が得られる。
また浮遊選鉱後の天然質黒鉛を中性雰囲気中で
2300℃以上に加熱すると、灰分が揮散し、灰分
0.1％以下の高純度のものが得られる。
容易に予想されるように、灰分の多い天然質黒
鉛を使用した電刷子は、摺動相手の銅リングやコ
ンミユテーターを摩耗させることが多い。そして
このことはまた、電刷子の摩耗をも促進する。発
明者はここで、耐摩耗特性の改善のため、灰分量
0.5％以下の高純度の天然質黒鉛を使用すること
を試みた。このような電刷子は摺動相手の摩耗を
抑制したが、電刷子自体の摩耗は従来の灰分0.6
〜１％のものに比べかえつて増加した。
［発明の目的］
この発明は、天然質黒鉛を用いた電刷子の耐摩
耗特性を改善し、電刷子自体の摩耗と摺動相手側
の摩耗の双方を抑制することを目的とする。
［発明の構成］
この発明の電刷子は、灰分量0.03〜0.5重量％
の天然質黒鉛と長さ0.03〜１mmの炭素繊維とを含
有せしめると共に、前記の炭素繊維の含有量を電
刷子の全重量に対し0.1重量％超〜５重量％未満
としたことを特徴とする。
ここに電刷子の形状・構造は既に周知であり、
適宜のものを用い得る。また電刷子にはこれ以外
に種々の添加物を加えることができ、例えば銅や
銀、錫、アルミニウム等の金属粉末を添加しても
良く、また二硫化モリブデンや窒化硼素等の固体
潤滑材を添加しても良い。
用いる天然質黒鉛は、0.03〜0.5％の灰分量ま
で精製したものであれば任意の精製法によるもの
を用いることができる。好ましい精製法は、化学
的な処理による灰分の溶出除去や、高温での灰分
の揮散を用いたものである。なお灰分量は黒鉛を
酸化し炭素を除去した際の残存無機物の量から決
定するものとし、具体的には空気中1000℃で処理
した際の残存無機物の量から決定する。
炭素繊維は、ポリアクリロニトリル等の繊維原
料を用いたものや、ピツチを原料としたもの等の
適宜のものを用い得る。しかしそのグレードは、
高温で処理した黒鉛グレードの方が、低温で処理
した炭素グレードのものよりも好ましい。炭素繊
維の長さは、混合・分散が容易で電刷子や摺動相
手の摩耗防止効果に優れた0.03〜１mmとする。こ
れは黒鉛粉や銅粉等との混合を容易にするため
で、３mm以上の長さでは均一な混合・分散が困難
である。
炭素繊維の添加量は、電刷子本体に対する添加
量で0.1重量％超〜５重量％未満とし、0.1重量％
以下では効果に乏しく、５重量％以上では電刷子
や摺動相手の摩耗を増す。ここに電刷子本体と
は、電刷子中の黒鉛や黒鉛と金属粉等の混合物の
成型体を意味し、電刷子からピグテールやイン青
銅板等の取り付け構造部を除いたものである。
本発明の電刷子の製造には、通常の電刷子の製
造方法をそのまま適用できる。例えばフエノール
樹脂等の合成樹脂からなる結合材で処理した灰分
量0.03〜0.5％の天然質黒鉛と炭素繊維とを混合
し、あるいはこれに銅粉等の金属粉末や二硫化モ
リブデンよ窒化硼素等を混合し、プレスにて加圧
成型した後、焼成して電刷子とすれば良い。また
天然質黒鉛と炭素繊維とを予め混合した後に、結
合材で処理しても良い。以下に実施例を示す。
［実施例］
銅粉40重量部（以下単に「部」と表記する。）
と、化学処理により灰分量を0.5重量％まで精製
した高純度の天然質黒鉛をフエノール樹脂ワニス
で処理したもの60部と、長さ約0.13mmのピツチ系
炭素繊維、（黒鉛グレードのクレカチヨツプ
M201S、クレカチヨツプは呉羽化学株式会社の
商品名）、0.3部とを均一に混合した。これを厚さ
５mm幅８mm、長さ18mmの直方体状の電刷子の形状
にプレス成型し、250℃で焼成して電刷子とした
（実施例１）。
焼成温度を700℃に変えた他は、実施例１と同
様にして電刷子を得た（実施例２）。
2300℃で処理し灰分量を0.03重量％とした天然
質黒鉛に、長さ約0.3mmのポリアクリロニトリル
系炭素繊維（トレカMLD300トレカは東レ株式会
社の商品名）を混合し、フエノール樹脂ワニスで
処理した。この黒鉛粉60部と銅粉40部とを混合
し、700℃で焼成して同様の電刷子とした。電刷
子中の炭素繊維の含有量は、0.6重量％（実施例
３）と3.0重量％（実施例４）、および4.8重量％
（実施例５）の３種とした。
炭素繊維を長さ約0.7mmのクレカチヨツプ
M207S（クレカチヨツプは呉羽化学株式会社の商
品名）とした他は、実施例２と同様にして電刷子
を得た（実施例６）。
灰分量0.4重量％の天然質黒鉛に長さ約0.13mm
の炭素繊維（呉羽化学株式会社製のクレカチヨツ
プM201S）を混合し、フエノール樹脂ワニスで
処理し、プレス成型後に700℃で焼成し、同様の
電刷子を得た（実施例７）。電刷子中の炭素繊維
含有量は１重量％である。
灰分量0.03重量％の天然質黒鉛に上記の長さ約
0.13mmの炭素繊維を混合し、フエノール樹脂ワニ
スで処理した後、実施例７と同様にして電刷子を
得た（実施例８）。電刷子中の炭素繊維含有量は
３重量％である。
フエノール樹脂ワニスで処理した灰分量0.8重
量％の天然質黒鉛60部と、銅粉40部とを混合し、
700℃で焼成して同様の電刷子とした（比較例
１）。
また灰分量0.4重量％の天然質黒鉛を用いたこ
と以外は、比較例１と同様にして、電刷子を得た
（比較例２）。
灰分量0.035重量％の人造黒鉛（株式会社エス
イーシー製 商品名SGP25）に上記の長さ約0.13
mmの炭素繊維を混合し、フエノール樹脂ワニスで
処理した後、プレス成型して700℃で焼成して電
刷子を得た（比較例３）。電刷子中の炭素繊維含
有量は３重量％である。
これらの電刷子を自動車用の交流ジエネレータ
ーに装着し、摺動相手を銅リングとし500時間使
用して、電刷子や銅リングの摩耗量を測定した。
なお銅リングは直径23mm、リングの回転数は
12000rpm、電流は5A、電刷子の周囲温度は100
℃である。結果を表に示す。
[Industrial Application Field] The present invention relates to electric brushes used in rotating electric machines such as motors and generators, and particularly relates to improving the wear resistance characteristics thereof. [Prior art] Natural graphite is usually produced by finely pulverizing raw ore containing a large amount of ash, such as from Sri Lanka or Madagascar.
It is purified using the flotation method and sold commercially. Such commercially available natural graphite usually contains about 0.7 to 2.0% by weight of ash. When natural graphite is used for electric brushes, it generally has an ash content of about 0.6 to 1% by weight. Below, % represents weight %. To further improve the purity of natural graphite, if the ash is removed through chemical treatment after flotation, the ash content can be reduced to 0.2.
High purity natural graphite of ~0.5% can be obtained.
In addition, natural graphite after flotation is processed in a neutral atmosphere.
When heated above 2300℃, the ash content evaporates and the ash content
High purity of 0.1% or less can be obtained. As can be easily expected, electric brushes made of natural graphite with a high ash content often wear out the copper rings and commutators they slide against. This also accelerates the wear of the electric brush. Here, the inventor has decided to increase the ash content in order to improve the wear resistance properties.
An attempt was made to use natural graphite with a high purity of 0.5% or less. Although this kind of electric brush suppressed the wear of the sliding partner, the wear of the electric brush itself was lower than the conventional ash content of 0.6.
It actually increased compared to ~1%. [Object of the Invention] The object of the present invention is to improve the wear resistance of an electric brush using natural graphite, and to suppress both the wear of the electric brush itself and the wear of the sliding counterpart. [Structure of the invention] The electric brush of this invention has an ash content of 0.03 to 0.5% by weight.
natural graphite and carbon fibers with a length of 0.03 to 1 mm, and the content of the carbon fibers is more than 0.1% by weight and less than 5% by weight based on the total weight of the electric brush. . The shape and structure of the electric brush is already well known;
Any suitable material may be used. In addition, various additives can be added to the electric brush, such as metal powders such as copper, silver, tin, and aluminum, and solid lubricants such as molybdenum disulfide and boron nitride. May be added. The natural graphite to be used may be one obtained by any purification method as long as it has been purified to an ash content of 0.03 to 0.5%. Preferred purification methods include elution and removal of ash by chemical treatment and volatilization of ash at high temperatures. The ash content is determined from the amount of inorganic matter remaining when graphite is oxidized and carbon is removed, and specifically, it is determined from the amount of inorganic matter remaining when graphite is treated at 1000° C. in air. As the carbon fiber, any suitable carbon fiber may be used, such as one using a fiber raw material such as polyacrylonitrile, or one using pitch as a raw material. However, the grade is
Graphite grades treated at high temperatures are preferred over carbon grades treated at low temperatures. The length of the carbon fiber is 0.03 to 1 mm, which is easy to mix and disperse and has an excellent effect of preventing wear on electric brushes and other sliding objects. This is to facilitate mixing with graphite powder, copper powder, etc. If the length is 3 mm or more, uniform mixing and dispersion is difficult. The amount of carbon fiber added shall be more than 0.1% by weight and less than 5% by weight relative to the electric brush body, and 0.1% by weight.
If it is less than 5% by weight, the effect will be poor, and if it is more than 5% by weight, it will increase the wear of the electric brush and sliding objects. Here, the electric brush body refers to a molded body of graphite in the electric brush or a mixture of graphite and metal powder, and is the electric brush excluding the attachment structure parts such as the pigtail and the bronze plate. To manufacture the electric brush of the present invention, a conventional electric brush manufacturing method can be applied as is. For example, natural graphite with an ash content of 0.03 to 0.5% treated with a binder made of synthetic resin such as phenolic resin is mixed with carbon fiber, or metal powder such as copper powder, molybdenum disulfide, boron nitride, etc. are added to this. The mixture may be mixed, pressure-molded using a press, and then fired to form an electric brush. Alternatively, natural graphite and carbon fiber may be mixed in advance and then treated with a binder. Examples are shown below. [Example] 40 parts by weight of copper powder (hereinafter simply referred to as "parts")
, 60 parts of high-purity natural graphite that has been chemically treated to reduce the ash content to 0.5% by weight and treated with phenolic resin varnish, and pitch carbon fiber approximately 0.13 mm in length (graphite grade creka tip).
0.3 parts of M201S and 0.3 parts of Kurekachiyoppu (trade name of Kureha Chemical Co., Ltd.) were mixed uniformly. This was press-molded into the shape of a rectangular parallelepiped electric brush with a thickness of 5 mm, a width of 8 mm, and a length of 18 mm, and baked at 250° C. to obtain an electric brush (Example 1). An electric brush was obtained in the same manner as in Example 1 except that the firing temperature was changed to 700°C (Example 2). Natural graphite treated at 2300°C with an ash content of 0.03% by weight is mixed with polyacrylonitrile carbon fibers (Torayka MLD300 is a product name of Toray Industries, Inc.) approximately 0.3mm in length, and treated with phenolic resin varnish. did. 60 parts of this graphite powder and 40 parts of copper powder were mixed and fired at 700°C to make a similar electric brush. The content of carbon fiber in the electric brush is 0.6% by weight (Example 3), 3.0% by weight (Example 4), and 4.8% by weight.
(Example 5). Carbon fiber with a length of about 0.7mm
An electric brush was obtained in the same manner as in Example 2, except that M207S (Kurekatyop is a trade name of Kureha Chemical Co., Ltd.) was used (Example 6). Made of natural graphite with an ash content of 0.4% by weight and a length of approximately 0.13mm.
A similar electric brush was obtained by mixing carbon fibers (Kurekatyop M201S manufactured by Kureha Chemical Co., Ltd.), treating with phenolic resin varnish, press molding, and firing at 700° C. (Example 7). The carbon fiber content in the electric brush is 1% by weight. Approximately the above length is made of natural graphite with an ash content of 0.03% by weight.
After mixing 0.13 mm carbon fiber and treating with phenolic resin varnish, an electric brush was obtained in the same manner as in Example 7 (Example 8). The carbon fiber content in the electric brush is 3% by weight. Mix 60 parts of natural graphite with an ash content of 0.8% by weight treated with phenolic resin varnish and 40 parts of copper powder,
A similar electric brush was made by firing at 700°C (Comparative Example 1). An electric brush was also obtained in the same manner as Comparative Example 1 except that natural graphite with an ash content of 0.4% by weight was used (Comparative Example 2). Artificial graphite with an ash content of 0.035% by weight (manufactured by SEC Co., Ltd., product name SGP25) has the above length of approximately 0.13
mm carbon fibers were mixed, treated with phenolic resin varnish, press-molded and fired at 700°C to obtain an electric brush (Comparative Example 3). The carbon fiber content in the electric brush is 3% by weight. These electric brushes were attached to an automotive alternating current generator and used for 500 hours with a copper ring as the sliding partner, and the amount of wear on the electric brush and copper ring was measured.
The diameter of the copper ring is 23 mm, and the number of rotations of the ring is
12000rpm, current is 5A, electric brush ambient temperature is 100
It is ℃. The results are shown in the table.
【表】
表から、黒鉛中の灰分量を減少させると、リン
グの摩耗量は減少するが、電刷子の摩耗量は逆に
増加することが判る（比較例１、２）。次にこれ
に炭素繊維を混合すると、リングと電刷子の双方
の摩耗を抑制できることが判る（例えば比較例２
と実施例２）。また灰分量は0.5％以下であれば、
本質的な差は生じないことが判る（例えば実施例
２と実施例３）。炭素繊維の量的効果を検討する
と、0.6重量％で十分な効果が得られており、添
加量をますとむしろ摩耗を速めることが判る（実
施例３、４、５）。従つて炭素繊維の添加量は、
0.1〜５重量％が好ましく、より好ましくは0.1〜
４重量％、更に好ましくは0.1〜1.5重量％とす
る。
なおここでは特定の材料に付いて実施例を説明
したが、公知技術を加味し適宜に変更して実施し
得ることはいうまでもない。
［発明の効果］
以上に説明した様にこの発明によれば、灰分含
有量を0.5重量％以下とした天然質黒鉛に３mm以
下の長さの炭素繊維を混合することにより、摺動
相手の摩耗と電刷子自体の摩耗の双方を抑制する
ことができる。ここで炭素繊維を加えず灰分のみ
を減少させると、摺動相手の摩耗を抑制できる
が、電刷子自体の摩耗はむしろ増加する。これに
対して低灰分の黒鉛に炭素繊維を添加すると、摺
動相手の摩耗を更に減少させると共に、電刷子の
摩耗を著しく減少させることができる。[Table] From the table, it can be seen that when the ash content in graphite is reduced, the amount of wear on the ring decreases, but the amount of wear on the electric brush increases (Comparative Examples 1 and 2). Next, it can be seen that by mixing carbon fiber with this, it is possible to suppress the wear of both the ring and the electric brush (for example, Comparative Example 2
and Example 2). Also, if the ash content is 0.5% or less,
It can be seen that there is no essential difference (for example, Example 2 and Example 3). When examining the quantitative effect of carbon fiber, it was found that a sufficient effect was obtained at 0.6% by weight, and that increasing the amount added actually accelerated wear (Examples 3, 4, and 5). Therefore, the amount of carbon fiber added is
0.1 to 5% by weight is preferable, more preferably 0.1 to 5% by weight.
4% by weight, more preferably 0.1 to 1.5% by weight. Although the embodiments have been described here with reference to specific materials, it goes without saying that the embodiments can be implemented with appropriate changes taking into account known techniques. [Effects of the Invention] As explained above, according to the present invention, by mixing carbon fiber with a length of 3 mm or less with natural graphite with an ash content of 0.5% by weight or less, wear of the sliding partner is reduced. It is possible to suppress both the wear of the electric brush itself and the wear of the electric brush itself. If only the ash content is reduced without adding carbon fiber, the wear of the sliding partner can be suppressed, but the wear of the electric brush itself will actually increase. On the other hand, when carbon fiber is added to graphite with a low ash content, it is possible to further reduce the wear of the sliding partner and to significantly reduce the wear of the electric brush.