一、汽車發電機不發電是怎么回事

汽車(che)交(jiao)流(liu)(liu)發電(dian)(dian)(dian)機(ji)(ji)正常發電(dian)(dian)(dian)，必(bi)須(xu)具備兩個條件： 一是(shi)勵磁(ci)電(dian)(dian)(dian)路(lu)、定子繞組電(dian)(dian)(dian)路(lu)和(he)整流(liu)(liu)器必(bi)須(xu)工(gong)作正常； 二是(shi)交(jiao)流(liu)(liu)發電(dian)(dian)(dian)機(ji)(ji)轉子必(bi)須(xu)旋轉。汽車(che)發電(dian)(dian)(dian)機(ji)(ji)不(bu)發電(dian)(dian)(dian)可能是(shi)某些零(ling)部(bu)件出(chu)現了問題，以下是(shi)常見的汽車(che)發電(dian)(dian)(dian)機(ji)(ji)不(bu)發電(dian)(dian)(dian)的原因(yin)：

1、二極管(guan)擊穿，不(bu)起(qi)整流作用。

2、電刷在電刷架內(nei)卡住(zhu)，發(fa)電機因不勵(li)磁(ci)而(er)不能發(fa)電。

3、轉(zhuan)子的(de)(de)磁(ci)場線(xian)圈(quan)不通電：轉(zhuan)子線(xian)圈(quan)的(de)(de)折疊層(ceng)數多，部分線(xian)圈(quan)在(zai)浸絕緣漆時(shi)，沒有浸到(dao)線(xian)圈(quan)底(di)(di)層(ceng)中去，底(di)(di)層(ceng)線(xian)圈(quan)匝與匝之間(jian)(jian)存(cun)在(zai)一(yi)定的(de)(de)間(jian)(jian)隙。隨著發(fa)動機轉(zhuan)速的(de)(de)變(bian)化，底(di)(di)層(ceng)線(xian)圈(quan)將(jiang)(jiang)存(cun)在(zai)不同的(de)(de)離(li)心力。線(xian)圈(quan)收縮、膨(peng)脹的(de)(de)頻率，決定了線(xian)圈(quan)和(he)引(yin)線(xian)角度(du)大小變(bian)換(huan)的(de)(de)次數，常見(jian)磁(ci)場線(xian)圈(quan)到(dao)滑環的(de)(de)引(yin)線(xian)，特別是底(di)(di)層(ceng)線(xian)圈(quan)的(de)(de)引(yin)線(xian)使(shi)用過久，將(jiang)(jiang)產生金(jin)屬疲(pi)勞而折斷。

4、定子線圈相間短路或(huo)搭鐵(tie)。

5、轉(zhuan)子的爪極松(song)動(dong)(dong)：若在軸上稍有松(song)動(dong)(dong)，則爪極內端(duan)面(mian)與磁鐵端(duan)面(mian)之間就會有間隙產生(sheng)，磁場(chang)線(xian)圈產生(sheng)的磁通就會在此漏(lou)掉，導致定(ding)子的磁通大大減少(shao)，定(ding)子線(xian)圈感應的電(dian)動(dong)(dong)勢也因(yin)此大大減小，以致于(yu)不能(neng)產生(sheng)足夠的電(dian)壓對(dui)蓄電(dian)池進(jin)行充電(dian)。

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二、汽車電機不發電故障如何檢修

1、就車檢測法

汽車發(fa)電(dian)機故障時，可以不拆卸發(fa)電(dian)機，在(zai)車上對其檢測，概(gai)略判斷是(shi)否有故障。

（1）萬用表電壓檔檢測

將萬(wan)用(yong)表(biao)(biao)旋(xuan)鈕(niu)旋(xuan)至直(zhi)流電(dian)(dian)(dian)(dian)壓(ya)30V檔(dang)（或用(yong)一般的(de)直(zhi)流電(dian)(dian)(dian)(dian)壓(ya)表(biao)(biao)適當檔(dang)），把紅表(biao)(biao)筆接(jie)(jie)發(fa)電(dian)(dian)(dian)(dian)機“電(dian)(dian)(dian)(dian)樞”接(jie)(jie)柱(zhu)，黑表(biao)(biao)筆接(jie)(jie)外殼，讓發(fa)動(dong)機運(yun)轉(zhuan)在(zai)中速以上，12V電(dian)(dian)(dian)(dian)氣系統(tong)的(de)電(dian)(dian)(dian)(dian)壓(ya)標準(zhun)值(zhi)應在(zai)14V左(zuo)右，24V電(dian)(dian)(dian)(dian)氣系統(tong)的(de)電(dian)(dian)(dian)(dian)壓(ya)標準(zhun)值(zhi)應在(zai)28V左(zuo)右。若測的(de)電(dian)(dian)(dian)(dian)壓(ya)為蓄(xu)電(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)壓(ya)，則(ze)表(biao)(biao)明發(fa)電(dian)(dian)(dian)(dian)機不發(fa)電(dian)(dian)(dian)(dian)。

（2）外接電流表檢測

當汽車儀表(biao)板上(shang)沒有電(dian)(dian)流表(biao)時(shi)，可用外接(jie)直(zhi)流電(dian)(dian)流表(biao)來(lai)檢(jian)測。先把發(fa)(fa)電(dian)(dian)機(ji)(ji)“電(dian)(dian)樞(shu)”接(jie)柱(zhu)導線(xian)拆下(xia)，再將量程為(wei)20A左右的(de)直(zhi)流電(dian)(dian)流表(biao)正極接(jie)發(fa)(fa)電(dian)(dian)機(ji)(ji)“電(dian)(dian)樞(shu)”，負極導線(xian)接(jie)上(shang)述拆下(xia)接(jie)頭(tou)。當發(fa)(fa)動(dong)機(ji)(ji)在中(zhong)速以上(shang)運轉（不使用其(qi)他(ta)電(dian)(dian)器設備）時(shi)，電(dian)(dian)流表(biao)有3A~5A充(chong)電(dian)(dian)指示，表(biao)明發(fa)(fa)電(dian)(dian)機(ji)(ji)工作正常，否則發(fa)(fa)電(dian)(dian)機(ji)(ji)不發(fa)(fa)電(dian)(dian)。

（3）試燈（汽車燈泡）法

當沒有萬用表和直流電表時，可用汽車燈泡做一試燈來檢測。將燈泡兩端焊接(jie)(jie)適當長度(du)的(de)導(dao)線(xian)，并在(zai)其兩端接(jie)(jie)上鍔魚夾(jia)。檢測前先將發(fa)電(dian)(dian)(dian)機“電(dian)(dian)(dian)樞”接(jie)(jie)柱的(de)導(dao)線(xian)拆下，再將試(shi)(shi)燈的(de)一(yi)端夾(jia)住(zhu)發(fa)電(dian)(dian)(dian)機“電(dian)(dian)(dian)樞”接(jie)(jie)柱，另一(yi)端搭鐵，當發(fa)動機中速運轉時，試(shi)(shi)燈亮度(du)說明發(fa)電(dian)(dian)(dian)機工(gong)作正(zheng)常，否則發(fa)電(dian)(dian)(dian)機不發(fa)電(dian)(dian)(dian)。

（4）改變發動機轉速、觀察大燈亮度法

起(qi)動發動機后，打開(kai)大燈(deng)，讓(rang)發動機轉(zhuan)速(su)從怠速(su)逐漸提(ti)(ti)高到中等轉(zhuan)速(su)，大燈(deng)的(de)亮度(du)若隨轉(zhuan)速(su)的(de)提(ti)(ti)高而增加，說明發電(dian)機工作正常(chang)，否(fou)則為不發電(dian)。

（5）拆下蓄電池搭鐵看發動機（汽油機）是否工作法

當(dang)車上(shang)沒(mei)有(you)(you)微機(ji)控制電(dian)(dian)子裝置(zhi)時，可以(yi)用(yong)此種方法檢測。把發(fa)動機(ji)控制在中(zhong)速以(yi)上(shang)，拆(chai)下蓄電(dian)(dian)池搭鐵線(xian)（一般是斷(duan)開(kai)蓄電(dian)(dian)池搭鐵線(xian)上(shang)的控制總開(kai)關），若(ruo)發(fa)動機(ji)工(gong)作正常(chang)，說明發(fa)電(dian)(dian)機(ji)發(fa)電(dian)(dian)，否則發(fa)電(dian)(dian)機(ji)有(you)(you)故障。

2、車下不解體檢測與判斷

維修汽車發電(dian)機故障(zhang)也(ye)可以選擇(ze)從車上拆下發電(dian)機后，用(yong)下述方(fang)法檢(jian)查，進(jin)一(yi)步確(que)定故障(zhang)。

（1）用小燈泡（手電燈泡）判斷

把手電(dian)(dian)燈(deng)泡的(de)(de)兩端接上導線做(zuo)成小試燈(deng)，接于(yu)發電(dian)(dian)機(ji)“電(dian)(dian)樞”和(he)外殼(ke)之(zhi)間。用(yong)導線將蓄電(dian)(dian)池（或相(xiang)同電(dian)(dian)壓的(de)(de)干電(dian)(dian)池）正、負(fu)極分別連接在發電(dian)(dian)機(ji)的(de)(de)兩磁場接柱“F1”、“F2”（內搭鐵的(de)(de)交流(liu)發電(dian)(dian)機(ji)接“F”和(he)“搭鐵”接柱）上，讓蓄電(dian)(dian)池給發電(dian)(dian)機(ji)激磁。用(yong)手快速轉動發動機(ji)皮帶盤，小試燈(deng)說明發電(dian)(dian)機(ji)工(gong)作正常，否(fou)則發電(dian)(dian)機(ji)不發電(dian)(dian)。

（2）萬用表電壓檔判斷

讓蓄電(dian)(dian)(dian)池給發(fa)電(dian)(dian)(dian)機激磁(ci)（接(jie)(jie)線方法同2．1），將萬(wan)(wan)用表(biao)選擇在直流電(dian)(dian)(dian)壓(ya)(ya)3－5V（或一般直流電(dian)(dian)(dian)壓(ya)(ya)表(biao)適當(dang)檔(dang)）檔(dang)，黑、紅(hong)表(biao)筆分(fen)別(bie)接(jie)(jie)“搭鐵”和發(fa)電(dian)(dian)(dian)機“電(dian)(dian)(dian)樞”接(jie)(jie)柱，用手轉(zhuan)動皮帶盤，萬(wan)(wan)用表(biao)（或直流電(dian)(dian)(dian)壓(ya)(ya)表(biao)）指針應(ying)有擺動，否則發(fa)電(dian)(dian)(dian)機不發(fa)電(dian)(dian)(dian)。

（3）萬用表電阻檔檢測與判斷

用萬(wan)用表(biao)R×1電(dian)(dian)阻檔(dang)，測量各接(jie)線柱之(zhi)間(jian)的電(dian)(dian)阻（不同型號(hao)發(fa)電(dian)(dian)機的電(dian)(dian)阻值(zhi)不同，下表(biao)為JF522A型發(fa)電(dian)(dian)機）值(zhi)，與正(zheng)常(chang)值(zhi)比較，可以判斷出發(fa)電(dian)(dian)機是否有故障。

（4）示波器法檢測與判斷

將發(fa)電(dian)機裝在電(dian)器試驗臺上，連接好示波器與發(fa)電(dian)機之(zhi)間的導線(xian)，把發(fa)電(dian)機控制在中等轉(zhuan)速，發(fa)電(dian)機正常工作及各種(zhong)故障所對應的電(dian)壓波形。