變幅油缸：

1變幅油缸的型式

有：雙作(zuo)(zuo)用活塞(sai)式油缸(gang)(gang)，單作(zuo)(zuo)用柱塞(sai)式油缸(gang)(gang)，雙作(zuo)(zuo)用二級伸(shen)縮油缸(gang)(gang)。

雙作用活塞式(shi)油缸(gang)應用普遍。油缸(gang)有(you)兩個通油口，當A口進(jin)油時B口回油；若B口進(jin)油則A口回油，活塞6的往復(fu)運動(dong)都(dou)依靠壓力(li)有(you)的作用。

單作(zuo)(zuo)用柱(zhu)塞(sai)(sai)式(shi)（或活塞(sai)(sai)式(shi)）油(you)(you)(you)缸(gang)(gang)只有一(yi)個通(tong)油(you)(you)(you)口，壓(ya)力油(you)(you)(you)只能(neng)向(xiang)油(you)(you)(you)缸(gang)(gang)中(zhong)柱(zhu)塞(sai)(sai)的一(yi)側供(gong)油(you)(you)(you)，柱(zhu)塞(sai)(sai)在壓(ya)力油(you)(you)(you)作(zuo)(zuo)用下向(xiang)一(yi)個方向(xiang)運動(dong)，柱(zhu)塞(sai)(sai)的返回行(xing)程則(ze)靠起重(zhong)e799bee5baa6e79fa5e98193e58685e5aeb931333264623165臂重(zhong)力推動(dong)，如LT1040型汽車起重(zhong)機變幅油(you)(you)(you)缸(gang)(gang)。

雙作(zuo)用(yong)二級伸縮油(you)缸(gang)(gang)是(shi)套(tao)裝(zhuang)(zhuang)結構(gou)，兩(liang)級活塞桿象拉桿天線套(tao)裝(zhuang)(zhuang)在油(you)缸(gang)(gang)桶內，結構(gou)比較(jiao)復(fu)雜，有四個通(tong)油(you)口。其特點是(shi)油(you)缸(gang)(gang)伸出工(gong)作(zuo)行程長(chang)，縮回時(shi)油(you)缸(gang)(gang)長(chang)度較(jiao)短，適用(yong)于大型起重機(ji)。如(ru)LT1200型汽車起重機(ji)變(bian)幅(fu)油(you)就是(shi)這種結構(gou)的。

2變幅型式

1） 根據(ju)油缸(gang)(gang)(gang)(gang)的(de)數量(liang)不同，液(ye)壓支柱(zhu)報價，變(bian)幅(fu)(fu)油缸(gang)(gang)(gang)(gang)有單(dan)缸(gang)(gang)(gang)(gang)式和雙(shuang)缸(gang)(gang)(gang)(gang)式。單(dan)缸(gang)(gang)(gang)(gang)變(bian)幅(fu)(fu)推(tui)力小(xiao)，但容易調整，方便維修，不存在(zai)同步(bu)(bu)不良問(wen)題，一般用(yong)在(zai)小(xiao)型(xing)輪式起(qi)重機(ji)上。雙(shuang)缸(gang)(gang)(gang)(gang)變(bian)幅(fu)(fu)推(tui)力大，能改(gai)善起(qi)重臂側向受力，為使兩缸(gang)(gang)(gang)(gang)同步(bu)(bu)良好，通(tong)常采取兩缸(gang)(gang)(gang)(gang)共用(yong)通(tong)油管路(lu)，并以(yi)起(qi)重臂剛度(du)來保持(chi)同步(bu)(bu)，它多用(yong)于(yu)中(zhong)，大型(xing)輪式起(qi)重機(ji)。

2） 變幅油缸的布置方式

按(an)其(qi)(qi)油缸與起重臂的相互位置(zhi)(zhi)不同，可分為(wei)前置(zhi)(zhi)式(shi)(shi)、后置(zhi)(zhi)式(shi)(shi)和后拉式(shi)(shi)三(san)種。其(qi)(qi)中前置(zhi)(zhi)式(shi)(shi)變(bian)幅(fu)油缸以所需推力(li)小，并能改善起重臂受力(li)而得到廣(guang)泛應用。

前置(zhi)式特點：①變幅推力小(xiao)，可采(cai)用小(xiao)直(zhi)徑油(you)缸。②臂架(jia)懸臂部分短，臂架(jia)受力有利。③臂架(jia)下方有效(xiao)空間小(xiao)。

后(hou)置式特點：①油缸(gang)后(hou)移，對起重機穩定有(you)利(li)。②需要(yao)的變幅推力大(da)。③臂架(jia)(jia)懸臂部(bu)分長，臂架(jia)(jia)受力不(bu)利(li)。④臂架(jia)(jia)下方有(you)效空間大(da)。

后拉式(shi)特(te)點：只要用于非伸縮行架式(shi)臂架，臂架前(qian)方(fang)空(kong)間(jian)大(da)。

酸雨(yu)腐蝕：由于(yu)環(huan)境污染的(de)加重(zhong)，某些城市(shi)酸雨(yu)現象比較(jiao)嚴(yan)重(zhong)，而在(zai)這(zhe)樣的(de)環(huan)境下我們的(de)車則可(ke)能會增大損壞的(de)可(ke)能。

2

污水、油膩等(deng)(deng)物腐(fu)(fu)蝕：由(you)于底盤經(jing)常會與(yu)污水、油膩等(deng)(deng)物質接觸(chu)，而(er)這(zhe)些物質中的化學成分會慢慢腐(fu)(fu)蝕底盤以及底盤上(shang)的零件。

3

融雪(xue)劑(ji)腐(fu)蝕(shi)：冬天用(yong)來融雪(xue)的融雪(xue)劑(ji)以及(ji)海水都可以腐(fu)蝕(shi)我們的底盤。

4海(hai)水(shui)腐蝕(shi)：如(ru)果你自己(ji)車去海(hai)邊外一定不要將車開到(dao)海(hai)里，海(hai)水(shui)對(dui)底(di)盤的(de)(de)腐蝕(shi)性(xing)會非常的(de)(de)強。

一(yi)、起重機(ji)的供電特點

交流起重(zhong)(zhong)機電(dian)(dian)(dian)(dian)(dian)源由公共(gong)的(de)(de)(de)交流電(dian)(dian)(dian)(dian)(dian)網供(gong)(gong)(gong)電(dian)(dian)(dian)(dian)(dian)，液(ye)壓(ya)支柱價格，由于(yu)(yu)起重(zhong)(zhong)機的(de)(de)(de)工作(zuo)是(shi)經常(chang)移動的(de)(de)(de)，因此其(qi)與電(dian)(dian)(dian)(dian)(dian)源之(zhi)間不能采(cai)用固定連接方(fang)(fang)式(shi)，對于(yu)(yu)小(xiao)型起重(zhong)(zhong)機供(gong)(gong)(gong)電(dian)(dian)(dian)(dian)(dian)方(fang)(fang)式(shi)采(cai)用軟電(dian)(dian)(dian)(dian)(dian)纜供(gong)(gong)(gong)電(dian)(dian)(dian)(dian)(dian)，隨著大車(che)或(huo)小(xiao)車(che)的(de)(de)(de)移動，供(gong)(gong)(gong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)纜隨之(zhi)伸(shen)展和(he)疊卷(juan)。對于(yu)(yu)一般橋式(shi)起重(zhong)(zhong)機常(chang)用滑線(xian)和(he)電(dian)(dian)(dian)(dian)(dian)刷供(gong)(gong)(gong)電(dian)(dian)(dian)(dian)(dian)。三(san)(san)相(xiang)交流電(dian)(dian)(dian)(dian)(dian)源接到沿車(che)間長度方(fang)(fang)向(xiang)架設(she)的(de)(de)(de)三(san)(san)根主滑線(xian)上(shang)，再通過電(dian)(dian)(dian)(dian)(dian)刷引到起重(zhong)(zhong)機的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)氣(qi)(qi)設(she)備上(shang)，首(shou)入駕(jia)駛室中的(de)(de)(de)保護盤(pan)上(shang)的(de)(de)(de)總電(dian)(dian)(dian)(dian)(dian)源開(kai)關，然后再向(xiang)起重(zhong)(zhong)機各電(dian)(dian)(dian)(dian)(dian)氣(qi)(qi)設(she)備供(gong)(gong)(gong)電(dian)(dian)(dian)(dian)(dian)。對于(yu)(yu)小(xiao)車(che)及其(qi)上(shang)的(de)(de)(de)提(ti)升(sheng)機構等(deng)電(dian)(dian)(dian)(dian)(dian)氣(qi)(qi)設(she)備，則(ze)經位于(yu)(yu)橋架另一側(ce)的(de)(de)(de)輔助滑線(xian)來供(gong)(gong)(gong)電(dian)(dian)(dian)(dian)(dian)。

滑線(xian)通常用角(jiao)鋼、圓(yuan)鋼、V形鋼軌來制成(cheng)。當電(dian)流(liu)值很大或滑線(xian)太長時，為減少滑線(xian)電(dian)壓降(jiang)，常將角(jiao)鋼與鋁排逐斷并聯，以減少電(dian)阻值。在交流(liu)系統中，圓(yuan)鋼滑線(xian)因趨膚效應的(de)影響，只適用于短線(xian)路或小電(dian)流(liu)的(de)供電(dian)線(xian)路。

二、電路構成

10t交流橋式(shi)(shi)起(qi)重機電(dian)(dian)(dian)氣控制(zhi)(zhi)的(de)(de)全電(dian)(dian)(dian)路(lu)如圖(tu)8－10所(suo)示。10t橋式(shi)(shi)起(qi)重機只有一個吊鉤，液壓支柱哪家好(hao)，但大車(che)(che)(che)采用分(fen)(fen)別(bie)(bie)驅(qu)(qu)動(dong)，所(suo)以共用了四(si)臺繞線(xian)轉(zhuan)子異步(bu)電(dian)(dian)(dian)動(dong)機拖動(dong)。起(qi)重電(dian)(dian)(dian)動(dong)機M1、小車(che)(che)(che)驅(qu)(qu)動(dong)電(dian)(dian)(dian)動(dong)機M2、大車(che)(che)(che)驅(qu)(qu)動(dong)電(dian)(dian)(dian)動(dong)機M3和M4；分(fen)(fen)別(bie)(bie)由(you)三(san)(san)只凸輪控制(zhi)(zhi)器(qi)控制(zhi)(zhi)：QM1控制(zhi)(zhi)M1、QM2控制(zhi)(zhi)M2、QM3同步(bu)控制(zhi)(zhi)M3與M4；R1～R4分(fen)(fen)別(bie)(bie)為(wei)四(si)臺電(dian)(dian)(dian)動(dong)機轉(zhuan)子電(dian)(dian)(dian)路(lu)串入的(de)(de)調(diao)速電(dian)(dian)(dian)阻器(qi)；YB1～YB4則分(fen)(fen)別(bie)(bie)為(wei)四(si)臺電(dian)(dian)(dian)動(dong)機的(de)(de)制(zhi)(zhi)動(dong)電(dian)(dian)(dian)磁鐵。三(san)(san)相電(dian)(dian)(dian)源(yuan)由(you)QS1引入，威海液壓支柱，并由(you)接觸器(qi)KM控制(zhi)(zhi)。過(guo)流繼電(dian)(dian)(dian)器(qi)KI0～KI4提供過(guo)電(dian)(dian)(dian)流保護(hu)(hu)，其(qi)中KI1～KI4為(wei)雙線(xian)圈式(shi)(shi)，分(fen)(fen)別(bie)(bie)保護(hu)(hu)M1、M2、M3與M4；KI0為(wei)單線(xian)圈式(shi)(shi)，單獨串聯在(zai)主電(dian)(dian)(dian)路(lu)的(de)(de)一相電(dian)(dian)(dian)源(yuan)線(xian)中，作總電(dian)(dian)(dian)路(lu)的(de)(de)過(guo)電(dian)(dian)(dian)流保護(hu)(hu)。

該(gai)電路(lu)的(de)控制(zhi)原理已在分析圖2-6時介(jie)紹(shao)過，不同(tong)的(de)是凸(tu)輪控制(zhi)器(qi)QM3共有17對觸點，比QM1、QM2多了五對觸點，用于控制(zhi)另一臺電動機(ji)的(de)轉(zhuan)子電路(lu)，因此可(ke)以同(tong)步控制(zhi)兩臺繞線轉(zhuan)子異步電動機(ji)。下面(mian)主要介(jie)紹(shao)該(gai)電路(lu)的(de)保(bao)護電路(lu)部(bu)分。