1 简介

真(zhen)空泵(beng)(beng)(beng)是一种旋转式(shi)变(bian)容真(zhen)空泵(beng)(beng)(beng)须有前级泵(beng)(beng)(beng)配合方可使用在较宽的压力范围内有较大的抽速对被(bei)抽除气体中含有灰尘和水(shui)蒸汽不敏感广(guang)泛用于冶金、化工、食品、电子镀(du)膜等行(xing)业。[1]

2 特点

(1)在较宽(kuan)的压力(li)范围内有较大的抽速；

(2)转(zhuan)子具有良好的几何对称(cheng)性，故振动(dong)小(xiao)，运转(zhuan)平稳。转(zhuan)子间(jian)(jian)(jian)及转(zhuan)子和壳体间(jian)(jian)(jian)均有间(jian)(jian)(jian)隙，不(bu)用润滑，摩擦损失小(xiao)，可大大降低(di)驱动(dong)功率，从而可实现较(jiao)高转(zhuan)速；

(3)泵腔内(nei)无需(xu)用油密封和润滑，可(ke)减少油蒸气对真空系统的污(wu)染；

(4)泵腔内(nei)无压缩，无排(pai)气阀。结构简单、紧(jin)凑，对被抽气体中的(de)灰尘和水蒸汽不敏感；

(5)压缩(suo)比较低，对氢(qing)气(qi)(qi)抽气(qi)(qi)效(xiao)果(guo)差(cha)；

(6)转子(zi)表面为(wei)形状较(jiao)为(wei)复(fu)杂的曲线(xian)柱面，加工和检(jian)查(cha)比(bi)较(jiao)困难。

3 结构

（1） 泵总(zong)体(ti)结构型式

真空(kong)泵(beng)的泵(beng)体的布置结构决(jue)定了(le)泵(beng)的总(zong)体结构。

立式(shi)结构的(de)进、排气口水平设置，装配和连(lian)接管路都比较(jiao)方便。但(dan)泵(beng)的(de)重(zhong)心较(jiao)高，在高速运转(zhuan)时稳定性差(cha)，故这种型式(shi)多用于小(xiao)泵(beng)。

卧(wo)式泵(beng)的进气(qi)口在上，排气(qi)口在下。有(you)时(shi)为了真空系统(tong)管(guan)道安装连接(jie)(jie)(jie)方(fang)便(bian)，可将排气(qi)口从水平方(fang)向(xiang)接(jie)(jie)(jie)出，即进、排气(qi)方(fang)向(xiang)是相(xiang)互垂(chui)直的。此时(shi)，排气(qi)口可以从左或右两个(ge)方(fang)向(xiang)开口，除接(jie)(jie)(jie)排气(qi)管(guan)道一端(duan)外，另(ling)一端(duan)堵死(si)或接(jie)(jie)(jie)旁(pang)通阀。这种泵(beng)结构重心低，高(gao)速运转时(shi)稳定性好。一般大(da)、中型泵(beng)多采用此种结构。

泵的(de)两个(ge)转(zhuan)子(zi)轴与水平面(mian)垂直安(an)装(zhuang)。这种结构(gou)装(zhuang)配间隙容易控制(zhi)，转(zhuan)子(zi)装(zhuang)配方便(bian)，泵占地面(mian)积小(xiao)。但(dan)泵重心较高(gao)且齿轮拆装(zhuang)不便(bian)，润滑机构(gou)也相对复(fu)杂(za)。

（2） 泵的传动方式

真空泵的(de)两(liang)个(ge)转(zhuan)(zhuan)子是通过一(yi)对高(gao)精度齿(chi)轮来实现(xian)其相对同步运(yun)转(zhuan)(zhuan)的(de)。主(zhu)动(dong)(dong)轴(zhou)(zhou)通过联(lian)轴(zhou)(zhou)器(qi)与电(dian)机联(lian)接。在传(chuan)动(dong)(dong)结构布(bu)置上(shang)主(zhu)要有(you)(you)以(yi)下两(liang)种(zhong)：其一(yi)是电(dian)动(dong)(dong)机与齿(chi)轮放(fang)在转(zhuan)(zhuan)子的(de)同一(yi)侧如(ru)图。从(cong)动(dong)(dong)转(zhuan)(zhuan)子由电(dian)动(dong)(dong)机端齿(chi)轮直接传(chuan)过去带动(dong)(dong)，这样主(zhu)动(dong)(dong)转(zhuan)(zhuan)子轴(zhou)(zhou)的(de)扭(niu)转(zhuan)(zhuan)变(bian)形小，则两(liang)个(ge)转(zhuan)(zhuan)子之间(jian)的(de)间(jian)隙不会(hui)因主(zhu)动(dong)(dong)轴(zhou)(zhou)的(de)扭(niu)转(zhuan)(zhuan)变(bian)形大而改变(bian)，故使转(zhuan)(zhuan)子之间(jian)的(de)间(jian)隙在运(yun)转(zhuan)(zhuan)过程中均匀(yun)。这种(zhong)传(chuan)动(dong)(dong)方式(shi)的(de)最大缺点是：a.主(zhu)动(dong)(dong)轴(zhou)(zhou)上(shang)有(you)(you)三个(ge)轴(zhou)(zhou)承，增加了泵的(de)加工(gong)和(he)装配难度，齿(chi)轮的(de)拆装及调整也不便；b.整体结构不匀(yun)称(cheng)，泵的(de)重心(xin)偏(pian)向电(dian)动(dong)(dong)机和(he)齿(chi)轮箱一(yi)侧。

    极限(xian)(xian)真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)”是(shi)真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)泵的(de)一(yi)个重要参数，是(shi)反(fan)应泵抽(chou)气(qi)能力的(de)特性值(zhi)(zhi)(zhi)，是(shi)与真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)泵相关的(de)一(yi)个数值(zhi)(zhi)(zhi)，不同(tong)的(de)真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)泵可(ke)以(yi)有不同(tong)的(de)“极限(xian)(xian)真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)”度。而(er)“理(li)论真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)”是(shi)理(li)论研(yan)究时(shi)的(de)一(yi)个概念，是(shi)排(pai)除各种实际(ji)因素的(de)影响而(er)提炼出(chu)的(de)一(yi)种最理(li)想(xiang)的(de)真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)状(zhuang)态。真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)容(rong)器经(jing)充(chong)分(fen)抽(chou)气(qi)后(hou)，稳(wen)定(ding)在某一(yi)真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)度，此真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)度称为极限(xian)(xian)真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)。通(tong)常(chang)真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)容(rong)器须经(jing)12小(xiao)时(shi)炼气(qi)，再经(jing)12小(xiao)时(shi)抽(chou)真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)，最后(hou)一(yi)个小(xiao)时(shi)每(mei)隔10分(fen)钟测量一(yi)次(ci)，取其10次(ci)的(de)平均值(zhi)(zhi)(zhi)为极限(xian)(xian)真(zhen)(zhen)(zhen)(zhen)空(kong)(kong)(kong)(kong)(kong)(kong)(kong)(kong)值(zhi)(zhi)(zhi)。