圆弧-摆线-渐开线型罗茨泵转子型线参数选择范围

Parameter Selection Range for Circular Arc-Involute-Cycloid Type Rotor Profile of Roots Pump

罗茨泵转子型线是罗茨泵的关键。零流量压缩比高的罗茨真空泵、湿式罗茨泵真空泵和罗茨鼓风机均要求泵工作时转子与壳体之间及两转子之间气体泄漏较小，这样可改善泵的低压下性能，即提高泵的抽气效率。转子型线为“圆弧－摆线－渐开线”就可以满足这一要求。文中给出了泵的参数选择图，从图中可以看出泵的参数选择范围，文中说明了该图边界的性状．由该图可查出泵的容积利用系数λ同转子顶圆半径Ｒｍ与节圆半径Ｒ之比 Ｒｍ／Ｒ以及同渐开线压力角α的关系。 λ＝ｆ（Ｒｍ／Ｒ，ａ）。图中用计算机绘出了几个比较特征参数下转子型线及其啮合情况，借此可根据实际需要来选择系的转子型线参数。此种转子型线工艺性良好。可仿型法加工（只需两个工位）。还可以用范成法加工其渐开线部分，余下部分用成型铣刀加工。若以范成法加工型线渐开线部分时，设计转子型线时可选取渐开线基圆半径ｒ为整数．以便于其工艺装备的设计。

The Rotor profile is the key for Roots pump. The Roots vacuum pump with high compress ratio at zero displacement,wet type Roots pump and Roots blower all require less gas leakage between rotor and housing, two rotors during the operation. To do so, characteristics at low pressure can be improved, that is to improve the pump efficiency. The pump whose rotor profile is circular arc- involute-cycloid can meet this demand. The parameter option figure is given in the paper and parameter option range can be seen from the figure. The characteristic and shape of the figure boundary is also illustrated in the paper. The relationship among λ (volume utilization coefficient), Rm/R (the ratio of head circle radius and pitch circle radius)and a (involute pressure angle) can be looked up. The rotor profile and rotor meshing under some typical parameters are drawn by computer in the figure. The rotor profile parameters can be selected according to actual requirements. Such kind of rotor profile has good process characteristic. It can be processed by forming (only two working positions are needed ) and involute part can be processed by generation.The rest part can be form-cut with a disk-type milling cutter. If the involute part of the profile is processed by generation, the whole number of involute basic radius may be selected when designing the rotor profile, so that, the technological equipment design can be made easier.