由于各螺杆(gǎn)的相互齧合以及(ji)螺杆與襯筒内壁(bi)的緊密配合，在泵(bèng)的吸入口和排出(chu)口之間，就會被分(fèn)隔成一個或多個(ge)密封空間。随着螺(luo)杆的轉動和齧合(he)，這些密封空間在(zài)泵的吸入端不斷(duan)形成，将吸入室中(zhong)的液體封入其中(zhōng)，并自吸入室沿螺(luo)杆軸向連續地推(tui)移至排出端，将封(fēng)閉在 各空間中的(de)液體不斷排出，猶(yóu)如一螺母在螺紋(wen)回轉時被不斷向(xiang)前推進的情形那(nà)樣，其中螺紋圈數(shù)看做液體，當螺釘(dìng)旋轉時螺紋在轉(zhuan)動時就相當于液(ye)體在螺杆泵裡面(miàn)的情形，這就是螺(luo)杆泵的基本工作(zuò)原理。螺杆與殼體(ti)之間的密封面是(shi)一個空間曲面。在(zài)這個曲面上存在(zai)着諸如ab或de之類的(de)非密封區，并且與(yu)螺杆的凹槽部分(fèn)形成許多三角形(xíng)的缺口abc、def。這些三角(jiǎo)形 的缺口構成液(yè)體的通道，使主動(dòng)螺杆凹槽A與從動(dòng)螺杆上的凹槽B、C相(xiàng)連通。而凹槽B、C又沿(yán)着自己的螺線繞(rào)向背面， 并分别和(hé)背面的凹槽D、E相連(lián)通。由于在槽D、E與槽(cáo)F(它屬于另一頭螺(luo)線)相銜接的密封(feng)面上，也存在着類(lei)似于正面的三角(jiǎo)形缺口a’b’c’，所以D、F、E也将(jiang)相通。這樣，凹槽ABCDEA也(yě)就組成一個“∞” 形的(de)密封空間(如采用(yong)單頭螺紋，則凹槽(cáo)将順軸向盤饒螺(luó)杆，将吸排口貫通(tōng)，無法形成密封)。不(bú)難想象，在這樣的(de)螺杆 上，将形成許(xǔ)多個獨立的“∞”形密(mì)封空間，每一個密(mi)封空間所占有的(de)軸向長度恰好等(děng)于累杆的導程t。因(yīn)此，為了使螺杆能(néng)吸、排油口分隔開(kai)來，螺杆的螺紋段(duan)的長度至少要大(da)于一個導程。Due to the mutual engagement of each screw and screw and the close coordination of the liner wall, between the inlet and outlet of the pump, can be divided into one or more of the sealed space.With the rotation of the screw and the meshing, the sealed space in pump suction side form unceasingly, the liquid from the suction chamber seal in among them, and the suction chamber along the screw axial continuously goes on to the discharge end, will be closed in the space of the liquid discharge, like a nut in screw rotation being constantly move forward, the screw thread turns as liquid, when screw rotating screw rotation is equivalent to the liquid in the inside of the screw pump, this is the basic work principle of screw pump.The sealing surface between screw and shell is a space curved surface.Exist on the surface of the sealing section, such as ab or DE and screw groove part of the form many the gap of the triangle ABC, def.These triangular gap formation fluid channels, make active screw groove with A driven screw groove on the connected to B and C.And groove B, C and along their spiral around to the back, and, respectively, and on the back of the groove connected to D and E.Due to the tank D, E and F (it belongs to another head spiral) of corresponding seal surface, there are also similar to the positive triangle gap a 'b' c ', so D, F, E will also is same.So, grooves ABCDEA on forming a "up" form of the sealed space (such as using single thread, axial disc groove will arrange spare screw, connecting the suction PaiKou, unable to form a seal).It is not hard to imagine that in this kind of screw, will form a number of independent "up" form sealed space, each of the sealed space occupied the axial length equals the tired stem lead t.Therefore, in order to make the screw suction and discharge of oil can be separated, the length of the screw thread of at least than a lead.