由于各(gè)螺杆的相互齧(niè)合以(yǐ)及螺杆與(yǔ)襯筒(tǒng)内壁的緊密配(pèi)合，在(zài)泵的(de)吸入口和排出(chū)口之(zhī)間，就(jiù)會被(bèi)分隔(gé)成一(yī)個或(huò)多個密封空間(jiān)。随着螺杆(gǎn)的轉(zhuǎn)動和(hé)齧合，這些(xiē)密封(fēng)空間在泵的吸(xī)入端不斷(duàn)形成(chéng)，将吸入室(shì)中的(de)液體封入(rù)其中，并自吸入(rù)室沿螺杆軸向連續地推移至(zhì)排出(chū)端，将(jiāng)封閉在 各空間中的(de)液體不(bú)斷排出(chū)，猶如(rú)一(yī)螺(luó)母在(zài)螺(luó)紋回轉時被(bèi)不斷向前推進(jìn)的情形那(nà)樣，其(qí)中螺紋圈數看做液體，當螺釘(dìng)旋轉時螺紋在(zài)轉動(dòng)時就相當(dāng)于液體在(zài)螺杆(gǎn)泵裡面的情形，這就(jiù)是螺杆泵(bèng)的基本工(gōng)作原(yuán)理。螺杆與(yǔ)殼體(tǐ)之間(jiān)的(de)密封面(miàn)是一個空(kōng)間曲(qǔ)面。在這個曲面(miàn)上存(cún)在着諸如(rú)ab或de之(zhī)類的非密(mì)封區，并且(qiě)與螺(luó)杆的(de)凹(āo)槽(cáo)部分(fèn)形成許多三角(jiǎo)形的缺口(kǒu)abc、def。這些(xiē)三角形 的缺口(kǒu)構成液體(tǐ)的通(tōng)道，使主動(dòng)螺杆凹槽(cáo)a與從動螺(luó)杆(gǎn)上的凹(āo)槽b、c相(xiàng)連通。而凹槽b、c又(yòu)沿着自己的螺(luó)線繞向背(bèi)面， 并(bìng)分别和背面的凹(āo)槽d、e相連通。由(yóu)于在槽d、e與槽(cáo)f(它屬于另一(yī)頭螺(luó)線)相(xiàng)銜接(jiē)的密(mì)封面上(shàng)，也存在(zài)着類似(sì)于(yú)正面(miàn)的三角形缺口a’b’c’，所以d、f、e也(yě)将(jiāng)相通(tōng)。這樣(yàng)，凹槽abcdea也就(jiù)組成(chéng)一個“∞” 形的(de)密封(fēng)空間(jiān)(如采(cǎi)用單頭(tóu)螺紋，則(zé)凹槽将順(shùn)軸向(xiàng)盤饒螺杆，将吸排口貫(guàn)通，無法(fǎ)形成密封(fēng))。不難(nán)想象，在這樣的(de)螺杆 上，将形成(chéng)許多個獨(dú)立的(de)“∞”形密(mì)封空間，每(měi)一(yī)個(gè)密封空間(jiān)所占有的(de)軸向(xiàng)長度(dù)恰好(hǎo)等于累杆(gǎn)的(de)導(dǎo)程t。因(yīn)此，為了使螺杆能吸、排油口分(fèn)隔開來(lái)，螺杆的(de)螺紋段的(de)長度至少要(yào)大(dà)于一(yī)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.