由于各螺杆的相(xiàng)互齧合以及螺杆與襯筒内壁(bì)的緊密(mì)配合，在泵的吸入口和(hé)排出(chū)口之間，就會被分(fèn)隔成一個或多個(gè)密封空間(jiān)。随着(zhe)螺杆的轉動和齧合(hé)，這些密封空間在泵的吸入端不斷(duàn)形成，将吸入室(shì)中的液體封(fēng)入(rù)其中(zhōng)，并自吸入室沿螺杆軸向(xiàng)連續地推(tuī)移至(zhì)排出端，将封(fēng)閉在 各(gè)空間中的液體(tǐ)不斷排出，猶如一螺母在螺紋(wén)回轉時被不斷向前推進(jìn)的情形那(nà)樣，其中螺紋(wén)圈(quān)數看做液體，當螺釘(dìng)旋轉時螺紋在轉動時就相當于液體在螺杆泵裡面的情形，這就是(shì)螺杆泵的基本工作原(yuán)理。螺杆與殼體之間的密封面是一個空(kōng)間曲面。在(zài)這個曲面上存在(zài)着諸如ab或de之類的(de)非密(mì)封區，并且與(yǔ)螺杆的(de)凹(āo)槽(cáo)部分形成許多三角形的缺口abc、def。這些三角(jiǎo)形 的缺口構成液體的通道，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(yòu)沿着自(zì)己(jǐ)的螺線繞(rào)向背面， 并分别和背面(miàn)的凹槽(cáo)D、E相連通。由于在槽D、E與槽F(它屬于另一頭螺(luó)線)相銜接的密封面上，也存在(zài)着類似于正面的三角(jiǎo)形缺口a’b’c’，所以D、F、E也将相通(tōng)。這樣，凹槽ABCDEA也就組成一個“∞” 形的密封空間(如采用單頭螺紋，則凹槽(cáo)将順軸向盤饒螺杆(gǎn)，将吸(xī)排口貫通，無法(fǎ)形成密封)。不難想象，在這樣的(de)螺杆 上，将形成許(xǔ)多個(gè)獨立的(de)“∞”形密(mì)封空間，每一個(gè)密(mì)封空間所占有(yǒu)的(de)軸向長度恰好等(děng)于(yú)累杆(gǎn)的導程t。因此，為了使螺杆(gǎn)能吸(xī)、排油口分隔開來，螺杆的螺紋段的長度至少要大(dà)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.