In the manufacture of vacuum pump, the design of cylinder block surface is relatively important. Taking rotary vane vacuum pump as an example, when the pump works, it mainly depends on the change of elementary volume of blade on cylinder block surface to obtain vacuum. This means that the volume of the pump elementary surface depends on the actual situation of the cylinder body surface. Therefore, in the actual manufacture, the reasonable design of cylinder surface can improve the pumping speed and pump efficiency. The vacuum pump manufacturer points out that the advantage of the equipment is that the price of the rotary vane vacuum pump is decisive.
Rotary vane vacuum pump is a kind of volumetric fluid machinery. When rotating, centrifugal force keeps the top of the slider in contact with the inner wall of the cylinder block. The rotor drives the slider to slide along the inner wall of the cylinder block. A closed working chamber is formed between the upper and lower end caps, slider, rotor and cylinder block to realize gas inhalation, compression and discharge. It has the advantages of large pumping speed, small volume, and can extract a certain amount of condensable gas. It is widely used in machinery, electronics, chemical industry, automobile and other industries. The common slide vane vacuum pumps include single chamber, double chamber and three chamber slide vane vacuum pumps. In order to obtain better performance, the design of cylinder block profile is particularly important. Relevant studies have proposed multiple function profiles, trigonometric function profiles and multi-segment combination curves, but each working chamber of the corresponding cylinder block is symmetrical structure, with a larger exhaust volume, resulting in a smaller content-to-volume ratio and a lower compression efficiency.
In order to increase the volume ratio of slide vane vacuum pump and enrich the type of cylinder block profile, the invention provides a design method of cylinder block and profile of double cavity slide vane vacuum pump. The sinusoidal helix is used to construct the cylinder block profile, changing the proportion of the central angle corresponding to the curve of the suction and discharge section, so as to form two identical asymmetric working chambers between the cylinder block and the rotor, reduce the exhaust volume and increase the content volume ratio. All curves on the cylinder block profile satisfy the second derivative continuity, which ensures that no rigid and flexible impact occurs when the top of the slide is in contact with the inner wall of the cylinder block.
At present, most vacuum pumps adopt the principle of eccentric motion of cylinder block and rotor blade. For example, some common single-stage rotary vane vacuum pumps usually adopt eccentric position of a rotor in the retrofitted stator chamber. When the rotor rotates, because of eccentricity, the blade inertia force on the rotor slides close to the inner surface of the stator to achieve volume change and complete air extraction and exhaust. Process. This stator curve has the advantages of simple structure, convenient processing, low rejection rate, good interchangeability and low cost. It is suitable for mass I production. It has good dynamic balance performance when rotating at high speed and is easy to achieve higher rotational speed.
Of course, there are shortcomings in the design of any pump, which needs to be adjusted in the design and manufacture to meet the actual use requirements.
Taking EVP rotary vane vacuum pump as an example, the eccentric distance between the pump vane cylinder and the rotor is reasonably controlled to prevent the blade from pulling out and reduce the stress on the blade. So its service life is also relatively improved. At the same time, many pumps manufactured in our country are prone to jam after running for a long time, resulting in excessive contact clearance between the surface of the rotor and stator inner curve, increasing leakage and shock vibration, and generating noise. The pumping rate is low. Because of a certain eccentricity, the pumping rate is limited and it is difficult to improve. Therefore, in view of the shortcomings of the traditional structural design, we need to solve these problems through new blade design and cylinder surface design.