The vortex dry pump, with its unique performance advantages, has always been the vacuum cleaner to obtain the highly anticipated products of the equipment industry. Traditional vortex dry pumps, due to their weaknesses in the sealing technology and machining accuracy, have made it impossible to perform the performance advantages of the oil-free vortex compression technology in many applications, thereby limiting its large number of applications. The floating oil-free scroll dry pump, through the fine force balance, gives full play to the performance advantages of oil-free scroll compression technology, making it the most anticipated new product in the field of clean vacuum access equipment. This article analyzes the basic working principle of the scroll vacuum pump, the sealing and machining accuracy of the traditional scroll dry pump, and then leads to the characteristics and performance advantages of the floating scroll dry pump structure. Finally, through the comparison of experimental data, clarify the micro floating The overwhelming performance advantages of the vortex dry pump and the prospects for future market development.
Overview
The clean and pollution-free vacuum environment has always been the ideal vacuum environment pursued by the scientific community and enterprises. With the continuous development of science and technology, vacuum technology has become increasingly widespread in all walks of life. The industrial society has constantly put forward new requirements for realizing and guaranteeing the rationality, reliability, safety and technological progress of the vacuum process. As a new type of vacuum pump developed in the 1980s, the vortex dry vacuum pump has always been expected by the industry because of the unparalleled performance advantages of its other structural vacuum pumps. However, due to the structural characteristics of the conventional scroll dry vacuum pump, Due to the high requirements for processing accuracy, the characteristics of vortex compression structures have not been fully utilized, and the performance has been optimized. Thus, large-scale applications cannot be achieved in actual industrial production. The floating scroll dry pump structure solves the defects and limitations in the traditional scroll dry pump structure and pushes the performance of the scroll dry pump to a higher exhibition. The product is more stable and reliable, and the volumetric efficiency and cost performance are higher. It is more suitable for applications in scientific instruments, portable instrument industry, semiconductor, new material industry, biopharmaceutical industry, food industry, and all vacuum environment that require no oil pollution.
How the scroll vacuum pump works
The working principle of the scroll vacuum pump stems from an invention patent of Creux in 1905. The invention uses a pair of intermeshing ones, one of which is fixed and the other is a circular translational “iso-pitch involute†side wall. Kind of compressed structure. The DeKalb coordinates of any point on the vortex are as follows:
X=α. (cos θ+ θ. sin θ)
Y=α. (sin θ+ θ. cos θ)
The constant α represents the radius of the axis and θ represents the expansion angle.
The swirl disk of a scroll vacuum pump is a scroll disk structure formed by one or more involute spirals having one end connected to a flat surface. A fixed scroll and an orbiting scroll are cross-assembled with each other, and a phase difference of 180° is ensured between the two by an anti-rotation mechanism, and the spiral sidewalls are connected by a wire, so that a pair of vortexes are combined. The disk pair constitutes the basic pumping mechanism of the scroll vacuum pump. A pair of symmetrical crescent chambers are formed between the fixed scroll and the orbiting scroll, and the orbiting scroll is driven by the crankshaft to make a circular translation around the fixed scroll to periodically change the volume of the crescent-shaped sealing chamber. , The contact point of the fixed scroll moves along the scroll surface to achieve suction, compression and exhaust cycle.
Structure Design and Characteristics of Traditional Rotary Dry Pumps
The leakage of the scroll vacuum pump mainly includes radial leakage through the axial engagement gap of the scroll profile and tangential leakage through the radial engagement gap of the profile. Theoretical studies and tests have confirmed that the axial seal at the top of the scroll disc has a decisive effect on the performance of the pump, in particular the ultimate vacuum of the pump, and the gap between the scroll disc itself and the air chamber and the performance of the seal on the pump. Plays a very important role.
In the design of the traditional scroll dry pump, radial leakage is solved by means of the top seal, and tangential leakage is solved by the method of controlling the clearance between the movable scroll disk and the fixed scroll disk wall. In today's market, in the main product line of the main typical manufacturers, the top seal is used to mill a sealing groove at the top of the fixed scroll disc pair, and then the PTFE sealing strip is pressed gently into the sealing groove along the center point of the profile line. The entire sealing strip protruding sealing groove must be controlled within a very small range in order to achieve the desired effect of the top sealing. The sealing of each air chamber is determined by the gap between the side walls of the scroll and the relative sliding speed, and it must also be controlled within a very small range. Such a precision imposes very high demands on the processing equipment and assembly accuracy. At present, in order to ensure the precision of the products, various manufacturers must use parts matching and use special tools to perform positioning and assembly in order to ensure the precision of the products, so as to ensure the precision requirements of the vortex plate. However, due to the accuracy limit that can be achieved, the conventional scroll dry pump can only pump between 3.6m3/hr to 60m3/hr, and its ultimate vacuum is mainly concentrated at 1Pa to 10Pa. Only Edwards's nXDS series. There are two products whose ultimate vacuum degree is said to reach 0.7Pa. However, Edwards's scroll dry pump adopts bellows seal, and there are still major problems in product life and reliability. Its market acceptance is still very high. limited.
The structure of a conventional scroll dry pump needs to achieve the required performance. The above accuracy is required as a guarantee. At the same time, during the entire operation of the pump, there will be friction between the components and it will take a long time to compress the gas. Gas extraction, so the precision structure also needs to be able to cope with thermal expansion and contraction of the pump during operation. Due to the influence of the structure of the moving and fixed scrolls and the working environment, the temperature rise and deformation of the scroll during operation, and the amount of deformation are not the same, the gap between the movable scroll and the fixed scroll will follow the working conditions. Variety. If the gap is too large, the ultimate vacuum degree of the pump will be difficult to reach, the clearance will be too small, and friction and even bite will occur between the moving and fixed scrolls, leading to a sharp rise in temperature, a drop in the efficiency of the pump, or damage to the dynamic and static vortexes. The wall surface of the disk resulted in the failure of the pump.
During long-term operation, the top seal will continue to generate a large amount of dust. The dust will not only cause new pollution to the surrounding environment, but excessive dust will accumulate in the compression chamber of the pump. In the event of abnormal stoppage of the pump, the dust will be directly discharged back into the vacuum system and directly contaminate the vacuum system. At the same time, due to constant wear and tear, radial leakage will increase continuously. After running for a period of time, the pumping rate and ultimate vacuum degree of the pump will be affected to a great extent. At the same time, due to wear, the pump needs regular maintenance and regular replacement of the PTFE sealing strip. As a result, not only the performance of the pump is reduced, but also its use cost is greatly increased. When the gas leakage gradually becomes larger, the repeated compression of the gas is serious. In the long term, the reliability of the pump will be directly reduced, and the service life will be greatly reduced.
Due to the structural specificity of the conventional scroll dry pump, the pump's ability to treat dust and water vapor is very poor. If the pump sucks large particles of hard dust, the hard particles will damage the side walls of the fixed scroll pair due to direct compression, increase the side wall clearance, directly affect the sealing performance, and serious damage may directly damage the pump. structure. If the amount of water vapor entering the inlet of the scroll vacuum pump is too large, the water vapor undergoes a phase change during compression and is converted into a liquid. As a result, the water accumulated in the pump can quickly contaminate and corrode the inside of the pump, especially the bearing, and eventually lead to a pump. The water accumulated inside makes the pump not reach the original ultimate vacuum. For this reason, conventional vortex dry pumps often use “knocking†to remove water and water vapor, while “knocking†structures precisely reduce the ultimate vacuum of the vacuum pump.
It can be seen that the traditional scroll dry pump design has advantages over other conventional dry pumps, but it fails to fully exploit the advantages of the scroll compression technology and fails to improve the performance of the scroll dry pump. High levels limit some direct applications of vortex dry pumps.
Structure design and characteristics of floating scroll dry pump
The floating vortex compression technology achieves a completely sealed state by maintaining a proper contact with the fixed scroll during the dynamic operation of the orbiting scroll under the condition of no oil or micro oil. It also minimizes frictional losses, thereby maximizing volumetric efficiency and reliability, making it one of the most ideal clean vacuum equipment.
Due to its fine force balance structure, the floating scroll dry pump enables the gas to be compressed away from adiabatic and near isothermal process, reducing power consumption. Dynamic scrolls can use other engineering plastics than aluminum. Taking PEEK as an example, in the dynamic operation process, it can be directly contacted and sealed with an aluminum fixed scroll, solving the technical problems of "radial leakage" and "tangential leakage" existing in conventional vortex technology and improving its sealing performance. Reduce leakage between compression chambers, increase compression efficiency and ultimate vacuum. At the same time, the self-lubrication performance of PEEK material and aluminum anodized film can basically offset the frictional force generated by the contact movement between the movable vortex reels, making the pump work in the best working and sealed state throughout the entire life cycle. It will not result in the reduction of extreme vacuum and slow pumping speed due to long working hours.
A "fathead" structure is arranged at the top of the scroll-shaped profile of the floating scroll dry pump structure, which promotes its theoretical dead volume to be "zero", and combines the radial and axial floating ability during the dynamic movement of the movable scroll reel. The structure dry pump has stronger steam treatment capacity and dust tolerance, and will not directly damage the pump due to the "water hammer" effect because of excessive compression and condensation of liquid water in an excessive water vapor working environment. .
Due to the above structural features, the floating scroll dry pump not only does not require a PTFE top seal, but also is not affected by the thermal expansion and contraction during the entire long-term continuous operation, and runs continuously for 10,000 hours throughout the entire life cycle. The moving scroll wear does not exceed 0.1mm. The floating structure allows the moving scroll to automatically compensate for its wear. Compared to the traditional oil-free scroll dry pump, the floating scroll dry pump is cleaner, more reliable, fewer wearing parts, less maintenance, and lower operating costs.
Based on the floating vortex compression technology, Cisco Vortex Technology (Hangzhou) Co., Ltd. has a series of vacuum pump products, including micro-vacuum pumping speeds of 0.1 m3/hr, 0.3m3/hr, 1.2m3/hr, and 3m3/hr. The ultimate vacuum degree is 30Pa to 0.5Pa, and it has been successfully applied to mass spectrometers, specific surface instruments, leak detectors, clearers, and scientific research and mobile phones, chips and other semiconductor production processes. Two industrial grade products, pumping speed of 18m3/hr and 60m3/hr, the highest ultimate vacuum is 0.1Pa, is currently in crystal growth furnace, PECVD and other equipment testing applications.
SVF-5 micro-floating oil-free scroll dry pump, the maximum ultimate vacuum of 5Pa, size 182 × 94 × 94mm, the whole weight of only 1.1Kg, very suitable for portable scientific instruments.
Comparison of experimental data
In laboratory applications, small-scale clean vacuum devices commonly used are oil-free diaphragm pumps or oil-free diaphragm pumps and turbo pump sets, in particular, some professional scientific instruments and testing instruments. The use of imported oil-free diaphragm pump and molecular pump group. In the following, we compare the actual test data of a 1.8m3/hr inlet diaphragm pump and a 1.2m3/hr floating scroll dry pump (SVF-E2-20) with a TurboLab80 molecular pump.
From Fig. 6, it can be clearly seen that the ultimate vacuum degree of the floating scroll dry pump of SVF-E2-20 is obviously higher than that of the imported diaphragm pump, and the ultimate vacuum degree of the KF fittings and bellow hose is used in the same device. It is higher than the ultimate vacuum when using plastic tubing and fittings. From Table 1, it can be seen that when the molecular pump TurboLab 80 is connected, the time reaches 2×10-2 Pa (2×10-4 mbar), the diaphragm pump group is 4 minutes, and the SVF-E2-20 quick plug connection pump group is 42 seconds. , KF connected to the pump set for 30 seconds. In the ultimate vacuum degree of the pump group, the diaphragm pump group can only reach 10-4Pa, and the SVF-E2-20 KF connection pump group can reach 10-5Pa. If the vacuum degree is high, the molecular pump combines heat drying to remove water. By way of steam, the ultimate vacuum attainable with the SVF-E2-20 KF-connected pump will be higher.
Experiments have shown that under the same premise, the 1.2m3/hr floating scroll dry pump is at least two orders of magnitude higher than the 1.8m3/hr inlet diaphragm pump, and the pumping speed performance is also significantly higher than the latter.
market expectation
The floating scroll dry pump structure solves the technical problems of “side leakage†and “radial leakage†that exist in the traditional scroll technology through fine force balance. The moving scroll and the fixed scroll reel are in motion. In direct contact sealing, the top seal structure is removed and the friction loss is minimized, so that the floating scroll dry pump improves the performance of the traditional scroll dry pump to a higher level, increasing its direct application field and truly exerting The technical advantages of vortex dry pumps. Make the floating scroll dry pump a truly ideal choice for cleaning equipment.
In the field of small and micro vacuum pumps, the floating scroll dry pump has increased vacuum by 2 orders of magnitude for clean high vacuum applications such as portable mass spectrometers, particle counters, vacuum stations, leak detectors, and various aviation Space, medicine, food and other applications filled the blank. We have seen that since the introduction of our miniature vacuum pumps at trade fairs and company websites, major vacuum equipment companies have ordered micropump prototypes from us and are mostly used in portable vacuum equipment products.
In the area of ​​medium-sized and large-scale vacuum pumps In the past decade, oil-free dry pumps have gradually expanded and replaced various vacuum pumps with oil in the semiconductor manufacturing market. However, the vacuum market is not satisfied with the vacuum degree and reliability of the existing oil-free dry vacuum pumps, and it is expected to satisfy the clean, oil-free, high-vacuum and reliable operation products. Our floating oil-free dry pumps are a positive answer to the market. All major vacuum equipment manufacturing companies that use our miniature vacuum pumps expressly express their willingness to cooperate with us. We have expectations and confidence in the prospect of entering this $40 billion vacuum pump market.
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