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As a kind of volumetric pumping system, vortex vacuum pump has attracted more and more attention because of its simple structure, low vibration noise, high reliability and good pumping characteristics.
Because there is no oil and sealed liquid inside, the pollution of the pump oil is effectively eliminated so as to obtain a clean vacuum. However, on the other hand, due to the lack of lubrication and sealing of oil, the meshing of the scroll is confined only by clearance, so that the performance of the pump will depend on the machining accuracy and the solid lubrication performance of the scroll. In this paper, the application of solid lubrication technology in scroll vacuum pump has been studied.
1 vortex vacuum pump in the friction part due to the vortex vacuum pump is sealed by clearance, in order to improve pumping speed and reduce the limit pressure, we must control the gap to reduce leakage. The clearance between the closed chambers consists mainly of radial clearance and axial clearance, as shown. When the gap is very small, due to the processing and assembly errors and the heating deformation at work, it is easy to contact, resulting in friction. According to the location of friction, the friction between the top of the tooth and the friction of the teeth are divided into two parts. The friction between the top and bottom of the moving disk (stationary disk) and the bottom of the bottom of the stationary disk (moving disk); and the friction between the teeth occurs at the radial gap between the moving disk and the flank of the static disk. Mechanical friction on the one hand will lead to loss of power, on the other hand will cause the vortex wall wear, bite, or even lock, causing the vortex pump damage. The two contact surfaces at the gap must take measures in scroll compressor lubrication, oil lubrication generally take to solve, but cannot scroll vacuum pump in the presence of oil, so we must seek the methods to solve the solid lubrication.
The mechanism and influencing factors of 2 solid lubrication the so-called solid lubrication refers to the plating and spraying methods of solid lubricant adhesive solid lubrication film formed on the friction surface, the friction surface formed in the dual transfer film friction occurs in the lubricant inside, thus achieves the reduced friction and wear reduction objective. There are many kinds of solid lubricants, and the lubrication mechanism is complex. They can be divided into soft metal, metal compound, inorganic and organic etc.. No matter what kind of solid lubricant, which depends on whether the lubrication performance in friction is formed on the surface of whether the transfer transfer film having a low coefficient of friction and wear resistance, strong adhesion and how factors such as transfer film substrate. The lubrication characteristics of the solid lubricant film are related to the hardness of the base material, the dual material and its surface roughness, and the coefficient of thermal expansion.
Because of the advantages of low friction coefficient, high and low temperature performance, good chemical stability and free from environmental atmosphere, polytetrafluoroethylene (FIFE) has become one of the most widely used materials. But because of its characteristics of crystal structure determines that it is easy to wear, in order to compensate for this shortcoming, usually don't use PTFE, but the use of added FTFE filled with various additives, in the lubrication of scroll vacuum pump in the extensive use of the lubricating material, friction parts here for the vacuum pump to introduce different solid lubrication the tooth side friction solid lubricant 3 tooth side friction occurred in the radial clearance at the moving plate and the static disk tooth side surface meshing. Because the tooth side clearance seal to prevent leakage in order to reduce the leakage through the radial clearance, the radial clearance value is generally very small, this time due to the machining precision and assembly precision and the pump temperature is easy to make contact between the vortex, resulting in dynamic and static disc disc tooth side friction, lock the death of each bite and pump can cause severe vortex body.
The friction of the scroll is usually solved by forming a solid lubricant film on the surface of the base. In the choice of coating material should first consider its tribological properties, but also should consider the reasonable matching between the coating and the substrate, such as physical and mechanical properties of the coating material, the bonding strength between the coating and the substrate etc.. The reasonable match of coating and base material should include the following content: the elastic modulus of the coating and the base material is close to the degree. If the difference between the two is large, when subjected to external force, the interface will produce greater stress, easy to make the coating and substrate stripping.
The thermal expansion coefficient of the two should be close. Otherwise, when the system heats up, the thermal stress will also cause the coating to fall off.
The hardness of the base material should be large enough. The solid lubricant film plays a lubrication role by sharing the load between the base material. The higher the hardness of the base material, the smaller the coefficient of friction of the solid lubricant film and the more wear-resistant it is.
A large number of experimental results show that improving the hardness of the substrate can effectively improve the wear resistance and prolong the service life of the lubricating film.
In the scroll vacuum pump and scroll compressor, the scroll disk is generally treated by hardening. For example, the aluminum alloy substrate is treated by anodic oxidation, and the steel is treated with NI*P chemical plating to improve its hardness and corrosion resistance. The quality of the coating determines the overall performance of the pump, and how to coat a solid lubricant film on the scroll surface, which has good wear resistance, good lubricity and is difficult to fall off, has become a key technical problem in the development of the scroll machine.
The flatness and parallelism of the solid lubrication crown and the bottom surface of the 4 tooth crown determine the sealing performance of the tooth crown and the bottom plane. When the machining accuracy is low, the contact friction of the |J region will appear in the local area. This