Introduction to bushing
Bushing is a supporting part used outside mechanical parts to achieve sealing, wear protection and other functions. It refers to the ring sleeve that acts as a gasket. In the field of valve application, the bushing is in the bonnet, and generally uses corrosion resistant materials such as polytetrafluoroethylene or graphite for sealing.
In moving parts, the wear of parts is caused by long-term friction. When the clearance between the shaft and the hole is worn to a certain extent, the parts must be replaced. Therefore, the designer selects the material with lower hardness and better wear resistance as the shaft sleeve or bushing in the design, which can reduce the wear of the shaft and seat. When the shaft sleeve or bushing is worn to a certain extent, it can save the cost of replacing the shaft or seat. Generally speaking, The bushing and the seat adopt interference fit, while the bushing and the shaft adopt clearance fit. Because wear can not be avoided in any case, it can only prolong the service life, and the shaft parts are relatively easy to process; There are also some new designers who do not like this design. They think that this is to increase the cost during manufacturing, but after a period of use, they still need to be modified in this way during maintenance. However, it is easy to reduce the accuracy of the equipment due to the simple reason. The secondary processing can not guarantee the position of the center of the seat hole. The shaft sleeve has a low speed in some parts, Places with high radial load and high clearance requirements (such as camshaft) are used to replace the rolling bearing (in fact, the shaft sleeve is also a sliding bearing). The material requirements are low hardness and wear resistance. The inner hole of the shaft sleeve can be ground and scraped to achieve a high fitting accuracy. There must be an oil groove on the inner wall. The lubrication of the shaft sleeve is very important. In case of dry grinding, the shaft and shaft sleeve will soon be scrapped. It is recommended to scrape the inner hole wall of the shaft sleeve during installation, In this way, many small pits can be left. The enhanced lubrication bushing and shaft sleeve are selected according to different industrial and mining conditions. The most important conditions are: pressure, speed, pressure-velocity product, lubrication state, and load property. The automatic type selection of bushing is included.
Wrap the valve rod, which is worn and can be replaced easily. If the bushing is not used, the parts will be replaced after wear. Therefore, the replacement is to replace the bushing (during the design, the hardness of the bushing will be reduced to make it become a wear part in the friction pair). Because of its convenient processing, low replacement cost and easy replacement. Of course, there are guiding functions, which are secondary.
Characteristic
Miniature linear bushing bearing is a very small linear motion guide machine with a diameter of 3~5mm, which rotates with the shaft, and the contact edge moves infinitely in a straight line in the direction of the shaft. Features:
1.Low friction impedance: the steel ball can move stably in a straight line with a small friction impedance due to the correct orientation of the retainer.
2.Stainless steel: stainless steel series is also available, which is suitable for the purpose of corrosion resistance.
3.Exquisite design: small size, can be designed in delicate mechanical equipment.
4.Rich changes: In addition to the standard type, there is also a series of high-rigidity long type, which can be selected according to the purpose.
Role of bushing
Bushing has high flexibility and can play a lot of roles. Generally speaking, bushing is a kind of component to protect equipment. The use of bushing can reduce the wear, vibration and noise of equipment, and has the effect of corrosion prevention. The use of bushing can also facilitate the maintenance of mechanical equipment and simplify the structure and manufacturing process of equipment.
The role of bushing in practical work is closely related to its application environment and purpose. In the field of valve application, the bushing is installed in the valve cover to cover the valve stem, so as to reduce the leakage of the valve and achieve the sealing effect. In the field of bearing application, the use of bushing can reduce the wear between bearing and shaft seat and avoid the increase of clearance between shaft and hole.
Material of bushing
Bushings are mostly made of soft metal, rubber, nylon and non-metallic polymers. These materials are relatively soft and have low cost. In various harsh working environments, the bushing bears vibration, friction and corrosion to protect the wrapped parts, while the bushing itself is easy to replace after damage, with low cost and good economy.
Bushing selection factors
Bushing has a wide range of applications and a wide variety of types. To select a suitable bushing, it is necessary to consider its use purpose, and select different types of bushings under different working conditions. The main conditions to be considered in the selection of bushing are the pressure, velocity, pressure-velocity product and load property that the bushing should bear. In addition, whether the bushing is lubricated or not determines its service effect and life.
Practical application
Application: packaging machinery, textile machinery, mining machinery, metallurgical machinery, printing machinery, tobacco machinery, forging machinery, various machine tools and interchangeable mechanical transmission connection. For example: pulley, sprocket, gear, propeller, large fan and other various connections; Features: large torque, high precision, convenient and quick assembly and disassembly, simple operation, good positioning, low scrap rate of matched shaft and hub, reusable, and no damage to the mating surface, which is the most ideal and economical choice at present.
1.Installation: The bushing has been coated with lubricating oil before leaving the factory, and can be directly installed and used. During installation, first screw three bolts into the screw hole of the flange of the other piece evenly distributed along the circumference, and then push the inner sleeve and outer sleeve apart. Then put the expansion sleeve into the hub hole at the design position, and tighten the bolts with a force measuring wrench. The tightening method is that each bolt is only tightened to 1/4 of the rated torque at a time. The tightening sequence is bounded by the opening, and the left and right are tightened symmetrically and crosswise in order to ensure that the rated torque value is reached.
2.Disassembly: loosen all bolts for several turns before disassembly. Then screw in the bolt top and loosen the expansion sleeve crosswise in the removed screw hole.
3.Protection: prevent expansion sleeve pollution during installation. On machines operating in the open air or with poor working environment, anti-rust grease shall be regularly applied to the exposed end face of the expansion sleeve and bolts, and the expansion sleeve type with good anti-rust property shall be selected. The expansion coupling sleeve is a new and advanced mechanical basic component in modern times. It is a new type of keyless coupling device widely used in the world today to realize the connection between machine parts and shafts, and realize the load transmission by tightening the pressure and friction generated between the containment surfaces by tightening the 12.9 high-strength screws.
