Bushing is used outside mechanical parts to achieve sealing, wear and tear protection and other supporting parts, refers to the role of a gasket ring. In the field of valve application, bushing in the valve cover, generally using PTFE or graphite and other corrosion-resistant materials for sealing.
In the moving parts, the wear of the parts is caused by long-term friction. When the gap between the shaft and the hole is worn to a certain extent, the parts must be replaced. Therefore, when designing, the designer chooses the material with lower hardness and better wear resistance as the bushing or bushing, which can reduce the wear of the shaft and seat, when the bushing or bushing is worn. The sleeve is worn to a certain extent and replaced, which can save the cost of replacing the shaft or seat. Generally speaking, bushing and seat adopt interference fit, while shaft adopt clearance fit, because wear can only be prolonged in any case or can not be avoided, while shaft parts are relatively easy to process. The new designers do not like this design. They think that it will increase the cost in manufacturing. But after a period of use, they still need to be reformed according to this method in maintenance. However, the reformation will easily reduce the accuracy of the equipment. The reason is very simple. Secondary processing can not guarantee the location of the seat hole center. The sleeve is used to replace the rolling bearing in some places where the speed is low, the radial load is high and the clearance requirement is high (such as camshaft). In fact, the sleeve is also a kind of sliding bearing. The material requirement is low hardness and wear resistance. The inner hole of the sleeve can be grinded and scraped to achieve high matching accuracy. There must be oil groove on the inner wall. The lubrication of axle sleeve is very important, if dry grinding, the axle and axle sleeve will soon be discarded. It is recommended here that the inner hole wall of axle sleeve be scraped during installation, so that many small pits can be left. The enhanced lubrication bushing and axle sleeve are selected according to different industrial and mining conditions. The most important conditions are: pressure, velocity, pressure-velocity product, lubrication state, load properties. The automatic selection of bushing is included.
The valve stem is wrapped and worn, so it can be easily replaced. If no bushing is used, parts will be replaced after wear and tear. So the bushing should be replaced (the hardness of the bushing should be reduced when it is designed so that it can be used as a bearing part in the friction pair). Because of its convenient processing, low replacement cost and easy replacement. Of course, there are also guiding functions, which are secondary.