Layout and strengths of the rotating shaft lip seal

Source: China Bearing Network Time: 2014-10-02

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Rotary shaft lip seals are generally called oil seals; they are widely used in gearboxes, drive axles, etc. of construction machinery; such as the front and rear output shafts of the gearbox; the final drive of the drive axle, the wheel edge, etc.; The oil chamber and the outside are blocked; the inner seal oil; the external dustproof. At present, many domestic oil seal layouts are used; the basic layout includes some rubber seals, metal skeletons or metal shells and metal springs.
First, the sealing mechanism of the oil seal The seal of the oil seal is formed by the interference between a flexible sealing element (leather, rubber, polytetrafluoroethylene, polychlorotrifluoroethylene or polyimide) and the rotating shaft. Its sealing mechanism is: the appearance of the seal between the lip seal and the shaft, the coexistence of dry conflict, the dip lubrication and the fluid lubrication; and the continuous replacement of the episode. Dry conflict episodes and abrasions; fluid lubrication episodes leaking; The oil seal lip and the shaft interface form a stable fluid dynamic oil film; the oil film thickness is about 00025mm, this oil film is used for lubrication; it also acts as a seal. The oil film is too thick; the fluid will leak, the oil film Too. The benzyl latitude éˆ éˆ è ¡ãƒ è ¡ãƒ è ¡ãƒ è®² è®² è®² å› è€Œ å› è€Œ å› è€Œ å› è€Œ å› è€Œ å› è€Œ å› è€Œ å› è€Œ å› è€Œ å› è€Œ å› è€Œ å› è€Œ å› è€Œ å› è€Œ å› è€Œ å› è€Œ å› è€Œ å› è€Œ å› è€Œ å› è€Œ å› è€Œ å› è€Œ å› è€Œ å› è€Œ å› è€Œ å› è€Œ å› è€Œ å› è€Œ å› è€Œ å› è€Œ å› è€Œ å› è€Œ å› è€Œ å› è€Œ. To provide conditions for the formation of a thin and stable gap lubricant film. In the process of layout depiction, device application; the current common oil seal rules are very strict; this is the delay of the fault As laid danger.
Second, the lack of existing oil seals1. In the layout depiction; because many of the currently selected oil seals are directly subjected to interference cooperation with the rotating shaft to complete the dynamic seal; the deflection degree of the rotating shaft, scale error, out-of-roundness, appearance roughness, etc. are very strict Needs:
1) the degree of partial pain of the shaft; the degree of partial pain directly affects the distribution of the contact stress of the lip of the oil seal; the general demand is within 0.3 mm (shaft diameter is 50-80 mm; oil seal line speed is 10-15 m/s); In many cases, it is very difficult to do. For example, the skill of the drive axle finalizer oil seal is required: the middle line of the input flange is slightly smaller than the middle line of the oil seal seat hole by more than 0.1 mm. The line depends on the intermediate orientation of the bearing seat and the bracket cooperation; the middle line of the input flange is determined by the intermediate orientation of the spline with the automatic spiral bevel gear; the offset of the two intermediate lines is difficult to control at 0 Within 1mm scale.
2) Scale error of the shaft: As long as the scale error of the shaft is correctly selected, the function of the sealing function can be obtained. The excessive shaft will add the touch load on the lip end; and the too small shaft will make the seal on the lip touch surface. Pressure is not enough. Pressure too much to promote premature failure of the seal; and too little touch pressure will lead to leakage.
3) Out of roundness of the shaft: The out-of-roundness of the shaft can cause the elastomeric sealing lip to deform or lose its elasticity according to the irregular movement of the shaft; then it causes fatigue damage.
4) shaft surface roughness; general rule is Ra1. 6 ~ 3. 2um; appearance is too lubric; not conducive to the formation and adherence of oil film; dry friction of the seal ring; simple burn; lead to leakage, too rough; The oil seal failed early.
2. In terms of device application: it is necessary to apply a small amount of grease on the oil seal lip before the device; because the oil seal lip has an interference with respect to the shaft; it is necessary to pay attention to and prevent changes such as sealing lip extrusion and extrusion; When the shaft end does not have a cone, rounded corners and threads, it should be more important; otherwise it will simply scratch the lip and affect the sealing effect.
3. The existing oil seal is more sensitive to the damage of the shaft surface; very fine damage can have a great impact on its sealing effect and the life of the operation; even directly lead to leakage.
Third, the layout of the new oil seal and its strengths The first feature of the new oil seal is that an oil seal inner hub coated with a layer of corrugated rubber is depicted between the rotating shaft and the oil seal lip; during operation; the inner hub rotates with the coaxial; The oil seal completes the dynamic seal between its lip and the outer surface of the inner hub. Its strengths are:
1. The inner part of the oil seal is covered with a layer of corrugated rubber; it can be used to the large degree of partial pain of the rotating shaft (generally only about 0.5 mm) and the larger scale error of the shaft; there is better axial and Radial buffer function. This oil seal shows excellent sealing function in the muddy water test under the condition of 0. 5mm and 800rpm. It also shows a very long application in the life test of 50000km. Lifespan.
2. Because the seal is completed between the oil seal lip and the inner hub; therefore, the shaft is not required for roundness and appearance roughness; it is not sensitive to the minor damage of the shaft surface; the reliability of the oil seal is improved.
3. The inner hub is covered with a layer of rubber; the oil seal can be stably placed on the shaft; if the rubber is coated with grease on the outside of the device, the device becomes simpler.
4. A labyrinth channel is depicted between the oil chamber and the outside world; and two dust lips are placed in the channel; the main lip is kept at a distance from the dusty water; the service life of the oil seal is extended.
Fourth, the new oil seal is placed between the main lip of the oil seal and the rotating shaft with a cushioning oil seal inner hub; the oil seal main lip does not directly touch the shaft; then it is useful to reduce the axial pain, rough surface, shaft not The external unfavorable factors such as roundness disturb the seal; together, the device is simplified; the sealing effect is improved; the service life is extended; the oil seal has been put into use on the drive axle of the XCMG loader;

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