Key Technology for Bearing Manufacture(3)

Sealing technology

Technology summary

Corresponding sealing devices are mounted on the two end faces of newly developed rolling bearings. On one hand, they can prevent lubricating grease (oil) inside the bearing from running off in use and ensure the bearing is in lubricating state. On the other hand, they can protect the bearing and not allow dust or harmful gas outside to enter into the bearing lumen, so the damage to bearing is avoided. Rubber or engineering plastic lock rings are common, and there are also lock ring stamped by steel sheet (or called dust cap). Sealing structures are various, but the sealing effects are different. If there is clearance between the lock ring and the bearing, the seal is called non-contact seal. The smaller the clearance, the better the sealing effect, but permissible rotate speed area of the shaft is also smaller. If there is no clearance between the lock ring and the bearing, the seal is called contact seal. The larger the contact area of the lock ring lip, the better the sealing effect, but permissible rotate speed area of the shaft is smaller. Sealing technology is mainly to research and develop corresponding sealing devices applied in different working conditions and compatibility of the lock ring material and corresponding lubricating grease etc.

Development trend at home and abroad

Big bearing corporations in Japan (NSK, Toyal etc.) represent the direction of bearing sealing technology development. They have an early history in sealing technology development direction and bearing unit technology, and their research has remarkable depth. Their sealing technology is rather mature at present. Multiple seal lip is developed from single seal lip, and non-contact seal is developed from contact seal. For production type, there are ball bearing and roller bearing. Following international development trend, our country has developed several main types of bearings, such as deep groove ball bearing, water pump bearing, railway (conical roller) bearing, needle roller bearing and short cylindrical rolling bearing which are all provided with lock ring. Wherein, the output of deep groove ball bearing is the largest, and its application is the widest. According to quality detecting results of sealed bearing from State Bureau of Quality and Technical Supervision recently, sealed bearing structure design problem in our country has big problems, the sealing effect is not good, and grease leak phenomenon is serious, so customers react sharply. After analysis, we discover that the main reasons are mainly the irrational existing lock ring structure design in our country, inner race without seal groove and low manufacturing accuracy etc. Therefore, the trend of bearing sealing technology in henceforth is: make deep groove ball bearing be the representative, launch sealing technology test, and seek optimal lock ring structure and optimal seal clearance; launch sealing material research and seek aging-resistant, high temperature and corrosion resistant material to prepare for technological base for the work under high temperature or harmful gas condition.

Primary research coverage and objectives

According to current situation in our country, namely the sealed bearing is provided with inferior quality, the main research coverage henceforth is: first, reinforce research and test, filtrate lock ring structure of deep groove ball bearing, and develop corresponding bearing inner race seal groove structure; carry through upgrade of existing deep groove ball bearing sealing structure, and strive for making the sealability of this type of bearing catch up the advanced level of bearing of the same type produced in the 1990s abroad. Second, combining with car industry development in our country, develop high temperature sealed bearing which can do permanent work in high temperature of 120-1800C. Third, make railway vehicle bearing as the representative, develop new sealing structure for conical, cylindrical rolling bearing series.

Denoise technology

Technology summary

Bearing noise is main environmental pollution source, and is also important target that should be controlled in bearing industry. The noise limit is very important to bearing of household appliances, office machine and instrument. Within more than one decade, domestic bearing industry did much work in lowering bearing noise, and the bearing denoise level is greatly enhanced. Compared with abroad, there is still a gap. An outstanding problem reflected by customers is “abnormal sound”, namely a type of irregular sudden sound generated in bearing operation, even screech. Influence factors of bearing noise are plentiful and complex. They should be analyzed and researched from bearing integral design and each component of bearing, namely the inner race, the outer race, the holder, the rolling element and the lubricating oil (grease). They should also be analyzed and researched from other aspects, such as the material and the machining process of each component, and equipments, technics and material adopted in the project. This is the basis related to bearing noise technology.

Development trend at home and abroad

The development of technology is endless. Although the bearing denoise level of foreign advanced bearing corporations (NSK, SKF etc.) is high, they still put forward further development direction, namely the development of "mute" bearing. The development trend of noise technology for domestic bearing products is: first, solve bearing "abnormal sound"; second, make the vibration decreasing level reach a new level, say, to catch up the bearing level of the 1990s in advanced countries.

Primary research coverage and objectives

To solve bearing "abnormal sound" problem and make vibration decreasing level reach a new level, limit to control swing is added in technology standard. Accordingly, the primary coverage is to enhance roundness of rolling element surface and raceway, to solve guide stationarity between holder and rolling element, and to lower the uniformity between impurity graininess of lubricating oil (grease) and its contact to corresponding rolling surface. The roughness control degree of rolling element should reach 0.001μm. The grain of lubricating grease impurity should be no greater than 0.01μm. Enhance true roundness of holder ball socket, and make the run-out quantity between holder and rolling element reach 0.01μm.