Bearing is an indispensable key component of modern industry, known as mechanical equipment, ‘heart’, its bearing capacity will directly affect the technical level of equipment, is a measure of a country's scientific and technological, industrial strength is an important standard. But with the evolution of the downstream industry development, the traditional rolling bearing more and more ‘unbearable burden’. Equipment large-scale, high-speed trend, more demanding operating conditions and high reliability requirements, the bearing technology has put forward a new challenge.

China's bearing industry after more than 40 years of development, bearing products and manufacturing level has made great progress, has a considerable scale and development basis. With the progress and development of technology, the performance and requirements of bearings also put forward higher and higher requirements. In this paper, mainly from the low-friction and high-speed precision two aspects of bearing technology development trend.

Low friction

Tribological technology is the core technology of bearings, a new generation of bearings is a significant technical feature of the design of friction reduction. Rolling bearings relative to plain bearings, itself belongs to the ‘friction bearing’. The challenge of the new generation of friction-reducing design is to reduce the friction torque, which is already extremely low, by up to 80%.

In new energy vehicle applications, low-friction bearings are required to reduce energy losses; in aerospace applications, bearings are required to have low-temperature friction resistance.

Bearing friction is not constant, it depends on the rolling body, raceway and cage between the lubrication film in a certain friction phenomenon. Affect the bearing low friction technical indicators mainly include wide diameter ratio, bearing clearance, bearing wall thickness, as well as for extreme (extreme) working conditions of the special design.

(1) wide diameter ratio: for radial bearings, wide diameter ratio (B / d) is usually in the 0.35-1.5 between, and for thrust bearings, large small diameter ratio (D2 / D1) usually take <2. Choose a larger value will increase the bearing capacity, but at the same time will increase the deformation of the shaft and the sensitivity of the two bearing holes are not the same as the axis of the sensitivity.

(2) bearing clearance: bearing clearance has a significant impact on the working performance of the bearing. Excessive clearance may lead to increased wear and operating accuracy is reduced, while the clearance is too small may lead to bearing overheating and temperature rise is too high, need to leave a large enough clearance. General non-lubricated bearing diameter clearance is good not less than 0.075mm.

(3) bearing wall thickness: the impact of running performance with the increase in bearing volume and more obvious. In order to ensure that the strength permit, the wall thickness should be as small as possible, in order to reduce the impact on the running performance.

(4) Extreme (extreme) working conditions design: in extreme working conditions, such as cryogenic vacuum environment, need a special design of bearings to adapt to the very low temperature and high pressure environment. For example, solid lubrication rolling bearing in the field of aerospace applications, through the inner and outer ring of high-power joint cooling temperature control, radial and axial joint electromagnetic loading technology to achieve a very low temperature / wide temperature range, high vacuum and other extreme operating conditions coexist under the rolling bearings.

3 High-speed precision

Bearing of high speed and low speed is not to bearing itself speed to measure, but to its line speed to divide. Generally speaking, bearings with a linear velocity of 60 metres per second are considered to be high-speed bearings. High-speed bearings usually have smoother surfaces and the distance between the inner and outer rings is very small, thus requiring higher bearing accuracy. The main factors affecting the high speed of bearings include bearing type, size, load, lubrication method, material and type of cage, bearing load, preload, driving method, size of bearing clearance and bearing combination.

1) Bearing type and size: different types of bearings differ in structure and material, and the larger the size, the larger the rotational inertia, all of which will affect the bearing speed.

2) Load: the greater the load on the bearing, the greater the frictional resistance, thus affecting the speed.

3) Lubrication: suitable lubrication can reduce friction and wear, and increase the speed of the bearing.

4) Material and type of cage: it also affects the rotational speed of the bearing.

5) Bearing load: the limiting speed of rolling bearing is the high speed achieved under certain load and lubrication conditions, which is very much related to the bearing type, size, direction, lubrication method, clearance, cage structure, cooling conditions and so on.

(6) Preload: excessive preload will lead to the contact stress between the rolling body and raceway surface increases, heat generation increases, which in turn leads to further increase the preload inside the bearing, so that the bearing is more prone to wear and reduce the limiting speed.