What are bearings
Bearing is an important component in contemporary mechanical equipment. Its main function is to support the mechanical rotating body, reduce the friction coefficient during its movement, and ensure its rotary accuracy.
Origin of Bearing Development
bearing The early form of linear motion bearings was a row of wooden rods placed under a row of pry plates. Modern linear motion bearings use the same operating principle, except that balls are sometimes used instead of rollers. The simplest rotary bearing was the bush bearing, which was simply a bushing sandwiched between the wheel and the axle. This design was later replaced by the rolling bearing, which is a bushing with many cylindrical rollers instead of the original bushing, each rolling body acting like a separate wheel.
An early example of a ball bearing was found on an ancient Roman ship built in 40 B.C., discovered on Lake in Italy: a wooden ball bearing was used to support a rotating tabletop. A ball bearing is said to have been described by Leonardo i around 1500. Among the various of ball bearings, one important point is that the balls can collide with each other, causing additional friction.
In the 17th century, Galileo gave the earliest description of a “caged ball” ball bearing. At the end of the 17th century, C. of England designed and manufactured ball bearings, and installed them on mail carriages for trial, and P. Worth of England obtained the patent of ball bearings.
Bearings tips The earliest practical rolling bearing with cage is the watchmaker John Harrison in 1760 for the production of chronograph and invented. At the end of the eighteenth century, H.R. Hertz of Germany published a paper on the contact stress of ball bearings.
On the basis of Hertz’s achievement, R. of Germany, A. Sweden and others conducted a large number of experiments and contributed to the development of rolling bearing design theory and fatigue life calculation. Subsequently, N.P. Russia applied Newton’s law of viscosity to calculate bearing friction. The first patent on ball grooves was granted to Philip Vaughan of n in 1794.
In 1883, Fischer laid the foundation of the bearing industry with his proposition to use suitable production machines to grind steel balls of the same size and accurate roundness. O. Reynolds of England made a mathematical analysis of Thor’s discovery and derived the Reynolds equation, which has since laid the foundation for the theory of hydrodynamic pressure lubrication.
Bearing classification
Bearings are divided into deep groove ball bearings, tapered roller bearings, cylindrical roller bearings, angular contact ball bearings, spherical roller bearings, self-aligning ball bearings, hub bearings, hub unit bearings, needle roller bearings, linear bearings, outer spherical bearings, stainless steel outer spherical bearings, thrust ball bearings, thrust roller bearings, clutch bearings, rod end bearings, joint bearings, thrust spherical roller bearings, etc.
Bearing load
Bearings tips Bearing load means the load on the bearing in use, there are transverse load and longitudinal load, etc. The bearings are used to support the rotating shaft. The shaft may be subjected to radial or axial loads, and these loads will act on the bearings, such as the helical gear shaft on the reducer, and axial loads will be generated during the transmission process.
Axial refers to the direction along the axis of the shaft, radial is perpendicular to it is along the radius direction of the shaft. So the axial load of the bearing refers to the load generated in the axial direction of the bearing.
In layman’s terms, this is the force that pushes the inner ring of the bearing out of the outer ring.
The types of bearings in order of their ability to bear axial load are: cylindrical roller bearings < ball bearings < tapered roller bearings < end bearings. Among them, cylindrical roller bearings do not bear axial load at all, while end bearings are specially designed to bear axial load.
Bearing life
Bearings tips Under a certain load, the number of revolutions or hours experienced by the bearing before pitting occurs, known as bearing life. Due to the
manufacturing accuracy, material uniformity differences, even if the same material, the same size of the same batch of bearings, in the same working conditions, its life length is not the same.
If the statistical life of 1 unit, the longest relative life of 4 units, the shortest for 0.1-0.2 units, the longest and shortest life ratio of 20-40 times. 90% of the bearing does not produce pitting, the number of revolutions or hours experienced called bearing rated life for comparison bearing resistance to pitting bearing bearing capacity, the rated life of a million revolutions (106), the maximum load can be withstood for Basic rated dynamic load, expressed in C. That is, the bearing in the rated dynamic load C role, this bearing work a million revolutions (106) without pitting failure of the reliability of 90%, the greater the C bearing capacity is higher.
Bearing lubrication method
The lubrication method of bearings is divided into grease lubrication and oil lubrication. In order to make the bearings play the function well, first of all, we should choose the suitable lubrication method for the use conditions and purpose. If only lubrication is considered, the lubricity of oil lubrication is dominant. However, grease lubrication has the advantage of simplifying the structure around the bearing, comparing the advantages and disadvantages of grease lubrication and oil lubrication.
Lubrication should pay special attention to the amount, whether it is oil lubrication or grease lubrication, the amount of too little lubrication is not sufficient to affect the bearing life, the amount of too much will produce a large resistance, affecting the speed.
Bearing sealing method
The sealing of the bearing can be divided into two types: self-sealing and additional sealing. The so-called bearing with seal is the bearing itself is manufactured to have sealing performance device. Such as bearing with dust cover, seal ring, etc.. This seal occupies very little space, easy to install and remove, the cost is also relatively low.
The so-called bearing with sealing performance device, is in the installation of end caps and other internal manufacturing with a variety of performance sealing device. Bearing seals are divided into non-contact seals and contact seals. The non-contact seals are suitable for high speed and high temperature applications, and have different structural forms such as gap type, labyrinth type and gasket type. Contact seals are suitable for medium and low speed operating conditions, commonly used in the form of felt seals, leather bowl seals and other structural forms.
Bearing maintenance and installation
1、Improve lubrication quality, control the pressure, temperature and flow of oil, and strengthen oil filtration.
2, the use of fuel and lubricants in line with the provisions.
3, control the temperature state of the diesel generator set, working in the case of too cold and too hot are unfavorable. Cold days, the diesel engine should be warmed up before starting, and turn the crankshaft by hand to make the oil into the friction surface.
4, bearing and journal surface quality and geometry should be strictly guaranteed.
5, bearing clearance should be appropriate, the generator set is too large to produce shock, too small is poor lubrication, may burn tile.
How to ensure that the bearings work reliably
6. bearing clearance should be appropriate, too large to produce impact, too small is poor lubrication, may burn tile.
7. bearing and journal surface quality and geometry should be strictly guaranteed.
8. improve the quality of lubrication, control the pressure, temperature and flow of oil, strengthen the oil filtration.
9, the use of fuel and lubricants in line with the provisions.
Bearing installation method.
Generally, since most of them are shaft rotating, the inner ring needs interference fit. For cylindrical hole bearings, more presses are used to press in, or more hot mounting methods are used. The occasion of tapered hole, directly mounted on the tapered shaft, or with a sleeve installation.
Installed to the shell, the general clearance fit more, the outer ring has a surplus, usually pressed in with a press, or also cooled and installed with the cold shrink fit method. Using dry ice as coolant, the occasion of cold shrink fit installation, the moisture in the air will condense on the surface of the bearing. Therefore, proper measures are required. Hopefully, the bearing package will be opened only before the upcoming installation.
General grease lubrication, no cleaning, direct filling grease. For lubricating oil lubrication, it is not necessary to clean it in general
In order to make the bearing give full play to and maintain its proper performance for a long time, regular maintenance must be done bearing effectively (regular inspection). Through appropriate regular inspection, to achieve early detection of failure, to prevent accidents before they occur, to improve productivity and economy is very important.
