(Components in machinery and equipment)
Bearing (Bearing) is an important component in contemporary machinery and equipment. Its main function is to support a mechanical rotating body, reduce the friction coefficient during its movement , and ensure its accuracy of rotation.
- Supports rotating parts and reduces friction
- Plain and rolling bearings
- Metallurgy, wind power, mining machinery, aerospace
An early form of linear motion bearing was a row of wooden rods placed under a row of skid plates. Modern linear motion bearings use the same working principle, but sometimes balls are used instead of rollers. The simplest rotary bearing is a bushing bearing, which is just a bushing sandwiched between the wheel and the axle. This design was subsequently replaced by rolling bearings, which replaced the original bushings with many cylindrical rollers , each rolling body acting like a separate wheel.
An example of an early ball bearing was found on an ancient Roman ship built in 40 BC on Lake Nano, Italy: A wooden ball bearing was used to support a rotating table. It is said that Leonardo Da Vinci described a ball bearing around 1500. Among the various immature factors of ball bearings, it is very important that the balls will collide with each other, causing additional friction. But this can be prevented by putting the balls in small cages. In the 17th century, Galileo made the earliest description of "cage ball" ball bearings. At the end of the 17th century, C. Vallo of the United Kingdom designed and manufactured ball bearings and installed them on postal vehicles for trial. The British company P. Worth obtained patents for ball bearings. The earliest practical rolling bearing with a cage was invented by watchmaker John Harrison in 1760 for the H3 chronograph. At the end of the eighteenth century, HR Hertz of Germany published a paper on contact stress of ball bearings. On the basis of Hertz's achievements, R. Striber of Germany, A. Palmeren of Sweden and others carried out a lot of experiments and contributed to the development of design theory and fatigue life calculation of rolling bearings. Subsequently, Russia's NP Petrov applied Newton's law of viscosity to calculate bearing friction. The first patent on ball channels was obtained by Carmarthen's Philip Vaughn in 1794.
In 1883, Friedrich Fischer put forward the idea of grinding steel balls of the same size and accurate roundness with a suitable production machine , laying the foundation for the bearing industry. O. Reynolds of the United Kingdom conducted a mathematical analysis of Thor's findings, derived the Reynolds equation , and laid the foundation for fluid dynamic lubrication theory.
According to the National Bureau of Statistics, in 2011, there were 1,416 companies in China's bearing manufacturing industry (annual sales income of more than 20 million yuan), and the total industrial output value for the year reached 193.211 billion yuan, a year-on-year increase of 27.59%. The year-on-year growth was 30.30%; the total profit was 12.523 billion yuan, an increase of 26.54% over the previous year. It is estimated that by 2015, China's bearing production is expected to exceed 28 billion sets, and its main business income is expected to reach 210 billion yuan, becoming the world's largest bearing production and sales base.
At present, China's bearing industry is facing three major problems: low concentration of production, low R & D and innovation capabilities, and low level of manufacturing technology.
First, the concentration of industrial production is low. Of the world's approximately 30 billion US dollars in bearing sales, the world's eight largest multinational companies account for 75% to 80%. Germany's two major companies account for 90% of its national total, Japan's five companies account for 90% of its national total, and the US one accounts for 56% of its national total. The 10 largest bearing companies in China, such as axle bearings, account for only 24.7% of the entire industry, and the production concentration of the top 30 companies is only 37.4%.
Second, low R & D and innovation capabilities. The industry's basic theoretical research is weak, and participation in the formulation of international standards is weak. There are fewer original technologies and fewer patented products.
At present, our design and manufacturing technology is basically imitated, and our product development capability is low, as shown in the following: Although the supporting rate for domestic hosts has reached 80%, high-speed railway passenger cars, mid-to-high-end cars, computers, air conditioners, high-level rolling mills, etc The supporting and maintenance bearings of the main engine are basically imported.
Third, the level of manufacturing technology is low. China's bearing industry manufacturing process and process equipment technology have developed slowly, with a low NC rate for turning and low level of grinding automation. There are only more than 200 automatic production lines in the country. Advanced heat treatment processes and equipment that are important to bearing life and reliability, such as controlled atmosphere protection heating, double refinement, and bainite quenching, have low coverage, and many technical problems have not been solved. The research and development of new steel grades for bearing steel, the improvement of steel quality, and the development of related technologies such as lubrication, cooling, cleaning, and abrasive tools, have not yet been able to meet the requirements for improving the level and quality of bearing products. As a result, the process capability index is low, the consistency is poor, the product processing size is large in dispersion, and the inherent quality of the product is unstable, which affects the accuracy, performance, life and reliability of the bearing.
Under a certain load, the number of revolutions or hours that a bearing experiences before pitting occurs is called bearing life.
The life of a rolling bearing is defined by the number of revolutions (or the number of hours of operation at a certain speed): A bearing within this life should undergo initial fatigue damage (peeling or defect) on any of its bearing rings or rolling elements. However, whether in laboratory tests or in actual use, it can be clearly seen that under the same working conditions, the appearance of the same bearing, the actual life is greatly different. In addition, there are several different definitions of bearing "life". One of them is the so-called "working life", which means that the actual life that a bearing can achieve before being damaged is caused by wear and tear, usually not caused by fatigue, but by Caused by wear, corrosion, seal damage, etc.
To determine bearing life standards, link bearing life to reliability.
Due to the difference in manufacturing accuracy and material uniformity, even if the same batch of bearings of the same material and the same size are used under the same working conditions, their lifespans are not the same. If the statistical life is 1 unit, the longest relative life is 4 units, the shortest is 0.1-0.2 units, and the ratio of the longest to the shortest life is 20-40 times. 90% of the bearings do not cause pitting, and the number of revolutions or hours experienced is called the rated bearing life  .
Dynamic load rating
In order to compare the bearing capacity of the bearing against pitting corrosion, when the rated service life of the bearing is specified to be one million revolutions (106), the maximum load that can be supported is the basic dynamic load rating, expressed as C.
That is to say, under the action of the rated dynamic load C, the reliability of this kind of bearing working for one million revolutions (106) without pitting failure is 90%. The larger the C, the higher the bearing capacity.
For basic dynamic load rating
1. Radial bearings refer to pure radial load
3．Radial thrust bearings refer to the radial component that produces pure radial displacement
According to the data of "China Bearing Manufacturing Industry Production and Sales Demand Forecast and Transformation and Upgrade Analysis Report", from 2009 to 2013, China's bearing manufacturing industry's total industrial output value has been increasing year by year. In 2013, the industry realized a total industrial output value of 249.363 billion yuan, a year-on-year increase of 12.92%.
An analysis of the data in the past five years found that the sales income of China's bearing manufacturing industry also showed a year-on-year increase from 2009 to 2013. In 2013, it realized sales income of 249.012 billion yuan, a year-on-year increase of 11.80%.
The rapid development of China's bearing industry, from small to many bearing types, product quality and technical level from low to high, and industry scale from small to large, has formed a professional production system with basically complete product categories and a reasonable production layout.
Sliding bearings have no rolling elements regardless of the inner and outer rings, and are generally made of wear-resistant materials . Commonly used for low-speed, light-duty, lubricating, and mechanically difficult to rotate parts.
The sliding contact surface of the articulated bearing is spherical, which is mainly suitable for swing motion, tilt motion and rotary motion.
The self- aligning bearings are divided into self-aligning bearings according to their working ability .---- The raceways are spherical, bearings that can adapt to the angular deviation and angular movement between the two raceway axis lines, and non-aligning bearings ( rigid bearings ). ---- Bearing that can resist the angular deviation of the axial line between the raceways.
It can be divided into separable bearings and non-separable bearings according to whether their parts (ferrules) can be separated.
According to its structural shape (if there is no filling groove, with or without the shape of the inner and outer rings and ferrules, the structure of the ribs, and even with or without a cage, etc.), it can also be divided into a variety of structural types.
Divided into miniature bearings (<26mm), small bearings (28-55mm), small and medium bearings (60-115), medium and large bearings (120-190mm), large bearings (200-430mm) and special bearings according to their outer diameter . Large bearings (> 440mm).