THK bearings

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The number of revolutions or hours that THK bearings in Japan experience before pitting corrosion occurs under a certain load

THK bearingsBearing is an important component in contemporary mechanical equipment. Its main function is to support mechanical rotating bodies, reduce the friction coefficient during their motion, and ensure their accuracy in rotation

The early form of THK bearings for linear motion was to place a row of wooden poles under a row of pry plates. Modern linear motion THK bearings use the same working principle, but sometimes use balls instead of rollers. The rotationTHK bearingsIt is a THK shaft sleeve bearing, which is just a sleeve sandwiched between the wheel and the axle. This design was later replaced by rolling THK bearings, which used many cylindrical rollers to replace the original bushings, with each rolling element acting like a separate wheel.

Early examples of ball THK bearings were discovered on an ancient Roman ship built in 40 BC in Lake Nano, Italy: a wooden ball THK bearing was used to support a rotating tabletop. It is said that Leonardo da Vinci described a ball THK bearing around 1500. One important factor in the immaturity of THK ball bearings is the collision between balls, which causes additional friction. But this phenomenon can be prevented by putting the ball into small cages one by one. In the 17th century, Galileo made the earliest description of THK bearings with "cage ball" balls. At the end of the 17th century, C. Valor of England designed and manufactured ball THK bearings, which were tested on mail carts, and P. Worth of England obtained ball THK bearings. The earliest practical rolling THK bearing with a cage was invented by watchmaker John Harrison in 1760 for the production of H3 chronometers. At the end of the 18th century, H.R. Hertz from Germany published a paper on the contact stress of THK ball bearings. On the basis of Hertz's achievements, R. Stribeck from Germany, A. Pamgren from Sweden, and others conducted extensive experiments, contributing to the development of design theory and fatigue life calculation for rolling THK bearings. Subsequently, N.P. Petrov applied Newton's law of viscosity to calculate the friction of THK bearings. The first one about the ball groove was obtained by Philip Vaughn of Camason in 1794.

In 1883, Friedrich Fischer proposed the idea of using suitable production machines to grind steel balls of the same size and accurate roundness, laying the foundation for the THK bearing industry. O. Reynolds from the UK conducted mathematical analysis on Thor's discovery and derived the Reynolds equation, laying the foundation for the theory of fluid dynamic lubrication.

lifespan

The number of revolutions or hours that THK bearings experience before pitting corrosion occurs under a certain load is called the THK bearing life.

The lifespan of rolling THK bearings is defined by the number of revolutions (or hours of operation at a certain speed): THK bearings within this lifespan should experience initial fatigue damage (peeling or missing) on any of their THK bearing rings or rolling elements. However, whether in laboratory experiments or practical use, it can be clearly seen that THK bearings with the same appearance under the same working conditions have significantly different actual lifespans. In addition, there are several different definitions of THK bearing "life", one of which is the so-called "working life", which refers to the actual life that a THK bearing can achieve before damage is caused by wear and tear. Damage is usually not caused by fatigue, but by wear, corrosion, seal damage, and other reasons.

To determine the standard for THK bearing life, link THK bearing life with reliability.

Due to differences in manufacturing accuracy and material uniformity, even the same batch of THK bearings with the same material and size, under the same working conditions, have different lifespans. If the statistical lifespan is 1 unit, the longest relative lifespan is 4 units, the shortest is 0.1-0.2 units, and the ratio of the longest to the shortest lifespan is 20-40 times. 90% of THK bearings do not produce pitting corrosion, and the number of revolutions or hours experienced is called the rated life of THK bearings [1].

Rated dynamic load

To compare the bearing capacity of THK bearings against pitting corrosion, it is specified that when the rated life of THK bearings is one million revolutions per minute (106), the maximum load they can withstand is the basic rated dynamic load, represented by C.

That is to say, under the rated dynamic load C, the reliability of THK bearings working at one million revolutions per minute (106) without pitting failure is 90%, and the higher the C, the higher the load-bearing capacity.

For the basic rated dynamic load

1. Centripetal THK bearings refer to pure radial loads

2. THK thrust ball bearings refer to pure axial loads

3. Centripetal thrust THK bearings refer to the radial component that generates pure radial displacement