"Bearings" are a type of mechanical parts, but do you know what they do?

In fact, bearings are so vital to the mechanical industry that they are called the "bread and butter" of the industry. They can be used in a variety of machines, but since they are performed in the dark, for most people who are not in the machine industry, the first reaction to hearing the word is probably "what is that?"

So today we will talk about what is a bearing.

What is a bearing?

Bearings are "parts that assist the rotation of objects", they are the non-stop rotating shafts that are supported inside the machine. Machines that use bearings include cars, airplanes, generators, and more. Even household appliances that we use every day, such as refrigerators, vacuum cleaners, and air conditioners, have bearings. Bearings are the rotating shafts that support the wheels, gears, turbines, rotors, etc. in these machines, and can ensure that these parts rotate more smoothly.

Machines of all types require a large number of shafts to rotate, which means bearings are so ubiquitous in industry that they have been dubbed the "bread and butter of the machine industry". At first glance, bearings look like simple mechanical parts, but without them we wouldn't be able to survive.

The role of bearings: 

why are they so important? What role do bearings play in keeping a machine running smoothly?

Bearings mainly have the following two functions.

Feature 1: Reduce friction and make rotation smoother

Friction is bound to occur between the rotating shaft and the parts that support the rotation. Bearings are used between these two components. Bearings reduce friction and allow for smooth rotation. This reduces energy consumption. This is the most important function of the bearing.

Function 2: Protect the parts that support the rotation and maintain the correct position of the axis of rotation

A large amount of force is required between the rotating shaft and the part supporting the rotation. The function of the bearing is to prevent this force from causing damage to the components supporting the rotation and to maintain the correct position of the rotating shaft. This function of the bearing allows us to reuse the machine for a long time.

What is the scope of use of the bearing? What would we do without them?

To what extent our daily lives depend on bearings. Usually you don't see them, so it's hard to imagine, right? Let's talk about cars, because that's what we all know.

As a kid, you probably played with an electric toy race car at least once, right? You may remember the bearings for the wheels. But what about real cars? How many bearings does a car need?

Figure: Main installation positions of automotive bearings

① Equipment (parts) that generate power

Examples: alternators, turbochargers, etc.

②Steering equipment (parts)

Examples: Steering Gears, Pumps, etc.

③ Equipment (parts) that transmit power

Example: Transmission, Differential, etc.

④ Equipment (parts) for driving a car

Example: Wheels, Suspension, etc.

All these bearings play a very important role.

I feel that if the car does not have bearings, it will be difficult to rotate and consume a lot of energy, and the part that supports the rotation will be damaged almost immediately. Therefore, without bearings, we would not be able to drive a car safely and comfortably. In this way, the bearings are constantly working in places we can't see, making our lives more comfortable.

Conclusion: Bearings are the mechanical parts that make the world go round

Bearings play a vital role in our daily lives, but it is precisely because of their importance that we must continually strive to make them more precise and durable. In addition, it is essential for the development of machine technology that we continue to develop bearings capable of working in increasingly demanding and more specialized conditions.

How to ensure the normal operation of the bearing?

 One of the most important is to ensure the lubricity of the bearing.

Lubrication (or more correctly, improper or insufficient lubrication) is one of the main causes of equipment failure in industrial applications. Without it, sliding, rolling or meshing surfaces experience significant friction, heat and wear, resulting in increased noise, reduced accuracy and shortened equipment life.

One of the most important characteristics of a lubricant is its viscosity (or, in the case of grease lubricants, the viscosity of the base oil). But viscosity is similar to friction in a fluid. So why do you need friction (lubrication) to reduce friction (bearings)?

Tribology is the basis for the study and application of friction, lubrication and wear between two surfaces in relative motion.

Viscosity directly affects the level of friction in the fluid

Viscosity is a property of a fluid that is caused by the internal shear resistance of the fluid. When fluid moves under laminar flow conditions, there is no turbulence (as is the case in most bearing lubrication situations), and the microscopic layers of fluid flow over each other, like a stack of paper, each moving slightly faster than a sheet of paper . When moving between these microscopically thin layers of fluid, the cohesive forces between them must be overcome. The resistance caused by these cohesive forces is a major determinant of fluid viscosity.

In laminar flow, the microscopic layers of the fluid flow against each other, and internal resistance to this shear force increases viscosity.

The role of viscosity in reducing bearing friction

Bearing surfaces, no matter how well machined, polished and clean they are, will not be completely free from unevenness (peaks) and friction. When two bearing surfaces (for example, balls and raceways or rollers and raceways) come into contact, the asperities on the surfaces interfere with each other. One of the primary effects of lubrication is to separate surfaces and reduce or eliminate disturbances from surface roughness, thereby significantly reducing friction and wear.

However, when the surfaces are stationary (or moving at very low speeds), the pressure between them essentially "squeezes" the lubrication between the surfaces. Although there is a thin lubricating film, but not enough to separate the unevenness of the two surfaces, there is still significant contact. This is called boundary lubrication.

In boundary lubrication, friction, heat and wear mainly depend on the interaction between the surfaces, although chemical reactions between the lubricant and the surfaces can also cause wear. Time spent in boundary lubrication conditions can significantly affect bearing performance and life.

As bearing speed increases, lubrication is "sucked" into the contact area.

As speed increases, more lubrication is "pulled" into the space between the bearing surfaces, creating a thicker lubricant film. This causes an increase in pressure on the lubricating film, which in turn increases the viscosity of the lubricant (according to the pressure-viscosity coefficient of the lubricant). But there is a transition where the surfaces separate in some places as the speed increases, but in others there is still interference between the roughness, this is called mixed lubrication.

Eventually, when sufficient speed is reached, the lubricating layer becomes large enough to separate the unevenness of the two surfaces, and the increased viscosity gives the lubricant sufficient film strength to support the load by elastically deforming the bearing surfaces. This lubrication method is called elastohydrodynamic lubrication.