A bearing is a machine element that constrains relative motion to only the desired motion, and reduces friction between moving parts. The design of the bearing may, for example, provide for free linear movement of the moving part or for free rotation around a fixed axis;or it may prevent a motion by controlling the vectors of normal forces that bear on the moving parts. Most bearings facilitate the desired motion by minimizing friction.
The bearing in its current form was developed towards the end of the 19th century. It was initially made by hand.
Nowadays, bearings are one of the most commonly used machine parts because their rolling motion makes almost all movements easier and they help reduce friction.
Bearings are classified broadly according to the type of operation, the motions allowed, or to the directions of the loads (forces) applied to the parts.
Bearings have this key functions :
-The basic function of bearings is principally to reduce mechanical friction & Reducing friction means:
- machinery will run more efficiently
- there will be less frictional wear, extending the operating life of the machinery
- preventing abrasion burn, avoiding mechanical breakdown
-Bearings also contribute to lower energy consumption by reducing friction and allowing the efficient transmission of power. This is just one way in which bearings are environmentally friendly.
Components of bearing
Bearings usually consist of the following components:
- Two rings or discs with raceways
- Rolling elements in the form of rollers or balls
- A cage which keeps the rolling elements apart and guides them
There are at least 6 common types of bearing, each of which operates on different principles:
- Plain bearing, consisting of a shaft rotating in a hole. There are several specific styles: bushing, journal bearing, sleeve bearing, rifle bearing, composite bearing.
- Rolling-element bearing, in which rolling elements placed between the turning and stationary races prevent sliding friction. There are two main types:
- Ball bearing, in which the rolling elements are spherical balls.
- Roller bearing, in which the rolling elements are cylindrical, taper or spherical rollers.
- Jewel bearing, a plain bearing in which one of the bearing surfaces is made of an ultrahard glassy jewel material such as sapphire to reduce friction and wear.
- Fluid bearing, a noncontact bearing in which the load is supported by a gas or liquid.
- Magnetic bearing: in which the load is supported by a magnetic field.
- Flexure bearing: in which the motion is supported by a load element which bends.
Bearings are not used only in cars, but in all kinds of machinery such as:
- Industrial machines
- air conditioners
- vacuum cleaners
- photocopy machines
- It is mainly used in motors manufacturing, which is the basis of machines and industry.
The benefits of lubricating a rolling bearing can be summarized as follows:
- Alleviation of friction and wear
- Removal of friction heat
- Longer bearing life
- Rust prevention
- Protection against contamination by foreign matter