A mechanical bearing is a component used between two parts, which allow rotational or pad movement, reducing friction and improving performance to save energy.
Metal and plastic bearings are found everywhere, from refrigerators to computers to the 100 or so bearings in cars. The concept behind them is simple: rolling is better than sliding. Without bearings, your car's wheels would rattle, the teeth of the transmission gears wouldn't engage, and the car wouldn't run smoothly. They consist of a smooth inner and outer metal surface for the metal ball to roll on. The balls or rollers help "carry" the load and the equipment runs more efficiently.
There are many different types of bearings, each used for a specific purpose and designed to carry a specific type of load, radial or thrust. Here we will look at 6 of the most popular types: rolling bearings, plain bearings, jewel bearings, fluid bearings, magnetic bearings and flexible bearings.
1) Rolling element bearings
Rolling element bearings place balls or rollers between two rings (or "seat rings") and allow movement with little rolling resistance and sliding. These bearings include ball bearings and roller bearings.
Ball bearings are the most common type of rolling bearing. These bearings can carry radial and thrust loads, but are usually used where the loads are relatively small. Due to their construction, there is not much contact with the balls on the inner and outer rings. If the bearing is overloaded, the balls can deform and damage the bearing. Roller bearings are able to carry heavier radial loads, such as conveyor belts, because they do not use balls. Instead, they have cylinders that allow more contact between the raceways, thus spreading the load over a larger area. However, this type of bearing is not designed to carry very large thrust loads.
2) Plain bearings
Plain bearings are the simplest type of bearing, consisting of only the bearing surfaces, without rolling elements. They have a high load carrying capacity, are usually the cheapest, and have a much longer service life than other types, depending on the material.
3) Gemstone Bearings
Jeweled bearings are plain bearings with a metal shaft that rotates in a jeweled pivot hole. They carry the load by rolling the shaft slightly off-center and are often used in mechanical watches or clocks. This is because they have low and predictable friction, which improves the accuracy of the watch.
4) Fluid Bearings
Fluid bearings use a thin layer of gas or liquid to support their loads and can be divided into two types: hydrodynamic bearings and hydrostatic bearings. Fluid-powered bearings use rotation to form the fluid against the inner surface of the lubrication wedge. In hydrostatic bearings, the fluid - usually oil, water or air - depends on an external pump.
Fluid bearings are used in high load, high speed or high precision applications where ordinary ball bearings cannot handle or will increase vibration and noise.
5) Magnetic Bearings
Magnetic bearings support moving parts without physical contact, relying instead on a magnetic field to carry the load. They require continuous power input to keep the load stable, and therefore require a backup bearing in the event of power or control system failure.
Magnetic bearings have very low and predictable friction and are capable of operating without lubrication or vacuum. They are increasingly used in industrial machines such as turbines, motors and generators.
6) Flexural Bearings
A typical flexural bearing is a part that connects two other parts, such as a hinge, in which the motion is supported by a bent load element. These bearings need to be bent repeatedly, so material selection is key. Some materials will fail after repeated bending, even at low loads, but with the right materials and bearing design, flexural bearings can have an indefinite life. Another distinguishing feature of these bearings is their fatigue resistance. Many other bearings that rely on balls or rollers will fatigue as the rolling elements flatten against each other.
评论
发表评论