Introduction:
Bearings are used to reduce friction between two bodies. With the help of bearings it becomes possible, for example, to allow a rotating shaft to rotate in a stationary housing, as is the case with a wheel bearing.
There are two types of bearings: plain bearings and rolling-element bearings. Rolling-element bearings can be divided into six types. These are described in the following chapters.
Plain bearing:
A plain bearing itself has no moving parts. This bearing is used, among other things, as a connecting-rod bearing. The bearing slides along the moving components and therefore requires external lubrication. An engine crankshaft contains oil channels so there is always a certain amount of oil present between the bearing and the crankshaft. This keeps frictional resistance to a minimum. In the event of a lack of lubrication, e.g. when driving without oil, damage to the plain bearing occurs immediately.
Deep-groove ball bearing:
The deep-groove ball bearing is one of the most commonly used types of rolling-element bearing, consisting of an inner and an outer ring with balls in between. The balls are enclosed by the grooves in the inner and outer ring. Deep-groove ball bearings are suitable for high rotational speeds and require little maintenance.
Tapered roller bearing:
Tapered (roller) bearings have an inner and an outer ring with a cage with tapered rollers in between. Tapered roller bearings are used to absorb axial loads. The advantage of the tapered rollers is that they have a larger contact surface. As a result, they can withstand greater forces. This type of bearing is used, among other things, in the gearbox as an input-shaft bearing or as a wheel bearing on cars fitted with drum brakes.
Angular contact bearing:
An angular contact bearing can accommodate radial loads well, but axial loads only in one direction. The raceways of the inner and outer rings are offset relative to each other, creating a contact angle. The angle determines the direction in which the axial loads can be absorbed. Under axial load the ball bearings are in principle pressed “more against the outer ring”. This type of bearing can be manufactured with one or two rows of ball bearings. In the image below, the bearing is made with a single row of ball bearings.
Cylindrical roller bearing:
The cylindrical roller bearing consists of an inner and an outer ring with cylindrical rollers in a cage in between. A cylindrical roller bearing can only accommodate radial loads. Due to its cylindrical shape, the bearing is also well suited to absorb impact-type movements.
Needle bearing:
The needle bearing consists, among other things, of a cage with a large number of needle rollers. Due to the small diameter of a needle roller, needle bearings can be used in confined installation spaces. Other advantages of the needle bearing include a high load-carrying capacity, suitability for high speeds and easy installation.
Thrust bearing:
The thrust bearing can only absorb axial loads. The bearing consists of rings with raceways. The lower ring can be mounted on a shaft and the upper ring on the housing. The thrust bearing is often used as a release bearing in a car clutch.
Spherical roller bearing:
The spherical roller bearing is suitable for taking up very heavy radial loads and allows for angular misalignment of the shaft. The barrel-shaped rollers align themselves in the outer raceway. The spherical roller bearing is also equipped with a lubrication groove and various lubrication holes to allow grease to be forced into the bearing during maintenance.
