Needle roller bearing – Construction And Application

What is Needle Roller Bearing  :

A needle roller bearing is a special type of roller bearing which uses long, thin cylindrical rollers resembling needles. Ordinary roller bearings’ rollers are only slightly longer than their diameter, but needle bearings typically have rollers that are at least four times longer than their diameter.Like all bearings, they are used to reduce the friction of a rotating surface.

Compared to ball bearings and ordinary roller bearings, needle bearings have a greater surface area in contact with the races, so they can support a greater load. They are also thinner, so they require less clearance between the axle and the surrounding structure.

Needle bearings are heavily used in automobile components such as rocker arm pivots, pumps, compressors, and transmissions. The drive shaft of a rear-wheel drive vehicle typically has at least eight needle bearings (four in each U joint) and often more if it is particularly long, or operates on steep slopes.

Construction :

A needle roller bearing is a bearing that uses small cylindrical rollers. These rollers are used to reduce friction of a rotating surface. Compared with ball bearings, needle roller bearings have a large surface area that is in contact with the bearing raceway journals.

The typical structure of a needle roller bearing comprises an inner race (or sometimes just a shaft), a needle cage which orientates and contains the needle rollers, the needle rollers themselves, and an outer raceway. There are many different designs of needle roller bearing, including drawn cup, precision race, caged roller, and thrust roller. Here, we consider the caged roller type.

The function of a caged needle roller bearing is to support radial loads and rotational speeds. Here, a cage guides and retains the rollers. Caged designs normally come in single and double row designs, with a wide variety of cage materials being available, including steel, plastic (PA66) and aluminium. Multiple row bearing designs boost load carrying capacity.

Cages, whether steel or plastic, can be made in a variety of different constructions, including solid cage, single split and split halves (two-piece). These cages can also incorporate lubrication passages and other custom designed features.

Application Of Needle Roller Bearing :

Typical applications for caged needle roller bearings are gearboxes, automotive power transmission systems, two and four stroke engines, planetary gear sets and air compressors.

Regardless of which type of the four main types of needle roller bearing is selected for an application, engineers should consider a variety of factors before making their decision as early in the design phase as possible: the size/design envelope, type of load, load capacity, speed, temperature, misalignment, housing and shaft specifications, service life and lubrication requirements.

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