Rolling Bearing Fundamentals

By changing these and their combination a rolling bearing can be optimized for almost every application

Key components

How to select a bearing

Outer ring

Inner ring

Rolling element

cage

Ball cylindrical roller tapered roller

symmetricalBarrel roller

asymmetricalBarrel roller

Needle roller

How to select a bearing

Radial load

Axial load

speed

Misalignment

Temperature

Main stress factors that require spezialized bearings for different applications:

How to select a bearing

Radial load

Axial load

The axial load bearing capacity of a rolling bearing can be judged from its contact angle

Axial load

Inclined load

An inclined load may be split into two components : Radial load FR and Axial load FA

The larger the rolling elements and the higher the speed of the bearing the higher is the centrifugal force pressing the rolling elements against the outer ring raceway. This means an extra load on the oil film and on the raceways.

Speed

Static misalignment can arise from the processing of the bearing seatings from a shaft or a housing, especially if the seatings are manufactured not in one setting

Static misalignment

Dynamic misalignment is caused by shaft deflection as a result of operating loads.

Dynamic misalignment

Dynamic-Static misalignment

Suitability for higher temperatures is a matter of the material of the rings, rolling elements and cages. Therefore it cannot be judged simply from the design of a bearing.

Temperature

Temperature

Permissible operating temperatures for Rolling bearings and their components

Bearing steel 150°C

Cages – Brass/Steel 300°C

Cages – Polyamide 120°C

Cages – Phenolic 110°C

Seals – NBR (RSR) 110°C

Shields (ZR) 300°C

Thrust ball bearing Thrust ancular contact ball bearing

Thrust cylindrical roller bearing

Thrust spherical roller bearing

Radial-Ball Bearings

Radial-Roller Bearings

Deep groove ball bearing

Ancular contact ball bearingSingle row douple row

Four point ball bearing

Self aligning ball bearing

Cylindrical roller bearing

Tapered roller bearing

Barrel roller bearing

Spherical roller bearing

Bearing types

- it keeps the rolling elements apart to prevent mutual contact- it keeps the rolling elements evenly spaced to ensure a more even load distribution- it guides the rolling elements in the unloaded bearing zones- it prevents the rolling elements from falling out of separable and slewable bearings, thereby facilitating bearing mounting.

Cage design

Pressed cages are usually made from sheet steel, but sometimes also from brass sheet. They offer the advantages of a light weight and low material cost. If manufactured in large numbers, they are economic in spite of the expensive manufacturing tools.Solid cages are made from brass, steel, light metal or textile-laminated phenolic resin. They are manufactured either by machining, by injection moulding of plastic materials or by sintering metals.

Cage design

Pressed cageJ

Pressed cageJN

Machined cageM

Machined cageMP

Machined cageM

Pressed cageJPA

Machined cageM1

Machined cageTV

Machined cageTVP

Machined cageTVP

Cage design

Temperatures for polyamid cages

-40°Clower limit

+120°C upper limit

+150°C some hours (approx. 5h)

+180°C short peak temperature (approx. 5min.)

+255°C Melting point

Continous operating temperature

Cage design

Cage design

The clearance defines the way which a bearing ring can move in radial or in axial direction against to the other ring.

Rolling Bearing Clearance

Gr

Ga

We distinguish the clearance between a non-mounted bearing and a mounted bearing. The clearance of a mounted bearing should be small as possible that the shaft is guided well. The clearance of a non mounted bearing will reduce during mounting because of the tight fits. It also reduce during operation if the inner ring is warmer than the outer ring. For this the clearance of a non mounted bearing should be bigger.

Rolling Bearing Clearance

Radial Clearance influences the Bearing load zone (Radial clearance optimized for high load zone)

Rolling Bearing Clearance

Radial Clearance influences the Bearing load zone (to high radial clearance - small load zone)

Rolling Bearing Clearance

Designing of Rolling Bearing arrangements

In order to guide and support a rotating shaft, at least two bearings are required which are arranged at a certain distance from each other. Depending on the application, a bearing arrangement with locating and floating bearing, with adjusted bearings or with floating bearings can be selected.

Rolling Bearing arrangements

Due to machining tolerances the centre distances between the shaft seats and the housing seats are often not exactly the same with a shaft which is supported by two radial bearings. Warming- up during operation also causes the distances to change. These differences in distance are compensated for in the floating bearing.The locating bearing guides the shaft axially and transmit external axial forces.

Locating-floating arrangement

Locating-floating arrangement

Locating-floating arrangement

Locating-floating arrangement

Locating-floating arrangement

The floating bearing arrangement is an economical solution where close axial guidance of the shaft is not required. The shaft can shift by the axial clearance s relative to the housing. The value s is determined depending on the guiding accuracy in such a way that detrimental axial preloading of the bearings is prevented even under unfavourable thermal conditions.

Floating bearing arrangement

With NJ cylindrical roller bearings, length is compensated in the bearings. Inner and outer rings can be fitted tightly.

Floating bearing arrangement

In non - seperable bearings one ring is fitted loosely to allow displacement.

Floating bearing arrangement

Elastic adjustment of deep-groove ball bearings

Floating bearing arrangement