bearings classification and working

MEA ENGINEERING COLLEGE PERINTHALMANNA

NASEEL IBNU AZEEZ.M.PAssistant ProfessorDepartment of Mechanical EngineeringEmail:naseel@live.com

BearingsBearing is a machine component which supports another machine element (known as journal).It permits relative motion between the contact surfaces of the members, while carrying the load

Classification of Bearings• Based on the Direction of Load1. Radial Bearing

Load acting perpendicular to the direction of motion of moving element2. Thrust Bearing

Load acts along the axis of rotation

• Based on Nature of Contact1. Sliding Contact Bearing

Sliding takes place between the fixed and moving element of bearing and its also known as plain bearing

2. Rolling Contact BearingsBalls or rollers introduced between moving and

fixed elements and it is also known as anti-friction bearings

Sliding Contact Bearing/Journal Bearing• Types of Journal Bearings

Types of Journal Bearings Based on Lubrication

Journal Bearing

Hydrodynamic Bearing

Hydrostatic Bearing

• Hydrodynamic Bearing

It is a lubricated journal bearing that uses fluid, liquid or gas lubricants to separate the moving surfaces completely without an external pressure supply, required pressure to support journal inside the bearing is generated from wedging action inside the journal

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Journal (Sleeve) BearingsLoad is transferred through a lubricant in sliding contact

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Journal (Sleeve) BearingsThick-film lubrication (hydrodynamic), pressure distribution, and film thickness.hmin = minimum film thickness, c = radial clearance, e = eccentricity

• Hydrostatic BearingsIt is also known as externally pressurized

lubrication in which the pressurized lubricant pumped into clearance of bearing and journal hence it can support higher loads even at stationary conditions with very low starting friction resulting very low tear an wear. But they are very expensive

Rolling Contact BearingsRolling contact bearings are also known as antifriction bearings.The load, speed, and operating viscosity of the lubricant affect the friction characteristics of a rolling bearing.These bearings provide coefficients of friction between 0.001 and 0.002.The designer must deal with such matters as fatigue, friction, heat, lubrication, kinematics problems, material properties, machining tolerances, assembly, use and cost

Rolling Contact BearingsRolling contact bearings are also known as antifriction bearings.The load, speed, and operating viscosity of the lubricant affect the friction characteristics of a rolling bearing.These bearings provide coefficients of friction between 0.001 and 0.002.The designer must deal with such matters as fatigue, friction, heat, lubrication, kinematics problems, material properties, machining tolerances, assembly, use and cost

Construction of bearing

The rolling contact bearings are composed of four elements.

i. Outer raceii. Inner raceiii.Rolling elementiv.Cage of retaining ring

Roller contact bearing With its parts

i. Outer ring (or) Outer race

ii. Inner ring (or) inner race

iii. Rolling elementsiv. Cage or retaining

ring

Construction Diagram :

Classification of rolling bearings

i. Ball Bearing• Deep groove (Conrad) bearing• Filling notch ball bearing• Angular contact bearings (AC)

ii. Roller Bearing • Cylindrical bearings• Needle bearings• Tapered bearings• Spherical bearings

Classified into two types

Ball BearingsDeep groove bearing

Single row of deep groove ball bearing can combinational of radial and thrust load.Load capacity is limited by the number of ballsPrimarily designed to support radial loads, the thrust capacity is about 70% of radial load capacity

Filling notch ball bearings

Bearings have the same basic radial construction as Conrad type. However, a filling notch (loading groove) permits more balls to be used.

Radial load capacity is 20 – 40% higher than Conrad type.

Thrust load capacity drops to 20% (2 directions) of radial load capacity.

Angular contact Ball bearings (AC)

The centerline of contact between the balls and the raceway is at an angle to the plane perpendicular to the axis of rotation.Used for high radial and thrust load applications

RADIAL AND ANGULAR BEARING

Standardization of bearings

Roller Bearings

Roller bearings have higher load capacity than ball bearings, load is transmitted through line contact instead of point contact.

Helical rollers are made by winding rectangular material into roller. Due to inherent flexibility they are capable of taking considerable misalignment.

A roller with length much larger than diameter is known as needle roller and are used where radial space is limited. Cage nay be absent in needle roller bearings.

ROLLER BEARINGS