Summary of "9.2 Подшипники качения"

Summary of the Video “9.2 Подшипники качения” (Rolling Bearings)

Main Ideas and Concepts

1. Purpose and Function of Bearings

Bearings enable free rotation of shafts by reducing friction (rolling friction is much lower than sliding friction).
They support and transmit forces acting on shafts, including radial, axial, and circumferential forces.
Bearings are not frictionless but significantly reduce friction compared to direct contact.

2. Types of Bearings and Their Characteristics

Bearings contain balls or rollers (cylindrical, conical, needle-shaped).
They can be single-row or double-row.
Different bearings are designed to handle different loads:
- Radial loads (perpendicular to shaft axis)
- Axial loads (along the shaft axis)
- Combined loads

Examples:

Single-row radial ball bearing: handles mainly radial loads and small axial loads.
Spherical roller bearing: allows angular misalignment, handles heavy loads.
Radial thrust roller bearing: handles both radial and axial loads.
Needle roller bearing: thin, elongated rollers, used where space is limited.
Large thrust bearing: designed only for axial loads.

Additional notes:

Ball bearings have lower friction and are more efficient but handle lower loads than roller bearings.
Roller bearings have higher load capacity but higher friction and heat generation.

3. Force Transmission in Bearings

Forces from gears (axial, radial, circumferential) are transmitted through the shaft to the bearing inner ring, then via rolling elements to the outer ring, and finally to the housing or bolts.
Bearings must be selected and arranged to handle these forces appropriately.

4. Bearing Design and Components

Inner ring fits on the shaft.
Outer ring fits into the housing.
Rolling elements (balls or rollers) roll between the rings.
Separator (cage) keeps rolling elements evenly spaced.
Seals prevent dirt ingress and oil leakage.
Some bearings have plastic or metal seals; others are open.

5. Bearing Dimensional Series and Accuracy Classes

Bearings come in different dimensional series (ultra-light to super-heavy) based on load requirements.
Accuracy classes (e.g., 0, 6, 5, 4, 2) define manufacturing precision and affect friction, vibration, service life, and speed capability.
Higher precision bearings cost significantly more.
Typical industrial use favors moderate precision classes unless high speed or precision is required.

6. Bearing Durability and Load Ratings

Two main load ratings:
- Static load rating (C0): maximum load bearing can withstand without permanent deformation (important for slow or stationary shafts).
- Dynamic load rating (C): load that a bearing can endure for a specified number of revolutions (usually 1 million) without fatigue.
Equivalent dynamic load is calculated to account for combined radial and axial loads, rotation, shocks, and temperature.
Service life calculation involves these load ratings, load conditions, and reliability factors.
If service life is insufficient, options include using larger bearings, heavier series, or improving lubrication and alignment.

7. Lubrication and Maintenance

Lubricants used include plastic greases and liquid oils.
Liquid oil lubrication is preferred for lower friction.
Seals and protective rings prevent contamination by dirt and metal particles.
Proper lubrication extends bearing life and prevents abrasive wear.

8. Bearing Arrangement and Mounting

Bearings typically work in pairs on opposite sides of the shaft.
Arrangement types include:
- Thrust pairs (bearings facing opposite directions to handle axial loads).
- Floating bearings allow axial movement to accommodate shaft expansion due to heat.
Bearings can be mounted using flanges, nuts, washers, retaining rings, and adjusting rings or shims for axial clearance.
Adjustments prevent shaft wobble and excessive bearing preload.
Over-tightening bearings reduces life due to increased friction and heat.

9. Installation and Removal

Bearings are press-fitted onto shafts with interference fits.
Pressing must apply force on the bearing’s inner ring to avoid damage.
Removal tools include pullers that press on the inner ring.
Design should allow access for removal tools (e.g., threaded holes for screwing out bearings).
Good design considers manufacturability and maintainability.

Methodology / Instructions Presented

Calculating Equivalent Dynamic Load

Identify radial (Fr) and axial (Fa) forces.
Calculate force ratio: Fa / Fr.
Use tables to find coefficients X, Y, and e based on the force ratio.
Apply linear interpolation if exact values are not in the table.
Calculate equivalent load: P = X * Fr + Y * Fa
Adjust for operating conditions (shocks, temperature) using coefficients.

Calculating Bearing Service Life

Use dynamic load rating (C) and equivalent load (P).
Apply formula for service life in revolutions or hours, incorporating reliability and operating conditions.
Compare calculated life with required service life.
If insufficient, select a bearing with higher load rating or improve conditions.

Bearing Installation

Use press to fit bearing on shaft, pressing only on inner ring.
Ensure design allows tool access for bearing removal.
Use washers, nuts, and retaining rings to fix bearing axially.
Use seals and protective rings to prevent contamination and oil leakage.

Bearing Arrangement

Use paired bearings arranged to handle axial and radial loads.
Choose arrangement (e.g., thrust, tension) based on load directions and shaft length.
Provide axial clearance adjustment via shims or adjustable nuts.
Allow for shaft thermal expansion by using floating bearings or appropriate clearance.

Speakers / Sources Featured

Primary Speaker: Unnamed lecturer or instructor explaining rolling bearings in Russian, likely a mechanical engineering professor or industry expert.
Referenced Textbooks and Standards:
- Ivanov’s textbook (bearing durability calculations)
- GOST standards for bearing dimensions and load ratings
- Dunaev textbook on machine parts design
Software Mentioned:
- Compass 3D (for selecting standard bearings)

This summary encapsulates the detailed explanations of rolling bearing types, functions, design considerations, calculations, and practical installation/removal tips provided in the video.