Bearing speed limit and friction coefficient

The speed of the bearing is mainly limited by the temperature rise caused by friction and heat inside the bearing. When the speed exceeds a certain limit, the bearing can not continue to rotate due to burns and the like. Bearing speed limit is defined as the limit value that does not cause frictional heating and continuous rotation of the burn. Therefore, the bearing speed limit depends on the type of bearing, size and accuracy as well as lubrication, quality and quantity of lubricants, cage materials and types, load conditions and other factors. Various types of bearings with grease lubrication and oil lubrication (oil bath lubrication) limit speed, respectively, contained in the bearing size table, the value that the standard design of the bearing under normal load conditions (C / P> = 13, Fa / Fr In addition, Lubricant may not be suitable for high-speed rotation depending on its type and grade, but may not be suitable for high-speed rotation. Corrected load at speed limit C / na = f1 * f2 * n where na: corrected speed limit, rpm f1: Correction factor related to load conditions (Figure 8.1) f2: Correction factor related to combined load (Figure 8.2) n: Limiting speed in normal load condition, rpm (refer to bearing size table) C: Basic dynamic load rating, N {kgf} P: Equivalent dynamic load, N {kgf} Fr: Radial load, N {kgf} Fa: Axial load, N {kgf} Limiting speed for ball bearings with seals With contact seals ) The limiting speed of the ball bearing is limited by the linear speed of the contact surface of the sealing ring, and the allowable linear speed depends on the rubber material of the sealing ring. Precautions for High Speed ​​Rotation The bearing rotates at a high speed, especially at a speed close to or exceeding the limit speed , The following main points should be paid attention to: (1) Analysis of bearing internal clearance using precision bearing (2) (Reduction of internal clearance of bearings taking temperature into account) (3) Type of material for cage analysis (For high speed rotation, Suitable for use with copper alloy or phenolic resin cut cage. There are also suitable for high-speed rotation of the synthetic resin molding cage) (4) analysis of lubrication (using high-speed rotating circulation lubrication, jet lubrication, oil mist lubrication and oil and gas lubrication Etc.) Coefficient of friction of the bearing (reference) In order to facilitate comparison with plain bearings, the frictional torque of a rolling bearing can be calculated according to the inner diameter of the bearing by the following formula: M = uPd / 2 where M: friction torque, mN.m {kgf.mm} u: friction coefficient, Table 1 P: Bearing load, N {kgf} d: bearing nominal diameter, mm friction coefficient u by the bearing type, bearing load, speed, lubrication and other more influential, under normal conditions, stable rotation The friction coefficient reference values ​​are shown in Table 1. For plain bearings, generally u = 0.01-0.02, and sometimes 0.1-0.2.