Date: 2013-08-20

Bearing speed limit and the friction coefficient

Mainly by the speed of the bearing friction inside the bearing temperature rise caused by heat restrictions, when the speed exceeds a certain limit, the bearings will be unable to continue due to the burn rotation. Bearing speed limit is not generated friction heat can cause burns continuously rotating the threshold.
Therefore, bearing speed limit depends on the bearing type, size and accuracy as well as lubrication, lubricant quality and quantity of material and type of cage, load conditions and other factors. Various types of bearings lubricated with grease and oil lubrication (oil bath lubrication) speed limit are set out in the bearing dimension tables, the values expressed in the general standard design bearing load conditions (C / P> = 13, Fa / Fr <= about 0.25) when the speed of rotation of the limit value. In addition, the lubricant according to the different types and grades, although better than the other properties may not apply to high-speed rotation.
Fixed speed limit load conditions C / P <13 (ie, equivalent dynamic load P exceeds basic dynamic load rating C is about 8%), or exposure to synthetic load in the axial load exceeds 25% of the radial load, use the following formula for the speed limit to be amended. na = f1 * f2 * n here na: revised speed limit, rpm f1: load conditions associated with the correction factor f2: with synthetic load-dependent correction factor n: normal load conditions speed limit, rpm (refer to bearing size Table) C: Basic dynamic load, N {kgf} P: Equivalent dynamic load, N {kgf} Fr: radial load, N {kgf} Fa: axial load, N {kgf} Limiting ball bearings with seals speed with contact seals (RS type) ball bearing speed limit by sealing contact surface line speed restrictions, allowing wire speed depends on the rubber seal.
Precautions speed rotating bearings rotating at high speed, especially speed close to or exceed the speed limit listed in dimension tables, the main should note the following:
(A) use of precision bearings
(2) analysis of the bearing internal clearance (considering the temperature rise of the bearing internal clearance reduction)
(3) the material of the cage type (for high-speed rotation, suitable for cutting copper alloy or phenolic resin cage. There are also suitable for high speed rotation of the synthetic resin molded cage)
(4) Analysis of Lubrication (used for high-speed rotation of the circulating lubrication, spray lubrication, oil mist lubrication and oil lubrication lubrication) bearing friction coefficient (reference) In order to facilitate comparison with the sliding bearings, rolling bearing friction torque can be diameter calculated by the following formula: M = uPd / 2 where M: friction torque, mN.m {kgf.mm} u: friction coefficient, bearing load, N {kgf} d: bearing nominal diameter, mm by the friction coefficient u Bearing Type , bearing load, speed, lubrication methods of influence.

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