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Bearing speed limit and the friction coefficient

Date锛2013-09-30 9:26:12

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 ( Figure 8.2) n: normal load conditions limit speed, rpm ( refer to the bearing dimensions table ) C: basic dynamic load , N {kgf} P: equivalent dynamic load , N {kgf} Fr: radial load , N {kgf} Fa: axial load , N {kgf} with a ring ball bearing speed limit 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:
( 1 ) 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, table 1 P: bearing load , N {kgf} d: bearing nominal diameter , mm coefficient of friction u by the bearing type, bearing load, speed , lubrication methods of larger, generally stable under the conditions of rotation of the reference value of friction coefficient shown in Table 1 . The slide bearing , generally u = 0.01-0.02, sometimes up to 0.1-0.2 .

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