General conditions of stable rotation friction coefficient reference value shown sliding bearings in general 0.010.020.10.2 various types of bearing friction coefficient bearing type friction coefficient. In order to facilitate comparison with sliding bearings, rolling bearing friction moment can be calculated by the following formula according to the bearing inner diameter. M = uPd / 2 (M: friction torque, mN.m; u: friction coefficient, Table 1; P: bearing load, N; d: bearing nominal inner diameter, mm). Friction coefficient u is affected by bearing type, bearing load, speed, lubrication, etc. The reference value of friction coefficient for stable rotation under general conditions is shown below. For sliding bearings, generally u = 0.01-0.02, sometimes up to 0.1-0.2. Composite bearing friction coefficient: 0.03-0.18 Bearing type Friction coefficient u Deep groove ball bearing 0.0010-0.0015 Angular contact ball bearing 0.0012-0.0020 Spherical ball bearings 0.0008-0.0012 Cylindrical roller bearings 0.0008-0.0012 Full complement needle roller bearings 0.0025-0.0035 Needle roller bearings with cage 0.0020-0.0030 Tapered roller bearings 0.0017-0.0025 Spherical roller bearings 0.0020-0.0025 Thrust ball bearings 0.0010-0.0015 Thrust spherical roller bearings 0.0020-0.0025 4、The choice of rolling bearing lubrication method Rolling bearing is an important mechanical components, a mechanical equipment performance can be fully developed depends on the bearing lubrication is appropriate, it can be said that lubrication is necessary to ensure the normal operation of the bearing, it plays an important role in improving the bearing bearing capacity and service life. Regardless of the form of lubrication, lubrication in the rolling bearing can play the following role. (1) reduce the friction between the metal, slow down its wear. (2) the formation of oil film to increase the contact area, reduce contact stress. (3) to ensure that rolling bearings can be in high-frequency contact stress, a long time to normal operation, to extend the fatigue life. (4) eliminate frictional heat, reduce the working surface temperature of the bearing, to prevent burns. (5) play a dust, rust, corrosion prevention role. Therefore, the correct lubrication is very important for the normal operation of rolling bearings. The content of rolling bearing lubrication design mainly includes: the determination of reasonable lubrication method, the correct choice of lubricant, the quantitative calculation of lubricant dosage and the determination of oil change cycle. Rolling bearing lubrication can generally be divided into three categories according to the type of lubricant used: oil lubrication, grease lubrication and solid lubrication. Among them, oil lubrication has a wider temperature range than other lubrication methods, more suitable for high speed and high load conditions of the work of the bearing; at the same time, because oil lubrication also has the equipment maintenance and lubricant replacement is convenient, the system of friction vice such as gears can be lubricated at the same time, so far, the bearing using oil lubrication is the most common. Grease lubrication has the advantages of simple sealing device, low maintenance costs and low cost of grease, etc., in the low speed, medium speed, medium temperature operation of the bearing is very common. Especially in recent years, the introduction of anti-wear additives to improve the lubricating properties of grease, so that grease lubrication has been more widely used. If the use of oil lubrication and grease lubrication can not achieve the required lubrication conditions of the bearing, or can not meet the specific working conditions, then you can use solid lubricants, or try to improve the lubrication performance of the bearing itself. The rotational speed of the bearing is mainly limited by the temperature rise caused by the frictional heat inside the bearing. When the rotational speed exceeds a certain limit, the bearing will not be able to continue rotating due to burns, etc. The limiting speed of a bearing is the limit value that can be continuously rotated without generating frictional heat that causes burns. Therefore, the limiting speed of a bearing depends on various factors such as the type, size and accuracy of the bearing, as well as the lubrication method, the quality and quantity of the lubricant, the material and type of the cage, and the load conditions. The limit speed of each type of bearing with grease lubrication and oil lubrication (oil bath lubrication) is shown in the table of bearing size, and the value indicates the limit value of rotating speed of standard design bearing under general load condition (C/P>=13,Fa/Fr<=0.25 or so). In addition, depending on the type and grade of lubricant, it may be better than other performance but not suitable for high speed rotation. ________________________________________ Correction of limiting speed When the load condition C/P<13 (i.e. the equivalent dynamic load P exceeds about 8% of the basic rated dynamic load C), or when the axial load in the synthetic load exceeds 25% of the radial load, the limit speed is corrected by the following formula. ***************** na=f1*f2*n ***************** Here na: corrected limiting speed, rpm f1: correction factor related to load conditions (Fig. 8.1) f2: correction factor related to the synthetic load (Figure 8.2) n : limiting speed under general load conditions, rpm (refer to the table of bearing dimensions) C ：Basic dynamic load rating, N{kgf} P : Equivalent dynamic load, N{kgf} Fr : Radial load, N{kgf} Fa : Axial load, N{kgf} ________________________________________ Limit speed of ball bearing with sealing ring The limiting speed of ball bearings with contact seals (RS type) is limited by the linear speed of the contact surface of the seal, and the permissible linear speed depends on the rubber material of the seal. _____________________________________ Precautions for High Speed Rotation When the bearing is rotating at high speed, especially when the speed is close to or exceeds the limiting speed recorded in the dimension table, the following matters should be noted. (1) Use precision bearings (2) Analysis of the internal clearance of the bearing (considering the reduction of the internal clearance of the bearing due to temperature rise) (3) Analysis of the type of cage material (for high-speed rotation, suitable for the use of copper alloy or phenolic resin cut cage. In addition, there are also suitable for high-speed rotation of synthetic resin molding cage) (4) analysis of the lubrication method (the use of high-speed rotation of the cycle of lubrication, injection lubrication, oil mist lubrication and oil and gas lubrication and other lubrication methods) ________________________________________ Friction coefficient of the bearing (reference) For comparison with sliding bearings, the frictional moment of rolling bearings can be calculated by the following formula according to the bearing inner diameter. **************** M=uPd/2 **************** Here, M: frictional moment, mN.m{kgf.mm} u: coefficient of friction, Table 1 P: bearing load, N{kgf} d: nominal inner diameter of the bearing, mm Friction coefficient u is affected by bearing type, bearing load, speed, lubrication method, etc. The reference value of friction coefficient for stable rotation under general conditions is shown in Table 1. For sliding bearings, generally u = 0.01-0.02, and sometimes up to 0.1-0.2.  

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