Bearing limit speed and friction coefficient - bearing knowledge

Rotational speed of the bearing are mainly affected by the inside of the bearing temperature rise caused by friction heat, when the speed exceeds a certain limit, the bearing will can't continue to rotate for burns, etc. Bearing limit rotational speed is not burned to produce friction heat and the threshold of the continuous rotation. Therefore, bearing limit speed depends on the type, size, and precision bearings and lubrication method, the quantity and quality of the lubricant, keep the frame material and a variety of factors such as type and load conditions. All kinds of bearing with grease lubrication and oil lubrication ( Oil bath lubrication) When the limit speed respectively in each table bearing size, its numerical representation standard design of bearing in the general load conditions, C / P> =13,Fa/Fr< = 0. 25 or so) The threshold of the next rotation speed. In addition, the lubricant according to their kinds and brands, may also is superior to other performance but is not suitable for high speed rotation. Limit speed of the fixed load condition C/P< 13 ( The equivalent dynamic load P more than about 8% of the basic dynamic load rating C) , or synthetic load under the axial load in more than 25% of radial load, to use the type of limit speed. Na na: * = f1 f2 * n here revised the limit speed, RPM f1: correction factor related to the load condition of f2: correction factor related to the synthetic load n: general load under the condition of the limit speed, RPM ( With reference to the bearing size table) C: the basic dynamic load rating, N { kgf} P: equivalent dynamic load, N { kgf} Fr: radial load, N { kgf} Fa: axial load, N { kgf} With seals limit speed of the ball bearing contact sealing ring ( RS) Ball bearing limit rotational speed is limited by a sealing ring contact surface linear velocity, allowing linear velocity depends on the rubber sealing ring. High-speed rotating note bearing rotating at high speed, especially the speed close to or exceeds the limit speed of the dimension table records, should pay attention to the following main items: ( 1) Use the precision bearing ( 2) Analysis of bearing internal clearance ( Considering the temperature rise of bearing internal clearance reduction) ( 3) Analysis of the cage material type ( For high-speed rotation, suitable for use of copper alloy cage or phenolic resin system. But there are also suitable for high speed spinning of synthetic resin molding cage) ( 4) Analysis of lubrication methods ( Lubrication is suitable for high speed rotating cycle, spray lubrication, and lubrication oil mist lubrication and oil lubrication methods) The friction coefficient of bearing ( Reference) Compared with sliding bearing, for ease of rolling bearing friction torque can be calculated on bearing inner diameter by type: M = uPd / 2 M here: friction torque, mN. m { kgf。 mm} U: the coefficient of friction, bearing load, N { kgf} D: bearing nominal diameter, mm u friction coefficient by bearing type, bearing load, the influence of the rotational speed, lubrication, etc.