| The rotation resistance is an important indicator to measure the performance of the idler,which is directly related to the operating efficiency and cost of the belt conveyor.At present,the research on the rotation resistance of the idler is limited to the two factors of speed and load.However,the characteristics and the amount of grease inside the idler also have a huge impact on the rotation resistance,and it will also affect the service life and manufacturing cost of the idler.Therefore,the research in this paper introduces the influence of the grease characteristics and the filling amount,and strives to study the characteristics of the rotation resistance of the idler more comprehensively.It is of great significance to improve the performance and reduce the rotation resistance of the idler,improve the operating efficiency of the belt conveyor.This paper first analyzes the structure of the idler,and concludes that the rotation resistance of the idler is mainly composed of the frictional resistance of the bearing and the viscous resistance of the labyrinth seal.Then the mechanism of these two components was studied separately:Based on the Hertz elasticity theory,the motion of the idler bearing and the contact stress were analyzed.The different sources of bearing friction resistance and the corresponding friction torque calculation method were studied.For grease-lubricated idler bearings,there are differences in the friction resistance characteristics caused by the difference in grease characteristics and the amount of grease filling.Then,the formation mechanism of the viscous resistance of the idler labyrinth sealing device was studied,and the corresponding theoretical calculation formula was derived.It is concluded that the viscous resistance of the labyrinth seal has nothing to do with the external load,only related to its own structure and the viscosity of the filled grease.Secondly,in order to study the influence of grease on the resistance of the idler bearing accurately,based on the rheological characteristics of the grease,the flow characteristics of the grease in the bearing cavity were simulated and analyzed by using Fluent software.From the simulation results,it is concluded that the centrifugal force of the bearing is the main factor affecting the distribution of grease,and the grease will gradually stick to the outer raceway as the bearing speed and the amount of grease filling increase,the accumulated grease increases the frictional torque of the bearing.According to the distribution law of grease in the bearing cavity,the theoretical calculation model between amount of grease filling and bearing resistance was established.The overall calculation formula of the friction resistance moment of the grease-lubricated idler bearing was improved by introducing the cut-in heating reduction coefficient and lean oil backfill reduction coefficient.Then,in order to obtain the change rule of the rotation resistance of the idler accurately,aiming at the shortcomings of the existing idler resistance testing device,the idler resistance testing bench was designed based on the principle of static lubrication.The mechanical system,hydraulic system and electrical control system in the test bench were designed,and the selection of main electrical components was completed.The use of hydrostatic bearings in the resistance test device minimizes the resistance of the test bench and improves the accuracy of the test system.Finally,the experimental study on the rotation resistance of the idler was carried out,and the experimental results verified the accuracy of the theoretical model established.It is concluded that under the condition of a fixed load,the rotation resistance of the idler has an exponential relationship with the amount of grease filling in the bearing,and increases with the amount of grease filling.When the amount of grease filling is between 40%and 50%,the lubricating grease that plays an effective role in the bearing cavity reaches the most.When the rotation speed of the idler and the amount of grease filling in the bearing are fixed,the rotation resistance of the idler is approximately proportional to the radial load.At the same time,the rotation resistance of the idler will increase with the increase of the rotation speed.When the rotation speed exceeds 300 r/min,the increase in resistance begins to decrease due to the rheological characteristics of the grease. |
