Research On The Torque Characteristics Of Mixed Friction In Soft Start Of Controlled Start Transmission

Scraper conveyor is an indispensable equipment in fully mechanized mining face.It is often used as coal transportation equipment in mine.It has the advantages of large transportation volume,long distance transportation and long service life.The temporary shutdown may occur due to chain jamming or overload in dreadful condition of mine.So scraper conveyor may start with load or overload,which greatly increases the impact load and reduces the life of scraper conveyor.Controlled start transmission(CST)has the advantages of soft start,multi-machine power balance and overload protection,and soft start of scraper conveyor can be realized ideally.So the research of controlled start transmission is of great significance to heavy scraper conveyor.However,the shear force of oil film is not enough to transmit the load torque during the start-up process of load or overload,so that the soft start can’t be realized.It is necessary to study the torque characteristics of the mixed friction stage of hydro-viscous drive in depth.Taking the controlled start transmission of scraper conveyor as the research object,considering the inertia force and the permeability of paper-based friction material,the average flow model and rough surface contact model in the mixed friction stage were built,and the bearing capacity and torque model of oil film and micro-peak were deduced.The load-bearing capacity and torque characteristics of friction pairs in mixed friction stage were analyzed by calculation.The results show that in the mixed friction stage,the bearing capacity and torque increase with the decrease of film thickness.The micro-peak bearing capacity and torque increase gradually,the oil film bearing capacity is contrary to the trend.When the film thickness ratio decreases to about 0.75,the main part of bearing capacity and torque gradually changes from oil film to rough surface.Combining the start-up process of the CST with the structure of planetary transmission,the oil film change rate was calculated and fitted through the calculation of load conditions.The bearing capacity and torque characteristics of the soft start process of the CST were calculated.The effects of load,start-up time,contact area,oil viscosity,and permeability and friction coefficient on the speed and torque of soft start process were analyzed.The results show that the bearing capacity and torque of the micro-peak increase continuously and are always greater than the bearing capacity and torque of oil film in mixed friction stage,the bearing capacity and torque of oil film decrease continuously.The torque of friction is inversely proportional to the speed of friction plate,and the torque will increase suddenly when the friction pair joins.Finally,the torque characteristics of the soft start process of the controlled start transmission were studied by experiment,and compared with the theoretical calculation in order to verify the accuracy of the conclusion.The conclusion provides theoretical support for torque prediction and control design of scraper conveyor controllable starting device during soft starting process.