Torsional Vibration Analysis Of Shearer Cutting Unit

Cutting unit is a very important part of shearer, the stability of cutting unit transmission system directly affect safety and efficiency of the shearer. Cutting unit system is mainly composed of gears, if the working frequency of gears is close to inherent frequency of the system, the resonance will occur; This will cause gear damage of cutting unit and reduce the life of gears, then the safety and reliability of shearer will be affected. As limited by machining equipment as well as the surrounding environment, the machining accuracy of gears can’t reach the ideal state, so the back lash is formed between two gears. The back lash is also formed between two meshing gears because of the machining error of gear box and installation error of gears, the gear back lash will influence the transmission gears of cutting unit.The main purpose of this paper was to determine the inherent frequency and modal flexibility of the cutting unit, to ensure that the cutting unit work within a reasonable range of frequencies, to find out the influence that gear back lash have effect on angular acceleration of cutting unit transmission system, to find out variation regulation that gear back lash have effect on angular acceleration of different transmission gear, and to provide more reasonable and more safety gear design basis for the cutting unit.Each transmission gear of cutting unit was transformed to motor shaft, and shaft system of cutting unit was established. ANSYS Workbench simulation software was applied to calculate the torsional stiffness of single gear pair. Torsional stiffness is multiplied by coefficient of coincidence will be average torsional stiffness of gear pair. Average torsional stiffness was transformed to the motor shaft, then substituded it to transfer matrix of the shaft system, the inherent frequency of cutting unit shaft system was got, and the dangerous mode of cutting unit was analysised. AMESim simulation software was applied to build modeling of cutting unit system, and different back lash was set, then started a simulation for cutting unit system.The calculated results show that the working frequency of the motor is far from inherent frequency of cutting unit shaft system, and the cutting unit works within a safety frequency range, so the resonance phenomenon will not occur. The simulation results of backlash show that the backlash has increased the angular acceleration of each transmission gear, and backlash has a more obvious effect on the angular acceleration of first four gear. The increase angular acceleration of the gears will generate too much impact, accelerate the tooth surface damage, and break teeth because of gear overload.According to above conclusions, to reduce the torsional vibration of cutting unit system should try to minimize gear back lash, and specially minimize machining error and installation error of the first four gears. The author put forward a torque correction coefficient of gear in this paper, and it provide a new calculation method for gear preliminary calculation.