Design And Related Technology Research Of Variable Lead Spiral Pair For Subway Doors

The variable lead screw is applied to the transmission part of subway door,which can improve the reliability and running stability of subway door.It is of great application value and research significance.In this paper,taking the variable lead screw as the research object.It designs the variable lead helix screw for subway door,researches the stress and lubrication condition between spiral roller and spiral groove.Besides with the fuzzy comprehensive evaluation applied,the variable lead helix designed is optimized.In addition,the paper puts out the CNC machining simulation of variable lead screw.Firstly,the advantage of variable lead helix mechanism applied to the transmission of subway gate is described.According to the width of the subway door and the movement time,the parameters of the variable lead screw radius,rotational speed and variable lead helix are designed.At the same time,the three-dimensional modeling method of variable lead screw is introduced.Secondly,according to the motion of the spiral roller in the spiral groove,it is found that there is a sliding motion of the roller.In order to improve the service life of the spiral roller,the contact stress and the film thickness between the helical roller and the helical groove are calculated to satisfy the allowable contact stress of the spiral pair material and realize the state of elasticity lubrication.Thirdly,through the modal analysis of the variable lead screw rod,it is concluded that the natural frequency is low,and the vibration is easy to be produced.In order to improve the stability of the screw movement,four alternative motion schemes are proposed for lead functions.The fuzzy evaluation method is used to evaluate the scheme,and the law of the simple harmonic trapezoid is obtained.Then according to the influence of the time parameter to the motion characteristic and the distance parameter S0.3,the time parameters of each time period are determined.Finally,four-axis NC milling method is used for machining lead screw.The milling force generated in the milling process is simulated by using DEFORM-3 D,whose parameters are exhausted into MASTERCAM for milling process simulation.Ultimately,the procedure of variable lead screw screw CNC machining is generated automatically.