随动磨削中船用曲轴自动校直系统研究

Research on Automatic Alignment System for the Crankshaft of Marine Diesel Engine in Tangential Point Tracing Grinding

船用柴油机曲轴轴线不连续、长径比大,刚性差,在自身巨大的重力和随动磨床夹具夹紧力的作用下容易产生复杂的弹性变形,曲轴各档主轴颈的同轴度变差,严重影响连杆颈的磨削精度。研究一种曲轴随动磨削中的自动校直系统,设计主轴颈中心位置在机检测装置,建立主轴颈中心偏移量计算模型,并分析影响测量结果的主要因素。并对伺服中心架机构进行运动学分析,以主轴颈中心偏移量为输入,建立中心架上下支撑头位置计算模型。通过与其理想位置比较,得到了支撑头位置调整量,从而实现随动磨削前工件的自动校直。试验表明自动校直系统应用于某一八缸船用曲轴,取得了与人工校直相似的效果,且大大降低了劳动强度,提高了大型船用曲轴随动磨削的自动化程度。

The crankshaft of marine diesel engine, with the discontinuous axis, the big length to diameter ratio and the poor rigidity, generates the complex elastic deformation under its enormous gravity and clamping force. The deformation causes the poor coaxiality of all the main journals, which has the detrimental effect on the grinding precision. An automatic alignment system integrated into the crankshaft tangential point tracing grinder is studied. An on-machine measuring device of main journals＇ central position and the corresponding calculation model of the deviation of main journal＇s center are proposed. The influences of geometric error and position error of measuring device on the measured results are analyzed. On the basis of the kinematic analysis of servo steady rest and the deviation of main journal＇s center, the calculation model of position of the upper and lower support heads are established. The adjustment amounts of support heads are obtained by comparing their current and desired positons, which are employed to align the workpiece automatically in tangential point tracing grinding. The results of the experiments, using a crankshaft of eight throws demonstrate that the automatic alignment system not only works as effectively as the manual alignment but reduces the labor intensity and increases the automation of tangential point tracing grinding as well.