JPS55136508A - Controlling method for sheet thickness under condition of roll running at different circumferential speed - Google Patents

Abstract

PURPOSE:To exactly control the sheet thickness without time delay, by detecting the speed difference between upper and lower rolls, by comparing this difference with the reference speed difference, and by controlling the screw position so as to eliminate this deviation obtained from above comparison. CONSTITUTION:At rolling the material 3 by the rolling rolls 1, 2, assume that only the lower roll 2 is driven by the motor 4. The circumferential speeds V1, VD, of upper and lower rolls 1, 2, are detected by the speed meters 5, 6. Since the rolled material's outgoing speed is given by U1=(1+f1)V1=(1+fD)VD, the speed ratio is given by phi=V1/VD=(1+fD)/(1+f1). Since the forward slips f1, fD, are functions of the draft percentage gamma, if the draft percentage gamma changes, the speed ratio phi changes too. Therefore, the ratio phi is operated by the operator 7 and is compared with the set reference speed ratio phi0 by the comparator 8 to obtain the deviation DELTAphi=phi-phi0, which is multiplied by the gain by the operator 9 to give the variation DELTAS of the rolling reduction. The screw down motor 10 is controlled according to this variation DELTAS, and the screw 11 corrects the roll gap so as to make phi=0. As a result, the draft percentage is made always a constant value.