Motor controlling method and apparatus

Abstract

In a sheet conveying stepping motor control method and apparatus, a microcomputer controls a stepping motor for intermittently conveying a sheet in different manners for high-speed, low-to-intermediate speed and fractional conveyance, using a motor driver capable of selecting a motor excitation current from values of high, intermediate and low levels. For the high-speed conveyance, the stepping motor is driven by two-two phase excitation with step-up and step-down control. The excitation current is set to the intermediate level during the initial step, and then to the high level during the later steps, and then to the low level during the final step. For the low-to-intermediate speed conveyance, the excitation is performed by self-start driving. One-two phase excitation is performed during the initial step and the final step, and two-two phase excitation is performed therebetween. The excitation current is set to the high level during the one-phase excitation in one-two phase excitation, and to the intermediate level during the two-phase excitation. The excitation period in one-two phase excitation is longer than that in two-two phase excitation. For the fractional conveyance, the motor is driven by one-two phase excitation. The excitation current is increased in three steps during the initial one-phase excitation period, and in two steps during the later periods. During the final two-phase excitation period, the excitation current is reduced from the intermediate to low levels. The excitation period by the low current during the final two-phase excitation is relatively long.