MOTOR SPEED CONTROL

摘要

PLL speed control for the motor 705 of an electrophotographic copier comprises an optical rotary encoder 706 and associated divider 707 outputting pulses fG to a counter 709 and to a phase comparator 710, and a reference frequency oscillator 701 and divider 702 outputting clock pulses fr to the counter 709 and to the phase comparator 710 via counter 708. The outputs of the comparator 710 and counter 709 are combined to produce a PWM signal for driver 704 of the motor. A set speed value corresponding to the copy scale factor is supplied to the CPU Q102 of which the elements 708-715 are part. The set value controls the initial counts which are set in counters 708 and 709. Other aspects of the copier are described in detail, including a brake control function (Figs. 15) whereby the motor is braked at the end of a scan to return the optical system to its home position whatever the motor approach speed may be. Braking may be by reversing the motor or by the action of a solenoid or hysteresis clutch brake.