| 摘要 |
1,181,692. Automatic control of speed. INTERNATIONAL BUSINESS MACHINES CORP. March 6, 1967 [March 28, 1966], No.10381/67. Heading G3R. The speed of a reversible motor PCM, e.g. driving a type bar in a printing device, is controlled by a system in which, when the motor is slow, a bi-stable "accelerate trigger" 38 is gated on by reference pulses (from single shot device 40) and off by motor speed pulses (from magnetic disc 34), and when fast a "decelerate trigger" 46, which causes reverse energization of the motor, is triggered on by the motor pulses and off by the reference ones and hunting is reduced by means not shown in Fig.2. The motor, which is of printed circuit construction, is energized from a D.C. source via transistors which are switched by the trigger circuits Fig.6 (not shown). Hunting is reduced in Figs.4 and 7 (not shown) by an auxiliary circuit which causes the motor to be energized continuously for a predetermined brief time in a direction which hastens correction; this occurs upon the second trigger pulse following a change from accelerate to decelerate or vice versa. The complete system comprises logic circuitry and photo-cell detectors of print bar position, and provides for the motor to be accelerated from rest by continuous energization for a predetermined time and to be similarly decelerated to stop beyond a predetermined position, the stopping point being such, that, upon reversal, the print bar will have aquired full speed by the time that position is reached. The reference single shot device 40 is operated by sub-division of pulses from a clock 42, the sub-dividing counter also being used to determine the starting and stopping time. A "checking circuit" (100) comprising further logic devices de-energises the motor in the event of typebar jam, feedback or amplifier failure, clock failure or failure of the triggers to reset, and the motor drive circuit includes biasing of the transistors to prevent simultaneous energization in both directions. |
