JPS6369476A - Servo-motor control circuit in optical system for duplicator - Google Patents

Abstract

PURPOSE:To enable a speed to he stably controlled without irregular rotation, by enhancing the resolution of an encoder in a range where a CPU controlling the speed of a servo-motor does not fall into control incapability. CONSTITUTION:The resolution of an encoder 7 is determined to be of irregular rotation allowable on 400% magnifications. Input signal D0 is of clock direct from the encoder 7, and signal L1 is of frequency divided by 2, and signal D2 is of frequency divided by 4. When the input of magnification is provided, then values are set at ports C0, C1 according to the data selector input(D0-D1) according to the magnification in respective ranges, to a CPU 1 for input. By the CPU 1, the clock interval of the input signal D0 is measured, and the output of a value according to a difference between the interval and a clock interval set according to the magnification is directed to a timer 3 from a data bus. A sevo-motor 6 is driven according to the value.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a control circuit for a servo motor used to drive an optical system of a copying machine.

(Prior art) As a method for controlling the rotational speed of a servo motor, the clock from the encoder is input to the CPU interrupt, the time between the clocks is measured, and the difference from the set time is subjected to proportional-integral control. A method of controlling the rotational speed of a servo motor by applying a voltage to the servo motor using a PWM (pulse width modulation) method is already known.

When using a servo motor to read originals in a copying machine, to transport the original, or to scan the optical system, to change the magnification from 50 to 400%, for example, the rotation speed of the servo motor must be inversely proportional to the magnification ratio. You can set it to the value you want.

Furthermore, since the rotation speed of the servo motor is approximately proportional to the voltage, if a voltage inversely proportional to the magnification ratio is applied to the servo motor, the rotation speed of the servo motor can be obtained in accordance with the magnification ratio.

By the way, in order to reduce uneven rotation of the servo motor, it is possible to increase the clock number/rotation of the encoder, but since the number of rotations varies depending on the magnification, the clock interval from the encoder that is input to the interrupt of the CPU that controls the rotation speed is However, at a certain magnification, the clock interval from the encoder becomes shorter than the CPU's interrupt processing time, making it impossible for the CPU to control the rotation speed.

For this reason, the resolution of the encoder is determined so that when the rotational speed is the fastest among the magnification ratios, the clock from the encoder is longer than the interrupt processing time of the CPU controlling the rotational speed. However, this has the problem that when the rotation speed is a slow magnification, the resolution of the encoder is low and uneven rotation speed occurs.

(Purpose) The present invention was made based on this background, and in order to reduce uneven rotation of the servo motor, the resolution of the encoder is used to control the speed of the servo motor.
The purpose is to increase tJ within a range that does not cause it to become uncontrollable.

(composition) First, the present invention will be explained in detail.

The uneven rotation of the servo motor is greater when the rotation speed is slow.
Therefore, the resolution of the encoder is determined based on the rotational unevenness that can be tolerated when the magnification is 400%. As the magnification decreases, the rotation speed increases, so for example, when the magnification is 400% to 200%, input the clock from the encoder directly to the CPU interrupt.
For magnification IQ 9% to 100%, the clock from the encoder is divided by 2, and for magnification 99 to 50%, the click from the encoder is divided by 4 and input to the CPU interrupt, thereby using a CPU with less uneven rotation. Rotation speed control is possible.

FIG. 1 is a control block diagram showing one embodiment of the present invention.

1 is CPU, 2 is data selector, 3 is timer, 4 is AND gate, 5 is transistor, 6 is servo motor, 7
is an encoder, and 8°9 is a flip-flop.

Data selector (74LS151) 2 is select input A
, B, and C are all 11 L 11, the input signal of Do is selected and output from Y. A-1H", B, C
When is “L”, the input signal of D is selected.B-H
When "A" and "C" are "L", the input signal of D8 is selected. The input signal D0 is clocked directly from the encoder 7,
D is a signal whose frequency is divided by 2, and D8 is a signal whose frequency is divided by 4 (the frequency is divided by a D flip-flop).

In addition, select inputs A and B have boats Co and Co, depending on the magnification.
A signal is input from Ci (select human power C is always “■
(Leave it at 2”).

The flowchart shown in Fig. 2 shows that when 0 magnification is input, depending on which input of the data selector inputs (D, ~pg) is input to the CPUI, depending on the magnification of each range, the boat
Insert 7 letters in cr.

Next, when the servo motor ON signal is input, the baud) B becomes H''.The CPU measures the clock interval from the encoder 7, compares it with the clock interval set according to the magnification, and takes into account the difference. The value is output from the data bus to timer 3.A square wave is output from the OUT of timer 3 according to the value.This operation continues until the servo motor OFF signal comes.When the servo motor OFF signal comes, the boat is switched off. Set B to @L'', turn off the servo motor 6, and proceed to the next step. The 0N-OFF and magnification of the motor 6 are serially input (RXD) from the main control (not shown).
) will be sent to.

When the copying magnification is 50 to 400%, the difference in rotational speed of the servo motor 6 is eight times. When the speed is high, stable speed control without rotational unevenness can be achieved by dividing the clock so that the clock interval from the encoder 7 input to the CPUI is independent of the magnification.

(Effects) The present invention is as described above, and according to the control circuit according to the present invention, uneven rotation of the servo motor can be minimized.

[Brief explanation of the drawing]

FIG. 1 is a control block diagram according to an embodiment of the present invention, and FIG.
The figure is a flowchart. 1--CPU, 2--Data selector, 6--Servo motor, 8.9--Flip-flop. 2nd diagram 2nd entrance

Claims (1)

[Claims] In a circuit that inputs the encoder clock of the servo motor of the optical system used to change magnification in a copying machine to a CPU interrupt, and controls the rotation speed of the servo motor according to the time between clocks, the encoder clock is input according to the copying magnification. A servo motor control circuit for an optical system of a copying machine, which divides the frequency and inputs the frequency to a CPU interrupt.