JP2642638B2 - Scanner control method for copier - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanner control method for a copy machine of a fixed platen type.

2. Description of the Related Art FIG. 8 schematically shows an optical system configuration of a conventional copying machine of this type. First, a scanner optical system 2 is provided below a contact glass 1 for setting a document (not shown). As a result, an image formed by the reflected light from the original is formed on the drum-shaped photoconductor 3 via the scanner optical system 2. The scanner optical system 2 includes a first scanner 7 including an illumination light source 4, a reflection plate 5, a first mirror 6, and the like, and a second and third mirrors.
A second scanner 10 composed of 8, 9 and the like, an imaging lens 11, a fourth mirror 12, and the like. 13 is a dustproof glass.

Here, the first scanner 7 and the second scanner 10 have a 2: 1 speed under a driving system configuration as shown in FIG. 9 so that the optical path length reflected from the original does not change during scanning. It is driven reciprocally by a DC motor 14 and a scanner wire 15 at a ratio (the configuration of the drive system itself in FIG. 6 is well known, and detailed description is omitted). A scanner home position sensor (hereinafter, referred to as an HP sensor) 16 having a reflection type photointerrupter, which is located at a reference position of the scanner optical system 2 and serves as a detecting means, is provided at a predetermined position of the apparatus main body. . A part of the first scanner 7 is provided with an HP shielding plate 17 that can shield the sensor unit of the HP sensor 16 when the home position is reached.

Under such a configuration, the scanner optical system 2 is driven to scan rightward from the HP state as shown by the solid line in FIG. The positions of the first and second scanners 7, 10 indicated by phantom lines in FIG. 8 indicate the maximum movement positions in the forward movement. The scanning optical system 2 that has completed the exposure scanning moves forward toward the home position HP again. Here, when the scanner optical system 2 moves backward, it is generally driven at a higher speed than during forward movement, and deceleration control is performed when approaching the home position HP. And HP shield plate 17 is HP sensor
When the motor 14 crosses the home position HP from the overrun position by switching the rotation direction of the motor 14 from reverse rotation (scanner backward movement direction) to normal rotation (scanner forward movement direction).
It is to return to.

The stop control to the home position HP position by the forward movement of the scanner optical system 2 will be described in detail. First, the operation of the scanner optical system 2 for one cycle is as shown in FIG. In FIG. 10, the horizontal axis represents the time axis, and the vertical axis represents the rotation speed (or the first
The operation is shown by taking the speed of the scanner 7), and the actual rotational speed (or the scanner speed) of the DC motor 14 becomes a solid line with respect to the target value indicated by the broken line.

Here, the control operation for the home position HP
This will be described with reference to the drawings. In the drawing, the operation characteristic A 'indicated by the solid line is the case where the target value is met, the operation characteristic B' indicated by the one-dot chain line is lower than the target value, and the operation characteristic C 'indicated by the two-dot chain line is the case where it is higher than the target value. In the conventional method, the DC motor 14 is not forwarded from when the HP sensor 16 detects the first scanner 7 to when it detects that the rotation direction of the DC motor 14 has changed from counterclockwise CCW to clockwise CW. A constant operation amount (constant PWM (pulse width modulation) ON time) is always given to the moving side. As a result, the overrun amount and stop position of the HP sensor 16 (= home position Chillon HP position) of the first Sukiyana 7, operation overrun in the case of characteristic B 'is the area S ₁ shown hatched Indicated by the integral value,
The stop position is indicated by the difference S ₁ −S ₂ between the integrated values of the regions S ₁ and S ₂ . In the case of the other operation characteristics A 'and C', the overrun amount and the stop position are based on these. Therefore, according to the conventional method, as apparent from the operation characteristics A ', B', and C 'in FIG.
According to the rotation speed (scanner speed) of the DC motor 14 when passing through the HP sensor 16 when the first scanner 7 moves backward,
The overrun amount and the stop position vary.

This variation causes the following inconvenience. First, when the overrun amount is large, the scanning optical system 2
(In particular, the first scanner 7) collides with another member. If the first scanner 7 stops on the forward side relative to the HP sensor 16 in a state where S ₁ −S ₂ <0, the speed is required until the scanner optical system 2 reaches the leading end of the image of the document. Appear on the copy as image blurring without being fixed. In general, the copying operation is sequence-controlled based on the time when the scanner optical system 2 reaches the leading edge of the image, and the determination as to whether the scanner optical system 2 has reached the leading edge of the image is made by disconnecting from the HP sensor 16. This is performed by counting the number of pulses by the encoder pulse from. As a result, if the scanning optical system 2 has already deviated from the HP sensor 16 on the forward movement side at the start of the scanning optical system 2 as described above, an error occurs in the count value, and the copy sequence is disordered. This causes inconvenience such that the leading edge of the image does not match the leading edge of the transfer paper.

The present invention has been made in view of such a point, and even when the reference position passing speed varies at the time of the returning operation of the scanner optical system to the reference position, the variation of the overrun amount and the stop position of the scanner optical system is reduced. It is an object of the present invention to provide a scanner control method for a copying machine that can reduce the number of copies and perform a stable copying operation.

To achieve the above object, the present invention provides a scanner optical system for exposing and scanning an original, a motor for driving the scanner optical system in a reciprocating direction, and a pulse generator for generating a pulse synchronized with the rotation speed of the motor. Means, measuring means for measuring the interval of the pulse generated from the pulse generating means,
Control means for controlling the operation of the motor based on the result of measurement by the measuring means; and detecting means for detecting passage of the scanner optical system to a reference position, wherein the scanner optical system stops at a reference position by a reciprocating operation. In the control, a stop amount is controlled by a pulse width control based on the forward movement amount in addition to the motor in addition to a constant forward movement amount obtained in accordance with the pulse interval at the time of detecting the reference position passage. Is what you do.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 7. The same parts as those shown in FIGS. 8 to 10 are denoted by the same reference numerals.

First, FIG. 4 shows a configuration of a control circuit of the scanner optical system 2. A micro computer 20 serving as control means is provided. This microcomputer 20 is, for example, μPD7811
The microcomputer 20 is connected to a programmable interval timer 21 using, for example, a μPD8253C as a measuring means. Further, the DC motor 14 for the scanner optical system 2 is provided by the microcomputer.
The drive 20 is connected via drive transistors Tr _{1 to} Tr ₄ to be driven and controlled. That is, when the transistors Tr ₁ and Tr ₃ are on and the transistors Tr ₂ and Tr ₄ are off, the DC motor 14
Is supplied with a current that rotates clockwise (CW), and the DC motor 14 rotates counterclockwise (CCW) with the transistors Tr ₂ and Tr ₄ turned on and the transistors Tr ₁ and Tr ₃ turned off. Current is supplied. Here, the DC motor 14
The scanning optical system 2 moves forward and the DC motor 14
The scanner optical system 2 is set so as to move backward when is rotated in the counterclockwise direction CCW.

Further, a rotary encoder 22 as pulse generating means is directly connected to the DC motor 14. Here, the encoder 22 generates two pulse signals having different phases according to the rotation amount and the rotation direction of the DC motor 14. One is A
One is a phase encoder pulse ENCA and the other is a B-phase encoder pulse ENCB. The A-phase encoder pulse ENCA is input to the counter input terminal CI of the micro computer 20 via the buffer 23. Thereby, the micro computer 2 measures the pulse interval of the A-phase encoder pulse ENCA by the counter 012 (the oscillation frequency of the oscillator 24 of the micro computer 20 × / 12) inside the micro computer. The input signal to the counter input terminal CI is used as an interrupt input, and during the processing of an interrupt program described later, measurement data (TIME
R / EVENT COUNTER CAPURE REGISTER (ECPT) value), calculate the rotation speed of the DC motor 14 based on this data,
It calculates an error from the target rotation speed, calculates a motor control amount (ON time of pulse width modulation PWM control) by a proportional / integral control operation, and outputs (loads data to the programmable interval timer 21).

The encoder pulses ENCA and ENCB are input to the input terminal PC7 of the micro computer 20 via the buffers 23 and 25 and the flip-flop 26, and are used for phase difference detection to determine the rotation direction of the DC motor 14. An oscillator 27 is connected to the timer 21 to obtain a clock signal.

Thus, the control of the DC motor 14 is performed by PWM control. That is, data of the PWM cycle is loaded into the counter 0 of the timer 21, and a square wave of the PWM cycle is output from the output OUT0 of the counter 0. This signal is the gate input of counter 1. This is the counter 1 ON time data of the PWM signal is loaded, Wanshiyotsuto output synchronized with the PWM period is output from OUT1, controls ON / OFF of the transistor Tr ₃ or Tr ₄ through the gate circuits 28 and 29.

FIG. 5 shows a waveform example of such PWM control. In this figure, even when the variable ON time t _ON PWM period t (=
t _ON + t _OFF ) is constant.

Here, counter 0 is set to mode 3: square wave rate generator, and counter 1 is set to mode 1: programmable one shot. Since the PWM cycle t is constant, the count number of the counter = 0 may be loaded only once. _Each time the _tON time of the PWM is changed, the count number of the counter 0 is loaded.

Next, the contents of the modes 3 and 1 of the programmable interval timer 21 will be described. Mode 3 in Figure 6
3 shows a timing chart of (square wave rate generator). In this case, it operates as a counter for dividing the input clock by n. The duty ratio when the count number is even is 1/2, and when the count number is odd, the duty ratio is (n-1) / 2n. For example, the count number n =
At 5, the duty ratio is 2/5 (active low)
Becomes When this mode is selected by the control word, OUT0 = 1, and the count number is loaded as GATE1 = 1. Thus, counting is started. When the count number is even, the first half of the count is OUT
0 = 1, the latter half becomes OUT0 = 0. When the count number is odd, the first half (n + 1) / 2 of the count becomes OUT0 = 1 and the second half (n-1) / 2 becomes OUT0 = 0. If GATE1 = 0,
In synchronization with the falling edge, OUT0 becomes 1 and the counting stops. Thereafter, when GATE1 = 1, counting is restarted from the initial value. Then, when the count is loaded during the counting, a new counting is started from the next cycle. If the count number is even, the counter is decremented by 2; if it is odd, the first 1 when OUT0 = 1.
It is decremented by 1 on the clock and 2 from the second clock
It is decremented by one. When OUT0 = 0, the value is decremented by 3 in the first clock, and decremented by 2 from the second clock.

Fig. 7 shows mode 1 (programmable one shot)
The timing chart of FIG. This is to output a one-shot pulse (active low) of a designated length. When this mode 1 is selected by the control word, OUT0 = 1, and the GA
Triggered by the rise of TE1 to start counting.
OUT0 = 0 during counting, and OUT0 = 1 again when counting is completed. In other words, the pulse width becomes a one-shot output of the active row corresponding to the count number. When a trigger is applied during counting (when GATE1 is changed from 0 to 1), counting starts again from the initial value. Note that loading the count number during counting does not affect the count being executed, but when a trigger is applied, counting starts with a new count number.

Thus, in the present embodiment, the amount of movement to the forward movement side is variably controlled according to the rotation speed (or the scanner speed) of the DC motor 14 at the time when the HP sensor 16 detects the backward movement of the scanner optical system 2. Is what you do. FIG. 1 shows the state of the stop control for the home position HP according to the method of the present embodiment, corresponding to FIG. That is, the operation characteristic A indicated by the solid line is the same as the target value, the operation characteristic B indicated by the one-dot chain line is lower than the target value, and the operation characteristic C indicated by the two-dot chain line is higher than the target value.

Here, a theoretical formula for calculating the operation amount of the DC motor 14 from the rotation speed of the DC motor 14 when the HP sensor 16 is detected will be described. First, rotation speed omega ₀ of the HP sensor 16 detects when the DC motor _14, when the overrun target value [psi, the angular acceleration to decelerate the DC motor 14 becomes = -ω ₀ ² / 2ψ.

Further, the torque T generated by the DC motor 14 is represented by K _{T as the} motor torque constant, V _{MM as the} motor power supply voltage, R as the motor armature resistance, t as the PWM cycle, and t _{ON as} the ON time of the PWM (where t ≧
t _ON ), and regarding the induced voltage generated at both ends of the motor in proportion to the rotation speed of the DC motor 14, if the motor rotation speed is small near the stop control, and this induced voltage generated by the motor is small and negligible, Becomes When the inertia of the DC motor 14 is set to J and the sliding load is neglected, from both these equations, based on the relational expression of T = J, Is established. This equation becomes t _ON = Kω ₀ ² _{(where, K = -Rt / 2ψV MM K} T). In other words, the operation amount is the DC motor when the HP sensor 16 is detected.
It is a function of the number of rotations ω ₀ of 14.

FIG. 2 shows a waveform of each part and a timing chart of the CI interrupt processing during stop control of the scanner optical system 2 at the home position HP, and FIG. 3 shows a flowchart of the CI interrupt processing. First, every time the A-phase encoder pulse ENCA falls, the CI interrupt processing is performed. In such an interruption process, first, the current state of the scanner optical system 2 determines the forward movement and the backward movement. On the other hand, when returning, it is determined whether the HP sensor 16 has detected the first scanner 7 (HP shielding plate 17) (H level) or not (L level). HP at the stage of interrupt ~
Since the sensor 16 is at the L level and does not detect the first scanner 7, proportional / integral control is performed to control the scanner optical system 2 (first scanner 7) so that the scanner speed corresponds to the current scanner position. Do.

Then, the HP sensor 16 detects the first scanner 7 and
When the level is reached, a stop control process for the home position HP position is started. In this process, first, the flag ST
Determine whether P is set to 1 or not. The flag STP is used to output the operation amount only once when the output of the HP sensor 16 changes from the L level to the H level. The flag STP is initially set to 0. Here, when the output of the HP sensor 16 changes from L level to H level, the interruption interval of the encoder 22, that is, the content of ECPT is read. In other words, this data makes the HP sensor 16 the first scanner 7
Is the value of the speed (motor speed) at the time of crossing (the reciprocal of this data is proportional to the speed). Based on this, the operation amount of the DC motor 14 is calculated and PWM output is performed. Then, the flag STP is set to 1. Such processing is processing by a CI interrupt.

After that, when a CI interrupt occurs, the flag STP is set to 1, so the PC 7 determines whether the motor rotation direction has changed from the backward movement CCW to the forward movement CW, and the rotation direction changes. Until you do, do nothing even if there is an interrupt like (that is, do not change the PWM output value)
To return. If the rotation direction changes as in the case of the CI interrupt, the DC motor 14 is turned off, the CI interrupt is masked, and the routine returns.

Effect As described above, the present invention provides the motor with a certain amount of forward movement amount obtained in accordance with the pulse interval at the time of detecting the passage of the reference position during the stop control to the reference position by the backward movement of the scanner optical system. In addition, since stop control is performed by pulse width control based on this forward movement amount, even if the speed at the time of passing the reference position fluctuates, the overrun amount of the scanner optical system is kept constant and the stop position variation is suppressed. Thus, a good copying operation can be performed.

[Brief description of the drawings]

1 is an explanatory view of a stop control operation showing an embodiment of the present invention, FIG. 2 is a timing chart, FIG. 3 is a flow chart, FIG. 4 is a block diagram, and FIG. 5 is a timing chart of a PWM control operation. FIG. 6 is a timing chart for explaining mode 3, FIG. 7 is a timing chart for explaining mode 1, FIG. 8 is a side view showing a schematic configuration of a general optical system, and FIG. 9 is a schematic perspective view thereof. FIG. 10 is a timing chart of a scanner cycle operation, and FIG. 11 is an explanatory view showing a conventional control method. 2 ... scanner optical system, 14 ... motor, 16 ... HP sensor (detection means), 20 ... microcomputer (control means), 21 ... programmable interval timer (measurement means), 22 ... encoder (pulse generation means)

Claims (2)

(57) [Claims] 1. A scanner optical system for exposing and scanning a document, a motor for driving the scanner optical system in a reciprocating direction, pulse generating means for generating a pulse synchronized with the number of rotations of the motor, and the pulse generating means. Measuring means for measuring the interval of the pulse generated from, a control means for controlling the operation of the motor based on the measurement result by this measuring means, and a detecting means for detecting the passage of the scanner optical system reference position, At the time of stop control to the reference position by the backward movement of the scanner optical system, a certain amount of forward movement in the forward direction obtained in accordance with the pulse interval at the time of detection of passage of the reference position is added to the motor, and the forward movement is performed. A scanner control method for a copying machine, wherein stop control is performed by pulse width control based on an amount. 2. The cycle of the pulse width modulation control is represented by t, the ON time within the cycle t is represented by t _ON , and the overrun target value is represented by ψ.
, The rotational speed of the motor upon detection of passage of the reference position is ω ₀ , the motor armature resistance is R, and the motor torque constant is K _T
And then, when the motor supply voltage and V _MM, the forward direction operation amount t _ON = Kω ₀ ² _{(where, K = -Rt / 2ψV MM K} T) first the claims, which is a 2. The method of controlling a scanner of a copying machine according to claim 1.