JPH02232641A - Method for controlling scanner optical system of copying machine - Google Patents

Abstract

PURPOSE:To smoothly control the speed reduction of the scanner optical system even if the speed of the scanner optical system has variance about a target value by reducing the speed of the scanner optical system according to calculation expressions as the target values of plural prepared return speeds in speed reduction or by selecting the best speed reduction curve in a data table. CONSTITUTION:The speed of the scanner optical system is reduced according to the calculation expressions as the target speeds of the prepared return speeds in speed reduction or by selecting the best speed reduction curve in the data table according to the difference between the moving speed and return speed target value of the scanner optical system when the movement distance of the scanner optical system reaches a specific distance. In another way, the start position of the speed reduction of the scanner optical system is varied according to the difference. Consequently, even if the return speed and target speed are different from each other owing to a difference in return start position and variance in mechanical load among copying machines, the speed reduction of the scanner optical system is smoothly controlled and stable copying operation is performed.

Description

[Detailed description of the invention]

The present invention relates to a method for controlling a scanner optical system of a copying machine with a fixed document table.

[111 The general configuration of the optical system of this type of copying machine is outlined in Section 8.
It is shown in the figure. An exposure optical system including a scanner optical system 2 is provided below a contact glass 1 on which a document (not shown) is placed. As a result, the reflected light from the original is imaged onto the drum-shaped photoreceptor 3. The scanner optical system 2 consists of a first scanner 7 consisting of an illumination light source 4, a reflector 5, a first mirror 6, etc., and a second scanner 10 consisting of second and third mirrors 8, 9, etc., and is fixed to the main body of the device. The imaging lens l1 and . The fourth mirror 12 and the like constitute an exposure system. 13 is dustproof glass. The first scanner 7 and the second scanner 10 are arranged so that the length of the optical path reflected from the document does not change during scanning. By constructing a wire lobe drive system using the principle of a movable pulley as shown in FIG. 9, reciprocation is driven by a DC motor 14 and scanner wire 15 at a speed ratio of 2:1 (the configuration of the drive system itself is well known). (Therefore, detailed explanation will be omitted). The main body of the apparatus is provided with a scanner home position sensor (hereinafter referred to as HP sensor) 16 having a reflective photointerrupter configuration and serving as a reference position detection means for the scanner optical system 2. The first scanner 7 is provided with an HP shielding plate 17 that can shield the sensor section of the HP sensor 16 when the first scanner 7 reaches the home position. With this configuration, the scanner optical system 7.10 is driven rightward from the HP state shown by the solid line in FIG. 8 to expose and scan the document surface. The positions of the first and second scanners 7, 10 shown by virtual lines in FIG. 8 indicate the maximum movement positions of the reciprocating motion. After completing the exposure scan, the scanner optical system 2 moves back toward the home position again. In this case, during the backward movement of the scanner optical system 2, it is generally driven at a higher speed than during the forward movement, and when it approaches the home position HP, it is decelerated by $18. and,
[{By changing the rotation direction of the motor 14 from reverse rotation (scanner backward movement direction) to forward rotation (scanner forward movement direction) when the P shielding plate 17 crosses the HP sensor 16, the overrun position is moved to the home position} {I am trying to return it to P. Below, such deceleration fill control of the backward movement of the scanner optical system 2 will be explained in detail. First, if we consider the operation of the scanner optical system 2 for one cycle, it will be as shown in Figure 10. In FIG. 10, the horizontal axis shows the time, and the vertical axis shows the rotation speed of the DC motor 14 (or the speed of the first scanner 7), and shows the actual rotation speed of the DC motor 14. (i or scanner speed) is shown as a solid line with respect to the target value shown as a broken line. Next, the deceleration control operation during the backward movement will be explained with reference to FIG. In the figure, the dashed line is the target speed. The operating characteristic A' shown by the one-dot chain line is that because the backward movement start position was close to the home position, the scanner speed reached the deceleration start point before reaching the target speed Vo from the start of the backward movement to the start of deceleration. This is a case where the speed V is 80% of the target speed V.
Further, the operating characteristic B' shown by a solid line shows the case where the speed V at the start of deceleration is faster than the target speed Vo, which is 120%. In the conventional method, the start position of deceleration was fixed and one type of deceleration control was performed for all operating characteristics. As a result, in the case of the operating characteristic A', the first scanner 7 continues to accelerate even after passing the deceleration start position.
Only when the scanner speed exceeds the target speed does it start decelerating. For this reason, overshoot is likely to occur when changing from acceleration to deceleration, making the operation of the scanner optical system 2 unstable. Furthermore, when the amount of overshoot is large, the scanner speed when reaching the home position is too fast to perform normal stop control, and the stop position varies. In the case of operation characteristic B', the deceleration start position is too close to the home position with respect to the scanner speed, and the target speed curve during deceleration is too gentle, so the scanner speed becomes faster when the home position is reached. The above results in the following dissonance. First, if an overshoot occurs when the first scanner changes from acceleration to deceleration, the operation of the scanner optical system 2 becomes unstable, and when the overshoot converges, the scanner optical system 2 itself vibrates, and the copying machine Shaking of the whole area occurs. Additionally, if the amount of overshoot is large or the scanner speed is too fast at the start of deceleration, the overshoot may not fully converge before reaching the home position, or the home position may not be reached without sufficient deceleration. There may be cases where this is the case. In either case, the stop control at the home position cannot be performed properly, resulting in the scanner colliding with other parts, or
If the stop position is on the forward side of the home position, the speed will not be constant before the scanner reaches the leading edge of the original image during the next copying operation, resulting in problems such as blurring of the image on the copy. occurs. SUMMARY OF THE INVENTION The present invention takes into consideration the above-mentioned actual circumstances of the backward movement operation of a scanner optical system, and provides a system that allows the return movement to be performed even if the return speed and target speed are different due to differences in the return movement start position or variations in the mechanical loads of individual copying devices. The object of the present invention is to provide a method for controlling the scanner optical system of a copying machine that can smoothly control the deceleration of the scanner optical system and perform stable copying operations. In order to solve the above-mentioned problem, the control method of the scanner optical system of the present invention for ゛ starts the backward movement of the scanner optical system with a predetermined return speed as a target value when the scanner optical system moves back,
When the scanner optical system reaches the predetermined position, it starts decelerating,
In a scanner optical system control method that decelerates the return speed using a predetermined calculation formula or data table as a target value, and stops when it reaches the reference position, when the scanner optical system has moved a predetermined distance. Depending on the difference between the moving speed of the scanner optical system and the return speed target value above, select the optimal deceleration curve from the above calculation formula or data table, which is a target value of return speed during deceleration. to decelerate the scanner optical system, or according to the difference between the moving speed of the scanner optical system and the above return speed target value when the moving distance of the scanner optical system reaches a predetermined distance. It is characterized by changing the start position of deceleration of the scanner optical system. When performing deceleration control for the backward movement of the scanner optical system, the deceleration start position and target speed data at deceleration are not fixed, and the optimal deceleration control is performed according to the scanner speed. Even if the speed of the optical system varies with respect to the target value, the deceleration control of the scanner optical system can be performed smoothly.This prevents vibration of the scanner optical system and rocking of the copier body, making it easy to stop at the home position. You can make them do it. Hereinafter, one embodiment of the present invention will be described in detail based on the drawings. 1 to 7 are diagrams showing an embodiment of the present invention, and the same parts as those shown in FIGS. 8 to 10 are indicated by the same reference numerals. First, Figure 4 shows the scanner optical system 2.
The configuration of the control circuit is shown below. A microcomputer 20 is provided as a control means. The microcomputer 20 is, for example, a μPD7811G, and a programmable interval timer 21, which is a measuring means, is connected to the microcomputer 20, for example, a μPD8253C. Further, the conveying DC motor 14 of the scanner optical system 2 is connected to the microcomputer 20 via drive transistors TrI-Tr4, and is driven and controlled. That is, the transistor Tr
I. When Tr3 is on and transistors Tr2 and Tr4 are off, a clockwise (CW) rotating current is supplied to the DC motor 14, and transistors 7'r2 and Tr4 are on and transistors TrI and Tr3 are off. A current is supplied to the DC motor 14 to rotate it counterclockwise (CCW). Here, the DC motor 14 is rotated counterclockwise C.
When the DC motor 14 rotates in the W direction, the scanner optical system 2 moves forward, and when the DC motor 14 rotates counterclockwise CCW, the scanner optical system 2 moves forward.
is set to move in a double direction, and a rotary encoder 22 as a pulse generating means is directly connected to this DC motor 14. Here,
The encoder 22 generates two pulse signals with different phases depending on the amount and direction of rotation of the DC motor 14. One is the A-phase encoder pulse ENCA, and the one in the pond is
One is the B-phase encoder pulse ENCB. The A-phase encoder pulse ENCA is input to the counter input terminal CI of the microcomputer 20 via the buffer 23. Thereby, the microcomputer 2 measures the pulse interval of the A-phase encoder pulse ENCA using the counter φ12 inside the microcomputer (the oscillation frequency Xi/12) of the oscillator 2.1 of the microcomputer 20. The input signal to this counter in-at terminal Cr is an interrupt input, and encoder interval measurement data (TIM
ER/EVENT COUNTER CAPURE
REGISTER (ECPT) value》, and based on this data calculate the rotation speed of DC motor I4 (scanner speed), calculate the error from the target rotation speed (target speed), and calculate proportional/integral f/I. 97fRfllll <ON time of pulse tm'RmPWMiiI@>> and output <load data to programmable interval timer 21>. Further, the encoder pulses ENCA and ENCB are input to the input terminal PC7 of the microcomputer 20 via the buffers 23 and 25 and the flip-flop 126, and are used for phase difference detection to determine the direction of rotation of the DC motor 14. Further, an oscillator 27 is connected to the timer 21 to obtain a clock signal. Thus, ilII0l of the DC motor 14 is performed under PWM control. That is, the counter O of the timer 21 is set to PW.
The data of M cycles is loaded and the output of counter 0 is OUT.
A square wave with a PWM period is output from O. This signal is the gate input of counter 1. This counter 1 is loaded with the ON time data of the PWM signal, and the PWM signal is
! A one-shot output synchronized with the first period is output from OUTI, and is sent to the transistor Tr via gate circuits 28 and 29.
3 or Tr. ON/OFF control. Figure 5 shows an example of waveforms for such PWM control. This figure shows that even if E t am changes when ON, the PWM cycle (s+topp) remains constant. Here, counter O is set to mode 3: square wave rate generator and counter 1 is set to mode 3: programmable one-shift. Since the PWM period t is constant, the load of the count number of counter 0 You only need to do it once. Then, each time the PWM to, 1 hour is changed, the count number of the counter 0 is loaded. Next, the contents of mode 3 and mode 1 of the programmable interval timer 21 will be explained. Figure 6 shows mode 3 (
The timing chart of the square wave rate generator) is shown below. In this case, it operates as an n-divided counter of the input clock. Note that the duty ratio when the count number is an even number is 1/2, and the duty ratio when the count number is an odd number is (n-1)/2n. For example, the number of counters n
When =5, the duty ratio is 2/5 (active low). Therefore, when this mode is selected with the control word, it becomes OUTO1 and GATE 1.
Load the count number as =1. This will start counting. When the count number is even, the first half of the count 1, .'2 is OLITO=1. Second half L/2 is O
It becomes UTO 10. When the count number is odd, what half of the count (n+-1>/2 is OUT = 1, the second half (n-
1). / 2 becomes OUTO=O, GATEI
==0, OUTO- is synchronized with the falling edge.
It reaches 1 and the count stops. After that, GATE L
When = 1, the count is reset from the initial value. If the count block is loaded during counting, a new count will start 1m from the next cycle. If the count number is even, the counter is decremented by 2, and if it is odd, the counter is decremented by 1 at the first clock when OUTO=1.
It is decremented, and from the second klovk onwards, it is decremented by 2. Figure 7 shows the timing chart for mode 1 (programmable one seat). This outputs a one-shot pulse (active low) of the specified length. When this mode 1 is selected by the control word, it becomes OUTO1, and after loading the count number, it is triggered by the rising edge of GATE L and starts counting. During counting, OUTO=O, and when counting ends, OLITO=1 again. In other words, it is an active low one-shot output whose pulse width corresponds to the count number. If you apply a trigger while counting (
When GATEL is changed from 0 to 1), counting starts again from the initial value. Note that loading a count number while counting does not affect the running count, but when a trigger is applied, counting starts with a new count number. Therefore, in this embodiment, a plurality of target speed calculation formulas or data tables for deceleration are prepared depending on the number of rotations of the DC motor 14 (or scanner deceleration) at a predetermined position during the backward motion of the scanner optical system 2. The optimal one is selected from among these and deceleration control is performed. Figure 1-1, 1st
Figure-2 shows the reduction 'J! I le 1
The state of the control is shown in correspondence with the first figure. That is, the operation stability A shown by the solid line in FIG. 1-1 is determined by the time t. When the scanner speed of is 80% of the target speed, the first
〜2 The operation stability B shown by the solid line in Figure 2 is determined by the time it takes to pass through a predetermined position.
When the scanner speed at is 120% of the target speed,
Deceleration start time for each. Stable deceleration can be achieved by setting the target speed curve at the time of deceleration to a suitable value as shown by the branch line. Fig. 2 is a flowchart of CI interrupt processing, Fig. 3-1 is a flowchart of processing for selecting an optimum deceleration start position and an optimum deceleration control data table from the scanner speed at t1 when passing a predetermined position in scanner return control; −
Figure 2 shows a flowchart of deceleration control. First, CI interrupt processing ■ to ■ is performed every time the AI encoder pulse ENCA falls. In such interrupt processing, first, it is determined whether the current state of the scanner optical system 2 is forward or backward, and if it is forward, the counter (SCADD) is incremented without indicating the current position of the scanner optical system 2. Afterward, perform forward processing (not shown). On the other hand, if it is a backward movement, a counter (SCADD) indicating the current position of the scanner optical system 2
Decrement ■ and perform backward processing ■. In the backward motion processing, first check whether the scanner optical system 2 has reached a predetermined scanner speed measurement position based on the value of the counter (SCADD), and when it has reached the position, call subroutine SCANR1, which will be explained later. ■Determine the deceleration start position and deceleration control data table. Next, check whether the scanner optical system 2 has passed the deceleration start position determined in step 2. If not, set the normal scanner return speed V. Substitute it into the variable (TARGET) that indicates the target value of the scanner speed, and perform the proportional/integral system m to control the scanner optical system 2 to the desired speed. In addition, if the deceleration start position has already been passed, whether the HP sensor 16 has detected the first scanner 7 (HP shielding plate 17) (ON) or not (OF
F) Determine ■. In the case of process ■, the HP sensor is still OFF, and at this time the subroutine SC, which will be explained later,
Call ANR2 and check the target speed corresponding to the scanner position from the data table hidden in ■ (TARGET
) and perform proportional/integral control of [stock]. Also,
If the HP sensor is ON, the stop control process for the home position position is entered. Next, the subroutine SCANRI will be explained based on Fig. 3-1. This process is performed only once when the scanner optical system 2 reaches the scanner speed measurement position in the CI interrupt process, and first, the interrupt interval of the encoder 22, that is, the contents of ECPT are corrupted. In other words, this data is the value of the speed V (motor rotation speed) when the scanner optical system 2 passes the scanner speed measurement position (the reciprocal of this data is proportional to the speed). 11 ■ Next, calculate the ratio of the target speed vo and the actual speed V obtained in ■ using Basentage, substitute it into the variable (VRAT), and select the appropriate data table for the eel according to this. The selected data table number (in this example, 3 types (1 to 3)) is specified as (TA
Assign ■～■ to BLEN). Further, if the percentage of the previously determined target speed ■o and the actual speed V is less than 80% or greater than 120%, it is assumed that the scanner optical system 2 is abnormal and an abnormality process [phase] is performed. The subroutine SCANR2 in FIG. 3-2 is called at a CI interrupt from when the scanner optical system 2 passes the deceleration start position until it reaches the home position. In this process, the data table number (TAB
Based on the data table, the position of the scanner optical system 2 is determined by ff ((SCADD)).
The scanner optical system 2 retrieves the speed data according to the
Variable that indicates the target value of the speed of (T A. R G E
T). Here, ■, ■ are data table 1
is selected, and the data in the data table (label name: TABLE 1) provided on the tOM where the offset/soto is equal to the value of (SCADD) is transferred to the scanner optical system 2. Assign to (TARGET) as target speed data for the current position. Similarly ■
, ■ is when data table 2 (label name 2 TABLE2) is selected, and ■ is when data table 3 (label name + TABLE2) is selected.
Indicates the case where ABLE3) is selected, and ■,■
In the same way, use the value of (SC A. DD) as the offset value and fetch the data (TARGET).
Assign to . In this embodiment, the data for deceleration control to be selected is a data table, but the same control can be performed even if this is a calculation formula, and in this case, the subroutine SCAN
Instead of selecting the data table in R1 - ■, select one of the multiple calculation formulas, and in subroutine SCANR2, set the target speed calculated from this calculation formula to (TARGET). Just substitute. 911 As described above, when performing deceleration control of the backward motion of the scanner optical system, the deceleration start position and target speed data at the time of deceleration are not fixed, but the optimal deceleration control is performed according to the scanner speed. Therefore, even if the speed of the scanner optical system varies from the target value, the deceleration control of the scanner optical system can be performed smoothly. This prevents vibration of the scanner optical system and shaking of the copier body, and returns to the home position. It is also possible to stop the system without difficulty.

[Brief explanation of the drawing]

1-1 and 1-2 are curve diagrams showing the double-motion characteristic curves of the scanner optical system according to the present invention, respectively, and FIG.
Figure 3-1 is a flowchart of the process of selecting the optimum deceleration start position and data table for optimum deceleration control from the scanner speed when passing a predetermined position in the scanner return control; Flowchart of deceleration control, Figure 4 shows the control circuit of the scanner optical system,
Fig. 5 is a curve diagram showing an example of a waveform controlled by pulse width modulation Ii11, Figs. 6 and 7 are timing charts of two modes of the programmable interval timer, and Fig. 8 is a copying machine with a conventional scanner optical system. 9 is a perspective view showing an example of a drive device for the scanner optical system, FIG. 10 is a curve diagram showing one cycle of operation of the scanner optical system, and FIG. ]The l figure is that j!
It is a curve diagram showing the deceleration i4 control operating characteristics when the engine is moving. 2... Scanner optical system, 3... Photosensitive drum, 7... First scanner, 10... Second scanner, l4... Scanner optical system drive motor, 20... Microcomputer range Feng Mu No. 3-1 Fig. 3-1;

Claims (2)

[Claims] (1) an exposure optical system including a scanner optical system capable of reciprocating motion; a scanner transport motor for transporting the scanner optical system; and a movement speed detection means for detecting the movement speed of the scanner optical system. , a method for controlling the scanner optical system of an optical device of a copying machine, comprising a moving distance detecting means for detecting a moving distance of the scanner optical system, the method comprising: controlling the scanner optical system when the scanner optical system moves backward; Starts the return movement with a predetermined return speed as the target value, starts deceleration when the scanner optical system reaches the predetermined position, decelerates with the return speed as the target value according to a predetermined calculation formula or data table, and returns to the reference position. In a scanner optical system control method in which the scanner optical system is stopped when the scanner optical system reaches a predetermined distance, a plurality of deceleration speeds are prepared depending on the difference between the moving speed of the scanner optical system when the moving distance of the scanner optical system reaches a predetermined distance and the above return speed target value. A method for controlling a scanner optical system, characterized in that the scanner optical system is decelerated by selecting an optimal deceleration curve from the above calculation formula or a data table, which is a target value of the return speed of the scanner. (2) an exposure optical system including a scanner optical system capable of reciprocating motion; a scanner transport motor for transporting the scanner optical system; and a movement speed detection means for detecting the movement speed of the scanner optical system. , a method for controlling the scanner optical system of an optical device of a copying machine, comprising a moving distance detecting means for detecting a moving distance of the scanner optical system, the method comprising: controlling the scanner optical system when the scanner optical system moves backward; Starts the return movement with a predetermined return speed as the target value, starts deceleration when the scanner optical system reaches the predetermined position, decelerates with the return speed as the target value according to a predetermined calculation formula or data table, and returns to the reference position. In a scanner optical system control method that stops the scanner optical system when the scanner optical system reaches a predetermined distance, the scanner optical system is decelerated according to the difference between the moving speed of the scanner optical system when the moving distance of the scanner optical system reaches a predetermined distance and the above return speed target value. A method for controlling a scanner optical system, characterized in that the starting position of the scanner is changed.