JPH02158765A - Image scanning device - Google Patents

Abstract

PURPOSE:To always stop a scanning system at a prescribed home position by obtaining timing for starting a brake on the middle of returning by means of counting pulses which are generated according to the rotating speed of a motor for allowing the scanning system to go and return on the middle of going and also on the middle of returning of the scanning system. CONSTITUTION:Whenever image exposure and reading are performed, a motor 30 is driven so that the scanning system 3 may go by the necessary quantity for scanning and may return to the home position, and a pulse generating means 33 is allowed to work with the driving of the motor 30, and the pulses being in synchronism with the rotation of the motor 30 are generated. On the middle of going and returning of the scanning system 3, the pulses generated in the pulse generating means 33 are counted by a counting means. In a control means, position information which changes from moment to moment on the middle of going and on the middle of returning of the scanning system 3 is obtained based on a pulse counting signal, so that the brake is rightly applied at a prescribed position on this side of the home position on the middle of returning of the scanning system 3. Thus, the scanning system 3 can be allowed to stop at the home position with accuracy.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an image scanning device used in copying machines and image leagues, and more specifically, the present invention relates to an image scanning device used in copying machines and image leagues. The present invention relates to an image scanning device that performs image exposure or reads images.

(Prior Art) Recently, copying machines and image readers are required to be faster and faster. Accordingly, in order to shorten the processing time when copying multiple sheets from a single original or continuously scanning multiple originals, the scanning system operates at full power during the backward motion, which is unrelated to scanning. The scanning system is moved backwards at high speed. Therefore, it is difficult to accurately stop the reciprocating scanning system at the home position. Conventionally, to satisfy this requirement, a brake switch is provided at a predetermined position before the home position of the scanning system, and when the scanning system reaches the position where the brake switch is activated during its backward movement, the brake switch is activated to apply the brakes to the motor. I hang it to make sure it stops correctly at the home position.

On the other hand, Japanese Patent Application Laid-Open No. 55-1635 uses software control to stop the scanning system at the home position during backward movement.
It is disclosed in Publication No. 60. This method moves the scanning system backward for a certain period of time and measures the amount of displacement during this certain period of time.
The brake is applied with a driving force corresponding to this amount of displacement to stop the vehicle.

(Problems to be Solved by the Invention) In the above-mentioned conventional brake switch system, in addition to the fixed position switch that detects the scanning start position of the scanning system, another switch and wiring for it are required, which increases the cost. Become.

Furthermore, the conventional software control described above avoids complicating the structure. However, it is not direct to measure the amount of movement of the scanning system in terms of operating time, and changes in the amount of movement of the scanning system with respect to operating time are due to changes in load due to warpage of the scanning system's mirrors, aging of bearings, and dust adhesion. unable to cope. For this reason, the scanning system cannot be accurately stopped at a predetermined position at all times.

Therefore, the present invention utilizes the pulse generating means provided in conjunction with the motor to control the operation of the scanning system to control the braking operation during the backward motion of the scanning system, thereby eliminating the need for special installation members. The actual displacement of both reciprocating motions of the scanning system is obtained as a direct pulse signal, and software control based on this is used to apply the brakes at appropriate timings at all times during the reciprocating motion of the scanning system, thereby solving the above-mentioned conventional problems. It is an object of the present invention to provide an image scanning device for a copying machine that can solve the problem.

(Means for Solving the Problems) In order to achieve the above-mentioned objects, the present invention provides an image scanning device that scans an original by forward movement of a scanning system that is reciprocated by a motor to expose an image or read an image. means for generating pulses in accordance with the rotational speed of the motor; means for counting pulses generated by this means during both forward and backward movement of the scanning system; and means for starting braking during the backward movement based on the count by this means. The present invention is characterized by comprising a control means for stopping the scanning system at the home position at a certain timing.

It is preferable that the counting means has different counting methods during forward movement and backward movement of the scanning system.

(Function) Each time an image is exposed or read, the motor is driven to move the scanning system forward by the required scanning amount and then back to the home position. The pulse generating means is operated in conjunction with the driving of the motor, and generates pulses synchronized with the rotation of the motor. During forward and backward movement of the scanning system, the pulses generated by the pulse generating means are counted by the counting means, and the count signal is given to the control means. The pulses are synchronized with the rotation of the scanning system motor, and are directly related to the amount of displacement during forward and backward movement of the scanning system, and are caused by warpage of the scanning system's mirror, aging of the bearings, or dirt. Even if the load torque fluctuates due to adhesion and the speed of the scanning system changes over time, the torque is generated in accordance with the actual amount of movement. Therefore, the control means can accurately obtain positional information that changes from time to time during the forward and backward movements of the scanning system based on the pulse count signal, and can set a predetermined position before the home position during the backward movement of the scanning system. The brake can be applied correctly to stop the scanning system at the home position accurately.

In particular, if the counting means uses different counting methods during the forward and backward movements of the scanning system, the speeds during the forward and backward movements of the scanning system will be significantly different, and the frequency of the generated pulses will vary. Although the frequencies are different, it is possible to accurately count during forward movement and backward movement by using a counting method suitable for these frequencies.

(Example) An embodiment of the present invention shown in the drawings will be described.

FIG. 1 schematically shows an image forming section of a copying machine.

A scanning optical system 3 is provided between the document platen glass 1 and the angry light drum 2 below. The scanning optical system 3 includes an illumination lamp 5 and a first mirror 6 held on a first movable stage 4 constituting a scanner, second and third mirrors 9 and 10 held on a second movable stage 8, and a projection light. Lens 11, fourth mirror 12
Consisting of

A pair of drive wires 21 are stretched on both sides of the portion where the first moving table 4 and the second moving table 8 move. Each drive wire 21 is passed from above between the left and right boobies 1J22, 23 of the same diameter, and the portion 21a of the pulley 22 is passed from above to the bottom of the pulley 22, and then the end plate of the second movable table 8 The hook is turned around the pulley 24 provided on the outer surface and folded back, and its end 21c
is fixed to the fixing member 25. The portion 21d of the pulley 23 is hooked to the lower side of the boo IJ 23, and then hooked to the pulley 24 of the second movable table 8 and folded back. It is fastened through.

Also, the boot I of the portion 2ia on the pulley 22 side of each wire 21
A portion between J 22 and the pulley 24 is fixed to the first movable base 4. 28 indicates the fastening portion. A DC motor 30 is connected to the rotation shaft 29 of the pulley 23, and a reduction gear 31 is connected to the rotation shaft 29 of the pulley 23.
They are connected via a timing belt 32. Furthermore, an encoder 33 is connected to the rotating shaft 30a of the motor 30,
Pulses are generated in synchronization with the rotation of the motor 30.

When the motor 30 is operated in the direction of arrow a, the wire 21 is driven in the direction of arrow A. At this time, the first moving table 4, which is directly fixed to the wire 21, moves the wire 21 in the direction of arrow C.
1/n' (n: copying magnification), which is the same speed as mirror 1, scans the image of the original on platen glass 1 in a range corresponding to the copy size and magnification, and 6.9.1
0.12 and the projection lens 11, images of the original are sequentially slit-exposed onto the flash drum 2. At this time, the second moving table 8 moves the boule 1724 by the movement of the part 21d of the pulley 23 becoming longer as the part 21a on the boo 1J22 side becomes shorter when the wire 21 is driven in the direction of the arrow A. is moved at a speed of 1/2n in the direction of arrow C, and the light exposure length of the scanning optical system 3 is kept constant during scanning.

An eraser lamp (not shown), a charger, a developing device, a transfer charger, and a cleaning device (not shown) are arranged around the photoreceptor drum 2, and the surface uniformly charged by the charger is exposed to the above-mentioned light to generate an electrostatic latent. form an image.

This electrostatic latent image is developed into a toner image by a developing device, and is transferred onto a transfer material fed in synchronization with the toner image by a transfer charger.

After the transfer, residual toner is removed from the surface of the photosensitive drum 2 by a cleaning device, and then residual charge is removed by an eraser lamp.

The copy magnification is changed by, for example, moving the projection lens 11 in the optical axis direction and adjusting the conjugate length.

At the end of the scan, motor 30 is reversed. As a result, the wire 21 is driven in the direction opposite to the arrow C, and the first and second moving platforms 4.8 are moved in the direction opposite to the arrow C and returned to their home positions.

To control the operation of the scanning optical system 3, the motor 30 is driven by a drive circuit shown in FIG. 2 and controlled by a control circuit shown in FIG. Also, for this control, the scanning optical system 3
A switch 34 for detecting whether the first movable base 4 is at the home position is provided in the movement path of the first movable base 4, and is pressed when the first movable base 4 is at the home position.

The drive circuit shown in FIG. 2 will be explained. A DC power source E is connected to the motor 30 via four bridge-connected switching transistors rr and -Tr4. The transistors Tr, , and Trs are turned on when the base voltage is "low", and the transistor Trt5Tra is turned on when the base voltage is "high", and the motor 30 is adjusted appropriately depending on the combination of their on and off states. to rotate, reverse, or stop.

Transistors Tr+ to Tra each have a diode D.
, ~D4 are connected in parallel to form a bypass when a back electromotive force is generated.

The input terminal 35a receives either a "high" signal as a forward rotation signal or a "low" signal as a reverse rotation signal.
It is connected to the input side of the D gate AND, and the base of the transistor Trl, and is connected to the A
Input side of ND gate ANDx and transistor Tr=
connected to the base of.

The other input terminal 35b receives either a "high" signal as an energization on signal or a "low" signal as an energization off signal by pulse d for motor energization.
Connected to the D gate AND and AND20 input sides. AND game) AND.

The output side of is a transistor Tr! On the base of , also AN [
) game) The output sides of ANDZ are connected to the bases of transistors Tr, respectively.

The table below shows the on/off state of each transistor Tr, =Tr, depending on the combination of input signals to each input terminal 35a, 35b, the on/off state of the motor 30, and the forward/reverse direction when on. As per 1.

Table 1 The control circuit shown in FIG. 3 will be explained. In this circuit, a one-chip microcomputer (hereinafter referred to as a microcomputer) 41 is dedicated to controlling the scanning optical system 3, and this circuit is connected to a microcomputer (not shown) (hereinafter referred to as a mask) that controls various other operations of the copying machine. ).

The microcomputer 41 includes CPU42, ROM43, and RAM4.
4, an input port 45, an output port 46, a P output port 47, a register 48, a timer unit 49, and an oscillation circuit 50 for generating an internal system clock fclk. The timer unit 49 includes a counter XP that directly counts the encoder pulse e as position information of the first moving table 4, and also has a counter XP that divides the input of the encoder pulse e by four during the return of the first moving table 4 to generate an interrupt. There is a frequency divider circuit PDC that makes the counter χF count by 4 each time the interrupt occurs. There is no need to count XF, and the software processing time will be in time. Note that the encoder pulse e is output from the encoder 33 and the output FG is from the waveform shaping circuit 1.
At step 50, the signal is converted into a rectangular wave and input to the microcomputer 41.

The input boat 45 receives a photographing magnification signal MAG from the mask.
A signal 5CAN requesting the start of scanning and a signal HOME indicating whether the scanning optical system 3 is at the home position are given. The signal MAG indicates the copying magnification selected in the copying machine, and the microcomputer 41 sets the scanning speed accordingly. The signal SCAM is normally "low" and becomes "high" when a scan start request is issued. Signal HOMB is the scanning optical system 3
is considered “high” only when is in the home position,
Otherwise, it is set to 0 low.

A forward/reverse rotation signal f of the motor 30 is output from the output port 46, and is input to the input terminal 35a of the drive circuit 51 shown in FIG. From the PWM output port 47, the oscillation circuit 5
A PWM pulse for constant speed scanning control with a frequency obtained by dividing the system clock feLIE, which is oscillated at 0, by 256, or deceleration control at the start of scanning system 3's constant speed scan or until the start of return after constant speed control, or full For deceleration return control following power return, the duty of the pulse is set to 100%, and the off time of the pulse is controlled by an interrupt performed by a timer setting based on the on and off edges of encoder pulse e (Figure 4). The PWM motor energization pulse ratio is inputted to the input terminal 35b of the drive circuit 51 in FIG. 2. The motor 30 is controlled by these inputs.

In this control, as shown in FIG. 4, the scanning optical system 3
Control of the state of acceleration scan A from 1 to 1 until reaching the target speed V, control of the state of constant scan B that scans a predetermined range at a constant speed after reaching the target speed V, and control of the state of constant scan B that scans a predetermined range at a constant speed when the target speed V is reached, and when the constant speed scan ends A state of deceleration scanning C in which the motor 30 is temporarily decelerated to speed 0 in order to move the scanning optical system 3 backward, and a state of full power return D in which the motor 30 is subsequently reversed at full power and the scanning optical system 3 is moved backward. control of the state, and control of the state of deceleration return E, which decelerates the motor 30 to speed 0 and stops it by applying a brake to stop the scanning optical system 3 in the state of full power return D at the home position.

Control in acceleration scan A is performed by inputting a "high" signal to the input terminal 35a, and setting a timer to the input terminal 35b to set a certain off time tOFF from each on edge of the encoder pulse generated in accordance with the rotation of the motor 30. Then, the on-edge of the next encoder pulse is the on-edge time t. An energizing pulse d set to H is input (FIG. 5(a)).

This energizing pulse d is obtained by an internal interrupt INT-P set by a timer from an interrupt INT-E caused by each on/off edge of the encoder pulse e. Accelerated scanning (^)
At the beginning of , the rotation of the motor 30 is slow and the interval between encoder pulses e is long, so the on time tON of the motor 30 is equal to the off time t. The motor 30 is strongly accelerated by a sufficiently long and strong energizing torque for the FF. As the speed approaches the target speed V for constant speed scanning B, the on-time t decreases as the encoder pulse e interval becomes smaller. H off time t. 1
．． As the ratio to

When the target speed V reaches point F in FIG. 4, the microcomputer 41 determines that one target speed V has been reached based on the interval between the encoder pulses e at that time. Based on this, the control of the motor 30 is switched to constant speed scanning B control. In this control, the motor 30 is controlled at a constant speed by using the PWM pulse as the motor energization pulse d, and as will be described in detail later, the acceleration α during energization when the target speed V is reached. N and acceleration αOFF when not energized
Then, PWM is calculated using these two parameters as
The duty of the motor energizing pulse d is rewritten for each encoder pulse (Fig. 6).

The timing of this rewriting is when encoder pulse e is turned on.
can only be obtained by the interrupt INT-H by each edge off (FIG. 5(b)), so during this time the internal side interrupt INT-H
-P is prohibited.

This achieves constant speed control, and when the scanning end position is reached, deceleration scanning (C) is performed. In this deceleration scan (C), the input terminal 35a is switched to "low" to apply a braking force, and the off time is controlled by the motor energization pulse d in the same way as in the acceleration scan (A) (see Fig. 5). (C)
), when the input terminal 35a is "low" and the input terminal 35b is "low", only the transistor Tr is turned on in FIG. At this time, since the scanning optical system 3 is moving in the scanning direction, this movement causes the shaft 30a of the motor 30 to rotate, and a back electromotive force in the opposite direction to the arrow a is generated in a closed loop of the motor 30, the diode D3, and the transistor Tr. occurs, and brakes the rotation of the motor 30 rotating in the scanning direction a. This is what is called regenerative braking.

On the other hand, the input terminal 35a is "low" and the input terminal 35b is "low".
In the "high" state, the transistors Trl and Tr are turned on, and the current of the DC power source E flows in the direction opposite to the arrow a, applying braking to the motor 30 in an attempt to rotate it in the return direction.In this way, the scanning optical system 3 The case in which braking is applied by rotating the motor 30 in a direction opposite to the direction of movement is so-called forced braking.

At the beginning of the deceleration scan (C) in Figure 4, the interval between the encoder pulses e is shorter than the set off time, so only the regenerative brake works.The braking force from this regenerative brake is relatively weak (the scanning optical system is gradually decelerated to 5. When the deceleration progresses and the interval between encoder pulses e becomes longer than the off time, the forced brake is also activated in addition to the regenerative brake, and deceleration is performed with strong braking.

Next, when the interval between encoder pulses e becomes longer than a predetermined time, the return process shown in FIG. 4(D) is entered. In order to shorten the return time, the input terminal 35b is kept on, that is, the motor energizing pulse d is kept on, so that it is fixed at "high 1" and energized all the time. So-called full power return (D) is performed. (Figure 5(d))
.

Here, it is desired that the scanning optical system 3 is accurately stopped at the home position after this full power return. To satisfy this requirement, the full power return (D) is switched to the deceleration return (E) at a position slightly before the home position.

The start timing of this deceleration return (E) is determined by counting the encoder pulse e by the counter XF of the timer unit 49 from the time when the home switch is turned off at the start of scanning, and from the time point shown in FIG. Count value up to X. By subtracting f, the position of the first moving platform 4 during the return is determined, and from the home switch 34, the brake start period regular position (
It is determined when the count value x, f corresponding to the distance to FIG. 4 J) is reached.

Note that the subtraction at this time corresponds to software processing by performing four subtractions each time the above-mentioned external interrupt is generated when each of the on and off edges of the encoder pulse e is detected four times as described above.

When the count value reaches x, f, the same off-time control as in the case of deceleration scanning (c) is performed to stop at the home position.

To explain the above main control in more concrete detail, the timer unit 49 of the microcomputer 41 uses its free run counter PRC to count the system clock f, divided by 4 of □, which is input from the oscillation circuit 50, as a reference clock. , generates an external interrupt signal INT-B by detecting each on/off image edge of the encoder pulse e;
The value of the free run counter FRC at the time of detection is captured in the register 48, and the count value is used as the speed detection information of the L motor 30 for determining the pulse Ii of the encoder pulse e.

Note that the reduction ratio of the reduction gear 31 is 1/N, and the drive pulley 31a is
Let the diameter be D, and the scanning speed V at the same magnification by the motor 30,
When seen as the speed of the timing belt 32, the motor 3
The relationship between the rotational speed R0 and the speed V at 0 is as follows. Therefore, if the encoder pulse width (-period) at the same magnification is TSI, and the number of encoder pulses per one revolution of the motor 30 is G, then the timer unit 49 uses the PWM register PWMR provided therein to control the timer unit 49 by 25 seconds of the system clock fCLK.
A high-level active pulse corresponding to the value set in the PWM register PWMR is generated and output at a frequency divided by six. The resolution of this PWH is 2+2, and the pulse width duty PWMduty is expressed by PWMduty.

Furthermore, when the timer unit 49 counts the value set in the TMF register TMFR, it generates the above-mentioned internal interrupt signal INT-F.

Here, constant speed scanning (B) control by the PWM output port 47 will be described. Acceleration α when the PWM motor energization pulse energizes the up motor 30 at the target speed ■
. 8 and the acceleration α when the power is turned off. The difference with FF is 6th
As shown in the figure, if △■, in order to reach the target speed V during the upper period of the PWM motor energization pulse, the upper period of the PWM motor energization pulse must be T1, and the ratio of the energization on time to this T be Y. Then, α0N-Y-TPΔV=α0FF(I Y)TP
−・−■ holds true. Therefore, Y becomes.

Next, consider the case where the encoder external interrupt INT-E occurs at time 0 in FIG.

Assuming that the speed error is ΔV at this time, in order to reach the target speed ■ by the time when the next encoder external interrupt INT-E occurs, one cycle of the encoder pulse corresponding to the target speed ■ must be Then, the time from 0 to reach is approximately TSI/2,
During this period, N on the PWM motor energization pulse is as follows.

Therefore, it is preferable to correct the value obtained by dividing the speed error ΔV in equation 0 by N by adjusting the duty of one PWM motor energization pulse. At this time, the PWM motor energization pulse generation ratio Y is as follows.

Considering the speed error ΔV here, speed detection is performed by determining the width of the encoder pulse e by the count number of the free run counter FRC between external interrupts 1878, so the measurement pulse at the 0 point is as shown in FIG. TM width. 8. If the target pulse width is TSI, the speed V when the pulse width is TSI is Ro and G of the formula
, is expressed as more.

As a result, the PWM motor energization pulse generation ratio is given by formula (2).

TI'l in the denominator of the second term on the right side of this [phase] equation. L
.

TSI, the on-ratio Y of the PWM motor energizing pulse d2 is given by the [phase] equation. Similarly, when the speed error is Δ■, the speed v0 is given by the pulse width being TMON. Therefore, the speed error Δ■ becomes.

The width of the encoder pulse e is determined by the count by the free run counter FRC inside the CPU 42, and the free run counter FRC counts the frequency divided by 4 of the system clock fCLK as a reference clock, so TI' of the second term on the right side of Eq. l. 8. TSI free run counter FR
C count value TM. Expressed in Nf 5TSIf, αON 10 αoiy αON + αOFF T
ST”.

Therefore, the set value PWMl to the PWM register PWMR
? .

teeth, αON+αOFF αON ten αOFF becomes.

Next, in FIG. 4, acceleration α when the motor is energized at the target speed V at point (F). , and the acceleration α (IFF
We will explain how to find this.

In FIG. 8, at the time Kt when the speed reaches the target speed V, the edge of the next encoder pulse e is detected.
PWM motor energization pulse rate up to 100%
, and the full power is turned on, and from the time of K, P is set to 4 at the time of detecting the edge of the next encoder pulse.
The acceleration is measured by prohibiting the WM motor energization pulse force and maintaining the non-energized state.

If the velocity changes from V to vl at time K, then the acceleration α at this time. 8 is given by the following equation.

Here, on the right side of formula 0, the first term = CBIAS, the second term
Term = PRATII! Then, PWMRa=CBIA
S +PRATE (TM., f-TSIf) ---
・[Phase] Here, in the denominator of formula ■, TSI, ζTSI
.

becomes.

Furthermore, if the speed changes from vl to vt at point 4, the acceleration at this time (αOFF>0) is [
Phase], [phase] expressions are expressed by the count values TSIf, , TSIIf , , TSTZf of the free run counter FRC,
G.R.

Here, TSL, ζTSI, rstzζT in the denominator
SI, therefore ■, α of the [stock] formula. 8. α. Substituting CBIAS 5PRATE in the formula [phase] using FF results in the following.

Therefore, by calculating the value of the above formula, constant speed scanning (
The optimal parameters for control B) can be determined.

Next, based on the flowcharts shown in FIGS. 9 to 11,
A specific flow of control in this embodiment will be explained.

FIG. 9 shows the main routine controlled by the microcomputer 41.

When the power is turned on and the microcomputer is reset, initial settings are performed in step #1. This is internal RAM4
4. Clear the PWM register PWMR, etc., and
The output state of the output port 47 is turned off and the motor energization signal d is set to "0". This d=0 corresponds to a state in which the input terminal 35b of the motor drive circuit shown in FIG. 2 is "low" and turns off the motor 30, and d=1 corresponds to a "high" state.

After initial setting, it is determined in step #2 whether the home switch 34 is on. When turned on, scanning optical system 3
is at the home position, that is, the scanning start position, and the process advances to step #3, where it waits until a scanning request signal 5CAN is received from a mask (not shown). When the scanning request signal 5CAN is output, the copy magnification signal MA is output in step #4.
The magnification M by G is input into the memory m, and in step #5, an encoder pulse width TSIf for controlling the scanning speed corresponding to the copy magnification is calculated.

This calculation of TSIf is based on the clock of the free run counter FRC, so M
It becomes GRo4.

In step #5, x and f, which determine the scan length and the distance from the home switch to the point at which the brake starts, are also calculated. xof is the length calculated from the paper size PSIZE and the magnification, and the preliminary scanning amount X1llll! (distance from the home switch off to the top of the image).

Here, the rising edge, falling edge, and movement amount a from falling edge to rising edge of the encoder pulse are V.

Therefore, the scanning length X, f converted into a pulse count value at the magnification M becomes P. Furthermore, if the distance from the home switch 34 to the point at which the brake starts is Xi, then from the [phase] formula, the pulse count conversion at the distance xI is 4fi x If, where PSIZE is the maximum paper passing size in this embodiment. .

In the next step #6, the forward/reverse signal f is set to “1”, f
=1 corresponds to a state in which the input terminal 35a of the drive circuit 51 in FIG. 2 is "high" and causes forward rotation, and f=0 corresponds to a state in which it is "low" to cause reverse rotation.

In the next step #7, a predetermined value T is set in the memory tOFF of the energization off time for controlling the acceleration scan (^). Set FFI. This is the external interrupt INT- shown in Figure 10.
Used in H's interrupt subroutine.

In step #8, 409 is set in register P%1MR of PWH.
Set 6. In other words, the duty of the PWM motor energizing pulse is set to 100%, and the PWM output port 47
The off-time control is performed using PW.
Turn on the output state of M output port 47, that is, d=1
It is also performed to start energizing the motor 30.

In step #9, the control mode of accelerated scanning (A) is set by setting MODE←1, and in the following step #10, external interrupt INT-B by encoder pulse e is enabled.

In the next step #11, the scanning optical system 3 moves away from the home switch 34 in the control of the accelerated scan (A) at the initial stage of scanning, and the home switch 34 is turned off.
Proceed to step 12. Here, the counter XF for measuring the scanning length is cleared (.This causes the counter xp to count the amount of movement of the scanning optical system 3 since it actually started scanning from the cleared state.

In the following step #13, it is determined whether or not the calculated scanning length has been scanned based on whether the count value xf of the counter XF has reached xof corresponding to a predetermined scanning length. When xf = x, f, at which the scanning ends, the process proceeds to step #14, where the forward/reverse rotation signal f is set to "0" to bring about a braking state by reverse drive in the normal rotation state.

Next, in step #15, a predetermined value TOFFII that determines the brake force is set in the off-time memory tOFF, and in step #16, MODI! Set to 2 and set to deceleration scanning (C) control mode.

Thereafter, switching from the deceleration scanning state to the acceleration state with full power return is performed in the subroutine of external interrupt INT-H.

In step #17, it is determined whether the brake start time has been reached depending on whether xf=x, f, and if xf=x, f reaches the brake start time, the process advances to step #18 and the forward/reverse signal f is sent. 1 to set the braking state by forward rotation drive during reverse rotation.

In the following step #19, a predetermined value T is determined to determine the braking force at the end of the return. Set FF3 in the off-time memory tOFF, and set MODE=3 in step #20 to set the deceleration mode at the end of return.

Next, the process proceeds to step #21, in which it is determined whether the scanning optical system 3 has reached the home position of ROMB-1, and if it has reached the home position, the process proceeds to step #22. Step #22
Then, it is determined whether MODE=4. This mode is set in the external interrupt INT-E subroutine, and if it is 0M0DH-4, which means the end of return, step #2
3, the output of the PWM output port 47 is turned off, and in the following step #24, the interrupt is disabled. This completes one reciprocating operation, returns to step #3, and waits for the next scan request from the mask.

On the other hand, if the home switch 34 is turned off in step #2, the process moves to step #25. Here, a constant speed return magnification MR [! T
In the following step #26, the magnification MRE is set as in step #5.
TSIf for constant speed return corresponding to T is calculated. Therefore, xof, x, and f are not calculated here.

Next, in step #27, the forward and reverse rotation signal f is set to "0" so that the motor 30 is driven in the reverse direction, and steps #28 to
At #31, the same processing as steps #7 to #10 is performed.

However, the off-time memory t. The FF has a predetermined value T that determines the braking force for constant speed return. F□ is set. Continuing (in step #32, the home switch 34
It is determined whether or not is turned on, and if it is turned on, it means that the scanning optical system 3 has returned to the home position, and the process proceeds to steps #33 to #35, where the forward/reverse signal f is set to 01".
As in the case of steps #18 to #20, a braking operation is performed by driving forward rotation during reverse rotation. However, in this case, the off-time memory tOFF contains a predetermined value T to determine the braking force in this case. FFI is set. Next, the process moves to step #22 and waits until the braking is completed, and then the same process as described above is performed.

The interrupt INT-H subroutine shown in FIG. 10 will be explained. As described above, this interrupt is performed in response to each on/off edge of the encoder pulse e. When an interrupt occurs, first, in step #51, the value Ta of the free run counter FRC, which is the current time signal, is stored in the memory ta. Next, in step #52, the value Ti obtained by subtracting the previous encoder interrupt time Tb from the content Ta of the memory ta is calculated.
is stored in the pulse width memory ti.

In the following step #53, Ta is stored in the memory tb for the next encoder pulse interrupt process.

Furthermore, in step #54, the mode is determined, and if it is not the constant speed scanning (B) control mode (MODE=O), the process proceeds to step #55. If the control mode is deceleration scanning (C) (MODE=2), the process moves to step #80.
Otherwise, in the next step #56, it is determined whether the control mode is acceleration scanning (A) (MODB=1).

If the control mode is accelerated scanning (^), the process moves to step #60 and the state ST in the accelerated scanning (8) control mode is determined. Here, if 5T=O, the process moves to step #61, and it is determined whether the measured pulse width Ti is less than or equal to TSIf calculated in the main routine. In other words, it is determined whether the target speed V has been reached, and if it has not been reached, the process moves to step #65 and the PWM register PW? 'lR for 40
96 to set the PWM motor energization pulse utility to 100% and turn off the output state of the PWM output boat 47.

In the following step #66, T calculated in the main routine is
. FF to timer F register TMF of timer unit 49
By assigning it to R and enabling the interrupt of timer F in the next step #67, register TMFR is set from this time.
After the count value set in 4 is counted using fCLK divided by 4 as the reference clock, timer F interrupt I
Generate NT-P.

If the target speed is 7 or more (Ti≦TSIF) in step #61, move to step #62 and perform acceleration scanning (8).
The state ST in the control mode is incremented, and interrupts by timer F are prohibited in the following step #63.

Next, in step #64, the output state of the PWM output port 47 is turned on. Therefore, from this point on, there is no interruption by timer F α. 8. α. Enter the measurement mode of □.

If 5T is not 0 in step #60, step #70
Then, it is determined whether 5T=1. If 5T=1, the process proceeds to step #71, the state ST is incremented, and the pulse width Ti measured at the current time is stored in the memory tsi+f of TSIIf in the following step #72. Next, in step #73, the PWM register PWMR is set to "0", that is, the power is turned off, and in the following step #74, internal interrupts by timer F are prohibited.

If 5T is not 1 in step #70, step #75
Clear ST to "0" and set the measured pulse width Ti at the current time to TSI in step #76.
Store in tf memory tsid.

Next, in step #77, the pulse width TSI, f when the motor is energized and the pulse width rsI when the motor is not energized are determined using the method described above.
α from zr. 8. Calculate αOFF and use CBIA from this
Calculate S and PRATE.

In the following step #78, the constant speed scanning (B) control mode (
Set MODE=O).

In step #55, the control mode (MOD) of deceleration scanning (C) is
E=2), the process moves to step #80, where Ti is the pulse width TST corresponding to the control end speed of deceleration scanning (C).
It is determined whether the speed of the scanning optical system 3 has become equal to or higher than OP, that is, whether the speed of the scanning optical system 3 has become below the deceleration scanning control speed.
If the above is the case, proceed to step #65 and perform the aforementioned accelerated scanning (
In the case of control A), the same off-time control is performed. If it is below, move to step #81 and return end deceleration mode (
MODE=3). If it is the return end deceleration mode, the process moves to step #82, sets the return end mode (MODE=4), and then returns to the main routine from the external interrupt INT-H subroutine.

If the mode is not MODE=3 in step #81, the process proceeds to step #83 and full power return mode (MODE
E-5), and in the following step #84, set the PWM register PWMR to 4096, that is, set the duty to 100.
% and turn on the PWM output port 47. Next, in step #85, the interrupt of timer F is disabled, thereby starting full power return.

In addition, in step #56, the acceleration scanning (A) control mode (M
ODE=1), move to step #57,
It is determined whether it is the return end deceleration mode (MODB=3).

If MODE=3, the process moves to step #80 and the same process as described above is performed; otherwise, the process moves to step #58, where it is determined whether the mode is full power return mode (MODE=5). If 0M0DE=5, the process proceeds to step #58. #90
Then, the pulse count value xf of the counter XF during the return is decremented by four in cooperation with the frequency dividing circuit FDC, and then the main routine is returned.

If MODE=5 is not determined in step #58, then if it is the return end mode (MODE=4), the process returns to the main routine.

In step #54, the constant speed scanning (B) control mode (MOD) is selected.
If H=0), the process moves to step #58 and the value calculated from the difference between the CB summer AS, PRATE and the target pulse width TSIf calculated in the above-mentioned method and the current measured pulse width Ti is stored in the PWM register PW? After setting to IR, the process moves to step #91 to increment the pulse count value xf of the counter XF during scanning, and then returns to the main routine.

If MODE=O in step #54, step #59
The process proceeds to step #91, where the duty of the PWM motor energizing pulse is calculated using the optimum parameters in the constant speed scanning (A) control, and stored in the PWM register PWMR.

The subroutine of internal interrupt INT-F by timer F shown in FIG. 11 will be explained. When interrupts are enabled (INTP enabled) and the count value set in the timer F register TMFR is counted based on the reference clock, an internal interrupt INT-F is generated, and the process proceeds to step #4.
0, the output of the PWM output port 47 is changed from the OFF state to the ON state, and then the process returns to the main routine.

Note that in the case of a copying machine or the like that performs a preliminary scan when the power is turned on, the acceleration α at the time of energization during constant speed scanning during this preliminary scan. By determining H and αOFF when the current is not energized, it is possible to drive the scanning optical system 3 appropriately and stop it at the home position in accordance with the actual load torque of the scanning optical system 3 at that time from the time of the first copy. can be controlled.

Further, although the above embodiment describes a copying machine that scans the original by moving the optical system, a copying machine of the type that moves the original table can also use the same control as described above to reciprocate the original table at higher speed and more accurately. be able to. Further, the present invention can also be applied to controlling the operation of a scanner in an image reading device other than a copying machine.

(Effects of the Invention) According to the present invention, pulses generated in accordance with the rotational speed of the motor that reciprocates the scanning system are counted both during the forward and backward movements of the scanning system. Since the drive control is performed so that the scanning system is stopped at the home position upon obtaining the brake start timing, the switch and wiring for detecting the brake position can be omitted.
It is possible to properly judge the actual position at any given time without being affected by fluctuations in load torque caused by warping of the mirror in the scanning system, deterioration of the bearing over time, or dirt adhesion. The scanning system can be stopped at a predetermined home position at all times by applying a brake at this position.

In particular, if the scanning system uses different pulse counting methods during its forward and backward movements, even if the scanning system is moved back at full power and at high speed in order to shorten the required time for copying multiple sheets, Soft control can be easily achieved by sufficiently responding to the increase in pulse frequency.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an image forming section showing an embodiment of the present invention applied to an optically movable copying machine, FIG. 2 is a drive circuit diagram of a drive motor of a scanning optical system, and FIG. 3 is a drive circuit diagram of a drive motor of a scanning optical system. A control circuit diagram for controlling the circuit, Fig. 4 is a speed diagram of the first moving stage for scanning, a corresponding time chart of the home switch and a count change diagram of encoder pulses, and Fig. 5 is a diagram of the speed diagram of the first moving stage for scanning. Diagrams showing encoder pulses and energization signals based on the encoder pulses at various control points during reciprocating motion, FIGS. 6 and 7
The figure is a diagram explaining the method of setting the duty in one cycle of the PWM motor energization pulse, FIG. 10 is a flowchart showing the main routine of control by the microcomputer for controlling the scanning system, FIG. 10 is a flowchart showing the subroutine for external interrupt INTE, and FIG. 11 is a flowchart showing the subroutine for internal interrupt INT-F.

Claims (2)

[Claims] (1) In an image scanning device that scans a document and exposes an image or reads an image by the forward movement of a scanning system that is reciprocated by a motor, a means for generating pulses according to the rotational speed of the motor, and a means for generating pulses according to the rotational speed of the motor; A means for counting pulses during both forward and backward movement of the scanning system, and a control means for obtaining the brake start timing during the backward movement based on the count by this means and stopping the scanning system at the home position. A copying machine scanning device characterized by: (2) The scanning device for a copying machine according to claim 1, wherein the counting means uses different counting methods during forward movement and backward movement of the scanning system.