JPH02159879A - Picture scanning device - Google Patents

Abstract

PURPOSE:To attain speed control without storing a control pattern by calculating acceleration at the time of energizing and acceleration at the time of non- energizing at a prescribed time point and determining a parameter executing the speed control of a scanning system based on this acceleration. CONSTITUTION:A signal MAG given to an input port 45 shows a copying magnification selected in a copying machine and in a microcomputer 41, scanning speed is set in correspondence to the magnification. When object speed is attained, by the microcomputer 41, it is judged from the interval of an encoder pulse (e) at that time that the object speed is attained. Based on this judgement, the control of a motor 30 is switched to the control of constant speed scanning. In this control, the PWM pulse of a PWM output port 47 is defined as a motor energizing pulse (d) and the constant speed control of the motor 30 is executed. However, when the object speed is attained, the acceleration at the time of energizing and the acceleration at the time of non-energizing are calculated. After that, these two types of the acceleration are defined as the parameter and the duty of the pulse (d) is rewritten at every pulse (e). Thus, in correspondence to the loading torque of the scanning system at such a time point, the scanning speed can be set suitable.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image scanning device used in a copying machine or an image league, and more particularly to an image scanning device that is driven by a motor to scan an image.

BACKGROUND OF THE INVENTION In order to copy or read an image by scanning it with a moving scanning system, stability of the scanning speed is required.

However, in the scanning system, the load torque fluctuates due to warping of the Moller, aging of the bearing, or dirt adhesion, so when driven by a DC motor or the like, the drive torque tends to vary.

A method to deal with this problem is disclosed in Japanese Patent Application Laid-open No. 138248/1983. This method calculates the torque when reciprocating the scanning system from the drive current of the DC motor, and selects and executes the optimal control pattern corresponding to the calculated torque from a table of control patterns stored in advance. It has become.

(Problem H to be Solved by the Invention) However, in the above-mentioned conventional method, the severe control pattern is provided only in stages, and therefore it cannot properly respond to actual torque fluctuations that change in various ways. Moreover, it is disadvantageous to have to store many types of control patterns (the amount of data stored increases), and since the scanning speed is set for each magnification in a copier that can change the magnification, the control pattern table is It must be provided corresponding to the magnification, and a huge amount of data must be stored.

Therefore, the present invention calculates the acceleration when the scanning system is energized and the acceleration when it is not energized at a predetermined point in time when the scanning system is actually moved, and determines the control parameter for the speed of the scanning system based on this. The object of the present invention is to provide an image scanning device that can achieve proper speed control based on the actual load torque of the scanning system from time to time without having to memorize control patterns. .

(Means for Solving the Problems) In order to achieve the above objects, the present invention provides an image scanning device that scans and copies or reads images using a scanning system driven by a motor. The control means controls the duty of the motor energizing pulse so as to scan at the speed, and the speed detection means of the scanning system, and the control means determines a predetermined value when the scanning system operates based on the speed information from the speed detection means. The present invention is characterized in that the acceleration when energized and the acceleration when energized are calculated at the time point , and parameters for controlling the speed of the scanning system are determined based on the calculated accelerations.

(Function) The motor is energized according to the duty of the energizing pulse, and is driven at a speed and torque according to the duty. At this time, the scanning system driven by the motor is first accelerated by inertia and then reaches a predetermined speed, and the speed of this scanning system is detected by the speed detection means. - The force control means calculates the acceleration when energized and the acceleration when not energized at a predetermined time point based on the speed information from the speed detection means, but the relationship between these two accelerations is determined by the scanning system at the speed at the predetermined time point. contains information on the load torque and the corresponding required drive torque that it has at that point, so based on that information, the scanning speed of the scanning system can be adjusted to correspond to the load torque at that point in the scanning system. Appropriate parameters to control can be determined.

If the predetermined time point is at or just before the scanning system reaches the target speed for scanning, the information can be directly obtained corresponding to the target speed, and no correction or adjustment is required, making control easier. This is preferable because it can be achieved by appropriate and simple control.

(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 table glass 1 and the photosensitive 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 pulleys 22 and 23 of the same diameter, and the portion 21a on the pulley 22 side is passed below the boot IJ 22, and then the end plate of the second movable table 8 The hook is turned and folded back to the boot 1J24 provided on the outer surface, and the end 21
c is fixed to the fixing member 25. The part 21d on the pulley 23 side is hooked to the lower side of the boo 1J23, and the second
The pulley 24 of the movable table 8 is turned and folded back, and its end 21e is fixed to a fixing member 26 via a tension spring 27.

Also, the part 21a of each wire 21 on the pulley 22 side has a boot'
A portion between J22 and the pulley 24 is fixed to the first movable base 4. 28 indicates the fastening portion. Pulley 2
A DC motor 30 is connected to the rotating shaft 29 of No. 3 via a reduction gear 31 and a timing belt 32. Further, an encoder 33 is connected to the rotating shaft 30a of the motor 30, and generates pulses in synchronization with the rotation of the motor 30.

When the motor 30 is operated in the direction of arrow a, the wire 2I 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.
It is moved at a speed of 1/n (n: copy magnification), which is the same speed as 1,
The image of the original on the original table glass 1 is scanned in a range corresponding to the copy size and magnification, and the first to fourth mirrors 6.9.10.
12 and a projection lens 11, images of the original are sequentially slit-exposed onto the photosensitive drum 2. At this time, the second movable table 8 is operated by the boot 11 when the wire 21 is driven in the direction of the arrow.
The pulley 23 becomes shorter as the portion 21a in Example 22 becomes shorter.
As the side portion 21d becomes longer, the pulley 2
4, is moved in the direction of arrow C at a speed of 1/2n,
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 by a developing device to become a toner image, and is transferred by a transfer charger onto a transfer sheet that is sent in synchronization with the toner image.

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 Trl to Tra. The transistors Tr, Tr3 are turned on when the base voltage is "low", and the transistors Tr2, Tr are turned on when the base voltage is "high".
Depending on the combination of off states, the motor 30 is appropriately rotated forward, reversed, or stopped.

Transistors Tr and ~Tra each have a diode D.
1 to 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.
ND game) AND + input side and transistor Tr
, and the input side of the AND gate AND z via the inverter I and the transistor T
connected to the base of r.

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.
It is connected to the input terminals of ND gates AND and AND2. AND gate AND.

The output side of is connected to the base of transistor Trz, and also connected to AND
The output sides of the gates AND, are respectively connected to the bases of the transistors Tr.

Table 1 below shows the on/off state of each transistor Tr to Tr4 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. It is as follows.

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. ).

Microcomputer 41 is CPIJ42, ROM43, RAM
44, human powered boat 45, output port 46, PWl'l
output boat 47, register 48, timer unit 49,
Each of the oscillator circuits 50 is provided to generate an internal system clock fclk. The timer unit 49 includes a counter XF that directly counts the encoder pulse e as position information of the first moving table 4, and a
During the return, there is a frequency divider circuit FDC that divides the input of the encoder pulse e by 4 to generate an interrupt, and causes the counter XF to count by 4 each time the interrupt occurs. Even if the rotation is made, the counter XP does not need to count until the edge of the encoder pulse e is detected four times, and the software processing time is sufficient. Note that the encoder pulse e is an output FG from the encoder 33 which is converted into a rectangular wave by the waveform shaping circuit 150 and input to the microcomputer 41 .

Signal MAG of photographing magnification is sent from the mask to human power port 45.
, a scan start request signal SCAM, and a signal HOME indicating whether the scanning optical system 3 is at the home position. The signal MAG indicates the copying magnification selected in the copying machine, and the microcomputer 41 sets the scanning speed accordingly. The signal 5CAN is normally set to "low" and is set to "high" when a scan start request is made.The signal FIOME is set to "high" only when the scanning optical system 3 is at the home position, and is set to "low" at other times. Ru.

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. The oscillation circuit 50 is connected from the PWM output port 47.
A PWM pulse for constant speed scanning control with a frequency obtained by dividing the system clock fCLK oscillated by 256, or deceleration control at the rise to constant speed scanning of scanning system 3 or until the start of return after constant speed control, full power For deceleration return control following return, the duty of the pulse is set to 1.
00%, the PWM motor energization pulse ratio, called the pulse whose off time is controlled by an interrupt performed by the timer setting based on the on and off edges of the encoder pulse °e (Fig. 4), is used as the second It is input to the input terminal 35b of the drive circuit 51 in the figure. These inputs cause motor 3
0 control is performed.

As shown in FIG. 4, this control is performed when 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 O 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.

In the acceleration scan A, a "high" signal is input to the input terminal 35a, and a certain OFF time is set from each on-edge to the input terminal 35b of an encoder pulse generated in accordance with the rotation of the motor 30. A timer is set for the FF, and the on-edge time is t until the next encoder pulse on-edge. An energizing pulse d set to N 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 of the motor 30 is t. N is 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. ,
The ratio to F becomes smaller, and the acceleration for driving the motor 30 gradually becomes weaker.

When the target speed reaches point F in FIG. 4, which is the target speed ■, the microcomputer 41 determines that the target speed V has been reached based on the interval of 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, but as will be described in detail later, the acceleration α when energizing reaches the target speed ■. 8 and acceleration α when not energized. FF
Then, PWM is calculated using these two parameters as
The duty of the energizing pulse d is rewritten for each encoder pulse (FIG. 6).

The timing of this rewriting is when encoder pulse e is turned on.
It is obtained only by the interrupt INT-H by each off edge (FIG. 5(b)). Therefore, during this period, the internal side INT
-F 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" in order 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 (^) (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 direction opposite to the arrow a is generated in the closed loop of the motor 30 and the diode D3 transistor TrI. Then, a brake is applied to 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 Tr and Tr4 are turned on, and the current of the DC power supply 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 Fig. 4, the interval between the encoder pulses e is shorter than the set off time, so only the regenerative brake is activated. is gradually decelerated. 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 energization pulse d is kept on, so that it is fixed at "high" and energized at all times. A so-called full power return (D) is performed (Fig. 5 c))
.

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 I in FIG. 4 when the scanning ends during the return. 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 predetermined brake start 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 counts the frequency divided by four of the system clock fCLK input from the oscillation circuit 50 as a reference clock using its free run counter FRC, and Generates external interrupt signal INT-E by detecting each on/off edge of pulse e, captures the free run counter FRCO value at the time of detection on register 4, and uses that count value to determine the pulse width of encoder pulse e. This is the speed detection information of the simulator 30.

Note that the reduction ratio of the reduction gear 31 is 17N, 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, the encoder pulse width at the same magnification (-period!III) is TSI,
If the number of encoder pulses per rotation of the motor 30 is G, then the following equation is obtained.

The timer unit 49 uses the PWM register PWMR provided therein to control the system clock fCLK by 25 seconds.
At a frequency divided by 6, a high-level active pulse corresponding to the value set in the PWM register PWMR is generated and output. The resolution of 20PIIM is 212, and the pulse width duty PWMduty is expressed by PWMduty.

Furthermore, the timer unit 49 has a TMF register TMFI?
When the value set in this register TMFR is counted, the above-mentioned internal interrupt signal INT-F is generated.

Here, constant speed scanning (B) control by the PWM output port 47 will be described. Acceleration α when the motor 30 is energized by the single motor energization pulse d at the target speed ■.

Acceleration α when N and electricity are cut off. 1. If the difference is △■ as shown in FIG. 7, where the on-time ratio is y, αON ``l' TPΔV=α0FF(I Y)T
P ---=■ holds true. Therefore, it is preferable to correct Y by adjusting the value obtained by dividing ■ by N into the speed error in formula 0 by one PWM motor energization pulse-utility adjustment. The PWM motor energization pulse-on ratio Y at this time is as follows.

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

Assuming that the speed error is Δ■ at this time, in order to reach the target speed ■ by the time KI when the next encoder external interrupt INT-E occurs, one period of the encoder pulse corresponding to the target speed V must be Then, from 0,
The time it takes to reach is approximately TSI/2, and the PWM motor energization pulse -N during this time is .

Considering the speed error △V 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 INTE, so the measurement at the 0 point is as shown in Figure 7. If the pulse width is TMoN and the target pulse width is TSI, the speed V when the pulse width is TSI is given by Ro and G in the formula,
, more TSI GR.

becomes. Similarly, when the speed error is 8V, the speed v0 is determined by setting the pulse width to TMoH.

TM,N ShiH.

becomes. Therefore, the speed error △■ is It is expressed as

As a result, the PWM motor energization pulse generation ratio is determined by the count by the counter FRC, which is 0 to 1, and the free run counter FRC is set to 4 of the system clock fCLK.
Since the frequency division is counted as the reference clock, the name of the second term on the right side of equation 0. 8. TSI as free run counter FRC
The count value TM. When expressed as Nf and TSIf, it becomes.

In the denominator of the second term on the right side of this [phase] equation, TMON″=
=TSr, the on-ratio Y of the PWM motor energization pulse d2 is given by the [phase] equation.

Therefore, the setting value PWM to the PWM register PWMR is
R.

teeth, becomes.

The width of the encoder pulse e is determined by the function inside the CPU 42. Here, on the right side of the equation 0, the first term = CBIAS, the second term =
If PRATE, then PWMRo=CBIAS +PRATE(TMoHf
TSIf) -1---@.

Next, the acceleration α when the motor is energized at the target speed V at point (F) in FIG. A method of determining H and the acceleration αOFF during non-energization will be explained.

In FIG. 8, at time 2 when the speed reaches the target speed V, at the time when the edge of the next encoder pulse e is detected, 3
PWM motor energization pulse rate up to 100%
from the time of K3 to 4 when the edge of the next encoder pulse is detected.
The acceleration is measured by prohibiting the energizing pulse force of the M motor and keeping it in a non-energized state.

Assuming that the speed changes from ■ to vl at K3, the acceleration at this time is α. 8 is given by the following equation.

V, -V TSI TSI I.

Furthermore, if the speed changes from ■1 to v2 at point 4, the acceleration at this time (αOFF>0) is TSIt #TSI in the denominator, TSIzζTSI, so ■, α in the [phase] equation. 8.α. By substituting CBIAS and PRATE in formula 0 using FF, here, in the denominator of 2〇, TSL, L=tTSI, -・--1-
-■ 2nd As above, convert the [phase] and [phase] expressions to the free run counter FR.
C-(7) Force '77) value TSIfSTSI+f, T
STzf te is expressed as follows.

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

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 boat 47 is turned off and the motor energization signal d is set to "0". This d=0 corresponds to a state where 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 "no\no" 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. Here, the process waits until a scan 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
6) It becomes 10 4.

Step #5 also calculates the scan length and xof, which determines the distance from the home switch to the point at which the brake starts. x and f are obtained by the sum of the length calculated from the paper size PSIZE and the magnification M, and the preliminary scan 11XHE (distance from the home switch off to the leading edge 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 xof converted to the pulse count value at the magnification M is 2GR (1 P).Furthermore, if the distance from the home switch 34 to the point at which the brake starts is xl, then from the [phase] equation, the distance of The pulse count conversion is 4f1 x and f Ir*. Here, PSIZE is the maximum paper passing size in this embodiment.

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

In the next step #7, the memory t of the energization off time for the acceleration scan (A) control is stored. A predetermined value T for FF. Set FFI. This is the external interrupt INT- shown in Figure 10.
Used in E's interrupt subroutine.

In step #8, 4096 is set in the PWH register PWMR.
Set. That is, the duty of the PWM motor energizing pulse is set to 100%, and the off-time control is performed using the PWM output port 47. Here again PWM
It also turns on the output state of the output port 47, completely sets d=1, and starts energizing the motor 30.

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

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 XP for measuring the scanning length is cleared. As a result, the counter XF counts the amount of movement of the scanning optical system 3 since it actually started scanning from the clear state.

In the following step #13, it is determined whether the calculated scanning length has been scanned or not, and the count value xf of the counter XF corresponds to the predetermined scanning length. The determination is made based on whether f has been reached. xf-x where scanning ends. When f is reached, proceed to step #14,
The forward/reverse rotation signal f is set to "O" to create a braking state by reverse rotation drive in the normal rotation state.

Next, in step #15, a predetermined value T for determining the brake force is stored in the off-time memory tOFF. Set FFZ, set MODE to 2 in step #16, and perform deceleration scanning (
Set to control mode C).

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=xlf, and if xf=x1f reaches the brake start time, the process proceeds to step #18 and sets the forward/reverse signal f to 1. Set to brake 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. FF3 off time memory t. yr, and set MODE=3 in step #20 to set the deceleration mode at the end of return.

Next, the process proceeds to step #21, and it is determined whether the scanning optical system 3 has reached the home position (80M12=1). If it has reached the home position, the process proceeds to step #22. Step #
MODII in 22! = 4. This mode is set in the external interrupt INT-H subroutine and signifies the end of return. MODI! If = 4, the process moves to step #23, where the output of the PIIM output port 47 is turned off, and the subsequent step #24 sets the interrupt disabled state. 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 predetermined constant speed return magnification MRET is set in the copy magnification memory m, and a return operation to the home position is performed. In the following step #26, the magnification MRET is set as in step #5.
Calculate TSIF for constant speed return corresponding to . Therefore, here it is X. The calculations of f and xlf are not performed.

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. □4 is set. In the following step #32, the home switch 34
If it is 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 r is set to "1".
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. FF2 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. 1O 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 the acceleration scanning (1
) control mode (MODE=1).

If the control mode is accelerated scanning (A), 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 ■ has been reached, and if it has not been reached, the process moves to step #65 and the PWM register I'WMR is set to 4096.
is set to set the PWM motor energization pulse duty 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
. □ is the timer F register TMPH of the timer unit 49.
By assigning the value to 0 and enabling the interrupt of timer F in the next step #67, timer F is activated after the elapse of the count value set in register TMFR from this time using fcLK divided by 4 as the reference clock. Interrupt TN
Generate T-F.

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. Enter the N, αOFF measurement mode.

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, where the state ST is incremented, and in the following step #72, the measured Saretahalus width Ti at the current time is stored in the memory tsi,f of rsLf.

Next, in step #73, the PWM register PWMR is set to “
0'', that is, the power is turned off, and in the subsequent 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.
d Store in memory tsi, f.

Next, in step #77, the pulse width TS1. when the motor is energized is determined by the method described above. f and pulse width TSI when motor is not energized
α from tf. 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 of deceleration scanning (C) (?l0
DE-2), the process moves to step #80, and Ti is the pulse width T corresponding to the control end speed of the deceleration scan (C)!
? It is determined whether the speed of the scanning optical system 3 has become equal to or higher than OF, that is, whether the speed of the scanning optical system 3 has become equal to or less than the deceleration scanning control speed. off-time control. If it is below, the process moves to step #81 and it is determined whether the return end deceleration mode (MODE=3) is in effect. If it is the return end deceleration mode, move to step #82 and set the return end mode (MODE-4), then
Main routine from external interrupt INT-H subroutine
Return to Chin.

If the mode is not MODE=3 in step #81, proceed to step #83 and enter full power return mode (MODE=3).
DE=5), and in the following step #84, the P register PWMI? is set to 4096, that is, the duty is set to 100%, and the PWM output port 47 is turned on. Next, in step #85, the interrupt of timer F is disabled, thereby starting the full power IJ turf.

In addition, in step #56, the acceleration scanning (A) control mode (M
ODI! = bow), the process moves to step #57, and it is determined whether the return end deceleration mode (MODE=3) is selected.

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, and it is determined whether the mode is full power return mode (MODE=5). If MODE=5, step #9
After proceeding to 0 and decrementing the pulse count value xf of the counter XF during return by four in cooperation with the frequency dividing circuit FDc, the process returns to the main routine.

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, constant speed scanning (B) control mode (MO=
DB-=0), the process moves to step #58 and the value calculated from the difference between CBrAS, 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 PWM. After setting R, proceed to step #91 and check the counter x being scanned.
After incrementing the pulse count value xf of F, the process 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. Interrupt enable (INTP)
) is being performed, and when the count value set in the timer F register TMFR is counted based on the reference clock, an internal interrupt rNT-P is generated and step #
After changing the output of the PWM output boat 47 from the off state to the on state at step 40, 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. 8 and α when not energized. By determining the FF, it is possible to appropriately control the driving and stopping of the scanning optical system 3 to 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.

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. The present invention can also be applied to control the operation of a scanner in an image reading device other than a copying machine.

(Effects of the Invention) According to the present invention, the control means for controlling the duty of the motor energizing pulse so that the scanning system reaches a predetermined speed is controlled at a predetermined speed based on the detection information of the moving speed of the scanning system by the speed detection means. It calculates the acceleration when energized and the acceleration when not energized at a point in time, and controls the speed of the scanning system based on that.
Since the relationship between the two accelerations includes information on the load torque that the scanning system has at the speed at the predetermined time and the corresponding required driving torque, the load on the scanning system at that time is The scanning speed can be set appropriately in response to the torque at all times, and the accuracy is much improved compared to step-by-step control that requires memorizing control patterns, and it also stores a huge amount of data. Since this is not necessary, it is advantageous in terms of control.

[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 INT-H, and FIG. 11 is a flowchart showing the subroutine for internal interrupt INT-F. Scanning optical system motor...--Encoder microcomputer---------1--PWM output port timer unit 33...--11--・・・・・・−・47−・ Drive circuit

Claims (1)

[Claims] (1) In an image scanning device that scans and copies or reads images using a scanning system driven by a motor, a control means for controlling the duty of motor energizing pulses so that the scanning system scans at a predetermined speed; system speed detection means, the control means calculates the acceleration when the scanning system is energized and the acceleration when it is not energized at a predetermined point in time when the scanning system operates based on the speed information from the speed detection means; An image scanning device characterized in that a parameter for controlling the speed of a scanning system is determined based on.