JPH02159991A - Constant speed controller of motor - Google Patents

Abstract

PURPOSE:To facilitate arbitrary setting of the frequency of a motor driving pulse by a method wherein the speed of the motor is identified by an encoder pulse generated synchronously with the rotation of the motor and the duty of the motor driving pulse generated separately is controlled in accordance with the result of the identification to perform the constant speed control of the motor. CONSTITUTION:A DC motor 30 is linked with the rotary shaft 29 of pulleys 23 by a deceleration gear 31 and a timing belt 32. Further, an encoder 33 is linked with the rotary shaft 30a of the motor 30 to generate a pulse synchronously with the rotation of the motor 30. In other words, a pulse generating means which generates a pulse synchronously with the rotation of the motor 30 is provided. Further, a means which compares the duration of the pulse generated by the pulse generating means with a target pulse duration corresponding to the target speed of the motor 30 and makes calculation and a control means which controls the duty of a motor driving pulse generated separately in accordance with the results of the comparison and calculation so as to obtain the target speed are provided. With this constitution, the motor driving pulse having an arbitrary frequency can be employed separately from the pulse generated synchronously with the rotation of the motor 30.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a constant speed control device for a motor, and more specifically to a motor that moves at a constant speed, such as a scanning system that scans an original image in a copying machine. This invention relates to a constant speed control device for a motor that drives a mechanism that requires the following.

(Prior art) Conventionally, in order to control the speed of the motor that drives the scanning system of a copying machine, encoder pulses synchronized with the rotation of the motor are
This is converted, compared with a reference voltage corresponding to the target speed, amplified, and then subjected to pulse width modulation processing to be used as an energization signal to the motor, which is used in actual machines.

Another method that has been adopted in actual equipment is one that inputs encoder pulses that are synchronized with the rotation of the motor into a calculation means, compares and calculates them, and obtains an energization signal that is synchronized with the encoder pulses to control the speed of the motor. ing.

(Problem to be solved by the invention) However, in the above-mentioned conventional device, the timing of energizing the motor is synchronized with the encoder pulse generated in synchronization with the rotation of the motor, and the maximum magnification is Since the pulse width of the encoder pulse becomes longer, low-frequency noise called "peeler" is generated. Furthermore, since the pulse width of the encoder pulse differs depending on the magnification ratio, low-frequency noise of different sounds depending on the magnification ratio is generated, which may be unpleasant to the ears.

Furthermore, the long energization cycle makes it impossible to precisely control the speed of the motor, and constant speed control tends to become unstable.

Therefore, the present invention determines the speed of the motor using an encoder pulse that is generated in synchronization with the rotation of the motor, and controls the duty of a pulse for energizing the motor, which is different from the encoder pulse, according to the result of this determination to maintain the motor at a constant speed. It is an object of the present invention to provide a motor speed control device that can freely set the frequency of motor energizing pulses to reduce noise and improve the stability of constant speed control.

(Means for Solving the Problems) In order to achieve the above objects, the present invention provides a pulse generating means that generates pulses synchronized with the rotation of a motor, and a pulse generating means that generates pulses that are synchronized with the rotation of a motor, and a pulse generating means that generates a pulse with a target pulse width corresponding to a target speed of the motor. Compare with
The present invention is characterized by comprising a calculation means and a control means for controlling the duty of another motor energizing pulse in accordance with the results of the comparison and calculation so as to obtain the target speed.

(Function) In the above configuration of the present invention, the calculation means compares and calculates the pulses generated from the pulse generation means in synchronization with the rotation of the motor with the target pulse corresponding to the target speed, so that the speed of the motor is adjusted to the target speed. It is determined by comparing with The control means controls the duty of another motor energizing pulse according to the result of this determination, but regardless of the frequency of the motor energizing pulse, the motor approaches the target speed and returns to a constant speed depending on the duty setting. can be controlled. Therefore, it is possible to use pulses of a high specific frequency that can be used as an energization signal for constant speed control and that can finely control the speed of the motor.

(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 pulley 22, and then the end plate of the second moving table 8 The hook is turned around a pulley 24 provided on the outer surface and folded back, and its end 21c is fixed to a fixing member 25. Part 2 of 23 pulleys
The hook 1d is turned on the lower side of the pulley 23, and then the hook is turned and folded back on the pulley 24 of the second moving table 8, and the end 2
1e is fixed to a fixing member 26 via a tensile spring 27.

In addition, the boot 1 of the portion 21a of each wire 21 on the pulley 22 side
It is fixed to the first movable base 4 at a part between the IJ22 and the IJ24. 28 indicates the fastening portion. Boo I
A DC motor 30 is connected to a reduction gear 31 on the rotating shaft 29 of J23.
, are connected via 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 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.
The first to fourth mirrors 6 are moved at a speed of 1/n (n: copy magnification), which is the same speed as the mirror 1, and scan the original image on the document table glass 1 in a range corresponding to the copy size and magnification. .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 moving table 8
When the wire 21 is driven in the direction of the arrow, the pulley 23 becomes shorter as the portion 21a on the pulley 22 side becomes shorter.
Due to the movement of the example part 21d becoming longer, Boo IJ
24 at a speed of 172n in the direction of arrow C, keeping the light exposure length of the scanning optical system 3 constant during scanning.

The photosensitive drum 2 is surrounded by an eraser lamp, a charger, a developing device, a transfer charger, and a cleaning device (not shown). 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 photoreceptor 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-Tr4. The transistors Tr1 and Tr3 are turned on when the base voltage is "low", and the transistors Tr, Tr4 are 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.

Each of the transistors Trl to Tr4 has a diode D.
I''' D a 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.
The input side of the D gate AND, and the transistor Tr,
A is connected to the base of A through an inverter I.
ND game) ANDt input side 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 input sides of the D gates AND and ANDt. The output side of the AND gate ANDI is a transistor T.
The output side of the AND gate AND2 is connected to the base of the transistor Tr.

The on/off state of each transistor Tr, ~Tra depending on the combination of input signals to each input terminal 35a, 35b,
Table 1 below shows the on/off states of the motor 30 and whether the motor 30 is in forward or reverse direction when on.

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

The microcomputer 41 includes CPU42, ROM43, and RAM4.
4, an input port 45, an output port 46, a Pth 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 XF that directly counts the encoder pulse e as position information of the first moving table 4, and also has a counter XF 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 FDC that makes the counter XF count by 4 each time the interrupt occurs. There is no need to count XP, and the software processing time will be in time. Note that the encoder pulse e is the output PG from the encoder 33 and the waveform shaping circuit 1
At step 50, the signal is converted into a rectangular wave and input to the microcomputer 41.

The input port 45 receives the image magnification signal MAG from the mask.
, a scan start request signal 5CAN, and a signal 110MB 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 SCAM is normally "low" and becomes "high" when a scan start request is issued. Signal HOMII! is set to "high" only when the scanning optical system 3 is at the home position, and is set to "low" at other times.

The output boat 46 outputs a forward/reverse rotation signal f of the motor 30, which is input to the input terminal 35a of the drive circuit 51 shown in FIG. The oscillation circuit 50 is connected to the PWM output boat 47.
A PWM pulse for constant speed scanning control with a frequency obtained by dividing the system clock fCL generated by For deceleration return control following power return, the duty of the pulse is set to 1.
00%, a PWM motor energizing pulse d, which is a pulse whose off time is controlled by an interrupt performed by a timer setting, is output based on the on and off edges of the encoder pulse e (Fig. 4), and this is shown in Fig. 2. The input terminal 35b of the drive circuit 51 is manually inputted. These inputs cause the motor 30
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 ■, 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 is finished 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 O 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, an energizing pulse d is input with an on-time tON set to the on-edge of the next encoder pulse (FIG. 5(a)).

This energizing pulse d is obtained by an internal interrupt INT-F set by a timer from an interrupt INT-E caused by each on/off edge of the encoder pulse e. Accelerated scanning (A)
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. On the other hand, the motor 30 can be strongly accelerated by sufficiently long and strong energizing torque. As the speed approaches the target speed V for constant speed scanning B, the interval between encoder pulses e becomes smaller, and the off time t of the on time toH decreases. 1
．． As the ratio to

When the target speed V reaches point F in FIG. 4, 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, and as will be described in detail later, the acceleration α during energization when the target speed V is reached. N and acceleration α when not energized. FF
Then, PWM is calculated using these two parameters as
The motor energization pulse weight 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-8 by each edge off (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" 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, the shaft 30a of the motor 30 is rotated by this movement, and the motor 30 and the diode D are rotated.

A back electromotive force in the direction opposite to the arrow a is generated in the closed loop of the transistor Tr, and the motor 30 rotates in the scanning direction a.
applies a brake to the rotation of. This is what is called regenerative braking.

On the other hand, the input terminal 35a is "low" and the input terminal 35b is "1".
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. The braking force produced by this regenerative brake is relatively weak, and the scanning optical system 3 is gradually decelerated. When deceleration progresses and the interval between encoder pulses e becomes longer than the off time, forced braking is also activated in addition to regenerative braking, 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 (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 (II) 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. 4 1 when the scanning ends during the return. The position of the first movable platform 4 during return is determined by subtracting the count value xof up to, and the predetermined brake start position (
The determination is made when the count value xlf 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 xlf, 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 detail, the timer unit 49 of the microcomputer 41 counts the frequency divided by four of the system clock fcLII manually input from the oscillation circuit 50 by the sono free run counter FRC as a reference clock, and also counts the frequency divided by four as a reference clock. Generates an external interrupt signal INT-E by detecting each on/off edge of the pulse e, captures the value of the free run counter FRC at the time of detection into the register 48, and determines the pulse width of the encoder pulse e based on the count value. This is the speed detection information of the L motor 30.

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 VP 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 vP 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 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 this PWH is 2'! and
The pulse width duty PWMduty is further determined by the timer unit 49 using the TMF register ↑MFH, and when the value set in this register TMFR is counted, the timer unit 49 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 energizing the PWM motor energization pulse-remotor 30 at the target speed V
The difference between the acceleration αOFF when ON and when the current is turned off is the 6th
If ΔV as shown in the figure, in order to reach the target speed V during the PWM motor energization pulse cycle, if the PWM motor energization pulse cycle is TP and the ratio of the energization on time to this TP is Y, then (rQ14 H'1-TpΔV = αoFF(l
Y) Tr =-=-■ holds true. Therefore Y
Hato becomes.

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

At this time, if the speed error is Δ■, 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 When TSI is assumed, the time from 0 to reach is approximately TSI/2,
The number N of PGIM motor energizing pulses d during this time is given by the pulse width TSI, and the speed V when the pulse width is TSI is TSI from Ro and G of the formula
G.R.

becomes. Similarly, when the speed error is ΔV, the speed v0 has a pulse width of TM. 8.

Therefore, it is preferable to correct the value obtained by dividing the speed error ΔV in equation 0 by N by one PWM motor energization pulse-utility adjustment. The PWM motor energization pulse-on ratio Y at this time is as follows.

Considering the speed error Δ■ 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 INT and E, so as shown in FIG. Governing the measurement pulse width at 8. Become a target. Therefore, the speed error ΔV is expressed as ΔV.

As a result, the PWM motor energization pulse-on ratio changes from type 0 to GR6TM. It becomes 8.

TM in the denominator of the second term on the right side of this [phase] equation. , 4ζ
Considering TSI, the on-ratio Y of the PWM motor energizing pulse d□ is calculated from the [phase] formula as follows: αON+αorr αON+αOF
It becomes F.

The width of the encoder pulse e is determined by the count by the free run counter FRC inside the CP[I42, and the free run counter FRC is determined by the count of the free run counter FRC in the system clock fcLll.
Since the frequency division is counted as the reference clock, the law of the second term on the right side of Equation 0. N, TSI as free run counter FRC
The count value TM. When expressed as Nf 5TSIf, it becomes.

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

22.0 On the right side of the equation, the first term = CBIAS, the second term
Assuming PRATB, PWMRomo CBIAS 10 PRATIl! (TM.s
fTSIf) ・・・−・−■.

Next, the acceleration αON when the motor is energized and the acceleration α when the motor is not energized at the target speed V at point (P) in FIG. A method for finding FF 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 utility up to 100%
, the full power is turned on, and from the time of K, the PW is set to 4 at the time of detecting the edge of the next encoder pulse.
The acceleration is measured by prohibiting the energizing pulse-steel force of the M motor and keeping it in a non-energized state.

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

TSI Δtz= Approximately, it becomes as follows.

G.R.

Here, in the denominator of the formula [phase], TSIIζTSI, therefore [phase], α of ■2. 8. Substituting CBIAS and PRATE in equation 0 using αOFF gives the following equation.

Furthermore, if the speed changes from vl to vt at point 4, the acceleration (α. FF>O) at this time is the same as above.
, the [phase] formula is the count value T of the free run counter FRC.
GR is expressed as SIf, TSllf, and TSTzf.
.

Here TSIIζTSI in the denominator, TSI! ζ
TSI.

becomes.

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. Is this the internal I? A.M.
44, clear the PWM register PWl'lR, etc.
The output state of the PWM output boat 47 is turned off and the motor energization signal d is set to "O". This d=o 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. Here, the process waits until a scan request signal 5CAN is received from a mask (not shown). When the scanning request signal SCAM 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 performed using the clock of the free run counter FRC as a reference.

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. xof is the length calculated from the paper size PSIZE and the magnification M, and the preliminary scanning amount XHII! (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.

a= −・・・・− [phase] GR
0, so the scanning length xof converted to the pulse count value at the magnification M is V.

becomes. Further, if the distance from the home switch 34 to the time point when braking is started is x1, the pulse count conversion value x, fc at the distance of X is obtained from the [phase] equation. 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 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, the memory t of the energization off time for the acceleration scan (A) control is stored. □ has a predetermined value T. Set F□. This is used in the interrupt subroutine of external interrupt INT-H shown in FIG.

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 boat 47, that is, sets d=1, and starts energizing the motor 30.

In step #9, set MODE+1 to accelerate scanning (A)
In the following step #10, the external interrupt INT-E is enabled by the 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 XF 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.

Continuing (In step #13, it is determined whether the calculated scanning length has been scanned or not based on whether the count value χf of the counter Proceed to step #14,
The forward/reverse rotation signal f is set to "0" to create a braking state by reverse rotation drive in the normal rotation state.

Next, in step #15, a predetermined value TOWWt that determines the brake force is set in the off-time memory tOFF, and in step #16, MODE is set to 2 and 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 based on whether xf=x1f, and if xf=x, f reaches the brake start time, the process proceeds to step #18 and sets the forward/reverse signal f to 1. to set the 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. FFff is set in the off time memory tOFF, and in step #20 MODII!
= 3 to set the deceleration mode at the end of return.

Next, the process proceeds to step #21, and the scanning optical system 3 reaches the home position (HO?). If! It is determined whether MODE = 1, and if it has been reached, the process proceeds to step #22. In step #22, it is determined whether MODE = 4. This mode is an external interrupt INT-II! It is set in the subroutine and means the end of return. If MODB=4, the process moves to step #23, where the output of the PWM 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.
TSIf for constant speed return corresponding to is calculated. Therefore, calculations of χ, f, x, and f are not performed here.

Next, in step #27, the forward/reverse signal f is turned on 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. , F is a predetermined value T that determines the braking force for constant speed return. FF4 is set. In the following step #32, home switch 3
4 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 "1" and step # As in the case of #18 to #20, the brake operation is performed by forward rotation drive during reverse rotation. However, in this case, a predetermined value TOFFI is set in the off-time memory tOFF to determine the braking force in this case. 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 scan (B) control mode (MODE=0''), the process proceeds to step #55. If so, proceed to step #80, otherwise proceed to the next step #56 to perform accelerated scanning (A
) control mode (MODB-1) is determined.

If the control mode is accelerated scanning (A), the process moves to step #60 and the state ST in the accelerated scanning (A) control mode is determined. If 5T=O, the process moves to step #61 and the measured pulse , it is determined whether the width Tl is less than or equal to TSIf calculated in the main routine. In other words, target speed■
If it has not reached step #65, the PWM register PWMR is set to 409.
6 is set to set the PWM motor energization pulse duty to 100% and turn off the output state of the PWM output port 47.

In the following step #66, T calculated in the main routine is
Turn off the timer F register TMF of the 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 equal to or higher than the target speed V (Ti≦TSIf) in step #61, the process moves to step #62 and accelerates scanning (A).
Increment the state ST in the control mode of
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. ,4,α. 27 enters the measurement mode.

If 5T=O is not found 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 the pulse width Ti measured at the current time is stored in the memory tsi, f- of TSI, f 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 the next step #74
Disables internal interrupts by timer F.

If 5T is not 1 in step #70, step #75
Clear ST to "O'" and set the measured pulse width Ti at the current time to TSI in the following step #76.
! f memory ts1. Store in f.

Next, in step #77, the pulse width TSIIf when the motor is energized and the pulse width TSI when the motor is not energized are determined using the method described above.
! α than f. Calculate N, αOFF, and from this CBrA
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, and Ti is the pulse width T3□ corresponding to the control end speed of deceleration scanning (C).
. 1 or more, that is, whether the speed of the scanning optical system 3 has become less than or equal to 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) is present. 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, proceed to step #83 and proceed to full power return mode (MODE=3).
f! -5'), and in the subsequent step #84, the P register PHMR is set to 4096, that is, the duty is set to 10.
Full power return is started by setting the timer F to 0% and turning on the PWM output port 47. Then, in step #85, interrupts of timer F are disabled.

In addition, in step #56, the acceleration scanning (A) control mode (M
ODB=1), move to step #57,
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 #90
Then, the pulse count value xf of the counter χF that is being returned is decremented by four in cooperation with the frequency dividing circuit FDC, and then the main routine is returned.

If the gate σDE=5 is not determined in step #58, therefore, in the return end mode (MODE=4), the process returns directly to the main routine.

In step #54, the constant speed scanning (B) control mode (MOD) is selected.
i! = 0), proceed to step #58 and set the value calculated from the difference between CBIAS, PRATE and the target pulse width TSIf calculated in the above method and the current measured pulse width Ti in the PWM register PWMR. 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 (JNTP enabled) and the count value set in the timer F register TMFR is counted based on the reference clock, an internal interrupt INT-P is generated, and 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. 8 and α when not energized. .

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 synchronization with the rotation of the motor are used to determine the motor speed, and the motor energization is controlled in order to bring the motor to a predetermined speed in accordance with this determination. The motor energization pulse is set separately and its duty is controlled according to the motor speed judgment result to control the motor at a constant speed.The motor energization pulse is a pulse generated in synchronization with the rotation of the motor. Separately, it is possible to use pulses of any desired frequency, which produces less noise, and by adopting pulses for energizing the motor with an appropriate frequency that can finely control the speed of the motor, noise is reduced and the scanning system of the copying machine is driven. It is possible to eliminate the problem of different sounds being emitted depending on the high magnification and improve the stability of constant speed control of the motor. And the pulse for energizing the motor is PWM.
If a one-chip microcomputer with an output port is used, the present invention can be realized at low cost with simple equipment and software processing.

[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 period of the PWM motor energizing pulse, Figure 8 is a diagram explaining the method of detecting each acceleration when energized and de-energized at the target speed point in scanning, FIG. 9 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. Motor encoder microcomputer P output boat timer unit drive circuit

Claims (1)

[Claims] (1) Pulse generating means for generating pulses synchronized with the rotation of the motor, means for comparing and calculating the pulse width with a target pulse width corresponding to the target speed of the motor, and means for generating pulses corresponding to the results of this comparison and calculation. 1. A constant speed control device for a motor, comprising: control means for controlling the duty of a pulse for energizing the motor to obtain the target speed.