JPH0434730B2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a scanning system that is reciprocated by a DC motor,
For example, the present invention relates to a method for controlling the deceleration of a scanning system for slit exposure of an original image onto a photoreceptor in an electrophotographic copying machine.

Prior Art Generally, the image scanning system in an electronic copying machine is
After being driven in the forward direction in various scanning modes depending on the size of the original or copy paper or the copying magnification, that is, at various scanning speeds and scanning distances, it is driven in the backward direction from the forward end position. It is designed to return to the forward movement starting position.

Conventionally, in order to shorten the time required for the backward movement, the machine was driven at full power during the backward movement, and a fixed switch installed in the middle of the scanning path started braking from the moment the scanning system was turned on to control the braking force. to return it to its normal position.

Such a scanning system must be able to accurately return to its home position. If the stop position of the scanning system varies, it is necessary to provide a sufficient preparatory movement distance for the start of the next scan, which results in negative effects such as an increase in the size of the scanning device and an increase in the reciprocating movement time. It is.

Problems to be Solved by the Invention If the same braking force can always be obtained in order to return the scanning system to its home position, it is necessary to use the same timing when the scanning system returns from a predetermined forward movement end position. You can control it with. However, in reality, the braking force itself changes due to increases in temperature of the motor and driver elements, so if braking is performed at the same timing, the stop position of the scanning system will vary.

Purpose The present invention has been made in view of the above-mentioned problems, and the object thereof is to provide a system that has a simple configuration and is capable of controlling braking during each backward movement of a scanning system that is reciprocated multiple times in a scanning mode in which the scanning distance is the same. An object of the present invention is to provide a method for controlling the deceleration of a scanning system by correcting the timing and returning the scanning system to a normal position.

Means for Solving the Problems In order to achieve the above object, the scanning system deceleration control method according to the present invention provides a scanning system deceleration control method according to the present invention. is a scanning system deceleration control method in which the scanning system is driven in the backward movement direction from the forward movement end position, and then is braked at a predetermined deceleration timing to return to the forward movement start position. The speed of the scanning system at the movement start position is measured, and if this measured speed is faster than a predetermined speed, the next deceleration timing is determined according to the measured speed, while the measured speed is slower than the predetermined speed. In this case, the next deceleration timing is determined in accordance with the distance from the position where the speed of the scanning system has been decelerated to the predetermined speed to the forward movement start position.

DESCRIPTION OF THE PRINCIPLE OF THE INVENTION Before explaining the embodiments, the principle of the idea of the present invention will be explained here.

FIGS. 1 and 2 are graphs showing speed changes during backward movement of the scanning system in the control method according to the present invention, and the broken line shows speed changes during optimal deceleration, which is the purpose of control. After scanning, the scanning system starts a backward movement and returns while accelerating, and then starts braking after a certain delay (DELAY) after turning on the brake switch. Then, after sufficiently decelerating, it returns to the home position, comes into contact with a damper material, etc., and stops. Further, the scanning system starts the next forward movement as necessary.

During the above return movement, the speed at the home position
V'home becomes important. This is because if V'home is too early, the damper material will not provide stable deceleration, causing the vehicle to deviate from the home position and stop, or abnormal vibrations to occur during the next forward movement, making it impossible to obtain a good image. . On the other hand, if it is too slow, the time required for backward movement will be longer and the copying speed will be lowered.

Therefore, in the present invention, the speed V'home at the home position of the scanning system is (always) controlled to a predetermined speed Vhome even if the braking force fluctuates.

FIG. 1 is an example of correction based on distance measurement. That is, as shown by the solid line, the scanning system turns on the brake switch and moves a certain distance (DELAY) before applying braking. After that, it is assumed that the scanning system decelerates to a predetermined speed Vhome before reaching the home position, and while further decelerating, reaches the home position at the deceleration V'home.

At this time, measure the distance (Δx) from the predetermined speed Vhome position to the home position, add this (Δx) to (DELAY), and apply braking according to the corrected (DELAY) during the next return movement. As shown, the speed at the home position is the specified speed.
Become Vhome. Measurement speed V'home is the specified speed
Correction is possible even if the damper is faster than Vhome and (Δx<0), but in general it is not possible to take a large value (Δx) because the damper contacts the damper immediately.

In such a case, as shown in FIG. 2, correction can be made using the velocity V'home at the home position. Basically, find the distance (Δx) until it is decelerated to a predetermined speed Vhome after deceleration (DELAY)
Correct to. (Δx) is the measured velocity when approximated by assuming that the acceleration (α) near the home position is constant.
It is determined by V'home, and becomes -Δx=f(V'home) =-(V'home) ² /2α...Equation (1). Correction by fV'home is [V'home＜
Vhome] is also possible, but V'home
As the difference from Vhome increases, (α) also changes, making calculations more complicated.

Actually, when used to control the scanning system of a copying machine, the optimal (DELAY) is unknown, so the first
As shown in the figure, clearly [Vhome>V'home]
(X ₀ ) is used as the initial value of (DELAY). This increases the first round trip time, but the image is good, and from the second time onwards, the measurement speed
By repeating the above control according to V'home, the optimum deceleration operation or an operation extremely close to it can always be obtained.

Embodiments Hereinafter, embodiments of the scanning system deceleration control method according to the present invention will be described with reference to the accompanying drawings.

This example is applied to an electrophotographic copying machine.
In Fig. 3, 1 is a scanning system including an illumination system, and 2 is a scanning system including an illumination system.
is a DC motor (scan motor), and the scanning system 1 is reciprocated by this DC motor 2, that is, forward movement in the direction of arrow A (hereinafter referred to as scan) and backward movement in the opposite direction (hereinafter referred to as return). be done.

3 is an encoder composed of Hall elements,
It is installed on the rotating shaft of the DC motor 2 and generates a pulse signal proportional to its rotation speed.
can be detected at a speed of

Reference numeral 4 denotes a home switch, which detects whether or not the scanning system 1 is at the home position (scan start position), and emits an on signal when it is at the home position, and otherwise emits an off signal. When it is detected by this detection signal that the scanning system 1 is not at the home position at the start of scanning, control is performed to return the scanning system 1 to the home position. 5 is a brake switch that detects that the scanning system 1 has reached a predetermined position when returning;
In the flowchart described later, this is used as a reference position detection means for the braking start timing during backward movement.

FIG. 4 is a block diagram of a control circuit for controlling the movement of the scanning system, and 20 is a microcomputer for controlling the scanning system. The copying machine has various control objects in addition to the scanning system, and these are controlled by a microcomputer (not shown), hereinafter referred to as a master.

The microcomputer 20 includes a central processing unit (CPU), read-only memory (ROM), random access memory (RAM),
Input port (INPUT), output port (OUTPUT), counter Tf, timer register Tw
(INPUT) receives control request signals (MAG), (SCAN), and (BRAKE) from the master.
is input. A signal (MAG) indicates the selected magnification, and this signal sets the scanning speed.
The signal (SCAN) indicates forward movement when it is “1” and backward movement when it is “0”. The signal (BRAKE) becomes "1" while the scanning system 1 turns on the brake switch 5 during backward movement.

A motor drive signal D and a forward/reverse signal F are output from (OUTPUT) to the switching circuit 21, thereby controlling the DC motor 2.

(CPU) has two interrupt terminals, and one terminal receives the output of the encoder 3 from the waveform shaping circuit 22.
Encoder pulses shaped by are input. The other terminal is connected to a timer register Tw, and a timer value (Tw), which will be explained in the flowchart described later, is set in the timer register Tw. Timer register Tw is this timer value (Tw)
and the reference time Tf of the counter Tf that counts the reference pulses of the external reference oscillator 23, and when they match, an interrupt signal is input (to the CPU).

FIG. 5 shows a specific example of the switching circuit 21.

The DC power supply E is connected to the DC motor 2 through bridge-connected transistors (Tr ₁ ) to (Tr ₄ ), and the diodes D ₁ to _{D 4} connect each transistor (Tr ₁ ) to form a bypass for the back electromotive voltage. )~(Tr ₄ )
are connected in parallel.

Input terminal 9a receives forward rotation signal “H” and reverse rotation signal “L”.
“ is input, and gate (AND ₁ )
It is connected to the input side of the AND gate ( _AND2 ) and _the base of the transistor ( _Tr3 ) via the inverter I. The other input terminal 9b has an on signal “H” and an off signal “L”
is input, and gate (AND ₁ ),
(AND ₂ ) is connected to the input side.

Further, the output side of the AND gate (AND ₁ ) is connected to the base of the transistor (Tr ₂ ), and the output side of the AND gate (AND ₂ ) is connected to the base of the transistor (Tr ₄ ).

In the above configuration, in the forward rotation mode FD, the transistor (Tr ₃ ) is turned on when the input terminal 9a is "H", and the AND gate (AND ₁ ) becomes "H" when the input terminal 9b is "H". Transistor ( _Tr2 )
is turned on, current flows in the direction of arrow a, and motor 2 rotates in the normal direction. In addition, in the reverse mode RD, the input terminal 9a switches to "L" and the transistor (Tr ₁ ) turns on, and when the input terminal 9b goes "H", the AND gate (AND ₂ ) becomes "H" and the transistor turns on. (Tr ₄ ) is turned on, current flows in the direction of arrow b, and motor 2 rotates in reverse.

On the other hand, in the brake mode (FS), input terminal 9a is set to "H" and input terminal 9b is set to "L" at the time of return.
to turn on only the transistor (Tr ₃ ). In this case, the power to the motor 2 is cut off, but the arrow a that attempts to reverse the rotation of the motor 2
A back electromotive force is generated in the direction. This back electromotive voltage flows through the transistor (Tr ₃ ), the motor 2, and the diode D ₁ , and brakes the motor 2 against reverse rotation, that is, regenerative braking is applied.

Note that the diodes D ₁ , D ₂ , D ₃ , and D ₄ cut off the back electromotive force during forward rotation and the back electromotive force generated when switching modes, and the transistors (Tr ₁ ), (Tr ₂ ), and (Tr ₃ ) ,
(Tr ₄ ) to prevent abnormal voltage from being applied.

Here, the feature of the present invention is that during each return movement of the scanning system that is reciprocated multiple times in a scanning mode in which the scanning distance is the same, the timing at which braking is applied to the scanning system 1 that is returning at full power. is successively corrected using data measured during braking on the previous return, and braking is started at the optimal timing.
The principle is as described above with reference to FIGS. 1 and 2.

Here, specific control will be described.

6, 7, and 8 are flowcharts explaining the control of the microcomputer 20,
FIG. 6 shows the main routine, FIG. 7 shows the routine for external interrupt (INT-N) caused by encoder pulses, and FIG. 8 shows the routine for timer interrupt (INT-NT) caused by timer register Tw.

First, the main routine shown in FIG. 6 will be explained.

When the reset is applied, the motor drive signal D is set to "0" in step (1s). D=0 corresponds to the "L" state of the input terminal 9b in the switching circuit of FIG. 5, and D=1 corresponds to the "H" state.

Next, in step (2s), the braking timing (DELAY) is set to an initial value (X ₀ ).

Furthermore, in step (3s) it waits until there is a scan request from the master, and when a scan request (SCAN = 1) is issued, it inputs the copy magnification (MAG) in step (4s), and responds to the copy magnification in step (5s). Calculate the reference encoder pulse interval (Ts) to control the scan speed. This reference encoder pulse interval (Ts) is obtained by multiplying the preset encoder pulse interval (To) at the same magnification by the copying magnification.

Subsequently, in step (6s), the forward/reverse rotation signal F is set to "1". F=1 corresponds to the state where the input terminal 9a is "H" in the switching circuit shown in FIG.
0 corresponds to the "L" state.

Following this, the scanning system 1 starts forward movement by setting the motor drive signal D to "1" in step (7s).

In step (8s), the counter (SYNC) for synchronizing the encoder pulse and the interrupt routine is set to "2", and the processing mode in the interrupt routine is set to constant speed control mode, that is,
(MODE) to "1" and enable interrupts in the following step (9s). From the permission of this interrupt, the control of the scanning system 1 is handled by the interrupt routine.
In the main routine, the scan request (SCAN) is “0”
Wait in step (10s) until

Note that the time for (SCAN = 1) depends on the size of the copy paper,
This is determined on the master side depending on the copy magnification.

When (SCAN = 0), in step (11s) the motor enters the speed measurement mode, that is, (MODE) is set to "0", in step (12s) the motor drive signal is turned off, and in order to make a return motion, step ( At step (13s), the forward/reverse signal is set to reverse (F=0), and at step (14s), the motor drive signal is turned on (D=1). The reason why the interrupt processing is switched to a constant speed measurement mode is that once the interrupt processing is interrupted, synchronization with the encoder pulse must be achieved again in the next interrupt processing, which causes a delay in control. When the drive is turned on, the scanning system 1 starts returning to the home position. At this time, the central processing unit (CPU) does not perform any control, so acceleration continues.

After this, in step (15s), the scanning system 1 enters a standby state until the brake switch 5 is turned on, in other words, until the scanning system 1 returns to the position of the brake switch 5, which is the reference position for deceleration control. When the brake switch 5 is turned on, in step (16s), the complement of the current deceleration control timing (DELAY) is set in the counter (POS) that measures the amount of movement of the scanning system 1, and the external interrupt routine (INT-
E) Set the process to encoder pulse counting mode, that is, set (MODE) to "3". The external interrupt routine (INT-E) adds "1" to the counter (POS) for each encoder pulse. Therefore, the scanning system 1 is connected to the brake switch 5.
If you move by (DELAY) after turning on, the counter (POS) will be zero. When this is detected in step (17s), the reverse rotation drive is turned off (D=0) in step (18s), and the forward/reverse rotation signal is set to normal rotation (F=0) in step (19s). As a result, regenerative braking is applied to the motor 2, and the scanning system 1 starts decelerating.

Thereafter, the main routine starts checking the current deceleration state. That is, in step (20s), a flag (FAST) for checking whether or not the braking start timing is early is cleared. Then, in step (21s), the external interrupt routine (INT-E) is set to the mode for timing check, that is,
Set (MODE) to “2” and step (22s)
The scanner is in a standby state until the home switch 4 is turned on, in other words, until the scanning system 1 returns to the home position. When the home switch 4 is turned on, interrupts are prohibited in step (23s) and processing of the external interrupt routine (INT-E) is stopped. At this time,
At step (24s), determine whether the flag (FAST) is “0” or not, and set the deceleration start timing (DELAY).
Correct. First, if the flag (FAST) is "0" and the timing is slow, in step (25s), correction is made according to the speed of the home position using equation (1) described above. However, the encoder pulse interval (Ti) corresponding to the measurement speed is used. On the other hand, if the flag (FAST) is “1” and the timing is early,
Correction is made based on the difference between the position (TMPRG) at which the speed has been decelerated to a predetermined speed at the home position in step (26s) and the count number (POS). When the correction is completed, the process returns to step (3s) and is ready to start scanning. In this way, the control of the main routine is extremely simple.

Figure 8 shows the timer interrupt routine (INT-T)
This routine is processed by interrupting the main routine every time the timer value (Tw) set by the external interrupt routine (INT-E) times up. In other words, when a timer interrupt occurs,
In step (31s), the motor drive signal D is set to "0".

Next, the external interrupt routine (INT-E) will be explained using FIG. This routine is processed by interrupting the main routine every time a pulse is generated from the encoder 3 that detects the rotation of the motor 2.

When an interrupt occurs in FIG. 7, first, in step (41s), the value Tf of the counter (Tf), which is the reference time in the microcomputer 20, is set in a register (Tc) in a predetermined area of the random access memory (RAM). Copy to. Therefore, the register (Tc) indicates the current pulse generation time (Tc) of the encoder 2.

Next, at step (42s) counter (SYNC)
Determine the value of , and if it is other than zero, step (43s)
``1'' is subtracted from the counter value. This counter (SYNC) is used to synchronize the encoder pulses and the interrupt routine. Since at least two encoder pulses are required to determine the pulse interval of encoder 3, the calculation result of the pulse interval between them is invalidated. It is set for the purpose of In this embodiment, the initial value of the counter (SYNC) is set to "2" in order to ignore even the first pulse.

In step (44s), the pulse interval (Ti) of the encoder 3 is determined. This operation is a step (41s)
Current encoder pulse generation time (Tc) and previous encoder pulse generation time (Tp) set in
It can be obtained by taking the difference between The previous encoder pulse generation time (Tp) is stored in the register (Tc).
Similarly, it is stored in a register (Tp) set in random access memory (RAM), and is updated by copying the current encoder pulse generation time (Tc) to the register (Tp) in the next step (45s). be done.

In the next steps (46s), (47s), and (48s), mode determination is performed. In this example, the mode speed measurement mode (MODE=0), constant speed control mode (MODE=
1) Timing check mode (MODE=2)
and pulse counting mode (MODE=3).

In the speed measurement mode (MODE=0), the speed measurement in steps (41s) to (45s) is performed and the process immediately returns to the main routine.

In the case of constant speed control mode (MODE=1), the on time (Ton) of the motor 2 for a predetermined speed is calculated in step (49s). Here, the on time (Ton) is the difference between the encoder pulse interval (Ti) measured during the on time (Ttyp) set corresponding to the predetermined speed and the reference encoder pulse interval (Ts) for the predetermined speed. It is obtained by adding the values multiplied by (K). For (Ttyp), (Ts), and (K)K), different values are used depending on the copying magnification during forward movement.

On time (Ton) determined in this way
is added to the current time (Tf) in step (50s) and set in the timer register Tw. As mentioned above, the timer register Tw is constantly compared with the counter Tf indicating the current time, and when the two match, a timer interrupt is generated, so a timer interrupt is generated exactly (Ton) after the timer register Tw is set. Therefore, the motor 2 is turned on during this time.

In case of pulse counting mode (MODE=3),
The determination in step (48s) is "NO", and the process moves to step (55s), where only the position (POS) of the scanning system 1 is updated.

In the case of timing check mode (MODE = 2), the flag (FAST) is used to check whether the position where the speed has been decelerated to the predetermined speed Vhome has already been measured in step (52s), and if it has been measured (FAST = 1), pulse counting is performed. Mode (MODE=
As in 3), only the position (POS) is updated in step (55s). If not measured (FAST=
0) compares the pulse interval (Ti) corresponding to the current speed with the pulse interval (Thome) corresponding to the predetermined speed Vhome in step (53s), and
Check if the speed has decreased to below. If the speed of the scanning system 1 is faster than the predetermined speed Vhome, only the position (POS) is updated in step (55s). If the speed is decelerating below the predetermined speed Vhome, the current position (POS) is saved in the temporary storage register (TMPRG) in step (54s). At the same time, since the deceleration timing was too early, the flag (FAST) is set to "1". Finally, the position (POS) is updated and the process returns to the main routine.

Effects of the Invention As is clear from the above explanation, according to the present invention, the reciprocating motion can be performed multiple times in the scanning mode in which the scanning distance is the same, with a simple configuration without controlling the speed or braking force itself during the reciprocating motion. By correcting the braking timing during each backward movement of the scanning system, the optimum braking state can always be obtained.

Therefore, when reciprocating copying is performed multiple times over the same scanning distance, braking is always performed at the optimal timing, despite changes in braking force due to errors in the scanning system or drive motor, or changes in conditions. , the scanning system returns to its home position accurately.

Therefore, the stopping position of the scanning system does not vary, and as a result, the preliminary movement distance at the start of scanning can be shortened, and the scanning device can be made smaller and the copying operation time can be shortened.

[Brief explanation of drawings]

The drawings show an embodiment of the control method according to the present invention, and FIGS. 1 and 2 show the return movement of the scanning system.
Figure 3 is a perspective view of the scanning system, Figure 4 is a block diagram of the control means, Figure 5 is a motor control circuit diagram, Figures 6, 7, and 8 are control diagrams. It is a flowchart diagram of a means. 1...Scanning system, 2...Motor, 3...Encoder, 4...Home switch, 5...Brake switch, 20...Microcomputer, Vhome
...Predetermined speed, V'home...Measurement speed, Tf...Counter, Tw...Timer register.

Claims (1)

[Claims] 1. During the backward movement of a scanning system that is reciprocated multiple times in a scanning mode in which the scanning distance is the same, after driving the scanning system from the forward movement end position in the backward movement direction,
A scanning system deceleration control method that returns to the forward movement start position by braking at a predetermined deceleration timing, and measures the speed of the scanning system at the forward movement start position during the backward movement, and if this measured speed is lower than the predetermined speed. If the speed of the scanning system is faster than the predetermined speed, the next deceleration timing is determined according to the measured speed, while if the measured speed is slower than the predetermined speed, an arbitrary starting position is determined from the position where the speed of the scanning system is reduced to the predetermined speed. 1. A scanning system deceleration control method, characterized in that the next deceleration timing is determined according to the distance.