JPH0454951B2 - - Google Patents

Description

Detailed Description of the Invention Technical Field The present invention relates to a scanning device in which a scanning system is reciprocated by a DC motor, and in particular to deceleration control during the backward movement of the scanning device. It is used as a scanning device for

Prior Art Generally, the image scanning system in an electronic copying machine is
It has various scanning modes, ie, scanning speed and scanning distance, depending on the size of the original or copy paper or the copying magnification. Therefore, as a scanning device, it is necessary to control the backward movement so that the scanning system always stops at a fixed position (home position) for various scanning speeds and scanning distances. If the stop position of the scanning system varies, it is necessary to provide a sufficient preliminary movement distance for the start-up at the start of scanning, which results in disadvantages such as an increase in the size of the scanning device and an increase in the reciprocating time.

Conventionally, in order to achieve the return of the scanning system to the normal position as described above, speed control or braking force control was performed even during the backward movement. However, this makes the control complicated, and in particular, the more various scanning modes there are, the more complicated the control and configuration become.

Purpose The present invention was made in view of the above-mentioned drawbacks, and its purpose is to have a simple configuration that allows return to the normal position in any scanning mode, and to eliminate production errors and Another object of the present invention is to provide a scanning device that can easily deal with changes in each device over time.

Summary In order to achieve the above object, the scanning device according to the present invention includes a detection means for detecting the speed at each position of the scanning system, and a reference speed at each position of the scanning system during backward movement. rewritable storage means for the scanning system; speed detection values corresponding to each position detected by the detection means during backward movement of the scanning system; and storage values corresponding to each position stored in the storage means; The present invention is characterized in that it comprises a comparison means for comparing the values, and a braking start means for starting braking when the detected speed value exceeds the stored value as a result of the comparison by the comparison means.

Embodiment Hereinafter, an embodiment of a scanning device according to the present invention will be described with reference to the accompanying drawings. This embodiment is applied to an electronic copying machine, and in FIG. 1, 1 is a scanning system including an illumination system, 2 is a DC motor, and the scanning system 1 is moved back and forth by this DC motor 2, that is, indicated by the arrow A. It is possible to move forward in one direction and backward in the opposite direction.

3 is an encoder, which is installed on the rotating shaft of the DC motor 2 and generates pulses proportional to its rotation speed; the number of pulses indicates the position of the scanning system 1, and the pulse interval indicates the speed of the scanning system 1 at that position. can be detected. Reference numeral 4 denotes a home switch, which detects whether the scanning system 1 is at the home position (scanning start position), and emits an on signal when it is at the home position, and otherwise emits an off signal. 5 is a brake switch, which detects the reference position for controlling the scanning system 1 described below and the braking start position during test scanning, and issues an on signal when the scanning system 1 reaches a predetermined position. , otherwise it issues an off signal.

FIG. 2 shows a control circuit for reciprocating the scanning system 1. 6 is a microcomputer that is the central part of the control, and has readable and writable random access memory (RAM) for storing data for braking control, read-only memory (ROM), an 8-bit internal counter C, and input/output. It consists of ports (I/O), etc.

Reference numeral 7 denotes a motor control circuit, which energizes the DC motor 2 in response to signals from the microcomputer 6 in accordance with constant speed forward rotation, reverse rotation, and braking operation. A reference oscillator 8 emits fixed frequency pulses to the microcomputer 6 for measuring the pulse interval from the encoder 3. In the microcomputer 6, the pulses from the reference oscillator 8 are counted by an internal counter C, and the number of rotations of the DC motor 2, that is, the speed of the scanning system 1, is calculated from the counted value.

FIG. 3 shows a specific example of the motor control circuit 7. The DC power supply E is connected to the DC motor 2 via bridge-connected transistors _Tr1 to _Tr4 ,
Diodes D ₁ -D ₄ are connected in parallel with each transistor Tr ₁ -Tr ₄ to form a bypass for back electromotive voltage.

Input terminal 9a receives forward rotation signal “H” and reverse rotation signal “L”
is input, and is connected to the input side of AND gate AND ₁ and the base of transistor Tr ₁ , and is connected to the AND gate through inverter I.
Connected to the input side of AND ₂ and the base of transistor Tr ₃ . The other input terminal 9b receives an on signal "H" and an off signal "L", and is connected to the input sides of the AND gates _AND1 and _AND2 .

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 normal rotation mode, the input terminal 9a is "H" and the transistor Tr ₃ is turned on,
When the input terminal 9b is "H", the AND gate _AND1 becomes "H", the transistor _Tr2 is turned on, the current flows in the direction of the arrow a, and the motor 2 rotates in the normal direction. In addition, in the reverse mode, the input terminal 9a is “L”
, the transistor Tr ₁ turns on, and when the input terminal 9b goes "H", the AND gate AND ₂ goes "H" and the transistor Tr ₄ turns on, and the current flows as indicated by the arrow b.
direction and the motor 2 reverses.

On the other hand, in the brake mode, the input terminal 9a is switched to "H" and the input terminal 9b is switched to "L" in the reverse state to turn on only the transistor _Tr3 . In this case, the power supply to the motor 2 is cut off, but a back electromotive force is generated in the direction of arrow a, which attempts to reverse the rotation of the motor 2. This back electromotive voltage is
It flows through Tr ₃ , the motor 2 and the diode D ₁ , and brakes the motor 2 from reversing.

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 prevent abnormal voltages from occurring in the transistors Tr ₁ , Tr ₂ , Tr ₃ , and Tr ₄ . prevent it from being applied.

The scanning of the scanning system 1 is started in synchronization with other processes of the copying machine, such as rotation of the photoreceptor or paper feeding of the copying machine. These other processes are controlled by other microcomputers not shown in FIG. Hereinafter, this microcomputer will be referred to as the master. The two signals shown in Figure 2,
Scan and test are signals for master control and synchronization. The master issues a scan signal or a test signal as a scan request to the microcomputer 6 in order to synchronize with the predetermined timing of other processes. The scan signal is for executing an actual scan, and the test signal is for executing a test scan. Here, the test scan refers to a scan for reading into a random access memory (RAM) data on the optimum braking state when the scanning system 1 moves backward from the maximum scanning distance. The test signal is input from the master at a timing independent from other processes when the power is turned on.

That is, in this embodiment, the reference speed during braking at each position of the scanning system 1 is detected by the encoder 3 in a test scan executed when the power is turned on, and is stored in a random access memory (RAM), and then Sometimes, the detected value by the encoder 3 is compared with the stored value, and when the detected value exceeds the stored value, the DC motor 2 is braked. The position of the scanning system 1 is detected by the number of pulses of the encoder 3, and the speed is detected by the pulse interval.

The test scan is executed every time the power is turned on, and the values stored in the random access memory (RAM) are rewritten. As mentioned above, braking is performed using the back electromotive force of the DC motor 2, and the braking control start position (reference position) during actual scanning is the same as the braking starting position when the reference speed was memorized during the test scan. has been done.

FIGS. 4A to 4D are flowcharts of the control program executed by the microcomputer 6. Hereinafter, specific control will be explained in detail with reference to this flowchart.

In the microcomputer 6, when the power is first turned on, internal parameters are initialized in a step, and then the microcomputer 6 waits for a scan start signal. As mentioned above, there are two types of scanning: scanning as part of the actual copying process, which is carried out by a scan signal from the master, and test scanning, which is carried out by a test signal, for optimal data reading.

In the step, the mode flag is reset to "0", and in the step it is determined whether or not the scan start signal is a scan signal. The mode flag distinguishes between the two scans, and when it is "0" it indicates an actual scan, and when it is "1" it indicates a test scan. If the answer is ``YES'' in the step, proceed to the step.
If "NO", the mode flag is set to "1" in step, and it is determined in step whether or not the scanning start signal is a test signal. If the answer is “NO” in the step, return to the step,
If “YES”, proceed to step. That is, wait until the scanning start signal is input in steps ~,
When a scan start signal is input, it is determined whether the signal is a scan signal or a test signal, and scanning is started from step.

In this step, the motor control circuit 7 is set to constant speed normal rotation mode. As a result, the DC motor 2 is started to rotate forward at a constant speed, and the scanning system 1 starts scanning (forward movement) at a constant speed. Here, the actual scan and the test scan are the same.

Scanning (forward movement) is performed by checking the signal received while waiting for the scanning start signal at step . That is, in step it is determined whether the mode flag is "0" or not,
If "YES", wait until the scan signal is turned off and proceed to the step, then "NO"
If so, wait until the test signal is turned off and proceed to step. In this step, the motor control circuit 7 is set to reverse/on mode. At this point, the scanning system 1 starts returning to the home position.

Regarding the backward movement of the scanning system 1, the case of test scanning will be explained first.

As mentioned above, when the control of the DC motor 2 is switched to the reverse/on mode in step, unlike the constant speed forward rotation mode, the rotation direction of the motor 2 is reversed and constant speed control is not performed, and the power supply is turned off. E is now directly connected to the motor 2. At this time, if there is no change in the power source E and the load, the acceleration of the motor 2 decreases in proportion to the rotational speed due to the back electromotive force generated by the rotation of the motor 2. Therefore, the rotational speed of the motor 2, that is, the speed of the scanning system 1, decreases from the start of the return, as shown in FIG. 5, and after reaching zero, accelerates in the return direction. If the reverse/on mode continues, as the rotational speed of the motor 2 increases, the back electromotive force also increases, so the acceleration decreases and approaches a certain value as indicated by the dotted line X in FIG.

On the other hand, the microcomputer 6 continues to wait for the brake switch 5 to be turned on at step. When it is confirmed in step that the brake switch 5 is on, the switch resets the flag (REQ) to "0". This flag (REQ) is a flag to be exchanged with an interrupt processing routine to be described later, and becomes "1" at the optimum braking timing. The brake switch 5 functions to issue the timing of the optimum braking start position in the test scan, and after confirming that the test scan is in step, switches the motor control circuit 7 to the brake mode in step. Furthermore, each parameter (IXP),
Clear (T ₁ ) and (C) and enable interrupts at step.

In the case of this test scan, when the interrupt processing routine completes reading of data in the optimum braking state, the flag (REQ) is set to "1" by the interrupt routine. In the main routine, when it is confirmed that the flag (REQ) is set to "1" in step, the motor control circuit is set to brake mode in step, and scanning is started again after waiting for home switch 4 to be turned on in step. Back to waiting at the traffic light.

If a brake signal is output to the motor control circuit 7 during recovery, the power from the power source E is cut off, but
Braking is performed by the back electromotive force generated when the motor 2 rotates. At this time, the acceleration is caused by the back electromotive force of the motor 2.
Since the number of rotations of the motor 2 after starting braking, that is, the speed of the scanning system 1, is proportional to the rotation of the fifth
Asymptotically approaches zero as shown by curve Y in the figure. However, since a small constant negative acceleration also acts due to friction on the sliding surface of the scanning system 1, when the speed becomes low, the scanning system 1 decelerates linearly and stops. Actually scanning system 1
In this way, the motor returns to the home position before stopping, and is forcibly stopped by a damper or the like.

In the above test scan, the relationship between the position and speed of the scanning system 1 during deceleration as shown in FIG. 5 is stored in a random access memory (RAM). The installation position of the brake switch 5 is set so that the speed when the scanning system 1 returns to the home position is the optimum speed with respect to the time constant of the damper and the like. In addition, in order to use the data obtained in the test scan as the reference for all actual scans, the scanning distance in this test scan is set so that the position where the maximum speed in all scans is achieved is the position after brake switch 5. Set to maximum.

Next, the case of actual scanning will be explained.

The return start in the actual scan is performed by the motor control circuit 7 in a step similar to the test scan described above.
This is done by issuing a reverse/on signal. However, braking control is performed by scanning system 1 in steps.
Wait until the brake switch 5 is turned on. When it is confirmed in this step that the brake switch 5 is on, the flag (REQ) is set to "0" in this step.
The resetting is similar to the test scan described above, but since the determination is "NO" in the step, no brake signal is issued, and an interrupt is permitted in the step. Then, the step continues to wait for the flag (REQ) to be set to "1" in the interrupt processing routine, and the step returns "YES".
When this happens, a brake signal is issued to the motor control circuit 7 in step, that is, the input terminal 9b is turned off to start braking.

Thereafter, as in the test scan, it is confirmed in step that the scanning system 1 has returned to the home position by turning on the home switch 4, and the process returns to waiting for a scan start signal.

In this actual scanning, the timing to start braking is determined as follows.

That is, after detecting that the brake switch 5 is turned on in the above step, the position and speed of the scanning system 1 are detected based on the number of pulses of the encoder 3 and the pulse interval, and are equal to the speed in the optimum braking state, that is, during test scanning. or faster than that, it is determined that it is the timing to start braking.

FIG. 6 shows the speed change of the scanning system 1 when braking is applied in this manner, and the dotted line shows the speed change during test scanning. The solid line I shows the speed change during each actual scan during the same-size small-size copying, and the solid line shows the speed change during each actual scan during the reduced-size copying. Note that the scanning distance of the test scan is set to be the same as the actual scanning distance during full-size maximum size copying.

As shown in Fig. 6, in the actual scan where the scanning distance is shorter than the test scan, the speed at the time of passing the brake switch 5 does not reach the speed of the test scan, which is the optimum braking operation. do not have. Therefore, when the brake switch 5 is turned on, the current position and speed are measured by the interrupt processing routine and compared with the speed at the optimum braking operation. Thereafter, the scanning system 1 continues to accelerate until it reaches a speed equal to that during optimal braking operation. At this time, the flag (REQ) is set to "1" in the interrupt processing routine to notify the main routine that it is time to start braking, and a brake signal is output in step to start braking. The subsequent return operation depends on the speed at the start of braking, unless there is a change in the load. In this case, the speed of the scanning system 1 at the time of starting braking is equal to the speed at the same position during the optimum braking operation, and is therefore the same as the optimum braking operation.

FIGS. 4C and 4D show flowcharts of the interrupt processing pattern, which consists of two processing routines (INT-E) and (INT-T).

(INT-T) is a processing routine for measuring the speed of the scanning system 1. The speed of the scanning system 1 is measured as the pulse interval from an encoder 3 that detects the rotational speed of the DC motor 2. In this embodiment, as described above, the microcomputer 6 having a built-in 8-bit counter C is used as the control means. Counter C counts pulses input to the external clock terminal (ECK) of microcomputer 6, and at the same time as it overflows and returns to zero, a counter interrupt occurs. At this time, the main routine is temporarily interrupted and the process moves to (INT-T). In this embodiment, a 200 KHz clock pulse is input from the reference oscillator 8 to the external clock terminal (ECK). Therefore, 2 ⁸ = 256 clocks (t _nax =
A counter interrupt occurs every 1.28ms).

Specifically, (INT-T) performs a process of adding the above (t _nax =256) to the interval timer ( _TI ) for measuring the pulse interval from the encoder 3. This interval timer ( _TI ) is one of the registers of random access memory (RAM).

On the other hand, (INT-E) measures the position of the scanning system 1, reads optimal braking data, and determines the optimal braking timing. First, the position of the scanning system 1 is measured as follows. Since the pulses from the encoder 3 are generated according to the amount of movement of the scanning system 1,
By counting these pulses, the distance traveled from a certain point can be determined. In this embodiment, the brake switch 5 is set as the reference position for starting counting.
is in the on position. Since the data to be stored is for the optimum braking operation, by setting the reference position to the position corresponding to turning on the brake switch 5, both the processing and the number of data can be minimized. Also, the data stored is not as a speed value for ease of processing;
The pulse interval from encoder 3 is measured by internal counter C.
It is treated as the number of pulses of the reference oscillator 8 counted by . In addition, regarding the position of the scanning system 1, the reference position of the encoder 3 [brake switch 5 on]
The number of pulses from is stored in RAM (IXP), which will be described later.

Below, with reference to Figure 4 C and D (INT-E)
The processing routine will be explained.

When a pulse from the encoder 3 is input to the external interrupt terminal (INT) of the microcomputer 6, an external interrupt occurs, interrupting the main routine processing and moving to (INT-E), where the interrupt is executed as described above. After the processing routine ends, control returns to the main routine. Also, if an interrupt occurs while one interrupt is being processed, the latter interrupt will be suspended until the former interrupt processing is completed, and after the former interrupt processing is completed,
The latter interrupt processing is performed without returning control to the main routine. At the same time, when an interrupt occurs, the counter interrupt is processed with priority.

First, in step, the scanning system 1 returns to the home position and it is determined whether the home switch 4 is turned on. If it is on, the flag (REQ) is set to ``1'' regardless of the current speed using the step 〓〓. If it is off, the current internal counter C is stored in the interval timer T _I at the step.
Add the value c of , find the current pulse interval, and calculate T _Ic
Set to . Therefore, interval timer T _I
If counter C overflows n times, then
This means that the number of pulses is 256×n+C.
Then, the interval timer T _I and internal counter C are cleared, and measurement of the next pulse interval is started. Next, in step it is determined whether the mode flag is "1", that is, it is determined whether the current scan is a test scan or an actual scan.

If the step is ``YES'', that is, in the case of a test scan, the current pulse interval T _Ic is stored in the area indicating the current position of the random access memory (RAM) indicated by the index pointer (IXP) in the step. Next, at step 〓〓, 1 is added to the index pointer (IXP) to update the position, and the interrupt processing ends. The index pointer (IXP) is reset to "0" when the brake switch 5 is turned on, that is, at the step of the main routine described above, and by adding 1 to each pulse from the encoder 3, the index pointer (IXP) is reset to "0". The current distance from the brake switch 5 (reference position) can be known. In this way, during the test scan, the change in speed from brake switch 5 to home switch 4 is stored in random access memory (RAM).

On the other hand, if the step is "ON", that is, in the case of actual scanning, the current pulse interval T _Ic and the optimal braking operation at the current position indicated by the index pointer (IXP) are determined in the step 〓〓. Compare and judge with pulse interval RAM (IXP). When T _Ic is larger, that is, when the current speed is still slow, 1 is added to the index pointer (IXP) at step 〓〓.
is added to update the current position and end the interrupt processing. Conversely, when T _Ic is smaller or equal, that is, when the current speed is faster than or equal to the speed at the optimum braking operation, it is determined that it is the timing to start braking. And flag (REQ) at step 〓〓
is set to ``1'' to inform the main routine, and since subsequent interrupt processing is unnecessary, subsequent interrupts are prohibited at step 〓〓.

Note that the following precautions must be taken when determining the timing to start braking.

The position data based on the pulse interval and number of pulses of the encoder 3 that indicate the speed are both discrete, and the acceleration is particularly large at the start of braking, and varies greatly with each pulse of the encoder 3. Therefore, when determining the optimal braking timing, the speeds rarely match at all, and the judgment is made based on whether the speed approaches or exceeds the speed at the optimal braking operation. At this time, an error occurs. This error increases as the braking start timing becomes faster, so care must be taken. A countermeasure is to shorten the sampling time so that the change in speed is sufficiently small, that is, to increase the number of pulses of the encoder 3.

Further, in the present invention, it is necessary to store data on speed changes during optimal braking operation, which serves as a reference. Methods include storing the data as fixed data in a microcomputer, and reading it by test scanning as in this embodiment. In the former case, there is no need for a test scan, so the actual scan can be performed from the beginning, but if the optimum braking state differs from the stored data due to a change in load, etc., it is difficult to correct it. In the latter case, a test scan must be performed before the actual scan, and in random access memory (RAM) where data is lost when the power is turned off, a test scan must be performed every time the power is turned on. However, if it has a backup function that prevents data loss even when the power is turned off, it is only necessary to back up the data once. The advantage of the latter is that it has adaptability to changes in load and the like. For example, in this embodiment, even if the load changes, data can be corrected simply by adjusting the position of the brake switch 5 and performing a test scan.

Effects As is clear from the above explanation, the present invention includes a detection means for detecting the speed at each position of the scanning system, and a rewriting method for storing the reference speed during backward movement at each position of the scanning system. A speed detection value corresponding to each position detected by the detection means during the backward movement of the scanning system is compared with a stored value corresponding to each position stored in the storage means. Since it is equipped with a comparison means and a braking start means that starts braking when the detected speed value exceeds the stored value as a result of the comparison by the comparison means, the speed or braking force itself during the return movement is not controlled. With a simple configuration, it is possible to reliably obtain an optimal control state corresponding to various scanning modes depending on copying magnification and the like.

That is, in the present invention, since the timing of starting braking is determined only by the position and speed of the scanning system, there is no need for correction based on the scanning speed or scanning distance, or correction using auxiliary acceleration means such as spring charge at the start of the return operation. Further, the control means itself does not require a special speed control circuit during the return operation, and has a simpler structure as a whole than a conventional position control servo system.

Further, as shown in the above embodiment, if the storage means is a rewritable memory, it becomes easy to make adjustments for each copying machine or for changes over time. If you do this, you can always obtain optimal braking conditions. In addition, an encoder that generates pulses according to the movement of the scanning system is used as a detection means, and the position of the scanning system is determined by the number of pulses from the reference position.
By detecting the scanning of the scanning system at the reference position at pulse intervals, the position and speed of the scanning system can be detected with a single detection means, eliminating the need to detect and correlate the two with separate equipment. It will be destroyed. Furthermore, if the reference position is set as the braking start position when the reference speed is stored in the storage means, only the minimum necessary data is stored in the storage means, which has the advantage of requiring less storage capacity.

[Brief explanation of the drawing]

The drawings show an embodiment of the scanning device according to the present invention, in which FIG. 1 is a perspective view of the scanning system, FIG. 2 is a block diagram of the control means, FIG. 3 is a motor control circuit diagram, and FIG.
Figures A to D are flowcharts of the control means, Figure 5 is a graph showing the speed change of the scanning system during backward movement during test scanning, and Figure 6 is a graph showing the speed change of the scanning system during actual scanning. be. 1... Scanning system, 2... DC motor, 3... Encoder, 4... Home switch, 5... Brake switch, 6... Microcomputer, 7...
Motor control circuit, 8...Reference oscillator.

Claims (1)

[Claims] 1. After the scanning system is moved by a motor at a predetermined speed during forward movement and at an accelerated rate during backward movement,
A scanning device that applies predetermined braking to stop at a scanning start position includes a detection means for detecting the speed at each position of the scanning system, and a means for storing a reference speed during backward movement at each position of the scanning system. A rewritable storage means, and a speed detection value corresponding to each position detected by the detection means during the backward movement of the scanning system is compared with a stored value corresponding to each position stored in the storage means. 1. A scanning device comprising: a comparison means for comparing the detected speed with the stored value; and a braking start means for starting braking when the detected speed value exceeds the stored value as a result of the comparison by the comparison means. 2. The scanning device according to claim 1, wherein the reference speed stored in the storage means is a speed detected by the detection means during reciprocating motion prior to copying.