JPH0441329B2 - - Google Patents

Description

TECHNICAL FIELD The present invention relates to a scanning device in which a scanning system in a copying machine or the like is reciprocated by a DC motor.

BACKGROUND ART In recent years, the functions of copying machines have been required to be faster and faster, and in particular, the scanning system of a copying machine having a reduction copying function is required to be faster than copy paper conveyance speed. To this end, an on/off control system using a DC motor has been proposed in place of the conventional system of transmitting the driving force of a main motor via a clutch.

The control of a DC motor is to obtain the speed by controlling the on time for a certain period of time or a certain number of revolutions. This on/off control is performed by calculations based on the measured speed and numerical values stored in the memory of the microcomputer, but while it is not constant speed control, the speed changes during startup, braking, and direction change. Time Smooth has the disadvantage that a large amount of control data must be stored in order to achieve speed changes, and control using such control data is also extremely complex. Smooth acceleration/deceleration control is essential in order to minimize impact on the scanning system. The smaller the impact on the scanning system, the shorter the preliminary travel distance.
The scanning system can be made lightweight and compact,
This is because speeding up can be achieved.

Purpose/Summary The present invention was made in view of the above points, and provides a scanning device using a DC motor control method that can perform smooth acceleration/deceleration control without requiring a large amount of storage capacity or complicated control. The purpose is to provide

The above object includes a pulse generating means that generates a pulse according to the rotation of the DC motor, a timing means that measures a predetermined time each time the pulse generating means generates a pulse, and a DC motor that generates a pulse during acceleration or deceleration. This is achieved by a control means that controls the power supply to the motor to be turned off while the timer measures a predetermined time, and to be turned on from the time the predetermined time elapses until the next pulse is generated.

The interval between the pulses is longer when the speed of the scanning system is slow, and becomes shorter when the speed of the scanning system is faster. Therefore, if we set a constant off time and use the remaining on time, when the speed of the scanning system is slow, the on time will be longer and when the speed is faster, the on time will be shorter, so when accelerating, the acceleration will be large at low speeds. As the speed approaches the constant control speed, the acceleration decreases, and during deceleration, the braking force is small at high speeds, and as the speed becomes low, a large braking force can be applied.

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 electrophotographic copying machine, and in FIG. 1, 1 is a scanning system including an illumination system, 2 is a DC motor, and scanning system 1
is reciprocated by this DC motor 2, that is, forward in the direction of arrow A 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 the number of rotations thereof.

A home switch 4 detects that the scanning system 1 is at the home position (scanning start position). 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. A brake switch 5 detects that the scanning system 1 has reached a predetermined position during the return, and is used as a signal to start braking during the return in the flowchart described later.

FIG. 2 shows a switching circuit for controlling the DC motor 2, and in this figure, the DC power supply E is connected to bridge-connected transistors Tr ₁ to _{Tr 4} .
connected to the DC motor (2) through the diode
D ₁ to _{D 4} are connected in parallel with each transistor Tr ₁ to _{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 mand 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 .

Next, the principle of the present invention will be implemented through the operation of the circuit shown in FIG. To explain the principle, the movement of the scanning system 1 is as shown in Fig. 3A, when the movement of the scanning system 1 is continuously shifted from forward movement under constant speed control to deceleration, direction change, acceleration, and forward movement under constant speed control. Take for example.

In the constant speed scan, the input terminal 9a is "H" and the input terminal 9b is controlled to be turned on or off based on the measurement of pulses from the encoder 2. At this time, when the input terminal 9b is "H", transistors Tr ₂ and Tr ₃ are on, and the current from the DC power supply E is as shown in Figure 2a.
direction, driving the DC motor 2 in the forward direction.

Next, when the vehicle is decelerating in the forward direction, the input terminal 9a is switched to "L" in order to apply a braking force, and the input terminal 9b is controlled on and off by the control method of the present invention. In other words, a constant off time is set for each encoder pulse generated in response to the rotation of the DC motor 2, and the on time is controlled until the next encoder pulse.

Input terminal 9a is “L” and input terminal 9b is “L”
In the state shown in FIG. 2, only the transistor Tr ₁ is turned on. Since the scanning system 1 is moving in the forward direction, the rotation of the motor shaft due to this movement generates a back electromotive force in the direction of arrow b in the closed loop of the DC motor 2 diode D ₃ transistor Tr ₁ , which causes the rotation in the forward direction. provide braking. Hereinafter, braking using this back electromotive force will be referred to as regenerative braking. On the other hand, when the input terminal 9a is "L" and the input terminal 9b is "H", transistors Tr ₁ and Tr ₄ are turned on, and the current of the DC power supply E flows in the direction of arrow b, causing the DC motor 2 to move in the backward direction. Try to rotate it. The case in which braking is applied by rotating the scanning system 1 in the opposite direction to the moving direction is hereinafter referred to as forced braking.

Returning to FIG. 3A, at the beginning of deceleration, the interval between encoder pulses is shorter than the set off time, so only regenerative braking is activated. The scanning system 1 is gradually decelerated by the relatively weak braking force of this regenerative brake, and when the encoder pulse interval becomes longer than the off time, the forced brake also works together with the regenerative brake, decelerating with a strong braking force (Figure 3, bottom). ，
(see c).

In this way, a weak braking force is initially applied and the braking force is gradually strengthened, making it possible to decelerate very smoothly.

By the way, in the applicant's previous proposal, as shown by the dotted line in Figure 3, first only regenerative braking (from point O to point A in the diagram), then only forced braking (from point A to point B in the diagram) However, with regenerative braking, the braking force becomes weaker as the speed decreases, so it takes longer to decelerate. On the other hand, compared to this, the system of the present invention can perform deceleration in a sufficiently short time.

When the deceleration ends, the scanning system 1 is accelerated in the backward movement direction. The circuit state at this time is exactly the same as the state during deceleration described above, only the actual moving direction of the scanning system 1 is different. Therefore, the above input terminal 9
When a is "L" and the input terminal 9b is "H", a driving force is forcibly applied, and when the input terminal 9a is "L" and the input terminal 9b is "L", it is a state of inertial movement.

At the beginning of acceleration, the interval between encoder pulses is long, so the ON time of the DC motor 2 is also long, and the powerful acceleration is caused by the strong current torque. As the speed approaches the constant speed control speed, the pulse interval becomes shorter and the acceleration force gradually becomes weaker. Therefore, even during acceleration, the control system of the present invention can perform very smooth acceleration.

As described above, the control system of the present invention can obtain smooth speed changes with simple control in all of deceleration, acceleration, and continuous transition from deceleration to acceleration when changing direction. It is clear that the above description can also be applied to acceleration from the scan start position, direction change from backward movement to forward movement, and deceleration when stopping at the scan start position.

FIG. 4 is a block diagram of a control circuit for controlling the movement of the scanning system, and in this figure, 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 macrocomputer.

The microcomputer 20 has a central processing unit CPU and a read-only memory.
ROM, random access memory RAM, input port INPUT, output port OUTPUT, counter
Consists of Tf, timer register Tw, INPUT
is the control request signal MAG from the masters,
SCAN and BRAKE are input. Signal MAG indicates the selected magnification and sets the scanning speed. Signal SCAN is “1” and forward movement is “0”
to instruct return movement. The signal BRAKE becomes "1" while the scanning system 1 turns on the brake switch 5 during backward movement.

From OUTPUT, a motor drive signal D and a forward/reverse rotation signal F are outputted to a switching circuit 21 shown in FIG. 2, whereby the DC motor 2 is controlled.

CUP has two interrupt terminals, and one terminal receives the output of the encoder 3 from the waveform shaping circuit 2.
The encoder pulse shaped in step 2 is 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.
The timer register Tw compares this timer value Tw with a reference time Tf of a counter Tf that counts reference pulses from the external reference oscillator 23, and when the two match, inputs an interrupt signal to the CPU.

Figure 5 A, B, and C are microcomputers 20
FIG. 5A is a flowchart explaining the control of the main routine, FIG. 5B is a routine for timer interrupt INT-T by timer register Tw, and FIG. 5C is a flowchart for explaining external interrupt INT-E by encoder pulse. shows the routine.

First, to explain the main routine of FIG. 5A, when a reset is applied in step, the motor drive signal D is set to "0" in step. When D=0, the input terminal 9b is “L” in the switching circuit shown in Figure 2.
D=1 corresponds to the "H" state.

Next, the step waits until there is a scanning request from the master, and when the scanning request is issued (SCAN = 1), the copying magnification MAG is input in the step, and the reference encoder pulse is applied to control the scanning speed corresponding to the copying magnification. Calculate the interval Ts. This reference encoder pulse interval Ts is obtained by multiplying a preset encoder pulse interval To at equal magnification by a copying magnification.

Subsequently, in a step, the forward/reverse rotation signal F is set to "1". F=1 corresponds to the state in which the input terminal 9a is "H" in the switching circuit shown in FIG. 2, and F=0 corresponds to the "L" state.
corresponds to the state of

Following this, the scanning system 1 starts forward movement by setting the motor drive signal D to "1" in a step. In this step, the counter SYNC for synchronizing the encoder pulse and the interrupt routine is set to "2", the processing mode in the interrupt routine is set to acceleration control mode (MODE = 1),
Enable interrupts in the next step. Control of the scanning system from permission of this interrupt is processed by the interrupt routine, and the main routine waits in steps until the scan request SCAN becomes "0". During this time, acceleration control and normal constant speed control based on the control method of the present invention are performed. The time for SCAN=1 is determined by the master side depending on the copy paper size and copy magnification.

When SCAN=0, the speed measurement mode (MODE=0) is set in step, the motor drive signal is turned off in step, and the forward/reverse signal is set in reverse (F=0) in step. The reason why the interrupt processing is switched to the temporary speed measurement only 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.

Following the step, a deceleration control mode (MODE=2) is set in a step, and deceleration control according to the present invention is performed in an interrupt routine.
In the interrupt routine, when deceleration is completed, the motor is turned on and the speed measurement mode is set. In the speed measurement mode, speed control is not performed, so the scanning system is moved forward at full power. During this time, the main routine is on standby, and when a braking request (BRAKE = 1) is issued from the master (step), the motor is turned off, the forward/reverse signal F is switched to forward rotation (F = 1), and the motor is turned off (step). Set the deceleration control mode (MODE=2) and wait until the mode changes to the speed measurement mode (MODE=0) (step).

When the speed measurement mode is set, interrupts are disabled in step, the motor is turned off in step, and the process returns to step.

In this way, the control of the main routine is extremely simple.

FIG. 5B shows the timer interrupt routine INT-T, which is the external interrupt routine INT-T.
Each time the timer value Tw set by -E expires, the main routine is interrupted and processed.

When a timer interrupt occurs, the first step is to determine the ON/OFF state of the on/off flag. The on-off flag ONOFF is a flag set in an external interrupt routine, and if ONOFF=1, the motor drive signal D is set to D=0 in a step. on the other hand,
If ONOFF=0, set the motor drive signal D to D=1 in step.

As mentioned in the explanation of the principle, constant speed control controls the on time between encoder pulse intervals, and the control according to the present invention sets a constant off time between encoder pulse intervals. Therefore, in constant speed control, the on/off flag is set to ONOFF=1, and the motor is turned off in steps by a timer interrupt after the set on-time has elapsed.

On the other hand, in the control according to the present invention, the on/off flag is set to ONOFF=0, and the motor is turned on in steps by a timer interrupt after a certain off time has elapsed.

Next, use Figure 5C to create an external interrupt routine.
Explain INT-E. This routine
The processing is performed by interrupting the main routine every time a pulse is generated from the encoder 3 that detects the rotation of the main routine.

When an interrupt occurs in FIG. 5C, the value Tf of the counter Tf, which is the reference time in the microcomputer, is first copied to the register Tc set in a predetermined area of the RAM at step . Therefore, the register Tc is the generation time Tc of the current encoder pulse.
will be shown.

Next, the value of the counter SYNC is determined at step 〓〓, and if it is other than zero, "1" is subtracted from the count value at step 〓.

This counter SYNC is used to synchronize the encoder pulses and the interrupt routine.Since at least 2 encoder pulses are required to determine the encoder pulse interval, it is set to invalidate the pulse interval calculation results during that time. be done. In this example, since the first pulse is also ignored, the counter
The initial value of SYNC is set to "2".

In step 〓, the pulse interval Ti of the encoder is determined.

This calculation is obtained by taking the difference between the current encoder pulse generation time Tc set in step 〓〓 and the previous encoder pulse generation time Tp. The previous encoder pulse generation time Tp is stored in the register Tp set in the RAM like the register Tc, and is updated by copying the current encoder pulse generation time Tc to the register Tp in the next step 〓〓. .

In the next step, the mode is determined. In this example, the modes are speed measurement mode (MODE=0), acceleration control mode (MODE=1),
There are four types of settings: deceleration control mode (MODE=2) and constant speed control mode (MODE=3).
MODE=0 is set in the main routine and in the step below, MODE=1 and 2 are set in the main routine, and MODE=3 is set in the step below.

In the speed measurement mode (MODE=0), just measure the speed of steps 〓〓〓 to 〓〓 and immediately return to the main routine.

In the case of constant speed control mode (MODE=3), after determining whether the counter SYNC is "0" at step 〓〓, the motor on time for the target speed is calculated and set in the temporary memory register Ton ( Step〓〓) Set the on-off flag ONOFF to “1” (Step〓), and set the motor drive signal D to “1”. Here, the on time Ton is the value obtained by multiplying the on time Ttyp set corresponding to the target speed by a coefficient Ki by the difference between the measured encoder pulse interval Ti and the reference encoder pulse interval Ts corresponding to the target speed. Obtained by adding. Different values are used for Ttyp, Ts, and Ki during double movement depending on the copying magnification.

The on-time Ton thus determined is added to the current time Tf in step <<> 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 will be generated exactly at the time Ton after the timer register Tw is set. During this time, the motor is on.

Next, in the case of acceleration control mode (MODE=1),
First, in step 〓, it is determined whether synchronization is achieved, and if synchronization is achieved, whether the measured encoder pulse interval Ti has become less than the reference encoder pulse interval Ts corresponding to the target speed, that is, whether the target speed has been reached. Make a judgment (Step〓〓), and if YES, change the mode to constant speed control mode with Step〓. If NO in either step or step, it is assumed that the start-up is in progress, and the off time Tchopl is set in the temporary memory register Ton (step), the on-off flag ONOFF is set to "0", and the motor drive signal D is set.
are set to "0". (Steps〓〓〓〓.

The value set in the temporary storage register Ton is added to the timer register Tw by the operation of step 〓〓. In this case, off-time control is used, so the motor is turned off from the time the timer register Tw is set until the time Tchopl has elapsed.

In the case of deceleration control mode (MODE=2), first determine whether synchronization is achieved in step 〓〓, and if synchronization is established, the measured encoder pulse interval Ti becomes the pulse interval Tstop corresponding to the deceleration control end speed. It is determined whether the speed of the scanning system has fallen below the deceleration control end speed (step 〓), and if YES, the mode is switched to the speed measurement mode (MODE=0) at step 〓. If NO in any of the steps, it is assumed that the deceleration is in progress, and the set off time Tchop2 is set in the temporary memory register Ton (step), and the steps are processed in the same way as in the acceleration control mode. .
As a result, the motor is turned off until the time Tchop2 has elapsed since the timer register Tw was set.

According to the above flowchart, the scanning system performs scanning under acceleration control according to the present invention, constant speed control, and deceleration control according to the present invention, and then, after full power acceleration, is subjected to deceleration control according to the present invention. Return and stop at home position. In the case of copying a large number of sheets, the return deceleration and the scan acceleration are performed successively. In either case, acceleration/deceleration control is extremely smooth.

The off time according to the present invention is shown by the types of time Tchop1 and Tchop2 shown in FIG.
Tchop1 corresponds to changes in scanning speed due to changes in copying magnification, and time Tchop2 corresponds to changes in deceleration start speed due to changes in scanning distance. A plurality of Tchop1 and time Tchop2 are provided to perform optimal acceleration/deceleration control. There is.

Effects As described in detail above, the present invention provides a scanning device in which a scanning system is reciprocated by a DC motor, including a pulse generating means that generates pulses in accordance with the rotation of the DC motor, and a pulse generating means that generates pulses. a timer that measures a predetermined time each time the DC motor is accelerated;
Since the control means is provided for controlling the clocking means to be turned off while counting a predetermined time and turned on after the elapse of the predetermined time until the next pulse is generated, very smooth adjustment control can be achieved. can be done easily.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a scanning device to which the present invention is applied;
Figure 2 is a switching circuit diagram of a DC motor, Figure 3 is a switching circuit diagram of a DC motor.
Figure A is a diagram showing the movement of the scanning system to explain the principle.
Figures 3B and 3C are diagrams showing encoder pulses and energizing torque corresponding to Figure 3B, Figure 4 is a block diagram of the control means, and Figures 5A, B, and C are flowcharts of the control means. be. 1...Scanning system, 2...DC motor, 3...Encoder.

Claims (1)

[Claims] 1. A scanning device in which a scanning system is reciprocated by a DC motor, comprising: pulse generation means for generating pulses in accordance with the rotation of the DC motor; and a predetermined period of time each time the pulse generation means generates a pulse. a timer for measuring time; and a timer for turning off the current to the DC motor during acceleration or deceleration while the timer measures a predetermined time, and turning it on for a period from the elapse of the predetermined time until the next pulse is generated. What is claimed is: 1. A scanning device comprising: a control means for controlling the scanning device to control the scanning device; 2. Claim 1, characterized in that the predetermined time measured by the timer is changed according to the constant speed control speed after acceleration and/or the deceleration start speed.
Scanning device as described in Section.