JPS62210442A - Image forming device - Google Patents

Abstract

PURPOSE:To relax a shock at the time of braking and to reduce variance in stop position by performing electric power generation braking like a short- circuiting brake and backward rotation braking like a forward rotation brake in combination according to the speed of an optical system. CONSTITUTION:When optical systems 31 and 32 move backward, clock pulses are counted down to confirm the positions of the optical systems based on the feedback signal of an encoder 21 as well as in forward movement, further, a motor 20 is braked and reduced in speed from before the home positions of the optical systems, which are stopped within a specific range so as to hold their stop positions constant. Trailing motor driving is turned off with the detection signal of an image front end detection sensor 36 and brake control is performed up to an optical system home position detection sensor. There are 32 optical system clock pulses in this period and brake control is performed once at every 4 pulses and 7 times in total. Specially, the electric power braking is performed by the short-circuiting brake 4 times firstly and the backward rotation braking is performed then 3 times.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming apparatus such as a copying machine or a facsimile machine, and particularly to brake control of a motor that drives an optical scanner of the apparatus.

[Prior Art] Conventionally, brake control for this type of optical scanner has been performed by adjusting the time for applying forward rotation braking (reverse braking) according to the speed at the moment the image tip is cut. This speed measurement is generally performed using an encoder pulse signal that is generated within a certain period of time from the moment the tip of the image is cut. In addition, by developing this control method, the speed can be measured several times, for example, eight times, between the tip of the image and the home position, and the forward rotation brake can be applied several times depending on the measured speed. I was worried.

[Problems to be Solved by the Invention] However, the above-described brake control in the conventional device has the disadvantage that the shock during braking is large and the stopping position deviates from the home position.

An object of the present invention is to provide an image forming apparatus that can reduce the shock to the image forming apparatus caused by the braking operation of such an optical scanner, and can suppress variations in stopping position caused by forward rotation braking. With the goal.

[Means for Solving the Problems] In order to achieve the present object, the present invention includes a reversible electric motor that reciprocates an optical system for document scanning, a speed detection means that detects the moving speed of the optical system, and an optical system. a signal generating means for generating a signal instructing the start of braking; and a braking control means for braking the electric motor using dynamic braking and reverse braking in accordance with the detected output of the speed detecting means based on the output signal of the signal generating means. It is characterized by the following:

[Function] In the present invention, the document scanning optical system is reciprocally driven by a reversible electric motor such as a DC motor, and the moving speed of the optical system is detected by a speed detection means such as an encoder. A signal generating means instructs the optical system to start braking. Then, the braking control means having arithmetic means such as a microcomputer turns off the power to the electric motor according to the output signal of the signal generating means, and operates the electric motor using dynamic braking and reverse braking according to the detected output of the speed detecting means. Braking is applied to stop the optical system at a predetermined position. In this way, the present invention uses both dynamic braking, such as short braking, and reverse braking, such as forward braking, depending on the speed of the optical system, so the shock during braking is softened and the variation in stopping position is reduced. becomes less.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

A. Basic configuration FIG. 1 shows the basic configuration of an embodiment of the present invention. In this figure, a is an electric motor such as a reversible C motor that reciprocates the document scanning optical system. b is speed detection means consisting of a sensor such as an encoder that detects the moving speed of the optical system. A signal generating means C generates a braking start signal instructing the optical system to start braking, and generally uses an image leading edge detection sensor that detects when the optical system passes the leading edge position of the document. d is a braking control means, which brakes the electric motor using a dynamic braking (short brake) and a reverse braking (forward braking) according to the detected output of the speed detecting means, using the output signal of the signal generating means C; This causes the optical system to stop at a fixed position.

B. Structure of Embodiment FIG. 2 shows the circuit structure of the main part of the embodiment of the present invention. In this figure, 1 is a numeric keypad for specifying the speed of the motor 20, which will be described later, and 2 is a keypad for the microcomputer 3 that controls the speed. This is an oscillator that drives an internal counter. The microcomputer (hereinafter referred to as microcomputer) 3 has a first counter 3A and a second counter 3B, and has control information stored in advance in internal storage means as shown in FIGS. 3, 8, and 1O. The speed of the motor 20 is controlled according to the means. Further, the first counter 3A counts the clock of the oscillator 2 and generates a reference frequency signal FS for phase comparison in accordance with the motor speed designation from the numeric keypad 1. The second counter 3B receives a feedback signal F from the encoder 21, which will be described later.
In synchronization with G, a speed control signal FV of pulses with a constant width is generated in accordance with the above-mentioned motor speed designation.

4 is an output line of the speed control signal FV of the microcomputer 3, and 5 is an output line of the phase comparison signal PC generated by the microcomputer 3 using the above-mentioned reference frequency signal FS and the above-mentioned feedback signal FG.

6 is an adder circuit that adds the above-mentioned phase comparison signal pc and speed control signal FV, 7 is a comparator that performs pulse width modulation (PWM) on the integral value of the output of the adder circuit 6, and 8 is an adder circuit that adds the output of the adder circuit 6. A capacitor that creates a triangular wave; 9 is a threshold level control signal P output from the microcomputer 3;
LL, D-A that performs digital-to-analog conversion to DAT
(digital to analog) converter.

A pair of drivers 10 and 11 (first motor drive circuit) drive the motor 20 in forward rotation, and a pair of drivers 12 and 13 (second motor drive circuit) drive the motor 20 in reverse rotation. 14 is a variable resistor (volume) that adjusts the reverse rotation speed of the motor 20.

15 is a threshold level control signal P of the microcomputer 3
LL, output line to DAT, 16 is the output line of the forward rotation brake signal BIC of the microcomputer 3, 17 is the output line of the short brake signal surface of the microcomputer 3, 18 is the switching control signal FW for switching the motor 20 between forward rotation and reverse rotation. /The output line from the microcomputer 3 of the RV, 19 is the drive (ON) and stop (ON) of the motor 20.
This is the output line from the microcomputer 3 of the control signal (ONloFF) for switching the FF).

A motor 20 drives an optical system scanner (not shown).
It is a C motor. The encoder 21 detects the rotation speed of the motor 20 and supplies the microcomputer 3 with a feedback signal FG corresponding to the detected rotation speed.

The forward rotation brake signal pressure from the microcomputer 3 causes the motor 20, which is currently in reverse rotation, to rotate in the forward direction, thereby performing reverse braking to stop the rotation. In addition, by short-circuiting the input terminal of the motor 20 by the short brake signal R from the microcomputer 3, the motor 20
Performs dynamic braking to cancel the back electromotive force and stop rotation.

Incidentally, the continuous magnification change by the motor 20 described above can be realized by continuously changing the scanning speed of the optical system when the speed of the drum (photosensitive drum) is constant. For example, when copying at the same size, the frequency of the feedback signal FG of the encoder 21 of the optical system drive motor 20 is set to 1.
Hz (period T = 1 m5), and when the magnification is changed in steps of 1%, the period T of the feedback signal FG is 0, 0.
It changes every in+s. The first counter 3A inverts the output port each time it counts up, so
By causing the oscillator 2 to oscillate at a predetermined frequency T (for example, 100 IZ) and setting the count value corresponding to the motor speed designation (multiplying factor) specified with the numeric keypad 1 in the first counter 3A, the first counter 3A The above-mentioned reference frequency signal FS is produced by this.

The adder circuit 6 receives the speed control signal F output from the microcomputer 3.
V and the phase comparison signal pc are added, and the output of the adder circuit 6 is integrated by a filter consisting of a resistor and a capacitor 8, and then subjected to pulse width modulation (PW) using a threshold level determined by the signal PLL-DATA of the comparator 7.
M), and the driver 10.11 or 12.13 drives the motor 20 in forward or reverse rotation according to this modulation signal, so that the motor 20 is kept constant with the reference frequency signal FS according to the motor speed command from the numeric keypad 1. The phase difference is controlled to be . 1' Next, an example of the phase comparison and speed control operations by the microcomputer 3 in FIG. 2 will be explained with reference to the flowcharts in FIGS. 3A to 3C and the waveform diagram in FIG. 4.

Note that St, Sl, . . . in FIG. 3 represent steps of the control procedure. The same applies to the cases of FIG. 8 and FIG. 1θ, which will be described later.

First, in the main routine shown in FIG.
SL). If there is a change in this setting value (Sl),
Set the set value (data) to the first counter 3A53
) to start the countdown. Here, the first
After the countdown of the counter 3A is completed (S4), an interrupt signal is generated, the set value is automatically reset, and the countdown is repeated.

Next, the speed control signal FV will be described. When the feedback signal FG from the encoder 21 of the motor 20 falls, the signal shown in FIG.
After entering the FG interrupt routine of B) and saving the register (Sll), reset the speed control signal FV (512)
, 1 of the reference frequency signal FS corresponding to the magnification of numeric keypad 1
/2 FS is set in the second counter 3B and started (513), and if the phase difference of the feedback signal FG with respect to the reference frequency signal FS is O~2π (51
4) After returning the register (518), return.

On the other hand, the phase difference is not O~2π (514),
If it is 2π or more (515), lower the threshold level (5ta), otherwise, if the phase difference is less than O, increase the threshold level (5ta).
517), and after the register is restored (518), the process returns to the main routine.

Further, after the second counter 3B has finished counting down, the FV interrupt shown in FIG. 3(C) occurs, and after saving the register (521), the speed control signal FV is set (S22), as shown in FIG. After generating the speed control signal FV, the register is restored (523) and the process returns to the main routine.

As shown in FIG. 4, when the above-mentioned phase difference is 0 to 2π,
The phase comparison signal PC is repeatedly set and reset at the falling edge of the reference frequency signal FS and the feedback signal FG, and if the phase of the feedback signal FG is delayed by 2π or more, the phase comparison signal p
c maintains the set state, and after detecting that the feedback signal FG falls twice during one cycle of the reference frequency signal FS, repeats the above-mentioned operation with a phase difference of 0 to 2π.

Conversely, when the phase of the feedback signal FG leads the reference frequency signal FS, that is, when the phase difference becomes O or less, the phase comparison signal pc maintains the reset state and the feedback signal FG After detecting that the reference frequency signal FS falls twice during the period, the above-mentioned phase difference O~2 is detected.
Repeat the operation of π.

Further, a phase comparator (not shown) outputs "00" when the phase difference of the feedback signal FG is 0 to 2π, "°01" when the feedback signal FG is delayed by a phase difference of 2π or more, and "°01" when the feedback signal FG has a phase difference of 2π or more. When is less than 0, a 2-bit lock signal of "10" is output, and the microcomputer 3 reads this signal and controls the judgment in the FG interrupt routine shown in FIG. 2(B).

Next, the drive control on both sides of the optical system of this embodiment, which includes the halogen lamp 31, first scanning mirror 32, etc. shown in FIG. 5, will be described. As shown in this figure, the optical system 31.3
2 is directly driven by a DC motor 20 via a wire 33.

The encoder 21 attached to the DC motor 20 generates a clock pulse (feedback signal FG) according to the moving distance of the optical system.
) occurs. Further, when the flag plate 34 attached to the lower part of the base of the first scanning mirror 32 crosses the position detection sensors 35 and 36 such as photocouplers fixed to the main body,
A position detection signal is output. One of these sensors3
5 is an optical system home position detection sensor that detects the home position of the optical system, and the other 36 is an image leading edge detection sensor that detects the leading edge position of the document. Note that 37 is a pulley.

When the optical systems 31 and 32 move forward, the DC motor 20 is driven and controlled by the PLL (phase lock loop) control of the microcomputer 3 at a speed corresponding to the copying magnification set from the numeric keypad 1. The distance that the optical system advances is determined by the count value of the first counter 3A that counts the optical system clock pulses of the oscillator 2 from the time of detection by the image leading edge detection sensor 36,
It is determined by the set magnification and transfer paper size. The relationship between this magnification M, the optical system clock pulse Y of the oscillator 2, and the transfer paper size is shown in FIG. The calculation formula used in this figure is Y clock = ((L/M) + 5) ÷ 0.88 ... (1
). L is the feeding length of the transfer paper (mm), and M is the magnification (100% = 1.50% = 0.5.120% = 1.
2) The constant "5" (mm) indicates the slit width of the optical system, and means that an extra scan is performed by that amount.

o, aa' are 0 per clock for the optical system of this embodiment.
．． This shows that it is configured to move 88mm.

Further, it is assumed that the maximum size of the document is A3 size, and the maximum value of the scanning clock is up to the clock when A3 size is 100% (same size).

On the other hand, when moving backward, the vehicle moves backward at a constant speed that is 2.5 times that of forward movement. When moving backward, the clock pulse is subtracted, and the position of the optical system is confirmed based on the feedback signal from the encoder 21, similar to when moving forward. In addition, in order to keep the stopping position constant during backward movement, the motor 20 is braked to decelerate the optical system from before the optical system home position, and the optical system is controlled to be stopped within a predetermined range. In this embodiment, the image leading edge detection sensor 3
The reverse drive is turned off in response to the detection signal 6, and brake control is performed between this and the optical home position detection sensor 35. This distance is, for example, 55 mm, which is equivalent to 32 optical system clock pulses. These 32 pulses are divided into 4 pulses, and brake control is performed once every 4 pulses, totaling 7 times.

Particularly, the first four times are performed by short braking using dynamic braking, and the third time is using forward braking using reverse braking. The timing of the above-mentioned brake control is shown in FIG.
The control procedure for the brake control is shown in FIG.

In the brake control in this embodiment, the optical system advance signal ■ is sent to the driver 10.11 of the motor 20 according to the speed of the optical system.
to slow down the optical system.

In FIG. 7, when the time tn for moving four pulses is measured by the microcomputer 3 based on the feedback signal FG, the moving speed of the optical system can be determined. Based on this speed, the brake time (forward-on time) Xn (msE(:)) from the current time is determined.

However, when the number of samplings of the optical system clock pulse is nth, the inertial force of the optical system has also decreased, so it is necessary to correct the brake time x n according to the number of samplings. Therefore, the brake time Xn is determined by
...Calculate as (2). Here, K is a factor depending on the characteristics of the motor 20.

On the other hand, when the speed of the optical system is slow, the home position cannot be reached by inertia alone, so the reverse signal is turned on again. From the third time onwards, if the calculation result is less than O, the brake will not be turned on.

Assuming that the constant K mentioned above is 10, the braking time Xn for the time tn for moving 4 pulses and the number of samplings n
The relationship between (msEc) is shown in Table 1.

(Hereinafter, blank spaces) Table 1 (tn snow ms) The brake control program of this embodiment shown in the flowchart of Fig. 8 is executed as a subprogram in the "optical system clock interrupt processing" program shown in Fig. 1O. exists (see 568 in Fig. 1θ). That is, this brake control program is a control process that is executed once every time a feedback signal FG pulse output from the encoder 21 of the optical system motor 20 is generated.

The brake flag at step 531 in FIG.
This is a flag that is set when the image leading edge signal from the image leading edge detection sensor 36 is interrupted while the optical system is moving backward in "Image leading edge interruption", and the reverse signal is turned off in response to this, and this brake flag The brake control program shown in this figure will be executed only when is set.

Also, executing the brake control program means that the encoder pulse of the feedback signal FG has arrived once, so when the brake flag is set (531)
In the next step, the value of the "pulse" register is incremented by +1 (532), and when the pulse occurs three times in total, the process advances to the next step (533). In the next step, clear the "Pulse" register 534) and prepare for the next sampling.Also, since the value of tn, the time it takes to move 4 pulses to 2m5EC@, is increased by +1, the value of tn is Read (S35), then read the value of the above-mentioned constant from the internal memory (536)
). In the next step, the number of sampling times n is incremented by +1 (537), and based on these data tn, K, and n, the braking time Xn is calculated based on the above-mentioned calculation formula (2) (S38).

Next, in the next step, clear the tn register for speed detection 539), check whether the above calculation result Xn is less than θ540), and if Xn is greater than 0, check whether n = 4 or not. 541), if n = 4, apply the short brake (542), if n is greater than 5, turn on the forward brake 543), and then apply the forward brake after a time of Xn (SEC) has elapsed. The timer value is set to turn off (S44).

If Xn of the above calculation result is 0, do nothing (S45)
.

Furthermore, when the calculation result Xn is negative (S45) and the number of sampling times n is within the second time (S46), the backward rotation of the motor 20 is turned on for I Xn I m5EC (
547).

Thereafter, when the sampling number n ends 7 times in the END (end) check (S49), the brake flag is reset (550) and the present brake control program is ended.

FIG. 9 shows an example of control results based on the control procedure shown in FIG. 8.

In FIG. 9, D indicates that the forward signal is output in seven pulses under normal speed control. E shows the control result when the speed at the tip of the image is faster than normal, and indicates that up to n=4, the respective braking times overlap and as a result, forward signals are input continuously. F indicates a case where the speed at the tip of the image is slower than normal, and n=1 and 2 indicate that reverse movement is on.

By controlling the motor 20 in this manner, it is possible to obtain a copying machine that can sufficiently cope with changes in speed and inertia caused by changes in the load on the optical system due to changes over time.

In addition, in the above control example, a method of reversing the DC motor was used as a deceleration means, but even when an electromagnetic brake is used, the position of the optical system is detected in the same way as in the above control example, and the position of the optical system is detected accordingly. Exactly the same effect can be obtained by controlling the on-time of the electromagnetic brake.

Further, a similar effect can be obtained by using a hysteresis clutch brake as the deceleration means. In this case, it is also possible to adjust the degree of application of the brake by controlling the clutch drive current instead of controlling the brake application time.

In particular, in the case of a hysteresis clutch brake, due to magnetic coupling, there is no wear surface and there is no need to worry about deterioration over time, and the torque is determined by the current regardless of the rotation speed, which is advantageous.

Note that the flowchart of FIG. 1θ has no direct relation to the present invention except for step 588, so a detailed explanation thereof will be omitted.

[Effects of the Invention] As explained above, according to the present invention, short braking (dynamic braking) and forward braking (reverse braking) are used together, and the degree of application of the brake is detected and fed back to the control system. By doing this, the brakes are optimally controlled, so the shock during braking can be softened compared to when braking is controlled using only the forward brake, and the stopping position of the optical system caused by the forward brake can be reduced. This has the effect of suppressing the variation in .

[Brief explanation of drawings]

Figure 1 is a block diagram showing the basic configuration of an embodiment of the present invention, Figure 2 is a circuit diagram showing the circuit configuration of an embodiment of the invention, and Figures 3 (A), (B), and (C) are Figure 2. 4 is a waveform diagram showing the output waveform of the signal of the embodiment of FIG. 2, FIG. 5 is a front view showing the configuration of the optical system part of the embodiment of the present invention, FIG. 6 is a diagram showing the relationship between the optical system clock pulse and the transfer paper size in the embodiment of the present invention, FIG. 7 is a diagram showing the timing of brake control in the embodiment in FIG. 2, and FIG. FIG. 9 is a timing chart showing an example of control results based on the control procedure of FIG. 8; FIG. 10 is a flow chart showing the ill operation of the microcomputer shown in FIG. 2. l...numeric keypad, 2...oscillator, 3...microcomputer, 3A...
・First counter, 3B...Second counter, 6...Addition circuit, 7...Comparator, 8...Capacitor, 9...D-A converter, lO~13...Driver, 14... Volume (variable resistance), 20... Motor, 21... Encoder, 31... Halogen lamp, 32... First scanning mirror, 34... Flag plate, 35.36...・Sensor. Figure 1 of the Arotsuku diagram showing the carrying of a palanquin and a gutter.

Claims (1)

[Scope of Claims] 1) a) a reversible electric motor that reciprocally drives an optical system for document scanning; b) speed detection means that detects the moving speed of the optical system; and c) a device that detects the start of braking of the optical system. a signal generating means for generating an instruction signal; and d) a braking control means for braking the electric motor using dynamic braking and reverse braking according to the detected output of the speed detecting means, based on the output signal of the signal generating means. An image forming apparatus comprising: 2) The image forming apparatus according to claim 1, wherein the speed detecting means detects the moving speed of the optical system at every predetermined timing during braking. 3) The apparatus according to claim 1 or 2, wherein the signal generating means is an image leading edge detection sensor that detects when the optical system passes the leading edge position of the document. Forming device. 4) In the apparatus according to any one of claims 1 to 3, the braking control means includes calculation means for calculating the deceleration rate of the optical system based on the detection output of the speed detection means. , a determining means for determining the number or timing of execution of the dynamic braking and the reverse braking based on the calculation result of the calculating means, short braking means for performing the dynamic braking according to the determination of the determining means, and the reverse braking. What is claimed is: 1. An image forming apparatus that sequentially drives forward rotation brake means for performing