JPH10274911A - Image forming apparatus and drive control method for image forming apparatus - Google Patents

Abstract

(57) [Summary] [Problem] To be controlled by fluctuation of drive characteristics of drive means,
To stop the optical system at a predetermined position with good reproducibility and high positional accuracy. When the optical system performs a back scan at a second speed, a stop timing of a motor is controlled based on a time measured by an internal timer of a CPU.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for controlling a driving state of a document exposing unit for exposing and scanning a document, and a driving control method for the image forming apparatus.

[0002]

2. Description of the Related Art FIG. 7 is a cross-sectional view illustrating a schematic configuration of a conventional image forming apparatus, and corresponds to a digital copying apparatus to which an automatic document feeder 1 can be connected.

In FIG. 1, reference numeral 1000 denotes a main body of a copying apparatus (image forming apparatus), 1 denotes an automatic document feeder for feeding a document to an exposure position, and 2 denotes a document table glass as a document table.

Reference numeral 4 denotes an optical system as image reading means, which comprises an original illumination lamp (exposure lamp) 3, a scanning mirror 9, and a lens 8. The optical system 4 is driven by a motor (not shown). Then, the original is illuminated by the exposure lamp 3 while being scanned by the motor, and reflected light from the original is imaged on the photosensitive drum 11 by the scanning mirror 9 and the lens 8.

The optical system 4 is required at a required speed in accordance with a set magnification (any of 64% to 200%) from the left to the right in the drawing, and is required according to the set paper type (size) and magnification. When the scanning is performed for a distance equal to the length of the optical system 4, the optical system 4 is inverted and controlled to a constant back speed. The scanning is stopped at the home position which is the scanning start position of No. 4.

[0006] A DC motor is generally used as a driving motor, and a motor which performs phase-locked loop (PLL) control for controlling the number of rotations to suppress rotation unevenness sufficiently is used.

The PLL control means that the signal is detected using a signal generator FG or the like that generates a signal having a frequency according to the number of rotations of the motor, and the signal is detected by a rotation frequency fn passed through a waveform shaping circuit and a reference signal generator. Is a control in which the phase is compared with a reference frequency fref required for a predetermined number of rotations to be generated, and the two phases are made coincident to keep the speed constant.

Generally, in a DC brushless motor integrated with a controller, a lock signal and an LD signal (Lock signal) are generally regarded as locked (the phases match) when the speed is pulled within several percent of a predetermined speed. Detect).

In a state where the image forming apparatus is incorporated in the image forming apparatus,
If the lock signal does not return within a predetermined time after sending the motor ON signal, the predetermined rotation control operation has not been performed, and it can be determined that the motor is abnormal.

On the other hand, a primary charger 12, a developing unit 13, a transfer charger 16 and a separation charger 22 are provided around the photosensitive drum 11. And the like constitute an image recording means.

The photosensitive drum 11 is rotated by a main motor (not shown) in the direction of the arrow shown in FIG.
Corona charged by the primary charger 12 and the optical system 4
When the reflected light from the original forms an image, an electrostatic latent image is formed. This electrostatic latent image is developed by the developing device 13 and visualized as a toner image.

On the other hand, at the bottom of the main body 1000, a cassette 15 for stacking and storing sheet materials 30 for transfer is provided. The sheet materials 30 separated and fed one by one by the , Through the transport path 19 to the photosensitive drum 11.

The sheet material 30 conveyed to a position just before the transfer charger 16 is timed using the detection signal of the sensor 14 so that the front end of the sheet material 30 coincides with the front end of the toner image. 11, and the toner image is transferred by the transfer charger 16. After the transfer, the transfer paper is separated from the photosensitive drum 11 by the separation charger 22, guided to the fixing device by the conveyor belt 23, and fixed by both the pressure roller 10 and the heating roller 11, and thereafter, the discharge roller 18. Is discharged out of the main body 1000.

On the other hand, in recent years, an image forming apparatus having an operation mode called drift reading has been proposed. This means that the original is not scanned by the above-described optical system, the optical system is fixed, and the original itself is moved by the automatic original feeder 1,
The original is scanned by the exposure lamp 3.

FIG. 8 shows the automatic document feeder 1 shown in FIG.
6A to 6D are schematic diagrams for explaining the correspondence between document feeding and the optical system 4 according to the first embodiment.

When a copy start command is input, the automatic document feeder 1 sends the first document to a predetermined position on the platen glass (see FIG. 8A). The optical system 4 waits at the home position L401 for scanning, and waits for the operation of the automatic document feeder 1 to be completed before the first position.
Is scanned. The optical system 4 moves to the home position (home position) L402 in the reading mode without stopping after the scanning is completed. Home position L4
In order to securely fix the optical system at 02, the optical system 4 secures a locked state by a fixing and holding means described later.

After the completion of the movement of the optical system 4 to the home position L402, the automatic document feeder 1 continuously feeds the second and subsequent originals at a predetermined scanning speed (see (FIG. 8) c), (d)).

FIG. 9 is a view for explaining a lock mechanism for temporarily fixing the position of the optical system 4 at the home position L402 in the reading mode shown in FIG.

In the figure, 411 is a lock lever, 41
Reference numeral 2 denotes a lock disk, which rotates mechanically in conjunction with a motor for operating the optical system 4 via a timing belt or the like. A lock bar 413 is fixed on the lock disk 412 and fixedly holds (locks) the optical system 4 by fitting with the lock lever 411. Note that the lock lever 411 is
Although not particularly shown, the up / down operation is performed by a solenoid or the like.

Since the first original performs a normal scanning operation, the lock lever 411 is in the state shown in FIG. 9A and performs an operation of a predetermined scanning length. Thereafter, the vehicle continues to move forward, and the lock lever 411 is lifted by a solenoid or the like just before the home position L402 in the drifting reading mode, as shown in FIG. 9B.

The optical system 4 is decelerated by applying a brake, and when the lock bar 413 shifts to a low speed state, it pushes against the lock lever 411 as shown in FIG. 9C. Thereafter, a solenoid (not shown) is turned off, and FIG.
(D), the lock lever 411 and the lock bar 4
13 is fitted, the optical system 4 is in a fixed holding state, and the motor is turned off.

[0022]

In the image forming apparatus constructed as described above, the stop control of the optical system 4 at the time of returning to the original after scanning the original is controlled by the number of pulses in the forward direction if a pulse motor is used. However, the DC motor scans for a predetermined time using the timing of the sensor and then reverses, applies a brake using the timing of the sensor, and stops at the start position.

In this case, the stop position must be changed due to variations in the brakes of the motor alone, variations in the load of each device, changes in the magnetic force due to temperature rise, and the like.

For example, in the case of a back scan, the brake works more strongly and stops before the home position, which is the scan start position. In the case of continuous copying, an operation of returning to the home position for each sheet occurs.
A predetermined copy speed cannot be obtained.

Conversely, if the braking effect is weakened, the stop position overruns the scan start position, and may hit the housing and cause mechanical destruction.

Therefore, a width sufficient to absorb the variation must be provided on the side opposite to the scanning direction from the scanning start position, which is a bottleneck for miniaturization of the device.

Further, in the image forming apparatus having the above-mentioned flow reading mode, when the optical system 4 is locked, an impact is generated due to a collision between the lock lever 411 and the lock bar 413 due to the mechanism. Therefore scanning speed (magnification)
Therefore, it is necessary to change the braking time so that the scanning speed is sufficiently low at the time of collision regardless of the scanning speed, and that the scanning is stabilized and the impact is minimized so as not to be pressed in the high speed region.

However, there are many parameters other than the scanning speed that affect the braking effect, such as variations in the motor and changes in the braking amount due to a rise in temperature during continuous operation. May be pressed against the lock member in a state where the force is too effective.

At this time, since the amount of energy at the time of collision changes with the square of the velocity, if the velocity is not sufficiently low,
As compared with the setting speed, the impact at the time of the collision becomes remarkably large, which not only reduces the durability but also causes the collision sound. In addition, the repulsion force at the time of collision increases dramatically as the speed increases, and the rebound force becomes larger than the pushing force of the motor at the time of the state transition from FIG. 9C to FIG. 9D. In this case, there is also a problem that the lock mechanism is not locked at the fixed position and comes off during a short time during which the lock mechanism operates.

Conversely, if the brake is applied too much, the speed becomes lower than the predetermined speed when the brake is released. Therefore, control is performed to return to the predetermined speed due to the characteristics of the control motor, and the full torque current is reduced. A flowing situation occurs. If the lock lever 411 and the lock bar 413 are fitted at this time, the motor cannot be rotated in spite of the full torque acceleration state, so that the motor is locked and an abnormal state is detected and an error occurs. There are serious problems such as damage to the motor and damage to the motor.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to capture the start-up characteristics according to the current state of the driving means and to back scan the original exposure means to obtain a predetermined characteristic. By accurately determining the stop timing when stopping at the position, the image forming apparatus can stop the optical system at a predetermined position with good reproducibility and high positional accuracy without being affected by fluctuations in the driving characteristics of the driving unit. It is an object of the present invention to provide an apparatus and a drive control method for an image forming apparatus.

[0032]

According to a first aspect of the present invention, there is provided a document exposing means for exposing a document, and scanning of the document exposing means is started at a predetermined position and is scanned at a constant first speed. Driving means, measuring means for measuring the time from the start of scanning of the document exposing means by the driving means to reaching the first speed, and when the document exposing means performs back scanning at a second speed, Control means for controlling the stop timing of the driving means based on the time measured by the measuring means.

According to a second aspect of the present invention, there is provided a detecting means for detecting that the document exposing means has passed a predetermined image leading edge position for starting exposure of the document, wherein the control means comprises a detecting means for detecting the document. The driving means is stopped when a time measured by the measuring means elapses after detecting that the document exposing means has passed a predetermined image leading end position by means.

According to a third aspect of the present invention, the driving means is constituted by a DC motor having a built-in controller.

According to a fourth aspect of the present invention, the controller outputs a predetermined timing signal at a timing at which the first speed determined according to a set magnification is reached.

According to a fifth aspect of the present invention, there is provided an original exposing means for exposing an original, a driving means for starting scanning of the original exposing means from a predetermined position and scanning at a first speed, and an original by the driving means. Measuring means for measuring the time from the start of scanning by the exposure means to the first speed, document feeding means capable of circulating and feeding each document separated from the document bundle from a predetermined position, and Setting means for setting the original feeding mode of the feeding means to one of the original fixed mode and the original flowing mode; and setting the original exposure means to a predetermined stop position when the original flowing mode is set by the setting means. Holding means for fixing and holding the document, and when the document exposing means approaches the stop position while scanning at the first speed, the driving means based on the time measured by the measuring means. In which a control means for decelerating the third speed of controlling the speed timing.

According to a sixth aspect of the present invention, the holding means holds and stops the document exposing means approaching at the third speed.

According to a seventh aspect of the present invention, there is provided a drive control method for an image forming apparatus for controlling a drive unit for starting scanning of a document exposing unit for exposing a document from a predetermined position and scanning at a constant first speed. A measuring step of measuring a time from the start of scanning of the document exposing means by the driving means to the first speed, and a determination of determining a stop timing of the driving means based on the measured time. Process and
A stopping step of stopping the driving unit based on the determined stop timing when the document exposing unit performs the back scan at the second speed.

[0039]

BEST MODE FOR CARRYING OUT THE INVENTION

[First Embodiment] FIG. 1 is a block diagram illustrating the configuration of an image forming apparatus according to a first embodiment of the present invention.

In the figure, reference numeral 501 denotes a controller-integrated DC brushless motor (motor) for reciprocating the optical system 4 in a predetermined direction. Reference numeral 502 denotes a CPU, which executes a control program stored in a memory resource such as a ROM (not shown) to transmit an operation ON / OFF signal to the motor 501, receive a lock (LD) signal, perform predetermined arithmetic processing, and the like. 42
A home position sensor (sensor) 1 detects a home position of the optical system 4 and outputs a detection signal to the CPU 5.
02 is output. Reference numeral 422 denotes an image sensor (sensor) which detects a document scanning start position and outputs the detection signal to the CPU 50.
Output to 2.

FIGS. 2A and 2B are schematic diagrams showing the positions of the sensors 421 and 422 for detecting the optical system 4 shown in FIG. 1, wherein FIG. 2A corresponds to a scan preparation state, and FIG. Corresponds to the state.

In the figure, L401 is a home position, a position where the optical system 4 waits until the optical system 4 starts scanning, and a state where the optical system 4 is stopped at this position is detected by the sensor 421. L403 is the image tip position (image tip)
Then, the sensor 422 detects that the optical system 4 has reached the position where the optical system 4 starts scanning the leading end of the image.

The optical system 4 has a home position L4
01, a predetermined speed (a speed determined by a set image forming magnification c (to be described later)) is reached during the movement to the image destination position L403. Is started.

FIG. 3 is a characteristic diagram for explaining the rising characteristic of the optical system 4 shown in FIG. 1 when scanning a document. The vertical axis represents the scanning speed Vb (mm / sec) of the optical system 4, and the horizontal axis represents the scanning speed. Indicates a time t (sec).

In the figure, the origin is the home position L401 where the home position sensor 421 is arranged, and the time t on the horizontal axis reaches the image sensor 422 arranged at the leading end L403 of the image, and the time a Is the time from the completion of acceleration of the optical system 4 until the motor 501 detects the control lock and outputs the lock signal LD. If the scanning speed at 100% magnification is Vmm / sec, the magnification C
%, The scanning speed Vc is Vc = V / c * 100, and the distance La required for the time a from the stop state to the control lock state can be derived from La = a * Vc / 2.

FIG. 4 is a characteristic diagram for explaining the fall characteristic of the optical system 4 shown in FIG. 1 during back scanning. The vertical axis indicates the scanning speed Vb (mm / sec) of the optical system 4 and the horizontal axis indicates the scanning speed. The axis indicates time t (sec).

In the figure, an optical system 4 includes an image sensor 42.
2 is detected, the reverse rotation brake is applied after a time t2 seconds, and control for switching to the short brake is performed after a time t1 seconds from the detection, and the optical system 4 is stopped.

In this case, the home position L4
01 and the front end L403 of the image are L = t2 * Vb + t1 * Vb /, where Vb is the back scan speed.
2 and the speed ratio Vc / Vb is Vc / Vb = a / t1.
Accordingly, the times t1 and t2 are calculated.

Specifically, in FIG. 3, when a reverse rotation signal (reverse rotation brake) is applied in the state of Vc, deceleration having a gradient opposite to the acceleration angle shown in the time from "0" to "a" in FIG. The speed reaches 0 mm / sec after a seconds. Therefore, in FIG. 4, the time t1 for applying the reverse brake is
Since t1 = (Vb / Vc) × a, t1 = a
In the back scan, the distance from the detection of the image sensor 422 to the position where the brake is turned on is represented by Lb.
Then, the distance Lb = L−t1 * Vb / 2, and the L
By inputting the value of L, the distance Lb = t2 *
Vb.

Accordingly, the time t2 until the reverse braking is applied is calculated by t2 = Lb / Vb. Therefore,
After the start signal of the motor 501 is turned on, the timing at which the acceleration is completed and a certain scanning speed is reached, that is, the motor 501 detects the control lock, and the lock signal L
The time a until the output of D is output is measured by an internal timer of the CPU 502, and the timing of outputting the off signal of the motor 501 is controlled by the CPU 502 based on the measurement data. The appropriate stop control is always performed in accordance with the motor state without depending on temperature, temperature, and aging, and the motor can be stopped at a predetermined position.

In the image forming apparatus configured as described above, the document exposing means (optical system 4) for exposing the document and the first speed at which the document exposing means starts scanning from a predetermined position and becomes constant Driving means (DC motor 501) for scanning by means of the scanning means, measuring means (timer of CPU 502) for measuring the time from the start of scanning of the document exposing means by the driving means until the first speed is reached, and the document exposing means Controlling the stop timing of the driving means based on the time measured by the measuring means when performing back scan at the second speed (CPU 502 executes and controls a control program stored in ROM) Therefore, a stop timer for stopping the original exposing means at a predetermined position by back-scanning the original exposing means by grasping the startup characteristic according to the current state of the driving means. Can be determined accurately timing, not dependent on variations in the driving characteristic of the driving means, it is possible to perform a document scanning at any time.

Further, there is provided a detecting means (image sensor 422) for detecting that the document exposing means has passed a predetermined image leading edge position for starting exposure of the document, and the control means (CPU 502) When the time measured by the internal timer elapses after the tip sensor 422 detects that the document exposing means has passed the predetermined image leading end position, the motor 501
Is stopped, the stop timing when the optical system 4 is back-scanned and stopped at a predetermined position can be accurately determined.

Further, the motor 501 is constituted by a DC motor having a controller built therein, and the controller makes a predetermined timing signal (lock signal) at the timing when the first speed determined according to the set magnification is reached. L
Since D) is output, the timing at which the document exposure means reaches the first speed determined according to the set magnification can be detected, and the control means can be notified of that timing.

Hereinafter, a drive control method for the image forming apparatus according to the present invention will be described with reference to a flowchart shown in FIG.

FIG. 5 is a flowchart showing an example of a drive control procedure of the image forming apparatus according to the present invention. In addition,
(1) to (10) show each step, and each procedure is a CPU.
It is assumed that it is stored in a ROM or the like built in the 502. It is assumed that an internal timer is built in the CPU 502.

First, the motor 501 is turned on and the internal timer is started (1). Next, it waits for the lock signal LD to be output from the controller of the motor 501 (2). When the lock signal LD is output, the timer is stopped, and the time t2 is calculated based on the above-described formula (3). . Next, the process waits for the sensor 422 to detect the optical system 4 (4). When the sensor 422 detects the optical system 4, scanning of a document by the optical system 4 (a first speed based on the set magnification) is started. (5).

Next, the optical system 4 waits for the scanning of the original scanning area (set by the set magnification and paper size) to be completed (6), and upon detecting the end of the scanning area, the motor 501 is reversed. To start the back scan at the second speed (7).

Next, when the sensor 422 detects the optical system 4 (8), the time of the time t2 is started by the internal timer, and when the time of the time t2 is finished (9), the motor 501 is started.
Is turned off (10), and the process ends. It is needless to say that the steps (1) to (10) are repeated when the number of images formed on the document is plural.

The drive control procedure of the image forming apparatus configured as described above is such that the document exposing means (optical system 4) for exposing a document starts scanning from a predetermined position and scans at a constant first speed. A driving control procedure of the image forming apparatus for controlling the means, wherein a measuring step of measuring a time from the start of scanning of the document exposing means by the driving means (motor 501) until the first speed is reached (FIG. 5) Step (1)), a determining step of determining a stop timing of the driving unit based on the measured time (Step (3) of FIG. 5), and a step of performing back scanning at a second speed by the document exposing unit. And a stopping step (steps (4) to (10) in FIG. 5) of stopping the driving means based on the determined stopping timing. Te, the stop timing when the document exposure means by backscan stopped at a predetermined position can be determined precisely, does not depend on fluctuations of the driving characteristic of the driving means, it is possible to perform a document scanning at any time.

[Second Embodiment] In the above embodiment, a case has been described in which the scanning position of the optical system 4 during back scanning during document scanning is controlled with high accuracy. The present invention can also be applied to a case where stop control of the motor 501 is performed when stopping at a set pouring position when performing document scanning in the pouring mode. Hereinafter, the embodiment will be described.

FIG. 6 is a characteristic diagram for explaining the rising characteristic of the optical system 4 in scanning an original in the image forming apparatus according to the second embodiment of the present invention. The vertical axis indicates the scanning speed Vc (mm) of the optical system 4. / Sec), and the horizontal axis represents time t (sec)
Is shown.

In the figure, the origin is the home position L401 where the home position sensor 421 is disposed, and the time t on the horizontal axis is the time until the image sensor 422 disposed at the leading end L403 of the image is reached. Is the time from the completion of acceleration of the optical system 4 until the motor 501 detects the control lock and outputs the lock signal LD.

Since the optical system 4 stops at the lock position in the pouring mode, the optical system 4 outputs a reverse rotation signal (reverse rotation brake).
Is applied, deceleration is performed at a gradient opposite to the acceleration angle shown in FIG. 3, and the speed reaches 0 mm / sec after a second. In the present embodiment, the basic speed V (magnification = 100%) even when the optical system 4 is not stopped and is driven at any scanning speed.
Time required for stabilizing at a speed of, for example, 10%
3 is derived from t3 = a * 0.9 * 100 / Vc.

In the image forming apparatus configured as described above, the document exposing means (optical system 4) for exposing the document and the document exposing means are started at a predetermined position and are scanned at the first speed. Driving means (motor 501);
Measuring means (C) for measuring the time from the start of scanning of the document exposing means by the driving means until the first speed is reached.
An internal timer of the PU 502), a document feeder (automatic document feeder 1) capable of circulating and feeding each document separated from the document bundle from a predetermined position, and setting the document feed mode of the document feeder to document fixed. A setting unit (an operation unit (not shown)) for setting one of a mode and a document pouring mode, and fixing the document exposing unit at a predetermined stop position when the document pouring mode is set by the setting unit. When the holding means (the lock lever 411, the lock disk 412, the lock bar 413, etc.) and the document exposing means approach the stop position while scanning at the first speed, the measurement means measures. Control means for controlling the deceleration timing of the driving means based on time to decelerate to a third speed (the CPU 502 executes a control program stored in the ROM Since a control to), when the driving mode poured optical system 4, the motor 50
(1) The deceleration process to the speed for fixedly maintaining the speed corresponding to the current rising characteristic can be started at an appropriate timing and surely completed, thereby reliably avoiding a situation in which device destruction is caused.

Therefore, the start signal for driving the optical system is turned on.
After that, the time a from when the acceleration is completed to when the motor 501 detects the control lock and outputs the lock signal LD is CP
U502 measures the time of an internal timer or the like, and derives a time t3 for applying the brake to a desired speed therefrom,
By controlling the brake timing of the motor 501, the transition from the scan speed to the lock speed is performed stably without depending on variation, temperature, and aging.

According to the above-described embodiment, the time from the start of the operation of the original exposure driving means to the output of the control lock detection signal is measured, and the stop control is performed. By performing control using the calculated value using the measured value, it is possible to always stop at the same position without being affected by the variation of the motor and the temperature, and to improve the stop accuracy, and it is not necessary to secure the variation radiation. Therefore, the size of the device can be reduced.

Further, the fixed position holding (locking) operation at the same speed can be stably performed in all the devices, so that the noise reduction, the reliability of the lock mechanism can be improved, and the life of the components can be extended. Becomes

[0068]

As described above, the first embodiment according to the present invention is described.
According to the invention, a document exposing means for exposing a document, a driving means for starting the scanning of the document exposing means from a predetermined position and scanning at a constant first speed, and a scanning of the document exposing means by the driving means Measuring means for measuring the time from the start to reaching the first speed, and the driving means based on the time measured by the measuring means when the document exposure means performs back scan at the second speed. Control means for controlling the stop timing, so that it is possible to accurately determine the stop timing when stopping the original exposure means at a predetermined position by back-scanning the document exposure means by capturing the startup characteristics according to the current state of the drive means. The optical system can be stopped at a predetermined position with good reproducibility and high positional accuracy without being affected by fluctuations in the driving characteristics of the driving means. Is not influenced by movement, it is possible to perform a document scanning at any time.

According to the second invention, there is provided detecting means for detecting that the document exposing means has passed a predetermined image leading edge position for starting exposure of the document, and the control means comprises After detecting that the document exposing means has passed the predetermined image leading edge position, the driving means is stopped when the time measured by the measuring means elapses, so that the document exposing means is back-scanned and stopped at the predetermined position. It is possible to accurately determine the stop timing at which the stop is performed.

According to the third and fourth inventions, the driving means is constituted by a DC motor including a controller, and the controller reaches the first speed determined according to a set magnification. Since the predetermined timing signal is output at the set timing, the document exposing means can detect the timing at which the first speed determined according to the set magnification is reached, and notify the control means of the detection.

According to the fifth and sixth aspects of the invention, the document exposing means for exposing the document, the driving means for starting the scanning of the document exposing means from a predetermined position and scanning at the first speed, and the driving means Measuring means for measuring the time from the start of scanning of the document exposing means to reaching the first speed; document feeding means capable of circulating and feeding each document separated from the document bundle from a predetermined position; Setting means for setting the original feeding mode of the feeding means to either the original fixed mode or the original flowing mode; and stopping the original exposure means for a predetermined stop when the original flowing mode is set by the setting means. Holding means for fixedly holding at a position, when the document exposing means approaches the stop position while scanning at the first speed, based on a time measured by the measuring means, Control means for controlling the speed timing to reduce the speed to the third speed, so that when the document exposure means is driven in the pouring mode, the speed is reduced to a speed which is fixedly held in accordance with the current rising characteristic of the drive means. It is possible to start the processing at an appropriate timing and to surely complete the processing, thereby reliably avoiding a situation that causes equipment destruction.

According to the seventh aspect of the present invention, there is provided a drive control method for an image forming apparatus for controlling a drive unit for starting scanning of a document exposing unit for exposing a document from a predetermined position and scanning at a constant first speed. A measuring step of measuring a time from the start of scanning of the document exposing unit by the driving unit to the first speed, and a determining step of determining a stop timing of the driving unit based on the measured time. A stopping step of stopping the driving means based on the determined stop timing when the document exposing means performs back scanning at a second speed. , And the stop timing when the document exposure unit is back-scanned and stopped at a predetermined position can be accurately determined, and is not affected by fluctuations in the drive characteristics of the drive unit. , It is possible to perform a document scanning at any time.

Therefore, it is possible to always stop at the same position without being influenced by the variation of the motor and the temperature, to improve the stopping accuracy, and it is not necessary to secure the variation width. Play.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an image forming apparatus according to a first exemplary embodiment of the present invention.

FIG. 2 is a schematic diagram showing an arrangement position of each sensor for detecting the optical system shown in FIG.

FIG. 3 is a characteristic diagram illustrating a rising characteristic of the optical system illustrated in FIG. 1 during scanning of a document.

FIG. 4 is a characteristic diagram illustrating a fall characteristic of the optical system shown in FIG. 1 during back scanning.

FIG. 5 is a flowchart illustrating an example of a drive control procedure of the image forming apparatus according to the present invention.

FIG. 6 is a characteristic diagram illustrating a rising characteristic of an optical system in scanning an original in an image forming apparatus according to a second exemplary embodiment of the present invention.

FIG. 7 is a cross-sectional view illustrating a schematic configuration of a conventional image forming apparatus.

8 is a schematic diagram for explaining the correspondence between the document feeding by the automatic document feeder shown in FIG. 7 and the optical system.

FIG. 9 is a diagram illustrating a lock mechanism for temporarily fixing the position of the optical system at the home position of the reading mode shown in FIG. 8;

[Explanation of symbols]

 421 Home position sensor 422 Image sensor 501 Motor (DC motor) 502 CPU

Claims (7)

[Claims] 1. A document exposing unit for exposing a document, a driving unit for starting scanning of the document exposing unit from a predetermined position and scanning at a first constant speed, and a scanning start of the document exposing unit by the driving unit. Measuring means for measuring the time from when the first speed is reached, and stopping the driving means based on the time measured by the measuring means when the document exposure means performs back scan at the second speed. An image forming apparatus comprising: control means for controlling timing. 2. The apparatus according to claim 1, further comprising: detecting means for detecting that the document exposing means has passed a predetermined image leading edge position for starting exposure of the document. After detecting that it has passed the image tip position,
2. The image forming apparatus according to claim 1, wherein the driving unit is stopped when a time measured by the measuring unit has elapsed. 3. An image forming apparatus according to claim 1, wherein said driving means is constituted by a DC motor including a controller. 4. The image forming apparatus according to claim 3, wherein the controller outputs a predetermined timing signal at a timing when the first speed determined according to a set magnification is reached. 5. A document exposing means for exposing a document, a driving means for starting scanning of the document exposing means from a predetermined position and scanning at a first speed, and a driving means for starting the scanning of the document exposing means by the driving means. Measuring means for measuring the time required to reach the speed of 1; document feeding means capable of circulating and feeding each document separated from the document bundle from a predetermined position; and a document feeding mode of the document feeding means. Setting means for setting any one of a document fixing mode and a document flow mode; and a holding means for fixing and holding the document exposure means at a predetermined stop position when the document flow mode is set by the setting means. When the document exposing unit approaches the stop position while scanning at the first speed, a deceleration timing of the driving unit is controlled based on a time measured by the measuring unit. Control means for reducing the speed to a third speed. 6. The image forming apparatus according to claim 5, wherein the holding unit holds and stops the document exposing unit approaching at the third speed. 7. A drive control method for an image forming apparatus, comprising: controlling a driving unit that starts scanning a document exposing unit that exposes a document from a predetermined position and performs scanning at a constant first speed; A measuring step of measuring a time from the start of scanning of the document exposure means to the first speed, a determining step of determining a stop timing of the driving means based on the measured time, A driving control method for the image forming apparatus, comprising: a stopping step of stopping the driving unit based on the determined stop timing when performing the back scan at the second speed.