JPH0799424B2 - Optical system drive for image forming apparatus - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to speed control of a scanning system in an image forming apparatus such as a copying machine or a printer having an optical scanning system driven by a pulse motor.

2. Description of the Related Art A general copying machine having an optical scanning system will be briefly described with reference to FIG.

A simple internal structure of a general electrophotographic copying machine is shown in FIG.

A platen glass 2 serving as a document placing table is stretched on the top surface of the copying machine casing 1, and a document 3 is placed at a predetermined position on the platen glass 2.

An exposure lamp 4 movably supported in the left-right direction is provided near the lower surface of the platen glass 2, and scans while illuminating the surface of the original 3 in a slit shape through the platen glass 2.

The light reflected by the original 3 is the first, second, third mirrors 5, 6, 7, lenses
An image is formed by reaching the photoconductor 10 via an optical system such as the eighth and fourth mirrors 9.

Around the photoconductor 10, a charging device 11, a discharging lamp 12, a developing device 13, a transfer device 14, and a cleaning device 15 are arranged in this order in the rotational direction of the photoconductor.

The surface of the photoconductor is uniformly charged by the charger 11, an electrostatic latent image is formed by the optical system, the charge of the unnecessary latent image portion is removed by the charge eliminating lamp 12, and the toner is attached by the developer 13. The transfer device 14 transfers the toner image onto the paper, the toner remaining on the surface is removed by the cleaning device 15, and the paper on which the toner image is transferred is fixed by the fixing device.
It is fixed by 16, and the above one cycle of the image pickup process is completed.

Here, the static elimination lamp 12 is a plurality of small light sources arranged in the width direction of the photoconductor, and removes charges between the electrostatic latent images formed on the photoconductor surface by an optical system or both sides of the electrostatic latent image. Unnecessary charges are removed to prevent unnecessary toner from being adhered by the developing device 13 in the next stage to unnecessary portions, and unnecessary images such as black stripes are formed on the edges of the paper. It can be prevented from occurring.

As described above, since the static elimination lamp 12 conventionally works after exposure by the optical system, its operation timing may be set at an appropriate time after the formation of the electrostatic latent image by exposure.

However, in recent years, along with the downsizing of the body of the copying machine, it is often installed not between the exposure position and the developing device 13 but between the charging device before the exposure position.

When the charge eliminating lamp 12 is arranged between the charger 11 and the exposure position, the charger 11 uniformly charges the surface of the photoconductor 10 and then the charge eliminating lamp 12 removes unnecessary charges, so that the unnecessary portion is hidden during exposure. It prevents the formation of images.

However, in the case of this type of copying machine, it is possible to turn off the light after the unnecessary charge is removed by turning on the static elimination lamp 12 on the photoconductor 10 rotating at a constant speed, and then a latent image can be formed. It takes time to wait for the exposure to reach the exposure position of the determined portion, and if the timing control is not performed, a necessary copy image cannot be obtained.

The present invention has been made in view of the above points, and an object of the present invention is to prevent a defect such as a partial loss of a copied image due to the provision of a charge eliminating unit before the exposure position on the surface of the photoconductor, and to perform a stable and accurate operation. The point is to provide an optical system driving device capable of obtaining a copied image.

Means and Actions for Solving Problems In order to achieve the above-mentioned object, the present invention forms an image with an optical scanning system in which a document is scanned and exposed while reflected light from the document is exposed at a predetermined position of a photoconductor. In the apparatus, a charging device for uniformly charging the photoconductor is provided, and the charging device is disposed downstream of the photoconductor charging position of the charging device and upstream of the image forming position of the optical scanning system, and prior to exposure by the optical scanning system. Static electricity removing means for removing static electricity from the front end portion of the image and ending static electricity removal at substantially the same time as scanning of the optical scanning system, and magnification setting means for setting a copying magnification.
The final scanning speed setting means for setting the final scanning speed of the scanning system based on the magnification set by the same magnification setting means, and the speed up to the same speed based on the final scanning speed set by the final scanning speed setting means. Step scanning speed / time setting means for dividing the ascending into speeds of several steps and setting the moving time at each speed, and drive control means for controlling the drive of the scanning system based on the setting of the step scanning speed / time setting means And a pulse motor that drives the scanning system under the control of the drive control means, and the step scanning speed / time setting means scans the distance from the scanning start position to the document reading start position by the optical scanning system. The step scanning speed and time are set so that the time until the static elimination end position of the front end portion of the image by the static elimination unit on the photoconductor moves to the exposure position of the optical scanning system And an optical system driving device of an image forming apparatus.

Since the charging device is provided with a discharging unit disposed downstream of the photosensitive member charging position and upstream of the image forming position of the optical scanning system, and discharging the front end portion of the image prior to exposure by the optical scanning system, By controlling the charge eliminating means, unnecessary charges on the surface of the photoconductor are removed to prevent unnecessary adhesion of toner to prevent unnecessary consumption of toner, and it is also possible to eliminate the black band at the edge of paper. It is possible to prevent the occurrence of an image in advance, and also contribute to downsizing of the main body of the copying machine.

The stepwise scanning speed / time setting means determines the stepwise scanning speed, and the time setting means determines the time required for the optical scanning system to scan the distance from the scanning start position to the document reading start position by the static elimination means on the photoconductor. Since the stepwise scanning speed and time are set so that the charge removal end position at the front end of the image is equal to or longer than the time to move to the exposure position of the optical scanning system, the charge removal is performed at the beginning of the document reading because the charge removal means is provided. It is possible to avoid such a problem that the charge is removed by the means and a part of the copied image is lost.

Further, the exposure can be started in a state where the optical system reaches a constant final scanning speed, and a stable and accurate copied image can be obtained.

Embodiment An embodiment of the copying machine according to the present invention shown in FIGS. 2 to 6 will be described below.

The internal structure of the copying machine is substantially the same as that shown in FIG. 1, but as shown in FIG. 2, the discharge lamp 12 is located between the charger 11 and the exposure position.

The photoconductor 10 rotates at a constant speed, and is sequentially charged, discharged, exposed,
Development and each process are performed.

The surface of the photoconductor 10 uniformly charged by the charger 11 has unnecessary charges removed by the charge eliminating lamp 12 that is turned on at a required timing, but an image is formed by the optical system at the charge eliminated portion. However, an electrostatic latent image is not formed.

Therefore, if the position on the surface of the photoconductor 10 at which the discharge lamp 12 has finished lighting is set to P, the charge after P is not discharged,
Since it is a portion capable of forming a latent image, it is necessary to start the exposure after P reaches the exposure position Q by the optical system.

It takes a certain time T from the time when the static elimination lamp 12 is turned off until P reaches Q.

FIG. 2 is a perspective view showing a drive mechanism of the optical scanning system.

The copier casing 1 is laid horizontally to the left and right.
A first mirror 5, a second mirror 6, and a third mirror 7 are slidably mounted on the left and right between a guide shaft 20 and a guide plate 21 which are fixed to each other.

Although not shown in the figure, the exposure lamp 4 is mounted on the first mirror 5 so as to slide integrally.
A detection body 23 is provided on the slide portion 22 that slidably holds the first mirror 5 so as to project forward.

The second and third mirrors 6 and 7 are installed at an angle of 90 ° and slide together, and the slide portion 24 of the mirrors 6 and 7 is provided with a pulley 25 exposed forward. .

The first mirror 5 and the second mirrors 6, 7 are driven by a single motor 26 via a rope 27.

That is, one of the ropes 27 wound around the drive shaft of the motor 26 is fixed to the mounting portion projecting on the slide portion 22 of the first mirror 5, and then the slide portion 24 of the second and third mirrors 6 and 7. It is wound around the protruding pulley 25 half a turn, and its end is fixed to the copier casing 1.

The other end of the rope 27 is wound half a turn around a pulley 28 fixed to the casing 1 of the copying machine on the left side, and then the slide portion 24.
The end portion of the pulley 25 is fixed to the copier casing 1 again by half-turning around the pulley 25 protruding from the casing.

Therefore, when the motor 26 is driven and the first mirror 5 moves at the speed V via the rope 27, the second and third mirrors 6 and 7 follow the first mirror 5 at a speed V / 2 which is half the speed. To move.

Since the second mirrors 6 and 7 move to follow the speed of the first mirror 5 at V / 2, even if the original 3 on the platen glass 2 is exposed and scanned by the exposure lamp 4 integrated with the first mirror 5, The optical path length of the reflected light on the document surface to the lens 8 can be kept unchanged.

In order to detect the position of the scanning system, the photo interrupter 40 that detects the detection body 23 is fixed at a predetermined position.

FIG. 4 is a principal part explanatory view showing the scanning start position X and the exposure start position Y of the first mirror 5.

The first mirror 5 is controlled so as to always be at the scanning start position X when stopped, and reaches the exposure start position Y after a short time has elapsed since the scanning started.

The exposure start position Y is the original 3 placed on the platen glass 2.
Registration position, which is a position fixed by the positioning plate 29.

The exposure start position Y is the original document exposure start position, that is, the original document reading start position, and is different from the lighting start position of the exposure lamp 4.

The exposure lamp 4 has to have a stable light amount at the original reading start position, and therefore it is normally lit at the start of scanning of the optical scanning system, and the edge of the platen glass 2 is started before starting the original reading. Light is reflected by the reflection surface (usually white) such as the inner surface of the casing or the inside of the casing, which reaches the surface of the photoconductor and exposes the portion where the latent image can be formed after the electricity elimination by the electricity elimination lamp is completed. ing.

However, the charge removal of the unnecessary latent image portion is performed mainly by the charge eliminating lamp.

The scanning state of the exposure lamp 4 and the first mirror 5 is shown in FIG.

FIG. 7A shows the scanning distance 1 with respect to time t, and FIG. 7B shows the scanning speed v with respect to time t.

Until the final scanning speed V during exposure, constant velocities v ₁ , v ₂ ... are determined for each stage, and the velocities are gradually increased by controlling the moving times t ₁ , t _2, ... for each velocity. A so-called slew-up method of increasing the height is adopted.

The speed is increased by the slew-up method from the scanning start position X to immediately before the exposure start position Y, and exposure scanning is performed from the exposure start position Y at a constant final scanning speed V.

Therefore, since exposure is always performed from the beginning to the end at a constant scanning speed, an accurate and stable copy image can be obtained.

When the exposure scanning is completed (exposure ending position Z), the moving speed is decreased step by step to reach the scanning ending position W.

Then, subsequently, this time, the return scan is entered and the scan start position X is returned.

The above is one cycle of optical system scanning, and the scanning state varies depending on the copy magnification.

That is, since the final scanning speed V varies depending on the copy magnification, for example, when the reduction magnification is set to a higher value, the final scanning speed V increases, so that a curve shown by a broken line in FIG. 5 is drawn.

Since the final scanning speed must already be reached at the exposure start position Y, the rate of increase in speed is large, and the time required to reach the normal exposure start position Y, that is, the time ta from the scan start to the exposure start is short. Become.

Looking at the relationship with the lighting control of the static elimination lamp 12, the static elimination lamp 12 is extinguished at about the same time as the start of normal scanning, and the latent image-capable portion is formed on the surface of the photoconductor 10 thereafter, so that the latent image-capable portion starts from the scanning start. It is necessary to prevent the exposure from being started during the time T until reaching the exposure position Q.

However, since ta is short until the copying is started to such an extent that the copying magnification is set to the reduction side, exposure may be started before the time T has elapsed.

Therefore, the present invention controls the increase rate of the scanning speed so that the exposure is started after the elapse of the T time at the reduction ratio.

The control method is the movement time at each stage scanning speed v ₁ , v _2.
This is done by setting t ₁ , t ₂ ... appropriately.

A block diagram of the above control system will be described with reference to FIG.

The central part of the control system is the CPU 30, which is controlled by using the RAM 32 at any time according to the program written in the ROM 31.

Signals are input to the CPU 30 through the input interface 33 from a magnification setting button 35, a start button 36, and the like on the operation panel provided on the front side of the top of the copying machine casing 1.

Further, the CPU 30 outputs a control signal to the lamp drive circuit 37, the motor drive circuit 38 and the like via the output interface 34, and the lamp drive circuit 37 causes the static elimination lamp 12 to operate.
Is turned on, and the motor drive circuit 38 drives the pulse motor 26.

When an appropriate magnification is entered with the magnification setting button 35, the CP
U30 produces the final scanning speed V corresponding to the magnification, and as described above, the moving time t ₁ , t of the speeds v ₁ , v ₂ ... ₂ ……
Is calculated and recorded in RAM32.

Now, when the time T is entered in FIG. 5 (a) and the intersection of the time T and the exposure start position Y is C, the movement time t ₁ , t so that the curve of the scanning distance with respect to time passes below the intersection C. ₂ ... is decided.

Then, when the copy start button 36 is pressed, a control signal is output to the motor drive circuit 38 to scan the optical system in accordance with the moving times t ₁ , t ₂ ... recorded in the RAM 32, and the motor 26 that scans the optical system is driven. To be done.

At the start of copying, the static elimination lamp 12 is off,
The static elimination lamp 12 is turned on for an appropriate time to return to the scanning start position X by the return scanning, removes the electric charge of the unnecessary portion of copying, and is controlled by the CPU 30 to turn off when returning to the copying start position.

In the case of continuous copying, the above cycle will be repeated.

As described above, in the present embodiment, it is possible to avoid the possibility that a copy image is lost due to the static elimination lamp 12 being disposed before the exposure position Q.

The present embodiment can be applied to the case where the copy magnification is continuously changed, or when the predetermined magnification is set in several steps. However, when the predetermined magnification is set, the scanning speeds v ₁ and v are set in advance. _When the moving times t ₁ , t ₂ for each ... are written in the ROM 31 in advance for each magnification and the magnification is input by the copy start button 36, the movement times corresponding to the same magnification
t _1, t ₂ ...... may be selected.

EFFECTS OF THE INVENTION Since the present invention has a charge eliminating unit on the downstream side of the photoconductor charging position and on the upstream side of the image forming position of the optical scanning system, unnecessary charge on the surface of the photoconductor is removed by controlling the charge eliminating unit. It is possible to prevent wasteful consumption and prevent unnecessary images such as black bands at the edges of the paper from occurring, and also contribute to downsizing of the main body of the copying machine.

The time required for the step scanning speed / time setting means to scan the distance from the scanning start position to the document reading start position is equal to or longer than the time required for the discharging end position at the front end of the image by the discharging means on the photoconductor to move to the exposure position. Since the stepwise scanning speed and time are set so that the charge removal means is provided, it is possible to avoid problems such as charge removal at the beginning of the document reading and loss of part of the copied image.

Further, by starting the exposure with the optical system reaching a constant final scanning speed, a stable and accurate copy image can be obtained.

[Brief description of drawings]

FIG. 1 is an internal schematic diagram of a general copying machine, FIG. 2 is an internal schematic diagram of one embodiment of the copying machine according to the present invention, and FIG. 3 is a perspective view showing a drive mechanism of an optical scanning system of this embodiment. 4 and 5 are explanatory views showing the scanning position of the optical scanning system of this embodiment, FIG. 5 is a view showing the scanning state of the optical scanning system, and FIG. 6 is a block diagram of the control system of this embodiment. . 1 ... Copier casing, 2 ... Platen glass, 3 ...
... manuscript, 4 ... exposure lamp, 5 ... first mirror, 6 ...
Second mirror, 7 ... Third mirror, 8 ... Lens, 9 ...
4th mirror, 10 ... photoreceptor, 11 ... charging device, 12 ... charging lamp, 13 ... developing device, 14 ... transfer device, 15 ... cleaning device, 16 ... fixing device, 20 ... guide Shaft, 21 ……
Guide plate, 22 …… Slide part, 23 …… Detector, 24 …… Slide part, 25 …… Pulley, 26 …… Motor, 27 …… Rope, 28 …… Pulley, 29 …… Positioning plate, 30 …… CPU, 31
...... ROM, 32 …… RAM, 33 …… Input interface, 34
...... Output interface, 35 …… Magnification setting button, 36
...... Copy start button, 37 ...... Lamp drive circuit, 38 ...... Motor drive circuit, 40 ...... Photo interrupter.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H02P 8/14 H02P 8/00 304 A

Claims (1)

[Claims] 1. An image forming apparatus comprising an optical scanning system for scanning and exposing a document while exposing light reflected from the document at a predetermined position of the photoconductor, and a charger for uniformly charging the photoconductor, and the charger. Is provided downstream of the charging position of the photoconductor and upstream of the image forming position of the optical scanning system, the front end portion of the image is discharged prior to the exposure by the optical scanning system, and the scanning of the optical scanning system is started. Static elimination means for terminating static electricity at approximately the same time, magnification setting means for setting a copy magnification, final scanning speed setting means for setting the final scanning speed of the scanning system based on the magnification set by the magnification setting means, and final scanning Based on the final scanning speed set by the speed setting means, the speed increase until reaching the same speed is divided into several speeds and the moving time at each speed is set.
A time setting means, a drive control means for controlling the drive of the scanning system based on the setting of the same-stage scanning speed / time setting means, and a pulse motor for driving the scanning system under the control of the drive control means, The stepwise scanning speed / time setting means determines the time required for the optical scanning system to scan the distance from the scanning start position to the original reading start position, and the discharging end position at the front end of the image by the discharging means on the photoconductor is An optical system driving device for an image forming apparatus, wherein a stepwise scanning speed and time are set so as to be equal to or longer than a time for moving to an exposure position of the optical scanning system.