JPH0588534A - Image formation device by simultaneous development and cleaning system - Google Patents

Abstract

PURPOSE:To enable secure cleaning operation and shorten a preparatory rotation time. CONSTITUTION:While an exposed part irradiated with a laser scanning beam B and an unexposed part are formed on the peripheral surface of a photosensitive drum 1 passed through an electrostatic charger 2 and residual toner sticking on the unexposed part is attracted to the side of a developing roller 6 by utilizing the potential difference between the side of the photosensitive body 1 and a developing roller 6 applied with a developing bias ¦Vb¦ to clean the unexposed part, toner is supplied from the side of the developing roller 6 to the exposed part to perform development. This simultaneous development and cleaning system image forming device is provided with a delay time setting means 21 and a delay driving control means 20 which stops the rotation of the developing roller 6 during t2 from the preparatory rotation start time t1 of the photosensitive drum 1 to lapse of the setting delay time Ts set by the delay time setting means 21 and then drives and rotates the developing roller 6 at t2 after the set delay.

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 of a cleaning simultaneous developing system.

[0002]

2. Description of the Related Art A developing device and a waste toner collecting device including a scraping blade are arranged on both sides of a photosensitive drum with a transfer device interposed therebetween so that development and cleaning of residual toner on the photosensitive drum can be performed independently. In contrast to the well-known image forming apparatus, the present applicant has previously proposed an image forming apparatus shown in FIG. 3 which is a so-called simultaneous developing cleaning system in which development and cleaning are performed at the same time (for example, JP-A-3-7972). According to this simultaneous development cleaning method, epoch-making effects such as reduction of running cost due to reduction of toner consumption, downsizing of the apparatus, and cleaning without damaging the photosensitive drum can be obtained.

In FIG. 3, 1 is a photosensitive drum as an image carrier, 2 is a charger, 3 is a developing device, and 7 is a transfer device.
Further, the developing device 3 is of a contact type one-component non-magnetic developing system using an elastic conductive roller (developing roller) 6 as a developer (toner) carrier, and the one-component toner T0 contained in the box 4 is The charging blade 5 made of silicon rubber or the like forms charged toner T1 and is supplied to the photosensitive drum 1 side for development.

Further, 20 is a control device, which is the main motor 1
1, the laser emission source 12 for light irradiation, the switch 14 for the developing bias power source (-Vb), the switch 13 for the charger power source (-Vo), etc. are drive-controlled at the timing shown in FIG.
The opening / closing switch 15 of the transfer device 7 is also drive-controlled in the same manner. The developing roller 6 is synchronously rotated by the main motor 11 together with the photosensitive drum 1.

In the image forming apparatus having such a configuration, when the main motor 11 is preliminarily rotationally driven by the controller 20 at time t1 in FIG. 4, the photosensitive drum 1 and the developing roller 6 are synchronously rotated. Further, the peripheral surface of the photosensitive drum 1 is charged to the charging potential −Vo at the time of image formation by the charger 2, and then the time t
In FIG. 3, the exposed portion irradiated with the laser scanning beam B (hatched in FIG. 4) based on the image data has the potential −Vr. The unexposed portion remains at the charging potential −Vo. On the other hand, the developing roller 6 is also charged to the developing bias potential −Vb from time t1.

As shown in FIG. 5 (C), the charging potential -Vr of the exposed portion has the same polarity as the developing bias potential -Vb to the developing roller 6, but its absolute value is low (| Vr | <| Vb |).
Therefore, the charged toner T1 on the developing roller 6 is
As shown in (3), the developing toner T3 is adsorbed to the exposed portion by an electric field action. In other words, it is developed [Fig. 5
(C)]. The toner T4 remaining on the developing roller 6 is
It is collected in the developing device 3 and reused.

This developing toner T3 is then transferred to the opposite surface (front surface) of the paper P by the transfer device 7 of FIG.
As shown in (D), it is transferred as image toner T5.

On the other hand, the toner (T6) may remain on the photosensitive drum 1 after the transfer. This residual toner T6
Is charged to the above potential -Vo in the charger 2 as shown in FIG. However, as shown in FIG. 5B, the residual toner T6 adhering to the exposed portion after that is charged to the potential -Vr, which is lower in absolute value than the developing bias potential -Vb, as shown in FIG. Absent. Rather,
This is advantageous because it can be effectively used for the development shown in FIG.

On the other hand, the residual toner T6 adhering to the unexposed portion shown in FIG. 5B remains at the charging potential -Vo having the same polarity as the developing bias potential -Vb of the developing roller 6 and a high absolute value.

Therefore, as shown in FIG. 5C, the residual toner T6 is attracted to the developing roller 6 side by the electric field action. That is, the residual toner T attached to the unexposed portion
Since No. 6 is removed from the photosensitive drum 1, it is understood that cleaning is performed here. Further, the removed residual toner T6 can be reused as the supplied toner T1 in FIGS. 3 and 5C.

Thus, the cleaning is performed at the upstream position where the photosensitive drum 1 and the developing roller 6 come into contact with each other, and subsequently, the development is simultaneously performed at the downstream side.

Here, after the scanning of the laser scanning beam B based on the image data is completed at time t3 in FIG. 4 and the development, transfer, and paper discharge of the exposed portion are completed, the controller 20 is in the main state. Motor 11, charger 2 (1
3) Stop the laser emission source 12 and the like.

[0013]

By the way, in order to form an image with such an apparatus, preparatory work such as preparatory rotation for raising the photosensitive drum 1 to a prescribed number of revolutions and stabilization of each potential is required. For this reason, the control device 20 drives and controls each unit at the timing (t1) before scanning the laser scanning beam B as shown in FIG.

Considering restarting, the photosensitive drum 1
The peripheral surface portion between P2 and P1 shown in FIG. 3 does not pass through the charger 2 at the start of preparatory rotation (t1), and the developing roller 6
Will be in contact with. Therefore, the peripheral surface portion between P2 and P1 is naturally not charged to the charging potential −Vo during image formation, and depending on the length of the stop time and the like, as shown in FIG. 6, the development bias turned on at time t1. The residual potential -Vs may be lower in absolute value than the potential -Vb.

Then, the development (│Vb│) shown in FIG.
Electric field action (| Vb | − | Vs |) similar to − | Vr |)
Will occur. That is, the supply toner T1 carried by the rotating developing roller 6 to which the developing bias potential −Vb is applied and which has the residual potential −Vs is the photosensitive drum 1.
A large amount is attached to the peripheral surface portion between P2 and P1. Originally, the opposite phenomenon to cleaning occurs.

Therefore, after passing through the developing roller 6, it scatters and contaminates the inside of the apparatus. Further, when the amount of adhesion becomes large, even if the charger 2 is passed through the charger 2 several times during the preparatory rotation, the image is formed without being charged to a predetermined value (-Vo) and being adhered to the peripheral surface portion between the P2-P1. At some times, it may be transferred onto the paper P, and the image quality may deteriorate. Increasing the preparatory rotation time to prevent this impedes rapid image formation and is unacceptable.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus of the simultaneous development type which is capable of performing reliable cleaning and quickly forming a high quality image while shortening the preparation rotation time.

[0018]

According to the present invention, an exposed portion and an unexposed portion irradiated with light are formed on the peripheral surface of a photosensitive drum which has passed through a charger, and the photosensitive drum side and the developing roller side to which a developing bias is applied. The residual toner adhering to the unexposed area is adsorbed to the developing roller side by using the potential difference between and to clean the unexposed area, and at the same time toner is supplied from the developing roller side to the exposed area for development. In a cleaning type image forming apparatus, a delay time setting unit and the developing roller are set between the start of preparatory rotation of the photosensitive drum before image formation and the lapse of a set delay time set by the delay time setting unit. Delay drive control means for driving the developing roller to rotate after the rotation is stopped and the set delay time has elapsed.

[0019]

According to the present invention, an appropriate delay time is set in the delay time setting means, and the preparatory rotation operation is started. Then, the delay drive control means delays the set delay time and drives the developing roller to rotate. That is, the rotation of the developing roller is stopped during the set delay time. Therefore, even when the developing roller stops rotating, there is a potential difference between the residual potential of the photosensitive drum and the bias potential of the developing roller, but compared to the case where the developing roller is rotated simultaneously with the photosensitive drum,
The amount of toner attached to the photosensitive drum can be greatly reduced. Therefore, the residual toner can be reliably cleaned while shortening the preparation rotation time, and a high-quality image can be quickly formed.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. The image forming apparatus of the main development simultaneous cleaning type is
As shown in FIG. 1, the basic structure is the same as the conventional structure shown in FIG. 3, and a delay time setting means 21 and a delay drive control means (20) are provided to start the preparatory rotation of the photosensitive drum 1. The rotation of the developing roller 6 is stopped for a set delay time (Ts), and the rotational drive is started after the set delay time elapses.

First, the delay time setting means 21 is connected to the control device 20 as shown in FIG. 1 and has an arbitrary time (Ts).
Can be set. In this embodiment, the means 21 is of the key input type, but may be of another structure (for example, a type which is stored in advance in a memory such as a digital switch or a ROM).

In the case of this embodiment, the delay drive control means is constituted by the CPU, ROM, RAM, etc., and is composed of the CPU, ROM, etc. of the control unit 20 for driving the entire apparatus, and their components. The developing roller 6 is configured to be stopped by using the function of the developing roller 6 before starting the preparatory rotation of the photosensitive drum 1 at the time t1 shown in FIG. 2 before the set delay time Ts elapses, and after the elapse of the time t2. In, the developing roller 6 is formed so as to start driving to rotate.

The photosensitive drum 1 enters the preparatory rotation by inputting a signal STR from the control device 20 shown in FIG. 1 to the motor driver 11D and rotating the main motor 11. The rotation driving source of the developing roller 6 also serves as the main motor 11.

Therefore, the clutch 11D is interposed between the rotary shaft of the main motor 11 and the rotary shaft of the developing roller 6, and the delay drive control means 20 delays the signal STR by the set delay time Ts. By outputting STR and turning on the clutch 11D, the developing roller 6 is started to rotate.

When a dedicated motor separate from the main motor 11 is used for the developing roller 6, it may be formed so that the signal D.STR is input to the driver of the dedicated motor.

Next, the operation will be described. First, the set delay time Ts selected from various conditions is set in the delay time setting means 21. When the photosensitive drum 1 is in the position state shown in FIG. 1 immediately before the start of preparatory rotation, the set delay time Ts is required until the peripheral surface portion between P2 and P1 passes the developing roller 6 as the photosensitive drum 1 rotates. It is preferable to set the time to be the minimum time. As described above with reference to FIG. 6, the peripheral surface portion between P2 and P1 has the developing bias |
This is because there is a case where the potential is | Vs | whose absolute value is smaller than Vb |.

At time t1 in FIG. 2, the controller 20 inputs the signal STR shown in FIG. 1 to the driver 11D to start the main motor 11 for preparatory rotation. Also, the charger 2
(13), laser light source, developing bias power source (14)
N However, the delay drive control means (20) outputs the signal D before the set delay time Ts elapses from the time t1 in FIG.
・ Do not output STR. That is, the developing roller 6 remains stopped rotating.

Therefore, at the peripheral surface portion of the photosensitive drum 1 passing through the developing roller 6 and having a potential (-Vr) whose absolute value is smaller than the developing bias -Vb, the toner T1 from the developing roller 6 side is subjected to an electric field action due to the potential difference. There is a possibility that they will adhere, but the amount of adhesion is small because the developing roller 6 is not rotating. This is because the new toner T0 is not supplied onto the developing roller 6. Of course,
After that, the potential (-V
Since o) has a larger absolute value than the developing bias −Vb, the original cleaning is performed.

Thus, at time t2 when the set delay time Ts elapses, the signal D.STR is output, the clutch 11D is turned on, and the developing roller 6 is rotated by the rotational power of the motor 11. That is, the developing roller 6 is in the developing standby state.

At time t1, the residual potential −Vr
The peripheral surface parts P2-P1 shown in FIG. 1 also have a predetermined potential if they pass through the charger 2 as the photosensitive drum 1 rotates.
It is charged to Vo. At time t3, the laser scanning beam B is emitted, and the subsequent operations are similar to those of the conventional example.

However, according to this embodiment, the delay time setting means 21 and the delay drive control means (20) are provided, and the set delay time (Ts) elapses from the start of the preparatory rotation of the photosensitive drum 1 (t1). Until that time, the developing roller 6 is stopped to rotate and is driven to rotate after that time. Therefore, the residual potential of the peripheral surface portion (P2-P1) passing through the developing roller 6 without passing through the charger 2 (- Vs) and developing roller 6
The amount of toner (T1) that may adhere to the peripheral surface portion (P2-P1) from the developing roller 6 side due to the potential difference from the developing bias (-Vb) of 1 can be kept to a very small amount.
Therefore, reliable cleaning can be performed during the preparatory rotation of the photosensitive drum 1.

Further, since the toner T1 adhered to the peripheral surface portion of P2-P1 is small, the original cleaning can be surely performed only by passing the charging device 2 once. Therefore, a large amount of toner T1 from the side of the developing roller 6 which is rotating to the P2-P1 peripheral surface portion passing through the developing roller 6 immediately after the start of the preparation rotation.
The preparation rotation time can be significantly shortened as compared with the conventional example in which is attached. Therefore, high-quality and quick image formation can be performed.

In the above embodiment, the laser emission source 1
The laser scanning beam B from 2 irradiates the photosensitive drum 1 with light for drawing a latent image.
2) may be formed by a so-called line head in which EL elements are arranged.

[0034]

As described above, according to the present invention, in the image forming apparatus of the simultaneous development cleaning system, the delay time setting means for setting the delay time from the start of the preparatory rotation of the photosensitive drum and the development before the set delay time elapses. Since the roller is configured to stop rotating and to be driven to rotate after that time, toner that adheres to the peripheral surface portion of the photosensitive drum that passes through the developing roller without passing through the charger even by reverse cleaning development. The amount can be minimized.

Therefore, reliable cleaning can be performed, and a high-quality image can be rapidly formed while significantly shortening the preparation rotation time.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention.

FIG. 2 is likewise a timing chart for explaining the operation.

FIG. 3 is an overall configuration diagram showing a conventional example.

FIG. 4 is also a timing chart for explaining a conventional operation.

FIG. 5 is a diagram for explaining the operating principle of the simultaneous development cleaning method.

FIG. 6 is a diagram for explaining a problem of the conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging device 3 Developing device 4 Box 5 Charging brush 6 Developing roller 7 Transfer device 11 Main motor 11D Clutch 12 Laser emission source 20 Control device (delay drive control means) 21 Delay time setting means B Laser scanning beam | Vb | Development bias Ts Setting delay time

Claims (1)

[Claims] 1. An exposed portion and an unexposed portion irradiated with light are formed on the peripheral surface of a photosensitive drum which has passed through a charger, and the potential difference between the photosensitive drum side and the developing roller side to which a developing bias is applied is utilized to make the unexposed portion. In an image forming apparatus of the simultaneous developing cleaning system in which the residual toner adhering to the exposed portion is adsorbed to the developing roller side to clean the unexposed portion and at the same time the toner is supplied from the developing roller side to the exposed portion for development. Delay time setting means and rotation of the developing roller are stopped and set delay time elapses from the start of preparatory rotation of the photosensitive drum before image formation until the set delay time set by the delay time setting means elapses. An image forming apparatus of the simultaneous developing cleaning system, characterized by further comprising: a delay drive control means for driving the developing roller to rotate.