JPH0220893A - Electrophotographic device - Google Patents

Abstract

PURPOSE:To surely remove toner from the surface of a photosensitive body and to prevent deterioration in the photosensitive body by driving a photosensitive body driving means until toner adhesion part, which is formed on the surface of the photosensitive body before and after a developing bias is turned off, passes through a cleaning device after the developing bias is turned off. CONSTITUTION:The photosensitive body driving means 7 for removing toner is controlled by using a developing bias control signal for generating developing bias control signal different from a control signal for rotating the photosensitive body driving means 7, or using a control signal of the photosensitive body driving means. Thus, after a ready signal indicating that the developing bias is turned off by a developing bias impressing means 8 is inputted, or a post- rotating signal based on a main motor control signal is inputted, the main motor 7 can be further rotated for a prescribed period of time with the developing bias OFF. Therefore, fatigue of the photosensitive body caused by toner adhesion on the surface of the photosensitive body drum 1 for a long time is prevented, so that the life of the photosensitive body is prolonged, and an excellent image can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to electrophotographic devices such as electrostatic transfer copying machines and laser printers.

[Conventional technology]

2. Description of the Related Art Conventionally, so-called normal rotation printers and reversal printers, which are based on copying machines, have been known as electrophotographic apparatuses. In this type of printer, a laser light source, an LED (light emitting diode), a liquid crystal shutter, or the like is used as a light source in place of the dgen lamp used in copying machines. The light source is activated by receiving a control signal and irradiates the photoreceptor drum with light to form an electrostatic charge image on the surface of the photoreceptor drum.

The above-mentioned normal rotation printer uses a normal rotation development method similar to that used in copying machines, and does not irradiate light to the area corresponding to the black background, which is the area that will eventually become black when transferred to transfer paper. Exposure is performed by irradiating light onto a portion corresponding to a white background, which is a portion that becomes a white background. On the other hand, unlike copying machines, reversal printers employ a reversal development method in which light is irradiated onto areas corresponding to black backgrounds, and light is not irradiated onto areas corresponding to white backgrounds. In addition, in a reversing printer, by uniformly charging the surface of the photoreceptor drum and applying a developing bias of the same polarity as the surface of the photoreceptor drum, the white background can be maintained at a predetermined level without causing fogging on the white background. It is designed to be reproduced. Note that this state results in a black solid copy in a copying machine using a normal rotation development method.

The above-mentioned conventional reversal printer has a structure in which the normal rotation development method of a copying machine is used as is, and it is simply switched to a reversal development method. For example, in an idling state from when the main switch as a power switch is turned ON until reaching a ready state where printing is possible, the following operations are performed.

First, as shown in (k) in Figure 7, when the main switch is turned on, the main motor starts after 0.5 seconds as shown in (ffi), and in synchronization with this, the photoreceptor drum starts rotating. Start. After 0.1 seconds from the start of the main motor, the main charger reaches 3.0 seconds, as shown in (m).
．． ONL for 0 seconds, the surface of the photoreceptor drum is uniformly charged to a predetermined potential. Next, as shown in (n), the static elimination lamp turns ON after 0.5 seconds have elapsed from the start of the main charger.

The residual potential on the surface of the photoreceptor drum is removed. After that, the main charger is turned on for 3.0 seconds and then turned off, and the static elimination lamp is turned on for another 1.0 seconds.
do. After the static elimination lamp is turned off, the main motor continues to rotate for another 0.5 seconds and then stops.

[Problem to be solved by the invention]

However, the application timing of the developing bias used in copying machines is synchronized with the operating timing of the main motor, and in reversing printers that follow this method, the application timing of the developing bias is also synchronized with the operating timing of the main motor. It's in sync. When operated at such timing, no problem occurs in normal rotation development type copying machines and printers, but in reverse rotation printers, the problem arises that developer toner adheres to the surface of the photoreceptor drum. If the device stops under such conditions and is left unused for a long time, the photoreceptor may deteriorate, making it impossible to maintain normal functions, and the inside of the device may become dirty due to toner scattering. It has points.

[Means to solve the problem]

In order to solve the above-mentioned problems, the electrophotographic apparatus of the present invention includes a
A developing device that develops the electrostatic charge image formed on the photoconductor and a cleaning device that removes residual toner on the surface of the photoconductor are provided. In an electrophotographic apparatus to which a developing bias is applied, after the developing bias is turned off, the photoreceptor driving means is driven until the toner adhering portion formed on the photoreceptor surface before and after the developing bias is turned off passes a cleaning device. This configuration includes a control means for controlling the

[For production]

According to the above configuration, after the developing bias is turned off, the control means drives the photoreceptor driving means until the toner adhering portion formed on the photoreceptor surface before and after the developing bias is turned off passes the cleaning device. Therefore, the toner-attached portion is reliably removed from the photoreceptor surface. Therefore, deterioration of the photoreceptor due to long-term adhesion of toner is eliminated, good images can be obtained, and staining of the inside of the machine due to toner scattering can be eliminated.

The specific control of the photoreceptor driving means for removing the toner adhering portion is performed by using a developing bias control signal for generating a developing bias different from the control signal for rotating the photoreceptor driving means, or by using a developing bias control signal for generating a developing bias different from the control signal for rotating the photoreceptor driving means. By using the photoconductor driving means control signal for rotating the driving means, after inputting the ready signal indicating the development bias OFF based on the above-mentioned developing bias control signal, or after inputting the post-rotation signal based on the main motor control signal. This can be done by inputting , and then further rotating the main motor for a predetermined period of time with the developing bias OFF.

[Embodiment 1] An embodiment of the present invention will be described below based on FIGS. 1 to 5.

As shown in FIG. 1, a reversal development type printer (hereinafter referred to as a reversal printer) as an electrophotographic apparatus according to the present invention has a photoreceptor drum l made of OPC. Around this photosensitive drum 1, a main charger 2, a developing device 3 having a magnet roller (hereinafter referred to as MG roller) 3a, a transfer charger 4, a cleaning device 5 having a cleaning blade 5a, and a static elimination lamp 6 are installed in this order. They are arranged along the rotational direction of the photoreceptor drum 1.

The above main charger 2 connects the surface of the photoreceptor drum 1 to -
It is designed to be charged to a negative potential of 500 to -600V. This potential corresponds to the potential of a portion corresponding to a black background, which is a portion that will eventually become a q black background when transferred to transfer paper. Note that the charging polarity of the photoreceptor drum 1 is selected from negative charging or positive charging depending on the type and sensitivity of the photoreceptor used in the photoreceptor drum 1. The developing device 3 is configured to supply toner as a developer onto the surface of the photosensitive drum 1 using an MG roller 3a.

The developing device 3 contains a developer consisting of toner and an iron powder carrier. This developer is for negative charging, which is the same as the charging polarity of the main charger 2. The transfer charger 4 is configured to transfer the toner image formed on the surface of the photosensitive drum 1 onto a transfer paper. The cleaning device 5 is configured to remove toner remaining on the photoreceptor drum 1 using a cleaning blade 5a.

The static elimination lamp 6 is designed to remove residual potential on the surface of the photoreceptor drum 1.

Further, a laser beam irradiation means (not shown) is disposed near the photoreceptor drum 1, and the laser beam projected from this laser beam irradiation means is applied to the surface of the photoreceptor drum 1 between the main charger 2 and the developing device 3. irradiated, the photoreceptor drum l
An electrostatic charge image is formed on the surface of the

Further, this printer includes a main motor 7 as a photosensitive member driving means for rotating the photosensitive drum 1, a developing bias applying means 8 for applying a developing bias to the developing bag/place 3, and a control means 9. The developing bias applied to the developing bag w3 by the developing bias applying means 8 is -300.
It is set to ~-350v. The control means 9 drives the main motor 7 after the developing bias is turned off until the toner adhering portion formed on the surface of the photoreceptor drum 1 passes through the cleaning device 5 before and after the developing bias is turned off. It is designed to be controlled. In this embodiment, the developing bias applying means 8 and the main motor 7 are controlled by separate and independent control signals, and the driving time of the main motor 7 after the main charger 2 is turned off is such that the photosensitive drum 1 can rotate approximately once. The time is set so that the toner adhesion area generated after the developing bias is turned off can pass through the cleaning device 5.

In the above configuration, first, the operation from turning on the main switch as a power switch until reaching the ready state where printing is possible will be described.

When the main switch is turned on, the main motor 7 is turned on by the control operation of the control means 9, as shown in FIG. 2(a).
will start after 0.5 seconds. When the main motor 7 starts, the photosensitive drum 1 starts rotating in synchronization with this. Also, at the same time as the main motor starts, (d) and (e)
), the static eliminating lamp 6 and the developing bias applying means 8 are activated, and the residual potential on the surface of the photosensitive drum 1 is removed, and a developing bias of -300 to -350 is applied to the developing device 3. Ru. Then, as shown in (C), the main charger 2 is started 0.3 seconds after the start of the main motor, and the surface of the photoreceptor drum 1 is -
It is charged to 500 to -600V.

Thereafter, when the ready state is reached, the developing bias is turned off, and 0.3 seconds later, the main charger 2 is turned off, as shown in (e). Further, the main motor 7 continues to operate for 2.9 seconds after the main charger 2 is turned off, and then is stopped. During the 2.9 seconds from when the main motor 7 is turned off until the main motor 7 is turned off during this main charge, the photosensitive drum 1 rotates about one revolution.

In the above-mentioned operation, after the developing bias is turned off, toner adheres to the surface of the photoreceptor drum 1 facing the developing device 3, and a black solid area, which is a toner-attached area, is generated. However, since the photosensitive drum 1 continues to rotate for another 2.9 seconds, which corresponds to one revolution, after the developing bias is turned off, the black areas pass through the cleaning device 5 and are removed.

Next, during the printing operation on the transfer paper, the surface of the photosensitive drum l is exposed to the laser light projected from the laser light irradiation means, and the potential applied from the main charger 2 is removed. An electrostatic charge image is formed. The electrostatic charge image formed on the photosensitive drum 1 is developed with toner supplied from the MG roller 3a of the developing device 3, and becomes a toner image. This developing operation is performed by a reversal developing method. The image visualized as described above is transferred onto the transfer paper supplied to the photosensitive drum 1 by the transfer charger 4. The toner image transferred to the transfer paper is then fixed to the transfer paper by a fixing device.

On the other hand, the toner remaining on the photoreceptor drum l after the transfer operation by the transfer charger 4 is scraped off by the cleaning blade 5a of the cleaning device 5 and collected into the cleaning device 5.

Residual charges are removed from the surface of the photoreceptor drum l cleaned in this way by a static elimination lamp 6. At this time as well, the control operation of the control means 9 causes the photosensitive drum 1 to rotate for an additional 2.9 seconds after the main charger 2 is turned off, which is after the developing bias is turned off, as shown in FIG. After the bias is turned off, the solid black portion formed on the surface of the photosensitive drum 1 at the portion facing the developing device 3 passes through the cleaning device 5 and is removed.

Thereafter, the photosensitive drum 1 is charged again by the main charger 2, and the same process is repeated to perform a printing operation.

Here, a description will be given of the influence caused by the 0N10FF relationship between the operation timing of the main charger 2 during development, that is, the surface potential of the photosensitive drum 1, and the developing bias.

First, as shown in Figure 3, main charger 2 is turned on.
If the developing bias is turned off at this time, developer drop (hereinafter referred to as developer drop) and carrier lifting occur in area A, resulting in poor printing performance.

On the other hand, as shown in FIG.
When the developing bias is turned on at F, unnecessary toner adheres to the surface of the photoreceptor drum 1 in area B, resulting in black spots.

Further, in FIG. 5, the timing is set so that the area C where the main charger 2 is OFF and the developing bias is ON is as narrow as possible in order to prevent solid black and the resulting drop in development. In this case, it is possible to turn off the main charger 2 and turn on the developing bias at the same time, but since a deviation occurs due to inertia of the main motor, etc., it is recommended to turn off the main charger 2 earlier than the turning off of the developing bias. The black solid portion caused by the above-mentioned timing deviation is removed by passing through the cleaning device 5 as described above.The main charger 2 is OFF. Further, after the developing bias is turned off, unnecessary toner does not adhere to the surface of the photoreceptor drum 1.

[Embodiment 2] Another embodiment of the present invention will be described below based on FIG. 6.

In this embodiment, the control means 9 uses a developing bias control signal that generates a developing bias, and performs control to stop the main motor 7 after a predetermined time has elapsed after the developing bias is turned off. That is, the developing bias O
The main motor 7 is kept rotating even after the developing bias is turned off for a predetermined period of time long enough for the toner adhering portion generated before the FF to pass through the cleaning device 5.

First, as shown in (f), when the main switch is turned on, the main motor 7 is started 0.5 seconds later as shown in (g) by the control operation of the control means 9. When the main motor 7 starts, the photosensitive drum 1 starts rotating in synchronization with this. Further, as shown in (j), the developing bias applying means 8 is activated almost simultaneously with the activation of the main motor, and a developing bias is applied to the developing device 3. and,
As shown in (h), from the start of the main motor 7,
．． The main charger 2 starts after 1 second, and the surface of the photoreceptor drum 1 is uniformly charged, and the static elimination lamp 6 starts turning on after 0.5 seconds from the start of the main motor, as shown in N). When activated, the residual potential on the surface of the photoreceptor drum 1 is removed. Thereafter, the main motor 7 operates for 3.0 seconds and then is turned off, 1.0 seconds after that, the static elimination lamp 6 is turned off, and 0.5 seconds after that, the developing bias is turned off. The main motor 7 continues to operate for 1.1 seconds from the time when the developing bias is turned off, and then is stopped.

In the above operation, before the developing bias is turned off, a black solid area as a toner adhering area is generated on the surface of the photoreceptor drum 1 facing the developing device 3, but after the developing bias is turned off, the main motor is turned off. 1 until 7 turns OFF
．． The black solid portion passes through the cleaning device 5 and is removed in one second. On the other hand, even after the printing operation, the black solid area formed at this time is removed by controlling the main motor 7 to stop 1.1 seconds after the development bias is turned off, as in the case above. be done.

〔Effect of the invention〕

As described above, the electrophotographic apparatus of the present invention includes a developing device that develops an electrostatic charge image formed on the photoreceptor, and a developing device that develops an electrostatic charge image formed on the photoreceptor, and a developing device that removes residual toner on the surface of the photoreceptor, around the photoreceptor driven by the photoreceptor driving means. In an electrophotographic apparatus in which a cleaning device for removing toner is provided, and a developing bias is applied to the developing device to prevent unnecessary toner from adhering to the surface of the photoreceptor, the developing bias is turned off after the developing bias is turned off.
The configuration includes a control means for driving the photoreceptor driving means until the toner adhering portion formed on the surface of the photoreceptor passes through the cleaning device before and after the photoreceptor.

Therefore, unnecessary toner adhering to the photoreceptor can be reliably removed under general operation timing settings in which, for example, the photoreceptor drive timing and the development bias application timing are the same timing. This allows the surface of the photoreceptor to

Fatigue of the photoreceptor due to long-term toner adhesion can be prevented, the life of the photoreceptor can be extended, and good images can be obtained. Further, since unnecessary toner is collected by the cleaning device, it is possible to prevent toner from scattering inside the machine, and it is possible to suppress dirt inside the machine. Furthermore, it is possible to lengthen the maintenance period for the inside of the aircraft by the user, which also has the effect of reducing the total cost.

[Brief explanation of the drawing]

1 to 5 show an embodiment of the present invention, in which FIG. 1 is an explanatory diagram showing the configuration of the main parts of a reversal development type printer, which is an electrophotographic device, and FIG. Figure 1 is a timing chart showing the operation of the reversal development type printer from power-on to reaching the ready state, and Figures 3 to 5 are timing charts showing the influence of the 0N10FF relationship between the main charger and the developing bias, respectively. The chart, FIG. 6 shows another embodiment, and is a timing chart showing the operation of the printer from power-on to reaching the ready state, and FIG. 7 shows a conventional example, in which reverse development is performed. 3 is a timing chart showing the operation of the printer according to the above-mentioned method from when the power is turned on until it reaches a ready state. 1 is a photoconductor drum (photoconductor), 2 is a main charger,
3 is a developing device, 5 is a cleaning device, 7 is a main motor (photoreceptor driving means), 8 is a developing bias applying means, 9
is a control means. Patent applicant: Sharp Dai-kugyozuyoi Co., Ltd.

Claims (1)

[Scope of Claims] 1. A developing device that develops an electrostatic charge image formed on the photoreceptor around the photoreceptor driven by the photoreceptor driving means;
In an electrophotographic apparatus, a cleaning device for removing residual toner on the surface of the photoreceptor is provided, and a developing bias is applied to the developing device to prevent unnecessary toner from adhering to the surface of the photoreceptor. An electrophotographic apparatus comprising: a control means for driving a photoreceptor driving means after the developing bias is turned off until a toner adhesion portion formed on the surface of the photoreceptor passes through a cleaning device before and after the development bias is turned off.