JPH0816817B2 - Electrophotographic equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electrophotographic apparatus such as an electrostatic transfer type copying machine and a laser printer.

[Conventional technology]

2. Description of the Related Art So-called forward rotation printers and reversal printers to which a copying machine is applied are known as electrophotographic apparatuses. In this type of printer, a laser beam, an LED (issuing diode), a liquid crystal shutter, or the like is used as a light source instead of a halogen lamp used in a copying machine. The above light source operates by receiving a control signal, and irradiates the photosensitive drum with light to form an electrostatic charge image on the surface of the photosensitive drum.

The above-described forward rotation printer uses the same forward development method as a copying machine, and does not irradiate light to the black background corresponding portion, which is the portion that finally becomes a black background when transferred to the transfer paper, and finally Exposure is performed by irradiating light on a white background corresponding portion which is a white background portion. On the other hand, in the reverse printer,
Unlike a copying machine, a reversal development method is adopted, and light is applied to a black background corresponding portion and light is not irradiated to a white background corresponding portion. In a reversing printer, the surface of the photoconductor drum is uniformly charged and a developing bias of the same polarity as that of the surface of the photoconductor drum is applied, so that the white background, which is the background, is not fogged and the white background maintains a predetermined level. It is supposed to be reproduced. It should be noted that this state is a black solid copy in a copying machine of the normal development type.

The above-mentioned conventional reversal printer has a structure in which the normal development method of the copying machine is used as it is and is switched to the reversal development method. For example, in the idling state from when the main switch as the power switch is turned on until the ready state for printing is reached, the following operation is performed.

First, when the main switch is turned on as shown in (k) of FIG. 7, the main motor is turned on by 0.5 as shown in ().
It starts after a second, and the photosensitive drum starts rotating in synchronization with this. After 0.1 seconds has passed from the start of the main motor, as shown in (m), the main charger turns on for 3.0 seconds.
N, the surface of the photosensitive drum is uniformly charged to a predetermined potential. Next, as shown in (n), the static elimination lamp is turned on 0.5 seconds after the start of the main charger, and the residual potential on the surface of the photosensitive drum is removed.
After that, the main charger turns on for 3.0 seconds and then turns off, then the static elimination lamp turns on for another 1.0 second. And after turning off the static elimination lamp, the main motor rotates for another 0.5 seconds,
Stop after.

[Problems to be Solved by the Invention]

However, the application timing of the developing bias used in the copying machine is synchronized with the operation timing of the main motor, and in the reverse printer that follows this method, the application timing of the developing bias is the same as the operation timing of the main motor. Are in sync. When operating at such a timing, no problems occur in the copier and printer of the normal rotation developing system, but in the reversing printer, there is a problem that the toner of the developer adheres to the surface of the photosensitive drum. If the apparatus stops in such a state and is left for a long time, the photoconductor is deteriorated, the normal function cannot be maintained, and the inside of the machine is polluted due to toner scattering. Have a point.

[Means for solving the problem]

In order to solve the above problems, an electrophotographic apparatus of the present invention includes a developing device that develops an electrostatic charge image formed on a photoconductor around a photoconductor driven by a photoconductor driving unit, and a photoconductor surface. And a cleaning device for removing residual toner from the developing device, and the developing device is applied with a developing bias adjusted so as to prevent unnecessary toner from adhering to the surface of the photoconductor. In the apparatus, after the developing bias is turned off, there is provided a control means for driving the photosensitive body driving means until the toner adhesion portion formed on the surface of the photosensitive body before and after the developing bias is turned off passes through the cleaning device. .

[Work]

According to the above configuration, after the developing bias is turned off, the control unit drives the photosensitive drum until the toner adhesion portion peculiar to the reversal developing method formed on the surface of the photosensitive drum before and after the developing bias is turned off passes through the cleaning device. Since the means is driven, the toner adhesion portion is surely removed from the surface of the photoconductor.
Therefore, the deterioration of the photoconductor due to the toner adhering for a long time can be eliminated, a good image can be obtained, and the stain inside the machine due to the scattering of the toner can be eliminated.

The specific control of the photosensitive member driving means for removing the toner adhering portion uses a developing bias control signal for generating a developing bias different from the control signal for rotating the photosensitive member driving means, or 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 development bias control signal, or the post-rotation signal based on the main motor control signal After inputting, the main motor can be further rotated for a predetermined time while the developing bias is OFF.

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

A reversal development type printer (hereinafter referred to as a reversal printer) as an electrophotographic apparatus according to the present invention has a photosensitive drum 1 made of OPC as shown in FIG. Around the 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 blade 5a.
The cleaning device 5 having the above and the discharge lamp 6 are arranged in this order along the rotation direction of the photosensitive drum 1.

The main charger 2 covers the surface of the photosensitive drum 1
It is designed to be charged to a negative potential of 500 to -600V. This electric potential corresponds to the electric potential of the portion corresponding to the black background, which is the portion that finally becomes the black background when transferred to the transfer paper. still,
The charging polarity of the photoconductor drum 1 is selected from negative charge or plasma charge depending on the type and sensitivity of the photoconductor used for the photoconductor drum 1. The developing device 3 supplies toner as a developer to the surface of the photosensitive drum 1 by the MG roller 3a. The developing device 3 contains a developer composed of toner and an iron powder carrier. This developer is for negative charging, which has the same charge polarity as the main charger 2. The transfer charger 4 is adapted 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 the toner remaining on the photosensitive drum 1 with the cleaning blade 5a. The static elimination lamp 6 removes the residual potential on the surface of the photosensitive drum 1.

Further, a laser light irradiation unit (not shown) is arranged in the vicinity of the photosensitive drum 1, and the laser light projected from this laser light irradiation unit is on the surface of the photosensitive drum 1 between the main charger 2 and the developing device 3. Irradiation causes an electrostatic charge image to be formed on the surface of the photosensitive drum 1.

Further, the printer is provided with a main motor 7 as a photosensitive member driving unit for rotating the photosensitive drum 1, a developing bias applying unit 8 for applying a developing bias to the developing device 3, and a control unit 9. The developing bias applied to the developing device 3 by the developing bias applying unit 8 is -300 to
It is set to −350V. After the developing bias is turned off, the control means 9 controls the photosensitive drum 1 before and after the developing bias is turned off.
The toner adhering portion formed on the surface of the cleaning device 5 is
The control is such that the main motor 7 is driven until the vehicle passes. In this embodiment, the developing bias applying means 8 and the main motor 7 are controlled by independent control signals, and the main charger is
The drive time of the main motor 7 after 2 OFF is set to a time during which the photosensitive drum 1 can rotate almost once, and the developing bias
The toner adhering portion generated after turning off can pass through the cleaning device 5.

In the above-mentioned configuration, first, the operation after the main switch as the power switch is turned on until the ready state for printing is reached will be described.

When the main switch is turned on, the control operation of the control means 9 causes the main motor 7 to move as shown in FIG.
Will start in 0.5 seconds. When the main motor 7 starts,
In synchronization with this, the photosensitive drum 1 starts rotating. Simultaneously with the activation of the main motor 7, as shown in (d) and (e), the static elimination lamp 6 and the developing bias applying means 8 are activated to remove the residual potential on the surface of the photosensitive drum 1, and A developing bias of -300 to -350V is applied to the developing device 3. Then, as shown in (c), the main charger 2 is activated 0.3 seconds after the activation of the main motor 7, and the surface of the photosensitive drum 1 is -500.
It is charged to ~ -600V.

After that, when the ready state is reached, the developing bias is turned off and the main charger 2 is turned off 0.3 seconds after that, as shown in (e). Furthermore, the main charger 2 is O
The main motor 7 continues to operate for 2.9 seconds after the FF, and then is stopped. This main charger 2 is OF
In 2.9 seconds from when F is turned off until the main motor 7 is turned off,
The photosensitive drum 1 makes about one rotation.

In the above-described operation, after the developing bias is turned off, toner specific to the reversal developing method is attached to the surface of the photosensitive drum 1 facing the developing device 3, and a black solid portion is generated. However, after the developing bias is turned off, the photosensitive drum 1 is further rotated for 2.9 seconds corresponding to one rotation, so that the black solid portion passes through the cleaning device 5,
Will be removed.

Next, during the printing operation on the transfer paper, the surface of the photosensitive drum 1 is exposed by the laser light projected from the laser light irradiating means, and the electric 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 by the toner supplied from the MG roller 3a of the developing device 3 to form a toner image. This developing operation is performed by the reversal developing method. The image visualized as described above is transferred by the transfer charger 4 onto the transfer paper supplied to the photosensitive drum 1. The toner image transferred to the transfer paper is then fixed on the transfer paper by the fixing device.

On the other hand, the toner remaining on the photosensitive drum 1 after the transfer operation by the transfer charger 4 is scraped off by the cleaning blade 5 a of the cleaning device 5 and collected in the cleaning device 5. The surface of the photoconductor drum 1 thus cleaned is removed of residual charges by the charge eliminating lamp 6. Also at this time, as shown in FIG. 2, the developing bias OF is controlled by the control operation of the control means 9.
After the main charger 2 is turned off after F, the photoconductor drum 1 further rotates for 2.9 seconds. Therefore, the black solid part formed on the surface of the photoconductor drum 1 facing the developing device 3 after the development bias is turned off Passing through the cleaning device 5,
To be removed. After that, the photosensitive drum 1 is charged again by the main charger 2, and the same process is repeated thereafter, and the printing operation is performed.

Here, the influence of the ON / OFF 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 will be described.

First, as shown in FIG. 3, the main charger 2 is turned on.
If the developing bias is turned off at this time, in the area A, the developer falls (hereinafter referred to as “development”) and the carrier rises, and the printability deteriorates.

On the other hand, as shown in FIG. 4, the main charger 2 is OF
In the case of F, when the developing bias is turned on, unnecessary toner adheres to the surface of the photosensitive drum 1 in the area B, and black solid occurs.

Further, in FIG. 5, the timing is set so that the area C in which the main charger 2 is OFF and the developing bias is ON is as narrow as possible in order to prevent black solid and decoloring due to the black solid. At this time, it may be possible to turn off the main charger 2 at the same time as the developing bias is turned on. However, since the main motor 7 may be displaced due to inertial driving, the main charger 2 is turned off earlier than the developing bias is turned off. It is set to control devegetation. Then, the black solid portion caused by the above timing deviation is removed by passing through the cleaning device 5 as described above. After the main charger 2 is turned off and the developing bias is turned off, unnecessary toner does not adhere to the surface of the photosensitive drum 1.

Second Embodiment Another embodiment of the present invention will be described below with reference to FIG.

In the present embodiment, the control means 9 uses a developing bias control signal for generating a developing bias, and controls the main motor 7 to stop after a predetermined time has passed after the developing bias is turned off. That is, development bias OF
The main motor 7 is rotated even after the developing bias is turned off for a predetermined time such that the toner adhering portion generated before F can pass through the cleaning device 5.

First, as shown in (f), when the main switch is turned on, the control operation of the control means 9 activates the main motor 7 after 0.5 seconds as shown in (g). When the main motor 7 is activated, the photosensitive drum 1 starts rotating in synchronization with this. Further, as shown in (i), the developing bias applying means 8 is activated almost in synchronization with the activation of the main motor 7, and the developing bias is applied to the developing device 3. And
As shown in (h), from the start of the main motor 7, 0.
After 1 second has elapsed, the main charger 2 is activated, the surface of the photoconductor drum 1 is uniformly charged, and as shown in (i), after 0.5 seconds has elapsed from the activation of the main motor 7,
The charge eliminating lamp 6 is activated to remove the residual potential on the surface of the photosensitive drum 1. After that, when the main motor 7 is operated for 3.0 seconds, the main motor 7 is turned off, 1.0 seconds later, the static elimination lamp 6 is turned off, and 0.5 seconds later, the developing bias is turned off. Then, the main motor 7 is continuously operated for 1.1 seconds after the developing bias is turned off, and then stopped.

In the above operation, before the developing bias is turned off, a black solid portion as a toner adhering portion is formed on the surface of the photosensitive drum 1 facing the developing device 3, but the main motor is turned off after the developing bias is turned off. In 1.1 seconds until 7 is turned off, the black solid part passes through the cleaning device 5 and is removed. On the other hand, even after the printing operation, the black solid portion formed at this time is removed by the control in which the main motor 7 is stopped 1.1 seconds after the development bias is turned off, as in the above case. .

〔The invention's effect〕

As described above, the electrophotographic apparatus of the present invention has a developing device for developing an electrostatic charge image formed on the photoconductor and a residual toner on the surface of the photoconductor around the photoconductor driven by the photoconductor driving means. In a reversal development type electrophotographic apparatus in which a cleaning device for removing is provided, and a development bias adjusted so as to prevent unnecessary toner from adhering to the surface of the photoconductor is applied to the development device, After the bias is turned off, a control means for driving the photoconductor driving means is provided until the toner adhesion portion formed on the surface of the photoconductor before and after the development bias is turned off passes through the cleaning device.

Therefore, for example, in a reversal development type electrophotographic apparatus using a general operation timing setting in which the driving timing of the photoconductor and the application timing of the developing bias are the same, unnecessary toner attached to the photoconductor is used. Can be reliably removed. As a result, fatigue of the photoconductor due to long-term adhesion of toner to the surface of the photoconductor can be prevented, the life of the photoconductor can be extended, and good images can be obtained. Further, since the unnecessary toner is collected by the cleaning device, it is possible to prevent the toner from scattering in the machine, and it is possible to suppress the stain in the machine. Further, it is possible to prolong the maintenance cycle of the inside of the machine by the user, and it is possible to reduce the total cost also from this.

[Brief description of drawings]

1 to 5 show an embodiment of the present invention. FIG. 1 is an explanatory view showing the structure of the main part of a reversal development type printer which is an electrophotographic apparatus, and FIG. FIG. 1 is a timing chart showing an operation from turning on the power to reaching a ready state in the reversal development type printer shown in FIG. 1, and FIGS. 3 to 5 show influences due to ON / OFF relations between the main charger and the developing bias, respectively. The timing chart shown in FIG. 6 shows another embodiment,
FIG. 7 is a timing chart showing the operation from the power-on of the printer to the ready state, and FIG. 7 shows a conventional example, showing the operation from the power-on to the ready state of the reversal development type printer. It is a timing chart. 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 (photosensitive member driving means), 8 is a developing bias applying means, and 9 is a developing bias applying means.
Is a control means.

Claims (1)

[Claims] 1. A developing device for developing an electrostatic charge image formed on the photosensitive member and a cleaning device for removing residual toner on the surface of the photosensitive member are provided around the photosensitive member driven by the photosensitive member driving means. , In the reversal development type electrophotographic device where a developing bias adjusted to prevent unnecessary adhesion of toner to the surface of the photoconductor is applied to the above developing device, the developing bias is turned off after the developing bias is turned off. An electrophotographic apparatus comprising: a control unit that drives a photoconductor driving unit until a toner adhesion portion formed on the surface of the photoconductor before and after a time passes a cleaning device.