JPH1184827A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent filming from occurring in an image forming device. SOLUTION: When an image is formed, the surface of an image carrier 1 is uniformly electrified by setting potential difference between an electrification means 2 and the surface of the carrier 1 to be equal to over a prescribed value. Then, developing is electrostatrically supplied to the carrier 1 from a developing means 5 by setting the potential difference between the developing means 5 and the surface of the carrier 1 to be equal to over the prescribed value. Besides, the developer image of the surface of the carrier 1 is transferred on a transfer material by the potential difference between a transfer means 7 and the surface of the carrier 1. When the image is not formed, the potential difference between at least one of the electrification means, the developing means and the transfer means and the surface of the image carrier is set to be under a voltage for stopping discharge.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a copier, a facsimile,
The present invention relates to an electrophotographic image forming apparatus such as a printer.

[0002]

2. Description of the Related Art In this type of image forming apparatus, an electrostatic latent image formed by exposing the surface of an image carrier uniformly charged by a charging device to an image by an exposing device is visualized by a developer and transferred. Transfer to material.

When the potential difference between the charging device, the developing device, the transfer device and the image carrier exceeds a predetermined value (discharge stop voltage), a discharge occurs. As shown in FIG. 11, the amount of discharge (the amount of current flowing into the photoconductor) from the charging device or the like to the surface of the image bearing member is determined by the potential difference ΔV ( (Discharge potential before discharge), and when this potential difference ΔV is less than the discharge stop voltage ΔV ′, no discharge occurs. The discharge stop voltage is independent of the potential difference ΔV,
Discharge stop voltage in low humidity environment, determined only by humidity environment.
V 'is about 500 V, and the discharge stop voltage 高 V' in a high humidity environment
Is about 400V.

When the discharge occurs, the toner (residual toner) remaining on the surface of the image carrier after the transfer process is fused to the surface of the image carrier, or nitrogen oxides (NO _x ) are generated, thereby causing May adhere to the surface of the body. If such filming is present on the surface of the image carrier, it causes image quality deterioration such as image density reduction and image deletion. The amount of residual toner NO _X or fusion adhering to the surface of the image carrier (filming amount) increases with an increase of the discharge amount (current inflow into the image bearing member).

[0005] In order to prevent the image quality from deteriorating, it is necessary to remove the filming once generated. In the case of an image forming apparatus provided with a cleaning blade for collecting the residual developer and discarding it outside the apparatus, the filming can be mechanically scraped and removed by the cleaning blade.

[0006]

However, without providing the cleaning blade, the residual developer is recovered by a voltage applied to the developer carrier of the developing device and a potential difference on the surface of the image carrier. A cleanerless image forming apparatus has a lower efficiency of mechanically removing and removing filming than an apparatus having a cleaning blade, and image quality is likely to be degraded due to filming.

The present invention has been made to solve the problems in the conventional image forming apparatus, and has been made to prevent the occurrence of filming.

[0008]

In order to solve the above-mentioned problems, an image forming apparatus according to the present invention comprises a developing means for developing an electrostatic latent image formed by exposing a surface of an image carrier charged by a charging means by an exposure means. In an image forming apparatus in which the image is visualized by a developer supplied by a developer and then transferred to a transfer material by a transfer unit, at the time of image formation, the potential difference between the charging unit and the surface of the image carrier is set to a predetermined value or more, and the surface of the image carrier is set to a predetermined value or more. The developer is electrostatically supplied from the developing unit to the image carrier by uniformly charging, and the potential difference between the developing unit and the surface of the image carrier is set to a predetermined value or more. The developer image on the surface of the image bearing member is transferred to the transfer material by the potential difference between the image bearing member and the surface of the image bearing member during non-image formation. The above picture It is characterized by setting to less than the potential difference at the time of formation.

In the image forming apparatus of the present invention, at the time of non-image formation, the potential difference with the surface of at least one of the charging means, the developing means and the transfer means is set smaller than the potential difference at the time of image formation. The amount of discharge between the body and the body can be reduced. Thus, while reducing the amount of adhered to the surface of the image bearing member of the NO _X generated amount and occurs of the NO _X by the discharge, it is possible to prevent fusion of the image bearing member surface residual developer, filming The amount can be reduced.

In particular, the charging voltage means at the time of non-image formation,
If the potential difference between at least one of the developing unit and the transfer unit and the surface of the image carrier is set to be less than the discharge stop voltage, the occurrence of discharge between the surface and the image carrier is prevented, and the discharge amount is reduced to almost zero. It can be. In this case, N
O adhesion of _X to generate and image bearing member surface, it is possible to prevent fusion of the image bearing member surface residual developer, it is possible to prevent the occurrence of filming.

The present invention is preferably applied to a cleaner-less type image forming apparatus in which a developer remaining on the surface of an image carrier after transfer to a transfer material is recovered by a developing means. In the case of a cleanerless type, the efficiency of mechanically shaving filming is low because it does not include a cleaning blade or the like, but by reducing the discharge amount during non-image formation that causes filming as described above, A decrease in image quality due to filming can be suppressed. However, the present invention is not limited to the cleanerless type, but can also be applied to an image forming apparatus having a cleaning blade or the like.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention switches the voltage applied to a charging device, a developing device and a transfer device between an image forming operation and a non-image forming operation. The potential difference between them is set to be equal to or lower than the discharge stop voltage so as to prevent discharge from occurring during non-image formation, thereby preventing the occurrence of filming.

(First Embodiment) FIG. 1 shows a cleanerless image forming apparatus according to a first embodiment of the present invention. The normal charging polarity of the developer is negative (-).

Around the photoreceptor 1 which is driven to rotate in a direction indicated by an arrow A by a motor 9a, a charging device 2, an exposing device 3, a developing cleaning device 5 including a developing sleeve 4, and a transfer device 7 including a transfer roller 6 Are arranged in order. In FIG. 1, reference numeral 8 denotes a control device that controls the charging device 2, the exposure device 3, the developing cleaning device 5, and the like.

The charging brush 10 provided in the charging device 2
Are arranged along the axial direction of the photoreceptor 1, and a contact 1 made of hairy fibers is attached to a cored bar 10 a constituting a rotation axis.
0b is densely implanted. This charging brush 1
0 indicates that the contact 10b is in contact with the surface of the photoconductor 1;
In addition, the motor 9b is driven to rotate in a direction indicated by an arrow B in the figure. A power supply 13A is connected to the cored bar 10a. The potential of the voltage (charging potential V _C ) supplied from the power supply 13A to the charging brush 10 is controlled by the control device 8
Is adjusted by

Exposure device 3 is a light beam 1 corresponding to image data.
4 is irradiated on the surface of the photoconductor 1.

The developing sleeve 4 of the developing and cleaning device 5 comes into contact with the surface of the photosensitive member 1 with a predetermined contact width, and is driven to rotate in the direction of arrow C by a motor 9c. A voltage is applied to the developing sleeve 4 from a power supply 13B. The potential (developing potential V _B ) of the voltage applied to the developing sleeve 4 from the power supply 13B is adjusted by the control device 8.

The transfer roller 6 of the transfer device 7 is rotated in the direction of arrow D by a motor 9d. A voltage is applied to the transfer roller 6 from a power supply 13C. The potential of this voltage (transfer potential V _T ) is adjusted by the control device 8.

Next, the operation of the present embodiment will be described with reference to FIG. From time t1 to time t4,
The motors 9a to 9d operate to rotate the photoconductor 1, the charging brush 10, the developing sleeve 4, and the transfer roller 6 in rotation. During the operation of the motor (from time t1 to time t4), the period from time t2 to time t3 is the time of image formation in which the image forming operation is performed, and before and after that, that is, from time t1 to time t2 and from time t3 to time t4. The motors 9a to 9d are operating, but the image forming operation is not performed, that is, at the time of non-image formation.

At the time of image formation (from time t2 to time t3)
To, -1200 V charging potential V _C, the development potential V _B -3
00V, setting the transfer potential V _T to + 1000V. At the time of image formation, the surface potential (surface potential V _S ) of the surface of the photoconductor 1 at a portion of the photoconductor 1 that is not exposed by the exposure device 3 is as shown in FIG. First, as described above, the charging potential V _S
Is set to -1200 V, the surface potential V _S up to the developing sleeve 4 becomes -800 V. Further, since the developing potential V _B is set to −300 V, the surface potential V _S
There potential difference △ V between the photosensitive member 1 surface and the developing sleeve 4 is -800V is about 500V, the discharge from the photosensitive member 1 surface toward the developing sleeve 4 is caused, the surface potential V _S is attenuated. Moreover, between the transfer device 7 of the charging device 2, the surface potential V _S by the transfer voltage V _T applied to the transfer device 7 becomes + 100 V.

On the other hand, as shown in FIG. 4, at the time of image formation, a portion irradiated with the light beam 14 from the exposure device 3
Surface potential V _S is attenuated from -800V to -100V. This potential attenuation section, the developer charged negatively from the transfer sleeve 4 of the developing device 5 to the development potential V _B of -300V is applied is supplied. The developer supplied to the potential attenuator is transferred to the sheet 19 by a transfer voltage applied to the transfer roller 6 of the transfer device 7. The surface potential V _s of the photosensitive member 1 that has passed through the transfer device 7 becomes + 300 V. The portion where the surface potential V _S becomes + 300 V returns to the position facing the charging device 2 with the rotation of the photosensitive member 1. Since the charging potential V _C is set to −1200 V as described above, the potential difference ΔV between the portion where the surface potential V _S is +300 V and the charging brush 10 is 1500 V, which exceeds the discharge stop voltage. Therefore, the surface potential V _S of the photosensitive member 1 discharge is generated toward the photosensitive member 1 from the charging brush 10 becomes -800 V.

At the time of non-image formation (before rotation) before the start of image formation from time t1 to time t2, and from time t3 to time t
At the time of image formation after completion of the non-image formation to 4 (when post-rotation), -1000 V charging potential V _C, the development potential V _B -50
0V, thereby setting a transfer potential V _T to -500 V. Since setting the charge potential Vc to -1000 V, as shown in FIG. 5, the surface potential V _S of the photosensitive member 1 becomes -600 V. Since the development potential V _B as described above is set to -500 V, the potential difference △ V between the developing sleeve 4 surface of the photosensitive member 1 is 10
0 V, which is less than the firing voltage △ V ′, which is about 500 V in a low humidity environment and about 400 V in a high humidity environment. Therefore, no discharge occurs between the photoconductor 1 and the developing sleeve 4.
Also, since the set of transfer potential V _T to -500 V,
The potential difference ΔV between the transfer roller 6 and the surface of the photoconductor 1 is 100 V, which is lower than the discharge starting voltage ΔV ′. Therefore, no discharge occurs between the photoconductor 1 and the developing sleeve 4. Thus, in the first embodiment, the charging before the time of rotation when the post-rotation potential V _C, the developing is set lower than when the voltage V _B and the transfer potential V _T imaging, developing sleeve 4 and transferring the photosensitive member 1 surface By setting the potential difference ΔV with the roller 6 to be less than the discharge stop voltage ΔV ′, no discharge is generated between the photoconductor 1 and the developing sleeve 4 or the transfer roller 6. Therefore,
Fusion of by discharge generator to the photosensitive member 1 adhesion or residual developer to the photosensitive member 1 of the NO _X can be prevented.

[0023] (Second Embodiment) The second embodiment has a configuration for switching only the potential different from that of the time of image formation transfer potential V _T to the non-image formation. That is, as shown in FIG. 6, during the pre-rotation (time t1 to time t2) and the post-rotation (time t3 to time t4), the charging potential V _C is reduced by −12.
00V, the development potential V _B although the same potential when the set image formed -300V (time t3 from time t2), at the time of image forming transfer potential V _T is + 1000V before rotation and at -500V during post-rotation Switching. Since the non-image-formed as described above also set the charge potential V _C to -1200 V, as shown in FIG. 7, the surface potential V _S -8
While the 00V, be switched to transfer potential V _T to -500 V, the potential difference △ V between the transfer roller 6 and the photosensitive member 1 surface is 300 V, the discharge starting voltage △ V 'below. Therefore, it is possible to prevent the occurrence of discharge between the transfer roller 6 the surface of the photosensitive member 1 can be prevented from adhering to the photosensitive member 1 of the NO _X and the residual developer by the discharge. The second
Other configurations and operations of the embodiment are the same as those of the above-described first embodiment.

(Third Embodiment) In the third embodiment, FIG.
As shown in, the charge potential V _C and transfer potential V _T to the non-image-forming switching to 0V, and has a configuration for switching the development potential V _B to + 100 V. Charge potential V _{C is set} to 0 during pre-rotation
By setting to V, the surface potential V _S becomes 0 V as shown in FIG. Because switched the development potential V _B to + 100 V, the potential difference △ V between the developing sleeve 4 and the photosensitive member 1 surface is 100 V, which is lower than the discharge stop voltage △ V '. Therefore, discharge between the photoconductor 1 and the developing sleeve 4 can be prevented. Further, for switching the transfer potential V _T to 0V, and the potential difference △ V between the transfer roller 6 photoreceptor 1 surface
Is 100 V, which is lower than the discharge stop voltage ΔV ′. Therefore, discharge between the photoconductor 1 and the transfer roller 6 can be prevented. Thus in the third embodiment, since it is possible to prevent the developing sleeve 4 and the transfer roller 6 a discharge between the photosensitive member 1, it is possible to prevent adhesion of the NO _X and the residual developer by the discharge.

[0025] without the 0V the development potential V _B at the time of rotation before the, + is the is set to 100 V, and the time of image formation by applying a reverse polarity voltage (reverse bias), the developing sleeve 4 surface This is to prevent the developer from migrating to the surface of the photoconductor 1. That is, for example, setting the development potential V _B of the front during the rotation to -300 V, the developing sleeve 4
Since the potential of the surface of the photoconductor 1 is more positive than the surface of the photoconductor 1, the toner on the surface of the developing sleeve 4 of the negatively charged developer is transferred to the surface of the photoconductor 1. Therefore, it is necessary to prevent the developer in the developing potential V _B positive side set to the developing sleeve 4 surface of the photosensitive member 1 surface potential V _S developing sleeve 4 than that moves to the photosensitive member 1 surface.

As shown in FIG. 8, at time t3 the time of rotation after the image formation is completed to start the development potential V _B +100
Switched to V, the transfer is switched to the potential V _T to + 100 V, the charging potential V _C is switched to 0V from the time t3 to a predetermined time △ t elapsed time t3 '.

[0027] The remembering this way time delay with respect to switching of the development potential V _B and transfer potential V _T to the switching of the charging potential V _C at the time of post-rotation, the surface potential V _S to the photosensitive member 1 surface
This is to prevent a portion where is positive from remaining. That is, at the time t3, the rear end of the sheet 19 passes through the opposing portion between the transfer roller 6 and the photoreceptor 1, and as shown in FIGS.
As shown in the figure, the surface potential V _S is −
There are an 800 V portion, a +100 V portion, and a +300 V portion. If such a portion having a positive surface potential V _S remains, a so-called PC memory is generated. Therefore, the charging potential V _C is set to −1200 V for a predetermined time Δt after the completion of image formation as described above, so that the photosensitive member 1
The surface potential V _C of the entire surface of the device is once set to −800 V,
The surface potential V _S is eliminated portion is positive.

[0028] When the time t3 'in the charge potential V _C switches to 0V, and the photosensitive member 1 the surface potential V _S is -800V
From the surface, the development potential V _B is + 100 V at which the developing sleeve 4 and the transfer potential V _T discharge occurs toward between the transfer roller 6 is 0V, the surface potential V _S decays to -400 V. In this state, as shown in FIG.
_{Since B} is switched to +100 V, the potential difference ΔV between the developing sleeve 4 and the surface of the photoconductor 1 is 500 V, which is smaller than the voltage ΔV at the time of image formation. And filming can be prevented from occurring. Note that the developing potential V _B during post-rotation is
Is not limited to +100 V, and the surface potential V _S (−400
V) may be set on the positive side. For example, the developing potential V _B
May be set to 0V or -200V. If the developing potential V _B is set to be more positive than the surface potential V _S in this way,
It is possible to prevent the developer charged to the negative polarity from migrating from the developing sleeve 4 to the surface of the photoconductor 2. Further, the potential difference △ V between the transfer for the potential V _T switches to 0V, and the transfer roller 6 and the photosensitive member 1 surface is -400 V, the image formation at the time of the potential difference △ V smaller. Accordingly, the amount of discharge between the photoconductor 1 and the transfer roller 6 can be reduced, and occurrence of filming can be prevented.

It should be noted that the present invention is not limited to the above embodiment, and various modifications are possible. For example, the charge potential V _C between the image in performing the continuous printing, the development potential V _B and transfer potential V _T may be set to a value similar to the non-image-formation of the third embodiment from the first . Also, 0V the transfer potential V _T of the non-image-forming in the second embodiment
May be set. In this case, the potential difference ΔV between the transfer roller and the photosensitive member surface during non-image formation is 800 V, which is smaller than the potential difference ΔV during image formation, so that the amount of discharge can be reduced and filming can be prevented. .

[0030]

As is apparent from the above description, in the image forming apparatus according to the present invention, at the time of non-image formation, the potential difference between at least one of the charging means, the developing means and the transfer means and the surface of the image carrier is determined. Since the potential difference is set to be less than the potential difference at the time of image formation, the discharge amount between the image carrier and the charging unit, the developing unit, and the transfer unit when the potential difference is set to be less than the discharge stopping potential can be reduced. In particular, when the potential difference between the charging means and the like and the surface of the image carrier during non-image formation is set to be less than the discharge stop voltage, the occurrence of discharge can be prevented. Further, by preventing the reduction or discharge generation amount of discharge, preventing adhesion of the image bearing member surface of the NO _X generated during discharge, the fusion of the image bearing member surface fusion of the residual developer As a result, filming on the surface of the image carrier can be prevented from occurring.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus according to a first embodiment.

FIG. 2 is a diagram showing switching of a charging potential, a developing potential, and a transfer potential in the first embodiment.

FIG. 3 is a schematic configuration diagram illustrating a potential of a photoconductor and the like during image formation (no exposure) according to the first embodiment.

FIG. 4 is a schematic configuration diagram illustrating a potential of a photoconductor and the like during image formation (with exposure) according to the first embodiment.

FIG. 5 is a schematic configuration diagram illustrating a potential of a photoconductor and the like during non-image formation in the first embodiment.

FIG. 6 is a diagram showing switching of a charging potential, a developing potential, and a transfer potential in a second embodiment.

FIG. 7 is a schematic configuration diagram illustrating a potential of a photoconductor and the like during non-image formation in a second embodiment.

FIG. 8 is a diagram showing switching of a charging potential, a developing potential, and a transfer potential in a third embodiment.

FIG. 9 is a schematic configuration diagram illustrating a potential of a photoconductor and the like during pre-rotation in a third embodiment.

FIG. 10 is a schematic configuration diagram illustrating a potential of a photoconductor and the like at the time of post-rotation in a third embodiment.

FIG. 11 is a graph showing a relationship between a potential difference before discharge and a discharge amount.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor 2 charging device 3 exposure device 5 developing device 7 transfer device 8 control device 9a, 9b, 9c, 9d motor

Claims (3)

[Claims] An electrostatic latent image formed by exposing a surface of an image carrier charged by a charging unit to light by an exposure unit is visualized by a developer supplied from a development unit, and then transferred to a transfer material by a transfer unit. In the image forming apparatus, when forming an image, the surface of the image carrier is uniformly charged by setting the potential difference between the charging unit and the surface of the image carrier to a predetermined value or more,
The developer is electrostatically supplied from the developing unit to the image carrier by setting the potential difference between the developing unit and the image carrier surface to a predetermined value or more, and the potential difference between the transfer unit and the image carrier surface is increased by the potential difference. While transferring the developer image on the surface of the image carrier to the transfer material, at the time of non-image formation, the potential difference between at least one of the charging unit, the developing unit, and the transfer unit and the surface of the image carrier during the image formation. An image forming apparatus, wherein the potential difference is set to be less than the potential difference. 2. The image forming apparatus according to claim 1, wherein a potential difference between at least one of the charging voltage unit, the developing unit, and the transferring unit during non-image formation and the surface of the image carrier is set to be less than a discharge stop voltage. 2. The image forming apparatus according to 1. 3. The image forming apparatus according to claim 1, wherein the image forming apparatus is a cleanerless type in which developer remaining on the surface of the image carrier after transfer to a transfer material is recovered by a developing unit. .