JP2017211642A - Static elimination method for latent image carrier, and image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a static elimination method for a latent image carrier that can suppress trouble such as ground part development of toner and toner falling from occurring even when an exposure width of exposure means using a light emitting element is made narrower up to a maximum print pattern width of an image formation apparatus.SOLUTION: A printer 100 comprises a photoreceptor 2, an electrostatic charging roller 4 which uniformly and electrostatically charges the photoreceptor 2, an LEDH 70 which exposes the photoreceptor 2 to form an electrostatic latent image, a developing device 5 which supplies a developer to the electrostatic latent image formed on the photoreceptor 2 to perform development, and a primary transfer roller 19. Then the printer 100 comprises an end electrostatic discharging LED 80 which electrostatically discharges the photoreceptor 2 separately from the LEDH 70, and a static elimination method for the photoreceptor 2 used for this printer 100 comprises: electrostatically discharging an exposure region by the LEDH 70 in a longer direction in a development region of the photoreceptor 2 through exposure of the LEDH 70; and electrostatically discharging a region other than the exposure region by the LEDH 70 with the end electrostatic discharging LED 80.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method for neutralizing a latent image carrier and an image forming apparatus using the same.

  Conventionally, a latent image carrier, a charging unit that uniformly charges the latent image carrier, an exposure device as an exposure unit that exposes the latent image carrier to form an electrostatic latent image, and a developer on the electrostatic latent image. There is known an image forming apparatus including a developing unit that supplies and develops, and a transfer unit that transfers a developed toner image to a transfer target. In such an image forming apparatus, there is also known an image forming apparatus that neutralizes the surface of the latent image carrier when the surface movement of the latent image carrier is stopped after the transfer of the toner image by the transfer unit.

For example, Patent Document 1 describes the following image forming apparatus.
After the transfer onto the transfer object (paper), the surface of the uniformly charged latent image carrier (photoreceptor drum) is exposed by an exposure means (LED optical unit) using a light emitting element for forming an electrostatic latent image. The exposure removes the charge to a charge removal potential in the vicinity of 0 [V] (−50 to −100 [V]) to stop the endless movement of the latent image carrier.
In this image forming apparatus, the exposure area width (the width in which the LED can emit light) in the main scanning direction (hereinafter simply referred to as the main scanning direction) by the exposure unit is set in the main scanning direction within the standard of the recording material capable of image formation. The width is the same as the maximum size (letter size).
In this way, by eliminating the charge in the area of the latent image carrier that is equal to or larger than the maximum width of the recording material on which image formation is performed by the exposure unit, the areas on the latent image carrier corresponding to both ends of the recording material in the main scanning direction (photosensitive It is described that the carrier and toner adhering to the left and right ends of the body drum can be prevented.

In recent years, in the field of electrophotographic image forming apparatuses, in addition to use in offices of companies and the like, use in home offices and homes of general users has increased. More than ever before.
However, in the conventional image forming apparatus in which the exposure width by the exposure unit using the light emitting element is larger than the maximum size of the recording material in the main scanning direction, the space required for installation is difficult to reduce in the main scanning direction of the exposure unit. The size cannot be reduced, and it may be difficult to reduce the size of the image forming apparatus.
On the other hand, if the exposure width by the exposure means using the light emitting element is reduced to the maximum print pattern width of the image forming apparatus to reduce the size, both ends of the development width corresponding to the maximum width of the recording material cannot be subjected to static discharge exposure. Problems such as development of a background portion of toner and toner dropping occur near the portion.

  In order to solve the above-described problems, the invention according to claim 1 is directed to a latent image carrier, charging means for uniformly charging the latent image carrier, and exposing the latent image carrier to electrostatic latent image. An exposure unit using a light emitting element for forming an image; a developing unit for supplying a developer to the electrostatic latent image formed on the latent image carrier; and developing the developed toner image on a transfer target A transfer means for transferring, and after the transfer of the toner image by the transfer means, when the surface movement of the latent image carrier is stopped, the latent image carrier is used in an image forming apparatus that neutralizes the surface of the latent image carrier. In the method for neutralizing an image carrier, the image forming apparatus includes a neutralization unit that neutralizes the latent image carrier separately from the exposure unit, and the exposure in a main scanning direction within a development region of the latent image carrier. The exposure area by the means is neutralized by exposure of the exposure means, In the main scanning direction of the development area of the latent image bearing member, outside the exposure area by the exposing unit is characterized in that for discharge said charge removing means.

  According to the present invention, even when the exposure width of the exposure unit using the light emitting element is reduced to the maximum print pattern width of the image forming apparatus, the latent image holding capable of suppressing the occurrence of problems such as toner background development and toner dropping. A method of neutralizing the body can be provided.

A schematic configuration diagram of a printer according to an embodiment. FIG. 3 is an enlarged explanatory view of a process unit for K provided in the printer. FIG. 3 is an arrangement explanatory diagram of a cross section perpendicular to the longitudinal direction of the photosensitive member of the constituent member related to static elimination exposure around the photosensitive member according to the first embodiment. FIG. 3 is an explanatory diagram illustrating arrangement of constituent members related to static elimination exposure around the photosensitive member in the longitudinal direction of the photosensitive member according to the first exemplary embodiment. FIG. 6 is an explanatory diagram of an example of an arrangement position of an end charge eliminating LED of a photoreceptor according to a modification example of Example 1. According to the second exemplary embodiment, when the adjustment / printing operation is started after being left for a long time after the printing operation, and the photosensitive member is not discharged during the previous printing operation, and the next printing operation is started. Explanatory drawing of surface potential. The figure which showed the example of the relationship between the background potential and the developer amount developed on the background part on the photoreceptor. Explanatory drawing of the example of the photoreceptor static elimination sequence in the case of performing static elimination exposure only by LEDH which is an exposure means. FIG. 6 is an explanatory diagram of arrangement of constituent members related to static elimination exposure around a photoconductor around a photoconductor according to a second embodiment. Explanatory drawing of the relationship between the discharge exposure range of each LEDH and edge part static elimination LED, the distance between each, and the rotational speed of a photoreceptor based on Example 2. FIG. Explanatory drawing of the photoreceptor static elimination sequence of the specific example 1 and the specific example 2. FIG. Explanatory drawing of the photoreceptor static elimination sequence of the specific example 3 and the specific example 4. FIG. FIG. 10 is an explanatory diagram of a photoconductor neutralization sequence of Example 5. FIG. 6 is an explanatory diagram of an example of potential characteristics of a photoconductor used in Example 2.

Hereinafter, an embodiment of an image forming apparatus using a method for neutralizing a latent image carrier to which the present invention is applied will be described with reference to a plurality of examples and modifications.
First, the basic configuration and operation of an A3-compatible full-color printer (hereinafter referred to as printer 100), which is an image forming apparatus according to the present embodiment, will be described with reference to FIGS.
FIG. 1 is a schematic configuration diagram of a printer 100 according to this embodiment, and FIG. 2 is an enlarged explanatory diagram of a K process unit 1 provided in the printer 100.
Here, both the schematic configuration diagram of FIG. 1 and the enlarged explanatory diagram of FIG. 2 show a cross section from the side of the printer 100 of the present embodiment, the right side in the figure is the front side of the printer 100, The left side is the rear side.

The printer 100 is a tandem, intermediate transfer system that includes four process units 1Y, M, C, and K for forming yellow (Y), magenta (M), cyan (C), and black (K) toner images. This is a color printer.
The four process units 1Y, 1M, 1C, and 1K use Y, M, C, and K toners of different colors as image forming materials, respectively. Is done.
Here, FIGS. 1 and 2 illustrate the configuration of the printer 100 of the contact one-component development system, but the characteristic configuration of the present embodiment can be applied to the non-contact and two-component development systems.

Next, the image forming process of the printer 100 will be described using the process unit 1K for forming a K toner image as an example.
As shown in FIG. 2, a drum-shaped photoreceptor 2K as a latent image carrier has a conductive support, a photoconductive layer, and an insulating layer as a basic structure, as is well known. .
First, the surface potential of the photoreceptor 2K is charged to a uniform potential by the operation of the charging roller (charging device) 4K. Thereafter, when image information is input, light based on the image information is oscillated from an LED head (hereinafter referred to as LEDH70) and selectively irradiated onto the surface of the photoreceptor 2K. The surface potential of the exposed photoconductor 2K is light attenuated, and an electrostatic latent image corresponding to the image signal is formed.

On the other hand, a constant bias voltage is applied to the developing roller 11K which is a developer carrying member provided in the developing unit 7K of the developing device 5K, and the photosensitive member 2K carrying the electrostatic latent image is connected to the developing roller 11K. When contacted, a potential difference is generated between the photoreceptor 2K and the developing roller. Due to this potential difference, the toner adhering to the developing roller 11K by magnetic force adheres to the exposed portion of the surface of the photoreceptor 2K, and the electrostatic latent image on the surface of the photoreceptor 2K is visualized. Thereafter, the toner image on the surface of the photosensitive member 2K is transferred onto the intermediate transfer belt 16.
The residual toner on the surface of the photoreceptor 2K is scraped off from the surface of the photoreceptor 2K by a cleaning blade provided in the photoreceptor cleaning device 3K. Thereafter, the surface of the photosensitive member 2K is neutralized by the LED H70, and waits for the next image printing operation or the next image printing operation.

In the other color process units 1Y, 1M, and 1C, Y, M, and C toner images are formed on the photoreceptors 2Y, 2M, and 2C, respectively, in the same manner as the process unit 1K. The recording material is transferred onto a sheet (sheet) S which is a recording material conveyed upward.
As shown in FIG. 2, the developing device 5K includes a vertically long hopper 6K that stores K toner and a developing unit 7K.

In the hopper 6K, toner is supplied from the toner cartridge 13K according to the amount of toner reduced by printing so that a constant amount of toner is always stored.
The hopper 6K includes an upper conveying screw 8K that is rotationally driven by driving means, a lower conveying screw 9K that is rotationally driven by driving means below the toner in a vertical direction, and a toner that is rotationally driven by driving means in the vertical direction. A supply roller 10K and the like are disposed.
The K toner in the hopper 6K moves toward the toner supply roller 10K by its own weight while being agitated by the rotational driving of the upper conveying screw 8K and the lower conveying screw 9K.
The toner supply roller 10K has a metal core and a roller portion made of foamed resin or the like coated on the surface of the metal core, and the K toner in the developing device 5K is adhered to the surface of the roller portion. Rotate.

In the developing unit 7K of the developing device 5K, a developing roller 11K that rotates while being in contact with the photoreceptor 2K and the toner supply roller 10K, and a thinning blade 12K that has a tip in contact with the surface thereof are disposed. .
The K toner adhered to the negatively charged toner supply roller 10K in the hopper 6K is supplied to the surface of the developing roller 11K while negative charge is injected at the contact portion between the negatively charged developing roller 11K and the toner supply roller 10K. Is done.
When the supplied K toner passes through the contact position between the roller and the thinning blade 12K as the developing roller 11K rotates, the layer thickness on the roller surface is regulated.
Similar operations are performed in the developing devices 5Y, 5M, 5C of other colors.
In FIGS. 1 and 2, an LED H 70 is disposed above the photoconductors 2Y, 2M, 2C, and 2K in the vertical direction.

The LEDH 70 provided corresponding to each process unit 1 causes a light emitting element (LED) at a predetermined position to emit light based on image information. As a result, the photosensitive members 2Y, M, C, and K in the process units 1Y, M, C, and K are exposed, and electrostatic latent images for Y, M, C, and K are exposed on the photosensitive members 2Y, M, C, and K. Is formed.
Here, the LED H 70 has a plurality of light emitting elements such as LEDs arranged in the longitudinal direction of the photosensitive member, and similarly irradiates light through a lens arranged in the longitudinal direction of the photosensitive member 2 to the surface of the photosensitive member 2. Perform an electrostatic latent image.
Here, the light emitted from the LEDH 70 forms an image by an electrostatic latent image, and therefore, light having high resolution and directivity is used. About this light emitting element, what is necessary is just to have the same resolution and directivity, such as not only LED but organic EL element.

Then, the K toner whose layer thickness has been regulated adheres to the electrostatic latent image for K on the surface of the photoreceptor 2K in the development region (development position) that is the contact portion between the developing roller 11K and the photoreceptor 2K.
The electrostatic latent image for K is developed into a K toner image by the adhesion of the toner.
The K process unit has been described above with reference to FIG. 2, but the Y, M, and C process units 1Y, M, and C also perform the same process on the surfaces of the photoreceptors 2Y, M, and C, respectively. M and C toner images are formed.

Below the process units 1Y, 1M, 1C, and 1K, a transfer unit 15 that is endlessly moved in the counterclockwise direction in the drawing while an endless intermediate transfer belt 16 is stretched is disposed.
In addition to the intermediate transfer belt 16, the transfer unit 15 serving as transfer means includes a driving roller 17, a driven roller 18, four primary transfer rollers 19Y, M, C, and K, a belt cleaning device 21, and the like.
The intermediate transfer belt 16 is stretched by a driving roller 17, a driven roller 18, and four primary transfer rollers 19Y, 19M, 19C, and 19K that are disposed inside the loop.
The intermediate transfer belt 16 is moved endlessly in the same direction by the rotational force of the driving roller 17 that is driven to rotate counterclockwise in the drawing by the driving means.

The four primary transfer rollers 19Y, 19M, 19C, and 19K sandwich the intermediate transfer belt 16 that is moved endlessly in this manner between the photoreceptors 2Y, 2M, 2C, and 2K.
By this sandwiching, primary transfer nips for Y, M, C, and K where the front surface of the intermediate transfer belt 16 and the photoreceptors 2Y, 2M, 2C, and 2K abut are formed.
A positive primary transfer bias is applied to the primary transfer rollers 19Y, 19M, 19C, and 19K by a transfer bias power source, whereby the electrostatic latent images on the photoreceptors 2Y, 2M, 2C, and 2K are transferred to the primary transfer rollers 19Y, M, C, and K. A transfer electric field is formed between the rollers 19Y, 19M, 19C, and 19K.
Here, instead of the primary transfer rollers 19Y, 19M, 19C, and 19K, those capable of forming a transfer electric field such as a transfer charger and a transfer brush can be used.

When the Y toner formed on the surface of the photoreceptor 2Y of the Y process unit 1Y enters the primary transfer nip for Y as the photoreceptor 2Y rotates, the photoreceptor 2Y is affected by the action of the transfer electric field or nip pressure. Primary transfer is performed on the intermediate transfer belt 16 from above. The intermediate transfer belt 16 onto which the Y toner image has been primarily transferred in this way passes through the primary transfer nip for M, C, K along with its endless movement, and M on the photoreceptors 2M, C, K. , C, and K toner images are sequentially transferred onto the Y toner image in a superimposed manner.
A four-color toner image is formed on the intermediate transfer belt 16 by the primary transfer of the superposition.

The secondary transfer roller 20 of the transfer unit 15 is disposed outside the loop of the intermediate transfer belt 16 and sandwiches the intermediate transfer belt 16 between the drive roller 17 inside the loop.
By this sandwiching, a secondary transfer nip where the front surface of the intermediate transfer belt 16 and the secondary transfer roller 20 abut is formed.
A positive secondary transfer bias is applied to the secondary transfer roller 20 by a transfer bias power source.
By applying this bias, a secondary transfer electric field is formed between the secondary transfer roller 20 and the drive roller 17 connected to the ground.

Below the transfer unit 15, a paper feed cassette 30 that accommodates a plurality of sheets S stacked in a bundle is disposed so as to be slidable with respect to the printer housing.
In the paper feed cassette 30, a paper feed roller 30a is brought into contact with the top paper S of the paper bundle, and the paper S is rotated by rotating it in a counterclockwise direction in the drawing at a predetermined timing. The paper is sent out toward the conveyance path 31 after feeding.
A registration roller pair 32 is disposed near the end of the post-feed conveyance path 31. The registration roller pair 32 immediately after the sheet S fed from the sheet feeding cassette 30 is sandwiched between the rollers. Stop rotation. Then, rotational driving is resumed at a timing at which the sandwiched sheet S can be synchronized with the four-color toner image on the intermediate transfer belt 16 in the above-described secondary transfer nip, and the sheet S is sent out toward the secondary transfer nip.

The four-color toner image on the intermediate transfer belt 16 brought into close contact with the paper S at the secondary transfer nip is subjected to batch secondary transfer onto the paper S under the influence of the secondary transfer electric field and nip pressure, and the white color of the paper S Together with a full color toner image.
The sheet S on which the full-color toner image is formed on the surface in this way is separated from the secondary transfer roller 20 and the intermediate transfer belt 16 by curvature when passing through the secondary transfer nip. Then, the toner is fed into a fixing device 34 described later via a post-transfer conveyance path 33.
Here, untransferred toner that has not been transferred to the paper S is attached to the intermediate transfer belt 16 after passing through the secondary transfer nip.
This transfer residual toner is cleaned from the belt surface by the belt cleaning device 21 in contact with the front surface of the intermediate transfer belt 16.

The fixing device 34 forms a fixing nip with a fixing roller 34a containing a heat source such as a halogen lamp and a pressure roller 34b that rotates while contacting the fixing roller 34a with a predetermined pressure.
The sheet S fed into the fixing device 34 is sandwiched between the fixing nips such that the unfixed toner image carrying surface is in close contact with the fixing roller 34a. Then, the toner is softened by the influence of heating and pressurization, and the full-color image is fixed on the paper S.
The sheet S discharged from the fixing device 34 passes through a post-fixing conveyance path 35 and is discharged out of the apparatus by a pair of discharge rollers 36 and is stacked on a stack portion that is an upper surface of the upper cover 50 of the casing. .

Here, when any one of the process units 1 that are consumables is replaced, the LED H 70 disposed in the vicinity of the photoconductor 2 becomes an obstacle, and thus needs to be retreated from the vicinity of the photoconductor 2.
The upper cover 50 and the middle cover 40 are rotatably held with respect to the main body housing with the rotation shaft 51 as a fulcrum, and are opened and closed when exchanging consumables.
LEDH70 is hold | maintained at the head holder 71, and is urged | biased by the direction which approaches the photoreceptor 2 with a spring member. Further, the head holder 71 is held by a connecting member 76, and one end of the connecting member 76 is rotatably held with respect to the middle cover 40 via a rotating portion 77.
Since the connecting member 76 is held by the middle cover 40, the LEDH 70 is brought into contact with and retracted from the photoreceptor 2 in conjunction with opening and closing of the middle cover 40.

In the development system as described above, the surface potential of the photoreceptor 2 that was left when the developing device 5 was started up is in the vicinity of 0 [V]. For this reason, a positive voltage is applied to the developing roller so that the negatively charged toner is not developed, and the image forming apparatus starts to move.
At this time, if the surface potential of the photosensitive member 2 remains negative at the time of the previous operation shutdown, when a positive voltage is applied to the developing roller 11 at the next startup of the operation, the gap between the developing roller 11 and the photosensitive drum 2 is reached. The potential difference at becomes large. As a result, unintended defective toner such as reversely charged toner or weakly charged toner adheres to the surface of the photoreceptor 2.
As a result, a background stain that develops on the background portion where the toner should not adhere is generated, and if the amount of the background stain toner is large, the toner is dropped or the toner is scattered in the apparatus.

In the above, description has been made by taking the development system of the contact one-component development system as an example. However, in the non-contact development system as well, the background stain due to the adhesion of the defective toner is generated, and in the two-component development system, in addition to the same problem Carrier scattering is also a problem.
In order to prevent the above-described problems, the printer 100 exposes the surface of the photoconductor 2 with the LEDH by the width of the developing roller 11 in order to discharge the potential of the surface of the photoconductor 2 to near 0 [V] when the operation is stopped. Static electricity is removed.
However, structures necessary for the development system such as a holding member for the photosensitive member 2, a holding member for the developing roller 11, a gap management member for the photosensitive member 2 and the LED H 70 are densely packed at both ends of the developing area of the photosensitive member 2. . For this reason, the LED H 70 cannot be disposed up to the end of the development area of the photoconductor 2, and it is difficult to eliminate the charge in the development area of the photoconductor 2 without omission.

When the LED H 70 is disposed up to the end of the photoconductor 2, the above holding member and the like must be arranged outside the developing area of the photoconductor 2, and the process unit to which the holding member and the like are attached is extended. Also, the main body of the printer 100 in which it is built is also enlarged.
Therefore, the printer 100 according to the present embodiment is configured to perform static elimination by attaching an end static elimination LED 80 as static elimination means different from the LED H 70 (see FIG. 3).
Hereinafter, a method for neutralizing the photoreceptor 2 that is a latent image carrier that can be suitably used in the printer 100 according to the present embodiment, and a configuration thereof will be described with reference to a plurality of examples and modifications.

Example 1
First, a static elimination method for the photosensitive member 2 that can be used in the printer 100 of the present embodiment and Example 1 of the configuration related thereto will be described with reference to the drawings.
FIG. 3 is a layout explanatory diagram of a cross section perpendicular to the photosensitive member longitudinal direction (main scanning direction) of the constituent members related to static elimination exposure around the photosensitive member 2 according to the present embodiment. FIG. 4 is an explanatory view of the arrangement of the constituent members related to the static elimination exposure around the photosensitive member 2 in the longitudinal direction of the photosensitive member according to the present embodiment, and FIG. 4A is a drawing of the developing roller 11 on the photosensitive member 2. The arrangement explanatory drawing paying attention to the developing width, the writing width by the LEDH 70, and the writing width outside the developing width (outside the LEDH exposure area). FIG. 4B is an explanatory view of the arrangement focusing on the end neutralization LED that performs static elimination exposure outside the writing width in the development width on the photoreceptor 2.

As shown in FIG. 3, around the photosensitive member 2, a photosensitive member that removes transfer residual toner remaining on the photosensitive member 2 without being primarily transferred to the charging roller 4, the LEDH 70, the developing roller 11, and the intermediate transfer belt 16. A cleaning device 3 and the like are arranged.
In addition, in the configuration of this embodiment, neutralization is performed in the vicinity of both ends in the longitudinal direction of the development region of the photosensitive member 2 between the uniform charging position by the charging roller 4 and the discharging exposure position (latent image writing position) by the LED H70. An end static elimination LED 80 which is a static elimination means for exposure is disposed away from the photoreceptor 2.
With respect to the longitudinal direction of the photoreceptor 2, as shown in FIG. 4A, the developing width that is the developer carrying width on which the developing roller 11 carries the developer with respect to the writing width that is the exposure area by the LED H70. When is large, an area outside the exposure area of the LEDH 70 is formed.
This area is subjected to static elimination exposure by the end static elimination LED 80 attached in the present embodiment, and improvement of defects such as dirt on the outside of the exposure area of the LED H 70 and toner dropping is performed.

The purpose of the static elimination exposure by the edge static elimination LED 80 is to eliminate static electricity outside the exposure area of the LED H 70, and does not require strict accuracy during an electrostatic latent image during a printing operation. For this reason, the edge charge-removing LED 80 has a lower resolution than the LED H 70 and is installed above the LED H 70. By irradiating the diffused light instead of irradiating light with high directivity of the LED H 70, the non-exposed region The neutralization exposure is performed by irradiating the surrounding area including
In this way, by exposing the periphery from a position farther from the surface of the photoreceptor 2 than the LEDH 70, all of the non-exposure areas that fluctuate due to the positional deviation of the photoreceptor 2, the developing roller 11, and the head holder 71 that is a holding member of the LEDH 70 are all. Can be eliminated.
Then, the timing at which the edge neutralizing LED 80 performs static elimination exposure outside the exposure area of the LED H 70 is performed after the printing operation or the adjustment operation of the printer 100.

As described above, the method for neutralizing the photosensitive member 2 according to this embodiment is used in the following printer 100.
Photoconductor 2, charging roller 4 for uniformly charging photoconductor 2, LEDH 70 using an LED that exposes photoconductor 2 to form an electrostatic latent image, and electrostatic latent image formed on photoconductor 2 And a developing device 5 that performs development by supplying a developer to the printer 100. A primary transfer roller 19 for transferring the developed toner image to the intermediate transfer belt 16 is also provided. When the surface movement of the photoconductor 2 is stopped after the transfer of the toner image by the primary transfer roller 19, the surface of the photoconductor 2 is moved. This is a printer 100 that performs static elimination.
In addition, the printer 100 includes an edge neutralizing LED 80 that neutralizes the photosensitive member 2 in addition to the LED H 70, and the exposure region by the LED H 70 in the longitudinal direction in the developing region of the photosensitive member 2 performs neutralization by exposure of the LED H 70. On the other hand, in the longitudinal direction in the developing area of the photoreceptor 2, the outside of the exposure area by the LED H 70 is neutralized by the edge neutralizing LED 80.

By configuring in this way, the following effects can be achieved.
When the operation of the developing device 5 is started, the surface potential of the left photosensitive member 2 is in the vicinity of 0 [V]. Therefore, when the toner charged with “−” is used, the developing device 5 is prevented from being developed. A developing voltage “+” is applied to the developing roller 11 to start moving.
If the surface potential of the photosensitive member 2 remains “−” at the previous operation shutdown, the potential difference in the development region is caused by the development voltage “+” applied to the developing roller 11 at the next operation startup. The toner becomes large and unintended toner or defective toner adheres to the surface of the photoreceptor 2. As a result, the toner is developed on a background portion where the toner should not adhere, and this causes toner drop and toner scattering in the apparatus.

In order to suppress the occurrence of such a problem, in a conventional image forming apparatus in which the exposure width by the exposure unit using the light emitting element is larger than the maximum size in the main scanning direction of the recording material, there is a space required for installation. The size in the main scanning direction of the exposure means that is difficult to downsize cannot be reduced.
For this reason, there is a possibility that it is difficult to reduce the size of the image forming apparatus.
Here, the reason why the space required for installation is difficult to downsize is that, as described above, both ends of the developing area of the photosensitive member 2 and the like are the holding member of the photosensitive member 2, the holding member of the developing roller 11, the photosensitive member 2, and the LED H70. Structures necessary for the development system, such as gap management members, are densely packed. For this reason, it is because LEDH70 cannot be arrange | positioned to the edge part of the image development area | region of the photoreceptor 2. FIG.

On the other hand, in the static elimination method of the present embodiment, even if the exposure width by the LED H 70 is narrowed to the maximum print pattern width of the printer 100, the static electricity exposure by the LED H 70 and the static elimination by the edge static elimination LED 80 separately from the LED H 70 are performed. The entire development width can be eliminated.
Therefore, even if the exposure width by the LED H 70 using LEDs is reduced to the maximum print pattern width of the printer 100, it is possible to provide a method for eliminating the charge of the photoreceptor 2 that can suppress the occurrence of problems such as toner background development and toner dropping.
Further, even if the LEDH70 having a print pattern width <development width is used for static elimination of the photosensitive member 2, it is possible to carry out static elimination exposure to both ends of the development width of the photosensitive member 2, and the background of the toner without extending the LEDH70. Problems such as partial development and toner dropping can be solved.

Further, in the method for neutralizing the photosensitive member 2 according to the present embodiment, the edge neutralizing LED 80 serving as a neutralizing unit performs neutralizing exposure on the photosensitive member 2 using a light emitting element such as an LED.
With this configuration, it is possible to easily reduce the size of the static elimination means, and it is possible to suppress wear of the photoreceptor 2 over time by adopting a non-contact static elimination method that performs static elimination exposure.

Further, in the method for neutralizing the photoconductor 2 of the present embodiment, the end neutralization LED 80 serving as a neutralization unit can be configured such that the amount of light for exposing the photoconductor 2 is different from that of the LED H70.
By configuring in this way, the following effects can be achieved.
The discharge exposure performed by the LED H 70 and the edge charge-removing LED 80 is intended to discharge the area outside the exposure area by the LED H 70 without leakage, and does not require strict accuracy as in forming an electrostatic latent image.
For this reason, by making the amount of light for exposing the photosensitive member 2 different between the LED H 70 and the end charge eliminating LED 80, it becomes possible to increase the degree of freedom in setting the distance to the photosensitive member 2 with the charge eliminating means, and to reduce the size of the printer 100. Can contribute.

Moreover, in the static elimination method of the photoreceptor 2 of the present embodiment, the end static elimination LED 80 can be configured to have a different resolution when exposed from the LED H70.
By configuring in this way, the following effects can be achieved.
The discharge exposure performed by the LED H 70 and the edge charge-removing LED 80 is intended to discharge the area outside the exposure area by the LED H 70 without leakage, and does not require strict accuracy as in forming an electrostatic latent image.
For this reason, by making the resolution when exposing the photosensitive member 2 different between the LED H 70 and the end charge eliminating LED 80, in addition to the freedom of setting the distance to the photosensitive member 2, the freedom of setting the resolution of the end charge eliminating LED 80 is also possible. This can increase the size and cost of the printer 100.

Further, in the method for neutralizing the photoconductor 2 according to the present embodiment, the distance between the photoconductor 2 and the end neutralization LED 80 can be longer than the distance between the photoconductor 2 and the LED H70.
With this configuration, the end neutralization LED 80 can be disposed away from the periphery of the photosensitive member 2 where the constituent members related to the development system are concentrated, which can further contribute to the miniaturization of the printer 100.
Further, in the method for neutralizing the photosensitive member 2 of the present embodiment, the neutralization range for neutralizing the edge neutralizing LED 80 and the LED H70 is longer than the development area in the longitudinal direction of the photosensitive member 2.
With this configuration, the development area on the photoconductor 2 can be reliably discharged without leakage.

(Modification)
In the present embodiment described above, as shown in FIG. 3, the edge neutralizing LED 80 is arranged between the charging position by the charging roller 4 and the neutralizing exposure position by the LED H 70, but according to the neutralizing method of the photoreceptor 2 of the present embodiment. The arrangement position of the edge charge eliminating LED 80 is not limited to such a position.
Below, the several example of the arrangement position of the edge part static elimination LED 80 which concerns on the static elimination method of the photoreceptor 2 of this modification is demonstrated using figures.

  FIG. 5 is an explanatory diagram of an example of an arrangement position of the end charge eliminating LED 80 of the photosensitive member 2 according to a modification of the present embodiment. FIG. 5A illustrates the surface movement direction of the photosensitive member 2, the primary transfer nip. FIG. 6 is an explanatory diagram of an example in which an end neutralization LED 80 is arranged so as to perform static elimination exposure at a position between the photosensitive member and the photosensitive member cleaning device 3. FIG. 5B shows the direction of surface movement of the photosensitive member 2, and the edge neutralization so that the neutralization exposure is performed at the position between the neutralization exposure position by the LED H 70 and the development position where the development roller 11 faces the photosensitive member 2. It is explanatory drawing of the example which has arrange | positioned LED80.

As the arrangement position of the end charge eliminating LED 80, for example, if the layout and cost of the arrangement place of the components around the photoconductor 2 including the end charge eliminating LED 80 allow, FIG. 5 (a) and FIG. 5 (b). You may arrange | position in the position of the process unit 1 like this.
That is, as shown in FIG. 5 (a), the end neutralization LED 80 may be arranged so as to carry out static elimination exposure in the surface movement direction of the photosensitive member 2, and the position between the primary transfer nip portion and the photosensitive member cleaning device 3. good.
Further, as shown in FIG. 5B, the edge neutralizing LED 80 is positioned between the surface movement direction of the photosensitive member 2, the position where the LED H 70 is subjected to the neutralizing exposure, and the developing position where the developing roller 11 faces the photosensitive member 2. May be arranged so as to be subjected to static elimination exposure.

(Example 2)
Next, a method for neutralizing the photosensitive member 2 that can be used in the printer 100 of the present embodiment and Example 2 relating to the configuration will be described.

Here, the method for removing the charge of the photosensitive member 2 of this embodiment is to light up the LEDH 70 as the exposure unit and the end charge removal LED 80 as the discharge unit at appropriate timings, and according to these. The development voltage, charging voltage, and transfer voltage are switched.
Except for the above differences, the static elimination method and the configuration of the photoreceptor 2 of this embodiment are the same as those of the first embodiment described above. Therefore, the same or similar configurations and the effects thereof will be described by omitting them as appropriate, and similar components will be described with the same reference numerals unless otherwise distinguished.

First, the reason why the photosensitive member 2 as a latent image carrier is subjected to static elimination exposure by the LEDH 70 as an exposure unit will be described with reference to the drawings.
FIG. 6 shows a case in which the adjustment / printing operation is started after being left for a long time after the printing operation according to the present embodiment, and the next time the printing operation is started without performing the charge removal on the photoconductor during the previous printing operation. FIG. 6 is an explanatory diagram of the surface potential of the photoreceptor 2. 6A is an explanatory diagram when the adjustment / printing operation is started after being left for a long time after the printing operation, and FIG. 6B is an explanatory diagram when the charging start portion reaches the developing region. FIG. FIG. 6C is an explanatory diagram of the surface potential of the photoconductor 2 when the next printing operation is started without performing the photoconductor neutralization during the previous printing operation.

In an electrophotographic image forming apparatus such as a printer or a multifunction peripheral, as shown in FIG. 6A, the surface potential of the photoconductor 2 that has been left for a long time since the end of the previous (printing / machine) operation is Near to 0 [V] due to dark decay.
For this reason, when the operation is started again, the development voltage “+” (for example, +250 [V]) is applied immediately after the operation is started in order to prevent the development of “−” charged toner.
Also, as shown in FIG. 6A, after applying a charging voltage “−” (for example, −1100 [V]) to the charging roller 4 is started, charging of the photosensitive member 2 is started as shown in FIG. 6B. The development voltage applied to the development roller 11 is switched to “−” at the timing when the part reaches the development area. Thereafter, the development voltage “−” is continuously applied while the machine operation continues.

On the other hand, if the next operation is started immediately after the previous operation is finished, the surface charge of the photoconductor 2 is not as shown in FIG. Is “−” (for example, −500 [V]).
In this state, at the start of the next operation, the development voltage “+” (for example, +250 [V]) is applied to the developing roller 11 to increase the potential difference in the developing portion (developing region), that is, the absolute value of the background potential. (For example, −750 [V]).
Such a large size may cause an unintended increase in toner consumption, toner drop, and in-machine toner scattering.
In order to suppress the occurrence of such a problem, at the end of the operation, in order to discharge the surface potential of the photosensitive member in the vicinity of 0 [V], a photosensitive member discharging sequence for discharging the entire width (developing width) of the photosensitive member 2 is performed. .

Here, the background potential will be described, and the relationship with the development amount will be described with reference to the drawings.
FIG. 7 is a diagram showing an example of the relationship between the background potential and the amount of developer developed (attached) on the background portion on the photoreceptor 2.
The background potential is defined by the difference between the surface potential of the latent image carrier such as the photosensitive member 2 in the development region and the development potential (surface potential-development voltage).
The “−” charged toner is developed if the background potential is “+”. Conversely, even if the background potential increases to the “−” side, the development amount may increase as shown in FIG. Are known. For this reason, in a situation where toner is not desired to be developed as much as possible, in this embodiment, the background potential is set to -100 to -300 [V].

Next, an example of a photosensitive member static elimination sequence in the case where the static elimination exposure is performed using only the LEDH 70 as an exposure unit will be described with reference to the drawings.
FIG. 8 is an explanatory diagram of an example of a photosensitive member charge removal sequence in the case where the charge exposure is performed only by the LEDH 70 as an exposure unit. FIG. 8A shows a charge HVP as a charge voltage output and (primary) transfer. It is explanatory drawing of an example with the setting freedom of (primary) transfer HVP which is a voltage output. FIG. 8B is an explanatory diagram of an example in which the charging voltage output is turned off when the point (position) at which the static elimination exposure on the photoreceptor 2 starts reaches the position where the LED H 70 performs static exposure. It is.

Here, timing A shown in FIG. 8A and FIG. 8B is a start point of the photosensitive member charge removal sequence, and an arbitrary point (the discharge exposure is started by the LED H70 on the photosensitive member 2). Hereinafter, the discharge exposure start point is referred to as the timing at the transfer area.
Further, in the figure, a timing B indicated by B is a timing at which the discharge exposure start point reaches a discharge exposure region (exposure region) by the LED H70, and a timing B indicated by B is a discharge exposure region by the discharge exposure start point by the LED H70. It is time to reach.
In the figure, a timing C indicated by C is a timing at which the static elimination exposure start point reaches the development area, and a timing D indicated by D is a distance of one cycle + α after the static exposure exposure start point is subjected to the static elimination exposure. This is the timing when the surface moves.

  8A and 8B, the time indicated by T1 (A to B) is the time for the discharge exposure start point to move from the transfer area to the discharge exposure area by the LED H70, and at T2. The time shown is the time for the discharge exposure start point to move from the charged area to the discharge exposure area. The time indicated by T3 (B to C) is the time when the charge removal exposure start point moves from the charge removal exposure region to the development region, and the time indicated by T4 (B to D) is the time when the charge removal exposure start point is photosensitive. This is the time for the surface to move by one round of the body (+ α).

Before starting any of the photosensitive member charge elimination sequences, the LED H70 is turned off, the charging HVP is normally output (-), the development voltage output HVP is normally output (-), and the transfer HVP is normally output (+). It is in the adjustment operation or printing operation that drives the body motor.
In the example shown in FIG. 8A, the photosensitive motor is in a driving state when it is in an adjustment operation or a printing operation, and stops at timing D.
The discharge exposure is turned on (ON) at timing B when the discharge exposure start point reaches the discharge exposure area by the LED H 70 and turned OFF at timing D.
The charge HVP has reached the position where the charge removal exposure start point has reached the charge area, or from timing D, the time required for the charge removal exposure start point to reach the charge exposure area from the charge area: T2 is reached. At the time, the normal output (-) is switched to OFF.

The development HVP is switched to “+” output opposite to the normal output (−) at the timing when the static elimination exposure start point reaches the development area, and turned OFF at timing D.
The (primary) transfer HVP is switched from the normal output (+) to OFF at the timing A when the static elimination exposure start point reaches the transfer region. Alternatively, the output is switched to “weak” output, and is turned off at the end of the charge removal sequence of the photosensitive member whose surface has been moved by the distance of one rotation + α after the charge removal exposure, that is, at timing D.
The example shown in FIG. 8A has a degree of freedom in setting the charging HVP and the (primary) transfer HVP as described above.

The example shown in FIG. 8B is different from the example shown in FIG. 8A described above only in the following timing.
The charging HVP is switched from the normal output (−) to OFF at the timing B when the discharge exposure start point reaches the discharge exposure area.
The (primary) transfer HVP is always switched from the normal output (+) to the “weak” output at the timing A when the discharge exposure start point reaches the transfer area, and after the discharge exposure, only the distance of one cycle + α. It is turned off at the end of the surface-moving photoconductor neutralization sequence, that is, at timing D.

By using any one of the examples of the photosensitive member charge elimination sequence shown in FIG. 8A and FIG. 8B described above, the entire developing width of the photosensitive member 2 is subjected to static elimination exposure with the LED H70, thereby obtaining a good photosensitive member. Static elimination can be performed.
However, in general, the maximum print pattern width of the LEDH 70 that is an exposure means for writing the print pattern is generally narrower than the development width (print pattern width <development width). The entire width cannot be subjected to static elimination exposure.
For this reason, in the static elimination method of Example 1 and this Example mentioned above, and its structure, it is supposed that the edge static elimination LED 80 which is another static elimination means will be arrange | positioned outside the exposure range of LEDH70.

Here, the arrangement of the constituent members related to each development system (development process) around the photosensitive member 2 is confirmed again with reference to FIGS. 3 and 4 used in the description of the first embodiment, with a more simplified diagram. Keep it.
FIG. 9 is an explanatory view of the arrangement of the constituent members related to static elimination exposure around the photosensitive member 2 according to the present embodiment, and FIG. 9A is an explanatory view of the arrangement of the cross section orthogonal to the longitudinal direction of the photosensitive member. FIG. 9B is an explanatory diagram of arrangement in the longitudinal direction of the photosensitive member.

In this embodiment, as the means for static elimination exposure of the photosensitive member 2, as shown in FIGS. 9A and 9B, the LED H 70 which is the exposure means for writing the print pattern and the outside of the exposure range by the LED H 70 are eliminated. An end static elimination LED 80 is used.
The edge neutralizing LED 80 is preferably attached before and after the LED H 70 with respect to the rotation direction of the photosensitive member 2. In this embodiment, as shown in FIG. 9A, the LEDH 70 is attached to the head holder 71, which is an LEDH holding member, on the upstream side (see FIG. 1). Further, as shown in FIG. 9B, the discharge exposure area is attached so as to overlap at both ends with respect to the exposure area of the LED H70.

As described above, as shown in FIGS. 9A and 9B, the LEDH 70 that is an exposure unit and both ends of the photosensitive member 2 in the longitudinal direction with respect to the rotation direction (surface movement direction) of the photosensitive member 2. In many cases, the end neutralization LEDs 80 which are neutralization means for neutralizing the vicinity are arranged at different positions.
If the discharge exposure start timing of the LED H 70 and the end charge removal LED 80 cannot be set appropriately, depending on the discharge exposure start timing of the LED H 70 and the end charge removal LED 80 at the end of the operation, Variations increase.
If it is so large, the surface portion of the photosensitive member 2 that has not been subjected to the discharge exposure by either the LED H 70 or the edge discharge LED 80 stops in the development region, and troubles such as toner background development and toner dropping occur. There is an increased risk that the suppression effect is partially reduced in the main scanning direction of the latent image carrier.

  Therefore, in the method for neutralizing the photosensitive member 2 according to the present exemplary embodiment, the neutralization exposure start timing of each of the LED H 70 and the end neutralization LED 80 at the end of the operation is adjusted, and the neutralization start region in the longitudinal direction of the photosensitive member 2 is aligned. The background part development, toner dropping and toner scattering in the machine were eliminated.

Here, with reference to the drawings, in the rotation direction (surface movement direction) of the photoreceptor 2, the discharge exposure ranges of the LED H 70 and the end charge removal LED 80, the distance between them, and the rotation speed (surface movement speed) of the photoreceptor 2. Explain the relationship with the (linear speed).
FIG. 10 is an explanatory diagram of the relationship between the discharge exposure ranges of the LED H 70 and the end charge removal LEDs 80, the distances between them, and the rotational speed (surface movement) of the photoreceptor 2 according to the present embodiment.

As shown in FIG. 10, the distance between the most exposed point in the surface movement direction of the photoreceptor 2 in the static elimination exposure range by the edge neutralization LED 80 and the exposed portion on the photoreceptor 2 by the LED H 70 is Lmax [mm]. .
Further, the distance between the most downstream exposure point in the surface movement direction of the photoconductor 2 in the static elimination exposure range by the edge static elimination LED 80 and the exposed portion on the photoconductor 2 by the LED H70 is Lmin [mm].
Further, if the rotational speed of the photosensitive member 2, that is, the linear velocity on the surface of the photosensitive member 2 is V [mm / s], and the time from the start of static elimination exposure by the edge static elimination LED 80 to the start of static elimination exposure by the LED H70 is T [s]. To do.

At the end of the operation, in order to align the discharge exposure range in the discharge start region in the longitudinal direction of the photoreceptor 2 by the LED H 70 and the end discharge LED 80, the discharge start of the end discharge LED 80 is set to Lmin / V = T. It suffices to start earlier than the start of static elimination exposure of the LEDH 70 by time.
However, it is difficult to set and maintain the arrangement of the photoconductor 2, the edge charge eliminating LED 80, the LED H70, and the like and the surface moving speed of the photoconductor 2 to the target values not only at the time of production of the printer 100 but also at the time of operation. is there.
In view of this, in the static elimination method for the photosensitive member 2 of the present embodiment, the setting is made so as to satisfy the relationship of the following formula 1.
Lmin ≦ V · T ≦ Lmax (Formula 1)

By configuring in this way, the following effects can be achieved.
By setting Lmax [mm], Lmin [mm], and T [s] so as to satisfy the above (Equation 1), the discharge exposure start timing of each of the LEDH 70 and the edge discharge LED 80 at the end of the operation is adjusted. The variation in the static elimination start area in the longitudinal direction of the photosensitive member 2 can be reduced.
By reducing in this way, the surface portion of the photoconductor that has not been subjected to the discharge exposure in either the LEDH 70 or the edge discharge LED 80 stops at the developing section, and the occurrence of problems such as toner background development and toner dropping is generated. It can be reduced that the effect of suppressing the partial decrease in the longitudinal direction of the photoreceptor 2.
Therefore, even if the exposure width by the LED H 70 using the LED is reduced to the maximum print pattern width of the printer 100, there is provided a method for neutralizing the photosensitive member 2 that can more effectively suppress the occurrence of problems such as toner background development and toner dropping. Can be provided.

Next, a plurality of specific examples of an example of the photosensitive member static elimination sequence in the case where the photosensitive member 2 is subjected to the static elimination exposure with the LEDH 70 which is the exposure unit for writing the print pattern and the end static elimination LED 80 which exposes the outside of the exposure range. Will be described with reference to the drawings.
11, FIG. 12, and FIG. 13 are explanatory diagrams of examples of the photoreceptor neutralization sequence of the method for neutralizing the photoreceptor 2 of this embodiment. FIG. 11A is an explanatory diagram of the photoconductor charge elimination sequence of Example 1, FIG. 11B is an explanatory diagram of the photoconductor charge elimination sequence of Example 2, and FIG. FIG. 12B is an explanatory diagram of the photoconductor charge elimination sequence of Example 4, and FIG. FIG. 13 is an explanatory diagram of the photosensitive member charge removal sequence of the fifth specific example.
In the following description of each specific example, the same configuration as that of each example of the photosensitive member static elimination sequence in the case where the static elimination exposure is performed using only the LEDH 70 serving as the exposure unit described with reference to FIG. 8 is appropriately omitted. To explain.

(Specific example 1)
First, specific example 1 of the photosensitive member charge elimination sequence of this embodiment will be described.
In the specific example shown in FIG. 11A, as in the example described with reference to FIG. 8A, the discharge exposure by the LED H70 is the timing at which the discharge exposure start point by the LED H70 reaches the discharge exposure region by the LED H70. Turn ON at B and turn OFF at timing D.
On the other hand, the discharge exposure by the edge discharge LED 80 starts the discharge exposure start of the edge discharge LED 80 earlier by the time of Lmin / V = T than the discharge exposure start timing by the LED H70. Specifically, it is turned ON at the timing when the charge removal exposure start point by the end charge removal LED 80 reaches the charge removal exposure region by the edge charge removal LED 80. Then, it is turned OFF at timing D.

The charging HVP is switched from the normal output (−) to OFF as shown in FIG. 11A at the time when the charge elimination exposure start point by the LED H 70 reaches the charging region. It can also be turned off.
As in FIG. 8A, the development HVP is switched to an output of “+” opposite to the normal output (−) at the timing when the static elimination exposure start point by the LED H 70 reaches the development area, and is turned off at the timing D. To. Here, the time when the photosensitive member moves from the LEDH discharge exposure area to the development area will be described using T3. The development HVP needs to be switched from the “−” output to the “+” output after T3 of the timing B. This is to prevent the toner from being developed.

The (primary) transfer HVP is switched from the normal output (+) to the “weak” output at the timing A when the static elimination exposure start point by the LED H 70 reaches the transfer area. Then, after the static elimination exposure, the photosensitive member static elimination sequence that has moved the surface by the distance of one round + α is turned OFF at the end of the static elimination sequence, that is, at timing D.
Here, the control timing of the photoreceptor motor and the (primary) transfer HVP is the same as that in FIG.

That is, after the time T1 when an arbitrary point on the photosensitive member 2 moves from the transfer region to the discharge exposure region by the LED H70 (timing B) at the timing A which is the start point of the photosensitive member charge removal sequence, the edge discharge LED 80 starts to emit light. Let
Assuming that the time from the start of exposure lighting of the edge charge eliminating LED 80 to the start of the charge removal exposure lighting of the LED H 70 is T, the edge charge eliminating LED 80 starts exposure at the timing B time: T minutes. This is for the purpose of aligning the neutralization start position in the longitudinal direction of the photoreceptor 2 between the end portion and the non-end portion.
Then, after the surface position of the photosensitive member 2 at timing B moves after a time of T1 + α: T4 (timing D), the machine is stopped. Here, as “+ α”, in this embodiment, a time corresponding to a time of moving 5 to 10 [mm] with respect to the peripheral length 94 [mm] of the photosensitive member 2 is set.

(Specific example 2)
Next, specific example 2 of the photosensitive member charge elimination sequence of this embodiment will be described.
The photoconductor neutralization sequence of this specific example differs from the specific example 1 described above only at the timing at which the end neutralization LED 80 is turned off, that is, when the end neutralization LED 80 is stopped from emitting light (end of exposure).
In this specific example shown in FIG. 11B, as described above, only the light body static elimination sequence of Specific Example 1 and the timing for stopping the light emission (end of exposure) of the end static elimination LED 80 are different.
Specifically, from the start of exposure of the edge charge eliminating LED 80 (start of charge removal exposure), as shown in FIG. 11B, when the photosensitive member 2 moves by a distance of one rotation + α, light emission is stopped (exposure is completed). Light emission can be stopped (exposure end) between that time and timing D.

(Specific example 3)
Next, specific example 3 of the photosensitive member charge elimination sequence of this embodiment will be described.
The photosensitive member charge elimination sequence of this specific example is different from the specific example 1 described above only in the timing at which the charging HVP is turned off or weakened.
In this specific example shown in FIG. 12A, the discharge exposure by the LED H70 is performed at a position earlier than the timing D by the time T2 when an arbitrary point of the photosensitive member 2 moves from the charged region to the discharge exposure region of the LED H70. When the starting point arrives, the charging HVP is turned off. Or, after weakening at this time, it is turned OFF at timing D.

  Here, as in the specific example 1 and the specific example 2, the charging HVP can decrease the output value or turn off the output before the movement of the timing B by T2 and thereafter, and before the timing D at the timing T2. It is necessary to turn it off. This is because the photosensitive member 2 is neutralized (not charged). That is, the timing for turning off the charging HVP can be set between the timing shown in FIG. 11A and the timing shown in FIG.

(Specific example 4)
Next, specific example 4 of the photosensitive member charge elimination sequence of this embodiment will be described.
The photosensitive member charge elimination sequence of this specific example differs from the above-described specific example 1 by the (primary) transfer OFF timing.
In this specific example shown in FIG. 12B, the normal output (+) is switched to OFF (off) at the timing A when the discharge exposure start point by the LED H 70 reaches the (primary) transfer region.
Here, as in this specific example shown in FIG. 12B, the (primary) transfer HVP is turned off after timing A, or output as in specific examples 1, 2 and 3. It is possible to weaken the value or turn off the output. This is to prevent the photosensitive member surface potential from being charged to “+” by excessively setting the primary transfer voltage to “+”.

(Specific example 5)
Next, specific example 5 of the photoconductor charge elimination sequence of this embodiment will be described.
The photoconductor neutralization sequence of this specific example differs from the specific example 1 described above only at the timing of switching the charging HVP. Further, the timing for switching the charging HVP is different from the above-described specific example 2, specific example 3, and specific example 4.
In this specific example shown in FIG. 13, the switching (changing) timing of the charging HVP is aligned with the timing B, thereby reducing the trigger operation and reducing the load of the software operation processing.

Next, an example of the potential characteristic of the photoreceptor 2 used in this embodiment will be described with reference to the drawings.
FIG. 14 is an explanatory diagram of an example of the potential characteristic of the photosensitive member 2 used in this embodiment, and FIG. 14A is an explanatory diagram of a change in the surface potential of the photosensitive member 2 over time. (B) is an explanatory view of a change in surface potential accompanying a change in light amount when the photosensitive member 2 is subjected to static elimination exposure.

Regarding the surface potential of the photoreceptor 2, the following has been conventionally known.
As shown in FIG. 14A, a potential on the “−” side is obtained by applying a charging voltage. Then, even if it does not shine light with LEDH70, edge part static elimination LED80, etc., the surface attenuation | stimulus slightly approaches and dark attenuation arises. Then, when light is applied by the LED H 70, the edge charge-removing LED 80, or the like, the surface potential rapidly approaches 0 [V] and light attenuation occurs.
Further, the exposure amount of the photosensitive member by the LED H 70 and the edge neutralizing LED 80 used in the method for neutralizing the photosensitive member 2 of the present embodiment is the light amount P shown in FIG. 14B in the fastest state of the photosensitive member 2 during mechanical operation. In addition, the light attenuation is set to be sufficient.
Here, the fastest state of the photosensitive member 2 is a state in which the surface moving speed of the photosensitive member 2 moves at the fastest state, the exposure time by the LED H 70 and the edge charge eliminating LED 80 is the shortest, and each exposure energy is minimized. That is.

Here, the photoconductor exposure area of the LED H70 is as small as about 50 to 100 [μm] for each spot diameter, whereas the edge neutralizing LED 80 is in [mm] units (in this embodiment, the rotation direction of the photoconductor is 1). ˜2 mm) and a wide range (20 times in this embodiment).
While the photosensitive member 2 passes through these regions, the photosensitive member 2 receives energy such as the light amount P by each light source and drops the surface potential.
Even when the passing distance at this time is n (0 ≦ n ≦ 1) (the amount of light received by the photosensitive member is nP), the photosensitive member surface potential is close to 0 [V].
Therefore, in the area of the edge charge eliminating LED 80, the point that can be regarded as the completion of the charge removal on the photoreceptor is located between the most upstream point and the most downstream point of the charge removal exposure area by the edge charge eliminating LED 80.

Next, consideration will be given to the deterioration with time of the edge neutralizing LED 80 in the method for neutralizing the photoreceptor 2 of the present embodiment.
Since the amount of light emission decreases according to the light emission time, the point at which the charge removal on the photosensitive member in the edge discharge exposure region is completed shifts to the downstream side as the edge charge removal LED 80 is used over time.
The printer 100 includes a counter that measures the light emission time corresponding to the edge discharge exposure, and a control that corrects the edge discharge exposure completion point in accordance with the counter value. Timing deviation can be prevented.

Specifically, the configuration is as follows.
Ta [s] is the time from the start of exposure by the edge charge eliminating LED 80 to the start of exposure by the LED H 70 in a state where the usage history of the edge charge eliminating LED 80 is relatively small.
Also, the time from the start of exposure by the edge charge eliminating LED 80 to the start of exposure by the LED H 70 in a state where the usage history of the edge charge eliminating LED 80 is relatively large is defined as Tb [s].
When defined as described above, the following expression 2 is satisfied.
Lmin ≦ V · Tb ≦ V · Ta ≦ Lmax (Formula 2)

By configuring in this way, the following effects can be achieved.
With respect to the deterioration over time due to the use of the edge neutralizing LED 80, it is possible to prevent the development of the background portion of the toner and to avoid the problem of toner dropping and toner scattering in the apparatus.

Next, the case where the printer 100 has a mode in which the machine operation speed is reduced to a normal half speed, for example, when the printing paper is set to “thick paper” is described.
In this way, in the printer 100 that drives the photosensitive member 2 at a plurality of rotation speeds (linear speeds), when “the machine operation speed is low” and “lighting at the edge discharge charge is performed with a normal light amount” immediately before the machine operation is stopped, In the area of partial discharge exposure, the points that can be considered that the charge removal on the photosensitive member is completed are as follows.
That is, it is located upstream from the normal speed.
Even when the printer 100 is configured in this way, timing deviation can be prevented by providing the printer 100 with control for correcting the end static elimination exposure completion point in accordance with the rotational speed of the photosensitive member 2.

Specifically, the configuration is as follows.
It is assumed that the printer 100 can drive the surface of the photoreceptor 2 at a plurality of rotational speeds.
Here, the rotational speed of the surface of the photosensitive member 2 during high-speed driving is Vh [mm / s].
In addition, the time from the start of exposure by the edge charge eliminating LED 80 at the time of high-speed driving to the start of exposure by the LED H 70 is Th [s].
On the other hand, the rotational speed of the surface of the photosensitive member 2 during low-speed driving is set to Vl [mm / s].
Further, the time from the start of exposure by the edge charge eliminating LED 80 during low speed driving to the start of exposure by the LED H 70 is defined as Tl [s].
When defined as described above, the following expression 2 is satisfied.
Lmin ≦ Vh · Th ≦ Vl · Tl ≦ Lmax (Formula 3)

By configuring in this way, the following effects can be achieved.
In the printer 100 having different driving speed (rotational speed) modes of the photoconductor 2, it is possible to prevent the background development of the toner in each driving speed mode and to avoid the problem of toner dropping and in-machine toner scattering.

  The image forming apparatus according to the present exemplary embodiment uses the above-described embodiments and the method for neutralizing the photoconductor 2 according to the modified example, and thus the same as the method for neutralizing the photoconductor 2 according to each of the above-described examples and the modified example. Therefore, it is possible to provide the printer 100 that can achieve various effects.

As described above, the present embodiment has been described with reference to the drawings. However, the specific configuration is limited to the configuration of the printer 100 that is a tandem-type color equipped with the above-described method for neutralizing the photoreceptor 2 of the present embodiment. However, the design may be changed without departing from the scope of the invention.
For example, the present invention can also be applied to an image forming apparatus such as a monochrome printer, a facsimile machine, a copying machine, and a multifunction machine having any of these functions.

What was demonstrated above is an example, and there exists an effect peculiar for every following aspect.
(Aspect A)
A latent image carrier such as the photosensitive member 2, a charging unit such as a charging roller 4 for uniformly charging the latent image carrier, and a light emitting element such as an LED that exposes the image carrier to form an electrostatic latent image. Developed using an exposure means such as an LEDH (LED head) 70 using a toner, a developing means such as a developing device 5 for supplying a developer to the electrostatic latent image formed on the latent image carrier, and developing the developer. A transfer means such as a primary transfer roller 19 for transferring a toner image to a transfer medium such as an intermediate transfer belt 16, and after the transfer of the toner image by the transfer means, the surface movement of the latent image carrier is stopped. In addition, in the method of neutralizing a latent image carrier used in an image forming apparatus such as the printer 100 that neutralizes the surface of the latent image carrier, the image forming apparatus neutralizes the latent image carrier separately from the exposure unit. End static elimination LED80 etc. A neutralization unit is provided, and, among the development area of the latent image carrier, an exposure region by the exposure unit is neutralized by exposure of the exposure unit, and a region outside the exposure region by the exposure unit is neutralized by the neutralization unit. And

According to this, as described in the present embodiment, the following effects can be achieved.
Since the surface potential of the latent image carrier left unattended at the start-up of the developing means is near 0 [V], the development means develops the toner so that the toner is not developed when using toner charged to “−”. A developing voltage “+” is applied to the agent carrying member to start moving.
If the surface potential of the latent image carrier remains “−” at the previous operation fall, the development voltage “+” applied to the developer carrier at the next start of operation causes The potential difference increases, and unintended toner and defective toner adhere to the surface of the latent image carrier. As a result, the toner is developed on a background portion where the toner should not adhere, and this causes toner drop and toner scattering in the apparatus.

In order to suppress the occurrence of such a problem, in a conventional image forming apparatus in which the exposure width by the exposure unit using the light emitting element is larger than the maximum size in the main scanning direction of the recording material, there is a space required for installation. The size in the main scanning direction of the exposure means that is difficult to downsize cannot be reduced.
For this reason, there is a possibility that it is difficult to reduce the size of the image forming apparatus.

On the other hand, in the static elimination method of this aspect, even if the exposure width by the exposure means using the light emitting element is reduced to the maximum print pattern width of the image forming apparatus, the static elimination exposure by the exposure means and the static elimination means provided separately from the exposure means By removing the electric charge, the entire developing width of the latent image carrier can be removed.
Therefore, even if the exposure width by the exposure means using the light emitting element is narrowed to the maximum print pattern width of the image forming apparatus, the latent image carrier neutralizing method can suppress the occurrence of problems such as toner background development and toner dropping. Can provide.
Further, even if an exposure unit having a print pattern width <development width is used for neutralization of the latent image carrier, it is possible to perform static elimination exposure to both ends of the development width of the latent image carrier, without extending the exposure unit. In addition, it is possible to eliminate problems such as toner background development and toner dropping.

(Aspect B)
In (Aspect A), the charge eliminating unit performs charge exposure on the latent image carrier using a light emitting element such as an LED.
According to this, as described in the present embodiment, it is easy to reduce the size of the static eliminator, and also suppress wear of the latent image carrier over time by adopting a non-contact static eliminator that performs static elimination exposure. be able to.

(Aspect C)
In (Aspect B), the charge eliminating unit is different from the exposing unit in the amount of light for exposing the latent image carrier.
According to this, as described in the present embodiment, the following effects can be achieved.
The purpose of static elimination exposure performed by the exposure means and the static elimination means is to eliminate static electricity outside the exposure area by the exposure means, and does not require strict accuracy as in the formation of an electrostatic latent image.
For this reason, it is possible to increase the degree of freedom of setting the distance to the latent image carrier by the charge eliminating unit by making the amount of light for exposing the latent image carrier different between the exposure unit and the charge eliminating unit, thereby reducing the size of the image forming apparatus. Can contribute to

(Aspect D)
In (Aspect B) or (Aspect C), the static elimination means is different in resolution when exposed from the exposure means.
According to this, as described in the present embodiment, the following effects can be achieved.
The purpose of static elimination exposure performed by the exposure means and the static elimination means is to eliminate static electricity outside the exposure area by the exposure means, and does not require strict accuracy as in the formation of an electrostatic latent image.
For this reason, by making the resolution when exposing the latent image carrier different between the exposure unit and the neutralization unit, in addition to the freedom of setting the distance to the latent image carrier, the freedom of setting the resolution of the neutralization unit is also increased. Therefore, the image forming apparatus can be reduced in size and cost.

(Aspect E)
In any one of (Aspect A) to (Aspect D), a distance between the latent image carrier and the charge eliminating unit is longer than a distance between the latent image carrier and the exposure unit.
According to this, as described in the present embodiment, the static eliminator can be arranged away from the periphery of the latent image carrier on which the constituent members related to the development system are concentrated, which further reduces the size of the image forming apparatus. Can contribute.

(Aspect F)
In any one of (Aspect A) to (Aspect E), a charge removal range of charge removal between the charge removal unit and the exposure unit is greater than or equal to a development region in the main scanning direction of the latent image carrier such as the longitudinal direction of the photoreceptor 2. It is characterized by a length.
According to this, as described in the present embodiment, the development area on the latent image carrier can be reliably discharged without leakage.

(Aspect G)
In any one of (Aspect A) to (Aspect F), the static elimination unit performs static exposure on the latent image carrier using a light emitting element.
Lmax [mm], the distance between the most upstream point of exposure by the static eliminating unit and the exposed part on the latent image carrier by the exposing unit,
Lmin [mm] is a distance between the most downstream point of exposure by the charge eliminating unit and the exposed portion on the latent image carrier by the exposure unit,
The linear velocity of the surface of the latent image carrier is V [mm / s],
When the time from the start of exposure by the static elimination means to the start of exposure by the exposure means is T [s],
It is characterized by satisfying the relationship of the following formula 1.
Lmin ≦ V · T ≦ Lmax (Formula 1)

According to this, as described in the present embodiment, the following effects can be achieved.
There are many cases where the discharge start position of the exposure means and the discharge means in the surface movement direction of the latent image carrier is different, and depending on the start timing of the discharge exposure of the exposure means and the discharge means at the end of the operation, The variation in the static elimination start area in the scanning direction increases.
If it is so large, the surface portion of the latent image carrier that has not been subjected to static elimination exposure by either the exposure means or the static elimination means stops in the development area, causing problems such as toner background development or toner dropping. There is an increased risk that the effect of suppressing the partial decrease in the main scanning direction of the latent image carrier.

On the other hand, by setting Lmax [mm], Lmin [mm], and T [s] so as to satisfy the above (Expression 1), the discharge exposure start timing of the exposure unit and the discharge unit at the end of the operation is adjusted. In addition, it is possible to reduce variations in the static elimination start area in the main scanning direction of the latent image carrier.
By reducing in this way, the surface portion of the latent image carrier that has not been subjected to static elimination exposure by either the exposure means or the static elimination means stops in the development area, causing problems such as toner background development and toner dropping. It can be reduced that the effect of suppressing the occurrence of the partial drop in the main scanning direction of the latent image carrier.
Therefore, even if the exposure width by the exposure means using the light emitting element is narrowed to the maximum print pattern width of the image forming apparatus, the latent image carrier that can better suppress the occurrence of problems such as toner background development and toner dropping. Can be provided.

(Aspect H)
In (Aspect G), Ta [s] represents the time from the start of exposure by the static elimination means to the start of exposure by the exposure means in a state where the use history of the static elimination means is relatively small.
When the time from the start of exposure by the static elimination means to the start of exposure by the exposure means in a state where the usage history of the static elimination means is relatively large is Tb [s]
A neutralizing method for a latent image carrier, characterized by satisfying the relationship of the following formula 2.
Lmin ≦ V · Tb ≦ V · Ta ≦ Lmax (Formula 2)

According to this, as described in the present embodiment, the following effects can be achieved.
With respect to the deterioration over time due to the use of the charge eliminating means, it is possible to prevent the development of the background portion of the toner and to avoid the problem of toner dropping and toner scattering in the apparatus.

(Aspect I)
In (Aspect G) or (Aspect H), the image forming apparatus can drive the surface of the latent image carrier at a plurality of linear speeds.
Vh [mm / s], the linear velocity of the surface of the latent image carrier during high-speed driving,
Th [s] represents the time from the start of exposure by the static elimination means during the high-speed driving to the start of exposure by the exposure means,
Vl [mm / s] is the linear velocity of the surface of the latent image carrier during low-speed driving,
When the time from the start of exposure by the static elimination unit during the low-speed driving to the start of exposure by the exposure unit is Tl [s],
A neutralizing method for a latent image carrier, characterized by satisfying the relationship of the following expression (3).
Lmin ≦ Vh · Th ≦ Vl · Tl ≦ Lmax (Formula 3)

According to this, as described in the present embodiment, the following effects can be achieved.
In an image forming apparatus having different driving speed modes of the latent image carrier, it is possible to prevent the background development of the toner in each driving speed mode, and to avoid the problem of toner dropping and in-machine toner scattering.

(Aspect J)
A latent image carrier, charging means for uniformly charging the latent image carrier, exposure means using a light emitting element that exposes the latent image carrier to form an electrostatic latent image, and the latent image carrier In the image forming apparatus, the image forming apparatus includes: a developing unit that supplies a developer to the electrostatic latent image formed on the developing unit; and a discharging unit that discharges the latent image carrier separately from the exposing unit. Any one of (Aspect A) to (Aspect I) can be used as a charge eliminating method for discharging the carrier.
According to this, as described in the present embodiment, it is possible to provide an image forming apparatus that can achieve the same effect as the method for neutralizing a latent image carrier of any one of (Aspect A) to (Aspect I). .

DESCRIPTION OF SYMBOLS 1 Process unit 2 Photoconductor 3 Photoconductor cleaning apparatus 4 Charging roller 5 Developing apparatus 11 Developing roller 15 Transfer unit 16 Intermediate transfer belt 19 Primary transfer roller 70 LEDH (LED head)
71 Head holder 80 End static elimination LED
100 Printer S Paper

Japanese Patent No. 3457083

Claims (10)

A latent image carrier, charging means for uniformly charging the latent image carrier, exposure means using a light emitting element that exposes the latent image carrier to form an electrostatic latent image, and the latent image carrier A developing means for supplying a developer to the electrostatic latent image formed thereon to develop the toner image, and a transferring means for transferring the developed toner image to the transfer target,
In the method of neutralizing a latent image carrier used in an image forming apparatus for neutralizing the surface of the latent image carrier when the surface movement of the latent image carrier is stopped after the transfer of the toner image by the transfer unit,
The image forming apparatus includes a discharging unit that discharges the latent image carrier separately from the exposure unit,
The exposure area by the exposure means in the main scanning direction in the development area of the latent image carrier is neutralized by exposure of the exposure means, and the exposure means in the main scanning direction in the development area of the latent image carrier. A method for neutralizing a latent image carrier, wherein the charge is removed by the neutralizing means outside the exposure area. The method for neutralizing a latent image carrier according to claim 1,
The method for neutralizing a latent image carrier, wherein the neutralization unit performs exposure to remove the latent image carrier using a light emitting element. The method for neutralizing a latent image carrier according to claim 2,
The method of neutralizing a latent image carrier, wherein the neutralizing unit is different from the exposure unit in the amount of light that exposes the latent image carrier. In the method for neutralizing a latent image carrier according to claim 2 or 3,
The method of neutralizing a latent image carrier, wherein the neutralizing unit has a different resolution from the exposing unit when exposed. In the static elimination method of the latent image carrier according to any one of claims 1 to 4,
A method of neutralizing a latent image carrier, wherein a distance between the latent image carrier and the neutralizing unit is longer than a distance between the latent image carrier and the exposing unit. The method for neutralizing a latent image carrier according to any one of claims 1 to 5,
The method for neutralizing a latent image carrier, wherein a neutralization range for neutralizing the neutralization unit and the exposure unit is equal to or longer than a developing region in the main scanning direction of the latent image carrier. The method for neutralizing a latent image carrier according to any one of claims 1 to 6,
The static elimination means is a static elimination exposure of the latent image carrier using a light emitting element,
Lmax [mm], the distance between the most upstream point of exposure by the static eliminating unit and the exposed part on the latent image carrier by the exposing unit,
Lmin [mm] is a distance between the most downstream point of exposure by the charge eliminating unit and the exposed portion on the latent image carrier by the exposure unit,
The linear velocity of the surface of the latent image carrier is V [mm / s],
When the time from the start of exposure by the static elimination means to the start of exposure by the exposure means is T [s],
A neutralizing method for a latent image carrier, which satisfies the relationship of the following formula 1.
Lmin ≦ V · T ≦ Lmax (Formula 1) The method for neutralizing a latent image carrier according to claim 7,
Ta [s] is the time from the start of exposure by the static elimination means to the start of exposure by the exposure means in a state where the usage history of the static elimination means is relatively small.
When the time from the start of exposure by the static elimination means to the start of exposure by the exposure means in a state where the usage history of the static elimination means is relatively large is Tb [s]
A neutralizing method for a latent image carrier, characterized by satisfying the relationship of the following formula 2.
Lmin ≦ V · Tb ≦ V · Ta ≦ Lmax (Formula 2) In the method for neutralizing a latent image carrier according to claim 7 or 8,
The image forming apparatus can drive the surface of the latent image carrier at a plurality of linear speeds,
Vh [mm / s], the linear velocity of the surface of the latent image carrier during high-speed driving,
Th [s] represents the time from the start of exposure by the static elimination means during the high-speed driving to the start of exposure by the exposure means,
Vl [mm / s] is the linear velocity of the surface of the latent image carrier during low-speed driving,
When the time from the start of exposure by the static elimination unit during the low-speed driving to the start of exposure by the exposure unit is Tl [s],
A neutralizing method for a latent image carrier, characterized by satisfying the relationship of the following expression (3).
Lmin ≦ Vh · Th ≦ Vl · Tl ≦ Lmax (Formula 3) A latent image carrier, charging means for uniformly charging the latent image carrier, exposure means using a light emitting element that exposes the latent image carrier to form an electrostatic latent image, and the latent image carrier In an image forming apparatus comprising: a developing unit that supplies a developer to the electrostatic latent image formed in the developing unit; and a discharging unit that discharges the latent image carrier separately from the exposing unit.
An image forming apparatus using the latent image carrier neutralization method according to claim 1 as a static elimination method for neutralizing the latent image carrier.

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