JP2005196057A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic image forming device that can prevent the occurrence of ghosting due to a history of a previous image at the time another image is formed even after many copies of the same image are formed continuously. <P>SOLUTION: A discharging means 12 is sectionalized into a plurality of sections in the axial direction of an electrostatic latent image support 2, and is so composed as to independently control the discharging capability. An image density in the rotational direction of the electrostatic latent image support 2 in the image information is summed up for each area corresponding to the section of the discharging means 12 in the axial direction of the electrostatic latent image support 2. An image-density distribution in the axial direction of the electrostatic latent image support is calculated, and by multiplying the number of copies of the transferred material 18 to be output on the basis of the same image information by the image-density distribution based on the image information, a total image-density distribution for each area in the axial direction of the electrostatic latent image support is calculated. The electrophotographic image forming device is characterized in that the neutralization capability for each section of the neutralization means 12 is controlled according to the total image-density distribution. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electrophotographic image forming apparatus such as a copying machine or a printer.

2. Description of the Related Art An image forming apparatus based on an electrophotographic method is widely used because of its excellent merit that an image having an arbitrary shape from various kinds of information can be obtained on the spot and as many recorded images at a high speed.
Such an image forming apparatus mainly includes a photosensitive member (electrostatic latent image carrier) formed of a cylindrical rotating member, and a charging unit that is sequentially arranged around the photosensitive member in the rotation direction and uniformly charges the surface thereof. And an exposure device (latent image forming means) for exposing the surface of the photoconductor to form an electrostatic latent image based on instructed image information, and developing to obtain a toner image by supplying toner to the electrostatic latent image An apparatus (developing means), a transfer means for transferring the obtained toner image directly or via an intermediate transfer body, and a potential remaining on the surface of the electrostatic latent image carrier after transfer are removed. A static eliminator (static elimination means).

  In accordance with image information from the outside or image information captured by a scanner, the surface of the photoconductor is exposed imagewise by the exposure device, developed by the developing device, and transferred by the transfer unit. After the residual toner is cleaned as necessary, the surface of the photoreceptor is neutralized by the static eliminator, and the photoreceptor is ready for the next image forming cycle.

The surface of the photoreceptor can be subjected to a new image forming cycle by the charge removal of the charge eliminator. However, the photoconductor is not less fatigued by the exposure of the exposure apparatus. A photoconductor that has not been sufficiently neutralized may cause the history of the previous image to appear as a ghost during the next image formation.
Various studies have been made on the generation of ghosts due to the history of the photoreceptor.

  For example, Patent Document 1 discloses a technique for setting the wavelength of static elimination light to be longer than the wavelength of writing light. Patent Document 2 discloses a technique for changing the intensity of static elimination light in accordance with drum life characteristics. Further, Patent Document 3 discloses a technique for controlling the light neutralization width in accordance with the transfer width in a system using a contact charger of a roll charging system. Furthermore, Patent Document 4 discloses a technique for changing the intensity of static elimination light in accordance with the density of the entire image.

  However, even when there is no problem with the output of several sheets, especially when the same image is output continuously, the difference in image density in the image density distribution in the axial direction of the photoconductor is more noticeable depending on the location. In this case, there is a difference in how the history is received between a region having a high image density and a region having a low image density, and a ghost in which the history remains in the next image may occur. In particular, when a color image is to be formed, this problem is serious because a single color density difference due to a ghost is recognized as a color difference, and even a slight color difference is easily recognized.

・ JP-A-7-302024 ・ JP-A-8-006449 ・ JP-A-8-016054 ・ JP-A-8-069230

  Accordingly, an object of the present invention is to solve the above problems. Specifically, in an electrophotographic image forming apparatus, even when a plurality of identical images are continuously formed, a ghost due to the history of the previous image does not occur when the next image is formed. An object is to provide a forming apparatus.

The above object is achieved by the present invention described below. That is, the present invention includes at least an electrostatic latent image carrier comprising a cylindrical rotating body, a charging means for sequentially charging the surface around the electrostatic latent image carrier, and instructed image information. A latent image forming means for exposing the surface of the electrostatic latent image carrier to form an electrostatic latent image, developing means for supplying toner to the electrostatic latent image to obtain a toner image, and the obtained toner image An image forming apparatus comprising: transfer means for transferring the toner image to a recording medium directly or via an intermediate transfer body; and neutralizing means for removing the potential remaining on the surface of the electrostatic latent image carrier after transfer. ,
The static elimination means is configured to be fractionated into a plurality of sections in the axial direction of the electrostatic latent image carrier, and to be able to independently control the static elimination capability for each of the fractionated sections; and ,
For each region corresponding to the section of the static eliminating unit in the axial direction of the electrostatic latent image carrier, the image density in the rotation direction of the electrostatic latent image carrier in the image information is summed, and the electrostatic latent image carrier Image density distribution calculating means for calculating an image density distribution in the axial direction of the body;
The total image density distribution for each region in the axial direction of the electrostatic latent image carrier by multiplying the number of transferred objects to be output by the same image information and the image density distribution by the image information. Image density distribution summing means for calculating
An image forming apparatus comprising: a charge eliminating control unit that controls a charge eliminating capability for each of the sections of the charge eliminating unit according to the total image density distribution.

  In the present invention, first, with respect to one piece of image information, the static density in the image information is calculated for each region corresponding to the section of the static eliminating unit in the axial direction of the electrostatic latent image carrier by the image density distribution calculating unit. The image density in the rotation direction of the electrostatic latent image carrier is summed, and the image density distribution in the axial direction of the electrostatic latent image carrier is calculated.

In addition, the image density distribution summing unit multiplies the number of transferred objects to be output by the image information by the image density distribution by the image information, and the region in the axial direction of the electrostatic latent image carrier. The total image density distribution for each is calculated.
And the static elimination control means controls the static elimination capability for each section of the static elimination means according to the total image density distribution.

That is, according to the total image density distribution in the axial direction of the electrostatic latent image carrier, by controlling the static elimination ability of the static elimination means, the surface of the electrostatic latent image carrier is subject to damage caused by exposure. Thus, the static elimination capability of the static elimination means can be changed, and the fatigue level of the surface of the electrostatic latent image carrier can be leveled.
Therefore, according to the image forming apparatus of the present invention, even when the same image is formed in succession, there is a great possibility that a ghost due to the history of the previous image will occur when the next image is formed. It is suppressed.

  Even when the image exists in the same region, the degree of receiving the image history varies depending on the recorded image density (for example, whether it is a halftone image or a solid image), and the electrostatic latent image carrier is fatigued. The degree will also change. Therefore, in order to correct this, in the image forming apparatus of the present invention, the image density distribution calculating unit uses the value obtained by multiplying the apparent density of the image by a coefficient corresponding to the image density level as the image density. It is desirable to calculate the density distribution. In the present invention, the “appearance density of an image” refers to the ratio of the area where an image exists regardless of the image density to the total area of the target area where the image can be formed by purely counting the area of the image.

In the present invention, for a plurality of image information, the total image density distribution information is integrated to obtain an integrated image density distribution, and there is integrated information storage means for storing this,
It is desirable that the static elimination control means controls the static elimination means in consideration of the integrated image density distribution.

  When fatigue of the latent electrostatic image bearing member accumulates due to long-term use, the way of receiving the history changes depending on the portion of the surface. By obtaining the distribution and taking this into account when controlling the static eliminator, the degree of fatigue accumulation can be corrected.

  It is preferable that the present invention be applied to an image forming apparatus that forms a color image on a recording medium because the effects of the present invention are particularly remarkable. When a color image is to be formed, a monochromatic density difference due to a ghost is recognized as a color difference and the ghost is easily recognized, but this problem is remarkably suppressed by applying the present invention.

  In the image forming apparatus of the present invention, the circumference of the electrostatic latent image carrier is longer than the length of the recording medium in the transport direction, and the image is synchronized (at the same location on the surface of the electrostatic latent image carrier). In the case where the same images are always overlapped), the configuration of the present invention in which leveling is performed using only information in the axial direction cannot completely solve the problem. That is, even if the position of the electrostatic latent image carrier in the axial direction is the same, the circumferential length of the electrostatic latent image carrier is longer than the length of the recording medium in the transport direction. In the case of the above, there are a portion where the image is always formed and a portion where the image is not formed, and the configuration of the present invention is not effective for leveling the fatigue degree in the circumferential direction. Of course, since the effect of the present invention is exhibited in leveling the fatigue degree in the axial direction, even in that case, the effect of the present invention is not completely absent.

  However, in the present invention, particularly when the electrostatic latent image carrier and the image are not synchronized, the circumference of the electrostatic latent image carrier is shorter than the length of the recording medium in the transport direction. In some cases, it is particularly effective. Due to the recent trend toward miniaturization and space saving, the electrostatic latent image carrier has been reduced in diameter, and it can be said that the configuration of the present invention is effective in most cases.

  According to the present invention, in the electrophotographic image forming apparatus, even when the same image is formed in succession, a ghost due to the history of the previous image may occur when the next image is formed. It is possible to provide an image forming apparatus that does not exist. In particular, when obtaining a color image in which even a slight ghost is easily recognized as a color difference, the ghost problem is remarkably improved by employing the present invention.

Hereinafter, the present invention will be described in detail with reference to preferred embodiments.
<First Embodiment>
FIG. 1 is a schematic configuration diagram of a first embodiment which is an example of an image forming apparatus of the present invention. This image forming apparatus includes, as a basic configuration, a cylindrical photosensitive drum (electrostatic latent image carrier) 2 on which a latent image is formed by irradiating image light after uniform charging. A charging device 4 for uniformly charging the surface of the photosensitive drum 2 around the photosensitive drum 2 and an exposure device (exposure means) 6 for irradiating the photosensitive drum 2 with image light to form a latent image on the surface. A developing device (developing means) 8 for selectively transferring toner to a latent image on the surface of the photosensitive drum 2 to form a toner image; and a toner image formed on the surface of the photosensitive drum 2 on a sheet (recording target) ) Transfer device (transfer means) 14 for transferring to 18 and forming an unfixed image, fixing device 10 for fixing the unfixed image with heat and pressure, and cleaning device 22 for collecting toner remaining on the surface of the photosensitive drum 2. And the potential remaining on the surface of the photosensitive drum 2 is removed. It comprises a discharging lamp (discharging means) 12 for. In the image forming apparatus of the present invention, among these basic configurations, the configuration excluding the neutralizing lamp 12 can be applied with a conventionally known configuration as it is, and therefore detailed description thereof is omitted also in the present embodiment.

  FIG. 2 is a schematic plan view showing the relationship between the photosensitive drum 2 and the charge removal lamp 12 as seen from the direction perpendicular to the axis of the photosensitive drum 2. In FIG. 2, illustrations of components other than the photosensitive drum 2 and the charge removal lamp 12 are omitted. The static elimination lamp 12 arranged in parallel to the axial direction of the photosensitive drum 2 is divided into eight sections a to h over the entire area A where an image is formed on the surface of the photosensitive drum 2. Each of these sections is independent, and a separate charge removal light is irradiated toward a region corresponding to the section of the charge removal lamp 12 in the axial direction of the surface of the photosensitive drum 2. This charge removal light can be controlled independently for each section of its charge removal capacity (that is, light quantity).

Image information I-1 from an image reading apparatus such as a scanner is sent to the image processing apparatus 102 and converted into image information I-2 of a latent image for toner image formation. The surface of the body drum 2 is exposed. In place of the image information from the image reading apparatus 100, image information from an information processing medium such as an image output signal from a document / graphic editing software in a personal computer is used as image information I-1 in this embodiment. be able to.
The image information I-2 is also sent to the charge removal control device 106. The sheet quantity information I-3 input to the operation panel 104 is also sent to the charge removal control device 106 to be used for controlling the charge removal lamp 12.

  FIG. 3 is a block diagram for explaining the processing steps inside the static elimination control device 106. Image information I-2 from the image processing apparatus 102 is sent to the image density distribution calculating means 110 in the static elimination control apparatus 106. In the image density distribution calculating unit 110, the image density in the rotation direction of the photosensitive drum 2 in the image information I-2 is totaled for each region corresponding to the section of the static elimination lamp 12 in the axial direction of the photosensitive drum 2, and the photosensitive member is obtained. An image density distribution in the axial direction of the drum 2 is calculated and sent to the image density distribution summing unit 114 as image density distribution information I-X.

  On the other hand, the number information I-3 from the operation panel 104 is sent to the output number storage means 112 in the static elimination control device 106. The sheet number information I-3 once stored in the output sheet number storage unit 112 is sent to the image density distribution summing unit 114 as the sheet number information Y corresponding to the image density distribution information I-X. In this embodiment, the sheet number information I-3 is temporarily stored in the output sheet number storage unit 112, but may be directly sent to the image density distribution summing unit 114.

In the image density distribution summing unit 114, “the number of transferred objects to be output by the same image information” (output number) by the number information Y and “image density by the image information” by the image density distribution information I-X. The total image density distribution for each area in the axial direction of the photosensitive drum 2 (area corresponding to the section of the charge removal lamp 12) is calculated. The obtained total image density distribution information I-Z is sent to the static elimination control means 116, and the static elimination capability control signal I- that can appropriately control the static elimination capability of each section a to h of the static elimination lamp 12 based on the information. 4 is sent to the static elimination lamp 12, and the static elimination lamp 12 is appropriately controlled to neutralize the surface of the photosensitive drum 2.
In FIG. 3, in order to explain the processing steps inside the static elimination control device 106, the blocks are described separately for each means, but each means may be configured to be processed by one computer.
The processing steps inside the static elimination control device 106 will be described with specific examples.

  FIG. 4A shows an example of image information. In this example, as shown by the arrows in the drawing, a case where a solid image TA and a halftone image TB having two shapes and image densities are formed on the paper 18 conveyed toward the drawing information. Cite. Of course, the actual image generally has a more complicated shape and image density, but the processing steps inside the static elimination control device 106 will be described with simplified image information for convenience of explanation. I will do it.

  The solid image TA is an image having an image density of 100% formed in an inverted T shape, and the halftone image TB is an image having an image density of 50% formed in a rectangular shape. The image information shown in FIG. 4A is sent as it is as image information I-2 from the image processing apparatus 102 to the image density distribution calculating means 110 in the static elimination control apparatus 106.

In the image density distribution calculating unit 110, the image density in the rotation direction of the photosensitive drum 2 in the image information I-2 is totaled for each region corresponding to the sections a to h of the static elimination lamp 12 in the axial direction of the photosensitive drum 2. An image density distribution is obtained.
FIG. 4B shows the obtained image density distribution as a graph. The inverted T-shaped solid image TA is a section of the corresponding static elimination lamp 12 (hereinafter simply referred to as “section”, and any one of a to h will be attached and the corresponding area of the photosensitive drum 2 will be described. Is simply referred to as “region” and is similarly given any one of a to h.) The highest density in b to d, especially in the section c that exists long in the rotation direction (circumferential direction) of the photosensitive drum 2. It has become. Also in FIG. 4B, the position of the region c is expressed with the highest image density. That is, when a large number of sheets are output, the position of the region c on the photosensitive drum 2 has the highest degree of fatigue.

On the other hand, the rectangular halftone image TB has the same image density in the rotation direction (circumferential direction) of the photosensitive drum 2 over the sections f and g, and has a lower image density than the sections b and d. Therefore, the image density is also lowered. Also in FIG. 4B, the regions f and g have a density about half that of the regions b and d.
The image density distribution obtained as described above is sent to the image density distribution summing unit 114 as image density distribution information I-X.

Further, as described above, the image density distribution summing unit 114 calculates the total image density distribution for each of the areas a to h in the axial direction of the photosensitive drum 2 from the number information Y and the image density distribution information I-X. Is done. This total image density distribution is obtained by simply multiplying the image density distribution shown in FIG. 4B by the number of output sheets, so that the absolute value is different and the graph shape is the same as in FIG. 4B. .
Then, the total image density distribution information I-Z is sent to the static elimination control means 116, and “light fatigue distribution” is predicted in advance based on the information, and the static elimination lamp 12 is controlled.

The effects of photoconductor fatigue include (1) the case where the residual potential of the photoconductor becomes high, and as a result the image becomes thin, and (2) the apparent photoconductor sensitivity becomes high due to the deterioration of charge retention. There are two cases where the resulting image is darker.
In the case of (1) above, specifically, the region c that is assumed to have the highest degree of fatigue is irradiated with the static elimination light having the highest static elimination ability, and then the region that is assumed to have a relatively high degree of fatigue. b and d are irradiated with a static elimination light having a sufficient static elimination ability, and the regions f and g where a half degree of fatigue is assumed are appropriately irradiated with a static elimination light, and the remaining regions a, e, and h are irradiated. The neutralizing ability of the sections a to h is appropriately controlled so that the neutralizing light is emitted so that the charged potential can be neutralized. Then, the surface is neutralized in a properly leveled state.

On the other hand, in the case of (2) above, control opposite to that in the case of (1) above is performed. That is, the lowest (but sufficient for static elimination) static elimination light is applied to the region c assumed to have the highest degree of fatigue.
Which of the above cases depends on the type (characteristic) of the photoconductor used. The point of the present embodiment (and the present invention) is that the static elimination lamp can be controlled based on the distribution of light fatigue.

  As described above, in the present embodiment having the configuration of the present invention, the surface of the photosensitive drum 2 is controlled by controlling the discharging capability of the discharging lamp 12 according to the total image density distribution in the axial direction of the photosensitive drum 2. According to the damage received by exposure, the static elimination ability by the static elimination lamp 12 can be changed, and the fatigue level of the photosensitive drum 2 can be leveled.

  In the above example, the formed image density is taken into account when calculating the image density distribution. Even when the image exists in the same region, the degree of receiving the image history changes depending on the image density, and the degree of fatigue of the photosensitive drum 2 also changes. Therefore, the above configuration capable of correcting this is preferable. It can be said. However, in the present invention, it is not an essential requirement to consider the image density. Even if the charge removal capability is controlled only by the density based on the apparent area of the formed image (“apparent density of the image”), Needless to say, it is preferable to consider the image density, since it is possible to obtain a certain effect according to the present invention.

  Considering the image density accurately means that the image density distribution calculating means calculates the image density distribution using the value obtained by multiplying the apparent density of the image by the image density level as the image density. That is, in the above example, the regions f and g in which the halftone image TB with the image density of 50% is formed in the regions b and d in which the solid image TA with the image density of 100% is formed are the appearance of the image. The upper area is the same and the apparent density of the image is the same, but the latter image density is half that of the former, so when calculating the image density distribution, the latter is calculated as half the former image density. Is done. Further, a coefficient may be further multiplied according to the image density. For example, the influence of the image density may be adjusted by multiplying the image density by 100%, the image density by 50% by the coefficient 0.7, and the image density by 30% by the coefficient 0.5.

  The image density may be detected steplessly between 0% and 100%, and this may be used as the image density level. However, the actual image is dense, and the image density is accurately detected steplessly for one region. However, it is not so easy, and the control of the charge removal capability is not so precise that it is used for the control of the charge removal capability. Therefore, the image density level is divided into predetermined image density stages (for example, range 1: image density less than 20%, range 2: 20% to less than 50%, range 3: 50% to 100%). In this case, only the image density level corresponding to the target image is detected, and the center value thereof (in the above example, range 1: 10%, range 2: 35%, range 3: 75%). May be used for the conversion of the image density.

  The charge removal capability of the charge removal lamp 12 can be adjusted by the irradiation time and / or the irradiation intensity of the charge removal light. For example, the number of light emitting segments may be controlled by arranging the light emitting segments in an array so that each light emitting segment can be controlled independently. Of course, it is not necessary to calibrate so that each light emitting segment can be controlled completely independently, and as a result, it is only necessary to control the number of light emitting segments.

  In addition, even in areas that are not damaged by electrostatic latent image formation, static elimination must be performed, so the static elimination lamp with the minimum static elimination capability and the static elimination capability that is not variable is adjustable. It is also possible to perform the above-described control for the latter charge eliminating lamp in parallel with the other charge eliminating lamp. In this case, the arrangement of the neutralizing lamps for the front and rear persons may be located upstream or downstream with respect to the rotation direction of the photosensitive drum 2.

  In the above description, it has been shown that the configuration of the present embodiment is effective when a plurality of the same images are output. However, in this embodiment, as shown in FIG. 1 or FIG. An apparatus (integrated information storage means) 108 is provided and configured to reflect past output trends.

  As shown in FIG. 3, the total image density distribution information calculated by the image density distribution summing unit 114 is also sent to the integrated information storage device 108 as I-5. The accumulated information storage device 108 accumulates the total image density distribution information I-5 for a plurality of pieces of image information to obtain an accumulated image density distribution, and stores this. The obtained integrated image density distribution information I-6 is sent to the static elimination control means 116 at any time or as appropriate, and the static elimination lamp 12 is feedback-controlled in consideration of this.

  If fatigue of the photosensitive drum 2 accumulates due to long-term use, the way of receiving history changes depending on the surface portion. That is, a region that has experienced large fatigue tends to fatigue even with a small amount of light. Therefore, the accumulated image density distribution information I-5 is integrated to obtain an integrated image density distribution I-6, and this is taken into account when controlling the static elimination lamp 12, thereby correcting the degree of accumulation of fatigue. . For example, an area where fatigue has accumulated in the past history can be controlled to be different from other areas even when the image density is about the same as other areas at the time of image formation. Thus, by reflecting the past output tendency, fatigue leveling can be realized at a higher level.

  In the case of this configuration, the accumulated information storage device 108 stores information every time even when the output images are different one by one, as well as when the same output image continues plurally. Will reflect the past history with high accuracy. Therefore, leveling of the fatigue level of the photosensitive drum 2 can be realized with high accuracy from a long-term viewpoint.

  As described above, in the present exemplary embodiment, the configuration of the present invention has been described by taking an example of an image forming apparatus capable of forming a monochromatic image. However, the image forming apparatus of the present invention is limited to the configuration of the present exemplary embodiment. Instead, as long as the configuration of the present invention is provided, various configurations can be changed and added based on known knowledge.

For example, a configuration using a static elimination lamp as the static elimination means has been described as an example. However, the static elimination means in the present invention is not limited to that using a static elimination lamp, and conventionally known static elimination means, for example, a static electricity using a corotron or a scorotron. You may employ | adopt an electrical static elimination means. In that case, the charge removal capability can be controlled by the magnitude of the electrostatic force.
For all other configurations, those skilled in the art can appropriately replace or add other configurations to the configurations of the present invention based on conventionally known knowledge, and such cases are also included in the scope of the present invention. Is.

<Second Embodiment>
FIG. 5 is a schematic configuration diagram of a second embodiment which is another example of the image forming apparatus of the present invention. This image forming apparatus basically forms unfixed toner images of respective color components of yellow (Y), magenta (M), cyan (C), and black (K) based on image information by an electrophotographic method. An intermediate transfer belt (intermediate transfer member) on which the unfixed toner images formed by the two image forming units 48Y, 48M, 48C, 48K and the respective image forming units 48 (48Y, 48M, 48C, 48K) are transferred. 90, a secondary transfer device 60 for transferring an unfixed toner image laminated and transferred onto the peripheral surface of the intermediate transfer belt 90 to a sheet (recording medium material) 68, and a sheet 68 on which the unfixed toner image is transferred. It basically comprises a fixing device 62 for fixing by heat and pressure. A one-dot chain line with an arrow in the drawing indicates a conveyance path of the paper 68. The sheets 68 are supplied one by one from a sheet feeding unit (not shown). As the toner, a wax-containing toner is used.

  The image forming units 48Y, 48M, 48C, and 48K are arranged in a parallel state with a certain interval along the horizontal direction, and all of them have the same configuration. Each of these image forming units 48 is the image forming apparatus described in the first embodiment, that is, the photosensitive drum 2, the charging device 4, the exposure device 6, the developing device 8, the transfer device 14, and the cleaning device in FIG. 22 and the charge removal lamp 12 are basically the same, the fixing device 10 is removed from the image forming apparatus, and the transfer target is changed from the paper 18 to the intermediate transfer belt 90. It is.

  In each exposure apparatus, a latent image of each color component of yellow (Y), magenta (M), cyan (C), and black (K) is formed based on the image information. An unfixed toner image is formed on each photosensitive drum by the accommodated developing device, and is laminated and transferred onto the peripheral surface of the intermediate transfer belt 90. Since the basic configuration of each of these image forming units 48 is the same as that of the first embodiment, a detailed description thereof will be omitted.

  The intermediate transfer belt 90 is stretched between a drive roll 54 that is rotationally driven by a rotational drive source (not shown), a support roll 52 that is driven to rotate and supports the intermediate transfer belt 90, and an opposing roll 64 in the secondary transfer device 60. In addition, it is disposed between the drive roll 54 and the support roll 52 so as to pass through the transfer position of the photosensitive drum in each image forming unit 48. The intermediate transfer belt 90 rotates in the direction of arrow I by the drive roll 54.

  The intermediate transfer belt 90 is not particularly limited, and a conventionally known belt can be used without any problem. For example, a belt having a two-layer structure in which a surface layer is formed on the belt base material surface is used. In the present embodiment, an endless belt-shaped intermediate transfer member is used. However, a roll-shaped intermediate member may be used in the present invention.

  The main part of the secondary transfer device 60 is composed of an opposing roll 64 and a secondary transfer roll 66 that are arranged to face each other with the intermediate transfer belt 90 interposed therebetween. A sheet 68 is inserted into a nip portion formed between the secondary transfer roll 66 and the intermediate transfer belt 90, and an electrostatic action is applied to transfer an unfixed toner image on the surface of the intermediate transfer belt 90 to the surface of the sheet 68. It is configured to transfer to. There is no restriction | limiting in particular as the secondary transfer apparatus 60, A conventionally well-known structure can be employ | adopted without a problem. The fixing device 62 has the same configuration as that of the fixing device 10 in the first embodiment, and there is no particular limitation in the present embodiment, and any conventionally known device can be used without any problem. It will be omitted.

In the image forming apparatus of this embodiment having such a basic configuration, a color image is formed as follows.
First, in each image forming unit 48, the four color unfixed toner images formed on the respective photosensitive drums are electrostatically transferred from a transfer device (corresponding to the transfer device 14 in the first embodiment) as a primary transfer unit. The primary transfer is sequentially performed so as to be superimposed on the surface of the intermediate transfer belt 90 by a proper transfer action.

The unfixed toner image transferred and carried on the intermediate transfer belt 90 is transferred to the paper 68 by being conveyed so as to pass through the secondary transfer device 60 as the belt rotates. That is, the unfixed toner image on the surface of the intermediate transfer belt 90 is electrostatically transferred while being in contact with the paper 68 inserted along with the intermediate transfer belt 90 in the nip portion between the opposing roll 64 and the secondary transfer roll 66. Is done.
When the paper 68 on which the toner image has been transferred is discharged from the secondary transfer device 60, it is fixed by the fixing device 62 via the conveyance guide 58 and then discharged out of the system. As a result, a full color image is formed on one side of the paper 68.

  In the present embodiment, the configuration of the present invention is applied to each image forming unit 48 (48Y, 48M, 48C, 48K) that forms an unfixed toner image of four colors. That is, for each color component of yellow (Y), magenta (M), cyan (C), and black (K), each image forming unit 48 uses the color-separated image information and the number information to be output. The static elimination lamp (12) is configured to be controlled. Even when the configuration of the present invention is not applied to all four colors, the present invention is also included in the scope of the present invention, for example, when the configuration of the present invention is applied only to an image forming unit having a color that easily causes a ghost problem. Of course.

  When a color image is to be formed, a multi-color (up to four colors in the present embodiment) toner images are stacked to form a full-color image. Therefore, a single color density difference due to a ghost is recognized as a color difference, and a ghost is recognized. Cheap. However, by applying the present invention as in the present embodiment, the ghost is effectively improved, and this color difference problem is remarkably suppressed.

  As described above, in the present exemplary embodiment, the configuration of the present invention has been described using an example of an image forming apparatus capable of forming a color image, but the image forming apparatus of the present invention is limited to the configuration of the present exemplary embodiment. However, as long as the configuration of the present invention is provided, various configurations can be changed or added based on known knowledge.

  For example, without using an intermediate transfer member, a single photosensitive drum (electrostatic latent image carrier) has a plurality of color developing means (for example, toner colors similar to those in this embodiment are incorporated, and development for each color is performed. It is also possible to form a color image sequentially using a rotary developing machine that can transfer the image onto a sheet (recording medium) and stack the images each time. When the present invention is applied to the image forming apparatus in this case, since a plurality of colors are sequentially formed on the surface of one photosensitive drum, an image density distribution is calculated for each color, and the image information is the color immediately after the color. Therefore, the number of output sheets is counted as one, and the image density distribution and the total image density distribution have an equal relationship after all.

However, in the long run, it is considered that the unevenness of the fatigue level of the surface of the photosensitive drum is accumulated, and color-separated images are often similar in shape to each other. It is preferable to apply. In particular, if the configuration having the above-described integrated information storage means is adopted, the effect is great.
For all other configurations, those skilled in the art can appropriately replace or add other configurations to the configurations of the present invention based on conventionally known knowledge, and such cases are also included in the scope of the present invention. Is.

1 is a schematic configuration diagram illustrating an example of an image forming apparatus of the present invention. FIG. 2 is a schematic plan view showing a relationship between the photosensitive drum (electrostatic latent image carrier) and a static elimination lamp (static elimination means) in FIG. 1 as seen from a direction perpendicular to the axis of the photosensitive drum. FIG. 3 is a block diagram for explaining processing steps inside a static elimination control device in the image forming apparatus shown in FIG. 2. (A) is the top view which shows the specific image information illustrated when explaining the process process inside a static elimination control apparatus, (b) is a graph which shows the image density distribution obtained from the image information is there. It is a schematic block diagram which shows another example of the image forming apparatus of this invention.

Explanation of symbols

  2: photosensitive drum (electrostatic latent image carrier), 4: charging device (charging means), 6: exposure device (latent image forming means), 8: developing device (developing means), 10, 62: fixing device ( Fixing means), 12: Static elimination lamp (static elimination means), 14: Transfer device (transfer means), 18, 68: Paper (recording medium), 22: Cleaning device, 48: Image forming unit, 52: Support roll, 54 : Driving roll, 58: conveyance guide, 60: secondary transfer device, 64: counter roll, 66: secondary transfer roll, 90: intermediate transfer belt (intermediate transfer member), 100: image reading device, 102: image processing device 104: Operation panel 106: Static elimination control device 108: Accumulation information storage device 110: Image density distribution calculation means 112: Output number storage means 114: Image density distribution summation means 11 : Neutralization control means

Claims (5)

At least an electrostatic latent image carrier made of a cylindrical rotating body, a charging means for sequentially charging the surface around the electrostatic latent image carrier, and the electrostatic latent image based on instructed image information. A latent image forming unit that exposes the surface of the image carrier to form an electrostatic latent image, a developing unit that supplies toner to the electrostatic latent image to obtain a toner image, and the obtained toner image directly or in the middle An image forming apparatus comprising: transfer means for transferring to a recording medium via a transfer body; and charge eliminating means for removing a potential remaining on the surface of the electrostatic latent image carrier after transfer,
The static elimination means is configured to be fractionated into a plurality of sections in the axial direction of the electrostatic latent image carrier, and to be able to independently control the static elimination capability for each of the fractionated sections; and ,
For each region corresponding to the section of the static eliminating unit in the axial direction of the electrostatic latent image carrier, the image density in the rotation direction of the electrostatic latent image carrier in the image information is summed, and the electrostatic latent image carrier Image density distribution calculating means for calculating an image density distribution in the axial direction of the body;
The total image density distribution for each region in the axial direction of the electrostatic latent image carrier by multiplying the number of transferred objects to be output by the same image information and the image density distribution by the image information. Image density distribution summing means for calculating
An image forming apparatus comprising: a charge eliminating control unit configured to control a charge eliminating capability for each of the sections of the charge eliminating unit according to the total image density distribution. 2. The image density distribution calculating unit according to claim 1, wherein the image density distribution calculating unit calculates the image density distribution using the value obtained by multiplying the apparent density of the image by a coefficient corresponding to an image density level as the image density. Image forming apparatus. For a plurality of image information, the total image density distribution information is integrated to obtain an integrated image density distribution, and there is integrated information storage means for storing this,
The image forming apparatus according to claim 1, wherein the static elimination control unit controls the static elimination unit in consideration of the integrated image density distribution. The image forming apparatus according to claim 1, wherein a color image is formed on a recording medium. The image forming apparatus according to claim 1, wherein a circumferential length of the electrostatic latent image carrier is shorter than a length of the recording medium in a conveyance direction.

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