JP2014160185A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus having image forming bodies to be worn uniformly.SOLUTION: When image forming bodies, excluding an image forming body located at the uppermost stream along a moving path of an intermediate transfer body from among a plurality of image forming bodies, are defined as image forming bodies of interest, toner amount adjustment control is executed to the image forming bodies of interest, so as to form a toner band formed with toner of the amount corresponding to the density of toner which constitutes a toner image formed on an upstream image forming body located upstream of the image forming bodies of interest.

Description

  The present invention relates to an image forming apparatus.

  In Patent Document 1, when image formation having an image density less than a certain level is continuously performed, a toner band in a corresponding region is removed in order to remove deposits on the photoconductor and suppress wasteful toner consumption. Is controlled in accordance with the image density in the drum axis direction.

JP 2000-112298 A

  An object of the present invention is to make the wear of the image forming body uniform.

According to a first aspect of the present invention, a plurality of arranged image forming bodies on which a toner image having a toner density distribution corresponding to image information is formed while rotating, and
An intermediate transfer body that circulates including a movement path along the plurality of image forming bodies, receives the transfer of the toner images formed on each of the plurality of image forming bodies, and transfers the toner images to a recording medium all at once; ,
A plurality of cleaners for contacting each of the plurality of image forming bodies to a region after the transfer of the toner image to the intermediate transfer body to remove remaining toner;
A fixing device that forms an image composed of a fixed toner image on the recording medium by fixing the toner image transferred onto the recording medium on the recording medium;
When each image forming body excluding the image forming body located at the most upstream position along the moving path among the plurality of image forming bodies is a target image forming body, the target image is formed on the target image forming body. A control unit that executes toner amount adjustment control for forming a toner band composed of toner in an amount corresponding to the density of toner constituting the toner image formed on the upstream image forming body positioned on the upstream side of the forming body; An image forming apparatus comprising:

  According to a second aspect of the present invention, when the control unit executes the toner amount adjustment control, each of the plurality of upstream image forming bodies is formed on the target image forming body where the plurality of upstream image forming bodies exist. 2. The image according to claim 1, wherein a toner band made up of an amount of toner corresponding to a density integrated over the plurality of upstream image forming bodies of toner constituting the toner image is formed. Forming device.

  According to a third aspect of the present invention, when the control unit executes the toner amount adjustment control, the toner formed on the target image forming member and the upstream image forming member when viewed from the target image forming member. According to the present invention, a toner band made up of an amount of toner corresponding to the density of the toner constituting the toner image formed on the target image forming body is formed in accordance with the density of the toner constituting the image. The image forming apparatus according to claim 1 or 2.

  According to a fourth aspect of the present invention, the toner amount adjustment is performed for each of the plurality of regions when the control unit divides the plurality of image forming bodies arranged along the movement path into a plurality of regions corresponding to each other in the rotation axis direction. 4. The image forming apparatus according to claim 1, wherein the image forming apparatus executes control.

  According to a fifth aspect of the present invention, when the image forming body is rotated over a predetermined number of cycles or more than a predetermined number of images when the control unit forms an image based on one piece of image information. 5. The image forming apparatus according to claim 1, wherein the toner amount adjustment control is executed when an image is formed. 6.

  A sixth aspect of the present invention is the image forming apparatus according to any one of the first to fifth aspects, wherein the toner is a toner having an external additive containing zinc stearate.

  According to the image forming apparatus of the first aspect, the wear of the image forming body is made uniform as compared with the case where this configuration is not provided.

  According to the image forming apparatus of the second aspect, the wear of the image forming body is made more uniform as compared with, for example, the case of considering only the nearest upstream image forming body.

  According to the image forming apparatus of the third aspect, the wear of the image forming body is made more uniform as compared with the case where only the upstream image forming body is considered.

  According to the image forming apparatus of the fourth aspect, the wear in the rotation axis direction can be made more uniform as compared with the case where the area of the image forming body in the rotation axis direction is not divided.

  According to the image forming apparatus of the fifth aspect, the toner amount adjustment control can be executed at an effective timing.

  According to the image forming apparatus of the sixth aspect, the toner amount adjustment control works effectively.

1 is a configuration diagram illustrating an embodiment of an image forming apparatus of the present invention. It is explanatory drawing of the phenomenon which generate | occur | produces at the time of image formation. FIG. 5 is a diagram showing an experimental result in which the influence of the formation of a toner image by the upstream image forming engine on the wear of the photosensitive drum of the downstream image forming engine is examined. 6 is a flowchart illustrating a print creation sequence. FIG. 3 is a conceptual diagram in which a photosensitive drum is divided into four regions in the rotation axis direction.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a configuration diagram showing an embodiment of an image forming apparatus of the present invention.

  The image forming apparatus 1 shown in FIG. 1 includes image forming engines 10Y, 10M, 10C, and 10K using toners of yellow (Y), magenta (M), cyan (C), and black (K) in parallel. This is a tandem type color printer. According to this color printer, a single color image can be printed, and a full color image composed of four color toner images can be printed. The toner cartridges 18Y, 18M, 18C, and 18K contain YMCK color toners.

  Since the four image forming engines 10Y, 10M, 10C, and 10K have substantially the same configuration, the image forming engine 10Y corresponding to yellow will be described as a representative example. The image forming engine 10Y includes a photoreceptor drum 11Y, a charging device 12Y, an exposure device 13Y, a developing device 14Y, a primary transfer device 15Y, and a photoreceptor cleaner 16Y. Of the image forming engine 10Y, the photosensitive drum 11Y, the charging device 12Y, the developing device 14Y, and the photosensitive cleaner 16Y are provided in the process cartridge CR. The process cartridge CR is detachably attached to the main body of the image forming apparatus 1. A total of four photosensitive drums 11Y, 11M, 11C, and 11K provided for each of the four image forming engines 10Y, 10M, 10C, and 10K are examples of the “plurality of image forming bodies” in the present invention. Equivalent to.

  The photosensitive drum 11Y is provided with a photosensitive layer on the surface of a cylindrical substrate, holds an image formed on the surface, and rotates in the direction of arrow A around the axis of the cylinder. The charging device 12Y, the exposure device 13Y, the developing device 14Y, the primary transfer device 15Y, and the photoconductor cleaner 16Y are arranged around the photoconductor drum 11Y in the order of the arrow A.

  The charging device 12Y is a device that charges the surface of the photosensitive drum 11Y. The charging device 12Y in this embodiment is a charging roll that contacts the surface of the photosensitive drum 11Y. A voltage is applied to the charging device 12Y, and the surface of the contacting photosensitive drum 11Y is charged. The exposure device 13Y is a device that exposes the surface of the photoreceptor drum 11Y with exposure light to form an electrostatic latent image on the surface of the photoreceptor drum 11Y. The exposure device 13Y emits a laser beam modulated in accordance with an image signal supplied from the outside of the image forming apparatus 1, and scans the photosensitive drum 11Y with the laser beam. The developing device 14Y develops the electrostatic latent image formed on the surface of the photoreceptor drum 11Y using a developer, and forms an unfixed toner image on the surface of the photoreceptor drum 11Y. Toner is supplied from the toner cartridge 18Y to the developing device 14Y. This toner is coated with an external additive such as silica (Si) or zinc stearate (ZnSt). The developing device 14Y charges the toner and the magnetic carrier by stirring the developer in which the magnetic carrier and the toner are mixed, and develops the surface of the photoreceptor drum 11Y with the charged toner. The primary transfer device 15Y is a roll disposed at a position facing the photosensitive drum 11Y with the intermediate transfer belt 30 interposed therebetween. The primary transfer device 15Y transfers a toner image on the photosensitive drum 11Y to the intermediate transfer belt 30 by applying a voltage to the photosensitive drum 11Y. The photoconductor cleaner 16Y includes a hard rubber cleaning blade 161Y that is abutted against the surface of the photoconductor drum 11Y. By this cleaning blade 161Y, the surface of the photoconductor drum 11Y is transferred by the primary transfer device 15Y. The surface of the photosensitive drum 11Y is cleaned by scraping off unnecessary materials such as toner remaining in the performed portion.

  The image forming apparatus 1 also includes an intermediate transfer belt 30, a fixing device 60, a sheet conveying device 80, and a control device 100. The intermediate transfer belt 30 is an endless belt that is stretched between belt support rolls 31 to 35. The intermediate transfer belt 30 circulates in the direction of arrow B passing through the image forming engines 10Y, 10M, 10C, and 10K and the secondary transfer device 50. A toner image of each color is transferred to the intermediate transfer belt 30 from the image forming engines 10Y, 10M, 10C, and 10K. The intermediate transfer belt 30 moves while holding the toner images of these colors.

  The secondary transfer device 50 is a roll that rotates with the intermediate transfer belt 30 and the paper P interposed between the backup roll 34 which is one of the belt support rolls 31 to 35. The secondary transfer device 50 transfers the toner image on the intermediate transfer belt 30 onto the paper P by applying a voltage having a polarity opposite to the charging polarity of the toner.

  The fixing device 60 is a device that fixes the toner image on the paper P. The fixing device 60 includes a heating roll 61 and a pressure roll 62, and a heater is disposed in the heating roll 61. The heating roll 61 and the pressure roll 62 are each rotated in the direction of further transporting the paper P that has been transported while holding the unfixed toner image before fixing, and heats and presses the paper P between each other. . In the fixing device 60, the unfixed toner image is fixed on the paper P in this way, and the paper P is further sent downstream in the transport direction.

  The paper transport device 80 includes a take-out roll 81 that takes out the paper P stored in the paper container T, a transport roll 82 that transports the taken paper P, a registration roll 84 that transports the paper P to the secondary transfer device 50, Also, a discharge roll 86 for discharging the paper P to the outside is provided. The paper transport device 80 transports the paper P along a paper transport path R that passes through the secondary transfer device 50 and the fixing device 60.

  The control device 100 is responsible for overall control of the image forming apparatus 1. The control device 100 also serves as an example of a control unit according to the present invention.

  The basic operation of the image forming apparatus 1 shown in FIG. 1 will be described.

  In the yellow image forming engine 10Y, the photosensitive drum 11Y is rotationally driven in the direction of arrow A, and the surface of the photosensitive drum 11Y is charged by the charging device 12Y. The exposure device 13Y irradiates the surface of the photosensitive drum 11Y with exposure light based on an image signal corresponding to yellow among the image signals supplied from the outside, thereby forming an electrostatic latent image on the surface of the photosensitive drum 11Y. Form. Yellow toner is supplied from the toner cartridge 18Y to the developing device 14Y. The developing device 14Y forms a toner image by developing the electrostatic latent image on the photosensitive drum 11Y with toner. The photosensitive drum 11Y rotates while holding a yellow toner image formed on the surface. The toner image formed on the surface of the photosensitive drum 11Y is transferred to the intermediate transfer belt 30 by the primary transfer device 15Y. After the transfer, the toner remaining on the photoconductive drum 11Y is removed by the photoconductive cleaner 16Y.

  The intermediate transfer belt 30 is cyclically moved in the arrow B direction. The image forming engines 10M, 10C, and 10K corresponding to colors other than yellow form toner images corresponding to the respective colors, and transferred to the intermediate transfer belt 30 by the image forming engine 10Y, similarly to the image forming engine 10Y. The toner image of each color is transferred so as to be superimposed on the toner image.

  The paper P is taken out from the paper container T by the take-out roll 81. The paper P is transported by the transport roll 82 and the registration roll 84 along the paper transport path R in the direction of arrow C toward the secondary transfer device 50. The registration roll 84 sends the paper P to the secondary transfer device 50 so as to match the timing at which the toner image is transferred from the intermediate transfer belt 30 onto the paper P. The secondary transfer device 50 transfers the toner image on the intermediate transfer belt 30 onto the paper P. The sheet P onto which the toner image has been transferred is conveyed from the secondary transfer device 50 to the fixing device 60, and is sandwiched between a heating roll 61 and a pressure roll 62 that constitute the fixing device 60, and is subjected to heating and pressure. As a result, the toner image on the paper P is fixed on the paper P. In this way, an image composed of a fixed toner image is formed on the paper P. The paper P on which the image is formed is discharged to the outside of the image forming apparatus 1 by a discharge roll 86. After the transfer by the secondary transfer device 50, the toner remaining on the intermediate transfer belt 30 is removed by the belt cleaner 90.

  In this image forming apparatus 1, a toner band is formed every time a predetermined number of prints are performed and at a predetermined timing such as when the power is turned on.

  The toner bands are formed on the photosensitive drums 11Y, 11M, 11C, and 11K of all the image forming engines 10Y, 10M, 10C, and 10K under the control of the control device 100. Here, as in the above description, the image forming engine 10Y will be described.

  When forming a toner band on the photosensitive drum 11Y, the surface of the photosensitive drum 11Y is charged by the charging device 12Y and the electrostatic latent image for the toner band is formed by the exposure device 13Y in the same manner as in normal image formation. Is formed. This electrostatic latent image is, for example, a uniform electrostatic latent image with an image density of 30% in both the direction of the rotation axis of the photosensitive drum 11Y and the rotation direction indicated by the arrow A. The uniform electrostatic latent image is developed with toner by the developing device 14Y, and a toner band having a uniform toner density is formed on the surface of the photosensitive drum 11Y.

  In this embodiment, when the toner band is formed, voltage application to the primary transfer device 15Y for transfer to the intermediate transfer belt 30 is stopped. Therefore, the toner band formed on the surface of the photoreceptor drum 11Y reaches the photoreceptor cleaner 16Y without being transferred to the intermediate transfer belt 30, and is scraped off by the cleaning blade 161Y. However, a part of the toner forming the toner band and a part of the external additive of the toner remain in the cleaning blade 161Y and the contact portion with the photosensitive drum 11Y, and the cleaning blade 161Y and the photosensitive drum 11Y. It has the effect of suppressing the increase in frictional resistance. Thereby, the cleaning blade 161Y is prevented from being curled or chipped, and the wear of the photosensitive drum 11Y is controlled.

  A toner band that reaches a predetermined number of prints or is formed at a predetermined timing is referred to herein as a “normal toner band”.

  However, as will be described below, with this normal toner band alone, there is a risk of uneven wear on any of the photosensitive drums 11Y, 11M, 11C, and 11K. For this reason, in the present embodiment, as described below, a toner band different from the normal toner band is also formed.

  FIG. 2 is an explanatory diagram of a phenomenon that occurs during image formation. Here, two image forming engines 10Y and 10M are schematically shown. Here, the image forming engine 10Y represents an upstream image forming engine, and the image forming engine 10M represents a downstream image forming engine.

  FIG. 2A shows a state immediately after the toner image 90Y formed by the image forming engine 10Y that is the upstream image forming engine is transferred to the intermediate transfer belt 30. FIG.

  FIG. 2B shows a state immediately after the toner image 90M formed by the image forming engine 10M that is the downstream image forming engine is transferred to the intermediate transfer belt 30.

  As shown in FIG. 2A, the toner image 90Y formed on the upstream photosensitive drum 11Y is transferred onto the intermediate transfer belt 30 by the action of the primary transfer device 15Y. A part of the toner 91Y remains on 11Y.

  The toner 91Y contains silica (Si) and zinc stearate (ZnSt), which are external additives for the toner. When the silica (Si) reaches the cleaning blade 161Y, it acts to promote wear on the surface of the photoreceptor drum 11Y. On the other hand, when zinc stearate (ZnSt) reaches the cleaning blade 161Y, it acts to suppress wear on the surface of the photoreceptor drum 11Y.

  Next, as shown in FIG. 2B, the toner image 90M formed on the downstream photosensitive drum 11M is formed on the upstream photosensitive drum 11Y and is conveyed by the intermediate transfer belt 30. The toner image is transferred onto the intermediate transfer belt 30 so as to overlap the toner image 90Y. At this time, a part of the toner 91M remains on the photosensitive drum 11M.

  The toner 91M on the photosensitive drum 11M is formed by the upstream image forming engine 10Y in addition to the residual toner that is formed on the photosensitive drum 11M and not transferred onto the intermediate transfer belt 30. Of the toner image 90Y conveyed by the transfer belt 30, a component reversely transferred from the intermediate transfer belt 30 to the photosensitive drum 11M is included. Of the external additive contained in the toner image 90Y, zinc stearate (ZnSt) accounts for a large proportion of the reversely transferred component.

  That is, since the reversely transferred component is rich in zinc stearate (ZnSt), the toner 91M on the photosensitive drum 11M is richer in zinc stearate (ZnSt) than in silica (Si). Therefore, when the toner 91M reaches the cleaning blade 161M, it acts in a direction in which the wear of the photosensitive drum 11M is suppressed.

  When the image density of the toner image 90Y formed by the upstream image forming engine 10Y is high, the amount of external additive is correspondingly large and the amount of zinc stearate (ZnSt) that is almost selectively reversely transferred is also large. Become. This is because the higher the image density of the toner image 90Y formed by the upstream image forming engine 10Y, the higher the ratio of zinc stearate (ZnSt) contained in the toner 91M on the photosensitive drum 11M to Syria (Si). As a result, the wear of the photosensitive drum 11M is further suppressed. In other words, this means that the degree of wear of the photosensitive drum 11M constituting the downstream image forming engine 10M depends on the image density of the toner image 90Y formed by the upstream image forming engine 10Y. Yes. If the image forming conditions such as the charging condition and the exposure condition are the same, the density of the image finally formed differs depending on the degree of wear of the photosensitive drum, and the image forming condition depends on the degree of wear of the photosensitive drum. Need to be adjusted.

  Further, when the toner image 90Y having an image density distributed in the direction of the rotation axis of the photosensitive drum 11Y is formed by the upstream image forming engine 10Y, the degree of wear of the downstream photosensitive drum 11M is determined by the rotation axis. Will be different in direction. This means that the film thickness of the surface of the photosensitive drum 11M has a distribution in the rotation axis direction. That is, this means that when a toner image having a uniform image density in the rotation axis direction is formed on the photosensitive drum 11M, a toner image having density unevenness in the rotation axis direction is formed.

  FIG. 3 is a diagram showing experimental results in which the influence of the formation of the toner image by the upstream image forming engine on the wear of the photosensitive drum of the downstream image forming engine is examined.

  The horizontal axis indicates the position of the photosensitive drum in the rotation axis direction, and the vertical axis indicates the wear rate of the photosensitive drum 11C in the image forming engine 10C. As shown in FIG. 1, the image forming engine 10C is located third along the traveling direction (arrow B direction) of the intermediate transfer belt 30, and two image forming engines 10Y are disposed upstream of the image forming engine 10C. , 10M exists.

  Here, in the most upstream image forming engine 10Y, the toner image TBY is formed at two positions Y1 and Y2 in the rotation axis direction on the photosensitive drum 11Y. Similarly, toner images TBM are formed at two positions M1 and M2 in the rotation axis direction on the photosensitive drum 11M of another upstream image forming engine 10M. Further, the toner image TBC is formed at itself, that is, at two positions C1 and C2 in the rotation axis direction on the photosensitive drum 11C of the image forming engine 10C.

  After repeating this many times, the wear rate at each point in the rotational axis direction of the photosensitive drum 11C of the image forming engine 10C was measured. The square symbol in FIG. 3 represents the wear rate at each point in the rotational axis direction. This wear rate represents the wear amount (nm) per 1000 cycles of the photosensitive drum when the toner images TBY, TBM, and TBC having the pattern shown in FIG. 3 are printed on a sheet corresponding to A4.

  As can be seen from FIG. 3, the wear rate at the positions where the toner images TBY and TBM are formed by the upstream image forming engines 10Y and 10M is reduced. That is, it can be seen that when the toner image is formed by the upstream image forming engines 10Y and 10M, the wear of the photosensitive drum 11C of the downstream image forming engine 10C is suppressed. Examining in detail, as described above, an external additive of toner from the toner image formed by the upstream image forming engines 10Y and 10M and conveyed to the image forming engine 10C by the intermediate transfer belt 30 is the photosensitive drum 11C. It was found that the phenomenon of reverse transcription was observed. In addition, it was found that the ratio of zinc stearate (ZnSt) that suppresses wear is significantly higher in the reversely transferred external additive than silica (Si) that promotes wear of the photosensitive drum 11C.

  The toner image TBC created by the image forming engine 10C, which is itself, contains both silica (Si) and zinc stearate (ZnSt) at an appropriate ratio, which is large against the wear of the photosensitive drum 11C. There is no impact. However, when examined in detail, the influence of silica (Si) was slightly stronger than that of zinc stearate (ZnSt), and the wear was slightly advanced as compared with a region where no toner image was formed.

  Here, the influence on the wear of the photosensitive drum 11C of the image forming engine 10C due to the formation of the toner image by the image forming engines 10Y and 10M is shown, but this relationship is related to the plurality of image forming engines 10Y, 10M, and 10C. , 10K is the same. That is, the image forming engine 10M is influenced by the upstream image forming engine 10Y, the image forming engine 10C is affected by the two upstream image forming engines 10Y and 10M, and the image forming engine 10K is upstream. The three side image forming engines 10Y, 10M, and 10C are affected.

  The image forming apparatus 1 according to the present embodiment shown in FIG. 1 is based on the above-described knowledge, and in addition to the above-mentioned “normal toner band”, the downstream side due to the influence of the toner image formation in the upstream side image forming engine. A toner band for controlling wear of the photosensitive drum constituting the image forming engine is formed.

  FIG. 4 is a flowchart showing a print creation sequence.

  FIG. 5 is a conceptual diagram in which the photosensitive drum is divided into four regions in the rotation axis direction.

  In the image forming apparatus 1 shown in FIG. 1, when there is a print start instruction, an image signal is acquired (step S01) and printing (image formation) is executed (step S02). This image signal is not a toner band signal, but an image signal representing an image that the user intends to print, and an image is formed on the paper. In step S02, the required number of prints according to the instruction is executed.

  After the end of printing, a determination sequence (steps S03 to S09) for determining whether or not to form a toner band is executed as follows. When the determination result that the toner band should be formed is obtained, the toner band is formed (step S10).

  First, in step S03, the image density D is calculated for each photosensitive drum and for each region.

  5A and 5B are image diagrams in which the photosensitive drum is divided into four regions a, b, c, and d as an example in the rotation axis direction. In step S03, the average image density for each of the photosensitive drums 11Y, 11M, 11C, and 11K and for each of the four areas divided as shown in FIGS. Calculation is performed.

  Here, FIG. 5 (A) shows an example of the image density for each area of the engine upstream of the own engine, and FIG. 5 (B) shows an example of the image density for each area of the own engine. Is shown. When the own engine shown in FIG. 5B is the image forming engine 10M, the upstream engine shown in FIG. 5A means the image forming engine 10Y. When the engine shown in FIG. 5B is the image forming engine 10C, the upstream engines are two engines, the image forming engine 10Y and the image forming engine 10M, and each region shown in FIG. The image density for each of the ad is a value obtained by adding the image densities of the two regions a to d corresponding to each other of the two engines. Further, when the engine shown in FIG. 5C is the image forming engine 10K, the upstream engines are the three image forming engines 10Y, 10M, and 10C, and each region a to d shown in FIG. The image density of the three engines is obtained by adding the image densities of the areas a, b, c, and d of the three engines.

  Next, in step S04, an image density difference ΔD11 between the regions of the upstream engine is calculated.

In the example shown in FIG. 5 (A), the image densities of the areas a to d of the upstream engine are 0%, 30%, 0%, and 0%, respectively. Therefore, the image density difference ΔD11 is
△ D11 = 30% -0% = 30%
It becomes.

In step S05,
△ D11 ≧ 30%
It is determined whether or not.

△ D11 <30%
In this case, the print creation sequence is terminated without forming a toner band. Regarding the wear of the photosensitive drum of the own engine, in this embodiment, when the image density difference ΔD between the upstream engine areas is less than 30%, the area between the areas affected by the wear by the toner image created by the upstream engine The disparity is considered to be within the error range, and the creation of the toner band is postponed.

In step S05,
△ D11 ≧ 30%
If it is determined, the process proceeds to step S06, where the maximum value Dmax and the minimum value Dmin of the image density difference ΔD12 between upstream and downstream are calculated. The calculation of the image density difference ΔD12 is performed between corresponding areas, that is, between the areas a, b, c, and d.

In the case of the example shown in FIG. 5, the image density of each of the areas a to d is subtracted from the image density of each of the areas a to d in FIG. 5A to subtract the image density of each of the areas a to d in FIG. △ D12 is
△ D12 = -3%, 30%, -3%, -3%
Is calculated. Therefore, the maximum value Dmax and the minimum value Dmin are respectively
Dmax = 30%
Dmin = -3%
It becomes.

In step S07,
Dmax ≧ 0%
It is determined whether or not.

Dmax <0%
In this case, since the influence of the toner image of the upstream engine is canceled by the toner image of the own engine, this sequence is terminated without forming a toner band.

In step S07,
Dmax ≧ 0%
If it is determined, the process proceeds to step S08,
Dmax−Dmin ≧ 30%
It is determined whether or not.

Dmax-Dmin <30%
In this case, since the toner image formation in the own engine cancels out the influence of each region due to the toner image of the upstream engine to the extent considered to be an error range, the toner band is not formed at this time as well. End this sequence.

In step S08,
Dmax−Dmin ≧ 30%
In step S09, it is further determined whether or not the number of cycles of the photosensitive drum 11 during the current printing is 60 cycles or more. Instead of the number of cycles of the photosensitive drum 11, it may be determined whether or not the current print number is 30 or more in terms of A4. When the number of cycles of the photosensitive drum 11 is less than 60 cycles, or when the number of printed sheets is less than 30, even if the above various conditions are satisfied, the influence is small, so that a toner band is not formed. This sequence ends.

If it is determined in step S09 that the current cycle number of the photosensitive drum 11 is 60 cycles or more, or the current print number is 30 or more, a toner band is formed (step S10). The toner band formed here is a toner band corresponding to the image density for uniformizing the influence of the toner image formed by the upstream engine.

  FIG. 5C shows an example of the toner band formed in step S10 of FIG.

As described above, in the example shown in FIGS. 5A and 5B, the image density difference ΔD12 for each of the regions a to d between the upstream engine and the own engine is
△ D12 = -3%, 30%, -3%, -3%
It is. That is, the region b is greatly affected by the toner image of the upstream engine.

  Therefore, in the example shown in FIG. 5C, a toner band is formed only in the region b. The image density of the toner band and the width in the process direction (arrow A direction shown in FIG. 1) may be adjusted according to the value of the image density difference ΔD12, the number of cycles of the photosensitive drum 11 or the number of prints. .

  FIG. 5D shows another example of the toner band formed in step S10 of FIG.

  In FIG. 5D, toner bands are formed for all the regions a to d. The image density or the width in the process direction is adjusted for the region b in which the value of the toner band image density difference ΔD12 is large.

  In this embodiment, whether or not the toner image formed by the upstream image forming engine is affected is checked by steps S05 and S07 to S09 in FIG. A toner band as shown in FIG. 5C or FIG. 5D is temporarily formed, and the influence thereof is reduced.

  The determination as to whether or not to form a toner band and the image density and width of the toner band when the toner band is formed are among the four image forming engines 10Y, 10M, 10C, and 10K shown in FIG. This is performed for each of the three image forming engines 10M, 10C, and 10K except the most upstream image forming engine 10Y. Thereby, the wear of the photosensitive drums 11M, 11C, and 11K of these three image forming engines 10M, 10C, and 10K is controlled.

  Here, the calculation is performed by dividing into four areas a to d in the direction of the rotation axis, but the calculation may be performed by dividing the calculation into a larger number of areas. Alternatively, it may be divided into a smaller number of regions, and the calculation may be performed with the entire region in the rotation axis direction as one region without being divided into regions.

  When the calculation is performed as one region, the maximum value Dmax and the minimum value Dmin in step S06 in FIG. 4 cannot be calculated. In this case, ΔD12 ≧ 0% is adopted instead of Dmax ≧ 0% in step S07. However, step S08 may be omitted.

  In the present embodiment, the difference in image density between the upstream engine and the own engine is taken into consideration, but the toner image of the own engine is not taken into consideration with respect to the toner image of the own engine and the toner band of the own engine according to the image density of the upstream engine. The necessity of formation and the image density and width of the toner band of the own engine may be determined.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10Y, 10M, 10C, 10K Image forming engine 11Y, 11M, 11C, 11K Photosensitive drum 12Y Charging device 13Y Exposure device 14Y Developing device 15Y Primary transfer device 16Y Photoconductor cleaner 18Y, 18M, 18C, 18K Toner cartridge 30 intermediate transfer belt 31 to 35 belt support roll 34 backup roll 50 secondary transfer device 60 fixing device 61 heating roll 62 pressure roll 80 paper transport device 81 take-out roll 82 transport roll 84 registration roll 86 discharge roll 90 belt cleaner 90Y, 90M toner image 91Y, 91M toner 100 control device 161Y, 161M, 161C, 161K Cleaning blade

Claims (6)

A plurality of arranged image forming bodies on which a toner image having a toner density distribution according to image information is formed while rotating;
An intermediate transfer body that circulates including a movement path along the plurality of image forming bodies, receives the transfer of the toner images formed on each of the plurality of image forming bodies, and transfers the toner images to a recording medium all at once; ,
A plurality of cleaners for contacting each of the plurality of image forming bodies to a region after the transfer of the toner image to the intermediate transfer body to remove remaining toner;
A fixing device that forms an image composed of a fixed toner image on the recording medium by fixing the toner image transferred onto the recording medium on the recording medium;
When each image forming body excluding the image forming body located at the most upstream position along the moving path among the plurality of image forming bodies is a target image forming body, the target image is formed on the target image forming body. A control unit that executes toner amount adjustment control for forming a toner band composed of toner in an amount corresponding to the density of toner constituting the toner image formed on the upstream image forming body positioned on the upstream side of the forming body; An image forming apparatus comprising:   When the control unit executes the toner amount adjustment control, a toner image formed on each of the plurality of upstream image forming bodies is formed on the target image forming body on which the plurality of upstream image forming bodies exist. 2. The image forming apparatus according to claim 1, wherein a toner band made of an amount of toner corresponding to a density integrated over the plurality of upstream image forming bodies is formed.   When the control unit executes the toner amount adjustment control, the toner constituting the toner image formed on the upstream image forming body when viewed from the focused image forming body on the focused image forming body And a toner band made of an amount of toner corresponding to the density of toner constituting the toner image formed on the target image forming body. 2. The image forming apparatus according to 2.   The controller executes the toner amount adjustment control for each of the plurality of areas when the plurality of image forming bodies arranged along the movement path are divided into a plurality of areas corresponding to each other in the rotation axis direction. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   When the control unit rotates the image forming body over a predetermined number of cycles or forms an image of a predetermined number or more during image formation based on one image information. The image forming apparatus according to claim 1, wherein the toner amount adjustment control is executed.   6. The image forming apparatus according to claim 1, wherein the toner is a toner having an external additive containing zinc stearate.

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