JP5376233B2 - Image forming apparatus, program, and control apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that suppresses wasteful consumption of toner. <P>SOLUTION: The image forming apparatus is equipped with: an image holder for holding a toner image thereon; an image forming section for forming a toner image on the image carrier; a detecting section for detecting the density of a toner image formed by the image forming section; a signal image forming control section for receiving an input of an image signal and causing the image forming section to form an image signal toner image corresponding to the image signal; a potential difference control section for causing the image forming section to form a patch toner image with predetermined image density and controlling a development contrast potential difference in order to determine flying force for toner on the image holder in the image forming section, according to the detection result of the patch toner image obtained by the detecting section; and a band formation control section for increasing toner consumption by causing the image forming section to form a toner band, different from the image-signal toner image corresponding to the image signal and the patch toner image, when a development contrast potential difference reaches a predetermined value. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an image forming apparatus, a program, and a control apparatus.

  For example, as an image forming apparatus typified by a printer, there is a type that develops the surface of an image holding member such as a photosensitive member with toner by a developing device. In addition, in order to prevent the toner from staying in the developing unit for a long time and deteriorating, the number of image dots formed on the image carrier is counted, and when the number of image dots is less than the threshold value, a developing operation is performed to perform toner development. An image forming apparatus is known that consumes (see, for example, Patent Document 1). In addition, an image forming apparatus that forms a patch image for density measurement and consumes toner by performing a developing operation when the density of the patch image is equal to or lower than a reference density is known (for example, see Patent Document 2). .

Japanese Patent Laid-Open No. 2004-125829 JP 2007-147782 A

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus, a program, and a control apparatus that suppress consumption of useless toner.

An image forming apparatus according to claim 1 is provided.
An image carrier for holding a toner image formed on the surface;
An image forming unit for forming a toner image by flying toner on the image carrier;
A detection unit for detecting the density of the toner image formed by the image forming unit;
A signal image formation control unit that receives an input of an image signal and causes the image forming unit to form an image signal toner image corresponding to the image signal;
A patch toner image having a predetermined image density is formed on the image forming unit, and a toner on the image carrier in the image forming unit is detected according to a detection result of the patch toner image by the detection unit. A potential difference control unit that controls the development contrast potential difference that determines the flying force of
When the development contrast potential difference becomes a predetermined value, the image forming unit forms a toner band different from both the image signal toner image corresponding to the image signal and the patch toner image. And a band formation control unit for increasing the consumption amount of the battery.

  The image forming apparatus according to claim 2 is characterized in that the value is one of an upper limit value and a lower limit value of a control range of the development contrast potential difference by the potential difference control unit.

  According to a third aspect of the present invention, in the image forming apparatus, the value is a predetermined value within a first range predetermined from an upper limit value and a lower limit value or more of a control range of the development contrast potential difference by the potential difference control unit. It is any one of the values within the second range.

  The image forming apparatus according to claim 4, wherein the value is a value out of a range set apart from an upper limit value and a lower limit value in a control range of the development contrast potential difference by the potential difference control unit. To do.

  In the image forming apparatus according to claim 5, the band formation control unit increases the length of the toner band formed on the image forming unit in the direction in which the image holding member holds and moves the toner image. The toner consumption is increased.

  The image forming apparatus according to claim 6 is characterized in that the band formation control unit increases the toner consumption by increasing the image density of a toner band formed on the image forming unit.

  The image forming apparatus according to a seventh aspect is characterized in that the band formation control unit increases the amount of toner consumption by increasing the frequency with which the image forming unit forms the toner band.

A control device according to an eighth aspect is a control device that controls the image forming apparatus,
The image forming apparatus is
An image carrier for holding a toner image formed on the surface;
An image forming unit for forming a toner image by flying toner on the image carrier;
A detection unit for detecting the density of the toner image formed by the image forming unit;
A signal image formation control unit that receives an input of an image signal and causes the image forming unit to form an image signal toner image corresponding to the image signal;
A patch toner image having a predetermined image density is formed on the image forming unit, and a toner on the image carrier in the image forming unit is detected according to a detection result of the patch toner image by the detection unit. And a potential difference control unit that controls the development contrast potential difference that determines the flying force of
This controller is
When the development contrast potential difference controlled by the potential difference control unit becomes a predetermined value, the image forming unit has a toner different from both the image signal toner image corresponding to the image signal and the patch toner image. A band forming control unit that increases the amount of toner consumed by forming the band is provided.

A program according to claim 9 is a program that is incorporated in a computer communicably connected to an image forming apparatus and causes the computer to function as a control device that controls the image forming apparatus.
The image forming apparatus is
An image carrier for holding a toner image formed on the surface;
An image forming unit for forming a toner image by flying toner on the image carrier;
A detection unit for detecting the density of the toner image formed by the image forming unit;
A signal image formation control unit that receives an input of an image signal and causes the image forming unit to form an image signal toner image corresponding to the image signal;
A patch toner image having a predetermined image density is formed on the image forming unit, and the toner on the image carrier in the image forming unit is detected according to the detection result of the patch toner image by the detection unit. A potential difference control unit that controls the development contrast potential difference that determines the flying force;
This program
When the development contrast potential difference controlled by the potential difference control unit becomes a predetermined value, the image forming unit has a toner different from both the image signal toner image corresponding to the image signal and the patch toner image. It is characterized by functioning as a band formation control unit that increases the amount of toner consumed by forming the band.

  According to the image forming apparatus of the first aspect, wasteful toner consumption due to the toner band can be suppressed as compared with the case where the present configuration is not provided.

  According to the image forming apparatus of the second aspect, the toner consumption is suppressed as compared with the case where the toner consumption amount by the toner band is increased before the development contrast potential difference reaches the upper limit value and the lower limit value.

  According to the image forming apparatus of the third aspect, the toner density can be corrected with a margin.

  According to the image forming apparatus of the fourth aspect, the toner density can be corrected with a margin.

  According to the image forming apparatus of the fifth aspect, the toner consumption can be accurately controlled by a simple method.

  According to the image forming apparatus of the sixth aspect, it is possible to suppress an increase in the area required for forming the toner band.

  According to the image forming apparatus of the seventh aspect, it is possible to control the toner consumption without changing the state of the collected toner image itself.

  According to the control device of the eighth aspect, wasteful toner consumption due to the toner band can be suppressed as compared with the case where this configuration is not provided.

  According to the program according to claim 9, useless toner consumption due to the toner band can be suppressed as compared with the case where this configuration is not provided.

1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment of the present invention. It is a block diagram which shows the circuit structure of the control part shown in FIG. 3 is a graph showing a potential distribution on the surface of a photoreceptor. It is a graph which shows the relationship between an exposure amount and a developing potential difference. FIG. 3 is a diagram illustrating a part of an intermediate transfer belt. 6 is a graph showing control of a development potential difference for each color image forming unit. 5 is a flowchart for describing image forming processing in the image forming apparatus. It is a flowchart which shows the detail of the pattern length calculation process shown in FIG. FIG. 4 is a view showing a part of an intermediate transfer belt on which a toner band for preventing wobbling is formed. 6 is a graph showing a transition of a development potential difference for each color image forming unit of the image forming apparatus according to the second embodiment. It is a flowchart which shows the detail of the pattern length calculation process in 2nd Embodiment. 14 is a graph showing control of a development potential difference for each color image forming unit in the third embodiment. It is a flowchart which shows the detail of the pattern length calculation process in 3rd Embodiment. 10 is a flowchart illustrating image forming processing in the image forming apparatus according to the fourth embodiment. It is a flowchart which shows the detail of the calculation process of the pattern density in 4th Embodiment. 10 is a flowchart illustrating image forming processing in an image forming apparatus according to a fifth embodiment. It is a flowchart which shows the detail of the pattern creation space | interval calculation process in 5th Embodiment. 14 is a flowchart illustrating image forming processing in an image forming apparatus according to a sixth embodiment. It is a flowchart which shows the detail of the calculation process of the pattern density in 7th Embodiment. It is a flowchart explaining the upper limit electric potential difference correction process in 8th Embodiment. FIG. 10 is a diagram illustrating a part of an intermediate transfer belt in a modification using a result measured in a previous setup process for controlling a developing potential difference. FIG. 22 is a diagram showing a part of an intermediate transfer belt arranged differently from FIG. 21. It is a block diagram of a system explaining a 9th embodiment of the present invention. It is a block diagram which shows schematic structure of the control computer shown in FIG. 24 is a flowchart showing processing of the image forming apparatus shown in FIG. 24 is a flowchart showing processing of the image forming apparatus shown in FIG.

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

First Embodiment Image Forming Apparatus Configuration
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the first embodiment of the present invention.

  An image forming apparatus 1 shown in FIG. 1 forms an electrostatic latent image, develops it with toner, forms a toner image, and finally transfers and fixes the toner image on a sheet, thereby fixing toner on the sheet. An apparatus for forming an image composed of an image. In the image forming apparatus 1 of the present embodiment, image forming units 10Y, 10M, 10C, and 10K are arranged in parallel for each color of yellow (Y), magenta (M), cyan (C), and black (K). The tandem type color printer is capable of printing a single color image and printing a full color image composed of four color toner images. Since the four image forming units 10Y, 10M, 10C, and 10K have substantially the same configuration, the image forming unit 10Y corresponding to yellow will be described as a representative example. Photoconductor 11Y, charger 12Y for charging the surface of photoconductor 11Y, developer 14Y for developing the surface of photoconductor 11Y with toner, primary transfer device 15Y for transferring a toner image to an intermediate transfer belt, and surface of photoconductor 11Y And a photoreceptor cleaner 16Y for cleaning the printer. The photoconductor 11Y has a cylindrical surface and rotates in the direction of arrow a that is around the axis of the cylinder. The photoreceptor 11Y maintains the surface potential by holding the applied charge, but when irradiated with light, the irradiated portion releases the charge and the surface potential (absolute value of the potential) decreases. The potential of the irradiated portion depends on the amount of light received.

  Further, the image forming apparatus 1 includes an exposure device 20 that irradiates each of the image forming units 10Y, 10M, 10C, and 10K with exposure light based on an image signal supplied from the outside, and a toner cartridge that stores toners of CMYK colors. 18Y, 18M, 18C, and 18K, the intermediate transfer belt 30 to which the toner image is transferred from the photoreceptors 11Y, 11M, 11C, and 11K of each color, and the second transfer unit 50 that transfers the toner image from the intermediate transfer belt 30 to the sheet. A fixing device 60 that fixes the toner to the paper, a belt cleaner 70 that collects the toner from the intermediate transfer belt 30, a paper transport unit 80 that transports the paper, a paper container 40 that stores the paper, and the paper And a control unit 1A for controlling each part of the image forming apparatus 1 are also provided. The exposure device 20 includes a light emitter 21 and a polygon mirror 22, and light emitted from the light emitter 21 is irradiated to the photoreceptors 11Y, 11M, 11C, and 11K by the polygon mirror 22 and optical parts (not shown). The The intermediate transfer belt 30 is an endless belt-like member supported by belt support rolls 31, 32, 33, and 34, and passes through the image forming units 10Y, 10M, 10C, and 10K and the second transfer unit 50 in this order. Circulately moves in the direction b. The belt cleaner 70 brings a blade into contact with the intermediate transfer belt 30 to scrape and collect the toner on the intermediate transfer belt 30. A density sensor 36 is provided on the intermediate transfer belt 30 downstream of the image forming units 10Y, 10M, 10C, and 10K. The density sensor 36 measures the density of the toner image formed by the image forming units 10Y, 10M, 10C, and 10K and transferred to the intermediate transfer belt 30. The paper transport unit 80 transports the paper along a paper transport path r that passes through the second transfer device 50 and the fixing device 60, and picks up a pick-up roll 81 that picks up the paper stored in the paper container 40. There are provided a roll 82 for scooping the paper, a transport roll 83 for transporting the paper, a registration roll 84 for transporting the paper to the second transfer device 50, and discharge rolls 86 and 87 for discharging the paper to the outside.

  Here, the photoconductors 11Y, 11M, 11C, and 11K correspond to an example of the image carrier in the present invention. Further, the combination of the exposure device 20, the chargers 12Y, 12M, 12C, and 12K and the developing devices 14Y, 14M, 14C, and 14K corresponds to an example of the image forming unit referred to in the present invention.

  FIG. 2 is a block diagram showing a circuit configuration of the control unit shown in FIG.

  A control unit 1A shown in FIG. 2 is an embedded computer connected to each unit of the image forming apparatus 1, and is executed by the CPU 101 that performs arithmetic processing and control of each peripheral unit by executing a program. A memory 102 as a storage medium for storing programs and data and storing calculation results by the CPU 101, an image data IF (interface) 103 for receiving an image signal representing image data from the outside, and exchange of signals with each unit shown in FIG. A mechanism IF 104, a sensor IF 105 that receives a signal from the density sensor 36, and a communication IF 106 that communicates with an external device to transmit and receive data. The CPU 101, the memory 102, the image data IF 103, the mechanism IF 104, and the sensor IF 105 are connected to each other via a bus. The control unit 1A controls the operation of each unit shown in FIG. 1 based on the image signal received by the image data IF 103 and the signal received by the sensor IF 105 by the CPU 101 executing the control program stored in the memory 102.

[Basic operation of image forming apparatus]
The basic operation of the image forming apparatus 1 shown in FIG. 1 will be described. In the image forming unit 10Y, the photoconductor 11Y is rotationally driven in the direction of arrow a, and a charge is applied to the surface of the photoconductor 11Y by the charger 12Y. The exposure unit 20 forms an electrostatic latent image by irradiating the photoconductors 11Y, 11M, 11C, and 11K of the image forming units 10Y, 10M, 10C, and 10K with exposure light based on image signals supplied from the outside. . The exposure device 20 irradiates the photoconductors 11Y, 11M, 11C, and 11K with exposure light corresponding to data corresponding to each color in the image signal. As a representative example, yellow (Y) will be described. The exposure device 20 irradiates the surface of the photoconductor 11Y with exposure light based on an image signal corresponding to yellow among image signals supplied from the outside. An electrostatic latent image is formed on the surface. The developing device 14Y forms a toner image by developing the electrostatic latent image with yellow toner. Toner 14Y is supplied with toner from toner cartridge 18Y. The supplied toner circulates in the developing unit 14Y while being mixed with the magnetic carrier and stirred in the developing unit 14Y, and is consumed by the development of the developing unit 14Y. The photoconductor 11Y holds the toner image upon receiving the yellow toner image. The toner image formed on the surface of the photoreceptor 11Y is transferred to the intermediate transfer belt 30 by the primary transfer unit 15Y. After transfer, the toner remaining on the photoreceptor 11Y is collected and removed by the photoreceptor cleaner 16Y.

  The intermediate transfer belt 30 is moved in the direction of the arrow b by the support rolls 31 to 34, and the image forming units 10M, 10C, and 10K corresponding to colors other than yellow are in the same manner as the image forming unit 10Y. The toner images corresponding to the above are formed, and the toner images of the respective colors are transferred onto the intermediate transfer belt 30 so as to be superimposed on the toner images transferred by the image forming unit 10Y. A toner image corresponding to the image signal is thus formed on the intermediate transfer belt 30 and moves while holding the toner image. Here, the toner image corresponding to the image signal corresponds to an example of the image signal toner image referred to in the present invention.

  On the other hand, the paper in the paper container 40 is taken out by the pick-up roll 81, and is transported in the direction of arrow c toward the second transfer device 50 through the paper transport path r by the separating roll 82, the transport roll 83, and the registration roll 84. The The second transfer device 50 transfers the toner image on the intermediate transfer belt 30 to the paper by applying a transfer bias potential between the intermediate transfer belt 30 and the paper. The toner image is finally transferred onto the paper by the second transfer device 50. The sheet is further conveyed to the fixing device 60, and the toner image transferred onto the sheet is fixed. In this way, an image is formed on the paper. The toner remaining on the intermediate transfer belt 30 after the transfer by the second transfer device 50 is collected and removed by the belt cleaner 70.

  In the image forming units 10Y, 10M, 10C, and 10K, toner images that are not intended for transfer onto paper are also formed. Such toner images include a patch image for comparison with a target density when adjusting the toner density, and a toner band image for forcibly consuming toner in the developing devices 14Y, 14M, 14C, and 14K. . The patch image and the toner band image are formed by the chargers 12Y, 12M, 12C, and 12K of the image forming units 10Y, 10M, 10C, and 10K, the developing units 14Y, 14M, 14C, and 14K, and the exposure device 20, and are subjected to intermediate transfer. Although it is transferred to the belt 30, it is collected and removed by the belt cleaner 70 without being transferred to the paper by the second transfer device 50. When the patch image and the toner band image pass through the transfer position, the second transfer device 50 applies a reverse bias potential whose electric field is opposite to the transfer bias potential, or transfers the transfer roll to the intermediate transfer belt 30. By keeping away from the transfer roll, the transfer roll is prevented from being stained with toner. That is, the patch image and the toner band image are collected by the belt cleaner 70 after passing through the transfer area in the second transfer device 50. Here, the toner band image corresponds to an example of the toner band referred to in the present invention. By forming the toner band image, the toner in the developing device 14 is forcibly consumed. A more detailed description of the toner band image will be given later, and the control of the toner density using the patch image will be described first.

[Density control]
The toner density of the toner image formed in each of the image forming units 10Y, 10M, 10C, and 10K is controlled by the developing potential difference Vdev applied to the photoreceptors 11Y, 11M, 11C, and 11K.

  FIG. 3 is a graph showing the potential distribution on the surface of the photoreceptor.

  The density adjustment is performed independently for each of the photoconductors 11Y, 11M, 11C, and 11K. However, since the principle of the potential and the adjustment method are common to each color, the yellow image forming unit 10Y will be described as a representative.

  The graph of FIG. 3 represents a potential distribution in a state where a part of the surface of the photoconductor 11Y is irradiated with light from the exposure device 20 after being charged by the charger 12Y. The vertical axis of the graph is the potential, the downward direction of the graph is the direction approaching the potential 0V, and the upward direction is the direction in which the absolute value of the potential increases. For example, the image forming apparatus 1 according to the present embodiment is a type in which the charger 12Y charges the photoreceptor 11Y negatively, and the upward direction is a negative potential and the absolute value is large, but the reverse polarity is temporarily charged. In the case of this type, if the upward direction is the direction in which the positive potential increases, the description will be the same.

  As shown in FIG. 3, the surface of the photoreceptor 11Y is first uniformly charged to the charging potential VH by the charger 12Y. Thereafter, the absolute value of the potential of the exposed portion irradiated with the exposure light by the exposure device 20 decreases to the exposure potential VL. The developing roll 141 of the developing device 14Y that supplies the developer containing toner has the same polarity as the charging potential VH and is intermediate between the charging potential VH and the exposure potential VL, more specifically, the charging potential VH. A near developing bias Vb is applied. As a result, the toner adheres to the exposure potential VL portion of the surface of the photoreceptor 11Y while avoiding the charging potential VH portion. That is, the toner adheres to the exposed part irradiated with the exposure light by the exposure device 20.

  Here, the potential difference between the exposure potential VL and the development bias Vb is referred to as a development potential difference Vdev. The toner density is the toner density in the toner adhesion portion of the toner image formed by the developing device 14Y, and is the amount per unit area of the toner adhering to the exposure portion. The development contrast potential difference Vdev determines the flying force of the toner on the surface of the photoreceptor 11Y, and the toner density corresponds to the magnitude of the development potential difference Vdev. Therefore, in the image forming apparatus 1 of the present embodiment, by controlling the exposure amount of light irradiated by the exposure device 20, the exposure potential VL is changed to control the development potential difference Vdev, and the toner of the formed toner image The concentration is controlled. The exposure amount is a product of the light intensity and the exposure time. In this embodiment, the scanning speed by the exposure light is fixed, and the exposure amount is a voltage supplied to the exposure unit 20 based on the control of the control unit 1A. It is controlled by the light intensity according to.

  FIG. 4 is a graph showing the relationship between the exposure amount and the development potential difference.

  As shown in FIG. 4, the larger the exposure amount (here, the light intensity), the greater the development potential difference Vdev.

  As the light from the exposure device 20 becomes stronger and the exposure potential VL (absolute value thereof) decreases, the development potential difference Vdev increases and the toner density of the toner image increases. On the contrary, the light of the exposure device 20 becomes weaker and the exposure potential VL (absolute value) increases, so that the development potential difference Vdev is reduced and the toner density of the toner image is reduced.

  3 and 4 show an upper limit potential difference VdevH and a lower limit potential difference VdevL, which are upper and lower limits of the range in which the development potential difference Vdev can be set in the image forming apparatus 1. The upper limit potential difference VdevH and the lower limit potential difference VdevL are determined according to the capability of the exposure device 20, the specifications of the photoconductor 11Y and the developing device 14Y, and the state of the apparatus. More specifically, the upper limit potential difference VdevH is set to a limit at which a so-called white image defect due to magnetic carrier jump does not occur, while the lower limit potential difference VdevL is set to a limit at which a thin line is formed at an appropriate density. ing. The control unit 1A controls the development potential difference Vdev between the upper limit potential difference VdevH and the lower limit potential difference VdevL so that the toner density of the formed toner image becomes the target density.

  The density of the image formed on the paper varies depending on the degree of wear of the member, temperature and humidity, and the state of the toner in the developing device 14, and there are also machine differences. Therefore, in the image forming apparatus 1 of the present embodiment, the toner density of the toner image formed on the sheet is adjusted by executing a setup process for adjustment every time image formation is performed on a predetermined number of sheets. To do. To adjust the toner density of the toner image, a patch image for testing is formed and transferred onto the intermediate transfer belt 30, and the deviation of the density of the patch image transferred onto the intermediate transfer belt 30 from the target density is corrected. By doing.

  FIG. 5 is a diagram illustrating a part of the intermediate transfer belt.

  In the image forming apparatus 1 of the present embodiment, a setup process is executed each time image formation is performed on a predetermined number of sheets such as 100 sheets, and a patch image is formed. In FIG. 5, on the intermediate transfer belt 30, the K color patch images PK1 and PK2 formed by the K color image forming unit 10K, and the C color patch image PC1 formed by the C color image forming unit 10C. PC 2, M color patch images PM1 and PM2 formed by the M color image forming unit 10M, and K color patch images PY1 and PY2 formed by the Y color image forming unit 10Y are shown. FIG. 5 also shows toner band images BC and BM formed on the intermediate transfer belt 30. The toner band images BC and BM will be described later.

  The patch images PK1, PK2 to PM1, PM2 are formed on the intermediate transfer belt 30 so as not to overlap each other, and are formed with a predetermined pattern density (halftone dot density). The figure shows an example in which patch images PY1, PM1, PC1, PK1 having a relatively dark pattern density and patch images PY2, PM2, PC2, PK2 having a relatively light pattern density are formed for each color of YMCK. Has been. These patch images PK1, PK2 to PM1, PM2 are formed at positions corresponding to the density sensor 36 in the width direction intersecting with the moving direction b of the intermediate transfer belt 30. Accordingly, the patch images PK1, PK2 to PM1, PM2 pass over the density sensor 36 as the intermediate transfer belt 30 moves in the direction b, and the respective densities are sequentially detected by the density sensor 36. A signal representing the detection result by the density sensor 36 is transmitted to the control unit 1A. The control unit 1A compares the detection result of the density sensor 36 with the target density for each color, and adjusts the development potential difference Vdev so as to correct the deviation between the detected density and the target density. For example, the control unit 1A corrects the deviation when the density detected for the patch image PY1 out of the two patch images PY1 and PY2 formed by the image forming unit 10Y is lower than the expected target density. Thus, the development potential difference Vdev is increased. More specifically, the control unit 1A increases the supply voltage to the exposure unit 20 to increase the intensity of exposure light with respect to the photoconductor 11Y of the exposure unit 20 and decrease the absolute value of the exposure potential VL. Increase the development potential difference Vdev.

  The patch images PK1, PK2 to PM1, and PM2 formed by the setup process are collected by the belt cleaner 70 and not transferred to the paper as described above, but development is performed using these patch images PK1, PK2 to PM1, and PM2. By controlling the potential difference Vdev, the toner density of the toner image transferred onto the paper in the normal printing operation is adjusted to the target density.

  Here, as a result of controlling the developing potential difference Vdev, the developing potential difference Vdev may reach the upper limit potential difference VdevH or the lower limit potential difference VdevL.

  FIG. 6 is a graph showing the control of the development potential difference for the image forming units of the respective colors.

  The horizontal axis of the graph represents the number of sheets (PV) on which image formation has been performed, and the setup process is executed at timings PV1, PV2, and PV3 for each predetermined number of sheets. The vertical axis represents the development potential difference Vdev, and four development potential differences Vdev are shown for the image forming units 10Y, 10M, 10C, and 10K of the respective colors. In the setup process executed at the timings PV1, PV2, and PV3, the development potential difference Vdev is adjusted based on the density detection of the patch image. For example, the M development potential difference Vdev is set to the upper limit potential difference VdevH in the setup process at the timing PV3. Thus, it is difficult to make further adjustment by the development potential difference Vdev. In such a situation, for example, when formation of an image having a small average image density (that is, an image having many white portions) is continuously executed for a long time, the toner is not consumed by the developing device 14 (14M in this case) This is likely to occur by circulating in the developing unit 14 while stirring over a long period of time. In this case, the toner remaining in the developing device 14 is more strongly charged by long-term stirring and strongly electrostatically couples with the magnetic carrier, so that the toner separates from the magnetic carrier and adheres to the surface of the photoreceptor 11 during development. To be prevented. In addition, the surface of the toner particles is scraped by being stirred for a long time. These are collectively referred to as toner deterioration. It should be noted that the toner does not necessarily deteriorate when the formation of an image having a small average image density is continuously executed for a long time. However, as the toner deteriorates, the toner density cannot be set to the target density only by controlling the development potential difference Vdev. For example, the toner density may not reach the target density even when the development potential difference Vdev is increased to the upper limit potential difference VdevH. In this embodiment, when the developing potential difference Vdev reaches the upper limit potential difference VdevH and becomes a value that cannot be further controlled, the control unit 1A sends the image signal to the corresponding image forming units 10Y, 10M, 10C, and 10K. A toner band different from the corresponding toner image and patch image is formed.

  In the graph of FIG. 6, the C-color development potential difference Vdev reaches the lower limit potential difference VdevL contrary to the above-described setup process at the timing PV2 and the timing PV3. Such a situation occurs, for example, when the toner in the developing device 14C is in a higher temperature or higher humidity state than normally assumed, and the toner tends to adhere excessively to the surface of the photoreceptor 11Y during development. . In the present embodiment, even when the development potential difference Vdev reaches the lower limit potential difference VdevL and falls outside the controllable range, the control unit 1A causes the corresponding image forming units 10Y, 10M, 10C, and 10K to form toner bands. The arrows in FIG. 6 indicate the timing at which the toner band is formed.

[Toner Band]
The intermediate transfer belt 30 shown in FIG. 5 shows toner band images BM and BC formed by the image forming units 10M and 10C, respectively, in the setup process of the timing PV3 shown in FIG. The toner band images BM and BC are formed on the intermediate transfer belt 30 moving in the moving direction b following the patch images PK1, PK2 to PM1, and PM2. The toner band images BM and BC are rectangles extending over substantially the entire width in the width direction intersecting with the movement direction b. In the example shown in FIG. 6, the length L in the movement direction b is 100 mm. The toner band images BM and BC have a pattern density (halftone dot density) of 70%. The toner band images BM and BC are not transferred onto the sheet by the second transfer unit 50 but are collected by the belt cleaner 70. By forming the toner band image BM, the B-color developing device 14B consumes deteriorated toner, and new toner is supplied to compensate for this consumption. Therefore, the target toner is controlled by controlling the development potential difference Vdev. It becomes possible to control the concentration again. In the M-color developing device 14M, for example, high-humidity toner is consumed, so that the control to achieve the target toner density can be performed again by controlling the development potential difference Vdev. In the setup process of timing PV3, the development potential difference Vdev for Y and K colors is in a controllable range, that is, in a range larger than the lower limit potential difference VdevL and smaller than the upper limit potential difference VdevH. The toner band images BY and BK have a length L of 0 mm, that is, are not formed.

[Operation]
FIG. 7 is a flowchart illustrating an image forming process in the image forming apparatus.

  Processing in the image forming apparatus 1 is controlled by a control unit 1A that executes a program stored in the memory 102 (see FIG. 1). FIG. 7 and FIG. 8 described later represent this program. The process shown in FIG. 7 is executed every time an image forming job accompanied by image data is received from the outside.

  When the image data is received, the image forming apparatus 1 first executes a normal image forming process (step S10). In the image forming process, the control unit 1A is configured such that the image forming units 10Y, 10M, 10C, and 10K photoconductors, chargers, developing units, and primary transfer units, the exposure unit 20, the intermediate transfer belt 30, and the second transfer unit 50. Then, the fixing device 60 and the paper transport unit 80 are controlled to form an image corresponding to the image data on the paper.

  Next, the control unit 1A determines whether or not it is a pattern creation execution timing, that is, whether or not to perform a setup process (step S12). Specifically, the control unit 1A counts the number of sheets on which images have been formed in the normal image forming process, and when the counting result reaches a predetermined number, for example, 100 (Yes in step S12). ), Setup processing (steps S13 to S15) is executed. The setup process (steps S13 to S15) is executed independently for each color of YMCK.

  In the setup process, first, a patch image creation and detection process is executed (step S13). The control unit 1A controls each of the image forming units 10Y, 10M, 10C, and 10K to form the patch images PK1, PK2, PY1, and PY2 illustrated in FIG. 5 on the intermediate transfer belt 30. Then, the control unit 1A reads the detection signal from the density sensor 36 in accordance with the passage timing of the patch images PK1, PK2 to PY1, PY2.

  Next, the control unit 1A executes a pattern length calculation process (step S14). In the pattern length calculation process, the control unit 1A compares the densities of the patch images PK1, PK2 to PY1, PY2 detected in the patch image creation and detection process (step S13) with the expected target density, and sets the development potential difference Vdev. At the same time, the length L of the toner band image is calculated according to the value of the development potential difference Vdev. Next, the control unit 1A creates a toner band image pattern corresponding to the calculated length L of the toner band image in the pattern creation process (step S15). By this processing, for example, a toner band image as shown in FIG. 5 is formed. In the pattern length calculation process (step S14), a toner band is not substantially formed for the color whose length L is calculated as 0 mm.

  Finally, it is confirmed whether or not the image formation for the received job has been completed. If not completed (No in step S16), the processing from step S10 is repeated. All the processing is terminated.

  FIG. 8 is a flowchart showing details of the pattern length calculation process shown in FIG. Note that the pattern length calculation process shown in FIG. 7 is executed independently for each color, as already described in step S14.

  First, the control unit 1A calculates an average image density D% of all images formed after the previous setup process (step S140). This is used when it is determined to create a toner band for preventing the belt cleaner 70 from twisting (step S144).

  Next, the control unit 1A executes processing for calculating and setting the development potential difference Vdev (step S141). In this process, the control unit 1A compares the density detected by the density sensor 36 with the target density for the patch images PK1, PK2 to PM1, and PM2 formed by the image forming units 10Y, 10M, 10C, and 10K. The developing potential difference Vdev for correcting the deviation is calculated. As an actual calculation method, it is possible to adopt a method by reading a table in which the correspondence between the density deviation and the development potential difference Vdev is recorded in advance, or a method by calculating an expression for approximating the experience value. Also, the control unit 1A sets the calculated value as a new development potential difference Vdev. In the present embodiment, a range including the lower limit potential difference VdevL and the upper limit potential difference VdevH of the development potential difference Vdev, that is, a range that is greater than or equal to the lower limit potential difference VdevL and less than or equal to the upper limit potential difference VdevH is set as a range in which the toner density of the toner image by the development potential difference Vdev can be controlled. Yes. Therefore, when the calculated new development potential difference Vdev is larger than the upper limit potential difference VdevH, it is limited to VdevH, and when it is smaller than the lower limit potential difference VdevL, it is limited to VdevL. In the process of step S141, the toner density of the toner image is adjusted to the target density by adjusting the development potential difference Vdev.

  In this embodiment, when the developing potential difference Vdev becomes the lower limit potential difference VdevL or the upper limit potential difference VdevH and falls outside the controllable range, the size of the created toner band image is increased. More specifically, when the development potential difference Vdev is within a controllable range, the length of the toner band image is 0 mm, that is, the toner band image is not created, or a toner band for preventing wrinkles having a length of 10 mm is created. When the development potential difference Vdev is outside the controllable range, the length of the toner band image is expanded to 100 mm. Here, the length L of the toner band image is the length in the direction in which the intermediate transfer belt 30 moves, that is, the length in the direction in which the photoconductor 11 moves while holding the toner image. This will be described more specifically below.

  The controller 1A determines whether or not the calculated development potential difference Vdev is equal to the upper limit potential difference VdevH (step S142). When the calculated development potential difference Vdev is equal to the upper limit potential difference VdevH and is outside the range determined by the development potential difference Vdev (Yes in step S142), the length L of the toner band image is set to 100 mm (step S145). In this case, toner supply for the toner band image is performed (step S146). Thus, a toner band image is formed, and when the toner in the developing device is consumed (step S15), new toner corresponding to the consumed amount is replenished.

  If it is determined in step S142 that the development potential difference Vdev is not equal to the upper limit potential difference VdevH (No in step S142), the control unit 1A determines whether the calculated development potential difference Vdev is equal to the lower limit potential difference VdevL (step S142). S143). When the calculated development potential difference Vdev is equal to the lower limit potential difference VdevL and control by the development potential difference Vdev reaches the limit (Yes in step S143), the length L of the toner band image is set to 100 mm (step S147). Note that when the development potential difference Vdev is the lower limit, the toner density of the toner image is too high, so that toner replenishment is not executed unlike step S146.

  When it is determined that the calculated development potential difference Vdev is not equal to the lower limit potential difference VdevL (No in step S143), the control unit 1A determines whether the average image density D% of the image calculated in step S140 is less than 3%. Is determined (step S144). When the average image density D% is 3% or more (No in step S144), the length L of the toner band image is set to 0 mm (step S148). If the average image density D% is less than 3% (Yes in step S144), it means that almost no toner has been consumed since the previous setup process. The photoconductor cleaners 16Y, 16M, 16C, and 16K and the belt cleaner 70 scrape unnecessary toner by bringing the blade into contact with the surfaces of the photoconductor 11Y and the intermediate transfer belt 30, but in a situation where the toner is not consumed. The toner acting as a lubricant at the contact portion is extremely insufficient and the frictional force becomes large, and the blade may be bent by the movement of the photoconductor 11Y or the intermediate transfer belt 30. When the average image density D% is less than 3% (Yes in Step S144), the control unit 1A according to the present embodiment creates a toner band for blurring. Since the toner band for blurring is not intended for toner consumption but for lubrication, the length L of the toner band image is set to 10 mm (step S149).

  FIG. 9 is a diagram illustrating a part of the intermediate transfer belt on which a toner band for preventing wobbling is formed.

  On the intermediate transfer belt 30 shown in FIG. 9, in addition to the patch images PK1, PK2 to PM1, PM2 and the C and M toner band images BC and BM shown in FIG. Toner band images BK and BY for preventing blurring are also formed by the portions 10Y and 10K.

  By setting the length of the toner band image for blurring, even when the development potential difference Vdev does not exceed the control range, the toner band for blurring is formed when the average image density is low, and the photoreceptor 11Y. , 11M, 11C, and 11K and the surfaces of the photoreceptor cleaners 16Y, 16M, 16C, and 16K, and the lubrication between the intermediate transfer belt 30 and the belt cleaner 70 are maintained.

  Referring back to FIG. 8 again, when it is determined in step S144 that the average image density D% is not less than 3 (No in step S144), the control unit 1A sets the length L of the toner band image. 0 mm. In this case, the toner band image of the color is not created and the toner is not consumed.

  When the development potential difference Vdev is out of the controllable range by the processing in steps S142 to S146 in FIG. 8 and the processing in S15 in FIG. 7, the length of the formed toner band image is increased to 100 mm. By forming the toner band image, the deteriorated toner or the hygroscopic toner in the developing device is forcibly consumed, and the toner density can be controlled by the development potential difference Vdev. On the other hand, when the development potential difference Vdev is within a controllable range, a toner band image is not created or even if it is created, only a 10 mm long toner band for blurring is created. Since the toner consumption by the toner band image is proportional to the length of the toner band image, the toner consumption is accurately controlled as the length of the toner band image. In this embodiment, for example, wasteful toner consumption is suppressed as compared with a configuration in which a toner band is formed immediately when the density exceeds a threshold value.

  Here, the control unit 1A that executes the normal image forming process in step S10 corresponds to an example of the signal image forming control unit according to the present invention, and the control for executing the developing potential difference calculation and setting process in step S141. The section 1A corresponds to an example of a potential difference control section referred to in the present invention. Further, the control unit 1A that executes the processing from step S142 to S149 and the pattern creation processing of step S15 corresponds to an example of a band formation control unit according to the present invention.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In the following description of the second embodiment, the diagram showing the configuration of the first embodiment is used as it is, and the same elements as those in the first embodiment are denoted by the same reference numerals. Differences from the above-described embodiment will be described.

  FIG. 10 is a graph showing the transition of the development potential difference with respect to each color image forming unit of the image forming apparatus according to the second embodiment.

  In the image forming apparatus according to the second embodiment, a range from the upper limit potential difference VdevH to a potential difference that is lower by a predetermined potential difference α, for example, several percent, that is, a range from VdevH−α to VdevH, or a lower limit potential difference VdevL. For example, a toner band image is formed when the development potential difference Vdev is set in a range up to a potential difference higher by a predetermined potential difference β such as several percent, that is, in a range of VdevL or more and VdevL + β or less.

  In the second embodiment, the range of the potential difference α from the upper limit potential difference VdevH to VdevH−α corresponds to an example of the first range in the present invention, and the range of the potential difference β from the lower limit potential difference VdevL to VdevL + β is referred to in the present invention. This corresponds to an example of the second range.

  FIG. 11 is a flowchart showing details of pattern length calculation processing in the second embodiment.

  In the first embodiment described above, it is determined whether or not the calculated development potential difference Vdev is equal to the upper limit potential difference VdevH (step S142 in FIG. 8), whereas in the pattern length calculation process of the second embodiment, the calculation is performed. It is determined whether or not the development potential difference Vdev is equal to or greater than VdevH−α (step S242). In the first embodiment, it is determined whether or not the calculated development potential difference Vdev is equal to the lower limit potential difference VdevL (step S143 in FIG. 8). In the pattern length calculation process of the second embodiment, the calculated development potential difference is determined. It is determined whether or not the potential difference Vdev is equal to or less than VdevL + β (step S243).

  In the second embodiment, wasteful toner consumption is suppressed as in the first embodiment, and a toner band image is formed before the development potential difference Vdev reaches a value at which the toner density of the toner image cannot be controlled. In other words, the density correction is performed more quickly and with a margin.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. In describing the third embodiment below, differences from the first embodiment will be described.

  FIG. 12 is a graph showing the control of the development potential difference for the image forming units of the respective colors in the third embodiment.

  In the image forming apparatus according to the third embodiment, the range of the developing potential difference Vdev between the lower limit potential difference VdevL and the upper limit potential difference VdevH, which is far from the lower limit potential difference VdevL and the upper limit potential difference VdevH and can control the toner density with a margin. Is predetermined as a steady control range. In the third embodiment, a toner band image is formed when the development potential difference Vdev is a value outside the steady control range. The steady control range in the third embodiment corresponds to an example of a predetermined range according to the present invention.

  FIG. 13 is a flowchart showing details of pattern length calculation processing in the third embodiment.

  In the first embodiment described above, it is determined whether or not the calculated development potential difference Vdev is equal to the upper limit potential difference VdevH (step S142 in FIG. 8), whereas in the pattern length calculation process of the third embodiment, the calculation is performed. It is determined whether or not the development potential difference Vdev is larger than the upper limit of the steady control range (step S342). In the first embodiment, it is determined whether or not the calculated development potential difference Vdev is equal to the lower limit potential difference VdevL (step S143 in FIG. 8). In the pattern length calculation process of the second embodiment, the calculation is performed. It is determined whether or not the development potential difference Vdev is smaller than the lower limit of the steady control range (step S343).

  In the third embodiment, as in the second embodiment, the correction of the toner density using the toner band is executed earlier.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. In the following description of the fourth embodiment, differences from the first embodiment will be described.

  FIG. 14 is a flowchart illustrating image forming processing in the image forming apparatus according to the fourth embodiment. The image forming apparatus of the first embodiment described above controls the size of the toner band image to be formed. The image forming apparatus of the fourth embodiment controls the pattern density of the toner band.

  In the process shown in FIG. 14, the control unit 1A (see FIG. 1) performs a pattern density Cin calculation process (step S43) after the patch image creation and detection process (step S13), and calculates the calculated pattern density (network). A toner band image is formed at a point density) (step S45).

  FIG. 15 is a flowchart showing details of pattern density calculation processing in the fourth embodiment.

  In the processing shown in FIG. 15, when the calculated development potential difference Vdev is equal to the upper limit potential difference VdevH and is outside the range defined by the control of the development potential difference Vdev (Yes in step S142), the pattern density Cin of the toner band image is 100. % (Step S445). When the calculated development potential difference Vdev is equal to the lower limit potential difference VdevL and is outside the range defined by the control of the development potential difference Vdev (Yes in step S143), the pattern density Cin of the toner band image is set to 100% (step S447). If the average image density D% of the image calculated in step S140 is 3% or more (No in step S144), the pattern density Cin of the toner band image is set to 0% (step S448), but the average image density If D% is less than 3% (Yes in step S144), the pattern density Cin of the toner band image is set to 10% (step S449).

  14 and 15, when the development potential difference Vdev becomes the upper limit potential difference VdevH or the lower limit potential difference VdevL, the pattern density of the formed toner band image increases from 0% (or 10%) to 100%. The toner consumption amount, that is, the toner recovery amount by the belt cleaner 70 increases. Even when the pattern density increases from 10% to 100% and the toner consumption increases, the size of the toner band image is fixed, and the expansion of the area of the toner band image on the intermediate transfer belt 30 is suppressed. .

[Fifth Embodiment]
Next, a fifth embodiment of the present invention will be described. In the following description of the fifth embodiment, differences from the first embodiment will be described.

  FIG. 16 is a flowchart illustrating image forming processing in the image forming apparatus according to the fifth embodiment. The image forming apparatus according to the first embodiment described above controls the state of the formed toner band image, whereas the image forming apparatus according to the fifth embodiment controls the frequency with which the toner band image is formed.

  In the process shown in FIG. 16, after the normal image forming process is executed (step S10), the control unit 1A (see FIG. 1) adds 1 to the number of sheets SetupPV representing the number of sheets on which images have been formed since the previous setup process. (Step S51). Further, the control unit 1A determines whether or not the number of sheets SetupPV is equal to or greater than a pattern creation interval (step Setup interval) indicating an interval for performing the setup process (Step S52). The pattern creation interval is set by a pattern creation interval calculation process in step S54 described later. If the number of sheets SetupPV is equal to or greater than the pattern creation interval (Yes in step S52), the control unit 1A executes the following setup process assuming that it is the toner band image creation timing.

  In the setup process, the control unit 1A executes a patch image creation and detection process (step S13), and executes a pattern creation interval calculation process (step S54). Thereafter, the control unit 1A creates a toner band image pattern (step S55). Here, for each of CMYK, a fixed toner band image having a length of 100 mm and a pattern density of 70% is formed. Thereafter, the number of sheets SetupPV is initialized to 0 (step S56).

  FIG. 17 is a flowchart showing details of pattern creation interval calculation processing in the fifth embodiment.

  In the processing shown in FIG. 17, when the calculated development potential difference Vdev is equal to the upper limit potential difference VdevH and is outside the range defined by the control of the development potential difference Vdev (Yes in step S142), the pattern creation interval (step setup interval) is 40 sheets are set (step S545). When the calculated development potential difference Vdev is equal to the lower limit potential difference VdevL and is outside the range defined by the control of the development potential difference Vdev (Yes in step S143), the pattern creation interval (step setup interval) is 40 ( Step S547). If the development potential difference Vdev is larger than the lower limit potential difference VdevL and smaller than the upper limit potential difference VdevH (No in step S143), the pattern creation interval (step setup interval) is set to 200 (step S548).

  When the development potential difference Vdev becomes the upper limit potential difference VdevH or the lower limit potential difference VdevL by the processing of FIGS. 14 and 15, the toner band image is formed at a frequency of once from 200 normal image formations to 40 times. Increase to once per sheet. Therefore, the toner consumption increases.

[Sixth Embodiment]
In the embodiment described so far, the density sensor 36 detects the density of the patch image. Next, a sixth embodiment in which the density sensor is not used will be described. The sixth embodiment is different from the image forming apparatus shown in FIG. 1 in that the density sensor is not provided and the processing of the control unit. Therefore, the diagram showing the configuration of the first embodiment is used as it is. The same elements as those in the first embodiment are denoted by the same reference numerals, and differences from the first embodiment will be described.

  FIG. 18 is a flowchart illustrating image forming processing in the image forming apparatus according to the sixth embodiment.

  In the process shown in FIG. 18, the control unit 1A (see FIG. 1) adds 1 to the number of sheets SetupPV representing the number of sheets on which images have been formed since the previous setup process after the normal image forming process is executed (step S10). In step S61, it is further determined whether or not the number of sheets SetupPV is equal to or greater than a pattern creation interval (step setup interval) representing an interval for performing the setup process (step S62). The pattern creation interval in this embodiment is a fixed value such as 100 sheets. If the number of sheets SetupPV is equal to or greater than the pattern creation interval (Yes in step S62), the control unit 1A executes the following setup process assuming that it is the toner band image creation timing.

  In the setup process (step S63), the control unit 1A causes the environmental temperature and humidity, the rotational speed integrated value of the photoconductors 11Y, 11M, 11C, and 11K, the rotational speed integrated value of the developing roll 141, and the subsequent setup process, for example. The number of dots (ICDC) of an image formed in a predetermined period is detected. Then, the control unit 1A calculates a development potential difference Vdev for forming a toner image having an appropriate density according to the result detected in the process of step S63 (step S641), and the calculated development potential difference Vdev is equal to the upper limit potential difference VdevH. It is determined whether or not they are equal (step S642). When the developing potential difference Vdev is equal to the upper limit potential difference VdevH (Yes in step S642), the control unit 1A performs toner band image formation (step S65) and toner supply (step S646), and initializes the number of sheets SetupPV. (Step S66).

  The control unit 1A that executes the processes of steps S63 and S641 corresponds to an example of the density control unit according to the present invention.

[Seventh Embodiment]
In the embodiments described so far, the development potential difference Vdev based on the light intensity control by the exposure device 20 is controlled as an adjustment factor for setting the toner density of the toner image to the target density. A seventh embodiment in which the developing bias Vb is used will be described. In the following description of the seventh embodiment, differences from the first embodiment will be described.

  The developing bias Vb is a voltage applied to the developing roll 141 of the developing device 14Y as described with reference to the graph of FIG. By controlling the developing bias Vb instead of the exposure potential VL due to exposure of the photosensitive member, the developing potential difference Vdev can be changed and the density of the toner image can be adjusted.

  FIG. 19 is a flowchart showing details of pattern length calculation processing in the seventh embodiment.

  After calculating the average image density D% (step S140), the control unit 1A executes calculation and setting processing for the developing bias Vb (step S741). Thereafter, the control unit 1A determines whether or not the calculated development bias Vb is an upper limit of a range that can be set as the development bias Vb (step S742). When the developing bias Vb is equal to the upper limit (Yes in step S742), the length L of the toner band image is set to 100 mm (step S145), and toner is replenished (step S146). Even when the developing bias Vb is equal to the lower limit of the settable range (Yes in step S743), the length L of the toner band image is set to 100 mm (step S147).

  The developing bias Vb in the seventh embodiment corresponds to an example of an adjustment factor in the present invention.

[Eighth Embodiment]
In the first embodiment described above, the upper limit potential difference VdevH of the development potential difference Vdev has been described as a fixed value. Next, an eighth embodiment in which the upper limit potential difference varies will be described. In the following description of the eighth embodiment, differences from the first embodiment will be described.

  FIG. 20 is a flowchart illustrating an upper limit potential difference correction process according to the eighth embodiment.

  In the eighth embodiment, the upper limit potential difference correction process shown in FIG. 20 is performed immediately after the calculation and setting process (step S141) of the development potential difference Vdev in the pattern length calculation process of the first embodiment shown in FIG. It is different from the first embodiment in that it is executed. Since the other points are the same as those in the first embodiment, only the upper limit potential difference correction process in FIG. 20 will be described.

  In the upper limit potential difference correction process shown in FIG. 20, the control unit 1A detects the temperature and humidity of the environment of the image forming apparatus using a temperature sensor and a humidity sensor (not shown) (step S1411), and based on the detection result, the Vdev upper limit environment. A correction amount is calculated (step S1412). Next, the control unit 1A detects the degree of deterioration of the developer from the number of sheets on which images have been formed and the average image density (step S1413), and based on the detection result, determines the Vdev upper limit development deterioration correction amount. Calculate (step S1412). Next, the control unit 1A detects the deterioration of the photoconductor from the accumulated rotational speed of the photoconductor (step S1415), and calculates the Vdev upper limit photoconductor deterioration correction amount based on the detection result (step S1416). Next, the control unit 1A adds the Vdev upper limit environment correction amount, the Vdev upper limit development deterioration correction amount, and the Vdev upper limit photoreceptor deterioration correction amount calculated by the above processing to the reference Vdev upper limit value serving as a calculation reference. Thus, the upper limit potential difference VdevH is obtained. By using the obtained upper limit potential difference VdevH in the determination process shown in FIG. 8 (step S142), an appropriate determination according to the environmental conditions changing every moment and the degree of deterioration of the photoconductor is performed.

[Modification]
In the first to fifth embodiments described above, patch image formation and density measurement are performed in one setup process, and the determination result of the value of the development potential difference Vdev controlled according to the density measurement result is reflected. The toner band image is thus formed, but the control of the development potential difference Vdev may use the result of the density measurement of the patch image measured in the previous setup process. In this case, the time lag from the patch image formation to the toner band image formation is reduced.

  FIG. 21 is a diagram illustrating a part of the intermediate transfer belt in a modification in which the density measurement result measured in the previous setup process is used to control the development potential difference.

  As shown in FIG. 21, the time lag from the patch image formation to the toner band image formation is shortened, so that the patch image PY2 formed on the intermediate transfer belt 30 and the toner band image BK Is narrower than the arrangement shown in FIG. As a result, the range used for the setup process on the intermediate transfer belt is reduced, and normal image formation is started earlier.

  FIG. 22 is a view showing a part of the intermediate transfer belt arranged differently from FIG.

  When the density measurement result of the patch image measured in the previous setup process is used to control the development potential difference Vdev, as shown in FIG. 22, the positions of the patch images PK1, PK2 to PM1, PM2, and the toner band image It is also possible to reverse the positional relationship with BK.

[Ninth Embodiment]
In the image forming apparatus 1 described so far, each control process is executed by a control unit incorporated therein. Subsequently, at least a part of the process is performed by an external computer connected to the image forming apparatus. A ninth embodiment controlled by the above will be described.

  FIG. 23 is a block diagram of a system for explaining a ninth embodiment of the present invention.

  A control computer 90 is communicably connected to the image forming apparatus 1 ′ shown in FIG. 23 via a computer network, for example. The control computer 90 is a device for remotely operating the image forming apparatus 1 ′, receives various data representing the internal state from the image forming apparatus 1 ′, and based on the received data, controls the image forming apparatus 1 ′. Control data for controlling the operation is transmitted to the image forming apparatus 1 ′. The image forming apparatus 1 ′ differs from the image forming apparatus 1 according to the first embodiment shown in FIGS. 1 and 2 in the processing of the control unit, and the internal hardware configuration is the same. 2 and FIG. 2 will be used as they are.

  FIG. 24 is a block diagram showing a schematic configuration of the control computer shown in FIG.

  The control computer 90 is, for example, a personal computer, and stores a CPU 901 that performs arithmetic processing and control of each peripheral unit, a memory 902 that stores a program 900 executed by the CPU 901, and stores a calculation result by the CPU 901, and an image forming apparatus 1 ′. A communication IF 903 that performs data communication with the communication interface 903, and a display control unit 904 that displays a control status on a display or the like. The communication IF 903 is connected to the communication IF 106 of the image forming apparatus 1 ′ and exchanges data. The CPU 901 controls the operation of the image forming apparatus 1 ′ by executing the program 900. Here, the control computer 90 is an embodiment of the control device of the present invention, and the program 900 is an embodiment of the program of the present invention.

  FIG. 25 is a flowchart showing processing of the image forming apparatus shown in FIG.

  Of the processes shown in FIG. 25, the same processes as those of the image forming apparatus according to the first embodiment shown in FIG. In the process shown in FIG. 25, the control unit 1A of the image forming apparatus calculates the average image density D% (step S84) after executing the patch image creation and detection process (step S13), and calculates the development potential difference Vdev. A setting process is executed (step S84). The processes in steps S84 and S84 are the same as the processes in steps S140 and S141 shown in FIG.

  Next, the control unit 1A executes a data transmission process and transmits data representing the development potential difference Vdev and the average image density D to the control computer 90 (step S87). Next, the control unit 1A executes pattern length data reception processing, and obtains pattern length data from the control computer 90 (step S88). Next, in the pattern creation process (step S88), the control unit 1A creates a toner band image pattern corresponding to the length L of the toner band image. In the pattern creation process of the control unit 1A in the image forming apparatus 1 ′, the pattern is formed according to the pattern length L obtained from the control computer 90, and the formation of the toner band image is controlled by the control computer 90. Has been.

  FIG. 26 is a flowchart showing processing of the control computer shown in FIG.

  The control computer 90 receives data representing the development potential difference Vdev and the average image density D from the image forming apparatus 1 '(step S90). Next, the control computer 90 determines whether the development potential difference Vdev of the received data is equal to the upper limit potential difference VdevH (step S91) and whether it is equal to the lower limit potential difference VdevL (step S92). When the development potential difference Vdev obtained by reception is equal to either the upper limit potential difference VdevH or the lower limit potential difference VdevL and the control by the development potential difference Vdev reaches the limit (Yes in step S142), the length L of the toner band image is set to 100 mm. (Steps S96 and S97). The control computer 90 also determines the average image density D% (step S98), and sets the length of the toner band for blurring prevention (steps S98 and S98). The processes in steps S91 to S98 are the same as steps S142 to S149 (FIG. 8) in the control unit 1A of the image forming apparatus according to the first embodiment. Finally, the control computer 90 transmits the set pattern data length to the image forming apparatus 1 ′ (see FIG. 23).

  In this manner, the toner band formation in the image forming apparatus 1 ′ is remotely controlled by the control computer 90.

  In the above-described embodiment, an example of a tandem type color printer is shown as the image forming apparatus. However, the image forming apparatus referred to in the present invention is not limited to this, and is, for example, a monochrome printer that does not have an intermediate transfer belt. May be. In the case of a printer that does not use an intermediate transfer belt, for example, it is possible to employ a configuration in which the density sensor detects the density of the patch image on the surface of the photoreceptor, and the toner in the toner band image is collected only by the photoreceptor cleaner.

  In the above-described embodiment, an example of a printer is shown as the image forming apparatus. However, the image forming apparatus referred to in the present invention is not limited to a printer, and may be a copying machine or a facsimile, for example.

  In the above-described embodiment, an example of a combination of a charger, an exposure unit, and a developing unit is shown as the image forming unit according to the present invention. However, the image forming unit according to the present invention is not limited to this, for example, An electrode array may directly apply a potential corresponding to an image to the image carrier. In this case, the toner density can be controlled as a potential applied by the electrode array.

  In the first to fifth embodiments described above, as an example of the image formation control unit according to the present invention, an example in which a toner band image is formed when the development potential difference Vdev deviates from either the upper limit or the lower limit. However, the present invention is not limited to this. For example, as described in the sixth embodiment, a toner band may be formed only when the upper limit is exceeded.

  In the above-described embodiment, as an example of the density control unit and the image formation control unit according to the present invention, an example is shown in which each process is executed in a setup process that is executed every time an image is formed on a predetermined number of sheets. However, the present invention is not limited to this, and the control of the toner density of the toner image and the formation of the toner band are performed, for example, when the power of the image forming apparatus is turned on or immediately after the parts are replaced. There may be.

  In the above-described embodiment, an example in which a toner band image for preventing blurring is formed even when the control of the adjustment factor cannot be removed has been described. However, the present invention is not limited to this. The image may not be formed.

  In the embodiment described above, the control example of the exposure potential VL and the control example of the development bias Vb have been described as the control of the development potential difference according to the present invention. However, the present invention is not limited to this. It may be time or an AC voltage component.

1A Control unit 1 Image forming apparatus 10Y, 10M, 10C, 10K Image forming unit 11Y, 11M, 11C, 11K Photoconductor 12Y, 12M, 12C, 12K Charger 14Y, 14M, 14C, 14K Developer 15Y, 15M, 15C, 15K primary transfer device 16Y, 16M, 16C, 16K photoconductor cleaner 20 exposure device 30 intermediate transfer belt 36 density sensor

Claims (7)

An image carrier for holding a toner image formed on the surface;
An image forming unit that forms a toner image by flying toner on the image carrier;
A detection unit for detecting the density of the toner image formed by the image forming unit;
A signal image formation control unit which receives an input of an image signal and causes the image forming unit to form an image signal toner image corresponding to the image signal;
A patch toner image having a predetermined image density is formed on the image forming unit, and toner on the image holding member in the image forming unit is determined according to a detection result of the patch toner image by the detection unit. A potential difference control unit that controls the development contrast potential difference that determines the flying force of
The development contrast potential difference is a predetermined value. The control range of the development contrast potential difference by the potential difference control unit is a value within a first range that is predetermined from an upper limit value and a predetermined value that is greater than or equal to a lower limit value. When the value is within the second range, the image forming unit forms a first toner band that is different from both the image signal toner image corresponding to the image signal and the patch toner image. An image forming apparatus comprising: a band formation control unit that increases consumption. The band formation control unit increases the toner consumption by increasing the length of the first toner band formed on the image forming unit in the direction in which the image carrier holds and moves the toner image. the image forming apparatus according to claim 1 Symbol mounting, characterized in that one which. 3. The image formation according to claim 1, wherein the band formation control unit increases toner consumption by increasing an image density of the first toner band formed on the image formation unit. apparatus. The banding controller, 3 any one of claims 1, characterized in that by increasing the frequency of forming the first toner band to the image forming section is intended to increase the consumption of toner The image forming apparatus described. The band formation control unit forms the patch toner image this time after the development contrast potential is not a predetermined value and the potential control unit causes the image formation unit to form the patch toner image last time. When the average image density of the toner image formed by the image forming unit is less than a predetermined image density, a second toner band is formed in the image forming unit, and the development contrast potential difference Is a predetermined value, the amount of toner consumption is increased by causing the image forming unit to form the first toner band that consumes more toner than the second toner band. The image forming apparatus according to claim 1. A control device for controlling an image forming apparatus,
The image forming apparatus includes:
An image carrier for holding a toner image formed on the surface;
An image forming unit that forms a toner image by flying toner on the image carrier;
A detection unit for detecting the density of the toner image formed by the image forming unit;
A signal image formation control unit which receives an input of an image signal and causes the image forming unit to form an image signal toner image corresponding to the image signal;
A patch toner image having a predetermined image density is formed on the image forming unit, and toner on the image holding member in the image forming unit is determined according to a detection result of the patch toner image by the detection unit. And a potential difference control unit that controls the development contrast potential difference that determines the flying force of
This controller is
The development contrast potential difference controlled by the potential difference control unit is a predetermined value, and the value within the first range predetermined from the upper limit value and the lower limit of the control range of the development contrast potential difference by the potential difference control unit When the value falls within a predetermined second range equal to or greater than the value , a toner band different from both the image signal toner image corresponding to the image signal and the patch toner image is formed in the image forming unit. A control device comprising a band formation control unit that increases the amount of toner consumed by the operation. A program that is incorporated in a computer communicably connected to an image forming apparatus and causes the computer to function as a control device that controls the image forming apparatus,
The image forming apparatus includes:
An image carrier for holding a toner image formed on the surface;
An image forming unit that forms a toner image by flying toner on the image carrier;
A detection unit for detecting the density of the toner image formed by the image forming unit;
A signal image formation control unit which receives an input of an image signal and causes the image forming unit to form an image signal toner image corresponding to the image signal;
A patch toner image having a predetermined image density is formed on the image forming unit, and the toner on the image carrier in the image forming unit is detected according to a detection result of the patch toner image by the detection unit. A potential difference control unit that controls the development contrast potential difference that determines the flying force;
This program
The development contrast potential difference controlled by the potential difference control unit is a predetermined value, and the value within the first range predetermined from the upper limit value and the lower limit of the control range of the development contrast potential difference by the potential difference control unit When the value falls within a predetermined second range equal to or greater than the value , a toner band different from both the image signal toner image corresponding to the image signal and the patch toner image is formed in the image forming unit. A program for functioning as a band formation control unit that increases the amount of toner consumed by the toner.

Images