JP2017075996A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can avoid an increase in the number of components due to installation of a mechanical detection sensor to detect the rotational attitude of a rotator.SOLUTION: An image forming apparatus comprises: image formation control means that executes image formation control of forming toner images with an image forming part including photoreceptors being rotators; rotational attitude detection means that detects the rotational attitude of the photoreceptors; image density detection means that detects the density of an image of a toner pattern for detecting unevenness in the density of images formed by the image forming part; and density unevenness information calculation means that calculates density unevenness information on periodical unevenness in the density of the images occurring at the rotational period of the photoreceptors on the basis of a result of detection performed by the rotational attitude detection means and a result of detection performed by the image density detection means. The rotational attitude detection means detects the rotational attitude of the photoreceptors on the basis of a result of measurement of photoreceptor motor torque that is a characteristic value changing at the same period as the rotational period of the photoreceptors.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image forming apparatus.

  Conventionally, as an image forming apparatus, based on a detection result of a rotation attitude detection unit that detects a rotation attitude of a rotary body such as a latent image carrier or a developer carrier, and a detection result of a toner pattern for detecting image density unevenness There is one that detects periodic image density unevenness that occurs in the rotation period of a rotating body.

  As an image forming apparatus of this type, Patent Document 1 discloses, as a rotation attitude detection unit, a detected object that moves around in unison with the rotation of a rotating body, and a photo interrupter that detects that it passes through a detection area. The structure provided with the rotation attitude | position detection sensor comprised is described.

  However, in the rotation posture detection means described in Patent Document 1, it is necessary to install a mechanical rotation posture detection sensor, which may lead to an increase in the number of parts and an increase in manufacturing cost by providing the rotation posture detection sensor. .

  In order to solve the above-described problem, the invention of claim 1 is directed to an image formation control unit that executes image formation control by an image forming unit including a rotator, and a rotation posture detection unit that detects a rotation posture of the rotator. The image density detecting means for detecting the image density of the toner pattern for detecting the density unevenness of the image formed by the image forming section, the detection result of the rotation posture detecting means and the detection result of the image density detecting means, In the image forming apparatus having density unevenness information calculating means for calculating density unevenness information of periodic image density unevenness generated in the rotation cycle of the rotating body, the rotation posture detecting means has the same cycle as the rotation cycle of the rotating body. The rotational posture of the rotating body is detected based on the measurement result of the characteristic value that changes in step (a).

  According to the present invention, there is an excellent effect that it is possible to avoid an increase in the number of parts due to the installation of a mechanical detection sensor in order to detect the rotational posture of the rotating body.

6 is a graph showing the relationship between fluctuations in the motor torque of the photoreceptor and the rotational position detection signal. 1 is a schematic configuration diagram of a copying machine. Schematic explanatory drawing of an image forming part. FIG. 3 is a block diagram illustrating an example of a main configuration of a control system of a copying machine. The block diagram of the toner adhesion amount sensor for black. FIG. 3 is a configuration diagram of a color toner adhesion amount sensor. 6 is a flowchart showing a flow of image forming condition determination processing in the copying machine. FIG. 4 is an explanatory diagram illustrating an example in which a toner pattern of each color is detected by a single toner adhesion amount sensor. FIG. 4 is an explanatory diagram illustrating an example in which toner patterns of respective colors are detected by different toner adhesion amount sensors. FIG. 4 is an explanatory diagram illustrating an example of a relationship between a photoreceptor rotation position detection signal and a toner adhesion amount detection signal. FIG. 4 is an explanatory diagram showing a flow from acquiring a toner adhesion amount detection signal and a rotational position detection signal to obtaining density unevenness information. The graph which shows the difference in the density nonuniformity information of the 1st to 3rd week resulting from a measurement error. FIG. 4 is an explanatory diagram illustrating an example of a relationship between a rotation position detection signal and a toner adhesion amount detection signal and image forming conditions determined based on these signals.

Hereinafter, an embodiment of an electrophotographic color laser copying machine (hereinafter simply referred to as a copying machine 500) employing a tandem type intermediate transfer system will be described as an image forming apparatus to which the present invention is applied.
FIG. 2 is a schematic configuration diagram of the copying machine 500. In FIG. 2, reference numeral “100” denotes a copying machine main body, reference numeral “200” denotes a paper feeding device on which the copying machine main body 100 is placed, and reference numeral “300” denotes a scanner attached to the upper portion of the copying machine main body 100. Reference numeral “400” denotes an automatic document feeder (ADF) mounted on the scanner 300.

  The copying machine main body 100 is provided with an intermediate transfer belt 10 formed of an endless belt as an intermediate transfer member at the center thereof. The intermediate transfer belt 10 is stretched around support rollers (14, 15, 16) as three support rotating bodies, and rotates in the clockwise direction (arrow A direction) in FIG.

  An intermediate transfer belt cleaning device 17 for removing residual toner remaining on the intermediate transfer belt 10 after image transfer is provided on the left side of the second support roller 15 in FIG. 2 among the three support rollers. Of the three support rollers, the belt portion stretched between the first support roller 14 and the second support roller 15 has yellow (Y), magenta (M), cyan (C) along the belt moving direction. ), Four image forming portions 18 (Y, M, C, K) of black (K) are arranged to face each other. These four image forming units 18 (Y, M, C, K) constitute a tandem type image forming unit 20 as image forming means. In the copying machine 500, the third support roller 16 is a driving roller. An exposure device 21 as an exposure unit is provided above the image forming unit 20.

  On the opposite side of the image forming unit 20 with the intermediate transfer belt 10 interposed therebetween, a secondary transfer device 22 as a second transfer unit is provided. In the secondary transfer device 22, a transfer conveyance belt 24, which is an endless belt as a transfer sheet conveyance member, is stretched between two rollers (231, 232). The transfer conveying belt 24 is provided so as to be pressed against the third support roller 16 via the intermediate transfer belt 10. The toner image on the intermediate transfer belt 10 is transferred to the transfer sheet S as a recording medium by the secondary transfer device 22. The surface of the transfer conveyance belt 24 is cleaned by a conveyance belt cleaning device 170.

  A tension roller 311 is provided inside the intermediate transfer belt 10 between the first support roller 14 and the third support roller 16. A toner adhesion amount sensor 310 as an image density detection unit is disposed on the outer portion of the intermediate transfer belt 10 facing the tension roller 311.

A fixing device 25 for fixing the toner image transferred onto the transfer sheet S is provided on the left side of the secondary transfer device 22 in FIG. The fixing device 25 has a configuration in which a pressure roller 27 is pressed against a fixing belt 26 that is a heated endless belt.
The secondary transfer device 22 also has a sheet conveyance function for conveying the transfer sheet S after transferring the toner image from the intermediate transfer belt 10 to the transfer sheet S to the fixing device 25. Below the secondary transfer device 22 and the fixing device 25, a sheet reversing device 28 for reversing the transfer sheet S so as to record images on both sides of the transfer sheet S is provided.

  When copying using the copying machine 500, a document is set on the document table 30 of the automatic document feeder 400. Alternatively, the automatic document feeder 400 is opened, a document is set on the contact glass 32 of the scanner 300, and the automatic document feeder 400 is closed and pressed by it. Thereafter, when the start switch is pressed, when the document is set on the automatic document feeder 400, the document is transported and moved onto the contact glass 32. When an original is set on the contact glass 32, the scanner 300 is immediately driven. Next, the first traveling body 33 and the second traveling body 34 are caused to travel.

Light is emitted from the light source of the first traveling body 33 and reflected light from the document surface is reflected toward the second traveling body 34 by the mirror of the first traveling body 33. The light reflected by the mirror of the second traveling body 34 enters the reading sensor 36 through the imaging lens 35 and the contents of the original are read.
In parallel with this document reading operation, the third support roller 16 is rotationally driven by an intermediate transfer belt drive motor which is a drive source of the intermediate transfer belt 10. As a result, the intermediate transfer belt 10 moves in the clockwise direction in FIG. 2, and the remaining two support rollers (14, 15) (driven rollers) rotate along with the movement.

  At the same time, the drum-shaped photosensitive member 40 (Y, M, C, K) as a latent image carrier is rotated in each image forming unit 18 (Y, M, C, K). Then, each individual photoconductor 40 (Y, M, C, K) is exposed and developed using color-specific information for yellow, magenta, cyan, and black, thereby forming a monochromatic toner image (visual image) ( Visualize).

The toner images on the individual photoreceptors 40 (Y, M, C, and K) are sequentially transferred onto the intermediate transfer belt 10 so as to overlap each other, thereby forming a composite color toner image on the intermediate transfer belt 10.
In parallel with the image formation described above, one of the paper feeding rollers 42 of the paper feeding device 200 is selectively rotated to feed the transfer sheet S from one of the paper feeding cassettes 44 provided in the paper bank 43 in multiple stages. Then, the paper is separated one by one by the separation roller 45 and put into the paper feed path 46. The transfer sheet S in the paper feed path 46 is transported by the transport roller 47 and guided to the paper feed path in the copying machine main body 100, and is abutted against the registration roller pair 49 and stopped. Alternatively, the manual sheet feeding roller 50 is rotated, the transfer sheet S on the manual tray 51 is fed out, separated one by one by the manual separation roller 52, put into the manual sheet feeding path 53, and also abutted against the registration roller pair 49. stop.

  The registration roller pair 49 is rotated in synchronization with the composite color toner image on the intermediate transfer belt 10, the transfer sheet S is sent between the intermediate transfer belt 10 and the secondary transfer device 22, and transferred by the secondary transfer device 22. A color toner image is transferred onto the sheet S. After the toner image is transferred, the transfer sheet S is transported by the transfer transport belt 24 and sent to the fixing device 25. The fixing device 25 applies heat and pressure to the transfer toner image by the fixing belt 26 and the pressure roller 27. To fix. After fixing, the transfer sheet S is switched by the switching claw 55 and discharged by the discharge roller pair 56 and stacked on the discharge tray 57. Alternatively, it is switched by the switching claw 55 and put into the sheet reversing device 28, where it is reversed and guided again to the transfer position, and after the toner image is recorded on the back surface, it is discharged onto the discharge tray 57 by the discharge roller pair 56.

  After the toner image is transferred, the intermediate transfer belt 10 removes residual toner by the intermediate transfer belt cleaning device 17 and prepares for image formation by the image forming unit 20 again. In general, the registration roller pair 49 is often used while being grounded, but a bias can be applied to remove the paper dust of the transfer sheet S.

  The four image forming units 18 (Y, M, C, and K) have substantially the same configuration except that the colors of the toners to be used are different from each other. Therefore, “Y” that indicates the color of the toner to be used will be described below. , “M”, “C”, and “K” are appropriately omitted.

FIG. 3 is a schematic explanatory diagram of the image forming unit 18.
The image forming unit 18 has a charging roller 60 as a charging unit, a potential sensor 70 as a latent image potential detecting unit, a developing device 61 as a developing unit, a photoconductor cleaning device 63, and a charge removing device around the photoconductor 40. It has.
At the time of image formation, the photosensitive member 40 is rotated in the direction of arrow B by the photosensitive member driving motor 401. After the surface of the photoconductor 40 is uniformly charged by the charging roller 60, image data such as the above-described original document from the exposure device 21 is exposed with the exposure light L to form an electrostatic latent image on the surface of the photoconductor 40. .

The color image signal based on the image data from the scanner 300 is subjected to image processing such as color conversion processing in an image processing unit, and is output to the exposure device 21 as an image signal of each color of Y, M, C, and K. The exposure device 21 converts the image signal of each color from the image processing unit into an optical signal, and scans and exposes the uniformly charged surface of each photoconductor 40 based on the optical signal, thereby exposing the electrostatic latent image. Form an image.
A developing bias is applied to the developing roller 61a as a developer carrying member of the developing device 61, and a developing potential that is a potential difference is formed between the electrostatic latent image on the photosensitive member 40 and the developing roller 61a. . The toner on the developing roller 61a is transferred from the developing roller 61a to the electrostatic latent image on the photoconductor 40 by this developing potential, whereby the electrostatic latent image is developed and a toner image is formed.

A toner concentration sensor 312 is provided on the bottom surface below the developer conveying screw 61b in the developing device 61, and the toner concentration can be detected at any time.
The toner image formed on the photoreceptor 40 is primarily transferred onto the intermediate transfer belt 10 by a primary transfer device 62 (see FIG. 2) as a first transfer unit. After the toner image is transferred, the surface of the photoconductor 40 is cleaned of residual toner by the photoconductor cleaning device 63 and is discharged by the static eliminator to prepare for the next image formation.
The toner images formed on the surfaces of the individual photoreceptors 40 are primarily transferred while being superimposed on the intermediate transfer belt 10.

  The copying machine main body 100 includes a photosensitive member driving motor control unit 71 that controls driving of a photosensitive member driving motor 401 that is a driving source of the photosensitive member 40, and drives a developing roller driving motor 610 that is a driving source of the developing roller 61a. A developing roller drive motor control unit 72 is provided. Each of the four image forming units 18 includes a photosensitive member driving motor 401, a photosensitive member driving motor control unit 71, a developing roller driving motor 610, and a developing roller driving motor control unit 72.

In recent electrophotographic image forming apparatuses, there is an increasing demand for image quality, and in particular, reduction of uneven density in a page of a printed image is one of the problems. The unevenness in density includes those caused by various factors such as exposure and charging. In the copying machine 500 according to this embodiment, the non-uniformity is generated at the rotation cycle of the photosensitive member 40 and the rotation cycle of the developing roller 61a in the sub-scanning direction. Image density unevenness.
This image density unevenness is caused by the fact that the electric field between the photoconductor 40 and the developing roller 61a fluctuates due to rotational fluctuation and sensitivity unevenness of the photoconductor 40 and the developing roller 61a, and the toner adhesion amount changes periodically. ing.

  As a method for improving this, a method of performing control to periodically modulate image forming conditions such as a developing bias and a charging bias so as to cancel periodic electric field fluctuations due to rotational fluctuation and sensitivity unevenness of the photoreceptor 40 and the developing roller 61a. There is. By this method, image density unevenness in the rotation period of the rotating body such as the photoconductor 40 and the developing roller 61a is reduced.

As described above, in the conventional image forming apparatus that performs control to periodically modulate the image forming conditions, the rotation posture detection sensor that detects the rotation positions of the photosensitive member and the developing roller, and the toner adhesion amount on the intermediate transfer belt are detected. A toner adhesion amount sensor is attached. When executing control for periodically modulating the image forming conditions, first, a toner image having a predetermined image pattern is formed, and the photosensitive body (or developing roller) cycle is determined from the rotation posture detection sensor and the toner adhesion amount sensor. The information such as the phase and amplitude of the toner density unevenness that is repeated in step 1 is acquired. Next, the image forming apparatus creates a control table for periodically modulating image forming conditions such as a developing bias and a charging bias based on the information, and controls the image forming conditions according to the table.
However, in the conventional image forming apparatus that performs control to periodically modulate the image forming conditions, it is necessary to provide a mechanical rotation posture detection sensor, which has a problem that leads to an increase in the number of parts and an increase in manufacturing cost. .

  On the other hand, in the copying machine 500 of the present embodiment, the rotational posture of the rotating body is detected based on the measurement result of the motor torque of the rotating body, which is a characteristic value that changes at the same cycle as the rotating cycle of the rotating body. Yes. Thereby, in order to reduce the image density unevenness caused by the rotational shake and sensitivity unevenness of the rotating body such as the photosensitive member or the developing roller, when executing the control for correcting the image forming condition in the rotation cycle of the rotating body, The rotational posture of the rotating body can be detected without using a mechanical rotational position detection sensor. Therefore, the conventional mechanical rotation posture detection sensor becomes unnecessary, and the number of parts and the manufacturing cost can be reduced.

FIG. 4 is a block diagram illustrating an example of a configuration of a main part of the control system of the copying machine 500.
The control unit 80 as a control means is a microcomputer including a CPU (Central Processing Unit) 81 and a ROM (Read Only Memory) 83 as a storage means connected to the CPU 81 via a bus line 82. The control unit 80 also includes a RAM (Random Access Memory) 84, an I / O interface unit 85, and the like.
The control unit 80 forms a toner image corresponding to the image information on the photoconductor 40 by the image forming unit 20 including the photoconductor 40 as a rotating body and the developing roller 61a, and finally forms the toner image with a recording material. Image formation control for transferring onto a certain transfer sheet S is executed.

Various sensors such as a toner adhesion amount sensor 310, a toner concentration sensor 312, and a potential sensor 70 are connected to the control unit 80 via an I / O interface unit 85. Various sensors such as a toner adhesion amount sensor 310, a toner concentration sensor 312, and a potential sensor 70 of the copying machine main body 100 send information detected by each sensor to the control unit 80. Further, a charging bias power source 86 that applies a charging bias to the charging roller 60 and a developing bias power source 87 that applies a developing bias to the developing roller 61 a are connected to the control unit 80 via an I / O interface unit 85. Further, the control unit 80 includes a primary transfer bias power source 88 that applies a predetermined primary transfer bias to the primary transfer device 62, and an exposure that applies a predetermined voltage or supplies a predetermined current to the light source of the exposure device 21. The setting unit 89 is connected via the I / O interface unit 85. The control unit 80 is connected to a paper feeding device 200, a scanner 300, and an automatic document feeder 400 via an I / O interface unit 85. Further, a photosensitive member driving motor control unit 71 and a developing roller driving motor control unit 72 are connected to the control unit 80 via an I / O interface unit 85.
The control unit 80 controls each unit based on control target values of image forming conditions (for example, charging bias, developing bias, exposure amount, primary transfer bias, etc.).

For example, the ROM 83 or the RAM 84 stores a conversion table that stores information related to conversion of the output value of the toner density sensor 312 to the toner adhesion amount per unit area. The ROM 83 or RAM 84 also has control targets for image forming conditions (for example, charging bias, developing bias, exposure amount, primary transfer bias) of the individual image forming units 18 (Y, M, C, K) in the copying machine 500. A value is stored.
The control unit 80 may be configured using, for example, an IC or the like as a semiconductor circuit element manufactured for control in the copying machine 500, instead of a computer device such as a microcomputer.

The configuration of the toner adhesion amount sensor 310 will be described with reference to FIGS.
FIG. 5 shows the configuration of the black toner adhesion amount sensor 310K, and FIG. 6 shows the configuration of the color toner adhesion amount sensor 310T.

  As shown in FIG. 5, the black toner adhesion amount sensor 310K includes a light emitting element 310a made of a light emitting diode (LED) or the like, and a regular reflection light receiving element 310b that receives regular reflection light. The light emitting element 310 a irradiates light on the intermediate transfer belt 10, and the irradiated light is reflected on the surface of the intermediate transfer belt 10. The regular reflection light receiving element 310b receives regular reflection light of the reflected light.

  As shown in FIG. 6, the color toner adhesion amount sensor 310T includes a light emitting element 310a made of a light emitting diode (LED) or the like, a regular reflection light receiving element 310b that receives specular reflection light, and a diffuse reflection that receives diffuse reflection light. A light receiving element 310c. The light emitting element 310a irradiates light onto the intermediate transfer belt 10 as in the case of the black toner adhesion amount sensor 310K, and this irradiation light is reflected by the surface of the intermediate transfer belt 10. The regular reflection light receiving element 310b receives regular reflection light of the reflected light, and the diffuse reflection light receiving element 310c receives diffuse reflection light of the reflected light.

  In the copying machine 500, a GaAs infrared light emitting diode having a peak wavelength of emitted light of 950 [nm] is used as the light emitting element 310a. Further, as the regular reflection light receiving element 310b and the diffuse reflection light receiving element 310c, Si phototransistors having a peak light receiving sensitivity of 800 [nm] are used. The light emitting element 310a and the light receiving elements (310b, 310c) may have different peak wavelengths and peak light receiving sensitivity.

The black toner adhesion amount sensor 310K and the color toner adhesion amount sensor 310T are disposed with a distance (detection distance) of about 5 mm between the belt surface of the intermediate transfer belt 10 which is a detection target. Has been. In the copying machine 500, the toner adhesion amount sensor 310 is provided in the vicinity of the surface of the intermediate transfer belt 10, and image forming conditions are determined based on the toner adhesion amount on the intermediate transfer belt 10. The toner adhesion amount sensor 310 may be disposed near the surface of each photoconductor 40 (Y, M, C, K) or near the surface of the transfer conveyance belt 24.
The output from the toner adhesion amount sensor 310 is converted into an adhesion amount by an adhesion amount conversion algorithm. The adhesion amount conversion algorithm is the same as in the prior art.

FIG. 7 is a flowchart showing the flow of image forming condition determination processing in the copying machine 500.
First, the control unit 80 as the first image forming condition determining unit forms a first toner image pattern (S1) as shown in FIG. The amount is detected (S2-1).

At the same time, as will be described in detail later, the photoconductor 40, which is a rotating body, based on the motor drive current that drives the motors (401, 610) by the photoconductor drive motor controller 71 and the developing roller drive motor controller 72. Then, the rotational position of the developing roller 61a is detected (S2-2). In the copying machine 500, the rotation position is detected from the measurement result of the motor torque, which is a characteristic value that changes at the same period as the rotation period of the rotating body, without using the rotation position detection sensor.
From these detection results, density unevenness information between the rotation cycle of the photoconductor 40 (Y, M, C, K) and the rotation cycle of the developing roller 61a (Y, M, C, K) at the time of creating the first toner image pattern. Is detected (described later with reference to FIGS. 10 and 11).

Based on this detection result, a first image forming condition is calculated, and a control table is created (S3). Based on the determined first image forming condition, the control unit 80 as the first control unit controls the image forming unit (S4).
Next, in a state where the first image forming condition of the copying machine is reflected, that is, in a state where the image forming means is controlled based on the first image forming condition, the control unit 80 as the second image forming condition determining means is Then, as shown in FIG. 8 or FIG. 9 described later, a second toner image pattern is formed (S5). Then, similarly to the formation of the first toner image pattern, the toner adhesion amount is detected by the toner adhesion amount sensor 310 (S6-1).

At the same time, as in the formation of the first toner image pattern, the rotational positions of the photosensitive member 40 and the developing roller 61a, which are rotating members, are detected (S6-2).
From these detection results, density unevenness between the rotation cycle of the photoconductor 40 (Y, M, C, K) and the rotation cycle of the developing roller 61a (Y, M, C, K) when the second toner image pattern is created. Information is detected (S7). Based on this detection result, a second image forming condition is calculated, and a control table is created (S8).
Then, image forming condition correction control is performed during printing using the detected rotation position detection signal and the calculated first and second image forming conditions.
The operation of each step in FIG. 7 will be specifically described below.

8 and 9 are explanatory diagrams illustrating an example of a toner image pattern for detecting uneven image density.
FIG. 8 is an explanatory diagram of an example in which the toner adhesion amount of the toner image pattern is detected using only one toner adhesion amount sensor 310, and each color toner pattern is detected by a single toner adhesion amount sensor 310. It is explanatory drawing which shows an example. A belt-shaped single density toner image pattern “TPK” or “TPC” of each color in the detection region of the toner adhesion amount sensor 310 disposed in the center in the width direction orthogonal to the moving direction of the intermediate transfer belt 10 indicated by an arrow A. , “TPM” and “TPY” are sequentially formed to detect density unevenness.
The length of each toner image pattern is at least one period of each photoconductor circumferential length DL in order to calculate variations in density unevenness information described later.

FIG. 9 is an explanatory diagram of an example in which the toner adhesion amount of the toner image pattern is detected using a plurality of toner adhesion amount sensors 310, and shows an example in which the toner pattern of each color is detected by different toner adhesion amount sensors 310. It is explanatory drawing. In the configuration shown in FIG. 9, the toner adhesion amount sensors 310 (Y, M, C, K) of the respective colors are arranged at intervals in the width direction orthogonal to the moving direction of the intermediate transfer belt 10. A toner image pattern corresponding to each detection region of each toner adhesion amount sensor 310 (Y, M, C, K) is formed, and density unevenness is detected.
In this case as well, as in the case of FIG. 8, the toner image pattern is a single band-shaped density pattern, and has a length of at least one period of each photoconductor circumference DL.

  The arrangement positions of the individual potential sensors 70 (Y, M, C, K) in the width direction with respect to the individual photoreceptors 40 (Y, M, C, K) are the toner adhesion amount sensors 310 (Y, M, C, K). ) In the width direction. As shown in FIG. 8, when the toner adhesion amount sensor 310 is single, the arrangement position of each potential sensor 70 (Y, M, C, K) in the width direction corresponds to the position of the toner adhesion amount sensor 310. The center portion thus made becomes the arrangement position.

  The first toner image pattern is a single density pattern, which is a so-called solid image pattern. The second toner image pattern is a halftone single density pattern having a lower density than the first toner image pattern. The shapes of the first toner image pattern and the second toner image pattern in the present embodiment are the shapes shown in FIG. 8 or FIG.

In the copying machine 500, based on the detection result of the first toner image pattern that is a solid image, a control table of at least one of the developing bias and the exposure power is created as the first image forming condition. Further, based on the detection result of the second toner image pattern, which is a halftone image, a charging bias control table is created as the second image forming condition.
In the copying machine 500, first, a first toner image pattern of a solid image is formed, and a control table for developing bias or exposure power is created. Next, with the development bias or exposure power control table applied, a second toner image pattern of a halftone image is formed to create a charging bias control table. Since this method also modulates the charging bias, density unevenness due to control is less likely to occur even in halftones where the background potential is dominant, and image density unevenness can be reduced regardless of image density.

FIG. 1 is a graph showing the relationship between fluctuations in the motor torque of the photoreceptor and the rotational position detection signal.
As the output of the rotation posture detection sensor used in the conventional image density unevenness reduction control described in Patent Document 1 and the like, the output is repeated at the rotation cycle of the photosensitive member as shown in the upper graph of FIG. Here, for example, information on the rotation position (rotation posture) of the photoconductor can be obtained with reference to a point where the output is rapidly decreased.

The lower graph in FIG. 1 shows an example of a measurement result of torque fluctuation of the photosensitive member driving motor 401 when the photosensitive member 40 is driven in the copying machine 500. The drive torque of the photoconductor drive motor 401 is
It fluctuates at the same cycle as the rotation cycle of the photoconductor 40 due to the rotational shake of the photoconductor 40 or the like. The photoconductor drive motor controller 71 controls the current value applied to the photoconductor drive motor 401 so that the photoconductor 40 rotates at a constant speed even if the drive torque of the photoconductor drive motor 401 varies. When the driving torque of the photosensitive member driving motor 401 increases, the current value of the photosensitive member driving motor 401 also increases. Therefore, by measuring this current value, the fluctuation of the photosensitive member motor torque that is the driving torque of the photosensitive member driving motor 401 is measured. Can be measured.

  The photoconductor motor torque fluctuates at the same cycle as the rotation cycle of the photoconductor 40. In the copying machine 500, instead of the output of the rotation attitude detection sensor that obtains the upper graph in FIG. 1, a characteristic value that fluctuates in the same period as the rotation period of the rotating body, such as a photoconductor motor torque, is used to form an image. Condition correction control is performed. For example, if the peak position of the output shown in the lower graph in FIG. 1 is specified and that position is used as a reference, information on the rotational position (rotational attitude) of the photoconductor is obtained in the same manner as the output of the rotational attitude detection sensor. be able to. Therefore, based on the current value applied to the photoconductor drive motor 401 by the photoconductor drive motor control unit 71, the control unit 80 can calculate a rotational position detection signal as shown by the upper graph in FIG.

  Here, the torque of the photoconductor drive motor 401 is taken as an example of the characteristic value that changes in the same cycle as the rotation cycle of the photoconductor 40. However, if the characteristic value changes in the same cycle as the rotation cycle of the photoconductor 40. The rotational position may be detected using the characteristic value. Although the example of the photoconductor 40 has been described here, the rotation position of the developing roller 61a is detected based on the characteristic value (torque of the developing roller drive motor 610) that changes in the same cycle as the rotation cycle. To do.

FIG. 10 shows a photosensitive member rotation position detection signal (upper) calculated based on torque fluctuations of the photosensitive member driving motor 401 when a toner image pattern for detecting image density unevenness is formed, and a toner adhesion amount sensor 310. 5 is a measurement example of a toner adhesion amount detection signal (lower) detected by the above.
Here, an example of a signal corresponding to three cycles of the circumference of the photoreceptor 40 is shown. As shown in FIG. 10, the toner adhesion amount detection signal fluctuates at the same cycle as the rotation position detection signal. Here, the measurement example of the rotation position detection signal of the photoconductor 40 is shown, but the same measurement example is also performed for the rotation position detection signal of the developing roller 61a.

FIG. 11 shows a flow from obtaining the toner adhesion amount detection signal and the rotation position detection signal of the photosensitive member 40 described with reference to FIG. 10 to obtaining density unevenness information.
In the control unit 80, the toner adhesion amount detection signal (the lower diagram in FIG. 10) can be separated for each rotation cycle of the photoreceptor 40 by using the rotational position detection signal (the upper diagram in FIG. 10) of the photoreceptor 40. For example, in FIG. 10, when the detection start portion (where the output starts to drop) of the rotational position detection signal of the photoconductor 40 is set to time “0”, a signal for one cycle of the photoconductor 40 is taken out and shown in FIG. As described above, the density unevenness information of the rotation cycle of the photoconductor 40 can be acquired for three rounds.

  The density unevenness information (toner adhesion amount detection signal) for a plurality of cycles of the photoreceptor 40 obtained in this way includes measurement errors based on various factors, as shown in FIG. The phase and amplitude in the information vary. The control unit 80 has amplitudes “A1”, “A2”, “A3” and phases “θ1”, “θ2”, “θ” 3 of the toner adhesion amount detection signals for three periods of the photoconductor 40 of FIG. Is calculated. These calculations may be executed using, for example, orthogonal detection processing or fast Fourier transform (FFT) processing.

  The control unit 80 calculates the amplitudes “A1”, “A2”, “A3”... And the phases “θ1”, “θ2”, “θ3”. Is stored in the RAM 84 as amplitude information and position information of density unevenness information. Then, it is used for image forming condition correction control described in FIG.

In the above description, the example in which the phase information and the amplitude information of the density unevenness are acquired from the raw output of the toner adhesion amount detection signal for one period of the photoconductor 40 is shown. The average of the output of the toner adhesion amount detection signals for a plurality of circumferences of the photoconductor 40 may be averaged and processed into data for one cycle, and density unevenness information may be acquired in the same manner as described above.
Further, although the amplitude information of the toner adhesion amount detection signal has been described as density unevenness information, it may be converted into toner adhesion amount to obtain amplitude information.
Further, the acquisition of density unevenness information in the rotation cycle of the photoconductor 40 has been described, but information is also acquired in the same manner for the image density unevenness in the rotation cycle of the developing roller 61a.

The image density unevenness caused by the rotation cycle of the developing roller 61a is shorter than the image density unevenness caused by the rotation cycle of the photoconductor 40, and the density fluctuation amplitude is also small. Therefore, even if the toner adhesion amount detection signal is separated for each rotation cycle of the developing roller 61a as shown in FIG. 12, the density unevenness in the rotation cycle of the developing roller 61a is buried in the density unevenness in the rotation cycle of the photoconductor 40. There is a possibility that the detection error of unevenness information becomes large.
Therefore, when detecting density unevenness information of the rotation cycle of the developing roller 61a, density unevenness information of the rotation cycle of the photoconductor 40 detected by the above-described method is removed from the toner adhesion amount detection signal. And after processing a waveform, you may detect the density nonuniformity information of the rotation period of the developing roller 61a.

FIG. 13 illustrates a rotation position detection signal and a toner adhesion amount detection signal when a toner image pattern for detecting image density unevenness is formed, and an image formation condition (control table) determined by the control unit 80 based on these signals. An example of the relationship is shown.
Here, a measurement example for two cycles of the photoconductor 40 is shown. The toner adhesion amount detection signal fluctuates in the same cycle as that of the rotational position detection signal, and the image forming condition (control table) is determined so as to have an opposite phase to the toner adhesion amount detection signal.
The charge bias, development bias, and exposure power, which are the actual image density control parameters, are negatively signed, or the amount of adhesion decreases as the absolute value increases, so they are expressed uniformly as “reverse phase”. Is not appropriate.
Here, it is expressed as “reverse phase” in the sense that a control table is created in a direction that cancels the fluctuation in the adhesion amount indicated by the toner adhesion amount detection signal, that is, a control table that creates an adhesion amount fluctuation in the opposite phase is created.

The gain for determining the control table, that is, the value [V] of the variation amount of the control table with respect to the variation amount [V] of the toner adhesion amount detection signal is ideally determined from the theoretical value. Desired. However, when an actual machine is installed, it is highly likely that the actual machine will be verified based on theoretical values and ultimately determined from experimental data.
The control table determined with the gain determined in this way has the timing relationship shown in FIG. 13 with the rotational position detection signal. Here, it is assumed that the head of the control table is the time when the rotational position detection signal is generated. If this control table is a development bias control table, it is necessary to determine the application timing of the control table in consideration of the distance between the development nip and the toner adhesion amount sensor 310.

If the distance between the developing nip and the toner adhesion amount sensor 310 is an integral multiple of the circumference of the photoconductor 40, it can be applied from the top of the control table in accordance with the timing of the rotational position detection signal. good.
If the distance between the developing nip and the toner adhesion amount sensor 310 is deviated from an integral multiple of the circumference of the photoconductor 40, the control table may be applied by shifting the timing by the deviation distance. .

So far, the case where the developing bias is periodically changed has been described, but the image forming conditions controlled by the control unit 80 may be exposure power, charging bias, or the like. Similar to the development bias, in the case of an exposure power control table, the control table is applied in consideration of the distance between the exposure position and the toner adhesion amount sensor 310. In the case of the charging bias control table, the control table is applied in consideration of the distance between the charging position and the toner adhesion amount sensor 310.
The copier 500 corrects image forming conditions during printing using the control table thus created and the rotational position detection signal described above, and reduces image density unevenness.

  The image forming condition determination process described above may be performed at a timing at which the rotational position of the photosensitive member 40 (Y, M, C, K) with respect to the copying machine 500 main body can be changed. This timing is immediately after the photosensitive member 40 is set, that is, at the time of initial setting, at the time of replacement, at the time of detachment and the like. This is because, when the photoconductor 40 is mechanically removed from the copying machine 500, there is a high possibility that the occurrence state of image density unevenness in the rotation cycle of the photoconductor 40 will change. There is also a reason that the relationship with the characteristic value used as the rotational position detection signal is shifted.

When initially setting the photosensitive member 40 for which no control table has been created, it is necessary to first create a control table by performing a series of image forming condition determination processes. When the photoconductor 40 is replaced, the control table corresponding to the new photoconductor 40 is recreated because the new photoconductor 40 has a difference in shake characteristics and photosensitivity characteristics compared to the photoconductor 40 used so far. There is a need.
Further, even when the photoreceptor 40 is simply detached for maintenance, there is a possibility that a change in the mounting state of the photoreceptor 40 accompanying the removal of the photoreceptor 40, that is, a change in the deviation between the photoreceptor axis and the rotation axis may occur. is there. In addition, since the relationship between the position of the flare characteristic and photosensitivity characteristic unevenness of the photoconductor 40 and the characteristic value used as the rotational position detection signal described above is deviated, it is necessary to recreate the control table.

For the reasons described above, it is necessary to perform image formation condition determination processing (control table creation / update) immediately after the photosensitive member 40 is set.
The image forming condition determination process may be performed at a printing interval of a certain number of recording media. Thus, even when the detected density unevenness information changes with time, it can be updated to an optimal control table.

  Image forming condition determination processing may be performed when environmental conditions in the apparatus change. Of the environmental conditions, particularly when the temperature condition changes, the tube of the photoconductor 40 expands and contracts in accordance with the thermal expansion coefficient of the tube of the photoconductor 40. For this reason, there is a possibility that the occurrence of density unevenness changes due to changes in the profile of the photoreceptor 40 and changes in the development gap fluctuation.

  In order to cope with this change, it is necessary to perform image formation condition determination processing (control table creation / update) when environmental conditions change. As a method for determining the trigger, for example, a method may be used in which there is a temperature change of N [deg] or more as compared to the previous execution of the image forming condition determination process (control table creation / update). Thereby, even when the detected density unevenness information changes due to a change in environmental conditions, it can be updated to an optimal control table.

  The configuration for detecting the rotation posture of the rotating body based on the measurement result of the characteristic value that changes at the same cycle as the rotation cycle of the rotating body is not limited to the configuration of the above-described embodiment.

  What was demonstrated above is an example, and there exists an effect peculiar for every following aspect.

(Aspect A)
Image forming control means such as a control unit 80 for performing image formation control by an image forming unit such as the image forming unit 20 including a rotating body such as the photosensitive member 40 or the developing roller 61a, and a control unit for detecting the rotation posture of the rotating body. Rotating posture detecting means such as 80 and a toner adhesion amount sensor 310 for detecting the image density of the toner pattern for detecting unevenness in image density such as the first toner image pattern and the second toner image pattern formed by the image forming unit The control unit 80 calculates density unevenness information of periodic image density unevenness generated in the rotation cycle of the rotating body based on the detection result of the image density detection means, the detection result of the rotation posture detection means, and the detection result of the image density detection means. In an image forming apparatus such as a copier 500 having density unevenness information calculation means such as a photoconductor driving mode, the rotation posture detection means is a photoconductor drive mode that changes at the same cycle as the rotation cycle of the rotary body. 401 or for detecting the rotational position of the rotating body on the basis of the measurement results of the characteristic value of the motor torque or the like of the developing roller drive motor 610.
According to this, as described in the above embodiment, in order to detect the rotation posture of the rotating body, the detection result of the characteristic value that changes in the same cycle as the rotation cycle of the rotating body is used. The rotational posture of the rotating body can be detected without using a detection sensor. Therefore, it is possible to avoid an increase in the number of parts due to the installation of a mechanical detection sensor for detecting the rotational posture of the rotating body.

(Aspect B)
In the aspect A, the characteristic value is determined by the rotating body control means such as the photosensitive member driving motor control unit 71 or the developing roller driving motor control unit 72 that controls the rotation of the rotating body such as the photosensitive member 40 or the developing roller 61a. Fluctuation values of driving torque and the like in a rotating body control system (photosensitive member driving motor 401 and photosensitive member driving motor control unit 71, developing roller driving motor 610 and developing roller driving motor control unit 72, etc.) that performs control to rotate at a constant speed. It is.
According to this, as described in the above embodiment, it is possible to realize a configuration for detecting the rotational posture of the rotating body without installing a mechanical detection sensor.

(Aspect C)
In either aspect A or B, the characteristic value is a driving torque of a driving source of a rotating body such as the photosensitive member driving motor 401 or the developing roller driving motor 610.
According to this, as described in the above embodiment, it is possible to realize a configuration in which a characteristic value that changes at the same cycle as the rotation cycle of the rotating body such as the photoconductor 40 or the developing roller 61a is measured.

(Aspect D)
In any one of the aspects A to C, the density unevenness information is the amplitude information “A1”, “A2” of periodic image density unevenness generated in the rotation cycle of the rotating body such as the photoconductor 40 or the developing roller 61a, This includes at least one of “A3”... And phase information “θ1”, “θ2”, “θ3”.
According to this, as described in the above embodiment, it is possible to obtain amplitude information and phase information for the image density unevenness of the rotation period of the rotator, and to prevent periodic image density unevenness that occurs in the rotation period of the rotator. It can be reduced appropriately.

(Aspect E)
In any one of the aspects A to D, the density unevenness information is information obtained by detecting image density unevenness for one period of the rotating body such as the photoconductor 40 or the developing roller 61a, or an image for a plurality of periods of the rotating body. This is information on image density unevenness for one period obtained by averaging density unevenness detected.
According to this, as described in the above embodiment, the density unevenness information of the rotation period of the rotating body is the raw data for one period of density unevenness or the data obtained by averaging the density unevenness for a plurality of periods for one period. Can be obtained from
In the case of a configuration based on raw data for one cycle of density unevenness, the measurement time of density unevenness information is short and toner consumption can be suppressed. Further, in the case of a configuration based on data obtained by averaging density unevenness for a plurality of periods in one period, density unevenness information with higher accuracy can be obtained.

(Aspect F)
In any of the aspects A to E, an image such as an image forming condition determination process for determining an image forming condition for reducing periodic image density unevenness based on a calculation result of the density unevenness information calculating unit such as the control unit 80 The image forming condition determining control unit such as the control unit 80 for performing the forming condition determining control is provided, and the image forming condition determining control unit includes a first image such as a solid image formed as a toner pattern for detecting the first image density unevenness. First image forming conditions such as developing bias or exposure power are determined based on density unevenness information of one toner image pattern, and the first image formed as a toner pattern for detecting second image density unevenness Second image forming conditions such as a charging bias are determined based on density unevenness information of a second image pattern such as a halftone image having a density different from that of the image pattern.
According to this, as described in the above embodiment, it is possible to reduce image density unevenness regardless of the image density.

(Aspect G)
In the aspect F, the first image forming condition is a developing condition such as a developing bias or an exposing condition such as an exposure power.
According to this, as described in the above embodiment, it is possible to modulate the development condition or the exposure condition and reduce the image density unevenness of the solid image.

(Aspect H)
In either embodiment F or G, the second image forming condition is a charging condition such as a charging bias.
According to this, as described in the above embodiment, it is possible to modulate the charging condition and reduce the image density unevenness of the halftone image.

(Aspect I)
In any one of the aspects F to H, the first image pattern is a single density pattern.
According to this, as described in the above embodiment, density unevenness information of a single density pattern can always be obtained.

(Aspect J)
In any one of the aspects F to I, the second image pattern is a single density pattern having an image density lower than that of the first image pattern.
According to this, as described in the above embodiment, by detecting a pattern thinner than the first image pattern, it is possible to obtain density unevenness information with high control accuracy with respect to a halftone image density.

(Aspect K)
In any of the aspects F to J, the image forming condition determination control unit such as the control unit 80 rotates the rotating body such as the photosensitive member 40 or the developing roller 61a detected by the rotation posture detection unit such as the control unit 80. In synchronization with the posture, image formation condition determination control such as image formation condition determination processing and operation control of the image forming unit such as the image forming unit 20 according to the determined image formation condition are performed.
According to this, as described in the above embodiment, the image forming conditions such as the determined control table can be operated at an appropriate timing.

(Aspect L)
In any of the aspects F to K, the image forming condition determining control such as the image forming condition determining process of the image forming condition determining control unit such as the control unit 80 is performed by rotating the rotating member such as the photosensitive member 40 or the developing roller 61a. Execute when posture can change.
According to this, as described in the above embodiment, the image forming condition is corrected in a state where the relationship between the rotational posture of the rotating body and the characteristic value such as the motor torque is shifted due to the change of the rotational posture. It is possible to prevent the control to be performed.

(Aspect M)
In the aspect L, when the rotational posture of the rotating body such as the photoconductor 40 or the developing roller 61a can be changed, at least one of the initial mounting of the rotating body, the replacement of the rotating body, and the attachment / detachment of the rotating body. Time.
According to this, as described for the above-described embodiment, even when a deviation occurs in the relationship between the rotational posture of the rotating body and the characteristic value such as the motor torque at the time of initial mounting, replacement, or removal of the rotating body, The image forming conditions can be appropriately corrected by the image forming condition determination control again.

(Aspect N)
In any of the aspects F to M, the image forming condition determining control such as the image forming condition determining process of the image forming condition determining control unit such as the control unit 80 is performed on the recording material such as the transfer sheet S to which the toner image is transferred. Perform at regular intervals.
According to this, as described in the above embodiment, even when the detected density unevenness information changes with time, it is possible to update the image forming conditions such as an optimal control table.

(Aspect O)
In any one of the aspects F to N, the image forming condition determination control such as the image forming condition determining process of the image forming condition determining control unit such as the control unit 80 is performed according to the environmental condition in the image forming apparatus such as the copying machine 500. This is done at the time of change.
According to this, as described in the above embodiment, even when the detected density unevenness information changes due to a change in environmental conditions, it can be updated to an optimal image forming condition such as a control table.

DESCRIPTION OF SYMBOLS 10 Intermediate transfer belt 14 First support roller 15 Second support roller 16 Third support roller 17 Intermediate transfer belt cleaning device 18 Image forming unit 20 Image forming unit 21 Exposure device 22 Secondary transfer device 24 Transfer conveyance belt 25 Fixing device 26 Fixing Belt 27 Pressure roller 28 Sheet reversing device 30 Document table 32 Contact glass 33 First traveling body 34 Second traveling body 35 Imaging lens 36 Reading sensor 40 Photosensitive body 42 Paper feed roller 43 Paper bank 44 Paper feed cassette 45 Separating roller 46 Paper feed path 47 Conveying roller 49 Registration roller pair 50 Manual paper feed roller 51 Manual feed tray 52 Manual separation roller 53 Manual paper feed path 55 Switching claw 56 Paper discharge roller pair 57 Paper discharge tray 60 Charging roller 61 Developing device 61a Developing roller 61b Developer Conveying screw 62 Primary transfer device 63 Body cleaning device 70 potential sensor 71 photoconductor drive motor controller 72 developing roller drive motor control unit 80 control unit 82 bus lines 83 ROM
84 RAM
85 I / O interface unit 86 Charging bias power source 87 Development bias power source 88 Primary transfer bias power source 89 Exposure setting unit 100 Copying machine main body 170 Conveying belt cleaning device 200 Paper feeding device 300 Scanner 310 Toner adhesion amount sensor 310a Light emitting element 310b Regular reflection light reception Element 310c Diffuse reflection light receiving element 310K Black toner adhesion amount sensor 310T Color toner adhesion amount sensor 311 Tension roller 312 Toner density sensor 400 Automatic document feeder 401 Photoconductor drive motor 500 Copying machine 610 Development roller drive motor DL Photoconductor circumference L Exposure light S Transfer sheet

JP 2014-119713 A

Claims (15)

Image formation control means for executing image formation control by an image forming unit including a rotating body;
A rotation attitude detection means for detecting the rotation attitude of the rotating body;
Image density detecting means for detecting an image density of a toner pattern for detecting unevenness in image density formed by the image forming unit;
Density unevenness information calculating means for calculating density unevenness information of periodic image density unevenness generated in the rotation cycle of the rotating body based on the detection result of the rotation posture detecting means and the detection result of the image density detecting means; In an image forming apparatus having
The image forming apparatus according to claim 1, wherein the rotation posture detection unit detects the rotation posture of the rotating body based on a measurement result of a characteristic value that changes at the same cycle as the rotation cycle of the rotating body. The image forming apparatus according to claim 1.
The image forming apparatus according to claim 1, wherein the characteristic value is a fluctuation value in a control system of the rotating body that performs control of rotating the rotating body at a constant speed by a rotating body control unit that controls rotation of the rotating body. The image forming apparatus according to claim 1, wherein:
The image forming apparatus, wherein the characteristic value is a driving torque of a driving source of the rotating body. The image forming apparatus according to any one of claims 1 to 3,
The image forming apparatus, wherein the density unevenness information includes at least one of amplitude information and phase information of the periodic image density unevenness generated in a rotation cycle of the rotating body. The image forming apparatus according to claim 1,
The density unevenness information is information obtained by detecting image density unevenness for one cycle of the rotating body, or an image for one cycle obtained by averaging image density unevenness for a plurality of cycles of the rotating body. An image forming apparatus comprising density unevenness information. The image forming apparatus according to claim 1,
An image forming condition determining control unit that performs image forming condition determining control for determining an image forming condition for reducing the periodic image density unevenness based on a calculation result of the density unevenness information calculating unit;
The image forming condition determination control means determines a first image forming condition based on the density unevenness information of the first image pattern formed as the first toner pattern for detecting image density unevenness; and The second image forming condition is determined based on the density unevenness information of the second image pattern having a density different from that of the first image pattern formed as the second toner density unevenness detection toner pattern. An image forming apparatus. The image forming apparatus according to claim 6.
The image forming apparatus according to claim 1, wherein the first image forming condition is a developing condition or an exposing condition. The image forming apparatus according to claim 6 or 7,
The image forming apparatus, wherein the second image forming condition is a charging condition. The image forming apparatus according to any one of claims 6 to 8,
The image forming apparatus according to claim 1, wherein the first image pattern is a single density pattern. The image forming apparatus according to any one of claims 6 to 9,
The image forming apparatus, wherein the second image pattern is a single density pattern having an image density lower than that of the first image pattern. The image forming apparatus according to claim 6, wherein:
The image forming condition determination control unit synchronizes with the rotation posture of the rotating body detected by the rotation posture detection unit, and controls the image formation condition determination control and the image forming unit according to the determined image formation condition. An image forming apparatus characterized by controlling the operation of the image forming apparatus. The image forming apparatus according to claim 6,
The image forming condition determining control of the image forming condition determining control unit is executed when the rotation posture of the rotating body can be changed. The image forming apparatus according to claim 12.
When the rotational posture of the rotating body can change,
2. An image forming apparatus according to claim 1, wherein the image forming apparatus is at least one of an initial mounting of the rotating body, an exchange of the rotating body, and an attachment / detachment of the rotating body. The image forming apparatus according to any one of claims 6 to 13,
The image forming condition determining control of the image forming condition determining control means is performed at intervals of a predetermined number of the recording materials to which a toner image is transferred. The image forming apparatus according to any one of claims 6 to 14,
2. The image forming apparatus according to claim 1, wherein the image forming condition determining control of the image forming condition determining control unit is performed when an environmental condition in the image forming apparatus changes.

Images