JP5218163B2 - Image forming apparatus and toner density adjustment program - Google Patents

Description

  The present invention relates to an image forming apparatus and a toner density adjustment program.

  2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer to which an electrophotographic system is applied, a two-component developer composed of a carrier and toner is used. As control (toner concentration control) for maintaining the toner concentration (toner amount / (toner amount + carrier amount)) of the developing unit two-component developer, (A) toner supply control based on image data, and (B) density sensor And toner replenishment control based on the detected patch density value.

  At this time, there is an unstable element in the toner density control (B). Unstable elements include steady-state errors (uncorrected errors) due to density sensor assembly status, density sensor accuracy variations, etc., and provisional errors due to variations in mixing conditions of two-component developer components immediately after shipment or when cartridges are replaced. .

  In Patent Document 1, when the developer is in an initial state, the toner density control level for sensor control is changed to a control level lower than normal toner density control (development bias is changed from 300 V to 380 V). Is disclosed. As a result, the toner adhesion amount at the time of developing the reference pattern is increased, and the toner density is intentionally erroneously detected as being high, and as a result, the toner density is lowered. At the same time, the photosensitive member charging potential is controlled to prevent a decrease in image density.

  In Patent Document 2, when a reference density is stored, the amount of reflected light of the gradation pattern image is measured on the photosensitive member to detect the density, and the density gradation pattern is obtained. In comparison, a technique for correcting charging / exposure / development conditions is disclosed.

  In Patent Document 3, an average value of toner density of a new color developer is obtained by a toner density sensor, and it is determined whether or not the developer is new for each color. The offset value is added to obtain the target value of the toner density of the developer.If the developer is not new, the offset value is added to the average value of the new developer to obtain the target value, and the measurement result measured for each color is obtained. A technique is disclosed in which toner supply is performed when the toner density is lower than the target value compared to the target value, and toner supply is stopped when the toner density is higher.

  In Patent Document 4, two types of developed images having different development conditions are created on a photosensitive member at a predetermined time, and the relationship between the two types of detection values obtained by detecting the densities of the two types of developed images by the density detector. In response to this, a technology including a toner replenishment control unit that controls toner replenishment by the toner replenishing unit is disclosed.

JP 2000-47439 A JP-A-5-035104 JP 2001-66845 A JP 2003-14059 A

  In consideration of the above facts, the present invention does not perform toner density control by the density detection unit until the provisional error is stabilized, and at the start of toner density control by the density detection unit, the toner caused by steady error for each density detection unit The purpose is to avoid concentration fluctuations.

  According to the first aspect of the present invention, the electrostatic latent image formed on the image carrier is developed using a two-component developer composed of two components of toner and carrier stored in the developing unit. An image forming unit that forms an image on a recording sheet, and a toner is supplied to the developing unit based on an image forming amount by the image forming unit, and the toner concentration of the two-component developer stored in the developing unit is set. A density detecting unit reads a density value of a reference image formed by the first toner density adjusting unit and the image forming unit to adjust, and based on the read density value, replenishes toner to the developing unit, A second toner density adjusting means for adjusting the toner density of the two-component developer stored in the developing section; and only the first toner density control means in a preset unstable period of the two-component developer. To adjust the toner density. After the unstable period, the toner density adjustment execution control means for starting the toner density adjustment by the second toner density control means, and the density detection of the reference image by the density detector during the unstable period. And a target density correction unit that corrects a target density at the time of density detection of a reference image by the density detection unit based on a difference between the density value and a target density corresponding to a preset toner density. ing.

  According to a second aspect of the present invention, in the first aspect of the invention, the unstable period is the number of recording sheets on which an image is formed by the predetermined image forming unit, or the predetermined number of the recording sheets. Based on at least one of the number of pixels formed by the image forming means.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the target value density correction means determines in advance a difference between the density value of the reference image and the target density by the density detector. The target density correction is stopped when the target density is equal to or smaller than the set value or when the target density correction is repeated a predetermined number of times.

  According to a fourth aspect of the present invention, there is provided a toner density adjustment program for causing a computer to function as the image forming apparatus according to any one of the first to third aspects.

  According to the first or fourth aspect of the invention, as compared with the case where the present configuration is not provided, the toner density is not controlled by the density detecting unit until the provisional error is stabilized, and the toner density by the density detecting unit is not used. At the start of control, it is possible to avoid toner density fluctuations caused by steady errors for each density detection unit.

  According to the second aspect of the present invention, the toner density control means can be switched as compared with the case where the present configuration is not provided.

  According to the third aspect of the present invention, the target density can be determined with higher accuracy than in the case where the present configuration is not provided.

1 is a schematic diagram of a printer according to an embodiment of the present invention. It is a block diagram which shows the hardware constitutions of the control unit in the printer which concerns on this Embodiment. FIG. 5 is a functional block diagram for patch density detection control in a print control management unit according to the present embodiment. 7 is a flowchart illustrating a toner density detection control routine in a print control management unit according to the present embodiment. 6 is a graph showing a relationship between a patch density and a toner density related to a target value and a detection value according to the present embodiment, and toner density adjustment control.

  FIG. 1 shows a printer 10 as an image forming apparatus. The printer 10 is a digital printer that forms a full-color image or a monochrome image.

  Above the inside of the printer 10, toner cartridges 11Y, 11M, 11C, and 11K that contain yellow (Y), magenta (M), cyan (C), and black (K) toners are replaceably provided. . In the following description, Y, M, C, and K are given to the reference numerals of the members corresponding to the colors of yellow, magenta, cyan, and black (black) for distinction.

  One ends of toner supply paths 13Y, 13M, 13C, and 13K are connected to the toner cartridges 11Y, 11M, 11C, and 11K, respectively. The toner supply paths 13Y, 13M, 13C, and 13K are formed of circular pipe members and are arranged downward along the side surface of the printer 10, but the intermediate paths are not shown. ing.

  Further, in the center of the printer 10, four image forming units 12 (12Y, 12M, 12C, 12K) corresponding to Y, M, C, and K developers are diagonally downward to the right in the front view of FIG. It is arrange | positioned in the state which accumulated a part toward each other.

  The image forming unit 12 includes a photoreceptor 28. Around the photoreceptor 28, a charging roll as an example of a charging device that contacts the surface of the photoreceptor 28 and uniformly charges the photoreceptor 28, and the exposure light L is formed on the photoreceptor 28. A developing unit that develops the electrostatic latent image with each color developer (toner), an erase lamp as an example of a static eliminator that performs static elimination by irradiating the surface of the photoreceptor 28 after transfer, and photosensitivity after static elimination A cleaning unit for cleaning the surface of the body 28 is provided.

  The developer is a mixture of a non-magnetic type toner and a magnetic carrier. Here, the other ends of the toner supply paths 13Y, 13M, 13C, and 13K are connected to the four image forming units 12Y, 12M, 12C, and 12K, respectively, and toner of each color is supplied to each image forming unit 12. It is like that.

  A transfer unit 14 is provided above the image forming units 12Y, 12M, 12C, and 12K. The transfer unit 14 is disposed inside the intermediate transfer belt 16 and the intermediate transfer belt 16, and four primary transfer members that multiplex-transfer the toner images of the image forming units 12 </ b> Y, 12 </ b> M, 12 </ b> C, and 12 </ b> K onto the intermediate transfer belt 16. Primary transfer rolls 18Y, 18M, 18C, and 18K, and a secondary transfer roll 20 that transfers the toner images superimposed on the intermediate transfer belt 16 onto the recording paper P.

  The intermediate transfer belt 16 includes a drive roll 22 that is driven by a motor (not shown), a tension roll 24 that adjusts the tension of the intermediate transfer belt 16, and a backup roll 26 that is disposed to face the secondary transfer roll 20. It is wound around the roller group with a constant tension, and is driven to rotate in the direction of arrow X (counterclockwise direction) in FIG.

  The primary transfer rolls 18Y, 18M, 18C, and 18K are disposed to face the photoreceptors 28 (28Y, 28M, 28C, and 28K) of the respective image forming units 12Y, 12M, 12C, and 12K with the intermediate transfer belt 16 interposed therebetween. . The primary transfer rolls 18Y, 18M, 18C, and 18K are applied with a transfer bias voltage having a polarity opposite to the toner polarity (positive polarity in this embodiment as an example) by a power supply unit (not shown). Yes. The secondary transfer roll 20 is also applied with a transfer bias voltage having a polarity opposite to the toner polarity by the power supply unit.

  A cleaning device 30 is provided on the outer peripheral surface of the intermediate transfer belt 16 where the drive roll 22 is provided. The cleaning device 30 includes a cleaning brush 32 and a cleaning blade 34, and residual toner and paper dust on the intermediate transfer belt 16 are removed by the cleaning brush 32 and the cleaning blade 34.

  In the vicinity of the side surface of the printer 10 opposite to the conveyance path of the recording paper P, a control unit 36 that performs drive control of each part of the printer 10 is provided. An exposure unit that forms an electrostatic latent image by irradiating the surface of the charged photoreceptor 28 with exposure light L (LY, LM, LC, LK) corresponding to each color on the lower side of the image forming unit 12. 40 is provided.

  The exposure unit 40 is composed of one unit common to the four image forming units 12Y, 12M, 12C, and 12K, and modulates four semiconductor lasers (not shown) according to the color material gradation data of each color. Thus, the exposure light LY, LM, LC, LK is emitted from these semiconductor lasers according to the gradation data. Note that the exposure unit 40 may be individually provided in each image forming unit 12.

  The exposure unit 40 is hermetically sealed with a rectangular frame 38, and an fθ lens (not shown) for scanning each exposure light L in the main scanning direction and a polygon mirror 42 are provided therein. On the upper surface of the frame 38, glass windows 44Y, 44M, and 44C for emitting four exposure lights LY, LM, LC, and LK toward the photoreceptors 28 of the image forming units 12Y, 12M, 12C, and 12K. , 44K are provided.

  Here, the exposure light LY, LM, LC, and LK emitted from the semiconductor laser of the exposure unit 40 is applied to the polygon mirror 42, and the light reflected from the polygon mirror 42 is deflected and scanned through the fθ lens. The exposure lights LY, LM, LC, and LK deflected and scanned by the polygon mirror 42 are scanned and exposed to exposure points on the photosensitive member 28 via an optical system (not shown) including an imaging lens and a plurality of mirrors. The

  On the other hand, a paper feed cassette 46 in which the recording paper P is stored is disposed below the exposure unit 40. A sheet conveyance path 50 for conveying the recording sheet P is provided vertically above the end of the sheet feeding cassette 46.

  In the sheet conveyance path 50, a sheet feeding roll 48 that feeds the recording sheet P from the sheet feeding cassette 46, a sheet separating and conveying roll pair 52 that feeds the recording sheet P one by one, and an image on the intermediate transfer belt 16. Is provided with a paper leading edge alignment roll 54 for adjusting the movement timing of the recording paper P and the conveyance timing of the recording paper P. Here, the recording paper P sequentially sent out from the paper feed cassette 46 by the paper feed roll 48 passes through the paper transport path 50 and is secondary to the intermediate transfer belt 16 by the paper tip alignment roll 54 that rotates intermittently. It is once transported to the transfer position and stopped.

  A fixing device 60 is provided above the secondary transfer roll 20. The fixing device 60 includes a heated heating roll 62 and a pressure roll 64 pressed against the heating roll 62. Here, the recording paper P on which the toner image of each color has been transferred by the secondary transfer roll 20 is fixed by heat and pressure at the pressure contact portion between the heating roll 62 and the pressure roll 64, and the recording paper P is transported downstream in the conveyance direction. A discharge roller 66 as an example of a discharge device provided in the printer 10 is discharged to a discharge unit 68 provided in the upper part of the printer 10. Residual toner, paper dust, and the like are removed from the surface of the intermediate transfer belt 16 after the secondary transfer process of the toner image by the cleaning device 30.

  As shown in FIG. 2, the control unit 36 includes a main control unit 70. The main control unit 70 includes a CPU 72, a RAM 74, a ROM 76, an I / O (input / output unit) 78, and a bus 80 such as a data bus or a control bus for connecting them.

  Connected to the I / O 78 is a print control management unit 88 for controlling and managing each processing system such as a transport system in the printer 10, a scanning exposure system for image formation, and a development system.

  More specifically, the print control management unit 88 is connected to the conveyance control unit 100, the scanning exposure control unit 102, the development control unit 104, the transfer control unit 106, and the fixing control unit 108, and manages the control of each unit. .

  The print control management unit 88 may be configured to be directly connected to the bus 80 instead of the I / O 78. Here, the control related to printing is integrated in the print control management unit 88, but the main control unit 70 may execute the control.

  A UI (user interface) 82 is connected to the I / O 78. The UI 82 has a function of receiving an input instruction from the user and notifying the user of information related to image processing. Further, a hard disk 84 is connected to the I / O 78. The I / O 78 is connected to the communication line network 90 via the I / F 86.

  FIG. 3 is a block diagram functionally showing density detection control of the patch 110 (including the raw surface of the intermediate transfer belt 16) in the print control management unit 88. Note that this block diagram is classified according to function to the last, and does not limit the hardware configuration of the print control management unit 88.

  The print control management unit 88 is provided with an image formation execution control unit 114, to which the conveyance control unit 100, the scanning exposure control unit 102, the development control unit 104, the transfer control unit 106, and the fixing control unit 108 are connected. . Hereinafter, the conveyance control unit 100, the scanning exposure control unit 102, the development control unit 104, the transfer control unit 106, and the fixing control unit 108 are collectively referred to as a sub control unit 99. The status of processing by the sub-control unit 99 is sequentially output to the image formation execution control unit 114 as log information.

  The image formation execution control unit 114 is supplied with a patch formation instruction signal during toner density control. The image formation execution control unit 114 controls each of the sub-control units 99 based on the input of the patch formation instruction signal, and forms the patch 110 on the intermediate transfer body 16 at an appropriate time described later.

  Here, a period determination unit 116 is connected to the image formation execution control unit 114. Based on the log information of the image formation execution control unit 114, it is determined whether the toner cartridge 11 is in an unstable period or a stable period.

  After the printer 10 is installed or the toner cartridge 11 is replaced (the initial state of the toner cartridge 11), the toner density varies greatly depending on the stirring state of the toner cartridge 11 and the like. For this reason, a certain period of time (in this embodiment, the number of printed sheets (PV) = 300) is defined as an unstable period from when printing is executed until the developer is stirred and the toner concentration is stabilized. Specifically, the period determination unit 116 determines an unstable period when PV is less than 300 (PV> 300), and determines a stable period when PV is 300 or more (PV ≦ 300).

  The print management control unit 88 also includes a first toner density adjustment control execution unit 118 that controls the toner density based on the amount of printed image data (number of pixels), the density of the formed patch 110, and the target patch density (target And a second toner density adjustment control execution unit 120 that controls the toner density based on the value). Therefore, the toner density adjustment by the second toner density adjustment control execution unit 120 is not executed during the unstable period.

  The period determination unit 116 is connected to the toner density adjustment unit determination unit 122. The period determining unit 116 outputs an identification signal indicating the determined unstable / stable period to the toner density adjusting unit determining unit 122.

  The toner density adjustment means determination unit 122 determines whether the first toner density adjustment control execution unit 118 or the second toner density adjustment control execution unit 120 should execute toner density adjustment based on the identification signal. In addition, the toner density adjustment unit determination unit 122 is connected to the first toner density adjustment control execution unit 118 and the second toner density adjustment control execution unit 120.

  That is, when the identification signal indicates an unstable period, a signal indicating an activation instruction is output to the first toner density adjustment control execution unit 118. On the other hand, when the identification signal indicates a stable period, a signal indicating an activation instruction is output to the first toner density adjustment control execution unit 118 and the second toner density adjustment control execution unit 120.

  When the toner cartridge 11 is in the initial state, the first toner concentration adjustment control execution unit 118 calculates the amount of toner consumed from the amount of image data because the toner concentration in the toner cartridge 11 is known in advance. The toner density control is executed by replenishing the developer based on the amount.

  On the other hand, a density sensor 112 is connected to the development control unit 114 of the sub control unit 99. The second toner density adjustment control execution unit 120 executes toner density control by replenishing the developer based on the density of the patch 110 read by the density sensor 112 and the target patch density (target value). .

  By the way, in the present embodiment, the toner density control in the second toner density adjustment control execution unit 120 is performed only at the stable time, and is not affected by the provisional error due to the toner density variation when the toner cartridge 11 is in the initial state. I am doing so. However, in the case of the second toner density control, it is necessary to eliminate the steady state error for each density sensor 112 due to the assembled state of the density sensor 112, variation in accuracy of the density sensor 112, and the like.

  Here, the toner density adjusting unit determining unit 122 is connected to the target value updating unit 124. The toner density adjustment unit determination unit 122 outputs a target value adjustment instruction to the target value update unit 124 simultaneously with an activation instruction to the first toner density adjustment control execution unit 118.

  At this time, the first toner density adjustment control execution unit 118 is connected to the synchronization control unit 126. The first toner density adjustment control execution unit 118 outputs toner density adjustment execution timing information to the synchronization control unit 126 based on an activation instruction from the toner density adjustment unit determination unit 122.

  The target value update unit 124 and the synchronization control unit 126 are connected, and the subsequent processing is executed in synchronization here.

  The synchronization control unit 126 is connected to the density sensor detection value reading unit 128. The synchronization control unit 126 outputs an instruction to read the detection value of the density sensor 112 based on the information from the first toner density adjustment control execution unit 118.

  The density sensor detection value reading unit 128 is connected to the image formation execution control unit 114. The density sensor detection value reading unit 128 acquires the detection value (patch density) of the density sensor 112 via the image formation execution control unit 114 based on the reading instruction. The density sensor detection value reading unit 128 is connected to the difference Δ calculation unit 130. The density sensor detection value reading unit 128 outputs the detection value to the difference Δ calculation unit 130.

  On the other hand, the target value update unit 124 is connected to the difference Δ calculation unit 130. The target value update unit 124 outputs the current target value, that is, the old target value, to the difference Δ calculation unit 130.

  Here, the old target value from the target value update unit 124 and the detection value from the density sensor detection value reading unit 128 are input to the difference Δ calculation unit 130. The difference Δ calculation unit 130 calculates a difference Δ between the old target value and the detected value. More specifically, the difference Δ is obtained by multiplying the difference between the old target value and the detected value by a coefficient K (Δ = (old target value−detected value) × K).

  The difference Δ calculation unit 130 is connected to the new target value calculation unit 132. The difference Δ calculation unit 130 outputs the calculated Δ value to the new target value calculation unit 132.

  The new target value calculation unit 132 calculates a new target value based on the Δ value. The new target value is calculated by adding the Δ value to the old target value.

  The new target value calculation unit 132 is connected to the target value update unit 124. The new target value calculation unit 132 outputs the calculated new target value to the target value update unit 124. The target value update unit 124 updates the new target value as a new target value.

  Note that each time the toner density control is executed by the first toner density adjustment control execution unit 118, the update process of the target value of the patch density is continued.

  On the other hand, the second toner density adjustment control execution unit 120 is connected to the target value update unit 124. The second toner density adjustment control execution unit 120 reads the current new target value from the target value update unit 124 based on the activation instruction from the toner density adjustment unit determination unit 122. Accordingly, the second toner density adjustment control execution unit 120 executes toner density control based on the new target value and the detection value of the density sensor 112.

  The operation of this embodiment will be described below.

(Image formation procedure)
The image data is further converted into color material gradation data of four colors of yellow (Y), magenta (M), cyan (C), and black (K) and sequentially output to the exposure unit 40. In the exposure unit 40, each exposure light L is emitted according to the color material gradation data of each color, and each photoconductor 28 is scanned and exposed to form a latent image (electrostatic latent image).

  The electrostatic latent image formed on the photoreceptor 28 is visualized as a toner image of each color of yellow (Y), magenta (M), cyan (C), and black (K) by the developing unit (development). ). The toner images of the respective colors sequentially formed on the photoreceptors 28 of the image forming units 12Y, 12M, 12C, and 12K are sequentially multiplexed on the intermediate transfer belt 16 by the four primary transfer rolls 18Y, 18M, 18C, and 18K. Transcribed.

  The respective color toner images transferred onto the intermediate transfer belt 16 are secondarily transferred onto the conveyed recording paper P by the secondary transfer roll 20. Then, the toner images of the respective colors on the recording paper P are fixed by the fixing device 60, and the recording paper P after fixing is discharged to the discharge tray 68.

  Residual toner, paper dust, and the like are removed from the surface of the photoreceptor 28 after the toner image transfer process is completed by the cleaning unit 76. Further, residual toner, paper dust, and the like on the intermediate transfer belt 16 are removed by the cleaning device 30.

  FIG. 4 is a flowchart showing a toner density detection control routine in the print control management unit 88 according to the present embodiment.

  In step 150, it is determined whether it is time to adjust the toner density. For example, when printing of a predetermined PV (for example, 100 sheets of A4 size) is completed with a predetermined paper size, or when the printer 10 is turned on. After waiting for a positive determination, the routine proceeds to step 152.

  In step 152, it is determined whether the toner cartridge 11 is unstable or stable. If the time is unstable (in this embodiment, PV> 300), the process proceeds to step 154. On the other hand, if it is a stable time (in this embodiment, PV ≦ 300), the routine proceeds to step 156.

  In step 154, toner density control (toner density adjustment based on the amount of image data) by the first toner density adjustment control execution unit 118 is selected.

  In the next step 158, a reference image (patch 110) formation instruction is issued from the print control management unit 88. As a result, the sub-control unit 99 controls each unit to form a predetermined patch 110.

  In step 160, the accumulated image data amount is read. For example, the cumulative image data amount (for example, the total number of pixels and the toner consumption amount) after the previous toner supply (or after the replacement of the toner cartridge 11) is read.

  In step 162, the toner replenishment amount is calculated from the accumulated image data amount in step 160. In the next step 164, an instruction is given to supply the toner supply amount. Specifically, the consumed toner amount may be replenished from the toner cartridge 11. Note that the processing related to steps 160 to 164 is the first toner concentration adjustment processing by the first toner concentration adjustment control execution unit 118.

  In step 166, the target value (old target value) of the patch density in the second toner density adjustment control is read. In the next step 168, the detection value of the density sensor 112 (the density of the patch 110 formed in step 158) is read out.

  In step 170, a difference Δ between the old target value read in step 166 and the detected value read in step 168 is calculated. In the next step 172, a new target value is calculated (new target value = (Δ × K) + old target value).

  For example, in FIG. 5, when the old target value is “160” and the detection value of the density sensor 112 is “100”, Δ is “60”. At this time, if the coefficient K is “−0.4”, 60 × (−0.4) +160, and the new target value is “136”.

  In step 174, the target value is updated, and the process returns to step 150.

  On the other hand, when the stable time is reached in step 152 and the process proceeds to step 156, the first toner density adjustment control process, that is, toner replenishment based on the accumulated image data amount in steps 160, 162, and 164 is performed.

  In the next step 175, toner density control (toner density adjustment by patch density) by the second toner density adjustment control execution unit 120 is selected. At this time, the target value of the patch density which is a reference for toner density adjustment is read out. As a result, the target value is fixed to the new target value updated in step 174.

  In the next step 176, a reference image (patch 110) formation instruction is issued from the print control management unit 88. As a result, the sub-control unit 99 controls each unit to form the patch 110. In the next step 178, the detection value of the density sensor 112 is read.

  In step 180, the toner replenishment amount is calculated from the target value read in step 156 and the detected value in step 178. In the next step 182, an instruction is given to replenish the toner replenishment amount, and the process returns to step 150.

  As a result, as shown in FIG. 5, since the toner density of the toner cartridge 11 is known in advance during the unstable period, the toner density adjustment based on the amount of image data is executed by the first toner density adjustment control execution unit 118. At the same time, the patch density target value update process is executed, and the toner density adjustment process based on the reference image density is executed by the second toner density adjustment control execution unit 120 using the updated target value at the stable time. .

  In the present embodiment, PV = 300 is used as a threshold value for the determination of the stable time / unstable time, but the present invention is not limited to this, and the image data amount (pixel count value) may be used as a reference. Further, the update of the target value of the patch density is repeated, and the update of the target value is stopped when the difference from the detection value of the density sensor 112 becomes equal to or smaller than the predetermined value or when the target value is updated a predetermined number of times. You may do it.

  In the present exemplary embodiment, the determination of each toner cartridge 11 is not provided. However, the present invention is not limited to this, and the stable time / unstable time is determined for each toner cartridge 11, and even one is determined as the unstable time. For example, the first toner density adjustment control may be executed for all the cartridges 11, or the toner density adjustment control may be different for each toner cartridge 11.

  Further, the value of the coefficient K in the present embodiment is not limited and may be changed every time. For example, you may make it determine according to both change rate.

10 Printer 11 Toner Cartridge 12 Image Forming Unit (Image Forming Unit, Developing Unit)
28 Photosensitive member (image carrier)
88 Print control management unit (first toner density adjustment control execution unit, second toner density adjustment control execution unit, target density correction means)
110 patch (reference image)
112 Concentration sensor (concentration detector)
118 First toner concentration adjustment control execution unit (first toner concentration adjustment control execution unit)
120 Second toner concentration adjustment control execution unit (second toner concentration adjustment control execution unit)

Claims (4)

Image formation that forms an image on recording paper by developing an electrostatic latent image formed on an image carrier using a two-component developer composed of two components, toner and carrier, stored in a developing unit. Means,
A first toner concentration adjusting unit that replenishes toner to the developing unit based on an image forming amount by the image forming unit and adjusts a toner concentration of a two-component developer stored in the developing unit;
Two-component development stored in the developing unit by reading the density value of the reference image formed by the image forming unit with a density detecting unit, replenishing toner to the developing unit based on the read density value Second toner concentration adjusting means for adjusting the toner concentration of the agent;
During the unstable period of the two-component developer set in advance, the toner density is adjusted only by the first toner density control means, and after the unstable period has elapsed, the toner density adjustment by the second toner density control means is performed. Toner density adjustment execution control means for starting
During the unstable period, density detection of the reference image is performed by the density detection unit, and the density of the reference image by the density detection unit is based on a difference between the density value and a target density corresponding to a preset toner density. Target density correction means for correcting the target density at the time of detection;
An image forming apparatus.   The unstable period is based on at least one of a predetermined number of recording sheets on which images are formed by the image forming unit or a predetermined number of pixels on which images are formed by the image forming unit. The image forming apparatus according to claim 1.   The target value density correction unit is configured to detect when the difference between the density value of the reference image by the density detection unit and the target density is equal to or less than a predetermined set value, or when the target density correction is repeated a predetermined number of times. 3. The image forming apparatus according to claim 1, wherein the correction of the target density is stopped.   A toner concentration adjustment program for causing a computer to function as the image forming apparatus according to any one of claims 1 to 3.