JP2010217379A - Toner residual amount monitoring device, image forming apparatus, toner residual amount monitoring program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To discriminate that a toner residual amount becomes zero with high accuracy. <P>SOLUTION: When toner concentration of a high concentration reference image exceeds a third threshold S3 and becomes low concentration, it is determined that fluctuation of developability occurs, and a first threshold S1 and a second threshold S2 are shifted to a high concentration side at a fixed rate (see the first threshold (corrected) S1H and the second threshold (corrected) S2H shown by a two-dot chain line). By shifting to the first threshold (corrected) S1H and the second threshold (corrected) S2H, it is possible to forcibly supply toner at a triangular mark F, and determination is made at the same toner concentration as that in property in a steady state. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a toner remaining amount monitoring device, an image forming apparatus, and a toner remaining amount monitoring program.

  In an image forming apparatus using a two-component developer, in order to control the toner density (toner amount / (toner amount + carrier amount)) (for example, the target is about 8 wt%), a reference image (patch image) is regularly displayed. The toner amount is adjusted based on the density value of the reference image that is formed and read by the density sensor. In this specification, there is a case where the two-component developer is simply referred to as “developer” or “toner” when it is not necessary to clearly distinguish the toner from the carrier.

  In this case, the steady-state reference image density is the dynamic range (detection) of the density sensor so that it covers a wide range of toner density (for example, 2 to 12 wt%) and can cope with environmental fluctuations in the surroundings. (Range) is set to be the central area. For this reason, a halftone (gray image) reference image is adopted as the reference image for toner density control.

  The correlation between the toner density and the reference image density, for example, changes in direct proportion (y = ax + b), but the factor (developability) including the type of developer, the surrounding environment, and the specifications of the image forming apparatus As a result, the characteristics are translated. In other words, the slope a of the direct proportional formula does not change, but the constant b varies.

  By the way, in the toner density control, when the density value of the reference image is extremely thin, the presence / absence of toner to be replenished, that is, the presence / absence of the remaining amount of toner is determined.

  More specifically, two threshold values are set for the target density of the reference image, and compared with the output value from the density sensor.

  That is, a threshold relatively far from the target density (hereinafter referred to as “first threshold”) and a threshold relatively close to the target density (hereinafter referred to as “second threshold”). Is set to be lower than the first threshold value as a result of detection by the density sensor, and even if the toner is forcibly replenished, the density does not return to the higher value than the second threshold value. It is determined that there is almost no remaining toner (empty determination).

  For reference, Patent Document 1 discloses that when the toner density of the developing device is adjusted with a reference image, the target value of the reference image is corrected based on the output image and the toner charge amount. .

  Further, in Patent Document 2, it is possible to form a reference image having relatively low density, medium density, and high density and detect a development curve state, thereby detecting a developer abnormality and controlling the toner density. It is disclosed.

JP 2005-017627 A JP-A-7-271173

  The present invention provides a toner remaining amount monitoring device, an image forming apparatus, and a toner remaining amount monitoring program that can accurately determine that the remaining amount of toner has become empty as compared with the case without this configuration. Is the purpose.

  According to a first aspect of the present invention, there is provided a density sensor for detecting the density of a reference image based on halftone image data that is disposed opposite to an image carrier and developed by a developer generated by a toner component and a carrier component. When the density of the reference image detected by the density sensor is lower than the first threshold value, which is lower than the target density and relatively far from the target density, it is compulsory. And at least after the forced supply by the forced supply means, the density of the reference image detected by the density sensor is lower than the target density and relatively close to the target density. When the density does not become higher than the second threshold value, the determination means for determining that the remaining amount of toner is insufficient, and a high density gradation data higher than the reference image formed on the image holding body. Concentration group When the density when the image is detected by the density sensor exceeds a predetermined third threshold value and becomes low density, the first threshold value and the second threshold value are set as the first threshold value and the second threshold value, respectively. And a correction unit that performs correction so as to approach the target density side.

  According to a second aspect of the present invention, in the first aspect of the present invention, the halftone image data is image data of a gradation of a region located in the middle when the entire gradation width is equally divided into three. .

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the high density gradation data is a floor of a region located on the highest density side when the entire gradation width is divided into a plurality of parts. Key image data.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects of the present invention, the correction unit is configured to perform the original first threshold value and the second threshold value. 60%.

  According to a fifth aspect of the present invention, in the first aspect of the present invention, the first threshold is reached when the concentration becomes higher than the third threshold value. There is further provided return means for returning the value and the second threshold value to the original level.

  A sixth aspect of the present invention is an image forming apparatus equipped with the toner remaining amount monitoring device according to any one of the first to fifth aspects.

  A seventh aspect of the present invention is a toner remaining amount monitoring program that causes a computer to execute the toner remaining amount monitoring according to any one of the first to fifth aspects.

  According to the first aspect of the present invention, it is possible to accurately determine that the remaining amount of toner is empty as compared with the case where this configuration is not provided.

  According to the second aspect of the present invention, the detection range of the toner density can be expanded as compared with the case where this configuration is not provided.

  According to the third aspect of the present invention, the toner density-reference image density characteristic can be obtained on the lower density side than the target density without depending on the developability as compared with the case without this configuration. Can do.

  According to the fourth aspect of the present invention, it is possible to maximize the monitoring accuracy of the remaining amount of toner as compared with the case where this configuration is not provided.

  According to the fifth aspect of the present invention, when the toner component is normally replenished, the original first threshold value and the second threshold value can be restored.

  According to the sixth aspect of the present invention, it is possible to accurately determine that the remaining amount of toner is empty as compared with the case where this configuration is not provided.

  According to the seventh aspect of the present invention, it is possible to accurately determine that the remaining amount of toner is empty as compared with the case where this configuration is not provided.

1 is a schematic diagram of a printer according to an embodiment. It is a block diagram which shows the hardware constitutions of the control unit in the printer which concerns on this Embodiment. FIG. 6 is a characteristic diagram showing a toner density-halftone reference image density characteristic curve according to the present embodiment. FIG. 6 is a characteristic diagram showing a toner density-high density reference image density characteristic curve according to the present embodiment. FIG. 5 is a block diagram functionally illustrating toner remaining amount monitoring control in a print control management unit according to the present exemplary embodiment. 6 is a flowchart showing a flow for toner density control and empty detection control according to the present embodiment.

  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 tubular members.

  The toner cartridges 11Y, 11M, 11C, and 11K are provided with toner dispensers (not shown).

  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 an electrostatic latent image with a two-component developer of each color, an erase lamp as an example of a static elimination device that performs static elimination by irradiating the surface of the photoreceptor 28 after transfer, and a photoreceptor after static elimination And a cleaning unit for cleaning the surface of 28.

  The two-component 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 the toner of each color forms each image by driving the toner dispenser. The unit 12 is supplied.

  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.

  Further, a density sensor 112 is provided on the outer peripheral surface of the intermediate transfer belt 16 where the tension roll 24 is provided. The density sensors 112 are provided at both ends of the intermediate transfer belt 16 in the width direction, and mainly have an eye for detecting the density of a reference image for observing the state of image density and toner density (TC). Yes.

  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. The exposure unit 40 may be provided for each image forming unit 12 individually.

  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.

  Here, the reference image for image density control using the density sensor 112 and the reference image for toner density control basically have the same shape but the difference in the density pattern. is there.

  As the reference image for image density control, a plurality of stepwise reference images from low density to high density are formed, and an image density characteristic curve based on the exposure amount, development bias, etc. is drawn, and appropriate for all density areas Develop a correct correction value.

  On the other hand, the reference image for controlling the toner density may basically be a single density. However, the toner density is detected in a wide range (for example, 2 wt% to 8 wt%), and at the center of the detectable range (dynamic range) of the density sensor 112 so that it can be detected even if the surrounding environment changes. It is preferable to set. As a result, a reference image of halftone (gray image) is applied.

  Further, in the toner density control, the remaining amounts of the toner cartridges 11Y, 11M, 11C, and 11K are determined.

  FIG. 3 shows a toner density-halftone reference image characteristic curve, and a solid line A is a characteristic in a steady state.

  Assuming that the target of toner density is 0.8 wt%, the target of the output value of the density sensor 112 that has detected the halftone reference image density at this time is set to a numerical value of about 102 to 105 on the vertical axis. This numerical value is a numerical value indicating that the higher the value is, the lower the density is.

  When the toner density changes, particularly when the halftone reference image density becomes lighter, the toner density is maintained at the target value by increasing when supplying toner at the time of image formation in order to correct the target value. This is toner density control. In the toner density control, naturally, the halftone reference image density may be increased. In this case, the toner in the developing unit is discarded.

  However, when the toner density does not reach the target and becomes lower than the predetermined first threshold value S1 (see the position of the black circle (●) mark C in FIG. 3), the toner dispenser is forcibly driven. Then, the toner is replenished and the recovery state is observed. As a result of observation, if the density exceeds the second threshold value S2 (see the position of the white circle (◯) mark D in FIG. 3), it is determined that there is a remaining amount of toner. On the other hand, if the second threshold value S2 is not exceeded as a result of the observation (see the position of the cross (X) mark E in FIG. 3), the remaining amount of the toner cartridges 11Y, 11M, 11C, and 11K is determined to be insufficient. To do.

  Incidentally, the toner density-halftone reference image density characteristic, which is the basis for the toner density control and the basis for the remaining amount determination, varies depending on the developing property.

  The developability is a variation including the type of developer, the surrounding environment, and the specifications of the image forming apparatus.

  As shown in FIG. 3, the correlation between the toner density and the reference image density changes in direct proportion (y = ax + b), but includes the type of developer, the surrounding environment, and the specifications of the image forming apparatus. Depending on the developability, the properties move in parallel. In other words, the slope a of the direct proportional formula does not change, but the constant b changes and shifts as indicated by a two-dot chain line B, for example. Note that the correlation between the toner density and the reference image density is not limited to a direct proportion and may change in a quadratic function. In any case, it is a so-called downward-sloping curve, and the variation due to developability is parallel movement.

  When the remaining amount of toner is determined under this shifted characteristic curve (two-dot chain line B in FIG. 3), the toner density when the first threshold value S1 is exceeded (black circle (●) mark C in FIG. 3). 'Is a lower density side than the toner density when exceeding the first threshold value S1 in the normal state characteristic curve (see the solid line A in FIG. 3), and this difference becomes a detection delay. This is a cause of deteriorating the accuracy of toner remaining amount determination.

  Therefore, in the present embodiment, a change (mainly, a change toward the low density side) of the toner density-halftone reference image density characteristic curve is detected by the third sensor by detecting the density sensor 112 of the high density reference image. Judgment is made by comparing with the threshold value.

  As shown in FIG. 4, in the high density reference image (so-called black solid image), when the toner remains sufficiently and is maintained at a proper toner density or higher, the density sensor 112 that has detected the high density reference image. Although the output value changes at a constant level, it has a characteristic of gradually changing to a lower density side when the toner density reaches about 4 wt% to 5 wt%.

  Therefore, when the output value of the density sensor 112 at which the toner density of the high density reference image is 4 wt% to 5 wt% is set as the third threshold value, and the density becomes lower than the third threshold value S3, It is determined that a change in developability has occurred, and the first threshold value S1 and the second threshold value S2 in FIG. 3 are shifted to a high density side at a certain rate (in the two-dot chain line in FIG. 3). First threshold value (correction) S1H and second threshold value (correction) S2H shown).

  By setting the first threshold value (correction) S1H and the second threshold value (correction) S2H, it is possible to perform forced toner supply at the Δ mark F in FIG. The determination is made with the same toner density.

  FIG. 5 is a functional block diagram for toner density control and toner remaining amount monitoring control in the print control management unit 88. Each block in FIG. 5 is classified according to function, and the hardware configuration of the print control management unit 88 is not limited.

  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. .

  A toner density control unit 116 is connected to the image formation execution control unit 114. The toner density control unit 116 stores the toner density-halftone reference image density characteristic map shown in FIG. The toner density control unit 116 is supplied with a toner density control execution instruction signal from the image formation execution control unit 114. Based on the toner density control execution instruction signal, the toner density control unit 116 to start.

  When the toner density control unit 116 is activated, first, an instruction signal for forming an intermediate reference image is sent to the image formation execution control unit 114 and an execution instruction is given to the high density reference image formation instruction unit 118. Send a signal. Based on the execution instruction signal, the high density reference image formation instruction unit 118 sends an instruction signal for forming a high density reference image to the image formation execution control unit 114.

  As a result, the image formation execution control unit 114 controls 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 thus the halftone reference image and the high density reference image. Each of these is formed on the intermediate transfer belt 16, for example.

  The formed halftone reference image and high density reference image are formed in a line along the conveyance direction of the intermediate transfer belt 16, and the density is detected by the density sensor 112 with a time difference.

  A value detected by the density sensor 112 of the intermediate reference image is sent to the toner density control unit 116, and toner density control management is executed.

  The high density reference image formation instructing unit 118 is connected to the high density reference image detected value reading unit 120. When the high density reference image formation instruction unit 118 issues a high density image formation instruction to the image formation execution control unit 114, the image formation execution control unit 114 is provided to the high density reference image detection value reading unit 120. To read the detection value of the high density reference image by the density sensor 112.

  The toner density control unit 116 is connected to the toner remaining amount determination unit 122 and sends the density sensor detection value obtained from the image formation execution control unit 114 to the toner remaining amount determination unit 122 as it is. The toner remaining amount determination unit 122 is connected to the threshold value memory 126 via the threshold value correction execution unit 124.

  When the correction by the threshold correction execution unit 124 is not executed (when the toner density-halftone reference image density characteristic is in a steady state indicated by a solid line A in FIG. 3), the toner remaining amount determination unit 122 The first threshold value S1 and the second threshold value S2 stored in the memory 126 are read, and the remaining toner amount is determined.

  That is, when the density becomes lower than the first threshold value S1 (see the black circle (●) mark C on the solid line A in FIG. 3), the development controller 104 is instructed to forcibly drive the toner dispenser, and the toner The toner density control is continued, and the extent to which the toner density is restored as a result of the forced toner supply is observed.

  As a result of the observation, if the density is higher than the second threshold value S2 (see the white circle (◯) mark D on the solid line A in FIG. 3), it is determined that there is a remaining amount of toner, and the second threshold is reached. When the density is maintained lower than the value S2 (see the cross (X) mark E on the solid line A in FIG. 3), it is determined that “no toner remaining (empty)”.

  The toner remaining amount determination unit 122 is connected to the notification control unit 128. When the toner remaining amount determination determines that there is no toner remaining (empty) (empty detection), a notification instruction signal is sent to the notification control unit 128. Is sent out. Based on this notification instruction, the notification control unit 128 controls the UI 82 to notify that the toner cartridges 11Y, 11M, 11C, and 11K are empty.

  On the other hand, the detection value by the density sensor 112 of the high density reference image read by the high density reference image detection value reading unit 120 is sent to the comparison unit 130.

  The comparison unit 130 stores the above-described toner density-high density reference image density characteristic map shown in FIG.

  When the detection value detected by the density sensor 112 from the high density reference image is input from the high density reference image detection value reading unit 120 to the comparison unit 130, the third threshold value S3 is set from the threshold memory 126. Read and compare both.

  This comparison result is sent to the threshold value correction necessity determination unit 132 to determine whether or not the threshold values (that is, the first threshold value S1 and the second threshold value S2) need to be corrected. .

  As shown in FIG. 4, when the detection value read from the high density reference image is determined to exceed the third threshold value S3, the determination that the correction is necessary is performed regardless of the developability. This is when 4 wt% to 5 wt% or less.

  In such a case, the toner density-halftone reference image density characteristic curve in the low density state (see the two-dot chain line B in FIG. 3) from the steady state toner density-halftone reference image density characteristic curve (see solid line A in FIG. 3). It is necessary to correct the threshold value so that the first threshold value (correction) S1H and the second threshold value (correction) S2H match the characteristic curve of the two-dot chain line B. The rejection determination unit 132 sends a correction execution signal to the threshold correction execution unit 124.

  Based on this correction execution signal, the threshold correction execution unit 124 corrects and reads out the first threshold S1 and the second threshold S2 when the toner remaining amount determination unit 122 reads out the first threshold S1 and the second threshold S2. (First threshold value (correction) S1H and second threshold value (correction) S2H).

  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. 6 is a flowchart showing empty detection determination control of the toner cartridges 11Y, 11M, 11C, and 11K accompanying the toner density control according to the present embodiment.

  In step 200, it is determined whether or not it is the toner concentration control time. If a negative determination is made, the process proceeds to step 202, and it is determined whether or not the developer (toner) is forcibly replenished in the previous toner concentration control. Is done. If a negative determination is made in step 202, this routine ends.

(Toner density control + empty judgment prediction)
If an affirmative determination is made in step 200, it is determined that it is the toner density control time + empty determination prediction time, and the process proceeds to step 204 to instruct to form a halftone reference image. An instruction to form a reference image is issued, and the process proceeds to step 208. By this instruction, a halftone reference image and a high density reference image are formed on the intermediate transfer belt 16.

  In step 208, the density sensor 112 is used to detect the density Pm of the halftone reference image formed on the intermediate transfer belt 16 and the density Pd of the high density reference image, which are instructed in steps 204 and 206.

  In the next step 210, the detection values Pm and Pd of the density sensor 112 are read, then the process proceeds to step 212, the third threshold value S3 is read, and the process proceeds to step 214.

  In step 214, the density Pd of the high density reference image is compared with the third threshold value S3. As a result of the comparison, if it is determined that Pd ≧ S3, the toner density-halftone reference image density characteristic curve shifts from the steady state (solid line A) to the low density state (two-dot chain line B) in FIG. In step 216, the first threshold value S1 is corrected to S1H, then the process proceeds to step 218, the second threshold value S2 is corrected to S2H, and the process proceeds to step 222 (control). The above is SS1 ← S1H, SS2 ← S2H). When this correction is uniformly performed at a predetermined ratio, it may be shifted to the high density side by about 60%. In addition, you may make it shift according to a detailed calculation instead of shifting uniformly.

  If it is determined in step 214 that Pd> S3, it is determined that the toner density-halftone reference image density characteristic curve maintains the steady state (solid line A) in FIG. , The process proceeds to step 220, and if the current value is the first threshold value (correction) S1H and the second threshold value (correction) S2H, the correction is canceled (SS1 ← S1 in terms of control) , SS2 ← S2), the process proceeds to step 222.

  In step 222, toner density control based on the halftone reference image is executed. This toner density control is a conventional control in which when the toner density is low, the amount of toner is increased during image formation, and when the toner density is high, the toner stored in the developing unit is discarded and reduced. Details are omitted.

  In the next step 224, the density Pm of the halftone reference image is compared with the current first threshold value SS1 (S1 or SH1). As a result of this comparison, if Pm <SS1, there is no possibility that the developer will be emptied, so this routine ends. As a result of the comparison in step 224, if Pm ≧ SS1, the developer may be nearly empty (near empty), so the process moves to step 226 to drive the toner dispenser and forcefully An instruction is given to replenish the developer, and this routine ends.

(Empty judgment after forced replenishment)
On the other hand, if an affirmative determination is made in step 202, it is determined that it is the empty determination time after forced replenishment, the process proceeds to step 228, an instruction to form a halftone reference image is issued, and the process proceeds to step 230. By this instruction, a halftone reference image is formed on the intermediate transfer belt 16.

  In step 230, the density sensor 112 is used to detect the density Pm of the halftone reference image that is instructed in step 228 and formed on the intermediate transfer belt 16.

  In the next step 232, the detection value Pm of the density sensor 112 is read, and the process proceeds to step 234.

  In step 234, the density Pm of the halftone reference image is compared with the current second threshold value SS2 (S2 or SH2). As a result of this comparison, if Pm <SS2, the toner density has returned by forced replenishment, so there is no possibility that the developer will be emptied, and this routine ends. As a result of the comparison in step 234, if Pm ≧ SS2, the toner density does not recover even if forcible replenishment. Therefore, it is determined that the developer is empty, and the process proceeds to step 236, where empty determination notification control is performed. And this routine ends.

  In this embodiment, when the forced supply of the developer is executed, only the halftone reference image is formed, and it is determined whether the density is lower than the second threshold value S2 (or S2H). However, it may be executed at the next toner density control timing.

P Recording paper 10 Printer (image forming device)
11Y, 11M, 11C, 11K Toner cartridge 12Y, 12M, 12C, 12K Image forming unit 14 Transfer unit 16 Intermediate transfer belt 18Y, 18M, 18C, 18K Primary transfer roll 20 Secondary transfer roll 28Y, 28M, 28C, 28K Photoconductor 36 control unit 40 exposure unit 60 fixing device 70 main control unit 88 print control management unit 100 transport control unit 102 scanning exposure control unit 104 development control unit 106 transfer control unit 108 fixing control unit 114 image formation execution control unit (forcible supply unit)
116 toner density control unit 118 high density reference image formation instruction unit 120 high density reference image detection value reading unit 122 toner remaining amount determination unit (determination unit)
124 threshold correction execution unit (correction means)
126 Threshold Memory 128 Notification Control Unit 130 Comparison Unit (Correction Unit)
132 Threshold correction necessity determination unit (correction means)

Claims (7)

A density sensor for detecting the density of a reference image based on halftone image data that is arranged opposite to the image carrier and developed by the developer generated by the toner component and the carrier component;
When the density of the reference image detected by the density sensor is lower than the first threshold, which is a density lower than the target density and relatively far from the target density, forcibly. Forced supply means for supplying at least toner components;
After the forcible supply by the forcible supply means, the density of the reference image detected by the density sensor is lower than the target density and higher than the second threshold value that is a density relatively close to the target density. A determination unit that determines that the remaining amount of toner is insufficient when the density is not reached;
When the density sensor detects a high density reference image formed with higher density gradation data than the reference image on the image carrier, the density exceeds a predetermined third threshold value, and the density is low. A correction means for correcting the first threshold value and the second threshold value closer to the target density side,
A toner remaining amount monitoring device.   2. The toner remaining amount monitoring device according to claim 1, wherein the halftone image data is image data of a gradation in a region located in the middle when the entire gradation width is equally divided into three.   The toner remaining amount monitoring device according to claim 1, wherein the high density gradation data is image data of a gradation of a region located on the highest density side when the entire gradation width is divided into a plurality of parts.   4. The toner remaining amount monitoring device according to claim 1, wherein the correction unit sets 60% of the original first threshold value and the second threshold value. 5.   The said 1st threshold value and a 2nd threshold value are further returned to the original level at the time of becoming a density | concentration higher than the said 3rd threshold value. 5. The toner remaining amount monitoring device according to any one of 4 above.   An image forming apparatus equipped with the toner remaining amount monitoring device according to any one of claims 1 to 5.   6. A toner remaining amount monitoring program for causing a computer to execute the toner remaining amount monitoring according to claim 1.

Images