JP2007010721A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus having a developing device that can correct an error of measurement by optical detection of a developer conveyance amount and reduce stress to a developer. <P>SOLUTION: Disclosed is the image forming apparatus in which the developing device having an optical sensor detecting the developer conveyance amount is arranged opposite a developing sleeve rotating while carrying a developer layer, the image forming apparatus being characterized in that the developer layer is formed by being moved to the developing sleeve through a developer supply roller in the developing device and the developer conveyance amount on the developing sleeve is calculated from a measured value A detected by the optical sensor during developer conveyance and a measured value B detected in the absence of a developer on the developing sleeve. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus having a developing device for image formation such as an electrophotographic copying machine, a printer, and a FAX.

  Conventionally, as one method of an electrophotographic image forming apparatus, a charging unit, an image exposure unit and a developing unit are arranged around a photoconductor as an image carrier, and the charging unit charges the photoconductor and the image exposure unit. An image forming apparatus is used in which a latent image is formed on a photoreceptor and a toner image is formed by contact reversal development of the electrostatic latent image with a developing device as a developing unit.

  In recent years, with the advancement of advanced information technology, the need for high-quality image forming apparatuses based on digital technology is increasing. In order to meet these requirements, it is essential to reduce the diameter of the developer composed of toner and carrier.

  It is important to control the amount of developer transported on the developing sleeve because the density increases as the particle size of the developer increases, the spacing between the developers decreases, and the fluidity of the developer tends to decrease. It becomes.

  That is, if the developer transport amount is less than the appropriate value, sufficient developability cannot be obtained, and if it is greater than the appropriate value, developer clogging (packing) occurs in the carrier adhesion and the development region (nip portion). This is because, in the case of a developer composed of a carrier having a small particle diameter, carrier adhesion and developer clogging are likely to occur, so the appropriate range of developer transport amount is narrower than that of a conventional large particle diameter carrier. ing. Accordingly, more accurate management of the conveyance amount is required.

  Conventionally, a technique for measuring the developer conveyance amount on the developing sleeve and the following technique for adjusting (hereinafter also referred to as control) to an appropriate developer conveyance amount from the measurement result have been proposed.

As an example, the contact between the developer and the piezoelectric sensor in the development area is detected, the developer transport amount is calculated from the measured value, and the developer layer on the developing sleeve is controlled by the developer so that the proper transport amount is obtained. A method for adjusting the gap between the blade and the developing sleeve (for example, see Patent Document 1) has been proposed, but it has a drawback that the output value does not change linearly according to the conveyance amount. There is also a method for detecting the reflected light from the developer layer on the developing sleeve and adjusting the thickness of the developer regulating blade (for example, see Patent Document 2).
JP 2002-258613 A JP 2000-267436 A

  However, in the method using an optical sensor that detects reflected light on the developer layer on the developing sleeve, the installation location of the optical sensor is at a position opposite to the developing sleeve, so the detection window of the optical sensor due to toner scattering from the developing sleeve. Contamination is unavoidable, and it is necessary to correct measurement errors due to contamination of the detection window. Regarding the method for adjusting the carry amount, according to the above two documents, both detection methods have an advantage that the developer restriction blade is used for adjusting the developer carry amount and the carry amount can be adjusted with a simple configuration. There is a drawback in that a great stress is given to the developer in the regulation part. In particular, when a developer having a small particle size toner and a small particle size carrier is employed in order to pursue high image quality, developer destruction due to stress becomes more serious than conventional developers. Therefore, there is a demand for technical means that accurately measures the developer conveyance amount and has less developer stress.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus having a developing device capable of minimizing measurement errors due to contamination of the detection window as described above, reducing developer stress as much as possible, and extending the life of the developer. And

  In the image forming apparatus provided with a developing device having an optical sensor for detecting a developer conveyance amount facing a developing sleeve that carries and rotates the developer layer, the developer layer includes a developer in the developing device. And a measurement value A detected when the developer is transported by the optical sensor and a measurement detected when the developer is not on the development sleeve. An image forming apparatus, wherein a developer conveyance amount on the developing sleeve is calculated from the value B.

  Measurement errors due to contamination of the detection window of the optical sensor are reduced, the conveyance amount can be accurately measured, and developer regulation is performed by a developer supply roller having a wide regulation gap, so that stress on the developer is reduced. .

  Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described.

  FIG. 1 is an explanatory diagram showing the overall configuration of the image forming apparatus.

  In FIG. 1, the image forming apparatus includes a double-sided document automatic feeder RADF and an image forming apparatus main body A.

  The double-sided document automatic feeder RADF is located at the upper part of the image forming apparatus main body A and can be opened and closed. The document on the document feed tray a is transported to a paper feed roller b, a separation roller c, a registration roller d, and a transport drum e, and the document is transported.

  Next, the image forming apparatus main body A includes an image reading apparatus 1, a control unit 2 as a control means, an image writing apparatus 3, an image forming means 4, a cassette paper feeding means 5, a conveying means 6, a fixing device 7, and a paper discharging means. 8 and re-transport means 9 and the like.

  The optical system of the image reading apparatus 1 includes an exposure unit 14 including a light source and a first mirror, a V mirror unit 15 including a second mirror and a third mirror, a lens 16, and a CCD image sensor 17. Document reading by the double-sided document automatic feeder RADF is performed at a position where the exposure unit 14 is stopped at the initial position below the slit exposure glass 13. Reading a document on the platen glass 11 is performed while moving the exposure unit 14 and the V mirror unit 15.

  Image information of the original image read by the image reading apparatus 1 is subjected to image processing by the control unit 2 including image processing means, converted into a signal as image data, and temporarily stored in a memory. Output light from a semiconductor laser (not shown) included in the image writing means 3 is applied to the photosensitive drum 21 which is an image carrier to form an electrostatic latent image.

  In the image forming unit 4, a charge (negative charge in the present embodiment) is added to the photosensitive drum 21, which is a photosensitive member, by the charger 22, and the electrostatic latent image is irradiated by laser light irradiation from the image writing unit 3. And the electrostatic latent image is visualized by the developing device 23 according to the present invention to become a toner image (negative charge in the present embodiment). Details of the developing device will be described later. Next, the sheet is transported from the cassette sheet feeding means 5 and transferred onto the sheet P, which is a transfer material synchronized with the toner image, by the transfer unit 29A, and the sheet P is peeled off by the separator 29B. The paper P on which the toner image has been transferred is conveyed by the conveying means 6, fixed by the fixing means 7, and discharged to the paper discharge tray 81 outside the apparatus by the paper discharge means 8. On the other hand, the transfer residual toner is removed by a cleaning device 26 as a cleaning means.

  In the case of duplex copying, the paper P on which the image is formed on the first side is sent to the re-transport unit 9 by the transport path switching plate 82, reversed, and again after the image is formed on the second side in the image forming unit 4. Then, the paper is discharged by a paper discharge means 8 to a paper discharge tray 81 outside the apparatus. In the case of reverse paper discharge, the paper P branched from the normal paper discharge path by the transport path switching plate 82 is switched back and upside down in the reverse paper discharge unit 83 and then discharged from the apparatus by the paper discharge means 8. The paper is discharged to the paper tray 81.

  Next, a developing device provided with a mechanism for measuring a developer transport amount (hereinafter simply referred to as a transport amount) according to the present invention and adjusting it to an optimum transport amount will be described.

  FIG. 2 shows an enlarged view of a developing device including a supply roller for supplying a developer onto the developing sleeve.

  In the following drawings, members having the same reference numerals as those in FIG. 1 have the same functions.

  In FIG. 2, the developing device 23 includes a developing sleeve 321, a developer supply roller 232, a developer regulating blade 233, a stirring member 234, an optical sensor S, and the like.

  Inside the developing sleeve 231, magnetism generating means (magnet rolls) N and S having a fixed magnetic body are provided, and the developer engages with a driving source (not shown) and rotates counterclockwise. As the developing sleeve 231 rotates, the developing sleeve 231 is conveyed to the developing region D while adhering to the sleeve surface. A developer supply roller 232 (hereinafter simply referred to as a supply roller) is provided to face the roll surface of the developing sleeve 231 in parallel and at a constant interval, and the surfaces of the opposite portions of both rolls are opposite ( Rotate to travel in the counter) direction. Further, the supply roller 232 is provided with magnetism generating means (magnet rolls) N and S having a fixed magnetic body, and pumps up the developer from the agitation unit M for mixing and agitating the developer and the toner to develop it. It has a role of shifting onto the sleeve 231 and rotates counterclockwise by power from a drive source (not shown). The developer regulating blade 233 (hereinafter simply referred to as a regulating blade) regulates the developer layer on the supply roller 232 to a predetermined thickness. All of the supplied developer is transferred to the developing sleeve, and after being used for development, is returned to the stirring unit M. Therefore, the developer is regulated not on the developing sleeve 231 as in the prior art but on the supply roller 232. This is because not only the restriction place is different, but also the conveyance amount on the supply roller 232 can be set larger than that on the developing sleeve 231, so that the restriction gap between the restriction blade 233 and the supply roller 232 is in the prior art. It can be set wider than the regulation gap between the regulation blade and the developing sleeve, and the developer stress can be reduced. Reference numeral 234 denotes a developer stirring member. S is an optical sensor, and an LED (light emitting diode) is used as a light emitting element, and a PD (photodiode) is used as a light receiving element. The developer concentration on the developing sleeve 231 is detected, and the measured value is transmitted to the control unit 2 to calculate the transport amount.

  Next, a method for detecting the developer conveyance amount in the present invention will be described.

  With respect to the optical sensor S, the optical sensor S is generally installed with an opening so that a detection window of the optical sensor S is not in contact with the developer layer on the developing sleeve 231. In many cases, the gap between the surface of the developing sleeve 231 not carrying the developer and the detection window of the optical sensor S is set to about 1 to 10 mm. Further, the optical sensor S is opposed to the downstream side in the rotation direction from the opposed portion (the place where the developer moves) on the developing sleeve 231 with respect to the supply roller 232. The optical sensor S may be opposed to the downstream side of the developing region D in the rotation direction of the developing sleeve 231 (in this case, it is necessary to oppose the upstream side of the downstream developer reservoir and the developer stripping portion). ).

  As described above, the optical sensor S measures the conveyance amount on the developing sleeve 231. As the number of prints progresses, the detection window of the optical sensor becomes dirty due to toner scattering from the developing sleeve 231 that rotates at high speed. is there. This contamination of the detection window is an unavoidable problem and has a considerable influence on the measurement of the amount of reflected light (causes measurement errors). Therefore, it is necessary to correct so that the conveyance amount can be accurately grasped even if the detection window is contaminated.

  Hereinafter, the correction method will be described. In order to improve the measurement accuracy, the reflected light amount of the surface (background) of the developing sleeve 231 that does not carry the developer for each predetermined number of prints and the developer when the developer is conveyed is compared, and the optical sensor S Calibration is possible. In other words, when measuring the amount of reflected light from the surface (background) of the developing sleeve 231 in a state in which no developer is carried, if the rotation of the supply roller 232 is stopped, the developing sleeve 231 will have a short time later. Since there is no developer, the amount of light reflected from the background of the developing sleeve 231 can be detected. In other words, the amount of reflected light from the developer on the developing sleeve can be calibrated from the ratio of the amount of reflected light from the background of the developing sleeve when the detection window is clean and when it is dirty.

  The control unit 2 calculates the carry amount based on the output voltage from the optical sensor S corresponding to the reflected light amount. That is, if the developer transport amount is large, the amount of reflected light is small, and the output voltage of the optical sensor S is low. If the carry amount is small, the amount of reflected light increases, and the output voltage becomes high. From this relationship, the carry amount can be obtained from the reflected light amount.

  Now, the reflected light amount (measured value) when the developer is carried on the developing sleeve 231 is A, the supply roller 232 is stopped, and the reflected light amount (measured value) when there is no developer on the developing sleeve 231. ) Is B, if A / B is used as the corrected reflected light amount ratio, the contamination of the detection window of the optical sensor S can be corrected, and the carry amount can be calculated. If the transport amount is not an appropriate value, the peripheral speed α of the developing sleeve 231 and the peripheral speed of the supply roller 232 can be controlled to an accurate transport amount by changing the peripheral speed ratio β / α to β. (The amount of reflected light described below means the amount of reflected light after correcting the detection window dirt).

  That is, it is possible to select the peripheral speed ratio β / α so that the transport amount calculated through the measured value by the optical sensor becomes a target value, and adjust the transport amount.

  Now, the conveyance amount adjustment method in the present embodiment will be described with reference to FIG. 2. The regulation gap between the supply roller 232 and the regulation blade 233 is set wide, and the developer conveyance amount on the supply roller 232 is the same as that on the developing sleeve 231. It is set to be larger than the carry amount (in this embodiment, about 2 to 5 times).

  In order to set the transport amount on the developing sleeve 231 smaller than that on the supply roller 232, the surface movement speed (circumferential speed) of the supply roller 232 may be set slower than the surface movement speed (circumferential speed) of the development sleeve 231. (For example, to make the transport amount on the developing sleeve 231 1/3 times the transport amount on the supply roller 232, the surface moving speed of the supply roller 232 is set to 1/3 times the surface moving speed of the developing sleeve 231. Just do it.)

  When the measured amount detected and calculated by the optical sensor S is smaller than the target value, the conveyance amount is adjusted to the target value by increasing the rotation number of the supply roller 232 (or decreasing the rotation number of the developing sleeve 231). do it.

  Note that the program for calculating the developer conveyance amount on the developing sleeve 231 from the measured ratio of the reflected light amount (sensor output voltage) from the developer layer and the program for the peripheral speed ratio to obtain an appropriate conveyance amount are those of the image forming apparatus. It is stored in the control unit 2.

  Next, the tendency of change in the amount of reflected light due to toner density and temperature and humidity will be described with reference to FIG.

  It is also known that the amount of reflected light varies depending on the toner concentration and environmental (temperature and humidity) conditions. Therefore, the transport amount can be corrected in consideration of this change.

  FIG. 3 is a diagram illustrating the relationship between the conveyance amount and the reflected light amount (sensor output) accompanying changes in toner density and environmental conditions.

Taking a black developer as a specific example, in FIG. 3A, when the transport amount (unit is g / m ² or mg / cm ² ) is large, the coverage ratio on the developing sleeve 231 by the black developer. Increases the amount of reflected light. Further, when the toner density changes low even when the transport amount is the same, the ratio of the carrier having a higher specific gravity increases, the volume per unit weight of the developer decreases, and the amount of reflected light depends on the black developer on the developing sleeve 231. Increased due to reduced coverage.

  In FIG. 3B, the amount of reflected light changes when the environmental (temperature / humidity) conditions change even if the transport amount and the toner density are the same. The higher the absolute humidity, such as high temperature and high humidity, the greater the amount of reflected light. This is because the volume per unit weight of the developer is reduced due to a decrease in the charge amount of the developer, and the non-coverage ratio by the black developer on the developing sleeve 321 is reduced.

  A transport amount calculation program is also created in consideration of the tendency of the reflected light amount and the transport amount due to the above toner density and environmental conditions. Considering this change, a temperature / humidity sensor S1 and a toner concentration sensor S2 (see FIG. 2), which are environmental data detection means, are provided, and the conveyance amount can be controlled.

  In this case, when the carry amount is calculated from the reflected light amount, correction is made in accordance with the toner density and the environmental data so that the carry amount can be accurately grasped. In addition, when there is little change in the developer bulk due to the toner concentration or the environment, the transport amount may be accurately grasped without performing the above correction. Also, if the toner density or environmental data is out of the predetermined range, it is judged that it is difficult to accurately grasp the transport amount even if the above correction is performed, and the transport amount measurement and the transport amount adjustment are not performed. You may do it.

  Note that it is preferable that the conveyance amount measurement and adjustment be performed during the warm-up of the image forming apparatus and every time a predetermined number of printed sheets is achieved.

  Next, a confirmation experiment for confirming the effect of the present invention will be described.

-Confirmation experiment 1 (see Fig. 2)
Experimental conditions
Image forming device: Digital monochrome machine
Copy speed: A4 landscape feed, 75 sheets / minute
Process speed: 420mm / sec
Image area / non-image area: 62.5 / 37.5
Photoconductor drum diameter: 80 mm
Charging voltage: -700V
<Development sleeve related>
Development device See Fig. 2
Developing sleeve potential: -500V
Photoconductor solid exposure potential: -50V
Development bias AC component: 1.0 kV _pp (rectangular wave, 5 kHz)
Exposure unit: Semiconductor laser (wavelength 780nm)
Development sleeve diameter: 30 mm (5 poles)
Development sleeve magnetized part length: 330mm
The gap between the photosensitive drum and the developing sleeve: about 0.3 mm
Developer sleeve developer transport amount: approx. 250 ± 40 g (target value)
Development sleeve moving speed / process speed: 2.0
<Related to transport amount adjustment (control) means (supply roller)>
Supply roller diameter: 20mm / 3 poles
Supply roller to developing sleeve surface gap: about 1.0 mm
Supply roller to regulating blade gap: approx. 2.0 mm
Supply roller surface moving speed (peripheral speed): Development sleeve surface moving speed (peripheral speed)
Ratio of 0.1 to 0.5 (variable)
(Counter direction to each other)
Center line of developing sleeve and supply roller
Angle between straight line connecting horizon and horizontal line: 30 ° (supply roller is lower)
Supply roller magnetized part length: 330mm
Supply roller layer forming pole: magnetic pole density peak value = 40 mT (half width)
40 °)
<Optical sensor related>
Light emitting element: LED (central wavelength 680 nm)
Light receiving element: PD (photodiode)
Optical path: specular reflection type
Detection window to developing sleeve gap: 8.0 mm
Transport amount detection position: Near the center of the developing roller axial direction, development pole
More upstream of the developing sleeve rotation direction
Near the adjacent pole
Carrying amount measurement frequency: Reflected light quantity A (developer layer) is 500 pre
Every time, or when warming up
Reflected light quantity B (sleeve surface) is 100
Every 0 prints or warm up
Time
After printing if printing is in progress
<Detection correction for detection window>
When measuring both reflected light amount A and B: Transported from “reflected light amount A / reflected light amount B”
Quantity calculation
When measuring only reflected light amount A: “Reflected light amount A / countermeasure at the last measurement in the past”
Carrying amount calculation from “irradiance B”
<Other transport amount correction function>
Correction based on toner density data: None
Correction by temperature / humidity data: None
<Developer related>
Toner: Polymerized toner with a volume average particle size of 4.5 μm
(black)
Carrier: Volume average particle size 25 μm, magnetization strength 60
emu / g
Toner concentration: 6%
In addition to the confirmation experiment 1 described above, two comparative experiments using a regulating blade that is a known developer layer forming method were performed (FIG. 4).

  FIG. 4 is a diagram illustrating an example of a known transport amount control method.

Comparative experiment 1 (FIG. 4 (a))
<Optical sensor related>
Light emitting / receiving element, mounting, detection conditions: Same as in Confirmation Experiment 1, except that supply low
Measurement of reflected light quantity B because there is no
Impossible
<Related to transport amount adjustment means (regulator blade)>
Regulating blade / developing sleeve distance: 0.3 to 0.7 mm (standard = 0.5 m)
m) Adjust the interval according to the result of the transport amount measurement.
Centerline of developing sleeve and regulating blade
Angle between straight line connecting horizon and horizontal line: 50 ° (regulator blade is higher)
Comparative experiment 2 (FIG. 4 (b))
Transport amount measurement, adjustment: None
Carrying amount regulation: Fixed regulation blade
Regulating blade / developing sleeve spacing: 0.5mm (constant)
Centerline of developing sleeve and regulating blade
Angle between straight line connecting horizon and horizontal line: 50 ° (regulator blade is higher)
Under the above experimental conditions, the following live-action tests of Confirmation Experiment 1 and Comparative Experiments 1 and 2 were performed to compare the performance.

<Test contents>
Print pattern: Monochrome image with an average print rate of 6%
Printing mode: A4 size continuous printing (100,000 prints)
Environment (temperature, humidity): 20 ° C, 50% (0 to 20,000 prints)
30 ° C, 80% (20,000-50,000 prints)
10 ° C, 20% (50,000 to 80,000 prints)
20 ° C, 50% (80,000 to 100,000 prints)
Confirmation of solid density transition: Solid image transmission density every 5000 prints
Measured and measured with an X-Rite densitometer.
If it is in the range of 1.35 to 1.45
Passed and judged
Confirmation of fog density transition: X-Rit on white background every 5000 prints
e The relative reflection density measured with a densitometer is 0.0.
If it is 06 or less, it is determined to be acceptable.
Carrier adhesion confirmation: Vertical line pair putter for every 5000 puddings
Visually evaluate the carrier adhesion level of the
If the degree is less than the limit sample
Pass and Judgment ・ Experimental Results Results shown in Table 1 were obtained. In the table, ○ means pass and × means fail.

  In Table 1, in the case of Confirmation Experiment 1, since the carry amount measurement and the carry amount adjustment are performed, fluctuations in the carry amount are suppressed, and the solid density is always in the proper range. Moreover, there was no occurrence of carrier adhesion due to excessive transport amount. When measuring the conveyance amount, the supply roller is stopped and the reflected light from the surface of the developing sleeve not carrying the developer is measured and corrected as a countermeasure against the optical sensor detection window contamination, so that the accurate conveyance amount can be measured. Furthermore, because the developer layer is regulated by a low-speed rotating supply roller, the stress on the developer can be reduced, the toner charging performance is less degraded, and image fogging due to insufficient toner charging until the end of the experiment. There wasn't.

  On the other hand, in the case of Comparative Experiment 1 in which the supply roller is not present and the optical sensor detection window dirt correction cannot be performed, the gap between the regulating blade and the developing sleeve on the developing sleeve is adjusted to suppress the variation in the conveying amount. Although the amount temporarily changes around the target value, erroneous detection of the conveyance amount often occurs due to contamination of the optical sensor detection window due to toner scattering from the developing sleeve, leading to variation in the conveyance amount. Therefore, in the second half of the test, the sensor detection window becomes dirty, the amount of reflected light is reduced, and if the amount of conveyance is large, it is detected. Therefore, the control to reduce the amount of conveyance works, and the solid density is controlled to be low (especially at low temperatures). Low humidity environment). Although there was no carrier adhesion due to excessive transport amount, the developer was stressed by restricting the developer on the high-speed developing sleeve, so that the charging performance of the toner deteriorated. Image fogging due to insufficient charging of the image. Further, in the case of Comparative Experiment 2 in which the transport amount measurement and the transport amount adjustment are not performed, excessive solid concentration and carrier adhesion occur due to an increase in the transport amount in a high-temperature and high-humidity environment. Insufficient concentration occurred. Further, by regulating the developer on the high-speed rotating developing sleeve, stress was applied to the developer, resulting in a decrease in toner charging performance, and image fogging due to insufficient toner charging occurred in the latter half of the experiment.

  From the above, the effect of the present invention applied to the confirmation experiment 1 was confirmed.

  In the confirmation experiment 1, the conveyance amount is not corrected according to the toner density and environment (temperature and humidity) conditions. Needless to say, if this correction is added, the conveyance amount can be controlled with higher accuracy. Yes.

1 is an explanatory diagram illustrating an overall configuration of an image forming apparatus. FIG. 2 is an enlarged view of a developing device including a supply roller that supplies a developer onto a developing sleeve. It is a figure which shows the relationship between the conveyance amount accompanying the change of a toner density | concentration and environmental conditions, and reflected light amount (sensor output). It is a figure which shows the example of a well-known conveyance amount control system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image reading apparatus 2 Control part 21 Photoconductor drum 23 Developing apparatus 231 Developing sleeve 232 Developer supply roller 233 Developer control blade 234 Stirring member S Optical sensor S1 Toner density sensor S2 Temperature / humidity sensor D Development area

Claims (3)

In the image forming apparatus provided with a developing device having an optical sensor for detecting a developer conveyance amount facing a developing sleeve that carries and rotates the developer layer, the developer layer includes a developer in the developing device. And a measurement value A detected when the developer is transported by the optical sensor and a measurement detected when the developer is not on the development sleeve. An image forming apparatus, wherein a developer conveyance amount on the developing sleeve is calculated from the value B. When the developing sleeve or the developer supply roller has a variable rotation speed, the peripheral speed of the developing sleeve is α, and the peripheral speed of the developer supply roller is β, the value of β / α is changed, The image forming apparatus according to claim 1, wherein the developer conveyance amount calculated through a measured value by an optical sensor is adjusted to a target value. When calculating the developer transport amount, the developer transport is based on the measured values measured by the toner concentration detecting means for detecting the toner density of the developer and the environment data detecting means for detecting the operating environment including at least humidity. The image forming apparatus according to claim 1, wherein the amount is corrected.

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