JP2006259334A - Image forming apparatus, color image forming apparatus, and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably maintain images of high quality regardless of passage of time or environmental variances by efficiently detecting the variance in characteristic values of a two-component developer including the degree of deterioration of the developer and optimizing a control value in accordance with the variance of the developer. <P>SOLUTION: An image forming apparatus includes a photoreceptor drum 100, a developing unit 300 which stores a developer G including toner and carrier and develops an electrostatic latent image on the surface of the photoreceptor drum 100 by the toner, and a permeability sensor 350 for detecting toner concentration of the developer G in the developing unit 300, and can execute a plurality of image output modes (a standard linear speed and linear speeds 1 and 2 for thick paper mode). The image forming apparatus is provided with a control part 37 which detects the toner concentration in at least one image output mode and compares an output value from the permeability sensor 350 at the time of an environmental variance with a control reference value, obtains a difference from the comparison result, and updates an image density control parameter for determining the amount a toner T supplied to the developing unit 300. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, a plotter, or the like, or a composite machine composed of at least one of these, a color image forming apparatus, and an image forming method using the same.

Among recent image forming apparatuses, copying machines and laser printers are required to have high image quality, and at the same time, have high durability and high stability. In other words, there is little change in image quality due to environmental fluctuations, and a stable image must be provided over time. Conventionally, a two-component developer composed of a non-magnetic toner and a magnetic carrier (hereinafter simply referred to as “developer”) is held on a developing sleeve as a developer carrying member, and a magnetic brush is formed by a magnetic pole included in the developing sleeve. There is widely known a two-component development system in which development is performed by applying a developing bias to a developing sleeve at a position facing a photoconductor as an image carrier.
This two-component development method is currently widely used because it can be easily colored. In this system, the developer is transported to the developing area as the developing sleeve rotates. As the developer is transported to the development area, a large number of magnetic carriers in the developer (hereinafter sometimes simply referred to as “carriers”) gather together with the toner along the magnetic field lines of the developing pole to form a magnetic brush. To do.

  In these two-component development systems, unlike the one-component development system, it is very important to control the weight ratio (toner density) between the toner and the carrier accurately in order to improve the stability of the image. For example, if the toner concentration is too high, background stains may occur on the image, or the detail resolution may be reduced. Further, when the toner density is low, there are problems that the density of the solid image portion is lowered and carrier adhesion occurs. Therefore, it is necessary to control the toner replenishment amount and adjust the toner concentration in the developer to an appropriate range. Here, the toner density control is performed by comparing the magnetic permeability output value: Vt as the toner density detection value by the toner density detecting means (magnetic permeability sensor) with the toner density reference value: Vref and supplying the toner based on the result. This is done by setting the amount.

  As a method and method for detecting the toner concentration, a method using a magnetic permeability sensor is generally used. In this method, the change in the magnetic permeability of the developer due to the change in the toner density is compared with the output of the reference density to detect the current value of the toner density (for example, Patent Documents 1 to 5, 7 and 8).

As another toner density detection method, there is a method using an optical sensor. A reference pattern is formed on a photosensitive drum or an intermediate transfer belt, and the reflection density of an image portion and a non-image portion of the pattern is measured by the optical sensor. The toner density is detected based on the result (see, for example, Patent Documents 6 and 9).
. In addition, a method is also known in which a reference pattern is created between sheets even during printing, and the reference value Vref of the magnetic permeability sensor is sequentially controlled.
However, there is a demand to reduce excessive consumption of toner by creating a pattern between sheets as much as possible, and correction is not performed by creating a reference pattern between sheets. Further, when creating a pattern on the intermediate transfer belt, it is necessary to install a cleaning device on the secondary transfer roller, and there is a tendency to suppress pattern creation between papers as much as possible from the viewpoint of mechanical cost reduction. In such a case, it is necessary to more accurately perform toner concentration control by the magnetic permeability sensor alone at the time of continuous printing or image mode change (change of process linear velocity).

In these two-component developing devices, particularly color image forming devices, additives such as silica and titanium oxide are externally added to the toner surface in order to improve toner dispersibility. These additives are vulnerable to mechanical stress and thermal stress, and a phenomenon of being buried in the toner or detached from the surface occurs during stirring in the developing device. As a result, the flowability and charging characteristics of the developer (including toner and carrier) change, and the bulk density changes.
Also, over time, fluidity changes and bulk density changes due to a change in the shape of the carrier surface, separation and accumulation of toner external additives, and a decrease in CA (carrier charging ability) due to carrier coat film abrasion.
These changes become an obstacle for the magnetic permeability sensor to accurately detect the toner concentration. For example, in the case of a system that has a plurality of image output modes and the rotation speed of the stirring screw in the developing device changes accordingly, the output value changes even at the same toner concentration, but the developer deterioration state, The amount of correction changes depending on the usage situation, and it becomes difficult to correct accurately.

JP 2002-207357 A Japanese Patent Laid-Open No. 2002-14588 JP-A-9-236983 JP-A-5-232814 JP 7-28325 A JP 2002-258547 A JP 2003-280355 A JP 2004-20614 A JP-A-7-168436

In the technique described in Japanese Patent Laid-Open No. 2002-207357 (Patent Document 1), the toner concentration in the developing device is detected by a toner concentration detecting means (permeability sensor), and the detected value is compared with a threshold value. A technique is used in which the toner density in the developing device is controlled and the threshold value for the detection value of the toner density detecting means is changed in accordance with the change in the linear velocity of the photosensitive member.
However, in the above method, it is considered that control is possible at the beginning, but since correction due to deterioration over time is not taken into consideration, it is difficult to maintain high-quality image stability over a long period of time. it is conceivable that.

  In the technique described in Japanese Patent Laid-Open No. 2002-14588 (Patent Document 2), the threshold value of the toner concentration sensor (permeability sensor) is changed according to the rotation speed of the developing device (conveyance screw). As with the former technique, since correction due to deterioration over time is not taken into consideration, it is considered difficult to maintain the stability of a high-quality image over a long period of time.

  In the technique described in Japanese Patent Application Laid-Open No. 2003-280355 (Patent Document 7), Vc (control voltage or Vcnt) is used in order to align the Vt value that is the output value of the toner density sensor SD (magnetic permeability sensor) for toner density control. : Sensor control voltage) is changed. When the Vc value is changed, the characteristic (sensitivity) of the toner density sensor SD may change greatly, and it is difficult to change it easily. Further, the adjustment of the Vc value requires time for adjustment because it is necessary to adjust the voltage to about the target Vt value by changing the voltage by about 10 points by the two-division method, for example. Further, at the time of adjustment, it is necessary to set the toner density to a reference value (8% by weight). Therefore, it can be considered to increase the time required for process control.

  Therefore, the present invention has been made in view of the above points, and it is possible to efficiently detect a change in the characteristic value of the developer and optimize the control value in accordance with the change in the developer, thereby aging or environmental fluctuations. Sometimes, the main object is to provide an image forming apparatus, a color image forming apparatus, and an image forming method capable of stably maintaining a high-quality image. Another object of the present invention is to provide an image forming apparatus, a color image forming apparatus, and an image forming apparatus that can achieve the effects described below.

In order to solve the above-described problems and achieve the above-described object, the invention according to each claim employs the following characteristic means and configuration.
The invention according to claim 1 contains a two-component developer containing an image carrier that forms a latent image on the surface, and a toner and a magnetic carrier that is disposed opposite to the image carrier and holds the toner. And a developing means for developing the latent image on the surface of the image carrier with toner, and a toner concentration detecting means for detecting the toner concentration of the two-component developer in the developing means, and having a plurality of process linear speeds. In the image forming apparatus capable of executing a plurality of image output modes accompanied by a change, the toner density detecting means at the time of executing the image output mode is performed by executing toner density detection in at least one of the image output modes when the environment changes. A control means for comparing the detected value from the control reference value, obtaining a difference from the comparison result, and updating an image density control parameter for determining a toner replenishment amount to the developing means; Characterized in that it.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the control unit executes all of the plurality of image output modes, thereby detecting the toner density at the time of executing all the image output modes. The image density control parameter is updated based on a detection value from the means.

  According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, the control unit executes the at least two image output modes, thereby executing the toner density detecting unit during execution of the at least two image output modes. The developer characteristics including the degree of deterioration of the two-component developer are detected by calculating the inclination with respect to the process linear velocity based on the detected value from the above.

  According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the control unit detects a developer characteristic including a degree of deterioration of the two-component developer. The mode for updating the image density control parameter is individually executed.

  According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the toner density detecting means is a magnetic permeability sensor that detects the magnetic permeability of the two-component developer. Features.

  According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the control unit corrects a detection value from the toner density detection unit when the image output mode is executed. It is characterized by doing.

  According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects, the control unit detects the developer characteristic value including the degree of deterioration of the two-component developer. It performs according to.

  According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the first to seventh aspects, the control unit detects the detection of the developer characteristic value including the degree of deterioration of the two-component developer based on environmental fluctuations. It performs according to it, It is characterized by the above-mentioned.

  A ninth aspect of the present invention is the image forming apparatus according to any one of the first to eighth aspects, further comprising a plurality of developing means capable of developing using toner of at least two colors, and the two-component developer. The color image forming apparatus is characterized in that the developer characteristic values including the degree of deterioration can be detected independently by the plurality of developing units.

  In a tenth aspect of the present invention, a developer carrier that is disposed opposite to the image carrier and has a magnet therein carries a two-component developer including toner and a magnetic carrier that holds the toner. Developing means for transporting a component developer to a developing area formed between the image carrier and developing a latent image formed on the surface of the image carrier with toner supplied from the developer carrier And a toner density detecting means for detecting the toner density of the two-component developer in the developing means, and an image forming method capable of executing a plurality of image output modes with a change in a plurality of process linear speeds By executing toner density detection in at least one of the image output modes when the environment changes, the detection value from the toner density detection means during execution of the image output mode is compared with a control reference value. And calculates a difference from the comparison result, and updates the image density control parameter that determines the supply amount of toner to the developing unit.

  According to the present invention, a novel image forming apparatus, color image forming apparatus, and image forming method can be provided by solving the above-described problems. That is, according to the present invention, changes in developer characteristics are measured in accordance with environmental fluctuations and developer deterioration, and the correction amount of the detection value (output value Vt) from the toner concentration detection means (particularly the magnetic permeability sensor) is accurately determined. By calculating and updating, higher stability can be obtained.

Embodiments including the best mode for carrying out the present invention will be described below with reference to the drawings. The constituent elements such as members and components having the same functions and shapes in the embodiment, the modified examples, the examples, and the like will be omitted after being described once by giving the same reference numerals. In order to simplify the drawings and the description, even components that are to be represented in the drawings may be omitted as appropriate without being specifically described in the drawings. In the case of quoting and explaining constituent elements such as published patent gazettes, the reference numerals are shown in parentheses to distinguish them from those of the embodiment, modified examples, and examples.
(First embodiment)
1 to 7 show an image forming apparatus according to a first embodiment of the present invention.
First, an overall configuration of an image forming apparatus to which the present invention is applied will be described with reference to FIG. The image forming apparatus shown in the figure is a full color image forming apparatus 50 as an example, and an image carrier for each of four colors of yellow (Y), magenta (M), cyan (C), and black (Bk). And a developing device as a developing means, and sequentially transfer toner images of each color onto a transfer material as an example of a sheet-like recording medium (hereinafter, further described in “transfer paper”). Thus, the tandem apparatus configuration forms a full-color image.

  In FIG. 1, reference numeral 40 denotes an apparatus main body of the full-color image forming apparatus 50. In the apparatus main body 40 of the full-color image forming apparatus 50, four photoconductors 1Y, 1M, 1C, and 1Bk as image carriers are arranged in this order from the right to the left in the figure in the upper left direction. ing. For each of the photoreceptors 1Y, 1M, 1C, and 1Bk, image forming units 22Y, 22M, and 22C for forming images of four colors of yellow (Y), magenta (M), cyan (C), and black (Bk). , 22Bk are arranged. A full color image is formed by these image forming units 22Y, 22M, 22C, and 22Bk. Since the image forming units 22Y, 22M, 22C, and 22Bk for the respective colors perform the same configuration and operation, only the yellow (Y) image forming unit 22Y disposed in the rightmost part will be described. Description of the other image forming units 22M, 22C, and 22Bk is omitted by attaching the same Arabic numerals to the same portions and adding alphabetical characters representing the colors.

  The image forming unit 22Y is a drum-shaped photoreceptor 1Y (hereinafter referred to as “photoreceptor drum 1Y”) and a charging unit that is disposed around the photoreceptor drum 1Y and repeatedly forms yellow (Y) images. Charging device 2Y, exposure 4Y irradiated from an exposure device as an exposure means (not shown), developing device (hereinafter sometimes referred to as "developing device") 3Y as developing means, cleaning device 6 as cleaning means, and the like It is composed of

The photosensitive drum 1Y is supported on a housing side plate (not shown) of the apparatus main body 40 so as to be rotatable clockwise in FIG. The exposure apparatus includes a laser light scanning optical system including a laser diode (LD) (not shown) that generates and emits laser light according to an image signal, a polygon mirror (not shown) that scans the laser light emitted from the LD, and the like. (Not shown) and exposure 4Y is performed.
In FIG. 1 below the arrangement positions of the photosensitive drums 1Y, 1M, 1C, and 1Bk of the image forming units 22Y, 22M, 22C, and 22Bk, a transfer sheet P as an example of a transfer material that is a sheet-like recording medium is adsorbed. Then, the conveying transfer belt 5 that is conveyed is stretched oppositely. The conveyance transfer belt 5 is stretched between the driving roller 15 and the driven roller 17 and travels and conveys in the direction of the arrow (counterclockwise) in the figure. The conveyance transfer belt 5 has a function as a conveyance transfer unit that electrostatically attracts, carries, and conveys the transfer paper P.

  In FIG. 1 facing the respective photosensitive drums 1Y, 1M, 1C, and 1Bk, transfer devices 8Y, 8M, 8C, and 8Bk each including a transfer roller as a contact transfer unit with the conveyance transfer belt 5 interposed therebetween are disposed. Has been. The transfer devices 8Y, 8M, 8C, and 8Bk are arranged on the transfer paper P on which the toner images of the respective colors formed on the photosensitive drums 1Y, 1M, 1C, and 1Bk are electrostatically adsorbed by the transport transfer belt 5 and transported. Has a well-known function of transferring by the action of an electric field. The transfer sheet P is transferred at a predetermined timing by selecting one of the sheet feeding sections 19-1 to 19-3 disposed in the lower portion of the apparatus main body 40. Sent out.

  The paper feeding units 19-1 to 19-3 differ only in the size in which the transfer paper P is stacked and stored, and have the same configuration. Therefore, the paper feeding unit 19-1 will be described as a representative. The paper feeding unit 19-1 includes a paper feeding cassette 21 on which transfer paper P is stacked and stored, and a paper feeding roller 20 that is disposed above the paper feeding cassette 21 and feeds the uppermost transfer paper P one by one. The transfer roller P is mainly composed of a pair of registration rollers 18 and the like that feed the transfer paper P fed by the paper feed roller 20 at a predetermined timing. A transfer material guide plate and a conveyance roller pair (not shown) are disposed in the transfer material conveyance path between the sheet feeding roller 20 and the registration roller pair 18.

In the left side of the apparatus main body 40 in FIG. 1, which is downstream of the transfer material conveyance path, a separation device (not shown) for separating the transfer paper P from the conveyance transfer belt 5 is driven via the conveyance transfer belt 5. 15 is provided opposite to 15. On the left side of the separation device is a fixing roller 9 having a fixing roller and a pressure roller for fusing and fixing the toner images of the respective colors transferred onto the transfer paper P. Further, the fixing device 9 is discharged above the fixing device 9. A pair of paper discharge rollers 24 via a guide plate (not shown), and a paper discharge tray (not shown) for discharging the transfer paper P on which a toner image is formed at the lower right side of the paper discharge roller pair 24. 2) is provided.
FIG. 1 mainly shows a control unit (not shown) having a function and configuration of a control means for updating an image density control parameter for determining a toner replenishment amount to each developing device 3Y, 3M, 3C, 3Bk. A control device) for each of the image forming units 22Y, 22M, 22C, and 22Bk (image forming stations), which will be described in detail later.

The full-color image forming apparatus 50 has a configuration capable of executing a plurality of image output modes accompanied by a change in a plurality of process linear velocities, like the conventional image forming apparatus.
Here, the “image output mode” refers to a high-speed, low-speed mode or the like that involves a change in the process linear velocity. In the present embodiment, the process linear velocity in each mode is 205 (mm / s) in the standard mode, 115 (mm / s) in the linear velocity 1 and 77 (mm / s) in the linear velocity 2, respectively.
Here, the standard mode is, for example, the fastest copy speed (image forming speed) when copying to plain paper, and the linear speed 1 is, for example, a medium speed copy speed when copying to thick paper. No. 2 corresponds to an extremely low copying speed when copying with good image quality on thick paper.

Next, the operation during full color image formation will be described.
When a full color image formation signal is transmitted by a key operation on an operation panel (not shown), the image forming units 22Y, 22M, 22C of yellow (Y), cyan (C), magenta (M), and black (Bk) 22Bk operates at predetermined timings, and toner images of the respective colors are formed on the photosensitive drums 1Y, 1M, 1C, and 1Bk. When this is exemplified by the image forming unit 22Y, the photosensitive drum 1Y rotates in the clockwise direction in FIG. 1 and the outer surface thereof is uniformly charged by the charging device 2Y, and then the image from the LD of the exposure device 3Y. A laser beam is irradiated according to the signal, and is exposed and imaged on the photosensitive drum 1Y while being scanned by the polygon mirror, thereby forming an electrostatic latent image. Then, when the photosensitive drum 1Y on which the electrostatic latent image is formed faces the developing device 3Y, the developing sleeve 302 (see FIG. 2), which is also called a developing roller that is a developer carrying member in the developing device 3Y, is used in the developing device 3Y. Is transferred to the developing nip region facing the photoreceptor drum 1Y, so that the toner in the developer is supplied and attached to the electrostatic latent image formed on the surface of the photoreceptor drum 1Y, and developed. A yellow (Y) visualized toner image is formed on the photosensitive drum 1Y.
In the other color image forming units 22M, 22C, and 22Bk, toner images are formed in the same manner as the image forming unit 22Y.

On the other hand, the transfer paper P set in the paper feed cassette 21 is taken out by the paper feed roller 20, sent to the registration roller pair 18 along the transfer material conveyance path, and then transferred to the registration paper P by the registration roller pair 18. The leading edge is sent to the transfer area of the transfer portion of the photosensitive drum 1Y in synchronization with the yellow (Y) toner image of the first color formed on the photosensitive drum 1Y.
At the transfer position of the yellow (Y) toner image of the first color, the yellow (Y) toner image is transferred onto the transfer paper P by the action of the electric field formed by the transfer device 8Y. The paper P is electrostatically attracted to the transport transfer belt 5 and is transported by the transport transfer belt 5. The transfer paper P onto which the yellow (Y) toner image is transferred in this way is transferred between the transfer devices 8M, 8C, 8Bk provided for each color in turn and the photosensitive drums 1M, 1C, 1Bk. The cyan (C) toner image, the magenta (M) toner image, and the black (Bk) toner image formed on the photosensitive drums 1M, 1C, and 1Bk are sequentially transferred onto the transfer paper P. Is done. In this way, the toner images of all colors are transferred onto the transfer paper P, so that a full-color toner image is formed on the transfer paper P.

  The transfer paper P on which the full-color toner image is formed is separated from the transfer transfer belt 5 by the separation device and then sent to the fixing device 9 where the full-color toner image is melted and pressure-fixed by the fixing device 9. The image is completed and discharged onto a paper discharge tray (not shown) via a paper discharge roller pair 24 of the paper discharge unit 23.

  On the other hand, in the cleaning device 6Y, residual toner or the like remaining on the surface of the photosensitive drum 1Y without being completely transferred to the transfer paper 8 is removed by a cleaning blade, and collected and stored in a waste toner bottle 10 through a waste toner collection path (not shown). The The surface of the photosensitive drum 1Y that has passed through the cleaning device 6Y is then uniformly charged by the charging device 2Y, and the next image forming process is repeated. The same operation is performed in the remaining image forming units 22M, 22C, and 22Bk in the same manner.

FIG. 2 shows the main part of the image forming unit of the full-color image forming apparatus 50, the periphery of the developing device, and the control configuration thereof. In order to simplify the description, the image forming unit illustrated in FIG. 2 represents any one of the image forming units 22Y, 22M, 22C, and 22Bk illustrated in FIG. The image forming unit of the image forming apparatus is also shown.
In FIG. 2, reference numeral 100 denotes a drum-shaped photosensitive member (hereinafter referred to as “photosensitive drum”) as an image carrier, and reference numeral 300 denotes an electrostatic latent image formed on the photosensitive drum 100. A developing device (hereinafter referred to as “developing device”) as a developing unit that develops the image to make it visible (visualized), and symbol G indicates a two-component developer.
The photosensitive drum 100 is a general expression of the photosensitive drums 1Y, 1M, 1C, and 1Bk shown in FIG. 1, for example, and the developing device 300 is also an example of the developing devices 3Y, 3M, 3C, and 3Bk shown in FIG. It is a general expression.

The photoconductor drum 100 is a photoconductor that has photoconductivity and forms an electrostatic latent image on its surface, and is made of, for example, a well-known organic photoconductor. The photosensitive drum 100 is rotationally driven by a drive motor (not shown) as drive means in the clockwise direction indicated by an arrow in FIG. The image bearing member is not limited to the photosensitive drum 100, and may be, for example, a belt-shaped photosensitive member.
Around the photosensitive drum 100, as shown in FIG. 1, in the order of the rotation direction indicated by the arrows in FIG. The developing device 300, a transfer device (not shown), and a cleaning device (not shown) are arranged, and these constitute an image forming unit.

The developing device 300 is disposed opposite to the photosensitive drum 100 and includes a two-component developer G (hereinafter simply referred to as “carrier C”) including a toner T and a magnetic carrier C (hereinafter simply referred to as “carrier C”) that holds the toner T. Development as a developer carrying member that carries a developer (sometimes referred to as a “developer”), transports the developer to a developing region formed between the photosensitive drum 100 and a magnet (not shown) inside. A developing sleeve 302, also called a roller, is provided, and has a function and configuration for developing an electrostatic latent image formed on the surface of the photosensitive drum 100 with toner T supplied from the developing sleeve 302.
The developing sleeve 302 has both ends of its shaft on the casing side walls (not shown) formed on the front side and the back side of the paper surface of the developing device casing 301 which is a housing in which the developing sleeve 302 is housed. It is supported rotatably (counterclockwise) and is driven to rotate in the same direction by a driving means (not shown).

In addition to the developing sleeve 302, the developing device 300 is supported by a casing side wall (not shown) so as to be rotatable in the rotation direction (counterclockwise) indicated by an arrow in both drawings, as shown in FIGS. A first conveying screw unit 305 fixed to one stirring shaft and a second stirring shaft fixed to a second stirring shaft supported by the casing side wall (not shown) so as to be rotatable in the rotation direction (clockwise) indicated by an arrow in both drawings. A conveying screw part 304 and a doctor blade 303 as a developer layer thickness regulating means / member for regulating the developer G moved from the first conveying screw part 305 and carried on the outer peripheral surface of the developing sleeve 302 to a predetermined layer thickness. Etc. is mainly composed of.
The developing device casing 301 is integrally formed with a partition wall that partitions the first transport screw unit 305 and the second transport screw unit 304. In FIG. 2, reference numeral 310 denotes a toner supply unit housing that covers the upper periphery of the developing sleeve 302. The proximal end of the doctor blade 303 is fastened and fixed to the inner wall of the developer casing 301 by fastening means (not shown).

The developer G is shown as a sand pattern in FIGS. 1 and 2. In the developing device 300, for example, the new toner is supplied to the second conveying screw unit 304 side through a toner bottle (not shown) containing new toner and a supply path (not shown) connected to the supply port. The toner is supplied to the toner supply unit. The toner T includes, for example, a polyester as a main material, a pigment or a colorant (in this embodiment, for example, at least two colors of yellow, magenta, cyan, and carbon black because it is a color image forming apparatus), a charge control agent, silica, titanium oxide, and the like. However, other known materials may be used.
Further, the developing device 300 includes, for example, a carrier bottle (not shown) containing a new carrier, a replenishment path (not shown) connected to the supply port, and a powder for feeding and feeding a new carrier or a new developer. A new carrier or a new developer is directly supplied through a Mono pump (not shown) which is a kind of pump. The carrier C is made of, for example, a ferrite core with an insulating resin coated around it, but may of course be another known one.
As shown in both figures, the developer G circulates between the first conveying screw part 305 fixed to the first stirring shaft and the second conveying screw part 304 fixed to the second stirring shaft. .

  The developer G moves from the first conveying screw portion 305 in the developing unit constituting the developing device 300 to the developing sleeve 302 by a pumping magnetic pole (not shown) of the developing sleeve 302. Thereafter, as the developing sleeve 302 rotates in the direction of the arrow in FIG. 2, the developer G is transported to the vicinity of the doctor blade 303 by the magnetic field of the transport pole and the frictional force on the surface of the developing sleeve 302. The developer G transported to the vicinity of the doctor blade 303 temporarily stays in the doctor upstream portion 320, and the layer thickness is regulated by the gap Gd between the doctor edge portion 303a which is the tip of the doctor blade 303 and the outer peripheral surface of the developing sleeve 302. After that, it is conveyed to the development area.

A predetermined developing bias is applied to the developing region, and a developing electric field is formed in the direction in which the toner T is urged to the electrostatic latent image formed on the photosensitive drum 100. Developed on drum 100. Further, the developer G that has passed through the developing region leaves the developing sleeve 302 at the developer separating pole position on the developing sleeve 302 and returns to the first conveying screw unit 305. Thereafter, the developer G moves to the second conveying screw unit 304, is adjusted to an appropriate toner concentration by the toner replenishing unit, and is conveyed again to the developing sleeve 302.
At the bottom of the developing device casing 301, a magnetic permeability sensor 350 as a toner concentration detecting means for detecting the concentration of the toner T in the developer G in the developing device 300 is disposed and attached with the inner wall exposed. .

  After completion of the development process, the toner developed on the photosensitive drum 100 is transferred to a transfer sheet by a transfer device (not shown), that is, a transfer roller (not shown) constituting a transfer device (not shown) in a monochromatic image forming apparatus. In the color image forming apparatus 50 shown in FIG. 1, the image is transferred onto the transfer paper P via the conveyance transfer belt 5 or an intermediate transfer belt (not shown) as an intermediate transfer member. At this time, the residual toner remaining on the photosensitive drum 100 is removed and collected by a cleaning device omitted in FIG.

The control configuration will be described with reference to the block diagram of FIG.
The detailed configuration and advantages of the magnetic permeability sensor 350 are the same as those described in paragraphs “0007” to “0008” of Japanese Patent Laid-Open No. 2002-207357 (Patent Document 1), for example. Omitted.
In the vicinity of the outer peripheral surface of the photosensitive drum 100, a toner adhesion amount detection that detects a toner adhesion amount of a toner image (a test toner image) formed on the photosensitive drum 100 and outputs a toner adhesion amount detection signal. An optical sensor 30 as means is arranged. The optical sensor 30 is composed of, for example, a reflective photosensor. In the full-color image forming apparatus 50 of FIG. 1, the optical sensor 30 detects the toner adhesion amount of the toner image (test toner image) formed on the transport transfer belt 5.

  The magnetic permeability sensor 350 and the optical sensor 30 (shown in the installation position in FIG. 1) are connected to the I / O board 31 via an A / D converter (not shown). The control unit 37 mainly includes a CPU (Central Processing Unit) 32, a ROM (Read Only Memory) 20, a RAM (Read / Write Memory) 34, and an I / O board 31. Here, the RAM 34 means a broad concept storage device including an NV-RAM (a memory backed up by a power source such as a battery or a non-volatile memory such as a flash memory) for the sake of simplicity.

  A control command signal is transmitted from the CPU 32 to the toner replenishment drive motor 14 that drives a replenishment device (not shown) (not shown) via the I / O board 31. The RAM 34 stores a Vt register that temporarily stores an output value Vt related to toner density transmitted from the magnetic permeability sensor 350 via the I / O board 31, and Vref that stores a control reference value Vref of toner density in the developing device 300. A register, a Vs register for storing the output value Vs from the optical sensor 30, and the like are provided. The ROM 33 stores a toner density control program and an image density control parameter correction program according to a flowchart to be described later.

The CPU 32 of the control unit 37 has various functions as a control unit that performs the following control while calling the program stored in the ROM 33.
The CPU 32 executes toner density detection in at least one image output mode when the environment changes, thereby comparing an output value as a detection value from the magnetic permeability sensor 350 during execution of the image output mode with a control reference value, It has a function as a control unit that obtains a difference from the comparison result and updates an image density control parameter that determines the replenishment amount of the toner T to the developing device 300.
The CPU 32 executes all of the plurality of image output modes, and thereby determines the replenishment amount of the toner T to the developing device 300 based on the output value from the magnetic permeability sensor 350 when all the image output modes are executed. It has a function as a control means for updating the density control parameter.

Further, the CPU 32 executes the at least two image output modes, and calculates the inclination with respect to the process linear velocity based on the output value from the magnetic permeability sensor 350 when the at least two image output modes are executed. It has a function as a control means for detecting the developer characteristics including the degree of deterioration of the developer G.
Further, the CPU 32 individually detects a developer characteristic including the degree of deterioration of the developer G, thereby individually executing a mode for updating an image density control parameter that determines the replenishment amount of the toner T to the developing device 300. As a function.
The CPU 32 also has a function as a control unit that corrects an output value from the magnetic permeability sensor 350 when the image output mode is executed.
Further, the CPU 32 detects the developer characteristic value including the degree of deterioration of the developer G, for example, the number of image formations recognized by a write signal such as a laser beam from the exposure device to the photosensitive drum 100, and the photosensitive drum. At least one of engine driving time (total travel distance) by counting and recognizing the total number of revolutions of 100 (or the transfer transfer belt 5) and environmental fluctuations due to a temperature / humidity signal transmitted from the temperature / humidity sensor 340. It has a function as a control means to be executed in response.

First, a toner replenishment control operation executed for each printing will be described. The following various control operations are executed under the control of the CPU 32 of the control unit 37 (hereinafter, sometimes referred to as “control unit 37” for the sake of simplicity of explanation), and thus the description by the CPU 32 is omitted.
With reference to FIG. 3, the relationship between the output value Vt, which is the detected value of the magnetic permeability sensor 350, and the toner concentration (weight percent: wt%) will be described. In FIG. 3, the vertical axis, which is also the y axis, shows the output value Vt (V) from the magnetic permeability sensor 350, and the horizontal axis, which is also the x axis, shows the toner concentration (weight percent: wt%). In a certain toner density range, a linear approximation is possible. In other words, the output value Vt (V) and the toner concentration (% by weight) shown in FIG. 3 can be expressed by a substantially linear function y = −0.5519x + 5.8144.
As can be seen from the figure, the higher the toner density, the smaller the output value Vt. Using this characteristic, when the output value Vt of the magnetic permeability sensor 350 is larger than the control reference value Vref, the toner replenishing drive motor 14 of the toner replenishing unit of the developing device 300 is driven to perform the toner replenishing operation.

Hereinafter, the developer characteristic value measuring method and the correcting method of this embodiment will be described in detail.
In FIG. 4, the vertical axis that is also the y-axis indicates the output value Vt (V) from the magnetic permeability sensor 350, and the horizontal axis that is also the x-axis indicates the process linear velocity (mm / s). A linear approximation is possible within a certain toner density range. In other words, the output value Vt and the process linear velocity shown in FIG. 4 can be represented by a substantially linear function y = −0.008x + 3.0559.
In the case of an image forming apparatus having a plurality of process linear velocities (for example, see the full-color image forming apparatus 50 in FIG. 1), when the process linear velocities are different, the output value Vt of the magnetic permeability sensor 350 has the same toner concentration. However, it is output as a different value. Therefore, it is necessary to correct the output value Vt of the magnetic permeability sensor 350 for each linear velocity. This is because the output value Vt of the magnetic permeability sensor 350 greatly deviates from the control reference value Vref, so that proper toner replenishment control becomes difficult.

A procedure for correcting the output value of the magnetic permeability sensor for each of the plurality of process linear velocities will be described with reference to the flowchart of FIG.
First, in step S1, an image output mode (print mode), that is, a linear velocity is detected. In step S2, the output value Vt ′ output from the magnetic permeability sensor 350 is detected. Here, the output value Vt ′ (hereinafter, “output value” is omitted in each flowchart) is a value itself output from the magnetic permeability sensor 350 and is not corrected. Next, the process proceeds to step S3 to determine what process linear velocity is. If it is the standard linear velocity, the output value Vt is updated with no correction, and the output value Vt = output value Vt ′ (step S4 and step S5).

  If it is other than the standard linear velocity, the process proceeds to step S6. If the linear velocity is 1, the output value Vt is updated as the output value Vt = Vt′−ΔVt1 (step S5). In the case of the linear velocity 2, the output value Vt is updated as the output value Vt = Vt′−ΔVt2 (step S5). Here, ΔVt1 and ΔVt2 are correction amounts (V). In the present embodiment, the process linear velocity in each mode is 205 (mm / s), the linear velocity 1 is 115 (mm / s), and the linear velocity 2 is 77 (mm) as described above. / S).

In this correction, the correction amount for each linear velocity is generally a fixed value obtained through experiments. However, since the developer fluidity and bulk density change with the progress of developer deterioration, the output value of the magnetic permeability sensor 350 varies greatly, and it is difficult to correct the output value Vt accurately over time. It became.
In addition, since a fixed value cannot be corrected in consideration of changes in developer characteristics due to environmental fluctuations, the operation may become unstable at high temperature and high humidity or low temperature and low humidity. Furthermore, when a fixed value is used, it is impossible to correct variations in the magnetic permeability sensor 350 itself, variations in the magnetic permeability sensor 350 installation, differences in developer production lots, etc. There has been a demand for a method for determining the correction value in consideration of the fluctuation factors. In this embodiment, higher stability is obtained by measuring changes in developer characteristics according to environmental changes and developer deterioration, and accurately calculating and updating the correction amount of the output value Vt of the magnetic permeability sensor 350. Is possible.

Next, the flow of developer characteristic value measurement will be described with reference to FIG.
In the figure, first, in step S10, for example, a drive unit (hereinafter referred to as “engine”) of the image forming apparatus shown in FIGS. 1 and 2 is driven in the standard linear velocity mode. In step S11, the toner density detection value Vt′0 before correction is acquired. Next, in step S12, the engine is driven in the linear speed 1 mode, and Vt′1 is acquired in step S13. Similarly, in step S14, driving is performed in the linear velocity 2 mode, and Vt′2 is acquired in step S15. In step S16, correction amounts: ΔVt1 and ΔVt2 are calculated according to the following equations.
ΔVt1 = Vt′1−Vt′0 (1)
ΔVt2 = Vt′2−Vt′0 (2)
Thereafter, in step S17, ΔVt1 and ΔVt2 are updated, stored in the NV-RAM of the RAM 34, and the process ends.

In the present embodiment, the correction amount calculation timing described above is set so that the value is measured and updated every 1000 image formation sheets (printed sheets). In addition, the developing device 300 is unitized. In the case of a new developing unit, it is desirable to calculate the correction amount when it is replaced with a new one or when the developer is replaced. For this reason, the present embodiment has a mode in which the correction amount can be calculated independently, so that correction can be arbitrarily executed. As another method, the temperature / humidity sensor 340 is provided, and the correction amount is calculated in accordance with the output value, whereby correction with higher accuracy is possible.
In this embodiment, a correction amount measurement mode is provided separately. However, in order to further reduce the time, a correction value is calculated from the output value Vt of the permeability sensor 350 before and after the image output mode changes during the print job. It may be updated.

Next, a developer characteristic measurement flow for shortening the process control time will be described with reference to FIG.
In the figure, first, in step S20, the engine is driven in the standard linear velocity mode. In step S21, the toner density detection value Vt′0 before correction is acquired. Next, in step S22, the engine is driven in the linear speed 1 mode, and Vt′1 is acquired in step S23. Next, in step S24, using the Vt′0 and Vt′1 acquired in steps S21 and S23, the inclination and y intercept of the approximate straight line of Vt ′ with respect to the linear velocity are acquired. ΔVt′2 is calculated from this approximate straight line. Next, in step S25, ΔVt1 and ΔVt2 are calculated using the above equations (1) and (2). Thereafter, in step S26, ΔVt1 and ΔVt2 are updated, stored in the NV-RAM, and the process ends.

Thus, by calculating the inclination and calculating the correction amount for each linear velocity, it is not necessary to measure the detection value in all image output modes, leading to a reduction in measurement time. In the present embodiment, an image forming apparatus having three linear velocities is taken as an example, but the same measurement can be performed in an image forming apparatus having more image output modes.
In this embodiment, since the output value Vt value of the magnetic permeability sensor itself can be corrected according to the degree of change, the magnetic permeability is compared with the control according to Japanese Patent Laid-Open No. 2003-280355 (Patent Document 7). In order to align the output value Vt of the sensor, the control voltage Vcnt is not changed, that is, the characteristic (sensitivity) of the magnetic permeability sensor is not changed greatly, and the control voltage Vcnt value is adjusted by, for example, the two-divided method. Since it is not necessary to adjust the voltage to about 10 points to achieve the target Vt value, the time required for the adjustment can be greatly shortened.

  The present embodiment is not limited to the full-color image forming apparatus 50 shown in FIG. 1 or the example shown in FIG. 2, and color image formation having a plurality of developing devices (developing devices) that can be developed using toner of at least two colors. Needless to say, even when the present invention is applied to an apparatus, the same actions and effects can be achieved in accordance with the above-described contents.

As described above, since the conventional correction method using fixed values cannot be corrected by taking into account changes in developer characteristics due to environmental fluctuations, operation may become unstable at high temperatures and high humidity or low temperatures and low humidity. . Furthermore, when a fixed value is used, it is impossible to correct variations in the permeability sensor itself, variations in the permeability sensor installation, differences in developer production lots, and the like.
However, according to the present embodiment, the CPU 32 performs toner density detection in at least one image output mode when the environment changes, so that an output as a detection value from the magnetic permeability sensor 350 when the image output mode is executed. By comparing the value with the control reference value, obtaining the difference from the comparison result, and updating the image density control parameter that determines the replenishment amount of the toner T to the developing device 300, the CPU 32 also has a plurality of image output modes. By executing all of the above, the image density control parameter for determining the replenishment amount of the toner T to the developing device 300 is updated based on the output value from the magnetic permeability sensor 350 when executing all the image output modes. Measure changes in developer characteristics according to environmental changes and developer deterioration, and compensate for the output value Vt from the permeability sensor 350. The amount to be to accurately calculate and update, it is possible to obtain a greater stability.

According to the present embodiment, the control unit 37 (CPU 32) sets the image density control parameter that determines the replenishment amount of the toner T to the developing device 300 by detecting the developer characteristics including the degree of deterioration of the developer G. By executing the update mode individually, it is possible to arbitrarily update the image density control parameter, and it is possible to stably maintain a high-quality image. In addition, when the developing device is replaced with a new one or when the developer is replaced, an immediate response can be made.
In addition, according to the present embodiment, since the magnetic permeability sensor 350 is used as the toner concentration detecting means, the output value of the magnetic permeability sensor 350 changes with respect to the change in the fluidity of the developer, etc. The change state of the value can be grasped.
Further, according to the present embodiment, the control unit 37 (CPU 32) optimizes the control value according to the developer change by correcting the output value from the magnetic permeability sensor 350 at the time of executing the image output mode. Therefore, it is possible to stably maintain a high-quality image over time or when the environment changes.
Further, according to the present embodiment, the control unit 37 (CPU 32) detects the developer characteristic value including the degree of deterioration of the developer G by, for example, a laser / write signal from the exposure device to the photosensitive drum 100. By executing according to the number of recognized image forming sheets, it becomes possible to optimize the control value according to the change in the developer over time, so that a high-quality image can be stably maintained. .
Further, according to the present embodiment, the control unit 37 (CPU 32) detects the developer characteristic value including the degree of deterioration of the developer G, for example, the environmental fluctuation caused by the temperature / humidity signal transmitted from the temperature / humidity sensor 340. By executing according to at least one, it is possible to follow a rapid environmental change, and it is possible to stably maintain a high-quality image.
In addition, according to the present embodiment, a plurality of developing devices (developing units) that can be developed using at least two color toners are provided, and a plurality of developer characteristic values including the degree of deterioration of the two-component developer are detected. In the case of a color image forming apparatus that can be independently executed by a developing device (developing unit), the degree of change in developer differs for each image forming unit (image station). However, for example, when only a monochrome image is output, a setting such as increasing the number of executions of the black image forming unit Bk can be performed, and correction can be performed more efficiently.
Further, according to the present embodiment, the control unit 37 (CPU 32) executes at least two image output modes, and based on the output value from the magnetic permeability sensor 350 at the time of executing the at least two image output modes. By detecting the developer characteristics including the degree of deterioration of the developer G by calculating the inclination with respect to the process linear velocity and calculating the correction amount of each linear velocity, the detection value is measured in all image output modes. This eliminates the need for measurement time.

(Modification)
A modification of the first embodiment will be described with reference to FIGS. 8 and 9.
As described above, since the characteristic value of the developer changes with time, the output value of the magnetic permeability sensor 350 changes. For example, as shown in FIG. 8, the slope of Vt ′ with respect to the linear velocity is greatly different between the initial developer and the developer after running. Therefore, the developer characteristic value change state (developer deterioration state) can be determined from the change in inclination, and correction can be performed.

With reference to FIG. 9, the flow regarding the measurement of the developer characteristic value in the case where the execution possibility of the correction of the output value of the magnetic permeability sensor is taken into consideration will be described.
First, in step S30 of the figure, the engine is driven in the standard linear velocity mode. In step S31, an output value Vt′0 that is a detected value of the toner density before correction is acquired. Next, in step S32, the engine is driven in the linear speed 1 mode, and Vt′1 is acquired in step S33. Next, in step S34, using the Vt′0 and Vt′1 acquired in step S31 and step S33, the inclinations of the approximate straight line of Vt ′ with respect to the linear velocity: α and y intercept are acquired. Thereafter, in step S35, it is determined whether or not correction is performed. The determination is performed according to the following equation (3).
| Αn−αn−1 | ≧ α0 (3)
Here, αn is the current value of the slope, αn−1 is the previous slope, and α0 is the control reference value. The value of α0 is a value uniquely determined for each developer, such as the control toner density of the developer and the carrier particle size.
When correcting, it progresses to step S36 and calculates (DELTA) Vt1 and (DELTA) Vt2 using said (1) Formula and (2) Formula. Thereafter, in step S37, ΔVt1 and ΔVt2 are updated, stored in the NV-RAM, and the process ends. On the other hand, if no correction is performed in step S35, the process ends.

  According to the present embodiment, the control unit 37 (CPU 32) executes at least two image output modes, and thereby performs a process based on output values from the magnetic permeability sensor 350 when the at least two image output modes are executed. By detecting the developer characteristics including the degree of deterioration of the developer G by calculating the inclination with respect to the linear velocity and calculating the correction amount of each linear velocity, it is necessary to measure the detection value in all image output modes. This will lead to a reduction in measurement time. In addition, it is possible to perform toner correction control in consideration of whether or not the output value of the magnetic permeability sensor can be corrected.

  The color image forming apparatus to which the present invention is applied is not limited to the full color image forming apparatus 50 shown in FIG. 1, but for example, four colors of yellow (Y), magenta (M), cyan (C), and black (Bk) Each is provided with a photoconductor as an image carrier, a developing device as a developing means, etc., and an electrostatic latent image is formed on a plurality of photoconductors by an exposure means (optical scanning device etc.). Are developed with different color toners for each image carrier, and the toner images formed on the respective photoreceptors are sequentially transferred onto the intermediate transfer member, and then transferred onto a transfer material as a sheet-like recording medium. Of course, the present invention can also be applied to a full-color image forming apparatus for obtaining a color image or a color image forming apparatus for two or more colors.

As described above, it can be said that the image forming method according to claim 10 described in the section for solving the problems is used in the first embodiment and the modification.
As described above, the present invention has been described with respect to specific embodiments and the like, but the technical scope disclosed by the present invention is not limited to those exemplified in the above-described embodiments and the like. It will be apparent to those skilled in the art that various embodiments, modifications, and examples can be configured within the scope of the present invention in accordance with the necessity and application.

1 is a schematic configuration diagram of a full-color image forming apparatus showing a first embodiment of the present invention. FIG. 2 is a partial cross-sectional front view of a main part showing a periphery of the photosensitive drum and the developing device of FIG. It is a graph showing the relationship between a toner density | concentration and the output value of a magnetic permeability sensor. 7 is a graph showing a relationship between a plurality of process linear velocities and output values of a magnetic permeability sensor corresponding to the process linear velocities when the toner density is the same. It is a flowchart in the case of correct | amending the output value of a magnetic permeability sensor for every some process linear velocity. It is a flowchart regarding the measurement of a developer characteristic value. 6 is a flowchart relating to measurement of developer characteristic values for shortening process control time. 6 is a graph showing a relationship between a plurality of process linear velocities and an output value of a magnetic permeability sensor corresponding thereto when a change in developer characteristic value with time is used as a parameter. 6 is a flowchart relating to measurement of developer characteristic values in consideration of whether or not correction of an output value of a magnetic permeability sensor is taken into consideration.

Explanation of symbols

1Y, 1M, 1C, 1Bk, 100 Photosensitive drum (image carrier)
2Y, 2M, 2C, 2Bk charging device (charging means)
3Y, 3M, 3C, 3Bk, 300 Developer (Developer, Developer)
8Y, 8M, 8C, 8Bk transfer roller (constituting transfer means)
14 Toner replenishment drive motor 30 Optical sensor (toner adhesion amount detection means)
32 CPU (control means)
33 ROM (constituting control means)
34 RAM (constituting control means)
37 Control part (control means)
50 Full-color image forming device 340 Temperature / humidity sensor (environmental fluctuation condition)
350 Magnetic permeability sensor (toner concentration detection means)
C carrier G developer P transfer paper (example of sheet-like recording medium)
T Toner

Claims (10)

An image carrier that forms a latent image on the surface, and a two-component developer that is disposed opposite to the image carrier and includes a toner and a magnetic carrier that holds the toner. A plurality of image output modes including a developing means for developing a latent image with toner and a toner density detecting means for detecting the toner density of the two-component developer in the developing means, and a plurality of process linear speeds being changed. In an image forming apparatus capable of executing
By executing toner density detection in at least one of the image output modes when the environment changes, the detection value from the toner density detection means at the time of execution of the image output mode is compared with a control reference value, and from the comparison result An image forming apparatus comprising: a control unit that obtains a difference and updates an image density control parameter that determines a replenishment amount of toner to the developing unit. The image forming apparatus according to claim 1.
The control means updates the image density control parameter based on detection values from the toner density detection means when executing all the image output modes by executing all of the plurality of image output modes. An image forming apparatus. The image forming apparatus according to claim 1.
The control means calculates an inclination with respect to the process linear velocity based on a detection value from the toner density detection means when the at least two image output modes are executed by executing at least two image output modes. Thus, the developer characteristics including the deterioration degree of the two-component developer are detected. The image forming apparatus according to any one of claims 1 to 3,
The image forming apparatus according to claim 1, wherein the control unit individually executes a mode for updating the image density control parameter by detecting developer characteristics including a degree of deterioration of the two-component developer. The image forming apparatus according to any one of claims 1 to 4,
An image forming apparatus, wherein the toner density detecting means is a magnetic permeability sensor for detecting magnetic permeability of a two-component developer. The image forming apparatus according to claim 1,
The image forming apparatus according to claim 1, wherein the control unit corrects a detection value from the toner density detection unit when the image output mode is executed. The image forming apparatus according to any one of claims 1 to 6,
The image forming apparatus according to claim 1, wherein the control unit detects a developer characteristic value including a degree of deterioration of the two-component developer according to the number of image formations. The image forming apparatus according to any one of claims 1 to 7,
The image forming apparatus according to claim 1, wherein the control unit detects a developer characteristic value including a degree of deterioration of the two-component developer according to an environmental change. The image forming apparatus according to any one of claims 1 to 8,
A plurality of developing means capable of developing using toner of at least two colors;
A color image forming apparatus characterized in that detection of developer characteristic values including a degree of deterioration of a two-component developer can be independently performed by the plurality of developing units. A developer carrier disposed opposite to the image carrier and having a magnet therein carries a two-component developer including toner and a magnetic carrier for holding the toner, and the two-component developer is placed on the image carrier. Developing means for developing the latent image formed on the surface of the image carrier with the toner supplied from the developer carrier, and two parts within the developer means. In an image forming method capable of executing a plurality of image output modes accompanied by a change in a plurality of process linear speeds, using a toner concentration detecting means for detecting a toner concentration of a component developer.
By executing toner density detection in at least one of the image output modes when the environment changes, the detection value from the toner density detection means at the time of execution of the image output mode is compared with a control reference value, and from the comparison result An image forming method characterized in that an image density control parameter for determining a difference and determining a replenishment amount of toner to the developing means is updated.

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