JP2002214853A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent scattering of toner and sticking of carrier. SOLUTION: Information A on a first process means and information B on a second process means are detected. Based upon the information A, a determination means determines whether the control of the first process means is necessary. When the determination means determines the control of the first process means is necessary, the control of the first process means is executed, and thereafter the control of the second process means is executed, based the information B. When the determination means determines that the control of the first process means is unnecessary, the control of the first process means is not executed, but the control of the second process means is executed, based upon the information B. Information A includes information on toner concentration relating to the toner concentration control of a developing means and information on the amount of toner attached to an image carrier after development. Information B includes at least one of information on electrifying potential of an electrifying means, amount of writing light of an image writing means, or development bias of the developing means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic copying machine, a facsimile, and a printer, and more particularly, to an image forming potential related to an image forming potential for forming a toner image on an image carrier. The present invention relates to an image forming apparatus including a process control unit that performs process control such as toner density control of a developer that forms a toner image from a latent image.

[0002]

2. Description of the Related Art An image forming apparatus of this type generally includes a photosensitive member as an image carrier, a charging device for charging the photosensitive member, and a device for forming a latent image on the photosensitive member charged by the charging device. An exposure device, a developing device for developing a latent image on the photoconductor to form a toner image on the photoconductor, and a transfer device for transferring the toner image formed on the photoconductor to transfer paper as a recording medium Various image forming means such as a cleaning device for removing the residual toner on the photoreceptor after the transfer and a fixing device for fixing the toner image transferred on the transfer paper to the transfer paper are provided.

In this type of image forming apparatus,
Conventionally, in order to obtain a desired output image quality, an image forming potential control for controlling an image forming potential such as a latent image potential for forming a toner image on the photosensitive member, and a method for forming a toner image from a latent image 2
Various process controls such as toner replenishment control for adjusting the toner concentration of the component developer are performed.

The above-described toner supply control is performed, for example, as follows. First, as shown in FIGS. 7 and 8, a plurality of (three in this case) latent image patterns 20a, 20b, and 20 having a predetermined potential are formed on a photoconductor (here, a photoconductor drum) 200.
Form c. Next, the latent image patterns 20a, 20
Infrared light is emitted toward the photoconductor 200 from the reflection density sensor 205 for detecting the toner adhesion amount after the development of b and 20c. As shown in FIG. 8, the reflection density sensor 205 emits infrared light toward the photoconductor 200.
5a, and a light receiving element 205b that receives specularly reflected infrared light (a light beam whose incident angle and reflection angle are equal) from the photoconductor 200.

The reflection density sensor 205 has a light receiving element 2
Based on the amount of the regular reflection light received by the reference numeral 05b, it is detected whether or not the toner adhesion amount after development of the latent image patterns 20a, 20b, and 20c is the target toner adhesion amount of the output image. .

Here, when the light amount of the regular reflection light received by the light receiving element 205b is large, that is, when the toner adhesion amount of the latent image patterns 20a, 20b, and 20c after the development is insufficient, the light receiving element A toner supply signal is output from 205b.

When a toner supply signal is output from the light receiving element 205b, an appropriate amount of toner is supplied from a toner supply device (not shown) to the developing device. As a result, the toner concentration of the developer supplied to the photoconductor from the developing device is optimized, and the amount of toner adhered to the toner image formed on the photoconductor 200 can achieve the desired output image quality. It becomes the amount of toner adhesion.

On the other hand, the image forming potential control is performed, for example, as follows. Similar to the toner supply control described above,
First, as shown in FIG. 9, a plurality of latent image patterns 30a, 30b,
0c... And the latent image patterns 30a, 30
are developed on the photoreceptor 200 to form patterns having different toner adhesion amounts.

Next, the latent image patterns 30a, 30b, 3
0c... And the latent image patterns 30a, 30a detected by a potential sensor (not shown).
The development characteristics (development γ) of the developing device are obtained from the relationship with the surface potentials of b, 30c,. Then, the grid voltage of the charging device, the developing bias of the developing device, and the LD of the exposure device are adjusted so that the toner adhesion amount after development of the latent image patterns 30a, 30b, 30c... (Semiconductor laser) Controls light emission power and the like.
As a result, the image forming potential of the toner image formed on the photoconductor 200 is optimized, and the toner adhesion amount of the toner image becomes the toner adhesion amount at which the desired output image quality can be obtained.

Thus, in this type of image forming apparatus,
By the toner supply control and the image forming potential control described above, the toner concentration of the developer supplied to the photoconductor from the developing device,
If the image forming potential of the toner image formed on the photoreceptor 200 is optimized, the toner adhesion amount of the toner image can be favorably maintained in an ideal state in which a desired output image quality can be obtained. It is considered something.

However, in this type of image forming apparatus, in reality, a toner image is formed only with a developer of a specific color, an image area is extremely large, or almost normal image formation is not performed. In addition, image formation is performed in various cases, such as when only the automatic control such as the above-described potential control or the like where toner supply is not performed is performed. Here, in the toner supply control, normally, unless a toner image is formed on the photoconductor 200, toner supply from the toner supply device to the developing device is not performed. For this reason, if the developing ability of the developing device (the ability to visualize the latent image of the developing device) is higher or lower than a standard level, the toner adhesion amount of the toner image is controlled only by the image forming potential control. There was a case where a problem that it could not be completed occurred.

Conventionally, in order to solve such a problem, the toner is supplied from the developing device to the photosensitive member by supplying toner to the developing device or consuming the developer in the developing device at a specific timing. An image forming apparatus has been developed which performs the so-called self-check in which the above-described image forming potential control is performed after the toner concentration of the developer is adjusted.

The above-described image forming potential control in this image forming apparatus is executed as a special job at a timing different from a normal toner image forming routine. For example, the image forming potential control is performed immediately after turning on the power of the image forming apparatus in which the fixing device is cold, after executing a predetermined number of image forming jobs,
And after a predetermined time has elapsed since the previous image forming potential control.

Such a special job for self-check is effective for maintaining image quality. In particular,
In the color image forming apparatus, more stable process control can be performed by performing the above-described various controls over time for each color based on a lot of information.

JP-A-10-83115 discloses an image forming apparatus which forms a toner image on an image carrier by means of charging, exposure and development, and records this toner image on a recording material. Means for calculating a state relating to development characteristics of the image carrier by the means; and at least one of agitation of developer, toner replenishment, and toner consumption of the developing means.
An image forming apparatus comprising: a developer aging execution unit that executes two processes; and a unit that controls the developer aging execution unit so that the calculated state becomes a desired state. I have.

[0016]

As described above, the developing capacity before the potential control is desirably within a predetermined range. At this time, if the toner density is high, problems such as toner scattering and background contamination occur. If the toner concentration is low, a problem such as carrier adhesion that deteriorates image quality occurs. For example, if the gap between the developing device and the photoconductor is wide, the developing capacity is reduced. If toner is replenished to compensate for this, the toner density will increase and work in a direction that leads to toner scattering. Further, in a high-temperature and high-humidity environment, the developing capacity for a latent image is increased due to a decrease in the charge amount of the toner, and if toner replenishment is reduced and toner is consumed in order to compensate for the decrease, the toner concentration is reduced, leading to carrier adhesion. In terms of image quality, undesired background contamination and image omission occur. Further, the toner concentration at which such a problem occurs varies depending on environmental conditions that affect the charge amount of the toner.

In the image forming apparatus configured to execute the special job for the self-check as described above, the execution of the special job takes time for each color on the basis of a lot of information. Is performed.
For this reason, there is a problem that the user cannot perform image formation using the image forming apparatus for a predetermined time during which the control is performed.

Conventionally, in consideration of such operability of the user, the special job has been executed by utilizing the time when the fixing device warms up when the power is turned on every morning. However, in recent image forming apparatuses, it is desired to reduce the startup time, and it is difficult to secure a sufficient time to execute the special job.

In an image forming apparatus that is frequently used without powering down for 24 hours, such as an image forming apparatus installed in a convenience store or the like, the user needs to wait for the special job. There has been a problem that there is often no room to reserve or a standby place while the special job is being executed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to prevent the occurrence of toner scattering and carrier adhesion, and to maintain the target image quality for a long period of time. Another object of the present invention is to provide an image forming apparatus capable of shortening the time for process control.

[0021]

In order to achieve the above object, the invention according to claim 1 comprises an information detecting means for detecting information A relating to a first process means and information B relating to a second process means. Determining means for determining whether to execute the control of the first process means based on the information A among the information A and B detected by the information detecting means. When it is determined that the control of the first process means needs to be performed, the control of the first process means is performed, and then at least the information A or B of the information A or B is detected by the information detection means. B, based on the information B detected by the information detection means, a first control mode in which the control of the second process means is performed, and the determination means performs control of the first process means. No need to If it is determined, the control of the second process means is executed based on the information B of the information A and B detected by the information detection means without executing the first control mode. In the image forming apparatus performing the second control mode, the information A is information on the toner density related to the toner density control of the developing means as the first process means and information on the toner adhesion amount on the image carrier after development. Wherein the information B is information relating to at least one of a charging potential of a charging unit as the second process unit, a writing light amount of the image writing unit, and a developing bias of the developing unit.

According to a second aspect of the present invention, in the image forming apparatus of the first aspect, the developing means includes a plurality of developing devices in which a plurality of color toners are individually stored.

According to a third aspect of the present invention, there is provided information A relating to toner density control of a plurality of developing units constituting a developing unit, a charging potential of a charging unit, a writing light amount of an image writing unit, and a developing bias of the developing unit. Information detecting means for detecting information B relating to at least one of the above, and whether or not to execute the toner density control of each of the developing devices based on the information A among the information A and B detected by the information detecting means. Determination means for determining whether or not it is necessary to execute the toner density control of any one of the developing devices. The toner concentration control of the developing device determined to be necessary is executed, and then the information A,
B, at least the information B is detected again for the developing device on which the toner density control has been performed, and based on the information B detected by the information detecting means, the charging potential of the charging means, the writing light amount of the image writing means, A first control mode in which at least one of the developing biases of the developing units is controlled, and the determination unit determines that it is not necessary to execute the toner density control of any one of the developing units. In this case, based on the information B of the information A and B detected by the information detecting means, the first control mode is not executed for the developing device for which it is determined that the toner density control need not be executed. A second control mode for controlling at least one of a charging potential of the charging unit, a writing light amount of the image writing unit, and a developing bias of the developing unit. In the image forming apparatus, the information A
Includes information on toner density related to toner density control of the developing device and information on a toner adhesion amount on the image carrier after development, and the information B includes a charging potential of the charging unit, a writing potential of the image writing unit. This is information on at least one of the light amount and the developing bias of the developing device.

The invention according to claim 4 is the invention according to claim 2 or 3.
In the image forming apparatus described above, each of the developing devices has a configuration for performing development by moving to a predetermined developing position, and based on at least information A among the information A and B detected by the information detecting means. A determination operation of the determination unit that determines whether to perform the toner density control of each of the developing devices; and a toner concentration control operation of the development device that determines that the determination unit needs to perform the toner density control. Are successively executed for each developing device moved to the developing position.

The invention according to claim 5 is the invention according to claims 1, 2, and 3
In the image forming apparatus as described in (4), if the toner density information related to the toner density control of the developing means as the first process means is not within a predetermined range, the toner adhesion amount on the image carrier after development , And the toner density control is performed prior to the above information.

The invention according to claim 6 is the invention according to claims 1, 2,
6. The image forming apparatus according to 3, 4, or 5, wherein
The control target value of the toner density control of the developing means as the process means is changed according to environmental conditions.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below. This embodiment is an embodiment of an electrophotographic color copying machine as an image forming apparatus. First, the schematic configuration and operation of the present color copying machine will be described with reference to FIG. The color copying machine includes a color image reading device (hereinafter, referred to as a color scanner) 1, a color image recording device (hereinafter, referred to as a color printer) 2, a paper feed bank 3, and the like.

The color scanner 1 includes a contact glass 1
The original 4 placed on the original 01 is illuminated by an illumination lamp 102, and its reflected light is reflected by mirror groups 103a, 103b, 10b.
An image is formed on the color sensor 105 via the lens 3c and the lens 104, and the illumination lamp 102 and the mirror group 103 are formed.
The original 4 is scanned by the movement of a, 103b, 103c,
The color image information of the document 4 is, for example, red, green, blue (hereinafter, referred to as red, green, blue).
(Each of R, G, and B) is read and converted into an electric image signal, or the R, G, and B image signals are stored in a memory. When a memory is used, R, G, and B color image data are obtained by one original scan. In this embodiment, the color sensor 105 is composed of R, G, and B color separation means and a photoelectric conversion element such as a CCD.
The color images of B3 colors are read simultaneously.

An image processing unit (not shown) performs color conversion processing based on the intensity levels of the image signals separated into R, G, and B colors from the color scanner 1 and outputs black (hereinafter, referred to as Bk). , Cyan (hereinafter, referred to as C), magenta (hereinafter, referred to as M), and yellow (hereinafter, referred to as Y) color image data are sequentially obtained. Then, the color printer 2 receives Bk, C, M, and Y from the image processing unit.
Bk, C, M, Y in order according to the color image data of each color
An image of each color is formed, and these images are superimposed to form a final four-color superimposed full-color image.

The operation of the color scanner 1 for obtaining the color image data of each of the Bk, C, M and Y colors is as follows. The color scanner 1 includes a color printer 2 described later.
Receiving a scanner start signal which is timed with the operation of the illumination lamp 102 and the mirror groups 103a and 103
The original 4 is scanned by moving the optical system composed of b, 103c, etc. in the leftward direction of the arrow, and color image data of three colors R, G, and B are output to the image processing unit, and one color is scanned for each scan. Image data is obtained from the image processing unit. By repeating this operation a total of four times, four color image data are sequentially obtained. Then, the color printer 2 sequentially forms images of Bk, C, M, and Y based on the color image data of Bk, C, M, and Y from the image processing unit, and superimposes these images to form a final image. To form a full four-color superimposed full-color image.

The color printer 2 includes a photoconductor (here, a drum-shaped photoconductor) 200 as an image carrier, a writing optical unit 220 as an image writing unit, a revolver developing unit 230 as a developing unit, and an intermediate transfer unit 5.
00, a secondary transfer unit 600 as a secondary transfer unit,
The image forming apparatus includes a fixing device 270 and the like.

The photosensitive member 200 is driven to rotate by a driving unit (not shown) and rotates counterclockwise as indicated by an arrow.
As shown in a partially enlarged manner in FIG. 2, a photoconductor cleaning device 201, a static elimination lamp 202, a charger 203 as charging means, and a surface potential sensor 20 constituting information detecting means.
4, the selected developing device of the revolver developing unit 230,
A reflection density sensor 205, an intermediate transfer unit 500, and the like that constitute information detection means are arranged. Charger 203
Is applied with a voltage from a charging power supply (not shown) to uniformly charge the photoconductor 200. The surface potential sensor 204 detects the surface potential of the photoreceptor 200 and generates a reflection density sensor 205
Optically detects the reflection density of the photoconductor 200.

The writing optical unit 220 converts color image data input from the color scanner 1 via the image processing unit into an optical signal, and performs optical writing corresponding to the image of the original 4 on the photosensitive member 200. Then, an electrostatic latent image is formed on the photoconductor 200. This writing optical unit 22
Numeral 0 denotes a semiconductor laser 221 as a light source, a laser emission drive control unit (not shown), a polygon mirror 222 and its rotation drive motor 223, an f / θ lens 224, a reflection mirror 225, and the like. The semiconductor laser 221 is
The laser emission drive control unit is driven and controlled by the color image data input from the color scanner 1 via the image processing unit, and emits a laser beam modulated by the color image data. This laser light is applied to the polygon mirror 22
2 is repeatedly scanned in the main scanning direction, and the photoconductor 200 is scanned via an f / θ lens 224, a reflection mirror 225, and the like.
Is irradiated.

Further, the revolver developing unit 230
k developing device 231Bk, C developing device 231C, M developing device 23
1M, Y developing device 231Y and these developing devices 231B
k, 231C, 231M, and 231Y in a counterclockwise direction indicated by an arrow, and a revolver rotation drive unit, and each developing unit 231B
Bk for supplying Bk toner, C toner, M toner, and Y toner to k, 231C, 231M, and 231Y, respectively.
It is composed of toner supply units for each color of C, M, and Y.

Each developing unit 231Bk, 231C, 231
M and 231Y denote a developing sleeve as a developer carrying member that rotates by contacting a spike of developer with the surface of the photosensitive member 200 to develop an electrostatic latent image on the photosensitive member 200; It is composed of a developer paddle or the like as a stirring means which rotates for pumping and stirring. The toner supply units of the respective colors are driven by toner supply motors (not shown), so that the developing units 231Bk, 231C, 231M,
The toner is supplied to the developing unit 231Bk, 2Y.
31C, 231M and 231Y agitate the internal developer and the toner supplied from the toner supply unit with a developer paddle.

Each developing unit 231Bk, 231C, 231
M and 231Y include a two-component developer composed of Bk toner and ferrite carrier, a two-component developer composed of C toner and ferrite carrier, a two-component developer composed of M toner and ferrite carrier, and a Y toner and ferrite. A two-component developer including a carrier is stored, and the toner of each color of Bk, C, M, and Y is charged to a negative polarity by stirring with the ferrite carrier. Further, a developing bias in which an AC voltage Vac is superimposed on a negative DC voltage Vdc is applied to a developing sleeve in each of the developing units 231Bk, 231C, 231M, and 231Y by a developing bias power supply (not shown). The bias is applied to the metal substrate layer of the photoconductor 200 at a predetermined potential.

In the stand-by state of the present color copying machine, the revolver developing unit 230 has the Bk developing unit 231K set at 45 degrees before the developing position. Reading of a document image for obtaining Bk color image data is started, and the color image data from the color scanner 1 is input to the writing optical unit 220 via the image processing unit, and the writing optical unit 220 receives the color image data from the image processing unit. B
The optical writing by the laser beam and the formation of the electrostatic latent image are started based on the k color image data (hereinafter, the electrostatic latent image based on the Bk image data is referred to as a Bk latent image. Similarly, electrostatic latent images and electrostatic latent images based on Y image data are also referred to as C latent images, M latent images, and Y latent images).

The revolver developing unit 230 includes the photosensitive member 2
Before the front end of the Bk electrostatic latent image reaches the developing position to develop from the front end of the Bk electrostatic latent image on
1Bk is moved to the developing position, the rotation of the Bk developing sleeve in the Bk developing unit 231B is started, and the Bk electrostatic latent image on the photoconductor 200 is developed with Bk toner to form a Bk toner image. Thereafter, the developing operation of the Bk electrostatic latent image on the photoconductor 200 is continued. When the rear end of the Bk electrostatic latent image passes the developing position and moves a predetermined distance, the next operation is immediately performed. The revolver developing unit 230 rotates until the color developing device reaches the developing position. This is completed at least before the leading end of the electrostatic latent image based on the next image data reaches the Bk development position.

The intermediate transfer unit 500 includes an intermediate transfer belt 501, which is an intermediate transfer member stretched over a plurality of rollers described later. This intermediate transfer belt 50
1, a secondary transfer belt 601 as a transfer material carrier of the secondary transfer unit 600, a secondary transfer bias roller 605 as a secondary transfer charge applying unit, and a belt cleaning device 504 as an intermediate transfer body cleaning unit. A lubricant application brush 505 serving as a lubricant application unit is disposed so as to face the intermediate transfer belt 501.

A position detection mark is provided on the inner peripheral surface (or outer peripheral surface) of the intermediate transfer belt 501. However, on the outer peripheral surface side of the intermediate transfer belt 501, it is necessary to devise a method for providing a position detection mark so as to avoid the pass area of the belt cleaning device 504, and there is a case where it is difficult to arrange the mark. A position detection mark is provided on the inner peripheral surface side of the intermediate transfer belt 501. The optical sensor 514 as a sensor for detecting the mark includes the intermediate transfer belt 50.
1 is provided at a position between the bias roller 507 and the drive roller 508 which are bridged.

The intermediate transfer belt 501 includes a primary transfer bias applying roller 507, a belt driving roller 508, a belt tension roller 509, a secondary transfer opposing roller 510, and a cleaning opposing roller 51 as primary transfer charge applying means.
1 and the earth roller 512. These rollers 507 to 512 are formed of a conductive material, and each roller 508 to 51 other than the primary transfer bias roller 507.
2 is grounded.

The primary transfer bias roller 507 has a primary transfer power source 801 for which constant current control or constant voltage control is performed.
Accordingly, a transfer bias controlled to a current or voltage of a predetermined magnitude according to the number of superimposed toner images on the intermediate transfer belt 501 is applied. Further, the intermediate transfer belt 50
1 is driven in the direction of the arrow by a belt drive roller 508 that is rotationally driven by a drive motor (not shown).
The intermediate transfer belt 501 is made of a semiconductor or an insulator and has a single-layer or multilayer structure. The intermediate transfer belt 501 is set larger than the maximum paper-passable size in order to overlap the toner images formed on the photoconductor 200.

In a transfer section (hereinafter referred to as a primary transfer section) for transferring the toner image on the photosensitive member 200 to the intermediate transfer belt 501, a primary transfer bias roller 507 and an earth roller 5
At 12, the intermediate transfer belt 501 is stretched so as to be pressed against the photoconductor 200, thereby forming a nip portion having a predetermined width between the photoconductor 100 and the intermediate transfer belt 501.

The lubricant applying brush 505 grinds the zinc stearate 506 as a lubricant formed in a plate shape,
The polished fine particles are applied to the intermediate transfer belt 501. The lubricant application brush 505 is also configured to be able to contact and separate from the intermediate transfer belt 501 by a contact and separation mechanism (not shown), and is controlled to contact the intermediate transfer belt 501 at a predetermined timing.

The secondary transfer unit 600 includes a secondary transfer belt 601 stretched over three support rollers 602, 603, and 604. The secondary transfer belt 601 has a stretched portion between the support rollers 602 and 603. Secondary transfer opposing roller 5
10 can be pressed against. One of the three support rollers 602, 603, and 604 is a driving roller that is rotationally driven by a driving unit (not shown), and the driving roller drives the secondary transfer belt 601.

The secondary transfer bias roller 605 is a secondary transfer means, and is disposed so as to sandwich the intermediate transfer belt 501 and the secondary transfer belt 601 between the secondary transfer opposing roller 510 and a constant current control. Transfer power supply 8 performing
02, a transfer bias of a predetermined current is applied. Further, the supporting roller 6 is configured such that the secondary transfer belt 601 and the secondary transfer bias roller 605 can take a position where the secondary transfer belt 601 is pressed against the secondary transfer opposing roller 510 and a position where the secondary transfer bias roller 605 is separated therefrom.
An unillustrated contact / separation mechanism for driving the 02 and secondary transfer bias rollers 605 is provided. The two-dot chain line in FIG.
The position where the next transfer belt 601 and the support roller 602 are separated from the secondary transfer opposing roller 510 is shown. The solid line in FIG. 2 indicates that the secondary transfer belt 601 and the support roller 602 are in pressure contact with the secondary transfer opposing roller 510. Indicates the position.

The pair of registration rollers 650 includes an intermediate transfer belt 501 and a secondary transfer belt 6 sandwiched between a secondary transfer bias roller 605 and a secondary transfer opposing roller 510.
During the period 01, a transfer paper as a transfer material is fed at a predetermined timing. Fixing device 270 for secondary transfer belt 601
A transfer sheet static elimination charger 606 as a transfer material static eliminator and a belt static eliminator 607 as a transfer material carrier static eliminator are opposed to a portion stretched around the supporting roller 603 on the side of the side. A cleaning blade 608 serving as a transfer material carrier cleaning unit is provided on a portion of the secondary transfer belt 601 that is stretched around the lower support roller 604.
Is in contact.

The transfer paper discharging charger 606 discharges the electric charge held on the transfer paper, thereby separating the transfer paper from the secondary transfer belt 601 with the strength of the transfer paper itself. The belt static elimination charger 607 eliminates electric charges remaining on the secondary transfer belt 601. In addition, the cleaning blade 608 removes substances attached to the surface of the secondary transfer belt 601 and performs cleaning.

In the color copying machine thus constructed, when the A4 horizontal feed repeat copying cycle is started, the photosensitive member 100 and the intermediate transfer belt 501 are rotationally driven by a drive motor (not shown) in the direction shown by the arrow. It rotates at the same linear velocity at the primary transfer position. A mark 550 is provided on the back side of the intermediate transfer belt 501. The mark 550 moves together with the intermediate transfer belt 501, and an optical sensor 514 is attached to a stationary member in a predetermined passage area where the mark 550 passes.

As the optical sensor 514, a reflection type photo sensor (or a transmission type photo sensor) is used. When a reflective photo sensor is used as the optical sensor 514, a member such as a reflective tape is attached to the intermediate transfer belt 501, and the reflective photo sensor is used to apply a mark from the low reflective surface on the intermediate transfer belt 501 to the mark 550. What is necessary is just to read the place where the mark changes, or the place where the mark 550 changes to a surface with low reflectivity on the intermediate transfer belt 501.

As the photosensitive member 200 and the intermediate transfer belt 501 rotate, two Bk toner image screens, two C toner image screens, two M toner image screens, and two Y toner image screens are formed. The toner image, the C toner image, the M toner image, and the Y toner image are primarily transferred from the photoconductor 200 to the intermediate transfer belt 501 by the transfer bias applied to the primary transfer bias roller 507, and finally on the intermediate transfer belt 501. A full-color toner image of four colors is formed on two screens. If only one copy operation is performed, Bk
One toner image formation, one C toner image formation, one M toner image formation, one Y toner image formation are performed, and these Bk toner image, C toner image, M toner image, and Y toner image are transferred to the photosensitive member. The primary transfer is performed from 200 to the intermediate transfer belt 501, and a full-color toner image of four colors is finally formed on the intermediate transfer belt 501 on one screen.

The toner image formation is performed as follows. The charging charger 201 uses the photoconductor 100 by corona discharge.
Is uniformly charged to a predetermined potential with a negative charge. A fixed time after the detection of the mark 550 by the optical sensor 514, the writing optical unit 220 performs raster exposure on the photoconductor 200 based on the Bk image signal from the image processing unit. At this time, the photoreceptor 100 initially uniformly charged
In the exposed portion of the surface, the charge proportional to the exposure light amount disappears, and a Bk latent image is formed.

When the negatively charged Bk toner on the Bk developing roller in the Bk developing device 231Bk comes into contact with the Bk latent image, the toner does not adhere to the unexposed portion of the photoconductor 200, and the exposed portion is exposed. Has a toner attached thereto, and a Bk toner image similar to the Bk latent image is formed. The Bk toner image formed on the photoconductor 200 is transferred to the surface of the intermediate transfer belt 501 that is driven at a constant speed in a state of contact with the photoconductor 200 at the primary transfer position. Hereinafter, photosensitive member 2
The transfer of the toner image from 00 to the intermediate transfer belt 501 is called belt transfer. Some untransferred residual toner remaining on the surface of the photoconductor 200 after the belt transfer is
In order to prepare for reuse, the photosensitive member is cleaned by the photoconductor cleaning device 201 and is uniformly discharged by the discharge lamp 202.

On the photoconductor 200 side, the process proceeds to the C image forming process after the Bk image forming process. At a predetermined timing, reading of the original image for obtaining the C image data by the color scanner 1 is started. G and B color image data are output to the image processing unit, and the image processing unit outputs C image data to the writing optical unit 220. The writing optical unit 220 forms a C latent image on the surface of the photoconductor 200 by performing laser beam writing on the photoconductor 200 based on the C image data from the image processing unit.

Then, the revolver developing unit 400 performs a rotating operation after the photosensitive member 200 has passed the rear end portion of the preceding Bk latent image + a predetermined distance and before the front end portion of the C latent image has arrived to perform C developing. The developing device 231C is set to the developing position, and the C latent image is developed by the C developing device 231C to become a C toner image.

Thereafter, the C developing device 231C continues developing the C latent image area on the photoconductor 200, but when the C latent image on the photoconductor 200 has passed the predetermined distance, the Bk development has been completed. Revolver developing unit 23 as in the case of the developing unit 231Bk.
0 performs the rotation operation to move the next M developing device 231M to the developing position. This is also completed before the leading end of the next M latent image reaches the developing position.

The C toner image formed on the photoreceptor 200 is superimposed on the Bk toner image on the surface of the intermediate transfer belt 501 which is driven at a constant speed in a contact state with the photoreceptor 200 at the primary transfer position. Is done. Photoreceptor 20 after belt transfer
A small amount of untransferred residual toner remaining on the surface of the photoconductor 0 is cleaned by the photoconductor cleaning device 201 and is uniformly discharged by the discharge lamp 202 in preparation for reuse of the photoconductor 200.

On the photoconductor 200 side, the process proceeds to the M image forming process after the C image forming process. At a predetermined timing, reading of a document image for obtaining M image data by the color scanner 1 is started. The color image data of G and B colors is output to the image processing unit, and the M image data is output from the image processing unit to the writing optical unit 220. The writing optical unit 220 forms a latent image on the surface of the photoconductor 200 by performing laser beam writing on the photoconductor 200 based on the M image data from the image processing unit.

Then, the revolver developing unit 400 performs a rotation operation after the photosensitive member 200 has passed the rear end of the preceding C latent image + a predetermined distance and before the front end of the M latent image has reached, thereby performing M developing. 231M is set to the development position, and the M latent image is
The toner image is developed by the developing unit 231M and becomes an M toner image.

Thereafter, the M developing unit 231M continues to develop the M latent image area on the photoconductor 200, but when the rear end of the M latent image on the photoconductor 200 and a predetermined distance have passed, the Bk development is started. Revolver developing unit 23 as in the case of the developing unit 231Bk.
0 performs the rotation operation to move the next Y developing device 231Y to the developing position. This is also completed before the leading end of the next Y latent image reaches the developing position.

The M toner image formed on the photosensitive member 200 has a Bk toner image and a C toner image on the surface of the intermediate transfer belt 501 that is driven at a constant speed in a state of contact with the photosensitive member 200 at the primary transfer position. The belt is transferred in an overlapping manner. A small amount of untransferred residual toner remaining on the surface of the photoconductor 200 after the belt transfer is cleaned by the photoconductor cleaning device 201 and uniformly discharged by the discharge lamp 202 in preparation for reuse of the photoconductor 200. .

On the photoconductor 200 side, the process proceeds to the Y image forming process after the M image forming process. At a predetermined timing, reading of a document image for obtaining Y image data by the color scanner 1 is started. The G and B color image data are output to the image processing unit, and the Y image data is output from the image processing unit to the writing optical unit 220. The writing optical unit 220 forms a Y latent image on the surface of the photoconductor 200 by performing laser beam writing on the photoconductor 200 based on the Y image data from the image processing unit.

Then, the revolver developing unit 400 performs a rotation operation after the photosensitive member 200 has passed the rear end of the preceding M latent image + a predetermined distance and before the front end of the Y latent image has arrived to perform the Y developing. Device 231Y is set to the development position, and the Y latent image is Y
The toner is developed by the developing device 231Y to form a Y toner image.

Thereafter, the Y developing unit 231Y continues to develop the Y latent image area on the photoconductor 200. Revolver developing unit 23 as in the case of the developing unit 231Bk.
0 performs the rotation operation to move the next Y developing device 231Y to the developing position.

The Y toner image formed on the photosensitive member 200 has a Bk toner image, a C toner image and a B toner image on the surface of the intermediate transfer belt 501 that is driven at a constant speed in contact with the photosensitive member 200 at the primary transfer position. The belt is transferred in superposition with the M toner image, and a full-color image of four colors is formed. A small amount of untransferred toner remaining on the surface of the photoconductor 200 after the belt transfer is cleaned by the photoconductor cleaning device 201 to prepare for the reuse of the photoconductor 200, and the charge removing lamp 202 is used.
The charge is removed evenly.

As described above, on the intermediate transfer belt 501, Bk, C, M,
The Y color toner images are sequentially aligned and transferred to the same surface to form a four-color superimposed full-color image. At the time when the image forming operation is started, the transfer paper P is fed from the paper supply bank 3 or the manual feed tray 210 and stands by at the nip of the registration roller 650. The paper supply bank 3 can hold transfer papers of a size normally used, for example, up to A3 used in Japan and Europe and DLT (double letter size) in North America. The manual feed tray 210 can further load a long A3 sheet, such as an A3 sheet, an irregular shape, a cardboard, or the like.

When the leading edge of the full-color image on the intermediate transfer belt 501 reaches the secondary transfer portion where the nip is formed by the secondary transfer facing roller 510 and the secondary transfer bias roller 605, the leading edge of the transfer paper P is just The registration roller 65 is aligned with the end of the full-color image.
0 is driven, and registration of the transfer paper P with the full-color image is performed.

Then, the transfer paper P is transferred to the intermediate transfer belt 501.
The sheet passes through the secondary transfer portion while being superimposed on the above full-color image. At this time, by the transfer bias applied to the secondary transfer bias roller 605 by the secondary transfer power source 802,
A four-color superimposed full-color image on the intermediate transfer belt 501 is collectively transferred onto the transfer paper P.

Thereafter, the transfer paper P is transferred to the secondary transfer belt 60.
In the movement direction of the first transfer belt, the charge is removed when the sheet passes through the opposing portion between the transfer sheet charge removal unit 606 and the secondary transfer belt 601 disposed downstream of the secondary transfer unit.
The sheet is peeled off from the fixing device 01 and sent to the fixing device 270. The transfer sheet P has a toner image fused and fixed at a nip portion between an upper roller 271 and a lower fixing roller 272 of the fixing device 270, and is sent by a pair of discharge rollers (not shown) to be stacked face up on a copy tray (not shown) outside the apparatus. A full color copy is obtained. Further, the toner remaining on the surface of the intermediate transfer belt 501 after the transfer of the toner image onto the transfer paper P is cleaned by a belt cleaning device 504 pressed against the intermediate transfer belt 501 by a separation / contact mechanism (not shown).

At the time of repeat copying, the operation of the color scanner 1 and the image formation on the photosensitive member 200 are performed at a predetermined timing on the third surface (Y) of the third surface following the image forming process of the fourth color (Y) on the second surface. The process proceeds to the first color (Bk) image forming process. Further, the intermediate transfer belt 501 transfers the first and second four-color superimposed full-color images to the transfer paper in a batch transfer process, and then places the third sheet of Bk in the area where the surface is cleaned by the belt cleaning device 504. The toner image is transferred to the belt. Thereafter, the operation is the same as that of the first and second sheets.

The above is the copy mode for obtaining a four-color full-color copy. In the three-color copy mode and the two-color copy mode, the same operation as described above is performed for the designated color and the number of times. . In the case of the single-color copy mode, only the developing device of the predetermined color of the revolver developing unit 230 is in the developing operation state until the copying of the predetermined number of sheets is completed, and the belt cleaning device 504 is pressed against the intermediate transfer belt 501. The copying operation is performed while the state is maintained.

FIG. 10 schematically shows a control system according to this embodiment. The main control unit 601 as a control unit receives output values of a fixing temperature sensor 602 for detecting a fixing temperature of the fixing device 270, a surface potential sensor 204, a reflection density sensor 205, a toner density sensor 607, and the like. Bias power source 603, primary transfer power source 80
1. Revolver developing unit 230, writing optical unit controller 604, toner supply motor 605B for each of the above colors
k, 605C, 605M, 605Y, the charging power source 6
06 is controlled.

Here, the writing optical unit control unit 60
Reference numeral 4 controls the light emission power (writing light amount) of the semiconductor laser 221 in the writing optical unit 220.
The toner density sensor 607 is connected to each of the Bk developing units 231Bk,
C developing device 231C, M developing device 231M, Y developing device 231
The sensor is a type of sensor that is installed in Y and detects the toner density (the ratio of toner to carrier) of the two-component developer by detecting the magnetic permeability of the magnetic material of the two-component developer in the vicinity.
FIG. 11 shows the output characteristics of the toner density sensor 607. As the toner concentration sensor 607, an optical sensor that detects the toner concentration of the developer on the developing sleeve may be used.

Next, a self-check in the color copying machine of the present embodiment will be described. The self-check routine of the main control unit 601 in the color copying machine according to the present embodiment will be described with reference to FIG. This self-check routine is basically performed as needed, such as when the color copying machine is started, every time a predetermined number of copies are made, every certain time, or the like (STEP 1).

Here, for example, when the color copier is started, the main control unit 601 first executes a self-check routine in order to distinguish the power-on state from the abnormality processing such as a jam. Then, based on an input signal from a fixing temperature sensor 602 for detecting the fixing temperature of the fixing device 270, it is determined whether or not the fixing temperature of the fixing device 270 exceeds 100 ° C.
If the temperature exceeds 00 ° C., it is determined to be abnormal and the potential control is not performed.

If the fixing temperature of the fixing device 270 does not exceed 100 ° C., or if the timing of copying a predetermined number of copies or every certain time is reached, the main control unit 601 determines in STEP 2 By checking the output value of the potential sensor 204, the surface potential of the photoconductor 200 is checked. If the surface potential of the photoconductor 200 is not within a predetermined range, it is determined that the surface potential of the photoconductor 200 is abnormal. Notify.

Next, the main control unit 601 controls the photosensitive member 20
When the surface potential of 0 is within a predetermined range, the reflection density sensor 205 detects
00, the output value of the reflection density sensor 205 is determined based on the output value so that the reflection light with respect to the light emitted from the reflection density sensor 205 to the background portion of the photoconductor 200 becomes a constant value. To adjust.

In the normal potential control, the control may be performed only by changing the image forming potential. However, the developing units 231Bk and 23
When the developing ability of 1C, 231M, and 231Y decreases to a level lower than a predetermined level, it is impossible to increase the image density only by the image forming potential. Further, the developing units 231Bk, 231C, 23
If the developing capacity of 1M, 231Y rises to a predetermined level or more, there is a possibility that problems such as poor gradation, toner scattering, and toner sticking to the developing sleeve may occur. It is difficult or impossible to directly prevent these problems with the image forming potential, and it is basically necessary to control the toner concentration to an ideal state in a short time.

Therefore, in this embodiment, a toner supply mode and a toner consumption mode for adjusting the toner density are performed. First, in STEP 4, the main control unit 601 controls the revolver rotation drive unit of the revolver developing unit 230 to move the developing device of the developing ability detection color to the developing position, and first moves the Bk developing device 231 </ b> K to the developing position. , And thereafter, after the determination in STEP 10, the C developing device 2
31C, the M developing device 231M, and the Y developing device 231Y are sequentially moved so as to come to the developing position.

Next, the main control unit 601 executes SYEP5
The charging power supply 606 and the writing optical unit 220
To form a latent image pattern on the photoconductor 200.
Here, as shown in FIG. 7, the electrostatic latent images (here, three latent image patterns) 20 a, 20 b, and 20 c of the maximum writing are applied to the central portion in the width direction on the photoconductor 200 in the rotation direction of the photoconductor 200. Are formed at predetermined intervals along. The three latent image patterns 20a, 20b, and 20c are, for example, rectangular latent image patterns each having a side of 40 mm formed at intervals of 10 mm.

The main controller 601 reads the output value of the surface potential sensor 204 with respect to the potential of each of the latent image patterns 20a, 20b, 20c and stores it in the RAM.
The three latent image patterns 20a, 20b, and 20c are visualized by a Bk developing device 231Bk at the developing position to become a Bk toner image, and the main control unit 601 outputs a plurality of output values of the reflection density sensor 208 for the Bk toner image. Sampled twice and stored in the RAM as Vpi (i = 1 to 3). Then, the main control unit 601 determines that Vpi / 3 = Vp
To calculate the average developing ability (toner adhesion amount) of the Bk developing device 231K with respect to the solid portion.

At the same time, the main control section 601 samples the output value of the toner density sensor 607 for the developer in the Bk developing device 231Bk set at the developing position and stores it in the RAM as Vti (i = 1 to 50). I do. Then, the main control unit 601 obtains Vti / 50 = Vt, thereby obtaining an average toner concentration of the developer in the Bk developing device 231Bk.

Next, the main control unit 601 determines in STEP6
Vt is within a predetermined range (threshold YY ≦ Vt ≦ threshold X
X), and if Vt is not within the predetermined range, it is determined in STEP 20 whether Vt is greater than the threshold value XX. If Vt is larger than the threshold value XX, the main control unit 601 determines that the toner concentration of the developer in the Bk developing device 231Bk is low, and turns on the Bk toner supply motor 605Bk for one second in the toner supply mode in STEP21 and turns it off for one second. By repeatedly operating 10 times in a cycle, the Bk developing device 23
Bk toner is supplied to 1Bk, and then the process proceeds to STEP11. As a result, the toner concentration of the developer in the Bk developing device 231Bk increases.

If Vt is not larger than the threshold value XX (if Vt is smaller than the threshold value YY), the main controller 601 determines that the toner concentration of the developer in the Bk developing device 231Bk is high. Controlling the charging power supply 606 and the writing optical unit 220 to form a latent image of an internal pattern on the photoconductor 200,
This latent image is developed by a Bk developing unit 231Bk to form an A4 size full-size halftone solid image for 10 internal pattern forming operations.
Proceed to 1. At this time, the main control unit 601 controls the paper feed system such as the paper feed bank 3 and the registration roller 650 so that the transfer paper is not fed, and controls the contact / separation mechanism to control the secondary transfer belt 601 and the support roller 602. To the secondary transfer facing roller 51
Separate from 0. The entire halftone solid image on the photoconductor 200 is removed by the photoconductor cleaning device 201,
The photoconductor 200 is uniformly discharged by the discharge lamp 202. Thereby, the toner of the developer in the Bk developing device 231Bk is consumed, and the toner concentration of the developer in the Bk developing device 231Bk decreases.

The main control unit 601 determines in STEP 11
STEP4-STEP6, STEP20, STEP21
Alternatively, it is determined whether or not the processing of STEP 22 has been completed for all the colors of Bk, C, M, and Y, and STEPs 4 to 6, and ST
The processing of EP20, STEP21 or STEP22 is B
If all the colors of k, C, M, and Y have not been completed, STEP 4
Return to STEP4-STEP6, STEP20, ST
If the processing of EP21 or STEP22 has been completed for all the colors of Bk, C, M, and Y, the process proceeds to STEP12 to enter the potential control section.

Further, the main control unit 601 determines in STEP 6
And Vt is within a predetermined range (threshold YY ≦ Vt ≦ threshold XX).
In step 7, it is determined whether or not Vp is smaller than the threshold X, and if Vp is smaller than the threshold X, B is determined.
It is determined that the developing capacity of the k developing device 231Bk is low, and the STE
At P8, the Bk toner supply motor 6 is set to the toner supply mode.
The Bk toner is supplied from the Bk toner supply unit to the Bk developing device 231Bk by repeatedly operating the 05Bk for 10 seconds in a cycle of ON for 1 second and OFF for 1 second, and then proceeds to STEP11. Thereby, the Bk developing device 231
Bk development ability is increased.

If Vp is greater than or equal to threshold value X, main control section 601 determines in step 9 whether Vp is greater than threshold value Y. If Vp is greater than threshold value Y, the developing capability of Bk developing device 231Bk is high. And STEP 1
0, a toner consumption mode is set, and the charging power supply 606 and the writing optical unit 220 are controlled to form a latent image of an internal pattern on the photoreceptor 200.
An internal pattern forming operation of developing an A4 size full-size halftone solid image by developing at 31 Bk
Then, the process proceeds to STEP11. At this time, the main control unit 601 controls the paper feed bank 3, the registration rollers 6
The transfer system is controlled so that the transfer paper is not fed, and the contact / separation mechanism is controlled to control the secondary transfer belt 601 and the support roller 6.
02 is separated from the secondary transfer facing roller 510. The entire halftone solid image on the photoconductor 200 is removed by the photoconductor cleaning device 201, and the photoconductor 200 is uniformly discharged by the discharge lamp 202. Thereby, the toner of the developer in the Bk developing device 231Bk is consumed, and the developing ability of the Bk developing device 231Bk is reduced.

Further, if Vp is within a predetermined range (if threshold value X ≦ Vp ≦ threshold value Y), main control section 601 determines that
It proceeds to the next STEP 11 as it is. Main control unit 601
Is STEP11, STEP4 to STEP6, and S
STEP7, STEP8 or STEP7, STEP9, S
The processing of STEP10 or STEP7, STEP9 is Bk,
It is determined whether or not the processing has been completed for all the colors of C, M, and Y, and STEP
4-STEP6 and STEP7, STEP8 or ST
EP7, STEP9, STEP10 or STEP7, S
If the processing in STEP 9 has not been completed for all the colors of Bk, C, M, and Y, the process returns to STEP 4 and repeats STEP 4 to STEP 6 and STEP 7, STEP 8 or STEP 7, STEP
9. If the processing of STEP 10 or STEP 7 or STEP 9 has been completed for all the colors of Bk, C, M, and Y, STEP 12
To enter the potential control section.

In STEP 12, the main control section 601 controls the revolver rotation drive section of the revolver developing unit 230 in the same manner as in STEP 4 to move the developing unit of the developing ability detection color to the developing position. Vessel 2
31K is moved to the development position.
After the determination of P14, the C developing device 231C and the M developing device 231
The M and Y developing units 231Y are sequentially moved to the developing position.

Next, the main control unit 601 executes STEP 1
3, the charging power supply 606 and the writing optical unit 22
0 is controlled to form a latent image pattern on the photoconductor 200. Here, as shown in FIG. 9, electrostatic latent images (N latent image patterns) 30a, 30b, 30c... The photoconductors 200 are formed at predetermined intervals along the rotation direction. As this latent image pattern, for example, rectangular latent image patterns 30a, 30b, 30c... Each having a side of 40 mm and having 10 different gradation densities are formed at intervals of 10 mm.

The main controller 601 reads the output value of the surface potential sensor 204 with respect to the potentials of the latent image patterns 30a, 30b, 30c,.
To be stored. Latent image patterns 30a, 3 on photoconductor 200
0b, 30c ... are Bk set at the developing position.
The toner image is developed by the developing device 231K to form a Bk toner image. The main control unit 601 sets the output value of the reflection density sensor 205 for the Bk toner image to Vpi (i = 1 to N) and sets R
Store in AM.

Next, the main control unit 601 executes STEP1.
In step 4, the processing of STEP12 and STEP13 is performed using Bk, C,
It is determined whether or not the processing has been completed for all the colors of M and Y, and STEP 1
2. If the processing in STEP 13 has not been completed for all the colors Bk, C, M, and Y, the process returns to STEP 12. Accordingly, the main control unit 601 sequentially forms the latent image patterns 30a, 30b, 30c... For four colors on the photoconductor 200, and the latent image patterns 30a, 30b, and 3 for these four colors.
The output value of the surface potential sensor 204 corresponding to the potential of 0c... Is read and stored in the RAM. The latent image patterns 30a, 30b, 30c,... For the four colors are Bk developing device 231Bk, C developing device 231C, and M developing device 23 for each color.
B is developed by the 1M and Y developing devices 231Y, respectively.
k, C, M, and Y color toner images.
Reference numeral 01 stores the output value of the reflection density sensor 205 for each color toner image in the RAM as Vpi (i = 1 to N) for each color.

The main control unit 601 operates as the photosensitive member 20.
0 is uniformly charged by the charger 203 and the output power (write light amount) of the semiconductor laser 221 is changed via the write optical unit control unit 604 to change the latent image pattern 30.
a, 30b, 30c,... are formed to develop these patterns. However, the invention is not limited to such a method, and the developing bias power supply 603 is controlled without operating the writing optical unit 220 to perform each development. Apparatus 231Bk, 231
The latent image pattern patterns 30a, 30b, and 30c are switched by switching the developing bias potentials of C, 231M, and 231Y.
.. May be formed and these patterns may be developed.

Next, the main control unit 601 executes STEP 1
2. If the processing of STEP 13 is completed for all the colors of Bk, C, M, and Y, the process proceeds to STEP 15, and in the toner adhesion amount calculation processing, the output value of the reflection density sensor 205 stored in the RAM is stored in the ROM. With reference to the table, the amount of toner attached per unit area is converted and stored in the RAM. FIG. 4 shows each of the latent image patterns 30a, 30b,
The relationship between the potential data obtained by the surface potential sensor 204 and the toner adhesion amount data obtained by the toner adhesion amount calculation processing for the areas 30c,... Is plotted on the xy plane. . Here, the x-axis indicates the potential potential (the difference between the developing bias potential VB and the surface potential VD of the photoreceptor 200: VB-VD) (unit V), and the y-axis indicates the toner adhesion amount per unit area (mg / cm). ² ).

An infrared light reflection type sensor such as the optical reflection density sensor 205 in this embodiment is generally
As shown in FIG. 4, the saturation characteristic is exhibited in the multi-adhesion portion where the toner adhesion amount is large, and the obtained detection value does not correspond to the actual toner adhesion amount. Therefore, if the toner adhesion amount is calculated using the detection value of the reflection density sensor 208 obtained in the multi-adhesion portion as it is, a toner adhesion amount different from the actual toner adhesion amount will be obtained. The toner supply control based on the toner adhesion amount cannot be performed accurately.

Therefore, in the present embodiment, the main control unit 6
01 is a latent image pattern 30a, 30b, 30c
.. for each surface potential sensor 204 and reflection density sensor 20
5 and the data of the toner adhesion amount after development for each of the latent image patterns 30a, 30b, 30c,... Of each color are converted into potential data Xn (n = 1 to 10).
Is selected only in the linear section of the relationship between the data and the toner adhesion amount data Yn (development γ characteristic of the developing device). Then, the main control unit 6
01 is the potential data Xn (n = 1 to 1) of the straight section.
0) and the toner adhesion data Yn by applying the least squares method to each of the developing devices 231Bk, 231C,
A linear approximation of the development characteristics of 31M and 231Y is performed by a method described later, and an approximate linear equation (E) of the development characteristics is obtained.
Is obtained for each color, and the control potential is calculated for each color using the approximate linear equation (E).

The main controller 601 uses the following equation for the calculation of the least squares method. Xave = ΣXn / k (1) Yave = ΣYn / k (2) Sx = Σ (Xn-Xave) × (Xn-Xave) (3) Sy = Σ (Yn-Yave) × (Yn−Yave) (4) Sxy = Σ (Xn−Xave) × (Yn−Yave) (5) Latent image pattern 30 a obtained from surface potential sensor 204 and reflection density sensor 205, When the approximate linear equation (E) obtained from the data of the potentials of the latent images 30a, 30b, 30c,... And the amount of toner adhesion after development of the latent image patterns 30a, 30b, 30c, is Y = A1 × X + B1, the coefficient A
1, B1 can be expressed as A1 = Sxy / Sx (6) B1 = Yave−A1 × Xave (7) using the above variables.

Further, the correlation coefficient R of the approximate linear equation (E)
Can be expressed as follows: R × R = (Sxy × Sxy) / (Sx × Sy) (8) In the present embodiment, the main control unit 601
Surface potential sensor 204 and reflection density sensor 205 for each color
And the latent image patterns 30a, 30b, 30c obtained from
.. Potential data Xn, latent image patterns 30a, 30
b, 30c... after-development toner adhesion data Yn
K (five in this case) data sets (X1 to X5, Y1 to Y5), (X2 to X6, Y2 to
Y6), (X3-X7, Y3-Y7), (X4-X8,
Y4 to Y8), (X5 to X9, Y5 to Y9), (X6 to
X10, Y6 to Y10) are taken out, and the above-described equation (1) is obtained.
The linear approximation calculation is performed according to (8) to (8), and the correlation coefficient R is calculated to obtain the following six sets of approximate linear equations and the correlation coefficients (9) to (14).

Y11 = A11 × X + B11; R11 (9) Y12 = A12 × X + B12; R12 (10) Y13 = A13 × X + B13; R13 (11) Y14 = A14 × X + B14; R14 · (12) Y15 = A15 × X + B15; R15 (13) Y16 = A16 × X + B16; R16 (14) The main control unit 601 obtains six sets of approximate linear equations obtained for each color. Of the correlation coefficients R11 to R16, a set of approximate linear equations corresponding to the one having the maximum value is selected as the approximate linear equation (E).

Next, in the above-described selected approximate linear equation (E) for each color, the main control unit 601 determines the value of X when the value of Y becomes the necessary maximum toner adhesion amount Mmax as shown in FIG. The value, that is, the value Vmax of the development potential is calculated. Bk developing device 231Bk, C developing device 231
The developing bias potential VB of the C, M developing device 231M and the Y developing device 231Y and the surface potential (exposure potential) VL of the image exposure of each color on the photoreceptor 200 are expressed by the following formulas (15) and (16). Vmax = (Mmax−B1) / A1 (15) VB−VL = Vmax = (Mmax−B1) / A1 (16) The relationship between VB and VL is expressed by an approximate linear method. It can be expressed using the coefficient of (E).

Therefore, the equation (16) is as follows: Mmax = A1 × Vmax + B1 (17)

Here, the relationship between the charged potential VD of the photosensitive member 200 before exposure and the developing bias potential VB is represented by a linear equation as shown in FIG. 5, that is, Y = A2 × X + B2 (18) From the x-coordinate VK (development start voltage of the developing device) at the intersection with the x-axis and the filth margin voltage Vα experimentally obtained, it is given by VD-VB = VK + Vα (19)

Therefore, the relationship between Vmax, VD, VB and VL is
It is determined by equations (16) and (19). In this embodiment, Vmax is used as a reference value, and the control voltage VD, V
The relationship between B and VL is determined in advance by experiments or the like, and as shown in the following Table 1, a table is formed as a potential table and R
It is stored in the OM.

[0104]

[Table 1]

Next, the main control unit 601 executes STEP1.
In step 6, for each color, the V calculated from the potential table is calculated.
A potential table having Vmax closest to max is selected, and the control voltages VB, VD, and VL corresponding to Vmax in the selected potential table are set as target potentials. Next, the main control unit 601 controls the emission power of the semiconductor laser 221 in the writing optical unit 220 via the writing optical unit control unit 604 so as to be the maximum light amount in STEP17 and STEP18. Thereby, the photosensitive member 20
0 is uniformly charged by the charger 203 and is exposed by the writing optical unit 220 with the maximum writing light amount.
The main control unit 601 detects the residual potential of the photoconductor 200 by taking in the output value of the surface potential sensor 204 with respect to the residual potential of the portion of the photoconductor 200 exposed to the maximum writing light amount. Then, the main control unit 601
When the residual potential is not 0, the target potentials VB, VD, and VL determined by the selected potential table are corrected by the residual potential to obtain a target potential.

Next, the main control unit 601 executes STEP 1
In step 9, the charging power supply 606 is adjusted so that the charging potential of the charger 203 on the photoconductor 200 becomes the target potential VD, and the semiconductor laser 221 in the writing optical unit 220 is controlled via the writing optical unit control unit 604. The light emission power is adjusted so that the exposure potential of the photoconductor 200 becomes the target potential VL, and the Bk developing device 231Bk, the C developing device 231C, the M developing device 231M, and the Y developing device 23
1Y is equal to the target potential VB.
The developing bias power supply 603 is adjusted so that

As described above, in the present embodiment, the toner concentration of the two-component developer in the developing device and the development amount (toner adhesion amount) on the image carrier are detected. Here, if only the development amount on the image carrier such as the development γ is detected as information for controlling the toner density, the overall gradation can be within a predetermined range. In some cases, it is difficult to detect the toner scattering due to the rise or the partial carrier adhesion due to the decrease in the toner concentration, and it may be difficult to control the toner. Even in such a case, in the present embodiment, by adding the detection information of the toner density as the information for controlling the toner density, it is possible to prevent the occurrence of toner scattering, carrier adhesion, and the like. It is possible to maintain the desired good image quality for a long period of time by maintaining within the range.

That is, in this embodiment, the information detecting means (here, the surface potential sensor 204) for detecting the information A on the developing means as the first processing means and the information B on the charging means as the second processing means , A reflection density sensor 205) and a determination unit (here, a determination unit) for determining whether to execute the control of the first process unit based on the information A of the information A and B detected by the information detection unit. And a main control unit 601). When the determination unit determines that the control of the first process unit needs to be performed, the control unit executes the control of the first process unit. A first step of causing the information detecting means to detect at least the information B among the information A and B, and controlling the second process means based on the information B detected by the information detecting means; A control mode, and when the determination means determines that it is not necessary to execute the control of the first process means, the information A detected by the information detection means without executing the first control mode. , B of information B
In the image forming apparatus which performs the second control mode for executing the control of the second process means based on the information A, the information A includes the toner density related to the toner density control of the developing means as the first process means. And information on the amount of toner adhering on the image carrier after development.
Is information on at least one of the charging potential of the charging means (here, the charger 203) as the second process means, the writing light amount of the image writing means, and the developing bias of the developing means. In addition, it is possible to prevent the occurrence of carrier adhesion and the like, to maintain the toner concentration in a predetermined range, and to maintain desired good image quality for a long time.

In this embodiment, if the toner density information relating to the toner density control of the developing means as the first process means is not within a predetermined range, the information of the toner adhesion amount on the image carrier after development is obtained. , Priority is given to controlling the toner density, so that a decrease in image quality can be prevented.

By the way, as in the above embodiment, the potential control including the toner replenishment mode and the toner consumption mode is an important control for maintaining a constant image quality, especially in a color copying machine. However, since the toner supply mode and the toner consumption mode are usually unnecessary, the number of times of detection of the developing ability and the number of movements of the developing device are large,
Even when the toner supply mode and the toner consumption mode are not required, there is a problem that the self-check time is long.

Therefore, in another embodiment of the present invention, in the color copying machine of the above embodiment, the self-check time is shortened by a new method as described below. The self-check in this embodiment will be described with reference to the flowchart shown in FIG. In FIG. 6, steps 1 to 4 are the same as those in FIG.

In FIG. 6, in STEP 5 ′, the main control unit 601 determines the developing capability detecting method of each developing unit in STEP 5 in FIG. 3 (the method using the maximum writing latent image patterns 20 a, 20 b, and 20 c in FIG. 7). 3 is different from the method of detecting the developing ability of each developing device in STEP13 of FIG. 3 (the latent image patterns 30a,
0b, 30c...), The developing ability of each developing device is detected.

In STEP 7 ′ and STEP 9 ′ of FIG. 6,
The main control unit 601, like STEP 15 in FIG.
For each developing device, the development γ (potential data Xn (n = 1 to 1)
0) and the toner adhesion amount data Yn, the slope of the linear section: the slope of the approximate linear equation (E)) is calculated.
Then, it is determined whether to enter the toner supply mode or the toner consumption mode based on the result. That is, the main control unit 601 determines that the development γ of the developing device is small and the toner supply mode should be started if the development γ <threshold X, and the development γ of the development device if the development γ> threshold Y. It is determined that it is too large to enter the toner consumption mode.

Accordingly, the detection of the developing ability in STEP 5 'of FIG. 6 is the same as the detection of the developing ability of STEP 5 in FIG.
And the detection of the developing ability of the toner supply mode at the same time.
The result of the detection of the developing ability of the TEP 5 'can be used as it is as the result of the developing ability detection for the potential control. As a result, the self-check time when the normal toner replenishment mode and toner consumption mode are not required can be greatly reduced.

In this case, it is necessary to be able to determine whether to execute the toner replenishment mode and the toner consumption mode and to perform the calculation for the potential control based on the information based on the same latent image pattern. The calculation result of the development γ calculated from the information based on the latent image pattern was used for the determination and the calculation for the potential control. Here, the information on the developing means is affected by the photoconductor potential if the information is merely a toner adhesion amount, but the information on the development γ is not affected even if the photoconductor potential changes. It is convenient to reflect the above mode.

Therefore, in this embodiment, each developing unit 231
Bk, 231C, 231M, and 231Y, if it is determined that it is not necessary to execute the toner density control of the developing device, that is, STEP7 'and STEP7 in FIG.
If it is determined to be “N” in 9 ′, STEP8, STEP10, and STEP13 of FIG. 6 are not executed for the developing device for which it is determined that the toner density control does not need to be executed. In other words, only the developing devices for which it is determined that the toner density control needs to be executed in STEP7 'and STEP9' in FIG.
13 or STEP10 and STEP13 are executed.

Thus, for example, a plurality of developing devices 231
Bk, 231C, 231M, and 231Y, the first developing unit that makes the determination (the main control unit 601)
Therefore, when it is determined that the toner density control does not need to be performed, the problem that the process control is performed without performing the determination by the determination unit on another developing device does not occur.

As described above, the latent image patterns 30a, 30b, 30c,. 30a, 30b,
When the configuration is such that the density information after development of 30c... Is detected, STEP7 'and STEP9' in FIG.
When it is determined to be “N”, the reflection density sensor 205
Latent image patterns 30a, 30b for re-detection by
30c... Need not be formed, and wasteful toner consumption can be eliminated.

Here, as in the present embodiment, each developing unit 23
In an image forming apparatus including a revolver-type developing device 230 having a configuration in which 1Bk, 231C, 231M, and 231Y move to a predetermined developing position to perform development, at least the toner density control detected by the reflection density sensor 205 is performed. Information A and information B relating to at least one of a charging potential of the charger 203 as a charging unit, a writing light amount of the writing optical unit 220 as an image writing unit, and a developing bias of a revolver type developing device 230 as a developing unit. Of the developing unit 231Bk, 231C, 231M, and 231Y based on the information A, and a determining operation of the determining unit (main control unit 601) for determining whether to execute the toner density control, and the determining unit. Density control operation of the developing unit that has determined that it is necessary to execute toner density control And it is preferable to continuously executed for each developing device is moved to the developing position.

That is, the judging operation of the judging means and the toner concentration controlling operation of the developing device which the judging means judges that the toner density control needs to be executed are performed for each developing device moved to the developing position. By executing in succession,
The determination operation of the determination unit and the toner concentration control operation do not need to be performed again by moving to the developing position for each developing device, and the time required for switching each developing device to the developing position is minimized. Process control can be performed in a shorter time.

As described above, in the present embodiment, S in FIG.
The detection of the developing capability of the TEP 13 is performed only for the developing device in which the toner has been supplied and the toner has been consumed, whereby the detection of the developing capability for controlling the potential for each single color is completed, which leads to a reduction in time. In other words, in the controlled state, it is generally considered that the special modes of the toner supply mode and the toner consumption mode are not necessary, so that in many cases, the time is shortened,
It becomes possible to mount a control system that can cope with a case where the developing capacity becomes excessively high or low. In FIG. 6, STEP6, STEP8, STE
P10, STEP13 to STEP22 are the same as those in FIG.

In another embodiment of the present invention, in any one of the above two embodiments, a temperature / humidity sensor is provided as environmental condition measuring means for detecting the environmental conditions (temperature and humidity) of the color copying machine. , The main control unit 601 fetches the output value of the temperature and humidity sensor, and based on the output value, the thresholds XX and YY of STEP6 and STEP20, and ST
The thresholds X and Y of EP7, STEP9, STEP7 'and STEP9' are corrected according to environmental conditions (temperature and humidity), for example, as shown in FIG. 12, low temperature low humidity, normal temperature normal humidity, and high temperature high humidity. As a result, the toner density and the development γ are maintained in such a manner that the image quality is kept good according to each environment, and the image quality can be maintained for a long time in the environment over time.

The present invention is not limited to the above embodiments, but can be applied to image forming apparatuses such as electrophotographic copying machines, facsimile machines, and printers other than the above embodiments.

[0124]

As described above, according to the present invention, the occurrence of toner scattering, carrier adhesion, etc. can be prevented, the desired image quality can be maintained for a long time, and the time for process control can be shortened. can do

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing an embodiment of the present invention.

FIG. 2 is an enlarged schematic view showing a part of the embodiment.

FIG. 3 is a flowchart showing a self-check operation in the embodiment.

FIG. 4 is a diagram illustrating potential data obtained by a surface potential sensor for a latent image pattern on a photoconductor and toner adhesion amount data obtained by a toner adhesion amount calculation process of a reflection density sensor output value in the embodiment; It is the figure which plotted the relationship on the xy plane.

FIG. 5 is a characteristic diagram illustrating a relationship among a potential, a toner adhesion amount, and each control potential in the embodiment.

FIG. 6 is a flowchart illustrating a self-check operation according to another embodiment of the present invention.

FIG. 7 is a diagram illustrating a latent image pattern formed on a photoconductor in the embodiment.

FIG. 8 is a schematic diagram showing a reflection density sensor for detecting the reflection density of the photoconductor and the photoconductor.

FIG. 9 is a diagram showing a latent image pattern formed on a photoconductor in the embodiment.

FIG. 10 is a block diagram schematically showing a control system of the embodiment.

FIG. 11 is a characteristic diagram illustrating output characteristics of the toner density sensor according to the embodiment.

FIG. 12 is a diagram illustrating a relationship between each threshold value and environmental conditions according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Color scanner 2 Color printer 3 Paper feed bank 200 Photoconductor 201 Photoconductor cleaning device 203 Charger 204 Surface potential sensor 205 Reflection density sensor 507 Primary transfer bias roller 220 Writing optical unit 230 Revolver developing unit 500 Intermediate transfer unit 600 Secondary Transfer unit 270 Fixing device

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H027 DA02 DA04 DA07 DA10 DA11 DA12 DA14 DD07 DE02 DE07 EA01 EA02 EA05 EA06 EA08 EA20 EC03 2H030 AD17 BB13 BB24 BB34 BB36 BB38 BB54 2H077 AE06 CA11 DA03 DA10 DB18 DA47

Claims (6)

[Claims] An information detecting means for detecting information A relating to a first process means and information B relating to a second processing means, and information A among the information A and B detected by the information detecting means. And a determination unit for determining whether to execute the control of the first process unit based on the determination of the need to execute the control of the first process unit. Executing the control of the first process means. Thereafter, the information detection means detects at least the information B among the information A and B, and based on the information B detected by the information detection means, A first control mode for executing control of the second process means; and executing the first control mode when the determination means determines that the control of the first process means does not need to be executed. Without the above information A second control mode for executing the control of the second process means based on the information B of the information A and B detected by the means, wherein the information A is the first control mode. The information B includes the information of the toner density related to the toner density control of the developing means as the process means and the information of the toner adhesion amount on the image carrier after the development. An image forming apparatus comprising: information on at least one of a charging potential, a writing light amount of an image writing unit, and a developing bias of the developing unit. 2. An image forming apparatus according to claim 1, wherein said developing means includes a plurality of developing devices each containing a plurality of color toners. 3. Information A relating to toner density control of a plurality of developing devices constituting a developing device, and information relating to at least one of a charging potential of a charging device, a writing light amount of an image writing device, and a developing bias of the developing device. B, and a determination unit for determining whether to execute the toner density control of each of the developing units based on the information A among the information A and B detected by the information detection unit. When the determination means determines that it is necessary to execute the toner density control of any of the developing devices, it is determined that the toner density control needs to be performed. The toner density control of the developing device is executed. Thereafter, at least the information B of the information A and B is detected again by the information detecting means for the developing device for which the toner density control has been executed, and the information detection is performed. A first control mode for controlling at least one of a charging potential of the charging unit, a writing light amount of the image writing unit, and a developing bias of the developing unit based on the information B detected by the unit; When the means determines that it is not necessary to execute the toner density control of any of the developing devices, the first control mode relating to the developing device that has determined that the toner density control is not required to be executed. Without performing the above, based on the information B among the information A and B detected by the information detecting means, the charging potential of the charging means, the writing light amount of the image writing means, and the developing bias of the developing device. In the image forming apparatus which performs the second control mode for executing at least one of the control, the information A includes toner density information relating to toner density control of the developing device. And a toner adhesion amount of information on the image bearing member after the image, the information B is at least one of the charging potential of the charging unit, the write light intensity of the image writing means, the developing device of the developing bias
An image forming apparatus comprising: 4. An image forming apparatus according to claim 2, wherein each of said developing units moves to a predetermined developing position to perform development, and at least said information detected by said information detecting means is obtained. Based on information A of A and B,
The determination operation of the determination unit that determines whether or not to execute the toner density control of each of the developing devices, and the toner concentration control operation of the development device that determines that the determination unit needs to perform the toner density control are performed. An image forming apparatus which continuously executes the processing for each developing device moved to the developing position. 5. The image forming apparatus according to claim 1, wherein the information on the toner density relating to the toner density control of the developing means as the first process means is not within a predetermined range. An image forming apparatus that performs toner density control in preference to information on a toner adhesion amount on an image carrier after development. 6. An image forming apparatus according to claim 1, wherein a control target value of toner density control of said developing means as said first process means is changed according to environmental conditions. An image forming apparatus comprising: