JP2002372845A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of keeping toner amount in a developing device proper even when much toner is consumed at the time of forming an image. SOLUTION: This image forming device is equipped with the developing device and a supply device, and the toner is supplied to the developing device from the supply device. The device is provided with a control means to arithmetically calculate the insufficient supply amount of every cycle based on required supply amount necessary in every cycle and toner maximum supply amount attainable in every cycle in course of an image forming cycle in which a toner image is formed on a recording medium and to shift operation from the image forming cycle to an idle rotation cycle in which the toner image is not formed on the recording medium when the cumulative value of insufficient supply amount exceeds a specified upper limit value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile, and a multifunction peripheral thereof, and more particularly, to a technique for supplying toner to a developing device.

[0002]

2. Description of the Related Art Conventionally, image forming apparatuses such as copying machines and printers using an electrophotographic system (electrostatic transfer system) are widely known. Among such image forming apparatuses, there is an image forming apparatus that includes a developing device and a toner supply device and supplies toner from the toner supply device to the developing device during image formation or the like.

On the other hand, in recent years, miniaturization and space saving of image forming apparatuses have been promoted, and developing apparatuses have also been miniaturized. In particular, for a full-color image forming apparatus that needs to include a plurality of developing devices corresponding to three colors of yellow, magenta, and cyan, or four colors obtained by adding black thereto, the demand for downsizing of the developing devices is more severe. It has become something. As the size of the developing device decreases, the amount of toner that can be stored in the developing device necessarily decreases. Therefore, it is necessary to more finely control the amount of toner supplied from the toner supply device to the developing device.

In order to solve such a problem, conventionally, a toner patch is formed on an image carrier or a transfer body and the density thereof is measured to indirectly increase or decrease the amount of toner in the developing device (toner density). Is detected, and the amount of toner supplied from the toner supply device to the developing device is controlled (TC process control).

[0005]

However, if a state in which a large amount of toner is consumed continues, such as when images having a relatively high area coverage are continuously formed, the amount of toner supplied to the developing device is reduced. The amount of toner consumed by the developing device may increase, and a desired image density may not be obtained. In particular, in the case of a full-color image forming apparatus,
A decrease in density immediately leads to poor image quality, which is not preferable.

The present invention has been made in view of such technical problems, and an object thereof is to maintain an appropriate amount of toner in a developing device even when a large amount of toner is consumed during image formation. To provide an image forming apparatus capable of performing the above.

[0007]

According to the present invention, there is provided an image forming apparatus comprising a developing device and a supply device, wherein a toner image is formed on a recording medium in an image forming apparatus for supplying toner from the supply device to the developing device. During the cycle, the shortage supply amount for each cycle is calculated based on the required supply amount required for each cycle and the maximum supply amount of toner possible for each cycle, and the accumulated value of the shortage supply amount becomes a predetermined upper limit value. The control means shifts from an image forming cycle to an idling cycle in which a toner image is not formed on a recording medium.

The control means calculates a shortage supply amount in each cycle based on a required supply amount required in each cycle and a maximum toner supply amount possible in each cycle during the idling cycle. When the accumulated value of the insufficient supply amount falls below a predetermined lower limit value, it is possible to shift from the idling cycle to the image forming cycle.

When the present invention is applied to a multi-color (full-color) image forming apparatus, it can be configured as follows. That is, the present invention includes a plurality of developing devices corresponding to each color, and a plurality of supply devices corresponding to each developing device,
The control means shifts from the image forming cycle to the idling cycle when the accumulated value of the insufficient supply amount corresponding to a certain color exceeds a predetermined upper limit value. Further, during the idling cycle, the control means calculates the shortage supply amount for each cycle based on the required supply amount required for each cycle and the maximum supply amount of toner possible for each cycle, and corresponds to each color. If all the accumulated values of the shortage supply amounts fall below a predetermined lower limit value, it is possible to shift from the idling cycle to the image forming cycle.

The control means determines that the image forming apparatus has failed if the accumulated value of the insufficient supply does not fall below the predetermined lower limit even though the idle rotation cycle has been performed for the predetermined upper limit cycle. be able to.

The required supply amount is determined based on the area coverage ratio for each cycle and / or the immediately preceding toner density control. More specifically, the required supply amount in the image forming cycle is determined based on the area coverage ratio for each image forming cycle and the immediately preceding toner density control, and the required supply amount in the idling cycle is determined based on the immediately preceding toner concentration control. It is determined based on. Here, the toner density control refers to controlling the toner density in the developing device (TC process control).

[0012]

FIG. 1 shows a full-color printer 100 as an image forming apparatus according to an embodiment of the present invention. FIG. 2 shows the image forming main part of the full-color printer 100 shown in FIG. 1 in more detail. In addition, the arrow in FIG. 2 has shown the rotation direction of each rotating member. Hereinafter, the basic configuration of the image forming apparatus and the operation in the image forming mode will be described.

As shown in FIG. 1, the full-color printer 100 is roughly divided into a printer main body 101 and a paper feed tray section 102. The printer body (image forming means) 101 includes an image forming unit 1, an exposing device unit 12, toner cartridges 14Y to 14K for yellow Y, magenta M, cyan C, and black K, and respective colors (not shown) from the toner cartridges 14Y to 14K. Each of the toner supply flexible pipes 15Y to 15K extending to the developing device corresponding to
A control unit 6, a power supply unit 5, and a fixing unit 4 are provided.

A pair of feed rolls 41, a pair of first transport rolls 42, a pair of registration rolls 43,
A second transport roll pair 45 (in the fixing unit 4), a third transport roll pair 46, and a discharge roll pair 47 are provided.

Further, as shown in FIG. 2, the image forming unit 1 of the printer main body 101 includes yellow Y, magenta M,
Photoconductor drums (image carriers) 10Y to 10K corresponding to the respective colors of cyan C and black K, charging rolls 11Y to K for primary charging that contact these photoconductor drums 10Y to K, and developing devices corresponding to the respective colors 13Y to K, and a first primary intermediate transfer drum (primary intermediate transfer member) that comes into contact with two of the four photosensitive drums (photosensitive members) 10Y to 10K.
21a and a second primary intermediate transfer drum (primary intermediate transfer member) 21b that contacts the other two photosensitive drums 10C and 10K.
And the first and second primary intermediate transfer drums 21a, 21
b, a secondary intermediate transfer drum (secondary intermediate transfer member)
2 and a final transfer roll (final transfer body) 30 that comes into contact with the secondary intermediate transfer drum 22, constitute a main part thereof. The final transfer roll 30 is configured to be detachable from the printer main body 101.

The photosensitive drums 10Y to 10K have a common tangent plane M
Are arranged at regular intervals so as to have Further, the first primary intermediate transfer drum 21a and the second primary intermediate transfer drum 21b each
They are arranged so as to be parallel to the Y to K axes and have a relation of a plane object with a predetermined target plane as a boundary. Further, the secondary intermediate transfer drum 22 is arranged such that the rotation axis is parallel to each of the photosensitive drums 10Y to 10K.

A signal corresponding to the image information for each color is rasterized by an image processing unit (not shown) and input to the exposure unit 12. In the exposure device unit 12, the laser beams 12Y to 12K corresponding to the respective colors of yellow Y, magenta M, cyan C, and black K are modulated and applied to the photosensitive drums 10Y to 10K of the corresponding colors.

Around each of the photosensitive drums 10Y to 10K,
An image forming process for each color is performed by a known electrophotographic method. First, as the photoconductor drums 10Y to 10K, for example, photoconductor drums using an OPC photoconductor having a diameter of 20 mm are used.
Is driven to rotate at a rotation speed of, for example, 95 mm / sec. As shown in FIG. 2, the surfaces of the photoreceptor drums 10Y to 10K have charging rolls 11Y to 11K as contact-type charging devices.
Then, by applying a DC voltage of about -840V, for example, it is charged to about -300V. The contact-type charging device includes a roll-type charging device, a film-type charging device, and a brush-type charging device, but any type may be used. In this embodiment, a charging roll generally used in an electrophotographic apparatus in recent years is employed. The photosensitive drums 10Y to 10K
In this embodiment, DC is applied to charge the surface of
Although only the charging method of application is adopted, a charging method of AC + DC application may be used.

After that, the surfaces of the photosensitive drums 10Y to 10K are irradiated with laser beams 12Y to 12K corresponding to the respective colors of yellow Y, magenta M, cyan C, and black K by a laser optical unit as an exposure device (not shown). Thus, an electrostatic latent image corresponding to the input image information for each color is formed. When an electrostatic latent image is written on the photosensitive drums 10Y to 10K by the laser optical unit, the surface potential of the image exposure unit is eliminated to about -60 V or less.

Further, yellow Y, magenta M, cyan C, and black K formed on the surfaces of the photosensitive drums 10Y to 10K.
The electrostatic latent image corresponding to each color is developed by the developing device 1 of the corresponding color.
The image is developed by 3Y to 3K and is visualized as a toner image of each color on the photosensitive drums 10Y to 10K.

The developing devices 13Y to 13K are filled with a two-component developer composed of toners of different colors, yellow Y, magenta M, cyan C, and black K, and a carrier. As the type of toner to be used, pulverized toner or spherical toner can be considered, but in this embodiment, spherical toner is used. In addition, since the irregular shaped toner such as the pulverized toner has a large contact surface with respect to the adhesion surface, the adhesion force is large, and it is difficult to transfer the toner to the surface of the transfer destination. On the other hand, since the spherical toner has a small contact surface with respect to the adhesion surface, the adhesion force is small and the transfer efficiency is high. Further, as a method for producing a spherical toner, a method of subjecting a toner produced by an emulsion polymerization method, a suspension polymerization method, a dissolution suspension method, or a kneading and pulverizing method to a heat treatment is known. The spherical toner is defined as M1 ≦ 125, preferably M1 ≦ 120, when the shape factor M1 is represented by the following equation.
Means M1 = (π · dmax2 / 4A) × 10
0, dmax: maximum diameter of toner, A: cross-sectional area of toner

The developing devices 13Y to 13K are supplied with toners of respective colors from the toner cartridges 14Y to 14K shown in FIG. 1 via the toner supply flexible pipes 15Y to 15K. The replenished toner is sufficiently stirred with the carrier by the auger 133 and triboelectrically charged to a negative polarity. Inside the developing roll 130, a magnet roll (not shown) having a plurality of magnetic poles arranged at a predetermined angle is arranged in a fixed state. The developer conveyed to the vicinity of the surface of the developing roll 130 by the paddle 132 that conveys the developer to the developing roll 130 is subjected to a developer amount regulating member 131.
The amount conveyed to the developing unit is regulated by the control. In this embodiment, the amount of the developer on the developing roll 130 is 30 to 50 g / m ² , and the charge amount of the toner on the developing roll 130 at this time is approximately 20 g / m ^2.
It is about 35 .mu.C / g.

The toner supplied onto the developing roll 130 is in the form of a magnetic brush composed of carrier and toner by the magnetic force of the magnet roll, and the magnetic brush contacts the photosensitive drums 10Y to 10K. I have. An AC + DC developing bias voltage is applied to the developing roll 130 to remove the toner on the developing roll 130 from the photosensitive drum 10Y.
To K, a toner image is formed by developing the electrostatic latent image. In this embodiment, the developing bias voltage is such that the AC component is 4 kHz, 1.5 kVpp,
The C component is about -200V.

Next, the yellow Y, magenta M, cyan C, and black K toner images formed on the respective photosensitive drums 10Y to 10K are transferred to the first primary intermediate transfer drum 21a and the second primary transfer drum 21a. The primary transfer is electrostatically performed on the intermediate transfer drum 21b. That is, the yellow Y and magenta M toner images formed on the photoconductor drums 10Y and 10M are transferred onto the photoconductor drums 10C and 10K on the first primary intermediate transfer drum 21a.
The cyan C and black K toner images formed above are
The primary transfer is performed on the second primary intermediate transfer drum 21b. Therefore, on the first primary intermediate transfer drum 21a, the monochrome image transferred from either the photoconductor drum 10Y or 10M and the two-color toner image transferred from both the photoconductor drums 10Y and 10M are superimposed. A double-color image is formed. Further, on the second primary intermediate transfer drum 21b, a similar single color image and a similar double color image are formed from the photosensitive drums 10C and 10K.

The first and second primary intermediate transfer drums 2
The surface potential required for electrostatically transferring a toner image from the photosensitive drums 10Y to 10K onto the photosensitive drums 1a and 21b is +250.
About 500V. This surface potential is set to an optimum value depending on the charged state of the toner, the ambient temperature, and the humidity. The ambient temperature and the humidity can be easily known by detecting the resistance value of a member having a characteristic in which the resistance value changes depending on the ambient temperature and the humidity. As described above, when the charge amount of the toner is in the range of 20 to 35 μC / g and the environment is normal temperature and normal humidity, the first and second charge amounts are set.
The surface potential of the primary intermediate transfer drums 21a and 21b is +
About 400V is desirable.

The first and second primary intermediate transfer drums 21a and 21b used in this embodiment have, for example, an outer diameter of 42 mm.
mm, and the electric resistance value R is set to about 10 ⁸ Ω. First and second primary intermediate transfer drums 21a and 21b
Is a cylindrical rotating body having a single-layer or multiple-layer surface with flexibility or elasticity.
A low-resistance elastic rubber layer (R = 10 ² to 10 ³ Ω) typified by conductive silicone rubber or the like is formed on a metal pipe as a metal core made of e or Al to a thickness of about 0.1 to 10 mm. Is provided. Further, the outermost surfaces of the first and second primary intermediate transfer drums 21a and 21b are typically coated with a high release layer (R = 10 ⁵⁾ having a thickness of 3 to 100 μm made of fluoro rubber in which fluoro resin fine particles are dispersed. .About.10 ⁹ Ω) and bonded with a silane coupling agent-based adhesive (primer).

What is important here is the resistance value and the surface releasability.
And the resistance value of the high release layer is R = 10 ^Five ~Ten⁹ About Ω
The material is particularly limited as long as it has a high release property.
Not. The first and second primary intermediate transfer drums 21
a and b are the first and second primary cleaning rows, respectively.
23a and 23b are rotatably mounted. This
These primary cleaning rolls 23a and 23b are made of metal, respectively.
Conductive brush flocking tape is applied to the roll body
It is coated and has a predetermined cleaning bias.
Be added.

The single-color or double-color toner images formed on the first and second primary intermediate transfer drums 21a and 21b are electrostatically secondarily transferred onto the secondary intermediate transfer drum 22. You. Accordingly, on the secondary intermediate transfer drum 22, a final toner image from a single color image to a quadruple color image of yellow Y, magenta M, cyan C, and black K is formed.

The surface potential required for electrostatically transferring a toner image from the first and second primary intermediate transfer drums 21a and 21b onto the secondary intermediate transfer drum 22 is +600.
It is about 1200V. This surface potential is set to an optimum value according to the charged state of the toner, the ambient temperature, and the humidity, as in the case of the transfer from the photosensitive drums 10Y to 10K to the first primary intermediate transfer drum 21a and the second primary intermediate transfer drum 21b. Will be set. What is needed for transcription is
Since it is a potential difference between the first and second primary intermediate transfer drums 21a and 21b and the secondary intermediate transfer drum 22,
It is necessary to set a value corresponding to the surface potential of the second primary intermediate transfer drums 21a and 21b. As described above, the charge amount of the toner is in the range of 20 to 35 .mu.C / g, and the surface potential of the first and second primary intermediate transfer drums 21a and 21b is about +400 V in a normal temperature and normal humidity environment. In this case, the surface potential of the secondary intermediate transfer drum 22 is +80
0V, that is, the first and second primary intermediate transfer drums 2
It is desirable that the potential difference between 1a, 21b and the secondary intermediate transfer drum 22 be set to about + 400V.

The secondary intermediate transfer drum 22 used in this embodiment has, for example, an outer diameter of 42 mm, which is the same as the first and second primary intermediate transfer drums 21a and 21b, and a resistance value of about 10 ¹¹ Ω. Is set. Further, the secondary intermediate transfer drum 22 is also a first and a second primary intermediate transfer drum 21a,
Similar to 21b, the surface of a single layer or a plurality of layers is a cylindrical rotating body having flexibility or elasticity, and is generally placed on a metal pipe as a metal core made of Fe, Al, or the like. , A low-resistance elastic rubber layer (R = 10 ² to 10 ³ Ω) represented by a conductive silicone rubber or the like has a thickness of 0.1 to 10
mm. Further, the secondary intermediate transfer drum 2
The outermost surface of No. 2 is typically formed as a high release layer having a thickness of 3 to 100 μm made of fluororubber in which fluororesin fine particles are dispersed, and bonded with a silane coupling agent-based adhesive (primer). I have.

What is important here is the resistance value and the releasability of the surface, as in the first and second primary intermediate transfer drums 21a and 21b. However, the resistance value of the secondary intermediate transfer drum 22 depends on the first and second primary intermediate transfer drums 21a and 21a.
It must be set higher than b. Otherwise, the secondary intermediate transfer drum 22 charges the first and second primary intermediate transfer drums 21a and 21b, and it is difficult to control the surface potential of the first and second primary intermediate transfer drums 21a and 21b. Become. The material is not particularly limited as long as it satisfies such conditions. The secondary intermediate transfer drum 22
, A secondary cleaning roll 24 is attached so as to be driven and rotatable. The secondary cleaning roll 24 is configured by covering a metallic roll body with a flocking tape of a conductive brush, and a predetermined secondary cleaning bias is applied.

Next, the final toner image from the single-color image to the quadruple-color image formed on the secondary intermediate transfer drum 22 is transferred onto the sheet S passing through the sheet transport path P by the final transfer roll 30. Next is transferred. This sheet passes through a pair of registration rolls 43 through a sheet feeding process, and is sent to a nip portion between the secondary intermediate transfer drum 22 and the final transfer roll 30.
After this final transfer step, the final toner image formed on the paper is fixed by the fixing roller pair 44 in the fixing unit 4, and a series of image forming processes is completed.

The final transfer roll 30 has, for example, an outer diameter of 20.
mm, and the resistance value R is set to about 10 ⁸ Ω. As shown in FIG. 3, the final transfer roll 30 has a coating layer 3 made of urethane rubber or the like on a metal shaft 31.
2 and a coating is applied thereon as required. The optimum value of the voltage applied to the final transfer roll 30 varies depending on the ambient temperature, humidity, the type of paper (resistance value, etc.), and is generally about +1200 to 5000 V.
In this embodiment, a constant current method is employed, and a current of about +10 μA is applied under a reference environment to obtain a substantially appropriate transfer voltage (+1600 to 2000 V).

In the series of transfer steps, when the toner image passes through the transfer portion of each transfer step, a part of the positive toner in the (-) charged image is reversed by Paschen discharge or charge injection. Polar (+) charged toner may occur. The (+) charged toner flows back to the upstream side without being transferred to the next step, and thus adheres and accumulates on the charging devices 11Y to 11K having the highest negative potential. The portions of the charging devices 11Y to 11K to which the toner adheres are activated by the discharge, and the surface potential of the photoconductor drums 10Y to 10K tends to increase. Therefore, the portion where the toner adheres much, the portion where the toner adheres little, The surface potential of the photoconductor drums 10Y to 10K becomes uneven in the portion where the toner does not adhere. If the surface potentials of the photoconductor drums 10Y to 10K become uneven, even if the surface of the photoconductor drums 10Y to 10K is uniformly exposed to an image in order to form an electrostatic latent image, the nonuniformity of the latent image potential will occur. This causes a difference in the amount of development, so that the density unevenness becomes conspicuous especially when an attempt is made to develop a halftone image.

Therefore, in order to prevent the occurrence of density unevenness due to the toner attached to the charging devices 11Y to 11K, in this embodiment, there is a predetermined number of sheets before printing operation, after printing operation, every predetermined number of sheets during continuous printing, and the like. The following cleaning operation is performed at a predetermined timing.

Charging devices 11Y-K, photosensitive drums 10Y-
K, first and second primary intermediate transfer drums 21a, 21b
By applying voltages to the rotating bodies of the secondary intermediate transfer drum 22 and the final transfer roll 30 in order such that the final transfer roll 30 has the largest negative potential, a voltage having a potential gradient is applied to the rotating body of the charging device 11Y. To K, the (+) charged toner of the opposite polarity deposited and deposited during the printing operation is sequentially transferred and moved to the final transfer roll 30 in the cleaning operation, and a blade provided in contact with the final transfer roll 30 is provided. Is collected by the cleaning device 31 including the final cleaning member 32. This cleaning device 31
As shown in FIG. 4, each has a blade-shaped final cleaning member 32, a toner collection box 33, a support frame 34, a static eliminator 35 provided on the support frame 34, and a bias plate 36.

In this embodiment, the surface potentials of the charging devices 11Y to 11K are 0 V, and the surface potentials of the photosensitive drums 10Y to 10K are-
300V, the first and second primary intermediate transfer drums 21a,
The surface potential of the secondary intermediate transfer drum 22 is set to -1300 V, and the surface potential of the final transfer roll 30 is set to -2000 V. This potential gradient is obtained by supplying a voltage to the metal part (shaft, pipe) of each member. For example, the first and second primary intermediate transfer drums 21a and 21b or the secondary intermediate transfer drum 22 are used. If a desired surface potential can be obtained depending on the relationship between the resistance values of these members by electrically floating them, such a method may be adopted. In such a minus application cleaning mode, that is, the reverse polarity (+) charged toner collecting mode, it is possible to prevent the occurrence of density unevenness due to the toner attached to the charging devices 11Y to 11K.

An optical density sensor 7 is arranged around the cleaning device 31 at the axial center of the final transfer roll 30 so as to be located on the radial extension of the outer periphery of the final transfer roll 30. ing. The optical density sensor (detection means) 7 includes a sensor main body 70 and a holder 71 for fixing the sensor main body 70. As shown in FIG. 5A, the optical density sensor 7 is a specular reflection type sensor that detects specular reflection light, and has a predetermined incident angle φ with respect to a detection position on the surface of the final transfer roll 30. A light emitting element 70a composed of an LED or the like arranged only at an angle, and a light reflected from the light emitting element 70a to a detection position on the surface of the final transfer roll 30 to be specularly reflected from the detection position. And a light receiving element 70b, such as a phototransistor, which is arranged at an angle of reflection equal to the predetermined incident angle with respect to the detection position on the surface of the transfer roll 30.

As the optical density sensor 7, as shown in FIG. 5B, a diffuse reflection type sensor for detecting diffused light may be used. Further, both a specular reflection type sensor and a diffuse reflection type sensor may be used. In this case,
By detecting the toner density based on both the specular reflection component and the scattered light component, the detection accuracy of the toner density can be further improved.

In the xerography method and the like, since static electricity is used, the image density tends to fluctuate due to environmental fluctuations and aging. For this reason, a process control mode (control mode) is provided separately from the image forming mode to control the electrophotographic process while measuring the density of the toner patch using the optical density sensor 7 in response to environmental fluctuations and changes over time. Is preferred.

The process control mode includes a TC process control mode (toner density control mode) for controlling the toner density (the ratio between the toner and the carrier in the developer) in each of the developing devices 13Y to 13K. Potential process control mode (image density control mode) for controlling the toner density of the toner image transferred on the paper
And exists. In any of these process control modes, a test toner patch is formed on the surface of an image density detection medium such as a photoreceptor, an intermediate transfer member, or a transfer roll or transfer belt on paper, and the density is optically measured. Various image forming processes (image forming conditions) are detected by the density sensor and controlled, but a preferable image density detecting medium differs depending on the characteristics of each process control.

That is, in the TC process control mode, an image density detection medium close to each of the developing devices 13Y to 13K is used so that the ratio of toner and carrier in each of the developing devices 13Y to 13K can be detected more accurately. For example, it is preferable to detect toner patches on the surfaces of the photoconductor drums 10Y to 10K. On the other hand, in the potential process control mode, an image density detection medium close to the paper, for example, a toner patch on the surface of the secondary intermediate transfer drum 22 or the final transfer roll 30 is detected so that the toner density on the paper can be detected more accurately. Is preferred.

However, detecting the toner patches on the photosensitive drums 10Y to 10K requires four optical density detecting means for each of the photosensitive drums 10Y to 10K. First and second primary intermediate transfer drums 21a, 21b
If it is above, two optical density detecting means may be used. If it is on the secondary intermediate transfer drum 22 or on the final transfer roll 30, one optical density detecting means may be used.

Therefore, in this embodiment, a single optical density sensor 7 is used with emphasis on the simplicity of the configuration of the apparatus, and the toner patch on the final transfer roll 30 is detected in both process control modes. I decided that. On the other hand, in the TC process control mode, the ratio of the toner and the carrier in each of the developing devices 13Y to 13K can be detected as accurately as possible (even on the final transfer roll 30 that has undergone multiple transfers). The transfer rate in the TC process control mode is particularly high. For example, the toner amount of the test patch toner image formed on the photosensitive drums 10Y to 10K is more than 90% or 95% on the final transfer roll 30. The image forming conditions were controlled so as to transfer the image by at least%.

FIG. 6 is a block diagram illustrating an image forming condition control system of the full-color printer 100 according to the present embodiment.

As shown in the figure, this control system is mainly composed of a control unit 60, and an input unit for inputting a signal to the control unit 60 measures the toner density on the final transfer roll 30. In addition to an optical density sensor 7 for measuring the temperature and humidity in the full-color printer 100, a main controller 61 for inputting information on the mode, printing speed, and other information of multi-color or single-color of the full-color printer 100 is provided. No. The control unit 60 and the main control unit 61 are both functionally implemented in the control unit 6 of the printer main body 101.

On the other hand, the output section from which a signal is output from the control section 60 includes a charging power supply section 110Y-K for applying a charging voltage to each of the charging rolls 11Y-K, and laser beams 12Y-K corresponding to each color. Exposure unit 1 for irradiating
2. (Development power supply units 131Y to 131K for applying a developing bias voltage to the developing rolls 130Y to 130K, (drive units for) the toner supply flexible pipes 15Y to 15K, the first and second primary intermediate transfer drums 21a. , B, a primary transfer power supply section 210 a, b for applying a primary transfer voltage, and a secondary transfer power supply section 22 for applying a secondary transfer voltage to the secondary intermediate transfer drum 22.
0, a final transfer power supply unit 300 for applying a final transfer current to the final transfer roll 30, a primary cleaning power supply unit 230a, b for applying a primary cleaning voltage to each of the first and second primary cleaning rolls 23a, b, and a secondary cleaning. A secondary cleaning power supply unit 240 that applies a secondary cleaning voltage to the roll 24 is exemplified.

The control section 60 sends the mode (image forming mode, potential process control mode, TC control mode), printing speed (8 PPM or 16 PPM), print color (multiple) of the full color printer 100 from the main control section 61. A signal indicating color or single color), a signal indicating the toner density of the toner patch P from the optical density sensor 7, and a signal indicating the temperature and humidity in the full-color printer 100 are input from the environment sensor 8. And
The toner image as the image I is formed on the sheet S based on these input signals and image forming conditions provided in the control unit 60 in advance. Further, a toner image as a toner patch P1 is formed on the final transfer roll 30 based on these input signals and image forming conditions and toner patch creation conditions provided in the control unit 60 in advance. Further, a toner image as a toner patch P2 is formed on the final transfer roll 30 based on these input signals and image forming conditions and toner patch creation conditions provided in the control unit 60.

Here, the conditions for the main controller 61 to determine that the potential process control mode is necessary are as follows.
For example, immediately after the power is turned on to the full-color printer 100, when a predetermined number of images have been formed (in the image forming mode) from the previous potential process control mode, or when there is a user's explicit instruction. Is mentioned. Similarly, the main controller 61 determines that the TC process control mode is necessary, for example, when the power is turned on to the full-color printer 100, when a predetermined number of images have been transferred from the previous TC process control mode. For example, when forming is performed (in the image forming mode), or when there is an explicit instruction from the user. Hereinafter, the operation of each control mode will be described in detail.

O Potential process control mode First, the main control section 61 determines the mode of the full-color printer 100 (image forming mode, potential process control mode, and TC control mode), and the environmental sensor 8 determines the temperature and humidity in the full-color printer 100. However, when the signals indicating the printing speed and the printing color are respectively input from the main control unit 61, the control unit 60 selects an appropriate one according to the situation from the image forming conditions and the toner patch creation conditions stored in advance. Choose one.

For example, when a signal is input from the main control unit 61 indicating that the mode is the potential process control mode, the printing speed is 16 PPM, the printing color is multicolor, and the temperature and humidity are the reference environment from the environment sensor 8. The control unit 60
Indicates the image forming conditions for the primary intermediate transfer drum 21
The same 400 [V] as the primary transfer potential applied to a and b in the image forming mode and 900 [V] as the secondary transfer potential applied to the secondary intermediate transfer drum 22 are applied to the final transfer roll 30. 6 [μA] as the transfer current, 190 [V] as the primary cleaning voltage applied to the primary cleaning rolls 23a and b, 210 [V] as the secondary cleaning voltage, and the (target) of the photosensitive drum 10.
-300 [V] is selected as the charging potential, and -200 [V] is selected as the DC component of the developing bias voltage. Further, the control unit 60 selects the coverage input of 33.3% as the toner patch creation condition.

Based on the image forming conditions and toner patch preparation conditions selected in this way, the full-color printer 1
00 forms a toner image P1 as a toner patch on the final transfer roll 30, and performs potential process control.

FIG. 7 is a flowchart for explaining the operation of the potential process control VC. Hereinafter, based on this flowchart, the potential process control VC
Will be described in more detail.

First, in a state where the toner patch P1 is not transferred, the surface of the final transfer roll 30 at the position where each toner patch P1 is formed is detected by the optical density sensor 7, and the output of the optical density sensor 7 at this time is detected. Vcln is stored (step ST101). Next, based on the above-described image forming conditions and toner patch creation conditions, the toner patches P1 (Y) to (K) for each color of yellow, magenta, cyan, and black are obtained as shown in FIG. Is formed on the final transfer roll 30 (step ST
102).

FIG. 8A illustrates the toner patch P1 formed at the center of the final transfer roll 30 in the axial direction. This toner patch P1 is
Yellow P (Y), cyan P
(C), magenta P (M), and black P (K) in this order. The size of each toner patch P1 is 11 [mm] in the sub-scanning direction X and 12 [mm] in the main scanning direction Y. The interval D between the toner patches P1 is configured to be 3 [mm]. In the present embodiment, each toner patch P1
Is formed at the axial center of the final transfer roll 30,
As shown in FIG. 8 (b), the final transfer roll 30 may be formed at an axial end. In that case, it is necessary to change the installation position of the optical density sensor 7.

Thereafter, the areas of the yellow, magenta, cyan, and black toner patches P1 (Y) to (K) formed on the final transfer roll 30 are optical density sensors as shown in FIG. 7 at 0.5mm pitch 16
The average value Vpatch is obtained by detecting points (step ST10).
3). Here, as shown in FIG. 9A, a specular reflection type optical density sensor 7 is used.
As shown in (b), a diffuse reflection type sensor for detecting diffused light may be used, or both sensors may be used.

Then, the average value of each color is used as the final transfer roll 3
0 surface (state where toner patch P1 is not transferred)
The ratio Vpatch / Vcln divided by the value is used as a substitute value for the density (step ST104). Here, the final transfer roll 3
The ratio with the value of the elementary surface of 0 is the final transfer roll 3
This is for correcting a change in the reflectance of the zero element surface and a change in the LED light emission amount.

As a result, Vpatch / Vcln for each color
Is compared with a predetermined value (step ST105), and if the obtained density of the toner patch P1 is lower than the predetermined density, the control unit 60 determines the DC component V of the developing bias voltage according to the difference.
more it increases the absolute value of _dc, at the same time (to raise the absolute value of the voltage applied to the charging roller 11 as a result) to further increase the absolute value of the charging potential V _h of the photosensitive drum 10 (step ST 106). By doing so, FIG.
As shown in (b), the electric field in the developing direction formed between the developing roll 130 and the image portion on the photosensitive drum 10 increases, the amount of toner to be developed increases, and the image density increases.

On the other hand, if the determined density of the toner patch P1 is higher than the predetermined density, the control unit 60 reduces the absolute value of the DC component _Vdc of the developing bias voltage according to the difference, and at the same time (charges). The absolute value of the voltage applied to the roll 11 is reduced, and as a result, the charging potential V _{h of the} photosensitive drum 10 is reduced.
Is made smaller (step ST106). By doing so, as shown in FIG. 10C, the electric field in the developing direction formed between the developing roll 130 and the image portion on the photosensitive drum 10 is reduced, and the amount of toner to be developed is reduced. , The image density decreases.

TC process control mode Toner replenishment measures the image density from a print image signal and controls the replenishment time so as to replenish the toner corresponding to the amount of toner used according to the result. However, according to this method, when the development amount fluctuates, the amount of toner used fluctuates, and the balance with the amount of replenished toner deviates, so that the toner density in the developing device 13 fluctuates. Therefore, the toner patch P2 is created, the density is detected, and the toner supply amount is corrected according to the result.

First, the main control unit 61 determines the mode of the full-color printer 100 (different of image forming mode, potential process control mode, and TC control mode), the environmental sensor 8 determines the temperature and humidity in the full-color printer 100, and the main control unit. When a signal indicating a printing speed and a printing color is input from 61, the control unit 60 selects an appropriate one according to the situation from among the image forming conditions and toner patch creation conditions stored in advance.

For example, when a signal is input from the main control unit 61 indicating that the mode is the potential process control mode, the printing speed is 16 PPM, the printing color is multicolor, and the temperature and humidity are the reference environment from the environment sensor 8. The control unit 60
Indicates the image forming conditions for the primary intermediate transfer drum 21
360 [V] as a primary transfer potential applied to a and b,
810 [V] as a secondary transfer potential applied to the secondary intermediate transfer drum 22, 6 [μA] as a final transfer current applied to the final transfer roll 30, the primary cleaning roll 2
3a, a primary cleaning voltage applied to b is 190
[V] is 210 [V] as a secondary cleaning voltage.
Is -28 as the (target) charged potential of the photosensitive drum 10.
9 [V] as a DC component of the developing bias voltage is -20.
0 [V] is selected. The control unit 60 also controls the coverage input 100 as a toner patch creation condition.
Select%.

Based on the image forming conditions and toner patch creation conditions selected in this way, the full-color printer 1
00 forms a toner image P2 as a toner patch on the final transfer roll 30, and performs TC process control.

FIG. 11 is a flowchart for explaining the operation of the TC process control. Hereinafter, the operation of the TC process control will be described in more detail based on this flowchart.

First, in a state where the toner patch P2 is not transferred, the control unit 60 detects the surface of the final transfer roll 30 at the position where the toner patch P2 is formed by the optical density sensor 7, and the optical density at this time is detected. The output Vcln of the sensor 7 is stored (step ST201). next,
Based on the above-described image forming conditions and toner patch creation conditions, the toner patches P2 (Y) to (K) for each color of yellow, magenta, cyan, and black are shown in FIG.
As shown in (a), it is formed on the final transfer roll 30 (step ST202). Here, unlike the image forming mode and the potential process control mode, in this TC process control mode, the developing bias voltage is developed only with a DC component, and the AC component is not superimposed.

Thereafter, the area of the yellow, magenta, cyan and black toner patches P2 (Y) to (K) is set to 0.5 mm by the optical density sensor 7 as shown in FIG.
The average value Vpatch is obtained by detecting 16 points at the pitch (step ST203). Here, as shown in FIG. 9A, a specular reflection type optical density sensor 7 is used, but as shown in FIG. 11B, a diffuse reflection type sensor for detecting diffused light is used. Alternatively, both sensors may be used.

Then, the average value of each color is used for the final transfer roll 3
0 surface (state where toner patch P2 is not transferred)
The ratio Vpatch / Vcln divided by the value is used as a substitute value for the density (step ST204).

As a result, if the obtained toner patch density is lower than the predetermined density, the controller 60 measures the image density from the print image signal in advance according to the difference because the toner density is low (step ST210). ) Correction is made so that the toner supply amount is greater than the determined toner supply amount (step ST220) (step ST206). Conversely, if the test patch is higher than the predetermined density, the control unit 6
0 indicates that the toner density is high, so the image density is measured in advance from the print image signal according to the difference (step ST
210) Determined toner supply amount (step ST22)
Correction is made so that the toner supply amount is smaller than 0) (step ST208).

Here, when the density of the toner patch P2 is lower than the predetermined density, the control unit 60 controls the driving unit of each of the toner supply flexible pipes 15Y to 15K so that the driving time becomes longer than a specified time. The driving units of the pipes 15Y to 15K are controlled (see FIG. 6).

Example As described above, the full-color printer 10 according to this embodiment is
At 0, the TC process control is performed every time a predetermined number n (16 in this embodiment) of the image is formed. FIG.
4 illustrates the relationship between the TC process control and the image forming mode in the present embodiment. As shown in the figure, an image forming mode (k + 1) exists between one TC process control (k) and the next TC process control (k + 1), and this image forming mode (k + 1)
Has 16 image forming cycles (1) to (16) for forming toner images I (1) to (16) on 16 recording media p (1) to (16), respectively.

In the first half of the first to eight image forming cycles (1) to (8), the image density is measured from the print image signal (step ST2 in FIG. 11).
10) and the determined toner supply amount and the toner supply amount corrected (increased or decreased) by the TC process control (k) (steps ST206 and ST208 in FIG. 11).
See). On the other hand, in the latter half of the image forming cycle (9) to (16) from 9 to 16,
The toner supply amount determined by measuring the image density from the print image signal (see step ST210 in FIG. 11) is supplied.

Further, during the image forming cycle, the controller 60 controls the required supply amount D (Y) required for each cycle.
To (K) and the maximum supply amount M of toner that can be obtained in each cycle.
The shortage supply amount for each cycle is calculated based on (Y) to (K), and image formation is performed when the accumulated values A (Y) to (K) of the shortage supply amount exceed a predetermined upper limit value A (MAX). The cycle shifts from the cycle to the idle cycle in which no toner image is formed on the recording medium, and a sufficient toner supply is ensured. Then, during the idling cycle, the required supply amount D required for each cycle
The shortage supply amount for each cycle is calculated based on (Y) to (K) and the maximum toner supply amount M (Y) to (K) possible for each cycle, and the accumulated value A (Y) of the shortage supply amount is calculated. If (K) falls below a predetermined lower limit value A (min), the process shifts from the idling cycle to the image forming cycle. Hereinafter, these image forming cycles (1) to (16) and the idling cycle will be described as examples of the present invention.

FIG. 13 is a functional block diagram illustrating a toner supply control system by the control unit 60. The toner supply control system is formed around a control unit 60. The control unit 60 is provided with information on image densities ACR (Y) to (K) corresponding to each color from the exposure device unit 12 and a main control unit. 6
1 is input from the control unit 60 to the toner supply flexible pipes 15Y to 15K corresponding to the respective colors.
(I: Y) / S (Y) to S (i: K) / S (K) and feed stop and feed start signals to the main controller 61 are output.

The control unit 60 has a nonvolatile memory 6
01 and a working memory 602. Various setting values are stored in the nonvolatile memory 601. That is, “10 units” is set as the upper limit value A (MAX) of the insufficient supply amount accumulated value, and the lower limit value A (m
in), “16 times” as the cycle number i (MAX) of the image forming cycle between the TC process controls, “4 units” as the maximum toner supply amount M for a certain recording medium p, and an idle cycle. In the nonvolatile memory 601, “5 sec” is set as the initial time S (MAX), “1 sec” is set as the additional idle cycle time ΔS, and “5 times” is set as the upper limit number j (MAX) of the additional idle cycle. Is stored in On the other hand, the working memory 602 stores various parameters. That is, the required supply amounts D (Y) to (K) corresponding to the respective colors and the accumulated values A (Y) to (K) of the insufficient supply amounts corresponding to the respective colors are stored in the working memory 602 as parameters. .

The upper limit value A (MA
The unit “unit” used in X) and the like means the number of times the toner conveying member in the toner supply flexible pipe 15 is rotated, “1 unit” means “one rotation”, and the time is 0.5 sec. Cost. Therefore, “10 units” means that the conveying member in the toner supply flexible pipe 15 is rotated 10 times, and the time required for the rotation is 5 seconds.

FIGS. 14 to 18 are flowcharts for explaining the toner supply operation of the full-color printer 100 in the image forming mode. Hereinafter, the toner supply operation will be described based on these flowcharts.

FIG. 14 shows the relationship between the TC process controls (TC process controls (k) and (k +
3 is a flowchart for explaining a basic toner supply operation (see 1)). As shown in the figure, the control unit 60 first sets the parameter i to “i = 1” (see step S1), and accumulates the insufficient supply amount A (1: Y) corresponding to each color.
ＡA (1: K) is calculated (step S2). And
The accumulated values A (1: Y) to A (1: K) are compared with an upper limit value A (MAX) stored in the nonvolatile memory 601 in advance.

When none of the accumulated values A (1: Y) to A (1: K) satisfies A (1) ≧ A (MAX) (A
If (1) <A (MAX)), an image forming cycle is performed (step S4). On the other hand, the accumulated value A (1: Y) ~
If any of A (1: K) satisfies A (1) ≧ A (MAX), an idling cycle is performed (step S).
5).

Thereafter, i (= 1) and the upper limit value i (MAX) (= 1) stored in the nonvolatile memory 601 in advance.
6), the parameter i is updated to "i = i + 1" (step S7), and steps S2 to S7 are repeated until i becomes 16 (until 16 image forming cycles are performed). On the other hand, when the parameter i = i (MAX) holds, the next TC process control (k + 1) is performed (see FIG. 12).

FIG. 15 is a flowchart illustrating step S2 of FIG. 14 in more detail. First, the control unit 60
Obtains the toner supply amount D (i: TC) based on the TC process control (k) (step S22). FIG.
9 illustrates the toner supply amount D (i: TC). Note that each circular arrow in the figure indicates the toner supply amount for one rotation of the toner conveying member in the toner supply flexible pipe 15, that is, "1 unit".

Here, when the consumption of each color toner is small as a whole, such as when a text image is continuously formed in the previous image forming mode (k), as shown in FIG. The toner supply amount D (i: TC) based on the TC process control (k) in the image forming cycle (i: i <8) in the image forming mode (k + 1) is small as a whole (D (i) : TC: Y) = D (i: TC:
M) = D (i: TC: C) = D (i: TC: K) = “1
unit").

Further, in the previous image forming mode (k), black and white photographic images are continuously formed, for example, the consumption of black toner alone is large, and the consumption of other yellow, magenta, and cyan toners is compared. If it was not enough,
As shown in FIG. 9B, the image forming mode (k + 1)
In the image forming cycle (i <8), the toner supply amount D (i: TC) based on the TC process control (k) is large only in the black toner supply amount D (i: TC: K) (D (i) : TC: K) = “2 units”), the other yellow, magenta, and cyan toner supply amounts D (i: TC:
Y), D (i: TC: M) and D (i: TC: C) are small (D (i: TC: Y) = D (i: TC:
M) = D (i: TC: C) = "1 unit").

Further, in the case where the consumption of each color toner is large as a whole, for example, full-color photographic images are continuously formed in the previous image forming mode (k), FIG.
As shown in FIG. 3C, the toner supply amount D (i: i) in the image forming cycle (i <8) in the image forming mode (k + 1).
TC) is large overall (D (i: TC: Y)
= D (i: TC: M) = D (i: TC: C) = D (i:
TC: K) = "2 units").

Next, the control unit 60 controls the toner supply amount D (i: I) based on the image density (area coverage ratio) ACR of the image I (i) to be formed on the recording medium p (i).
ACR) is obtained (step S22). FIG. 20 illustrates the toner supply amount D (i: ACR). Note that each circular arrow in the figure indicates the toner supply amount for one rotation of the toner conveying member in the toner supply flexible pipe 15,
That is, it means “1 unit”.

Here, when the image density is low such that the image I (i) is a text image and the consumption of each color toner for the recording medium p (i) is predicted to be small as a whole,
As shown in FIG. 20A, this image forming cycle (i)
Toner supply amount D (i: AC) based on image density ACR at
R) is small overall (D (i: ACR:
Y) = D (i: ACR: M) = D (i: ACR: C) =
D (i: ACR: K) = "1 unit").

Further, the image density of black is high such that the image I (i) is a black-and-white photographic image, but the image densities of other yellow, magenta and cyan are low. Consumption is large but other yellow,
If the magenta and cyan toner consumptions are predicted to be small, the black toner supply amount D (i: ACR) based on the image density ACR in this image forming cycle (i) as shown in FIG. : K) but many (D (i: AC
R: K) = “3 units”), other yellow, magenta, and cyan toner supply amounts D (i: ACR: Y), D
(I: ACR: M) and D (i: ACR: C) are small (D (i: ACR: Y) = D (i: ACR:
M) = D (i: ACR: C) = "0 unit").

If the consumption of each color toner on the recording medium p (i) is predicted to be small as a whole, such as when the image I (i) is a full-color photographic image, FIG.
As shown in (c), the toner supply amount D (i: ACR) based on the image density ACR in the image forming cycle (i) becomes large as a whole (D (i: ACR: Y) = D).
(I: ACR: M) = D (i: ACR: C) = D (i:
ACR: K) = "3 units").

Next, the controller 60 controls the toner supply amount D (i: T) based on the TC process control (K) obtained earlier.
C) and (see step S21), toner supply amount D based on image density (area coverage ratio) ACR of image I (i)
From (i: ACR) and (Step S22), the required supply amount D (i) in the image forming cycle (i) is calculated (Step S23). That is, the required supply amount D (i:
Y) = D (i: TC: Y) + D (i: ACR: Y), required supply amount D (i: M) = D for magenta toner
(I: TC: M) + D (i: ACR: M), required supply amount D (i: C) for cyan toner = D (i: TC:
C) + D (i: ACR: C), required supply amount D (i: K) = D (i: TC: K) + D for black toner
(I: ACR: K).

Next, the control unit 60 calculates the accumulated toner supply amount D (i) obtained beforehand and the insufficient supply amount up to the previous image forming cycle (i-1) stored in the working memory 602. From A (i-1) and the maximum toner supply amount M stored in the nonvolatile memory 601 in advance, the accumulated value A (i) of the insufficient supply amount up to the image forming cycle (i) is represented by A (i). )
= A (i-1) + D (i) -M. That is, the accumulated value A (i: Y) of the insufficient supply amount of the yellow toner until the image forming cycle (i) is represented by A (i: Y) = A
As (i-1: Y) + D (i: Y) -M, the accumulated value A (i: M) of the insufficient supply amount of magenta toner is represented by A (i:
M) = A (i−1: M) + D (i: M) −M, and the accumulated value A (i: C) of the insufficient supply amount of cyan toner is represented by A
Assuming that (i: C) = A (i-1: C) + D (i: C) -M, the accumulated value A (i: K) of the insufficient supply amount of black toner.
A (i: K) = A (i−1: K) + D (i: K) −
Each is calculated as M. The maximum toner supply amount M
Is selected based on the size information in the transport direction of the recording medium p (i) input from the main control unit 61, does not depend on the color of the toner, and is “4 units” in the present embodiment.

FIG. 16 is a flowchart illustrating the image forming cycle (i) of step S4 of FIG. 14 in more detail. First, the control unit 60 compares the accumulated value A (i) (Step S2) of the insufficient supply amount up to the image forming cycle (i) previously obtained with “0” (Step S41). Here, when “A (i)> 0” is satisfied, the toner supply amount S (i) in the image forming cycle (i) is set to S (i) = M
(Step S44), the supply of toner is started (Step S45). On the other hand, when “A (i)> 0” is not satisfied (when “A (i) ≦ 0” is satisfied), the toner supply amount S (i) in the image forming cycle (i) is set to S.
(I) = A (i) + M (step S42), and the accumulated value A of the insufficient supply amount until the image forming cycle (i)
(I) is updated to A (i) = 0 (step S43),
The supply of toner is started (step S45).

FIG. 21 shows steps S41 to S4 in FIG.
5 describes a specific example of the processing of No. 5.

First, the supply of yellow toner will be discussed. A (i-1: Y) = 0, D (i: Y) = 3 (D
(I: TC: Y) = 1, D (i: ACR: Y) = 2),
Since M = 4 (common), A (i: Y) = A (i-1:
Y) + D (i: Y) -M = 0 + 3-4 = -1 <0 (step S41). Therefore, S (i: Y) = A
The calculation is performed with (i: Y) + M = -1 + 4 = 3 (step S42), and A (i: Y) is updated to 0 (from -1) (step S43). Then, during the image forming cycle (i), when the maximum supply amount is “4 units”, yellow toner is supplied by “3 units” (step S45, see FIG. 13). Note that A (Y) is A
(I-1: Y) = From "your unit" to A (i: Y) =
"0 units" has not changed.

Next, supply of magenta toner will be discussed. A (i-1: M) = 1, D (i: M) = 3 (D
(I: TC: M) = 2, D (i: ACR: M) = 1),
Since M = 4 (common), A (i: M) = A (i−1:
M) + D (i: M) -M = 1 + 3-4 = 0 (step S41). Therefore, S (i: M) = A (i:
M) + M = 0 + 4 = 4 (step S4)
2) Further, A (i) is updated to 0 (step S4)
3). Then, during the image forming cycle (i), when the maximum supply amount is "4 units", magenta toner is supplied by "4 units" (step S45, see FIG. 13). A (M) is reduced from A (i−1: M) = “1 unit” to A (i: M) = “0 unit”.

Next, the supply of cyan toner will be discussed. A (i-1: C) = 3, D (i: C) = 2 (D
(I: TC: C) = 1, D (i: ACR: C) = 1),
Since M = 4 (common), A (i: C) = A (i-1:
C) + D (i: C) -M = 3 + 2-4 = 1> 0 (step S41). Therefore, S (i: M) = M is set (step S44). And an image forming cycle (i)
Where the maximum supply amount is "4 units",
Units of cyan toner are supplied (step S4).
5, see FIG. 13). In addition, A (C) is A (i-1:
C) = “3 units” and A (i: C) = “1 unit”.

Next, supply of black toner will be examined. A (i-1: K) = 2, D (i: C) = 5 (D
(I: TC: K) = 2, D (i: ACR: C) = 3),
Since M = 4 (common), A (i: K) = A (i-1:
K) + D (i: K) -M = 2 + 5-4 = 3> 0 (step S41). Therefore, S (i: K) = M is set (step S44). And an image forming cycle (i)
Where the maximum supply amount is "4 units",
The unit supplies black toner for the unit (step S
45, see FIG. 13). A (K) is A (i-1:
K) = “2 units” to A (i: K) = “3 units”.

Then, the control section 60 issues a control command to the main control section 61 to start feeding the recording medium p (i) (step S46, see FIG. 13), and ends the image forming cycle (i).

FIG. 17 is a flowchart for explaining the idling cycle in step S5 of FIG. 14 in more detail.

First, the control unit 60 stops feeding the recording medium p (i) (step S51, see FIG. 13). Next, the control unit 60 sets a value S (MAX) previously stored in the nonvolatile memory 601 as the toner supply amount S in the idling cycle (step S52). Then, the control unit 60 starts the supply of the toner (Step S)
53), the cumulative value A (i-1) of the insufficient supply amount up to the image forming cycle (i-1) is updated (step S54).
That is, as the toner is supplied into the developing device 13,
The accumulated value A (i-1) of the insufficient supply amount is reduced accordingly.

Here, the set value S (MAX) is 5 seconds as described above, which corresponds to “10 units” as the toner supply amount. On the other hand, in order to shift from the image forming cycle to the idling cycle (step S5), the accumulated value A (i) becomes the upper limit value A (MAX) = “10 units”.
Is reached (step S3). Therefore, normally, when the toner is supplied by the set value S (MAX), the accumulated value A (i-1) becomes the lower limit value A (min) = "0" (step S54), and the image formation is started again from the idle cycle. Transition to a cycle.

However, TC process control (k)
If the value of the accumulated value A (i-1) does not decrease smoothly due to the effect of the above, that is, even if the toner is supplied only for the set value S (MAX), the accumulated value A (i-1) does not become 0. A case exists (step S54), and in that case, the process shifts to an additional idling cycle (step S55).

FIG. 18 is a flowchart illustrating the step S55 of FIG. 17 and the additional idling cycle in more detail.

First, the control unit 60 sets the parameter j to "j
= 1 ”(step S551). Next, the parameter j is compared with the maximum value j (MAX) of the parameter j stored in advance in the nonvolatile memory 601 (step S552). Here, parameter j = maximum value j (M
If (AX) = 5 (upper limit cycle) is satisfied, the control unit 60 stops image formation as an error (because the accumulated value of the insufficient supply amount does not decrease despite sufficient toner supply). To the main controller 61 (see FIG. 13).

On the other hand, the parameter j is still the maximum value j (MA
If X) has not been reached, a value ΔS previously stored in the non-volatile memory 601 is set as the toner supply amount S in the additional idling cycle (step S553). Then, the control unit 60 starts the supply of the toner (Step S)
554), the cumulative value A (i-1) of the insufficient supply amount up to the image forming cycle (i-1) is updated (step S55).
5). That is, as the toner is supplied into the developing device 13, the accumulated value A (i-1) of the insufficient supply amount is reduced accordingly.

Here, ΔS is 1 second as described above, which corresponds to “2 units” as the toner supply amount. Then, the accumulated value A (i-1) becomes the lower limit value A (mi
n) = “0” is determined (step S55)
6). When the accumulated value A (i-1) = 0, the process shifts from the additional idling cycle to the image forming cycle again. on the other hand,
If the accumulated value A (i-1) has not yet reached 0, the parameter j is updated to "j = j + 1" (step S55).
7), repeat the processing from step S552. Less than,
The same is true.

FIG. 22 is a flowchart showing step S3 in FIG.
A specific example (1) of the processing of steps S52 to S54 will be described.

The accumulated value A (i-1) of the insufficient supply amount up to the image forming cycle (i-1) is expressed as A (i-1: Y) = Y (y-1) = Y (y-1)
“7 units”, A (i−1: M) = “8 units”,
A (i-1: C) = "6 units", A (i-1: K)
= "9 units". The required supply amount D (i) of the image forming cycle (i) is D
(I: Y) = D (i: TC: Y) + D (i: ACR:
Y) = 2 + 2 = “4 units”, D (i: M) = D
(I: TC: M) + D (i: ACR: M) = 2 + 1 =
"3 units", D (i: C) = D (i: TC: C) +
D (i: ACR: C) = 1 + 2 = “3 units”, D
(I: K) = D (i: TC: K) + D (i: ACR:
K) = 2 + 3 = “5 units”.

Therefore, the accumulated value A (i) of the insufficient supply amount up to the image forming cycle (i) is calculated as
(I: Y) = A (i-1: Y) + D (i: Y) -M = 7
+ 4-4 = “7 units”, A (i: M) = A (i−
1: M) + D (i: M) -M = 8 + 3-4 = “7 units”, A (i: C) = A (i−1: C) + D (i: C)
−M = 6 + 3-4 = “5 units”, A (i: K) = A
(I-1: K) + D (i: K) -M = 9 + 5-4 = “1
0 units ”.

Therefore, the cumulative value A (i: K) = the upper limit value A
(MAX) is satisfied (step S3), and the process proceeds to the idling cycle without performing the image forming cycle (i).

Then, toner is supplied for the set value S (MAX) = “10 units” (S53). Here, not only the supply of the black toner whose accumulated value A (i) is equal to the upper limit A (MAX) is performed, but also the supply of other yellow, cyan, and magenta toners is performed.

That is, when the supply of the toner for one unit in the idling cycle is completed, the accumulated value A (i−
1) The accumulated value A (i-1: Y) corresponding to yellow is changed to "7 → 6 units", and the accumulated value A corresponding to magenta is
(I-1: M) goes to "8 → 7 units", the cumulative value A (i-1: C) corresponding to cyan goes to "6 → 5 units",
The cumulative value A (i−1: K) corresponding to black is “9 → 8”
To "units".

When the toner supply for six units is completed by repeating the idle cycle for each unit, the accumulated value A (i−1: C) corresponding to cyan becomes “1 →
0 unit ", and the supply of the cyan toner is not performed in the subsequent idling cycle. Similarly, when the supply of toner for 7 units is completed, the accumulated value A (i−1: Y) corresponding to yellow decreases to “1 → 0 unit”, and for the yellow toner, the toner supply is performed in the subsequent idle cycle. When the toner supply for 8 units is completed without performing the operation, the accumulated value A (i−1: M) corresponding to magenta is reduced to “1 → 0 unit”. Not performed.

On the other hand, when the supply of the toner of 9 units is completed, the accumulated value A (i-1: K) corresponding to black also decreases to "1 → 0 unit". Supply.

In the case of any of the toners, when the supply of the toner is completed (step S53), the accumulated value A (i−
1: Y), A (i-1: M), A (i-1: C), A
(I-1: A) are all "0". Therefore, A (i-1) = 0 (step S54), and the process proceeds to the next image forming cycle (i).

FIG. 23 is a flowchart showing steps S3 and FIG.
Another specific example (2) of the processing of steps S52 to S54 will be described. In the specific example (2) shown in FIG. 22 described above, when the supply of the toner for the set value S (MAX) is completed, the accumulated values A (i−1: Y) and A (i−1:
M), A (i-1: C), and A (i-1: A) are all 0, but in the specific example shown in FIG. The case where the accumulated value A (i-1) does not become 0 when the accumulated value A (i-1) is added during the cycle and the supply of the toner for the set value S (MAX) is finished as a result will be described. Things.

The accumulated value A (i-1) of the shortage supply amount up to the image forming cycle (i-1) is obtained by A (i-1: Y) = Y (y-1) = Y (y-1)
“7 units”, A (i−1: M) = “8 units”,
A (i-1: C) = "6 units", A (i-1: K)
= "9 units". The required supply amount D (i) of the image forming cycle (i) is D
(I: Y) = “4 units”, D (i: M) = “3 units”, D (i: C) = “3 units”, D (i: K)
= "5 units".

Therefore, the accumulated value A (i) of the shortage supply amount up to the image forming cycle (i) is equal to A
(I: Y) = “7 units”, A (i: M) = “7 units”, A (i: C) = “5 units”, A (i: K)
= "10 units". Therefore, the accumulated value A (i:
K) = upper limit A (MAX) holds (step S)
3) Shift to the idle cycle without performing the image forming cycle (i).

Further, the required supply amount for each toner is added even during this idle cycle by the TC process control (k). That is, D (idling: Y) = 3 units corresponding to yellow, and D (idling: Y) corresponding to magenta.
(Idling: M) = 2 units, D (idling: C) = 1 unit corresponding to cyan, D (idling:
K) = 3 units are added.

Then, toner is supplied for the set value S (MAX) = “10 units” (S53). Here, not only the supply of the black toner whose accumulated value A (i) becomes equal to the upper limit A (MAX) is performed, but also the supply of other yellow, cyan, and magenta toners is performed.

That is, when the supply of toner for one unit in the idling cycle is completed, the accumulated value A (i−
1), the cumulative value A (i-1: Y) corresponding to yellow is "7 + 3 = 10 → 9 units", and the cumulative value A (i-1: M) corresponding to magenta is "8 + 2 = 10 → 9". The cumulative value A (i−1: C) corresponding to cyan is “6 + 1 = 7 → 6 units”, and the cumulative value A (i−1: K) corresponding to black is “9 + 3 = 12 → 11”. To "units".

When the toner supply for seven units is completed by repeating the idle rotation cycle for each unit, the accumulated value A (i−1: C) corresponding to cyan becomes “1 →
0 unit ", and the supply of the cyan toner is not performed in the subsequent idling cycle. Similarly, 10
When the supply of the toner for the unit is completed, the accumulated value A (i-1: Y) corresponding to yellow decreases to "1 → 0 unit". The accumulated value A (i−1: M) corresponding to magenta is reduced to “1 → 0 unit”, and no toner is supplied for magenta toner in the subsequent idle cycle.

On the other hand, even if the supply of toner for 10 units is completed, the accumulated value A (i-1: K) corresponding to black decreases to "3 → 2 units", but does not become 0 yet (step). S54). Therefore, the process proceeds to the additional idling cycle (S55), and the toner is supplied at the supply amount ΔS (= 2 units) (step S554).

When the supply of the black toner for a total of 12 steps is completed (step S554), the accumulated value A (i−
1: Y), A (i-1: M), A (i-1: C), A
(I-1: A) is all 0. Therefore, A
(I-1) = 0 (step S556), and the flow proceeds to the next image forming cycle (i).

[0123]

As described above in detail, according to the present invention, there is provided an image forming apparatus capable of appropriately maintaining the amount of toner in a developing device even when a large amount of toner is consumed during image formation. .

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a full-color printer according to an embodiment of the present invention.

FIG. 2 illustrates the image forming unit of the full-color printer shown in FIG. 1 in more detail.

FIG. 3 illustrates a cross section of a final transfer roll.

FIG. 4 is a diagram for explaining in detail a peripheral configuration of a final transfer roll.

FIG. 5 illustrates the configuration and operation of an optical density sensor main body.

FIG. 6 is a functional block diagram illustrating an image forming condition control system of the full-color printer shown in FIG. 1;

FIG. 7 is a flowchart illustrating an operation in a potential process control mode.

FIG. 8 illustrates a toner patch formed on a final transfer roll.

FIG. 9 illustrates the configuration and operation of an optical density sensor main body.

FIG. 10 illustrates adjustment of a charging potential and a developing bias potential.

FIG. 11 is a flowchart illustrating an operation in a TC process control mode.

FIG. 12 is a diagram for explaining the relationship between TC process control and an image forming mode therebetween.

FIG. 13 is a functional block diagram illustrating a toner supply control system of the full-color printer according to the embodiment;

FIG. 14 is a flowchart illustrating a procedure of toner supply control of the full-color printer according to the embodiment;

FIG. 15 is a flowchart illustrating a part of the flowchart of FIG. 14 (calculation of the accumulated value A) in more detail;

FIG. 16 is a flowchart illustrating a part (image forming cycle) of the flowchart of FIG. 14 in more detail;

FIG. 17 is a flowchart illustrating a part (idling cycle) of the flowchart of FIG. 14 in more detail;

FIG. 18 is a flowchart illustrating a part (additional idling cycle) of the flowchart of FIG. 17 in more detail;

FIG. 19 illustrates a required toner supply amount D (i: TC) based on TC process control.

FIG. 20 illustrates a required toner supply amount D (i: ACR) based on the image density ACR.

FIG. 21 is a diagram for explaining an increase / decrease of a cumulative value A of an insufficient supply amount.

FIG. 22 illustrates an example of processing from an image forming cycle (i-1) to a next image forming cycle (i) through an idling cycle.

FIG. 23 illustrates an example of processing from an image forming cycle (i-1) to a next image forming cycle (i) through an idling cycle and an additional idling cycle.

[Explanation of symbols]

100 full-color printer (image forming apparatus), 1 image forming unit, 6 control unit, 60 control unit (control means), 601 nonvolatile memory, 602
Working memory, 61 Main control unit, 12 Exposure unit, 14 Toner cartridge, 15 Toner supply flexible pipe (supply device), 10 Photosensitive drum (image carrier), 11 Charging roll, 13 Development Apparatus, 130
Developing roll, 21 Primary intermediate transfer drum, 22 Secondary intermediate transfer drum, 30 Final transfer roll, 7 Optical density sensor, 8 Environmental sensor, 9 Display panel (display unit), P toner patch ( Image density control detection patch or toner density control detection patch), p: recording medium, I:
Toner image,

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideaki Tanaka 3-7-1, Fuchu, Iwatsuki-shi, Saitama, F-term in Fuji Xerox Co., Ltd. Iwatsuki Office (Reference) 2H030 AB02 BB33 BB36 BB38 2H077 AA25 AD36 DA03 DA08 DA18 DA63 DA78 DB02 DB21 EA03 GA13

Claims (6)

[Claims] 1. An image forming apparatus comprising a developing device and a supply device, wherein toner is supplied from the supply device to the developing device. In an image forming cycle for forming a toner image on a recording medium, each cycle includes Calculates the insufficient supply amount for each cycle based on the required supply amount required and the maximum toner supply amount possible for each cycle, and records from the image forming cycle when the cumulative value of the insufficient supply amount exceeds a predetermined upper limit. An image forming apparatus comprising: a control unit that shifts to an idle cycle in which a toner image is not formed on a medium. 2. The control means calculates a shortage supply amount in each cycle based on a required supply amount required in each cycle and a maximum supply amount of toner possible in each cycle during an idling cycle, The image forming apparatus according to claim 1, wherein when the accumulated value of the insufficient supply amount falls below a predetermined lower limit value, the process shifts from the idling cycle to the image forming cycle. 3. A control device comprising: a plurality of developing devices corresponding to each color; and a plurality of supply devices corresponding to each developing device, wherein the control unit determines that a cumulative value of an insufficient supply amount corresponding to a certain color is a predetermined upper limit value. The image forming apparatus according to claim 1, wherein the image forming apparatus shifts from the image forming cycle to the idling cycle when the rotation speed exceeds the threshold value. 4. The control means calculates a shortage supply amount in each cycle based on a required supply amount required in each cycle and a maximum supply amount of toner possible in each cycle during an idling cycle, 4. The image forming apparatus according to claim 3, wherein a transition from the idling cycle to the image forming cycle is performed when all the accumulated values of the respective shortage supply amounts corresponding to the respective colors fall below a predetermined lower limit. 5. The control unit determines that the image forming apparatus has failed if the accumulated value of the insufficient supply amount does not fall below a predetermined lower limit value even though the idle rotation cycle is performed for a predetermined upper limit cycle. The image forming apparatus according to claim 2. 6. The image forming apparatus according to claim 1, wherein the required supply amount is determined based on an area coverage ratio for each cycle and / or immediately before toner density control.