JP2002357935A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device by which an excellent output image is obtained in an image forming mode and an excellent patch complying with the purpose is obtained in a density control mode. SOLUTION: This image forming device is equipped with an image forming means for forming a toner image based on an image forming condition, a detection means for detecting the density of the toner image, and a control means for controlling the image forming means and the detection means. The control means allows the image forming means to form the toner image as a detection patch based on the 1st image forming condition and the detection means to detect the density of the detection patch, and changes the 2nd image forming condition based on the detected result in the control mode, and allows the image forming means to form the toner image as the output image based on the 2nd image forming condition in the image forming mode. In the device, the 1st and the 2nd image forming conditions can be set independently.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention employs an image forming system such as an electrophotographic system, an electrostatic recording system, an ionography system, a magnetic recording system, etc., and forms a color or black and white image. More specifically, the present invention relates to an image forming apparatus using an electrophotographic method such as a multifunction peripheral, and more particularly to an improvement in an image forming apparatus having an image forming mode and a density control mode.

[0002]

2. Description of the Related Art Conventionally, image forming apparatuses such as copiers and printers using an electrophotographic system have been widely known. In these image forming apparatuses, a density control mode (process control mode) is provided separately from a normal image forming mode in order to stably maintain good image quality for a long period of time. 2. Description of the Related Art There is known a technique of forming a toner image (patch), measuring the density of the patch, and changing and updating the charged potential of a photoconductor and a developing bias in an image forming mode based on the measurement result.

[0003]

However, when forming a toner image as an output image in the image forming mode, preferable image forming parameters such as a charging potential, a developing bias, and a transfer bias, and a patch as a patch in the density control mode. These respective image forming parameters that are preferable when forming a toner image do not always match. For example, in the image forming mode, a color toner image obtained by superimposing toner images of a plurality of colors may be formed. On the other hand, in the density control mode, a single color toner image is always formed. Bias and the like are different.

If the same image forming parameters are used in the image forming mode and the density control mode, a good toner image cannot be obtained in the image forming mode in some cases. , A good toner image cannot be obtained, and as a result, a situation may occur in which effective density control cannot be performed.

The present invention has been made in view of such technical problems, and has as its object to obtain a good output image in an image forming mode and to provide a good output image in a density control mode according to the purpose. An object of the present invention is to provide an image forming apparatus capable of obtaining a patch.

[0006]

That is, the present invention provides an image forming means for forming a toner image on the basis of certain image forming conditions (image forming parameters), a detecting means for detecting the density of the toner image, Control means for controlling the formation means and the detection means, the control means causing the image formation means to form a toner image as a detection patch in the control mode based on the first image forming condition, The second image forming condition is changed based on the detection result, and the toner image as the output image in the (next) image forming mode is changed to the second image forming condition. In an image forming apparatus that causes the image forming unit to form based on image forming conditions, the first image forming condition and the second image forming condition can be set independently.

Here, the image forming conditions include, for example, when the image forming means includes a latent image carrier and charging means for uniformly charging the surface of the latent image carrier, the charging of the surface of the image carrier is performed. Potential, the image forming means includes a latent image carrier, and a developing means for developing a latent image formed on the surface of the latent image carrier with toner,
When the image forming unit includes a latent image carrier and a transfer unit that transfers a toner image formed on the surface of the latent image carrier to a recording medium, the transfer bias may be used. Transfer bias of the means.

The density control mode includes a toner density control mode for controlling the density of the toner in the developing means,
An image density control mode for controlling the density of the toner (toner image) of the output image is given.

More specifically, the image forming apparatus having the toner density control mode includes a two-component developing means as one of the image forming means, and a toner density control mode as one of the control modes. The image forming condition for controlling toner density as one of the first image forming conditions, and the ratio of the toner to the carrier of the secondary developing means as one of the second image forming conditions. Means for causing the image forming means to form a toner image as a detection patch in the toner density control mode based on image forming conditions for toner density control, and causing the detection means to detect the density of the detection patch; The ratio of the toner and the carrier of the secondary developing means is changed based on the toner image as the output image in the (next) image forming mode. Of) those to be formed in the image forming means and the like on the basis of the second image forming condition.

More specifically, the image forming apparatus having one image density control mode includes an image density control mode as one of the control modes and an image density control mode as one of the first image forming conditions. The control unit causes the image forming unit to form a toner image as a detection patch in the image density control mode based on the image formation condition for image density control, and detects the density of the detection patch in the image density control mode. The second image forming condition is changed based on the detection result, and the toner image as an output image in the (next) image forming mode is changed based on the (changed) second image forming condition. To be formed by the image forming means.

An image forming apparatus provided with both a toner density control mode and an image density control mode more specifically includes a two-component developing means as one of the image forming means and the control mode as the control mode. The toner density control mode and the image density control mode are used as the first image forming condition, the toner density control image forming condition and the image density control image forming condition are used as one of the second image forming conditions. The control unit includes a toner image as a detection patch in a toner density control mode based on a toner density control image forming condition, wherein the control unit causes the image forming unit to form a toner image.
The density of the detection patch is detected by the detection means, and the ratio between the toner and the carrier of the secondary developing means is changed based on the detection result. In the image density control mode, the toner image as the detection patch is subjected to image density control. The second image forming condition is changed based on the detection result, and the second image forming condition is changed based on the detection result. In the mode, a toner image as an output image is formed by the image forming means based on the (changed) second image forming condition, and the toner density control image forming condition, the image density control image forming condition, Can be set independently.

The image forming conditions include not only those which can be set independently but also other elements such as a toner density control detection patch and an image density control detection patch as the detection patches. The image density control detection patch may be such that at least one of its coverage input, shape, size, and formation position (in the rotation axis direction of the image carrier or transfer body) can be independently set.

The image forming speed of the detection patch for toner density control is included as one of the image forming conditions for toner density control, and the image forming speed of the detection patch for image density control is included as one of the image forming conditions for image density control. And both of these image forming speeds may be independently settable. That is, the image formation speed of the toner density control detection patch takes a constant value without depending on the image formation speed of the toner image as the output image, so that the detection accuracy according to the purpose can be improved. On the other hand, the image formation speed of the toner density control detection patch depends on the image formation speed of the toner image as an output image, so that the detection accuracy according to the purpose can be improved.

Although the control mode is performed in the non-image forming mode, the toner density control mode may be performed after (immediately) the end of the image forming mode. It may be performed before (immediately) the start of the forming mode.

By the way, the first image forming condition and the second image forming condition are set independently of each other, and each image forming condition is set based on the following conditions. For example, the control unit may determine whether the image forming unit forms a single-color toner image or a multi-color toner image in which the single-color toner images are superimposed. It is also possible to set environment detecting means for detecting ambient temperature and / or humidity, and the control means based on the temperature and / or humidity detected by the environment detecting means. Can be set, and the speed of forming the toner image by the image forming means can be changed. The control means can control the first and / or second speed based on the speed of forming the toner image by the image forming means. Two image forming conditions can be set.

The detecting means is for detecting the density of the toner image. The detecting means can detect the density of the toner image on the image carrier, the transfer member, and the recording medium. Further, the detecting means can detect the density of the toner image on the final transfer medium onto which the toner image is finally transferred. The final transfer medium refers to a recording medium such as a sheet or a final transfer body.

In a case where the detecting means detects the density of the toner image on the final transfer body, the image forming means includes an image carrier and a contact-type transfer means for contacting the image carrier. The detecting means may detect the density of the toner image on the contact transfer means. More specifically, the contact-type transfer unit includes an intermediate transfer member that contacts the image carrier, and a final transfer member that contacts the intermediate transfer member, and the detection unit includes a toner on the final transfer member. The one that detects the density of an image or the contact-type transfer unit includes a primary intermediate transfer body that contacts the image carrier, a secondary intermediate transfer body that contacts the primary intermediate transfer body, and the secondary intermediate transfer body. And a final transfer member that comes into contact with the first transfer member, and the detection unit detects the density of the toner image on the final transfer member.

As a more specific embodiment of the latter, that is, an image forming apparatus provided with a primary intermediate transfer member and a secondary intermediate transfer member as intermediate transfer members, the image forming means is provided for cyan, magenta, yellow, Four latent image carriers for black, a pair of primary intermediate transfer members that respectively contact two latent image carriers of the four latent image carriers, and one pair of primary intermediate transfer members that contact the pair of primary intermediate transfer members. The image forming apparatus includes a secondary intermediate transfer member and a final transfer member that comes into contact with the secondary intermediate transfer member, and the detection unit detects the density of a toner image on the final transfer member.

As described above, the present invention can be applied to a color image forming apparatus (of course, a single color (for example, black)).
It can also be applied to a dedicated image forming apparatus).

As a basic configuration of the color image forming apparatus, the image forming means includes a plurality of image carriers corresponding to each single color and a plurality (of the same number) of developing devices corresponding to each image carrier. And an image forming unit including one image carrier and a plurality of developing units corresponding to each single color.

As a more specific mode of the former, the image forming means comprises three latent image carriers for cyan, magenta, and yellow, and cyan, magenta, A device including three developing units for yellow, one intermediate transfer member that contacts each latent image carrier, and a final transfer member that contacts the intermediate transfer member; , Yellow, and black latent image carriers, cyan, magenta, yellow, and black developing means corresponding to each latent image carrier, and contact with each latent image carrier One that includes one intermediate transfer member and a final transfer member that contacts the intermediate transfer member. The intermediate transfer member may be a roll or an endless belt.

As a more specific embodiment of the latter, the image forming means contacts one latent image carrier, three developing means for cyan, magenta, and yellow, and the latent image carrier. A device including one intermediate transfer member and a final transfer member that comes into contact with the intermediate transfer member; and the image forming unit includes one latent image carrier and four latent images for cyan, magenta, yellow, and black. And an intermediate transfer member that contacts the latent image carrier and a final transfer member that contacts the intermediate transfer member. In addition,
The intermediate transfer member may be in the form of a roll or an endless belt, and a plurality (three or four) of developing means may be integrally formed as a rotary developing means.

[0023]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a full-color printer 10 as an image forming apparatus according to an embodiment of the present invention.
It indicates 0. 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. Printer body 101
Are the toner cartridges 14Y to 14K for the image forming unit 1, the exposure device unit 12, the yellow Y, magenta M, cyan C, and black K, and each of the toner cartridges 14Y to 14K extending to the developing device corresponding to each color (not shown). The toner supply flexible pipes 15Y to 15K, the control unit 6, the power supply unit 5, and the 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, and a charging roll (contact type charging device) 11 for primary charging that comes into contact with these photoconductor drums 10Y to 10K.
Developing device (two-component developing means) 1 corresponding to Y to K and each color
3Y to K and two of the four photosensitive drums 10Y to 10K.
The first primary intermediate transfer drum (intermediate transfer member) 21a that contacts one of the photoconductor drums 10Y and 10M, and the second primary intermediate transfer drum (intermediate transfer member) 21b that contacts the other two photoconductor drums 10C and 10K. And a secondary intermediate transfer drum (intermediate transfer member) 22 that contacts the first and second primary intermediate transfer drums 21a and 21b, and a final transfer roll (final transfer member) that contacts the secondary intermediate transfer drum 22 30 constitutes the main part.

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 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 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.

Thereafter, 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.

Each of the developing devices 13Y to 13K is 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 this magnetic brush comes into contact with 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 toner images of the respective colors of yellow Y, magenta M, cyan C, and black K 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, 21
1b is that the surface composed of a single layer or a plurality of layers is flexible,
Alternatively, a low-resistance elastic rubber layer (R = R) represented by a conductive silicone rubber or the like is formed on a metal pipe as a metal core made of Fe, Al, or the like, which is a cylindrical rotating body having elasticity. 10 ² to 10 ³ Ω) in a thickness of about 0.1 to 10 mm. 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 fine particles of fluoro resin 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 releasability of the surface.
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 secondarily electrostatically 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 the toner images 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 surface releasability as in the case of 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 in 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 adhered to the charging devices 11Y to 11K, in this embodiment, there are a predetermined number of sheets before printing, after printing, and at the time of continuous printing. 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
Has a blade-like 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.

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 7 includes a sensor body 70 and the sensor body 7.
And a holder 71 for fixing the “0”. 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. Light-emitting element 7 such as an LED or the like arranged only at an angle
0a, the light-emitting element 70a irradiates the detection position on the surface of the final transfer roll 30 with light, and detects specular reflected light that is specularly reflected from the detection position. And a light receiving element 70b composed of a phototransistor or the like which is disposed at an angle of reflection equal to the incident angle of the light.

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 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.

The above is the image forming mode (including the cleaning operation) in the full-color printer configured as described above. In the xerography method and the like, since the static electricity is used, the image density is changed due to environmental fluctuation and aging. Easy to fluctuate. For this reason, it is preferable to provide a process control mode (control mode) in addition to the image forming mode to control the electrophotographic process in response to environmental fluctuations and changes over time.

Next, the process control mode in the full-color printer configured as described above and the configuration related thereto will be described.

The process control mode includes a TC process control mode (toner density control mode) for controlling the toner density (the ratio of 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 detecting 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.

On the other hand, 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 the present embodiment, a single optical density detecting means (optical density sensor 7) is used with an emphasis on the simplicity of the apparatus configuration, and the final transfer roll 30 is used in both process control modes. Is detected. 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 (the final transfer roll 30 that has been transferred a plurality of times) is changed.
In order to be able to detect as accurately as possible, the transfer rate in the TC process control mode is particularly high, for example, the photosensitive drums 10Y to 10K.
The image forming conditions are controlled so that the toner amount of the test patch toner image formed thereon is transferred to the final transfer roll 30 by 90% or more, or 95% or more.

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 an image forming condition control unit 60, and the input unit for inputting a signal to the image forming condition control unit 60 is a final transfer roll 30. In addition to the optical density sensor 7 for measuring the above toner density, the environmental sensor 8 for measuring the temperature and humidity in the full-color printer 100, the mode of the full-color printer 100, the printing speed, and other information of multicolor or single color are input. The main control unit 61 performs the operation. In addition,
Both the image forming condition control unit 60 and the main control unit 61 are functionally realized in the control unit 6 of the printer main body 101.

On the other hand, output units from which signals are output from the image forming condition control unit 60 include charging power supply units 110Y to 110K for applying a charging voltage to the charging rolls 11Y to 11K.
The exposure device unit 12 for irradiating the laser beams 12Y to K corresponding to each color, the developing power supply units 131Y to 131K for applying a developing bias voltage to the developing rolls 130Y to 130K, and the toner supply flexible pipes 15Y to 15K. Driving section), primary transfer power supply sections 210a, b, for applying a primary transfer voltage to the first and second primary intermediate transfer drums 21a, 21b.
A secondary transfer power supply unit 220 for applying a secondary transfer voltage to the secondary intermediate transfer drum 22, a final transfer power supply unit 300 for applying a final transfer current to the final transfer roll 30, a first and a second primary cleaning rolls 23a, b , A primary cleaning power supply unit 230a for applying a primary cleaning voltage to
b, a secondary cleaning power supply unit 240 that applies a secondary cleaning voltage to the secondary cleaning roll 24.

FIG. 7 conceptually illustrates the structure and function of the image forming condition control unit 60 shown in FIG.

As shown in the figure, the image forming condition control unit 6
In 0, an image forming condition table T0 for the image forming mode, an image forming condition table T1 for the potential process control mode, and an image forming condition table T2 for the TC process control mode are provided as image forming conditions.

Each image forming condition table T0, T1, T2
Each has a plurality (five types in this embodiment: # 1 to # 5) corresponding to the level of temperature and humidity. For example, the image forming condition table T0 corresponding to the reference environment is used as the image forming condition table T0 for the image forming mode.
(# 1), an image forming condition table T0 (# 2) corresponding to a higher temperature and higher humidity environment than the reference environment, and an image forming condition table T0 (# corresponding to a higher temperature and low humidity environment than the reference environment.
3) An image forming condition table T0 (# 4) corresponding to an environment where the temperature is lower and higher than the reference environment, and an image forming condition table T0 (# 5) corresponding to an environment where the sound level is lower and lower than the reference environment. The same applies to the other image forming condition tables T1 and T2.

[0064]

[Table 1] Table 1 shows each image forming condition table T corresponding to the reference environment.
It explains the contents of 0, T1, and T2. The image forming conditions are roughly divided into transfer conditions and image forming conditions. The transfer conditions include a primary transfer voltage [V], a secondary transfer voltage [V], a tertiary transfer current [μA],
A primary cleaning voltage [V] and a secondary cleaning voltage [V] are provided. The image forming conditions include a charging potential [V] of the photosensitive drum 10 and a developing bias voltage [V]. In addition, these image forming conditions include the printing speed (16
PPM or 8PPM) or print color (multicolor or single color: print color itself).

For example, in the image forming mode, it can be seen that the primary transfer voltage is 400 [V] when the printing speed is 16 PPM and the printing colors are multicolor. Further, the image forming condition in the image forming mode is described as a range, which means that the image forming condition fluctuates within the range as a result of the potential process control. For example, it means that the charging potential in the image forming mode can be changed in a range of-(250 to 330) [V]. Further, the arrow “←” in Table 1 means that it is the same as the left numerical value in the immediately preceding image forming mode. For example, in the potential process control mode, the primary transfer voltage when the printing speed is 16 PPM and the printing color is multicolor is 400 [V], which is the same as that in the immediately preceding image forming mode.

Here, the image forming conditions T0 and T2 are set independently of each other. Further, the image forming conditions T1 and T2 are set independently of each other. On the other hand, the image forming condition T
Some of the transfer conditions during 0 and T1, the primary transfer voltage [V], and the secondary transfer voltage [V] are dependent. That is,
The primary transfer voltage [V] and the secondary transfer voltage [V] of the image forming condition T1 have the same values as the primary transfer voltage [V] and the secondary transfer voltage [V] of the immediately preceding image forming condition T0.

The image forming condition control unit 60 includes a toner patch preparation condition table t1 for the potential process control mode and a toner patch preparation condition table t2 for the TC process control mode as toner patch preparation conditions.

[0068]

[Table 2] Table 2 describes the contents of the toner patch creation conditions t1 and t2. Each toner patch preparation condition includes a patch size, a patch interval, a patch formation position, a coverage input C _in , and a patch pattern.

FIGS. 8 and 9 explain the toner patch P created based on the toner patch creation conditions t1 and t2 more specifically. FIG. 8A illustrates the toner patch P formed at the axial center of the final transfer roll 30. This toner patch P has a yellow color in the rotation direction of the final transfer roll 30.
(Y), cyan P (C), magenta P (M), and black P (K) in this order. The size of each toner patch P is 11 [mm] in the sub-scanning direction X and 12 [mm] in the main scanning direction Y. m
m], and the interval D between the toner patches P is 3 [mm]. In this embodiment, both the toner patch P1 created based on the toner patch creation condition t1 and the toner patch P2 created based on the toner patch creation condition t2 are located at the axial center of the final transfer roll 30. But the toner patches P1 and P2
One or both of them may be formed at the axial end of the final transfer roll 30 as shown in FIG. 8B. In that case, it is necessary to change the installation position of the optical density sensor 7.

FIG. 9A illustrates a patch pattern of the toner patch P1. This patch pattern has a coverage input C _in of 33.3% (１ ／).
In other words, the toner patch includes a horizontal 2on4off, that is, a toner portion for two lines extending in the main scanning direction and a non-toner portion for four lines also extending in the main scanning direction. The resolution of the full-color printer 100 is 600 L
PI. Besides this, coverage input C _in
9 (b), a diagonal 2on4off toner patch as shown in FIG. 9 (c), and FIGS. 9 (d) and 9 (e).
Other toner patches, such as, can also be used. Also, the coverage input C _in can take other values (for example, 30%, 40%, etc.). In addition,
Patch pattern of the toner patch P2 is a coating that coverage input C _in was mentioned 100%.

The toner patch preparation conditions t1 and t2 are set independently of each other. In the present embodiment, the coverage input C _in a patch pattern with both the toner patch forming condition t1 and t2 are set independently.

The image forming condition controller 60 includes a main controller 6
1 to the mode of the full color printer 100 (image forming mode, potential process control mode, TC control mode), printing speed (8 PPM or 16 PPM)
), A signal indicating a printing color (different of multicolor or single color), a signal indicating the toner density of the toner patch P from the optical density sensor 7, and a temperature and humidity in the full-color printer 100 from the environment sensor 8, respectively. Signal is input. Then, a toner image as the image I is formed on the sheet S based on these input signals and the image forming conditions T0 provided in the image forming condition control unit 60.
Further, a toner image as a toner patch P1 is formed on the final transfer roll 30 based on these input signals and the image forming condition T1 and the toner patch creating condition t1 provided in the image forming condition control unit 60. I do. further,
Based on these input signals and the image forming condition T2 and the toner patch creating condition t2 provided in the image forming condition control unit 60, a toner image as the toner patch P2 is formed on the final transfer roll 30.

FIG. 10 is a flowchart for explaining the operation of the main controller 61 and the image forming condition controller 60. First, the main controller 61 determines whether or not the potential process control mode is necessary (after the image forming mode ends) (step S1). If necessary, the image forming condition controller 60 executes the potential process control mode. (Step S
2) After or when unnecessary, the image forming condition control unit 60 executes the image forming mode (step S3). After executing the image forming mode, the main control unit 61
Determines whether the TC process control mode is necessary (step S4), and if necessary, the image forming condition control unit 60 executes the TC process control mode (step S5), or if not necessary, The main control unit 61 determines whether or not to end the operation (step S6). If the operation is not to be ended, the process returns to step S1 again.

Here, the conditions for the main control section 61 to determine that the potential process control mode is necessary include:
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.

FIG. 11 is a timing chart for explaining an example of transition of the operation mode of the full-color printer 100. Hereinafter, step S1 → step S3 → step S
4 → Operation S when step S6 and step advance
(I-1) in Example 1, Step S1 → Step S2 →
The operation W (i) when the step proceeds from step S3 to step S4 to step S6 is described in the second embodiment, step S
Operation W (i + 1) when step proceeds from 1 → step S3 → step S4 → step S5 → step S6
Will be described in detail as Example 3.

Embodiment 1 (Image Forming Mode) The operation W (i-1) according to this embodiment is performed in the image forming mode J.
(I-1) only.

First, when a mode of the full-color printer 100 (an image forming mode, a potential process control mode, or a TC control mode) is input from the main control unit 61, the image forming condition control unit 60 An appropriate image forming condition is selected from the conditions T0 to T2 (see FIG. 7). Here, since the signal indicating the image forming mode is input from the main control unit 61, the image forming condition control unit 60
The image forming condition T0 is selected from 0 to T2.

Next, based on the temperature and humidity in the full-color printer 100 input from the environment sensor 8, an appropriate image forming condition T0 is selected from the image forming conditions T0 (# 1 to # 5) ( (See FIG. 7). For example, when a signal indicating that the environment in the full-color printer 100 is the reference environment is input from the environment sensor 8, the image forming condition control unit 60 determines from among the image forming conditions T0 (# 1 to # 5). The image forming condition T0 (# 1) is selected.

Further, based on the signals indicating the printing speed and the printing color inputted from the main controller 61, the image forming conditions T
An appropriate image forming condition is selected from 0 (# 1) (see FIG. 7). For example, when a signal indicating that the printing speed in this image forming mode J (i-1) is 16 PPM and the printing color is multicolor (color) is input from the main control unit 61, the image forming condition control unit 60 Indicates the image forming condition T0 (#
From 1), 400 [V] as a primary transfer potential applied to the primary intermediate transfer drums 21a and 21b, 900 [V] as a secondary transfer potential applied to the secondary intermediate transfer drum 22,
The final transfer current applied to the final transfer roll 30 is 7
For [μA], 200 [V] is selected as the primary cleaning voltage applied to the primary cleaning rolls 23a and 23b, and 220 [V] is selected as the secondary cleaning voltage (see Table 1). The image forming condition control unit 60 is updated in the potential control mode before the image forming mode J (i-1), and is stored in the image forming condition control unit 60. (For example,
-300 [V]) and the DC component of the developing bias voltage (for example, -200 [V]).

The full-color printer 100 forms a toner image I as a print image on the paper S based on the image forming conditions selected as described above (see FIG. 7). Since the specific image forming operation has already been described, the description thereof is omitted here.

Embodiment 2 (Potential Process Control Mode → Image Forming Mode) The operation W (i) according to the present embodiment comprises a potential process control mode VC and an image forming mode J (i).

O Potential process control mode First, when a mode (an image forming mode, a potential process control mode, or a TC control mode) of the full-color printer 100 is input from the main control unit 61, the image forming condition control unit 60 An appropriate image forming condition is selected from the forming conditions T0 to T2, and an appropriate toner patch forming condition is selected from the toner patch forming conditions t1 or t2 (see FIG. 7). Here, since the signal indicating the potential process control mode is input from the main control unit 61, the image forming condition control unit 60 determines the image forming condition T1 from the image forming conditions T0 to T2 and the toner patch forming conditions t1 and t2. , The toner patch creation condition t1 is selected.

Next, based on the temperature and humidity in the full-color printer 100 input from the environment sensor 8, an appropriate image forming condition T1 is selected from the image forming conditions T1 (# 1 to # 5) ( (See FIG. 7). For example, when a signal indicating that the environment in the full-color printer 100 is the reference environment is input from the environment sensor 8, the image forming condition control unit 60 determines from the image forming conditions T1 (# 1 to # 5). The image forming condition T1 (# 1) is selected.

Further, based on the signals indicating the printing speed and the printing color inputted from the main control section 61, the image forming conditions T
1 (# 1), an appropriate image forming condition is selected (see FIG. 7). For example, the operation W (i) from the main control unit 61
When the signal indicating that the printing speed is 16 PPM and the printing color is multi-color (color) is input, the image forming condition control unit 60 sets the primary intermediate transfer drum out of the image forming conditions T1 (# 1). The same primary transfer potential as that applied to the image forming mode J (i-1) 400 is applied to the primary transfer potentials 21a and 21b.
[V] is set to 9 as the secondary transfer potential applied to the secondary intermediate transfer drum 22, which is the same as that in the image forming mode J (i-1).
00 [V] as the final transfer current applied to the final transfer roll 30, 6 [μA]
190 as the primary cleaning voltage applied to a and b
[V] is 210 [V] as a secondary cleaning voltage.
As the (target) charging potential of the photosensitive drum 10, -300 [V], which is the same as in the previous image forming mode J (i-1),
As the DC component of the developing bias voltage, the same -200 [V] as in the previous image forming mode J (i-1) is selected.

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 (see FIG. 7), and performs potential process control.

FIG. 12 shows a potential process control VC.
6 is a flowchart for explaining the operation of FIG. Hereinafter, based on this flowchart, the potential process control V
The operation of C will be described in more detail.

First, in a state where the toner patch P1 has not been transferred, the surface of the final transfer roll 30 is detected by the optical density sensor 7, and the output Vcl of the optical density sensor 7 at this time is detected.
n is stored (step ST101). Next, the toner patches P1 (Y) to (K) for each color of yellow, magenta, cyan, and black based on the image forming condition T1 (# 1) and the toner patch creating condition t1 described above.
Is formed on the final transfer roll 30 as shown in FIG. 8A (step ST102).

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 with 1 pitch of 0.5 mm
The average value Vpatch is obtained by detecting six points (step ST1).
03). Here, as shown in FIG.
Although a specular reflection type optical density sensor 7 is used, FIG.
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 calculated by using 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). If the obtained density of the toner patch P1 is lower than the predetermined density, the image forming condition control unit 60 determines the absolute value of the DC component _Vdc of the developing bias voltage according to the difference. And at the same time (increase the absolute value of the voltage applied to the charging roll 11 and consequently) further increase the absolute value of the charging potential of the photosensitive drum 10 (step ST106). By doing so, as shown in FIG. 14B, the electric field in the developing direction formed between the developing roll 130 and the image portion on the photosensitive drum 10 increases, and 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 image forming condition controller 60 reduces the absolute value of the DC component _Vdc of the developing bias voltage according to the difference, At the same time (as a result of lowering the absolute value of the voltage applied to the charging roll 11), the absolute value of the charging potential of the photosensitive drum 10 is further reduced (step ST10).
6). By doing so, as shown in FIG. 14C, 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.

Here, for example, when the density of the toner patch P1 is low as a whole, the value of the (target) charging potential of the photosensitive drum 10 is changed from -300 [V] to -320 [V].
The value of the DC component _Vdc of the developing bias voltage corresponding to yellow (the DC component of the developing bias voltage applied to the developing roll 130Y) is updated in accordance with the density of each of the toner patches P1 (Y) to (K). -200 [V] to -210
[V], the value of the DC component _Vdc of the developing bias voltage corresponding to magenta (the DC component of the developing bias voltage applied to the developing roll 130M) is changed from -200 [V] to -215.
[V], the value of the DC component _Vdc of the developing bias voltage corresponding to cyan (the DC component of the developing bias voltage applied to the developing roll 130C) is changed from -200 [V] to -210.
[V], the value of the DC component _Vdc of the developing bias voltage corresponding to black (the DC component of the developing bias voltage applied to the developing roll 130K) is changed from -200 [V] to -220.
[V], and the values are stored as the image forming condition T0.

[0093]

[Table 3] Table 3 shows the image forming condition T0 (# 1) in the image forming condition control unit 60 updated in the potential process control mode VC of the operation W (i). It can be seen that the image forming conditions (charging potential [V] and developing potential [V]) in the image forming conditions have been updated by the potential process control mode VC.

In the present embodiment, the developing bias and the supply voltage to the charging device are adjusted. However, any device that adjusts the density or gradation of an image may be used. The exposure conditions and the gradation characteristics of the image may be adjusted, or the peripheral speed ratio between the developing roller 130 and the photosensitive drum 10 may be adjusted. Further, these may be combined.

Image forming mode When the potential process control mode VC ends, the mode shifts to the image forming mode J (i). First, when a mode (an image forming mode, a potential process control mode, or a TC control mode) of the full-color printer 100 is input from the main control unit 61, the image forming condition control unit 6
“0” selects an appropriate image forming condition from the image forming conditions T0 to T2 (see FIG. 7). Here, since the signal indicating the image forming mode is input from the main control unit 61, the image forming condition control unit 60 selects the image forming condition T0 from the image forming conditions T0 to T2.

Next, based on the temperature and humidity in the full-color printer 100 input from the environment sensor 8, an appropriate image forming condition T0 is selected from the image forming conditions T0 (# 1 to # 5) ( (See FIG. 7). For example, when a signal indicating that the environment in the full-color printer 100 is the reference environment is input from the environment sensor 8, the image forming condition control unit 60 determines from among the image forming conditions T0 (# 1 to # 5). The image forming condition T0 (# 1) is selected.

Further, based on the signals indicating the printing speed and the printing color inputted from the main control section 61, the image forming conditions T
An appropriate image forming condition is selected from 0 (# 1) (see FIG. 7). For example, when a signal indicating that the printing speed in this image forming mode J (i) is 16 PPM and the printing color is multicolor (color) is input from the main control unit 61, the image forming condition control unit 60 Among the image forming conditions T0 (# 1), 400 [V] is set as the primary transfer potential applied to the primary intermediate transfer drums 21a and 21b, and the secondary intermediate transfer drum 22
900 [V] as the secondary transfer potential applied to the final transfer roll 30, and 7 [μA] as the final transfer current applied to the final transfer roll 30.
Is selected as the primary cleaning voltage applied to the primary cleaning rolls 23a and 23b, and 200 [V] is selected as the secondary cleaning voltage (Table 3).
reference).

The image forming condition control section 60 controls the potential control mode V before the image forming mode J (i).
C, the (target) charged potential of the photosensitive drum 10 stored in the image forming condition control unit 60, -320.
[V] and DC component of each developing bias voltage, yellow:
-210 [V], magenta: -215 [V], cyan:
-210 [V] and black: -220 [V] are selected (see Table 3).

The full-color printer 100 forms a toner image I as a print image on the paper S based on the image forming conditions selected as described above (see FIG. 7). Since the specific image forming operation has already been described, the description thereof is omitted here.

Embodiment 3 (Image Forming Mode → TC Process Control Mode) The operation W (i + 1) according to the present embodiment is performed in the image forming mode J
(I + 1) and TC process control mode.

Image forming mode This image forming mode J (i + 1) is substantially the same as the previous image forming mode J (i), and therefore, description thereof will be omitted.

○ TC process control mode Toner replenishment measures the image density from the 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, when a mode of the full-color printer 100 (an image forming mode, a potential process control mode, or a TC control mode) is input from the main control unit 61, the image forming condition control unit 60 sets the image forming condition T0.
To T2 and an appropriate toner patch creation condition from the toner patch creation conditions t1 and t2 (see FIG. 7). Here, since the signal indicating the TC process control mode is input from the main control unit 61, the image forming condition control unit 60 determines the image forming conditions T0 to T
2, the image forming condition T2 is selected, and the toner patch creating condition t2 is selected from the toner patch creating conditions t1 and t2.

Next, based on the temperature and humidity in the full-color printer 100 input from the environment sensor 8, an appropriate image forming condition T2 is selected from the image forming conditions T2 (# 1 to # 5) ( (See FIG. 7). For example, when a signal indicating that the environment in the full-color printer 100 is the reference environment is input from the environment sensor 8, the image forming condition control unit 60 determines from the image forming conditions T2 (# 1 to # 5). The image forming condition T2 (# 1) is selected.

Further, based on the signals indicating the printing speed and the printing color inputted from the main control section 61, the image forming conditions T
2 (# 1), an appropriate image forming condition is selected (see FIG. 7). For example, when a signal indicating that the printing speed in the TC process control TC is 16 PPM and the printing color is multicolor (color) is input from the main control unit 61, the image forming condition control unit 60 T2 (#
From 1), 360 [V] is applied as the primary transfer potential applied to the primary intermediate transfer drums 21 a and 21 b, and 810 [V] is applied as the secondary transfer potential applied to the secondary intermediate transfer drum 22.
The final transfer current applied to the final transfer roll 30 is 6
[ΜA], 190 [V] as the primary cleaning voltage applied to the primary cleaning rolls 23a and 23b, 210 [V] as the secondary cleaning voltage, and -289 [V] as the (target) charging potential of the photosensitive drum 10. ] As a DC component of the developing bias voltage, yellow: -210
[V], magenta: -215 [V], cyan: -200
[V] and black: -210 [V] are selected (see Table 1).

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 P2 as a toner patch on the final transfer roll 30 (see FIG. 7), and performs TC process control.

FIG. 15 shows the TC process control TC.
6 is a flowchart for explaining the operation of FIG. Hereinafter, based on this flowchart, the TC process control T
The operation of C will be described in more detail.

First, the image forming condition control unit 60 detects the surface of the final transfer roll 30 with the optical density sensor 7 in a state where the toner patch P2 is not transferred, and outputs the output Vcln of the optical density sensor 7 at this time. It is stored (step ST201). Next, the image forming condition T described above is used.
2 (# 1) and the toner patch creation condition t2,
For each color of yellow, magenta, cyan and black,
As shown in FIG. 8A, the toner patches P2 (Y) to (K) are formed on the final transfer roll 30 (Step S).
T202). Here, the image forming mode (J (i-1),
J (i), J (i + 1)) and the potential process control mode VC, in the image forming condition T2, the developing bias voltage is developed with only the DC component, and the AC component is not superimposed.

Thereafter, the area of the yellow, magenta, cyan, and black toner patches P1 (Y) to (K) is set to 0.5 m by the optical density sensor 7 as shown in FIG.
The average value Vpatch is obtained by detecting 16 points at a pitch of m (step ST203). Here, FIG.
As shown in (a), a specular reflection type optical density sensor 7 is used.
However, as shown in FIG. 13B, 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 determined by using 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 image forming condition control unit 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 performed so that the toner supply amount is larger than the determined toner supply amount (Step ST220) (Step ST210).
206). Conversely, when the test patch is higher than the predetermined density, the image forming condition control unit 60 measures the image density from the print image signal in advance according to the difference because the toner density is high (step ST210), and is determined. Correction is made so that the toner supply amount is smaller than the toner supply amount (step ST220) (step ST208).

Here, for example, when the density of the toner patch P2 is lower than the predetermined density, the image forming condition control unit controls the driving time of the driving unit of each of the toner supply flexible pipes 15Y to 15K so as to be longer than the specified time. Reference numeral 60 controls the driving units of the pipes 15Y to 15K (see FIG. 6).

[0113]

As described in detail above, according to the present invention, it is possible to obtain a good output image in the image forming mode and obtain a good patch according to the purpose in the density control mode. An apparatus can be provided.

[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 a control system of the full-color printer shown in FIG.

FIG. 7 is a diagram illustrating a configuration and a function of an image forming condition control unit illustrated in FIG. 6;

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

FIG. 9 is a view for explaining an aspect of a toner patch.

FIG. 10 is a flowchart illustrating a basic operation of the full-color printer shown in FIG. 1;

FIG. 11 is a timing chart for explaining an example of the operation of the full-color printer shown in FIG.

FIG. 12 is a flowchart illustrating the operation in the potential process control mode shown in FIG. 10 in more detail;

FIG. 13 illustrates the configuration and operation of the optical density sensor main body.

FIG. 14 illustrates adjustment of a charging potential and a developing bias potential.

FIG. 15 is a flowchart illustrating the operation of the TC process control mode shown in FIG. 10 in more detail.

[Explanation of symbols]

Reference Signs List 100 full-color printer (image forming apparatus), 1 image forming unit (image forming unit), 6 control unit (control unit), 12 exposure unit (image forming unit), 14 toner cartridge (image forming unit) , 15: Flexible toner supply pipe (image forming means), 10: photosensitive drum (image carrier), 11: charging roll (charging means), 13: developing device (two-component developing means), 130: developing roll, 21 ... Primary intermediate transfer drum (primary intermediate transfer body: contact type transfer means), 22 ... secondary intermediate transfer drum (secondary intermediate transfer body: contact type transfer means), 30
... Final transfer roll (final transfer medium: final transfer body: contact transfer means), 7: optical density sensor (detection means), 8: environment sensor (environment detection means), T0: image forming condition table (first image) Forming condition), T1 image forming condition table (second image forming condition: image forming condition for image density control), T2 ... image forming condition table (second image forming condition: image forming condition for toner density control), P1: toner patch (detection patch for image density control), P2: toner patch (detection patch for toner density control)

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) G03G 15/06 101 G03G 15/06 101 15/16 15/16 21/00 384 21/00 384 21/14 372 21 / 20 534 (72) Inventor Makoto Kanai 3-7-1, Fuchu, Iwatsuki-shi, Saitama, Fuji Xerox Co., Ltd. ROX Co., Ltd. Iwatsuki Office F-term (reference) 2H027 DA02 DA03 DA04 DA06 DA09 DA13 DA14 DA32 DD07 DD09 DE02 DE07 DE09 EA01 EA03 EA05 EA06 EB04 EC04 EC06 EC08 EC09 EC18 EC20 ED03 ED06 ED09 ED10 ED24 EE07 AFA2 EF07 FA28 AD01 AD02 AD08 AD17 AD18 AD19 BB02 BB16 BB34 BB36 BB38 BB42 BB46 BB54 2H073 AA02 AA03 AA05 BA04 BA13 BA28 BA33 CA03 CA22 2H200 FA01 FA02 FA18 GA12 GA14 GA16 GA22 GA23 GA29 GA30 GA34 GA45 GA47 GA53 GB57 GA60 GA60 HB12 HB22 HB45 HB46 HB47 HB48 JA02 JA23 JA25 JA26 JA27 JA28 JA29 JA30 JB10 JC02 JC09 JC12 JC13 JC15 JC16 JC17 JC18 JC19 JC20 KA01 LA12 LA19 LA40 LB02 LB03 LB09 LB13 LB18 LB35 LB36 LB38 LB39 MA03 MA20 MB02 MB06 MC08 NA02 NA19 NA23

Claims (17)

[Claims] An image forming unit that forms a toner image based on a certain image forming condition; a detecting unit that detects a density of the toner image; and a control unit that controls the image forming unit and the detecting unit. The control unit causes the image forming unit to form a toner image as a detection patch in the control mode based on the first image forming condition, and causes the detection unit to detect the density of the detection patch;
The image forming apparatus changes the second image forming condition based on the detection result, and causes the image forming unit to form a toner image as an output image in the image forming mode based on the second image forming condition. An image forming apparatus, wherein the first image forming condition and the second image forming condition can be set independently. 2. A method according to claim 1, further comprising a two-component developing means as one of said image forming means, a toner density control mode as one of said control modes, and a toner density control image forming as one of said first image forming conditions. The condition includes, as one of the second image forming conditions, a ratio between the toner and the carrier of the secondary developing unit. The control unit controls the toner density as a detection patch in the toner density control mode. The image forming unit is formed based on the image forming conditions for use, the density of the detection patch is detected by the detecting unit, the ratio of the toner and the carrier of the secondary developing unit is changed based on the detection result, The image forming apparatus according to claim 1, wherein the image forming unit causes the image forming unit to form a toner image as an output image in the image forming mode based on the second image forming condition. . 3. An image density control mode as one of the control modes, and an image formation condition for image density control as one of the first image formation conditions. A toner image as a detection patch is formed by the image forming unit based on the image forming condition for image density control, the density of the detection patch is detected by the detection unit, and a second image forming condition is determined based on the detection result. The image forming apparatus according to claim 1, wherein the image forming unit is configured to cause the image forming unit to form a toner image as an output image in the image forming mode based on the second image forming condition. 4. A method according to claim 1, further comprising a two-component developing means as one of said image forming means, a toner density control mode and an image density control mode as said control modes, and an image forming condition for toner density control as said first image forming condition. And the image forming condition for image density control, the ratio of the toner and the carrier of the secondary developing unit as one of the second image forming conditions, respectively, the control unit as a detection patch in the toner density control mode. Is formed by the image forming unit based on the image forming condition for toner density control, the density of the detection patch is detected by the detection unit, and the toner and the carrier of the secondary developing unit are determined based on the detection result. In the image density control mode, the toner image as a detection patch is changed based on the image forming condition for image density control. Forming the toner image as an output image in the image forming mode by changing the second image forming condition based on the detection result. The image forming apparatus according to claim 1, wherein the image forming unit forms the image based on the image forming condition, and the image forming condition for controlling the toner density and the image forming condition for controlling the image density can be independently set. 5. The detection patch includes a toner density control detection patch and an image density control detection patch, wherein the toner density control detection patch and the image density control detection patch have a coverage input, a shape, and a size. The image forming apparatus according to claim 4, wherein at least one of the formation positions can be independently set. 6. An image forming speed of the detection patch for toner density control as one of the image forming conditions for toner density control, and an image forming speed of the detection patch for image formation density as one of the image forming conditions for image density control. The image forming apparatus according to claim 5, further comprising a speed, wherein both of the image forming speeds can be independently set. 7. The toner density control mode is performed immediately after the end of the image forming mode.
The image forming apparatus according to any one of the above. 8. The image forming apparatus according to claim 3, wherein the image density control mode is performed immediately before the start of the image forming mode. 9. The control unit according to claim 1, wherein the image forming unit forms a single color toner image or a multicolor toner image formed by superimposing the single color toner image. The image forming apparatus according to claim 1, wherein the image forming condition is set. 10. An environment detecting means for detecting an ambient temperature and / or humidity, wherein the control means detects the first and / or second based on the temperature and / or humidity detected by the environment detecting means. 10. An image forming condition is set.
The image forming apparatus according to any one of the above. 11. A toner image forming speed of said image forming means can be changed, and said control means can control a first and / or a toner image based on a toner image forming speed of said image forming means.
The image forming apparatus according to claim 1, wherein a second image forming condition is set. 12. The image forming unit includes a latent image carrier and a charging unit that uniformly charges the surface of the latent image carrier, and one of the first and / or second image forming conditions. The image forming apparatus according to claim 1, wherein the image forming apparatus includes a charged potential on a surface of the image carrier. 13. The image forming apparatus according to claim 1, wherein the image forming unit includes: a latent image carrier; and a developing unit configured to visualize a latent image formed on the surface of the latent image carrier with toner. The image forming apparatus according to claim 1, wherein one of the image forming conditions includes a developing bias of the developing unit. 14. The first and / or second image forming apparatus, wherein the image forming unit includes a latent image carrier and a transfer unit that transfers a toner image formed on the surface of the latent image carrier to a recording medium. 14. The image forming apparatus according to claim 1, wherein one of the forming conditions includes a transfer bias of the transfer unit. 15. The image forming apparatus according to claim 1, wherein the detecting unit detects a density of the toner image on a final transfer medium onto which the toner image is finally transferred. 16. An image forming apparatus comprising: an image carrier; and a contact-type transfer unit that comes into contact with the image carrier, and wherein the detection unit detects a density of the toner image on the contact-type transfer unit. Item 16. An image forming apparatus according to any one of Items 1 to 15. 17. The image forming unit contacts four latent image carriers for cyan, magenta, yellow, and black, and contacts two latent image carriers of each of the four latent image carriers. A pair of primary intermediate transfer members, and one secondary intermediate transfer member that contacts the pair of primary intermediate transfer members,
The image forming apparatus according to claim 1, further comprising: a final transfer member that contacts the secondary intermediate transfer member, wherein the detection unit detects a density of the toner image on the final transfer member.