JP2001356554A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of preventing cost rising associated with the increase of an optical density detection means and the prolongation of a density detecting cycle and capable of accurately detecting the density of a toner image for detecting image density. SOLUTION: In this image forming device, a transfer rate in the case of transferring a monochrome toner image formed on an image carrier to an intermediate transfer body and a transfer rate in the case of finally transferring the toner image transferred to the intermediate transfer body to a recording medium are set to be high, and the toner image for controlling the image density is formed on the surface of the intermediate transfer body or a final transfer rotating body, and the density of the toner image formed on the surface of the intermediate transfer body or the final transfer rotating body is detected by the optical density detection means, then an image forming condition is controlled based on the detected result by the optical density detection means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic system,
The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile that employs an image forming method such as an electrostatic recording method, an ionography method, and a magnetic recording method to form a color or black and white image. (Test patch)
Is formed on an image density detecting medium such as an intermediate transfer member or a transfer roll, and the density of the toner image for controlling the image density is detected by an optical density detecting means. And the like for controlling an image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer for forming a color or black-and-white image employing this type of electrophotographic system, an image having a desired density is formed, and thus a desired brightness is obtained. In order to form a color image of color, saturation, and chromaticity, a toner image (hereinafter, referred to as a “test patch”) for controlling the image density of each color is formed on the photosensitive drum, and the density of the test patch is optically measured. The image forming apparatus is configured to detect an image with a density sensor and control an image forming parameter, a toner supply parameter, and the like according to the result.

In such an image forming apparatus,
Japanese Patent Application Laid-Open No. Hei 8
The one disclosed in -44122 and the like has already been proposed.

The image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 8-44122 includes a detecting pattern forming means for forming an image density detecting pattern on a photoreceptor, and a density detecting means formed by the detecting pattern forming means. A primary transfer means for transferring the pattern onto the intermediate transfer member, a secondary transfer means for secondary transferring the density detection pattern transferred on the intermediate transfer member onto the transfer roller, and a density detection pattern on the transfer roller. A density detecting means for detecting the image density, and a control means for controlling the image density by comparing the density detected by the density detecting means with a reference density, and a white conductive transfer roller as the transfer roller It is configured to be used.

[0005]

However, the prior art described above has the following problems. That is, in the case of the image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 8-44122, the image density of the density detection pattern is detected on the transfer roller. This is not a system that achieves a high transfer rate. Therefore, when the density detection pattern formed on the photoreceptor is primarily transferred onto the intermediate transfer member, and when the density detection pattern transferred on the intermediate transfer member is transferred to the transfer roller. 2 on
At the time of the next transfer, there is a problem that the density detection pattern remaining on the photoreceptor and the intermediate transfer member has a great influence, and the density of the density detection pattern cannot be detected with high accuracy.

In this case, in order to match the image densities of the respective colors, it can be said that there is little problem because the position where the density of the density detection pattern is detected is close to the final transfer position.
If it is desired to adjust the toner charge amount or the toner density in the developing device based on the density detection result of the density detection pattern, if the detection accuracy of the density detection pattern is low, the toner charge amount and the toner density are adjusted. However, there is a problem that the accuracy at the time of performing the operation is reduced.

In order to solve such a problem, in order to increase the detection accuracy of the density detection pattern, the density of the density detection pattern on the intermediate transfer body before and after the transfer is detected, and the transfer residual is detected. Needs to be calculated and corrected. In this case, it is necessary to detect the density of the pattern for density detection before transfer on the intermediate transfer body and the density of the pattern for density detection after transfer on the intermediate transfer body, and two density detection means are required. A new problem arises in that the cost increases accordingly. In order to use only one density detecting unit, the density detecting unit detects the density of the pattern for density detection on the intermediate transfer member before transfer, and then rotates the intermediate transfer member one more turn. It is necessary to detect the density of the density detection pattern on the transfer body after transfer, which causes another problem that the density detection cycle of the density detection pattern becomes longer. However, even in this case, since the density detection pattern formed on the photoconductor is primarily transferred on the intermediate transfer member due to the influence of the primary transfer residue,
Not preferred.

The image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 8-44122 is a four-cycle system in which a photosensitive member is rotated four times to form a full-color image. The same problem occurs even when the image forming units for four colors are arranged along the body to form a so-called tandem configuration.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and has an object to increase the cost and lengthen the cycle of density detection due to an increase in the number of optical density detection means. It is an object of the present invention to provide an image forming apparatus capable of preventing the occurrence of an image density and detecting the density of the toner image for image density detection with high accuracy.

[0010]

That is, according to the first aspect of the present invention, there are provided a plurality of image carriers on which single-color toner images of different colors are formed, and a plurality of image carriers arranged in contact with or close to the image carriers. And one or more intermediate transfer members to which the respective monochromatic toner images formed on the image carrier are transferred, and a toner image transferred to the one or more intermediate transfer members on a recording medium. And a final transfer rotator for transferring the image onto the intermediate transfer member, wherein the image forming device transfers a single-color toner image formed on an image carrier onto an intermediate transfer member. The transfer rate and the transfer rate when the toner image transferred on the intermediate transfer body is finally transferred onto the recording medium are set high, and the toner image for image density control is transferred to the intermediate transfer body or the final transfer rotation. Formed on the surface of the body, the intermediate transfer Alternatively, the density of the toner image formed on the surface of the final transfer rotating body is detected by an optical density detecting unit, and the image forming condition is controlled based on the detection result of the optical density detecting unit. Image forming apparatus.

According to a second aspect of the present invention, in the image forming apparatus, the transfer rate when transferring a single-color toner image formed on an image carrier onto an intermediate transfer member, and the intermediate transfer member 2. The image forming apparatus according to claim 1, wherein an overall transfer rate including a transfer rate when the toner image transferred onto the recording medium is finally transferred is set to 90% or more. It is.

Further, according to the invention described in claim 3, the image forming apparatus uses a spherical toner.
3. The image forming apparatus according to claim 1, wherein a transfer rate of the toner image is set high.

[0013] Still further, the invention described in claim 4 is as follows.
The image forming apparatus is configured such that transfer conditions for forming a toner image for controlling image density on the surface of an intermediate transfer body or a final transfer rotating body are different from those for image formation. Item 4. The image forming apparatus according to any one of Items 1 to 3.

According to a fifth aspect of the present invention, in the image forming apparatus, the image forming apparatus further comprises a cleaning means for cleaning a surface of the image density detecting medium by detecting the density of the image density controlling toner image. After cleaning the image density control toner image formed on the surface of the image density detection medium, the next image density control toner image or image is placed on the image density detection medium for at least one round. The image forming apparatus according to any one of claims 1 to 4, wherein the image forming apparatus is not formed.

After the image density control toner image formed on the surface of the image density detection medium is cleaned, the next image density control toner image or image is not removed for at least one turn. By configuring so that the toner is not formed on the medium, there is a possibility that the toner may remain on the image density detection medium without being cleaned by one-time cleaning. Prevents the deterioration of the detection accuracy of the toner image due to the formation of the toner image for controlling the image density on the recording medium, and prevents the deterioration of the image and the adhesion of the residual toner to the recording medium when forming the image. can do.

In particular, in an image forming apparatus using a spherical toner, the effect is remarkable because the toner remains on the image density detecting medium without being cleaned by a single cleaning and is cheap.

According to a sixth aspect of the present invention, in the image forming apparatus according to the first aspect of the present invention, the image forming apparatus is configured to control the image density control of all colors within one rotation of an image density detection medium for detecting the density of the image density control toner image. 2. The method according to claim 1, wherein the toner image is formed.
An image forming apparatus according to any one of claims 1 to 5.

As described above, by forming the image density control toner images of all the colors within one rotation of the image density detection medium for detecting the density of the image density control toner image, one time In the cleaning, the toner may remain on the image density detection medium without being cleaned, and it is possible to prevent the detection accuracy of the toner image from lowering due to the formation of the toner image for image density control on the residual toner. .

In particular, in an image forming apparatus using a spherical toner, the effect is remarkable because the toner remains on the image density detecting medium without being cleaned by a single cleaning and is cheap.

Further, according to the present invention, a plurality of single-color toner images are obtained by forming each latent image according to input information for each color and developing each latent image with a toner of a corresponding color. An image forming apparatus that forms a color image by fixing the plurality of single-color toner images on a recording medium, wherein each latent image is formed according to input information for each color, and the latent images correspond to each other. Three or more image carriers on which each single-color toner image is formed by developing with a color toner, or each latent image corresponding to input information for each color is sequentially formed, and each latent image is formed by a toner of a corresponding color. A single image carrier on which each single-color toner image is sequentially formed by development, and arranged in contact with or close to the image carrier;
One or a plurality of intermediate transfer members to which each single-color toner image formed on the image carrier is transferred, and transfer the toner images transferred onto the one or more intermediate transfer members to a recording medium And a final transfer rotator for forming a color image through at least two or more toner image transfer steps, wherein the image forming apparatus comprises a single-color toner image formed on an image carrier. The transfer rate when transferring the toner image onto the intermediate transfer body and the transfer rate when finally transferring the toner image transferred onto the intermediate transfer body onto a recording medium are set to be high. Forming an image on the surface of the intermediate transfer body or the final transfer rotator; detecting the density of the toner image formed on the surface of the intermediate transfer body or the final transfer rotator by optical density detection means; In the detection result of the detection means An image forming apparatus characterized by being configured to control the image forming conditions Zui.

As described above, according to the first to seventh aspects of the present invention, the transfer rate when transferring the monochromatic toner image formed on the image carrier onto the intermediate transfer member, and the intermediate transfer member The transfer rate at the time of finally transferring the toner image transferred on the recording medium is set high, and a toner image for image density control is formed on the surface of the intermediate transfer body or the final transfer rotating body, The density of the toner image formed on the surface of the intermediate transfer body or the final transfer rotator is detected by an optical density detection unit, and image forming conditions are controlled based on the detection result of the optical density detection unit. In addition to the above-described configuration, the toner image for controlling the image density formed on the image carrier is transferred onto the surface of the intermediate transfer body or the final transfer rotating body at a high transfer rate. be able to. Therefore, on the surface of the intermediate transfer body or the final transfer rotator, a toner image for controlling image density formed on the image carrier and a toner image for controlling image density substantially the same can be formed. By detecting the toner image for image density control formed on the surface of the intermediate transfer body or the final transfer rotating body by the optical density detecting means, a plurality of optical density detecting means becomes unnecessary and the number of optical density detecting means increases. It is possible to prevent the accompanying cost increase and lengthening of the density detection cycle, and it is possible to detect the density of the toner image for image density detection with high accuracy.

[0022]

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

Embodiment 1

FIG. 1 shows a tandem type full-color printer as an image forming apparatus according to Embodiment 1 of the present invention. In addition, the arrow in FIG. 1 has shown the rotation direction of each rotating member.

As shown in FIG. 1, this full-color printer has photosensitive drums (image carriers) 11, 12, and 13 for cyan (C), magenta (M), yellow (Y), and black (K). Image forming units 1, 2, 3,
4 and charging rolls for primary charging (contact type charging devices) 21, 22, 23,
24 and laser beams 31, 32, 33, of respective colors of cyan (C), magenta (M), yellow (Y), and black (K).
A laser optical unit (exposure device) (not shown) for irradiating the light, 34, developing devices 41, 42, 43, 44, and two of the four photosensitive drums 11, 12, 13, and 14;
1st primary intermediate transfer drum (intermediate transfer body) that contacts 12
A second primary intermediate transfer drum (intermediate transfer member) 52 that contacts the first and second photosensitive drums 13 and 14; and a secondary intermediate contact drum that contacts the first and second primary intermediate transfer drums 51 and 52. The transfer drum (intermediate transfer body) 53 and the secondary intermediate transfer drum 53
The main part is constituted by a final transfer roll (transfer member) 60 that comes into contact with the transfer roller.

The photosensitive drums 11, 12, 13, and 14 are arranged at regular intervals so as to have a common tangent plane M. Further, the first primary intermediate transfer drum 51 and the second primary intermediate transfer drum 52 have their respective rotating shafts of the photosensitive drums 11, 1.
They are arranged so as to be parallel to the axes 2, 13, and 14 and have a plane object relation with a predetermined object plane as a boundary. Further, the secondary intermediate transfer drum 53 includes the photosensitive drums 11, 12, 13, 14
And the rotation axis are parallel to each other.

A signal corresponding to image information for each color is rasterized by an image processing unit (not shown) and input to a laser optical unit (not shown). In this laser optical unit, laser beams 31, 3 of cyan (C), magenta (M), yellow (Y), and black (K) are used.
2, 33, 34 are modulated, and the photoconductor drums 11, 1 of the corresponding color are modulated.
Irradiated on 2, 13, 14

Around the photosensitive drums 11, 12, 13, and 14, an image forming process for each color is performed by a known electrophotographic method. First, the photosensitive drums 11, 12, 1
For example, photosensitive drums using an OPC photosensitive member having a diameter of 20 mm are used as the photosensitive drums 3, 14, and these photosensitive drums 11, 12, 13, and 14 are driven to rotate at a rotation speed of, for example, 95 mm / sec. You. The photosensitive drums 11, 12, 13, 14
As shown in FIG. 1, the surface of is charged to about -300 V, for example, by applying a DC voltage of about -840 V to the charging rolls 12, 22, 32, and 42 as contact-type charging devices. 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. Further, in this embodiment, in order to charge the surfaces of the photosensitive drums 11, 12, 13, and 14, a charging method of applying only DC is used, but a charging method of applying AC + DC may be used.

Thereafter, the surfaces of the photosensitive drums 11, 12, 13, and 14 are coated with cyan (C), magenta (M), yellow (Y), and black (K) by a laser optical unit as an exposure device (not shown). Laser light 31, corresponding to each color
32, 33, and 34 are irradiated, and an electrostatic latent image corresponding to the input image information for each color is formed. Photoconductor drum 11, 12, 13, 14
In the method, when an electrostatic latent image is written by the laser optical unit, the surface potential of the image exposed portion is eliminated to about -60 V or less.

An electrostatic latent image corresponding to each color of cyan (C), magenta (M), yellow (Y), and black (K) formed on the surface of the photosensitive drums 11, 12, 13, and 14. Are developed by the developing devices 41, 42, 43, and 44 of the corresponding colors, and cyan (C) is formed on the photosensitive drums 11, 12, 13, and 14,
It is visualized as a toner image of each color of magenta (M), yellow (Y), and black (K).

In this embodiment, the developing devices 41, 42, 4
3, 44, a magnetic brush contact type two-component developing method is adopted, but the scope of the present invention is not limited to this developing method, and other developing methods such as a non-contact type developing method are used. It goes without saying that the present invention can be sufficiently applied also to the above.

The developing devices 41, 42, 43, and 44 contain toners of cyan (C), magenta (M), yellow (Y), and black (K) of different colors, and a developer composed of a carrier. Is filled. These developing devices 41, 42,
When the toner is supplied from a toner supply device (not shown), the supplied toner is sufficiently stirred with the carrier by the auger 404 and charged by friction. Developing roll 40
Inside 1, a magnet roll (not shown) having a plurality of magnetic poles arranged at a predetermined angle is arranged in a fixed state. A paddle 403 for transporting the developer to the developing roll 401
Accordingly, the amount of the developer transported to the vicinity of the surface of the developing roll 401 is regulated by the developer amount regulating member 402 to the amount transported to the developing section. In this embodiment, the amount of the developer on the developing roll 401 is 30 to 50 g / m ² ,
At this time, the charge amount of the toner present on the developing roll 401 is about -20 to 35 μC / g.

The toner supplied onto the developing roll 401 is in the form of a magnetic brush composed of a carrier and toner due to the magnetic force of the magnet roll, and this magnetic brush is applied to the photosensitive drums 11, 12, 13, and 14. Is in contact with An AC + DC developing bias voltage is applied to the developing roll 401 to apply toner on the developing roll 401 to the photosensitive drums 11, 12, and 12.
By developing the electrostatic latent image formed on 13, 14
A toner image is formed. In this embodiment, the developing bias voltage is 4 kHz for AC, 1.5 kVpp, and -2 for DC.
It is about 30V.

Next, the respective photosensitive drums 11, 12, 13, 14
The toner images of the respective colors of cyan (C), magenta (M), yellow (Y), and black (K) formed on the first primary intermediate transfer drum 51 and the second primary intermediate transfer drum 52
Is electrostatically secondary-transferred. The cyan (C) and magenta (M) toner images formed on the photoconductor drums 11 and 12 are formed on the first primary intermediate transfer drum 51 by yellow (C) and magenta (M) toner images formed on the photoconductor drums 13 and 14, respectively. The toner images of Y) and black (K) are respectively transferred onto the second primary intermediate transfer drum 52. Accordingly, on the first primary intermediate transfer drum 51, the monochrome image transferred from either of the photosensitive drums 11 and 12 and the two-color toner image transferred from both of the photosensitive drums 11 and 12 are superimposed. A double-color image is formed. Also, on the second primary intermediate transfer drum 52, similar single color images and double color images are formed from the photosensitive drums 13 and 14.

The first and second primary intermediate transfer drums 5
The surface potential required for electrostatically transferring the toner images from the photosensitive drums 11, 12, 13, and 14 onto the surface 1, 52 is approximately +250 to 500 V. 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 .mu.C / g and the environment is normal temperature and normal humidity, the surface potential of the first and second primary intermediate transfer drums 51 and 52 becomes , + 380V is desirable.

The first and second primaries used in this embodiment
The intermediate transfer drums 51 and 52 have, for example, an outer diameter of 42 mm.
And the resistance is 10⁸It is set to about Ω. 1st, 2nd
The primary intermediate transfer drums 51 and 52 are single-layer or
Consists of flexible or elastic cylindrical
Rotating body, generally made of metal such as Fe or Al
Conductive silicone rubber on metal pipe as core
Low resistance elastic rubber layer (R = 10^Two~Ten^ThreeΩ)
Is provided with a thickness of about 0.1 to 10 mm. Furthermore,
The outermost surfaces of the first and second intermediate transfer drums 51 and 52 are typically
Is fluororubber with fluororesin microparticles dispersed in a thickness of 3 to
100 μm high release layer (R = 10^Five~Ten⁹Ω)
And connect with a silane coupling agent-based adhesive (primer).
Is being worn. What is important here is the resistance value and surface release.
And the resistance of the high release layer is R = 10 ^Five~Ten⁹About Ω
Yes, as long as the material has a high mold release property, the material is particularly limited
Not done.

The single-color or double-color toner images formed on the first and second primary intermediate transfer drums 51 and 52 are
The image is electrostatically tertiarily transferred onto the secondary intermediate transfer drum 53. Therefore, on the secondary intermediate transfer drum 53, a final toner image from a single color image to a quadruple color image of cyan (C), magenta (M), yellow (Y), and black (K) is formed. Will be.

The surface potential required for electrostatically transferring the toner images from the first and second primary intermediate transfer drums 51 and 52 onto the secondary intermediate transfer drum 53 is about +600 to 1200 V. . The surface potential is the same as when the toner is transferred from the photosensitive drums 11, 12, 13, and 14 to the first primary intermediate transfer drum 51 and the second primary intermediate transfer drum 52. Will be set to the optimum value. Also, since what is necessary for the transfer is the potential difference between the first and second primary intermediate transfer drums 51 and 52 and the secondary intermediate transfer drum 53, the first and second primary intermediate transfer drums 51 and 5 are required.
It is necessary to set the value according to the surface potential of 2.
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 51 and 52 is +380 V under normal temperature and normal humidity environment. In this case, the surface potential of the secondary intermediate transfer drum 53 is about +880 V, that is, the potential difference between the first and second primary intermediate transfer drums 51 and 52 and the secondary intermediate transfer drum 53 is +880 V. It is desirable to set to about 500V.

The secondary intermediate transfer drum 53 used in this embodiment has an outer diameter of, for example, 42 mm, which is the same as the first and second primary intermediate transfer drums 51 and 52, and has a resistance value of 10 ¹¹ Ω.
Set to about. Also, the secondary intermediate transfer drum 53 has a single-layer structure, similarly to the first and second primary intermediate transfer drums 51 and 52.
Alternatively, the rotating body is a cylindrical rotating body having a flexible or elastic surface having a plurality of layers, and is generally made of conductive silicone rubber or the like on a metal pipe as a metal core made of Fe, Al, or the like. A typical low-resistance elastic rubber layer (R =
10 ² to 10 ³ Ω) in a thickness of about 0.1 to 10 mm. Further, the outermost surface of the secondary intermediate transfer drum 53 is typically made of a fluoro rubber in which fluoro resin fine particles are dispersed, having a thickness of 3 to
It is formed as a high release layer having a thickness of 100 μm, and is bonded with a silane coupling agent-based adhesive (primer). What is important here is the resistance and the releasability of the surface as in the case of the first and second primary intermediate transfer drums 51 and 52. However, the resistance value of the secondary intermediate transfer drum 53 needs to be set higher than those of the first and second primary intermediate transfer drums 51 and 52. Otherwise, the secondary intermediate transfer drum 53 charges the first and second primary intermediate transfer drums 51 and 52, and it is difficult to control the surface potential of the first and second primary intermediate transfer drums 51 and 52. Become. The material is not particularly limited as long as it satisfies such conditions.

Next, the final toner image from the single color image to the quadruple color image formed on the secondary intermediate transfer drum 53 is
The third transfer is performed by the final transfer roll 60 onto the sheet passing through the sheet transport path P. This paper passes through a paper transport roll 90 through a paper feeding step (not shown), and is fed into a nip portion between the secondary intermediate transfer drum 53 and the final transfer roll 60. After this final transfer step, the final toner image formed on the paper is fixed by the fixing device 70, and a series of image forming processes is completed.

The final transfer roll 60 has, for example, an outer diameter of 20 m.
m, and the resistance value is set to about 10 ⁸ Ω. As shown in FIG. 2, the final transfer roll 60 is formed by providing a coating layer 62 made of urethane rubber or the like on a metal shaft 61 and coating the coating layer 62 as necessary. The optimal value of the voltage applied to the final transfer roll 60 varies depending on the ambient temperature, humidity, type of paper (resistance value, etc.), and is generally about +1200 to 5000 V. In this embodiment, a constant current method is adopted, and a current of about +6 μA is applied under a normal temperature and normal humidity environment, so that an almost appropriate transfer voltage (+1600
~ 2000V).

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 21, 22, 23, and 24 having the highest negative potential. The portions of the charging devices 21, 22, 23, and 24 to which toner adheres are activated by discharging, and the surface potential of the photoconductor drums 11, 12, 13, and 14 tends to increase, and thus the portions where toner adheres frequently In addition, the surface potentials of the photosensitive drums 11, 12, 13, and 14 are uneven at portions where toner is little attached and portions where toner is not attached. When unevenness occurs in the surface potential of the photoconductor drums 11, 12, 13, and 14, an image is uniformly exposed on the surface of the photoconductor drums 11, 12, 13, and 14 to form an electrostatic latent image. Also, since the latent image potential becomes uneven and the development amount becomes different, the density unevenness becomes conspicuous especially when a halftone image is to be developed.

Therefore, such charging devices 21, 22, 23,
In this embodiment, in order to prevent the occurrence of density unevenness due to the toner adhered to the sheet 24, the following cleaning operation is performed at a predetermined timing, such as before a printing operation, after a printing operation, or at a predetermined number of sheets with continuous printing. It has become.

Charging devices 21, 22, 23, 24, photosensitive drum 1
1, 12, 13, 14, the first and second primary intermediate transfer drums 51,
52, the secondary intermediate transfer drum 53, the final transfer roll 60, so that the final transfer roll 60 has the highest negative potential,
By applying a voltage with a potential gradient in order,
During the printing operation, the (+) charged toner of the opposite polarity deposited and deposited on the charging devices 21, 22, 23, and 24 is sequentially transferred and moved to the final transfer roll 60, and contacts the final transfer roll 60. It is collected by a cleaning device 80 including a final cleaning member 801 such as a blade provided.

In this embodiment, the charging devices 21, 22, 2
The surface potential of 3, 24 is 0 V, and the photosensitive drums 11, 12, 13, 14
, The surface potential of the first and second primary intermediate transfer drums 51 and 52 is -800 V, the surface potential of the secondary intermediate transfer drum 53 is -1300 V, and the surface potential of the final transfer roll 60 is-. Two
000 V is set. 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 51 and 52 or the secondary intermediate transfer drum 53 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, a (+) charged toner collection mode of opposite polarity, it is possible to prevent the occurrence of density unevenness due to the toner attached to the charging devices 21, 22, 23, and 24.

The above is the image forming process in the full-color printer configured as described above. 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, it is desirable to control the process in response to environmental fluctuations and changes over time.

As one of the methods, a test toner patch is formed on the surface of an image density detecting medium such as a photoreceptor, an intermediate transfer member, or a transfer roll or a transfer belt on paper, and the density is determined by optical density. There is a method of detecting and controlling with a sensor.

In this embodiment, on the image density detecting medium such as the final transfer roll 60 and the secondary intermediate transfer drum 53, the position is shifted in the process direction to the same position in the axial direction, and the image density is controlled. (Hereinafter, referred to as “test patch”), a single optical density detecting unit can detect the test patch of each color.

In order to detect a test patch on the photosensitive drums 11, 12, 13, and 14, it is necessary to provide four optical density detecting means for each of the photosensitive drums 11, 12, 13, and 14. I will. On the first and second primary intermediate transfer drums 51 and 52, two optical density detecting means may be used. As long as it is on the secondary intermediate transfer drum 53 or on the final transfer roll 60, one optical density detecting means may be used. Further, in the case where the image density is controlled by the test patch, the downstream process is preferable because the condition is closer to the paper. That is, the secondary intermediate transfer drum
53, and more preferably, the final transfer roll 60 is preferably an image density detection medium for detecting the density of the test patch.

Regarding the detection position and the like of the test patch,
The biggest reasons are described below.

In general, it is difficult to transfer 100% of the toner image formed on the photosensitive drums 11, 12, 13, and 14, and the normal transfer rate is about 70 to 90%. The toner amount of the toner image decreases after the transfer. That is, in the case where the test patch is detected in the state before the transfer and the density of the toner is controlled, accurate control cannot be performed unless the transfer amount is predicted and controlled. However, since the transfer rate of the toner image varies depending on the environment and the state of the developer, it is difficult to accurately predict the transfer amount of the toner image.

On the other hand, in order to accurately judge and control the state of the process before the transfer, it is preferable to detect the test patch in an upstream process immediately after the development for forming the test patch. That is, it is better to detect the density of the test patch on the photoreceptor than on the intermediate transfer member, on the transfer roll or on the transfer belt, rather than on the transfer belt, by the optical density sensor.

That is, when the process state on the upstream photosensitive member is determined based on the density information of the test patch detected in the downstream process such as the transfer roll and the intermediate transfer member, the transfer rate is affected. Control becomes difficult.

An example of controlling the state of the process based on the density information of the test patch is the toner density in a two-component developing device. When the two-component developing method is used, it is important to control the ratio of toner and carrier (toner density) in the developing device.

One reason for this is that the toner development amount depends on the toner charge amount, and the toner charge amount also depends on the toner concentration. The toner development amount increases as the toner charge amount decreases, and decreases as the toner charge amount increases. The toner charge amount decreases as the toner concentration increases, and increases as the toner concentration decreases. Further, the toner charge amount decreases in a high humidity environment and increases in a low humidity environment.

One reason is that the toner density has an appropriate range. If the toner concentration is too high, the toner charge amount becomes too low, and the low-charged toner adheres to the background of the image on the photoreceptor, causing fogging, or blows out from the developing device as a cloud, and the inside of the device is filled with toner. It will be stained. Conversely, if the toner concentration is too low, the toner charge becomes too high, making it difficult to transfer, causing unevenness such as brushing of the developed toner image, or using a semiconductive carrier or a conductive carrier. In this case, carriers are injected into the image due to charge injection and adhere.

As described above, since there is a correlation between the toner development amount and the toner charge amount, the toner density can be controlled by adjusting the toner supply amount to the developing device from the test patch density. It is premised that the density of the test patch can be accurately detected, and in order to accurately detect the density of the test patch, it is necessary to always consider the influence of the transfer of the toner image.

For this reason, as a result of various studies, the present inventors have determined that a system having a high transfer rate is required in order to accurately control both the density and image quality on paper and the process state to determine the process state. We conclude that it is necessary. If the transfer rate is high, there is almost no difference in the density of the test patch on the photoreceptor, on the intermediate transfer body, on the transfer roll, or on the transfer belt. The patch density may be detected at any position.

The transfer rate is preferably such that the toner amount of the test patch toner image formed on the photoreceptor on the transfer roll or the transfer belt is 90% or more, and preferably 95% or more.

In the above-described color printer, in order to increase the transfer rate, the toner image formed on the photosensitive drum as described above is transferred onto a sheet via a primary and secondary intermediate transfer member. In addition, the effect of the shape of the toner particles is large.

An irregular shaped toner such as a pulverized toner is
Since the contact surface is larger than the adhesion surface, the adhesion force is large,
It is difficult to transfer to the transfer destination surface. 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.

As a method of producing a spherical toner, a method of subjecting a toner produced by an emulsion polymerization method, a suspension polymerization method, a solution suspension method or a kneading and pulverizing method to a heat treatment is known.

Here, the spherical toner means that when the shape factor M1 is represented by the following equation, M1 ≦ 125, preferably M1 ≦ 1
20. M1 = (π · dmax ² / 4A) × 100 dmax: maximum diameter of toner A: cross-sectional area of toner

On the other hand, in the image forming apparatus having the configuration as in the present embodiment, the secondary intermediate transfer body 53 or the final transfer roll
If a toner image for controlling the image density of each color (hereinafter referred to as a “test patch”) is formed at the same position in the axial direction on the axis 60 and shifted in the process direction, a single optical density sensor is used. A test patch can be detected. In order to detect a test patch on the photoconductor, four optical density sensors are required for each photoconductor, that is, two optical density sensors may be used for the primary intermediate transfer member.

In the case where the image density is controlled by the test patch, the downstream process is preferable because the condition is closer to the paper. That is, the secondary intermediate drum 53, more preferably the final transfer roll 60, is preferably used as an image density detection medium for detecting the density of the test patch.

In this embodiment, the test patch is transferred onto the final transfer roll 60, and the density of the test patch transferred onto the final transfer roll 60 is detected by an optical density sensor.

In the test patch, a non-image area, in which no image is formed, under the same charging, exposure, development, and transfer conditions as in image formation, cyan (C), magenta (M), and yellow (Y ) And black (K), test patches 200 of 12% × 12 mm with an image density of 40% are formed on the final transfer roll 60 at intervals of 3 mm as shown in FIG.

As shown in FIG. 4, the optical density sensor 100 is disposed at the center of the final transfer roll 60 in the axial direction so as to be located on the outer circumference of the final transfer roll 60 and on an extension in the radial direction. ing. This optical density sensor 100
Is fixedly mounted in the holder 101. A cleaning device 80 having a blade-like final cleaning member 801 is provided below the final transfer roll 60.
Are arranged. In FIG. 4, reference numeral 802 denotes a toner collection box; 803, a support frame for the final transfer roll 60;
Denotes a static eliminator provided on the support frame 803, and 805 denotes a bias plate.

As shown in FIG. 5, the optical density sensor 100 is a specular reflection type sensor for detecting specular reflection light. A light emitting element 102 composed of an LED or the like disposed at an angle φ, and a light reflected from the light emitting element 102 to a detection position on the surface of the final transfer roll 60 and specularly reflected from the detection position. And a light receiving element 103 composed of a phototransistor or the like arranged at an angle of reflection equal to the predetermined incident angle with respect to the detection position on the surface of the final transfer roll 60.

The optical density sensor 100 includes:
As shown in FIG. 6, 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, the detection accuracy of the toner density can be further improved by detecting the toner density based on both the specular reflection component and the scattered light component.

FIG. 7 is a block diagram showing a control circuit of the image density control device according to this embodiment.

In FIG. 7, reference numeral 300 denotes the optical density sensor 100.
A control circuit 301 including a CPU or the like for controlling the image density based on the detection result of the control circuit 301, based on an output signal from the control circuit 300, a voltage Vc applied to the charging devices 21, 22, 23, and 24;
A potential control circuit for controlling the developing bias voltage Vbias applied to the developing devices 41, 42, 43, 44, and 302 is a charging device 21, 22, 23, 24
A high-voltage power supply for applying a predetermined voltage Vc to the
A high-voltage power supply for applying a predetermined developing bias voltage Vbias to 41, 42, 43, 44, and 304, a toner density control circuit for controlling toner supply to the developing device based on an output signal from the control circuit 300, respectively It is.

In the above configuration, the image forming apparatus according to this embodiment can prevent the cost increase and the lengthening of the density detection cycle due to the increase of the optical density detection means as follows. The density of the toner image for image density detection can be detected with high accuracy.

That is, in the image forming apparatus according to this embodiment, as shown in FIG.
In the state where the test patch is not transferred, the surface of the final transfer roll 60 is detected by the optical density sensor 100, and the output Vcln of the optical density sensor 100 at this time is stored (step 101). Next, under the same charging, exposure, development, and transfer conditions as those used in image formation, a 12 × 12 mm image density of 40% for each color of cyan (C), magenta (M), yellow (Y), and black (K). As shown in FIG. 3, test patches 200 are formed on the final transfer roll 60 at intervals of 3 mm (step 102).

In this embodiment, the test patch
The transfer conditions for transferring 200 to the final transfer roll 60 are as follows:
It is configured to be different from the image forming time. When the test patch 200 is directly transferred onto the final transfer roll 60, since there is no paper, the appropriate transfer conditions are different from those at the time of printing, and there is no creeping of the transfer current due to the paper. Is set to be small.

Thereafter, the cyan (C), magenta (M), yellow (Y),
In the test patch 200 of each color of black (K), FIG.
(A) or an optical density sensor as shown in FIG.
Detects 16 points at a pitch of 0.5 mm at 100 and averages Vpatc
h is obtained (step 103). Here, FIG.
As shown in (a), a specular reflection type optical density sensor 100 is used.
Is used. Then, the average value of each color is
The ratio Vpatch / Vcln divided by the value of the elementary surface of 60 is used as a substitute value of the density (step 104). Here, the ratio with the value of the elementary surface of the final transfer roll 60 is determined by the final transfer roll 60
This is for correcting the variation in the reflectance of the 60 elementary surfaces and the variation in the LED light emission amount.

As a result, Vpatch / Vcln for each color
Is compared with a predetermined value (step 105). When the obtained density of the test patch is lower than the predetermined density, the absolute value of the DC of the developing bias is increased according to the difference, and at the same time, the voltage applied to the charging device is increased. Then, as shown in FIG. 10B, the charging potential of the photosensitive drum is increased (step 106). By doing so, as shown in FIG. 10B, the electric field in the developing direction formed between the developing roll of the developing device and the image portion of the electrostatic latent image on the photosensitive drum becomes large, and the image is developed. And the image density increases.

On the contrary, when the obtained density of the test patch is higher than the predetermined density, the absolute value of the DC of the developing bias is reduced in accordance with the difference, and at the same time, the voltage applied to the charging device is reduced. As shown in c), the charged potential of the photosensitive drum is reduced (step 108). By doing so, as shown in FIG. 10C, the electric field in the developing direction formed between the developing roll of the developing device and the image portion of the electrostatic latent image on the photosensitive drum is reduced, and the image is developed. The amount of toner to be used decreases, and the image density decreases. At this time, the adjustment amount of the developing bias and the supply voltage to the charging device is determined by the detected density of the test patch.

Here, the developing bias and the supply voltage to the charging device are adjusted, but any device that adjusts the density or gradation of the image may be used. The exposure condition and the gradation characteristics of the image may be adjusted, or the peripheral speed ratio between the developing roll and the photosensitive drum may be adjusted. Further, these may be combined.

In this embodiment, the photosensitive drums 11, 1
The transfer rates when transferring the toner images formed on 2, 13, 14 onto the first and second primary intermediate transfer drums 51, 52, and the first and second primary intermediate transfer drums 51, 52 The transfer rate when the toner image transferred on the second intermediate transfer drum 53 is transferred onto the secondary intermediate transfer drum 53, and the toner image transferred on the secondary intermediate transfer drum 53 is transferred onto a recording medium or a final transfer roll 60. The transfer rate of the entire toner image including the transfer rate at the time of transfer on the upper side is set to be as high as 90% or more, preferably 95%, and the photosensitive drums 11, 12, 13, 14 and the first A cleaner-less system in which cleaning means is not provided on the surfaces of the second and third primary intermediate transfer drums 51 and 52, and the secondary intermediate transfer drum 53.
The test patch 200 formed thereon is transferred at a high transfer rate onto the final transfer roll 60 for detecting the density of the test patch 200.

For this reason, in this embodiment, the density of the test patch 200 can be detected in a state substantially equal to the state formed on the photosensitive drums 11, 12, 13, and 14. It is possible to prevent an increase in cost and a lengthening of the density detection cycle due to the increase, and it is possible to detect the density of the toner image for image density detection with high accuracy.

In the color printer shown in FIG. 1, two color toner images are transferred from the photosensitive drums 11, 12, 13, and 14 onto the first and second primary intermediate transfer drums 51 and 52, respectively. The first and second primary intermediate transfer drums 51 and 52 are configured to transfer toner images onto the secondary intermediate transfer drum 53 from the first and second primary intermediate transfer drums 51 and 52, respectively. , 52, it is sufficient to transfer two toner images, so that a higher transfer rate can be obtained as compared with a case where four toner images are transferred in a multiplex manner on one intermediate transfer member. Further, also on the secondary intermediate transfer drum 53, two integrated toner images (two for each color) which have been transferred onto the first and second primary intermediate transfer drums 51 and 52 may be transferred. Therefore, after all, 4
A higher transfer rate can be obtained compared to a case where two toner images are transferred in a multiplex manner. As a result, combined with the use of the spherical toner, a high transfer rate can be obtained in total.

Experimental Example 1 Next, the present inventors prototyped a printer as shown in FIGS. 1 and 2 and made the final transfer roll 60 under the following image forming conditions.
An experiment was conducted in which a test patch 200 having three densities was formed thereon, and the density of the test patch 200 was detected by the optical density sensor 100.

That is, the toner concentration of 4.5%, 6.5
% And 8.5% of a developer are prepared, and a solid image is printed under a fixed potential condition. The potential condition is the photoconductor charging potential Vh-320V
, The solid image potential V1-60 V, and the DC component Vdc-240 V of the developing bias.

Solid image density Toner charging amount (μC / g) 4.5% 6.5% 8.5% 4.5% 6.5% 8.5% Y 1.23 1.45 1.67 28 26 23 M 1.27 1.48 1.66 27 24 20 C 1.22 1.44 1.59 30 26 24 K 1.27 1.45 1.62 26 23 20

When the potential condition was changed based on the test patch density for the developer having the toner density of the above three conditions, the image density could be made substantially constant even if the toner density was different.

[0087]

[0088]

[0089]

[0090]

Image forming conditions AC component of development PP 1.5 KV Frequency 4 kHz Waveform Sine wave First intermediate transfer member surface potential +380 V Second intermediate transfer member surface potential +880 V Final transfer roll +6 μA Developer Toner diameter Y, M, C 7.5 μm K 8.0 μm Shape factor M1 118 to 120 Carrier diameter 45 μm Environment 22 ° C / 55% RH

As described above, in the experimental example 1, the image density control is applied to various conditions (color and toner density), and the effect of the control is described.

EXPERIMENTAL EXAMPLE 2 Next, the present inventors prepared a developer in which the toner concentration of each color was 6.5%, and conducted an experiment to check how the toner concentration fluctuated by continuous printing.

The toner replenishment was performed by measuring the image density from the print image signal and controlling the toner replenishment time according to the result. In addition, a cycle of printing 8, 4, and 4 images of 5%, 10%, and 20% image density of each color was repeated, and a total of 1000 images were printed.

The potential conditions at the time of printing were a photoconductor charging potential Vh-320V, a solid image potential V1-60V, and a developing bias DC component Vdc-240V.

Since the toner replenishment depends only on the measured value of the image density, the deviation gradually occurs, and the toner density at the start of printing is 5% to 7.5% as shown in FIG.
It fluctuated.

Next, as shown in FIG. 12, after printing a predetermined number of sheets (for example, 16 sheets), a test patch was formed, and an experiment was performed to correct the toner supply amount based on the result.

For toner supply, the image density is measured from the print image signal, and the supply time is controlled so as to supply toner corresponding to the amount of toner used according to the result. However, in this method, when the development amount fluctuates, the amount of toner used fluctuates, and the balance with the amount of replenished toner deviates, and the toner density in the developing device fluctuates.

For this reason, a test patch is created to detect the density, and the toner supply amount is corrected according to the result.

The test patch is a non-image area. At a timing when no image is formed, the image density is 12 mm × 1 with an image density of 40% for each color under predetermined charging, exposure, development and transfer conditions.
Test patches of 2 mm are formed on the final transfer roll 60 at intervals of 3 mm.

For the detection, first, the bare surface of the final transfer roll 60 on which no test patch is mounted is detected by the optical density sensor, and the output is stored. Next, 16 points in the test patch of each color are detected at a pitch of 0.5 mm, and an average value is obtained. Then, a ratio obtained by dividing the average value of each color by the value of the elementary surface is used as a substitute value of the density. The reason for taking the ratio with the bare surface is to correct the variation of the reflectance of the bare surface.

As a result, if the obtained test patch is lower than the predetermined density, the toner density is low, and the correction is made so as to increase the toner supply amount according to the difference. Conversely, if the test patch has a higher density than the predetermined density, the toner density is high, and correction is made to reduce the toner supply amount according to the difference.

The test patch had an image density of 100%, and the potential condition for forming the test patch was fixed. The photosensitive member charging potential Vh-320V, DC component Vdc-240V of the developing bias
, AC components were turned off.

FIG. 13 shows the results of the above experiment.
The fluctuation of the toner density was ± 0.4%, which indicates that the toner density can be improved.

As described above, the experimental example 2 describes the result of confirming the effect of the method of forming and correcting a test patch while controlling the toner density only by the image density.

Experimental Example 3 Further, the present inventors performed both the potential control of Experimental Example 1 and the toner supply amount control of Experimental Example 2 to perform continuous printing.

The potential control was performed by forming a test patch every time 16 sheets were printed. Other than that, it was the same as Experimental example 1 and Experimental example 2.

FIGS. 14 and 15 show the results of Experimental Example 3 above. As is clear from FIGS. 14 and 15, the fluctuation of the image density of each color is 0.06 or less and the fluctuation of the toner density is ± 0.5%. It turned out that it can be controlled as follows. As described above, Experimental Example 3 describes the results of confirming the effect of the method combining image density control and toner density control.

In the above experimental example, the developing bias and the supply voltage to the charging device are adjusted, but other image forming parameters may be adjusted as long as the image density or gradation can be adjusted. . That is, the exposure condition and the gradation characteristics of the image may be adjusted, or the peripheral speed ratio between the developing roll and the photoconductor may be adjusted. Further, these may be appropriately combined.

In the above experimental example, a two-component developing device is used, but the developing method is not particularly limited.

Further, the present invention can be applied to the case where a test patch is formed and the process is controlled based on the density detection result.

[0112]

As described above, according to the present invention,
Provided is an image forming apparatus capable of preventing an increase in cost and an increase in a density detection cycle due to an increase in optical density detection means and capable of detecting the density of a toner image for image density detection with high accuracy. Can be.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a color printer as an image forming apparatus according to Embodiment 1 of the present invention.

FIG. 2 is a sectional view showing a final transfer roll of a color printer as an image forming apparatus according to Embodiment 1 of the present invention.

FIG. 3 is a perspective view showing a final transfer roll of a color printer as an image forming apparatus according to Embodiment 1 of the present invention.

FIG. 4 is a configuration diagram showing an optical density sensor of the image density control device according to the first embodiment of the present invention.

FIG. 5 is a configuration diagram showing an optical density sensor of the image density control device according to the first embodiment of the present invention.

FIG. 6 is a configuration diagram showing an optical density sensor of the image density control device according to the first embodiment of the present invention.

FIG. 7 is a block diagram showing a control circuit of the image forming apparatus according to Embodiment 1 of the present invention.

FIG. 8 is a flowchart showing a control operation of the image density control device according to the first embodiment of the present invention.

FIGS. 9A and 9B show Embodiment 1 of the present invention.
FIG. 3 is a configuration diagram illustrating a detection state of an optical density sensor of the image forming apparatus according to the first embodiment.

FIGS. 10A to 10C are potential explanatory diagrams illustrating an image density control method of the image forming apparatus according to the first embodiment of the present invention.

FIG. 11 is a graph showing the relationship between the number of prints and the toner density.

FIG. 12 is a flowchart illustrating a toner density control operation.

FIG. 13 is a graph showing the relationship between the number of prints and the toner density.

FIG. 14 is a graph showing the relationship between the number of prints and the image density.

FIG. 15 is a graph showing the relationship between the number of prints and the toner density.

[Explanation of symbols]

 1, 2, 3, 4 Image forming unit 11, 12, 13, 14 Photoconductor drum (image carrier) 21, 22, 23, 24 Charging roll (contact type charging device) 31, 32, 33, 34 Laser beam 41 , 42, 43, 44 Developing device 401 Developing roll 402 Developer amount regulating member 403 Paddle 404 Auger 51, 52 Primary intermediate transfer drum (Intermediate transfer body 53 Secondary intermediate transfer drum (Intermediate transfer body) 60 Final transfer roll (Final transfer Rotating body) 61 Metal shaft 62 Coating layer 80 Cleaning device 801 Final cleaning member 802 Toner collection box 803 Support frame 804 Static eliminator 805 Bias plate 90 Paper transport roll 100 Optical density sensor 101 Holder 102 Light emitting element 103 Light receiving element 200 Test patch P paper Transport path

Continued on the front page (72) Inventor Hideaki Tanaka 3-7-1, Fuuchi, Iwatsuki-shi, Saitama, Fuji Xerox Co., Ltd. Iwatsuki Office (72) Inventor Seiji Kasagi 3-7-1, Fuuchi, Iwatsuki-shi, Saitama, (72) Inventor Hiromitsu Koizumi 3-7-1, Fuwauchi, Iwatsuki-shi, Saitama Prefecture, F-term in the Iwatsuki Office of Fuji Xerox Co., Ltd. (Reference) 2H027 DA09 DA41 DE41 DE07 EA01 EA05 EA06 EB04 EC03 EC06 EC07 EC09 ED09 ED10 HB20 2H030 AB02 AD16 BB02 BB34 BB36 BB42 BB46 BB54 BB56 2H032 AA05 AA15 BA07 BA16 BA23 CA02 CA13 CA15

Claims (7)

[Claims] A plurality of image carriers on which single-color toner images of different colors are formed; and a plurality of single-color toner images formed on the image carrier, which are disposed in contact with or close to the image carriers. One or more intermediate transfer bodies to be transferred, and a final transfer rotator for transferring the toner image transferred onto the one or more intermediate transfer bodies to a recording medium, and a color image is formed. In the image forming apparatus for forming, the image forming apparatus, the transfer rate when transferring the monochromatic toner image formed on the image carrier on the intermediate transfer body, and the toner image transferred on the intermediate transfer body The transfer rate at the time of final transfer onto a recording medium is set high, and a toner image for image density control is formed on the surface of the intermediate transfer body or the final transfer rotating body, and the intermediate transfer body or the final transfer rotation is formed. Density of toner image formed on body surface Was detected by optical density detection means, the image forming apparatus characterized by being configured to control the image forming conditions based on a detection result of the optical density detection means. 2. The image forming apparatus according to claim 1, wherein the transfer rate at which the monochromatic toner image formed on the image carrier is transferred onto the intermediate transfer body, and the toner image transferred onto the intermediate transfer body is recorded on a recording medium. 2. The image forming apparatus according to claim 1, wherein an overall transfer rate including a transfer rate at the time of final transfer on the upper side is set to 90% or more. 3. The image forming apparatus according to claim 1, wherein the image forming apparatus uses a spherical toner to set a high transfer rate of the toner image. 4. The image forming apparatus according to claim 1, wherein a transfer condition for forming the toner image for controlling the image density on the surface of the intermediate transfer member or the final transfer rotator is different from that for image formation. The image forming apparatus according to claim 1, wherein: 5. The image forming apparatus according to claim 1, wherein the image density detecting medium for detecting the density of the toner image for controlling image density is provided with cleaning means for cleaning a surface of the image density detecting medium. After cleaning the toner image for image density control formed on
The image forming apparatus according to claim 1, wherein a next image toner for controlling image density or an image is not formed on the image density detection medium during a period equal to or longer than the circumference. 6. The image forming apparatus according to claim 1, wherein the image forming apparatus forms the image density controlling toner images of all the colors within one rotation of the image density detecting medium for detecting the density of the image density controlling toner image. The image forming apparatus according to claim 1. 7. A latent image corresponding to input information of each color is formed, and each latent image is developed with a toner of a corresponding color to obtain a plurality of single-color toner images. An image forming apparatus that forms a color image by being fixed thereon, wherein each latent image is formed according to input information for each color, and each latent image is developed with a toner of a corresponding color to form a single color toner. Three or more image carriers on which images are formed, or each latent image according to input information for each color is sequentially formed, and each latent image is developed with a toner of a corresponding color to sequentially form a single-color toner image. A single image carrier, and one or a plurality of intermediate transfer members that are arranged in contact with or in close proximity to the image carrier, and onto which each single-color toner image formed on the image carrier is transferred. Recording the toner image transferred onto the one or more intermediate transfer members on a recording medium; An image forming apparatus comprising: a final transfer rotating body for transferring to a body; and forming a color image through at least two or more toner image transfer steps. The image forming apparatus is formed on an image carrier. Image density control by setting a high transfer rate when transferring a single-color toner image onto an intermediate transfer body and a transfer rate when finally transferring a toner image transferred onto the intermediate transfer body onto a recording medium Forming a toner image on the surface of the intermediate transfer body or the final transfer rotator, detecting the density of the toner image formed on the surface of the intermediate transfer body or the final transfer rotator by optical density detection means, An image forming apparatus, wherein an image forming condition is controlled based on a detection result of the optical density detecting means.