JP2006154059A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which secures the most faithful color reproducibility even for a transfer material of the highest quality and maintains a conventional level of color reproducibility even for rough paper. <P>SOLUTION: The image forming apparatus includes an image carrier for carrying a toner image, a moving member, a transfer means for transferring the toner image on the image carrier to the moving member or a transfer material carried on the moving member, and an image detection means for detecting information of a test pattern formed on the moving member, and an image formation condition to the image carrier is controlled on the basis of information detected by the image detection means. A transfer current which is caused to flow to the transfer means when transferring the test pattern to the moving member is made larger than a transfer current which is caused to flow to the transfer means when transferring the tone image to the transfer material. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus using an electrophotographic system, for example, an image forming apparatus such as a copying machine, a printer, and a FAX (facsimile).

  In recent years, image forming apparatuses using an electrophotographic system have been improved in speed, image quality, and color, and various types of copying machines, printers, and fax machines have been put on the market.

  The color image forming apparatus includes a direct transfer method in which toner is directly transferred from an image forming unit to a transfer material, and an intermediate transfer method in which toner is transferred to a transfer material via an intermediate transfer member.

  Among these, the direct transfer method is advantageous in reducing the size of the image forming apparatus. Among them, image forming units for forming a plurality of different color toner images are juxtaposed in series in the transfer direction of a transfer material carried on a transfer belt as a transfer material carrying member, from the plurality of image carrying members to the transfer material. The method of sequentially transferring the toner images in a multiple manner is called an in-line color image forming apparatus, which is capable of forming a color image at high speed, and is considered to be the main force in the future.

  In general, a color image forming apparatus has a function of automatically executing calibration periodically in order to always provide an accurate color image. Factors that cause the color to vary include changes in the environment in which it is used and usage history of various consumables.

  An example of calibration is as follows.

  That is, a density detection toner image (patch) is created on the transfer belt directly on a trial basis, the density is detected by an optical image density detector, and the charging voltage, exposure intensity, Feedback is applied to dynamic image forming conditions such as a developing voltage and correction of an image data signal when forming a hearton image. Hereinafter, this calibration is referred to as image density control. For example, Patent Document 1 discloses image density control that is executed in an in-line color image forming apparatus.

  Conventionally, when image density control is executed, a configuration that ensures the stability of image density control by applying a transfer high pressure that can achieve transfer efficiency almost equivalent to the transfer efficiency to a standard transfer material. It was common to do. In other words, a transfer voltage at which a transfer current substantially equal to the transfer current that flows when transferring to a standard transfer material flows is applied when executing image density control. Therefore, normally, the transfer voltage applied at the time of image density control is smaller than the transfer voltage applied when the toner is transferred to the transfer material.

JP 2004-252161 A

  However, there are various types of transfer materials. The transfer efficiency to the transfer material varies depending on the type of transfer material. In general, a transfer material having a smoother surface improves transfer efficiency because the degree of adhesion between the transfer material and the image carrier increases. Even with rough paper, a method that improves the transfer efficiency by increasing the current flowing to the transfer means may be taken, but due to the roughness of the surface, it causes local abnormal discharge phenomenon. This may cause an incentive and may lead to a decrease in image quality. In short, with the current technology, it is impossible to maintain high transfer efficiency regardless of the transfer material.

  Recently, in order to improve the image quality, media that have been coated on the surface to increase the smoothness are generally on the market. A typical example is called glossy paper. A user who uses glossy paper or the like is expected to require the most faithful color reproducibility with high glossiness and high image quality.

  However, in the method described in the conventional example, image density control is executed based on the standard (intermediate) transfer efficiency of a commercially available transfer material under the condition of the transfer efficiency equivalent to the standard transfer efficiency. In addition, various feedback processes during image formation are performed. That is, this control was not optimized for a transfer material with good transfer efficiency such as glossy paper. Therefore, conventionally, the glossy paper or the like that requires the most accuracy by the user has not been configured so as to exhibit the most faithful color reproducibility.

  To solve this problem, simply perform image density control based on the transfer efficiency of the highest quality transfer material and use it as a reference, and use it as the basis for various feedback during image formation. This can be dealt with by performing the processing, but in this case, there is a disadvantage that the color reproducibility of the rough paper or the like is significantly reduced.

  The present invention has been made in view of the above-mentioned problems, and the purpose of the process is to ensure the most faithful color reproducibility with respect to the highest quality transfer material, and also with respect to rough paper, An object of the present invention is to provide an image forming apparatus capable of maintaining the level of color reproducibility.

  To achieve the above object, the present invention provides an image carrier that carries a toner image, a moving body, and a toner image on the image carrier that is transferred to the moving body or a transfer material carried on the moving body. Transfer means and image detection means for detecting information of a test pattern formed on the moving body, and based on the information detected by the image detection means, image forming conditions on the image carrier are determined. In the image forming apparatus to be controlled, the transfer current that flows to the transfer unit when the test pattern is transferred to the moving body is set to be larger than the transfer current that flows to the transfer unit when the toner image is transferred to the transfer material. Features.

  The present invention also provides an image carrier that carries a toner image, a moving body, a transfer unit that transfers the toner image on the image carrier to the moving body or a transfer material carried on the movable body, An image forming apparatus that includes image detection means for detecting information of a test pattern formed on the movable body, and that controls image forming conditions on the image carrier based on information detected by the image detection means The image detection means is executed a plurality of times by changing the transfer current passed through the transfer means, and the detection result of the image detection means executed a plurality of times is determined based on information on the type of transfer material to be printed. And determining whether to control image forming conditions on the image carrier.

  According to the present invention, by making the transfer current that flows when the test pattern is transferred to the moving body larger than the transfer current that flows when the toner image is transferred to the transfer material, the transfer efficiency at the time of detecting the image density is the highest. Since the transfer efficiency for high-quality transfer materials can be made almost equal, the reliability of image forming condition control on the image carrier for the highest-quality transfer materials is increased, and the most faithful color reproducibility is ensured. I can do it now.

  Further, according to the present invention, based on information on the type of transfer material, either correction of image forming condition control on the image carrier or image density detection executed a plurality of times by changing the transfer voltage is performed. By determining whether to control the image forming condition on the image carrier using the detection result, it becomes possible to maintain the same level of color reproducibility as with conventional paper even on rough paper.

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

<Embodiment 1>
FIG. 1 is a schematic cross-sectional view of an engine unit of a color image forming apparatus using an electrophotographic process according to the present embodiment.

  Four independent and detachable processes having a photosensitive drum as an image carrier for Y toner, M toner, C toner, and Bk toner, a developing device as a developing means, and a cleaning device as a collecting means. The cartridges 7 are juxtaposed in the vertical direction, and the toner images of different colors formed by the process cartridges 7 are sequentially superimposed on the transfer material P adsorbed by the transfer belt 11 (transfer material carrier) as a moving body. A full-color image is obtained by transferring. The transfer material P is fed from the sheet feeding unit 17 at the bottom of the color image forming apparatus, conveyed upward, and then discharged to the sheet discharge tray 26.

  In FIG. 1, reference numeral 1 denotes a rotating drum type electrophotographic photosensitive member (hereinafter referred to as “photosensitive drum”) that is repeatedly used, and is driven to rotate at a predetermined peripheral speed (process speed).

  The photosensitive drum 1 is uniformly charged to a predetermined polarity and potential (minus in the present embodiment) by a primary charging roller (primary charger) 2 serving as charging means in the course of rotation, and then image exposure means 1 to 4 color component images (for example, yellow, magenta, cyan, black) of each target color image by receiving image exposure by 3 (configured by a laser diode, a polygon scanner, a lens group, etc.) An electrostatic latent image corresponding to the component image) is formed.

  Subsequently, the electrostatic latent image is developed by a developing unit of each image forming station. Each developing sleeve 4 carrying toner in a developing device (yellow, magenta, cyan, black) as developing means for storing toner of each color is rotated by a rotation driving device (not shown), and the photosensitive drum 1 is developed in the developing process. It is arrange | positioned so that it may oppose. Each color toner that is negatively frictionally charged in each developer and carried on each developing sleeve 4 is electrostatically developed on each photosensitive drum 1 to form a toner image of each color.

The transfer belt 11 is rotationally driven at substantially the same peripheral speed as that of the photosensitive drum 1 while being in contact with each photosensitive drum 1. The transfer belt 11 is composed of an endless film-like member having a thickness of about 100 to 150 μm and having a volume resistivity of 10 ⁸ to 10 ¹² Ωcm. The volume resistivity is a value obtained by applying 100 V at a temperature of 23.5 ° C. and a relative humidity of 60% with a high resistance meter R8340 manufactured by ADVATEST, using a measurement probe in accordance with JIS-K6911. It is.

  The transfer material P fed from the paper feed cassette 17 is fed toward the adsorbing roller 22 that is driven to rotate relative to the transfer belt 11 by a registration roller pair 19 that is driven and rotated at a predetermined timing. The transfer belt 11 is electrostatically adsorbed. At this time, in order to electrostatically attract the transfer material P to the transfer belt 11, a predetermined voltage is applied to the attracting roller 22. As a result, a charge is applied to the surface of the transfer material P, a mirroring force is generated between the transfer material 11 and the transfer material P is electrostatically attracted to the transfer belt 11.

The suction roller 22 is formed by molding a solid rubber on a core metal having a diameter of 6 mm, and is configured to apply a high-pressure bias for suction to the core metal. The suction roller 22 is a solid rubber roller having a diameter of 12 mm in which carbon black is dispersed for resistance adjustment in EPDM rubber, and a resistance value of 500 V is wound around the roller outer periphery with a metal foil having a width of 1 cm. The resistance value when voltage is applied is adjusted to about 10 ⁵ to 10 ⁶ Ω. In order to ensure releasability, a coating layer may be provided on the surface layer.

  The transfer material P adsorbed on the transfer belt 11 is applied to the transfer roller 12 disposed opposite to the photosensitive drum 1 with the transfer belt 11 interposed between each process cartridge (each image forming station) 7. The toner images of different colors are transferred from the photosensitive drum 1 by the action of static electricity due to the high pressure.

The transfer roller 12 is formed by molding a solid rubber on a core metal having a diameter of 6 mm, and is configured to apply a high-voltage bias for transfer to the core metal. The transfer roller 12 is a solid rubber roller having a diameter of 12 mm in which carbon black is dispersed for resistance adjustment in epichlorohydrin rubber rubber, and the resistance value is adjusted to about 2 × 10 ⁷ Ω by the measurement method described above.

  Then, the transfer material P separated by curvature at the separation position where the transfer belt 11 and the roller 71 come into contact with each other is fixed to the transfer material P by heating and pressurizing the full-color toner image by the fixing device 20, so Discharged to the outside of the image forming apparatus main body.

  After the toner image is transferred from the photosensitive drum 1 to the transfer material P on the transfer belt 11, the toner (transfer residual toner) remaining on the photosensitive drum 1 is removed by the cleaning blade 6 of the cleaning device (collecting means). To be recovered. The collected toner is accumulated in a waste toner tank (waste toner tank) in the cleaning device.

  Next, image density control in the present embodiment will be described.

  A density detection sensor 40 is disposed in the body facing the transfer belt 11. In general, in an electrophotographic color image forming apparatus, the characteristics of toner and the above-described key parts change depending on various conditions such as replacement of consumables, change in the environment to be used, and the number of printed sheets. The change in the characteristics is manifested as a change in image density and a change in color reproducibility. That is, the original correct color tone cannot be obtained due to this variation. Therefore, in this embodiment, in order to always obtain a desired color tone, a density detection toner image (patch) is created on the transfer belt 11 on a trial basis, and the density is detected by the density detection sensor 40. Then, based on the detection result, image density control for controlling various process parameters is performed. Various process parameters include charging voltage, developing voltage, laser modulation, and the like.

  As shown in FIG. 2, the density detection sensor 40 includes an LED light emitting element 40 a having a wavelength of 950 nm, a light receiving element 40 b such as a photodiode, and a holder, and infrared rays from the light emitting element 40 a are patched on the transfer drum 4. The density of the patch T is measured by irradiating T and measuring the reflected light from the T with the light receiving element 40b. The reflected light from the patch T includes a regular reflection component and an irregular reflection component. Basically, the regular reflection component is light reflected by the transfer belt 11 as a base, and the amount of reflected light decreases as the amount of toner increases. The irregular reflection component is light scattering by toner, and the amount of reflected light increases as the amount of toner increases. However, the black toner exceptionally absorbs the infrared light of 950 nm used in this embodiment, so that the amount of reflected light decreases as the toner amount increases. In any case, the amount of toner can be detected regardless of whether the amount of specular reflection or the amount of irregular reflection is detected.

  In the present embodiment, a method of detecting a regular reflection component is adopted. As described above, the specular reflection component is the reflected light of the transfer belt 11, and the detection accuracy (S / N) can be easily increased by employing the transfer belt 11 having a high reflectance. .

  In the density detection sensor 40 shown in FIG. 2, the irradiation angle and the light receiving angle are set to be the same so that the regular reflection light component from the patch T can be secured in the light receiving element 40b. With reference to the normal I, the irradiation angle to the patch T is 30 °, and the light receiving angle of the reflected light from the patch T is 30 °. In order to minimize the intrusion of irregular reflection components as much as possible, the aperture diameter on the light receiving side is set small (about 1.5 mm).

  Next, a specific example of the density control method will be described.

  As the patch pattern, a 10 mm × 10 mm square pattern is used. This is a halftone pattern subjected to a specific dither process. Then, while changing a specific process parameter, a plurality of patches are created, the engine state is grasped from the density value, and the image creation parameter is controlled so that an appropriate image can be obtained. The specific process parameters referred to here are development voltage, charging voltage, image image data, and the like.

  Here, a method for controlling image image data will be described with reference to FIG.

  Hereinafter, this control is referred to as halftone control. A plurality of halftone pattern patches subjected to a specific dither process are created while changing their gradation (exposure time for the dither matrix), and their density is detected by the density detection sensor 40. The horizontal axis shows the ratio of the exposure time (100% when the entire dither matrix is exposed) (100% when the entire dither matrix is exposed), and corresponds to the gradation. In this embodiment, eight patches are created. The vertical axis in FIG. 3A is obtained by converting the result detected by the density detection sensor 40 into an image density. FIG. 3 (b) is obtained by normalizing FIG. 3 (a) with an estimated maximum density (density at an exposure time of 100%) and linearly interpolating each point. Hereinafter, this curve is referred to as a “primary γ curve”.

  As can be seen from the result of FIG. 3B, the gradation (exposure time ratio) and density are not in a linear relationship. This is because exposure ON / OFF control and emission intensity follow-up (light emission does not stop immediately after switching from ON to OFF), potential profile of electrostatic latent image formed by exposure, development This is due to various factors such as characteristics.

  That is, if the exposure time for the dither matrix is selected simply based on the image density instruction from the host, the color tone will be shifted. For this reason, it is necessary to prevent a shift in color tone (color reproducibility) using a table (hereinafter referred to as an LUT (Look Up Table)) that converts an image density instruction from the host into an exposure time for the dither matrix. . By creating an LUT as shown in FIG. 4A based on the “primary γ curve”, a linear relationship (FIG. 4B) exists between the image density instruction from the host and the actual density. Born and able to perform accurate color reproduction. In other words, the LUT is a table in which the vertical axis and the horizontal axis of the “primary γ curve” are interchanged. The above is the outline of the halftone control.

  Next, a method for detecting the type of transfer material P (hereinafter referred to as media detection) in the present embodiment will be described with reference to FIGS.

  FIG. 5 is a schematic cross-sectional view showing a schematic configuration of an apparatus for detecting the surface smoothness of the transfer material P and the amount of reflected light or transmitted light.

  It is arranged in the middle of the registration roller 19 and the suction roller 22 in the transfer path of the transfer material P (not shown). The transfer material P fed from the paper feed cassette 17 is temporarily stopped immediately before entering the suction roller 22. Then, the type of the transfer material P is determined by the following method.

  As shown in FIG. 5, the media detection sensor 123 includes a reflection LED 1111 serving as a light irradiation unit, a CMOS area sensor 1110 serving as a reading unit, and a lens 1113 serving as an imaging lens.

  Light using the LED 1111 for reflection as a light source is applied to the surface of the transfer material P.

  The reflected light from the transfer material P is condensed through the lens 1113 and imaged on the CMOS area sensor 1110. Thereby, the surface image of the transfer material P is read.

  In the present embodiment, the LED 1111 is arranged so that the LED light irradiates the surface of the transfer material P obliquely with a predetermined angle as shown in FIG.

  FIG. 6 is a diagram showing the relationship between the surface of the transfer material P read by the CMOS area sensor 1110 of the media detection sensor 123 and an example in which the output from the CMOS area sensor 1110 is digitally processed to 8.8 pixels.

  The digital processing is performed by converting the analog output from the CMOS area sensor 1110 into 8-bit pixel data by A / D conversion (not shown) as conversion means.

  In FIG. 6, reference numeral 40 denotes a surface enlarged image of the so-called rough paper transfer material A, which is relatively rough in the surface property of the transfer material P and the unevenness due to the fibers of the transfer material P can be easily identified. 41 is an enlarged image of the surface of the so-called plain paper transfer material B that is normally used in a general office, and 42 is an enlarged image of the surface of the transfer material C of glossy paper in which the paper fibers are sufficiently compressed. .

  These images 40 to 42 read into the CMOS sensor 1110 are digitally processed into the images 43 to 45 shown in FIG.

  Thus, the image on the surface varies depending on the type of the transfer material P. This is a phenomenon that occurs mainly because the fiber state on the paper surface is different.

  At this time, the reflected light amount of the transfer material P is detected from the total or average value of the light input to each pixel. At this time, only the result of one light receiving pixel may be used.

  As described above, the image obtained by reading the surface of the transfer material P by the CMOS area sensor 1110 and digitally processing it can be discriminated based on the surface state of the paper fiber of the transfer material P and the amount of reflected light.

  In the image comparison calculation, the maximum density pixel Dmax and the minimum density pixel Dmin are derived from the result of reading a plurality of images on the surface of the transfer material P. This is executed for each read video and averaged.

  That is, when the paper fiber on the surface is rough like the transfer material A, many shadows of the fiber are generated. As a result, the difference between the bright part and the dark part becomes large, and Dmax−Dmin becomes large.

  On the other hand, on the surface such as the transfer material C, the shadow of the fiber is small and Dmax−Dmin is small.

  By this comparison, the roughness of the surface of the transfer material P is determined.

  Next, transfer performance (transfer efficiency) to a transfer material in the present embodiment will be described with reference to FIG.

  The transfer efficiency when transferring the toner image varies greatly depending on the type of the transfer material P. In general, the transfer material P having a smoother surface improves the transfer efficiency because the degree of adhesion between the transfer material P and the photosensitive drum 1 increases. That is, transfer efficiency decreases in the order of glossy paper, plain paper, and rough paper. Even if it is rough paper, the transfer efficiency can be improved to some extent by increasing the current passed through the transfer roller 12, but due to the roughness of the surface, it causes local abnormal discharge phenomenon. This may cause an incentive and may lead to a decrease in image quality.

  In addition, when a transfer current that is too large is applied, an image defect called a transfer memory may occur. The transfer memory means that when an excessive transfer current flows into the photosensitive drum 1, the potential of the photosensitive drum 1 is greatly lowered, so that subsequent charging of the photosensitive drum 1 by the charging roller 2 is not in time, and the photosensitive drum 1 is not in time. This is a phenomenon in which 1 cannot be returned to a predetermined potential. More specifically, the transfer memory is manifested as a phenomenon of “halftone density increase after the second round of the photosensitive drum 1. In summary, in this embodiment, an abnormal discharge phenomenon and a transfer memory occur. In other words, the control is performed so that the maximum transfer current flows through the transfer roller 12 within the range where the transfer is not performed.

FIG. 7 shows glossy paper (HP
High Gloss Paper 32 #) and plain paper (HP Color)
This plots the relationship between gradation (exposure time for dither matrix) and image density when printed on Laser Paper 24 #). The image density was measured with RD918 manufactured by Gretag Macbeth. As described above, the density of glossy paper is higher than that of plain paper in all gradation regions, and it can be seen that the glossy paper has high transfer efficiency. This tendency is particularly remarkable on the high concentration side.

  Next, a transfer current when the patch T is transferred to the transfer belt 11 during the image density control in the present embodiment will be described.

  In the present embodiment, as shown in FIG. 8, the array of eight halftone patches provided for each color is set to be shorter than the circumference of the photosensitive drum 1. This is to prevent the above-described transfer memory from being affected during image density control. In this embodiment, in order to achieve the highest transfer efficiency, the maximum transfer current is allowed to flow in a range where the abnormal discharge phenomenon does not occur. The surface of the transfer belt 11 used in this embodiment is much smoother than the transfer material. Therefore, the abnormal discharge phenomenon is less likely to occur, and a considerably large transfer current can be passed. Table 1 shows transfer current values in the present embodiment under the environment of 23 ° C./50% RH. This is shown in comparison with the transfer current at the time of transfer to glossy paper or plain paper described above.

表１を参照すれば、分かる通り、本実施例の構成では、画像濃度制御時の転写電流は転写材へ転写する際の転写電流よりも高い値に設定されるようになっている。光沢紙(HP High Gloss Paper 32#) は平滑であり異常放電が発生しにくく、その観点で普通紙(HP Color Laser Paper 24#)よりも転写電流が多く流すことが可能になっている。普通紙(HP Color Laser Paper 24#)に関しては、異常放電現象が転写電流を決定する制約条件となっている。尚、画像濃度制御時は、上述のように、転写メモリの影響を受けないような構成としてあるので、それは転写電流を設定する上での制約条件とはならない。図７に本実施の形態におけるハーフトーン制御時に対する濃度検出結果を示している。

As can be seen from Table 1, in the configuration of this embodiment, the transfer current at the time of image density control is set to a value higher than the transfer current at the time of transfer to the transfer material. Glossy paper (HP High Gloss Paper 32 #) is smooth and less likely to cause abnormal discharge. From this point of view, more transfer current can flow than plain paper (HP Color Laser Paper 24 #). For plain paper (HP Color Laser Paper 24 #), the abnormal discharge phenomenon is a limiting condition for determining the transfer current. Note that the image density control is configured not to be affected by the transfer memory as described above, and thus does not constitute a restriction condition for setting the transfer current. FIG. 7 shows the density detection result for the halftone control in this embodiment.

  Next, the LUT (lookup table) correction method in this embodiment will be described with reference to FIG.

  When a high transfer voltage as shown in the present embodiment is applied during the hearton control, as shown in FIG. 9, the “primary γ curve” detected during the halftone control and the image transferred on the glossy paper The “primary γ curve” agrees very well. That is, for glossy paper, it can be said that accurate color reproducibility can be ensured by using the LUT calculated by halftone control.

  However, it can be seen that there is a large deviation from the “primary γ curve” of plain paper. This is because the transfer efficiency for plain paper is too low compared to the transfer efficiency for the transfer belt 11 during halftone control. In this embodiment, when the medium is detected as plain paper or rough paper as a result of the media detection, the LUT calculated by the halftone control is corrected and corrected in consideration of the difference in transfer efficiency. Image formation was performed using an LUT.

Specifically, this is performed as follows. Here, a plain paper having a difference in transfer efficiency as shown in FIG. 7 will be described as an example.
(1) An image density reduction rate table is prepared for the highest quality transfer material (here, glossy paper) having the maximum transfer efficiency (FIG. 10).
(2) The density detection result of each patch obtained by the halftone control is converted using the table of FIG. 10 (FIG. 11A).
(3) An LUT for plain paper is created using the converted patch density (FIG. 11B).

  The same processing is performed for a rough paper in the same manner by preparing an image density reduction rate table. As a result, it is possible to form an image with an optimum LUT corresponding to the detection result of the media detection (glossy paper, plain paper, rough paper), so that an image that is always faithfully reproduced in color can be provided. Become. Among these, for glossy paper, since the LUT can be created without converting the halftone detection result, the error factor is minimized, and a particularly excellent color reproduction image can be provided.

  In this embodiment, the transfer material is automatically determined by the image forming apparatus using the media detection sensor 123, and the optimum LUT is selected according to the determination result. The determination method is not limited to this. For example, it is also possible to obtain transfer material type information from designation on a printer driver or operation panel.

  In the present embodiment, the halftone control for controlling the image image data is described as an example of the image density control. However, the present invention is not limited to this. The present invention can also be applied to the case where the charging voltage and the development voltage are controlled based on the patch density detected by the density detection sensor 40.

<Embodiment 2>
In this embodiment, in the electrophotographic apparatus having the same configuration as that of the first embodiment, the image density detection is performed a plurality of times while changing the transfer current, and according to the information on the transfer material obtained by means such as media detection, Of the control performed a plurality of times, it is determined which of the detection results to control various process parameters.

  Hereinafter, also in the present embodiment, halftone control will be described as an example.

In this embodiment, halftone control is repeated three times. Then, three LUTs are created based on the respective detection results. These three LUTs are used for glossy paper, plain paper, and rough paper, respectively. In summary, control is performed according to the following flow.
(1) Transfer current setting (Setting 1)
(2) Halftone control execution LUT1 creation (for glossy paper)
(3) Transfer current change (setting 2)
(4) Halftone control execution LUT2 creation (for plain paper)
(5) Transfer current change (setting 3)
(6) Halftone control execution LUT2 creation (for rough paper)
Next, each transfer current setting (setting 1, setting 2, setting 3) will be described.

  For the transfer current of setting 1 (for glossy paper), the transfer current (20 μA) described in the first embodiment may be used. The transfer current settings in the settings 2 and 3 may be set to transfer currents that give substantially the same transfer efficiency as that of plain paper and rough paper.

  FIG. 12 shows the relationship between the density detection result and the transfer current in the image forming apparatus according to the present embodiment. For reference, the density measurement results on plain paper (HP Color Laser paper 24 #) shown in FIG. 7 are listed. From this experimental result, it was found that if a transfer current of 12 μA is used for image density detection, the transfer efficiency is almost the same as that when transferring to plain paper. Therefore, in the present embodiment, setting 2 is set to 12 μA. The transfer current of setting 3 can also be set by performing the same process for rough paper.

1 is a schematic cross-sectional view of an image forming apparatus according to Embodiment 1 of the present invention. It is a block diagram of the density | concentration detection sensor which concerns on Embodiment 1 of this invention. It is the figure which showed the density | concentration detection sensor detection result and prime gamma curve which concern on Embodiment 1 of this invention. It is the figure which showed the LUT which concerns on Embodiment 1 of this invention, and the normalized density | concentration after conversion by it. It is a block diagram of the media detection sensor which concerns on Embodiment 1 of this invention. It is a figure which shows the transcription | transfer material detection result of LED for reflection of the media detection sensor which concerns on Embodiment 1 of this invention. It is the figure which showed media type dependence of the transfer efficiency which concerns on Embodiment 1 of this invention. FIG. 6 is an array diagram of halftone patches during halftone control according to Embodiment 1 of the present invention. It is the figure which showed the media type dependence of the elementary | gamma γ curve which concerns on Embodiment 1 of this invention. It is the figure which showed the density fall rate in the plain paper which concerns on Embodiment 1 of this invention. It is the figure which showed the correction | amendment of LUT by the media type which concerns on Embodiment 1 of this invention. It is a figure which shows the relationship between an image density and the exposure ratio with respect to a dither matrix.

Explanation of symbols

1a to 1d Image carrier (photosensitive drum)
2a to 2d Charging means (primary charger, primary charging roller)
3a to 3d exposure means (image exposure means)
4a to 4d Developing sleeve 6a to 6d Cleaning blade 7a to 7d Process cartridge (image forming station)
DESCRIPTION OF SYMBOLS 11 Transfer belt 12a-12d Transfer roller 17 Paper feed cassette 19 Registration roller 20 Fixing device 22 Adsorption roller 26 Paper discharge tray 40 Density detection sensor 40a Light emitting element 40b Light receiving element 65 Crimp release cam 123 Media detection sensor 1110 CMOS area sensor 1111 For reflection LED
1112 Transparent LED
1113 Lens P Transfer material

Claims (6)

An image carrier for carrying a toner image, a moving body, a transfer means for transferring the toner image on the image carrier to the moving body or a transfer material carried on the moving body, and formed on the moving body In the image forming apparatus for controlling the image forming conditions on the image carrier based on the information detected by the image detecting means, the image detecting means for detecting the information of the test pattern that is performed,
An image forming apparatus, wherein a transfer current that flows to the transfer unit when the test pattern is transferred to a moving body is made larger than a transfer current that flows to the transfer unit when a toner image is transferred to a transfer material.   The image forming apparatus according to claim 1, wherein control of image forming conditions on the image carrier is corrected based on information relating to a type of transfer material. An image carrier for carrying a toner image, a moving body, a transfer means for transferring the toner image on the image carrier to the moving body or a transfer material carried on the moving body, and formed on the moving body In the image forming apparatus for controlling the image forming conditions on the image carrier based on the information detected by the image detecting means, the image detecting means for detecting the information of the test pattern that is performed,
Using the detection result of the image detection means executed a plurality of times based on information on the type of transfer material to be printed, changing the transfer current flowing through the transfer means and executing the image detection means a plurality of times. An image forming apparatus for determining whether to control image forming conditions on the image carrier.   4. The image forming apparatus according to claim 2, wherein information relating to the transfer material is acquired based on a detection result by a transfer material type automatic detection unit provided in the image forming apparatus.   The image forming apparatus according to claim 2, wherein information related to the type of transfer material is notified from the controller to the engine.   6. The control of the image forming condition is to control exposure timing and exposure time by an exposure unit that forms an electrostatic latent image on the image carrier in association with image data. The image forming apparatus according to any one of the above.

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