JP2014222294A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can suppress an increase in toner consumption and an increase in waiting time, while suppressing occurrence of difference in image density and hue of output images between image forming modes using different image forming units.SOLUTION: When a tandem type image forming apparatus of an intermediate transfer system including five image forming units performs specified color printing using some of image forming units of the five image forming units, forms images of toner patches for determination with the image forming unit arranged on the uppermost stream of the image forming units to be used in the specified color printing, and determines necessity of execution of specified color process control using the image forming units to be used in the specified color printing on the basis of a detection result of the amount of toner attached to the toner patches for determination.

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, and a printer, and more particularly to an image forming apparatus that transfers toner images formed by a plurality of image forming units onto a transfer target.

  Conventionally, this type of image forming apparatus includes four image forming units for forming toner images of Y (yellow), M (magenta), C (cyan), and K (black), and four toner images of YMCK. Are known that can output a full-color image by superimposing the image on a transfer material or a recording material carried on the transfer material. Such an image forming apparatus has an image forming mode (printing mode) such as a black and white mode, a full color mode, and a two-color mode, and can form an image according to the selected image forming mode. In such an image forming apparatus, conventionally, an image forming unit of a color that is not necessary for image formation is separated from the transfer target so as not to disturb the toner image on the transfer target. . Japanese Patent Application Laid-Open No. 2005-228561 discloses a developing unit that develops an image carrier while rotating the image carrier of the image forming unit without separating the image forming unit of a color that is not necessary for image formation. An image forming apparatus that stops the developing operation is disclosed.

  For example, when image formation is performed in the red / black two-color mode, it is conceivable that all the image forming units of YMCK are operated to form an image and a red / black image is output. In this case, since the Y toner image and the M toner image are superimposed to express red, the C image forming unit is caused to perform an image forming operation even though it is not necessary to use the C image forming unit. Become. Needless to say, if the image forming section is operated to form an image, the wear of the components and the toner deterioration progress unnecessarily, and more power is consumed. Therefore, it is preferable to stop unnecessary image forming operations for image forming units that are not necessary for image formation, according to the selected image forming mode.

  In particular, in recent years, electrophotographic image forming apparatuses are equipped with five image forming units including transparent toner (clear toner) in addition to the four conventional YMCK image forming units in order to meet high image quality requirements. Things have been proposed. In such an image forming apparatus, when an image is formed using an image forming unit using only YMCK, when an image is formed using a two-color image forming unit including transparent toner, only the image forming unit using transparent toner is used. Image formation. Therefore, the use frequency of the image forming mode in which it is not necessary to perform the image forming operation for all the image forming units is higher than that of the conventional image forming apparatuses. Therefore, in such an image forming apparatus, there is a great advantage of performing control to stop an unnecessary image forming operation of an image forming unit that is not necessary for image formation according to an image forming mode.

  However, when control is performed to stop an unnecessary image forming operation of an image forming unit that is not necessary for image formation according to the image forming mode, there is a problem that the image density and color are different depending on the selected image forming mode. Occur. For example, when a yellow portion of an image formed in the full color mode is compared with a yellow portion of an image formed in the two-color mode, the yellow color of the image formed in the two-color mode becomes darker than that in the full-color mode. This is due to the following reason.

  That is, when an image is formed in the full color mode, all the image forming portions of YMCK are operated to form an image. Therefore, during the transfer operation for transferring the M toner image and the C toner image to the transfer target, The Y toner that has already been transferred to the body is reversely transferred to the M or C image carrier, and the amount of Y toner adhered per unit area on the transferred body is reduced. Hereinafter, the toner adhesion amount per unit area is simply referred to as “toner adhesion amount”.

On the other hand, in the case of forming an image in the yellow and black two-color mode, the M and C image forming portions are not operated to perform the image forming operation. Therefore, the amount of Y toner attached is not reduced. In the conventional image forming apparatus, the image density condition corresponding to the Y toner adhesion amount is adjusted under the condition in the full color mode in which reverse transfer of Y toner occurs. For this reason, yellow in the full color mode in which reverse transfer of Y toner occurs is expressed by the target image density and color, but yellow in the two-color mode of yellow and black in which reverse transfer of Y toner does not occur The amount of adhesion increases, resulting in a higher density than the target image density.
In addition, when two or more color toner images such as red and blue are superimposed and expressed in color, not only the image density but also the color are different due to the difference in the reverse transfer amount for each color.

As a configuration for improving such a problem, the applicant described in Japanese Patent Application No. 2012-129945 (hereinafter referred to as “Prior Application 1”) and Japanese Patent Application No. 2012-275502 (hereinafter referred to as “Prior Application 2”). An image forming apparatus is proposed.
In the prior application 1, the reverse transfer rate when the toner image passes through the other image forming unit is digitized, and the image forming condition is set so that the toner adhesion amount is reduced by the amount reduced by the reverse transfer in the full color mode. A method for calculating the optimum image forming conditions in various printing modes by changing them is presented. However, in the method presented in the prior application 1, the calculated value of the reverse transcription rate used for the control is constant, and the actual reverse transcription rate is affected by error factors such as the environment. There is a problem that the accuracy of the control is lowered when the control is performed.

  On the other hand, in the prior application 2, not only the image density control for driving all the image forming units used in the full color mode but also a part of the image forming units such as the image forming unit used in the “K toner + transparent toner” mode. A method for controlling the driving image density is presented. Here, the image density control described in the prior application 2 is also called process control, and is an image forming condition in which a plurality of patch patterns having different toner adhesion amounts can be formed to obtain a desired toner adhesion amount. Is a control for calculating.

  In the prior application 2, before executing the image forming mode for driving only a part of the image forming units, the image density control is performed by driving only a part of the image forming units used in the image forming mode. Since image density control corresponding to each printing mode is performed, it is possible to calculate optimum image forming conditions in various printing modes. However, since the image density control forms a plurality of patch patterns having different toner adhesion amounts, the toner is consumed and more time is required. In the configuration of the prior application 2, the image density control is executed in accordance with the change of the print mode. Therefore, there is a possibility that a problem of an increase in toner consumption and an increase in waiting time of the user due to the control may occur.

  The present invention has been made in view of the above problems, and an object of the present invention is to suppress the occurrence of a difference in image density or color of an output image between image forming modes using different image forming units. An object of the present invention is to provide an image forming apparatus capable of suppressing an increase in toner consumption and an increase in waiting time.

  In order to achieve the above object, the invention according to claim 1 of the present application is such that an image forming unit that performs a transfer operation for transferring a toner image formed on an image bearing member to the surface of a transferred member to be moved is a transferred member. A plurality of image forming units arranged in the surface moving direction, and a part of the plurality of image forming units not performing the transfer operation, the transfer target surface moving direction upstream from the part of the image forming unit Image formation using a first image formation mode in which image formation is performed using another image formation unit located in the position, and two or more image formation units including the part of the image formation unit and the other image formation unit An image of one or more image forming units selected from the plurality of image forming units in accordance with an image forming mode selected from a plurality of image forming modes including a second image forming mode to be performed A toner image based on image information is formed on the carrier, and the toner is In an image forming apparatus having image formation control means for performing image formation control for transferring an image onto the transfer material or onto a recording material carried on the transfer material, the amount of toner adhering to the transfer material A toner adhering amount detecting means for detecting a toner image, and a plurality of toner patches formed on the transfer medium using the other image forming unit in a state where the part of the image forming unit is not performing a transfer operation. An image density adjustment toner patch is formed, the toner adhesion amount of the first image density adjustment toner patch is detected by the toner adhesion amount detection means, and based on the toner adhesion amount detected by the toner adhesion amount detection means The first image density condition determination control for determining the first image density condition is performed, and the second image density control comprising a plurality of toner patches on the transfer medium using the two or more image forming units. A toner patch is formed, the toner adhesion amount of the second image density adjustment toner patch is detected by the toner adhesion amount detection means, and the second image is based on the toner adhesion amount detected by the toner adhesion amount detection means. Image density condition determination means for performing second image density condition determination control for determining density conditions, and the image formation control means performs the second image density condition determination control at a predetermined timing, and When the second image mode is selected, image control is performed under the second image density condition determined by the second image density condition determination control. When the first image formation mode is selected, the partial image formation is performed. A toner patch for determination having a smaller number than that of the first image density adjusting toner patch is formed on the transfer object using the other image forming unit in a state where the unit is not performing a transfer operation, Based on the detection result obtained by detecting the toner adhesion amount of the determination toner patch by the toner adhesion amount detection means, it is determined whether or not the first image density condition determination control is to be performed. When the first image density condition determination control is performed, the image control is performed with the first image density condition determined in the first image density condition determination control, and the second image density condition is determined to be unnecessary. Image control is performed under the second image density condition determined by the determination control.

  According to the present invention, it is possible to suppress an increase in toner consumption and an increase in waiting time while suppressing occurrence of a difference in image density and color of an output image between image forming modes using different image forming units. There is an excellent effect that it is possible to do.

1 is a schematic configuration diagram illustrating a configuration example of a copier according to an embodiment. FIG. 2 is a schematic configuration diagram illustrating a configuration example of an image forming unit in the copier. FIG. 2 is a block diagram illustrating an example of a main configuration of a control system of the copier. 6 is a flowchart showing an outline of a flow of image density control in the embodiment. FIG. 3 is a schematic diagram illustrating a positional relationship between an image forming unit of each color and an intermediate transfer belt as an example of designated color printing. 5 is a flowchart showing a specific example of determining whether or not a designated color process control is necessary in the flowchart shown in FIG.

Hereinafter, an embodiment in which the present invention is applied to a copying machine as an image forming apparatus will be described with reference to the drawings.
In this embodiment, there are provided five image forming units that perform image formation using five types of toners of transparent (S), yellow (Y), magenta (M), cyan (C), and black (K). The image forming apparatus will be described as an example, but is not limited thereto. Therefore, even if the image forming apparatus includes an image forming unit that forms an image using toner other than the five types, or an image forming apparatus having a number of image forming units other than five, the same applies. The present invention can be applied.

FIG. 1 is a schematic configuration diagram showing a configuration example of a copying machine (hereinafter referred to as a copying machine 600) according to the present embodiment.
The copier 600 is a tandem type electrophotographic image forming apparatus that employs an intermediate transfer (indirect transfer) method. The copier 600 includes a printer unit 100, a paper feed unit (paper feed table) 200, a scanner 300, and an automatic document feeder (ADF) 400 that constitute the image forming apparatus main body. The paper feeding device 200 is a recording material supply unit that has a printer unit 100 mounted thereon and supplies a recording material (recording medium) to the printer unit 100. The scanner 300 is an image reading unit attached on the printer unit 100, and the automatic document feeder 400 is a document carrying unit attached on the scanner 300.

  The printer unit 100 is provided with an intermediate transfer belt 10 as an intermediate transfer member, which is a transfer target composed of an endless belt, at the center thereof. The intermediate transfer belt 10 is stretched around support rollers (14, 15, 16) as three support rotating bodies, and rotates in the clockwise direction in the figure. Among these three support rollers, on the left side of the second support roller 15 in the figure, an intermediate transfer belt cleaning device 17 is provided as a cleaning means for removing residual toner remaining on the intermediate transfer belt 10 after image transfer. Yes. Further, of the three support rollers, a tandem image forming unit 20 is disposed opposite to a belt portion stretched between the first support roller 14 and the second support roller 15 as shown in FIG. . The tandem image forming unit 20 includes five image forming units 18 of transparent (S), yellow (Y), magenta (M), cyan (C), and black (K) along the belt moving direction of the opposed belt portions. (18S, 18Y, 18M, 18C, 18K) is an image forming unit arranged side by side.

  In the copying machine 600, the third support roller 16 is a drive roller that is driven by a drive source (not shown). Further, a belt portion stretched between the first support roller 14 and the third support roller 16 serves as a toner adhesion amount detecting means for detecting the toner adhesion amount of the toner image transferred onto the intermediate transfer belt 10. A toner adhesion amount sensor 310 is disposed opposite to the toner adhesion amount sensor 310. The toner adhesion amount sensor 310 is constituted by an optical sensor using light reflection, for example. Further, a backup roller 311 as a sensor facing member that supports the back surface side (inner peripheral surface side) of the intermediate transfer belt 10 is provided at a position facing the toner adhesion amount sensor 310 with the intermediate transfer belt 10 interposed therebetween. Yes.

  As shown in FIG. 1, an exposure device 21 as an exposure unit is provided above the tandem image forming unit 20. Further, on the opposite side of the tandem image forming unit 20 with the intermediate transfer belt 10 interposed therebetween, a secondary transfer device 22 as a second transfer unit is provided. In the secondary transfer device 22, a secondary transfer belt 24, which is an endless belt as a recording material conveying member, is stretched between two secondary transfer belt support rollers (231, 232). The secondary transfer belt 24 is provided so as to be pressed against the third support roller 16 via the intermediate transfer belt 10. The secondary transfer device 22 transfers the toner image on the intermediate transfer belt 10 to a transfer sheet P that is a recording material (recording medium). A secondary transfer belt cleaning device 170 that cleans the outer peripheral surface of the secondary transfer belt 24 is provided on the lower side of the secondary transfer belt 24 in the drawing.

  Further, on the left side of the secondary transfer device 22 in the drawing, a fixing device 25 is provided as a fixing unit for fixing the toner image transferred onto the transfer sheet P. The fixing device 25 has a configuration in which a pressure roller 27 as a pressure member is pressed against a fixing belt 26 as a fixing member that is a heated endless belt. The secondary transfer device 22 also has a sheet conveying function for conveying the transfer sheet P after the toner image is transferred from the intermediate transfer belt 10 to the fixing device 25.

  Further, in the copier 600, a sheet reversing device 28 is provided below the secondary transfer device 22 and the fixing device 25 in parallel with the longitudinal direction of the tandem image forming unit 20 (the arrangement direction of the image forming units). ing. The sheet reversing device 28 is recording material reversing means for reversing the transfer sheet P so as to record images on both sides of the transfer sheet P.

  When making a copy using the copying machine 600, a document is set on the document table 30 of the automatic document feeder 400. Alternatively, the automatic document feeder 400 is opened, a document is set on the contact glass 32 of the scanner 300, the automatic document feeder 400 is closed, and the document is pressed by the automatic document feeder 400. Thereafter, when a start switch of an operation display unit (not shown) is pressed, when the document is set on the automatic document feeder 400, the automatic document feeder 400 conveys the document, moves the document onto the contact glass 32, and scans the scanner. 300 is driven. On the other hand, when an original is set on the contact glass 32, the scanner 300 is immediately driven.

  Next, the first traveling body 33 and the second traveling body 34 are caused to travel. Then, the first traveling body 33 emits light from the light source and further reflects the reflected light from the document surface toward the second traveling body 34 and reflects by the mirror of the second traveling body 34 and passes through the imaging lens 35. The image is read into the image reading sensor 36 and the original content is read. In parallel with this document reading, a third support roller 16 as a drive roller is rotationally driven by a drive motor (not shown) as a drive source. As a result, the intermediate transfer belt 10 moves in the clockwise direction in the drawing, and the first support roller 14 and the second support roller 15 that are the remaining two support rollers (driven rollers) are rotated along with the surface movement. Rotate.

  At the same time, the drum-shaped photosensitive member 40 (40S, 40Y, 40M, 40C, 40K) as an image carrier is rotated in each image forming unit 18 (18S, 18Y, 18M, 18C, 18K). The Then, each photoconductor 40 (40S, 40Y, 40M, 40C, 40K) is exposed using color-specific information of transparent, yellow, magenta, cyan, and black to form a latent image, and the latent image is developed by the developing device. The toner is developed using toner of each color (including transparent, the same applies hereinafter). As a result, transparent, yellow, magenta, cyan, and black monochromatic toner images (visual images) are formed on the five photoreceptors 40 (40S, 40Y, 40M, 40C, and 40K), respectively. Then, the toner images on the respective photoreceptors 40 (40S, 40Y, 40M, 40C, 40K) are transferred by a primary transfer device (primary transfer roller) 62 (62S, 62Y, 62M, 62C, 62K) as a primary transfer unit. The images are sequentially transferred onto the intermediate transfer belt 10 so as to overlap each other. As a result, a composite toner image is formed on the intermediate transfer belt 10.

In parallel with the image formation in the tandem image forming unit 20 described above, one of the paper feed rollers 42 of the paper feed device 200 is selectively rotated and transferred from one of the paper feed cassettes 44 provided in the paper bank 43 in multiple stages. The sheet P is fed out. The transfer sheets P fed out from one of the paper feed cassettes 44 are separated one by one by the separation roller 45 and enter the paper feed path 46, and are transported by the transport roller 47 to the paper feed path in the printer unit 100. It is guided and stops against the registration roller pair 49.
If the use of the transfer sheet P on the manual feed tray 51 is selected, the manual feed roller 50 rotates to feed out the transfer sheet P on the manual feed tray 51, and the manual separation roller 52 feeds the sheets one by one. Into the manual feed path 53. Then, similarly to the case where the transfer sheet P is supplied from the sheet feeding device 200, the transfer sheet P stops against the registration roller pair 49.
After the transfer sheet P hits the registration roller pair 49, the registration roller pair 49 rotates in synchronization with the synthesized toner image on the intermediate transfer belt 10, and the second transfer between the intermediate transfer belt 10 and the secondary transfer device 22. The transfer sheet P is fed to the next transfer position. At the secondary transfer position, the color toner image on the intermediate transfer belt 10 is transferred onto the transfer sheet P by the secondary transfer device 22.

  After transfer of the toner image, the transfer sheet P is conveyed by the secondary transfer belt 24 and sent to the fixing device 25, and heat and pressure are applied by the fixing belt 26 and the pressure roller 27 by the fixing device 25. The transferred toner image is fixed. In the case of single-sided printing, the fixed transfer sheet P is switched by the switching claw 55 and discharged by the discharge roller 56 and is stacked on the discharge tray 57. In the case of double-sided printing, the transfer sheet P on which the toner image has been fixed is switched to the conveyance destination by the switching claw 55 and enters the sheet reversing device 28 where it is reversed and guided again to the secondary transfer position, and on the back surface. Also, after the image is transferred, it is discharged onto the discharge tray 57 by the discharge roller 56.

  The intermediate transfer belt 10 after the transfer of the toner image is removed by the intermediate transfer belt cleaning device 17 to remove residual toner remaining on the intermediate transfer belt 10 after the toner image is transferred, and the tandem image forming unit 20 forms an image again. Prepare. Here, the registration roller pair 49 is generally used while being grounded, but it is also possible to apply a bias for removing paper dust from the sheet.

  FIG. 2 is a schematic configuration diagram illustrating a configuration example of one of the five image forming units 18 of the tandem image forming unit 20. The five image forming units 18 (18S, 18Y, 18M, 18C, and 18K) have substantially the same configuration except that the colors of the toners to be used are different, so that S, Y, M, C, and K are hereinafter described. In the following description, the suffix indicating the color of the toner to be used is omitted as appropriate.

  As shown in FIG. 2, the image forming unit 18 includes a charging device 60 as a charging unit, a potential sensor 70 as a potential detecting unit, a developing unit 61 as a developing unit, and an image carrier around a drum-shaped photoreceptor 40. A photoconductor cleaning device 63 as a body cleaning means is provided. Further, between the photosensitive member cleaning device 63 and the charging device 60, a neutralization device (not shown) as a neutralization unit is provided.

  At the time of image formation, the photoreceptor 40 is rotationally driven in the direction of arrow D by a drive motor (not shown). Then, after the surface of the photoreceptor 40 is uniformly charged by the charging device 60, the photosensitive member 40 is exposed to the writing light L emitted from the exposure device 21 based on the above-described image data of the original or the like, and is electrostatic latent image. Is formed. A color image signal based on image data (image information) from the scanner 300 is subjected to image processing such as color conversion processing in an image processing unit (not shown), and is exposed as an image signal of each color of S, Y, M, C, and K. It is output to the device 21. When forming a latent image on the black photoconductor 40K, the exposure device 21 converts the K image signal from the image processing unit into an optical signal, and the black photoconductor uniformly charged based on the optical signal. An electrostatic latent image is formed by scanning and exposing the surface of the body 40K. Similarly, latent images are formed on the photoreceptors 40 (40S, 40Y, 40M, and 40C) of other colors.

  In the developing device 61, the electrostatic latent image on the photoreceptor 40 is developed using a two-component developer containing toner and magnetic particles (carrier). A developing roller 61a as a developer carrying member for carrying a developer provided in the developing device 61 is rotationally driven at a predetermined rotational speed by a developing roller driving unit (not shown). A predetermined developing bias is applied to the developing roller 61a by a developing bias setting unit (developing bias power source) (not shown), and there is a potential difference between the electrostatic latent image on the photoreceptor 40 and the developing roller 61a. A development potential is formed. The toner on the developing roller 61a is transferred from the developing roller 61a to the electrostatic latent image on the photoconductor 40 by this developing potential, whereby the electrostatic latent image is developed and a single color toner image of each color is formed. Further, a toner concentration sensor 312 as a toner concentration detecting means is provided on the bottom surface of the developer conveying screw in the developing device 61, and detects the toner concentration of the two-component developer in the developing device 61 as needed. be able to.

  The monochromatic toner image formed on the photoreceptor 40 is transferred to the intermediate transfer belt 10 by a primary transfer device (primary transfer roller) 62 to which a predetermined primary transfer bias is applied by a primary transfer bias setting unit (primary transfer bias power source) described later. Primary transfer is performed on the top (see FIG. 1). After the toner image is transferred, the photoconductor 40 is cleaned of residual toner by the photoconductor cleaning device 63 and is discharged by a charge removal device (not shown) to prepare for the next image formation.

  Such an image forming operation is performed in each color image forming section 18 (18S, 18Y, 18M, 18C, 18K). Then, S, Y, M, C, and K single colors formed on the respective photoreceptors 40 (40S, 40Y, 40M, 40C, and 40K) by the image forming units 18 (18S, 18Y, 18M, 18C, and 18K). The toner image is primarily transferred while being superimposed on the intermediate transfer belt 10.

  The copier 600 can execute a full color + transparent mode, a full color mode, a single color mode, a two color mode, a three color mode, and a four color mode as image forming modes. The full color + transparent mode is an image forming mode in which a full color image is formed using all the five image forming units 18 (18S, 18Y, 18M, 18C, 18K). The full color mode is an image forming mode in which a full color image is formed using the four image forming units 18 (18Y, 18M, 18C, and 18K) excluding the transparent image forming unit 18S.

  The monochromatic mode is an image forming mode in which a monochromatic image is formed using any one of the four image forming units 18 (18Y, 18M, 18C, 18K) excluding the transparent image forming unit 18S. The two-color mode is an image forming mode in which an image is formed using any two of the five image forming units 18 (18S, 18Y, 18M, 18C, and 18K). The three-color mode is an image forming mode in which an image is formed using any three of the five image forming units 18 (18S, 18Y, 18M, 18C, 18K). In the four-color mode, an image is formed using any three of the four image forming units 18 (18Y, 18M, 18C, 18K) excluding the transparent image forming unit 18S and the transparent image forming unit 18S. Is an image forming mode for forming the image.

  As an image formed in the two-color mode, for example, a red single-color image, a blue single-color image, a green single-color image, a “yellow + black” two-color image, a “cyan + black” two-color image, and a “magenta + Two-color image of “black”. Further, the image formed in the two-color mode includes a yellow single color image of “yellow + transparent”, a cyan single color image of “cyan color + transparent”, a magenta single color image of “magenta color + transparent”, and “black + transparent”. Black single-color images. The same applies to the three-color mode and the four-color mode.

In the copying machine 600, contact / separation means (not shown) for individually contacting / separating each photoreceptor 40 (40S, 40Y, 40M, 40C, 40K) to the intermediate transfer belt 10 is provided. This contact / separation means moves each image forming unit 18 (18S, 18Y, 18M, 18C, 18K) up and down by a driving device (not shown), thereby each photoconductor 40 (40S, 40Y, 40M, 40C, 40K). Is moved toward and away from the intermediate transfer belt 10. By this contact / separation means, the photoreceptor 40 of any image forming unit 18 can be brought into contact with or separated from the intermediate transfer belt 10.
In the copying machine 600, the image forming unit 18 (18S, 18Y, 18M, 18C, 18K) used for image formation differs depending on the image forming mode. For this reason, the image forming section 18 (18S, 18Y, 18M, 18C, 18) not used for image formation is separated from the intermediate transfer belt 10 during the image forming operation in the image forming mode.

FIG. 3 is a block diagram illustrating an example of a configuration of a main part of the control system of the copying machine 600.
The copying machine 600 includes a control unit 500 configured by a computer device such as a microcomputer. The controller 500 controls the image forming operation in a plurality of image forming modes (full color + transparent mode, full color mode, single color mode, two color mode, three color mode, four color mode). Specifically, the control unit 500 functions as an image formation control unit that performs drive control of one or more image forming units 18 selected from the plurality of image forming units 18 in accordance with the image forming mode. Further, the control unit 500 functions as an image density condition determination unit that performs image density condition determination control for determining an image density condition so that the density of the output image becomes a target image density.

  The control unit 500 includes a CPU (Central Processing Unit) 501, a ROM (Read Only Memory) 503, a RAM (Random Access Memory) 504, and an I / O interface unit 505. The ROM 503 and the RAM 504 are storage means connected to the CPU 501 via the bus line 502. The CPU 501 executes various calculations and drive control of each unit by executing a control program which is a computer program incorporated in advance. The ROM 503 stores in advance fixed data such as computer programs and control data. The RAM 504 functions as a work area for storing various data in a rewritable manner.

Various sensors such as a toner adhesion amount sensor 310, a toner concentration sensor 312, and a potential sensor 70 of the printer unit 100 are connected to the control unit 500 via the I / O interface unit 505. Here, various sensors such as the toner adhesion amount sensor 310, the toner density sensor 312, and the potential sensor 70 of the printer unit 100 send information detected by the sensors to the control unit 500.
A charging bias setting unit (charging bias power source) 330 that applies a predetermined charging bias to the charging device 60 is connected to the control unit 500 via the I / O interface unit 505. The control unit 500 is connected to a development bias setting unit (development bias power source) 340 that applies a predetermined development bias to the development roller 61 a of the development device 61. Further, the control unit 500 has a primary transfer bias setting unit (primary transfer bias setting unit) that applies a predetermined primary transfer bias to the primary transfer device 62 (62S, 62Y, 62M, 62C, 62K) via the I / O interface unit 505. Bias power source) 350 is connected.

The control unit 500 is connected to an exposure setting unit (light source power source unit) 360 that applies a predetermined voltage to the light source of the exposure apparatus 21 or supplies a predetermined current. Further, a paper feeding device 200, a scanner 300, and an automatic document feeder 400 are connected to the control unit 500 via an I / O interface unit 505.
The control unit 500 controls each unit based on the control target value of the image forming condition.

  In the ROM 503 or the RAM 504, for example, a conversion table (not shown) that stores information related to conversion of the output value of the toner density sensor 312 to the toner adhesion amount per unit area is stored. The ROM 503 or the RAM 504 stores control target values of image forming conditions of the image forming units 18 (18S, 18Y, 18M, 18C, 18K) for each of a plurality of image forming modes in the copying machine according to the present embodiment. Yes. Examples of stored image forming conditions include a charging bias, a developing bias, an exposure amount, and a primary transfer bias.

  The control unit 500 may be configured using an IC or the like as a semiconductor circuit element manufactured for control in the copying machine 600, instead of a computer device such as a microcomputer.

  The control unit 500 configured as described above performs image density control, also called process control, at a predetermined timing. Predetermined timings include when the power is turned on, before starting the print job (before starting the image forming operation), after printing a predetermined number (500 sheets) (when the image forming operation is interrupted), after finishing the print job (ending the image forming operation) Timing) (timing exclusive from the image forming operation).

  In the image density control (potential control) of the copying machine 600, first, a plurality of pattern images having different toner adhesion amounts are formed using one or more image forming units 18. At this time, the potential of the electrostatic latent image of the pattern image is detected by the potential sensor 70, and the toner adhesion amount of the toner pattern of the pattern image transferred onto the intermediate transfer belt 10 is detected by the toner adhesion amount sensor 310. Further, the toner density sensor 312 detects the toner density in the developing device 61 in the one or more image forming units 18 at that time.

Based on the detection results, the control unit 500 charges the bias, the developing bias, and the exposure amount (applied voltage or applied current) so that the toner attached amount having a predetermined specific image density becomes a predetermined target attached amount. Then, control target values (image density conditions) for the toner density and the toner density are calculated. That is, the detection value of the toner adhesion amount of the toner pattern detected by the toner adhesion amount sensor 310 and the detection value of the toner density detected by the toner concentration sensor 312 are input to the control unit 500. Further, a detected value of the post-exposure surface potential of the photoconductor 40 detected by the potential sensor 70, a current developing bias value, and a target adhesion amount value are input. When these values are input, as the image density conditions, the charging target of the charging device 60, the developing bias of the developing device 61, and the exposure amount of the exposure device 21 (applied voltage or applied current of the exposure device), Then, the control target value of the toner density in the developing device 61 is output.
According to the optimum image density condition (control target value), a stable image density is provided by controlling the application bias and toner supply of each device during the subsequent image forming operation.

  Here, the image density control performed by the control unit 500 of the present embodiment is roughly divided into first image density condition determination control and second image density condition determination control. The first image density condition determination control is performed using the other image forming units 18 without using some of the five image forming units 18 (18S, 18Y, 18M, 18C, 18K). This is control for determining an image density condition using an imaged toner pattern. On the other hand, the second image density condition determination control is a determination control for determining an image density condition using a toner pattern formed using all of the five image forming units 18 (18S, 18Y, 18M, 18C, 18K). It is. At the time of the first image density condition determination control, the unused image forming units are stopped from being driven and separated from the intermediate transfer belt 10.

In this embodiment, five image forming units 18 (18S, 18Y, 18M) using five types of toners of transparent (S), yellow (Y), magenta (M), cyan (C), and black (K). , 18C, 18K). In such an image forming apparatus, it is possible to execute a single color mode, a two-color mode, a three-color mode, a four-color mode including a full-color mode, and a five-color mode that is a full-color + transparent mode.
In the monochrome mode, it is possible to form a toner image composed of only one of S, Y, M, C, and K toners. In the two-color mode, any one of S + Y, S + M, S + C, S + K, red, green, blue, K + Y, K + M, and K + C toner images can be formed. In the three-color mode, a toner image of any one of S + Y + M, S + Y + C, S + Y + K, S + M + C, S + M + K, S + C + K, Y + M + C, Y + M + K, Y + C + K, and M + C + K can be formed. In the four-color mode, a toner image of any one of S + Y + M + C, S + Y + M + K, S + Y + C + K, S + M + C + K, and Y + M + C + K (full color) can be formed. In the five-color mode, an S + Y + M + C + K (full color + transparent) toner image can be formed.
In the present embodiment, optimum image density conditions can be stored and set for each of these image forming modes.

The second image density condition determination control is performed at all timings such as when the power is turned on, after printing a predetermined number (500 sheets) (when the image forming operation is interrupted), after the end of the print job, among the predetermined timings described above. Color process control. If the print job is in the five-color mode before the start of the print job, the print job may be executed at a timing before the start of the print job.
The first image density condition determination control is image density control that is executed before the start of a print job other than the five-color mode.

  During the first image density condition determination control, the image density condition is calculated using another image forming unit 18 other than some unused image forming units 18. Specifically, the first image density condition which is the image density condition is calculated using the image forming unit 18 used in the image forming mode except for the five-color mode (S + Y + M + C + K). Then, the calculated first image density condition is recorded as an image density condition when an image is formed in the corresponding image forming mode. Thereby, in the subsequent image forming operation, image forming control is performed under the image density condition calculated using the same image forming unit 18 as the image forming unit 18 used in the image forming mode at the time of the image forming operation. . For example, the image density condition calculated by executing the first image density control using only the black image forming unit 18K and the transparent image forming unit 18S corresponding to K color (black) and S (transparent) is “KS”. It is recorded as an image density condition when an image is formed in the “two-color mode”. Then, it is used as an image density condition when an image is formed in the “KS two-color mode” immediately after the calculation.

On the other hand, during the second image density condition determination control, all the image forming units 18 (18S, 18Y, 18M, 18C, and 18K) are used. Therefore, the image density conditions calculated thereby are all color process control image density conditions ( The second image density condition) is recorded. Thus, when image formation is performed in the subsequent five-color mode, image formation control is performed using the all-color process control image density condition.
Even when image formation is performed in an image formation mode other than the five-color mode, if the first image density condition determination control is not executed before the execution of the image formation mode, all-color process control image density Image formation control is performed using conditions. Hereinafter, image forming modes other than the five-color mode are also referred to as “partially unused image forming modes”.

  Note that it is not always necessary to perform image density condition determination control corresponding to all image formation modes, and image density condition determination control may be omitted for some image formation modes. For example, an image formation mode that has little effect on image quality even when an image is formed under an image density condition that uses or corrects an image density condition that corresponds to another image formation mode, or an image formation mode that is used less frequently The image density condition determination control corresponding thereto may be omitted.

Next, features of the copying machine 600 according to the present embodiment will be described.
In the copying machine 600, when the drive of some image forming units 18 is stopped and a designated color printing command for image formation in a partially unused image forming mode for driving other image forming units 18 is received, A toner patch of the corresponding color used in the partially unused image forming mode is formed. A toner adhesion amount sensor 310 detects the toner adhesion amount of the toner patch. Then, based on the detection result, the control unit 500 executes process control (first image density condition determination control) in which only the image forming unit 18 used in the partially unused image forming mode is brought into contact with the intermediate transfer belt 10. It is determined whether or not. Only when it is determined that execution is necessary, first image density condition determination control is performed by driving only the image forming unit 18 used in the partially unused image forming mode, and the optimum in the partially unused image forming mode is executed. The image forming conditions are determined.

As a result of intensive studies by the present inventors, the reverse transfer rate fluctuates due to the influence of error factors such as the environment and individual differences of the image forming unit 18, and the influence of reverse transfer is not considered depending on the use environment. It turns out that there are good cases.
As described above, since the reverse transfer rate fluctuates due to the influence of the error factor, if the control is performed using a constant reverse transfer rate as in the prior application 1, the accuracy of the control is lowered.
Also, since the influence of reverse transfer may not be considered depending on the conditions, as in the prior application 2, the first image density condition determination control corresponding to all the partially unused image forming modes is executed. If this occurs, the amount of toner consumed increases and the waiting time of the user increases due to control.

On the other hand, in the copying machine 600 according to the present embodiment, it is determined whether or not the first image density condition determination control is necessary. If it is determined that the first image density condition determination control is necessary, the first image density condition determination control is performed. An optimum image forming condition in the unused image forming mode is determined. For this reason, when an image is formed in the image forming unit 18 under the same image forming conditions in the five-color mode and the partially unused image forming mode, even if the toner adhesion amount fluctuates due to the influence of reverse transfer, The image can be formed under image forming conditions suitable for the image forming mode.
Further, in the copying machine 600 of the present embodiment, it is determined whether or not the first image density condition determination control needs to be executed, and when it is determined that the execution is not necessary, that is, when the influence of the reverse transfer rate need not be considered. The first image density condition determination control is not executed, and the control is performed using the second image density condition. For this reason, compared with the invention described in the above-mentioned prior application 2, it is possible to suppress an increase in toner consumption and an increase in waiting time of the user due to control.

FIG. 4 is a flowchart showing an outline of the flow of image density control when receiving a designated color printing command which is image formation in the partially unused image forming mode in the copying machine 600.
In the copying machine 600, when a designated color printing command is issued (S1), only the photoreceptor 40 of the color used for image formation of the designated color (hereinafter referred to as “corresponding color”) is brought into contact with the surface of the intermediate transfer belt 10. The other color photoreceptors 40 are separated from the intermediate transfer belt 10. Then, only the image forming unit 18 of the corresponding color is driven (S2), and the image forming unit 18 positioned at the most upstream in the moving direction of the intermediate transfer belt 10 among the image forming units 18 of the corresponding color before printing is used. Image a toner patch for determination. The toner adhesion amount of the determination toner patch on the intermediate transfer belt 10 is detected by using the toner adhesion amount sensor 310 (S3).

Based on the detection result of the toner adhesion amount, the control unit 500 determines whether or not it is necessary to execute process control (first image density condition determination control) corresponding to the designated color printing (S4).
If the control unit 500 determines that the execution is not necessary (“No” in S4), the process control corresponding to the designated color printing is not executed. Then, designated color printing is started under the image density condition of the image forming unit 18 of the corresponding color under the all-color process control image density condition (the same image forming condition as in the five-color mode) (S7).
If the control unit 500 determines that execution is necessary (“Yes” in S4), process control corresponding to the designated color printing (first image density condition determination control) is executed (S5), and an appropriate image forming condition ( The first color density condition is changed (S6), and designated color printing is performed (S7).

FIG. 5 is a schematic diagram showing the positional relationship between the image forming unit 18 of each color and the intermediate transfer belt 10 as an example of the designated color printing described above.
In FIG. 5, as an example of designated color printing, an example of performing designated color printing in the KS two-color mode in which the corresponding color is transparent and black is shown, but even in other partially unused image forming modes, Similarly, the present invention can be applied.

In the copying machine 600, the second image density condition determination control is executed at the above-described predetermined timing such as when the power is turned on, and all color process control image density conditions (second image density conditions) are calculated and recorded in advance. Yes.
When the copier 600 receives a specified color printing command in the KS two-color mode, the transparent image forming unit 18S and the black image forming unit 18K corresponding to the corresponding colors of transparent and black, respectively. The body 40S and the black photoconductor 40K are brought into contact with the surface of the intermediate transfer belt 10. On the other hand, the other photoreceptors 40 (40Y, 40M, and 40C) are separated from the intermediate transfer belt 10. Then, only the transparent image forming unit 18S and the black image forming unit 18K are driven.

Before performing printing in the KS two-color mode, as shown in FIG. 5, the image forming unit 18S for transparent use, which is the most upstream of the image forming units 18 (18S, 18K) in contact with the photoreceptor 40, is used. Image a toner patch for determination. The image forming condition of the determination toner patch is that the image density condition is the all-color process control image density condition calculated by the previous all-color process control, and one patch is formed with a solid image.
The toner adhesion amount of the imaged determination toner patch is detected using the toner adhesion amount sensor 310. Based on the toner adhesion amount detected at this time, the controller 500 determines whether or not it is necessary to execute process control (designated color process control) using only the transparent photoconductor 40S and the black photoconductor 40K.

  In the designated color printing that drives the other image forming units 18 without driving some of the image forming units 18 by determining whether or not the specified color process control needs to be executed immediately before performing the designated color printing. The target image density can be obtained from the first sheet. In addition, when there are a plurality of image forming units 18 to be driven by the designated color printing, among the image forming units 18 to be driven, the toner for determination is determined by using the image forming unit 18 positioned at the most upstream in the moving direction of the intermediate transfer belt 10. Create a patch. Accordingly, the determination toner patch formed by the image forming unit 18 located at the most upstream position, which is easily affected by the reverse transfer generated at the position where the photoreceptor 40 of the downstream image forming unit 18 faces the intermediate transfer belt 10. Can be used for determination control. Therefore, it is possible to accurately determine whether or not to execute the designated color process control.

  Furthermore, since the determination toner patch is formed using the all-color process control image density condition calculated by the all-color process control, the adhesion amount can be obtained with high accuracy. In addition, since only one determination toner patch is created, it is possible to minimize the toner consumption and the waiting time of the user as compared with the case where the designated color process control is performed regardless of necessity. Furthermore, since the toner adhesion amount is detected by using a solid image toner patch as a determination toner patch, it is determined whether or not it is necessary to carry out the designated color process control in a state where there is less influence of dust and background stains than a halftone image. Can be done.

  In the above description, the control for detecting the toner adhesion amount of the determination toner patch using the toner adhesion amount sensor 310 used for detecting the toner adhesion amount of the pattern image during the process control has been described. As the toner adhesion amount detection means for detecting the toner adhesion amount of the determination toner patch, a toner adhesion amount detection means is provided separately from the toner adhesion amount sensor 310 as in the determination toner patch sensor 410 shown in FIG. Also good.

FIG. 6 is a flowchart showing a specific example of the necessity determination (S4) of the designated color process control in the flowchart shown in FIG. Steps indicated by “S4-1” and “S4-2” in FIG. 6 are examples of steps indicated by “S4” in FIG.
The control unit 500 of the copying machine 600 detects the toner adhesion amount of the determination toner patch described with reference to FIG. 5 (S3 in FIG. 4). Thereafter, a comparison is made between the detected toner adhesion amount A, which is the detected toner adhesion amount, and the target value B, which is a solid toner target adhesion amount of a predetermined corresponding color (transparent) (S4-1).
In this comparison, if the difference between the toner adhesion amount detection value A and the target value B is less than a certain threshold value α (“No” in S4-2), it is determined that execution of the designated color process control is unnecessary, and designated color printing is performed. Start (S7).
In the above comparison, if the difference between the toner adhesion amount detection value A and the target value B is greater than or equal to a certain threshold value α (“Yes” in S4-2), it is determined that the designated color process control needs to be executed. At this time, the designated color process control using the image forming section 18 (18S, 18K) of the corresponding color is executed (S5).

  The target value B is a predetermined target adhesion amount value used in process control. If the difference between the toner adhesion amount detection value A and the target value B of the determination toner patch is less than a certain threshold value α, the toner adhesion amount in the designated color printing is the target adhesion without executing the designated color process control. The range is close to the quantity. This state is a state in which the difference in image density and color between the all-color printing (the above five-color mode) and the designated color printing is suppressed.

  When the designated color process control is executed, at least one of the charging condition, exposure condition, developing condition, and transfer condition in the image forming unit 18 (18S, 18K) of the corresponding color is changed from the result of the designated color process control. Then, the image forming conditions for designated color printing are determined. After the image forming conditions for designated color printing are determined, designated color printing is started. By performing control only when the difference between the toner adhesion amount detection value A and the target value B is equal to or greater than a certain threshold value α, unnecessary waiting time and unnecessary toner consumption by the user can be reduced. Further, regardless of designated color printing or all color printing (five color mode), the image density can be maintained within a certain range near the target value.

  As described above, when the copier 600 receives a designated color printing command, it forms a toner patch requiring determination of the corresponding color, and the toner adhesion amount sensor 310 detects the toner adhesion amount. Then, based on the detection result, it is determined whether or not the designated color process control is to be executed. The designated color process control is executed only when necessary, and the optimum image forming conditions for the designated color printing are determined. Thus, since control is performed only when necessary, an increase in toner consumption and an increase in waiting time can be minimized as compared with the configuration of the prior application 2. In addition, since the designated color process control is performed when necessary, it is possible to obtain the image forming conditions suitable for the designated color printing corresponding to the higher accuracy than the configuration of the prior application 1.

What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
(Aspect A)
An image forming unit such as an image forming unit 18 that performs a transfer operation for transferring a toner image formed on an image carrier such as a photosensitive member 40 to the surface of a transfer target such as an intermediate transfer belt 10 that moves on the surface is transferred. A plurality of image forming units arranged in the body surface moving direction, and a part of the plurality of image forming units not performing the transfer operation, upstream of the part of the image forming unit in the moving direction of the transfer target surface A first image forming mode such as a single color mode, a two-color mode, a three-color mode, and a four-color mode, and a part of the image forming units and other image forming units. A plurality of image forming modes according to an image forming mode selected from a plurality of image forming modes including a second image forming mode such as a five-color mode for forming an image using two or more image forming units including One or more images selected from the part Control for image formation that forms a toner image based on image information on the image carrier of the image forming unit and transfers the toner image onto a transfer material or a recording material such as a transfer sheet P carried on the transfer material. In an image forming apparatus such as a copier 600 having an image formation control unit such as the unit 500, a toner adhesion amount detection unit such as a toner adhesion amount sensor 310 for detecting the adhesion amount of toner adhering to the transfer object; The first image density adjusting toner patch comprising a plurality of toner patches is formed on the transfer object using the other image forming unit in a state where the image forming unit is not performing the transfer operation. The first image density adjustment toner patch is detected by the toner adhesion amount detecting means, and the first image density condition is determined based on the toner adhesion amount detected by the toner adhesion amount detecting means. The first image density condition determination control such as color process control is performed, and a second image density adjustment toner patch composed of a plurality of toner patches is formed on the transfer medium using the two or more image forming units. All colors for detecting the toner adhesion amount of the second image density adjustment toner patch by the toner adhesion amount detection means and determining the second image density condition based on the toner adhesion amount detected by the toner adhesion amount detection means Image density condition determining means such as a control unit 500 for performing second image density condition determining control such as process control. When the first image forming mode is selected, the image forming control means In a state where some image forming units are not performing the transfer operation, the number is smaller than that of the first image density adjusting toner patches on the transfer medium using the other image forming units. An image of the determination toner patch is formed, and whether or not the first image density condition determination control is necessary is determined based on a detection result obtained by detecting the toner adhesion amount of the determination toner patch by the toner adhesion amount detection unit. When it is determined that the execution is necessary, the first image density condition determination control is performed, and the image control is performed with the first image density condition determined by the first image density condition determination control. In this case, image control is performed under the second image density condition determined by the second image density condition determination control.
According to this, as described in the above embodiment, it is possible to suppress an increase in toner consumption and an increase in waiting time while suppressing the occurrence of a difference in image density and color of the output image. Become. This is due to the following reason.
That is, in the first image forming mode, reverse transfer does not occur when a toner image formed using the other image forming unit passes through the partial image forming unit. On the other hand, in the second image forming mode, there is a possibility that reverse transfer occurs when a toner image formed using the other image forming unit passes through the part of the image forming unit. Therefore, when the same image density condition is used for the other image forming units between the first image forming mode and the second image forming mode, there is a difference in image density or color of the output image between them. May occur.
In this aspect, during the first image density condition determination control for determining the first image density condition, the partial image formation through which the first image density adjustment toner patch formed in the other image forming unit passes is performed. The part is not transferring. Therefore, the toner patch for adjusting the first image density is not affected by the reverse transfer in the part of the image forming unit, like the toner image in the first image forming mode. Therefore, by using the first image density condition as the image density condition in the first image forming mode, the image density and color tone in the first image forming mode can be aimed. This is because it is determined based on the toner adhesion amount of the first image density adjustment toner patch that is not affected by the reverse transfer in the partial image forming unit.
In addition, during the second image density condition determination control for determining the second image density condition, the part of the image forming unit through which the second image density adjusting toner patch formed in the other image forming unit passes is included. The transfer operation is performed. Therefore, the second image density adjustment toner patch is affected by reverse transfer in the part of the image forming unit, like the toner image in the second image forming mode. Therefore, by using the second image density condition as the image density condition in the second image forming mode, the image density and color in the second image forming mode can be aimed. This is because it is determined based on the toner adhesion amount of the second image density adjustment toner patch affected by the reverse transfer in the partial image forming unit.
However, as a result of extensive studies by the present inventors, the reverse transcription rate fluctuates due to the influence of error factors such as the environment, and depending on the use environment, the influence of reverse transcription may not be considered. I found out. As described above, when both the second image density condition determination control and the first image density condition determination control are executed even when it is not necessary to consider the influence of the reverse transfer, an increase in toner consumption or control by the user due to the control is performed. The problem of increased latency occurs.
In this aspect, when the first image forming mode is selected, a determination toner patch having a smaller number than the first image density adjustment toner patch is formed. Then, based on the detection result obtained by detecting the toner adhesion amount of the determination toner patch by the toner adhesion amount detection means, it is determined whether or not the first image density condition determination control is necessary. Similar to the toner image in the first image forming mode, the determination toner patch used in this determination is not affected by the reverse transfer in the part of the image forming units. An image of a toner image that has been formed based on the measurement value of the toner adhesion amount of the determination toner patch and the image density condition of the determination toner patch and has been affected by reverse transfer in the partial image forming unit. The toner adhesion amount is compared. If the value at the time of comparison is less than a certain threshold value such as the threshold value α, it is determined that the first image density condition determination control need not be performed as the case where the influence of reverse transfer need not be considered. On the other hand, if the comparison value is equal to or greater than a certain threshold value, it is determined that the first image density condition determination control is necessary as the case where it is necessary to consider the influence of reverse transfer.
If it is determined that execution is necessary, the first image density condition determination control is performed, and the image control is performed with the first image density condition determined in the first image density condition determination control. Image density and color can be targeted.
On the other hand, if it is determined that the execution is not necessary, it is not necessary to consider the influence of the reverse transfer in the part of the image forming unit. Therefore, the image control is performed using the second image density condition in the first image forming mode. However, the image density and color can be aimed. Further, when it is determined that the execution is unnecessary, it is not necessary to form a first image density adjustment toner patch including a plurality of toner patches having a larger number than the determination toner patch. For this reason, when it is not necessary to consider the influence of reverse transfer, it is possible to suppress an increase in toner consumption and an increase in waiting time as compared with the first image density condition determination control.
In the aspect A, since image control is performed under image density conditions suitable for the first image formation mode and the second image mode, a difference in image density and color of the output image occurs between these image formation modes. Suppress. Further, when it is not necessary to consider the influence of reverse transfer, it is possible to suppress an increase in toner consumption and an increase in waiting time.
For this reason, according to the aspect A, it is possible to suppress an increase in toner consumption and an increase in waiting time while suppressing a difference in image density and color of the output image.
(Aspect B)
In the aspect A, whether or not the first image density condition determination control such as the designated color process control is necessary is determined by the first image forming mode such as the single color mode, the two color mode, the three color mode, and the four color mode. Immediately before forming.
According to this, as described in the above embodiment, it is possible to determine whether or not it is necessary to execute the first image density condition determination control before the image formation in the first image formation mode. Therefore, when an image is formed in the first image forming mode, a target image density can be obtained from the first sheet.
(Aspect C)
In the aspect A or B, the first image forming mode such as the single-color mode, the two-color mode, the three-color mode, and the four-color mode includes two or more image forming units including other image forming units such as the transparent image forming unit 18S. Image forming unit (transparent image forming unit 18S, black image forming unit 18K, etc.), and the determination toner patch is one of two or more image forming units used in the first image forming mode. Then, an image is formed by using an image forming unit (transparent image forming unit 18S, etc.) located at the most upstream position in the moving direction of the surface of the transfer medium such as the intermediate transfer belt 10.
According to this, as described in the above embodiment, when the reverse transfer occurs, the determination is performed using the determination toner patch that is most easily affected by the reverse transfer and is formed using the most upstream image forming unit. Will do. Therefore, it is possible to accurately determine whether or not the first image density condition determination control such as the designated color process control is necessary.
(Aspect D)
In Aspects A to C, the determination toner patch has one patch, the image pattern is a solid image, and the all-color process control image density condition determined by the second image density condition determination control such as the all-color process control The second image density condition such as
According to this, as described in the above embodiment, since the determination toner patch is imaged under the same image density condition as the second image density condition, the adhesion amount can be obtained with high accuracy. In addition, since only one determination toner patch is created, an increase in toner consumption and an increase in the waiting time of the user can be minimized. Furthermore, since the determination toner patch is a solid image, it is determined whether or not the first image density condition determination control such as the designated color process control is necessary with less influence of dust and background stains than the halftone image. Can be done.
(Aspect E)
In any one of the aspects A to D, the determination as to whether or not the first image density condition determination control such as the designated color process control is performed is performed by detecting the toner adhesion amount detection value (toner adhesion amount detection) of the determination toner patch. If the difference between the target value such as the target value B and the target value B is less than a certain threshold value such as the threshold value α, it is determined that the first image density condition determination control is not necessary, In this case, it is determined that the first image density condition determination control is necessary.
According to this, as described in the above embodiment, the first image density condition determination control is performed when the difference between the detected value of the toner adhesion amount of the determination toner patch and the target value is equal to or greater than a certain threshold value. Thus, the image density can be maintained within a certain range near the target value.
(Aspect F)
In any of the aspects A to D, the plurality of image forming units such as the five image forming units 18 (18S, 18Y, 18M, 18C, and 18K) are charged by the charging device 60 that charges the image carrier such as the photoreceptor 40, respectively. A charging unit such as an exposure unit 21 that exposes the charged surface of the image carrier according to image information, and a developing unit 61 that develops the latent image formed on the image carrier by exposure with toner. And a transfer means such as a primary transfer device (primary transfer roller) 62 for transferring a toner image formed on the image carrier by development to a transfer target such as the intermediate transfer belt 10. The first image density condition and the second image density condition determined by the image density condition determining means such as the control unit 500 include at least one of charging conditions, developing conditions, exposure conditions, and transfer conditions in a plurality of image forming units. It is included in the conditions.
According to this, as described in the above embodiment, the optimum charging condition, exposure condition, developing condition, and transfer condition for each image forming mode can be determined, and the image density and color of the output image can be appropriately set. It can be aimed.
(Aspect G)
In any one of the aspects A to F, a plurality of image forming units such as the five image forming units 18 (18S, 18Y, 18M, 18C, and 18K) are formed on the image carrier such as the photoreceptor 40 by transparent toner. Includes a transparent image forming section such as a transparent image forming section 18S for transferring the transparent toner image formed on the transfer medium such as the intermediate transfer belt 10 to the transfer target, and is formed by the transparent image forming section. The toner image is configured to be transferred to the transfer medium before the toner image formed by another image forming unit such as the other four image forming units 18 (18Y, 18M, 18C, 18K). Yes.
According to this, as described in the above embodiment, in the image forming apparatus having such a configuration, it is possible to suppress the occurrence of a difference in image density or color of the output image between the image forming modes. .

10 intermediate transfer belt 14 first support roller 15 second support roller 16 third support roller 17 intermediate transfer belt cleaning device 18 image forming unit 18S transparent image forming unit 18K black image forming unit 20 tandem image forming unit 21 exposure device 22 Secondary transfer device 24 Secondary transfer belt 25 Fixing device 26 Fixing belt 27 Pressure roller 28 Sheet reversing device 30 Document table 32 Contact glass 33 First traveling member 34 Second traveling member 35 Imaging lens 36 Image reading sensor 40 Photosensitive member 40K black photoconductor 40S transparent photoconductor 42 paper feed roller 43 paper bank 44 paper feed cassette 45 separation roller 46 paper feed path 47 transport roller 49 registration roller pair 50 manual paper feed roller 51 manual feed tray 52 manual feed separation roller 53 manual feed Paper path 55 Switching claw 56 Discharge roller 57 Discharge tray 60 charging device 61a developing roller 61 developing device 62 primary transfer device 63 photoconductor cleaning device 70 potential sensor 100 printer unit 170 secondary transfer belt cleaning device 200 paper feeding device 300 scanner 310 toner adhesion amount sensor 311 backup roller 312 toner density sensor 400 Automatic document feeder 410 determination toner patch sensor 500 control unit 501 CPU
502 Bus line 503 ROM
504 RAM
505 Interface unit 600 Copying machine L Writing light P Transfer sheet

JP 2005-157145 A

Claims (7)

A plurality of image forming portions that perform a transfer operation for transferring the toner image formed on the image carrier to the surface of the transfer target surface that moves on the surface are arranged in the transfer target surface movement direction,
Other image forming units located on the upstream side in the moving direction of the transfer target surface with respect to some of the image forming units in a state in which some of the plurality of image forming units are not performing the transfer operation A first image forming mode for forming an image using
A second image forming mode for forming an image using two or more image forming units including the part of the image forming unit and the other image forming unit;
In accordance with an image forming mode selected from a plurality of image forming modes including
Forming a toner image based on image information on an image carrier of one or more image forming units selected from the plurality of image forming units;
In an image forming apparatus having an image formation control means for performing image formation control for transferring the toner image onto the transfer body or a recording material carried on the transfer body.
A toner adhesion amount detecting means for detecting the adhesion amount of the toner adhering to the transfer object;
Forming a first image density adjustment toner patch composed of a plurality of toner patches on the transfer object using the other image forming unit in a state where the partial image forming unit is not performing a transfer operation; A first image in which a toner adhesion amount of the first image density adjustment toner patch is detected by the toner adhesion amount detection unit, and a first image density condition is determined based on the toner adhesion amount detected by the toner adhesion amount detection unit While implementing concentration condition determination control,
A second image density adjustment toner patch comprising a plurality of toner patches is formed on the transfer medium using the two or more image forming units, and the toner adhesion amount of the second image density adjustment toner patch is set as described above. Image density condition determining means for performing second image density condition determination control for detecting the toner adhesion amount detecting means and determining the second image density condition based on the toner adhesion amount detected by the toner adhesion amount detecting means; Have
The image formation control means performs the second image density condition determination control at a predetermined timing,
When the second image mode is selected, image control is performed with the second image density condition determined in the second image density condition determination control,
When the first image forming mode is selected, the first image density adjustment is performed on the transfer medium using the other image forming unit in a state where the part of the image forming units is not performing a transfer operation. A determination toner patch having a smaller number than the toner patch is formed, and the first image density condition determination control is performed based on a detection result obtained by detecting the toner adhesion amount of the determination toner patch by the toner adhesion amount detection unit. Determine the necessity of implementation,
If it is determined that implementation is necessary, the first image density condition determination control is performed, and the image control is performed with the first image density condition determined in the first image density condition determination control.
An image forming apparatus characterized by performing image control under the second image density condition determined by the second image density condition determination control when it is determined that implementation is unnecessary. The image forming apparatus according to claim 1.
The determination as to whether or not the first image density condition determination control is necessary is immediately before forming an image in the first image forming mode. The image forming apparatus according to claim 1 or 2,
In the first image forming mode, image formation is performed using two or more image forming units including the other image forming unit.
The determination toner patch is formed using an image forming unit located at the most upstream in the moving direction of the surface of the transfer object, of two or more image forming units used in the first image forming mode. Image forming apparatus. The image forming apparatus according to any one of claims 1 to 3,
The determination toner patch has one patch, and the image pattern is solid, and an image is formed under the second image density condition determined by the second image density condition determination control. apparatus. The image forming apparatus according to claim 1,
Whether or not the first image density condition determination control is necessary is determined when the difference between the detection value of the toner adhesion amount of the determination toner patch and the target value is less than a certain threshold value, An image forming apparatus, characterized in that it is determined that the execution of the density condition determination control is unnecessary, and that it is determined that the execution of the first image density condition determination control is necessary when the predetermined threshold value is exceeded. The image forming apparatus according to claim 1,
Each of the plurality of image forming units includes a charging unit that charges the image carrier, an exposure unit that exposes a charged surface of the image carrier according to image information, and the image carrier by the exposure. Developing means for developing the formed latent image with toner, and transfer means for transferring the toner image formed on the image carrier by the development to the transfer target,
The first image density condition and the second image density condition determined by the image density condition determining unit include at least one of charging conditions, developing conditions, exposure conditions, and transfer conditions in the plurality of image forming units. An image forming apparatus. The image forming apparatus according to claim 1,
The plurality of image forming units include a transparent image forming unit that transfers a transparent toner image formed on the image carrier with transparent toner to the transfer target,
An image characterized in that the transparent toner image formed by the transparent image forming unit is transferred to the transfer target before the toner image formed by another image forming unit. Forming equipment.

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