Image forming apparatus

Abstract

To compare densities of intermediate gradation of toner images of the same color formed by different image forming sections.SOLUTION: An image forming apparatus 10 includes a first image forming unit 30 and a second image forming unit 50, a secondary transfer unit 74 that is provided corresponding to the first image forming unit 30 and secondarily transfers a toner image of an intermediate transfer body 40 to a recording paper P, a secondary transfer unit 76 that is provided corresponding to the second image forming unit 50 and secondarily transfers a toner image of the intermediate transfer body 60 to the recording paper P, and a CPU. The CPU, when receiving an instruction to output a black color chart, executes a mode in which a color chart of a correction patch image having a density of intermediate gradation formed by an image forming unit 32K and an image forming unit 52K is secondarily transferred to the recording paper P and output.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD

[0001] The present invention relates to an image forming apparatus. BACKGROUND ART

[0002] Patent Document 1 discloses a technology relating to an image forming apparatus used in electrophotographic copying machines, printers and the like. In this prior art, the density measurement result of a reference patch obtained by an optical sensor is compared with a target value of the reference patch for toner supply control to control toner supply to a developing device, and when the density measurement result of the reference patch obtained by the optical sensor is compared with a target value of the reference patch for gradation control to control image forming conditions that affect a formed image, only the target value of the reference patch for toner supply control is changed in accordance with a measurement result obtained by a counter that counts the number of printed sheets using developer.

[0003] Patent Document 2 discloses a technology relating to a color image forming apparatus. In this prior art, the color balance of a first color image forming apparatus is adjusted to match the color balance of a second color image forming apparatus.

[0004] Patent Document 3 discloses a technology relating to an image forming apparatus including an image forming unit capable of forming an image on paper, an image reading unit capable of reading an image output from the image forming unit, and capable of calculating information from the image reading unit to perform gradation correction for the image forming unit. In this prior art, the image forming apparatus comprises a control unit that changes the degree of influence of paper reflectance depending on gradation to perform correction to obtain predetermined gradation characteristics. PRIOR ART DOCUMENTS PATENT DOCUMENTS

[0005] Patent Document 1 Japanese Unexamined Patent Publication No. 2001-066837 Patent Document 2 Japanese Patent No. 3020987 Patent Document 3 Patent No. 5665782 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] In an image forming apparatus having multiple image forming units, each having an intermediate transfer body onto which toner images formed by multiple image forming units are primary transferred, and which secondary transfers the toner images of these intermediate transfer bodies to a recording medium, if different image forming units have image forming units of the same color, the toner images cannot be compared to each other even if there are differences in the density of intermediate tones between toner images of the same color.

[0007] In view of the above facts, the present invention aims to provide an image forming apparatus having a plurality of image forming units, each having an intermediate transfer body to which toner images formed by a plurality of image forming units are primary transferred, and which secondary transfers the toner images of the intermediate transfer bodies of these plurality of image forming units onto a recording medium, in which the density of intermediate tones of toner images of the same color formed by different image forming units can be compared. [Means for solving the problem]

[0008] The first embodiment includes a plurality of image forming units, and a toner image formed by the plurality of image forming units is first transformed photo The image forming apparatus comprises: a plurality of image forming units each having an intermediate transfer body; a plurality of secondary transfer units provided corresponding to each of the plurality of image forming units for secondary transfer of the toner image of the intermediate transfer body to a recording medium; and a processor, wherein different image forming units have image forming units of the same color, and when the processor receives an instruction to output a color chart of the same color, it executes a mode in which it secondary transfers and outputs the color chart of the toner image of the intermediate gradation density formed by the image forming unit of the same color to the recording medium for each image forming unit.

[0009] The second embodiment is the image forming apparatus according to the first embodiment, wherein the mode forms and outputs the color chart on a single recording medium.

[0010] The third embodiment is an image forming apparatus according to the second embodiment, wherein the rows of toner images of intermediate densities formed for each image forming unit constituting the color chart are arranged side by side on a single recording medium.

[0011] The fourth embodiment is an image forming apparatus according to any one of the first to third embodiments, wherein the mode receives input of the target density to be adjusted in the density of the intermediate tones of the color chart and the reference image forming unit after outputting the color chart.

[0012] The fifth aspect is an image forming apparatus according to the fourth aspect, wherein the mode performs a correction to match the density of the toner image of the same color at the target density formed by a reference image forming unit to the density of the toner image of the same color formed by another image forming unit.

[0013] The sixth embodiment is an image forming apparatus according to the fourth embodiment, comprising a detection device for detecting the density of the toner image, wherein the mode forms a reference patch image of the target density of the reference image forming unit and a target patch image of the target density of another image forming unit and has the detection device detect them, a plurality of target patch images with different densities from the target density are formed in the other image forming unit based on the density difference between the two and have the detection device detect them, and the input density of the target density when the image forming section of the same color of the other image forming unit forms the toner image is read as the input density of the target patch image with the closest density to the reference patch image.

[0014] The seventh aspect is an image forming apparatus according to the sixth aspect, wherein the mode changes the density of the target patch image and reshapes it until the density difference between the reference patch image and the target patch image with the closest density falls within a predetermined range.

[0015] According to an eighth aspect, the image forming apparatus according to the fifth aspect is configured such that, in the mode, after receiving an input of the target density and the reference image forming unit, the color chart is secondarily transferred onto the recording medium and output again. [Effects of the Invention]

[0016] In the image forming apparatus according to the first aspect, compared to a case where a same-color color chart is not secondarily transferred onto a recording medium and output, it is possible to make the halftone densities of same-color toner images comparable.

[0017] In the image forming apparatus according to the second aspect, compared to a case where a same-color color chart is divided into a plurality of recording media, secondarily transferred and output, it is possible to accurately compare the halftone densities of same-color toner images.

[0018] In the image forming apparatus according to the third aspect, compared to a case where toner images forming a same-color color chart are output in a single row, it is possible to accurately compare the halftone densities of same-color toner images.

[0019] In the image forming apparatus according to the fourth aspect, compared to a case where only the target density is input, it is possible to uniform the halftone densities of same-color toner images.

[0020] In the image forming apparatus according to the fifth aspect, compared to a case where no correction is performed, it is possible to uniform the halftone densities of same-color toner images.

[0021] In the image forming apparatus according to the sixth aspect, compared to a case where the input density is not re-read, it is possible to uniform the halftone densities of same-color toner images.

[0022] In the image forming apparatus according to the seventh aspect, compared to a case where a target patch image is not re-formed, it is possible to more accurately uniform the halftone densities of same-color toner images.

[0023] In the image forming apparatus according to the eighth aspect, compared to a case where a color chart of the same color is not secondarily transferred onto a recording medium and output again, it can be easily confirmed that the halftone densities of toner images of the same color are aligned. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] [Figure 1] FIG. 1 is a configuration diagram of an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 1 is a partially enlarged view thereof. [Figure 3] FIG. 2 is a block diagram showing an example of the hardware configuration of the image forming apparatus. [Figure 4] FIG. 3 is a schematic diagram schematically showing a configuration of a main part of the image forming apparatus according to the first embodiment. [Figure 5] FIG. 4 is a block diagram showing an example of a functional configuration of a control device. [Figure 6] FIG. 5 is a diagram showing an example of a color chart. [Figure 7] FIG. 6 is a graph illustrating an example of a relationship between input density and output density. [Figure 8] FIG. 7 is a graph illustrating an example of a LUT for reinterpreting input values. [Figure 9] FIG. 8 is a flowchart showing a flow of density correction mode. [Figure 10] FIG. 9 is a flowchart showing a flow of image formation. MODE FOR CARRYING OUT THE INVENTION

[0025] <Embodiment> An image forming apparatus according to an embodiment of the present invention will be described.

[0026] In Figure 1, the width direction of the image forming apparatus 10 is denoted as the X direction, the height direction as the Y direction, and the depth direction as the Z direction, indicated by arrows X, Y, and Z, respectively. When it is necessary to distinguish between one side and the other side in the X, Y, and Z directions, the right side of the image forming apparatus 10 shown in Figure 1 is described as the +X side, the left side as the -X side, the top side as the +Y side, the bottom side as the -Y side, the front side as the +Z side, and the rear side as the -Z side. In this embodiment, recording paper P is used as an example of a recording medium, and the upstream side in the transport direction in which the recording paper P is transported is called the "transport direction upstream side," and the downstream side in the transport direction is called the "transport direction downstream side." In this embodiment, the image forming apparatus 10 is a so-called single-pass system, and printing is performed by the recording paper P passing in front of the first image forming unit 30 and the second image forming unit 50, which will be described later, only once each.

[0027] [Overall structure] First, I will explain the overall configuration of the image forming apparatus.

[0028] As shown in Figure 1, the image forming apparatus 10 includes an operation panel 95, a storage unit 12 for storing recording paper P as an example of a recording medium, a transport unit 11 for transporting the recording paper P along a transport path 19, and a first image forming unit 30 and a second image forming unit 50 for forming a toner image to be transferred to the recording paper P. A toner image is an image formed using toner as an example of a colorant such as a developer.

[0029] The storage section 12 is retractable from the main body 10A of the image forming apparatus 10, and stores the recording paper P inside.

[0030] The transport unit 11 is equipped with, in order from the upstream side in the transport direction, a discharge roll 13, a transport roll 14, a pair of resist rolls 15, a transport belt device 20, a fixing device 18, and a discharge roll 17, etc.

[0031] The discharge roll 13 sends the recording paper P stored in the storage unit 12 to the transport path 19 that constitutes the transport unit 11. The transport roll 14 transports the recording paper P along the transport path 19.

[0032] The resist roll pair 15 transports the recording paper P, which has been transported by the transport roll 14, to the upstream secondary transfer position TJ2, which will be described later. In this resist roll pair 15, the pinch roll 15B rotates in accordance with the resist roll 15A. The resist roll pair 15 then sandwiches the recording paper P between the resist roll 15A and the pinch roll 15B and transports the recording paper P downstream in the transport direction.

[0033] The conveyor belt device 20 transfers the toner image formed by the first image forming unit 30 and the second image forming unit 50 to the recording paper P, while conveying the recording paper P downstream in the conveying direction along the conveying path 19. Details of the conveyor belt device 20 will be described later.

[0034] The fixing device 18 has a pair of fixing rolls 16, and heats and pressurizes the recording paper P on which the toner image has been transferred as it passes between the pair of fixing rolls 16, thereby fixing the toner image to the recording paper P.

[0035] The discharge roll 17 discharges the recording paper P, on which the toner image has been fixed by the fixing device 18, to the discharge unit 9.

[0036] The first image forming unit 30 and the second image forming unit 50 are arranged side by side in the vertical direction. In this embodiment, the second image forming unit 50 is positioned above the first image forming unit 30. From another perspective, the second image forming unit 50 is positioned downstream of the first image forming unit 30 in the transport direction.

[0037] As shown in Figure 2, the first image forming unit 30 comprises four image forming sections 32 and an endless intermediate transfer belt 40 as an example of an intermediate transfer body. The intermediate transfer belt 40 is mounted so as to be rotatable counterclockwise when viewed from the front in Figure 2, and onto which the toner image formed by the four image forming sections 32 is transferred.

[0038] The image forming unit 32 comprises an image forming unit 32K that forms a black toner image, an image forming unit 32M that forms a magenta toner image, an image forming unit 32C that forms a cyan toner image, and an image forming unit 32Y that forms a yellow toner image. These four image forming units 32 are arranged in the order of image forming unit 32Y, image forming unit 32M, image forming unit 32C, and image forming unit 32K, starting from the upstream side (closer to the support roll 44 described later) in the direction of rotation of the intermediate transfer belt 40. Hereafter, the upstream side in the direction of rotation of the intermediate transfer belt 40 will be referred to as the "upstream side in the direction of rotation," and the downstream side in the direction of rotation will be referred to as the "downstream side in the direction of rotation." In other words, in the image forming unit 32, the image forming unit 32Y is located on the furthest downstream side in the direction of rotation.

[0039] Note that Y, M, C, and K are omitted in descriptions where it is not necessary to distinguish between them.

[0040] The image forming unit 32 includes a photoreceptor 33, a charging member 34 that charges the surface of the photoreceptor 33, an exposure device 35 that irradiates the charged photoreceptor 33 with exposure, and a developing device 36 that develops the electrostatic latent image formed by the exposure and visualizes it as a toner image.

[0041] The developing apparatus 36 has developing rolls 39Y, 39M, 39C, and 39K, and each has a developing bias applied by the power supply unit 159 (see Figure 3).

[0042] Furthermore, primary transfer rolls 37Y, 37M, 37C, and 37K are positioned opposite each photoreceptor 33 across the intermediate transfer belt 40 to transfer the toner image formed by the image forming unit 32 to the intermediate transfer belt 40. The intermediate transfer belt 40 is wrapped around a support roll 44 that supports the intermediate transfer belt 40 and a backup roll 42 that is positioned in the upstream secondary transfer unit 74, which will be described later. The primary transfer unit 70 is composed of the photoreceptor 33, the primary transfer rolls 37, and the intermediate transfer belt 40. The positions between the photoreceptors 33Y, 33M, 33C, and 33K and the intermediate transfer belt 40 are designated as primary transfer positions TY1, TM1, TC1, and TK1A, respectively.

[0043] The second image forming unit 50 has a similar configuration to the first image forming unit 30 described above, except that the colors it forms images of differ slightly. The second image forming unit 50 comprises four image forming sections 52 and an endless intermediate transfer belt 60 as an example of an intermediate transfer body. The intermediate transfer belt 60 is mounted so as to be rotatable counterclockwise when viewed from the front in Figure 2, and onto which the toner image formed by the four image forming sections 52 is transferred.

[0044] The image forming unit 52 has the same configuration as the image forming unit 32 of the first image forming unit 30. The intermediate transfer belt 60 and the primary transfer roll 57 (described later) also have the same configuration as the intermediate transfer belt 40 and primary transfer roll 37 of the first image forming unit 30. Furthermore, the other components constituting the second image forming unit 50 are the same as those of the first image forming unit 30.

[0045] The image forming unit 52 includes an image forming unit 52K that forms a black toner image, an image forming unit 52G that forms a gold toner image, an image forming unit 52S that forms a silver toner image, and an image forming unit 52W that forms a white toner image. The four image forming units 52 are arranged in the following order from the upstream side in the rotation direction, which in this example is closer to the support roll 64: image forming unit 52W, image forming unit 52S, image forming unit 52G, and image forming unit 52K. In other words, in the image forming unit 52, image forming unit 52K is located furthest downstream in the rotation direction, image forming units 52G and 52S are located upstream of image forming unit 52K in the rotation direction, and image forming unit 52W is located furthest upstream in the rotation direction.

[0046] Note that W, S, G, and K are omitted in descriptions where it is not necessary to distinguish between them.

[0047] The image forming unit 52 includes a photoreceptor 53, a charging member 54, an exposure device 55, and a developing device 56.

[0048] The developing apparatus 56 has developing rolls 59W, 59S, 59G, and 59K, and each has a developing bias applied by the power supply unit 159 (see Figure 3).

[0049] Furthermore, primary transfer rolls 57W, 57S, 57G, and 57K are positioned opposite each photoreceptor 53 across the intermediate transfer belt 60. The intermediate transfer belt 60 is wound around a support roll 64 and a backup roll 62 located in the downstream secondary transfer section 76, which will be described later. The primary transfer section 72 is composed of the photoreceptors 53, the primary transfer rolls 57, and the intermediate transfer belt 60. The positions between the photoreceptors 53Y, 53M, 53C, and 53W and the intermediate transfer belt 60 are designated as primary transfer positions TW1, TS1, TG1, and TK1B, respectively.

[0050] As shown in Figure 4, the developing units 36 of each color image forming section 32 of the first image forming unit 30 and the developing units 56 of each color image forming section 52 of the second image forming unit 50 are connected via supply paths 102 and 112 to a plurality of toner cartridges 100 and 110, each containing toner corresponding to a specific color. The toner contained in each toner cartridge 100 and 110 is supplied to the developing units 36 and 56 of each color via the supply paths 102 and 112 as needed by the operation of a supply device 120 (see Figure 3) provided in the supply paths 102 and 112. The supply device 120 (see Figure 3) is configured to supply toner individually from toner cartridges 100Y, 100M, 100C, 100K, 110W, 110S, 110G, and 110K to the developing units 36Y, 36M, 36C, 36K, 56C, 56W, 56G, and 56K, respectively.

[0051] [Details of the conveyor belt system] Next, we will describe the details of the conveyor belt device 20.

[0052] As shown in Figure 2, the conveyor belt device 20 is composed of an endless conveyor belt 21, support rolls 22 and 23 that support the conveyor belt 21, a conveyor roll 14, and secondary transfer rolls 24 and 25 positioned opposite the backup rolls 42 and 62, with the intermediate transfer belts 40 and 60 in between.

[0053] The secondary transfer roll 24 transfers the toner image formed on the intermediate transfer belt 40 of the first image forming unit 30 to the recording paper P, with the recording paper P and the transport belt 21 sandwiched between it and the backup roll 42. Similarly, the secondary transfer roll 25 transfers the toner image formed on the intermediate transfer belt 60 of the second image forming unit 50 to the recording paper P, with the recording paper P and the transport belt 21 sandwiched between it and the backup roll 62.

[0054] The secondary transfer section 74 includes a backup roll 42, a secondary transfer roll 24, and an intermediate transfer belt 40. The secondary transfer section 76 includes a backup roll 62, a secondary transfer roll 25, and an intermediate transfer belt 60.

[0055] Transfer biases are applied to the secondary transfer rolls 24 and 25 by the power supply unit 159 (see Figure 3).

[0056] Furthermore, the space between the intermediate transfer belt 40 and the transport belt 21 of the first image forming unit 30 is designated as the secondary transfer position TJ2, and the space between the intermediate transfer belt 60 and the transport belt 21 of the second image forming unit 50 is designated as the secondary transfer position TK2. Note that the secondary transfer position TK2 is the furthest downstream secondary transfer position.

[0057] Furthermore, the conveyor belt device 20 is equipped with a belt cleaning device (not shown) for cleaning the conveyor belt 21. The belt cleaning device (not shown) performs cleaning on the upstream side in the rotational direction of the furthest downstream secondary transfer position TK2 and on the downstream side in the rotational direction of the furthest upstream secondary transfer position TJ2. The position on the conveyor belt 21 that is cleaned by the belt cleaning device (not shown) is referred to as the cleaning position CL.

[0058] Here, each image forming section 32 of the first image forming unit 30 and each image forming section 52 of the second image forming unit 50 form a color chart 300 (see Figure 6) consisting of an automatic adjustment patch image for automatically adjusting the density and correction patch images 312A, 312B, 312C, 312D, 312E, 322A, 322B, 322C, 322D, and 322E, which will be described later, using each color toner. Hereafter, the correction patch images 312A, 312B, 312C, 312D, 312E, 322A, 322B, 322C, 322D, and 322E may be referred to as correction patch images 312 and 322.

[0059] As shown in Figure 4, a density sensor 150, which is an example of a detection device for detecting the density of the automatic adjustment patch image and correction patch image 312, 322 that have been secondarily transferred to the conveyor belt 21, is provided near the upper end of the conveyor belt 21. The density sensor 150 detects the density of the automatic adjustment patch image and correction patch image 312, 322 downstream of the furthest downstream secondary transfer position TK2, in the flat section 21Q between the secondary transfer position TK2 and the upper support roll 23 around which the conveyor belt 21 is wound.

[0060] The concentration sensor 150 should be positioned so as to be able to detect the concentrations of the automatic adjustment patch image and the correction patch images 312A, 312B, 312C, 312D, 312E, 322A, 322B, 322C, 322D, 322E, both upstream of the rotation direction of the downstream secondary transfer position TK2 and upstream of the rotation direction of the cleaning position CL.

[0061] The operation panel 95 of this embodiment shown in Figure 1 is a display with a touch panel superimposed on it, but is not limited to this. The operation panel 95 displays icon images as an example of images representing items that the user will operate on to perform a desired function. There are no restrictions on the type of icon image as long as it is something that the user will operate on, and icon images include, for example, buttons, scroll bars, checkboxes, and radio buttons. When the user operates on an icon image, a pre-associated process for the operation content is executed by the control device 80 (see Figure 3), which will be described later, and the response to the operation is displayed on the operation panel 95.

[0062] [Control device] Next, we will describe the control device 80 that controls the operation of the image forming apparatus 10.

[0063] Figure 3 is a block diagram showing the hardware configuration of the image forming apparatus 10. As shown in Figure 3, the control device 80 is electrically connected to the first image forming unit 30, the second image forming unit 50, the communication unit 90, the non-volatile memory 92, the supply device 120, the power supply device 159, the density sensor 150, and the operation panel 95, among others.

[0064] The control unit 80 has a CPU 81 (Central Processing Unit), ROM 82 (Read Only Memory), RAM 83 (Random Access Memory), and input / output interface (I / O) 84 connected via a bus. The CPU 81 is an example of a processor.

[0065] Here, ROM82 stores an image formation control program (not shown) to be executed by CPU81. The CPU81 then reads the image formation control program (not shown) from ROM82 and loads it into RAM83, thereby executing printing and other processes based on the image formation control program (not shown).

[0066] Furthermore, the I / O 84 is connected to the first image forming unit 30, the second image forming unit 50, the communication unit 90, and the non-volatile memory 92. The communication unit 90 is an interface for data communication between the image forming apparatus 10 and a terminal device such as a personal computer (not shown). The non-volatile memory 92 stores information necessary for the image forming apparatus 10 to perform image forming operations and the like.

[0067] The control device 80 performs various controls to form toner images on the intermediate transfer belt 40 (see Figure 2, etc.) using the image forming sections 32 (see Figure 2, etc.) of each color of the first image forming unit 30. Similarly, the control device 80 performs various controls to form toner images on the intermediate transfer belt 60 (see Figure 2, etc.) using the image forming sections 52 (see Figure 2, etc.) of each color of the second image forming unit 50.

[0068] Furthermore, the control device 80 controls the development bias applied to the development rolls 39Y, 39M, 39C, 39W, 59T, 59S, 59G, and 59K (see Figure 2, etc.) of the development units 36 and 56 by the power supply unit 159. In addition, the control device 80 controls the transfer bias applied to the secondary transfer rolls 24 and 25 (see Figure 2, etc.) by the power supply unit 159.

[0069] Furthermore, the control device 80 uses the supply device 120 to control the supply timing and supply amount of toner for each color toner supplied to the toner cartridges 100Y, 100M, 100C, 100K, 110W, 110S, 110G, 110K (see Figure 3) and the developing devices 36Y, 36M, 36C, 36K, 56W, 56S, 56G, 56K (see Figure 2, etc.).

[0070] Furthermore, the control device 80 performs two modes: one in which the density of the toner image is automatically adjusted (as described later), and another in which the user corrects the density.

[0071] Figure 5 is a block diagram showing an example of the functional configuration of the control device 80.

[0072] The control device 80 is configured as having a first control unit 810 and a first controller unit 830 for the first image forming unit 30, and a second control unit 820 and a second controller unit 850 for the second image forming unit 50.

[0073] The first control unit 810 and the second control unit 820 each have patch output units 812 and 822 and patch control units 814 and 824, respectively. The first controller unit 830 and the second controller unit 850 each consist of input receiving units 832 and 852, patch calculation units 834 and 854, density calculation units 836 and 856, LUT calculation units 838 and 858, and LUT storage units 839 and 859, respectively. "LUT" is an abbreviation for lookup table, which is a mathematical formula that defines the density adjustment of an image.

[0074] The input receiving units 832 and 852 have the function of sharing information input from the operation panel 95 between the first controller unit 830 and the second controller unit 850. They also have the function of passing information input from the operation panel 95 to the patch calculation units 834 and 854.

[0075] The patch calculation units 834 and 854 have the function of identifying the density to be corrected in the correction patch images 312 and 322 in the color chart 300 (see Figure 6), which will be described later, and requesting the patch control units 814 and 824 to output and calculate the correction patch image for the identified density.

[0076] The density calculation units 836 and 856 have the function of calculating the density of the correction patch image and requesting the LUT calculation units 838 and 858 to create a replacement LUT that reads the input values ​​described later. Furthermore, density information is shared between the density calculation unit 836 and the density calculation unit 856.

[0077] The LUT calculation units 838 and 858 have the function of creating replacement LUTs. The LUT storage units 839 and 859 have the function of saving the replacement LUTs created by the LUT calculation units 838 and 858.

[0078] The patch control units 814 and 824 have the function of sending density information of the correction patch image received from the patch calculation units 834 and 854 to the patch output units 812 and 824. In addition, the patch control units 814 and 824 receive density information of the density patch image detected from the density sensor 150 (see Figure 2) and pass the density information of the correction patch image to the density calculation units 836 and 856. The patch output units 812 and 822 have the function of forming and outputting a correction patch image based on the density information sent from the patch control units 814 and 824.

[0079] [Image forming process] Next, an overview of the image forming process in the image forming apparatus 10 will be described.

[0080] First, the CPU 81 of the control device 80 controls each image forming unit 32 so that a toner image is formed on the intermediate transfer belt 40 of the first image forming unit 30. Similarly, it controls each image forming unit 52 so that a toner image is formed on the intermediate transfer belt 60 of the second image forming unit 50.

[0081] Specifically, the CPU 81 applies a voltage to the charged members 34 and 54, and the charged members 34 and 54 charge the surfaces of the photoreceptors 33 and 53 to a predetermined potential. Subsequently, the control device 80, based on the image data acquired via the communication unit 90, irradiates the surfaces of the photoreceptors 33 and 53, which have been charged by the charged members 34 and 54, with exposure devices 35 and 55 to form an electrostatic latent image. As a result, an electrostatic latent image corresponding to the image data is formed on the surfaces of the photoreceptors 33 and 53.

[0082] Next, the CPU 81 develops the electrostatic latent image formed by the exposure devices 35 and 55 using the developing devices 36 and 56, and visualizes it as a toner image. Furthermore, the control device 80 uses the primary transfer rolls 37 and 57 to transfer the toner images formed on the surfaces of the photoreceptors 33 and 53 of each color onto the intermediate transfer belts 40 and 60.

[0083] In this way, the first image forming unit 30 forms a toner image on the intermediate transfer belt 40 by superimposing toners such as yellow (Y), magenta (M), cyan (C), and black (K). Similarly, the second image forming unit 50 forms a toner image on the intermediate transfer belt 60 by superimposing toners such as black (K), gold (G), silver (S), and white (W).

[0084] Here, the recording paper P, which has been sent from the storage unit 12 to the transport path 19 by the delivery roll 13, is sent to the secondary transfer position TJ2 upstream in the transport direction after the transport timing is adjusted by the register roll pair 15 based on the control of the control device 80. At this secondary transfer position TJ2, the recording paper P is transported between the backup roll 42 and the secondary transfer roll 24, and the toner image on the outer surface of the intermediate transfer belt 40 is transferred to the recording paper P. Then, the recording paper P with the transferred toner image is transported downstream in the transport direction to the secondary transfer position TK2 downstream in the transport direction.

[0085] At this time, the CPU 81 adjusts the timing of starting image formation so that the toner image formed on the intermediate transfer belt 60 of the second image forming unit 50 is superimposed and transferred onto the toner image on the recording paper P that has been transported from the upstream side in the transport direction.

[0086] The recording paper P, on which the toner images of each color formed by the first image forming unit 30 and the second image forming unit 50 are superimposed and transferred, is fixed by the fixing roll pair 16 of the fixing device 18, and then discharged by the discharge roll 17 to the discharge section 9 located at the top of the main body 10A of the image forming device.

[0087] [Automatic concentration adjustment] Next, I will explain the automatic adjustment of concentration.

[0088] The CPU 81 of the control device 80 forms automatic adjustment patch images for each color, transfers them to the conveyor belt 21, and has the density sensor 150 detect the transferred automatic adjustment patch images. In this embodiment, the densities of the automatic adjustment patch images are 100% and 20%.

[0089] The CPU 81 adjusts the development bias and exposure light amount of the developing rolls 59Y, 59M, 59C, 59W, 59T, 59S, 59G, and 59K based on the detection value of the density sensor 150. Specifically, the CPU 81 adjusts the development bias and exposure light amount so that the output density, which is the detected value when an auto-adjustment patch image with an input density of 100% is detected, corresponds to the value of an input density of 100%. It also adjusts the development bias and exposure light amount so that the output density, which is the detected value when an auto-adjustment patch image with an input density of 20% is detected, corresponds to the value of an input density of 100%.

[0090] Note that "input density" is the input grayscale value, and "output density" is the density of the toner image secondary transferred to the recording paper P. The output density can be detected by detecting the toner image secondary transferred to the transport belt 21 with the density sensor 150. The "density" of the toner image formed on the recording paper P is calculated from the ratio of the amount of light illuminating to the amount of light reflected (or transmitted). The density is calculated using the common logarithm of the reciprocal of the reflectance.

[0091] [Comparison of mid-tone densities in toner images of the same color] Next, we will explain how to make it possible to compare the density of intermediate tones of toner images of the same color formed by the image forming sections of different image forming units. Specifically, we will explain how to make it possible to compare the output density of the intermediate tones of the toner image of the image forming section 32K of the first image forming unit 30 and the output density of the intermediate tones of the toner image of the image forming section 52K of the second image forming unit 50 using a common intermediate tone, as shown in Figures 2 and 4. Note that "same color" means that the toner color, as an example of a developer, is the same.

[0092] In other words, in this embodiment, as shown in Figures 2 and 4, the first image forming unit 30 and the second image forming unit 50 each have the function of forming a toner image with black toner. The image forming apparatus 10 outputs a color chart 300 (see Figure 6) composed of intermediate tone density correction patch images 312 and 322 formed by the black image forming section 32K of the first image forming unit 30 and the black image forming section 52K of the second image forming unit 50, by secondary transfer to recording paper P, and also has a density correction mode in which the user visually checks the color chart 300 and corrects the density.Therefore, this density correction mode will be described next.

[0093] [Density Correction Mode] The user instructs the control panel 95 to perform density correction mode. Upon receiving this instruction, the control device 80 (see Figure 3) outputs the color chart 300 shown in Figure 6.

[0094] As shown in Figure 6, the color chart 300 consists of a column 310 of correction patch images 312A, 312B, 312C, 312D, and 312E formed from toner images, and a column 320 of correction patch images 322A, 322B, 322C, 322D, and 322E formed from toner images.

[0095] Specifically, column 310 consists of correction patch images 312A with an input density of 100%, correction patch image 312B with an input density of 80%, correction patch image 312C with an input density of 60%, correction patch image 312D with an input density of 40%, and correction patch image 312E with an input density of 20%, all formed by the image forming section 32K of the first image forming unit 30.

[0096] Column 320 consists of correction patch images 322A with an input density of 100%, correction patch image 322B with an input density of 80%, correction patch image 322C with an input density of 60%, correction patch image 322D with an input density of 40%, and correction patch image 322E with an input density of 20%, all formed by the image forming section 52K of the second image forming unit 50.

[0097] Columns 310 and 320 are formed side by side on a single recording sheet P. As mentioned above, when these correction patch images are not distinguished, they are referred to as "correction patch image 312 and correction patch image 322". The input density will be explained later.

[0098] Next to the correction patch images 312 and 322 for each density, a numerical value indicating each density is printed. In addition, above each row 310 and 320, the name of the corresponding image forming unit is printed. In this embodiment, the first image forming unit 30 is printed as "First Image Forming Unit," and the second image forming unit 50 is printed as "Second Image Forming Unit."

[0099] The user visually compares the correction patch images 312 and 322 of the color chart 300 to confirm whether the densities of the two images match.

[0100] In this example, the correction patch image 312C and correction patch image 322C, both with a density of 60%, are slightly different. Furthermore, in this example, correction patch image 322C is lighter than correction patch image 312C.

[0101] The user visually compares the 60% density correction patch image 312C and correction patch image 322C of the color chart 300 and decides whether to use the 60% density correction patch image 312C of the first image forming unit 30 or the 60% density correction patch image 322C of the second image forming unit 50 as the reference. In other words, the user decides whether to correct the density of the 60% density correction patch image 312C of the first image forming unit to match the density of the 60% density correction patch image 322C of the second image forming unit 50, or to correct the density of the 60% density correction patch image 322C of the second image forming unit 50 to match the density of the 60% density correction patch image 312C of the first image forming unit 30. The user's decision can be made by any method. In this embodiment, the decision is made subjectively by the user.

[0102] The density to be matched is referred to as the "target density," the image forming unit used as a reference is referred to as the "reference unit," and the image forming unit that corrects the density is referred to as the "correction unit."

[0103] In this example, the user decides to use a correction patch image 312C with a density of 60% from the first image forming unit as the reference. In other words, the user decides to set the "target density" to 60%, the "reference unit" to the first image forming unit 30, and the "correction unit" to the second image forming unit 50.

[0104] After making a decision, the user inputs from the control panel 95 (see Figure 1) that the target density for density correction should be 60% and that the first image forming unit 30 should be used as the reference unit.

[0105] Upon receiving this instruction, the control device 80 performs density correction to match the 60% density of the second image forming unit 50 to the 60% density of the first image forming unit 30. After this correction, it forms the color chart 300 on the recording paper P and outputs it, then exits the density correction mode.

[0106] The user visually checks the color chart 300 again. After checking, if there are no problems, or if there are problems but they are within an acceptable range, the process is completed. If the user determines that further density adjustment is necessary, they should contact a service technician or take other appropriate action.

[0107] Furthermore, if the density difference between the correction patch image 312C of the first image forming unit 30 and the correction patch image 322C of the second image forming unit 50 is within the acceptable range and no correction is needed to match the two, this will be displayed on the control panel 95. If the user finds this acceptable, or if there is a problem but it is within an acceptable range, they can proceed with the operation. If the user determines that density correction is necessary, they should contact a service technician or take other appropriate action.

[0108] [Density correction] Next, an example of a specific method for density correction, in which the CPU 81 of the control device 80 (see Figure 3) adjusts the density of the second image forming unit 50 formed on the recording paper P to match the density of the first image forming unit 30 (60%), will be explained using the flowchart in Figure 9. In this embodiment, the control device 80 stores numerical values ​​corresponding to the density. For example, in this embodiment, a density of 50% is stored as the numerical value 125.

[0109] When the CPU 81 receives an instruction from the user via the control panel 95 (see Figure 1) to perform density correction mode, it forms and outputs a color chart 300 on the recording paper P (step S100). The CPU 81 receives the target density and reference unit input by the user via the control panel 95 (step S102). In this example, as mentioned above, the target density is 60%, and the reference unit is the first image forming unit 30.

[0110] The CPU 81 forms correction patch images with input density equal to the target density in the correction unit and the reference unit, respectively, and transfers them to the transport belt 21 (step S104). The correction patch image formed in the correction unit is an example of the target patch image, and the correction patch image formed in the reference unit is an example of the reference patch image.

[0111] In this embodiment, the first image forming unit 30 forms a correction patch image 312C with an input density of 60%, and the second image forming unit 50 forms a correction patch image 322C with an input density of 60%, which are then transferred to the transport belt 21. The correction patch image 312C is an example of a reference patch image, and the correction patch image 322C is an example of a target patch image. As mentioned above, the input density will be explained later.

[0112] The CPU 81 uses the density sensor 150 to detect the density of the correction patch images of the correction unit and reference unit, which have been secondarily transferred to the transport belt 21 (step S106). In this example, the density of the correction patch images 312C and 322C, which have been secondarily transferred to the transport belt 21, is detected by the density sensor 150.

[0113] The CPU 81 calculates the density difference between the correction patch images of the correction unit and the reference unit, which have been secondarily transferred to the transport belt 21, and the target density (step S108). In this example, the CPU 81 calculates the density difference between correction patch image 312C, which has a density of 60%, and correction patch image 322C.

[0114] The CPU 81 determines whether the concentration difference between the two is within a preset range (step S110). In this embodiment, the concentration difference range is less than 0.05.

[0115] If the concentration difference is within the specified range (step S110: YES), the CPU 81 proceeds to step S112 and displays on the control panel 95 that the concentration difference between the two is within the specified range and no correction is necessary (step S112).

[0116] If the result is outside the range (step S110: NO), the CPU 81 proceeds to step S114, and, depending on the density difference, the correction unit forms multiple correction patch images as examples of the target patch image with input densities different from the target density and transfers them to the transport belt (step: S114). Specifically, if the density of the correction unit is higher than that of the reference unit, the correction unit forms a correction patch image with an input density lower than the target density. If the density of the correction unit is lower than that of the reference unit, the correction unit forms a correction patch image with an input density higher than the target density.

[0117] Furthermore, multiple correction patch images are formed with either a low or high input density, for example, at 2% increments in density compared to correction patch image 312C; in this example, three such images are formed.

[0118] In this embodiment, since the 60% density of the second image forming unit 50, which is the correction unit, is lighter than the 60% density of the first image forming unit 30, which is the reference unit, the second image forming unit 50 forms correction patch images with input densities higher than 60%, specifically densities of 62%, 64%, and 66%.

[0119] The CPU 81 detects the density of multiple correction patch images that have been secondarily transferred onto the transport belt 21 using the density sensor 150 (step S116).

[0120] The CPU 81 calculates the difference between these multiple correction patch images and the density of the correction patch image (in this example, correction patch image 312C (see Figure 6)) of the target density of the reference unit (first image forming unit 30) (step S118).

[0121] The CPU 81 determines whether there is a correction patch image among the multiple correction patch images whose density difference from the target density of the reference unit (first image forming unit 30 in this example) (correction patch image 312C in this example (see Figure 6)) is within the range (step: S120).

[0122] If there is nothing within the range (step S120: NO), the process returns to step S114, and again, according to the density difference, the correction unit forms multiple correction patch images at concentrations different from the target density and secondary transfers them to the transport belt (step: S114). At this time, correction patch images are formed at concentrations different from the previous time. For example, if the density of the correction unit is higher than that of the reference unit, correction patch images are formed at a lower input density than the previous time. If the density of the correction unit is lower than that of the reference unit, correction patch images are formed at a higher input density than the previous time. In this embodiment, for example, correction patch images with input densities of 68%, 70%, and 72% are formed.

[0123] If there are any within the range (step S120: YES), the process proceeds to step S122, where a conversion LUT is created that converts the density of the correction patch image within the range to a density of 60% of the input density. If there are multiple correction patch images within the range, the density with the smallest density difference is adopted (step S122).

[0124] Specifically, for example, suppose the difference between the correction patch image with an input density of 70% formed by the second image forming unit 50 and the correction patch image 312C with a density of 60% formed by the first image forming unit 30 is within the acceptable range. In this case, when the second image forming unit 50 forms a toner image with an input density of 60%, a conversion LUT is created that interprets the input density as 70%. The conversion LUT will be explained later.

[0125] CPU81 outputs the color chart 300 using a conversion LUT (step S124).

[0126] [LUT for reading] Next, we will explain the LUT for reinterpretation. As mentioned earlier, "LUT" is an abbreviation for Lookup Table, which is a mathematical formula that defines the density adjustment of an image. In this explanation, we will use a graph to make the concept of reinterpretation easier to understand, but the graph is not actually stored in the control device 80.

[0127] This graph shows the relationship between the input density and output density of the same color, and in this embodiment, the input density and output density of black. As mentioned above, the input density is the input grayscale value, and the output density is the density detected by the density sensor 150 of the secondary transferred toner image. Also, as mentioned above, in this embodiment, the input density and output density are stored in the control device 80 as corresponding numerical values.

[0128] Line N30 shows the relationship between the input density and output density of the image forming section 32K of the first image forming unit 30. Note that line N30 is shown as a straight line for clarity, but in reality, it is rarely a straight line.

[0129] Line N50 shows the relationship between the input density and output density of the image forming section 52K of the second image forming unit 50 when the image is formed without using a reinterpretation LUT. Line N51 shows the relationship between the input density and output density of the image forming section 52K of the second image forming unit 50 when the input values ​​are reinterpreted using a reinterpretation LUT. Note that the input density for line N51 is the value before reinterpretation.

[0130] As mentioned above, in line N50, the input density is 60%, but the output density is lower than 60%, at 55%. Then, when the input density of the image forming section 52K of the second image forming unit 50 is 70%, the output density becomes 60%. In other words, the input density of the correction patch image 312C is 60%, the density of the correction patch image 322C is 55%, and in step S120 above, the density of the correction patch within the range is 70%.

[0131] Therefore, a conversion LUT is created that converts the input density of the image forming section 52K of the second image forming unit 50 from 60% to 70%.

[0132] As mentioned above, automatic density adjustment automatically adjusts between 100% and 20% density, so we assume that the input density and output density match or nearly match at 100% and 20%. Therefore, we fix the 100% and 20% density values ​​and linearly interpolate the change from an input density of 60% to an input density of 70% as the maximum change to create a replacement LUT. Figure 7 is a conceptual graph illustrating the replacement LUT created by linear interpolation.

[0133] Here, we will explain the case where a LUT for reinterpretation has already been performed once to correct the density.

[0134] When adjusting the density for the second time or later, if the color chart 300 is formed on the recording paper P in step S100 and output, a conversion LUT is used. However, when the correction patch image is secondarily transferred to the transport belt 21 in step S104, etc., a conversion LUT is not used.

[0135] Therefore, for example, if there is already a conversion LUT that interprets an input density of 60% as an input density of 65%, a conversion LUT is created that interprets an input density of 70% as the output value for an input density of 60%, not 65%. In other words, as described above, a conversion LUT that interprets an input density of 60% as an input density of 70% is created and overwritten.

[0136] [Image Formation] Next, the image formation process when using a replacement LUT will be explained using the flowchart in Figure 10.

[0137] When the CPU 81 of the control device 80 (see Figure 3) receives a print instruction, it determines whether or not there is an instruction to use an image forming unit that requires reinterpreting input values ​​(step S200). In this embodiment, it determines whether or not there is an instruction to form an image using the image forming unit 52K of the second image forming unit 50.

[0138] If it is not necessary (step S200: NO), the CPU 81 proceeds to step S204 and forms an image on the recording paper P (step S204).

[0139] If necessary (step S200: YES), the CPU 81 proceeds to step S202, converts the input density by passing it through a conversion LUT, forms an image on the recording paper P, and outputs it (step S204).

[0140] <effect> Next, the operation of this embodiment will be described.

[0141] In the image forming apparatus 10 of this embodiment, a color chart 300 on which a patch image 312 for correcting intermediate tones of the image forming section 32K of the first image forming unit 30 and a patch image 322 for correcting intermediate tones of the image forming section 52K of the second image forming unit 50 are formed, is secondarily transferred to recording paper P and output. Therefore, the density of intermediate tones of the image forming section 32K of the first image forming unit 30 and the density of intermediate tones of the image forming section 52K of the second image forming unit 50 can be compared using a common intermediate tone.

[0142] From another perspective, compared to the case where the color chart 300 is not output, it is easy to confirm whether or not there is a difference between the density of the intermediate tones in the image forming section 32K of the first image forming unit 30 and the density of the intermediate tones in the image forming section 52K of the second image forming unit 50.

[0143] Furthermore, the color chart 300 is output by secondary transfer onto a single sheet of recording paper P. In this embodiment, two columns are formed on a single sheet of recording paper P: a column 310 of correction patch images 312A, 312B, 312C, 312D, and 312E, and a column 320 of correction patch images 322A, 322B, 322C, 322D, and 322E formed from toner images.

[0144] Therefore, compared to outputting the color chart on multiple sheets of recording paper P, it becomes possible to compare the density of intermediate tones using a common intermediate tone. From another perspective, it becomes possible to accurately confirm whether or not there are differences in the density of intermediate tones.

[0145] Furthermore, the column 310 of the correction patch image 312 and the column 320 of the correction patch image 320 are formed side by side and output. Therefore, compared to the case where the correction patch image 312 and the correction patch image 320 are formed and output as an example, it becomes possible to compare the density of common intermediate tones. From another perspective, it becomes possible to accurately confirm whether or not there is a difference in the density of intermediate tones.

[0146] Furthermore, after outputting the color chart 300, the system accepts input for the target density to be adjusted in the density of the color chart 300 (60% density in this embodiment) and a reference unit to be used as a reference (first image forming unit 30 in this embodiment). Therefore, compared to the case where only the target density is input, the density of the intermediate tones in the toner image of the image forming section 32K of the first image forming unit 30 and the toner image of the image forming section 52K of the second image forming unit 50 can be matched.

[0147] Furthermore, since a correction is performed to match the density of the toner image with an input density of 60% density formed by the image forming section 32K of the first image forming unit 30, which is used as a reference, the density of the toner image with an input density of 60% density formed by the image forming section 52K of the second image forming unit 50 can be matched to the density of the intermediate tones compared to when no correction is made.

[0148] Furthermore, when forming an image in the image forming section 52K of the second image forming unit 50, the input density is passed through a conversion LUT and converted. Therefore, compared to the case where the input density is not converted, the density of the intermediate tones in the toner image formed in the image forming section 32K of the first image forming unit 30 and the toner image formed in the image forming section 52K of the second image forming unit 50 can be made consistent.

[0149] Furthermore, the correction patch image formed by the second image forming unit 50, which is the correction unit, is reformed by changing the density of the correction patch image of the correction unit until the density difference between it and the correction patch image 322C of the target density of the second image forming unit 50, which is the reference unit, falls within the range.

[0150] Therefore, compared to the case where the density of the correction patch image formed in the second image forming unit 50 is not changed and it is not reformed, the density of the intermediate tones of the toner image formed in the image forming section 32K of the first image forming unit 30 (the reference unit) and the image forming section 52K of the second image forming unit 50 (the correction unit) can be matched more accurately.

[0151] Furthermore, after density correction, the input values ​​are passed through a conversion LUT to form a color chart 300 on recording paper P and output. Therefore, the user can easily confirm that the density of the intermediate tones of the toner image formed by the image forming section 32K of the first image forming unit 30, which is the reference unit, and the image forming section 52K of the second image forming unit 50, which is the correction unit, have been matched.

[0152] <Other> Furthermore, the present invention is not limited to the embodiments described above.

[0153] For example, in the above embodiment, the user inputs the execution of the density correction mode, the target density, and the reference unit from the operation panel 95, but this is not limited to this. For example, the user may input from a personal computer, smartphone, tablet terminal, etc., which are electrically connected to the image forming apparatus 10 by wire or wireless.

[0154] Furthermore, in the above embodiment, for example, the first image forming unit 30, the second image forming unit 50, and the black toner image of the image forming apparatus 10 were the same color, but this is not limited to this. For example, all four colors may be the same color. When multiple colors are the same color, the target density and reference unit are determined and input for each color, and the CPU creates a conversion LUT for correction for each color. For example, the target density for cyan is 40% and the reference unit is the first image forming unit 30, and the target density for magenta is 60% and the reference unit is the second image forming unit 50, and so on.

[0155] Furthermore, for example, in the above embodiment, the image forming apparatus 10 had two image forming units, a first image forming unit 30 and a second image forming unit 50, but it is not limited to this. An image forming apparatus may have three or more image forming units. Also, the image forming units 30 and 50 each had four image forming sections 32 and 52, but it is not limited to this. An image forming unit only needs to have two or more image forming sections.

[0156] Here, we will describe the case of an image forming apparatus equipped with three or more image forming units. One image forming unit is designated as the reference unit, and the image forming units that adjust the density to match it are designated as correction units. There may be one correction unit or multiple correction units. In this case, the user may also input the correction units that adjust the density in addition to the reference unit.

[0157] Furthermore, the color chart 300 shown in Figure 6 is just an example and is not limited to it. For example, the density of the correction patch images 312 and 322 in the color chart 300 was in 20% increments, but the increments could be 20% or more, or less than 20%. Also, the density increments can be made smaller as the density decreases. For example, densities of 3%, 5%, 10%, 15%, 20%, 30%, 40%, 60%, 80%, and 100%. In addition, the density increments can be changed for each color.

[0158] Furthermore, the various controls performed by the control device 80 may be interpreted as modes or as control modes.

[0159] Furthermore, although recording paper P was used as an example of a recording medium in the above embodiment, it is not limited to this. Other materials such as OHP sheets may also be used.

[0160] Furthermore, in the above embodiment, the processing that the CPU reads and executes software (programs) may be executed by various processors other than the CPU. Examples of such processors include PLDs (Programmable Logic Devices) such as FPGAs (Field-Programmable Gate Arrays) whose circuit configuration can be changed after manufacturing, and dedicated electrical circuits such as ASICs (Application Specific Integrated Circuits) which have a circuit configuration specifically designed to execute a particular process. The processing may be executed by one of these various processors, or by a combination of two or more processors of the same or different types (for example, multiple FPGAs, and a combination of a CPU and an FPGA). More specifically, the hardware structure of these various processors is an electrical circuit that combines circuit elements such as semiconductor elements.

[0161] Furthermore, while the above embodiments describe a configuration in which the program is pre-stored (installed) in ROM or storage, the program is not limited to this. The program may be provided in the form of a CD-ROM (Compact Disk Read Only Memory), DVD-ROM (Digital Versatile Disk Read Only Memory), USB (Universal Serial Bus) memory, etc. Alternatively, the program may be provided in the form of a download from an external device via a network.

[0162] Furthermore, the configuration of the image forming apparatus is not limited to the configuration of the above embodiment, and various configurations are possible. Moreover, the present invention can be implemented in various forms without departing from the spirit of the present invention.

[0163] [Note] (((1))) Multiple image forming units, and the toner images formed by the multiple image forming units are primary-transferred photo A plurality of image forming units having an intermediate transfer body, A plurality of secondary transfer units are provided corresponding to each of the plurality of image forming units, and transfer the toner image of the intermediate transfer body to a recording medium. Processor and Equipped with, Different image forming units have the same colored image forming section, The aforementioned processor, When an instruction to output a color chart of the same color is received, a mode is executed in which the color chart of the toner image of the same color and intermediate gradation density formed by the image forming section of each image forming unit is secondarily transferred to the recording medium and output. Image forming apparatus.

[0164] In the image forming apparatus (((1))), it is possible to easily check for differences in the density of intermediate tones of the toner image of the same color, compared to the case where a color chart of the same color is not secondarily transferred to a recording medium and output.

[0165] (((2))) The aforementioned mode is, The aforementioned color chart is formed on one of the recording media and output. The image forming apparatus described in (((1))).

[0166] In the image forming apparatus (((2))), compared to the case where a color chart of the same color is divided into multiple recording media and secondary transfer is performed for output, it is possible to accurately confirm whether or not there are differences in the density of intermediate tones of the toner image of the same color.

[0167] (((3))) The rows of toner images representing the intermediate tones, formed for each image forming unit constituting the color chart, are arranged side by side on a single recording medium. The image forming apparatus described in (((1))).

[0168] In the image forming apparatus (((3))), compared to outputting toner images that make up a color chart of the same color in a single line, it is possible to accurately confirm whether or not there are differences in the density of intermediate tones of the toner images of the same color.

[0169] (((4))) The aforementioned mode is, After outputting the aforementioned color chart, The system accepts input of the target density to be adjusted in the intermediate tone density of the color chart, and the image forming unit to be used as a reference. An image forming apparatus as described in any of (((1))) to (((3))).

[0170] In the image forming apparatus (((4))), the density of the intermediate tones of the toner image of the same color can be made uniform compared to when only the target density is input. (((5))) The aforementioned mode is, A correction is performed to match the density of the toner image of the same color at the target density formed by the reference image forming unit to the density of the toner image of the same color formed by another image forming unit. The image forming apparatus described in (((4))).

[0171] In the image forming apparatus (((5))), the density of the intermediate tones of the toner images of the same color can be made uniform compared to when no correction is made.

[0172] (((6))) The device includes a detection device for detecting the density of the toner image, The aforementioned mode is, A reference patch image of the target density of the reference image forming unit and a target patch image of the target density of another image forming unit are formed and detected by the detection device. Based on the difference in density between the two, multiple target patch images with different density from the target density are formed by other image forming units and detected by the detection device. The input density of the target density when the image forming section of another image forming unit of the same color forms the toner image is replaced with the input density of the target patch image that is closest in density to the reference patch image. The image forming apparatus described in (((4))) or ((((5))).

[0173] In the image forming apparatus (((6))), the density of the intermediate tones of the toner image of the same color can be made uniform compared to when the input density is not reinterpreted.

[0174] (((7))) The aforementioned mode is, The target patch image is reshaped by changing its density until the density difference between the reference patch image and the target patch image with the closest density falls within a predetermined range. An image forming apparatus as described in any of (((4))) to (((6))).

[0175] In the image forming apparatus (((7))), the density of the intermediate tones of the toner image of the same color can be matched more accurately compared to when the target patch image is not reformed.

[0176] (((8))) The aforementioned mode is, After receiving the input of the target concentration and the reference image forming unit, The color chart is again transferred to the recording medium and output. An image forming apparatus as described in any of (((4))) to (((7))).

[0177] In the image forming apparatus (((8))), it is easy to confirm that the density of the intermediate tones of the toner image of the same color has been standardized by comparing it with the case where the same color color chart is not secondarily transferred to the recording medium and output again. [Explanation of symbols]

[0178] 10 Image forming apparatus 30 First Image Forming Unit 32Y Image forming section 32C Image forming section 32M Image Forming Unit 40. Intermediate transfer belt (an example of an intermediate transfer material) 50 Second image forming unit 52W image forming section 52S Image forming unit 52G Image Forming Unit 52K image forming section 60 Intermediate Transfer Belt (An example of an intermediate transfer material) 74. Secondary transfer section (an example of a transfer section) 76. Secondary transfer section (an example of a transfer section) 80 Control device 81 CPU (an example of a processor) 150 Concentration Sensor (Example of a detection device) 300 Color Chart 310 columns 312A Correction patch image 312B Correction patch image 312C Correction patch image 312D Correction patch image 312E Correction patch image 320 columns 322A Correction patch image 322B Correction patch image 322C Correction patch image 322D Correction patch image 322E Correction patch image P Recording sheet (an example of a recording medium)

Claims

1. Multiple image forming units, each having multiple image forming units and an intermediate transfer body on which toner images formed by the multiple image forming units are first transferred, A plurality of secondary transfer units are provided corresponding to each of the plurality of image forming units, and transfer the toner image of the intermediate transfer body to a recording medium. A detection device for detecting the density of the toner image, Processor and Equipped with, Different image forming units have the same colored image forming section, The aforementioned processor, When an instruction to output the color chart of the same color is received, a mode is executed in which the color chart of the toner image of the same color with intermediate densities formed by the image forming section is secondarily transferred to the recording medium and output for each image forming unit. The aforementioned mode is, After outputting the aforementioned color chart, The system receives input of the target density to be adjusted in the intermediate tone density of the color chart and the reference image forming unit. A reference patch image of the target density formed by the toner image of the reference image forming unit, and a target patch image of the target density formed by the toner image of another image forming unit are formed and detected by the detection device. Based on the difference in density between the two, multiple target patch images with different density from the target density are formed by other image forming units and detected by the detection device. The input density of the target density when the image forming section of the same color of another image forming unit forms the toner image is replaced with the input density of the target patch image that is closest in density to the reference patch image. Image forming apparatus.

2. The mode is, The target patch image is reshaped by changing its density until the density difference between the reference patch image and the target patch image with the closest density falls within a predetermined range. The image forming apparatus according to claim 1.

3. A plurality of image forming units having a plurality of image forming units and an intermediate transfer body on which toner images formed by the plurality of image forming units are first transferred, A plurality of secondary transfer units are provided corresponding to each of the plurality of image forming units, and transfer the toner image of the intermediate transfer body to a recording medium. Processor and Equipped with, Different image forming units have the same colored image forming section, The aforementioned processor, When an instruction to output the color chart of the same color is received, a mode is executed in which the color chart of the toner image of the same color with intermediate densities formed by the image forming section is secondarily transferred to the recording medium and output for each image forming unit. The aforementioned mode is, After outputting the aforementioned color chart, The system receives input of the target density to be adjusted in the intermediate tone density of the color chart and the reference image forming unit. A correction is performed to match the density of the toner image of the same color at the target density formed by the reference image forming unit to the density of the toner image of the same color formed by another image forming unit. After receiving the input of the target concentration and the reference image forming unit, The color chart is again transferred to the recording medium and output. Image forming apparatus.

4. The mode is The aforementioned color chart is formed on one of the recording media and output. An image forming apparatus according to any one of claims 1 to 3.

5. The rows of toner images of intermediate densities formed for each image forming unit constituting the color chart are arranged side by side on a single recording medium. The image forming apparatus according to claim 4.

Images