Image forming apparatus, correction method, and program

Abstract

To provide an image forming apparatus, a correction method, and a program that can accurately correct a transfer voltage of a transfer unit.SOLUTION: An image forming apparatus 1 comprises: an image forming section 20 that has a plurality of image forming units 26 arranged in series along a travel direction of a transfer target body (intermediate transfer belt 27) and transferring toner images in a plurality of colors to the transfer target body, and that forms an image comprising a plurality of colors on a recording medium Q; a detection section 40 that detects the colors of the image formed by the image forming section 20; and a calculation section (control section 10) that calculates a correction value of a primary transfer voltage in the image forming unit 26 on the basis of the colors detected by the detection section 40. The colors detected by the detection section 40 include a first color equal to or more than a secondary color, a second color equal to or more than the secondary color, and a third color being a tertiary color.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus, a correction method, and a program. [Background technology]

[0002] In an electrophotographic image forming apparatus, for example, multiple image forming units are arranged in series along the running direction of an intermediate transfer belt, and the multiple image forming units form toner images of different colors and transfer the toner images to the intermediate transfer belt.

[0003] In such an image forming apparatus, the resistance value of the transfer section of each image forming unit changes due to changes in the internal temperature of the image forming apparatus during continuous printing. As a result, if the transfer voltage of the transfer section is output at a constant value, the amount of toner transferred changes, causing the image color to vary from the reference color. To suppress such changes in image color, the image forming apparatus detects the resistance of the image forming unit during continuous printing and corrects the transfer voltage of the transfer section based on that resistance.

[0004] However, when printing on continuous paper such as roll paper, a toner image based on the image selected by the user is always present in the transfer section. Therefore, the toner image based on the image selected by the user present in the transfer section introduces an error when detecting the resistance of the image forming unit, making it impossible to accurately detect the resistance. Therefore, when printing on continuous paper, it is difficult to correct the transfer voltage by detecting the resistance. For printing on continuous paper, known techniques include predicting and correcting the transfer voltage based on changes in the internal temperature of the image forming device or correcting the transfer voltage based on changes in the color of the image.

[0005] The image forming apparatus disclosed in Patent Document 1 determines that insufficient transfer or reverse transfer has occurred when the density of a single-color toner image consisting of only that color component is higher than the density of the color component of the bottom layer in the multi-color toner image formed on paper. The bottom color component in the multi-color toner image formed on paper is the top color component on the intermediate transfer belt. Next, the image forming apparatus corrects the transfer voltage in the image forming unit corresponding to that color component. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-191827 Summary of the Invention [Problem to be solved by the invention]

[0007] When forming a multi-color image, reverse transfer occurs at the transfer units corresponding to the colors constituting the multi-color image and at transfer units located downstream of the transfer units. The reverse transfer is a phenomenon in which toner transferred to the intermediate transfer belt is re-transferred onto the image carrier. Therefore, since the change in resistance value in the transfer section corresponding to each color acts in a complex manner for each color, there is a problem in that it is difficult to correct the transfer voltage of the transfer section to an optimum value. The invention of Patent Document 1 does not mention the influence of reverse transfer in a transfer section located downstream of the transfer section corresponding to the color that constitutes the multi-color, and therefore cannot solve the above problem.

[0008] An object of the present invention is to provide an image forming apparatus, a correction method, and a program that can correct the transfer voltage of a transfer unit with high accuracy. [Means for solving the problem]

[0009] The image forming apparatus according to claim 1 is made to achieve the above object, an image forming section including a plurality of image forming units arranged in series along the traveling direction of the transfer medium, each of which transfers a toner image of a plurality of colors onto the transfer medium, and which forms an image of a plurality of colors on the recording medium; a detection unit that detects the color of an image formed by the image forming unit; a calculation unit that calculates a correction value for a primary transfer voltage in the image forming unit based on the color detected by the detection unit; Equipped with The colors detected by the detection unit include a first color that is a secondary or higher color, a second color that is a secondary or higher color, and a third color that is a tertiary color.

[0010] The invention described in claim 2 is the image forming apparatus described in claim 1, The calculation unit calculates a correction value for the primary transfer voltage based on a primary transfer voltage at a first image forming unit that is located furthest downstream in the traveling direction among the image forming units corresponding to the constituent colors of the color detected by the detection unit, a primary transfer voltage at a second image forming unit that is located downstream in the traveling direction from the first image forming unit, and a reduction rate of toner transferred to the transfer object due to reverse transfer.

[0011] The invention described in claim 3 is the image forming apparatus described in claim 2, The reduction rate includes a first reduction rate, which is a reduction rate of the toner transferred to the transfer body by the first image forming unit due to reverse transfer in the first image forming unit, and a second reduction rate, which is a reduction rate of the toner transferred to the transfer body by the first image forming unit due to reverse transfer in the second image forming unit.

[0012] The invention described in claim 4 is the image forming apparatus described in claim 3, The first decrease rate is smaller than the second decrease rate.

[0013] The invention described in claim 5 is the image forming apparatus described in claim 2, The device includes a storage unit that stores the reduction rate.

[0014] The invention described in claim 6 is the image forming apparatus described in claim 2, The calculation unit calculates a correction value for the primary transfer voltage based on a change in the color coordinate of the color detected by the detection unit.

[0015] The invention described in claim 7 is the image forming apparatus described in claim 2, The image forming apparatus further includes a storage unit that stores a correspondence relationship between the amount of change in color detected by the detection unit and the primary transfer voltage.

[0016] The invention described in claim 8 is the image forming apparatus described in claim 2, The image forming apparatus includes a calculation mode for calculating a correspondence relationship between the amount of change in color detected by the detection unit and the primary transfer voltage.

[0017] The correction method according to claim 9 comprises: an image forming section including a plurality of image forming units arranged in series along the traveling direction of a transfer medium, each of which transfers a toner image of a plurality of colors onto the transfer medium, and which forms an image of a plurality of colors on a recording medium; a detection unit that detects the color of an image formed by the image forming unit; A correction method executed by an image forming apparatus comprising: a calculation step of calculating a correction value of a primary transfer voltage in the image forming unit based on the color detected by the detection unit; The colors detected by the detection unit include a first color that is a secondary or higher color, a second color that is a secondary or higher color, and a third color that is a tertiary color.

[0018] The program according to claim 10 comprises: an image forming section including a plurality of image forming units arranged in series along the traveling direction of a transfer medium, each of which transfers a toner image of a plurality of colors onto the transfer medium, and which forms an image of a plurality of colors on a recording medium; a detection unit that detects the color of an image formed by the image forming unit; A computer of an image forming apparatus comprising: a calculation unit that calculates a correction value for a primary transfer voltage in the image forming unit based on the color detected by the detection unit; The colors detected by the detection unit include a first color that is a secondary or higher color, a second color that is a secondary or higher color, and a third color that is a tertiary color. [Effects of the Invention]

[0019] According to the present invention, the transfer voltage of the transfer unit can be corrected with high precision. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a diagram showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention; [Figure 2] FIG. 2 is a functional block diagram showing a control structure of the image forming apparatus according to the present embodiment. [Figure 3] 1 shows an example of a patch image. [Figure 4] FIG. 10 is a diagram showing reverse transfer that occurs when a red patch image is formed. [Figure 5] FIG. 10 is a diagram showing reverse transfer that occurs when a green patch image is formed. [Figure 6] FIG. 10 is a diagram illustrating reverse transfer that occurs when a process black patch image is formed. [Figure 7] 10 is a flowchart showing a procedure for correcting a transfer voltage. [Figure 8] 10 is a flowchart illustrating a procedure for a correction value calculation process. [Figure 9] FIG. 10 is a diagram showing an example of a change in color of process black. [Figure 10] FIG. 10 is a diagram illustrating an example of a change in the color of red. DETAILED DESCRIPTION OF THE INVENTION

[0021] An embodiment of the present invention will be described below with reference to the drawings. The following is an embodiment of the present invention and is not intended to limit the present invention.

[0022] In the following description, a change in the color of an image from a reference color is also referred to as "a color change" or "color change." In the following description, a change in the amount of toner reverse-transferred (hereinafter also referred to as "reverse transfer amount") from a reference reverse transfer amount is also referred to as "a change in the reverse transfer amount of toner" or "a change in the reverse transfer amount of toner." In the following description, a change in the amount of toner transferred to a recording medium from a reference toner amount is also referred to as "a change in the amount of toner transferred to a recording medium." In the following description, a change in the resistance value at a transfer unit from a reference resistance value is also referred to as "a change in the resistance value at the transfer unit" or "a change in the resistance value at the transfer unit."

[0023] <1. Configuration of image forming device> The configuration of an image forming apparatus 1 in this embodiment will be described with reference to Figures 1 and 2. Figure 1 is a diagram showing a schematic configuration of the image forming apparatus 1 in this embodiment. Figure 2 is a functional block diagram showing the control structure of the image forming apparatus 1 in this embodiment.

[0024] The image forming apparatus 1 includes a control unit 10, a paper feed unit 15, an image forming unit 20, a detection unit 40, an operation display unit 50, a communication unit 60, and a storage unit 70. The units of the image forming apparatus 1 are connected to each other via a bus 99.

[0025] The control unit 10 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), etc. The CPU of the control unit 10 reads out various processing programs stored in the ROM or the storage unit 70, loads them into the RAM, and performs overall control of the operation of the image forming apparatus 1 in cooperation with the various programs loaded into the RAM.

[0026] The paper feed unit 15 supplies the recording medium Q to the image forming unit 20. The recording medium Q may be a sheet of paper separated into individual sheets, or may be a continuous sheet of paper such as roll paper. In the example shown in Fig. 1, the recording medium Q is roll paper.

[0027] The image forming unit 20 forms an image made up of multiple colors on the recording medium Q. The image forming section 20 includes an image forming unit 26Y, an image forming unit 26M, an image forming unit 26C, an image forming unit 26K, an intermediate transfer belt 27 as a transfer medium, a transfer roller 28, a cleaning section 29, a fixing section 30, and the like.

[0028] Image forming unit 26Y forms a yellow toner image. Image forming unit 26M forms a magenta toner image. Image forming unit 26C forms a cyan toner image. Image forming unit 26K forms a black toner image. In the following description, the colors corresponding to image forming unit 26Y, image forming unit 26M, image forming unit 26C, and image forming unit 26K are yellow, magenta, cyan, and black, respectively.

[0029] Image forming unit 26Y, image forming unit 26M, image forming unit 26C, and image forming unit 26K are arranged in series in this order from the upstream side of the traveling direction AR of intermediate transfer belt 27. Image forming unit 26Y, image forming unit 26M, image forming unit 26C, and image forming unit 26K each form a toner image of a corresponding color and transfer the toner image to intermediate transfer belt 27. Image forming unit 26Y includes a photoconductor 21Y, a charging device 22Y, an exposure device 23Y, a developing device 24Y, a transfer roller 25Y, etc. Image forming unit 26M includes a photoconductor 21M, a charging device 22M, an exposure device 23M, a developing device 24M, a transfer roller 25M, etc. Image forming unit 26C includes a photoconductor 21C, a charging device 22C, an exposure device 23C, a developing device 24C, a transfer roller 25C, etc. Image forming unit 26K includes a photoconductor 21K, a charging device 22K, an exposure device 23K, a developing device 24K, a transfer roller 25K, etc.

[0030] In the following description, when there is no need to distinguish between image forming units 26Y, 26M, 26C, and 26K, they will be referred to as "image forming units 26." When there is no need to distinguish between photoconductors 21Y, 21M, 21C, and 21K, they will be referred to as "photoconductors 21." When there is no need to distinguish between charging devices 22Y, 22M, 22C, and 22K, they will be referred to as "charging devices 22." When there is no need to distinguish between exposure devices 23Y, 23M, 23C, and 23K, they will be referred to as "exposure devices 23." When there is no need to distinguish between developing devices 24Y, 24M, 24C, and 24K, they will be referred to as "developing devices 24." In the following description, when there is no need to distinguish between transfer roller 25Y, transfer roller 25M, transfer roller 25C, and transfer roller 25K, they will be referred to as "transfer roller 25." In the following description, the area where the transfer roller 25 and the intermediate transfer belt 27 come into contact is referred to as the "transfer section."

[0031] The image forming unit 26 forms a toner image of the corresponding color as follows and transfers the toner image to the intermediate transfer belt 27. The charging device 22 charges the entire photoconductor 21 negatively. Next, the exposure device 23 irradiates the negatively charged photoconductor 21 with laser light based on the printing data. The printing data includes data for an image specified by the user and data for multiple patch images. A positive charge is generated in the areas irradiated with the laser light, and negative charges are eliminated. As a result, a latent image of the printing data is formed on the photoconductor 21. Next, the developing device 24 supplies negatively charged toner to the photoconductor 21. As a result, the toner adheres to areas of the photoconductor 21 that do not have a negative charge, making the latent image visible. In other words, a toner image based on the printing data is formed on the photoconductor 21. Next, the transfer roller 25 transfers the toner image formed on the photoconductor 21 to the intermediate transfer belt 27 using a transfer voltage (primary transfer voltage).

[0032] The intermediate transfer belt 27 travels in the travel direction AR, so that the toner images of the respective colors are superimposed on the intermediate transfer belt 27, and a toner image based on the print data is formed on the intermediate transfer belt 27.

[0033] Transfer roller 28 transfers the toner image based on the print data formed on intermediate transfer belt 27 onto the conveyed recording medium Q. As a result, a toner image based on the print data is formed on recording medium Q. Cleaning unit 29 collects toner remaining on intermediate transfer belt 27 without being transferred to recording medium Q.

[0034] The fixing unit 30 applies heat and pressure to the recording medium Q onto which the toner image has been transferred, thereby fixing the toner image to the recording medium Q. As a result, an image based on the print data is formed on the recording medium Q.

[0035] The detection unit 40 detects the color of each of the plurality of patch images formed on the recording medium Q. The detection unit 40 may also detect the color of each of the plurality of patch images formed on the intermediate transfer belt 27. The detection unit 40 outputs the result of detecting the color of each of the plurality of patch images to the control unit 10.

[0036] The operation display unit 50 includes a display unit such as a liquid crystal display and an operation unit such as a touch panel overlaid on the screen of the display unit. The operation display unit 50 displays various information such as the operation status and processing results of the image forming unit 20 on the display unit. The operation display unit 50 converts input operations to the operation unit into signals and outputs the signals to the control unit 10.

[0037] The communication unit 60 transmits and receives information to and from an external device (not shown). As an example, the control unit 10 receives print data from the external device via the communication unit 60.

[0038] The storage unit 70 is a non-volatile storage device such as a hard disk drive (HDD) or semiconductor memory that stores various data such as programs and image data. The storage unit 70 stores data such as program data and various setting data in a manner that allows the control unit 10 to read and write data.

[0039] The storage unit 70 stores a correspondence relationship between the amount of change in the color of an image formed by the image forming unit 20 and the amount of reverse transfer of toner that causes the change. The correspondence relationship between the amount of change in the color change and the amount of reverse transfer of toner is determined in advance through experiments. Specifically, the storage unit 70 stores a correspondence relationship between the amount of change in the magenta direction component of the color change of process black and the amount of reverse transfer of magenta toner that causes the change. The storage unit 70 stores a correspondence relationship between the amount of change in the color change of red and the amount of reverse transfer of magenta toner that causes the change. The storage unit 70 stores a correspondence relationship between the amount of change in the color change of green and the amount of reverse transfer of cyan toner that causes the change. The memory unit 70 stores the correspondence relationship between the amount of reverse transfer of toner when an image is formed by the image forming unit 20 and the transfer voltage of the transfer unit when reverse transfer occurs. The correspondence relationship between the amount of reverse transfer of toner and the transfer voltage is determined in advance through experiments. Specifically, the memory unit 70 stores the correspondence relationship between the amount of reverse transfer of magenta toner and the transfer voltage of the transfer unit of the image forming unit 26M. The memory unit 70 stores the correspondence relationship between the amount of reverse transfer of cyan toner and the transfer voltage of the transfer unit of the image forming unit 26C. The memory unit 70 stores the correspondence relationship between the amount of reverse transfer of cyan toner and the transfer voltage of the transfer unit of the image forming unit 26K. The correspondence relationship between the amount of change in color and the transfer voltage can be derived based on the correspondence relationship between the amount of change in color and the amount of reverse transfer of toner, and the correspondence relationship between the amount of reverse transfer of toner and the transfer voltage. In other words, the storage unit 70 stores the correspondence relationship between the amount of change in color of the image formed by the image forming unit 20 and the transfer voltage of the transfer unit when reverse transfer of toner occurs, which causes the change. The storage unit 70 stores a first reduction rate α (described later) and a second reduction rate β (described later) which are the reduction rates of the toner on the intermediate transfer belt 27 due to reverse transfer. The first reduction rate α and the second reduction rate β are determined in advance through experiments.

[0040] In the present invention, the control unit 10 corrects the transfer voltage of the target image forming unit corresponding to the patch image based on the color of each of the multiple patch images detected by the detection unit 40. The target image forming unit is an image forming unit that may affect the color of the image. Details of the target image forming unit will be described later.

[0041] <2. Patch image> The patch image will be described with reference to Fig. 3. Fig. 3 shows an example of the patch image. The patch image group P is formed in an area that will ultimately be discarded within the recording medium Q on which the image I designated by the user is formed, that is, an area outside the cutting lines CR1 and CR2. The patch images in the patch image group P include a patch image consisting of a first color that is a secondary or higher color, a patch image consisting of a second color that is a secondary or higher color, and a patch image consisting of a third color that is a tertiary color. A secondary color is a color made up of two colors selected from yellow, magenta, cyan, and black. A tertiary color is a color made up of three colors selected from yellow, magenta, cyan, and black. In this embodiment, the multiple patch images include a red patch image Pr, a green patch image Pg, and a process black patch image Ppk. The constituent colors of red are yellow and magenta. The constituent colors of green are yellow and cyan. The constituent colors of process black are yellow, magenta, and cyan. The patch image group P may include patch images that are composed of secondary or higher colors different from red and green (e.g., blue patch image Pb).The patch image group P may also include patch images that are composed of a single color (e.g., yellow patch image Py, magenta patch image Pm, cyan patch image Pc, and black patch image Pk).

[0042] 3. Occurrence of color changes in the formed image Next, a change in color in the image formed by the image forming unit 20 will be described. One of the factors that causes the color of the formed image to change is a change in the amount of reversely transferred toner due to a change in the resistance value at the transfer section of the image forming unit 26. When the amount of reversely transferred toner changes, the amount of toner transferred to the recording medium Q also changes, causing a change in the color of the image. In the present invention, reverse transfer is a phenomenon in which a portion of the toner transferred to the intermediate transfer belt 27 by the image forming unit 26 is transferred to the photosensitive element 21 in the image forming unit 26, or to the photosensitive element 21 in the image forming unit 26 located downstream of the image forming unit 26 in the running direction AR of the intermediate transfer belt 27.

[0043] 4 is a diagram showing reverse transfer that occurs when a red patch image Pr is formed. The red patch image Pr is formed by image forming unit 26Y and image forming unit 26M. More specifically, image forming unit 26Y transfers a yellow toner image to intermediate transfer belt 27. Next, image forming unit 26M transfers a magenta toner image to intermediate transfer belt 27 so that the magenta toner image is superimposed on the yellow toner image on intermediate transfer belt 27.

[0044] A magenta toner image is superimposed by image forming unit 26M on the yellow toner image transferred to intermediate transfer belt 27 by image forming unit 26Y. Therefore, when forming red patch image Pr, there is almost no reverse transfer of yellow toner. On the other hand, when forming red patch image Pr, part of the magenta toner transferred to intermediate transfer belt 27 by image forming unit 26M is reverse transferred to photoconductor 21M in image forming unit 26M. Furthermore, in image forming units 26C and 26K, which are located downstream of image forming unit 26M in the running direction AR of intermediate transfer belt 27, part of the magenta toner on intermediate transfer belt 27 is reverse transferred to photoconductor 21C and photoconductor 21K, respectively. When a red patch image Pr is formed, the reduction rate of the magenta toner on the intermediate transfer belt 27 due to reverse transfer to the photoconductor 21M is a first reduction rate α. When a red patch image Pr is formed, the reduction rate of the magenta toner on the intermediate transfer belt 27 due to reverse transfer to the photoconductor 21C and the photoconductor 21K is a second reduction rate β.

[0045] The total amount ΔMm(r) of magenta toner reverse transfer during formation of a red patch image Pr is expressed by the following formula (1): In the following formula (1), a function f is a function that converts the reverse transfer amount into a transfer voltage. Equation (1) ΔMm(r) = αf(Vm)+βf(Vc)+βf(Vk) α: 1st reduction rate β: 2nd reduction rate Vm: Transfer voltage at the transfer section of the image forming unit 26M Vc: Transfer voltage at the transfer section of the image forming unit 26C Vk: Transfer voltage at the transfer section of image forming unit 26K

[0046] Thus, when forming the red patch image Pr, of the image forming units 26Y and 26M that form the secondary color toner images that make up the red patch image Pr, reverse transfer of magenta toner occurs in the image forming unit 26M that is located at the most downstream side in the running direction AR of the intermediate transfer belt 27. Furthermore, reverse transfer of magenta toner occurs in the image forming units 26C and 26K that are located downstream of the image forming unit 26M in the running direction AR of the intermediate transfer belt 27. Therefore, a change in the resistance value of the transfer section in at least one of image forming units 26M, 26C, and 26K causes the amount of magenta toner reversely transferred to vary from the reference amount. As a result, the amount of magenta toner transferred to recording medium Q varies from the reference amount, and the color of red patch image Pr formed on recording medium Q varies from the reference color.

[0047] Therefore, the image forming units that may affect the color of the red patch image Pr are image forming unit 26M, which is one of the two image forming units that form the secondary color toner images that make up the red patch image and is located at the most downstream side in the running direction AR of the intermediate transfer belt 27, and image forming unit 26C and image forming unit 26K, which are located downstream of image forming unit 26M in the running direction AR of the intermediate transfer belt 27. The image forming unit that may affect the color of the red patch image Pr is the target image forming unit that corresponds to the red patch image Pr.

[0048] The target image forming unit corresponding to the patch image includes, among two or more image forming units that form toner images of secondary or higher colors that constitute the corresponding patch image, a first image forming unit that is located at the most downstream side in the running direction AR of intermediate transfer belt 27. The target image forming unit corresponding to the patch image includes a second image forming unit that is located downstream of the first image forming unit in the running direction AR of intermediate transfer belt 27. The first image forming unit corresponding to the red patch image Pr is the image forming unit 26M, and the second image forming units corresponding to the red patch image Pr are the image forming unit 26C and the image forming unit 26K.

[0049] 5 is a diagram showing reverse transfer that occurs when a green patch image is formed. The green patch image Pg is formed by image forming unit 26Y and image forming unit 26C. More specifically, image forming unit 26Y transfers a yellow toner image to intermediate transfer belt 27. Next, image forming unit 26C transfers a cyan toner image to intermediate transfer belt 27 so that the cyan toner image is superimposed on the yellow toner image on intermediate transfer belt 27.

[0050] When forming a green patch image Pg, part of the yellow toner transferred to intermediate transfer belt 27 by image forming unit 26Y is reverse-transferred to photoconductor 21M as image forming unit 26M passes. However, reverse transfer of yellow toner does not occur in image forming units 26C and 26K. Meanwhile, part of the cyan toner transferred to intermediate transfer belt 27 by image forming unit 26C is reverse-transferred to photoconductor 21C in image forming unit 26C. Furthermore, part of the cyan toner on intermediate transfer belt 27 is reverse-transferred to photoconductor 21K in image forming unit 26K, which is located downstream of image forming unit 26C in the running direction AR of intermediate transfer belt 27. When forming a green patch image Pg, the rate at which the cyan toner on the intermediate transfer belt 27 is reduced by being reverse-transferred to the photoconductor 21C is a first reduction rate α. When forming a green patch image Pg, the rate at which the cyan toner on the intermediate transfer belt 27 is reduced by being reverse-transferred to the photoconductor 21K is a second reduction rate β.

[0051] The total amount ΔMc(g) of cyan toner in reverse transfer when forming a green patch image Pg is expressed by the following formula (2): In the following formula (2), a function f is a function that converts the reverse transfer amount into a transfer voltage. Equation (2) ΔMc(g) = αf(Vc)+βf(Vk) α: 1st reduction rate β: 2nd reduction rate Vc: Transfer voltage at the transfer section of the image forming unit 26C Vk: Transfer voltage at the transfer section of image forming unit 26K

[0052] Thus, when forming green patch image Pg, of image forming units 26Y and 26C that form secondary color toner images that constitute the patch image, reverse transfer of cyan toner occurs in image forming unit 26C, which is located furthest downstream in the running direction AR of intermediate transfer belt 27. In addition, reverse transfer of cyan toner occurs in image forming unit 26K, which is located downstream of image forming unit 26C in the running direction AR of intermediate transfer belt 27. Therefore, a change in the resistance value of the transfer section in at least one of image forming units 26C and 26K causes the amount of cyan toner reversely transferred to vary from the reference amount, and as a result, the amount of cyan toner transferred to recording medium Q varies from the reference amount, and the color of green patch image Pg formed on recording medium Q varies from the reference color.

[0053] Therefore, the image forming units that may affect the color of the green patch image Pg are image forming unit 26C, which is located at the most downstream side in the running direction AR of intermediate transfer belt 27, of the two image forming units that form the secondary color toner images that make up the green patch image, and image forming unit 26K, which is located downstream of image forming unit 26C in the running direction AR of intermediate transfer belt 27. The image forming unit that can affect the color of the green patch image Pg is the target image forming unit that corresponds to the green patch image Pg. The first image forming unit corresponding to the green patch image Pg is the image forming unit 26C, and the second image forming unit corresponding to the green patch image Pg is the image forming unit 26K.

[0054] 6 is a diagram showing reverse transfer that occurs when a process black patch image is formed. The process black patch image Ppk is formed by image forming unit 26Y, image forming unit 26M, and image forming unit 26C. More specifically, image forming unit 26Y transfers a yellow toner image to intermediate transfer belt 27. Next, image forming unit 26M transfers a magenta toner image to intermediate transfer belt 27 so that the magenta toner image is superimposed on the yellow toner image on intermediate transfer belt 27. Next, image forming unit 26C transfers a cyan toner image to intermediate transfer belt 27 so that the cyan toner image is superimposed on the magenta toner image on intermediate transfer belt 27.

[0055] A magenta toner image is superimposed by image forming unit 26M on the yellow toner image transferred to intermediate transfer belt 27 by image forming unit 26Y. A cyan toner image is superimposed by image forming unit 26C on the magenta toner image transferred to intermediate transfer belt 27 by image forming unit 26M. Therefore, when forming process black patch image Ppk, there is almost no reverse transfer of yellow toner. On the other hand, when forming process black patch image Ppk, a portion of the magenta toner transferred to intermediate transfer belt 27 by image forming unit 26M is reverse transferred to photoconductor 21M in image forming unit 26M. Furthermore, a portion of the cyan toner transferred to intermediate transfer belt 27 by image forming unit 26C is reverse transferred to photoconductor 21C in image forming unit 26C. Furthermore, in image forming unit 26K located downstream of image forming unit 26C in the running direction AR of intermediate transfer belt 27, part of the cyan toner on intermediate transfer belt 27 is reverse-transferred to photoconductor 21K. When forming the process black patch image Ppk, the reduction rate of the magenta toner on the intermediate transfer belt 27 due to reverse transfer to the photoconductor 21M is a first reduction rate α. When forming the process black patch image Ppk, the reduction rate of the cyan toner on the intermediate transfer belt 27 due to reverse transfer to the photoconductor 21C is a first reduction rate α. When forming the process black patch image Ppk, the reduction rate of the cyan toner on the intermediate transfer belt 27 due to reverse transfer to the photoconductor 21K is a second reduction rate β.

[0056] The total amount ΔMm(pk) of magenta toner reverse transfer during formation of the process black patch image Ppk is expressed by the following formula (3): In the following formula (3), function f is a function that converts the reverse transfer amount into a transfer voltage. Equation (3) ΔMm(pk) = αf(Vm) α: 1st reduction rate Vm: Transfer voltage at the transfer section of the image forming unit 26M

[0057] Thus, when forming a process black patch image Ppk, among image forming units 26Y, 26M, and 26C that form tertiary color toner images that constitute the patch image, reverse transfer of magenta toner occurs in image forming unit 26M. Also, among the image forming units 26 that form tertiary color toner images that constitute the patch image, reverse transfer of cyan toner occurs in image forming unit 26C, which is located at the most downstream side in the running direction AR of intermediate transfer belt 27. Also, reverse transfer of cyan toner occurs in image forming unit 26K, which is located downstream of image forming unit 26C in the running direction AR of intermediate transfer belt 27. Therefore, when the resistance value of the transfer section in image forming unit 26M changes, the amount of magenta toner reversely transferred changes from the reference amount. When the resistance value of the transfer section in at least one of image forming unit 26C and image forming unit 26K changes, the amount of cyan toner reversely transferred changes from the reference amount. As a result, the amount of magenta and / or cyan toner transferred to recording medium Q changes from the reference amount, and the color of the process black patch image formed on recording medium Q changes from the reference color.

[0058] Therefore, the image forming units that may affect the color of the process black patch image Ppk are image forming unit 26M, image forming unit 26C, of ​​the three image forming units that form the tertiary color toner images that make up the process black patch image, which is located at the most downstream side in the running direction AR of the intermediate transfer belt 27, and image forming unit 26K, which is located downstream of image forming unit 26C in the running direction AR of the intermediate transfer belt 27. The image forming unit that may affect the color of the process black patch image Ppk is the target image forming unit that corresponds to the process black patch image Ppk.

[0059] As described above, during image formation, the reduction rate of the toner transferred onto the intermediate transfer belt 27 by the first image forming unit due to reverse transfer in the first image forming unit is a first reduction rate α. The reduction rate of the toner transferred onto the intermediate transfer belt 27 by the first image forming unit due to reverse transfer in the second image forming unit is a second reduction rate β. The first decrease rate α is smaller than the second decrease rate β.

[0060] <4. Operation of Image Forming Device> Next, the operation of the image forming apparatus 1 according to this embodiment will be described. When the image forming apparatus 1 receives a job from an external device via the communication unit 60, or when a job is input by the user via the operation display unit 50, the image forming apparatus 1 executes the transfer voltage correction process shown in FIG. The image forming apparatus 1 corrects the transfer voltage of the image forming unit 26, which may affect the color of the image, by executing the correction process for the transfer voltage.

[0061] (Transfer voltage correction process) The control unit 10 of the image forming apparatus 1 determines the image forming parameters for each of the plurality of image forming units 26 included in the image forming section 20 based on the image of the job (step S1).

[0062] Next, the control unit 10 causes the image forming unit 20 to form an image based on the print data on the recording medium Q, based on the image creation parameters determined in step S1 (step S2). The image based on the printing data includes a plurality of patch images. The plurality of patch images include a patch image made up of a first color that is a secondary or higher color, a patch image made up of a second color that is a secondary or higher color, and a patch image made up of a third color that is a tertiary color. As described above, in this embodiment, the patch image made up of the first color that is a secondary or higher color is a red patch image Pr. The patch image made up of the second color that is a secondary or higher color is a green patch image Pg. The patch image made up of the third color that is a tertiary color is a process black patch image Ppk.

[0063] Next, the control unit 10 causes the detection unit 40 to detect the color of each of the plurality of patch images formed by the image forming unit 20 in step S2 (step S3).

[0064] Next, the control unit 10 executes the correction value calculation process shown in Fig. 8 (step S4). By executing the correction value calculation process, the control unit 10 calculates, for each of the multiple patch images, a correction value for the transfer voltage in the target image forming unit 26 corresponding to the patch image, based on the color detected by the detection unit 40 in step S3. The control unit 10 functions as a calculation unit. Step S4 is a calculation step.

[0065] (Correction value calculation process) The control unit 10 calculates the magenta direction component ΔEm(pk) of the amount of change in the color of process black based on the detection result of the process black patch image Ppk by the detection unit 40 (step S41). The flow of calculating the magenta direction component ΔEm(pk) of the amount of change in the color of process black will be described below.

[0066] Figure 9 is a diagram showing an example of color changes in process black. "M" in Figure 9 indicates the position of magenta in the LAB color space, which is a color coordinate system. "Y" in Figure 9 indicates the position of yellow in the LAB color space. "C" in Figure 9 indicates the position of cyan in the LAB color space. When forming the process black patch image Ppk, if the resistance value of the transfer section of at least one of the image forming units 26M, 26C, and 26K changes, the color of the process black changes from the reference color. In one aspect, the color of the process black changes from the reference value Pbk to a value Pbk'. As described above, the color change of process black occurs due to the reverse transfer of magenta toner and the reverse transfer of cyan toner. Therefore, the color change of process black can be decomposed into vectors for the change in the magenta direction and the change in the cyan direction, as shown in Figure 9. The control unit 10 calculates the magenta direction component ΔEm(pk) of the process black color change by vector-decomposing the magenta direction change from the process black color change amount, and the cyan direction component ΔEc(pk) of the process black color change amount.

[0067] Next, the control unit 10 calculates the total amount ΔMm(pk) of magenta toner in reverse transfer corresponding to the color change when the process black patch image Ppk is formed (step S42). Specifically, the control unit 10 inputs the magenta direction component ΔEm(pk) of the process black color change calculated in step S41 into the correspondence relationship between the amount of change in the magenta direction component of the process black color change and the amount of reverse transfer of magenta toner that causes the change. As a result, the control unit 10 calculates the total amount ΔMm(pk) of reverse transfer of magenta toner that causes the magenta direction component ΔEm(pk) of the process black color change.

[0068] Next, the control unit 10 calculates a correction value ΔVm for the transfer voltage in the transfer portion of the image forming unit 26M (step S43). Specifically, the control unit 10 inputs the total amount ΔMm(pk) of magenta toner reverse transfer calculated in step S42 into the correspondence relationship between the amount of magenta toner reverse transfer and the transfer voltage of the image forming unit 26M. As a result, the control unit 10 calculates the transfer voltage of the image forming unit 26M that causes the total amount ΔMm(pk) of magenta toner reverse transfer. Next, the control unit 10 calculates the deviation ΔVm of the transfer voltage of the image forming unit 26M from a predetermined reference value based on the transfer voltage of the image forming unit 26M that causes the total amount ΔMm(pk) of magenta toner reverse transfer. The deviation ΔVm of the transfer voltage from the reference value is the correction value ΔVm of the transfer voltage.

[0069] Next, the control unit 10 calculates the amount of change ΔE(r) in the color of red based on the detection result of the red patch image Pr by the detection unit 40 (step S44). Fig. 10 is a diagram showing an example of a change in the color of red. "M" in Fig. 10 indicates the position of magenta in the LAB color space, which is a color coordinate system, and "Y" in Fig. 10 indicates the position of yellow in the LAB color space. When forming a red patch image Pr, if the resistance value of the transfer section changes in at least one of image forming units 26M, 26C, and 26K, the color of red changes, for example, from reference value R to value R'. In the example shown in Fig. 10, the color of red changes to value R', which is more yellow than reference value R. In the example shown in Fig. 10, the amount of change from reference value R to value R' is denoted as ΔE(r).

[0070] Next, the control unit 10 calculates the total amount ΔMm(r) of reverse transfer of magenta toner corresponding to the color change when the red patch image Pr is formed (step S45). Specifically, the control unit 10 inputs the amount of change in red color ΔE(r) calculated in step S44 into the correspondence relationship between the amount of change in red color change and the amount of reverse transfer of magenta toner that causes the change. As a result, the control unit 10 calculates the total amount ΔMm(r) of reverse transfer of magenta toner that causes the amount of change in red color ΔE(r).

[0071] Next, similar to the calculation of the amount of change ΔE(r) in the color of red, the control unit 10 calculates the amount of change ΔE(g) in the color of green based on the detection result of the green patch image Pg by the detection unit 40 (step S46). When the resistance value of the transfer unit in at least one of the image forming units 26C and 26K changes during the formation of the green patch image Pg, the color of green changes.

[0072] Next, the control unit 10 calculates the total amount ΔMc(g) of cyan toner in reverse transfer corresponding to the color change when the green patch image Pg is formed (step S47). Specifically, the control unit 10 inputs the amount of change in the green color ΔE(g) calculated in step S46 into the correspondence relationship between the amount of change in the green color change and the amount of reverse transfer of cyan toner that causes the change. As a result, the control unit 10 calculates the total amount ΔMc(g) of reverse transfer of cyan toner that causes the amount of change in the green color ΔE(g). If the total amount ΔMc(g) of reverse transfer of cyan toner that causes the amount of change in green color ΔE(g) is defined as a quantitative value Y, the quantitative value Y is expressed by the following formula (4) using the above formula (2). Equation (4) Y = αf(Vc)+βf(Vk)

[0073] Next, the control unit 10 calculates a correction value ΔVc of the transfer voltage in the transfer portion of the image forming unit 26C (step S48). The flow of calculating the correction value ΔVc of the transfer voltage in the transfer portion of the image forming unit 26C will be described below. The total amount ΔMm(r) of reverse transfer of magenta toner in the change in red color calculated in step S45 can be decomposed into "αf(Vm)" and "βf(Vc)+βf(Vk)" according to (1) above. In the above formula (1), ΔMm(r) is calculated in step S45. "αf(Vm)" is ΔMm(pk) according to the above formula (3), and is calculated in step S42. Therefore, the remaining amount X of the total amount in the reverse transfer of magenta toner in the color change of red, obtained by subtracting "αf(Vm)" from ΔMm(r), is a quantitative value, and according to the above formula (1), is expressed by the following formula (5). Equation (5) X = βf(Vc)+βf(Vk)

[0074] By subtracting the above formula (4) from the above formula (5), the function f(Vc) that converts the transfer voltage of the image forming unit 26C into the reverse transfer amount of cyan toner is expressed by the following formula (6). Equation (6) f(Vc) = (XY) / (β-α) The control unit 10 calculates X by subtracting αf(Vm), which is ΔMm(pk), from ΔMm(r). Y is calculated in step S47. The control unit 10 obtains the first decrease rate α and the second decrease rate β from the storage unit 70 and substitutes them. Using the above formula (6), the control unit 10 calculates the amount of reverse transfer of cyan toner when the transfer voltage of the image forming unit 26C deviates from the reference value by ΔVc. Next, the control unit 10 calculates the deviation amount ΔVc of the transfer voltage of the image forming unit 26C from the reference value based on the calculated amount of reverse transfer of cyan toner and the correspondence between the amount of reverse transfer of cyan toner and the transfer voltage of the image forming unit 26C. The deviation amount ΔVc of the transfer voltage from the reference value is the correction value ΔVc of the transfer voltage.

[0075] Next, the control unit 10 calculates the correction value ΔVk of the transfer voltage of the transfer unit of the image forming unit 26K (step S49), and ends the correction value calculation process. The flow of calculating the correction value ΔVk of the transfer voltage of the transfer unit of the image forming unit 26K will be described below. By substituting the above formula (6) into the above formula (4), the function f(Vk) that converts the transfer voltage of the image forming unit 26K into the reverse transfer amount of cyan toner is expressed by the following formula (7). Equation (7) f(Vk) = {Y-(α / β)X} / (β-α) The control unit 10 calculates the amount of reverse transfer of cyan toner when the transfer voltage of the image forming unit 26K deviates from the reference value by ΔVk using the above formula (7). Next, the control unit 10 calculates the deviation amount ΔVk of the transfer voltage of the image forming unit 26K from the reference value based on the calculated amount of reverse transfer of cyan toner and the correspondence between the amount of reverse transfer of cyan toner and the transfer voltage of the image forming unit 26K. The deviation amount ΔVk of the transfer voltage from the reference value is the correction value ΔVk of the transfer voltage. As described above, the control unit 10 calculates the correction value ΔVm for the transfer voltage of the image forming unit 26M, the correction value ΔVc for the transfer voltage of the image forming unit 26C, and the correction value ΔVk for the transfer voltage of the image forming unit 26K through the correction value calculation process. In the correction value calculation process, the control unit 10 calculates a correction value for the primary transfer voltage based on the primary transfer voltage in the first image forming unit, the primary transfer voltage in the second image forming unit, and the reduction rate of the toner transferred to the intermediate transfer belt 27 due to reverse transfer.

[0076] 7, the control unit 10 corrects the transfer voltage in the target image forming unit based on the correction value calculated in step S4 (step S5). More specifically, the control unit 10 corrects the transfer voltage for each of the image forming units 26M, 26C, and 26K by the correction value calculated in step S4. Next, the control unit 10 ends the correction process of the transfer voltage.

[0077] [Variations] In the above embodiment, the correspondence relationship between the amount of change in color and the amount of reverse transfer of toner that causes the change is predetermined, but is not limited to this. In the above embodiment, the correspondence relationship between the amount of reverse transfer of toner and the transfer voltage of the transfer unit when reverse transfer occurs is predetermined, but is not limited to this. Image forming apparatus 1 may have a calculation mode that calculates the correspondence relationship between the amount of change in color and the amount of reverse transfer of toner that causes the change, and the correspondence relationship between the amount of reverse transfer of toner and the transfer voltage of the transfer unit when reverse transfer occurs. In other words, image forming apparatus 1 may have a calculation mode that calculates the correspondence relationship between the amount of change in color of the image formed by image forming unit 20 and the transfer voltage of the transfer unit when reverse transfer of toner that causes the change occurs. When the calculation mode is selected, the control unit 10 causes the image forming unit 20 to form a patch image on the recording medium Q using a different transfer voltage each time. Next, the control unit 10 acquires the detection result of the color of the patch image formed on the recording medium Q by the detection unit 40. Next, the control unit 10 calculates the correspondence relationship based on the amount of color change in the patch image each time. This allows the correction value of the transfer voltage in the image forming unit 26 to be calculated using the above-mentioned correspondence relationship specific to the image forming apparatus 1, thereby improving the accuracy of the correction.

[0078] In the above embodiment, the multiple image forming units are image forming unit 26Y that forms a yellow toner image, image forming unit 26M that forms a magenta toner image, image forming unit 26C that forms a cyan toner image, and image forming unit 26K that forms a black toner image, but the multiple image forming units are not limited to this. The multiple image forming units may also include image forming units that form toner images of other colors (for example, white, transparent, gold, or silver).

[0079] <5. Effects> As described above, the image forming apparatus 1 of this embodiment has a plurality of image forming units 26 arranged in series along the running direction of the transfer medium (intermediate transfer belt 27), which transfer toner images of multiple colors onto the transfer medium, respectively, and is equipped with an image forming section 20 which forms an image consisting of multiple colors on a recording medium Q. The image forming apparatus 1 of this embodiment includes a detection unit 40 that detects the color of the image formed by the image forming unit 20. The image forming apparatus 1 of this embodiment includes a calculation section (control section 10) that calculates a correction value for the primary transfer voltage in the image forming unit 26 based on the color detected by the detection section 40. The colors detected by the detection unit 40 include a first color that is a secondary or higher color, a second color that is a secondary or higher color, and a third color that is a tertiary color. Therefore, by calculating the correction value of the transfer voltage based on the detected first, second, and third colors, which are the multiple multi-colors, a more optimal correction value can be calculated, thereby enabling the transfer voltage of the transfer unit to be corrected with high accuracy.

[0080] In the image forming apparatus 1 of this embodiment, the calculation unit (control unit 10) calculates a correction value for the primary transfer voltage based on the primary transfer voltage of the first image forming unit located at the most downstream position in the running direction among the image forming units corresponding to the constituent colors detected by the detection unit 40, the primary transfer voltage of the second image forming unit located downstream of the first image forming unit in the running direction AR of the transferee (intermediate transfer belt 27), and the reduction rate of the toner transferred to the transferee due to reverse transfer. Therefore, the correction value for the primary transfer voltage can be calculated taking into account the reverse transfer in the second image forming unit located downstream of the image forming unit corresponding to the constituent color in the running direction of the intermediate transfer belt 27. This allows a more optimal correction value to be calculated.

[0081] In the image forming apparatus 1 of this embodiment, the reduction rate includes a first reduction rate, which is the reduction rate of toner transferred to a transferee (intermediate transfer belt 27) by the first image forming unit due to reverse transfer in the first image forming unit, and a second reduction rate, which is the reduction rate of toner transferred to a transferee by the first image forming unit due to reverse transfer in the second image forming unit. Therefore, the correction value for the primary transfer voltage can be calculated taking into account the reverse transfer in the second image forming unit located downstream of the image forming unit corresponding to the constituent color in the running direction of the intermediate transfer belt 27. This allows a more optimal correction value to be calculated.

[0082] In the image forming apparatus 1 of this embodiment, the first reduction rate is smaller than the second reduction rate. Therefore, the correction value for the primary transfer voltage can be calculated taking into account the rate of toner reduction due to reverse transfer in each image forming unit 26. This allows a more optimal correction value to be calculated.

[0083] The image forming apparatus 1 of this embodiment includes a storage unit 70 that stores the reduction rate. Therefore, it is possible to save the trouble of calculating the reduction rate while the image forming apparatus 1 is in operation.

[0084] In the image forming apparatus 1 of this embodiment, the calculation unit (control unit 10) calculates a correction value for the primary transfer voltage based on a change in the color coordinates of the color detected by the detection unit 40. This allows the correction value of the primary transfer voltage to be calculated with higher accuracy.

[0085] The image forming apparatus 1 of this embodiment includes a storage unit 70 that stores the correspondence between the amount of color change detected by the detection unit 40 and the primary transfer voltage. Therefore, when a job is executed, it is possible to eliminate the need to calculate the correspondence between the amount of color change and the primary transfer voltage.

[0086] The image forming apparatus 1 of this embodiment has a calculation mode for calculating the correspondence relationship between the amount of change in color detected by the detection unit 40 and the primary transfer voltage. Therefore, the correction value for the primary transfer voltage can be calculated using the correspondence relationship between the amount of color change specific to the image forming apparatus 1 and the primary transfer voltage, thereby improving the accuracy of the correction.

[0087] The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, in the above embodiment, the transfer voltage in the image forming unit is corrected using a red patch image Pr, a green patch image Pg, and a process black patch image Ppk. However, the patch images used to correct the transfer voltage in the image forming unit are not limited to these. The patch images used to correct the transfer voltage in the image forming unit may include a patch image of a first color that is a secondary or higher color, a patch image of a second color that is a secondary or higher color, and a patch image of a third color that is a tertiary color.

[0088] The frequency of correction of the transfer voltage of the image forming unit may be increased in the early stages of printing so that the transfer voltage in the image forming unit is corrected at a speed faster than the speed at which the color of the image changes with changes in the temperature inside the image forming device 1.

[0089] In the above embodiment, image forming unit 26Y, image forming unit 26M, image forming unit 26C, and image forming unit 26K are arranged in this order from the upstream side in the running direction AR of intermediate transfer belt 27. However, the arrangement order of image forming unit 26Y, image forming unit 26M, image forming unit 26C, and image forming unit 26K is not limited to this.

[0090] In the above embodiment, the image forming method of the image forming apparatus 1 is a method in which a toner image is transferred from the photoreceptor 21 to the intermediate transfer belt 27, and then the toner image is transferred to the recording medium Q. However, a method in which a toner image is directly transferred from the photoreceptor 21 to the recording medium Q may also be used. In a method in which a toner image is directly transferred from the photoreceptor 21 to the recording medium Q, the recording medium Q is the "transferee" in this disclosure.

[0091] According to the transfer voltage correction method of this embodiment, there is no need to detect the resistance of the transfer section of the image forming unit in order to calculate the correction value of the transfer voltage in the image forming unit. Therefore, it is possible to use individual sheets of paper or continuous paper such as roll paper as the recording medium Q.

[0092] In addition, the specific configurations, operation contents and procedures shown in the above embodiments can be modified as appropriate within the scope that does not deviate from the spirit of the present invention. [Explanation of symbols]

[0093] 1 image forming apparatus, 10 control unit (calculation unit), 15 paper feed unit, 20 image forming unit, 21, 21C, 21K, 21M, 21Y photosensitive body, 22, 22C, 22K, 22M, 22Y charging device, 23, 23C, 23K, 23M, 23Y exposure device, 24, 24C, 24K, 24M, 24Y developing unit, 25, 25C, 25K, 25M, 25Y, 28 transfer roller, 26, 26C, 26K, 26M, 26Y image forming unit, 27 intermediate transfer belt (transfer receiving body), 29 cleaning unit, 30 fixing unit, 40 detection unit, 50 operation display unit, 60 communication unit, 70 memory unit, 99 bus, AR travel direction, CR1, CR2 cutting line, I image, P Patch image group, Pg Green patch image, Ppk Process black patch image, Pr Red patch image, Q Recording medium

Claims

1. an image forming section including a plurality of image forming units arranged in series along the traveling direction of a transfer medium, each of which transfers a toner image of a plurality of colors onto the transfer medium, and which forms an image of a plurality of colors on a recording medium; a detection unit that detects the color of an image formed by the image forming unit; a calculation unit that calculates a correction value for a primary transfer voltage in the image forming unit based on the color detected by the detection unit; Equipped with An image forming apparatus, wherein the colors detected by the detection unit include a first color that is a secondary or higher color, a second color that is a secondary or higher color, and a third color that is a tertiary color.

2. 2. The image forming apparatus according to claim 1, wherein the calculation unit calculates a correction value for the primary transfer voltage based on a primary transfer voltage in a first image forming unit that is located furthest downstream in the traveling direction among the image forming units corresponding to the constituent colors of the color detected by the detection unit, a primary transfer voltage in a second image forming unit that is located downstream in the traveling direction from the first image forming unit, and a reduction rate of toner transferred to the transfer body due to reverse transfer.

3. 3. The image forming apparatus according to claim 2, wherein the reduction rate includes a first reduction rate, which is a reduction rate of the toner transferred to the transfer body by the first image forming unit due to reverse transfer in the first image forming unit, and a second reduction rate, which is a reduction rate of the toner transferred to the transfer body by the first image forming unit due to reverse transfer in the second image forming unit.

4. The image forming apparatus according to claim 3 , wherein the first decrease rate is smaller than the second decrease rate.

5. The image forming apparatus according to claim 2 , further comprising a storage unit that stores the reduction rate.

6. The image forming apparatus according to claim 2 , wherein the calculation unit calculates the correction value of the primary transfer voltage based on a change in the color coordinate of the color detected by the detection unit.

7. The image forming apparatus according to claim 2 , further comprising a storage unit that stores a correspondence relationship between the amount of change in color detected by the detection unit and the primary transfer voltage.

8. The image forming apparatus according to claim 2 , further comprising a calculation mode for calculating a correspondence relationship between the amount of change in color detected by the detection unit and the primary transfer voltage.

9. an image forming section including a plurality of image forming units arranged in series along the traveling direction of a transfer medium, each of which transfers a toner image of a plurality of colors onto the transfer medium, and which forms an image of a plurality of colors on a recording medium; a detection unit that detects the color of an image formed by the image forming unit; A correction method executed by an image forming apparatus comprising: a calculation step of calculating a correction value of a primary transfer voltage in the image forming unit based on the color detected by the detection unit; A correction method, wherein the colors detected by the detection unit include a first color that is a secondary or higher color, a second color that is a secondary or higher color, and a third color that is a tertiary color.

10. an image forming section including a plurality of image forming units arranged in series along the traveling direction of a transfer medium, each of which transfers a toner image of a plurality of colors onto the transfer medium, and which forms an image of a plurality of colors on a recording medium; a detection unit that detects the color of an image formed by the image forming unit; A computer of an image forming apparatus comprising: a calculation unit that calculates a correction value for a primary transfer voltage in the image forming unit based on the color detected by the detection unit; The program, wherein the colors detected by the detection unit include a first color that is a secondary or higher color, a second color that is a secondary or higher color, and a third color that is a tertiary color.

Images