Image forming device and image forming method

Abstract

To provide an image forming device and an image forming method which can efficiently execute various condition adjustment processes which respectively are suitable for color printing and monochrome printing to stabilize an image quality.SOLUTION: An image forming device (100) is provided with an image forming part (3), a first image processing part (52) and a second image processing part (53). The first image processing part (52) executes a plurality of kinds of preset condition adjustment processes for adjusting an image formation condition in the image forming part (3) to a target image forming unit that is used for monochrome printing, of a plurality of image forming units (20), in order by specific number every time when an execution history of the monochrome printing satisfies a preset monochrome adjustment condition. The second image processing part (53) executes a plurality of kinds of condition adjustment processes to a target image forming unit that is used for color printing, of the plurality of image forming units (20), in order by specific number every time when an execution history of the color printing satisfies a preset color adjustment condition.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] An electrophotographic image forming apparatus includes an image forming unit that forms an image on a transfer medium based on input image data. The image forming apparatus may perform a condition adjustment process to adjust various image formation conditions, such as the amount of laser light and the developing bias voltage. A technique for controlling the execution frequency of the condition adjustment process in consideration of the frequency of color printing is also known (see, for example, Patent Document 1). In the condition adjustment process, a detection toner image used in the condition adjustment process is formed on a transfer medium such as an intermediate transfer belt, and the image formation conditions are adjusted based on the detection results such as the density and position of the detection toner. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-293240 Summary of the Invention [Problem to be solved by the invention]

[0004] However, since it takes time to collectively form the detection toner images used in multiple types of condition adjustment processes, increasing the frequency of the condition adjustment processes may affect printing efficiency.On the other hand, decreasing the frequency of the condition adjustment processes may lengthen the intervals between executions of the condition adjustment processes, which may result in unstable image quality.

[0005] SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus and an image forming method that can efficiently execute various condition adjustment processes suited to color printing and monochrome printing, thereby stabilizing image quality. [Means for solving the problem]

[0006] According to one aspect of the present invention, an image forming apparatus includes an image forming unit, a first image processing unit, and a second image processing unit. The image forming unit includes a plurality of image forming units corresponding to a plurality of colors, and performs monochrome printing to print monochrome images or color printing to print color images based on input image data. The first image processing unit sequentially executes a specific number of preset condition adjustment processes for adjusting image formation conditions in the image forming unit, targeting the image forming units used for the monochrome printing among the plurality of image forming units, each time a predetermined monochrome adjustment condition is satisfied by the execution history of the monochrome printing. The second image processing unit sequentially executes a specific number of preset condition adjustment processes for the image forming units used for the color printing among the plurality of image forming units, each time a predetermined color adjustment condition is satisfied by the execution history of the color printing.

[0007] According to another aspect of the present invention, an image forming method is executed by a processor of an image forming apparatus including a plurality of image forming units corresponding to a plurality of colors, and an image forming unit that performs monochrome printing to print monochrome images or color printing to print color images based on input image data. The image forming method includes a step of sequentially executing a specific number of predetermined condition adjustment processes for adjusting image formation conditions in the image forming unit, for an image forming unit used for the monochrome printing among the plurality of image forming units, each time a predetermined monochrome adjustment condition is satisfied in the execution history of the monochrome printing. The image forming method also includes a step of sequentially executing a specific number of predetermined condition adjustment processes for an image forming unit used for the color printing among the plurality of image forming units, each time a predetermined color adjustment condition is satisfied in the execution history of the color printing. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an image forming apparatus and an image forming method that can efficiently perform various condition adjustment processes suitable for color printing and monochrome printing, thereby stabilizing image quality. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view showing the configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing the system configuration of the image forming apparatus according to the embodiment of the present invention. [Figure 3] FIG. 3 is a schematic diagram showing the configuration of the image forming unit of the image forming apparatus according to the embodiment of the present invention. [Figure 4] FIG. 4 is a bottom view showing the configuration of the intermediate transfer belt of the image forming apparatus according to the embodiment of the present invention. [Figure 5] FIG. 5 is a flowchart showing an example of adjustment control processing executed in the image forming apparatus according to the embodiment of the present invention. [Figure 6] FIG. 6 is a diagram showing an example of the execution result of the adjustment control process executed in the image forming apparatus according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that the following embodiment is an example of a specific embodiment of the present invention and does not limit the technical scope of the present invention.

[0011] First, the configuration of an image forming apparatus 100 according to an embodiment of the present invention will be described with reference to FIGS.

[0012] For ease of explanation, the vertical direction in the installation state where image forming apparatus 100 is usable (the state shown in FIG. 1) is defined as the up-down direction D1. Also, the front-to-back direction D2 is defined with the left side of image forming apparatus 100 on the paper surface shown in FIG. 1 as the front (front face). Also, the left-to-right direction D3 is defined with the front face of image forming apparatus 100 in the installation state as the reference point.

[0013] Image forming apparatus 100 is a multifunction peripheral that has multiple functions, such as a scanning function for reading an image from an original document, a printing function for forming an image based on image data, a fax function, and a copy function. Note that the present invention may also be applied to image forming apparatuses such as printers, fax machines, and copy machines that are capable of forming images using an electrophotographic method.

[0014] As shown in FIGS. 1 and 2, the image forming apparatus 100 includes an ADF (Auto Document Feeder) 1, an image reading unit 2, an image forming unit 3, a paper feeding unit 4, an operation display unit 5, a storage unit 6, and a control unit .

[0015] The ADF 1 transports documents to be scanned by the scanning function, and includes a document setting section, a plurality of transport rollers, a document holder, and a paper ejection section.

[0016] The image reading unit 2 realizes the scanning function and includes a document table, a light source, a plurality of mirrors, an optical lens, and a CCD (Charge Coupled Device).

[0017] The image forming unit 3 realizes the printing function. Specifically, the image forming unit 3 forms a color or monochrome image on a sheet fed from the paper feed unit 4 according to an electrophotographic method.

[0018] The paper feed unit 4 supplies sheets to the image forming unit 3. The paper feed unit 4 includes a paper feed cassette, a manual feed tray, and multiple transport rollers. The control unit 7 can set the sheet type of the sheets to be printed and stored in the paper feed cassette in advance in response to a user operation. In particular, if the paper feed unit 4 is provided with multiple paper feed cassettes, the sheet type can be set for each paper feed cassette.

[0019] The operation display unit 5 is a user interface of the image forming apparatus 100. The operation display unit 5 has a display unit such as a liquid crystal display that displays various information in response to control instructions from the control unit 7, and an operation unit such as operation keys or a touch panel that inputs various information to the control unit 7 in response to user operations.

[0020] The storage unit 6 is a nonvolatile storage device. For example, the storage unit 6 is a nonvolatile memory such as a flash memory. The storage unit 6 may be an SSD (Solid State Drive) or an HDD (Hard Disk Drive).

[0021] The control unit 7 performs overall control of the image forming apparatus 100. As shown in FIG. 2, the control unit 7 includes a CPU 11, a ROM 12, and a RAM 13. The CPU 11 includes one or more processors that execute various types of arithmetic processing. The ROM 12 is a non-volatile storage device that stores in advance information such as control programs for causing the CPU 11 to execute various types of processing. The RAM 13 is a volatile or non-volatile storage device that is used as a temporary storage memory (work area) for the various types of processing executed by the CPU 11. The CPU 11 performs overall control of the image forming apparatus 100 by executing the various control programs that are stored in advance in the ROM 12.

[0022] The control unit 7 may be a control unit provided separately from a main control unit that performs overall control of the image forming apparatus 100. The control unit 7 may also be configured with an electronic circuit such as an integrated circuit (ASIC).

[0023] [Configuration of image forming unit 3] Next, the configuration of the image forming section 3 will be described with reference to Figures 1 to 4. Here, Figure 3 is a schematic diagram showing the configurations of the image forming unit 20, intermediate transfer belt 26, and secondary transfer roller 27. Also, Figure 4 is a bottom view showing the configurations of the photosensitive drum 31, intermediate transfer belt 26, drive roller 26A, and secondary transfer roller 27 of the image forming unit 24.

[0024] 1, the image forming section 3 includes four image forming units 20, an optical scanning device 25, an intermediate transfer belt 26, a secondary transfer roller 27, a fixing device 28, and a paper discharge tray 29. As shown in FIGS. 2 and 3, the image forming section 3 also includes four first power sources 40, a second power source 45, and a detection section 46. The image forming section 3 performs monochrome printing, which prints a monochrome image, or color printing, which prints a color image, based on input image data.

[0025] The four image forming units 20 include image forming units 21 to 24 corresponding to multiple colors. Image forming unit 21 (see FIG. 3) forms a Y (yellow) toner image. Image forming unit 22 (see FIG. 3) forms a C (cyan) toner image. Image forming unit 23 (see FIG. 3) forms an M (magenta) toner image. Image forming unit 24 (see FIG. 3) forms a K (black) toner image. As shown in FIGS. 1 and 3, the four image forming units 20 are arranged side by side in the order of yellow, cyan, magenta, and black from the front side of image forming apparatus 100 along the front-rear direction D2.

[0026] 3, each image forming unit 20 includes a photosensitive drum 31, a charging roller 32, a developing device 33, a primary transfer roller 34, and a drum cleaning unit 35. Each image forming unit 20 also includes a toner container 36 shown in FIG.

[0027] An electrostatic latent image is formed on the surface of the photosensitive drum 31. For example, the photosensitive drum 31 has a photosensitive layer made of amorphous silicon. The photosensitive drum 31 receives a rotational driving force supplied from a motor (not shown) and rotates in a drum rotation direction D4 shown in FIG. 3. As a result, the photosensitive drum 31 transports the electrostatic latent image formed on its surface.

[0028] A preset charging voltage is applied to the charging roller 32, which charges the surface of the photosensitive drum 31. For example, the charging roller 32 charges the surface of the photosensitive drum 31 to a positive polarity. The surface of the photosensitive drum 31 charged by the charging roller 32 is irradiated with light based on image data emitted from the optical scanning device 25. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 31.

[0029] The developing device 33 develops the electrostatic latent image formed on the surface of the photosensitive drum 31. The developing device 33 includes a pair of stirring members, a magnet roller, and a developing roller. The pair of stirring members stir the developer, which contains toner and a carrier, contained within the developing device 33. For example, the toner contained in the developer is positively charged due to friction with the carrier contained in the developer. The magnet roller draws up the developer stirred by the pair of stirring members and supplies the toner contained in the developer to the developing roller. The developing roller transports the toner supplied from the magnet roller to a position facing the photosensitive drum 31. Furthermore, the developing roller receives a preset development bias voltage and supplies the toner transported to the facing position to the photosensitive drum 31. As a result, toner is selectively supplied to an exposure area of ​​the photosensitive drum 31 irradiated with light emitted from the optical scanning device 25, thereby developing the electrostatic latent image formed on the surface of the photosensitive drum 31. The developing device 33 is supplied with toner from a toner container 36 .

[0030] Upon receiving a predetermined primary transfer current, the primary transfer roller 34 transfers the toner image formed on the surface of the photosensitive drum 31 onto the outer circumferential surface of the intermediate transfer belt 26. As shown in Fig. 3, the primary transfer roller 34 is disposed opposite the photosensitive drum 31 with the intermediate transfer belt 26 sandwiched therebetween. The intermediate transfer belt 26 is an example of a transfer-receiving body in the present invention.

[0031] The drum cleaning unit 35 removes the toner remaining on the surface of the photosensitive drum 31 after the toner image has been transferred by the primary transfer roller 34 .

[0032] The optical scanning device 25 emits light based on image data toward the surface of the photosensitive drum 31 of each image forming unit 20.

[0033] The intermediate transfer belt 26 is an endless belt member onto which the toner images formed on the surfaces of the photosensitive drums 31 of each image forming unit 20 are transferred. For example, the intermediate transfer belt 26 is made of a resin material such as polyimide. The intermediate transfer belt 26 is stretched with a predetermined tension by a drive roller 26A (see FIG. 3) and a tension roller 26B (see FIG. 3). The intermediate transfer belt 26 rotates in a belt rotation direction D5 shown in FIG. 3 when the drive roller 26A rotates due to a rotational driving force supplied from a motor (not shown). As a result, the intermediate transfer belt 26 transports the toner images transferred from each photosensitive drum 31 to a transfer position onto a sheet by a secondary transfer roller 27. After the toner images are transferred by the secondary transfer roller 27, the outer peripheral surface of the intermediate transfer belt 26 is cleaned by a belt cleaning unit 26C (see FIG. 3).

[0034] The secondary transfer roller 27 receives a preset secondary transfer current and transfers the toner image transferred onto the outer peripheral surface of the intermediate transfer belt 26 onto a sheet supplied from the paper feed unit 4. As shown in FIG. 3, the secondary transfer roller 27 is disposed opposite the drive roller 26A with the intermediate transfer belt 26 sandwiched therebetween.

[0035] 4, the size of the secondary transfer roller 27 in the axial direction (left-right direction D3) is smaller than the width (size in the left-right direction D3) of the intermediate transfer belt 26. Therefore, a non-contact area A3 (see FIG. 4) that does not come into contact with the secondary transfer roller 27 is generated on the outer circumferential surface of the intermediate transfer belt 26. The non-contact area A3 is an area on the outer circumferential surface of the intermediate transfer belt 26 outside the contact area A2 (see FIG. 4) that comes into contact with the secondary transfer roller 27, and includes the ends of the intermediate transfer belt 26 in the width direction.

[0036] The fixing device 28 fixes the toner image transferred onto the sheet by the secondary transfer roller 27 onto the sheet.

[0037] The sheet on which the toner image has been fixed by the fixing device 28 is discharged onto the paper discharge tray 29.

[0038] Of the four first power sources 40, first power source 41 (see FIG. 2) is a constant current power source that supplies the primary transfer current to the primary transfer roller 34 of the image forming unit 21. Of the four first power sources 40, first power source 42 (see FIG. 2) is a constant current power source that supplies the primary transfer current to the primary transfer roller 34 of the image forming unit 22. Of the four first power sources 40, first power source 43 (see FIG. 2) is a constant current power source that supplies the primary transfer current to the primary transfer roller 34 of the image forming unit 23. Of the four first power sources 40, first power source 44 (see FIG. 2) is a constant current power source that supplies the primary transfer current to the primary transfer roller 34 of the image forming unit 24. Each of the first power sources 40 supplies the primary transfer current set by the control unit 7 to the primary transfer roller 34. For example, the primary transfer current is a negative current.

[0039] The second power supply 45 is a constant current power supply that supplies the secondary transfer current to the secondary transfer roller 27. The second power supply 45 supplies the secondary transfer current set by the control unit 7 to the secondary transfer roller 27. For example, the secondary transfer current is a negative current.

[0040] The detection unit 46 is used to detect the density and position of the toner image transferred to the non-contact area A3 (see FIG. 4) on the outer circumferential surface of the intermediate transfer belt 26. For example, the detection unit 46 is a reflective photosensor including a light-emitting unit that emits light toward the non-contact area A3 of the intermediate transfer belt 26 and a light-receiving unit that receives light emitted from the light-emitting unit and reflected by the non-contact area A3 of the intermediate transfer belt 26. The detection unit 46 inputs an electrical signal corresponding to the density of the toner image to be detected to the control unit 7. The detection unit 46 detects the density of the toner image over a predetermined width in a direction perpendicular to the belt rotation direction D5 of the intermediate transfer belt 26, and the control unit 7 can detect the position of the toner image in the direction perpendicular to the belt rotation direction D5 based on the detection result of the detection unit 46. In the image forming apparatus 100, detection toner images, which will be described later, may be formed in non-contact areas A3 on both sides of the contact area A2 on the intermediate transfer belt 26, and two detectors 46 may be provided at positions where the detection toner images formed in the non-contact areas A3 on both ends can be detected. In this case, in the condition adjustment process, which will be described later, the image formation conditions are adjusted based on the detection results by the two detectors 46.

[0041] 3, the detection unit 46 is disposed downstream in the belt rotation direction D5 of the position where the toner image is transferred by the secondary transfer roller 27, and upstream in the belt rotation direction D5 of the position where the belt cleaning unit 26C cleans the outer circumferential surface of the intermediate transfer belt 26. Alternatively, the detection unit 46 may be disposed downstream in the belt rotation direction D5 of the photosensitive drum 31 of the image forming unit 24, and upstream in the belt rotation direction D5 of the position where the toner image is transferred by the secondary transfer roller 27.

[0042] [Configuration of control unit 7] Next, the configuration of the control unit 7 will be described with reference to FIG.

[0043] 2, the control unit 7 includes a print processing unit 50, a count processing unit 51, a first image processing unit 52, and a second image processing unit 53. Specifically, a condition adjustment program for causing the CPU 11 to function as each of the above-mentioned processing units is stored in advance in the ROM 12 of the control unit 7. The CPU 11 then executes the condition adjustment program stored in the ROM 12 to function as each of the above-mentioned processing units.

[0044] The condition adjustment program may be recorded on a computer-readable recording medium such as a CD, DVD, or flash memory, and may be read from the recording medium and stored in a storage device such as the memory unit 6. In addition, some or all of the print processing unit 50, count processing unit 51, first image processing unit 52, and second image processing unit 53 may be configured using electronic circuits such as an application specific integrated circuit (ASIC).

[0045] The print processing unit 50 executes print processing, including a normal image formation process in which a print image based on image data of the print target is formed in a predetermined print area A1 (see FIG. 4) on the intermediate transfer belt 26 by the image forming unit 3. Specifically, in the normal image formation process, the print processing unit 50 controls the optical scanning device 25 based on the image data of the print target to form an electrostatic latent image corresponding to each color on the photosensitive drum 31 of each image forming unit 20 at a predetermined timing. As a result, in each image forming unit 20, the electrostatic latent image formed on the photosensitive drum 31 is developed into a toner image, and the toner image is sequentially transferred to the intermediate transfer belt 26. Thereafter, the color or monochrome image formed on the intermediate transfer belt 26 is transferred to a sheet by the secondary transfer roller 27, and the intermediate transfer belt 26 is cleaned by the belt cleaning unit 26C.

[0046] In the normal image formation process, the print processing unit 50 controls the amount of laser light irradiated by the optical scanning device 25 based on the image data and input / output characteristics that indicate the relationship between input image data and the amount of light irradiated by the optical scanning device 25. In the normal image formation process, the print processing unit 50 also controls the development bias voltage in each image forming unit 20 to a value that is set in advance for that image forming unit 20. In the normal image formation process, the print processing unit 50 also controls the charging voltage, the primary transfer current, the secondary transfer current of the secondary transfer roller 27, and the like in each image forming unit 20.

[0047] Furthermore, in the normal image forming process, the print processing unit 50 sets the conveying speed (hereinafter referred to as "linear speed") of the intermediate transfer belt 26 to a speed preset for each print type depending on the sheet type (plain paper, thick paper, etc.) and print type (monochrome printing, color printing). For example, when the sheet type is thick paper, the print processing unit 50 slows the linear speed compared to when the sheet type is plain paper. Furthermore, when the print type is color, the print processing unit 50 slows the linear speed compared to when the print type is monochrome.

[0048] Furthermore, in the normal image forming process, the print processing unit 50 executes a preset inter-sheet process during the inter-sheet period between a process of forming an image based on one page of image data on the intermediate transfer belt 26 and a process of forming the next page of image data on the intermediate transfer belt 26. For example, in the inter-sheet process, cleaning of the photosensitive drum 31 is performed by the drum cleaning unit 35. Furthermore, in the inter-sheet process, various types of image processing may be executed for the image data corresponding to the next sheet in the normal image forming process.

[0049] The count processing unit 51 executes a counting process that counts the number of printed sheets in the image forming apparatus 100. The number of printed sheets counted in the counting process is used to determine the timing for executing the condition adjustment process, which will be described later, by the first image processing unit 52 and the second image processing unit 53. Specifically, the count processing unit 51 counts the number of monochrome printed sheets and the number of color printed sheets corresponding to each printing type, monochrome printing and color printing, as the execution history of monochrome printing and the execution history of color printing, and stores them in the storage unit 6. Furthermore, the count processing unit 51 resets the number of monochrome printed sheets to 0 when the condition adjustment process is executed by the first image processing unit 52, and resets the number of color printed sheets to 0 when the condition adjustment process is executed by the first image processing unit 52.

[0050] Furthermore, the count processing unit 51 updates a monochrome adjustment counter for sequentially switching the type of condition adjustment processing executed by the first image processing unit 52 every time the condition adjustment processing is executed by the first image processing unit 52. Furthermore, the count processing unit 51 updates a color adjustment counter for sequentially switching the type of condition adjustment processing executed by the second image processing unit 53 every time the condition adjustment processing is executed by the second image processing unit 53.

[0051] The first image processing unit 52 executes the condition adjustment process corresponding to the adjustment identification number indicated by the monochrome adjustment counter, and the second image processing unit 53 executes the condition adjustment process corresponding to the adjustment identification number indicated by the color adjustment counter.

[0052] The first image processing unit 52 executes a condition adjustment process to adjust the image formation conditions in the image forming unit 3 for the image forming unit 24 used for monochrome printing among the multiple image forming units 20. For example, the image formation conditions include the development bias voltage, the light intensity of the optical scanning device 25, the light irradiation timing of the optical scanning device 25, and input / output characteristics. In particular, the first image processing unit 52 executes a specific number of condition adjustment processes in sequence each time the monochrome printing execution history satisfies a preset monochrome adjustment condition. In this embodiment, the monochrome printing execution history is the number of monochrome prints, but it may also be the execution time of the monochrome printing. In this embodiment, the monochrome adjustment condition is that the number of monochrome prints reaches 30 (an example of a first threshold). In this embodiment, the first threshold used to determine whether the monochrome adjustment condition is met is greater than a second threshold used to determine whether the color adjustment condition is met, as described below. In other embodiments, the first threshold may be equal to or less than the second threshold. Furthermore, although the specified number is one in this embodiment, it may be two or three, etc., as long as it is less than the total number of types of condition adjustment processing.

[0053] The second image processing unit 53 executes a condition adjustment process for the image forming units 21-24 used for the color printing among the multiple image forming units 20. In particular, the second image processing unit 53 executes the multiple types of condition adjustment processes in sequence, a specific number at a time, each time the color printing execution history satisfies a preset color adjustment condition. In this embodiment, the color printing execution history is the number of color prints, but it may also be the execution time of the color printing. Note that in this embodiment, the color adjustment condition is that the number of color prints reaches 15 (an example of a second threshold). Also, in this embodiment, the specific number is one, but it may be two or three, etc., as long as it is less than the total number of types of condition adjustment processes.

[0054] In this embodiment, the multiple types of condition adjustment processes executed by the first image processing unit 52 or the second image processing unit 53 include a development bias voltage adjustment process, a light amount adjustment process, a positional deviation adjustment process, and an input / output characteristics adjustment process. Hereinafter, the condition adjustment process executed by the first image processing unit 52 may be referred to as a monochrome adjustment process, and the condition adjustment process executed by the second image processing unit 53 may be referred to as a color adjustment process.

[0055] Each of the condition adjustment processes executes a detection image formation process that forms a detection image used to adjust the image formation conditions, a detection process that detects the density or position of the detection image, and a correction process that corrects the image formation conditions based on the density or position of the detection image detected by the detection process.

[0056] In the detection image forming process, during the normal image forming process, a detection toner image X10 (an example of a detection image) used to adjust image formation conditions in the image forming unit 3 is formed by the image forming unit 3 in a non-contact area A3 (see FIG. 4) outside a print area A1 (see FIG. 4) on the intermediate transfer belt 26. In particular, the detection image forming process forms the detection toner image X10 during a period of the normal image forming process excluding the inter-sheet period. The print area A1 is an area inside a contact area A2 (see FIG. 4) on the outer circumferential surface of the intermediate transfer belt 26. For example, the print area A1 is a contact area on the outer circumferential surface of the intermediate transfer belt 26 with a sheet of the largest size that can be used in the image forming apparatus 100. Note that in other embodiments, the detection image forming process may be formed during the inter-sheet period or may be executed after the normal image forming process is executed.

[0057] In the detection image forming process, a detection toner image X10 is formed on the intermediate transfer belt 26 based on preset detection image data corresponding to each color. For example, the detection toner image X10 is a rectangular single-color image.

[0058] Specifically, in the detection image forming process executed by the first image processing unit 52, a detection toner image X10 corresponding to K (black) is formed on the intermediate transfer belt 26. In particular, when the first image processing unit 52 executes the light amount adjustment process, the development bias voltage adjustment process, or the input / output characteristic adjustment process, the first image processing unit 52 forms K (black) detection toner images X10 corresponding to mutually different preset densities on the intermediate transfer belt 26. Furthermore, when the first image processing unit 52 executes the misalignment adjustment process, the first image processing unit 52 forms K (black) detection toner images X10 at mutually different positions in the belt rotation direction D5 of the belt 26 at preset positions on the intermediate transfer belt 26. Note that in this embodiment, in the detection image forming process in the monochrome adjustment process, the detection toner image X10 is formed on the intermediate transfer belt 26 while the normal print image forming process for one page is being executed.

[0059] On the other hand, in the detection image forming process executed by the second image processing unit 53, a plurality of detection toner images X10 corresponding to K (black), C (cyan), M (magenta), and Y (yellow) are sequentially formed on the intermediate transfer belt 26. In particular, when the second image processing unit 53 executes the light amount adjustment process, the development bias voltage adjustment process, or the input / output characteristic adjustment process, the second image processing unit 53 forms a plurality of detection toner images X10 of K (black), C (cyan), M (magenta), and Y (yellow) corresponding to mutually different preset densities on the intermediate transfer belt 26. Furthermore, when the second image processing unit 53 executes the positional deviation adjustment process, the second image processing unit 53 forms a plurality of detection toner images X10 of K (black), C (cyan), M (magenta), and Y (yellow) at mutually different positions in the belt rotation direction D5 of the belt 26 at preset positions on the intermediate transfer belt 26. In this embodiment, in the detection image forming process in the color adjustment process, the detection toner image X10 may be formed on the intermediate transfer belt 26 while the normal print image forming process for multiple pages is being executed, or the detection toner image X10 may be formed on the intermediate transfer belt 26 while the normal print image forming process for one page is being executed.

[0060] In the detection process, the detection unit 46 is used to detect the density and position of the detection toner image X10 formed in the non-contact area A3 of the intermediate transfer belt 26. Note that the detection process may detect only either the density or the position of the detection toner image X10. For example, when the light amount adjustment process, the development bias voltage adjustment process, or the input / output characteristic adjustment process is performed, it is sufficient to detect at least the density of the detection toner image X10, and when the position deviation adjustment process is performed, it is sufficient to detect at least the position of the detection toner image X10.

[0061] In the correction process, a correction process is performed to adjust the image forming conditions based on the detection result by the detection processing unit 53. Specifically, the first image processing unit 52 performs the correction process on the image forming unit 24 corresponding to K (black). Furthermore, the second image processing unit 53 performs the correction process on the image forming units 21 to 24 corresponding to K (black), C (cyan), M (magenta), and Y (yellow).

[0062] Specifically, in the correction process in the development bias voltage adjustment process, the development bias voltage, which is one of the image forming conditions, is adjusted for the image forming unit 20 corresponding to the detection toner image X10 based on the difference between the density of the detection toner image X10 detected by the detection processing unit 53 and a preset first reference density. The first reference density is a preset initial value, or the density of the detection toner image X10 detected during the immediately preceding adjustment of the image forming conditions, etc.

[0063] In the correction process in the light amount adjustment process, the light amount of the optical scanning device 25, which is one of the image forming conditions, is adjusted for the image forming unit 20 corresponding to the detection toner image X10 based on the difference between the density of the detection toner image X10 detected by the detection processing unit 53 and a preset second reference density. Note that the second reference density is a preset initial value, or the density of the detection toner image X10 detected during the immediately preceding adjustment of the image forming conditions, etc.

[0064] In the correction process in the positional deviation adjustment process, the timing of light irradiation (image formation timing) by the optical scanning device 25, which is one of the image formation conditions, is adjusted for the image forming unit 20 corresponding to the detection toner image X10 based on the difference between the detection position of the detection toner image X10 detected using the detection processing unit 53 and a predetermined specific position.

[0065] In the correction process of the input / output characteristic adjustment process, the input / output characteristics, which are one of the image forming conditions, are adjusted for the image forming unit 20 corresponding to the detection toner image X10 based on the difference between the density of the detection toner image X10 detected by the detection processing unit 53 and a preset third reference density. The input / output characteristic adjustment process is sometimes generally referred to as a gamma correction process. The third reference density is a preset initial value or the density of the detection toner image X10 detected during the previous adjustment of the image forming conditions.

[0066] It should be noted that the image forming conditions adjusted in the condition adjustment process are not limited to those described here, and for example, the image forming conditions may include the charging voltage, the primary transfer current, and the secondary transfer current.

[0067] The storage unit 6 also stores correspondence information that associates adjustment identification numbers with the contents of condition adjustment processes. Specifically, in the correspondence information, the development bias voltage adjustment process is associated with the adjustment identification number "1," and the light intensity adjustment process is associated with the adjustment identification number "2." In addition, in the correspondence information, the positional deviation adjustment process is associated with the adjustment identification number "3," and the input / output characteristics adjustment process is associated with the adjustment identification number "4." The first image processing unit 52 executes the condition adjustment process corresponding to the adjustment identification number indicated by the monochrome adjustment counter, and the second image processing unit 53 executes the condition adjustment process corresponding to the adjustment identification number indicated by the color adjustment counter.

[0068] However, because it takes time to simultaneously form detection toner images used in multiple types of condition adjustment processes, increasing the frequency of the condition adjustment processes may affect printing efficiency. On the other hand, decreasing the frequency of the condition adjustment processes may result in longer intervals between executions of the condition adjustment processes, which may result in unstable image quality. In contrast, the image forming apparatus 100 according to this embodiment can efficiently execute various condition adjustment processes suited to color printing and monochrome printing, thereby stabilizing image quality.

[0069] [Adjustment control processing] 5, an example of the procedure of the adjustment control process executed by the control unit 7 in the image forming apparatus 100 and the image forming method of the present invention will be described. Here, steps S10, S11, etc. represent the numbers of the processing procedures (steps) executed by the control unit 7. The control unit 7 starts executing the adjustment control process when a normal image forming process is executed in which a print image is printed on a sheet based on image data to be printed. In other words, the adjustment control process is executed in parallel with the normal image forming process while the normal image forming process is being executed.

[0070] <Step S10> In step S10, the control unit 7 determines whether color printing is to be performed in the normal image forming process. If it is determined that color printing is to be performed (S10: Yes), the process proceeds to step S11. On the other hand, if it is determined that color printing is not to be performed and that monochrome printing is to be performed (S10: No), the process proceeds to step S21.

[0071] Specifically, when executing the normal image forming process, the print processing unit 50 of the control unit 7 may automatically select monochrome printing or color printing based on the image data of the print target. In this case, in step S10, the control unit 7 determines whether color printing will be performed based on the selection result by the print processing unit 50. Furthermore, the print processing unit 50 of the control unit 7 executes either monochrome printing or color printing according to the monochrome printing mode or color printing mode selected by a user operation at the start of the print process based on the image data of the print target. In this case, in step S10, the control unit 7 determines whether color printing will be performed based on the monochrome printing mode or color printing mode selected by a user operation. Furthermore, when executing step S10, the print processing unit 50 stores the print type of the current print target in the memory unit 6 as information on the previous print type.

[0072] <Step S11> In step S11, the count processing unit 51 of the control unit 7 increments both the number of color printed sheets and the number of monochrome printed sheets by 1. Note that the number of color printed sheets and the number of monochrome printed sheets in the image forming apparatus 100 are both 0.

[0073] <Step S12> In step S12, the second image processing unit 53 of the control unit 7 determines whether the color adjustment process is being executed. If it is determined that the color adjustment process is being executed (S12: Yes), the process proceeds to step S17. If it is determined that the color adjustment process is not being executed (S12: No), the process proceeds to step S13. That is, if the color adjustment process is being executed over the course of the normal image forming process for multiple pages (S12: Yes), the process proceeds to step S17, and steps S13 to S16 are omitted.

[0074] Note that, when the detection image forming process in the color adjustment process is executed during the normal image forming process for one page, step S12 may be omitted. In particular, since only one of the multiple types of condition adjustment processes is executed in the color adjustment process, it is conceivable that the condition adjustment process is executed during the normal image forming process for one page.

[0075] <Step S13> In step S13, the second image processing unit 53 of the control unit 7 determines whether the color adjustment conditions are met. Specifically, in this embodiment, the second image processing unit 53 determines that the color adjustment conditions are met when the number of color prints reaches 15. If it is determined that the color adjustment conditions are met (S13: Yes), the process proceeds to step S14. If it is determined that the color adjustment conditions are not met (S13: No), the process proceeds to step S17.

[0076] <Step S14> In step S14, the second adjustment processing unit 53 of the control unit 7 starts the condition adjustment processing corresponding to the value of the color adjustment counter among the multiple types of condition adjustment processing as the color adjustment processing. That is, the second adjustment processing unit 53 executes the multiple types of condition adjustment processing one by one in order every time the number of color printed sheets reaches 15.

[0077] Specifically, the second adjustment processing unit 53 executes the developing bias voltage adjustment process when the color adjustment counter is "1," and executes the light intensity adjustment process when the color adjustment counter is "2." Furthermore, the second adjustment processing unit 53 executes the misregistration adjustment process when the color adjustment counter is "3," and executes the input / output characteristic adjustment process when the color adjustment counter is "4." The color adjustment counter has an initial value of "1," and is updated in the order of "1" to "4" in step S16, which will be described later. As described above, the detection image formation process in the condition adjustment process is executed together with the normal image formation process, and a detection toner image X10 is formed in the non-contact area A3 outside the output area A1 in which a print image based on the image data is formed in the normal image formation process.

[0078] <Step S15> In step S15, the second adjustment processing unit 53 of the control unit 7 resets the number of color prints to 0. In this way, in the adjustment control process, the number of color prints is managed by step S11 and step S15, and the color adjustment process is executed every time 15 color prints are printed.

[0079] <Step S16> In step S16, the counter processing unit 51 of the control unit 7 updates the color adjustment counter. Specifically, if the color adjustment counter is "1", the counter processing unit 51 updates the color adjustment counter to "2", and if the color adjustment counter is "2", the counter processing unit 51 updates the color adjustment counter to "3". Furthermore, if the color adjustment counter is "3", the counter processing unit 51 updates the color adjustment counter to "4", and if the color adjustment counter is "4", the counter processing unit 51 updates the color adjustment counter to "1".

[0080] <Step S17> In step S17, the second adjustment processing unit 53 of the control unit 7 determines whether the normal image forming process for one page has been completed. If it is determined that the normal image forming process for one page has been completed (S17: Yes), the process proceeds to step S17, and if it is determined that the normal image forming process for one page has not been completed (S17: No), step S17 is repeatedly executed.

[0081] <Step S18> In step S18, the second adjustment processing unit 53 of the control unit 7 determines whether or not the color printing will continue. Specifically, the second adjustment processing unit 53 determines that the color printing will continue if the print type corresponding to the image data to be next printed is color printing. On the other hand, the second adjustment processing unit 53 determines that the color printing will not continue if the print type corresponding to the image data to be next printed is monochrome printing. The second adjustment processing unit 53 also determines that the color printing will not continue if there is no image data to be next printed. Here, if it is determined that the color printing will continue (S18: Yes), the process returns to step S11, and if it is determined that the color printing will not continue (S18: No), the process proceeds to step S19.

[0082] <Step S19> In step S19, the control unit 7 determines whether or not there is image data to be printed next. If it is determined that there is image data to be printed next (S19: Yes), the process returns to step S10. If it is determined that there is no image data to be printed next (S19: No), the adjustment control process ends.

[0083] <Step S20> In step S20, the first image processing unit 52 of the control unit 7 determines whether the printing type of the previous printing process based on the image data to be printed is color printing. Specifically, the first image processing unit 52 determines whether the previous printing type is color printing based on the information on the previous printing type stored in the storage unit 6 by the print processing unit 50. If it is determined that the previous printing type is color printing (S20: Yes), the process proceeds to step S21, and if it is determined that the previous printing type is not color printing (S20: No), the process proceeds to step S22.

[0084] In addition, the control unit 7 may store the type of the condition adjustment process (color adjustment process, monochrome adjustment process) executed immediately before in the adjustment control process in the storage unit 6. In this case, in step S20, the first image processing unit 52 may shift the process to step S21 if the condition adjustment process executed immediately before is the color adjustment process, instead of the print type of the print process based on the image data of the immediately previous print target. As a result, if the monochrome adjustment condition is satisfied and the immediately previous condition adjustment process has been executed by the second image processing unit 53, the first image processing unit 52 will execute the condition adjustment process in the order following the condition adjustment process executed immediately before by the second image processing unit 53.

[0085] <Step S21> In step S21, the first image processing unit 52 of the control unit 7 updates the monochrome adjustment counter to the value of the color adjustment counter. That is, if the printing type by the image forming unit 3 is switched from color printing to monochrome printing (S20: Yes), the first image processing unit 52 updates the monochrome adjustment counter to the adjustment identification number corresponding to the next in order of the condition adjustment process executed immediately before by the second image processing unit 53. As a result, after the printing type by the image forming unit 3 is switched from color printing to monochrome printing, if the monochrome adjustment condition is satisfied for the first time in step S23 described below (S23: Yes), the first image processing unit 52 executes the condition adjustment process corresponding to the adjustment identification number subsequent in order to the adjustment identification number corresponding to the color adjustment process executed immediately before by the second image processing unit 53.

[0086] When the printing type by the image forming unit 3 is switched from monochrome printing to color printing, the second image processing unit 53 does not update the color adjustment counter to the adjustment identification number corresponding to the next sequential number of the condition adjustment process executed immediately before by the second image processing unit 53. As a result, even if the color adjustment conditions are satisfied for the first time in step S13 after the printing type by the image forming unit 3 is switched from monochrome printing to color printing (S13: Yes), the second image processing unit 53 executes the condition adjustment process corresponding to the adjustment identification number subsequent to the adjustment identification number corresponding to the color adjustment process executed immediately before by the second image processing unit 53.

[0087] <Step S22> In step S22, the count processing unit 51 of the control unit 7 adds one to the number of monochrome printed sheets.

[0088] <Step S23> In step S23, the first image processing unit 52 of the control unit 7 determines whether the monochrome adjustment condition is met. Specifically, in this embodiment, the first image processing unit 52 determines that the monochrome adjustment condition is met when the number of monochrome prints reaches 30. If it is determined that the monochrome adjustment condition is met (S23: Yes), the process proceeds to step S24, and if it is determined that the monochrome adjustment condition is not met (S23: No), the process proceeds to step S27.

[0089] During steps S22 to S23, similar to step S12, the first image processing unit 52 of the control unit 7 determines whether the monochrome adjustment process is being executed, and if the monochrome adjustment process is being executed over the course of the normal image forming process for multiple pages, the process may proceed to step S27, and steps S23 to S26 may be omitted.

[0090] <Step S24> In step S24, the first image processing unit 52 of the control unit 7 starts the condition adjustment process corresponding to the value of the monochrome adjustment counter among the multiple types of condition adjustment processes as the monochrome adjustment process. That is, the first adjustment processing unit 52 executes the multiple types of condition adjustment processes one by one in order each time the number of monochrome printed sheets reaches 30.

[0091] Specifically, the first image processing unit 52 executes the developing bias voltage adjustment process when the monochrome adjustment counter is "1," and executes the light intensity adjustment process when the monochrome adjustment counter is "2." The second adjustment processing unit 53 executes the misregistration adjustment process when the monochrome adjustment counter is "3," and executes the input / output characteristic adjustment process when the monochrome adjustment counter is "4." The monochrome adjustment counter has an initial value of "1" and is updated to the value of the color adjustment counter in step S21, or is updated in the order of "1" to "4" in step S26, which will be described later. As described above, the detection image formation process in the condition adjustment process is executed together with the normal image formation process, and a detection toner image X10 is formed in the non-contact area A3 outside the output area A1 in which a print image based on the image data is formed in the normal image formation process.

[0092] In particular, as described above, when the printing type by the image forming unit 3 is switched from color printing to monochrome printing by the first image processing unit 52, the monochrome adjustment counter is updated to the value of the color adjustment counter in step S21. Therefore, after the printing type by the image forming unit 3 is switched from color printing to monochrome printing, in step S24, the condition adjustment process corresponding to the adjustment identification number next in order to the adjustment identification number corresponding to the color adjustment process executed immediately before by the second image processing unit 53 is executed.

[0093] <Step S25> In step S25, the first adjustment processing unit 52 of the control unit 7 resets the number of monochrome prints to 0. In this way, in the adjustment control process, the number of monochrome prints is managed by step S22 and step S25, and the monochrome adjustment process is executed every time 30 monochrome prints are printed.

[0094] <Step S26> In step S26, the counter processing unit 51 of the control unit 7 updates the monochrome adjustment counter. Specifically, if the monochrome adjustment counter is "1", the counter processing unit 51 updates the monochrome adjustment counter to "2", and if the monochrome adjustment counter is "2", the counter processing unit 51 updates the monochrome adjustment counter to "3". Furthermore, if the monochrome adjustment counter is "3", the counter processing unit 51 updates the monochrome adjustment counter to "4", and if the monochrome adjustment counter is "4", the counter processing unit 51 updates the monochrome adjustment counter to "1".

[0095] <Step S27> In step S27, the first adjustment processing unit 52 of the control unit 7 determines whether the normal image forming process for one page has been completed. If it is determined that the normal image forming process for one page has been completed (S27: Yes), the process proceeds to step S27, and if it is determined that the normal image forming process for one page has not been completed (S27: No), step S27 is repeatedly executed.

[0096] <Step S28> In step S28, the first adjustment processing unit 52 of the control unit 7 determines whether or not the monochrome printing will continue. Specifically, the first adjustment processing unit 52 determines that the monochrome printing will continue if the print type corresponding to the image data to be next printed is monochrome printing. On the other hand, the first adjustment processing unit 52 determines that the monochrome printing will not continue if the print type corresponding to the image data to be next printed is color printing. The first adjustment processing unit 52 also determines that the monochrome printing will not continue if there is no image data to be next printed. Here, if it is determined that the monochrome printing will continue (S28: Yes), the process returns to step S22, and if it is determined that the monochrome printing will not continue (S28: No), the process proceeds to step S19.

[0097] [Example of execution result of condition control process] An example of the result of the adjustment control process in the image forming apparatus 100 will be described below with reference to Fig. 6. Specifically, Fig. 6 shows the result of the adjustment control process when 50 color pages are printed as a first print job, 100 monochrome pages are printed as a second print job, and 50 color pages are printed as a third print job. Note that the following description will be given taking as an example a case where three print jobs, the first print job, the second print job, and the third print job, are executed consecutively. On the other hand, the same process is performed when a single print job includes a mixture of color printing and monochrome printing, as in the first print job, the second print job, and the third print job.

[0098] As shown in FIG. 6, assume that the number of monochrome prints and the number of color prints are 0 at the start of the first print job. Thereafter, when the 15th print is executed in the first print job, the number of color prints reaches the second threshold value of 15 (S13: Yes). At this time, the color adjustment counter has an initial value of "1." Therefore, the second image processing unit 53 executes the developing bias voltage adjustment process corresponding to the adjustment identification number "1" as the color adjustment process (S14).

[0099] Next, when the 30th sheet is printed in the first print job, the number of color prints reaches the second threshold of 15 sheets (S13: Yes). At this time, the color adjustment counter has been updated to "2" in step S16. Therefore, the second image processing unit 53 executes the light intensity adjustment process corresponding to the adjustment identification number "2" as the color adjustment process (S14).

[0100] Similarly, when the 45th sheet is printed in the first print job, the number of color prints reaches the second threshold of 15 (S13: Yes). At this time, the color adjustment counter has been updated to "3" in step S16. Therefore, the second image processing unit 53 executes the misregistration adjustment process corresponding to the adjustment identification number "3" as the color adjustment process (S14).

[0101] Then, when the 50th page is printed in the first print job, the first print job ends and the second print job starts. In the first print job, the number of monochrome prints and the number of color prints are incremented to "5" in step S11. Also, the value of the color adjustment counter is updated to "4" in step S16, and the value of the monochrome adjustment counter remains at "1."

[0102] Next, when the 25th sheet is printed in the second print job, the number of monochrome prints reaches the first threshold of 30 sheets (S23: Yes). At this time, the monochrome adjustment counter has been updated to "4," which is the value of the color adjustment counter, in step S21. Therefore, the first image processing unit 52 executes the input / output characteristics adjustment process corresponding to the adjustment identification number "4" as the monochrome adjustment process (S24).

[0103] Subsequently, when the 55th sheet is printed in the second print job, the number of monochrome printed sheets reaches the second threshold value of 30 sheets (S23: Yes). At this time, the monochrome adjustment counter has been updated to "1" in step S26. Therefore, the first image processing unit 52 executes the developing bias voltage adjustment process corresponding to the adjustment identification number "1" as the monochrome adjustment process (S24).

[0104] Similarly, when the 85th sheet is printed in the second print job, the number of monochrome prints reaches the first threshold of 30 sheets (S23: Yes). At this time, the monochrome adjustment counter has been updated to "2" in step S26. Therefore, the first image processing unit 52 executes the light intensity adjustment process corresponding to the adjustment identification number "2" as the monochrome adjustment process (S24).

[0105] Then, when the 100th page is printed in the second print job, the second print job ends and the third print job begins. In the second print job, the number of monochrome prints is incremented to "15" in step S22. Meanwhile, the number of color prints remains at "5." Also, the value of the monochrome adjustment counter is updated to "3" in step S26, and the value of the color adjustment counter remains at "4."

[0106] Subsequently, when the tenth sheet is printed in the third print job, the number of color prints reaches the second threshold of 15 sheets (S13: Yes). At this time, the color adjustment counter is "4." Therefore, the second image processing unit 53 executes the input / output characteristics adjustment process corresponding to the adjustment identification number "4" as the color adjustment process (S14).

[0107] Next, when the 25th sheet is printed in the third print job, the number of color prints reaches the second threshold of 15 sheets (S13: Yes). At this time, the color adjustment counter has been updated to "1" in step S16. Therefore, the second image processing unit 53 executes the developing bias voltage adjustment process corresponding to the adjustment identification number "1" as the color adjustment process (S14).

[0108] Similarly, when the 40th sheet is printed in the third print job, the number of color prints reaches the second threshold of 15 (S13: Yes). At this time, the color adjustment counter has been updated to "2" in step S16. Therefore, the second image processing unit 53 executes the light intensity adjustment process corresponding to the adjustment identification number "2" as the color adjustment process (S14).

[0109] As described above, in the image forming apparatus 100, by executing the adjustment control process, the plurality of types of condition adjustment processes are divided and executed in order, one by one, based on the execution history of the monochrome printing or the color printing, each time the execution conditions of the condition adjustment process are satisfied, in the monochrome printing or the color printing. Therefore, compared to when detection toners used for the plurality of types of condition adjustment processes are formed collectively, the execution time for each condition adjustment process can be shortened, and the frequency of execution of the condition adjustment processes is increased, making it possible to stabilize image quality.

[0110] In particular, when the monochrome adjustment conditions are met for the first time after the printing type by the image forming unit 3 is switched from color printing to monochrome printing, the first image processing unit 52 executes the condition adjustment process in the order following the condition adjustment process executed immediately before by the second image processing unit 53. This is because the color adjustment process executed by the second image processing unit 53 also adjusts the K (black) image forming unit 24, which is the adjustment target of the monochrome adjustment process. As a result, the monochrome adjustment process executes the condition adjustment process of the type subsequent to the color adjustment process, preventing redundant execution of the condition adjustment process of the type already executed in the color adjustment process, and making it possible to stabilize image quality in monochrome printing.

[0111] Furthermore, when the color adjustment conditions are met for the first time after the printing type by the image forming unit 3 is switched from monochrome printing to color printing, the second image processing unit 53 executes the condition adjustment process in the order following the condition adjustment process executed immediately before by the second image processing unit 53. This is because the monochrome adjustment process executed by the first image processing unit 52 does not adjust the C (cyan), M (magenta), and Y (yellow) image forming units 21-23, which are the adjustment targets of the color adjustment process. As a result, the color adjustment process executes the type of condition adjustment process subsequent to the previous color adjustment process, so that multiple types of condition adjustment processes can be executed in a preset order, making it possible to stabilize image quality in color printing.

[0112] [Notes on the Invention] The following is a summary of the invention extracted from the above-described embodiment. Note that the configurations and processing functions described in the following supplementary notes can be selected and combined as desired.

[0113] <Appendix 1> an image forming section including a plurality of image forming units corresponding to a plurality of colors, and performing monochrome printing for printing a monochrome image or color printing for printing a color image based on input image data; a first image processing unit that sequentially executes a predetermined number of types of condition adjustment processes for adjusting image formation conditions in the image forming units, each time the execution history of the monochrome printing satisfies a predetermined monochrome adjustment condition, for the image forming units used for the monochrome printing among the plurality of image forming units; a second image processing unit that sequentially executes a specific number of the plurality of types of condition adjustment processes on the image forming units used for the color printing among the plurality of image forming units each time an execution history of the color printing satisfies a preset color adjustment condition; An image forming apparatus comprising:

[0114] <Appendix 2> When the monochrome adjustment condition is satisfied for the first time after the printing type by the image forming unit is switched from the color printing to the monochrome printing, the first image processing unit executes the condition adjustment process in the order following the condition adjustment process executed immediately before by the second image processing unit. 2. The image forming apparatus according to claim 1.

[0115] <Appendix 3> when the color adjustment condition is satisfied for the first time after the printing type by the image forming unit is switched from the monochrome printing to the color printing, the second image processing unit executes the condition adjustment process in the order following the condition adjustment process executed immediately before by the second image processing unit. 3. The image forming apparatus according to claim 1 or 2.

[0116] <Appendix 4> a count processing unit that counts the number of printed sheets or the execution time of the monochrome printing as an execution history of the monochrome printing, and counts the number of printed sheets or the execution time of the color printing as an execution history of the color printing, the count processing unit adds the number of printed sheets or the execution time of the color printing to the execution history of the monochrome printing, the monochrome adjustment condition is that the execution history of the monochrome printing has reached a preset first threshold; the color adjustment condition is that the execution history of the color printing has reached a second threshold value that is set in advance; 4. The image forming apparatus according to claim 1.

[0117] <Appendix 5> the condition adjustment process includes any one or more of a development bias voltage adjustment process, a light amount adjustment process, a positional deviation adjustment process, and an input / output characteristic adjustment process; 5. The image forming apparatus according to any one of claims 1 to 4.

[0118] <Appendix 6> the first image processing unit and the second image processing unit form, during execution of a normal image forming process in which a print image based on image data of a print target is formed in a predetermined print area on a transfer target by the image forming unit, a detection image used in the condition adjustment process in an area outside the print area on the transfer target by the image forming unit; 6. The image forming apparatus according to any one of claims 1 to 5.

[0119] <Appendix 7> the specified number is 1; 7. The image forming apparatus according to any one of claims 1 to 6.

[0120] <Appendix 8> When the monochrome adjustment condition is satisfied and the previously executed condition adjustment process has been executed by the second image processing unit, the first image processing unit executes the condition adjustment process in the order following the previously executed condition adjustment process by the second image processing unit. 8. The image forming apparatus according to any one of claims 1 to 7.

[0121] <Appendix 9> a processor of an image forming apparatus including an image forming unit that includes a plurality of image forming units corresponding to a plurality of colors and performs monochrome printing for printing monochrome images or color printing for printing color images based on input image data, a step of sequentially executing a predetermined number of types of condition adjustment processes for adjusting image formation conditions in the image forming unit, the image forming unit being used for the monochrome printing among the plurality of image forming units, each time the execution history of the monochrome printing satisfies the predetermined monochrome adjustment condition; a step of sequentially executing a specific number of the plurality of types of condition adjustment processes for the image forming units used for the color printing among the plurality of image forming units each time an execution history of the color printing satisfies a preset color adjustment condition; An image forming method that performs the above. [Explanation of symbols]

[0122] 1 ADF 2 Image reading unit 3 Image forming unit 4 Paper feed section 5 Operation display section 6 Memory section 7 Control Unit 20 Image forming unit 25 Optical scanning device 26 Intermediate transfer belt 27 Secondary transfer roller 28 Fixing device 31 Photosensitive drum 32 Charging roller 33 Developing device 34 Primary transfer roller 35 Drum Cleaning Department 36 Toner container 40 1st power supply 45 2nd power supply 46 Detector 100 Image forming device

Claims

1. an image forming section including a plurality of image forming units corresponding to a plurality of colors, and performing monochrome printing for printing a monochrome image or color printing for printing a color image based on input image data; a first image processing unit that sequentially executes a predetermined number of types of condition adjustment processes for adjusting image formation conditions in the image forming units, each time the execution history of the monochrome printing satisfies a predetermined monochrome adjustment condition, with the plurality of image forming units being targeted for the image forming units used for the monochrome printing; a second image processing unit that sequentially executes a specific number of the plurality of types of condition adjustment processes on the image forming units used for the color printing among the plurality of image forming units each time an execution history of the color printing satisfies a preset color adjustment condition; An image forming apparatus comprising:

2. when the monochrome adjustment condition is satisfied for the first time after the printing type by the image forming unit is switched from the color printing to the monochrome printing, the first image processing unit executes the condition adjustment process in the order following the condition adjustment process executed immediately before by the second image processing unit. The image forming apparatus according to claim 1 .

3. when the color adjustment condition is satisfied for the first time after the printing type by the image forming unit is switched from the monochrome printing to the color printing, the second image processing unit executes the condition adjustment process in the order following the condition adjustment process executed immediately before by the second image processing unit. The image forming apparatus according to claim 2 .

4. a count processing unit that counts the number of printed sheets or the execution time of the monochrome printing as an execution history of the monochrome printing, and counts the number of printed sheets or the execution time of the color printing as an execution history of the color printing, the count processing unit adds the number of printed sheets or the execution time of the color printing to the execution history of the monochrome printing, the monochrome adjustment condition is that the execution history of the monochrome printing has reached a preset first threshold; the color adjustment condition is that the execution history of the color printing has reached a second threshold value that is set in advance; 4. The image forming apparatus according to claim 1.

5. the condition adjustment process includes any one or more of a development bias voltage adjustment process, a light amount adjustment process, a positional deviation adjustment process, and an input / output characteristic adjustment process; 4. The image forming apparatus according to claim 1.

6. the first image processing unit and the second image processing unit form, during execution of a normal image forming process in which a print image based on image data of a print target is formed in a predetermined print area on a transfer target body by the image forming unit, a detection image used in the condition adjustment process in an area outside the print area on the transfer target body by the image forming unit; 4. The image forming apparatus according to claim 1.

7. the specified number is 1; 4. The image forming apparatus according to claim 1.

8. When the monochrome adjustment condition is satisfied and the previously executed condition adjustment process has been executed by the second image processing unit, the first image processing unit executes the condition adjustment process in the order following the previously executed condition adjustment process by the second image processing unit. The image forming apparatus according to claim 1 .

9. a processor of an image forming apparatus including an image forming unit that includes a plurality of image forming units corresponding to a plurality of colors and performs monochrome printing for printing monochrome images or color printing for printing color images based on input image data, a step of sequentially executing a predetermined number of types of condition adjustment processes for adjusting image formation conditions in the image forming unit, the image forming unit being used for the monochrome printing among the plurality of image forming units, each time the execution history of the monochrome printing satisfies the predetermined monochrome adjustment condition; a step of sequentially executing a specific number of the plurality of types of condition adjustment processes for the image forming units used for the color printing among the plurality of image forming units each time an execution history of the color printing satisfies a preset color adjustment condition; An image forming method that performs the above.

Images