Image forming apparatus and image forming method

Abstract

To provide an image forming apparatus and an image forming method.SOLUTION: An image forming apparatus (100) comprises a first image processing unit (51) and a second image processing unit (52). The first image processing unit (51) executes, in double-sided printing processing of forming print images on a front face and a rear face of a sheet, print image forming processing corresponding to the front face and the print image forming processing corresponding to the rear face, according to different image forming conditions. The second image processing unit (52), when executing image forming processing for detection during execution of the double-sided printing processing, executes the image forming processing for detection according only to the image forming condition in the print image forming processing corresponding to a predetermined one of the front face and the rear face.SELECTED DRAWING: Figure 6

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 sheet based on input image data. The image forming apparatus then executes a print image forming process in which the image forming unit forms a print image based on the image data on a transfer medium such as an intermediate transfer belt. Furthermore, during the print image forming process, the image forming apparatus may also execute a detection image forming process that forms a detection toner image used to adjust image formation conditions in the image forming unit (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-119573 Summary of the Invention [Problem to be solved by the invention]

[0004] In some image forming apparatuses, a double-sided printing process is performed to print images on both the front and back sides of a sheet. In the double-sided printing process, the image forming conditions, such as the primary transfer current or the development bias voltage, in the image forming unit may differ between printing on the front side and printing on the back side. Therefore, adjusting the image forming conditions in the image forming unit based on the density or position of the detection toner images formed in the detection image forming process for both the front and back sides may result in a reduced effect.

[0005] An object of the present invention is to provide an image forming apparatus and an image forming method that can enhance the effect obtained by adjusting the image forming conditions executed when double-sided printing processing is executed. [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 forms an image on a transfer target based on input image data and transfers the image from the transfer target to a sheet. The first image processing unit executes a print image forming process in which the image forming unit forms a print image in a predetermined print area on the transfer target based on image data of the print target. When preset execution conditions are satisfied, the second image processing unit executes a detection image forming process in which the image forming unit forms a detection image used to adjust image formation conditions in the image forming unit in an area outside the print area on the transfer target. The first image processing unit executes a double-sided printing process in which the print image is formed on both the front and back sides of a sheet under different image formation conditions. When the second image processing unit executes the detection image forming process while the double-sided printing process is being executed, it executes the detection image forming process only under the image forming conditions in the printing image forming process corresponding to a predetermined one of the front side and the back side.

[0007] An image forming method according to another aspect of the present invention is a method executed by a processor of an image forming apparatus including an image forming unit that forms an image on a transfer medium based on input image data and transfers the image from the transfer medium to a sheet. The image forming method includes a first step and a second step. The first step executes a print image forming process in which the image forming unit forms a print image in a predetermined print area on the transfer medium based on image data of the print target. The second step executes a detection image forming process in which the image forming unit forms a detection image used to adjust image formation conditions in the image forming unit in an area on the transfer medium outside the print area, when preset execution conditions are satisfied. The first step executes a double-sided printing process in which the print image is formed on both the front and back sides of a sheet, with the print image forming process corresponding to the front side and the print image forming process corresponding to the back side being executed under different image formation conditions. In the second step, when the detection image forming process is executed during the double-sided printing process, the detection image forming process is executed only under the image forming conditions in the printing image forming process corresponding to a predetermined one of the front and back sides. [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 enhance the effect obtained by adjusting the image forming conditions executed when double-sided printing processing is executed. [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 schematic diagram 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 a print control process executed by the image forming apparatus according to the embodiment of the present invention. [Figure 6] FIG. 6 is a flowchart showing an example of the adjustment control process executed in the image forming apparatus according to the embodiment of the present invention. [Figure 7] FIG. 7 is a diagram schematically illustrating an example of a detection toner image formed on the intermediate transfer belt in the image forming apparatus according to the embodiment of the present invention. [Figure 8] FIG. 8 is a flowchart showing another example of the adjustment control process executed in the image forming apparatus according to the embodiment of the present invention. [Figure 9] FIG. 9 is a diagram schematically illustrating an example of a detection toner image formed on the intermediate transfer belt 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 based on input image data on a sheet supplied from the paper feed unit 4 by electrophotography.

[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 paper feed unit 4 also includes a double-sided printing mechanism 4A that turns over the sheet after an image has been formed on it by the image forming unit 3 and transports it again to the image forming unit 3. This allows the image forming apparatus 100 to perform a double-sided printing operation in which the image forming unit 3 forms images on both the front and back sides of the sheet.

[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 configuration of multiple image forming units 20, intermediate transfer belt 26, and secondary transfer roller 27. Also, Figure 4 is a schematic diagram showing the configuration of photosensitive drum 31 of image forming unit 24, intermediate transfer belt 26, drive roller 26A, and secondary transfer roller 27.

[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 forms a toner image based on input image data on the intermediate transfer belt 26, and transfers the toner image from the intermediate transfer belt 26 to a sheet.

[0025] The four image forming units 20 include image forming units 21 to 24. 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.

[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 units 46 are provided at positions facing the non-contact areas A3 (see FIG. 4) on both ends of the outer circumferential surface of the intermediate transfer belt 26. The two detection units 46 are used to detect the density and position of the toner image transferred to the non-contact areas A3. In this embodiment, the two detection units 46 are used to detect the density and position of a detection toner image X10 (described below) formed in the non-contact area A3.

[0041] For example, the detection unit 46 is a reflective photosensor that includes 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 the light that is 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 to the control unit 7 that corresponds to the density of the toner image to be detected.

[0042] 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.

[0043] [Configuration of control unit 7] Next, the configuration of the control unit 7 will be described with reference to FIG.

[0044] 2, the control unit 7 includes a first image processing unit 51, a second image processing unit 52, a detection processing unit 53, a count processing unit 54, and an adjustment processing unit 55. Specifically, an image formation 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 image formation program stored in the ROM 12 to function as each of the above-mentioned processing units.

[0045] The image forming program may be recorded on a computer-readable recording medium such as a CD, a DVD, or a flash memory, and may be read from the recording medium and stored in a storage device such as the memory unit 6. Some or all of the first image processing unit 51, the second image processing unit 52, the detection processing unit 53, the count processing unit 54, and the adjustment processing unit 55 may be configured using electronic circuits such as an application specific integrated circuit (ASIC).

[0046] The first image processing unit 51 executes a print image forming process in which the image forming unit 3 forms a print image based on image data to be printed, which is included in the print job to be executed, in a predetermined print area A1 (see FIG. 4) on the intermediate transfer belt 26. Specifically, the first image processing unit 51 controls the optical scanning device 25 based on the image data 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. Then, 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 print 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.

[0047] In the print image forming process, the first image processing unit 51 controls the amount of laser light emitted by the optical scanning device 25 based on preset input / output characteristics (gamma characteristics) and the image data. In the print image forming process, the first image processing unit 51 also controls the development bias voltage in each image forming unit 20 to a value preset for that image forming unit 20. In the print image forming process, the first image processing unit 51 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.

[0048] Furthermore, in the print image forming process, the first image processing unit 51 executes a preset inter-sheet process during an inter-sheet period P0 (see FIG. 5) between a process of forming a print image based on image data for one page on the intermediate transfer belt 26 and a process of forming a print image based on image data for the next page on the intermediate transfer belt 26. For example, in the inter-sheet process, cleaning of the photosensitive drum 31 by the drum cleaning unit 35 is executed. Also, in the inter-sheet process, various image processes may be executed for image data corresponding to the next page in the print image forming process.

[0049] Furthermore, the first image processing unit 51 controls the image forming unit 3, the paper feed unit 4, and the like in the image forming apparatus 100 to perform a double-sided printing process for executing the double-sided printing operation. Specifically, when performing the double-sided printing process for one sheet, the first image processing unit 51 supplies the sheet from the paper feed cassette to the image forming unit 3 and transfers a print image corresponding to the front side of the sheet onto the front side of the sheet. Then, the first image processing unit 51 causes the double-sided printing mechanism 4A to re-transport the sheet to the image forming unit 3 with the sheet turned upside down. Thereafter, the first image processing unit 51 causes the image forming unit 3 to transfer a print image corresponding to the back side of the sheet onto the back side of the sheet and discharges the sheet to the paper output tray 29. In particular, in the double-sided printing process, the first image processing unit 51 performs the print image formation process corresponding to the front side and the print image formation process corresponding to the back side under different image formation conditions.

[0050] Furthermore, when performing the double-sided printing process on a plurality of sheets, the first image processing unit 51 changes the execution order of the print image forming process for print images corresponding to each page on the front and back sides of the plurality of sheets. Specifically, when performing the double-sided printing process on three sheets, the first image processing unit 51 causes the image forming unit 3 to form the pages of the front side of the first sheet, the front side of the second sheet, the back side of the first sheet, the front side of the third sheet, the back side of the second sheet, and the back side of the third sheet in this order on the intermediate transfer belt cleaning unit 26.

[0051] On the other hand, when performing double-sided printing processing on three sheets, the first image processing unit 51 supplies the first sheet from the paper feed cassette to the image forming unit 3 and transfers the print image corresponding to the front side of the first sheet. Then, the first image processing unit 51 retracts the first sheet to the double-sided printing mechanism 4A of the paper feed unit 4.

[0052] Next, the first image processing unit 51 supplies a second sheet from the paper feed cassette to the image forming unit 3 and transfers a print image corresponding to the front side of the second sheet to the front side of the second sheet. Then, the first image processing unit 51 retracts the second sheet to the double-sided printing mechanism 4A, supplies the first sheet from the double-sided printing mechanism 4A to the image forming unit 3 and transfers a print image corresponding to the back side of the first sheet to the back side of the first sheet. Thereafter, the first image processing unit 51 ejects the first sheet to the paper output tray 29.

[0053] Similarly, the first image processing unit 51 supplies a third sheet from the paper feed cassette to the image forming unit 3 and transfers a print image corresponding to the front side of the third sheet to the front side of the third sheet. Then, the first image processing unit 51 retracts the third sheet to the double-sided printing mechanism 4A, supplies the second sheet from the double-sided printing mechanism 4A to the image forming unit 3 and transfers a print image corresponding to the back side of the second sheet to the back side of the second sheet. Thereafter, the first image processing unit 51 ejects the second sheet to the paper output tray 29.

[0054] Thereafter, the first image processing unit 51 supplies the third sheet from the double-sided printing mechanism 4A to the image forming unit 3, and transfers the print image corresponding to the back surface of the third sheet to the back surface of the third sheet. Thereafter, the first image processing unit 51 ejects the third sheet onto the paper ejection tray 29.

[0055] In this way, in the image forming apparatus 100, when double-sided printing processing is performed on a plurality of sheets, the order of the print image forming processing corresponding to the front and back sides of each of the sheets is changed, and transport control is performed for each of the sheets, thereby reducing the time required for the double-sided printing processing. Meanwhile, in another embodiment, even when the double-sided printing processing is performed on a plurality of sheets, the print image forming processing corresponding to the front and back sides of one sheet may be performed after the print image forming processing corresponding to the front and back sides of the next sheet, as in the case where the double-sided printing processing is performed on a single sheet.

[0056] The second image processing unit 52 executes a detection image formation process when a preset execution condition is satisfied. In the detection image formation process, a detection toner image X10 (an example of a detection image) used to adjust the 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. 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 an area on the outer circumferential surface of the intermediate transfer belt 26 that contacts a sheet of the largest size that can be used in the image forming apparatus 100. Note that the print area A1 and the contact area A2 may be the same area.

[0057] In this embodiment, since the detection toner image X10 is formed in the non-contact area A3 (see FIG. 4), compared to a configuration in which the detection toner image X10 is formed in the contact area A2, there is no need to provide a cleaning unit that removes the detection toner image X10 adhering to the secondary transfer roller 27 from the secondary transfer roller 27, making it possible to simplify the configuration. On the other hand, the detection toner image X10 may be formed in an area outside the print area A1 (see FIG. 4) but inside the contact area A2 (see FIG. 4). In this case, however, the detection unit 46 is 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 transfer position of the toner image by the secondary transfer roller 27.

[0058] Furthermore, the second image processing unit 52 forms, on the intermediate transfer belt 26, a detection toner image X10 including detection toner images corresponding to a plurality of colors corresponding to the plurality of image forming units 20, based on preset detection image data corresponding to each color. For example, the detection toner images X10 are a plurality of rectangular images formed at preset densities or positions that differ from one another.

[0059] In this embodiment, the execution condition is that the cumulative number of printed sheets in image forming apparatus 100 reaches a predetermined first reference number. For example, the first reference number is 100 or 200 sheets. The execution condition may also be that the number of printed sheets during execution of one print job reaches a predetermined second reference number. The execution condition may also be that a predetermined specific time has passed.

[0060] The detection processing unit 53 uses each of the detection units 46 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 processing unit 53 may detect only either the density or the position of the detection toner image X10. For example, if only the density correction process is performed in the adjustment process described below, it is sufficient to detect the density of the detection toner image X10, and if only the position deviation correction process is performed in the adjustment process described below, it is sufficient to detect the position of the detection toner image X10.

[0061] The count processing unit 54 executes a counting process to count the cumulative number of printed sheets in the image forming apparatus 100. The cumulative number of printed sheets counted in the counting process is used to determine the timing for executing the adjustment process by the adjustment processing unit 55. For example, the count processing unit 54 resets the count value to 0 each time the adjustment process is executed in the image forming apparatus 100. Note that the count processing unit 54 may also count the cumulative number of printed sheets for each printing type, such as color and monochrome.

[0062] The adjustment processing unit 55 executes an adjustment process for adjusting the image forming conditions based on the detection result by the detection processing unit 53. Specifically, the adjustment processing unit 55 executes a density correction process, a positional deviation correction process, and the like in the adjustment process.

[0063] In the density correction process, if the difference between the density of the detection toner image X10 detected by the detection processing unit 53 and a predetermined reference density is less than a predetermined threshold, the amount of light emitted by the optical scanning device 25 is adjusted as the image formation condition based on the difference. Furthermore, in the density correction process, if the difference between the density of the detection toner image X10 detected by the detection processing unit 53 and the reference density is equal to or greater than the threshold, the developing bias voltage is adjusted as the image formation condition based on the difference. For example, the reference density is the density of the detection toner image X10 detected during the previous adjustment of the image formation conditions. Note that the image formation conditions adjusted in the density correction process are not limited to the amount of light emitted by the optical scanning device 25 and the developing bias voltage. For example, the image formation conditions may include the input / output characteristics, the charging voltage, the primary transfer current, and the secondary transfer current.

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

[0065] Incidentally, the image forming apparatus 100 may perform the double-sided printing process in which images are printed on both sides of a sheet. In addition, in the double-sided printing process, the image formation conditions, such as the primary transfer current or the development bias voltage, in the image forming unit 3 may differ between printing on the front side and printing on the back side. Therefore, if the image formation conditions in the image forming unit 3 are adjusted based on the density or position of the detection toner images formed in the detection image formation process corresponding to both the front and back sides, the effect obtained by adjusting the image formation conditions may be reduced. In contrast, as described below, the image forming apparatus 100 according to this embodiment can enhance the effect obtained by adjusting the image formation conditions when the double-sided printing process is performed.

[0066] [Print control process] The control unit 7 executes the print control process each time the print image formation process based on image data for one page to be printed included in the print job to be executed is started. Here, an example of the procedure of the print control process executed by the control unit 7 in the image forming apparatus 100 will be described with reference to Fig. 5. Note that steps S1, S2, etc. represent the numbers of the processing procedures (steps) executed by the control unit 7.

[0067] <Step S1> In step S1, the first image processing unit 51 of the control unit 7 determines whether the print image formation process executed based on the print job to be executed in the image forming apparatus 100 is a double-sided printing process, based on the content of the print job. The content of the print job is set by an information processing device (not shown) that inputs image data to the image forming apparatus 100, or by a user operation on the operation display unit 5 of the image forming apparatus 100. If it is determined that the print image formation process executed based on the print job is a double-sided printing process (S1: Yes), the process proceeds to step S2, and if it is determined that it is not a double-sided printing process (S1: No), the process proceeds to step S3.

[0068] <Step S2> In step S2, the first image processing unit 51 of the control unit 7 determines whether the print image forming process to be executed is a front side printing process for forming an image on the front side of a sheet. If it is determined that the print image forming process to be executed is a front side printing process (S2: Yes), the process proceeds to step S3, and if it is determined that it is not a front side printing process (S2: No), the process proceeds to step S21.

[0069] <Step S3> In step S3, the first image processing unit 51 of the control unit 7 sets the image forming conditions in the print image forming process executed in step S4 described later to predetermined front image forming conditions. Specifically, the front image forming conditions include various setting values ​​such as the primary transfer current or the developing bias voltage.

[0070] <Step S21> In step S21, the first image processing unit 51 of the control unit 7 sets the image forming conditions in the print image forming process executed in step S4 described below to predetermined back-side image forming conditions. Specifically, in the back-side image forming conditions, the primary transfer current or the developing bias voltage is set to a lower value than in the front-side image forming conditions. This suppresses toner charge-up in the image forming unit 3.

[0071] <Step S4> In step S4, the first image processing unit 51 of the control unit 7 executes the printing process including the print image forming process in accordance with the image forming conditions set in step S3 or step S21.

[0072] [Adjustment control processing] Furthermore, the control unit 7 executes an adjustment control process each time the print image formation process based on image data for one page to be printed included in the print job to be executed is started. Here, an example of the procedure of the adjustment control process executed by the control unit 7 in the image forming apparatus 100 will be described with reference to Fig. 6. Note that steps S11, S12, etc. represent the numbers of the processing procedures (steps) executed by the control unit 7.

[0073] <Step S11> In step S11, the second image processing unit 52 of the control unit 7 determines whether the execution condition is met. If it is determined that the execution condition is met (S11: Yes), the process proceeds to step S12, and if the execution condition is not met (S11: No), the adjustment control process ends.

[0074] <Step S12> In step S12, the second image processing unit 52 of the control unit 7 determines whether the print image forming process to be executed is the front side printing process. If it is determined that the print image forming process to be executed is the front side printing process (S12: Yes), the process proceeds to step S13, and if it is determined that the print image forming process to be executed is not the front side printing process (S12: No), the process proceeds to step S14.

[0075] <Step S13> In step S13, the second image processing unit 52 of the control unit 7 executes the detection image formation process. That is, the second image processing unit 52 executes the detection image formation process based on the detection image data corresponding to the detection toner image X10 only while the first image processing unit 51 is executing the front surface printing process. As a result, as shown in FIG. 5, in the image forming unit 3, a print image based on the image data is formed in the print area A1 of the intermediate transfer belt 26, and a detection toner image X10 based on the detection image data is formed in the non-contact area A3 of the intermediate transfer belt 26. Note that the second image processing unit 52 does not form the detection toner image X10 on the intermediate transfer belt 26 while the sheet-to-sheet process is being executed (S12: Yes).

[0076] That is, when the print job to be executed is a double-sided printing process and a printing process for the back side of a sheet (hereinafter referred to as a "back side printing process") is executed as part of the double-sided printing process, the second image processing unit 52 of the control unit 7 does not execute the detection image formation process even if the execution conditions are satisfied. Therefore, in the image forming apparatus 100, the detection toner image X10 formed by the detection image formation process is formed under the image formation conditions (front side image formation conditions) when the front side printing process is executed to form a print image on the front side of a sheet in the double-sided printing process.

[0077] In another embodiment, it is also possible that the detection image formation process is not executed when the print job to be executed is a double-sided printing process, and the detection image formation process is executed when the front side printing process is executed within the double-sided printing process, and the detection image formation process is executed when the back side printing process is executed. That is, when the detection image formation process is executed during execution of a double-sided printing job in which the print image is formed on both the front side and the back side of a sheet, the second image processing unit 52 executes the detection image formation process only under the image formation conditions in the print image formation process corresponding to a predetermined one of the front side and the back side.

[0078] <Step S14> In step S14, the detection processing unit 53 of the control unit 7 uses the detection unit 46 to detect the density and position of the detection toner image X10 formed on the intermediate transfer belt 26 in step S13, and stores the detected density and position in the storage unit 6. The detected density and position of the detection toner image X10 are used in the adjustment process of the image formation conditions in step S16, which will be described later.

[0079] <Step S15> In step S15, the second image processing unit 52 of the control unit 7 determines whether the print job to be executed has ended. Specifically, the second image processing unit 52 of the control unit 7 determines that the print job has ended when the print image for the last page of the print job has been formed on the intermediate transfer belt 26. If it is determined that the print job has ended (S15: Yes), the process proceeds to step S16, and if it is determined that the print job has not ended (S15: No), the adjustment control process ends.

[0080] <Step S16> In step S16, the second image processing unit 52 of the control unit 7 executes the adjustment process based on the detection result of the detection toner image X10 by the detection unit 46. As a result, the print image formation process executed after execution of step S16 reflects the adjustment contents of the image formation conditions executed by the adjustment process in step S16. Also, in step S16, the second image processing unit 52 resets the cumulative number of printed sheets, which is used to determine whether the execution condition is satisfied, to 0. As a result, each time the cumulative number of printed sheets reaches the first reference number, it is determined that the execution condition is satisfied, and the adjustment process is executed.

[0081] In this embodiment, the case where the adjustment process is performed in step S16 will be described as an example, but the adjustment process may be performed at any timing after the density and position of each detection toner image X10 is detected in step S14. For example, part or all of the adjustment process may be performed between step S14 and step S15.

[0082] 7 is a diagram showing an example of the execution result of the adjustment control process according to the present embodiment, in which the content of the print job is a double-sided printing process for three sheets and the execution conditions of the adjustment process are satisfied.

[0083] 7, when the print image forming process is executed based on image data corresponding to the front surface of the first sheet, the detection image forming process is executed together with the print image forming process, whereby, in the region on the intermediate transfer belt 26 corresponding to the front surface of the first sheet, a print image based on the image data is formed in the print region A1 inside the contact region A2, and a detection toner image X10 is formed in the non-contact region A3.

[0084] Next, the print image forming process based on the image data corresponding to the front surface of the first sheet is completed, and after the inter-sheet period P0 has elapsed, the print image forming process is then executed based on the image data corresponding to the front surface of the second sheet. Here, when the print image forming process is executed based on the image data corresponding to the front surface of the second sheet, the detection image forming process is also executed together with the print image forming process. As a result, in the area on the intermediate transfer belt 26 corresponding to the front surface of the second sheet, a print image based on the image data is formed in the print area A1 inside the contact area A2, and a detection toner image X10 is formed in the non-contact area A3.

[0085] Subsequently, the print image forming process is completed based on the image data corresponding to the front side of the second sheet, and after the sheet interval P0 has elapsed, the print image forming process is executed based on the image data corresponding to the back side of the first sheet. Here, when the print image forming process is executed based on the image data corresponding to the back side of the first sheet, the detection image forming process is not executed. As a result, as shown in FIG. 7, in the area on the intermediate transfer belt 26 corresponding to the back side of the first sheet, a print image based on the image data is formed in the contact area A2, but the detection toner image X10 is not formed in the non-contact area A3.

[0086] Similarly, after that, the print image forming process is completed based on the image data corresponding to the back side of the first sheet, and after the inter-sheet period P0 has elapsed, the print image forming process is then executed based on the image data corresponding to the front side of the third sheet. Here, when the print image forming process is executed based on the image data corresponding to the front side of the third sheet, the detection image forming process is executed. As a result, in the area on the intermediate transfer belt 26 corresponding to the front side of the third sheet, a print image based on the image data is formed in the print area A1 inside the contact area A2, and a detection toner image X10 is formed in the non-contact area A3.

[0087] When the print image forming process based on the image data corresponding to the front side of the third sheet is completed and the inter-sheet period P0 has elapsed, the print image forming process is then executed based on the image data corresponding to the back side of the second sheet. Here, even when the print image forming process is executed based on the image data corresponding to the back side of the second sheet, the detection image forming process is not executed.

[0088] Thereafter, the print image forming process is completed based on the image data corresponding to the back side of the second sheet, and after the sheet interval P0 has elapsed, the print image forming process is executed based on the image data corresponding to the back side of the third sheet. Here, even when the print image forming process is executed based on the image data corresponding to the back side of the third sheet, the detection image forming process is not executed.

[0089] As described above, in the image forming apparatus 100 according to this embodiment, the detection image formation process for the detection toner image X10 is performed simultaneously with the front printing process, and the detection image formation process is not performed when the back printing process is performed. Then, in the image forming apparatus 100, the adjustment process is performed based on the detection result of the detection toner image X10 formed in the detection image formation process performed simultaneously with the front printing process. As a result, the adjustment process is performed based on the detection result of the detection toner image X10 formed under the same image forming conditions. Therefore, in the image forming apparatus 100, the effect of the adjustment process is enhanced compared to when the adjustment process is performed based on the detection result of the detection toner image X10 formed in both the front printing process and the back printing process, which have different image forming conditions.

[0090] [Other embodiments] In the above embodiment, the case where the detection image formation process is executed simultaneously with the print image formation process has been described. Meanwhile, in other embodiments, it is considered that the detection image formation process is executed during the inter-sheet period P0. Here, FIG. 8 is a diagram showing another example of the adjustment control process. Note that, among the adjustment control processes shown in FIG. 8, processes similar to the adjustment control process (see FIG. 6) described in the above embodiment are assigned the same reference numerals, and their description will be omitted.

[0091] <Step S121> 8, in step S12 of this embodiment, if it is determined that the print image forming process to be executed is the front side printing process (S12: Yes), the process proceeds to step S121. Then, in step S121, the second image processing unit 52 of the control unit 7 determines whether the inter-sheet period P0 has arrived.

[0092] For example, the second image processing unit 52 can determine that the inter-sheet period P0 has arrived when the irradiation of laser light from the optical scanning device 25 based on one page of image data included in the print job has started and the irradiation of laser light based on the image data has ended. Alternatively, the second image processing unit 52 may determine that the inter-sheet period P0 has arrived when a preset time has elapsed since the irradiation of laser light from the optical scanning device 25 based on one page of image data included in the print job has started.

[0093] When it is determined that the inter-sheet period P0 has arrived (S121: Yes), the process proceeds to step S13, and until the inter-sheet period P0 arrives (S121: No), the process waits in step S121. In this embodiment, the detection image formation process is executed in the inter-sheet period P0 in step S13.

[0094] 9 is a diagram showing an example of the execution result of the adjustment control process (see FIG. 8) according to the present embodiment, in which the content of the print job is a double-sided printing process for three sheets and the execution conditions of the adjustment process are satisfied.

[0095] 9, when the print image forming process is executed based on image data corresponding to the front surface of the first sheet, the detection image forming process is executed in the inter-sheet period P0 after the print image forming process is executed, whereby a detection toner image X10 is formed in the non-contact area A3 on the intermediate transfer belt 26 corresponding to the inter-sheet period P0 after the print image forming process corresponding to the front surface of the first sheet.

[0096] Next, when the inter-sheet period P0 following completion of the print image forming process corresponding to the front surface of the first sheet has elapsed, the print image forming process is executed based on image data corresponding to the front surface of the second sheet. Here, when the print image forming process is executed based on image data corresponding to the front surface of the second sheet, the detection image forming process is also executed during the inter-sheet period P0 following execution of the print image forming process. As a result, a detection toner image X10 is formed in the non-contact area A3 on the intermediate transfer belt 26 corresponding to the inter-sheet period P0 following the print image forming process corresponding to the front surface of the second sheet.

[0097] Subsequently, when the inter-sheet period P0 following completion of the print image forming process corresponding to the front side of the second sheet has elapsed, the print image forming process is then executed based on image data corresponding to the back side of the first sheet. Here, the detection image forming process is not executed during the inter-sheet period P0 following completion of the print image forming process based on image data corresponding to the back side of the first sheet. As a result, as shown in FIG. 9, the detection toner image X10 is not formed in the non-contact area A3 on the intermediate transfer belt 26 corresponding to the inter-sheet period P0 following the print image forming process corresponding to the back side of the first sheet.

[0098] Similarly, after the inter-sheet period P0 following completion of the print image forming process corresponding to the back side of the first sheet has elapsed, the print image forming process is then executed based on image data corresponding to the front side of the third sheet. Here, when the print image forming process is executed based on image data corresponding to the front side of the third sheet, the detection image forming process is also executed during the inter-sheet period P0 following execution of the print image forming process. As a result, a detection toner image X10 is formed in the non-contact area A3 on the intermediate transfer belt 26 corresponding to the inter-sheet period P0 following the print image forming process corresponding to the front side of the third sheet.

[0099] When the inter-sheet period P0 has elapsed after the print image forming process corresponding to the front side of the third sheet has ended, the print image forming process is then executed based on image data corresponding to the back side of the second sheet. Here, the detection image forming process is not executed during the inter-sheet period P0 after the print image forming process is executed based on image data corresponding to the back side of the second sheet.

[0100] Thereafter, when the inter-sheet period P0 after the end of the print image forming process corresponding to the back surface of the second sheet has elapsed, the print image forming process is then executed based on image data corresponding to the back surface of the third sheet. Here, the detection image forming process is not executed during the inter-sheet period P0 after the print image forming process is executed based on image data corresponding to the back surface of the third sheet.

[0101] As described above, in the image forming apparatus 100 according to this embodiment, the detection image formation process for the detection toner image X10 is performed during the inter-sheet period P0 after the front-side printing process is completed, and the detection image formation process is not performed during the inter-sheet period P0 after the back-side printing process is completed. Then, in the image forming apparatus 100, the adjustment process is performed based on the detection result of the detection toner image X10 formed during the detection image formation process performed during the inter-sheet period P0 after the front-side printing process is completed. As a result, the adjustment process is performed based on the detection result of the detection toner image X10 formed under the same image forming conditions. Therefore, in the image forming apparatus 100, the effect of the adjustment process is enhanced compared to when the adjustment process is performed based on the detection result of the detection toner image X10 formed during both the front-side printing process and the inter-sheet period P0 after the back-side printing process are completed, where the image forming conditions are different. Furthermore, in the image forming apparatus 100 of this embodiment, after the detection toner image X10 is detected in step S14, the adjustment process based on the detection result of the detection toner image X10 may be executed as the inter-sheet process during the inter-sheet period P0.

[0102] In another embodiment, the control unit 7 of the image forming apparatus 100 may automatically switch the content of the detection image formation process executed when the double-sided printing process is performed. For example, the control unit 7 may be capable of switching the operation mode of the image forming apparatus 100 between a first operation mode and a second operation mode. The first operation mode is an operation mode in which the image forming apparatus 100 prioritizes printing speed over image quality, and the second operation mode is an operation mode in which the image forming apparatus 100 prioritizes image quality over printing speed. When the double-sided printing process is performed and the first operation mode is being executed, the second image processing unit 52 executes the detection image formation process in a first detection mode in which the detection image formation process is executed simultaneously with the front-side printing process. When the double-sided printing process is performed and the first operation mode is being executed, the second image processing unit 52 executes the detection image formation process in a second detection mode in which the detection image formation process is executed during the inter-sheet period P0 after the front-side printing process is executed. That is, the second image processing unit 52 may be capable of switching between the first detection mode and the second detection mode. [Explanation of symbols]

[0103] 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 unit that forms an image based on input image data on a transfer receiving body and transfers the image from the transfer receiving body to a sheet; a first image processing unit that executes a print image forming process in which the image forming unit forms a print image in a predetermined print area on the transfer medium based on image data of a print target; a second image processing unit that, when a preset execution condition is satisfied, executes a detection image forming process in which the image forming unit forms a detection image used for adjusting the image forming conditions in the image forming unit in an area outside the print area on the transfer object; and Equipped with the first image processing unit executes the print image forming process corresponding to the front surface and the print image forming process corresponding to the back surface under different image forming conditions in a double-sided printing process for forming the print image on both the front and back surfaces of a sheet; When the second image processing unit executes the detection image forming process during the execution of the double-sided printing process, the second image processing unit executes the detection image forming process only under the image forming conditions in the print image forming process corresponding to a predetermined one of the front side and the back side. Image forming device.

2. the second image processing unit executes the detection image forming process only during execution of the print image forming process corresponding to one side in the double-sided printing process. The image forming apparatus according to claim 1 .

3. the second image processing unit executes the detection image forming process only during an inter-page period from the end of the print image forming process corresponding to one side in the double-sided printing process until the print image forming process corresponding to the next page is executed. The image forming apparatus according to claim 1 .

4. The second image processing unit The detection image forming process can be switched between a mode in which the detection image forming process is executed only during execution of the print image forming process corresponding to one side in the double-sided printing process, and a mode in which the detection image forming process is executed only during an inter-page period from the end of the print image forming process corresponding to one side in the double-sided printing process until the print image forming process corresponding to the next page is executed. The image forming apparatus according to claim 1 .

5. a processor of an image forming apparatus having an image forming unit that forms an image on a transfer medium based on input image data and transfers the image from the transfer medium to a sheet, a first step of executing a print image forming process in which the image forming unit forms a print image in a predetermined print area on the transfer medium based on image data of a print target; a second step of executing a detection image forming process in which, when a preset execution condition is satisfied, the image forming unit forms a detection image used for adjusting the image forming conditions in the image forming unit in an area outside the print area on the transfer medium; Equipped with the first step is a double-sided printing process for forming the print image on the front and back surfaces of a sheet, in which the print image forming process corresponding to the front surface and the print image forming process corresponding to the back surface are performed under different image forming conditions; In the second step, when the detection image forming process is executed during the execution of the double-sided printing process, the detection image forming process is executed only under the image forming conditions in the print image forming process corresponding to a predetermined one of the front surface and the back surface. Image forming method.

Images