Image forming apparatus and adjustment method

Abstract

To provide an image forming apparatus capable of suppressing the occurrence of a difference in the fluctuation amount of the image quality of an output image between a plurality of image forming speeds by simple control, and an adjustment method.SOLUTION: The image forming apparatus 100 includes an image forming processing portion 51 configured to execute an image forming process of forming, by using the image forming portion 3, an image on each of sheets that are sequentially conveyed by the sheet conveying portion 4, at any one of a plurality of image forming speeds, and an adjustment processing portion 52 configured to execute an adjustment process of adjusting an image quality of an output image that is output by the image forming portion 3, each time an execution timing that is common to the plurality of image forming speeds comes during execution of the image forming process.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] In an image forming device such as a printer that forms an image on a sheet based on image data, an adjustment process is performed to adjust the image quality of the output image (see, for example, Patent Document 1). For example, there is known an image forming device that performs the adjustment process each time an image is formed on a predetermined reference number of sheets during an image forming process that forms an image on each of sheets that are conveyed sequentially.

[0003] Further, there is known an image forming apparatus that executes the image forming process at one of a plurality of predetermined image forming speeds. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2020-116748 Summary of the Invention [Problem to be solved by the invention]

[0005] In an electrophotographic image forming apparatus, the charge amount of toner changes from moment to moment during the image formation process, thereby changing the density of the output image. In an electrophotographic image forming apparatus that performs the image formation process at one of multiple image formation speeds, if the adjustment process is performed each time an image is formed on the reference number of sheets, the slower the image formation speed, the longer the interval between executions of the adjustment process. Therefore, the amount of fluctuation in the image quality of the output image varies between the multiple image formation speeds. To address this issue, it is conceivable to set the reference number for each image formation speed. However, this configuration complicates control of the image forming apparatus.

[0006] An object of the present invention is to provide an image forming apparatus and an adjustment method that can suppress differences in the amount of fluctuation in the image quality of output images between a plurality of image forming speeds with simple control. [Means for solving the problem]

[0007] According to one aspect of the present invention, an image forming apparatus includes a sheet conveying unit, an image forming unit, an image formation processing unit, and an adjustment processing unit. The sheet conveying unit conveys a sheet. The image forming unit has an image carrier on which an electrostatic latent image is formed and a developing unit that develops the electrostatic latent image formed on the image carrier using toner, and forms an image on the sheet conveyed by the sheet conveying unit. The image forming processing unit executes an image formation process that uses the image forming unit to form an image on each of the sheets conveyed sequentially by the sheet conveying unit at one of a plurality of predetermined image formation speeds. The adjustment processing unit executes an adjustment process that adjusts the image quality of an output image output by the image forming unit each time a predetermined execution timing common to the plurality of image formation speeds arrives during the image formation process.

[0008] According to another aspect of the present invention, an adjustment method is performed in an image forming apparatus including a sheet conveying unit that conveys a sheet, an image carrier on which an electrostatic latent image is formed, and an image forming unit that has a developing unit that develops the electrostatic latent image formed on the image carrier with toner and forms an image on the sheet conveyed by the sheet conveying unit, and includes an image forming step and an adjustment step. In the image forming step, an image formation process is performed using the image forming unit to form an image on each of the sheets conveyed sequentially by the sheet conveying unit at one of a plurality of predetermined image formation speeds. In the adjustment step, an adjustment process is performed during the image formation process, each time a predetermined execution timing common to the plurality of image formation speeds arrives, to adjust the image quality of an output image output by the image forming unit. [Effects of the Invention]

[0009] According to the present invention, it is possible to suppress differences in the amount of fluctuation in the image quality of output images between a plurality of image forming speeds through simple control. [Brief explanation of the drawings]

[0010] [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 cross-sectional view 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 an operation control process executed by the image forming apparatus according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] 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.

[0012] [Configuration of image forming apparatus 100] First, the configuration of an image forming apparatus 100 according to an embodiment of the present invention will be described with reference to FIGS.

[0013] 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.

[0014] 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.

[0015] 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 sheet conveying unit 4, an operation display unit 5, a storage unit 6, and a control unit 7.

[0016] 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.

[0017] 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).

[0018] 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 sheet conveying unit 4 according to an electrophotographic method.

[0019] The sheet conveying section 4 conveys the sheet. The image forming section 3 forms an image on the sheet conveyed by the sheet conveying section 4. The sheet conveying section 4 includes a paper feed cassette, a manual feed tray, and a plurality of conveying rollers.

[0020] The operation display unit 5 is a user interface of the image forming apparatus 100. The operation display unit 5 has a display unit and an operation unit. The display unit displays various information in response to control instructions from the control unit 7. Specifically, the display unit is a display device such as a liquid crystal display. The operation unit inputs various information to the control unit 7 in response to user operations. Specifically, the operation unit is an operation device including operation keys and a touch panel.

[0021] The storage unit 6 is a non-volatile storage device, such as a flash memory.

[0022] 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 is a processor that executes 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.

[0023] 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).

[0024] [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 cross-sectional view showing the configuration of multiple image forming units 20, intermediate transfer belt 26, and secondary transfer roller 27. Also, Figure 4 is a bottom view showing the configuration of photosensitive drum 31, intermediate transfer belt 26, drive roller 40, and secondary transfer roller 27 of image forming unit 24.

[0025] 1, the image forming section 3 includes four image forming units 20, two optical scanning devices 25, an intermediate transfer belt 26, a secondary transfer roller 27, a fixing device 28, and a paper discharge tray 29. Also, as shown in FIG. 2, the image forming section 3 includes a density corrector 30, a voltage application unit 38, a light source 39, and a sensor 43.

[0026] Of the four image forming units 20, image forming unit 21 (see FIG. 3) forms a Y (yellow) toner image. Of the four image forming units 20, image forming unit 22 (see FIG. 3) forms a C (cyan) toner image. Of the four image forming units 20, image forming unit 23 (see FIG. 3) forms an M (magenta) toner image. Of the four image forming units 20, 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.

[0027] 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.

[0028] An electrostatic latent image is formed on the surface of photoreceptor drum 31. Photoreceptor 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, photoreceptor drum 31 transports the electrostatic latent image formed on its surface. Photoreceptor drum 31 is an example of an image carrier of the present invention.

[0029] 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.

[0030] The developing device 33 uses toner to develop 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 37 (see FIG. 3). The pair of stirring members stir the developer, which contains toner and a carrier, contained inside 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 picks up the developer stirred by the pair of stirring members and supplies the toner contained in the developer to the developing roller 37. The developing roller 37 transports the toner supplied from the magnet roller to a position facing the photosensitive drum 31. The developing roller 37 also supplies the toner transported to the facing position to the electrostatic latent image formed on the photosensitive drum 31 in response to the application of a preset development bias voltage. As a result, toner is selectively supplied to the 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 an example of a developing section of the present invention. The developing roller 37 is an example of a developing member of the present invention. The developing device 33 is supplied with toner from a toner container 36.

[0031] The voltage application section 38 is a power source capable of applying the development bias voltage to the development roller 37. The voltage application section 38 is provided corresponding to each of the image forming units 20.

[0032] The primary transfer roller 34 receives a supply of a preset primary transfer current and 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.

[0033] 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 .

[0034] The density correction unit 30 uses predetermined table data to correct the density of image data used to form an output image output by the image forming unit 3. Specifically, the density correction unit 30 corrects the density of the image data so that the relationship between the density of the image data input to the image forming unit 3 and the density of the output image becomes linear. In other words, the density correction unit 30 performs so-called gamma correction. The table data is data indicating a gamma table used for the gamma correction.

[0035] The density correction unit 30 and the table data are provided for each print color. The density correction unit 30 corresponding to Y (yellow) corrects the density of Y (yellow) image data based on first table data. The first table data is the table data corresponding to Y (yellow). The density correction unit 30 corresponding to C (cyan) corrects the density of C (cyan) image data based on second table data. The second table data is the table data corresponding to C (cyan). The density correction unit 30 corresponding to M (magenta) corrects the density of M (magenta) image data based on third table data. The third table data is the table data corresponding to M (magenta). The density correction unit 30 corresponding to K (black) corrects the density of K (black) image data based on fourth table data. The fourth table data is the table data corresponding to K (black).

[0036] The light source 39 emits light that is irradiated onto the photosensitive drum 31. The light source 39 emits light based on image data that has undergone density correction by the density corrector 30. A light source 39 is provided for each print color.

[0037] The two optical scanning devices 25 emit light based on image data toward the surfaces of the photosensitive drums 31 of the image forming units 20. The two optical scanning devices 25 are arranged side by side in the front-rear direction D2.

[0038] Of the two optical scanning devices 25, the optical scanning device 25 located on the front side emits light based on image data of Y (yellow) toward the photosensitive drum 31 of the image forming unit 21. The optical scanning device 25 located on the front side emits light based on image data of C (cyan) toward the photosensitive drum 31 of the image forming unit 22. Specifically, the optical scanning device 25 located on the front side includes a light source 39 corresponding to Y (yellow), a light source 39 corresponding to C (cyan), a first polygon mirror common to Y (yellow) and C (cyan), a first optical path corresponding to Y (yellow), and a second optical path corresponding to C (cyan). The light emitted from the light source 39 corresponding to Y (yellow) is scanned in the main scanning direction along the left-right direction D3 by the first polygon mirror and is irradiated onto the photosensitive drum 31 of the image forming unit 21 via a lens and a mirror located on the first optical path. Light emitted from the light source 39 corresponding to C (cyan) is scanned in the main scanning direction by the first polygon mirror and is irradiated onto the photosensitive drum 31 of the image forming unit 22 via a lens and a mirror arranged in the second optical path.

[0039] Of the two optical scanning devices 25, the optical scanning device 25 located on the rear side emits light based on image data of M (magenta) toward the photosensitive drum 31 of the image forming unit 23. The optical scanning device 25 located on the rear side emits light based on image data of K (black) toward the photosensitive drum 31 of the image forming unit 24. Specifically, the optical scanning device 25 located on the rear side includes a light source 39 corresponding to M (magenta), a light source 39 corresponding to K (black), a second polygon mirror common to M (magenta) and K (black), a third optical path corresponding to M (magenta), and a fourth optical path corresponding to K (black). The light emitted from the light source 39 corresponding to M (magenta) is scanned in the main scanning direction by the second polygon mirror and irradiated onto the photosensitive drum 31 of the image forming unit 23 via a lens and a mirror located on the third optical path. Light emitted from a light source 39 corresponding to K (black) is scanned in the main scanning direction by the second polygon mirror and irradiated onto the photosensitive drum 31 of the image forming unit 24 via a lens and a mirror arranged in the fourth optical path. The optical scanning device 25 scans the light emitted from the light source 39 to form an electrostatic latent image on the photosensitive drum 31. The optical scanning device 25 is an example of a latent image forming section of the present invention.

[0040] 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. The intermediate transfer belt 26 is stretched with a predetermined tension by a drive roller 40 (see FIG. 3) and a tension roller 41 (see FIG. 3). The intermediate transfer belt 26 rotates in a belt rotation direction D5 shown in FIG. 3 when the drive roller 40 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 42 (see FIG. 3).

[0041] 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 sheet conveying unit 4. As shown in Fig. 3, the secondary transfer roller 27 is disposed opposite the drive roller 40 with the intermediate transfer belt 26 sandwiched therebetween.

[0042] 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 A2 (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 A2 is an area outside the contact area A1 (see FIG. 4) on the outer circumferential surface of the intermediate transfer belt 26 that comes into contact with the secondary transfer roller 27, and is an area that includes the ends of the intermediate transfer belt 26 in the width direction.

[0043] The fixing device 28 fixes the toner image transferred onto the sheet by the secondary transfer roller 27 onto the sheet.

[0044] The sheet on which the toner image has been fixed by the fixing device 28 is discharged to the paper discharge tray 29.

[0045] The sensor 43 detects the density and position of the toner image transferred to the non-contact area A2 (see FIG. 4) on the outer circumferential surface of the intermediate transfer belt 26. For example, the sensor 43 is provided corresponding to each of the pair of non-contact areas A2. For example, the sensor 43 is a reflective optical sensor and includes a light-emitting unit that emits light toward the non-contact area A2 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 A2 of the intermediate transfer belt 26. As shown in FIG. 3, the sensor 43 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 42 cleans the outer circumferential surface of the intermediate transfer belt 26. The sensor 43 inputs an electrical signal corresponding to the density and position of the toner image to be detected to the control unit 7.

[0046] [Configuration of control unit 7] Next, the configuration of the control unit 7 will be described with reference to FIG.

[0047] As shown in FIG. 2, the control unit 7 includes an image formation processing unit 51 and an adjustment processing unit 52.

[0048] Specifically, an operation control 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 executes the operation control program stored in the ROM 12 to function as each of the above-mentioned processing units.

[0049] The operation control 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. Some or all of the processing units included in the control unit 7 may be configured with electronic circuits. The operation control program may also be a program for causing multiple processors to function as the processing units included in the control unit 7.

[0050] The image forming processing unit 51 executes an image forming process in which, at one of a plurality of predetermined image forming speeds, the image forming unit 3 forms an image on each sheet conveyed sequentially by the sheet conveying unit 4. The image forming speed is the number of prints per predetermined unit time. For example, the image forming speed is the number of prints per minute.

[0051] For example, the image formation processing unit 51 executes the image formation process at one of a first image formation speed, a second image formation speed, and a third image formation speed. The first image formation speed is the fastest image formation speed among the plurality of image formation speeds. The second image formation speed is the second fastest image formation speed among the plurality of image formation speeds. The third image formation speed is the slowest image formation speed among the plurality of image formation speeds.

[0052] For example, when an instruction to execute the image forming process is input, the image forming processing unit 51 executes the image forming process at the image forming speed corresponding to the type of sheet on which the output image is formed.

[0053] For example, when the type of sheet on which the output image is formed is "thin paper," the image forming processing unit 51 executes the image forming process at the first image forming speed. When the type of sheet on which the output image is formed is "plain paper," the image forming processing unit 51 executes the image forming process at the second image forming speed. When the type of sheet on which the output image is formed is "thick paper," the image forming processing unit 51 executes the image forming process at the third image forming speed.

[0054] The image formation processing unit 51 may determine the image formation speed to be applied when the image formation process is executed based on the basis weight of the sheet on which the output image is formed. Specifically, the image formation processing unit 51 may determine the image formation speed so that the larger the basis weight of the sheet on which the output image is formed, the slower the image formation speed to be applied when the image formation process is executed.

[0055] The adjustment processing unit 52 performs an adjustment process to adjust the image quality of the output image output by the image forming unit 3 during the execution of the image forming process.

[0056] For example, the adjustment process includes a first adjustment process, a second adjustment process, a third adjustment process, and a fourth adjustment process.

[0057] The first adjustment process is a process for adjusting the developing bias voltage. When the developing bias voltage corresponding to any one of the image forming units 20 changes, the density of the toner image formed by that image forming unit 20 changes. In other words, the first adjustment process can be said to be a process for adjusting the image quality (density) of the output image.

[0058] For example, in the first adjustment process, a first detection toner image of Y (yellow) is formed in each of a pair of non-contact areas A2 (see FIG. 4) on the intermediate transfer belt 26. That is, the first adjustment process includes a first toner image forming process of forming the first detection toner image on the photosensitive drum 31 of the image forming unit 21. The first detection toner image includes a plurality of first partial toner images arranged along the belt rotation direction D5 of the intermediate transfer belt 26. The plurality of first partial toner images are formed based on common image data. The plurality of first partial toner images are formed by applying different developing bias voltages to the developing rollers 37 of the image forming units 21. In the first adjustment process, a sensor 43 is used to detect the density of each of the first partial toner images included in the first detection toner image formed on the intermediate transfer belt 26. In the first adjustment process, a linear equation indicating the relationship between the voltage value of the developing bias voltage corresponding to the image forming unit 21 and the density of the toner image is obtained based on the detection result of the density of each of the first partial toner images. Then, in the first adjustment process, the developing bias voltage corresponding to the image forming unit 21 is adjusted based on a voltage value corresponding to a predetermined density calculated using the acquired linear equation. The developing bias voltages corresponding to the other image forming units 20 are also adjusted in the same manner as the developing bias voltage corresponding to the image forming unit 21. In the first adjustment process, four first detection toner images corresponding to each print color are formed in sequence, and the developing bias voltages corresponding to each print color are adjusted.

[0059] The second adjustment process is a process for adjusting the amount of light emitted from the light source 39. When the amount of light emitted from the light source 39 corresponding to one of the printing colors changes, the density of the toner image based on the electrostatic latent image formed by that light source 39 changes. In other words, the second adjustment process can be said to be a process for adjusting the image quality (density) of the output image.

[0060] For example, in the second adjustment process, a second detection toner image of Y (yellow) is formed in each of a pair of non-contact areas A2 (see FIG. 4) on the intermediate transfer belt 26. That is, the second adjustment process includes a second toner image forming process of forming the second detection toner image on the photosensitive drum 31 of the image forming unit 21. The second detection toner image includes a plurality of second partial toner images arranged along the belt rotation direction D5 of the intermediate transfer belt 26. The plurality of second partial toner images are formed based on common image data. The plurality of second partial toner images are formed by emitting different amounts of light from the light source 39 corresponding to Y (yellow). In the second adjustment process, a sensor 43 is used to detect the density of each of the second partial toner images included in the second detection toner image formed on the intermediate transfer belt 26. In the second adjustment process, a linear equation indicating the relationship between the amount of light emitted from the light source 39 corresponding to Y (yellow) and the density of the toner image is obtained based on the detection result of the density of each of the second partial toner images. Then, in the second adjustment process, the amount of light emitted from the light source 39 corresponding to Y (yellow) is adjusted based on the amount of light corresponding to a predetermined density calculated using the acquired linear equation. The amounts of light emitted from the light sources 39 corresponding to the other printing colors are also adjusted in the same way as the amount of light emitted from the light source 39 corresponding to Y (yellow). In the second adjustment process, four second detection toner images corresponding to each printing color are formed in sequence, and the amount of light corresponding to each printing color is adjusted.

[0061] The third adjustment process is a process for adjusting the table data. When the table data corresponding to any printing color changes, the density of the toner image formed using the table data changes. In other words, the third adjustment process can be said to be a process for adjusting the image quality (density) of the output image.

[0062] For example, in the third adjustment process, a third detection toner image of Y (yellow) is formed in each of a pair of non-contact areas A2 (see FIG. 4) on the intermediate transfer belt 26. That is, the third adjustment process includes a third toner image forming process of forming the third detection toner image on the photosensitive drum 31 of the image forming unit 21. The third detection toner image includes a plurality of third partial toner images arranged along the belt rotation direction D5 of the intermediate transfer belt 26. The plurality of third partial toner images are formed based on a plurality of image data each having a different density of Y (yellow). Therefore, the plurality of third partial toner images formed on the intermediate transfer belt 26 have different densities. In the third adjustment process, a sensor 43 is used to detect the density of each of the third partial toner images included in the third detection toner image formed on the intermediate transfer belt 26. In addition, in the third adjustment process, an equation indicating the relationship between the density of the Y (yellow) image data input to the image forming unit 3 and the density of the toner image formed on the intermediate transfer belt 26 is obtained based on the detection result of the density of each of the third partial toner images. Then, in the fourth adjustment process, the table data corresponding to Y (yellow) is adjusted based on the acquired equation so that the relationship between the density of the Y (yellow) image data input to the image forming unit 3 and the density of the toner image formed on the intermediate transfer belt 26 becomes linear. The table data corresponding to the other print colors are also adjusted in the same manner as the table data corresponding to Y (yellow). In the third adjustment process, four third detection toner images corresponding to each print color are formed sequentially, and the table data corresponding to each print color is adjusted.

[0063] The fourth adjustment process is a process for adjusting the position at which an electrostatic latent image is formed on each photosensitive drum 31 by the optical scanning device 25. When the position at which an electrostatic latent image is formed on any one of the photosensitive drums 31 by the optical scanning device 25 changes, the position at which the toner image of the printing color corresponding to that photosensitive drum 31 is formed on the sheet changes, causing color misalignment. In other words, the fourth adjustment process can be said to be a process for adjusting the image quality (color misalignment) of the output image.

[0064] For example, in the fourth adjustment process, a fourth detection toner image of Y (yellow) is formed in each of a pair of non-contact areas A2 (see FIG. 4) on the intermediate transfer belt 26. That is, the fourth adjustment process includes a fourth toner image forming process of forming the fourth detection toner image on the photosensitive drum 31 of the image forming unit 21. For example, the fourth detection toner image is a rectangular toner image formed based on predetermined image data. In the fourth adjustment process, a sensor 43 is used to detect the position of the fourth detection toner image formed on the intermediate transfer belt 26 (the position in the left-right direction D3 and the position in the belt rotation direction D5). Then, in the fourth adjustment process, the formation position of the electrostatic latent image on the photosensitive drum 31 of the image forming unit 21 is adjusted based on the detection result of the position of the fourth detection toner image. For example, in the fourth adjustment process, if the detection position of the third detection toner image in the left-right direction D3 is deviated from a predetermined position, the position of the lens arranged in the first optical path is adjusted to eliminate the deviation. Furthermore, in the fourth adjustment process, if the detection position of the third detection toner image in the belt rotation direction D5 is deviated from a predetermined position, the posture of the mirror arranged in the first light path is adjusted to eliminate the deviation. The formation positions of the electrostatic latent images on the photosensitive drums 31 of the other image forming units 20 are also adjusted in the same manner as the formation position of the electrostatic latent image on the photosensitive drum 31 of the image forming unit 21. In the fourth adjustment process, four fourth detection toner images corresponding to each print color are formed sequentially, and the formation positions of the electrostatic latent images corresponding to each print color are adjusted.

[0065] For example, the adjustment processing unit 52 executes one of the four adjustment processes selected in a predetermined order each time an execution timing described below arrives.

[0066] In the image forming apparatus 100, the charge amount of the toner changes from moment to moment during the execution of the image forming process, which causes the density of the output image to change.

[0067] In the image forming apparatus 100, if the adjustment process is performed each time a predetermined number of sheets are imaged, the slower the image formation speed, the longer the interval between executions of the adjustment process. Therefore, there is a difference in the amount of fluctuation in the image quality of the output image between the multiple image formation speeds. In other words, the slower the image formation speed, the greater the amount of fluctuation in the image quality of the output image. To address this issue, it is conceivable to set the reference number for each image formation speed. However, this configuration complicates the control of the image forming apparatus 100.

[0068] In contrast, in the image forming apparatus 100 according to an embodiment of the present invention, as described below, it is possible to suppress differences in the amount of fluctuation in the image quality of the output image between the multiple image forming speeds through simple control.

[0069] Specifically, the adjustment processing unit 52 executes the adjustment processing every time a predetermined execution timing common to the plurality of image forming speeds arrives during the execution of the image forming processing.

[0070] Here, the execution timing occurs at a longer cycle than the execution time of the adjustment process when the adjustment process is performed at the third image formation speed (an example of a specific image formation speed of the present invention), which is the slowest of the multiple image formation speeds. Furthermore, the execution timing occurs at a longer cycle than the execution time of the adjustment process when the adjustment process with the longest execution time is performed at the third image formation speed. By determining the execution timing in this manner, when the adjustment process is performed at the third image formation speed, it is possible to prevent the execution timing of the next adjustment process from occurring before the current adjustment process is completed. For example, the execution timing occurs when the drive time of the developing device 33 reaches an integer multiple of a predetermined reference time. The reference time is longer than the execution time of the adjustment process with the longest execution time when the adjustment process with the longest execution time is performed at the third image formation speed. The execution timing does not have to occur periodically.

[0071] The adjustment process does not necessarily include any one or more of the first adjustment process, the second adjustment process, the third adjustment process, and the fourth adjustment process.

[0072] [Motion control processing] 5, the adjustment method of the present invention will be described below along with an example of the procedure of the operation control process executed by the control unit 7 in the image forming apparatus 100. Here, steps S11, S12, etc. represent the numbers of the processing procedures (steps) executed by the control unit 7. Note that the operation control process is executed together with the image formation process when an instruction to execute the image formation process is input. Executing the image formation process in response to input of an instruction to execute the image formation process is an example of the image formation step of the present invention, and is executed by the image formation processing unit 51 of the control unit 7.

[0073] <Step S11> First, in step S11, the control unit 7 determines whether or not the driving of the developing device 33 has started in conjunction with the start of the image forming process.

[0074] Here, when the control unit 7 determines that the driving of the developing device 33 has started (Yes side of S11), the control unit 7 shifts the process to step S12. On the other hand, when the driving of the developing device 33 has not started (No side of S11), the control unit 7 waits for the driving of the developing device 33 to start in step S11.

[0075] <Step S12> In step S12, the control unit 7 starts measuring the driving time of the developing device 33.

[0076] <Step S13> In step S13, the control unit 7 determines whether or not the driving of the developing device 33 has been completed with the completion of the image forming process.

[0077] Here, when the control unit 7 determines that the driving of the developing device 33 has ended (Yes in S13), the control unit 7 shifts the process to step S16. On the other hand, when the driving of the developing device 33 has not ended (No in S13), the control unit 7 shifts the process to step S14.

[0078] <Step S14> In step S14, the control unit 7 determines whether or not the execution timing has arrived.

[0079] Specifically, the control unit 7 determines that the execution timing has arrived when the driving time of the developing device 33 measured in the process of step S12 reaches an integral multiple of the reference time.

[0080] Here, if the control unit 7 determines that the execution timing has arrived (Yes in S14), it shifts the process to step S15. On the other hand, if the execution timing has not arrived (No in S14), it shifts the process to step S13.

[0081] <Step S15> In step S15, the control unit 7 executes one of the four adjustment processes selected in a predetermined order. The process of step S15 is an example of an adjustment step of the present invention, and is executed by the adjustment processing unit 52 of the control unit 7.

[0082] <Step S16> In step S16, the control unit 7 ends the measurement of the driving time of the developing device 33.

[0083] In this way, in image forming apparatus 100, the adjustment process is executed each time the drive time of developing device 33 during the execution of the image formation process reaches an integer multiple of the reference time common to the plurality of image formation speeds. This makes it possible to suppress differences in the amount of fluctuation in the image quality of the output image between the plurality of image formation speeds, compared to a configuration in which the adjustment process is executed each time images are formed on the reference number of sheets. Furthermore, it is possible to avoid complex control of image forming apparatus 100, compared to a configuration in which the reference number is set for each image formation speed.

[0084] The size of the secondary transfer roller 27 in the axial direction (left-right direction D3) may be the same as the width of the intermediate transfer belt 26 (the size in the left-right direction D3). In this case, the sensor 43 may be disposed upstream of the transfer position of the toner image by the secondary transfer roller 27 in the belt rotation direction D5 and downstream of the transfer position of the toner image by the primary transfer roller 34 of the image forming unit 24 in the belt rotation direction D5. A cleaning member may be provided between the sensor 43 and the transfer position of the toner image by the secondary transfer roller 27. The cleaning member is movable between a contact position where the sensor 43 contacts the intermediate transfer belt 26 and a retracted position retracted from the contact position, and cleans the detection toner image formed during the adjustment process. If the execution timing arrives during the image formation process and the formation area of ​​the toner image corresponding to the output image overlaps with the formation area of ​​the detection toner image on the intermediate transfer belt 26, sheet conveyance by the sheet conveying unit 4 and formation of the toner image corresponding to the output image by the image forming unit 3 may be temporarily stopped until the adjustment process is completed.

[0085] [Notes on the Invention] The following will provide an outline 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.

[0086] <Appendix 1> an image forming unit having a sheet conveying unit that conveys a sheet, an image carrier on which an electrostatic latent image is formed, and a developing unit that develops the electrostatic latent image formed on the image carrier using toner, and that forms an image on the sheet conveyed by the sheet conveying unit; an image forming processing unit that executes an image formation process using the image forming unit to form an image on each of the sheets conveyed sequentially by the sheet conveying unit at one of a plurality of predetermined image forming speeds; and an adjustment processing unit that executes an adjustment process that adjusts the image quality of an output image output by the image forming unit each time a predetermined execution timing common to the plurality of image forming speeds arrives during the execution of the image forming process.

[0087] <Appendix 2> The image forming apparatus described in Appendix 1, wherein the adjustment process includes a toner image forming process for forming a predetermined detection toner image on the image carrier, and the execution timing is a timing that occurs at a longer cycle than the execution time of the adjustment process when the adjustment process is executed at a specific image formation speed that is the slowest among the multiple image formation speeds.

[0088] <Appendix 3> The image forming apparatus according to claim 1 or 2, wherein the developing unit includes a developing member that supplies the toner to the electrostatic latent image in response to application of a developing bias voltage, and the adjustment process includes a first adjustment process that adjusts the developing bias voltage.

[0089] <Appendix 4> An image forming apparatus according to any one of appendices 1 to 3, wherein the image forming unit includes a light source that emits light to be irradiated onto the image carrier, and the adjustment process includes a second adjustment process that adjusts the amount of light emitted from the light source.

[0090] <Appendix 5> An image forming apparatus according to any one of appendices 1 to 4, wherein the image forming unit includes a density correction unit that corrects the density of image data used to form the output image using predetermined table data, and the adjustment process includes a third adjustment process that adjusts the table data.

[0091] <Appendix 6> The image forming apparatus according to any one of appendices 1 to 5, wherein the image forming unit includes a latent image forming unit that forms the electrostatic latent image on the image carrier, and the adjustment process includes a fourth adjustment process that adjusts the formation position of the electrostatic latent image on the image carrier by the latent image forming unit.

[0092] <Appendix 7> An adjustment method performed in an image forming apparatus equipped with a sheet conveying unit that conveys a sheet, an image carrier on which an electrostatic latent image is formed, and an image forming unit that has a developing unit that develops the electrostatic latent image formed on the image carrier using toner, and forms an image on the sheet conveyed by the sheet conveying unit, the adjustment method including: an image forming step that performs an image formation process using the image forming unit to form an image on each of the sheets that are conveyed sequentially by the sheet conveying unit at one of a plurality of predetermined image forming speeds; and an adjustment step that performs an adjustment process that adjusts the image quality of an output image output by the image forming unit each time a predetermined execution timing common to the plurality of image forming speeds arrives during the execution of the image forming process. [Explanation of symbols]

[0093] 1 ADF 2 Image reading unit 3 Image forming unit 4 Sheet transport 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 30 Density correction section 31 Photosensitive drum 32 Charging roller 33 Developing device 34 Primary transfer roller 37 Developing roller 38 Voltage application section 39 Light source 43 Sensors 51 Image forming processing section 52 Adjustment processing section 100 Image forming device

Claims

1. a sheet conveying unit that conveys a sheet; an image forming unit including an image carrier on which an electrostatic latent image is formed and a developing unit that develops the electrostatic latent image formed on the image carrier with toner, and forms an image on the sheet transported by the sheet transport unit; an image forming processing unit that executes an image forming process to form an image on each of the sheets sequentially conveyed by the sheet conveying unit using the image forming unit at any one of a plurality of predetermined image forming speeds; an adjustment processing unit that executes an adjustment process to adjust the image quality of an output image output by the image forming unit every time a predetermined execution timing common to the plurality of image forming speeds arrives during execution of the image forming process; An image forming apparatus comprising:

2. the adjustment process includes a toner image forming step of forming a predetermined detection toner image on the image carrier; the execution timing is a timing that arrives at a cycle longer than the execution time of the adjustment process when the adjustment process is executed at a specific image formation speed that is the slowest among the plurality of image formation speeds; The image forming apparatus according to claim 1 .

3. the developing unit includes a developing member that supplies the toner to the electrostatic latent image in response to application of a developing bias voltage; the adjustment process includes a first adjustment process for adjusting the developing bias voltage; 3. The image forming apparatus according to claim 1.

4. the image forming unit includes a light source that emits light to be irradiated onto the image carrier; the adjustment process includes a second adjustment process of adjusting the amount of light emitted from the light source.

3. The image forming apparatus according to claim 1.

5. the image forming unit includes a density correcting unit that corrects the density of image data used to form the output image using predetermined table data; the adjustment process includes a third adjustment process for adjusting the table data; 3. The image forming apparatus according to claim 1.

6. the image forming unit includes a latent image forming unit that forms the electrostatic latent image on the image carrier, the adjustment process includes a fourth adjustment process of adjusting a position where the electrostatic latent image is formed on the image carrier by the latent image forming unit.

3. The image forming apparatus according to claim 1.

7. An adjustment method executed in an image forming apparatus including a sheet conveying unit that conveys a sheet, an image carrier on which an electrostatic latent image is formed, and an image forming unit that has a developing unit that develops the electrostatic latent image formed on the image carrier with toner, and forms an image on the sheet conveyed by the sheet conveying unit, an image forming step of performing an image forming process of forming an image on each of the sheets sequentially conveyed by the sheet conveying unit using the image forming unit at any one of a plurality of predetermined image forming speeds; an adjusting step of executing an adjustment process for adjusting the image quality of an output image output by the image forming unit every time a predetermined execution timing common to the plurality of image forming speeds arrives during the execution of the image forming process; Adjustment methods including:

Images