Image forming apparatus, image adjustment method

Abstract

To provide an image forming apparatus and image adjustment method that can suppress unnecessary execution of detection image forming processes and improve productivity in print image forming processes. [Solution] In the image forming apparatus (100), the second image processing unit (52) is capable of performing a detection image forming process during the inter-paper period, in which the image forming unit (3) forms a detection image used to adjust the image forming conditions in the image forming unit (3) in the printing area of ​​the transfer body (26). The adjustment processing unit (55) performs an adjustment process to adjust the image forming conditions in the image forming unit (3) based on the detection result of the detection image by the detection unit which detects the image characteristics of the detection image formed by the second image processing unit (52). The second image processing unit (52) then restricts the execution of the detection image forming process if the amount of change in image characteristics before and after the execution of an adjustment process performed in the past is less than a preset value.

Description

Technical Field

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

Background Art

[0002] In an image forming apparatus, a print image forming process for forming a print image based on image data on a transfer medium such as an intermediate transfer belt by an image forming unit is executed. In this type of image forming apparatus, an adjustment process for improving image quality may be executed by adjusting the image forming conditions by the image forming unit (see, for example, Patent Document 1). Specifically, when the adjustment process is executed, a detection image forming process for forming a detection image preset on the transfer medium is executed, and image characteristics such as the density of the detection image are detected using a detection unit such as a density sensor. Then, in the adjustment process, the image forming conditions are adjusted based on the detection result by the detection unit.

[0003] In the detection image forming process, during the execution of the print image forming process, the detection image forming process may be executed in a first mode in which a detection image is formed in an end region of the transfer medium where the print image is not formed. When the detection image forming process is executed in the first mode, a first detection unit provided at a position facing the end region is used to detect the image characteristics of the detection image.

[0004] Also, in the detection image forming process, using the intersheet period from after the end of the print image forming process corresponding to one page to before the execution of the print image forming process corresponding to the next page, the detection image forming process may be executed in a second mode in which a detection image is formed in an image forming region of the transfer medium where the print image is formed. When the detection image forming process is executed in the second mode, a first detection unit provided at a position facing the image forming region is used to detect the image characteristics of the detection image.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2010-266536 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, if the detection image formation process is executed in the second mode even when there is little need to adjust the image formation conditions, the productivity of the print image formation process may be unnecessarily reduced.

[0007] The object of the present invention is to provide an image forming apparatus and an image adjustment method that can suppress the unnecessary execution of detection image forming processes and improve productivity in print image forming processes. [Means for solving the problem]

[0008] An image forming apparatus according to one aspect of the present invention comprises a first image processing unit, a second image processing unit, and an adjustment processing unit. The first image processing unit performs a print image forming process based on image data to be printed, in which an image forming unit forms a print image in a predetermined printing area on the transfer surface. The second image processing unit is capable of performing a detection image forming process during the inter-page period between the completion of the print image forming process corresponding to one page and the execution of the print image forming process corresponding to the next page, in which the image forming unit forms a detection image in the printing area on the transfer surface, which is used to adjust the image forming conditions in the image forming unit. The adjustment processing unit performs an adjustment process to adjust the image forming conditions in the image forming unit based on the detection result of the detection image by a detection unit that detects the image characteristics of the detection image formed by the second image processing unit. The second image processing unit restricts the execution of the detection image forming process if the amount of change in the image characteristics before and after the execution of the adjustment process performed in the past is less than a preset value.

[0009] Another aspect of the present invention relates to an image adjustment method in which one or more processors perform a first step, a second step, and a third step. The first step is to perform a print image forming process in which an image forming unit forms a print image in a predetermined printing area on a transfer object based on image data to be printed. The second step is to perform a detection image forming process in the image forming unit in the printing area on the transfer object during the inter-page period between the completion of the print image forming process corresponding to one page and the execution of the print image forming process corresponding to the next page. The third step is to perform an adjustment process in which the image forming unit adjusts the image forming conditions based on the detection result of the detection image by a detection unit that detects the image characteristics of the detection image formed in the second step. The second step restricts the execution of the detection image forming process if the amount of change in the image characteristics before and after the execution of the adjustment process performed in the past is less than a preset value. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an image forming apparatus and an image adjustment method that can suppress the unnecessary execution of detection image forming processes and improve productivity in print image forming processes. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a cross-sectional view showing the configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] Figure 2 is a block diagram showing the system configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 3] Figure 3 is a schematic diagram showing the configuration of the image forming section of an image forming apparatus according to an embodiment of the present invention. [Figure 4] Figure 4 is a schematic diagram showing the configuration of the intermediate transfer belt of an image forming apparatus according to an embodiment of the present invention. [Figure 5]Figure 5 is a flowchart showing an example of an adjustment control process performed in an image forming apparatus according to an embodiment of the present invention. [Figure 6] Figure 6 is a schematic diagram showing an example of a detection image formed on an intermediate transfer belt in an image forming apparatus according to an embodiment of the present invention. [Figure 7] Figure 7 is a schematic diagram showing an example of a detection image formed on an intermediate transfer belt in an image forming apparatus according to an embodiment of the present invention. [Modes for carrying out the invention]

[0012] The embodiments of the present invention will be described below with reference to the attached drawings. Note that the following embodiments are merely examples of the present invention and do not limit the technical scope of the present invention.

[0013] First, the configuration of the image forming apparatus 100 according to an embodiment of the present invention will be described with reference to Figures 1 and 2.

[0014] For the sake of explanation, the vertical direction is defined as the up-down direction D1 when the image forming apparatus 100 is in a usable installation state (as shown in Figure 1). The front-to-back direction D2 is defined with the left side of the image forming apparatus 100 shown in Figure 1 as the front. The left-to-right direction D3 is defined with the front of the image forming apparatus 100 in the aforementioned installation state as the reference point.

[0015] The image forming apparatus 100 is a multifunction device having multiple functions, including a scanning function for reading an image from a document, a printing function for forming an image based on the image data, a fax function, and a copying function. The present invention may also be applied to image forming apparatuses such as printers, fax machines, and copiers capable of forming images using an electrophotographic method.

[0016] 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 7. Further, a thermometer and a hygrometer (not shown) are provided inside or outside the image forming apparatus 100, and the control unit 7 can acquire the ambient temperature and ambient humidity inside and outside the image forming apparatus 100 from the thermometer and the hygrometer.

[0017] The ADF 1 conveys the document to be read by the scanning function. The ADF 1 includes a document setting unit, a plurality of conveyance rollers, a document presser, and a paper discharge unit.

[0018] The image reading unit 2 realizes the scanning function. The image reading unit 2 includes a document table, a light source, a plurality of mirrors, an optical lens, and a CCD (Charge Coupled Device).

[0019] The image forming unit 3 realizes the printing function. Specifically, the image forming unit 3 forms a color or monochrome image on a sheet supplied from the paper feeding unit 4 by an electrophotographic method based on the input image data.

[0020] The paper feeding unit 4 supplies a sheet to the image forming unit 3. The paper feeding unit 4 includes a paper feed cassette, a manual feed tray, and a plurality of conveyance rollers. Further, the paper feeding unit 4 includes a duplex printing mechanism 4A that reverses the front and back surfaces of the sheet after the image is formed by the image forming unit 3 and re-conveys it to the image forming unit 3. Thereby, in the image forming apparatus 100, a duplex printing operation of forming images on the front and back surfaces of the sheet by the image forming unit 3 can be executed.

[0021] The operation display unit 5 is a user interface of the image forming apparatus 100. The operation display unit 5 includes a display unit such as a liquid crystal display that displays various information according to a control instruction from the control unit 7, and an operation unit such as an operation key or a touch panel that inputs various information to the control unit 7 according to a user's operation.

[0022] The storage unit 6 is a non-volatile storage device. For example, the storage unit 6 is a non-volatile memory such as flash memory. The storage unit 6 may also be an SSD (Solid State Drive) or an HDD (Hard Disk Drive).

[0023] The control unit 7 comprehensively controls the image forming apparatus 100. As shown in Figure 2, the control unit 7 comprises a CPU 11, a ROM 12, and a RAM 13. The CPU 11 includes one or more processors that execute various arithmetic processes. The ROM 12 is a non-volatile memory device in which information such as control programs for causing the CPU 11 to execute various processes is pre-stored. The RAM 13 is a volatile or non-volatile memory device used as temporary storage memory (work area) for various processes executed by the CPU 11. The CPU 11 comprehensively controls the image forming apparatus 100 by executing various control programs pre-stored in the ROM 12. The control unit 7 also has a clock function for measuring the current date and time.

[0024] Furthermore, the control unit 7 may be a separate control unit from the main control unit that comprehensively controls the image forming apparatus 100. Also, the control unit 7 may be composed of electronic circuits such as an integrated circuit (ASIC).

[0025] [Configuration of the image forming unit 3] Next, the configuration of the image forming unit 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, an intermediate transfer belt 26, and a secondary transfer roller 27. Figure 4 is a schematic diagram showing the configuration of the photoreceptor drum 31, intermediate transfer belt 26, drive roller 26A, and secondary transfer roller 27 of the image forming unit 24.

[0026] As shown in Figure 1, the image forming unit 3 comprises 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 output tray 29. The image forming unit 3 forms a toner image on the intermediate transfer belt 26 based on the input image data, and transfers the toner image from the intermediate transfer belt 26 to the sheet. Furthermore, as shown in Figures 2 and 3, the image forming unit 3 comprises four first power supplies 40, two second power supplies 45, and a detection unit 46.

[0027] The four image forming units 20 include image forming units 21 to 24. Image forming unit 21 (see Figure 3) forms a yellow (Y) toner image. Image forming unit 22 (see Figure 3) forms a cyan (C) toner image. Image forming unit 23 (see Figure 3) forms a magenta (M) toner image. Image forming unit 24 (see Figure 3) forms a black (K) toner image.

[0028] As shown in Figure 3, each image forming unit 20 includes a photoreceptor drum 31, a charging roller 32, a developing device 33, a primary transfer roller 34, a drum cleaning unit 35, and a detection unit 46. Each image forming unit 20 also includes a toner container 36 as shown in Figure 1.

[0029] An electrostatic latent image is formed on the surface of the photoreceptor drum 31. For example, the photoreceptor drum 31 has a photosensitive layer formed of amorphous silicon. The photoreceptor drum 31 receives rotational driving force supplied from a motor (not shown) and rotates in the drum rotation direction D4 shown in Figure 3. In this way, the photoreceptor drum 31 transports the electrostatic latent image formed on its surface.

[0030] The charging roller 32 charges the surface of the photoreceptor drum 31 when a preset charging voltage is applied. For example, the charging roller 32 charges the surface of the photoreceptor drum 31 in a positive polarity. The surface of the photoreceptor drum 31, which has been 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 photoreceptor drum 31.

[0031] The developing device 33 develops the electrostatic latent image formed on the surface of the photoreceptor drum 31. The developing device 33 comprises a pair of stirring members, a magnetic roller, and a developing roller. The pair of stirring members stir the developer containing toner and carrier housed inside the developing device 33. For example, the toner contained in the developer becomes positively charged by friction with the carrier contained in the developer. The magnetic roller pumps 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 magnetic roller to a position opposite the photoreceptor drum 31. The developing roller also receives a preset developing bias voltage and supplies the toner transported to the opposite position to the photoreceptor drum 31. As a result, toner is selectively supplied to the exposure area on the photoreceptor drum 31 that has been irradiated with light emitted from the light scanning device 25, and the electrostatic latent image formed on the surface of the photoreceptor drum 31 is developed. Furthermore, toner is supplied to the developing device 33 from the toner container 36.

[0032] The primary transfer roller 34 receives a preset primary transfer current and transfers the toner image formed on the surface of the photoreceptor drum 31 to the outer surface of the intermediate transfer belt 26. As shown in Figure 3, the primary transfer roller 34 is positioned opposite the photoreceptor drum 31, with the intermediate transfer belt 26 in between. The intermediate transfer belt 26 is an example of the material to be transferred according to the present invention.

[0033] The drum cleaning unit 35 removes toner remaining on the surface of the photoreceptor drum 31 after the toner image has been transferred by the primary transfer roller 34.

[0034] 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.

[0035] The intermediate transfer belt 26 is an endless belt member onto which the toner image formed on the surface of each photoreceptor drum 31 of the image forming unit 20 is transferred. For example, the intermediate transfer belt 26 is made of a resin material such as polyimide. The intermediate transfer belt 26 is stretched at a predetermined tension by a drive roller 26A (see Figure 3) and a tension roller 26B (see Figure 3). The intermediate transfer belt 26 rotates in the belt rotation direction D5 shown in Figure 3, as the drive roller 26A rotates in response to rotational driving force supplied from a motor (not shown). As a result, the intermediate transfer belt 26 transports the toner image transferred from each photoreceptor drum 31 to the transfer position to the sheet by the secondary transfer roller 27. After the toner image has been transferred by the secondary transfer roller 27, the outer surface of the intermediate transfer belt 26 is cleaned by a belt cleaning unit 26C (see Figure 3).

[0036] The secondary transfer roller 27 receives a preset secondary transfer current and transfers the toner image transferred to the outer surface of the intermediate transfer belt 26 to the sheet supplied from the paper feeding unit 4. As shown in Figure 3, the secondary transfer roller 27 is positioned opposite the drive roller 26A, with the intermediate transfer belt 26 in between.

[0037] As shown in Figure 4, the axial length (left-right direction D3) of the secondary transfer roller 27 is shorter than the widthwise length (left-right direction D3) of the intermediate transfer belt 26. Therefore, a non-image-forming region A2 (see Figure 4) is created on the outer surface of the intermediate transfer belt 26 that does not come into contact with the secondary transfer roller 27. The non-image-forming region A2 is the region outside the printing region A1 (see Figure 4) on the outer surface of the intermediate transfer belt 26, and includes the widthwise end of the intermediate transfer belt 26.

[0038] The fuser unit 28 fixes the toner image transferred to the sheet by the secondary transfer roller 27 to the sheet. Specifically, the fuser unit 28 includes a fuser roller positioned opposite the secondary transfer roller 27 and a heating heater for heating the fuser roller. In the fuser unit 28, the heating heater heats the fuser roller to a predetermined temperature, causing the toner image on the intermediate transfer belt 26 to melt and fix to the sheet as it passes between the fuser roller and the intermediate transfer belt 26. The sheet with the toner image fixed by the fuser unit 28 is then discharged into the output tray 29.

[0039] Of the four first power supplies 40, the first power supply 41 (see Figure 2) is a constant current power supply that supplies the primary transfer current to the primary transfer roller 34 of the image forming unit 21. Of the four first power supplies 40, the first power supply 42 (see Figure 2) is a constant current power supply that supplies the primary transfer current to the primary transfer roller 34 of the image forming unit 22. Of the four first power supplies 40, the first power supply 43 (see Figure 2) is a constant current power supply that supplies the primary transfer current to the primary transfer roller 34 of the image forming unit 23. Of the four first power supplies 40, the first power supply 44 (see Figure 2) is a constant current power supply that supplies the primary transfer current to the primary transfer roller 34 of the image forming unit 24. Each of the first power supplies 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 polarity current.

[0040] 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 polarity current.

[0041] The detection unit 46 includes a plurality of density sensors 461 to 463 used to detect image characteristics such as density and position of the detection image X10 formed on the intermediate transfer belt 26, which will be described later. As shown in Figure 3, each of the density sensors 461 to 463 is positioned downstream of the photoreceptor drum 31 of the image forming unit 24 in the belt rotation direction D5, and upstream of the toner image transfer position by the secondary transfer roller 27 in the belt rotation direction D5. Alternatively, each of the density sensors 461 to 463 may be positioned downstream of the toner image transfer position by the secondary transfer roller 27 in the belt rotation direction D5, and upstream of the cleaning position of the outer circumferential surface of the intermediate transfer belt 26 by the belt cleaning unit 26C.

[0042] As shown in Figure 4, the density sensor 461 is an example of the first detection unit according to the present invention and is provided at a position on the outer circumferential surface of the intermediate transfer belt 26 facing the printing area A1. In particular, in this embodiment, the density sensor 461 is provided at a position facing the center of the printing area A1 in the left-right direction D3. Furthermore, the density sensors 462 and 463 are examples of the second detection unit according to the present invention and are provided at positions on the outer circumferential surface of the intermediate transfer belt 26 facing the non-image forming areas A2 at both ends.

[0043] Each of the density sensors 461 to 463 is a reflective type photosensor comprising a light-emitting unit that emits light toward the intermediate transfer belt 26 and a light-receiving unit that receives the light emitted from the light-emitting unit and reflected by the intermediate transfer belt 26. Here, the amount of reflected light detected by the light-receiving unit of density sensors 461 to 463 changes depending on the density of the toner image formed at the position of the intermediate transfer belt 26 irradiated by the light-emitting unit. Each of the density sensors 461 to 463 then inputs an electrical signal to the control unit 7 corresponding to the amount of reflected light according to the density of the toner image to be detected. As a result, the control unit 7 can detect the density of the toner image based on the electrical signals input from density sensors 461 to 463.

[0044] In this embodiment, one density sensor 461 is provided at a position corresponding to the center of the printing area A1. However, the density sensor 461 may also be provided at a position opposite to another specific position within the printing area A1, such as between the center and the edge of the printing area A1. Furthermore, density sensors 461 may be provided at multiple positions in the left-right direction D3 within the printing area A1. In this embodiment, two density sensors 462 and 463 are provided as the second detection unit according to the present invention. However, only one of the density sensors 462 or 463 may be provided.

[0045] [Configuration of Control Unit 7] Next, the configuration of the control unit 7 will be described with reference to Figure 2.

[0046] As shown in Figure 2, the control unit 7 includes a first image processing unit 51, a second image processing unit 52, a detection processing unit 53, a counting processing unit 54, and an adjustment processing unit 55. Specifically, the ROM 12 of the control unit 7 is pre-stored with image forming programs that cause the CPU 11 to function as each of the above-mentioned processing units. The CPU 11 then functions as each of the above-mentioned processing units by executing the image forming programs stored in the ROM 12.

[0047] The image forming 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 storage unit 6. In addition, some or all of the first image processing unit 51, the second image processing unit 52, the detection processing unit 53, the counting processing unit 54, and the adjustment processing unit 55 may be composed of electronic circuits such as integrated circuits (ASICs).

[0048] The first image processing unit 51 performs a print image formation process in which the image forming unit 3 forms a print image based on the image data to be printed included in the print job to be executed in a predetermined print area A1 (see Figure 4) on the intermediate transfer belt 26. Hereinafter, the period during which the print image formation process in which a print image based on the image data is formed on the intermediate transfer belt 26 is performed may be referred to as the print period T0 (see Figures 6 and 7).

[0049] Specifically, the first image processing unit 51 controls the optical scanning device 25 based on the image data and forms electrostatic latent images corresponding to each color on the photoreceptor drum 31 of each image forming unit 20 at preset timings. Then, in each image forming unit 20, the electrostatic latent images formed on the photoreceptor drum 31 are developed as toner images, and these toner images are sequentially transferred to the intermediate transfer belt 26. After that, 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.

[0050] Furthermore, in the print image forming process, the first image processing unit 51 controls the amount of laser light irradiated by the optical scanning device 25 based on a preset input / output characteristic (gamma characteristic) and the image data. In addition, in the print image forming process, the first image processing unit 51 controls the development bias voltage in each image forming unit 20 to a preset value for each image forming unit 20. Moreover, in the print image forming process, the first image processing unit 51 also controls the charging voltage, the primary transfer current, and the secondary transfer current of the secondary transfer roller 27 in each image forming unit 20.

[0051] Furthermore, the first image processing unit 51 executes pre-configured inter-paper processing during the inter-paper period T1 (see Figures 6 and 7) between the print image formation process, which forms a print image on the intermediate transfer belt 26 based on image data for one page, and the print image formation process, which forms a print image on the intermediate transfer belt 26 based on image data for the next page. The first image processing unit 51 sets whether or not to execute inter-paper processing in the print job and the length of the inter-paper period T1 based on one or more image data included in the print job to be executed.

[0052] For example, in the image forming unit 3, when printing is performed continuously on small-sized sheets, a temperature difference occurs between the contact and non-contact portions of the fixing roller with respect to the sheet. Therefore, when printing is performed continuously on a preset small-sized sheet, the first image processing unit 51 may perform a waiting process as the inter-paper processing to equalize the temperature difference. Specifically, the first image processing unit 51 sets the waiting time according to preset conditions such as the number of small-sized sheets to be printed continuously or the size of the sheets. Therefore, the inter-paper period T1, including the waiting time, may change depending on the situation.

[0053] Furthermore, in the inter-paper processing, if a preset first condition is met, the heating element in the fixing device 28 may be controlled to adjust the temperature of the fixing roller. For example, the first condition is that a preset first number of print image forming processes are performed consecutively. In addition, in the inter-paper processing, if a preset second condition is met, the drum cleaning unit 35 may perform cleaning of the photoreceptor drum 31, etc. For example, the second condition is that a preset second number of print image forming processes are performed. In addition, in the inter-paper processing, various image processing operations may be performed on the image data corresponding to the next page in the print image forming process. Therefore, the inter-paper period T1 may change depending on whether or not such temperature adjustment of the fixing roller or cleaning of the photoreceptor drum 31 is performed.

[0054] Furthermore, the first image processing unit 51 changes the inter-paper interval T1 depending on whether or not the detection image forming process described later is performed by the second image processing unit, or the content of said detection image forming process. Therefore, when the detection image forming process is performed, the inter-paper interval T1 may be longer than when the detection image forming process is not performed.

[0055] The second image processing unit 52 executes the detection image formation process when the pre-set execution conditions are met. The second image processing unit 52 also has a limiting function that restricts the execution of the detection image formation process if the amount of change in the image characteristics before and after the execution of one or more adjustment processes described below that have been executed in the past is less than a pre-set specified value.

[0056] In particular, the second image processing unit 52 switches the operation mode of the detection image forming process to either the first mode or the second mode according to a preset switching condition and executes the detection image forming process. For example, the switching condition includes executing the detection image forming process in the first mode when an abnormality is detected in the density sensors 462 and 463. The switching condition may also include selecting a preset first mode or second mode by user operation.

[0057] In the detection image forming process, the detection image X10, used to adjust the image forming conditions in the image forming unit 3, is formed by the image forming unit 3 in the printing area A1 or the non-image forming area A2 (see Figure 4) on the intermediate transfer belt 26. The printing area A1 is the area on the outer surface of the intermediate transfer belt 26 where an image can be formed in the printing image forming process, and the non-image forming area A2 is the area on the outer surface of the intermediate transfer belt 26 outside of the printing area A1 (see Figure 4). For example, the printing area A1 is the contact area on the outer surface of the intermediate transfer belt 26 with the largest size sheet usable by the image forming apparatus 100. The printing area A1 may also be the area inside the area where the intermediate transfer belt 26 and the secondary transfer roller 27 are in contact. The non-image forming area A2 is any area where the detection image X10 does not adhere to the sheet in the printing image forming process.

[0058] Specifically, the second image processing unit 52 can execute the detection image formation process in multiple operating modes, including the first mode and the second mode. In the detection image formation process of the first mode, the detection image X10 is formed by the image forming unit 3 in the non-image forming area A2 of the intermediate transfer belt 26 while the print image formation process is being executed. In the detection image formation process of the second mode, the detection image X10 is formed in at least the print area A1 of the intermediate transfer belt 26 during the inter-page period T1 from the completion of the print image formation process corresponding to one page until the print image formation process corresponding to the next page is executed.

[0059] For example, the second image processing unit 52 forms a detection image X10 on the intermediate transfer belt 26, which includes detection images corresponding to multiple colors corresponding to multiple image forming units 20, based on preset detection image data corresponding to each color. For example, the detection image X10 corresponding to each color includes multiple rectangular or linear images formed at mutually different preset densities or positions.

[0060] Furthermore, in this embodiment, the execution condition is that the cumulative number of printed sheets in the image forming apparatus 100 reaches a predetermined first reference number. For example, the first reference number may be 100 sheets or 200 sheets. The execution condition may also be that the number of printed sheets during the execution of a single print job reaches a predetermined second reference number. Alternatively, the execution condition may be that a predetermined specific period of time has elapsed.

[0061] In the image forming apparatus 100, a detection image X10 is formed in the printing area A1 (see Figure 4) on the intermediate transfer belt 26, and the toner that forms the detection image X10 may adhere to the secondary transfer roller 27. Therefore, a cleaning unit is provided to remove the toner that adheres to the secondary transfer roller 27, but this is not shown or explained here.

[0062] The detection processing unit 53 uses the detection unit 46 to detect the density and position of the detection image X10 formed in the printing area A1 and the non-image forming area A2 of the intermediate transfer belt 26. The detection processing unit 53 may detect only one of the density or position of the detection image X10. For example, if only a density correction process is performed in the adjustment process described later, it is sufficient to detect the density of the detection image X10, and if only a positional misalignment correction process is performed in the adjustment process described later, it is sufficient to detect the position of the detection image X10.

[0063] Furthermore, the detection processing unit 53 can detect whether or not there is an abnormality in the density sensors 462 and 463. Specifically, the detection processing unit 53 determines that there is an abnormality in the density sensor 462 or 463 if the detected value of the toner image density by the density sensor 462 or 463 is less than a preset lower limit when no toner image is formed in the non-image-forming region A2 of the intermediate transfer belt 26. Also, the detection processing unit 53 determines that there is an abnormality in the density sensor 462 or 463 if the detected value of the toner image density by the density sensor 462 or 463 is greater than a preset upper limit when a toner image is formed in the non-image-forming region A2 of the intermediate transfer belt 26. For example, the detection processing unit 53 detects whether or not there is an abnormality in the density sensors 462 and 463 at a preset timing, such as before the execution of the print image forming process or before the execution of the detection image forming process. Alternatively, the detection processing unit 53 may determine whether or not there is an abnormality in the density sensors 462 or 463 during the execution of the detection image forming process.

[0064] The counting unit 54 performs a counting process to count the cumulative number of printed pages in the image forming apparatus 100. The cumulative number of printed pages counted by the counting process is used to determine the timing for performing the adjustment process by the adjustment unit 55. For example, the counting unit 54 resets the count value to 0 each time the adjustment process is performed in the image forming apparatus 100. The counting unit 54 may also count the cumulative number of printed pages for each printing type, such as color and monochrome.

[0065] The adjustment processing unit 55 performs an adjustment process to adjust the image formation conditions based on the detection results, such as the density and position of the detection image X10, obtained by the detection processing unit 53. This adjustment process is a so-called calibration process that includes density correction and position shift correction.

[0066] In the density correction process, if the difference between the density of the detection 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 this difference. Also, in the density correction process, if the difference between the density of the detection image X10 detected by the detection processing unit 53 and the reference density is greater than or equal to the threshold, the development bias voltage is adjusted as the image formation condition based on this difference. For example, the reference density is the density of the detection image X10 that was detected when the image formation condition was adjusted immediately before. Note that the image formation condition adjusted in the density correction process is not limited to the amount of light emitted by the optical scanning device 25 and the development bias voltage. For example, the image formation condition may include the input / output characteristics, the charging voltage, the primary transfer current, and the secondary transfer current.

[0067] In the positional shift correction process, the image formation timing by the image forming unit 20 of each color (the timing of light irradiation by the optical scanning device 25) is adjusted based on the difference between the detection position of the detection image X10 detected by the detection processing unit 53 and a predetermined specific position.

[0068] Incidentally, when the detection image forming process is performed in the second mode, it may be necessary to lengthen the inter-paper interval T1 in accordance with the time required for the detection image forming process. Therefore, in order to improve the productivity (printing efficiency) of the image forming apparatus 100, it is desirable to perform the detection image forming process in the first mode. However, if there is a malfunction or other abnormality in the density sensors 462 and 463 (first detection unit) used in the first mode, the effect of improving image quality through the adjustment process may not be obtained. In contrast, the image forming apparatus 100 according to this embodiment makes it possible to achieve a good balance between the effect of improving image quality through the adjustment process that adjusts the image forming conditions and improving productivity in the print image forming process, depending on the situation.

[0069] Furthermore, if the detection image formation process is executed in the second mode even when there is little need to adjust the image formation conditions, the productivity of the print image formation process may be unnecessarily reduced. In contrast, the image forming apparatus 100 according to this embodiment can suppress the unnecessary execution of the detection image formation process and improve the productivity of the print image formation process.

[0070] [Adjustment and control processing] The control unit 7 performs adjustment control processing each time the print image formation process based on the image data for one page to be printed is started for the print job to be executed. Here, with reference to Figure 5, an example of the procedure of the adjustment control processing performed by the control unit 7 in the image forming apparatus 100 will be described. Steps S10, S11, etc. represent the processing procedure (step) numbers performed by the control unit 7.

[0071] <Step S10> In step S10, the second image processing unit 52 of the control unit 7 determines whether the execution condition has been met. If it is determined that the execution condition has been met (S10:Yes), the process proceeds to step S11; if the execution condition has not been met (S10:No), the adjustment control process ends. The second image processing unit 52 also determines that the execution condition has been met if the detection counter N, described later, is 1 or greater.

[0072] <Step S11> In step S11, the second image processing unit 52 of the control unit 7 determines whether or not an abnormality has occurred in at least one of the density sensors 462 and 463 based on the detection result by the detection processing unit 53. If it is determined that an abnormality has occurred in at least one of the density sensors 462 and 463 (S11: Yes), the process moves to step S13. If it is determined that no abnormality has occurred in the density sensors 462 and 463 (S11: No), the process moves to step S111. As a result, the second image processing unit 52 switches between the first mode and the second mode and executes the detection image formation process based on whether or not an abnormality has occurred in the density sensors 462 and 463. That is, the second image processing unit 52 switches between the first mode and the second mode based on the detection result of the detection processing unit 53 regarding the presence or absence of an abnormality in the density sensors 462 and 463 and the switching condition.

[0073] The presence or absence of abnormalities in the density sensors 462 and 463 is detected by the detection processing unit 53 at a predetermined timing, such as before the execution of the print image forming process or before the execution of the detection image forming process. The detection processing unit 53 may also determine the presence or absence of abnormalities in the density sensors 462 and 463 during the execution of the detection image forming process. In this case, the second image processing unit 52 may switch the operation mode of the detection image forming process from the second mode to the first mode during the execution of the detection image forming process.

[0074] Furthermore, even if the second image processing unit 52 determines in step S11 that an abnormality has occurred in at least one of the density sensors 462 and 463, it may restrict the execution of the detection image forming process in the second mode if the preset conditions are met. Specifically, the control unit 7 sets whether or not to enable the alternative adjustment function that executes the detection image forming process in the second mode instead of the first mode when it determines that an abnormality has occurred in at least one of the density sensors 462 and 463, in response to the initial setup of the image forming apparatus 100 or a user operation of the operation display unit 5 which is performed at any time. Then, if the second image processing unit 52 determines in step S11 that an abnormality has occurred in at least one of the density sensors 462 and 463 and the alternative adjustment function is set to be enabled, it executes the detection image forming process in the second mode (S14). On the other hand, if the second image processing unit 52 determines in step S11 that an abnormality has occurred in at least one of the density sensors 462 and 463, but the alternative adjustment function is set to be disabled, it will terminate the adjustment control process without proceeding to step S12.

[0075] <Step S111> In step S111, the second image processing unit 52 of the control unit 7 controls the image forming unit 3 and executes the detection image forming process in the first mode while the first image processing unit 51 is executing the print image forming process.

[0076] Specifically, as shown in Figure 6, when the detection image formation process is performed in the first mode, during the printing period T0, the detection image X10 based on the detection image data is formed in the non-image formation regions A2 at both ends of the intermediate transfer belt 26. In this case, as shown in Figure 6, no detection image X10 is formed on the intermediate transfer belt 26 during the inter-page period T1 between each page. The two detection images X10 formed in the non-image formation regions A2 at both ends may be the same image or different images.

[0077] Thus, in step S111, the detection image forming process is executed in the first mode, in which the detection image X10 is formed in the non-image forming area A2 during the printing period T0. This suppresses a decrease in productivity in the printing image forming process.

[0078] <Step S12> In step S12, the second image processing unit 52 of the control unit 7 determines whether a pre-set restriction invalidation condition is met. The restriction invalidation condition is pre-set as a determination indicator for disabling the restriction function that restricts the execution of the detection image formation process in the second mode in step S13, which will be described later. If it is determined that the restriction invalidation condition is met (S12: Yes), the process proceeds to step S14; if it is determined that the restriction invalidation condition is not met (S12: No), the process proceeds to step S13. In other words, even if the restriction conditions described later are met, the second image processing unit 52 does not restrict the execution of the detection image formation process if the restriction invalidation condition is met.

[0079] Specifically, in step S18 described later, as a result of the adjustment process, the date and time the adjustment process was executed, the ambient temperature and humidity of the image forming apparatus 100 at the time the adjustment process was executed, etc., are stored in the storage unit 6. The restriction invalidation condition includes the fact that the difference between the ambient temperature or humidity at the time the adjustment process was most recently executed by the second image processing unit 52 and the current ambient temperature or humidity is greater than or equal to a predetermined value. That is, the restriction invalidation condition includes the fact that the ambient temperature or humidity of the image forming apparatus 100 has changed by a predetermined value or more since the adjustment process was executed by the adjustment processing unit 55. The restriction invalidation condition may also include the fact that the difference between the execution date and time recorded when the adjustment process was most recently executed by the second image processing unit 52 and the current date and time is greater than or equal to a predetermined period. That is, the restriction invalidation condition may also include the fact that the predetermined period has elapsed since the time the adjustment process was most recently executed by the second image processing unit 52 (the execution date and time). As a result, even if the limitations described later are met, if the operating environment of the image forming apparatus 100 changes, the execution of the detection image forming process in the second mode is not restricted, and the image quality is improved by executing the detection image forming process.

[0080] <Step S13> In step S13, the second image processing unit 52 of the control unit 7 determines whether or not a preset limiting condition is met. The limiting condition is preset as a determination indicator for restricting the execution of the detection image formation process in the second mode. If it is determined that the limiting condition is met (S13: Yes), the adjustment control process ends, and if it is determined that the restriction invalidation condition is not met (S13: No), the process moves to step S14. That is, if the second image processing unit 52 determines that the limiting condition is met, it restricts the execution of the detection image formation process which is executed in step S14 described below.

[0081] Here, the limiting condition is a condition set to determine that the amount of change in the image characteristics before and after the execution of the adjustment process performed in the past is small, and that the effect of the adjustment process is small. Specifically, in step S18 described later, as a result of each adjustment process, the image characteristics, which are the detection results of the detection image before and after the execution of the adjustment process, are stored in the storage unit 6. The limiting condition includes the fact that the amount of change between the image characteristics detected by the detection unit 46 for use in adjusting the image formation conditions in the previous (most recent) adjustment process and the image characteristics detected by the detection unit 46 after the execution of the adjustment process is less than a predetermined value. For example, the second image processing unit 52 determines that the limiting condition is satisfied when the difference in density detected from the detection image corresponding to the same density before and after the execution of the adjustment process is less than the predetermined value, and restricts the execution of the detection image formation process. Furthermore, the second image processing unit 52 may restrict the execution of the detection image forming process for all colors if the amount of change in the detection result of the detection image X10 before and after the execution of the adjustment process for at least one of the multiple colors is less than the predetermined value. On the other hand, the second image processing unit 52 may restrict the execution of the detection image forming process for all colors if the amount of change in the detection result of the detection image X10 before and after the execution of the adjustment process for all of the multiple colors is less than the predetermined value. In addition, the restriction condition may be that an index value such as the average value of the amount of change before and after multiple executions of the adjustment process is less than the predetermined value.

[0082] Furthermore, if the amount of change in the image formation conditions before and after the adjustment process performed in the past is small, the effect of the adjustment process will be small. Therefore, the limiting condition may include the fact that the amount of change in the image formation conditions before and after the execution of one or more of the adjustment processes performed in the past is less than a predetermined value. For example, the limiting condition may be that, when the development bias voltage is changed by the adjustment process, the difference in the development bias voltage before and after the change is less than a predetermined value.

[0083] Furthermore, whether the restriction invalidation condition in step S12 and the restriction condition in step S13 are satisfied is determined for each color of the detection image formed by the detection image forming process, and whether or not the execution of the detection image forming process in the second mode is necessary is determined for each color. That is, among the detection image forming processes corresponding to multiple colors performed by the second image processing unit 52, only the execution of the detection image forming process corresponding to the color whose change amount is less than the predetermined value may be restricted, while the detection image forming processes corresponding to other colors may be executed without restriction.

[0084] Furthermore, in this embodiment, the execution of the detection image forming process performed in the second mode is restricted, but in other embodiments, if the restriction conditions are met, the execution of the detection image forming process in the second mode may also be restricted. This suppresses the execution of unnecessary detection image forming processes and reduces toner consumption caused by such processes.

[0085] <Step S14> In step S14, the second image processing unit 52 of the control unit 7 controls the image forming unit 3 and executes the detection image forming process in the second mode when the print image forming process is executed by the first image processing unit 51.

[0086] Specifically, in step S14, the second image processing unit 52 waits to begin processing until the start of the inter-page period T1, which occurs between the completion of the print image forming process for one page and the execution of the print image forming process for the next page. When the start of the inter-page period T1 arrives, the second image processing unit 52 starts the detection image forming process. Subsequently, as shown in Figure 7, when the detection image forming process is executed in the second mode, the detection image X10 based on the detection image data is formed only in the print area A1 of the intermediate transfer belt 26 during the inter-page period T1 between each page. In this case, the detection image X10 is not formed in the non-image forming area A2 during the print period T0.

[0087] Thus, in step S14, the detection image formation process is executed in the second mode, in which the detection image X10 is formed only in the printing area A1 during the inter-paper period T1. As a result, in step S18, described later, the adjustment process is executed based on the detection image formed in the printing area A1 used in the printing image formation process, making it possible to enhance the effect of improving image quality in the printing image formation process. Furthermore, as mentioned above, even if an abnormality occurs in the density sensors 462 and 463, the detection image formation process is executed, making it possible to obtain the effect of improving image quality.

[0088] <Step S15> In step S15, the detection processing unit 53 of the control unit 7 uses the detection unit 46 to detect the density and position of the detection image X10 formed on the intermediate transfer belt 26 in step S111 or step S14, and stores them in the storage unit 6. The detection results, such as the density and position of the detection image X10, are used in the image formation condition adjustment process in step S17, which will be described later.

[0089] Specifically, if the detection image formation process is performed in the first mode in step S111, the density and position of the detection images X10 formed in two locations in the non-image formation areas A2 at both ends are detected by density sensors 462 and 463. Also, if the detection image formation process is performed in the second mode in step S14, the density and position of the detection image X10 formed in the central area of ​​the print area A1 are detected by density sensor 461.

[0090] <Step S16> In step S16, the second image processing unit 52 of the control unit 7 determines whether the detection image formation process corresponding to all colors has been completed. If it is determined that the detection image formation process corresponding to all colors has been completed (S16: Yes), the process moves to step S17. If it is determined that the detection image formation process corresponding to all colors has not been completed (S16: No), the adjustment control process ends.

[0091] Specifically, the second image processing unit 52 increments the detection counter N stored in the RAM of the control unit 7 by 1 each time the detection image forming process corresponding to one color is executed in step S111 or S14. The second image processing unit 52 also resets the detection counter N to 0 when the adjustment process is executed in step S17, which will be described later. The initial value of the detection counter N is 0. Then, in step S16, the second image processing unit 52 determines that the detection image forming process corresponding to all colors has been completed when the detection counter N is 4.

[0092] Furthermore, when the second image processing unit 52 executes the detection image forming process in step S111 or S14, if the detection counter N is 0, it executes the detection image forming process corresponding to the preset Y (yellow). Similarly, when the second image processing unit 52 executes the detection image forming process in step S111 or S14, if the detection counter N is 1, 2, or 3, it executes the detection image forming process corresponding to the preset C (cyan), M (magenta), and K (black), respectively. As a result, in steps S111 and S14, the second image processing unit 52 sequentially executes the detection image forming processes corresponding to all colors.

[0093] Furthermore, if the second image processing unit 52 is operating in the first mode when executing the detection image formation process corresponding to the first color, it is conceivable that the subsequent detection image formation processes corresponding to the three colors will also be executed in the first mode. Similarly, if the second image processing unit 52 is operating in the second mode when executing the detection image formation process corresponding to the first color, it is conceivable that the subsequent detection image formation processes corresponding to the three colors will also be executed in the second mode.

[0094] <Step S17> In step S17, the adjustment processing unit 55 of the control unit 7 performs an adjustment process to adjust the image formation conditions in the image formation unit 3 based on the detection result of the detection image X10 by the detection unit 46. As a result, the print image formation process performed after the execution of step S17 reflects the adjustment of the image formation conditions by the adjustment process in step S17. Also in step S17, the second image processing unit 52 of the control unit 7 resets the cumulative number of printed sheets to 0 and the detection counter N to 0 to determine whether the execution conditions are met.

[0095] Specifically, if the detection image formation process is performed in step S111 using the first mode, the adjustment process is performed based on the density and position of the detection images X10 formed in two locations in the non-image formation regions A2 at both ends. For example, if the detection image formation process is performed using the first mode, the adjustment processing unit 55 may adjust the image formation conditions based on the average value of the density and position of the detection images X10 formed in the two locations. Also, if the detection image formation process is performed in step S14 using the second mode, the adjustment process is performed based on the density and position of the detection image X10 formed in the central region of the print region A1.

[0096] In this embodiment, the adjustment process is described using the case where it is performed in step S17 as an example, but the adjustment process may be performed at any time after the detection of the density and position of each detection image X10 in step S15. For example, part or all of the adjustment process may be performed between step S15 and step S16. After the detection image X10 is detected in step S15, the adjustment process based on the detection result of the detection image X10 may be performed as the inter-paper processing during the inter-paper period T1. Furthermore, after the detection image X10 is detected in step S15, the adjustment process based on the detection result of the detection image X10 in the adjustment control process performed in the past may be performed at the start of the print image forming process.

[0097] Furthermore, after the execution of the adjustment process, the adjustment processing unit 55 causes the second image processing unit 52 to execute the detection image formation process and executes a post-adjustment acquisition process to acquire the image characteristics of the detection image after the adjustment process. If the image characteristics of the detection image used in the adjustment process were detected in the detection image formation process executed in the first mode, the adjustment processing unit 55 causes the detection image formation process to be executed in the first mode in the post-adjustment acquisition process as well. Similarly, if the image characteristics of the detection image used in the adjustment process were detected in the detection image formation process executed in the second mode, the adjustment processing unit 55 causes the detection image formation process to be executed in the second mode in the post-adjustment acquisition process as well. The timing of the execution of the post-adjustment acquisition process may be immediately after the execution of the adjustment process, but it may also be any predetermined timing after the execution of the adjustment process. For example, if the image characteristics of the detection image used in the adjustment process were detected in the detection image formation process executed in the first mode, the post-adjustment acquisition process may be executed together with the print image formation process, which is the first process executed after the adjustment process is performed. Furthermore, if the image characteristics of the detection image used in the adjustment process are those detected in the detection image forming process performed in the second mode, the post-adjustment acquisition process may be performed together with the inter-paper processing that is first performed after the adjustment process.

[0098] <Step S18> Subsequently, in step S18, the adjustment processing unit 55 performs result storage processing to store the results of the adjustment processing performed in step S17 in the storage unit 6. Specifically, the results of the adjustment processing include the date and time the adjustment processing was performed, the ambient temperature and humidity of the image forming apparatus 100 when the adjustment processing was performed, and the image characteristics, which are the detection results of the detection images before and after each adjustment processing. As a result, for example, the second image processing unit 52 can determine in step S12 whether the restriction invalidation condition and the restriction condition are satisfied based on the results of past adjustment processing stored in the storage unit 6.

[0099] As described above, the image forming apparatus 100 according to this embodiment switches between a first mode in which the detection image forming process is executed during the printing period T0 and a second mode in which the detection image forming process is executed during the inter-paper period T1. Therefore, an image forming apparatus and an image adjustment method are provided that can achieve a good balance between the effect of improving image quality through the adjustment process and improving productivity in the printing image forming process, depending on the situation.

[0100] In particular, in the image forming apparatus 100, when the limiting conditions are met, the execution of the detection image forming process is restricted, thereby suppressing unnecessary execution of the detection image forming process and improving productivity in the print image forming process. Furthermore, because unnecessary execution of the detection image forming process is suppressed, the amount of toner consumed by the detection image forming process is also reduced.

[0101] Furthermore, in this embodiment, the case in which a detection image X10 is formed in the printed area A1 during the detection image formation process in the second mode has been described. On the other hand, in other embodiments, the second image processing unit 52 may form a detection image X10 in both the non-image forming area A2 corresponding to one of the non-image forming areas A2 at both ends that does not have an abnormality, and in the printed area A1, during the detection image formation process in the second mode.

[0102] Furthermore, in this embodiment, the case in which the detection image X10 is formed in the center of the printing area A1 during the detection image formation process in the second mode has been described. On the other hand, in other embodiments, the detection image X10 may be formed in multiple areas of the printing area A1 that are located at different positions in the width direction during the detection image formation process in the second mode. For example, in other embodiments, during the detection image formation process in the second mode, detection images X10 may be formed in two areas of the printing area A1 that are located at different positions in the width direction, similar to the two detection images X10 formed in the non-image formation areas A2 at both ends.

[0103] Furthermore, the adjustment processing unit 55 may adjust the image formation conditions in the image formation unit 3 for each sheet size on which the printed image is formed by the image formation unit 3. In particular, for sheets where the length corresponding to the width direction of the printing area A1 (sheet width) is less than or equal to a predetermined specific width, the adjustment processing unit 55 may adjust the image formation conditions based only on the detection result of the detection image X10 formed in the printing area A1 from among the detection results of the detection image X10 in the detection image formation process executed in the second mode. For example, if the size of the sheet to be printed is a postcard, the adjustment processing unit 55 adjusts the image formation conditions in the image formation unit 3 based on the detection result of the detection image X10 formed in the non-image formation area A2 in the detection image formation process executed in the past. That is, for sheets with a width less than or equal to the specific width, the adjustment processing unit 55 may not reflect the detection result of the detection image X10 formed in the non-image formation area A2 in the adjustment of the image formation conditions. On the other hand, for sheets with a width wider than the specified width, the adjustment processing unit 55 may reflect the detection results of the detection image X10 formed in both the printing area A1 and the non-image forming area A2 in the adjustment of the image forming conditions. This makes it possible to enhance the effect of improving the image quality of the printed image in the print image forming process according to the width of the sheet.

[0104] [Notes on the invention] The following is an overview of the invention extracted from the above-described embodiments. Note that each configuration and processing function described below can be selected and combined as desired.

[0105] <Note 1> A first image processing unit performs a print image formation process in which an image forming unit forms a print image in a predetermined print area on the transfer object based on image data to be printed, A second image processing unit is provided that, during the inter-page period between the completion of the print image forming process corresponding to one page and the execution of the print image forming process corresponding to the next page, the image forming unit is capable of performing a detection image forming process in which a detection image used for adjusting the image forming conditions in the image forming unit is formed in the print area of ​​the transfer object. An adjustment processing unit that performs an adjustment process to adjust the image formation conditions in the image formation unit based on the detection result of the detection image by the detection unit that detects the image characteristics of the detection image formed by the second image processing unit, Equipped with, The second image processing unit restricts the execution of the detection image forming process if the amount of change in the image characteristics before and after the execution of the adjustment process performed in the past is less than a predetermined value. Image forming apparatus.

[0106] <Note 2> Even if the amount of change is less than the specified value, the second image processing unit will not restrict the execution of the detection image forming process if the pre-set restriction invalidation condition is met. The image forming apparatus described in Appendix 1.

[0107] <Note 3> The conditions for invalidating the restriction include the change in the ambient temperature or ambient humidity of the image forming apparatus after the adjustment process has been performed by the adjustment processing unit, which is greater than or equal to a preset value. The image forming apparatus described in Appendix 2.

[0108] <Note 4> The conditions for invalidating the restriction include the fact that a predetermined period has elapsed since the adjustment process was performed by the adjustment processing unit. An image forming apparatus as described in Appendix 2 or 3.

[0109] <Note 5> The second image processing unit restricts the execution of the detection image forming process corresponding to the color whose change amount is less than the specified value among the detection image forming processes corresponding to multiple colors performed by the second image processing unit. An image forming apparatus as described in any of the appendices 1 to 4.

[0110] <Note 6> One or more processors The first step is to perform a print image forming process in which an image forming unit forms a print image in a predetermined printing area on the transfer object based on the image data to be printed, A second step in which, during the inter-page period between the completion of the print image forming process corresponding to one page and the execution of the print image forming process corresponding to the next page, a detection image forming process is performed in which a detection image used for adjusting the image forming conditions in the image forming unit is formed in the print area of ​​the transfer object by the image forming unit, A third step involves performing an adjustment process to adjust the image formation conditions in the image formation unit based on the detection result of the detection unit, which detects the image characteristics of the detection image formed in the second step, An image adjustment method that performs the following: The second step restricts the execution of the detection image forming process if the amount of change in the image characteristics before and after the execution of the adjustment process performed in the past is less than a predetermined value. Image adjustment methods. [Explanation of symbols]

[0111] 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 Photoconductor Drum 32 Electrostatic Rollers 33 Developing equipment 34 Primary Transfer Roller 35 Drum Cleaning Department 36 Toner Containers 40 1st power supply 45 2nd power supply 46 Detection unit 461 Concentration sensor (first detection unit) 462 Concentration sensor (second detection unit) 463 Concentration sensor (second detection unit) 100 Image forming apparatus

Claims

1. A first image processing unit performs a print image formation process that forms a print image in a predetermined print area on the transfer object based on image data to be printed, A second image processing unit is provided that, during the inter-page period between the completion of the print image forming process corresponding to one page and the execution of the print image forming process corresponding to the next page, the image forming unit is capable of performing a detection image forming process in which a detection image used for adjusting the image forming conditions in the image forming unit is formed in the print area of ​​the transfer object. An adjustment processing unit that performs an adjustment process to adjust the image formation conditions in the image formation unit based on the detection result of the detection image by the detection unit that detects the image characteristics of the detection image formed by the second image processing unit, Equipped with, The second image processing unit restricts the execution of the detection image forming process if the amount of change in the image characteristics before and after the execution of the adjustment process performed in the past is less than a predetermined value. Image forming apparatus.

2. Even if the amount of change is less than the specified value, the second image processing unit will not restrict the execution of the detection image forming process if the pre-set restriction invalidation condition is met. The image forming apparatus according to claim 1.

3. The conditions for invalidating the restriction include the change in the ambient temperature or ambient humidity of the image forming apparatus after the adjustment process has been performed by the adjustment processing unit, which is greater than or equal to a preset value. The image forming apparatus according to claim 2.

4. The conditions for invalidating the restriction include the fact that a predetermined period has elapsed since the adjustment process was performed by the adjustment processing unit. The image forming apparatus according to claim 2.

5. The second image processing unit restricts the execution of the detection image forming process corresponding to the color whose change amount is less than the predetermined value among the detection image forming processes corresponding to multiple colors performed by the second image processing unit. An image forming apparatus according to any one of claims 1 to 4.

6. One or more processors A first step is to perform a print image forming process in which an image forming unit forms a print image in a predetermined printing area on the transfer object based on the image data to be printed, A second step in which, during the inter-page period between the completion of the print image forming process corresponding to one page and the execution of the print image forming process corresponding to the next page, a detection image forming process is performed in which a detection image used for adjusting the image forming conditions in the image forming unit is formed in the print area of ​​the transfer object by the image forming unit, A third step involves performing an adjustment process to adjust the image formation conditions in the image formation unit based on the detection result of the detection unit, which detects the image characteristics of the detection image formed in the second step, An image adjustment method that performs the following: The second step restricts the execution of the detection image forming process if the amount of change in the image characteristics before and after the execution of the adjustment process performed in the past is less than a predetermined value. Image adjustment methods.

Images