Image forming apparatus and image forming method

Abstract

To provide an image forming apparatus and image forming method that can achieve a good balance between the effect of improving image quality through calibration processing and improving productivity in print image forming processing, depending on the situation. [Solution] The image forming apparatus (100) comprises an image forming unit (3), a first image processing unit (51), and a second image processing unit (52). The second image processing unit (52) executes a detection image forming process in which the image forming unit (3) forms a detection image on the transfer target (26) that is used to adjust the image forming conditions in the image forming unit (3) when the preset execution conditions are met. The second image processing unit (52) then switches between a first mode in which the detection image forming process is executed during the execution of the print image forming process, and a second mode in which the detection image forming process is executed 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.

Description

Technical Field

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

Background Art

[0002] An electrophotographic image forming apparatus includes an image forming unit that forms an image on a sheet based on input image data. In the image forming apparatus, a print image forming process for forming a print image based on the image data on a transfer body such as an intermediate transfer belt is executed by the image forming unit. Further, in the image forming apparatus, a calibration process may be executed in which a preset detection image is formed on the transfer body, and the image forming conditions in the image forming unit are adjusted based on the detection result of the detection image (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the calibration process, during the execution of the print image forming process, a detection image may be formed in an end region of the transfer body. However, in this case, the adjustment of the image forming conditions is performed using the detection image formed in the end region of the transfer body. Therefore, there is a possibility that the effect of improving the image quality by adjusting the image forming conditions is reduced compared to the case where the detection image is detected in a print target region that is inside the end region of the transfer body and is used in the print image forming process.

[0005] On the other hand, in the calibration process, a detection image may be formed on the transfer target using the inter-page time 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. However, in this case, the inter-page time becomes longer, which may reduce productivity (printing speed) compared to when the detection image forming process is executed during the execution of the print image forming process.

[0006] The object of the present invention is to provide an image forming apparatus and an image forming method that can achieve a good balance between the effect of improving image quality through calibration processing and improving productivity in print image forming processing, depending on the situation. [Means for solving the problem]

[0007] An image forming apparatus according to one aspect of the present invention comprises an image forming unit, a first image processing unit, and a second image processing unit. The image forming unit forms an image on a transfer surface based on input image data and transfers the image from the transfer surface to a sheet. The first image processing unit performs a print image forming process in which the image forming unit forms a print image in a predetermined print area on the transfer surface based on the image data to be printed. The second image processing unit performs a detection image forming process in which the image forming unit forms a detection image on the transfer surface when preset execution conditions are met, which is used to adjust the image forming conditions in the image forming unit. The second image processing unit can switch between a first mode in which the detection image forming process is performed during the execution of the print image forming process, and a second mode in which the detection image forming process is performed 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.

[0008] An image forming method according to another aspect of the present invention is a method executed by a processor of an image forming apparatus, which includes an image forming unit that forms an image on a transfer surface based on input image data and transfers the image from the transfer surface to a sheet, and comprises a first step and a second step. The first step is to execute a print image forming process in which the image forming unit forms a print image in a predetermined print area on the transfer surface based on image data to be printed. The second step is to execute a detection image forming process in which the image forming unit forms a detection image on the transfer surface used to adjust the image forming conditions in the image forming unit when a preset execution condition is met. The second step is to execute by switching between a first mode in which the detection image forming process is executed during the execution of the print image forming process, and a second mode in which the detection image forming process is executed during the inter-page period from the completion of the print image forming process corresponding to one page until the execution of the print image forming process corresponding to the next page. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an image forming apparatus and an image forming method that can achieve a good balance between the effect of improving image quality through calibration processing and improving productivity in the printing image forming process, depending on the situation. [Brief explanation of the drawing]

[0010] [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]

[0011] 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.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] As shown in Figures 1 and 2, the image forming apparatus 100 comprises 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.

[0016] ADF1 conveys the document to be read by the scanning function. ADF1 includes a document set portion, a plurality of conveyance rollers, a document holder, and a paper discharge portion.

[0017] 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).

[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 supplied from the paper supply unit 4 by an electrophotographic method based on the input image data.

[0019] The paper supply unit 4 supplies sheets to the image forming unit 3. The paper supply unit 4 includes a paper supply cassette, a manual feed tray, and a plurality of conveyance rollers. Further, the paper supply unit 4 includes a duplex printing mechanism 4A that reverses the front and back surfaces of the sheet after the image is formed in 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.

[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 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.

[0021] The storage unit 6 is a non-volatile storage device. For example, the storage unit 6 is a non-volatile memory such as a flash memory. Note that the storage unit 6 may be an SSD (Solid State Drive) or an HDD (Hard Disk Drive).

[0022] 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 perform various arithmetic operations. The ROM 12 is a non-volatile memory device in which information such as control programs for causing the CPU 11 to perform various operations is pre-stored. The RAM 13 is a volatile or non-volatile memory device used as a temporary storage memory (work area) for the various operations performed 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.

[0023] 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).

[0024] [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.

[0025] 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. Furthermore, as shown in Figures 2 and 3, the image forming unit 3 comprises four first power supplies 40, a second power supply 45, and a plurality of detection units 46. The image forming unit 3 then 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.

[0026] 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.

[0027] 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, and a drum cleaning unit 35. Each image forming unit 20 also includes a toner container 36 as shown in Figure 1.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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).

[0035] 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.

[0036] As shown in Figure 4, the axial length (left-right direction D3) of the secondary transfer roller 27 is smaller than the widthwise length (left-right direction D3) of the intermediate transfer belt 26. Therefore, a non-contact region A3 (see Figure 4) is created on the outer circumferential surface of the intermediate transfer belt 26 that does not come into contact with the secondary transfer roller 27. The non-contact region A3 is the area on the outer circumferential surface of the intermediate transfer belt 26 that is outside the contact region A2 (see Figure 4) that comes into contact with the secondary transfer roller 27, and includes the end of the intermediate transfer belt 26 in the widthwise direction.

[0037] 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.

[0038] 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.

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

[0040] As shown in Figure 4, the image forming unit 3 is provided with three detection units 46. Specifically, the detection units 46 are provided at positions opposite to the non-contact areas A3 (see Figure 4) at both ends of the outer circumferential surface of the intermediate transfer belt 26. In addition, the detection units 46 are also provided at positions opposite to the printing area A1 (see Figure 4), which is a predetermined specific position on the outer circumferential surface of the intermediate transfer belt 26. In particular, in this embodiment, the detection unit 46 opposite to the printing area A1 is provided at a position opposite to the center of the printing area A1.

[0041] As shown in Figure 3, each of the detection units 46 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 detection units 46 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] Each detection unit 46 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. Each detection unit 46 inputs an electrical signal to the control unit 7 according to the density of the toner image to be detected.

[0043] The three detection units 46 then detect image characteristics such as density and position of the toner image transferred to the printing area A1 or the non-contact area A3. Specifically, in this embodiment, the three detection units 46 are used to detect image characteristics such as density and position of the detection image X10, which will be described later, formed in the printing area A1 or the non-contact area A3.

[0044] In this embodiment, one detection unit 46 is provided in the printing area A1 at a position corresponding to the center of the printing area A1. However, the detection unit 46 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, multiple detection units 46 may be provided at positions in the left-right direction D3 within the printing area A1.

[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 (first step) 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 printing period T0.

[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] The second image processing unit 52 executes the detection image formation process (second step) when the pre-set execution conditions are met. In particular, the second image processing unit 52 switches between the first mode and the second mode, described later, according to the pre-set conditions, and executes the detection image formation process.

[0055] In the detection image forming process described above, the image forming unit 3 forms a detection image X10, which is used to adjust the image forming conditions in the image forming unit 3, in the printing area A1, contact area A2, or non-contact area A3 (see Figure 4) on the intermediate transfer belt 26. The printing area A1 is the area inside the contact area A2 (see Figure 4) on the outer surface of the intermediate transfer belt 26, and the non-contact area A3 is the area outside the contact area A2 (see Figure 4) on the outer surface of the intermediate transfer belt 26. For example, the printing area A1 is the contact area with the largest size sheet usable by the image forming apparatus 100 on the outer surface of the intermediate transfer belt 26. The printing area A1 and the contact area A2 may be the same area.

[0056] Specifically, 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 pre-set 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 pre-set densities or positions.

[0057] 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 time has elapsed.

[0058] In this embodiment, as will be described later, a detection image X10 may be formed in the printing area A1 (see Figure 4) of the intermediate transfer belt 26. Therefore, a cleaning unit is also provided to remove the detection image X10 that adheres to the secondary transfer roller 27, but this is not shown or described here.

[0059] The detection processing unit 53 uses each of the detection units 46 to detect the density and position of the detection image X10 formed in the printing area A1 and the non-contact area A3 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] Incidentally, in the calibration process, a detection image may be formed in the edge region of the intermediate transfer belt 26 while the print image forming process is being executed. However, in this case, the image forming conditions are adjusted using the detection image formed in the edge region of the intermediate transfer belt 26. Therefore, the effect of improving image quality by adjusting the image forming conditions may be reduced compared to when the detection image is detected in the print target area used in the print image forming process, which is inside the edge region of the intermediate transfer belt 26. On the other hand, in the calibration process, a detection image may be formed on the intermediate transfer belt 26 using the inter-page period from the completion of the print image forming process corresponding to one page to the execution of the print image forming process corresponding to the next page. However, in this case, since the inter-page period is longer, productivity (printing speed) may decrease compared to when the detection image forming process is executed while the print image forming process is being executed. In contrast to this, as will be explained below, the image forming apparatus 100 according to this embodiment makes it possible to achieve both the effect of improving image quality through the calibration process and the improvement of productivity in the print image forming process, depending on the situation.

[0065] [Adjustment and control processing] The control unit 7 executes an adjustment control process each time the print image forming process based on the image data for one page to be printed included in the print job to be executed is started. Here, with reference to Figure 5, an example of the procedure of the adjustment control process executed by the control unit 7 in the image forming apparatus 100 will be described. Steps S10, S11, etc. represent the processing procedure (step) numbers executed by the control unit 7.

[0066] <Step S10> In step S10, the second image processing unit 52 of the control unit 7 determines whether the execution conditions have been met. If it is determined that the execution conditions have been met (S10:Yes), the process proceeds to step S11; if the execution conditions have not been met (S10:No), the adjustment control process ends.

[0067] <Step S11> In step S11, the second image processing unit 52 of the control unit 7 determines whether or not the detection image forming process can be executed during the inter-paper interval T1 set by the first image processing unit 51. Then, based on whether or not the detection image forming process can be executed, the second image processing unit 52 switches between the first mode and the second mode, as described later, and executes the process.

[0068] Specifically, the second image processing unit 52 determines that the detection image forming process can be executed during the inter-paper period T1 if the inter-paper period T1 is longer than a specific time set in advance as the time during which the detection image forming process corresponding to at least one color can be executed. If it is determined that the detection image forming process can be executed during the inter-paper period T1 (S11:Yes), the process proceeds to step S12, and if it is determined that the detection image forming process cannot be executed during the inter-paper period T1 (S11:No), the process proceeds to step S111.

[0069] In other embodiments, the second image processing unit 52 may switch between the first mode and the second mode depending on whether detection image forming processing corresponding to all colors can be performed during one or more inter-page periods T1 in a single job in which the print image forming processing for multiple pages is performed. Furthermore, in other embodiments, the second image processing unit 52 may switch between the first mode and the second mode in step S11 according to a preset user selection result. In other embodiments, the second image processing unit 52 may switch between the first mode and the second mode in step S11 according to the size of the sheet used in the print image forming processing.

[0070] <Step S111> In step S111, the second image processing unit 52 of the control unit 7 determines the number of colors in the detection image X10 formed in the non-contact area A3 during the detection image formation process executed in the first mode described later, according to the length of the sub-scanning direction (belt rotation direction D5) of each page. For example, for an A4 landscape page, a detection image X10 corresponding to one color is formed in the non-contact area A3, and for an A4 portrait page, where the length of the belt rotation direction D5 is longer than that of an A4 landscape page, a detection image X10 corresponding to two colors is formed in the non-contact area A3.

[0071] <Step S112> In step S112, 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 a preset first mode while the first image processing unit 51 is executing the print image forming process.

[0072] 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-contact areas A3 at both ends of the intermediate transfer belt 26. In this case, as shown in Figure 6, the detection image X10 is not 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-contact areas A3 at both ends are the same image. Furthermore, in the detection image formation process performed in the first mode, when the print image formation process for each page is performed, the detection images of the number of colors determined in step S111 are formed during the printing period T0 in which each page is printed.

[0073] Thus, in step S112, the detection image forming process is executed in the first mode, in which the detection image X10 is formed in the non-contact area A3 during the printing period T0. This suppresses a decrease in productivity in the printing image forming process.

[0074] <Step S12> In step S12, the second image processing unit 52 of the control unit 7 determines the number of colors (hereinafter referred to as "target color number") of the detection image X10 formed in the contact area A2 and the non-contact area A3 during the inter-paper period T1 in the detection image forming process executed in the second mode described later, according to the length of the inter-paper period T1.

[0075] For example, the second image processing unit 52 determines the number of target colors to be one if the inter-paper period T1 is longer than the time required to perform the detection image formation process for one color, but shorter than the time required to perform the detection image formation process for two colors. Similarly, the second image processing unit 52 determines the number of target colors to be two if the inter-paper period T1 is longer than the time required to perform the detection image formation process for two colors, but shorter than the time required to perform the detection image formation process for three colors. Furthermore, the second image processing unit 52 determines the number of target colors to be three if the inter-paper period T1 is longer than the time required to perform the detection image formation process for four colors.

[0076] <Step S13> In step S13, 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 a preset second mode when the print image forming process is executed by the first image processing unit 51.

[0077] Specifically, in step S13, the second image processing unit 52 waits to begin processing until the start of the inter-page period, which occurs between the completion of the print image formation process for one page and the execution of the print image formation process for the next page. When the start of the inter-page period arrives, the second image processing unit 52 starts the detection image formation process. In particular, in step S13, the second image processing unit 52 executes the detection image formation process corresponding to the number of colors corresponding to the number of target colors determined in step S12. As shown in Figure 7, when the detection image formation process is executed in the second mode, during the inter-page period T1 between each page, a detection image X10 based on the detection image data is formed in three locations on the intermediate transfer belt 26: the contact area A2 and the non-contact areas A3 at both ends. The three detection images X10 formed in the contact area A2 and the non-contact areas A3 at both ends are the same image. In this case, during the printing period T0, no detection image X10 is formed in the non-contact areas A3.

[0078] Thus, in step S13, the detection image forming process is executed in the second mode, in which a detection image X10 is formed in at least the print area A1 during the inter-paper period T1. As a result, the detection image forming process is executed using the inter-paper period T1 which is provided for other reasons, thus suppressing a decrease in productivity in the print image forming process.

[0079] <Step S14> In step S14, the detection processing unit 53 of the control unit 7 uses the detection unit 46 to detect the density and position of the detection image X10 formed on the intermediate transfer belt 26 in step S112 or step S13, 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 S16, which will be described later.

[0080] Specifically, if the detection image formation process is performed in the first mode in step S112, the density and position of the detection image X10 formed in two locations in the non-contact areas A3 at both ends are detected. If the detection image formation process is performed in the second mode in step S13, the density and position of the detection image X10 formed in a total of three locations: the central area of ​​the printed area A1 and the non-contact areas A3 at both ends are detected.

[0081] <Step S15> In step S15, 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 (S15: Yes), the process moves to step S16. If it is determined that the detection image formation process corresponding to all colors has not been completed (S15: No), the adjustment control process ends.

[0082] 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 S112 or S13. The second image processing unit 52 also resets the detection counter N to 0 when the adjustment process is executed in step S16, which will be described later. The initial value of the detection counter N is 0. Then, in step S15, 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.

[0083] Furthermore, when the second image processing unit 52 executes the detection image forming process in step S112 or S13, 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 S112 or S13, if the detection counter N is 1, 2, or 3, it executes the detection image forming process corresponding to the preset C (cyan), M (yellow), and K (black), respectively. As a result, in steps S112 and S13, the second image processing unit 52 sequentially executes the detection image forming processes corresponding to all colors.

[0084] 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.

[0085] <Step S16> In step S16, the adjustment processing unit 55 of the control unit 7 executes the adjustment process based on the detection result of the detection image X10 by the detection unit 46. As a result, the print image forming process executed after the execution of step S16 reflects the adjustments made to the image forming conditions by the adjustment process in step S16. Also in step S16, 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.

[0086] Specifically, if the detection image formation process is performed in the first mode in step S112, the adjustment process is performed based on the density and position of the detection images X10 formed in two locations in the non-contact areas A3 at both ends. If the detection image formation process is performed in the second mode in step S13, the adjustment process is performed based on the density and position of the detection images X10 formed in a total of three locations: the central area of ​​the printing area A1 and the non-contact areas A3 at both ends. For example, the adjustment processing unit 55 adjusts the image formation conditions based on the average value of the density and position of the detection images X10 formed in two or three locations.

[0087] In this embodiment, the adjustment process is described using the case where it is performed in step S16 as an example, but the adjustment process may be performed at any time after the detection of the density and position of each of the detection images X10 in step S14. For example, part or all of the adjustment process may be performed between step S14 and step S15. After the detection images X10 are detected in step S14, the adjustment process based on the detection result of the detection images X10 may be performed as the inter-paper processing during the inter-paper period T1. Furthermore, after the detection images X10 are detected in step S14, the adjustment process based on the detection result of the detection images X10 in the adjustment control process performed in the past may be performed at the start of the print image forming process.

[0088] 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 image forming method are provided that can achieve a good balance between the effect of improving image quality through calibration processing and improving productivity in the printing image forming process, depending on the situation.

[0089] Furthermore, in this embodiment, the case in which the detection image X10 is formed in both the contact area A2 and the non-contact area A3 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 only needs to form the detection image X10 in the printed area A1 in at least the contact area A2 during the detection image formation process in the second mode. In particular, in other embodiments, the second image processing unit 52 may form the detection image X10 only in the printed area A1 during the detection image formation process in the second mode.

[0090] Furthermore, in this embodiment, the case in which the detection image X10 is formed in the center of 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 detection image X10 may be formed in multiple areas of the printed area A1 that are 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, the same detection image X10 as the two detection images X10 formed in the non-contact areas A3 at both ends may be formed in two areas of the printed area A1 that are at different positions in the width direction.

[0091] Furthermore, the adjustment processing unit 55 may adjust the image formation conditions in the image forming unit 3 for each sheet size on which the printed image is formed by the image forming 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 forming unit 3 based on the detection result of the detection image X10 formed in the non-contact area A3 in the detection image formation process executed in the past. That is, for sheets with a width less than or equal to the specified width, the adjustment processing unit 55 may not reflect the detection result of the detection image X10 formed in the non-contact area A3 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-contact area A3 in the adjustment of the image formation conditions. This makes it possible to enhance the effect of improving the image quality of the printed image in the printing image formation process according to the width of the sheet. [Explanation of Symbols]

[0092] 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 100 Image forming apparatus

Claims

1. An image forming unit that forms an image on a transfer target based on input image data and transfers the image from the transfer target to a sheet, A first image processing unit performs a print image forming 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 executes a detection image formation process in which, when pre-set execution conditions are met, the image forming unit forms a detection image on the object to be transferred, which is used to adjust the image formation conditions in the image forming unit. Equipped with, The second image processing unit can switch between a first mode in which it executes the detection image forming process during the execution of the print image forming process, and a second mode in which it executes the 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. Image forming apparatus.

2. The second image processing unit executes the detection image forming process in the second mode if it is possible to perform the detection image forming process during the inter-paper period, and executes the detection image forming process in the first mode if it is not possible to perform the detection image forming process during the inter-paper period. The image forming apparatus according to claim 1.

3. The second image processing unit is: When the detection image formation process is performed in the first mode, the detection image is formed in the area outside the printed area of ​​the transfer object. When the detection image formation process is performed in the second mode, the detection image is formed in at least the printed area of ​​the transfer object. The image forming apparatus according to claim 1.

4. When the second image processing unit performs the detection image formation process in the second mode, it forms the detection image in the printed area and the area outside the printed area of ​​the object to be transferred. The image forming apparatus according to claim 3.

5. The second image processing unit is: When the detection image formation process is performed in the first mode, the detection image is formed in the area outside the printed area of ​​the transfer object. When the detection image formation process is performed in the second mode, the detection image is formed only in the printed area of ​​the transfer object. The image forming apparatus according to claim 1.

6. The second image processing unit determines the number of colors in which the detection image is formed in the detection image formation process performed in the second mode during the inter-paper period, according to the length of the inter-paper period. An image forming apparatus according to any one of claims 1 to 5.

7. The system includes an adjustment processing unit that adjusts the image formation conditions in the image formation unit based on the detection result of the detection image formed by the second image processing unit, If the width of the sheet used in the print image forming process performed by the first image processing unit is less than or equal to a predetermined specific width, the adjustment processing unit adjusts the image forming conditions in the image forming unit based on the detection results of the detection image formed in the print area of ​​the transfer object in the second mode of the detection image forming process. An image forming apparatus according to any one of claims 1 to 5.

8. A processor in an image forming apparatus, which includes an image forming unit that forms an image on a transfer surface based on input image data and transfers the image from the transfer surface to a sheet, A first step is to perform a print image forming process in which the image forming unit forms a print image in a predetermined printing area on the transfer body based on the image data to be printed, A second step is to perform a detection image formation process in which, when pre-set execution conditions are met, the image forming unit forms a detection image on the object to be transferred, which is used to adjust the image formation conditions in the image forming unit. An image forming method that performs the following: The second step is performed by switching between a first mode in which the detection image forming process is executed while the print image forming process is being executed, and a second mode in which the detection image forming process is executed during the inter-page period from the completion of the print image forming process corresponding to one page until the print image forming process corresponding to the next page is executed. Image forming method.

Images