Image forming device

Abstract

To provide an image forming apparatus which always maintains a correction value of the geometric characteristics of images on front and back at an optimum level.SOLUTION: An image forming apparatus 101 comprises: a printer 107 which forms an image on a sheet on the basis of an image formation condition; an image reading unit 231 which reads an adjustment image of an image formation condition formed on the sheet by the printer 107; and a CPU 222 which adjusts the image formation condition with the first adjustment for adjusting the image formation condition on the basis of a reading result obtained by reading the adjustment image by the image reading unit 231 from a product in which the adjustment image is added to the image according to a printing job, and the second adjustment for adjusting the image formation condition on the basis of the reading result obtained by reading the adjustment image by the image reading unit 231 from an adjustment chart in which the adjustment image is formed on the sheet. The CPU 222 performs the second adjustment before execution of the present printing job when a prescribed time elapses from the previous adjustment of the image formation condition.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus such as a printer, a copying machine, a facsimile machine, or a multifunction machine. [Background technology]

[0002] Products produced by commercial printing machines require stable print position accuracy on the front and back sides of a sheet. To achieve this, image forming devices perform automatic adjustment (hereinafter referred to as "front and back automatic adjustment") to automatically stabilize the print position accuracy on the front and back sides of a sheet. With front and back automatic adjustment, correction values ​​for the print positions (image formation positions) on the front and back sides are set for each paper feed deck, for example. During printing, the image writing position is adjusted according to the correction value set for the paper feed deck that fed the sheet. The image writing position is adjusted, for example, by offsetting it by an amount according to the correction value. The print position is adjusted by adjusting the writing position.

[0003] Patent Document 1 discloses an image forming apparatus that aims to stabilize print position accuracy. To stabilize print position accuracy, this image forming apparatus creates an adjustment chart by printing an adjustment image on a sheet as a mark for the print position. The adjustment image on the adjustment chart is read by an image reading sensor provided in the sheet transport path. The image forming apparatus feeds back the results of reading the adjustment image to the image formation conditions, adjusting the print position, image tilt, and other image geometric characteristics. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-11285 Summary of the Invention [Problem to be solved by the invention]

[0005] The optimal correction values ​​for the geometric characteristics of the front and back images vary depending on environmental conditions, such as the temperature inside the image forming device during printing, and sheet conditions, such as moisture absorption by the sheet. Therefore, it is preferable to perform automatic front and back adjustment as needed. Therefore, the correction values ​​for the geometric characteristics of the front and back images are sequentially adjusted using adjustment images (registration marks) formed in the bleed area of ​​the output to adjust the geometric characteristics. However, if the environmental conditions of the image forming device or the sheet conditions change due to a time interval after the previous adjustment, the optimal correction values ​​for the geometric characteristics of the front and back images may change. In this case, the geometric characteristics of the front and back images in subsequent jobs may no longer be corrected using the optimal correction values.

[0006] Generally, a user can select whether to enable or disable the front-and-back automatic adjustment. When the front-and-back automatic adjustment is disabled, the front-and-back automatic adjustment is not performed during printing of a job, and the geometric characteristics are adjusted to a fixed value without updating the correction values. For example, if a job in which the front-and-back automatic adjustment is enabled is followed by a job in which the front-and-back automatic adjustment is disabled, the correction values ​​last set in the job in which the front-and-back automatic adjustment is enabled are used in the job in which the front-and-back automatic adjustment is disabled. The correction values ​​are not updated in the job in which the front-and-back automatic adjustment is disabled. After that, when printing is started for a job in which the front-and-back automatic adjustment is enabled, the environmental conditions of the image forming apparatus or the sheet conditions may have changed because a long time has passed since the last time the correction values ​​were updated. As a result, the geometric characteristics may not be adjusted optimally.

[0007] The present invention has been made in view of the above-mentioned problems, and has as its object to provide an image forming apparatus that always maintains optimal correction values ​​for the geometric characteristics of the front and back images. [Means for solving the problem]

[0008] The image forming apparatus of the present invention includes an image forming unit that forms an image on a sheet by transferring an image formed on an intermediate transfer member to the sheet based on image forming conditions for adjusting the position of the image on the sheet, a fixing unit that is arranged downstream of the image forming unit in the conveying direction of the sheet and has at least one pair of a heating unit and a pressure unit, and fixes the sheet on which the image has been formed by the image forming unit, a first reading unit that is arranged downstream of the fixing unit in the conveying direction and reads the first side of the sheet by irradiating light onto the first side of the sheet and receiving reflected light, and a second reading unit that reads the second side of the sheet. and a control means, wherein the control means causes the image forming means to form an image including an adjustment image on the first surface and the second surface of a sheet, causes the reading means to read the first surface and the second surface of the sheet on which the image including the adjustment image has been formed, and generates the image forming conditions based on the result of reading the adjustment image by the reading means, and the control means causes the control means to execute a first job to form the first adjustment image, and then executes a second job not to form the adjustment image, and 4th Job If it is determined that a predetermined time has elapsed between the time when the second job is completed and the time when the second job is completed, a second adjustment image is formed. Third Job The present invention is characterized in that the following is executed. [Effects of the Invention]

[0009] According to the present invention, it is possible to optimally adjust the correction values ​​for the geometric characteristics of the front and back images when printing. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating the configuration of an image processing system. [Figure 2] system configuration diagram. [Figure 3] FIG. 1 is a diagram illustrating the configuration of an image forming apparatus. [Figure 4] An explanatory diagram of CIS. [Figure 5](a) to (f) are explanatory diagrams of the setting screen. [Figure 6] FIG. 10 is a diagram illustrating an example of job information. [Figure 7] Example of front and back auto adjustment information [Figure 8] FIG. 10 is a diagram illustrating an adjustment chart. [Figure 9] 10A to 10C are explanatory diagrams for automatic front and back adjustment using an adjustment chart. [Figure 10] 10 is a flowchart showing an image forming process. [Figure 11] 10 is a flowchart showing the processing of S1201. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, the embodiments will be described in detail with reference to the drawings.

[0012] (Image Processing System) 1 is a configuration diagram of an image processing system including an image forming apparatus according to this embodiment. The image processing system includes an image forming apparatus 101 and an external controller 102. The image forming apparatus 101 is, for example, a multifunction peripheral (MFP), a multifunction peripheral (MFP), etc. The external controller 102 is, for example, an image processing controller, a digital front end (DFE), a print server, etc.

[0013] The image forming apparatus 101 and the external controller 102 are communicatively connected via an internal LAN (Local Area Network) 105 and a video cable 106. The external controller 102 is connected to a client PC (Personal Computer) 103 via an external LAN 104. The external controller 102 obtains a print instruction (print job) from the client PC 103.

[0014] A printer driver having a function of converting image data into a print description language that can be processed by the external controller 102 is installed in the client PC 103. A user can issue a printing instruction via the printer driver using various applications. The printer driver transmits image data to the external controller 102 based on a print job from the user. The external controller 102 accepts a print job including image data from the client PC 103, performs data analysis and rasterization processing, and instructs the image forming apparatus 101 to print (form an image) based on the image data.

[0015] The image forming apparatus 101 is configured by connecting devices with multiple different functions, including a printing device 107, and is capable of complex printing processes such as bookbinding. The image forming apparatus 101 of this embodiment includes the printing device 107 and a finisher 109. The printing device 107 forms an image on a sheet fed from a paper feed unit provided at the bottom of the main body using a developer (e.g., toner). The printing device 107 forms images in yellow (Y), magenta (M), cyan (C), and black (K). A full-color image in which images of each color are superimposed is formed on the sheet. The sheet on which the image has been formed is transported from the printing device 107 to the finisher 109. The finisher 109 stacks the sheets on which the image has been formed.

[0016] Although this image processing system is configured such that an external controller 102 is connected to an image forming apparatus 101, the external controller 102 is not necessarily required. For example, the image forming apparatus 101 may be configured to directly receive a print job including image data from a client PC 103 via an external LAN 104. In this case, the image forming apparatus 101 performs the data analysis and rasterization processes that are performed by the external controller 102. In other words, the image forming apparatus 101 and the external controller 102 may be configured as an integrated unit.

[0017] (System Configuration) 2 is a diagram showing the system configuration for controlling the operation of the image processing system. Here, the controllers that control the operation of the image forming apparatus 101, the external controller 102, and the client PC 103 will be described.

[0018] ·Printing device The printing device 107 includes a communication interface (I / F) 217, a LAN I / F 218, and a video I / F 220 for communicating with other devices. The printing device 107 includes a CPU (Central Processing Unit) 222, a memory 223, a storage 221, an image reading unit 231, and an image processing unit 232 for controlling the operation of the printing device 107. The printing device 107 includes an exposure unit 227, an image creating unit 228, a fixing unit 229, and a paper feed unit 230 for forming an image. The printing device 107 includes an operation unit 224 and a display 225 as user interfaces. The printing device 107 includes a timer 251 and a temperature sensor 252 for adjusting correction values ​​for optimally correcting the geometric characteristics of the image on the front and back sides. Here, the geometric characteristics of the image include, for example, squareness and the printing position of the image on the sheet. These components are connected to each other via a system bus 233 so that they can communicate with each other.

[0019] The communication I / F 217 is connected to the finisher 109 via a communication cable 249 and controls communication with the finisher 109. When the printing device 107 and the finisher 109 operate in cooperation with each other, information and data are sent and received via the communication I / F 217. The LAN I / F 218 is connected to the external controller 102 via the internal LAN 105 and controls communication with the external controller 102. The printing device 107 receives print settings from the external controller 102 via the LAN I / F 218. The video I / F 220 is connected to the external controller 102 via the video cable 106 and controls communication with the external controller 102. The printing device 107 receives image data representing an image to be formed from the external controller 102 via the video I / F 220.

[0020] The CPU 222 comprehensively controls image processing and printing by executing computer programs stored in the storage 221. The memory 223 provides a work area for the CPU 222 to execute various processes. When performing image formation processing, the CPU 222 controls an exposure unit 227, an image forming unit 228, a fixing unit 229, and a paper feed unit 230.

[0021] The exposure unit 227 includes a photoconductor, a charging wire that charges the photoconductor, and a light source that exposes the photoconductor charged by the charging wire to light to form an electrostatic latent image on the photoconductor. The photoconductor may be, for example, a photosensitive belt with a photosensitive layer formed on the surface of a belt-shaped elastic member, or a photosensitive drum with a photosensitive layer formed on the surface of a cylinder. A charging roller may also be used instead of the charging wire. The exposure unit 227 charges the surface of the photoconductor to a uniform negative potential using the charging wire. The exposure unit 227 outputs a laser beam from the light source based on image data. The laser beam scans the uniformly charged surface of the photoconductor. This changes the potential of the photoconductor at the position irradiated by the laser beam, forming an electrostatic latent image on the surface. Four photoconductors are provided, one for each of the four colors: yellow (Y), magenta (M), cyan (C), and black (K). Electrostatic latent images corresponding to different color images are formed on the four photoconductors.

[0022] The image forming unit 228 transfers the toner image formed on the photosensitive member onto a sheet. The image forming unit 228 is equipped with a developing unit, a transfer unit, and a toner supply unit. The developing unit forms a toner image by attaching negatively charged toner from a developing cylinder to the electrostatic latent image formed on the surface of the photosensitive member. Four developing units are provided, one for each of the four colors: yellow (Y), magenta (M), cyan (C), and black (K). The developing units visualize the electrostatic latent image on the photosensitive member using toner of the corresponding color.

[0023] The transfer unit has an intermediate transfer belt and transfers toner images from the photosensitive drums to the intermediate transfer belt. A primary transfer roller is provided facing the photosensitive drums across the intermediate transfer belt. When a positive potential is applied to the primary transfer roller, the toner images from each of the four photosensitive drums are transferred onto the intermediate transfer belt in a superimposed state. This forms a full-color toner image on the intermediate transfer belt. The toner image formed on the intermediate transfer belt is transferred to a sheet by a secondary transfer roller, which will be described later. When a positive potential is applied to the secondary transfer roller, the full-color toner image is transferred from the intermediate transfer belt to the sheet.

[0024] The fixing unit 229 fixes the transferred toner image onto the sheet. The fixing unit 229 has a heater and a pair of rollers. The fixing unit 229 melts and fixes the toner image on the sheet by heating and pressurizing the toner image on the sheet using the heater and the pair of rollers. This forms an image on the sheet. The paper feed unit 230 has a conveying roller and various sensors on the conveying path and controls the sheet feeding operation.

[0025] The image reading unit 231 reads an image formed on a sheet being conveyed based on an instruction from the CPU 222. For example, when adjusting image formation conditions, the CPU 222 uses the image reading unit 231 to read an image for adjusting the image formation conditions formed on the sheet. The operation unit 224 is an input device that accepts input of various settings and operation instructions from the user. The operation unit 224 is, for example, various input keys or a touch panel. The display 225 is an output device that displays setting information of the image forming apparatus 101 and the processing status (status information) of a print job.

[0026] The timer 251 counts the time. The CPU 222 obtains the current date and time from the count value of the timer 251. The temperature sensor 252 measures the internal temperature of the printing device 107. The CPU 222 obtains the internal temperature, which is one of the environmental conditions, from the measurement result of the temperature sensor 252. Note that humidity may also be obtained as an environmental condition in addition to temperature.

[0027] Finisher The finisher 109, for example, staples a product output from the printing device 107. The finisher 109 includes a communication I / F 241, a CPU 242, a memory 243, and a paper discharge control unit 244. These components are connected to each other via a system bus 245 so that they can communicate with each other. The communication I / F 241 is connected to the printing device 107 via a communication cable 249 and controls communication between the finisher 109 and the printing device 107. When the finisher 109 and the printing device 107 operate in cooperation with each other, information and data are sent and received via the communication I / F 241. The CPU 242 executes a control program stored in the memory 243 and performs various controls required for paper discharge. The memory 243 stores the control program. The memory 243 also provides a work area when the CPU 242 executes various processes. The paper discharge control unit 244 discharges the transported sheets based on instructions from the CPU 242.

[0028] External Controller The external controller 102 includes a LAN I / F 213, a LAN I / F 214, and a video I / F 215 for communicating with other devices. The external controller 102 includes a CPU 208, a memory 209, and a storage 210 for controlling the operation of the external controller 102. The external controller 102 includes a keyboard 211 and a display 212 as user interfaces. These components are connected to each other via a system bus 216 so that they can communicate with each other.

[0029] The LAN I / F 213 is connected to the client PC 103 via the external LAN 104 and controls communication with the client PC 103. The external controller 102 acquires a print job from the client PC 103 via the LAN I / F 213. The LAN I / F 214 is connected to the printing device 107 via the internal LAN 105 and controls communication with the printing device 107. The external controller 102 transmits print settings to the printing device 107 via the LAN I / F 214. The video I / F 215 is connected to the printing device 107 via the video cable 106 and controls communication with the printing device 107. The external controller 102 transmits image data to the printing device 107 via the video I / F 215.

[0030] The CPU 208 executes computer programs stored in the storage 210 to comprehensively perform processes such as receiving image data transmitted from the client PC 103, RIP processing, and transmitting image data to the image forming apparatus 101. The memory 209 provides a work area for the CPU 208 to execute various processes. The keyboard 211 is an input device that accepts various setting inputs and operation instructions from the user. The display 212 is an output device that displays information about applications executed by the external controller 102 as still images or moving images.

[0031] Client PC The client PC 103 includes a CPU 201, a memory 202, a storage 203, a keyboard 204, a display 205, and a LAN I / F 206. These components are connected via a system bus 207 so that they can communicate with each other.

[0032] The CPU 201 controls the operation of the client PC 103 by executing computer programs stored in the storage 203. In this embodiment, the CPU 201 creates image data and transmits print jobs. The memory 202 provides a work area for the CPU 201 to execute various processes. The keyboard 204 and display 205 are user interfaces. The keyboard 204 is an input device that accepts instructions from a user. The display 205 is an output device that displays information about applications executed by the client PC 103 as still images or moving images. The LAN I / F 206 is connected to the external controller 102 via the external LAN 104 and controls communication with the external controller 102. The client PC 103 transmits a print job including image data to the external controller 102 via the LAN I / F 206.

[0033] The external controller 102 and image forming apparatus 101 are connected via an internal LAN 105 and a video cable 106, but any other configuration is acceptable as long as they are capable of transmitting and receiving data necessary for printing, and for example, they may be connected via only a video cable.Memory 202, memory 209, memory 223, and memory 243 may each be a storage device for holding data and programs.These memories may be, for example, volatile random access memory (RAM), non-volatile read only memory (ROM), storage, or universal serial bus (USB) memory.

[0034] (Configuration of image forming device) 3 is a configuration diagram of the image forming apparatus 101. A display 225 is provided on top of the printing device 107. The display 225 displays information on the printing status and settings of the image forming apparatus 101. Sheets on which images have been formed by the printing device 107 are transported to a finisher 109 provided downstream.

[0035] The printing device 107 includes, as the paper feed unit 230, multiple paper feed decks 301 and 302 and a transport path 303. Each paper feed deck 301 and 302 can accommodate different types of sheets. The top sheet of each paper feed deck 301 and 302 is separated and fed to the transport path 303. The printing device 107 includes, as the exposure unit 227, image forming units 304, 305, 306, and 307 for forming images. The printing device 107 forms color images. To this end, the image forming unit 304 forms a black (K) image (toner image). The image forming unit 305 forms a cyan (C) image (toner image). The image forming unit 306 forms a magenta (M) image (toner image). The image forming unit 307 forms a yellow (Y) image (toner image).

[0036] The printing device 107 includes, as the image creation unit 228, an intermediate transfer belt 308 onto which toner images are transferred from the image forming units 304, 305, 306, and 307, and a secondary transfer roller 309. The intermediate transfer belt 308 rotates clockwise in the figure, and toner images are transferred and superimposed on each other from the image forming units 307, 306, 305, and 304 in this order. As a result, a full-color toner image is formed on the intermediate transfer belt 308. The intermediate transfer belt 308 conveys the toner image to the secondary transfer roller 309 as it rotates. A sheet is conveyed to the secondary transfer roller 309 in synchronization with the timing at which the toner image is conveyed to the secondary transfer roller 309. The secondary transfer roller 309 transfers the toner image on the intermediate transfer belt 308 onto the conveyed sheet.

[0037] The printing apparatus 107 includes a first fuser 311 and a second fuser 313 as the fuser unit 229. The first fuser 311 and the second fuser 313 have the same configuration and fuse a toner image onto a sheet. To this end, the first fuser 311 and the second fuser 313 each include a pressure roller and a heating roller. The sheet is heated and pressurized as it passes between the pressure roller and the heating roller, melting and bonding the toner image. After passing through the second fuser 313, the sheet is transported to a transport path 314. The second fuser 313 is located downstream of the first fuser 311 in the sheet transport direction and is used to add gloss to the image on the sheet that has been fused by the first fuser 311 and to ensure fixation. For this reason, the second fuser 313 may not be used depending on the type of sheet and the content of the image formation process. A conveying path 312 is provided to convey the sheet that has undergone the fixing process in the first fixing device 311 without passing through the second fixing device 313.

[0038] A conveying path 315 and a reversing path 316 are provided after the conveying path 314 and the conveying path 312 join together. When double-sided printing is instructed, the sheet is conveyed to the reversing path 316. The conveying direction of the sheet conveyed to the reversing path 316 is reversed by the reversing path 316, and the sheet is conveyed to the double-sided conveying path 317. The reversing path 316 and the double-sided conveying path 317 reverse the side on which the image has been formed (first side). The sheet is conveyed to the conveying path 303 by the double-sided conveying path 317, and passes through the secondary transfer roller 309 and the fixing unit 229, where an image is formed on the second side, which is different from the first side.

[0039] In the case of single-sided printing, or in the case of double-sided printing in which images are formed on both sides, the sheet is conveyed to a conveying path 315. A conveying path 323 is arranged downstream of the conveying path 315 in the sheet conveying direction. On the conveying path 323, CISs (Contact Image Sensors) 321 and 322 are arranged opposite each other across the conveying path 323 as the image reading unit 231. FIG. 4 is an explanatory diagram of the CISs 321 and 322. The CIS 321 is an optical sensor that reads an image of the upper surface of the sheet conveyed on the conveying path 323. The CIS 322 is an optical sensor that reads an image of the lower surface of the sheet conveyed on the conveying path 323.

[0040] The CIS 321 includes an LED (Light Emitting Diode) 350 as a light source, a reading sensor 351 as a light receiving unit, and a white reference plate 352. The LED 350 irradiates the upper surface of the sheet when the sheet conveyed along the conveyance path 323 reaches the reading position. The reading sensor 351 includes multiple light receiving elements (photoelectric conversion elements) in a direction perpendicular to the sheet conveyance direction. Therefore, the direction perpendicular to the sheet conveyance direction is the main scanning direction of the CIS 321. The reading sensor 351 receives light reflected by the sheet. The multiple light receiving elements of the reading sensor 351 output output values ​​(electrical signals) based on the intensity of the received reflected light. The output values ​​(electrical signals) output from the multiple light receiving elements are transmitted to the CPU 222. In this manner, the image formed on the sheet is read. The white reference plate 352 is a calibration member (reference member) used during shading correction of the CIS 321. During shading correction, the LED 350 and the reading sensor 351 move to positions where they can read the white reference plate 352. Alternatively, during shading correction, the white reference plate 352 moves to the reading position of the LED 350 and the reading sensor 351. Shading correction of the CIS 321 is performed based on the reading result of the white reference plate 352. Therefore, during shading correction, the CIS 321 cannot read an image formed on a sheet.

[0041] Like CIS 321, CIS 322 includes an LED 353, a reading sensor 354, and a white reference plate 355. CIS 322 operates in the same manner as CIS 321, and reads an image formed on the lower surface of a sheet when the sheet conveyed along conveyance path 323 reaches the reading position. Note that, in addition to CISs 321 and 322, image reading unit 231 can also be realized by a CCD or CMOS sensor.

[0042] The printing device 107 of this embodiment is capable of forming adjustment images for adjusting image formation conditions on both sides of a sheet. A sheet on which an adjustment image is formed is called an adjustment chart. The printing device 107 prints the adjustment image on a sheet to create an adjustment chart, and reads the adjustment image using CIS 321 and CIS 322. The images of the adjustment chart read by CIS 321 and CIS 322 are stored in memory 223. The CPU 222 refers to memory 223, analyzes the images read by CIS 321 and CIS 322, and feeds the results back to the image formation conditions to adjust the image formation conditions.

[0043] For example, when the temperature inside the printing device 107 rises, the geometric characteristics of the image formed on the sheet vary compared to when the temperature inside the printing device 107 is low. The printing device 107 creates an adjustment chart and detects the geometric characteristics based on the reading results of the CISs 321 and 322. The CPU 222 performs affine transformation on the image data so that the detected geometric characteristics become ideal geometric characteristics. The printing device 107 forms an image on the sheet based on the image data converted by the CPU 222, thereby controlling the geometric characteristics of the image formed on the sheet. This allows the printing device 107 to suppress variations in the geometric characteristics of the image caused by fluctuations in the temperature inside the device.

[0044] The adjustment image formed on the adjustment chart may be an image for detecting geometric characteristics, an image for detecting image density, or an image for detecting color misregistration. When an adjustment image for detecting image density is formed, the CPU 222 generates image formation conditions for suppressing fluctuations in image density based on the reading results of the CIS 321 (or CIS 322). The CPU 222 controls the intensity of the light source of the exposure unit 227 based on the image formation conditions, thereby adjusting the image density of the printing device 107 to an ideal image density. Alternatively, the CPU 222 generates a one-dimensional gradation correction table for suppressing fluctuations in image density based on the reading results of the CIS 321 (or CIS 322). The CPU 222 converts image data based on the gradation correction table. The printing device 107 forms an image on a sheet based on the image data converted by the CPU 222, thereby adjusting the image density of the printing device 107 to an ideal image density.

[0045] Furthermore, when an adjustment image for detecting color misregistration is formed, the CPU 222 detects the color misregistration based on the reading result of the CIS 321 (or CIS 322). Based on the detected color misregistration, the CPU 222 corrects the color misregistration by controlling the position of the image formed on the photosensitive member by the exposure unit 227.

[0046] The adjustment image may be printed as an adjustment chart on a sheet different from the user image, or may be printed on the same sheet as the user image. When printed as an adjustment chart, the CPU 222 creates image data from the received image data in which the adjustment chart is inserted between the user image on the Nth page and the user image on the N+1th page each time the number of prints reaches a predetermined number N. When the adjustment image is formed on the same sheet as the user image, it is preferable that the adjustment image be formed in the cutting area of ​​the sheet. This is because the adjustment image is removed from the deliverable when cutting processing is performed. Here, the user image is an image included in the image data transferred from the client PC 103.

[0047] The adjustment chart is removed so as not to be mixed in with the print job results. To this end, the printing apparatus 107 is equipped with a flapper 324, a discharge path 326, a transport sensor 327, and a discharge tray 328. The adjustment chart, whose image (adjustment image) has been read by the CISs 321 and 322, is transported to the discharge path 326 by the flapper 324. The sheet transported to the discharge path 326 is discharged to the discharge tray 328.

[0048] If the sheet is not an adjustment chart, the sheet is transported by a flapper 324 from a transport path 323 to a downstream transport path 325. The sheet transported to the downstream transport path 325 is delivered to the finisher 109. When the printing device 107 receives a notification of a transport jam from the finisher 109, it switches the flapper 324 to the discharge path 326 side, regardless of whether the sheet is an adjustment chart or not, and discharges all sheets (residual sheets) in the machine to a discharge tray 328. Discharging the residual sheets to the discharge tray 328 reduces the burden on the user of clearing the jam.

[0049] The finisher 109 can stack sheets delivered from the printing device 107. The finisher 109 has a transport path 331 and a stack tray 332 on which sheets are stacked. Transport sensors 333, 334, 335, and 336 are provided on the transport path 331. Sheets transported from the printing device 107 are stacked on the stack tray 332 via the transport path 331. The transport sensors 333, 334, 335, and 336 detect the passage of a sheet transported along the transport path 331. If the transport sensors 333, 334, 335, and 336 do not detect the leading or trailing edge of the sheet in the transport direction even after a predetermined time has elapsed since the start of sheet transport, the CPU 242 determines that a transport jam (transport abnormality) has occurred in the finisher 109. In this case, the CPU 242 notifies the printing device 107 that a transport jam has occurred.

[0050] (How to set the front and back auto adjustment) The image forming apparatus 101 of this embodiment is capable of setting front and back auto adjustment, which automatically adjusts correction values ​​for image formation conditions (geometric characteristics) during printing. FIG. 5 is an explanatory diagram of a setting screen for setting front and back auto adjustment. The setting screen is displayed on the display 225 by the CPU 222. The user can set front and back auto adjustment from the setting screen using the operation unit 224. The user sets front and back auto adjustment before issuing a command to execute printing.

[0051] Fig. 5(a) is an initial screen. When the user selects the soft key "advanced mode" from the initial screen, the CPU 222 displays the advanced mode selection screen of Fig. 5(b) on the display 225. When the user selects the soft key "adjust" from the advanced mode selection screen, the CPU 222 displays the front and back auto adjustment setting screen of Fig. 5(c) on the display 225. When the user selects the soft key "set" from the front and back auto adjustment setting screen, the CPU 222 displays the adjustment frequency selection screen of Fig. 5(d) on the display 225.

[0052] When the user selects the "Real Time" soft key on the adjustment frequency selection screen, the CPU 222 sets an operating mode in which an adjustment image is formed on every page. When the user selects the "Adjustment Interval" soft key on the adjustment frequency selection screen, the CPU 222 displays the adjustment interval setting screen of FIG. 5(e) on the display 225. When the user inputs the number of sheets using the numeric keypad on the adjustment interval setting screen and presses the "OK" soft key, the front and back automatic adjustment is enabled. In the example of FIG. 5(e), the number of sheets in the adjustment interval is set to 10. An adjustment chart is created for each number of sheets set in the adjustment interval. In other words, front and back automatic adjustment is performed using the adjustment chart for each number of sheets set in the adjustment interval, and the image formation conditions (geometric characteristics) are adjusted. Note that when the user selects the "Cancel" soft key on the front and back automatic adjustment setting screen of FIG. 5(c), the front and back automatic adjustment is disabled.

[0053] When the front and back automatic adjustment is set, the CPU 222 displays an initial screen on the display 225. FIG. 5(f) shows the display 225 on which the initial screen is displayed, and includes a print button 601 and an interrupt button 602. When the user presses the print button 601, the CPU 222 executes printing. When the front and back automatic adjustment is enabled, the CPU 222 creates an adjustment chart for every number of sheets set in the adjustment interval. When the front and back automatic adjustment is disabled, the front and back automatic adjustment is not performed.

[0054] Automatic front and back adjustment can also be set for an interrupt print job, which is an interrupt process. The setting for an interrupt print job is made by the user pressing the interrupt button 602 during printing. After pressing the interrupt button 602, the user enables automatic front and back adjustment, sets the adjustment interval to a predetermined number of sheets (for example, five sheets), and presses the print button 601. As a result, an adjustment chart is created every five sheets during printing by the interrupt print job.

[0055] If a job is specified with the check box 603 in FIG. 5C checked, the front and back automatic adjustment using the adjustment chart is performed depending on the time elapsed since the previous front and back automatic adjustment. For example, the front and back automatic adjustment is performed if a predetermined time or more has passed since the previous front and back automatic adjustment. Details of the front and back automatic adjustment will be described later. If a job is specified with the check box 603 unchecked, the front and back automatic adjustment using the adjustment chart is not performed even if a predetermined time or more has passed since the previous front and back automatic adjustment. In this embodiment, whether or not to perform such front and back automatic adjustment is set for all jobs, but this setting may also be changed for each paper feed deck or sheet type. For example, it is possible to set the paper feed deck that stores expensive sheets not to perform the front and back automatic adjustment using the adjustment chart.

[0056] (Information when a print job is executed) 6 is a diagram showing an example of job information stored in memory 223 when a print job is executed. The job information is stored in memory 223 by CPU 222 in response to input of a print job or an interrupt print job.

[0057] Job information is managed by job ID. Job information includes the paper feed deck ID, the number of sheets in the adjustment interval, the front and back auto adjustment flag, the interrupt printing flag, and the previous job ID. The paper feed deck ID indicates the paper feed deck that feeds sheets for the print job. The number of sheets in the adjustment interval is the number set on the adjustment interval setting screen. The front and back auto adjustment flag indicates the setting status (enabled / disabled) of the front and back auto adjustment. For example, if the front and back auto adjustment is enabled, the front and back auto adjustment flag is set to "1," and if it is disabled, the front and back auto adjustment flag is set to "0." The interrupt printing flag indicates whether the job is an interrupt print job. For example, if it is an interrupt print job, the interrupt printing flag is set to "1," and if it is not an interrupt print job, the interrupt printing flag is set to "0." The previous job ID is the job ID of the interrupted print job if the job is an interrupt print job.

[0058] Correction values ​​for the geometric characteristics adjusted in the front and back automatic adjustment are set for each sheet feed deck. The correction values ​​for the geometric characteristics for each sheet feed deck are stored in the memory 223 as, for example, front and back automatic adjustment information. Fig. 7 is a diagram illustrating the front and back automatic adjustment information.

[0059] The front and back automatic adjustment information identifies which paper feed deck the front and back automatic adjustment information applies to by the paper feed deck ID (first paper feed deck ID 801). The front and back automatic adjustment information includes front and back registration adjustment values ​​(correction values) for each paper feed deck. The front and back registration adjustment values ​​are values ​​that adjust (offset) the image writing position for each of the front and back sides. The CPU 222 reads out the front and back automatic adjustment information at the start of print processing. For example, in the case of a print job in which sheets are fed from the paper feed deck 301 (first paper feed deck), the CPU 222 reads out the front and back registration main scanning offset value 802 and the front and back registration sub-scanning offset value 803 of the first paper feed deck ID 801 and offsets the image writing position. The front and back registration main scanning offset value 802 and the front and back registration sub-scanning offset value 803 are updated based on the results of reading the adjustment image.

[0060] The CPU 222 counts the total number of pages printed by the printing device 107. The adjustment execution number 804 holds the total number of pages printed at the time when the front and back auto adjustment was executed. The adjustment execution time 805 holds the time that the CPU 222 obtained from the timer 251 at the time when the front and back auto adjustment was executed. The adjustment execution temperature 806 holds the internal temperature that the CPU 222 obtained from the temperature sensor 252 at the time when the front and back auto adjustment was executed. When the check box 603 in FIG. 5(c) is checked to set whether or not to perform the front and back auto adjustment for each paper feed deck, the setting information is similarly held in the memory 223.

[0061] (Image for adjustment) FIG. 8 is an example diagram of an adjustment chart. When front / back automatic adjustment is enabled, an adjustment image is printed on a sheet for each number of sheets set in the adjustment interval to create an adjustment chart. The adjustment image on the front side of the adjustment chart is read by CIS 321, and the adjustment image on the back side is read by CIS 322. Based on the results of reading the adjustment images by CIS 321 and 322, CPU 222 calculates the amount of deviation of the adjustment image from the reference position and determines correction values ​​in the main scanning direction and sub-scanning direction (front / back registration main scanning offset value and front / back registration sub-scanning offset value). CPU 222 updates the automatic adjustment information in memory 223 using the determined correction values. For example, when feeding paper from paper feed deck 301, CPU 222 updates front / back registration main scanning offset value 802 and front / back registration sub-scanning offset value 803 using the determined correction values.

[0062] The adjustment image formed together with the user image is also the adjustment image shown in Fig. 8. The adjustment images are formed at the four corners of the user image. As with the adjustment chart, the correction values ​​for the adjustment image formed together with the user image are determined based on the results of reading by the CISs 321 and 322.

[0063] (Automatic front and back adjustment) FIG. 9 is an explanatory diagram of front-and-back automatic adjustment using an adjustment chart performed when the interval between executions of front-and-back automatic adjustment is long. As described above, optimal image formation conditions change depending on changes in the environmental conditions of the printing device 107 and the sheet condition of the sheet being printed. Therefore, if the next printing operation is performed a predetermined time after the previous front-and-back automatic adjustment, the correction values ​​used in the previous front-and-back automatic adjustment may not be sufficient to print with optimal geometric characteristics. In this embodiment, if a predetermined time or more has passed since the previous front-and-back automatic adjustment at the start of a job, front-and-back automatic adjustment is performed using an adjustment chart, and then printing is performed according to the print job, thereby generating a product using optimal correction values. In the following description, three adjustment charts are inserted between print jobs and the subsequent print job is performed. However, any number of adjustment charts may be inserted as long as the correction values ​​obtained as a result of the front-and-back automatic adjustment using the adjustment chart are reflected in the product.

[0064] FIG. 9A illustrates a case where job A, for which front and back auto adjustment is enabled, is printed one day later, and job B, for which front and back auto adjustment is enabled, is printed. The time interval between the printing of page 3 of job A and the start of job B is 24 hours, and it is determined that a predetermined time interval or more has elapsed. Therefore, an adjustment chart is inserted before the printing of page 1 of job B, and then the printing of page 1 of job B is executed. The criterion for determining whether to perform front and back auto adjustment using the adjustment chart in this case is determined by the configuration of the printing device 107. In this embodiment, it is determined that a predetermined time interval or more has elapsed if a time interval of one hour or more has elapsed. As described in FIG. 7 , the time acquired by the CPU 222 from the timer 251 during front and back auto adjustment is stored in the memory 223. This time is used to determine whether a predetermined time interval or more has elapsed based on the difference from the time when job B was executed.

[0065] The front-to-back correction value "3" for the first page of Job A is the correction value used when forming the image of the first page of Job A. The calculated correction value "5" for the first page of Job A is the correction value for the next page, determined by calculating the amount of misalignment from the results of reading the adjustment image for the first page of Job A. The calculated correction value "5" is set as the front-to-back correction value "5" for the second page of Job A, which is the next page. If an adjustment chart is not inserted, the calculated correction value "8" determined from the amount of misalignment due to the adjustment image for the third page of Job A is used as the front-to-back correction value for the first page of Job B. However, because the time interval between front-to-back automatic adjustments is long, this front-to-back correction value does not allow printing with optimal geometric characteristics. Therefore, a correction value is calculated using an adjustment chart before printing the first page of Job B begins. In this case, the calculated correction value "2" obtained by calculating the amount of misalignment using the adjustment chart is used as the front-to-back correction value for the first page of Job B. Using these correction values ​​allows the print product to be printed with optimal geometric characteristics.

[0066] FIG. 9B illustrates a case in which job C, for which front and back automatic adjustment is enabled, is printed, followed by job D, for which front and back automatic adjustment is disabled, and then job E, for which front and back automatic adjustment is enabled. Job D prints 100 sheets. 100 sheets are printed between the third page of job C and the start of job E, and it is determined that a predetermined time interval has elapsed. Therefore, after front and back automatic adjustment is performed using an adjustment chart, the first page of job E is printed. The criterion for determining whether to perform front and back automatic adjustment using an adjustment chart in this case is determined by the configuration of the printing device 107. In this embodiment, it is determined that a predetermined time interval has elapsed if a time interval long enough to print 100 or more sheets has elapsed.

[0067] As explained in FIG. 7, the memory 223 stores the total number of printed sheets at the time when the front and back automatic adjustment was performed. This total number of printed sheets is used to calculate the number of sheets printed without the front and back automatic adjustment as the difference from the total number of printed sheets at the start of job E. Based on this number of sheets, it is determined whether or not a predetermined time interval has elapsed. In this case, as explained in FIG. 9(a), the calculated correction value "2" obtained from the amount of misalignment calculated using the adjustment chart is used as the front and back correction value for the first page of job E. By using such a correction value, the product is printed with optimal geometric characteristics.

[0068] 9(c) illustrates a case where whether or not to perform front and back auto adjustment using an adjustment chart is determined based on a change in the internal temperature of the machine. Here, whether or not to perform front and back auto adjustment using an adjustment chart is determined based on the difference between the internal temperature when the final page of job F, for which front and back auto adjustment is enabled, is printed and the internal temperature when the next job G, for which front and back auto adjustment is enabled, is executed. If the difference in internal temperature is equal to or greater than a predetermined temperature, it is determined that a predetermined time interval or more has elapsed between jobs.

[0069] In FIG. 9C, the internal temperature when printing the final page of job F is 34°C, while the internal temperature when job G is executed is 25°C. In this case, it is determined that the interval between jobs has elapsed for a predetermined time interval or more while the internal temperature drops by 9°C, and automatic front and back adjustment is performed using the adjustment chart before starting printing of the first page of job G. In this case, the criterion for determining whether to perform automatic front and back adjustment using the adjustment chart is determined by the configuration of the printing device 107. In this embodiment, it is determined that the predetermined time interval or more has elapsed when a time interval long enough to cause a temperature change of 5°C or more has elapsed.

[0070] As explained in FIG. 7, the internal temperature of the machine at the time when the front and back auto adjustment is executed is stored in memory 223. This internal temperature is used to determine whether a predetermined time interval has elapsed based on the difference with the internal temperature at the time job G was executed. In this case, as explained in FIG. 9(a), the calculated correction value "2" obtained from the amount of deviation calculated using the adjustment chart is used as the front and back correction value for the first page of job G. By using such a correction value, the product is printed with optimal geometric characteristics.

[0071] In this embodiment, the memory 223 stores the correction value, the execution time of the last adjustment, the total number of printed sheets, and the internal temperature for each paper feed deck. The time interval from the previous automatic front / back adjustment is determined for each paper feed deck. If the correction value is independent of the paper feed deck, the time interval may be determined commonly for each paper feed deck. If there is a dependency between multiple paper feed decks, the time interval may be determined taking the dependency into consideration.

[0072] In this embodiment, an example is shown in which the paper feed deck can be set for each print job, and whether or not to insert an adjustment chart is determined at the beginning of the job. If the correction values ​​differ for each paper feed deck, the determination of whether or not to insert an adjustment chart may be made each time the paper feed deck for the sheets to be printed is switched.

[0073] A similar determination can be made for interrupt jobs. For example, if job A', which prints for 24 hours with front and back auto adjustment disabled, interrupts job A in FIG. 9A, 24 hours will have passed by the time job A resumes. Therefore, front and back auto adjustment using the adjustment chart will be performed before job A resumes. Similarly, in FIG. 9B, if job C', which prints 100 sheets with front and back auto adjustment disabled, interrupts job C, the time for printing 100 sheets will have passed by the time job C resumes. Therefore, front and back auto adjustment using the adjustment chart will be performed before job C resumes. Similarly, in FIG. 9C, if job F', which prints for a long period of time with front and back auto adjustment disabled, interrupts job F, the time for the internal temperature to change by more than the predetermined temperature will have passed by the time job F resumes. Therefore, job F will resume after the front and back auto adjustment using the adjustment chart. If the check box 603 in FIG. 5C is not checked, the front and back automatic adjustment using the adjustment chart will not be executed even if the time interval from the previous front and back automatic adjustment has elapsed for a predetermined time or more.

[0074] (Image formation process with automatic front and back adjustment) 10 is a flowchart showing the image forming process of this embodiment. This process is started when the printing apparatus 107 receives an instruction to start a print job from the operation unit 224 or the client PC 103.

[0075] When the CPU 222 receives an instruction to start a print job, it first performs a process to determine the time interval since the previous automatic front and back adjustment ended (S1201). This process determines whether or not automatic front and back adjustment using an adjustment chart is required before executing the job. The process of S1201 is also performed when the received print job is an interrupt job. If automatic front and back adjustment using an adjustment chart is required (S1202: Y), the CPU 222 determines whether or not automatic front and back adjustment is enabled for the currently received print job (S1203).

[0076] If the front and back auto adjustment is enabled (S1203: Y), the CPU 222 executes the front and back auto adjustment. First, the CPU 222 corrects the relative print position of each color before starting printing for the print job. To do so, the CPU 222 performs known color misregistration correction (S1221). This corrects color misregistration for the images of yellow (Y), magenta (M), cyan (C), and black (K). After the color misregistration correction is complete, the CPU 222 generates an adjustment chart (S1204). The CPU 222 executes the front and back auto adjustment using the generated adjustment chart, calculates the amount of misregistration in the image formation position based on the results of reading the adjustment image, and acquires a correction value corresponding to the amount of misregistration (S1205). The correction value is stored in the memory 223 as the correction value for the paper feed deck containing the sheets used in the job. At the same time, the CPU 222 updates values ​​stored in the memory 223, such as the total number of printed sheets at the time of adjustment execution. The CPU 222 repeatedly performs the front and back automatic adjustment using the adjustment charts until the adjustment of the correction values ​​using the adjustment charts is completed (S1206: N). In this embodiment, the front and back automatic adjustment is performed using three adjustment charts, as described in Fig. 9. That is, the processes of S1204 and S1205 are repeated three times.

[0077] If automatic front-and-back adjustment using the adjustment chart is not required (S1202: N) or if the print job is set to disable automatic front-and-back adjustment (S1203: N), the CPU 222 does not perform automatic front-and-back adjustment using the adjustment chart. In this case, the CPU 222 clears the adjustment execution counter (S1220) and starts printing by the print job. The adjustment execution counter indicates the number of sheets of output that have been continuously generated without automatic front-and-back adjustment. Note that in a text mode in which only text is printed or an office document mode in which an image is not formed on the entire surface of the sheet, misalignment of the print position between the front and back sides is not a problem. In such job modes, the CPU 222 may determine in the processing of S1201 not to insert an adjustment chart before executing the job.

[0078] When printing is started, the CPU 222 determines whether the job is set to enable front and back automatic adjustment (S1207). If front and back automatic adjustment is set to enable (S1207: Y), the CPU 222 determines whether the page to be formed is a target page for front and back automatic adjustment (S1208). If the adjustment frequency is set to "real time" on the adjustment frequency selection screen of FIG. 5(d), all pages become target pages for front and back automatic adjustment. If an "adjustment interval" is set on the adjustment frequency selection screen, the number of pages set on the adjustment interval setting screen of FIG. 5(e) is compared with the adjustment execution counter stored in the memory 223. If the adjustment execution counter is larger as a result of the comparison, it is determined that the page is a target page for front and back automatic adjustment.

[0079] If the page is a target page for front and back automatic adjustment (S1208: Y), the CPU 222 forms an image of a deliverable in which an adjustment image is added to a user image (S1209). The CPU 222 calculates the amount of misalignment of the image formation position based on the result of reading the adjustment image formed on the deliverable, and acquires a correction value corresponding to the amount of misalignment (S1210). The correction value is stored in the memory 223 as the correction value for the paper feed deck in which the sheets used in the job were stored. Thereafter, the CPU 222 clears the adjustment execution counter (S1211).

[0080] After clearing the adjustment execution counter, the CPU 222 determines whether printing up to the final page of the print job is complete and the print job is to be terminated (S1215). If the print job is not to be terminated (S1215: N), the CPU 222 repeats the processing from S1207 onwards. If the print job is to be terminated (S1215: Y), the CPU 222 terminates the image formation processing according to the print job.

[0081] If the page is not a target page for front and back automatic adjustment (S1208: N), the CPU 222 forms an image of the deliverable without adding an adjustment image (S1212). The CPU 222 increments the adjustment execution counter (S1214). After incrementing the adjustment execution counter, the CPU 222 determines whether printing up to the final page of the print job is complete and the print job is to be terminated (S1215). If the print job is not to be terminated (S1215: N), the CPU 222 repeats the processing from S1207 onwards. If the print job is to be terminated (S1215: Y), the CPU 222 terminates the image formation processing according to the print job.

[0082] If the front and back auto adjustment is set to disabled (S1207: N), the CPU 222 forms an image of the result without adding an adjustment image (S1213). After outputting the result, the CPU 222 determines whether printing up to the final page of the print job is complete and the print job is to be ended (S1215). If the print job is not to be ended (S1215: N), the CPU 222 repeats the processing from S1207 onwards. If the print job is to be ended (S1215: Y), the CPU 222 ends the image formation processing according to the print job.

[0083] As described with reference to FIG. 9, when the interrupted job is resumed after completion of the interrupt job, the CPU 222 may make a determination equivalent to S1201 and perform automatic front and back adjustment using the adjustment chart.

[0084] FIG. 11 is a flowchart showing the process of determining the time interval since the previous automatic front and back adjustment was completed in S1201.

[0085] 9B, the CPU 222 acquires the total number of printed sheets at the end of the previous front and back automatic adjustment and the current total number of printed sheets stored in the memory 223 (S1301). The CPU 222 determines whether the difference between the total number of printed sheets at the time of the previous front and back automatic adjustment and the current total number of printed sheets is equal to or greater than a predetermined threshold (a predetermined number of sheets) (S1302). As a result, it is determined whether or not a predetermined time interval has elapsed since the previous front and back automatic adjustment, based on the difference between the total number of printed sheets at the time of the previous front and back automatic adjustment and the current total number of printed sheets.

[0086] If the difference is equal to or greater than the predetermined threshold (S1302: Y), the CPU 222 determines that a predetermined time interval has elapsed since the previous front / back automatic adjustment. In this case, the CPU 222 determines that it is time to insert an adjustment chart before executing the print job and update the correction values ​​by front / back automatic adjustment (S1308).

[0087] If the difference is not equal to or greater than the predetermined threshold (S1302: N), the CPU 222 acquires the in-machine temperature at the time of the previous front / back auto adjustment stored in the memory 223, and acquires the current in-machine temperature from the temperature sensor 252 (S1303). The CPU 222 determines whether the difference between the in-machine temperature at the time of the previous front / back auto adjustment and the current in-machine temperature is equal to or greater than the predetermined threshold (above a predetermined temperature) (S1304). As a result, it is determined whether or not a predetermined time interval has elapsed since the previous front / back auto adjustment, based on the difference between the in-machine temperature at the time of the previous front / back auto adjustment and the current in-machine temperature.

[0088] If the difference is equal to or greater than the predetermined threshold (S1304: Y), the CPU 222 determines that a predetermined time interval has elapsed since the previous front / back automatic adjustment. In this case, the CPU 222 determines that it is time to insert an adjustment chart before executing the print job and update the adjustment correction values ​​by front / back automatic adjustment (S1308).

[0089] If the difference is not equal to or greater than the predetermined threshold (S1304: N), the CPU 222 acquires the time at which the previous front / back automatic adjustment ended, which is stored in the memory 223, and acquires the current time from the timer 251 (S1305). The CPU 222 determines whether the difference between the time at which the previous front / back automatic adjustment ended and the current time is equal to or greater than the predetermined threshold (a predetermined time or longer) (S1306). This determines whether a predetermined time interval or longer has elapsed since the previous front / back automatic adjustment.

[0090] If the difference is greater than or equal to the predetermined threshold (S1306: Y), the CPU 222 determines that a predetermined time interval has elapsed since the previous front / back auto adjustment. In this case, the CPU 222 determines that it is time to insert an adjustment chart before executing a print job and update the adjustment correction values ​​through front / back auto adjustment (S1308). If the difference is not greater than or equal to the predetermined threshold (S1306: N), the CPU 222 determines that it is not time to insert an adjustment chart before executing a print job and update the adjustment correction values ​​through front / back auto adjustment (S1307).

[0091] As described above, the process for determining the time interval since the previous automatic front and back adjustment was completed is performed. Thereafter, the CPU 222 performs the determination in S1202 based on the result of this determination process. Note that in this embodiment, the total number of printed sheets, the temperature inside the machine, and the time interval are all used as the determination conditions, but it may also be possible to determine whether to perform automatic front and back adjustment using the adjustment chart before executing a job based on one or more of these conditions.

[0092] As described above, according to this embodiment, even if a predetermined time or more has elapsed since the previous front and back automatic adjustment, it is possible to print under optimal image forming conditions (correction values).

Claims

1. an image forming means for forming an image on a sheet by transferring the image formed on the intermediate transfer member to the sheet based on image forming conditions for adjusting the position of the image on the sheet; a fixing unit disposed downstream of the image forming unit in a sheet conveying direction, the fixing unit having at least one pair of a heating unit and a pressure unit, and fixing an image formed on the sheet by the image forming unit; a reading means disposed downstream of the fixing means in the conveying direction, the reading means including a first reading unit that reads the first side of the sheet by irradiating light onto the first side of the sheet and receiving the reflected light, and a second reading unit that reads the second side of the sheet by irradiating light onto the second side of the sheet and receiving the reflected light; a control means; The control means forming an image including an adjustment image on the first surface and the second surface of the sheet by the image forming means; the reading unit reads the first and second surfaces of a sheet on which an image including the adjustment image is formed; generating the image forming conditions based on the result of reading the adjustment image by the reading means; the control means executes a first job to form a first adjustment image, and then executes a second job not to form the adjustment image, and when it determines that a predetermined time has elapsed between the execution of the first job and the execution of a fourth job, executes a third job to form a second adjustment image after the second job is completed. Image forming device.

2. an automatic adjustment is performed in the first job to automatically adjust correction values ​​of the image forming conditions for the first and second sides of the sheet, and the automatic adjustment is not performed in the second job; The image forming apparatus according to claim 1 .

3. the adjustment image is for adjusting the positions of the images formed on the first surface and the second surface of the sheet, respectively. The image forming apparatus according to claim 1 .

4. the first adjustment image and the second adjustment image are formed in an area to be removed from the sheet by a cutting process, an image included in image data received from outside the image forming apparatus is formed in an area of ​​the sheet on which the first adjustment image is formed that is not removed by the cutting process; an image included in the image data received from outside the image forming apparatus is not formed in an area of ​​the sheet on which the second adjustment image is formed that is not removed by the cutting process; The image forming apparatus according to claim 1 .

5. the control means does not execute the third job if the predetermined time has not elapsed between the execution of the first job and the execution of the fourth job. The image forming apparatus according to claim 1 .

6. the control unit generates the image forming conditions for the fourth job based on the reading result of the second adjustment image by the reading unit. The image forming apparatus according to claim 1 .

7. the control means controls the image forming means to form the second adjustment image on a plurality of sheets in the third job. The image forming apparatus according to claim 1 .

Images