Image forming apparatus

Abstract

To accurately adjust an image forming condition with a simple method.SOLUTION: An image forming apparatus comprises: an image reading unit 231 that reads an image for adjustment formed on a sheet; and a CPU 222 that adjusts an image forming condition on the basis of a result of reading of the image for adjustment performed by the image reading unit 231. The CPU 222 forms the image for adjustment on the sheet while a print job for forming a plurality of images on a plurality of sheets is executed, and adjusts the image forming condition on the basis of the result of reading of the image for adjustment performed by the image reading unit 231. The CPU 222 forms the image for adjustment on plain paper when the plurality of sheets are embossed paper.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to image forming apparatuses such as printers, copiers, facsimiles, and multifunction peripherals.

Background Art

[0002] Printed materials produced by commercial printing machines are required to have stable image density. Patent Document 1 discloses an image forming apparatus that aims to stabilize image density. This image forming apparatus prints an adjustment image for adjusting the image density on a sheet to create an adjustment chart. The adjustment chart is read by an image reading sensor provided in the sheet conveyance path. During the execution of a print job, the image forming apparatus periodically prints the adjustment chart and feeds back the reading result of the adjustment image by the image reading sensor to the image forming conditions, thereby realizing stable image density.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The adjustment of the image density is performed for each type of sheet. For example, when a printing job is executed using embossed paper with unevenness on the surface, an adjustment chart is created using the embossed paper to adjust the image density. Due to the unevenness on the surface of the embossed paper, the distance between the surface and the image reading sensor becomes unstable. Therefore, the image reading sensor cannot accurately read the adjustment image from the adjustment chart of the embossed paper. This indicates that the adjustment of the image density when using embossed paper cannot be performed with high precision. Also, not limited to the image density, when optically reading the adjustment chart to adjust the image forming conditions, the same problem occurs. Thus, an object of the present invention is to appropriately stabilize the image density regardless of the type of sheet used in the printing job.

Means for Solving the Problem

[0005] The image forming apparatus of the present invention includes an image forming means for forming an image on a sheet based on image forming conditions, a reading means for reading an adjustment image formed on the sheet, an adjustment means for adjusting the image forming conditions based on the reading result of the adjustment image by the reading means, and a control means for causing the image forming means to form the adjustment image on the sheet and causing the adjustment means to adjust the image forming conditions based on the reading result of the adjustment image by the reading means while a printing job for forming a plurality of images on a plurality of sheets is being executed by the image forming means. The control means is characterized in that when the plurality of sheets are of a first type, the adjustment image is formed on a second type of sheet different from the first type.

Effect of the Invention

[0006] According to the present invention, the image density can be appropriately stabilized regardless of the type of sheet used in the printing job.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Mode for Carrying Out the Invention

[0008] Hereinafter, embodiments will be described in detail with reference to the drawings.

[0009] (Image Processing System) FIG. 1 is a configuration diagram of an image processing system including the image forming apparatus of the present 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 machine, a multifunction peripheral (MFP), or the like. The external controller 102 is, for example, an image processing controller, a digital front end (DFE), a print server, or the like.

[0010] The image forming apparatus 101 and the external controller 102 are communicably 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 acquires a print instruction (print job) from the client PC 103.

[0011] The client PC 103 has a printer driver installed that has a function to convert image data into a print description language that can be processed by the external controller 102. The user can instruct printing via the printer driver using various applications. The printer driver transmits image data to the external controller 102 based on a job from the user. The external controller 102 receives 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 perform printing (image formation) based on the image data.

[0012] The image forming apparatus 101 is configured by connecting a plurality of different function devices including a printing device 107, and can perform complex printing processes such as binding. The image forming apparatus 101 of the present embodiment includes a printing device 107 and a finisher 109. The printing device 107 forms an image on a sheet fed from a paper feeding unit provided at the lower part of the main body using a developer (for example, toner). The printing device 107 forms images of 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 is formed is conveyed from the printing device 107 to the finisher 109. The finisher 109 stacks the sheets on which the images are formed on the stack tray 332.

[0013] This image processing system has a configuration in which the external controller 102 is connected to the image forming apparatus 101, but the external controller 102 is not necessarily required. For example, the image forming apparatus 101 may be configured to directly acquire a print job including image data from the client PC 103 via the external LAN 104. In this case, the image forming apparatus 101 performs the data analysis and rasterization processing that are performed by the external controller 102. That is, the image forming apparatus 101 and the external controller 102 may be integrally configured.

[0014] (System Configuration) FIG. 2 is a system configuration diagram for controlling the operation of the image processing system. Here, the system configurations of the image forming apparatus 101, the external controller 102, and the client PC 103 will be described.

[0015] · 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 forming unit 228, a fixing unit 229, and a paper feeding unit 230 for forming an image. The printing device 107 includes an operation unit 224 and a display 225 as a user interface. These components are connected to be communicable with each other via a system bus 233.

[0016] 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, information and data are transmitted 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 printing settings and image data from the external controller 102 via the LAN I / F 218. The video I / F 220 is connected to the external controller 102 via a video cable 106 and controls communication with the external controller 102. The printing device 107 receives image data representing an image to be printed from the external controller 102 via the video I / F 220.

[0017] The CPU 222 comprehensively controls image processing and printing by executing a computer program stored in the storage 221. The memory 223 provides a work area for the CPU 222 to execute various processes. When performing image forming processing, the CPU 222 controls the exposure unit 227, the image forming unit 228, the fixing unit 229, and the paper feeding unit 230.

[0018] The exposure unit 227 includes a photoreceptor, a charging wire for charging the photoreceptor, and a light source for exposing the photoreceptor charged by the charging wire to form an electrostatic latent image on the photoreceptor. The photoreceptor is, for example, a photosensitive belt having a photosensitive layer formed on the surface of a belt-shaped elastic member, or a photosensitive drum having a photosensitive layer formed on the surface of a cylinder. Also, a charging roller may be used instead of the charging wire. The exposure unit 227 charges the surface of the photoreceptor to a uniform negative potential by the charging wire. The exposure unit 227 outputs laser light from the light source based on the image data. The laser light scans the surface of the uniformly charged photoreceptor. As a result, the potential at the position irradiated with the laser light on the photoreceptor fluctuates, and an electrostatic latent image is formed on the surface. Four photoreceptors are provided corresponding to the four colors of yellow (Y), magenta (M), cyan (C), and black (K). Electrostatic latent images corresponding to images of different colors are formed on the four photoreceptors respectively.

[0019] The image forming unit 228 transfers the toner image formed on the photoreceptor to the sheet. The image forming unit 228 includes a developing device, a transfer unit, and a toner supply unit. The developing device adheres the toner charged negatively from the developing cylinder to the electrostatic latent image formed on the surface of the photoreceptor to form a toner image. Four developing devices are provided corresponding to the four colors of yellow (Y), magenta (M), cyan (C), and black (K). The developing device visualizes the electrostatic latent image on the photoreceptor with the toner of the corresponding color. When the toner amount inside the developing device becomes insufficient due to the formation of the toner image, the toner is replenished by the toner supply unit.

[0020] The transfer unit has an intermediate transfer belt, and transfers the toner image from each photoreceptor to the intermediate transfer belt. A primary transfer roller is provided at a position facing the photoreceptor with the intermediate transfer belt interposed therebetween. By applying a positive potential to the primary transfer roller, the toner images are superimposed and transferred from each of the four photoreceptors to the intermediate transfer belt. Thereby, a full-color toner image is formed on the intermediate transfer belt. The toner image formed on the intermediate transfer belt is transferred to a sheet by a secondary transfer roller described later. The secondary transfer roller transfers the full-color toner image from the intermediate transfer belt to the sheet by applying a positive potential.

[0021] The fixing unit 229 fixes the transferred toner image to the sheet. The fixing unit 229 has a heater and a roller pair. The fixing unit 229 melts and fixes the toner image on the sheet to the sheet by heating and pressing the toner image on the sheet with the heater and the roller pair. Thereby, an image is formed on the sheet. The paper feed unit 230 includes a transport roller and various sensors in the transport path, and controls the sheet feeding operation.

[0022] The image reading unit 231 reads the image formed on the transported sheet based on the instruction of the CPU 222. When adjusting the image forming conditions, for example, the CPU 222 causes the image reading unit 231 to read an image for adjusting the image forming conditions to be formed on the sheet. The image processing unit 232 sets the gain adjustment value of the image reading unit 231 and the like based on the reading result by the image reading unit 231. Such processing by the image processing unit 232 is reflected in the reading result of the image by the image reading unit 231. The operation unit 224 is an input device that receives inputs 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 the setting information of the image forming apparatus 101 and the processing status (status information) of the print job.

[0023] · Finisher The finisher 109 is, for example, a large-capacity stacker. 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 communicably connected to each other via a system bus 245. The communication I / F 241 is connected to the printing device 107 via a communication cable 249 and controls communication with the printing device 107. When the finisher 109 and the printing device 107 operate in cooperation, information and data are transmitted and received via the communication I / F 241. The CPU 242 executes a control program stored in the memory 243 and performs various controls necessary for paper discharge. The memory 243 stores the control program. Also, the memory 243 provides a work area when the CPU 242 executes various processes. The paper discharge control unit 244 discharges the conveyed sheet to the stack tray 332 based on an instruction from the CPU 242.

[0024] ·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 a user interface. These components are communicably connected to each other via a system bus 216.

[0025] The LAN I / F 213 is connected to the client PC 103 via the external LAN 104 and controls the 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 the communication with the printing device 107. The external controller 102 transmits print settings, image data, etc. 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 the communication with the printing device 107. The external controller 102 transmits image data to the printing device 107 via the video I / F 215.

[0026] The CPU 208 comprehensively performs processes such as receiving image data transmitted from the client PC 103, RIP processing, and transmitting the image data to the image forming apparatus 101 by executing a computer program stored in the storage 210. The memory 209 provides a work area when the CPU 208 executes various processes. The keyboard 211 is an input device that receives inputs of various settings and operation instructions from the user. The display 212 is an output device that displays information on the execution application of the external controller 102 as still images or videos.

[0027] · 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 to be communicable with each other via a system bus 207.

[0028] The CPU 201 controls the operation of the client PC 103 by executing a computer program stored in the storage 203. In this embodiment, the CPU 201 creates image data and performs print job transmission processing. The memory 202 provides a work area when the CPU 201 executes various processes. The keyboard 204 and the display 205 are user interfaces. The keyboard 204 is an input device that receives instructions from the user. The display 205 is an output device that displays information on the executed applications of the client PC 103 as still images or videos. 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 to the external controller 102 via the LAN I / F 206.

[0029] Note that the external controller 102 and the image forming apparatus 101 are connected by the internal LAN 105 and the video cable 106, but any configuration that can transmit and receive data necessary for printing is acceptable. For example, they may be connected only by the video cable. The memory 202, the memory 209, the memory 223, and the memory 243 may each be a storage device for holding data and programs. For these memories, for example, volatile RAM (Random Access Memory), non-volatile ROM (Read Only Memory), storage, USB (Universal Serial Bus) memory, etc. can be used.

[0030] (Configuration of Image Forming Apparatus) FIG. 3 is a configuration diagram of the image forming apparatus 101. A display 225 is provided above the printing apparatus 107. The display 225 displays information regarding the printing status and settings of the image forming apparatus 101. The sheet on which an image is formed by the printing apparatus 107 is conveyed to a finisher 109 provided in the subsequent stage.

[0031] The printing apparatus 107 includes, as a paper feeding unit 230, a multi-tray paper feeding stage 300 which is a manual feed tray, a plurality of paper feeding decks 301, 302, and a conveyance path 303. Different types of sheets can be accommodated in the multi-tray paper feeding stage 300 and each of the paper feeding decks 301, 302. The topmost sheet among the sheets accommodated in the multi-tray paper feeding stage 300 and each of the paper feeding decks 301, 302 is separated and fed to the conveyance path 303. The printing apparatus 107 includes, as an exposure unit 227, image forming units 304, 305, 306, 307 for forming an image. The printing apparatus 107 forms a color image. For this purpose, 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).

[0032] The printing apparatus 107 includes, as an image forming unit 228, an intermediate transfer belt 308 to which toner images are transferred from the respective image forming units 304, 305, 306, 307, and a secondary transfer roller 309. The intermediate transfer belt 308 rotates clockwise in the figure, and the toner images are superimposed and transferred in the order of the image forming unit 307, the image forming unit 306, the image forming unit 305, and the image forming unit 304. As a result, the intermediate transfer belt 308 carries a full-color toner image. The intermediate transfer belt 308 conveys the toner image to the secondary transfer roller 309 by rotating. In accordance with the timing at which the toner image is conveyed to the secondary transfer roller 309, the sheet is conveyed to the secondary transfer roller 309 via the conveyance path 303. The secondary transfer roller 309 transfers the toner image on the intermediate transfer belt 308 to the conveyed sheet.

[0033] The printing device 107 includes a fixing unit 229 having a first fixing device 311 and a second fixing device 318. The first fixing device 311 and the second fixing device 318 have the same configuration and fix the toner image onto the sheet. For this purpose, the first fixing device 311 and the second fixing device 318 each include a pressure roller and a heating roller. The sheet passes between the pressure roller and the heating roller, is heated and pressurized, and the toner image is melted and pressure-bonded onto the sheet. The sheet that has passed through the second fixing device 318 is conveyed to the conveyance path 314. Note that the second fixing device 318 is arranged downstream of the first fixing device 311 in the sheet conveyance direction and is used to add gloss to the image on the sheet that has been fixed by the first fixing device 311 and to ensure fixability. Therefore, the second fixing device 318 may not be used depending on the type of sheet and the content of the image forming process. In order to convey the sheet that has been fixed by the first fixing device 311 without passing through the second fixing device 318, a conveyance path 312 is provided.

[0034] After the conveyance path 314 and the conveyance path 312 merge, a conveyance path 315 and a reversing path 316 are provided. When double-sided printing is instructed, the sheet is conveyed to the reversing path 316. The sheet conveyed to the reversing path 316 has its conveyance direction reversed in the reversing path 316 and is conveyed to the double-sided conveyance path 317. By the reversing path 316 and the double-sided conveyance path 317, the surface (first surface) on which the image is formed of the sheet is reversed. The sheet is conveyed to the conveyance path 303 by the double-sided conveyance path 317, and an image is formed on the second surface by passing through the secondary transfer roller 309 and the fixing unit 229.

[0035] In the case of single-sided printing or when images are formed on both sides in double-sided printing, the sheet is conveyed to the conveyance path 315. A conveyance path 323 is arranged downstream of the conveyance path 315 in the sheet conveyance direction.

[0036] In the conveyance path 323, as the image reading unit 231, CIS (Contact Image Sensor) 321 and 322 are arranged to face each other across the conveyance path 323. FIG. 4 is an explanatory diagram of CIS 321 and 322. CIS 321 is an optical sensor that reads an image on the upper surface of the sheet conveyed through the conveyance path 323. CIS 322 is an optical sensor that reads an image on the lower surface of the sheet conveyed through the conveyance path 323.

[0037] CIS 321 includes an LED (Light Emitting Diode) 350 serving as a light source, a reading sensor 351 serving as a light receiving unit, and a white reference plate 352. LED 350 irradiates light onto the upper surface of the sheet at the timing when the sheet conveyed through the conveyance path 323 reaches the reading position. The reading sensor 351 includes a plurality of light receiving elements (photoelectric conversion elements) in a direction orthogonal to the conveyance direction of the sheet. Therefore, the direction orthogonal to the conveyance direction of the sheet becomes the main scanning direction of CIS 321. The reading sensor 351 receives the reflected light from the sheet by the light receiving elements. The plurality of light receiving elements of the reading sensor 351 output an output value (electrical signal) based on the intensity of the received reflected light. The output values (electrical signals) output from the plurality of light receiving elements are transmitted to the CPU 222. In this way, the image formed on the sheet is read. The white reference plate 352 is a calibration member (reference member) used during shading correction of CIS 321. During shading correction, LED 350 and the reading sensor 351 move to a position where they can read the white reference plate 352. Alternatively, during shading correction, the white reference plate 352 moves to the reading position of LED 350 and the reading sensor 351. Shading correction of CIS 321 is performed based on the reading result of the white reference plate 352.

[0038] CIS 322 includes an LED 353, a reading sensor 354, and a white reference plate 355, similar to CIS 321. CIS 322 operates in the same manner as CIS 321 and reads the image formed on the lower surface of the sheet at the timing when the sheet conveyed through the conveyance path 323 reaches the reading position. In addition to CIS 321 and 322, the image reading unit 231 can also be realized by a CCD or a CMOS sensor.

[0039] The printing apparatus 107 of the present embodiment can form an adjustment image for adjusting image formation conditions on both sides of a sheet. A sheet on which the adjustment image is formed is called an adjustment chart. The printing apparatus 107 prints the adjustment image on a sheet to create an adjustment chart, and reads the adjustment image by CIS321 and CIS322. The read images of the adjustment chart by CIS321 and CIS322 are stored in the memory 223. The CPU 222 refers to the memory 223, analyzes the read images by CIS321 and CIS322, feeds back to the image formation conditions, and adjusts the image formation conditions.

[0040] For example, when the internal temperature of the printing apparatus 107 rises, the image density of the image formed on the sheet fluctuates compared to when the internal temperature of the printing apparatus 107 is low. The printing apparatus 107 creates an adjustment chart and detects the image density based on the reading results of CIS321 and 322. The CPU 222 adjusts the image formation conditions so that the detected image density becomes an ideal image density. For example, the CPU 222 obtains the amount of change in the image density from the detected image density, and adjusts the image formation conditions so as to print with the same image density as when the internal temperature is low based on the obtained amount of change. The CPU 222 converts the image data based on the image formation conditions. The printing apparatus 107 forms an image on the sheet based on the image data converted by the CPU 222, thereby controlling the image density of the image formed on the sheet. Thereby, the printing apparatus 107 can suppress the fluctuation of the image density caused by the fluctuation of the internal temperature.

[0041] The adjustment image formed on the adjustment chart may be an image for detecting geometric characteristics such as print position and shape, or an image for detecting color deviation, in addition to the image for detecting the image density. When an adjustment image for detecting geometric characteristics is formed, the CPU 222 adjusts the image formation conditions to suppress the fluctuation of the geometric characteristics based on the reading result of CIS321 (or CIS322). By the CPU 222 performing image formation based on the image formation conditions, the geometric characteristics of the image printed by the printing apparatus 107 are adjusted to ideal geometric characteristics.

[0042] Also, when an adjustment image for detecting color misregistration is formed, the CPU 222 detects color misregistration based on the reading result of the CIS 321 (or CIS 322). The CPU 222 adjusts the image forming conditions to suppress the detected color misregistration. By controlling the position of the image formed on the photoreceptor by the exposure unit 227 based on the image forming conditions, the CPU 222 corrects the color misregistration.

[0043] The adjustment image may be printed on the peripheral portion of the sheet on which an image corresponding to the print job is printed, in addition to the adjustment chart on which only the adjustment image is printed on the sheet. When the adjustment image is printed on the peripheral portion, the sheet is cut by the finisher 109 at the peripheral portion where the adjustment image is printed. In the following description, the case of using the adjustment chart will be described.

[0044] The adjustment chart is excluded so as not to be mixed into the printed matter corresponding to the print job. For this purpose, the printing apparatus 107 includes a flapper 324, a discharge path 326, a conveyance sensor 327, and a discharge tray 328. The adjustment chart on which the adjustment image is read by the CISs 321 and 322 is conveyed to the discharge path 326 by the flapper 324. The sheet conveyed to the discharge path 326 is discharged to the discharge tray 328.

[0045] When the sheet is not the adjustment chart, the sheet is conveyed from the conveyance path 323 to the downstream conveyance path 325 by the flapper 324. The sheet conveyed to the downstream conveyance path 325 is delivered to the finisher 109. When the printing apparatus 107 acquires a notification of the occurrence of a conveyance jam from the finisher 109, regardless of whether it is the adjustment chart or not, the flapper 324 is switched to the discharge path 326 side to discharge all the sheets (residual paper) in the machine to the discharge tray 328. By discharging the residual paper to the discharge tray 328, the load of jam processing by the user is reduced.

[0046] The finisher 109 can stack the sheets delivered from the printing device 107. The finisher 109 includes a conveyance path 331 and a stack tray 332 for stacking sheets. Conveyance sensors 333, 334, 335, and 336 are provided in the conveyance path 331. The sheets conveyed from the printing device 107 are stacked on the stack tray 332 via the conveyance path 331. The conveyance sensors 333, 334, 335, and 336 detect the passage of the sheets conveyed through the conveyance path 331. If the leading or trailing edge of the sheet in the conveyance direction is not detected by the conveyance sensors 333, 334, 335, and 336 even after a predetermined time has elapsed since the start of sheet conveyance, the CPU 242 determines that a conveyance jam (conveyance abnormality) has occurred within the finisher 109. In this case, the CPU 242 notifies the printing device 107 that a conveyance jam has occurred.

[0047] (Automatic adjustment setting method) In the image forming apparatus 101 of the present embodiment, automatic adjustment for automatically adjusting image forming conditions during printing can be set. FIG. 5 is an exemplary view of a setting screen for setting automatic adjustment. The setting screen is displayed on the display 225 by the CPU 222. The user can set automatic adjustment from the setting screen using the operation unit 224. The user performs the setting of automatic adjustment before instructing the execution of printing.

[0048] FIG. 5(a) is the initial screen. When the user selects "application mode", which is a soft key, from the initial screen, the CPU 222 displays the selection screen for the application mode in FIG. 5(b) on the display 225. When the user selects "adjustment", which is a soft key, from the selection screen for the application mode, the CPU 222 displays the setting screen for automatic adjustment in FIG. 5(c) on the display 225. When the user selects "set", which is a soft key, from the setting screen for automatic adjustment, the CPU 222 displays the adjustment frequency selection screen in FIG. 5(d) on the display 225.

[0049] When the user selects "Adjustment Interval", which is a soft key, from 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 soft key "OK", the automatic adjustment becomes effective. In the example of Fig. 5(e), the number of sheets for the adjustment interval is set to 10. An adjustment chart is created for each number of sheets set for the adjustment interval. That is, automatic adjustment is performed and the image forming conditions are adjusted for each number of sheets set for the adjustment interval. Note that when the user selects "Cancel", which is a soft key, from the automatic adjustment setting screen, the automatic adjustment becomes ineffective.

[0050] When the automatic adjustment is set, the CPU 222 displays the initial screen on the display 225. Fig. 5(f) shows the display 225 on which the initial screen is displayed, and it is equipped with a print button 601 and an interrupt button 602. When the user presses the print button 601, the CPU 222 executes printing. When the automatic adjustment is effective, the CPU 222 creates an adjustment chart for each number of sheets set for the adjustment interval. When the automatic adjustment is ineffective, the adjustment chart is not created.

[0051] In the case of an interrupt print job, which is an interrupt process, the automatic adjustment can also be set. When the user presses the interrupt button 602 during printing, the setting of the interrupt print job is performed. After pressing the interrupt button 602, the user enables the automatic adjustment, sets the adjustment interval to a predetermined number of sheets (for example, 5 sheets), and presses the print button 601. As a result, an adjustment chart is created every 5 sheets during printing by the interrupt print job and the automatic adjustment is performed.

[0052] Fig. 5(g) is a paper feed stage selection screen. Although details will be described later, when the automatic adjustment is performed in an interrupt print job, the CPU 222 displays the paper feed stage selection screen on the display 225. The user can select the paper feed stage for feeding the sheet used for the adjustment chart on the paper feed stage selection screen.

[0053] (Information at the time of executing a print job) FIG. 6 is an exemplary diagram of job information stored in the memory 223 when a print job is executed. The job information is stored in the memory 223 by the CPU 222 in response to an input of a print job or an interrupt printing job.

[0054] The job information is managed by a job ID. The job information includes a paper feed deck ID, the number of sheets for the adjustment interval, an automatic adjustment flag, an interrupt printing flag, and the previous job ID. The paper feed deck ID indicates the paper feed deck that feeds sheets in the print job. The number of sheets for the adjustment interval is the number of sheets set on the adjustment interval setting screen. The automatic adjustment flag indicates the setting state of automatic adjustment. For example, if automatic adjustment is effective, the automatic adjustment flag is set to "1", and if it is ineffective, the automatic adjustment flag is set to "0". The interrupt printing flag indicates whether the job is an interrupt printing job. For example, if it is an interrupt printing job, the interrupt printing flag is set to "1", and if it is not an interrupt printing job, the interrupt printing flag is set to "0". The previous job ID is the job ID of the print job that was executed before the interruption when the job is an interrupt printing job.

[0055] The image forming conditions adjusted by automatic adjustment are set for each paper feed deck. The image forming conditions for each paper feed deck are stored in the memory 223 as, for example, automatic adjustment information. FIG. 7 is an exemplary diagram of the automatic adjustment information. In the present embodiment, the case where image density adjustment is performed by automatic adjustment will be described.

[0056] The automatic adjustment information is identified for each paper feed deck by the paper feed deck ID. The automatic adjustment information includes, for each paper feed deck, an image density offset value which is an adjustment value for the image density for each color. The image density offset value is an adjustment value for adjusting (offsetting) the image density of the image to be printed. The CPU 222 reads out the automatic adjustment information at the timing of the start of the printing process. For example, in the case of a job of feeding a sheet from the paper feed deck 301 (the first paper feed deck), the CPU 222 reads out the image density offset values for each color of the first paper feed deck ID 701 as adjustment values. That is, the CPU 222 reads out the image density offset value Y702, the image density offset value M703, the image density offset value C704, and the image density offset value K705. The CPU 222 adjusts the image formation conditions based on the read adjustment values for each color and adjusts the image density for each color.

[0057] The image density offset value Y, the image density offset value M, the image density offset value C, and the image density offset value K for each paper feed deck are updated after reading of the adjustment image. That is, these adjustment values are updated based on the reading result of the adjustment image.

[0058] FIG. 8 is an exemplary diagram of an adjustment chart. When automatic adjustment is set to be effective, for each number of sheets set at the adjustment interval, an adjustment image is printed on the sheet and an adjustment chart is created. The adjustment image is configured by arranging a plurality (here, 10) of patch images having different image densities (gradations) for each color in a straight line. Note that the patch images at both ends of the straight line have the same image density and are the maximum image density. The adjustment images are arranged for each color near the edge of the sheet. In the present embodiment, cyan and magenta patch images are printed near one side of the sheet, and yellow and black patch images are printed near the side opposite to the one side.

[0059] For the adjustment chart, the adjustment image on the front surface is read by CIS321, and the adjustment image on the back surface is read by CIS322. The CPU222 acquires the density values of the image density for each color based on the reading results of the adjustment chart by CIS321 and 322. The CPU222 determines the image density offset value based on the acquired density values of the image density for each color. The CPU222 updates the automatic adjustment information in the memory 223 with the determined image density offset value. For example, when the adjustment chart is created by a sheet fed from the paper feed deck 301 (the first paper feed deck), the CPU222 updates the image density offset value Y702 to the image density offset value K705 with the determined image density offset value.

[0060] (Printing process) FIG. 9 is a flowchart showing the printing process. The CPU222 acquires a print job and starts the printing process. In this embodiment, the paper feed deck 301 stores a sheet (e.g., plain paper) with few irregularities on the surface and on which the printed adjustment image can be accurately read by the image reading unit 231 (CIS321, 322). The paper feed deck 302 stores a sheet (e.g., embossed paper) with a rough surface and on which the printed adjustment image cannot be accurately read by the image reading unit 231 (CIS321, 322). Here, embossed paper is used as a representative of the sheet on which the adjustment image cannot be accurately read, but such a sheet is not limited to embossed paper as long as it is a type of sheet on which the image reading unit 231 (CIS321, 322) cannot accurately read. For example, a sheet with embossed surface is not limited to embossed paper and is a sheet on which the image reading unit 231 (CIS321, 322) cannot accurately read. The multi-tray paper feed stage 300 has a sheet (e.g., cardboard) with few irregularities on the surface and on which the printed adjustment image can be accurately read by the image reading unit 231 (CIS321, 322) placed (stored).

[0061] When the CPU 222 starts the printing process, it acquires job information corresponding to the printing job (S901). The CPU 222 determines whether automatic adjustment of the printing job is effective based on the automatic adjustment flag included in the acquired job information (S902). If the automatic adjustment is ineffective (S902: N), the CPU 222 performs normal image formation processing (automatic adjustment ineffective job) that does not include the automatic adjustment operation (S911).

[0062] If the automatic adjustment is effective (S902: Y), the CPU 222 determines whether the type of sheet set in the printing job is embossed paper (S903). If it is not embossed paper (S903: N), the CPU 222 performs normal image formation processing (automatic adjustment effective job without paper feed stage switching) that includes the automatic adjustment operation (S910). If it is embossed paper (S903: Y), the CPU 222 determines whether the automatic adjustment is performed for an interrupt printing job (S904). The interrupt printing job is a state in which "adjustment interval", which is a soft key, is selected on the adjustment frequency selection screen of FIG. 5(d). The interrupt printing job occurs every number of sheets set on the adjustment interval setting screen of FIG. 5(e).

[0063] If the automatic adjustment is not performed for the interrupt printing job (S904: N), the CPU 222 performs normal image formation processing (automatic adjustment effective job without paper feed stage switching) that includes the automatic adjustment operation (S910). If the automatic adjustment is performed for the interrupt printing job (S904: Y), the CPU 222 displays the paper feed stage selection screen of FIG. 5(g) on the display 225 (S905). Since the automatic adjustment using embossed paper reduces the adjustment accuracy, the automatic adjustment using other types of sheets is guided. Therefore, the paper feed stage selection screen displays other paper feed stages that accommodate sheets available for automatic adjustment. In the present embodiment, the paper feed deck 301 and the multi-tray paper feed stage 300 are displayed on the paper feed stage selection screen as paper feed stages that accommodate sheets available for automatic adjustment.

[0064] The user selects one of the soft keys "Multi-tray", "First paper feed deck", or "Do not adjust" on the paper feed stage selection screen and presses "OK". By pressing "OK", the CPU 222 obtains the selection content on the paper feed stage selection screen. When "Multi-tray" or "First paper feed deck" is selected (S906: Y), the CPU 222 determines that another paper feed stage has been selected. In this case, the CPU 222 performs image forming processing (automatic adjustment job with paper feed stage switching) including an automatic adjustment operation with paper feed stage switching (S907). When "Do not adjust" is selected (S906: N), the CPU 222 determines that no other paper feed stage has been selected. In this case, the CPU 222 cancels the automatic adjustment setting and performs normal image forming processing (automatic adjustment disabled job) (S911).

[0065] Note that the content of the paper feed stage selection screen in Fig. 5(g) is not limited to this, and any screen that allows the user to select a paper feed stage may be used. Also, the paper feed stage selection screen may be configured to eliminate "Do not adjust" and always require the selection of another paper feed stage.

[0066] After the CPU 222 prints an image on the sheet by any of the processes in S907, S910, and S911, it performs a determination process as to whether the print job has ended (S908). The CPU 222 makes this determination based on whether the printing of all pages instructed by the print job has ended. As a result of the print job end determination process, if the print job has not ended (S908: N), the CPU 222 repeats the processes after S901 until the print job ends. If the print job has ended (S908: Y), the CPU 222 ends the printing process.

[0067] (Automatic adjustment job with paper feed stage switching) Fig. 10 is a flowchart showing the automatic adjustment effective job with paper feed stage switching in S907.

[0068] Based on the paper feed deck ID included in the job information obtained in the process of S901, the CPU222 refers to the adjustment value set in the automatic adjustment information of the paper feed deck (S1001). The CPU222 determines the adjustment value based on the referred automatic adjustment information (S1002). That is, the CPU222 determines the adjustment value from the image density offset values Y702, 707, 712, the image density offset values M703, 708, 713, the image density offset values C704, 709, 714, and the image density offset values K705, 710, 715.

[0069] The CPU222 determines whether it is the start of the print job (S1003). If it is the start of the print job (S1003: Y), the CPU222 switches the paper feed stage and starts the automatic adjustment operation before starting printing (S1005). If it is not the start of the print job (S1003: N), the CPU222 determines that it is in the printing state and determines whether printing has been performed on the number of sheets corresponding to the adjustment interval (S1004). If printing has been performed on the number of sheets corresponding to the adjustment interval in the printing state (S1004: Y), the CPU222 switches the paper feed stage and starts the automatic adjustment operation (S1005).

[0070] In the process of S1005, for example, when "Multi Tray" is selected from the paper feed stage selection screen in the process of S906, the CPU222 switches the paper feed stage of the sheet to the multi-tray paper feed stage 300. The CPU222 starts the automatic adjustment operation using the sheet fed from the multi-tray paper feed stage 300. When "First Paper Feed Deck" is selected from the paper feed stage selection screen in the process of S906, the CPU222 switches the paper feed stage to the paper feed deck 301 and starts the automatic adjustment operation using the sheet fed from the paper feed deck 301.

[0071] The CPU 222 prints an adjustment image on the sheet fed from the switched paper feed tray to create an adjustment chart (S1006). The CPU 222 reads the adjustment image from the adjustment chart by the image reading unit 231 (CIS 321, 322) (S1007). The CPU 222 acquires an adjustment value for the image density based on the reading result (read image) of the adjustment image. The CPU 222 updates the adjustment value of the automatic adjustment information for the paper feed tray set in the print job with the acquired adjustment value (S1008). That is, the CPU 222 acquires the image density offset value Y, the image density offset value M, the image density offset value C, and the image density offset value K based on the read image. The CPU 222 updates the adjustment value of the paper feed tray set in the print job with the acquired image density offset value Y, the image density offset value M, the image density offset value C, and the image density offset value K.

[0072] After that, the CPU 222 switches the paper feed tray of the sheet to the paper feed tray set in the print job (S1009). The CPU 222 resets the count value L of the number of printed sheets to 0 and ends this process (S1010).

[0073] If the number of sheets printed in the printing state is less than the number of sheets at the adjustment interval (S1004: N), the CPU 222 performs normal image printing (S1011). After the image printing, the CPU 222 adds 1 to the count value L of the number of printed sheets and ends the process (S1212). As described above, the automatic adjustment effective job with paper feed tray switching is performed.

[0074] When a print job for image printing using an embossed paper is executed with auto-adjustment enabled in this way, the sheet used for the adjustment chart is switched to a sheet other than the embossed paper, and auto-adjustment is performed. The sheet other than the embossed paper is selected by the user. Here, the user selects a paper feed stage that accommodates a type of sheet other than the embossed paper, and auto-adjustment is performed using the sheet other than the embossed paper. For this purpose, auto-adjustment is performed without using a type of sheet for which it is difficult for the image reading unit 231 to read a high-precision image like the embossed paper, and adjustment of high-precision image formation conditions becomes possible.

[0075] (Auto-adjustment enabled job without paper feed stage switching) FIG. 11 is a flowchart showing an auto-adjustment enabled job without paper feed stage switching of S910. This process is a normal auto-adjustment enabled job.

[0076] The CPU 222 determines adjustment values (S1101, S1102) in the same manner as the processes of S1001 and S1002 in FIG. 10S. The CPU 222 determines whether printing has been performed on the number of sheets corresponding to the adjustment interval (S1103). When printing has been performed on the number of sheets corresponding to the adjustment interval (S1103: Y), the CPU 222 starts the auto-adjustment operation.

[0077] When starting the automatic adjustment operation, the CPU 222 prints an adjustment image on the sheet fed from the paper feed stage set in the print job to create an adjustment chart (S1104). The CPU 222 reads the adjustment image from the adjustment chart by the image reading unit 231 (CIS 321, 322) (S1105). The CPU 222 obtains an adjustment value for the image density based on the reading result (read image) of the adjustment image. The CPU 222 updates the adjustment value of the automatic adjustment information for the paper feed stage set in the print job with the obtained adjustment value (S1106). That is, the CPU 222 obtains the image density offset value Y, the image density offset value M, the image density offset value C, and the image density offset value K based on the read image. The CPU 222 updates the adjustment value of the paper feed stage set in the print job with the obtained image density offset value Y, the image density offset value M, the image density offset value C, and the image density offset value K. Thereafter, the CPU 222 resets the count value L of the number of printed sheets to 0 and ends this process (S1107).

[0078] When not printing on the sheets for the number of sheets of the adjustment interval (S1103: N), the CPU 222 performs normal image printing (S1108). After image printing, the CPU 222 adds 1 to the count value L of the number of printed sheets and ends the process (S1109). As described above, an automatic adjustment effective job without paper feed stage switching is performed.

[0079] (Automatic adjustment invalid job) FIG. 12 is a flowchart showing the automatic adjustment invalid job of S911.

[0080] When automatic adjustment is disabled, the CPU 222 refers to the automatic adjustment information of the paper feed deck based on the paper feed deck ID included in the job information obtained in the process of S901 (S1201). The CPU 222 determines adjustment values (image density offset value Y, image density offset value M, image density offset value C, image density offset value K) based on the referred automatic adjustment information (S1202). The CPU 222 prints an image corresponding to the print job on the sheet under the image forming conditions based on the determined adjustment values (S1203). The automatic adjustment disabled job is performed as described above.

[0081] As described above, in the present embodiment, when it is difficult to perform automatic adjustment due to the influence of the surface property of the sheet used for the adjustment chart, the adjustment chart is switched to a type of sheet with less influence of other surface properties for automatic adjustment. That is, when the surface property of the sheet used in the print job is not suitable for high-precision automatic adjustment, a sheet with a smoother surface property is used for the adjustment chart. Therefore, it is possible to adjust the image density with high precision by a simple method regardless of the surface property of the sheet. Although the case of adjusting the image density by automatic adjustment has been described in the present embodiment, the present embodiment is also effective when performing other automatic adjustments such as adjustment of geometric characteristics.

[0082] In the above example, when the sheet used for creating the adjustment chart is not suitable for automatic adjustment, the adjustment chart is created using the sheet fed from the paper feed tray selected by the user on the paper feed tray selection screen. The alternative sheet may be automatically selected by the image forming apparatus 101 in addition to the selection by the user.

[0083] In this case, for the image forming apparatus 101, the types (names, surface properties, etc.) of the sheets stored in each of a plurality of paper feed trays in advance are registered in the memory 223. When the CPU 222 interrupts a print job to perform automatic adjustment, it checks the type of sheet (or paper feed tray) specified in the print job. As a result of the check, if the sheet is not suitable for automatic adjustment, the CPU 222 checks the registered contents of the memory 223 to check the types of sheets stored in other paper feed trays. If a sheet suitable for automatic adjustment is stored in another paper feed tray, an adjustment chart is created using the sheet fed from that paper feed tray. If no sheet suitable for automatic adjustment is stored in another paper feed tray, automatic adjustment is disabled.

Claims

1. Image forming means for forming an image on a sheet based on image forming conditions; Reading means for reading an adjustment image formed on the sheet; Adjusting means for adjusting the image forming conditions based on the reading result of the adjustment image by the reading means; Control means for causing the image forming means to form the adjustment image on a sheet and causing the adjusting means to adjust the image forming conditions based on the reading result of the adjustment image by the reading means while a printing job for forming a plurality of images on a plurality of sheets is being executed by the image forming means; The control means is characterized in that when the plurality of sheets are of a first type, the adjustment image is formed on a second type of sheet different from the first type; An image forming apparatus.

2. The reading means is characterized in that it can read the adjustment image formed on the second type of sheet with higher accuracy than the adjustment image formed on the first type of sheet; The image forming apparatus according to claim 1.

3. The control means is characterized in that by using the reading result of the adjustment image of the adjustment chart formed by the second type of sheet rather than the reading result of the adjustment image of the adjustment chart created by the first type of sheet, the adjustment can be performed with high accuracy; The image forming apparatus according to claim 1.

4. Further comprising a plurality of paper feed trays for accommodating different types of sheets, The image forming means forms an image on a sheet fed from any one of the plurality of paper feed trays, The control means feeds paper from the paper feed tray for accommodating the first type of sheet when performing printing by the printing job, and feeds paper from the paper feed tray for accommodating the second type of sheet when performing the adjustment to create an adjustment chart; The image forming apparatus according to claim 1.

5. The control means is characterized in that when performing the adjustment by interrupting the printing by the printing job, a selection screen for selecting the paper feed tray for accommodating the sheet used for creating the adjustment chart is displayed on the display; The image forming apparatus according to claim 4.

6. The selection screen is characterized in that the paper feed tray accommodating the sheet that can be used for the adjustment is selectable; The image forming apparatus according to claim 5.

7. The control means is characterized in that the adjustment chart is created using the sheet accommodated in the paper feed tray selected from the selection screen; The image forming apparatus according to claim 5 or 6.

8. The selection screen is configured to be able to select a paper feed stage in which sheets available for the adjustment are accommodated and invalidation of the adjustment. When invalidation of the adjustment is selected from the selection screen, the control means invalidates the adjustment. The image forming apparatus according to claim 5.

9. The apparatus further includes registration means for registering the types of sheets accommodated in the plurality of paper feed stages. When interrupting the print job to perform the adjustment, the control means checks the type of the first type of sheet, and if the first type of sheet is the first type, refers to the registration means to check the types of other sheets. If there is a paper feed stage that accommodates the second type of sheet, the control means creates the adjustment chart using the sheets of the paper feed stage as the second type of sheet. The image forming apparatus according to claim 4.

10. If there is no paper feed stage that accommodates the second type of sheet, the control means invalidates the adjustment. The image forming apparatus according to claim 9.

11. The surface property of the second type of sheet is smoother than the surface property of the first type of sheet. The image forming apparatus according to claim 1.

12. The first type of sheet is a sheet having a concavo-convex surface. The image forming apparatus according to claim 11.

13. The first type of sheet is embossed paper. The image forming apparatus according to claim 12.

Images