JP2015036695A - Image forming apparatus, control method, and computer program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus configured to control the execution timing of calibration so as to reduce power consumption according to a fixing temperature.SOLUTION: An image forming apparatus 101 includes a fixing apparatus which fixes a toner image formed by electrophotography onto a recording medium by heat. The image forming apparatus 101 detects first the amount of toner applied on pages of a toner image, starting from the page a predetermined number of pages after a page currently in thermal fixation, and calculates a fixing temperature required for thermally fixing the pages on the basis of the detected amount of toner applied, to control the fixing apparatus according to the calculated fixing temperature. The image forming apparatus 101 decides the execution timing of calibration for correcting printout characteristics of a page, on the basis of the calculated fixing temperature.

Description

  The present invention relates to an image forming apparatus, a control method, and a computer program.

  There has been proposed an image forming apparatus that thermally fixes a toner image formed by an electrophotographic method onto a transfer sheet. This image forming apparatus determines the fixing temperature in the fixing device according to the amount of toner per unit area placed on the transfer paper. In general, the image forming apparatus determines a maximum value of the toner amount per unit area in advance, and performs temperature adjustment at a fixing temperature at which the image having the maximum value can be reliably fixed.

  However, depending on the image to be output, excessive heating is performed at the time of output of an image that greatly falls below the assumed maximum toner amount, for example, monochrome mode using only K toner, resulting in wasted power consumption.

  Japanese Patent Application Laid-Open No. 2004-228561 discloses an image forming apparatus that reduces power consumption by adjusting a fixing temperature in accordance with the amount of applied toner of image data to be printed.

JP 2000-242107 A

  In general, in a full-color copying machine, an image is formed by superposing a plurality of toners such as CMYK (cyan, magenta, yellow, black), etc., so the amount of toner (hereinafter referred to as toner amount) on the transfer paper tends to increase. It is in. Therefore, the heat capacity of the fixing roller is increased. For this reason, when the fixing device is in a state lower than a predetermined set temperature after turning on the power or at the end of sleep, the fixing warm-up time spent until the set temperature rises is long, and printing starts. There was a problem that waiting time until.

  To solve this problem, the amount of applied toner information acquired from the image data is notified to the fixing temperature control unit several pages before fixing, and the fixing temperature is controlled by setting the fixing temperature after several pages as a target. An image forming apparatus that performs fixing temperature control without sacrificing has been proposed. In this image forming apparatus, in order to notify toner application amount information of a page to be fixed after several pages, the print image is stored by the image storage operation called a spool for the number of detected toner application amounts. Is required.

  On the other hand, in general printers, in order to maintain the quality of an output image, it is necessary to perform a process for correcting print output characteristics of a printer engine, that is, calibration according to a change in state such as an environmental change. . In particular, calibration has become an extremely important process with the recent increase in resolution and color of printers. For this reason, the calibration is automatically executed when the power is turned on or when a predetermined number of pages have been printed without any notification from the printer engine.

  When calibration is executed during printing in the image forming apparatus, it is not necessary to fix the toner, so the heater of the fixing device is turned off or the energy saving state with low energy consumption is controlled. Therefore, in an image forming apparatus that adjusts the fixing temperature in accordance with the amount of applied toner, when calibration is performed before a page with a large amount of applied toner, the fixing device is raised to a high temperature in order to fix the page with a large amount of applied toner. Nevertheless, the temperature drops during calibration. After that, as the calibration is completed, it is necessary to raise the temperature of the fixing device to a high temperature again in order to fix a page with a large amount of applied toner. For this reason, the power consumption becomes larger compared to the case where the calibration is executed before the page with a small amount of applied toner, that is, in a state where the temperature of the fixing device is low.

  The present invention has been made to solve at least one of the above problems. An object of the present invention is to provide an image forming apparatus capable of controlling the execution timing of calibration to a timing capable of suppressing power consumption in accordance with the fixing temperature.

  An image forming apparatus according to an embodiment of the present invention includes a fixing unit that thermally fixes a toner image formed by an electrophotographic method onto a recording medium, and a predetermined number of pages from the currently heat-fixed page of the toner image. Detection means for detecting the amount of applied toner on pages after several pages, and a fixing temperature required for thermal fixing of the page based on the detected amount of applied toner, and according to the calculated fixing temperature Control means for controlling the fixing means, and determination means for determining the execution timing of calibration for correcting the print output characteristics of the page based on the calculated fixing temperature.

  According to the image forming apparatus of the present invention, it is possible to control the calibration execution timing to a timing capable of suppressing power consumption according to the fixing temperature.

1 is a diagram illustrating a system configuration example including an image forming apparatus according to an exemplary embodiment. 1 is a cross-sectional view of an image forming apparatus. 1 is an example of a functional block diagram of an image forming apparatus. FIG. 10 is a diagram illustrating toner loading amount detection processing by the image forming apparatus. FIG. 6 is a diagram illustrating a relationship between a toner loading amount and a fixing temperature of the image forming apparatus. 6 is a flowchart illustrating an example of fixing temperature control processing. It is a figure which shows an example of the temperature control process of a fixing device. It is a flowchart explaining the control process of the execution timing of a calibration. It is a figure explaining the control process of the execution timing of a calibration. It is a flowchart explaining the control process of the execution timing of a calibration. It is a figure explaining the control process of the execution timing of a calibration.

Example 1
FIG. 1 is a diagram illustrating a system configuration example including an image forming apparatus according to the present embodiment.
The image forming apparatus 101 processes various input data, performs image formation (image formation) to generate image data, and prints out the generated image data. For example, the print server 102 inputs a print job to the image forming apparatus 101 in accordance with an instruction from the client PC 103 or 104. The image forming apparatus 101, the print server 102, and the client PC communicate via a network.

  FIG. 2 shows an example of a cross-sectional view of the image forming apparatus of the present embodiment. In this example, the image forming apparatus 101 is a tandem color image forming apparatus that employs an intermediate transfer member 28 that is an example of an electrophotographic color image forming apparatus. The image forming apparatus 101 adjusts the temperature of the fixing device when the toner image formed by the electrophotographic method is thermally fixed onto a recording medium (transfer paper).

  The charging unit provided in the image forming apparatus 101 includes four injection chargers 23Y, 23M, 23C, and 23K for charging the photoreceptors 22Y, 22M, 22C, and 22K for each of Y, M, C, and K colors. . Each injection charger is provided with sleeves 23YS, 23MS, 23CS, and 23KS.

  The photoconductors 22Y, 22M, 22C, and 22K are rotated by the driving force of the drive motors 40Y, 40M, 40C, and 40K being transmitted. The drive motor rotates the photoconductors 22Y, 22M, 22C, and 22K in the counterclockwise direction according to the image forming operation.

  The exposure unit included in the image forming apparatus 101 irradiates the photosensitive members 22Y, 22M, 22C, and 22K with photosensitive light from the scanner units 24Y, 24M, 24C, and 24K, and selectively selects the surfaces of the photosensitive members 22Y, 22M, 22C, and 22K. To form an electrostatic latent image.

  The developing unit included in the image forming apparatus 101 includes four developing units 26Y, 26M, 26C, and 26K that perform development for each of Y, M, C, and K colors in order to visualize the electrostatic latent image. Each developing device is provided with sleeves 26YS, 26MS, 26CS, and 26KS. Each developing device 26 is detachable.

  The transfer unit included in the image forming apparatus 101 rotates the intermediate transfer member 28 in the clockwise direction in order to transfer the single color toner image from the photosensitive member 22 to the intermediate transfer member 28. Then, the transfer unit transfers the monochromatic toner image in accordance with the rotation of the photoconductors 22Y, 22M, 22C, and 22K and the primary transfer rollers 27Y, 27M, 27C, and 27K positioned opposite to the photoconductors 22Y, 22M, 22C, and 22K. The transfer unit applies an appropriate bias voltage to the primary transfer roller 27 and also makes a difference between the rotation speed of the photoconductor 22 and the rotation speed of the intermediate transfer body 28, thereby efficiently transferring a single color toner image on the intermediate transfer body 28. Transcript to. This is called primary transfer.

  Further, the transfer unit superimposes a single color toner image on the intermediate transfer body 28 for each station, and conveys the superimposed multicolor toner image to the secondary transfer roller 29 as the intermediate transfer body 28 rotates. Further, the transfer unit sandwiches and conveys the recording medium 11 from the paper feed tray 32 to the secondary transfer roller 29, and transfers the multicolor toner image on the intermediate transfer body 28 to the recording medium 11. An appropriate bias voltage is applied to the secondary transfer roller 29 to electrostatically transfer the toner image. This is called secondary transfer. The secondary transfer roller 29 contacts the recording medium 11 at a position 29a while transferring the multicolor toner image onto the recording medium 11, and is separated to a position 29b after the printing process.

  A fixing device 31 included in the image forming apparatus 101 includes a fixing roller 32 that heats the recording medium 11 and a fixing roller 32 that heats the recording medium 11 in order to melt and fix the multicolor toner image transferred to the recording medium 11 to the recording medium 11. A pressure roller 33 is provided for press-contacting with the pressure roller 33. The fixing roller 32 and the pressure roller 33 are formed in a hollow shape, and heaters 34 and 35 are incorporated therein, respectively.

  The fixing device 31 conveys the recording medium 11 holding the multicolor toner image by the fixing roller 32 and the pressure roller 33 and applies heat and pressure to fix the toner on the recording medium 11. The fixing device 31 is provided with a temperature sensor (not shown), and is controlled so that the fixing operation is performed only when a temperature sufficient for fixing is confirmed. The recording medium 11 after toner fixing is then discharged to a discharge tray (not shown) by a discharge roller (not shown), and the image forming operation is completed.

  The cleaning unit 30 provided in the image forming apparatus 101 cleans the toner remaining on the intermediate transfer member 28. Waste toner remaining after transferring the four-color multicolor toner image formed on the intermediate transfer member 28 to the recording medium 11 is stored in a cleaner container.

FIG. 3 is an example of a functional block diagram of the image forming apparatus.
The image forming apparatus 101 includes a system controller unit 301 and a print controller unit 302. The CPU (304, 315) provided in each controller unit reads the main program from the ROM according to the initial program in the ROM (306, 316) and stores it in the RAM (306, 317). The RAM is used as a main memory for program storage and work.

  The image processing unit 308 included in the system controller unit 301 includes an image generation unit 309, a color conversion processing unit 310, a toner application amount detection unit 311, and a halftone processing unit 312. The image generation unit 309 generates raster image data that can be printed based on print data received from a computer device (not shown), and outputs RGB data and attribute data indicating the data attribute of each pixel for each pixel. To do.

  The image forming apparatus itself may be provided with a reading unit, and the image generation unit 309 may process the image data read by the reading unit instead of the image data received from the computer device or the like. This reading means includes at least a CCD (Charge Coupled Device) or a CIS (Contact Image Sensor). Further, a processing unit that performs predetermined image processing on the read image data may be provided. Further, the image forming apparatus itself may not be provided with a reading unit, but may be configured to receive image data from an external reading unit via an interface (not shown).

  The color conversion processing unit 310 performs CMYK conversion on RGB data according to the toner color, and generates CMYK data and attribute data. The image data at this stage is data indicating the amount of CMYK toner, and is represented by 8 bits, for example, 0 to 255 as a value for each pixel. As a specific value, if each color is 0, it indicates that the toner is not used, and the density increases as the value increases, and 255 means the maximum density of each color. The toner amount is 255, which means 100%, and a value obtained by adding the toner amounts of each color of CMYK indicates the applied toner amount of the pixel.

  The toner application amount detection unit 311 detects the toner application amount for the CMYK data generated by the color conversion processing unit 310. A specific method for detecting the amount of applied toner will be described later with reference to FIG. The applied toner amount detection unit 311 sends the CMYK data and the attribute data for which the applied toner amount has been detected to the halftone processing unit 312. Further, the toner application amount detection unit 311 notifies the toner application amount information to the fixing temperature calculation unit 325 when the toner application amount detection for one page is completed.

  The halftone processing unit 312 performs halftone processing on the data of each color output from the applied toner amount detection unit 311. Halftone processing is, for example, screen processing or error diffusion processing. The screen process is a process of N-value using a predetermined plurality of dither matrices and input image data. Further, the error diffusion process performs N-value conversion by comparing the input image data with a predetermined threshold value, and the difference between the input image data and the threshold value at that time is applied to the surrounding pixels to be N-valued thereafter. This is a process of spreading.

  A fixing temperature calculation unit 325 included in the system controller unit 301 calculates a minimum temperature required for fixing based on the toner application amount detected by the toner application amount detection unit 311. Note that a method for calculating the minimum temperature necessary for fixing the toner application amount page from the toner application amount information will be described later with reference to FIG.

  The printer communication IF unit 313 and the controller communication IF unit 321 are IF units for performing communication between the system controller unit 301 and the print controller unit 302. The information communicated here includes, in addition to the image data to be printed, a control signal from the system controller unit 301, toner application amount information detected by the toner application amount detection unit 311, and the like.

  A fixing temperature control unit 319 included in the print controller unit 302 controls the temperature of the fixing device 320 based on the target temperature determined by the fixing temperature calculation unit 325. In order to maintain the quality of the output image, the calibration execution unit 324 executes a process for correcting the print output characteristics of the page, that is, calibration according to a state change such as an environmental change. The calibration control unit 323 controls the execution timing of a calibration scheduled to be performed upon completion of printing a predetermined number of sheets in consideration of the fixing temperature. A detailed procedure of the calibration execution timing control process will be described later with reference to FIG.

FIG. 4 is a diagram for explaining toner application amount detection processing by the image forming apparatus.
The amount of applied toner is the amount of toner per unit area, and will be described with the unit being%. Specifically, when the maximum value of each color of CMYK is set to 100%, when the maximum value is overlapped with two colors, the applied toner amount is defined as 200% for that pixel. Since each color gradation is provided, the applied toner amount can take a value between 0% and 100% for each color. For example, in the full-color printing mode, the maximum toner amount increases in the case of an image that fully uses CMYK four-color toner, and in the case of a monochrome image of K single color, the maximum toner amount decreases.

  First, the toner application amount detection unit 311 receives CMYK data and calculates a toner application amount necessary for each pixel. FIG. 4A shows a part of image data for one page. A minimum unit denoted by reference numeral 401 represents one pixel, and reference numeral 402 represents a pixel block of 3 × 3 pixel units. In addition, the numerical value indicated in the frame within one pixel in FIG. 4A indicates the toner applied amount for each pixel detected by the toner applied amount detecting unit 311.

  Next, the toner application amount detection unit 311 calculates an average value of the toner application amount in the pixel block in units of 3 × 3 pixel blocks. Here, the reason why the average value in the pixel block is calculated is that the temperature necessary for fixing an image generally depends on the amount of toner within a certain range, not the amount of applied toner per pixel. It is. In this example, the applied toner amount detection unit 311 calculates the average value in the pixel block, but the minimum value and the maximum value in the pixel block may be used. Note that reference numeral 403 in FIG. 4B represents one pixel block, and the numerical value described in the frame of the one pixel block represents an average value of the applied toner amount in each pixel block.

  Next, when the applied toner amount detection unit 311 finishes calculating the average value of the applied toner amount in the pixel block for one page, the maximum value is selected from the average values of all the blocks in one page. This is notified to the fixing temperature calculation unit 325 as the toner applied amount information of the page.

  FIG. 5 is a diagram illustrating the relationship between the toner application amount and the fixing temperature of the image forming apparatus. The horizontal axis represents the amount of applied toner, and the vertical axis represents the temperature required for fixing. In order to fix the toner without fixing failure, it is necessary to set the temperature of the fixing device to a fixing temperature at which the maximum value of the applied toner amount in the target page can be fixed reliably. Since the maximum amount of applied toner varies depending on the image data to be printed, the temperature required for fixing also differs for each image data. The larger the maximum amount of applied toner, the higher the required temperature.

  Referring to the graph of FIG. 5, for example, when the detection result by the toner application amount detection unit 311 is 200%, the minimum temperature required for fixing is T1, and when the detection result is 100%, T5 is required for fixing the target page. It can be seen that the minimum temperature is reached. That is, the fixing temperature is higher as the toner amount is larger, and the fixing temperature is lower as the toner amount is smaller.

  If the maximum amount of applied toner that appears in a printed page is raised to a temperature at which fixing is possible, problems such as fixing failure do not occur in the entire image. Therefore, the minimum temperature required for fixing the target page can be obtained from the applied toner amount information detected by the applied toner amount detection unit 311 described above.

  In this embodiment, the applied amount / temperature information indicating the relationship between the applied toner amount and the fixing temperature shown in the graph of FIG. 5 is stored in advance in the storage unit 307, the RAM 306, or the like in the form of a lookup table, for example. The minimum fixing temperature required for fixing the target page based on the applied toner amount information detected by the applied toner amount detection unit 311 and the stored applied amount / temperature information by the fixing temperature control unit 319. Is calculated.

  The image forming apparatus according to the present exemplary embodiment detects the amount of applied toner on a predetermined number of pages after the currently heat-fixed page in advance in order to control the temperature of the fixing unit without reducing productivity. In this example, it is assumed that the toner application amount of a page to be fixed after 4 pages is detected in advance with respect to the currently fixed page. In addition, immediately after the start of printing, if the temperature of the fixing device is controlled after detecting the amount of applied toner, the user cannot immediately respond to the printing instruction from the user, and the productivity is lowered. For this reason, the image forming apparatus does not control the fixing temperature until the fourth page from which printing is started, and controls the maximum toner amount that can be considered as an image forming apparatus to a fixing temperature at which fixing is possible. Temperature control is performed by detecting the loading amount.

  FIG. 6 is a flowchart illustrating an example of fixing temperature control processing by the image forming apparatus. FIG. 6A shows processing executed in accordance with the control of the CPU 304 of the system controller unit.

  First, the CPU 304 receives a print job input from the outside, such as an image reading unit or a PC, and starts a printing process (step S601). Subsequently, the CPU 304 determines whether or not the page (target page) to be subjected to image processing is the Nth page (fifth page) on which the temperature control is started (step S602). If the target page is not the fifth page or later for starting the temperature control, the process returns to step S602.

  If the target page is the fifth page or later on which temperature control is started, the process proceeds to step S603. Then, the toner application amount detection unit 311 detects the toner application amount of the page by, for example, the method described with reference to FIG. 4 (step S603). Note that the image processing apparatus 101 does not detect the toner application amount by the toner application amount detection unit 311 for the data up to the fourth page for which the temperature adjustment control is not executed, and fixes at the maximum temperature within the controllable temperature range. I do.

  Next, the minimum temperature (necessary fixing temperature) necessary for the fixing temperature determination unit 325 to fix the target page based on the toner application amount detected in step S603 has been described with reference to FIG. It calculates by the method (step S604).

  Next, the CPU 304 notifies the CPU 315 of the print controller 302 of the necessary fixing temperature calculated in step S603 via the print communication IF unit 313 (step S605). The CPU 304 determines whether there is a next page (step S606). If there is a next page, the process returns to step S603. If there is no next page, the process ends.

FIG. 6B shows processing executed in accordance with the control of the CPU 315 of the print controller unit.
First, the CPU 315 determines whether there is a print instruction from the system controller unit 301 (step S621). If there is no print instruction from the system controller unit 301, the process returns to step S621. If there is a print instruction from the system controller unit 301, the process proceeds to step S622.

  Next, the fixing temperature control unit 319 controls the temperature of the fixing device to a temperature Tmax at which the maximum toner amount can be fixed, and starts printing (step S622). The reason for controlling the temperature of the fixing device to the temperature Tmax is to print the first four pages without reducing productivity.

  Next, the CPU 315 determines whether the necessary fixing temperature has been received from the system controller unit 301 (step S623). If the necessary fixing temperature has not been received from the system controller, the process returns to step S623. If the necessary fixing temperature is received from the system controller, the process proceeds to step S624. The necessary fixing temperature to be received is a fixing temperature necessary for fixing a page to be fixed four pages after the currently fixed page.

  Next, the fixing temperature control unit 319 determines, as a control target page, a page having the maximum necessary fixing temperature among the pages for which the necessary fixing temperature has already been notified (step S624). The fixing temperature control unit 319 controls the temperature of the fixing device based on the current fixing temperature and the necessary fixing temperature of the control target page determined in step S624. Specifically, when it is necessary to reach the target temperature (required fixing temperature) by the control target page, the fixing temperature control unit 319 increases the temperature of the fixing device. When the fixing temperature can be lowered with respect to the target temperature, the fixing temperature control unit 319 reduces the temperature of the fixing device.

  Next, the CPU 315 determines whether there is a next page (step S626). If there is a next page, the process returns to step S623. If there is no next page, the process ends.

  FIG. 7 is a diagram showing an example of a temperature control process of the fixing device according to the flowchart shown in FIG. The horizontal axis represents the number of printed pages, and the vertical axis represents the fixing temperature when fixing the page. The amount of applied toner is expressed in% below the number of pages.

  In this example, it is assumed that the image forming apparatus 101 receives 14 pages of data as print target data. Further, it is assumed that the amount of applied toner on the 5th and 14th pages is 200%, and the amount of applied toner on the other pages is 100%.

  The relationship between the amount of applied toner and the minimum temperature required for fixing is as shown in FIG. 5. The temperature required for fixing an image with a toner applied amount of 200% is T1, and the amount of applied toner is 100%. The temperature necessary for fixing the image is T5.

  As shown in FIG. 7, the system controller unit 301 fixes the first to fourth pages at the maximum temperature T1 so as not to reduce the productivity. The system controller 301 detects the amount of applied toner on the fifth page while fixing the first page so that the fixing temperature is controlled from the fifth page. Further, when fixing the fifth page, the system controller unit 301 detects the amount of applied toner from the fifth page to the fourth page ahead, that is, the ninth page, and controls the fixing temperature using the necessary fixing temperature as a target temperature. Notification to the unit 319. In this example, T5 is notified as the target temperature.

  The detection of the applied toner amount when fixing the fifth page is image data from the fourth page ahead, that is, from the sixth page to the ninth page. The amount of applied toner in the 6th to 9th page data is 100%, and the target temperature is T5. Therefore, the fixing temperature control unit 319 determines that the fixing temperature can be lowered from the current temperature T1.

  On the other hand, when fixing the 10th page, the system controller unit 301 detects the amount of applied toner on the 14th page, and notifies the fixing temperature control unit 319 of the necessary fixing temperature as a target temperature. The amount of applied toner on the 14th page is 200%, and in order to print the 14th page, the fixing temperature needs to be T1. Since it is necessary to increase the temperature from the 11th page in order to set the temperature T1 on the 14th page, the fixing temperature control unit 319 performs control to increase the temperature of the fixing device. By performing the control as described above, it is possible to control the temperature of the fixing device in accordance with the amount of applied toner without reducing productivity, and to reduce power consumption.

Next, processing for controlling the execution timing of calibration during printing in the present embodiment will be described.
In this embodiment, when printing is performed continuously and the environmental density and elapsed time satisfy predetermined conditions, the printing operation is temporarily interrupted regardless of the printing operation, and calibration is automatically performed. Shall. As a result, it is possible to suppress variations in print density due to changes in conditions such as environmental temperature.

  In this embodiment, the calibration execution unit 324 generates patch pattern data, and forms a visible patch image with toner on the intermediate transfer member 28. Then, the visible image of the patch is optically read, and the calibration execution unit 324 performs calibration based on the read result. Note that the position where the patch is formed need not be on the intermediate transfer member, and the density of the patch based on the latent image on the photosensitive drum may be obtained by a potential sensor.

  FIG. 8 is a flowchart for explaining calibration timing control processing by the image forming apparatus according to the first embodiment. Each step of the flowchart of FIG. 8 is executed by the CPU 304, the CPU 315, and the calibration control unit 323 according to the control of each CPU.

  First, the CPU 304 determines whether a print job has been received (step S801). If no print job has been received, the process returns to step S801. If a print job is received, the CPU 304 executes a print process (step S802).

  The CPU 304 determines whether or not the predetermined number of printed sheets that need to be calibrated has been reached (step S803). If the predetermined number of prints that need to be calibrated has not been reached, the process returns to step S803. If the predetermined number of printed sheets that need to be calibrated is reached, the process advances to step S804. At this time, since the number of printed sheets has reached a predetermined number that needs to be calibrated, calibration needs to be performed.

  The calibration control unit 323 determines whether the fixing temperature of the page printed immediately after execution of the scheduled calibration is equal to or higher than a predetermined threshold (step S804). In this example, the threshold is set to A in advance. If the fixing temperature of the page to be printed immediately after execution of the scheduled calibration is not equal to or higher than the threshold value A, the process proceeds to step S806. Then, the calibration control unit 323 does not change the calibration execution timing (step S806).

  If the fixing temperature of the page to be printed immediately after execution of the scheduled calibration is equal to or higher than the threshold value A, the process proceeds to step S805. Then, the calibration control unit 323 detects the amount of applied toner in advance and sets the calibration execution timing before the printing process of the page having the minimum necessary fixing temperature among the pages for which the necessary fixing temperature has been calculated. Change (step S805). That is, the calibration control unit 323 changes the calibration execution timing before printing out a page corresponding to the minimum required fixing temperature among the pages for which the necessary fixing temperature has been calculated at the execution timing. As a result, the power consumption during the control of the fixing device 320 performed immediately after the execution of the calibration can be minimized.

FIG. 9 is a diagram illustrating a calibration execution timing control process according to the flowchart of FIG.
FIG. 9A is an example of a fixing temperature control process when printing a certain print job. FIG. 9 shows an example of temperature control during printing. In this example, the number of pages is set to 1p to 14p, but the description will be made assuming that the temperature control is already performed on the page indicated by 1p. The threshold A used for controlling the calibration execution timing will be described as the temperature T2.

  Assume that during the execution of a print job, a predetermined number of sheets that need to be calibrated is reached after printing the ninth page shown in FIG. The calibration control unit 323 refers to the fixing temperature of the page to be printed next to the scheduled calibration execution timing. Specifically, the calibration control unit 323 refers to the fixing temperature of the 10th page shown in FIG. In this example, the fixing temperature of the 10th page is T1, which is equal to or higher than the threshold A. Therefore, the determination process in step S804 in FIG. 8 is Yes, and the process branches to step S805.

  At this time, the amount of applied toner has already been detected, and the necessary fixing temperature is determined from the 10th page to the 14th page after 4 pages. Therefore, the calibration control unit 323 sets the calibration execution timing before printing the 14th page having the lowest necessary fixing temperature among the 10th to 14th pages.

  FIG. 9B shows an example of temperature control when the calibration is executed 10 pages before without applying this embodiment. FIG. 9C shows an example of temperature control when the present embodiment is applied and the calibration scheduled to be executed before page 10 is changed before page 14.

  By performing the calibration execution timing control process of the present embodiment described above, it is possible to perform temperature control including calibration in the image forming apparatus that controls the fixing temperature based on the image data. As a result, power consumption during calibration can be reduced.

(Example 2)
The image forming apparatus may be in an operation mode in which the calibration execution timing cannot be changed. For example, when the image forming apparatus is set to an image quality priority mode that prioritizes image quality, it is necessary to reliably execute calibration after printing a predetermined number of sheets. Therefore, the image forming apparatus according to the second embodiment performs temperature control that reduces power consumption when the operation mode is set so that the calibration execution timing cannot be changed.

  FIG. 10 is a flowchart illustrating a calibration execution timing control process performed by the image forming apparatus according to the second embodiment. Each step of the flowchart of FIG. 10 is executed by the CPU 304, the CPU 315, and the calibration control unit 323 according to the control of each CPU.

  Steps S1001 and S1002 are the same as steps S801 and S803 in FIG. In step S <b> 1002, the CPU 304 determines whether a predetermined number of prints that require execution of calibration have been performed. Specifically, the CPU 304 determines whether or not the page for which the toner application amount is detected in advance is a page to be printed at the scheduled calibration execution timing. For example, in FIG. 11, when the execution of calibration is scheduled when the 10th page is printed, the CPU 304 performs a predetermined number of prints that need to be calibrated when the 6th page is printed. Judge that it was broken.

  If the predetermined number of prints that require execution of calibration have not been performed, the process returns to step S1002. If a predetermined number of prints that require execution of calibration have been performed, the process proceeds to step S1004.

  Next, the CPU 304 determines whether or not the operation mode of the image forming apparatus is an operation mode in which the calibration execution timing can be changed (step S1004). That is, the CPU 304 executes the determination process in step S1004 when the page on which the toner amount is detected in advance is a page corresponding to the calibration execution timing. If the operation mode of the image forming apparatus is an operation mode in which the calibration execution timing can be changed, the process proceeds to step S1005. Steps S1005 to S1007 are the same as steps S804 to S806 in FIG.

  If the operation mode of the image forming apparatus is not an operation mode in which the calibration execution timing can be changed, the process advances to step S1008. Then, the CPU 305 notifies the fixing temperature control unit 319 of the execution of calibration as the execution of printing of the page with the applied toner amount 0 (step S1008). That is, the CPU 305 assumes that there is a virtual page between the ninth page printed just before the calibration is executed and the tenth page printed just after the calibration is executed, and the toner application amount of the virtual page Is notified to the fixing temperature control unit 319. The amount of applied toner on the virtual page notified by the CPU 305 is not limited to zero. The CPU 305 may notify a predetermined amount equal to or less than the toner application amount of the page for which the toner application amount has been detected as the toner application amount of the virtual page.

  The fixing temperature control unit 319 executes temperature control based on the notified information that the applied amount of toner on the virtual page is 0. Therefore, the temperature control performed when the sixth page is printed is executed with T5, which is the maximum value of the necessary fixing temperatures of the pages from the seventh page to the virtual page, as a target temperature. Thus, it is possible to reduce power consumption corresponding to the temperature that was scheduled to be raised for page fixing immediately after execution of calibration, that is, power consumption corresponding to the portion indicated by reference numeral 500 in FIG.

  By performing the control as described above, it becomes possible to perform temperature control including calibration even in the image forming apparatus when the calibration timing cannot be changed, and it is possible to reduce power consumption during calibration execution. it can.

(Other examples)
The present invention can also be realized by executing the following processing. Processing for supplying software (computer program) that realizes the functions of the above-described embodiment to a system or apparatus via a network or various storage media, and for the computer of the system or apparatus (or CPU, MPU, etc.) to read and execute the program It is. In this case, the program and the storage medium storing the program constitute the present invention.

101 Image forming apparatus 102 Print server 103, 104 Client PC

Claims (10)

Fixing means for thermally fixing a toner image formed by electrophotography on a recording medium;
Detecting means for detecting in advance the amount of applied toner on a predetermined number of pages after the currently heat-fixed page of the toner image pages;
A control unit that calculates a fixing temperature necessary for thermal fixing of the page based on the detected toner application amount, and controls the fixing unit according to the calculated fixing temperature;
An image forming apparatus comprising: a determination unit that determines a calibration execution timing for correcting a print output characteristic of a page based on the calculated fixing temperature. 2. The image according to claim 1, wherein the control unit controls the fixing unit using the fixing temperature of a page corresponding to the maximum fixing temperature among the pages for which the fixing temperature has been calculated as a target temperature. Forming equipment. The determination unit determines the execution timing of the calibration to a timing at which the power consumption during the control of the fixing unit performed immediately after the calibration is minimized. The image forming apparatus according to 2. The determination means changes the execution timing of the calibration before printing out a page corresponding to the minimum fixing temperature among the pages for which the fixing temperature has been calculated at the execution timing. The image forming apparatus according to any one of 1 to 3. The determination unit determines whether a fixing temperature of a page printed out immediately after execution of the calibration is equal to or higher than a threshold value, and determines the execution timing of the calibration when the fixing temperature of the page is equal to or higher than the threshold value. The image forming apparatus according to claim 4, wherein the image forming apparatus is changed before printing a page corresponding to the minimum fixing temperature. The determining unit is configured to execute the calibration with respect to the control unit when the image forming apparatus is in an operation mode in which the calibration execution timing cannot be changed. Notify you as a print run,
The image forming apparatus according to claim 1, wherein the control unit calculates the fixing temperature using the predetermined amount of applied toner. The determination unit cannot change the calibration execution timing when the page on which the toner amount is detected in advance is a page corresponding to the calibration execution timing. The image forming apparatus according to claim 6, wherein it is determined whether the operation mode is set. The image forming apparatus according to claim 6, wherein the predetermined amount is 0. A control method for an image forming apparatus comprising a fixing means for thermally fixing a toner image formed by electrophotography on a recording medium,
Detecting in advance the amount of applied toner of a predetermined number of pages from the currently heat-fixed pages of the toner image pages;
Calculating a fixing temperature required for thermal fixing of the page based on the detected amount of applied toner, and controlling the fixing unit in accordance with the calculated fixing temperature;
And a step of determining a calibration execution timing for correcting the print output characteristic of the page based on the calculated fixing temperature.   A computer program for causing a computer to execute the control method according to claim 9.

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