JP2016024408A - Image forming apparatus, control device, and control method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately adjust the fixation temperature even when a control for skipping a blank page is performed.SOLUTION: An image forming apparatus having a fixation device for thermally fixing a toner image on a recording medium comprises: detection means for detecting a toner applied amount for an input image; skip control means for performing a control for skipping image formation processing and fixation processing of an input image when the input image is a blank image; calculation means for calculating a target temperature of the fixation device on the basis of the toner applied amount detected by the detection means; and control means for controlling the temperature of the fixation device on the basis of the target temperature calculated by the calculation means. When the skip control means performs a control for skipping a prescribed number of sheets continuously, the control means controls the temperature of the fixation device on the basis of a prescribed target temperature in place of using the target temperature calculated by the calculation means.SELECTED DRAWING: Figure 7

Description

  The present invention relates to image fixing control.

  In recent years, regulations for power saving have become stricter, and further reduction of power consumption is required for image forming apparatuses. That is, the image forming apparatus is required to further reduce power consumption while maintaining a fixing temperature at which an image can be reliably fixed. In view of this, a technique for controlling the fixing temperature of the fixing device in accordance with the amount of applied toner determined from the image data has been proposed. For example, Patent Document 1 discloses a method of determining whether input image data is a photographic image or a character image, and fixing the photographic image by raising the fixing temperature of the fixing device compared to fixing the character image. ing. In Patent Document 1, it is possible to reduce the power consumption of the fixing device by adjusting the fixing temperature according to the amount of applied toner in the image data.

JP 2000-242107 A

  By the way, in the image forming apparatus, when a document to be output includes a blank page, blank page skip control for skipping print output for the blank page may be performed. However, when performing blank page skip control in the technique described in Patent Document 1, the fixing temperature cannot be appropriately controlled. Specifically, as a result of performing skip control, when a period during which fixing processing is not performed occurs, temperature control that appropriately realizes power saving may not be performed.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide a technique capable of appropriately adjusting the fixing temperature even when blank page skip control is performed. .

  In order to solve the above-described problems, an image forming apparatus according to the present invention has the following configuration. That is, in an image forming apparatus having a fixing device that thermally fixes a toner image on a recording medium, a detection unit that detects the amount of toner applied to the input image, and an image of the input image when the input image is a blank image A skip control unit that controls to skip the forming process and the fixing process; a calculation unit that calculates a target temperature of the fixing device based on a toner application amount detected by the detection unit; and a target temperature calculated by the calculation unit. And a control means for controlling the temperature of the fixing device based on the target temperature calculated by the calculation means when the control means controls the skip control means to skip a predetermined number of sheets continuously. Instead of using, the temperature of the fixing device is controlled based on a predetermined target temperature.

  According to the present invention, it is possible to provide a technique capable of appropriately adjusting the fixing temperature even when performing blank page skip control.

1 is a diagram illustrating a system configuration including an image forming apparatus according to a first embodiment. 1 is a cross-sectional view of a tandem color image forming apparatus. 1 is a block diagram of a configuration of an image forming apparatus. 6 is a diagram illustrating a toner application amount detection method in the image forming apparatus. FIG. FIG. 6 is a diagram illustrating a relationship between a toner applied amount and a fixing temperature. It is a figure which shows the structure of a blank paper determination part. It is a flowchart of fixing temperature control. 6 is a flowchart illustrating an example of generation processing of fixing temperature control information. It is a figure which shows an example of the temperature control of the fixing device in printing operation. FIG. 6 is a diagram illustrating an example of a document for blank page determination and a document for content determination. 6 is a diagram illustrating an example of fixing temperature control information. FIG.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. The following embodiments are merely examples, and are not intended to limit the scope of the present invention.

(First embodiment)
As a first embodiment of an image forming apparatus according to the present invention, a tandem color image forming apparatus will be described below as an example.

<System configuration>
FIG. 1 is a diagram showing a system configuration including an electrophotographic image forming apparatus 101 according to the first embodiment.

  The image forming apparatus 101 is an apparatus that processes various input data, forms an image on a print medium such as paper, and outputs a printed matter. The print server 102 is connected to the image forming apparatus 101 via a network, and the client PC 103 is connected to the image forming apparatus 101 via the network in the same manner as the print server 102.

  FIG. 2 is a cross-sectional view of the tandem color image forming apparatus 101. The tandem color image forming apparatus 101 forms an image by transferring the toner image to the recording medium 11 via the intermediate transfer body 28.

  The charging unit includes four photoreceptors 22Y, 22M, 22C, and 22K for charging the respective photoreceptors for each color of yellow (Y), magenta (M), cyan (C), and black (K). Injection chargers 23Y, 23M, 23C, and 23K. 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. In FIG. 2, each drive motor rotates the photoconductors 22Y, 22M, 22C, and 22K in the counterclockwise direction according to the image forming operation.

  The exposure unit uses the scanner units 24Y, 24M, 24C, and 24K to irradiate the photosensitive members 22Y, 22M, 22C, and 22K with photosensitive light, and selectively exposes the surfaces of the photosensitive members 22Y, 22M, 22C, and 22K. To do. Thereby, an electrostatic latent image is formed on each photoconductor.

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

  The transfer unit transfers the single color toner image from the photosensitive member 22 to the intermediate transfer member 28. In FIG. 2, the intermediate transfer member 28 rotates in the clockwise direction. Then, the monochromatic toner images are sequentially transferred to the intermediate transfer body 28 as the photoconductors 22Y, 22M, 22C, and 22K and the primary transfer rollers 27Y, 27M, 27C, and 27K positioned opposite to each other rotate. This is called primary transfer. In addition, by applying an appropriate bias voltage to the primary transfer roller 27 and making a difference between the rotation speed of the photoconductor 22 and the rotation speed of the intermediate transfer body 28, the monochromatic toner image is efficiently transferred onto the intermediate transfer body 28. can do.

  The transfer unit superimposes the single color toner image on the intermediate transfer body 28 and conveys the superimposed multicolor toner image to the secondary transfer roller 29 as the intermediate transfer body 28 rotates. Further, the recording medium 11 such as paper is nipped and conveyed from the paper feed tray to the secondary transfer roller 29, and the multicolor toner image on the intermediate transfer body 28 is transferred to the recording medium 11. At this time, 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.

  The fixing unit is a functional unit that thermally fixes the multicolor toner image transferred to the recording medium 11 to the recording medium 11. For this purpose, the fixing unit includes a fixing roller 32 that heats the recording medium 11 and a pressure roller 33 that presses the recording medium 11 against the fixing roller 32. The fixing roller 32 and the pressure roller 33 are formed in a hollow shape, and heaters 34 and 35 are incorporated therein. 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.

  Note that a temperature sensor (not shown) is attached to the fixing unit, and the fixing operation is controlled only when a temperature sufficient for fixing is confirmed. Thereafter, the recording medium 11 after toner fixing is discharged to a discharge tray (not shown) by a discharge roller (not shown), and the image forming operation ends.

  The cleaning unit 30 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 body 28 to the recording medium 11 is removed from the recording medium 11 by cleaning and stored in a cleaner container.

<Configuration of image forming apparatus>
FIG. 3 is a block diagram of the configuration of the image forming apparatus 101. The image forming apparatus 101 is roughly divided into a controller unit 301 (image processing unit) and a printing unit 302 (image forming unit). The controller unit 301 is a functional unit that receives print data from an external device and generates image data (raster image data) to be provided to the print unit 302. The print unit 302 is a functional unit that forms an image on a recording medium such as paper based on image data received from the controller unit 301.

  Each of the controller unit 301 and the print unit 302 includes a CPU, a ROM, a RAM, and a storage unit for executing a program. Each CPU reads the main program from the ROM according to the initial program stored in the ROM and stores it in the RAM. The RAM is used as a main memory for program storage and work.

  The image generation unit 309 generates raster image data that can be printed based on print data (print job) received from the client PC 103 or the like. The raster image data includes RGB data and attribute data indicating the data attribute of each pixel. The image generation unit 309 may be configured to handle image data read by a reading unit (scanner) installed in the image forming apparatus 101 itself. The reading unit herein may be a CCD (Charged Couple Device) reading unit or a CIS (Contact Image Sensor) reading unit. Further, a processing unit that performs predetermined image processing on the read image data may be provided. Further, the image forming apparatus 101 itself 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 the RGB data according to the toner color, and generates CMYK data. The image data at this stage is data indicating the amount of CMYK toner, and is expressed by, for example, 0 to 255 (8-bit value) in units of pixels. For example, if the values of all the colors are all “0”, it indicates that the toner is not used, the density increases as the value increases, and “255” means the maximum density.

  The applied toner amount detection unit 311 detects (derived) the applied toner amount for the CMYK data generated by the color conversion processing unit 310. In the following description, the applied toner amount is represented by a ratio (unit:%) when the maximum value of the toner weight per unit area is 100%. In each color of the pixel unit, the value “255” corresponds to 100% of the applied toner amount, and a value obtained by adding the applied toner amounts of the CMYK colors represents the applied toner amount of the pixel.

  For example, when two colors of the maximum value (100%) are overlapped, the applied toner amount of the pixel is 200%. Since each color has gradation, each color can take a value between 0% and 100%. For example, in the full-color printing mode, the maximum amount of applied toner increases in the case of an image that fully uses CMYK four-color toner. On the other hand, for example, in the case of a monochrome image of K single color, the maximum amount of applied toner is smaller. The applied toner amount detection unit 311 detects the applied toner amount per unit area in the entire page, and detects the maximum value as applied toner amount information. When the applied toner amount detection for one page is completed, the applied toner amount information is notified to the fixing temperature calculation unit 325.

  The fixing temperature calculation unit 325 is a functional unit that calculates the minimum temperature required for fixing by the fixing device 320 based on the toner application amount detected by the toner application amount detection unit 311. A specific method for calculating the minimum temperature will be described later with reference to FIG.

  Here, it has been described that the applied amount information detected by the applied toner amount detection unit 311 is notified to the fixing temperature calculation unit 325 to calculate the temperature information. However, the printing unit 302 may be configured to calculate the fixing temperature by notifying the printing unit 302 of the loading amount information detected by the toner loading amount detection unit 311 via the communication line 303. In other words, any configuration that can transmit the information for controlling the fixing temperature and determine the fixing temperature is sufficient. The content of the information to be transmitted may be information corresponding to fixing temperature control information shown in FIG.

  The halftone processing unit 312 performs halftone processing for each color of the CMYK data generated by the color conversion processing unit 310. As a specific configuration of the halftone processing unit, there is a screen processing method or an error diffusion processing method. In the screen processing, a predetermined plurality of dither matrices and input image data are used to make an N-value. 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.

  The blank document determination unit 327 is a functional unit that determines whether the document set on the document table is a blank sheet. The blank page skip control unit 328 is a functional unit that performs control to skip halftone image print output (image formation processing and fixing processing) processed by the halftone processing unit 312 based on the determination result of the blank document determination unit 327. .

  The printer communication IF unit 313 and the controller communication IF unit 321 are IF units for performing communication between the controller unit 301 and the print unit 302. The information communicated here includes various control signals, toner application amount information detected by the toner application amount detection unit 311 and the like in addition to image data (raster image data) to be printed. Also included are various information related to fixing device temperature control, such as detection results of copy-prohibited documents and image composition setting information.

  The fixing temperature control unit 319 is a functional unit that controls the temperature of the fixing device 320. Specifically, temperature control is performed based on the target temperature determined by the fixing temperature calculation unit 325, the applied toner amount information, and the fixing temperature control information 1100 shown in FIG.

<Detection of applied toner amount>
FIG. 4 is a diagram for explaining a toner application amount detection method in the image forming apparatus 101. In the following description, the applied toner amount is expressed as a ratio (unit:%) where the maximum value of the toner weight per unit area is 100%. In each color of the pixel unit, the value “255” corresponds to 100% of the applied toner amount, and a value obtained by adding the applied toner amounts of the CMYK colors represents the applied toner amount of the pixel.

  For example, when two colors of the maximum value (100%) are overlapped, the applied toner amount of the pixel is 200%. Since each color has gradation, each color can take a value between 0% and 100%. For example, in the full-color printing mode, the maximum amount of applied toner increases in the case of an image that fully uses CMYK four-color toner. On the other hand, for example, in the case of a monochrome image of K single color, the maximum amount of applied toner is smaller.

  When the applied toner amount detection unit 311 receives CMYK data (raster image data) generated by the color conversion processing unit 310, the applied toner amount detection unit 311 calculates a required applied toner amount for each pixel. FIG. 4A shows a part of image data processed by the toner application amount detection unit 311. The minimum unit indicated by 601 represents one pixel, and 602 represents a pixel block of 3 × 3 pixel units. In addition, the numerical value shown in each pixel in FIG. 4A represents the toner application amount for each pixel detected by the toner application amount detection unit 311.

  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 average value in the pixel block is calculated because 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. is there. For this reason, the average value in the pixel block is calculated here, but the minimum value and the maximum value in the pixel block may be used. One rectangle 403 in FIG. 4B corresponds to the 3 × 3 pixel block 402 in FIG. That is, FIG. 4B is a graph in which the average amount of applied toner for each pixel block is calculated with respect to FIG. 4A, and the numerical value described in the pixel block is the average of the applied toner amount of the pixel block. Represents a value.

  The applied toner amount detection unit 311 completes the calculation of the average applied toner amount in the pixel block for the image data for one page, and the applied toner amount having the maximum value in all the pixel blocks in the image data. The amount is determined as toner applied amount information of the target page. The determined toner application amount information is notified to the fixing temperature calculation unit 325.

<Fixing temperature determination based on toner loading>
As described above, the amount of applied toner means the amount of toner per unit area on the image. In order to fix the toner on the recording medium without fixing failure, it is necessary to set the temperature of the fixing device 320 to a fixing temperature at which the pixel (or pixel block) having the maximum toner amount in the target page can be fixed reliably. is there. Since the maximum amount of applied toner differs depending on the image data to be printed, the temperature required for fixing also differs for each image data. Specifically, the required temperature increases as the maximum amount of applied toner increases.

  FIG. 5 is a diagram showing the relationship between the toner application amount and the fixing temperature. The horizontal axis represents the amount of applied toner, and the vertical axis represents the temperature required for fixing. For example, it can be read that when the detection result by the toner application amount detection unit is 200%, the minimum temperature required for fixing is T1, and when the detection result is 100%, T5 is the minimum temperature required for fixing the target page.

  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, it is possible to obtain the minimum temperature required for fixing the page to be output based on the applied toner amount information detected by the above-described applied toner amount detection unit.

  Note that the relationship (relation data) shown in the graph of FIG. 5 is used in the temperature control of the fixing device, and therefore, it may be stored in the storage unit 307, the RAM 306, or the like in the form of a lookup table (LUT), for example.

<Blank detection>
FIG. 6A is a diagram illustrating a configuration of the blank document determination unit 327. The blank document determination unit 327 includes a blank page determination information generation unit 610 including a histogram generation unit 611 and an edge number counting unit 612, and a blank page determination unit 613. For example, document image data read by a scanner included in the image forming apparatus 101 is input to the blank document determination unit 327.

  The blank document determination unit 327 generates a histogram and edge number count value of the input image data, and outputs the generated histogram and edge number count value to the blank sheet determination unit 613.

  In the blank page determination unit 613, as shown in FIG. 6B, a document that has been determined to be content through histogram analysis is determined as content regardless of edge number analysis. The final determination of a document determined as a blank page candidate by histogram analysis differs depending on the edge number analysis. In other words, if the histogram analysis result is a blank page candidate determination and the edge analysis is also a blank page candidate determination, a blank page determination is made. On the other hand, even if the histogram analysis result is blank page candidate determination, content determination is made if the edge analysis result is content determination.

  The histogram analysis is obtained for each divided region of the image data, and the variance value is calculated from the calculation of the average value of the pixel values for each divided region and the calculated average value. In the histogram analysis, content determination is performed by comparing an average value and a variance value for each divided region with a threshold value.

  In the edge analysis, a region having the maximum value is detected from the number of edges for each divided region. The number of edges in this area is set to the maximum value, and the number of edges in each divided area is normalized with this maximum value. After normalization, content determination or blank page candidate determination is performed by comparing with the threshold value as the minimum value of the smallest value.

  Based on such histogram analysis and edge number count analysis, it is determined that the blank original 1000 or the colored paper original 1001 shown in FIG. 10A is a blank original. On the other hand, a document as shown in FIG. 10B is determined as a content document if it includes content such as characters and figures.

  Here, the configuration for determining a blank document based on the histogram analysis and the edge number counting analysis has been described. However, any existing method can be used to determine a blank document.

<Fixing temperature control based on toner load>
FIG. 7 is a flowchart illustrating a fixing temperature control process using the toner application amount detection result in the image forming apparatus 101 according to the first embodiment. S701 to S716 indicate processes executed under the control of the CPU 304 of the controller unit 301. On the other hand, S721 to S727 indicate processing executed under the control of the CPU 315 of the printing unit 302.

  First, processing in the controller unit 301 will be described. In step S <b> 701, the CPU 304 receives a setting as to whether or not to skip a blank page based on a blank page detection result via the operation unit of the image forming apparatus 101 or the operation unit of the client PC 103. If blank page skip is not performed, the process of step S701 is omitted.

  In step S702, the CPU 304 determines whether an instruction to start printing has been issued. When an instruction to start printing is given, a print job input from an image reading unit of the image forming apparatus 101 or an external device such as the client PC 103 is received and printing processing is started.

  In step S <b> 703, the CPU 304 controls the image generation unit 309 to generate raster image data that can be printed from the print data received from the client PC 103. Then, RGB data that is the generated raster image data is output for each pixel. In step S703, the original may be read using the reading unit of the image forming apparatus 101, and RGB data may be generated from the read data.

  In step S704, the CPU 304 controls the blank page determination unit 372 to determine whether the image data generated in step S703 is blank page image data. In step S <b> 705, if the CPU 304 determines that the blank page image is a blank page image, the CPU 304 proceeds to step S <b> 706. If it is determined that the image is not a blank image, the process proceeds to step S709.

  In step S706, the CPU 304 determines whether to skip printing of a blank image. If printing of a blank image is skipped, the process proceeds to step S708. On the other hand, if printing of a blank image is not skipped, the process proceeds to step S709.

  In step S <b> 708, the CPU 304 stores information indicating that the image is a skip image in the RAM 306. In step S709, the CPU 304 controls the color conversion processing unit 310 to convert RGB data into CMYK. In step S710, the CPU 304 controls the toner application amount detection unit 311 to detect the toner application amount for the CMYK data of the target page generated in step S709. The toner application amount detection method is as described above with reference to FIG.

  The toner amount detection is performed on CMYK contone image data for the following reason. That is, the amount of applied toner can be calculated more accurately when the amount of applied toner is detected for CMYK data, which is contone image data, than when the amount of applied toner is detected for a halftone image. . Of course, a configuration may be adopted in which the applied toner amount is calculated for an image after halftone.

  In step S711, the CPU 304 controls the fixing temperature calculation unit 325, and calculates the minimum temperature necessary for fixing the target page based on the applied toner amount information detected in step S710. Here, the method of calculating the minimum temperature necessary for fixing the target page from the toner application amount information is as described above with reference to FIG.

  In step S712, the CPU 304 controls the halftone processing unit 312 to perform screen processing or error diffusion processing on the CMYK data generated in step S707, thereby converting the CMYK data into N values. The image data after the halftone process is stored in the RAM 306.

  In step S713, the CPU 304 generates fixing temperature control information based on the minimum fixing temperature information calculated in step S709 and the print settings such as the blank page skip setting set in step S701. This fixing temperature control information will be described later with reference to FIG.

  In step S714, the CPU 304 determines whether or not the page to be processed is the Mth page or later (here, the fifth page or later) through the temperature control. If it is determined in step S714 that the processing target page is the fifth or subsequent page through the temperature control, the process proceeds to step S715. In step S714, when the page to be processed is before the Mth page, the process proceeds to step S716.

  In step S715, the CPU 304 notifies the fixing temperature control information generated in step S713 to the CPU 315 of the printing unit 302 via the printer communication IF unit 313. For example, in step S715, the applied toner amount calculated in step S710 is notified.

  If blank page skip control is performed in step S715, image data transfer and fixing operations are not performed. Therefore, the notification of the loading amount information may be skipped. By skipping the notification of the applied amount information, the correspondence relationship between the image data and the applied amount information can be prevented from shifting.

  In step S716, the CPU 304 determines whether or not there is a next page. If there is a next page, the processing from step S703 is repeated. If there is no next page, the process ends.

  Next, processing in the print unit 302 will be described. In step S721, the CPU 315 waits for a print instruction from the controller unit 301. If there is a print instruction from the controller unit 301, the process proceeds to S722.

  In step S722, the CPU 315 controls the fixing temperature control unit 319 to the temperature Tmax at which the maximum toner amount can be fixed in order to print the first four pages without reducing productivity, and starts printing. To do.

  In order to control the temperature of the fixing device prior to fixing the printed image, it is necessary to notify the applied toner amount information in advance for a predetermined page. For this reason, the image data to be printed and the number of pages necessary to notify in advance the toner application amount information and blank page skip information detected from the image data are accumulated. Accordingly, since the fixing temperature can be controlled in advance, the fixing temperature can be controlled without reducing productivity.

  Here, it is assumed that the image forming apparatus 101 is configured to notify in advance the amount of applied toner on a page to be fixed four pages later with respect to the currently fixed page.

  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 print instruction from the user, and productivity is lowered. For this reason, the fixing temperature control is not performed until the fourth page from which printing is started, and it is preferable to control the maximum toner amount assumed by the image forming apparatus 101 to a fixing temperature at which fixing is possible. Then, it is preferable to control the temperature by detecting the amount of applied toner from the image data of the fifth and subsequent pages after the start of printing.

  In step S723, the CPU 315 waits for reception of the fixing temperature control information necessary for fixing the target page, which is transmitted from the controller unit 301. If the fixing temperature control information is received from the controller unit 301 in S723, the process proceeds to step S724. The fixing temperature control information 1100 received here is information necessary for fixing a page to be fixed after four pages with respect to the page currently fixed.

  In step S724, the CPU 315 determines whether the blank page skip information in the fixing temperature control information received in step S723 is continuous (predetermined number of sheets) for a predetermined number of pages (continuous skip number) (L pages). If it is continuous for L pages or more, the process proceeds to step S728. If it is not continuous for L pages or more, the process proceeds to step S725.

  In step S725, the CPU 315 controls the fixing temperature control unit 319, and sets the page with the maximum temperature as the control target page from the plurality of fixing temperature control information 1100 up to the fourth page that has already been notified. On the other hand, in step S728, the CPU 315 sets the temperature of the fixing device during the inter-paper period as the control target value because the time interval between the sheets on which the fixing process is performed becomes wide.

  In step S726, the CPU 315 controls the fixing temperature control unit 319, and controls the temperature of the fixing device 320 with the current fixing temperature and the fixing temperature of the control target page determined in S725 or S728 as targets. Specifically, when the fixing temperature of the control target page is higher than the current fixing temperature, the temperature of the fixing device 320 is increased. When the fixing temperature of the control target page is lower than the current fixing temperature, control is performed so as to reduce the temperature of the fixing device 320. If the fixing temperature can be lowered with respect to the target temperature, control is performed to lower the temperature.

  In step S727, the CPU 315 determines whether the page is finished. If the page is not finished, the process from S723 is repeated, and when the page is finished, the process is finished.

<Fixing Temperature Control Information Generation Process (Step S713)>
FIG. 8 is a flowchart showing details of the fixing temperature control information generation process. As described above, this process is a process executed by the CPU 304.

  In step S <b> 801, the CPU 304 refers to the blank page skip information stored in the RAM 306 and determines whether a blank page is skipped. If it is determined that the blank page is skipped, the process proceeds to step S802. If it is determined that the blank page is not skipped, the process proceeds to step S803.

  In step S802, the CPU 304 adds blank page skip information as a record to the fixing temperature control information. On the other hand, in step S803, the CPU 304 determines whether the document is a copy-prohibited document. If it is determined that the document is a copy prohibited document, the process proceeds to step S804. If it is determined that the document is not a copy prohibited document, the process proceeds to step S806. Here, the “copy prohibited original” means an original designated to perform a predetermined painting process on the original page image.

  In step S804, the CPU 304 performs processing for filling the input image with a density equal to or higher than the process density. In step S805, the CPU 304 generates fixing temperature control information for the copy-prohibited document based on a correspondence table of fixing temperature control information described later with reference to FIG. The fixing temperature corresponding to the copy-prohibited document is a predetermined temperature necessary for stably fixing the amount of applied toner that is increased by the painting process. Since the amount of applied toner increases due to the painting process, it is necessary to increase the fixing temperature as compared with the case where it is determined that the document is not a copy-prohibited document.

  In step S806, the CPU 304 determines whether a background pattern or stamp composition is set. If it is determined that the copy-forgery-inhibited pattern or stamp composition is set, the process proceeds to step S807. If it is determined that the copy-forgery-inhibited pattern or stamp composition is not set, the process proceeds to step S809.

  In step S <b> 807, the CPU 304 performs a tint block or stamp composition process on the image after the halftone process stored in the RAM 306. In step S <b> 808, the CPU 304 generates fixing temperature control information when the background pattern or stamp is combined based on a correspondence table of fixing temperature control information described later with reference to FIG. 11.

  In step S809, the CPU 304 acquires the fixing temperature calculated in step S710 from the RAM 306 as fixing temperature control information. The acquired fixing temperature is notified to the printing unit 302 in step S713.

  In other words, the fixing temperature is determined as shown in FIG. 11 in accordance with the contents of image processing such as painting processing on a copy-prohibited document or composition processing of a background pattern or stamp. Note that the fixing temperature control information is not limited to information directly related to the fixing temperature, and may be a factor that causes an increase in the amount of applied toner or a factor that a paper interval period becomes empty. For example, as the fixing temperature control information, a print mode such as “copy prohibited original” or “background pattern” or “stamp” may be notified. The output control information of print image data such as “skip blank page” may be notified.

  FIG. 11 is a diagram illustrating an example of the fixing temperature control information 1100. Here, it is described that the toner application amount obtained from the image data in S710 or the fixing temperature obtained from the toner application amount in S711 is notified.

  The fixing temperature control information 1100 in the image forming apparatus 101 is not limited to the toner application amount and the fixing temperature, but may be the content of processing performed on the image data after the halftone process and the toner application amount necessary for the processing. The processing contents include, for example, image processing such as painting processing, stamp composition, and background pattern composition, print control such as blank page detection and blank page skip. Further, the amount of applied toner necessary for the processing content to be performed may be used. Alternatively, fixing temperature control information “up” and “down” may be generated and notified so as to control whether the fixing temperature is raised or lowered.

  As shown in FIG. 11, the fixing temperature control information may be stored in the RAM 317 of the printing unit 302 as a table of correspondence between processing contents, toner application amount, and fixing temperature. When the amount of applied toner is notified from the controller unit 301, the temperature of the fixing unit is controlled with reference to a table held in the RAM 317.

  FIG. 9 is a diagram illustrating an example of temperature control of the fixing device implemented in the processing flow shown in FIG. FIG. 9A shows an example of fixing temperature control in the case where there is no interval between sheets to be fixed by blank page skip control (the fixing device continuously performs fixing processing). On the other hand, FIG. 9B shows an example of fixing temperature control in the case where there is a gap between sheets to be fixed by blank page skip control. That is, an example of fixing temperature control in the case where the time interval between the thermal fixing performed before the blank page skip control and the thermal fixing performed after the blank page skip control is longer than a predetermined time is shown.

  The horizontal axis represents the number of printed pages, and the vertical axis represents the fixing temperature when fixing the page. Note that the amount of applied toner on a page is shown in% below the number of pages. In FIG. 9, the fixing temperature control information notified in advance for printing the target page is “applied amount information” and “blank page skip control information”. Therefore, in FIG. 9, the timing for notifying the applied amount information and the blank page skip control information is also shown.

  In FIG. 9A, the image data of the first page to the 14th page and the 18th page are received. Blank page skip control is performed on pages 15 to 17 (three consecutive pages). On the other hand, in FIG. 9B, image data of the first page to the 14th page is received. Blank page skip control is performed on pages 15 to 18 (four consecutive pages).

  9A and 9B, the image data of the first page to the 14th page is the same, the toner application amount of the fifth page and the 14th page is 200%, and the toner application amount of the other pages is 100%. In the image forming apparatus 101, the relationship between the applied toner amount and the minimum temperature required for fixing is as shown in FIG. A temperature required to fix an image with a toner applied amount of 200% is T1, and a temperature required to fix an image with a toner applied amount of 100% is T5.

  For the first to fourth pages, fixing is performed at the maximum temperature T1 so as not to reduce the productivity. In order to perform the fixing temperature control from the fifth page, the amount of applied toner on the fifth page is detected during fixing of the first page, and the detected amount of applied toner is notified to the fixing temperature control unit 319.

  Similarly, when fixing the fifth page, the amount of applied toner on the fourth page ahead (that is, the ninth page) is detected, and the minimum temperature required for fixing is notified to the fixing temperature control unit 319. Here, the target temperature T5 is notified.

  The detection of the applied toner amount when fixing the fifth page is the image data up to four pages ahead (that is, the sixth to ninth pages). Since the toner application amounts of the image data of the sixth page to the ninth page are all 100%, the target temperature is T5. Therefore, it is determined that the fixing temperature can be lowered from the current temperature T1.

  At the time of fixing the 10th page, the amount of applied toner on the 14th page is detected, and the lowest temperature that can be fixed is notified to the fixing temperature control unit 319. The amount of applied toner on the 14th page is 200%, and the fixing temperature needs to be T1 in order to fix the toner on the 14th page. Therefore, in order to control the fixing temperature of the 14th page to T1, the fixing temperature control unit 319 performs control to increase the temperature of the fixing device from the 11th page.

  When the eleventh page is fixed, it is detected that the blank page skip control is performed on the fifteenth page. Thereafter, it is detected that the 16th page is blank page skip control when the 12th page is fixed, and that the 17th page is blank page skip control when the 13th page is fixed. In the case of FIG. 9A, it is detected that the blank page skip control is executed continuously for 3 pages from the total 15th page. In this case, the fixing temperature control unit 319 is notified that blank pages are skipped for three consecutive pages.

  In FIG. 9A, when the toner application amount of the 18th page which is a non-blank page is detected at the time of fixing the 14th page, the image transfer is performed for the printing of the 18th page after the fixing of the 14th page. Since it is in time, the 18th page is printed without leaving a sheet interval.

  On the other hand, in FIG. 9B, at the time of fixing the 14th page, the 18th page is skipped, and the 4-page continuous blank page skip control is performed from the 15th page to the 18th page. In this case, since the next page to be fixed is not fixed when 14 pages are fixed, there is a paper interval to the next page to be printed. Further, when printing skip occurs, the printer operation may be initialized, and the paper interval may be increased for a certain time. In this case, the fixing temperature control unit 319 is notified that blank pages are skipped for four consecutive pages.

  When the fixing temperature control unit 319 receives a notification of blank page skip control that continues for four or more pages, the fixing temperature control is performed by setting the fixing temperature control during the interval between sheets where printing is not performed to a target temperature at T5. Then, during the interval between sheets, the fixing temperature control is started toward the temperature T5 necessary for fixing the 19th page at the timing when the amount information of the 19th non-blank page is notified.

  In order to control the fixing temperature of the 19th page, the fixing temperature control unit 319 can increase the fixing temperature from the current fixing temperature to T1 based on the timing at which the 19th page can be printed between sheets. The temperature starts to be raised from the timing (St).

  Note that FIG. 9 shows the fixing temperature control contents when four or more pages are continuous, but this continuous number is determined according to the interval between sheets generated by the blank page skip control.

  As described above, in order to notify the target page of the toner application amount four pages ahead and the blank page skip control information in advance, in S712, the image after halftone processing and the toner application amount of each page are held. Yes. In other words, image data for the number of pages necessary for prior notification is temporarily stored in the RAM 306, which is a spool memory, and the image transfer timing is adjusted.

  As described above, according to the first embodiment, it is possible to suitably control the fixing temperature during the inter-paper period that does not require fixing by detecting the blank page skip information in advance. That is, further power saving can be realized.

(Other examples)
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed.

  DESCRIPTION OF SYMBOLS 101 Image forming apparatus; 102 Print server; 103 Client PC; 301 Controller part; 302 Print part

Claims (10)

An image forming apparatus having a fixing device for thermally fixing a toner image on a recording medium,
Detection means for detecting the amount of toner applied to the input image;
Skip control means for controlling to skip image formation processing and fixing processing of the input image when the input image is a blank image;
Calculating means for calculating a target temperature of the fixing device based on a toner applied amount detected by the detecting means;
Control means for controlling the temperature of the fixing device based on the target temperature calculated by the calculating means;
Have
The control unit controls the temperature of the fixing device based on a predetermined target temperature instead of using the target temperature calculated by the calculation unit when the skip control unit controls to skip a predetermined number of sheets continuously. An image forming apparatus. The predetermined number of sheets is such that the time interval between the thermal fixing for the first input image executed before the skip control by the skip control means and the thermal fixing for the second input image executed after the skip control is longer than a predetermined time. The image forming apparatus according to claim 1, wherein the number of continuous skips is long. The image forming apparatus according to claim 1, further comprising a blank sheet determination unit that determines whether or not the input image is a blank sheet image. The blank sheet determination means includes
First determination means for performing blank sheet candidate determination based on an average value and a variance value of pixel values of pixels included in the input image;
Second determination means for performing blank sheet candidate determination based on the number of edges included in the input image;
Have
4. The image forming apparatus according to claim 3, wherein the input image determined as the blank candidate by the first determination unit and determined as the blank candidate by the second determination unit is determined as a blank image. 5. 5. The image forming apparatus according to claim 1, wherein the predetermined target temperature is a temperature of the fixing unit during an interval between sheets. When the input image is an image that requires a fill process or an image that requires a copy-forgery-inhibited pattern or stamp composition process, the calculation means adds the input process to the input image after the fill process or the composition process. The image forming apparatus according to claim 1, wherein a target temperature of the fixing device is calculated. A control device for controlling an electrophotographic image forming apparatus having a fixing device for thermally fixing a toner image on a recording medium,
Detection means for detecting the amount of toner applied to the input image;
Skip control means for controlling to skip image formation processing and fixing processing of the input image when the input image is a blank image;
Calculating means for calculating a target temperature of the fixing device based on a toner applied amount detected by the detecting means;
Output means for outputting a target temperature of the fixing device calculated based on the target temperature calculated by the calculating means to the image forming apparatus;
Have
The output unit outputs a predetermined target temperature to the image forming apparatus instead of outputting the target temperature calculated by the calculation unit when the skip control unit controls to skip a predetermined number of sheets continuously. Control device characterized. A control method of an image forming apparatus having a fixing device for thermally fixing a toner image on a recording medium,
A detection step for detecting the amount of toner applied to the input image;
A calculation step of calculating a target temperature of the fixing device based on the toner applied amount detected by the detection step;
A control step of controlling the temperature of the fixing device based on the target temperature calculated in the calculation step;
Including
In the control step, when the input image is a blank image, a skip control unit that controls to skip the image forming process and the fixing process of the input image controls to skip a predetermined number of times. A control method for an image forming apparatus, wherein the temperature of the fixing device is controlled using a predetermined target temperature instead of using the target temperature calculated in the calculation step. A control method of a control device for controlling an electrophotographic image forming apparatus having a fixing device for thermally fixing a toner image on a recording medium,
A detection step for detecting the amount of toner applied to the input image;
A calculation step of calculating a target temperature of the fixing device based on the toner applied amount detected by the detection step;
An output step of outputting the target temperature of the fixing device calculated based on the target temperature calculated in the calculation step to the image forming apparatus;
Including
In the output step, when the input image is a blank image, a skip control unit that controls to skip the image forming process and the fixing process of the input image controls to skip a predetermined number of times. A control method for a control apparatus, comprising: outputting a predetermined target temperature to the image forming apparatus instead of outputting the target temperature calculated in the calculation step.   A program for causing a computer to function as each unit of the image forming apparatus according to any one of claims 1 to 5.