JP2015087646A - Image forming apparatus, control method therefor, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that performing thinning processing for suppressing scattering in a state that scattering does not occur causes a thinning pattern to stand out, resulting in the deterioration of picture quality.SOLUTION: An information forming apparatus includes: deriving means for deriving the information of a recording material formed on a recording medium on the basis of image data; determining means for determining a fixing temperature for thermally fixing the recording material on the recording medium in accordance with the derived information of the recording material; selecting means for selecting a thinning pattern to be used for thinning processing to the image data on the basis of the determined fixing temperature; thinning means for performing the thinning processing of the image data by using the selected thinning pattern; and control means for controlling a fixing device on the basis of the determined fixing temperature such that the recording material formed on the basis of the image data to which the thinning processing has been applied is thermally fixed on the recording medium.

Description

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

  A technique for reducing power consumption by adjusting the fixing temperature according to the amount of applied toner of image data to be printed is disclosed (for example, see Patent Document 1).

  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) subjected to halftone processing. Therefore, in full-color image formation, the amount of toner (hereinafter referred to as toner amount) on the transfer paper tends to increase. Along with this, the heat capacity of the fixing roller required for fixing the toner increases.

  On the other hand, printers that use toner as a recording material are subjected to a “scattering phenomenon” suppression process. The “scattering phenomenon” is a phenomenon in which unfixed toner is scattered due to water or air contained in the toner being steamed or thermally expanded. The “scattering phenomenon” and the occurrence of the phenomenon are related to various environmental factors related to the printing process. Examples of environmental factors include the amount of water contained in toner and paper, room temperature, humidity, paper type, fixing temperature and fixing speed. It is known that a process of partially thinning out the toner amount has a certain suppression effect against this “scattering phenomenon”.

JP 2000-242107 A

  However, if the thinning process is always performed to suppress the toner scattering phenomenon, image deterioration is likely to occur. In other words, even if the scattering phenomenon does not occur due to the scattering phenomenon, if the thinning process for suppressing the scattering phenomenon is applied, the thinning pattern becomes conspicuous. As a result, there is a problem that the image quality is deteriorated.

  In order to solve the above problems, the present invention has the following configuration. That is, an image forming apparatus including a fixing device that thermally fixes a recording material formed based on image data to a recording medium, and derives information on the recording material formed on the recording medium based on the image data. A deriving unit; a determinating unit for determining a fixing temperature for thermally fixing the recording material to the recording medium in accordance with the derived recording material information; and the image data based on the determined fixing temperature. A selection means for selecting a thinning pattern used for thinning processing for the image, a thinning means for thinning the image data using the selected thinning pattern, and image data to which the thinning processing is applied. Control means for controlling the fixing device based on the determined fixing temperature so as to thermally fix the recording material to the recording medium.

  According to the present invention, it is possible to suppress deterioration in image quality due to thinning processing for suppressing the scattering phenomenon.

1 is a diagram illustrating an example of a system configuration including an image forming apparatus according to an embodiment. FIG. 3 is a cross-sectional view of a tandem image forming apparatus that employs an intermediate transfer member. 1 is a block diagram illustrating a configuration example of an image forming apparatus. FIG. 3 is an explanatory diagram regarding a toner application amount detection method of the image forming apparatus. FIG. 3 is an explanatory diagram relating to a printing rate detection method of an image forming apparatus. The figure which shows the relationship between a toner applied amount and a printing rate, and fixing temperature. The flowchart which shows the flow of data processing. 6 is a flowchart showing a flow of processing related to fixing temperature control. The figure which shows an example of the fixing temperature control in printing operation. The figure which shows an example of the table which shows the relationship between fixing temperature and a thinning process. The figure which shows a thinning process and its example. FIG. 6 is a diagram illustrating an example of fixing temperature control information.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

[System configuration]
FIG. 1 is a diagram illustrating an example of a system configuration including an image forming apparatus 101 according to an embodiment of the present invention.

  The image forming apparatus 101 processes various input data, performs image formation (image formation), and outputs a printed matter. The image forming apparatus 101 is connected to the print server 102 and the client PC 103 via the network 104. The image forming apparatus 101 has a copy function and a print function, and executes print processing using print data received from the print server 102 or the client PC 103. In the present exemplary embodiment, it is assumed that the image forming apparatus 101 can execute a thinning process for suppressing the scattering phenomenon of toner as a recording material in accordance with the fixing temperature during the printing process.

[Description of operation of image forming apparatus]
FIG. 2 shows a partial configuration of the image forming apparatus 101 shown in FIG. 1, and is a cross-sectional view of a tandem color image forming apparatus that employs an intermediate transfer member 28 as an example of an electrophotographic color image forming apparatus. is there. The image forming operation in the electrophotographic color image forming apparatus will be described with reference to FIG.

  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 color of YMCK as a charging unit. Each injection charger is provided with sleeves 23YS, 23MS, 23CS, and 23KS. The photoconductors 22Y, 22M, 22C, and 22K are driven to rotate according to the image forming operation by receiving the driving force of the drive motors 40Y, 40M, 40C, and 40K.

  The image forming apparatus 101 includes scanner units 24Y, 24M, 24C, and 24K that irradiate each photosensitive member with photosensitive light as an exposure unit, and selectively exposes the surface of each photosensitive member to generate an electrostatic latent image. Form.

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

  The image forming apparatus 101 includes an intermediate transfer member 28 as a transfer unit. In order to transfer the single color toner image from each photoconductor to the intermediate transfer member 28, the intermediate transfer member 28 rotates. Each single color toner image is transferred to the intermediate transfer member 28 as the photosensitive members 22Y, 22M, 22C, and 22K and the primary transfer rollers 27Y, 27M, 27C, and 27K positioned opposite to the photosensitive members 22Y, 22M, 22C, and 22K rotate. By applying a bias voltage to the primary transfer roller 27 and making a difference between the rotation speed of each photoconductor and the rotation speed of the intermediate transfer body 28, the single-color toner image is efficiently transferred onto the intermediate transfer body 28 to perform the primary transfer. Is done.

  Further, the single color toner image is superimposed on the intermediate transfer member 28 for each station, and the overlapped multicolor toner image is conveyed to the secondary transfer roller 29 as the intermediate transfer member 28 rotates. The recording medium 11 is nipped and conveyed from the paper feed tray 21 a to the secondary transfer roller 29, and the multicolor toner image on the intermediate transfer body 28 is transferred to the recording medium 11. A secondary transfer is performed by applying a bias voltage to the secondary transfer roller 29 and electrostatically transferring the toner image. The secondary transfer roller 29 contacts the recording medium 11 at a position 29a while the multicolor toner image is transferred onto the recording medium 11, and is separated to a position 29b after the printing process.

  The image forming apparatus 101 serves as a fixing unit in order to heat-fix the multicolor toner image transferred to the recording medium 11 and to press the recording medium 11 against the fixing roller 32 in order to thermally fix the multicolor toner image. A fixing device 31 having a 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. 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 includes a temperature sensor (not shown), and is controlled so that a fixing operation is performed 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 is completed.

  The cleaning unit 30 cleans the toner remaining on the intermediate transfer body 28 after the secondary transfer. The waste toner cleaned here is stored in a cleaner container (not shown).

  The image forming apparatus 101 includes, as paper feeding means, a paper feed tray 21a on which the recording medium 11 is loaded, and a manual feed unit 21b on which the user can manually feed the recording medium 11, and transports the paper from these positions to the image forming position. Thus, the recording medium 11 is fed.

[Block diagram of image forming apparatus]
Next, functions relating to fixing temperature control according to the present embodiment will be described with reference to FIG. FIG. 3 is a block diagram of the image forming apparatus 101 according to the present embodiment. As shown in FIG. 3, the image forming apparatus 101 is roughly divided into a system controller 301 and a print controller 302. Each controller includes CPUs 304 and 315, ROMs 305 and 316, and RAMs 306 and 317, respectively. Each CPU reads the main program from the ROM according to the initial program in the ROM and stores it in the RAM. The RAM is used as a main memory for program storage and work. The CPUs 304 and 315 and the RAMs 306 and 317 are connected to the individual constituent blocks shown in FIG. 3 by the system buses 314 and 322, and information and data are transmitted and received bidirectionally.

  A configuration of the image processing unit 308 of the system controller 301 will be described. The image generation unit 309 generates raster image data that can be printed from print data received from a computer device such as the print server 102 or the client PC 103, and generates RGB data and attribute data indicating the attribute of each pixel for each pixel. Output. Note that the image generation unit 309 may have a configuration in which a reading unit is provided in the image forming apparatus 101 itself and the image data read by the reading unit is handled instead of the image data received from the computer device. Here, the reading means includes at least a CCD (Charged 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. Alternatively, the image forming apparatus 101 itself may be configured to receive image data from an external reading unit via an interface (not shown) without providing the reading unit.

  The color conversion processing unit 310 performs CMYK conversion on the 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, for example, 8 bits of 0 to 255 as a value corresponding to each color for each pixel. Specifically, if the value of each color is “0”, it indicates that the toner is not used, 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 represents 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 image processing unit 308 sends the CMYK data and the attribute data for which the applied toner amount has been detected to the halftone processing unit 312. The print rate detection unit 327 detects the toner print rate for the CMYK data generated by the color conversion processing unit 310. A specific method of toner printing rate will be described later with reference to FIG. The image processing unit 308 sends the CMYK data and attribute data for which printing rate detection has been completed to the halftone processing unit 312. Further, the image processing unit 308 notifies the fixing temperature calculation unit 325 of the applied toner amount information at the time when the applied toner amount detection or toner printing rate detection for one page is completed.

  The applied toner amount detection process and the printing rate detection are switched depending on the printing color mode. In the case of color printing, a toner application amount detection process is performed, and in the case of monochrome printing, a printing rate detection process is performed. In the present embodiment, the toner application amount detection unit 311 and the printing rate detection unit 327 realize a derivation unit that derives information for thermally fixing the toner. In either case, the fixing temperature calculation unit 325 is notified at the end of the processing result.

  The fixing temperature calculation unit 325 calculates the minimum temperature required for fixing from the toner application amount detected by the toner application amount detection unit 311 or the printing rate detected by the printing rate detection unit 327. A method of calculating the minimum temperature necessary for fixing the toner amount of toner on the page from the toner amount information will be described later with reference to FIG. A method of obtaining from the printing rate will be described later with reference to FIG.

  Although it has been described that the applied toner amount information detected by the applied toner amount detection unit 311 is notified to the fixing temperature calculation unit 325 and the fixing temperature is calculated, the present invention is not limited to this. For example, the configuration is such that the applied toner amount information detected by the applied toner amount detection unit 311 is directly notified to the print controller 302 via the printer communication IF 313 and the communication line 303, and the fixing temperature is calculated on the print controller 302 side. Also good. In any case, any information may be used as long as information for controlling the fixing temperature is transmitted and the fixing temperature is determined, and the form of information to be transmitted is not limited. The content of the information to be transmitted is not particularly limited as long as it is similar to the fixing temperature control information shown in FIG.

  The halftone processing unit 312 performs halftone processing on the data output from the toner application amount detection unit 311 or the printing rate detection unit 327. A specific configuration of the halftone processing unit 312 includes a screen process or an error diffusion process. The screen processing is processing for converting input image data into N values using a plurality of predetermined dither matrices. The error diffusion process is a process of converting the input image data into an N-value by comparing it with a predetermined threshold, and diffusing the difference between the input image data and the threshold at that time to surrounding pixels to be N-valued thereafter. It is.

  The thinning processing unit 328 performs a thinning process for suppressing the toner scattering phenomenon. The thinning processing method is shown in FIG. As a thinning pattern for suppressing the scattering phenomenon, the thinning method is selectively changed in association with Level as shown in FIG. In this embodiment, the level indicating the thinning pattern is associated with the fixing temperature to control the thinning method.

  The printer communication IF 313 and the controller communication IF unit 321 are IF units for performing communication between the system controller 301 and the print controller 302. The information communicated here includes, in addition to image data, a control signal from the system controller 301, toner application amount information detected by the toner application amount detection unit 311, a copy-prohibited document detection result and image composition setting information, and Information related to fixing device temperature control is included.

  The fixing temperature control unit 319 controls the temperature of the fixing device 320 based on the target temperature or toner application amount information determined by the fixing temperature calculation unit 325 and the fixing temperature control information 1200 of FIG.

[Toner load detection method]
Next, the applied toner amount detection method according to the present embodiment will be described with reference to FIG. Here, the amount of applied toner means the amount of toner per unit area, and the unit is described as%. Specifically, when the maximum value of each color of CMYK is 100% and the maximum values for two colors are overlapped, the applied toner amount is defined as 200% for that pixel. Since each color has gradation, each color can take a value between 0% and 100%. For example, in the case of an image that fully uses CMYK four-color toners in the full-color printing mode, the maximum applied toner amount is 400%. On the other hand, in the case of a monochrome image of K single color, the maximum amount of applied toner is 100%.

  First, when the applied toner amount detection unit 311 receives CMYK data, it calculates an applied toner amount for each pixel. FIG. 4A shows a part of image data for one page, and a pixel 401 indicates one pixel as a minimum unit. A block 402 represents a pixel block in units of 3 × 3 pixels. Also, the numerical value shown in the frame within one pixel in FIG. 4A indicates the toner application amount for each pixel detected by the toner application amount detection unit 311.

  Next, an example of a scene in which the toner applied amount detection unit 311 calculates the average value of the toner applied amount in the block in units of 3 × 3 pixel blocks will be described. Here, the reason why the average value in the 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. is there. In the example of FIG. 4, a block size of 3 × 3 pixels is shown as an example, but the present invention is not limited to this, and an arbitrary size may be used. Further, although the average value in the block is calculated here, a configuration using the minimum value or the maximum value in the block may be used. The block 403 in FIG. 4B corresponds to the block 402 in FIG. The numerical value described in the frame of one block indicates the average value of the applied toner amount in each block.

  Subsequently, the toner application amount detection unit 311 derives the maximum value from the average values of all the blocks in one page when the calculation of the average value of the toner application amount in the block for one page is completed. Then, the fixing temperature calculation unit 325 is notified as a representative value of the applied toner amount information.

[Print rate detection method]
The print rate detection unit 327 shown in FIG. 3 detects the ratio of print pixels with respect to the print target area as the print rate. The printing rate is a ratio of the actual count number to the maximum count value of the total number of pixels occupying the area, and is obtained by the following formula. Further, the count and maximum count value in the area are derived based on the number of gradations of the pixel.
Printing rate = (pixel count in area / maximum value in area) × 100 [%] (Formula 1)
Pixel count in area = pixel gradation bit × black pixel count in area (Formula 2)
Maximum value in area = pixel gradation bit × total number of pixel counts in area (Formula 3)

  Further, as shown in FIG. 5, there are a case where the printing rate of the entire page is obtained (FIG. 5A) and a case where the printing rate for a predetermined area is detected (FIG. 5B). Note that the number of the predetermined areas is not limited to the illustrated example, and may be two or more regions. Further, the printing rate of the predetermined area may be detected individually for each area.

[Fixing temperature calculation method based on toner applied amount]
Next, a method for calculating the minimum fixing temperature necessary for fixing the target page based on the applied toner amount information detected by the applied toner amount detection unit 311 will be described with reference to FIG.

  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 without fixing failure, it is necessary to set the temperature of the fixing device 320 to a fixing temperature at which the maximum value of the toner application 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. At this time, the larger the maximum amount of applied toner, the higher the required fixing temperature.

  FIG. 6A is a diagram illustrating, as an example, the relationship between the applied toner amount and the fixing temperature according to the present embodiment. In FIG. 6A, the horizontal axis indicates the amount of applied toner, and the vertical axis indicates the temperature required for fixing. For example, when the detection result by the applied toner amount detection unit 311 is 200%, the minimum temperature required for fixing is T1 from FIG. Further, when the detection result by the applied toner amount detection unit 311 is 100%, it can be read that the minimum temperature required for fixing the target page is T5. FIG. 6A shows the total amount of applied toner, but a look-up table showing a correspondence relationship for each color may be used.

  If the temperature of the fixing device 320 is increased to a temperature at which the maximum amount of applied toner appearing in the printed page can be fixed, problems such as fixing failure do not occur in the entire image. For this reason, the minimum temperature required for fixing the target page is obtained from the information on the applied toner amount detected by the applied toner amount detection unit 311.

[Fixing temperature calculation method based on printing rate]
A fixing temperature calculation method based on the printing rate will be described with reference to FIG. Basically, it is the same as the method for calculating the fixing temperature shown in FIG. 6A, but in FIG. 6B, the horizontal axis indicates the printing rate, and the vertical axis indicates the temperature required for fixing. The maximum value of the printing rate is 100%. The fixing rate is the highest when the printing rate is 100%, and the fixing temperature decreases as the printing rate decreases.

  The relationship shown in the graph of FIG. 6 is used for temperature control of the fixing device 320, and is stored in the storage unit 307, the RAM 306, or the like in the form of a lookup table, for example.

[Data processing flow in system controller]
The data processing flow in the present invention will be described with reference to FIGS. The flowchart shows processing that is determined and executed under the control of the CPU 304 provided in the system controller 301 shown in FIG.

  In step S <b> 701, the CPU 304 causes the image generation unit 309 to generate raster image data that can be printed based on print data received from a computer device such as the print server 102. Then, the CPU 304 outputs RGB data and attribute data indicating the data attribute of each pixel for each pixel.

  In S702, the CPU 304 causes the color conversion processing unit 310 to perform CMYK conversion on the RGB data according to the toner color, and generates CMYK data and attribute data.

  In step S <b> 703, the CPU 304 determines whether to perform monochrome printing or color printing on the image data to be processed. If monochrome printing is performed (YES in S703), the process proceeds to S704, and if color printing is performed (NO in S703), the process proceeds to S705.

  In step S <b> 704, the CPU 304 causes the printing rate detection unit 327 to calculate the printing rate using the method described above. Thereafter, the process proceeds to S706. In step S <b> 705, the CPU 304 causes the applied amount detection unit 311 to detect the applied toner amount by the method described above. Thereafter, the process proceeds to S706. In S706, the CPU 304 uses the halftone processing unit 312 to N-value the image data processed in S702 by, for example, a screen processing or error diffusion processing method.

  In S707, the CPU 304 performs spool processing for temporarily accumulating the halftone processing result in S706 and the applied amount detection result in S704 or the printing rate detection result in S705 in the RAM 306 (S707). In the spool processing, image data to be printed and information detected from the image data are temporarily stored in the RAM 306. In the fixing operation, it is necessary to secure a time required for controlling the fixing temperature of the fixing device 320 to the target value. For this reason, in the spool processing here, the number of pages necessary for notification is accumulated prior to the fixing operation of the print image. As a result, the fixing temperature can be controlled without reducing productivity.

  In step S <b> 708, the CPU 304 determines whether the background pattern composition setting or the stamp print setting is set as the print setting. If set (YES in S708), the CPU 304 synthesizes a stamp image and a background pattern in the image data. If not set (NO in S708), the composition process is not performed, and the process proceeds to S710.

  In step S <b> 710, the CPU 304 determines a thinning processing method to be performed by the thinning processing unit 328 of the system controller 301. In the determination of the thinning processing method, a thinning pattern for the fixing temperature is set in advance as image data and fixing temperature control information as shown in FIG. As a thinning processing method, a thinning pattern is determined from the correspondence of thinning patterns corresponding to the fixing temperature. The table in FIG. 10 shows the relationship between the amount of applied toner and the fixing temperature during color printing shown in FIG. 6A, but the relationship between the printing rate and the fixing temperature during monochrome printing is also the same. It can be defined.

  In step S711, the CPU 304 performs the thinning process using the thinning process method determined in step S710. 10 and 11 show a specific example of the thinning processing by the thinning processing unit 328 in FIG. In the present embodiment, the table 1000 is defined in which a thinning pattern for the toner application amount and the fixing temperature is defined. The table 1000 is referred to in the thinning processing method determination process (S710) described above. The table 1000 is recorded on the RAM 306 shown in FIG.

  Also, examples of processing results of the thinning process corresponding to “Level” shown in the table 1000 are shown in images 1101 to 1104 in FIG. Level 0 shows an example in which thinning is not performed as shown in an image 1104. Level 1 shows a pattern in which every other pixel is drawn for one line as shown in an image 1103. Level 1 is a result of an increase in the thinning-out amount of one step as compared with Level 0.

  In Level 2, as shown in an image 1102, compared to Level 1, a thinning pattern in which thinning is performed by shifting one pixel unit by one pixel by two lines is shown. Level 2 is the result of increasing the thinning-out amount by one step compared to Level 1. In Level 3, as shown in the image 1101, the thinning result is the largest among the thinning methods shown here. That is, Level 3 is a pattern in which 2 pixel units are drawn for 3 lines. These thinning patterns may be changed according to the width of the black line to be thinned out.

  In the thinning patterns shown, the thinning amount is set in stages for each level. The correspondence is made by the thinning table 1000 shown above.

  Images 1105 to 1108 show examples in which a thinning pattern is applied to actual characters. As a thinning result obtained by applying a pixel pattern of Level 0 to Level 3 to the character “den”, the relationship between the thinning amount and the character is shown as images 1105 to 1108. In the image forming apparatus 101 according to the present invention, in conjunction with the control of the fixing temperature, control is performed so that such thinning applied to characters does not stand out as white spots. The image 1108 is an example in which the Level 3 thinning pattern is applied, but there are portions where thinning is performed locally for two lines. This shows an example in which the number of thinned lines is changed depending on the line width to be thinned.

  Note that the toner scattering phenomenon is less likely to occur as the fixing temperature is lower. Therefore, if the thinning level is lowered to Level 1 as in the image 1106, or the toner scattering phenomenon does not occur in the first place, the thinning table 1000 may be designed so as to select Level 0 that does not perform thinning. For example, when the fixing temperature is lower than a predetermined threshold value, control is performed so as not to perform thinning (Level 0).

  In step S <b> 712, the CPU 304 sends print image data, information related to the fixing temperature control temporarily stored in the spool processing in step S <b> 707, and a print execution instruction command to the print controller 302 via the printer communication IF 313 and the communication line 303. Send.

  The data processing flow in the system controller 301 has been described above.

[Fixing temperature control based on toner load detection result]
A fixing temperature control process using the toner application amount detection result according to the present embodiment will be described with reference to FIG. FIG. 8A shows processing executed under the control of the CPU 304 of the system controller 301. FIG. 8B shows processing executed under the control of the CPU 315 of the print controller 302. In FIG. 8, broken-line arrows indicate transmission / reception of the fixing temperature control information 1200 used during processing.

  First, processing executed based on the control of the CPU 304 of the system controller 301 will be described with reference to FIG.

  In step S801, when the CPU 304 receives a print job input from outside such as an image reading unit or a PC (YES in step S801), the CPU 304 starts print processing. As described above, in the present embodiment, the temperature of the fixing device 320 is controlled without reducing productivity, and thus the amount of applied toner on a page to be fixed after several pages is detected in advance. Here, for the sake of simplification of explanation, an example will be described in which the amount of applied toner on a page to be fixed four pages ahead is detected in advance for a page that is currently being fixed.

  Immediately after the start of printing, if the temperature of the fixing device 320 is controlled after detecting the amount of applied toner by the above-described processing steps, the user cannot immediately respond to the printing instruction from the user, and the productivity is lowered. For this reason, here, the fixing temperature control is not performed from the first page to the fourth page after printing is started, and the maximum toner applied amount considered as the image forming apparatus 101 is controlled to a fixing temperature at which fixing is possible. An example in which the toner application amount is detected from the image data of the fifth page and the fixing temperature is controlled will be described.

  In step S <b> 802, the CPU 304 determines whether the page on which image processing is to be performed is the Nth page or later (here, the fifth or later page) from which the fixing temperature control starts. If the page on which image processing is to be performed is the fifth or subsequent page on which fixing temperature control is started (YES in S802), the process proceeds to S803. If the page to be image processed is the page before starting the fixing temperature control (NO in S802), the processing target is moved to an unprocessed page.

  In step S803, the CPU 304 detects the amount of applied toner or the printing rate. As the applied toner amount, the applied toner amount detection unit 311 detects the applied toner amount of the page. As the printing rate, the printing rate detection unit 327 detects the printing rate of toner in a specific area of the page. The toner application amount detection method is as described above with reference to FIG. 4, and the printing rate detection method is as described above with reference to FIG. In the present embodiment, for the data up to the fourth page for which the fixing temperature control is not executed, the fixing is performed at the maximum temperature at which the maximum toner applied amount can be fixed. The fixing unit 320 of the image forming apparatus 101 may perform fixing using the maximum value that can be output during fixing.

  In step S804, the fixing temperature calculation unit 325 calculates the minimum temperature necessary for fixing the target page based on the applied toner amount information or the printing rate detected in step S803. Here, the method of calculating the minimum temperature necessary for fixing the target page from the toner application amount information or the printing rate is as described above with reference to FIG.

  In step S805, the CPU 304 generates fixing temperature control information based on the minimum fixing temperature information calculated in step S804 and the print settings. The fixing temperature control information will be described with reference to FIG. In S806, the CPU 304 determines a thinning pattern based on the fixing temperature control information determined in S805.

  In step S807, the CPU 304 notifies the CPU 315 of the print controller 302 of the fixing temperature control information necessary for printing the target page determined in step S705 via the printer communication IF 313.

  In step S808, the CPU 304 determines whether there is a next page. If there is a next page (NO in S808), the processing target is copied to an unprocessed page, and the processing from S803 is repeated. If processing for all pages has been completed (YES in S808), this processing flow ends.

  Next, processing executed based on the control of the CPU 315 of the print controller 302 will be described with reference to FIG.

  In step S821, the CPU 315 waits until a print instruction from the system controller 301 is received. If there is a print instruction from system controller 301 (YES in S821), the process proceeds to S822. In step S822, the fixing temperature control unit 319 controls the temperature of the fixing device 320 to a 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 step S823, the CPU 315 waits until the fixing temperature control information regarding the minimum temperature necessary for fixing the target page is received from the system controller 301. As described above, in this embodiment, it is assumed that the printing operation is continued from the first page to the fourth page. If fixing temperature control information has been received from system controller 301 (YES in S823), the process proceeds to S824. Note that the fixing temperature control information received here is information necessary for fixing a page to be fixed four pages ahead of the currently fixed page.

  In step S824, the fixing temperature control unit 319 sets the page with the maximum temperature as the control target page from the fixing temperature control information from the page that has already been notified and is four pages ahead.

  In S825, CPU 304 controls the temperature of fixing device 320 based on the current fixing temperature and the fixing temperature of the control target page determined in S824. Specifically, the CPU 304 raises the temperature of the fixing device 320 if necessary to reach the target temperature by the control target page. If the fixing temperature can be lowered with respect to the target temperature, the CPU 304 performs control to lower the temperature.

  In S826, the CPU 304 determines whether or not the page is finished. If the page is not finished (NO in S826), the process from S823 is repeated. If processing for all pages has been completed (YES in S826), this processing flow ends.

  FIG. 9 shows an example of temperature control of the fixing device 320 implemented in the processing flow shown in FIG. In FIG. 9, the horizontal axis indicates the number of printed pages, and the vertical axis indicates the fixing temperature when fixing the page. Note that the amount of applied toner on a page is expressed in% below the number of pages. In addition, as the fixing temperature control information to be notified in advance for printing the page, the timing for notifying the applied toner amount information is also shown. Here, the toner application amount at the time of color printing is described as an example, but the same applies to the case of the printing rate at the time of monochrome printing. Note that the temperature Tmax may be different between color printing and monochrome printing, or the same value may be used.

  FIG. 9 illustrates an example in which data for 14 pages is received, and the applied toner amount on the 5th and 14th pages is 200%, and the applied toner amount on the other pages is 100%. In this embodiment, the relationship between the applied toner amount and the minimum temperature necessary 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.

  In this example, for the first to fourth pages, fixing is performed at the maximum temperature T1 so as not to reduce the productivity in the printing process. Since the fixing temperature control is performed from the fifth page, the amount of applied toner on the fifth page is detected while fixing the first page.

  Similarly, when fixing the fifth page, the system controller 301 detects the amount of applied toner of the fourth page ahead, that is, the ninth page, and notifies the fixing temperature control unit 319 of the minimum temperature required for fixing. Here, 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.

  Similarly, when fixing the 10th page, the system controller 301 detects the amount of applied toner on the 14th page, and notifies the fixing temperature control unit 319 of the lowest fixable 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. In order to set the temperature T1 on the 14th page, it is necessary to increase the temperature from the 11th page. Therefore, the fixing temperature control unit 319 performs a control to increase and vary the temperature of the fixing device 320 step by step from the 11th page.

  FIG. 12 shows an example of fixing temperature control information 1200 notified from the system controller 301 to the print controller 302 in the fixing temperature control method of the present invention. In the description so far, the minimum fixing temperature is notified mainly from the applied toner amount and the printing rate information obtained from the image data. However, the fixing temperature control method of the present invention is not limited to this.

  For example, as shown in FIG. 12, as the fixing temperature control information, the processing contents (such as “stamp” and “background pattern” composition processing) applied to the image data after the halftone processing described above are notified. May be. Further, a value of “toner applied amount” or “printing rate” corresponding to the processing content to be performed may be notified. Alternatively, it may be fixing temperature information corresponding to the applied toner amount. Alternatively, the fixing temperature control information may be generated and notified in the form of “up” or “down” so as to alternatively control whether the fixing temperature is directly raised or lowered. On the print controller 302 side, the temperature control of the fixing device 320 is performed based on the notified fixing temperature control information.

  In addition, as such fixing temperature control information, a “processing content” as print setting, a toner application amount, and a fixing temperature correspondence table may be stored in the RAM 317 of the print controller 302 as a table. Further, the notification content from the system controller 301 may be referred to when it is replaced with the fixing temperature control information.

  Further, the fixing temperature for the toner on the recording medium may be determined according to the type of the recording medium in addition to the toner application amount and the printing rate.

  In this embodiment, in order to notify the applied toner amount detection result prior to the image to be printed out, that is, to detect the applied toner amount N pages ahead, output by spool processing (S705 in FIG. 7). The interval between the number of image pages and the number of applied toner notification pages is adjusted. In other words, image data for the number of pages necessary for prior notification is secured in the RAM 306 and temporarily stored, and the image transfer timing is adjusted.

  According to the present embodiment, it is possible to suppress image quality deterioration due to thinning processing for suppressing the scattering phenomenon. Furthermore, it becomes possible to control the fixing temperature of the fixing device according to the amount of applied toner or the printing rate without reducing the productivity, and the power consumption can be reduced.

<Other embodiments>
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.

Claims (14)

An image forming apparatus including a fixing device that thermally fixes a recording material formed based on image data to a recording medium,
Derivation means for deriving information of a recording material formed on a recording medium based on the image data;
Determining means for determining a fixing temperature for thermally fixing the recording material to the recording medium according to the information of the derived recording material;
Selection means for selecting a thinning pattern used for the thinning process for the image data based on the determined fixing temperature;
Thinning means for performing thinning processing of the image data using the selected thinning pattern;
Control means for controlling the fixing device based on the determined fixing temperature so as to thermally fix the recording material formed based on the image data to which the thinning processing is applied to the recording medium. An image forming apparatus.   The image forming apparatus according to claim 1, wherein the selection unit selects a thinning pattern having a larger thinning amount as the determined fixing temperature is higher.   The selection means and the thinning-out means control so that the thinning-out processing is not performed on the image data when the determined fixing temperature is lower than a predetermined value. The image forming apparatus described in 1. The derivation means, as the recording material information,
At the time of color printing, the loading amount of the recording material on the recording medium is derived,
4. The image forming apparatus according to claim 1, wherein a printing rate of the recording material on the recording medium is derived during monochrome printing. 5.   2. The processing by the deriving unit, the determining unit, the selecting unit, and the thinning unit is performed from a page after a predetermined page among a plurality of pages constituting the image data. 5. The image forming apparatus according to claim 4.   The control means controls the fixing device so that the maximum amount of the recording material that can be formed on the recording medium becomes a fixing temperature capable of fixing in the fixing operation of the page before the predetermined page. The image forming apparatus according to claim 5. The determining unit determines a fixing temperature from the page currently performing the fixing operation to N pages ahead (N> 1) for the image data,
7. The control unit according to claim 1, wherein the control unit controls the fixing temperature of the page that is currently performing the fixing operation so as to gradually change to the fixing temperature up to the Nth page. The image forming apparatus according to claim 1.   The image forming apparatus according to claim 7, further comprising a spool unit that spools images from the page currently performing the fixing operation to the N pages ahead.   9. The fixing device according to claim 1, wherein the determining unit further determines a fixing temperature based on a type of the recording medium or a content of a different image composition process with respect to the image data. The image forming apparatus described. An image forming apparatus including a fixing device that thermally fixes a recording material formed based on image data to a recording medium,
Determining means for determining a fixing temperature for thermally fixing a recording material formed on a recording medium based on the image data;
Thinning means for controlling thinning processing on the image data based on the determined fixing temperature;
Control means for controlling the fixing device based on the determined fixing temperature so as to thermally fix the recording material formed based on the image data to which the thinning processing is applied to the recording medium. An image forming apparatus. A control method of an image forming apparatus including a fixing device that thermally fixes a recording material formed based on image data to a recording medium,
A derivation step of deriving information of a recording material formed on a recording medium based on the image data;
A determining step for determining a fixing temperature for thermally fixing the recording material to the recording medium in accordance with the derived recording material information;
A selection step of selecting a thinning pattern to be used for thinning processing for the image data based on the determined fixing temperature;
A thinning step of performing a thinning process of the image data using the selected thinning pattern;
And a control step of controlling the fixing device based on the determined fixing temperature so as to thermally fix the recording material formed based on the image data to which the thinning process is applied to the recording medium. Characteristic control method. A control method of an image forming apparatus including a fixing device that thermally fixes a recording material formed based on image data to a recording medium,
A determining step for determining a fixing temperature for thermally fixing a recording material formed on a recording medium based on the image data;
A thinning process for controlling a thinning process for the image data based on the determined fixing temperature;
And a control step of controlling the fixing device based on the determined fixing temperature so as to thermally fix the recording material formed based on the image data to which the thinning process is applied to the recording medium. Characteristic control method. A computer comprising a fixing device for thermally fixing a recording material formed on the basis of image data to a recording medium;
Derivation means for deriving information of a recording material formed on a recording medium based on the image data;
Determining means for determining a fixing temperature for thermally fixing the recording material to the recording medium in accordance with the derived recording material information;
Selection means for selecting a thinning pattern to be used for thinning processing for the image data based on the determined fixing temperature;
Thinning means for performing thinning processing of the image data using the selected thinning pattern;
A function for controlling the fixing device based on the determined fixing temperature so as to thermally fix a recording material formed based on the image data to which the thinning process is applied to the recording medium. program. A computer comprising a fixing device for thermally fixing a recording material formed on the basis of image data to a recording medium;
Determining means for determining a fixing temperature for thermally fixing a recording material formed on a recording medium based on the image data;
Thinning means for controlling thinning processing on the image data based on the determined fixing temperature;
A function for controlling the fixing device based on the determined fixing temperature so as to thermally fix a recording material formed based on the image data to which the thinning process is applied to the recording medium. program.

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