Patent Publication Number: US-11397393-B2

Title: Image forming apparatus that controls primary fixing temperature and secondary fixing temperature

Description:
INCORPORATION BY REFERENCE 
     This application claims priority to Japanese Patent Application No. 2020-105697 filed on 18 Jun., 2020, the entire contents of which are incorporated by reference herein. 
     BACKGROUND 
     The present disclosure relates to an image forming apparatus. 
     An image forming apparatus based on electrophotography is configured to fix a toner image transferred to a printing sheet, for example with a fixing device of a heat-pressing type. The picture quality of the toner image fixed onto the printing sheet varies depending on the fixing temperature, and therefore it is important to properly control the fixing temperature. 
     Some of the existing image forming apparatuses (hereinafter, “first image forming apparatus”) are configured to control the fixing temperature of the fixing device, according to the basis weight and the type of the printing sheet. 
     Image forming apparatuses of another type (hereinafter, “second image forming apparatus”) are configured to adjust the fixing temperature according to a printing mode (e.g., full-color mode, monochrome mode, or toner-saving mode), with respect to each page. 
     Image forming apparatuses of still another type (hereinafter, “third image forming apparatus”) are configured to control the fixing temperature, according to the amount of toner applied to the printing sheet. 
     SUMMARY 
     The disclosure proposes further improvement of the foregoing techniques. 
     In an aspect, the disclosure provides an image forming apparatus including a fixing device, and a controller. The fixing device fixes a toner image onto a printing sheet to which the toner image corresponding to an image to be drawn by printing. The controller includes a processor, and acts as a print controller, a drawing controller, and an engine controller, when the processor executes a control program. The print controller receives a printing request. The drawing controller identifies an image to be drawn, through image processing of a page image designated by the printing request with respect to each page, and identifies a use amount of toner required for the image to be drawn. The engine controller controls a fixing temperature of the fixing device. The engine controller executes a primary fixing temperature control including controlling the fixing temperature according to color information designated by the printing request with respect to each page, and executes, after executing the primary fixing temperature control, a secondary fixing temperature control including controlling the fixing temperature according to the use amount of toner identified by the drawing controller. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic side view showing an internal mechanical structure of an image forming apparatus according to an embodiment of the disclosure; 
         FIG. 2  is a block diagram showing an essential part of the electrical configuration of the image forming apparatus according to the embodiment of the disclosure; and 
         FIG. 3  is a flowchart for explaining an operation of the image forming apparatus. 
     
    
    
     DETAILED DESCRIPTION 
     Hereafter, an embodiment of the disclosure will be described, with reference to the drawings. 
       FIG. 1  is a schematic side view showing an internal mechanical structure of an image forming apparatus according to the embodiment of the disclosure. The image forming apparatus  1  shown in  FIG. 1  is an apparatus having a printing function based on electrophotography, such as a printer, a facsimile machine, a copier, or a multifunction peripheral. 
     The image forming apparatus  1  includes a tandem-type color developing device. The color developing device includes photoconductor drums  1 A to  1 D, exposure devices  2 A to  2 D, and developing units  3 A to  3 D. The photoconductor drums  1 A to  1 D are photosensitive bodies respectively corresponding to four colors, namely cyan, magenta, yellow, and black. 
     The exposure devices  2 A to  2 D each scan the corresponding one of the photoconductor drums  1 A to  1 D with laser beam, to thereby form an electrostatic latent image. The laser beam is emitted in the direction orthogonal to the rotating direction (sub scanning direction) of each of the photoconductor drums  1 A to  1 D, in other words in the main scanning direction. The exposure devices  2 A to  2 D each include a laser scanning unit having a laser diode which is the source of the laser beam, and optical elements (e.g., lenses, mirrors, polygon mirrors) that conduct the laser beam to the corresponding one of the photoconductor drums  1 A to  1 D. 
     A charger such as a scorotron, a cleaning device, and an ionizer are provided around each of the photoconductor drums  1 A to  1 D. The cleaning device removes residual toner from the photoconductor drum, after primary transfer. The ionizer removes static electricity from the photoconductor drum, after the primary transfer. 
     The developing units  3 A to  3 D each include a toner cartridge in which the toner of the corresponding color out of cyan, magenta, yellow, and black is loaded, and a developer that applies the toner delivered from a toner hopper in the toner cartridge, to the corresponding one of the photoconductor drums  1 A to  1 D. The developing units  3 A to  3 D each apply the toner to the electrostatic latent image on the corresponding one of the photoconductor drums  1 A to  1 D, to thereby form a toner image. 
     The photoconductor drum  1 A, the exposure device  2 A, and the developing unit  3 A serve to develop a portion of the image corresponding to magenta. The photoconductor drum  1 B, the exposure device  2 B, and the developing unit  3 B serve to develop a portion of the image corresponding to cyan. The photoconductor drum  1 C, the exposure device  2 C, and the developing unit  3 C serve to develop a portion of the image corresponding to yellow. The photoconductor drum  1 D, the exposure device  2 D, and the developing unit  3 D serve to develop a portion of the image corresponding to black. 
     The image forming apparatus  1  also includes an intermediate transfer belt  4 , a drive roller  5 , a transfer roller  6 , a roller  7 , and a sensor  8 . The intermediate transfer belt  4  is an annular image carrier (intermediate transfer medium) disposed in contact with the photoconductor drums  1 A to  1 D, so that the toner image on each of the photoconductor drums  1 A to  1 D is transferred to the intermediate transfer belt  4 , as primary transfer. The intermediate transfer belt  4  is wound around the drive roller  5 , to be thereby driven to rotate in the direction from the contact position with the photoconductor drum  1 D toward the contact position with the photoconductor drum  1 A. 
     The transfer roller  6  causes the printing sheet transported thereto as will be subsequently described, to contact the intermediate transfer belt  4 , so that the toner image on the intermediate transfer belt  4  is transferred to the printing sheet, as secondary transfer. The printing sheet to which the toner image has been transferred is transported to the fixing device  9 . The fixing device  9  fixes the toner image, corresponding to an image to be drawn through the printing operation to be subsequently described, onto the printing sheet to which such toner image has been transferred. In this embodiment, the fixing operation is performed by heat-pressing. 
     The roller  7  includes a cleaning brush. The roller  7  causes the cleaning brush to contact the intermediate transfer belt  4 , to thereby remove the toner remaining on the intermediate transfer belt  4 , after the transfer of the toner image to the printing sheet, or after calibration. 
     The sensor  8  emits light to the intermediate transfer belt  4 , and detects the reflected light from the surface, or from the toner pattern on the surface of the intermediate transfer belt  4 . For example, the sensor  8  emits light and detects the reflected light, to and from a predetermined region on the intermediate transfer belt  4  (where a toner patch for calibration is transferred) at the time of calibration of toner gradation or toner density, and outputs an electrical signal according to the amount of the reflected light. 
     The image forming apparatus  1  also includes a plurality of paper cassettes  11  and  12 , a transport roller  27 , a resist roller  28 , and a resist sensor  29 . The paper cassettes  11  and  12  respectively accommodate printing sheets  31  and  32  therein. The paper cassettes  11  and  12  lift the printing sheets  31  and  32  upward with lifting plates  21  and  24 , to thereby cause the printing sheets  31  and  32  to contact pickup rollers  22  and  25 , respectively. The pickup rollers  22  and  25  respectively pick up the printing sheets  31  and  32  accommodated in the paper cassettes  11  and  12 , one by one from the top, toward feed rollers  23  and  26 . The feed rollers  23  and  26  respectively deliver the printing sheets  31  and  32 , picked up by the pickup rollers  22  and  25  from the paper cassettes  11  and  12 , one by one to a transport route. 
     The transport roller  27  is provided on the transport route, to be utilized in common by the printing sheets  31  and  32  transported from the paper cassettes  11  and  12 . 
     The resist roller  28  temporarily detains the printing sheet being transported, and delivers the printing sheet to the transfer position between the intermediate transfer belt  4  and the transfer roller  6 , at the timing for secondary paper feeding. The timing for the secondary paper feeding is determined by a controller  41  to be subsequently described, so as to allow the toner image on the intermediate transfer belt  4  to be transferred to a designated position on the printing sheet. 
     The resist sensor  29  is located close to the resist roller  28 . The resist sensor  29  optically detects that the printing sheet has reached the resist roller  28 , which corresponds to a secondary paper feeding position. 
       FIG. 2  is a block diagram showing an essential part of the electrical configuration of the image forming apparatus  1  according to the embodiment of the disclosure. As shown in  FIG. 2 , the image forming apparatus  1  includes the controller  41 , a printing device  42 , an operation panel  43 , and a communication device  44 . 
     The controller  41  is a computer including a processor such as a central processing unit (CPU) or an application specific integrated circuit (ASIC). The controller  41  realizes the functional units, with at least one of software and hardware. The controller  41  monitors and controls the internal devices such as the printing device  42 , and executes various types of data processing. 
     The printing device  42  is one of the internal devices, and configured to print a source image with the mechanical structure, for example shown in  FIG. 1 . 
     The operation panel  43  includes an input device  43 A having a touch panel for receiving a user&#39;s operation and hard keys, and a display device  43 B, for example constituted of an LCD panel for displaying an operation screen for the user. 
     The communication device  44  may be, for example, a wired or wireless network interface, a modem, or a peripheral equipment interface. The communication device  44  performs data communication, for example with a host apparatus. 
     The controller  41  acts as a print controller  51 , a drawing controller  52 , and an engine controller  53 . 
     The print controller  51  receives a printing request, and executes a printing job according to the printing request received, using the drawing controller  52  and the engine controller  53 . The print controller  51  receives the printing request, for example, from the host apparatus through the communication device  44 . 
     The drawing controller  52  executes image processing (e.g., color conversion, color correction, or half toning) to a page image designated by the printing request with respect to each page, to thereby identify the image to be drawn through the printing job, and determines a toner use amount required by the image to be drawn. 
     In this embodiment, the drawing controller  52  identifies the number of toner dots of the image to be drawn through the printing job, and determines the toner use amount, on the basis of the number of toner dots. In the case of color printing, the drawing controller  52  identifies the toner use amount on the basis of, for example, the total sum of the number of toner dots of a plurality of color planes (in this embodiment, cyan, magenta, yellow, and black). The drawing controller  52  calculates the toner use amount from the number of toner dots, for example using a predetermined function known through experiments. 
     The engine controller  53  controls the drive source that drives the foregoing rollers, a bias application circuit that applies a development vias and a primary transfer bias, the exposure devices  2 A to  2 D, and the fixing temperature of the fixing device  9 , more specifically the temperature of a fixing heater  9 A, so as to form the electrostatic latent image, develop, transfer, and fix the toner image, and feed and discharge the printing sheet. 
     In particular, the engine controller  53  controls the primary fixing temperature, according to color information (information designating one of color printing, monochrome printing, and blank, in other words no image to be printed) designated by the printing request with respect to each page, and then controls the secondary fixing temperature, after the primary fixing temperature is executed and the toner use amount is determined, on the basis of the toner use amount determined. 
     The print controller  51  sets a target fixing temperature according to the color information, when controlling the primary fixing temperature. When controlling the secondary fixing temperature, the print controller  51  sets the target fixing temperature, according to the toner use amount. Here, the print controller  51  obtains the target fixing temperature from the color information or the toner use amount, for example using a lookup table or a function. The lookup table or the function is established in advance through experiments, and implemented in the print controller  51 . 
     In this embodiment, the engine controller  53  controls the secondary fixing temperature, using both of the color information and the toner use amount. In other words, the print controller  51  sets the target fixing temperature for the secondary fixing temperature control, according to both of the color information and the toner use amount. 
     Further, the engine controller  53  controls the primary fixing temperature during a primary feeding of the printing sheet (while the printing sheet is transported from the paper cassette  11  or  12  to the resist roller  28 ), and controls the secondary fixing temperature during the secondary feeding of the printing sheet (while the printing sheet is transported from the resist roller  28  to the fixing device  9 ). 
     Hereunder, an operation of the image forming apparatus  1  will be described.  FIG. 3  is a flowchart for explaining the operation of the image forming apparatus  1 . 
     The print controller  51  causes the engine controller  53 , upon receipt of the printing request, to start the primary feeding of the printing sheet designated by the printing request (step S 1 ). After step S 1 , the print controller  51  sets the target fixing temperature for the primary fixing temperature control (hereinafter, “primary target fixing temperature”) according to the color information, notifies the primary target fixing temperature to the engine controller  53 , and causes the engine controller  53  to start the primary fixing temperature control (step S 2 ). The engine controller  53  controls the primary fixing temperature, so as to match the temperature of the fixing heater  9 A with the primary target fixing temperature. In other words, in the primary fixing temperature control, the engine controller  53  adjusts the temperature of the fixing heater  9 A so as to accord with the primary target fixing temperature, from the current temperature thereof. 
     The print controller  51  also causes the drawing controller  52 , upon receipt of the printing request, to execute the necessary image processing and the calculation of the toner use amount, with respect to each page (step S 3 ). 
     When the drawing controller  52  finishes the image processing and the calculation of the toner use amount, the print controller  51  causes the engine controller  53  to start the secondary feeding of the printing sheet (step S 4 ). After step S 4 , the print controller  51  sets the target fixing temperature for the secondary fixing temperature control (hereinafter, “secondary target fixing temperature”) according to the toner use amount and the color information, notifies the secondary target fixing temperature to the engine controller  53 , and causes the engine controller  53  to start the secondary fixing temperature control (step S 5 ). The engine controller  53  controls the primary fixing temperature, so as to match the temperature of the fixing heater  9 A with the secondary target fixing temperature. In other words, in the secondary fixing temperature control, the engine controller  53  adjusts the temperature of the fixing heater  9 A so as to accord with the primary target fixing temperature, from the primary target fixing temperature. Therefore, the adjustment range of the fixing temperature becomes smaller in the secondary fixing temperature control, and the fixing temperature of the fixing device  9  can reach the secondary target fixing temperature, in a short time. 
     After step S 5 , the print controller  51  causes the engine controller  53  to transfer the toner image from the intermediate transfer belt  4  to the printing sheet, transport the printing sheet to the fixing device  9 , and cause the fixing device  9  to fix the toner image onto the printing sheet, at the secondary target fixing temperature (step S 6 ). After the fixing process, the printing sheet is discharged. 
     Now, in the case of uniformly determining the fixing temperature according to the type of sheets or the printing mode, as with the first and the second image forming apparatus referred to above, the appropriate fixing temperature may fail to be set, for the toner image to be printed (i.e., fixed). 
     In addition, in the case of controlling the fixing temperature according to the amount of toner applied to the printing sheet, as with the third image forming apparatus referred to above, the control of the fixing temperature is started after the toner amount is identified. Therefore, it takes a long time to execute the printing operation, in other words the printing speed becomes slower. 
     With the arrangement according to the foregoing embodiment, in contrast, the print controller  51  receives the printing request. The drawing controller  52  executes the image processing to the page image designated by the printing request with respect to each page, to thereby identify the image to be drawn through the printing job, and determines the toner use amount required by the image to be drawn. The fixing device  9  fixes the toner image onto the printing sheet, the toner image corresponding to the image to be drawn and having been transferred to the printing sheet. The engine controller  53  controls the fixing temperature of the fixing device  9 . More specifically, the engine controller  53  controls the primary fixing temperature, according to color information designated by the printing request with respect to each page, and then controls the secondary fixing temperature, after the primary fixing temperature is executed and the toner use amount is determined, on the basis of the toner use amount determined. 
     Therefore, the printing operation can be executed in a relatively short time, and at the appropriate fixing temperature. 
     Various changes and modifications to the foregoing embodiment are obvious to those skilled in the art. Such changes and modifications may be made without departing from the scope and spirit of the subject, and without compromising the intended advantages. Thus, such changes and modifications are encompassed in the scope of the appended claims. 
     For example, although the image forming apparatus  1  according to the foregoing embodiment is based on an indirect transfer method, the image forming apparatus  1  may employ a direct transfer method. 
     The disclosure is applicable, for example, to an image forming apparatus based on electrophotography. 
     While the present disclosure has been described in detail with reference to the embodiments thereof, it would be apparent to those skilled in the art the various changes and modifications may be made therein within the scope defined by the appended claims.