JP2011064786A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which forms an image, which causes no difference in gloss and hue between pages, without spoiling the productivity of the image forming apparatus. <P>SOLUTION: A control unit 100 inputs image data, stores them (S100), determines whether at least either a difference in gloss or a difference in hue is to be reduced, when an image is formed, with reference to an image data printing rate (S102) or the like (S103), and changes forming order to form images so that it may give priority to the image formation of image data which require no reduction in gloss difference (S106). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to image formation control in accordance with a temperature change of a fixing device in an image forming apparatus.

  In an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, a toner image is formed on a recording material (also referred to as a transfer material, a sheet, or a recording medium), and this is heated and pressed to fix the image. Forming. In such a fixing device, a roller fixing method in which a pressure roller is pressed against a fixing roller having a built-in heater to form a fixing nip to fix a toner image has been conventionally employed.

  Also, in recent years, along with the response to higher speed and energy saving, belt fixing that has less heat capacity than the roller fixing method and can secure a wide fixing nip to extend the passage time of the recording material to the fixing nip. A method (for example, Patent Document 1) is also employed.

  However, the power supplied to the fixing device is limited in order to save energy, and the temperature of the fixing device is lowered due to lower heat capacity and higher speed. The temperature difference becomes more conspicuous with the stable temperature after the temperature drop due to.

FIG. 7 shows the temperature transition of the surface of the fixing belt when a sheet having a length of 210 mm and a basis weight of 105 g / m ² is conveyed at a speed of 50 sheets per minute using a belt fixing type fixing device. Is. When the fixing device reaches a predetermined temperature, the surface temperature of the fixing belt is controlled so as to maintain a constant temperature (205 ° C.). After that, when paper feeding is started, the surface temperature of the fixing belt is controlled so as to maintain a constant temperature, but it decreases as the paper passing time elapses, and finally stabilizes at about 150 ° C. To do. The temperature transition of the fixing belt shown in FIG. 7 shows the case of the above conditions. The speed of temperature decrease and the final stable temperature are the length in the feed direction of the recording material, the basis weight, the heat capacity, and the conveyance speed. The number of prints per unit time varies.

  As shown in FIG. 7, the toner image on the recording material conveyed to the fixing device in such a temperature state has a heating temperature difference of about 55 ° C. immediately after the start of paper feeding and when the surface temperature of the fixing belt is stabilized. It will have.

  The toner image differs in the melting state of the toner depending on the heating temperature, and the color and gloss differ. When a plurality of the same unfixed toner images are fixed using a fixing device having a temperature difference as described above, there is a problem that a difference in color and gloss occurs between the images. FIG. 8 shows the relationship between the fixing belt temperature and the gloss (glossiness), and the glossiness is measured using a gloss meter with an incident angle of 60 ° and a light receiving angle of 60 °. If the difference in glossiness is 5 or more, the difference can be distinguished significantly even visually. In this figure, the color component with the most significant difference in glossiness is magenta, and the difference is 7.5 between the fixing belt temperature of 205 ° C and 155 ° C. The maximum is 5, and the difference can be distinguished visually.

  Conventionally, for such problems, the number of recording materials passing through the fixing nip per unit time is reduced by reducing the conveying speed of the recording material disclosed in Patent Documents 2 and 3 and widening the conveying interval. Is controlled to reduce the temperature drop due to the paper passing.

JP 2004-341346 A Japanese Patent Laid-Open No. 10-186933 JP 2003-011461 A

  However, the method of slowing the recording material conveyance speed or extending the conveyance interval is effective in reducing the color difference and gloss difference. However, when a large amount of recording material is output, This significantly reduces the productivity of the user, which causes discomfort to the user. Furthermore, widening the sheet conveyance interval continuously drives the motors even when the sheet is not being conveyed, and wear of the conveyance device, the photosensitive member, and the fixing device proceeds, and the life of these devices is shortened. There are also challenges.

  The present invention has been made under such circumstances. In an image forming apparatus, color difference or gloss between pages of a recording material can be achieved without impairing productivity or shortening the life of each apparatus. The purpose is to prevent the difference.

  In the present invention, in order to solve the above-described problems, the image forming apparatus is configured as follows.

  (1) A storage unit for inputting and storing a plurality of pages of image data; a toner image is formed on a recording material based on the image data stored in the storage unit; and the toner image is stored on the recording material by a fixing unit. An image forming unit to be fixed; a determination unit that determines whether it is necessary to reduce at least one of a gloss difference and a color difference for each image data of a plurality of pages; and at least a gloss difference and a color difference by the determination unit Image formation is performed so that the image formation order of image data for which one reduction is necessary is later than the image formation order for image data for which at least one of gloss difference and color difference is not required to be reduced An image forming apparatus comprising: a control unit that changes the order.

  (2) A plurality of recording material supply means for supplying recording materials of different materials, a storage means for inputting and storing a plurality of pages of image data, and a recording material based on the image data stored in the storage means An image forming unit that forms a toner image and fixes the toner image to the recording material by a fixing unit; a determination unit that determines a printing rate for a printable area of one page for each image data of a plurality of pages; The image formation order is set so that the image formation order of the image data of the page for which the printing rate determined by the determination unit is equal to or greater than the predetermined value is later than the image formation order of the image data for the page of which the printing rate is less than the predetermined value. And an image forming apparatus comprising:

  (3) A plurality of recording material supply means for supplying recording materials of different materials, a storage means for inputting and storing a plurality of pages of image data, and a recording material based on the image data stored in the storage means An image forming unit that forms a toner image and fixes the toner image on the recording material by a fixing unit, and a page that is designated to form an image on a recording material of a specific material for each image data of a plurality of pages Determination means for determining the presence / absence of the image data, and forming an image on the recording material of the specific material by forming an image forming order of the image data of the page designated to form an image on the recording material of the specific material. An image forming apparatus comprising: control means for changing an image forming order so that the image forming order of an image of a non-designated page is later.

  According to the present invention, since the image forming apparatus reduces the gloss difference and the color difference of the image due to the fixing temperature difference, the gloss difference and the color difference are visually problematic when the temperature difference of the fixing device is large. Image formation of unacceptable character images, low printing rate images, and monochrome images is performed. In the stable state where the temperature difference of the fixing device is small and stable, the image forming apparatus can form an image without degrading its performance by selectively forming an image that should reduce the gloss difference and the color difference. It can be carried out.

Flowchart of the operation of the image forming apparatus of the first embodiment The flowchart about operation | movement of the post-processing apparatus of 1st Embodiment. 1 is a configuration diagram illustrating an image forming apparatus and a post-processing apparatus according to first and second embodiments. 1 is a configuration diagram illustrating a fixing device of an image forming apparatus according to a first embodiment. The figure which showed the page change of 1st Embodiment Flowchart of the operation of the image forming apparatus of the second embodiment Figure showing the temperature transition of the fixing belt surface of the belt fixing method Diagram showing the relationship between fixing belt temperature and gloss (glossiness)

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The embodiment described below is an example as means for realizing the present invention, and should be appropriately modified or changed according to the configuration and various conditions of the apparatus to which the present invention is applied. The present invention is not limited to the embodiment.

[First Embodiment]
A first embodiment of the present invention will be described in detail with reference to the drawings.

<Image forming unit>
FIG. 3 is a longitudinal sectional view showing a schematic configuration of the image forming apparatus in the present embodiment. This image forming apparatus is an electrophotographic full-color composite machine that functions as a printer, a copying machine, and a facsimile machine.

  First, an outline of the image forming unit will be described.

  The image reading unit 1 scans and exposes an image of the color image original O placed on the platen glass 1a by the moving optical system 1b, and photoelectrically reads it as a color separation image signal by the full color sensor (CCD) 1c. The color-separated image signal is subjected to predetermined image processing by the image processing unit 1 d and then sent to the control unit (control means) 100 of the image output unit 2. A document pressing plate or an automatic document feeder (ADF, RDF) 1e is disposed on the document table glass 1a of the image reading unit 1.

  The control unit 100 includes a CPU 101 and a memory 102, and functions such as driving of each load in the image forming apparatus, information collection analysis of sensors, data exchange with an operation unit (user interface), storage and processing of image data, and the like. Is responsible. The image forming apparatus is comprehensively controlled by the control unit 100.

  In the image output unit 2, UK (black), UM (magenta), UC (cyan), and UY (yellow) are the first to fourth image forming units. Tandem arrangement. Each image forming unit is composed of a laser exposure type electrophotographic process mechanism and has the same configuration. In each of the image forming units UK, UM, UC, UY, the electrophotographic photosensitive member 3 (hereinafter referred to as “drum”) is rotationally driven in the counterclockwise direction indicated by the arrow. The primary charger 4 uniformly charges the outer peripheral surface of the drum 3. The laser exposure unit 5 scans and exposes the uniformly charged surface of the drum 3 with the laser beam L to form an electrostatic latent image based on the color separation image signal. The developing device 6 visualizes the electrostatic latent image on the drum surface as a toner image. The developing device 6 of the first image forming unit UK contains black toner as a developer. Similarly, magenta toner is used for the developing device 6 of the second image forming unit UM, cyan toner is used for the developing device 6 of the third image forming unit UC, and the developing device 6 of the fourth image forming unit UY is used. Each of the yellow toners is accommodated.

  Then, based on the color separation image signal sent from the image processing unit 1d to the control unit 100, the first image forming unit UK controls so as to form a black toner image on the surface of the drum 3 at a predetermined control timing. Is done. Similarly, the second image forming unit UM has a predetermined magenta toner image, the third image forming unit UC has a cyan toner image, and the fourth image forming unit UY has a yellow toner image on the surface of the drum 3. It is controlled to form at the control timing.

  The toner image formed on the surface of the drum 3 of each image forming unit is transferred to the intermediate transfer belt (hereinafter referred to as “belt”), which is an endless and flexible intermediate transfer member that is rotationally driven by the primary transfer unit 7. In this case, the images are sequentially superimposed and transferred onto the surface 8. As a result, an unfixed full-color toner image is synthesized and formed on the surface of the belt 8 by superimposing the four toner images. In each image forming unit, the toner remaining on the drum 3 without being transferred to the belt 8 is removed by the cleaning device 9.

  The belt 8 is stretched around a driving roller 10, a driven roller 11 that also serves as a tension roller, and a secondary transfer counter roller 12, and is substantially the same speed as the rotational speed of the drum 3 in the clockwise direction of the arrow. Is driven to rotate. The belt portion between the driving roller 10 and the driven roller 11 is opposed or brought into contact with the lower surface of the drum 3 of each image forming unit to form the primary transfer portion 7. The primary transfer charger 13 is disposed on the back side of the belt 8 and at the position of each primary transfer portion 7, and a predetermined voltage is applied when the toner image is transferred.

  The unfixed full-color toner image synthesized and formed on the surface of the belt 8 reaches the secondary transfer unit 14 by the rotation of the belt 8. The secondary transfer portion 14 is formed by pressing the secondary transfer roller 15 with the belt 8 sandwiched between the secondary transfer counter roller 12 and the nip portion between the secondary transfer roller 15 and the belt 8 is 2. The next transfer unit 14. A sheet-like recording material (transfer material) P is fed from the paper feed unit 16 or the manual feed tray 19 to the secondary transfer portion 14 at a predetermined control timing, so that the surface of the recording material P is transferred. Unfixed full-color toner images on the surface of the belt 8 are sequentially transferred. A predetermined voltage is applied to the secondary transfer roller 15 when the toner image is transferred.

  The paper feeding unit 16 has upper and lower two-stage paper feeding cassettes 17 and 18, and the single sheet feeding operation of the recording material P from the paper feeding cassette at the level selected according to the recording material size or the like is performed at a predetermined control timing. Executed. The recording material P fed from the paper feed unit 16 or the manual feed tray 19 is conveyed to the registration roller 210 by the sheet path 200. At that time, the registration roller 210 is stopped, and the leading edge of the recording material P hits the nip portion. After that, the rotational driving of the registration roller 210 is started at the timing when the image forming units UK, UM, UC, UY start image formation. The rotation start timing of the registration roller 210 is set so that the leading edge of the recording material P and the leading edge of the toner image transferred from each image forming unit onto the belt 8 coincide with each other in the secondary transfer portion 14. ing.

  The cleaning unit 90 cleans the image forming surface of the belt 8, and the toner remaining on the belt 8 without being transferred to the recording material P is removed by the cleaning unit 90 in the secondary transfer unit 14.

  The recording material P that has received the secondary transfer of the toner image from the surface of the belt 8 at the secondary transfer unit 14 is separated from the surface of the belt 8 and introduced into the fixing device (fixing unit) F by the conveyance guide 220. The toner image is thermally fixed on the surface of the recording material P by the fixing device F. The recording material P exiting the fixing device F is conveyed by the inner and outer paper discharge rollers 230 and 240 and sent to the post-processing device 300.

  The image forming apparatus functions as a copying machine when a photoelectric read image signal of a document image is input from the image reading unit 1 to the control unit 100 of the image output unit 2. Further, when an image signal is input to the control unit 100 from an external host device such as a personal computer, the image forming apparatus functions as a printer. Further, the image forming apparatus receives an image signal received from the facsimile machine of the other machine into the control unit 100 or transmits a photoelectric read image signal of the original image by the image reading unit 1 to the facsimile machine of the other machine. Functions as a facsimile machine.

<Post-processing device>
The post-processing apparatus 300 shown in FIG. 3 receives the recording material P conveyed from the inner and outer paper discharge rollers 240 by the delivery roller 310 and conveys it to the sorting unit 320. The sorting unit 320 includes a shaft 322 that can be rotated by a solenoid mechanism (not shown) and a sorting plate 321, and the shaft 322 that can be rotated by an instruction from the control unit 100 is rotated to store the conveyed recording material P as a stocker. 340 or stocker 350. The recording material P1 on the stocker 340 and the recording material P2 on the stocker 350 are selectively conveyed by stocker paper feed rollers 342 and 352 in accordance with instructions from the control unit 100. The stocker transport rollers 343 and 353 transport the recording materials P1 and P2 transported from the respective stockers to the paper discharge roller 360. The paper discharge roller 360 discharges the conveyed recording materials P1 and P2 to a paper discharge tray 370 outside the post-processing apparatus 300.

<Fixing device F>
4 is a schematic cross-sectional view of a main part of the fixing device F shown in FIG. 3 and a block diagram of a control system. The fixing device F shown in FIG. 4 is a belt type / electromagnetic induction heating type device (IH fixing device).

  A fixing belt unit 31 as a fixing member and a pressure belt unit 32 as a pressure member are arranged vertically and are pressed against each other by a pressure mechanism (not shown), and between the fixing belt unit 31 and the pressure belt unit 32. A fixing nip portion N is formed. An induction heating coil unit 41 as a fixing belt heating unit is disposed on the upper side of the fixing belt unit 31.

  The fixing belt unit 31 includes an endless, first and second fixing roller 33 serving as a driving roller, a second fixing roller 34 serving as a tension roller, and suspended and stretched between the first and second fixing rollers 33 and 34. A flexible fixing belt 35 is included. The first fixing roller 33 and the second fixing roller 34 are arranged in parallel with each other and rotatably supported by a frame (not shown) of the fixing belt unit 31. The first fixing roller 33 is positioned downstream of the second fixing roller 34 in the recording material conveyance direction. A first pressure pad 36 is disposed on the inner surface side of the descending belt portion of the fixing belt 35. The first fixing roller 33, the second fixing roller 34, and the first pressure pad 36 are contact members that come into contact with the fixing belt 35.

  The pressure belt unit 32 includes a first pressure roller 37 as a driving roller, a second pressure roller 38 as a tension roller, and a tension between the first pressure roller 37 and the second pressure roller 38. An endless and flexible pressure belt 39 is provided. The first pressure roller 37 and the second pressure roller 38 are arranged so as to be bearing-supported so as to be substantially parallel to each other and freely rotatable with respect to a frame (not shown) of the pressure belt unit 32. The first pressure roller 37 is positioned downstream of the second pressure roller 38 in the recording material conveyance direction. A second pressure pad 40 is disposed on the inner surface side of the ascending belt portion of the pressure belt 39.

  Each of the first fixing roller 33, the second fixing roller 34, the first pressure roller 37, and the second pressure roller 38 is an elastic material in which an elastic material layer such as a heat resistant rubber is formed on the outer peripheral surface of the hollow core metal. Laura.

  Both the fixing belt 35 and the pressure belt 39 are electromagnetic induction exothermic members in which an elastic surface layer of silicone rubber is formed on the outer peripheral surface of a metal belt (for example, Ni) as a base layer. In the pressure state of the fixing belt unit 31 and the pressure belt unit 32, the first fixing roller 33 and the first pressure roller 37 are pressed against each other with the fixing belt 35 and the pressure belt 39 interposed therebetween. Further, the second fixing roller 34 and the second pressure roller 38 are pressed against each other with the fixing belt 35 and the pressure belt 39 interposed therebetween. Further, the first pressure pad 36 and the second pressure pad 40 are pressed against each other with the fixing belt 35 and the pressure belt 39 interposed therebetween. As a result, the lower belt portion of the fixing belt 35 and the upper belt portion of the pressure belt 39 are in pressure contact with each other, and a wide fixing nip portion N is formed in the recording material conveyance direction.

  The first fixing roller 33 is rotationally driven at a predetermined control speed in the clockwise direction of the arrow by the first fixing motor M1. The rotation of the first fixing roller 33 causes the fixing belt 35 and the second fixing roller 34 to rotate. The first pressure roller 37 is driven to rotate at a predetermined control speed in the counterclockwise direction of the arrow by the second fixing motor M2. By the rotation driving of the first pressure roller 37, the pressure belt 39 and the second pressure roller 38 are rotated. The first fixing motor M <b> 1 and the second fixing motor M <b> 2 that rotationally drive the fixing belt 35 and the pressure belt 39 are subjected to on / off control and rotational speed control by the control unit 100 via the motor driving circuit 103. . As a result, the rotation speeds of the fixing belt 35 and the pressure belt 39 are controlled to be substantially the same predetermined control speed in the fixing nip portion N. Note that the first fixing roller 33 and the first pressure roller 37 are connected to a connecting member such as a gear or a timing belt so as to rotate in conjunction with one of the first fixing motor M1 and the second fixing motor M2. It is also possible to have a configuration in which these are connected together.

  An induction heating coil unit (hereinafter referred to as a “coil unit”) 41 functions as a heating unit for the fixing belt 35 and is close to the upper surface of the fixing belt 35 above the second fixing roller 34 portion of the fixing belt unit 31. They are arranged facing each other. The coil unit 41 includes an induction heating coil (hereinafter referred to as “coil”) 42 and a magnetic core 43 such as a ferrite core or a laminated core. The coil 42 has a configuration in which, for example, a copper wire having a fusion layer and an insulating layer on its surface is wound a plurality of times. More specifically, the coil unit 41 electrically insulates, for example, a coil 42 formed by winding a litz wire as a wire into a horizontally long and flat sheet-like spiral coil, and a magnetic core 43 covering the coil 42. This is a horizontally long and plate-shaped member integrally molded with resin.

  The fixing belt 35 is induction-heated locally at the belt heating position, with the area facing the coil unit 41 as a belt heating position. That is, a high frequency current is passed through the coil 42 of the coil unit 41 from the excitation circuit 104 to generate an alternating magnetic flux (magnetic field). The magnetic flux is absorbed by the metal belt which is the base layer of the fixing belt 35 at the belt heating position, and a vortex induced current is generated in the metal belt, and the metal belt generates heat due to its inherent resistance. That is, the coil unit 41 also functions as magnetic flux generation means. As described above, the fixing belt 35 itself generates heat by electromagnetic induction and heats up at the belt heating position by the high-frequency current flowing through the coil 42.

  Further, the fixing belt 35 and the pressure belt 39 are rotationally driven, so that heat is supplied to the entire fixing device F and the temperature of the fixing device rises. Further, the surface temperature of the fixing belt 35 is detected by temperature detecting means TH such as a thermistor as the fixing device temperature. The temperature detection means TH is disposed in contact with the outer surface of the fixing belt 35 at or near the belt heating position, which is the opposed portion between the fixing belt 35 and the coil unit 41. Electrical information relating to the temperature of the fixing belt surface detected by the temperature detection means TH is input to the control unit 100 via the A / D converter 105.

  Based on the input information, the control unit 100 adjusts the amount of power supplied from the excitation circuit 104 to the coil unit 41 so as to control the surface temperature of the fixing belt 35 to be maintained at a predetermined temperature. That is, the temperature of the fixing device is adjusted by the control unit 100. In this embodiment, the fixing device is temperature-controlled so that the fixing temperature is 200 ° C., and the temperature detected by the temperature detecting means TH is maintained at the fixing temperature 200 ° C.

  When the fixing device is in a temperature control state, the recording material P on which the unfixed toner image t is formed on the surface is introduced from the image forming unit side into the fixing device F by the conveyance guide 220 and enters the fixing nip portion N. To do. In the process in which the recording material P is nipped and conveyed to the fixing nip N, the unfixed toner image t on the recording material P is recorded by the heat of the fixing belt 35 and the pressure belt 39 and the pressure of the fixing nip N. It is fixed to the surface of the material P by heat and pressure. The recording material that has passed through the fixing nip N is separated from the fixing belt 35 and the pressure belt 39 and discharged and conveyed.

  The thermo switch THS functions as a safety device for the fixing device, and is inserted in series from the excitation circuit 104 to the energization circuit for the coil 42 of the coil unit 41. The thermo switch THS is disposed in contact with the inner surface of the fixing belt 35 at or near the heating position of the fixing belt 35. When the fixing device F goes out of control for some reason and the temperature of the fixing belt 35 exceeds a predetermined limit temperature, the thermo switch THS cuts off the power supply from the excitation circuit 104 to the coil unit 41. Operate. In this embodiment, the thermo switch THS operates to cut off the power supply from the excitation circuit 104 to the coil unit 41 when the temperature of the contact portion with the fixing belt 35 exceeds 250 ° C.

  When the image forming apparatus is warmed up, the control unit 100 continuously rotates the fixing belt 35 and the pressure belt 39 at the first speed V1 for image formation. In the present embodiment, a maximum of 1,000 W of electric power is supplied from the excitation circuit 104 to the coil unit 41, and the fixing device is raised to a predetermined temperature of 205 ° C. In the image forming process, the control unit 100 continuously rotates the fixing belt 35 and the pressure belt 39 at the first speed V1 for image formation. In the present embodiment, the maximum temperature of 800 W is supplied from the excitation circuit 104 to the coil unit 41 to adjust the temperature to maintain the fixing temperature of 205 ° C.

<Operation of Image Forming Apparatus and Post-Processing Apparatus According to the Present Invention>
FIG. 1 is a flowchart showing the operation of the image forming apparatus of this embodiment, and FIG. 2 is a flowchart showing the operation of the post-processing apparatus. This operation is executed by the CPU 101 of the control unit 100 based on a program stored in a ROM (not shown) in the control unit 100.

  In the present embodiment, when image data of a recording medium consisting of a plurality of pages is input to the image forming apparatus, the control unit 100 temporarily stores the image data in the memory 102 (S100). The control unit 100 starts an image forming preparation operation (S101), and analyzes whether the input image data includes image information that should reduce the gloss difference or the color difference (S102). In the present embodiment, when the image data includes page information having a printing rate per page equal to or greater than a predetermined value (30% or more), an image that should reduce gloss difference and color difference is included. It is judged that This is because if the printing rate exceeds 30%, the possibility that the image data includes a halftone image or a solid image increases.

  Here, the printing rate is a rate at which printing is actually performed with respect to the entire printable area in one page of the recording material. For example, when printing in a printable area of 203.2 mm × 292.1 mm with a resolution of 600 dpi, if the printing rate is 100%, printing of 33,120,000 dots is performed, and the printing rate in the present embodiment is 30. If it is%, 9,936,000 dots are printed.

  In this embodiment, the print rate is used as a reference for determining whether or not the gloss difference and the color difference need to be reduced. However, the determination may be made based on whether the print target is a color image. Further, it may be determined whether or not the page is a target page depending on whether or not the user gives an instruction to reduce the gloss difference of the printed page.

  In addition, regarding whether or not it is necessary to reduce the gloss difference or the color difference, the target of the reduction necessity may be both the gloss difference and the color difference, or either the gloss difference or the color difference is the target. It may be.

  Next, the control unit 100 determines how many pages of the input image data have a printing rate of 30% or more (S103). If it is determined that the input image data does not include an image that needs to reduce the gloss difference and the color difference (the print rate of all the image data is less than a predetermined value (less than 30%)), control is performed. The unit 100 starts a normal image forming operation (S115). The control unit 100 determines whether there is image data to be imaged next (S117). If there is, the image forming operation is continued (S116), and if not, the operation proceeds to the image forming end operation (S123).

  If it is determined in step S103 that all pages have a printing rate of 30% or more, the control unit 100 shifts the control of the image forming apparatus to the gloss difference reduction mode (S118) (details will be described later).

  In step S103, when the input image data includes a page with a printing rate of 30% or more and a page with less than 30%, it is necessary to reduce the gloss difference and the color difference in the input image data. An image and an unnecessary image are mixed. Therefore, the control unit 100 changes the order of image formation so that printing starts from a page with a printing rate of less than 30% (S104). The control unit 100 replaces the image data stored in the memory 102 in the image formation order in order to form the image data stored in the input order in order from the page with the printing rate of less than 30% (S104). Then, the control unit 100 prohibits image formation with a printing rate of 30% or more (S105), and determines from the image data with a printing rate of less than 30% that it has been determined that reduction in gloss difference and color difference need not be considered. Image formation is performed in advance (S106).

が所定温度以下（１０℃以下）になるかどうかを比較・監視する（Ｓ１０９）。積算値Ｓｎが１０℃を超えている場合には、印字率３０％未満の画像データの画像形成が継続される。 In parallel with the image forming operation with a printing rate of less than 30%, the control unit 100 detects the temperature difference between the temperature data detected every second by the temperature detecting means TH in contact with the fixing belt 35 and the most recent temperature data. Pn is measured (S107). The temperature difference Pn is obtained as follows.
Pn = (temperature at n seconds) − (temperature at (n−1) seconds)
The control unit 100 is a value Sn obtained by integrating Pn for the latest 10 seconds (10 detections before 10 seconds).

It is compared and monitored whether or not the temperature is lower than a predetermined temperature (10 ° C. or lower) (S109). When the integrated value Sn exceeds 10 ° C., image formation of image data with a printing rate of less than 30% is continued.

  When it is determined that the integrated value Sn for the latest 10 seconds (predetermined time) is 10 ° C. or less, the control unit 100 determines that the fixing belt temperature is in a stable state. Then, the control unit 100 permits image formation for pages with a printing rate of 30% or more (S110), and starts image formation for pages with a printing rate of 30% or more (S111). Thereafter, even if image formation of a page with a printing rate of less than 30% remains, it is not necessary to reduce the gloss difference and the color difference, so that image formation can be performed in the same manner as image formation of a page with a printing rate of 30% or more. It is possible (S112, 114).

  The image-formed recording material is conveyed from the image forming apparatus to the post-processing apparatus. The post-processing device sorts the conveyed recording material to the stockers 340 and 350 by the sorting unit 320 based on the output order information (S200) of the recording material from the image forming apparatus (S202). Specifically, the recording material on which image data with a printing rate of less than 30% is printed is conveyed to the stocker 340 (S204) by setting the solenoid of the sorting unit 320 to OFF (S203). On the other hand, the recording material on which image data having a printing rate of 30% or more is printed is conveyed to the stocker 350 (S206) by setting the solenoid of the sorting unit 320 to ON (S205).

  If the image formation on the page with a printing rate of less than 30% is completed before the integrated value Sn of the temperature change of the fixing belt becomes 10 ° C. or less, the image forming apparatus is set separately according to an instruction from the control unit 100. Shifts to the gloss difference reduction mode (S108, S118).

  In the present embodiment, the control unit 100 permits image formation of a page with a printing rate of 30% or more (S119), and sets the conveyance interval of the recording material as the gloss difference reduction mode at the time of normal image formation (when not in the gloss difference reduction mode). 2) (S120). In this mode, the temperature of the fixing belt 35 is unlikely to decrease, so that the difference in gloss between pages during image formation is reduced, but conversely, the number of recording materials conveyed per unit time is reduced. Note that the recording material of the image formed in the gloss difference reduction mode and having a printing rate of 30% or more is conveyed to the stocker 350 by the post-processing device.

  By the way, in the flowchart of FIG. 1, once the image forming apparatus is set to the gloss difference reduction mode, the gloss difference reduction mode is maintained until all the image formation is completed. End up. Therefore, although not shown in the flowchart of FIG. 1, even in the gloss difference reduction mode, the following processing is added in the processing for determining the presence or absence of remaining page data to be image-formed, thereby reducing image formation productivity. Can be prevented. That is, when there are pages to be image-formed, the control unit 100 detects the fixing belt temperature and integrates the temperature change for the latest 10 seconds. The gloss difference reduction mode is reset to the normal image forming mode. As a result, the speed of image formation can be maintained in the same way as during normal image formation, and a reduction in image formation productivity can be minimized.

  Finally, when all image forming operations in the image forming apparatus are completed, as shown in FIG. 2, the post-processing apparatus performs page alignment (rearrangement) of the recording materials after the image formation loaded on the stockers 340 and 350. And the recording material is discharged. That is, based on the page order information (S208) from the image forming apparatus, the post-processing apparatus operates the stocker feed rollers 342 and 352, and the recording materials on the stockers 340 and 350 are arranged and discharged according to the input order of the image data. Page alignment is performed so as to be printed (S210 to S212). Then, the post-processing apparatus conveys the recording material to the paper discharge roller 360 and discharges the recording material arranged in the order of input pages onto the paper discharge tray 370.

  FIGS. 5A to 5D show image data input order, image formation order change, stacking and discharge order on each stocker, and discharge tray when actually forming an image of 20 pages per set. This shows a specific example of the loading order.

  First, in the page order of the input image information, the first is the first page, and the 20th is the 20th page in order (FIG. 5A).

  The control unit 100 calculates the printing rate of the image information of each page, and the first page, the third page, and the fifth page are images that should reduce gloss difference and color difference with a printing rate of 30% or more. The order of image formation is changed. That is, image formation is started in the order of the 20th page to the 6th page, the 4th page, and the 2nd page with a printing rate of less than 30%. The 5th page, the 3rd page, and the 1st page with a printing rate of 30% or more The control unit 100 changes the order so that the image formation order is last (FIG. 5B).

  The control unit 100 sequentially performs image formation on the 20th page, the 6th page, the 4th page, and the 2nd page without needing to reduce the gloss difference and the color difference until the fixing belt temperature is stabilized. When the fixing belt temperature is stabilized and image formation permission is set for an image that should reduce the gloss difference and color difference, the image forming apparatus sequentially performs image formation for the fifth page, the third page, and the first page. .

  In the post-processing device, the 20th to 6th pages with a printing rate of less than 30%, the 4th page, the 2nd page to the stocker 340, the 5th page with a printing rate of 30% or more, the 3rd page, the 1st page to the stocker 350 is loaded with the recording material after the image formation in this order (FIG. 5C). When the image formation for all pages is completed and the recording material is loaded on the stockers 340 and 350, the recording materials are loaded on the stocker in order from the bottom of the stockers 340 and 350 based on the input page order information. Are extracted in reverse order (opposite to the input order of image information). Specifically, first, the 20th page to the 6th page are taken out from the stocker 340 and stacked on the paper discharge tray 370. Next, the fifth page from the stocker 350, the fourth page from the stocker 340, and similarly the third to first pages are selectively taken out and stacked / discharged onto the discharge tray 370 (FIG. 5D). ). That is, the post-processing device functions as a paper discharge unit that rearranges the recording materials so that the page order is aligned.

  Note that when the image forming apparatus has a function of reversing the front and back of the recording material on which the image has been formed and transporting it to the stocker, the image formation is started in ascending order of the page numbers. That is, according to the above example, for pages with a printing rate of less than 30%, image formation is performed in the order of the second page, the fourth page, and the 6th to 20th pages. For pages with a printing rate of 30% or more, Image formation is performed in the order of the first page, the third page, and the fifth page.

  As described above, in this embodiment, the image forming apparatus determines whether to reduce the gloss difference and the color difference from the print rate of the input image data, and performs image formation based on the determination. The image formation of the page for which the gloss difference and the color difference should be reduced is performed when the temperature change of the fixing belt 35 is monitored and the temperature change amount is small and stable. The taste difference can be reduced. As a result, the recording material conveyance speed is not slowed or the conveyance interval is not extended, so that the productivity of the image forming apparatus is not lowered.

  This embodiment shows an induction heating type belt fixing method as an example, but the same applies to an image forming apparatus of a heat roller fixing method having an internal heat source or an induction heating type roller fixing method. Can do.

[Second Embodiment]
A second embodiment of the present invention will be described in detail with reference to the drawings.

  In the first embodiment, the control unit 100 determines whether to reduce the gloss difference and the color difference based on the image information (printing rate) of the input image data. In the present embodiment, the control unit 100 reduces the gloss difference and the color difference depending on whether or not the recording material used for image formation of the input image data is fed from a specific paper feed cassette (recording material supply device). Judge whether or not.

The image forming apparatus according to the second embodiment has the same configuration as that of FIG. 3 of the first embodiment, and description of other components is omitted by using the description of FIG. The paper feeding unit 16 of the image forming apparatus is equipped with two paper feeding cassettes 17 and 18, and recording materials having different attributes such as paper size and material can be set in the paper feeding cassette according to the purpose of use. . The user can input the attribute information of the recording material set in an arbitrary paper feed cassette to the image forming apparatus. In this embodiment, the paper feed cassette 17 has plain paper (normal copy paper) with a basis weight of 80 g / m ² , and the paper feed cassette 18 has a coating layer of synthetic resin or the like on the surface of the recording material to improve color development. Coated paper for the purpose of high gloss is set, and that fact is input to the image forming apparatus.

  FIG. 6 is a flowchart showing the operation of the image forming apparatus of this embodiment. This operation is executed by the CPU 101 of the control unit 100 based on a program stored in a ROM (not shown) in the control unit 100.

  When the image data of the recording medium composed of a plurality of pages is input to the image forming apparatus, the control unit 100 temporarily stores the image data in the memory 102 (S300). The control unit 100 starts an image formation preparation operation (S301), and determines whether or not the input image data includes a paper feed designation from a paper feed cassette in which coated paper is set at the time of image formation (S303).

  If the input image data does not specify image formation on the coated paper and does not include any image that needs to reduce the gloss difference and the color difference, a normal image forming operation is started (S315). The control unit 100 determines whether there is image data to be image-formed next (S317), and if so, continues the image-forming operation (S316), and if not, shifts to an image-forming end operation (S323).

  When the input image data includes an image that needs to reduce the difference in gloss and color difference (designation of image formation on coated paper), the control unit 100 performs image formation using plain paper. The order of image formation is changed so that printing starts from the page to be performed (S304). Therefore, the control unit 100 replaces the image data stored in the memory 102 in order to form the image data stored in the input order in order from the plain paper page (S304). Then, the control unit 100 prohibits image formation using the coated paper (S305), and precedes the image data using plain paper determined that it is not necessary to consider reduction in gloss difference and color difference. Formation is performed (S306).

  In parallel with the image formation on the plain paper, the control unit 100 calculates the temperature difference Pn between the temperature data detected every second by the temperature detection means TH abutted on the fixing belt 35 and the latest temperature data. Measurement is performed in the same manner as in the first embodiment (S307). As in the first embodiment, the control unit 100 compares and monitors whether or not the latest integrated value Sn for 10 seconds is equal to or lower than a predetermined temperature (10 ° C. or lower) (S309). When the integrated value Sn exceeds 10 ° C., image formation of image data using plain paper is continued.

  When it is determined that the integrated value Sn is 10 ° C. or less, the control unit 100 determines that the fixing belt temperature is in a stable state, permits image formation on the coated paper (S310), and applies to the coated paper. Image formation is started (S311). Thereafter, even if image formation on the plain paper remains, it is not necessary to reduce the gloss difference and the color difference, so that the image formation can be performed in the same manner as the coated paper (S312 and 314).

  The image-formed recording material is conveyed from the image forming apparatus to the post-processing apparatus. As in the first embodiment, in the post-processing apparatus, based on the information (paper feed designation) from the image forming apparatus, the sorting unit 320 sends the paper to the stocker 340, and in the case of coated paper. The recording material is distributed to the stocker 350.

  If the image forming on the plain paper is all completed before the integrated value Sn of the temperature change of the fixing belt becomes 10 ° C. or less, the control unit 100 shifts to a separately set gloss difference reduction mode. (S308, S318).

  The control unit 100 permits image formation on the coated paper (S319), and in this embodiment, sets the conveyance interval of the recording material to twice that during normal image formation as the gloss difference reduction mode (S320). In this mode, the temperature of the fixing belt 35 is unlikely to decrease, but conversely, the number of conveyed recording materials per unit time decreases. Note that the coated paper image formed in the gloss difference reduction mode is conveyed to the stocker 350 by the post-processing device.

  By the way, in the flowchart of FIG. 6, once the gloss difference reduction mode is entered, the gloss difference reduction mode is maintained until all the image formation is completed. Therefore, although not shown in the flowchart of FIG. 6, even in the gloss difference reduction mode, the following processing is added in the processing for determining the presence / absence of remaining page data to be image-formed, thereby improving the productivity of image formation. Decline can be prevented. That is, when there is remaining page data, the fixing belt temperature is detected and the temperature change for the latest 10 seconds is integrated. If the integrated value is below a predetermined temperature, the gloss difference reduction mode is set to the normal image forming mode. Reset to. As a result, the image formation speed can be maintained in the same manner as in normal image formation, and a reduction in image formation productivity can be prevented.

  When all image formation is completed, the post-processing device performs page alignment and discharge of the recording material, as in the first embodiment. That is, the post-processing apparatus aligns the recording materials after image formation loaded on the stockers 340 and 350 based on the page order information (S208) from the image forming apparatus (S210, S211 and S212) and inputs them. The recording materials arranged in the page order are discharged onto a discharge tray 370.

  As described above, in the present embodiment, it is determined whether or not to reduce the gloss difference and the color difference from the recording material designation information of the input image data, and image formation is performed based on the determination. The image formation of the page for which the gloss difference and the color difference should be reduced is performed when the temperature of the fixing belt 35 is monitored and the temperature change amount is small and stable. The difference is reduced and the productivity of the image forming apparatus is not lowered.

DESCRIPTION OF SYMBOLS 100 Control unit 300 Post-processing apparatus F Fixing apparatus TH Fixing belt temperature detection means

Claims (8)

Storage means for inputting and storing image data of a plurality of pages;
Image forming means for forming a toner image on a recording material based on the image data accumulated in the accumulating means, and fixing the toner image on the recording material by a fixing means;
Determining means for determining whether or not at least one of a gloss difference and a color difference needs to be reduced for each image data of a plurality of pages;
The image forming order of the image data determined to require reduction of at least one of the gloss difference and the color difference by the determination unit is the same as that of the image data for which it is determined that at least one of the gloss difference and the color difference needs to be reduced. Control means for changing the image formation order to be later than the image formation order;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, further comprising a discharge unit configured to discharge the recording material on which the image formation order is changed and the image formation is performed. Temperature detecting means for detecting the temperature of the fixing member of the fixing means, and
When the amount of change in the temperature of the fixing member in a predetermined time after starting image formation becomes equal to or lower than a predetermined temperature, the control unit determines that at least one of the gloss difference and the color difference needs to be reduced by the determination unit. The image forming apparatus according to claim 1, wherein image formation of the image data is performed.   Whether or not it is necessary to reduce at least one of the gloss difference and the color difference by the determination unit is determined by the printing rate of the image data stored in the storage unit, the presence or absence of a color image, or the gloss difference and color by the user. 4. The image forming apparatus according to claim 1, wherein the image forming apparatus performs the determination according to any one of presence / absence of an instruction to reduce at least one of the differences. A plurality of recording material supply means for supplying recording materials of different materials;
Storage means for inputting and storing image data of a plurality of pages;
Image forming means for forming a toner image on a recording material based on the image data accumulated in the accumulating means, and fixing the toner image on the recording material by a fixing means;
Determination means for determining a printing rate for a printable area of one page for each image data of a plurality of pages;
The image formation order is set so that the image formation order of the image data of the page for which the printing rate determined by the determination unit is equal to or greater than the predetermined value is later than the image formation order of the image data for the page of which the printing rate is less than the predetermined value. Control means to change;
An image forming apparatus comprising: Temperature detecting means for detecting the temperature of the fixing member of the fixing means, and
When the amount of change in the temperature of the fixing member in a predetermined time after the start of image formation becomes equal to or lower than a predetermined temperature, the control unit starts image formation of image data of a page whose printing rate is equal to or higher than the predetermined value. The image forming apparatus according to claim 5. A plurality of recording material supply means for supplying recording materials of different materials;
Storage means for inputting and storing image data of a plurality of pages;
Image forming means for forming a toner image on a recording material based on the image data accumulated in the accumulating means, and fixing the toner image on the recording material by a fixing means;
Determining means for determining the presence or absence of image data of a page designated to form an image on a recording material of a specific material for each image data of a plurality of pages;
The image forming order of the image data of the page specified to form an image on the recording material of the specific material is based on the image forming order of the image of the page not specified to form an image on the recording material of the specific material. Control means for changing the image formation order so that
An image forming apparatus comprising: Temperature detecting means for detecting the temperature of the fixing member of the fixing means, and
When the amount of change in the temperature of the fixing member in a predetermined time after the start of image formation becomes equal to or lower than a predetermined temperature, the control unit images the page designated to form an image on the recording material of the specific material. 8. The image forming apparatus according to claim 7, wherein image formation of data is started.

Images