JP2014157330A - Fixing apparatus and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a moving sheet from being wrinkled when a fixing roller partially expands.SOLUTION: A heating control unit controls a first partial heating unit and a second partial heating unit so that a temperature difference ▵Tp between a temperature of a first part a' of a fixing counter roller 152 heated by the first partial hating unit of a plurality of partial heating units and a temperature of a second part d' of the fixing counter roller 152 heated by the second partial heating unit falls within a predetermined range. The heating control unit controls expansion of the fixing counter roller 152 partially, to correct moving speed of a sheet. The sheet can be prevented from being wrinkled while reducing thermal energy to be supplied.

Description

  The present invention relates to a fixing device that fixes an image formed on a recording medium, and an image forming apparatus having the fixing device.

  2. Description of the Related Art Conventionally, a fixing device for fixing a toner image formed on the surface of a recording material by using a toner made of a heat-meltable resin in an image forming apparatus such as a copying machine, a printer, a facsimile, etc., is fixed to the recording material. ing.

  In such a fixing device, there are cases where an image area and a non-image area are mixed in the recording material. In such a case, fixing is necessary for the image area of the paper, and fixing is not necessary because there is no toner to be fixed in the non-image area. Patent Document 1 describes that the supply of thermal energy is reduced by controlling the heating roller so that the temperature of the part of the fixing roller corresponding to the non-image area is lower than the temperature of the part corresponding to the image area. ing.

  However, in many fixing devices, the fixing roller is formed of silicon rubber, and silicon rubber has a property of expanding when the temperature rises. As described in Patent Document 1, if the heating roller is controlled so that the temperature of the fixing roller portion corresponding to the image area is higher than the temperature of the fixing roller portion corresponding to the non-image area, the image area Only the corresponding part of the fixing roller becomes hot and expands. At this time, the portion of the fixing roller corresponding to the non-image area does not expand because of the low temperature.

  As described above, when a portion that expands and a portion that does not expand occur in the fixing roller, the speed at which the sheet moves varies depending on the portion that contacts the fixing roller. For this reason, there is a problem that the paper is wrinkled when the paper moves.

  In order to solve the above-described problems, the present invention provides a fixing device for fixing an image formed on a recording medium, the fixing counter roller for sandwiching and pressing the recording medium together with the fixing roller, and the fixing counter roller partially A plurality of partial heating units that are heated each time, a temperature of the first portion of the fixing counter roller heated by the first partial heating unit among the plurality of partial heating units, and a second partial heating unit that is heated And a heating control unit for controlling the first partial heating unit and the second partial heating unit so that the difference between the temperature of the second portion of the fixing facing roller and the temperature of the second partial heating unit falls within a predetermined range. To do.

  According to the present invention, of the plurality of partial heating units, the temperature of the first portion of the fixing counter roller heated by the first partial heating unit and the fixing counter roller heated by the second partial heating unit A heating control unit that controls the first partial heating unit and the second partial heating unit so that the difference from the temperature of the second part is within a predetermined range. It is possible to prevent the paper from being wrinkled.

1 is a diagram illustrating an overall configuration of an image forming apparatus 1. 2 is a diagram illustrating a configuration of a fixing unit 15. FIG. 2 is a perspective view illustrating a configuration of a fixing unit 15. FIG. 2 is a diagram illustrating a hardware configuration of a control unit of the image forming apparatus 1. FIG. 2 is a diagram illustrating a functional configuration of a control unit of the image forming apparatus 1. FIG. FIG. 3 is a process flow diagram illustrating an overview of a process in which the image forming apparatus 1 forms an image. 5 is a diagram illustrating an example of an image formed on a sheet P. FIG. 6 is a diagram illustrating an example of a temperature distribution and a shape of a fixing counter roller 152. FIG. 6 is a diagram illustrating another example of the temperature distribution and shape of the fixing counter roller 152. FIG. It is a figure which shows the relationship between temperature difference (DELTA) Tp and diameter difference (DELTA) R. It is a figure which shows the relationship between the heating time t and diameter difference (DELTA) R.

<< Configuration of the Embodiment >>
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram illustrating an overall configuration of an image forming apparatus 1 according to the present embodiment.

<Hardware configuration of image forming apparatus>
The image forming apparatus 1 forms an image on a sheet P that is an example of a recording medium by copying, printing, or the like. In the present embodiment, as shown in FIG. 1, a scanner unit 11 is provided at the top of the image forming apparatus 1. The scanner unit 11 generates RGB image information by optically reading a document placed on the contact glass 111. Specifically, the scanner unit 11 reads RGB image information by irradiating the sheet P with light and receiving the reflected light by a reading sensor 112 such as a CCD (Charge Coupled Devices) or a CIS (Contact Image Sensor). The RGB image information is information representing an image formed on the paper P, and includes the brightness of each color of red (R), green (G), and blue (B).

  Further, the image forming apparatus 1 is provided with a driving roller 141, a driven roller 142, and a secondary transfer roller 145, and an intermediate transfer belt 143 is bridged between the driving roller 141, the driven roller 142, and the secondary transfer roller 145. Yes. Four photosensitive drums 122C, 122M, 122Y, and 122K are provided so as to be in contact with the intermediate transfer belt 143. Images are formed on the photosensitive drums 122C, 122M, 122Y, and 122K with toners of cyan (C), magenta (M), yellow (Y), and black (K), respectively. The image formed on each photosensitive drum is transferred to the same portion of the surface of the intermediate transfer belt 143, so that a color toner image is formed on the surface of the intermediate transfer belt 143.

  A secondary transfer counter roller 146 is provided at a position facing the secondary transfer roller 145. In order to transfer the toner image formed on the surface of the intermediate transfer belt 143 onto the sheet P (hereinafter referred to as secondary transfer), the secondary transfer roller 145 is interposed between the secondary transfer counter roller 146 and the intermediate transfer belt 143. And apply a secondary transfer bias. A charge opposite to the electrostatic charge charged on the surface of the intermediate transfer belt 143 is applied as the secondary transfer bias.

  A charging unit 123C is provided in the vicinity of the photosensitive drum 122C. The charging unit 123C uniformly charges the surface of the photosensitive drum 122C. An exposure unit 124C is provided in the vicinity of the photosensitive drum 122C. The exposure unit 124 </ b> C forms an electrostatic latent image on the surface of the charged photosensitive drum 122 </ b> C based on the C toner adhesion amount determined by the control unit described later. Further, a developing unit 125C is provided in the vicinity of the photoconductive drum 122C. The developing unit 125C attaches toner to the photoconductive drum 122C on which the electrostatic latent image is formed, and the toner on the surface of the photoconductive drum 122C. Form an image.

  A primary transfer roller 144C is provided to face the photosensitive drum 122C. The primary transfer roller 144C applies a primary transfer bias in order to transfer the toner image on the surface of the photosensitive drum 122C to the intermediate transfer belt 143. A charge opposite to the electrostatic charge charged on the surface of the photosensitive drum 122C is applied as the primary transfer bias.

  In the following description, the one having the photosensitive drum 122C, the charging unit 123C, the exposure unit 124C, and the developing unit 125C is referred to as an image forming unit 12C. The image forming apparatus 1 includes image forming units 12M, 12Y, and 12K. The image forming apparatus 1 is the same as the image forming unit 12C except that images are formed using M, Y, and K color toners, respectively. It has a configuration.

  The paper supply unit 13 supplies the paper P between the secondary transfer roller 145 and the secondary transfer counter roller 146. The paper feed unit 13 includes a paper feed tray 131, a paper feed roller 132, a paper feed belt 133, and a registration roller 134. The paper feed tray 131 contains paper P. The paper feed roller 132 is provided to transport the paper P stored in the paper feed tray 131 toward the paper feed belt 133. The paper feed roller 132 provided in this way takes out the paper P at the top of the stored paper P one by one and places it on the paper feed belt 133.

  The paper feed belt 133 conveys the paper P taken out by the paper feed roller 132 toward the secondary transfer roller 145 and the secondary transfer counter roller 146. A registration roller 134 is provided on the paper feed belt 133 before the paper P reaches the secondary transfer roller 145. The registration roller 134 sends out the paper P at the timing when the portion of the intermediate transfer belt 143 where the toner image is formed reaches the position of the secondary transfer roller 145.

  The fixing unit 15 fixes the toner transferred from the intermediate transfer belt 143 to the paper P. Fixing means that the resin component of the toner is welded to the paper P when heat and pressure are simultaneously applied to the toner. In the fixing unit 15, a fixing roller 151 and a fixing counter roller 152 are provided to face each other. The fixing roller 151 presses the paper P while sandwiching the paper P onto which the toner has been transferred with the fixing facing roller 152.

  As shown in FIG. 2, the fixing roller 151 includes an aluminum roller core 151a having an outer diameter of 40 mm and a thickness of 1 mm, and a heat insulating layer 151b covering the surface of the roller core 151a. The heat insulating layer 151b is made of silicon rubber and has a thickness of 3 mm.

  In addition, a good heat conductive layer 151c is formed outside the heat insulating layer 151b. The good heat conductive layer 151c is formed of nickel, stainless steel, aluminum, copper, or a graphite sheet having higher heat conductivity than the heat insulating layer 151b. By forming the good heat conductive layer 151c in this way, it is possible to reduce the temperature unevenness of the fixing roller 151. In addition, a 5 to 30 μm release layer 151d made of a fluorine-based resin such as PFA or PTFE is formed outside the good heat conductive layer 151c. By forming the release layer 151d, the paper P pressed by the fixing roller 151 is easily separated from the paper P thereafter.

  The fixing counter roller 152 includes an aluminum roller core 152a having an outer diameter of 40 mm and a thickness of 2 mm, and a heat insulating layer 152b covering the surface of the roller core 152a.

  A heating unit 153 is provided near the side surface of the fixing roller 151. FIG. 3 is a perspective view showing the configuration of the fixing unit 15. As shown in FIG. 3, the heating unit 153 includes heaters 153a to 153g. The heaters 153 a to 153 g are arranged side by side in the axial direction of the fixing roller 151, and each heats a part of the fixing roller 151. Specifically, the heater 153a heats the portion a of the fixing roller 151 shown in FIG. 3, and the heater 153b heats the portion b. Similarly, the heaters 153c to 153g heat the portions c to g of the fixing roller 151, respectively.

  Further, a temperature measuring unit 154 for measuring the temperature of the fixing roller 151 is provided in the vicinity of the side surface of the fixing roller 151, and the temperature measuring unit 154 includes temperature sensors 154a to 154g. As shown in FIG. 3, the temperature sensor 154a measures the temperature of the portion a of the fixing roller 151 heated by the heater 153a. Similarly, the temperature sensors 154b to 154g measure the temperatures of the portions b to g of the fixing counter roller 152, respectively.

  Further, a temperature measuring unit 155 that measures the temperature of the fixing counter roller 152 is provided in the vicinity of the side surface of the fixing counter roller 152, and the temperature measuring unit 155 includes temperature sensors 155a to 155g. Since the fixing roller 151 heated by the heating unit 153 is in contact with the fixing counter roller 152 as described above, the heat from the fixing roller 151 moves and the fixing counter roller 152 is heated. As shown in FIG. 3, the temperature sensor 155a measures the temperature of the portion a 'of the fixing facing roller 152 facing the portion a of the fixing roller 151 heated by the heater 153a. Similarly, the temperature sensors 155b to 155g measure the temperatures of the portions b 'to g' of the fixing counter roller 152, respectively.

  In addition, a paper discharge port 10 is provided for discharging the paper P on which the image is fixed by being heated and pressed by the fixing roller 151 and the fixing counter roller 152 to the outside of the image forming apparatus 1.

  A display / operation unit 18 is provided outside the image forming apparatus 1. The display / operation unit 18 includes a panel display unit 181 and an operation unit 182. The panel display unit 181 is a touch panel or the like on which setting values, selection screens, and the like are displayed and receives input from the user. The operation unit 182 is a numeric keypad for the user to input various information related to image formation, a start key for the user to input a start instruction, and the like.

  Further, the image forming apparatus 1 is provided with a control unit for controlling the above-described units. FIG. 4 is a diagram illustrating a hardware configuration of the control unit of the image forming apparatus 1 according to the present embodiment. As shown in FIG. 4, the control unit includes a CPU (Central Processing Unit) 1011, a main memory (MEM-P) 1012, a North Bridge (NB) 1013, a South Bridge (SB) 1014, and an AGP (Accelerated Graphics Port) bus 1015. , An ASIC (Application Specific Integrated Circuit) 1016, a local memory (MEM-C) 1017, an HD (Hard Disk) 1018, an HDD (Hard Disk Drive) 1019, a PCI bus 1020, and a network I / F 1021.

  The CPU 1011 processes and computes data according to a program stored in the main memory 1012, and controls the operation of each unit described above. The main memory 1012 is a storage area of the control unit, and includes a ROM (Read Only Memory) 1012a and a RAM (Random Access Memory) 1012b. The ROM 1012a stores programs and data for realizing each function of the control unit. The program stored in the ROM 1012a is recorded in a computer-readable recording medium such as a CD-ROM, FD, CD-R, or DVD as a file in an installable or executable format and provided. May be.

  The RAM 1012b is used as a memory for drawing during development of programs and data and memory printing. The NB 1013 is a bridge for connecting the CPU 1011, the MEM-P 1012, the SB 1014, and the AGP bus 1015. The SB 1014 is a bridge for connecting the NB 1013 and peripheral devices. The AGP bus 1015 is a bus interface for a graphics accelerator card for speeding up graphics processing. The ASIC 1016 includes a memory controller that controls the MEM-C 1017, and a plurality of DMACs (Direct Memory Access Controllers) that rotate image data using hardware logic. The ASIC 1016 is connected to a network I / F 1021 such as a USB (Universal Serial Bus) interface and an IEEE 1394 (Institut of Electrical and Electronics Engineers 1394) interface via a PCI bus 1020.

  The MEM-C 1017 is a local memory used as a copy image buffer and a code buffer. The HD 1018 is a storage for accumulating image data, accumulating font data used during printing, and accumulating forms. The HDD 1019 controls reading or writing of data with respect to the HD 1018 according to the control of the CPU 1011. A network I / F 1021 transmits / receives information to / from an external device such as an information processing apparatus via a communication network.

<Functional Configuration of Image Forming Apparatus 1>
Next, the functional configuration of the control unit of the image forming apparatus 1 in the present embodiment will be described with reference to FIG. FIG. 5 is a diagram illustrating a functional configuration of the control unit of the image forming apparatus 1.

  The control unit controls the operation of the image forming apparatus 1. As shown in FIG. 5, the control unit 191, the input receiving unit 192, the image reading control unit 193, the image formation information generation unit 194, and the image formation control unit 196. A storage / reading processing unit 199 and a storage unit 1900. Each of these units is a function or means realized by operating according to a command from the CPU 1011 according to a program stored in the ROM 1012a shown in FIG. The control unit also includes a storage unit 1900 constructed by the ROM 1012a or the HD 1018 shown in FIG.

  The transmission / reception unit 191 is realized by the network I / F 1021 illustrated in FIG. 4 and receives RGB image information from an information processing apparatus or the like via the communication network. The RGB image information is information representing an image formed on the paper P, and is indicated using the lightness of each color of red (R), green (G), and blue (B). The input receiving unit 192 receives information input by the user through the display / operation unit 18 shown in FIG. The image reading control unit 193 controls the scanner unit 11 shown in FIG. 1 to optically read an image described in a document and generate RGB image information.

  The image formation information generation unit 194 generates image formation information based on the RGB image information received by the transmission / reception unit 191 or the RGB image information read by the scanner unit 11. Specifically, the image formation information generation unit 194 performs color space conversion processing on the RGB image information, and each of the toner adhesion amounts Vc, Vm, C, M, Y, and K attached to the paper P Vy and Vk are calculated for each pixel. Note that the image formation information generation unit 194 may perform undercolor removal processing, shading correction, position shift correction, color space conversion, gamma correction, and the like in addition to the color space conversion processing. Further, the image formation information is information representing the C, M, Y, and K toner adhesion amounts Vc, Vm, Vy, and Vk attached to each pixel in order to form an image on the paper P. .

  The image forming control unit 196 includes an image forming control unit 1962 that controls the image forming units 12C, 12M, 12Y, and 12K, a paper feed control unit 1963 that controls the paper feeding unit 13, a primary transfer roller 144, a secondary transfer roller 145, The image forming apparatus includes a transfer control unit 1964 that controls the intermediate transfer belt 143 and the like, and a fixing control unit 1965 that controls the fixing unit 15. The fixing control unit 1965 has a heating control unit 1965 a that controls the heating unit 153.

<< Processing and Operation of Embodiment >>
Subsequently, processing of the image forming system according to the present embodiment will be described with reference to FIGS. 6 to 11. FIG. 6 is a process flow diagram illustrating an outline of a process in which the image forming apparatus 1 forms an image.

  As shown in FIG. 6, first, the transmission / reception unit 191 receives RGB image information from an external information processing apparatus or the like (step S21). When the transmission / reception unit 191 receives the RGB image information, the image formation information generation unit 194 generates image formation information based on the RGB image information (step S22).

  Specifically, the image formation information generation unit 194 calculates toner adhesion amounts Vc, Vm, Vy, and Vk by performing color space conversion processing on the RGB image information. Note that the image formation information generation unit 194 may execute known image processing such as under color removal processing, color correction processing, and spatial frequency correction processing in addition to color space conversion processing on RGB image information. Further, the image formation information generation unit 194 calculates toner adhesion amounts Vc, Vm, Vy, and Vk for all the pixels on the paper P, and is an image that is information indicating the position on the paper P and the toner adhesion amount corresponding to the position. Generate formation information.

  When the image formation information is generated in step S22, the paper feed unit 13 performs a paper feed process under the control of the paper feed control unit 1963 (step S23). Specifically, the paper feed roller 132 of the paper feed unit 13 takes out the paper P stored in the paper feed tray 131 one by one and places it on the paper feed belt 133. The paper feed belt 133 moves in the direction of the arrow (A) shown in FIG. When the conveyed paper P reaches the registration roller 134, the registration roller 134 sandwiches the paper P and waits until the toner image formed on the surface of the intermediate transfer belt 143 reaches the secondary transfer roller 145. Then, at the timing when the toner image formed on the surface of the intermediate transfer belt 143 reaches the secondary transfer roller 145, the registration roller 134 feeds the paper P between the secondary transfer roller 145 and the secondary transfer counter roller 146.

  On the other hand, the image forming units 12C, 12M, 12Y, and 12K perform image forming processing for attaching each toner to the photosensitive drum 122 under the control of the image forming control unit 1962 (step S24). Specifically, the charging unit 123C uniformly charges the surface of the photosensitive drum 122C. Then, the exposure unit 124C irradiates the surface of the photosensitive drum 122C with laser light based on the toner adhesion amount Vc of the image formation information generated by the image formation information generation unit 194. As a result, an electrostatic latent image is formed on the surface of the photoconductive drum 122C for adhering the C-color toner having the toner adhesion amount Vc to the paper P.

  When the electrostatic latent image is formed on the surface of the photosensitive drum 122C, the developing unit 125C develops the electrostatic latent image using C-color toner. In this way, a C-color toner image is formed on the surface of the photosensitive drum 122C. Similarly, toner images of M, Y, and K toners are formed on the surfaces of the photosensitive drums 122M, 122Y, and 122K, respectively. Since these image forming processes are the same as the processes for forming a C-color toner image on the surface of the photosensitive drum 122C, the description thereof is omitted.

  When a toner image is formed on the surface of each photosensitive drum 122 with each toner, a transfer process is performed under the control of the transfer control unit 1964 (step S25). Specifically, first, the primary transfer roller 144 applies a primary transfer bias to the intermediate transfer belt 143. Then, the toner image on the surface of each photosensitive drum 122 is transferred to the intermediate transfer belt 143 (hereinafter referred to as primary transfer).

  The intermediate transfer belt 143 onto which the toner image has been transferred moves in the direction of the arrow (A) by the rotation of the driving roller 141 and the driven roller 142. Further, the registration roller 134 sends out the paper P at the timing when the portion of the intermediate transfer belt 143 to which the toner image is transferred reaches the secondary transfer roller 145. When the sheet P is sent out by the registration roller 134 and reaches the secondary transfer roller 145, the secondary transfer roller 145 sandwiches the sheet P and the intermediate transfer belt 143 between the secondary transfer counter roller 146, and the sheet P is subjected to the secondary transfer. Apply transfer bias. As a result, the toner image formed on the surface of the intermediate transfer belt 143 is transferred onto the paper P (hereinafter referred to as secondary transfer).

  As described above, when the toner image is transferred to the paper P, the fixing unit 15 performs a fixing process under the control of the fixing control unit 1965 (step S26). Specifically, first, when the conveyed paper P reaches a position where the fixing roller 151 and the fixing opposing roller 152 are in contact, the fixing roller 151 sandwiches the paper P between the fixing opposing roller 152. At this time, since the fixing roller 151 is heated by the heating unit 153, the paper P is heated at a predetermined temperature at the same time as being pressurized. The toner forming the toner image transferred onto the paper P is melted, and the toner is fixed to the paper P when the fixing roller 151 presses the paper P with the melted toner attached together with the fixing counter roller 152.

  Here, the heating control in the fixing process performed in step S26 will be described in detail. First, the heating control unit 1965a controls each heater of the heating unit 153 to heat each part of the fixing roller 151 based on the image formation information generated by the image formation information generation unit 194. Specifically, when the amount of toner attached to a predetermined portion of the paper P passing through the fixing roller 151 is not zero (hereinafter, this portion is referred to as an image portion), the portion of the paper P is covered with toner. An image is formed and the toner needs to be fixed. Therefore, the corresponding heater heats the fixing roller 151 so that the portion of the fixing counter roller 152 that pressurizes the image portion of the paper P reaches 160 ° C. When the amount of toner attached to a predetermined portion of the paper P passing through the fixing roller 151 is 0 (hereinafter, this portion is referred to as a non-image portion), the corresponding heater is a non-image portion of the paper P. The fixing roller 151 is heated so that the portion of the fixing counter roller 152 that pressurizes the pressure is 110 ° C. Note that the temperature of the fixing counter roller 152 measured by the temperature measuring unit 155 is used for controlling these temperatures.

  FIG. 7 is a diagram illustrating an example of an image formed on the paper P. The paper P is composed of an image portion on which the left image is formed and a non-image portion on which the right image is not formed. The paper P is fixed while proceeding in the direction of the arrow. When the fixing process is performed on such a sheet P, the heating control unit 1965a controls the heaters 153a to 153d so that the parts a ′ to d ′ of the fixing facing roller 152 in contact with the image part of the sheet P are controlled. The fixing roller 151 is heated so that the temperature becomes 160 ° C. The heating controller 1965a controls the heaters 153e to 153g to heat the fixing roller 151 so that the portions e to g of the fixing counter roller 152 in contact with the image portion of the paper P become 110 ° C. The heaters 153a to 153g are examples of the partial heating unit.

  In this description, the temperature of the portion of the fixing counter roller 152 that heats and presses the image portion of the paper P (hereinafter referred to as the image portion temperature) and the portion of the fixing counter roller 152 that heats and presses the non-image portion of the paper P. These temperatures (hereinafter referred to as non-image portion temperatures) are 160 ° C. and 110 ° C., respectively, but the non-image portion temperatures are determined as follows.

  Here, a process in which the heating control unit 1965a determines the non-image part temperature will be described. The fixing facing roller 152 is formed of silicon rubber as described above. Therefore, when heat is transferred from the fixing roller 151 heated by the heating unit 153 and the fixing counter roller 152 is heated to a high temperature, the silicon rubber expands. In this embodiment, since the temperature is controlled for each part of the fixing roller 151 by the heaters 153a to 153g, the silicon rubber that realizes the fixing facing roller 152 heated by each part of the fixing roller 151 is partially Inflate. As a result, the fixing facing roller 152 may partially expand, that is, the diameter of each portion may be different.

  The partial expansion of the fixing counter roller 152 will be described in detail with reference to FIGS. 3, 8, and 9. FIG. 8 is a diagram showing an example of the temperature distribution and shape of the fixing counter roller 152, and FIG. 8 (1) shows the temperature for each portion of the fixing counter roller 152. FIG. 8B is a view of the fixing facing roller 152 as viewed from the side. FIG. 9 is a diagram showing another example of the temperature distribution and shape of the fixing counter roller 152, and FIG. 9 (1) shows the temperature of each portion of the fixing counter roller 152. FIG. 9B is a view of the fixing facing roller 152 as viewed from the side. Also, the arrows in FIGS. 8B and 9B indicate the distances at which the portions on the side surface of the fixing facing roller 152 move per unit time.

  As shown in FIG. 3, the heaters 153 a to 153 g heat the portions a to g of the fixing roller 151. When the parts a to g of the fixing roller 151 are heated to a high temperature by the heater, the heat moves to the parts a ′ to g ′ of the fixing counter roller 152 in contact with the parts a to g, and the part a ′. Or part g ′ is heated. Therefore, when the heaters 153a to 153g heat the portions of the fixing counter roller 152 at different temperatures, the portions of the fixing counter roller 152 are heated to different temperatures.

  In the example shown in FIG. 8A, the temperature of the portion d 'in the fixing counter roller 152 is the highest, and the temperatures of the portions a' and g 'located at the ends are the lowest. As a result, the portion d 'of the fixing counter roller 152 expands, and the diameter of the portion d' of the fixing counter roller 152 becomes longer than the diameters of the portions a 'and g'. When the fixing counter roller 152 rotates in this state, the angular velocities of the portions d ′, a ′, and g ′ of the fixing counter roller 152 are the same, so that the diameter is long as shown in FIG. The portion of the paper P pressed by the portion d ′ moves faster than the portion of the paper P in contact with the portions a ′ and g ′.

  In the example shown in FIG. 9A, the fixing counter roller 152 has the lowest temperature at the portion d 'located at the center thereof, and the highest temperatures at the portions a' and g 'located at the ends. As a result, the part a ′ and the part g ′ of the fixing counter roller 152 expand, and the diameter of the part d ′ of the fixing counter roller 152 becomes shorter than the diameter of the part a ′ and part g ′. When the fixing counter roller 152 rotates in this state, the angular velocities of the portions d ′, a ′, and g ′ of the fixing counter roller 152 are the same, so that the diameter is short as shown in FIG. The part of the paper P in contact with the part d ′ moves slower than the part of the paper P pressed by the parts a ′ and g ′.

  When the fixing facing roller 152 partially expands in this way, a portion that moves fast and a portion that moves slowly occur in one sheet P in contact with the fixing facing roller 152, and as a result, the sheet P is wrinkled. End up.

  The difference between the maximum temperature Th and the minimum temperature Tl among the temperatures of the respective parts of the fixing counter roller 152 is defined as a temperature difference ΔTp, and the difference between the longest diameter and the shortest diameter among the diameters of the respective parts of the fixing counter roller 152 is the diameter. The relationship between the temperature difference ΔTp and the diameter difference ΔR when the difference ΔR is assumed will be described with reference to FIG. FIG. 10 is a diagram showing the relationship between the temperature difference ΔTp and the diameter difference ΔR. As shown in FIG. 10, it was found that the diameter difference ΔR increases as the temperature difference ΔTp increases.

  Further, it has been found through experiments that the paper sheet P is wrinkled and that the diameter difference ΔR is greater than or equal to a predetermined threshold value ΔRth. That is, when the temperature difference ΔTp is equal to or larger than the threshold value ΔTpth corresponding to the threshold value ΔRth, wrinkles occur in the paper P that moves while being in contact with the fixing counter roller 152. Although the threshold value ΔTpth is approximately 40 ° C., the threshold value ΔRth is ΔRth = R × 0 where R is the diameter of the fixing facing roller 152 when not heated. .05 (%).

  As described in the background art, it is possible to reduce energy consumption by not heating the portion of the fixing roller 151 that is in contact with the non-image portion of the paper P, but the fixing counter roller 152 that is in contact with the non-image portion of the paper P. If the temperature of this portion is too low, ΔTp becomes larger than ΔTpth and the paper P is wrinkled.

  Therefore, in order to reduce energy consumption and prevent the paper P from wrinkling, the temperature of the portion of the fixing counter roller 152 that contacts the image portion of the paper P (hereinafter referred to as the image portion temperature) and the non-image portion are in contact. The temperature of the portion of the fixing counter roller 152 in contact with the non-image portion is determined so that the temperature difference ΔTp, which is the difference from the temperature of the fixing counter roller 152 (hereinafter referred to as the non-image portion temperature), is within a predetermined range. To do. Specifically, the non-image portion temperature Tn is determined so that Tn ≧ Ti−ΔTpth when the image portion temperature Ti and the non-image portion temperature Tn of the fixing facing roller 152 are set.

  The image portion temperature Ti is determined so as to be suitable for the fixing process depending on the type of toner.

  In the above description, the fixing roller 151 heated by the heating unit 153 heats the fixing counter roller 152, but the heating unit 153 may heat the fixing counter roller 152.

  When the toner is fixed on the paper P by the fixing unit 15, the paper P is discharged out of the image forming apparatus 1 from the paper discharge port 10 (step S27).

<< Supplement of Embodiment >>
In the present embodiment, a portion of the fixing counter roller 152 that is in contact with the non-image portion of the sheet P is a non-image so that the temperature difference ΔTp between the image portion temperature Ti and the non-image portion temperature Tn of the fixing counter roller 152 does not exceed ΔTpth. The part temperature Tn may be controlled after a predetermined time has elapsed since the temperature of the part of the fixing counter roller 152 that is in contact with the image part of the paper P becomes the image part temperature Ti. This is because the silicon rubber forming the fixing counter roller 152 moves from the outside in contact with the fixing roller 151 and requires a predetermined time until the heat reaches the inside of the silicon rubber. That is, a predetermined time is required after the surface of the fixing counter roller 152 reaches the image portion temperature until the heat reaches the entire silicon rubber and the fixing counter roller 152 partially expands and the paper P is wrinkled. .

  The relationship between the heating time t and the diameter difference ΔR will be described with reference to FIG. The heating time t is the heating time after the temperature of the fixing counter roller 152 reaches the image portion temperature. As described above, it has been found that when the diameter difference ΔR is larger than the predetermined threshold value ΔRth, the paper P in contact with the fixing facing roller 152 is wrinkled. Further, as shown in FIG. 11, it was found that the diameter difference ΔR of the fixing facing roller 152 increases as the heating time t elapses. Therefore, immediately before the time tth when the diameter difference ΔR of the fixing facing roller 152 becomes larger than the predetermined threshold value, the heating portion is set so that the temperature of the portion in contact with the non-image portion in the fixing facing roller 152 becomes the non-image portion temperature Tn. 153 may heat the fixing roller 151 or the fixing counter roller 152. Depending on the material of the silicon rubber, the time tth is approximately 2 minutes.

  In this embodiment, the fixing counter roller 152 is realized by silicon rubber. However, the present invention can also be applied to the fixing counter roller 152 realized by other than silicon rubber.

  In the present embodiment, the heating unit 153 includes seven heaters 153a to 153g, but the number of heaters may be other than that.

  In this embodiment, the transmission / reception unit 191 receives image information in step S21. However, the reading sensor 112 controlled by the image reading control unit 193 receives an RGB image from a document sheet or the like placed on the contact glass 111. Information may be read.

  In this embodiment, the image forming apparatus 1 forms an image using C, M, Y, and K toners. However, the C, M, Y, and K toners are used. In addition, special toners such as clear toner and white toner may be used.

  In the present embodiment, the image forming apparatus 1 describes a process of forming an image based on RGB image information. However, the image forming apparatus 1 may form an image based on image information representing a monochrome image.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Paper discharge port 11 Scanner part 12 Image forming part 13 Paper feeding part 15 Fixing part 18 Display / operation part 111 Contact glass 112 Reading sensor 122 Photosensitive drum 123 Charging part 124 Exposure part 125 Developing part 131 Paper storage part 132 Feed roller 133 Feed belt 134 Registration roller 141 Drive roller 142 Driven roller 143 Intermediate transfer belt 144 Primary transfer roller 145 Secondary transfer roller 146 Secondary transfer counter roller 151 Fixing roller 152 Fixing counter roller 153 Heating unit 154 Temperature measuring unit 155 Temperature measurement unit 181 Panel display unit 182 Operation unit 191 Transmission / reception unit 192 Input reception unit 193 Image reading control unit 194 Image formation information generation unit 196 Image formation control unit 199 Storage / reading processing unit 1012 Main memory 1013 North bridge 1014 Sau Bridge 1015 AGP bus 1016 ASIC
1017 Local memory 1018 HD
1019 HDD
1020 PCI bus 1021 Network I / F
1900 Storage unit 1962 Image formation control unit 1963 Paper feed control unit 1964 Transfer control unit 1965 Fixing control unit 1965a Heating control unit

JP 2001-343860 A

Claims (7)

A fixing device for fixing an image formed on a recording medium,
A fixing opposing roller that sandwiches and presses the recording medium together with a fixing roller;
A plurality of partial heating units for heating the fixing facing roller for each part;
The temperature of the first part of the fixing counter roller heated by the first partial heating part and the temperature of the second part of the fixing counter roller heated by the second partial heating part among the plurality of partial heating parts A heating control unit for controlling the first partial heating unit and the second partial heating unit so that the difference between the first partial heating unit and the second partial heating unit,
A fixing device. A fixing device for fixing an image formed on a recording medium,
A fixing roller and a fixing counter roller that sandwich and press the recording medium, and
A plurality of partial heating portions for heating the fixing roller for each portion;
The temperature of the first portion of the fixing counter roller heated by the portion of the fixing roller heated by the first partial heating portion among the plurality of partial heating portions and the portion of the fixing roller heated by the second partial heating portion A heating control unit for controlling the first partial heating unit and the second partial heating unit so that the difference between the temperature of the second portion of the heated fixing facing roller and the temperature within a predetermined range;
A fixing device. The fixing device according to claim 1, wherein:
The fixing device is characterized in that a difference between the temperature of the first portion and the temperature of the second portion is approximately 40 ° C. The fixing device according to claim 1, wherein:
The difference between the temperature of the first part and the temperature of the second part is such that the difference between the diameter of the first part and the diameter of the second part of the fixing roller or the fixing counter roller is within a predetermined range. A fixing device characterized by a difference in temperature inside. The fixing device according to any one of claims 1 to 4, wherein
The first partial heating unit heats a portion of a fixing roller or a fixing counter roller that pressurizes a portion of the recording medium on which the image is formed,
The second partial heating unit heats a portion of a fixing roller or a fixing counter roller that pressurizes a portion of the recording medium where the image is not formed. A fixing device according to any one of claims 1 to 5,
A temperature measuring unit for measuring the temperature of each part of the fixing counter roller;
The fixing device, wherein the heating control unit controls the first partial heating unit and the second partial heating unit based on the temperature measured by the temperature measurement unit.   An image forming apparatus comprising the fixing device according to claim 1.

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