JP2006023533A - Transfer fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent firing from resulting in advance by restraining the rapid temperature rise of paper at the time of paper jamming in a secondary transfer fixing device in terms of fixing. <P>SOLUTION: In the secondary transfer type fixing device (12) of the image forming apparatus (1), a plurality of radiant heating sources (15) heating a transfer fixing member (13) from the outside are installed to be arranged in order on the upstream side of a nip part N between the transfer fixing member and a pressure member (14), so that the heat sources are dispersed to restrain output per one heat source. The device is provided with reflectors (22) individually corresponding to the respective radiant heat sources. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a fixing device used for an electrophotographic copying machine, a printer, a facsimile, and the like, and an image forming apparatus including the same.

  In an image forming apparatus such as a copying machine, a facsimile, a printer, or a printing machine, a copy or a recorded material is obtained by heating and fixing an unfixed image that is transferred and carried on a sheet such as a recording sheet. Can do. During fixing, the unfixed image is heated while nipping and transporting the sheet carrying the unfixed image, so that the developer contained in the unfixed image, in particular, the toner is melted and softened and penetrated into the sheet. Thus, the toner is fixed on the sheet.

  In this type of image forming apparatus, in addition to the simultaneous transfer and fixing method directly from the image carrier to the transfer member without passing through the transfer fixing member, a pressure member is pressed against the intermediate transfer member to form a nip, and toner is transferred to the nip. There is a secondary transfer fixing method in which heating is performed in front and the heated toner is fixed to a recording medium at a nip (see, for example, Patent Document 1 and Patent Document 2). In this method, the secondary transfer from the intermediate transfer member to the recording medium is performed not by electrostatic force but by fixing heat. Further, the toner heating time can be set longer.

Japanese Patent Laid-Open No. 10-63121 JP 2004-145260 A

  In the secondary transfer fixing device, toner heating on the transfer fixing member is necessary due to the configuration, but the use of a radiant heat source that directly heats the toner as a heating source for that purpose is highly efficient and effective. This is because the toner carried on the transfer and fixing member is heated from the outside because the toner interface is directly heated when it is transferred and fixed to a recording medium such as paper.

  By the way, in such a fixing device using direct radiant heating, when a paper jam occurs in the recording medium, if the control of the radiant heat source becomes uncontrollable due to a failure due to some cause, the paper is exposed to the radiant heat source. If clogged in position, there is a danger of overheating rapidly and fire.

  When a paper jam occurs, even if the paper is not jammed in a position where it is exposed to a radiant heat source, if the paper is jammed in a position where it is in contact with a reflector heated to a high temperature, the paper will be similarly heated. There is a risk of overheating and spontaneous ignition.

  Therefore, according to the present invention, in the transfer fixing apparatus of the secondary transfer fixing type on fixing and the image forming apparatus using the same, even when the paper is jammed and the paper is jammed at the position exposed to the radiation heating source, abnormal overheating does not occur. The objective is to reduce the risk of ignition by a simple structure.

  The present invention relates to a transfer fixing device including a transfer fixing member to which a toner image is transferred and a pressure member that presses the transfer fixing member to form a nip, and an outer side of the transfer fixing member on the upstream side of the nip. A plurality of radiant heat sources for heating the transfer fixing member or the toner image, and a plurality of reflectors corresponding to each of the plurality of radiant heat sources.

  This makes it possible to arrange multiple radiant heating sources, disperse the heat sources, suppress the output per heating source, reduce the rapid temperature rise of the paper at the time of paper jam and prevent ignition. it can.

  Further, according to the present invention, as the plurality of radiant heat sources and the reflecting plate are closer to the nip entrance, the heating capacity per unit area for the transfer fixing member by the pair of the radiant heat source and the reflecting plate is set to be smaller. It is characterized by. By disposing a plurality of radiant heat sources, dispersing the heat sources, and suppressing the output of the heat source particularly close to the nip portion, it is possible to prevent a rapid temperature rise of the paper at the time of paper jam. It is preferable to provide heating control means for individually controlling power supplied to the plurality of radiant heat sources.

  Further, the plurality of radiant heat sources may be configured to include at least two different light distribution distributions in the orientation distribution perpendicular to the recording medium conveyance direction. For example, radiant heat sources having different light distributions may have complementary and complementary light distributions. By doing so, it is possible to more reliably prevent an abnormal temperature rise at both ends of the transfer fixing member.

  It is preferable to provide a heat insulating layer on the outside of at least one of the reflectors. By providing the heat insulating layer on the outside of the reflector plate that may possibly come into contact with paper at the time of paper jam, abnormal heating and spontaneous ignition when the paper comes into contact can be prevented.

  Further, the transfer fixing member can be constituted by an endless belt. By using a transfer fixing member as a belt, it becomes possible to arrange a plurality of heat sources more easily than a roller configuration, and the degree of freedom in layout can be expanded.

  According to the present invention, in the image fixing device, a plurality of radiation heating sources are arranged to suppress the output per heating source, and the heat sources are dispersed to reduce the rapid temperature rise of the paper at the time of paper jam. It is possible to prevent ignition.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Here, a full-color copying machine will be described as an example. The following is an example of the best mode of the present invention, and it is easy for a person skilled in the art to make other embodiments within the scope of claims within the scope of the claims. It is not intended to limit the scope of the claims.

(First embodiment)
First, based on FIG. 1 and FIG. 2, an outline of a main part configuration and operation of a tandem type color copier as an image forming apparatus in the first embodiment of the present invention will be described. FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus according to the present invention, and FIG. 2 is an enlarged view of a main part showing a fixing device section. As shown in FIG. 1, the color copying machine 1 includes an image forming unit 100 including a fixing device 12 positioned at the center of the apparatus main body, a paper feeding unit 200 disposed below the image forming unit, and an image forming unit. A document reading unit 300, a document transport unit 400, and a paper transport unit 500 are provided above. The color copying machine 1 further includes a paper discharge tray, a double-side reversing unit (not shown), and the like. Reference numerals 16a to 16d denote sheet feeding trays (sheet feeding cassettes).

  In the image forming unit 100, an intermediate transfer belt 2 as an intermediate transfer body having a transfer surface extending in the horizontal direction is disposed. On the upper surface of the intermediate transfer belt 2, yellow (Y ), Magenta (M), cyan (C), and black (B) units for forming four color toner images, respectively. That is, the photoreceptors 3 (3Y, 3M, 3C, 3B) as image carriers capable of carrying an image of complementary color toners (yellow, magenta, cyan, black) are arranged in the order of the recording medium conveyance direction. The intermediate transfer belt 2 is juxtaposed along the transfer surface.

  Each of the photoconductors 3Y, 3M, 3C, and 3B is configured by a drum that can rotate in the same direction (counterclockwise direction in the drawing), and an image forming process is executed around the drum in synchronization with the rotation process. For this purpose, a charging device 4, a writing device 5 as an optical writing means, a developing device 6, a primary transfer device 7, and a cleaning device 8 are arranged. As in the case of the photoreceptor 3, alphabets attached to the respective symbols are attached corresponding to the toner colors. Each developing device 6 contains color toner of each color.

  The intermediate transfer belt 2 as an intermediate transfer member is wound around a driving roller 9 and a driven roller 10 and disposed at a position facing the photosensitive members 3Y, 3M, 3C, and 3B, and is movable in the clockwise direction in the drawing. It has a configuration. A cleaning device 11 for cleaning the surface of the intermediate transfer belt 2 is disposed at a position facing the driven roller 10.

  An electrostatic latent image is formed on the photoreceptor 3 (3Y to 3B). For example, when the photoreceptor 3Y is taken as an example, the surface thereof is uniformly charged by the charging device 4, and image information (data read by the image reading unit by the writing device 5 or an image sent from the outside such as a PC not shown) is used. An electrostatic latent image is formed by converting an optical signal such as a laser beam on the basis of (signal) and irradiating it on the photoreceptor 3Y. The electrostatic latent image is visualized as a toner image by a developing device 6Y containing yellow toner, and the toner image is primarily transferred onto the intermediate transfer belt 2 by a primary transfer device 7Y to which a predetermined bias is applied. Transcribed. In the other photoconductors 3M, 3C, and 3B, similar image formation is performed only with different toner colors (developing devices), and the toner images of the respective colors are sequentially transferred onto the intermediate transfer belt 2 and superimposed. The toner remaining on the photosensitive member 3 after the transfer is removed by the cleaning device 8, and the potential of the photosensitive member 3 is initialized by a neutralizing lamp (not shown) after the transfer to prepare for the next image forming process.

  A paper feed unit 200 stacks and stores paper P as a recording medium, and a paper feed roller 17 that feeds paper P in the paper feed tray 16 one by one in order from the top. And a pair of transport rollers 18 for transporting the fed paper P, and after the paper P is temporarily stopped and the oblique displacement is corrected, the leading edge of the image on the transfer fixing roller 13 and the pressure roller 14 and the transport direction A registration roller pair 19 is sent out toward the nip portion N at a timing when the predetermined position coincides. A fixing device 12 is provided in the vicinity of the driving roller 9.

  The fixing device 12 includes a transfer fixing roller 13 as a transfer fixing member to which a toner image is transferred, and a pressure roller 14 as a pressure member that presses the transfer fixing member to form a nip. The transfer fixing roller 13 and the pressure roller 14 are made of a metal pipe-shaped cored bar 53 such as aluminum, an elastic layer (rubber layer, etc.) of about 0.05 to 0.5 mm laminated on the surface thereof, and a fluorine resin system of 10 to 30 μm. It is composed of a release layer such as PFA or PTFE as a material. A plurality of halogen heaters 15 and a plurality of reflection plates 22 are provided on the upstream side of the nip portion N near the transfer fixing roller 13 as heating means for heating the toner image on the roller surface layer. The halogen heater 15 is disposed in a reflecting plate 22 as a reflecting member having a U-shaped cross section with the surface facing the fixing roller 13 open.

  The heating capacity per unit area of each halogen heater 15 and the reflecting plate 22 is designed to be lower as it is closer to the nip N side. That is, although the halogen heaters 15 having the same rating are used, the heating power closer to the nip portion N side becomes lower through the heating control means for individually controlling the power supplied to each halogen heater 15. It is set as follows. This is because if the paper is clogged near the nip entrance, the closer the radiant heating source and reflector are located near the nip entrance, the higher the probability of facing or contacting the paper. This is because it is desirable for safety that the output per unit area is weakened. In addition, you may make it arrange | position in order each halogen heater 15 from which ratings differ, without using a heating control means.

  If the light distribution in the longitudinal direction of the radiant heat source is uniform, if small size paper is passed continuously, heat is only taken from the center with respect to the longitudinal direction of the transfer and fixing member. There is a concern that the temperature will rise abnormally. If the transfer fixing member is abnormally heated, heat continues to move from the contact portion with the intermediate transfer member to the intermediate transfer member, and the intermediate transfer member is heated. When the intermediate transfer member is heated, the temperature in the entire apparatus tends to increase easily, or heat is transmitted to the contact portion with the photosensitive member, thereby causing problems such as toner fixation.

  Therefore, in the present embodiment, the light distributions of the halogen heaters 15 in the direction orthogonal to the recording medium conveyance direction are different from each other, one having a large heating area (irradiation area) arranged only in the center, The heating area | region arrange | positioned only at both ends is a large thing. In this way, by arranging multiple radiant heat sources having different light distributions that are complementary and complementary to each other, uniform and sufficient heating to the transfer fixing member is realized while suppressing the amount of heat generated by each radiant heat source. ing.

  Further, a thermistor (not shown) provided in a non-image area (image non-formation area) for measuring the surface temperature of the transfer fixing roller 13 and a heating control means are used to control on / off of the halogen heater 15 based on the respective surface temperatures. A temperature controller is provided to control the temperature.

  In addition, the release layers of the transfer fixing roller 13 and the pressure roller 14 are made of a conductive fluororesin material in which a conductive substance such as carbon is dispersed and connected to a cored bar to transfer between the release layers. A bias can be applied, the transfer bias can be lowered, and scattering during transfer can be suppressed.

  In the fixing device 12 in the present embodiment, as shown in FIG. 1, a transfer fixing (pressure) roller 13 (14) is interposed between the intermediate transfer belt 2 and the transfer fixing (pressure) roller 13 (14). A heat insulating plate 20 is provided as a heat transfer inhibiting member (heat shielding member) that suppresses heat radiation (heat transfer) to the intermediate transfer belt 2. The heat insulating plate 20 has an opening so as to suppress heat radiation to the intermediate transfer belt 2 as much as possible while preventing secondary transfer from the intermediate transfer belt 2 to the transfer fixing (pressing) roller 13 (14). And may be supported on either the fixing device casing (not shown) or the image forming apparatus main body.

  The heat insulating plate 20 is preferably a plate having a metallic luster with a low emissivity, and an excellent effect can be obtained particularly when two metal sheets are arranged with a minute gap or a heat insulating material interposed therebetween. Further, a thin plate containing a micro heat pipe structure used for cooling a CPU of a notebook personal computer may be used, and the heat transfer restraining member can be kept at a low temperature and heat transfer can be appropriately suppressed.

  In this embodiment, the intermediate transfer belt 2 is positioned on the most upstream side with respect to the transfer portion (the portion facing the transfer fixing (pressure) roller 13 (14)) with respect to the transfer fixing (pressure) roller 13 (14). A cooling roller 210 is provided as a cooling member for removing heat from the intermediate transfer belt 2 between the transfer portion for the photosensitive member 3B. The cooling roller 210 is made of a material having high thermal conductivity, and rotates in contact with the intermediate transfer belt 2. In the present embodiment, both the heat insulating plate 20 and the cooling roller 210 are provided. However, either one may be provided. According to this embodiment, the temperature of the intermediate transfer member can be reduced, and thermal deterioration on the intermediate transfer member side can be suppressed. Further, the degree of freedom in designing the transfer fixing member can be increased.

  Next, the operation of the fixing device 12 in the above embodiment will be described with reference to an enlarged view of a main part in FIG. The toner image T formed on the intermediate transfer belt 2 is negatively charged, and a bias is applied so that the drive roller 9 side is −0.5 kV to 2.0 kV and the core metal of the transfer fixing roller 13 is 0V. As a result, the images are sequentially transferred to the transfer fixing roller 13. At this time, the toner image T1 on the transfer fixing roller 13 is heated to a predetermined temperature by the halogen heater 15.

  Thereafter, the recording medium P is sent out from the registration roller 19 in synchronization with the timing at which the toner image T1 approaches (arrives) at the nip portion N, and the toner is heated by the pressurizing force and the heat held by the toner itself at the nip portion N. The image T1 is transferred and fixed to the recording medium P at the same time.

  As described above, since the process of heating only the toner image T in advance is sufficiently obtained, the heating temperature can be lowered as compared with the conventional method in which the toner T and the recording medium P are simultaneously heated. As a result of the experiment, it was confirmed that sufficient image quality was obtained even when the temperature of the transfer fixing roller 13 and the pressure roller 14 was as low as 110 to 120 ° C.

  Incidentally, in the conventional color image forming apparatus, in order to obtain a sufficient gloss, a heat amount about 1.5 times that of the black and white image forming apparatus is given in consideration of a temperature drop due to the paper. For this reason, the paper is heated more than necessary, and the adhesion between the toner and the paper is increased more than necessary.

  In this embodiment, the temperature for obtaining a sufficient gloss without considering the recording medium P can be set independently, so that the temperature (fixing set temperature) of the transfer fixing roller 13 can be lowered. Further, not only the adhesion between the toner T and the paper is not increased more than necessary, but also the paper P is heated only by the nip portion N and is not excessively heated, which contributes to energy saving.

  Furthermore, by suppressing the output per one of each halogen heater 15 as a radiant heating source and dispersing it in a plurality, even if the halogen heater 15 falls into an uncontrollable state in the event of a paper jam, Rapid temperature rise can be avoided.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. When the transfer fixing member is a roller, in order to arrange a plurality of radiation heating sources for the transfer fixing roller, the transfer fixing roller must have a large diameter in order to secure a space for it. There are restrictions. In order to improve this point, this embodiment has almost the same configuration as that of the first embodiment. As shown in the enlarged view of the main part in FIG. 55 and a transfer roller 56 for forming a nip N via the transfer and fixing belt 55, and a heating roller 57 for stretching the transfer and fixing belt 55 and heating the transfer and fixing belt 55 are provided. The transfer roller 56 has a metal roller such as aluminum or a rubber layer in which a conductor such as carbon is dispersed on the surface of the metal roller, and is connected to a bias applying unit (not shown).

  The transfer and fixing belt 55 has a three-layer structure, and a polyimide film as a base material is 70 μm from the inside, silicon rubber of an elastic layer is 200 μm, and PFA is coated on the surface by 20 μm. By making the release layer conductive PFA, the scattering of the transfer can be suppressed. Further, by providing the elastic layer, the heating surface can easily follow the unevenness of the toner T and the paper P when fixing at the nip portion N, and uneven glossiness of the image can be prevented and the image quality can be improved.

  The heating roller 57 is formed of an aluminum material in a cylindrical shape, and rotates following the transfer and fixing belt 55. Further, a halogen heater 15 and a reflection plate 22 for heating the toner image T1 are provided in the vicinity of the transfer fixing belt 55. Furthermore, a heat insulating layer 23 is provided on the outer side of the reflecting plate 22 that is closest to the nip portion N side, that is, on the outer side of the reflecting plate 22 that is likely to come into contact with paper when a paper jam occurs.

  A thermistor (not shown) provided in a non-image area for measuring the surface temperatures of the transfer fixing roller 13 and the transfer fixing belt 55 and a temperature controller (non-control) for controlling on / off of the halogen heater 15 based on the respective surface temperatures. The temperature of each halogen heater 15 can be controlled independently.

  The operation of this embodiment is almost the same as that of the first embodiment. The toner image T1 is transferred to the transfer and fixing belt 55, and the recording medium P is passed through the nip portion N. The toner image T1 is fixed.

  As described above, in the second embodiment, by configuring the transfer fixing member with the transfer fixing belt 55, it is possible to arrange a plurality of heat sources more easily than the configuration of the first embodiment using the transfer fixing roller 13. Yes.

  As described above with reference to the embodiment, in the present invention, the rapid temperature of the paper at the time of the paper jam is obtained by disposing a plurality of radiant heating sources, suppressing the output per one heating source, and dispersing the heat sources. It is possible to prevent the rise and reduce the ignition.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. 1 is a main part enlarged view showing a main part of an image forming apparatus according to a first embodiment of the present invention. It is a principal part enlarged view which shows the principal part of the image forming apparatus which is the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Color copying machine 2 ... Intermediate transfer belt 3 ... Photoconductor 4 ... Charging device 5 ... Writing device 6 ... Developing device 7 ... Primary transfer device (intermediate transfer body)
DESCRIPTION OF SYMBOLS 8 ... Cleaning device 9 ... Drive roller 10 ... Driven roller 11 ... Cleaning device 12 ... Fixing device 13 ... Transfer fixing roller (transfer fixing member)
14: Pressure roller (pressure member)
15 ... Halogen heater (radiant heating source)
DESCRIPTION OF SYMBOLS 16 ... Paper feed tray 17 ... Paper feed roller 18 ... Conveying roller pair 19 ... Registration roller 20 ... Heat insulation plate 21 ... Pressure spring 22 ... Reflecting plate 23 ... Heat insulation layer 53 ... Core metal 55 ... Transfer fixing belt (transfer fixing member)
56 ... transfer roller 57 ... heating roller 100 ... image forming unit 200 ... paper feeding unit 210 ... cooling roller N ... nip T, T1 ... toner image P ... paper

Claims (8)

In a transfer fixing device comprising a transfer fixing member to which a toner image is transferred, and a pressure member that presses the transfer fixing member to form a nip.
A plurality of radiant heat sources for heating the transfer fixing member or the toner image from the outside of the transfer fixing member upstream of the nip;
And a plurality of reflection plates corresponding to each of the plurality of radiant heat sources.   The heating power per unit area for the transfer fixing member by the pair of the radiant heat source and the reflecting plate is set to be smaller as the plurality of radiant heat sources and the reflecting plate are closer to the nip entrance. Item 2. The transfer fixing device according to Item 1.   The transfer fixing apparatus according to claim 1, further comprising a heating control unit that individually controls power supplied to the plurality of radiant heat sources.   2. The transfer fixing apparatus according to claim 1, wherein the plurality of radiant heat sources include a structure in which an orientation distribution in a direction orthogonal to a recording medium conveyance direction has at least two different light distributions.   5. The transfer fixing device according to claim 4, wherein the radiant heat sources having different light distributions have complementary and complementary light distributions.   The transfer fixing device according to claim 1, wherein a heat insulating layer is provided outside at least one of the reflecting plates.   The transfer fixing apparatus according to claim 1, wherein the transfer fixing member is an endless belt. An image forming apparatus comprising the transfer fixing device according to claim 1.

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