JP2014032374A - Fixing device and image forming device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To absorb/discharge surplus heat to prevent damage to an anti-overheating device, while preventing overshoot phenomenon during power interruption.SOLUTION: A fixing device includes: a fixing roller for fixing toner transferred on a sheet; a heating roller with a heat source having an endless fixing belt wound thereon together with the fixing roller; a cooling member in contact with an outer circumferential part of the heating roller across the fixing belt to cool the heat generated from the heat source; a cooling fan for dissipating the heat generated from the cooling member; and a power source for driving the cooling fan.

Description

  The present invention relates to a fixing device and an image forming apparatus using the same.

  A fixing device in a conventional image forming apparatus includes a heating roller maintained at a predetermined temperature, and a pressure roller that is pressed against the heating roller, and a nip portion formed by the pressure contact between the heating roller and the pressure roller. Thus, there is known a roller fixing method in which a sheet which is a transfer material carrying an unfixed toner image is heated while being nipped and conveyed.

  In addition, recently, a fixing roller disposed opposite to the pressure roller and an endless fixing belt stretched between the fixing roller and the heating roller are provided. In the formed nip portion, a belt fixing method is performed in which heat from a heating roller is applied to a sheet via a fixing belt to press and fix an unfixed toner image on the sheet.

  In a high-speed image forming apparatus, in order to maintain the amount of heat given to the paper from the fixing belt, it is necessary to increase the heat generation amount per unit time of the heat source inside the heating roller and continue to supply heat to the fixing belt via the heating roller. There is. In such a configuration, even if heat generation is stopped by the control means of the heat source at the end of the print job, the heat stored by the heat capacity of the heating roller is transferred to the fixing belt, and after the final sheet of paper has passed Since no medium deprives the fixing belt of heat, an overshoot phenomenon occurs in which the temperature of the fixing belt rises above the control temperature.

  When this overshoot phenomenon occurs, the amount of heat applied to the paper passing through the fixing unit in the immediately following job becomes excessive, or the temperature inside the apparatus rises, resulting in an overshoot such as a thermal fuse or temperature thermostat. The temperature rise prevention device may be damaged, and the image forming apparatus may become unusable.

  As a proposal to solve this problem, Patent Document 1 discloses that when the final sheet in a series of jobs passes through the nip portion, the temperature of the heating roller is lowered from the set temperature while the fixing device continues to rotate. And the control of changing the control temperature of the pressure roller from the set temperature to a lower temperature to suppress the occurrence of the overshoot phenomenon. Patent Document 2 discloses a configuration in which the temperature of the fixing belt is lowered by bringing a cooling member into contact with the fixing belt.

  However, although the countermeasure disclosed in Patent Document 1 is effective at the end of a normal job in which the fixing device continues to rotate, the occurrence of a paper jam inside the fixing device, the occurrence of an unexpected power interruption during printing, etc. In a situation where the rotation of the fixing device cannot be maintained, there is a problem that the occurrence of the overshoot phenomenon cannot be suppressed.

  Further, in the configuration disclosed in Patent Document 2, the temperature of the cooling member immediately rises only by the contact of the cooling member, and a sufficient cooling effect cannot be obtained. Further, a configuration in which a cooling member is provided with heat radiation fins and cooled by a fan is disclosed, but there is a problem that a cooling effect cannot be obtained because the fan is also stopped by an unexpected power cut or the like.

  Therefore, the present invention has been made in view of the above-described conventional problems, and efficiently absorbs and dissipates excess heat, thereby suppressing the occurrence of an overshoot phenomenon even when the power is turned off and preventing excessive temperature rise. It is an object of the present invention to provide a fixing device that does not damage the device.

  In order to solve the above-described problem, a fixing device according to the first aspect of the present invention includes a fixing roller that fixes toner transferred onto a sheet, and a heat source wound around the fixing roller and an endless fixing belt. A heating roller having, a cooling member that contacts the outer periphery of the heating roller across the fixing belt, cools the heat generated from the heat source, and a cooling fan that dissipates the heat generated from the cooling member; And a power supply for driving the cooling fan.

  According to the present invention, it is possible to obtain a fixing device that efficiently absorbs and dissipates excess heat, suppresses overshoot even when the power is turned off, and does not damage the excessive temperature rise prevention device.

FIG. 2 is a schematic configuration diagram illustrating a state in which a cooling member is in contact with a fixing belt in the fixing device according to the first exemplary embodiment of the present invention. FIG. 2 is a schematic configuration diagram illustrating a state in which a cooling member is separated from a fixing belt in the fixing device according to the first exemplary embodiment of the present invention. FIG. 2 is a schematic configuration diagram illustrating a state in which a cooling member is in contact with a fixing belt in the fixing device according to the first exemplary embodiment of the present invention. FIG. 9 is a schematic configuration diagram illustrating a state in which a cooling member is in contact with a fixing belt in a fixing device according to a second embodiment of the present invention. FIG. 6 is a schematic configuration diagram illustrating a state in which a cooling member is separated from a fixing belt in a fixing device according to a second embodiment of the present invention. FIG. 9 is a schematic configuration diagram illustrating a state in which a cooling member is in contact with a fixing belt in a fixing device according to a second embodiment of the present invention. FIG. 10 is a schematic configuration diagram illustrating a state in which a cooling member is in contact with a fixing belt in a fixing device according to a third embodiment of the present invention. FIG. 10 is a schematic configuration diagram illustrating a state in which a cooling member is separated from a fixing belt in a fixing device according to a third embodiment of the present invention. FIG. 10 is a schematic configuration diagram illustrating a state in which a cooling member is in contact with a fixing belt in a fixing device according to a third embodiment of the present invention. 1 is a schematic configuration diagram illustrating a configuration of an image forming apparatus including a fixing device according to an embodiment of the present invention.

  Next, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified thru | or abbreviate | omitted suitably. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine using an electrophotographic method, and more particularly to a fixing device that fixes a toner image formed on an image carrier onto a recording medium. The present invention relates to an image forming apparatus using. In short, the present invention is provided with a cooling member disposed in contact with the outer peripheral portion of the heating roller with the fixing belt interposed therebetween, and the cooling member has a contact / separation mechanism for contacting and separating the heating roller with the fixing belt interposed therebetween. By providing a cooling fan with a power supply that can be independently driven in the vicinity of the cooling member, excess heat is absorbed by bringing the cooling member into contact with the heating roller via the fixing belt, and the cooling fan is used. In this way, the occurrence of an overshoot phenomenon is suppressed by dissipating heat.

  First, the configuration of the fixing device in the first embodiment of the present invention will be described. FIG. 1 is a schematic configuration diagram illustrating a state in which a cooling member is in contact with a fixing belt in the fixing device according to the first embodiment of the present invention. In the fixing device 20 shown in FIG. 1, an endless fixing belt 3 is wound between the heating roller 1 and the fixing roller 2. The pressure roller 4 is disposed on the fixing roller 2 via the fixing belt 3 so as to be able to be depressurized / pressed by a pressure contact mechanism (not shown). When the pressure roller 4 is pressed, a nip portion N is formed between the pressure roller 4 and the fixing roller 2. The heating roller 1 includes a cored bar part and a surface release layer such as Teflon (registered trademark), and a heater 8 serving as a heat source is provided in the axial center hole of the cored bar part.

  In this embodiment, for example, the fixing roller 2 is formed by forming a silicone rubber having a thickness of several tens of mm on a core metal. The fixing belt 3 is a belt in which a silicone rubber layer is provided on a polyimide base material, and a PFA (Perfluoroalkoxy fluoroplastics) coating is applied to a surface layer. Further, the pressure roller 4 is configured by forming a silicone rubber layer having a thickness of several millimeters on a core metal and covering a surface layer with a PFA tube.

  The silicone rubber layer of the fixing roller 2 is configured to be sufficiently thicker and softer than the silicone rubber layer of the pressure roller 4, and the sheet P is fed by causing the pressure roller 4 to bite into the fixing roller 2. The structure is easy to peel off from the fixing belt 3. This is merely an example, and it is a matter of course that a configuration by combining various materials is possible depending on the purpose, application, and the like.

  The heat of the heating roller 1 is transmitted to the fixing belt 3, and the surface temperature of the fixing belt 3 is detected by the temperature detection device 9, and control is performed by turning on and off the heater 8 as a heat source so that this temperature becomes a constant temperature. It has been broken. A cleaning unit 10 is in contact with the pressure roller 4 on the downstream side of the nip portion N. Residues such as residual toner and paper dust transferred from the fixing belt 3 side adhere to the surface of the pressure roller 4 after the paper P has passed. These residues are removed and collected by the cleaning unit 10.

  The cleaning unit 10 includes a cleaning web 11 and a cleaning web contact member 12. A winding shaft 13 and a feeding shaft 14 are attached to the cleaning web 11, and the cleaning web 11 is wound by a driving mechanism (not shown). The cleaning web 11 is a roll having a thickness of about several tens of μm, and is in contact with the pressure roller 4 by a cleaning web contact member 12. On the downstream side of the nip portion N, an inlet guide plate 7 for guiding the paper P to the nip portion N is disposed.

  A cooling member 5 is in contact with the outer peripheral portion of the heating roller 1 via the fixing belt 3. When the cooling member 5 comes into contact with the fixing belt 3, the cooling member 5 can absorb excess heat of the heating roller 1 through the fixing belt 3. The cooling member contacting / separating mechanism 6 includes an eccentric cam and a stepping motor. When the cooling member 5 is separated from the fixing belt 3, the motor is driven and the cooling member 5 is lifted by the eccentric cam.

  Here, a state in which the cooling member is separated from the fixing member will be described with reference to FIG. FIG. 2 is a schematic configuration diagram illustrating a state in which the cooling member is separated from the fixing belt in the fixing device according to the first embodiment of the present invention. A cooling fan 17 is disposed in the vicinity of the cooling member 5. The cooling fan 17 is connected to a power source (capacitor) 18 as an independent power source for driving.

  The power source (capacitor) 18 is charged when the power of the image forming apparatus is turned on, and always has an electrostatic capacity that allows the cooling fan 17 to rotate for a predetermined time. After the power of the image forming apparatus is turned off, the cooling fan is fixed for a predetermined time. 17 can be driven. The independent power source 18 is not limited to a capacitor, and can be configured by a general battery or the like as another method.

  In this embodiment, the cooling member 5 includes a heat absorbing portion 52 that contacts the fixing belt 3 and absorbs heat, and a heat radiating portion 51 that dissipates the absorbed heat. The structure having a large surface area having a plurality of fins increases the heat dissipating ability and efficiently absorbs heat from the fixing belt 3.

  Next, the fixing device according to the first embodiment of the present invention will be described. FIG. 3 is a schematic configuration diagram illustrating a state in which the cooling member is in contact with the fixing belt in the fixing device according to the first embodiment of the present invention. In FIG. 3, the conveyance state detection unit 16 of the fixing belt 3 includes an encoder 161 disposed in a non-printing area of the fixing belt 3 and a sensor 162 that detects the rotation of the encoder 161. Only when it is detected by the sensor 162 that the rotation of the encoder 161 has stopped, the cooling member 5 is brought into contact with the fixing belt 3 to cause scratches caused by rubbing between the cooling member 5 and the fixing belt 3. To prevent.

  Further, only when the surface temperature of the fixing belt 3 detected by the temperature detection device 9 draws a rising curve that reaches a temperature that damages an excessive temperature rise prevention device such as a temperature fuse (not shown) or a temperature thermostat. By bringing the cooling member 5 into contact with the fixing belt 3, the waiting time until the start of the next job generated by the cooling operation can be minimized.

  Further, a force is applied to the cooling member 5 in a direction in which the cooling member 5 comes into contact with the fixing belt 3 by a spring 15. When the drive source of the cooling member contacting / separating mechanism 6 is cut off due to power interruption or the like, the cooling member 5 is always brought into contact with the fixing belt 3 by the extension force of the spring 15. Even in a situation where the separation mechanism 6 cannot be driven, it is possible to reliably suppress the occurrence of the overshoot phenomenon.

  Next, a fixing device according to the second embodiment of the present invention will be described. FIG. 4 is a schematic configuration diagram illustrating a state in which the cooling member is in contact with the fixing belt in the fixing device according to the second embodiment of the present invention. In FIG. 4, a cooling roller 50 is in contact with the outer peripheral portion of the heating roller 1 via the fixing belt 3.

  When the cooling roller 50 comes into contact with the fixing belt 3, the cooling roller 50 can absorb excess heat of the heating roller 1 through the fixing belt 3. The cooling roller contact / separation mechanism 60 includes an eccentric cam and a stepping motor. When the cooling roller 50 is separated from the fixing belt 3, the motor is driven and the cooling roller 50 is lifted by the eccentric cam.

  Here, a state where the cooling roller is separated from the fixing belt will be described with reference to FIG. FIG. 5 is a schematic configuration diagram illustrating a state in which the cooling member is separated from the fixing belt in the fixing device according to the second embodiment of the present invention. The cooling roller 50 can be rotationally driven by the cooling roller driving mechanism 19.

  A cooling fan 17 is disposed in the vicinity of the cooling roller 50. The cooling roller driving mechanism 19 and the cooling fan 17 are connected to a power source (capacitor) 18 as an independent power source for driving. The power source (capacitor) 18 is charged when the image forming apparatus is turned on, and always has a capacitance that allows the cooling roller driving mechanism 19 and the cooling fan 17 to rotate for a certain period of time, so that the image forming apparatus is turned off. After that, it is possible to drive the cooling roller driving mechanism 19 and the cooling fan 17 for a certain time. The independent power source 18 is not limited to a capacitor, and can be configured by a general battery or the like as another method.

  Next, a fixing device according to the second embodiment of the present invention will be described. FIG. 6 is a schematic configuration diagram illustrating a state in which the cooling member is in contact with the fixing belt in the fixing device according to the second embodiment of the present invention. In FIG. 6, the cooling roller driving mechanism 19 fixes via the cooling roller 50 so that when the cooling roller 50 contacts the fixing belt 3, the fixing belt 3 rotates in the direction opposite to the direction in which the paper P is conveyed. The belt 3 is rotated. As a result, the paper P that has jammed in the fixing device 20 is returned to the entrance side of the fixing device 20 so as to be easily removed, and the fixing belt 3 is rotated so that only a part of the fixing belt 3 is applied to the heating roller 1. Deformation and breakage caused by contact and overheating can be suppressed.

  In the fixing device 20 shown in FIG. 6, the conveyance state detection unit 16 of the fixing belt 3 includes an encoder 161 disposed in a non-printing area of the fixing belt 3 and a sensor 162 that detects the rotation of the encoder 161. ing. The cooling roller 50 is brought into contact with the fixing belt 3 only when the rotation of the fixing belt 3 is stopped. As a result, only a part of the fixing belt 3 comes into contact with the heating roller 1 and the cooling roller 5 can be brought into contact only when heat accumulates and there is a risk of deformation.

  In the fixing device 20 shown in FIG. 6, the surface temperature of the fixing belt 3 detected by the temperature detecting device 9 rises to reach a temperature that damages an excessive temperature rise prevention device such as a temperature fuse or a temperature thermostat (not shown). Only when the curve is drawn, the waiting time until the start of the next job generated by the cooling operation can be kept to a minimum by bringing the cooling roller 50 into contact with the fixing belt 3.

  Further, the cooling roller 50 is applied with a force in a direction in which the cooling roller 50 abuts the fixing belt 3. When the supply of the driving force of the cooling roller contact / separation mechanism 60 is cut off due to a power cut or the like, the cooling roller 50 is always brought into contact with the fixing belt 3 by the extension force of the spring 15, Even when the roller contact / separation mechanism 60 cannot be driven, the occurrence of the overshoot phenomenon can be reliably suppressed.

  Next, a fixing device according to a third embodiment of the present invention will be described. FIG. 7 is a schematic configuration diagram illustrating a state in which the cooling member is in contact with the fixing belt in the fixing device according to the third embodiment of the present invention. In FIG. 7, a cooling belt 500 is in contact with the outer peripheral portion of the heating roller 1 via the fixing belt 3.

  When the cooling belt 500 comes into contact with the fixing belt 3, the cooling belt 500 can absorb excess heat of the heating roller 1 through the fixing belt 3. The cooling belt 500 includes a driving roller 510 and a driven roller 520, the driving roller 510 is connected to the cooling belt driving mechanism 190, and the cooling belt 500 can be rotationally driven by the cooling belt driving mechanism 190.

  A cooling fan 17 is disposed in the vicinity of the cooling belt 500. The cooling belt drive mechanism 190 and the cooling fan 17 are connected to a power source (capacitor) 18 as an independent power source for driving. The power source (capacitor) 18 is charged when the image forming apparatus is turned on, and always has a capacitance that allows the cooling belt drive mechanism 190 and the cooling fan 17 to rotate for a certain period of time, so that the image forming apparatus is turned off. After that, it is possible to drive the cooling belt driving mechanism 190 and the cooling fan 17 for a predetermined time. The independent power source 18 is not limited to a capacitor, and can be configured by a general battery or the like as another method.

  The cooling belt contact / separation mechanism 600 includes an eccentric cam and a stepping motor. When the cooling belt 500 is separated from the fixing belt 3, the motor is driven and the cooling belt 500 is lifted by the eccentric cam.

  Here, a state where the cooling belt is separated from the fixing member will be described with reference to FIG. FIG. 8 is a schematic configuration diagram illustrating a state in which the cooling member is separated from the fixing belt in the fixing device according to the third embodiment of the present invention. The cooling belt driving mechanism 190 rotates the fixing belt 3 via the cooling belt 5 so that the fixing belt 3 rotates in the direction opposite to the direction in which the paper P is conveyed when the cooling belt 500 contacts the fixing belt 3. Let As a result, the paper P that has jammed in the fixing device 20 is returned to the entrance side of the fixing device 20 so as to be easily removed, and the fixing belt 3 is rotated so that only a part of the fixing belt 3 is applied to the heating roller 1. Deformation and breakage caused by contact and overheating can be suppressed.

  Next, a fixing device according to a third embodiment of the present invention will be described. FIG. 9 is a schematic configuration diagram illustrating a state in which the cooling member is in contact with the fixing belt in the fixing device according to the third embodiment of the present invention. In FIG. 9, the conveyance state detection means 16 of the fixing belt 3 includes an encoder 161 disposed in a non-printing area of the fixing belt 3 and a sensor 162 that detects the rotation of the encoder. The cooling belt 500 is brought into contact with the fixing belt 3 only when the rotation of the fixing belt 3 is stopped. Thus, only when a part of the fixing belt 3 is in contact with the heating roller 1 and heat is accumulated and there is a risk of deformation, the cooling belt 500 can be brought into contact.

  In the fixing device 20 shown in FIG. 9, the surface temperature of the fixing belt 3 detected by the temperature detecting device 9 rises to reach a temperature that damages an excessive temperature rise prevention device such as a temperature fuse or a temperature thermostat (not shown). Only when a curve is drawn, the waiting time until the start of the next job generated by the cooling operation can be kept to a minimum by bringing the cooling belt 5 into contact with the fixing belt 3.

  Further, a force is applied to the cooling belt 500 in a direction in which the cooling belt 500 contacts the fixing belt 3 by a spring 15. When the supply of the driving force of the cooling belt contact / separation mechanism 600 is cut off due to a power cut or the like, the cooling belt 500 is always brought into contact with the fixing belt 3 by the extension force of the spring 15. Even in a situation where the belt contact / separation mechanism 600 cannot be driven, the occurrence of overshoot can be reliably suppressed.

  Next, an image forming apparatus equipped with the above-described fixing device will be described with reference to FIG. FIG. 10 is a schematic configuration diagram illustrating the configuration of the image forming apparatus including the fixing device according to the embodiment of the present invention. The image forming apparatus 100 is a tandem intermediate transfer type color copying machine. As shown in FIG. 1, an image forming apparatus 100 includes an apparatus main body 101, a scanner 102 that is an image reading apparatus disposed above the apparatus main body 101, and an automatic document feeder disposed further above the scanner 102. (ADF: Auto Document Feeder) 103.

  A paper feed unit 104 including a plurality of paper feed cassettes 104 a, 104 b, 104 c, and 104 d is disposed at the lower part of the apparatus main body 101. An endless intermediate transfer belt 105 as an intermediate transfer member is disposed at a substantially central portion of the apparatus main body 101. The intermediate transfer belt 105 is supported around a plurality of support rollers 106, 107, 108, and the like, and is driven to rotate clockwise in FIG. 10 by a drive source (not shown).

  In the vicinity of the support roller 108, an intermediate transfer body cleaning device 109 for removing residual toner and the like remaining on the intermediate transfer belt 105 after the secondary transfer is provided. On the intermediate transfer belt 105 stretched between the support roller 106 and the support roller 107, yellow (Y), magenta (M), cyan (C), and black (K) along the conveyance direction. The four process cartridges 29Y, 29M, 29C, and 29K as the image forming means are arranged and arranged in this order to constitute the tandem image forming unit 30. However, these four color orders are examples and are not limited to these.

  The process cartridges 29Y, 29M, 29C, and 29K are provided with drum-shaped photosensitive drums 21Y, 21M, 21C, and 21K as image carriers. Hereinafter, the configuration of the process cartridges 29Y, 29M, 29C, and 29K is the same except for the toner color in the developer corresponding to the image data color to be exposed, and the other configurations are the same. A general description will be given by using the reference numerals from which are deleted.

  Around the photosensitive drum 21 in the process cartridge 29 are a protective layer forming device 22 for supplying an image carrier protecting agent to the surface of the photosensitive drum, a charging device 23 for uniformly charging the surface of the photosensitive drum, and an exposure device to be described later. Toner receiving portion from the latent image forming device 28, a developing device 25 for supplying toner to the latent image forming portion on the surface of the photosensitive drum 21 to visualize the toner, and a toner image on the surface of the photosensitive drum 21 in the middle A transfer device 26 for primary transfer to the transfer belt 105 and a cleaning device 24 for cleaning residual toner on the surface of the photosensitive drum 21 after transfer are disposed.

  Above the tandem image forming unit 30, a latent image forming device 28 as an exposure device is disposed. A secondary transfer roller 110 as a transfer device is disposed on the opposite side of the intermediate transfer belt 105 from the support roller 108. By the secondary transfer roller 110, the toner image on the intermediate transfer belt 105 is transferred to a sheet as an example of a sheet-like recording medium supplied from the paper supply unit 104.

  On the left side of the secondary transfer roller 110, a fixing device 20 according to an embodiment of the present invention for fixing a transfer image transferred onto a sheet is disposed. The fixing device 20 has a configuration in which a pressure roller 4 as a pressure member is pressed against the endless fixing belt 3. The detailed configuration and operation of the fixing device 20 will be described later. Below the fixing device 20, a sheet reversing device 112 for reversing the paper when an image is formed on both sides of the paper is disposed substantially parallel to the tandem image forming unit 30 described above.

  A series of processes for forming an image will be described below based on a negative-positive process, but will be briefly described by omitting reference numerals representing colors. A photosensitive drum 21 typified by a photosensitive member (OPC: Organic Photoconductor) having an organic photoconductive layer is neutralized by a neutralizing lamp (not shown) or the like, and is uniformly negatively charged by a charging roller of a charging device 23. When the photosensitive drum 21 is charged by the charging device 23, an appropriate size suitable for charging the photosensitive drum 21 to a desired potential with respect to the charging device 23 from a voltage application mechanism (not shown). Or a charging voltage obtained by superimposing an AC voltage thereon is applied.

  The charged photosensitive drum 21 is subjected to latent image formation with laser light irradiated by a latent image forming device 28 such as a laser optical system. Laser light is emitted from a semiconductor laser, and the surface of the photosensitive drum 21 is scanned in the direction of the rotational axis of the photosensitive drum 21 by a polygonal polygon mirror that rotates at high speed. The latent image formed in this way is developed with a developer composed of toner particles or a mixture of toner particles and carrier particles supplied on a developing sleeve (developing roller) which is a developer carrying member in the developing device 25. As a result, a visible toner image is formed.

  At the time of developing the latent image, a voltage of an appropriate magnitude between the exposed portion and the non-exposed portion of the photosensitive drum 21 with respect to the developing sleeve from a voltage application mechanism (not shown), or development in which an alternating voltage is superimposed on the developing sleeve. A bias is applied. A toner image formed on the photosensitive drum 21 corresponding to each color is transferred onto the intermediate transfer belt 105 by a transfer roller 26 constituting a transfer device (not shown) and supplied from the paper feeding unit 104 or from the manual feed tray 113. The toner image (color image) superimposed by the secondary transfer roller 110 is collectively transferred onto a sheet (transfer medium) as an example of the supplied sheet-like recording medium. Thereafter, the intermediate transfer belt 105 is separated from the photosensitive drum 21, and a transfer image is obtained.

  The toner particles remaining on the photosensitive drum 21 are collected by a cleaning blade or the like in the cleaning device 24. The sheet carrying the unfixed toner image after image transfer is conveyed to the fixing device 20 and heat and pressure are applied at the nip N between the fixing belt 3 and the pressure roller 4 wound around the fixing roller 2. The transferred image is fixed. The fixed sheet is discharged onto the discharge tray 116 by the discharge roller pair 115 and stacked.

  Alternatively, the conveyance path is switched by a switching claw (not shown) and conveyed to the sheet reversing device 112, where it is reversed and guided again to the transfer position, and an image is formed on the back surface. The paper is discharged and stacked on the paper tray 116. The intermediate transfer belt 105 after image transfer is freed of residual toner and the like by an intermediate transfer member cleaning device 109 and is ready for re-image formation by the tandem image forming unit 30.

  By applying the fixing device in the embodiment of the present invention described above with respect to the fixing device 20, damage to an excessive temperature rise prevention device such as a temperature fuse or a temperature thermostat is caused even when an unexpected power interruption occurs during a jam or printing. It is possible to provide an image forming apparatus that does not occur.

  As described above, according to the present invention, the pressure roller 4 is pressed against the heating roller 1 having the heat source 8 and the fixing roller 2 having the elastic layer on the outer periphery of the metal core and not having the heat source inside. And an endless fixing belt 3 that is stretched between the heating roller 1 and the fixing roller 2, and is formed by press-contact between the fixing roller 2 and the pressure roller 4. In a fixing device 20 that heats and fixes a sheet P carrying an unfixed toner image through a nip portion N between the roller 4 and the roller 4, it contacts the outer peripheral portion of the heating roller 1 with the fixing belt 3 interposed therebetween. The cooling member 5, the cooling roller 50, or the cooling belt 500 is provided, and the cooling member 5, the cooling roller 50, or the cooling belt 500 contacts and separates from the heating roller 1 with the fixing belt 3 interposed therebetween. Mechanism 6, cooling roller contact / separation mechanism 60 And the cooling fan 17 having the cooling belt contact / separation mechanism 600 and including the cooling member 5, the cooling roller 50, or the power supply 18 that can be driven independently in the vicinity of the cooling belt 500, and the cooling roller 50 that can be driven independently, or By providing the cooling belt 500, the cooling member 5, the cooling roller 50, or the cooling belt 500 is brought into contact with the heating roller 1 via the fixing belt 3 to absorb excess heat, and the cooling fan 17 is used for heat generation. It is possible to suppress the occurrence of the overshoot phenomenon by diverging.

  Further, according to the present invention, the cooling roller driving mechanism 19 and the cooling belt driving mechanism 190 are configured so that the fixing belt 3 conveys the paper P when the cooling roller 50 or the cooling belt 500 contacts the fixing belt 3. , The fixing belt 3 is rotated via the cooling roller 50 or the cooling belt 500 so as to rotate in the reverse direction, so that the jammed paper P in the fixing device 20 can be easily removed. When the fixing belt 3 is rotated while being returned to the side, it is possible to suppress deformation and breakage that occurs when only a part of the fixing belt 3 comes into contact with the heating roller 1 and is overheated.

  Furthermore, according to the present invention, the cooling member 5 includes the heat absorbing portion 52 that contacts the fixing belt 3 and absorbs heat, and the heat radiating portion 51 that releases the absorbed heat to the outside. It can absorb and dissipate excess heat and suppress the occurrence of overshoot phenomenon.

  Further, according to the present invention, the conveyance state detection means 16 for detecting the rotation state of the fixing belt 3 is provided, and the cooling member 5, the cooling roller 50, or the cooling belt 500 is provided only when the rotation of the fixing belt 3 is stopped. By causing the fixing belt 3 to be in contact with the heating roller 1, it is possible to suppress the occurrence of scratches or the like generated on the fixing belt 3 due to the contact of the cooling member 5, the cooling roller 50, or the cooling belt 500. In addition, only a part of the fixing belt 3 comes into contact with the heating roller 1 and the cooling member 5, the cooling roller 50, or the cooling belt 500 can be brought into contact only when there is a risk of deformation.

  According to the present invention, the temperature detecting device 9 for detecting the temperature of the fixing belt 3 is provided, and the contacting / separating mechanisms 6, 60, 60 for the cooling member 5, the cooling roller 50, and the cooling belt 500 according to the detected temperature. By including the control means for controlling 600, the surface temperature of the fixing belt 3 detected by the temperature detection device 9 reaches a temperature that damages the excessive temperature rise prevention device such as a temperature fuse or a temperature thermostat. Only when the rising curve is drawn, the cooling member 5, the cooling roller 50, or the cooling belt 500 can be brought into contact with the fixing belt 3, and the waiting time until the start of the next job generated by the cooling operation is minimized. Can be stopped.

  Further, according to the present invention, the cooling member contact / separation mechanism 6, the cooling roller contact / separation mechanism 60, and the cooling belt contact / separation mechanism 600 are performed when the power supply to the drive mechanism that rotationally drives the fixing belt 3 is cut off. Further, the configuration in which the cooling member 5, the cooling roller 50, or the cooling belt 500 is in contact with the heating roller 1 with the fixing belt 3 interposed therebetween suppresses the occurrence of an overshoot phenomenon even when the power is turned off. be able to.

  Furthermore, according to the present invention, by mounting the above-described fixing device 20 of the present invention, the temperature inside the device rises and damages an excessive temperature rise prevention device such as a temperature fuse or a temperature thermostat. No image forming apparatus can be provided.

  The present invention has been described above by the preferred embodiments of the present invention. While the invention has been described with reference to specific embodiments thereof, various modifications and changes can be made to these embodiments without departing from the broader spirit and scope of the invention as defined in the claims. is there.

DESCRIPTION OF SYMBOLS 1 Heating roller 100 Image forming apparatus 101 Apparatus main body 102 Scanner 103 Automatic document feeder (ADF)
104 Paper feed unit 104a, 104b, 104c, 104d Paper feed cassette 105 Intermediate transfer belt 106, 107, 108 Support roller 109 Intermediate transfer cleaning device 110 Secondary transfer roller 112 Sheet reversing device 115 Paper discharge roller pair 116 Paper output tray 2 Fixing Roller 3 Fixing belt 4 Pressure roller 5 Cooling member 51 Heat radiation part 52 Heat absorption part 50 Cooling roller 500 Cooling belt 6 Cooling member contact / separation mechanism 60 Cooling roller contact / separation mechanism 600 Cooling belt contact / separation mechanism 7 Entrance guide plate 8 Heat source ( heater)
DESCRIPTION OF SYMBOLS 9 Temperature detection apparatus 10 Cleaning unit 11 Cleaning web 12 Cleaning web contact member 13 Winding shaft 14 Delivery shaft 16 Conveyance state detection means 161 Encoder 162 Sensor 17 Cooling fan 18 Power supply (capacitor)
DESCRIPTION OF SYMBOLS 19 Cooling roller drive mechanism 190 Cooling belt drive mechanism 20 Fixing device 21Y, 21M, 21C, 21K Photosensitive drum 22 Protective layer forming device 23 Charging device 24 Cleaning device 25 Developing device 26Y, 26M, 26C, 26K Transfer device 28 Latent image formation Device 29Y, 29M, 29C, 29K Process cartridge 30 Tandem image forming unit

Japanese Patent No. 3880424 Japanese Patent No. 40000955

Claims (10)

A fixing roller for fixing the toner transferred to the paper;
A heating roller having a heat source wound around the fixing roller and an endless fixing belt;
A cooling member that abuts against the outer periphery of the heating roller across the fixing belt and cools the heat generated from the heat source;
A cooling fan that dissipates heat generated from the cooling member;
A power supply for driving the cooling fan;
A fixing device comprising:   A temperature detecting means for detecting a surface temperature of the fixing belt; and when the surface temperature reaches a predetermined temperature, the cooling member is brought into contact with the outer peripheral portion, and when the surface temperature does not reach the predetermined temperature, The fixing device according to claim 1, further comprising contact / separation means for separating a cooling member from the outer peripheral portion.   The apparatus further includes a conveyance state detection unit for detecting a conveyance state of the fixing belt, and when the conveyance state detection unit detects that the fixing belt is in a stopped state, the contact / separation unit moves the cooling member to the cooling member. The fixing device according to claim 2, wherein the fixing device is brought into contact with an outer peripheral portion.   A driving unit that drives the contacting / separating unit; and a contact unit that forcibly contacts the cooling member with the outer peripheral portion when the driving unit is not driven by the driving unit. The fixing device according to claim 2, wherein the fixing device is a fixing device.   5. The cooling device according to claim 1, wherein the cooling member includes an absorbing unit that contacts the fixing roller and absorbs heat generated from the heat source, and a heat radiating unit that releases the absorbed heat. The fixing device according to claim 1. A fixing roller for fixing the toner transferred to the paper;
A heating roller having a heat source wound around the fixing roller and an endless fixing belt;
A cooling member that abuts against the outer periphery of the heating roller across the fixing belt and cools the heat generated from the heat source;
A cooling fan that dissipates heat generated from the cooling member;
An image forming apparatus comprising: a fixing device having a power source for driving the cooling fan.   The fixing device further includes a temperature detecting unit that detects a surface temperature of the fixing belt, and when the surface temperature reaches a predetermined temperature, the cooling member is brought into contact with the outer peripheral portion to reach the predetermined temperature. The image forming apparatus according to claim 6, further comprising a contact / separation unit that separates the cooling member from the outer peripheral portion when the temperature does not reach.   The fixing device further includes a conveyance state detection unit that detects a conveyance state of the fixing belt. When the conveyance state detection unit detects that the fixing belt is in a stopped state, the contact / separation unit includes: The image forming apparatus according to claim 7, wherein the cooling member is brought into contact with the outer peripheral portion.   The fixing device further includes a drive unit that drives the contact / separation unit, and forcibly brings the cooling member into contact with the outer peripheral portion when the drive unit is turned off by the drive unit. 9. The image forming apparatus according to claim 7, further comprising a contact unit.   10. The cooling member according to claim 6, wherein the cooling member includes an absorbing unit that contacts the fixing roller and absorbs heat generated from the heat source, and a heat radiating unit that releases the absorbed heat. The image forming apparatus according to claim 1.

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