Fixing device and image forming apparatus

Abstract

To reliably remove a recording medium wound around an outer circumferential surface of a heating rotating body in comparison to a case where separation means that separates the recording medium wound around the outer circumferential surface of the heating rotating body is provided on the downstream side along the conveyance direction of the recording medium in a fixing region at the time of reverse rotation of the heating rotating body.SOLUTION: A fixing device comprises: a heating rotating body; pressing means for pressing a recording medium in a fixing region against the heating rotating body; reverse rotation means for rotating the heating rotating body in a direction reverse to the time of fixation when the recording medium is wound around the heating rotating body; and separation means for separating the recording medium wound in a relatively close proximity manner on the upstream side along the conveyance direction of the recording medium in the fixing region around the outer circumferential surface of the heating rotating body at the time of reverse rotation of the heating rotating body.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a fixing device and an image forming apparatus. [Background technology]

[0002] Conventionally, techniques relating to fixing devices have already been proposed, for example, as disclosed in Patent Documents 1 and 2.

[0003] Patent document 1 describes a fixing device that includes a drive source for rotating a fixing member forward and reverse, and a separation means for preventing the recording medium from becoming entangled when the fixing member rotates reversely while the recording medium is positioned in the fixing nip, and is configured with an adjustment mechanism for adjusting the value of the gap between the fixing member and the separation means.

[0004] In Patent Document 2, when separating a sheet wound around a first roller, a peeling section comes into contact with the first roller and a rotating section rotates the first roller in the reverse rotation direction, causing the sheet wound around the first roller to ride up onto the peeling section and be peeled off from the first roller, thereby separating the sheet from the first roller. The peeling section is disposed downstream of the fixing nip section. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2014-174542 A [Patent Document 2] JP 2005-309022 A Summary of the Invention [Problem to be solved by the invention]

[0006] The object of the present invention is to enable the recording medium wrapped around the outer peripheral surface of the heating rotor to be reliably removed when the heating rotor rotates in the reverse direction, compared to a case in which a peeling means for peeling off the recording medium wrapped around the outer peripheral surface of the heating rotor is provided downstream along the transport direction of the recording medium in the fixing area. [Means for solving the problem]

[0007] The invention described in claim 1 comprises a heating rotor, a pressurizing means for pressing a recording medium against the heating rotor in a fixing area; a reversing means for rotating the heating rotor in a direction opposite to that during fixing when the recording medium is wrapped around the heating rotor; a peeling means for peeling off the recording medium wound around the outer circumferential surface of the heating rotor on the upstream side of the fixing area in the conveying direction of the recording medium when the heating rotor rotates in the reverse direction; The fixing device is provided with:

[0008] The invention described in claim 2 is the fixing device described in claim 1, further comprising a detection unit that detects the passage of the recording medium on the downstream side of the fixing area in the transport direction of the recording medium.

[0009] The invention described in claim 3 is the fixing device described in claim 2, in which the amount of the recording medium wound around the heating rotatable body is determined based on the detection result of the detection means.

[0010] The invention described in claim 4 is the fixing device described in claim 1, wherein the peeling means is brought relatively close to the outer circumferential surface of the heating rotator by the movement of the heating rotator.

[0011] The invention described in claim 5 is a fixing device described in claim 2, in which the heating rotor is reversed and stopped so that the leading edge of the recording medium is positioned in the fixing area based on the detection result of the detection means.

[0012] The invention described in claim 6 is the fixing device described in claim 5, wherein the heating rotator is released from the pressurizing means before being rotated by the reversing means in the direction opposite to that during fixing.

[0013] The invention described in claim 7 is the fixing device described in claim 5, in which the heating rotator is rotated by the reversing means in a direction opposite to that during fixing, and then the pressurized state with the pressure means is released.

[0014] The invention described in claim 8 is the fixing device described in claim 5, wherein the heating rotator stops heating after the rotation in the direction opposite to that during fixing has stopped.

[0015] The invention described in claim 9 includes an image forming unit for forming an image on a recording medium, a fixing means for fixing the image on the recording medium; Equipped with The image forming apparatus uses the fixing device according to any one of claims 1 to 8 as the fixing means. Effect of the Invention

[0016] According to the invention described in claim 1, when the heating rotor rotates in the reverse direction, a peeling means for peeling off the recording medium wrapped around the outer peripheral surface of the heating rotor can be provided downstream in the conveying direction of the recording medium in the fixing area, making it possible to reliably remove the recording medium wrapped around the outer peripheral surface of the heating rotor, compared to a case in which the peeling means is provided downstream in the conveying direction of the recording medium in the fixing area.

[0017] According to the invention as recited in claim 2, wrapping of the recording medium can be detected more reliably than in the case where no detection means is provided.

[0018] According to the invention described in claim 3, it is possible to detect the amount of wrapping of the recording medium with higher accuracy compared to a case where the amount of wrapping of the recording medium is determined from a value other than the detection result of the detection means.

[0019] According to the invention described in claim 4, compared to the case where the peeling means is movable, the moving means for the peeling means can be omitted.

[0020] According to the invention as recited in claim 5, it is possible to avoid excessive reverse transport of the recording medium, compared to a case in which the leading edge of the recording medium is not stopped in the fixing area.

[0021] According to the invention described in claim 6, the peeling means can be brought closer to the heating rotor more easily than in the case where the pressure state is released after the heating rotor is rotated in the reverse direction.

[0022] According to the seventh aspect of the invention, the heating rotator can more reliably release the recording medium from the wrapping, compared to a case in which the pressurized state is released before the heating rotator is rotated in the reverse direction.

[0023] According to the invention described in claim 8, the heating rotor can avoid the image on the recording medium solidifying and making it difficult to peel off from the heating rotor, compared to a case in which heating is stopped before rotation in the opposite direction to that during fixing is stopped.

[0024] According to the invention described in claim 9, the recording medium wrapped around the outer peripheral surface of the heating rotor can be reliably removed compared to a case in which the fixing device described in any one of claims 1 to 8 is not used as the fixing means. [Brief description of the drawings]

[0025] [Figure 1] 1 is an overall configuration diagram showing an image forming apparatus to which a fixing device according to a first embodiment of the present invention is applied. [Diagram 2] 1 is a configuration diagram showing an image forming section of an image forming apparatus to which a fixing device according to a first embodiment of the present invention is applied. [Diagram 3] FIG. 2 is a configuration diagram showing a main part of the image forming apparatus. [Figure 4] FIG. 2 is a diagram illustrating the configuration of the image forming apparatus with a rear cover open. [Diagram 5]1 is a configuration diagram showing a fixing device according to a first embodiment of the present invention. [Figure 6] FIG. 2 is a cross-sectional view showing a heating roll and a pressure roll. [Figure 7] 1 is a side configuration diagram showing a fixing device according to a first embodiment of the present invention. [Figure 8] FIG. 2 is a configuration diagram showing a nip release state of the fixing device according to the first embodiment of the present invention. [Figure 9] FIG. 2 is a schematic diagram showing a recording paper wound around the surface of a heating roll. [Figure 10] FIG. 2 is a schematic diagram illustrating a fixing device in which a recording paper is wrapped around the surface of a heating roll. [Figure 11] FIG. 2 is a schematic diagram showing a recording paper completely wrapped around the surface of a heating roll. [Figure 12] 5 is a flowchart showing an operation of the fixing device according to the first embodiment of the present invention. [Figure 13] FIG. 2 is a configuration diagram showing a nip release state of the fixing device according to the first embodiment of the present invention. [Figure 14] FIG. 11 is a configuration diagram showing a fixing device according to a second embodiment of the present invention. [Figure 15] 7A to 7C are schematic diagrams illustrating the operation of a fixing device according to a second embodiment of the present invention. [Figure 16] 10 is a flowchart showing an operation of a fixing device according to a second embodiment of the present invention. [Figure 17] 7 is a configuration diagram showing the operation of a fixing device according to a second embodiment of the present invention; FIG. [Figure 18] FIG. 1 is a schematic diagram illustrating the operation of a conventional fixing device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0027] [Embodiment 1] Fig. 1 shows an overview of the entire image forming apparatus to which the fixing device according to the first embodiment is applied, and Fig. 2 shows an enlarged image forming section of the image forming apparatus. In Fig. 1, the symbol X indicates the horizontal direction (width direction) of the image forming apparatus, the symbol Y indicates the depth direction of the image forming apparatus, and the symbol Z indicates the vertical direction of the image forming apparatus.

[0028] <Overall configuration of image forming apparatus> The image forming apparatus 1 is configured as, for example, a color printer. As shown in FIG. 1, the image forming apparatus 1 includes a plurality of image forming devices 10, an intermediate transfer device 20, a paper feed device 50, and a fixing device 40 as an example of a fixing means according to the first embodiment. The plurality of image forming devices 10 form toner images developed with toner constituting a developer. The intermediate transfer device 20 holds the toner images formed by the image forming devices 10, and transports them to a secondary transfer position where the toner images are finally secondarily transferred onto a recording paper 5 as an example of a recording medium. The paper feed device 50 stores and transports the required recording paper 5 to be supplied to the secondary transfer position of the intermediate transfer device 20. The fixing device 40 fixes the toner image as an example of an image on the recording paper 5 secondarily transferred by the intermediate transfer device 20. In FIG. 1, reference numeral 1a denotes a device main body formed of a supporting structure member, an exterior cover, and the like.

[0029] In this embodiment 1, the image forming means for forming a toner image on a recording medium is made up of a plurality of image forming devices 10 and an intermediate transfer device 20. Note that the image forming means may be configured to include a single image forming device and to directly form a toner image on a recording medium from the image forming device without using the intermediate transfer device.

[0030] The imaging device 10 is composed of four imaging devices 10Y, 10M, 10C, and 10K that are dedicated to forming toner images of four colors, yellow (Y), magenta (M), cyan (C), and black (K), respectively. These four imaging devices 10 (Y, M, C, and K) are arranged in a row inclined along the horizontal direction X in the internal space of the device main body 1a.

[0031] As shown in FIG. 1, each of the image forming devices 10 (Y, M, C, K) includes a photoconductor drum 11 as an example of a rotating image holding means. Around the photoconductor drum 11, the following devices are mainly arranged. The main devices are a charging device 12, an exposure device 13, a developing device 14, a primary transfer device 15, a drum cleaning device 16, and the like. The charging device 12 charges the peripheral surface (image holding surface) of the photoconductor drum 11 on which an image can be formed to a required potential. The exposure device 13 irradiates the charged peripheral surface of the photoconductor drum 11 with light based on image information (signals) to form an electrostatic latent image (for each color) with a potential difference. The developing device 14 develops the electrostatic latent image with toner of the developer of the corresponding color (Y, M, C, K) to form a toner image. The primary transfer device 15 transfers each toner image to the intermediate transfer device 20. The drum cleaning device 16 removes and cleans toner and other adhering matter remaining on the image bearing surface of the photosensitive drum 11 after the primary transfer. Note that reference numerals indicating the photosensitive drum 11, charging device 12, etc. are given only to the yellow (Y) imaging device 10Y and are omitted for the other imaging devices 10 (M, C, K).

[0032] The photoconductor drum 11 has an image bearing surface formed on the peripheral surface of a grounded cylindrical or columnar substrate, the peripheral surface of which has a photoconductive layer (photosensitive layer) made of a photosensitive material. The photoconductor drum 11 is supported so as to rotate in the direction indicated by the arrow A by a driving force transmitted from a driving device (not shown).

[0033] The charging device 12 is composed of a contact-type charging roll that is arranged in contact with the photoconductor drum 11. A charging voltage is supplied to the charging device 12. When the developing device 14 performs reversal development, the charging voltage is a voltage or current of the same polarity as the charging polarity of the toner supplied from the developing device 14. A cleaning roll 121 that cleans the surface of the charging device 12 is arranged in contact with the rear side of the charging device 12.

[0034] The exposure device 13 is composed of an LED print head or the like that irradiates the photosensitive drum 11 with light according to image information using LEDs (Light Emitting Diodes) as a plurality of light emitting elements arranged along the axial direction of the photosensitive drum 11 to form an electrostatic latent image. When it is time to form a latent image, image information (signal) inputted by any means to the image forming apparatus 1 is transmitted to the exposure device 13. Note that the exposure device 13 may be one that irradiates the peripheral surface of the charged photosensitive drum 11 with laser light configured according to the image information inputted to the image forming apparatus 1 to form an electrostatic latent image.

[0035] As shown in FIG. 2, each of the developing devices 14 is configured by arranging a developing roll 141, stirring and conveying members 142 and 143, a layer thickness regulating member 144, and the like inside a housing 140 in which an opening and a developer storage chamber are formed. The developing roll 141 holds the developer 4 and conveys it to a development area facing the photosensitive drum 11. The stirring and conveying members 142 and 143 are made of screw augers or the like that stir the developer 4 while conveying it to pass through the developing roll 141. The layer thickness regulating member 144 regulates the amount (layer thickness) of the developer 4 held by the developing roll 141. In this developing device 14, a development voltage is supplied between the developing roll 141 and the photosensitive drum 11 from a power supply device (not shown). In addition, the developing roll 141 and the stirring and conveying members 142 and 143 are rotated in a required direction by a driving force transmitted from a driving device (not shown). Furthermore, as the developers 4 of the four colors, two-component developers containing non-magnetic toner and magnetic carriers are used.

[0036] 1, the primary transfer device 15 is a contact type transfer device equipped with a primary transfer roll that rotates in contact with the circumferential surface of the photoconductor drum 11 via the intermediate transfer belt 21 at the primary transfer position and is supplied with a primary transfer voltage. As the primary transfer voltage, a DC voltage showing a polarity opposite to the charging polarity of the toner is supplied from a power supply device (not shown).

[0037] 2, the drum cleaning device 16 is composed of a cleaning blade 161 and a sending member 162 arranged inside a container-shaped main body 160. The cleaning blade 161 removes and cleans adhering matter such as residual toner. The sending member 162 is composed of a screw auger or the like that collects the adhering matter such as toner removed by the cleaning blade 161 and conveys it to a collection system (not shown).

[0038] The intermediate transfer device 20 is disposed so as to be located above each of the image forming devices 10 (Y, M, C, K) in the vertical direction Z. The intermediate transfer device 20 is mainly composed of an intermediate transfer belt 21, a plurality of belt support rolls 22-26, a belt cleaning device 27, and a secondary transfer device 30. The intermediate transfer belt 21 is an example of an intermediate transfer means that moves in a circular manner in the direction indicated by the arrow B while passing through a primary transfer position between the photosensitive drum 11 and the primary transfer device 15 (primary transfer roll). The plurality of belt support rolls 22-26 support the intermediate transfer belt 21 so as to be able to move in a circular manner while maintaining the intermediate transfer belt 21 in a desired state from its inner circumference. The secondary transfer device 30 is disposed on the outer circumferential surface (image bearing surface) side of the intermediate transfer belt 21 supported by the belt support roll 25, and performs a second transfer of the toner image on the intermediate transfer belt 21 to the recording paper 5. The belt cleaning device 27 removes and cleans the toner, paper powder, and other deposits that remain on the outer circumferential surface of the intermediate transfer belt 21 after passing through the secondary transfer device 30.

[0039] The intermediate transfer belt 21 is an endless belt made of a material in which a resistance adjuster such as carbon black is dispersed in a synthetic resin such as polyimide resin, polyamide resin, or polyamideimide resin. The belt support roll 22 is configured as a drive roll. The belt support roll 23 is configured as a surface adjustment roll that maintains the running position of the intermediate transfer belt 21. The belt support roll 24 is configured as a tension applying roll that applies tension to the intermediate transfer belt 21. The belt support roll 25 is configured as a backup roll for secondary transfer. The belt support roll 26 is configured as a back support roll for the belt cleaning device 27.

[0040] The secondary transfer device 30 includes a secondary transfer roll 31 that rotates at a secondary transfer position. The secondary transfer position is an outer peripheral surface portion of the intermediate transfer belt 21 supported by the belt support roll 25 in the intermediate transfer device 20. A DC voltage having a polarity opposite to or the same as the charging polarity of the toner is supplied to the secondary transfer roll 31 or the belt support roll 25 of the intermediate transfer device 20 as a secondary transfer voltage.

[0041] The fixing device 40 is configured to include a heating roll 41 as an example of a heating rotator, a pressure roll 42 as an example of a pressure means, and the like. The heating roll 41 is heated by the heating means so that the surface temperature is maintained at a predetermined temperature. The pressure roll 42 rotates in contact with the heating roll 41 at a required pressure. In this fixing device 40, the contact area where the heating roll 41 and the pressure roll 42 contact each other becomes a fixing nip portion N as an example of a fixing region where a required fixing process (heating and pressure) is performed to fix an unfixed toner image to the recording paper 5. The fixing device 40 will be described in detail later.

[0042] The paper feeder 50 is disposed so as to be located below the imaging devices 10 (Y, M, C, K). This paper feeder 50 is mainly composed of one (or more) paper containers 51 and delivery devices 52, 53 that deliver recording paper 5 one sheet at a time from the paper container 51. The paper container 51 receives recording paper 5 of a desired size, type, etc., stacked on a stacking plate (not shown). The paper container 51 is attached so as to be able to be pulled out, for example, from the front side (the side the user faces during operation) of the device main body 1a, or from the left side in the illustrated example.

[0043] Examples of the recording paper 5 include thin paper such as plain paper or tracing paper used in electrophotographic copiers and printers, or OHP sheets made of a transparent film-like medium made of synthetic resin (PET, etc.). In order to further improve the smoothness of the image surface after fixing, it is preferable that the surface of the recording paper 5 is as smooth as possible. Examples of the recording paper 5 that can be used include coated paper in which the surface of plain paper is coated with resin or the like, and so-called thick paper with a relatively large basis weight such as art paper for printing.

[0044] A paper feed conveying path 56 is provided between the paper feed device 50 and the secondary transfer device 30. The paper feed conveying path 56 is composed of one (or more) paper conveying roll pairs 54 that convey the recording paper 5 sent out from the paper feed device 50 to the secondary transfer position, and a conveying guide material 55. The paper conveying roll pair 54, which is disposed in the paper feed conveying path 56 at a position immediately before the secondary transfer position, is configured as, for example, a roll (registration roll) that adjusts the conveying timing of the recording paper 5.

[0045] 3, a registration sensor 201 is disposed upstream of the paper transport roll pair 54 in the transport direction of the recording paper 5, as an example of a first detection means for detecting the leading edge of the recording paper 5 fed from the paper feeder 50. The registration sensor 201 includes an actuator 203 that rotates around a pivot 202. When the leading edge of the recording paper 5 passes the registration sensor 201, the actuator 203 rotates around the pivot 202, and the rotation of the actuator 203 is detected as the passage of the leading edge of the recording paper 5 by an optical sensor (not shown).

[0046] In addition, as shown in FIG. 1, transport guide members 57, 58, etc. are arranged between the secondary transfer device 30 and the fixing device 40 to guide the recording paper 5 sent out from the secondary transfer device 30 to the fixing device 40.

[0047] Downstream of the fixing device 40, there are provided a pair of paper discharge rolls 61 and a transport guide member 59 for discharging the recording paper 5 on which the toner image has been fixed by the fixing device 40 to a paper discharge section 60 located at the top of the device main body 1a.

[0048] 3, an exit sensor 204 is disposed at the exit of the fixing device 40 as an example of a second detection means for detecting the leading edge of the recording paper 5 that has been subjected to the fixing process. The exit sensor 204 includes an actuator 206 that rotates around a pivot 205, similar to the register sensor 201. When the leading edge of the recording paper 5 passes the exit sensor 204, the actuator 206 rotates around the pivot 205, and the rotation of the actuator 206 is detected as the passage of the leading edge of the recording paper 5 by an optical sensor (not shown).

[0049] As shown in FIG. 1, a switching gate 62 for switching the paper transport path is provided between the fixing device 40 and the paper discharge roll pair 61. The rotation direction of the paper discharge roll pair 61 can be switched between a forward direction (discharge direction) and a reverse direction. When forming an image on both sides of the recording paper 5, the rotation direction of the paper discharge roll pair 61 is switched from the forward direction (discharge direction) to the reverse direction after the rear end of the recording paper 5 with an image formed on one side passes the switching gate 62. The recording paper 5 transported in the reverse direction by the paper discharge roll pair 61 has its transport path switched by the switching gate 62 and is transported to a double-sided transport path 63 formed to be approximately vertical. The double-sided transport path 63 includes a paper transport roll pair 64 that transports the recording paper 5 to the paper transport roll pair 54 in an inverted state, transport guides 65 to 68, and the like.

[0050] 4, the image forming apparatus 1 according to the first embodiment is configured such that a rear cover 80 as an example of an opening / closing means provided on the rear side of the apparatus main body 1a can be opened and closed about a pivot fulcrum 81. By opening and closing the rear cover 80, it becomes possible to easily remove recording paper 5 that has experienced a transport failure (jam). Locations where transport failure of the recording paper 5 can occur include the paper feed transport path 56, the paper discharge transport path that is configured of the paper discharge roll pair 61 and the transport guide member 59, etc., the double-sided transport path 63, and the fixing device 40.

[0051] In Figure 1, symbol 70 indicates a manual feed tray that is openably and closably provided on the front (left side in the figure) of the device body 1a of the image forming device 1, and between the manual feed tray 70 and the paper transport roll pair 54 there is provided a feed device 71 that feeds out the recording paper 5 stored in the manual feed tray 70 one sheet at a time, and a manual feed paper transport path 76 that is composed of multiple paper transport roll pairs 72-74, a transport guide 75, etc.

[0052] In addition, the symbols 145 (Y, M, C, K) in Figure 1 indicate toner cartridges arranged in a direction perpendicular to the paper surface, each of which serves as a developer storage container containing developer including at least toner to be supplied to the corresponding developing device 14 (Y, M, C, K).

[0053] 1, reference numeral 100 denotes a control device as an example of a control means for comprehensively controlling the operation of the image forming apparatus 1. The control device 100 is configured to include a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), or a bus for connecting the CPU, the ROM, etc., a communication interface, etc. (not shown).

[0054] <Basic operations of image forming device> Hereinafter, a basic image forming operation by the image forming apparatus 1 will be described.

[0055] Here, the image forming operation will be described when forming a full-color image composed of a combination of toner images of four colors (Y, M, C, K) using the four image forming devices 10 (Y, M, C, K). Note that the image forming operation when forming an image by combining single-color or multiple-color toner images using one or more of the four image forming devices 10 (Y, M, C, K) is basically the same.

[0056] When the image forming apparatus 1 receives command information requesting printing, the four image forming devices 10 (Y, M, C, K), the intermediate transfer device 20, the secondary transfer device 30, the fixing device 40, etc. are started under the control of the control device 100.

[0057] In each imaging device 10 (Y, M, C, K), first, each photoconductor drum 11 rotates in the direction indicated by arrow A. The surface of each photoconductor drum 11 is charged to a required polarity (negative polarity in the first embodiment) and potential by each charging device 12. Next, exposure device 13 irradiates the charged surface of photoconductor drum 11 with light emitted based on an image signal obtained by converting image information input to image forming device 1 into each color component (Y, M, C, K). Then, an electrostatic latent image of each color component, constituted by a required potential difference, is formed on the surface of photoconductor drum 11.

[0058] Next, each developing device 14 (Y, M, C, K) supplies toner of the corresponding color (Y, M, C, K) charged to the required polarity (negative polarity) to the electrostatic latent image of each color component formed on the photoconductor drum 11, electrostatically attaching it to the electrostatic latent image, thereby developing it. Through this development, the electrostatic latent image of each color component formed on each photoconductor drum 11 is visualized as a toner image of four colors (Y, M, C, K) developed with the toner of the corresponding color.

[0059] Next, the toner images of each color formed on the photoconductor drums 11 of the imaging devices 10 (Y, M, C, K) are transported to a primary transfer position. Then, the primary transfer device 15 performs primary transfer of the toner images of each color onto the intermediate transfer belt 21 of the intermediate transfer device 20 rotating in the direction indicated by the arrow B, in such a manner that the toner images are superimposed in order.

[0060] In addition, in each of the imaging devices 10 (Y, M, C, K) where the primary transfer has been completed, the drum cleaning device 16 scrapes off any adhering matter to clean the surface of the photosensitive drum 11. This makes each of the imaging devices 10 (Y, M, C, K) ready for the next image formation operation.

[0061] Next, the intermediate transfer device 20 conveys the primarily transferred toner image to the secondary transfer position by the rotation of the intermediate transfer belt 21. Meanwhile, the paper feeder 50 sends out the required recording paper 5 to a paper feed path 56 in accordance with the image creation operation. In the paper feed path 56, a pair of paper feed rolls 54 as registration rolls feeds and supplies the recording paper 5 to the secondary transfer position in accordance with the transfer timing.

[0062] At the secondary transfer position, the secondary transfer roll 31 performs secondary transfer of the toner images on the intermediate transfer belt 21 all at once onto the recording paper 5. After the secondary transfer is completed, the belt cleaning device 27 in the intermediate transfer device 20 removes and cleans the surface of the intermediate transfer belt 21 to remove any toner or other deposits remaining thereon after the secondary transfer.

[0063] Next, the recording paper 5 onto which the toner image has been secondarily transferred is peeled off from the intermediate transfer belt 21 and the secondary transfer roll 31, and then transported along transport guide members 57, 58 to the fixing device 40. The fixing device 40 introduces the recording paper 5 carrying the unfixed toner image after the secondary transfer into the fixing nip portion N between the rotating heating roll 41 and pressure roll 42, and passes it through. As a result, the fixing device 40 performs the necessary fixing process (heating and pressurizing) to fix the unfixed toner image to the recording paper 5. After fixing is completed, the recording paper 5 is discharged by a paper discharge roll pair 61 via the transport guide member 59 to a paper discharge section 60 provided at the top of the device main body 1a.

[0064] By the above operation, a full-color image is output, which is formed by combining toner images made of four colors of toner T (Y, M, C, K).

[0065] <Configuration of the fixing device> FIG. 5 is a cross-sectional view showing the configuration of the fixing device according to the first embodiment.

[0066] As shown in FIG. 5, the fixing device 40 includes a heating roll 41 as an example of a heating rotor, and a pressure roll 42 as an example of a pressure means for pressing the recording paper 5 against the heating roll 41 at a fixing nip portion N as an example of a fixing area.

[0067] As shown in FIG. 6, the heating roll 41 has a cylindrical core metal 411, an elastic layer 412, and a release layer 413. The core metal 411 is made of metal such as stainless steel, aluminum, or iron (thin-walled high-tensile steel pipe). The core metal 411 is formed in a relatively thin cylindrical shape, and its heat capacity is set to be significantly small. The elastic layer 412 is made of a heat-resistant elastic material such as silicone rubber or fluororubber that coats the outer periphery of the core metal 411. The elastic layer 412 is also formed in a relatively thin cylindrical shape, and contributes to reducing the heat capacity of the heating roll 41. The release layer 413 is made of polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), or the like that is thinly coated on the surface of the elastic layer 412. A halogen lamp 414 is disposed inside the heating roll 41 as an example of a heating means.

[0068] The heating roll 41 is rotatably supported at both ends along its longitudinal direction (axial direction) by a swing arm 44 via a bearing member (not shown). The heating roll 41 is rotated at a required speed along the direction of arrow C by a drive motor (not shown) as an example of a reversing means (not shown) on the device main body 1a side via a drive gear (not shown) attached to one end along the axial direction. The drive motor is an example of a drive source. The heating roll 41 is configured to be rotatable in the direction of arrow C and in the direction of arrow D opposite to the direction of arrow C by a drive motor (not shown) even in a state in which the pressure contact with the pressure roll 42 is released. The pressure roll 42 is rotated by being pressed against the heating roll 41, which is driven to rotate, at the fixing nip N. In addition, the pressure roll 42 is not limited to being rotated by the heating roll 41, and may be configured to rotate the pressure roll 42.

[0069] The rotation speed of the heating roll 41, that is, the fixing speed, may be set to a number of speeds such as high speed, medium speed, and low speed depending on the basis weight and material of the recording paper 5, etc.

[0070] The surface temperature of the heating roll 41 is detected by a temperature sensor (not shown). The heating roll 41 controls the power supply to the halogen lamp 414 by a temperature control circuit (not shown) using a triac or the like based on the detection result of the temperature sensor. As a result, the heating roll 41 is heated so that its surface reaches a required fixing temperature.

[0071] On the other hand, as shown in Fig. 6, the pressure roll 42 has a cylindrical or columnar core 421, a relatively thick elastic layer 422, and a release layer 423. The core 421 is made of a metal such as stainless steel or iron. The core 421 is formed in a cylindrical shape with a relatively large outer diameter, and is set to have high rigidity. The elastic layer 422 is made of a heat-resistant elastic material such as silicone rubber or fluororubber that is relatively thickly coated on the outer periphery of the core 421. The release layer 423 is made of polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), or the like that is thinly coated on the surface of the elastic layer 422.

[0072] The pressure means is not limited to a pressure roll, and may of course be a means including a pressure belt made of an endless belt.

[0073] As shown in FIG. 5, the fixing device 40 includes a device frame 43 as an example of a housing. The device frame 43 is disposed inside an exterior cover (not shown) of the fixing device 40. The device frame 43 rotatably supports both ends of the pressure roll 42 along the axial direction. A swing arm 44 is also attached to the device frame 43 so as to be rotatable about a fulcrum 45. The swing arm 44 rotatably supports the heating roll 41. A tip end 44a of the swing arm 44 is biased toward the pressure roll 42 by an elastic member such as a coil spring (not shown). As a result, the heating roll 41 is pressed against the surface of the pressure roll 42 with a required pressing force during fixing.

[0074] 5 and 7, an eccentric cam 46 is in contact with the tip end 44a of the swing arm 44. The eccentric cam 46 is fixedly attached to both ends along the axial direction of a drive shaft 47. The eccentric cam 46 is driven to rotate a required amount via the drive shaft 47 by a drive motor 48, which is an example of a drive means.

[0075] 5, during fixing, the eccentric cam 46 rotates to a position where the eccentric portion 46a is retracted from the tip end 44a of the swing arm 44. Therefore, the heating roll 41 attached to the swing arm 44 is pressed against the surface of the pressure roll 42 with a required pressure by the biasing force of an elastic member such as a coil spring (not shown).

[0076] 8, during non-fixing, the eccentric cam 46 rotates to a position where the eccentric portion 46a abuts against the tip end 44a of the swing arm 44. Therefore, the heating roll 41 rotatably attached to the swing arm 44 moves to a retracted position away from the surface of the pressure roll 42 against the biasing force of an elastic member such as a coil spring (not shown).

[0077] In the illustrated embodiment, during non-fixing, the heating roll 41 is shown to be completely separated from the surface of the pressure roll 42. However, during non-fixing, the heating roll 41 does not need to be completely separated from the surface of the pressure roll 42, and may be in contact with the pressure roll 42 with a lower pressure contact force than during normal fixing.

[0078] In the fixing device 40 configured as described above, the fixing process may be performed on small-sized recording paper 5, such as B6 size (128×182 mm), A6 size (105×148 mm), or A5 size (148×210 mm), which is relatively short in the conveying direction of the recording paper 5. The length of these small-sized recording paper 5 along the conveying direction is shorter than that of other recording paper 5, such as A4 size. Therefore, in the case of longitudinal (LEF) feeding in which the long side of the recording paper 5 is positioned at the leading edge along the conveying direction, the recording paper 5 may be curved into a shape following the outer periphery of the heating roll 41 due to the pressure contact force of the pressure roll 42, and may wrap around the outer periphery of the heating roll 41, causing a conveying failure (jam), as shown in FIG. In this way, when a transport failure (jam) occurs in which the small-sized recording paper 5 wraps around the outer circumference of the heating roll 41, it is difficult for the user to visually confirm the problem because the length along the transport direction is short, as shown in Figure 10(a).

[0079] Therefore, in the conventional fixing device 40, when a transport failure (jam) is detected due to the recording paper 5 being wrapped around the outer periphery of the heating roll 41, as shown in Fig. 4, with the rear cover 80 of the device main body 1a open, the wrapping of the recording paper 5 may not be discovered and the recording paper 5 wrapped around the outer periphery of the heating roll 41 may not be removed, and the next printing operation may be started. Then, as shown in Fig. 11, the recording paper 5 may become completely wrapped around the outer periphery of the heating roll 41, making it impossible to remove the recording paper 5 from the heating roll 41, resulting in a technical problem in which a failure occurs that makes the image forming apparatus 1 itself, including the fixing device 40, unusable.

[0080] Therefore, a technique has been proposed for a fixing device in which, when the recording paper 5 wraps around the outer periphery of the heating roll 41, the heating roll 41 is rotated in the direction opposite to that during fixing to remove the recording paper 5 (Patent Documents 1-2, etc.).

[0081] However, even with these techniques, there still remain technical problems, such as the fact that, depending on the basis weight of the recording paper 5, it is difficult to visually confirm the recording paper 5 wrapped around the outer periphery of the heating roll 41, or that it is difficult to peel the wrapped recording paper 5 from the outer periphery of the heating roll 41.

[0082] Furthermore, when the heating roll 41 is rotated in the opposite direction to that during fixing, as shown in FIG. 10(b), depending on the amount of reversal of the heating roll 41, the recording paper 5 peeled off from the heating roll 41 may enter inside the device body 1a of the image forming device 1 along the intermediate transfer belt 21, resulting in a technical problem that it cannot be seen from the outside.

[0083] Therefore, the fixing device according to this embodiment 1 is configured to include a peeling means for peeling off the recording medium that is wrapped around the outer peripheral surface of the heating rotor in a relatively close proximity on the upstream side of the fixing area in the transport direction of the recording medium when the heating rotor rotates in the reverse direction.

[0084] That is, as shown in FIG. 5, the fixing device 40 according to this embodiment 1 is configured to release the pressure contact between the heating roll 41 and the pressure roll 42 and rotate the heating roll 41 in the opposite direction D to that during normal fixing.

[0085] As shown in Figures 7 and 8, on the outer periphery of the heating roll 41, when the heating roll 41 moves to a retracted position and rotates in the reverse direction, a peeling film 49 is provided as an example of a peeling means for peeling off the recording paper 5 that is relatively close to and wrapped around the outer periphery of the heating roll 41 on the upstream side of the fixing nip portion N in the transport direction of the recording paper 5, that is, below the fixing nip portion N in Figure 8.

[0086] 8, in the fixing device 40 according to the first embodiment, the recording paper 5 is transported from below to above in the vertical direction Z along transport guide members 57, 58 (see FIG. 1). An introduction port for introducing the recording paper 5 is opened in an exterior cover (not shown) of the fixing device 40 downward in the vertical direction Z. Therefore, when the heating roll 41 is reversed, it is desirable that the recording paper 5 peeled off from the surface of the heating roll 41 by the peeling film 49 is discharged as it is from the introduction port for the recording paper 5.

[0087] Therefore, in the fixing device 40 according to the first embodiment, as shown in FIG. 8, a leading end 49a of the peeling film 49 is positioned closer to the fixing nip N than the lower end of the heating roll 41.

[0088] The release film 49 is made of a Mylar film or the like having a required thickness. As shown in Fig. 7, the release film 49 is attached in a fixed state to a support plate 490 suspended between the left and right device frames 43 by double-sided tape, adhesive, or the like. The release film 49 is disposed, for example, in a non-contact state such that its tip 49a is close to the surface of the heating roll 41 with a small gap therebetween. The release film 49 may also be disposed such that its tip 49a comes into contact with the surface of the heating roll 41 with a weak force.

[0089] The release film 49 is disposed as a so-called doctor blade, inclined at a required inclination angle θ from downstream to upstream along the rotation direction D during reverse rotation on the surface of the heating roll 41 with respect to a tangent at the closest position to the heating roll 41. Note that an inclination angle θ of 45 degrees or less is more effective for peeling off the recording paper 5.

[0090] 8, during non-fixing, the heating roll 41 moves to a position where the outer circumferential surface of the heating roll 41 faces the tip 49a of the peeling film 49 with a small gap by a retraction action accompanying the rotation of the eccentric cam 46. The heating roll 41 is configured so that it can rotate in a direction D opposite to the rotation direction during fixing by a unique driving means (not shown) even in a state separated from the pressure roll 42. Note that the speed at which the heating roll 41 rotates in the opposite direction D is desirably set to a speed slower than that during normal fixing.

[0091] The amount of reverse rotation of the heating roll 41 in the reverse direction is calculated by the following formula (1). Reversal amount = V(t'-t) + a (1) Here, t is a theoretical timing time designed in advance from when the register sensor 201 turns ON to when the exit sensor 204 of the fixing device 40 turns ON, t' is the actual time (t'>t) from when the register sensor 201 turns ON and the exit sensor 204 detects a transport failure of the recording paper 5 to when the image forming apparatus 1 (fixing device 40) actually stops, V is the transport speed during fixing of the recording paper 5, and a is an arbitrary value that is set to be equal to or greater than the distance that allows the user to access the recording paper 5 for the smallest size of recording paper 5. Note that the arbitrary value a is set to different values ​​depending on the size of the recording paper 5.

[0092] When the recording paper 5 is not wrapped around the outer circumference of the heating roll 41, the recording paper 5 that has been fixed by the heating roll 41 and the pressure roll 42 is peeled off from the surface of the heating roll 41 due to its own rigidity, and the passage of the leading edge 5a is detected by the exit sensor 204 of the fixing device 40 located downstream of the fixing nip portion N.

[0093] On the other hand, when the recording paper 5 is wrapped around the outer circumference of the heating roll 41, the recording paper 5 that has been fixed by the heating roll 41 and the pressure roll 42 is not peeled off from the surface of the heating roll 41, as shown in Figure 3, but moves together with the surface of the heating roll 41, and when a poor transport of the recording paper 5 is detected, the fixing device 40 is stopped and the rotation of the heating roll 41 is also stopped.

[0094] The theoretical timing time t is stored in advance in a storage unit of the control device. The actual time t' may be measured by actually measuring the time from when the register sensor is turned on and when the exit sensor detects a transport failure of the recording paper 5 until the image forming device 1 (fixing device 40) actually stops, using a timer function provided in the control device, or may be a value that is set in advance with a certain margin in mind.

[0095] In the above-mentioned formula (1) for calculating the amount of reverse rotation of the heating roll 41, since an arbitrary value a is set in any case, a value stored in advance in the storage unit of the control device may be used for the actual time t′.

[0096] Furthermore, in the above-mentioned formula (1) for calculating the reverse rotation amount of the heating roll 41, if the arbitrary value a is too large, as described above, there is a risk that the recording paper 5 will enter inside the device main body 1a along the surface of the intermediate transfer belt 21, as shown in Fig. 10(b). It is desirable to set the arbitrary value a to a value that is easily visible to the user when the rear end of the recording paper 5 in which a transport failure has occurred is located near the secondary transfer device 30 and the rear cover of the device main body 1a is opened.

[0097] Considering that the value of V(t'-t) is not so large in the above-mentioned formula (1), the arbitrary value a plays a major role in the reverse rotation amount of the heating roll 41. The arbitrary value a is set so that when the reverse operation of the heating roll 41 is completed, the rear end in the transport direction of the recording paper 5 is located outside the inlet of the fixing device 40 and upstream of the secondary transfer position in the transport direction of the recording paper 5.

[0098] <Function of the Fixing Device> In the above configuration, in the fixing device according to embodiment 1, when the heating rotor rotates in the reverse direction, a peeling means for peeling off the recording medium wrapped around the outer peripheral surface of the heating rotor is provided downstream in the recording medium transport direction of the fixing area, making it possible to reliably remove the recording medium wrapped around the outer peripheral surface of the heating rotor as follows.

[0099] 1, in the image forming apparatus 1 to which the fixing device 40 according to the first embodiment is applied, the toner images of each color formed in each of the image forming devices 10 (Y, M, C, K) of yellow (Y), magenta (M), cyan (C) and black (K) are secondarily transferred collectively onto the recording paper 5 via the intermediate transfer belt 21. The toner images of each color secondarily transferred onto the recording paper 5 are transported to the fixing device 40, where they are heated and pressurized to be fixed onto the recording paper 5.

[0100] 3, a leading edge 5a of the recording paper 5 in the transport direction is detected by a registration sensor 201 arranged upstream in the transport direction of the paper transport roll pair 54. After the recording paper 5 is transported to the fixing device 40 and subjected to a fixing process, and is discharged from the fixing device 40, the leading edge 5a is detected by an exit sensor 204 arranged downstream in the transport direction of the recording paper 5 from the fixing device 40.

[0101] The control device 100 measures the time from when the leading edge 5a of the recording paper 5 is detected by the registration sensor 201 to when it is detected by the exit sensor 204, and if the measured time is not within a predetermined range, it determines that a transport problem (jam) has occurred in the recording paper 5, and immediately stops the image forming device 1.

[0102] As shown in FIG. 12, when the control device 100 detects a transport failure (jam) of the recording paper 5 (step 101), it calculates the amount of reverse rotation of the heating roll 41 of the fixing device 40 based on the formula (1) (step 102).

[0103] Thereafter, the control device 100 drives the drive motor 48 to separate the heating roll 41 from the pressure roll 42, thereby releasing the pressure contact state in the fixing nip portion N (step 103). That is, the fixing device 40 is in the state shown in FIG.

[0104] Next, the control device 100 executes a reversing operation to rotate the heating roll 41 in the direction opposite to that during normal fixing by the amount of reversal calculated based on the formula (1) (step 104). At this time, in the fixing device 40, the halogen lamp 414 of the heating roll 41 is energized, and the heating roll 41 is in a heated state. By heating the heating roll 41 in this way, when the heating roll 41 reverses its rotation, it is possible to prevent the toner image on the recording paper 5 from solidifying and becoming difficult to peel off from the heating roll 41, compared to the case where heating is stopped before stopping the rotation in the direction opposite to that during fixing.

[0105] Next, the control device 100 displays a message on the display unit of a user interface (not shown) to prompt the user to open the rear cover 80, thereby allowing the user to open the rear cover 80 of the image forming apparatus 1 (step 105).

[0106] 4, the user opens the rear cover 80 of the image forming apparatus 1 and manually removes the recording paper 5 that has been peeled off from the outer periphery of the heating roll 41 of the fixing device 40 and whose rear end is located between the fixing device 40 and the secondary transfer position, thereby completing the processing of the recording paper 5 for which a transport failure has occurred. Thereafter, the rear cover 80 of the image forming apparatus 1 is closed by the user. Note that the open / closed state of the rear cover 80 is detected by the control device 100.

[0107] Finally, the control device 100 drives the drive motor 48 to press the heating roll 41 against the pressure roll 42, and executes the required jam clearing sequence (step 106), which includes cleaning the photosensitive drums 11 of each of the imaging devices 10 (Y, M, C, K) for yellow (Y), magenta (M), cyan (C), and black (K) by the drum cleaning device 16 and cleaning the intermediate transfer belt 21 of the intermediate transfer device 20 by the belt cleaning device 27, and then restarts the printing operation.

[0108] In this way, in the fixing device 40 according to the first embodiment, when the recording paper 5 wraps around the outer periphery of the heating roll 41, the release film 49 arranged upstream of the fixing nip N can reliably peel the recording paper 5 from the surface of the heating roll 41. The state in which the recording paper 5 has been peeled off from the surface of the heating roll 41 by the release film 49 is as shown in FIG.

[0109] Furthermore, the fixing device 40 according to the above-mentioned embodiment 1 sets the amount of reverse rotation of the heating roll 41 to a value calculated based on a predetermined formula (1), so that it is possible to reliably prevent a situation in which the amount of reverse rotation of the heating roll 41 is excessive and the recording paper 5 peeled off from the surface of the heating roll 41 enters inside the device main body 1a along the surface of the intermediate transfer belt 21.

[0110] [Embodiment 2] 14 shows a fixing device according to a second embodiment of the present invention. The fixing device according to the second embodiment is configured to reverse and stop the heating rotor so that the leading edge of the recording medium is positioned in the fixing area based on the detection result of the detection means.

[0111] In the fixing device according to the second embodiment, the heating rotator is configured to be released from the pressurizing means after the reversing means rotates the heating rotator in the direction opposite to that during fixing. However, the heating rotator may be configured to be released from the pressurizing means before the reversing means rotates the heating rotator in the direction opposite to that during fixing.

[0112] 14, the fixing device 40 according to the second embodiment of the present invention is configured such that the release film 49 is provided on the swing arm 44, not on the device frame 43. The release film 49 provided on the swing arm 44 is disposed close to the surface of the heating roll 41 so that its tip faces the surface of the heating roll 41 with a small gap therebetween, when the heating roll 41 is in pressure contact with the pressure roll 42. The release film 49 may be disposed so that the gap is substantially zero, so that its tip comes into contact with the surface of the heating roll 41 with a weak force.

[0113] In addition, in the fixing device 40 according to the second embodiment of the present invention, when the heating roll 41 is rotated in the reverse direction, the amount of reversal of the heating roll 41 is calculated based on the following formula (1), in the same manner as in the first embodiment described above. Reversal amount = V(t'-t) + a (1)

[0114] However, in the fixing device 40 according to embodiment 2 of the present invention, as shown in Figures 15(a) and (b), the arbitrary value a in equation (1) is configured to reverse and stop the heating roll 41 so that the leading edge 5a of the recording paper 5 is positioned in the fixing nip portion N.

[0115] When the recording paper 5 wraps around the surface of the heating roll 41, as shown in FIG. 3, the time t is set based on the time when the leading edge of the recording paper 5 should be detected by the exit sensor 204 when the recording paper 5 does not wrap around the surface of the heating roll 41.

[0116] In formula (1), the amount of reverse rotation of the heating roll 41 is calculated taking into consideration the difference between the time t when the leading edge of the recording paper 5 should theoretically be detected by the exit sensor 204 and the time t' when the leading edge of the recording paper 5 is actually not detected by the exit sensor 204, a jam is detected, and the fixing device 40 actually stops.

[0117] Therefore, by setting the arbitrary value a in equation (1) to a length equal to the length of the transport path of the recording paper 5 from the fixing nip portion N of the fixing device 40 to the exit sensor 204, when the heating roll 41 is reversed, the leading edge 5a of the recording paper 5 can be stopped so as to be positioned at the fixing nip portion N where the heating roll 41 and the pressure roll 42 are pressed against each other.

[0118] There is an error of about ±2 mm in the positional accuracy of the leading edge 5a of the recording paper 5 during transport of the recording paper 5. On the other hand, the fixing nip portion N of the fixing device 40 usually has a length of 4 mm or more.

[0119] Therefore, the fixing device 40 according to embodiment 2 of the present invention actually makes it possible to stop the leading edge 5a of the recording paper 5 at the position of the fixing nip portion N when the heating roll 41 reverses by calculating the amount of reverse rotation of the heating roll 41 based on the above-mentioned equation (1).

[0120] In the fixing device according to the second embodiment, in the above-described configuration, when the heating rotor rotates in the reverse direction, a peeling means for peeling off the recording medium wrapped around the outer peripheral surface of the heating rotor is provided downstream in the conveying direction of the recording medium in the fixing area, making it possible to reliably remove the recording medium wrapped around the outer peripheral surface of the heating rotor as follows.

[0121] 1, in the image forming apparatus 1 to which the fixing device 40 according to the second embodiment is applied, the toner images of each color formed in each of the imaging devices 10 (Y, M, C, K) of yellow (Y), magenta (M), cyan (C) and black (K) are secondarily transferred collectively onto the recording paper 5 via the intermediate transfer belt 21. The toner images of each color secondarily transferred onto the recording paper 5 are transported to the fixing device 40, where they are heated and pressurized to be fixed onto the recording paper 5.

[0122] 3, a leading edge 5a of the recording paper 5 in the transport direction is detected by a registration sensor 201 arranged upstream in the transport direction of the paper transport roll pair 54. After the recording paper 5 is transported to the fixing device 40 and subjected to a fixing process, and is discharged from the fixing device 40, the leading edge 5a is detected by an exit sensor 204 arranged downstream in the transport direction of the recording paper 5 from the fixing device 40.

[0123] The control device 100 measures the time from when the leading edge 5a of the recording paper 5 is detected by the registration sensor 201 to when it is detected by the exit sensor 204, and if the measured time is not within a predetermined range, it determines that a transport problem (jam) has occurred in the recording paper 5, and immediately stops the image forming device 1.

[0124] As shown in FIG. 16, when the control device 100 detects a transport failure (jam) of the recording paper 5 (step 201), it calculates the amount of reverse rotation of the heating roll 41 of the fixing device 40 based on the formula (1) (step 202).

[0125] However, here, the amount of reversal of the heating roll 41 calculated based on formula (1) is set so that the leading edge 5a of the recording paper 5 stops at the position of the fixing nip portion N of the fixing device 40, as shown in FIG. 15(b), unlike in the first embodiment.

[0126] Thereafter, the control device 100 executes a reversing operation to rotate the heating roll 41 in the direction opposite to that during normal fixing by the reversal amount calculated based on the formula (1) (step 203). At this time, in the fixing device 40, the halogen lamp 414 of the heating roll 41 is energized, and the heating roll 41 is in a heated state.

[0127] Next, the control device 100 drives the drive motor 48 to separate the heating roll 41 from the pressure roll 42, thereby releasing the pressure contact state in the fixing nip portion N (step 204).

[0128] Thereafter, the control device 100 displays a message on the display unit of a user interface (not shown) to prompt the user to open the rear cover 80, thereby allowing the user to open the rear cover 80 of the image forming apparatus 1 (step 205).

[0129] Then, the user opens the rear cover 80 of the image forming apparatus 1 as shown in Fig. 4, and manually removes the recording paper 5 that has been peeled off from the outer periphery of the heating roll 41 of the fixing device 40 and whose rear end is located between the fixing device 40 and the secondary transfer position as shown in Fig. 17, thereby completing the processing of the recording paper 5 for which a transport failure has occurred. After that, the rear cover 80 of the image forming apparatus 1 is closed by the user.

[0130] Finally, the control device 100 drives the drive motor 48 to press the heating roll 41 against the pressure roll 42, and executes the required jam clearing sequence (step 206), which includes cleaning the photosensitive drums 11 of each of the imaging devices 10 (Y, M, C, K) for yellow (Y), magenta (M), cyan (C), and black (K) by the drum cleaning device 16 and cleaning the intermediate transfer belt 21 of the intermediate transfer device 20 by the belt cleaning device 27, and then restarts the printing operation.

[0131] In this way, by performing a reversal operation in which the heating roll 41 is rotated in the opposite direction to that during normal fixing by the reversal amount calculated based on equation (1), the leading edge 5a of the recording paper 5 wrapped around the surface of the heating roll 41 is stopped in a position at the fixing nip portion N, as shown in Figure 15 (b).

[0132] Therefore, in the second embodiment, as shown in FIG. 17, the leading edge 5a of the recording paper 5 stopped in the fixing nip portion N of the fixing device 40 can be easily removed by pulling it out.

[0133] Furthermore, in this embodiment 2, when the heating roll 41 rotates in the reverse direction, it is possible to reliably prevent the recording paper 5 from entering inside the device main body 1a along the surface of the intermediate transfer belt 21 due to an excessive amount of reverse rotation of the heating roll 41.

[0134] Furthermore, when the heating roll 41 reverses, as shown in FIG. 18, the amount of reversal of the heating roll 41 is not insufficient, and a large force is not required to rotate the heating roll 41 and pressure roll 42 that are pressed against each other when removing the recording paper 5.

[0135] The other configurations and operations are the same as those of the above-described embodiment, and therefore the description thereof will be omitted.

[0136] In the above embodiment, a full-color image forming apparatus has been described as an image forming apparatus, but the present invention is not limited to this and can of course be applied to a monochrome image forming apparatus as well.

[0137] (Additional Note) (((1))) A heating rotor; a pressurizing means for pressing a recording medium against the heating rotor in a fixing area; a reversing means for rotating the heating rotor in a direction opposite to that during fixing when the recording medium is wrapped around the heating rotor; a peeling means for peeling off the recording medium wound around the outer circumferential surface of the heating rotor on the upstream side of the fixing area in the conveying direction of the recording medium when the heating rotor rotates in the reverse direction; A fixing device comprising: (((2))) The fixing device according to (((1))) further comprises a detection unit that detects the passage of the recording medium on a downstream side of the fixing area in the transport direction of the recording medium. (((3))) The fixing device according to (((2))) specifies the amount of the recording medium wound around the heating rotatable body based on the detection result of the detection means. (((4))) The fixing device according to (((1))), wherein the peeling means comes relatively close to the outer circumferential surface of the heating rotor by the movement of the heating rotor. (((5))) The fixing device according to (((2))), wherein the heating rotator is rotated in the reverse direction and stopped so that the leading edge of the recording medium is positioned in the fixing area based on the detection result of the detection means. (((6))) The fixing device according to (((5))), wherein the heating rotator is released from the pressurizing means before the reversing means rotates the heating rotator in the direction opposite to that during fixing. (((7))) The fixing device according to (((5))), wherein the heating rotator is released from the pressurizing means after the reversing means has rotated the heating rotator in a direction opposite to that during fixing. (((8))) The fixing device according to (((5))), wherein the heating rotatable body stops heating after the rotation in the direction opposite to that during fixing has stopped. (((9))) an image forming means for forming an image on a recording medium; a fixing means for fixing the image on the recording medium; Equipped with An image forming apparatus using the fixing device according to any one of ((1))) to (((8))) as the fixing means.

[0138] According to the fixing device of (((1))), when the heating rotor rotates in the reverse direction, the recording medium wrapped around the outer peripheral surface of the heating rotor can be reliably removed, compared to a case in which a peeling means for peeling off the recording medium wrapped around the outer peripheral surface of the heating rotor is provided downstream in the conveying direction of the recording medium in the fixing area. According to the fixing device of (((2))), it is possible to reliably detect wrapping of the recording medium, compared to a case where no detection means is provided. According to the fixing device of (((3))), it is possible to detect the amount of wrapping of the recording medium with higher accuracy, compared to a case in which the amount of wrapping of the recording medium is determined from a value other than the detection result of the detection means. According to the fixing device of (((4))), the moving means for the peeling means can be omitted, as compared with the case where the peeling means moves. According to the fixing device of (((5))), it is possible to avoid excessive reverse transport of the recording medium, compared to a case in which the leading edge of the recording medium is not stopped in the fixing area. According to the fixing device of (((6))), the peeling means can be easily brought close to the heating rotor, compared to a case in which the pressure state is released after the heating rotor is rotated in the reverse direction. According to the fixing device of (((7))), the heating rotator can more reliably release the recording medium from the wrapping, compared to a case in which the pressure is released before the heating rotator is rotated in the reverse direction. According to the fixing device of (((8))), the heating rotor can avoid the image on the recording medium solidifying and making it difficult to peel it off from the heating rotor, compared to a case in which heating is stopped before rotation in the opposite direction to that during fixing is stopped. According to the image forming apparatus of (((9))), the recording medium wound around the outer circumferential surface of the heating rotor can be removed more reliably than in a case where the fixing device of any of (((1))) to (((8))) is not used as the fixing means. [Explanation of symbols]

[0139] 1...Image forming device 5. Recording paper 40...Fixing device 41…Heated roll 42...Pressure roll 49…Release film 100...Control device N: Fixing nip

Claims

1. A heating rotor; a pressurizing means for pressing a recording medium against the heating rotor in a fixing area; a reversing means for rotating the heating rotor in a direction opposite to that during fixing when the recording medium is wrapped around the heating rotor; a peeling means for peeling off the recording medium wound around the outer circumferential surface of the heating rotor on the upstream side of the fixing area in the conveying direction of the recording medium when the heating rotor rotates in the reverse direction; A fixing device comprising:

2. The fixing device according to claim 1 , further comprising a detection unit that detects the passage of the recording medium on a downstream side of the fixing area in the conveying direction of the recording medium.

3. 3. The fixing device according to claim 2, wherein the amount of the recording medium wound around the heating rotatable body is determined based on the detection result of the detection means.

4. 2. The fixing device according to claim 1, wherein the peeling means is brought relatively close to the outer circumferential surface of the heating rotor by the movement of the heating rotor.

5. 3. The fixing device according to claim 2, wherein the heating rotatable member is rotated in the reverse direction and stopped so that the leading edge of the recording medium is positioned in the fixing area based on the detection result of the detection means.

6. 6. The fixing device according to claim 5, wherein the heating rotator is released from the pressurizing means before the reversing means rotates the heating rotator in the direction opposite to that during fixing.

7. 6. The fixing device according to claim 5, wherein the heating rotator is released from the pressurizing means after the reversing means rotates the heating rotator in a direction opposite to that during fixing.

8. The fixing device according to claim 5 , wherein the heating rotatable member stops heating after the rotation in the direction opposite to that during fixing has stopped.

9. an image forming means for forming an image on a recording medium; a fixing means for fixing the image on the recording medium; Equipped with 9. An image forming apparatus using the fixing device according to claim 1 as the fixing means.

Images