Fixing device and image forming apparatus

Abstract

The invention relates to a fixing device and an image forming apparatus. The fixing device includes: a rotating body for heating; a pressurizing unit that pressurizes a recording medium onto the heating rotating body in a fixing region; a reversing unit that rotates the heating rotating body in a direction opposite to a direction during fixing when the recording medium is wound around the heating rotating body; and a peeling unit that peels the recording medium that is relatively close to and wound around an outer peripheral surface of the heating rotating body at an upstream side of the fixing region in a transport direction of the recording medium when the heating rotating body is reversed.

Description

Technical Field

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

[0002] Conventionally, as a technology related to the fixing device, for example, the technology disclosed in Patent Document 1 or Patent Document 2 has been proposed.

[0003] Patent document 1 discloses a fixing device comprising: a driving source for causing a fixing component to rotate forward and reversely; and a separation unit for preventing the recording medium from being drawn in when the fixing component rotates reversely when the recording medium is located in a fixing nip portion, and for comprising an adjustment mechanism for adjusting the value of the gap between the fixing component and the separation unit.

[0004] Patent document 2 discloses a fixing device having the following structure: when separating a sheet wound on a first roller, a peeling portion contacts the first roller, and a rotating portion rotates the first roller in a reverse rotation direction, so that the sheet wound on the first roller rides on the peeling portion to be peeled off from the first roller, so that the sheet is separated from the first roller. In addition, the peeling portion is arranged on the downstream side of the fixing nip portion.

[0005] Patent Document 1: Japanese Patent Application Publication No. 2014-174542

[0006] Patent Document 2: Japanese Patent Application Publication No. 2005-309022 Summary of the invention

[0007] An object of the present invention is to reliably remove the recording medium wound on the outer peripheral surface of the heating rotating body, compared with a case where the stripping unit is arranged on the downstream side of the fixing area along the conveying direction of the recording medium, and the stripping unit strips the recording medium wound on the outer peripheral surface of the heating rotating body when the heating rotating body is reversed.

[0008] The invention described in claim 1 is a fixing device comprising:

[0009] Heating rotating body;

[0010] a pressing unit for pressing the recording medium against the heating rotating body in a fixing area;

[0011] a reversing unit for rotating the heating rotator in a direction opposite to that during fixing when the recording medium is wound around the heating rotator; and

[0012] The peeling unit peels off the recording medium that is relatively close to and wrapped around the outer peripheral surface of the heating rotating body at the upstream side of the fixing region in the conveying direction of the recording medium when the heating rotating body is reversed.

[0013] The invention described in claim 2 is the fixing device described in claim 1, wherein a detection unit for detecting passage of the recording medium is provided on the downstream side of the fixing area along the conveyance direction of the recording medium.

[0014] The invention described in claim 3 is the fixing device described in claim 2, wherein the winding amount of the recording medium wound around the heating rotating body is determined based on the detection result of the detection unit.

[0015] The invention described in claim 4 is the fixing device described in claim 1, wherein the peeling unit is relatively close to the outer peripheral surface of the heating rotating body due to the movement of the heating rotating body.

[0016] The invention described in claim 5 is the fixing device described in claim 2, wherein the heating rotating body is reversed and stopped based on the detection result of the detection unit so that the leading end of the recording medium is located in the fixing area.

[0017] The invention described in claim 6 is the fixing device described in claim 5, wherein the heating rotating body is released from the pressurizing state by the pressurizing unit before the heating rotating body is rotated by the reversing unit in the direction opposite to that during fixing.

[0018] The invention described in claim 7 is the fixing device described in claim 5, wherein the heating rotating body is released from the pressurizing state by the pressurizing unit after being rotated by the reversing unit in the direction opposite to that during fixing.

[0019] The invention described in claim 8 is the fixing device described in claim 5, wherein the heating rotatable body stops heating after the rotation in the direction opposite to that during fixing stops.

[0020] The invention described in claim 9 is an image forming apparatus comprising:

[0021] an image forming unit that forms an image on a recording medium; and

[0022] a fixing unit, fixing the image on the recording medium,

[0023] As the fixing unit, the fixing device described in any one of aspects 1 to 8 is used.

[0024] Effects of the Invention

[0025] According to the first scheme of the present invention, compared with the case where the stripping unit is arranged on the downstream side of the fixing area along the conveying direction of the recording medium, the recording medium wound on the outer peripheral surface of the heating rotating body can be reliably removed. The stripping unit strips the recording medium wound on the outer peripheral surface of the heating rotating body when the heating rotating body is reversed.

[0026] According to the second aspect of the present invention, winding of the recording medium can be detected more reliably than in a case where no detection means is provided.

[0027] According to the third aspect of the present invention, the winding amount of the recording medium can be detected with higher accuracy than in the case where the winding amount of the recording medium is determined based on a value other than the detection result of the detection unit.

[0028] According to the fourth aspect of the present invention, compared with the case where the peeling unit is moved, the moving unit of the peeling unit can be omitted.

[0029] According to the fifth aspect of the present invention, compared with the case where the leading end of the recording medium is not stopped in the fixing area, it is possible to avoid excessive reverse conveyance of the recording medium.

[0030] According to the sixth aspect of the present invention, compared with the case where the pressurized state is released after the heating rotatable body is reversed, the peeling unit can be easily brought close to the heating rotatable body.

[0031] According to the seventh aspect of the present invention, the recording medium can be reliably unwound compared to the case where the pressurized state is released before the heating rotary body is reversed.

[0032] According to the eighth aspect of the present invention, compared with the case where the heating rotator stops heating before the rotation in the opposite direction to that during fixing stops, it is possible to prevent the image on the recording medium from being cured and being difficult to be peeled off from the heating rotator.

[0033] According to the ninth aspect of the present invention, compared with a case where the fixing device according to any one of the first to eighth aspects of the present invention is not used as the fixing unit, the recording medium wound around the outer peripheral surface of the heating rotating body can be removed reliably. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Embodiments of the present invention will be described in detail with reference to the following drawings.

[0035] Figure 1 is a diagram showing the overall structure of an image forming apparatus to which a fixing device according to Embodiment 1 of the present invention is applied;

[0036] Figure 2 is a structural diagram showing an image forming unit of an image forming apparatus to which a fixing device according to Embodiment 1 of the present invention is applied;

[0037] Figure 3 is a structural diagram showing the main parts of the image forming apparatus;

[0038] Figure 4 is a structural diagram showing a state in which a rear cover of the image forming apparatus is opened;

[0039] Figure 5 is a structural diagram showing a fixing device according to Embodiment 1 of the present invention;

[0040] Figure 6 is a cross-sectional structural diagram showing a heating roller and a pressure roller;

[0041] Figure 7 is a side structural diagram showing a fixing device according to Embodiment 1 of the present invention;

[0042] Figure 8 is a structural diagram showing a nip-released state of the fixing device according to the first embodiment of the present invention;

[0043] Fig. 9 is a schematic diagram showing a recording paper wound on the surface of a heating roller;

[0044] Fig.10 is a schematic structural diagram showing a fixing device in which a recording paper is wound around the surface of a heating roller;

[0045] Fig.11 is a schematic diagram showing a recording paper completely wound on the surface of a heating roller;

[0046] Fig.12 is a flowchart showing the operation of the fixing device according to the first embodiment of the present invention;

[0047] Fig.13 is a structural diagram showing a nip-released state of the fixing device according to the first embodiment of the present invention;

[0048] Fig.14 is a structural diagram showing a fixing device according to a second embodiment of the present invention;

[0049] Fig.15 is a schematic diagram showing the operation of the fixing device according to the second embodiment of the present invention;

[0050] Fig.16 is a flowchart showing the operation of the fixing device according to the second embodiment of the present invention;

[0051] Fig.17 is a structural diagram showing the operation of the fixing device according to the second embodiment of the present invention;

[0052] Fig.18 This is a schematic structural diagram showing the operation of a conventional fixing device. DETAILED DESCRIPTION

[0053] Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “embodiment”) will be described with reference to the drawings.

[0054] [Implementation Method 1]

[0055] Figure 1 is a diagram showing an overall overview of an image forming apparatus to which the fixing device according to the first embodiment is applied. Figure 2 FIG. 1 is an enlarged view showing an image forming unit of an image forming apparatus. Figure 1 In the figure, symbol X indicates the horizontal direction (width direction) of the image forming apparatus, symbol Y indicates the rear side direction of the image forming apparatus, and symbol Z indicates the vertical direction of the image forming apparatus.

[0056] <Overall Structure of Image Forming Apparatus>

[0057] The image forming device 1 is configured as, for example, a color printer. Figure 1 As shown, the image forming device 1 includes a plurality of image generating devices 10, an intermediate transfer device 20, a paper feeding device 50, a fixing device 40 as an example of a fixing unit involved in the present embodiment 1, and the like. The plurality of image generating devices 10 form a toner image developed with a toner constituting a developer. The intermediate transfer device 20 respectively holds the toner images formed by each image generating device 10 and finally conveys them to a secondary transfer position for secondary transfer onto a recording paper 5 as an example of a recording medium. The paper feeding device 50 accommodates and conveys 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 onto the recording paper 5 secondarily transferred by the intermediate transfer device 20. In Figure 1 In the figure, reference numeral 1a denotes a device main body formed of a supporting structural member, an exterior cover, and the like.

[0058] In the first embodiment, a plurality of image forming devices 10 and an intermediate transfer device 20 constitute an image forming unit for forming a toner image on a recording medium. Alternatively, the image forming unit may be configured to include a single image forming device, and to form a toner image directly from the image forming device on a recording medium without passing through an intermediate transfer device.

[0059] The image generating device 10 is composed of four image generating devices 10Y, 10M, 10C, and 10K that are specialized in forming toner images of four colors, namely yellow (Y), magenta (M), cyan (C), and black (K). These four image generating devices 10 (Y, M, C, K) are arranged in a row in a state of being inclined in the horizontal direction X in the internal space of the device body 1a.

[0060] like Figure 1As shown, each image generating device 10 (Y, M, C, K) is provided with a photosensitive drum 11 as an example of a rotating image holding unit. The following devices are mainly arranged around the photosensitive drum 11. The main devices are a charging device 12, an exposure device 13, a developing device 14, a primary transfer device 15, and a drum cleaning device 16. The charging device 12 charges the peripheral surface (image holding surface) of the photosensitive drum 11 that can form an image to a desired potential. The exposure device 13 irradiates the charged peripheral surface of the photosensitive drum 11 with light based on image information (signal) to form an electrostatic latent image (for each color) with a potential difference. The developing device 14 develops the electrostatic latent image with a toner of a developer of a 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 the toner and other attachments that remain and adhere to the image holding surface of the photosensitive drum 11 after the primary transfer. In addition, symbols indicating the photosensitive drum 11, the charging device 12, etc. are indicated only on the image generating device 10Y of yellow (Y), and are omitted on the other image generating devices 10 (M, C, K).

[0061] The photosensitive drum 11 is formed by forming an image holding surface having a photoconductive layer (photosensitive layer) made of a photosensitive material on the circumference of a grounded cylindrical or columnar substrate. The photosensitive drum 11 is supported to rotate in the direction indicated by arrow A by receiving a driving force transmitted from a driving device (not shown).

[0062] The charging device 12 is composed of a contact type charging roller arranged in contact with the photosensitive drum 11. A charging voltage is supplied to the charging device 12. When the developing device 14 performs reverse development, a voltage or current having the same polarity as the charging polarity of the toner supplied from the developing device 14 is supplied as the charging voltage. A cleaning roller 121 for cleaning the surface of the charging device 12 is arranged in contact with the back side of the charging device 12.

[0063] The exposure device 13 is composed of an LED print head, etc., which forms an electrostatic latent image by irradiating light corresponding to image information to the photosensitive drum 11 using a plurality of LEDs (Light Emitting Diodes) arranged in the axial direction of the photosensitive drum 11. The image information (signal) input to the image forming device 1 by an arbitrary unit when forming the latent image is transmitted to the exposure device 13. In addition, as the exposure device 13, an exposure device that irradiates the peripheral surface of the charged photosensitive drum 11 with a laser beam formed according to the image information input to the image forming device 1 to form an electrostatic latent image can be used.

[0064] like Figure 2As shown, the developing device 14 is configured by arranging a developing roller 141, stirring and conveying components 142, 143, and a layer thickness limiting component 144, etc., inside a frame 140 having an opening and a developer storage chamber. The developing roller 141 holds the developer 4 and conveys it to a developing area opposite to the photosensitive drum 11. The stirring and conveying components 142, 143 are composed of a screw augers, etc., which convey the developer 4 while stirring it through the developing roller 141. The layer thickness limiting component 144 limits the amount (layer thickness) of the developer 4 held on the developing roller 141. In the developing device 14, a voltage for development is supplied between the developing roller 141 and the photosensitive drum 11 from a power supply device not shown in the figure. In addition, the developing roller 141 or the stirring and conveying components 142, 143 are rotated in a desired direction by receiving a driving force transmitted from a driving device not shown in the figure. In addition, as the developer 4 of the above four colors, a two-component developer containing a non-magnetic toner and a magnetic carrier is used.

[0065] like Figure 1 As shown, the primary transfer device 15 is a contact type transfer device having a primary transfer roller, which rotates in contact with the peripheral surface of the photosensitive 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 having a polarity opposite to the charging polarity of the toner is supplied from a power supply device (not shown).

[0066] like Figure 2 As shown, the drum cleaning device 16 is composed of a cleaning blade 161 and a delivery member 162 disposed inside a container-shaped main body 160. The cleaning blade 161 removes and cleans the residual toner and other attached materials. The delivery member 162 is composed of an auger and the like, which collects the toner and other attached materials removed by the cleaning blade 161 and delivers them to a recovery system (not shown).

[0067] The intermediate transfer device 20 is arranged so as to be located above each image generating device 10 (Y, M, C, K) along the vertical direction Z. The intermediate transfer device 20 is mainly composed of an intermediate transfer belt 21, a plurality of belt support rollers 22 to 26, a belt cleaning device 27, and a secondary transfer device 30. The intermediate transfer belt 21 is an example of an intermediate transfer unit that circulates in the direction indicated by the arrow B while passing through the primary transfer position between the photosensitive drum 11 and the primary transfer device 15 (primary transfer roller). The plurality of belt support rollers 22 to 26 support the intermediate transfer belt 21 so as to be able to circulate while being maintained in a desired state from its inner periphery. The secondary transfer device 30 is arranged on the outer peripheral surface (image holding surface) side of the intermediate transfer belt 21 supported by the belt support roller 25 so as to transfer the toner image on the intermediate transfer belt 21 to the recording paper 5 for the second time. The belt cleaning device 27 removes and cleans toner, paper dust, and other attached materials that remain and adhere to the outer peripheral surface of the intermediate transfer belt 21 after passing through the secondary transfer device 30 .

[0068] As the intermediate transfer belt 21, for example, an endless belt made of a material in which a resistance adjusting agent such as carbon black is dispersed in a synthetic resin such as a polyimide resin, a polyamide resin, or a polyamide-imide resin is used. In addition, the belt support roller 22 is configured as a driving roller. The belt support roller 23 is configured as a surface leveling roller for maintaining the moving position of the intermediate transfer belt 21. The belt support roller 24 is configured as a tension applying roller for applying tension to the intermediate transfer belt 21. The belt support roller 25 is configured as a supporting roller for secondary transfer. The belt support roller 26 is configured as a back support roller of the belt cleaning device 27.

[0069] The secondary transfer device 30 includes a secondary transfer roller 31 that rotates at a secondary transfer position. The secondary transfer position is the outer peripheral surface portion of the intermediate transfer belt 21 supported by the belt support roller 25 in the intermediate transfer device 20. A DC voltage having a polarity opposite to or having the same polarity as the charging polarity of the toner is supplied to the secondary transfer roller 31 or the belt support roller 25 of the intermediate transfer device 20 as a secondary transfer voltage.

[0070] The fixing device 40 is configured to include a heating roller 41 as an example of a heating rotating body and a pressure roller 42 as an example of a pressure unit. The heating roller 41 is heated by the heating unit so that the surface temperature is maintained at a preset temperature. The pressure roller 42 rotates while contacting the heating roller 41 with a required pressure. In the fixing device 40, the contact portion between the heating roller 41 and the pressure roller 42 becomes a fixing nip N as an example of a fixing area for performing a required fixing process (heating and pressing) to fix the unfixed toner image on the recording paper 5. In addition, the fixing device 40 will be described in detail later.

[0071] The paper feeding device 50 is arranged so as to be located below the image generating device 10 (Y, M, C, K). The paper feeding device 50 is mainly composed of a single (or a plurality of) paper container 51 and feeding devices 52 and 53 for feeding recording paper 5 one by one from the paper container 51. The paper container 51 stores recording paper 5 of a desired size and type in a state loaded on a loading plate (not shown). And, the paper container 51 is installed so as to be pulled out, for example, toward the front side (the side facing when operated by the user) of the device body 1a, toward the left side in the example shown in the figure.

[0072] As the recording paper 5, for example, thin paper such as plain paper or tracing paper used in a copier or printer of an electrophotographic system, or OHP sheets made of a transparent film-like medium made of a synthetic resin (PET, etc.) can be cited. In order to further improve the smoothness of the image surface after fixing, for example, it is preferable that the surface of the recording paper 5 is as smooth as possible. As the recording paper 5, for example, coated paper in which the surface of plain paper is coated with a resin, so-called thick paper with a relatively large basis weight such as coated paper for printing, etc. can also be used.

[0073] 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 a single (or a plurality of) paper conveying roller pairs 54 that convey the recording paper 5 fed from the paper feed device 50 to the secondary transfer position and a conveying guide material 55. The paper conveying roller pair 54 disposed immediately before the secondary transfer position on the paper feed conveying path 56 is configured as a roller (registration roller) that adjusts the conveying timing of the recording paper 5, for example.

[0074] like Figure 3 As shown in the figure, a registration sensor 201 as an example of a first detection unit for detecting the leading end of the recording paper 5 fed from the paper feeding device 50 is arranged on the upstream side of the paper feeding roller pair 54 along the feeding direction of the recording paper 5. The registration sensor 201 includes an actuator 203 that rotates around a rotation fulcrum 202. When the leading end of the recording paper 5 passes through the registration sensor 201, the actuator 203 rotates around the rotation fulcrum 202, and the rotation of the actuator 203 is detected as the passing of the leading end of the recording paper 5 by an optical sensor (not shown).

[0075] And, if Figure 1 As shown, between the secondary transfer device 30 and the fixing device 40 , transport guide members 57 , 58 and the like are arranged to guide the recording paper 5 sent out from the secondary transfer device 30 to the fixing device 40 .

[0076] A paper discharge roller pair 61 and a conveyance guide member 59 are provided downstream of the fixing device 40 for discharging the recording paper 5 on which the toner image is fixed by the fixing device 40 to a paper discharge unit 60 disposed at the upper part of the apparatus body 1 a .

[0077] like Figure 3 As shown in FIG. 1 , an exit sensor 204 as an example of a second detection unit for detecting the leading end of the recording paper 5 subjected to the fixing process is arranged at the exit portion of the fixing device 40. Similar to the registration sensor 201, the exit sensor 204 includes an actuator 206 that rotates around a rotation fulcrum 205. When the leading end of the recording paper 5 passes through the exit sensor 204, the actuator 206 rotates around the rotation fulcrum 205, and the rotation of the actuator 206 is detected as the passing of the leading end of the recording paper 5 by an optical sensor (not shown).

[0078] like Figure 1 As shown, a switching gate 62 for switching the paper conveying path is provided between the fixing device 40 and the paper discharge roller pair 61. The rotation direction of the paper discharge roller pair 61 can be switched between the forward rotation direction (discharge direction) and the reverse direction. In the case where an image is formed on both sides of the recording paper 5, after the rear end of the recording paper 5 with an image formed on one side passes through the switching gate 62, the rotation direction of the paper discharge roller pair 61 is switched from the forward rotation direction (discharge direction) to the reverse direction. The recording paper 5 conveyed in the reverse direction by the paper discharge roller pair 61 has its conveying path switched by the switching gate 62 and is conveyed to a double-sided conveying path 63 formed in a substantially vertical direction. The double-sided conveying path 63 includes a paper conveying roller pair 64 and conveying guide devices 65 to 68 that convey the recording paper 5 to the paper conveying roller pair 54 in a state where the front and back sides are reversed.

[0079] Furthermore, in the image forming apparatus 1 according to the first embodiment, Figure 4 As shown in the figure, a rear cover 80 as an example of an opening and closing unit provided on the back side of the apparatus body 1a is configured to be openable and closable around a rotation fulcrum 81. By opening and closing the rear cover 80, the recording paper 5 that has been poorly conveyed (paper jammed) can be easily removed. As the part where the poorly conveyed recording paper 5 occurs, the paper feed conveying path 56, the paper discharge conveying path composed of the paper discharge roller pair 61 and the conveying guide member 59, or the double-sided conveying path 63, and the fixing device 40 can be cited.

[0080] exist Figure 1In the figure, symbol 70 indicates a manual tray which is openably and closably provided on the front side (the left side in the figure) of the device body 1a of the image forming device 1, and between the manual tray 70 and the paper conveying roller pair 54, there are provided a feeding device 71 for feeding out the recording paper 5 contained in the manual tray 70 one by one, and a manual paper feeding and conveying path 76 composed of a plurality of paper conveying roller pairs 72 to 74 and a conveying guide device 75.

[0081] And, in Figure 1 In the figure, the symbols 145 (Y, M, C, K) respectively represent a plurality of toner boxes as developer storage containers arranged in a direction perpendicular to the paper surface and containing developers containing at least toner supplied to the corresponding developing devices 14 (Y, M, C, K).

[0082] And, in Figure 1 In the figure, reference numeral 100 denotes a control device as an example of a control unit that centrally controls the operation of the image forming apparatus 1. The control device 100 is configured to include a CPU (Central Processing Unit) or a ROM (Read Only Memory), a RAM (Random Access Memory), or a bus or a communication interface that connects the CPU or ROM, etc. (not shown).

[0083] <Basic Operation of Image Forming Apparatus>

[0084] Hereinafter, a basic image forming operation by the image forming apparatus 1 will be described.

[0085] Here, the image forming operation when the four image generating devices 10 (Y, M, C, K) are used to form a full-color image composed of a combination of toner images of four colors (Y, M, C, K) will be described. In addition, the image forming operation when any one or more of the four image generating devices 10 (Y, M, C, K) are used to form an image composed of a combination of monochromatic or plural-color toner images is basically the same.

[0086] When receiving the instruction information requesting printing, the image forming apparatus 1 activates the four image generating devices 10 (Y, M, C, K), the intermediate transfer device 20 , the secondary transfer device 30 , the fixing device 40 , etc. under the control of the control device 100 .

[0087] In each image forming device 10 (Y, M, C, K), first, each photosensitive drum 11 rotates in the direction indicated by arrow A. The surface of each photosensitive drum 11 is charged to a desired polarity (negative polarity in Embodiment 1) and potential by each charging device 12. Next, the exposure device 13 irradiates the surface of the charged photosensitive drum 11 with light, which is emitted according to an image signal obtained by converting the image information input to the image forming device 1 into each color component (Y, M, C, K). Then, an electrostatic latent image of each color component composed of a desired potential difference is formed on the surface of the photosensitive drum 11.

[0088] Next, each developing device 14 (Y, M, C, K) supplies a toner of the corresponding color (Y, M, C, K) charged to a desired polarity (negative polarity) to the electrostatic latent image of each color component formed on the photosensitive drum 11 and electrostatically adheres the toner to develop the electrostatic latent image. Through this development, the electrostatic latent image of each color component formed on each photosensitive drum 11 is visualized as a toner image of four colors (Y, M, C, K) developed by the toner of the corresponding color.

[0089] Next, the toner images of the respective colors formed on the photosensitive drums 11 of the respective image generating devices 10 (Y, M, C, K) are conveyed to the primary transfer position. Then, the primary transfer device 15 performs primary transfer in a state where the toner images of the respective colors are sequentially superimposed on the intermediate transfer belt 21 rotating in the direction indicated by the arrow B of the intermediate transfer device 20.

[0090] After the primary transfer is completed, the drum cleaning device 16 of each image generating device 10 (Y, M, C, K) scrapes away the attached matter to clean the surface of the photosensitive drum 11. Thus, each image generating device 10 (Y, M, C, K) is ready to perform the next image generating operation.

[0091] Next, in the intermediate transfer device 20, the toner image primarily transferred by the rotation of the intermediate transfer belt 21 is held and transported to the secondary transfer position. On the other hand, in the paper feeding device 50, the required recording paper 5 is fed to the paper feeding transport path 56 in coordination with the image generation operation. On the paper feeding transport path 56, the paper feeding roller pair 54 as a registration roller feeds the recording paper 5 in coordination with the transfer timing and supplies it to the secondary transfer position.

[0092] At the secondary transfer position, the secondary transfer roller 31 secondary transfers the toner image on the intermediate transfer belt 21 to the recording paper 5. After the secondary transfer, the belt cleaning device 27 removes and cleans the toner and other attached materials remaining on the surface of the intermediate transfer belt 21 after the secondary transfer.

[0093] Next, the recording paper 5 to which the toner image is secondarily transferred is peeled off from the intermediate transfer belt 21 and the secondary transfer roller 31, and is then conveyed to the fixing device 40 along the conveying guide members 57 and 58. The fixing device 40 guides the recording paper 5 holding the unfixed toner image after the secondary transfer and passes it through the fixing nip N between the rotating heating roller 41 and the pressure roller 42. Thus, the fixing device 40 performs necessary fixing processing (heating and pressing) to fix the unfixed toner image on the recording paper 5. The recording paper 5 after the fixing is completed is discharged by the paper discharge roller pair 61 via the conveying guide member 59 to the paper discharge unit 60 provided at the upper part of the device body 1a.

[0094] Through the above operation, a full-color image formed by combining toner images composed of four color toners T (Y, M, C, K) is output.

[0095] <Structure of the fixing unit>

[0096] Figure 5 It is a cross-sectional structural diagram showing the fixing device according to the first embodiment.

[0097] like Figure 5 As shown, the fixing device 40 includes a heating roller 41 as an example of a heating rotating body, and a pressure roller 42 as an example of a pressure unit for pressing the recording paper 5 against the heating roller 41 in a fixing nip N as an example of a fixing area.

[0098] like Figure 6 As shown, the heating roller 41 has a cylindrical core rod 411, an elastomer layer 412 and an anti-sticking layer 413. The core rod 411 is made of metal such as stainless steel, aluminum or iron (thin-walled high-tensile steel pipe). The core rod 411 is formed into a relatively thin-walled cylindrical shape, and the heat capacity is set to be very small. The elastomer layer 412 is composed of a heat-resistant elastomer such as silicone rubber or fluororubber covering the outer periphery of the core rod 411. The elastomer layer 412 is also formed into a relatively thin-walled cylindrical shape, and helps to reduce the heat capacity of the heating roller 41. The anti-sticking layer 413 is composed of polytetrafluoroethylene (PTFE) or perfluoroalkoxyalkane (PFA) thinly covering the surface of the elastomer layer 412. A halogen lamp 414 as an example of a heating unit is arranged inside the heating roller 41.

[0099] Both ends of the heating roller 41 along its length direction (axial direction) are rotatably supported on the swing arm 44 via bearing components not shown in the figure. The heating roller 41 is rotationally driven in the direction of arrow C at a desired speed by a drive motor not shown as an example of a reversing unit on the side of the device body 1a via a drive gear not shown installed at one end along the axial direction. The drive motor is an example of a drive source. The heating roller 41 is configured to be able to rotate in the direction of arrow C and in the direction of arrow D which is opposite to the direction of arrow C by a drive motor not shown in the figure even in a state where the pressure contact with the pressure roller 42 is released. In addition, the pressure roller 42 is driven to rotate by being pressed against the rotationally driven heating roller 41 in the fixing nip portion N. In addition, the pressure roller 42 is not limited to the case where it rotates along the direction of the heating roller 41, and of course, it can also be configured to rotationally drive the pressure roller 42.

[0100] The rotation speed of the heating roller 41 , that is, the fixing speed, can be set to a plurality of speeds such as high speed, medium speed, and low speed according to the basis weight and material of the recording paper 5 .

[0101] The surface temperature of the heating roller 41 is detected by a temperature sensor (not shown). Based on the detection result of the temperature sensor, the heating roller 41 controls the power supply to the halogen lamp 414 by a temperature control circuit using a triac (not shown) or the like. As a result, the heating roller 41 is heated so that its surface reaches the desired fixing temperature.

[0102] On the other hand, Figure 6 As shown, the pressure roller 42 has a cylindrical or cylindrical core rod 421, a relatively thick elastomer layer 422, and an anti-sticking layer 423. The core rod 421 is made of metal such as stainless steel or iron. The core rod 421 is formed into a cylindrical shape with a relatively large outer diameter, and the rigidity is set high. The elastomer layer 422 is composed of a heat-resistant elastomer such as silicone rubber or fluororubber that is relatively thickly covered on the outer periphery of the core rod 421. The anti-sticking layer 423 is composed of polytetrafluoroethylene (PTFE) or perfluoroalkoxyalkane (PFA) that is thinly covered on the surface of the elastomer layer 422.

[0103] The pressurizing means is not limited to the pressurizing roller, and may include a pressurizing belt or the like formed of an endless belt.

[0104] like Figure 5As shown, the fixing device 40 includes a device frame 43 as an example of a frame body. The device frame 43 is arranged inside the outer cover of the fixing device 40 (not shown). The two end portions of the pressure roller 42 along the axial direction are rotatably supported on the device frame 43. In addition, a swing arm 44 is rotatably mounted on the device frame 43 with a fulcrum 45 as the center. The heating roller 41 is rotatably supported on the swing arm 44. The front end portion 44a of the swing arm 44 is pushed toward the pressure roller 42 side by an elastic member such as a coil spring (not shown). As a result, the heating roller 41 is pressed against the surface of the pressure roller 42 with a required pressure during fixing.

[0105] like Figure 5 and Figure 7 As shown, the eccentric cam 46 contacts the front end 44a of the swing arm 44. The eccentric cam 46 is fixed to both ends of the drive shaft 47 in the axial direction. The eccentric cam 46 is driven to rotate by a required amount via the drive shaft 47 by a drive motor 48 as an example of a drive unit.

[0106] like Figure 5 As shown, the eccentric cam 46 rotates to a position where the eccentric portion 46a is retracted from the front end portion 44a of the swing arm 44 during fixing. Therefore, the heating roller 41 mounted on the swing arm 44 is pressed against the surface of the pressure roller 42 with a required pressure by the urging force of an elastic member such as a coil spring (not shown).

[0107] On the other hand, Figure 8 As shown, the eccentric cam 46 rotates to a position where the eccentric portion 46a contacts the front end portion 44a of the swing arm 44 during non-fixing. Therefore, the heating roller 41 rotatably mounted on the swing arm 44 overcomes the urging force of an elastic member such as a coil spring (not shown) and moves to a retreat position away from the surface of the pressure roller 42.

[0108] In the illustrated embodiment, the heating roller 41 is shown as being completely separated from the surface of the pressure roller 42 during non-fixing. However, the heating roller 41 does not need to be completely separated from the surface of the pressure roller 42 during non-fixing, and may be in contact with the pressure roller 42 with a lower pressure than during normal fixing.

[0109] However, in the fixing device 40 configured as described above, as the recording paper 5, a small-sized recording paper 5 whose length along the conveying direction is relatively short, such as B6 size (128×182 mm), A6 size (105×148 mm), or A5 size (148×210 mm), is sometimes subjected to fixing processing. The length along the conveying direction of these small-sized recording paper 5 is shorter than that of other A4 size recording paper 5. Therefore, especially in the case of feeding the recording paper 5 in the length direction (LEF: Long edge feed) so that the long side of the recording paper 5 is located at the front end along the conveying direction, the recording paper 5 is bent into a shape imitating the outer periphery of the heating roller 41 by the pressing force of the pressure roller 42, such as Fig. 9 As shown in FIG. 1 , sometimes a poor transmission (paper jam) occurs when the small-sized recording paper 5 is wound around the outer periphery of the heating roller 41. Fig.10 As shown in (a), since the length along the conveying direction is short, it is difficult for the user to visually confirm it.

[0110] Therefore, in the conventional fixing device 40, when the recording paper 5 is wound around the outer periphery of the heating roller 41 and a conveying failure (paper jam) is detected, Figure 4 As shown, sometimes, when the rear cover 80 of the apparatus body 1a is opened, the next printing operation is started without finding that the recording paper 5 is wound and removing the recording paper 5 wound around the outer circumference of the heating roller 41. Fig.11 As shown, the recording paper 5 is completely wound around the outer circumference of the heating roller 41 , and the recording paper 5 cannot be removed from the heating roller 41 , causing a failure in which the image forming apparatus 1 including the fixing device 40 itself becomes unusable.

[0111] Therefore, in the fixing device, a technique has been proposed in which, when the recording paper 5 is wound around the outer circumference of the heating roller 41 , the heating roller 41 is rotated in the opposite direction to that during fixing to remove the recording paper 5 (Patent Documents 1 and 2, etc.).

[0112] However, these technologies still have the following technical problems: depending on the basis weight of the recording paper 5 , it is difficult to visually identify the recording paper 5 wrapped around the periphery of the heating roller 41 , or it is difficult to peel the wrapped recording paper 5 from the periphery of the heating roller 41 .

[0113] Furthermore, there is the following technical problem: when the heating roller 41 is rotated in the opposite direction to that during fixing, Fig.10 As shown in (b), depending on the reverse rotation amount of the heating roller 41, the recording paper 5 peeled off from the heating roller 41 enters the inside of the apparatus body 1a of the image forming apparatus 1 along the intermediate transfer belt 21 and becomes invisible from the outside.

[0114] Therefore, the fixing device according to the first embodiment is configured to include a peeling unit that peels off the recording medium that is relatively close to and wrapped around the outer peripheral surface of the heating rotating body at the upstream side of the fixing region in the conveying direction of the recording medium when the heating rotating body is reversed.

[0115] That is, Figure 5 As shown, in the fixing device 40 according to the first embodiment, the pressure contact between the heating roller 41 and the pressure roller 42 is released so that the heating roller 41 rotates in the direction D opposite to that in normal fixing.

[0116] like Figure 7 and Figure 8 As shown in the figure, a peeling film 49 as an example of a peeling unit is provided on the outer periphery of the heating roller 41. When the heating roller 41 moves to the retracted position and the heating roller 41 is reversed, the peeling film 49 peels off the upstream side of the fixing nip portion N along the conveying direction of the recording paper 5, that is, Figure 8 The recording paper 5 is relatively close to and wound around the outer peripheral surface of the heating roller 41 below the fixing nip N in the heating roller 41.

[0117] like Figure 8 As shown, in the fixing device 40 according to the first embodiment, the recording paper 5 is conveyed along the conveying guide members 57 and 58 (see Figure 1 ) is conveyed from the bottom to the top along the vertical direction Z. An inlet for introducing the recording paper 5 downward along the vertical direction Z is opened in the outer cover (not shown) of the fixing device 40. Therefore, when the heating roller 41 is reversed, the recording paper 5 peeled off from the surface of the heating roller 41 by the peeling film 49 is preferably discharged directly from the inlet for the recording paper 5, for example.

[0118] Therefore, in the fixing device 40 according to the first embodiment, Figure 8 As shown, the front end 49 a of the peeling film 49 is provided so as to be located closer to the fixing nip N than the lower end of the heating roller 41 .

[0119] The release film 49 is composed of a polyester film or the like having a desired thickness. Figure 7 As shown, the release film 49 is attached to a support plate 490 mounted between the left and right device frames 43 by double-sided tape or adhesive. The release film 49 is arranged in a non-contact state, for example, so that its front end 49a is close to the surface of the heating roller 41 with a small gap. Alternatively, the release film 49 may be arranged so that its front end 49a contacts the surface of the heating roller 41 with a weak force.

[0120] The peeling film 49 is arranged in a state of being inclined at a desired inclination angle θ relative to the surface of the heating roller 41 from the downstream side along the rotation direction D toward the upstream side when the reverse is performed, and is a so-called scraper. In addition, an inclination angle θ of 45 degrees or an angle smaller than 45 degrees is effective for peeling off the recording paper 5.

[0121] like Figure 8 As shown, the heating roller 41 moves to a position where the outer peripheral surface of the heating roller 41 faces the front end 49a of the peeling film 49 with a small gap therebetween by a retracting action accompanied by the rotation of the eccentric cam 46 during non-fixing. The heating roller 41 is configured to be rotatable in a direction D opposite to the rotation direction during fixing by a separate driving unit (not shown) even when the heating roller 41 is separated from the pressure roller 42. In addition, the speed at which the heating roller 41 rotates in the opposite direction D is preferably set to a speed slower than that during normal fixing, for example.

[0122] The reverse rotation amount for rotating the heating roller 41 in the opposite direction is obtained by the following formula (1).

[0123] Reversal amount = V(t'-t)+a……(1)

[0124] Here, t is a pre-designed theoretical timing time from when the registration sensor 201 is turned on to when the exit sensor 204 of the fixing device 40 is turned on, t' is an actual time from when the registration sensor 201 is turned on and when the exit sensor 204 detects that the recording paper 5 is not properly transported to when the image forming device 1 (fixing device 40) is actually stopped (t'>t), V is a transport speed when the recording paper 5 is fixed, and a is an arbitrary value and is set to a distance greater than or equal to the distance at which the user can access the recording paper 5 in the smallest size of the recording paper 5. In addition, the arbitrary value a is set to a different value depending on the size of the recording paper 5.

[0125] When the recording paper 5 is not wound around the periphery of the heating roller 41, the recording paper 5 that has been fixed by the heating roller 41 and the pressure roller 42 is peeled off from the surface of the heating roller 41 by its own rigidity, and the passage of the front end 5a is detected by the outlet sensor 204 of the fixing device 40 arranged on the downstream side of the fixing nip N.

[0126] On the other hand, in the case where the recording paper 5 is wound around the outer periphery of the heating roller 41, as shown in FIG. Figure 3 As shown, the recording paper 5 that has been fixed by the heating roller 41 and the pressure roller 42 is not peeled off from the surface of the heating roller 41 but moves together with the surface of the heating roller 41. When poor transmission of the recording paper 5 is detected, the fixing device 40 stops and the rotation of the heating roller 41 also stops.

[0127] In addition, the theoretical timing time t is pre-stored in the storage unit of the control device. In addition, regarding the actual time t', the control device has a timer function, and can actually measure the time from when the registration sensor becomes turned on and the conveyance failure of the recording paper 5 is detected by the outlet sensor to when the image forming device 1 (fixing device 40) actually stops, or it can be a value set in advance considering a certain degree of margin.

[0128] In the above-mentioned formula (1) for calculating the reverse rotation amount of the heating roller 41, an arbitrary value a is set in any case, and therefore the actual time t' can use a value stored in advance in the storage unit of the control device.

[0129] Furthermore, in the above formula (1) for calculating the reverse rotation amount of the heating roller 41, when the arbitrary value a is too large, as described above, Fig.10 As shown in (b), the recording paper 5 may enter the inside of the apparatus body 1a along the surface of the intermediate transfer belt 21. The arbitrary value a is preferably set to a value that is easily visible to the user when the rear end of the recording paper 5 that has been poorly transported is located near the secondary transfer device 30 and the back cover of the apparatus body 1a is opened.

[0130] Regarding the reverse amount of the heating roller 41, if the value of V(t'-t) in the above formula (1) is not such a large value, the arbitrary value a plays a great role. The arbitrary value a is set so that when the reverse action of the heating roller 41 is completed, the rear end of the recording paper 5 along the conveying direction is located outside the introduction port of the fixing device 40 and upstream of the secondary transfer position along the conveying direction of the recording paper 5.

[0131] <Function of the fixing device>

[0132] In the above structure, in the fixing device involved in this embodiment 1, as described below, compared with the case where the stripping unit is set on the downstream side of the fixing area along the conveying direction of the recording medium, the recording medium wound on the outer peripheral surface of the heating rotating body can be reliably removed, and the stripping unit strips the recording medium wound on the outer peripheral surface of the heating rotating body when the heating rotating body is reversed.

[0133] That is, in the image forming apparatus 1 to which the fixing device 40 according to the first embodiment is applied, Figure 1 As shown in the figure, the toner images of the respective colors formed in the image generating devices 10 (Y, M, C, K) of yellow (Y), magenta (M), cyan (C) and black (K) are secondarily transferred to the recording paper 5 via the intermediate transfer belt 21. The toner images of the respective colors secondarily transferred to the recording paper 5 are conveyed to the fixing device 40 and heated and pressed, thereby being fixed to the recording paper 5.

[0134] At this time, if Figure 3 As shown, the leading end 5a of the recording paper 5 along the conveying direction thereof is detected by the registration sensor 201 disposed on the upstream side of the paper conveying roller pair 54 along the conveying direction. Then, the recording paper 5 is conveyed to the fixing device 40 and subjected to the fixing process, and after being discharged from the fixing device 40, the leading end 5a thereof is detected by the outlet sensor 204 disposed on the downstream side of the fixing device 40 along the conveying direction of the recording paper 5.

[0135] The control device 100 measures the time from when the front end 5a of the recording paper 5 is detected by the registration sensor 201 to when it is detected by the exit sensor 204. If the measured time is not within a preset range, it is determined that a transport failure (paper jam) has occurred in the recording paper 5 and the image forming device 1 is stopped immediately.

[0136] like Fig.12 As shown, when a transport failure (paper jam) of recording paper 5 is detected (step ST101), control device 100 calculates the reverse rotation amount of heating roller 41 of fixing device 40 according to equation (1) (step ST102).

[0137] Then, the control device 100 drives the drive motor 48 to separate the heating roller 41 from the pressure roller 42, thereby releasing the pressure contact state in the fixing nip N (step ST103). Fig.13 Status shown.

[0138] Next, the control device 100 performs a reversing operation to rotate the heating roller 41 in the opposite direction to that during normal fixing by the reversing amount calculated according to the formula (1) (step ST104). In addition, at this time, in the fixing device 40, the halogen lamp 414 of the heating roller 41 is energized, and the heating roller 41 is heated. In this way, compared with the case where the heating is stopped before the rotation in the opposite direction to that during fixing is stopped, by heating the heating roller 41 when the heating roller 41 is reversed, it is possible to prevent the toner image on the recording paper 5 from being solidified and difficult to be peeled off from the heating roller 41.

[0139] Next, the control device 100 displays a message on the display unit of the user interface (not shown) to instruct the user to open the rear cover 80 , thereby causing the user to open the rear cover 80 of the image forming apparatus 1 (step ST105 ).

[0140] Furthermore, users can Figure 4The rear cover 80 of the image forming apparatus 1 is opened as shown, and the recording paper 5 peeled off from the outer periphery of the heating roller 41 of the fixing device 40 and whose rear end is located between the fixing device 40 and the secondary transfer position is manually removed, thereby completing the processing of the recording paper 5 with poor conveyance. Thereafter, the rear cover 80 of the image forming apparatus 1 is closed by the user. In addition, the open and closed state of the rear cover 80 is detected by the control device 100.

[0141] Finally, the control device 100 drives the driving motor 48 to press the heating roller 41 against the pressure roller 42, and executes the required paper jam clearing sequence (step ST106), including cleaning the photosensitive drum 11 of each image generating device 10 (Y, M, C, K) of 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 starts the printing action again.

[0142] Thus, in the fixing device 40 according to the first embodiment, when the recording paper 5 is wound around the outer periphery of the heating roller 41, the recording paper 5 can be reliably peeled off from the surface of the heating roller 41 by the peeling film 49 disposed on the upstream side of the fixing nip N. The state in which the recording paper 5 is peeled off from the surface of the heating roller 41 by the peeling film 49 is shown in FIG. Fig.13 shown.

[0143] Furthermore, in the fixing device 40 involved in the above-mentioned embodiment 1, the reversal amount of the heating roller 41 is set to a value calculated according to the preset formula (1), so that it is possible to reliably prevent the reversal amount of the heating roller 41 from being too large and the recording paper 5 peeled off from the surface of the heating roller 41 from entering the interior of the device body 1a along the surface of the intermediate transfer belt 21.

[0144] [Implementation Method 2]

[0145] Fig.14 1 is a diagram showing a fixing device according to Embodiment 2 of the present invention. In the fixing device according to Embodiment 2, the heating rotating body is reversely rotated and stopped based on the detection result of the detection unit so that the leading end of the recording medium is located in the fixing area.

[0146] Furthermore, in the fixing device according to the second embodiment, the heating rotating body is configured such that the pressing state with the pressing unit is released after the heating rotating body is rotated by the reversing unit in the direction opposite to that during fixing. Alternatively, the heating rotating body may be configured such that the pressing state with the pressing unit is released before the heating rotating body is rotated by the reversing unit in the direction opposite to that during fixing.

[0147] That is, in the fixing device 40 according to the second embodiment of the present invention, the structure is as follows: Fig.14As shown, the peeling film 49 is not provided on the device frame 43 but is provided on the swing arm 44. The peeling film 49 provided on the swing arm 44 is arranged close to the surface of the heating roller 41 so that its front end faces the surface of the heating roller 41 with a small gap therebetween when the heating roller 41 is pressed against the pressure roller 42. Alternatively, the peeling film 49 may be arranged so that its front end contacts the surface of the heating roller 41 with a weak force so that the gap becomes substantially zero.

[0148] Furthermore, in the fixing device 40 according to the second embodiment of the present invention, when the heating roller 41 is reversed, the reverse rotation amount of the heating roller 41 is calculated according to the following formula (1) similarly to the first embodiment.

[0149] Reversal amount = V(t'-t)+a……(1)

[0150] In the fixing device 40 according to the second embodiment of the present invention, Fig.15 (a) Fig.15 As shown in (b), the arbitrary value a of the formula (1) is configured so that the heating roller 41 is reversed and stopped so that the leading end 5a of the recording paper 5 is located at the fixing nip N.

[0151] In the case where the recording paper 5 is wound around the surface of the heating roller 41, as shown in FIG. Figure 3 As shown, the time t at which the leading end of the recording paper 5 should be detected by the exit sensor 204 when the recording paper 5 is not wrapped around the surface of the heating roller 41 is set as a reference.

[0152] In equation (1), the reverse rotation amount of the heating roller 41 is calculated by taking into account the difference between the time t at which the outlet sensor 204 theoretically detects the leading end of the recording paper 5 and the time t′ at which the fixing device 40 actually stops because the outlet sensor 204 does not detect the leading end of the recording paper 5 and a paper jam is detected.

[0153] Therefore, by setting the arbitrary value a of formula (1) to a length equal to the length of the conveying path of the recording paper 5 from the fixing nip N of the fixing device 40 to the outlet sensor 204, when the heating roller 41 is reversed, the front end 5a of the recording paper 5 can be stopped so that it is located at the fixing nip N where the heating roller 41 and the pressure roller 42 are pressed against each other.

[0154] In addition, the positional accuracy of the leading end 5a of the recording paper 5 when conveying the recording paper 5 has an error of about ±2 mm. On the other hand, the fixing nip N of the fixing device 40 generally has a length of 4 mm or more.

[0155] Therefore, in the fixing device 40 according to the second embodiment of the present invention, the reverse rotation amount of the heating roller 41 is calculated according to the above formula (1), so that the leading end 5a of the recording paper 5 can actually be stopped at the fixing nip N when the heating roller 41 is reversed.

[0156] In the above structure, in the fixing device involved in this embodiment 2, as described below, compared with the case where the stripping unit is set on the downstream side of the fixing area along the conveying direction of the recording medium, the recording medium wound on the outer peripheral surface of the heating rotating body can be reliably removed, and the stripping unit strips the recording medium wound on the outer peripheral surface of the heating rotating body when the heating rotating body is reversed.

[0157] That is, in the image forming apparatus 1 to which the fixing device 40 according to the second embodiment is applied, Figure 1 As shown in the figure, the toner images of the respective colors formed in the image generating devices 10 (Y, M, C, K) of yellow (Y), magenta (M), cyan (C) and black (K) are secondarily transferred to the recording paper 5 via the intermediate transfer belt 21. The toner images of the respective colors secondarily transferred to the recording paper 5 are conveyed to the fixing device 40 and heated and pressed, thereby being fixed to the recording paper 5.

[0158] At this time, if Figure 3 As shown, the leading end 5a of the recording paper 5 along the conveying direction thereof is detected by the registration sensor 201 disposed on the upstream side of the paper conveying roller pair 54 along the conveying direction. Then, the recording paper 5 is conveyed to the fixing device 40 and subjected to the fixing process, and after being discharged from the fixing device 40, the leading end 5a thereof is detected by the outlet sensor 204 disposed on the downstream side of the fixing device 40 along the conveying direction of the recording paper 5.

[0159] The control device 100 measures the time from when the front end 5a of the recording paper 5 is detected by the registration sensor 201 to when it is detected by the exit sensor 204. If the measured time is not within a preset range, it is determined that a transport failure (paper jam) has occurred in the recording paper 5 and the image forming device 1 is stopped immediately.

[0160] like Fig.16 As shown, when a transport failure (paper jam) of the recording paper 5 is detected (step ST201), the control device 100 calculates the reverse rotation amount of the heating roller 41 of the fixing device 40 according to the equation (1) (step ST202).

[0161] Here, the reverse rotation amount of the heating roller 41 calculated according to the formula (1) is different from that in the first embodiment, as shown in FIG. Fig.15 As shown in FIG. 5( b ), the front end 5 a of the recording paper 5 is set to stop at the fixing nip N of the fixing device 40 .

[0162] After that, the control device 100 performs a reversing operation (step ST203) to rotate the heating roller 41 in the opposite direction to that during normal fixing by the reversal amount calculated according to equation (1). In addition, at this time, in the fixing device 40, the halogen lamp 414 of the heating roller 41 is energized, and the heating roller 41 is in a heated state.

[0163] Next, the control device 100 drives the drive motor 48 to separate the heat roller 41 from the pressure roller 42 , thereby releasing the pressure-contact state in the fixing nip N (step ST204 ).

[0164] Thereafter, the control device 100 displays a message on the display unit of the user interface (not shown) indicating that the rear cover 80 should be opened, so that the user opens the rear cover 80 of the image forming apparatus 1 (step ST205 ).

[0165] Furthermore, users can Figure 4 Open the rear cover 80 of the image forming apparatus 1 as shown, and remove the Fig.17 As shown, the recording paper 5 peeled from the outer periphery of the heating roller 41 of the fixing device 40 and whose rear end is located between the fixing device 40 and the secondary transfer position is processed, thereby completing the processing of the recording paper 5 with poor conveyance. Thereafter, the rear cover 80 of the image forming apparatus 1 is closed by the user.

[0166] Finally, the control device 100 drives the driving motor 48 to press the heating roller 41 against the pressure roller 42, and executes the required paper jam clearing sequence (step ST206), including cleaning the photosensitive drum 11 of each image generating device 10 (Y, M, C, K) of 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 starts the printing action again.

[0167] Thus, by performing a reversal operation to rotate the heating roller 41 in the opposite direction to that in the normal fixing process by the reversal amount calculated according to the formula (1), Fig.15 As shown in (b), the leading end 5a of the recording paper 5 wound on the surface of the heating roller 41 stops in a state where it is located at the fixing nip N.

[0168] Therefore, in the second embodiment, by extracting Fig.17 As shown, the recording paper 5 whose leading end 5 a stops at the fixing nip N of the fixing device 40 can be easily removed.

[0169] Furthermore, in the second embodiment, when the heat roller 41 is reversed, it is possible to reliably prevent the heat roller 41 from being reversed too much and the recording paper 5 from entering the apparatus body 1 a along the surface of the intermediate transfer belt 21 .

[0170] In addition, when the heating roller 41 is reversed, as shown in FIG. Fig.18 As shown in the related art, the reverse rotation amount of the heating roller 41 is insufficient, so that when the recording paper 5 is removed, a large force is not required to rotate the heating roller 41 and the pressure roller 42 in pressure contact.

[0171] The other structures and functions are the same as those in the above-mentioned embodiment, so their description is omitted.

[0172] Furthermore, in the above-described embodiment, a full-color image forming apparatus is described as the image forming apparatus, but the present invention is not limited thereto and can of course be similarly applied to a monochrome image forming apparatus.

[0173] (Note) (((1)))

[0175] A fixing device, comprising:

[0176] Heating rotating body;

[0177] a pressing unit for pressing the recording medium against the heating rotating body in a fixing area;

[0178] a reversing unit for rotating the heating rotator in a direction opposite to that during fixing when the recording medium is wound around the heating rotator; and

[0179] The peeling unit peels off the recording medium that is relatively close to and wrapped around the outer peripheral surface of the heating rotating body at the upstream side of the fixing region in the conveying direction of the recording medium when the heating rotating body is reversed. (((2)))

[0181] The fixing device according to (((1))), wherein:

[0182] A detection unit for detecting passage of the recording medium is provided on the downstream side of the fixing area in the conveying direction of the recording medium. (((3)))

[0184] The fixing device according to (((2))), wherein:

[0185] The winding amount of the recording medium wound around the heating rotating body is determined based on the detection result of the detection unit. (((4)))

[0187] The fixing device according to (((1))), wherein:

[0188] The peeling unit is moved relatively close to the outer peripheral surface of the heating rotator by the movement of the heating rotator. (((5)))

[0190] The fixing device according to (((2))), wherein:

[0191] The heating rotator is reversed and stopped based on the detection result of the detection unit so that the leading end of the recording medium is located in the fixing area. (((6)))

[0193] The fixing device according to (((5))), wherein:

[0194] The heating rotating body releases the pressurized state with the pressurizing unit before the heating rotating body is rotated by the reversing unit in the direction opposite to that during fixing. (((7)))

[0196] The fixing device according to (((5))), wherein:

[0197] The heating rotating body is released from the pressurizing state by the pressurizing unit after being rotated by the reversing unit in the direction opposite to that during fixing. (((8)))

[0199] The fixing device according to (((5))), wherein:

[0200] The heating rotator stops heating after the rotation in the direction opposite to that during fixing stops. (((9)))

[0202] An image forming device comprising:

[0203] an image forming unit that forms an image on a recording medium; and

[0204] a fixing unit, fixing the image on the recording medium,

[0205] As the fixing unit, the fixing device described in any one of (((1))) to (((8))) is used.

[0206] According to the fixing device involved in (((1))), compared with the case where the stripping unit is arranged on the downstream side of the fixing area along the conveying direction of the recording medium, the recording medium wound on the outer peripheral surface of the heating rotating body can be reliably removed, and the stripping unit strips the recording medium wound on the outer peripheral surface of the heating rotating body when the heating rotating body is reversed.

[0207] According to the fixing device according to (((2))), winding of the recording medium can be detected more reliably than in a case where no detection unit is provided.

[0208] According to the fixing device of (((3))), the winding amount of the recording medium can be detected with high accuracy compared to a case where the winding amount of the recording medium is determined based on a value other than the detection result of the detection unit.

[0209] According to the fixing device according to (((4))), compared with the case where the peeling unit is moved, the moving unit of the peeling unit can be omitted.

[0210] According to the fixing device of (((5))), compared with a case where the leading end of the recording medium is not stopped in the fixing area, it is possible to avoid excessive reverse conveyance of the recording medium.

[0211] According to the fixing device of (((6))), the peeling unit can be easily brought close to the heating rotating body, compared with a case where the pressing state is released after the heating rotating body is reversed.

[0212] According to the fixing device according to (((7))), the winding of the recording medium can be reliably released compared to the case where the pressurized state is released before the heating rotating body is reversed.

[0213] According to the fixing device of (((8))), compared with a case where heating is stopped before the heating rotating body stops rotating in the direction opposite to that during fixing, the image on the recording medium can be prevented from being cured and being difficult to be peeled off from the heating rotating body.

[0214] According to the image forming device involved in (((9))), the recording medium wound around the outer peripheral surface of the heating rotating body can be reliably removed compared to the case where the fixing device described in any one of (((1))) to (((8))) is not used as the fixing unit.

[0215] The above-mentioned embodiments of the present invention are provided for the purpose of illustration and description. In addition, the embodiments of the present invention do not fully and exhaustively include the present invention, and do not limit the present invention to the disclosed methods. Obviously, various modifications and changes are self-evident to those skilled in the art to which the present invention belongs. The present embodiment is selected and described in order to most easily understand the principles of the present invention and its application. Thus, other technicians in the art can understand the present invention through various variations optimized for specific uses assumed to be various embodiments. The scope of the present invention is defined by the above claims and their equivalents.

[0216] Explanation of symbols

[0217] 1-image forming device, 5-recording paper, 40-fixing device, 41-heating roller, 42-pressing roller, 49-peeling film, 100-control device, N-fixing nip portion.

Claims

1. A fixing device comprising: Heating rotating body; a pressing unit for pressing the recording medium against the heating rotating body in a fixing area; a reversing unit for rotating the heating rotator in a direction opposite to that during fixing when the recording medium is wound around the heating rotator; and The peeling unit peels off the recording medium that is relatively close to and wrapped around the outer peripheral surface of the heating rotating body at the upstream side of the fixing region in the conveying direction of the recording medium when the heating rotating body is reversed.

2. The fixing device according to claim 1, wherein: A detection unit for detecting passage of the recording medium is provided on the downstream side of the fixing area in the conveying direction of the recording medium.

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

4. The fixing device according to claim 1, wherein: The peeling unit is moved relatively close to the outer peripheral surface of the heating rotator by the movement of the heating rotator.

5. The fixing device according to claim 2, wherein: The heating rotator is reversed and stopped based on the detection result of the detection unit so that the leading end of the recording medium is located in the fixing area.

6. The fixing device according to claim 5, wherein: The heating rotating body releases the pressurized state with the pressurizing unit before the heating rotating body is rotated by the reversing unit in the direction opposite to that during fixing.

7. The fixing device according to claim 5, wherein: The heating rotating body is released from the pressurizing state by the pressurizing unit after being rotated by the reversing unit in the direction opposite to that during fixing.

8. The fixing device according to claim 5, wherein: The heating rotator stops heating after the rotation in the direction opposite to that during fixing stops.

9. An image forming apparatus comprising: an image forming unit that forms an image on a recording medium; and a fixing unit, fixing the image on the recording medium, As the fixing unit, the fixing device according to any one of claims 1 to 8 is used.

Images