JP2008033068A - Fixing device and image forming apparatus equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device capable of suppressing image quality deterioration. <P>SOLUTION: The image fixing part (fixing device) 14 includes: a fixing roller 30 to fix a toner image that was transferred to a paper P on the paper P, also, to convey the paper P along a prescribed conveying path; a separating mechanism 50 provided on the downstream side of the conveying path of the fixing roller 30 so as to separate the paper P from the fixing roller 30. The separating mechanism 50 includes: a separating pawl 70 having a leading end part 71 that comes in contact with the circumferential surface of the fixing roller 30 to separate the paper P from the fixing roller 30; and a roller member 80 arranged so that it may project over the leading end part 71 toward the conveying path on the downstream side of the conveying path, to guide the paper P to the downstream side of the conveying path while rotating in contact with the paper P separated from the fixing roller 30. The leading end part 71 has a prescribed width in the rotating axis direction of the fixing roller 30, and the roller member 80 is positioned in an extension area R extending from the leading end part 71 in width along the downstream side of the conveying path. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fixing device for fixing a toner image transferred onto a sheet to the sheet, and an image forming apparatus including the same.

  Conventionally, there has been known an image forming apparatus configured to develop an electrostatic latent image on the surface of a photosensitive drum with toner to form a toner image and transfer the toner image onto a sheet to obtain an output image. There is known a fixing device that is provided in the image forming apparatus and fixes a toner image transferred onto a sheet to the sheet.

  This conventional fixing device includes a fixing roller that heats the paper, and a pressure roller that forms a nip region together with the fixing roller and presses the paper against the fixing roller. The sheet thus heated may be wound around the fixing roller by being sent out from the nip region between the two rollers while being attached to the fixing roller. In order to prevent the paper from being wound, the fixing device is generally provided with a separation claw for separating the paper from the fixing roller. The separation claw is disposed in the vicinity of the exit of the nip region and has a function of guiding the paper separated from the fixing roller to the downstream side of the conveyance path.

  However, as described above, when the paper is separated and guided by the separation claw, the image formed on the paper may be scratched by the separation claw. This is because the separation claw that is constantly in contact with the fixing roller becomes hot, and the toner on the paper melts (remelts) when the paper comes into contact with the high-temperature separation claw for a predetermined time.

  As a means for solving this inconvenience, for example, the paper separated from the fixing roller by the separation claw is switched from the separation claw on a guide member disposed at a position relatively close to the separation position (tip of the separation claw). A technique is known in which the guide member guides the transport path downstream. The guide member is provided separately from the separation claw and is held at a temperature lower than that of the separation claw. Therefore, when the paper contacts the guide member for a predetermined time, melting of the toner on the paper is suppressed. The

  However, in the above configuration, since the guide member needs to be arranged near the exit of the nip region between both rollers, the sheet fed from the nip region is conveyed in a state where it is strongly pressed against the guide member by its elasticity (elasticity). May be. As a result, there is an inconvenience that image rubbing (guide trace) occurs on the image surface of the paper.

Therefore, as a countermeasure against such image rubbing, a technique for guiding the paper separated from the fixing roller to the downstream side of the conveyance path with a rotatable roller or the like has been proposed (for example, see Patent Document 1). Patent Document 1 discloses a fixing device in which a roller member is attached to the outer side of a separation claw protection member that is disposed so as to sandwich the separation claw from both sides and swings together with the separation claw. The separation claw protection member rotates in a direction away from the fixing roller together with the separation claw when the paper is jammed, thereby preventing the separation claw and the fixing roller from being damaged due to the separation claw being excessively pressed against the fixing roller. ing. In addition, the paper separated from the fixing roller by the separation claw is configured to be guided to the roller member without contacting the separation claw protection member, thereby preventing image rubbing from occurring on the paper after fixing. It is preventing.
JP 2004-61854 A

  However, in the conventional fixing device as disclosed in Patent Document 1, since the roller member 280 is provided on the side of the separation claw 270 as shown in FIG. The paper P separated from the paper is conveyed while facing the separation claw 270. As a result, for example, when the paper P separated from the fixing roller undergoes a waving phenomenon or a reverse phenomenon, and a force is applied to displace the paper P in the direction approaching the separation claw 270, the separation claw 270 and the paper P Since the image surface (see the dotted line in FIG. 8) easily contacts, there is a disadvantage that the paper P is scratched by the separation claw 270. As a result, there is a problem that the image quality is degraded.

  SUMMARY An advantage of some aspects of the invention is that it provides a fixing device capable of suppressing a reduction in image quality and an image forming apparatus including the fixing device.

  In order to achieve the above object, a fixing device according to a first aspect of the present invention fixes a toner image transferred onto a sheet onto the sheet, and conveys the sheet along a predetermined conveyance path. And a separation mechanism provided on the downstream side of the conveyance path of the fixing roller and separating the paper from the fixing roller, wherein the separation mechanism contacts the peripheral surface of the fixing roller and the fixing A claw member having a leading end portion for separating the paper from the roller, and a protrusion projecting into the transport path at a position downstream of the leading end portion with respect to the transport path, contacting the paper separated from the fixing roller A rotating member that guides the sheet to the downstream side of the conveyance path while rotating the sheet, the leading end portion having a predetermined width in the rotation axis direction of the fixing roller, and the rotating member is a width of the leading end portion. And it is located in the extension area formed by extending along the conveying path downstream.

  In the fixing device according to the first aspect, as described above, the rotating member that protrudes to the conveyance path at a position downstream of the conveyance path from the front end of the claw member is disposed on the downstream side of the conveyance path. The rotating member can be disposed between the paper separated from the fixing roller by the tip portion and the claw member by being positioned in the extended region that extends along, for example, the paper separated from the fixing roller. When a phenomenon or a reverse phenomenon occurs and a force is applied to displace the paper in the direction approaching the claw member, the paper is difficult to contact the claw member. As a result, it is possible to prevent the occurrence of inconvenience that the paper separated from the fixing roller comes into contact with the claw member again and scratches are formed on the paper, so that deterioration in image quality can be sufficiently suppressed. .

  In the fixing device according to claim 1, preferably, the claw member has a width substantially equal to a width of the tip portion and extends to a downstream side of the transfer path of the tip portion; A hollow portion formed in the body portion so as to face the path, and the rotating member is disposed so as to enter the hollow portion. If comprised in this way, since a hollow part will be located in the extension area | region formed by extending the width | variety of a front-end | tip part along a conveyance path | route downstream, a rotating member can be easily located in the said extension area | region. Can do.

  In the fixing device according to claim 1 or 2, preferably, the hollow portion is formed near a center of the body portion in a rotation axis direction of the fixing roller. With this configuration, the rotating member can be arranged near the center of the claw member in the direction of the rotation axis of the fixing roller, so that when a force is applied to the paper in a direction in which the paper is close to the claw member. However, the paper is more difficult to contact the claw member.

  The fixing device according to any one of claims 1 to 3, preferably further comprising a holder member that holds the claw member, the holder member extending along a predetermined direction, and the claw member A first holding portion that holds the rotating member in a fixed manner, and a second holding portion that extends along the predetermined direction and holds the rotating member in the vicinity of the claw member, the rotating member being The second holding part is held by the second holding part in a state having a predetermined play in the extending direction of the second holding part so as to be separable from the claw member. If comprised in this way, a claw member will contact suitably from the extension direction of a 2nd holding | maintenance part with respect to a rotation member by said "play", for example, but a rotation member and a claw member are a non-contact state intermittently Therefore, it is possible to suppress the temperature of the rotating member from rising excessively while preventing the rotating member from falling off the second holding portion.

  In the fixing device according to any one of claims 1 to 4, it is preferable that at least a surface of the rotating member is made of a fluororesin (claim 5). The rotating member configured in this manner has excellent heat resistance and a low coefficient of friction against the paper. Examples of the fluororesin constituting the rotating member include tetrafluoroethylene / perfluoroalkoxyethylene copolymer (PFA) and tetrafluoroethylene resin (PTFE).

  According to a sixth aspect of the present invention, there is provided an image forming apparatus according to any one of the first to fifth aspects, wherein an image forming unit that transfers a toner image onto a sheet and the toner image transferred by the image forming unit are fixed on the sheet by heating. The fixing device according to claim 1 is provided.

  In the image forming apparatus according to the sixth aspect, as described above, the toner image transferred to the sheet by the image forming unit is fixed to the sheet by using the fixing device capable of sufficiently suppressing the deterioration of the image quality. Therefore, it is possible to easily form a high quality image while suppressing a decrease in image quality.

  According to the fixing device and the image forming apparatus of the present invention, the rotating member can be disposed between the sheet separated from the fixing roller by the leading end portion and the claw member. When a reverse phenomenon or the like occurs and a force for displacing the paper in the direction approaching the claw member is applied, the paper is difficult to contact the claw member. As a result, it is possible to prevent the occurrence of inconvenience that the paper separated from the fixing roller comes into contact with the claw member again and scratches are formed on the paper, so that deterioration in image quality can be sufficiently suppressed. .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional front view illustrating an overall configuration of a printer according to an embodiment of the present invention, and FIG. 2 is a front view illustrating a configuration of an image fixing unit of the printer illustrated in FIG. 3 to 6 are diagrams showing the separation mechanism of the image fixing unit shown in FIG. 2, and FIG. 7 shows the state of the paper guided by the roller member of the separation mechanism shown in FIG. FIG. First, an overall configuration of a printer 10 according to an embodiment of the present invention will be described with reference to FIG. In this embodiment, a case where the printer 10 is used as an example of the image forming apparatus of the present invention will be described.

  As shown in FIG. 1, the printer 10 according to the present embodiment feeds out one sheet at a time from a sheet storage unit 12 that stores and stacks sheets P to be printed and a sheet bundle stored in the sheet storage unit 12. The image forming unit 13 that performs image transfer processing on the sheet P and the image fixing unit 14 that performs fixing processing on the sheet P subjected to transfer processing by the image forming unit 13 are provided inside the apparatus main body 11. In addition, a paper discharge unit 15 for discharging the paper P subjected to the fixing process by the image fixing unit 14 is provided in the upper part of the apparatus main body 11. The image fixing unit 14 is an example of the “fixing device” in the present invention.

  The paper storage unit 12 includes a paper cassette 121 that can be attached to and detached from the apparatus main body 11 and that can store a plurality of paper P in a stacked manner. In addition, a pair of pickup rollers 122 for feeding out the paper P one by one from the paper bundle loaded in the paper cassette 121 is provided at the upper right end of the paper cassette 121 in the figure. Then, the sheet P fed out of the sheet cassette 121 by driving the pickup roller 122 is fed to the image forming section via the sheet feed conveyance path 123 and the registration roller pair 124 disposed at the downstream end of the sheet feed conveyance path 123. 13 is configured to be fed.

  The image forming unit 13 has a function of performing a transfer process on the paper P based on image information transmitted from a computer or the like (not shown), and has an axial center extending in the front-rear direction (a direction orthogonal to the paper surface of FIG. 1). A photosensitive drum 131 rotatably provided on the photosensitive drum 131, and a charger 132, an exposure device 133, and a charger 132 arranged in order clockwise from a position immediately above the photosensitive drum 131 along the circumferential surface of the photosensitive drum 131. The developing device 134, the transfer device 135, the transport belt 136, the cleaning device 137, and the static eliminator 138 are configured.

  The photosensitive drum 131 has an amorphous silicon layer laminated on the peripheral surface thereof, and is configured to easily form an electrostatic latent image and a toner image along the electrostatic latent image on the peripheral surface. ing.

  The charger 132 has a function of forming a uniform charge on the circumferential surface of the photosensitive drum 131 that rotates clockwise. In the example shown in FIG. 1, the charging device 132 is formed on the circumferential surface of the photosensitive drum 131 by corona discharge. A method of applying electric charge is used. In place of the charger 132, a charging roller that applies a charge by rotating the peripheral surface in contact with the peripheral surface of the photosensitive drum 131 is used instead of the charger 132 as a member that applies a charge to the peripheral surface of the photosensitive drum 131. May be.

  The exposure device 133 irradiates the circumferential surface of the rotating photosensitive drum 131 with a laser beam whose intensity is adjusted based on image data transmitted from an external device such as a computer, and the photosensitive drum 131 is rotated by the laser beam. It has a function of forming an electrostatic latent image on the peripheral surface of the photosensitive drum 131 by erasing the charge on the surface irradiated with the laser beam.

  The developing device 134 supplies toner to the peripheral surface of the photosensitive drum 131 to attach the toner to the portion where the electrostatic latent image is formed on the peripheral surface, and thereby the toner image is formed on the peripheral surface of the photosensitive drum 131. It has the function to form.

  The transfer device 135 applies a positively charged toner image formed on the peripheral surface of the photosensitive drum 131 to the paper P with respect to the paper P sent to the position immediately below the photosensitive drum 131 by driving the registration roller pair 124. It has a function of transferring, and is configured to impart a negative charge having a polarity opposite to that of the toner image to the paper P.

  The conveyance belt 136 conveys the paper P subjected to the transfer process by the transfer unit 135 toward the image fixing unit 14, and includes a driving roller 135a disposed on the transfer unit 135 side and an image fixing unit 14 side. It is stretched between the arranged driven rollers 135b. The transport belt 136 is driven to rotate in synchronism with the rotation of the photosensitive drum 131, so that the paper P is transported toward the fixing unit 14. Therefore, the sheet P that has reached the position immediately below the photosensitive drum 131 is directed toward the surface of the sheet P on which the toner image on the circumferential surface of the photosensitive drum 131 that is positively charged by the transfer unit 135 and the photosensitive drum 131 is negatively charged. Thus, after the transfer process is performed on the sheet P, the sheet P is fed toward the image fixing unit 14 by the circumferential driving of the conveyance belt 136.

  The cleaning device 137 is provided to remove and clean the toner remaining on the peripheral surface of the photosensitive drum 131 after the transfer process.

  The static eliminator 138 erases the charge remaining on the peripheral surface of the photosensitive drum 131. The peripheral surface of the photosensitive drum 131 from which the charge has been erased by the static eliminator 138 is subjected to the next image forming process. Therefore, it goes to the charger 132 again.

  The image fixing unit 14 performs a fixing process by heating the toner image on the sheet P while conveying the sheet P subjected to the transfer process by the image forming unit 13 along a predetermined conveyance path. A paper discharge conveyance path 141 is provided on the downstream side of the conveyance path of the image fixing unit 14, and the fixed paper P is discharged to the paper discharge unit 15 through the paper discharge conveyance path 141.

  The paper discharge unit 15 has a paper discharge tray 151 whose upper surface is formed in an arc shape, and the paper P discharged through the paper discharge conveyance path 141 is stacked on the paper discharge tray 151. Become.

  Next, the configuration of the image fixing unit 14 according to the present embodiment will be described in detail with reference to FIGS.

  As shown in FIG. 2, the image fixing unit 14 includes a fixing (heat) roller 30 capable of generating heat, and pressure (press) disposed below the fixing roller 30 so that the peripheral surface of the fixing roller 30 faces each other. ) The roller 40 and the housing 21 are provided. Then, the sheet P after the transfer process passes through the nip region N between the fixing roller 30 that is driven to rotate clockwise and the pressure roller 40 that is driven to rotate counterclockwise, thereby being heated from the fixing roller 30. Is given to the fixing process.

  The fixing roller 30 includes an outer cylinder 31 formed by coating a peripheral surface of a metal cylinder with a predetermined material, and a heat source (not shown) including, for example, a halogen lamp built in the outer cylinder 31. )). The outer cylinder 31 has an annular gear (not shown) fixed to one end thereof, and a drive rotation of a motor (not shown) installed at an appropriate position outside the housing 21 is annularly connected via a gear mechanism or the like. By being transmitted to the gear, the outer cylindrical body 31 is configured to be driven and rotated around the axis.

  The pressure roller 40 includes a cylindrical pressure roller body 41 and a pressure roller shaft 42 that is disposed concentrically with the pressure roller body 41 and penetrates the end wall of the pressure roller body 41. I have. In the nip region N, the pressure roller 40 is pressed against the peripheral surface of the outer cylindrical body 31 of the fixing roller 30 by an urging force of an urging means (not shown), and rotates in accordance with the driving rotation of the fixing roller 30. It is configured as follows.

  In such an image fixing unit 14, four sheets for separating the paper P to be wound around the peripheral surface of the fixing roller 30 from the peripheral surface of the fixing roller 30 (see FIG. 3) is arranged in parallel in the axial direction of the fixing roller 30 at a predetermined interval. As shown in FIG. 2, a discharge roller pair 142 is provided on the downstream side (left side in the figure) of the separation mechanism 50 to direct the paper P after the fixing process toward the paper discharge conveyance path 141.

  In the image fixing unit 14, the front end of the sheet P passes through the nip region N in the conveyance path from the nip region N between the fixing roller 30 and the pressure roller 40 to the discharge roller pair 142. Until the sheet P is reached, the sheet P is conveyed by the fixing roller 30 and the pressure roller 40, and after the front end of the sheet P reaches the discharge roller pair 142, the rear end of the sheet P passes through the nip region N. In the meantime, the fixing roller 30, the pressure roller 40, and the discharge roller pair 142 are configured to convey the paper P while being synchronized with each other. Further, after the trailing edge of the paper P passes through the nip region N, the paper P is transported only by the discharge roller pair 142.

  As shown in FIG. 2, the separation mechanism 50 is rotated around the holder member 60 rotatably provided around the support shaft 51, the separation claw 70 fixedly held by the holder member 60, and the holder member 60. The roller member 80 is held in a possible manner, and the tension coil spring 52 biases the holder member 60 in a predetermined direction. The separation claw 70 is an example of the “claw member” in the present invention, and the roller member 80 is an example of the “rotating member” in the present invention.

  The holder member 60 is disposed so as to be in a non-contact state with respect to the fixing roller 30 and is configured to include the separation claw 70 and the roller member 80. As shown in FIGS. 4 and 5, the holder member 60 includes a first holder 61 having a male structure and a second holder 62 having a female structure.

  As shown in FIG. 5, the first holder 61 has a side plate 61 a, a protrusion 61 c and a column 61 d formed on the surface of the side plate 61 a facing the second holder 62, and a cylindrical shape formed on the top of the side plate 61 a. The shaft insertion portion 61e. The protruding portion 61c is an example of the “first holding portion” in the present invention, and the support 61d is an example of the “second holding portion” in the present invention.

  The second holder 62 includes a side plate 62a, first engagement holes 62c and second engagement holes 62g formed at positions corresponding to the protrusions 61c and the columns 61d of the side plate 62a, and the shaft insertion portion 61e. And a shaft insertion portion 62e formed on the upper portion of the side plate 62a.

  Further, as shown in FIG. 6, the side plates 61a and 62a are each formed in a horizontally long shape when viewed from the front, and have guide portions 61f and 62f at the lower part on the upstream side of the conveyance path. The guide portion 61f (62f) is provided to smoothly guide the front end of the paper P to the roller member 80 in the conveyance path of the paper P between the separation claw 70 and the roller member 80.

  The protrusion 61c is provided to fix the holders 61 and 62 at a predetermined interval while holding the separation claw 70 in a fixed manner. That is, the protrusion 61c extends in a direction bridging between the side plates 61a and 62a arranged in parallel, and has a rectangular cross-sectional position restricting portion 61i, an opening 72 of a separation claw 70 and a second holder described later. 62 is sequentially press-fitted into the first engagement hole 62c, and is configured by a holding portion 61j having a cross-sectional shape that is slightly smaller than the position restricting portion 61i. When the position restricting portion 61i contacts the separation claw 70, The separation claw 70 is restricted from moving in the direction of the side plate 61 a of the first holder 61 by a predetermined amount or more. As shown in FIG. 4, the separation claw 70 that is press-fitted and held in the holding portion 61j while being regulated by the position regulating portion 61i of the protruding portion 61c is positioned approximately in the middle between the side plates 61a and 62a. .

  As shown in FIGS. 4 and 5, the column 61 d is configured to rotatably hold the roller member 80 in a state where it enters a hollow portion 74 of a separation claw 70 described later. As shown in FIG. 7, the column 61d is inserted into the column insertion hole 75 of the separation claw 70 in a non-contact state with respect to the separation claw 70 fixedly held by the holding unit 61j of the projection 61c. In the tip portion of the column 61d, the second engagement hole 62g of the second holder 62 is engaged. With this configuration, it is possible to suppress heat from being transferred from the separation claw 70 that is in contact with the fixing roller 30 to the roller member 80 via the support column 61d of the holder member 60 for a long time.

  As shown in FIG. 4, the shaft insertion portions 61 e and 62 e are arranged adjacent to each other when the holders 61 and 62 are assembled, and a support shaft 51 that rotatably supports the holder member 60. Is to be inserted. A hook portion 61k for attaching one end of the tension coil spring 52 (see FIG. 2) is integrally formed on the upper portion of the shaft insertion portion 61e.

  Such holder member 60 is preferably made of a heat resistant resin having excellent heat resistance, such as polyether ketone (PEK), polyimide (PI), and polyphenylene sulfide (PPS).

  As shown in FIGS. 4 to 6, the separation claw 70 is provided to separate the paper P from the fixing roller 30, and has an acute tip 71 that contacts the circumferential surface of the fixing roller 30 (see FIG. 6). And a body part 73 extending downstream of the transport path of the tip part 71. The leading end 71 has a predetermined width in the rotation axis direction of the fixing roller 30. Moreover, the trunk | drum 73 has the width | variety substantially corresponded with the width | variety of the front-end | tip part 71, the opening part 72 (refer FIG. 5) of the front view rectangular shape in which the projection part 61c of the holder member 60 is press-fitted, and a roller. It has the hollow part 74 which can accommodate the member 80, and the support | pillar insertion hole 75 in which the support | pillar 61d of the holder member 60 is inserted. The hollow portion 74 is formed so as to penetrate vertically in the vicinity of the center of the fuselage portion 73 in the rotation axis direction of the fixing roller 30 and extends the width of the tip portion 71 along the downstream side of the conveyance path. It is located within R (see FIG. 4). As shown in FIG. 7, the column insertion hole 75 is formed so as to sandwich the hollow portion 74 and has an inner diameter larger than the outer diameter of the column 61 d, so that the column insertion hole 75 can be inserted into the column insertion hole 75. It is comprised so that it may be in a non-contact state with the made support | pillar 61d.

  Further, as described above, the separation claw 70 is positioned and disposed so as to be positioned approximately in the middle of the side plates 61 a and 62 a of the holders 61 and 62, and the distal end portion 71 conveys the holder member 60. It is arranged so as to protrude from the end portion on the upstream side of the path (right side in the figure) toward the outside (the peripheral surface of the fixing roller 30). The leading end 71 abuts the peripheral surface of the fixing roller 30 by the tension of the tension coil spring 52 at a position spaced apart from the end of the nip region N on the downstream side in the conveyance direction (hereinafter referred to as the nip region outlet). ing.

  Such separation claw 70 is preferably configured such that at least the surface thereof is made of a fluororesin having higher heat resistance than the constituent material of the holder member 60. For example, the holder member 60 is made of polyphenylene sulfide (PPS). ), The surface of the separation claw 70 is preferably coated with a tetrafluoroethylene / perfluoroalkoxyethylene copolymer (PFA).

  The roller member 80 is configured to contact the sheet P separated from the fixing roller 30 and guide the sheet P to the downstream side of the conveyance path while rotating the sheet P. As shown in FIG. 5, the roller member 80 is inserted into the shaft hole 81 in a state of entering the hollow portion 74 of the separation claw 70, so that a part of the peripheral surface of the roller member 80 is the holder member 60. The holder member 60 is rotatably held in a state protruding from the lower part toward the external conveyance path (see FIG. 6). Further, as shown in FIG. 7, the roller member 80 in the hollow portion 74 is held by the column 61d in a state having predetermined play in the protruding direction of the column 61d so as to be separated from the separation claw 70. Yes. The roller member 80 of the present embodiment configured as described above is located in the extension region R (see FIG. 4) on the downstream side of the transport path from the front end portion 71, and is separated from the fixing roller 30 by the front end portion 71. The sheet P is arranged between the separated paper P and the separation claw 70.

  Such a roller member 80 has a surface coated with a fluororesin such as tetrafluoroethylene / perfluoroalkoxyethylene copolymer (PFA), tetrafluoroethylene resin (PTFE), etc., and has excellent heat resistance. And a low coefficient of friction against the paper P. Thereby, when the roller member 80 guides the paper P to the downstream side of the transport path while rotating, the physical load applied to the image of the paper P can be extremely reduced. In addition, you may comprise the roller member 80 whole with the said fluororesin.

  As shown in FIG. 2, the tension coil spring 52 is provided to urge the holder member 60 so that the tip 71 of the separation claw 70 contacts the peripheral surface of the fixing roller 30. The end is engaged with a locking portion 21 a formed on the casing 21 of the image fixing portion 14. By rotating the holder member 60 in a predetermined direction (counterclockwise direction in the illustrated example) by the tension of the tension coil spring 52, the tip 71 of the separation claw 70 is pressed against the peripheral surface of the fixing roller 30. Yes.

  In the image fixing unit 14 including the separation mechanism 50 configured as described above, the front end of the paper P separated from the fixing roller 30 by the separation claw 70 is guided by the separation claw 70 in the vicinity of the front end portion 71 of the separation claw 70. At the same time, it is guided by guide portions 61f and 62f of the holder member 60 on the downstream side from a position spaced a predetermined distance from the distal end portion 71 to the downstream side of the transport path, and further guided by the peripheral surface of the roller member 80 on the downstream side of the transport path. The That is, the member that guides the front end of the paper P is sequentially switched (switched) to the separation claw 70, the guide portion 61 f (62 f) of the holder member 60, and the roller member 80 as it goes downstream in the conveyance path. It has become.

  Further, when the front end of the paper P is guided by the guide portion 61f (62f), the paper P bridges between the nip region outlet and the guide portion 61f (62f), so that the paper P contacts the separation claw 70. Never do. Further, when the front end of the paper P reaches the roller member 80 and the paper P is guided by the peripheral surface of the roller member 80, the paper P bridges between the nip region outlet and the peripheral surface of the roller member 80. Therefore, the paper P does not contact the guide portion 61f (62f) and the separation claw 70. In particular, in this embodiment, the roller member 80 is disposed between the paper P separated from the fixing roller 30 and the separation claw 70. Even if a force that displaces the paper P in a direction approaching the separation claw 70 is applied, the paper P does not contact the separation claw 70.

  In addition, since the holder member 60 and the separation claw 70 are formed of separate members, the holder member 60 is lower than the separation claw 70 even when the separation claw 70 becomes high temperature due to contact with the fixing roller 30. The roller member 80 that is held at a temperature and is rotatably attached to the holder member 60 is held at a lower temperature than the holder member 60.

  In the present embodiment, as described above, the roller member 80 that projects into the conveyance path at a position downstream of the leading end portion 71 of the separation claw 70 is disposed along the downstream side of the conveying path. Since the roller member 80 can be disposed between the sheet P separated from the fixing roller 30 by the leading end portion 71 and the separation claw 70 by being positioned in the extended region R formed by extension, for example, from the fixing roller 30 When a wave phenomenon or a reverse phenomenon occurs in the separated paper P and a force that displaces the paper P in a direction approaching the separation claw 70 is applied, the paper P is difficult to contact the separation claw 70. As a result, it is possible to prevent the occurrence of inconvenience that the paper P separated from the fixing roller 30 comes into contact with the separation claw 70 again to form scratches on the paper P, so that deterioration in image quality is sufficiently suppressed. can do.

  Further, in the present embodiment, as described above, the roller member 80 is supported by the support column 61d in a state where the roller member 80 is inserted into the hollow portion 74 formed in the body portion 73 having a width that substantially matches the width of the tip portion 71. As a result, the hollow portion 74 is positioned in the extension region R formed by extending the width of the tip end portion 71 along the downstream side of the conveyance path, so that the roller member 80 is easily positioned in the extension region R. be able to.

  In the present embodiment, as described above, the hollow portion 74 is formed in the vicinity of the center of the body portion 73 in the rotation axis direction of the fixing roller 30, whereby the roller member 80 is rotated around the rotation shaft of the fixing roller 30 of the separation claw 70. Since the sheet P can be arranged near the center of the direction, even when a force that displaces the sheet P in the direction close to the separation claw 70 is applied to the sheet P, the sheet P becomes more difficult to contact the separation claw 70.

  Further, in the present embodiment, as described above, the roller member 80 is held by the support column 61d in a state having predetermined play in the extending direction of the support column 61d so as to be separated from the separation claw 70. By configuring, the roller member 80 appropriately comes into contact with the separation claw 70 from the direction in which the column 61d extends, while the roller member 80 and the separation claw 70 are intermittently in a non-contact state. It is possible to suppress the temperature of the roller member 80 from excessively rising while preventing the drop from 61d. Thereby, the influence which the roller member 80 has on the image of the paper P can be reduced while suppressing an increase in the number of parts.

  Further, in the present embodiment, as described above, the holder member 60 is disposed so as to be in a non-contact state with respect to the fixing roller 30, and the sheet of the guide portion 61 f (62 f) is in an operating state of the printer 10. By configuring the temperature of the contact portion with P to be lower than the temperature of the contact portion of the separation claw 70 with the paper P, the paper P separated from the fixing roller 30 by the separation claw 70 is separated from the separation claw 70. Since the guide part 61f (62f) of the holder member 60 having a temperature lower than that of the switch 70 can be switched and guided to the downstream side of the transport path by the guide part 61f (62f), the sheet P can be separated by a high temperature. The time for contact with can be reliably shortened. Thereby, the toner on the paper P separated from the fixing roller 30 can be prevented from melting (remelting).

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes all modifications within the meaning and scope equivalent to the scope of claims for patent.

  For example, in the above-described embodiment, an example in which the present invention is applied to the printer 10 including the image fixing unit 14 has been described. However, the present invention is not limited to this, and a copying machine or a facsimile other than the printer including the image fixing unit 14 may be used. The present invention can also be applied to an image forming apparatus.

1 is a cross-sectional front view illustrating an overall configuration of a printer according to an embodiment of the present invention. FIG. 2 is a front view showing an image fixing unit of the printer shown in FIG. 1. FIG. 3 is a Q direction arrow view showing a fixing roller and a separation mechanism of the image fixing unit shown in FIG. 2. FIG. 3 is a plan view showing a separation mechanism of the image fixing unit shown in FIG. 2. It is the top view which showed the state which decomposed | disassembled the separation mechanism shown in FIG. FIG. 3 is a front view showing a separation mechanism of the image fixing unit shown in FIG. 2. FIG. 7 is a side sectional view illustrating a state of a sheet guided by a roller member of the separation mechanism illustrated in FIG. 6. It is the schematic which showed the state of the paper guided by the roller member of the conventional separation mechanism.

Explanation of symbols

10 Printer (image forming device)
13 Image forming unit 14 Image fixing unit (fixing device)
30 Fixing roller 50 Separating mechanism 60 Holder member 61c Protruding part (first holding part)
61d Post (second holding part)
70 Separation claw (claw member)
71 Front end portion 73 Body portion 74 Hollow portion 80 Roller member (rotating member)
P Paper R Extension area

Claims (6)

A toner image transferred to a sheet is fixed on the sheet, and a fixing roller that conveys the sheet along a predetermined conveyance path, and a conveyance path downstream side of the fixing roller, and the sheet is removed from the fixing roller. A fixing device including a separation mechanism for separating;
The separation mechanism is
A claw member having a tip portion that contacts the peripheral surface of the fixing roller and separates the sheet from the fixing roller;
Rotation that is arranged so as to protrude into the conveyance path at a position downstream of the leading end portion, and that guides the conveyance path downstream while contacting the sheet separated from the fixing roller and rotating the sheet. Including members,
The tip portion has a predetermined width in the rotation axis direction of the fixing roller,
The fixing device according to claim 1, wherein the rotating member is positioned in an extension region formed by extending a width of the tip portion along a downstream side of the conveyance path. The claw member is
A trunk portion having a width substantially matching the width of the tip portion and extending downstream of the tip portion in the transport path;
A hollow part formed in the body part in a mode facing the transport path,
The fixing device according to claim 1, wherein the rotating member is disposed so as to enter the hollow portion.   The fixing device according to claim 1, wherein the hollow portion is formed near a center of the body portion in a rotation axis direction of the fixing roller. A holder member for holding the claw member;
The holder member is
A first holding portion that extends along a predetermined direction and holds the claw member fixedly;
A second holding portion that extends along the predetermined direction and holds the rotating member rotatably in the vicinity of the claw member;
The said rotating member is hold | maintained at the said 2nd holding | maintenance part in the state which has predetermined play in the extension direction of the said 2nd holding | maintenance part so that separation | spacing with respect to the said nail | claw member was possible. The fixing device according to any one of 1 to 3.   The fixing device according to claim 1, wherein at least a surface of the rotating member is made of a fluororesin. An image forming unit for transferring a toner image onto paper;
An image forming apparatus comprising: the fixing device according to claim 1, wherein the toner image transferred by the image forming unit is fixed on the sheet by heating.

Images