JP4680725B2 - Fixing device - Google Patents

Description

  The present invention relates to a fixing device for fixing a toner image transferred onto a sheet to the sheet.

  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 rotation member is attached to a separation claw protection member that swings 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, so that the separation claw and the fixing roller are prevented from being excessively pressed against the fixing roller and being damaged. ing. In addition, the paper separated from the fixing roller by the separation claw is configured to be guided to the rotating member without coming into contact with the separation claw protection member, thereby preventing image rubbing from occurring on the paper after fixing. It is preventing.
JP 2004-61854 A

  However, since the above-mentioned Patent Document 1 does not disclose a member that actively guides the paper separated by the separation claw toward the rotating member, for example, as shown in FIG. 8 as a comparative example, When the separation claw 70 and the roller member (rotating member) 80 are arranged in such a positional relationship that the conveyance direction of the paper P changes greatly, the paper P gently contacts the peripheral surface of the roller member 80. It is difficult to do so, and a large load is applied to the paper P. For this reason, a bridge phenomenon called “return” due to the stiffness (elasticity) of the paper P occurs, and there is a disadvantage that the bridge portion of the paper P abuts against the separation claw 70. As a result, scratches due to the separation claws are generated on the paper, which causes a problem that the image quality is deteriorated.

  SUMMARY An advantage of some aspects of the invention is that it provides a fixing device capable of suppressing deterioration in image quality regardless of the device configuration, paper quality, and the like. .

In order to achieve the above object, a fixing device according to claim 1 of the present invention fixes a toner image transferred onto a sheet to the sheet, and also fixes a fixing roller that conveys the sheet along a predetermined conveyance path; In the fixing device including a separating unit that separates the sheet from the fixing roller, the separating unit includes a claw member that contacts the peripheral surface of the fixing roller and separates the sheet from the fixing roller, a holder member that holds the claw member, First and second rotating members that are rotatably held by the holder member and guide the sheet separated from the fixing roller to the downstream side of the conveyance path while rotating, the holder member having a first side plate. 1 holder and the 2nd holder which has the 2nd side board which arranges the 1st side board at predetermined intervals, and is constituted, and the claw member is arranged between the 1st side board and the 2nd side board. The first A first holding part extending from the plate or the second side plate, and the first rotating member is disposed between the first side plate and the claw member and extends from the first side plate. The second holding member is rotatably held by the second holding portion, and the second rotating member is disposed between the second side plate and the claw member, and is extended by the third holding portion extending from the second side plate. The first side plate and the second side plate are rotatably held, and the sheet is transferred to the first and second rotating members in a conveyance path between the claw member and the first or second rotating member , respectively . It has the guide part which guides.

  In the fixing device according to the first aspect, as described above, by providing the guide portion that guides the paper to the rotating member in the conveyance path between the claw member and the rotating member, the paper separated from the fixing roller is provided. Since it can be actively guided to the rotating member by the guide portion, even if the claw member and the rotating member are arranged in a positional relationship that greatly changes the transport direction (path) of the separated paper, By gently switching the paper guiding member from the claw member to the rotating member via the guide portion, the paper can be smoothly brought into contact with the peripheral surface of the rotating member while suppressing a large change in the paper transport direction. Can do. In addition, by providing a guide portion in the conveyance path between the claw member and the rotating member, the paper separated from the fixing roller can be separated from the claw member on the guide portion of the holder member provided separately from the claw member. Since it can be switched and guided to the downstream side of the conveyance path by the guide portion, the contact time of the sheet with the high-temperature claw member contacting the peripheral surface of the fixing roller can be shortened. In addition, a guide portion is provided in the conveyance path between the claw member and the rotating member, and the guide portion is arranged near the tip of the claw member by configuring the guide portion to guide the paper to the rotating member. Even if the separated paper is conveyed while being pressed against the guide portion by its elasticity (elasticity), the rotating member guides the paper while rotating on the downstream side of the conveyance path, so the paper guide portion The degree of contact with can be sufficiently relaxed.

In the fixing device according to claim 1, preferably, the guide portion is configured to guide at least a front end of the sheet separated from the fixing roller by the claw member toward the peripheral surfaces of the first and second rotating members. (Claim 2). With this configuration, the front end of the sheet separated from the fixing roller can be actively guided toward the peripheral surface of the rotating member by the guide portion, so that the claw member and the guide portion are in contact with each other after separation. The load applied to the front end of the paper can be reduced by smoothly bringing the front end of the conveyed paper into contact with the peripheral surface of the rotating member.

  In the fixing device according to claim 1 or 2, preferably, the holder member is disposed so as to be in a non-contact state with respect to the fixing roller, and the guide portion is in contact with the sheet in the operating state of the device. The temperature of the portion is configured to be lower than the temperature of the contact portion of the claw member with the paper (claim 3). With this configuration, the paper separated from the fixing roller by the claw member can be switched to the guide portion of the holder member that is lower in temperature than the claw member, and guided to the downstream side of the conveyance path by the guide portion. As a result, it is possible to reliably reduce the time for the paper to contact the high-temperature claw member.

In the fixing device according to any one of claims 1 to 3 , it is preferable that at least a surface of the rotating member is made of a fluororesin ( claim 4 ). 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 the fixing device of the first aspect, since the sheet can be smoothly brought into contact with the peripheral surface of the rotating member while suppressing a large change in the conveyance direction of the sheet, the load applied to the sheet is reduced. can do. Accordingly, it is possible to suppress a part of the sheet from coming into contact with the claw member due to the return of the sheet and to cause the scratch to be generated on the sheet. Therefore, it is possible to suppress a decrease in image quality. Further, since the contact time of the sheet with the high-temperature claw member that contacts the peripheral surface of the fixing roller can be shortened, the toner on the sheet separated from the fixing roller can be prevented from being melted (remelted). . Also by this, it is possible to suppress the occurrence of scratches caused by the claw member in the image formed on the paper, so that it is possible to suppress the deterioration of the image quality. In particular, when the guide portion is disposed at a position relatively close to the tip of the claw member, the sheet separated from the fixing roller is guided from the claw member at a position relatively close to the tip of the claw member that is the separation position. Therefore, it is possible to further reduce the time for the sheet to contact the hot claw member. In addition, since the degree of contact of the paper with the guide portion can be sufficiently relaxed, it is possible to sufficiently suppress the occurrence of image rubbing on the image surface of the paper.

  According to the fixing device of the second aspect, after the separation, a load applied to the front end of the sheet by causing the front end of the sheet conveyed while being in contact with the claw member and the guide portion to smoothly contact the peripheral surface of the rotating member. Since this can be reduced, it is possible to further suppress the occurrence of a scratch caused by the claw member due to a part of the paper coming into contact with the claw member by returning the paper. As a result, a decrease in image quality can be sufficiently suppressed.

  According to the fixing device of the third aspect, since the time for which the paper contacts the high-temperature claw member can be surely shortened, the toner on the paper separated from the fixing roller is melted (remelted). Can be further suppressed.

According to the fixing device of the fourth aspect , since the rotating member has excellent heat resistance and a low coefficient of friction with respect to the sheet, the rotating member guides the sheet to the downstream side of the conveyance path while rotating. At this time, the physical load applied to the image on the paper can be extremely reduced.

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

  FIG. 1 is a diagram illustrating an overall configuration of a printer including an image fixing unit according to an embodiment of the present invention. FIGS. 2 to 6 are diagrams illustrating a configuration of an image fixing unit according to an embodiment of the present invention. It is. First, an overall configuration of a printer 10 including an image fixing unit 14 according to an embodiment of the present invention will be described with reference to FIG. The image fixing unit 14 is an example of the “fixing device” in the present invention.

  As shown in FIG. 1, the printer 10 according to the present embodiment includes a sheet storage unit 12 that stores and stores sheets (recording sheets) P to be printed, and a sheet bundle stored in the sheet storage unit 12. An image forming unit 13 that performs image transfer processing on the paper P that has been fed out one by one, and an image fixing unit 14 that performs fixing processing on the paper P that has been subjected to transfer processing by the image forming unit 13 are provided. In addition to being provided inside the main body 11, a paper discharge unit 15 for discharging the paper P subjected to fixing processing by the image fixing unit 14 is provided in the upper part of the apparatus main body 11.

  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 papers (recording papers) 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 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, on the exit side in the housing 21, four sheets P 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 (FIG. 3). The separation mechanism 50 is arranged in parallel with a predetermined interval in the axial direction of the fixing roller 30. The separation mechanism 50 is an example of the “separation means” in the present invention. 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 of the present embodiment, the path from the nip region N between the fixing roller 30 and the pressure roller 40 to the discharge roller pair 142 corresponds to the “conveying path” of the present invention. In this transport path, the paper P is transported by the fixing roller 30 and the pressure roller 40 until the front end of the paper P passes through the nip region N and reaches the discharge roller pair 142. From the time when the paper reaches the discharge roller pair 142 until the trailing edge of the paper P passes through the nip region N, the fixing roller 30, the pressure roller 40, and the discharge roller pair 142 convey the paper P while being synchronized with each other. Is configured to do. 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. A pair of roller members 80 (see FIG. 4) held in a possible manner and a tension coil spring 52 that urges 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 pair of roller members 80 is an example of the “ first and second rotating members” 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 has a shape that can 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 includes a first projection 61b, a second projection 61c, and a support column formed on a surface of the side plate 61a (first side plate) facing the second holder 62 of the side plate 61a. 61d and the cylindrical shaft insertion part 61e formed in the upper part of the side plate 61a are included. The second protrusion 61c is an example of the “first holding part” in the present invention, and the column 61d is an example of the “second holding part” in the present invention.

The second holder 62 includes a side plate 62a (second side plate), and a first hole 62b and a second hole formed at positions corresponding to the first protrusion 61b and the second protrusion 61c of the side plate 62a. 62c, a support 62d formed on the surface of the side plate 62a facing the first holder 61, and a shaft insertion portion 62e formed on the upper side of the side plate 62a corresponding to the shaft insertion portion 61e. The support 62d is an example of the “ third holding portion ” in the present invention.

  Here, in this embodiment, 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. Yes. 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. That is, the front end of the sheet P separated from the peripheral surface of the fixing roller 30 by the separation claw 70 is gradually corrected in the conveyance direction (path) by being guided by the guide portion 61f (62f), and the roller member 80 The peripheral surface can be smoothly contacted from the tangential direction.

  The first protrusion 61b is provided to fix the holders 61 and 62 at a predetermined distance from each other. That is, as shown in FIG. 4 and FIG. 5, the first protrusion 61b is press-fitted into a cylindrical base 61g and the first hole 62b of the second holder 62, and has a smaller diameter than the base 61g. The base plate 61g of the first protrusion 61b abuts on the side plate 62a of the second holder 62, so that the side plates 61a and 62a are held at a distance that matches the axial length of the base 61g. It has come to be.

  The second protrusion 61c is provided to hold the separation claw 70 in a fixed manner. That is, the second projecting portion 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 the separation claw 70 described later, and a second one. The two holders 62 are sequentially press-fitted into the second hole 62c of the holder 62, and are configured by a holding part 61j having a cross-sectional shape that is slightly smaller than the position restricting part 61i. When the position restricting part 61i comes into contact with the separation claw 70, The separation claw 70 is restricted from moving in the direction of the side plate 61a 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 restricted by the position restricting portion 61i of the second projecting portion 61c is positioned approximately in the middle between the side plates 61a and 62a. ing.

  As shown in FIG. 5, the columns 61 d and 62 d are arranged so as to face each other, and are configured to hold the roller member 80 rotatably. These columns 61d and 62d protrude from the side plates 61a and 61a in such a protruding amount that they are not in contact with the separation claw 70 fixedly held by the holding portion 61j of the second protrusion 61c.

  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-angled tip 71 that contacts the peripheral surface of the fixing roller 30 (see FIG. 6). And an opening 72 (see FIG. 5) having a rectangular shape in front view into which the second protrusion 61c of the holder member 60 is press-fitted. As described above, the separation claw 70 is positioned and disposed so as to be positioned approximately in the middle between the side plates 61 a and 62 a of the holders 61 and 62, and the distal end portion 71 is a conveyance path of the holder member 60. It is arranged so as to protrude from the end portion on the upstream side (right side in the figure) toward the outside (the peripheral surface of the fixing roller 30). The leading end 71 is located at a predetermined distance L1 (see FIG. 7) from the downstream end of the nip region N in the transport direction (hereinafter referred to as the nip region outlet), and is fixed by the tension of the tension coil spring 52. It is in contact with the peripheral surface of.

  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).

  As shown in FIG. 5, the pair of roller members 80 are rotatably supported by the columns 61d and 62d by inserting the columns 61d and 62d into the shaft holes 81, and are separated between the side plates 61a and 62a. It arrange | positions so that the nail | claw 70 may be pinched | interposed. The roller member 80 is held by the column 61d (62d) so as to be separated from the separation claw 70 in a state having a predetermined play in the protruding direction of the column 61d (62d). Further, as shown in FIG. 6, when the roller member 80 is held by the holder member 60, a part of the peripheral surface is exposed from the lower part of the holder member 60 toward the outside (inside the conveyance path). It is configured.

  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 separation mechanism 50 having the above-described configuration, as shown in FIG. 6, the front end portion 71 of the separation claw 70 protruding outward from the end portion on the upstream side of the conveyance path of the holder member 60 and the lower portion of the holder member 60 in the front view. The guide portion 61f (62f) of the holder member 60 is positioned between the roller member 80 exposed to the outside.

  Here, with reference to FIG. 6 and FIG. 7, the structure (arrangement position and dimension) of the separation mechanism 50 of this embodiment will be described in detail. In FIG. 7, the reference numerals other than the main members are not attached to prevent the reference signs from being mixed. As shown in FIG. 7, the separation mechanism 50 relates to the dimension of the separation mechanism 50 based on the parameter L1 related to the arrangement position of the separation mechanism 50 and the positional relationship between the constituent members (the guide member 60, the separation claw 70, and the roller member 80). It has five parameters L2 to L6.

  The parameter L1 indicates the distance between the nip region outlet and the tip 71 of the separation claw 70 as described above. The interval L1 is preferably about 2.0 mm or more and about 6.0 mm or less. This is because when the interval L1 is larger than about 6.0 mm, the toner on the sheet P and the fixing roller 30 are connected while the sheet P is conveyed from the exit of the nip area to the leading end 71 of the separation claw 70. Since the adhesion force increases, it becomes difficult to separate the paper P from the fixing roller 30, and the toner on the paper P is excessively melted. The tendency to not get on the street becomes remarkable. When the distance L1 is smaller than about 2.0 mm, the tip 71 of the separation claw 70 is placed on the circumferential surface of the pressure roller 40 due to fluctuations in the nip region N between the rollers 30 and 40 due to heat and driving. The possibility of contact increases.

  The parameter L2 indicates the distance between the tip 71 of the separation claw 70 and the point at which the paper P is switched from the separation claw 70 to the guide portion 61f (62f). The distance L2 is preferably about 1.0 mm or more and about 5.0 mm or less. This is because when the distance L2 is larger than about 5.0 mm, it is difficult to bridge the paper P between the exit of the nip region and the guide portion 61f (62f), and the paper P contacts the separation claw 70. It is because it becomes easy to do. When the distance L2 is smaller than about 1.0 mm, the front end of the paper P sent out from the nip region N is caught by the guide 61f (62f) due to the stiffness, and it is difficult to normally transport the paper P. The tendency to become remarkable.

  The parameter L3 indicates the distance between the sheet P conveying surface of the separation claw 70 and the lowest point of the roller member 80. This distance L3 is preferably not less than about 0.5 mm and not more than about 4.0 mm. This is because, when the distance L3 is larger than about 4.0 mm, the conveyance direction (path) of the paper P changes greatly, so that the above-mentioned “return” occurs in the paper P, and the paper P is separated from the separation claw 70. This is because there is a high possibility of contact with the surface. When the distance L3 is smaller than about 0.5 mm, it becomes difficult to bridge the paper P between the nip region outlet and the guide portion 61f (62f), and the paper P contacts the separation claw 70. This is because the possibility increases.

  The parameter L4 indicates an angle formed between the conveyance surface of the paper P of the separation claw 70 and the tangent line of the guide portion 61f (62f) at a point where the paper P is switched from the separation claw 70 to the guide portion 61f (62f). This angle L4 is preferably not less than about 135 ° and not more than about 175 °. This is because when the angle L4 is larger than about 175 °, it becomes difficult to secure a step between the conveyance surface of the sheet P of the separation claw 70 and the guide portion 61f (62f), and the lower limit of the parameter L3 is set. This is because it is difficult to bridge the paper P between the exit of the nip region and the guide portion 61f (62f), and the possibility that the paper P comes into contact with the separation claw 70 increases. When the angle L4 is smaller than about 135 °, the transport direction (path) of the paper P changes greatly as in the case where the upper limit of the parameter L3 is exceeded. This is because there is a high possibility that the paper P comes into contact with the separation claw 70.

  The parameter L5 indicates the distance between the lowest point of the guide portion 61f (62f) and the lowest point of the roller member 80. This distance L5 is preferably not less than about 0.5 mm and not more than about 3.0 mm. This is because when the distance L5 is greater than about 3.0 mm, the transport direction (path) of the paper P changes greatly, so that the paper P is returned and the paper P is pressed against the guide portion 61f (62f). This is because there is a high possibility of being touched or coming into contact with the separation claw 70. Further, when the interval L5 is smaller than about 0.5 mm, the paper P is conveyed while always sliding with respect to the guide portion 61f (62f), and therefore image rubbing (guide trace) on the image surface of the paper P. This is because toner tends to adhere to the guide portion 61f (62f).

  The parameter L6 indicates the interval between the point at which the paper P is switched from the separation claw 70 to the guide portion 61f (62f) and the point at which the paper P is switched from the guide portion 61f (62f) to the roller member 80. The distance L6 is preferably about 0.5 mm or more and about 3.0 mm or less. This is because, when the distance L6 is larger than about 3.0 mm, it is difficult to bridge the paper P between the exit of the nip region and the roller member 80, and the paper P contacts the guide portion 61f (62f). This is because there is a high possibility of doing so. When the distance L6 is smaller than about 0.5 mm, the transport direction (path) of the paper P changes greatly, so that the paper P is returned as described above, and the paper P contacts the separation claw 70. This is because the possibility increases.

  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 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. For example, when the temperature of the fixing roller 30 is about 190 ° C., the temperature of the contact portion of the separation claw 70 with the paper P is about 180 ° C., and the contact portion of the guide portion 61 f (62 f) of the holder member 60 with the paper P The temperature is about 125 ° C. Moreover, it is thought that the temperature of the surrounding surface of the roller member 80 at this time is a temperature further lower than about 125 degreeC.

  In the present embodiment, as described above, the guide portion 61 f (62 f) that guides the paper P to the roller member 80 is provided in the conveyance path between the separation claw 70 and the roller member 80, thereby separating from the fixing roller 30. Since the sheet P can be actively guided to the roller member 80 by the guide portion 61f (62f), the separation claw 70 and the roller member 80 greatly change the transport direction (path) of the sheet P after separation. Even when the paper P is separated, the member for guiding the separated paper P is switched from the separation claw 70 to the roller member 80 (see FIG. 8), as shown in FIG. The member that guides the sheet P is gently switched from the separation claw 70 to the roller member 80 through the guide portion 61f (62f), thereby suppressing a large change in the transport direction of the paper P. The sheet P can be smoothly brought into contact with the peripheral surface of the roller member 80. As a result, the load applied to the paper P can be reduced, so that the paper P can be prevented from coming into contact with the separation claw 70 due to the return of the paper P and causing the paper P to be scratched. . Therefore, it is possible to suppress a decrease in image quality.

  In the present embodiment, as described above, the guide portion 61f (62f) is provided in the conveyance path between the separation claw 70 and the roller member 80, whereby the paper P separated from the fixing roller 30 is separated at a high temperature. The separation claw 70 is switched on the guide portion 61f (62f) of the low temperature holder member 60 provided separately from the claw 70, and guided to the downstream side of the conveyance path by the low temperature guide portion 61f (62f). can do. For this reason, the contact time of the paper P with the high-temperature separation claw 70 in contact with the peripheral surface of the fixing roller 30 can be shortened, so that the toner on the paper P separated from the fixing roller 30 is melted (remelted). Can be suppressed. Also by this, it is possible to suppress the occurrence of scratches caused by the separation claw 70 in the image formed on the paper P, and thus it is possible to suppress a decrease in image quality. In particular, when the guide portion 61f (62f) is disposed at a position relatively close to the front end portion 71 of the separation claw 70, the paper P separated from the fixing roller 30 is moved to the front end portion of the separation claw 70 that is the separation position. Since the separation claw 70 can be switched to the guide portion 61f (62f) at a position relatively close to 71, it is possible to further reduce the time during which the paper P contacts the high temperature separation claw 70.

  In the present embodiment, as described above, the guide portion 61f (62f) is provided in the conveyance path between the separation claw 70 and the roller member 80, and the sheet P is fed to the roller member 80 in the guide portion 61f (62f). The guide portion 61f (62f) is disposed in the vicinity of the front end portion 71 of the separation claw 70, and the separated paper P is guided (elastic) by the guide portion 61f (elasticity). 62f), the roller member 80 guides the sheet P while rotating on the downstream side of the conveying path even if the sheet P is conveyed, so that the degree of contact of the sheet P with the guide portion 61f (62f) is sufficiently relaxed. can do. Thereby, it is possible to sufficiently suppress the occurrence of image rubbing on the image surface of the paper P.

  In the present embodiment, as described above, the guide portion 61 f (62 f) is configured to guide the front end of the paper P separated from the fixing roller 30 by the separation claw 70 toward the peripheral surface of the roller member 80. By doing so, the front end of the paper P separated from the fixing roller 30 can be positively guided toward the peripheral surface of the roller member 80 by the guide portion 61f (62f), so that the separation claw 70 and the guide portion are separated after separation. The load applied to the front end of the paper P can be reduced by making the front end of the paper P conveyed while being in contact with the 61f (62f) smoothly contact the peripheral surface of the roller member 80. As a result, it is possible to further suppress the occurrence of scratches caused by the separation claw 70 on the paper P because a part of the paper P comes into contact with the separation claw 70 due to the return of the paper P, thereby sufficiently reducing the image quality. Can be suppressed.

  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 further suppressed from being melted (remelted).

  In the present embodiment, as described above, the roller member 80 can be separated from the separation claw 70 and has a predetermined play in the extending direction of the column 61d (62d). The separation claw 70 is appropriately brought into contact with the roller member 80 from the direction in which the column 61d (62d) extends, while the roller member 80 and the separation claw 70 are intermittently in a non-contact state. Therefore, it is possible to suppress the temperature of the roller member 80 from excessively rising while preventing the roller member 80 from falling off the support column 61d (62d). 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 separation claw 70 and the roller member 80 that guides the paper P while rotating are positioned by the second protrusion 61c and the column 61d (62d) of the holder member 60. Even if the holder member 60, the claw member 70, and the roller member 80 are separately formed, the positional accuracy of the roller member 80 and the guide portion 61f (62f) with respect to the distal end portion 71 of the separation claw 70 is high. Can be maintained. Thus, the guide portion 61f (62f) for bringing the leading end 71 of the separation claw 70 into contact with the fixing roller 30 in the vicinity of the nip region N and guiding the paper P to the peripheral surface of the roller member 80 is provided. A configuration in which the separation claw 70 is disposed at a position relatively close to the downstream side of the conveyance path from the distal end 71 of the separation claw 70 can be easily realized.

  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 fixing device of the present invention is applied to the image fixing unit 14 provided in the printer 10 has been described. However, the present invention is not limited to this, and a copying machine other than a printer, a facsimile, or the like The present invention can also be applied to an image fixing unit provided in an image forming apparatus.

  Moreover, in the said embodiment, although the example which arrange | positions a pair of roller member 80 on both sides of the separation nail | claw 70 between the side plates 61a and 62a was shown, this invention is not limited to this, and a pair of roller member 80 is a side plate. You may make it arrange | position at the outer side of 61a and 62a, respectively. In this case, since the roller member 80 does not come into contact with the high-temperature separation claw 70, the temperature of the roller member 80 can be kept at a lower temperature. Further, the roller member 80 may be arranged only on one side of the separation claw 70 between the side plates 61a and 62a.

1 is a cross-sectional front view illustrating an overall configuration of a printer including an image fixing unit according to an embodiment of the present invention. FIG. 2 is a front view illustrating a configuration of an image fixing unit according to the embodiment illustrated 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 illustrating a configuration of a separation mechanism of the image fixing unit illustrated 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 of the separation mechanism shown in FIG. 2. FIG. 3 is a schematic diagram illustrating a sheet conveyance path in the image fixing unit illustrated in FIG. 2. FIG. 6 is a schematic diagram illustrating a sheet conveyance path in an image fixing unit according to a comparative example.

14 Image fixing unit (fixing device)
30 fixing roller 50 separation mechanism (separation means)
60 Holder member 61c 2nd protrusion part (1st holding | maintenance part)
61d, 62d Post (second holding part , third holding part )
61f, 62f Guide part 70 Separation claw (claw member)
80 Roller member ( first and second rotating members)
P paper

Claims (4)

A fixing device comprising: a fixing roller that fixes a toner image transferred to a sheet to the sheet, and that conveys the sheet along a predetermined conveyance path; and a separation unit that separates the sheet from the fixing roller.
The separating means includes
A claw member that contacts the peripheral surface of the fixing roller and separates the paper from the fixing roller;
A holder member for holding the claw member;
First and second rotating members that are rotatably held by the holder member and guide the sheet separated from the fixing roller to the downstream side of the conveying path while rotating,
The holder member is configured by combining a first holder having a first side plate and a second holder having a second side plate aligned with the first side plate at a predetermined interval,
The claw member is disposed between the first side plate and the second side plate, and is fixedly held by a first holding portion extending from the first side plate or the second side plate,
The first rotating member is disposed between the first side plate and the claw member, and is rotatably held by a second holding portion extending from the first side plate. The second rotating member is It is disposed between the second side plate and the claw member, and is rotatably held by a third holding part extending from the second side plate,
Each of the first side plate and the second side plate has a guide portion that guides the paper to the first and second rotating members in a conveyance path between the claw member and the first or second rotating member. A fixing device comprising: a fixing device; 2. The fixing according to claim 1 , wherein the guide portion guides at least a front end of a sheet separated from the fixing roller by the claw member toward a peripheral surface of the first and second rotating members. apparatus. The holder member is disposed in a non-contact state with respect to the fixing roller;
The temperature of the contact portion of the guide portion with the paper in the operating state of the apparatus is configured to be lower than the temperature of the contact portion of the claw member with the paper. Item 3. The fixing device according to Item 1 or 2. The fixing device according to claim 1 , wherein at least surfaces of the first and second rotating members are made of a fluororesin.

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