JP2021117426A - Fixing device and image forming apparatus including the same - Google Patents

Abstract

To provide a fixing device that can certainly separate a recording medium from a rotating body to be heated or a pressure rotating body and can also prevent a reduction in image quality, and provide an image forming apparatus including the same.SOLUTION: A fixing device comprises: a rotating body to be heated; a pressure rotating body; a heating unit; a separation pawl that separates a recording medium from the rotating body to be heated or the pressure rotating body; a fixing and conveying roller pair; and a peeling assisting member. The peeling assisting member has an arm part and a part to be pressed that project to the upstream side and the downstream side from a support shaft in a recording medium insertion direction, and is swingable between a first posture in which the arm part and the part to be pressed do not overlap a reference conveyance lucus of the recording medium and a second posture in which the arm part projects to overlap the reference conveyance locus. When the recording medium presses the part to be pressed, the peeling assisting member swings from the first posture to the second posture to peel the recording medium from the rotating body to be heated or the pressure rotating body, and when the recording medium reaches the fixing and conveying roller pair, the peeling assisting member returns to the first posture.SELECTED DRAWING: Figure 3

Description

The present invention relates to a fixing device used for an image forming device such as a copying machine, a printer, a facsimile, and a multifunction device thereof, and an image forming device provided with the fixing device, and more particularly to a method for suppressing wrapping of a recording medium around a fixing member. Is.

In order to fix a toner image on paper in an image forming apparatus, a fixing device provided with a fixing member in which a fixing roller or a fixing belt (rotating body to be heated) and a pressure roller (pressurizing rotating body) are pressed against each other is widely used. It is used. In this fixing device, paper is passed through a fixing nip portion formed by a heating roller and a pressure roller, and heat and pressure are applied to the toner image to melt and fix the toner image on the paper.

In such a fixing device, the molten toner may cause the paper to adhere to a fixing roller, a fixing belt, or a pressure roller (hereinafter referred to as a fixing roller) and wind around as it is. Therefore, a configuration has been proposed in which a separation claw is provided between the paper that has passed through the fixing nip portion and the fixing roller or the like, and the paper is conveyed while being slidably contacted along the separation claw.

When the separation claws are used to prevent paper wrapping, if the protrusions of the separation claws and the paper transport path overlap, the printed surface of the paper and the protrusions are always aligned when the paper is transported. It will be rubbed. Therefore, for example, when a solid image is printed, the glossiness of the portion of the printed surface that comes into contact with the separation claw and the portion that does not come into contact with each other may differ, and the image quality may deteriorate.

Patent Document 1 describes a roller member, a separation claw that is swingably arranged and whose tip is brought into contact with and separates from the roller member as the roller swings, and a rotating claw that overlaps with a transport path of recording paper so as to be rotatable. A fixing device that is disposed and has a guide roller that swings with the swing of the separation claw is disclosed.

According to the configuration of Patent Document 1, since the guide roller rotates with the transportation of the recording paper, the printed surface and the guide roller do not rub against each other, and the printed surface when a solid image is printed. It is described that the image quality can be improved because there is no difference in gloss between the portion in contact with the separation claw and the portion in contact with the separation claw.

Japanese Unexamined Patent Publication No. 2000-155493

In recent years, in order to improve the energy saving of the image forming apparatus, the melting point of the toner is often shifted to the low melting point side. Therefore, even if a roller that is driven to rotate with the transportation of the paper is provided as in the fixing device of Patent Document 1, the toner is rubbed by the stress concentration on the contact portion between the paper and the roller. As a result, contact marks may be generated on the contact portion of the image surface with the rollers, and the image quality may be deteriorated.

In view of the above problems, the present invention is a fixing device capable of reliably separating the recording medium from the heated rotating body or the heated rotating body, and also capable of suppressing deterioration of image quality, and an image provided with the fixing device. It is an object of the present invention to provide a forming apparatus.

In order to achieve the above object, the first configuration of the present invention includes a rotating body to be heated, a pressurized rotating body, a heating unit, a separation claw, a fixing transfer roller pair, and a peeling auxiliary member. This is a fixing device that melts and fixes an unfixed toner image on a recording medium by heating and pressurizing a recording medium that passes through a fixing nip portion. The pressurized rotating body is pressed against the heated rotating body to form a fixing nip portion. The heating unit heats the rotating body to be heated. The separation claw is arranged close to at least one of the heated rotating body and the pressurized rotating body on the downstream side of the fixing nip portion with respect to the insertion direction of the recording medium, and the recording medium is placed from the heated rotating body or the pressurized rotating body. To separate. The fixing transfer roller pair is arranged on the downstream side of the separation claw with respect to the insertion direction of the recording medium, and conveys the recording medium that has passed through the fixing nip portion. The peeling assisting member is arranged between the fixing nip portion and the fixing transport roller pair, and assists the separation of the recording medium from the heated rotating body or the pressurized rotating body by the separating claw. The peeling auxiliary member includes a support shaft substantially parallel to the rotation shaft core of the rotating body to be heated, an arm portion protruding upstream from the support shaft in the insertion direction of the recording medium, and a support shaft in the insertion direction of the recording medium. It has a pressed portion that protrudes to the downstream side. The peeling auxiliary member has a first posture in which the arm portion and the pressed portion do not overlap the reference transport trajectory of the recording medium connecting the fixing nip portion and the nip portion of the fixing transport roller pair, and the arm portion overlaps the reference transport track. It can swing between the second posture that protrudes toward the surface. The peeling auxiliary member swings from the first posture to the second posture when the recording medium conveyed along the separation claw presses the pressed portion to move the recording medium into a heated rotating body or a pressurized rotating body. When the recording medium reaches the fixed transport roller pair, it swings from the second posture to the first posture.

According to the first configuration of the present invention, the recording medium that has passed through the fixing nip portion is separated from the heated rotating body or the pressurized rotating body by the separation claw, and then the pressed portion of the peeling auxiliary member is pressed. The peeling auxiliary member swings in the second posture, and the arm portion projects so as to overlap the reference transport position. As a result, the recording medium is pressed against the arm portion and separated from the heated rotating body or the pressurized rotating body, so that the separation of the recording medium by the separation claw can be assisted. Further, since the peeling auxiliary member returns to the first posture after the recording medium reaches the fixing and conveying roller pair, no load is applied to the image area, and it is possible to prevent the recording medium from being conveyed poorly and the quality of the output image from being deteriorated. can.

Schematic cross-sectional view showing the internal structure of the image forming apparatus 100 on which the fixing apparatus 13 according to the first embodiment of the present invention is mounted. Side sectional view of the vicinity of the fixing device 13 in FIG. Partial enlarged view from the fixing nip portion N of the fixing device 13 to the fixing transfer roller pair 20 in FIG. A plan view of the arrangement of the fixing roller 131, the pressure roller 132, the separation claw 21, and the peeling auxiliary member 23 as viewed from the downstream side in the transport direction (upper side in FIG. 3). A view of the peeling auxiliary member 23 as viewed from the axial direction of the fixing roller 131. It is a side sectional view which shows the transport state of the paper S from the fixing nip part N to the fixing transport roller pair 20, and is the state which shows the state which the tip of the paper S is in contact with the pressed portion 234 of a peeling auxiliary member 23. It is a side sectional view which shows the transport state of the paper S from the fixing nip part N to the fixing transport roller pair 20, and is the figure which shows the state which the peeling auxiliary member 23 swings, and the transport trajectory of the paper S is corrected. It is a side sectional view which shows the transport state of the paper S from the fixing nip part N to the fixing transfer roller pair 20, and shows the state which the tip of the paper S has reached the nip part of the fixing transfer roller pair 20. Partial enlarged view from the fixing nip portion N of the fixing device 13 according to the second embodiment of the present invention to the fixing transfer roller pair 20. Partial enlarged view from the fixing nip portion N of the fixing device 13 according to the third embodiment of the present invention to the fixing transfer roller pair 20.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing an internal structure of an image forming apparatus 100 on which the fixing apparatus 13 according to the first embodiment of the present invention is mounted. In the main body of the image forming apparatus 100 (here, a color printer), four image forming portions Pa, Pb, Pc and Pd are arranged in order from the upstream side in the transport direction (left side in FIG. 1). These image forming units Pa to Pd are provided corresponding to images of four different colors (cyan, magenta, yellow, and black), and are cyan, magenta, and yellow, respectively, depending on each step of charging, exposure, development, and transfer. And black images are formed sequentially.

Photoreceptor drums (image carriers) 1a, 1b, 1c and 1d carrying visible images (toner images) of each color are disposed on these image forming portions Pa to Pd, and further, counterclockwise in FIG. An intermediate transfer belt 8 that rotates in the clockwise direction is provided adjacent to each image forming portion Pa to Pd. The toner images formed on the photoconductor drums 1a to 1d are sequentially primary-transferred and superimposed on the intermediate transfer belt 8 that moves while abutting on the photoconductor drums 1a to 1d. After that, the toner image primaryly transferred onto the intermediate transfer belt 8 is secondarily transferred by the secondary transfer roller 9 onto the paper S as an example of the recording medium. Further, the paper S on which the toner image is secondarily transferred is discharged from the image forming apparatus 100 main body after the toner image is fixed in the fixing device 13. An image forming process for each of the photoconductor drums 1a to 1d is executed while the photoconductor drums 1a to 1d are rotated clockwise in FIG. 1 by a main motor (not shown).

The paper S on which the toner image is secondarily transferred is housed in the paper cassette 16 arranged in the lower part of the main body of the image forming apparatus 100, and is housed in the second transfer roller 9 via the paper feed roller 12a and the resist roller pair 12b. And the nip portion of the intermediate transfer belt 8 with the drive roller 11. A sheet made of a dielectric resin is used for the intermediate transfer belt 8, and a seamless (seamless) belt is mainly used. Further, a blade-shaped belt cleaner 19 for removing toner and the like remaining on the surface of the intermediate transfer belt 8 is arranged on the downstream side of the secondary transfer roller 9.

Next, the image forming units Pa to Pd will be described. Around and below the rotatably arranged photoconductor drums 1a to 1d, charging devices 2a, 2b, 2c and 2d for charging the photoconductor drums 1a to 1d, and image information on each of the photoconductor drums 1a to 1d. The exposure apparatus 5 for exposing the above, the developing apparatus 3a, 3b, 3c and 3d for forming a toner image on the photoconductor drums 1a to 1d, and the developer (toner) remaining on the photoconductor drums 1a to 1d are removed. Cleaning devices 7a, 7b, 7c and 7d are provided.

When image data is input from a higher-level device such as a personal computer, first, the surfaces of the photoconductor drums 1a to 1d are uniformly charged by the charging devices 2a to 2d. Next, the exposure apparatus 5 irradiates light according to the image data to form an electrostatic latent image according to the image data on each of the photoconductor drums 1a to 1d. The developing devices 3a to 3d are filled with a predetermined amount of a two-component developer containing toners of cyan, magenta, yellow, and black, respectively. When the ratio of toner in the two-component developer filled in the developing devices 3a to 3d falls below the specified value due to the formation of the toner image described later, the toner containers 4a to 4d to the developing devices 3a to 3d are used. Toner is replenished. The toner in this developer is supplied onto the photoconductor drums 1a to 1d by the developing devices 3a to 3d, and is electrostatically adhered to the toners according to the electrostatic latent image formed by the exposure from the exposure device 5. A toner image is formed.

Then, an electric field is applied between the primary transfer rollers 6a to 6d and the photoconductor drums 1a to 1d at a predetermined transfer voltage by the primary transfer rollers 6a to 6d, and cyan, magenta, yellow, and cyan, magenta, yellow, and cyanide, magenta, yellow, and cyanide, magenta, and yellow on the photoconductor drums 1a to 1d are applied. The black toner image is primarily transferred onto the intermediate transfer belt 8. These four-color images are formed with a predetermined positional relationship predetermined for forming a predetermined full-color image. After that, in preparation for the subsequent formation of a new electrostatic latent image, the toner and the like remaining on the surfaces of the photoconductor drums 1a to 1d after the primary transfer are removed by the cleaning devices 7a to 7d.

The intermediate transfer belt 8 is hung between the driven roller 10 on the upstream side and the drive roller 11 on the downstream side, and the intermediate transfer belt 8 is counterclockwise as the drive roller 11 is rotated by the belt drive motor (not shown). When the rotation is started in the clockwise direction, the paper S moves from the resist roller pair 12b to the nip portion (secondary transfer nip portion) between the drive roller 11 and the secondary transfer roller 9 provided adjacent thereto at a predetermined timing. It is conveyed and the full-color image on the intermediate transfer belt 8 is secondarily transferred onto the paper S. The paper S on which the toner image is secondarily transferred is conveyed to the fixing device 13.

The paper S conveyed to the fixing device 13 is heated and pressurized by the fixing roller 131 and the pressure roller 132 (see FIG. 2), and the toner image is fixed on the surface of the paper S to form a predetermined full-color image. .. The paper S on which the full-color image is formed is divided into transport directions by the branching portions 14 branched in a plurality of directions, and is sent to the double-sided transport path 18 as it is (or after the images are formed on both sides), and the discharge roller pair It is discharged to the discharge tray 17 by 15.

FIG. 2 is a side sectional view of the periphery of the fixing device 13 in FIG. The fixing device 13 is a fixing method using a heat source of an electromagnetic induction heating method, and is arranged with a fixing roller 131 which is a heating member, a pressure roller 132 which is a pressure rotating body, and a fixing roller 131 facing the outer periphery of the fixing roller 131. It includes an induction heating unit 133 to be provided, and a temperature sensor 134 including a thermister or the like that detects the temperature of the surface of the fixing roller 131. The induction heating unit 133 and the temperature sensor 134 are fixed to the main body of the image forming apparatus 100, and the fixing roller 131 and the pressurizing roller 132 are rotatably held in the housing of the fixing device 13.

The fixing roller 131 is released from a base material 131a made of cylindrical stainless steel, an elastic layer 131d made of a silicon rubber sponge for imparting elasticity to a fixing nip portion N that is in pressure contact with the pressure roller 132, and an elastic layer 131d. A release layer 131e made of a fluororesin that imparts properties is provided, and a heat insulating layer 131b and an induction heating layer 131c are provided between the base material 131a and the elastic layer 131d in this order from the base material side.

The pressure roller 132 includes a base material 132a made of an aluminum core metal, an elastic layer 132b made of silicon rubber formed on the base material 132a to impart elasticity to the fixing nip portion N, and a fixing nip portion N. A mold release layer 132c made of a fluororesin tube covering the surface of the elastic layer 132b is provided in order to improve the mold release property when the unfixed toner image is melt-fixed.

Further, the pressurizing roller 132 is rotationally driven by a drive source (not shown) such as a motor, and is further pressurized toward the radial center of the fixing roller 131. As a result, when the pressure roller 132 is in pressure contact with the fixing roller 131 and the pressure roller 132 rotates, the fixing roller 131 is driven to rotate in the same direction at the fixing nip portion N.

The temperature sensor 134 has a paper passing area in the center of the fixing roller 131 in the axial direction (width direction) and both ends in the axial direction which are non-paper passing areas when small size paper such as A4 vertical size is passed. It is arranged so as to face and detects the temperature in each region. Based on the temperature detected by the temperature sensor 134, the electric power supplied to the induction heating unit 133 is controlled, and the surface of the fixing roller 131 is maintained at a predetermined temperature.

The induction heating unit 133 includes an exciting coil 133a, a hobin 133b, and a core 133c, and heats the fixing roller 131 by electromagnetic induction. It extends in the axial direction of the fixing roller 131 and is a part of the outer periphery of the fixing roller 131. They are arranged so as to surround each other.

The exciting coil 133a made of a copper wire is wound around the hobin 133b and is arranged in a spiral shape over a part of the outer periphery of the fixing roller 131 so as to orbit around the central portion of the core 133c in the axial direction. Further, the exciting coil 133a is connected to a high voltage power source (not shown), and generates magnetic flux by a high frequency current supplied from the power source. The magnetic flux generated from the induction heating unit 133 is generated in a direction parallel to the paper surface of FIG. 2 and penetrates the induction heating layer 131c of the fixing roller 131. An eddy current is generated around the magnetic flux of the induction heating layer 131c, and when the eddy current flows, Joule heat is generated by the electric resistance in the induction heating layer 131c, and the induction heating layer 131c generates heat.

The power of the high-voltage power supply is controlled based on the temperature detected by the temperature sensor 134 so that the fixing roller 131 reaches a predetermined temperature by the induction heating unit 133. Then, when the fixing roller 131 is heated and the temperature rises to a predetermined temperature, the paper S sandwiched between the fixing nip portions N is heated and pressed by the pressure roller 132, so that the powder on the paper S is pressed. The toner in the body state is melted and fixed.

After the toner is fixed, the paper S is discharged from the discharge roller pair 15 to the discharge tray 17 (see FIG. 1) via the fixing transport roller pair 20. The linear velocity of the fixing and conveying roller vs. 20 is set to be slightly faster than the linear velocity of the fixing roller 131 and the pressure roller 132 so that the conveyed paper S does not bend.

FIG. 3 is a partially enlarged view from the fixing nip portion N of the fixing device 13 in FIG. 2 to the fixing transfer roller pair 20. In FIGS. 3 and 6 to 10 described later, only the fixing roller 131, the pressure roller 132, the fixing transfer roller pair 20, the separation claw 21, the peeling auxiliary member 23, the transfer guide 25, and the paper S are shown. The description of other constituent members of the fixing device 13 is omitted. A separation claw 21, a peeling auxiliary member 23, and a transport guide 25 are arranged on the downstream side of the fixing nip portion N with respect to the paper transport direction.

The separation claw 21 separates the tip of the paper S after the fixing process from the surface of the fixing roller 131. The separation claw 21 has a predetermined angle so that the tip portion is directed toward the upstream side (counter direction) with respect to the rotation direction (counterclockwise direction) of the fixing roller 131 and the tip portion is close to the outer peripheral surface of the fixing roller 131. It is arranged in.

FIG. 4 is a plan view of the arrangement of the fixing roller 131, the pressure roller 132, the separation claw 21, and the peeling auxiliary member 23 as viewed from the downstream side (upper side in FIG. 3) in the transport direction. As shown in FIG. 4, the separation claws 21 are arranged at a plurality of locations (here, 5 locations) at equal intervals along the axial direction (left-right direction in FIG. 4) of the fixing roller 131.

The peeling assisting member 23 assists the peeling of the paper S from the surface of the fixing roller 131 after the tip of the paper S is separated from the surface of the fixing roller 131 by the separating claw 21. As shown in FIG. 4, the peeling auxiliary members 23 are arranged at equal intervals between the separation claws 21 arranged along the axial direction of the fixing roller 131 (here, four places).

FIG. 5 is a view of the peeling auxiliary member 23 as viewed from the axial direction of the fixing roller 131. The peeling auxiliary member 23 has a support shaft 231, an arm portion 232, a roller 233, and a pressed portion 234. The support shaft 231 has an axial direction substantially parallel to the rotation axis (rotation center) of the fixing roller 131, and is rotatably supported by the transfer guide 25 (see FIG. 3). The arm portion 232 extends in the radial direction from the outer peripheral surface of the support shaft 231. Specifically, the arm portion 232 extends from the support shaft 231 toward the upstream side (obliquely downward direction in FIG. 3) of the paper S in the transport direction. The roller 233 is rotatably supported by the tip of the arm portion 232.

The pressed portion 234 extends from the outer peripheral surface of the support shaft 231 in a direction different from that of the arm portion 232 (here, a direction substantially 90 ° away). Specifically, the pressed portion 234 extends from the support shaft 231 toward the downstream side (obliquely upward direction in FIG. 3) of the paper S in the transport direction. A torsion spring 27 is extrapolated to the support shaft 231. The torsion spring 27 urges the peeling auxiliary member 23 in the clockwise direction. A stopper 29 is arranged on the rotation trajectory of the arm portion 232. The stopper 29 regulates the clockwise rotation of the peeling auxiliary member 23 by abutting against the arm portion 232.

When no external force is applied to the peeling auxiliary member 23, the arm portion 232 is in contact with the stopper 29 due to the urging force (or its own weight) of the torsion spring 27, and as shown in FIG. The pressing portion 234 is held in an obliquely upward posture (first posture). When the peeling auxiliary member 23 is in the first posture, the roller 233 and the pressed portion 234 are arranged at positions that do not overlap with the normal transport track (reference transport track R, indicated by the alternate long and short dash line in FIG. 3) of the paper S. There is. The reference transfer track R is a straight line connecting the fixing nip portion N and the nip portion of the fixing transfer roller pair 20.

Further, here, the peeling auxiliary member 23 is held in the first posture by the torsion spring 27, but the peeling auxiliary member 23 is held in the first posture by the weight of the arm portion 232 and the roller 233. May be good.

Next, a mechanism for separating the paper S from the fixing roller 131 by the separation claw 21 and the release assisting member 23 will be described. FIG. 6 is a side sectional view showing a transport state of the paper S from the fixing nip portion N to the fixing transport roller pair 20, and the tip of the paper S passing through the fixing nip portion N is the pressed portion of the peeling auxiliary member 23. It is a figure which shows the state just before contacting with 234.

In the paper S that has passed through the fixing nip portion N, the marginal portion at the tip where the toner image is not formed rises from the fixing roller 131 and approaches the separation claw 21. The tip of the separation claw 21 enters between the fixing roller 131 and the margin portion of the paper S, so that the paper S is guided along the separation claw 21.

In the paper S, after the margin portion at the tip, an image region in which a toner image having a large adhesion to the fixing roller 131 is formed is separated from the fixing roller 131. Therefore, for example, the paper S on which the solid (solid) image is printed is curved in the direction closer to the separation claw 21 than the reference transport track R (indicated by the solid line in FIG. 6) and comes into contact with the roller 233 of the peeling auxiliary member 23. While being transported.

FIG. 7 is a diagram showing a state in which the peeling auxiliary member 23 swings to correct the transport trajectory of the paper S. When the paper S is further conveyed from the state of FIG. 6, the tip of the paper S comes into contact with the pressed portion 234 from below and pushes up the pressed portion 234 upward. As a result, the peeling auxiliary member 23 swings counterclockwise around the support shaft 231 against the urging force (or gravity) of the torsion spring 27. Then, the roller 233 at the tip of the arm portion 232 is projected to a position where it overlaps with the reference transport track R (second posture). As a result, the paper S is pressed in a direction away from the separation claw 21 against the adhesion force with the fixing roller 131, and the transport trajectory of the paper S is corrected to a position close to the reference transport track R.

FIG. 8 is a diagram showing a state in which the tip of the paper S reaches the nip portion of the fixing transfer roller pair 20. When the tip of the paper S reaches the fixing transfer roller pair 20, the paper S is pulled by the linear velocity difference between the fixing roller 131 and the pressure roller 132 and the fixing transfer roller pair 20, and is conveyed along the reference transfer track R. .. As a result, the paper S is separated from the peeling assisting member 23, and the peeling assisting member 23 returns to the first posture in which the arm portion 232 does not overlap the reference transport track R due to the urging force (or its own weight) of the torsion spring 27. Therefore, the load of the rollers 233 and the pressed portion 234 is not applied to the image area of the paper S, and it is possible to prevent the quality of the output image from deteriorating due to the occurrence of glossy streaks, scratches, and the like.

Further, since the peeling auxiliary members 23 are arranged at a plurality of places (4 places) in the width direction of the paper S, it is possible to secure a sufficient peeling force when peeling the paper S from the fixing roller 131. Further, by attaching the roller 233 to the tip of the arm portion 232 of the peeling auxiliary member 23, it is possible to more effectively reduce the occurrence of gloss streaks, rubbing marks, and the like.

FIG. 9 is a partially enlarged view from the fixing nip portion N of the fixing device 13 according to the second embodiment of the present invention to the fixing transfer roller pair 20. In the present embodiment, the peeling auxiliary member 23 is provided with rollers 233 on both the tip of the arm portion 232 and the tip of the pressed portion 234. The configuration of the other parts of the fixing device 13 is the same as that of the first embodiment.

According to the configuration of the present embodiment, by attaching the roller 233 to the tip of the pressed portion 234 in addition to the tip of the arm portion 232, the paper S pushes up the pressed portion 234 and passes through the paper S. Rubbing between the image area and the tip of the pressed portion 234 is suppressed. Therefore, it is possible to more effectively suppress the occurrence of glossy streaks and rubbing marks.

FIG. 10 is a partially enlarged view from the fixing nip portion N of the fixing device 13 according to the third embodiment of the present invention to the fixing transfer roller pair 20. In the present embodiment, the separation claw 21, the peeling auxiliary member 23, and the transport guide 25 are provided on both the fixing roller 131 side and the pressure roller 132 side. The configuration of the other parts of the fixing device 13 is the same as that of the first embodiment.

When images are formed on both sides of the paper S, the paper S that has passed through the fixing nip portion N after forming the image on the second side has a stronger adhesion to the pressure roller 132 on the back side on which the image on the second side is formed. As a result, the transport track of the paper S is curved in a direction closer to the pressure roller 132 than the reference transport track R.

Therefore, by arranging the separation claw 21 and the peeling auxiliary member 23 on the pressure roller 132 side as in the present embodiment, the paper S conveyed in the direction of winding around the pressure roller 132 during double-sided printing is pressurized. It is effectively peeled from the pressure roller 132 by the separation claw 21 on the roller 132 side and the peeling auxiliary member 23, and is transported along the reference transport track R. Therefore, it is possible to prevent deterioration of the quality of the output images on the front side and the back side of the double-sided printing.

In the third embodiment, the separation claw 21 and the peeling auxiliary member 23 are provided on both the fixing roller 131 side and the pressure roller 132 side. However, especially when the paper S is remarkably wrapped around the pressure roller 132. It is also possible to provide the separation claw 21 and the peeling auxiliary member 23 only on the pressure roller 132 side.

In addition, the present invention is not limited to each of the above embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, in each of the above embodiments, the roller 233 is attached to the tip of the arm portion 232 and the pressed portion 234 of the peeling auxiliary member 23, but the tip of the arm portion 232 and the pressed portion 234 is attached without attaching the roller 233. By forming it into a curved surface, it is possible to suppress the occurrence of glossy streaks and scratches.

Further, in each of the above embodiments, the roller heating type fixing device 13 provided with the fixing roller 131 as the rotating body to be heated has been exemplified, but for example, the fixing device of the belt heating type fixing device provided with the endless fixing belt or the like is used for fixing. Of course, it can be applied to a fixing device provided with a rotating body to be heated other than the roller 131 in exactly the same manner. Further, the heating method is not limited to the induction heating method using the induction heating unit 133 including the exciting coil and the core, and for example, a halogen heater can be used as the heating unit.

Further, in the vertical transport type fixing device 13 in which the paper S passes through the fixing nip portion N from the lower side to the upper side as shown in each of the above embodiments, the direction of gravity applied to the paper S is different from the peeling direction. , The action of gravity cannot be expected when the paper S is peeled from the fixing roller 131 or the pressure roller 132. Therefore, it is particularly effective to assist the peeling with the peeling assisting member 23. However, the present invention can be similarly applied to a horizontal transfer type fixing device in which the paper S passes horizontally through the fixing nip portion N.

Further, the image forming apparatus 100 is not limited to the tandem type color printer as shown in FIG. 1, and can be applied to various image forming apparatus provided with a fixing device such as a monochrome copier, a digital multifunction device, a facsimile and a laser printer. Is.

The present invention is a fixing device in which a recording medium is inserted through a fixing nip portion formed of a rotating body to be heated and a rotating body under pressure, and heat and pressure are applied to the toner image to melt and fix the toner image on the recording medium. It is available. By utilizing the present invention, it is possible to provide a fixing device capable of reliably separating the recording medium from the rotating body to be heated and suppressing deterioration of image quality, and an image forming device provided with the fixing device. ..

13 Fixing device 131 Fixing roller (rotating body to be heated)
132 Pressurized roller (pressurized rotating body)
133 Induction heating section (heating section)
20 Fixing transport roller vs. 21 Separation claw 23 Peeling auxiliary member 231 Support shaft 232 Arm part 233 Roller 234 Pressed part 25 Transport guide 27 Torsion spring (urging member)
100 Image forming device N Fixing nip

Claims (8)

The rotating body to be heated and
A pressurized rotating body that is pressed against the heated rotating body to form a fixing nip portion, and a pressurized rotating body.
A heating unit that heats the rotating body to be heated,
On the downstream side of the fixing nip portion with respect to the insertion direction of the recording medium, the heated rotating body and the pressurized rotating body are arranged close to at least one of the heated rotating body and the pressurized rotating body. With a separation claw that separates the recording medium,
A pair of fixing and conveying rollers arranged on the downstream side of the separating claw with respect to the insertion direction of the recording medium and conveying the recording medium that has passed through the fixing nip portion.
In a fixing device that melts and fixes an unfixed toner image on the recording medium by heating and pressurizing the recording medium that passes through the fixing nip portion.
A peeling assisting member that assists the separation of the recording medium from the heated rotating body or the pressurized rotating body by the separating claw is arranged between the fixing nip portion and the fixing transport roller pair.
The peeling auxiliary member includes a support shaft substantially parallel to the rotation shaft core of the rotating body to be heated, an arm portion protruding upstream from the support shaft in the insertion direction of the recording medium, and the recording from the support shaft. It has a pressed portion that protrudes downstream with respect to the insertion direction of the medium, and has a pressed portion.
A first posture in which the arm portion and the pressed portion do not overlap the reference transport trajectory of the recording medium connecting the fixing nip portion and the nip portion of the fixing transport roller pair, and the pressed portion is the reference transport trajectory. It is swingable between the second posture, which protrudes so as to overlap with the
The peeling auxiliary member swings from the first posture to the second posture when the recording medium conveyed along the separation claw presses the pressed portion, and the recording medium is pressed against the pressing portion. Peel off from the heated rotating body or the pressurized rotating body,
A fixing device characterized in that when the recording medium reaches the fixing transfer roller pair, it swings from the second posture to the first posture. The fixing device according to claim 1, wherein the peeling assisting member is provided with a roller that rotates in accordance with the recording medium at the tip of the arm portion. The fixing device according to claim 1 or 2, wherein the peeling assisting member is provided with a roller that rotates in accordance with the recording medium at the tip of the pressed portion. The fixing device according to any one of claims 1 to 3, further comprising an urging member that urges the peeling auxiliary member in a direction of swinging from the second posture to the first posture. .. The separation claws are arranged at a plurality of locations along the axial direction of the heated rotating body or the pressurized rotating body at equal intervals, and the peeling auxiliary members are arranged at equal intervals between the plurality of separation claws. The fixing device according to any one of claims 1 to 4, wherein the fixing device is arranged. A transport guide for guiding the recording medium that has passed through the fixing nip portion to the nip portion of the fixing transport roller pair is provided.
The fixing device according to any one of claims 1 to 5, wherein the peeling auxiliary member is rotatably supported by the transport guide. The fixing device according to any one of claims 1 to 6, wherein the insertion direction is a vertical transport type from the lower side to the upper side of the fixing nip portion. An image forming apparatus including the fixing device according to any one of claims 1 to 7.

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