JP2017215508A - Fixing device, guiding member, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device that enables a user to preferentially avoid any one of image failure due to dew condensation and image failure caused by guiding members according to a use environment.SOLUTION: There is provided a fixing device 20 comprising: a fixing member 21; a pressure rotating body 31 that is provided opposite to the fixing member; a heat source 25 that heats at least one of the fixing member and pressure rotating body; and a planar separation member 60 that is located on the downstream side in a recording material conveyance direction of a nip part N, provided on at least one of the fixing member and the pressure rotating body, and separates a recording material P passing through the nip part from the fixing member or the pressure rotating body. The fixing device 20 fixes an unfixed toner image on the recording material conveyed to the nip part, wherein the separation member is fixed to the fixing device; attachment parts 60i for attaching guiding members 61 attachable to the separation member are formed in the separation member; while attached to the separation member, the guiding members 61 project in the vertical direction from a guiding surface 60d of the separation member.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a fixing device, a guide member, and an image forming apparatus.

  Conventionally, a heat roller fixing device is known as a fixing device used in an image forming apparatus such as a printer or a copying machine. The heat roller fixing device includes a heat source such as a halogen lamp, and unfixed toner in a contact nip portion (fixing nip portion) of a pair of rotating bodies (fixing roller and pressure roller) that are pressed and rotated while being heated. The recording material on which the image is placed is passed, where the toner image is melted and fixed on the recording material. In addition, a heater is provided inside a flexible sleeve (fixing belt) based on heat-resistant resin or metal, and the toner image is held while the recording material is nipped and conveyed by the flexible sleeve and the pressure roller heated by the heater. There is a film heating type fixing device that heats and fixes a recording material to a recording material.

  In such a fixing device, since the toner carried on the recording material melts in the fixing nip when passing through the fixing nip, the toner acts as an adhesive and the recording material that has exited the fixing nip is It may not be separated from the surface of the fixing belt and may wrap around the surface. In addition, due to the stiffness of the recording material and the curvature of the fixing belt or the pressure roller, the recording material cannot be separated from the surface of the fixing belt or the pressure roller after passing through the fixing nip portion and is wound around the surface. Sometimes. Therefore, a separation plate, which is a plate-like separation member provided with the tip portion in contact with or close to the surface of the fixing belt or the pressure roller, is provided on the downstream side of the fixing nip portion in the recording material conveyance direction, thereby recording material. Is separated from the fixing belt and the pressure roller. When the separation plate is provided near the fixing belt heated by a heater, the separation plate is a metal that is less likely to be deformed or melted even at a high temperature compared to resin, has low thermal expansion, and is easy to provide a distance from the fixing belt with high accuracy. It is known to use a processed plate.

  However, when the fixing belt is heated from the cold state to the fixing possible temperature with the power turned off, the separation member whose temperature rises slower than the fixing belt and is relatively low in temperature is heated at the time of fixing or moisture in the air. Water vapor generated from the recorded material may adhere and cause condensation. For this reason, when the recording material conveyed through the fixing nip comes into contact with the dewed separating member, water droplets adhere to the recording material, resulting in irregularities in the recording material or image distortion.

  Therefore, by providing a guide member such as a roller or rib on the surface of the separation member to reduce the contact area between the separation member and the recording material, even if there is condensation on the guide surface of the separation member, the recording material contacts this There is known a configuration that prevents water droplets from adhering to the recording material.

  However, in the past, even when the separation member is used in a low humidity and high temperature environment and condensation does not occur, or when recording materials that are difficult to absorb moisture such as coated paper and OHP are used, it is not always necessary to take measures against condensation. There are cases where guide members such as rollers and ribs are installed, and the guide members are in strong contact with the image immediately after fixing, leaving traces on the image. Further, since the guide member needs to be arranged in the vicinity of the high-temperature fixing portion, it is necessary to select a special material excellent in heat resistance and toner releasability as the material of the guide member, which increases the cost of parts. There was a problem.

  For example, in the fixing device described in Patent Document 1, in order to prevent image defects due to condensation on the separation member, the recording material that has passed through the pressure contact portions of the pair of rotating members is peeled off from the surface of the rotating member and guided. It has the peeling member which does. The peeling member is composed of a single metal plate extending along the longitudinal direction of the press contact portion, and has a roller for reducing the contact area of the recording material to the peeling member.

  However, even if it is not necessary to take measures against image defects due to condensation, since the separation member is installed, there is a possibility that a mark may remain on the image due to the ribs and rollers installed on the separation member.

  Therefore, an object of the present invention is to provide a fixing device in which a user can preferentially avoid either an image defect due to condensation or an image defect due to a guide member according to a use environment.

  In order to solve this problem, a fixing member, a pressure rotator provided to face the fixing member, a heat source for heating at least one of the fixing member and the pressure rotator, and the fixing member Positioned downstream of the fixing nip formed by the pressure rotator in the recording material conveyance direction, provided for at least one of the fixing member and the pressure rotator, and passed through the fixing nip. A fixing device for fixing an unfixed toner image on the recording material conveyed to the fixing nip portion, and a flat plate-shaped separating member that separates the recording material from the fixing member or the pressure rotator. The separation member is fixed to the fixing device, and an attachment portion for attaching a guide member attachable to the separation member is formed on the separation member. When the guide member is attached, the guide member is separated from the separation member. Projecting at least a vertical direction from the guide surface of the wood, it proposes a fixing apparatus characterized by.

  The user can select an appropriate configuration of the separation member in accordance with the use environment of the apparatus, and give priority to either avoiding an image defect due to condensation or avoiding an image defect due to the guide member. In addition, the amount of special material used can be suppressed to the minimum necessary, and a device that leads to cost reduction can be proposed.

1 is a diagram illustrating a configuration of an entire image forming apparatus. 2 is a diagram illustrating a configuration of a fixing device 20 installed in the image forming apparatus main body 1. FIG. It is a figure which shows the specific structure of the general separation plate 60. FIG. FIG. 6 is a perspective view of a separation plate 60 provided in the fixing device 20 according to the present embodiment. 3 is a perspective view of a rear surface 60k of a separation plate 60. FIG. It is a perspective view of the separating plate 60 which shows the state which attached the rib 61 to the separating plate 60 shown in FIG. It is a perspective view of the separating plate 60 which shows the state which attached the rib 61 to the separating plate 60 shown in FIG. 6 is a perspective view showing a shape of a rib 61. FIG. It is side surface sectional drawing of the separating plate 60 to which the rib 61 was attached. It is a figure which shows the attachment procedure to the separating plate 60 of the rib 61. FIG. It is a top view of the separating plate 60 to which the rib 61 was attached. It is a perspective view which shows the modification of the rib 61. FIG. FIG. 6 is a partial perspective view of a longitudinal end portion of a separation plate 60 provided in the fixing device 20 according to the present embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
As shown in FIG. 1, the image forming apparatus according to the embodiment is a tandem color printer. Four bottles 102Y, 102M, 102C, and 102K corresponding to the respective colors (yellow, magenta, cyan, and black) are detachably (replaceable) installed in the bottle housing portion 101 above the image forming apparatus main body 1. ing. An intermediate transfer unit 85 is disposed below the bottle housing portion 101. Image forming units 4Y, 4M, 4C, and 4K corresponding to the respective colors (yellow, magenta, cyan, and black) are arranged in parallel so as to face the intermediate transfer belt 78 of the intermediate transfer unit 85.

  Photosensitive drums 5Y, 5M, 5C, and 5K are disposed in the image forming units 4Y, 4M, 4C, and 4K, respectively. Further, around each of the photosensitive drums 5Y, 5M, 5C, and 5K, a charging unit 75, a developing device 76, a cleaning unit 77, a charge eliminating unit, and the like are disposed. Then, an image forming process (charging process, exposure process, developing process, transfer process, cleaning process) is performed on each of the photoconductive drums 5Y, 5M, 5C, and 5K. An image of each color is formed on 5K. The photosensitive drums 5Y, 5M, 5C, and 5K are rotationally driven in the clockwise direction in FIG. 1 by a drive motor. Then, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K are uniformly charged at the position of the charging unit 75 (charging process). Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach the irradiation position of the laser light L emitted from the exposure unit 3, and electrostatic latent images corresponding to the respective colors are formed by exposure scanning at this position. (Exposure process). Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach a position facing the developing device 76, and the electrostatic latent image is developed at this position to form toner images of each color (developing process). ). Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach positions facing the intermediate transfer belt 78 and the primary transfer bias rollers 79Y, 79M, 79C, and 79K, and the photosensitive drums 5Y, 5M are located at this position. The toner images on 5C and 5K are transferred onto the intermediate transfer belt 78 (primary transfer step). At this time, a small amount of untransferred toner remains on the photosensitive drums 5Y, 5M, 5C, and 5K. Thereafter, the surfaces of the photoconductive drums 5Y, 5M, 5C, and 5K reach a position facing the cleaning unit 77, and untransferred toner remaining on the photoconductive drums 5Y, 5M, 5C, and 5K is removed at this position. It is mechanically recovered by a cleaning blade 77 (cleaning process). Finally, the surfaces of the photoconductive drums 5Y, 5M, 5C, and 5K reach a position facing the charge eliminating unit, and the residual potential on the photoconductive drums 5Y, 5M, 5C, and 5K is removed at this position. Thus, a series of image forming processes performed on the photosensitive drums 5Y, 5M, 5C, and 5K is completed.

  Thereafter, the toner images of the respective colors formed on the respective photosensitive drums through the developing process are transferred onto the intermediate transfer belt 78 in an overlapping manner. In this way, a color image is formed on the intermediate transfer belt 78. Here, the intermediate transfer unit 85 includes an intermediate transfer belt 78, four primary transfer bias rollers 79Y, 79M, 79C, and 79K, a secondary transfer backup roller 82, a cleaning backup roller 83, a tension roller 84, and an intermediate transfer cleaning unit 80. , Etc. The intermediate transfer belt 78 is stretched and supported by the three rollers 82 to 84 and is endlessly moved in the direction of the arrow in FIG. The four primary transfer bias rollers 79Y, 79M, 79C, and 79K sandwich the intermediate transfer belt 78 with the photosensitive drums 5Y, 5M, 5C, and 5K, respectively, thereby forming primary transfer nips. Then, a transfer bias reverse to the polarity of the toner is applied to the primary transfer bias rollers 79Y, 79M, 79C, and 79K. The intermediate transfer belt 78 travels in the direction of the arrow and sequentially passes through the primary transfer nips of the primary transfer bias rollers 79Y, 79M, 79C, and 79K. In this way, the toner images of the respective colors on the photosensitive drums 5Y, 5M, 5C, and 5K are primarily transferred while being superimposed on the intermediate transfer belt 78. Thereafter, the intermediate transfer belt 78 onto which the toner images of the respective colors are transferred in an overlapping manner reaches a position facing the secondary transfer roller 89. At this position, the secondary transfer backup roller 82 sandwiches the intermediate transfer belt 78 between the secondary transfer roller 89 and forms a secondary transfer nip. The four color toner images formed on the intermediate transfer belt 78 are transferred onto a sheet P as a recording material conveyed to the position of the secondary transfer nip. At this time, untransferred toner that has not been transferred to the paper P remains on the intermediate transfer belt 78. Thereafter, the intermediate transfer belt 78 reaches the position of the intermediate transfer cleaning unit 80. At this position, the untransferred toner on the intermediate transfer belt 78 is collected. Thus, a series of transfer processes performed on the intermediate transfer belt 78 is completed.

  Here, the sheet P conveyed to the position of the secondary transfer nip is conveyed from the sheet feeding unit 12 disposed below the apparatus main body 1 via the sheet feeding roller 97, the registration roller pair 98, and the like. Is. Specifically, a plurality of sheets P such as transfer sheets are stored in the sheet feeding unit 12 in a stacked manner. When the paper feed roller 97 is driven to rotate counterclockwise in FIG. 1, the uppermost paper P is fed toward the rollers of the registration roller pair 98. The paper P conveyed to the registration roller pair 98 is temporarily stopped at the position of the roller nip of the registration roller pair 98 that has stopped rotating. Then, the registration roller pair 98 is driven to rotate in synchronization with the color image on the intermediate transfer belt 78, and the paper P is conveyed toward the secondary transfer nip. Thus, a desired color image is transferred onto the paper P. Thereafter, the sheet P on which the color image is transferred at the position of the secondary transfer nip is conveyed to the position of the fixing device 20. At this position, the color image transferred on the surface is fixed on the paper P by heat and pressure generated by the fixing belt 21 and the pressure roller 31. Thereafter, the paper P is discharged out of the apparatus through a pair of paper discharge rollers 99. The paper P discharged out of the apparatus by the paper discharge roller pair 99 is sequentially stacked on the stack unit 100 as an output image. Thus, a series of image forming processes in the image forming apparatus is completed.

Next, the configuration of the fixing device 20 installed in the image forming apparatus main body 1 will be described in detail with reference to FIG.
As shown in FIG. 2, the fixing device 20 includes a fixing belt 21 as a belt-shaped fixing member, a nip forming member 26, a heat transfer member 22, a reinforcing member 23 that is a support member that supports the nip forming member 26, and a fixing device. A heater 25 is provided as a heat source for heating the belt 21. The heater 25 is provided inside the fixing belt 21. Further, the fixing device 20 includes a pressure roller 31 as a pressure rotator provided to face the fixing belt 21, a temperature sensor 40 disposed to face the fixing belt 21, and the pressure roller 31 to the fixing belt 21. A contact / separation mechanism 50 that contacts and separates, and a separation plate 60 that is provided on the fixing belt side and separates the paper P from the fixing belt 21.

  In addition to or instead of the heater 25 provided on the fixing belt 21 side, a heater as a heat source may be provided on the pressure roller 31 side as a pressure rotating body. In addition to or instead of the separation plate 60 provided on the fixing belt side, a separation plate for separating the paper P may be provided on the pressure roller side. The separation plate 60 is located downstream of the fixing nip portion N formed by the fixing belt 21 and the pressure roller 31 in the paper conveyance direction, and is provided for at least one of the fixing belt 21 and the pressure roller 31. This is a flat plate member that separates the recording material that has passed through the fixing nip from the fixing belt or the pressure roller.

  Here, the fixing belt 21 is a thin and flexible endless belt, and rotates in the direction of arrow A (counterclockwise) in FIG. The fixing belt 21 has a base material layer, an elastic layer, and a release layer sequentially laminated from the inner peripheral surface side which is a surface in sliding contact with the nip forming member 26, and the total thickness is 1 [mm]. It is set as follows.

  The base material layer of the fixing belt 21 has a layer thickness of 30 [μm] to 100 [μm], and is formed of a metal material such as nickel or stainless steel, or a resin material such as polyimide.

  The elastic layer of the fixing belt 21 has a layer thickness of 100 [μm] to 300 [μm], and is formed of a rubber material such as silicone rubber, foamable silicone rubber, and fluorine rubber. By providing the elastic layer, minute irregularities on the surface of the fixing belt 21 in the fixing nip portion N are not formed, and heat is uniformly transmitted to the toner image T on the paper P, thereby suppressing the generation of a scum skin image.

  The release layer of the fixing belt 21 has a layer thickness of 10 [μm] to 50 [μm]. The release layer is formed of a material such as PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), PTFE (polytetrafluoroethylene), polyimide, polyetherimide, PES (polyether sulfide), or the like. Yes. By providing the release layer, the releasability (peelability) for the toner is ensured.

The diameter of the fixing belt 21 is set to be 15 [mm] to 120 [mm]. In the present embodiment, the diameter of the fixing belt 21 is set to about 30 [mm].
A heat transfer member 22, a reinforcing member 23, a heater 25, a nip forming member 26, and the like are fixed on the inner peripheral surface of the fixing belt 21.

  The nip forming member 26 is formed in a concave shape so that the surface on the pressure roller 31 side follows the curvature of the pressure roller 31. Thereby, since the paper P is sent from the fixing nip portion N so as to follow the curvature of the pressure roller 31, it is possible to suppress a problem that the paper P after the fixing process is not attracted to and separated from the fixing belt 21.

  In this embodiment, the shape of the nip forming member 26 that forms the fixing nip portion N is formed in a concave shape so as to follow the curvature of the pressure roller 31, but the shape of the nip forming member 26 that forms the fixing nip portion N is used. May be formed in a planar shape.

  That is, the surface of the nip forming member 26 facing the pressure roller 31 can be formed to have a planar shape. As a result, the shape of the fixing nip portion N becomes substantially parallel to the image surface of the paper P, and the adhesion between the fixing belt 21 and the paper P is increased, so that the fixing property is improved. Further, since the curvature of the fixing belt 21 at the exit side of the fixing nip portion N is increased, the paper P sent out from the fixing nip portion N can be easily separated from the fixing belt 21.

  The heat transfer member 22 is a pipe-like member obtained by bending a sheet metal having a thickness of 0.1 [mm] into a substantially C shape so that one end and the other end face each other. The heat transfer member 22 is formed so as to directly face the inner peripheral surface of the fixing belt 21 at a position excluding the fixing nip portion N, and is formed in a concave shape inward at the position of the fixing nip portion N. A recess having an opening in which the nip forming member 26 is disposed is provided.

  Both ends of the heat transfer member 22 in the width direction are fixedly supported on the side plate of the fixing device 20. Further, the heat transfer member 22 is heated by the radiant heat (radiant light) of the heater 25 to heat the fixing belt 21. That is, the heat transfer member 22 is directly heated by the heater 25, and the fixing belt 21 is indirectly heated by the heater 25 through the heat transfer member 22.

  As a material of the heat transfer member 22, a metal heat conductor (a metal having heat conductivity) such as aluminum, iron, stainless steel, or the like can be used. In addition, the heating efficiency of the heat transfer member 22 and the fixing belt 21 can be improved by setting the thickness of the heat transfer member 22 to 0.2 [mm] or less. In the present embodiment, the heat transfer member 22 is formed of a stainless steel plate having a thickness of 0.1 [mm].

  The heater 25 is a halogen heater or a carbon heater, and both ends thereof are fixed to the side plate of the fixing device 20. The heat transfer member 22 is heated by the radiant heat of the heater 25 whose output is controlled by the power supply unit of the image forming apparatus main body. Further, the fixing belt 21 is entirely heated by the heat transfer member 22 at a position excluding the fixing nip portion N, and heat is applied to the toner image T on the paper P from the surface of the heated fixing belt 21.

  The output control of the heater 25 is performed based on the detection result of the belt surface temperature by the temperature sensor 40 such as a thermistor facing the surface of the fixing belt 21. By such output control of the heater 25, the temperature of the fixing belt 21 (fixing temperature) can be set to a desired temperature.

  As described above, in the fixing device 20 in the present embodiment, not only a part of the fixing belt 21 is locally heated, but the fixing belt 21 is almost entirely heated in the circumferential direction by the heat transfer member 22. It will be. Therefore, even when the speed of the apparatus is increased, the fixing belt 21 can be sufficiently heated to prevent the occurrence of fixing failure.

That is, since the fixing belt 21 can be efficiently heated with a relatively simple configuration, the warm-up time and the first print time are shortened, and the size of the apparatus is reduced.
Here, the gap G (gap at a position excluding the fixing nip portion N) between the fixing belt 21 and the heat transfer member 22 at normal temperature is greater than 0 [mm] and less than or equal to 1 [mm] (0 [mm] <G ≦ 1 [mm]). As a result, the area where the heat transfer member 22 and the fixing belt 21 are in sliding contact with each other can be prevented, and the problem of accelerated wear of the fixing belt 21 can be suppressed, and the heat transfer member 22 and the fixing belt 21 are too far away from each other. It can suppress that the heating efficiency of this falls.

  Further, since the heat transfer member 22 is provided close to the fixing belt 21, the circular posture of the flexible fixing belt 21 is maintained by the heat transfer member 22 to some extent. Damage can be reduced.

  Further, fluorine grease is applied between the fixing belt 21 and the heat transfer member 22 as a lubricant so that the wear of the fixing belt 21 is reduced even if the heat transfer member 22 and the fixing belt 21 are in sliding contact. Yes.

  In order to reduce the sliding resistance between the heat transfer member 22 and the fixing belt 21, a material having a low friction coefficient with respect to the fixing belt 21 on the sliding surface of the heat transfer member 22 that is in sliding contact with the inner peripheral surface of the fixing belt 21. The heat transfer member 22 may be formed. Further, a surface layer made of a material containing fluorine may be formed on the inner peripheral surface of the fixing belt 21.

  The reinforcing member 23, which is a support member that supports the nip forming member 26, is for reinforcing and supporting the nip forming member 26 that forms the fixing nip portion N, and is fixed to the inner peripheral surface side of the fixing belt 21. ing.

  The reinforcing member 23 is formed such that the length in the width direction (longitudinal direction) is equal to the length in the width direction (longitudinal direction) of the nip forming member 26, and both ends in the width direction are formed on the side plate of the fixing device 20. Fixedly supported.

  The reinforcing member 23 abuts the pressure roller 31 via the nip forming member 26, the fixing belt 21, and the sliding sheet 28, so that the nip forming member 26 applies the pressure force of the pressure roller 31 in the fixing nip portion N. It is restrained from being greatly deformed.

  In addition, in order to satisfy the function mentioned above, it is preferable to form the reinforcing member 23 with a metal material having high mechanical strength such as stainless steel or iron. In addition, a heat insulating member can be provided on a part or all of the surface of the reinforcing member 23 facing the heater 25, or a BA treatment or a mirror polishing treatment can be performed.

  As a result, heat from the heater 25 toward the reinforcing member 23 (heat for heating the reinforcing member 23) is used for heating the heat transfer member 22, so that the heating efficiency of the fixing belt 21 and the heat transfer member 22 is further improved. Will do.

  The pressure roller 31 that contacts the outer peripheral surface of the fixing belt 21 at the position of the fixing nip N has a diameter of about 30 [mm], and has an elastic layer 33 formed on a hollow cored bar 32. . A heat source such as a halogen heater can be provided inside the hollow cored bar 32.

  The elastic layer 33 of the pressure roller 31 is made of a material such as silicone rubber, foamable silicone rubber, or fluorine rubber. A thin release layer made of PFA, PTFE, or the like can be provided on the surface layer of the elastic layer 33.

  The pressure roller 31 is pressed against the fixing belt 21 to form a desired fixing nip portion N between both members. Both ends of the pressure roller 31 in the width direction are rotatably supported on the side plate of the fixing device 20 via bearings. The pressure roller 31 is provided with a gear that meshes with the drive gear of the drive mechanism. The pressure roller 31 is rotated in the direction of arrow B (clockwise) in FIG. 2 by the rotational driving force transmitted from the drive mechanism. Driven by rotation.

  When the elastic layer 33 of the pressure roller 31 is formed of a sponge-like material such as foamable silicone rubber, the pressure applied to the fixing nip portion N can be reduced. Can be reduced.

  Furthermore, since the heat insulation of the pressure roller 31 is enhanced and the heat of the fixing belt 21 is difficult to move to the pressure roller 31 side, the heating efficiency of the fixing belt 21 is improved.

  In this embodiment, the fixing belt 21 is formed so that the diameter of the fixing belt 21 is equal to the diameter of the pressure roller 31, but the diameter of the fixing belt 21 is smaller than the diameter of the pressure roller 31. You can also In this case, since the curvature of the fixing belt 21 at the fixing nip N is smaller than the curvature of the pressure roller 31, the sheet P sent out from the fixing nip N is easily separated from the fixing belt 21.

  In addition, the diameter of the fixing belt 21 can be formed to be larger than the diameter of the pressure roller 31, but the pressure roller 31 is independent of the relationship between the diameter of the fixing belt 21 and the diameter of the pressure roller 31. The applied pressure is not applied to the heat transfer member 22.

Hereinafter, a normal operation of the fixing device 20 configured as described above will be briefly described.
When the power switch of the image forming apparatus main body 1 is turned on, power is supplied from the power source provided in the image forming apparatus main body 1 to the heater 25, and the pressure roller 31 rotates in the direction of arrow B in FIG. Driving is started.

As the pressure roller 31 rotates in this way, the fixing belt 21 is also driven to rotate in the direction of arrow A in FIG. 2 due to the frictional force generated between the pressure roller 31 and the fixing belt 21.
The sheet P carrying the toner image T, which is an unfixed image, is conveyed in the direction of the arrow C1 in FIG. 2 while being guided by the guide plate, and the fixing nip N of the fixing belt 21 and the pressure roller 31 that are in a pressure contact state. To be sent to.

  The sheet P is heated by the fixing belt 21 heated by the heat transfer member 22 that receives heat from the heater 25 and the pressing force between the nip forming member 26 reinforced by the reinforcing member 23 and the pressure roller 31. The toner image T is fixed on the surface of the toner. Thereafter, the paper P sent out from the fixing nip N is conveyed in the direction of the arrow C2.

  At this time, the paper P may easily stick to the fixing belt 21 due to factors such as the type and state of the paper P, the environmental conditions in which the machine is placed, and the amount of toner attached. In such a case, the sheet P is picked up by the separation plate 60 and separated from the fixing belt 21 and conveyed in the direction of arrow C2. Thus, a series of fixing processes in the fixing device 20 is completed.

FIG. 3 is a diagram illustrating a specific configuration of a general separation plate 60.
The separation plate 60 can be rotated by fitting a rotation shaft hole 60 a of the separation plate 60 into a rotation shaft provided in the frame of the fixing device 20. The leading end 60c, which is the upstream end of the separation plate 60 in the sheet passing direction and has a function of separating the paper P from the fixing belt 21, has a clearance of less than 2 mm from the surface of the fixing belt 21. Hold and face each other. Positioning surfaces 60 b that are positioning portions for positioning the separating plate 60 with respect to the fixing belt 21 are provided at both ends in the longitudinal direction of the separating plate 60. Then, the separation plate 60 is biased toward the fixing belt 21 by the torsion spring, and the positioning surface 60b comes into contact with the non-image area on the surface of the fixing belt 21, so that the separation plate 60 is finally positioned with respect to the fixing belt 21. Made. The front end of the positioning surface 60b is bent, and the contact surface with the fixing belt 21 is formed smoothly.

  Further, since the fixing belt 21 and the separation plate 60 are positioned only by the separation plate, it is easy to adjust the gap between the fixing belt 21 and the separation plate 60. As shown in FIG. 2, the paper P on which the toner image is placed is fixed by the fixing belt 21 and comes out of the fixing nip portion N. At this time, it is ideal that the paper P is naturally separated from the fixing belt 21 by the curvature of the fixing belt 21 and the rigidity of the paper P. However, the paper P may be easily wound around the fixing belt 21 due to various factors such as the paper P, strain, humidity, and toner loading. The separation plate 60 separates the sheet P from the fixing belt 21 by picking up a slight lift of the leading edge of the sheet from the surface of the fixing belt 21 by the leading end portion 60 c.

  The separation plate 60 can be provided with the front end portion 60 c in contact with or close to the surface of the fixing belt 21. In FIG. 2, which is a cross-sectional view as viewed in the longitudinal direction, the front end portion 60 c of the separation plate 60 appears to be in contact with the fixing belt 21, but at least in the range of the paper width, the fixing belt surface and the front end portion 60 c of the separation plate 60. The gap is less than 2 [mm]. This is to prevent the surface of the fixing belt 21 from being damaged by the separation plate 60, because if the surface of the fixing belt 21 is damaged due to contact, the image will be affected by scratches when the toner is fixed.

  Further, the separating plate 60 extends in the longitudinal direction of the separating plate so as to penetrate the guide surface 60d facing the sheet P to be conveyed and the back surface 60k (FIG. 5) facing the fixing belt 21 on the side opposite to the guiding surface 60d. An opening 60e is provided over the sheet passing width direction. The separation plate 60 shown in FIG. 3 has four openings 60e.

  These openings 60e are holes through which water vapor generated when the paper P is heated escapes upward. When there is no opening 60e, the water vapor that has lost its escape is condensed on the back surface 60k of the separation plate 60 and the like, and flows down to the fixing belt 21 and further adheres to the paper P. Or a toner image abnormality may occur.

4 is a perspective view of the separation plate 60 provided in the fixing device 20 according to the present embodiment, and FIG. 5 is a perspective view of the back surface 60k of the separation plate 60.
As shown in FIG. 4, ribs that are attachment portions for attaching ribs 61, which are guide members that can be attached to the separation plate 60, to the portion of the guide surface 60 d between the adjacent openings 60 e of the separation plate 60. A mounting hole 60i is formed. The rib 61 will be described later with reference to FIGS. 6, 8, 9, etc., but the rib 61 protrudes at least in the vertical direction from the guide surface 60 d of the separation plate 60 when the rib 61 is attached. The rib attachment hole 60i in the longitudinal direction of the separation plate 60 is desirably arranged so as to avoid a position where an end in the width direction of a standard size sheet that can be used in the fixing device and the image forming apparatus passes. This is because if the paper edge passing position and the rib attachment hole 60i overlap, the edge in the width direction of the paper P may be caught by the rib attachment hole 60i, and the paper P may be folded or jammed.

  An opening e is provided between the rib attachment holes 60i formed in the separation plate 60 so as to pass through the guide surface 60d facing the paper P and the back surface facing the fixing belt 21 on the opposite side. ing. The separation plate 60 has six openings 60e in the longitudinal direction. By providing the opening 60e in the separation plate 60, condensation does not occur in the opening and the heat capacity of the separation plate 60 can be reduced, so that the effect of preventing image defects due to condensation can be enhanced.

  Further, a first bent portion 60f that is bent from the guide surface 60d side toward the fixing belt 21 and the back surface 60k (FIG. 5) is formed on the upstream side of the opening 60e in the sheet conveyance direction. Has been. Since the first bent portion 60f extending in the longitudinal direction receives a force from the sheet, the strength of at least the tip 60c side of the separation plate 60 can be maintained over the longitudinal direction of the separation plate. Thereby, the plate | board thickness of the separation plate 60 can be made thinner than the case where the 1st bending part 60f is not provided, and the heat capacity of the separation plate 60 can be reduced further. Therefore, as compared with the case where the opening 60e and the first bent portion 60f are not provided, when the heater 25 is turned on and started to warm from a low temperature environment, the temperature of the separation plate 60 can be quickly increased. Water droplets generated above can be evaporated at an early stage. Further, the first bent portion 60f bent toward the fixing belt 21 and the back surface 60k side does not interfere with the sheet passing.

  Also, a second bent portion 60g that is bent from the guide surface 60d side toward the fixing belt 21 and the back surface 60k (FIG. 5) is formed on the downstream side of the opening 60e in the sheet conveyance direction, which extends in the longitudinal direction. Has been. Thereby, the strength in the longitudinal direction of the separation plate 60 can be further increased.

  However, when printing is started while the separation plate 60 is not sufficiently heated, such as immediately after power-on in a low temperature environment, condensation occurs on the separation plate 60 even with the above-described configuration. However, image defects may occur. In order to avoid this, it is possible to attach ribs to the separation plate 60 later as shown in FIG.

6 is a perspective view of the separation plate 60 showing a state where the rib 61 is attached to the separation plate 60 shown in FIG. 4, and FIG. 7 is a separation showing a state where the rib 61 is attached to the separation plate 60 shown in FIG. 3 is a perspective view of a plate 60. FIG.
The rib 61 is a linear member that can be attached to and detached from the rib attachment hole 60 i of the separation plate 60 and protrudes from the surface of the separation plate 60 in a state of being attached to the separation plate 60. The rib 61 extends linearly in the paper transport direction. By mounting the rib 61 on the surface of the separation plate 60, the paper P is lifted and guided by the rib 61, and the contact area between the guide surface 60d of the separation plate 60 and the paper P can be reduced. Therefore, even if there is condensation on the guide surface 60d of the separation plate 60, it is difficult for the paper P to come into contact with the condensation, and water droplets can be prevented from adhering to the paper P. In addition, the rib 61 which is a linear member can reduce the shape of the rib attachment hole 60i formed on the separation plate, so that the rib 61 is not installed on the separation plate (FIGS. 4 and 5). It is possible to reduce the occurrence of edge folding or jamming of the paper due to the attachment hole 60i.

  The surface of the rib 61 that slides with the image surface of the paper P is preferably formed at an acute angle or has an R. Thereby, since the sliding area between the image surface and the rib 61 becomes smaller, it is possible to reduce the area of the rib trace on the image and the image disturbance due to the rubbing.

  The material of the rib 61 is preferably made of a fluororesin. Fluororesin is a special material with high heat resistance and excellent slidability and releasability. Therefore, the ribs 61 do not deform even on the separation plate 60 that becomes hot during fixing, and accumulation of foreign matters such as toner occurs. Hard to do. Therefore, the paper P can be stably passed for a long time.

FIG. 8 is a perspective view showing the shape of the rib 61.
As shown in FIG. 8A, the rib 61 has a guide surface 61e extending linearly in the paper transport direction. A flat upstream end 61a is formed upstream of the guide surface 61e. A fixing portion 61d provided on the left and right sides of the guide surface 61e and a positioning boss 61b protruding rearward of the guide surface 61e are formed at the longitudinal center of the guide surface 61e. As can be seen from FIG. 8B, the contact surface of the fixing portion 61d that contacts the guide surface 60d of the separation plate 60 is formed flat and is configured to be in close contact with the guide surface 60d. By forming the two fixing portions 61d on the left and right of the guide surface 61e, the rib 61 is stabilized and does not wobble with respect to the separation plate 60. The downstream side of the guide surface 61e is formed as a downstream side end portion 61c that snap-fits to the rib attachment hole 60i of the separation plate 60. When the rib 61 is attached to the separation plate 60 (FIG. 9), the guide surface 61e gradually increases from the guide surface 60d of the separation plate 60 from the upstream side toward the downstream side, and from the vicinity of the positioning boss 61b to the downstream side. The side edges 61c have the same height. Furthermore, the guide surface 61e is formed at an acute angle over its entire length, and its tip 61f is formed flat by chamfering. Accordingly, the paper P smoothly contacts the guide surface 61e, and the paper is not easily damaged.

FIG. 9 is a side sectional view of the separation plate 60 to which the rib 61 is attached, and FIG. 10 is a diagram illustrating a procedure for attaching the rib 61 to the separation plate 60.
As shown in FIG. 9, the rib 61 configured separately from the separation plate 60 is attached to a rib attachment hole 60 i provided in the guide surface 60 d of the separation plate 60 as illustrated. In a state where the rib 61 is attached, the rib 61 protrudes at least in the vertical direction from the guide surface 60 d of the separation plate 60.

The procedure for attaching the rib 61 to the separation plate 60 is as follows.
First, the user holds the rib 61 (FIG. 10A) and inserts the upstream end 61a of the rib 61 into the upstream rib attachment hole 60i (FIG. 10B). Next, the user inserts the positioning boss 61b of the rib 61 into the central rib mounting hole 60i which is a round hole (FIG. 10C), and finally the downstream end portion 61c of the rib 61 is a downstream side which is a square hole. The rib 61 is fixed to the separation plate 60 by snap fitting of the downstream end 61c (FIG. 10D). By using such a snap-fit attachment method, the user can easily attach the rib 61 to the separation plate 60 later. As described above, the shape of the separation plate 60 is configured so that it is possible to pass the paper without the rib 61, but it is possible to pass the paper with the rib 61 attached. Therefore, a user who uses the image forming apparatus in a situation in which condensation is likely to occur on the separation plate 60 can prevent image defects by attaching the rib 61 to the fixing device 20 later. Further, a countermeasure against condensation is not necessary, and a user who is more concerned about an image mark by the rib can use the image forming apparatus as it is without attaching the rib 61 to the separation plate 60. Since the rib 61 is provided only to the necessary users in this way, it is possible to reduce the average cost of the fixing device as compared with the case where the rib is previously mounted on all the fixing devices.

FIG. 11 is a plan view of the separation plate 60 to which the rib 61 is attached.
As illustrated, the rib 61 protrudes from the guide surface 60 d of the separation plate 60. The surface (guide surface 61e) of the rib 61 that slides with the image surface of the paper P is formed at an acute angle or has an R. The fixing portion 61 d is in close contact with the guide surface 60 d of the separation plate 60, and the rib 61 does not wobble with respect to the separation plate 60.

FIG. 12 is a perspective view showing a modification of the rib 61.
In addition to the rib configuration shown in FIG. 8, the rib 61 includes a roller 61g that can rotate about the shaft 61h between the upstream end 61a and the fixing portion 61d. The shaft 61h protrudes laterally from both sides of the guide surface 61e, and is mounted on the shaft 61h so that the roller 61g does not come off. Since the roller 61g protrudes above the guide surface 61e, the paper P separated from the surface of the fixing belt 21 by the tip 60c does not slide or slightly slides with the guide surface 61e. Is guided downstream. That is, the rib 61 has a roller 61g as a roller member protruding from the surface of the separation plate 60 when attached to the separation plate 60. Accordingly, the paper is more unlikely to be damaged than the ribs that are linear members, and it is less likely to cause rubbing and image defects.

  The surface of the roller 61g that slides on the image surface of the paper P is formed at an acute angle or has an R. Thereby, since the sliding area between the image surface and the roller 61g becomes smaller, it is possible to reduce the area of the rib trace on the image and image disturbance due to rubbing.

  The material of the roller 61g is preferably made of a fluororesin. Fluororesin is a special material with high heat resistance and excellent slidability and releasability. Therefore, the roller 61g does not deform even on the separation plate 60 that becomes hot during fixing, and accumulation of foreign matters such as toner occurs. Hard to do. Therefore, the paper P can be stably passed for a long time.

  The width of the rib attachment hole 60i corresponding to the upstream end 61a is such that the radius of the roller 61g is large and the roller 61g does not come into contact with the separation plate 60 before the rib 61 is snap-fit engaged with the separation plate 60. Or it is necessary to increase the vertical width.

FIG. 13 is a partial perspective view of the end portion in the longitudinal direction of the separation plate 60 provided in the fixing device 20 according to the present embodiment.
The rotation shaft hole 60 a of the separation plate 60 is fitted into a rotation shaft 63 provided in the frame 62 of the fixing device 20, and can be rotated together with the rotation shaft 63. Thus, the separation plate 60 is fixed to the fixing device side. Therefore, the user can attach or remove the separation plate 60 to or from the fixing device according to the usage environment. The rotating shaft 63 extends axially inward from the frame 62. The positioning surface 60 b of the separation plate 60 is in contact with the surface of the fixing belt 21 in the non-image region, and thereby the separation plate 60 is positioned with respect to the fixing belt 21. That is, the separation plate 60 has a positioning surface 60 b for the fixing belt 21. As described above, the tip of the positioning surface 60b is bent, and the contact surface with the fixing belt 21 is formed smoothly.

  As described above, in the present invention, the rib attachment holes 60i of the guide members such as the ribs 61 are provided in the separating plate 60 in an arrangement that does not hinder the sheet conveyance, and the user can attach the guide members as necessary. . It is possible to pass the paper without attaching the guide member to the fixing device, or to pass the paper with the guide member attached. In situations where condensation is likely to occur on the separation plate 60, such as when using in a high humidity / low temperature environment or when printing is often performed immediately after returning from sleep from a cold state, the user attaches a guide member to the separation plate. Image defects can be prevented. On the contrary, there is no need for countermeasures against condensation, and users who are more concerned about image quality who are more concerned about roller traces or rib traces from the guide member can use the fixing device as it is without wearing the guide member. .

20 fixing device 21 fixing belt (fixing member)
25 Heater (heat source)
31 Pressure roller (Pressure rotating body)
60 Separation plate (separation member)
60d Guide surface 60i Rib mounting hole (mounting part)
61 Rib (guide member)
N Fixing nip P Recording material

Japanese Patent No. 4311012

Claims (13)

A fixing member;
A pressure rotator provided to face the fixing member;
A heat source for heating at least one of the fixing member and the pressure rotating body;
The fixing nip formed by the fixing member and the pressure rotator is located on the downstream side in the recording material conveyance direction, and is provided for at least one of the fixing member and the pressure rotator. A plate-shaped separating member that separates the recording material that has passed through the fixing member or the pressure rotator, and
In a fixing device for fixing an unfixed toner image on a recording material conveyed to the fixing nip portion,
The separating member is fixed to a fixing device;
An attachment portion for attaching a guide member attachable to the separation member is formed on the separation member,
In a state where the guide member is attached, the guide member protrudes at least in the vertical direction from the guide surface of the separation member.   The fixing device according to claim 1, wherein the separation member has a positioning surface with respect to the fixing member.   The fixing device according to claim 1, wherein the attachment portion is disposed so as not to overlap a position where a width direction end portion of a recording material of a standard size that can be used in the fixing device passes.   The fixing device according to claim 1, wherein the guide member is a linear member that protrudes from a surface of the separation member in a state of being attached to the separation member.   The fixing device according to claim 4, wherein the surface of the linear member that slides with the image surface of the recording material is formed at an acute angle or has an R.   6. The fixing device according to claim 4, wherein a material of the linear member is a fluororesin.   The fixing device according to claim 1, wherein the guide member includes a roller member protruding from a surface of the separation member in a state of being attached to the separation member.   The fixing device according to claim 7, wherein a surface of the roller member that slides with an image surface of the recording material is formed at an acute angle or has an R.   The fixing device according to claim 7, wherein a material of the roller member is a fluororesin.   Between the mounting portions formed on the separation member, the guide surface facing the recording material and the back surface facing the fixing member or the pressure rotating body on the opposite side to the guide surface are penetrated. The fixing device according to claim 1, wherein an opening is provided.   A first bent portion that is bent from the guide surface side toward the back surface side is formed on the upstream side of the opening in the recording material conveyance direction that extends in the longitudinal direction. Item 11. The fixing device according to Item 10. A fixing member;
A pressure rotator provided to face the fixing member;
A heat source for heating at least one of the fixing member and the pressure rotating body;
The fixing nip formed by the fixing member and the pressure rotator is located on the downstream side in the recording material conveyance direction, and is provided for at least one of the fixing member and the pressure rotator. A plate-shaped separating member that separates the recording material that has passed through the fixing member or the pressure rotator, and
A guide member attachable to a fixing device for fixing an unfixed toner image on a recording material conveyed to the fixing nip portion;
The separating member is fixed to a fixing device;
The guide member can be attached to an attachment portion formed on the separation member,
In a state where the guide member is attached, the guide member protrudes at least in the vertical direction from the guide surface of the separation member. An image forming apparatus comprising the fixing device according to claim 1.

Images