JP5134918B2 - Sheet separating device for fixing device in image forming apparatus - Google Patents

Description

  The present invention relates to a sheet separating device of a fixing device in an image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine using an electrophotographic method, and particularly expands by heat from a heater arranged inside. The present invention relates to a sheet separating device of a fixing device in an image forming apparatus that can separate sheets without damaging a fixing roller.

  In image forming apparatuses such as copiers, printers, facsimiles, and composite machines using electrophotography, a toner image formed on a photoconductor is transferred to paper by electrophotography, and a heater is incorporated, for example. The toner image transferred by a fixing device composed of a fixing roller and a pressure roller is melted and fixed on a sheet. In many cases, the fixing roller used in the fixing device is subjected to Teflon (registered trademark) processing or the like in consideration of heat resistance characteristics while preventing the toner offset phenomenon.

  However, when the toner on the paper sandwiched between the fixing roller and the pressure roller is melted by the heat of the fixing roller, the toner may adhere to the fixing roller and the paper may be wound around the surface of the fixing roller.

  For this reason, for example, Patent Document 1 discloses a main body portion that is movable toward and away from the fixing roller, and a claw portion that is provided on the main body portion so as to face the surface of the fixing roller and separates the recording paper from the fixing roller. And a roller member that is rotatably attached to the main body and abuts against the surface of the fixing roller and rotates and holds the claw portion at a predetermined distance from the surface of the fixing roller. There has been disclosed a recording paper separation claw that can be reliably separated from the fixing roller and reliably prevent problems such as scraping the roller surface.

JP-A-6-156845

  However, in the configuration shown in Patent Document 1, the shape of the separation claw is complicated, so that the cost is high, and materials that can be used for the separation claw are limited to some types of heat-resistant resin. . In addition, because of the structure in which a rotatable roller member is directly attached to the separation claw body, a certain amount of clearance is required between the roller member mounting portion of the separation claw body and the roller member. If the separation claw main body and the roller member are made of a high resin, this gap must be increased. Therefore, when the gap between the claw portion and the roller surface when the roller is controlled to the fixing temperature is set to a predetermined value, the roller When the temperature is low, the gap between the claw portion and the roller surface becomes smaller than a predetermined value, and there is a possibility that the contact is worst.

  Therefore, in the present invention, regardless of the temperature of the fixing member, the gap between the surface of the fixing member and the leading end portion of the peeling guide member (hereinafter referred to as a paper separating member) is always substantially constant, Paper in a fixing device of an image forming apparatus that prevents image defects caused by scratches caused by contact with a fixing member and realizes energy saving and durability improvement by shortening warm-up without increasing space and cost. The problem is to provide a separation device.

In order to solve the above problems, a sheet separating device for a fixing device in an image forming apparatus according to the present invention is:
A heater is arranged inside, and the tip is not on the surface of the fixing roller on the downstream side in the rotation direction of the fixing roller that heats and melts and fixes the toner image formed on the photoconductor and transferred onto the sheet by electrophotography. In a sheet separating device of a fixing device in an image forming apparatus having a plate-shaped sheet separating member provided to be in contact,
The front end of the paper separating member is urged toward the fixing roller and is configured to be rotatable about a shaft fixed to the fixing device frame or the housing, and the paper separating member is formed at both ends along the rotational axis direction. each fixed multiple positioning member is, the fixing roller in contact with the surface contact with the rotary member to be rotated, that it has to keep the distance between the fixing roller and the paper separating member tip constant Features.

As thus, the positioning member of the sheet separating member and the sheet separating member is driven to rotate in contact with the fixing roller surface by making contact with the rotary member provided separately from the fixing roller is expanded by heat Even when the diameter is increased, the rotating member that rotates following contact with the surface of the fixing roller pushes up the sheet separating member by that amount, so that the distance between the leading edge of the sheet separating member and the fixing roller can be kept constant, and the sheet is separated. It is possible to prevent image defects caused by scratches due to contact of the member with the fixing roller, and to realize energy saving and durability improvement by shortening warm-up without increasing space and cost. In addition, by configuring the sheet separating member and the rotating member as separate members without integrating them, it is possible to simplify the shapes of the respective members, and the types of materials constituting each of them are less limited.

The rotating member is made of a material having a thermal expansion coefficient of 5 × 10 ⁻⁵ / K or less, so that the rotating member does not expand greatly even when heat from the fixing roller is transmitted to the rotating member. Thus, the distance between the front end of the sheet separating member and the fixing roller can be kept constant.

The front Symbol locating member screwed into the female threaded portion provided on the sheet separating member forms a thread shape, adjustably provided the distance between the fixing roller side tip and the fixing roller in the sheet separating member Accordingly, the positioning member can be easily fixed to the sheet separating member, and the distance between the leading end of the sheet separating member and the fixing roller can be easily adjusted.

  As described above, the sheet separating device of the fixing device in the image forming apparatus according to the present invention can always maintain a constant distance from the fixing roller at the front end of the sheet separating member regardless of the temperature of the fixing roller, thereby increasing space and cost. Therefore, it is possible to prevent image defects caused by scratches caused by contact of the sheet separating member with the fixing roller, thereby realizing energy saving, improved durability, improved image quality, etc. by shortening warm-up.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.

  FIG. 1 is a schematic cross-sectional view of a configuration of an image forming apparatus including a first embodiment of a sheet separating device for a fixing device according to the present invention. As described above, in the image forming apparatus, the electrostatic latent image formed on the photoconductor 10 by the electrophotographic method is developed by the developing device 11 to form a toner image, and the toner image is formed by the registration roller pairs 12 and 13. For example, the image is transferred to a recording sheet (hereinafter simply referred to as a sheet) sent to a transfer unit having the transfer roller 14. Thereafter, a heater 15 is disposed on the toner image on the sheet, and a fixing roller 16 and a pressure roller 17 for controlling the temperature based on a temperature detected by a temperature sensor 18 such as a thermistor provided in a non-sheet passing region on the surface, Is melted at the nip portion of the fixing device, and is fixed on the paper and discharged onto a paper discharge tray (not shown).

  The fixing roller 16 in this fixing device is provided with an elastic layer 162 such as silicon rubber having a thickness of 0.3 mm on the outer periphery of a core metal 161 such as aluminum having a thickness of about 1.0 mm, and further, PFA is provided on the surface of the elastic layer 162. Coated with a release layer 163 of a fluororesin such as (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), PTFE (polytetrafluoroethylene), FEP (tetrafluoroethylene-hexafluoropropylene copolymer), etc. 161 is provided with a heater 15 as a heat source to have an outer diameter of 25 mm.

  The pressure roller 17 is provided with an elastic layer 172 such as silicon rubber having a thickness of 5.5 mm on the outer periphery of a cored bar 171 such as aluminum or iron having a diameter of 14 mm. A fluororesin release layer 173 is coated to have an outer diameter of 25 mm, and is rotated while forming a nip portion with the fixing roller 16 by being pressed against the fixing roller 16 by a pressing means (not shown). It has become. Note that these numerical values relating to the fixing roller 16 and the pressure roller 17 are merely examples, and it is obvious that the present invention is not limited to these numerical values.

  Further, on the exit side in the sheet conveyance direction at the nip portion between the fixing roller 16 and the pressure roller 17, that is, on the downstream side in the rotation direction of the fixing roller 16, the shaft 191 serves as a fulcrum so as to be rotatable in the direction indicated by the arrow 192. A sheet separating member 19 that is supported and made of metal, heat resistant resin, or the like and is not in contact with the fixing roller 16 is provided. The surface of the sheet separating member 19 on the sheet conveying side is coated with a release layer made of fluororesin such as PFA or PTFE. Although not shown, the sheet separating member tip 193 is biased toward the fixing roller 16 by a spring or the like. ing. In the illustrated example, the sheet separating member 19 is a sheet separating plate that is not in contact with the fixing roller 16; however, as will be described later, a separating claw made of a heat-resistant resin or the like may be used.

  In this embodiment, the sheet separating member 19 is fixed with a rod-like or screw-like positioning member 21 in the form of a screw, and on the fixing roller 16 side, the rotation rotates in contact with the surface of the fixing roller 16 and rotates. A roller or roller 20 is provided as a member, and one end of the positioning member 21 is in contact with the rotating member 20.

  Therefore, even if the fixing roller 16 expands due to heat and its diameter increases, the rotating member 20 that rotates following the surface of the fixing roller 16 pushes up the sheet separating member 19 and pushes the sheet separating member 19 accordingly. The distance between the leading edge 193 and the fixing roller 16 is kept constant, preventing image defects caused by scratches caused by the contact of the sheet separating member 19 with the fixing roller 16, and without increasing space and cost. Energy saving and durability improvement can be realized by shortening warm-up. Further, since the sheet separating member 19 and the rotating member 20 are configured as separate members without being integrated, it is possible to simplify the shape of each, and the types of materials constituting each of them are less limited. .

  FIG. 2 is a perspective view showing a schematic configuration of the sheet separating member 19, the positioning member 21, and the rotating member 20. The sheet separating member 19 is formed by processing a sheet metal such as SUS having a thickness of about 1.0 mm into a “<” shape in cross section as shown in the figure, and projecting portions 191 serving as rotating shafts at both ends. A rod-like or screw-like positioning member 21 having a rod shape is fixed to the sheet separating member 19, and the rotating member 20 has substantially the same axial length as the fixing roller 16, and one end of the positioning member 21 is connected to the rotating member 20. It is made to contact.

  The positioning member 21 is fixed to the paper separating member 19 by providing a screw portion on the positioning member 21 and by screwing a female screw on the paper separating member 19 side so that the paper separating member tip 193 and the fixing roller 16 are engaged with each other. The interval can be adjusted, or if there is no need for adjustment, it can be fixed with an adhesive as it is. Further, when the fixing of the fixing portion by the screw-shaped contact is weak, the fixing may be assisted by using a heat-resistant type adhesive or the like, and the tip 193 of the paper separating member 19 is a separate member, and a SUS having a thickness of 0.2 mm. Alternatively, laser spot welding may be performed on a sheet metal such as the above.

The rotating member 20 has, for example, a roller shape made of a SUS material having an outer diameter of 5 mm. The material is not a resin having a large thermal expansion, but a material having a thermal expansion coefficient of 5 × 10 ⁻⁵ / K or less, for example, It is preferable to use SUS, Fe, glass, ceramic or the like. In the illustrated example, a solid SUS material is used, but this may be hollow. Furthermore, it is also preferable to coat or tube-coat the surface of the rotating member with a fluorine-based resin such as PFA or PTFE. By using such a low expansion coefficient material, even if heat from the fixing roller 16 is transmitted to the rotating member 20, the rotating member 20 does not expand greatly, and the sheet separating member front end 193 and the fixing roller are stably provided. The interval with 16 can be kept constant.

  FIG. 3 is a schematic cross-sectional view of a configuration of an image forming apparatus including a second embodiment of the sheet separating device of the fixing device according to the present invention. In the second embodiment shown in FIG. 3, the separation claw 30 is used as the paper separation member, and examples of the material constituting the separation claw 30 include heat-resistant resin and ceramic. Is preferably used. In FIG. 3, the same components as those in FIG. 1 are assigned the same reference numerals, and the description thereof is omitted. Reference numeral 31 denotes a roller or roller as a rotating member that rotates in contact with the surface of the fixing roller 16. In the separation claw 30, 301 is an axis of the sheet separating member 30, 302 is an arrow indicating the rotation direction of the sheet separating member 30, 303 is a leading end of the sheet separating member, and 304 is a positioning portion.

  Also in the second embodiment, as in the first embodiment described above, the separation claw 30 is biased toward the fixing roller 16 by a spring or the like, although the tip 303 is not shown, and the PFA on the paper transport side surface A release layer of fluororesin such as PTFE or PTFE is coated. Further, the contact portion of the separation claw 30 with the rotating member 31 is formed as a positioning portion 304, and this positioning portion 304 is formed with high accuracy so that the separation claw tip 303 keeps a certain distance from the surface of the fixing roller 16. .

  Therefore, as in the case of the first embodiment, even when the fixing roller 16 expands due to heat and its diameter increases, the rotating member 31 that rotates in contact with the surface of the fixing roller 16 pushes up the separation claw 30 by that amount, Since the distance between the tip 303 of the separation claw 30 and the fixing roller 16 is kept constant, image defects caused by scratches caused by contact of the separation claw 30 with the fixing roller 16 are prevented, and space and cost are thereby reduced. Without increasing, it is possible to realize energy saving and improved durability by shortening the warm-up. In addition, since the separation claw 30 and the rotating member 31 are configured as separate members without being integrated, it is possible to simplify each shape, and the types of materials constituting each are less limited.

4A and 4B are diagrams showing the relationship between the separation claw 30 and the rotating member 31. FIG. 4A shows a case where the rotating member 31 is composed of a roller substantially the same as the axial length of the fixing roller 16, and FIG. a separation claw _{35 1, 35. 2,} 35 3, 35 ₄ rotary member ₃₆ 1 of the roller-shaped to correspond _to, 36 _2, 36 3, 36 _{if 4} a provided. The number of separation claws 35 ₁ , 35 ₂ , 35 ₃ , and 35 ₄ is not limited to the example shown here, but when the maximum size paper handled by the image forming apparatus is, for example, A4, It is preferable to provide a predetermined interval between the end side and a position corresponding to, for example, a small size paper of about A6.

As an example, the rotating members 31 and 36 are made of a SUS material having an outer diameter of 5 mm. However, as in the case of Example 1 shown in FIG. A material of × 10 ⁻⁵ / K or less, for example, SUS, Fe, glass, ceramic, or the like may be used, or a solid SUS material may be configured to be hollow. By using such a low expansion coefficient material, even if heat from the fixing roller 16 is transmitted to the rotating member 31, the rotating member 31 does not expand greatly, and the sheet separating member leading end 303 and the fixing roller are stably expanded. The interval with 16 can be kept constant.

5 and 6 show the holding structure of the rotating members 31 and 36 of the second embodiment shown in FIG. 3, and FIG. 5 is substantially the same as the axial length of the fixing roller 16 as shown in FIG. 6 shows a case where a roller-like rotating member 36 is provided corresponding to the separation claws 35 ₁ , 35 ₂ , 35 ₃ , and 35 ₄ as shown in FIG. 4B. 5 and 6, the same components as those shown in FIGS. 1 to 3 are denoted by the same reference numerals.

  5A is a view as seen from a direction perpendicular to the axial direction of the fixing roller 16, FIG. 5B is a perspective view of the bearing member 52, FIG. 5C is a plan view of the side plate 50 of the fixing device, and FIG. Is a view of the fixing roller 16 as viewed from the axial direction, 16 is a fixing roller, 161 is a cored bar, 162 is an elastic layer such as silicon rubber having a release layer on its surface, 164 is a bearing, and 31 is a rotating member. , 311 is a roller portion, 312 is a rotating shaft, 50 is a side plate of the fixing device, and a part thereof is shown in FIG. 51 is a spring, 52 is a bearing member.

  The bearing member 52 includes a bearing portion 521 that holds the rotating shaft 312 of the rotating member 31 and is provided in a substantially semicircular shape. The main body is formed in a substantially rectangular parallelepiped shape. On the other hand, the fixing device side plate 50 has a circular hole 501 into which a bearing 164 for rotating the core 161 of the fixing roller 16 is fitted, a rectangular portion 502 into which a groove 522 provided in the bearing member 52 is fitted, and a spring. A rectangular portion 503 that receives the holding portion 523 and a protruding spring holding portion 504 that receives the spring 51 are also provided.

  In the holding structure of the rotating member 31, as shown in FIG. 5D, first, the spring 51 is fitted into the spring holding portion 504 of the fixing device side plate 50, and then the rotating shaft 312 of the rotating member 31 is fitted. The groove 522 that fits into the device side plate of the bearing member 52 is fitted into the rectangular portion 502 while the spring 51 is fitted into the spring holding portion 523 of the member 52. Then, while the bearing member 52 is pressed in the direction of the spring holding portion 504 against the pressing force of the spring 51, the rotating member 31 is rotatably held by fitting the bearing 164 of the fixing roller 16 into the hole 501 into which the bearing is fitted. To do.

  Next, FIG. 6A is a plan view of the rotating member holding plate 60 provided at the separation claw installation site, and FIG. 6B is a view seen from the axial direction of the fixing roller 16, as in FIG. 51 is a spring, 52 is a bearing member, 36 is a roller as a rotating member, 361 is a rotating shaft, 60 is a rotating member holding plate, 602 is a rectangular portion into which a groove 522 provided in the bearing member 52 is fitted, Reference numeral 603 denotes a rectangular portion that receives the spring holding portion 523, and reference numeral 604 denotes a protruding spring holding portion that receives the spring 51.

  In the holding structure of the rotating member 31 shown in FIG. 6, as shown in FIG. 6B, first, the spring 51 is fitted into the spring holding portion 604 of the rotating member holding plate 60, and then the rotating shaft of the rotating member 36. The groove 522 in the bearing member 52 is fitted into the rectangular portion 602 while the spring 51 is fitted into the spring holding portion 523 in the bearing member 52 fitted with 361. Then, while pressing the bearing member 52 in the direction of the spring holding portion 604 against the pressing force of the spring 51, the fixing roller 16 is attached to hold the rotating member 36 rotatably.

  In this way, no matter where the separation claw 30 is installed, when the fixing roller 16 expands due to heat and its diameter increases as described above, it contacts the surface of the fixing roller 16 and is driven. Since the rotating rotating members 31 and 36 push up the separation claw 30 correspondingly, the distance between the tip 303 of the separation claw 30 and the fixing roller 16 is kept constant as in the first embodiment, and the fixing roller of the separation claw 30 is maintained. Thus, it is possible to prevent image defects caused by flaws due to contact with 16 and to save energy and improve durability by shortening warm-up without increasing space and cost.

  According to the present invention, regardless of the temperature of the fixing roller 16, the gap between the surface of the fixing roller 16 and the front end portion 203 of the sheet separating member 20 can be made almost constant at all times. Therefore, it is possible to provide an image forming apparatus that can always output a beautiful image without causing damage due to contact.

1 is a schematic cross-sectional view of a configuration of an image forming apparatus including a first embodiment of a sheet separating device of a fixing device according to the present invention. FIG. 3 is a perspective view illustrating a schematic configuration of an abutting portion 191 provided on the sheet separating member 20, the interval adjusting member 21, and the fixing device frame 19. FIG. 5 is a schematic cross-sectional view of a configuration of an image forming apparatus including a second embodiment of a sheet separating device for a fixing device according to the present invention. FIG. 6A is a diagram illustrating the relationship between the separation claw 30 and the rotation member 31. FIG. 5A illustrates a case where the rotation member 31 is configured by a roller that is substantially the same as the axial length of the fixing roller 16, and FIG. _This is a case where roller-like rotating members 36 ₁ , 36 ₂ , 36 ₃ , and 36 ₄ are provided corresponding to ₁ , 35 ₂ , 35 ₃ , and 35 ₄ . FIG. 6 is a holding structure of the rotating member 31 having a length substantially the same as the axial length of the fixing roller 16 according to the second exemplary embodiment, and (A) is a view seen from a direction perpendicular to the axial direction of the fixing roller 16; (C) is a plan view of the side plate 50 of the fixing device, and (D) is a view seen from the axial direction of the fixing roller 16. 7 is a holding structure of a rotating member 36 provided at a site where the separation claw 30 is installed according to the second embodiment, where FIG. 7A is a plan view of a rotating member holding plate provided at a site where the separation claw is installed, and FIG. It is the figure seen from the direction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Photoconductor 11 Developing device 12, 13 Registration roller pair 14 Transfer roller 15 Heater 16 Fixing roller 161 Core metal 162 Elastic layer 163 such as silicon rubber Release layer 164 Bearing 17 Pressure roller 171 Core metal 172 Elastic layer 173 Release layer 18 Temperature Sensor 19 Paper Separating Member 191 Axis 192 Arrow 193 Paper Separating Member Tip 20 Rotating Member 21 Positioning Member

Claims (2)

A heater is arranged inside, and the tip is not on the surface of the fixing roller on the downstream side in the rotation direction of the fixing roller that heats and melts and fixes the toner image formed on the photoconductor and transferred onto the sheet by electrophotography. In a sheet separating device of a fixing device in an image forming apparatus having a plate-shaped sheet separating member provided to be in contact,
The front end of the paper separating member is urged toward the fixing roller and is configured to be rotatable about a shaft fixed to the fixing device frame or the housing, and the paper separating member is formed at both ends along the rotational axis direction. A plurality of positioning members fixed to each other, abutting on a rotating member that rotates in contact with the surface of the fixing roller, and keeps the distance between the front end of the sheet separating member and the fixing roller constant ;
The positioning member has a screw shape and is screwed into a female screw portion provided in the paper separating member, and is provided so that an interval between the fixing roller side tip and the fixing roller in the paper separating member can be adjusted. A sheet separating device for a fixing device in an image forming apparatus. The sheet separating device of the fixing device in the image forming apparatus according to claim 1, wherein the rotating member is made of a material having a thermal expansion coefficient of 5 × 10 ⁻⁵ / K or less.

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