JP2013134290A - Paper separation device, fixing device, and image forming apparatus - Google Patents

Abstract

A paper separation device that does not interfere with the conveyance of a weak recording medium such as thin paper and does not form a streak image on the surface of the recording medium is proposed.
A sheet separating device to be arranged on the downstream side in the sheet conveying direction of a nip portion formed by two adjacent rotating bodies, the tip of which is aligned in parallel to the axial direction of the rotating body. Alternatively, in the paper separating apparatus including a plurality of separating members, a plurality of recesses are formed on the paper rubbing surface of the separating member.
[Selection] Figure 6

Description

  The present invention relates to a fixing device mounted on an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine having these functions, and more particularly to a separation structure for separating a recording medium from a fixing member of a thermal fixing device. .

  In an image forming apparatus using toner for forming a visible image, a fixing device is provided to fix the toner image as a permanent image on a recording medium such as transfer paper. In the fixing device, the recording medium is carried on the recording medium by passing through the pressure contact portion formed by the heated and rotating fixing roller and fixing belt and the pressure roller and pressure belt rotating and pressing with the fixing roller and fixing belt. The toner is melted and the toner image is fixed on the recording medium.

  Toner composed mainly of resin melts at the press-contact part and adheres to the fixing roller and fixing belt. Therefore, a wax component is added to the toner, and the surface of the fixing roller and fixing belt is releasable. Various methods, such as coating with a material and applying a release agent such as silicone oil to the surface of the fixing roller or fixing belt, are used to prevent the fixing roller, the fixing belt, and the toner from sticking to each other. .

  Furthermore, by attaching a paper separation mechanism having a separation claw to the fixing roller or the fixing belt, the recording medium to be wound around the fixing roller or the fixing belt for the melted toner can be forcibly separated. Has been done.

  However, when the recording medium is forcibly separated from the fixing roller and the fixing belt, the toner image on the recording medium comes into contact with the separation claw and the conveying surface of the separation plate. Separation claw and separation plate are arranged in contact with or in close proximity to the pressure contact portion formed by the fixing roller / belt and the pressure roller / belt, so that the toner that has not cooled immediately after passing through the pressure contact portion, that is, in a molten state The remaining toner contacts the separation claw and the conveying surface of the separation plate. At this time, if the surface property of the separation claw or separation plate is rough, the molten toner is scratched and output as a streak image. On the contrary, if the surface properties of the separation claw or separation plate are smooth, the adhesion with the molten toner is increased to cause conveyance resistance, which causes a problem in the conveyance quality of the recording medium.

  Even if the condition of the separation claw or separation plate carrying surface is made appropriate and conditions that do not cause a streak image and do not cause a conveyance quality problem are realized at an early stage by repeating the paper feeding, In addition, the surface properties of the separation claw and the separation plate may be polished and smoothed by the recording medium. If the surface properties of the separation claw or separation plate become smooth, the adhesiveness with the molten toner increases, which causes a problem in the conveyance quality of the recording medium.

  For example, in the case of a separation member configuration in which a small gap is provided with the fixing roller / belt, the separation member must be disposed at a position away from the downstream side of the nip portion in consideration of the thickness of the separation member and the gap size. At a position away from the downstream of the nip portion, the component force in the direction perpendicular to the conveyance direction of the recording medium becomes strong. Therefore, the contact force of the toner on the recording medium to the separating member increases, which is disadvantageous for the streak image.

  The above problems become conspicuous in a recording medium whose surface is coated with a resin layer, which is called coated paper, which has recently been increasing in demand. Coated paper is a recording medium in which a resin layer is coated on normal paper fiber, and its rigidity (strain) becomes weak when heated by a fixing device. Therefore, the rigidity of the recording medium that opposes the adhesive force between the fixing roller or the fixing belt and the toner is weak, and the contact force of the toner to the separation claw or the separation plate is increased. Thereby, said problem becomes remarkable.

  Conventionally, streak images caused by contact between the conveying surface of the separating member and the toner have been regarded as a problem. For example, the shape of the separating nail on the conveying surface side is different between the end in the recording medium width direction and the center position, There has been proposed a configuration in which the center side is protruded from the surface side and the center side is retracted from the conveyance surface side (Patent Document 1), and an attempt is made to avoid the generation of a streak image.

  However, in the case of a recording medium having a low rigidity such as the above-described coated paper, in the configuration proposed in Citation 1, the contact force applied to the separation claw is concentrated on the separation claw on the end side, so that a stronger stripe image is obtained. Can be predicted.

  Another concern is that the toner adheres to the separation claw or the separation plate when the toner contacts the separation claw or the conveying surface of the separation plate. If fixed, the recording medium may be transported or the toner image may be scratched by the fixed toner, resulting in a streak image.

  In view of the conventional problems, an object of the present invention is to propose a paper separating apparatus that does not interfere with the conveyance of a weak recording medium such as thin paper and that does not form a streak image on the surface of the recording medium. is there.

  According to the present invention, the above problem is a paper separating device to be arranged on the downstream side in the paper transport direction of the nip portion formed by the two rotating bodies that are in contact with each other, and is parallel to the axial direction of the rotating body. In the sheet separating apparatus including a single or a plurality of separating members with the leading ends aligned, the problem is solved by forming a plurality of recesses on the sheet rubbing surface of the separating member.

  According to the present invention, since a plurality of dents are formed on the paper rubbing surface of the separating member, the conveyance resistance of the recording medium can be optimized, and even with a thin recording medium, the conveyance performance is excellent. A streak image that can be generated by rubbing with the toner image on the recording medium can also be prevented.

1 is a schematic diagram of an image forming apparatus. 1 is a side view of a fixing device according to an embodiment of the present invention. It is a conceptual diagram for demonstrating the paper separation apparatus which concerns on embodiment of this invention. It is a perspective view which shows the structure of a separation member. FIG. 5A is a side view and FIG. 5B is a cross-sectional view (cross section AA in FIG. 6) of the front end portion of the separation member. FIG. 6 is a diagram illustrating a state in which dimples are formed on a sheet conveying surface of a separating member. It is a figure which shows a mode that the groove part was formed in the paper conveyance surface of a separation member.

Hereinafter, one embodiment of the present invention will be described.
FIG. 1 is a schematic diagram of an image forming apparatus provided with a fixing device according to an embodiment of the present invention. The mechanism of the entire image forming apparatus is basically the same as the conventional one, and a predetermined apparatus necessary for forming an image around the photoreceptor, such as a charging unit, an exposure unit (writing unit), a developing unit, etc. However, since those skilled in the art are familiar with the configuration and operation, a brief description will be given.

  A sheet as a recording medium is conveyed to the transfer unit by the sheet feeding unit 31. On the other hand, the writing unit 32 exposes the photoconductor in the image forming unit 33 based on a signal from a scanner for reading a document or a signal from an external PC.

  The latent image exposed on the photoconductor is visualized by the image forming unit 33 and is primarily transferred to the transfer belt, and the unfixed toner image is secondarily transferred to the conveyed paper by the transfer unit 34. The unfixed toner image is fixed by the fixing device 35, peeled off from the fixing belt by the separation unit 7, and discharged outside the apparatus. In the case of double-sided image formation, the paper is reversed by the double-sided unit 36, conveyed again to the transfer unit, and then discharged through the fixing device 35 and the separation unit 7.

FIG. 2 is a side view of the fixing device 35 and the separation unit 7 according to the embodiment of the present invention. This figure shows a cross section perpendicular to the rotation axes of the fixing roller and the pressure roller.
A fixing roller 2 and a heating roller 4 are provided in the fixing belt 3, and a pressure roller 5 presses the fixing roller 2 through the fixing belt 3 to form a fixing nip portion. A halogen heater 6 as a heat source is built in the heating roller 4 and the pressure roller 5, and the sheet 9 carrying the unfixed toner image conveyed from the right side of the figure is sandwiched and heated at the fixing nip portion, It is the structure which fixes.

  For example, the fixing belt 3 is made of a polyimide resin having an inner diameter of 75 mm and a thickness of 90 μm. The surface of the substrate is 200 μm thick silicone rubber, and the outermost layer is 20 μm thick PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer). There is a coat. The fixing belt 3 is wound around a fixing roller 2 made of foamed silicone rubber having an outer diameter of 52 mm and a thickness of 14 mm, and a heating roller 4 made of an aluminum hollow cylinder having an outer diameter of 35 mm and a thickness of 0.6 mm.

  The pressure roller 5 is made of steel and covered with a 1.5 mm thick silicone rubber on a hollow core metal having a thickness of 1 mm, and has an outer diameter of 50 mm provided with a PFA tube in the outermost layer. The pressure roller 5 bites into the fixing roller 2 by 3 mm via the fixing belt 3 to form a nip width of about 14 mm.

  A separation unit 7 serving as a sheet separation device for separating (peeling) the sheet 9 from the fixing belt 3 is provided on the fixing belt 3 downstream side of the fixing nip portion. A separation member 1 is provided at the front end of the separation unit 7 on the fixing nip side. In this example, a plurality of separation members 1 as separation claws are provided in the axial direction of the fixing roller 2 and the pressure roller 5. However, the separating member 1 may be formed in a uniform claw shape that continuously extends the maximum width in the width direction of the assumed sheet to be separated. Such a shape is sometimes referred to as a separation plate, but here it is generalized and referred to as a separation claw. The paper separated by the function of the separating member 1 is then conveyed to the paper discharge unit by the guides of the fixing side guide plate and the pressure side guide plate.

In the figure, reference numeral 11 denotes a lever of the separation unit 7, and 12 denotes a tension spring for the separation unit 7.
FIG. 3 is a detailed view showing the configuration of the separation unit 7 including the separation member 1 in detail. The separating member 1 is configured to be rotatable about a support shaft 1b. Further, the separating member 1 is configured such that the position of the separating member head 1c can be finely adjusted with respect to the fixing belt 3 by the compression spring 7b and the adjusting screw 7a of the separating unit 7. The adjustment screw 7a is configured to be able to advance and retreat with respect to a screw hole provided in the separation unit 7 as a fixing member, and the separation member 1 can be swung around the support shaft 1b by the rotation of the adjustment screw 7a. As a result, the separating member 1 may be brought into contact with the fixing belt 3 or a predetermined gap, for example, a gap of about 0.1 to 0.6 mm may be provided. The contact can improve the certainty of forcibly separating the paper, and by taking a predetermined gap, the separation member and the fixing belt can be rubbed with each other while ensuring separation performance close to contact-type separation. This can be avoided, and there is no rubbing trace on the surface of the fixing belt.

  In the above description, the case where the separation unit 7 and the separation member 1 are applied to the fixing device has been described. However, there are various situations where the sheet-like medium is peeled off from the belt and the rollers, not limited to the fixing device. The separation member 1 and the separation unit 7 of the present invention can be used not only for a fixing device but also for a transfer device, for example.

  FIG. 4 is a perspective view showing an example of the configuration of the separating member 1. A plurality of separation members 1 provided in the separation unit 7 so as to be parallel to the axial direction of the fixing roller 2 are separated at the tip of the base material 1a having the support shaft 1b (the portion farthest from the support shaft on one side). A resin softer than the base material 1a is integrally formed by insert molding as the member tip (head) 1c. By using such a separating member 1, it is not permanently deformed even by an external pressure such as a paper jam, and a non-aggressive resin is used for the separating member tip 1 c, so that the other member is scratched. Problems such as attaching can be prevented.

  Moreover, since the base material 1a and the separation member front end portion 1c are integrally formed by insert molding, the positions of the support shaft 1b and the separation member front end portion 1c of the base material 1a can be formed with high accuracy. . Therefore, the separation performance is excellent as well as the separation member formed of the same material.

  FIG. 5 is also a diagram for explaining the separating member 1. 5A is an overall view of the separation member corresponding to FIG. 4, and FIG. 5B is a detailed view (AA cross section in FIG. 6) of the separation member front end part in which the range B shown in FIG. 5A is partially enlarged. In FIG. 5b, the separating member head 1c, whose outer shape is indicated by a bold line, has a resin claw shape integrated by insert molding so as to surround the tip of the base material. A fluorine-based resin is used as the material of the separation member head 1c. Since the fluororesin is excellent in slidability, it does not damage the other party even if it comes into contact, and it does not cause toner fixation because it is excellent in releasability to toner. As described above, the separation member 1 having excellent non-adhesiveness to the toner can be provided by using a fluorine resin as the material of the separation means head 1c. Alternatively, the material of the separation member head 1c may be a PEEK material, a PAI material, or a PI material, and the paper conveying surface 10 may be coated with a fluorine-based resin.

  Furthermore, in this example, a plurality of dimples 15 are formed, particularly in the front end region of the sheet conveying surface 10, as shown in FIG. 6, and therefore a plurality of concave portions are provided on the sheet conveying surface 10. . With such a shape portion, the area where the toner image on the paper contacts the separation member can be reduced, and since there is no ridge line parallel to the paper conveyance direction, generation of a streak image due to scratching the toner surface can be suppressed. The specific shape of the dimple is assumed to be a round shape, an oval shape, a teardrop shape, or the like. The concave portion is preferably arranged in a staggered manner, for example, so that the contact area in the main scanning direction between the toner surface of the paper and the separating member is uniform.

  Further, as a modification of the dimples, as shown in FIG. The grooves 16 preferably extend so that the longitudinal axis thereof is at an angle θ with respect to the paper transport direction, and are distributed symmetrically in the main scanning direction with respect to the center of the separating member 1. By forming the groove portion in this way, the area where the toner image on the paper contacts the separation member can be reduced, and since there is no ridge line parallel to the paper conveyance direction, generation of a streak image by scratching the toner surface is prevented. Can be suppressed.

2 Fixing roller 3 Fixing belt 4 Heating roller 5 Pressure roller 6 Halogen heater 7 Separation unit 7c Rotating fulcrum 9 Paper 10 Unfixed toner 11 Lever 12 Pulling spring 15 Dimple 16 Groove portion 35 Fixing device

JP 2006-189688 A

Claims (9)

  A sheet separating device to be arranged on the downstream side in the sheet conveying direction of a nip formed by two rotating bodies that come into contact with each other, and includes a single or a plurality of separations having tips aligned parallel to the axial direction of the rotating body A paper separating apparatus comprising a member, wherein a plurality of dents are formed on a paper rubbing surface of the separating member.   The sheet separating apparatus according to claim 1, wherein the recess is a dimple.   The sheet separating apparatus according to claim 1, wherein the recess has a groove shape provided with an inclination angle with respect to a sheet conveyance direction.   The sheet separating apparatus according to claim 1, wherein the separating member is a separating claw that abuts on a side of the rotating body on which a toner image is placed.   The paper according to claim 1, wherein the separation member is disposed with a predetermined gap with respect to a side on which the toner image is placed in the rotating body. Separation device.   The sheet separating apparatus according to claim 1, wherein at least a part of the sheet rubbing surface of the separating member is coated with fluorine.   The sheet separating apparatus according to claim 1, wherein at least a part of the sheet rubbing surface of the separating member is made of a fluororesin material.   A fixing device comprising the sheet separating device according to claim 1.   An image forming apparatus comprising the sheet separating apparatus according to claim 1.

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