JP2009229494A - Fixing device, and image forming device equipped with fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device capable of enhancing a durable life of a slide sheet, and allowing stable fixing processing, and an image forming device equipped with the fixing device. <P>SOLUTION: This fixing device has a rotor, an endless belt laid over a plurality of rollers, and a pressing member slide-moving on an inner circumferential face of the endless belt, pressed onto the rotor via the endless belt, and forming a fixing nip, at least a sliding face with the endless belt is coated with the slide sheet having a plurality of protrusions, in the pressing member, and each protrusion is formed into an asymmetrical shape having an inclination angle in a belt center side smaller than an inclination angle in an end part side, in a belt width-directional cross-section. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fixing device used in an electrophotographic copying machine, a printer, and the like, and more particularly to a fixing device using an endless belt and an image forming apparatus equipped with the fixing device.

  A belt nip type fixing device that forms a fixing nip by pressing an endless belt onto a rotating body via a belt with a fixed sliding pressing member provided on the inner peripheral surface of the belt. Can be formed.

  As an example, a method of forming a fixing nip by pressing the outer periphery of a heating roller including a heat source with a pressure roller provided on an inner peripheral surface of an endless belt and a pressing member that is fixedly slid (see FIG. 2A). ), A heating roller outer periphery is formed only by a pressing member provided on the inner peripheral surface of the endless belt, and a fixing nip is formed (see FIG. 2B), or an endless belt and an endless belt are arranged on the inner surface. There is a method of forming a fixing nip with the pressed member, a heating roller and a pressure roller (see FIG. 2C).

  FIG. 2 is a diagram showing a known embodiment of a belt nip type fixing device.

  In the belt nip type fixing device as shown in FIG. 2B, in order to reduce the sliding resistance between the endless belt and the pressing member, the pressing member is covered with a low friction sliding sheet, In order to reduce the frictional resistance with the endless belt, there is a known technique for applying a lubricant to the inner peripheral surface of the endless belt.

  Further, in the belt nip type fixing device as shown in FIG. 3, in order to reduce the contact area between the pressure belt (hereinafter also referred to as endless belt) 40 and the sliding sheet 441 and to reduce the friction, the sliding There is also a known technique for embossing the sheet 441 to provide large unevenness (see, for example, Patent Document 1).

  This document discloses a technique for embossing a symmetrical pyramid on a sliding sheet as shown in FIG.

  By performing such embossing, it is possible to slide with low frictional resistance by reducing the contact area with the inner surface of the endless belt.

  FIG. 3 is a diagram illustrating a main part of a fixing device that employs a sliding sheet that has been embossed.

FIG. 5 is a diagram illustrating an example of a sliding sheet that has been embossed.
JP 2002-148970 A

  However, in the embossed sliding sheet as shown in FIG. 5, as shown in FIG. 6, when the endless belt is conveyed (in the vertical direction of the paper in FIG. 6), the left and right side (X direction) movement is repeated. Both end portions E corresponding to the edge portion of the endless belt hit the embossed surface, and there was a problem that the embossed surface had a hole as shown in FIG.

  FIG. 6 is a diagram illustrating a contact state between the sliding sheet and the end portion of the endless belt.

  FIG. 7 is a view showing a cross section of an emboss in which a hole is generated by wear.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device capable of avoiding the above-described problems, improving the durable life of a sliding sheet and performing stable fixing processing, and an image forming apparatus equipped with the fixing device.

  The above object is achieved by the following configuration.

  (1) A rotating body, an endless belt stretched around a plurality of rollers, and slides on the inner peripheral surface of the endless belt, and presses against the rotating body via the endless belt to form a fixing nip. In the fixing device having a pressing member, the pressing member is covered with a sliding sheet having at least a sliding surface with the endless belt, and the protruding portion is a cross section in the belt width direction. A fixing device having an asymmetric shape in which an inclination angle on a belt center side is smaller than an inclination angle on an end side.

  (2) An image forming apparatus comprising the fixing device according to (1).

  Without increasing the sliding resistance between the endless belt and the sliding sheet, the durability life of the sliding sheet can be extended, and a stable fixing process can be performed.

  First, an image forming apparatus according to the present invention will be described with reference to FIG.

  In the description of the embodiment of the present invention, the technical scope of the present invention is not limited by the terms used in this specification.

  FIG. 1 is a schematic diagram illustrating an example of the overall configuration of the image forming apparatus.

  In FIG. 1, 10 is a photoconductor, 11 is a scorotron charger (hereinafter also simply referred to as a charger), 12 is a writing device as exposure means, 13 is a developing device as development means, and 14 is photosensitive. A cleaning device for cleaning the surface of the body 10, 15 a cleaning blade, 16 a developing sleeve, and 20 an intermediate transfer belt as a transfer body. The image forming unit 1 includes a photoconductor 10, a charger 11, a developing device 13, a cleaning device 14, and the like.

  Since the mechanical configuration of the image forming unit 1 for each color is the same, in FIG. 1, only the configuration of the Y (yellow) series is given a reference symbol, and M (magenta), C (cyan), and K Reference numerals are omitted for the black component.

  The arrangement of the image forming means 1 for each color is in the order of Y, M, C, and K with respect to the running direction of the intermediate transfer belt 20, and each photoreceptor 10 contacts the stretched surface of the intermediate transfer belt 20. At the contact point, the intermediate transfer belt 20 rotates in the same direction as the traveling direction and at the same linear speed.

  The intermediate transfer belt 20 is stretched around a driving roller 21, an earth roller 22, a tension roller 23, a static elimination roller 27, and a driven roller 24. The belt unit 3 is constituted by these rollers, the intermediate transfer belt 20, the transfer device 25 serving as transfer means, the cleaning device 28, and the like.

  The intermediate transfer belt 20 travels by the clockwise rotation of the drive roller 21 by a drive motor (not shown).

  The photosensitive member 10 is formed by forming a photosensitive layer such as a conductive layer, an a-Si layer, or an organic photosensitive member (OPC) on the outer periphery of a cylindrical metal base formed of, for example, an aluminum material, and the conductive layer is grounded. In the state, it rotates counterclockwise as indicated by the arrow in FIG.

  An electrical signal corresponding to the image data from the reading device 80 is converted into an optical signal by the image forming laser, and is projected onto the photoconductor 10 by the writing device 12.

  The developing device 13 is formed of a cylindrical non-magnetic stainless steel or aluminum material that maintains a predetermined interval with respect to the peripheral surface of the photoconductor 10 and rotates in the opposite direction at the closest position to the rotation direction of the photoconductor 10. The developing sleeve 16 enclosing the magnet is provided, and the developer is conveyed in the developing device 13 by the developing sleeve 16.

The intermediate transfer belt 20 is an endless belt having a volume resistivity of 10 ⁶ to 10 ¹² Ω · cm. A semiconductive seamless belt having a thickness of 0.04 to 0.10 mm, in which a conductive material is dispersed.

  The transfer device 25 has a function of transferring a toner image formed on the photoreceptor 10 onto the intermediate transfer belt 20 by applying a DC voltage having a polarity opposite to that of the toner.

  Reference numeral 26 denotes a transfer roller that can be brought into and out of contact with the earth roller 22, and is charged with a reverse polarity to the polarity of the toner image, and the toner image formed on the intermediate transfer belt 20 is transferred to the transfer material P at the nip portion S. Re-transfer to.

  A cleaning device 28 is provided to face the driven roller 24 with the intermediate transfer belt 20 interposed therebetween. After the toner image is transferred to the paper P, the residual toner on the intermediate transfer belt 20 is weakened by the charge removing roller 27 to which an AC voltage superimposed with a DC voltage having the same or opposite polarity as the toner is applied, and the cleaning blade 29 Removed by.

  70 is a paper feed roller, 71 is a timing roller, 72 is a paper cassette, and 73 is a transport roller.

  Reference numeral 4 denotes a fixing device. The sheet P on which the toner image on the intermediate transfer belt 20 is transferred is added to a heating roller 45 which is a rotating body including a heating source and an endless belt which is made of PI (polyimide) as a base material. The toner image is fixed by being sandwiched and pressed by a fixing nip T formed by a pressure belt 40 and a pressing device 44 (pressing rubber 442). The temperature near the surface of the heating roller 40 is detected by a temperature detection sensor (not shown), and is maintained in a predetermined fixing temperature range by the control unit B1. Details of the fixing device 4 will be described later.

  A paper discharge roller 81 discharges the fixed paper P to a paper discharge tray 82. A control unit B1 is a control unit that controls each drive unit, image forming process, fixing temperature, and the like.

  The belt nip type fixing device according to the present invention will be described below with reference to FIG.

  FIG. 3 is a diagram illustrating a main part of a fixing device that employs a sliding sheet that has been embossed.

In FIG. 3, the pressure belt 40 is stretched around a fixing driving roller 41, a steering (tension) roller 42, and a driven roller (paper entry side) 43 that is rotated by power from a driving unit (not shown). Drive counterclockwise at the same speed as the peripheral speed. In the pressure belt 40, polyimide is coated with silicone rubber as an elastic layer, and a PFA tube is coated as a release layer (polyimide 70 μm thickness, silicone rubber 0.2 mm thickness, hardness 30 ° JISA, PFA tube 30 μm thickness). .

  The heating roller 45 has a metal core covered with an elastic layer, and further a release layer (for example, outer diameter: 65 mm, core: aluminum tube (t = 5 mm), elastic layer: HTV silicone) Rubber (t = 1.5 mm), release layer: PFA tube (t = 30 μm)).

  The pressing device 44 includes a stay 443 that is a fixed metal base, a pressing rubber 442 that is a pressing member having a curved surface close to the curvature of the heating roller 45, which is attached to the stay 443, and the pressing rubber 442. It is composed of a sliding sheet 441 that covers the upper surface and a pressure release mechanism (not shown) (for example, stay: stainless steel, pressing rubber: silicone rubber 3 mm thick, hardness JIS 20 °, nip width: 20 mm).

  Both ends of the stay 443 are fixed to a support that is rotated by the press release mechanism. When the stay 443 is pressed, the support is pressed in the direction of arrow G by a not-shown press spring, and the pressing rubber 442 is used as the press belt. 40 is pressed against the heating roller 45 to form a wide fixing nip T (pressing load 60 kgf).

  That is, the pressing rubber 442 is released from contact with the heating roller 45 except for the fixing processing operation, and presses the heating roller 45 in accordance with the paper feed timing.

  The sliding sheet 441 covers the curved surface of the pressing rubber 442 to reduce sliding resistance with the pressure belt 40, and at the same time, is applied to the inner peripheral surface of the pressure belt 40 by the lubricant application member 444. There is also a function of preventing the applied oil from adhering to the pressing rubber 442. When oil adheres, the pressing rubber 442 is deformed due to oil swelling, and paper wrinkles are generated. Therefore, the width in the belt width direction of the sliding sheet 441 is longer than the width of the pressure belt 40 as shown in FIG. 4 so that oil does not enter from the belt width direction end of the sliding sheet 441 ( For example, pressure belt width 350 mm, sliding sheet width 360 mm). The sliding sheet 441 is preferably made of a heat-resistant resin and does not penetrate oil. In the present embodiment, a polyimide sheet (for example, t = 75 μm) is used. Embossing is applied so as to form a convex portion on the abutting surface side. The embossed shape will be described later.

  4 is a view showing a cross section (Z-Z) in the width (axis) direction of the sliding sheet, pressing rubber, pressure belt, and heating roller of FIG. 3 according to the present invention.

  In FIG. 4, both end portions of the sliding sheet 441 are fixed to the upstream and downstream sides of the stay 443. However, the sliding sheet formed in advance in a cylindrical shape is fixed to the stay only on the upstream side and the downstream side is free. Good.

  The steering roller 42 is made of, for example, a material in which a metal core is covered with silicone rubber, and one end of the steering roller 42 can be moved back and forth in the traveling direction of the pressure belt 40. Control of the steering roller 42 keeps the balance of the pressure belt 40 closer to the running side. That is, in the steering control, an actuator (not shown) that detects the edge position of the pressure belt 40 is in contact with the edge of the pressure belt 40, and one end of the steering roller 42 is changed according to the displacement amount of the actuator. This is done by moving the part by a predetermined amount.

  The lubricant applying member 444 is disposed between the driven roller 43 and the pressing rubber 442 by impregnating a non-woven fabric of heat-resistant fibers (for example, aramid fiber, PTFE (polytetrafluoroethylene) fiber) with oil.

  As described above, there is a problem that the edge portions of both ends of the endless belt (pressure belt 40) rub the embossed surface (see FIGS. 6 and 7), the emboss has a hole, and the sliding sheet breaks.

  The present invention is to prevent the above problems.

  3, 4, and 5, the pressure belt 40 is biased in the vertical direction (belt width direction) with respect to the traveling direction due to misalignment of the stretched rollers. For this reason, when one of the stretching rollers approaches the end by the steering control described above, the belt is returned to the center side.

  As shown in FIG. 7, in the conventional type of sliding sheet, the position of the embossment with the wear hole coincides with the movement range of the belt edge accompanying the movement of the belt in the belt width direction. It was confirmed that the emboss was worn even in the region where the pressing rubber 442 was not in contact, but this was because the belt edge (end) was moved to the side of the emboss (see FIG. 6) due to the shifting force of the belt when the belt moved in the width direction. It is considered that it is caught by the E part) and rubs and wears strongly.

  Hereinafter, the embossed shape of the sliding sheet 441 concerning embodiment of this invention is demonstrated.

  FIG. 8 is a plan view of the embossed sliding sheet according to the present invention and a cross-sectional view in the belt width direction.

  FIG. 9 is a diagram showing a cross-sectional shape in the belt width direction of one emboss of FIG.

  The embossed shape of the sliding sheet 441 according to the present invention is an asymmetric shape in which the inclination angle on the belt center side is smaller than the inclination angle on the end side with respect to the belt width direction in the cross section.

  The embossed shape shown in FIG. 9 has a height of 0.2 mm, an apex angle of 90 ° (preferably 80 ° to 100 °), an end side inclination angle of 70 °, and a central side inclination angle of 20 ° (15 ° to 30 °). The ridge line on the emboss center side is the belt width direction. The embosses are arranged at 1.0 mm intervals (see emboss intervals a and b in FIG. 8). The edge portion of the pressure belt 40 abuts against the side surface (ridge line) on the center side when moving from the center side to the end side, but the belt is in the direction of the arrow (dotted line) because the angle of inclination is gentle as shown in FIG. Escape to the upper side and do not rub the embossed forcefully. By making the inclination on the end side tight and making the vertex angle the same as the conventional one, it is possible to keep the sliding resistance low (In addition, when the emboss is pressed against the pressure belt, both are deformed and crushed somewhat. Therefore, the contact between the emboss and the pressure belt is not a point but a surface, so that the larger the vertex angle, the larger the contact area and the higher the sliding resistance).

  When creating an embossed sliding sheet, as shown in FIG. 10 (a), a polyimide sheet is placed on a pedestal laid with silicone rubber on the surface, and the polyimide sheet is sandwiched between the pedestal and an embossing die. Is formed.

  In making the mold, as shown in FIG. 10 (b), after cutting a groove having an A cross-sectional shape (asymmetric) so that a steel material such as S45C has a desired embossed shape, the B cross-sectional shape is perpendicular to this. By cutting into the groove, an asymmetrical embossed shape is obtained, and an embossing die is created by cutting in the direction shown in FIG.

  FIG. 10 is a schematic diagram for explaining a method of creating an embossing die for embossing and embossing.

  Next, Table 1 shows the results of experiments on the durability of the embossed sliding sheet of the present embodiment and the conventional example.

As an experimental condition, using the apparatus described in FIG. 3, in the conventional example, the height is 0.2 mm, the apex angle is 90 °, and both ends are 45 °, and in the embodiment, the height is 0.2 mm and the apex angle is 90 °. Thus, the end portion side was set to 70 ° and the central portion side was set to 20 °. Both emboss intervals a and b (see FIGS. 5 and 8) were 1.0 mm. Both materials are polyimide resin (t = 75μm), paper 80g / m ² (A4), paper feeding speed 65 sheets / min

  In Table 1, ◯ indicates that no wear hole is generated, and x indicates that a wear hole is generated.

  As can be seen from the experiment, in the conventional example, wear holes were generated when 200,000 sheets were passed, whereas it was confirmed that the embodiment did not generate even 300,000 sheets.

  In the present embodiment, as shown in FIG. 8, the embossing is arranged so that the ridge line on the center side is in the belt width direction (main scanning direction). An effect is obtained. As for the embossed shape, the same effect can be obtained with an asymmetrical shape constituted by a curved surface having no ridgeline, an asymmetrical shape constituted by a flat surface, or an asymmetrical shape combining a curved surface and a flat surface.

  Further, in the present embodiment, the entire width region of the sliding sheet is used with embossed left and right asymmetric shapes, but the embossed shape is formed symmetrically only in the region where the edge of the pressure belt contacts. But you can.

  As described above, the durability of the sliding sheet can be extended without increasing the sliding resistance between the endless belt and the sliding sheet, and a stable fixing process can be performed.

1 is a schematic diagram illustrating an example of an overall configuration of an image forming apparatus. 1 is a diagram showing a known form of a belt nip type fixing device. It is a figure which shows the principal part of the fixing device which employ | adopted the sliding sheet | seat in which embossing was performed. It is a figure which shows the cross section (XX) of the width | variety (axis) direction of the sliding sheet | seat of FIG. 3, a press rubber, a pressure belt, and a heating roller. It is a figure which shows an example of the sliding sheet to which the embossing was given. It is a figure which shows the contact state of a sliding sheet and an endless belt edge part. It is a figure which shows the cross section of the sliding sheet | seat in which the hole generate | occur | produced by abrasion. It is the top view of the embossing sliding sheet concerning the present invention, and the sectional view of the belt width direction. It is a figure which shows the cross-sectional shape of the belt width direction of one emboss of FIG. It is the schematic for demonstrating the preparation method of embossing die for embossing, and embossing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming means 4 Fixing device 40 Pressure (endless) belt 41 Driving roller 42 Steering (tension) roller 43 Driven roller 44 Pressing device 45 Heating roller 441 Sliding sheet 442 Pressing rubber 443 Stay 444 Lubricant application member

Claims (7)

A rotating member, an endless belt stretched between a plurality of rollers, and a pressing member that slides on an inner peripheral surface of the endless belt and presses the rotating member via the endless belt to form a fixing nip. In the fixing device, the pressing member is covered with a sliding sheet having a plurality of convex portions at least on a sliding surface with the endless belt, and the convex portion is a cross-section in the belt width direction and the belt center side. The fixing device has an asymmetric shape in which the inclination angle is smaller than the inclination angle on the end side. The fixing device according to claim 1, wherein the protrusion is formed by embossing. The fixing device according to claim 1, wherein the convex portion is located at a position where at least an edge portion of the belt contacts the sliding sheet. The fixing device according to claim 1, wherein the sliding sheet is made of polyimide. The fixing device according to claim 1, wherein the convex portion is configured by a linear ridge line. The fixing device according to claim 1, wherein an inclination angle of the belt center side is 15 ° to 30 °. An image forming apparatus comprising the fixing device according to claim 1.

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