JP2011257573A - Fixing device and image forming device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a belt-nip type fixing device capable of avoiding the nipping of a projecting portion of a slide sheet covering a pressing member in a nip portion, and an image forming device using the same.SOLUTION: A projecting portion 65A of a slide sheet 65 has a shape in which a center portion 65A1 in a direction orthogonal to a paper feeding direction projects more than both side end portions 65A2. Therefore, the lowering of pressure in a wedge-shaped clearance formed at a nip portion between a fixing roller 52 and a separation roller 55 can be suppressed, and excessive interference between the both side end portions 65A2 and the separation roller 55 is prevented to avoid the nipping of the projecting portion 65A.

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used in an image forming apparatus such as a copying machine, a printer, a fax machine, and the like, and more particularly to a belt nip type fixing device and an image forming apparatus using the same.

  A belt nip type fixing device includes a fixing roller having a heating source and a fixing belt unit facing the fixing roller.

  This belt nip type fixing device is provided with a pressing member for securing a nip width in the fixing belt unit and a separation roller for separating the paper from the fixing roller. It has the effect of being able to handle species.

  On the other hand, a wedge-shaped gap is formed in the nip region between the fixing roller and the fixing belt by the fixing belt, the pressing member, and the separation roller, and this gap becomes a low-pressure portion, and an image having a low icicle shape on the sheet image. There is a problem that noise occurs.

  Therefore, as shown in Patent Document 1, the portion close to the separation roller of the sliding sheet coated with the pressing member is disposed as close as possible to the nip portion between the separation roller and the fixing roller, and the wedge-shaped A device that suppresses the pressure drop in the gap is known.

JP 2006-146156 A

  In the technology disclosed in Patent Document 1, the portion of the sliding sheet that is close to the separation roller is generally closer to the nip portion between the separation roller and the fixing roller along the axial direction of the separation roller. It is pinched by this nip part, and the press-contact defect of a separation roller arises. For this reason, there is a possibility that a paper separation failure or a paper wrinkle occurs due to a decrease in the pressure contact force of the separation roller, or a driving torque increases due to wear of the separation roller and the sliding sheet.

  Therefore, the present invention can appropriately prevent the pressing member from protruding into the wedge-shaped gap of the sliding sheet, and can prevent the sliding sheet from being caught in the nip portion between the separation roller and the fixing roller. It is an object of the present invention to provide a fixing device that can prevent a separation failure, an image failure, and the like, and an image forming apparatus using the same.

  The present invention includes a heating rotator having a heating source, an endless belt that is suspended by a plurality of rotators and is in contact with the heating rotator, and a pressing member that presses the endless belt from the inside to the outside, A sliding sheet that covers the pressing member, and of the plurality of rotating bodies, the rotating body on the downstream side in the sheet feeding direction and the pressing member press the endless belt against the heating rotating body to form a nip region. The fixing device fixes the formed image to the sheet by passing the formed and image-formed sheet through the nip region, and the pressing member protrudes to the rotating body side downstream in the sheet feeding direction. The sliding sheet has a protruding portion on the downstream side in the paper feeding direction, which protrudes from the wedge-shaped tip of the pressing member toward the rotating body on the downstream side in the paper feeding direction. The direction is perpendicular to the paper feed direction That the central portion is formed in the protruding shape than the two side portions are the main features.

  According to the present invention, the protruding portion of the sliding sheet has a shape in which the central portion in the direction orthogonal to the sheet feeding direction protrudes from the both end portions. It is possible to suppress a pressure drop in a wedge-shaped gap formed between the rotating body on the downstream side in the paper direction. On the other hand, since both side end portions of the projecting portion have a projecting shape smaller than that of the central portion, excessive interference at the projecting portion end portion where interference with the opposing rotating body is likely to occur is avoided.

  As a result, the pressure drop in the wedge-shaped gap can be suppressed, image defects such as icicle-like gloss unevenness can be prevented, and paper separation failure, wrinkle generation, and drive torque increase due to pinching of the sliding sheet can be prevented. Can do.

1 is an overall configuration diagram conceptually showing an image forming apparatus as an embodiment of the present invention. FIG. 3 is an explanatory side view showing a fixing device. Side surface explanatory drawing which shows a press member. Explanatory drawing which expands and shows the protrusion part of a sliding sheet. Plane explanatory drawing which shows the relationship between the protrusion part of a sliding sheet | seat, and a hard rod. Plane explanatory drawing which shows the example from which the relationship between the protrusion part of a sliding sheet | seat and a hard rod differs.

    Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows the overall configuration of an image forming apparatus to which a fixing device according to the present invention is applied.

  The image forming apparatus 1 forms a full-color image in which photosensitive drums 31Y, 31M, 31C, and 31K as a plurality of photosensitive members face an intermediate transfer belt 41 as an example of an intermediate transfer member and are arranged in a vertical direction. This is called a tandem type color image forming apparatus.

  The image forming apparatus 1 includes an automatic document feeder ADF at the top thereof. The documents D placed on the document placement table 15 of the automatic document feeder ADF are separated one by one, sent out to the document conveyance path, and conveyed by the conveyance drum 16.

  The document reading unit 10 reads an image of the document D being conveyed at the document image reading position RP. The first conveyance guide G1 and the document discharge roller 17 discharge the document D that has been read to the document discharge tray 18.

  The image forming apparatus 1 includes the document reading unit 10, the exposure units 20Y, 20M, 20C, and 20K, the image forming units 30Y, 30M, 30C, and 30K, the intermediate transfer unit 40, the secondary transfer unit 42, the fixing unit 50, and the paper discharge. The reversing unit 70, the paper feeding unit 90, and the like are included in one casing.

  The document reading unit 10 irradiates the image of the document D with the lamp L at the document image reading position RP, guides the reflected light by the first mirror unit 11, the second mirror unit 12, and the lens 13, and An image is formed on the light receiving surface. The imaging device CCD photoelectrically converts incident light and outputs a predetermined image signal. The image reading control unit 14 performs processing such as A / D conversion, shading correction, and compression on the image signal, and converts it into image data in a storage unit of a control unit (not shown). The image data stored in the storage unit is subjected to appropriate image processing according to conditions set by the user, and output image data is generated.

  The exposure units 20Y, 20M, 20C, and 20K are photosensitive drums charged by the main charging units 32Y, 32M, 32C, and 32K in accordance with output information output based on output image data sent from the control unit. The surfaces of 31Y, 31M, 31C, and 31K are scanned and exposed with a laser beam, and electrostatic images for Y, M, C, and BK colors are formed on the photosensitive drums 31Y, 31M, 31C, and 31K.

  The image forming unit 30Y includes a photosensitive drum 31Y, and a main charging unit 32Y, a developing unit 33Y, a first transfer roller 34Y, and a cleaning unit 35Y arranged around the photoconductive drum 31Y. The other image forming units 30M, 30C, and 30K have the same configuration as that of the image forming unit 30Y, and the main charging units 32M, 32C, and 32K are arranged around the photosensitive drums 31M, 31C, and 31K, respectively. The developing units 33M, 33C, and 33K, the first transfer rollers 34M, 34C, and 34K, and the cleaning units 35M, 35C, and 35K are disposed.

  The developing units 33Y, 33M, 33C, and 33K are developed with yellow (Y), magenta (M), cyan (C), and black (BK) toners, thereby latent images on the photosensitive drums 31Y, 31M, 31C, and 31K. Visualize the image. As a result, yellow (Y), magenta (M), cyan (C), and black (BK) toner images are formed on the photosensitive drums 31Y, 31M, 31C, and 31K.

  The first transfer rollers 34Y, 34M, 34C, and 34K of the intermediate transfer unit 40 transfer the toner images formed on the photosensitive drums 31Y, 31M, 31C, and 31K in a superimposed manner on predetermined positions on the intermediate transfer belt 41. . A color image is formed on the intermediate transfer belt 41 by superimposing the toner images of the respective colors. The intermediate transfer belt 41 formed of an endless belt moves while rotating in the direction indicated by the arrow in FIG. 1 by the driving force of the belt driving roller 44. The cleaning units 35Y, 35M, 35C, and 35K remove the toner remaining on the surfaces of the photosensitive drums 31Y, 31M, 31C, and 31K after the transfer of the toner images.

  On the other hand, the secondary transfer unit 42 transports the color image superimposed and transferred on the intermediate transfer belt 41 from the trays PG1, PG2, and PG3 of the sheet feeding unit 90, and sends out the timing by the registration rollers 91. Transferred onto the printed paper P. The belt cleaning unit 43 cleans the surface of the intermediate transfer belt 41 that has finished transferring the color image to the paper P, and the cleaned intermediate transfer belt 41 is used for the next image transfer.

  The paper P carrying the toner image is sent to the fixing unit 50, and the fixing unit 50 pressurizes and heats the paper P to fix the toner image on the paper P.

  The paper discharge reversing unit 70 conveys the paper P after the fixing process by the fixing unit 50 and discharges the paper P to the paper discharge tray 75. When the paper P is reversed and discharged, the paper discharge guide 72 once guides the paper P downward, holds the rear end of the paper P between the paper discharge reverse rollers 73, and reversely conveys the paper P. 72 guides the paper P to the paper discharge roller 74 and discharges it.

  When image formation is performed also on the back side of the paper P, the paper discharge guide 72 conveys the paper P, which has been subjected to the fixing process of the toner image on the front surface, to the re-feed unit 80 below, and is fed by the re-feed reverse roller 81. After pinching the rear end, the paper P is reversed by reverse feeding and sent to the refeed conveyance path 82 for image formation on the back surface.

  The fixing unit 50 is configured as a belt nip type fixing device 51 shown in FIG.

  The fixing device 51 includes a fixing roller 52 as a heating rotator, and a belt unit 53 disposed below the fixing roller 52.

  The fixing roller 52 includes a metal core 52a and an elastic layer 52b made of silicon rubber or the like provided on the outer peripheral surface of the metal core 52a.

  The cored bar 52a incorporates a heater made of a halogen lamp or the like as a heating source, and the outer peripheral surface of the elastic layer 52b is covered with a thin release layer made of a PFA tube. In FIG. 2, the heater and the release layer are not shown.

  The belt unit 53 includes an endless belt 54 that is suspended by a plurality of rotating bodies described later and contacts the fixing roller 52, and a pressing member 60 that presses the endless belt 54 from the inside toward the outside.

  The endless belt 54 has, for example, a laminated structure in which a base made of polyimide has silicon rubber as an elastic layer and a PFA tube as a release layer.

  In this embodiment, the rotating body that suspends the endless belt 54 is arranged on the lower side of the separation roller 55 for separating the paper from the fixing roller 52, the inlet roller 56 for introducing the paper, and the inlet roller 56. Four rollers, a steering roller 57 provided and a tension roller 58 disposed below the separation roller 55, are used.

  The separation roller 55 is disposed on the downstream side in the sheet feeding direction of the fixing device 51, and is rotationally driven in a direction opposite to the fixing roller 52 as indicated by an arrow in FIG. The inlet roller 56 is disposed upstream of the fixing device 51 in the sheet feeding direction, and has a function of heating the endless belt 54 by incorporating a heater such as a halogen lamp. The steering roller 57 tilts the shaft core by swinging at least one end, and corrects the shift of the endless belt 54.

  The pressing member 60 is disposed on the inner side of the endless belt 54 between the separation roller 55 on the downstream side in the paper feeding direction and the inlet roller 56 on the upstream side in the paper feeding direction, and protrudes toward the separation roller 55. Is formed.

  The separation roller 55 and the pressing member 60 press the endless belt 54 against the fixing roller 52, thereby forming a nip region having a required width W in the sheet feeding direction.

  As shown in FIG. 3, the pressing member 60 includes an elastic body 61 that elastically sandwiches the endless belt 54 with the fixing roller 52, and a base body 62 on which the elastic body 61 is placed. The elastic body 61 and the base body 62 are connected to each other. It is supported and attached on a stay 63 that is a housing-side rigid member (not shown).

  The elastic body 61 includes, for example, a main elastic body 61A made of silicon rubber having a hardness of JIS A 10 °, and an auxiliary elastic body 61B made of a silicon sponge disposed adjacent to the upstream end of the main elastic body 61A in the paper feeding direction. It consists of

  The main elastic body 61 </ b> A is formed such that the surface facing the endless belt 54 is a curved surface close to the curvature of the fixing roller 52.

  The base 62 is made of a metal material such as stainless steel or aluminum, and has an elastic support surface that is a curved surface that approximates the curved surface of the main elastic body 61A.

  Accordingly, the main elastic body 61A and the base body 62 form a wedge shape substantially protruding toward the separation roller 55 side. A thin hard rod 64 made of a metal material such as stainless steel is provided as a pressing auxiliary member at the tip of the main elastic body 61A on the downstream side in the paper feeding direction. The elastic body 61 and the base body 62 are covered with a sliding sheet 65.

  The sliding sheet 65 is formed of a thin heat-resistant synthetic resin sheet having a low friction coefficient, covers the elastic body 61 and the base body 62 in the paper feeding direction, and tensions both end portions 65B folded back on the stay 63 side. The stay 63 is fastened and fixed by a screw member 67 via retainer plates 66A and 66B. Thereby, the elastic body 61 and the base body 62 are firmly supported and fixed on the stay 63.

  At the end of the stay 63 on the upstream side in the sheet feeding direction, a sheet stationary seat 63 a that defines the height of the sliding surface of the sliding sheet 65 is erected. The end of the sliding sheet 65 on the upstream side in the sheet feeding direction is folded along the upper surface of the sheet stationary seat 63a, and is folded by being pressed against the upper surface of the sheet stationary seat 63a by an L-shaped retainer plate 66A. Fastened and fixed so that no wrinkles occur.

  On the other hand, the folded portion of the sliding sheet 65 on the downstream side in the sheet feeding direction, specifically, the folded region of a required length from the hard rod 64 of the elastic body 61 is a metal shape retaining shape not shown provided on the inner surface side. It is stiffened with a plate.

  As shown in FIGS. 4 and 5, the sliding sheet 65 has a wedge-shaped tip of the elastic body 61 on the downstream side in the paper feeding direction, that is, a protruding portion that protrudes toward the separation roller 55 from the hard rod 64. 65A is provided so that the volume of the wedge-shaped gap formed on the downstream side of the nip region W in the sheet feeding direction can be sandwiched.

  The protruding portion 65A is formed by molding in advance a non-linear shape in which a central portion 65A1 in a direction orthogonal to the feeding direction of the sliding sheet 65 protrudes from both side end portions 65A2.

The protruding amount of the protruding portion 65 from the hard rod 64 is such that the protruding length l ₁ from the end of the hard rod 64 to the leading end of the protruding portion on the fixing roller pressing surface side of the sliding sheet 65 and the folding side from the fixing roller pressing surface. it can be defined by the protruding length l ₂ to the projecting tip of a hard rod 64 end.

In this embodiment, the hard rod 64 is formed in a straight shape as shown in FIG. Therefore, in this embodiment, for example, the outer diameter of the fixing roller 52 is 80φ, the thickness of the endless belt 54 is 300 μm, the outer diameter of the separation roller 55 is 20φ, the outer diameter of the hard rod 64 is 0.8φ, and the sliding sheet. the thickness of 65 when a 70 [mu] m, the amount of projection of the projecting portion 65, the fixing roller pressing surface side _{l 1} is 1.5mm in the center portion 65A1, a 1.0mm at both side end portions 65a2, and a folded side _{l 2} The central portion 65A1 can be formed to have a thickness of 1.0 mm, and both side end portions 65A2 can be formed to have a thickness of 0.5 mm.

  Further, the height of the pressing surface and the inclination angle of the pressing member 60 are adjusted by a spacer 68 interposed between the base body 62 and the stay 63.

  On the other hand, a lubricant supply member 69 is in contact with the inlet roller 56, and the lubricant is supplied to the inner peripheral surface of the endless belt 54 via the inlet roller 56.

  The lubricant supply member 69 can be composed of, for example, an oil-impregnated member made of felt such as aramid fiber and an oil regulating film having a porosity of about 30 to 80% in which a PTFE porous film is formed in a bag shape. . In this case, the oil impregnated member is preliminarily impregnated with the lubricating oil and stored, and the lubricating oil is supplied to the inlet roller 56 from the oil regulating film covering the outer periphery. For example, dimethyl silicon oil having a viscosity of 100 to 1000 CS is used as the lubricating oil. Alternatively, silicone oil such as methylphenyl silicone oil having a viscosity of 100 to 1000 CS can be used.

  According to the fixing device 51 of the present embodiment having the above configuration, the protruding portion 65A of the sliding sheet 65 has a shape in which a central portion 65A1 in a direction orthogonal to the paper feeding direction protrudes from both side end portions 65A2. It is said that. Therefore, the volume of the wedge-shaped gap formed in the nip portion between the fixing roller 52 and the separation roller 55 can be narrowed by the central portion 65A1, and the pressure drop in the wedge-shaped gap can be suppressed to a small level.

  On the other hand, the both side end portions 65A2 of the projecting portion 65A have a projecting shape smaller than that of the central portion 65A1, thereby preventing excessive interference at the both end portions 65A2 that are likely to interfere with the opposing separation roller 55. Thus, the protrusion 65A can be prevented from being caught in the nip portion between the fixing roller 52 and the separation roller 55.

  As a result, when used as a fixing device of the fixing unit 50 in the image forming apparatus 1, the pressure drop in the wedge-shaped gap can be suppressed to a small level, so that image defects such as icicle-shaped gloss unevenness can be prevented. Further, it is possible to prevent paper separation failure and wrinkles at the separation roller 55 due to the sandwiching of the sliding sheet 65 and an increase in driving torque of the separation roller 55.

  Further, in the present embodiment, since the protruding portion 65A of the sliding sheet 65 is formed in a non-linear shape by molding, it is possible to easily set the protruding shapes of the central portion 65A1 and the side end portions 65A2. .

  FIG. 6 shows an example in which the projecting shapes of the central portion 65A1 and the side end portions 65A2 of the projecting portion 65A of the sliding sheet 65 are different.

  In the second embodiment, first, one end of the sliding sheet 65 is fastened and fixed to the upstream side surface of the stay 63a in the sheet feeding direction, and then the base 62 and the elastic body 61 are moved in the sheet feeding direction by the sliding sheet 65. The other end is wrapped and fixed to the side surface of the stay 63a on the downstream side in the sheet feeding direction.

  When the terminal portion 65B on the downstream side in the sheet feeding direction of the sliding sheet 65 is fixed, the central portion of the terminal portion 65B is connected to the central portion 65A1 of FIG. As shown by, the screw member 67 is fastened and fixed to the stay 63. Then, the both end portions of the terminal portion 65B are fastened and fixed to the stay 63 by the screw member 67 in a state where the both end portions 65A2 of the projecting portion 65A are pulled as shown by the chain line in FIG. .

  As a result, as shown by a solid line in FIG. 6, the projecting shape of the central portion 65A1 of the projecting portion 65A is ensured to be large, and a non-linear shape is configured in which the projecting shapes are reduced at the both end portions 65A2 by the traction fixing.

  According to the means for forming the protruding portion 65A of the second embodiment, the sliding sheet 65 does not need to be molded, and can be advantageously obtained in terms of cost.

  Here, in the pressing mode of the pressing member 60 and the fixing roller 52, there is a concern that the central portion of the pressing member 60 sinks due to the pressure contact of the paper during image fixing, and the pressing force is insufficient. In order to avoid this, it is considered that a slight raised portion 68a is provided at the center portion on the substrate contact surface side of the spacer 68 interposed between the substrate 62 and the stay 63 as shown by a chain line in FIG. It is done.

  In this case, when the elastic body 61 and the base body 62 are covered with the sliding sheet 65 and are fastened and fixed on the stay 63, the elastic body 61 and the base body 62 are centered on the raised portion 68a by the tightening force of the sliding sheet 65. As a result, the sheet feeding direction and the direction perpendicular to the sheet feeding direction may be slightly bent and deformed.

  Even when the rigid rod 64 is formed in a straight shape, the elastic body 61 and the base body 62 are bent and deformed toward the downstream side in the sheet feeding direction with respect to the rigid rod 64 as shown by a broken line in FIG. Brings a bow-shaped fold. That is, the hard rod 64 has a shape in which a central portion in a direction orthogonal to the paper feeding direction protrudes from both end portions.

  However, according to the present invention, the protrusion 65A of the sliding sheet 65 has the central portion 65A1 in the direction orthogonal to the sheet feeding direction on both sides, regardless of the configuration of the first embodiment or the second embodiment. It is formed in a shape protruding from the portion 65A2. For this reason, even when the hard rod 64 is deformed like a bow, excessive interference with the separation roller 55 of the both side portions 65A2 is avoided, and a sufficient distance is provided between the central portion 65A1 and the central portion of the hard rod 64. It is possible to sufficiently exert the effect of suppressing the pressure drop in the wedge-shaped gap in the nip region W due to the protrusion of the central portion 65A1.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus 51 ... Fixing apparatus 52 ... Fixing roller (heating rotary body)
53... Fixing belt unit 54... Endless belt 55... Separation roller (rotating body on the downstream side in the paper feeding direction)
60 ... Pressing member 63 ... Rigid member 64 ... Hard rod (wedge-shaped tip of the pressing member)
65 ... Sliding sheet 65A ... Sliding sheet protrusion 65A1 ... Projecting center 65A2 ... Side side 65B ... Sliding sheet feed end portion W ... Nip region l ₁ ... Projecting heating Projection length l ₂ on the pressing surface side of the rotating body ... Projection length on the folding side of the projection

Claims (6)

A heating rotator having a heating source;
An endless belt that is hung on a plurality of rotating bodies and is in contact with the heating rotating body;
A pressing member that presses the endless belt from the inside toward the outside;
A sliding sheet covering the pressing member,
Of the plurality of rotating bodies, the rotating body on the downstream side in the sheet feeding direction and the pressing member press the endless belt against the heating rotating body to form a nip region, and the image-formed paper is transferred to the nip region. A fixing device for fixing the formed image to the paper by passing through
The pressing member has a wedge shape protruding toward the rotating body on the downstream side in the paper feeding direction,
The sliding sheet has, on the downstream side in the paper feeding direction, a protruding portion that protrudes toward the rotating body on the downstream side in the paper feeding direction from the wedge-shaped tip of the pressing member,
The fixing device is characterized in that a central portion in a direction orthogonal to the paper feeding direction is formed to protrude from both side end portions.   2. The fixing device according to claim 1, wherein the wedge-shaped tip of the pressing member has a shape in which a central portion in a direction orthogonal to a paper feeding direction protrudes from both end portions.   The fixing device according to claim 1, wherein the protruding portion of the sliding sheet is formed in advance by molding. The sliding sheet is fixed to a rigid member that supports at least the terminal portions on both sides in the paper feeding direction,
When the protrusion is fixed to the rigid member, the terminal portion on the downstream side in the sheet feeding direction of the sliding sheet,
After fixing the central portion of the terminal portion with a slack that can obtain a required amount of protrusion in the central portion of the protruding portion in advance, the protruding shape of the both side end portions of the terminal portion is reduced. The fixing device according to claim 1, wherein the fixing device is formed so as to have a different protruding shape by being fixed in a pulled state.   The protruding amount of the protruding portion of the sliding sheet is determined by the protruding length from the wedge-shaped tip corresponding position of the pressing member to the tip of the protruding portion on the heating rotor pressing surface side of the sliding sheet, and the heating rotor pressing 5. The fixing according to claim 1, wherein the fixing member is defined by a protruding length from a wedge-shaped tip corresponding position of the pressing member to a tip of the protruding portion on the folding side from the surface. apparatus. An image forming apparatus comprising the fixing device according to claim 1.

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