JP2010128143A - Fixing device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device capable of preventing irregular glossiness from being generated by generating an uneven temperature in a fixing belt, when providing a rib in a guide member positioned at an inner circumferential face side of the fixing belt and guiding the fixing belt, and capable of preventing a wrinkle from being generated in the fixing belt. <P>SOLUTION: The fixing device includes a rotating fixing roller having a heating means, the endless fixing belt driven by the fixing roller to be rotated, a pressurizing member which is deformed by pressing the fixing belt from the inner circumferential face side to bring the fixing belt into contact with the fixing roller, and forming a nip between the fixing roller and the fixing belt, and the guide member positioned at the inner circumferential face side of the fixing belt and guiding the fixing belt, and the plurality of ribs inclined toward a width-directional end of the guide member from a rotation-directional upstream of the fixing belt toward a downstream thereof is provided on a face at a side of the fixing belt in the guide member in the fixing device. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an FBN-type fixing device having a fixing belt, and an image forming apparatus including the fixing device.

  In an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine having these functions, a latent image corresponding to an original is formed on a photosensitive drum, and toner is applied to the latent image. Thus, the visualized toner image is transferred onto a recording material, and then the toner image on the recording material is fixed and discharged.

  When a color image is formed, Y, M, C, and K latent images corresponding to the original color are formed on four photosensitive drums, and the visualized four color toner images are endless. After the primary transfer onto the intermediate transfer belt, the toner image transferred onto the recording material is fixed on the recording material, and the toner image transferred onto the recording material is fixed and discharged.

  As a fixing device for fixing a toner image in this way, a recording material on which the toner image is transferred at a nip formed by a fixing roller incorporating a heating means such as a halogen lamp and a pressure roller for pressing the fixing roller. There is a heat roller fixing type fixing device that heats and pressurizes while sandwiching and conveying the sheet, and such a fixing device is widely used because of its simple configuration.

  By the way, in such a fixing device, in order to increase the speed, it is necessary to supply a sufficient amount of heat to the toner and the recording material. For this purpose, it is necessary to widen the nip width. In order to widen the nip width, it is conceivable to increase the load applied by the pressure roller to the fixing roller, the thickness of the elastic layer made of silicone rubber or the like in the pressure roller, the diameter of the two rollers, and the like. .

  However, when the load of the pressure roller and the thickness of the elastic layer are increased, the nip width in the central axis direction of the fixing belt may become non-uniform, which may cause uneven gloss and wrinkles on the recording material. Further, when the diameter of the roller is increased, there is a problem that not only the fixing device is increased in size but also the warm-up time is increased.

  In order to solve this problem, a fixing roller (fixing roll) that contains a halogen lamp and rotates with an elastic layer, an endless fixing belt (endless belt) that rotates by being driven by the fixing roller, and fixing A nip portion formed between the fixing roller and the fixing belt by being provided with a pressure pad (pressure pad) made of silicone rubber or the like disposed on the inner peripheral surface side of the belt, and the pressure pad pressing the fixing belt Thus, a so-called FBN (Free Belt Nip) type fixing device that heats and pressurizes a recording material onto which a toner image is transferred is conveyed (see, for example, Patent Document 1).

  According to this fixing device, the fixing belt pressed against the fixing roller by the pressure pad is elastically deformed toward the pressure pad, and a wide nip portion is formed between the fixing roller and the fixing belt. Therefore, although it is a small shape, it can cope with high speed, and since the heat capacity of the fixing belt is small, the warm-up time is shortened and energy is saved.

  Further, if the inner peripheral surface of the rotating fixing belt is brought into sliding contact with the non-rotating pressure pad, the driving torque of the fixing belt increases due to the frictional resistance, and there is a concern about increase in power consumption and wear of the fixing belt. Therefore, a sliding sheet (low friction sheet) formed of a low friction material is disposed between the fixing belt and the pressure pad, and further, silicone oil or the like is applied to the inner peripheral surface of the fixing belt by the lubricant application member. Lubricant is supplied to reduce frictional resistance.

In the fixing device of Patent Document 1, a guide member (downstream belt guide member) for guiding the fixing belt is provided on the inner peripheral surface side of the fixing belt, and the guide member is provided on the guide belt from the upstream side to the downstream side in the rotation direction of the fixing belt. A plurality of grooves inclined toward the center of the guide member in the width direction are formed. The purpose of this is to prevent the lubricant supplied to the inner peripheral surface of the fixing belt from moving to both ends of the fixing belt and to prevent leakage to the outside.
JP 2006-79965 A

  In an FBN type fixing device, a plurality of ribs are formed on a guide member to reduce the frictional resistance between the fixing belt and the guide member. The ribs are generally formed in parallel with the rotation direction of the fixing belt.

  However, when the fixing belt rotates, the fixing belt slides on the top of the rib and does not slide on the groove between the adjacent ribs. For this reason, in the width direction of the fixing belt, there are a portion that always slides on the rib and a portion that does not slide on the rib at all, and temperature unevenness occurs on the fixing belt due to frictional resistance. is there.

  In order to solve this problem, all surfaces of the fixing belt need to be in sliding contact with the rib during rotation.

  In the fixing device disclosed in Patent Document 1, the inclined groove is formed in the guide member to prevent the leakage of the lubricant as described above, so that the convex portion, that is, the rib between the adjacent grooves is also inclined. It is possible to make all the surfaces of the fixing belt slidably contact the ribs. However, since this rib is inclined in the direction of the central portion in the width direction of the guide member from the upstream side to the downstream side in the rotation direction of the fixing belt, a force toward the central portion acts on the inner peripheral surface of the fixing belt, The fixing belt is wrinkled, and the image quality of the fixed image tends to be uneven. In order to prevent wrinkles from occurring on the fixing belt, it is conceivable to increase the thickness of the fixing belt. However, if the thickness is increased, the fixing belt becomes difficult to be deformed, so that the separation performance of the recording material is lowered and the heat capacity is reduced. The advantage of the FBN method, which increases, shortens the warm-up time, and saves energy, is lost.

  The problem of preventing lubricant leakage can be solved by a simple method such as placing a flange-shaped member at the end of the fixing belt. It is not necessary to provide a groove having a shape as in Patent Document 1 on the member.

  In addition, Patent Document 1 does not consider any problem of wrinkles on the fixing belt.

  The present invention has been made in view of such a problem, and when a rib is provided on a guide member that is positioned on the inner peripheral surface side of the fixing belt and guides the fixing belt, temperature unevenness occurs in the fixing belt and gloss unevenness occurs. It is an object of the present invention to propose a fixing device in which no flaws occur and wrinkles are not generated on the fixing belt, and an image forming apparatus including the fixing device.

1. A fixing roller rotating with heating means;
An endless fixing belt driven and rotated by the fixing roller;
A pressure member that deforms itself by pressing the fixing belt from the inner peripheral surface side to press the fixing belt against the fixing roller, and forms a nip portion between the fixing roller and the fixing belt;
A guide member that is positioned on the inner peripheral surface side of the fixing belt and guides the fixing belt;
In the fixing device provided with
A plurality of ribs inclined in the direction of the width direction end portion of the guide member from the upstream side to the downstream side in the rotation direction of the fixing belt are provided on the surface of the guide member on the side of the fixing belt. Fixing device to do.

  2. 2. The fixing device according to 1 above, wherein the two adjacent ribs both have a portion located on a predetermined straight line formed in parallel with a rotation direction of the fixing belt.

  3. The fixing device according to claim 1 or 2, wherein the plurality of ribs are arranged line-symmetrically with respect to a central portion in the width direction of the guide member as an axis of symmetry.

  4). 4. The fixing device according to claim 1, wherein a low-friction sliding sheet is disposed between the fixing belt and the pressure member.

  5. 5. The fixing device according to claim 1, wherein an edge of a top portion of the rib is formed in an arc shape.

  6). An image forming apparatus comprising the fixing device according to claim 1.

  According to the fixing device of the present invention and the image forming apparatus including the fixing device, when the rib is provided on the guide member that is positioned on the inner peripheral surface side of the fixing belt and guides the fixing belt, the temperature of the fixing belt is increased. There is an effect that unevenness does not occur and gloss unevenness does not occur, and wrinkles do not occur on the fixing belt.

  Hereinafter, the present invention will be described based on an embodiment of the present invention, but the present invention is not limited to this embodiment.

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

  The image forming apparatus includes an image reading apparatus YS, an image forming apparatus GH, and the like. The image forming unit GH is called a tandem color image forming apparatus, and includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10K, an intermediate transfer member 6, a secondary transfer unit 7A, a fixing device 100, and a paper feeding unit. 20 etc.

  An image reading device YS including an automatic document feeder 501 and a document image scanning exposure device 502 is installed above the image forming unit GH. The document d placed on the document table of the automatic document feeder 501 is transported by a transport unit, and an image on one or both sides of the document is scanned and exposed by the optical system of the document image scanning exposure device 502, and the line image sensor CCD is scanned. Is read.

  An image signal formed by photoelectric conversion by the line image sensor CCD is subjected to analog processing, A / D conversion, shading correction, image compression processing, and the like in an image processing unit (not shown), and then exposure means 3Y, 3M. , 3C, 3K.

  The image forming unit 10Y that forms a yellow (Y) image includes a charging unit 2Y, an exposure unit 3Y, a developing device 4Y, a primary transfer unit 7Y, and a cleaning unit 8Y around the photosensitive drum 1Y. The image forming unit 10M that forms a magenta (M) color image includes a charging unit 2M, an exposure unit 3M, a developing device 4M, a primary transfer unit 7M, and a cleaning unit 8M around the photosensitive drum 1M. An image forming unit 10C for forming a cyan (C) color image includes a charging unit 2C, an exposure unit 3C, a developing device 4C, a primary transfer unit 7C, and a cleaning unit 8C around the photosensitive drum 1C. The image forming unit 10K that forms a black (Bk) image includes a charging unit 2K, an exposure unit 3K, a developing device 4K, a primary transfer unit 7K, and a cleaning unit 8K around the photosensitive drum 1K. The charging unit 2Y and the exposure unit 3Y, the charging unit 2M and the exposure unit 3M, the charging unit 2C and the exposure unit 3C, and the charging unit 2K and the exposure unit 3K constitute a latent image forming unit.

  The developing devices 4Y, 4M, 4C, and 4K include a two-component developer including yellow (Y), magenta (M), cyan (C), and black (K) toner having a small particle diameter and a carrier.

  The intermediate transfer body 6 is wound around a plurality of rollers and is rotatably supported.

  The fixing device 100 fixes a toner image on the recording paper P (recording material) by heating and pressing at a nip portion formed between a fixing roller 101 having a halogen lamp and a fixing belt 102.

  Each color image formed by the image forming units 10Y, 10M, 10C, and 10K is sequentially primary-transferred onto the rotating intermediate transfer body 6 by the primary transfer means 7Y, 7M, 7C, and 7K, and color image synthesis is performed. A toner image is formed.

  The recording paper P stored in the paper feed tray 21 is separated and fed by the paper feed roller 22 of the paper feed means 20, passes through a plurality of paper feed rollers 23, and enters the stopped registration roller 24. Paper is fed. Therefore, the roller is temporarily stopped, and the registration roller 24 starts to rotate at the timing when the positional relationship between the leading end and the toner image on the intermediate transfer member 6 accurately coincides, and is fed to the secondary transfer unit 7A for recording. A color image is secondarily transferred onto the paper P. The recording paper P to which the color image has been transferred is heated and pressurized by the fixing device 100, and the color toner image on the recording paper P is fixed. Thereafter, the sheet is sandwiched between the sheet discharge rollers 25 and placed on the sheet discharge tray 26 outside the apparatus.

  On the other hand, after the color image is transferred to the recording paper P by the secondary transfer means 7A, the residual toner is removed by the intermediate transfer body cleaning means 8A from the intermediate transfer body 6 from which the recording paper P is separated by curvature.

  Although the above is an image forming apparatus that forms a color image, an image forming apparatus that forms a monochrome image may be used.

  Next, the fixing device 100 according to the present invention will be described with reference to the enlarged sectional view of FIG. The fixing device 100 is an FBN type fixing device.

  The fixing roller 101 includes a halogen lamp (heating means) H in the center, and a cylindrical cored bar 101A made of aluminum, iron, or the like, and an elastic layer 101B made of silicone rubber having high heat resistance and covering the cylindrical cored bar 101A. And a release layer 101C made of a fluororesin such as PFA (perfluoroalkoxy) or PTFE (polytetrafluoroethylene) and further covering the elastic layer 101B.

  The fixing belt 102 is composed of a base made of polyimide and a release layer made of PFA or PTFE covering the outer surface of the base, and is formed endlessly.

  The pressure pad 103 (pressure member) is made of, for example, silicone rubber having a hardness of about 10 ° JISA, and is held by a holder 108 made of heat resistant resin together with a base metal plate 104 made of stainless steel and a base member 105 made of heat resistant resin. Yes. A compression spring 106 is disposed on the back surface of the base member 105.

  The separation member 107 is disposed on the downstream side in the conveyance direction of the recording paper P with respect to the pressure pad 103 in order to improve the separation of the fixed recording paper P. The separating member 107 is made of a heat-resistant resin such as PPS, polyimide, polyester, or polyamide, or a metal such as aluminum, and the tip is formed in an arc having a large curvature. A metal frame 110 that holds the holder 108 is disposed at the center.

  The sliding sheet 111 is formed by coating a glass fiber sheet with fluororesin (PTFE) or Teflon (registered trademark), and between the fixing belt 102 and the pressure pad 103 and between the fixing belt 102 and the separation member 107. One end is fixed to the frame 110.

  The guide member 109 is positioned on the inner peripheral surface side of the fixing belt 102 and is held by the frame 110 and guides the fixing belt 102 at a position where the sliding sheet 111 is not disposed.

  The oil pad 112 is made of sponge or the like, impregnated with a lubricant made of silicone oil or the like, held by the guide member 109, and pressed against the inner peripheral surface of the fixing belt 102.

  In the fixing device 100 configured as described above, the fixing roller 101 heated by the halogen lamp H and driven by a driving unit (not shown) rotates in the clockwise direction. The pressure pad 103 is pressed by the compression spring 106 via the base metal plate 104 and the base member 105, and the pressure pad 103 presses the fixing belt 102 against the fixing roller 101 via the sliding sheet 111 and is elastic by itself. Deform. Further, the separating member 107 presses the fixing belt 102 against the fixing roller 101 via the sliding sheet 111.

  Accordingly, the fixing belt 102 rotates counterclockwise by the rotation of the fixing roller 101 and slides on the sliding sheet 111 and the guide member 109. Further, since the fixing belt 102 is pressed against the fixing roller 101 by the pressure pad 103 and elastically deforms together with the pressure pad 103, a wide nip portion N is formed between the fixing belt 102 and the fixing roller 101. The unfixed toner on the conveyed recording paper P is heated and pressurized at the nip portion N and fixed.

  The separating member 107 presses the fixing belt 102 against the fixing roller 101 via the sliding sheet 111, and elastically deforms the elastic layer 101B and the release layer 101C of the fixing roller 101 into a concave shape having a large curvature. Accordingly, the recording paper P fixed at the nip portion N is reliably peeled off and separated from the fixing roller 101 without using a separation claw or the like.

  The inner peripheral surface of the fixing belt 102 slides on the sliding sheet 111 during rotation. However, since the sliding sheet 111 has a small friction coefficient, the frictional resistance between the two is small. Further, since silicone oil as a lubricant is supplied from the oil pad 112 to the inner peripheral surface of the fixing belt 102 and the outer surfaces of the sliding sheet 111 and the guide member 109, the frictional resistance is further reduced.

  Here, as shown in FIG. 3, in order to further reduce the frictional resistance when the fixing belt 102 slides on the guide member 109, a plurality of ribs 109A are formed on the surface of the guide member 109 on the fixing belt 102 side. To do. FIG. 3A is a development view of the outer surface of the guide member 109, and FIG. 3B is an enlarged cross-sectional view of the outer surface of the guide member 109.

  In FIG. 3A, C is a center portion of the guide member 109 in the width direction. Further, the fixing belt 102 rotates with respect to the guide member 109 from the arrow direction. Each rib 109 </ b> A is formed to be inclined in the direction of the width direction end portion of the guide member 109 from the upstream side to the downstream side in the rotation direction of the fixing belt 102. Each rib 109 </ b> A is arranged line-symmetrically with the center portion C in the width direction of the guide member 109 as the axis of symmetry. Further, the two adjacent ribs 109 </ b> A both have portions located on a predetermined straight line L formed in parallel with the rotation direction of the fixing belt 102.

  As a result, each part of the fixing belt 102 is always in sliding contact with any one of the ribs 109A, so that temperature unevenness does not occur in the fixing belt 102, and therefore gloss unevenness does not occur in the fixed image. Further, since a force that tensions the fixing belt 102 to the outside in the width direction is applied by the rib 109A, the fixing belt 102 is not wrinkled, and the image quality of the fixed image is kept uniform.

  In order for the fixing belt 102 to slide smoothly with respect to the rib 109A, it is desirable that the edge 109A1 at the top of the rib 109A is formed in an arc shape.

Here, an experiment for confirming the occurrence of uneven gloss and flaws on the fixing belt when various ribs are provided on the guide member will be described.
(1) Experimental conditions Fixing device: Shape as shown in FIG. 2 Fixing roller: Outer diameter 40 mm
Fixing belt: 35mm inside diameter
Fixing temperature: 190 ° C
Nip pressure: 50kgf
Nip width: 10mm
(2) Experimental results Table 1 shows.

The meanings of the items in Table 1 are as follows.
・ Rib direction Parallel: Parallel to fixing belt rotation direction Outward: Inclination direction of fixing belt in the width direction from the upstream side to the downstream side of the fixing belt Inward direction: Upstream direction of the fixing belt Ribs that are inclined and adjacent to the central portion in the width direction of the fixing belt from the downstream side to the downstream side None: There is no portion located on a predetermined straight line formed in parallel with the rotation direction of the fixing belt.

Yes: Both have portions located on a predetermined straight line formed parallel to the rotation direction of the fixing belt.
(3) Discussion Regarding the occurrence of uneven gloss and the occurrence of wrinkles on the fixing belt, it was proved that the presence of adjacent ribs facing outward in the rib direction is the best.

  Further, in the case where there are adjacent ribs facing outward in the rib direction, an experiment was also performed to check the occurrence of uneven gloss by changing the rib angle, rib width, and rib pitch with respect to the rotation direction of the fixing belt. This is shown in Table 2.

  As a result, it was found that gloss unevenness did not occur under any conditions, and therefore the occurrence of gloss unevenness was not affected by the rib angle, rib width, and rib pitch.

  Note that the cross-sectional shape of the rib shown in FIG. 3B is rectangular, but it may be trapezoidal.

  Further, the rib does not necessarily have to be inclined linearly, and may be inclined with a curve.

1 is a configuration diagram of an image forming apparatus. FIG. 3 is an enlarged cross-sectional view of a fixing device. It is a figure which shows the rib of a guide member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Fixing apparatus 101 Fixing roller 102 Fixing belt 103 Pressure pad 109 Guide member 109A Rib 109A1 Edge 111 Sliding sheet H Halogen lamp N Nip part P Recording paper

Claims (6)

A fixing roller rotating with heating means;
An endless fixing belt driven and rotated by the fixing roller;
A pressure member that deforms itself by pressing the fixing belt from the inner peripheral surface side to press the fixing belt against the fixing roller, and forms a nip portion between the fixing roller and the fixing belt;
A guide member that is positioned on the inner peripheral surface side of the fixing belt and guides the fixing belt;
In the fixing device provided with
A plurality of ribs inclined in the direction of the width direction end portion of the guide member from the upstream side to the downstream side in the rotation direction of the fixing belt are provided on the surface of the guide member on the side of the fixing belt. Fixing device to do. 2. The fixing device according to claim 1, wherein the two adjacent ribs have both portions located on a predetermined straight line formed in parallel with a rotation direction of the fixing belt. The fixing device according to claim 1, wherein the plurality of ribs are arranged line-symmetrically with respect to a central portion in the width direction of the guide member as an axis of symmetry. The fixing device according to claim 1, wherein a low-friction sliding sheet is disposed between the fixing belt and the pressure member. The fixing device according to claim 1, wherein an edge of a top portion of the rib is formed in an arc shape. An image forming apparatus comprising the fixing device according to claim 1.

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