JP2009288399A - Fixing device and image-forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device which prevents a pressing roller from being worn due to the edge parts of a fixing belt, whose length in the width direction is shorter than the pressing roller, even if the fixing belt meanders, and prevents a lubricant from leaking. <P>SOLUTION: The fixing device is provided with: a rotary member which rotates; an endless fixing belt which has a lubricant on its inner peripheral surface and is in contact with the rotary member to rotate; a pressing member which presses the fixing belt toward the rotary member from the inner peripheral surface side; a sliding member arranged between the fixing belt and the pressing member; and a pressing roller which is one of rollers on which the fixing belt is stretched and brings the fixing belt into contact with the rotary member by pressing, wherein at least the surface across the width direction is made of metal. The fixing device fixes a toner image on a recording medium at a nip part formed between the rotary member and the fixing belt. Furthermore, the surface roughness of the end area of the pressing roller to be in contact with the edge parts in the width direction of the fixing belt , is smaller than the surface roughness of the center area thereof located closer to the center in the width direction than the end part area. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fixing device having an endless 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 to a recording material, and then the toner image of 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 the four photosensitive drums, respectively, 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 and discharged after the secondary transfer onto the recording material.

  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 increase the nip width, it is possible to increase the load by which the pressure roller presses the fixing roller, the thickness of the elastic layer formed of silicone rubber or the like in the pressure roller, the diameter of the two rollers, and the like. Conceivable.

  However, when the load of the pressure roller and the thickness of the elastic layer are increased, the nip width in the axial direction may become non-uniform, which may cause uneven fixing and wrinkling of 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 (heat fixing roll) rotating with a halogen lamp incorporated therein, a fixing belt (endless belt) stretched between a plurality of stretching rollers (supporting rolls), and a fixing belt are provided. A pressing member (pressure applying member) that presses in the direction of the fixing roller from the inner peripheral surface side, and a recording material on which the toner image is transferred is sandwiched by a nip formed between the fixing roller and the fixing belt A fixing device that heats and pressurizes while carrying is known (for example, see Patent Document 1).

  Such a fixing device can cope with high speed because a wide nip portion is formed between the fixing roller and the fixing belt, and the heat capacity of the fixing belt is small, so that the warm-up time is shortened and energy saving is achieved. Has the advantage.

  In this fixing device, a tension roller (hereinafter referred to as a pressure roller) that is one of tension rollers that stretch the fixing belt and is disposed on the exit side of the nip portion presses the fixing belt, thereby fixing the fixing belt. Is pressed against the fixing roller. Since the elastic layer of the fixing roller is deformed by the pressing roller and the vicinity of the exit of the nip portion is concave, the fixed recording material is separated and discharged without adhering to the fixing roller.

  Further, since the pressing member is made of silicone rubber or the like, if the fixing belt slides as it is, a large frictional force is generated. Therefore, a low-friction sliding sheet formed of a fluororesin-coated glass fiber sheet or the like is fixed between the fixing belt and the pressing member so that the fixing belt slides on the sliding sheet. Yes. Further, in order to further reduce the frictional resistance between the fixing belt and the sliding sheet, a lubricant applying member for applying a lubricant such as silicone oil to the inner peripheral surface of the fixing belt is also provided.

  Further, due to the parallelism and twisting of the stretching rollers such as the fixing roller and the pressing roller, the fixing belt is likely to be skewed or meandered in the width direction during rotation. In order to suppress this deviation and meandering, one inclination of the stretching roller other than the pressing roller is controlled.

  By the way, the length in the axial direction of the portion of the stretching roller that contacts the fixing belt is generally longer than the width of the fixing belt.

  As a result, a phenomenon occurs in which the edge in the width direction of the fixing belt is in sliding contact with the stretching roller and the surface of the stretching roller is worn.

  In order to solve this problem, in the fixing device having the same configuration as that of Patent Document 1, the tension strength of the end region where the edge in the width direction of the fixing belt is slidably contacted with the tension roller that stretches the fixing belt. There is known a fixing device in which the thickness (hardness) is made larger than the central region where the edge portion is not in sliding contact and the dynamic friction coefficient of the end region is made smaller than that of the central region (see Patent Document 2).

The phenomenon that the surface of the tension roller is worn is remarkable in the pressure roller that presses the fixing belt and is in closest contact with the fixing belt. Particularly, when the pressure roller is formed of metal, metal wear powder is generated by the fixing belt. There arises a problem that the inner peripheral surface of the roller and other stretching rollers are worn.
JP-A-11-45018 JP 2007-139809 A

  In the fixing device as described in Patent Document 2, the lubricant applied to the inner peripheral surface of the fixing belt is applied to both ends at the contact portion between the fixing belt and the stretching roller (particularly, the pressing roller having a large contact pressure with the fixing belt). It is easy to cause a problem that it is pushed out and leaks. If the lubricant leaks, the internal lubricant may be depleted, and the frictional resistance between the fixing belt and the sliding sheet may increase to increase the driving torque. There is no description in Patent Document 2 regarding the problems relating to such problems and the means for solving them.

  The present invention has been made in view of such a problem. Even when a fixing belt shorter than the width of the pressing roller meanders, the pressing roller is not worn by the edge of the fixing belt, and the lubricant does not leak out. It is an object of the present invention to propose a fixing device and an image forming apparatus including the fixing device.

  The object is achieved by the invention described below.

1. A rotating member that rotates;
An endless fixing belt having a lubricant on an inner peripheral surface and rotating in pressure contact with the rotating member;
A pressing member that presses the fixing belt from the inner peripheral surface toward the rotating member;
A sliding member disposed between the fixing belt and the pressing member;
One of the rollers for stretching the fixing belt, wherein at least the surface is formed of metal over the width direction, and the pressing roller presses the fixing belt against the rotating member;
Have
In a fixing device for fixing a toner image on a recording material at a nip formed between the rotating member and the fixing belt,
In the pressing roller, the surface roughness of the end region with which the edge in the width direction of the fixing belt can contact is formed to be smaller than the surface roughness of the central region located on the center side of the end region in the width direction. A fixing device.

  2. 2. The fixing device according to 1, wherein the rotating member is a roller having a heating source.

  3. 2. The fixing device according to 1, wherein the rotating member is an endless belt stretched around a plurality of rollers.

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

  According to the fixing device and the image forming apparatus of the present invention, even if the fixing belt having a width shorter than that of the pressing roller meanders, the pressing roller is hardly worn by the edge of the fixing belt, and metal wear powder is hardly generated. Further, there is no problem that the lubricant applied to the inner peripheral surface of the fixing belt is pushed out at both ends and leaks at the contact portion between the fixing belt and the pressing roller, and the lubricant is not depleted.

  Embodiments relating to the fixing device of the present invention will be described below with reference to the drawings.

  First, an example of an image forming apparatus using the fixing device of the present invention will be described based on the configuration diagram of FIG.

  The image forming apparatus includes an image forming apparatus main body GH and an image reading apparatus YS.

  The image forming apparatus main body GH is called a tandem type color image forming apparatus, and a plurality of sets of image forming units 10Y, 10M, 10C, and 10K, a belt-like intermediate transfer member 5, a sheet feeding and conveying unit, a fixing device 8, and the like. Consists of.

  An image reading device YS including an automatic document feeder 201 and a document image scanning exposure device 202 is installed on the upper part of the image forming apparatus main body GH. The document d placed on the document table of the automatic document feeder 201 is transported by a transport unit, and one or both images of the document are scanned and exposed by the optical system of the document image scanning exposure device 202 and read into the line image sensor CCD. It is.

  A 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, and then exposure means 3Y, 3M, 3C, 3K. Sent to.

  In the image forming unit 10Y that forms a yellow (Y) image, a charging unit 2Y, an exposure unit 3Y, a developing unit 4Y, and a cleaning unit 7Y are arranged around the photosensitive drum 1Y. In the image forming unit 10M that forms a magenta (M) color image, a charging unit 2M, an exposure unit 3M, a developing unit 4M, and a cleaning unit 7M are arranged around the photosensitive drum 1M. In the image forming unit 10C that forms a cyan (C) color image, a charging unit 2C, an exposure unit 3C, a developing unit 4C, and a cleaning unit 7C are arranged around the photosensitive drum 1C. In the image forming unit 10K that forms a black (K) image, a charging unit 2K, an exposure unit 3K, a developing unit 4K, and a cleaning unit 7K are arranged 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 device 3C, and the charging unit 2K and the exposure device 3K constitute a latent image forming unit.

  The developing units 4Y, 4M, 4C, and 4K include a two-component developer composed of a toner having a small particle size of yellow (Y), magenta (M), cyan (C), and black (K) and a carrier.

  The intermediate transfer member 5 is wound around a plurality of rollers and is rotatably supported.

  The fixing device 8 heats and pressurizes the toner image on the recording paper (recording material) P at a nip portion formed between the heated fixing roller 81 and the fixing belt 82 to fix the toner image.

  Thus, each color image formed by the image forming units 10Y, 10M, 10C, and 10K is sequentially transferred to the rotating intermediate transfer body 5 by the transfer means 6Y, 6M, 6C, and 6K (primary transfer), and color. A combined toner image is formed. The recording paper P stored in the paper feeding cassette 20 is fed by the paper feeding means 21 and is conveyed to the transfer means 6A through the paper feeding rollers 22A, 22B, 22C, 22D, the registration rollers 23, etc. A color image is transferred to P (secondary transfer). The recording paper P to which the color image has been transferred is heated and pressurized by the fixing device 8 and the color toner image on the recording paper P is fixed. Thereafter, the sheet is sandwiched between the sheet discharge rollers 24 and placed on the sheet discharge tray 25 outside the apparatus.

  On the other hand, after the color image is transferred to the recording paper P by the transfer means 6A, the residual toner is removed by the cleaning means 7A from the intermediate transfer body 5 from which the recording paper P is separated by curvature.

  The image forming apparatus for forming a color image has been described above. However, an image forming apparatus for forming a monochrome image may be used, or an intermediate transfer member may or may not be used.

  Next, an embodiment of the main configuration of the fixing device 8 of the present invention will be described with reference to FIG. This figure is a cross-sectional view of the recording paper P in the transport direction.

  The fixing device 8 mainly includes a fixing roller 81 (rotating member) that rotates, an endless fixing belt 82 that rotates in pressure contact with the fixing roller 81, and presses the fixing belt 82 from the inner peripheral surface toward the fixing roller 81. It is comprised from the press member 90 to do.

  The fixing roller 81 incorporates a halogen lamp (heating source) H in the center, covers the cylindrical cored bar 81A made of metal such as aluminum or stainless steel, and the cylindrical cored bar 81A, and elastic made of heat-resistant silicone rubber. A layer 81B and a surface layer 81C made of a PFA (perfluoroalkoxyethylene) tube that further covers the elastic layer 81B.

  The fixing belt 82 is composed of a base made of polyimide and a surface layer covering the base and made of PFA or the like, and is formed in an endless shape.

  The fixing belt 82 is stretched by a pressing roller 83, an entrance roller 84 and a steering roller 85.

  The pressing roller 83 is disposed on the exit side of the nip portion N, and presses the fixing belt 82 to press the fixing belt 81.

  The entrance roller 84 is disposed on the entrance side of the nip portion N and does not directly press the fixing belt 82 against the fixing roller 81, but presses the fixing belt 82 positioned between the pressing roller 83 and the fixing roller 81. A nip portion N that is long in the conveyance direction of the recording paper P is formed.

  Then, the toner image on the recording material P is fixed at the nip portion N formed between the fixing roller 81 and the fixing belt 82 by the entrance roller 84, the pressing member 90, and the pressing roller 83.

  The steering roller 85 changes the parallelism with respect to the pressing roller 83 and the entrance roller 84 based on the result of detecting the position of the edge of the fixing belt 82 by a sensor (not shown), so that the fixing belt 82 in the width direction is changed. It has a mechanism (not shown) that corrects the shift.

  The pressing roller 83, the entrance roller 84, and the steering roller 85 are made of metal such as stainless steel.

  Further, the steering roller 85 needs to have a predetermined frictional force with the fixing belt 82 in order to ensure the ability to correct the deviation of the fixing belt 82, and heat-resistant rubber may be formed on the surface.

  The pressing member 90 includes a holder 91, a shim 92, a support plate 93, a pressure pad 94, and a sliding sheet 95.

  The holder 91 is made of stainless steel or the like, and a shim 92 made of heat-resistant resin, a support plate 93 made of stainless steel, and a pressure pad 94 made of silicone rubber are laminated on the holder 91 in order. A compression spring (not shown) presses the shim 92 and presses the fixing belt 82 against the fixing roller 81 via the pressure pad 94.

  The sliding sheet 95 (sliding member) is formed of a glass fiber sheet coated with a fluororesin or the like, and covers the periphery of each member from the holder 91 to the pressure pad 94. The length of the sliding sheet 95 in the width direction is longer than the length of the pressure pad 94 in the width direction. By providing the sliding sheet 95 having a low friction coefficient, the pressure pad 94 having a high friction coefficient does not come into contact with the fixing belt 92.

  The lubricant application member 87 is configured by covering a felt impregnated with silicone oil or the like with a porous resin sheet, and slidably contacts the inner peripheral surface of the fixing belt 82 to apply the lubricant to the inner peripheral surface.

  The above members except for the fixing roller 81 are supported by a frame (not shown), operate in contact with and separate from the fixing roller 81, and the fixing belt 82 is in pressure contact with the fixing roller 81, and the fixing belt 82 is fixed. The posture of the frame can be switched to a separated state separated from the roller 81. When the recording paper P is fixed, the nip portion N is formed by switching to the pressure contact state, and when the jammed recording paper P is removed, the recording paper P is switched to the separated state.

  In the fixing device 8 as described above, the fixing roller 81 heated by the halogen lamp H and driven by a driving device (not shown) rotates in the clockwise direction. The pressing roller 83 and the pressing member 90 are in the above-described pressure contact state, and the pressing roller 83 and the pressure pad 94 press the fixing belt 82 against the fixing roller 81. Accordingly, a wide nip portion N is formed between the fixing roller 81 and the fixing belt 82. Further, since the fixing belt 82 rotates counterclockwise by the rotation of the fixing roller 81, when the recording paper P on which the toner image is transferred is conveyed, it is nipped by the nip portion N and is heated and pressurized and fixed. The

  Further, the pressing roller 83 presses so that the fixing belt 82 bites into the fixing roller 81, and the elastic layer 81B is elastically deformed into a concave shape, so that the fixed recording paper P is partially ejected with a large curvature. Then, it is reliably separated from the fixing roller 81.

  When the fixing belt 82 rotates, the lubricant application member 87 applies lubricant to the inner peripheral surface of the fixing belt 82, so that the fixing belt 82 slides smoothly on the sliding sheet 95.

  Here, due to the parallelism and twisting of the fixing roller 81, the pressing roller 83, and the entrance roller 84, a phenomenon occurs in which the fixing belt 82 is offset or meanders in the width direction. Although the movement of the fixing belt 82 is suppressed within a predetermined meandering range by the control of the steering roller 85 described above, the pressing roller 83 that strongly presses the fixing belt 82 is longer in width than the fixing belt 82, so that the fixing that comes into sliding contact is performed. The edge of the belt 82 in the width direction easily wears the surface. The metal wear powder generated by this wear causes the inner peripheral surface of the fixing belt 82, the tension roller such as the entrance roller 84, and the sliding sheet 95 to wear.

  Further, there is a problem that the lubricant applied to the inner peripheral surface of the fixing belt 82 is pushed out to both ends and leaks at the contact portion between the fixing bell 82 and the pressing roller 83. As a result, the lubricant is depleted, the frictional resistance between the fixing belt 82 and the sliding sheet 95 is increased, and the driving torque may be increased.

  On the other hand, the smoother the outer peripheral surface of the pressing roller 83, the lower the frictional resistance between the edge in the width direction of the fixing belt 82 and the pressing roller 83, and the wear of the pressing roller 83 by the fixing belt 82 can be reduced. Become. However, if the entire pressing roller 83 is finished to be smooth, it becomes difficult to hold the lubricant between the fixing belt 82 and the pressing roller 83, and the lubricant does not adhere to the fixing belt 82 at the contact portion between the fixing belt 82 and the pressing roller 83. There is a risk of leakage by being pushed out in the width direction. In order to prevent the lubricant from leaking out, it is necessary that the pressure roller 83 should be finished rough rather than smoothly so that the lubricant can be retained.

  Therefore, in order to solve the conflicting problem of reducing wear of the pressure roller 83 and preventing leakage of the lubricant, at least the surface is formed of metal over the width direction of the pressure roller 83, and the pressure roller The surface roughness of the end region where the width direction edge of the fixing belt 82 can be contacted at 83 is made small, and the surface roughness of the center region where the edge of the fixing belt 82 cannot be contacted is made large. In other words, the surface roughness of the end region where the edge of the fixing belt 82 can be contacted may be made smaller than the surface roughness of the central region where the edge of the fixing belt 82 cannot contact.

  On the other hand, in the steering roller of Patent Document 2, the material is different between the end region and the center region, and the end portion is plated and the center portion is rubber. However, the surface roughness is not described, and the strength or We focus on the coefficient of friction. However, it is difficult to prevent the lubricant from leaking out only with the strength or the coefficient of friction.

  An example of the pressure roller 83 formed in this way is shown in FIG.

  In FIG. 3, the fixing belt 82 having a width of 340 mm is stretched by a pressing roller 83 having an axial length of 354 mm. The fixing belt 82 is in the position of the solid line by design, but is actually shifted in the width direction as described above, so that the movement amount is set to ± 6 mm. In this case, even if the fixing belt 82 is shifted to the left or right, the edge region 82A in the width direction of the fixing belt 82 contacts the central region 83A of 326 mm excluding the end region 83B of 14 mm from both ends of the pressing roller 83. Absent. On the other hand, the end region 83 </ b> B has a margin with respect to the deviation of the fixing belt 82, but most of the end region 83 </ b> B comes into contact with the widthwise edge portion 82 </ b> A of the fixing belt 82.

  Therefore, when the pressing roller 83 is formed of stainless steel (for example, SUS303), the surface roughness of the center region 83A is, for example, Ry6.3S or more and Ry12.6S or less, and the surface roughness of the end region 83B is, for example, By finishing to Ry3.2S or less, the lubricant does not leak out. It is further desirable to finish the end region 83B to Ry1.6S or less.

  In order to form the central region 83A and the end region 83B having different surface roughness on the pressing roller 83, for example, the end region 83B may be polished after the entire pressing roller 83 is ground.

  In addition, the pressure roller for changing the surface roughness according to the present invention is not limited to the pressure roller 83 of the fixing device 8 shown in FIG. 2, and for example, a twin belt type fixing device 100 as shown in FIG. The pressing roller 104 may be used. In FIG. 4, an endless lower fixing belt 105 is stretched around a pressing roller 104 and a lower entrance roller 106, and an endless upper fixing belt 102 (rotating member) is connected to a fixing roller 101 and a halogen lamp H (heating source). An upper entrance roller 103 is stretched and a pressure roller 104 presses the lower fixing belt 105 against the upper fixing belt 102. Therefore, in order to reduce the wear of the pressing roller 104 as described above, the surface roughness may be changed between the central region and the end region of the pressing roller 104. In some cases, the surface roughness of the fixing roller 101 may be changed.

1 is a configuration diagram of an image forming apparatus. FIG. 3 is a cross-sectional view of a main part of the fixing device. It is a figure which shows the edge part area | region and center area | region in a press roller. FIG. 2 is a schematic view of a twin belt type fixing device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 8 Fixing device 81 Fixing roller 82 Fixing belt 82A Width direction edge part 83,104 Pressure roller 83A Center area 83B End area 87 Lubricant application member 90 Pressing member 94 Pressure pad 95 Sliding sheet 102 Upper fixing belt N Nip part H Halogen lamp P Recording paper

Claims (4)

A rotating member that rotates;
An endless fixing belt having a lubricant on an inner peripheral surface and rotating in pressure contact with the rotating member;
A pressing member that presses the fixing belt from the inner peripheral surface toward the rotating member;
A sliding member disposed between the fixing belt and the pressing member;
One of the rollers for stretching the fixing belt, wherein at least the surface is formed of metal over the width direction, and the pressing roller presses the fixing belt against the rotating member;
Have
In a fixing device for fixing a toner image on a recording material at a nip formed between the rotating member and the fixing belt,
In the pressing roller, the surface roughness of the end region with which the edge in the width direction of the fixing belt can contact is formed to be smaller than the surface roughness of the central region located on the center side of the end region in the width direction. A fixing device. The fixing device according to claim 1, wherein the rotating member is a roller having a heating source. The fixing device according to claim 1, wherein the rotating member is an endless belt stretched around a plurality of rollers. An image forming apparatus comprising the fixing device according to claim 1.

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