JP5003240B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a 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 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 width direction may become non-uniform, and there is a possibility that fixing unevenness and wrinkling of the recording material may occur. 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 having an elastic layer made of silicone rubber and having a heating means such as a halogen lamp built in the center and rotating, and an endless fixing belt driven and rotated by the fixing roller And a pressure pad disposed on the inner circumferential surface of the fixing belt, and the fixing belt is pressed against the fixing roller by pressing the fixing belt toward the fixing roller with the pressure pad, and the fixing roller and the fixing belt Patent Document 1 discloses a fixing device of a type that forms a nip portion for fixing a toner image on a recording material in between, a so-called FBNF (Free Belt Nip Fuser) type fixing device (see Patent Document 1). .

  According to this fixing device, the fixing belt pressed against the fixing roller by the pressure pad is elastically deformed, and a wide nip portion is formed between the fixing roller and the fixing belt. Therefore, it is possible to cope with high speed and the fixing device is not enlarged. Furthermore, since the heat capacity of the fixing belt is small, the warm-up time is shortened and energy is saved.

  In such an FBNF type fixing device, if the sliding resistance between the fixing belt and the pressure pad is large, the power consumption of the motor driving the fixing roller increases, the reduction gear of the motor is damaged, the fixing Problems such as image displacement due to belt displacement and accelerated wear of the inner surface of the fixing belt occur.

  Therefore, a sliding sheet obtained by coating a glass fiber sheet with fluororesin (PTFE) or Teflon (registered trademark) is disposed between the inner peripheral surface of the fixing belt and the pressure pad. Since the sliding sheet has a small coefficient of friction, the sliding resistance between the fixing belt and the pressure pad is reduced, and the occurrence of the above-described problems is reduced.

  In addition, an oil pad formed of sponge or the like and impregnated with a lubricant made of silicone oil or the like is pressure-bonded to the inner peripheral surface of the fixing belt, so that the lubricant is transferred from the oil pad to the inner peripheral surface of the fixing belt or a sliding sheet. Therefore, the sliding resistance is further reduced, and the occurrence of the above problems is further reduced.

  However, by repeating the fixing process, the lubricant on the outer surface of the sliding sheet gradually moves to the end portion in the width direction (the direction perpendicular to the recording material conveyance direction) and leaks out, and the outer peripheral surface of the fixing belt. There is a risk of adhesion. In such a case, the lubricant adheres to the recording material and the recording material is contaminated, or the recording material slips and an image shift occurs, so that the lubricant is finally exhausted.

  In order to solve such a problem, a pair of guide members that support and guide both ends of the fixing belt are inclined toward the center in the width direction of the fixing belt from the upstream side to the downstream side in the rotation direction of the fixing belt. A fixing device provided with a plurality of grooves is disclosed in a patent publication (see Patent Document 2).

In Patent Document 2, the lubricant adhered to the inner surface of the fixing belt by this configuration is sent to the inside of the fixing belt along a plurality of grooves, and the lubricant leaks from the end of the fixing belt and adheres to the recording material. The content that it is possible to prevent this is described.
JP 2002-357964 A JP 2002-357968 A

  In the fixing device disclosed in Patent Document 2 of the prior art, a pair of guide members that support and guide both ends of the fixing belt are arranged in the center in the width direction of the fixing belt from the upstream side to the downstream side in the rotation direction of the fixing belt. A plurality of inclined grooves are provided, and the lubricant is sent along the grooves to the inside of the fixing belt.

  However, since the lubricant used in the fixing device has a low viscosity, it may volatilize and be depleted. Therefore, a lubricant having a relatively high viscosity is used. Therefore, the lubricant that has entered the groove does not move easily, and if the groove is eventually filled with the lubricant and clogged, leakage from the end cannot be prevented. Further, since various wear powders are mixed in the lubricant due to long-term use of the fixing device, the lubricant is also difficult to move.

  Therefore, the configuration of Patent Document 2 can prevent the leakage of the lubricant as compared with the case where no measures are taken, but it is not a sufficient measure for long-term use.

  The present invention has been made in view of such a problem, and a fixing device capable of reliably preventing leakage of a lubricant from an end portion even with a long-term use with a simple configuration, and an image forming apparatus including the fixing device The purpose is to propose.

The object is achieved by the invention described below.
1. A fixing roller rotating with heating means;
An endless fixing belt driven and rotated by the fixing roller;
A pair of guide members for supporting and guiding both ends in the width direction of the rotating fixing belt from the inner peripheral surface side;
For fixing the toner image on the recording material between the fixing roller and the fixing belt by pressing the fixing belt toward the fixing roller from the inner peripheral surface side to press the fixing belt against the fixing roller. A pressure member that forms a nip portion of
A lubricant supply member for supplying a lubricant to the inner peripheral surface of the fixing belt;
In the fixing device provided with
A guide portion for guiding the fixing belt in the guide member is formed in a cylindrical shape, and the fixing portion is formed on the guide portion from the upstream side to the downstream side in the rotation direction of the fixing belt along the outer surface of the guide portion. An end surface having a first edge inclined toward the center in the width direction of the belt, and the position of the first edge from the most upstream side in the rotation direction of the fixing belt along the outer surface of the guide. A fixing device , comprising: an opening having a second edge portion orthogonal to a rotation direction of the fixing belt and extending in a center direction of the fixing belt in the width direction .
2. 2. The fixing device according to 1, wherein the first edge portion is formed in a square shape.
3. 1 or 2, wherein the opening is disposed in the vicinity of a portion of the guide portion facing the nip portion and upstream of the portion in the rotation direction of the fixing belt. The fixing device described.
4). A sliding member disposed between an inner peripheral surface of the fixing belt and the pressure member;
An end portion of the sliding member in a direction orthogonal to the rotation direction of the fixing belt is disposed on the radially inner side of the cylindrical guide portion so as to face the opening portion. The fixing device according to claim 1.
An image forming apparatus comprising the fixing device according to any one of 5.1 to 4.

  According to the fixing device and the image forming apparatus of the present invention, since the leakage of the lubricant from the end portion can be surely prevented even when used for a long time, the lubricant adheres to the recording material and the recording material is contaminated. There is no event that the recording material slips and an image shift occurs and the lubricant is not finally exhausted.

  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 6, a sheet feeding and conveying unit, a fixing device 9, 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 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 202, and the line image sensor CCD is scanned. Is read.

  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 8Y are arranged 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 unit 4M, and a cleaning unit 8M 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 8C 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 8K 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 body 6 is wound around a plurality of rollers and is rotatably supported.

  The fixing device 100 heats and pressurizes the toner image on the recording paper (recording material) P at a nip portion formed between the heated fixing roller 101 and the fixing belt 102 and fixes the toner image.

  Thus, each color image formed by the image forming units 10Y, 10M, 10C, and 10K is sequentially transferred onto the rotating intermediate transfer body 6 by the transfer means 7Y, 7M, 7C, and 7K (primary transfer). A toner image synthesized with a color 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 7A via the paper feeding rollers 22A, 22B, 22C, 22D, the registration rollers 23, etc. A color image is transferred onto P (secondary transfer). 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 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 7A, the residual toner is removed by the cleaning means 8A from the intermediate transfer body 6 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 100 of the present invention will be described with reference to FIG. FIG. 2 is a cross-sectional view orthogonal to the width direction of the fixing belt 102 and the like.

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

  The fixing belt 102 includes a base made of polyimide having a thickness of about 100 μm, and a release layer made of PFA or PTFE having a thickness of about 25 μm covering the outer surface of the base. Is formed.

  The pressure pad 103 (pressure member) is made of silicone rubber having a hardness of about 10 ° JISA, and is made of a heat resistant resin together with a base metal plate 104 made of stainless steel and a base member 105 made of a heat resistant resin. It is held by the holder 108. 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 in order to improve the separation of the fixed recording paper P. The separation member 107 is made of a heat-resistant resin or a metal such as aluminum and has a tip formed in an arc having a large curvature, and is held by a base sheet metal 104 or the like and a holder 109 made of the heat-resistant resin.

  The holders 108 and 109 are held by a metal frame 110 disposed in the center.

  The sliding member 111 is formed by coating a glass fiber sheet with fluororesin (PTFE) or Teflon (registered trademark), between the inner peripheral surface of the fixing belt 102 and the pressure pad 103, and within the fixing belt 102. Arranged between the peripheral surface and the separating member 107, one end is fixed to the frame 110.

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

  When the fixing belt 102 is rotated, the holder 108 guides the fixing belt 102 via the sliding member 111, and the holder 109 also has a function as a guide member that directly guides 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 member 111. Further, the separating member 107 presses the fixing belt 102 against the fixing roller 101 via the sliding member 111.

  Accordingly, the fixing belt 102 rotates counterclockwise by the rotation of the fixing roller 101 and is pressed against the fixing roller 101 by the pressure pad 103 to be elastically deformed, so that a wide width is provided between the fixing belt 102 and the fixing roller 101. A nip portion N is formed. The unfixed toner on the conveyed recording paper P is heated and pressurized at the nip portion N and fixed.

  Further, the inner peripheral surface of the fixing belt 102 slides on the sliding member 111 during rotation, but since the sliding member 111 has a small friction coefficient, the sliding 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 surface of the sliding member 111, the sliding resistance is further reduced.

  Next, the configuration of the end portion of the fixing belt 102 will be described with reference to a longitudinal sectional view of the fixing device shown in FIG. Although FIG. 3 shows only the right end of the fixing device, it is bilaterally symmetric and the same applies to the left end. The same members as those shown in FIG. 2 are denoted by the same reference numerals.

  In FIG. 3, the fixing belt 102 extends in the width direction, and both ends thereof are supported by the guide portions 116 </ b> A of the pair of guide members 116 from the inner peripheral surface side. Furthermore, both guide members 116 are supported by a rotating member 117, whose operation will be described later.

  The frame 110 also extends in the longitudinal direction, and both end portions are respectively inserted and fixed in square holes 116G provided in the pair of guide members 116.

  Here, the shape of the guide member 116 will be described in detail with reference to the perspective view of FIG.

  The guide portion 116A of the guide member 116 is formed in a cylindrical shape. However, in the nip portion N, the fixing belt 102 is pressed and recessed by the fixing roller 101. Accordingly, the portion of the guide portion 116A facing the nip portion N correspondingly is cut out in a rectangular shape. Is formed.

  Further, the portion of the guide portion 116A facing the nip portion N, that is, the upstream side in the rotation direction (arrow A) of the fixing belt 102 with respect to the notch portion 116H, is located upstream from the upstream side in the rotation direction of the fixing belt 102. An opening 116B having an end surface 116C inclined toward the center in the width direction of the fixing belt 102 is formed. An edge 116D formed by the end surface 116C and the outer surface of the guide portion 116A is formed in a square shape. In addition, regarding the square shape of the edge portion 116D, it is preferably formed at a right angle of 90 degrees, but it is not necessarily 90 degrees, and an acute angle of 45 ° to an obtuse angle of 120 ° is acceptable. Further, the edge portion 116D may have a very small arc or may be chamfered. In short, the edge portion 116D may be formed in a shape that can scrape off the silicone oil adhering to the inner peripheral surface of the fixing belt 102.

  Further, the edge 116E perpendicular to the rotation direction of the fixing belt 102 does not necessarily have to be formed in a square shape, and may be formed in an arc shape.

  In the fixing device in which the end portion is formed as described above, when the fixing belt 102 rotates in the direction of the arrow A in FIG. 4, the silicone oil adhering to the inner peripheral surface of the fixing belt 102 is attached to the fixing belt 102 at the edge portion 116D. It is scraped off toward the center in the width direction and falls from the opening 116B. Therefore, the silicone oil does not leak from the end of the fixing belt 102 and go around the outer surface, and the silicone oil does not adhere to the recording paper P and the recording paper P is not contaminated. Moreover, since it is an opening part unlike the groove | channel of a prior art, even if it is a highly viscous lubricant, it will not clog.

  Further, an end 111A of the sliding member 111 extends below the opening 116B, and the dropped silicone oil adheres to the end 111A. For this reason, the dropped silicone oil is reused as a lubricant.

  The inclination angle of the end surface 116C with respect to the rotation direction of the fixing belt 102 is desirably in the range of 30 ° to 45 °.

  Furthermore, it is desirable that the opening 116B is located in the vicinity of the portion of the guide portion 116A facing the nip portion N, that is, in the vicinity of the notch portion 116H, and upstream of the portion. By arranging the opening 116B in this way, the possibility of leaking from the end of the fixing belt 102 and reaching the outer surface of the fixing belt 102 is reduced.

  In addition, a plurality of openings 116B may be formed in the guide portion 116A.

  Next, the fixing belt 102 is separated from the fixing roller 101 together with the pressure unit described above for shipping the image forming apparatus, jamming of recording paper, and maintenance, and the fixing roller 101 by the fixing belt 102 is used. Crimp releasing means for releasing the crimping to is provided. This crimp release means will be described with reference to FIG. FIG. 5A is a diagram of a state when the fixing device is used, and FIG. 5B is a diagram in which the pressure-bonding to the fixing roller 101 by the fixing belt 102 is released.

  In FIG. 5A, the rotation member 117 is pivotally supported by the support shaft 131 and can be rotated. Then, the end portion 117A of the rotating member 117 is pressed by the compression spring 132, and the rotating member 117 is urged counterclockwise. Accordingly, the fixing belt 102 is also rotated via the guide member 116, and the fixing belt 102 is pressed against the fixing roller 101.

  Further, when releasing the pressure bonding of the fixing belt 102 to the fixing roller 101, the cam 133 is rotated as shown in FIG. When the cam 133 rotates, the bottom 117B of the rotating member 117 is pressed by the cam 133, and the rotating member 117 rotates clockwise against the urging force of the compression spring 132. Accordingly, the fixing belt 102 is also rotated through the guide member 116, and the fixing belt 102 is retracted from the fixing roller 101, so that the pressure bonding to the fixing roller 101 by the fixing belt 102 is released.

  Next, a comparative experiment regarding the shape of the guide portion will be described.

  The experiment was performed in three ways: when nothing was processed in the guide portion, when the guide portion was provided with a plurality of grooves as in the prior art, and when the opening portion was provided as in the above embodiment.

Items common to the three types of guides are as follows.
・ Fixing device: Configuration as shown in FIG. 2 ・ Sliding sheet: Glass fiber sheet coated with fluororesin (PTFE) ・ Oil pad: t = 4.7 mm, W = 10 mm, L = 360 mm, weight per unit area 3 g of dimethyl silicone oil having a viscosity of 1000 cs as a lubricant was impregnated at 950 g / m ² .
・ Guide part: Outer diameter 34mm, width 10mm
The shape and dimensions of the groove and the opening are shown in FIG. FIG. 6 is a development view of the guide unit.

  FIG. 6A is a diagram in the case where a plurality of grooves are provided, and 10 grooves are formed at a pitch of 10.7 mm with an inclination of 30 ° on the entire outer peripheral surface of the guide portion. The cross-sectional shape of the groove is rectangular and has a width of 2 mm and a depth of 1 mm. In addition, the width and depth of the groove are larger than the groove described in Patent Document 2.

  FIG. 6B is a diagram in the case where an opening is provided, and one opening is formed on the outer peripheral surface of the guide portion with an inclination of 30 °. The edge 116D is formed at a right angle.

  Using these three kinds of guides, the fixing device was operated up to 300 kc times. Note that 1 kc means 1000 times of fixing.

  And it judged to three steps by visual observation.

  ○: No lubricant leaks from the end of the fixing belt.

  Δ: Lubricant leaks at the end of the fixing belt, but does not go around the outer peripheral surface of the fixing belt.

  X: Lubricant leaks from the end of the fixing belt and wraps around the outer peripheral surface of the fixing belt.

  The above experimental results are shown in Table 1.

  According to Table 1, there was no significant difference between the unimplemented and the groove type, but there was a large difference between the groove type and the opening type.

1 is a configuration diagram of an image forming apparatus. FIG. 3 is a cross-sectional view in a direction orthogonal to the axial direction of the fixing device. FIG. 3 is a cross-sectional view in the axial direction of the fixing device. It is a perspective view of a guide member. It is a figure of a pressure release means. It is an expanded view of the guide part regarding a groove | channel and an opening part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Fixing device 101 Fixing roller 102 Fixing belt 103 Pressure pad 111 Sliding member 112 Oil pad 116 Guide member 116A Guide part 116B Opening part 116C End surface 116D Edge part 116H Notch part H Halogen lamp P Recording paper N Nip part

Claims (5)

A fixing roller rotating with heating means;
An endless fixing belt driven and rotated by the fixing roller;
A pair of guide members for supporting and guiding both ends in the width direction of the rotating fixing belt from the inner peripheral surface side;
For fixing the toner image on the recording material between the fixing roller and the fixing belt by pressing the fixing belt toward the fixing roller from the inner peripheral surface side to press the fixing belt against the fixing roller. A pressure member that forms a nip portion of
A lubricant supply member for supplying a lubricant to the inner peripheral surface of the fixing belt;
In the fixing device provided with
A guide portion for guiding the fixing belt in the guide member is formed in a cylindrical shape, and the fixing portion is formed on the guide portion from the upstream side to the downstream side in the rotation direction of the fixing belt along the outer surface of the guide portion. An end surface having a first edge inclined toward the center in the width direction of the belt, and the position of the first edge from the most upstream side in the rotation direction of the fixing belt along the outer surface of the guide. A fixing device , comprising: an opening having a second edge portion orthogonal to a rotation direction of the fixing belt and extending in a center direction of the fixing belt in the width direction . The fixing device according to claim 1, wherein the first edge portion is formed in a square shape. The opening is disposed in the vicinity of a portion of the guide portion facing the nip portion and upstream of the portion in the rotation direction of the fixing belt. The fixing device according to claim 2. A sliding member disposed between an inner peripheral surface of the fixing belt and the pressure member;
An end portion of the sliding member in a direction orthogonal to the rotation direction of the fixing belt is disposed on the radially inner side of the cylindrical guide portion so as to face the opening portion. Item 4. The fixing device according to any one of Items 1 to 3. An image forming apparatus comprising the fixing device according to claim 1.

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