JP2006039112A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the number of times of replacement of a fixing unit having a still belt member by easy replacement of the belt member to prolong the lifetime of the unit, by providing a mechanism which periodically replaces the still belt member consumed by dirt and wear due to paper powder, powdery shavings, etc. <P>SOLUTION: A fixing device wherein an endless belt or a belt having an end part fixed is brought into surface contact with a fixing roller as a pressing member and a transfer material bearing an unfixed toner is carried between the fixing roller and the belt to fix an image is provided with a mechanism for releasing a pressure to the belt brought into surface contact with the fixing roller, a belt member for removing the belt released from the pressure, and a belt fixing mechanism for making the belt member attachable and removable. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fixing device used in various image forming apparatuses such as an electrophotographic copying machine and a printer.

  In general, a fixing device used in various image forming apparatuses such as an electrophotographic copying machine and a printer has a fixing roller composed of a hollow roller, and a pressure roller as a pressure unit pressed against the fixing roller. When the transfer material on which the unfixed toner image is formed is passed through the nip portion that is the pressure contact area between these two rollers, the transfer material is transferred by a heating source such as a halogen heater disposed inside the fixing roller. The upper unfixed toner image is heated and fixed. However, in recent years, image forming apparatuses have been required to reduce cost, reduce warm-up time, and save energy.

  However, since the general heat roller fixing device uses a pressure roller, it is expensive and requires a large installation space. Further, when the fixing roller core is thinned for shortening the warm-up, there is a problem that a large nip cannot be formed due to deformation problems such as bending of the fixing roller by the pressure roller.

  Furthermore, when the pressure roller is used, heat of the fixing roller is dissipated to the pressure roller having a large heat capacity, which causes a problem that the warm-up time is long and the power consumption increases. In order to alleviate such a problem, a fixing device in which a stationary belt as a pressing member is brought into surface contact with the fixing roller and a transfer material carrying unfixed toner is passed between the fixing roller and the belt. Are disclosed in Patent Documents 1 to 3 and the like.

  The fixing device composed of the fixing roller and the stationary belt can alleviate all the above-mentioned problems and is extremely advantageous, but has a large problem in the transferability of the transfer material at the fixing portion. That is, the fixing roller and the stationary belt do not apply a large pressure, and the transfer material must be conveyed by friction with the fixing roller.

  Therefore, various attempts have been made to reduce the coefficient of friction on the surface of the stationary belt in order to improve the transportability of the fixing device including the fixing roller and the stationary belt.

Japanese Patent Application Laid-Open No. 60-104977 Japanese Patent Laid-Open No. Sho 62-135865 Japanese Patent Laid-Open No. 62-166379

  However, when a recording medium to be fixed, such as paper on which toner is placed, passes through the fixing device, the end of the recording medium and the other part are closer to the end when the stationary belt and the fixing roller are pressed. It is known that the pressure increases. By increasing the pressure, when the recording medium is paper, paper dust is likely to be generated in a portion where the pressure is high. It has been found that, due to the occurrence of paper dust, the pressure member is more worn by the paper dust than the other portions.

  It was also found that the toner adheres to the separation claw that separates the paper (recording medium) and the fixing roller at the fixing exit, which adheres to the stationary belt when the paper is not passed, and the adhered toner wears the stationary belt. . The abrasion due to the paper dust or the like creates a band-like portion where wear progresses quickly in the recording medium conveyance direction, and significantly shortens the life of the stationary belt member.

  If the stationary belt is fixed to the fixing unit, the belt cannot be replaced due to a significant decrease in the service life of the stationary belt. Therefore, the fixing unit must be replaced, increasing the number of replacements due to the short life of the unit and serviceability. Will be reduced.

  According to the present invention, in a fixing unit having a stationary belt member, by providing a mechanism for replacing a stationary belt member consumed due to dirt or abrasion due to paper dust, shaving powder, or the like at a certain period, the belt member can be easily The purpose of the replacement is to reduce the number of times the fixing unit is replaced and extend the life of the unit.

  In order to achieve the above object, the invention according to claim 1 is a transfer in which an endless or end-fixed belt is brought into surface contact with a fixing roller as a pressing member, and unfixed toner is carried between the fixing roller and the belt. In a fixing device for conveying and fixing a material, a mechanism for releasing the pressure of the belt in surface contact with the fixing roller, a belt member for removing the pressure-released belt, and a belt fixing mechanism for detaching the belt member It is characterized by having.

  According to a second aspect of the present invention, in the first aspect of the invention, the belt fixing mechanism that allows the belt member to be detached is operated to a position where the belt member to be detached can be replaced when the belt member is detached from the apparatus main body. It is characterized by that.

  According to a third aspect of the present invention, in the first aspect of the present invention, at least one of the belt member and the belt fixing mechanism has a guide mechanism that regulates a fixing direction.

  According to the present invention, in a fixing unit having a stationary belt member, a belt is provided by replacing a stationary belt member that has been consumed due to dirt or abrasion due to paper dust, shaving powder, or the like at regular intervals. The members can be easily replaced, the number of replacement of the fixing unit can be reduced, and a long-life unit can be realized. Further, since the belt member can be easily replaced, serviceability can be improved and the cost of replacement parts can be reduced.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

<Practical form 1>
Hereinafter, an embodiment in which the present invention is applied to a laser beam printer which is an image forming apparatus will be described.

  FIG. 2 is a diagram showing a schematic configuration of the image forming apparatus. The image forming apparatus includes a process cartridge 100 that stores image forming means for forming an image on a transfer sheet, which is a recording material as a transfer material, by an electrophotographic method. The illustrated process cartridge 100 includes an OPC photosensitive member (hereinafter referred to as a photosensitive member) 1 having a diameter of 30 mm as an image carrier, a charging roller 2 as a charging unit, a developing unit 3 as a developing unit, and a cleaning unit as a cleaning unit. 4 etc. are compactly integrated.

  A latent image writing unit 5 for writing an electrostatic latent image on the photoreceptor 1 is provided on the side of the process cartridge 100. For example, the latent image writing unit 5 emits light from a semiconductor laser by a control signal from a controller corresponding to image information, scans the laser light with a polygon mirror that is driven to rotate, and scans the optical path of the laser light. An optical signal 6 corresponding to image information can be written on the photosensitive member through a converging lens and a lens for correcting the surface tilt of the polygon mirror, a mirror for deflecting the laser beam, and the like.

  Below the process cartridge 100, there are a paper feed roller 9 and a separation pad 11 for separating and feeding the transfer paper 8 as a transfer material stored in the paper feed cassette 7 one by one. The transfer paper 8 fed by the paper feed roller 9 has the leading edge of the image formed on the photosensitive member 1 and the leading edge of the transfer paper 8 almost at the nip portion between the photosensitive member 1 and the transfer roller 10. At the same time, they are conveyed by the registration rollers 12 in synchronism with the rotation of the photosensitive member 1. Further, above the process cartridge 100, there is provided a fixing device 16 comprising a fixing roller 14 incorporating a heater 13 therein and a stationary belt 15 that presses against the fixing roller 14 to form a wide nip.

  The fixing device 12 including the fixing roller 14 and the stationary belt 15 will be described in detail later. A discharge roller 18 for discharging the transfer paper 8 that has passed through the nip N between the fixing roller 14 and the stationary belt 15 to the discharge tray 17 is provided downstream of the fixing device 12 in the transfer paper conveyance direction. Is provided.

  A bias can be applied to the transfer roller 10, the charging roller 2, and the developing unit 3 in order to perform image formation and transfer. In addition, an open / close cover 901 that forms the left side surface of the transfer path of the transfer paper 8 is attached to the image forming apparatus so as to be openable and closable. In the opening / closing cover 901, the static eliminating brush 19 is disposed together with the transfer roller 10.

  A manual feed unit 20 for manually feeding transfer paper is attached to the open / close cover 901 of the image forming apparatus so as to be freely opened and closed. The transfer paper fed using the manual feed unit 20 is conveyed to the registration roller 11 by the rotation of the manual paper feed roller 21 provided on the printer main body side. The manual feed unit 20 is configured to be stored in a manual feed unit storage portion formed on the outer side of the opening / closing cover 901 when not in use.

  Next, the fixing device using the stationary belt used in this image forming apparatus will be explained a little more.

The fixing device includes a thin fixing roller 201 (outside diameter 30 mm, core metal thickness 0.4 mm) made of a pipe material such as aluminum or iron and a belt 202 as a pressing member pressed against the fixing roller 201. And heat-resistant release material such as Teflon (trade name) (semi-conductive 105 of about 15 to 30 μm on the surface layer)
A release layer 203 made of a fluororesin of ˜1012 Ω · cm) is formed. A halogen heater 204 as a heat source is provided inside the fixing roller 201, and a separation claw 205 that prevents the transfer material from being wrapped around the fixing roller 201 and a temperature detection sensor 206 that detects the surface temperature are disposed on the surface. Yes. The separation claw 205 and the temperature sensor 206 are fixed to a heat resistant resin cover 207 and are in contact with the fixing roller 201.

  The belt 202 is required to have heat resistance and a low friction coefficient. The image forming apparatus includes a Teflon (trade name) sheet, a Teflon-coated sheet on a polyimide sheet, a composite sheet in which a Teflon sheet is bonded on a heat-resistant sheet such as a polyimide sheet, and glass fiber. Teflon-coated sheet on cloth made of heat-resistant fiber such as, heat-resistant fiber hardened with heat-resistant rubber such as silicone rubber or fluorine rubber, and further Teflon-coated or Teflon sheet bonded to it, or Furthermore, it is possible to use multi-porous fluororesin such as Poeflon and Gore-Tex (trade name). In particular, use of porous fluororesin such as Porefluoron or Gore-Tex (trade name) is desirable because it has air permeability and prevents the occurrence of image distortion and wrinkles due to the generation of water vapor in the nip portion. One end of the belt 201 is fixed to the guide plate 20. The other end is changed in direction by a rotatable belt support rod 209 and bonded to the sheet metal 210. The tension spring 211 pulls the sheet metal 210 and the belt 202 has a certain tension spring at both ends of the front of the sheet (front of the paper). And is pulled with a total pressure of 8 kg.

  A pressure member 212 is attached to the back side of the surface of the belt 202 that contacts the fixing roller. The pressurizing member 212 is made by impregnating a felt made of heat-resistant fibers with silicone oil. Oil is supplied from the felt to the porous belt surface, and friction with the transfer material is further reduced. The pressure member 212 is uniformly and lightly loaded by the ita spring, and is loaded with a total pressure of about 1 kg. The leaf spring is bonded to the resin member 213 of the cover. As a result, the required surface pressure of the fixing nip is added, and the fixing property is improved. The pressure belt is attached to the opening / closing cover 901 and is pressurized by closing the opening / closing cover. This cover is fixed by means (not shown), and its position is fixed accurately.

  A paper discharge roller 215 that guides the transfer material separated from the fixing roller to the paper discharge tray 214 is disposed above the fixing roller 201. The paper discharge roller 215 is made of a pair of silicone rubber (rubber hardness of 35 to 60 ° JIS-A), and a cylinder having an outer diameter of 12 mm and a length of 15 mm is attached to a metal rotary shaft having an outer diameter of 8 mm. or. The rotation shaft is mounted in parallel with the fixing roller, and is loaded with a total pressure of 2 kg in order to increase the transfer material conveyance force.

  In the image forming apparatus having such a configuration, first, the photoreceptor 1 rotates at a linear speed (circumferential speed) of 47.13 mm / sec, and is uniformly charged (−600 V) by the charge from the charging roller 2 during the rotation. The Next, the latent image writing unit 5 is driven based on the image information, whereby the image information is formed as an electrostatic latent image in the charging area (image forming area) of the photoreceptor 1. At this time, the potential of the exposed portion is about −100V. The electrostatic latent image formed on the photosensitive member 1 is developed with a developer (minus toner) supplied to the photosensitive member 1 by the developing roller 31 of the developing unit 3 to become a visible image (toner image). (Reversal development) A developing bias is applied to the developing roller, for example, a DC voltage of -400 V and an AC voltage of 1600 V between peaks at a frequency of 2000 Hz are applied. As a development method, a jumping development method is used, and image formation is performed by image exposure and reversal development methods.

  On the other hand, while the toner image is being formed on the photosensitive member 1, the transfer paper 8 is pulled out from the paper feed cassette 7 by the paper feed roller 9, and conveyed upward by the guide 9-a. With the leading edge of the paper 8 in contact with the nip portion of the registration roller 12, the transfer paper 8 is temporarily put on standby. The transfer sheet 8 starts rotating with the registration roller 12 in synchronization with the rotation of the photosensitive member 1 at the timing when the leading end of the transfer paper 8 and the leading end of the toner image coincide with each other. The toner image on the photosensitive member 1 is transferred to a transfer position formed at a nip with a transfer roller 10 as a transfer member that rotates in contact with the photosensitive member 1.

  A transfer bias of about 500 to 6000 V is applied to the transfer roller 10. The toner image is transferred to the transfer material by this bias. Then, the transfer paper 8 onto which the toner image has been transferred is conveyed to a nip portion N formed by the fixing roller 14 and the stationary belt 15 of the fixing device 16, and the toner image is fixed on the transfer material by the fixing device and discharged. The paper is discharged onto the paper discharge tray 17 by the paper roller 18. During this time, residual toner remaining on the photosensitive member 1 without being transferred onto the transfer paper 8 in the transfer process of the toner image onto the transfer paper 8 is transferred to the photosensitive member 1 by the cleaning blade 22 of the cleaning unit 4. It is scraped from above, removed by the feed blade 23, and collected in the cleaning container.

  Next, a fixing device which is a characteristic part of the image forming apparatus having the configuration of the present invention will be described.

  In a fixing device composed of a fixing roller and a polyimide stationary belt, paper dust generated due to an increase in pressure at the end of the paper to be passed advances wear of the stationary belt. When the number of passing sheets exceeds 5000 due to the contact pressure of the stationary belt, the surface roughness of the polyimide at the end of the paper where the paper dust accumulates becomes about twice as large as that. It has been found that if the paper dust does not accumulate on the stationary belt, the surface roughness hardly changes even when the number of paper passes exceeds 5000.

  Accordingly, the life of the fixing unit can be extended by replacing the stationary belt with an unused belt or cleaning the belt every less than 5000 sheets, for example, 4000 sheets.

  1, 3 and 4 show a characteristic configuration of the present embodiment.

  The image forming apparatus includes a fixing roller 201, a stationary belt member 202, and a stationary belt pressure frame 302 that fixes the stationary belt member 202.

  For example, the stationary belt pressure frame 302 may include a mechanism for pressing the stationary belt 202 against the fixing frame. At the time of replacement, as shown in FIG. 3B, the belt pressure frame 302 rotates to release the pressure. The rotation angle is set so that the stationary belt attaching / detaching direction opens more than the vertical direction of the installation surface so that it can be easily exchanged. The stationary belt member is fixed by a stationary belt posture holding portion 303 of the belt pressure frame 302 and a stationary belt fixing guide 203 of the stationary belt 202. The stationary belt posture holding unit 303 is a mechanism (such as a snap fit) that can be easily attached and detached, so that the stationary belt fixing guide 203 and the stationary belt 202 can be easily replaced. Also, by fixing the angle between the guide and the belt surface, the belt member can be fixed at a constant thickness without changing the amount of pressure each time it is replaced by simply setting the belt pressure frame in place. It can be brought into contact with the roller.

  The exchange procedure is shown in the side view of FIG.

  From the set state (1), the belt pressure frame 302 is rotated to release the pressure (2). The used belt member 202 is removed from the belt pressure frame 302 opened to an angle at which the replacement work is easy (3).

  A new stationary belt member or a cleaned belt member 202 is fixed to the stationary belt posture holding portion 303 in accordance with the stationary belt fixing guide 203 (4). The belt pressure frame 302 to which the belt member 202 is fixed is rotated to a predetermined position and brought into contact with the fixing roller 201, thereby setting the predetermined pressure amount (5, 6).

<Embodiment 2>
A second embodiment of the present invention will be described with reference to FIGS.

  In contrast to the first embodiment, the belt member 202 is removed from the fixing device or the image forming apparatus main body without removing the belt member 202 from the belt fixing frame 302 after the pressure is released. The belt pressure frame 302 with the belt member is removed. Desorption and fixing are performed by the pressure holding unit 101.

  By exchanging the belt member 202 together with the pressurizing frame 302, it is possible to reduce the possibility of damage to the belt and adhesion of dirt to the belt at the time of replacement, and to improve exchangeability.

  The present invention is applicable to a fixing device used in various image forming apparatuses such as an electrophotographic copying machine and a printer.

1 is a schematic explanatory diagram of a fixing device according to a first embodiment of the present invention. 2 is a cross-sectional explanatory view of an image forming apparatus including a fixing device. FIG. 1 is a schematic explanatory diagram of a fixing device according to a first embodiment of the present invention. 1 is a schematic explanatory diagram of a fixing device according to a first embodiment of the present invention. It is a schematic explanatory drawing of the fixing device which concerns on Embodiment 2 of this invention. It is a schematic explanatory drawing of the fixing device which concerns on Embodiment 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Pressure frame holding | maintenance part 201 Fixing roller 202 Static belt member 203 Static belt fixing guide 204 Heater 210 Separation hook 302 Static belt pressure frame 303 Static belt attitude | position holding | maintenance part S Recording medium

Claims (3)

In a fixing device that performs fixing by bringing a transfer material carrying unfixed toner between the fixing roller and the belt, as a pressing member to the fixing roller, by bringing the endless or end-fixed belt into surface contact.
A fixing device comprising: a mechanism that releases pressure of a belt that is in surface contact with a fixing roller; a belt member that removes the pressure-released belt; and a belt fixing mechanism that allows the belt member to be attached and detached.   2. The fixing device according to claim 1, wherein the belt fixing mechanism that allows the belt member to be detached is operated to a position where the belt member to be detached can be replaced when the belt member is detached from the apparatus main body.   The fixing device according to claim 1, wherein at least one of the belt member and the belt fixing mechanism has a guide mechanism that regulates a fixing direction.

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