JP4715572B2 - Fixing device - Google Patents

Description

  The present invention relates to an unfixed toner image formed on a transfer material, mounted on an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine having these functions. And a fixing device for fixing an image by applying pressure and heating.

  Conventionally, a fixing device used in an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile machine, and a multifunction machine having these functions has a fixing roller maintained at a predetermined temperature and an elastic layer. A heating roller fixing system that presses and heats a transfer material on which an unfixed toner image is formed is sandwiched and conveyed by a fixing nip formed by a pressure roller that is in pressure contact with the fixing roller. Widely adopted from high-speed machines, monochrome machines to color machines.

  Using a fixing belt for the fixing device, lowering the heat capacity with the fixing belt, and making the temperature controlled heater directly press contact with the fixing belt, greatly improving the heat conduction efficiency, requiring little power saving and warming up time. A belt fixing type fixing device and an image forming apparatus designed for quick start have been proposed and used recently.

  In a fixing roller type fixing device, a technique for forming a fixing roller with a soft elastic layer is demanded as the image quality of a toner image is increased and the printing speed is increased. By using a soft roller as the fixing roller, it is possible to uniformly fix a solid image with a high printing rate or a color image composed of multilayer toner images.

  Further, in the fixing device of the fixing belt type, the fixing support roller that is wound around the fixing belt and presses against the pressure rotator via the fixing belt is a soft roller, so that a solid image having a high printing rate or a multi-layer A color image composed of a toner image can be fixed uniformly.

  In such a fixing device, in order to prevent toner from adhering to a heating rotator such as a fixing roller and a fixing belt and a decrease in fixing ability due to occurrence of an offset due to this, an outer peripheral surface of the heating rotator Cleaning means is provided for cleaning.

  Cleaning means mounted on the fixing device include a roller type and a web type.

The fixing device proposed in Patent Document 1 includes a cleaning unit that contacts and separates a web containing abrasive particles in a heat-resistant non-woven fabric, and a release agent supply unit that applies silicone oil to the fixing roller. Is.
Japanese Patent Laid-Open No. 10-207280

  It has been found that by using a heating roller as a soft roller, the surface state of the heating rotor affects the fixed image. Thus, various methods have been devised that do not deteriorate the surface state of the heating rotator. For example, there are a contact / separation device for the cleaning means, non-contact of the fixing separation claw to the surface of the heating rotator, separation clawless fixing, separation claw swinging device, and the like.

  Due to the high image quality of the toner image, there is a problem of paper edge traces generated on the surface of the heating rotator at both ends in the paper width direction orthogonal to the conveyance direction of the paper passing through the fixing nip.

  Paper edge portions at both ends in the paper width direction are attached with a large amount of paper dust due to cutting processing or the like, and the surface property of the heating rotator is different from other portions, so that paper edge marks are generated.

  For this reason, immediately after a small-size sheet having a small paper width passes through the fixing nip, when a large-size sheet having a wide paper width is passed through and fixed, both ends of the small-size paper in the paper width direction are heated by the heating rotor. Paper edge traces may be generated on the surface of the paper, and the paper edge traces may be transferred to large size paper. This paper edge trace gradually disappears when large-size paper is passed for a while, but in order to improve the fixing quality, it is necessary to take measures to remove the paper edge trace for all the paper passing paper.

  In the fixing device disclosed in Japanese Patent Application Laid-Open No. 2005-228561, a measure for removing the paper edge trace is not taken by merely removing the foreign matter adhering to the fixing roller by bringing the web into and out of contact with the fixing roller.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device that maintains a high-quality image by removing a paper edge trace and making the surface property of a heating rotator uniform.

  The above object can be achieved by the following solutions.

  A heating rotator that is heated by a heating source and a pressure rotator that is in pressure contact with the heating rotator, and carries an unfixed image at a fixing nip formed by the heating rotator and the pressure rotator. In the fixing device for holding and conveying the recording medium to be fixed, a contact member that comes in contact with the outer peripheral surface of the heating rotator is provided so that the contact member can be changed when the width of the recording medium is changed. A fixing device comprising control means for controlling to contact the outer peripheral surface of the heating rotator.

  The image forming apparatus of the present invention can obtain the following effects by the configuration described above.

  1. A paper edge trace adhering to the outer peripheral surface of the heating rotator at the time of fixing is cleaned by an abutting member, and the surface property of the heating rotator is made uniform, whereby a high-quality image can be maintained.

  2. The contact member controls the outer peripheral surface of the heating rotator to be rubbed by the control means only when changing the width of the recording medium. The outer peripheral surface of the body is not damaged.

  Embodiments of the present invention will be described below. The description in this column does not limit the technical scope of the claims or the meaning of terms.

  FIG. 1 is a cross-sectional view showing an embodiment of a heating roller type fixing device 10.

  The fixing device 10 includes a fixing roller (heating rotator) 11 heated by a heating source 13, a pressure roller (pressure rotator) 12 heated by a heating source 14, and the like.

  Around the fixing roller 11, a cleaning unit 17, a temperature sensor TS 1, a thermostat for preventing an abnormal temperature (not shown), and the like are arranged. A temperature sensor TS2, a thermostat for preventing abnormal temperature, and the like are also disposed around the pressure roller 12.

  As the heating sources 13 and 14, a halogen lamp, induction heating means, or the like is used.

  The fixing roller 11 includes a heat conductive substrate (core metal) 111, an elastic layer 112, a covering layer 113, and the like.

  The temperature sensor TS <b> 1 detects the surface temperature of the fixing roller 11. The control means controls the surface temperature of the fixing roller 11 to a predetermined temperature based on the detection signal of the temperature sensor TS1.

  When a recording medium (hereinafter referred to as a sheet) S is introduced into a fixing nip N where the fixing roller 11 and the pressure roller 12 are in pressure contact, heat from the fixing roller 11 heated by the heating source 13 is applied to the sheet S. Then, the toner image t on the paper S is heated and fixed.

  The fixing roller 11 is a cylindrical member having an outer diameter of 20 to 70 mm. As the cylindrical heat conductive substrate 111, an aluminum material having good heat conductivity is mainly used, and a nonmagnetic stainless steel material, heat resistant glass, or the like is also used. The heat conductive substrate 111 has a required mechanical strength and a thickness (wall thickness) of 0.8 to 10 mm.

  The elastic layer 112 is made of synthetic rubber such as silicone rubber or fluorine rubber, for example. Further, in order to cope with speeding up of image formation, a method of improving thermal conductivity by blending 5-30% by mass of a metal oxide powder such as silica, alumina, magnesium oxide or the like as a filler in the synthetic rubber is preferable. . The mixed filler is preferably a highly conductive one like the conductive carbon black. By doing in this way, the electrical resistance (volume resistivity) of the elastic layer 112 can be easily set low. The elastic layer 112 has a thickness (wall thickness) of 0.3 to 3 mm, preferably 1 to 3 mm, and a JIS-A rubber hardness of 5 Hs to 30 Hs.

  In order to improve the releasability from the toner on the outside (outer peripheral surface) of the elastic layer 112, a 20 to 80 μm thick PFA (fluororesin) tube or a fluororesin (PFA or PTFE) paint is used. A heat-resistant coating layer 113 having a good thermal conductivity and a heat-resistant coating layer 113 is provided which is applied with 20 to 100 μm, or formed with silicone rubber or fluorine rubber having a layer thickness of 20 to 500 μm. The covering layer 113 improves the releasability with the toner and enhances the durability of the elastic layer 112.

  A pressure roller 12 as a lower cylindrical fixing member that forms a pair with the upper fixing roller 11 is a cylindrical member, and includes a heat conductive base 121, an elastic layer 122, and a coating layer 123. The constituent members of the pressure roller 12 are formed with substantially the same material and characteristics as the constituent members of the fixing roller 11.

  For example, a thermally conductive substrate 121 using STKM having a thickness of 1 to 3 mm, and a sponge-like thickness using, for example, a silicone rubber layer, a fluorine rubber layer, or a foamed material of silicone rubber on the outer peripheral surface of the thermally conductive substrate 121. (Thickness) A roller having an outer diameter of about 30 to 700 mm formed by an elastic layer 122 made of a thick rubber layer having a thickness of 0.3 to 5 mm and a rubber hardness of 30 Hs to 70 Hs (JIS-A rubber hardness). Is done. On the outer side (outer peripheral surface) of the elastic layer 122, a coating layer 123 is formed that covers a tube of heat-resistant fluororesin such as PFA or PTFA having releasability.

  A planar fixing nip portion is provided between the upper fixing roller 11 rotatably supported at a fixed position and the lower pressure roller 12 pressed against the fixing roller 11 by a spring biased pressing means 15. N is formed and the toner image t is fixed.

  The sheet S that has passed through the fixing nip N of the fixing device 10 is separated from the outer peripheral surface of the fixing roller 11 by the separation claws 16A and 16B, and is nipped by a conveyance roller (not shown) and conveyed outside the apparatus.

  A cleaning unit 17 is disposed around the fixing roller 11. The cleaning means 17 includes a cleaning web 171 that contacts and cleans the fixing roller 11, a cleaning roller 172 that rotates by pressing the cleaning web 171 against the fixing roller 11, a web former winding shaft 173 that winds and accommodates the cleaning web 171, and cleaning A web winding shaft 174 for winding the web 171 and a driving means (not shown) for driving and rotating the web winding shaft 174 are configured.

  FIG. 2A is a partial plan view of the fixing roller 11 and the paper edge mark cleaning means 18, and FIG.

  The paper edge trace cleaning means 18 moves the contact member (scraper) 181 to press and separate the tip of the contact member 181 from the fixing roller 11. The abutting member 181 is a thin plate member made of a material having good release properties and heat resistance, for example, polytetrafluoroethylene (PTFE) or polyimide (PI).

  The support member 182 that fixes and holds the abutting member 181 with an adhesive or the like slides on the upper surface of the fixing member 183 and moves while being guided by a guide member (not shown). The support member 182 is urged by the spring 184 and presses against the circumferential surface of the cam 185.

  A rotating shaft 186 of the cam 185 is rotatably supported by the fixed member 183. A rotation transmission member 187 such as a gear is connected to the shaft end of the rotation shaft 186, and the cam 185 is rotated by a drive source (not shown).

  When the cam 185 starts rotating, the support member 182 moves in the direction of the outer peripheral surface of the fixing roller 11, and the front end portion of the contact member 181 contacts the outer peripheral surface of the fixing roller 11. Clean the paper edge marks that have occurred.

  FIG. 3A is a cross-sectional view showing a state where the tip of the contact member 181 is in contact with the outer peripheral surface of the fixing roller 11 in the normal direction.

  FIG. 3B is a cross-sectional view showing another embodiment of the paper edge mark cleaning means 18.

  The tip of the abutting member 181 abuts against the outer peripheral surface of the fixing roller 11 in a counter shape, and cleans the paper edge trace generated on the outer peripheral surface of the fixing roller 11.

  The paper edge trace cleaning means 18 operates the paper edge trace cleaning means 18 only at the time of job switching when the width of the paper S is changed from the small size to the large size, so that the contact member 181 is placed on the outer peripheral surface of the fixing roller 11. The outer peripheral surface of the fixing roller 11 is cleaned by contact.

  Further, the paper edge mark cleaning means 18 releases the contact with the fixing roller 11 after rotating the fixing roller 11 one or more times after contacting the tip of the contact member 181 with the fixing roller 11.

  Further, the paper edge mark cleaning means 18 causes the contact member 181 to contact the fixing roller 11 when the paper S on which an unfixed image having a high original blackening rate is formed near the end surface passes through the fixing nip N. The outer peripheral surface of the fixing roller 11 is cleaned.

  FIG. 4 is a plan view showing the arrangement of the contact members 181 of the paper edge mark cleaning means 18.

  The two contact members 181 are mounted symmetrically on the support member 182 in the paper width direction and are movable in the direction of the fixing roller 11. The sheet S on which an image is formed has a minimum sheet width (Lmin) of 100 mm or more and a maximum sheet width (Lmax) of 324 mm. Further, it is assumed that the center in the width direction of the sheet S on which an image is formed passes through the center of the fixing device 10. The alternate long and short dash lines indicate both end surfaces of the paper S of various sizes in the paper width direction.

  The length L in the sheet width direction of the two contact members 181 is formed to be (Lmax−Lmin) / 2. Each contact member 181 cleans paper edge marks of various sizes of paper S generated on the outer peripheral surface of the fixing roller 11.

  FIG. 5 is a sectional view showing another embodiment of the paper edge mark cleaning means.

  The contact member 19 of the paper edge mark cleaning means is formed in a rotatable roller shape, and the length L in the paper width direction is formed in the same manner as in FIG. As shown in FIG. 5A, the contact member 19 stands by at a position separated from the outer peripheral surface of the fixing roller 11 in the initial state.

  The contact member 19 is moved from the initial state by a driving unit (not shown) before the image forming job for the paper S having a narrow paper width is completed and the printing job for the paper S having a wide paper width is started next. Then, it is brought into contact with the outer peripheral surface of the fixing roller 11. At the same time, when the contact member 19 is rotated in the same direction as the fixing roller 11, the contact point where the fixing roller 11 and the contact member 19 contact each other is rotated in the opposite direction to be formed on the outer peripheral surface of the fixing roller 11. The left edge of the paper is cleaned by the contact member 19.

  FIG. 6 is a cross-sectional view showing still another embodiment of the paper edge mark cleaning means. In the figure, parts having the same functions as those in FIG. Further, differences from FIG. 5 will be described.

  The contact member 19 of the paper edge mark cleaning means is formed in a rotatable roller shape, and the length L in the paper width direction is formed in the same manner as in FIG. The contact member 19 is in contact with the outer peripheral surface of the fixing roller 11 in an initial state, and is driven to rotate.

  When cleaning the paper edge mark, the rotation of the contact member 19 is locked, and the outer peripheral surface of the fixing roller 11 is rubbed by the stopped contact member 19 to form the outer peripheral surface of the fixing roller 11. Clean the paper edge marks.

  FIG. 7 is a cross-sectional view of a fixing device using a fixing belt.

  The fixing device 20 according to the present invention includes a fixing roller 22 disposed inside a fixing belt (heating rotator) 21, a heating roller 23, a heating source 24, and a pressure roller (pressurizing) disposed outside the fixing belt 21. Rotating body) 25, heating source 26, and the like.

  The fixing belt 21 is composed of an endless belt member, and is wound around the outer periphery of the fixing roller 22 and the heating roller 23. The fixing belt 21 is made of a resin material, and a heat-resistant resin belt such as polyimide is used as a base, and the outer (outer peripheral surface) of the base is covered with silicone rubber as a rubber layer. The surface of the layer is coated with PFA (perfluoroalkoxy) or coated with a PFA tube.

  The fixing roller 22 faces the pressure roller 25 and supports the fixing belt 21 on one of the inner peripheral surfaces of the fixing belt 21. The fixing roller 22 includes a cylindrical metal pipe made of STKM (carbon steel pipe for mechanical structure), a silicone rubber layer provided on the outer peripheral surface of the metal pipe, and a soft coating layer provided on the outer side of the silicone rubber layer. Configured as a roller.

  The heating roller 23 supports the fixing belt 21 on the other inner peripheral surface of the fixing belt 21. The heating roller 23 is configured as a roller member in which a metal pipe made of a heat conductive material such as an aluminum alloy material as a base and a coating layer made of PFA are formed on the outer peripheral surface of the metal pipe.

  Inside the heating roller 23, a heating source 24 as a heating element is disposed. The heating source 24 is a halogen lamp, a carbon heater, a xenon lamp, or the like, and generates radiant heat.

  The pressure roller 25 sandwiches the fixing belt 21 and the transfer material P and presses against the fixing roller 22. Inside the pressure roller 22, a heating source 26 as a heating element is disposed.

  The surface temperature of the fixing belt 21 is detected by the temperature sensor TS1, and is maintained at a predetermined temperature by a control unit (not shown). The surface temperature of the pressure roller 25 is detected by the temperature sensor TS2, and is maintained at a predetermined temperature by a control means (not shown).

  The fixing roller 22 is rotatably disposed at a fixed position, and the heating roller 23 is elastically biased in a direction away from the fixing roller 22 by a pressing means such as a spring (not shown). As a result, the fixing belt 21 is stretched with an appropriate pressure.

  A driving means (not shown) rotates the fixing roller 22 and rotates the fixing belt 21 in a driven manner. Alternatively, the driving unit may rotationally drive the pressure roller 25, convey the fixing belt 21 by the pressure roller 25, and rotate the fixing belt 21 in a driven manner. Further, driving may be input to both the fixing roller 22 and the pressure roller 25.

  A fixing nip N is formed between the fixing roller 22 and the pressure roller 25 with the fixing belt 21 heated by the heating roller 23 interposed therebetween. The fixing device 20 fixes the single color toner image or the multicolor toner image on the transfer material P through the fixing nip portion N by heating and pressing.

  The cleaning means 27 for cleaning the fixing belt 21 includes a cleaning roller 271, a cleaning web 272, a web former winding shaft 273, a web winding shaft 274, an intermediate roller 275, and the like. The cleaning web 272 is taken up by a driving means (not shown). It is done.

  In addition to the cleaning unit 27, a paper edge mark cleaning unit 28 is disposed in the vicinity of the outer peripheral surface of the fixing belt 21. The paper edge trace cleaning means 28 has substantially the same configuration as the paper edge trace cleaning means 18 shown in FIG. 2, and is operated only when the width of the paper S is changed, thereby causing the contact member (scraper) 281 to be fixed. The paper edge trace generated on the outer peripheral surface of the fixing belt 21 is cleaned by contacting the outer peripheral surface of the fixing belt 21. As a result, an image forming apparatus provided with a fixing device that maintains the surface quality of the heating rotator and maintains a high-quality image is provided.

FIG. 3 is a cross-sectional view showing an embodiment of a fixing device of a heating roller type. FIG. 4 is a partial plan view of a fixing roller and a paper edge mark cleaning unit, and an AA cross-sectional view. FIG. 3 is a cross-sectional view illustrating a state in which a tip portion of a contact member is in contact with an outer peripheral surface of a fixing roller. The top view which shows arrangement | positioning of the contact member of a paper edge trace cleaning means. Sectional drawing which shows other embodiment of a paper edge trace cleaning means. Sectional drawing which shows other embodiment of a paper edge trace cleaning means. 2 is a cross-sectional view of a fixing device using a fixing belt.

Explanation of symbols

10, 20 Fixing device 11 Fixing roller (heating rotating body)
12 Pressure roller (Pressure rotating body)
17 Cleaning means 18, 28 Paper edge mark cleaning means 181, 281 Contact member (scraper)
182 Support member 183 Fixing member 184 Spring 185 Cam 186 Rotating shaft 187 Rotation transmission member 19 Contact member 21 Fixing belt (heating rotator)
22 Fixing roller 23 Heating roller 25 Pressure roller (Pressure rotating body)
27 Cleaning means S Recording medium (paper)
N Fixing nip

Claims (10)

A heating rotator that is heated by a heating source and a pressure rotator that is in pressure contact with the heating rotator, and carries an unfixed image at a fixing nip formed by the heating rotator and the pressure rotator. In the fixing device for holding and conveying the recording medium to be fixed, a contact member that comes in contact with the outer peripheral surface of the heating rotator is provided so that the contact member can be changed when the width of the recording medium is changed. The fixing device is provided with a control unit that controls to contact the outer peripheral surface of the heating rotator, and the contact member is formed of a material having releasability and heat resistance . The control means performs control to release the contact with the heating rotator after rotating the heating rotator one or more times after contacting the contact member with the heating rotator. The fixing device according to claim 1. The control unit controls the contact member to contact the heating rotator when a recording medium on which an unfixed image having a high original blackening ratio is formed near the end surface passes through the fixing nip portion. The fixing device according to claim 1. The control means controls drive means for moving the contact member from an initial position separated from the heating rotator to a position where the contact member contacts the heating rotator. 4. The fixing device according to any one of items 1 to 3. The portion of the contact member that contacts the heating rotator has a length that includes both end faces in the width direction perpendicular to the conveyance direction of recording media of various sizes that pass through the fixing nip portion. The fixing device according to claim 1. The fixing device according to claim 1, wherein the material having releasability and heat resistance is polytetrafluoroethylene or polyimide. 7. The contact member according to claim 1, wherein the contact member has a plate shape, and a tip portion having releasability and heat resistance is in contact with the outer peripheral surface of the heating rotator so as to be able to contact and separate. The fixing device according to Item 1. 7. The contact member according to claim 1, wherein the contact member has a roller shape having an elastic layer and a release layer and a heat-resistant surface layer on a rotating shaft, and slidably rubs against the heating rotating body. The fixing device according to claim 1. The fixing device according to claim 1, wherein the heating rotator is a fixing roller having a heating source. 9. The fixing belt according to claim 1, wherein the heating rotator is a fixing belt that winds a heating roller having a heating source and a fixing support roller in pressure contact with the pressure rotator. The fixing device described.

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