JP2009229792A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce occurrence of image defects due to scars and stripes occurring on a surface of a fixing member, for a long period of time in a fixing device employing a heat and pressure fixing system. <P>SOLUTION: The fixing device includes: a fixing belt module 61 including a rotationally driven fixing roll 611 and a fixing belt 610 stretched around the fixing roll 611; a pressure roll 62 which is driven to rotate to form a nip part N which a paper P passes, between the pressure roll itself and the fixing belt 610 while pressing the fixing roll 611 through the fixing belt 610; and a surface adjustment roll 618 which adjusts a surface shape of the fixing belt 610 in contact with the fixing belt 610, is heated by a halogen heater 618a disposed in the surface adjustment roll 618 so that the temperature of the surface adjustment roll 618 becomes higher than that of the fixing belt 610. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a fixing device or the like, and more particularly to a fixing device or the like in a copying machine or a printer using an electrophotographic system.

  Conventionally, in an electrophotographic image forming apparatus, generally, a toner image formed on a recording material such as paper is fixed on the recording material by a thermal pressure fixing method. The thermal pressure fixing method includes a method in which an unfixed toner image is heated and pressed at a nip formed by a fixing roll and a pressure roll with a built-in heater and fixed on a recording material (roll nip method), and the inner side of an endless belt. Then, there is a method (belt nip method) in which a recording material is pressed against a fixing roll by a pressure pad to form a nip portion.

  In recent years, in a fixing device that employs a thermal pressure fixing method, a surface layer of the fixing member may be formed using a fluororesin in order to impart high releasability to the surface of the fixing member. The surface layer of the fluororesin having a relatively low hardness is easily damaged by the paper edge or paper width edge supplied to the nip portion. For this reason, there has been reported a technique for preventing such scars and streaks from being transferred to the image surface after fixing and causing image defects.

  As such a technique, Japanese Patent Application Laid-Open No. H10-228561 discloses a contact member that contacts the fixing member in a fixing device that can fix an unfixed image to a recording medium that passes through a position where the fixing member and the pressure member are opposed to each other. It is described that by making the surface roughness Ra1 larger than the surface roughness Ra2 of the fixing member, scratches and streaks generated on the fixing member can be eliminated and image disturbance can be prevented.

  In Patent Document 2, an endless fixing belt suspended by a plurality of rollers including a heating roller and an nip portion N that presses the endless fixing belt and fixes toner on the transfer paper P are formed. Separation is achieved by including a pressure roller, a separating unit that contacts the surface of the endless fixing belt and prevents the transfer paper P from being wrapped around the endless fixing belt, and a polishing unit that polishes the surface of the endless fixing belt. There are described a fixing device and an image forming apparatus using the fixing device that make the belt scratches by the nails inconspicuous and provide image quality without streaks.

JP 2007-034068 A JP 2006-317881 A

By the way, in the fixing device adopting the thermal pressure fixing method, the surface of the fixing member is damaged by the edge of the paper passed through the nip portion and the edge of the paper width, and such a scar causes uneven gloss in the image after fixing. It is known to be. Such gloss unevenness is considered to be caused by a difference between the surface roughness of the portion damaged by the edge of the paper or the edge of the paper width and the surface roughness of the other portion. For this reason, for example, by polishing the surface of the fixing member on which the scar remains using a predetermined polishing means, it is possible to reduce the distribution of the surface roughness generated on the surface of the fixing member.
However, it is conceivable that the toner remaining on the surface of the fixing member adheres to the surface of the polishing means during the long-time operation, and the adhered toner causes further damage to the surface of the fixing member. Further, when toner is deposited on the surface of the polishing means, there is a problem that a predetermined effect cannot be obtained.

  The present invention has been made to solve such problems. That is, an object of the present invention is to suppress the adhesion or accumulation of toner on the polishing means in a fixing device employing a thermal pressure fixing method, and to generate image defects due to scars and streaks generated on the surface of the fixing member. Is to reduce over a long period of time.

  According to the present invention, a fixing device and an image forming apparatus according to the following claims are provided.

According to a first aspect of the present invention, there is provided a fixing member that is rotationally driven, and a pressure member that is driven and rotated by the fixing member while pressing the fixing member and forms a nip portion through which the recording material passes. A surface shape adjusting member that adjusts the surface shape of the fixing member while being in contact with the fixing member; and a heating unit that heats the surface shape adjusting member so that the surface temperature of the surface shape adjusting member is higher than the surface temperature of the fixing member. The fixing device is characterized by comprising:
The invention according to claim 2 is the fixing device according to claim 1, wherein the surface shape adjusting member roughens the surface roughness of the surface shape of the fixing member as compared with that before contact.

According to a third aspect of the present invention, the surface shape adjusting member comprises: a base made of a cylindrical roll; and a surface adjusting layer including a fluororesin and inorganic particles having an average particle diameter of 2 μm to 50 μm laminated on the surface of the base. The fixing device according to claim 1, comprising: a fixing device;
The invention according to claim 4 is the fixing device according to claim 3, wherein the inorganic particles contained in the surface adjustment layer are spherical aluminum oxide having an average particle diameter of 3 μm to 10 μm.

  The invention according to claim 5 is characterized in that the surface shape adjusting member rotates following the rotation of the fixing member while being in contact with the fixing member. Device.

  According to a sixth aspect of the present invention, there is provided a toner image forming portion that forms a toner image, a transfer portion that transfers a toner image formed by the toner image forming portion onto a recording material, and a transfer portion that transfers the toner image onto the recording material. A fixing unit that fixes the toner image on the recording material, and the fixing unit passes the fixing material between the fixing roll, the fixing belt stretched over the fixing roll, and the fixing belt. A pressure roll that forms a nip portion to be heated, and heated to a temperature higher than the surface temperature of the fixing belt, and rotates with the fixing belt while being in contact with the fixing belt. An image forming apparatus comprising a surface shape adjusting member that adjusts to a surface.

  The invention according to claim 7 is characterized in that the surface shape adjusting member includes a base made of a cylindrical roll, and a surface adjusting layer including a fluororesin and inorganic particles having an average particle diameter of 2 μm to 50 μm laminated on the surface of the base. The image forming apparatus according to claim 6, wherein the surface of the fixing belt is adjusted to a predetermined surface roughness Ra by being driven and rotated by the fixing belt.

  According to the first aspect of the present invention, it is possible to suppress the toner from adhering to or accumulating on the surface adjustment member over a long period of operation as compared with the case where the present configuration is not provided, and the toner is generated on the surface of the fixing member. It is possible to reduce the gloss difference of the toner image due to a scar or the like.

  According to the second aspect of the invention, by adjusting the surface state of the fixing member, the diffused light on the surface of the image is increased and the unevenness of the image gloss is reduced.

  According to the third aspect of the present invention, compared to the case where the surface adjustment layer does not contain a fluororesin, the release property of the surface adjustment member is improved and the adhesion or accumulation of toner on the surface adjustment member is further suppressed. it can.

  According to the fourth aspect of the invention, the surface shape of the fixing belt is adjusted according to the type of inorganic particles contained in the surface adjustment layer.

  According to the fifth aspect of the present invention, the surface of the fixing member can be provided with a concavo-convex shape similar to a paper entry flaw as compared with the case where this configuration is not provided.

  According to the sixth aspect of the present invention, the occurrence of image defects due to scars and streaks generated on the surface of the fixing member is reduced as compared with the case where this configuration is not provided.

  According to the seventh aspect of the invention, the surface shape of the fixing belt is adjusted in accordance with the type of inorganic particles contained in the surface adjustment layer, and image gloss unevenness is reduced, as compared with the case where the present configuration is not provided. To do.

  Hereinafter, the best mode (embodiment) for carrying out the present invention will be described. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary. Also, the drawings used are used to describe the present embodiment and do not represent the actual size.

(Image forming device)
FIG. 1 is a diagram illustrating an overall configuration of an image forming apparatus 1 to which the exemplary embodiment is applied. An image forming apparatus 1 shown in FIG. 1 is a so-called tandem color printer, and an image forming process unit 10 that forms an image corresponding to image data of each color, and a control unit 30 that controls the operation of the entire image forming apparatus 1. For example, an image processing unit 35 that is connected to an external device such as a personal computer (PC) 3 or an image reading device 4 and performs predetermined image processing on image data received from these devices. A power supply 50 is provided.

The image forming process unit 10 includes four image forming units 11Y, 11M, 11C, and 11K (also collectively referred to as “image forming unit 11”), which are examples of toner image forming units arranged in parallel at regular intervals. ) Is provided. Each of the image forming units 11 is a photosensitive drum 12 as an example of an image carrier that forms an electrostatic latent image and holds a toner image, and a charger 13 that uniformly charges the surface of the photosensitive drum 12 with a predetermined potential. A developing unit 14 for developing the electrostatic latent image formed on the photosensitive drum 12 and a cleaner 15 for cleaning the surface of the photosensitive drum 12 after transfer are provided.
Each image forming unit 11 is configured in substantially the same manner except for the toner stored in the developing device 14. Each image forming unit 11 forms yellow (Y), magenta (M), cyan (C), and black (K) toner images.

  Further, the image forming process unit 10 exposes the photosensitive drums 12 disposed in the respective image forming units 11, and the respective color toner images formed on the photosensitive drums 12 of the respective image forming units 11. Are superimposed on the intermediate transfer belt 20 and the intermediate transfer belt 20 that sequentially transfer (primary transfer) each color toner image formed by each image forming unit 11 to the intermediate transfer belt 20. A secondary transfer roll 22 that batch-transfers (secondary transfer) the transferred color toner images onto a sheet P that is a recording material (recording sheet), and a fixing unit that fixes the secondary-transferred color toner images on the sheet P ( The fixing device 60 is an example of the fixing device). In the image forming apparatus 1 of the present embodiment, the intermediate transfer belt 20, the primary transfer roll 21, and the secondary transfer roll 22 constitute a transfer unit.

  In the image forming apparatus 1 according to the present embodiment, the image data input from the PC 3 or the image reading apparatus 4 is subjected to predetermined image processing by the image processing unit 35 and then each image is formed via an interface (not shown). Sent to unit 11. For example, in the image forming unit 11Y that forms a yellow (Y) color toner image, the photosensitive drum 12 is uniformly charged at a predetermined potential by the charger 13 while rotating in the direction of arrow A, and the laser exposure unit 40 Scanning exposure is performed with laser light whose lighting is controlled based on the image data transmitted from the image processing unit 35. Thereby, an electrostatic latent image related to a yellow (Y) color image is formed on the photosensitive drum 12. The electrostatic latent image formed on the photosensitive drum 12 is developed by the developing device 14, and a yellow (Y) color toner image is formed on the photosensitive drum 12. Similarly, magenta (M), cyan (C), and black (K) toner images are formed in the image forming units 11M, 11C, and 11K, respectively.

  Each color toner image formed by each image forming unit 11 is sequentially electrostatically attracted by the primary transfer roll 21 onto the intermediate transfer belt 20 moving in the direction of arrow B, thereby forming a superimposed toner image in which the respective color toners are superimposed. Is done. The superimposed toner image on the intermediate transfer belt 20 is conveyed to a region (secondary transfer portion T) where the secondary transfer roll 22 is disposed as the intermediate transfer belt 20 moves. When the superimposed toner image is conveyed to the secondary transfer unit T, the sheet P is transferred from one of the selected sheet holding units 71a and 71b in accordance with the timing at which the superimposed toner image is conveyed to the secondary transfer unit T. It is supplied to the next transfer portion T. Then, the superimposed toner image is collectively electrostatically transferred onto the conveyed paper P by the action of the transfer electric field formed by the secondary transfer roll 22 in the secondary transfer portion T.

Thereafter, the sheet P on which the superimposed toner image is electrostatically transferred is peeled off from the intermediate transfer belt 20 and conveyed to the fixing device 60 by the conveying belts 76 and 77. The toner image on the paper P conveyed to the fixing device 60 is fixed on the paper P by receiving a fixing process using heat and pressure by the fixing device 60. Then, the paper P on which the fixed image is formed is conveyed to a paper discharge stacking unit (not shown) provided in the discharge unit of the image forming apparatus 1.
In this way, image formation in the image forming apparatus 1 is repeatedly executed for the number of printed sheets.

(Fixing device)
Next, the fixing device 60 will be described.
FIG. 2 is a side sectional view showing a configuration of the fixing device 60 of the present embodiment. The fixing device 60 includes a fixing belt module (fixing member) 61, a pressure roll (pressure member) 62 disposed in pressure contact with the fixing belt module 61, and a halogen heater (heating means) 618a therein. A surface adjusting roll (surface shape adjusting member) 618 that adjusts the surface of the fixing belt 610 to a predetermined surface roughness Ra while being in contact with a fixing belt 610 of the fixing belt module 61 described later.

(Fixing member)
The fixing belt module 61 includes a fixing belt (endless belt) 610 as an example of a belt member, a fixing roll (rotating member) 611 that rotates while the fixing belt 610 is stretched, and a tension roll 612 that spans the fixing belt 610 from the inside. The fixing belt 610 is applied to the above-described surface adjustment roll 618 while correcting the posture of the fixing belt 610 between the external heating roll (heating member) 613 and the fixing roll 611 and the tension roll 612 over which the fixing belt 610 is passed from the outside. Opposed roll 614 provided at a position opposite to the sheet, and disposed in a downstream area in the nip portion N, which is an area where the fixing belt module 61 and the pressure roll 62 are pressed against each other, and peels the paper P from the fixing belt 610. Peeling pad (peeling member) 64, downstream of the nip portion N, and a fixing bell 610 is provided with a idler roll 615 to pass over the fixing belt 610 in the region before they are passed over the fixing roll 611 again.

The fixing roll 611 is made of, for example, a cylindrical core roll (core metal) made of aluminum having an outer diameter of 65 mm, a length of 360 mm, and a thickness of 10 mm, and a fluorine resin having a thickness of 200 μm as a protective layer for preventing metal wear on the core roll surface. It is a hard roll formed by coating. The fixing roll 611 receives a driving force from a driving motor (not shown) and rotates in the direction of arrow C at a surface speed of, for example, 440 mm / s.
In addition, a halogen heater 616 a rated at 900 W is disposed as a heating source inside the fixing roll 611, and the image forming apparatus 1 is based on a measurement value of a temperature sensor 617 a disposed so as to contact the surface of the fixing roll 611. The controller 30 (see FIG. 1) controls the surface temperature of the fixing roll 611 to 150 ° C.

  The fixing belt 610 is a deformable endless belt having a circumferential length of 314 mm and a width of 340 mm, for example. The fixing belt 610 has a multilayer structure, and is made of, for example, a base layer formed of a polyimide resin having a thickness of 80 μm and a 200 μm-thick silicone rubber laminated on the surface side (outer peripheral surface side) of the base layer. An elastic body layer and a release layer made of a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA) tube having a thickness of, for example, 30 μm and further coated on the elastic body layer. The elastic layer here is used to improve the image quality of the color image by deforming the surface of the fixing belt 610 following the unevenness of the toner image on the paper P and supplying heat uniformly to the entire toner image. Provided. Note that the material, thickness, hardness, and the like of the configuration of the fixing belt 610 are appropriately selected according to the apparatus design conditions such as the purpose of use and the use conditions. The fixing belt 610 is moved in the direction of arrow D by the fixing roll 611.

The tension roll 612 is a cylindrical roll formed of aluminum having an outer diameter of 30 mm, a thickness of 2 mm, and a length of 360 mm, for example. Inside the tension roll 612, a halogen heater 616b rated at 1500 W is disposed as a heating source, and the surface temperature is controlled to 190 ° C. by the temperature sensor 617b and the control unit 30 (see FIG. 1).
Further, spring members (not shown) that press the fixing belt 610 outward are disposed at both ends of the tension roll 612. Thereby, the tension roll 612 has a function of adjusting the tension of the fixing belt 610 to a predetermined value (for example, 15 kgf).

  Further, a belt edge position detection mechanism (not shown) for detecting the edge position of the fixing belt 610 is disposed in the vicinity of the tension roll 612. The tension roll 612 is provided with an axial displacement mechanism that displaces the contact position in the axial direction of the fixing belt 610 according to the detection result of the belt edge position detection mechanism, and controls the meandering (belt walk) of the fixing belt 610. It also functions as a meandering control roll (steering roll).

The external heating roll 613 is a cylindrical roll formed of aluminum having an outer diameter of 25 mm, a thickness of 2 mm, and a length of 360 mm, for example. Inside the external heating roll 613, a halogen heater 616 c rated at 1000 W is disposed as a heating source, and the surface temperature is controlled to 190 ° C. by the temperature sensor 617 c and the control unit 30 (see FIG. 1). .
As described above, the surface temperature of the fixing belt 610 stretched over the fixing roll 610, the tension roll 612, and the external heating roll 613 differs depending on the circumferential position. For example, at the position where the surface adjustment roll 618 is pressed, It is 180 degreeC-185 degreeC.

The surface adjustment roll 618 is provided with a halogen heater 618a as a heating means, and is a cylindrical roll having an outer diameter of 30 mm and a length of 350 mm, for example. Spring members (not shown) are provided at both ends of the surface adjustment roll 618, and the surface of the fixing belt 610 is usually contact pressure of 2 kgf / cm ^{2 to} 5 kgf / cm ² , preferably 2.5 kgf / cm ² to. Pressing at 3 kgf / cm ² . The surface adjustment roll 618 will be described later.
The facing roll 614 provided at a position facing the surface adjustment roll 618 across the fixing belt 610 is, for example, a sponge roll having an elastic layer having an outer diameter of 20 mm and a length of 380 mm.

The peeling pad 64 is a block member having a substantially arc-shaped cross section, and is made of a rigid body such as a metal such as SUS or a highly rigid resin. The pressure roll 62 is fixedly disposed over the entire axial direction of the fixing roll 611 at a position near the downstream side of the area where the pressure roll 62 is pressed against the fixing roll 611 via the fixing belt 610. The peeling pad 64 is installed so as to uniformly press the fixing belt 610 toward the pressure roll 62 with a predetermined load (for example, 10 kgf).
The idler roll 615 is a cylindrical roll formed of stainless steel having an outer diameter of 12 mm and a length of 360 mm, for example. The fixing belt 610 that has passed through the nip portion N is disposed near the downstream side in the movement direction of the fixing belt 610 of the peeling pad 64 so that the fixing belt 610 smoothly moves toward the fixing roll 611.

(Pressure member)
The pressure roll 62 includes, for example, a cylindrical roll 621 made of aluminum having a diameter of 45 mm and a length of 360 mm as a base, and an elastic layer 622 having a thickness of 10 mm made of silicone rubber and a PFA tube having a thickness of 100 μm in this order from the base. It is a soft roll formed by laminating a release layer 623 made of The pressure roll 62 is installed so as to be pressed against the fixing belt module 61. As the fixing roll 611 of the fixing belt module 61 rotates in the direction of arrow C, the pressure roll 62 follows the fixing roll 611 and moves in the direction of arrow E. Rotate to. The moving speed is 440 mm / s, which is the same as the surface speed of the fixing roll 611.

(Surface adjustment roll 618)
Next, the surface adjustment roll 618 of the surface shape adjustment member will be described.
FIG. 3 is a diagram illustrating a cross-sectional structure of the surface adjustment roll 618 in the present embodiment. As shown in FIG. 3, the surface adjustment roll 618 has a base 618b made of a metal cylindrical roll, and a surface adjustment layer 618d in contact with the fixing belt 610 (see FIG. 2).

Also, a halogen heater 618a rated at 500 W is provided as a heating means inside the base 618b, and the image forming apparatus 1 is based on the measured value of the temperature sensor 618e arranged so as to contact the surface of the surface adjustment layer 618d. The control unit 30 (see FIG. 1) controls the surface temperature of the surface adjustment roll 618 to be higher than the surface temperature of the fixing belt 610.
By making the surface temperature of the surface adjustment roll 618 higher than the surface temperature of the fixing belt 610, adhesion of toner to the surface of the surface adjustment roll 618 can be prevented. Here, the surface temperature of the surface adjustment roll 618 is usually set to 10 ° C. or more higher than the fixing belt temperature, and preferably set to 15 ° C. or more higher than the fixing belt temperature. It is set as follows.
The base 618b is a cylindrical roll formed of stainless steel (SUS) having an outer diameter of 30 mm and a length of 350 mm, for example.

The first embodiment of the surface adjustment layer 618d of the surface adjustment roll 618 shown in FIG. 3 includes a fluororesin and inorganic particles having an average particle diameter of 2 μm to 50 μm, and is fixed to the surface of the substrate 618b via the primer layer 618c. Can be mentioned.
When the surface adjustment layer 618d contains a fluororesin and inorganic particles having an average particle diameter of 2 μm to 50 μm, the surface of the fixing belt 610 is polished according to the kind of the inorganic particles, or particles of inorganic particles are formed on the surface of the fixing belt 610. An uneven shape corresponding to the diameter can be provided. Then, by adjusting the surface of the fixing belt 610 within a predetermined surface roughness Ra, the occurrence of image defects due to scars and streaks generated on the surface of the fixing belt 610 during the fixing operation is reduced. be able to.
At this time, the surface of the fixing belt 610 is preferably adjusted to have a surface roughness Ra of 0.5 μm to 0.2 μm, particularly 0.1 μm to 0.15 μm.

  In this case, examples of the fluororesin contained in the surface adjustment layer 618d include polytetrafluoroethylene (PTFE); tetrafluoroethylene-perfluoromethyl vinyl ether copolymer (MFA), tetrafluoroethylene-perfluoroethyl vinyl ether copolymer Examples thereof include tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA) such as coalesced (EFA) and tetrafluoroethylene-perfluoropropyl vinyl ether copolymers. Furthermore, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), polychlorotrifluoride ethylene (PCTFE), polyvinyl fluoride (PVF) Etc.

Among these fluororesins, polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoromethyl vinyl ether copolymer (MFA), and tetrafluoroethylene-perfluoroethyl vinyl ether are particularly preferred from the standpoints of heat resistance and mechanical properties. A tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) such as a polymer (EFA) or a tetrafluoroethylene-hexafluoropropylene copolymer (FEP) is preferably used.
By including a fluororesin in the surface adjustment layer 618d, it is possible to prevent toner from adhering to the surface of the surface adjustment roll 618, thereby maintaining the performance of the surface adjustment roll 618 over a long period of time. Become.

  Examples of the inorganic compound constituting the inorganic particles contained in the surface adjustment layer 618d include silicon carbide, barium sulfate, aluminum oxide, graphite, magnesium sulfate, calcium carbonate, magnesium carbonate, antimony oxide, titanium oxide, zinc oxide, and iron oxide. Zinc sulfide, zinc, lead, nickel, aluminum, copper, iron, stainless steel, bentonite, montmorillonite, synthetic mica and the like. Among these, silicon carbide, barium sulfate, aluminum oxide and the like are preferable, and aluminum oxide is particularly preferable.

The average particle size of the inorganic particles is preferably 2 μm or more and 50 μm or less. If the average particle size of the inorganic particles is excessively small, the shape imparted to the surface of the fixing belt becomes small, so that the surface roughness tends to be difficult to change. On the other hand, if the average particle diameter is excessively large, the shape imparted to the surface of the fixing belt becomes large, and the surface roughness tends to be difficult to change.
Examples of the shape of the inorganic particles include a spherical shape, a rod shape, a needle shape, and a fibrous shape, and a spherical shape is preferable among them.

  In the present embodiment, in the surface adjustment layer 618d, the amount of the inorganic particles relative to the fluororesin is usually 5 parts by weight or more, preferably 20 parts by weight or more, particularly preferably 30 parts by weight or more with respect to 100 parts by weight of the fluororesin. . Moreover, it is 50 parts weight or less normally, Preferably it is 40 parts weight or less. When the amount of the inorganic particles relative to the fluororesin is excessively small, the surface adjustment ability tends to decrease because the contact between the inorganic particles and the fixing belt is small. On the other hand, when the amount of inorganic particles is excessively large, the local pressure between the inorganic particles and the fixing belt is lowered, so that the surface adjustment ability tends to be lowered.

  The thickness of the surface adjustment layer 618d is usually preferably no less than half and no more than 2/3 of the size of the inorganic particles used. If the thickness of the surface adjustment layer 618d is excessively thin, the inorganic particles tend to fall off. Moreover, since the height which has come out on the surface of the inorganic particle will become small when the thickness of the surface adjustment layer 618d is too thick, there exists a tendency for surface adjustment capability to fall.

The primer layer 618c has a role as an adhesive layer that covers and adheres the surface adjustment layer 618d to the base 618b. Examples of the material constituting the primer layer 618c include an addition reaction type silicone rubber, a silane coupling agent, an epoxy adhesive, and the like.
By forming the primer layer 618c using these compounds, it is possible to bond the base 618b and the surface adjustment layer 618d.

Next, as a second embodiment of the surface adjustment layer 618d, the surface of the base 618b described above is subjected to blasting to form a predetermined uneven shape, and this is prepared by coating with a fluororesin. Can be mentioned.
In this case, by applying a predetermined load to bring the surface adjustment roll 618 into contact with the surface of the fixing belt 610 (see FIG. 2), the uneven shape formed on the surface of the surface adjustment roll 618 is embossed, and the fixing belt 610 is pressed. It becomes possible to give a predetermined uneven | corrugated shape to the surface of this. Similarly to the first embodiment of the surface adjustment layer 618d, the surface of the fixing belt 610 is adjusted to a range of a predetermined surface roughness Ra, and image defects due to scars and streaks generated on the surface of the fixing belt 610 are obtained. Can be reduced.
In this case, the fluororesin may be fixed to the surface of the base 618b that has been subjected to the blasting process via the primer layer 618c, or a pre-formed fluororesin tube or the like is heated without providing the primer layer 618c. It may be fused.

(Method for Preparing Surface Adjustment Roll 618)
The method for preparing the surface adjustment roll 618 is not particularly limited. For example, a method of preparing a mixed solution in which a fluororesin and inorganic particles are dissolved in a common solvent and applying the mixed solution to the surface of the substrate 618b to a predetermined thickness. Is mentioned. Moreover, after immersing the base body 618b in the above-described mixed solution containing the fluororesin and the inorganic particles, a method of lifting the substrate and removing the solvent may be used. By the preparation method described above, the surface adjustment layer 618d of the surface adjustment roll 618 is prepared such that the surface roughness Ra is 2 μm to 10 μm, preferably 4 μm to 5 μm.

Next, a fixing operation in the fixing device 60 of the present embodiment will be described.
The sheet P on which the unfixed toner image has been electrostatically transferred in the secondary transfer portion T (see FIG. 1) of the image forming apparatus 1 is transferred to the nip of the fixing device 60 by the conveyance belts 76 and 77 and the inlet guide 78 of the fixing device 60. It is conveyed toward the portion N (see FIG. 2: arrow F direction). The unfixed toner image on the surface of the paper P passing through the nip portion N is fixed on the paper P by pressure and heat acting on the nip portion N.
The paper P passing through the nip portion N is weakened in adhesion with the fixing belt 610 that is largely bent when the peeling pad 64 is pressed against the pressure roll 62, and the paper P itself has a stiffness. Peel from fixing belt 610.
Then, the paper P separated from the fixing belt 610 is guided by the peeling guide plate 83 disposed on the downstream side of the nip portion N. Thereafter, the paper P is removed from the machine by the paper discharge guide 65 and the paper discharge roll 66. (See FIG. 2), the fixing process is completed.

Next, during the operation of the fixing device 60, a load of 20 kgf is normally applied to the surface adjustment roll 618 by spring members (not shown) disposed at both ends of the surface adjustment roll 618. As a result, the surface adjustment roll 618 contacts the surface of the fixing belt 610. Then, the fixing belt 610 is sandwiched between the surface adjustment roll 618 and the opposing roll 614, and the surface adjustment roll 618 is driven to rotate in the direction of arrow F in accordance with the rotation of the fixing belt 610.
By rotating the surface adjustment roll 618 following the rotation of the fixing belt 610, it is possible to give the surface of the fixing belt 610 irregularities having a shape similar to a paper entry scratch generated on the surface of the fixing belt 610.
At this time, the temperature of the surface adjustment layer 618d is maintained higher than the surface temperature of the fixing belt 610 by the halogen heater 618a provided inside the surface adjustment roll 618, and the toner remaining on the surface of the fixing belt 610. Is prevented from adhering to the surface of the surface adjustment roll 618.
At this time, the surface conditioning roll 618, to obtain the surface pressure ^{2kgf / cm 2 ~3kgf / cm 2} . The surface temperature of the fixing belt 610 is 150 ° C. to 200 ° C.

Next, when the surface adjustment layer 618d includes a fluororesin and inorganic particles having an average particle diameter of 2 μm to 50 μm, the surface shape of the fixing belt 610 is adjusted according to the type of the inorganic particles.
For example, in the case of silicon carbide (SiC) having an average particle diameter of 2 μm to 12 μm, the surface of the fixing belt 610 is polished by the surface adjustment roll 618 to form minute irregularities. Therefore, the diffused light on the surface of the toner image is increased, and the difference in contrast between the scars and streaks on the surface of the fixing belt 610 and the other portions is reduced.
Also, in the case of a spherical aluminum oxide having an average particle diameter of 3μm~10μm _(Al 2 _{O 3),} by embossing the inorganic particles contained in the surface conditioning layer 618d, spherical aluminum oxide on the surface of the fixing belt 610 (Al ₂ An uneven shape corresponding to the shape of O ₃ ) is given. For this reason, similarly, the diffused light on the surface of the toner image increases, and the difference in contrast between the scars and streaks on the surface of the fixing belt 610 and other portions is reduced.

  Hereinafter, the present invention will be described more specifically based on examples and comparative examples. In addition, this invention is not limited to a following example, unless the summary is exceeded.

Example 1
As described above, in the fixing device 60 shown in FIG. 2, as the surface adjustment roll 618, a metal roll core made of SUS having an axial length of 320 mm and a diameter of φ20 is the base 618b, and the primer layer 618c is formed on the surface of the base 618b. Then, a surface adjustment layer 618d containing 30 parts by weight of spherical aluminum oxide (Al ₂ O ₃ ) having an average particle diameter of 30 μm was laminated on 100 parts by weight of the PFA resin. At this time, the surface roughness Ra of the surface adjustment layer 618d brought into contact with the fixing belt 610 is 4 μm to 5 μm.
In addition, the thickness of the surface adjustment layer 618d of the surface adjustment roll 618 is 10 μm to 15 μm.

Next, a load of 20 kgf is applied to the surface adjustment roll 618, the surface adjustment roll 618 is brought into contact with the surface of the fixing belt 610, and the fixing belt 610 is sandwiched between the surface adjustment roll 618 and a φ20 facing roll 614 having an elastic layer. The surface adjustment roll 618 was driven to rotate along with the rotation of the fixing belt 610. Further, the surface adjustment layer 618d was heated by a halogen heater 618a provided in the surface adjustment roll 618 so that the temperature of the surface adjustment layer 618d was 195 ° C to 200 ° C.
At this time, the surface conditioning roll 618, to obtain the surface pressure ^{2kgf / cm 2 ~3kgf / cm 2} . The surface temperature of the fixing belt 610 is 180 ° C. to 190 ° C.

Subsequently, the fixing device 60 is operated, and after passing 10k A4 sheets of A4 paper, which is likely to generate offset toner, by vertical feeding, the presence or absence of contamination on the surface of the surface adjustment roll 618 is obtained. The change in the gloss unevenness of the image over time was evaluated.
As a result, even after 10 k sheets of A4 paper were fed in the vertical feed, the surface of the surface adjustment roll 618 was not stained due to the toner remaining on the surface of the fixing belt 610.
Further, no gloss unevenness was observed in an image obtained by adjusting the surface state of the fixing belt 610 by bringing the surface adjustment roll 618 into contact with the fixing belt 610.

(Example 2)
In Example 1, as the surface adjustment roll 618, a surface adjustment layer 618d including 30 parts by weight of silicon carbide (SiC) having an average particle diameter of 4 μm with respect to 100 parts by weight of the PFA resin was prepared on the surface of the base 618b by flow coating. . At this time, the surface roughness Ra of the surface adjustment layer 618d is 0.5 μm to 0.8 μm. In addition, the thickness of the surface adjustment layer 618d of the surface adjustment roll 618 is 1 μm to 2 μm.
Next, a load of 20 kgf is applied to the surface adjustment roll 618, and the surface of the surface adjustment layer 618d is heated to 195 ° C. to 200 ° C. by the halogen heater 618a. I drove 60. At this time, the surface conditioning roll 618, to obtain the surface pressure ^{2kgf / cm 2 ~3kgf / cm 2} . The surface temperature of the fixing belt 610 is 180 ° C. to 190 ° C.
As a result, the surface of the surface adjustment roll 618 was not soiled even after 10 k sheets of A4 paper were fed vertically. Further, no uneven gloss was observed in the obtained image.

(Comparative example)
In Example 1, instead of the surface adjustment roll 618, the surface of an SUS roll having an axial length of 320 mm and a diameter of φ20 is subjected to blasting, and a surface roughness Ra of 0.5 μm to 0. The fixing device 60 was operated in the same manner as in Example 1 except that the one adjusted to 8 μm was used. This SUS roll does not have a halogen heater inside.
As a result, as the number of A4 sheets passed by vertical feeding increases, the surface of the SUS roll becomes dirty, and the effect of adjusting the surface state of the surface of the fixing belt 610 is greatly reduced. Further, uneven gloss was observed in the obtained image.

1 is a schematic configuration diagram of an image forming apparatus to which the exemplary embodiment is applied. FIG. 2 is a cross-sectional view illustrating a schematic configuration of a fixing device. It is a figure explaining the cross-section of the surface adjustment roll in this Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 11 (11Y, 11M, 11C, 11K) ... Image forming unit, 20 ... Intermediate transfer belt, 60 ... Fixing device, 61 ... Fixing belt module, 62 ... Pressure roll, 610 ... Fixing belt, 611 ... Fixing roll, 613 ... External heating roll, 618 ... Surface adjustment roll, 618a ... Halogen heater

Claims (7)

A fixing member that is driven to rotate;
A pressure member that rotates following the fixing member while pressing the fixing member to form a nip portion through which the recording material passes.
A surface shape adjusting member that adjusts the surface shape of the fixing member while being in contact with the fixing member;
Heating means for heating so that the surface temperature of the surface shape adjusting member is higher than the surface temperature of the fixing member;
A fixing device.   The fixing device according to claim 1, wherein the surface shape adjusting member roughens the surface roughness of the surface shape of the fixing member as compared with that before contact.   2. The fixing device according to claim 1, wherein the surface shape adjusting member includes a base made of a cylindrical roll, and a surface adjusting layer that is laminated on the surface of the base and includes a fluororesin.   The fixing device according to claim 3, wherein the surface adjustment layer further includes inorganic particles having an average particle diameter of 2 μm to 50 μm.   5. The fixing device according to claim 1, wherein the surface shape adjusting member rotates following the rotation of the fixing member while being in contact with the fixing member. 6. A toner image forming unit for forming a toner image;
A transfer unit that transfers the toner image formed by the toner image forming unit onto a recording material;
A fixing unit that fixes the toner image transferred onto the recording material by the transfer unit onto the recording material,
The fixing unit is
A fixing roll;
A fixing belt stretched over the fixing roll;
A pressure roll forming a nip portion through which the recording material passes between the fixing belt and the fixing belt;
A surface shape adjusting member that is heated to a temperature higher than the surface temperature of the fixing belt, rotates with the fixing belt in contact with the fixing belt, and adjusts the surface of the fixing belt to a predetermined surface roughness Ra. An image forming apparatus.   The surface shape adjusting member has a base made of a cylindrical roll, and a surface adjusting layer including a fluororesin and inorganic particles having an average particle diameter of 2 μm to 50 μm laminated on the surface of the base, and is driven to rotate by the fixing belt. The image forming apparatus according to claim 6, wherein the surface of the fixing belt is adjusted to a predetermined surface roughness Ra.

Images