JP2019197096A - Fixing device and rubbing sheet used therefor - Google Patents

Abstract

To provide a fixing device capable of simply rubbing a fixing member and suitable for the downsizing and cost reduction of the device, and a rubbing sheet used therefor.SOLUTION: The fixing device comprises: first and second rotors forming a nip part for sandwiching and conveying a recording material carrying a toner image; a heating member for heating the nip part; and a rubbing sheet inserted into a part of area in the recording material conveying direction in the nip part and having a rubbing surface for changing surface properties in at least one of the first and second rotors.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a fixing device used in an image forming apparatus capable of forming an image on a recording material such as a copying machine, a printer, or a facsimile employing an electrophotographic system, and a rubbing sheet used therefor.

  As a fixing device, a nip portion is formed by the first and second rotating bodies, and a recording material carrying a toner image is nipped and conveyed while being pressurized and heated to fix the toner image on the recording material. It has been. In recent years, as described in Patent Document 1, a free belt type fixing device that uses a thin belt as a first rotating body and fixes an unfixed toner image on a recording material via the thin belt. It has been known.

  In such first and second rotating bodies, a difference in surface properties between the paper passing area and the non-paper passing area due to endurance causes a difference in gloss on the image. In particular, at the edge position of the paper (boundary portion between the paper passing area and the non-paper passing area), since the burr portion generated at the time of cutting the paper passes, the surface property is easily deteriorated and the gloss difference is easily generated.

  As a means for uniformly recovering the surface property of such a rotating body, Patent Document 2 describes that a roughening roller with abrasive grains attached is pressed against the surface of a fixing roller as a rotating body and rubbed. ing. Thereby, the surface property of a rotary body can be maintained in a fixed state, and the gloss difference mentioned above can be recovered.

JP 2010-181840 A JP 2007-199596 A

  However, in the above conventional example, in addition to the first and second rotating bodies that form the fixing nip portion, a third rotating body (roughening) that performs a rubbing process on the surface of the first rotating body as a fixing member. It is necessary to provide a roller.

  An object of the present invention is to provide a fixing device that can perform a rubbing process of a fixing member with a simpler rubbing member and a rubbing sheet as a simpler rubbing member.

  In order to achieve the above object, a fixing device according to the present invention includes first and second rotating bodies that form a nip portion that sandwiches and conveys a recording material carrying a toner image, and a heating member that heats the nip portion. And a rubbing sheet that is inserted into a partial area of the nip portion in the recording material conveyance direction and has a rubbing surface that changes the surface properties of at least one of the first and second rotating bodies. And

  The abrasive sheet according to the present invention is used in a fixing device including first and second rotating bodies that form a nip portion for nipping and conveying a recording material carrying a toner image, and the recording material conveyance in the nip portion. A polishing sheet inserted into a partial region in the direction, characterized by having a rubbing surface facing at least one surface of the first and second rotating bodies.

  According to the present invention, it is possible to provide a fixing device that can perform a rubbing process of a fixing member with a simpler rubbing member and a rubbing sheet as a simpler rubbing member.

1 is a schematic cross-sectional view of an image forming apparatus equipped with a fixing device according to an embodiment of the present invention. 1 is a schematic cross-sectional view of a fixing device according to an embodiment of the present invention. FIG. 2 is a perspective view showing the inside of the fixing device according to the embodiment of the present invention. FIG. 3 is a perspective view showing a pressure mechanism of the fixing device according to the embodiment of the present invention. FIG. 3 is a cross-sectional view of the fixing device according to the embodiment of the present invention when pressed. FIG. 3 is a cross-sectional view of the fixing device according to the embodiment of the present invention when pressure is released. It is sectional drawing which shows the retracted state of the rubbing sheet which concerns on embodiment of this invention. It is sectional drawing which shows the state just before insertion of the rubbing sheet | seat which concerns on embodiment of this invention. It is sectional drawing which shows the insertion state of the rubbing sheet which concerns on embodiment of this invention. It is sectional drawing which shows the state before the retreat transfer of the rubbing sheet | seat which concerns on embodiment of this invention. It is sectional drawing of the mechanism which rotates the polishing sheet holder which concerns on embodiment of this invention.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

<< First Embodiment >>
(Image forming device)
First, a schematic configuration of a full-color printer that employs an electrophotographic system as an image forming apparatus 10 according to an embodiment of the present invention will be described with reference to FIG. Such an image forming apparatus 10 includes an image forming unit (image forming device) 11 that forms a toner image (toner image) and a recording material that conveys a recording material P that transfers the toner image formed by the image forming unit 11. A transport unit 12. Examples of the recording material include sheet materials such as a transfer sheet, electrostatic recording paper, OHP sheet, printing paper, and format paper.

  The image forming unit 11 has a so-called tandem configuration in which a plurality of image forming stations 1 a, 1 b, 1 c, and 1 d are arranged in the running direction of the intermediate transfer belt 13. In each of the image forming stations 1a, 1b, 1c, and 1d, yellow, magenta, cyan, and black toner images are formed, respectively. In the case of the present embodiment, each of the image forming stations 1a, 1b, 1c, and 1d is configured by a process cartridge (a photosensitive drum and a developing device that will be described later are integrally held) as a cartridge that can be attached to and detached from the image forming apparatus main body. .

  Each image forming station forms a toner image as follows. First, the surface of the photosensitive drum 14 is charged by a charging device such as a charging roller, and an electrostatic latent image is formed by exposing the charged surface of the photosensitive drum 14 by a laser according to image information by the exposure device 15. . Next, the electrostatic latent image is developed with toner by a developing device, thereby forming a toner image on the surface of the photosensitive drum 14.

  The toner image formed on the surface of the photosensitive drum 14 of each image forming station is sequentially transferred to the intermediate transfer belt 13 by the primary transfer unit T1, and a full-color toner image is formed on the intermediate transfer belt 13. It is formed. In the primary transfer portion T1, a primary transfer roller 16 is disposed as a primary transfer portion that is disposed to face the photosensitive drum 14 and the intermediate transfer belt 13 therebetween. A toner image on the photosensitive drum 14 is transferred to the intermediate transfer belt 13 by applying a primary transfer bias between the primary transfer roller 16 and the photosensitive drum 14.

  The toner image on the intermediate transfer belt 13 is transferred to the recording material P conveyed by the recording material conveyance unit 12 at the secondary transfer unit T2. In the secondary transfer portion T2, a secondary transfer inner roller 17a and a secondary transfer outer roller 17b are disposed so as to face each other with the intermediate transfer belt 13 therebetween. The toner image on the intermediate transfer belt 13 is transferred to the recording material P by applying a secondary transfer bias between the secondary transfer inner roller 17a and the secondary transfer outer roller 17b.

  In this embodiment, the intermediate transfer belt 13, the secondary transfer inner roller 17a, and the secondary transfer outer roller 17b constitute a transfer device 40. The recording material P onto which the toner image has been transferred by the transfer device 40 is heated and pressed by a fixing device (fixing device) 100, whereby the toner image is fixed. That is, the fixing device 100 fixes the toner image on the recording material. Details of the fixing device 100 will be described later. The recording material P on which the toner image is fixed is discharged to a discharge tray 19 by a discharge roller 18.

  The recording material transport unit 12 is composed of a plurality of transport rollers. The recording material P stored in the cassette 20 is picked up by a pickup roller 21, separated one by one by a separation roller 22, and transported to a transport path 23. To do. The recording material P conveyed to the conveyance path 23 is conveyed to the secondary transfer unit T2 in synchronization with the toner image formed on the image forming unit 11 by the registration roller pair 24.

  Further, the recording material P discharged from the fixing device 100 is discharged to the discharge tray 19 as described above, and is reversed and conveyed to the reverse conveyance path 30 to perform duplex printing. The recording material P transported through the reverse transport path 30 joins the transport path 23 and is transported to the secondary transfer portion T2 as described above.

  In the case of this embodiment, an open / close door 26 is provided in an image forming apparatus main body (hereinafter referred to as an apparatus main body) 25 in which various devices as described above are arranged. The opening / closing door 26 is provided on the side on which the conveyance path 23 and the fixing device 100 are disposed so as to be rotatable about a rotation shaft 27. By opening the door 26, the fixing device 100 and the conveyance path 23 are exposed, and the fixing device 100 can be attached and detached and the recording material jammed in the conveyance path 23 can be removed. For this purpose, the fixing device 100 is detachably provided on the apparatus main body 25.

  Further, a roller on one side of a pair of conveyance rollers such as a registration roller pair 24 arranged in the conveyance path 22 and a secondary transfer outer roller 17b constituting the secondary transfer portion T2 are provided on the opening / closing door 26 side. . When the opening / closing door 26 is opened, it is separated from the opposing roller and the intermediate transfer belt 13.

(Fixing device)
Next, details of the fixing device 100 according to the embodiment of the present invention will be described with reference to FIGS. 2 and 4. The fixing device 100 includes a fixing belt (hereinafter referred to as a belt) 101 that is a heating rotator as a first rotator, and a pressure roller 102 that is a pressure rotator as a second rotator. A fixing nip portion (hereinafter referred to as a nip portion) N is formed between the belt 101 and the pressure roller 102 for nipping and conveying the recording material P carrying the toner image. Then, the fixing process is performed by heating the toner image formed on the recording material P passing through the nip portion N by the heater 104 as a heating source and pressurizing the nip portion N by the pressurizing mechanism.

  Further, a polishing sheet 150 as a rubbing member having a rubbing surface that changes the surface property of one of the first and second rotating bodies is provided on the rotation center shaft 102a of the pressure roller 102 with respect to the nip portion N. So that it can be inserted and retracted (details will be described later). When the recording material P is guided to the nip portion N by the inlet guide 140, the abrasive sheet 150 is retracted to the inside of the recording material conveyance guide surface 140a of the inlet guide 140 with respect to the nip portion N (right side in FIG. 2). ing.

  A belt 101 shown in FIGS. 2 and 4 is a cylindrical heat-resistant member in which an elastic layer is formed on a cylindrical thin-walled metal base layer, and the track regulation disposed at both ends of the belt 101 in the longitudinal direction. The member 105 (FIG. 2) is loosely fitted. Here, regarding the members (the belt 101, the core metal of the pressure roller, etc.) constituting the fixing device of the present embodiment, the longitudinal direction is a direction parallel to the rotation axis of the pressure roller 102 or the rotation of the pressure roller 102. The direction coincides with the axis line. This longitudinal direction is also a direction intersecting (orthogonal) with the conveyance direction of the recording material P in the nip portion N.

  In order to reduce the heat capacity and improve the quick start performance, such a belt 101 has an elastic layer made of a rubber material having a high thermal conductivity layered on a metal base layer such as SUS having a total thickness of 300 μm or less. Forming. A fluororesin release layer is formed on the surface to form an endless shape having an inner diameter of about 25 mm.

  In this embodiment, the base layer is made of SUS having a thickness of about 30 μm, the elastic layer is made of silicone rubber having a thickness of about 250 μm and a thermal conductivity of about 1.0 W / m · K, and the release layer is made of a PFA tube having a thickness of about 30 μm. Using.

  The PFA layer as the release layer is preferably a highly releasable sheet or coat layer. For example, a fluororesin layer can be used. Further, a sheet-like member having high heat resistance typified by polyester, polyethylene terephthalate, polyimide amide or the like may be used as a base layer, and a conductive layer may be further stacked thereon, and a surface release layer may be stacked thereon.

  The pressure roller 102 is composed of a cored bar made of a metal such as iron and a heat-resistant / elastic material layer such as silicone rubber, fluororubber, or fluororesin that is concentrically formed and coated around the cored bar. A release layer is provided on the surface layer. For example, the release layer may be made of a material having good release properties and heat resistance such as fluororesin, silicone resin, fluorosilicone rubber, fluororubber, silicone rubber, PFA, PTFE, FEP.

  In this embodiment, the pressure roller 102 has a core metal diameter of 15 mm, an elastic layer thickness of 5 mm, silicone rubber having an Asker hardness of 64 °, a PFA tube thickness of the release layer of 50 μm, and a pressurization with an outer diameter of about 25 mm. A roller.

  The pressure roller 102 is rotatably supported by mounting pressure roller bearings 108 made of a heat resistant resin such as PEEK, PPS, or liquid crystal polymer at both ends in the longitudinal direction of the cored bar. The pressure roller 102 is driven by a motor 131 (FIG. 4) of a fixing driving unit 130 (FIG. 4) provided in the apparatus main body 25. The belt 101 is driven to rotate by rotating the pressure roller 102, and conveys the recording material P sandwiched by the nip portion N.

  As described above, the track regulating member 105 that externally fits both ends of the belt 101 in the longitudinal direction is a member made of heat-resistant resin such as PET, PPS, and LCP. Such a track regulating member 105 is movably supported on the side plate of the fixing device 100, supports the belt 101 so as to be rotatable, and is disposed in the case of the fixing device 100. The track regulating member 105 guides the rotation of the belt 101 and functions as an abutting portion in the longitudinal direction of the belt 101.

  Inside the belt 101, stays 106 are arranged in the longitudinal direction, and both ends of the stays 106 are supported by the track regulating member 105. Such a stay 106 is a member mainly made of metal such as iron or SUS.

  Further, a pressure contact member 107 is disposed on the stay 106 on the pressure roller 102 side. Then, the stay 106 is pressed against a relatively soft pressure contact member 107 made of a resin, so that the pressure contact member 107 has strength in the longitudinal direction and the pressure contact member 107 is corrected. The pressure contact member 107 is a heat-resistant and heat-insulating member having a substantially semicircular cross section. For example, it is formed of a material having good insulation and heat resistance such as phenol resin, polyimide resin, polyamide resin, polyamideimide resin, PEEK resin, PES resin, PPS resin, PFA resin, PTFE resin, and LCP resin.

  The pressure contact member 107 is intended to improve the conveyance stability during the rotation of the belt 101 and the back-up of the belt 101, the pressurization of the nip portion N formed by the pressure contact with the pressure roller 102 via the belt 101. To play a role.

  A ceramic heater (hereinafter referred to as a heater) 104 as a heating source is fitted and supported in a groove formed along the longitudinal direction on the surface of the press contact member 107 on the nip portion N side. The heater 104 is basically composed of an elongated and thin plate-like ceramic substrate and a heating resistor layer provided on the surface of the substrate. The heater 104 is a low temperature that rises with a sudden rise characteristic when energized to the heating resistor layer. Heat capacity heater.

  A chip thermistor is provided on the substrate opposite to the heating resistor layer with the ceramic substrate interposed therebetween. The thermistor is adhesively fixed on an electrode pattern formed in advance by thick film printing on the opposite side of the region where the heating resistor exists, and monitors the temperature of the ceramic substrate. Furthermore, a thermistor is also provided at a position in the vicinity of the longitudinal end of the heating resistor layer. The thermistor is fixed to the substrate at a predetermined pressure by a pressing means such as a spring (not shown) in order to detect a temperature exceeding the heat resistance temperature of the adhesive.

  In the present embodiment, oil is applied to a lubricant (not shown) between the heater 104 and the belt 101. The oil is preferably a silicone oil that can be used in a high temperature environment.

(Belt pressure mechanism)
Next, a pressure mechanism (contact / separation mechanism) related to the pressure contact operation and the pressure release operation of the fixing device 100 will be described with reference to FIGS. 5 shows a state where the pressure roller 102 and the belt 101 are in pressure contact, and FIG. 6 shows a state where the pressure is released.

  As shown in FIG. 3, the belt 101 is supported by the fixing frame 115 via a stay 106 and a track regulating member 105 provided at both ends in the longitudinal direction. The pressure roller 102 is supported by the fixing frame 115 via pressure roller bearings 108 provided at both ends in the longitudinal direction.

  At the time of the pressure contact operation of the fixing device 100, as shown in FIG. 4, the belt 101 is supported by the pressure lever 112 via the track restricting member 105, and the rotation center shaft 111 (FIG. 3) is the center of rotation. The pressure roller 101 is pressed by the pressure spring 113 in a state where it can swing. In this embodiment, the applied pressure is 125 N on one end side in the longitudinal direction, and the total applied pressure (both end sides in the longitudinal direction) is 250 N.

  During the pressure release operation of the fixing device 100, as shown in FIG. 4, the pressure lever 112 is swung and rotated by the rotation operation of the cam 120 (FIG. 3) driven by the cam drive unit 90. Push up. As a result, the belt 101 and the pressure roller 102 are released from pressure (state shown in FIG. 6).

  This pressure release operation is performed in order to improve the operability of removing the jammed recording material when the recording material P is jammed while the recording material P is being conveyed at the nip portion N. Alternatively, it is performed so that no pressure contact mark is left on the belt 101 or the pressure roller 102 in a pressure contact state for a predetermined time or longer.

  Further, as shown in FIG. 4, a sensor flag 121 is provided on the same axis as the cam shaft 123 that is a support shaft of the cam 120 as means for detecting the pressure contact position and the pressure release position during the rotation of the cam 120. The sensor flag 121 rotates in synchronization with the rotation of the cam 120, and the rotation direction position is detected by the contact / separation sensor 122. The contact / separation sensor 122 transmits infrared light within the sensor, and the sensor flag 121 transmits a signal by blocking or transmitting the infrared light.

(Belt rubbing mechanism)
Next, in describing the belt rubbing mechanism of the present embodiment, first, the polishing sheet 150 as a rubbing member (rubbing sheet) for recovering the surface properties of the belt 101 will be described. The abrasive sheet 150 is a sheet provided with a rubbing layer formed by closely adhering abrasive grains as a rubbing material via an adhesive layer on a sheet-like base material. By making the rubbing member into a sheet shape, a cheaper rubbing member can be employed than when a roller-shaped rubbing member is employed, and a simpler rubbing member can be obtained. In the present embodiment, twill weave cloth is used as the base material, and white alundum (WA) having an average particle diameter of about 12 μm is used as the rubbing material.

  In addition, as the substrate, a substrate such as paper, plain woven fabric, or resin film can be used. Moreover, as a rubbing material, it is preferable to use a thing with an average particle diameter of 5 micrometers or more and 20 micrometers or less, and a rubbing member is manufactured by adhere | attaching the abrasive grain of this average particle diameter to a base material. For example, what uses the following materials in the range of this average particle diameter is mentioned. That is, examples include aluminum oxide, aluminum hydroxide oxide, silicon oxide, cerium oxide, titanium oxide, zirconia, lithium silicate, silicon nitride, and silicon carbide.

  Alternatively, an iron oxide, chromium oxide, antimony oxide, diamond, or a mixture of any of these abrasive grains may be used.

  Here, the particle size of the abrasive grains was 100 or more randomly extracted using a scanning electron microscope S-4500 (manufactured by Hitachi, Ltd.), and image processing analyzer Luzex3 (manufactured by Nireco Corporation). ) To calculate the number average particle size. For example, 100 or more abrasive grains randomly extracted from the polishing sheet 150 are peeled off from the polishing sheet 150 and measured.

  In the present embodiment, the configuration in which the abrasive sheet 150 is rubbed against the belt 101 by providing a rubbing layer on the surface of the abrasive sheet 150 that is in contact with the belt 101 is described as an example. It is good also as a structure which rubs 102. FIG. That is, the polishing sheet 150 may be configured to rub against the pressure roller 102 by providing a rubbing layer on the surface of the polishing sheet 150 on the side in contact with the pressure roller 102.

  Next, a mechanism for inserting or retracting the polishing sheet 150 with respect to the nip portion N will be described with reference to FIGS. The polishing sheet 150 is fixed to a polishing sheet holder 151 as a holding member that can be rotated and stopped in forward and reverse directions. Then, as shown in FIG. 7, when the polishing sheet holder 151 rotates in the direction of arrow A, a retracted state before being inserted into the nip portion N is obtained. FIG. 7 shows a state where the polishing sheet 150 is retracted, while FIG. 9 shows a state where the polishing sheet 150 is inserted into the nip portion N from the upstream side in the recording material conveyance direction.

  In FIG. 7, a rotation gear 152 is provided on the polishing sheet holder 151 that is rotatably supported on the rotation center shaft 102 a of the pressure roller 102. Then, as shown in FIG. 11, by operating a drive motor 154 as a drive source provided on the frame 115, the rotation gear 152 is rotated via the drive gear 153, and the polishing sheet holder 151 is rotated. Let

  As shown in FIG. 7, the polishing sheet holder 151 has a sensor flag portion 151a as means for detecting the insertion position and the retraction position during the rotation operation, and the rotation direction position is detected as the rotation position. Sensor 155 detects. The rotation position detection sensor 155 transmits infrared light in the sensor, and the sensor flag unit 151a transmits a signal by either shielding or transmitting the infrared light.

(Abrasion sheet nip insertion operation)
Next, an operation of inserting the polishing sheet 150 into the nip portion N will be described with reference to FIGS. In the state where the polishing sheet 150 shown in FIG. 7 is retracted, the belt 101 is first rotated by the rotation of the pressure roller 102. Next, when the drive motor 154 operates and the rotation gear 152 rotates in the direction of arrow A via the gear 153, the polishing sheet holder 151 rotates in the direction of arrow A.

  When the polishing sheet holder 151 rotates in the direction of arrow A, the tip of the polishing sheet 150 fixed to the polishing sheet holder 151 is directed in the direction of the nip portion N along the inlet guide 140 as shown in FIG. As the polishing sheet holder 151 further rotates and the polishing sheet 150 reaches the inlet of the nip portion N, the protrusion 151b of the inlet guide 140 contacts the polishing sheet holder 150 at the same time. As a result, as shown in FIG. 8, the inlet guide 140 rotates in the direction of arrow C around the rotation shaft 141 and closes the conveyance path of the recording material P upstream of the nip portion N.

  In the image forming apparatus according to the present exemplary embodiment, as illustrated in FIG. 1, the conveyance path from the image forming unit to the fixing device is in the vertical direction. In other words, it is provided such that the upstream end in the conveyance direction of the nip portion N is located below the downstream end of the nip portion N in the direction of gravity. For this reason, scraping powder on the surface layer of the belt 101 generated by the polishing of the polishing sheet 150 or paper powder adhering to the belt 101 peeled off by polishing of the polishing sheet 150 is between the image forming portion and the nip portion N. There is a risk of falling into the conveyance path of the recording material P. The inlet guide 140 prevents this.

  In other words, the inlet guide 140 is arranged such that when the rubbing process by the polishing sheet 150 is performed in the image forming apparatus in which the upstream end in the transport direction of the nip portion N is located below the downstream end in the transport direction of the nip portion N. It is located at a position that covers the upstream end of the conveyance direction of the part N. As a result, the inlet guide 140 located at the guide position when the paper is passed functions as a cover member that covers the upstream end of the nip portion N in the transport direction during the rubbing.

  Thereafter, as shown in FIG. 9B, the leading end position of the polishing sheet 150 is located upstream of the center position Nc of the nip portion N in the transport direction of the recording material P (for example, the central position in the recording material transport direction). At that position, the polishing sheet 150 is fixed. That is, when the tip of the polishing sheet 150 reaches the predetermined position, the sensor flag portion 151a of the polishing sheet holder 151 blocks light reaching the rotation position detection sensor 155. As a result, a signal is transmitted, and the drive motor 154 that rotates the polishing sheet holder 150 is stopped.

(Rubbing operation with abrasive sheet)
In the present embodiment, during the rubbing process, the polishing sheet 150 is inserted and fixed in a partial region in the recording material conveyance direction in the nip portion. Then, the belt 101 is rubbed on the surface of the belt 101 while the belt 101 is rotated by the rotation of the pressure roller in a region excluding the partial region in the nip portion.

(Retraction operation of polishing sheet)
In the state where the polishing sheet 150 is inserted into the nip portion N as shown in FIG. 9, at the time of non-rubbing processing, the rotation of the belt 101 which has been driven and rotated is stopped by first stopping the rotation of the pressure roller 102. To do. Then, as shown in FIG. 10, the belt 101 and the pressure roller 102 move from a pressure contact (contact state) state to a pressure release state (separation state).

  Next, when the drive motor 154 operates and the rotation gear 152 rotates in the arrow B direction via the gear 153 as shown in FIG. 10, the polishing sheet holder 151 rotates in the arrow B direction. Thereafter, when a signal is transmitted by the sensor flag portion 151a of the polishing sheet holder 151 being transmitted through the rotation position detection sensor 155, the polishing sheet holder 151 is rotated by a predetermined amount, and the polishing sheet 150 is stopped at the retracted position. Let Further, the entrance guide 140 rotates in the direction of arrow D about the rotation shaft 141 when the projection 151b contacts the polishing sheet holder 150, and returns to a position where the recording material P can be introduced into the nip N. It is.

  In order to provide a high-quality image with reduced gloss difference due to durability while maintaining quick start and energy saving in a free belt type fixing device, the surface property of the belt must be uniform. desirable. However, in the conventional free belt type fixing device, when the rubbing member is brought into contact with the entire sheet passing area of the fixing belt, the contact pressure of the rubbing member escapes in the sheet passing area, and the rubbing member is rubbed. There was a situation where the member could not contact the fixing belt uniformly.

  This is because the track regulating member for guiding the inner peripheral surface of the belt end is provided, the contact pressure of the rubbing member is concentrated in the paper passing area near the belt end guided by the track regulating member, This is because the contact pressure of the rubbing member escapes in the paper passing area without the track regulating member. That is, since the rubbing member cannot uniformly contact the fixing belt, rubbing unevenness occurs, and it is difficult to uniformly recover the surface property of the belt.

  In contrast, according to the present embodiment, in the fixing device of the free belt type, the abrasive sheet 150 is fixedly provided in a partial region in the recording material conveyance direction in the nip portion, and the recording material conveyance direction in the nip portion is fixed. The belt is driven by the rotation of the pressure roller in an area excluding the partial area. For this reason, in the present embodiment, the polishing sheet 150 can uniformly abut against the entire sheet passing area of the belt 101. Then, the surface property of the belt 101 can be recovered uniformly.

  Further, in this embodiment, the member that contacts the belt for the rubbing process is only the polishing sheet 105 having a smaller heat capacity than the roughing roller (metal roller), and therefore, the influence on shortening the warm-up is small.

  Furthermore, in this embodiment, when the polishing sheet 150 is inserted into the nip portion N, the inlet guide 140 can be rotated by the polishing sheet holder 151 to block the recording material P conveyance path upstream of the nip N. Accordingly, it is possible to prevent the rubbing residue on the surface layer of the belt 101 generated by the rubbing of the polishing sheet 150 from entering the transfer portion or the like upstream of the nip portion N. Therefore, it is possible to prevent the occurrence of image defects due to foreign matter mixing from the fixing device to the transfer unit or the like.

<< Second Embodiment >>
In the first embodiment, an example of a configuration in which the polishing sheet 150 is provided as a rubbing member having a rubbing surface that changes the surface properties of one of the first and second rotating bodies has been described. Specifically, a rubbing layer was provided on one surface of the polishing sheet 150 (the surface facing the belt 101), and used as means for recovering the surface properties of the belt 101. However, a rubbing layer may be provided on both surfaces of the polishing sheet 150. Thereby, by inserting / retracting one polishing sheet 150 into / from the nip portion N, the surface properties of both the belt 101 and the pressure roller 102 can be recovered simultaneously.

  In order to improve the gloss of the double-sided image, it is desirable to make the surface properties of not only the belt 101 but also the pressure roller 102 uniform. In this case, providing roughening rollers for each of the belt 101 and the pressure roller 102 increases the number of members in contact with each other and increases the heat capacity, which may impair the effect of shortening the warm-up using the belt. However, in the present embodiment, it is possible to provide a fixing device capable of fixing a high-quality image with reduced gloss difference caused by durability while maintaining quick start performance and energy saving performance.

(Modification)
In the above-described embodiment, the preferred embodiment of the present invention has been described. However, the present invention is not limited to this, and various modifications can be made within the scope of the present invention.

(Modification 1)
In the embodiment described above, the rubbing process is performed on the fixing belt, or the fixing belt and the pressure roller, but may be a pressure roller. Further, it may be a fixing roller, or a fixing roller and a pressure roller.

(Modification 2)
In the embodiment described above, the heater is used as the heating member that heats the nip portion via the rotatable fixing member, but the present invention is not limited to this. For example, a fixing member that can rotate by electromagnetic induction using an exciting coil or by energization may generate heat.

(Modification 3)
In the above-described embodiment, the endless belt is provided on the first rotating body among the first rotating body and the second rotating body forming the fixing nip portion, but the endless belt is the first rotating body. You may provide in both a rotary body and a 2nd rotary body.

(Modification 4)
In the above-described embodiment, the sheet P as a recording material on which a toner image is formed is a sheet material such as a transfer sheet, electrostatic recording paper, OHP sheet, printing paper, and format paper. It is a waste. That is, it includes plain paper, resin-made sheets that are substitutes for plain paper, cardboard, overhead projectors, and the like. More specifically, for example, regular or irregular plain paper, thick paper, thin paper, envelope, postcard, seal, resin sheet, OHP sheet, glossy paper, and the like are included. In the embodiment described above, for the sake of convenience, the recording material (sheet) P has been described using terms such as passing paper, but the recording material in the present invention is not limited to paper.

(Modification 5)
In the above-described embodiment, an apparatus for fixing an unfixed toner image on a sheet has been described as an example. However, the present invention is not limited to this. In order to improve the gloss of the image, the present invention can be similarly applied to a device (also referred to as a fixing device in this case) that heats and presses a toner image supposedly attached to a sheet.

101..Fusing belt (first rotating body), 102..Pressure roller (second rotating body), 150..Abrasive sheet

Claims (12)

First and second rotating bodies that form a nip portion for nipping and conveying a recording material carrying a toner image;
A heating member for heating the nip portion;
A rubbing sheet that is inserted into a partial region in the recording material conveyance direction in the nip portion and has a rubbing surface that changes a surface property of at least one of the first and second rotating bodies;
A fixing device.   The first rotating body is an endless fixing belt, the second rotating body is rotationally driven by a driving source, and the first rotating body is driven and rotated by the second rotating body. The fixing device according to claim 1.   The first rotating body is a fixing roller, the second rotating body is rotationally driven by a driving source, and the first rotating body is driven and rotated by the second rotating body. Item 4. The fixing device according to Item 1.   When the rubbing process is performed, the rubbing sheet inserted in the partial area is fixed in a state where the first and second rotating bodies rotate in an area excluding the partial area in the nip portion. The fixing device according to any one of claims 1 to 3, wherein   5. The rubbing sheet is inserted from an upstream side in the recording material conveyance direction in the nip portion, and a leading end position is fixed at a central position in the recording material conveyance direction in the nip portion. The fixing device according to any one of the above. The fixing device is a device that is attached to the image forming apparatus such that the upstream end in the transport direction of the nip portion is positioned below the downstream end in the transport direction of the nip portion.
6. The fixing device according to claim 1, further comprising a member positioned at a position that covers an upstream end in a conveyance direction of the nip portion when the rubbing process is performed by the rubbing sheet. .   The fixing device according to claim 1, wherein the rubbing sheet is fixed to a holding member that can be rotated and stopped in the forward and reverse directions.   The fixing device according to claim 7, wherein a rotation axis of the holding member coincides with a rotation axis of the second rotating body.   And a contact / separation mechanism that forms a contact state in which the first rotating body contacts the second rotating body and a separated state in which the first rotating body is separated from the second rotating body. The fixing device according to any one of claims 1 to 8. The rubbing sheet is fixed to a holding member capable of rotating and stopping in the forward and reverse directions,
During the rubbing process, the rubbing sheet is inserted into the partial area in the contact state,
The fixing device according to claim 9, wherein the rubbing sheet is retracted from the partial area in the separated state during the non-rubbing process.   The said rubbing sheet has the 1st and 2nd rubbing surface which changes each surface property of the said 1st and 2nd rotary body, The any one of Claim 1 thru | or 10 characterized by the above-mentioned. The fixing device described. A slide inserted in a partial area of the nip portion in the recording material conveyance direction, which is used in a fixing device including first and second rotating bodies that form a nip portion for nipping and conveying a recording material carrying a toner image. A rubbing sheet,
A rubbing sheet comprising a rubbing surface facing at least one surface of the first and second rotating bodies.