JP2017021320A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the occurrence of an abnormal image by properly restoring the state of a surface of a fixing belt 24.SOLUTION: There is provided a fixing device 20 comprising a fixing belt 24 that is heated by a heating roller 21, and a pressure roller 23 that is arranged to be capable of pressing at least part of the fixing belt 24 to form a nip part between the fixing belt 24 and pressure roller 23; and conveys a recording medium P carrying an unfixed toner image T to the nip part to fix the unfixed toner image T to the recording medium P, the fixing device 20 including a rubbing member 30 that rubs a surface of the fixing belt 24, a surface state detection sensor 32 that detects the state of the surface of the fixing belt 24, and control means 35 that causes the rubbing member 30 to execute an operation to rub the fixing belt 24 in two or more different execution times according to a result of detection performed by the surface state detection sensor 32.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a fixing device and an image forming apparatus.

  Various image forming apparatuses using an electrophotographic system have been devised as image forming apparatuses such as copying machines, facsimiles, and printers, and are well-known techniques. In the image forming process, an electrostatic latent image is formed on the surface of the photosensitive drum as an image carrier, and the electrostatic latent image on the photosensitive drum is developed with a toner as a developer to be visualized and developed. The image is transferred to a recording material (also called a recording medium, paper, or recording paper) by a transfer device to carry the image, and the unfixed toner image on the recording material is fixed by a fixing device using pressure, heat, or the like. It is established.

  Various types of fixing devices have been proposed. For example, a fixing roller disposed opposite to a pressure roller, and an endless fixing belt (fixing) stretched between the fixing roller and the heating roller. A non-fixed toner image is applied to the recording material by applying heat of the heating roller to the recording material through the fixing belt at a nip portion formed by pressure contact between the pressure roller and the fixing belt. A belt fixing method in which pressure is applied and fixed is known.

  In such a fixing device, the surface of the fixing member may be roughened by the edge portion of the recording material as the recording material is conveyed to the nip portion. A portion (hereinafter, referred to as roughness or surface roughness) becomes a streak and appears as a glossy streak on the image, which may result in an abnormal image.

  On the other hand, there are known a rubbing member and a polishing member that reduce the surface roughness of the fixing member by rubbing and polishing the surface of the fixing member to restore the surface state of the fixing member.

  As a fixing device including an abrasive member, for example, Patent Document 1 discloses an endless fixing belt, a pressure roller that presses against the endless fixing belt and forms a nip portion that fixes toner on a transfer sheet, A fixing device is disclosed that includes a separating unit that contacts the surface of the endless fixing belt and prevents the transfer paper from being wound around the endless fixing belt, and a polishing unit that polishes the surface of the endless fixing belt.

  As a control of the polishing operation by the polishing member, Patent Document 2 discloses a fixing device that counts the number of sheets of recording material to be passed and performs the polishing operation at a timing when the predetermined number of sheets is reached.

  By the way, the ease of formation of roughness on the surface of the fixing member by the edge portion of the recording material depends on the cutting state of the recording material. That is, when the recording material is cut, burrs are generated at the edge portion of the recording material, but when cutting is performed such that the edge portion has burrs (large burrs), the burrs at the edge portions form the fixing member. Rough conditions will change.

  When a recording material that has burrs at the edge (hereinafter referred to as edge disadvantaged paper) is passed, the roughness becomes severe, and when a recording material that has small burrs at the edge is passed. Roughness is difficult to form.

  In Patent Document 3, the rubbing mode is executed at an execution interval corresponding to the type of sheet, that is, the burr height, thereby preventing the execution of unnecessary rubbing mode and preventing uneven glossiness of the output image. An image heating apparatus configured as described above is disclosed.

  In order to prevent the formation of roughness on the surface of the fixing member due to burrs on the edge of the recording material, a deburring device that removes burrs on the edge has been proposed. It is difficult to lose, and the cost is enormous.

  In recent years, in the field of commercial printing, high speed and high image quality are progressing, and it is required to support various recording materials. For this reason, for example, when a recording material such as a transparent film and a special recording material having an edge burr are passed, roughening of the fixing member is likely to be formed. Further, roughening of the fixing member is easily formed by passing the paper at a high speed.

  As described above, the surface of the fixing member is likely to be rough due to the passage of the edge disadvantageous paper or the special paper having a large burr and the increase in the speed of the fixing device. Even if the rubbing operation is performed after the surface roughness of the fixing member becomes very rough, the surface state cannot be sufficiently recovered. Moreover, in order to fully recover the surface state, a long rubbing operation has been required.

  In Patent Document 3, the rubbing mode is executed at an execution interval corresponding to the type of sheet, but there remains room for examination in the execution timing and execution time of the rubbing operation.

  Accordingly, the present invention provides a fixing device capable of appropriately recovering the surface state of the fixing member and suppressing the occurrence of abnormal images by performing the rubbing operation of the fixing member at an appropriate timing and execution time. For the purpose.

  In order to achieve such an object, a fixing device according to the present invention is arranged so that a fixing member heated by a heating unit and at least a part of the fixing member can be pressed, and a nip portion is formed between the fixing member and the fixing member. In a fixing device that transports a recording material carrying an unfixed toner image to the nip portion and fixes the unfixed toner image on the recording material, the surface of the fixing member is slid. A rubbing member for rubbing, a surface state detecting means for detecting the surface state of the fixing member or the recording material, and the rubbing member at two or more different execution times according to the detection result by the surface state detecting means. Control means for executing a rubbing operation of the fixing member.

  According to the present invention, it is possible to appropriately recover the surface state of the fixing member and suppress the occurrence of abnormal images.

1 is a schematic configuration diagram showing an embodiment of an image forming apparatus according to the present invention. 1 is a schematic configuration diagram showing an embodiment of a fixing device according to the present invention. FIG. 6 is an explanatory diagram of detection of a surface state of a fixing belt by a surface state detection sensor. It is a graph which shows the relationship between the number of passing sheets and the belt surface roughness when each recording material of plain paper, plain paper (unfavorable paper) and special paper is passed. 6 is a graph showing the relationship between the number of sheets passing and the belt surface roughness when the fixing speed is different. 6 is a graph showing the relationship between the sensor output value and the surface roughness of the fixing belt. It is a graph which shows the relationship between the number of integrated paper passing and a sensor output value. It is a schematic block diagram (1) which shows the other example of a fixing device. It is a schematic block diagram (2) which shows the other example of a fixing device. It is a graph which shows the relationship between the sheet passing number by the difference in nip surface pressure, and belt surface roughness. It is a schematic block diagram which shows other embodiment of a fixing device. It is explanatory drawing of the detection of the surface state of a recording medium by a surface state detection sensor. It is a graph which shows the relationship between the sensor output value of a surface state detection sensor, and belt surface roughness. It is a graph which shows the relationship between the cumulative number of sheets passed and the belt surface roughness.

  Hereinafter, the configuration according to the present invention will be described in detail based on the embodiment shown in FIGS.

[First Embodiment]
(Image forming device)
An image forming apparatus according to an embodiment of the present invention will be described with reference to FIG. Examples of the image forming apparatus include an embodiment that forms an image using toner, such as a printer, a copying machine, and a fax machine, and a fixing apparatus that fixes a toner image (unfixed image) formed on a sheet as a recording medium. Is provided.

  FIG. 1 is a schematic configuration diagram showing an image forming apparatus main body 100 of the present embodiment. The image forming apparatus main body 100 of the present embodiment is a tandem type intermediate transfer type, and includes a sheet feed table 200 having a sheet feed tray 44 at a lower portion.

  Further, inside the image forming apparatus main body 100, a tandem type intermediate transfer type tandem type image forming unit 11 in which a plurality of image forming units 18Y, 18M, 18C, and 18K are arranged in parallel is provided. Subscripts Y, M, C, and K attached to these symbols indicate yellow, magenta, cyan, and black colors, respectively.

  The image forming apparatus main body 100 is provided with an endless belt-like intermediate transfer member (hereinafter referred to as an intermediate transfer belt) 10 near the center. The intermediate transfer belt 10 is supported by being wound around a plurality of rollers 14, 15, 15 ′, 16, etc., and can be rotated and conveyed clockwise in FIG. 1.

  In the configuration example of FIG. 1, a cleaning device 17 for the intermediate transfer belt is provided on the downstream side in the rotation direction of the intermediate transfer belt 10 of the secondary transfer counter roller 16 which is one of such support rollers. The cleaning device 17 removes residual toner remaining on the intermediate transfer belt 10 after image transfer.

  The upper part of the intermediate transfer belt 10 that is stretched between the support roller 14 and the support roller 15 has four colors of yellow (Y), magenta (M), cyan (C), and black (K) along the conveyance direction. Image forming means 18Y, 18M, 18C, 18K are arranged. The symbol is abbreviated as 18 (Y, M, C, K) below.

  In this way, the four image forming means 18 (Y, M, C, K) are arranged side by side to constitute the tandem image forming unit 11 as described above. Each image forming means 18 (Y, M, C, K) of the tandem type image forming unit 11 is a photosensitive drum 40 (image bearing member for carrying toner images of yellow, magenta, cyan, and black). Y, M, C, K).

  Two exposure devices 12 are provided on the tandem image forming unit 11 as shown in FIG. Each exposure device 12 is provided corresponding to two image forming means (18Y and 18M, 18C and 18K). Each exposure device 12 includes, for example, a light source device such as a semiconductor laser, a semiconductor laser array, or a multi-beam light source, a coupling optical system, a common optical deflector such as a polygon mirror, and two scanning imaging optical systems. Is an optical scanning exposure apparatus. Each exposure device 12 exposes each photosensitive drum 40 (Y, M, C, K) according to the image information of each color of yellow, magenta, cyan, and black to form an electrostatic latent image.

  Further, the following members are provided around the photosensitive drum 40 (Y, M, C, K) of each image forming unit 18 (Y, M, C, K). It includes a charging device that uniformly charges each photosensitive drum prior to exposure, a developing device that develops the electrostatic latent image formed by exposure with toner of each color, and a photosensitive device that removes transfer residual toner on the photosensitive drum. And a body cleaning device.

  Further, primary transfer rollers 62 (Y, M, C, K) are provided at primary transfer positions for transferring toner images from the respective photosensitive drums 40 (Y, M, C, K) to the intermediate transfer belt 10. Yes. The primary transfer rollers 62 (Y, M, C, K) are provided so as to face the respective photosensitive drums 40 (Y, M, C, K) with the intermediate transfer belt 10 interposed therebetween, and serve as primary transfer means. It becomes a component.

  Among the plurality of support rollers that support the intermediate transfer belt 10, the support roller 14 is a drive roller that rotationally drives the intermediate transfer belt 10, and is connected to a motor via a drive transmission mechanism (not shown) such as a gear, a pulley, or a belt. Has been. Further, when a black single color image is formed on the intermediate transfer belt 10, the support rollers 15 and 15 'other than the support roller 14 are moved by a moving mechanism (not shown), and the photosensitive drum 40 (Y, M , C) can be separated from the intermediate transfer belt 10. In addition, the backup roller 63 is also provided as a supporting roller.

  A secondary transfer device 13 is provided on the opposite side of the intermediate transfer belt 10 from the tandem image forming unit 11. In the example of FIG. 1, the secondary transfer device 13 applies the transfer electric field by pressing the secondary transfer roller 16 ′ against the secondary transfer counter roller 16, thereby converting the image on the intermediate transfer belt 10 into a sheet shape. Transfer to a sheet of recording medium.

  In addition, a fixing device 20 for fixing the transfer image on the paper is provided beside the secondary transfer device 13. The sheet on which the image has been transferred by the secondary transfer device 13 is conveyed to the fixing device 20 by a conveyance belt 38 supported by two rollers 37. Of course, the conveyance belt 38 may be a fixed guide member, a conveyance roller, a conveyance roller, or the like.

  Further, in the example of FIG. 1, a sheet reversing device 39 that reverses and conveys the sheet so as to record images on both sides of the sheet is provided below the tandem image forming unit 11, the secondary transfer device 13, and the fixing device 20. Yes.

  Further, the conveyance of the paper is performed as follows. First, one of the paper feed rollers 42 of the paper feed table 200 is selectively rotated to feed the paper from one of the paper feed trays 44 provided in multiple stages in the paper bank 43. The fed paper is separated one by one by the separation roller 45 and introduced into the paper feed path 46, conveyed by the conveyance roller pair 47, and guided to the paper feed path 48 in the image forming apparatus main body 100. After that, it is abutted against the positioning roller (registration roller) pair 49 and stopped.

  When using the manual feed tray 51, the paper feed roller 50 is rotated to feed out the paper on the manual feed tray 51. The fed paper is separated one by one by the separation roller 52 and then fed manually. The paper is introduced into the paper path 53 and stopped in contact with the positioning roller pair 49 in the same manner.

  Thereafter, the positioning roller pair 49 is rotated in synchronization with the formation of the full-color toner image on the intermediate transfer belt 10, and the sheet is sent to the secondary transfer position between the intermediate transfer belt 10 and the secondary transfer roller 16 ′. . Then, the full-color toner image on the intermediate transfer belt 10 is collectively transferred onto the paper.

  The sheet on which the toner image has been transferred is conveyed by the conveying belt 38 and sent to the fixing device 20. After the toner image transferred by heat and pressure is fixed by the fixing device 20, the discharge roller is fixed. 56 is discharged onto the paper discharge tray 57 and stacked.

  In the case of double-sided copying, a sheet with an image fixed on one side is introduced into the sheet reversing device 39 and reversed, and then guided again to the secondary transfer position, where the image is also transferred to the back side and fixed by the fixing device 20. Then, the paper is discharged onto a paper discharge tray 57 by a discharge roller 56.

(Fixing device)
The fixing device according to the present embodiment is provided with a fixing member (fixing belt 24) heated by a heating unit (heater 25 of the heating roller 21) and at least a part of the fixing member so as to be pressed. A pressure member (pressure roller 23) that forms a nip portion therebetween, and transports a recording material (recording medium P) carrying an unfixed toner image (unfixed toner image T) in the nip portion; In a fixing device (fixing device 20) for fixing the unfixed toner image on a recording material, a rubbing member (rubbing member 30) for rubbing the surface of the fixing member and a surface state detection for detecting the surface state of the fixing member Means (surface state detection sensor 32), and control means (control means 35) for executing the rubbing operation of the fixing member by the rubbing member at two or more different execution times according to the detection result by the surface state detection means, Have In addition, the code | symbol in embodiment and the example of application are shown in a parenthesis.

  FIG. 2 shows an example of the fixing device 20, and is a schematic sectional view in the axial direction of the fixing roller 22.

  The fixing device 20 includes a heating roller 21, a fixing roller 22, a fixing belt 24 stretched between the heating roller 21, the fixing roller 22, and the tension roller 27, and the fixing roller 22 by pressing the fixing roller 22. A pressure roller 23 for forming a nip portion is provided. The heating roller 21 has a heater 25 as a heat source, and the pressure roller 23 has a heater 26 as a heat source.

  The fixing device 20 heats the recording medium P carrying the unfixed toner image T through the nip portion between the fixing belt 24 and the pressure roller 23 formed by the pressure contact between the fixing roller 22 and the pressure roller 23. Fixing is performed. The heating roller 21, the fixing roller 22, and the pressure roller 23 are pivotally supported so as to be rotatable in the longitudinal direction of the casing of the fixing device 20, and the driving means and the like of each roller are fixedly held on the casing.

  The recording medium P that has passed through the nip portion is separated at its leading end by a separation plate 28 disposed on the fixing roller 22 side or a separation plate 29 disposed on the pressure roller 23 side, and is discharged to the next process. The separation plates 28 and 29 as separation members disposed on the fixing roller 22 side and the pressure roller 23 side are not limited to plate-like members, and separation claws may be used.

  The heating roller 21 is a thin cylindrical body made of, for example, a metal material, and a heater 25 as a heat source is fixed inside the cylindrical body. As the heater 25, for example, a halogen heater or a carbon heater can be used. Further, both end portions of the heater 25 are fixed to the casing of the fixing device 20. The heater 25 may be induction heating means (IH heating means) for heating the heating roller 21 from the outside.

  The output of the heater 25 is controlled by a power supply unit (AC power supply) of the apparatus main body, and the heating roller 21 is heated by the radiant heat from the heater 25. Further, heat is applied to the unfixed toner image T on the recording medium P from the surface of the fixing belt 24 heated by the heating roller 21. The output control of the heater 25 is performed based on the detection result of the belt surface temperature by the temperature sensor 31 such as a thermopile provided at a position facing the surface of the fixing belt 24. The installation position and the number of installation of the temperature sensor are not limited to this, and a temperature sensor for detecting the temperature of the pressure roller 23, a temperature sensor for detecting the temperature of the fixing roller 22, and the like are provided, and based on this, a heater is provided. 25 and 26 may be controlled.

  The fixing belt 24 is wound around the fixing roller 22 and the heating roller 21, and is in close contact with the heating roller 21 and the fixing roller 22. The fixing nip portion is configured by pressing the pressure roller 23 against the fixing belt 24 configured as described above at a position corresponding to the fixing roller 22.

  The fixing belt 24 is, for example, an endless belt having a multilayer structure in which an elastic layer such as silicone rubber and a release layer are sequentially laminated on a base layer made of PI (polyimide) resin and having a layer thickness of 90 μm.

  The elastic layer of the fixing belt 24 has a layer thickness of about 200 μm and is formed of an elastic material such as silicone rubber, fluorine rubber, and foamable silicone rubber. The release layer of the fixing belt 24 has a layer thickness of about 20 μm and is formed of PFA (tetrafluoroethylene perfluoroalkyl vinyl ether copolymer resin), polyimide, polyetherimide, PES (polyether sulfide), or the like. ing. By providing the release layer on the surface layer of the fixing belt 24, the releasability (peelability) for the toner (toner image) is ensured.

  The fixing belt 24 is composed of, for example, a PI belt, which is an endless film of a heat-resistant resin having a thickness of 90 μm, and the surface layer has an anti-offset agent such as PFA (tetrafluoroethylene perfluoroalkyl vinyl ether copolymer resin). Is coated.

  The fixing roller 22 does not have a heat source, and is formed by covering a highly rigid core material (core metal) such as metal (iron or aluminum) with a thick elastic layer such as silicone rubber.

  Similar to the fixing roller 22, the pressure roller 23 is a roller member in which an elastic layer such as fluorine rubber, silicone rubber, and foamable silicone rubber is formed on a core metal such as SUS304. A heater 26 as a heat source is fixed inside the cylindrical body. In addition, it is good also as a structure which does not have the heater 26. FIG.

  The fixing roller 22 and the pressure roller 23 are rubber rollers arranged to face each other. When the pressure roller 23 is pressed toward the center of the fixing roller 22 via the fixing belt 24, the pressure roller 23. And a fixing belt 24 form a nip portion. Further, the nip width can be controlled by controlling the pressing force (pressing force) of the pressure roller 23 toward the fixing roller 22.

  The control unit 35 is a controller that executes various controls of the fixing device 20. The control unit 35 controls the driving unit that drives the fixing roller 22 to rotate the fixing roller 22 in the clockwise direction. As the fixing roller 22 rotates, the pressure roller 23 and the fixing belt 24 that are in pressure contact with the fixing roller 22 rotate at the same speed.

  Further, a rubbing member 30 that is pressed against the fixing belt 24 with a predetermined pressure and rotates as the fixing belt 24 rotates is provided on the outer peripheral surface of the fixing belt 24.

  The rubbing member 30 is urged by the fixing belt 24 to rub and polish the surface of the fixing belt 24 to restore the surface property of the fixing belt 24 to obtain a surface state suitable for fixing. The rubbing member 30 has, for example, a surface layer having a predetermined roughness on a metal core, and the surface layer has a concavo-convex shape on the order of several tens of μm, for example, and the surface roughness is the surface of the fixing belt 24. Greater than roughness.

  The rubbing member 30 is preferably capable of modifying the surface state over the entire region in the direction (axial direction) orthogonal to the conveying direction of the surface of the fixing belt 24. At this time, the rubbing member 30 may be provided in the entire area in the axial direction, or the rubbing member 30 having a predetermined length may be provided with a driving means that can move in the axial direction so that the desired position in the axial direction is provided. By making it movable, the surface state may be modified over the entire region in the axial direction. It should be noted that it may be provided so that the surface state of at least the passage region of the edge portion can be modified according to the width of the recording medium P to be passed.

  The rubbing member 30 includes driving means controlled by the control means 35, and is rotationally driven with a predetermined linear velocity difference from the fixing belt 24 in the forward direction or the reverse direction of the fixing belt 24. The The rubbing member 30 is preferably separable from the fixing belt 24.

  The surface state detection sensor 32 is a surface state detection unit that detects the surface property of the fixing belt 24 in an area (edge portion) where at least the edge portion of the recording medium P passes. Since the edge portion varies depending on the size of the recording medium P, detection at a plurality of edge portions is possible. Further, the surface state detection sensor 32 can detect the surface properties of both the edge portion and the sheet passing region (also referred to as a non-edge portion or a sheet passing portion) that is a passing region excluding the edge portion of the recording medium P. Is preferred.

  As the surface state detection sensor 32, for example, an optical sensor including a light emitting unit and a light receiving unit that detects reflected light from the fixing belt 24 with respect to light emission from the light emitting unit can be used. The surface state detection sensor 32 may be any sensor that can detect the surface property of the fixing belt 24 and is not limited to an optical sensor. Further, the installation position in the rotation direction of the fixing belt 24 is not limited to the example of FIG.

  A configuration example of an optical sensor that is the surface state detection sensor 32 will be described. 3A and 3B, each of an area (edge portion) through which the edge portion of the recording medium P passes and a paper passing area (non-edge portion) that is a passing area excluding the edge portion of the recording medium P are shown. An example of the surface state of the fixing belt 24 is shown.

  The surface state detection sensor 32 detects reflected light Lr from the surface of the fixing belt 24 with respect to the incident light Li generated by light emission. In the non-edge portion having a smooth surface, there is little diffused light, and in the edge portion having a rough surface, the ratio of the diffused light Ld is increased. Therefore, the surface roughness of the fixing belt 24 can be detected based on the intensity of the reflected light Lr with respect to the light emitted from the surface state detection sensor 32.

  An example of the detection method will be described. The detection result in the region through which the edge portion of the recording medium P passes becomes the sensor output that detects the reflected light Lr1 shown in FIG. Further, the detection result in the paper passing area is a sensor output that detects the reflected light Lr2 shown in FIG.

  Here, the image defect due to the edge portion of the recording medium P is caused by the surface of the fixing belt 24 being roughened by the edge portion of the recording medium P, and the surface state of the fixing belt 24 being different between the edge portion and the sheet passing area. This occurs when the gloss changes between the fixed image portion in contact with the edge portion and the fixed image portion in contact with the sheet passing area.

  Therefore, by calculating the difference between the reflected light Lr1 and the reflected light Lr2, the surface state of the fixing belt 24 that can cause image defects can be detected.

  Although the example in which the roughness of the surface of the edge portion of the fixing belt 24 is detected from the difference in reflected light in both the edge portion and the sheet passing area has been described, the edge of the fixing belt 24 is determined only from the detection value for the edge portion. You may detect the roughness of the surface of a part.

  In the example of the optical sensor in FIG. 3, the detection value of the reflected light Lr1 from the edge portion is lower as the surface of the fixing belt 24 is rougher and the sensor output value is lower. However, the sensor output value is higher as the surface is rougher. A sensor configuration may be used.

  The tension roller 27 has a role of giving a certain tension to the fixing belt 24 stretched between two roller members, and is formed of, for example, a cylindrical aluminum tube. In the example of FIG. 2, the tension roller 27 is provided on the inner peripheral side of the fixing belt 24, but may be provided on the outer peripheral side of the fixing belt 24.

  It is also preferable to provide a cleaning unit around the fixing belt 24 for removing residual toner remaining on the surface of the fixing belt 24. Further, the fixing device 20 shown in FIG. 2 is an example of a fixing device capable of executing the rubbing control described below, and the configuration of the fixing device 20 is not limited to this.

(Rubbing control)
Next, the rubbing control by the fixing device 20 according to the present embodiment will be described.

  As described above, in commercial image forming apparatuses that have recently been increased in speed, special paper and the surface of the fixing belt 24 are more likely to be damaged by burrs on the surface of the fixing belt 24 due to its fixing speed. When the paper is passed after the surface becomes extremely rough, the surface roughness of the fixing belt 24 is difficult to recover even if the rubbing operation is executed with the same rubbing operation time as before, and the rubbing for a long time. Is becoming necessary.

  Therefore, in the fixing device 20 according to the present embodiment, the surface roughness of the fixing belt 24 is reduced from the edge portion to the non-edge by executing the rubbing operation at short intervals and for a short time in addition to the conventional rubbing operation. It controls to keep the state close | similar to a part equally. Details will be described below.

  This rubbing control is executed by the control means 35 (controller) of the fixing device 20. The controller is composed of a microcomputer including a CPU, ROM, RAM, I / O interface and the like. In this embodiment, the control unit 35 is provided in the fixing device 20, but is not limited thereto, and may be provided in the image forming apparatus main body 100.

  Edge disadvantageous papers include plain paper that has a high burr height and number of burrs (referred to as plain paper (disadvantaged paper)) and special paper such as transparent media with high hardness.

  FIG. 4 is a graph showing the relationship between the number of sheets to be passed and the surface roughness of the fixing belt 24 (belt surface roughness) when the recording materials of plain paper, plain paper (unfavorable paper), and special paper are passed. is there.

  As shown in FIG. 4, there is a correlation between the type of the recording material and the belt surface roughness, and the transition of the belt surface roughness changes each time the number of sheets to be passed is overlapped depending on the recording material to be passed. As shown in FIG. 4, it can be said that special paper, plain paper (unfavorable paper), and plain paper are likely to be rough in this order.

  FIG. 5 is a graph showing the relationship between the number of sheets passing and the belt surface roughness when the fixing speed (linear speed) is different.

  As shown in FIG. 5, there is a correlation between the fixing speed and the belt surface roughness, and when a certain number of sheets are passed by an apparatus having a high fixing speed, the belt surface roughness becomes rough at an early stage.

  Even if the rubbing operation by the rubbing member 30 is performed after the surface roughness becomes very rough, the surface state of the fixing belt 24 can be sufficiently recovered because the polishing is insufficient in a short operation time. In some cases, glossy streaks on the image remain. Further, it is not preferable to take one rubbing operation for a long time because it leads to an increase in unnecessary rubbing operation.

  Therefore, in the fixing device 20 according to the present embodiment, the occurrence of abnormal images is prevented by executing a rubbing operation in a short time before the surface roughness of the fixing belt 24 becomes difficult to recover. is there. Specifically, the fixing device 20 includes the surface state detection sensor 32 described above, and determines the rubbing operation time from two or more different rubbing operation times according to the detection result.

  FIG. 6 is a diagram showing the relationship between the sensor output value of the surface state detection sensor 32 and the surface roughness of the fixing belt 24. Each sensor output value and the surface roughness at that time are plotted and linearly approximated. The graph is shown. As shown in FIG. 6, the sensor output value of the surface state detection sensor 32 and the surface roughness of the fixing belt 24 are correlated. A sensor output value V (also referred to as an output value) in FIG. 6 is a difference between the detection values of the reflected light Lr1 and the reflected light Lr2.

  Therefore, in the fixing device 20 according to the present embodiment, the optimum rubbing operation execution timing and rubbing operation execution time are determined according to the detection result (sensor output value) of the surface state detection sensor 32. .

For example, in the fixing device 20 that executes a rubbing operation (also referred to as a normal rubbing operation) in which the rubbing operation time is S1 when the sensor output value exceeds V _B , the sensor output value is V _A (V _{When A} <V _B ) is exceeded, a short-time rubbing operation (also referred to as an additional rubbing operation) in which the rubbing operation time is S2 (S2 ≦ S1) is executed.

  FIG. 7 is an explanatory diagram of the rubbing operation by the fixing device 20 according to the present embodiment, and is a graph showing the relationship between the cumulative number of sheets passed and the sensor output value. The sensor output value V in FIG. 7 is a difference between the detection values of the reflected light Lr1 and the reflected light Lr2.

7, indicated by ● (1), when the sensor output value exceeds the V _B, shows a case of executing the normal rubbing operation of the rubbing operation time S1. Further, (2) indicated by ■ indicates that in addition to the normal rubbing operation of (1), when the sensor output value exceeds _VA , an additional rubbing operation of the rubbing operation time S2 was executed. Shows the case.

  As shown in FIG. 7, in the example (2) in which the additional rubbing operation is performed, the sensor output value (that is, the belt surface roughness) becomes a normal rubbing when the predetermined number of sheets N1 is reached. This is better than the case (1) in which only the rubbing operation is performed. It can be seen that the surface state can be more suitably recovered by performing the additional rubbing operation. Therefore, the edge portion of the fixing belt 24 can be recovered to a state close to the non-edge portion before it becomes difficult to recover.

  It should be noted that even if the rubbing operation is performed every predetermined number of accumulated sheets or the rubbing operation time is a fixed value of 1, a certain effect can be obtained, but the rubbing operation time is excessive. As a result, the life of the rubbing member 30 may be shortened, or conversely, there may be a problem that the gloss streak does not disappear completely due to insufficient execution time.

On the other hand, the fixing device 20 according to the present embodiment detects the detection result (sensor When the detected value exceeds the first threshold value (V _B ) according to the output value), in addition to the control for executing the rubbing operation for the first execution time (S1), the second threshold value ( Even when V _A , however, V _A <V _B ) is exceeded, control is performed so that the rubbing operation is executed only for the second execution time (S2, where S2 ≦ S1).

  Thus, by performing the additional rubbing operation at a short interval and a time shorter than the normal rubbing operation, it is possible to prevent the surface state from being difficult to recover.

  Note that it is preferable that the execution start timing of the rubbing operation is after a job is passed (between jobs). If the next job is not sent immediately after the paper is passed, it is possible to reduce the decrease in productivity due to the rubbing operation.

Further, in this embodiment, two threshold values V _A and V _B are provided for the sensor output value, and when the respective threshold values are exceeded, the rubbing operation is performed with different rubbing operation times. A threshold value may be provided, and the rubbing operation may be performed at three or more different rubbing operation times.

<Control example 1>
Next, a first control example of the fixing device 20 according to the present embodiment will be described.

  An example in which the fixing belt 24 performs a rubbing operation according to the result of the output value V, where V is the output value when the surface property of the region through which the edge of the recording medium P passes is detected by the surface state detection sensor 32. Indicates.

  In the first control example, the surface roughness of the fixing belt 24 increases as the sensor output value V of the surface state detection sensor 32 increases, and the surface of the fixing belt 24 decreases as the sensor output value V of the surface state detection sensor 32 decreases. The roughness is small.

  Table 1 shows the relationship between the output value V from the surface state detection sensor 32 and the corresponding rubbing operation time (rubbing time).

As shown in Table 1, if the output value V is V _A ≦ V ≦ V _B , the rubbing operation time S2 is executed. If V _B ≦ V, the rubbing operation is performed for the rubbing operation time S1. Yes. However, S2 ≦ S1, V _A <V _B.

Next, Table 2 shows an output value by the surface state detection sensor 32 after passing the paper when the job is repeated several times (output value after passing the paper), a rubbing operation time when the rubbing operation is performed, The relationship with the output value (after-rubbing output value) by the surface state detection sensor 32 after the rubbing operation is shown. Here, V _A = 2 and V _B = 3.

In the first job, since the output value after passing the paper does not exceed both V _A and V _B , the rubbing operation is not performed. In the second job, since the post-sheet output value V is V ≧ _VA , the rubbing operation is performed for the rubbing operation time S2.

Also in the third to fifth jobs, since the post-sheet output value V is V ≧ _VA , the rubbing operation is performed for the rubbing operation time S2. The sixth jobs, since the output value V after the sheet passing is a V ≧ V _B, performs time amount corresponding rubbing operation of the rubbing operation time S1. The output value after rubbing can be suppressed by the above control.

<Control example 2>
Next, a second control example of the fixing device 20 according to the present embodiment will be described. It is preferable that at least one of two or more output value threshold values for starting the rubbing operation can be arbitrarily set.

Here, an example will be described in which a plurality of patterns of combinations of two threshold values V _A and V _B are stored in the storage unit of the control means 35 so that the user can select a pattern. Table 3 shows examples of patterns A to C of combinations of output value thresholds.

  For example, for most users who pass the same paper width section continuously, if the output value threshold is set large (slow), the rubbing operation will not be executed frequently, and the rubbing operation will not be performed. The waiting time due to the execution of the operation is reduced.

In Table 3, pattern A is the values of V _A and V _{B in} the first control example. On the other hand, the pattern B is a value smaller than the values of V _A and V _{B in} the first control example. By setting the threshold value small (strict) and finely executing the rubbing operation, the surface properties of the edge portion and the paper passing area can be kept close to each other, which is advantageous for users who place importance on print quality.

On the other hand, the pattern C is a value larger than the values of V _A and V _{B in} the first control example. Setting the threshold value to be large (relaxed) and avoiding frequent rubbing operations reduces the waiting time, which is advantageous for users who place importance on productivity.

  For example, for most users who pass the same paper width section continuously, if the output value threshold is set large (slow), the rubbing operation will not be executed frequently, and the rubbing operation will not be performed. The waiting time due to the execution of the operation is reduced.

<Control example 3>
Next, a third control example of the fixing device 20 according to the present embodiment will be described. It is preferable that at least one of the two or more rubbing operation times can be arbitrarily set.

  Here, an example will be described in which a plurality of combinations of two rubbing operation times S1 and S2 are stored in the storage unit of the control means 35, and the user can select a pattern. Table 4 shows examples of patterns A to C of combinations of rubbing operation times.

  In Table 4, pattern A is the values of S1 and S2 in the first control example. On the other hand, the pattern B is a time shorter than S1 and S2 in the first control example. For example, the rubbing operation is executed finely by combining with the pattern B of the control example 2, but since the time for one rubbing operation is short, the waiting time is reduced, and the surface property of the edge portion and the sheet passing area is reduced. Can be kept close to each other.

  On the other hand, the pattern C is a time longer than the values of S1 and S2 in the first control example. For example, by combining with the pattern C of the control example 2, the rubbing operation is not executed frequently, but the time for one rubbing operation is lengthened, the waiting time is reduced, and the surface of the edge portion and the sheet passing area Sex can be kept close.

  According to the fixing device according to the present embodiment described above, by carrying out the rubbing operation of the fixing member at an appropriate timing and execution time, a certain amount of unfavorable paper or special paper having severe burr at the edge of the recording material is passed. The surface condition of the fixing member can be appropriately recovered even when the paper is fed or when a large amount of damage is caused when a certain amount of paper is passed at a high speed. Therefore, it is possible to suppress the occurrence of gloss streaks and suppress abnormal images. In addition, unnecessary rubbing execution operation can be reduced and the life of the rubbing member can be extended.

(Other configuration examples)
Hereinafter, other embodiments of the fixing device according to the present invention will be described. In addition, description about the same point as the said embodiment is abbreviate | omitted suitably.

  FIG. 8 shows another example of the fixing device 20 and is a schematic sectional view in the axial direction of the fixing roller 22. In the example of FIG. 2, the rubbing member 30 is provided at a position facing the fixing roller 22 with the fixing belt 24 interposed therebetween, but the installation position of the rubbing member 30 on the outer periphery of the fixing belt 24 is not limited to this. Absent. For example, as shown in FIG. 8, it is also preferable to provide a counter roller 34 at a position facing the rubbing member 30 with the fixing belt 24 interposed therebetween. Thereby, good polishing performance can be obtained.

  FIG. 9 shows another example of the fixing device 20 and is a schematic sectional view in the axial direction of the fixing roller 22. As shown in FIG. 9, as the rubbing member 30, it is also preferable to provide two or more rubbing members 30a and 30b (two in FIG. 9) having different performances with different surface roughnesses. The rubbing members 30a and 30b are provided so as to be capable of being pressed and separated from the fixing belt 24, respectively, and one of the rubbing members 30 is selected by the control means 35 and the rubbing operation is executed. For example, the rubbing member 30a can be used for a normal rubbing operation, and the rubbing member 30b can be used for an additional rubbing operation.

[Second Embodiment]
Hereinafter, other embodiments of the fixing device and the image forming apparatus according to the present invention will be described. The fixing device according to the second embodiment is provided with a fixing member (fixing belt 24) heated by a heating unit (heater 25 of the heating roller 21) and at least a part of the fixing member so as to be capable of being pressed. A pressure member (pressure roller 23) that forms a nip portion between the recording material and the recording material (recording medium P) carrying an unfixed toner image (unfixed toner image T) in the nip portion. In the fixing device (fixing device 20) for fixing the unfixed toner image on the recording material, a rubbing member (rubbing member 30) for rubbing the surface of the fixing member and a surface for detecting the surface state of the recording material A state detection unit (surface state detection sensor 33) and a control unit (control unit 35) for executing the rubbing operation of the fixing member by the rubbing member at two or more different execution times according to the detection result by the surface state detection unit. And having . In addition, description about the same point as the said embodiment is abbreviate | omitted suitably.

  In addition to the above-mentioned special paper and plain paper (unfavorable paper) being passed, in the fixing device with a relatively wide nip width and high surface pressure, the surface of the fixing member is likely to be rough and abnormal images are generated. It's easy to do.

  FIG. 10 is a graph showing the relationship between the number of sheets passing and the belt surface roughness due to the difference in the nip surface pressure of the fixing device 20. As shown in FIG. 10, there is a correlation between the nip surface pressure and the belt surface roughness. When a fixed number of sheets are passed through a fixing device having a high nip surface pressure, the surface roughness on the belt becomes rough at an early stage. End up.

  As described above, even if the rubbing operation by the rubbing member 30 is performed after the surface roughness becomes very rough, the polishing is insufficient in a short operation time, and the surface state of the fixing belt 24 is sufficiently obtained. In some cases, glossy streaks on the image remain. Further, it is not preferable to take one rubbing operation for a long time because it leads to an increase in unnecessary rubbing operation.

  Therefore, in the fixing device 20 according to the present embodiment, the occurrence of abnormal images is prevented by executing a rubbing operation in a short time before the surface roughness of the fixing belt 24 becomes difficult to recover. is there. Specifically, the fixing device 20 includes a surface state detection sensor 33 that detects the surface property of the end portion (edge portion) in the width direction of the recording medium P, and two or more different depending on the detection result. The rubbing operation time is determined from the rubbing operation time.

  FIG. 11 shows an example of the fixing device 20 according to the second embodiment, and is a schematic cross-sectional view in the axial direction of the fixing roller 22. The fixing device 20 shown in FIG. 11 replaces the surface condition detection sensor 32 for the fixing belt shown in the first embodiment, and the recording medium P is positioned at any position upstream of the fixing device 20 in the transport direction. A surface condition detection sensor 33 for a recording medium for detecting the surface property of the edge portion is provided.

  The surface state detection sensor 33 may be provided at any position upstream of the fixing device 20 in the transport direction. For example, the surface state detection sensor 33 may be provided in the paper bank 43 that is a paper feed unit of the image forming apparatus 100. it can. In the paper bank 43, for example, it is preferable that the paper bank 43 is attached to a guide member that guides the recording medium P in the paper feed tray 44. Since the guide member is displaced according to the size of the recording medium P, it is possible to detect the end position of the recording medium P without providing a mechanism for displacing the detection position of the surface state detection sensor 33, thereby reducing costs. Can do.

  As the surface state detection sensor 33, for example, an optical sensor including a light emitting unit and a light receiving unit that detects reflected light from the recording medium P with respect to light emission from the light emitting unit can be used. The surface state detection sensor 33 may be any sensor that can detect the surface property of the recording medium P, and is not limited to an optical sensor.

  As shown in FIG. 12, the surface state detection sensor 33 detects the reflected light Lr from the recording medium P with respect to the incident light Li generated by light emission. The surface state detection sensor 33 is only required to be able to detect reflected light at least at the edge portion in the vicinity of the cut surface of the recording medium P. It is also preferable to be able to detect the reflected light at both the edge portion and obtain the difference.

  For example, as shown in FIG. 12B, the non-edge portion of the recording medium P has a smooth surface, so there is little diffused light, and as shown in FIG. The ratio of Ld increases. Therefore, the surface property of the recording medium P can be detected by detecting the intensity of the reflected light Lr with respect to the light emission of the surface state detection sensor 33.

  The image defect due to the edge of the recording medium P occurs when the surface of the fixing belt 24 is roughened by the edge portion of the recording medium P. For this reason, the belt surface becomes rougher as the edge of the recording medium P has a burr. In this embodiment, the surface state detection sensor 33 is used to detect the roughness of the burrs at the edge of the recording medium P, thereby detecting the degree of influence on the roughness of the belt surface.

  FIG. 13 is a diagram showing the relationship between the sensor output value (V) of the surface state detection sensor 33 and the surface roughness of the fixing belt 24. Each sensor output value and the surface roughness at that time are plotted, and a straight line is plotted. An approximated graph is shown. As shown in FIG. 13, the sensor output value of the surface state detection sensor 33 and the surface roughness of the fixing belt 24 are correlated.

  FIG. 14 is an explanatory diagram of the rubbing operation by the fixing device 20 according to the second embodiment, and is a graph showing the relationship between the cumulative number of sheets passed and the belt surface roughness.

  In FIG. 14, (1) indicated by ▪ represents the case where the normal rubbing operation for the rubbing operation time S1 is executed for every sheet passing number N1. Further, (2) indicated by ▲ is an additional rubbing operation for the rubbing operation time S2 (S2 ≦ S1) for every N2 sheets (N2 <N1) in addition to the normal rubbing operation of (1). The case where is executed is shown. Further, (3) indicated by ● represents an additional sliding operation time S3 (S3 ≦ S1) for each sheet passing number N3 (N3 <N2 <N1) in addition to the normal sliding operation of (1). The case where the rubbing operation is executed is shown. In addition to the normal rubbing operation of (1), both of the additional rubbing operations of (2) and (3) may be executed.

  As shown in FIG. 14, in the examples of (2) and (3) in which the rubbing operation was performed with a short rubbing time, the belt surface roughness was greater than that in the case of (1) when the number of sheets passed N1. Therefore, after the normal rubbing operation for the rubbing operation time S1 with the sheet passing number N1, the surface state can be recovered more suitably.

  As described above, in addition to executing the normal rubbing operation for a predetermined rubbing operation time for each predetermined number of sheets to be passed, a time equal to or shorter than the normal rubbing operation at a shorter interval than this. By performing an additional rubbing operation, it is possible to prevent the surface state from being difficult to recover.

  In other words, even if the rubbing operation time is a fixed value of 1, there is an effect of preventing gloss streaks, but the problem is that the life of the rubbing member 30 is shortened due to excessive execution time, and conversely the execution The problem that the gloss streaks do not disappear completely due to lack of time remains. In addition, in the method of determining the rubbing operation time according to the brand of the recording medium P, brands that have not been passed in the past cannot be dealt with. The rubbing operation time cannot be determined without confirmation. On the other hand, in the fixing device 20 according to the present embodiment, the above problem can be solved by controlling based on the output result of the surface state detection sensor 33 of the recording medium P.

  Further, not only how the burrs stand at the edge portion but also the number of burrs affects the ease with which scratches are formed on the fixing belt 24. For example, if the number of burrs standing at the same level is large, scratches are likely to be formed on the fixing belt 24. Therefore, it is preferable that the surface state detection sensor 33 also detects the number of burrs. By reflecting this in the detection result, it is possible to execute an additional rubbing operation with higher accuracy and to prevent the surface state from being difficult to recover.

  It is also preferable to change and control the nip width by controlling the pressure applied to the fixing roller 22 side of the pressure roller 23 according to the detection result of the surface state detection sensor 33. Needless to say, the pressing force may be controlled even when the control based on the detection result of the surface state detection sensor 32 (first embodiment) is performed.

<Control example 1>
Next, a first control example of the fixing device 20 according to the second embodiment will be described.

  In the first control example, the output value that is the detection result of the surface property of the recording medium P by the surface state detection sensor 33 is V12, and the number of sheets to be passed for each paper width category of the recording medium P according to the result of the output value V12. An example will be described in which the cumulative number is counted while weighting, and the rubbing operation is performed when the counter exceeds a certain threshold.

Table 5 is a table showing the relationship between the output value V12 of the surface state detection sensor 33 and the weighting coefficient of the integrated number corresponding to the output value V12. As shown in Table 5, the weighting coefficient is α when the output value V12 is V12 < _VA , the weighting coefficient is β when V _A ≦ V12 <V _B , and the weighting coefficient is γ when V _B ≦ V12. To do. Here, α = 0.5, β = 1, γ = 2, V _A = 3, and V _B = 5.

  Table 6 is a graph showing the relationship between the sensor output value (V12), the weighting coefficient, the number of sheets passed, the total number of sheets for each job, and the total number of sheets accumulated when a job with the same paper width and different brands is repeated several times. .

  In the first job, since the sensor output value is 2.2, the weighting coefficient is α. Further, since the number of sheets to be passed is 1000, the cumulative number of sheets in the first job is 0.5 × 1000 = 500. In the second job, since the sensor output value is 4.3, the weighting coefficient is β. Further, since the number of sheets to be passed is 100, the accumulated number of sheets in the second job is 1.0 × 100 = 100. Similarly, the total number of sheets in the third job is 400, and the total number of sheets in the fourth job is 300.

  In the fifth job, since the sensor output value is 5.3, the weighting coefficient is γ. Further, since the number of sheets to be passed is 200, the accumulated number of sheets in the fifth job is 2.0 × 200 = 400. Similarly, in the sixth job, the cumulative number is 300.

  Table 7 shows an example of the threshold value (L) of the number of sheets to be passed for starting the rubbing operation and the respective rubbing operation time. That is, a rubbing operation for S1 time is executed every 10,000 sheets (threshold L1), and a rubbing operation is performed for S2 hours (S2 ≦ S1) every 4000 sheets (threshold L2). Is shown. For example, after the sixth job in Table 5 is completed, the total number of accumulated sheets is 2000, so that both the threshold values L1 and L2 are not exceeded. Therefore, the rubbing operation is not performed at this time.

  Table 8 shows an example of the counter of the accumulated number for each paper width category. Here, five paper width sections are provided. Cases 1 to 5 show counter values at a certain time.

  In Case 1, the paper width category 4 exceeds the threshold value L2. That is, the rubbing operation for S2 time is executed once.

  In Case 2, since no paper width division exceeds the threshold values L1 and L2, the rubbing operation has not been executed yet.

  In Case 3, the threshold value L2 is exceeded in the paper width categories 2 and 5. For this reason, the rubbing operation for S2 hours is executed at each timing when the cumulative number of sheets in each paper width section exceeds L2 (two times in total).

  In Case 4, the threshold values L1 and L2 are exceeded in the paper width category 2. In this case, the rubbing operation for S2 time is executed twice and the rubbing operation for S1 time is executed once.

  In Case 5, the thresholds L1 and L2 are exceeded in the paper width section 3, and the threshold L2 is also exceeded in the paper width section 5. In this case, the rubbing operation for S2 time is executed three times and the rubbing operation for S1 time is executed once.

  When the cumulative number is counted for each paper width and the rubbing member 30 can be moved in the axial direction, the rubbing member 30 is appropriately moved in the axial direction to at least the edge of the corresponding paper width section. What is necessary is just to perform a rubbing operation | movement about the peripheral position of a part.

  Further, the threshold values L1 and L2 and the rubbing times S1 and S2 in each rubbing operation are stored in the control means 35, and it is also preferable that these values can be arbitrarily set and changed by the user.

  For example, when an abnormal image of gloss streaks due to surface roughness cannot be resolved sufficiently with a preset rubbing time, it is possible to set an optimum polishing time by changing the rubbing time to a longer setting by the user. Become. On the other hand, in the case of mainly using a recording material that does not easily roughen the surface, it is possible to extend the life of the rubbing member 30 and the fixing belt 24 by changing the setting of the rubbing time to be short.

<Control example 2>
Next, a second control example of the fixing device 20 according to the second embodiment will be described. In the second control example, an example in which the nip width is varied according to the detection result of the surface state detection sensor 33 will be described. Note that when this control is performed, it is not necessary to weight the number of sheets to be passed. This is because the scratches on the fixing belt 24 are hardly formed by changing the nip width.

Table 9 is a table showing the relationship between the output value V12 of the surface state detection sensor 33 and the nip width of the fixing device 20 according to the output value V12. As shown in Table 9, and the nip width a, b a nip width when the _{V A} ≦ V12 _{<V B,} the nip width when the _{V B} ≦ V12 c when the output value V12 is V12 _{<V A} (Where a>b> c). Here, V _A = 3 and V _B = 5, but it is needless to say that the threshold value may be different from that of the control example 1.

  Table 10 shows the relationship between the sensor output value and the nip width in each job.

  In the first job, since the sensor output value is 5.1, the nip width is changed to c. In the second job, since the sensor output value is 3.1, the nip width is changed to b. In the third job, since the sensor output value is 4.5, the nip width remains b. In the fourth job, since the sensor output value is 5.5, the nip width is changed to c. In the fifth job, since the sensor output value is 1.2, the nip width is changed to a.

  According to the fixing device according to the second embodiment described above, by performing the rubbing operation of the fixing member at an appropriate timing and execution time, disadvantageous paper and special paper with severe burr at the edge of the recording material can be fixed. The surface state of the fixing member can be appropriately recovered even when the amount of paper is passed or when the damage is great when the paper is passed at a high speed at a constant rate. In particular, it is suitable for the fixing device 20 having a relatively high speed, a wide nip width, and a high surface pressure. Therefore, it is possible to suppress the occurrence of gloss streaks and suppress abnormal images. In addition, unnecessary rubbing execution operation can be reduced and the life of the rubbing member can be extended.

  The above-described embodiment is a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 10 Intermediate transfer belt 11 Tandem type image forming part 12 Exposure device 13 Secondary transfer device 14 Support roller 15 Support roller 15 'Support roller 16 Secondary transfer counter roller 16' Secondary transfer roller 17 Cleaning device 18 Image forming means 20 Fixing device 21 Heating roller 22 Fixing roller 23 Pressure roller 24 Fixing belt 25 Heater 26 Heater 27 Tension roller 28 Separating plate 29 Separating plates 30, 30a, 30b Rub member 31 Temperature sensor 32 Surface condition detection sensor (for fixing belt)
33 Surface condition detection sensor (for recording media)
34 Counter roller 35 Control means 37 Roller 38 Conveying belt 39 Sheet reversing device 40 Photosensitive drum 42 Paper feed roller 43 Paper bank 44 Paper feed tray 45 Separating roller 46 Paper feed path 47 Carriage roller pair 48 Paper feed path 49 Positioning roller pair 50 Feed roller 51 Manual feed tray 52 Separating roller 53 Manual feed path 56 Discharge roller 57 Discharge tray 62 Primary transfer roller 63 Backup roller 100 Image forming apparatus main body 200 Paper feed table T Unfixed toner image P Recording medium

JP 2006-317881 A JP 2009-237250 A JP, 2015-18034, A

Claims (10)

A fixing member heated by a heating means;
A pressure member that is arranged to be able to press at least a part of the fixing member and that forms a nip portion with the fixing member,
In a fixing device that conveys a recording material carrying an unfixed toner image to the nip portion and fixes the unfixed toner image on the recording material,
A rubbing member for rubbing the surface of the fixing member;
Surface state detection means for detecting the surface state of the fixing member or the recording material;
And a control unit that causes the rubbing member to perform a rubbing operation of the fixing member at two or more different execution times in accordance with a detection result by the surface state detection unit. The control means includes
When the detection value of the surface state detection means exceeds a first threshold, the rubbing operation is executed in a first execution time,
When the second threshold value set for the detection value indicating that the surface state of the fixing member is better than the first threshold value is exceeded, the second execution time is equal to or less than the first execution time. The fixing device according to claim 1, wherein the rubbing operation is executed in time.   The fixing device according to claim 1, wherein the control unit causes the rubbing operation to be performed between jobs.   2. The surface state detecting means for detecting the surface state of the fixing member is an optical sensor that emits light from a light emitting portion toward the fixing member and receives reflected light from the fixing member. 4. The fixing device according to any one of items 1 to 3. The surface state detecting means for detecting the surface state of the fixing member includes an edge portion through which an edge portion of the recording material passes and a paper passing portion which is a paper passing range of the recording material other than the edge portion. The surface state of the fixing member can be detected,
The fixing device according to claim 1, wherein a difference between detection values at the edge portion and the paper passing portion is set as a detection result.   The surface state detecting means for detecting the surface state of the recording material is an optical sensor that emits light from a light emitting portion toward the recording material and receives reflected light from an end portion of the recording material. The fixing device according to claim 1.   The control means controls a pressing force of the pressure member toward the fixing member in accordance with a detection result by the surface state detection means to change the width of the nip portion. The fixing device according to any one of 1 to 6. At least one value of the first threshold and the second threshold;
The fixing device according to claim 2, wherein at least one of the first execution time and the second execution time can be arbitrarily set.   An image forming apparatus comprising the fixing device according to claim 1.   The image forming apparatus according to claim 9, wherein the surface state detection unit that detects a surface state of the recording material is provided in a paper feeding unit of the recording material.