JP2014215376A - Fixing apparatus, control method thereof, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable highly stable rubbing operation of a fixing member.SOLUTION: A fixing apparatus 20 includes a fixing belt 24, a pressure roller 23, and a polishing member 26 which can be brought into pressure-contact with and separated from the fixing belt 24 and polishes a surface of the fixing belt 24 in pressure-contact with the fixing belt 24. The fixing apparatus 20 conveys a recording medium P carrying an unfixed toner image T in a nip part N, and fixes the unfixed toner image T to the recording medium P. The separated polishing member 26, which is not in pressure-contact with the fixing belt 24, is preliminarily rotated in the same direction as a conveyance direction of the fixing belt 24 in a position where the polishing member 26 comes into pressure-contact with the fixing belt 24, and the preliminarily-rotated polishing member 26 is brought into pressure-contact with the fixing belt 24. After that, the rotation speed of the polishing member 26 is changed.

Description

  The present invention relates to a fixing device, a fixing device control method, and an image forming apparatus. More specifically, the present invention relates to a fixing device mounted on an image forming apparatus such as a copying machine, a facsimile, and a printer, and a control method for the fixing device.

  Various image forming apparatuses using an electrophotographic system have been devised as image forming apparatuses such as copying machines, facsimile machines, printers, or their combined machines, and are well known in the art. 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 medium (also referred to as paper, recording paper, sheet, or recording material) by a transfer device to carry the image, and the toner image on the recording medium is fixed by a fixing device using pressure or heat. It is established.

  Various types of fixing devices have been proposed. For example, the fixing device includes a fixing roller (fixing member) maintained at a predetermined temperature, and a pressure roller (pressure member) that presses the fixing roller. There is known a roller fixing system in which a recording medium carrying an unfixed toner image is heated while being nipped and conveyed by a fixing nip portion (nip portion) formed by pressure contact between a pressure roller and a fixing roller, and is fixed.

  Further, the image forming apparatus includes a fixing roller disposed opposite to the pressure roller (pressure member), and an endless fixing belt (fixing member) stretched between the fixing roller and the heating roller. A belt fixing method is known in which heat from a heating roller is applied to a recording medium through a fixing belt at a nip formed by pressure contact with the belt, thereby pressing and fixing an unfixed toner image to the recording medium. Yes.

  However, when a recording medium is passed through the fixing device, the surface of a fixing member such as a fixing roller or a fixing belt is damaged due to paper passing, paper dust, offset toner, and the like, and is gradually roughened. There is a problem. In particular, as a major cause of scratches, burrs at both ends (curvature of the ends) that occur during cutting of the recording medium are known.

  That is, when recording media of the same size are continuously passed through the fixing device, the positions where the burrs, which are both ends of the recording medium of the fixing member, pass through are easily roughened and damaged.

  Use in a state in which the surface of the fixing member is dirty or rough in this way leads to gloss streaks and gloss unevenness, which leads to image deterioration.

  On the other hand, a technique has been proposed in which the fixing member is rubbed to make the surface property uniform and suppress abnormal images such as gloss streaks.

  For example, Patent Document 1 discloses a fixing device that includes a fixing member that fixes toner on a recording medium and a pressure member that forms a nip that contacts the fixing member and passes through the recording medium. There is disclosed a fixing device in which a cleaning body abuts and an auxiliary cleaning member abuts from the inside to the outside of a range corresponding to a predetermined sheet passing size on the surface of the fixing member. According to Patent Document 1, paper dust accumulated on the surface of the fixing member is removed by bringing the rotary cleaning body into contact with the surface of the fixing member, thereby preventing glossy streaks from occurring during image formation. be able to.

  Patent Document 2 discloses a fixing member that heats and fixes a toner image on a recording material, a pressure member that forms a fixing nip portion that is in contact with the fixing member and holds a recording material that carries the toner image, and a fixing member. A surface recovery means having a rubbing member for rubbing the surface and performing a surface recovery process for recovering the surface property of the fixing member, and a control for controlling the surface recovery process corresponding to the contamination of the surface of the rubbing member A fixing device provided with a unit. According to Patent Document 2, it is possible to prevent the occurrence of uneven gloss.

  Further, Patent Document 3 discloses a heating unit for fusing and fixing toner on a recording paper, a pressure roller that presses the heating unit to form a nip, and a seamless fixing that is nipped by the nip and rotated and conveyed by the pressure roller. A fixing device having a film or the like, and having a polishing means for wiping and polishing the surface layer in contact with the fixing film, rotating in contact with the fixing film in the same direction as the conveying direction of the film, and faster than the conveying speed of the fixing film is disclosed. Yes. According to Patent Document 3, it is possible to prevent image quality from being deteriorated due to offset toner or slip generated between a film and a transfer material.

  Patent Document 2 discloses that the refresh roller, which is a rubbing member, can be pressed against and separated from the fixing roller, the fixing roller is 50 mm / s clockwise, and the refresh roller is clockwise. It is disclosed that a surface recovery process is performed in which the contact pressure between the fixing roller and the refreshing roller is 7N by rotating at 400 mm / s. That is, it is disclosed that the surface recovery process is performed at a refresh roller speed eight times that of the fixing roller.

  Further, Patent Document 3 discloses that a polishing roller as a polishing means rotates at a double speed in the same direction as the fixing film conveyance direction.

  Here, when the surface of the fixing member is rubbed with the abrasive member, if the state is stopped and separated from the separated state, the fixing belt may be locally damaged. It will be necessary to stop. In order to prevent the occurrence of such scratches and to shift from the operation state of the apparatus to the continuous rubbing operation, it is conceivable that the rotation is started in a state where the polishing member and the fixing member are separated and then pressed. ing.

  However, as in the above-mentioned patent document, the surface speed of the polishing member is set to be higher than the surface speed of the fixing member, the rotation is started in a state where the polishing member and the fixing member are separated from each other, and then the pressure is brought into contact with the polishing. When the surface of the fixing member is rubbed with the member, the following problem may occur. That is, due to the difference in surface speed between the polishing member and the fixing member, an abrupt torque change (rotation driving torque of the polishing member) due to friction occurs at the moment when the fixing member surface and the polishing member surface come into contact (pressure contact), The load is applied to the polishing member, the driving means for controlling the rotation of the polishing member, and the mechanism for controlling the contact / separation operation of the polishing member, the polishing operation becomes unstable, and local flaws occur on the fixing member. There was a fear.

  Therefore, the present invention reduces a sudden torque change that may occur during pressure contact when the abrasive member is rubbed against a state where the polishing member is in contact with the fixing member, and the fixing member is highly stable. An object of the present invention is to provide a fixing device capable of realizing the sliding operation.

  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. A pressure member that is capable of being pressed and separated from the fixing member, and a polishing member that rubs the surface of the fixing member while being in pressure contact with the fixing member. In a fixing device that conveys a recording medium carrying a contact toner image and fixes the unfixed toner image on the recording medium, the polishing member is placed in a separated state before the polishing member is pressed against the fixing member. The polishing member is preliminarily rotated in a rotational direction that is the same as the conveying direction of the fixing member at a position where the polishing member is in pressure contact with the fixing member, and the polishing member is pressed against the fixing member in the preliminary rotation state. After the, thereby changing the rotational speed of the polishing member.

  According to the present invention, the rubbing operation of the fixing member by the polishing member can be stably executed.

1 is a cross-sectional view illustrating an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a side cross-sectional view illustrating a configuration of an embodiment of a fixing device according to the present invention, and illustrates a state in which an abrasive member is separated from a fixing belt. FIG. 3 is a diagram illustrating a state in which an abrasive member is pressed against a fixing belt in the fixing device illustrated in FIG. 2. 6 is a graph showing the relationship between the fixing belt surface speed and the polishing member surface speed. 6 is a graph showing the rotational driving torque of the polishing member when the surface speed of the polishing member is brought into contact with the surface speed of the fixing belt at a constant speed and when the contact is made at 6 times speed.

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

(Image forming device)
FIG. 1 is a schematic configuration diagram illustrating the overall configuration of a tandem type color copier that is an embodiment of an image forming apparatus according to the present invention. The outline and operation of the internal configuration of the image forming apparatus will be described with reference to FIG.

  In FIG. 1, 1 is an image forming apparatus main body, 2 is a writing unit that emits laser light based on input image information, 3 is a document conveying unit that conveys a document D to a document reading unit 4, and 4 is image information of the document D. A document reading unit to be read, 7 is a paper feed unit for storing a recording medium P (not shown) such as transfer paper, 9 is a registration roller for adjusting the conveyance timing of the recording medium P, and 11Y, 11M, 11C, and 11BK are each color. Photosensitive drums on which toner images of (yellow, magenta, cyan, black) are formed, 12 is a charging unit that charges the respective photosensitive drums 11Y, 11M, 11C, and 11BK, and 13 is each photosensitive drum 11Y, 11M, A developing unit that develops the electrostatic latent images formed on 11C and 11BK, and 14 transfers the toner images formed on the photosensitive drums 11Y, 11M, 11C, and 11BK on the recording medium P in an overlapping manner. That a transfer bias roller (primary transfer bias roller), 15 denotes the photosensitive drums 11Y, 11M, 11C, a cleaning unit for collecting the untransferred toner on 11BK.

  Reference numeral 16 denotes an intermediate transfer belt cleaning unit that cleans the intermediate transfer belt 17, 17 an intermediate transfer belt on which toner images of a plurality of colors are transferred and superimposed, and 18 a color toner image on the intermediate transfer belt 17 on the recording medium P. A secondary transfer bias roller 20 for transferring the toner image onto the recording medium P indicates a fixing device for fixing the toner image on the recording medium P.

  Hereinafter, an operation during normal color image formation in the image forming apparatus will be described. First, the document D is transported from the document table in the direction of the arrow in the drawing by the transport rollers of the document transport unit 3 and placed on the contact glass 5 of the document reading unit 4. Then, the document reading unit 4 optically reads the image information of the document D placed on the contact glass 5. Specifically, the document reading unit 4 scans the image of the document D on the contact glass 5 while irradiating light emitted from an illumination lamp. Then, the light reflected by the document D is imaged on the color sensor via the mirror group and the lens. The color image information of the document D is read for each RGB (red, green, blue) color separation light by the color sensor, and then converted into an electrical image signal. Further, color conversion processing, color correction processing, spatial frequency correction processing, and the like are performed by the image processing unit based on the RGB color separation image signals to obtain yellow, magenta, cyan, and black color image information.

  Then, the image information of each color of yellow, magenta, cyan, and black is transmitted to the writing unit 2. The writing unit 2 emits laser light (exposure light) based on the image information of each color toward the corresponding photosensitive drums 11Y, 11M, 11C, and 11BK.

  On the other hand, the four photosensitive drums 11Y, 11M, 11C, and 11BK are rotated clockwise in FIG. First, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK are uniformly charged at a portion facing the charging unit 12 (charging process). Thus, a charged potential is formed on the photosensitive drums 11Y, 11M, 11C, and 11BK. Thereafter, the charged surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK reach the irradiation positions of the respective laser beams.

  In the writing unit 2, laser light corresponding to the image signal is emitted from the four light sources corresponding to each color. Each laser beam passes through a different optical path for each color component of yellow, magenta, cyan, and black (exposure process).

  Laser light corresponding to the yellow component is irradiated on the surface of the first photosensitive drum 11Y from the left side of the drawing. At this time, the yellow component laser light is scanned in the rotation axis direction (main scanning direction) of the photosensitive drum 11Y by a polygon mirror that rotates at high speed. Thus, an electrostatic latent image corresponding to the yellow component is formed on the photosensitive drum 11Y charged by the charging unit 12.

  Similarly, the laser beam corresponding to the magenta component is irradiated onto the surface of the second photosensitive drum 11M from the left side of the paper, and an electrostatic latent image corresponding to the magenta component is formed. The cyan component laser light is applied to the surface of the third photosensitive drum 11C from the left side of the paper, and an electrostatic latent image of the cyan component is formed. The black component laser beam is applied to the surface of the fourth photosensitive drum 11BK from the left side of the paper, and an electrostatic latent image of the black component is formed.

  Thereafter, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK on which the electrostatic latent images of the respective colors are formed reach the positions facing the developing unit 13, respectively. Then, the respective color toners are supplied from the developing units 13 onto the photosensitive drums 11Y, 11M, 11C, and 11BK, and the latent images on the photosensitive drums 11Y, 11M, 11C, and 11BK are developed (developing step).

  Thereafter, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK after the development process reach the opposed portions to the intermediate transfer belt 17, respectively. Here, a transfer bias roller 14 is installed at each facing portion so as to contact the inner peripheral surface of the intermediate transfer belt 17. Then, the toner images of the respective colors formed on the photosensitive drums 11Y, 11M, 11C, and 11BK are sequentially superimposed and transferred onto the intermediate transfer belt 17 at the position of the transfer bias roller 14 (primary transfer process). .

  Then, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK after the transfer process reach positions facing the cleaning unit 15, respectively. Then, the untransferred toner remaining on the photosensitive drums 11Y, 11M, 11C, and 11BK is collected by the cleaning unit 15 (cleaning process).

  Thereafter, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK pass through a static elimination unit (not shown), and a series of image forming processes on the photoconductive drums 11Y, 11M, 11C, and 11BK is completed.

  On the other hand, the intermediate transfer belt 17 on which the toners of the respective colors on the photoconductive drums 11Y, 11M, 11C, and 11BK are transferred (carried) are run in the clockwise direction in the drawing and are connected to the secondary transfer bias roller 18. Reach the opposite position. The color toner image carried on the intermediate transfer belt 17 is transferred onto the recording medium P at a position facing the secondary transfer bias roller 18 (secondary transfer step).

  Thereafter, the surface of the intermediate transfer belt 17 reaches the position of the intermediate transfer belt cleaning unit 16. Then, the untransferred toner adhered on the intermediate transfer belt 17 is collected by the intermediate transfer belt cleaning unit 16, and a series of transfer processes in the intermediate transfer belt 17 is completed.

  Here, the recording medium P conveyed between the intermediate transfer belt 17 and the secondary transfer bias roller 18 (secondary transfer nip) is conveyed from the paper supply unit 7 via the registration roller 9 and the like. is there.

  Specifically, the recording medium P fed by the paper feeding roller 8 from the paper feeding unit 7 that stores the recording medium P is guided to the registration roller 9 after passing through the conveyance guide. The recording medium P that has reached the registration roller 9 is conveyed toward the secondary transfer nip at the same timing.

  Then, the recording medium P on which the full-color image is transferred is guided to the fixing device 20 by the transport belt. In the fixing device 20, a color image (toner) is fixed on the recording medium P at a nip between a fixing roller 22 as a fixing member and a pressure roller 23 as a pressure member.

  Then, the recording medium P after the fixing step is discharged as an output image outside the apparatus main body 1 by a paper discharge roller, and a series of image forming processes is completed.

(Fixing device)
[Basic configuration]
Next, the configuration and control of the fixing device 20 included in the image forming apparatus 1 will be described. The fixing device according to the present embodiment is arranged so that at least a part of the fixing member (fixing belt 24) heated by the heating unit (induction heating unit 25) can be pressed, and between the fixing member. A pressure member (pressure roller 23) that forms a nip portion (nip portion N) is provided on the fixing member so as to be capable of being pressed against and separated from the fixing member, and the surface of the fixing member is rubbed against the fixing member while being in pressure contact with the fixing member. A recording member (recording medium P) carrying an unfixed toner image (toner image T) in the nip portion, and fixing the unfixed toner image to the recording medium. In the fixing device (fixing device 20), the polishing member is in the same direction as the conveying direction of the fixing member at a position where the polishing member is in pressure contact with the fixing member in a separated state before the polishing member is pressed against the fixing member. rotation Was pre-rotated in direction, after it is pressed against the polishing member to the fixing member at the preliminary rotation state, thereby changing the rotational speed of the polishing member. In addition, the code | symbol in embodiment and the example of application are shown in a parenthesis.

  2 and 3 show an example of the fixing device 20 of the belt fixing method and induction heating method, and are schematic sectional views in the axial direction of the fixing roller 22. 2 shows a state in which the polishing member 26 included in the fixing device 20 is in pressure contact with the fixing belt 24, and FIG. 3 shows a state in which the polishing member 26 is separated from the fixing belt 24.

  As shown in FIG. 2, an induction heating type fixing device 20 includes a fixing roller 22 having an elastic layer 22b on the outer periphery of a metal core 22a, a heating roller 21 heated by induction heating means 25, and a heating roller 21. An endless fixing belt 24 stretched between the fixing roller 22 and a pressure which is disposed on the outer peripheral side of the fixing belt 24 and forms a nip portion N (fixing nip portion) with the fixing roller 22. A roller 23, an induction heating means 25 for heating the heating roller 21, and a polishing member provided so as to be capable of being pressed against and separated from the fixing belt 24 and rubbing the surface of the fixing belt 24 while being in pressure contact with the fixing belt 24 26.

  The fixing device 20 includes a recording medium P (toner image T) carrying an unfixed toner image (toner image T) in a nip N between the fixing belt 24 and the pressure roller 23 formed by pressure contact between the fixing roller 22 and the pressure roller 23. Paper), and heat 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 a longitudinal direction of a housing (not shown) of the fixing device 20, and driving means (motors) of each roller (not shown) are provided in a housing. It is held fixed on the body.

  The heating roller 21 has, for example, a length in the longitudinal direction (axial direction) of 320 mm and an outer diameter of 40 mm, and is formed by sequentially forming a conductive heat generating layer, an elastic layer, and a cored bar layer that are heat generating member bodies.

  The heat generation layer is formed of a metal member having good conductivity and good heat conductivity suitable for electromagnetic induction heating because eddy current is easily generated by an alternating magnetic field. As a metal suitable for electromagnetic induction heating, a metal having high resistance is generally known. However, even if the resistance is low, a metal member having good heat conductivity is thinned to make a substantial layer of the heat generating layer. The resistance value can be arbitrarily set, and the heat generation amount can be adjusted.

  As the heat generating layer, for example, a structure in which copper having a thickness of 10 μm is plated on a nonmagnetic stainless steel layer having a thickness of 50 μm can be used. Since the heat generating layer only needs to have good electrical conductivity and good heat transfer, other metal layers such as silver, aluminum, magnesium, etc., or nickel or magnetic stainless steel, which are magnetic materials, may be used.

  For the elastic layer, for example, an elastic body such as fluorine rubber, silicon rubber, or fluorosilicon rubber is used. The elastic layer is made of sponge rubber to suppress heat transfer to the inside of the heating roller and to keep the heat of the heat generating layer heat-insulated.

  The metal core layer is a support for the entire heating roller 21 and uses a metal such as iron or aluminum in order to ensure rigidity. It is also possible and preferable that the cored bar layer is made of a nonmagnetic or insulating material such as nonmagnetic stainless steel or ceramic so as not to affect induction heating. For example, using SUS304, which is a nonmagnetic stainless steel having an outer diameter of 22 mm and a thickness of 2.0 mm, the energy of induction heating can be concentrated in the heat generating layer without loss.

  The fixing belt 24 is wound around the fixing roller 22 and the heating roller 21, is in close contact with the heating roller 21 and the fixing roller 22, and is indirectly heated by the induction heating unit 25 through the heating roller 21. The nip portion N 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 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 offset prevention such as PFA (tetrafluoroethylene bar fluoroalkyl vinyl ether copolymer resin). The agent is coated. In particular, by using PFA for the surface layer, scratches on the surface of the fixing belt 24 can be suitably suppressed.

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

  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. A nip portion N is formed between the fixing belt 24 and the fixing belt 24.

  Further, the driving unit drives the fixing roller 22 to rotate 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. In this embodiment, the driving means is provided on the fixing roller 22 and the pressure roller 23 and the like rotate together. However, even if the driving means is provided on other rollers, the driving means is provided with a plurality of rollers. May have.

  The induction heating means 25 is for inductively heating the heat generating layer which is the surface layer of the heating roller 21 by the magnetic field generated by the excitation / demagnetization coil. The heating roller 21 is heated by the induction heating unit 25, and the toner image T of the recording medium P is conveyed while being heated and melted at the nip portion N by the reverse rotation of the pressure roller 23 and the fixing belt 24. Note that the heating means is not limited to the induction heating means for heating the heating roller 21 from the outside, and a heater such as a halogen heater or a carbon heater may be provided inside the heating roller 21. Further, a heater may be provided inside the pressure roller 23.

  Further, based on a temperature signal from a temperature detection unit such as a thermistor (not shown), the induction heating unit 25 is controlled so as to maintain a fixing temperature at which the fixing belt 24 can be fixed satisfactorily.

  According to the fixing device 20 having this configuration, the recording medium P on which the toner image T is formed is conveyed to the nip portion N from a pre-fixing guide (not shown) disposed on the upstream side of the fixing belt 24 in the sheet conveying direction. The toner image T on the recording medium P is heated and melted at the nip portion N, whereby the toner image T is fixed. Thereafter, the recording medium P is separated by a separation plate or the like, and is discharged from a paper discharge unit on the downstream side in the paper transport direction.

[Abrasive material]
As described above, if the recording medium P is repeatedly passed through the nip portion N of the fixing device 20, scratches due to the edges of the recording medium P may occur on the surface of the fixing belt 24. When the flaw becomes deeper, a difference in toner fixability occurs between the flawed portion and the flawless portion of the fixing belt 24, which may cause uneven gloss and streaks on the image.

  Accordingly, the fixing device 20 of the present embodiment includes a polishing member 26 that can be pressed against and separated from the fixing belt 24, and the surface of the fixing belt 24 is covered by the polishing member 26 at a predetermined interval or at an arbitrary timing. By rubbing and leveling the roughness of the belt surface, the difference in fixing property is eliminated and gloss unevenness is suppressed.

  As the polishing member 26, a known cleaning roller or the like can be applied. For example, a cleaning roller having a polishing layer formed on the outer periphery of the core metal can be used. The core metal is a support for the entire polishing member 26, and is made of a metal material such as iron or aluminum in order to ensure rigidity. The cored bar may be made of a nonmagnetic or insulating material such as nonmagnetic stainless steel or ceramic.

  The polishing layer is formed by dispersing abrasive grains in a binder (binder layer) such as rubber or resin. Here, as the material of the binder, silicon rubber, fluororesin, or the like can be used. Further, as the material of the abrasive grains, white alumina, brown alumina, pulverized alumina, light red alumina, green silicon carbide, black silicon carbide, diamond, CBN (cubic boron nitride) and the like can be used.

  Further, the polishing member 26 is connected to a driving unit different from the driving unit of the fixing roller 22 and is rotated by a predetermined rotation amount by the driving unit. As a driving means for rotating the polishing member 26, for example, a stepping motor is preferably used. In the present embodiment, as will be described later, since it is possible to suppress a sudden torque fluctuation that may occur when the polishing member 26 is pressed, it is possible to apply a relatively inexpensive motor such as a stepping motor.

  Here, the polishing member 26 can be brought into contact with and separated from the fixing belt 24 in the arrow direction shown in FIG. 3 while being rotated by the driving means. Contact / separation control means for bringing the polishing member 26 into and out of contact with the fixing belt 24 is not particularly limited. For example, an urging means for urging the polishing member 26 in a direction in which the polishing member 26 is pressed against the fixing belt 24; And a mechanism (such as a cam) for releasing the urging force.

  In the fixing device 20 of the present embodiment, the polishing member 26 and the fixing belt 24 are separated from each other before the sliding operation (polishing operation) is performed with the polishing member 26 pressed against the fixing belt 24 (FIG. 2). The polishing member 26 is preliminarily rotated in a rotational direction (a direction in which surface velocity vectors coincide) in the same direction as the conveyance direction of the fixing belt 24 at a position where the polishing member 26 is in pressure contact with the fixing belt 24 (referred to as a pressure contact portion). Is.

  At this time, the surface speed of the polishing member 26 (speed at the pressure contact portion) [mm / s] is 0.8 to 1.mm higher than the surface speed of the fixing belt 24 (speed at the pressure contact portion) [mm / s]. It is preferable to control the drive so as to be in the range of 2 times (80 to 120%). Most preferably, drive control is performed so that the surface speed of the polishing member 26 is equal to the surface speed of the fixing belt 24.

  After the polishing member 26 is in the preliminary rotation state as described above, the polishing member 26 is pressed against the fixing belt 24 in this preliminary rotation state (FIG. 3). After the press contact, the rotational speed of the polishing member 26 is increased and the fixing belt 24 is rubbed (polished) for a predetermined time (for example, 3 minutes).

  It is preferable to increase the rotational speed of the polishing member 26 so that the surface speed of the polishing member 26 after this increase is in the range of 2 to 8 times the surface speed of the fixing belt 24. Most preferably, the surface speed of the polishing member 26 is controlled to be 6 times the surface speed of the fixing belt 24.

  After performing the rubbing operation for a predetermined time, the polishing member 26 is separated while rotating at the rotation speed at the time of rubbing, and then the rotation is stopped to end the rubbing operation.

  Regarding the control method of the fixing device 20 described above, FIG. 4 is a graph showing the change over time in the surface speeds of the polishing member 26 and the fixing belt 24. Further, FIG. 5 shows a case where the polishing member 26 and the fixing belt 24 shown in FIG. 4 are brought into contact with each other at a constant surface speed. The graph which shows the time-dependent change of the rotational drive torque [N * m] of the grinding | polishing member 26 in the case of making it contact in the state of 6 times the surface speed of the belt 24 is shown.

  As shown in FIG. 5, when the contact is made at 6 × speed, the difference in surface speed between the polishing member 26 and the fixing belt 24 is large, so that an impact load is applied and a large torque is generated. On the other hand, when contact is made at a constant speed, there is no impact due to the linear speed, so there is no sudden change in torque, and the contact can be made smoothly.

  According to the fixing device 20 according to the present embodiment described above, preliminary rotation is performed so that the surface speeds of the polishing member and the fixing member are close to a constant speed in a separated state, and the number of rotations of the polishing member is increased after press contact. By obtaining the polishing performance, it is possible to suppress a sudden torque change at the moment when the polishing member and the fixing member come into contact with each other and to sufficiently rub the fixing member. By suppressing this torque change, the load on the polishing member, the driving means for controlling the rotation of the polishing member, and the mechanism for controlling the contact / separation operation of the polishing member is suppressed, so that the polishing operation can be performed stably and fixed. Generation of local scratches on the member can be suppressed. Therefore, a stable and highly reliable rubbing operation can be realized, and the quality of the fixed image can be improved.

  In the above-described embodiment, the belt fixing type fixing device has been described as an example. However, the fixing device method is not limited to this, and for example, by a pressure contact between a pressure roller and a heating roller (fixing roller). Applied to other fixing system fixing devices such as a roller fixing system that forms a nip part, or a film fixing system that uses a film member stretched between a fixing roller and a heating roller instead of a fixing belt that is a belt member Of course, it may be.

  In addition, by using the image forming apparatus (FIG. 1) including the fixing device 20 having the above-described configuration, it is possible to stably perform the rubbing operation of the fixing member, and an image forming apparatus with high image stability. Can be realized.

  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 1 Image forming apparatus 2 Writing part 3 Original conveyance part 4 Original reading part 5 Contact glass 7 Paper feed part 8 Paper feed roller 9 Registration roller 11Y, 11M, 11C, 11BK Photosensitive drum 12 Charging part 13 Developing part 14 Transfer bias roller ( Primary transfer bias roller)
DESCRIPTION OF SYMBOLS 15 Cleaning part 16 Intermediate transfer belt cleaning part 17 Intermediate transfer belt 18 Secondary transfer bias roller 20 Fixing device 21 Heating roller 22 Fixing roller 22a Core metal 22b Elastic layer 23 Pressure roller 24 Fixing belt 25 Induction heating means 26 Abrasive member D Original N Fixing nip P Recording medium T Unfixed toner image

JP 2006-259341 A JP 2011-175067 A JP 2006-98930 A

Claims (9)

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 forms a nip portion with the fixing member;
A polishing member provided so as to be capable of being pressed against and separated from the fixing member, and rubbing the surface of the fixing member in a state of being pressed against the fixing member;
In a fixing device that conveys a recording medium carrying an unfixed toner image to the nip portion and fixes the unfixed toner image on the recording medium.
In a separated state before the polishing member is pressed against the fixing member, the polishing member is pre-rotated in a rotational direction that is the same as the conveying direction of the fixing member at a position where the polishing member is in pressure contact with the fixing member. Let
A fixing device, wherein the rotational speed of the polishing member is changed after the polishing member is brought into pressure contact with the fixing member in the preliminary rotation state.   2. The fixing device according to claim 1, wherein a surface speed of the polishing member in a pre-rotation state is in a range of 80 to 120% with respect to a surface speed of the fixing member.   The fixing device according to claim 1, wherein a surface speed of the polishing member in the preliminary rotation state is equal to a surface speed of the fixing member.   4. The fixing device according to claim 1, wherein the surface speed of the polishing member after the change from the pre-rotation state is in a range of 2 to 8 times the surface speed of the fixing member. 5. .   After changing the number of rotations of the polishing member and rubbing for a predetermined time, after rotating the polishing member away from the fixing member at the changed number of rotations, the rotation of the polishing member is stopped. The fixing device according to any one of claims 1 to 4.   6. The fixing member according to claim 1, wherein the fixing member is a belt member stretched around a plurality of roller members, and PFA is used for a surface layer of the belt member. Fixing device.   The fixing device according to claim 1, wherein a stepping motor is used as a driving unit that rotates the polishing member. 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 forms a nip portion with the fixing member;
A polishing member provided so as to be capable of being pressed against and separated from the fixing member, and rubbing the surface of the fixing member in a state of being pressed against the fixing member;
A method for controlling a fixing device that conveys a recording medium carrying an unfixed toner image to the nip portion and fixes the unfixed toner image on a recording medium,
In a separated state before the polishing member is pressed against the fixing member, the polishing member is pre-rotated in a rotational direction that is the same as the conveying direction of the fixing member at a position where the polishing member is in pressure contact with the fixing member. Step to
And a step of changing the number of rotations of the polishing member after the polishing member is brought into pressure contact with the fixing member in the preliminary rotation state.   An image forming apparatus comprising the fixing device according to claim 1.

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