JP2012058356A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device and image forming apparatus by which, in the case where a web mechanism is installed, an amount of web of the web mechanism is wound is efficiently controlled according to an amount of offset toner adhering to a fixing belt or pressure rotor and offset toner is securely and efficiently removed.SOLUTION: The fixing device includes: a web mechanism 70 configured such that the surface of the fixing belt 21 or pressure rotor 31 is cleaned by winding the web 71 disposed in contact with the fixing belt 21 or pressure rotor 31 and, at the same time, running the web 71 in a predetermined direction; and temperature detecting means 43 for detecting the temperature of the core metal 22a of the fixing auxiliary roller 22. Based on the detection result of the temperature detecting means 43, the web mechanism 70 varies an amount of web 71 wound per unit time.

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine thereof, and a fixing device installed therein, and in particular, a web mechanism for cleaning the surface of a fixing belt and a pressure rotating body. The present invention relates to an installed fixing device and an image forming apparatus.

Conventionally, a belt-type fixing device using an endless fixing belt is widely known as an image forming apparatus such as a copying machine or a printer (see, for example, Patent Document 1).
Such a belt-type fixing device includes a heating roller in which a heater (heating means) is provided, a fixing auxiliary roller (fixing roller) in which an elastic layer is formed on a metal core, and a heating roller and a fixing auxiliary roller. It is composed of a fixing belt supported and supported, a pressure roller (pressure rotator) that is in pressure contact with the auxiliary fixing roller via the fixing belt, and the like. Then, the recording medium is conveyed between the fixing belt and the pressure roller (the nip portion), and the toner image on the recording medium is fixed.

On the other hand, in Patent Document 2 and the like, in order to solve the problem that the offset toner attached on the fixing roller is reattached on the recording medium, the roller travels in a predetermined direction while winding a web (cleaning web) contacting the fixing roller. A technique for installing a web mechanism for cleaning the surface of the fixing roller is disclosed. Further, in Patent Document 2, it is assumed that the offset toner is likely to adhere to the fixing roller when the surface temperature of the fixing roller does not reach the reference value, and the web feed amount (winding amount) in the web mechanism is described. ) Is increased to improve the cleaning performance of the web mechanism.
Note that “offset” is a phenomenon in which a part of toner forming an image on a recording medium adheres to a fixing member or a pressure rotator during a fixing process. The “offset toner” is toner that adheres to the fixing member and the pressure rotating body due to the “offset”.

  When a conventional belt type fixing device is installed, the web winding amount (feed amount) in the web mechanism is efficiently adjusted according to the amount of offset toner attached to the fixing belt and the pressure rotating body. Could not be controlled. That is, as in Patent Document 2, even when the surface temperature of the fixing belt does not reach the reference value, even if the web winding amount in the web mechanism is controlled to be large, the fixing belt and the pressure rotator are attached. In some cases, the offset toner cannot be removed sufficiently.

As a result of repeated research, the inventor of the present application has a low correlation between the surface temperature of the auxiliary fixing roller and the degree of thermal expansion of the elastic layer formed on the core metal of the auxiliary fixing roller. I knew that there was. That is, in the fixing auxiliary roller that does not have a heat source such as a heater and contributes to the formation of the nip portion, even if the roller surface temperature is somewhat high, the temperature inside the elastic layer is not so high, and The degree of thermal expansion of the layer is so small that the nip width at the nip portion formed with the pressure rotator may not be sufficiently secured. Such a phenomenon has been particularly prominent when the apparatus is started up (for example, in the morning). If the fixing process is performed in a state where a sufficient nip width is not formed as described above, even if the surface temperature of the fixing belt is sufficiently high, a larger amount of offset toner than the normal offset toner is generated. In the web mechanism that controls the amount of winding of the web based on the surface temperature of the fixing belt that is adhered to the pressure rotating body and approximates the surface temperature of the auxiliary fixing roller, the offset toner can be sufficiently removed. There wasn't.
In order to solve such a problem, a method of setting the web winding amount in the web mechanism high in advance may be considered, but in such a case, the web consumption cycle is accelerated, which is inefficient. .

  The present invention has been made to solve the above-described problems. When the web mechanism is installed, the web winding in the web mechanism is performed according to the amount of offset toner adhering to the fixing belt and the pressure rotating body. It is an object of the present invention to provide a fixing device and an image forming apparatus that can efficiently control the amount to be taken and can reliably and efficiently remove offset toner.

  The fixing device according to the first aspect of the present invention is a fixing device that heats and melts a toner image and fixes the toner image on a recording medium, and includes a heating roller heated by a heating means, and an elastic material on the mandrel. A fixing auxiliary roller having a layer formed thereon, a fixing belt stretched by the heating roller and the fixing auxiliary roller, and a nip through which the recording medium is conveyed by being pressed against the fixing auxiliary roller via the fixing belt A pressure rotator that forms a portion, and a web mechanism that cleans the surface of the fixing belt or the pressure rotator by running the web in contact with the fixing belt or the pressure rotator in a predetermined direction. Temperature detecting means for detecting the temperature of the core metal of the fixing auxiliary roller, and the web mechanism is configured to generate a unit time of the web based on a detection result of the temperature detecting means. It is to vary the Rino winding amount.

  The fixing device according to a second aspect of the present invention is the fixing device according to the first aspect, wherein the web mechanism detects the temperature when the temperature detected by the temperature detecting means does not reach a predetermined value. Compared with the case where the temperature detected by the detecting means has reached the predetermined value, the web is controlled so that the amount of winding is increased.

  According to a third aspect of the present invention, in the fixing device according to the second aspect, the web mechanism is configured such that the temperature detected by the temperature detecting means is a second predetermined value that is greater than the predetermined value. When the temperature is reached, the winding amount of the web is controlled to be smaller than when the temperature detected by the temperature detection means does not reach the second predetermined value. .

  According to a fourth aspect of the present invention, there is provided the fixing device according to the first aspect, wherein the temperature of the outer peripheral surface of the heating roller or the auxiliary fixing roller is detected directly or indirectly. And a web mechanism for varying the winding amount of the web based on a detection result of the temperature detection means and a detection result of the second temperature detection means.

  According to a fifth aspect of the present invention, in the fixing device according to the fourth aspect, the web mechanism is configured such that the temperature detected by the temperature detecting means and the temperature detected by the second temperature detecting means. When the average temperature does not reach a predetermined value, the amount of winding of the web is controlled to be larger than when the average temperature reaches the predetermined value.

  The fixing device according to a sixth aspect of the present invention is the fixing device according to the fifth aspect, wherein the web mechanism is configured such that the temperature detected by the temperature detecting means and the temperature detected by the second temperature detecting means. When the average temperature of the web reaches a second predetermined value that is greater than the predetermined value, the amount of winding of the web is smaller than when the average temperature does not reach the second predetermined value. It is controlled to be smaller.

  A fixing device according to a seventh aspect of the present invention is the fixing device according to any one of the first to sixth aspects, wherein the number of sheets of the recording medium continuously passed through the nip portion, or Detecting means for detecting a driving time during which the auxiliary fixing roller is continuously driven to rotate, and the web mechanism is configured so that each time the number of sheets passing or the driving time detected by the detecting means increases, The amount of winding is controlled to be small.

  An image forming apparatus according to an eighth aspect of the present invention includes the fixing device according to any one of the first to seventh aspects.

  In the present invention, the winding amount per unit time of the web mechanism in the web mechanism is variable based on the detection result of the temperature detecting means for detecting the temperature of the core metal of the auxiliary fixing roller. Provided are a fixing device and an image forming apparatus in which a web winding amount in a web mechanism is efficiently controlled according to the amount of offset toner attached to a body, and offset toner is reliably and efficiently removed. be able to.

1 is an overall configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. 2 is a configuration diagram illustrating a fixing device. FIG. It is another block diagram which shows a fixing device. 6 is a control table showing control of the web mechanism based on the temperature of the core metal of the fixing auxiliary roller. It is another control table which shows control of the web mechanism based on the temperature of the core metal of a fixing auxiliary roller. 6 is a control table showing the control of the web mechanism based on the temperature of the core metal of the fixing auxiliary roller and the surface temperature of the heating roller. 6 is a control table showing the control of the web mechanism based on the temperature of the core metal of the fixing auxiliary roller and the surface temperature of the auxiliary fixing roller. It is a control table which shows control of a web mechanism based on the number of continuous paper passing. It is a control table which shows control of a web mechanism based on continuous drive time.

Embodiment.
Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

First, the configuration and operation of the entire image forming apparatus will be described with reference to FIG.
In FIG. 1, reference numeral 1 denotes an apparatus main body of a tandem color copier as an image forming apparatus, 2 a writing unit that emits laser light based on input image information, and 3 an original conveying unit that conveys an original D to an original reading unit 4. 4 is a document reading unit that reads image information of the document D, 6 is a conveyance roller, 7 is a paper feed unit that accommodates a recording medium P such as transfer paper, 9 is a registration roller that adjusts the conveyance timing of the recording medium P, 11Y, 11M, 11C, and 11BK are photosensitive drums on which toner images of respective colors (yellow, magenta, cyan, and black) are formed, 12 is a charging unit that charges the photosensitive drums 11Y, 11M, 11C, and 11BK, and 13 Is a developing unit for developing an electrostatic latent image formed on each of the photosensitive drums 11Y, 11M, 11C, and 11BK, and 14 is formed on each of the photosensitive drums 11Y, 11M, 11C, and 11BK. A transfer bias roller (primary transfer bias roller) for transferring the toner image superimposed on the recording medium P, and 15 a cleaning unit for collecting untransferred toner on the photosensitive drums 11Y, 11M, 11C, and 11BK. Show.

  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 19 for transferring the toner image onto the recording medium P, a conveying belt 19 for conveying the recording medium P after the secondary transfer process toward the fixing device 20, and a toner image (unfixed image) on the recording medium P fixed. 1 shows a belt-type fixing device.

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 counterclockwise in FIG. First, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK are uniformly charged at a portion facing the charging unit 12 (this is a 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 separate optical path for each of the yellow, magenta, cyan, and black color components (this is an 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 photoconductive drums 11Y, 11M, 11C, and 11BK on which the electrostatic latent images of the respective colors are formed reach 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 (development process). .)
Thereafter, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK after the development process reach the facing portions of 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 (in the primary transfer process). is there.).

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 (this is a cleaning process).
Thereafter, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK pass through a neutralization 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 photosensitive drums 11Y, 11M, 11C, and 11BK are transferred (carrying) are run in the clockwise direction in the drawing and are connected to the secondary transfer bias roller 18. Reach the opposite position. Then, a 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 transported between the intermediate transfer belt 17 and the secondary transfer bias roller 18 (secondary transfer nip) is transported from the paper supply unit 7 via the registration roller 9 and the like. It is a thing.
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 19. In the fixing device 20, the color image (toner) is fixed on the recording medium P at the nip portion between the fixing belt and the pressure roller.
Then, after the fixing process, the recording medium P is transported by the transport roller 6 and then discharged as an output image outside the apparatus main body 1 by the paper discharge roller, thereby completing a series of image forming processes.

Next, the configuration and operation of the fixing device 20 installed in the image forming apparatus main body 1 will be described in detail with reference to FIGS.
FIG. 2 is a configuration diagram showing the fixing device 20. FIG. 3 is another configuration diagram showing the fixing device 20, and is a diagram mainly showing the configuration of the pressure adjusting mechanism.
As shown in FIG. 2, the fixing device 20 includes a fixing auxiliary roller 22, a heating roller 23, a fixing belt 21 as a fixing member, a tension roller 24, a pressure roller 31 as a pressure rotator, and three temperature sensors 41 to 41. 43, a guide plate 35, and the like.

  Here, the fixing belt 21 is a multi-layered endless belt (with a layer thickness of about 90 μm) in which an elastic layer and a release layer are sequentially laminated on a base layer made of a resin material such as PI (polyimide). .) The elastic layer of the fixing belt 21 is formed of an elastic material such as fluorine rubber, silicone rubber, or foamable silicone rubber. The release layer of the fixing belt 21 is formed of PFA (tetrafluoroethylene barfluoroalkyl vinyl ether copolymer resin), polyimide, polyetherimide, PES (polyether sulfide), or the like. By providing the release layer on the surface layer of the fixing belt 21, the releasability (peelability) for the toner T (toner image) is ensured. The fixing belt 21 is stretched and supported by three roller members (a fixing auxiliary roller 22, a heating roller 23, and a tension roller 24), and travels in the direction of the arrow in FIG. The tension roller 24 is in contact with the outer peripheral surface of the fixing belt 21 and applies a predetermined tension to the fixing belt 21. By using the fixing belt 21 having a low heat capacity as the fixing member, the temperature rise characteristic of the apparatus is improved.

In the fixing auxiliary roller 22, an elastic layer 22b (having an Asker C hardness of about 25 to 50) made of foamed silicone rubber having a layer thickness of about 15 mm is formed on a metal core 22a made of a metal material such as SUS304. The roller member having an outer diameter of about 52 mm is pressed against a pressure roller 31 as a pressure rotator via the fixing belt 21 to form a nip portion. By forming the elastic layer 22b from a foamed material, the nip width (nip amount) at the nip portion can be set relatively large, and the heat of the fixing belt 21 is difficult to transfer to the auxiliary fixing roller 22. The shaft portion of the auxiliary fixing roller 22 is connected to the drive motor 61 and is driven to rotate clockwise in FIG.
In the present embodiment, foamed silicone rubber is used as the material of the elastic layer 22b. However, fluorine rubber, silicone rubber, or the like can be used as the material of the elastic layer 22b.
Here, on the outer peripheral surface of the cored bar 22a of the auxiliary fixing roller 22 (the end in the roller axis direction, in the vicinity of the portion where the elastic layer 22b is not formed and the bearing 34 is inserted). A third temperature sensor 43 (thermistor) is installed as temperature detecting means for detecting the temperature of the cored bar 22a. The winding amount of the web 71 in the web mechanism 70 is controlled based on the detection result of the third temperature sensor 43 (temperature detection means), which will be described in detail later.

The heating roller 23 is a hollow roller member having an outer diameter of about 38 mm made of a metal material having high thermal conductivity such as aluminum, and a heater 25 (heat source) as a heating means is fixed inside the cylindrical body. It is installed. The surface of the heating roller 23 is anodized to improve the corrosion resistance.
The heater 25 (heating means) of the heating roller 23 is a halogen heater, and both ends thereof are fixed to a side plate (not shown) of the fixing device 20. Then, the heating roller 23 is heated by radiant heat from the heater 25 whose output is controlled by an AC power source (not shown) of the apparatus main body 1, and further, the recording medium starts from the surface of the fixing belt 21 heated by the heating roller 23. Heat is applied to the toner image T on P. The output control of the heater 25 (heating means) is performed based on the detection result of the belt surface temperature by the first temperature sensor 41 (thermistor) in contact with the surface (outer peripheral surface) of the fixing belt 21. Specifically, the AC voltage is applied from the AC power source to the heater 25 for the energization time determined based on the detection result of the first temperature sensor 41. By such output control of the heater 25, the temperature (fixing temperature) of the fixing belt 21 can be adjusted and controlled to a desired temperature (target control temperature).
The first temperature sensor 41 also functions as a second temperature detection unit that indirectly detects the temperature of the outer peripheral surface of the heating roller 23 via the fixing belt 21, and the detection result of the web mechanism 70 described later. Can be used for control. Further, a second temperature sensor 42 (thermistor) functioning as second temperature detecting means for indirectly detecting the temperature of the outer peripheral surface of the auxiliary fixing roller 22 via the fixing belt 21 is installed, and the detection result will be described later. It can be used to control the web mechanism 70. Control of the web mechanism 70 using such second temperature detection means will be described in detail later.

  In the present embodiment, the tension roller 24 is installed and a predetermined tension is applied to the fixing belt 21. However, the heating roller 23 can be functioned as a tension roller without the tension roller 24 being installed. Specifically, the heating roller 23 is held so as to be swingable in the left-right direction in FIG. 2 with respect to the side plate of the fixing device 20, and the heating roller 23 is urged to the right side in FIG. 23 functions as a tension roller that applies a predetermined tension to the fixing belt 21. In such a case, the fixing belt 21 is stretched and supported only by two roller members (the fixing auxiliary roller 22 and the heating roller 23).

The pressure roller 31 as a pressure rotating body has an outer diameter of about 50 mm, and mainly includes a cored bar 32 and an elastic layer 33 (layer) formed on the outer peripheral surface of the cored bar 32 via an adhesive layer. And a thickness of about 3 mm). The elastic layer 33 of the pressure roller 31 is formed of a solid rubber material such as fluorine rubber or silicone rubber. A thin release layer made of PFA or the like can be provided on the surface layer of the elastic layer 33.
The pressure roller 31 is in pressure contact with the auxiliary fixing roller 22 via the fixing belt 21 by the pressure adjusting mechanism 55 to 58 shown in FIG. In this way, a desired nip portion is formed between the pressure roller 31 and the fixing belt 21. In this embodiment, the compression amount of the elastic layer 22b of the auxiliary fixing roller 22 is set to about 3 to 4 mm, and the nip width of the nip portion is set to about 14 mm (which is an appropriate value in a normal state). Yes. Note that the pressure adjustment mechanisms 55 to 58 are respectively installed at both ends in the width direction of the fixing device 20.

The pressure adjustment mechanisms 55 to 58 (nip width adjustment mechanism) adjust the pressure (pressure contact force) at the nip portion between the auxiliary fixing roller 22 and the pressure roller 31.
Specifically, with reference to FIG. 3, the pressure roller 31 is rotatably held on the side plate of the fixing device 20 through the bearings 34 at both ends. The bearing 34 is held in a slot formed in a side plate of the fixing device 20 so as to be movable in the vertical direction. As shown in FIG. 3, the pressure adjusting mechanism acts on the pressure lever 55 that engages the bearing 34 of the pressure roller 31 and the pressure lever 55 so that the pressure roller 31 faces the fixing auxiliary roller 22. A cam member 56 (eccentric cam) that is energized, a second drive motor 62 that rotationally drives the cam member 56, a position sensor 57 that detects the posture of the cam member 56 in the rotational direction, and a pressure lever 55 are brought into contact with the cam member 56. For this purpose, a spring 58 for urging the pressure lever 55 is used. The pressure lever 55 is held on the side plate of the fixing device 20 so as to be rotatable about a support shaft 55a.
And the cam member 56 moves the pressurization lever 55 in the direction which increases / decreases the pressurizing force of a nip part. That is, when it is desired to set the pressing force at the nip portion high, the cam member 56 is driven to rotate clockwise from the state shown in FIG. 3, and the pressure lever 55 pushes the pressure roller 31 upward via the bearing 34. The pressure (surface pressure) of the pressure roller 31 against the fixing belt 21 (fixing auxiliary roller 22) is increased. On the other hand, when it is desired to set the pressing force at the nip portion low, the cam member 56 is driven to rotate counterclockwise from the state shown in FIG. 3 so that the pressure lever 55 repels the weight of the pressure roller 31 and the repulsion at the nip portion. It moves downward by the force and the urging force of the spring 58 to reduce the pressure (surface pressure) of the pressure roller 31 against the fixing belt 21 (fixing auxiliary roller 22).
The posture of the cam member 56 in the rotational direction is determined by optically detecting the presence or absence of a detected plate 56a fixed to the shaft portion of the cam member 56 and rotating integrally with the cam member 56 by a position sensor 57. Be recognized.

  As described above, the pressure adjustment mechanisms 55 to 58 adjust the pressure (nip pressure) of the pressure roller 31 against the auxiliary fixing roller 22. The pressure adjustment mechanisms 55 to 58 apply pressure at the nip portion when the recording medium P is not passed through the nip portion (when the image is not formed such as when the power is turned off, when warming up, when waiting, etc.). The operation is performed so that the pressure is reduced (or the pressure roller 31 is separated from the fixing auxiliary roller 22). This prevents a large nip pressure from being locally applied to the elastic layer 22b of the auxiliary fixing roller 22 and the elastic layer 33 of the pressure roller 31 for a long period of time, and compression sets are generated in the elastic layers 22b and 31. The trouble is reduced.

Here, in the present embodiment, as shown in FIG. 2, a web mechanism 70 that contacts the outer peripheral surface of the pressure roller 31 and cleans the surface of the pressure roller 31 is installed. The web mechanism 70 moves offset webs (mainly on the fixing belt 21) attached to the surface of the pressure roller 31 by rolling the web 71 in contact with the pressure roller 31 (pressure rotator) while traveling in a predetermined direction. It is the offset toner that has been transferred to the pressure roller 31 and is then cleaned.
Specifically, the web mechanism 70 includes a web 71, a winding roller 72, a web roller 73, a pressing roller 74, a driving motor 75, and the like. The web 71 is a non-woven fabric made of aramid fiber, polyester fiber or the like impregnated with silicon oil. The web 71 is wound around the web roller 73, and the winding roller 72 coupled to the drive motor 75 performs the winding operation (rotation driving in the counterclockwise direction in FIG. 2). The dirt on the surface of the pressure roller 31 is wiped off while moving to. The web 71 is urged by a pressing roller 74 provided with urging means (not shown), and is pressed against the pressure roller 31 with a predetermined pressure. When the web 71 wound around the web roller 73 disappears, part or all of the web mechanism 70 is replaced with a new one.
The web mechanism 70 controls the winding amount of the web 71 based on the detection result of the third temperature sensor 43 (temperature detection means) that detects the temperature of the cored bar 22a of the auxiliary fixing roller 22. However, this will be described in detail later.

Referring to FIG. 2, guide plates 35 for guiding the conveyance of the recording medium P are respectively provided at the entrance side and the exit side of the contact portion (nip portion) between the fixing belt 21 and the pressure roller 31. It is arranged. The guide plate 35 is fixed to the side plate of the fixing device 20.
Although not shown, a separation plate is disposed at a position facing the outer peripheral surface of the fixing belt 21 and in the vicinity of the exit side of the nip portion. The separation plate prevents a problem that the recording medium P after the fixing process is wound around the fixing belt 21 along the travel of the fixing belt 21.

Hereinafter, the operation of the fixing device 20 during normal paper feeding will be described.
When the power switch of the apparatus main body 1 is turned on, an AC voltage is applied (powered) from an AC power source (not shown) to the heater 25, and the fixing auxiliary roller 22 is rotationally driven by the drive motor 61. The fixing belt 21, the heating roller 23, and the pressure roller 31 rotate (follow) in the direction of the arrow in FIG.
Thereafter, the recording medium P is fed from the paper supply unit 7 and the toners of the respective colors on the photosensitive drums 11Y, 11M, 11C, and 11BK are carried on the recording medium P as unfixed images. The recording medium P carrying the unfixed image T (toner image) is conveyed in the direction of the arrow Y10 in FIG. 2 and fed into the nip portion between the fixing belt 21 and the pressure roller 31 that are in a pressure contact state. The toner image T is fixed on the surface of the recording medium P by the heating by the fixing belt 21 and the pressing force of the fixing belt 21 (fixing auxiliary roller 22) and the pressure roller 31. Thereafter, the recording medium P sent out from the nip portion by the rotating fixing belt 21 and the pressure roller 31 is conveyed in the direction of the arrow Y11.

Hereinafter, a characteristic configuration and operation of the fixing device 20 in the present embodiment will be described.
In the present embodiment, the web mechanism 70 winds the web 71 per unit time based on the detection result of the third temperature sensor 43 as temperature detecting means for detecting the temperature of the core 22a of the auxiliary fixing roller 22. The amount (feed amount) is variably controlled.
Specifically, referring to FIG. 4, the temperature Ts of the cored bar 22a detected by the third temperature sensor 43 (temperature detecting means) is set to a predetermined value (in this embodiment, set to 55 ° C.). Compared to the case where the temperature Ts of the cored bar 22a detected by the third temperature sensor 43 has reached a predetermined value (in this embodiment, it is set to 55 ° C.) when not reached. The web mechanism 70 (drive motor 75) is controlled so that the winding amount of 71 becomes large.

Specifically, information related to the temperature Ts of the cored bar 22 a detected by the third temperature sensor 43 (temperature detection means) is sent to the control unit 60.
When the controller 60 determines that the temperature Ts of the cored bar 22a detected by the third temperature sensor 43 is 55 ° C. or less, the elastic layer 22b (rubber layer) of the auxiliary fixing roller 22 is detected. The internal temperature is not so high, the degree of thermal expansion of the elastic layer 22b is small, and the nip width in the nip portion formed between the pressure roller 31 is not sufficiently secured and hot offset is likely to occur. As an example, on / off control of the drive motor 75 for running the web 71 is performed so as to operate at 10 second intervals for 5 seconds (intermittent operation of 5 seconds on and 5 seconds off is repeated). As a result, a relatively large amount of offset toner adhering to the pressure roller 31 is efficiently removed by the web 71 in which the winding amount is increased and the cleaning performance is improved.
In contrast, if the controller 60 determines that the temperature Ts of the cored bar 22a detected by the third temperature sensor 43 exceeds 55 ° C., the elastic layer 22b ( The temperature inside the rubber layer) is sufficiently high, the degree of thermal expansion of the elastic layer 22b is in a normal state, and the nip width at the nip portion formed with the pressure roller 31 is sufficiently ensured to be hot. Assuming that the offset is relatively difficult to occur, the web 71 is moved so that the reference operation is performed for 5 seconds at intervals of 12.5 seconds (intermittent operation of 5 seconds on and 7.5 seconds off is repeated). On / off control of the drive motor 75 for traveling is performed. As a result, a relatively small amount of offset toner adhering to the pressure roller 31 is efficiently removed by the web 71 in which the winding amount is decelerated and the cleaning performance is lowered.

  Thus, the web in the web mechanism 70 is based on the detection result of the third temperature sensor 43 that detects the temperature of the cored bar 22a of the auxiliary fixing roller 22 (according to the amount of offset toner attached to the pressure roller 31). By optimizing the winding amount per unit time of 71 without excess or deficiency, the offset toner can be reliably and efficiently removed without advancing the consumption cycle of the web 71.

Further, in the present embodiment, the web mechanism 70 has a case where the temperature of the cored bar 22a of the auxiliary fixing roller 22 detected by the third temperature sensor 43 has reached a second predetermined value larger than the predetermined value described above. In addition, the winding amount (feed amount) of the web 71 is variably controlled so as to be smaller than when the temperature detected by the third temperature sensor 43 does not reach the second predetermined value.
Specifically, referring to FIG. 5, the temperature Ts of the cored bar 22a detected by the third temperature sensor 43 (temperature detection means) is set to a second predetermined value (in this embodiment, 105 ° C.). When the temperature Ts of the cored bar 22a detected by the third temperature sensor 43 has not reached a predetermined value (in this embodiment, it is set to 105 ° C.). Thus, the web mechanism 70 (drive motor 75) is controlled so that the winding amount of the web 71 becomes small.

Specifically, information related to the temperature Ts of the cored bar 22 a detected by the third temperature sensor 43 (temperature detection means) is sent to the control unit 60.
When the controller 60 determines that the temperature Ts of the metal core 22a detected by the third temperature sensor 43 is 105 ° C. or less (55 ° C. <Ts ≦ 105 ° C.), the elastic layer 22b Assuming that the degree of thermal expansion is in a normal state and that the nip width in the nip portion formed with the pressure roller 31 is sufficiently secured and hot offset is relatively unlikely to occur, 12.5 seconds On / off control of the drive motor 75 for running the web 71 is performed so that a reference operation is performed at intervals of 5 seconds (intermittent operation of 5 seconds on and 7.5 seconds off is repeated).
On the other hand, if the control unit 60 determines that the temperature Ts of the cored bar 22a detected by the third temperature sensor 43 exceeds 105 ° C., the elastic layer The degree of thermal expansion of 22b is in a normal state, and the nip width at the nip portion formed with the pressure roller 31 is sufficiently secured, and the surface temperature (fixing temperature) on the fixing belt 21 is also sufficient. A drive motor 75 for running the web 71 so as to operate at a 15-second interval for 5 seconds (intermittent operation of 5 seconds on and 10 seconds off is repeated) on the assumption that the hot offset is more difficult to occur. ON / OFF control is performed. As a result, a smaller amount of offset toner adhering to the pressure roller 31 is efficiently removed by the web 71 in which the winding amount is further decelerated and the cleaning performance is further reduced.

  Thus, the web in the web mechanism 70 is based on the detection result of the third temperature sensor 43 that detects the temperature of the cored bar 22a of the auxiliary fixing roller 22 (according to the amount of offset toner attached to the pressure roller 31). By optimizing the winding amount per unit time of 71 without further excess or deficiency, the offset toner can be removed more reliably and efficiently without shortening the consumption cycle of the web 71.

Here, in the present embodiment, the winding amount per unit time of the web 71 in the web mechanism 70 is determined based only on the detection result of the third temperature sensor 43 that detects the temperature of the cored bar 22 a of the fixing auxiliary roller 22. Controlled.
On the other hand, the detection result of the third temperature sensor 43 that detects the temperature of the cored bar 22a of the auxiliary fixing roller 22 and the second temperature detection means that indirectly detects the temperature of the outer peripheral surface of the heating roller 23. The winding amount per unit time of the web 71 in the web mechanism 70 can be controlled based on the detection result of the one temperature sensor 41.
Specifically, referring to FIG. 6, the temperature Ts of the cored bar 22a detected by the third temperature sensor 43 (temperature detection means) and the heating roller detected by the first temperature sensor 41 (second temperature detection means). When the average temperature ((Ts + Tp) / 2) of the surface temperature Tp of 23 does not reach a predetermined value (in this embodiment, it is set to 105 ° C.), the average temperature ((Ts + Tp) / 2) has reached a predetermined value (in this embodiment, it is set to 105 ° C.), the web mechanism 70 (drive motor 75) so that the winding amount of the web 71 becomes larger. Is controlled.

Specifically, information related to the temperature Ts of the cored bar 22a detected by the third temperature sensor 43 (temperature detection means) and the surface of the heating roller 23 detected by the first temperature sensor 41 (second temperature detection means). Information related to the temperature Tp is sent to the control unit 60, respectively. And those average temperature ((Ts + Tp) / 2) is calculated | required.
When the controller 60 determines that the average temperature ((Ts + Tp) / 2) is 105 ° C. or less, the temperature inside the elastic layer 22b (rubber layer) of the auxiliary fixing roller 22 is so high. Assuming that the degree of thermal expansion of the elastic layer 22b is small and a nip width in the nip portion formed between the elastic layer 22b and the pressure roller 31 is not sufficiently secured and hot offset is likely to occur for 10 seconds. On / off control of the drive motor 75 for traveling the web 71 is performed so as to operate at intervals of 5 seconds (intermittent operation of 5 seconds on and 5 seconds off is repeated). As a result, a relatively large amount of offset toner adhering to the pressure roller 31 is efficiently removed by the web 71 in which the winding amount is increased and the cleaning performance is improved.
On the other hand, when the controller 60 determines that the average temperature ((Ts + Tp) / 2) exceeds 105 ° C., the inside of the elastic layer 22b (rubber layer) of the auxiliary fixing roller 22 is determined. The temperature is sufficiently high, the degree of thermal expansion of the elastic layer 22b is in a normal state, and the nip width at the nip portion formed between the pressure roller 31 and the nip portion is sufficiently secured so that hot offset is relatively unlikely to occur. Drive motor for running the web 71 so as to perform a reference operation that operates for 5 seconds at 12.5 second intervals (an intermittent operation of 5 seconds on and 7.5 seconds off is repeated) 75 on / off control is performed. As a result, a relatively small amount of offset toner adhering to the pressure roller 31 is efficiently removed by the web 71 in which the winding amount is decelerated and the cleaning performance is lowered.

Thus, in addition to the detection result of the third temperature sensor 43 that detects the temperature of the cored bar 22a of the fixing auxiliary roller 22, the detection result of the first temperature sensor 41 that indirectly detects the surface temperature of the heating roller 23 is used. Therefore, the web 71 consumption cycle is accelerated by optimizing the winding amount of the web 71 per unit time in the web mechanism 70 without excess or deficiency (according to the amount of offset toner adhering to the pressure roller 31). Therefore, the offset toner can be removed reliably and efficiently.
In particular, the surface temperature of the heating roller 23 detected by the first temperature sensor 41 while the fixing belt 21 is traveling is the surface temperature (outer peripheral surface) of the auxiliary fixing roller 22 when the fixing belt 21 is traveling. The average temperature ((Ts + Tp) / 2) of the temperatures detected by the two temperature sensors 41 and 43 is substantially equal to the internal temperature of the elastic layer 22b of the auxiliary fixing roller 22. Therefore, it is possible to accurately grasp the change in the amount of offset toner based on the degree of expansion of the elastic layer 22b of the fixing auxiliary roller 22, and the effect of the above-described embodiment can be ensured.

Here, even when such control is performed, the average temperature ((Ts + Tp) / 2) is set to a second predetermined value larger than a predetermined value (in this embodiment, set to 105 ° C.). When the temperature reaches the web mechanism 70 (drive motor 75), the winding amount of the web 71 is smaller than when the average temperature ((Ts + Tp) / 2) does not reach the second predetermined value. Can be controlled. As a result, the winding amount of the web 71 per unit time in the web mechanism 70 is further optimized without excess or deficiency, and offset toner can be removed more reliably and efficiently without shortening the consumption cycle of the web 71. it can.
In addition, when performing control as described above, instead of the first temperature sensor 41 that indirectly detects the temperature of the outer peripheral surface of the heating roller 23, the temperature that directly detects the temperature of the outer peripheral surface of the heating roller 23. A sensor can also be used.

Here, in the present embodiment, the winding amount per unit time of the web 71 in the web mechanism 70 is determined based only on the detection result of the third temperature sensor 43 that detects the temperature of the cored bar 22 a of the fixing auxiliary roller 22. Controlled.
On the other hand, the detection result of the third temperature sensor 43 that detects the temperature of the cored bar 22a of the auxiliary fixing roller 22 and the second temperature detecting means that indirectly detects the temperature of the outer peripheral surface of the auxiliary fixing roller 22 are used. Based on the detection result of the second temperature sensor 42, the winding amount of the web 71 in the web mechanism 70 per unit time can be controlled.
In detail, referring to FIG. 7, the temperature Ts of the cored bar 22a detected by the third temperature sensor 43 (temperature detecting means) and the fixing assistance detected by the second temperature sensor 41 (second temperature detecting means). When the average temperature ((Ts + Tm) / 2) of the surface temperature Tm of the roller 22 does not reach a predetermined value (in this embodiment, it is set to 105 ° C.), the average temperature ((Ts + Tm) ) / 2) reaches a predetermined value (in this embodiment, it is set to 105 ° C.). The web mechanism 70 (drive motor 75) is set so that the winding amount of the web 71 becomes larger. ) Is controlled.

Specifically, information related to the temperature Ts of the cored bar 22a detected by the third temperature sensor 43 (temperature detecting means) and the fixing auxiliary roller 22 detected by the second temperature sensor 42 (second temperature detecting means). Information relating to the surface temperature Tm is sent to the controller 60, respectively. And the average temperature ((Ts + Tm) / 2) is calculated | required.
When the controller 60 determines that the average temperature ((Ts + Tm) / 2) is 105 ° C. or less, the temperature inside the elastic layer 22b (rubber layer) of the auxiliary fixing roller 22 is so high. Assuming that the degree of thermal expansion of the elastic layer 22b is small and a nip width in the nip portion formed between the elastic layer 22b and the pressure roller 31 is not sufficiently secured and hot offset is likely to occur for 10 seconds. On / off control of the drive motor 75 for traveling the web 71 is performed so as to operate at intervals of 5 seconds (intermittent operation of 5 seconds on and 5 seconds off is repeated). As a result, a relatively large amount of offset toner adhering to the pressure roller 31 is efficiently removed by the web 71 in which the winding amount is increased and the cleaning performance is improved.
On the other hand, when the control unit 60 determines that the average temperature ((Ts + Tm) / 2) exceeds 105 ° C., the inside of the elastic layer 22b (rubber layer) of the auxiliary fixing roller 22 is determined. The temperature is sufficiently high, the degree of thermal expansion of the elastic layer 22b is in a normal state, and the nip width at the nip portion formed between the pressure roller 31 and the nip portion is sufficiently secured so that hot offset is relatively unlikely to occur. Drive motor for running the web 71 so as to perform a reference operation that operates for 5 seconds at 12.5 second intervals (an intermittent operation of 5 seconds on and 7.5 seconds off is repeated) 75 on / off control is performed. As a result, a relatively small amount of offset toner adhering to the pressure roller 31 is efficiently removed by the web 71 in which the winding amount is decelerated and the cleaning performance is lowered.

As described above, in addition to the detection result of the third temperature sensor 43 that detects the temperature of the core metal 22a of the auxiliary fixing roller 22, the detection result of the second temperature sensor 42 that indirectly detects the surface temperature of the auxiliary fixing roller 22 is used. (In accordance with the amount of offset toner adhering to the pressure roller 31), the web 71 consumption cycle is optimized by optimizing the winding amount per unit time of the web 71 in the web mechanism 70. The offset toner can be removed reliably and efficiently without accelerating.
In particular, the surface temperature of the auxiliary fixing roller 22 detected by the second temperature sensor 42 is substantially the same as the surface temperature of the auxiliary auxiliary roller 22 (the temperature of the outer peripheral surface) even when the fixing belt 21 is not running. Therefore, the average temperature ((Ts + Tm) / 2) of the temperatures detected by the two temperature sensors 42 and 43 is substantially equal to the internal temperature of the elastic layer 22b of the auxiliary fixing roller 22. Therefore, it is possible to accurately grasp the change in the amount of offset toner based on the degree of expansion of the elastic layer 22b of the fixing auxiliary roller 22, and the effect of the above-described embodiment is further ensured.

Here, even when such control is performed, the average temperature ((Ts + Tm) / 2) is set to a second predetermined value larger than a predetermined value (in this embodiment, set to 105 ° C.). When it reaches, the web mechanism 70 (drive motor 75) reduces the winding amount of the web 71 compared to the case where the average temperature ((Ts + Tm) / 2) does not reach the second predetermined value. Can be controlled. As a result, the winding amount of the web 71 per unit time in the web mechanism 70 is further optimized without excess or deficiency, and offset toner can be removed more reliably and efficiently without shortening the consumption cycle of the web 71. it can.
When performing the control as described above, the temperature of the outer peripheral surface of the auxiliary fixing roller 22 is directly detected instead of the second temperature sensor 42 that indirectly detects the temperature of the outer peripheral surface of the fixing auxiliary roller 22. A temperature sensor can also be used.

Here, in the present embodiment, when continuous paper is passed, the paper passing detected by the counter 62 as detection means for detecting the number of papers of the recording medium P that is continuously passed through the nip portion. The web mechanism 70 can be controlled so that the winding amount of the web 71 decreases as the number of sheets increases. The reason for performing such control is that the internal temperature of the elastic layer 22b of the auxiliary fixing roller 22 gradually increases as the number of continuous paper passes increases, and the degree of thermal expansion of the elastic layer 22b approaches the normal state. This is because the nip width at the nip portion formed between the pressure roller 31 and the pressure roller 31 is sufficiently secured so that hot offset is hardly caused.
Specifically, referring to FIG. 8, when the number of continuous sheets to be passed is 500 or less, the drive motor 75 operates so as to operate for 5 seconds at intervals of 10 seconds (intermittent operation of 5 seconds on and 5 seconds off is repeated). ON / OFF control is performed, and when the number of continuous sheets is 501 to 1000, the drive motor 75 is operated so as to operate for 5 seconds at intervals of 11 seconds (intermittent operation of 5 seconds on and 6 seconds off is repeated). ON / OFF control is performed, and when the number of continuous paper passes is 1001 or more, it operates for 5 seconds at 12.5 second intervals (intermittent operation of 5 seconds on and 7.5 seconds off is repeated). On / off control of the drive motor 75 is performed so that the above is performed. Such control of the web mechanism 70 is performed together with the control of the web mechanism 70 described above with reference to FIG.
As a result, the winding amount of the web 71 per unit time in the web mechanism 70 is further optimized without excess or deficiency, and offset toner can be removed more reliably and efficiently without shortening the consumption cycle of the web 71. it can.

Further, in the present embodiment, when the fixing device 20 is continuously driven by continuous paper passing or the like, a detection unit (not shown) that detects a driving time for continuously rotating the fixing auxiliary roller 22 is illustrated. Each time the driving time detected by the timer (which is a timer for detecting the driving time of the driving motor 61 and is provided in the control unit 60) is increased, the winding amount of the web 71 is reduced. The web mechanism 70 can be controlled. The reason for performing such control is that the internal temperature of the elastic layer 22b of the auxiliary fixing roller 22 gradually increases as the driving time of the auxiliary fixing roller 22 increases, and the degree of thermal expansion of the elastic layer 22b is in a normal state. This is because the nip width at the nip portion formed between the pressure roller 31 and the pressure roller 31 is sufficiently secured so that hot offset is hardly caused.
Specifically, referring to FIG. 9, when the continuous drive time is 300 seconds or less, the drive motor 75 is operated so as to operate at intervals of 10 seconds for 5 seconds (intermittent operation of 5 seconds on and 5 seconds off is repeated). When the on / off control is performed and the continuous drive time is 301 to 600 seconds, the drive motor 75 is turned on so that it operates for 5 seconds at intervals of 11 seconds (intermittent operation of 5 seconds on and 6 seconds off is repeated). -When the off control is performed and the continuous drive time is 601 seconds or more, the reference operation is performed for 5 seconds at 12.5 second intervals (intermittent operation of 5 seconds on and 7.5 seconds off is repeated). Thus, on / off control of the drive motor 75 is performed. Such control of the web mechanism 70 is performed together with the control of the web mechanism 70 described above with reference to FIG.
As a result, the winding amount of the web 71 per unit time in the web mechanism 70 is further optimized without excess or deficiency, and offset toner can be removed more reliably and efficiently without shortening the consumption cycle of the web 71. it can.

  As described above, in the present embodiment, the unit of the web 71 in the web mechanism 70 is based on the detection result of the third temperature sensor 43 (temperature detection means) that detects the temperature of the cored bar 2 a of the auxiliary fixing roller 22. Since the winding amount per time is variable, the winding amount of the web 71 in the web mechanism 70 is efficient in accordance with the amount of offset toner attached to the fixing belt 21 and the pressure roller 31 (pressure rotating body). Thus, the offset toner is reliably and efficiently removed from the fixing belt 21 and the pressure roller 31.

In the present embodiment, the web mechanism 70 is configured so that the web 71 contacts the outer peripheral surface of the pressure roller 31, but the web mechanism 70 is configured so that the web 71 contacts the outer peripheral surface of the fixing belt 21. You can also
And even if it is such a case, the effect similar to this Embodiment can be acquired.

Further, in the present embodiment, the amount of winding of the web 71 per unit time is varied by variably controlling the operation interval of the web 71 in the web mechanism 70 (on / off ratio of the drive motor 75). On the other hand, the amount of winding of the web 71 per unit time can be varied by variably controlling the traveling speed of the web 71 in the web mechanism 70 (the rotation speed of the winding roller 72 by the drive motor 75). .
And even if it is such a case, the effect similar to this Embodiment can be acquired.

In the present embodiment, contact type thermistors are used as the temperature sensors 41 to 43, respectively. On the other hand, as the temperature sensors 41 to 43, non-contact type temperature sensors such as a thermopile and a non-contact type thermistor can be used.
And even if it is such a case, the effect similar to this Embodiment can be acquired.

In the present embodiment, the pressure roller 31 is used as the pressure rotator, but a pressure belt may be used as the pressure rotator.
Further, in the present embodiment, the heater 25 is used as a heating unit for heating the heating roller 23. However, as a heating unit for heating the heating roller 23, an excitation coil (a heating unit corresponding to an electromagnetic induction heating type fixing device) is used. Or a resistance heating element can be used as a heating means.
In those cases, the same effects as those of the present embodiment can be obtained.

In the present embodiment, the present invention is applied to one fixing device 20 installed in the image forming apparatus 1. On the other hand, when a plurality of fixing devices are installed in the image forming apparatus 1 in order to adjust the glossiness of the fixed image, the present invention is applied to all or a part of the plurality of fixing devices. You can also
Even in this case, substantially the same effect as the present embodiment can be obtained.

  It should be noted that the present invention is not limited to the present embodiment, and it is obvious that the present embodiment can be modified as appropriate within the scope of the technical idea of the present invention, other than suggested in the present embodiment. is there. In addition, the number, position, shape, and the like of the constituent members are not limited to the present embodiment, and the number, position, shape, and the like suitable for implementing the present invention can be achieved.

1 image forming apparatus body (apparatus body),
20 fixing device,
21 fixing belt (fixing member),
22 fixing auxiliary roller,
22a cored bar, 22b elastic layer,
23 Heating roller,
25 heater (heating means),
31 Pressure roller (pressure rotating body),
41 1st temperature sensor (2nd temperature detection means),
42 2nd temperature sensor (2nd temperature detection means),
43 3rd temperature sensor (temperature detection means),
70 web mechanism,
71 Web, P Recording medium.

JP 2006-235021 A JP 2003-140504 A

Claims (8)

A fixing device that heats and melts a toner image and fixes the toner image on a recording medium,
A heating roller heated by a heating means;
A fixing auxiliary roller having an elastic layer formed on a cored bar,
A fixing belt stretched between the heating roller and the fixing auxiliary roller;
A pressure rotator that forms a nip portion through which the recording medium is conveyed by being pressed against the fixing auxiliary roller via the fixing belt;
A web mechanism that cleans the surface of the fixing belt or the pressure rotator by running in a predetermined direction while winding the web that contacts the fixing belt or the pressure rotator.
Temperature detecting means for detecting the temperature of the core metal of the fixing auxiliary roller;
With
The fixing device according to claim 1, wherein the web mechanism varies a winding amount of the web per unit time based on a detection result of the temperature detection unit.   When the temperature detected by the temperature detection means does not reach a predetermined value, the web mechanism is more effective than the case where the temperature detected by the temperature detection means reaches the predetermined value. The fixing device according to claim 1, wherein the fixing device is controlled to increase a winding amount.   When the temperature detected by the temperature detection means has reached a second predetermined value that is greater than the predetermined value, the web mechanism changes the temperature detected by the temperature detection means to the second predetermined value. The fixing device according to claim 2, wherein the amount of winding of the web is controlled to be smaller than a case where the web has not reached. A second temperature detecting means for directly or indirectly detecting the temperature of the outer peripheral surface of the heating roller or the fixing auxiliary roller;
The fixing device according to claim 1, wherein the web mechanism varies the winding amount of the web based on a detection result of the temperature detection unit and a detection result of the second temperature detection unit. .   When the average temperature of the temperature detected by the temperature detection means and the temperature detected by the second temperature detection means does not reach a predetermined value, the web mechanism reaches the predetermined value. The fixing device according to claim 4, wherein the amount of winding of the web is controlled so as to be larger than that of the case where the web is wound.   When the average temperature of the temperature detected by the temperature detection means and the temperature detected by the second temperature detection means has reached a second predetermined value larger than the predetermined value, the web mechanism is The fixing device according to claim 5, wherein the winding amount of the web is controlled to be smaller than when the average temperature does not reach the second predetermined value. A detecting means for detecting the number of sheets of the recording medium that is continuously passed through the nip portion or the driving time during which the fixing auxiliary roller is continuously driven to rotate;
7. The web mechanism is controlled so that the amount of winding of the web decreases as the number of passing sheets detected by the detecting means or the driving time increases. The fixing device according to any one of the above.   An image forming apparatus comprising the fixing device according to claim 1.

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