JP2011022263A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remove foreign matters fixed to the surface of an evenly heating roller, in a fixing device in which the evenly heating roller makes the temperature distributions of a fixing rotator and pressure rotator in the direction of a rotary shaft even. <P>SOLUTION: The outermost layer of the evenly heating roller 7 is used as a release layer 72. A brush roller 8 for cleaning the surface of the evenly heating roller 7 is provided. The temperature of the evenly heating roller 7 is made to be higher than the melting temperature of toner. The brush roller 8 is rotated and driven to clean the surface of the evenly heating roller 7. Preferably, the brush roller 8 is freely brought into contact with/separated from the surface of the evenly heating roller 7. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fixing device, and more specifically, heats an unfixed toner image by passing a member to be transferred through a nip portion formed by press contact between a fixing rotator having a heating unit and a pressure rotator. The present invention relates to a fixing device that pressurizes and melts and fixes to a member to be transferred.

  In an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine having these functions, an electrostatic latent image corresponding to an original is formed on a photosensitive drum, and the electrostatic latent image is formed on the electrostatic latent image. The toner image is made to adhere to the toner image, and the visualized toner image is transferred onto the member to be transferred. Thereafter, the toner image on the member to be transferred is fixed and discharged.

  As a device for fixing the toner image transferred on the transfer member, the toner image is transferred at a nip portion formed by press-contacting a fixing rotator incorporating a heating means such as a halogen lamp and a pressure rotator. The fixing device of the heat roller fixing system that heats and presses while holding and transferring the transferred member has been widely used due to the simplicity of the device configuration.

  In such a conventional fixing device, in a region through which the member to be transferred has passed, heat is taken away by the member to be transferred, and the temperature is lowered. For this reason, a temperature distribution is generated between a region through which the member to be transferred passes and a region through which the member to be transferred does not pass. Further, when a pressure roller having an elastic layer is used, if the temperature distribution is generated, a difference in outer diameter occurs due to thermal expansion, and the peripheral speed of the pressure roller is different in the axial direction. Therefore, for example, when a large size paper is fixed after a small size paper is continuously fixed, problems such as uneven fixing of images and hot offset may occur due to the temperature distribution generated as described above. is there. Further, when the sheet conveying speed of the fixing device is different in the axial direction, noise such as “bleeding” may occur in the image, or the sheet may be wrinkled.

  Therefore, a technique has been proposed in which a temperature-uniforming roller such as a heating roller or a heat pipe is brought into contact with the fixing rotator or the pressure rotator to eliminate the temperature distribution in the rotation axis direction of the fixing rotator or the pressure rotator. (For example, see Patent Documents 1 and 2).

JP 2003-84597 JP 2007-192901 A

  According to the proposed technique, the temperature distribution in the rotation axis direction of the fixing rotator and the pressure rotator is largely eliminated. However, when the fixing process is performed for a long period of time, toner, paper dust, and the like may adhere to the fixing rotator and the pressure rotator, and may be transferred and fixed to the surface of the temperature-uniforming roller. If the toner or the like is fixed to the surface of the temperature-uniforming roller, the fixing member may damage the fixing rotator or the pressure rotator in contact with the temperature-uniforming roller.

  FIG. 3 shows the state of the surface of the temperature-uniforming roller after the fixing process of 100,000 sheets of A4 size paper on which characters having an image density of 20% are transferred in the fixing device in which the temperature-uniforming roller is pressed against the pressure roller. The vertical axis represents the surface roughness (μm) of the soaking roller, and the horizontal axis represents the axial position (mm) of the soaking roller. From this figure, it can be seen that foreign matter is adhered to the surface of the temperature-uniforming roller.

  FIG. 4 shows the surface state of the pressure roller that was in pressure contact with the temperature-uniforming roller shown in FIG. 3, with the vertical axis being the surface roughness (μm) of the pressure roller and the horizontal axis being the same as described above. It is expressed as an axial position (mm) of the pressure roller. From this figure, it can be seen that a groove is formed at a position of the pressure roller corresponding to the fixed material of the temperature-uniforming roller. That is, the pressure roller was shaved by the fixed material on the surface of the temperature-uniforming roller, and a groove was formed on the outer peripheral surface.

  The present invention has been made in view of such conventional problems, and an object of the present invention is to fix the temperature distribution in the rotation axis direction of the fixing rotator and / or the pressure rotator with a temperature-uniforming roller. An object of the present invention is to make it possible to remove foreign matters adhering to the surface of the temperature-uniforming roller.

  The fixing device of the present invention that achieves the object includes a fixing rotator having a heating means, a pressure rotator that presses against the fixing rotator to form a nip portion, the fixing rotator, and the pressure rotator. And a temperature-uniforming roller that makes the temperature distribution in the direction of the rotation axis uniform and contacts with the surface of at least one of the rotating bodies, and passes through a nip portion through a member to be transferred on which an unfixed toner image is formed on one surface. A fixing device that heats and pressurizes the toner image to melt and fix the toner image on a transfer member, and the outermost layer of the temperature equalizing roller is a release layer and the surface of the temperature equalizing roller is cleaned And a cleaning unit that cleans the surface of the temperature-uniforming roller with the cleaning unit by setting the temperature of the temperature-uniforming roller higher than the melting temperature of the toner.

  From the viewpoint of preventing deterioration and deformation of the cleaning means and extending the service life, it is preferable to provide the cleaning means so as to be able to contact and separate from the surface of the temperature equalizing roller.

  From the viewpoint of effectively removing the fixed matter on the surface of the temperature-uniforming roller, it is preferable to use a rotatable brush roller as the cleaning means.

  The soaking roller may have a heat pipe or a heating means.

  From the standpoint of suppressing soiling on the surface of the temperature-uniforming roller, it is preferable to provide a temperature-uniforming roller so as to be able to contact and separate from the surface of the rotating body. Further, the surface roughness of the soaking roller is preferably in the range of 20 to 50 μm.

  It is preferable that the surface of the temperature equalizing roller is cleaned by the cleaning unit every time the cumulative number of images formed exceeds a predetermined number.

  In the fixing device of the present invention, the outermost layer of the temperature equalizing roller is a release layer, and a cleaning unit for cleaning the surface of the temperature equalizing roller is provided, and the temperature of the temperature equalizing roller is set higher than the melting temperature of the toner. Since the surface of the temperature-uniforming roller is cleaned by the cleaning means at a high level, the foreign matter adhered to the surface of the temperature-uniforming roller can be effectively removed, and the fixing rotating body and / or the pressure contacted by the temperature-uniforming roller It is possible to prevent the surface of the rotating body from being damaged by the foreign matter.

1 is a schematic diagram illustrating an example of an image forming apparatus (printer) equipped with a fixing device of the present invention. 1 is a schematic configuration diagram illustrating an example of a fixing device of the present invention. It is a figure which shows the surface roughness of the conventional heat equalizing roller. It is a figure which shows the surface roughness of the conventional pressure roller.

  Hereinafter, the fixing device according to the present invention will be described in more detail with reference to the drawings. However, the present invention is not limited to these embodiments.

  FIG. 1 is a schematic view showing an example of an image forming apparatus equipped with a fixing device according to the present invention. The image forming apparatus in FIG. 1 is a tandem digital color printer (hereinafter, simply referred to as “printer”). Of course, in addition to a printer, the present invention can also be applied to a copying machine having a scanner, a facsimile, or a multi-function machine having these functions combined. In the following, when it is necessary to clarify whether the device or member to be described is yellow (Y), magenta (M), cyan (C), or black (K), The description will be made by adding the characters “(Y)”, “(M)”, “(C)”, and “(K)” to the reference numerals, and otherwise omitting those characters.

  The printer 1 includes an intermediate transfer belt 11 at substantially the center of the inside thereof. The intermediate transfer belt 11 is stretched around the outer periphery of the roller 12, the tension roller 13, and the guide rollers 14 and 15, and is driven to rotate counterclockwise. The tension roller 13 is slidably attached to the outside and is urged by the pressing spring S from the inside to the outside of the intermediate transfer belt 11. Thus, the intermediate transfer belt 11 is always in a tensioned state.

  Below the lower horizontal portion of the intermediate transfer belt 11, four image forming portions 2Y, 2M, 2C, and 2B respectively corresponding to yellow (Y), magenta (M), cyan (C), and black (B) colors. Are arranged in this order along the intermediate transfer belt 11. Each of the image forming units 2Y, 2M, 2C, and 2B includes photosensitive drums 21Y, 21M, 21C, and 21B, respectively. Around each of the photosensitive drums 21Y, 21M, 21C, and 21B, the chargers 22Y, 22M, 22C, and 22B, the print head units 23Y, 23M, 23C, and 23B, and the developing unit 24Y are sequentially arranged along the rotation direction. , 24M, 24C, 24B and cleaners 25Y, 25M, 25C, 25B are arranged, respectively. The print head units 23Y, 23M, 23C, and 23B are configured by a large number of LEDs arranged in the main scanning direction parallel to the axial direction of the photosensitive drum.

  Primary transfer rollers 30Y, 30M, 30C, and 30B are provided at positions facing the respective photosensitive drums 21Y, 21M, 21C, and 21B with the intermediate transfer belt 11 interposed therebetween. A secondary transfer roller 16 is pressed against the portion of the intermediate transfer belt 11 supported by the roller 12. A nip portion between the secondary transfer roller 16 and the intermediate transfer belt 11 becomes a secondary transfer region 17. The toner image formed on the intermediate transfer belt 11 in the secondary transfer region 17 is transferred to the conveyed paper (transfer target member) P.

  A paper feed cassette 91 is detachably disposed at the bottom of the printer 1. The sheets P stacked and housed in the sheet feeding cassette 91 are pulled out one by one from the uppermost one by the rotation of the sheet feeding roller 92 and sent out to the transport path 93. The conveyance path 93 extends from the paper feed cassette 91 to the paper discharge tray 98 through the nip portion of the timing roller pair 94, the secondary transfer region 17, and the fixing device T. The paper P sent out from the paper feed cassette 91 is conveyed to the timing roller pair 94 and is sent out to the secondary transfer area 17 at a predetermined timing.

  The fixing device T includes a fixing roller (fixing rotator) 4, a pressure roller (pressure rotator) 5 that is in pressure contact with the fixing roller 4, and a magnetic flux generating unit (heating) that is disposed apart from the outer periphery of the fixing roller 4. Means) 6. As the paper P passes through the nip portion between the fixing roller 4 and the pressure roller 5, the toner image secondarily transferred onto the paper P is heated and melted and fixed on the paper P. Details of the fixing device T will be described later.

  A schematic operation of the printer 1 having such a configuration will be described. First, in the full color mode for outputting a color image, when an image signal is input from an external device (for example, a personal computer) to an image signal processing unit (not shown) of the printer 1, the image signal processing unit converts the image signal to yellow, A digital image signal color-converted to cyan, magenta, and black is created, and this signal is transmitted to the LED drive circuit for the print head. This drive circuit performs exposure by causing the print head units 23Y, 23M, 23C, and 23B of the image forming units 2Y, 2M, 2C, and 2B to emit light based on the input digital signals. This exposure is performed with a time difference in the order of the print head units 23Y, 23M, 23C, and 23B. Thereby, electrostatic latent images for the respective colors are formed on the surfaces of the photosensitive drums 21Y, 21M, 21C, and 21B.

  The electrostatic latent images formed on the photosensitive drums 21Y, 21M, 21C, and 21B are developed by the developing devices 24Y, 24M, 24C, and 24B, respectively, and become toner images of the respective colors. Then, the toner images of the respective colors are sequentially primary-transferred and superimposed on the intermediate transfer belt 11 that rotates counterclockwise in the figure by the action of the primary transfer rollers 30Y, 30M, 30C, and 30B.

  The toner image formed on the intermediate transfer belt 11 in this way reaches the secondary transfer region 17 as the intermediate transfer belt 11 moves. On the other hand, the paper P sent out from the paper feed cassette 91 to the transport path 93 is transported to the secondary transfer region 17 by the timing roller pair 94 at the timing when the toner image reaches the secondary transfer region 17. A voltage having a polarity opposite to the charging polarity of the toner is applied to the secondary transfer roller 16. As a result, in the secondary transfer region 17, the superimposed color toner images are secondarily transferred collectively from the intermediate transfer belt 11 to the paper P. The toner remaining on the intermediate transfer belt 11 after the secondary transfer is collected by a belt cleaner (not shown).

  The sheet P onto which the toner image has been secondarily transferred is sent to the fixing device T through the conveyance path 93, where the toner image is fixed on the sheet P by passing through the nip portion. Then, the paper P is discharged to the paper discharge tray 98.

  FIG. 2 shows a schematic diagram of the fixing device T used in the printer 1 of FIG. In the fixing device T, the fixing roller 4 and the pressure roller 5 are pressed against each other, and a magnetic flux generator 6 is provided on the outer periphery of the fixing roller 4 at a position facing the fixing roller 4 at a distance. A soaking roller 7 is pressed against the pressure roller 5, and a brush roller (cleaning means) 8 is provided so as to be in contact with the surface of the soaking roller 7. Hereinafter, each member will be described in order.

  The fixing roller 4 includes a hollow cylindrical cored bar 41, an elastic layer 42 formed on the outer periphery of the cored bar 41, and an endless belt 43 provided in an unbonded state on the outer periphery of the elastic layer 42. As a material of the cored bar 41, a heat resistant resin such as polyphenylene sulfide (PPS) can be used in addition to a metal material such as aluminum or iron. When electromagnetic induction heating means is used as the heating means as in the present embodiment, it is preferable to use a nonmagnetic material such as aluminum in order to prevent the cored bar 41 from being heated by electromagnetic induction.

  The elastic layer 42 is formed from a member having heat resistance and elasticity. For example, a silicon sponge body is suitable as such a member. If a sponge body is used as the elastic layer 42, the endless belt 43 can be insulated and held, and at the same time, the endless belt 43 can be bent, so that the length of the nip portion between the fixing roller 4 and the pressure roller 5 can be increased. . For example, when a silicon sponge material is used for the elastic layer 42, the thickness is preferably in the range of 2 mm to 10 mm, more preferably in the range of 3 mm to 7 mm. The hardness of the elastic layer 42 is preferably in the range of 20 degrees to 60 degrees, more preferably in the range of 0 degrees to 50 degrees with an Asker rubber hardness meter.

  The endless belt 43 has a laminated structure of an electromagnetic induction heat generating layer 431, an elastic layer 432, and a release layer 433 from the inner peripheral side as shown in the partial enlarged view of FIG. The endless belt 43 is provided on the outer periphery of the elastic layer 42 in an unbonded state. The electromagnetic induction heat generating layer 431 is a layer that generates Joule heat by excitation by the magnetic flux generator 6. The material is preferably a magnetic metal material such as nickel, magnetic stainless steel, or iron. Moreover, you may use what mixed the magnetic metal particle in resin. The thickness of the electromagnetic induction heat generating layer 431 is preferably, for example, in the range of 10 μm to 100 μm, and more preferably in the range of 20 to 50 μm.

  The elastic layer 432 of the endless belt 43 is a layer for improving the adhesion between the paper P and the surface of the endless belt 43, and a member having heat resistance and elasticity is used. For example, heat-resistant elastomers such as silicon rubber and fluorine rubber that can withstand use at the fixing temperature are preferably used. Note that various fillers may be mixed in the elastic layer 432 for the purpose of thermal conductivity, reinforcement, and the like. Examples of the heat conductive particles include diamond, silver, copper, aluminum, marble, and glass. In addition, silica, alumina, magnesium oxide, boron nitride, beryllium oxide, and the like can be used. The thickness of the elastic layer 432 is, for example, preferably in the range of 10 μm to 800 μm, more preferably in the range of 100 μm to 300 μm. Moreover, the hardness of the elastic layer 432 is, for example, preferably in the range of 1 degree to 80 degrees, more preferably in the range of 5 degrees to 30 degrees in terms of JIS hardness. As the silicone rubber, one-component, two-component or three-component or more silicone rubber, LTV type, RTV type or HTV type silicone rubber, condensation type or addition type silicone rubber can be used.

  The release layer 433 of the endless belt 43 is a layer for improving the surface release property of the endless belt 43, and a material that can withstand use at a fixing temperature is used. For example, fluorine resins such as silicon rubber, fluorine rubber, PFA, PTFE, FEP, and PFEP are exemplified. The thickness of the release layer 433 is preferably, for example, in the range of 5 μm to 100 μm, and more preferably in the range of 10 μm to 50 μm. In addition, you may add a electrically conductive material, an abrasion-resistant material, a good heat conductive material, etc. as a filler in the mold release layer 433 as needed. Further, in order to improve the interlayer adhesion, an adhesion treatment with a primer or the like may be performed.

  In FIG. 2, the pressure roller 5 is formed by laminating an elastic layer 52 and a release layer (not shown) in this order on a hollow cylindrical cored bar 51. As the metal core 51, a heat resistant resin such as PPS can be used in addition to a metal material such as aluminum or iron. As the elastic layer 52, the same material as that of the elastic layer 42 of the fixing roller 4 can be preferably used here. As the release layer, the same material as the release layer 432 of the endless belt 43 can be preferably used here.

  The pressure roller 5 is biased toward the fixing roller 4 by a biasing member such as a spring, and forms a nip portion with the fixing roller 4. For example, the pressure roller 5 may be pressed against the fixing roller 4 with a load of 300 N to 500 N so that the length of the nip portion is within a range of 5 mm to 10 mm. Note that the load may be changed according to the type of the paper P or the like. Further, here, the pressure roller 5 is rotationally driven at a predetermined speed by a drive mechanism such as a motor. On the other hand, the fixing roller 4 is rotated by the rotation of the pressure roller 5 by the pressure frictional force with the pressure roller 5. Note that these rotational driving may be performed by using the fixing roller 4 as a main drive and the pressure roller 5 as a driven rotation.

  In FIG. 2, the magnetic flux generator 6 is configured by a coil part 61 and a core part 62 covered with a coil hobbin 63. The coil unit 61 is wound around a coil hobbin 63 disposed so as to cover a part of the outer periphery of the fixing roller 4, and a litz wire bundled with thin wires is wound in the axial direction (in the direction perpendicular to the paper in FIG. 2). It is an extension. The coil hobbin 63 is made of a resin material having high heat resistance and holds the coil part 61. The core portion 62 is made of a ferromagnetic material such as ferrite (having a relative permeability of about 1000 to 3000), and is for forming an efficient magnetic flux toward the heat generating layer, and extends in the axial direction. It is installed so as to face the provided coil part 61.

  A high-frequency inverter (not shown) is connected to the magnetic flux generator 6, and an AC current of 10 kHz to 100 kHz is applied from the high-frequency inverter to the coil unit 61, so that the electromagnetic induction heating layer 431 of the endless belt 43 generates heat. However, the surface temperature of the endless belt 43 is maintained at a predetermined temperature.

  The soaking roller 7 includes a hollow cylindrical base 71, a release layer 72 formed on the surface of the base 71, and a halogen heater (heating means) 73 disposed at the axial center of the base 71. For the release layer 72, a material that can withstand use at the fixing temperature is used, and for example, a fluororesin such as PFA, PTFE, FEP, and PFEP is preferably used. Although there is no limitation in particular in the surface roughness of the mold release layer 72, the range of 20-50 micrometers is preferable, for example. Moreover, the thickness of the release layer 72 is preferably in the range of 20 μm to 50 μm, for example. A temperature sensor 74 is disposed at the outer peripheral separation position of the temperature equalizing roller 7. The halogen heater 73 is controlled to be turned on and off based on the temperature detected by the temperature sensor 74, and the temperature equalizing roller 7 is maintained at a predetermined temperature.

  The soaking roller 7 is biased toward the pressure roller 5 by a biasing member (not shown) such as a spring, and forms a nip portion with the pressure roller 5. For example, the soaking roller 7 may be pressed against the pressure roller 5 with a load of 100 N to 120 N so that the length of the nip portion is within a range of 1 mm to 5 mm. The soaking roller 7 is rotated by the rotation of the pressure roller 5 by the pressure frictional force with the pressure roller 5.

  The soaking roller 7 is preferably provided so as to be movable with respect to the pressure roller 5 between a pressure contact position and a separation position. For example, the surface of the temperature-uniforming roller 7 can be prevented from being soiled by setting the temperature-uniforming roller 7 to the pressure contact position during the fixing process and by setting the temperature-uniforming roller 7 to the separated position during non-fixing, that is, during standby. Conventionally known moving means such as a solenoid can be used as means for moving the soaking roller 7.

  The soaking roller 7 used in the present invention only needs to have an effect of making the temperature distribution in the rotation axis direction of the fixing roller 4 and / or the pressure roller 5 uniform, and is a heating means such as a halogen heater. May not necessarily be included. For example, a so-called heat pipe in which a heat medium such as water or alcohol capable of repeating a liquefied state and a vaporized state by thermal circulation is enclosed in a vacuum state can be suitably used.

  The brush roller 8 as a cleaning means is rotatably provided so as to be in contact with the surface of the soaking roller 7. The brush roller 8 is formed by winding a strip-shaped base fabric in which a large number of brush fibers 82 are planted around a metal core 81 in a spiral shape. The material of the brush fiber 82 is preferably one having heat resistance equal to or higher than the melting temperature of the toner. For example, polyphenylene sulfide having a heat resistance temperature of 160 to 190 ° C. can be suitably used.

  The brush roller 8 is rotated so that the rotational drive is transmitted from a driving source of the pressure roller 5 through a gear (not shown), and the brush fiber 82 contacts the surface of the temperature-uniforming roller 7. The rotation direction of the brush roller 8 is the same as that of the soaking roller 7 at the contact portion. At that time, it is preferable that the peripheral speed of the tip portion of the brush fiber 82 is the same as or faster than the peripheral speed of the surface of the temperature-uniforming roller 7. Of course, the rotation direction of the brush roller 8 may be opposite to that of the temperature-uniforming roller 7 at the contact portion. However, from the viewpoint of the service life of the brush fiber 82, the rotational torque, etc., the brush roller 8 It is desirable to rotate in the same direction as the soaking roller 7 at the part. The peripheral speed of the surface of the soaking roller 7 and the peripheral speed of the tip of the brush roller 8 are usually preferably in the range of 150 to 270 mm / sec.

  The brush roller 8 is preferably provided so as to be movable between a contact position and a separation position with respect to the temperature-uniforming roller 7. For example, it is preferable that the brush roller 8 is normally set as the separation position and the contact position when cleaning the surface of the temperature-uniforming roller 7. As described above, the contact with the temperature-uniforming roller 7 only at the time of cleaning can suppress the deterioration of the brush roller 8 and the temperature-uniforming roller 7 and extend the life. As a means for moving the brush roller 8, a conventionally known moving means such as a solenoid can be used.

  Although there is no particular limitation on the length of the brush fiber 82, in order to suppress the falling of the hair of the brush fiber 82, it is generally desirable that the length is 2 mm or less. The tip of the brush fiber 82 is an end surface perpendicular to the length direction. The length of the brush fiber 82 is the length of the brush fiber portion that is free except the fiber portion fixed to the cored bar 81.

  In the fixing device T having such a configuration, cleaning of the soaking roller 7 is performed by energizing the halogen heater 73 of the soaking roller 7 until the surface temperature of the soaking roller 7 reaches about the melting temperature of the toner. To do. A preferable surface temperature of the soaking roller 7 is usually in the range of 100 to 150 ° C. Then, the soaking roller 7 and the brush roller 8 are rotated, and foreign matters such as toner and paper dust adhered to the surface of the soaking roller 7 are scraped off by the brush fibers 82 of the brush roller 8. There is no particular limitation on the cleaning time, but it is usually about several tens of seconds. The cleaning time is preferably performed every time the cumulative number of image formations exceeds a predetermined number (for example, 100,000).

  As described above, in the embodiment described above, the brush roller 8 is used as the cleaning unit. However, the present invention is not limited to this, and conventionally known cleaning units such as a cleaning blade, a scraper, and a pad can be used. . However, among these, the brush roller 8 is preferable from the viewpoints of torque, wear, deterioration in use, and the like. Further, although the electromagnetic induction heating method has been used as the heating means, the heating means of the present invention is not limited to this, and conventionally known heating means such as infrared irradiation heating with a halogen lamp can be used. In addition, when using heating means other than the electromagnetic induction heating method, the electromagnetic induction heat generating layer 431 made of a magnetic metal material is not necessary as a configuration of the endless belt 43.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these examples at all.

Example Using the image forming apparatus shown in FIG. 1, cleaning experiment of the temperature-uniforming roller with a brush roller was performed by changing the surface layer type of the temperature-uniforming roller and the surface temperature of the temperature-uniforming roller during cleaning. It was. Specifically, after printing 100,000 sheets of 20% image density characters on A4 size paper (basis weight 64 g / m ² ) under environmental conditions of temperature: 23 ° C. and relative humidity: 65%, brush The roller was driven to clean the soaking roller. The surface of the soaking roller after cleaning was visually observed to evaluate the cleaning state. The experimental results are shown in Table 1. The melting temperature of the toner used here is 104.degree.

○: Foreign matter on the surface of the temperature equalizing roller was removed within 20 seconds after the start of cleaning.
Δ: Foreign matter on the surface of the temperature equalizing roller was removed within 20 seconds to 60 seconds after the start of cleaning.
X: Foreign matter on the surface of the temperature equalizing roller was not removed even after 60 seconds from the start of cleaning.

  As is apparent from Table 1, when the surface temperature of the temperature equalizing roller is 100 ° C. or lower, that is, lower than the melting temperature of the toner, the surface of the temperature equalizing roller regardless of the type of the surface layer of the temperature equalizing roller. The foreign matter adhered to the surface was not removed. In addition, when the heat equalizing roller is not provided with a release layer and the core metal (aluminum) is left as it is, the surface temperature of the heat equalizing roller is fixed to the surface of the temperature equalizing roller even if the surface temperature of the heat equalizing roller is higher than the toner melting temperature The foreign material was not removed.

  On the other hand, when a release layer is provided on the temperature equalizing roller and the surface temperature of the temperature equalizing roller is equal to or higher than the toner melting temperature, it adheres to the surface of the temperature equalizing roller within 60 seconds after the start of cleaning. Foreign matter has been removed.

  In the fixing device of the present invention, the temperature distribution in the rotation axis direction of the fixing rotator and the pressure rotator is made uniform by the temperature-uniforming roller, and the foreign matter fixed to the surface of the temperature-uniforming roller is removed by the cleaning means. Therefore, the fixing process can be stably performed over a long period of time, which is useful.

4 Fixing roller (fixing rotating body)
5 Pressure roller (Pressure rotating body)
6 Magnetic flux generator (heating means)
7 Soaking roller 8 Brush roller (cleaning means)
P paper (transferred member)
T fixing device 72 release layer 73 halogen heater (heating means)

Claims (8)

A fixing rotator having heating means, a pressure rotator that presses against the fixing rotator to form a nip portion, and a surface of at least one of the fixing rotator and the pressure rotator, A temperature-uniforming roller that equalizes the temperature distribution in the direction of the rotation axis, and heats and pressurizes the toner image by passing a transfer member having an unfixed toner image formed on one side through the nip. In a fixing device that melts and fixes to a member to be transferred,
The outermost layer of the temperature equalizing roller is a release layer, and a cleaning means for cleaning the surface of the temperature equalizing roller is provided,
The fixing device characterized in that the temperature of the temperature equalizing roller is set higher than the melting temperature of the toner, and the surface of the temperature equalizing roller is cleaned by the cleaning means.   The fixing device according to claim 1, wherein the cleaning unit is capable of contacting and separating from a surface of the temperature-uniforming roller.   The fixing device according to claim 1, wherein the cleaning unit is a rotatable brush roller.   The fixing device according to claim 1, wherein the soaking roller is a heat pipe.   The fixing device according to claim 1, wherein the soaking roller has a heating unit.   The fixing device according to any one of claims 1 to 5, wherein the heat equalizing roller is freely contactable to and away from the surface of the at least one rotating body.   The fixing device according to claim 1, wherein a surface roughness of the temperature-uniforming roller is in a range of 20 to 50 μm.   The fixing device according to claim 1, wherein cleaning of the surface of the soaking roller by the cleaning unit is performed every time the cumulative number of images formed exceeds a predetermined number.