JP6598562B2 - Image forming apparatus and image heating apparatus - Google Patents

Description

  The present invention relates to an image heating apparatus and an image forming apparatus. This image heating apparatus is mounted and used as a fixing device in an image forming apparatus such as an electrophotographic system or an electrostatic recording system capable of forming an image on a recording material such as a copying machine, a facsimile machine, or a printer.

  Examples of the image heating device include a fixing device that fixes an unfixed image on a recording material, and a gloss increasing device that increases the glossiness of an image by heating the image fixed on the recording material. .

  Conventionally, in order to fix an image formed on a recording material (sheet: hereinafter referred to as paper) with toner in an image forming apparatus such as a copying machine, a facsimile, or a printer using an electrophotographic method, A fixing device which is an image heating device is used. As a fixing device, a fixing device using a roller or belt-like fixing member as a heating rotator and a roller or belt-like pressing member as a pressure rotator is generally used.

  In recent years, an oilless fixing method for fixing an unfixed image made of toner containing a release agent has been widely used. Accordingly, a heating rotator is widely used that has an elastic layer made of silicone rubber or fluororubber and a release layer that is a surface layer provided on the elastic layer. The release layer is generally formed of a tube or a coating made of a material having excellent release properties such as a fluororesin.

  The oilless fixing method is advantageous in that uneven glossiness (gross unevenness) of the image due to oil streaks is less likely to occur than the oil fixing method in which silicone oil or the like is applied to the fixing roller as a release agent. is there. In recent years, toners with higher melting properties have been actively developed. By increasing the melting property of the toner, the toner can be melted uniformly and satisfactorily by the fixing device. As a result, the toner layer after fixing is formed more uniformly and smoothly, so that the gloss (glossiness) of the image is improved.

  Therefore, for example, according to the oilless fixing method, it is possible to pursue an image with higher gloss and higher image quality than before with respect to high gloss paper such as coated paper.

  However, in such an image forming apparatus, the surface property of the fixing member is partially deteriorated every time the fixing process and the heat treatment are repeated, and the deteriorated surface property of the fixing member is directly copied onto the surface of the fixed image, There is a problem that a uniform glossy state of the image surface cannot be obtained.

  Therefore, a technique has been proposed in which the surface roughness of the fixing member surface layer is maintained in a constant state by bringing a rubbing member into contact with the surface layer of the fixing member. In Patent Document 1, as a rubbing member, a technology for rotationally driving refreshing by forming a nip by bringing a rotatable refresh roller having a surface layer bonded with alumina abrasive grains into contact with the surface layer of a fixing member has been put into practical use. ing.

  Further, when the rubbing member rubs the surface layer of the fixing member, a small amount of toner or paper powder melted on the surface layer of the fixing member and tube residue forming the surface layer of the fixing member adhere to the surface of the refreshing roller. If these adhere, the surface property of the refreshing roller may deteriorate, and the effect of maintaining the surface roughness of the surface of the fixing member in a constant state may not be exhibited. As a countermeasure, Patent Document 2 proposes a technique for cleaning the surface by bringing a cleaning roller using an elastic layer made of a heat-resistant elastic material such as silicone rubber or fluororubber as a surface layer into contact with the refreshing roller. Yes.

JP 2008-040363 A JP 2008-040365 A

  On the other hand, the following knowledge was acquired with respect to the cleaning roller by examination of the present inventors. That is, in order to maintain the surface roughness of the fixing member surface layer in a constant state, it is desirable to maintain the surface roughness of the refresh roller at a predetermined value. The cleaning roller removes fine foreign matters such as paper dust and tube residue clogged between abrasive grains of the refreshing roller. However, since the cleaning roller is configured to clean the refresh roller only during the refresh operation, it is difficult to sufficiently remove fine foreign substances clogged between the abrasive grains of the refresh roller.

  For this reason, if the refresh operation is performed more than a predetermined number of times, foreign matter accumulates between the abrasive grains of the refresh roller, the surface roughness of the refresh roller cannot be maintained, and the surface roughness of the fixing member surface layer is maintained at a constant state. It has been found that it reduces the ability to do.

  An object of the present invention is to maintain the surface roughness of the rubbing rotary member and to extend the life.

In order to achieve the above object, a typical configuration of an image forming apparatus according to the present invention cooperates with a first rotating body that heats a toner image on a recording material at a nip portion and the first rotating body. A pair of rotating bodies with a second rotating body that forms the nip portion and contacts the surface of the recording material opposite to the toner image carrying surface, and the first rotating body with a peripheral speed difference. A first rubbing rotator capable of executing a rubbing process for rubbing the surface of the first rotator by contact; and the first rubbing rotator with respect to the surface of the first rotator. The peripheral speed difference between the first contact / separation mechanism that contacts and separates, the rotatable first cleaning member that contacts and cleans the surface of the first rubbing rotator, and the second rotator A second rubbing rotator capable of executing a rubbing process for rubbing the surface of the second rotator by contacting the second rotator, and the second rubbing rotator A second contact / separation mechanism that contacts and separates the surface of the second rotating body, a second cleaning member that contacts the surface of the second sliding rotating body and cleans the surface, and the first sliding member. A first cleaning mode for rotating the first rubbing rotator and the first cleaning member when the rubbing rotator is separated from the first rotating body; and the second rubbing rotator, And a second cleaning mode for rotating the second rubbing rotator and the second cleaning member when separated from the second rotator, and an execution unit that executes the second cleaning mode. To do.
Further, a typical configuration of the image forming apparatus according to the present invention for achieving the above object includes a first rotating body and a second rotating body that heat a toner image on a recording material at a nip portion, and A first rubbing rotary body capable of executing a rubbing process for rubbing the surface of the first rotating body by contacting the first rotating body with a peripheral speed difference; and the first rubbing A first contact / separation mechanism that contacts and separates the rotating body from the surface of the first rotating body, and a rotatable first cleaning that contacts the surface of the first rubbing rotating body and cleans the surface. When the member and the first rubbing rotator are separated from the first rotating body, a first cleaning mode is executed in which the first rubbing rotator and the first cleaning member are rotated. And an execution unit.

Further, a typical configuration of the image heating apparatus according to the present invention for achieving the above object includes a first rotating body and a second rotating body that heat a toner image on a recording material at a nip portion, and A rubbing rotary body capable of performing a rubbing process for rubbing the surface of the first rotating body by contacting the first rotating body with a difference in peripheral speed, and the rubbing rotating body are connected to the first rotating body. A contact / separation mechanism for contacting / separating the surface of the rotating body, a rotatable cleaning member that contacts the surface of the rubbing rotating body and cleans the surface of the rubbing rotating body, and the first rotating body A driving force is transmitted from the first rotating body to the rubbing rotating body when the first rotating body rotates, and a first gear provided on the rubbing rotating body, and a second gear provided on the rubbing rotating body. is the way have a rotation transmission mechanism forming a gear train between said first gear and said second gear, said of said rotatable rubbing member Regardless contact and separation of the first rotary member, the cleaning member is in said first rotating member is rotated, characterized in that cleaning the surface of said rotatable rubbing member.

  According to the present invention, the surface roughness of the rubbing rotary member can be maintained, and the life can be extended.

It is a flowchart which shows cleaning execution operation | movement of a refresh roller. 1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to an embodiment. It is a block diagram of a control system. FIG. 3 is a cross-sectional view (at the time of a pressure operation) showing the configuration of the fixing device. FIG. 3 is a cross-sectional view (at the time of a pressure operation) showing the configuration of the fixing device. FIG. 3 is a cross-sectional view of a fixing refresh mechanism and a pressure refresh mechanism that are operating. It is a one part perspective view of a pressure refresh mechanism. It is a figure which shows refreshing roller surface roughness transition. It is a figure which shows the refreshing roller surface roughness transition at the time of cleaning time extension. It is a flowchart which shows the flow of control.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, although an Example is an example of the best embodiment in this invention, this invention is not limited by an Example.

Example 1
[Image forming apparatus]
FIG. 2 is a longitudinal sectional view showing a schematic configuration of the image forming apparatus 100 in the present embodiment. FIG. 3 is a block diagram of the control system. This image forming apparatus 100 can operate based on image information input to the control unit 80 from an external terminal 200 such as a personal computer (PC) and can form a toner image on a sheet (recording material) P. This is a tandem type color electrophotographic printer. Since this printer configuration is well-known, its description will be simplified.

  Reference numeral 1 denotes an image forming unit inside the image forming apparatus main body 100A, which includes four image forming units U (Y, M, C, K) and an intermediate transfer belt unit 8. Each image forming unit U includes a photosensitive drum 2, a charger 3, a laser scanner 4, a developing device 5, a primary transfer charger 6, a drum cleaner 7, and the like. In addition, in order to avoid complication of the figure, description of the codes of these devices with respect to the image forming units UM, UC, and UK is omitted.

  Each image forming unit U forms yellow (Y), magenta (M), cyan (C), and black (K) toner images on the drum 2. Then, the toner images of the four colors are sequentially superimposed and preliminarily transferred from the drum 2 of each image forming unit U to the intermediate transfer belt 9 so that an unfixed full-color toner image is formed on the belt 9. It is formed.

  Then, the paper P is introduced at a predetermined control timing into the secondary transfer nip portion, which is a pressure contact portion between the belt 9 and the secondary transfer roller 12, and the toner image on the belt 9 is secondary to the paper P. Transcribed. The sheet P is separated and fed from the sheet feeding cassette 10 and is introduced into the secondary transfer nip portion through the conveyance path a including the registration roller pair 11. The paper P exiting the secondary transfer nip is separated from the belt 9 and introduced into a fixing device (fixing unit: hereinafter referred to as a fixing device) F through a conveyance path b. The surface of the belt 9 after paper separation is cleaned by a belt cleaner 13 and repeatedly used for image formation.

  The paper P introduced into the fixing device F undergoes thermal fixing of the toner image. In the single-sided printing mode (single-sided printing mode), the paper P exiting the fixing device F is guided to the paper discharge path c by the flapper 14 and is discharged to the tray 15 as a full-color image forming product for single-sided printing. The

  In the double-sided printing mode (double-sided printing mode), the first-side printed paper P that has exited the fixing device F is guided to the reverse path d side by the flapper 14. Then, the paper is reversely fed through the switchback conveyance path e, enters the conveyance path a via the double-side conveyance path f, and is reintroduced into the secondary transfer nip portion in a state where the front and back sides are reversed. As a result, a toner image is formed on the second side of the paper P. Thereafter, as in the single-sided printing mode, the paper P is transported through the fixing device F and the paper discharge path c, and is discharged to the tray 15 as a full-color image formed product for double-sided printing.

  In the case of mono-color image formation, the image forming unit U necessary for forming the image performs an image forming operation, and the other image forming units do not perform the image forming operation only by the drum 2 rotating idly.

  The control unit (execution unit) 80 controls the image forming apparatus 100 as a whole, but FIG. 3 mainly shows portions related to the external terminal (host device) 200 and the operation unit 150 fixing device F. Image information input from the external terminal 200 to the control unit 80 is processed by the controller 82, and image formation information is input to the CPU 81. This is processed between the image processing unit 86, the RAM 84, and the ROM 85 to form an image.

  The operation unit 150 is connected to the CPU 81 via the I / F unit 83. The operation unit 150 is a user interface (UI: User Interface, manual operation unit) for setting an image forming mode and inputting various instructions from a user (operator) and notifying the user of the state of the apparatus.

  The operation unit 150 includes an input unit 150a (FIG. 2) and a display unit (UI screen) 150b. Various operation keys (buttons) and the like (not shown) are arranged on the input unit 150a. The display unit 150b is a touch panel type liquid crystal screen (not shown), which displays various types of information and various operation buttons. Various settings for operations performed by the image forming apparatus 100 are also input by the displayed operation buttons. Various settings of operations performed by the image forming apparatus 100 can also be input to the control unit 80 via the UI screen (display unit: not shown) of the external terminal 200.

  The CPU 81 is electrically connected to each control unit (the controllers 89 and 92, the heater control unit 90, the temperature detection unit 91, and the like) of the fixing device F. The fixing device F is controlled by the CPU 81 to control the conveyance speed of the paper P, the surface temperatures of the fixing roller 40 and the pressure roller 41 described later, and can fix the toner image on the paper. Further, various controls described later are performed.

[Fixer]
FIG. 4 is an enlarged schematic view of the fixing unit F of the image forming apparatus 100 of FIG. The fixing device F in this embodiment is a heat roller type apparatus having a fixing roller 40 and a pressure roller 41 as a pair of rotating bodies that form a fixing nip (nip portion) N.

  That is, the fixing device F includes a fixing roller (first rotating body) 40 as a rotatable fixing member having a halogen heater 40a as a heating element therein. Moreover, it has a pressure roller (second rotating body) 41 as a rotatable pressing member having a halogen heater 41a as a heating element inside. Further, a pressure attaching / detaching mechanism 30 for the pressure roller 41 with respect to the fixing roller 40 is provided. In addition, a fixing refresh mechanism 50 that recovers the surface property of the fixing roller 40 is provided. Further, a pressure refresh mechanism 60 that recovers the surface property of the pressure roller 41 is provided. It has a housing (fixing device exterior) 43 that accommodates these.

  The fixing roller 40 is a rotating body that heats the toner image on the paper (on the recording material) at the fixing nip N, and contacts the surface of the paper P carrying the unfixed toner image T to fix the toner image T. The fixing roller 40 is formed by providing an elastic layer 40c made of a rubber layer on a metal core shaft (base layer) 40b and further covering a release layer 40d as a surface layer thereon. In this example, 1.0 mm of silicone rubber having a rubber hardness of 20 ° (JIS-A 1 kg load) was molded as an elastic layer on a hollow metal core made of aluminum having an outer diameter of 68 mm. Further, a roller having an outer diameter of 70 mm, whose surface was coated with a fluororesin having a thickness of 50 μm as a release layer, was used.

  As the release layer 40d, a fluororesin tube in which a fluororesin excellent in releasability was formed in a tube shape was used. As the fluororesin, PFA resin (tetrafluoroethylene resin, copolymer of perfluoroalkoxyethylene resin), PTFE (tetrafluoroethylene resin), or the like is used. In this example, a PFA resin tube was used as the release layer 40d. The thickness of the release layer 40d, which is the surface layer of the fixing roller 40, is preferably 30 μm or more and 100 μm or less.

  In the fixing roller 40, both end portions in the longitudinal direction (rotation axis direction) of the cored bar 40b rotate via bearings (not shown) between side plates on one end side and the other end side in the longitudinal direction of the upper frame 43A of the housing 43, respectively. Supported as possible. Then, in response to the transmission of the driving force of the fixing drive motor 44 (FIG. 3), it is rotationally driven in the clockwise direction indicated by the arrow R40 at a predetermined peripheral speed. In this embodiment, the surface moving speed (circumferential speed) of the fixing roller 40 is 250 mm / sec. The peripheral speed of the fixing roller 40 corresponds to the process speed (image output speed) of the image forming apparatus 100.

  Electric power is supplied from the power supply unit 45 controlled by the control unit 80 to the halogen heater 40a to generate heat. As a result, the fixing roller 40 is heated from the inside. Then, the surface temperature of the fixing roller 40 is detected by a temperature sensor (thermistor) 42 a and the detected temperature information is fed back to the control unit 80. Based on the input information, the controller 80 adjusts the surface temperature of the fixing roller 40 to about 150 to 180 ° C., which is the temperature at which the toner can be fixed to the paper P. This temperature control temperature has different set values depending on the type of the paper P and the like.

  The pressure roller 41 is a rotating body that is arranged in parallel to the lower side of the fixing roller 40, forms a fixing nip N in cooperation with the fixing roller 40, and contacts the surface opposite to the toner image carrying surface of the paper P. is there. The pressure roller 41 is formed by providing an elastic layer 41c made of a rubber layer on a metal core shaft (base layer) 41b and further covering a release layer 41d as a surface layer thereon. In this example, 2.0 mm of silicone rubber having a rubber hardness of 20 ° (JIS-A 1 kg load) was molded as an elastic layer on a hollow cored bar made of aluminum having an outer diameter of 48 mm. Further, a roller having an outer diameter of 50 mm and having a surface coated with a fluororesin having a thickness of 50 μm as a release layer was used.

  The pressure roller 41 is lifted in a direction in pressure contact with the fixing roller 40 by a pressure operation of the pressure attaching / detaching mechanism (moving mechanism) 30 and has a predetermined width with respect to the sheet conveying direction X between the pressure roller 41 and the fixing roller 40 as shown in FIG. It is moved to a pressure position (fixing position) where the fixing nip N is formed. Further, the pressure roller 41 is lifted in the direction away from the fixing roller 40 by the pressure releasing operation of the pressure attaching / detaching mechanism 30 and the fixing nip with the fixing roller 40 is eliminated as shown in FIG. (Standby position).

  The configuration of the pressure attaching / detaching mechanism 30 will be described. In the lower frame 43 </ b> B of the housing 43, a pressure attaching / detaching mechanism 30 is provided on each of one end side and the other end side of the pressure roller 41. Since these two mechanisms 30 have a symmetrical structure, one of them will be described below as a representative.

  Reference numeral 20 denotes a pressure roller support frame, which is rotatable about the hinge shaft 31 with respect to the lower frame 43B of the housing 43. One end side and the other end side of the pressure roller 41 are rotatably supported by a pressure roller support frame 20 of the pressure attachment / detachment mechanism 30 on the corresponding side via a bearing (not shown). . A pressure frame 21 below the pressure roller support frame 20 is rotatable about a hinge shaft 31. Reference numeral 22 denotes a pressure spring as an urging means disposed between the pressure roller support frame 20 and the pressure frame 21.

  A pressure cam 34 receives the lower surface of the pressure frame 21. The pressure cam 34 is fixedly disposed on the pressure cam shaft 32. The driving force of the pressurizing motor 36 (FIG. 3) controlled by the control unit 80 is transmitted to the pressurizing cam shaft 32 via the gear train 36a to the pressurizing gear 35 fixed to the pressurizing cam shaft 32. To be rotated.

  The pressurizing cam shaft 32 is controlled to rotate, and the pressurizing cam 34 is brought to a rotation angle posture in which the large protuberance is directed upward as shown in FIG. It is lifted and rotated to the center. In conjunction with this, the pressure roller support frame 20 is pushed up and rotated about the hinge shaft 31 via the pressure spring 22. As a result, the pressure roller 41 is moved to a pressure position where a predetermined fixing nip N is formed by contacting the fixing roller 40 with a predetermined pressing force (for example, 800 N) by the compression reaction force of the pressure spring 22. (Pressurization operation state of the pressure attaching / detaching mechanism 30).

  On the other hand, from the state of FIG. 4, the pressurization cam shaft 32 is controlled to rotate, and the pressurization cam 34 is stopped at the rotational angle posture in which the small ridges are directed upward as shown in FIG. The pressurizing frame 21 is pivoted down around the hinge shaft 31. For this reason, the pressure roller support frame 20 is also pivoted down about the hinge shaft 31 via the pressure spring 22, thereby eliminating the fixing nip N between the pressure roller 41 and the fixing roller 40. It is moved to the separation position (pressure release operation state of the pressure attaching / detaching mechanism 30).

  The pressure roller 41 is moved to the pressure position during the image forming operation of the image forming apparatus 100. At the time of non-image formation, it is moved to a separated position. When the pressure roller 41 is moved to the pressure position, the pressure roller 41 is driven to rotate by the fixing roller 40 and rotates counterclockwise as indicated by an arrow R41. Electric power is supplied from the power supply unit 45 controlled by the control unit 80 to the halogen heater 41a to generate heat. Thereby, the pressure roller 41 is heated from the inside. Then, the surface temperature of the pressure roller 41 is detected by the temperature sensor 42 b, and the detected temperature information is fed back to the control unit 80.

  Based on the input information, the control unit 80 increases the surface temperature of the pressure roller 41 so that the gloss difference between the first and second surfaces during the fixing operation in the double-sided printing mode does not widen and the fixing roller 40 is increased by pressurization. Adjust the temperature so that the temperature does not fall. In this embodiment, the temperature is adjusted to 90 to 110 ° C. When it greatly exceeds the temperature control temperature, it is cooled to the temperature control temperature as a target by a cooling fan (not shown) or the like. This temperature control temperature has different set values depending on the type of the paper P and the like.

  The sheet P carrying the unfixed toner image T introduced into the fixing device F through the conveyance path b from the image forming unit 1 side enters the fixing nip N and is nipped and conveyed. As a result, the paper P is heated and pressurized, and the toner image T is melted and thermally fixed to the paper P. The paper P exiting the fixing nip N is separated from the fixing roller 40 and goes out of the fixing device F.

[Fixing refresh mechanism]
A fixing refresh mechanism 50 that recovers the surface property of the fixing roller 40 will be described. The fixing refresh mechanism 50 includes a refresh roller 52 as a rubbing member (first rubbing rotary body) for recovering the surface property of the fixing roller 40. The refresh roller 52 can perform a rubbing process for rubbing the surface of the fixing roller 40 by contacting the refreshing roller 52 with a difference in peripheral speed.

  In the refresh roller 52, abrasive grains are closely bonded to the surface of a stainless steel core having a diameter of 12 mm via an adhesive layer. It is preferable to use abrasive grains having a count (granularity) of # 1000 to # 4000 in accordance with the target glossiness of the image. The average grain size of the abrasive grains is about 16 μm when the count (grain size) is # 1000, and about 3 μm when the count is # 4000. The abrasive grains are alumina-based (also called “alundum” or “morundum”). Alumina is the most widely used abrasive grain in the industry and has higher hardness in each step than the surface of the fixing roller 40, and has excellent abrasiveness because the particles have an acute-angled shape.

  In this example, abrasive grains with a count (grain size) of # 2000 (average particle size is 7 μm) are used, the surface roughness (Ra) is 2.0 to 4.0 μm, and the average spacing of unevenness (Sm). Is about 10-20 μm.

  In this embodiment, the refresh roller 52 is described in which abrasive grains are closely bonded to a stainless steel core through an adhesive layer. The refresh roller 52 is not limited to this, and the surface of the stainless steel core may be processed into a desired surface property by blasting or the like.

  The refresh roller 52 is rotatably supported by support members 52a provided at both ends in the longitudinal direction (rotation axis direction). The refresh roller 52 can be driven to rotate by transmitting the driving force of the refresh motor 54 controlled by the control unit 80 via the gear train 54a.

  The support members 52a at both ends in the longitudinal direction of the refresh roller 52 are urged by pressure springs (not shown) as urging means, so that the refresh roller 52 presses the fixing roller 40 with a predetermined pressure. Is done. As a result, a rubbing nip having a predetermined width is formed between the refresh roller 52 and the fixing roller 40 in the respective surface movement directions. The refresh roller 52 may be rotated at the contact portion (sliding portion) between the refresh roller 52 and the fixing roller 40 so that the surface movement direction thereof is either the forward direction or the reverse direction.

  The refresh roller 52 is arranged so as to be in contact / separation (contact / separation) with respect to the surface of the fixing roller 40 by an attaching / detaching mechanism (first contact / separation mechanism) controlled by the control unit 80. Although a specific configuration of the attaching / detaching mechanism 51 is omitted in the drawing, an appropriate mechanism configuration such as a mechanism using an electromagnetic solenoid or a mechanism using a cam can be used. FIG. 4 shows a state in which the refresh roller 52 is separated from the fixing roller 40. FIG. 6A shows a state in which the refresh roller 52 is in contact with the fixing roller 40.

  The fixing refresh mechanism 50 has a rotatable cleaning roller (first cleaning member) 53 that contacts the refresh roller 52 and cleans the surface.

  The cleaning roller 53 is a brush roller having an outer diameter of about φ10 mm, in which a pile brush in which a fiber bundle is planted is wound around the surface of a metal bar made of metal (stainless steel or iron + plating) of φ6 mm. In this embodiment, a polyimide yarn having a wire diameter of 2 denier (about φ14 μm) is used as the pile yarn, and the fiber bundle is knitted on an aramid fiber base fabric to create an original fabric of the pile brush. Then, the raw material of the pile brush cut into a predetermined width is bonded to the core metal with a silicone adhesive while being wound around the core bar, thereby processing the brush roller.

  The cleaning roller 53 is rotatably supported by support members (not shown) provided at both ends in the longitudinal direction (rotation axis direction), and the support members are respectively attached by pressure springs (not shown) as biasing means. Be forced. As a result, it is always in contact with the refreshing roller 52 and is arranged so as to be able to rotate following the rotation of the refreshing roller 52.

[Pressure refresh mechanism]
The pressure refresh mechanism 60 that recovers the surface property of the pressure roller 41 will be described. The pressure refresh mechanism 60 has a refresh roller 62 as a rubbing member (second rubbing rotating body) for recovering the surface property of the pressure roller 41. The refresh roller 62 can perform a rubbing process for rubbing the surface of the pressure roller 41 by contacting the pressure roller 41 with a peripheral speed difference. The configuration of the refresh roller 62 is the same as that of the refresh roller 52 in the fixing refresh mechanism 50 described above.

  The refresh roller 62 is rotatably supported by support members 67 disposed on both ends in the longitudinal direction (rotation axis direction). The support member 67 is supported to be rotatable about the hinge shaft 68 with respect to the pressure roller support frame 20.

  As shown in FIG. 7, a drive gear 66 is provided at one end of the refresh roller 62, and the pressure roller 41 is connected via a drive input gear 64 and an idler gear 65 provided at the end of the pressure roller 41. The rotation drive is transmitted and can be rotated. That is, these gears 64, 65, 66 are rotation transmission mechanisms that rotate the refresh roller 62 when the pressure roller 41 rotates.

  The lower surface of the support member 67 is received by an attachment / detachment cam (second contact / separation mechanism) 61 that is fixed to the pressure cam shaft 32 of the pressure attachment / detachment mechanism 30 with a phase shifted from the pressure cam 34. The rotation of the pressurizing cam shaft 32 is controlled, and the detachable cam 61 is stopped at the rotational angle posture with the large raised portion facing upward as shown in FIG. It is lifted and rotated around the center. As a result, the refresh roller 62 is pressed against the pressure roller 41 with a predetermined pressure. Thus, a rubbing nip having a predetermined width is formed between the refresh roller 62 and the pressure roller 41 in each surface movement direction.

  The refresh roller 62 may be rotated at the contact portion (sliding portion) between the refresh roller 62 and the pressure roller 41 so that the surface movement direction thereof is either the forward direction or the reverse direction.

  On the other hand, from the state of FIG. 6 (b), the rotation of the pressure cam shaft 32 is controlled, and the detachable cam 61 is brought into a rotation angle posture with the small bulging portion facing upward as shown in FIG. As a result, the support member 67 is pivoted down around the hinge shaft 68. As a result, the refresh roller 62 is separated from the pressure roller 41.

  As described above, the refresh roller 62 is brought into contact / separated with the surface of the pressure roller 41 while the rotation drive of the pressure roller 41 is transmitted to the pressure roller 41 by the rotation control of the detachable cam 61. It is arranged to be able to (contact / separate).

  The pressure refresh mechanism 60 has a cleaning roller 63 for cleaning the refresh roller 62. The configuration of the cleaning roller 63 is the same as that of the cleaning roller 53 in the fixing refresh mechanism 50. The cleaning roller 63 is rotatably supported by support members 63a provided at both ends in the longitudinal direction (rotation axis direction). The support member 63a is urged by a pressure spring 63b (FIG. 7) as urging means, so that the support member 63a is always in contact with the refresh roller 62 and can be rotated by the rotation of the refresh roller 52. Has been placed.

[Difference in surface layer change between fixing roller and pressure roller]
The difference in surface layer change between the fixing roller 40 and the pressure roller 41 will be described. Generally, the temperature of the fixing roller 40 is adjusted to be higher than that of the pressure roller 41, and the fixing roller 40 needs to melt the toner and fix the toner image T on the paper P. Therefore, a change in surface roughness is easily reflected in the glossiness on the image. For this reason, scratches on the edge of the paper that are not noticeable on the pressure roller 41 are easily recognized as uneven gloss on the image on the fixing roller 40.

  Further, since the amount of paper dust per sheet is very small, the paper dust hardly adheres to the surface of the fixing roller 40 on which toner is fixed. On the other hand, in the case of the surface of the pressure roller 41, during printing, the surface on which the toner image is not formed on the paper P hits the surface of the pressure roller 41, so that paper dust tends to adhere. And even if a small amount of paper dust accumulates on the surface layer, the releasability of the surface layer of the pressure roller 41 is greatly reduced, so that paper dust and toner are likely to adhere.

  As described above, the fixing roller 40 and the pressure roller 41 whose surface layer state changes due to different reasons are considered to be determined in different flows in order to rub the roller surface layer.

[Refresh operation]
The refresh operation will be described. In this embodiment, as described above, the fixing refresh mechanism 50 is used to improve the gloss unevenness caused by the transfer of scratches on the surface of the fixing roller 40 onto the image by passing the edge portion of the paper P using the refresh roller 52. Works. In addition, the pressure refresh mechanism 60 operates so as to improve the gloss unevenness caused by the deterioration of the surface property of the pressure roller 41 due to paper dust or the like attached by the passage of the paper P using the refresh roller 62.

  That is, the refreshing rollers 52 and 62 make fine rubbing scratches over the entire length in the longitudinal direction on the fixing roller 40 and the pressure roller 41, thereby eliminating the difference in surface roughness. Further, a small amount of paper dust or the like adhering to the surface layer of the pressure roller 41 is scraped off. As a result, the low-gloss streaks transferred on the image and the gloss level difference between the paper passing area and the non-paper passing area are eliminated by the fixing roller 40 and the pressure roller 41. Further, since the scratches on the fixing roller 40 and the pressure roller 41 by the refresh rollers 52 and 62 are changed to a large number of fine scratches, the scratches cannot be visually recognized on the image.

  Specifically, in the fixing roller 40 and the pressure roller 41 having a release layer such as a fluororesin on the surface layer, the surface roughness Rz of the non-sheet passing region of the paper is about 0.1 μm to 0.3 μm. The surface roughness Rz of the paper passing area is about 0.5 μm to 2.0 μm. On the other hand, the surface roughness Rz of the surface property lowering portion due to adhesion of paper edge portions, paper powder, etc. is about 1.0 to 4.0 μm. Therefore, the surface roughness Rz of the rubbing scratches applied to the fixing roller 40 and the pressure roller 41 is set to 0.5 μm or more and 2.0 μm or less by the refresh rollers 52 and 62.

  In addition, surface roughness (ten-point average roughness) Rz uses a surface roughness measuring instrument SE-3400 of Kosaka Laboratory Ltd., and the feed rate is 0.5 mm / s as a measurement condition, and the cutoff is: Measurement was performed at 0.8 mm and measurement length: 2.5 mm.

  The refresh rollers 52 and 62 need not always keep rubbing against the fixing roller 40 and the pressure roller 41 during image formation. For example, a sheet passing counter (number counter) 88 (FIG. 3) may be provided, and the rubbing operation may be automatically executed periodically according to the number of sheets passed. In addition, an execution button (manual operation key) may be provided in the operation unit 150 of the image forming apparatus 100 as a user mode so that the user can execute a rubbing operation in a timely manner when the user is concerned about gloss unevenness on the image.

  For this purpose, the fixing device 100 according to the present exemplary embodiment includes attachment / detachment mechanisms 51 and 61 that enable the refresh rollers 52 and 62 to be attached to and detached from the fixing roller 40 and the pressure roller 41.

  The control unit 80 operates the attaching / detaching mechanism 51 of the fixing refresh mechanism 50 to bring the refresh roller 52 into contact with or away from the fixing roller 40. Further, the control unit 80 controls the operation of the motor 54 that transmits the rotational driving force to the refresh roller 53, and rotates the refresh roller 52 for a predetermined time.

  Further, the controller 80 causes the motor 36 to operate the detachable cam 61 so that the refresh roller 62 contacts or separates from the pressure roller 41. The control unit 80 controls the rotation time of the pressure roller 41 that transmits the rotational driving force to the refresh roller 63, and rotates the refresh roller 62 for a predetermined time.

  As described above, in this embodiment, the fixing / refreshing mechanism 50 can contact / separate the refreshing roller 53 with respect to the fixing roller 40. Further, the pressure refresh mechanism 60 is configured so that the refresh roller 63 can be brought into contact with / separated from the pressure roller 41. Then, the surface of the fixing roller 40 and the pressure roller 41 is brought into contact with the refresh rollers 53 and 63 at a desired timing from the separated state of the refresh rollers 53 and 63 during normal image formation for a desired time. Can be improved.

[Refreshing roller surface contamination]
Next, the surface contamination of the refresh roller will be described. FIG. 8 shows the surface of the refresh rollers 52 and 62 when the refresh operation is executed for 5 seconds every time 500 sheets of A4 size paper on which a single-color halftone image having an image data density of about 0.5 is passed. The transition of the roughness Rz is shown.

  “Fixing member—during printing” is a case where a refresh operation for the fixing roller 40 is executed during printing.

  “Fixing member at standby” is a case where the refresh operation for the fixing roller 40 is executed during standby (the printing operation is temporarily interrupted).

  “Pressurizing member—during printing” is a case where a refresh operation for the pressure roller 41 is executed during printing.

  “Pressure member—in standby” refers to the case where the refresh operation for the pressure roller 41 is executed during standby (the printing operation is temporarily interrupted).

  When the roughness of the surface layer of the refresh roller is lowered, the refresh capability is also lowered. As a result of experiments, in order to improve the surface conditions of the surface layers of the fixing roller 40 and the pressure roller 41, it has been found that the surface roughness Rz of the refresh rollers 52 and 62 is 7 to 8 μm or more. Based on this value, the refresh roller 62 of the pressure roller 41 has almost no change between when the refresh operation is executed during printing and when the refresh operation is executed during standby.

  However, in the refresh roller 52 of the fixing roller 40, when a refresh operation is performed during printing, the refresh roller 52 is less than the reference value with less than one-third of the 100,000 sheets passed when the refresh operation is performed during standby. You can see that

  The reduction in the surface roughness is caused by clogging of the surface of the refreshing roller 52 with toner or paper powder offset on the surface layer of the fixing roller 40. Further, the surface of the refreshing roller 52 with reduced roughness was colored with toner.

  From this result, it was verified that when the refresh operation of the fixing roller 40 is performed at the time of printing as compared with the case of performing at the time of standby, the surface roughness is greatly reduced because dirt is attached to the surface of the refresh roller.

  Accordingly, it can be seen that the refresh operation of the fixing roller 40 is preferably executed after the printing is once completed.

  On the other hand, the refresh operation of the pressure roller 41 has almost no difference between when it is executed during printing and when it is executed during standby. Therefore, it was determined that there is no problem even if the pressure roller refresh operation is executed during printing.

  The reason why the surface of the pressure roller 41 is not soiled during printing is considered as follows. The toner on the paper is melted by being heated between the fixing nip formed by the fixing roller 40 and the pressure roller 41 and fixed on the paper. At that time, most of the toner is fixed on the paper side, but it is generally known that a part of the toner adheres to the fixing roller 40 side. This is called hot offset. This hot offset is likely to be offset toward the fixing roller 40 because the higher the temperature of the fixing roller 40 in contact with the toner, the higher the temperature of the toner and the overmelting of the toner.

  On the other hand, in the case of single-sided printing, the pressure roller 41 has no hot offset because the surface on which no image is formed contacts the pressure roller 41. In the case of double-sided printing, the image surface once fixed on the first surface comes into contact with the pressure roller 41, but the temperature control temperature of the pressure roller 41 is very low compared to the temperature of the fixing roller 40; The image once fixed is a firmly fixed toner surface. Therefore, it is difficult for the toner to be hot-offset on the pressure roller 41 side.

  In FIG. 9, the refresh operation is executed for 5 seconds every time 500 sheets of A4 size paper on which a single-color halftone image having an image data density of about 0.5 is passed. Thereafter, the surface roughness Rz of the refresh rollers 52 and 62 is shown when the refresh rollers 52 and 62 are separated from the fixing roller 40 and the pressure roller 41 for 60 seconds and the cleaning rollers 53 and 63 are contacted and rotated. It is a thing.

  “Fixing member at standby” is a case where the refresh operation for the fixing roller 40 is executed during standby (the printing operation is temporarily interrupted).

  “Pressurizing member—during printing” is a case where a refresh operation for the pressure roller 41 is executed during printing.

  When the roughness of the surface layer of the refresh roller is lowered, the refresh capability is also lowered. As a result of experiments, in order to improve the surface conditions of the surface layers of the fixing roller 40 and the pressure roller 41, it has been found that the surface roughness Rz of the refresh rollers 52 and 62 is 7 to 8 μm or more. Using this value as a reference, it can be seen that both the refresh roller 52 of the fixing roller 40 and the refresh roller 62 of the pressure roller 41 increase the durable number reaching the reference value to about 600,000 and improve the durability.

  Therefore, after the refresh operation, the refresh roller is rotated away and the cleaning roller contact rotation time is extended to remove fine foreign matters such as paper dust and tube waste clogged between the abrasive grains of the refresh roller. It was verified that it improved.

  Next, the refresh execution flow will be described.

  The refresh execution flow will be described with reference to the flowchart of FIG. The refresh operation (second cleaning mode) for scraping paper dust and the like of the pressure roller 41 is performed in the flow of steps (1) to (7) in the refresh operation (first cleaning mode) for the edge flaw of the fixing roller 40. Steps (1), (8), (9), and (13) to (15) are executed in the flow.

  When printing is started, (1) it is detected that the sheet has passed through the fixing device 1, and (2) a sheet width number counter corresponding to the sheet width passed is converted into A4 (210 mm) transport length. Add with. For example, in the case of passing A3 vertical size (420 mm) paper, a paper width number counter having a width of 297 mm is incremented by +2 for two A4 transport lengths. If any value of the paper width counter is equal to or greater than the edge scratch occurrence number threshold value, the flow proceeds to the flow (4), and fixing refresh is executed. If it is less than the edge scratch occurrence number threshold, the flow of (1) to (3) is repeated as long as printing is continued.

  After (1), the flow of (8) is also performed in parallel. This is an operation for counting the number of sheets to be passed since it is a measure against contamination of paper dust. As in (2), the A4 transport length converted number is added to the number counter. Then, (9) if the sheet passing number counter value is equal to or greater than the paper dust contamination number threshold, the process proceeds to (13). Here, as in (3), the process can proceed even if the flow proceeds to (4) to (7). However, since the print job is temporarily stopped, the productivity of the printer is reduced. Therefore, it is more desirable to continue printing as much as possible and to execute processing during that time.

  Next, operations below (4) and (13) will be described. (4) to (7) are processes performed by temporarily interrupting the printing operation. In (4), the time required for fixing refresh is calculated from each recording material width counter value. Here, since the purpose of the fixing refresh is a paper edge scratch, the refresh time is determined based on a paper width number counter value that counts the number of sheets having a predetermined width or less. In this embodiment, the threshold value for the number of edge scratches is 3000 sheets, and the refresh operation time is 30 seconds.

  Next, the execution time of the pressure roller refresh is also calculated in (5). This is because if printing is stopped, productivity is not further affected by performing not only fixing refresh but also pressure refresh simultaneously. Here, since the purpose of the pressure refresh is paper dust stains, the refresh time is determined based on the sheet passing count value. In this embodiment, the threshold value for the number of paper dust stains is 1000, and the refresh operation time is 10 seconds.

  Of course, even if pressure refresh is not executed at this timing, it can be executed during printing, but when only a small number of copies are repeated, the pressure refresh operation can be executed during printing. There may be no case. For this reason, the operation is executed if there is an operable state.

  When the execution time of each refresh is calculated, (6) the printing is interrupted, and after the last sheet is removed from the fixing device F, the operations of (7) fixing refresh and pressure refresh are executed.

  On the other hand, (13) to (15) are processes for performing a refresh operation during printing. In (13), the required pressure refresh time is calculated from the sheet passing counter. Also in this case, since the purpose of the pressure refresh is paper dust contamination, the refresh time is determined based on the sheet passing count value. In this embodiment, the threshold value for the number of paper dust stains is 1000, and the refresh operation time is 10 seconds. (14) The execution of the pressure refresh is permitted, and (15) the pressure refresh is performed.

  As described above, the contact / separation mechanism 30 that contacts and separates the pressure roller 41 from the fixing roller 40 is provided. Then, after the introduction of the paper into the apparatus, the rotation time of the refresh roller 62 and the cleaning roller 63 can be adjusted by adjusting the pressure contact time of the pressure roller 41.

  Next, the execution flow of the refresh roller cleaning mode will be described with reference to the flowchart of FIG. In this embodiment, after completion of execution of (7) fixing refresh and (15) pressurization refresh during a paper passing job, a cleaning mode for cleaning the refresh rollers 52 and 62 by the cleaning rollers 53 and 63 is executed. .

  In the cleaning mode of the refresh roller 52, after execution of fixing refresh (7-1), the refresh roller 52 is separated from the fixing roller 40 by the attaching / detaching mechanism 51 (7-2). The refresh roller 52 is rotated for a predetermined time by the motor 54, and the surface layer of the refresh roller 52 is cleaned by the cleaning roller 53 that is driven to rotate relative to the refresh roller 52 (7-3). Then, when the motor 54 stops, the rotation of the refresh roller 52 and the cleaning roller 53 stops (7-4).

  As described above, the refresh roller 62 can be rotated by the rotational driving of the pressure roller 41 regardless of contact / separation with the pressure roller 41. Therefore, the refresh roller 62 also rotates during the rotation of the pressure roller 41. It is configured to always rotate. Therefore, the cleaning roller 63 is also driven to rotate with respect to the refresh roller 62 while the pressure roller 41 is rotating.

  In the cleaning mode of the refresh roller 62, after performing the pressure refresh (15-1), the detachment mechanism 61 separates the refresh roller 62 from the pressure roller 41 (15-2).

  In the state shown in FIG. 4, the pressure roller 41 is rotated for a predetermined time, and the surface layer of the refresh roller 62 is cleaned by the cleaning roller 63 driven to rotate with respect to the refresh roller 62 (15-3). As shown in FIG. 5, when the pressure roller 41 is separated from the fixing roller 40 (15-4), the rotation of the pressure roller 41 is stopped and the rotation of the refresh roller 62 and the cleaning roller 63 is also stopped ( 15-5).

  As described above, according to this embodiment, after the refresh roller 52 is separated from the fixing roller 40, the refresh roller 52 is rotated by the motor 54 for a predetermined time, thereby cleaning the dirt accumulated on the surface of the refresh roller 52. It becomes possible. As a result, it is possible to maintain the surface roughness of the refresh roller 52 necessary for the surface roughness of the fixing roller 40, and to extend the life of the refresh roller 52.

  Further, the rotation of the pressure roller 41 is transmitted to the refresh roller 62, and the rotation of the pressure roller 41 is always performed while the cleaning roller 63 is in contact with the surface of the refresh roller 62. This makes it possible to clean the dirt accumulated on the surface of the refresh roller 62. Accordingly, it is possible to maintain the surface roughness of the refresh roller 62 necessary for the surface roughness of the pressure roller 41, and the life of the refresh roller 62 can be extended.

《Other matters》
(1) The contact / separation mechanism 30 that contacts and separates the fixing roller 40 and the pressure roller 41 may have a solitary structure that contacts and separates the fixing roller 40 from the pressure roller 41, or pressurizes with the fixing roller 40. An isolated configuration in which both of the rollers 41 are brought into contact with and separated from each other may be employed.

  (2) The pair of rotating bodies 40 and 41 of the image heating device may not be both roller bodies as in the embodiment. An apparatus configuration in which one is a roller body and the other is an endless belt, or an apparatus configuration in which both are endless belts may be employed.

  (3) In the embodiment, the image heating device has been described by taking a fixing device that heats and fixes an unfixed toner image formed on a sheet (on a recording material) as an example, but is not limited thereto. The present invention can also be applied to an apparatus that increases the gloss (glossiness) of an image by reheating a toner image fixed or assumed on the paper P.

  F..Image heating device, 40..First rotating body (fixing roller), 41..Second rotating body (pressure roller), 52..First rubbing rotating body (fixing refresh roller), 53 .. First cleaning member (cleaning roller), 51 .. First contact / separation mechanism, 62 .. Second rubbing rotary member (pressure refresh roller), 63 .. Second cleaning member (cleaning) Roller), 61... Second contact / separation mechanism, 80.. Execution unit (control unit), P.

Claims (9)

The first rotating body for heating the toner image on the recording material at the nip portion and the first rotating body cooperate with the first rotating body to form the nip portion and contact the surface opposite to the toner image carrying surface of the recording material. A pair of rotating bodies with a second rotating body to perform,
A first rubbing rotary body capable of executing a rubbing process for rubbing the surface of the first rotating body by contacting the first rotating body with a peripheral speed difference; and
A first contact / separation mechanism for contacting and separating the first rubbing rotary body with respect to the surface of the first rotary body;
A first cleaning member that rotates to contact the surface of the first rubbing rotary body to clean the surface, and the second rotation by contacting the second rotary body with a difference in peripheral speed. A second rubbing rotary body capable of performing a rubbing process for rubbing the surface of the body;
A second contacting / separating mechanism for contacting and separating the second rubbing rotating body with respect to the surface of the second rotating body;
A second cleaning member that contacts the surface of the second rubbing rotator and cleans the surface;
A first cleaning mode for rotating the first rubbing rotator and the first cleaning member when the first rubbing rotator is separated from the first rotating body; An execution unit for executing a second cleaning mode for rotating the second rubbing rotary body and the second cleaning member when the rubbing rotary body is separated from the second rotating body; An image forming apparatus comprising:   A first rotating body and a second rotating body for heating the toner image on the recording material at the nip portion;
  A first rubbing rotary body capable of executing a rubbing process for rubbing the surface of the first rotating body by contacting the first rotating body with a peripheral speed difference; and
  A first contact / separation mechanism for contacting and separating the first rubbing rotary body with respect to the surface of the first rotary body;
  A rotatable first cleaning member that contacts the surface of the first rubbing rotator and cleans the surface;
  An execution unit for executing a first cleaning mode for rotating the first rubbing rotator and the first cleaning member when the first rubbing rotator is separated from the first rotating body; And an image forming apparatus. A first rotating body and a second rotating body for heating the toner image on the recording material at the nip portion;
A rubbing rotator capable of executing a rubbing process for rubbing the surface of the first rotator by contacting the first rotator with a peripheral speed difference; and
A contacting / separating mechanism for contacting and separating the rubbing rotating body with respect to the surface of the first rotating body;
A rotatable cleaning member that contacts the surface of the rubbing rotator and cleans the surface of the rubbing rotator;
A first gear provided on the first rotating body;
A second gear provided on the rubbing rotary body;
Rotation that forms a gear train between the first gear and the second gear such that a driving force is transmitted from the first rotating body to the rubbing rotating body when the first rotating body rotates. A transmission mechanism;
The cleaning member cleans the surface of the rubbing rotating body while the first rotating body is rotating , regardless of the contact and separation of the rubbing rotating body with respect to the first rotating body. Image heating device. A contact / separation mechanism for contacting / separating the second rotating body with respect to the first rotating body; and adjusting the pressure contact time of the second rotating body after the introduction of the recording material to the apparatus is completed. The image heating apparatus according to claim 3 , wherein the rotation time of the rubbing rotary body and the cleaning member can be adjusted. The image heating apparatus according to claim 3, wherein the rubbing rotary body has abrasive grains on a surface thereof. The image heating apparatus according to claim 5 , wherein the abrasive grains are alumina-based abrasive grains. The image heating apparatus according to claim 3 , wherein the cleaning member is a brush roller.   The second rotator is a heating rotator having a heater, and the first rotator is a pressure member that forms a nip portion that sandwiches and conveys the heating rotator and a recording material, and the sliding rotator The image heating apparatus according to claim 3, wherein the image heating apparatus abuts on the pressure member.   The image heating apparatus according to claim 8, wherein the rubbing rotary member performs an operation of rubbing the pressure member during a heating operation of heating an image on the recording material.