Fixing device and image forming apparatus

Abstract

To shorten the downtime of an apparatus while achieving a reduction in cost and size of the apparatus.SOLUTION: A fixing device comprises: a heating rotating body that heats a recording material carrying a toner image; a pressure rotating body that is in contact with the heating rotating body to form a nip part, and fixes the toner image to the recording material together with the heating rotating body; a rubbing member that is provided so that it can be brought into contact with and separated from the heating rotating body, the rubbing member being in contact with the heating rotating body to rub its surface; and a control unit that controls the rotation speed of the heating rotating body. In a state where the rubbing member and the heating rotating body are separated from each other and the recording material is conveyed to the nip part, the control unit controls the heating rotating body at a first rotation speed, and in a state where the rubbing member and the heating rotating body are in contact with each other and the recording material is not conveyed to the nip part, controls the heating rotating body at a second rotation speed faster than the first rotation speed.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a fixing device that fixes a toner image on a recording material and an image forming apparatus equipped with the same. [Background technology]

[0002] In a fixing device used in an image forming apparatus, as the number of sheets of recording material passing through increases, scratches occur in the circumferential direction of the fixing roller due to the cut edges (hereinafter referred to as paper edges) that occur when the recording material is cut, and these scratches appear as streaks in the image.

[0003] As a countermeasure, Patent Document 1 discloses a technique for carrying out a refreshing operation in which a rubbing member is brought into contact with the fixing roller to prepare the surface of the fixing roller that comes into contact with the edge of the paper in a predetermined state.

[0004] Furthermore, in Patent Document 1, a plurality of rubbing members are brought into contact with the surface of the fixing roller, thereby shortening the downtime of the device, that is, the time required for the aforementioned refreshing operation. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-88498 Summary of the Invention [Problem to be solved by the invention]

[0006] However, although the above-described conventional configuration can reduce downtime of the device, the provision of multiple rubbing members poses a problem of increased costs due to the increased number of parts.

[0007] Furthermore, since it is necessary to provide a drive source for driving the rubbing member, the increase in the installation space leads to an increase in the size of the device, which has been an issue.

[0008] SUMMARY OF THE INVENTION It is therefore an object of the present invention to reduce the downtime of an apparatus while realizing a reduction in the cost and size of the apparatus. [Means for solving the problem]

[0009] A typical configuration of the present invention includes a heating rotor that heats a recording material carrying a toner image, a pressure rotor that forms a nip by contacting the heating rotor and fixes the toner image to the recording material together with the heating rotor, a rubbing member that is arranged so as to be able to approach and separate from the heating rotor and that contacts the heating rotor and rubs its surface, and a control unit that controls the rotation speed of the heating rotor, wherein the control unit controls the heating rotor to a first rotation speed when the rubbing member and the heating rotor are separated and a recording material is transported to the nip, and controls the heating rotor to a second rotation speed that is faster than the first rotation speed when the rubbing member and the heating rotor are in contact and no recording material is transported to the nip. [Effects of the Invention]

[0010] According to the present invention, it is possible to reduce the cost and size of the device while shortening the downtime of the device. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is an explanatory diagram of a configuration of an image forming apparatus. [Figure 2] FIG. 2 is a perspective view of a main part of the fixing device. [Figure 3] FIG. 2 is an explanatory diagram of a cross-sectional configuration of a refreshing roller. [Figure 4] FIG. 10 is a perspective view of a separation mechanism for the refreshing roller. [Figure 5] FIG. 2 is an explanatory diagram of a configuration of a fixing device. [Figure 6] 10 is a flowchart showing a flow of control of a fixing roller refreshing operation. [Figure 7] 1A and 1B are diagrams illustrating the surface roughness of a fixing roller. [Figure 8]FIG. 10 is a table showing the effects of the present embodiment compared with a comparative example. [Figure 9] FIG. 1 is a schematic cross-sectional view of a fixing device equipped with an endless belt. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described in detail by way of example with reference to the drawings. However, the dimensions, materials, shapes, relative positions, etc. of the components described in the following embodiments may be changed as appropriate depending on the configuration of the device to which the present invention is applied and various conditions, and are not intended to limit the scope of the present invention to those alone.

[0013] <Image forming device> 1 is an explanatory diagram of the configuration of an image forming apparatus 100. The image forming apparatus 100 is a tandem type intermediate transfer type full-color copying machine.

[0014] As shown in FIG. 1, image forming apparatus 100 has a yellow image forming unit Pa, a magenta image forming unit Pb, a cyan image forming unit Pc, and a black image forming unit Pd arranged in an upward linear section of intermediate transfer belt 7. Image forming units Pa, Pb, Pc, and Pd form yellow toner images, magenta toner images, cyan toner images, and black toner images on photosensitive drums 3a, 3b, 3c, and 3d, respectively. The toner images of each color formed on each photosensitive drum are sequentially superimposed and primarily transferred onto intermediate transfer belt 7. The four-color, four-layer toner image thus primarily transferred is transported by intermediate transfer belt 7 and is secondarily transferred collectively onto recording material P by outer secondary transfer roller 11. The recording material P onto which the toner image has been secondarily transferred is delivered to fixing device 9, where it is heated and pressurized to fix the toner image to its surface.

[0015] The image forming units Pa, Pb, Pc, and Pd are configured almost identically except that the colors of toner filled in the developing devices 1a, 1b, 1c, and 1d are different: yellow, magenta, cyan, and black. Therefore, in the following, only the image forming unit Pa will be explained, and the other image forming units Pb, Pc, and Pd will be understood by replacing the "a" at the end of the reference numeral with "b," "c," and "d."

[0016] The image forming section Pa has a charging device 2a, an exposure device 5a, a developing device 1a, a primary transfer device 6a, and a cleaning device 4a arranged around a rotating photosensitive drum 3a.

[0017] The photosensitive drum 3a has a photosensitive layer on its surface, the charge potential of which decreases when irradiated with light, and carries an electrostatic image and a toner image.

[0018] The charging device 2a charges the surface of the photosensitive drum 3a to a uniform charging potential.

[0019] The exposure device 5a scans the charged surface of the photosensitive drum 3a with a laser beam modulated according to the density of each color along the scanning line of the image to be formed, thereby reducing the charge potential on the surface of the photosensitive drum 3a in accordance with the amount of exposure, and forming an electrostatic image of the image.

[0020] The developing device 1a electrically attaches charged toner to the electrostatic image on the photosensitive drum 3a, thereby developing the electrostatic image into a toner image.

[0021] The primary transfer device 6a electrically charges the intermediate transfer belt 7 passing through it to a polarity opposite to the polarity of the toner image, thereby electrically transferring the toner image on the photosensitive drum 3a to the intermediate transfer belt 7.

[0022] The cleaning device 4a removes toner remaining on the photosensitive drum 3a after escaping the primary transfer onto the intermediate transfer belt 7, thereby preparing for the next toner image formation.

[0023] The intermediate transfer belt 7 is supported by being stretched over a drive unit 15, a tension roller 13, and a secondary transfer inner roller 14, and rotates in the direction of the arrow in the figure. The intermediate transfer belt 7 transports the toner images, which have been sequentially transferred and superimposed from the photosensitive drums 3a, 3b, 3c, and 3d, to the pressure contact portion between the intermediate transfer belt 7, which is supported by the secondary transfer inner roller 14, and the secondary transfer outer roller 11.

[0024] The inner secondary transfer roller 14 is connected to a ground potential. In the process of nipping and conveying the recording material between the intermediate transfer belt 7 and the outer secondary transfer roller 11, with the recording material superimposed on the toner image, a voltage of a polarity opposite to the charge polarity of the toner image is applied to the outer secondary transfer roller 11. As a result, the four-color, four-layer toner image on the intermediate transfer belt 7 is electrically moved to the recording material P and secondary-transferred all at once.

[0025] The recording materials P are stored in cassettes 10 according to size, and are pulled out of the cassettes 10, separated into individual sheets, and made to wait by registration rollers 12. The registration rollers 12 feed the recording materials P to the pressure contact portion between the intermediate transfer belt 7 and the secondary outer transfer roller 11 in synchronization with the toner image on the intermediate transfer belt 7.

[0026] The cleaning device 19 removes the residual toner remaining on the intermediate transfer belt 7 after escaping the secondary transfer, to prepare for the next primary transfer of a toner image.

[0027] The fixing device 9 sandwiches and conveys the recording material P carrying the four-color, four-layer toner image between a fixing roller 40 and a pressure roller 41, and heats and presses the toner image to fix it to the recording material. The recording material with the fixed toner image is discharged outside the body of the image forming apparatus 100.

[0028] <Fixing device> 2 is a perspective view of the main part of the fixing device, FIG. 3 is an explanatory diagram of the cross-sectional configuration of the refreshing roller, FIG. 4 is a perspective view of the separating mechanism of the refreshing roller, and FIG. 5 is an explanatory diagram of the configuration of the fixing device.

[0029] 2, fixing device 9 has fixing roller 40 as a heating rotator heated from the inside by halogen heater 40H and pressure roller 41 heated from the inside by halogen heater 41H, which are pressed together to form fixing section (nip section) T3. The entire fixing device including fixing roller 40 and pressure roller 41 is covered by a heat-insulating housing (not shown).

[0030] Thermistors 40S and 41S are in contact with the fixing roller 40 and pressure roller 41, respectively, on the upstream side (the recording material feed side) of fixing unit T3. Thermistor 40S detects the surface temperature of fixing roller 40 and feeds it back to the output of halogen heater 40H. Thermistor 41S detects the surface temperature of pressure roller 41 and feeds it back to the output of halogen heater 41H.

[0031] 5, the fixing roller 40 and the pressure roller 41 are connected to a driving device 34. The driving device 34 is a driving unit that drives the fixing roller 40 and the pressure roller 41. The driving speed of the driving device 34 is controlled by a control unit 110. The pressure roller 41 is biased by a pressure mechanism (not shown) and is pressed against the fixing roller 40 with a total pressure of approximately 800 N (80 kgf).

[0032] The fixing roller 40 is a heating rotor that heats a recording material carrying an image. The fixing roller 40 has an outer diameter of 70 mm, and is made of a hollow aluminum core 40a with an outer diameter of 68 mm, a 1.0 mm thick elastic layer 40b, and a 30 μm thick release layer 40c covering the surface. The elastic layer 40b is made of silicone rubber with a rubber hardness of 20 degrees (when loaded with 10 N according to the JIS-A measurement method). The release layer 40c is made of a tube material using a fluororesin such as PFA (tetrafluoroethylene, perfluoroalkoxyethylene copolymer) or PTFE (tetrafluoroethylene).

[0033] The pressure roller 41 is a pressure rotating body that forms a nip portion (fixing portion T3) with the fixing roller 40. The pressure roller 41 has an outer diameter of 50 mm, with a 1.0 mm thick elastic layer 41b formed on an aluminum hollow core 41a with an outer diameter of 48 mm, and a 30 μm thick release layer 41c covering the surface. The materials of the elastic layer 41b and the release layer 41c are the same as those of the fixing roller 40.

[0034] Temperature control circuit 107 adjusts the output of halogen heater 40H by feeding back the output of thermistor 40S, and also adjusts the output of halogen heater 41H by feeding back the output of thermistor 41S. Temperature control circuit 107 controls the surface temperatures of both fixing roller 40 and pressure roller 41 to 165°C±1°C, thereby ensuring a necessary and sufficient fixing temperature in fixing unit T3.

[0035] A cleaning device 32 is disposed on the outlet side of the fixing unit T3. The cleaning device 32 cleans the fixing roller 40 by rubbing a nonwoven cleaning web against the surface of the rotating fixing roller 40. The control unit 110 detects the output of the angle sensor Sd and controls the motor 33 to intermittently wind up the cleaning web.

[0036] Here, by disposing a release layer 40c of fluororesin on the surface of the fixing roller 40, the adhesion of the heat-fused toner image is quickly eliminated without applying a lubricant such as oil to the fixing roller 40, and the recording material is effectively separated from the fixing roller 40 by curvature.

[0037] However, since the surface condition of the fixing roller 40 is directly transferred to the surface of the melted toner image without the use of a lubricant, the surface condition of the fixing roller 40 must be maintained uniformly over time with little local variation. Therefore, every time a certain number of sheets have been fixed, a rotating refresh roller 93 is pressed against the rotating fixing roller 40 to roughen the surface and restore the surface condition.

[0038] (Refresh Roller) That is, the fixing device 9 is equipped with a refreshing roller 93 as a rubbing member. The refreshing roller 93 is a rotating body. As shown in FIG. 3, the refreshing roller 93 has a stainless steel core 93a with a diameter of 12 mm and abrasive grains 93b densely adhered to the surface thereof via an adhesive layer 93c. The grit size of the abrasive grains 93b is changed to a value between #1000 and #4000 depending on the application (target gloss level of the image). The average grain size of the abrasive grains 93b is approximately 16 μm for #1000 grit and approximately 3 μm for #4000 grit.

[0039] The abrasive grains 93b are alumina-based (commonly known as "alundum" or "morundum"). Alumina-based abrasive grains are the most widely used industrially, and are significantly harder than the surface of the fixing roller 40. The sharp-angled particles provide excellent roughening properties (refreshing and leveling).

[0040] The refreshing roller 93 is provided so as to be able to approach and separate from the fixing roller 40, and contacts the fixing roller 40 and rubs its surface to adjust the surface properties to a predetermined state. The refreshing roller 93 is disposed downstream of the fixing unit T3. The refreshing roller 93 is also disposed downstream of the cleaning device 32.

[0041] 4, the refreshing roller 93 has bearings 45 that rotatably support both ends of a shaft 94 of the refreshing roller 93, which are fixed to support arms 46 that rotate around a rotation shaft 47. The refreshing roller 93 is provided so that it can move toward and away from the fixing roller 40 by the support arms 46 that support both ends of the shaft 94. A pair of pressure springs 48, disposed at both axial ends of the refreshing roller 93, bias the respective support arms 46, thereby pressing the refreshing roller 93 against the fixing roller 40 with a total pressure of 100 N.

[0042] It has been confirmed that if the pressure of the refreshing roller 93 is less than 10N, the roughening ability is insufficient, and if it exceeds 150N, the roughening quality is impaired. Therefore, the pressure is preferably 10N or more and 150N or less.

[0043] (separation mechanism) In this way, the refreshing roller 93 is provided by the support arm 46 so that it can be moved toward or away from the fixing roller 40, and is pressed against the fixing roller 40 by the pressure spring 48 with a predetermined pressure. The refreshing roller 93 is brought into contact with or separated from the fixing roller 40 by the separation mechanism 31. The operation of the separation mechanism 31 is controlled by the control unit 110. That is, the separation mechanism 31 is controlled so that it separates the refreshing roller 93 from the fixing roller 40 during printing, and brings the refreshing roller 93 into contact with the fixing roller 40 during the refreshing operation. A pair of separation mechanisms 31 are arranged symmetrically at both ends of the fixing device 9 in the axial direction.

[0044] The separation mechanism 31 rotates the support arm 46, which supports the shaft 94 of the refreshing roller 93, around the rotation shaft 47 to separate the refreshing roller 93 from the fixing roller 40. A refreshing roller drive input gear 50 (see FIG. 2) is fixed to one end 94a of the shaft 94.

[0045] The separating mechanism 31 includes a motor 58 whose driving is controlled by the control unit 110, a cam 56 that is rotated by the motor 58, and a retracting arm 52 that is rotated around a rotation shaft 53 by the cam 56. The retracting arm 52 has a guide surface 57 that abuts against the cam 56 and a drive end 55 that abuts against a drive arm 46a of the support arm 46. The drive arm 46a is connected to the support arm 46 and rotates integrally therewith (see FIG. 4). The retracting arm 52 is biased by a drive spring 54 in a direction in which the drive end 55 presses the drive arm 46a to separate the refreshing roller 93 from the fixing roller 40. The force with which the drive spring 54 pulls the support arm 46 via the drive end 55 is greater than the force with which the pressure spring 48 pulls the support arm 46 in the opposite direction.

[0046] The control unit 110 operates the motor 58 to rotate the cam 56 , thereby rotating the retracting arm 52 around the rotation shaft 53 and separating the refreshing roller 93 from the fixing roller 40 .

[0047] The cam 56 presses down the guide surface 57 of the retracting arm 52 against the biasing force of the drive spring 54, thereby moving the drive end 55 away from the drive arm 46a and leaving the rotation of the support arm 46 to the pressure spring 48.

[0048] Therefore, when the cam 56 rotates and the rotation of the retracting arm 52 is entrusted to the drive spring 54, the drive end 55 of the retracting arm 52, which is biased by the drive spring 54, rotates the drive arm 46a, and the refreshing roller 93 moves away from the fixing roller 40. The rotation angle of the cam 56 is detected by an angle sensor Sc (see FIG. 2) and fed back to the control unit 110.

[0049] (Drive transmission mechanism) 2, the fixing device 9 has a drive transmission mechanism 35 that transmits a rotational drive force from the fixing roller 40 to the refreshing roller 93. The drive transmission mechanism 35 has a refreshing roller drive transmission gear 49, a refreshing roller drive input gear 50, and an idler gear 51. The refreshing roller drive transmission gear 49 is provided at the shaft end of the fixing roller 40 and is a drive transmission part that transmits a drive force to the refreshing roller 93. The refreshing roller drive input gear 50 is provided at the shaft end of the refreshing roller 93 and is a drive input part that is separably connected to the refreshing roller drive transmission gear 49 and rotates the refreshing roller 93.

[0050] The idler gear 51 is axially supported on the fuser roller 40 side and meshes with the refresh roller drive transmission gear 49. On the other hand, the refresh roller drive input gear 50 is axially supported on the support arm 46 side and meshes with the idler gear 51 when the refresh roller 93 is in pressure contact with the fuser roller 40. The separation distance of the refresh roller 93 from the fuser roller 40 in the separated state is greater than the tooth heights of the refresh roller drive input gear 50 and the idler gear 51. Therefore, when the support arm 46 rotates in the separation direction, the meshing between the refresh roller drive input gear 50, which is axially supported on the support arm 46 side, and the idler gear 51, which is axially supported on the fuser roller 40 side, is released, and the rotation of the refresh roller 93 automatically stops.

[0051] This allows the refreshing roller 93 to be rotated by distributing the driving force of the fixing roller 40 during pressure contact without using a clutch mechanism, and the refreshing roller 93 to stop rotating during separation.

[0052] Furthermore, the positional relationship between the idler gear 51 and the refreshing roller drive input gear 50 is set so as not to affect the pressing force of the refreshing roller 93 against the fixing roller 40. The drive transmission force from the idler gear 51 to the refreshing roller drive input gear 50 does not have a component force in the direction in which the refreshing roller 93 presses against or separates from the fixing roller 40. In other words, the meshing between the idler gear 51 and the refreshing roller drive input gear 50 is set to a so-called neutral position with respect to the rotation of the support arm 46 about the rotary shaft 47.

[0053] The refreshing roller 93 is driven by the drive transmission mechanism 35 to rotate in the same rotational direction (clockwise) as the fixing roller 40. The refreshing roller 93 is biased by a pair of pressure springs 48 arranged at both ends to press against the fixing roller 40. As described above, the refreshing roller 93 has a large number of abrasives on its surface. As a result, the refreshing roller 93 rotates in the counter direction, in which its surface moves in the opposite direction to the surface of the fixing roller 40, and rubs against the surface of the fixing roller 40, thereby restoring the surface condition of the fixing roller 40.

[0054] 2, the fixing roller 40 is rotationally driven by the driving device 34 through a drive input gear 44 fixed to the opposite side of the drive transmission mechanism 35. The drive input gear 44 is engaged with a gear train (not shown) that rotates the pressure roller 41 at the same surface speed as the fixing roller 40. In other words, the fixing roller 40 and the pressure roller 41 are rotationally driven by the driving device 34.

[0055] The drive transmission mechanism 35 transmits the driving force from a refreshing roller drive transmission gear 49 fixed to the fixing roller 40, via an idler gear 51, to a refreshing roller drive input gear 50 fixed to the refreshing roller 93. The gear ratio of the drive transmission mechanism 35 is set so that when the drive device 34 is driven at the printing speed, the peripheral speed of the fixing roller 40 is 400 mm / sec and the peripheral speed of the refreshing roller 93 is 200 mm / sec.

[0056] The control unit 110 controls the rotation speeds of the fixing roller 40 and the pressure roller 41. During printing, the control unit 110 drives the drive unit 34 at a printing speed. The printing speed is a first driving speed at which the recording material P is nipped and transported in the fixing unit T3 (nip portion) and the toner image is heated and pressurized to fix it to the recording material P, and the fixing roller 40 is driven to rotate at a first rotation speed. On the other hand, during a refreshing operation, the control unit 110 drives the drive unit 34 at a refreshing speed that is faster than the printing speed. The refreshing speed is a second driving speed at which the fixing roller 40 is driven to rotate at a second rotation speed that is faster than the first rotation speed when no recording material is transported to the fixing unit T3 (nip portion).

[0057] The above-described drive transmission mechanism 35 causes the refreshing roller 93 and the fixing roller 40 to rotate in the same direction, and the refreshing roller 93 rotates in the counter direction (the direction in which the surfaces move in opposite directions) relative to the fixing roller 40. The relative speed between the fixing roller 40 and the refreshing roller 93, which rotate relative to each other in the counter direction, is 600 mm / sec.

[0058] <Fuser roller refresh control> Next, the refreshing operation using the refreshing roller will be described.

[0059] 5, when the user is concerned about uneven gloss or gloss streaks in the fixed image, the user can operate the operation panel 108 to call up the user mode and start a refresh operation using the refresh roller 93 at any time. At this time, the touch panel of the operation panel 108 displays options for the refresh operation time and a refresh operation start button.

[0060] Furthermore, when small-sized recording materials are continuously processed, a refresh operation using the refresh roller 93 is automatically performed every time a predetermined number of sheets is counted, as will be explained below. In the following explanation, 500 sheets is used as an example of the predetermined number of sheets to be counted, but the present invention is not limited to this.

[0061] The refresh operation using the refresh roller 93 is a refresh operation in which the refresh roller 93 is brought into contact with the target rotating body (such as the fixing roller 40), and the surface of the rotating body that comes into contact with the edge of the paper is rubbed, thereby adjusting the surface properties to a predetermined state.

[0062] Furthermore, a small-sized recording material is defined as a recording material whose length in the width direction (longitudinal direction of the fixing roller) perpendicular to the conveying direction of the recording material is smaller than the maximum printable width. In the following explanation, an A4-sized recording material is used as an example of a small-sized recording material, but the small-sized recording material is not limited to this.

[0063] The refreshing operation is particularly preferable when the length in the width direction (longitudinal direction of the fixing roller) perpendicular to the conveying direction of the recording material is smaller than the maximum printable width, in order to prepare the surface of the rotating body that comes into contact with the edge of the paper in a predetermined state. However, the refreshing operation is not limited to small-sized recording materials, and is effective for preparing or restoring the surface of the rotating body that comes into contact with the edge of the paper to a predetermined state.

[0064] The refreshing operation will be explained using Figures 6 and 7. Figure 6 is a flowchart showing the control flow of the refreshing operation of the fixing roller, and Figure 7 is an explanatory diagram showing the surface roughness of the fixing roller in the longitudinal direction. Figure 7(a) shows the surface roughness of the fixing roller before the refreshing operation, and Figure 7(b) shows the surface roughness of the fixing roller after the refreshing operation.

[0065] 6, when an image formation job is started, the control unit 110 starts counting the number of fixed small-size (A4 size) recording materials (S11). Then, when the count reaches 500 sheets (YES in S12), the control unit 110 continues counting and waits for the job to end (S11 to S13).

[0066] Then, when the job is completed (YES in S13), the time for the refreshing operation to prepare the surface of the fixing roller 40 is set according to the number of sheets counted up to that point (500 sheets+α) (S14).

[0067] Then, with the rotation of the fixing roller 40 stopped (S15), the motor 58 is operated to rotate the cam 56, and the refreshing roller drive input gear 50 shown in FIG. 2 is brought into mesh with the idler gear 51. That is, the control unit 110 connects the refreshing roller drive input gear 50 to the refreshing roller drive transmission gear 49 with the rotation of the refreshing roller 93 and fixing roller 40 stopped. Then, before the refreshing roller 93 comes into contact with the fixing roller 40, the drive device 34 is started to rotate the fixing roller 40 and the refreshing roller 93. That is, the control unit 110 starts driving the refreshing roller 93 with the refreshing roller 93 and fixing roller 40 separated from each other.

[0068] At this time, the drive speed of the drive device 34 is controlled by the control unit 110 to a refresh speed (second drive speed) that is faster than the print speed (first drive speed). Therefore, the fixing roller 40 is rotated at a refresh speed (second rotation speed, 600 mm / sec) whose peripheral speed is faster than the print speed (first rotation speed, 400 mm / sec). The refreshing roller 93 is rotated at a refresh speed (300 mm / sec) whose peripheral speed is faster than the print speed (200 mm / sec) (S16).

[0069] As described above, the refreshing roller 93 rotates in a counter direction (the direction in which the surfaces move in opposite directions) in which its surface moves in the opposite direction to the surface of the fixing roller 40. Therefore, the relative speed between the fixing roller 40 and the refreshing roller 93, which rotate relative to each other in the counter direction, is the sum of their respective peripheral speeds (900 mm / sec).

[0070] Then, the motor 58 is further operated to rotate the cam 56, and the refreshing roller 93, which is in a rotating state, is pressed against the rotating fixing roller 40, thereby starting the refreshing operation (S17). That is, after the control unit 110 starts driving the refreshing roller 93 while the refreshing roller 93 and the fixing roller 40 are spaced apart, the refreshing roller 93 is brought into contact with the fixing roller 40 to start the refreshing operation of rubbing its surface. The refreshing roller 93 is driven to rotate at a peripheral speed different from the surface speed of the fixing roller 40 while in contact with the surface of the fixing roller 40.

[0071] When the time for the refreshing operation set according to the number of counted sheets has elapsed (YES in S18), the driving of the driving device 34 is stopped, and the rotation of the fixing roller 40 and the refreshing roller 93 is stopped (S19).

[0072] Then, the motor 58 is operated in the direction opposite to that during pressure contact to rotate the cam 56, thereby separating the refreshing roller 93 from the fixing roller 40 (S20).

[0073] Thereafter, the count of the number of small-sized recording materials fixed is reset (S21), and the process waits for the next job.

[0074] 6, in order to avoid collision noise when the refresh roller drive input gear 50 and the idler gear 51 mesh together, the refresh roller drive input gear 50 and the idler gear 51 are meshed together while the rotation of the fixing roller 40 is stopped. However, this is not limited to this. For example, the refresh roller drive input gear 50 and the idler gear 51 may be meshed together while the fixing roller 40 is rotating all the time without stopping the rotation of the fixing roller 40.

[0075] 7(a), scratches are formed due to the edges of the small-sized recording material in region C of the fixing roller 40, where both edges in the width direction perpendicular to the conveying direction of the recording material pass, from the previous refresh operation through fixing 500 sheets to the end of the job. Also, in region A of the fixing roller 40 where the small-sized recording material passes, the surface quality becomes rougher than in region B where the small-sized recording material does not pass.

[0076] However, the surface condition of the areas A, B, and C of the fixing roller 40 is uniformly smoothed by being rubbed by the refreshing roller 93 (abrasive grains of #1000 to #4000) throughout the refreshing operation. Specifically, as shown in FIG. 7(b), after the refreshing operation is completed, the entire area in the longitudinal direction (axial direction) of the fixing roller 40 has a substantially uniform surface condition.

[0077] <Reduction of equipment downtime> Next, the effect of reducing apparatus downtime by using a refresh speed higher than the print speed during the refresh operation will be described with reference to FIG. 8, in comparison with a comparative example in which the refresh operation is performed using the print speed.

[0078] In the comparative example, when the refreshing operation is performed, the drive device 34 is driven at a first drive speed. That is, in the comparative example, the fixing roller 40 rotates at the printing speed, and therefore its peripheral speed is 400 mm / sec. On the other hand, the peripheral speed of the refreshing roller 93 is 200 mm / sec due to the gear ratio of the drive transmission mechanism 35. Therefore, in the comparative example, the relative speed between the fixing roller 40 and the refreshing roller 93 is 600 mm / sec.

[0079] Here, in order to achieve a nearly uniform surface condition over the entire longitudinal (axial) area of the fixing roller 40, the refresh roller 93 needs to be rotated approximately 36,000 mm in the counter direction (the direction in which the surfaces move in opposite directions) relative to the fixing roller 40.

[0080] Therefore, in the comparative example, since the relative speed is 600 mm / sec, a refresh time of 60 seconds is required, and at the same time, the downtime of the device is approximately 60 seconds.

[0081] In contrast, in this embodiment, when performing the refreshing operation, the drive device 34 is driven at a second driving speed that is faster than the first driving speed. That is, in this embodiment, the fixing roller 40 rotates at a refreshing speed that is faster than the printing speed, so its peripheral speed is 600 mm / sec. Meanwhile, the peripheral speed of the refreshing roller 93 is 300 mm / sec due to the gear ratio of the drive transmission mechanism 35. Therefore, in this embodiment, the relative speed between the fixing roller 40 and the refreshing roller 93 is 900 mm / sec.

[0082] Therefore, in this embodiment, the relative speed is faster (900 mm / sec) than in the comparative example, so a refresh time of 40 seconds is required, and the downtime of the device is reduced by approximately 20 seconds compared to the comparative example.

[0083] The fixing roller 40 has an outer diameter of Φ70 mm, so the outer circumference is approximately 220 mm, and the refreshing roller 93 rotates 36,000 mm. Therefore, in both the comparative example and this embodiment, the refreshing roller 93 passes over the fixing roller 40 approximately 164 times, thereby achieving a nearly uniform surface condition in the axial direction.

[0084] As described above, according to this embodiment, the refreshing roller 93 is driven by the drive device 34 that drives the fixing roller 40, and a relative speed difference is created between the fixing roller 40 and the refreshing roller 93 by the gear ratio of the drive transmission mechanism 35, so that the surface condition of the fixing roller 40 is refreshed at a refreshing speed that is faster than the printing speed. This eliminates the need to provide multiple rubbing members or a driving source for the rubbing members, making it possible to reduce the size and cost of the fixing device while shortening the downtime of the device.

[0085] In the above-described embodiment, the refreshing roller 93 is pressed against the fixing roller 40 to perform the refreshing operation, and the downtime of the device is reduced by using the refreshing speed. However, the present invention is not limited to this. It is also possible to fix the refreshing roller drive transmission gear to the pressure roller 41, press the refreshing roller 93 against the pressure roller 41 to perform the refreshing operation, and reduce the downtime of the device by using the refreshing speed.

[0086] In addition, in the above-mentioned embodiment, an example was given of a case where a refresh operation is performed after the number of sheets of recording material P having a size smaller than the maximum width passing through the nip portion (fixing portion T3) of the fixing device 9 reaches a predetermined number, but this is not limited to this.

[0087] For example, regardless of the size of the recording material, the refreshing operation may be performed after a predetermined number of recording materials P have passed through the nip portion (fixing portion T3) of the fixing device 9. In this case, the same effect as in the above-described embodiment can be obtained.

[0088] Alternatively, the refreshing operation may be performed after the job in which the recording material P carrying the toner image passes through the nip portion (fixing portion T3) of the fixing device 9 is completed. In this case, the same effect as in the above-described embodiment can be obtained.

[0089] In the above-described embodiment, a fixing roller with a halogen heater disposed therein is exemplified as a heating rotator, but the present invention is not limited to this. For example, a heating rotator in which a halogen heater is disposed inside a belt to heat the belt may be used. Alternatively, a heating rotator in which an electromagnetic induction (IH) heating element is disposed outside the belt to heat the belt may be used. Alternatively, other heating elements may be used as the heating element for heating the belt. Furthermore, a pressure roller with a halogen heater disposed therein is exemplified as a pressure rotator that forms a nip with the heating rotator, but as with the above-described heating rotator, the present invention is not limited to this. In any configuration, the same effects can be obtained by applying the present invention.

[0090] In the above-described embodiment, an example was described in which the present invention is applied to an electrophotographic full-color image forming apparatus having multiple photosensitive drums, but the present invention is not limited to this and can also be applied to image forming apparatuses of various types, monochrome image forming apparatuses, etc.

[0091] In the above-described embodiment, a printer is used as an example of an image forming apparatus, but the present invention is not limited to this. For example, other image forming apparatuses such as a copier or facsimile machine, or other image forming apparatuses such as a multifunction peripheral that combines the functions of these, may also be used. Furthermore, while the image forming apparatus uses an intermediate transfer member, sequentially transfers toner images of each color onto the intermediate transfer member in a superimposed manner, and then transfers the toner images carried on the intermediate transfer member to a recording material all at once, the present invention is not limited to this. It may also be an image forming apparatus using a recording material carrier, sequentially transfers toner images of each color onto a recording material carried on the recording material carrier in a superimposed manner. Similar effects can be achieved by applying the present invention to the fixing devices used in these image forming apparatuses.

[0092] The heating rotator is not limited to the fixing roller 40, but may be an endless belt 42. FIG. 9 shows a configuration in which the heating rotator is an endless belt 42. The belt 42 as the heating rotator is suspended between a heating roller 42a, a steering roller 42c, and a pad 42b. The heating roller 42a has a halogen heater 42H, which is disposed on the inner circumferential surface of the belt 42 and transfers heat to the belt 42. The pad 42b, together with the pressure roller 41, forms a nip portion (fixing portion T3) via the belt 42. The steering roller 42c is a roller that oscillates to control the position of the belt 42 in the width direction of the belt 42. The configuration shown in FIG. 9 may also be used. [Explanation of symbols]

[0093] P... Recording material T3: Fixing section (nip section) 9...Fuser (image heating device) 31...Separation mechanism 34...Driver (drive unit) 35...Drive transmission mechanism 40...Fuser roller (heating rotor) 41...Pressure roller (pressure rotating body) 48...Pressure spring 49... Refresh roller drive transmission gear (drive transmission part) 50... Refresh roller drive input gear (drive input part) 51...Idler gear 93 ... Refresh roller (rubbing member) 100...Image forming device 110...control unit

Claims

1. a heating rotor for heating a recording material carrying a toner image; a pressure rotating body that forms a nip portion by contacting the heating rotating body and fixes a toner image onto a recording material together with the heating rotating body; a rubbing member that is provided so as to be able to approach and separate from the heating rotor and that comes into contact with the heating rotor and rubs the surface thereof; a control unit for controlling the rotation speed of the heating rotor, The control unit controlling the heating rotor to a first rotation speed in a state where the rubbing member and the heating rotor are separated and the recording material is conveyed to the nip portion; a fixing device characterized in that, when the friction member and the heating rotor are in contact with each other and no recording material is transported to the nip portion, the heating rotor is controlled to a second rotation speed that is faster than the first rotation speed.

2. a drive transmission mechanism that transmits a rotational drive force from the heating rotor to the friction member, 2. The fixing device according to claim 1, wherein the fixing device is a fixing device for fixing a toner image onto a recording medium.

3. The drive transmission mechanism includes: a drive transmission unit that transmits a driving force of the heating rotor to the friction member; 3. The fixing device according to claim 2, further comprising: a drive input portion separably connected to the drive transmission portion to rotate the rubbing member.

4. 3. The fixing device according to claim 2, wherein the rubbing member is a rotating body that is rotated at a peripheral speed different from the surface speed of the heating rotating body while in contact with the surface.

5. 4. The fixing device according to claim 3, wherein the rubbing member is a rotating body that is rotated in a counter direction such that a surface of the rubbing member moves in a direction opposite to a surface of the heating rotating body.

6. the control unit starts driving the rubbing member in a state where the rubbing member and the heating rotor are spaced apart, and then the rubbing member comes into contact with the heating rotor and rubs against the heating rotor; 4. The fixing device according to claim 3.

7. In a state where the rotation of the rubbing member and the heating rotor is stopped, the control unit starts driving the rubbing member, and then the rubbing member comes into contact with the heating rotor and rubs against the heating rotor.

7. The fixing device according to claim 6, wherein the fixing device is a fixing device for fixing a toner image onto a recording medium.

8. When the rotation of the friction member and the heating rotor is stopped, the drive input unit is connected to the drive transmission unit, and then the friction member comes into contact with the heating rotor and rubs against the heating rotor.

8. The fixing device according to claim 7,

9. 2. The fixing device according to claim 1, wherein the rubbing member contacts and rubs against the heating rotary member after the number of recording materials passing through the nip portion reaches a predetermined number and the job is completed.

10. 8. The fixing device according to claim 7, wherein the number of sheets of recording material whose width direction perpendicular to the conveying direction of the recording material is smaller than the maximum width that pass through the nip portion reaches a predetermined number, and after the job is completed, the rubbing member is brought into contact with the heating rotating body and rubbed against it.

11. a heating rotor for heating a recording material carrying a toner image; a pressure rotating body that forms a nip portion by contacting the heating rotating body and fixes a toner image onto a recording material together with the heating rotating body; a rubbing member that is provided so as to be able to approach and separate from the pressure rotating body and that comes into contact with the pressure rotating body and rubs the surface thereof; a control unit that controls the rotation speed of the pressure rotating body, The control unit controlling the pressure rotating body to a first rotation speed in a state where the rubbing member and the pressure rotating body are separated and the recording material is conveyed to the nip portion; a fixing device characterized in that, when the friction member and the pressure rotating body are in contact with each other and no recording material is transported to the nip portion, the pressure rotating body is controlled to a second rotation speed that is faster than the first rotation speed.

12. The heating rotor is an endless belt.

2. The fixing device according to claim 1, wherein the fixing device is a fixing device for fixing a toner image onto a recording medium.

13. a heating roller disposed on the inner circumferential surface of the belt and suspending the belt; 13. The fixing device according to claim 12.

14. an image forming unit that forms an image; a fixing device that nip-conveys and conveys a recording material carrying an image and fixes the image, An image forming apparatus, comprising the fixing device according to claim 1 .

Images