JP2023073090A - Fixing device and image forming apparatus - Google Patents

Abstract

To remove a larger amount of attachment attached to an outer peripheral surface of a fixing rotating body.SOLUTION: A fixing device 40 has a removal member 46 that rubs outer peripheral surfaces of fixing rotating bodies 41, 42, 43 to remove an attachment W attached to the outer peripheral surfaces, and brings the outer peripheral surfaces of the fixing rotating bodies to be heated into contact with a recording material P to fix an image to the recording material. When the temperature of the fixing rotating bodies exceeds a predetermined temperature lower than a temperature during fixing, the removal member removes the attachment attached to the outer peripheral surfaces of the fixing rotating bodies after the temperature of the fixing rotating bodies falls to the predetermined temperature or less.SELECTED DRAWING: Figure 5

Description

The present invention relates to a fixing device and an image forming apparatus.

Conventionally, there is provided a removing member for rubbing the outer peripheral surface of the fixing rotator to remove deposits adhering to the outer peripheral surface, and the image is removed by bringing the outer peripheral surface of the heated fixing rotator into contact with the recording material. A fixing device for fixing onto a recording material is known.

In Patent Document 1, a cleaning web (removing member) is used to remove wax adhering to the outer peripheral surface of a heat-fixing roller (fixing rotating body) (wax dispersedly contained in the toner melts and adheres during fixing). A fixing device having a configuration is disclosed. In this fixing device, in order to efficiently remove the wax, the wax in a liquid state is wiped off by the cleaning web while the temperature of the outer peripheral surface of the heat fixing roller is maintained at a temperature equal to or higher than the melting point of the wax.

However, the conventional fixing device has a problem that it is impossible to completely remove deposits such as wax adhering to the outer peripheral surface of the fixing rotating body.

In order to solve the above-described problems, the present invention has a removing member that rubs the outer peripheral surface of a fixing rotator to remove deposits adhering to the outer peripheral surface, and removes the outer periphery of the fixing rotator that is heated. A fixing device for fixing an image on a recording material by bringing a surface thereof into contact with the recording material, wherein the removing member removes the fixing rotator when the temperature of the fixing rotator exceeds a predetermined temperature lower than the fixing temperature. is removed from the outer peripheral surface of the fixing rotator after the temperature of the fixing rotator has fallen below the predetermined temperature.

According to the present invention, it is possible to remove more deposits adhering to the outer peripheral surface of the fixing rotator.

1 is a schematic configuration diagram showing an example of a printer according to an embodiment; FIG. FIG. 2 is a cross-sectional view of a fixing roller and a heating roller in a direction orthogonal to the roller shafts, showing a schematic configuration of a fixing device in the printer; FIG. 2 is a cross-sectional view of a fixing roller and a heating roller in a direction orthogonal to the roller shafts, showing the schematic configuration of the fixing device; FIG. 4 is an explanatory diagram showing an example of an image on a sheet on which a glossy afterimage is generated; FIG. 4 is an explanatory view showing how a wax component of toner on paper adheres to a fixing belt; 5 is a flow chart showing the flow of control in a refresh mode for removing deposits from the outer peripheral surface of the fixing belt in the embodiment; FIG. 5 is a schematic configuration diagram showing a modified example of the fixing device according to the embodiment; 5 is a graph showing the results of an effect confirmation test for confirming the effect of suppressing glossy afterimages by the fixing device according to the embodiment.

An embodiment in which the present invention is applied to a fixing device of an image forming apparatus will be described below.
FIG. 1 is a schematic configuration diagram showing an example of an electrophotographic printer as an image forming apparatus according to an embodiment.
As shown in FIG. 1, the printer 100 of this embodiment includes four image forming units 2Y, 2Y for forming yellow (Y), magenta (M), cyan (C), and black (K) toner images. 2M, 2C and 2K are provided. The printer 100 has a so-called tandem type configuration in which these four image forming units 2 are arranged along the endless moving direction of the intermediate transfer belt 61 as an image carrier.

The printer 100 includes a paper feed path 30, a pre-transfer transport path 31, a manual paper feed path 32, a manual feed tray 33, a pair of registration rollers 34, a transport belt unit 35, a fixing device 40, a transport switching device 50, a paper discharge path 51, and a paper feed path 31. A pair of paper rollers 52, a paper discharge tray 53, and the like are provided. Further, it has two optical writing units 1YM and 1CK, a primary transfer unit 60, a secondary transfer unit 78, a first paper feed cassette 101, a second paper feed cassette 102, and the like.

The four image forming units 2Y, 2M, 2C, and 2K respectively have drum-shaped photosensitive members 3Y, 3M, 3C, and 3K, which are latent image carriers. Also, the first paper feed cassette 101 and the second paper feed cassette 102 accommodate bundles of paper P, which are sheets, respectively. Then, the uppermost sheet P in the sheet bundle is sent out toward the sheet feeding path 30 by rotationally driving the first feeding roller 101a or the second feeding roller 102a.

On the right side of the housing of the printer 100 in FIG. 1, a manual feed tray 33 is arranged so as to be openable and closable with respect to the housing. be. The uppermost sheet P in the manually fed sheet bundle is sent out toward the paper feed path 30 through the manual paper feed path 32 by the delivery roller of the manual feed tray 33 .

The two optical writing units 1YM and 1CK each have a laser diode, a polygon mirror, various lenses, and the like. Based on image information read by a scanner, which is an external device of the printer 100, or image information sent from a personal computer, the laser diodes are driven, and the photoreceptors 3Y, 3M, 3C, and 3K of the image forming unit are driven. is optically scanned. Specifically, the photosensitive members 3Y, 3M, 3C, and 3K of the image forming units 2Y, 2M, 2C, and 2K are rotationally driven counterclockwise in FIG. 1 by driving means.

The first optical writing unit 1YM performs optical scanning processing by irradiating the yellow photoreceptor 3Y and the magenta photoreceptor 3M, which are being driven, with laser light while being deflected in the rotation axis direction. As a result, electrostatic latent images based on the yellow image information and the magenta image information are formed on the yellow photoreceptor 3Y and the magenta photoreceptor 3M, respectively.
The second optical writing unit 1CK performs optical scanning processing by irradiating the cyan photoreceptor 3C and the black photoreceptor 3K that are being driven with laser light while being deflected in the rotation axis direction. As a result, electrostatic latent images based on the cyan image information and the black image information are formed on the cyan photoreceptor 3C and the black photoreceptor 3K, respectively.

The imaging units 2Y, 2M, 2C, and 2K support the photoreceptors 3Y, 3M, 3C, and 3K and various devices arranged therearound as one unit on a common support. They are integrally attached to and detached from the housing of the printer 100 . The image forming units 2Y, 2M, 2C, and 2K have the same configuration except that they use different colors of toner. Therefore, in the following description, Y, M, C, and K indicating colors of toner to be used are omitted as appropriate.

The image forming unit 2 has a photosensitive member 3 and a developing device 4 for developing an electrostatic latent image formed on the surface of the photosensitive member 3 into a toner image. The image forming unit 2 also has a charging device 5 that uniformly charges the surface of the photosensitive member 3 that is driven to rotate. Further, the image forming unit 2 includes a drum cleaning device 6 for cleaning transfer residual toner adhering to the surface of the photoreceptor 3 after passing through a primary transfer nip corresponding to each color, which will be described later.

The photoreceptor 3 is a drum-shaped one in which a photosensitive layer is formed by applying an organic photosensitive material having photosensitivity to a tube made of aluminum or the like. An endless belt may be used instead of the drum.

The developing device 4 has a rotatable developing sleeve made of a non-magnetic pipe and a magnet roller disposed in the hollow of the developing sleeve so as not to rotate together with the sleeve. Then, an electrostatic latent image is formed on the photoreceptor 3 by a two-component developer (hereinafter simply referred to as developer) containing magnetic carriers and non-magnetic toners of each color carried on the surface of the developing sleeve by the magnetic force generated by the magnet roller. to develop.

The respective color toners in the respective color toner bottles 103Y, 103M, 103C and 103K are appropriately replenished to the respective color development devices 4Y, 4M, 4C and 4K by respective color toner supply devices. A toner concentration sensor is provided in the developing device 4 as a toner concentration detecting means. The toner density sensor detects the magnetic permeability of the developer caused by the carrier, which is a magnetic material. The controller controls the driving of the toner replenishing device for each color based on a comparison between the output value from the toner concentration sensor for each color and the output target value from the sensor, which is the toner concentration target value. As a result, the toner density of the developer is kept within a certain range (for example, 4 [wt %] to 9 [wt %]).

The drum cleaning device 6 is of a type that scrapes off transfer residual toner from the surface of the photoreceptor 3 with a cleaning blade made of polyurethane rubber brought into contact with the photoreceptor 3 . Other methods may be used instead of such methods. In order to improve the cleaning performance, the drum cleaning device 6 has a rotatable fur brush in contact with the photoreceptor 3 in addition to the cleaning blade. The fur brush also serves to scrape off the lubricant from the solid lubricant and apply it to the surface of the photoreceptor 3 while making fine powder.

A charge removing lamp is arranged above the photoreceptor 3 , and the charge removing lamp is also a part of the image forming unit 2 . The static elimination lamp irradiates the surface of the photoreceptor 3 after passing through the portion facing the drum cleaning device 6 to eliminate static electricity. The neutralized surface of the photoreceptor 3 is uniformly charged by the charging device 5 and then optically scanned by the optical writing unit 1 described above. The charging device 5 is rotated while being supplied with a charging bias from a power source. Instead of such a system, a scorotron charger system that charges the photoreceptor 3 in a non-contact manner may be employed.

A primary transfer unit 60 is arranged below the four image forming units 2Y, 2M, 2C, and 2K. This primary transfer unit 60 includes an intermediate transfer belt 61 stretched by a plurality of rollers 63, 67, 68, 69, and 70. As shown in FIG. The primary transfer unit 60 moves the intermediate transfer belt 61 in the clockwise direction (direction of arrow A) in FIG. to move endlessly. Thus, a primary transfer nip for each color is formed where the photoreceptors 3Y, 3M, 3C and 3K and the intermediate transfer belt 61 are in contact.

In the vicinity of the primary transfer nip for each color, primary transfer rollers 62Y, 62M, 62C, and 62K arranged inside the belt loops press the intermediate transfer belt 61 toward the photosensitive members 3Y, 3M, 3C, and 3K. . A primary transfer bias is applied to each of the four primary transfer rollers 62Y, 62M, 62C and 62K by a primary transfer power source. Thus, a primary transfer electric field is formed in the primary transfer nip for each color to electrostatically move the toner images on the photoreceptors 3Y, 3M, 3C, and 3K toward the intermediate transfer belt 61 .

A Y toner image, an M toner image, and a C toner image are formed on the outer peripheral surface of the intermediate transfer belt 61 which sequentially passes through the primary transfer nips for each color as the intermediate transfer belt 61 endlessly moves clockwise in FIG. The image and the K toner image are sequentially superimposed and primarily transferred. A four-color superimposed toner image is formed on the outer peripheral surface of the intermediate transfer belt 61 by this superimposed primary transfer.

A secondary transfer unit 78 is arranged below the intermediate transfer belt 61 in FIG. The secondary transfer unit 78 has an endless secondary transfer belt 77, a ground driven roller 72, a secondary transfer driving roller 71, a secondary belt cleaning device 76, a toner adhesion amount detection sensor 64, and the like. The secondary transfer belt 77 is tensioned by a grounded driven roller 72 disposed on the inner peripheral side thereof and a secondary transfer drive roller 71 , and rotates as the secondary transfer drive roller 71 is driven to rotate. 1 endlessly in the counterclockwise direction (arrow B direction).

The secondary transfer belt 77 of the secondary transfer unit 78 has a portion of the secondary transfer belt 77 on which it is wound around the ground driven roller 72 contacting a portion of the intermediate transfer belt 61 of the primary transfer unit 60 on which the secondary transfer bias roller 68 is wound. forming a secondary transfer nip. A secondary transfer bias output from a secondary transfer power supply is applied to the secondary transfer bias roller 68 on the inner peripheral surface side of the intermediate transfer belt 61 , while the inner peripheral surface side of the secondary transfer belt 77 is grounded. The driven roller 72 is grounded. Thereby, a secondary transfer electric field is formed in the secondary transfer nip.

A registration roller pair 34 is disposed on the right side of the secondary transfer nip in FIG. Send out to the secondary transfer nip at the right timing. In the secondary transfer nip, the superimposed four-color toner image on the intermediate transfer belt 61 is collectively secondary-transferred onto the paper P under the influence of the secondary transfer electric field and nip pressure, and together with the white color of the paper P, a full-color image is formed.

Secondary transfer residual toner adheres to the outer peripheral surface of the intermediate transfer belt 61 after passing through the secondary transfer nip. This secondary transfer residual toner is removed from the surface of the intermediate transfer belt 61 by the intermediate transfer belt cleaning device 75 of the primary transfer unit 60 .

After passing through the secondary transfer nip, the sheet P is separated from the intermediate transfer belt 61 and the secondary transfer belt 77 and transferred to the transport belt unit 35 . The conveying belt unit 35 stretches an endless conveying belt 36 between a conveying driving roller 37 and a conveying driven roller 38, and rotates the conveying driving roller 37 in a counterclockwise direction (arrow C direction in FIG. 1). ) endlessly. Then, while holding the sheet P delivered from the secondary transfer nip on the upper stretched surface of the transport belt 36 , the sheet P is transported as the transport belt 36 moves endlessly, and the sheet P is delivered to the fixing device 40 .

The paper P fed into the fixing device 40 is sandwiched between the fixing nip formed by the contact between the endless fixing belt 41 and the pressure roller 44 . Then, the toner image is fixed on the surface of the paper P by the action of pressure, heat, or the like.

The paper P on which the toner image is transferred to the first surface by the secondary transfer nip and the toner image is fixed on the first surface by the fixing device 40 is sent out toward the transport switching device 50 . In the printer 100, the transport switching device 50, the retransmission path 54, the switchback path 55, the post-switchback transport path 56, and the like constitute retransmission means. The transport switching device 50 switches the subsequent transport destination of the paper P received from the fixing device 40 between the paper discharge path 51 and the re-feed path 54 .

Specifically, when executing a single-sided mode print job in which an image is formed only on the first side of the paper P, the paper discharge path 51 is set as the transport destination. As a result, the paper P with the image formed only on the first side is sent to the paper discharge roller pair 52 via the paper discharge path 51 and discharged onto the paper discharge tray 53 outside the apparatus. In addition, when a print job in a duplex mode for forming images on both sides of the paper P is executed, when the paper P on which images are fixed on both sides is received from the fixing device 40, the transport destination is paper ejection. 51 is set. As a result, the paper P with images formed on both sides is discharged onto the paper discharge tray 53 outside the machine.

On the other hand, when the paper P with the image fixed only on the first side is received from the fixing device 40 during execution of the print job in the double-sided mode, the transport destination is set to the re-feeding path 54 . A switchback path 55 is connected to the resending path 54 , and the sheet P sent to the resending path 54 enters this switchback path 55 . Then, when the entire region of the paper P in the transport direction enters the switchback path 55, the transport direction of the paper P is reversed and the paper P is switched back.

The switchback path 55 is connected to a post-switchback transport path 56 in addition to the resending path 54 , and the sheet P that has been switched back enters the post-switchback transport path 56 . At this time, the paper P is turned upside down. Then, the paper P that has been turned upside down is sent again to the secondary transfer nip via the post-switchback transport path 56 and the above-described paper feed path 30 . The paper P on which the toner image has been transferred to the second surface by the secondary transfer nip passes through the fixing device 40 to fix the toner image on the second surface. , and a pair of paper discharge rollers 52 to discharge the paper onto a paper discharge tray 53 .

2 and 3 are cross-sectional views of the fixing roller 42 and the heating roller 43 in a direction orthogonal to the roller shafts, showing the schematic configuration of the fixing device 40 in this embodiment.

The fixing device 40 shown in FIGS. 2 and 3 includes a fixing belt 41 that contacts the surface of the paper P on which the unfixed toner image is formed. The fixing belt 41 is stretched around a fixing roller 42 that is a fixing belt driving roller and a heating roller 43 that is a fixing belt driven roller. The fixing belt 41 rotates clockwise in FIGS. 2 and 3 by rotationally driving the fixing roller 42 in the clockwise direction (direction of arrow D) in FIGS.

The fixing belt 41 is, for example, an endless belt having a multi-layer structure in which an elastic layer such as silicone rubber and a release layer are sequentially laminated on a base layer made of PI (polyimide) resin and having a predetermined layer thickness. The elastic layer of the fixing belt 41 is made of an elastic material such as silicone rubber, fluororubber, or foamed silicone rubber. The release layer of the fixing belt 41 is made of, for example, PFA (tetrafluoroethylene perfluoroalkyl vinyl ether copolymer resin), polyimide, polyetherimide, PES (polyether sulfide), or the like. By providing the release layer on the surface layer of the fixing belt 41, the releasability (separability) of the toner (toner image) is ensured.

As a specific example, the fixing belt 41 uses a PI layer as a base layer, a silicone rubber layer as an elastic layer, and a PFA resin layer as a release layer. etc.

The heating roller 43 is a heating member composed of a rotating body containing a fixing heater 45 as a heating body. be. The fixing heater 45 heats the heating roller 43 , and the heating roller 43 heats the fixing belt 41 .

The heating roller 43 is, for example, a thin cylindrical body made of a metal material, and the fixing heater 45 is fixed inside the cylindrical body. As the fixing heater 45, for example, a halogen heater, a carbon heater, or the like can be used. Both ends of the fixing heater 45 are fixed to the housing of the fixing device 40 . Further, the fixing heater 45 may be induction heating means (IH heating means) for heating the heating roller 43 from the outside.

The fixing roller 42 does not have a heat source, and is made of, for example, a highly rigid core material such as metal (iron or aluminum) covered with a thick elastic layer such as silicone rubber.

The fixing device 40 has a pressure roller 44 below the fixing roller 42 . The pressure roller 44 is provided so as to face the fixing roller 42 with the fixing belt 41 therebetween, and is pressed against the fixing roller 42 via the fixing belt 41 by the pressure mechanism. When the fixing roller 42 is driven to rotate by the drive mechanism, the fixing belt 41 rotates, and the pressure roller 44 rotates with the fixing belt 41 in the counterclockwise direction (arrow E direction) in FIGS. Rotate.

Like the fixing roller 42, the pressure roller 44 is, for example, a roller member in which an elastic layer of fluororubber, silicone rubber, foamed silicone rubber, or the like is formed on a metal core such as SUS304. Also, a pressure heater may be provided inside the cylindrical body as a heat source.

The surface temperature of the fixing belt 41 is detected by a temperature sensor 49 as temperature detection means. The control unit 400 functions as temperature control means, and controls the fixing heater 45 based on the output value of the temperature sensor 49 so that the surface temperature of the fixing belt 41 reaches a target temperature. ON/OFF control, PID control, or the like is used to control the fixing heater 45 . The position and number of temperature sensors to be installed are not limited to those of this embodiment. , the fixing heater 45 may be controlled based on this.

The sheet P bearing the unfixed toner image is conveyed into the fixing device 40 along the inlet guide plate 49a as indicated by the arrow α in FIG. through a fusing nip that forms through the At the fixing nip formed by the fixing belt 41 and the pressure roller 44 controlled to the target temperature, the toner image on the paper P is melted and fixed on the paper P. FIG. After passing through the fixing nip, the paper P is separated from the fixing belt 41 and the pressure roller 44 by the fixing separation plate 49b and the pressure separating claw 49c at the fixing nip exit, and passes through the transport path in the transport switching device 50 and the paper discharge path 51. As a result, it is sent out of the main body of the printer 100 .

In addition, as shown in FIGS. 2 and 3, the fixing device 40 includes a pressure roller cleaning device 110 that cleans the surface of the pressure roller 44. As shown in FIG. The pressure roller cleaning device 110 includes a cleaning web 11 that is a belt-shaped cleaning member, a web holding shaft 11b, a web winding shaft 11a, and a web contact roller 11c. One end of the cleaning web 11 is fixed to the web take-up shaft 11a, the other end is fixed to the web holding shaft 11b, and the portion of the cleaning web 11 between the web take-up shaft 11a and the web holding shaft 11b is a web contact roller. 11 c presses against the surface of the pressure roller 44 .

The web take-up shaft 11a is driven to rotate in the direction of arrow G1 in FIG. Moving in the G2 direction, the unused portion contacts the pressure roller 44 . The unused portion of cleaning web 11 is wrapped around web retaining shaft 11b. 2, the web holding shaft 11b rotates in the direction of arrow G3 in FIG. It is paid out toward the contact part with. By cleaning the surface of the pressure roller 44 with the cleaning means using the cleaning web 11 as the cleaning member, it is possible to continue cleaning the pressure roller 44 using the part of the cleaning member that does not have any deposits. . Therefore, it is possible to keep the surface of the pressure roller 44 free from adhering substances.

Next, a method for removing deposits adhering to the outer peripheral surface of the fixing belt 41 will be described.
The wax dispersed in the toner on the paper P melts and adheres to the outer peripheral surface of the fixing belt 41 during fixing. If such wax remains adhered to the outer peripheral surface of the fixing belt 41, the image on the sheet P to be fixed thereafter will have uneven glossiness called afterimage of glossiness. More specifically, for example, a solid image portion (a portion to which toner is attached with a high image density) and a low image density portion or a blank portion (a portion to which toner is attached with a low image density or a portion to which no toner is attached) are mixed. It may fix the image. In this case, the amount of wax adhering to the fixing belt 41 differs between the solid image portion and the low image density portion or blank portion. Therefore, if this fixing belt 41 is used as it is for the subsequent fixing process, the image will be separated between the image portion in contact with the fixing belt portion with a large amount of wax and the image portion in contact with the fixing belt portion with a small amount of wax. Glossy afterimages that show a difference in gloss are generated.

FIG. 4 is an explanatory diagram showing an example of an image on the paper P on which a glossy afterimage has occurred.
FIG. 5 is an explanatory diagram showing how the wax component (wax W) of the toner Td on the paper P adheres to the fixing belt 41. As shown in FIG.
The image shown in FIG. 4 shows an example of an image in which a uniform solid image portion Pd is formed except for some marginal portions Pw, and a glossy afterimage is generated. The arrow α indicates the transport direction of the paper P, and the length L indicates the length of one round of the fixing belt 41 in the paper transport direction.

When the paper P is passed through the fixing device 40 and the solid image portion Pd is fixed, as shown in FIG. 41. Therefore, for example, in the case of the image example shown in FIG. 4, the wax W of the solid image portion Pd (toner Td) on the upstream side in the sheet conveying direction adheres to the fixing belt 41, and this wax W again enters the fixing nip as the fixing belt rotates. , it adheres to the solid image portion Pd on the same sheet P on the downstream side.

On the other hand, when the margin Pw is fixed, the wax W does not adhere to the fixing belt 41 corresponding to the margin Pw. Therefore, for example, in the case of the image example shown in FIG. 4, the wax W does not adhere to the portion of the fixing belt 41 corresponding to the margin Pw. Therefore, when this portion reaches the fixing nip again with the rotation of the fixing belt 41 and comes into contact with the solid image portion Pd on the downstream side in the conveying direction of the same paper P, the contact portion Pu of the solid image portion Pd is touched. , the wax W does not adhere.

As a result, as shown in FIG. 4, in the portion on the downstream side of the paper P in the transport direction, the solid image portion Pd includes a portion Pu having a relatively small adhesion amount of the wax W and a portion Pu having a relatively small adhesion amount of the wax W. Gloss unevenness occurs between the relatively large portion (solid image portion Pd other than Pu).

The wax W adhering to the fixing belt 41 is volatilized by applying a certain amount of heat, but the time from fixing to the next fixing depends on the printing speed. difficult. Further, in order to lengthen the time from fixing to next fixing without changing the printing speed, it is necessary to lengthen the circumferential length of the fixing belt 41 . I don't like it.

Therefore, conventionally, in order to suppress problems that may occur due to deposits such as wax W adhering to the fixing belt 41, such as the glossy afterimage, the outer peripheral surface of the fixing belt 41 is rubbed to remove the adhesive. There are fixing devices that have a removing member that removes adhering deposits. However, in the conventional fixing device, the adhered matter (wax W, etc.) to be removed is removed by rubbing the removing member against the fixing belt 41 which is still hot enough to become liquid. In this case, it was found that the deposits in the liquid state easily slipped through the removing member, and the deposits could not be completely removed by the removing member.

Therefore, in the present embodiment, when the temperature of the fixing belt 41 exceeds a predetermined temperature, after the temperature of the fixing belt 41 drops below the predetermined temperature, the adherents (wax W, etc.) adhering to the outer peripheral surface of the fixing belt 41 are removed. Remove. The "predetermined temperature" here is set to a temperature (an arbitrary temperature below the freezing point) at which the adherents to be removed, which are in a liquid state at the fixing temperature, solidify, and is set to at least a temperature lower than the fixing temperature. be.

As a result, in the present embodiment, even if the adhered matter to be removed (wax W or the like) is in a liquid state at the fixing temperature, the adhered matter is removed by the removal member after waiting for the adhered matter to solidify. can be removed. As a result, the solidified (solidified) adhering matter can be removed from the outer peripheral surface of the fixing belt 41 by scraping or scraping it off with the removing member. The method of scraping off or scraping off the solidified adhering matter with the removing member makes it more difficult for the adhering matter to pass through the removing member and removes more of the adhering matter from the outer peripheral surface of the fixing belt 41 than the method of wiping off the adherent matter in the liquid state. It is possible to

A refresh mode for removing the wax W and the like from the outer peripheral surface of the fixing belt 41 in this embodiment will be described below.
The fixing device 40 of this embodiment is provided with a refresh roller 46 which is a rotating body as a removing member that rubs the surface of the fixing belt 41 . The refreshing roller 46 is a polishing roller having a polishing layer, which is a surface layer, around a metal core. The polishing layer preferably has a surface roughness (ten-point average roughness Rz) of 40 [μm] or more. The refreshing roller 46 is rotatably supported by a roller bracket 47, and can be rotationally driven in the rotation direction of the fixing belt 41 (arrow F direction in FIG. 3) by a motor 46a.

When the control unit 400 executes the refresh mode, the refresh roller 46 is driven to rotate at a predetermined relative speed with respect to the fixing belt 41 while being in contact with the outer peripheral surface of the fixing belt 41 as shown in FIG. . As a result, the outer peripheral surface of the fixing belt 41 is rubbed and polished by the refreshing roller 46 . This polishing removes adherents such as wax W adhering to the outer peripheral surface of the fixing belt 41, thereby suppressing the occurrence of glossy afterimages.

The refreshing roller 46 of this embodiment is provided so as to contact the portion of the fixing belt 41 wound around the fixing roller 42 . As a result, the fixing roller 42 can receive the pressure force with which the refreshing roller 46 presses the fixing belt 41 , and the refreshing roller 46 can be brought into contact with the fixing belt 41 with a high contact pressure. Therefore, the fixing belt 41 can be rubbed by the refreshing roller 46 with a high rubbing force.

In this embodiment, the roller bracket 47 supporting the refreshing roller 46 is rotatably supported about a rotation shaft 47a. The roller bracket 47 is biased by biasing means in the clockwise direction in FIG. 2 about the rotary shaft 47a.

The eccentric cam 48 is rotationally driven by a motor 48 a controlled by the control section 400 , and the rotational position of the eccentric cam 48 is controlled by the control section 400 . During the image forming operation (at least when the paper P is passing through the fixing nip), the eccentric cam 48 is rotated to the rotational position shown in FIG. 2, and the roller bracket 47 assumes the rotational position shown in FIG. A roller 46 is arranged in a state separated from the fixing belt 41 .

On the other hand, when executing the refresh mode (for example, when power is turned on, when returning from a standby state, etc.), the control unit 400 rotates the eccentric cam 48 to the rotational position shown in FIG. takes the rotation position shown in . As a result, the refreshing roller 46 is placed in contact with the fixing belt 41 . Then, the controller 400 removes adherents such as wax on the fixing belt 41 by executing a refresh mode in which the outer peripheral surface of the fixing belt 41 is polished to remove adherents such as wax W.

FIG. 6 is a flow chart showing the control flow of the refresh mode for removing the wax W and the like from the outer peripheral surface of the fixing belt 41 in this embodiment.
In the present embodiment, when the refresh mode execution timing arrives, such as when power is turned on, when returning from a standby state, or when a print job ends, the control unit 400 first detects the temperature of the fixing belt 41 detected by the temperature sensor 49. A temperature (fixing temperature) is acquired (S1). Then, the control unit 400 determines whether or not the acquired fixing temperature is equal to or lower than a predetermined temperature (S2). At this time, the refreshing roller 46 is separated from the fixing belt 41 .

The predetermined temperature in the present embodiment is set to a temperature at which the wax W solidifies, since the adhered matter to be removed is the wax W that is in a liquid state at the fixing temperature (the target temperature for the fixing process). This predetermined temperature is preferably 60° C. or lower.

If the acquired fixing temperature is equal to or lower than the predetermined temperature (Yes in S2), the control unit 400 executes the refresh mode (S6), brings the refresh roller 46 into contact with the outer peripheral surface of the fixing belt 41, It is rotationally driven at a predetermined relative speed. As a result, the outer peripheral surface of the fixing belt 41 is rubbed and polished by the refreshing roller 46, and as a result, adherents such as wax W adhering to the outer peripheral surface of the fixing belt 41 are removed, and the occurrence of glossy afterimages is suppressed. be.

On the other hand, when the acquired fixing temperature exceeds the predetermined temperature (No in S2), the control section 400 executes the refresh mode after the fixing temperature becomes equal to or lower than the predetermined temperature. At this time, for example, the control unit 400 may wait until the fixing temperature becomes equal to or lower than a predetermined temperature with the heat source such as the fixing heater 45 stopped, and then execute the refresh mode. However, in this case, it takes a long time until the fixing temperature becomes equal to or lower than the predetermined temperature.

Therefore, for example, the fixing belt 41 is idled while the heat source such as the fixing heater 45 is stopped, thereby cooling the fixing belt 41 and shortening the time until the fixing temperature becomes equal to or lower than a predetermined temperature. preferable.

Further, in order to further shorten the time required for the fixing temperature to become equal to or lower than the predetermined temperature, a cooling member 80 may be provided as cooling means for cooling the outer peripheral surface of the fixing belt 41, as shown in FIG. A cooling member 80 shown in FIG. 7 is provided in a non-contact manner at a predetermined position facing the outer peripheral surface of the fixing belt 41 . As the cooling member 80, it is preferable to use, for example, a fan (blowing means), but it is not limited to this. Other cooling means may be used as long as they can be used.

Further, as shown in FIG. 7, the cooling member 80 is preferably arranged so as to cool the fixing belt 41 from the outlet of the fixing nip to the position detected by the temperature sensor 49 in the rotation direction of the fixing belt 41. preferable. If the cooling member 80 is provided downstream of the temperature sensor 49 in the rotation direction of the fixing belt 41, the time until the cooled fixing belt portion is detected by the temperature sensor 49 becomes longer, and the execution of the refresh mode becomes longer. This is because the start is delayed.

Moreover, it is preferable that the cooling member 80 is provided on the upstream side of the refreshing roller 46 in the rotation direction of the fixing belt 41 as shown in FIG. In this case, since the wax W on the fixing belt 41 immediately after being cooled by the cooling member 80 can be removed by the refreshing roller 46 , the wax W in a solidified state can be removed more stably by the refreshing roller 46 . That is, if the cooling member 80 is provided downstream of the refresh roller 46 in the rotation direction of the fixing belt 41 , it takes time for the cooled fixing belt portion to reach the polishing position by the refresh roller 46 . As a result, the fixing belt 41 is exposed to a high-temperature atmosphere during that time, and the temperature of the fixing belt 41 rises. As a result, the wax W that has not been sufficiently solidified is removed by the refreshing roller 46, and there is a risk that a sufficient removal effect cannot be obtained. .

Next, the results of an effect confirmation test for confirming the effect of suppressing glossy afterimages by the fixing device 40 according to the present embodiment will be described.
FIG. 8 is a graph showing the results of an effect confirmation test for confirming the effect of suppressing glossy afterimages by the fixing device 40 in this embodiment.

The graph shown in FIG. 8 shows a comparative example in which the refresh mode is executed in the state of the fixing temperature (hot state) and an example in which the refresh mode is executed in a state cooled to a predetermined temperature (60° C.) (cold state). It is a comparison result with a form. In this effect confirmation test, image formation was performed on a predetermined test image, and the glossiness afterimage rank when the contact time (polishing time) of the refresh roller 46 in the refresh mode was changed was evaluated in each of the comparative example and the embodiment. bottom. Regarding the gloss afterimage rank, the larger the numerical value of the rank, the less the gloss afterimage.

When polishing was performed with the refreshing roller 46 in a hot state as in the comparative example, as shown in FIG. was ranked 3 at 6 minutes. However, an evaluation of rank 3 or higher could not be obtained even if the polishing time was longer than 8 minutes. This is probably because, for example, the wax W is in a liquid state during polishing by the refreshing roller 46 , and thus the wax W easily slips through the contact position of the refreshing roller 46 . Further, for example, it is considered that the wax W played the role of a lubricant and the rubbing and polishing effects of the refreshing roller 46 were impaired.

On the other hand, when polishing was performed with the refreshing roller 46 in a cold state as in the embodiment, as shown in FIG. The evaluation of rank 5 was maintained even if the polishing time was lengthened. This is because the wax W is in a solid state during polishing by the refreshing roller 46, so that the wax W is less likely to pass through the contact position of the refreshing roller 46, and the wax W cannot be scraped off or scraped off by the polishing of the refreshing roller 46. I think it's because I was able to do it. In addition, it is believed that the role of the wax W as a lubricant was reduced and the rubbing and polishing effects of the refreshing roller 46 were not impaired, so that the wax W could be scraped off or scraped off by the polishing of the refreshing roller 46 . be done.

According to the present embodiment, gloss afterimages can be suppressed more than when polishing is performed with the refreshing roller 46 in a hot state. Furthermore, since the glossy afterimage can be suppressed in a shorter time, deterioration of the fixing belt 41 due to rubbing of the refreshing roller 46 can be suppressed, and the life of the fixing belt 41 can be extended.

What has been described above is only an example, and each of the following aspects has a unique effect.
[First aspect]
A first mode is a removing member (for example, a refresh roller 46) that rubs against the outer peripheral surface of a fixing rotating body (for example, a fixing belt 41, a fixing roller 42, and a heating roller 43) to remove deposits adhering to the outer peripheral surface. and fixing an image on a recording material (e.g., paper P) by bringing the outer peripheral surface of the heated fixing rotator into contact with the recording material, wherein the removing member is the fixing rotator when the temperature exceeds a predetermined temperature which is lower than the fixing temperature, after the fixing rotator reaches the predetermined temperature or less, the adhering matter (e.g., wax W) adhering to the outer peripheral surface of the fixing rotator is removed. It is characterized by
It has been found that the conventional method of removing the deposits with a removing member such as a cleaning web when the fixation rotating body is at a high temperature, when the deposits to be removed, such as wax, are in a liquid state, cannot completely remove the deposits with the removal member. . This is because the adherents in a liquid state easily slip through the removing member, and the adherents in a liquid state act as a lubricant, impairing the rubbing and polishing effects of the removing member. It is believed that there is.
Therefore, in this aspect, when the temperature of the fixing rotator exceeds a predetermined temperature, the toner adheres to the outer peripheral surface of the fixing rotator after the temperature of the fixing rotator drops below the predetermined temperature (temperature lower than the fixing temperature). Deposits are removed. According to this, by setting the predetermined temperature to a temperature at which the deposit to be removed, which is in a liquid state at the fixing temperature, solidifies (an arbitrary temperature below the freezing point of the deposit), the solidified state ( It is possible to scrape or scrape off the adhering matter (in a solidified state) from the outer peripheral surface of the fixing rotating body with a removing member. The method of scraping or scraping off the solidified adhering matter with the removing member removes more adhering matter from the outer peripheral surface of the fixing rotating body than the method of wiping off the adhering matter in the liquid state, as shown by the results of the effect confirmation test described above. can be removed.

[Second aspect]
According to a second aspect, in the first aspect, the removing member is configured to be able to come into contact with and separate from the outer peripheral surface of the fixing rotator, and when the temperature of the fixing rotator exceeds the predetermined temperature, the fixing member It is characterized in that after the rotating body has reached the predetermined temperature or less, it is brought into contact with the outer peripheral surface of the fixing rotating body to remove the adhering matter.
According to this, it is possible to keep the removing member away from the fixing rotator when the process (refresh mode) of removing the adhering matter by rubbing the outer peripheral surface of the fixing rotator with the removing member is not executed. . As a result, unnecessary rubbing of the fixing rotator by the removing member can be avoided, and the service life of the fixing rotator can be extended.

[Third aspect]
A third aspect is the first or second aspect, wherein the predetermined temperature is a temperature at which a liquid deposit to be removed (e.g., wax W) solidifies when the temperature of the fixing rotator is the fixing temperature. It is characterized by
According to this, it is possible to remove a larger amount of such adhering matter to be removed from the outer peripheral surface of the fixing rotator.

[Fourth aspect]
A fourth aspect is characterized in that, in the third aspect, the predetermined temperature is a temperature of 60° C. or less.
According to this, it is possible to remove more of the wax component of the toner adhering to the outer peripheral surface of the fixing rotator from the outer peripheral surface of the fixing rotator.

[Fifth aspect]
A fifth aspect is characterized in that, in any one of the first to fourth aspects, cooling means (for example, a cooling member 80) for cooling the outer peripheral surface of the fixing rotator is provided.
According to this, the temperature of the outer peripheral surface of the fixing rotator can be lowered to the predetermined temperature or lower in a shorter period of time, so that it is possible to more quickly remove deposits adhering to the outer peripheral surface of the fixing rotator.

[Sixth aspect]
According to a sixth aspect, in any one of the first to fifth aspects, the removing member is a rubbing rotary body (for example, a refreshing roller 46) that rotates so as to rub the outer peripheral surface of the fixing rotary body. It is characterized.
According to this, it is possible to scrape and remove deposits adhering to the outer peripheral surface of the fixing rotator with a simple structure.

[Seventh aspect]
A seventh aspect is characterized in that, in the sixth aspect, the rubbing rotator is rotationally driven at a linear velocity faster than the linear velocity of the fixing rotator in a direction to rotate together with the outer peripheral surface of the fixing rotator. It is.
According to this, it is possible to scrape and remove deposits adhering to the outer peripheral surface of the fixing rotator with a simple structure.

[Eighth aspect]
An eighth aspect is characterized in that in the sixth or seventh aspect, the outer peripheral surface of the rubbing rotary member has a surface roughness Rz of 40 [μm] or more.
According to this, it is possible to appropriately remove deposits adhering to the outer peripheral surface of the fixing rotator.

[Ninth aspect]
A ninth aspect is characterized in that, in any one of the sixth to eighth aspects, an elastic layer is provided under the surface layer of the rubbing rotary member.
According to this, it is possible to appropriately remove deposits adhering to the outer peripheral surface of the fixing rotator.

[Tenth Aspect]
A tenth aspect is any one of the first to ninth aspects, wherein the removing member has a temperature higher than a predetermined temperature lower than a temperature during fixing when power is turned on or when returning from a standby state. and removing deposits adhering to the outer peripheral surface of the fixing rotator after the fixing rotator is cooled to the predetermined temperature or less.
According to this, when the power is turned on or when returning from the standby state, the removing member can remove the deposits adhering to the outer peripheral surface of the fixing rotator.

[11th aspect]
An eleventh aspect is an image forming apparatus (for example, the printer 100) comprising the fixing device according to any one of the first to tenth aspects.
It is possible to provide an image forming apparatus in which problems that may occur due to deposits adhering to the outer peripheral surface of the fixing rotator are suppressed.

1: optical writing unit 2: image forming unit 3: photoreceptor 4: developing device 5: charging device 6: drum cleaning device 40: fixing device 41: fixing belt 42: fixing roller 43: heating roller 44: pressure roller 45 : Fixing heater 46 : Refreshing roller 46a : Motor 47 : Roller bracket 47a : Rotating shaft 48 : Eccentric cam 48a : Motor 49 : Temperature sensor 49a : Entrance guide plate 49b : Fixing separation plate 49c : Pressure separation claw 60 : Primary transfer Unit 61 : Intermediate transfer belt 62 : Primary transfer roller 68 : Secondary transfer bias roller 71 : Secondary transfer driving roller 75 : Intermediate transfer belt cleaning device 76 : Secondary belt cleaning device 77 : Secondary transfer belt 78 : Secondary transfer Unit 80: Cooling member 100: Printer 400: Control section

Japanese Patent Application Laid-Open No. 2007-047450

Claims (11)

It has a removing member for rubbing the outer peripheral surface of the fixing rotator to remove deposits adhering to the outer peripheral surface, and the heated outer peripheral surface of the fixing rotator is brought into contact with the recording material to transfer the image to the recording material. A fixing device for fixing to
When the temperature of the fixing rotator exceeds a predetermined temperature lower than the temperature at the time of fixing, the removal member removes deposits that adhere to the outer peripheral surface of the fixing rotator after the temperature of the fixing rotator drops below the predetermined temperature. A fixing device characterized by removing The fixing device according to claim 1,
The removal member is configured to be able to come into contact with and separate from the outer peripheral surface of the fixing rotator, and when the temperature of the fixing rotator exceeds the predetermined temperature, the temperature of the fixing rotator drops below the predetermined temperature. , a fixing device that abuts on the outer peripheral surface of the fixing rotating body to remove adhering matter. 3. The fixing device according to claim 1, wherein
The fixing device, wherein the predetermined temperature is a temperature at which a liquid deposit to be removed is solidified when the temperature of the fixing rotating body is the fixing temperature. The fixing device according to claim 3,
The fixing device, wherein the predetermined temperature is a temperature of 60° C. or less. The fixing device according to any one of claims 1 to 4,
A fixing device comprising cooling means for cooling an outer peripheral surface of the fixing rotating body. The fixing device according to any one of claims 1 to 5,
The fixing device, wherein the removing member is a rubbing rotary body that rotates so as to rub the outer peripheral surface of the fixing rotary body. The fixing device according to claim 6,
The fixing device, wherein the rubbing rotator is rotationally driven at a linear velocity higher than a linear velocity of the fixing rotator in a direction to rotate together with the outer peripheral surface of the fixing rotator. The fixing device according to claim 6 or 7,
The fixing device, wherein the outer peripheral surface of the rubbing rotary member has a surface roughness Rz of 40 [μm] or more. The fixing device according to any one of claims 6 to 8,
A fixing device, wherein an elastic layer is provided under the surface layer of the rubbing rotary member. The fixing device according to any one of claims 1 to 9,
When the temperature of the fixing rotator exceeds a predetermined temperature lower than the temperature at the time of fixing when the power is turned on or when returning from a standby state, the removing member removes the A fixing device that removes deposits adhering to the outer peripheral surface of a fixing rotator. An image forming apparatus comprising the fixing device according to claim 1 .

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