JP2010160208A - Fixing device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device capable of recognizing easily an exchanging time of a fixing roller with a simple constitution, and improving its reliability. <P>SOLUTION: This fixing device includes: the fixing roller 39 provided with a mold releasing layer 45 on the surface; a pressure roller 40 arranged oppositely to the fixing roller 39, for nipping and conveying a transfer paper S by cooperation with the fixing roller 41; a separation pawl 41 for preventing sticking of the transfer paper onto a paper-passing domain surface of the fixing roller 39, in contact with the paper-passing domain surface of the fixing roller 39; and a contact member 43 to be brought into contact with the surface of the fixing roller 39 on a non-contact portion with the separation pawl 41. Abrasion speed of the mold releasing layer 45 at the contact portion of the contact member 43 is set to be higher than abrasion speed of the mold releasing layer 45 at the contact portion of the separation pawl 41. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fixing device and an image forming apparatus mounted on an image forming apparatus such as a copying machine, a printer, a facsimile, or a multifunction machine functionally equipped with the electrophotographic method.

  Conventionally, image forming apparatuses such as electrophotographic copying machines, printers, facsimiles or multifunction machines equipped with these functions are equipped with a fixing device that heats and fixes a toner image formed on the surface of a transfer paper. This is well known.

  Further, as shown in FIG. 4, such a fixing device includes a fixing roller 1 heated by an internal heating method or an external heating method using a heating source (not shown) such as a fixing heater, and a fixing roller 1. A pressure roller 2 that nips and conveys the transfer paper in cooperation with the pressure contact, and a separation claw 3 that contacts the surface of the fixing roller 1 to prevent the transfer paper from sticking to the surface of the fixing roller 1 due to heat transfer. The thing equipped with these is known.

  At this time, the fixing roller 1 includes a cored bar 1a based on aluminum, iron, or the like, and a fluororesin such as PFA or PTFE provided on the surface of the cored bar 1a to prevent adhesion of toner, paper powder, and the like. And a release layer 1b made of a system material.

  On the other hand, in such a fixing roller 1, the release layer 1 b of the fixing roller 1 is worn over time due to friction between the fixing roller 1 and the transfer paper that is generated when the paper is passed, and the image is clear. Therefore, it is preferable to replace the fixing roller 1 when a certain amount of wear occurs.

  At this time, for example, the release layer 1b is multi-layered with a colored release layer so that the user can recognize the life of the fixing roller 1, and the replacement time is determined by a change in the color of the release layer 1b due to wear. Is known (for example, see Patent Document 1).

  However, since the separation claw 3 for separating the transfer paper is in contact with the surface of the fixing roller 1, the release layer 1b has not only friction with the transfer paper generated during nip conveyance, but also FIG. As shown in FIG. 5, wear is generated due to friction caused by the contact of the separation claw 3 and the amount of wear differs between the contact portion and the non-contact portion of the separation claw 3.

  Accordingly, when the wear amount of the release layer 1b partially increases and reaches the wear limit at which the metal core 1a is exposed as shown in FIG. 5B, the surface of the fixing roller 1 is separated from the wear portion and the wear limit. The gloss level is extremely different from that of the portion, and there is a risk that image defects such as uneven gloss and offset of the transfer paper, or problems such as occurrence of JAM or paper wrinkles due to toner adhesion may occur.

  Therefore, with regard to consumables in which such aged deterioration occurs, the state of the fixing roller 1 is monitored by a sensor or the like, and a state in which replacement or the like is necessary with reference to the monitored part (for example, a reflection level). A technique for notifying the replacement when it becomes a problem (for example, see Patent Document 2), and a known counter that presets the timing at which the consumables reach the replacement level as the predicted number of sheets to be replaced and counts each image forming process. For example, a technique for notifying the replacement when the predicted replacement number of sheets has been reached (see, for example, Patent Document 3) is considered.

  However, in the fixing roller 1 described above, for example, as disclosed in Patent Document 1, simply recognizing the wear amount of the release layer 1b based on the manifestation of the colored release layer, the mere sheet passing region and the like. Since the amount of wear of the release layer 1b is partially different depending on the contact portion of the separation claw 3, etc., the determination as to where the replacement should be made becomes unclear.

  In addition, as disclosed in Patent Document 2, a technique for monitoring the amount of light reflected from the fixing roller 1 with a sensor and notifying the replacement when a preset reference light amount level is reached is particularly high in a high-temperature environment. An expensive sensor has to be disposed in the vicinity of a certain fixing roller 1, which not only increases the cost of parts, but also causes a problem that the replacement time cannot be recognized if a sensor failure occurs.

  Further, as disclosed in Patent Document 3, in the technique of counting the preset predicted replacement number of sheets, for example, the sheet number counter is reset even though the fixing roller 1 is not replaced. There is a possibility that the function may not function sufficiently due to a human error such as forgetting to reset the sheet passing number counter even though the fixing roller 1 is replaced, or a mechanical failure such as software control or counter memory abnormality. There was a problem such as.

  Note that, in general, the number of sheets to be passed at the replacement time is set with a margin secured against the number of sheets that the release layer 1b provided on the surface of the actual fixing roller 1 reaches the wear limit.

  For example, even if it is determined that the replacement time of the fixing roller 1 has been reached after 100,000 sheets have passed, the release layer 1b on the surface of the fixing roller 1 on the surface of the sheet passing portion is notified. Actually, the film thickness is set so as to reach the wear limit at which the core bar 1b is exposed when 120,000 sheets are passed, so that no problem occurs when 100,000 sheets are passed.

  Therefore, if the counter reset as described above is reset early or if you forget to reset, the gap between the notification timing of the replacement time for maintenance etc. and the actual life timing will spread, There will be actual damage such as notification at a time when there is no problem, or problems such as image defects occurring without ordering replacement parts.

  As described above, the conventional fixing device has a problem in that the reliability is low when the replacement timing of the fixing roller is notified.

JP 2003-263049 A JP 2000-081815 A JP-A-10-177326

  SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a fixing device that can easily recognize the replacement timing of a fixing roller while having a simple configuration and can improve the reliability thereof. To do.

  The fixing device according to the present invention includes a fixing roller having a release layer on a surface thereof, a pressure member that is disposed to face the fixing roller and nip-conveys transfer paper in cooperation with the fixing roller, and the fixing roller A separation member that is in contact with the surface of the sheet passing area and prevents the transfer paper from sticking to the surface of the sheet passing area of the fixing roller. And a wear rate of the release layer at the contact portion of the contact member is made faster than a wear rate of the release layer at the contact portion of the separation member.

  A fixing roller provided with a release layer on the surface; a pressure member disposed opposite to the fixing roller to nip-transfer the transfer paper in cooperation with the fixing roller; and a sheet passing area surface of the fixing roller. And a separation member that prevents the transfer paper from adhering to the surface of the sheet passing area of the fixing roller, and contacts the surface of the fixing roller at a non-contact portion with the separation member. A contact member is provided, and the film thickness of the release layer at the contact portion of the contact member is made thinner than the film thickness of the release layer at the contact portion of the separation member.

  At this time, it is preferable that the contact member is in contact with the surface of the non-sheet passing area of the fixing roller.

  In addition, the film thickness of the release layer at the contact portion of the separation member is determined as follows: the aging wear rate of the release layer associated with the sheet passing in the sheet passing region of the fixing roller and the aging wear rate associated with the contact with the separation member. It is preferable that the thickness is set to be thicker than the wear amount in the film thickness direction considering the total wear rate.

  The film thickness of the release layer at the contact portion of the contact member corresponds to the number of sheets to be passed at the fixing roller replacement time set in advance based on the wear rate of the release layer at the contact portion of the separation member. It is preferable that the thickness is set to be thicker than the film thickness and smaller than the film thickness corresponding to the number of sheets to be passed at the fixing roller lifetime.

  Further, the contact member determines the wear rate of the release layer at the contact portion of the contact member according to the hardness and friction coefficient of the material used and the contact pressure with respect to the fixing roller. It is characterized by being faster than the wear rate of the mold layer.

  At this time, it is preferable that the contact member contacts and separates from the fixing roller in conjunction with the nip conveyance of the transfer paper by the cooperation of the fixing roller and the pressure member.

  Furthermore, a sheet passing detection unit that detects the passing of the transfer sheet, and a drive unit that causes the tip of the contact member to contact the surface of the fixing roller in synchronization with the sheet passing detection by the sheet passing detection unit. It is characterized by.

  Moreover, it is preferable that the abrasion state of the said release layer accompanying the contact of the said contact member is visible.

  In addition, an image forming apparatus according to the present invention includes the fixing device according to any one of claims 1 to 8, and the fixing roller includes a conductive metal core and an insulating material provided on a surface of the metal core. And a notifying unit for notifying the replacement timing of the fixing roller by conduction with contact between the core metal exposed by wear of the release layer and the contact member. It is characterized by.

  Although the fixing device of the present invention has a simple configuration, it can easily recognize the replacement time of the fixing roller and can improve the reliability thereof.

FIG. 2 is an explanatory diagram of a printer as an image forming apparatus equipped with the fixing device of the present invention. (Example 1) 2A and 2B are explanatory diagrams of the fixing device of the present invention, in which FIG. 1A shows a non-nip conveyance state and FIG. 2B shows a nip conveyance state. (Example 1) 2A and 2B are explanatory diagrams of a main part of the fixing device according to the present invention, in which FIG. (Example 1) It is explanatory drawing of the conventional fixing device. It is explanatory drawing of the principal part in the conventional fixing apparatus, (A) is before abrasion and (B) is explanatory drawing of the principal part of an abrasion state.

  In the fixing device according to the present invention, it is possible to easily recognize the replacement time of the fixing roller while having a simple configuration, and to improve the reliability of the fixing roller at a non-contact portion with the separation member. The contact member that contacts the surface of the contact member is provided, and the wear rate of the release layer at the contact portion of the contact member is made faster than the wear rate of the release layer at the contact portion of the separation member.

  Next, an embodiment according to the fixing device of the present invention will be described with reference to the drawings. The following examples are preferred specific examples of the fixing device of the present invention, and may have various technically preferable limitations. However, the technical scope of the present invention particularly limits the present invention. Unless otherwise stated, the present invention is not limited to these embodiments.

  FIG. 1 is an explanatory view of a printer as an image forming apparatus equipped with the fixing device of Embodiment 1 according to the present invention, FIG. 2 is an explanatory view of the fixing device of Embodiment 1 according to the present invention, and FIG. 3 is according to the present invention. FIG. 3 is an explanatory diagram of a main part of the fixing device according to the first exemplary embodiment.

(Overall configuration of image forming apparatus)
As shown in FIG. 1, a printer 11 as an image forming apparatus according to Embodiment 1 of the present invention includes a paper feed cassette 13 that is slidably stored in a printer main body 12 as an image forming apparatus main body, and a paper supply cassette 13. A paper feed unit 15 for taking out transfer paper (not shown) stored in the storage space 14 of the paper cassette 13, a manual feed tray 16 arranged in front of the printer main body 12, and transfer paper (set on the manual feed tray 16 ( (Not shown), a manual feed unit 17 for taking out, a transport path 18 for transporting transfer paper supplied from the respective paper feed units 15, 17, and each feed unit 15 on the upstream side of the transport path 18 in the sheet transport direction. , 17, the registration roller pair 19 disposed downstream of the sheet conveyance direction from the merging portion, and the registration roller pair 19 disposed downstream of the registration roller pair 19 in the sheet conveyance direction and supplied from the toner container 20. An image forming unit 21 that forms a transfer image on one surface of the transfer paper with a developer such as toner, and a toner that is disposed on the downstream side in the sheet transport direction of the transport path 18 relative to the image forming unit 21 and formed on one surface of the transfer paper A fixing device 22 that fixes an image, and a transport path from the downstream side of the transport path with respect to the fixing device 22 in the transport path 18 from the downstream side of the registration roller pair 19 when forming a transfer image on the other surface of the transfer paper that has passed through the fixing device 18 is provided with a reverse path 23 that is pulled back to the upstream side of the transport path 18 and a paper discharge section 24 provided at the end of the transport path 18.

(Configuration of toner container 20)
The toner container 20 stores replenishment toner inside the container body 25. The replenishing toner is agitated by a paddle 26 made of a flexible resin material or the like, and is conveyed by the spiral 27 in the transfer paper width direction (the depth direction in FIG. 1), and then forms an image at the predetermined position. Supplied to the developing device 28 of the section 21.

(Configuration of developing device 28)
The developing device 28 supplies the toner for replenishment supplied from the toner container 20 to the photosensitive drum 29 of the image forming unit 21 while stirring, and a pair of spirals is partitioned inside by a partition wall 30. 31 and 32 are arranged.

  Both ends of the partition wall 30 (in the depth direction in FIG. 1) are open so as to communicate between both ends of the spirals 31 and 32, and are directed toward one side of the developing device 28 by the spiral 31 provided below the spiral 27. After the toner is agitated and conveyed (forward path), the toner is turned back at the open end of the partition on one side, and the replenishing toner is agitated and conveyed (return path) toward the other side of the developing device 28 by the spiral 32. A circulation conveyance path is formed that is turned back again at the open end of the partition wall. In addition, a developing roller 33 that supplies replenishing toner is disposed in the spiral 32 so as to face the photosensitive drum 29.

  The developing roller 33 is disposed so that the peripheral surface thereof faces the peripheral surface of the photosensitive drum 29. Accordingly, the replenishment toner being conveyed to the developing roller 33 is supplied to the peripheral surface of the photosensitive drum 29 via the developing roller 33, thereby forming a toner image on the peripheral surface of the photosensitive drum 29. Become. At this time, the developing roller (magnet roller) 33 supplies the toner to the photosensitive drum 29 while appropriately stirring so as not to aggregate the toner.

(Configuration of the image forming unit 21)
The image forming unit 21 includes, for example, a charging device 34, an exposure device 35, and a developing device 28 in the order of the image forming process along the rotation direction of the photosensitive drum 29 (see the arrow in the drawing) around the photosensitive drum 29 made of amorphous silicon. (Developing roller 33)-A transfer device 36-a cleaning device 37-a static elimination device 33 are provided.

  As a result, in the image forming unit 21, the photosensitive drum 29 is rotationally driven at a predetermined process speed (circumferential speed) by a driving unit (not shown), and the surface thereof is uniformly charged to a predetermined polarity and potential by the charging device 34. .

  An electrostatic latent image is formed on the surface of the charged photosensitive drum 29 by the exposure device 35. Here, the exposure device 35 irradiates the surface of the photosensitive drum 29 with the laser beam P based on the image data included in the print data output from the personal computer or the like, and irradiates the surface of the photosensitive drum 29 with the laser beam. An electrostatic latent image corresponding to the image information is formed by removing the charge of the portion.

  The electrostatic latent image formed on the surface of the photosensitive drum 29 is developed as an unfixed toner image by electrostatically attaching the toner having the charge supplied from the toner container 20 by the developing device 28. Further, the unfixed toner image is transferred onto the transfer paper as a transfer image by the transfer device 36.

  At this time, the photosensitive drum 29 on which the unfixed toner image is transferred onto the transfer paper is subjected to a removal process of residual toner and the like by the cleaning device 37, and then removed by the charge removal device 38 for charging at the next image formation. Processing is performed.

(Configuration of exposure device 35)
The exposure device 35 processes image data included in print data transmitted from a personal computer (not shown), for example, and irradiates the surface of the photosensitive drum 29 with the laser light P. In addition to the image data described above, the print data here includes, for example, data relating to various settings such as the number of image forming processing units, enlargement / reduction ratio, color / monochrome designation, and image density. The exposure device 35, as an image forming apparatus, processes, for example, image data read by an image reading unit in the case of a copying function, and image data received via a telephone line or the like in the case of a facsimile function.

(Configuration of transfer device 36)
A transfer voltage is applied to the transfer device 36, and the toner image formed on the surface of the photosensitive drum 29 is transferred by the applied voltage while the transfer paper is nipped and conveyed in cooperation with the photosensitive drum 29.

(Configuration of static elimination device 38)
The neutralization device 38 uses an LED light source or the like, and neutralizes the photosensitive drum 29 charged by the charging device 34.

(Configuration of Fixing Device 22)
As shown in FIGS. 2A and 2B, the fixing device 22 has a pair of fixing roller 39 and pressure roller 40 disposed opposite to each other with the conveyance path 18 interposed therebetween, and a tip close to the surface of the fixing roller 39. A separation claw 41 serving as a separating member, a detection switch 42 that is disposed on the downstream side of the conveyance path 18 with respect to the nip conveyance portion by the fixing roller 39 and the pressure roller 40, and detects the transfer sheet S after the fixing. And a contact member 43 that rotates in conjunction with the transfer paper detection state of the switch 42.

(Configuration of the fixing roller 39)
The fixing roller 39 includes, for example, a hollow pipe-shaped metal core 44 made of a conductive metal, a release layer 45 such as a PFA tube (for example, a film thickness of 30 μm) provided on a surface layer of the metal core 44, and a metal core 44. And a heating source 46 such as a halogen heater disposed on the axis of the fixing roller 39. The fixing roller 39 is internally heated by heating of the heating source 46. An elastic layer made of a conductive material may be provided between the cored bar 44 and the release layer 45.

(Configuration of the pressure roller 40)
The pressure roller 40 includes a cored bar 47 and an elastic layer 48 such as silicone rubber provided on the surface layer of the cored bar 47. A release layer such as a PFA tube may be provided on the surface layer of the elastic layer 48.

(Configuration of separation claw 41)
The separation claw 41 as a separation member is made of a heat-resistant resin or a metal such as SUS, and the tip of the separation claw 41 is in contact with the surface of the fixing roller 39, thereby preventing the transfer paper S after being fixed from sticking. Further, for example, as shown in FIGS. 3A and 3B, the separation claw 41 is provided at a plurality of locations in the sheet passing region H along the width direction of the transfer sheet S set near the center of the fixing roller 39. It contacts the surface of the fixing roller 39. In addition, the material of the separation claw 41 is not particularly limited, and may be an independent type in addition to a plurality of integrated types as shown in FIG.

(Configuration of the detection switch 42)
As shown in FIG. 3A, the detection switch 42 always has its front end facing the conveyance path 18 (OFF state), and is rotated by the transfer paper S when the transfer paper S is nipped. In this way, a known device is used in which the switch is turned on, and a gear 49 is provided at the center of rotation.

  The detection switch 42 is a known detection switch for detecting the JAM of the transfer sheet S near the fixing device 22 and for counting the number of sheets passing depending on the ON / OFF state. Further, after the transfer paper S is nipped and rotated, the detection switch 42 is brought into an OFF state in which the front end faces the conveyance path 18 due to its own weight, the pressure of the return spring, or the like when the transfer paper S is nipped. Automatically recovers.

(Configuration of contact member 43)
The contact member 43 is made of a metal piece such as SUS or a heat-resistant resin coated, and as shown in FIG. 3A, near one end portion that is out of the sheet passing area H of the fixing roller 39. The non-sheet passing area is set so that the front surface and the tip of the fixing roller 39 are in contact with each other in the non-sheet passing area. Further, the contact member 43 can be rotated via the gear 50, and the gear 49 and the gear 50 of the detection switch 42 are interlocked via the interlocking gear 51.

  As a result, the contact member 43 is not in contact with the surface of the fixing roller 39 in a state where the transfer sheet S does not pass with respect to the detection switch 42, and in a state where the detection switch 42 detects the transfer sheet S. It contacts the surface of the fixing roller 39.

  Accordingly, the contact member 43 contacts the surface of the fixing roller 39 when the detection switch 42 is detecting the transfer sheet S and wears the release layer 45, and the detection switch 42 does not detect the transfer sheet S. Sometimes, the release layer 45 is not worn away from the surface of the fixing roller 39.

  The contact member 43 can set the film wear rate of the release layer 45 by selecting a material different from the material of the separation claw 41 or making it different from the contact pressure of the separation claw 41 with the surface of the fixing roller 39. . In this case, the material of the contact member 43 is made of a material harder than the separation claw 41 or is set to a pressure stronger than the contact pressure of the contact member 43, thereby increasing the wear rate of the release layer 45 with which the contact member 43 contacts. And the wear limit can be reached faster than other release layers.

  In addition, the contact member 43 can easily set the wear rate only by the film thickness of the release layer 45 by selecting the same material as the material of the separation claw 41 and by using the same pressure as the contact pressure with the surface of the fixing roller 39. can do. That is, by setting the film thickness of the release layer 45 with which the contact member 43 contacts to be thin, it is possible to reach the wear limit earlier than other release layers.

  Next, the function of the contact member 43 of the present invention will be specifically described.

  First, the transfer sheet S is passed through the nip between the fixing roller 39 and the pressure roller 40 which is a pressure unit pressed against the fixing roller 39, whereby the heating of the heating source 46 and the pressure roller 40 are heated. The unfixed toner image transferred to the surface of the transfer paper S (the fixing roller 39 side) by the pressurizing action is fixed.

  When the leading edge of the transfer sheet S that has passed through the fixing nip is peeled off from the fixing roller 39 by the separation claw 41, the detection switch 42 detects the passage of the transfer sheet S and is used for JAM detection or sheet count. At the same time, the rotational displacement of the detection switch 42 is transmitted to the contact member 43 via the gears 49, 50, 51, so that the contact member 43 is not in contact with the fixing roller 39 in synchronization with the detection of the sheet passing by the detection switch 42. Contact with the release layer 45 in the paper passing area.

  The film thickness of the release layer 45 in the non-sheet passing region is, for example, the case where the portion where the tip of the separation claw 41 is in contact with the release layer 45 in the sheet passing region H is the fastest wear portion. Further, the film thickness at the fastest wear portion of the release layer 45 in the sheet passing region H is set to the replacement time of the fixing roller 39 with 100,000 sheets passed, and the release layer 45 is completely transferred with 120,000 sheets passed. When it is set as the life time when the core metal 47 is worn out, the film thickness is set such that the core metal 47 is exposed due to wear associated with the contact of the contact member 43 when 110,000 sheets are passed.

  At this time, the film thickness of the release layer 45 in the non-sheet-passing region takes into consideration the hardness, frictional resistance value, contact pressure, etc. associated with the material used for the contact member 43 and the thickness (elasticity). Thus, the film thickness (= wear rate) is set as required. In the present embodiment, the wear rate of the release layer 45 is worn at substantially the same speed at the contact portion with the contact member 43 and the contact portion with the separation claw 41 (paper passing time≈number of sheets). Is set. Therefore, the contact member 43 is preferably set to the same material, thickness, weight, and contact pressure as the separation claw 41.

  Then, as shown in FIG. 3B, when the number of passing sheets reaches approximately 110,000 sheets, the release layer 45 is left in the sheet passing area where the separation claw 41 is in contact, In the non-sheet passing region where the contact member 43 is in contact, the release layer 45 is completely worn away (wear limit).

  As a result, when the cored bar 44 is exposed by contact of the release layer 45 in the non-sheet passing region of the fixing roller 39 with the contact member 43, the replacement timing of the fixing roller 39 is determined by visually observing the exposure of the cored bar 44. Can be recognized.

  Further, the cored bar 44 is made of a conductive member, and the contact member 43 is provided with a switching function that allows the cored bar 44 to come into contact with the cored bar 44. Can also be notified.

  Note that the degree of wear of the release layer 45 in the sheet passing region H varies depending on the type, thickness, size, image type, and the like of the transfer sheet S to be passed, and is unstable and difficult to predict. The degree of wear of the contact portion 43 with the contact member 43 in the non-sheet passing region of the release layer 45 is determined by the sheet passing time (≈the number of sheets) if the setting as a design parameter is determined. It is possible to set.

  As described above, according to the fixing device 22 of the present invention, it is possible to easily visually determine whether the replacement time of the fixing roller 21 has been reached with a simple configuration.

  Further, the contact member 43 is disposed near the end of the fixing roller 41 that is a non-sheet passing area, and the replacement time is visually observed near the end, so that the contact member 43 is from the sheet passing area H that is near the center of the fixing roller 41. In addition, it is possible to make the installation place in the machine easily visible.

  In the above embodiment, the fixing device of the present invention is applied to the printer 11. However, it is needless to say that the fixing device of the present invention can be applied to all image forming apparatuses such as copying machines and multifunction machines.

DESCRIPTION OF SYMBOLS 22 ... Fixing device 44 ... Core metal 45 ... Release layer 39 ... Fixing roller 40 ... Pressure roller (pressure member)
41 ... separation claw (separation member)
43 ... Contact member

Claims (10)

A fixing roller provided with a release layer on the surface; a pressure member disposed opposite to the fixing roller to nip-transfer the transfer paper in cooperation with the fixing roller; and a surface of a sheet passing area of the fixing roller. A separation member that prevents the transfer paper from sticking to the surface of the paper passing area of the fixing roller,
A contact member that contacts the surface of the fixing roller at a non-contact portion with the separation member, and the wear rate of the release layer at the contact portion of the contact member is determined by the release layer at the contact portion of the separation member. The fixing device is characterized in that it is faster than the wear rate of. A fixing roller provided with a release layer on the surface; a pressure member disposed opposite to the fixing roller to nip-transfer the transfer paper in cooperation with the fixing roller; and a surface of a sheet passing area of the fixing roller. A separation member that prevents the transfer paper from sticking to the surface of the paper passing area of the fixing roller,
A contact member that is in contact with the surface of the fixing roller at a non-contact portion with the separation member, and the thickness of the release layer at the contact portion of the contact member is set to the release layer at the contact portion of the separation member. The fixing device is characterized in that it is thinner than the film thickness.   The fixing device according to claim 1, wherein the contact member is in contact with a surface of a non-sheet passing region of the fixing roller.   The film thickness of the release layer at the contact portion of the separation member is determined as follows: the aging wear rate of the release layer associated with the sheet passing in the sheet passing region of the fixing roller and the aging wear rate associated with the contact with the separation member. The fixing device according to claim 3, wherein the fixing device is set to be thicker than a wear amount in a film thickness direction in consideration of a combined total wear rate.   The film thickness of the release layer at the contact portion of the contact member is thicker than the film thickness corresponding to the preset number of sheets to be passed at the fixing roller replacement time and corresponding to the number of sheets to be passed at the fixing roller lifetime. The fixing device according to claim 3, wherein the fixing device is set thinner than the fixing device.   The contact member determines the wear rate of the release layer at the contact portion of the contact member according to the hardness and friction coefficient of the material to be used and the contact pressure with respect to the fixing roller, and the release layer at the contact portion of the separation member. The fixing device according to claim 1, wherein the fixing device is faster than the wear rate.   7. The contact member according to claim 1, wherein the contact member contacts and separates from the fixing roller in conjunction with transfer sheet nip conveyance by cooperation of the fixing roller and the pressure member. The fixing device according to 1.   A sheet passing detection unit that detects the passing of the transfer sheet; and a driving unit that brings the tip of the contact member into contact with the surface of the fixing roller in synchronization with the sheet passing detection by the sheet passing detection unit. The fixing device according to claim 7.   The fixing device according to any one of claims 1 to 8, wherein the wear state of the release layer accompanying the contact of the contact member is visible.   A fixing device according to any one of claims 1 to 9, wherein the fixing roller includes a conductive metal core and the insulating release layer provided on a surface of the metal core. An image forming apparatus comprising: a notifying unit for notifying the replacement timing of the fixing roller by conduction with the contact between the metal core exposed by the abrasion of the release layer and the contact member; .

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