JP2017116756A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device that can accurately detect the degree of wear of surface layers of a fixing rotor and a pressure rotor at a precise timing, and an image forming apparatus.SOLUTION: A surface layer 34 of a pressure roller 31 (pressure rotor) with which a plurality of separation pawls 37A to 37E (separation members) are in contact is formed of a conductive material, and an elastic layer 33 that is a layer below the surface layer 34 is formed of an insulating material. The plurality of separation pawls 37A to 37E each have an electrode 37a provided on part or all of a portion in contact with the pressure roller 31, and a resistance detection part 62 (detection means) is provided to detect the value of resistance between the electrodes 37a.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine thereof, and a fixing device installed therein.

  Conventionally, in fixing devices in image forming apparatuses such as copying machines and printers, current fluctuations in the drive motor that drives the contact mechanism of the pressure roller, the number of jams occurring at the position of the fixing device, and the tip of the separation plate A technique for predicting a failure of a fixing device by detecting the displacement of the fixing device is known (for example, see Patent Document 1).

On the other hand, in Patent Document 2, etc., the recording medium after the fixing process is surely separated without being wound around a fixing rotator such as a fixing roller or a fixing belt, or a pressure rotator such as a pressure roller or a pressure belt. As described above, a technique is disclosed in which a plurality of separation claws (separation members) are brought into contact with the surface of a fixing rotator or a pressure rotator.
Specifically, in the fixing device, a pressure rotator is brought into pressure contact with the fixing rotator, and a nip portion (fixing nip) through which a recording medium is conveyed is formed. Then, the toner image on the recording medium conveyed to the nip portion is fixed on the recording medium by the heat received from the fixing rotating body and the pressure of the nip portion. Even if the recording medium sent out from the nip portion is adsorbed to the fixing rotator or the pressure rotator, a plurality of separation media that contact the fixing rotator or the pressure rotator on the exit side of the nip portion are provided. The member (separation claw) is forcibly separated from the fixing rotator and the pressure rotator and is transported toward the paper discharge transport path.
Here, a plurality of separation members (separation claws) are installed at positions separated in the width direction according to the number of sizes so as to correspond to recording media having different sizes in the width direction.

  The conventional fixing device cannot accurately detect the degree of wear of the surface layer on the fixing rotator or the pressure rotator at an accurate timing. For this reason, an abnormality may occur in the fixed image, or a jam (paper jam) may occur at the position of the fixing device.

  The present invention has been made to solve the above-described problems, and a fixing device in which the degree of wear of a surface layer in a fixing rotator or a pressure rotator is accurately detected at an accurate timing, and An object is to provide an image forming apparatus.

  The fixing device according to the present invention includes a fixing rotator that heats and fixes a toner image on a recording medium, a pressure rotator that forms a nip portion by which the recording medium is conveyed by being pressed against the fixing rotator, A recording medium that is installed at a position apart in the width direction and abuts on the surface of the pressure rotator or the fixing rotator and is sent out from the nip portion is sent from the pressure rotator or the fixing rotator. A plurality of separating members to be separated, and the pressure rotating body or the fixing rotating body with which the plurality of separating members come into contact has a surface layer formed of a conductive material, and a lower layer of the surface layer is insulated. Each of the plurality of separation members is formed of a conductive material, and an electrode is provided on a part or all of the portion that contacts the pressure rotator or the fixing rotator, and between the electrodes of the plurality of separation members. Detect resistance value That the detection means in which is provided.

  According to the present invention, it is possible to provide a fixing device and an image forming apparatus in which the degree of wear of the surface layer on the fixing rotator or the pressure rotator is accurately detected at an accurate timing.

1 is an overall configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. 2 is a configuration diagram illustrating a fixing device. FIG. FIG. 3 is a schematic view showing a main part of the fixing device in a width direction. 6 is a flowchart illustrating a control flow performed in the fixing device. 10 is a flowchart illustrating a control flow performed by the fixing device as Modification 1. FIG. 10 is a configuration diagram illustrating a fixing device as a second modification.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

First, the overall configuration and operation of the image forming apparatus 1 will be described with reference to FIG.
In FIG. 1, 1 is a tandem color copier as an image forming apparatus, 2 is a writing unit that emits laser light based on input image information, 3 is a document conveying unit that conveys a document D to a document reading unit 4, and 4 is An original reading unit that reads image information of the original D, 7 is a paper feeding unit that accommodates a recording medium P such as transfer paper, 9 is a registration roller (timing roller) that adjusts the conveyance timing of the recording medium P, 11Y, 11M, 11C and 11BK are photosensitive drums on which toner images of respective colors (yellow, magenta, cyan, and black) are formed, 12 is a charging unit that charges the photosensitive drums 11Y, 11M, 11C, and 11BK, and 13 is each photosensitive member. Developing units for developing the electrostatic latent images formed on the drums 11Y, 11M, 11C, and 11BK, and 14 are formed on the photosensitive drums 11Y, 11M, 11C, and 11BK, respectively. Primary transfer bias rollers for transferring superimposed on the recording medium P the toner image, 15 denotes each of the photosensitive drums 11Y, 11M, 11C, cleaning unit for collecting the untransferred toner on 11BK, a.

  Reference numeral 16 denotes an intermediate transfer belt cleaning unit that cleans the intermediate transfer belt 17, 17 an intermediate transfer belt on which toner images of a plurality of colors are transferred and superimposed, and 18 a color toner image on the intermediate transfer belt 17 on the recording medium P. A secondary transfer bias roller 20 for transferring the toner image onto the recording medium P is a fixing device for fixing the toner image (unfixed image) on the recording medium P.

Hereinafter, a printing operation at the time of normal color image formation in the image forming apparatus will be described.
First, the document D is transported from the document table in the direction of the arrow in the drawing by the transport rollers of the document transport unit 3 and placed on the contact glass 5 of the document reading unit 4. Then, the document reading unit 4 optically reads the image information of the document D placed on the contact glass 5.

  Specifically, the document reading unit 4 scans the image of the document D on the contact glass 5 while irradiating light emitted from an illumination lamp. Then, the light reflected by the document D is imaged on the color sensor via the mirror group and the lens. The color image information of the document D is read for each RGB (red, green, blue) color separation light by the color sensor, and then converted into an electrical image signal. Further, color conversion processing, color correction processing, spatial frequency correction processing, and the like are performed by the image processing unit based on the RGB color separation image signals to obtain yellow, magenta, cyan, and black color image information.

  Then, the image information of each color of yellow, magenta, cyan, and black is transmitted to the writing unit 2. The writing unit 2 emits laser light (exposure light) based on the image information of each color toward the corresponding photosensitive drums 11Y, 11M, 11C, and 11BK.

On the other hand, the four photosensitive drums 11Y, 11M, 11C, and 11BK are rotated counterclockwise in FIG. First, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK are uniformly charged at a portion facing the charging unit 12 (this is a charging process). Thus, a charged potential is formed on the photosensitive drums 11Y, 11M, 11C, and 11BK. Thereafter, the surfaces of the charged photosensitive drums 11Y, 11M, 11C, and 11BK reach the irradiation positions of the respective laser beams.
In the writing unit 2, laser light corresponding to the image signal is emitted from the four light sources corresponding to each color. Each laser beam passes through a separate optical path for each of the yellow, magenta, cyan, and black color components (this is an exposure process).

  The laser beam corresponding to the yellow component is applied to the surface of the first photosensitive drum 11Y from the left side of the paper. At this time, the yellow component laser light is scanned in the rotation axis direction (main scanning direction, width direction) of the photosensitive drum 11Y by a polygon mirror that rotates at high speed. Thus, an electrostatic latent image corresponding to the yellow component is formed on the photosensitive drum 11Y charged by the charging unit 12.

  Similarly, the laser beam corresponding to the magenta component is irradiated on the surface of the second photosensitive drum 11M from the left side of the paper, and an electrostatic latent image corresponding to the magenta component is formed. The cyan component laser light is applied to the surface of the third photosensitive drum 11C from the left side of the drawing to form an electrostatic latent image of the cyan component. The black component laser light is applied to the surface of the fourth photoconductive drum 11BK from the left side of the drawing to form an electrostatic latent image of the black component.

Thereafter, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK on which the electrostatic latent images of the respective colors are formed reach positions facing the developing unit 13, respectively. Then, the respective color toners are supplied from the developing units 13 onto the photosensitive drums 11Y, 11M, 11C, and 11BK, and the latent images on the photosensitive drums 11Y, 11M, 11C, and 11BK are developed (development process). .)
Thereafter, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK after the development process reach the facing portions of the intermediate transfer belt 17, respectively. Here, a primary transfer bias roller 14 is installed at each facing portion so as to be in contact with the inner peripheral surface of the intermediate transfer belt 17. Then, the toner images of the respective colors formed on the photosensitive drums 11Y, 11M, 11C, and 11BK are sequentially superimposed and transferred onto the intermediate transfer belt 17 at the position of the primary transfer bias roller 14 (primary transfer). Process.)

Then, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK after the transfer process reach positions facing the cleaning unit 15, respectively. Then, the untransferred toner remaining on the photosensitive drums 11Y, 11M, 11C, and 11BK is collected by the cleaning unit 15 (this is a cleaning process).
Thereafter, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK pass through the static eliminating unit, and a series of image forming processes in the photoconductive drums 11Y, 11M, 11C, and 11BK is completed.

On the other hand, the intermediate transfer belt 17 on which the toners of the respective colors on the photosensitive drums 11Y, 11M, 11C, and 11BK are transferred (carrying) are run in the clockwise direction in the drawing and are connected to the secondary transfer bias roller 18. Reach the opposite position. Then, a color toner image carried on the intermediate transfer belt 17 is transferred onto the recording medium P at a position facing the secondary transfer bias roller 18 (secondary transfer step).
Thereafter, the surface of the intermediate transfer belt 17 reaches the position of the intermediate transfer belt cleaning unit 16. Then, the untransferred toner adhered on the intermediate transfer belt 17 is collected by the intermediate transfer belt cleaning unit 16, and a series of transfer processes in the intermediate transfer belt 17 is completed.

Here, the recording medium P transported between the intermediate transfer belt 17 and the secondary transfer bias roller 18 (secondary transfer nip) is transported from the paper supply unit 7 via the registration roller 9 and the like. It is a thing.
Specifically, the recording medium P fed by the paper feeding roller 8 from the paper feeding unit 7 that stores the recording medium P is guided to the registration roller 9 after passing through the conveyance guide. The recording medium P that has reached the registration roller 9 is conveyed toward the secondary transfer nip at the same timing.

Then, the recording medium P on which the full-color image is transferred is guided to the fixing device 20 by the transport belt. In the fixing device 20, a color image (toner image) is fixed on the recording medium P at a nip portion (fixing nip) between the fixing belt and the pressure roller (a fixing step).
Then, the recording medium P after the fixing step is discharged as an output image outside the apparatus main body 1 by a paper discharge roller, and a series of image forming processes is completed.

Next, the configuration and operation of the fixing device 20 installed in the image forming apparatus main body 1 will be described in detail with reference to FIGS.
As shown in FIGS. 2 and 3, the fixing device 20 includes a fixing belt 21 as a fixing rotator, a fixing auxiliary roller 22, a heating roller 23, a heater 25 as a heating unit, a temperature sensor 40, and a pressure rotator. The pressure roller 31, the separation plate 38, a plurality of separation claws 37 </ b> A to 37 </ b> E as a plurality of separation members, a tension spring 39 as a biasing member, a guide plate 35, and the like.

Here, a fixing belt 21 (fixing member) as a fixing rotating body is an endless belt having a multilayer structure in which an elastic layer and a release layer (surface layer) are sequentially laminated on a base layer made of a resin material such as polyimide. It is. The elastic layer of the fixing belt 21 is formed of an elastic material such as fluorine rubber, silicone rubber, or foamable silicone rubber. The release layer of the fixing belt 21 is made of PFA (tetrafluoroethylene bar fluoroalkyl vinyl ether copolymer resin) or the like. By providing the release layer on the surface layer of the fixing belt 21, the releasability (peelability) for the toner T (toner image) is ensured. The fixing belt 21 is stretched and supported by two roller members (a fixing auxiliary roller 22 and a heating roller 23), and travels in the direction of the arrow in FIG. By using the fixing belt 21 having a low heat capacity as the fixing member, the temperature rise characteristic of the apparatus is improved.
In this embodiment, in order to apply a predetermined tension to the fixing belt 21 stretched and supported by the fixing auxiliary roller 22 and the heating roller 23, the tension roller is pressed against the outer peripheral surface of the fixing belt 21. It can also be configured.

  The fixing auxiliary roller 22 is a roller member in which an elastic layer 22b made of a foam material such as foamable silicone rubber is formed on a core metal 22a such as SUS304, and is fixed to a pressure roller 31 as a pressure rotating body. A nip portion (fixing nip) is formed by pressure contact with the belt 21. By forming the elastic layer 22b from a foamed material, the nip width (nip amount) in the fixing nip can be set relatively large, and the heat of the fixing belt 21 is difficult to transfer to the auxiliary fixing roller 22. The fixing auxiliary roller 22 rotates in the clockwise direction in FIG.

  The heating roller 23 is a hollow roller member made of a metal material such as aluminum or stainless steel, and a heater 25 (heat source) as a heating unit is fixed inside the cylindrical body. By setting the thickness of the heating roller 23 to be relatively thin, the heat capacity of the heating body is reduced and the temperature rise characteristic of the apparatus is improved (rise time is shortened).

The heater 25 (heating means) provided in the heating roller 23 is a halogen heater, and both ends thereof are fixed to the side plate of the fixing device 20. Then, power is supplied from the power supply unit to the heater 25 in a state where the main switch of the image forming apparatus main body 1 is turned on. The heating roller 23 is heated by the radiant heat from the heater 25 whose output is controlled by the control unit 60, and heat is further applied to the toner image T on the recording medium P from the surface of the fixing belt 21 heated by the heating roller 23. It is done.
The output control of the heater 25 is performed based on the detection result of the belt surface temperature by the temperature sensor 40 that faces the surface of the fixing belt 21 in a non-contact manner. Specifically, the AC voltage is applied to the heater 25 for the energization time determined based on the detection result of the temperature sensor 40 (thermopile). By such output control of the heater 25, the temperature (fixing temperature) of the fixing belt 21 can be adjusted and controlled to a desired temperature (target control temperature).

  The pressure roller 31 (pressure member) as a pressure rotator mainly includes a cored bar 32 made of a metal material, and an elastic layer 33 formed on the outer peripheral surface of the cored bar 32 through an adhesive layer. And a surface layer 34 (release layer) formed on the outer peripheral surface of the elastic layer 33. The elastic layer 33 of the pressure roller 31 has a layer thickness of about several millimeters, and is formed of an elastic material such as insulative foamable silicone rubber, fluorine rubber, or silicone rubber. The surface layer 34 of the pressure roller 31 has a layer thickness of about several tens of μm to several hundreds of μm, and is formed of a low friction material such as PFA (PFA tube) having conductivity. By providing a release layer having conductivity as the surface layer 34 of the pressure roller 31, the releasability (peelability) for the toner T (toner image) is ensured, and the recording medium P is applied to the pressure roller 31. It is possible to reduce the problem that the separability is reduced due to electrostatic adsorption.

The pressure roller 31 is pressed against the auxiliary fixing roller 22 via the fixing belt 21 by a pressure mechanism. In this way, a desired nip portion is formed between the pressure roller 31 and the fixing belt 21. Note that a pressure mechanism that pressurizes the pressure roller 31 against the fixing belt 21 (fixing auxiliary roller 22) with a predetermined pressure contact force may be configured so that the pressure contact force can be released (or reduced in pressure).
In the present embodiment, the elastic layer 33 of the pressure roller 31 has a smaller thickness and a lower hardness than the elastic layer 22 b of the auxiliary fixing roller 22. As a result, the nip portion between the pressure roller 31 and the fixing belt 21 (fixing auxiliary roller 22) is formed so that the fixing auxiliary roller 22 is recessed and conforms to the roller shape of the pressure roller 31, as shown in FIG. Will be. Therefore, the recording medium P sent out from the nip portion can easily draw a locus along the roller shape of the pressure roller 31.

With reference to FIG. 2, a guide plate 35 for guiding the conveyance of the recording medium P is disposed on the entrance side of the contact portion (a fixing nip) between the fixing belt 21 and the pressure roller 31. . The guide plate 35 is fixed to the side plate of the fixing device 20.
Further, a separation plate 38 is provided at a position facing the outer peripheral surface of the fixing belt 21 (fixing rotator) and in the vicinity of the exit side of the nip portion (fixing nip) with a small gap from the fixing belt 21. It is arranged. By installing the separation plate 38, it is possible to reduce a problem that the recording medium P after the fixing process is wound around the fixing belt 21 along the travel of the fixing belt 21.

2 and 3, a plurality of separating members are positioned in contact with the outer peripheral surface of the pressure roller 31 (pressure rotator) near the exit side of the nip portion (fixing nip). Separation claws 37A to 37E are arranged.
The plurality of separation claws 37 </ b> A to 37 </ b> E (separation members) are respectively installed at positions separated in the width direction (the vertical direction in FIG. 2 and the left-right direction in FIG. 3). Specifically, in the present embodiment, the first separation claw 37A and the fifth separation claw 37E are at both ends in the width direction, the third separation claw 37C is at the center in the width direction, and the second separation claw 37B is the first separation. A fourth separation claw 37D is installed between the fifth separation claw 37E and the third separation claw 37C between the claw 37A and the third separation claw 37C.
Each of the five separation claws 37A to 37E is installed so as to be rotatable about a support shaft, and is energized by a tension spring 39 to be on the surface of the pressure roller 31 (pressure rotator). Abut. The recording medium P delivered from the nip portion is separated from the pressure roller 31 by the separation claws 37A to 37E. That is, by installing the separation claws 37 </ b> A to 37 </ b> E, it is possible to reduce a problem that the recording medium P after the fixing process is wound around the pressure roller 31 along the travel of the pressure roller 31.
The separation claws 37 </ b> A to 37 </ b> E are each provided with an electrode 37 a at a portion in contact with the pressure roller 31, which will be described in detail later.

The fixing device 20 configured as described above operates as follows.
When the main switch of the apparatus main body 1 is turned on, an AC voltage is applied (powered) to the heater 25.
When a print command (print job command) is input, the pressure roller 31 is rotationally driven in the direction of the arrow (counterclockwise) in FIG. 2 by a drive motor (drive means), and the fixing belt 21 ( The auxiliary fixing roller 22 and the heating roller 23) are driven to rotate in the direction of the arrow (clockwise) in FIG. Thereafter, the recording medium P is fed from the paper supply unit 7, and the toner image on the intermediate transfer belt 17 is carried on the recording medium P as an unfixed image at the position of the secondary transfer bias roller 18. The recording medium P carrying the unfixed image T (toner image) is conveyed in the direction of the arrow Y10 in FIG. 2 and fed into the nip portion between the fixing belt 21 and the pressure roller 31 that are in a pressure contact state. The toner image T is fixed on the surface of the recording medium P by the heating by the fixing belt 21 and the pressing force of the fixing belt 21 (fixing auxiliary roller 22) and the pressure roller 31. Thereafter, the recording medium P sent from the nip portion by the rotating fixing belt 21 and the pressure roller 31 is separated by the separation claws 37A to 37E and conveyed in the direction of the arrow Y11.

Hereinafter, a characteristic configuration and operation of the fixing device 20 (image forming apparatus 1) of the present embodiment will be described in detail.
As described above with reference to FIG. 2, in the present embodiment, the pressure roller 31 (pressure rotator) with which the plurality of separation claws 37 </ b> A to 37 </ b> E (separation members) abut is electrically conductive. An elastic layer 33 made of a conductive material and serving as a lower layer of the surface layer 34 is formed of an insulating material.

Here, with reference to FIGS. 2 and 3, in the fixing device 20 according to the present embodiment, the plurality of separation claws 37 </ b> A to 37 </ b> E are each provided with an electrode on a part or all of the portion in contact with the pressure roller 31. 37a is provided. Specifically, the separation claws 37A to 37E are formed of a heat-resistant low-friction resin material, and an electrode 37a made of a metal material (or resin material) having conductivity and low-friction properties is embedded in the tip portion thereof. It is.
And the resistance detection part 62 (resistance measurement apparatus) as a detection means which detects the resistance value between the electrodes 37a in these some separation claws 37A-37E is provided. As the resistance detection unit 62, a known one can be used, and among the five electrodes 37a, an electric resistance value is detected from a change in current when a predetermined voltage is applied between the two electrodes 37a. It is.

And according to the magnitude | size of the resistance value detected by the resistance detection part 62 (detection means), the grade of the abrasion of the surface layer 34 in the pressure roller 31 which several separation nail | claw 37A-37E contact | abuts is judged. become.
Specifically, when the surface layer 34 of the pressure roller 31 (which is a surface layer having conductivity) is almost entirely worn and the elastic layer 33 is exposed or close to the state, the five electrodes 37a. No matter how the two electrodes 37a are selected, the electrodes 37a are in contact with or close to the insulating elastic layer 33, and the electrical conductivity between the electrodes 37a is reduced. Therefore, the resistance value between the electrodes 37a becomes larger than when the surface layer 34 is not worn. From such a change in resistance value, the degree of wear of the surface layer 34 can be determined.
Further, due to the sliding contact with the edge portion of the recording medium P and the separation claws 37 </ b> A to 37 </ b> E, the surface layer 34 of the pressure roller 31 is locally worn in a part of the width direction and the elastic layer 33 is exposed or close to it. Even if it becomes a state, the wear position is specified by comparing the resistance value between the electrodes 37a of each combination while changing the combination of the two electrodes 37a to be selected among the five electrodes 37a. Is possible.
The electrode 37a may be at least two of the plurality of separation claws 37. In particular, the more the plurality of separation claws having the electrode 37a are arranged uniformly in the width direction, the higher the detection accuracy.

Thus, in this embodiment, since the plurality of separation claws 37A to 37E having the electrode 37a and the resistance detection unit 62 are provided, the wear of the surface layer 34 on the pressure roller 31 is relatively simple. Can be accurately detected at a precise timing. Therefore, there is a possibility that the degree of wear of the surface layer 34 of the pressure roller 31 is advanced, an abnormality occurs in the fixed image, or a jam (paper jam) occurs at the position of the fixing device 20. It is possible to grasp the state in advance and prompt the user to perform maintenance at an appropriate timing. That is, it is possible to perform maintenance of the fixing device 20 at an appropriate timing before problems such as abnormal images and jams occur.
In particular, the surface layer 34 of the pressure roller 31 is formed of a relatively thin PFA tube, and if a large amount of wear occurs, secondary side effects such as breakage may occur. Will be useful.

Here, in the present embodiment, when the resistance value X detected by the resistance detection unit 62 (detection means) exceeds the first predetermined value A, the pressure roller 31 with which the plurality of separation claws 37A to 37E abut. When the resistance value X detected by the resistance detector 62 exceeds a second predetermined value B (> A) larger than the first predetermined value A, a plurality of separation claws are notified. A control flow is executed in which the image forming operation is interrupted until the pressure roller 31 in contact with 37A to 37E is replaced.
Specifically, when the detection result detected by the resistance detection unit 62 is sent to the control unit 60 and the control unit 60 determines that the resistance value X exceeds the first predetermined value A, the display panel 61 ( Announcement such as “Maintenance of the fixing device (pressure roller) is necessary. Please contact a service person” is displayed on the exterior of the image forming apparatus main body 1.
In addition, when the control unit 60 determines that the resistance value X exceeds the second predetermined value B, the display panel 61 “printing operation cannot be performed until the fixing device (pressure roller) is maintained. The image forming operation is suspended until the pressure roller 31 is replaced.
By performing such control, the replacement maintenance of the pressure roller 31 that has deteriorated wear is surely performed, and the fixed image becomes abnormal or a jam occurs at the position of the fixing device 20. Defects will be suppressed.

In the present embodiment, the control flow described above is executed before a series of image forming operations (print jobs) is started. That is, before the series of printing operations is started, the resistance value X is detected by the resistance detection unit 62, and according to the resistance value X, the printing operation is performed as it is, or a maintenance display is displayed on the display panel 61. And a control flow for interrupting the image forming operation is performed.
By performing such control, it is possible to reliably prevent problems due to wear of the surface layer 34 of the pressure roller 31 before the print job.

Specifically, referring to the control flow of FIG. 4, first, when a print job command is input to the image forming apparatus 1 by a user pressing a print key or the like (steps S1 and S2), a resistance detection unit. The resistance value X of the pressure roller 31 (surface layer 34) is detected by 62 (step S3).
And it is discriminate | determined whether resistance value X is smaller than the 1st predetermined value A (step S4). As a result, when it is determined that the resistance value X is smaller than the first predetermined value A, it is determined that the wear of the surface layer 34 of the pressure roller 31 has not progressed, and the printing operation is performed based on the command in step S2. Is performed (step S8), and this flow is ended (step S9).
On the other hand, if it is determined in step S4 that the resistance value X is not smaller than the first predetermined value A, it is further determined whether the resistance value X is smaller than the second predetermined value B ( Step S5). As a result, when it is determined that the resistance value X is smaller than the second predetermined value B, it is assumed that the wear of the surface layer 34 of the pressure roller 31 has progressed to some extent, and the pressure roller 31 is displayed on the display panel 61. Is displayed to urge the user to exchange (step S6). Then, a printing operation is performed based on the command in step S2 (step S8), and this flow is finished (step S9).
On the other hand, if it is determined in step S5 that the resistance value X is not smaller than the second predetermined value B, it is assumed that the wear of the surface layer 34 of the pressure roller 31 has progressed considerably. The printing operation in the forming apparatus 1 (the printing operation based on the command in step S2) is interrupted, and a message indicating that the pressure roller 31 has reached the end of its life is displayed on the display panel 61 (step S7). The process ends (step S9).

<Modification 1>
FIG. 5 is a flowchart showing a control flow performed in the fixing device as the first modification, and corresponds to FIG. 4 in the present embodiment.
In Modification 1, the series of image forming operations is performed after the series of image forming operations is started and after the number of prints N related to the series of image forming operations has reached a predetermined number C. Sometimes, the control flow described above is executed. That is, after the series of printing operations is started and the number N of printed sheets reaches the predetermined number C, the resistance value X is detected by the resistance detecting unit 62 during the printing operation, and the resistance Depending on the value X, a control flow is performed in which the printing operation is performed as it is, the maintenance display is performed on the display panel 61, and the image forming operation is interrupted.
By performing such control, even when a large amount of printing is performed in one print job and the wear of the surface layer 34 progresses during the print job, the pressure roller 31 is surely obtained. Problems due to wear of the surface layer 34 can be suppressed.

Specifically, referring to the control flow in FIG. 5, first, when a printing operation is started based on a print job command (steps S10 and S11), whether the number of printed sheets N has reached a predetermined number of sheets C is displayed in the counter information. Based on the determination (step S12). When the number N of printed sheets reaches the predetermined number C, the resistance value X of the pressure roller 31 (surface layer 34) is detected by the resistance detection unit 62 (step S13).
And it is discriminate | determined whether resistance value X is smaller than the 1st predetermined value A (step S14). As a result, when it is determined that the resistance value X is smaller than the first predetermined value A, it is assumed that the wear of the surface layer 34 of the pressure roller 31 has not progressed, and the printing operation in step S11 is continued. This is done (step S18), and this flow is finished (step S19).
On the other hand, if it is determined in step S14 that the resistance value X is not smaller than the first predetermined value A, it is further determined whether the resistance value X is smaller than the second predetermined value B ( Step S15). As a result, when it is determined that the resistance value X is smaller than the second predetermined value B, it is assumed that the wear of the surface layer 34 of the pressure roller 31 has progressed to some extent, and the pressure roller 31 is displayed on the display panel 61. Is displayed to prompt the exchange (step S16). Then, the printing operation in step S11 is continuously performed (step S18), and this flow is finished (step S19).
On the other hand, if it is determined in step S15 that the resistance value X is not smaller than the second predetermined value B, it is assumed that the wear of the surface layer 34 of the pressure roller 31 has progressed considerably. The printing operation (the printing operation of step 11) in the forming apparatus 1 is interrupted to stop the operation of the image forming apparatus 1, and the display panel 61 displays that the pressure roller 31 has reached the end of its life (step). S17), this flow is finished (step S19).

<Modification 2>
FIG. 6 is a configuration diagram showing a fixing device as a second modification, and corresponds to FIG. 2 in the present embodiment.
In the present embodiment, the present invention is applied to the belt-type fixing device 20 of the heater type, in which the plurality of separation claws 37A to 37E are in contact with the pressure roller 31, but the fixing device to which the present invention is applied. 20 is not limited to this type, and can be installed in various types of fixing devices.
For example, as shown in FIG. 6A, a roller type fixing device 20 of a heat heater type is a fixing roller 28 (a heater 25 is installed in a hollow portion of a core metal portion, and an elastic layer or It is also possible to apply the present invention to a roller member in which a plurality of separation claws 37 </ b> A to 37 </ b> E are in contact with the pressure roller 31.
Further, as shown in FIG. 6B, an electromagnetic induction type (IH type) roller type fixing device 20 includes a fixing roller 28 (induction in which an elastic layer and an excitation coil are wound on a cored bar portion). And a plurality of separation claws 37 </ b> A to 37 </ b> E are in contact with the pressure roller 31. The present invention can be applied to anything.
Also, a resistance heating type roller type fixing device is provided with a fixing roller 28 (installed so that the resistance heating element is in contact with the hollow portion of the cored bar, and an elastic layer, a release layer, etc. are laminated on the cored bar. The present invention can also be applied to a structure in which a plurality of separation claws 37 </ b> A to 37 </ b> E are in contact with the pressure roller 31.
Even in such a case, substantially the same effect as that of the present embodiment can be obtained.
Further, as shown in FIGS. 6A and 6B, a plurality of separation claws 47A to 47E (separation members) for preventing the recording medium P from being wrapped around the fixing roller 28 as a fixing rotating body are provided. In the case of being installed, electrodes are provided for the plurality of separation claws 47A to 47E in the same manner as the separation claws 37A to 37E for the pressure rotator, and the surface of the fixing roller 28 is detected by the resistance detection unit. It can also be configured to detect the resistance value of the layer (release layer). In that case, in the fixing rotator, the surface layer (release layer) is formed of a conductive material, and the elastic layer, which is the lower layer of the surface layer, is formed of an insulating material.
In such cases, the degree of wear of the surface layer in the fixing rotator (fixing roller 28) can be accurately detected at an appropriate timing.

As described above, in the fixing device 20 according to the present embodiment, the surface layer 34 of the pressure roller 31 (pressure rotator) with which the plurality of separation claws 37A to 37E (separation members) abut is formed of a conductive material. Thus, the elastic layer 33, which is the lower layer of the surface layer 34, is formed of an insulating material. Each of the plurality of separation claws 37 </ b> A to 37 </ b> E is provided with an electrode 37 a on a part or all of the portion in contact with the pressure roller 31, and a resistance detection unit that detects a resistance value between the electrodes 37 a. 62 (detection means) is provided.
As a result, the degree of wear of the surface layer 34 on the pressure roller 31 can be accurately detected at an appropriate timing.

In the present embodiment, the pressure roller 31 is used as the pressure rotator, but a pressure belt can also be used as the pressure rotator.
In such a case, the same effect as that of the present embodiment can be obtained.

It should be noted that the present invention is not limited to the present embodiment, and it is obvious that the present embodiment can be modified as appropriate within the scope of the technical idea of the present invention, other than suggested in the present embodiment. is there. In addition, the number, position, shape, and the like of the constituent members are not limited to the present embodiment, and the number, position, shape, and the like suitable for implementing the present invention can be achieved.
For example, the number of the plurality of separation claws 37A to 37E is not limited to the five described above, and the number of the electrodes 37a may not be the same as the number of the plurality of separation claws. Alternatively, the electrode 37a may be disposed at a position outside the paper region (width direction end). In this case, the degree of wear of the surface layer between the electrode 37a in the paper passing area and the electrode 37a outside the paper passing area can be detected. In this case, the electrode 37a may use a separation claw 37 having the same configuration as that of the separation claw 37 disposed in the sheet passing area. On the other hand, since it is not necessary to use for paper separation, another shape having no separation function such as the separation claw 37 may be used.

1 image forming apparatus (image forming apparatus main body),
20 fixing device,
21 fixing belt (fixing rotating body),
22 fixing auxiliary roller,
23 Heating roller,
25 heater (heating means),
31 Pressure roller (pressure rotating body),
37A-37E separation claw (separation member),
37a electrode (conduction part),
38 separator plate,
39 Tension spring (biasing member),
62 Resistance detection unit (detection means), P recording medium.

JP 2013-25060 A JP 2011-164446 A

Claims (6)

A fixing rotator for heating and fixing the toner image on the recording medium;
A pressure rotator that forms a nip portion to which a recording medium is conveyed by being pressed against the fixing rotator; and
A recording medium that is installed at a position apart in the width direction and abuts on the surface of the pressure rotator or the fixing rotator and is sent out from the nip portion is sent from the pressure rotator or the fixing rotator. A plurality of separating members to be separated;
With
The pressure rotator or the fixing rotator with which the plurality of separation members abut is formed of a surface layer made of a conductive material, and a lower layer of the surface layer is made of an insulating material,
Each of the plurality of separating members is provided with an electrode on a part or all of a part in contact with the pressure rotator or the fixing rotator,
A fixing device, comprising: a detecting unit configured to detect a resistance value between the electrodes in the plurality of separating members.   The degree of wear of the surface layer in the pressure rotator or the fixing rotator with which the plurality of separation members abut is determined according to the magnitude of the resistance value detected by the detecting means. The fixing device according to claim 1.   When the resistance value detected by the detection means exceeds a first predetermined value, a notification is given to prompt replacement of the pressure rotator or the fixing rotator with which the plurality of separation members abut, When the resistance value detected by the detection means exceeds a second predetermined value that is larger than the first predetermined value, the pressure rotating body or the fixing rotating body with which the plurality of separating members abut is exchanged. The fixing device according to claim 1, wherein a control flow in which the image forming operation is interrupted is executed.   The fixing device according to claim 3, wherein the control flow is executed before a series of image forming operations is started.   After the series of image forming operations is started and the series of image forming operations are performed after the number of prints related to the series of image forming operations reaches a predetermined number, the control flow is The fixing device according to claim 3, wherein the fixing device is executed.   An image forming apparatus comprising the fixing device according to claim 1.

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