JP2015090425A - Fixing apparatus and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing apparatus configured to prevent a slide-contact member or cleaning means from being worn and deteriorated with time, in cleaning a surface of the slide-contact member which comes into sliding contact with a fixing member, while preventing a part of a surface layer of the slide-contact member from being cut and falling during cleaning, and to provide an image forming apparatus.SOLUTION: In cleaning a surface of a slide-contact member 61 which rubs on a fixing belt 21 (fixing member), a cleaning member 62 (cleaning means) cleans the surface of the slide-contact member 61 in a non-contact manner from a position apart from the slide-contact member 61 with an AC voltage applied thereto.

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 a fixing device installed in an image forming apparatus such as a copying machine or a printer, a rubbing member is slidably contacted with the surface of the fixing member for the purpose of recovering the surface state of the fixing member such as a fixing roller over time. A technique for making the surface roughness of the fixing member uniform is widely known (see, for example, Patent Documents 1 and 2).

Specifically, in the fixing device, a pressure roller (pressure rotator) such as a pressure roller or a pressure belt is brought into pressure contact with a fixing member (fixing rotator) such as a fixing roller or a fixing belt. Is formed. Then, the recording medium is conveyed between the fixing member and the pressure member (the nip portion), and the toner image on the recording medium is fixed.
In such a fixing device, the surface of the fixing member is damaged over time due to the edge of the recording medium P (paper) passed through the nip portion, and therefore, the rubbing member is slid on the surface of the fixing member at a predetermined timing. In contact, the surface roughness of the fixing member is made uniform to restore the surface state. In order to maintain the function of the rubbing member over time, the cleaning member is brought into contact with the surface of the rubbing member to remove toner, paper dust, and the like attached to the rubbing member.

  In the conventional fixing device described above, the cleaning member is in direct contact with the rubbing member, so that the rubbing member itself or the cleaning member deteriorates over time, or the surface layer of the rubbing member during cleaning. There was a problem that a part of the machine was cut off and dropped.

  The present invention has been made to solve the above-described problems. When cleaning the surface of the sliding contact member that is in sliding contact with the fixing member, the sliding contact member and the cleaning means are less likely to wear and deteriorate over time. It is an object of the present invention to provide a fixing device and an image forming apparatus that are less likely to cause a problem that a part of a surface layer of a sliding contact member is scraped and dropped.

  According to a first aspect of the present invention, there is provided a fixing device that travels in a predetermined direction, heats and melts a toner image and fixes the toner image on the recording medium, and press-contacts the fixing member to the recording medium. The pressure member that forms a nip portion to which the toner is conveyed and the surface of the fixing member are configured so as to be able to come into contact with and separate from each other. And a cleaning means for cleaning the surface of the slidable contact member in a non-contact manner from a position separated from the slidable contact member in a state where an alternating voltage is applied.

  According to the present invention, when cleaning the surface of the slidable contact member slidably contacting the fixing member, the slidable contact member and the cleaning means are unlikely to wear and deteriorate over time, and a part of the surface layer of the slidable contact member is scraped during cleaning. Therefore, it is possible to provide a fixing device and an image forming apparatus that are less likely to fall.

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. It is the schematic which shows operation | movement with a sliding contact member and a cleaning means. It is the schematic which shows a sliding contact member and a cleaning means in the width direction. It is a figure which shows the waveform of the alternating voltage applied to a sliding contact member. It is a graph which shows the relationship between the separation distance of a sliding contact member and a duct, and the cleaning rate of a sliding contact member. It is the schematic which shows the sliding contact member and the cleaning means as a modification in the width direction.

Embodiment.
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 configuration and operation of the entire image forming apparatus 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, 6 is a conveyance roller, 7 is a paper feed unit that accommodates a recording medium P such as transfer paper, and 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 (image carriers) on which toner images of respective colors (yellow, magenta, cyan, and black) are formed, and 12 is on the photosensitive drums 11Y, 11M, 11C, and 11BK. A charging unit for charging, 13 is a developing unit for developing an electrostatic latent image formed on each photoconductor drum 11Y, 11M, 11C, and 11BK, and 14 is each photoconductor drum 11Y, 11M, 1 C, a primary transfer bias roller for transferring a toner image formed on 11BK over the recording medium P, 15 is a cleaning unit for collecting untransferred toner on the photosensitive drums 11Y, 11M, 11C, 11BK, Indicates.

  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 19 for transferring the toner image onto the recording medium P, a conveying belt 19 for conveying the recording medium P after the secondary transfer process toward the fixing device 20, and a toner image (unfixed image) on the recording medium P being fixed. A belt-type fixing device 80 is a double-sided conveyance unit that conveys the recording medium P that has been printed on the front side toward the image forming unit when performing double-sided printing.

Hereinafter, an operation during 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 charged surfaces of the 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).

  Laser light corresponding to the yellow component is irradiated on the surface of the first photosensitive drum 11Y from the left side of the drawing. At this time, the yellow component laser light is scanned in the rotation axis direction (main scanning 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 onto 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 paper, and an electrostatic latent image of the cyan component is formed. The black component laser beam is applied to the surface of the fourth photosensitive drum 11BK from the left side of the paper, and an electrostatic latent image of the black component is formed.

Thereafter, the surfaces of the photoconductive 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 transfer bias roller 14 is installed at each facing portion so as to contact 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 transfer bias roller 14 (in the primary transfer process). is there.).

Then, the surfaces of the photosensitive 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 a neutralization unit (not shown), and a series of image forming processes on 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 19. In the fixing device 20, the color image (toner) is fixed on the recording medium P at the nip portion between the fixing belt and the pressure roller.
Then, after the fixing process, the recording medium P is transported by the transport roller 6 and then discharged as an output image outside the apparatus main body 1 by the paper discharge roller, thereby completing a series of image forming processes.

  Note that when “double-sided printing mode” for performing printing on both sides (front side and back side) of the recording medium P is selected, the recording medium P that has completed the fixing process on the front side is The paper is not discharged as it is, but is guided to the double-sided conveyance unit 80 where the conveyance direction is reversed and then conveyed toward the position of the secondary transfer bias roller 18 again. Then, an image is formed on the back surface of the recording medium P by the image forming process similar to that described above at the position of the secondary transfer bias roller 18, and then the image is conveyed through a fixing process in the fixing device 20. After being conveyed by the roller 6, the paper is discharged as an output image outside the apparatus main body 1 by a paper discharge roller.

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 FIG.
As shown in FIG. 2, the fixing device 20 includes a fixing auxiliary roller 22, a heating roller 23, a fixing belt 21 as a fixing member (fixing rotator), a tension roller 24, and a pressurizing member (pressure rotator). The pressure roller 31, the temperature sensor 40, a sliding contact member 61 (sliding contact roller), a cleaning member 62 as a cleaning means, a guide plate 35, and the like.

  Here, the fixing belt 21 as a fixing member is an endless belt having a multilayer structure in which an elastic layer and a release layer are sequentially laminated on a base layer made of a resin material. 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 formed of PFA (tetrafluoroethylene barfluoroalkyl 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 21, the releasability (peelability) for the toner T (toner image) is ensured. The fixing belt 21 is stretched and supported by three roller members (a fixing auxiliary roller 22, a heating roller 23, and a tension roller 24), and travels in the direction of the arrow in FIG. The tension roller 24 is in contact with the outer peripheral surface of the fixing belt 21 and applies a predetermined tension to the fixing belt 21. By using the fixing belt 21 having a low heat capacity as the fixing member, the temperature rise characteristic of the apparatus is improved.

The fixing auxiliary roller 22 has an outer diameter in which an elastic layer 22b (having Asker C hardness of about 25 to 50) made of foamed silicone rubber having a layer thickness of about 15 mm is formed on a core metal 22a such as SUS304. It is a roller member of about 52 mm, and a nip portion is formed by pressure contact with a pressure roller 31 as a pressure member via a fixing belt 21. By forming the elastic layer 22b from a foamed material, the nip width (nip amount) at the nip portion 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 has a shaft connected to a drive motor (not shown), and is driven to rotate clockwise in FIG.
In the present embodiment, foamed silicone rubber is used as the material of the elastic layer 22b. However, fluorine rubber, silicone rubber, or the like can be used as the material of the elastic layer 22b.

The heating roller 23 is a hollow roller member having an outer diameter of about 38 mm made of a metal material having high thermal conductivity such as aluminum, and a heater 25 (heat source) as a heating means is fixed inside the cylindrical body. It is installed. The surface of the heating roller 23 is anodized to improve the corrosion resistance.
The heater 25 of the heating roller 23 is a halogen heater, and both ends thereof are fixed to a side plate (not shown) of the fixing device 20. Then, the heating roller 23 is heated by the radiant heat from the heater 25 whose output is controlled by the power supply unit 66 (AC power supply) of the apparatus main body 1, and further on the recording medium P from the surface of the fixing belt 21 heated by the heating roller 23. Heat is applied to the toner image T. The output control of the heater 25 (heating means) is performed based on the detection result of the belt surface temperature by the temperature sensor 40 (thermopile) that faces the surface of the fixing belt 21 in a non-contact manner. Specifically, the AC voltage is applied from the power supply unit 66 to the heater 25 for the energization time determined based on the detection result of the temperature sensor 40. 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 as a pressure member has an outer diameter of about 50 mm, and mainly includes a cored bar 32 and an elastic layer 33 (layer thickness) formed on the outer peripheral surface of the cored bar 32 via an adhesive layer. Is about 3 mm). The elastic layer 33 of the pressure roller 31 is formed of a solid rubber material such as fluorine rubber or silicone rubber. A thin release layer made of PFA or the like can be provided on the surface layer of the elastic layer 33. In the present embodiment, a heater for heating the pressure roller 31 can be installed inside the pressure roller 31.

Referring to FIG. 2, guide plates 35 for guiding the conveyance of the recording medium P are respectively provided at the entrance side and the exit side of the contact portion (nip portion) between the fixing belt 21 and the pressure roller 31. It is arranged. The guide plate 35 is fixed to the side plate of the fixing device 20.
Although not shown, a separation plate is disposed at a position facing the outer peripheral surface of the fixing belt 21 and in the vicinity of the exit side of the nip portion. In addition, a separation plate is disposed at a position facing the outer peripheral surface of the pressure roller 31 and in the vicinity of the outlet side of the nip portion. These separation plates cause a problem that the recording medium P after the fixing process is wound around the fixing belt 21 along the travel (rotation) of the fixing belt 21, and the recording medium P after the fixing process is rotated by the pressure roller 31. The trouble which winds around the pressure roller 31 along is suppressed.
The fixing device 20 according to the present exemplary embodiment cleans the surface of the sliding contact member 61 and the sliding contact member 61 that are in sliding contact with the fixing belt 21 at a predetermined timing to make the surface roughness of the fixing belt 21 uniform. A cleaning member 62 as a cleaning means is also installed, which will be described in detail later.

Hereinafter, the operation of the fixing device 20 during normal paper feeding will be described.
When the power switch of the apparatus main body 1 is turned on, an AC voltage is applied (powered) from the power supply unit 66 to the heater 25, and the fixing auxiliary roller 22 is rotationally driven by a drive motor (not shown). The fixing belt 21, the heating roller 23, and the pressure roller 31 rotate (follow) in the direction of the arrow in FIG.
Thereafter, the recording medium P is fed from the paper supply unit 7 and the toners of the respective colors on the photosensitive drums 11Y, 11M, 11C, and 11BK are carried on the recording medium P as unfixed images. 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 out from the nip portion by the rotating fixing belt 21 and the pressure roller 31 is conveyed in the direction of the arrow Y11.

Hereinafter, a characteristic configuration and operation of the fixing device 20 in the present embodiment will be described.
2 to 4, the fixing device 20 according to the present embodiment is provided with a sliding contact member 61 (sliding contact roller) and a cleaning member 62 as a cleaning unit.
The slidable contact member 61 is configured to be able to contact and separate from the surface of the fixing belt 21 (fixing member) by a contact / separation / drive mechanism 68. As the contact / separation / drive mechanism 68, the slidable contact member 61 is urged to the separated position (the position shown in FIGS. 2 and 3A), or the urging force of the urging member is resisted. The sliding contact member 61 may be configured by a cam that pushes the fixing belt 21 toward the fixing belt 21 or a motor that rotationally drives the cam. In the present embodiment, the contact / separation / drive mechanism 68 is provided with a drive motor that rotationally drives the sliding contact member 61 in the clockwise direction of FIG.

The sliding contact member 61 is brought into sliding contact with the fixing belt 21 (fixing member) at a predetermined timing to make the surface roughness of the fixing belt 21 uniform. Specifically, the sliding contact member 61 is a roller in which a surface layer (sliding contact layer) in which abrasive grains are dispersed in a binder resin (having conductivity) is formed on a conductive core metal. It is a member, and fine irregularities are formed on its surface.
Each time a predetermined number of sheets (for example, 1000 sheets) is passed, the contact / separation / drive mechanism 68 is operated at the time of non-image formation after the image forming process is completed, and the separation position (FIG. 2, FIG. 3 (B)) is moved to the contact position (position of FIG. 3 (A)). Then, while the fixing belt 21 is traveling in the arrow direction, the contact / separation / drive mechanism 68 is rotationally driven for a predetermined time so that the sliding contact member 61 is slidably contacted with the fixing belt 21 in the counter direction.
Accordingly, even if the surface of the fixing belt 21 is damaged over time due to the edge of the recording medium P (paper) passed through the nip portion, the portion is uniformly roughened by the sliding contact member 61 together with the other portions. (It is made uniform so as to be in a certain surface roughness range), and the surface state of the fixing belt 21 is restored to be close to the initial state. Therefore, the occurrence of fixed image defects such as uneven gloss due to surface deterioration of the fixing belt 21 can be reliably reduced.

Here, in the present embodiment, in order to stably maintain the function of the sliding contact member 61 as described above over time, a cleaning member 62 (cleaning means) that cleans the surface of the sliding contact member 61 is installed. ing. In other words, the cleaning member 62 is for removing the toner, paper powder, and abrasives adhering to the sliding contact member 61 by sliding contact with the fixing belt 21 without clogging the surface of the sliding contact member 61. It is.
The cleaning member 62 in this embodiment cleans the surface of the sliding contact member 61 in a non-contact manner from a position away from the sliding contact member 61 in a state where an AC voltage (AC voltage) is applied from the AC power supply 67. Is configured to do.

Specifically, referring to FIGS. 2 to 4, the cleaning member 62 sucks air from the vicinity of the surface of the sliding contact member 61 via the duct 63 installed at a position facing the sliding contact member 61 or the duct 63. And a suction fan 64 as a suction device.
The duct 63 is formed of a resin material or the like, and is opposed to the entire area in the width direction (the direction perpendicular to the paper surface in FIGS. 2 and 3 and the left-right direction in FIG. 4) with respect to the sliding contact member 61. It is arranged. The duct 63 is formed so that the opening on one end side faces the sliding contact member 61 (the sliding contact member 61 in the separated position), and the opening on the other end side is connected to the suction fan 64. The portions excluding these openings are covered with wall surfaces so that air does not leak.

In this embodiment, the sliding contact member 61 is cleaned by the cleaning member 62 when the sliding contact member 61 is separated from the fixing belt 21.
Specifically, as shown in FIG. 3A, the suction fan 64 is turned off when the sliding contact member 61 is in contact with the fixing belt 21 (during the surface roughness uniforming operation). Then, as shown in FIG. 3B, the sliding contact member 61 is rotated by the contact / separation / drive mechanism 68 immediately after the surface roughness uniforming operation is finished and the sliding contact member 61 is separated from the fixing belt 21. While driving, the suction fan 64 is turned on for a predetermined time, and the sliding contact member 61 is evenly cleaned in the circumferential direction.

  As described above, in this embodiment, the cleaning member 62 is configured so that the sliding contact member 61 can be cleaned without contact with the sliding contact member 61 without contacting the sliding contact member 61. The trouble that the contact member 61 itself and the cleaning member 62 wear and deteriorate, and the trouble that a part of the surface layer of the sliding contact member 61 is scraped and dropped during cleaning can be prevented. In particular, in this embodiment, an AC voltage is applied to the sliding contact member 61 (in this embodiment, it is applied to the cored bar), so that toner, paper powder, or the like attached to the sliding contact member 61 is attached. The kimono is less likely to be electrostatically attracted to the sliding contact member 61, and the cleaning efficiency of the cleaning member 62 can be increased.

A specific operation flow during the above-described cleaning will be described in detail.
First, when the slidable contact member 61 (the slidable contact member 61 for which the surface roughness uniformizing operation has been completed) in sliding contact with the fixing belt 21 is moved to the separated position, the separated position is set as a home position (not shown). The home position is detected by the detection sensor. Thereafter, a predetermined AC voltage is applied from the AC power source 67 to the sliding contact member 61, and the rotation driving of the sliding contact member 61 by the contact / separation / drive mechanism 68 is started, and suction (cleaning) by the suction fan 64 is started. Is done. Then, after the suction (cleaning) for a certain time by the suction fan 64 is finished, the suction by the suction fan 64 is stopped, the application of the AC voltage from the AC power supply 67 is stopped, and the rotation drive by the contact / separation / drive mechanism 68 is performed. Stopped and a series of cleaning operations by the cleaning member 62 is completed.

Here, with reference to FIG. 5, in this Embodiment, the alternating voltage (applied from alternating current power supply 67) applied to the sliding contact member 61 at the time of the cleaning by the cleaning member 62 (cleaning means) is as follows. The waveform is a rectangular wave, and is formed so that the ratio between the application time t1 having a positive polarity and the application time t2 having a negative polarity is different.
Specifically, in the waveform of the AC voltage, the ratio of the application time t1 having a positive polarity to the application time t0 (= t1 + t2) for one period of the rectangular wave is X% (= t1 / t0 × 100), and the rectangular wave 1 When the ratio of the application time t2 having negative polarity to the application time t0 for the period is Y% (= t2 / t0 × 100),
X> Y ≧ 5%
Is set to hold. Specifically, in this embodiment, X is set to 92% and Y is set to 8%.
In this way, by applying rectangular wave AC voltages having different ratios of positive and negative polarity application times to the sliding contact member 61, rectangular wave AC voltages having the same positive and negative polarity application time ratios are applied to the sliding contact member 61. In comparison with the case where a sine wave AC voltage is applied to the sliding contact member 61, it is possible to make leakage less likely to occur during voltage application. Therefore, the magnitude of the AC voltage to be applied can be set relatively large, and the cleaning efficiency by the cleaning member 62 can be increased.
Note that the minimum application time ratio is set to 5% or more in order to surely form rectangular waves with different positive and negative application time ratios.

In the present embodiment, referring to FIG. 4, the separation distance X between the duct 63 and the sliding contact member 61 at the time of cleaning by the cleaning member 62 is set to 10 mm or less in order to increase the cleaning efficiency by the cleaning member 62. Has been.
As shown in FIG. 6, when the separation distance X between the sliding contact member 61 and the duct 63 is varied and the change in the cleaning rate in the sliding contact member 61 is experimentally confirmed, the suction force of the suction fan 64 is determined. This is because the cleaning rate tends to be extremely lowered when the separation distance X exceeds 10 mm.
The cleaning rate A (%) in the sliding contact member 61 is the polishing powder weight in the surface layer of the sliding contact member 61 after cleaning, where the weight of polishing powder in the surface layer of the sliding contact member 61 before cleaning is B0 (mg). When the weight is B1 (mg),
A = (B0−B1) / B0 × 100
Is a value obtained by the following formula.

In the present embodiment, the duct 63 is disposed so as to face the sliding contact member 61 in the entire width direction.
On the other hand, as shown in FIG. 7, the duct 63 (cleaning member 62) is moved together with the suction fan 64 from the one end side in the width direction to the other end side in the width direction with respect to the sliding contact member 61 by the moving mechanism 70. It can also be configured so that the opposing position can be moved. In the example of FIG. 7, the cleaning member 62 is moved from the home position to the other end side while the suction fan 64 is turned on at the time of cleaning, with one end in the width direction (the left side in FIG. 7) as the home position. It is reciprocated so as to return to the home position (the movement route indicated by the one-dot chain line arrow).
In such a case, the cleaning member 62 itself can be reduced in size.

  As described above, in the present embodiment, when the surface of the sliding contact member 61 that is in sliding contact with the fixing belt 21 (fixing member) is cleaned, it is separated from the sliding contact member 61 in a state where an AC voltage is applied. Since the cleaning member 62 (cleaning means) for cleaning the surface of the slidable contact member 61 in a non-contact manner is installed from the position where the slidable member has been removed, the slidable contact member 61 and the cleaning member 62 are less likely to wear and deteriorate over time. It is possible to make it difficult to cause a problem that a part of the surface layer of the member 61 is scraped and dropped.

In this embodiment, the pressure roller 31 is used as the pressure member, but a pressure belt or a pressure pad may be used as the pressure member. In this embodiment, the fixing belt 21 is used as the fixing member. However, a fixing roller or a fixing film may be used as the fixing member.
Further, in this embodiment, the heater 25 is used as a heating unit for heating the fixing member. However, an exciting coil (a heating unit corresponding to an electromagnetic induction heating type fixing device) is used as a heating unit for heating the fixing member. It can also be used, and a resistance heating element can be used as a heating means.
In those cases, the same effects as those 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.

  In this application, the “sliding contact member” is a member for contacting the fixing member and uniforming the surface roughness regardless of the contact state with the fixing member. It is defined as a broad concept including members such as the disclosed rubbing member, roughing roller, and polishing member.

1 image forming apparatus (image forming apparatus main body),
20 fixing device,
21 fixing belt (fixing member),
22 fixing auxiliary roller,
23 Heating roller,
25 heater (heating means),
31 Pressure roller (pressure member),
40 temperature sensor,
61 sliding contact member,
62 Cleaning member (cleaning means),
63 Duct,
64 Suction fan (suction device),
67 AC power supply, 68 Contact / separation mechanism.

JP 2008-40365 A JP 2007-199596 A

Claims (10)

A fixing member that travels in a predetermined direction and heats and melts the toner image to fix it on the recording medium;
A pressure member that forms a nip portion by which the recording medium is conveyed by being pressed against the fixing member;
A slidable contact member configured to be able to come into contact with and separate from the surface of the fixing member, and to slidably contact the fixing member at a predetermined timing to equalize the surface roughness of the fixing member;
Cleaning means for cleaning the surface of the sliding contact member in a non-contact manner from a position spaced from the sliding contact member in a state where an alternating voltage is applied;
A fixing device comprising:   The AC voltage applied to the sliding contact member at the time of cleaning by the cleaning means is such that the waveform thereof is a rectangular wave, and the ratio between the application time for positive polarity and the application time for negative polarity is different. The fixing device according to claim 1. In the AC voltage waveform, the ratio of the application time having a positive polarity to the application time for one cycle of the rectangular wave is X%, and the ratio of the application time having a negative polarity to the application time for one cycle of the rectangular wave is Y. %
X> Y ≧ 5%
The fixing device according to claim 2, wherein the following relationship is established. The cleaning means includes
A duct installed at a position facing the sliding contact member;
A suction device for sucking air from the vicinity of the surface of the sliding contact member via the duct;
The fixing device according to claim 1, wherein the fixing device is provided.   The fixing device according to claim 4, wherein a separation distance between the duct and the sliding contact member during cleaning by the cleaning unit is set to 10 mm or less.   The fixing device according to claim 4, wherein the duct is disposed so as to face the entire area in the width direction with respect to the sliding contact member.   5. The duct according to claim 4, wherein the duct is configured to be movable with a moving mechanism so that the opposing position is variable from the one end side in the width direction to the other end side in the width direction with respect to the sliding contact member. Item 6. The fixing device according to Item 5.   The fixing device according to claim 1, wherein the cleaning unit cleans the sliding contact member when the sliding contact member is separated from the fixing member.   The fixing device according to claim 1, wherein the sliding contact member includes a surface layer in which abrasive grains are dispersed in a binder resin.   An image forming apparatus comprising the fixing device according to claim 1.

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