JP2020085933A - Fixing device and image forming apparatus - Google Patents

Abstract

To efficiently and sufficiently cool a cleaning member cleaning a surface of a fixing rotating body or a pressure rotating body when the cleaning member moves to a separation position.SOLUTION: There is installed a cleaning roller 35 (cleaning member) configured to be movable between a contact position where it is in contact with a surface of a pressure roller 31 (pressure rotating body) and a separation position where it is separated from the surface through the operation of moving mechanisms 38, 51 (moving means). There is also installed a cooling roller 36 (cooling member) that is in contact with the cleaning roller 35 moved to the separation position. The heat capacity of the cooling roller 36 is set to be larger than the heat capacity of the cleaning roller 35.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 composite machine thereof, and a fixing device installed therein.

2. Description of the Related Art Conventionally, in a fixing device in an image forming apparatus such as a copying machine or a printer, a technique of installing a cleaning member so as to contact the surface of a fixing rotary member or a pressure rotary member and cleaning the surface is widely known. (For example, refer to Patent Document 1).

More specifically, in the fixing device disclosed in Japanese Patent Laid-Open No. 2004-135, the pressure rotator (pressure roller) is in pressure contact with the fixing rotator (fixing sleeve), and a nip portion (fixing nip) for transporting the sheet is formed. ing. Then, the toner image on the sheet conveyed to the nip portion is fixed on the sheet by the heat received from the fixing rotating member and the pressure at the nip portion.
Further, in Patent Document 1, the fixing device includes a cleaning roller (cleaning member) that moves so as to be able to come into contact with and separate from the pressure rotating body, and a second cleaning roller that comes into contact with the cleaning roller that has moved to the separated position. is set up. Then, the cleaning roller cleans the surface of the pressure rotating body at the position where it abuts against the pressure rotating body, and is cleaned by the second cleaning roller at the position separated from the pressure rotating body. Further, when the cleaning roller is separated from the pressure rotating body, the cleaning roller is cooled to some extent.

In the conventional fixing device, when the cleaning member that comes in contact with the surface of the fixing rotator or the pressure rotator and cleans the adhered substances such as toner and paper dust reaches a high temperature to a certain degree, There has been a problem that the adhered matter that has moved from the surface of the rotator to the surface of the cleaning member moves to the surface of the fixing rotator or the pressure rotator again and stains the surface.
On the other hand, in the fixing device disclosed in Patent Document 1, the cleaning member is cooled to some extent when the cleaning member is separated from the pressurizing rotary member, but the cooling efficiency is low. It was not possible to sufficiently prevent such problems.

The present invention has been made to solve the above-mentioned problems, and when the cleaning member that cleans the surface of the fixing rotator or the pressure rotator is moving to the separated position, the cleaning member is efficient. Another object of the present invention is to provide a fixing device and an image forming apparatus that are sufficiently cooled.

A fixing device according to the present invention includes a fixing rotator that heats a toner image to fix it on the surface of a sheet, a pressure rotator that forms a nip portion where a sheet is conveyed by being pressed against the fixing rotator, and a moving member. By the operation of the means, a cleaning member configured to be movable between a contact position in contact with the surface of the fixing rotary member or the pressure rotary member and a separated position separated from the surface, and the separated position to the separated position. A cooling member that contacts the moved cleaning member, and the heat capacity of the cooling member is set to be larger than the heat capacity of the cleaning member.

According to the present invention, when the cleaning member for cleaning the surface of the fixing rotator or the pressure rotator is moved to the separated position, the cleaning member is efficiently and sufficiently cooled, and the fixing device and the image. A forming device can be provided.

1 is an overall configuration diagram showing an image forming apparatus according to an embodiment of the present invention. It is a block diagram which shows a fixing device. FIG. 6 is a diagram showing a state in which the cleaning roller has moved to a separated position and is in contact with the cooling roller. FIG. 5 is a schematic view showing a state in which the cleaning roller is in contact with the pressure roller in the width direction. 6 is a flowchart showing contact/separation control of a cleaning roller. FIG. 8 is an enlarged view showing a state where a cleaning roller is in contact with a pressure roller as a first modification. FIG. 9 is an enlarged view showing a state in which a cleaning roller is in contact with a pressure roller as a second modification. 9A and 9B are an enlarged view showing a state where a cleaning roller is in contact with a pressure roller and a enlarged view showing a state where a cleaning roller is in contact with a cooling member, as a third modification. FIG. 11 is a configuration diagram showing a fixing device as a fourth modification. FIG. 13 is a configuration diagram showing a fixing device as a fifth modification.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and the duplicate description thereof will be appropriately simplified or omitted.

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 a laser beam based on input image information, 3 is a document transport unit that transports a document D to a document reading unit 4, and 4 is a document transport unit. The document reading unit that reads the image information of the document D is shown.
Further, 7 is a paper feed unit for accommodating sheets P such as paper, 9 is a registration roller (timing roller) for adjusting the conveyance timing of the sheet P, and 11Y, 11M, 11C and 11BK are respective colors (yellow, magenta, cyan, 2 shows a photoconductor drum on which a black toner image is formed.

Further, 12 is a charging unit that charges the surface of each photoconductor drum 11Y, 11M, 11C, 11BK, and 13 is a development that develops the electrostatic latent image formed on the surface of each photoconductor drum 11Y, 11M, 11C, 11BK. Reference numeral 14 denotes a primary transfer bias roller for transferring the toner image formed on the surface of each of the photoconductor drums 11Y, 11M, 11C and 11BK so as to be superimposed on the surface of the sheet P, and 15 denotes each of the photoconductor drums 11Y, 11M and 11C. , A cleaning unit for collecting the untransferred toner remaining on the surface of 11BK.
Further, 16 is an intermediate transfer belt cleaning unit for cleaning the intermediate transfer belt 17, 17 is an intermediate transfer belt on which toner images of a plurality of colors are superimposed and transferred, and 18 is a color toner image on the intermediate transfer belt 17 on the sheet P. A secondary transfer bias roller for transferring, and a fixing device 20 for fixing the toner image (unfixed image) on the sheet P.

Hereinafter, the operation of the image forming apparatus during normal color image formation will be described.
First, the document D is transported from the document table 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 the light emitted from the illumination lamp. Then, the light reflected by the document D is imaged on the color sensor through the mirror group and the lens. The color image information of the document D is read by the color sensor for each color separation light of RGB (red, green, blue), and then converted into an electrical image signal. Further, a color conversion process, a color correction process, a spatial frequency correction process, and the like are performed in the image processing unit based on the RGB color-separated 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. Then, the writing unit 2 emits laser light (exposure light) based on the image information of each color toward the surfaces of the corresponding photoconductor drums 11Y, 11M, 11C, and 11BK.

On the other hand, the four photoconductor drums 11Y, 11M, 11C, and 11BK are rotating counterclockwise in FIG. Then, first, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK are uniformly charged at the portion facing the charging section 12 (a charging step). In this way, a charging potential is formed on the surfaces of the photoconductor drums 11Y, 11M, 11C, 11BK.
After that, the surfaces of the charged photoconductor drums 11Y, 11M, 11C, and 11BK reach the irradiation positions of the respective laser lights (the exposure process). Specifically, in the writing unit 2, laser light corresponding to image signals is emitted from each of the four light sources corresponding to each color. Each laser beam will pass through a different optical path for each of the yellow, magenta, cyan, and black color components.

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

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

After that, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK on which the electrostatic latent images of the respective colors are formed reach the positions facing the developing unit 13, respectively. Then, the toners of the respective colors are supplied from the developing units 13 to the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK, and the latent images formed on the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK are developed. (This is a developing step.).
After that, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK after the developing process reach the portions facing the intermediate transfer belt 17, respectively. Here, the primary transfer bias roller 14 is installed at each of the facing portions so as to come into contact with the inner peripheral surface of the intermediate transfer belt 17. Then, at the position of the primary transfer bias roller 14, the toner images of the respective colors formed on the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK are sequentially superimposed and transferred onto the intermediate transfer belt 17 (primary transfer). It is a transfer process.).

Then, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK after the transfer process reach the positions facing the cleaning unit 15, respectively. Then, the cleaning unit 15 collects the untransferred toner remaining on the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK (cleaning step).
After that, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK pass through the static eliminator, and the series of image forming processes on the photoconductor drums 11Y, 11M, 11C, and 11BK are completed.

On the other hand, the intermediate transfer belt 17 on which the toners of the respective colors on the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK are transferred (carried) in an overlapping manner, runs in the clockwise direction in FIG. Reach the opposite position. Then, the color toner image carried on the intermediate transfer belt 17 is transferred onto the sheet P at a position facing the secondary transfer bias roller 18 (secondary transfer step).
Then, the surface of the intermediate transfer belt 17 reaches the position of the intermediate transfer belt cleaning unit 16. Then, the untransferred toner attached on the intermediate transfer belt 17 is collected by the intermediate transfer belt cleaning unit 16, and a series of transfer processes on the intermediate transfer belt 17 is completed.

Here, the sheet P conveyed between the intermediate transfer belt 17 and the secondary transfer bias roller 18 (which is the secondary transfer nip) is conveyed from the paper feeding unit 7 via the registration rollers 9 and the like. It is a thing.
More specifically, the sheet P fed by the sheet feeding roller 8 from the sheet feeding unit 7 that stores the sheet P is guided to the registration roller 9 after passing through the conveyance path. The sheet P reaching the registration roller 9 is conveyed toward the secondary transfer nip at the same timing.

Then, the sheet P on which the full-color image is transferred is guided to the fixing device 20 by the conveyor belt. In the fixing device 20, the color image (toner image) is fixed on the surface of the sheet P at the nip portion (fixing nip) between the fixing roller and the pressure roller (a fixing step).
Then, the sheet P after the fixing process is discharged as an output image to the outside of the apparatus main body 1 by the paper discharging 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 FIG. 2, the fixing device 20 includes a fixing roller 21 as a fixing rotary member, a heater 25 as a heating unit, a pressure roller 31 as a pressing rotary member, a cleaning roller 35 as a cleaning member, and a cooling member. The cooling roller 36, the temperature sensors 40, 41 and 45, the arm member 38 (moving means), and the like.

Here, the fixing roller 21 (fixing member) as a fixing rotating body is a roller member having a multilayer structure in which an elastic layer and a release layer are sequentially laminated on a cored bar 21a made of a metal material such as stainless steel. In addition, the nip portion (fixing nip) is formed by being brought into pressure contact with the pressure roller 31 as a pressure rotator.
The elastic layer of the fixing roller 21 is made of an elastic material such as fluororubber, silicone rubber, and expandable silicone rubber. The release layer of the fixing roller 21 is formed of PFA (tetrafluoroethylene bar fluoroalkyl vinyl ether copolymer resin) or the like. By providing the releasing layer on the surface layer of the fixing roller 21, the releasing property (releasing property) for the toner T (toner image) is secured. The fixing roller 21 is rotationally driven in the clockwise direction in FIG. 2 by the drive mechanism.

A heater 25 (heat source) as a heating unit is fixedly provided inside the fixing roller 21 (core metal 21a) having a hollow structure.
The heater 25 (heating means) is a halogen heater, and both ends thereof are fixed to the side plates of the fixing device 20. Then, with the main switch of the image forming apparatus main body 1 turned on, electric power is supplied from the power supply unit to the heater 25. Then, the fixing roller 21 is heated by radiant heat from the heater 25 whose output is controlled by the controller 50, and heat is applied to the toner image T on the sheet P from the surface of the fixing roller 21 which is further heated.
The output control of the heater 25 is performed based on the detection result of the roller surface temperature by the temperature sensor 40 facing the surface of the fixing roller 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). With such output control of the heater 25, the temperature of the fixing roller 21 (fixing temperature) can be adjusted and controlled to a desired temperature (target control temperature).

The pressure roller 31 (pressure member) as a pressure rotating body is mainly composed of a cored bar 32 and an elastic layer 33 formed on the outer peripheral surface of the cored bar 32 with an adhesive layer interposed therebetween. The elastic layer 33 of the pressure roller 31 is made of a material such as foamable silicone rubber, fluororubber, or silicone rubber. A thin release layer made of PFA or the like may be provided on the surface of the elastic layer 33.
Then, the pressure roller 31 is pressed against the fixing roller 21 by the pressure mechanism. Thus, a desired nip portion is formed between the pressure roller 31 and the fixing roller 21.
The pressure roller 31 is driven to rotate counterclockwise in FIG. 2 in accordance with the rotation of the fixing roller 21.

The fixing device 20 according to the present exemplary embodiment includes a cleaning roller 35 that removes (cleans) adhering substances such as toner and paper dust that adhere to the surface of the pressure roller 31, and a cleaning roller for the pressure roller 31. There are also provided moving mechanisms 38 and 51 (moving means) for contacting and separating 35, a cooling roller 36 for cooling the cleaning roller 35, a temperature sensor 45 for detecting the temperature of the cleaning roller 35, and the like. More on this later.

The fixing device 20 configured as described above operates as follows.
When the main switch of the apparatus body 1 is turned on, an AC voltage is applied (powered) to the heater 25.
Then, when a print command (print request) is input, the drive mechanism starts the rotational driving of the fixing roller 21 in the clockwise direction and the driven rotation of the pressure roller 31 in the counterclockwise direction. After that, the sheet P is fed from the sheet feeding unit 7, and the toner image on the intermediate transfer belt 17 is carried on the sheet P as an unfixed image at the position of the secondary transfer bias roller 18. The sheet P carrying the unfixed image T (toner image) is conveyed in the direction of the arrow in FIG. 2 and is fed to the nip portion between the fixing roller 21 and the pressure roller 31 in the pressure contact state. Then, the toner image T is fixed on the surface of the sheet P by the heating by the fixing roller 21 and the pressing force of the fixing roller 21 and the pressure roller 31. Then, the sheet P after the fixing process is sent from the nip portion in the direction of the arrow by the rotating fixing roller 21 and pressure roller 31.

Hereinafter, the characteristic configuration and operation of the fixing device 20 (image forming apparatus 1) in the present embodiment will be described in detail.
As described above with reference to FIG. 2 and the like, the fixing device 20 includes a fixing roller 21 as a fixing rotating member that heats and fixes the toner image on the surface of the sheet P, or by pressing the fixing roller 21. A pressure roller 31 is installed as a pressure rotating body that forms a nip portion where the sheet P is conveyed.
The fixing device 20 according to the present embodiment is provided with a cleaning roller 35 as a cleaning member and a cooling roller 36 as a cooling member.

With reference to FIGS. 2 and 3, the cleaning roller 35 as a cleaning member comes into contact with the surface of the pressure roller 31 (pressure rotating body) by the operation of moving mechanisms 38 and 51 as moving means. (The position indicated by the solid line in FIG. 2) and the separated position (the position indicated by the broken line in FIG. 2 and the position indicated in FIG. 3) away from the surface of the pressure roller 31. It is configured to be movable.

Specifically, in the present embodiment, the cleaning roller is a roller member made of a metal material and is rotatably held by the arm member 38. The cleaning roller 35 is for contacting with the surface of the pressure roller 31 to remove adhered matters such as toner and paper dust adhered to the surface of the pressure roller 31 for cleaning. By cleaning the surface of the pressure roller 31, not only the pressure roller 31 itself is directly cleaned but also the fixing roller 21 is indirectly cleaned, and the sheet P passing through the fixing nip is not cleaned. Problems such as being contaminated with toner or paper dust and losing part of the image can be reduced.

Here, the arm member 38 is held in the housing of the fixing device 20 so as to be swingable in the directions of the double-headed arrow in FIG. 2 around the support shaft 38a. A forward/reverse bidirectional rotation type drive motor 51 is connected to the support shaft 38a of the arm member 38 via a gear train.
Then, when the drive motor 51 is driven in the forward direction by the control of the control unit 50, the arm member 38 rotates in the counterclockwise direction in FIG. 2 about the support shaft 38a, and as shown in FIG. The roller 35 comes into contact with the pressure roller 31 (moves to the contact position). On the other hand, when the drive motor 51 is driven in the reverse direction under the control of the control unit 50, the arm member 38 rotates in the clockwise direction in FIG. 2 about the support shaft 38a, and as shown in FIG. Then, the cleaning roller 35 is separated from the pressure roller 31 (moves to the separated position).
That is, the drive motor 51 and the arm member 38 function as a moving unit (moving mechanism) that moves the cleaning roller 35.

Further, referring to FIGS. 2 and 3, as shown in FIG. 3, the cooling roller 36 as a cooling member contacts the cleaning roller 35 (cleaning member) that has moved to the separated position to cool the cleaning roller 35. To do.
More specifically, in the present embodiment, the cooling roller 36 is a roller member made of a metal material, and is rotatably held in the casing of the fixing device 20. Further, in the present embodiment, the cooling roller 36 is connected to the motor 52, and is configured to be rotatable counterclockwise in FIG. 3 under the control of the motor 52 by the control unit 50.
Then, as shown in FIG. 3, when the cleaning roller 35 is separated from the pressure roller 31 at a predetermined timing and moves to the separated position, the cleaning roller 35 contacts the cooling roller 36. Then, as the motor 52 is driven to rotate the cooling roller 36 in the counterclockwise direction, the cleaning roller 35 is cooled by the cooling roller 36 while the cleaning roller 35 is rotated in the clockwise direction. ..

Here, in the present embodiment, the cleaning roller 35 is not always in contact with the pressure roller 31, but the cleaning roller 35 is appropriately separated from the pressure roller 31. This is because the cleaning roller 35 is always brought into contact with the pressure roller 31, and heat is directly received from the pressure roller 31 so that the temperature of the cleaning roller 35 is high to some extent (hereinafter, referred to as “melting temperature” as appropriate). When it reaches the pressure roller 31, the adhered substances such as toner and paper dust that have moved from the surface of the pressure roller 31 to the surface of the cleaning roller 35 again move to the surface of the pressure roller 31 (reverse movement), This is because the surface of the pressure roller 31 is soiled.

Therefore, it is necessary to quickly move the cleaning roller 35 to the separated position before the cleaning roller 35 reaches the “melting temperature” to prevent the adhered matter from moving from the cleaning roller 35 to the pressure roller 31.
Then, after the cleaning roller 35 is cooled at the separated position without directly receiving the heat of the pressure roller 31 and becomes equal to or lower than the “melting temperature”, the cleaning roller 35 is brought into contact with the pressure roller 31 again and the original state. Cleaning should be restarted. However, when the cleaning roller 35 is moved to the separated position to cool the cleaning roller 35 by natural heat dissipation or to bring the cleaning roller 35 into contact with an object having a small heat capacity to cool the cleaning roller 35, the temperature of the cleaning roller 35 becomes equal to or lower than the “melting temperature”. Therefore, the time (cooling time) until the cleaning roller 35 is brought into contact with the pressure roller 31 again and the original cleaning is restarted becomes long. Then, in the meantime, as described above, a problem occurs due to the adhered matter adhering to the pressure roller 31. Therefore, when the cleaning roller 35 is moved to the separated position, it is necessary to actively and efficiently cool the cleaning roller 35 sufficiently.

Therefore, in this embodiment, the heat capacity of the cooling roller 36 (cooling member) is set to be larger than that of the cleaning roller 35 (cleaning member).
Specifically, in the present embodiment, the cooling roller 36 is formed of a material having a sufficiently large heat capacity as compared with the cleaning roller 35, and is formed so as to have a sufficiently large volume. Particularly, in the present embodiment, the cooling roller 36 is set to have a volume four times or more that of the cleaning roller 35.
As a result, heat transfer from the cleaning roller 35 to the cooling roller 36 is promoted, and the cleaning roller 35 is positively and efficiently and sufficiently cooled in a short time.

Further, in the present embodiment, the thermal conductivity of the cooling roller 36 (cooling member) is set to be higher than the thermal conductivity of the cleaning roller 35 (cleaning member).
Specifically, in this embodiment, the cooling roller 36 is made of copper or a copper alloy, which is a material having a very high thermal conductivity. The cleaning roller 35 is formed of stainless steel or the like, which is a metal material having a lower thermal conductivity than copper or copper alloy.
As a result, heat transfer from the cleaning roller 35 to the cooling roller 36 is promoted, and the cleaning roller 35 is positively and efficiently and sufficiently cooled in a short time.
Although the cleaning roller 35 is made of a metal material in the present embodiment, the cleaning roller 35 may be made of a heat resistant resin material having a low thermal conductivity.

Further, in the present embodiment, it is preferable to enhance the heat dissipation of the cooling roller 36 and the cleaning roller 35.
Specifically, in order to promote positive heat radiation between the cooling roller 36 and the cleaning roller 35 that has moved to the separated position, an air flow can be formed by a fan or the like in the vicinity thereof. Further, the surface area of the cooling roller 36 can be set sufficiently large.
As a result, the cleaning roller 35 is positively and efficiently cooled sufficiently in a short time.

Here, as described above, the cleaning roller 35 positioned at the contact position directly receives heat from the pressure roller 31 and reaches the “melting temperature”. However, the temperature of the cleaning roller 35 is Since it is complicatedly changed by various factors (for example, the size and thickness of the sheet P, the sheet passing pattern, the temperature of the pressure roller 31 and the fixing roller 21, etc.), the timing of reaching the “melting temperature” can be accurately set. Hard to predict.
For example, when sheets P (small size sheets) having a small size in the width direction are continuously passed, the normal size sheet P is affected by the excessive temperature rise in the non-sheet passing area of the pressure roller 31. The cleaning roller 35 is more likely to reach the “melting temperature” than when the sheet is passed.
Therefore, it is preferable to directly detect the temperature of the cleaning roller 35 located at the contact position.

More specifically, as shown in FIGS. 2 and 4, the fixing device 20 according to the present embodiment serves as a contact temperature detecting means for detecting the temperature of the cleaning roller 35 (cleaning member) located at the contact position. A temperature sensor 45 is installed. More specifically, the temperature sensor 45 is a contact type temperature sensor such as a contact type thermistor, and is held by the arm member 38 so that its detection surface contacts the cleaning roller 35.
Then, when the temperature detected by the temperature sensor 45 (contact temperature detecting means) becomes equal to or higher than a predetermined value A (“melting temperature”), the cleaning roller 35 located at the contact position is detected. The moving means (drive motor 51) is controlled so as to move to the separated position shown in FIG.
In this way, the temperature sensor 45 directly detects the temperature of the cleaning roller 35 located at the contact position, and the timing when the cleaning roller 35 reaches the “melting temperature” can be reliably grasped, and the cleaning roller 35 can be detected. By separating them at a timing, it is possible to prevent the reverse movement of the adhering substances from the cleaning roller 35 to the pressure roller 31 while maintaining the cleaning function of the cleaning roller 35 as much as possible.

Here, as shown in FIG. 4, the temperature sensor 45 controls the temperature of the cleaning roller 35 outside the region of the maximum sheet passing region M (which is the range in the width direction of the sheet P of the maximum size that can pass the sheet). It is arranged to detect.
The pressure roller 31 (and the fixing roller 21) is deprived of heat by the sheet P in the paper passing area, so that the temperature outside the maximum paper passing area M is likely to be the highest. Since the temperature of the cleaning roller 35 which receives heat from the pressure roller 31 tends to be the highest outside the area of the maximum paper passing area M, the temperature sensor 45 detects the temperature at that position, so that the cleaning roller 35 “melts out”. It becomes possible to quickly grasp the timing when the temperature is reached.

The “melting temperature” described above also changes depending on the toner used, the components of the paper powder, and the like. Therefore, it is possible to set the above-mentioned predetermined value A to an optimum value for each model using different toner, or to change the above-mentioned predetermined value A according to the conveyed sheet P.

Further, in the present embodiment, the temperature sensor 45 also functions as a separation time temperature detection unit that detects the temperature of the cleaning roller 35 located at the separation position as shown in FIG. That is, since the temperature sensor 45 is installed on the arm member 38 so as to come into contact with the cleaning roller 35, the temperature can be detected even when the cleaning roller 35 moves to the separated position.
Then, when the temperature detected by the temperature sensor 45 (separation temperature detection means) becomes equal to or lower than the predetermined temperature B, the cleaning roller 35 located at the separation position is moved to the contact position (drive motor). 51) is controlled.
The predetermined temperature B is sufficiently lower than the predetermined value A (“melting temperature”) described above, and even if the cleaning roller 35 is sufficiently cooled and moved to the contact position again, It is a temperature at which the reverse movement of the adhered matter from the cleaning roller 35 to the pressure roller 31 does not occur.
By performing such control, the cleaning roller 35 is moved from the separated position to the contact position in a state where the cleaning roller 35 is not sufficiently cooled, and the cleaning roller 35 adheres to the pressure roller 31. It is possible to prevent the problem that the reverse movement of the above occurs.

In the present embodiment, one temperature sensor 45 is made to function as both the contact temperature detecting means and the contact temperature detecting means, but a temperature sensor functioning as the contact temperature detecting means is used. It is also possible to separately provide the temperature sensor that functions as the temperature detecting means at the time of separation. In such a case, both of the temperature sensors are not on the arm member 38, but on a fixed position of the apparatus casing (a position where the temperature of the cleaning roller 35 in the contact state can be detected and a cleaning roller 35 in the separated state). It is located at a position where the temperature of can be detected.

Further, in the present embodiment, the phenomenon in which the adhered matter moves backward from the cleaning roller 35 located at the contact position toward the pressure roller 31 is caused by the temperature of the pressure roller 31 in addition to the temperature of the cleaning roller 35. When the size is also affected, the cleaning roller 35 is operated by the temperature detected by the temperature sensor 41 that detects the surface temperature of the pressure roller 31 in addition to the temperature detected by the temperature sensor 45 described above. The timing of moving to the separated position may be variable.
Specifically, even if the temperature of the cleaning roller 35 reaches a constant value, the temperature of the pressure roller 31 is low, and a phenomenon in which the adhered material moves in the reverse direction compared to when the temperature of the pressure roller 31 is high occurs. If it is difficult, control the cleaning roller 35 to move from the contact position to the separation position when the sum of the temperature of the cleaning roller 35 and the temperature of the pressure roller 31 reaches a predetermined value. You can

Here, in the present embodiment, the cleaning roller 35 is configured to rotate both at the contact position shown in FIG. 2 and at the separated position shown in FIG. Has been done.
More specifically, as described above, when the pressure roller 31 is in contact with the cooling roller 36, the rotation is accompanied by rotation of the pressure roller 31, and when it is in contact with the cooling roller 36, it is rotated together with rotation of the cooling roller 36. There is.
As a result, as compared with the case where the cleaning roller 35 does not rotate, the cleaning surfaces contacting the pressure roller 31 at the contact position are exchanged, so that the cleaning ability of the cleaning roller 35 is enhanced and the cooling roller at the separated position. Since the surface to be cooled that contacts the 36 is replaced, the cleaning roller 35 is easily cooled.

Further, in the present embodiment, the cooling roller 36 is configured to rotate by the drive of the motor 52 at least when the cleaning roller 35 is located at the separated position and is in contact therewith.
Specifically, in this embodiment, the cooling roller 36 is rotationally driven only when the cleaning roller 35 is moving to the separated position.
As a result, as compared with the case where the cooling roller 36 does not rotate, the cooling surfaces contacting the cleaning roller 35 are replaced at the separated position, and the cooling capacity of the cooling roller 36 is enhanced.

FIG. 5 is a flowchart collectively showing the contact/separation control of the cleaning roller 35 described above.
As shown in FIG. 5, first, it is determined whether or not the cleaning roller 35 is in the contact position where it contacts the pressure roller 31 (step S1). Specifically, whether the cleaning roller 35 is in the contact position or the separated position can be grasped by, for example, optically detecting the position of the arm member 38 with a photo sensor.
As a result, when it is determined that the cleaning roller 35 is at the contact position, the temperature sensor 45 determines whether the temperature of the cleaning roller 35 is equal to or higher than the predetermined value A (step S2). Then, when it is determined that the temperature of the cleaning roller 35 is equal to or higher than the predetermined value A, it is determined that the adhering matter on the pressure roller 31 moves backward, and the moving mechanisms 38 and 51 separate the cleaning roller 35. It is moved to the position (step S3).
On the other hand, when it is determined in step S1 that the cleaning roller 35 is not in the contact position but in the separated position, the temperature sensor 45 determines whether the temperature of the cleaning roller 35 is equal to or lower than the predetermined temperature B. (Step S4). When it is determined that the temperature of the cleaning roller 35 is equal to or lower than the predetermined temperature B, it is determined that the cleaning roller 35 is sufficiently cooled, and the moving mechanisms 38 and 51 bring the cleaning roller 35 to the contact position. It is moved (step S5).

<Modification 1>
FIG. 6 is an enlarged view showing a state where the cleaning roller 35 is in contact with the pressure roller 31 as a first modification.
As shown in FIG. 6, in the fixing device 20 of the first modification, a non-contact temperature sensor 46 such as a thermopile or a non-contact thermistor is fixed near the portion where the cleaning roller 35 contacts the pressure roller 31. Have been installed.
The non-contact temperature sensor 46 detects the temperature of the cleaning roller 35 located at the contact position and the temperature of the pressure roller 31 with which the cleaning roller 35 contacts within a predetermined viewing angle θ to detect the contact temperature. It functions as a detection means. The non-contact type temperature sensor 46 is installed at a position apart from the target object for detecting the temperature, and is configured to detect the temperature of the target object within the range of the viewing angle θ. In the first modification, the non-contact temperature sensor 46 is arranged so that both the surface of the cleaning roller 35 contacting the pressure roller 31 and the surface of the pressure roller 31 are within the viewing angle θ. is doing.
As a result, the temperature in which both the temperatures of the cleaning roller 35 and the pressure roller 31 are reflected is detected by the non-contact temperature sensor 46. Then, when the temperature detected by the non-contact temperature sensor 46 reaches a predetermined value, the cleaning roller 35 is moved from the contact position to the separation position.
In the non-contact temperature sensor 46 as described above, as described in the above embodiment, the phenomenon in which the adhered substance moves backward from the cleaning roller 35 located at the contact position toward the pressure roller 31 is a cleaning roller. This is useful when the temperature of the pressure roller 31 is affected in addition to the temperature of 35.

<Modification 2>
FIG. 7 is an enlarged view showing a state in which the cleaning roller 35 as the modified example 2 is in contact with the pressure roller 31, and is a view corresponding to FIG. 6 in the modified example 1.
As shown in FIG. 7, in the fixing device 20 according to the modified example 2, a non-contact type temperature sensor 47 such as a thermopile or a non-contact type thermistor is fixed near the contact position and the separated position of the cleaning roller 35. is set up.
The non-contact temperature sensor 47 can detect not only the temperature of the cleaning roller 35 located at the separated position but also the temperature of the cleaning roller 35 moved from the separated position to the contact position within a predetermined viewing angle θ. And functions as the temperature detecting means at the time of separation. In other words, the non-contact temperature sensor 47 functions not only as the contact temperature detection means but also as the separation temperature detection means. Specifically, in the second modification, the surface of the cleaning roller 35 that is in contact with the pressure roller 31 at the time of contact enters the viewing angle θ of the non-contact temperature sensor 47, and contacts the cooling roller 36 at the time of separation. The cleaning roller 35 is arranged so that the surface of the cleaning roller 35 can also enter.
As a result, it becomes possible to detect the temperature of the cleaning roller 35 at the time of contact and the temperature of the cleaning roller 35 at the time of separation with one sensor at the fixed position.

<Modification 3>
FIG. 8A is an enlarged view showing a state in which the cleaning roller 35 as the third modification is in contact with the pressure roller 31, and in FIG. 8B, the cleaning roller 35 contacts the cooling member 37. It is an enlarged view which shows the contact state.
As shown in FIG. 8, the fixing device 20 according to the third modification uses a non-rotating cooling member 37 for cooling the cleaning roller 35.
More specifically, in the cooling member 37 in Modification 3, at least a portion contacting the cleaning roller 35 is formed of a gel sheet 37a having a thermal conductivity of 40 W/m·K or more. More specifically, the cooling member 37 has a high thermal conductivity and is a deformable gel sheet on a high thermal conductivity member 37b (base portion) formed of a material having a high thermal conductivity such as copper or a copper alloy. 37a is attached.
When such a cooling member 37 is used, most of the surface of the cleaning roller 35 that has moved to the separated position is covered with the gel sheet 37a (becomes a biting state), and the cleaning roller 35 is used. Will be efficiently cooled through the large surface area.
Even when the cooling member 37 is configured in this way, the same effect as that of the present embodiment can be obtained.

<Modification 4>
FIG. 9 is a configuration diagram showing a main part of the fixing device 20 as the modified example 4, and is a diagram corresponding to FIG. 2 in the present embodiment.
As shown in FIG. 9, in Modification 4, the cleaning roller 35 (cleaning member) is configured to contact the surface of the fixing roller 21 as a fixing rotating member to clean the surface of the fixing roller 21.
Also in Modification 4, as in the case of the present embodiment, when the temperature sensor 45 detects that the temperature of the cleaning roller 35 in contact with the fixing roller 21 is equal to or higher than a predetermined value A′, cleaning is performed. The roller 35 is moved from the contact position to the separated position and abuts on the cooling roller 36. Further, when the temperature sensor 45 detects that the temperature of the cleaning roller 35 contacting the cooling roller 36 becomes equal to or lower than the predetermined temperature B′, the cleaning roller 35 is moved from the separated position to the contact position. Become.
With such a configuration, the cleaning roller 35 for cleaning the surface of the fixing roller 21 is efficiently and sufficiently cooled while the cleaning roller 35 for cleaning the surface is moving to the separated position. The same effect can be obtained.

<Modification 5>
FIG. 10 is a configuration diagram showing a fixing device 20 as a modified example 5, and is a diagram corresponding to FIG. 2 in the present embodiment.
In the present embodiment, the present invention is applied to the roller type fixing device 20 of the thermal heater type, but the fixing device 20 to which the present invention is applied is not limited to such a type, and various fixing devices can be used. System fixing device.
For example, as shown in FIG. 10A, the present invention can be applied to a belt-type fixing device 20 of a thermal heater type (which is a fixing device using a fixing belt 22 as a fixing rotating member). You can also In such a case, the fixing belt 22 is stretched and supported by a plurality of roller members such as the fixing auxiliary roller 23, the heating roller 24 and the tension roller. Further, the fixing auxiliary roller 23 comes into pressure contact with the pressure roller 31 via the fixing belt 22 to form a nip portion. Further, the heater 25 is fixedly installed inside the heating roller 24 having a hollow structure.
Further, as shown in FIG. 10B, the present invention can also be applied to an electromagnetic induction type (IH type) roller type fixing device 20. In such a case, in the fixing roller 21, an elastic layer, a heat generating layer that is electromagnetically induction-heated by the induction heating unit 70 around which an exciting coil is wound, a release layer, and the like are laminated on the core metal part. Will be things.
Although not shown, the present invention can also be applied to a resistance heating type roller fixing device. In such a case, the fixing roller is installed so that the resistance heating element abuts on the hollow portion of the cored bar, and the elastic layer and the release layer are laminated on the cored bar.
Even in such cases, it is possible to obtain substantially the same effect as that of the present embodiment.

As described above, in the fixing device 20 according to the present exemplary embodiment, the contact positions that contact the surface of the pressure roller 31 (pressure rotating body) by the operation of the moving mechanisms 38 and 51 (moving means), and the contact position thereof. A cleaning roller 35 (cleaning member) configured to be movable between the separated position away from the surface and the separated position is installed. Further, a cooling roller 36 (cooling member) that comes into contact with the cleaning roller 35 that has moved to the separated position is installed. The heat capacity of the cooling roller 36 is set to be larger than that of the cleaning roller 35.
As a result, when the cleaning roller 35 that cleans the surface of the pressure roller 31 is moving to the separated position, the cleaning roller 35 is cooled efficiently and sufficiently.

In this embodiment, the pressure roller 31 is used as the pressure rotating body, but a pressure belt may be used as the pressure rotating body.
Then, even 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 appropriately modified, other than what is suggested in the present embodiment, within the scope of the technical idea of the present invention. is there. Further, the number, position, shape, etc. of the constituent members are not limited to those in the present embodiment, and the number, position, shape, etc. suitable for carrying out the present invention can be adopted.

In the present application, the “width direction” is defined as a direction orthogonal to the sheet conveyance direction.
In addition, in the present application, “sheet” is defined to include all sheet-shaped recording media such as coated paper, label paper, OHP sheet, and film sheet in addition to normal paper.

1 image forming apparatus (image forming apparatus main body),
20 fixing device,
21 fixing roller (fixing rotator),
25 heater (heating means),
31 pressure roller (pressure rotating body),
35 cleaning roller (cleaning member),
36 cooling rollers,
37 cooling member,
37a gel-like sheet, 37b high thermal conductive member,
38 arm members (moving means),
45 temperature sensor (contact temperature detection means, separation temperature detection means),
46 Non-contact temperature sensor (contact temperature detection means),
47 Non-contact type temperature sensor (temperature detecting means during separation),
51 drive motor (moving means),
P sheet (recording medium).

JP, 2011-95372, A

Claims (11)

A fixing rotator that heats the toner image to fix it on the surface of the sheet,
A pressure rotating body that forms a nip portion where a sheet is conveyed by being pressed against the fixing rotating body;
A cleaning member configured to be movable between an abutting position that abuts the surface of the fixing rotator or the pressure rotator and a separated position that is separated from the surface by an operation of the moving unit,
A cooling member that contacts the cleaning member that has moved to the separated position;
Equipped with
A fixing device, wherein the heat capacity of the cooling member is set to be larger than that of the cleaning member. The fixing device according to claim 1, wherein the thermal conductivity of the cooling member is set to be higher than the thermal conductivity of the cleaning member. A contact temperature detecting means for detecting the temperature of the cleaning member located at the contact position,
The moving means is controlled so that the cleaning member located at the contact position moves to the separated position when the temperature detected by the contact temperature detection means exceeds a predetermined value. The fixing device according to claim 1 or 2. The contact temperature detecting means detects the temperature of the cleaning member positioned at the contact position and the temperature of the fixing rotating member or the pressure rotating member contacting the cleaning member within a predetermined viewing angle. The fixing device according to claim 3, wherein the fixing device is a non-contact type temperature sensor. A separating temperature detecting means for detecting the temperature of the cleaning member located at the separating position,
When the temperature detected by the separation temperature detection unit is equal to or lower than a predetermined temperature, the moving unit is controlled so that the cleaning member located at the separation position moves to the contact position. The fixing device according to any one of claims 1 to 4. The temperature detection means at the time of separation is a non-contact temperature sensor configured to detect the temperature of the cleaning member moved from the separation position to the contact position within a predetermined viewing angle. The fixing device according to claim 5. The fixing device according to claim 1, wherein the cooling member is made of copper or a copper alloy. 7. The cooling member according to claim 1, wherein at least a portion contacting the cleaning member is formed of a gel-like sheet having a thermal conductivity of 40 W/mK or more. The fixing device described. 9. The cleaning member is a cleaning roller, and rotates both when it is located at the contact position and when it is located at the separation position. The fixing device according to claim 1. The cooling member is a cooling roller, and rotates at least when the cleaning roller is in contact with the cleaning roller at the separated position. Fixing device. An image forming apparatus comprising the fixing device according to claim 1.

Images