JP2008170649A - Image forming apparatus, fixing device and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To facilitate the cleaning of a fixing member used for the fixing of an image. <P>SOLUTION: The control section makes an external heating roll and an internal heating roll into a waiting state till each temperature of the external heating roll and the internal heating roll reaches 150°C (step 201). Then, the control section drives a driving source provided at a movement section, and moves a pressure member toward the direction of the external heating roll (step 202). Next, the control section sets the objective temperature of the internal heating roll to 210°C, and makes the heater into an on state (step 203). Thereafter, the control section circularly drives the fixing belt in succession (step 204), and starts cleaning. In the cleaning mode, the temperature of the fixing belt is made higher than that of the outer surface of the external heating roll. Further, the temperature difference between the fixing belt and the external heating roll in the contact part is made wider than that compared with that upon a fixing mode. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, and a multifunction machine of these, a fixing device used in the image forming apparatus, and the like.

  In an image forming apparatus such as a copying machine or a printer, for example, a fixing process is performed in which a recording material on which a toner image (image) is held is heated and pressed to fix the toner image on the recording material. In this case, the toner image may not be completely fixed on the recording material and may adhere to a fixing member such as a fixing belt, a fixing roll, or a pressure roll. The toner adhering to the fixing member may be transferred to the recording material when the other recording material is fixed, and the recording material may be soiled. In view of this, there has been proposed a technique for cleaning the fixing member by feeding a sheet to the fixing member and attaching toner on the fixing member to the fed sheet (see, for example, Patent Document 1).

JP 2003-29563 A

  By the way, when the fixing member is cleaned by feeding the recording material, control for feeding the paper or the like becomes necessary, and the processing becomes complicated.

  Accordingly, the present invention has been made to solve the technical problems as described above, and an object thereof is to simplify the cleaning of a fixing member used for fixing an image.

  For this purpose, an image forming apparatus to which the present invention is applied includes a first fixing member that is rotatably arranged, a rotation fixing contact with the first fixing member, and a first fixing member. The recording material holding the image in the contact area is passed through a second fixing member for fixing the image on the recording material, and the first fixing member is rotatably contacted with the outer peripheral surface of the first fixing member. An external heating member that heats the member, and a cleaning member that cleans the outer peripheral surface of the external heating member, in a state in which the temperature difference between the first fixing member and the external heating member is different from that at the time of fixing. A foreign matter is attached to the external heating member from the first fixing member, and the foreign matter attached to the external heating member is removed by the cleaning member.

  Here, the temperature difference can be characterized by being larger than the temperature difference between the first fixing member and the external heating member at the time of fixing. In addition, the image forming apparatus further includes a heating member that heats the first fixing member, and the external heating member is upstream in the rotation direction of the first fixing member with respect to the contact area and downstream in the rotation direction of the first fixing member with respect to the heating member. It can be characterized by being arranged. Furthermore, the cleaning member can be characterized in that the position relative to the external heating member can be changed.

  Further, when the present invention is regarded as a fixing device, the fixing device to which the present invention is applied is arranged such that the first fixing member rotatably arranged, the first fixing member rotatably contacted, A recording material holding an image is passed through a contact area with the first fixing member, and a second fixing member that fixes the image on the recording material and a peripheral contact surface of the first fixing member are rotatably arranged. An external heating member that heats the first fixing member, and a cleaning member that cleans foreign matter adhered to the external heating member by creating a temperature difference between the first fixing member and the external heating member.

  Here, the cleaning member is arranged to be able to be pressed against the external heating member, and the pressing force with which the cleaning member presses the external heating member can be adjusted. In addition, a heating source is provided, and a heating member that heats the first fixing member is further provided, and when the temperature difference is set between the first fixing member and the external heating member, the heating source is turned off. Can be characterized. The external heating member may include a heating source, and the heating source may be turned off when a temperature difference is generated between the first fixing member and the external heating member.

  Further, when the present invention is regarded as a program, the program to which the present invention is applied is arranged such that the first fixing member that is rotatably arranged and the first fixing member are rotatably contacted with the first fixing member. A recording material holding an image is passed through a contact area with the fixing member, and a second fixing member for fixing the image on the recording material is rotatably contacted with the outer peripheral surface of the first fixing member. In an image forming apparatus provided with an external heating member that heats one fixing member, the first fixing member and an external device are cleaned when the first fixing member is cleaned after the image is fixed on the recording material. The function of changing the temperature difference between the first fixing member and the external heating member at the contact portion with the heating member to a state different from the temperature difference when fixing is performed, and the first difference in a state where the temperature difference is different. And a function of rotating the fixing member.

According to the first aspect of the present invention, it is possible to provide an image forming apparatus capable of simplifying cleaning of a fixing member used for fixing an image.
According to the second aspect of the present invention, the foreign matter attached to the fixing member is easily attached to the external heating member, and the fixing member can be effectively cleaned.
According to the third aspect of the present invention, the temperature difference between the fixing member and the external heating member can be increased as compared with the case where the present configuration is not provided, and the cleaning efficiency can be increased. It becomes.
According to the fourth aspect of the present invention, for example, the contact pressure between the external heating member and the cleaning member can be increased, and the cleaning efficiency can be increased.

According to the fifth aspect of the invention, cleaning of the fixing member used for fixing the image can be simplified.
According to the sixth aspect of the present invention, for example, the contact pressure between the external heating member and the cleaning member can be increased, and the cleaning efficiency can be increased.
According to the seventh aspect of the invention, cleaning can be performed while suppressing power consumption.
According to the eighth aspect of the invention, it is possible to perform cleaning while suppressing power consumption.
According to the ninth aspect of the invention, cleaning of the fixing member can be simplified in the image forming apparatus or the like.

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings.
-First embodiment-
FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus according to the first embodiment. The image forming apparatus shown in FIG. 1 is an intermediate transfer type image forming apparatus generally called a tandem type. The image forming apparatus includes a plurality of image forming units 1Y, 1M, 1C, and 1K that form toner images of respective color components by electrophotography. Further, a primary transfer unit 10 that sequentially transfers (primary transfer) the color component toner images formed by the image forming units 1Y, 1M, 1C, and 1K to the intermediate transfer belt 15 is provided. Further, a secondary transfer unit 20 is provided that collectively transfers (secondary transfer) the superimposed toner image transferred onto the intermediate transfer belt 15 onto a sheet P that is a recording material (recording paper). In addition, a fixing device 60 that fixes the second-transferred image on the paper P is provided. Furthermore, the control part 40 which controls operation | movement of each apparatus (each part) is provided.

  In the present embodiment, the following electrophotographic devices are sequentially arranged in each of the image forming units 1Y, 1M, 1C, and 1K. Around the photosensitive drum 11 rotating in the direction of arrow A, a charger 12 for charging the photosensitive drum 11 is provided. Further, a laser exposure device 13 (an exposure beam is indicated by a symbol Bm in the drawing) for writing an electrostatic latent image on the photosensitive drum 11 is provided. Further, a developing device 14 is provided that stores toner of each color component and visualizes the electrostatic latent image on the photosensitive drum 11 with the toner. Further, a primary transfer roll 16 is provided for transferring each color component toner image formed on the photosensitive drum 11 to the intermediate transfer belt 15 by the primary transfer unit 10. Further, a drum cleaner 17 for removing residual toner on the photosensitive drum 11 is provided.

The primary transfer unit 10 includes a primary transfer roll 16 that is disposed to face the photosensitive drum 11 with the intermediate transfer belt 15 interposed therebetween.
The secondary transfer unit 20 includes a secondary transfer roll 22 disposed on the toner image carrying surface side of the intermediate transfer belt 15 and a backup roll 25. The secondary transfer roll 22 is grounded, and is pressed against the backup roll 25 with the intermediate transfer belt 15 interposed therebetween.
The control unit 40 (computer) includes a CPU (Central Processing Unit) that controls the operation of each device (each unit), a ROM (Read Only Memory) in which a program is recorded, and a RAM (temporarily storing various data). Random Access Memory).

Next, a basic image forming process of the image forming apparatus according to the present embodiment will be described. In the image forming apparatus according to the present embodiment, image data is output from an image reading device (not shown) or the like. The image data is subjected to predetermined image processing by an image processing apparatus (not shown), converted into color material gradation data of four colors Y, M, C, and K, and output to the laser exposure unit 13.
The laser exposure unit 13 irradiates the photosensitive drums 11 of the image forming units 1Y, 1M, 1C, and 1K, for example, with an exposure beam Bm emitted from a semiconductor laser in accordance with the input color material gradation data. Yes. After the surface of each photoconductive drum 11 is charged by the charger 12, the surface is scanned and exposed by the laser exposure unit 13 to form an electrostatic latent image.

The formed electrostatic latent images are converted into Y (yellow), M (magenta), C (cyan), and K (black) toners by the developing devices 14 of the image forming units 1Y, 1M, 1C, and 1K. Developed as an image.
On the other hand, the intermediate transfer belt 15 is circulated at a predetermined speed in the direction of arrow B shown in FIG. 1 by various rolls such as a drive roll 31 driven by a motor (not shown) having excellent constant speed. . The toner images formed on the photosensitive drums 11 are sequentially electrostatically attracted onto the intermediate transfer belt 15 in the primary transfer unit 10 where the photosensitive drums 11 and the intermediate transfer belt 15 come into contact with each other. A toner image superimposed thereon is formed.

  After the superimposed toner image is formed on the surface of the intermediate transfer belt 15, the intermediate transfer belt 15 moves and the toner image is conveyed to the secondary transfer unit 20. In the secondary transfer unit 20, the secondary transfer roll 22 is pressed against the backup roll 25 via the intermediate transfer belt 15. At this time, the paper P transported by the transport roll 52 and the like at the same timing is sandwiched between the intermediate transfer belt 15 and the secondary transfer roll 22 in the secondary transfer unit 20. In the secondary transfer unit 20, a secondary transfer bias is applied between the secondary transfer roll 22 and the backup roll 25, and a secondary transfer electric field is formed between both members.

  The unfixed toner image carried on the intermediate transfer belt 15 is electrostatically transferred collectively onto the paper P in the secondary transfer unit 20. Thereafter, the sheet P on which the toner image has been electrostatically transferred is transported as it is while being peeled off from the intermediate transfer belt 15 by the secondary transfer roll 22, and transported downstream of the secondary transfer roll 22 in the sheet transport direction. It is conveyed to the belt 55. The transport belt 55 transports the paper P to the fixing device 60 at an optimal transport speed. In the fixing device 60, the paper P on which the toner image is transferred is heated and pressed, and the toner image is fixed on the paper P. Then, the sheet P that has been fixed is discharged outside the image forming apparatus.

Next, the fixing device 60 will be described.
FIG. 2 is a side sectional view showing a schematic configuration of the fixing device 60. The fixing device 60 includes a fixing belt module 61 and a pressure roll 62 disposed in pressure contact with the fixing belt module 61 as main parts.
The fixing belt module 61 includes a fixing belt 610 as an example of a first fixing member, and a fixing roll 611 that is rotationally driven while stretching the fixing belt 610. The fixing belt module 61 includes an internal heating roll 612 that is disposed inside (inside) the fixing belt 610 and stretches the fixing belt 610 from the inside and heats the fixing belt 610 from inside (inside). The fixing belt module 61 includes an external heating roll 613 that stretches the fixing belt 610 from the outside and heats the fixing belt 610 from the outside (external side).

Further, the fixing belt module 61 is a peeling region disposed in the vicinity of the fixing roll 611 in a downstream region in the nip portion N (contact region) where the fixing belt module 61 and the pressure roll 62 are in pressure contact with each other. A pad 64 is provided. The fixing belt module 61 includes an idler roll 615 that stretches the fixing belt 610 on the downstream side of the nip portion N. Further, the fixing belt module 61 includes a cleaning member 617 (cleaning member) for cleaning the surface of the external heating roll 613.
The fixing belt 610 is a flexible endless belt. Then, a base layer made of polyimide or the like having a thickness of about 80 μm, an elastic layer made of silicone rubber or the like having a thickness of about 50 μm laminated on the surface side (outer peripheral surface side) of the base layer, and further on the elastic body layer And a surface layer (release layer) formed of a fluororesin having a thickness of about 30 μm.

The fixing roll 611 (heating member) is formed in a cylindrical shape, and includes a metal roll (not shown) serving as a base and a resin layer (not shown) that covers the outer surface of the roll. . Further, a heater 616a is disposed inside the fixing roll 611 as a heating source. For this reason, the fixing roll 611 also has a function of heating the fixing belt 610 stretched outside.
The internal heating roll 612 (heating member) is made of metal and is formed in a cylindrical shape. Further, the internal heating roll 612 is formed to have a smaller diameter than the fixing roll 611. Further, the internal heating roll 612 includes a heater 616b as a heating source therein, and the internal heating roll 612 is heated by the heater 616b. Further, spring members (not shown) are provided at both ends of the internal heating roll 612, and the internal heating roll 612 is urged against the fixing belt 610 by the spring members.

The external heating roll 613 as an external heating member is a cylindrical roll. Inside the external heating roll 613, a heater 616c as a heating source is disposed. For this reason, the external heating roll 613 has both a function of stretching the fixing belt 610 and a function of heating the fixing belt 610 from the outer peripheral surface side. As will be described in detail later, the external heating roll 613 has a function of removing offset toner attached to the fixing belt 610.
The cleaning member 617 is provided with a web 617 a that contacts the outer surface of the external heating roll 613 and removes toner adhering to the outer surface. Further, the cleaning member 617 includes a holding unit 617b that holds an unused web in the form of winding, and a supply unit 617c that supplies the web 617a from the holding unit 617b to the external heating roll by winding the web. ing.

  Further, the cleaning member 617 includes a pressing member 617d that presses the web 617a disposed between the holding unit 617b and the supply unit 617c against the external heating roll 613, and a direction in which the pressing member 617d approaches the external heating roll 613 and the separation. And a moving part 617e that moves in a direction (see arrow G in the figure). The moving unit 617e is composed of, for example, a driving source such as a motor and a movable member that is movable by receiving a driving force from the driving source. An example of the movable member is a cam. In the present embodiment, the external heating roll 613 is configured to rotate following the movement of the fixing belt 610. The web 617a removes the toner attached to the rotating external heating roll 613 and cleans the surface of the external heating roll 613.

The peeling pad 64 is a block member having a substantially arc shape in cross section formed of a rigid body such as SUS metal or resin. The peeling pad 64 is disposed at a position near the downstream side of a region where the pressure roll 62 is pressed against the fixing roll 611 via the fixing belt 610. The peeling pad 64 is installed so as to press the pressure roll 62 uniformly with a predetermined load over a predetermined width region via the fixing belt 610.
The idler roll 615 is a cylindrical roll. Further, the idler roll 615 is disposed in the vicinity of the downstream side of the fixing pad 610 in the traveling direction of the fixing belt 610 so that the fixing belt 610 that has passed through the peeling pad 64 smoothly moves toward the fixing roll 611.
The pressure roll 62 as the second fixing member has a cylindrical roll 621 as a base. And the elastic layer 622 and the release layer 623 are laminated | stacked in order from the base | substrate side, and the soft roll is comprised. The pressure roll 62 is installed so as to be pressed against the fixing belt module 61.
Further, in the present embodiment, a nip portion N is formed in which the toner image held on the sheet is fixed by the fixing belt module 61 and the pressure roll 62 disposed in pressure contact with the fixing belt module 61. Has been.

  Next, the operation of the fixing device 60 will be described. In the fixing device 60 according to the present exemplary embodiment, the toner image held on the recording material is fixed to the recording material. The fixing device 60 adheres to the fixing belt 610 when, for example, an image offset described later occurs in the fixing mode. Two modes, a cleaning mode (cleaning mode) for removing (cleaning) offset toner (an example of foreign matter), are provided. In these modes, the fixing device 60 performs different operations under the control of the control unit 40. Hereinafter, the operation of the fixing device 60 will be described separately for the fixing mode and the cleaning mode.

First, the operation in the fixing mode will be described.
In the fixing mode, first, the sheet holding the toner image is introduced into the nip portion N by the transport belt 55 (see FIG. 1). At this time, the fixing roll 611 rotates in the direction of arrow C in response to a driving force from a driving source (not shown) such as a motor. Further, the fixing belt 610 rotates in the direction of arrow D following the fixing roll 611 as the fixing roll 611 rotates. Further, the pressure roll 62 also rotates in the direction of arrow E following the rotation of the fixing belt 610.
The sheet introduced into the nip portion N is conveyed downstream by the rotating fixing belt 610 and the pressure roll 62. In this nip portion N, the sheet is pressed and heated by the fixing belt 610 and the pressure roll 62. As a result, the toner image is fixed on the paper. The sheet is heated by a fixing belt 610 heated by a fixing roll 611, an internal heating roll 612, and an external heating roll 613.

The fixing belt 610 that has passed through the nip N moves along the side surface of the peeling pad 64. As a result, the advancing direction of the fixing belt 610 changes abruptly so as to bend toward the idler roll 615. For this reason, the sheet subjected to the pressurizing and heating action at the nip portion N cannot follow the change in the advancing direction of the fixing belt 610 when it exits the nip portion N.
As a result, the sheet is peeled from the fixing belt 610 by the so-called “koshi”. In this way, the curvature separation with respect to the paper P is stably performed at the exit of the nip portion N. The paper P separated from the fixing belt 610 is guided in the traveling direction by the peeling guide plate 83 disposed on the downstream side of the nip portion N. The paper P guided by the peeling guide plate 83 is then discharged out of the apparatus by a paper discharge guide (not shown) and a paper discharge roll (not shown), and the fixing process is completed.

By the way, when the fixing process is performed as described above, the fixing belt 610, the internal heating roll 612, and the external heating roll 613 are adjusted to a predetermined temperature by the control unit 40 in order to appropriately fix the toner image on the paper. The
FIG. 3 is a flowchart showing processing executed by the control unit 40 in the fixing mode. In this flowchart, the case where the fixing belt 610 is adjusted to 200 ° C. is illustrated.

First, the control unit 40 sets the temperature of the fixing belt 610 at the time of fixing to 200 ° C. (step 101). Next, the control unit 40 sets the target temperature of the internal heating roll 612 to 210 ° C., and turns on the heater 616b provided inside the internal heating roll 612 (step 102). Further, the control unit 40 sets the target temperature of the external heating roll 613 to 210 ° C., and turns on the heater 616c provided inside the external heating roll 613 (step 103). Further, although not shown in the flowchart, the control unit 40 turns on the heater 616a disposed inside the fixing roll 611.
Next, the control unit 40 determines whether or not the temperature of the internal heating roll 612 has exceeded 210 ° C. based on an output from a temperature sensor (not shown) provided in the vicinity of the outer surface of the internal heating roll 612 (Step S40). 104). If it is determined that the temperature of the internal heating roll 612 does not exceed 210 ° C. (less than 210 ° C.), the process returns to step 104. When it is determined in step 104 that the temperature of the internal heating roll 612 has exceeded 210 ° C., the control unit 40 turns off the heater 616b (step 105).

  On the other hand, the control unit 40 determines whether or not the temperature of the external heating roll 613 has exceeded 210 ° C. based on an output from a temperature sensor (not shown) provided in the vicinity of the outer surface of the external heating roll 613 (Step S40). 106). If it is determined that the temperature of the external heating roll 613 does not exceed 210 ° C. (less than 210 ° C.), the process returns to step 106. When it is determined in step 106 that the temperature of the external heating roll 613 has exceeded 210 ° C., the control unit 40 turns off the heater 616c (step 107). Although not shown in this flowchart, the control unit 40 appropriately controls the heater 616a based on a sensor provided near the outer surface of the fixing roll 611.

The fixing belt 610 is heated to about 210 ° C. by the internal heating roll 612. However, since the fixing belt 610 itself does not include a heating source, natural cooling is performed when moving toward the external heating roll 613. The Therefore, the temperature of the fixing belt 610 is lower than 210 ° C. when reaching the external heating roll 613. On the other hand, as described above, the temperature of the external heating roll 613 is controlled to about 210 ° C. by the control unit 40. For this reason, the surface temperature of the external heating roll 613 is higher than the temperature of the fixing belt 610 at the contact portion where the fixing belt 610 and the external heating roll 613 are in contact with each other.
However, since the distance between the internal heating roll 612 and the external heating roll 613 is not so far, the temperature drop when the fixing belt 610 reaches the external heating roll 613 from the internal heating roll 612 is very small. For this reason, the temperature difference between the external heating roll 613 and the fixing belt 610 at the contact portion is very small.

  After the processing in steps 105 and 107 is executed, the control unit 40 determines whether or not all the fixing processing has been completed (step 108). When all the fixing processes are finished, all the processes shown in this flowchart are finished. On the other hand, when it is determined in step 108 that all the processes have not been completed, the control unit 40 executes the processes in and after step 104 again. In Step 104 and Step 106, when it is determined that the temperature of the internal heating roll 612 and the external heating roll 613 does not exceed 210 ° C., the control unit 40 turns on the heater 616b and the heater 616c. The heater 616a is also turned on when the temperature of the fixing roll 611 is lower than the predetermined temperature.

Next, the operation in the cleaning mode will be described.
In this cleaning mode, the fixing belt 610 is cleaned. It is desirable that all the toner images on the paper are fixed on the paper, but a phenomenon of so-called offset occurs in which a part of the toner forming the toner image is moved (transferred) to the fixing belt 610 without being completely fixed. There is a case. For example, when the toner image is still in the melted state near the exit of the nip portion N, all or a part of the toner moves to the fixing belt 610 and adheres to the fixing belt 610. In addition, when fixing, a part of the toner may move to the fixing belt 610 even when the temperature of the fixing belt 610 is lower than a predetermined temperature. When the fixing operation is performed in a state where the toner has moved to the fixing belt 610 as described above, the toner attached to the fixing belt 610 may move to the paper in the fixing mode and stain the paper.
Therefore, in this embodiment, a cleaning mode is provided in order to suppress the occurrence of this contamination.

FIG. 4 is a flowchart showing processing executed in the cleaning mode.
The cleaning mode can be appropriately performed, for example, before the fixing process or after the fixing process is completed. The cleaning mode can be performed at a specific timing such as when a jam (paper jam) occurs in the image forming apparatus.

This flowchart illustrates a process executed after a jam occurs in the image forming apparatus and the jam is removed. In this embodiment, when a jam occurs in the image forming apparatus, the control unit 40 turns off the heaters 616a, 616b, and 616c. The processing shown below shows processing that starts from the state where the heaters 616a, 616b, and 616c are turned off.
After detecting that the jam has been removed, the control unit 40 first places the external heating roll 613 and the internal heating roll 612 in a standby state until the temperature of the external heating roll 613 and the internal heating roll 612 reaches 150 ° C. (Step 201). More specifically, the control unit 40 circulates and drives the fixing belt 610 by a drive source (not shown) until the temperature of the external heating roll 613 and the internal heating roll 612 decreases to 150 ° C., and the external heating roll 613 and the internal heating roll The roll 612 is idled.

  Next, the control unit 40 drives the drive source provided in the moving unit 617e in the cleaning member 617, and moves the pressing member 617d toward the external heating roll 613 (step 202). In this embodiment, the pressing amount of the pressing member 617d after the movement with respect to the external heating roll 613 is 2.0 mm. In the fixing mode (normal mode), the pressing amount of the pressing member 617d against the external heating roll 613 is 0.5 mm. In the fixing mode, the pressing member 617d can be completely separated from the external heating roll 613. By moving the pressing member 617d as described above, the pressing force with which the pressing member 617d presses the external heating roll 613 increases, and the contact pressure between the web 617a and the external heating roll 613 increases.

Next, the control unit 40 sets the target temperature of the internal heating roll 612 to 210 ° C., and turns on the heater 616b (step 203). In the cleaning mode, the heater 616b is turned on in this way, but the heater 616a provided on the fixing roll 611 and the heater 616c provided on the external heating roll 613 are not turned on.
Thereafter, the control unit 40 continues to drive the fixing belt 610 that has been circulated in Step 201 to circulate (Step 204), and starts cleaning. When cleaning is performed, the temperature of the fixing belt 610 is about 210 ° C. at the contact portion between the fixing belt 610 and the external heating roll 613, and the surface temperature of the external heating roll 613 is about 150 ° C.

When performing the cleaning, the temperature difference between the fixing belt 610 and the external heating roll 613 is preferably 10 ° C. or more. This is because if the temperature is less than 10 ° C., the toner does not move so much from the fixing belt 610 to the external heating roll 613, and cleaning may not be performed properly. In addition, it becomes more preferable when a temperature difference shall be 50 degreeC or more.
Further, when cleaning is performed, the temperature of the fixing belt 610 is preferably set to 120 ° C. to 200 ° C. When the temperature is lower than 120 ° C., the toner attached to the fixing belt 610 is not likely to be melted, and is in a state of being fixed to the fixing belt 610, making it difficult to transfer to the external heating roll 613. As a result, it becomes difficult to obtain sufficient cleaning performance. On the other hand, when the temperature is higher than 200 ° C., the reliability of the material forming the fixing belt 610 is likely to be lowered.

  Moreover, when performing cleaning, it is preferable that the temperature of the external heating roll 613 shall be 70 to 150 degreeC. Although it is possible to obtain the cleaning performance even if the temperature is less than 70 ° C., if the temperature is less than 70 ° C., the standby time described in Step 201 above, that is, the time until the external heating roll 613 is lowered to the predetermined temperature is long. turn into. Further, as described above, the temperature of the fixing belt 610 is preferably a relatively high temperature of 120 ° C. or higher, and if it is set to 70 ° C. or higher, a temperature difference capable of obtaining sufficient cleaning performance is formed between the fixing belt 610 and the fixing belt 610. Can do. On the other hand, if the temperature is higher than 150 ° C., it is difficult to increase the temperature difference with the fixing belt 610.

  Thereafter, the control unit 40 determines whether or not the cleaning is completed (step 205). For example, the control unit 40 can grasp the elapsed time with a timer or the like after executing the process of step 204, and can determine that the cleaning is completed when the elapsed time reaches a predetermined time. When it is determined in step 205 that the cleaning is completed, the control unit 40 turns off the heater 616b (step 206). On the other hand, if it is determined in step 205 that the cleaning has not ended, the process returns to step 205. After the process in step 206 is completed, the control unit 40 drives a drive source provided in the moving unit 617e to move the pressing member 617d in a direction away from the external heating roll 613 (step 207). By the processing in step 207, the pressing member 617d returns to the position where it is arranged in the fixing mode. Thereafter, the control unit 40 stops the circulation driving of the fixing belt 610 (step 208) and ends the processing.

By the way, in the fixing mode, as shown in FIG. 3, the heater 616b provided on the internal heating roll 612 and the heater 616c provided on the external heating roll 613 were turned on. For this reason, in the fixing mode, the temperature of the external heating roll 613 is higher, and the temperature difference between the fixing belt 610 and the external heating roll 613 is very small.
On the other hand, in the cleaning mode, the heater 616b provided on the internal heating roll 612 is turned on in step 203 as described above, but the heater 616c provided on the external heating roll 613 is not turned on but is turned off. It has become. As a result, in the cleaning mode, the temperature of the fixing belt 610 is higher than the temperature of the outer surface of the external heating roll 613. In addition, as a result of the heater 616c disposed inside the external heating roll 613 being turned off, the temperature difference between the two at the contact portion between the fixing belt 610 and the external heating roll 613 becomes larger than that in the fixing mode. .

According to the inventor's knowledge, there is a tendency that the toner easily moves from a member having a high temperature to a member having a low temperature. There is also a tendency that the greater the temperature difference between the members, the easier the toner moves.
Therefore, in the cleaning mode of the present embodiment, as described above, the temperature of the fixing belt 610 is set higher than the temperature of the external heating roll 613, and the temperature difference between the fixing belt 610 and the external heating roll 613 is fixed. It is in a state larger than the temperature difference between the two in the mode. The fixing belt 610 is circulated and driven to move (transfer) toner from the fixing belt 610 to the external heating roll 613 after setting the temperature difference to be large.

It should be noted that both the heater 616b provided on the internal heating roll 612 and the heater 616c provided on the external heating roll 613 are turned on, and the heat generation amount of the both is made different to thereby make the fixing belt 610 and the external heating roll 613 different. A temperature difference can be formed between the two. However, in this case, power consumption increases. Therefore, in the present embodiment, the heater 616b is turned on and the heater 616c is turned off to form a temperature difference.
In the cleaning mode, when the fixing belt 610 is heated, for example, the heater 616a provided on the fixing roll 611 can be turned on. However, in this case as well, there is a problem that power consumption increases. On the other hand, since the fixing belt 610 has a small heat capacity, the heater 616b can be sufficiently heated without using the heater 616a. Therefore, in this embodiment, only a part of the heaters (heater 616b) among the plurality of heaters is turned on.

Further, the fixing belt 610 can be heated not by the internal heating roll 612 but by the fixing roll 611. However, in this case, power consumption increases.
The fixing roll 611 has a resin layer formed on the outer surface of a metal roll serving as a base. On the other hand, the internal heating roll 612 is formed of only a metal roll. For this reason, the internal heating roll 612 has a smaller heat capacity and a higher heating efficiency when heated by the heater. In addition, the internal heating roll 612 is formed to have a smaller diameter than the fixing roll 611. In this case, the internal heating roll 612 is in a state where the heating efficiency is better. As a result, when the fixing roll 611 is used, the power consumption increases. Therefore, in the present embodiment, the fixing belt 610 is heated by the internal heating roll 612.

By the way, when the fixing belt 610 is heated by the internal heating roll 612 as described above, the cleaning efficiency varies depending on the arrangement position of the external heating roll 613.
As described above, the temperature of the fixing belt 610 gradually decreases after passing through the internal heating roll 612. In particular, after entering the nip portion N, heat is taken away by the fixing roll 611, the pressure roll 62, and the peeling pad 64, so that the temperature rapidly decreases. Therefore, the temperature of the fixing belt 610 is lower than the fixing roll 611 in the moving direction of the fixing belt 610 and upstream of the internal heating roll 612 in the moving direction of the fixing belt 610. When the external heating roll 613 is provided in a portion where the temperature is low, the temperature difference between the fixing belt 610 and the external heating roll 613 is reduced. For this reason, in the present embodiment, the external heating roll 613 is provided downstream of the internal heating roll 612 in the movement direction of the fixing belt 610 and upstream of the nip portion N in the movement direction of the fixing belt 610. ing.

  In order to improve the cleaning performance, it is desirable that the contact pressure between the web 617a and the surface of the external heating roll 613 is high. In view of this, in the present embodiment, as shown in step 202, a process of causing the pressing member 617d to approach the external heating roll 613 is performed. The web 617a may be directly pressed against the fixing belt 610. However, if the web 617a is pressed, the surface of the fixing belt 610 is scraped and worn by the web 617a. In particular, when a fluororesin is provided on the surface layer of the fixing belt 610 as in the present embodiment, wear easily proceeds. When wear occurs, it becomes difficult to obtain a high-quality image. Even if the image quality is initially high, it is difficult to maintain this state for a long time. Therefore, in this embodiment, the web 617a is not pressed directly against the fixing belt 610 but is pressed against the external heating roll 613.

  Further, in the present embodiment, as shown in step 207, when the cleaning mode ends, the pressing member 617d moves away from the external heating roll 613, and the web 617a and the external heating roll 613 The contact pressure is reduced. If the contact pressure is always high, the rotational resistance of the external heating roll 613 will increase. As a result, when the fixing belt 610 is circulated and driven in the fixing mode, a problem such as an increase in power consumption occurs. Further, when the contact pressure is high, the surface of the external heating roll 613 is scraped by the web 617a to cause roughness. As a result, the surface of the fixing belt 610 is also roughened and affects the image to be fixed. For this reason, in this embodiment, it is set as the structure which moves the press member 617d in the direction away from the external heating roll 613 after completion | finish of cleaning mode.

-Second Embodiment-
Next, a second embodiment will be described.
FIG. 5 is a side sectional view showing a schematic configuration of the fixing device 60 according to the second embodiment.
In the first embodiment, the external heating roll 613 is disposed downstream of the internal heating roll 612 in the moving direction of the fixing belt 610, and the fixing belt 610 is moved more than the nip portion N (fixing roll 611). Was located upstream in the direction. On the other hand, in 2nd Embodiment, the arrangement position of the external heating roll 613 is varied. In addition, about the function similar to 1st Embodiment, the same code | symbol is used and the description is abbreviate | omitted here.

In the present embodiment, as described above, the arrangement position of the external heating roll 613 is different from that in the first embodiment. Specifically, the external heating roll 613 is disposed on the upstream side in the moving direction of the fixing belt 610 with respect to the internal heating roll 612, and further on the downstream side in the moving direction of the fixing belt 610 with respect to the nip portion N and the fixing roll 611. Is arranged.
In this embodiment, a fixing mode and a cleaning mode are also provided. In each of these modes, processing similar to that shown in the first embodiment is performed.

  That is, in the fixing mode, a sheet is introduced into the nip portion N and a fixing process is performed. Further, temperature control as shown in FIG. 3 is performed. In the cleaning mode, the process shown in FIG. 4 is performed. That is, in the cleaning mode, the heater 616b provided in the internal heating roll 612 is turned on, and the fixing belt 610 is at a predetermined temperature. On the other hand, the external heating roll 613 is not heated and the temperature is low. As a result, the offset toner adhering to the fixing belt 610 moves to the external heating roll 613. The toner that has moved to the external heating roll 613 is removed by the cleaning member 617.

  As described in the first embodiment, the fixing belt is located downstream of the nip portion N and the fixing roll 611 in the movement direction of the fixing belt 610 and upstream of the internal heating roll 612 in the movement direction of the fixing belt 610. 610 is in a low temperature state. In this embodiment, the external heating roll 613 is brought into contact with a portion of the fixing belt 610 where the temperature is low. For this reason, in this embodiment, the temperature difference between the fixing belt 610 and the external heating roll 613 is smaller than that in the first embodiment. In the present embodiment, if the fixing belt 610 is heated not by the internal heating roll 612 but by the fixing roll 611, the temperature difference can be increased.

  In the first and second embodiments described above, the example in which the toner moves from the high temperature side member (fixing belt 610) to the low temperature side member (external heating roll 613) has been described, but depending on the type of toner, A case of moving from the low temperature side to the high temperature side is also conceivable. For example, it is difficult to move in a state where there is not much temperature difference between the members, but when the temperature difference between the members occurs to some extent and both members are kept at a relatively high temperature, the low temperature side to the high temperature side It is also conceivable that there is toner that moves to In such a case, for example, the temperature of the fixing belt 610 and the external heating roll 613 is raised, and the temperature of the external heating roll 613 is made higher than the temperature of the fixing belt 610. Thereby, the offset toner adhering to the fixing belt 610 can be moved to the external heating roll 613 side.

Here, the result of the cleaning according to the above embodiment will be described together with a comparative example.
FIG. 6 shows the state of the fixing belt 610 after cleaning the toner constituting the solid image formed on the fixing belt 610 in the first embodiment.
More specifically, solid images formed of single-layer, two-layer, and three-layer offset toners are formed on the fixing belt 610, and these solid images are cleaned and the state of the fixing belt 610 after the cleaning is performed. Was observed.
In this figure, the cleaning result when the process of FIG. 4 is performed is described as “this embodiment” in the figure, the process of step 202 and step 203 in FIG. 4 is omitted, and the process of step 201 and step 204 is performed. The result when it is performed is described as “Comparative Example” in the figure.

Further, “◯” in the figure indicates that the solid image can be almost removed and the cleaning result is good. “Δ” indicates that a part of the solid image remains on the fixing belt 610. “X” indicates that the solid image could hardly be removed and the cleaning was poor.
As shown in the figure, in the comparative example, although a single layer had a slight cleaning effect, solid images could hardly be removed in two and three layers, resulting in poor cleaning. On the other hand, in this embodiment, it was possible to confirm the removal of the solid image under any condition of single layer, two layers, and three layers.

1 is a schematic configuration diagram illustrating an image forming apparatus according to a first embodiment. FIG. 2 is a side sectional view illustrating a schematic configuration of a fixing device. 6 is a flowchart illustrating processing executed by a control unit in a fixing mode. It is the flowchart which showed the process performed in cleaning mode. FIG. 6 is a side cross-sectional view illustrating a schematic configuration of a fixing device according to a second embodiment. FIG. 3 shows the state of the fixing belt after cleaning, with the toner constituting the solid image formed on the fixing belt in the first embodiment being cleaned. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 40 ... Control part, 62 ... Pressure roll, 610 ... Fixing belt, 611 ... Fixing roll, 612 ... Internal heating roll, 613 ... External heating roll, 616a-616c ... Heater, 617 ... Cleaning member, N ... Nip part

Claims (9)

A first fixing member rotatably disposed;
Second fixing for fixing the image on the recording material by passing a recording material that is rotatably disposed on the first fixing member and holding an image in a contact area with the first fixing member. A member,
An external heating member that is rotatably disposed on the outer peripheral surface of the first fixing member and heats the first fixing member;
A cleaning member for cleaning the outer peripheral surface of the external heating member,
A foreign matter is adhered from the first fixing member to the external heating member in a state in which the temperature difference between the first fixing member and the external heating member is different from that at the time of fixing. An image forming apparatus for removing foreign matter adhering to a heating member.   The image forming apparatus according to claim 1, wherein the temperature difference is larger than a temperature difference between the first fixing member and the external heating member during fixing. A heating member for heating the first fixing member;
The external heating member is disposed upstream of the contact area in the rotation direction of the first fixing member and downstream of the heating member in the rotation direction of the first fixing member. The image forming apparatus according to 1.   The image forming apparatus according to claim 1, wherein the cleaning member is disposed so that its position relative to the external heating member can be changed. A first fixing member rotatably disposed;
Second fixing for fixing the image on the recording material by passing a recording material that is rotatably disposed on the first fixing member and holding an image in a contact area with the first fixing member. A member,
An external heating member that is rotatably disposed on the outer peripheral surface of the first fixing member and heats the first fixing member;
A cleaning member for cleaning a foreign matter adhered to the external heating member by creating a temperature difference between the first fixing member and the external heating member;
Including a fixing device. The cleaning member is arranged to be able to press the external heating member,
The fixing device according to claim 5, wherein the pressing force with which the cleaning member presses the external heating member is adjustable. A heating source, further comprising a heating member for heating the first fixing member;
6. The fixing device according to claim 5, wherein the heating source is turned off when the temperature difference is set between the first fixing member and the external heating member. The external heating member includes a heating source,
6. The fixing device according to claim 5, wherein the heating source is turned off when the temperature difference is set between the first fixing member and the external heating member. A first fixing member rotatably disposed;
Second fixing for fixing the image on the recording material by passing a recording material that is rotatably disposed on the first fixing member and holding an image in a contact area with the first fixing member. A member,
A computer provided in an image forming apparatus, comprising: an external heating member that is rotatably contacted with an outer peripheral surface of the first fixing member and that heats the first fixing member;
After the fixing of the image to the recording material, when the first fixing member is cleaned, the first fixing member and the external heating member are in contact with each other at the contact portion between the first fixing member and the external heating member. A function to make the temperature difference different from the temperature difference when fixing,
A function of rotating the first fixing member in a state where the temperature difference is different;
A program to realize

Images