JP2008233232A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device capable of restraining degradation in image quality and releasing performance, and to provide an image forming apparatus. <P>SOLUTION: A releasing pad 64 has a curved face 64c formed downstream of a pressing face 64b in the moving direction of a fixing belt 610. The place where the pressure of the fixing belt 610 on a pressure roll 62 is released is between the curved face 64c and pressure roll 62. Paper passed through a pressing area is released from pressure in the pressure releasing place. In the pressure releasing place, the fixing belt 610 is curved because the curved face 64c is pressed. Consequently, the paper that has reached the pressure releasing place is released from the pressure applied by the pressure roll 62, and cannot follow a change in the fixing belt 61 in its advancing direction. Accordingly, the paper is released from the fixing belt 610 by its own stiffness when passed through the pressure releasing place. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer, and a fixing device used in the image forming apparatus.

  Conventionally, in order to enable self-separation of the recording material from the fixing belt, the exit separating portion surface is located on the inner side of the fixing belt at a position corresponding to the outlet separating portion of the nip portion formed by the fixing roll and the pressure roll. A belt fixing device including a fixing member having a shape with a large curvature has been proposed (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 2003-5565

  Here, when the sheet is peeled off from the fixing belt by providing a member that bends the fixing belt on the downstream side of the nip portion, the recording material that holds the toner image depends on the position of the bending member. On the other hand, a region where pressure from a pressure roll or the like is not applied may be formed. When such a region is formed, thermal expansion of water vapor due to vaporization of moisture in the recording material or air existing in the toner gap may occur. If water vapor or thermal expansion occurs, the toner image may be disturbed due to, for example, a blister phenomenon, and the image quality may be deteriorated. In addition, the position of the member to be bent may change due to changes over time of the member, and the recording material peeling performance may deteriorate.

  SUMMARY An advantage of some aspects of the invention is to provide a fixing device and the like that can suppress a reduction in image quality and a reduction in peeling performance.

  For this purpose, a fixing device to which the present invention is applied includes a belt-like member that is rotatably arranged, a fixing member that is arranged inside the belt-like member, and the belt-like member via the belt-like member. A pressure contact member that is disposed in pressure contact with the fixing member and that fixes an image held on the recording material to the recording material; and a pressure contact member that forms a gap between the belt-shaped member and the belt-shaped member. The belt-like member that presses the belt-like member from the inside on the side to bring the belt-like member and the pressure contact member into contact with each other, and the belt-like member that has passed through the pressure surface is bent in a direction away from the pressure contact member. And a separating member that separates the belt-shaped member from the pressure contact member in a curved region of the shaped member.

  Here, the separation surface may be characterized in that the belt-shaped member is separated from the pressure contact member on the upstream side in the movement direction of the belt-shaped member in the curved region. The pressing surface presses the belt-shaped member against the pressure contact member over the entire area of the pressing surface, and the belt-shaped member pressed over the entire area is brought into contact with the pressure contact member. Can do.

  From another point of view, the fixing device to which the present invention is applied includes a belt-like member that is rotatably arranged at a predetermined speed, a fixing member that is arranged inside the belt-like member, and the belt A pressure contact member that is disposed in pressure contact with the fixing member via a belt-like member, and that forms a nip portion between the belt-like member and that fixes the image held on the recording material to the belt, and the belt more than the nip portion. A contact portion that presses the belt-shaped member from the inside on the downstream side in the moving direction of the belt-shaped member to bring the belt-shaped member into contact with the pressure contact member, and the belt-shaped member that has passed through the contact portion is not in contact with the pressure contact member A belt having a first surface provided with a non-contact portion and a belt-like member that is brought into the non-contact state by the non-contact portion at a position where the belt-like member can be reached within 20 msec. Pressure It includes a second surface which is curved in a direction away from the member, a pressing member comprising, a.

  Here, the second surface may be arranged at a position where the belt-like member brought into the non-contact state by the non-contact portion can reach within 10 msec. In addition, the pressing force with which the contact portion presses the belt-like member can be adjusted.

  Further, when the present invention is regarded as an image forming apparatus, an image forming apparatus to which the present invention is applied includes an image forming unit that forms an image on a recording material, and an image formed on the recording material by the image forming unit. A fixing device for fixing the recording material to the recording material. The fixing device includes a belt-shaped member rotatably disposed, a fixing member disposed inside the belt-shaped member, and the belt-shaped member. A pressure contact member that is disposed in pressure contact with the fixing member and fixes the image held on the recording material to the recording material between the pressure contact member and the belt-shaped member, and the movement of the belt-shaped member relative to the nip. A pressure surface that presses the belt-shaped member from the inside on the downstream side in the direction to bring the belt-shaped member and the pressure contact member into contact with each other, and the belt-shaped member that has passed through the pressure surface is bent in a direction away from the pressure contact member. The bell The belt-shaped member in the curved region of the Jo member and having a, a pressing member and a spacing surface to separate from the pressing member.

According to the first aspect of the present invention, it is possible to provide a fixing device capable of suppressing a reduction in image quality as compared with a case where this configuration is not provided.
According to the second aspect of the present invention, the peeling performance of the recording material can be improved as compared with the case where the recording material is not provided.
According to invention of Claim 3, generation | occurrence | production of a blister can be suppressed compared with the case where it does not have this structure.
According to the invention described in claim 4, it is possible to provide a fixing device capable of suppressing a decrease in peeling performance as compared with the case where the present configuration is not provided.
According to the fifth aspect of the present invention, it is possible to improve the quality of the image as compared with the case where the present configuration is not provided.
According to the sixth aspect of the present invention, it is possible to easily provide a providing device that can suppress a decrease in peeling performance as compared with a case where the present configuration is not provided.
According to the seventh aspect of the present invention, it is possible to provide an image forming apparatus capable of suppressing deterioration in image quality as compared with the case where the present configuration is not provided.

-First embodiment-
Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a schematic configuration diagram showing an image forming apparatus to which the present invention is applied. 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).

  Inside the intermediate transfer belt 15, various rolls such as a drive roll 31 that is stretched from the inside and rotated by a motor (not shown) having excellent constant speed are provided. ing. Further, a transport belt 55 that transports the paper P on which secondary transfer has been performed, a fixing device 60 that fixes the toner image of the paper P transported by the transport belt 55 to the paper P, and the operation of each device (each unit). And a control unit 40 for controlling.

  In the present embodiment, the following electrophotographic devices are sequentially arranged in each of the image forming units 1Y, 1M, 1C, and 1K. First, a charger 12 for charging the photosensitive drum 11 is disposed around the photosensitive drum 11 rotating in the direction of arrow A. 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. A drum cleaner 17 for removing residual toner on the photosensitive drum 11 is also 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 holding surface side of the intermediate transfer belt 15 and a backup roll 25. The secondary transfer roll 22 is disposed in pressure contact with the backup roll 25 with the intermediate transfer belt 15 interposed therebetween.
The control unit 40 includes a CPU (Central Processing Unit) that controls the operation of each device (each unit), a ROM (Read Only Memory) that stores a program, a RAM (Random Access Memory) that stores various data, and the like. ing.

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. This image data is subjected to predetermined image processing by an image processing device (not shown), and converted into color material gradation data of four colors of Y (yellow), M (magenta), C (cyan), and K (black). 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. 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 developed as toner images of Y, M, C, and K colors by the developing devices 14 of the respective image forming units 1Y, 1M, 1C, and 1K. On the other hand, the intermediate transfer belt 15 is circulated and driven at a predetermined speed in the direction of arrow B shown in FIG. 1 by various rolls such as a drive roll 31. 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 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 held 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 conveyed by the secondary transfer roll 22 to a conveyance belt 55 provided on the downstream side of the secondary transfer roll 22 in the sheet conveyance direction. 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 shown in FIG. 1 includes a fixing belt module 61 and a pressure roll 62 arranged in pressure contact with the fixing belt module 61.

  The fixing belt module 61 includes an endless fixing belt 610 that is rotatably provided, a fixing roll 611 that is rotatably provided inside the fixing belt 610, and a tension roll 612 that stretches the fixing belt 610 from the inside. And. Also, an external heating roll 613 that stretches the fixing belt 610 from the outside and heats the fixing belt 610 from the outside, and an attitude correction roll 614 that corrects the attitude of the fixing belt 610 between the fixing roll 611 and the tension roll 612. It is equipped with. Further, a peeling pad that promotes peeling of the paper P from the fixing belt 610 in a downstream area in the nip portion N where the fixing belt module 61 and the pressure roll 62 are in pressure contact with each other and in the vicinity of the fixing roll 611. 64. Further, a support member 617 that supports the peeling pad 64 and a spring member 618 that presses the peeling pad 64 toward the pressure roll 62 are provided. Further, a support member 619 that is provided so as to be movable in a direction approaching and separating from the peeling pad 64 (see arrow G in the drawing) and supports one end of the spring member 618, and a fixing belt 610 on the downstream side of the nip portion N. And an idler roll 615 that stretches.

  The fixing belt module 61 includes a heating source 616 a such as a halogen heater that is disposed inside the fixing roll 611 and heats the fixing roll 611, and a halogen that is disposed inside the external heating roll 613 and heats the external heating roll 613. And a heating source 616c such as a heater. Further, a heating source 616b such as a halogen heater provided inside the tension roll 612 for heating the tension roll 612 is provided. Further, a drive source (not shown) such as a motor for rotating the fixing roll 611 and a tension roller 612 are arranged in the vicinity of both ends of the tension roll 612. And a spring member (not shown) for applying the tension.

The fixing belt 610 is a flexible endless belt having a predetermined width and a predetermined circumference. The fixing belt 610 includes, for example, a base layer formed of polyimide resin or the like, an elastic layer made of silicone rubber or the like laminated on the surface side (outer peripheral surface side) of the base layer, and further coated on the elastic layer. And a release layer made of a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA) tube or the like.
The fixing roll 611 is a hard roll that is not covered with an elastic layer and is formed by coating the surface of an aluminum cored bar (core roll) with a heat resistant resin (fluororesin). The fixing roll 611 functions as one of fixing members. In this embodiment, a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) is used as the heat resistant resin.

The tension roll 612 is a cylindrical roll formed of, for example, aluminum.
The peeling pad 64 is a member provided along the axial direction of the fixing roll 611, and a member having a substantially arc shape in cross section. The peeling pad 64 is formed of, for example, SUS metal or resin. Further, 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 (“roll nip portion N1”). Further, the peeling pad 64 is installed so as to uniformly press the pressure roll 62 with a predetermined load over a predetermined width region via the fixing belt 610. As a result, the “peeling pad nip portion N2” is formed.

  The pressure roll 62 uses 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, the pressure roll 62 is provided to be movable in a direction approaching the fixing belt module 61 and a direction away from the fixing belt module 61 (in the direction of arrow F in the figure) by a driving source (not shown). The pressure roll 62 functions as one of the pressure contact members.

  Next, the operation of the fixing device 60 will be described. When fixing is performed by the fixing device 60, first, the pressure roll 62 that is separated from the fixing belt module 61 is pressed against the fixing belt module 61 by a driving source (not shown). Next, the paper P on which the toner image is held is introduced into the nip portion N. 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). Further, the fixing belt 610 is rotated 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 paper P introduced into the nip portion N is conveyed downstream by the rotating fixing belt 610 and the pressure roll 62, and sequentially passes through the roll nip portion N1 and the peeling pad nip portion N2.

  The paper P is subjected to pressure and heating action from the fixing belt 610 and the pressure roll 62 in the process of passing through the roll nip portion N1 and the peeling pad nip portion N2. As a result, the toner image is fixed on the paper P. On the other hand, the fixing belt 610 that has passed through the peeling pad nip portion N2 moves along the side surface of the peeling pad 64 thereafter. 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 P cannot follow the change in the advancing direction of the fixing belt 610 when it leaves the peeling pad nip portion N2. As a result, the sheet is peeled from the fixing belt 610 by the so-called “koshi”. In this manner, curvature separation with respect to the sheet is stably performed at the exit of the nip portion N. The sheet separated from the fixing belt 610 is guided in the traveling direction by a peeling guide plate (not shown) disposed on the downstream side of the nip portion N. When the fixing process is completed in this way, the pressure roll 62 is retracted from the fixing belt module 61 by a driving source (not shown) and is disposed at a predetermined position separated from the fixing belt module 61.

Here, the fixing device 60 will be described in more detail.
FIG. 3 is an explanatory view showing the periphery of the peeling pad 64 in detail.
As shown in the figure, the peeling pad 64 in the present embodiment has an outer surface of the pressure roll 62 sandwiched between an inner surface 64a disposed opposite to the outer peripheral surface of the fixing roll 611 with a predetermined gap. And a pressing surface 64b disposed to face the surface (release layer 623 (see FIG. 2)). The peeling pad 64 has a curved surface 64c disposed on the downstream side in the moving direction of the fixing belt 610 with respect to the pressing surface 64b, and an outer surface disposed on the downstream side in the moving direction of the fixing belt 610 with respect to the curved surface 64c. 64d. This peeling pad 64 functions as one of the pressing members.

As described above, the inner side surface 64 a is disposed at a position having a predetermined gap from the outer peripheral surface of the fixing roll 611, and is disposed along the outer peripheral surface of the fixing roll 611.
The pressing surface 64b is disposed on the downstream side of the roll nip portion N1, and the upstream tip portion thereof is connected to the inner side surface 64a, and the tip portion of the peeling pad 64 is formed in a wedge shape together with the inner side surface 64a. is doing. And in this embodiment, generation | occurrence | production of the blister in the exit part of the roll nip part N1 is suppressed by arrange | positioning the front-end | tip part formed in this wedge shape close to the roll nip part N1. The pressing surface 64b functions as one of the first surfaces.

  In addition, the pressing surface 64b is formed so that the cross section thereof is linear or follows the outer surface shape of the pressure roll 62 when the fixing roll 611 is in pressure contact, and has a predetermined curvature. Is formed. Further, the pressing surface 64 b is disposed in contact with the inner peripheral surface of the fixing belt 610. The pressing surface 64b is pressed against the pressure roll 62 via the fixing belt 610 with a pressure capable of suppressing the blister. Further, the entire pressing surface 64 b is pressed against the pressure roll 62 via the fixing belt 610 in order to suppress the generation of blisters. As a result, a pressing portion that applies pressure to the sheet P is formed between the fixing belt 610 and the pressure roll 62 at a position facing the pressing surface 64 b.

  The curved surface 64c is disposed downstream of the pressing surface 64b in the moving direction of the fixing belt 610 as described above. The curved surface 64c functions as one of the separation surface and the second surface. The curved surface 64c is formed in a state of being continuous with the pressing surface 64b, and is curved so as to be separated from the outer surface of the pressure roll 62 toward the downstream side in the moving direction of the fixing belt 610. Further, the curved surface 64c is formed with a curvature larger than the curvature of the pressing surface 64b. Further, the curved surface 64 c is pressed against the inner peripheral surface of the fixing belt 610. As a result, the fixing belt 610 that has passed through the pressing portion bends away from the pressure roll 62 in the region where the curved surface 64c is formed (hereinafter, the region where the fixing belt 610 is curved is referred to as a “curved region”). .)

  In addition, the curved surface 64 c is pressed against the pressure roll 62 via the fixing belt 610 on the upstream side in the formation direction (upstream side in the movement direction of the fixing belt 610). Further, the curved surface 64 c is not pressed against the pressure roll 62 via the fixing belt 610 on the downstream side in the formation direction. Therefore, when the fixing belt 610 that has passed through the pressing portion reaches a region where the curved surface 64c is not pressed and arranged on the pressure roll 62 via the fixing belt 610, the pressure (pressure) is applied to the pressure roll 62. ) Is canceled.

  The outer side surface 64d is formed continuously with the curved surface 64c and has a curvature smaller than that of the curved surface 64c. In the present embodiment, the outer surface 64d has a cross section that is linear. The outer side surface 64d is disposed to face the inner peripheral surface of the fixing belt 610, and is formed so as to be separated from the fixing belt 610 as the fixing belt 610 advances.

  In the present embodiment, a position where the pressure of the fixing belt 610 on the pressure roll 62 is released (hereinafter referred to as “pressure release position”) is disposed between the curved surface 64 c and the pressure roll 62. The Then, the paper P that has passed through the pressing portion is released from pressure at this pressure release position. In this pressure release position, the fixing belt 610 is in a curved state because the curved surface 64c is pressed and arranged as described above. As a result, the paper P that has reached the pressure release position is not subjected to pressure from the pressure roll 62, and at the same time cannot follow the change in the traveling direction of the fixing belt 610. For this reason, the sheet P is peeled off from the fixing belt 610 by its own “stiffness” when passing through the pressure release position. Since the separation performance improves as the traveling direction of the fixing belt 610 and the traveling direction of the paper P are different, it is preferable to provide the pressure release position on the upstream side of the curved region of the fixing belt 610 as shown in FIG. .

  In the present embodiment, a pressure capable of suppressing blistering is applied to the paper P at the pressing portion, and the pressure between the fixing belt 610 and the pressure roll 62 is released at a portion where the fixing belt 610 is curved. It becomes the composition which is done. For this reason, it becomes possible to apply the pressure which can suppress a blister to paper P until just before peeling. As a result, good fixing image quality can be obtained, and good peeling performance can be secured.

  Incidentally, the position of the peeling pad 64 with respect to the pressure roll 62 or the like may change even if the state shown in FIG. For example, the position of the peeling pad 64 may change as the hardness of the elastic layer 622 or the like in the pressure roll 62 changes over time. In addition, for example, the position of the peeling pad 64 may change due to a change in sliding resistance between the peeling pad 64 and the inner peripheral surface of the fixing belt 610. Furthermore, the position of the peeling pad 64 may change due to a change with time of a spring member (not shown) that presses the peeling pad 64 toward the pressure roll 62. If the position of the peeling pad 64 changes, a situation may occur in which the paper P is not peeled from the fixing belt 610.

FIG. 4 is an explanatory diagram showing in detail the periphery of the peeling pad 64 when the position of the peeling pad 64 changes.
When the position of the peeling pad 64 with respect to the pressure roll 62 or the like changes, the peeling pad 64 may sink into the pressure roll 62 and the pressure roll 62 may be recessed as shown in FIG. As a result, the pressure release position disposed at the position facing the curved surface 64c may move downstream in the moving direction of the fixing belt 610 and disposed at the position facing the outer surface 64d. When the pressure release position is arranged in this manner, the traveling direction of the paper P at the pressure release position is in a state along the traveling direction of the fixing belt 610. As a result, it is difficult to peel off the paper from the fixing belt 610, and there is a possibility that a peeling failure such as winding of the paper P around the fixing belt 610 may occur. Therefore, in order to suppress the occurrence of such a problem, the following configuration may be employed.

-Second Embodiment-
FIG. 5 is an explanatory diagram showing in detail the periphery of the peeling pad 64 in the second embodiment.
As shown in the figure, in the present embodiment, the downstream side in the formation direction of the pressing surface 64 b and the curved surface 64 c are brought into a state of floating from the pressure roll 62, and these are not attached to the pressure roll 62 via the fixing belt 610. It arrange | positions so that it may be in a press state. In other words, in this embodiment, the fixing belt 610 is not in contact with the outer surface of the pressure roll 62 between the pressure surface 64 b and the curved surface 64 c and the pressure roll 62. As a result, a non-pressurized portion where the fixing belt 610 is not pressed against the pressure roll 62 is formed in the area that has been the pressing portion in the first embodiment.

Thus, when the peeling pad 64, the pressure roll 62, etc. are arrange | positioned, the peeling pad 64 becomes difficult to sink into the pressure roll 62. FIG. As a result, it is possible to suppress the winding of the paper P around the fixing belt 610.
By the way, when the non-pressurized portion is formed in which the fixing belt 610 is not pressed against the pressure roll 62, the pressure on the paper P is not performed until the paper is peeled off at the peeling portion. As a result, in this non-pressurized portion, water vapor due to vaporization of water in the paper P and thermal expansion of air existing in the toner gaps may occur, and the toner image may be disturbed, that is, blisters may occur and image The quality of the product may be reduced. On the other hand, even if there is a non-pressurized portion, if the distance is short, the generation of blisters can be suppressed, and the deterioration of image quality can be suppressed.

  Therefore, the inventor conducted an experiment and visually examined the influence on the image by the passage time (the length of the non-pressurized portion) when the fixing belt 610 passes through the non-pressurized portion. The experimental conditions are as follows. In this experiment, the effect of paper type was also investigated.

The temperature of the fixing belt 610:
-When the paper P is an OK top coat (84.9 [g / m ² ], manufactured by Oji Paper Co., Ltd.)… 160 [° C.]
・ When paper P is mirror coat platinum (84.9 [g / m ² ], manufactured by Fuji Xerox Office Supply Co., Ltd.)… 175 [° C]
-When the paper P is an OK top coat (127.9 [g / m ² ], manufactured by Oji Paper Co., Ltd.)… 175 [° C]
Process speed (moving speed of fixing belt 610): 264 [mm / sec]
-Specifications of fixing belt 610:
-Diameter of fixing belt 610: φ168 [mm]
-Layer structure of fixing belt 610:
-Release layer: PFA (thickness: 30 [μm])
-Elastic layer: silicone rubber (thickness: 160 [μm])
・ Base layer: Polyimide (thickness: 90 [μm])

-Specifications of fixing roll 611:
-Diameter of fixing roll 611: φ100 [mm]
Configuration of fixing roll 611: A PFA surface layer (thickness: 300 [μm]) was formed on a core roll made of aluminum.
・ Specifications of the pressure roll 62:
・ Pressure roll 62 diameter: φ65 [mm]
Structure of the pressure roll 62: A silicon (Si) rubber intermediate layer (thickness: 10 [mm]) and a PFA surface layer (thickness: 100 [μm]) were formed on the cylindrical roll 621.
・ Specifications of peeling pad 64 ・ Material: Stainless steel ・ Shape of pressing surface 64b: Flat (straight section)
The length of the pressing surface 64b in the moving direction of the fixing belt 610: 11 [mm]
-Curvature radius of curved surface 64c: 3 [mm]
Fixing load at the roll nip portion N1 (pressing load of the pressure roll 62 against the fixing roll 611): 1471 [N] (150 [kgf])
-Pressure load of the peeling pad 64 against the pressure roll 62: 490.3 [N] (50 [kgf])

Hereinafter, experimental results will be described.
FIG. 6 shows the influence on the image by the passage time (length of the non-pressurized portion) when a predetermined portion of the fixing belt 610 passes through the non-pressurized portion.
As shown in the figure, there is no pressure-free part (the time for passing through the pressure-free part is 0 [msec] (the length of the pressureless part: 0 [mm])). When the time for passing through the pressure part was 10 [msec] (length of the non-pressurized part: 2.6 [mm]), generation of blisters could not be confirmed.

In addition, when the time for passing through the non-pressurized portion is 20 [msec] (length of the non-pressurized portion is 5.3 [mm]), blisters are generated in an OK top coat (84.9 [g] / m ² ]) and mirror-coated platinum (84.9 [g / m ² ]), the generated blisters were able to ensure sufficient image quality.
Furthermore, when the time for passing through the non-pressurized portion is 30 [msec] (the length of the non-pressurized portion is 7.9 [mm]), the OK top coat (84.9 [g / m ² ]) that is thin paper is used. In addition, it was confirmed that a blister that significantly deteriorates the image quality occurs in mirror coated platinum (84.9 [g / m ² ]). It was confirmed that the image quality of mirror coat platinum (84.9 [g / m ² ]) was lower than that of OK top coat (84.9 [g / m ² ]). On the other hand, in the case of an OK top coat (127.9 [g / m ² ]) which is a cardboard, although the generation of blisters was confirmed, this blister was in a state where image quality could be sufficiently secured.

  As a result, it can be seen that the longer the time required to pass through the non-pressurized portion (the longer the length of the non-pressurized portion), the easier the blister occurs. On the other hand, even if the non-pressurized part was present, it was confirmed that the image quality could be sufficiently ensured if the time passing through the non-pressurized part was 20 [msec] or less. For this reason, when the time for passing through the non-pressurized portion is 20 [msec], the peeling performance can be maintained over a long period while balancing the image quality and the peeling performance. In addition, it will become more preferable when the time which passes a non-pressurization part shall be 10 [msec] or less.

In addition, in the case of thin cast paper such as OK top coat (84.9 [g / m ² ]) and mirror coat platinum (84.9 [g / m ² ]), the fixing temperature is increased to give gloss. However, blistering tends to occur when the fixing temperature is high. And if a non-pressurization part is formed like this embodiment, it will become easier to produce a blister. However, by setting the time for passing through the non-pressurized portion to 20 [msec] or less as in the present embodiment, it is possible to sufficiently ensure the quality of the image even on a sheet in which blisters are likely to occur.

  In the above-described embodiment, as described above, the spring member 618 that presses the peeling pad 64 toward the pressure roll 62 and the spring member that is movable in the direction approaching and separating from the peeling pad 64 are provided. A support member 619 that supports one end of 618 is provided. For this reason, by moving the support member 619, it is possible to adjust the pressing force acting on the peeling pad 64 from the spring member 618. As a result, the position of the peeling pad 64 with respect to the pressure roll 62 can be adjusted, and the pressure release position can be varied along the moving direction of the fixing belt 610. For this reason, when the fixing device 60 is manufactured, it is assumed that the pressure release position is disposed at a position different from the positions shown in the first embodiment and the second embodiment due to the tolerance of each member. In addition, the pressure release position can be easily adjusted by moving the support member 619.

1 is a schematic configuration diagram illustrating an image forming apparatus to which the present invention is applied. FIG. 2 is a side sectional view illustrating a schematic configuration of a fixing device. It is explanatory drawing which showed the peeling pad periphery in detail. It is explanatory drawing which showed the periphery of the peeling pad in detail when the position of a peeling pad changed. It is the figure which showed the peeling pad periphery in 2nd Embodiment. This shows the influence on the image by the passage time (length of the non-pressurized portion) when a predetermined portion of the fixing belt passes through the non-pressurized portion.

Explanation of symbols

60 ... fixing device, 62 ... pressure roll, 64 ... peeling pad, 64b ... pressing surface, 64c ... curved surface, 610 ... fixing belt, 611 ... fixing roll

Claims (7)

A belt-like member disposed rotatably;
A fixing member disposed inside the belt-shaped member;
A pressure contact member that is disposed in pressure contact with the fixing member via the belt-shaped member, and that forms a nip portion between the belt-shaped member and that fixes the image held on the recording material on the recording material;
A pressing surface that presses the belt-shaped member from the inside on the downstream side of the nip in the moving direction of the belt-shaped member to bring the belt-shaped member into contact with the pressure contact member, and the belt-shaped member that has passed through the pressing surface. A separating surface that curves in a direction away from the pressure contact member and separates the belt-shaped member from the pressure-contact member in a curved region of the belt-shaped member;
Including a fixing device.   The fixing device according to claim 1, wherein the separation surface separates the belt-shaped member from the pressure contact member on the upstream side in the movement direction of the belt-shaped member in the curved region.   2. The pressing surface presses the belt-shaped member against the pressure contact member over the entire area of the pressing surface, and contacts the belt-shaped member pressed over the entire area with the pressure contact member. The fixing device described. A belt-like member disposed rotatably at a predetermined speed;
A fixing member disposed inside the belt-shaped member;
A pressure contact member that is disposed in pressure contact with the fixing member via the belt-shaped member, and that forms a nip portion between the belt-shaped member and that fixes the image held on the recording material on the recording material;
A contact portion that presses the belt-like member from the inside at a downstream side of the nip portion in the moving direction of the belt-like member, and a belt-like member that has passed through the contact portion. A first surface provided with a non-contact portion that is brought into a non-contact state with the pressure contact member, and a belt-like member brought into the non-contact state by the non-contact portion are disposed at a position where the belt-like member can reach within 20 msec. A pressing member comprising: a second surface that curves the belt-like member in a non-contact state in a direction away from the pressure contact member;
Including a fixing device.   The fixing device according to claim 4, wherein the second surface is disposed at a position where the belt-like member brought into the non-contact state by the non-contact portion can reach within 10 msec.   The fixing device according to claim 4, wherein the pressing force with which the contact portion presses the belt-like member is adjustable. An image forming unit that forms an image on the recording material, and a fixing device that fixes the image formed on the recording material by the image forming unit to the recording material,
The fixing device includes:
A belt-like member disposed rotatably;
A fixing member disposed inside the belt-shaped member;
A pressure contact member that is disposed in pressure contact with the fixing member via the belt-shaped member, and that forms a nip portion between the belt-shaped member and that fixes the image held on the recording material on the recording material;
A pressing surface that presses the belt-shaped member from the inside on the downstream side of the nip in the moving direction of the belt-shaped member to bring the belt-shaped member into contact with the pressure contact member, and the belt-shaped member that has passed through the pressing surface. A separating surface that curves in a direction away from the pressure contact member and separates the belt-shaped member from the pressure-contact member in a curved region of the belt-shaped member;
An image forming apparatus comprising:

Images