JP5045069B2 - Fixing device - Google Patents

Description

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

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 holding a toner image is heated and pressurized to fix the toner image on the recording material.
The fixing device used for the fixing process is composed of, for example, a belt-like member that is heated by a heating source such as a heater and is movable, and a roll-like member that is disposed in pressure contact with the belt-like member. The thing which was done is mentioned. A nip portion is formed in the pressure contact portion between the belt-shaped member and the roll-shaped member to perform heating and pressure treatment on the introduced paper. In such a fixing device, when the recording material holding the toner image is inserted into the nip portion, the toner image is fixed on the recording material under the action of heating and pressing.

  In the fixing device, the toner image on the recording material is melted when receiving a heating action at the nip portion. The melted toner image functions as an adhesive for bonding the belt-shaped member and the recording material, and the recording material after passing through the nip may remain attached to the belt-shaped member. For this reason, it is necessary to provide a mechanism for peeling the recording material from the belt-like member. As such a mechanism, for example, a fixing member that presses the belt-shaped member against the roll-shaped member and increases the curvature of the belt-shaped member on the downstream side of the pressure contact portion formed by the belt-shaped member and the roll-shaped member. The provided one has been proposed (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 2003-5565

  By the way, when the belt-shaped member is pressed against the roll-shaped member using the fixing member on the downstream side of the pressure-contacting portion formed by the belt-shaped member and the roll-shaped member, a portion where the pressure contacting portion and the fixing member are disposed; A nip portion that heats and pressurizes the recording material is also formed between the two. In order to obtain stable fixing performance, it is desirable that the pressure at the nip is uniform in the axial direction, but it is difficult to maintain a uniform pressure when, for example, the fixing member is bent or distorted. It becomes difficult to obtain stable fixing performance. Further, when the fixing member is bent or distorted, the fixing member and other members in the fixing device may come into contact with each other, and the member may be worn or damaged. Even in such a case, it is difficult to maintain stable fixing performance.

  Accordingly, the present invention has been made to solve the above technical problems, and an object of the present invention is to provide a fixing device having stable fixing performance.

  For this purpose, a fixing device to which the present invention is applied includes a belt-like member that is rotatably provided, a first fixing member that is provided inside the belt-like member, and a belt-like member. A second fixing member that is disposed in pressure contact with the first fixing member and fixes an image held on the recording material between the fixing member and the belt-like member; the first fixing member and the second fixing member; A pressing member that presses the belt-shaped member against the second fixing member on the downstream side of the pressure contact portion formed by the member, and a uniform pressing load when the pressing member presses the second fixing member via the belt-shaped member And uniformizing means for achieving the same.

  Here, the uniformizing means can be characterized by comprising a pressing member that deforms in a direction to equalize the pressing load when the second fixing member is pressed through the belt-shaped member. In addition, the pressing member may be provided with a deformation in a direction opposite to a direction in which the pressing member is deformed when the second fixing member is pressed through the belt-shaped member. Further, the pressing surface on which the pressing member presses the second fixing member via the belt-shaped member has a portion that is recessed from the predetermined portion when the pressing member presses the second fixing member via the belt-shaped member. It can be characterized by being formed in a state protruding from the predetermined portion.

  The pressing member further includes an applying member that applies a pressing force when the pressing member presses the second fixing member via the belt-like member to a predetermined portion of the pressing member, and the pressing member passes the belt-like member through the second member. One part constituting a part of the pressing surface that presses the fixing member is located closer to the belt-like member than the other part that constitutes a part of the pressing surface and is located closer to the predetermined part than the one part. It can be characterized by. Further, the uniformizing means may be constituted by a pressing member having a protruding portion protruding toward the first fixing member.

  From another point of view, a fixing device to which the present invention is applied includes a belt-like member that is rotatably provided, a first fixing member that is provided at a position facing the belt-like member, and a belt-like member. A second fixing member that is disposed in pressure contact with the first fixing member and fixes the image held on the recording material between the belt-shaped member and the first fixing member and the first fixing member. A pressing member that presses the belt-shaped member against the second fixing member on the downstream side of the press contact portion formed by the two fixing members, and a first fixing member provided at a position facing the first fixing member in the pressing member. And a protruding portion protruding toward the member.

  Here, the first fixing member or / and the protruding portion may include a sliding layer that makes sliding with the protruding portion or the first fixing member favorable. Moreover, the protrusion part can be characterized by comprising a rotating member provided rotatably. Further, the surface hardness of the first fixing member may be larger than the surface hardness of the protrusion.

According to the first aspect of the present invention, a fixing device having stable fixing performance can be provided.
According to the second aspect of the invention, as compared with the case not having this constitution, for example, it is possible to perform the fixing process smoothly.
According to the third aspect of the present invention, for example, it is possible to extend the life of the first fixing member as compared with the case where this configuration is not provided.
According to the fourth aspect of the present invention, it is possible to extend the life of the first fixing member as compared with the case where this configuration is not provided.

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 fixing device 60 for fixing the secondary 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. First, a charger 12 for charging the photosensitive drums 11 is disposed around the photosensitive drums 11 rotating in the arrow A direction. 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, and a RAM (Random Access Memory) that temporarily stores various data. Etc.

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 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 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 to which the present invention is applied. The fixing device 60 mainly includes a fixing belt module 61 and a pressure roll 62 disposed in pressure contact with the fixing belt module 61.

  The fixing belt module 61 includes an endless fixing belt 610 (belt-like member) that is rotatably provided, a fixing roll 611 that is rotatably provided, and a tension roll 612 that stretches the fixing belt 610 from the inside. I have. Further, the fixing belt module 61 stretches the fixing belt 610 from the outside and corrects the posture of the fixing belt 610 between the external heating roll 613 that heats the fixing belt 610 from the outside, and the fixing roll 611 and the tension roll 612. And a posture correction roll 614 for performing. Further, the fixing belt module 61 includes a peeling pad 64 in a downstream region 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. 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. Furthermore, the fixing belt module 61 includes a support member 65 that supports the peeling pad 64 and a spring member 67 (an example of an applying member) that presses the peeling pad 64 toward the pressure roll 62.

  Further, the fixing belt module 61 includes a heating source 616a that is disposed inside the fixing roll 611 and heats the fixing roll 611, and a heating source 616c that is disposed inside the external heating roll 613 and heats the external heating roll 613. I have. Further, the fixing belt module 61 includes a heating source 616 b that is provided inside the tension roll 612 and heats the tension roll 612. Further, the fixing belt module 61 is disposed near a driving source (not shown) such as a motor for rotating the fixing roll 611 and both ends of the tension roll 612, and the tension roll 612 faces the direction opposite to the fixing belt 610. And a spring member (not shown) that applies a predetermined tension to the fixing belt 610.

The fixing roll 611 as the first fixing member is a hard roll that is not covered with an elastic layer and is formed by covering a surface of an aluminum core metal (core roll) with a heat resistant resin (fluororesin). In this embodiment, a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) is used as the heat resistant resin.
The peeling pad 64 as a pressing member is a member formed in a thin plate shape with, for example, SUS metal or resin, and a member having a substantially arc shape in cross section. The peeling pad 64 is disposed in the vicinity of the downstream side of the region where the pressure roll 62 is pressed against the fixing roll 611 via the fixing belt 610 (“roll nip portion N1”: see FIG. 3). Further, the peeling pad 64 is installed so as to uniformly press the pressure roll 62 over a predetermined axial region with a predetermined load via the fixing belt 610. As a result, a “peeling pad nip portion N2” (see FIG. 3) described later is formed.

The support members 65 are provided on both sides of the fixing roll 611 (one is not shown). One end portion of each support member 65 is attached to an attachment portion 64 b (see FIG. 3) provided at the end portion in the longitudinal direction of the peeling pad 64. Although not shown, the other end of each support member 65 is attached coaxially with the fixing roll 611 so as to be rotatable. Thereby, the peeling pad 64 is supported by the support member 65 at both ends, and is provided to be rotatable with respect to the fixing roll 611 within a predetermined range.
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, as shown by an arrow F in the drawing, the pressure roll 62 is provided so as to be movable in a direction approaching and separating from the fixing belt module 61.

Next, the nip portion N where the fixing belt module 61 and the pressure roll 62 are pressed against each other will be described.
FIG. 3 is a schematic cross-sectional view showing the vicinity of the nip N. As shown in FIG. As shown in FIG. 2, in the fixing device 60, the nip portion N is formed by the pressure contact between the fixing belt module 61 and the pressure roll 62. In the nip portion N, the pressure roll 62 is disposed so as to come into pressure contact with the outer peripheral surface of the fixing belt 610 in a region (wrapped region) where the fixing belt 610 is wound (wrapped) around the fixing roll 611. Yes. With this arrangement, a roll nip portion (first nip portion) N1 is formed.
Here, the fixing roll 611 that is one of the rolls forming the roll nip portion N1 is a hard roll as described above. The pressure roll 62, which is the other roll forming the roll nip portion N1, is a soft roll coated with an elastic layer 622. For this reason, when the pressure roll 62 is pressed against the fixing roll 611, the elastic layer 622 of the pressure roll 62 is deformed to form the roll nip portion N1.

  On the other hand, on the downstream side of the roll nip portion N1 and in the vicinity of the fixing roll 611, a peeling pad 64 and a spring member 67 that presses the peeling pad 64 toward the pressure roll 62 (see arrow G in the figure) are arranged. Has been. For this reason, the fixing belt 610 positioned between the peeling pad 64 and the pressure roll 62 is pressed against the surface of the pressure roll 62 by the peeling pad 64. As a result, a peeling pad nip portion (second nip portion) N2 in which the fixing belt 610 is wrapped on the surface of the pressure roll 62 is formed downstream of the roll nip portion N1. Although details will be described later, in the present embodiment, the roll nip portion N1 side of the region (the press contact portion between the release pad 64 and the pressure roll 62) N2T in the release pad nip portion N2 where the release pad 64 is disposed. In this state, the boundary region N2S is formed. Further, the peeling pad 64 in the present embodiment is provided with an attachment portion 64b to which the support member 65 is attached. Although details will be described later, the peeling pad 64 is provided with a sliding sheet 66 a that suppresses contact between the peeling pad 64 and the fixing roll 611.

  Next, the operation of the fixing device 60 will be described with reference to FIGS. When fixing is performed by the fixing device 60, first, the paper P on which the toner image is held is introduced into the nip portion N by the conveyance 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). 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 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. The sheet P is heated by the fixing belt 610 heated by the fixing roll 611, the tension roll 612, and the external heating roll 613.

The fixing belt 610 that has passed through the peeling pad nip portion N2 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 paper P that has been pressurized and heated at the nip N cannot follow the change in the direction of travel of the fixing belt 610 when it exits the nip N.
As a result, the sheet P is peeled off from the fixing belt 610 by the so-called “koshi” (self-strip). In this way, the curvature separation with respect to the paper P is stably performed at the exit of the nip portion N. The sheet P peeled off from the fixing belt 610 is then discharged out of the apparatus by a discharge guide (not shown) and a discharge roll (not shown), and the fixing process is completed.

Incidentally, in the boundary region N2S shown in FIG. 3, there is no member that presses the fixing belt 610 against the fixing roll 611 and the pressure roll 62. Therefore, the nip pressure in the boundary region N2S (hereinafter, the nip pressure in the boundary region N2S is referred to as Pn) is formed only by the tension of the fixing belt 610. As a result, the nip pressure Pn in the boundary region N2S is between the nip pressure in the roll nip portion N1 and the nip pressure in the region N2T where the peeling pad 64 is disposed. The nip pressure Pn in the boundary region N2S is relatively lower than the nip pressure in the roll nip portion N1 and the nip pressure in the region N2T in which the peeling pad 64 is disposed.
The sheet holding the toner image is heated and pressurized at the roll nip portion N1, and the toner image is melted and pressed. At that time, water in the paper is vaporized to generate water vapor, and air existing in the toner gap (a space between the powder toners) is thermally expanded. However, since a high nip pressure is applied at the roll nip portion N1, an air gap (bubbles) due to water vapor or expanded air does not occur between the fixing belt 610 and the pressure roll 62.

  However, if the portion where the nip pressure Pn is low is formed over a wide range as in the boundary region N2S, bubbles that are suppressed in the roll nip portion N1 may be generated without being suppressed in the boundary region N2S. is there. In the state where bubbles are generated and the toner is not completely solidified, when the paper P enters the high nip pressure region N2T where the peeling pad 64 is disposed, the toner image is disturbed by the bubbles. This causes a phenomenon that a minute hole is formed in the fixed image or an image defect such as unevenness occurs.

Further, when the peeling pad 64 is formed thick, sliding resistance with the fixing belt 610 increases. If the sliding resistance is large, there is a possibility that problems such as wrinkles occurring on the fixing belt 610 and slippage between the fixing belt 610 and the fixing roll 611 may occur. Further, in the present embodiment, the sheet P is peeled off from the fixing belt 610 at the exit of the nip portion N by its so-called “koshi”. When the sheet is peeled off from the fixing belt 610 by the “stiffness” of the sheet as described above, it is desirable to increase the curvature of the fixing belt 610 at the exit of the nip portion N.
Therefore, in the present embodiment, the peeling pad 64 is formed in a thin plate shape, and the peeling pad 64 formed in this way is arranged close to the fixing roll 611 and along the fixing roll 611.

On the other hand, as described in FIG. 3 and the like, the peeling pad 64 is pressed in the direction in which the pressure roll 62 is positioned by the spring member 67. Then, due to this pressing, the peeling pad 64 is distorted (bent). In particular, when it is formed of a thin plate like the peeling pad 64 of this embodiment, distortion is likely to occur.
FIG. 4 is an explanatory diagram showing distortion generated in the conventional peeling pad 64. This figure has shown the state which looked at the peeling pad 64 from the front. FIG. 4A shows a state where the pressing load by the spring member 67 is not acting, and FIG. 4B shows a state where the pressing load by the spring member 67 is acting.

  Note that the peeling pad 64 includes a main body portion 64a serving as a base of the peeling pad 64 and an attachment portion 64b. The attachment portions 64b are provided at both ends in the longitudinal direction of the main body portion 64a, and are disposed in a state of protruding outward from the main body portion 64a. Also, on the pressure roll 62 (see FIG. 2) side of the main body portion 64a, a bottom surface 64c (pressing surface) that contacts the fixing belt 610 when the peeling pad 64 presses the fixing belt 610 toward the pressure roll 62. Is formed. The bottom surface 64c is formed flat in the axial direction.

As shown in FIG. 4A, when the pressing load from the spring member 67 does not act on the peeling pad 64, the bottom surface 64c is in a state of maintaining a flat shape in the axial direction.
However, as shown in FIG. 4B, when a pressing load is applied to the peeling pad 64 from the spring member 67, distortion (deflection) occurs in the peeling pad 64. In the longitudinal direction of the peeling pad 64, a substantially uniform load acts on the bottom surface 64c from the pressure roll 62 side, whereas the spring member 67 applies a part of the peeling pad 64 (attachment portion 64b). Only the load acts. As a result, the peeling pad 64 is bent so as to be concave toward the pressure roll 62 (see FIG. 2). For this reason, the bottom surface 64c also becomes concave toward the pressure roll 62, and is deformed so as to be more concave than a virtual straight line (predetermined portion) (see a broken line in the figure) connecting both end portions 64d of the bottom surface 64c.

For example, when a pressing load is applied to the peeling pad 64 under the following conditions, the bottom surface 64c of the peeling pad 64 is depressed (displaced) by about 0.1 mm at the center in the longitudinal direction of the peeling pad 64. Become.
A pressing load at which each spring member 67 presses each mounting portion 64b: 343N (35kgf) (a total of 686N (70kgf) pressing load acts on the peeling pad 64 by both spring members 67)
-Material of peeling pad 64: SUS304
-Thickness of the peeling pad 64: 3.0 mm
The length of the contact portion between the peeling pad 64 and the fixing belt 610 (corresponding to N2T): 40 mm
The length that the peeling pad 64 presses the pressure roll 62 via the fixing belt 610 in the longitudinal direction of the peeling pad 64: 370 mm

When the bottom surface 64c is deformed as described above, the pressing load when the peeling pad 64 presses the pressure roll 62 via the fixing belt 610 becomes non-uniform. As a result, the nip pressure in the peeling pad nip portion N2 (see FIG. 3) becomes non-uniform, and there is a possibility that a defect will occur in the fixed image. Specifically, since the nip pressure is reduced at the central portion in the longitudinal direction of the peeling pad 64, it is impossible to sufficiently heat and press the paper near the central portion. As a result, gloss unevenness may occur near the center of the paper.
In the above description, the non-uniformity of the pressing load generated in the longitudinal direction of the peeling pad 64 has been described. However, the non-uniformity of the pressing load is not limited to the longitudinal direction of the peeling pad 64 but the width direction of the peeling pad 64 (fixing belt). 610 movement direction, process direction). Therefore, in the present embodiment, the peeling pad 64 that can make the pressing load uniform and suppress the occurrence of image defects is used.

  FIG. 5 is an explanatory view showing the peeling pad 64 in the present embodiment. FIG. 5A shows a state where the pressing load by the spring member 67 is not acting, and FIG. 5B shows a state where the pressing load by the spring member 67 is acting. In addition, about the function similar to the peeling pad 64 shown in FIG. 4, the same code | symbol is used and the description is abbreviate | omitted here.

  As shown in FIG. 5A, the bottom surface 64c in the present embodiment is formed in a state of being convex in advance toward the pressure roll 62 side. More specifically, the bottom surface 64c protrudes most at the longitudinal center portion (an example of one location) of the peeling pad 64, and an end portion 64d (other location) of the bottom surface 64c is drawn in a gentle curve from the projected portion. 1 example). Further, the bottom surface 64c is in a state of protruding from a virtual straight line (predetermined portion) (see a broken line in the figure) connecting both end portions 64d of the bottom surface 64c. Furthermore, in the present embodiment, the end portion 64d is disposed closer to the attachment portion 64b (predetermined location) where the pressing load from the spring member 67 acts than the center portion.

  When a pressing load is applied to the peeling pad 64 using the spring member 67 from this state as shown in FIG. 5B, the peeling pad 64 is recessed toward the pressure roll 62 as in FIG. It deforms (curves) to become. For this reason, the bottom surface 64c also deforms following this deformation. However, in the present embodiment, as described above, the bottom surface 64c is in a curved state that is convex in advance toward the pressure roll 62 side, and thus the bottom surface 64c is substantially flat after deformation. That is, in this embodiment, the shape of the non-flat surface is given to the bottom surface 64c before the deformation so that the bottom surface 64c becomes substantially flat after the peeling pad 64 is deformed.

  In addition, such a design of the peeling pad 64 can be performed based on the measurement result by measuring the amount of distortion (deflection) of the bottom surface 64c by actual measurement or simulation, for example. Specifically, the shape and the amount of distortion (deflection) when the bottom surface 64c is distorted are determined by actual measurement or simulation. And while giving the shape which protruded in the reverse direction to the distortion direction to the bottom face 64c, let the protrusion amount be the same as the distortion amount. By this method, it is possible to design the peeling pad 64 capable of making the pressing force uniform. Also, the peeling pad 64 can be deformed in advance in the direction opposite to the strain (deflection) direction of the peeling pad 64 and the pressing force can be made uniform by making the deformation amount the same as the strain amount. 64 can be designed.

For example, in FIG. 4B, the example in which the peeling pad 64 is recessed by about 0.1 mm at the center in the longitudinal direction of the peeling pad 64 has been described. However, the peeling pad 64 in FIG. A substantially central portion of 64c is protruded by about 0.1 mm toward the pressure roll 62 side. Further, portions other than the central portion of the bottom surface 64c are also protruded toward the pressure roll 62 by an amount corresponding to the dent amount (displacement amount).
4 and 5, the example in which the peeling pad 64 is distorted in the longitudinal direction of the peeling pad 64 has been described. However, the peeling pad 64 is not limited to the longitudinal direction, but the width direction (the moving direction of the fixing belt 610, the process direction). ) Is also distorted. Thus, even if it is a case where it bends in the width direction, the amount of distortion (deflection) of the bottom face 64c is measured by actual measurement or simulation, and the peeling pad 64 can achieve a uniform pressing load based on this measurement result. Can be designed.

  Further, when the peeling pad 64 is distorted (bent), the peeling pad 64 and the fixing roll 611 come into contact with each other, and the peeling pad 64 and the fixing roll 611 may be worn or damaged. In particular, as described above, the peeling pad 64 according to the present embodiment is formed of a thin plate-like member and thus has a configuration that is easily deformed. Further, when the peeling pad 64 is distorted, the pressing load when the peeling pad 64 presses the pressure roll 62 via the fixing belt 610 becomes non-uniform. As a result, the nip pressure in the peeling pad nip portion N2 (see FIG. 3) becomes non-uniform, and there is a possibility that a defect will occur in the fixed image. Therefore, in the present embodiment, the occurrence of these problems is suppressed by adopting the following configuration.

FIG. 6 is a perspective view showing the peeling pad 64 in the present embodiment. In addition, about the function similar to the peeling pad 64 shown in FIG. 5 etc., the description is abbreviate | omitted here using the same code | symbol.
FIG. 6A is a side surface (a portion facing the fixing roll 611) on the fixing roll 611 side of the main body portion 64a, and a slide protruding toward the fixing roll 611 side at a substantially central portion in the longitudinal direction of the main body portion 64a. The state which provided the moving sheet | seat 66a is shown.

The sliding sheet 66a as an example of the protruding portion is a surface formed of a base material layer (thickness 0.4 mm) formed of polyimide and attached to the peeling pad 64, a fluororesin (for example, PFA) and glass cloth. Layer (sliding layer) (thickness 0.13 mm). The size of the sliding sheet 66a is 20 mm × 20 mm. In addition, although the sheet-like thing was illustrated in this figure, what has the same function can be formed, for example in the form of apply | coating.
In the present embodiment, as described above, the sliding sheet 66a protrudes toward the fixing roll 611, and even if the peeling pad 64 is distorted, the sliding sheet 66a contacts the fixing roll 611. To do. For this reason, the contact between the peeling pad 64 and the fixing roll 611 can be suppressed.
The sliding sheet 66a slides with the fixing roll 611 when fixing is performed. For this reason, it is preferable to form a sliding layer including at least the surface containing a fluororesin on the fixing roll 611 side, and in this embodiment, the surface of the fixing roll 611 is coated with PFA as described above. Has been.

FIG. 6B shows a state in which a bearing 66b (rotating member) as a protruding portion is provided on the side surface of the main body portion 64a on the fixing roll 611 side. In the drawing, a plurality of bearings 66b having an outer diameter of 6 mm and a width of 3 mm that rotate in the same direction as the rotation direction of the fixing roll 611 are provided on the side surface of the main body portion 64a on the fixing roll 611 side (three in the present embodiment). The provided aspect is illustrated.
In the present embodiment, like the sliding sheet 66a described above, the bearing 66b protrudes toward the fixing roll 611, and even if the peeling pad 64 is distorted, the bearing 66b is fixed to the fixing roll 611. Contact with. For this reason, the contact between the peeling pad 64 and the fixing roll 611 can be suppressed.

  As described above, the sliding sheet 66a slides (contacts) with the fixing roll 611 when fixing is performed. Further, the bearing 66b also comes into contact with the fixing roll 611 when fixing is performed. For this reason, the surface of the fixing roll 611 is worn or deformed, and the life of the fixing roll 611 may be shortened. Therefore, for example, the hardness (surface hardness) of the portion of the sliding sheet 66a or the bearing 66b that comes into contact with the fixing roll 611 can be configured to be smaller than the hardness of the surface of the fixing roll 611. As such a configuration, for example, an aspect in which the surface of the bearing 66b is coated with PFA and the fixing roll 611 is formed of aluminum.

1 is a schematic configuration diagram illustrating an image forming apparatus to which the present invention is applied. 1 is a side sectional view showing a schematic configuration of a fixing device to which the present invention is applied. It is a schematic sectional drawing showing the vicinity area of a nip part. It is explanatory drawing shown about the distortion which arises in the conventional peeling pad. It is explanatory drawing which showed the peeling pad in this embodiment. It is the perspective view which showed the peeling pad in this embodiment.

Explanation of symbols

62 ... Pressure roll, 64 ... Peeling pad, 66a ... Sliding sheet, 66b ... Bearing, 67 ... Spring member, 610 ... Fixing belt, 611 ... Fixing roll

Claims (6)

A belt-like member provided rotatably;
A first fixing member provided at a position facing the belt-like member;
A second fixing member disposed so as to be in pressure contact with the first fixing member via the belt-shaped member and fixing an image held on the recording material between the belt-shaped member and the recording material; ,
The belt-shaped member is formed along the width direction of the belt-shaped member and is formed on the downstream side of the press-contact portion formed by the first fixing member and the second fixing member. thereby pressed toward the second fixing member, a pressing member which is displaced along the rotation direction of the belt-shaped member is deformed along with the pressing,
An applying member for applying a pressing force when the pressing member presses the second fixing member via the belt-shaped member to both ends of the pressing member;
A projecting portion provided at a central portion in the longitudinal direction of the pressing member at a position facing the first fixing member in the pressing member and projecting toward the first fixing member;
Including a fixing device.   2. The fixing according to claim 1, wherein the first fixing member and / or the protrusion includes a sliding layer that facilitates sliding with the protrusion or the first fixing member. apparatus.   The fixing device according to claim 1, wherein the protruding portion is configured by a rotating member that is rotatably provided.   The fixing device according to claim 1, wherein a surface hardness of the first fixing member is larger than a surface hardness of the protruding portion.   The fixing device according to claim 1, wherein the protruding portion is formed by attaching a sheet-like member to the pressing member. The central portion in the longitudinal direction of the pressing surface where the pressing member presses the second fixing member via the belt-shaped member constitutes a part of the pressing surface and is closer to the both end portions than the central portion. The fixing device according to claim 1, wherein the fixing device is located closer to the belt-like member than other portions located in the belt.

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