JP2007171842A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device in which positional relation between a fixing roller and a peeling member is stabilized. <P>SOLUTION: On a side surface of the fixing device, a bearing 69 which is a bearing member provided at a periphery of a support part 611b of the fixing roller 611, a support member (rocking component) 68 fitted to the bearing 69 so as to be rockable, and a connection member 67 connecting the support member 68 and a peeling pad 64 are provided. The peeling pad 64 is arranged along the axis of the fixing roller 611 with a nearly constant space 71 with respect to the fixing roller 611. The support member 68 is formed in a thin plate shape and a nearly U shape with one side open, and an engagement part formed in an arcuate shape is formed at a nearly center part of the support member. This engagement part is locked to a periphery part of the bearing 69, then, the support member 68 can rock on the center axis of the fixing roller 611 in a circumferential direction of the fixing roller 611. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fixing device used in an image forming apparatus such as a copying machine and a printer, and more particularly to a fixing device including a rotatable belt member.

  2. Description of the Related Art Conventionally, a two-roller fixing technique is known in which a sheet on a sheet is nipped and conveyed by a nip formed by a fixing roller and a pressure roller, whereby toner on the sheet is heated and pressed to be fixed. When this technology is applied to a high-speed machine of 250 mm / s or more, heat is rapidly taken away from the surface of the fixing roller by the paper. For this reason, the heat supply from the heating means inside the roller is not in time, and the surface temperature is lowered (temperature droop). In addition, when small-size paper is continuously passed, heat is removed only in the paper passage area in the axial direction of the fixing roller, resulting in temperature unevenness. As a result, there is a problem that fixing failure, paper wrinkles, heat deterioration of the fixing roller, or the like occurs.

  In order to solve this problem, a belt fixing device using a fixing belt on the side in contact with the toner image has been proposed (for example, see Patent Document 1). However, in order to employ this technology in a high-speed machine, it is necessary to increase the fixing belt temperature in order to give a predetermined amount of heat to the toner, or to increase the outer diameter of the fixing roller and the pressure roller to widen the nip width. is there. Actually, there is a limit to raising the temperature due to heat resistance problems of the fixing belt, heating roller, fixing roller, etc., and a method of increasing the nip width is adopted. However, the curvatures of the fixing roller and the pressure roller are reduced, causing a problem that the sheet cannot be peeled off from the fixing belt in the sheet discharge area of the fixing nip.

  In order to solve this problem, a second nip is provided on the downstream side of the fixing nip formed by the fixing roller and the pressure roller so that a peeling member such as a fixing member or a small-diameter roller contacts the pressure roller from the back surface of the fixing belt. There has been proposed a method of separating paper by increasing the curvature in the discharge area (see, for example, Patent Documents 2 to 4). However, this method has a wide width between the fixing nip and the downstream second nip, in which there is a wide range of a non-pressurized area where the nip pressure is almost zero and a low pressure area where the nip pressure is reduced. There is a possibility that water vapor from the inserted paper cannot be suppressed in the non-pressurized region or the low-pressurized region and can be generated. Then, the bubbles move around between the fixing belt and the paper, thereby disturbing the toner image and causing problems such as poor fixing or image disturbance. Therefore, by providing the peeling member close to the fixing nip and reducing the non-pressurized area and the low-pressurized area, it is possible to suppress the disturbance of the toner image due to the generation of water vapor.

JP-A-6-31801 Japanese Patent Laid-Open No. 2003-5565 JP 2003-43848 A JP 2003-337488 A

However, the peeling member is not always at a fixed position and may fluctuate. For example, when fixing a thick sheet, the inner peripheral surface side of the fixing belt rises by the sheet thickness compared to a thin sheet. As a result, the position of the peeling member in contact with the fixing belt may also vary. Also, the position of the peeling member may change when the pressing load of the pressure roller to the fixing roller is changed, that is, when the fixing load is changed. Further, when the pressure roller is provided so as to be able to come in contact with and away from the fixing roller, the load applied to the peeling member may change as the pressure roller comes in contact with and separates, and the peeling member may move.
For this reason, if a separation member such as a fixed member or a small-diameter roller is provided in the vicinity of the fixing nip, the positional relationship between the separation member and the fixing roller also changes due to fluctuation or movement of the separation member. There is a possibility that problems such as interference between the member and the fixing roller may occur.

  SUMMARY An advantage of some aspects of the invention is that it provides a fixing device capable of stabilizing the positional relationship between a fixing roller and a peeling member. .

  For this purpose, a fixing device to which the present invention is applied is a fixing device that fixes a toner image carried on a recording material, and is stretched over a rotatable fixing roller and a fixing roller. A pressure member that forms a nip portion between a fixing belt provided rotatably and a fixing belt that presses against the fixing roller and through which the recording material passes, and the fixing belt Located at a distance from the roller, the fixing belt is pressed against the pressure member in the vicinity of the pressure contact portion between the fixing roller and the pressure member, and the recording material is peeled from the fixing belt by bending the fixing belt. And a peeling member attached to the fixing roller so as to be swingable in the circumferential direction of the fixing roller, and a swing shaft serving as the center of the swing is formed substantially parallel to the central axis of the fixing roller. A swinging member That.

  Here, the peeling member can be characterized in that the attachment position with respect to the swinging member can be adjusted. Further, the peeling member may be formed in a substantially arc shape extending along the circumferential direction of the fixing roller. Further, the peeling member has an upstream edge located on the upstream side in the advancing direction of the fixing belt on the pressing surface with the fixing belt, and the angle of the upstream edge is the pressure contact portion between the fixing roller and the pressure member. The wedge-shaped region formed in the vicinity of the downstream side is less than the wedge angle, and the curvature radius of the upstream edge tip is 0.1 mm or less.

  Further, the peeling member has a downstream edge located on the downstream side in the advancing direction of the fixing belt on the pressing surface with the fixing belt, and the curvature radius of the downstream edge is 5 mm or less. Can do. Further, a pressing means for pressing the peeling member against the fixing belt is further provided, and the pressing means linearly moves between the spring member that applies a pressing force to the fixing belt to the peeling member, and the spring member and the peeling member. The urging force of the spring member is transmitted to the peeling member via the movable member. Further, the pressurizing member may be a roller-shaped member. The pressurizing member includes a roller-like member and a pressurizing belt that is rotatably stretched around the roller-like member and conveys the recording material together with the fixing belt. it can.

  From another point of view, the fixing device to which the present invention is applied is a fixing device that fixes a toner image carried on a recording material, and is stretched around a rotatable fixing roller and a fixing roller. A pressure member that forms a nip portion through which a recording material passes between a fixing belt that is rotatably provided and a fixing belt that is arranged to press the fixing roller and is stretched over the fixing roller; The fixing belt is disposed at a gap with respect to the fixing roller. The fixing belt is pressed against the pressure member in the vicinity of the downstream side of the press contact portion between the fixing roller and the pressure member, and the fixing belt is bent to remove the recording material from the fixing belt. A peeling member for peeling, and a support member that supports the peeling member so as to be movable around the fixing roller, and when the peeling member supported by the support member moves around the fixing roller, Against the fixing roller It can be characterized in that that attitude is maintained.

  Further, the peeling member can be characterized by being formed by bending a metal member. Further, the inner surface of the peeling member facing the fixing roller may be characterized by having substantially the same curvature as the outer peripheral surface of the fixing roller. Further, the peeling member may be characterized in that a pressing surface for pressing the fixing belt is formed as a flat surface or a curved surface that follows the surface shape of the pressing member. Furthermore, the peeling member can be characterized by being formed with a substantially constant thickness.

  According to the present invention, it is possible to provide a fixing device that can stabilize the positional relationship between the fixing roller and the peeling member.

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 according to the present 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 to a sheet as a recording material (recording sheet). In addition, a fixing device 60 is provided for fixing the second-transferred image (toner image carried on the paper) on the paper. 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 (the exposure beam is indicated by 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 roller 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 intermediate transfer belt 15 is circulated and driven (rotated) at a predetermined speed in the direction of arrow B shown in FIG. 1 by various rollers such as a driving roller 31 driven by a motor (not shown) having excellent constant speed. ing.
The primary transfer unit 10 includes a primary transfer roller 16 disposed to face the photosensitive drum 11 with the intermediate transfer belt 15 interposed therebetween. The toner images on the respective photosensitive drums 11 are sequentially electrostatically attracted to the intermediate transfer belt 15 so that the toner images superimposed on the intermediate transfer belt 15 are formed.
The secondary transfer unit 20 includes a secondary transfer roller 22 disposed on the toner image carrying surface side of the intermediate transfer belt 15 and a backup roller 25. The secondary transfer roller 22 is disposed in pressure contact with the backup roller 25 with the intermediate transfer belt 15 interposed therebetween. Further, the secondary transfer roller 22 is grounded and a secondary transfer bias is formed between the secondary transfer roller 22 and the backup roller 25, and the toner image is secondarily transferred onto the sheet conveyed to the secondary transfer unit 20.

  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 apparatus (IIT) (not shown) or the like. The image data is subjected to predetermined image processing by an image processing device (IPS) (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

  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 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. The toner image formed on the photosensitive drum 11 is transferred onto the intermediate transfer belt 15 in the primary transfer unit 10 where each photosensitive drum 11 and the intermediate transfer belt 15 abut.

  After the toner images are sequentially primary transferred onto 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 roller 22 is pressed against the backup roller 25 via the intermediate transfer belt 15. At this time, the sheet conveyed by the conveying roller 52 and the like in time is sandwiched between the intermediate transfer belt 15 and the secondary transfer roller 22. The unfixed toner image carried on the intermediate transfer belt 15 is electrostatically transferred collectively onto the paper in the secondary transfer unit 20. Thereafter, the sheet on which the toner image has been electrostatically transferred is conveyed as it is while being peeled off from the intermediate transfer belt 15 by the secondary transfer roller 22, and is provided on the downstream side of the secondary transfer roller 22 in the sheet conveyance direction. To 55. The conveyor belt 55 includes two support rollers and a belt stretched around these support rollers. Then, the inside of the belt is sucked and negative pressure is applied to adsorb the sheet to the belt, and the sheet is stably conveyed to the fixing device 60 at an optimum conveyance speed.

Next, the fixing device 60 to which the exemplary embodiment is applied will be described.
FIG. 2 is a cross-sectional view illustrating a schematic configuration of the fixing device 60 according to the embodiment. The fixing device 60 includes a fixing belt module 61 as a main part. In addition, a pressure roller 62 formed as a roller as an example of a pressure member disposed in pressure contact with the fixing belt module 61 is provided as a main part.

  The fixing belt module 61 includes a fixing belt 610 as an example of a belt member, a cylindrical fixing roller 611 that is rotationally driven while stretching the fixing belt 610, and a tension roller that stretches the fixing belt 610 from the inside. 612. The fixing belt module 61 includes a heating roller 613 that stretches the fixing belt 610 from the outside, and a posture stabilization roller 614 that stabilizes the posture of the fixing belt 610 between the fixing roller 611 and the tension roller 612. . Further, the fixing belt module 61 is an example of a peeling member disposed in the vicinity of the fixing roller 611 in a downstream region in the nip portion N where the fixing belt module 61 and the pressure roller 62 are in pressure contact with each other. The peeling pad 64 is provided. The fixing belt module 61 includes an idler roller 615 that stretches the fixing belt 610 on the downstream side of the nip portion N. In addition, the fixing belt module 61 includes a cleaning web 66 for cleaning the surface of the heating roller 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 It is comprised with the mold release layer which consists of about 30 micrometers PFA etc. which were coat | covered. The fixing belt 610 moves (rotates) in the direction of arrow D as the fixing roller 611 rotates.

The fixing roller 611 receives the driving force from the driving unit 78 (see FIG. 5) and rotates in the direction of arrow C. In addition, a heater 616a is disposed inside the fixing roller 611 as a heating source.
In addition, the tension roller 612 is a cylindrical roller, and a heater 616b is disposed therein as a heating source. Therefore, the tension roller 612 has a function of stretching the fixing belt 610 and a function of heating the fixing belt 610 from the inner peripheral surface side. In addition, spring members (not shown) that press the fixing belt 610 outward are disposed at both ends of the tension roller 612 to apply tension to the entire fixing belt 610.

  Furthermore, the heating roller 613 is a cylindrical roller, and a heater 616c serving as a heating source is disposed therein. For this reason, the heating roller 613 has not only a function of stretching the fixing belt 610 but also a function of heating the fixing belt 610 from the outer peripheral surface side. Therefore, in this embodiment, a configuration in which the fixing belt 610 is heated by the fixing roller 611, the tension roller 612, and the heating roller 613 is employed.

  The pressure roller 62 has a cylindrical roller 621 as a base. Then, an elastic layer 622 and a release layer 623 are sequentially laminated from the substrate side to constitute a soft roller. The pressure roller 62 is installed so as to be pressed against the fixing belt module 61. As the fixing roller 611 of the fixing belt module 61 rotates in the direction of arrow C, the fixing roller 611 is driven to rotate in the direction of arrow E. The pressure roller 62 includes a heater 624 as a heating source therein, and the pressure roller 62 is heated to a predetermined temperature by the heater 624. Further, the fixing device 60 includes a peeling guide plate 83 that guides a sheet discharged from a nip portion N described later to a sheet discharge device (not shown).

Next, the nip portion N where the fixing belt module 61 and the pressure roller 62 are pressed against each other will be described in detail.
FIG. 3 is a schematic cross-sectional view showing the vicinity of the nip N. As shown in FIG. In the nip portion N, a pressure roller 62 is disposed so as to be in 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 roller 611. Yes. With this arrangement, a roller nip portion (first nip portion) N1 is formed.

  Here, in the fixing device 60 of the present embodiment, as described above, the fixing roller 611 that is one of the rollers that form the roller nip portion N1 is not covered with an elastic layer, and is an aluminum core (core roller). The hard roller is formed by coating a heat resistant resin (fluororesin) on the surface of The pressure roller 62, which is the other roller forming the roller nip portion N1, is a soft roller coated with an elastic layer 622. With such a configuration of the fixing roller 611 and the pressure roller 62, the roller nip portion N1 is formed by deforming the elastic layer 622 of the pressure roller 62 in the roller nip portion N1 of the present embodiment.

  Further, in the vicinity of the downstream side of the roller nip portion N1, a peeling pad 64 is disposed with a predetermined gap 71 from the fixing roller 611, and the peeling pad 64 presses the fixing belt 610 against the surface of the pressure roller 62. ing. Accordingly, a peeling pad nip portion (second nip portion) N2 in which the fixing belt 610 is wrapped on the surface of the pressure roller 62 is formed downstream of the roller nip portion N1.

  The peeling pad 64 forming the peeling pad nip portion N2 is formed in a substantially arc shape whose cross section extends along the circumferential direction of the fixing roller 611, and in the axial direction of the fixing roller 611 near the downstream side of the roller nip portion N1. Is arranged. Then, the fixing belt 610 after passing through the peeling pad nip portion N <b> 2 rotates following the side surface of the peeling pad 64. As a result, the advancing direction of the fixing belt 610 is rapidly changed by the peeling pad 64 so as to bend in the direction of the idler roller 615 (see FIG. 2). For this reason, the sheet that has passed through the roller nip portion N1 and the peeling pad nip portion N2 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, the curvature separation with respect to the sheet is stably performed at the exit portion of the peeling pad nip portion N2. The paper 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 peeling pad nip portion N2.

  When the peeling pad nip portion N2 is formed continuously to the roller nip portion N1, the roller nip portion N1 is located in a region (the pressure contact portion between the peeling pad 64 and the pressure roller 62) N2T in the peeling pad nip portion N2 where the peeling pad 64 is disposed. A boundary region N2S is formed on the side. In the boundary region N2S, there is no member that directly presses the fixing belt 610 against either the fixing roller 611 or the pressure roller 62. For this reason, in this boundary region N2S, the fixing belt 610 is pressed against the pressure roller 62 only by its own tension.

  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, when the separation pad 64 is disposed at a predetermined distance or more away from the downstream end N1E of the roller nip portion N1, the nip pressure Pn in the boundary region N2S is equal to the nip pressure of the roller nip portion N1 and the separation pad 64. This is a gap with the nip pressure in the provided region N2T. For this reason, it forms as an area | region where the nip pressure Pn fell low. The nip pressure Pn in the boundary region N2S is relatively lower than the nip pressure in the roller nip portion N1 and the nip pressure in the region N2T where the peeling pad 64 is disposed. Further, the nip pressure Pn may be almost zero.

  In the fixing process by the fixing device 60 of the present embodiment, the paper carrying the toner image is heated and pressed at the roller nip portion N1, and the toner is melt-pressed. At that time, from the paper or toner that has received heat in the roller nip portion N1, the water in the paper evaporates to generate water vapor, or the air in the toner tends to thermally expand. However, since a high nip pressure is applied at the roller nip portion N <b> 1, an air gap (bubble) due to water vapor or expanded air does not occur between the fixing belt 610 and the pressure roller 62.

  However, if the nip pressure Pn in the boundary region N2S with the roller nip portion N1 in the peeling pad nip portion N2 is formed in a low state, the air bubbles suppressed by the roller nip portion N1 cannot be suppressed in the boundary region N2S. May occur. Then, when the bubble is generated and enters the region N2T where the nip pressure is high, the bubble generated in the boundary region N2S moves around on the surface of the sheet by the high nip pressure. As a result, the toner image on the sheet is immediately after passing through the roller nip portion N1, and the melted toner is not yet completely solidified. . As a result, a fine hole may occur in the fixed image, or an image defect such as uneven gloss may occur.

  Therefore, in the fixing device 60 of the present embodiment, the peeling pad 64 is disposed in the vicinity of the fixing roller 611 in the vicinity of the downstream side of the roller nip portion N1. By installing the peeling pad 64 in this way, the width of the boundary region N2S between the roller nip portion N1 and the region N2T where the peeling pad 64 is disposed can be set as narrow as possible. As a result, the region pressed against the pressure roller 62 only by the tension of the fixing belt 610 is narrowed. Therefore, the nip pressure Pn can be increased in the boundary region N2S. As a result, the water vapor or the air that is to be thermally expanded that has been suppressed by the high nip pressure in the roller nip portion N1 is gradually released along a path that passes through the peeling pad nip portion N2. For this reason, it is possible to suppress the occurrence of the phenomenon of bubbles moving around as described above, and the toner image that has not yet been completely solidified is hardly disturbed, thereby suppressing the occurrence of image defects. be able to.

  Further, the peeling pad 64 is disposed in the vicinity of the fixing roller 611 while having substantially the same curvature as the outer peripheral surface 611d of the fixing roller 611 formed in a cylindrical shape. The peeling pad 64 in the present embodiment is a block member having a substantially arc-shaped cross section formed of a rigid body such as SUS metal or resin. Further, the peeling pad 64 causes the pressure roller 62 to pass through the fixing belt 610 over a predetermined width region (for example, a width of 2 to 10 mm along the traveling direction of the fixing belt 610), and a predetermined load (for example, 10 kgf). It is installed to press evenly.

  In the present embodiment, the peeling pad 64 has an upstream edge 64c on the upstream side in the advancing direction of the fixing belt 611 and a downstream edge 64d on the downstream side of the contact surface 64b (pressing surface) with the fixing belt 611. Have. And the front-end | tip R1 of the upstream edge 64c is formed sharply (a curvature radius is 0.1 mm or less). Further, the angle α of the upstream edge 64c is an acute angle. More specifically, the angle α of the upstream edge 64c is equal to or less than the wedge angle β of the wedge-shaped region Q formed near the downstream side of the pressure contact portion between the fixing roller 611 and the pressure roller 62. By adopting such a configuration, the peeling pad 64 can be disposed so as to enter the vicinity of the fixing nip. Therefore, the boundary region N2S can be made slightly narrow, and fixing failure or image disturbance can be suppressed. it can.

The curvature radius R2 at the downstream edge 64d is 5 mm or less. In addition, 3-5 mm is desirable for the curvature radius R2. As a result, the curvature at the tip of the downstream edge becomes larger than the curvature of the fixing roller 611 (outer diameter 65 mm), and good peeling performance can be obtained.
Further, in the peeling pad 64, a contact surface 64 b that contacts the inner peripheral surface of the fixing belt 610 is formed into a planar shape (straight shape) by grinding and is formed so as to follow the surface of the pressure roller 62. . Further, the contact surface 64b is provided with a low sliding layer (not shown) formed from a sliding sheet or the like obtained by coating a woven fabric of heat resistant fiber with a fluororesin. Accordingly, it is possible to smoothly rotate the fixing belt 610 while ensuring an appropriate nip pressure. The contact surface 64b can also be formed by a curved surface that follows the surface shape of the pressure roller 62.

  Further, the inner surface 64 a of the peeling pad 64 has substantially the same curvature as the outer peripheral surface 611 d of the fixing roller 611. Specifically, the outer diameter of the fixing roller 611 is 65 mm, and the radius of curvature of the inner surface 64a of the peeling pad 64 is 33 mm. The gap 71 between the fixing roller 611 and the peeling pad 64 is adjusted to 0.5 mm. Thus, if the curvatures of the inner surface 64a and the outer peripheral surface 611d of the fixing roller 611 are substantially the same, the peeling pad 64 can be disposed in the vicinity of the outer peripheral surface 611d of the fixing roller 611. As a result, since the position of the upstream end portion 64c can also be disposed in the vicinity of the fixing roller 611, the width of the boundary region N2S can be reduced. Further, if the inner side surface 64a is formed along the outer peripheral surface 611d of the fixing roller 611, the cross-sectional area can be secured larger than that of the peeling pad 64 formed so as not to be along, and the rigidity can be increased. It becomes possible.

Further, as described above, the peeling pad 64 has a certain length (height) in the direction along the circumferential direction of the fixing roller 611. The peeling pad 64 receives a pressure load from the pressure roller 62. If the length of the peeling pad 64 along the circumferential direction of the fixing roller 611 is small (if the height is not sufficient), sufficient rigidity is obtained. Cannot be secured, and there is a possibility that the longitudinal direction of the peeling pad 64 is bent. In the present embodiment, as described above, the inner side surface 64a is formed along the outer peripheral surface 611d of the fixing roller 611 to increase the cross-sectional area, and the load direction (of the fixing roller 611 of the fixing roller 611) is increased. The shape has a certain length in the circumferential direction). Thereby, even if the pressing load applied to the peeling pad 64 is set to 1 kgf / cm ² , the amount of bending that occurs in the longitudinal direction of the peeling pad 64 can be reduced. As a result, it is possible to suppress fixing unevenness and to stably run the fixing belt 610.

FIG. 4 is a side view of the fixing device 60.
On the side surface of the fixing device 60, a bearing 69 that is a bearing member provided on the outer periphery of the support portion 611 b of the fixing roller 611 and a substantially U-shape that is swingably attached to the bearing 69 are formed. A support member (swing member) 68 and a connection member 67 that connects the support member 68 and the peeling pad 64 are provided. Further, a pressing means 65 that presses the peeling pad 64 in the direction of the pressure roller 62 via the connection member 67 is provided.

Further, the support member 68 and the like described in FIG. 4 will be described in detail.
FIG. 5 is an explanatory diagram showing a configuration when the periphery of the fixing roller 611 is viewed from the direction of the arrow A in FIG. In the drawing, the fixing belt 610 and the pressing means 65 are not shown to show the fixing roller 611, the peeling pad 64, and the like.
As shown in the figure, the fixing roller 611 includes a fixing portion 611a formed at a substantially central portion, a support portion 611b provided on both sides of the fixing portion 611a and having a smaller diameter than the fixing portion 611a, and one of the fixing rollers 611a. And a gear portion 611c formed at the end of the support portion 611b. Both supporting portions 611b are rotatably attached to a supported member 70 such as a housing via a bearing 69. A driving unit 78 such as a motor is connected to the gear unit 611c, and the fixing roller 611 is rotated by receiving a driving force by the driving unit 78.

  On the other hand, the peeling pad 64 is disposed along the axial direction of the fixing roller 611 with a substantially constant gap 71 from the fixing roller 611. At both ends of the peeling pad 64, connection members 67 for connecting the peeling pad 64 and the support member 68 are provided. The connecting member 67 is formed between the peeling pad 64 and the support member 68 and connected to the peeling pad 64 and the supporting member 68. The connecting member 67 is formed on the top of the connecting member main body 67a. (See FIG. 4) and a convex portion 67b that abuts.

  The support member 68 has a thin plate shape and is formed in a substantially U shape with one side open (see FIG. 4), and a fitting portion 68a formed in an arc shape is formed in a substantially central portion thereof. ing. The fitting portion 68 a is locked to the outer peripheral portion of the bearing 69, so that the support member 68 is disposed so as to be able to swing in the circumferential direction of the fixing roller 611 around the central axis of the fixing roller 611. Has been. That is, in the present embodiment, the swing center of the support member 68 and the center axis of the fixing roller 611 are configured to coincide with each other. Even when the center of swing of the support member 68 and the center axis of the fixing roller 611 are not completely coincident (when knitted), the center axis of the fixing roller 611 and the center of swing of the support member 68 are substantially the same. If formed in parallel, the gap 71 between the peeling pad 64 and the fixing roller 611 can be made substantially constant in a limited swing region of the support member 68. Therefore, also in this case, interference between the peeling pad 64 and the fixing roller 611 can be prevented.

  Further, when the bearing 69 is locked to the supported member 70 so as not to rotate, the support member 68 can be configured to swing with respect to the bearing 69. Further, when the bearing 69 is configured to rotate to some extent with respect to the supported member 70, the supporting member 68 is configured to swing with respect to the supported member 70 via the bearing 69. You can also. Further, the support member 68 can swing with respect to the bearing 69 and can swing with respect to the supported member 70 via the bearing 69. Since the support member 68 is provided on the support portion 611b via the bearing 69, the support member 68 is not affected by the rotation of the fixing roller 611. Further, the support member 68 is formed with a long hole 68b (see FIG. 6) as a penetrating portion to be described later, and a screw member 63 as a fastening member is inserted into the long hole 68b.

Here, operation | movement of the supporting member 68, etc. are demonstrated with FIG.
For example, during the contact / separation operation in which the pressure roller 62 is separated from the fixing roller 611, the pressing load applied to the peeling pad 64 from the pressure roller 62 decreases. Further, when the fixing load is changed by changing the fixing load by moving the pressure roller 62 close to or away from the fixing roller 611, a load is applied to the peeling pad 64 or the load is reduced. Alternatively, the load applied to the peeling pad 64 also varies when the paper to be fixed is changed from thin paper to thick paper or vice versa.
Thus, when the load applied to the peeling pad 64 varies, the position of the peeling pad 64 may also vary. As a result, there is a possibility that the width of the boundary region N2S (see FIG. 3) cannot be maintained constant. For this reason, there is a possibility that the peeling pad 64 and the fixing roller 611 interfere (contact), and conversely, as a result of the expansion between the peeling pad 64 and the fixing roller 611, the boundary region N2S is expanded, thereby ensuring stable fixing. May not be possible.

For example, when the fixing load is increased, a method of bringing the pressure roller 62 closer to the fixing roller 611 can be considered. In this case, the amount of biting of the pressure roller 62 with respect to the fixing roller 611 changes due to the approach of the pressure roller 62. Then, an upward load is applied to the peeling pad 64.
In the present embodiment, the support member 68 is provided so as to be able to swing around the fixing roller 611 as described above. On the other hand, the peeling pad 64 is provided via a connecting member 67 on the support member 68 that is rotatably provided. As a result, the peeling pad 64 also has a constant radius around the fixing roller 611 via the support member 68 and can swing around the central axis of the fixing roller 611.

  For this reason, even when an upward load is applied to the peeling pad 64, the peeling pad 64 can be smoothly moved upward along the circumferential direction of the fixing roller 611 and the peeling pad to the fixing roller 611. 64 postures can be maintained. Specifically, the gap 71 between the peeling pad 64 and the fixing roller 611, the arrangement angle of the peeling pad 64 with respect to the fixing roller 611, and the like can be maintained substantially constant. As a result, interference between the peeling pad 64 and the fixing roller 611 can be prevented. Further, the boundary region N2S (see FIG. 3) that causes the image defect is maintained with the minimum width. Therefore, stable fixing properties and component reliability can be ensured.

  Conversely, when the load applied to the peeling pad 64 decreases due to a change in the fixing load or the like, the peeling pad 64 tries to move downward, but the peeling pad 64 attached to the support member 68 is attached to the fixing roller 611. The periphery moves downward along the circumferential direction of the fixing roller 611. At that time, the peeling pad 64 moves while maintaining the posture with respect to the fixing roller 611 as described above. For this reason, interference between the peeling pad 64 and the fixing roller 611 can be prevented. Further, the boundary region N2S (see FIG. 3) that causes the image defect is maintained with the minimum width. Therefore, in this case as well, stable fixability and component reliability can be ensured.

  That is, when the load on the peeling pad 64 fluctuates, the peeling pad 64 swings (rotates) around the fixing roller 611 with a substantially constant radius along the circumferential direction of the fixing roller 611. For this reason, interference between the peeling pad 64 and the fixing roller 611 can be prevented. Further, since no interference occurs, it is possible to attach the peeling pad 64 with a slight gap (0.5 mm in the present embodiment) between the fixing pad 611 and the fixing pad 611. Therefore, the boundary region N2S (see FIG. 3) that causes image defects can be set with a slight width (2 mm or less), and this width can be maintained even if the peeling pad 64 moves. Become.

Next, the periphery of the pressing means 65 will be described.
FIG. 6 is an explanatory view showing details of the periphery of the pressing means 65 in FIG.
The pressing means 65 includes a rod member 65e that is a linear slider as a movable member that comes into contact with the convex portion 67b (see also FIG. 5) of the connection member 67, and a spring member that urges the rod member 65e toward the peeling pad 64. 65d. Further, the pressing means 65 includes a spring receiving member 65c that receives the spring member 65d, and an adjustment member 65a that adjusts the position of the spring receiving member 65c. The pressing means 65 includes a guide member 65f that guides the moving direction of the rod member 65e, and a positioning member 65b that meshes with a screw portion formed on the adjustment member 65a to position the adjustment member 65a.

The rod member 65e receives the urging force of the spring member 65d provided in contact with one end surface, and presses the convex portion 67b provided in the connection member 67 on the other end surface. A protrusion 65e1 is formed at the center of the end surface of the rod member 65e with which the spring member 65d abuts to prevent lateral displacement of the spring member 65d. The protrusion 65e1 is positioned in the space formed at the center of the spring member 65d, thereby preventing the spring member 65d from shifting in the lateral direction.
On both side surfaces of the rod member 65e, guide members 65f are provided along the longitudinal direction of the rod member 65e. The guide member 65f is in contact with the side surface of the rod member 65e so as to slide, and regulates the moving direction so that the rod member 65e moves linearly.
The spring member 65d is a coiled compression spring, and is positioned between the rod member 65e and the spring receiving member 65c. By appropriately changing the spring constant and the like, the spring member 65d is interposed via the rod member 65e and the connection member 67. The pressing force applied to the peeling pad 64 can be adjusted.

The spring receiving member 65c is a member that receives the spring member 65d at one end of the spring member 65d. A protrusion 65c1 is also formed at the center of the surface of the spring receiving member 65c facing the rod member 65e. Similar to the protrusion 65e1 formed on the rod member 65e, the protrusion 65c1 is located in the space formed at the center of the spring member 65d, preventing the spring member 65d from shifting, and the spring member 65d being positioned at a fixed position. It plays a role to do. It is also possible to provide a load cell on the spring receiving member 65c and measure the urging force generated from the spring member 65d.
The tip of the adjustment member 65a is in contact with the spring receiving member 65c, and the position of the spring receiving member 65c is adjusted back and forth (up and down in the drawing) by moving the adjustment member 65a back and forth. As a result, the pressing load applied to the peeling pad 64 in the direction of the pressure roller 62 can be adjusted.

The positioning member 65b includes a meshing portion (not shown) that meshes with a screw portion formed on the peripheral surface of the adjustment member 65a. The meshing portion and the screw portion of the adjustment member 65a mesh with each other, whereby the adjustment member 65a. The position of the adjustment member 65a can be arranged at a fixed position.
The biasing force generated by the spring member 65d is transmitted to the connection member 67 through the rod member 65e. Since the peeling pad 64 is connected to the connection member 67, the urging force is finally transmitted to the peeling pad 64. As a result, a stable pressing force can be applied from the peeling pad 64 to the fixing belt 610.

On the other hand, the connection member main body 67a constituting the connection member 67 is locked to the support member 68 as described in FIG.
The support member 68 is formed with two elongated holes 68 b formed so as to penetrate in the axial direction of the fixing roller 611. Then, the screw members 63 are inserted into the respective long holes 68b, and the screw members 63 are screwed into the screw holes 67c (see FIG. 7) formed in the connection member main body 67a, so that the support member 68 is connected. It is configured to be engaged with the member 67. The long hole 68b is formed to extend in the axial direction of the fixing roller 611. For this reason, as shown by the broken line in the figure, the connecting member 67 can be moved closer to or away from the fixing roller 611. As a result, the position of the peeling pad 64 connected to the connection member 67 can also be arranged so as to approach or separate from the fixing roller 611, and the gap 71 between the peeling pad 64 and the fixing roller 611 or the boundary region N2S (see FIG. 3) can be adjusted.

Next, operations of the peeling pad 64 and the pressing means 65 will be described.
FIG. 7 is an explanatory view showing the peeling pad 64 and the pressing means 65 in detail.
FIG. 7A shows a state in which the peeling pad 64 has moved upward, that is, in a direction away from the pressure roller 62 (see FIG. 6), and FIG. The state which moved to the direction approaching the pressure roller 62 is shown.
As shown in FIG. 7A, when the peeling pad 64 moves upward, the rod member 65e is pressed from below by the connecting member 67 connected to the peeling pad 64 and moves upward. As a result of the rod member 65e moving upward, the spring member 65d positioned between the rod member 65e and the spring receiving member 65c is compressed and receives the pressing force from the connecting member 67. On the other hand, as shown in FIG. 7B, when the peeling pad 64 moves downward, the rod member 65e receives the urging force of the spring member 65d as the connecting member 67 moves downward, and the connecting member 67 Move following the movement.

In the present embodiment, the peeling pad 64 and the connecting member 67 locked to the peeling pad 64 do not move linearly but on the outer peripheral surface 611d (see FIG. 3) of the fixing roller 611 as described above. A curved motion is performed in a substantially arc shape along.
Here, the spring member 65d can be brought into direct contact with the connection member 67 without the rod member 65e. However, since the connecting member 67 performs a curved motion as described above, the spring member 65d is bent, and there is a possibility that the urging force by the spring member 65d cannot be sufficiently applied to the connecting member 67. That is, when the spring member 65d is brought into direct contact with the connection member 67, the spring member 65d does not compress and expand linearly, but compresses and expands in a bent shape.

In such a state, the spring member 65d is in an unstable state, and may be bent or buckled, or if the bending is large, the spring member 65d may fly off. The urging force of the spring member 65d is applied to the connection member 67. And may not be sufficiently applied.
Therefore, in this embodiment, the spring member 65d does not directly contact the connecting member 67 that moves in a curved manner, but adopts a form that presses the rod member 65e that reciprocates linearly. For this reason, the bending of the spring member 65d as described above can be prevented, and the urging force by the spring member 65d can be stably applied to the peeling pad 64.

Next, another embodiment of the peeling pad 64 will be described.
FIG. 8 is an explanatory view showing a peeling pad 64 formed by bending a sheet metal.
Examples of the method of manufacturing the peeling pad 64 include a method of cutting out from a SUS block material, and a method of bending a sheet metal into, for example, an L shape. However, in the case of cutting out from the block material, there is a problem that there is no mass productivity such as high manufacturing cost and long manufacturing time. In addition, a sheet metal that is bent in an L shape to form a contact surface with the fixing belt 610 using a bent surface is insufficient in strength and can minimize the boundary region N2S shown in FIG. There are problems such as difficulty in fixing and image disturbance.

  The peeling pad 64 shown in this figure is subjected to a gentle bending process on a sheet metal as a metal member, and has a curvature substantially the same as the curvature of the outer peripheral surface 611d following the profile of the outer peripheral surface 611d of the fixing roller 611. A sheet metal is curved. The peeling pad 64 has a substantially constant thickness, has a predetermined length in the circumferential direction of the fixing roller 611, and is formed in an arc shape. A contact surface 64 b is formed on the end surface that contacts the fixing belt 610 by grinding so as to substantially follow the surface of the pressure roller 62. Then, as shown in the figure, it is disposed at a position with a predetermined gap 71 between the fixing roller 611 and the fixing roller 611. Since the peeling pad 64 in this embodiment is simply bent, it is easy to manufacture and has a rigidity that can suppress bending even when pressed against the pressure roller 62 with a predetermined load (10 to 50 kgf). is doing. The peeling pad 64 is partially bent by using so-called brake bending, and is formed in a curved shape and a linear shape. However, the peeling pad 64 having a gentle curve as a whole is formed. You can also.

-Second Embodiment-
FIG. 9 is an explanatory view showing a cross section of the fixing device 60 according to the second embodiment.
The fixing device 60 in the present embodiment has the same configuration on the fixing belt module 61 side as that in the first embodiment, but has a different configuration on the pressure roller 62 side. This figure is a cross-sectional view, and the support member 68 and the pressing means 65 shown in FIG. 4 are omitted. Moreover, in this figure, it demonstrates centering on a different point from 1st Embodiment.

  In the present embodiment, a pressure belt 80 is provided on the side that presses the fixing roller 611 as a pressure member that is rotatably provided so as to sandwich and convey the sheet on which the toner image is transferred together with the fixing belt 610. It has been. Further, there is provided a pressure roller 62 formed in a roller shape as a pressure member arranged to stretch the pressure belt 80 and press the fixing roller 611. Further, a steering roller 81 that stretches the pressure belt 80 together with the pressure roller 62, and a heating roller 82 that is provided with a heater inside the pressure roller 62 that stretches the pressure belt 80 are provided. A pressure pad 83 as a pressure member is provided on the inner peripheral surface side of the pressure belt 80, and the pressure pad 83 is fixed to the fixing roller 611 via the pressure belt 80 and the fixing belt 610. Is pressed.

In the region where the fixing belt 610 and the pressure belt 80 are in contact (the region from the pressure contact portion between the pressure roller 62 and the fixing roller 611 to the pressure contact portion between the pressure pad 83 and the fixing roller 611), the nip Part N is formed. The sheet on which the toner image is formed is introduced into the nip portion N and heated and pressed to fix the toner image.
Also in the embodiment shown in the figure, as described in the first embodiment, the boundary region N2S (see FIG. 3) that prevents interference between the peeling pad 64 and the fixing roller 611 and causes image defects. ) Can be maintained with the minimum width.

1 is a schematic configuration diagram illustrating an image forming apparatus according to an exemplary embodiment. 1 is a cross-sectional view illustrating a schematic configuration of a fixing device according to an embodiment. 3 is a schematic cross-sectional view showing a vicinity region of a nip portion N. FIG. It is a side view of a fixing device. FIG. 5 is an explanatory diagram showing a configuration when the periphery of the fixing roller is viewed from the direction of arrow A in FIG. 4. It is explanatory drawing which showed the detail of the press means periphery in FIG. It is explanatory drawing which showed the peeling pad and the press means in detail. It is explanatory drawing which showed the peeling pad formed by curving a sheet metal. FIG. 6 is an explanatory diagram illustrating a cross section of a fixing device according to a second embodiment.

Explanation of symbols

60 ... fixing device, 62 ... pressure roller, 64 ... peeling pad, 64a ... inside surface, 64b ... contact surface, 64c ... upstream edge, 64d ... downstream edge, 65 ... pressing means, 65d ... spring member, 65e ... Rod member, 68 ... Swing member (support member), 80 ... Pressure belt, 610 ... Fixing belt, 611 ... Fixing roller, 611d ... Outer peripheral surface, Q ... Wedge-shaped area, N ... Nip part

Claims (13)

A fixing device for fixing a toner image carried on a recording material,
A rotatable fixing roller;
A fixing belt that is stretched around the fixing roller and rotatably provided;
A pressure member that is arranged to press the fixing roller and forms a nip portion through which a recording material passes between the fixing belt and the fixing belt stretched around the fixing roller;
The fixing belt is disposed with a gap therebetween, and the fixing belt is pressed against the pressure member in the vicinity of the pressure contact portion between the fixing roller and the pressure member, and the fixing belt is bent. A peeling member for peeling the recording material from the fixing belt;
A swinging member to which the peeling member is attached and provided so as to be swingable in the circumferential direction of the fixing roller, the swinging shaft being the center of swinging being formed substantially parallel to the central axis of the fixing roller When,
Including a fixing device.   The fixing device according to claim 1, wherein the peeling member is provided so that an attachment position with respect to the swinging member can be adjusted.   The fixing device according to claim 1, wherein the peeling member is formed in a substantially arc shape extending along a circumferential direction of the fixing roller. The peeling member has an upstream edge located on the upstream side in the advancing direction of the fixing belt on the pressing surface with the fixing belt,
The angle of the upstream edge is equal to or less than the wedge angle of the wedge-shaped region formed in the vicinity of the downstream side of the pressure contact portion between the fixing roller and the pressure member,
The fixing device according to claim 1, wherein a radius of curvature of the upstream edge tip is 0.1 mm or less. The peeling member has a downstream edge located on the downstream side in the advancing direction of the fixing belt on the pressing surface with the fixing belt,
The fixing device according to claim 1, wherein a radius of curvature of the downstream edge is 5 mm or less. A pressing means for pressing the peeling member against the fixing belt;
The pressing means includes a spring member that applies a pressing force to the fixing belt to the peeling member, and a movable member that is arranged to linearly move between the spring member and the peeling member,
The fixing device according to claim 1, wherein an urging force of the spring member is transmitted to the peeling member via the movable member.   The fixing device according to claim 1, wherein the pressure member is a roller-shaped member.   The pressure member includes a roller-shaped member and a pressure belt that is rotatably stretched around the roller-shaped member and conveys a recording material together with the fixing belt. Item 4. The fixing device according to Item 1. A fixing device for fixing a toner image carried on a recording material,
A rotatable fixing roller;
A fixing belt that is stretched around the fixing roller and rotatably provided;
A pressure member that is arranged to press the fixing roller and forms a nip portion through which a recording material passes between the fixing belt and the fixing belt stretched around the fixing roller;
The fixing belt is disposed with a gap therebetween, and the fixing belt is pressed against the pressure member in the vicinity of the pressure contact portion between the fixing roller and the pressure member, and the fixing belt is bent. A peeling member for peeling the recording material from the fixing belt;
A support member that supports the peeling member so as to be movable around the fixing roller,
The fixing device, wherein the peeling member supported by the supporting member maintains a posture with respect to the fixing roller when moving around the fixing roller.   The fixing device according to claim 9, wherein the peeling member is formed by bending a metal member.   The fixing device according to claim 10, wherein an inner side surface of the peeling member facing the fixing roller has substantially the same curvature as an outer peripheral surface of the fixing roller.   The fixing device according to claim 10, wherein the peeling member has a pressing surface that presses the fixing belt formed as a flat surface or a curved surface that follows the surface shape of the pressing member.   The fixing device according to claim 9, wherein the peeling member has a substantially constant thickness.

Images