JP2019174849A - Fixing device and image forming apparatus - Google Patents

Abstract

To provide a fixing device that can relatively easily form high-precision convex shape parts so as to improve reliability of components and reduce inspection cost.SOLUTION: A fixing device includes: an endless fixing belt 82; a fixing belt holding member 86 that holds the fixing belt 82; a pressure member 88 that is in contact with the outer peripheral surface of the fixing belt 82; a nip forming member 83 that is arranged inside the fixing belt 82 to be in contact with the pressure member 88 with the fixing belt 82 therebetween and thereby fixing a nip; a sheet-metal nip support member 84 that supports the nip forming member 83; a side plate 87 that fixes the fixing belt holding member 86 and the nip support member 84; and a pressure mechanism that brings the pressure member 88 into pressure contact with the nip forming member 83 with the fixing belt 82 therebetween. The nip support member 84 has both end faces as a shear plane, and is in contact with the nip forming member 83 at one shear plane 92 and is supported by the side plate 87 at the other shear plane 93.SELECTED DRAWING: Figure 7

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile, and more particularly to a configuration of a fixing device.

  A pipe-shaped metal heat conductor and a heat source are provided inside the endless belt, the endless belt is heated via the metal heat conductor, and is further contacted with the metal heat conductor via the endless belt to form a nip portion. A fixing device having a pressure roller and moving the endless belt in the circumferential direction in accordance with the rotation of the pressure roller is known (see, for example, “Patent Document 1”). With this configuration, the entire endless belt constituting the fixing device can be warmed, the first print time from the heating standby time can be shortened, and the lack of heat during high-speed rotation can be solved.

  There is also known a fixing device having a configuration capable of forming a nip by directly heating the endless belt with a heat source by providing only a member that forms a nip inside the endless belt, a member that supports the member, and a heat source. (See, for example, “Patent Document 2”). With this configuration, since the heat capacity around the heat source is reduced, the first print time from the heating standby time can be shortened.

  In the conventional configuration, since the support member that supports the nip member needs to penetrate through the belt, it becomes a doubly supported beam that supports the load received from the nip surface at both ends. At this time, it is preferable that the volume of the support member is as small as possible in order to reduce the size of the fixing device and reduce the extra heat capacity. However, since the support member needs to form a nip width by supporting the load received from the elastic pressure roller, if the strength of the support member is reduced by reducing the volume of the support member, the center of the support member bends in a direction to escape from the nip surface, A uniform nip width in the longitudinal direction cannot be obtained.

  As a means for solving this problem, a method of offsetting the bending by making the central portion in the longitudinal direction of the nip forming member or the support member convex toward the nip surface in advance can be considered. In order to obtain it, it is necessary to form the convex shape portion with an accuracy of 0.05 mm or less, and it is costly to inspect all parts.

  The present invention provides a fixing device that solves the above-described problems, improves the reliability of parts by a configuration that can form a convex portion with high accuracy relatively easily, and can reduce inspection costs and the like. With the goal.

  The invention described in claim 1 is an endless fixing belt, a fixing belt holding member that holds the fixing belt, a pressure member that comes into contact with an outer peripheral surface of the fixing belt, and the fixing belt disposed inside the fixing belt. A nip forming member that forms a nip by contacting the pressure member via the fixing belt, a sheet metal nip supporting member that supports the nip forming member, the fixing belt holding member, and the nip supporting member are fixed. And a pressure mechanism that presses the pressure member against the nip forming member via the fixing belt, and the nip support member has sheared surfaces at both ends, and the nip forming member is opposed to the nip forming member. While contacting with one shearing surface, the other shearing surface is supported by the side plate.

  According to the present invention, since the nip forming member can be positioned by the shear surface formed on the nip support member made of a sheet metal that is easy to obtain dimensional accuracy, one accurate shear surface can be easily formed, A fixing device capable of improving the reliability and reducing the inspection cost can be provided.

1 is an external view of an image forming apparatus to which an embodiment of the present invention can be applied. 1 is a schematic view of an image forming apparatus to which an embodiment of the present invention can be applied. 1 is an external view showing a state in which an exterior cover of an image forming apparatus to which an embodiment of the present invention can be applied is removed. FIG. 3 is a schematic diagram illustrating an internal configuration of a fixing device including an example of a sheet conveying device included in an image forming apparatus to which an embodiment of the present invention can be applied. 1 is a schematic front sectional view of a fixing device illustrating an embodiment of the present invention. 1 is a schematic plan view of a fixing device illustrating an embodiment of the present invention. 1 is a schematic plan view of a fixing device with an endless belt removed according to an embodiment of the present invention. It is the schematic explaining the stay used for one Embodiment of this invention. It is the schematic explaining the pressurization mechanism used for one Embodiment of this invention. It is the schematic explaining the pad support surface used for the modification of one Embodiment of this invention. It is the schematic explaining the pad support surface used for the other modification of one Embodiment of this invention.

Hereinafter, an example of an embodiment for carrying out the present invention will be described with reference to the drawings.
An example of a sheet conveying apparatus to which the present invention is applied and an image forming apparatus 100 using a fixing device incorporating the same are intended for a printer. However, the present invention is not limited to this. The machine can be the target.
In FIG. 1, the image forming apparatus 100 includes a front-rear direction (a direction indicated by an arrow X) as a first direction, a left-right direction (a direction indicated by an arrow Y) as a second direction perpendicular thereto, and a third direction. The main body is composed of a rectangular parallelepiped casing having a vertical direction (direction indicated by an arrow X).
In each of the above directions, the direction indicated by the arrow X corresponds to the width direction of the sheet as a recording medium parallel to the longitudinal direction of the front and rear direction of the image forming apparatus 100 and a fixing member used in the fixing apparatus 20 and a counter rotating body described later. ing.
In the image forming apparatus 100, a document scanning device 200 is mounted on the upper part of the image forming unit described in detail in FIG. 2 in the vertical direction (Z direction). A paper discharge tray 17 used as a section is formed.
An exterior cover 100A that is an openable and closable opening / closing member is provided on one side of the width direction (Y direction) that is the left-right direction of the image forming apparatus 100, and is provided inside by opening the exterior cover 100A. The fixing device 20 is visible from the outside as shown in FIG.

The image forming apparatus 100 has the configuration shown in FIG. In FIG. 2, the document scanning device 200 shown in FIG. 1 is omitted.
In the image forming apparatus 100 shown in FIG. 2, the visible image formed on each of the photoconductive drums 120Y, 120C, 120M, and 120Bk faces the photoconductive drum 120 and moves with respect to the transfer belt 11 that can move in the arrow A1 direction. Are sequentially transferred. This transfer process corresponds to the primary transfer process, and each image is sequentially transferred onto the transfer belt 11 to form a superimposed transfer image. Thereafter, a secondary transfer process is performed on the paper P on which a recording sheet or the like is used, whereby the superimposed transfer image is collectively transferred onto the paper P.

  Around each photosensitive drum 120, an apparatus for performing an image forming process as the photosensitive drum rotates is disposed. The following is a description of the photosensitive drum 120Bk that performs black image formation. A charging device 30Bk, a developing device 40Bk, a primary transfer roller 12Bk, and a cleaning device 50Bk that perform image forming processing are arranged along the rotation direction of the photosensitive drum 120Bk. For writing performed after charging, an optical scanning device 8 described later is used.

  In the superimposing transfer on the transfer belt 11, the visible images formed on the respective photosensitive drums 120 are sequentially superimposed and transferred onto the transfer belt 11 in the process in which the transfer belt 11 moves in the A1 direction. In the primary transfer process, the transfer bias is applied using the primary transfer rollers 12Y, 12C, 12M, and 12Bk disposed to face the respective photosensitive drums 120 with the transfer belt 11 interposed therebetween, thereby causing the downstream transfer from the upstream side in the A1 direction. It is performed sequentially toward the side.

  The photosensitive drums 120Y, 120C, 120M, and 120Bk are accommodated in the process cartridge, and are arranged in this order from the upstream side in the arrow A1 direction. Each photosensitive drum 120 is provided in an image station for forming yellow, cyan, magenta, and black images. As a configuration for executing the primary transfer process, a transfer belt unit 10 including a transfer belt 11 and each primary transfer roller 12 facing each photoconductor drum 120 with the transfer belt 11 interposed therebetween is used. The image superimposed and transferred onto the transfer belt 11 is collectively transferred onto the paper P by the secondary transfer roller 5 constituted by a roller that rotates with the transfer belt 11.

In the image forming apparatus 100, in addition to the process cartridge and transfer belt unit 10 described above, an optical scanning device 8 as an optical writing device disposed facing the lower side of the four image stations, and a cleaning device for the transfer belt 11. 13 is provided.
The optical scanning device 8 includes a semiconductor laser as a light source, a coupling lens, an fθ lens, a toroidal lens, a mirror, a rotating polygon mirror, and the like. The optical scanning device 8 has a writing light Lb corresponding to each color for each photosensitive drum 120 (in FIG. 2, for convenience, only a black image station is labeled, but the same applies to other image stations). ). Thereby, an electrostatic latent image is formed on each photosensitive drum 120.

The following apparatus is used for the image forming apparatus 100.
The image forming apparatus 100 sets the sheet feeding device 61 that feeds the paper P onto which the images superimposed and transferred in the secondary transfer are collectively transferred, and the registration timing of the paper P that is fed from the sheet feeding device 61. And a registration roller pair 4 that is fed to the secondary transfer position. Further, the image forming apparatus 100 includes a sensor (not shown) that detects that the leading edge of the sheet P has reached the registration roller pair 4.

  The paper P onto which the toner image T superimposed and transferred onto the transfer belt 11 in the secondary transfer process is transferred in a batch is conveyed to a fixing device 20 (see FIG. 2) described later, and the toner image is fixed. The paper P after fixing is discharged through a paper discharge roller 7 toward a paper discharge tray 17 provided outside the main body of the image forming apparatus 100. Reference numerals 9Y, 9C, 9M, and 9Bk in FIG. 2 indicate new toner supply tanks for the developing devices provided in the image stations of the respective colors.

  As shown in FIG. 4, the fixing device 20 is used to fix the toner image T after transfer, which is carried on the paper P, by melting and infiltrating it with heat and pressure, and has the flexibility to be rotated while being heated. The fixing belt 21 is provided. In addition to the fixing belt 21, the fixing device 20 includes a pressure roller 22 that is a counter rotating body that forms a nip portion N by applying pressure to the fixing belt 21 in contact with the fixing belt 21. Is provided. Inside the fixing belt 21, there is provided a heater 23 having a halogen lamp as a heat source for heating a portion other than the nip portion N, in this embodiment, the region of the fixing belt 21 that moves around the nip portion N. Yes.

  Inside the fixing belt 21, a nip forming member 24 that is a base member for forming a nip disposed inside the fixing belt 21, a stay 25 that supports the nip forming member 24, and light emitted from the heater 23. And a reflection member 26 that reflects the light to the fixing belt 21 is provided. Although not shown in detail, the nip forming member 24 that is a base member for forming a nip has a sliding sheet (low friction sheet) wound around a base pad as a member that contacts the fixing belt 21. In the nip forming member 24 shown in the figure, the shape of the nip portion N is flat, but the shape of the nip portion N is not limited to this shape. For example, when it is formed in a concave shape along the peripheral surface of the pressure roller 22, the leading edge of the paper P passing through the nip portion N is close to the pressure roller 22, so that the separation from the fixing belt 21 is improved. There are advantages.

  The temperature of the fixing belt 21 is detected by a temperature sensor 27 provided on the side where the paper P enters the nip portion, and used for feedback processing of the heater 23. In FIG. 4, an arrow F indicates the conveyance direction of the paper P. The fixing belt 21 is an endless belt formed in a thin and flexible sleeve shape, and is composed of a base material and a release layer located on the surface thereof. For the base material, a metal material such as nickel or SUS or a resin material such as polyimide is used. For the release layer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE), or the like having releasability with respect to the toner is used.

  The pressure roller 22 includes a cored bar 22a, an elastic layer 22b made of foamable silicone rubber, silicone rubber, or fluororubber provided on the surface of the cored bar 22a, and PFA provided on the surface of the elastic layer 22b. It is constituted by a release layer 22c made of PTFE or the like. The pressure roller 22 is pressed toward the fixing belt 21 by a pressure mechanism 204 described later, and is in contact with the nip forming member 24 as a base member through the fixing belt 21 in contact with the fixing belt 21. At the place where the pressure roller 22 and the fixing belt 21 contact each other, the elastic layer 22b of the pressure roller 22 is crushed so that pressure is applied to the fixing belt 21 and the nip forming member 24 has a predetermined width. The nip portion N is secured.

  The pressure roller 22 is rotationally driven by a drive source such as a motor (not shown) provided in the printer body. When the pressure roller 22 is rotationally driven, the driving force is transmitted to the fixing belt 21 through the nip portion N, and the fixing belt 21 is driven to rotate. In the configuration shown in FIG. 4, the pressure roller 22 is a solid roller, but may be a hollow roller. In that case, a heating source such as a halogen heater using radiant heat may be disposed inside the pressure roller 22. Further, when the elastic layer 22b is not provided, the heat capacity is reduced and the fixability is improved. However, when the unfixed toner is crushed and fixed, minute irregularities on the belt surface are transferred to the image and uneven glossiness is formed on the solid portion of the image. May occur. In order to prevent this, it is desirable to provide an elastic layer having a thickness of 100 μm or more. Aluminum, iron, stainless steel, or the like can be selected as the pipe-shaped metal used for the hollow roller. In the case where a heat source is provided in the pressure roller 22, in order to prevent the support from being heated by radiant heat from the heat source, a heat insulating layer may be provided on the surface of the support or a heat ray reflecting surface by mirror treatment may be provided. desirable. The heat source in this case is not limited to the halogen heater described above, and an IH heater, a resistance heating element, a carbon heater, or the like can be used.

  FIG. 9 shows a pressure mechanism 204 of the pressure roller 22, and the pressure mechanism 204 includes a substrate 204A and a pressure roller urging plate 204B supported so as to be swingable with respect to the substrate 204A. . The pressure roller urging plate 204B is supported with the lower end side of the substrate 204A in FIG. 9 as a swing fulcrum, and the swing end is normally attached to the fixing belt 21 by a spring 205 disposed between the substrate 204A. A swinging behavior is given.

  At the lower end of the substrate 204A, an input gear 206 to which a driving force is transmitted from the apparatus main body side is rotatably supported by a support shaft 206A. An idle gear 208 provided on a mounting plate 207 used for attachment to the apparatus main body is meshed with the input gear 206, and an output gear 209 supported coaxially with the pressure roller 22 is engaged with the idle gear 208. Meshed. The substrate 204A and the pressure roller urging plate 204B can swing as shown by arrows in FIG. 9 with the support shaft 206A as a swing fulcrum. The swing direction corresponds to a direction in which the pressure roller 22 is pressed against the fixing belt 21 to apply pressure to the nip portion and a direction in which the pressure is released from the nip portion.

  The swing operation of the substrate 204A and the pressure roller urging plate 204B is performed by the eccentric cam 210 disposed on the back side of the swing end of the substrate 204A and the bearing 211 that is rotatably supported on the substrate 204A side so as to come into contact therewith. Is done. That is, when the bearing 211 is pushed and moved by the large diameter portion of the rotational phase of the eccentric cam 210, the pressure roller 22 moves toward the fixing belt 21. When the position of the eccentric cam 210 facing the bearing 211 changes from the large diameter portion to the small diameter portion, the pressure roller 22 moves in a direction in which the nip pressure is released.

  The image forming apparatus 100 using the fixing device 20 having the above configuration is provided with a paper transport device for transporting paper, and an example of the paper transport device 300 passes through the nip portion N of the fixing device 20. Intended for paper. As shown in FIG. 4, the sheet conveying apparatus 300 conveys the sheet P that has passed through the nip portion N continuously to the outlet side of the fixing apparatus 20 toward the sheet discharge tray 17 (see FIG. 2). Is configured.

  Here, the characteristic part of the present invention in the image forming apparatus 100 having the above-described configuration will be described. In the fixing device 20 described above, as described in the section “Problems to be Solved by the Invention”, in order to obtain a uniform nip surface, the convex portion of the nip forming member 24 is accurate to 0.05 mm or less. It is necessary to form them, and costs are required for inspection of all parts. A configuration for solving this problem will be described below.

  5 and 6 show a fixing device 81 used in an embodiment of the present invention in place of the fixing device 20. The fixing device 81 includes a fixing belt 82 that is an endless belt. The fixing belt 82 includes a pad 83 that is a nip forming member, a stay 84 that is a nip support member that determines the position of the pad 83, and a fixing belt 82. A heater 85 for heating is provided. Both ends of the fixing belt 82 are supported by holders 86 that are fixing belt holding members, and the stay 84 and the holder 86 are supported by side plates 87. On the front side of the fixing belt 82, a pressure roller 88 as a pressure member is disposed at a position facing the pad 83, and the pressure roller 88 is a spring (not shown) provided near both ends of the support shaft. Is pressed toward the pad 83 to form a nip surface 89.

  In the above-described configuration, during the fixing operation, the pressure roller 88 is rotated in the clockwise direction in FIG. 5 by a driving force from a driving mechanism (not shown), and the fixing belt 82 travels following this, and the heater 85 is moved to the fixing belt. Heat 82 directly. Thereafter, when sufficient heat is accumulated, the sheet passing is started, the sheet 91 on which the toner 90 is transferred is conveyed from the lower side of FIG. 5, and the sheet 91 passes through the nip surface 89, whereby the toner 90 is transferred to the sheet 91. To be established.

  In the fixing operation described above, when the nip width is narrow and the amount of heat applied to the toner 90 is too small, the toner 90 cannot be sufficiently melted and the toner 90 cannot be fixed to the paper 91. On the other hand, even when the nip width is wide and the amount of heat applied to the toner is too large, the toner 90 has excessive fluidity beyond the rubbery region and cannot be fixed on the paper 91. In order to avoid the occurrence of such a problem, it is necessary to suppress variations in nip width due to various factors. One of the variations in the nip width is that the stay 84 is bent by a load received from the pressure roller 88, the nip width in the central portion is narrowed, and a deviation occurs in the nip width.

  In order to eliminate the above-described problems, in the present invention, in order to correct the nip width deviation due to bending, the pad support surface 92 which is one shear surface of the stay 84 is centered from both longitudinal ends as shown in FIG. It forms so that it may become convex shape gradually as it goes to the part. With such a configuration, the deflection of the stay 84 is canceled out.

  As shown in FIG. 8, the stay 84 includes a stay upper 84a, a stay lower 84b, and a stay right 84c. The stay upper 84a is a sheet metal material, and the lower end surface in FIG. 8 is formed by a linear shear surface in the longitudinal direction. The upper end surface in FIG. 8 of the stay upper 84a is formed as a shear surface having a shape that gradually becomes convex as it goes from both ends in the longitudinal direction toward the center. The upper end surface of the stay upper 84a passes through the surface of the stay right 84c, and a pad support surface 92 which is one shear surface is formed by the upper end surface. The stay lower portion 84b is also a sheet metal material, and the lower end surface in FIG. 8 is formed of a linear shear surface in the longitudinal direction. The upper end surface in FIG. 8 of the stay lower portion 84b is separated from the upper end surface of the upper stay portion 84a by a predetermined distance as the stay lower portion 84b is bent halfway, and gradually protrudes from both longitudinal ends toward the central portion. It is formed with a shearing surface having a shape. The upper end surface of the stay lower portion 84b also penetrates the surface of the stay right 84c, and a pad support surface 92 that is one shear surface is formed by the upper end surface. The upper stay 84a and the lower stay 84b are fixed by welding, bonding, caulking, screwing, or the like, and each stay 84a, 84b is fixed by welding, bonding, caulking, screwing, or the like. The lower end surface of each stay 84a, 84b constitutes a stay support surface 93 which is the other shear surface, and the stay 84 is formed by fitting the stay support surface 93 into a hole 87a drilled in the side plate 87. It is supported by the side plate 87.

  According to the above-described configuration, the pad 83 can be positioned by the shear surface formed on the sheet metal stay 84 that is easy to obtain dimensional accuracy, so that the accurate pad support surface 92 can be easily formed, and the reliability of the parts can be improved. It is possible to provide a fixing device that can improve inspection performance and reduce inspection costs. Further, each pad support surface 92 is formed so as to gradually protrude from both longitudinal end portions to the center portion, thereby canceling out the nip deviation due to the deflection of the stay 84 and uniform nips. Can be obtained.

  Further, in the above configuration, each pad support surface 92 is formed so as to be gradually convex as it goes from both ends in the longitudinal direction to the center portion. However, instead of each pad support surface 92, as shown in FIG. It is good also as the pad support surface 92a formed so that it might become circular arc shape. Thereby, the pad 83 is prevented from coming into contact with the pad support surface 92a in a straight line, a more uniform nip can be obtained, and damage to the pad 83 can be prevented. Further, in the above configuration, a plurality of pad support surfaces 92 are formed in a discontinuous comb shape, but instead of each pad support surface 92, a pad support surface 92b formed continuously as shown in FIG. Good. However, it is possible to finely adjust the shape of the shearing surface individually by dividing and forming, and it is possible to easily ensure the reliability of the parts. In addition, by configuring the stay 84 from three sheet metal upper esthetics 84a, lower stays 84b, and right stays 84c, the stays 84 can be formed with a minimum number of parts, thereby reducing costs and facilitating assembly. Can do.

As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to this specific embodiment, Unless it is specifically limited by the above-mentioned description, this invention described in the claim is described. Various modifications and changes are possible within the scope of the gist of the invention.
The effects described in the embodiments of the present invention are only the most preferable effects resulting from the present invention, and the effects of the present invention are limited to those described in the embodiments of the present invention. is not.

81 Fixing device 82 Fixing belt 83 Nip forming member (pad)
84 Nip support member (stay)
86 Fixing belt holding member (holder)
87 Side plate 88 Pressure member (Pressure roller)
92 One shear surface (pad support surface)
93 Other shear surface (stay support surface)
100 Image forming apparatus

JP 2007-334205 A Japanese Patent Laid-Open No. 2007-233011

The invention described in claim 1 is an endless fixing belt, a fixing belt holding member that holds the fixing belt, a pressure member that comes into contact with an outer peripheral surface of the fixing belt, and the fixing belt disposed inside the fixing belt. a nip forming member for forming a nip with the fixing belt in contact with the pressure member, and Runi-up support member to support the nip forming member and the nip supporting member and the fixing belt holding member supporting And a pressing mechanism that presses the pressing member against the nip forming member via the fixing belt, the nip support member having a first stay member and a second stay member, The one stay member and the second stay member each have one shearing surface in contact with the nip forming member and the other shearing surface in contact with the side plate so as to support a load received from the pressure member, Serial the one shearing surface of the first stay member and the second stay member is a predetermined distance, and wherein the other of the shearing surface is supported by the side plate.

Claims (6)

An endless fixing belt,
A fixing belt holding member for holding the fixing belt;
A pressure member in contact with the outer peripheral surface of the fixing belt;
A nip forming member disposed inside the fixing belt and forming a nip by contacting the pressure member via the fixing belt;
A sheet metal nip support member for supporting the nip forming member;
A side plate for fixing the fixing belt holding member and the nip support member;
A pressure mechanism that presses the pressure member against the nip forming member via the fixing belt,
The fixing device in which both end surfaces of the nip support member are shear surfaces, which are in contact with the nip forming member at one shear surface, and the other shear surface is supported by the side plate. The fixing device according to claim 1.
The fixing device according to claim 1, wherein the one shearing surface is formed so as to gradually protrude from both ends in the longitudinal direction toward the center. The fixing device according to claim 2.
The fixing device is characterized in that the one shearing surface is formed in an arc shape. The fixing device according to any one of claims 1 to 3,
The fixing device according to claim 1, wherein the one shear surface has a discontinuous comb shape. In the fixing device according to any one of claims 1 to 4,
The fixing device according to claim 1, wherein the nip support member is formed of three sheet metals.   An image forming apparatus comprising the fixing device according to claim 1.

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