JP2017009940A - Thermal fixing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate a force to spread a recording material to both end parts without giving a difference to the conveying speed of a nip length direction and thereby to enable the generation of a paper wrinkle to be prevented.SOLUTION: A thermal fixing apparatus includes: a rotation body having a driving source; a pressing member (404) for pressing the rotation body; an endless belt member (402) abutting against the rotation body, forming a nip part, and slidably rotating; an end part holding member (410) for holding the belt member by an end part; and a heat generating member (403) for heating either the rotation body or the belt member or both of them. The thermal fixing apparatus makes the belt member slidably rotate by rotating the rotation body, and sandwiches and transfers the recording material to the nip part, and heats and presses the recording material by the nip part. The rotation axis is expanded and contracted from the surface layer to the elastic member and from the surface layer to the base material of the belt member by providing an inclination to the belt rotation axis on an end part holding groove (411) in the end part holding member (410) corresponding to the rotation of the belt member.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image heating apparatus that suppresses the occurrence of paper wrinkles in an image heating apparatus that performs a heating and pressing process on a recording material carrying a toner image.

  Conventionally, transfer to recording materials (transfer material sheet, electrofax sheet, electrostatic recording paper, OHP sheet, printing paper, format paper, etc.) by image forming process means (electrophotographic process, electrostatic recording process, magnetic recording process, etc.) As a fixing device for permanently fixing an unfixed toner image of image information formed and supported by a method or a direct method to the recording material surface by heating and pressing, a heating device of a heat roller method or a film heating method is widely used. It has been. A heating device of a film heating method is proposed in Patent Documents 1 to 4 and the like.

  Furthermore, recent image forming apparatuses tend to increase the pressurizing force at the nip portion in order to ensure good fixability as the printing speed increases.

  However, in the film heating type heating apparatus, when the applied pressure is increased, there is a problem that paper wrinkles are likely to occur when the recording material is nipped and conveyed at the nip portion, particularly in a recording material that has absorbed moisture.

  Conventionally, in a film heating type heating device, by forming the pressure roller in a reverse crown shape, the conveyance speed at both ends in the nip longitudinal direction is made faster than the conveyance speed at the center, and the recording material is arranged at both ends. A technique is used in which a force that spreads to the side is generated, thereby preventing the occurrence of paper wrinkles (Patent Document 5).

JP-A-63-313182 Japanese Patent Laid-Open No. 2-157878 JP-A-4-044075 JP-A-4-204980 JP, 2010-107623, A

  However, in a heating device in which the conveyance speed at both ends in the nip longitudinal direction is faster than the conveyance speed at the center as in Patent Document 5, the film may be twisted due to the difference in speed. This phenomenon is particularly likely to occur when recording paper (hereinafter referred to as small size paper) having a paper width smaller than that of the heating element is continuously fed. When passing small size, the non-passing part at both ends of the pressure roller rises in temperature than the passing part (temperature rise of the non-passing part) and becomes thicker, so both ends of the film transport speed in the nip longitudinal direction This is because the disparity at the center becomes even larger.

  Accordingly, an object of the present invention is to prevent the generation of paper wrinkles and the generation of film twist even when the speed of an image forming apparatus using a film heating type heating apparatus is increased. It is to provide a heating device and an image forming apparatus.

An image forming apparatus according to the present invention includes a rotating body having a driving source, a pressurizing member that pressurizes the rotating body, an endless belt member that is in contact with the rotating body to form a nip portion and is slidably rotated, An end holding member that holds the belt member at the end, and a heating member that heats the rotating body and / or the belt member, and the belt member is driven to rotate by rotating the rotating body. At the same time, the recording material is sandwiched and conveyed in the nip part, and the recording material is heated and pressurized in the nip part.
By providing the end holding member with an inclination with respect to the belt rotation axis, the surface layer, the elastic member, or the base material of the belt member expands and contracts in the longitudinal direction as the belt member rotates. .
The inclination of the end holding member is in the range of 2 to 3% of the longitudinal length L of the belt.
The belt member is characterized in that a rib is provided on a surface layer member, an elastic member, or a base material at an end portion of the belt.
The end holding member has a different longitudinal depth according to a circumferential phase.

  According to the image forming apparatus of the present invention, it is possible to generate a force for spreading the recording material to both ends without making a difference in the nip longitudinal conveyance speed, thereby preventing the occurrence of paper wrinkles.

1 is a schematic diagram of an image forming apparatus in an embodiment of the present invention. 1 is a schematic diagram of a heat fixing apparatus in an embodiment of the present invention. It is explanatory drawing of the pressurization mechanism of a fixing device. It is a schematic diagram of the fixing film member in the Example of this invention. It is a schematic diagram of the fixing film structure in the Example of this invention. It is a schematic diagram of the fixing film edge part holding member in the Example of this invention. It is a schematic diagram which shows the relationship of the tensile stress in the Example of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention provides another embodiment in which part or all of the configuration of the embodiment is replaced with the alternative configuration as long as the pressure of the heating nip is released and the film member is rotated to move the lubricant. But it can be done.

  In the present embodiment, only main parts related to toner image formation / transfer will be described. However, in addition to necessary equipment, equipment, and a housing structure, various printers, various printing machines, copiers, fax machines, multifunction machines, etc. Can be implemented in In addition, about the general matter of the image heating apparatus shown by patent documents 1-4, illustration is abbreviate | omitted and the overlapping description is abbreviate | omitted.

[Example of image forming apparatus]
FIG. 1 is an explanatory diagram of the configuration of the image forming apparatus. As shown in FIG. 1, the image forming apparatus 10 is a tandem type full-color printer in which image forming units 10Y, 10M, 10C, and 10K are arranged along an intermediate transfer belt 31.

  In the image forming unit 10 </ b> Y, a yellow toner image is formed on the photosensitive drum 11 </ b> Y and is primarily transferred to the intermediate transfer belt 31. In the image forming unit 10M, a magenta toner image is formed on the photosensitive drum 11M, and is primarily transferred onto the yellow toner image on the intermediate transfer belt 31. In the image forming units 10C and 10K, a cyan toner image and a black toner image are formed on the photosensitive drums 11C and 11K, respectively, and similarly, the toner images on the intermediate transfer belt 31 are sequentially superimposed and sequentially transferred.

  The four color toner images carried on the intermediate transfer belt 31 are collectively secondary transferred onto the recording material P by the secondary transfer portion T2. The recording material P drawn from the recording material cassette 20 by the pickup roller 21 and separated one by one by the separation roller waits at the registration roller 23, and performs secondary transfer in synchronization with the toner image on the intermediate transfer belt 31. Sent to the part T2.

  The recording material P onto which the toner image has been secondarily transferred at the secondary transfer portion T2 is heated and pressurized by the fixing device 40 and fixed on the surface, and then discharged onto the discharge tray 64 through the discharge roller 63. The

  The image forming units 10Y, 10M, 10C, and 10K are configured substantially the same except that the color of the toner used in the developing device attached thereto is different from yellow, magenta, cyan, and black. Hereinafter, the image forming unit 10Y will be described, and the other image forming units 10M, 10C, and 10K will be described by replacing “Y” at the end of the reference code with “M”, “C”, and “K”.

  In the image forming unit 10Y, a corona charger 12Y, an exposure device 13Y, a developing device 14Y, a transfer blade 17Y, and a cleaning device 15Y are arranged around the photosensitive drum 11Y. The photosensitive drum 11Y is composed of a metal cylinder on which a negatively charged photosensitive layer is formed, and rotates in a direction indicated by an arrow at a predetermined process speed. The corona charger 12Y charges the surface of the photosensitive drum 11Y to a uniform negative potential. The exposure device 13Y writes an electrostatic image of the image on the surface of the charged photosensitive drum 11Y. The developing device 14Y stirs and charges the two-component developer, and reversely develops the electrostatic image on the photosensitive drum 11Y with the negatively charged toner.

  The transfer blade 17Y presses the inner surface of the intermediate transfer belt 31 to form a primary transfer portion between the photosensitive drum 11Y and the intermediate transfer belt 31. By applying a positive DC voltage to the transfer blade 17Y, the toner image carried on the photosensitive drum 11Y is primarily transferred to the intermediate transfer belt 31.

  The secondary transfer roller 35 sandwiches the intermediate transfer belt 31 between the counter roller 34 and forms a secondary transfer portion T <b> 2 between the intermediate transfer belt 31 and the secondary transfer roller 35. The secondary transfer unit T2 overlaps and conveys the recording material P on the intermediate transfer belt 31 carrying the toner image, and applies a positive direct current voltage to the secondary transfer roller 35, so that the intermediate transfer belt 31 The toner image is secondarily transferred to the recording material P.

[Fixing Device of First Embodiment]
The fixing device according to the first embodiment of the present invention will be described below. FIG. 2 is an explanatory diagram of the configuration of the fixing device. FIG. 3 is an explanatory diagram of a pressure mechanism of the fixing device. FIG. 4 is an explanatory diagram of the fixing film in this embodiment.

  As shown in FIG. 2, the fixing device 40 presses the driving member (402) from below to the film member (405) supported on the inner surface by the rubbing members (404, 403), thereby A heating nip (N) is formed. In the process in which the recording material P passes through the heating nip (N), heat is supplied from the resistance heating element (403b) to the recording material P through the film member (405), so that the unfixed toner image t is softened. Then, it is fixed on the surface of the recording material P. Such a pressure roller driving type and tensionless film heating type image heating apparatus are disclosed in Japanese Patent Application Laid-Open Nos. 4-44075 to 44083, Japanese Patent Application Laid-Open Nos. 4-204800 to 204984, and the like.

  The film guide 404, the heater 403, the stay 406, and the fixing film 405 are determined in mutual positional relationship by end caps (428: FIG. 3) arranged at both ends in the longitudinal direction, thereby constituting the fixing film unit 401. .

  A film guide 404, which is an example of a rubbing member, serves as a support member for an elastic heater 403, which will be described later, and a guide member for an inner surface of the fixing film 405, and has a high heat resistance, heat resistance, and rigidity. Etc. The film guide 404 is a horizontally long member whose longitudinal direction is perpendicular to the drawing, and a heater elasticity 403 is fitted into a groove provided along the longitudinal direction of the lower surface of the film guide 404 so as to be insulated and fixedly held.

  A stay 406, which is an example of a pressure member, is a metal U-shaped beam member that reinforces the film guide 404, and is disposed so as to penetrate the fixing film 405 in the longitudinal direction.

  As shown in FIG. 4A, the fixing film 405 as an example of a belt member is formed of a cylindrical resin film material having excellent heat resistance as a flexible member and having an outer diameter of 30 mm. The fixing film 405 is a thin film cylinder of a metal base layer 412 having a thickness of about 30 μm to 100 μm. An elastic layer 408 made of silicon rubber is disposed on the base layer with a primer layer (adhesive layer) interposed therebetween, so that release from softened toner is performed. A coat 411 such as PFA or PTFE for imparting properties is applied. Further, as shown in FIG. 4b, ribs 409 made of polyimide resin are applied to both ends of the fixing film in the circumferential direction of the film, and the ribs are disposed on the elastic layer 408 via an adhesive.

  The inner peripheral length of the fixing film 405 is larger than the outer peripheral length of the assembly including the film guide 404, the heater 403, and the stay 406. Accordingly, the fixing film 405 is loosely fitted around the film guide 404, the heater 403, and the stay 406 so that the circumferential length has a margin.

  A pressure roller 402, which is an example of a drive member, sandwiches the fixing film 405 between the heater 403 of the fixing film unit 401 and the lower surface of the stay 406. The pressure roller 402 is formed to have a diameter of 30 mm by disposing an elastic layer 402b made of silicon rubber on the outer peripheral surface of the metal shaft 402a. A release layer 402c such as PFA having a thickness of about 10 to 100 μm is provided on the surface of the elastic layer 402b via a primer layer (adhesive layer).

  The pressure roller 402 is in contact with the fixing film 405 and is driven to rotate at a predetermined peripheral speed in the direction of arrow C, which is the conveyance direction of the recording material P. As the pressure roller 402 rotates, a rotational force in the direction of arrow D acts on the fixing film 405 by the frictional force between the pressure roller 402 and the fixing film 405 in the heating nip N. As a result, the fixing film 405 rotates around the film guide 404 by causing the inner surface of the fixing film 405 to slide in close contact with the downward surface of the heater 403 in the heating nip N.

  As shown in FIG. 5, the circumferential shape of the fixing film 405 is regulated by holding the longitudinal end portions of the fixing film by a film shape holding member (hereinafter referred to as a flange 410).

  As shown in FIG. 5, the flange 410 is provided with a groove 411 for holding a rib 409 disposed at the end of the fixing film. The groove 410 is rotated by the rotation of the pressure roller 402 with which the fixing film 405 abuts. It keeps rotating at substantially the same peripheral speed as the recording paper conveyance speed while closely contacting and rubbing against the heating surface of the film guide 404 on which the heater 403 is disposed.

  The recording material P is introduced into the heating nip N in a state in which the fixing film 405 is rotated by being driven to rotate by the pressure roller 402, and the heater 403 is heated to a predetermined target temperature by energization. A recording material P carrying an unfixed toner image t is introduced between the fixing film 405 and the pressure roller 402, and the toner image carrying surface of the recording material P is in close contact with the outer surface of the fixing film 405. Pass through the heating nip N together. At this time, the heat of the heater 403 is applied to the recording material P through the fixing film 405, and the unfixed toner image t is heated and fixed on the surface of the recording material P. The recording material P that has passed through the heating nip N is separated from the surface of the fixing film 405 and is discharged and conveyed.

  As shown in FIG. 3, the pressure mechanisms 420 arranged at both ends of the stay 406 in the longitudinal direction urge the stay 406 toward the pressure roller 402 with a variable pressing force during image heating. As a result, the elastic layer 402 b of the pressure roller 402 is elastically deformed along the contour lines of the film guide 404 and the heater 403 to form a heating nip N necessary for the fixing device 40. When pressed toward the pressure roller 402, the stay 406 prevents the film guide 404 and the heater 403 from being bent and deformed.

  The film guide 404 has a length of 360 mm in the longitudinal direction and the pressure roller 402 has a rubber (elastic layer) length of 330 mm, whereas the length of the fixing film 405 in the longitudinal direction is 340 mm. In the pressure roller 402, both ends of the metal shaft 402a are supported by a bearing 426 fixed to the frame of the fixing device 40 so as to be both supported and rotatable.

  The pressurizing mechanism 420 operates the drive motor 421 to rotate the cam shaft 423 and rotate the pair of pressurizing cams 422 to raise and lower one end of the pressurizing spring 427. As a result, the force with which the pressure spring 427 presses both ends of the stay 406 changes, and the pressure applied to the fixing film 405 can be changed.

  Here, in the first embodiment of the present invention, the groove 411 formed in the circumferential direction of the flange 410 is disposed with a predetermined inclination with respect to the rotation axis of the fixing film 405 as shown in FIG. The

  Specifically, as shown in FIG. 6b, from the upper portion 410a of the circumferential position to the lower portion 410b, the groove 411 is in the range of 1 to 1.5% of the longitudinal length L of the fixing film 405, and the groove 411 The fixing belt 405 is configured such that the longitudinal length of the upper circumferential position 410a is the shortest and the longitudinal length of the circumferential lower section 410b is the longest. If the amount of strain (elongation) of the elastic layer 408 in the fixing film 405 at this time is Y, the fixing film 405 is pulled most outward in the longitudinal direction in the region of the lower circumferential position 410b according to the rotation angle of the fixing film. As described above, the maximum amount of Y is in the range of 1 to 1.5% of the longitudinal length L of the fixing film 405.

  Since the flange 410 is inclined on the flanges at both ends of the longitudinal direction, the elastic layer 408 of the fixing film 405 is pulled outward in the longitudinal direction by 2 to 3% of the longitudinal length L as a whole. Since the fixing film 405 used in this embodiment has a longitudinal length L of 340 mm, the circumferential position lower portion 410b of the flange 405 in this embodiment is separated from the longitudinal central direction by about 3 to 4 mm as compared with the circumferential position upper portion 410a. An inclination is applied.

  As a result, even when thin paper or small-size paper is passed as the recording paper, the recording paper receives a stress F that is pulled outward in the longitudinal direction in the region of the lower circumferential position 410b immediately before entering the fixing nip. FIG. 7 shows the relationship between the tensile stress F and the rotation angle of the fixing film 405 when the present embodiment is applied. The tensile stress F is calculated from the Young's modulus of the silicon rubber elastic layer 408 of the fixing film and the amount of strain (elongation) due to the inclination applied to the flanges 410 at both ends.

  As shown in FIG. 7, the tensile stress F increases toward the circumferential position lower portion 410b, reaches the maximum value Fmax at the circumferential position lower portion 410b, decreases, and then decreases toward the circumferential position upper portion 410a. The minimum value 0 is taken at. At this time, since the tensile stress F is equally applied to the longitudinal position, the contact surface of the recording paper conveyed to the fixing device with the fixing film 405 receives the stress F that is pulled outward in the longitudinal direction, like the fixing film 405. Become. Further, the lower circumferential position 410b is an area immediately before the recording paper enters the fixing nip, and the inclination does not change in the phase where the recording paper is in the fixing nip.

Next, the verification experiment shown below was performed about the inclination of the said flange 410, and the effective range was determined. (Table 1)
In Table 1, the flange inclination is changed to a range of 0.5 to 3% with respect to the longitudinal length L, and the fixing film length used for the verification is verified using 100 mm, 200 mm, 340 mm, and 420 mm. Results are shown. The recording paper used in this experiment had a basis weight of 64 g and a Young's modulus of 3000 MPa.

  As shown in Table 1, when the inclination of the flange 410 was 1% or less with respect to the longitudinal length, paper wrinkles were generated regardless of the longitudinal length of the fixing film. Further, when the longitudinal length of the fixing film was 200 mm or less, when the flange inclination exceeded 2%, the toner image surface passing through the fixing nip was displaced due to the distortion (elongation) amount of the fixing film.

  This phenomenon was caused even when the fixing film longitudinal length was 340 mm or more and the flange inclination was 2%. This is because the tensile stress F necessary for preventing paper wrinkles is determined by the elastic layer Young's modulus of the fixing film and the strain (elongation) amount Y (%) due to the flange inclination. It shows that it does not depend on the size.

  However, even when the tensile stress F is the same, that is, when the strain (elongation) amount Y (%) is the same, if the fixing film length is different, the length (mm) that the fixing film actually expands and contracts is fixed. The longer the length of the film, the larger it becomes. Therefore, when the longitudinal length of the fixing film was 200 mm or less, no image displacement occurred when the flange inclination was 2%. However, even when the longitudinal length of the fixing film was 340 mm, the image displacement occurred. As a result, it occurred.

  In view of the above verification results and the maximum sheet size (A3 width: 420 mm) that can be supported by the fixing device in the future, a configuration that can prevent paper wrinkles stably regardless of the longitudinal length of the fixing film is used. The groove 411 is inclined so as to be away from the longitudinal center direction of the fixing film in the range of 1 to 1.5% of the longitudinal length L of the fixing film 405 from the upper portion 410a to the lower portion 410b of the circumferential position. And

  As described above, as a result of earnest examination by applying this embodiment, it has been confirmed that the recording paper receives a pulling force outward in the longitudinal direction in the region immediately before entering the fixing nip, thereby preventing the occurrence of paper wrinkles. Yes.

  This embodiment can also be used in different configurations of the film fixing system.

N nip, P sheet, T toner, 1 heat fixing device, 10 image forming unit,
11 Photosensitive drum, 12 charger, 13 laser scanner, 14 developer,
15 cleaner, 17 primary transfer blade, 20 paper cassette,
25 Multi-feed tray, 23 Registration roller, 30 Transfer device,
31 Intermediate transfer film, 35 Secondary transfer roller, 40 Fixing device,
55 fixing conveyance member, 401 fixing film unit, 405 fixing film member,
406 Support stay, 420 Pressure mechanism, 402 Pressure roller

Claims (4)

A rotating body having a driving source, a pressure member (404) for pressurizing the rotating body, an endless belt member (402) which contacts the rotating body to form a nip portion and slides and rotates, and the belt member An end holding member (410) held at the end, and a heat generating member (403) for heating either or both of the rotating body and the belt member, and rotating the rotating body In the heating and fixing device that rotates the driven material while nipping and conveying the recording material in the nip portion, and heating and pressurizing the recording material in the nip portion,
By providing the end holding groove (411) in the end holding member (410) with an inclination with respect to the belt rotation axis, the surface layer, the elastic member, or the base material of the belt member is rotated as the belt member rotates. A heat fixing device that expands and contracts in the longitudinal direction. 2. The heat fixing apparatus according to claim 1, wherein an inclination of the end holding groove (411) in the end holding member (410) is 3% or less of a longitudinal length of the belt member (402). The heat fixing apparatus according to claim 1, wherein the belt member is provided with a rib on a surface layer member, an elastic member, or a base material at an end portion of the belt. The heat fixing device according to claim 1, wherein the end holding member has a different depth in a longitudinal direction according to a circumferential phase.