JP5966451B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device and an image forming apparatus capable of preventing the endless fixing belt provided in an image forming apparatus using an electrophotographic system from being displaced and holding the end portion of the endless fixing belt constant. In particular, by reducing the contact resistance between the end of the endless fixing belt and the guide member that contacts the endless fixing belt, the fixing device can prevent damage to the endless fixing belt and improve durability. And an image forming apparatus.

An image forming process in an image forming apparatus using an electrophotographic method includes a step of forming an electrostatic latent image on the surface of a photosensitive drum as an image carrier, and a toner as a developer from the electrostatic latent image on the photosensitive drum. Developed by a process such as developing a visible image, transferring the developed image to a recording sheet by a transfer device, and fixing a toner image on the recording sheet by a fixing device using heat or pressure. ing.
In a fixing device, a roller pair composed of a heating roller and a pressure roller facing each other, or a fixing rotator constituted by a fixing belt or a combination thereof is arranged, and the conveyed recording paper is pressed against the pressure roller. The toner image is fixed on the recording paper by applying heat and pressure when the recording paper passes through the nip portion between the fixing belt and the fixing belt.
As a heating method of the fixing belt, there are a method in which the fixing belt is directly heated by a heat source and a method in which the fixing belt is indirectly heated through a heating member. However, from the viewpoint of energy saving in recent years, in order to shorten the waiting time from the power-on of the image forming apparatus to the image forming executable state (quick start property) or to reduce the power consumption during standby (power saving). Many have low heat capacity, high thermal conductivity, and downsizing.

FIG. 11 is a schematic cross-sectional view showing a configuration example of a conventional fixing device adopting a belt fixing method.
A fixing device 100 shown in FIG. 11 includes a halogen heater 121 as a heat source, a heat-resistant endless fixing belt 122, a pressure roller 123 as a pressure member, and a pressure for forming a nip portion N. A pad 124 is provided. In the fixing device 100, a recording sheet 125 carrying an unfixed image is introduced into the nip portion N by a transport mechanism or the like in the image forming apparatus. The recording paper 125 introduced into the nip portion N is conveyed while being sandwiched between the pressure roller 123 that is rotationally driven and the endless fixing belt 122, so that heat and pressure are applied to the nip portion N, and an unfixed image is obtained. Is fixed to the recording paper 125.
Typical materials used for the base material of the heat resistant endless fixing belt are polyimide (PI), polyamideimide (PAI), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), and polyethersulfone (PES). And functional polymer materials such as heat-resistant liquid crystal polymer (LCP) such as polysulfone (PS) and Xyder. Recently, a fixing device using a metal belt having a thickness of 0.1 mm or less is also known. In general, metal materials are often superior in terms of mechanical strength and thermal conductivity as compared with polymer materials and resins, and thus are considered suitable from the viewpoint of energy saving. SUS, nickel, copper, aluminum, and the like are preferable as the endless fixing belt as a metal material suitable for high durability of the fixing device.

In addition, an image forming apparatus using an endless fixing belt having an elastic layer and a release layer has been proposed in order to prevent image defects after fixing and obtain high-quality image quality with high glossiness.
By having an elastic layer, the pressure followability with respect to the irregularities on the surface of the recording paper is increased, and the elastic layer also follows the toner, thereby suppressing the uneven temperature of heat applied to the toner by the fixing belt. be able to. As a result, there is no difference in the toner melting state, and uneven fixing can be prevented. As a material suitable for the elastic layer, a silicone compound is preferable.
Further, the release layer prevents the molten toner from adhering to the elastic layer (hot offset), and all the molten toner can be fixed on the recording paper side. In a special environment, when the fixing temperature is low, even if the toner that has melted in the worst case adheres (cold offset), it can be self-cleaned at the next paper feed due to its releasability. The function as a fixing belt can be maintained. Moreover, the glossiness of the fixed image can be increased by having an appropriate hardness in the layer itself. In view of the above, a fluororesin is suitable as a material for forming the release layer.
When a metal base material is used as the base material of the endless fixing belt, the conductive member may be placed close to the inside of the unit and self-heated by an induction heating method. In this case, a heat source is unnecessary, and a more power-saving fixing device can be obtained.

By the way, in the fixing device as described above, the endless fixing belt is displaced in the axial direction due to the pressure roller facing the endless fixing belt, the endless fixing belt, and variations in the accuracy of parts constituting the nip portion. It is known to occur.
FIG. 12 is a schematic perspective view of the fixing device shown in FIG. FIG. 13 is a schematic diagram illustrating an example of a cross-sectional structure along the axial direction of the fixing device. FIG. 14 is a schematic diagram illustrating a cross-sectional structure along the axial direction of the fixing device illustrated in FIG. 11. As shown in FIG. 12, the endless fixing belt 122 is deviated in a direction (axial direction) orthogonal to the rotating direction. In addition to the above-described component variations, the cause of the deviation may be that the temperature distribution in the axial direction of the heat source is not uniform, and that the temperature unevenness of the endless fixing belt due to the difference in sheet passing size occurs.

Therefore, a structure in which a guide member 126 as shown in FIGS. 12 and 14 is arranged at the end in the axial direction in order to keep the position of the end of the endless fixing belt 122 constant with respect to the shift is proposed. Yes. Alternatively, a highly flexible detent stopper 128 is provided on the inner peripheral surface of the end portion in the axial direction of the endless fixing belt 122 as shown in FIG. 3, and the heating roller 127 disposed on the inner peripheral side of the endless fixing belt 122. A configuration has been proposed in which a shift stop stopper 128 is abutted against an end portion in the axial direction to prevent the shift.
However, as shown in FIG. 11, when there is a portion of the endless fixing belt 122 that is directly heated by a heat source (halogen heater 121), various polymer materials are applied to the endless fixing belt for safety reasons. It is difficult to use. Further, in the configuration as shown in FIG. 13 in which the stopper stopper 128 made of a highly flexible elastic material is provided on the inner peripheral surface, the endless fixing belt 122 is directly connected to a heat source (halogen heater 121 for the reason described above. In many cases, it is not employed in a fixing device (eg, FIG. 11) having a portion heated by the above. Therefore, in the fixing device 100 configured as shown in FIG. 11, it is common to use a metal material for the endless fixing belt 122.

  However, in the case where the endless fixing belt is made of a metal material, the flexibility is generally poor due to the nature of the material. In addition, since the above-described deviation occurs, contact resistance with the guide member 126 that restricts the position of the end face is generated, and fatigue cracks often occur from the end face of the endless fixing belt. Further, in the nip portion N in the fixing device, the endless fixing belt 122 repeats a wave-like curve in the rotational movement direction in accordance with the shape of the pressure roller 123 and the pressure pad 124, so that it is subjected to bending distortion. It will be repeatedly driven and stopped. Therefore, cracks have progressed from the end face of the endless fixing belt, making it difficult to maintain heat resistance and durability. In addition, since the guide member 126 that regulates the position of the end face is often made of resin to reduce the cost of the fixing device, in actual use, the endless fixing belt 122 comes in contact with a substantially identical locus. As a result, wear progresses over time, and wear marks and grooves are formed in the guide member 126. When wear marks and grooves are formed, the guide member 126 comes into contact with the endless fixing belt 122 through the grooves, and the contact resistance increases with time. As a result, the endless fixing belt 122 receives intermittent torsional stress, which is one of the factors that reduce the durability of the endless fixing belt 122.

Here, Patent Document 1 describes an invention for preventing end face cracking of an endless fixing belt made of nickel electroforming. In Patent Document 1, a nickel endless belt is cut at a desired axial length, and the outer periphery of the cut surface is chamfered with a soft abrasive paper disk of No. 800-1500, and all chamfered shapes are lost. Instead, the step generated in the circumferential direction of the cut surface is removed by grinding, and the roughness of the end surface is set to 5 μm or less, thereby preventing the end surface crack destruction.
Patent Document 2 describes an invention that prevents the elastic layer of the endless fixing belt from being broken and reduces the resistance generated between the end of the metal base and the flange. Patent Document 2 is an invention relating to an endless fixing belt having a metal base material and an elastic layer laminated on the metal base material, with the end in the width direction of the metal base material protruding outward from the elastic layer. In addition, chamfered portions are respectively formed at the outer peripheral surface side corner and the inner peripheral surface side corner of the width direction end of the metal base.

However, the invention of Patent Document 1 is an invention for preventing the progress of cracks and breakage of the base material starting from the cutting step, and does not improve the durability of the endless fixing belt.
The invention of Patent Document 2 prevents the elastic layer from coming into direct contact with the flange by making the length in the width direction of the elastic layer laminated on the endless fixing belt shorter than the length in the width direction of the metal substrate. Stay on. Further, the contact resistance of the chamfered portion is only reduced for the metal base material. Therefore, wear of the resin flange due to contact with a metal substrate having high hardness is inevitable. Further, when the protruding width of the metal base is set to 5 to 20 mm, there is a problem that a portion having low rigidity is generated as the fixing belt, and there is a risk that the metal base cannot withstand the bending stress at the end face.
The present invention has been made in view of the above-described circumstances, and reduces the contact resistance between the endless fixing belt and the endless fixing belt, thereby preventing the endless fixing belt from being damaged and durability. An object of the present invention is to provide a fixing device capable of improving the above.

In order to solve the above problems, the present invention forms a nip portion between an endless fixing belt that is a hollow cylindrical body, a heat source that heats the endless fixing belt, and the endless fixing belt. A fixing device comprising: a pressure roller; and a guide member having a slidable member that slidably and rotatably supports the inner surfaces of both ends of the endless fixing belt. A thrust member integrated with a movable member and having a slidable support surface that slidably supports both ends in the thrust direction of the endless fixing belt; The direction cross-sectional shape is a convex shape with a curved tip, and the thrust direction cross-sectional shape of the slidable support surface of the flange portion that contacts the convex shape portion is a curved concave shape, and the curvature of the convex shape portion Than the curvature of the concave portion And wherein the hearing.

  In the present invention, both end edges in the thrust direction of the endless fixing belt are in contact with the slidable support surfaces of the guide members that support both ends of the endless fixing belt. The shape of both end edges in the thrust direction of the endless fixing belt is a convex shape with a curved tip, the cross-sectional shape in the thrust direction of the slidable support surface of the flange portion is a curved concave shape, and the curvature of the convex portion is Since the curvature is set to be larger than the curvature of the concave portion, the contact between the endless fixing belt and the annular slidable member is made as close as possible to the line contact, and the frictional resistance can be reduced. Further, due to the concavo-convex shape relationship between the two members, variations in the rotation trajectory of the endless fixing belt can be suppressed, the force in the direction of tearing the endless fixing belt in the axial direction can be suppressed, and the overall stress load can be reduced. As a result, durability of the endless fixing belt can be improved.

1 is a schematic configuration diagram illustrating a color printer as an image forming apparatus according to an embodiment of the present invention. 1 is a schematic cross-sectional view showing a fixing device according to an embodiment of the present invention. FIG. 3 is a schematic perspective view of the fixing device shown in FIG. 2. FIG. 3 is a schematic diagram illustrating a cross-sectional structure along the axial direction of the fixing device illustrated in FIG. 2. It is BB sectional drawing in FIG. 4 of the guide member which concerns on one Embodiment of this invention. It is a perspective view of a guide member concerning one embodiment of the present invention. (A)-(c) is the schematic diagram which showed the relationship between the endless fixing belt which concerns on one Embodiment of this invention, and an annular slidable member. (D)-(f) is the schematic diagram which showed the comparative example of an endless fixing belt and an annular slidable member. It is a table | surface which shows a durability test result when a SUS base material is used as a base material of an endless fixing belt (corresponding to Example 1). It is a table | surface which shows the durability test result when a nickel base material is used as a base material of an endless fixing belt (corresponding to Example 2). FIG. 10 is a schematic cross-sectional view showing an example of the configuration of a conventional fixing device employing a belt fixing method. FIG. 12 is a schematic perspective view of the fixing device shown in FIG. 11. FIG. 3 is a schematic diagram illustrating an example of a cross-sectional structure along the axial direction of the fixing device. FIG. 12 is a schematic diagram illustrating a cross-sectional structure along the axial direction of the fixing device illustrated in FIG. 11.

[Image Forming Apparatus as an Application Example of the Present Invention]
FIG. 1 is a schematic configuration diagram showing a color printer as an image forming apparatus according to an embodiment of the present invention. The color printer 20 includes an image forming unit 30 that forms an image by an electrophotographic method, a transfer unit 37 that transfers a toner image formed by the image forming unit 30 to a sheet as a recording medium, and a transfer unit 37. A fixing unit (fixing device 41) that melts and fixes the transferred toner image on the paper.
The image forming unit 30 is a known photoconductor drum 31K, a magenta photoconductor drum 31M, a cyan photoconductor drum 31C, a yellow photoconductor drum 31Y, and a known photoconductor drum 31 corresponding to each photoconductor drum 31. This is an electrophotographic image forming unit provided with a toner developing unit 32 (32K, 32M, 32C, 32Y), a transfer unit 33 (33K, 33M, 33C, 33Y), and the like. In this example, based on image data input from the outside, the optical system unit 35 exposes each photosensitive drum 31 corresponding to each color to form a latent image, and each toner developing unit 32 develops a visible image. Each toner image is transferred to the intermediate transfer belt 36 to form a color toner image, and further transferred to a sheet of recording medium conveyed by the transfer unit 37.

The paper is fed from the paper feed cassette 38 by the paper feed roller 39, the timing is set by the registration roller 40, the color toner image is transferred by the transfer unit 37, and sent to the fixing device 41. The sheet on which the toner image has been transferred is heated and pressed by the fixing device 41 and undergoes a toner image fixing process. The fixed sheet is discharged to a discharge tray 43 outside the apparatus by a discharge roller 42.
In the color printer 20, stable fixing can be realized by using a fixing device composed of a heat source such as the endless fixing belt 22, the halogen heater 21, and the pressure roller 23, as shown below, in the fixing device 41. High-quality and high-quality image formation is performed.

[Fixing Device as an Application Example of the Present Invention]
An example of a fixing device to which the present invention is applied will be described with reference to FIGS. FIG. 2 is a schematic cross-sectional view showing a fixing device according to an embodiment of the present invention. FIG. 3 is a schematic perspective view of the fixing device shown in FIG.
As shown in the drawing, the fixing device 41 includes a hollow cylindrical endless fixing belt 22 that is flexible and rotates in a predetermined direction, a halogen heater 21 as a heat source for heating the endless fixing belt 22, and an endless type. A pressure roller 23 as a pressure rotator for forming a nip portion N between the endless fixing belt 22 and a sliding member that supports the inner surfaces of both ends of the endless fixing belt 22 so as to be slidably rotatable. And a guide member 50 (see FIG. 3).
The halogen heater 21 is disposed on the inner peripheral side of the endless fixing belt 22 and heats the endless fixing belt 22 immediately before the nip portion N. As the heat source, in addition to the halogen heater, a ceramic heater, a carbon heater, or the like can be used. When a metal substrate is used as the fixing belt substrate, a heating device using a temperature raising method by IH (electromagnetic heating) may be installed. In the case of using a halogen heater, if an inner surface coating film in which carbon black or the like is dispersed is formed on the inner surface of the fixing belt, radiant heat from far infrared rays can be efficiently transferred to the fixing belt.

In the illustrated fixing device 41, the endless fixing belt 22 is of a type in which both ends in the width direction are supported by a pair of guide members 50, but a plurality of pairs of guide members 50 may be provided. Further, the guide member 50 may be disposed in a fixing device of a type that is wound around a plurality of rollers.
The base material of the endless fixing belt 22 may be a metal belt such as nickel or SUS or an endless belt (or film) using a heat resistant resin material such as polyimide. Specifically, the endless fixing belt 22 is made of a metal material such as stainless steel (SUS), nickel, copper, or aluminum, polyimide (PI), polyamideimide (PAI), polyphenylene sulfide (PPS), polyether ether ketone ( It is preferable to use a functional polymer material such as a heat-resistant liquid crystal polymer (LCP) such as PEEK), polyethersulfone (PES), polysulfone (PS), or Xyder.

In the case of using a metal material, the endless fixing belt 22 is crushed at the nip portion N, so that it is designed in consideration of the generation of bending stress. In general, when a metal thin film roll is used, the surface strain is reduced, which is advantageous for repeated bending fatigue, while the yield strength against torsional stress is reduced. Therefore, in order to maintain the functionality as a fixing belt, a metal belt having a thickness of 20 to 40 μm is preferable.
A release layer made of a fluororesin such as a PFA resin layer or a PTFE resin layer is formed on the surface layer of the endless fixing belt 22 so that the toner on the transfer paper as a fixing material does not adhere. Give it. An elastic layer formed of a silicone rubber layer or the like may be interposed between the base material of the endless fixing belt 22 and the release layer. Without this silicone rubber layer, the heat capacity is reduced and the fixability / warm-up property is improved, but when the unfixed image is crushed and fixed, subtle irregularities on the belt surface are transferred to the image and the image There is a problem in that a crusty skin-like mark remains on the solid portion. In order to improve this, it is necessary to provide a silicone rubber layer of 100 μm or more. Due to the deformation of the silicone rubber layer, subtle unevenness is absorbed and the skin image is improved.

  The endless fixing belt 22 is moved around in the circumferential direction by an external roller. For example, in the embodiment shown in FIGS. 2 and 3, the pressure roller 23 is rotationally driven by a drive source (not shown), and the driving force is transmitted from the pressure roller 23 to the endless fixing belt 22 at the nip portion N. As a result, the endless fixing belt 22 rotates. In this way, the endless fixing belt 22 moves while being sandwiched by the nip portion N. Further, the outer shape displacement of the endless fixing belt 22 in the portion other than the nip portion N is regulated by the guide members 50 arranged at both ends of the endless fixing belt 22. The endless fixing belt 22 is regulated so as not to be separated from the halogen heater 21 by a certain distance or more by being guided by the guide member 50.

  FIG. 4 is a schematic diagram showing a cross-sectional structure along the axial direction of the fixing device shown in FIG. The cross-sectional shape in the thrust direction at both ends in the thrust direction of the endless fixing belt 22 in the present embodiment is a convex shape (convex shape portion 22a) whose tip is curved. The convex portion 22a is formed by pressing an abrasive tape (not shown) against the edge portion in the width direction while rotating the endless fixing belt 22. By adjusting the pressing force and pressing time of the polishing tape, the curvature of the convex portion 22a can be adjusted (see FIG. 7). When the curvature is large, the protruding amount in the thrust direction (axial direction) of the convex portion 22a is large (FIG. 7A), and when the curvature is large, in the thrust direction (width direction) of the convex portion 22a. The amount of protrusion of this becomes small (FIG. 7C). Accordingly, the shape of the convex portion 22 a may be defined from the protruding amount of the convex portion 22 a with respect to the thickness of the base material of the endless fixing belt 22.

The pressure roller 23 is provided with a silicone rubber layer which is an elastic layer 23b on the outer periphery of the metal roller 23a, and a PFA resin layer or a PTFE resin layer which is a fluorine resin on the surface in order to obtain releasability on the surface. A fluororesin layer such as is provided. As shown in FIGS. 3 and 4, the longitudinal length of the pressure roller 23 is shorter than that of the endless fixing belt 22, and the elastic layer 23 b of the pressure roller 23 is in pressure contact with the endless fixing belt 22.
The pressure roller 23 is pressed against the endless fixing belt 22 by a pressing means such as a spring 28 in the direction of arrow A shown in FIG. 2, and the elastic layer 23b is crushed and deformed. A predetermined nip width is formed in the nip portion N. The pressure roller 23 may be a solid roller, but is preferably hollow in order to reduce the heat capacity. The pressure roller 23 may also be provided with a heat source such as a halogen heater.

The silicone rubber layer that forms the elastic layer 23b may be a solid rubber, but if no heat source is provided inside the pressure roller 23, sponge rubber may be used. Sponge rubber is more preferable from the viewpoint of power saving because it has a higher heat insulating property and is less likely to lose heat of the fixing belt.
The pressure roller 23 is rotated by a driving force transmitted through a gear or the like from a driving source such as a motor provided in an image forming apparatus such as the color printer 20 on which the fixing device 41 is mounted.

As shown in FIGS. 2 and 4, a pressure pad 24 is disposed on the inner peripheral side of the endless fixing belt 22. The pressure pad 24 serves as a nip forming member that forms the nip portion N into a predetermined shape by being pressed against the pressure roller 23 via the endless fixing belt 22. The pressure pad 24 is held at both ends in the longitudinal direction by guide members 50 that are fixedly arranged, and slides directly on the inner surface of the endless fixing belt 22 or indirectly through a sliding sheet (not shown). It is supposed to be.
The illustrated nip portion N (pressure pad 24) has a flat shape, but may have a concave shape having a concave portion on the pressure roller 23 side or other shapes. Note that when the nip portion N has a concave shape, the discharge direction of the leading edge of the recording paper 25 entering the nip portion N is closer to the pressure roller 23 and the separation is improved, so that the occurrence of paper jam is suppressed. The effect can be obtained.
With the above configuration, it is possible to realize a fixing device that is inexpensive, has a fast warm-up, saves power, and stabilizes the temperature of the entire belt.

[Relationship between endless fixing belt and guide member]
The guide member and the relationship between the guide member and the endless fixing belt will be described.
5 is a cross-sectional view of the guide member according to an embodiment of the present invention, taken along line BB in FIG. FIG. 6 is a perspective view of a guide member according to an embodiment of the present invention.
The guide member 50 includes a slidable member 51 that supports the inner surfaces of both ends in the axial direction of the endless fixing belt 22 so as to be slidable and rotatable, and a thrust direction of the endless fixing belt 22 that is integrated with the slidable member 51. And a flange portion 55 having a slidable support surface 53 that slidably supports both end edges.

The slidable member 51 has a substantially cylindrical shape or a columnar shape, and a slidable peripheral surface 57 that slidably supports inner surfaces at both ends in the thrust direction of the endless fixing belt 22, and a thrust direction of the endless fixing belt 22. It has a configuration in which non-contact portions 59 that do not contact the inner surfaces of both end portions are alternately arranged in the circumferential direction.
The non-contact part 59 is a recess disposed at a predetermined interval in the circumferential direction of the slidable member 51. In the present embodiment, four recesses (non-contact portions 59) having a width of 8 mm and a depth of 3 mm are formed at equal intervals in the circumferential direction with respect to the cylindrical slidable member 51 having an outer diameter of φ39 mm. .
By forming the non-contact portion 59 in this way, the area of the contact portion (slidable peripheral surface 57) between the inner peripheral surface of the endless fixing belt 22 and the slidable member 51 is reduced. Accordingly, it is possible to reduce the frictional resistance between the inner peripheral surface of the endless fixing belt 22 and the slidable member 51 and reduce the torsional stress acting on the endless fixing belt 22, and the endless fixing belt 22 can be reduced in the width direction. It becomes difficult to twist between a center part and both ends. Further, since the stress load on the endless fixing belt 22 can be reduced by reducing the contact area between the endless fixing belt 22 and the slidable peripheral surface 57, the durability of the endless fixing belt 22 can be improved. it can.
The non-contact portion 59 can be effectively obtained by forming at least two locations at equal intervals in the circumferential direction of the slidable member 51, but the shape, size, And the quantity can be arbitrarily set. Further, it is desirable that the corner portion 61 formed between the slidable peripheral surface 57 and the non-contact portion 59 is chamfered.

The flange portion 55 includes an annular slidable member 63 on which a slidable support surface 53 is formed, and a disk-shaped flange member 65 that supports the annular slidable member 63. The flange portion 55 is formed by integrally attaching the annular slidable member 63 to the flange member 65. The slidable support surface 53 may be integrally formed from the same member as the flange member 65.
The annular slidable member 63 has a predetermined thickness (left and right in FIG. 4) with respect to a predetermined radial length (length in the vertical direction in FIG. 4: inner and outer diameter difference) and a thrust direction of the endless fixing belt 22. An annular member having a length in the direction). The inner diameter (diameter) of the annular slidable member 63 is substantially the same length as the outer diameter (diameter) of the slidable peripheral surface 57 of the slidable member 51.
The surface facing the edge of the endless fixing belt 22 is a slidable support surface 53, and its cross-sectional shape in the thrust direction is a curved concave shape (concave portion). The curvature of the slidable support surface 53 is set smaller than the curvature of the convex portion 22a. In the present embodiment, the annular slidable member 63 is inserted so as to be sandwiched between the flange member 65 and the edge of the endless fixing belt 22, and the slidable support surface 53 faces the endless fixing belt 22 side. Arrange.
The annular slidable member 63 can be composed of any one of polyamideimide (PAI), polyetheretherketone (PEEK), or fluororesin. When the above materials are used, the mechanical properties and heat resistance at the fixing temperature are excellent, and slidability can be expected. Therefore, it is possible to prevent wear of the flange portion and damage to the endless fixing belt 22. That is, durability can be improved.

〔Example〕
An embodiment of the present invention will be described with reference to FIG. FIGS. 7A to 7C are schematic views showing the relationship between an endless fixing belt and an annular slidable member according to an embodiment of the present invention. As described above, the thrust direction cross-sectional shape of both end edges in the thrust direction of the endless fixing belt 22 in the present embodiment is a convex shape (convex shape portion 22a) with a curved tip, and both ends in the thrust direction of the endless fixing belt 22 are in the thrust direction. The cross-sectional shape in the thrust direction of the slidable support surface 53 of the annular slidable member 63 that supports the edge is a curved concave shape. The curvature of the convex portion 22 a is set larger than the curvature of the slidable support surface 53.

[Example 1 of endless fixing belt]
As a base material for the endless fixing belt, a SUS thin film roll having a thickness of 30 μm, an inner diameter of 40 mm, and a length of 350 mm was used. As an elastic layer, a silicone rubber (Toray Dow Corning) layer is formed to 100 μm by spray coating, and a primer (Toray Dow Corning) is applied thereon, and a PFA tube (Kurabo Co., Ltd.) is applied as a release layer. The product was coated with 30 μm and dried at 200 ° C. for 30 minutes to obtain an endless belt.
Thereafter, the endless belt was rotated to press the polishing tape against the end face in the width direction, thereby forming the convex portion 22a and completing the endless fixing belt 22. The amount of protrusion of the convex portion was adjusted by adjusting the pressing force and pressing time of the polishing tape. Specifically, a convex portion having a protrusion amount of 30 μm which is the same as the substrate thickness (FIG. 7A), and a convex portion having a protrusion amount of 15 μm which is ½ of the substrate thickness (FIG. 7 (b)), and convex portions (FIG. 7 (c)) each having a protrusion amount of 10 μm, which is 1/3 of the substrate thickness, were obtained.

[Example 2 of endless fixing belt]
A nickel thin film roll having a thickness of 30 μm, an inner diameter of 40 mm, and a length of 350 mm was used as the base material of the endless fixing belt. A silicone rubber (made by Toray Dow Corning) layer as an elastic layer is formed by spray coating to a thickness of 100 μm, and a primer (made by Toray Dow Corning Co.) is applied thereon, and a PFA tube (made by Kurabo Industries Co., Ltd.) as a release layer. ) Was coated at 30 μm and dried at 200 ° C. for 30 minutes to obtain an endless belt. On the inner surface of the endless belt, a PTFE film in which carbon black is dispersed is formed by spray coating in order to absorb radiant heat from the halogen heater.
Thereafter, a polishing tape was pressed against the end face in the width direction while rotating the endless belt to form a convex portion, and the endless fixing belt 22 was completed. The amount of protrusion of the convex portion was adjusted by adjusting the pressing force and pressing time of the polishing tape. Specifically, a convex portion having a protrusion amount of 30 μm which is the same as the substrate thickness (FIG. 7A), and a convex portion having a protrusion amount of 15 μm which is ½ of the substrate thickness (FIG. 7 (b)), and convex portions (FIG. 7 (c)) each having a protrusion amount of 10 μm, which is 1/3 of the substrate thickness, were obtained.

[Examples of annular sliding member]
For each of the endless fixing belts 22 shown in the first and second embodiments, the outer diameter φ43 mm, the inner diameter φ39 mm, the wall thickness (the length corresponding to the thrust direction of the endless fixing belt 22) 2 mm, An annular slidable member made of PTFE was prepared so as to have a concave shape in which one side of the opposite side was recessed by 50 μm in the thrust direction. This was inserted so as to be sandwiched between the flange member and the endless fixing belt, and the concave shape was arranged facing the endless fixing belt 22 (FIGS. 7A to 7C).
In any of the embodiments, the curvature A of the end face of the endless fixing belt 22 is set to be larger than the concave curvature B formed on the surface of the annular slidable member 63.

[Durability evaluation]
With respect to the endless fixing belts shown in Examples 1 and 2 and the examples of the annular slidable member, a durability test was performed using an actual machine.
The thing of the form shown in FIG. 8 was prepared as a comparison object of an endurance test. 8D to 8F are schematic views showing comparative examples of the endless fixing belt and the annular slidable member.
FIG. 8D shows an example in which an annular slidable member 71 that does not form a concave portion is disposed on the endless fixing belt 70, although the same convex portion 70a as in FIG. 8C is formed. FIG. 8E shows an example in which an endless fixing belt 70 is provided with an annular slidable member 71 that does not have a convex portion and does not have a concave portion. FIG. 8 (f) is an example in which the end portion of the endless fixing belt 70 is subjected to square chamfering 70 b and the annular slidable member 71 is not formed with a concave portion. Regarding the endless fixing belt, the configuration other than the end shape is the same as the endless fixing belt shown in the first and second embodiments. The material of the annular slidable member 71 is the same as that of the annular slidable member 63.

FIG. 9 is a table showing the durability test results when a SUS substrate is used as the substrate of the endless fixing belt (corresponding to Example 1). FIG. 10 is a table showing durability test results when a nickel base material is used as the base material of the endless fixing belt (corresponding to Example 2). The durability test was performed three times for each example and comparative example (in the table, durability (1) to (3)).
As shown in FIGS. 9 and 10, in the durability test corresponding to FIGS. 7A to 7C, it was confirmed visually that the rotation trajectory of the endless fixing belt was stable. Although the paper was passed 300K times or more, all the results were good.
On the other hand, the following problems occurred in the comparative example. In the case of FIG. 8D, the contact state between the endless fixing belt and the annular slidable member is linear contact as in the case of (a) to (c). However, since the contact area is small, the endless fixing is performed. The rotation trajectory of the belt 22 was not stable. In FIG. 8 (e), there is a case where abnormal noise is generated from the start of rotation. In particular, when an SUS substrate is used as the substrate of the endless fixing belt, the durability is low, and all cracks are broken. In FIG. 8 (f), although no abnormal noise was generated, the desired durability was not obtained and all cracks were broken.
As described above, by setting the curvature of the convex portion 22 a of the endless fixing belt 22 to be larger than the curvature of the slidable support surface 53 formed on the surface of the annular slidable member 63, contact between the two is possible. Becomes line contact, and mutual frictional resistance can be reduced. Further, since the surface of the annular slidable member 63 has a concave shape, the rotation locus of the endless fixing belt 22 can be stabilized.

As described above, in the present embodiment, the heated member heated by the heat source such as the halogen heater 21 is the thrust of the endless fixing belt 22, the pressure pad 24 for forming the nip portion, and the endless fixing belt 22. Only the guide members 50 arranged at both ends in the direction. Because the number of parts is smaller than the conventional belt fixing system, where multiple rollers are arranged inside the endless fixing belt or the tension roller is in contact with the outer peripheral surface of the endless fixing belt. , Low heat capacity and downsizing can be realized. For this reason, the temperature rise at the time of heating is quick, and the warm-up time can be shortened. Further, since the endless fixing belt 22 is generally warmed during the remaining heat standby, unlike the conventional fixing method, when the fixing execution is requested, the entire endless fixing belt 22 is already warmed substantially uniformly. Therefore, fixing can be performed immediately, and the first print time in the mounted image forming apparatus can be shortened.
Further, when a metal base material is used as the endless fixing belt 22, the heat conductivity of the base material is excellent, and the temperature deviation of the entire fixing belt can be reduced. As a result, temperature unevenness (= Therefore, stable fixing property can be obtained.

Further, in the present embodiment, the heat capacity inside the endless fixing belt can be reduced (because no extra members are heated), and the heat conversion efficiency is increased as compared with the conventional surf fixing and belt fixing methods. Further, even if the halogen heater 21 serving as a heat source runs away due to some trouble and becomes in a continuous heating state, the heat-resistant pressure pad 24 and both ends of the endless fixing belt 22 are provided inside the endless fixing belt 22. Since only the heat-resistant guide member 50 is disposed, the resin member is not deformed during runaway as in surf fixing, and the silicone rubber is not destroyed as in a known belt fixing device. .
In addition, the halogen heater 21 is used as a heat source, the halogen heater 21 is disposed at the center of the endless fixing belt 22 (a position corresponding to the rotation center), and the inner surface of the endless fixing belt 22 is a black body surface. As shown, the inner circumference is painted with black pigment all around. As an example of the black pigment, a water-dispersed PTFE paint blended with carbon black or the like can be used. With the above configuration, the endless fixing belt 22 is warmed as a whole, and can satisfy the fixing function.

Further, when it is necessary to further improve the fixability by increasing the heat supply at the nip portion N, the heat of the halogen heater 21 is reflected toward the nip portion N using a reflector or the like, and the nip portion N It is good to heat locally. By locally heating the nip portion N, the amount of heat supplied so as to compensate for the heat deprived of the recording paper 25, which is a fixing material, increases, so that the fixing property is satisfied even in high-speed fixing (image formation). Is possible. At the entrance of the nip portion N (upstream side in the sheet conveyance direction), the temperature difference with the sheet is the largest, so it is necessary to supply the largest amount of heat. Therefore, it is preferable to locally heat the upstream side of the nip portion N in the sheet conveyance direction.
Even when the nip portion N is locally heated, the endless fixing belt 22 is composed of the same metal heat conductor. Therefore, if the amount of heat supplied to the paper is excessive, heat is generated in the areas other than the nip portion. By being transmitted, a stable temperature can be maintained, so that an image having no unevenness in fixability and glossiness can be obtained.

Further, as the halogen heater 21, a method of using a directional halogen heater in which a half surface of a glass tube is mirror-finished, and a method of arranging a ceramic heater close to the nip portion are conceivable.
By using a halogen heater as the heat source in this manner, it is not necessary to use a coil or a core as in the case of induction heating, so the number of parts is reduced and the overall heat capacity and cost of the fixing unit can be reduced. In addition, since the setting of the end temperature can be changed with a simpler structure than a ceramic heater or the like, an inexpensive configuration can be achieved.
In the configuration of the present embodiment, the endless fixing belt 22 moves with respect to the fixed pressure pad 24 and is in sliding contact with the nip portion N. If the frictional force at the interface is strong, the endless fixing belt 22 is endless over time. The fixing belt 22 may be scraped and damaged. Therefore, when a lubricant such as grease or oil is applied to the interface between the pressure pad 24 and the endless fixing belt 22, or the pressure pad material is coated with a heat-resistant and slidable resin. Good. By doing so, it becomes possible to reduce the frictional force, so that the problem of friction can be improved.

  However, since the lubricant is rotated by the rotation of the endless fixing belt 22, the lubricant at the important nip portion N may be reduced or eliminated. Therefore, a mesh-like lubricating sheet impregnated with the lubricant is interposed between the pressure pad 24 and the endless fixing belt 22 so that the lubricant is stably supplied to the nip portion N, and is sandwiched at the interface. It is also possible. The lubricating sheet is fixed to the pressure pad 24 and is always present at the interface of the nip portion N.

In the present embodiment, the annular slidable member is disposed between the endless fixing belt and the flange member so that the endless fixing belt and the flange member are not in direct contact with each other, and the annular slidable member is provided. By bringing the endless fixing belt into contact with each other, the frictional resistance of the endless fixing belt can be reduced. Therefore, the endless fixing belt can be prevented from being damaged and the durability can be improved.
In addition, since the contact portion between the endless fixing belt and the annular slidable member has a curved convex shape and a concave shape, the contact is not a surface contact, but is as close to a line contact as possible, and the frictional resistance is reduced to zero. You can get closer.
Since the convex part of the endless fixing belt is stably contained within the concave part of the annular slidable member, it is possible to suppress variations in the rotation trajectory of the endless fixing belt, and the end face of the endless fixing belt is The force generated parallel to the existing surface, in other words, the surface orthogonal to the axial direction of the endless fixing belt can be suppressed. Accordingly, the force in the direction of tearing the endless fixing belt in the width direction can be suppressed, and the overall stress load can be reduced. As a result, durability of the endless fixing belt can be improved.

Further, since at least two non-contact portions are provided at equal intervals on the slidable peripheral surface of the slidable member that contacts the inner peripheral surfaces of both end portions in the width direction of the endless fixing belt, the endless fixing belt The contact area of the flange can be reduced, and the stress load on the endless fixing belt can be reduced. Therefore, the durability of the belt can be improved.
Further, the endless fixing belt has a metal base material, an elastic layer laminated on the surface of the metal base material, and a release layer, and a fluororesin is laminated on the inner peripheral surface. The mechanical properties, heat resistance, and high thermal conductivity of the metal substrate can be expected, and a power-saving fixing device can be obtained. In addition, slidability with the slidable peripheral surface of the slidable member due to the lamination of fluororesin on the inner peripheral surface, and high image quality due to having an elastic layer / release layer. It can be a fixing device.
In addition, since the annular slidable member is made of either polyamideimide, polyetheretherketone, or fluororesin, it has excellent mechanical properties and heat resistance at the fixing temperature, and can be expected to slide. It is possible to prevent wear and prevent damage to the endless fixing belt. That is, durability can be improved.
Further, by including the fixing device according to the present embodiment, it is possible to provide an image forming apparatus with high durability, power saving, and high image quality.

  DESCRIPTION OF SYMBOLS 20 ... Color printer, 21 ... Halogen heater, 22 ... Endless fixing belt, 22a ... Convex shape part, 23 ... Pressure roller, 24 ... Pressure pad, 25 ... Recording paper, 28 ... Spring, 30 ... Image formation part, DESCRIPTION OF SYMBOLS 31 ... Photosensitive drum, 32 ... Toner developing part, 33 ... Transfer part, 35 ... Optical system unit, 36 ... Intermediate transfer belt, 37 ... Transfer part, 38 ... Paper feed cassette, 39 ... Paper feed roller, 40 ... Registration roller , 41: fixing device, 42: paper discharge roller, 43 ... paper discharge tray, 50 ... guide member, 51 ... slidable member, 53 ... slidable support surface, 55 ... flange portion, 57 ... slidable peripheral surface , 59 ... non-contact part, 61 ... corner part, 63 ... annular slidable member, 65 ... flange member, 70 ... endless fixing belt, 70a ... convex shaped part, 70b ... chamfering 70b, 71 ... annular slidability Member, 100... Fixing device, 21 ... halogen heater, 122 ... endless fixing belt, 123 ... pressing roller, 124 ... pressure pad, 125 ... recording sheet, 126 ... guide member, 127 ... heating roller, 128 ... deviation stopper Stopper

JP 2004-86083 A JP 2011-75816 A

Claims (7)

An endless fixing belt that is a hollow cylindrical body, a heat source that heats the endless fixing belt, a pressure roller that forms a nip portion between the endless fixing belt, and inner surfaces of both ends of the endless fixing belt A guide member having a slidable member that supports each of the slidingly and rotatably, and a fixing device comprising:
Each guide member includes a flange portion having a slidable support surface that is integrated with the slidable member and slidably supports both end edges in the thrust direction of the endless fixing belt,
The thrust direction cross-sectional shape of both end edges in the thrust direction of the endless fixing belt is a convex shape with a curved tip.
The cross-sectional shape in the thrust direction of the slidable support surface of the flange portion that contacts the convex shape portion is a curved concave shape,
The fixing device according to claim 1, wherein a curvature of the convex portion is larger than a curvature of the concave portion.   The slidable member includes a slidable peripheral surface that slidably supports the inner surfaces of both ends in the thrust direction of the endless fixing belt, and a non-contact portion that does not contact the inner surfaces of both ends of the endless fixing belt in the thrust direction. The fixing device according to claim 1, wherein the fixing device is configured to be alternately arranged in a circumferential direction.   The endless fixing belt includes a metal base, an elastic layer and a release layer sequentially laminated on the outer surface of the metal base, and a fluororesin laminated on the inner peripheral surface of the metal base. The fixing device according to claim 1, wherein the fixing device is provided.   4. The fixing device according to claim 1, wherein the slidable member is made of any one of polyamideimide, polyetheretherketone, and fluororesin. 5.   The fixing device according to claim 1, wherein the heat source heats the endless fixing belt by radiant heat.   The nip forming member for forming the nip portion into a predetermined shape by being pressed against the pressure roller via the endless fixing belt is provided on an inner peripheral side of the endless fixing belt. Item 6. The fixing device according to any one of Items 1 to 5. An image forming apparatus comprising: a fixing device according to any one of claims 1 to 6.

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