JP2017215449A - Fixation device and image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixation device in which a separation part of a separation member for separating a recording material from a fixation belt can be located at a predetermined position even if a heating-side assembly part and an elastic roller changes in position relation.SOLUTION: A fixation device according to the present invention comprises: a housing; an elastic roller supported to the housing in a shaft center fixation fashion, and driven to rotate; a fixation belt driven by the elastic roller; a nip formation member; a support member supporting the nip formation part; a holding member holding the fixation belt and both ends of the support member, and movable between a pressurization position and a depressurization position with respect to the housing; a pressurization member pressurizing the holding member; and a separation member comprising a separation part for separating a recording material. The separation member is supported by the housing movably in a moving direction of the holding member and also rotatably, and energized toward the fixation belt to abut on at least one of the nip formation member, support member, holding member, and fixation belt when the holding member moves to the pressurization position, so that the separation part of the separation member is located at a predetermined position for the fixation belt.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a fixing device and an image forming apparatus including the fixing device.

  A fixing device used in an electrophotographic image forming apparatus performs fixing by melting and penetrating a toner image carried on a recording material by applying heat and pressure.

  In recent years, the market demands shortening of the time (warm-up time) required from a normal temperature state to a predetermined printable temperature, such as when power is turned on. There is also a demand for shortening the time (first print time) from when a print request is received to when a print operation is performed through a print preparation and paper discharge is completed.

  In response to these requirements, for example, Patent Document 1 discloses that in an arrangement using an endless belt, it is possible to warm the entire belt, shorten the first print time from the heating standby time, and reduce the amount of heat during high-speed rotation. A fixing device that can be solved is disclosed.

  The fixing device of Patent Document 1 has a configuration in which the endless belt is indirectly heated through the metal heat conductor, but a configuration in which the endless belt is directly heated (without the metal heat conductor) is also considered. . This further shortens the first print time and enables cost reduction without using a metal heat conductor.

  An object of the present invention is to provide a fixing device that can position the separation portion of the separation member at a predetermined position with respect to the fixing belt even if the positional relationship between the heating side assembly portion and the elastic roller changes.

  The above-described problems are provided in a housing, an elastic roller that is supported by the housing in an axially fixed manner and driven to rotate, an endless fixing belt that is driven to rotate in contact with the elastic roller, and an inner side of the fixing belt. A nip forming member that forms a fixing nip between the fixing belt and the elastic roller, a support member that supports the nip forming member, and both ends of the fixing belt and the support member, A holding member that is supported so as to be movable to a pressure position or a depressurization position, a pressure member that presses the holding member in the direction of the elastic roller, and a fixing nip downstream side, and fixing the recording material to the fixing nip And a separation member that includes a separation unit that separates the belt from the belt. The separation member is movable and rotatable in the movement direction of the holding member, and is supported by the housing. And when the holding member moves to the pressure position, the nip forming member, the support member, the holding member, or the fixing belt contacts at least one of the separation belt and the separation member. This is solved by a fixing device in which the separation portion of the member is positioned at a predetermined position with respect to the fixing belt.

  In the fixing device of the present invention, since the separation member is positioned by any one of the nip forming member, the support member, the holding member, and the fixing belt, the separation member is changed even if the positional relationship between the heating side assembly portion and the elastic roller is changed. Can be positioned at a predetermined position with respect to the fixing belt.

1 is a schematic diagram illustrating a cross section of a color printer that is an embodiment of an image forming apparatus. 1 is a schematic diagram according to an embodiment of a fixing device installed in an image forming apparatus. FIG. 3 is a perspective view of the fixing device shown in FIG. 2. It is a schematic diagram which shows the support structure of a separation member. FIG. 4 is an enlarged view showing a positional relationship between a separation member and a fixing belt. FIG. 6 is an enlarged view showing a positional relationship between a conventional separating member and a fixing belt, where (a) shows a case where the fixing belt is separated, (b) shows a case where it is in an appropriate position, and (c) shows a case where it is close. Show. It is a schematic diagram which shows the support structure (at the time of pressurization) of the separation member which concerns on 2nd Embodiment. It is a schematic diagram which shows the support structure (at the time of depressurization) of the separation member which concerns on 2nd Embodiment. It is a schematic diagram which shows the support structure (at the time of depressurization) of the separation member which concerns on 3rd Embodiment. It is a schematic diagram which shows the structure (at the time of pressurization) of the separation member and scraper member which concern on 4th Embodiment. It is an enlarged view of the front-end | tip part of the scraper member of FIG. It is a schematic diagram which shows the structure (at the time of depressurization) of the separation member and scraper member which concern on 4th Embodiment. It is an enlarged view of the front-end | tip part of the scraper member of FIG. It is a figure which shows the preliminary operation timing of the separation member containing a scraper member. It is a schematic diagram which shows the contact | adherence state of a scraper member and a separation member.

  Hereinafter, before describing the embodiments, preliminary matters for facilitating understanding of the embodiments will be described.

  In the fixing device described above, a separation member is disposed at the nip exit. This separating member can separate the recording material by bringing the tip (separating portion) close to the surface of the fixing belt (endless belt), and can suppress the occurrence of jamming around the fixing belt.

  It is desirable that the separation portion of the separation member is provided with a gap (gap) at least in the width in which the recording material of the fixing belt passes. The reason is that paper dust, toner, and additives constituting the toner are deposited and adhered to the separation part, which may cause scratches on the fixing belt, and heat is released to the separation member, resulting in poor energy efficiency. Is mentioned.

  On the other hand, in order to increase the ability to separate the recording material, it is desirable to set the gap between the separation portion of the separation member and the fixing belt as narrow as possible. The recording material generates a force that sticks to the fixing belt due to the toner image, and when the toner adheres to the leading end of the recording material, the recording material is sent around the fixing belt. Therefore, the recording material can be scooped up if the separating portion of the separating member is as close as possible to the fixing belt.

  By the way, in the fixing device described above, in order to eliminate jammed paper clogging, the heating side assembly portion (a general term for a fixing belt and a nip forming member held by a holding member) and a pressure roller are separated / abutted. The nip can be depressurized / pressurized. At this time, the positional relationship of the fixing belt, the nip forming member, and the elastic roller changes due to the distortion of the elastic layer of the elastic roller, the pressing force of the pressure member and / or the variation of the outer diameter of the elastic roller, thermal expansion, and the like. . As a result, the following problems are likely to occur.

  First, when the gap between the separation member and the fixing belt is increased, the separation performance is reduced, and winding jam is likely to occur under disadvantageous conditions. Or, the separation member and the fixing belt may come into contact with each other and the fixing belt may be damaged, and an abnormal image may be generated. Further, when the separation member and the fixing belt come into contact, heat escapes to the separation member, which leads to a decrease in thermal efficiency.

  As described above, the gap between the separation member and the fixing belt needs to be set large in consideration of the above-described variation, and there is a problem of deterioration of separation due to an increase in the gap.

  In the following embodiments, a fixing device that can position the separation portion of the separation member at a predetermined position with respect to the fixing belt even when the positional relationship between the heating side assembly portion and the elastic roller changes will be described.

(First embodiment)
FIG. 1 is a schematic diagram illustrating a cross section of a color printer that is an embodiment of an image forming apparatus. The color printer is a tandem system in which image forming units for forming a plurality of color images are juxtaposed along the belt extending direction, but the present invention is not limited to this system. It is also possible to target not only printers but also copying machines and facsimile machines.

  As shown in FIG. 1, photoconductors 20 </ b> Y, 20 </ b> C, 20 </ b> M, and 20 </ b> Bk that are image carriers are arranged in parallel at the center of the image forming apparatus 1. Each of the photoconductors 20Y, 20C, 20M, and 20Bk can form images corresponding to yellow (Y), cyan (C), magenta (M), and black (Bk), respectively. Since these image forming units have the same configuration except for the difference in developer (toner) color, in the following description, the subscripts Y, C, M, and Bk in the reference numerals will be omitted as appropriate.

  Around each photoreceptor 20, a charging member 30, a developing device 40, and a cleaning unit 50 are provided. The photosensitive member 20 is driven to rotate clockwise, and a charging member 30 is pressed against the surface of the photosensitive member 20, and the charging member 30 is driven to rotate as the photosensitive member 20 is driven to rotate. In addition, a predetermined bias voltage is applied to the charging member 30 from a high voltage power source, so that the surface of the rotating photoreceptor 20 can be uniformly charged. The photosensitive member 20, the charging member 30, the developing device 40, and the cleaning unit 50 are each detachably disposed from the image forming apparatus 1.

  Below the four photoconductors 20, an exposure device 8 is provided in parallel therewith. The exposure apparatus 8 includes constituent members such as a light source, a polygon mirror, an f-θ lens, and a reflection mirror. The exposure device 8 exposes each photoconductor 20 charged by the charging member 30 based on image information formed according to image data of each color toner, and forms an electrostatic latent image on each photoconductor 20. produce. The electrostatic latent image formed on the photoconductor 20 using the exposure device 8 is developed and visualized by applying each color toner when passing through the developing device 40 by the rotation of the photoconductor 20. .

  Note that toner bottles 9Y, 9C, 9M, and 9Bk filled with toners of yellow, cyan, magenta, and black are disposed above the inside of the image forming apparatus 1. A predetermined replenishment amount of toner is replenished from the toner bottles 9Y, 9C, 9M, and 9Bk to the color developing devices 40Y, 40C, 40M, and 40Bk through a conveyance path (not shown).

  Further, an endless belt-like intermediate transfer belt 11 configured as an intermediate transfer member is disposed opposite to the photosensitive member 20 of each image forming unit, and each photosensitive member 20 contacts the surface of the intermediate transfer belt 11. ing. The intermediate transfer belt 11 is configured by being wound around a plurality of support rollers (for example, support rollers 72 and 73). In the illustrated example, the support roller 73 is connected to a drive motor as a drive source (not shown), and the intermediate transfer belt 11 is rotated counterclockwise in the figure by the drive of the drive motor. The rotatable support roller 73 also rotates. A primary transfer roller 12 is disposed inside the intermediate transfer belt 11 so as to be opposed to the photoconductor 20 with the belt interposed therebetween. A primary transfer bias is applied to the primary transfer roller 12 from a high voltage power source, and the toner image visualized by the developing device 40 is primarily transferred to the intermediate transfer belt 11.

  The primary transfer residual toner that is not primarily transferred and remains on the photoconductor 20 is removed by the cleaning unit 50 in preparation for the next image forming operation by the photoconductor 20, and the toner on the photoconductor 20 is completely removed. Removed.

  Further, a secondary transfer roller 5 as a secondary transfer device is provided on the downstream side in the driving direction of the intermediate transfer belt 11. The secondary transfer roller 5 faces the support roller 72 with the intermediate transfer belt 11 interposed therebetween, and the secondary transfer roller 5 and the support roller 72 form a secondary transfer nip portion via the intermediate transfer belt 11. ing. The image forming apparatus 1 further includes a registration roller pair 4 in addition to a sheet feeding device 61 and a feeding roller 3 as a stacking unit for sheets S as recording materials. Further, a fixing device 100 and a paper discharge roller pair 7 are provided on the downstream side in the transport direction of the paper S when viewed from the secondary transfer roller 5.

  Subsequently, an image forming operation will be described. First, the photoconductor 20 is driven to rotate clockwise by a drive source. At this time, the surface of the photoconductor 20 is irradiated with light from a static eliminator (not shown) to initialize the surface potential. Next, the surface of the photoconductor 20 is uniformly charged to a predetermined polarity by the charging member 30. Next, the surface of the photoconductor 20 is irradiated with laser light from the exposure device 8, thereby forming an electrostatic latent image on the surface of the photoconductor 20. The image information exposed on each photoconductor 20 at this time is single-color image information obtained by separating a desired full-color image into yellow, cyan, magenta, and black toner color information. The electrostatic latent image formed on the photoreceptor 20 is visualized as a visualized toner image by being supplied with each color toner (developer) from the developing device 40 when passing through the developing device 40.

  The intermediate transfer belt 11 is driven to run counterclockwise in the figure, while a primary transfer voltage having a polarity opposite to the toner charging polarity of the toner image formed on the photoconductor 20 is applied to the primary transfer roller 12. Is done. As a result, a transfer electric field is formed between the photoconductor 20 and the intermediate transfer belt 11, and the toner image on the photoconductor 20 is electrostatically transferred onto the intermediate transfer belt 11 that is driven to rotate in synchronization with the photoconductor 20. Primary transfer. In this way, the respective color toner images that are primarily transferred are superimposed on the intermediate transfer belt 11 at successive timings from the upstream side in the transport direction of the intermediate transfer belt 11 to form a desired full-color image.

  On the other hand, the sheets S on which an image is formed are separated and fed one by one from a bundle of sheets stacked on the sheet feeding device 61 to the registration roller pair 4 by a conveying member such as a feeding roller 3. At that time, the leading edge of the conveyed paper S hits the nip portion of the registration roller pair 4 which has not started to rotate, forms a loop, and registration of the paper S is performed. After that, at the timing of the full color toner image carried on the intermediate transfer belt 11, the rotational driving of the registration roller pair 4 is started, and the secondary transfer nip portion constituted by the support roller 72 and the secondary transfer roller 5. The sheet S is sent out toward.

  In the present embodiment, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the surface of the intermediate transfer belt 11 is applied to the secondary transfer roller 5, whereby the full color toner image formed on the surface of the intermediate transfer belt 11 is transferred to the sheet S. It is transcribed at the same time. Next, the sheet S to which the toner image has been transferred is conveyed to the fixing device 100, and heat and pressure are applied when passing through the fixing device 100, and the toner image is fixed on the sheet S as a permanent image. Then, the sheet S is discharged to a sheet discharge section such as a discharge tray via the pair of discharge rollers 7, and the image forming operation is completed. The residual toner remaining on the intermediate transfer belt 11 without being transferred at the secondary transfer nip is removed and collected by the intermediate transfer belt cleaning means 13.

  The above description is an image forming operation when a full-color image is formed on the paper S. A single-color image is formed using any one of the photoconductors 20, or a two-color or three-color image is formed. It can also be formed. When monochrome printing is performed using the printer of this embodiment, an electrostatic latent image is formed only on the photoreceptor 20Bk, developed by the same means, transferred to the paper S, and fixed by the fixing device 100. That's fine.

  FIG. 2 is a schematic diagram according to an embodiment of a fixing device mounted on the image forming apparatus. The fixing device 100 includes a housing 120, an elastic roller 122, a fixing belt 124, a heat source 126, a nip forming member 128 provided inside the fixing belt 124, and a support member 130 that supports the nip forming member 128. With. Further, the fixing device 100 includes a holding member 132 that holds both ends of the fixing belt 124 and the support member 130, a pressure member 134 that presses the holding member 132, a separation member 136 that separates the recording material from the fixing belt 124, and the like. Is provided.

  The housing 120 forms the entire fixing device. In the figure, for the sake of easy understanding, a broken line is shown and most of the drawing is omitted.

  The elastic roller 122 is supported by the housing 120 in an axially fixed manner, and is driven to rotate by a driving force transmitted from a driving source such as a motor via a gear. In the elastic roller 122, an elastic rubber layer 112 is formed on the core metal 110, and a release layer (PFA or PTFE layer) is provided on the surface in order to obtain releasability. The elastic roller 122 may be a hollow roller or may have a heating source such as a halogen heater in the roller. The elastic rubber layer 112 may be solid rubber, but if there is no heater inside the elastic roller 122, sponge rubber may be used. Sponge rubber is more preferable because heat insulation is enhanced and heat of the fixing belt 124 is not easily removed.

  The fixing belt 124 is driven to rotate in contact with the elastic roller 122 and is directly heated by radiant heat from the inner peripheral side by the heating source 126. In this configuration, the number of halogen heaters that are the heat sources 126 is two with different light distributions in the axial direction. Of course, the number of heaters may be one or three or more. The halogen heater is an example of a radiation type heat source. The heating source 126 may be the illustrated halogen heater, but may be IH (Induction Heating), a resistance heating element, a carbon heater, or the like.

  The fixing belt 124 is an endless belt (or film) using a metal belt such as nickel or SUS or a resin material such as polyimide. The surface layer of the belt has a release layer such as a PFA or PTFE layer, and has a release property so that toner does not adhere. There may be an elastic layer formed of a silicone rubber layer or the like between the belt substrate and the PFA or PTFE layer. When there is no silicone rubber layer, the heat capacity is reduced and the fixability is improved, but when the unfixed image is crushed and fixed, minute irregularities on the belt surface are transferred to the image, and the image has a crusty skin shape. There arises a problem that the gloss unevenness (zudder skin image) remains. 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, fine irregularities are absorbed and the skin image is improved.

  Inside the fixing belt 124, there is a nip forming member 128 that forms a fixing nip portion N between the fixing belt 124 and the elastic roller 122, and directly on the inner surface of the fixing belt 124 (or indirectly through a sliding sheet). ) It comes to slide. Although the shape of the nip portion is flat in the drawing, it may be a concave shape or other shapes. When the nip portion has a concave shape, the discharge direction of the leading end of the recording material is closer to the elastic roller, and the separability is improved, so that jamming is suppressed. Note that the nip forming member 128 may also serve as a planar heating element as a heating unit, and can locally heat the fixing belt 124 at the position of the nip portion.

  Further, inside the fixing belt 124, there is a support member 130 (stay) for supporting the nip portion. The support member 130 prevents the nip forming member 128 that receives pressure from the elastic roller 122 from being bent, and can obtain a uniform nip width in the axial direction. In addition, a reflection member is provided between the heat source 126 and the support member 130, and wasteful energy consumption due to the support member 130 being heated by radiant heat from the heat source 126 or the like is suppressed. Here, instead of providing the reflecting member, the same effect can be obtained even if the surface of the supporting member 130 is heat-insulated or mirror-finished.

  The support member 130 is held by holding members 132 (flange) at both ends. The holding member 132 holds the fixing belt 124, the nip forming member 128, the support member 130, and the heating source 126 at both ends. Hereinafter, these components are referred to as a heating side assembly portion. The holding member 132 is configured to be movable (arrow A in the figure) with respect to the housing 120. On the opposite side of the holding member 132 to the elastic roller 122, there is provided a pressure member 134 that can rotate with respect to the housing 120 and presses the holding member 132 toward the elastic roller 122. The pressure member 134 is urged by urging means (for example, a pressure release cam 138 that is rotated by a drive motor or the like, and a pressure spring 140). Therefore, the holding member 132, that is, the heating side assembly portion is disposed (pressurized) at a pressure position that forms a fixing nip when the paper is passed, and is a pressure-removed position to eliminate permanent compression distortion of the elastic roller when the paper is not passed. Evacuated (depressurized).

  The fixing belt 124 rotates along with the elastic roller 122. In the illustrated case, the elastic roller 122 is rotated by a driving source, and the driving force is transmitted to the belt at the fixing nip portion N, whereby the fixing belt 124 is rotated. The fixing belt 124 is sandwiched and rotated at the fixing nip portion N, and travels while being guided by the holding member 132 at both ends other than the fixing nip portion. With the above configuration, it is possible to realize a fixing device that is inexpensive and has a fast warm-up.

  The separation member 136 is located downstream of the fixing nip and separates the recording material from the fixing belt 124. Since the separating member is a characteristic part of the present invention, it will be described in more detail below.

  FIG. 3 is a perspective view of the fixing device shown in FIG. 2, and FIG. 4 is a schematic diagram showing a support structure of the separating member. In FIG. 3, the pressure member 134 and the urging means are omitted for the sake of clarity.

  As shown in FIG. 3, the holding member 132 and the housing 120 have shapes such as a guide and a rail, and the holding member 132 can move in the axial direction of the elastic roller 122. In other words, the heating side assembly can be moved in the direction of arrow A by the pressure member 134 (see FIG. 2), and a fixing nip can be formed (pressurized) by applying a load to the elastic roller 122 side during paper feeding. In addition, when the paper is not passed, the elastic roller can be released from the compressed state (depressurization) by removing or retracting the load.

  The separating member 136 shown on the right side of FIG. 3 includes a separating portion 136a for scooping and separating the recording material from the fixing belt 124, an abutting portion 136b at both ends of the separating portion 136a that contacts the fixing belt 124, and a separating member 136. And a support shaft 136c serving as a rotation center. The contact part 136b is provided so as to protrude from the separation part 136a.

  As shown in FIGS. 3 and 4, the casing 120 is provided with a long hole 120a, and the support shaft 136c of the separation member 136 is inserted into the long hole 120a. Since the long hole 120a has a shape that allows the support shaft 136c to move only in the same direction as the movement direction of the holding member 132, the separation member 136 is supported so as to be rotatable and movable with respect to the housing 120. Further, the support shaft 136 c of the separation member 136 is urged toward the fixing belt 124 by urging means 142 (for example, a spring) attached to the housing 120.

  On the other hand, the holding member 132 has a positioning portion 144 that comes into contact with the support shaft 136c of the separating member 136 when moved to the pressurizing position. Therefore, since the separating member 136 is positioned at a predetermined position with respect to the holding member 132 by the positioning unit 144, the separating unit 136a can be positioned at a predetermined position with respect to the fixing belt 124. Of course, at this predetermined position, the separation portion 136a of the separation member 136 is set in advance to a desired gap position (gap g) with respect to the fixing belt 124.

  FIG. 5 is an enlarged view showing the positional relationship between the separation member and the fixing belt. The fixing belt 124 is set wider than the sheet passing width, and in order to reduce the frictional resistance in the non-image area, a fluorine-based coating or the like is formed or a member having a small frictional resistance is formed. As shown in FIG. 5, when the abutting portion 136b of the separating member 136 is brought into contact with the non-image area of the fixing belt 124, the separating portion 136a is separated from the fixing belt 124 in the image area by a predetermined gap (gap g). ). Thereby, the separation part 136a of the separation member 136 can keep the gap g to a minimum while following the rotation locus of the fixing belt 124. Further, the region where the contact portion 136b is in contact with the fixing belt 124 has a small frictional resistance, so that the rotation of the fixing belt 124 is not affected.

  As described above, in the fixing device 100 according to the present embodiment, even if the positional relationship among the fixing belt 124, the nip forming member 128, and the elastic roller 122 changes, the separation unit 136 a of the separation member 136 is predetermined with respect to the fixing belt. Can be positioned at Further, since the separation member 136 makes the contact portion 136b contact the fixing belt 124, the separation portion 136a can follow the rotation locus of the fixing belt 124, and the recording material can be stably separated.

(Modification)
In the above-described embodiment, the positioning member 144 is provided on the holding member 132, but instead, the positioning member 144 may be provided on the nip forming member 128 or the support member 130 and brought into contact with the separation member 136. Further, the contact portion 136b of the separation member 136 may be eliminated so that the separation member 136 does not contact the fixing belt 124. In this case, there is an advantage that the load on the fixing belt 124 is eliminated.

  In the present embodiment, the QSU fixing type member is used as the heating side assembling unit. However, SURF, FBN, belt fixing, and roller fixing can also be applied. The present invention can be applied as long as the fixing member side is movable with respect to the pressure member.

  As a supplement, a conventional separating member will be described. 6A and 6B are enlarged views showing the positional relationship between the conventional separating member and the fixing belt. FIG. 6A shows a case where the fixing belt is separated, FIG. 6B shows a case where the fixing belt is in an appropriate position, and FIG. Indicates the case.

  As a premise, it is assumed that the support shaft 136c of the separation member 136 is fixed to the housing 120, and the position of the heating side assembly portion varies in the moving direction. The reasons for the variation include that the hardness (rubber hardness) and the outer diameter of the elastic roller 122 vary, and that the outer diameter of the elastic roller increases due to thermal expansion.

  When the fixing belt 124 is separated (FIG. 6A), the separation member 136 is close to the fixing nip, and the distance and time until the separation from the fixing belt 124 is reduced. Therefore, the separability is deteriorated. Further, since the gap between the separating member 136 and the fixing belt 124 is widened, it is easy to generate a fixing wrap jam in which the paper S enters the gap.

  When the fixing belt 124 is close (FIG. 6C), the separation member 136 is separated from the fixing nip, and the gap between the separation member 136 and the fixing belt 124 is narrowed. Therefore, the separation property of the paper S is improved, but the possibility that the separation member 136 and the fixing belt 124 come into contact with each other increases. At the time of contact, there is a risk of energy savings and belt damage due to toner adhesion.

  In order to place the separation member 136 at the target position (FIG. 6B) with respect to the fixing belt 124, the variation of the elastic body (rubber) of the elastic roller 122 is reduced, and the fixing position of the separation member 136 is set. It is conceivable to dispose the fixing belt 124 away from the fixing belt 124. However, the former has a yield problem, and the latter has a component layout problem. Furthermore, even with these, it is difficult to minimize the gap. From these, it can be said that the present invention has a remarkable effect as compared with the prior art.

(Second Embodiment)
FIG. 7 is a schematic diagram showing a support structure (at the time of pressurization) of the separation member according to the second embodiment, and FIG. 8 is a schematic diagram showing a support structure (at the time of depressurization) of the separation member. 7 and 8, the same components as those in FIG. 4 are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 7, in the present embodiment, a gap adjusting unit 148 is provided in the housing 120. The gap adjusting unit 148 may be a shaft that penetrates between the housings 120 as a separate body, or a convex member attached to the housing 120. Further, it may be formed integrally with the housing 120 (for example, a convex member obtained by bending a part of the housing 120). As shown in FIG. 7, the gap adjusting unit 148 is separated from the separating member 136 during pressurization.

  When the separation member 136 and the heating side assembly portion are integrally moved from the pressurization position to the depressurization position, the gap adjustment portion 148 comes into contact with the separation member 136. When the retracting operation further proceeds, the positioning portion 144 provided in the heating side assembly portion and the support shaft 136c are separated from each other, while the separation member 136 is fixed at the position by the gap adjusting portion 148.

  As a result, the gap g at the time of depressurization (see FIG. 8) becomes larger than the gap g at the time of pressurization (see FIG. 7). In the present embodiment, the gap g at the time of depressurization is set to 2 mm.

  The effect of this embodiment will be described using experimental results. As a condition, it is assumed that the recording material is wound around the fixing belt 124 when the user passes a thin paper that is not guaranteed as the recording material. The recording material was thin paper on which a three-color solid image was placed, and was wound around the fixing belt 124. The force for pulling out the wound thin paper was measured with a force gauge. The results are shown in Table 1.

  As shown in Table 1, the sheet with the gap adjusting portion 148 was able to be removed with a smaller pulling force than the gap adjusting portion 148 was not. Accordingly, it can be said that the operability (removal of paper jam) is superior when the gap adjusting unit 148 is provided. The reason why the pull-out force is reduced is that the gap adjusting portion 148 has a large gap at the time of jam processing, so that the jammed paper and the separating member 136 do not come into contact with each other when the rolled jammed paper is pulled out. On the other hand, without the gap adjusting unit 148, the gap during the jam processing is small, so that the separating member 136 comes into contact with the sheet and becomes a load. As a result, the jam paper pulling force increased.

(Third embodiment)
FIG. 9 is a schematic diagram illustrating a support configuration (at the time of depressurization) of the separation member according to the third embodiment. 9, the same components as those in FIG. 4 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the present embodiment, only one gap adjusting unit 148 is provided. In this configuration, the position of the separation member 136 is determined by two points, that is, the support shaft 136c of the separation member 136 and the gap adjusting portion 148, and the gap g at the time of decompression can be made larger than that in the second embodiment.

  A sheet with high slidability (for example, a low friction member such as BEAREE FL3030) may be provided between the gap adjusting portion 148 and the separating member 136 (contact portion), or one of the gap adjusting portion 148 and the separating member 136 may be provided. May be subjected to a low friction treatment such as fluorine. By improving the slidability of the gap adjusting portion 148 and the separating member 136, it is possible to prevent deformation due to a decrease in rigidity of the separating member 136 due to wear of the contact portion 136b and, as a result, variation in the gap amount during pressurization. .

(Fourth embodiment)
FIG. 10 is a schematic view showing the configuration (at the time of pressurization) of the separating member and the scraper member according to the fourth embodiment, and FIG. 11 is an enlarged view of the tip portion of the scraper member. 10, the same components as those in FIG. 4 are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 10, the scraper member 150 is fixed to the housing 120. The scraper member 150 is made of a metal plate such as SUS or a heat resistant resin such as PPS or PI. As shown in FIG. 11, the tip position of the separating member 136 and the tip position of the scraper member 150 are separated by a distance H1 during pressurization. The tip of the scraper member 150 may be in contact with or separated from the separating member 136, and it is sufficient that a sufficient distance is secured with respect to the fixing belt 124.

  FIG. 12 is a schematic view showing the configuration of the separating member and the scraper member (at the time of depressurization), and FIG. 13 is an enlarged view of the tip portion of the construction scraper member. 12, the same components as those in FIG. 4 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The operation at the time of depressurization of the separating member 136 and the scraper member 150 will be described with reference to FIGS. The scraper member 150 moves from the position of the broken line to the position of the solid line when the separating member 136 performs the depressurization operation. That is, the tip positions of the separating member 136 and the scraper member 150 approach H2 from the distance H1 (H1> H2). At that time, the tip of the scraper member 150 moves while contacting the surface opposite to the separation surface (surface for conveying the recording material) of the separation member 136 at least in the second half of the depressurization operation. By this operation, foreign matters such as fixed toner are peeled off from the front end portion of the separating member 136.

  In this way, the scraper member 150 contacts the separation member 136 from the pressurizing position to the depressurizing position using the bending force of the member. Therefore, the separation member 136 can be cleaned (foreign matter removal) with a simple configuration without providing a complicated mechanism.

  FIG. 14 is a diagram illustrating the preliminary operation timing of the separation member including the scraper member. In the present embodiment, before starting printing (before reaching the timing St), preliminary operations (cleaning operations) of Y1 to Y2 for performing pressurization / decompression are performed.

  If the fixed toner is not completely removed, the viscosity of the fixed toner remaining while the printing operation is stopped (non-heated state) increases due to the temperature drop, and the scraper member 150 and the separation member 136 may be in close contact (see FIG. 15). ). Preliminary operations are performed so that the separation portion 136a of the separation member 136 is in a predetermined position during printing so that the recording material can be separated.

  It is more effective to perform the preliminary operation a plurality of times according to the amount of the fixed toner remaining. In the present embodiment, the number of preliminary operations (the number of cleanings) is increased as the total number of printed sheets printed by the fixing device 100 increases. This is because the remaining amount of the remaining fixed toner tends to increase as the cumulative number of printed sheets increases.

  The preliminary operation (Y1 to Y2) shown in FIG. 14 starts after the temperature of the fixing belt 124 reaches the target temperature T1 that is the toner melting temperature (Ta (msec)). This is because the viscosity of the residual toner is lowered by raising the temperature, and the close contact state between the scraper member 150 and the separating member 136 is easily eliminated. After the preliminary operation (Y1 to Y2), when the surface temperature of the fixing belt 124 reaches the target temperature T2 that is the recording material printing temperature, the printing operation is started.

  The target temperature T1 is set to a temperature lower than the target temperature T2 that is the recording material printing temperature. In this embodiment, T1 = 80 ° C. This is because the fixing belt 124 is heated in the depressurized state (the fixing belt 124 is in a non-rotating state), thereby preventing the fixing belt from being damaged due to local heating.

  In this way, it is possible to prevent malfunction of the separating member 136 including the scraper member 150 due to the remaining fixed toner.

  The present invention has been described in detail above using the embodiment. This embodiment is an example, and can be used with various modifications within a range not departing from the gist. For example, Embodiments 1 to 4 may be used in combination.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 3 Feeding roller 4 Registration roller pair 5 Secondary transfer roller 7 Paper discharge roller pair 8 Exposure apparatus 9 Toner bottle 11 Intermediate transfer belt 12 Primary transfer roller 13 Intermediate transfer belt cleaning means 20 Photoconductor 30 Charging member 40 Development Device 50 Cleaning means 61 Sheet feeding device 72 Support roller 73 Support roller 100 Fixing device 110 Core metal 112 Elastic rubber layer 120 Housing 120a Long hole 122 Elastic roller 124 Fixing belt 126 Heating source 128 Nip forming member 130 Support member 132 Holding member 134 Pressure member 136 Separation member 136a Separation part 136b Contact part 136c Support shaft 138 Pressure release cam 140 Pressure spring 142 Biasing means 144 Positioning part 148 Gap adjustment part 150 Scraper member N Fixing nip part S paper

Japanese Patent No. 4818826

Claims (19)

A housing,
An elastic roller that is supported by the housing in an axially fixed manner and driven to rotate;
An endless fixing belt that rotates in contact with the elastic roller, and
A nip forming member provided inside the fixing belt and forming a fixing nip between the fixing belt and the elastic roller;
A support member for supporting the nip forming member;
A holding member that holds both ends of the fixing belt and the support member, and is supported so as to be movable to a pressurizing position or a depressurizing position with respect to the housing;
A pressure member that pressurizes the holding member in the direction of the elastic roller;
A fixing device that is located downstream of the fixing nip and includes a separation member that includes a separation unit that separates the recording material from the fixing belt;
The separation member is movable and rotatable in the movement direction of the holding member and is supported by the housing and is urged toward the fixing belt, and when the holding member moves to the pressure position. Abutting at least one of the nip forming member, the support member, the holding member, and the fixing belt,
The fixing device, wherein the separation portion of the separation member is positioned at a predetermined position with respect to the fixing belt. The separation member has support shafts at both ends,
The housing includes an elongated hole that supports the support shaft so as to be movable and rotatable in a moving direction of the holding member, and an elastic body that urges the support shaft toward the fixing belt. Item 4. The fixing device according to Item 1. The holding member has a positioning portion;
The said positioning part contact | abuts to the said support shaft of the said separation member when the said holding member is moved to the said pressurization position or the said depressurization position with respect to the said housing | casing. The fixing device described.   The separation member has a contact portion that contacts a non-image area of the fixing belt, and the contact portion contacts the fixing belt, so that the separation portion is positioned at a predetermined position with respect to the fixing belt. The fixing device according to claim 1, wherein the fixing device is a fixing device.   5. The gap adjusting unit according to claim 1, further comprising a gap adjusting unit configured to make a gap between the separating unit of the separating member and the fixing belt larger than that at the time of pressurization when the pressure is released. Fixing device.   The gap adjusting part is formed integrally with the housing or fixed separately, and contacts the separation member when the holding member moves from the pressurizing position to the depressurizing position, The fixing device according to claim 5, wherein the gap is increased.   The fixing device according to claim 6, wherein a low friction member is provided between the separation member and the gap adjusting unit.   The fixing device according to claim 6, wherein a low-friction process is performed on at least one surface of the region where the separation member abuts on the gap adjusting unit and the gap adjusting unit. Equipped with a scraper member to remove foreign matter,
The fixing device according to claim 1, wherein a tip end portion of the scraper member is positioned at the separation portion of the separation member.   The fixing device according to claim 9, wherein the scraper member is attached to the housing.   The distance between the separation portion of the separation member and the tip of the scraper member when the separation member is positioned at the time of nip formation is the distance between the separation portion of the separation member and the tip of the scraper member during decompression. The fixing device according to claim 9, wherein the fixing device is larger than the distance.   The fixing device according to claim 9, wherein the separation portion of the separation member moves while being in contact with a tip portion of the scraper member by an operation at the time of depressurization.   13. The fixing according to claim 9, wherein the separation member is cleaned by the scraper member before the printing is started by moving from the depressurization position to the pressurization position. apparatus.   The fixing device according to claim 13, wherein cleaning of the separating member by the scraper member is performed a plurality of times before printing is started.   The fixing device according to claim 14, wherein the number of cleanings of the separation member before the start of printing by the scraper member is determined according to a total number of printed sheets separated by the separation member.   16. The fixing device according to claim 15, wherein the separation member is cleaned by the scraper member before starting printing after the surface temperature of the fixing belt reaches a target temperature T1, which is a toner melting temperature. .   The fixing device according to claim 16, wherein the target temperature T1 is lower than a target temperature T2 at the time of recording material printing.   The fixing device according to claim 1, wherein a radiation type heat source is provided inside the fixing belt.   An image forming apparatus comprising the fixing device according to claim 1.

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