JP4595615B2 - Fixing device, image forming apparatus using the same, and peeling guide member - Google Patents

Description

  The present invention relates to a fixing device that heats and fixes an unfixed toner image formed on a recording material using an electrophotographic method or an electrostatic recording method, and more particularly to a fixing device that uses an endless fixing belt. .

Conventionally, in an image forming apparatus such as a copying machine or a printer using an electrophotographic method, an unfixed toner image formed and supported on a recording material by an intermediate transfer method or a direct transfer method is used as a permanently fixed image. As a fixing method, a heating and pressing type fixing device has been widely used.
As this heating and pressurizing method, for example, a recording material carrying an unfixed toner image is fixed at a mutual press contact portion of the roll pair by rotating a press roll pair of a heating roll (fixing roll) and a press roll. By passing the toner image through the nip region, the toner image is fixed by heat and pressure on the recording material.

  In such a fixing device, in order to prevent the recording material from being wound around the fixing roll, a peeling member is often provided downstream of the fixing nip region of the fixing roll. Claw-like and plate-like members are known as peeling members, but a fixing device that fixes a color image, in particular, may cause damage to the fixing roll due to local loads that are likely to damage the fixing roll. In many cases, a plate-like member is used (see, for example, Patent Document 1).

In Patent Document 1, the plate-like release member is configured by molding an elastic body on a metal base material, so that it is possible to prevent damage to the fixing roll and to reliably release the recording material from the fixing roll. It is shown.
However, when such a plate-like peeling member is disposed close to the fixing roll, it contacts the fixing roll due to the influence of member variation, mounting error, thermal expansion, etc., and wears the surface of the fixing roll, or the toner on the peeling member itself. There is a possibility that image defects may occur due to the occurrence of the deposition. On the other hand, if the peeling member is installed at a position that is too far from the fixing roll, the recording material peeling performance may be hindered. Therefore, it is desirable that the peeling member is disposed close to the fixing roll at a stable position.

On the other hand, proposals that focus on the contact state between the peeling member and the recording material have also been made. That is, paying attention to the contact between the side edge of the peeling member facing the fixing roll and the recording material, a proposal to disperse the contact pressure (see, for example, Patent Document 2) and an adverse effect caused by the contact are attempted. There is a proposal (see, for example, Patent Document 3).
Patent Document 2 describes that the shape of the side edge on the nip side of the peeling member is a shape that follows the shape of the exit of the nip region. For example, when the fixing roll and the pressure roll have a so-called reverse crown shape. Is formed in an arc shape so that the central portion of the side edge of the peeling member protrudes toward the pressure roll side, and in the crown shape, it forms an arc shape so as to protrude toward the fixing roll side. Furthermore, in the case of a uniform shape, it is intended to make the contact with the recording material uniform by making the shape parallel to the fixing roll as it is.
However, usually, in the nip area between the fixing roll and the pressure roll, the feeding speed of the recording material differs between the end part and the center part in the longitudinal direction of the nip area due to the dimensional tolerance of these members and the mounting intersection. The edge of the recording material is easily peeled off due to the adhesive effect of the toner on the recording material, and the central side of the recording material is easily taken in the direction of the fixing roll. For this reason, in the above-described method, when the recording material comes into contact with the side edge of the peeling member, the recording material receives resistance there, and, for example, paper wrinkles or corner folds are caused by the conveying force to the recording material that follows (provided in the nip area). Etc. are likely to occur.

  On the other hand, in Patent Document 3, a side edge shape facing the fixing roll side of the peeling member is a shape in which both ends are protruded to the fixing roll side, and only a part of the leading edge of the recording material hits the side edge. Proposals have been made to eliminate harmful effects such as jamming by preventing the whole from contacting at the same time.

Japanese Patent Laid-Open No. 2002-82564 (Embodiment of the Invention, FIG. 2) JP 2002-287555 A (Second Embodiment, FIG. 5) JP 2002-287554 A (first embodiment, FIG. 2)

However, even if only a part of the tip of the recording material is applied to the side edge of the plate-like peeling member, depending on the shape of the side edge, the conveyance of the recording material may be hindered.
Further, in the shape in which both ends of the peeling member are projected to the fixing roll side, after the leading edge of the recording material hits the side edge of the peeling member, the center side of the recording material hits the side edge as it is, and the paper wrinkle It will also cause problems such as.
The present invention has been made to solve the above technical problem, and is intended to ensure stable peeling guide performance of a recording material sent from a fixing device.

That is, in the basic configuration of the present invention, as shown in FIGS. 1A, 1B and 1C, the unfixed toner image T on the recording material 2 is heated in the contact nip region N while being in contact with each other. A pair of fixing members 1 (1a, 1b) for pressure fixing and at least one of the fixing members 1 are provided facing the downstream side of the contact nip area N, and the recording material 2 is peeled from the fixing member 1. The peeling guide member 3 has a member main body 3a extending in the longitudinal direction of the contact nip region N, and the fixing main body 1 side edge of the member main body 3a extends from the center to both ends. A receiving portion 3b that continuously protrudes toward the fixing member 1 is formed, and on the recording material conveyance path 4 side of the member main body 3a, a recording material conveyance path from both longitudinal ends of the member main body 3a toward the central portion. 4 includes a concave portion that is continuously separated from the recording material guide. Characterized in that the formation of the 3c.
Note that the phantom line (two-dot chain line) in FIG. 1A shows the recording material conveyance path when the recording material 2 is wound around the fixing member 1 side, and (b) The figure which looked at the peeling guide member 3 from A direction, (c) has shown the figure seen from the B direction.

  In such technical means, the fixing member 1 is not limited as long as the fixing member 1 can be used in a fixing system that heats and pressurizes, and may be either a roll shape or a belt shape, and the position of the heating source 5 is fixed to both. The aspect provided in the member 1 (1a, 1b) may be sufficient, the aspect provided in one side may be sufficient, and it may be provided in either the inside of the fixing member 1, or the exterior.

Further, the peeling guide member 3 is not particularly limited as long as it prevents the recording material 2 after fixing from being wound around the fixing member 1.
In the present invention, in the receiving portion 3b of the peeling guide member 3, the recording material 2 after fixing gradually climbs on the peeling guide member 3 from both ends (both sides) of the leading end of the recording material 2. The recording material 2 can be smoothly carried on the peeling guide member 3. Further, since the recording material guide surface 3c is provided with a concave portion, the recording material 2 having the tip riding on the peeling guide member 3 can easily follow the peeling guide member 3 even when the center of the recording material 2 is raised. Will be guided. Further, the recording material 2 receives a force in the direction in which the recording material 2 becomes flat by the recording material guide surface 3c, and the subsequent recording material 2 is smoothly conveyed and guided. Therefore, it is possible to prevent the recording material 2 from being wound around the fixing member 1, and to prevent the occurrence of wrinkles, corner breaks, and the like when hitting the peeling guide member 3.
In this case, the peeling guide member 3 may be disposed on either of the pair of fixing members 1 (1a, 1b) as long as the recording material 2 is prevented from being wrapped around. There is no problem.
Note that “continuously” may be changed linearly or may be changed in a curved manner. Moreover, it means that there is no problem even if it is an aspect including a straight line and a curved line.

In addition, the receiving portion 3b of the peeling guide member 3 is preferably a curved or smooth shape, and the recording material 2 discharged from the contact nip region N is more smoothly received. To become housed.
Furthermore, if the shape of the receiving portion 3b is different from the outlet shape of the contact nip region N, for example, when the outlet shape of the contact nip region N is wider than both ends in the longitudinal direction, the contact nip region N The two feeding speeds at both ends of the recording material 2 at the center become faster than the central portion, and the central portion of the recording material 2 discharged from the contact nip area N is lifted from both ends toward the toner image surface side. The usefulness of 3b will be further exhibited.

Further, from the viewpoint of reducing the frictional resistance between the peeling guide member 3 and the recording material 2, at least the receiving portion 3b and the recording material guide surface 3c of the peeling guide member 3 are released to reduce the frictional resistance with the recording material 2. It is preferred that a layer is applied. Thereby, the conveyance guide of the recording material 2 becomes smoother.
Further, it is preferable that the member main body 3a of the peeling guide member 3 is provided with a plurality of ribs along the recording material conveyance direction so that the leading end locus of these ribs becomes the recording material guide surface 3c. By reducing the contact area between the recording material 2 and the recording material guide surface 3c, the frictional resistance can be further reduced, and the conveyance guideability of the recording material 2 can be further improved.

In the present invention, from the viewpoint of stabilizing the peeling performance of the recording material 2, the fixing member 1 and the peeling guide member 3 are arranged in contact with each other at a portion of the receiving portion 3 b of the peeling guide member 3 where the recording material 2 does not contact. Has been. By doing so, it is possible to reduce mounting errors caused by temperature changes and various variations, and it is possible to keep the clearance between the peeling guide member 3 and the fixing member 1 uniform. It is possible to secure the peel guide performance. At this time, the portions where the peeling guide member 3 comes into contact with the fixing member 1 (both ends of the receiving portion 3b of the peeling guide member 3 in the present invention) are non-conveying regions of the recording material 2, and thus come into contact temporarily. Even if a flaw or the like occurs on the surface of the fixing member 1, there is no problem in the fixing performance to the recording material 2, the peeling performance of the recording material 2, and the peeling guide performance.

  In the present invention, it is preferable that the peeling guide member 3 has a heating source 5 and is opposed to the fixing member 1 side facing the unfixed toner image T surface. In this way, after the unfixed toner image T is fixed, even if the recording material 2 is brought to the fixing member 1 side by the adhesive force of the toner, the peeling guide performance in the peeling guide member 3 is effective. To be able to function. The fixing member 1 may be provided with a release layer such as a fluorine-based resin layer on the surface, for example, from the viewpoint of suppressing toner adhesion.

In the above-described aspect, the other fixing member 1 (for example, 1b) facing the fixing member 1 (for example, 1a) is preferably an endless belt. In this case, a wide contact nip area N is secured. In addition, the fixing device can be downsized. The endless belt may have any heat resistance, and a resin-based or metal-based material is used. However, a resin-based one is preferable from the viewpoint of temperature efficiency during fixing.
Further, in the above-described endless belt mode, a peeling pressure member that contacts the back surface of the endless belt corresponding to the downstream side of the contact nip area N and forms a peeling nip area between the fixing member 1 and the endless belt is provided. It is preferable that the endless belt is pressed toward the elastic roll member by the peeling pressure member, so that a peeling nip region effective for peeling the recording material 2 from the fixing member 1 is formed.

  Further, it is preferable that the contact length in the recording material conveyance direction of the peeling nip area by the peeling pressure member is set wider on the end in the longitudinal direction than the central part in the longitudinal direction of the peeling nip area. The sending speed of both ends (edge side) of the recording material 2 fed from the nip area can be made faster than the feeding speed of the central part, and both edges of the recording material 2 sent from the peeling nip area are rotated first. It becomes easy to deform in the direction away from the member 1 quickly, so that both ends of the front end can be effectively placed on the receiving portion 3b of the peeling guide member 3.

Furthermore, the present invention is intended not only for the fixing device described above but also for an image forming apparatus. In this case, an image carrier that carries a toner image and a toner image on the image carrier are recorded on the recording material. A transfer member for transferring the image on the recording medium and a fixing device for fixing the unfixed toner image T transferred onto the recording material may be provided, and the fixing device described above may be provided as the fixing device.
Furthermore, the present case is also directed to a peeling guide member used in the above-described fixing device.

According to the present invention, a pair of fixing members that heat and press fix an unfixed toner image, and a peeling guide member that peels and guides the recording material facing the downstream side of the contact nip region of at least one of the fixing members. A member main body that extends in the longitudinal direction of the contact nip region, and the member main body includes a receiving portion that continuously protrudes from the center toward both ends toward the fixing member, and from both longitudinal ends of the member main body. Since the recording material guide surface is provided with a concave portion that is continuously separated from the recording material conveyance path toward the central portion, the separation guide performance of the recording material delivered from the pair of fixing members is improved, and recording is performed. It becomes possible to prevent the material from being wound around the fixing member side.
Further, since the peeling guide member is disposed in contact with the fixing member at a portion of the receiving portion where the recording material does not contact, the mounting error caused by temperature change and various variations can be reduced, and the clearance from the fixing member can be reduced. Can be kept uniform, and stable peeling guide performance by the peeling guide member can be secured.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
Embodiment 1
FIG. 2 shows Embodiment 1 of an image forming apparatus to which the present invention is applied. In the figure, the image forming apparatus of the present embodiment is provided with an apparatus main body 10 having an image forming unit 20 capable of forming a color image, and an image reading unit 11 for reading a document on the upper part of the apparatus main body 10. At the same time, a document feeding device 12 for feeding a document to the image reading unit 11 is disposed above, while a multi-stage feed for supplying paper as a recording material is provided below the image forming unit 20 of the apparatus body 10. The paper cassettes 51 to 53 are arranged so that they can be pulled out.

  The image forming unit 20 used in the present embodiment employs, for example, an electrophotographic system, and includes four colors of yellow (Y color), magenta (M color), cyan (C color), and black (K color). This is a so-called tandem type configuration in which the color image forming units 21 (21 a to 21 d) are arranged in parallel on the intermediate transfer belt 30. Therefore, the toner images of the respective colors formed by the respective image forming units 21 (21a to 21d) are sequentially primary-transferred and multiplexed on the intermediate transfer belt 30, and the multiplexed toner images are secondary-transfer device 35. Are collectively transferred onto the paper conveyed from the paper feed cassettes 51 to 53 and guided to the fixing device 40. It should be noted that the color arrangement of the four-color image forming units 21 is not limited to this order, and may be any other order.

  The image forming unit 21 (21a to 21d) in the present embodiment includes a photosensitive drum 22 that forms and supports each color component toner image, a charging device 23 such as a charging roll that charges the photosensitive drum 22, and a charged photosensitive member. A laser exposure device 24 that forms a latent image on the photosensitive drum 22, a developing device 25 that visualizes the electrostatic latent image on the photosensitive drum 22, and a toner image on the photosensitive drum 22 are primarily transferred onto the intermediate transfer belt 30. For example, a primary transfer device 26 including a primary transfer roll and a cleaning device 27 for cleaning residual toner remaining on the photosensitive drum 22 are configured. In the present embodiment, the laser exposure device 24 exposes the entire four-color image forming unit 21 with one laser exposure device 24.

  Further, the intermediate transfer belt 30 is stretched around a plurality of stretching rolls 31 to 33, and is circulated and conveyed using, for example, the stretching roll 31 as a driving roll. However, the tension roll 33 is placed opposite to the backup roll. Further, a belt cleaning device 36 for removing residual toner on the intermediate transfer belt 30 is disposed at a position facing the tension roll 32 of the intermediate transfer belt 30.

Here, the paper transport system in the present embodiment is as follows. A vertical conveyance path 61 extending substantially vertically upward from each of the paper feed cassettes 51 to 53, a main conveyance path 62 extending in a substantially horizontal direction on the downstream side of the vertical conveyance path 61, and the most downstream vicinity of the main conveyance path 62. The retraction conveyance path 63 extends downward in a substantially Y shape, and the reverse conveyance path 64 extends substantially horizontally from the middle of the retraction conveyance path 63 and leads to the vertical conveyance path 61.
In the main conveyance path 62, a registration roll 54 that regulates the positioning of the paper, a secondary transfer device 35 that collectively transfers the toner images multiplexed on the intermediate transfer belt 30, and a paper on which the toner images are collectively transferred. A conveying belt 55 that conveys the toner, a fixing device 40 that fixes the toner image on the sheet, and a discharge roll 56 that discharges the sheet to a storage tray 57 that is disposed on the side of the apparatus main body 20 to store the sheet.
In these conveyance paths 61 to 64, conveyance members such as a conveyance roll and a conveyance guide for ensuring the conveyance of the paper are appropriately disposed.

  In particular, the fixing device 40 of the present embodiment is as shown in FIG. In the drawing, a fixing roll 41 having a heating source 42 such as a halogen lamp inside, an endless belt 43 that rolls with the fixing roll 41 and sandwiches and conveys paper, and a back surface side of the endless belt 43 are arranged in contact with each other. A separation nip member 47 that forms a separation nip region between the fixing roll 41 and the endless belt 43 and an upstream side of the separation nip member 47, and a fixing nip region between the fixing roll 41 and the endless belt 43. The pre-nip member 46 to be formed is a main component.

The fixing roll 41 in this embodiment includes a cylindrical core 41a made of metal such as aluminum having excellent mechanical strength and good thermal conductivity, and an elastic layer such as silicone rubber formed on the surface of the core 41a. 41b and a release layer 41c that covers the surface of the elastic layer 41b and is provided to prevent the offset of the unfixed toner image on the paper.
Here, the material of the core 41a is not particularly limited as long as it has mechanical strength and good thermal conductivity. For example, a metal or alloy such as aluminum, stainless steel, steel, or brass is used.
Further, the elastic layer 41b is not limited to silicone rubber, and may be, for example, fluorine rubber as long as it has heat resistance. The method of forming the elastic layer 41b on the surface of the core 41a is not particularly limited, An injection molding method or a coating method can be employed.
Further, the release layer 41c may be any material that has heat resistance and appropriate release properties for the toner. For example, fluorine rubber or fluorine resin is used.
Furthermore, the heating source 42 inside the fixing roll 41 is not particularly limited as long as it has a shape and structure that can be accommodated inside the core 41a, and may be appropriately selected according to the purpose.

  In this embodiment, a temperature sensor 48 that measures the surface temperature of the fixing roll 41 is provided around the fixing roll 41, and heating is performed by the temperature sensor 48 so as to control the surface temperature of the fixing roll 41. The temperature of the source 42 is controlled. The temperature sensor 48 is not particularly limited as long as it can measure the surface temperature of the fixing roll 41. For example, a temperature sensitive element such as a thermistor or a posistor can be used.

On the other hand, the endless belt 43 may have a single layer structure, but in the present embodiment, a belt having a laminated structure in which a release layer is provided on the surface of the substrate is used.
As the base material of the endless belt 43, if it has heat resistance, for example, a resin base material such as thermosetting polyimide, thermoplastic polyimide, polyamide, or polyamideimide, or a metal base material such as stainless steel, nickel, or copper is used. . Further, the release layer is preferably one having good releasability of toner adhering to the surface, and examples of the material include PTFE (polytetrafluoroethylene) and PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer). ) And FEP (tetrafluoroethylene-hexafluoropropylene copolymer).

In the present embodiment, on the back surface side of the endless belt 43, a peeling nip member 47 and a pre-nip member 46 that constitute a fixing pressure member in a concave portion of a support body 44 made of metal or the like whose section is substantially concave. Are attached so as to come into contact with the endless belt 43, respectively. In FIG. 3, symbol S indicates a sheet on which an unfixed toner image is transferred.
The peeling nip member 47 located on the downstream side forms a peeling nip region between the fixing roll 41 and the endless belt 43, and is a highly rigid material made of a metal or alloy such as aluminum, stainless steel, steel, copper, brass, etc. It is constituted by.

On the other hand, the pre-nip member 46 located on the upstream side is formed of an elastic material such as silicone rubber, forms a fixing nip region between the fixing roll 41 and the endless belt 43, and stably fixes an unfixed toner image on the paper. It is supposed to be. In the present embodiment, the surface of the pre-nip member 46 has a low frictional resistance, such as a fluororesin sheet, to keep the frictional resistance with the endless belt 43 small and to make the endless belt 43 rotate more smoothly. The friction sheet 46a is bonded and fixed.
Examples of the low friction sheet 46a include PTFE (polytetrafluoroethylene resin), PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) and the like from the viewpoints of workability and low friction. Further, a glass fiber as a substrate and impregnated with fluorine resin or bonded with a fluorine resin sheet may be used.

  Further, in the present embodiment, a belt traveling guide 45 made of a rigid and low thermal conductive resin is provided in the endless belt 43 below the support body 44 in order to smoothly rotate the endless belt 43. .

Therefore, in this embodiment, as shown in FIG. 4, the elastic layer 41b of the fixing roll 41 is deformed by the peeling nip member 47, and this portion functions as a peeling nip region.
Further, the shape of the peeling nip member 47 in the present embodiment has a shape as shown in FIG. 5, and the shape of the portion in contact with the endless belt 43 at the end portion and the center portion in the longitudinal direction is different. Yes. That is, the curvature Ce of the end portion and the curvature Cc of the central portion are formed such that the curvature Cc of the central portion is larger and gradually becomes smaller toward the end portion.
Accordingly, the contact pressure between the peeling nip member 47 and the endless belt 43 is substantially the same, but the shape of the peeling nip region is different between the central portion and the end portion, that is, the contact length between the peeling nip member 47 and the fixing belt 43 ( The sheet conveyance direction) is different between the center portion and the end portion, and the contact length of the end portion is set wide.
In the figure, the two-dot chain line (virtual line) of the peeling nip region shape indicates a case where the upstream side shape of the peeling nip region shape is linear by devising the shape of the peeling nip member 47. Such a peeling nip region shape may be used.

In particular, in this embodiment, as shown in FIG. 3, a peeling guide member 70, which is a feature point of the present case, is provided at a position facing the fixing roll 41 on the downstream side of the peeling nip region.
In the present embodiment, the peeling guide member 70 includes a member main body 71 extending in the longitudinal direction of the peeling nip region, and an edge of the member main body 71 on the fixing roll 41 side, and both ends thereof are closer to the fixing roll 41 than the center portion. It has a receiving portion 72 that protrudes, and further has a sheet guide surface 73 that includes a concave portion whose center portion is separated from the path side from both ends on the path side on which the sheet S after fixing of the member main body 71 is conveyed. ing.

FIGS. 6A and 6B show the shape of the peeling guide member 70 of FIG. 3 as viewed from the α direction and the β direction. The receiving portion 72 has both end portions 72e at the central portion with respect to the sheet conveying direction. It has a substantially chevron-like shape protruding toward the upstream side from 72c. In the present embodiment, the member main body 71 on the downstream side of the receiving portion 72 of the peeling guide member 70 is provided with a plurality of ribs 74 for reducing the contact resistance with the paper S along the paper transport direction. The leading ends of these ribs 74 form a substantially mountain-shaped sheet guide surface 73.
Then, from the receiving portion 72 to the paper guide surface 73, a release layer made of a fluororesin is coated, so that the frictional resistance with the paper S is further reduced.
In this example, the receiving portion 72 and the paper guide surface 73 are chevron-shaped, but the present invention is not limited to this, and may be a curved shape. Further, the smoothly changing shape may be a paper peeling guide. It is preferable when performing. In this example, the rib 74 is provided. However, the rib 74 may not be formed if the frictional resistance with the paper S does not hinder. Further, instead of the rib 74, the member main body 71 may be processed into such a shape.

Furthermore, in this embodiment, both end portions 72e of the receiving portion 72 of the peeling guide member 70 are in contact with the fixing roll 41 so that the gap between the fixing roll 41 and the peeling guide member 70 does not change.
As the peeling guide member 70, a metal material such as aluminum or steel can be used in addition to stainless steel, and a heat resistant resin such as PBT (polybutylene terephthalate) or PPS (polyphenylene sulfide) is used. You may do it.

Next, the operation of the present embodiment will be described first with reference to FIG. 2 focusing on the sheet conveyance system of the image forming apparatus.
The paper S sent out from any of the paper feed cassettes 51 to 53 advances along the vertical conveyance path 61 and is positioned and regulated by a registration roll 54 provided in the main conveyance path 62, and then to the secondary transfer device 35. move on.
On the other hand, the color toner images transferred onto the intermediate transfer belt 30 by the image forming unit 21 (21 a to 21 d) are conveyed on the intermediate transfer belt 30 and reach the secondary transfer device 35.
The multiplexed toner images on the intermediate transfer belt 30 are collectively transferred onto the paper S by the secondary transfer device 35. The sheet S on which the toner images are collectively transferred is transported by the transport belt 55 and reaches the fixing device 40. Then, the toner image is fixed on the paper S by the fixing device 40, proceeds on the main conveyance path 62 as it is, and is discharged from the discharge roll 56 to the storage tray 57.

  Here, when performing double-sided recording on a sheet, the sheet S that has been fixed by the fixing device 40 is temporarily retreated from the main conveyance path 62 to the retreat conveyance path 63 side. Then, after sufficiently proceeding along the retreat conveyance path 63, when the rear end of the sheet S exceeds the entrance of the reversal conveyance path 64, a predetermined conveyance roll in the retreat conveyance path 63 performs a reversing operation, and The sheet S is reversed and conveyed to the reverse conveyance path 64 side. The reversely transported paper S is transported again to the main transport path 62 with the front and back sides of the paper S reversed, and a new toner image is formed. Thereafter, the toner is discharged from the fixing device 40 to the storage tray 57 via the discharge roll 56.

Next, the operation of the fixing device 40 will be described with reference to FIG.
When the sheet onto which the toner images are batch-transferred is inserted into the fixing device 40, the sheet is nipped and conveyed between the fixing roll 41 and the endless belt 43 in the fixing nip region formed by the pre-nip member 46, and is transferred by the fixing roll 41. Stable fixing is achieved by sufficient temperature and sufficient pressure.
In the peeling nip region by the peeling nip member 47, the feeding speed of the edge (both ends) of the paper S becomes faster than the feeding speed of the central portion of the paper S due to the shape effect of the peeling nip member 47. The force that approaches is applied. Therefore, the sheet S is easily peeled off from the fixing roll 41. On the other hand, the force that moves the paper S toward the center acts on the upstream side of the separation nip region to force the paper S outward from the edge. Therefore, even if a large force is applied to the paper S in the separation nip region, the paper wrinkles. Can be prevented.

FIGS. 7A and 7B show this effect. FIG. 7A shows the case where the upstream and downstream shapes of the peeling nip region RN are substantially similar, and FIG. 7B shows the peeling nip. The upstream side of the region RN is linear, and the downstream side represents the same shape as (a).
In such a shape of the peeling nip area RN, both (a) and (b) have a longer contact length at the end than the central part of the peeling nip area RN. Faster at the end side. Therefore, on the downstream side of the peeling nip region RN, a force F1 acts in a direction to bring the sheet S toward the center, while on the downstream side, the recording material receives outward forces F2 and F3 as reaction forces. At this time, when the shape of the downstream side separation nip region RN is linear (as shown in FIG. 5B), the outward force F3 can be applied, and therefore the sheet S in the separation nip region RN. Even if the squeezing action is added to the paper, it becomes possible to further prevent paper wrinkling.
As described above, the sheet S discharged from the peeling nip region RN is also discharged with the central portion of the sheet S projecting toward the fixing roll 41 with the help of the adhesive force of the toner to the fixing roll 41 (see FIG. 3). The

Further, FIG. 8 shows the peeling guide action of the paper S of the peeling guide member 70, so that the shape of the paper S discharged from the nip region between the fixing roll 41 and the endless belt 43 and the shape of the peeling guide member 70 are shown. It is the figure shown typically. Therefore, the peeling guide member 70 is shown in a separated state without contacting the fixing roll 41.
In the drawing, the sheet S discharged from the peeling nip area is discharged with the central portion Sc at the leading end of the sheet protruding toward the fixing roll 41 due to a difference in the feeding speed or the like. This means that the paper is discharged in a state where both sides Se of the front end of the paper are lower than the central portion Sc.
When the sheet S discharged in such a shape reaches the receiving portion 72 of the peeling guide member 70, first, the sheet S enters under the receiving portion 72 from both sides Se side of the sheet S (runs on the receiving portion 72). .

  The sheet S in which both sides Se enter the receiving portion 72 receives a force in a direction intersecting with the sheet conveyance direction, and acts so that the both side Se side of the leading end of the sheet is directed further downward. At this time, since the central portion Sc at the leading end of the sheet does not reach the receiving portion 72 of the peeling guide member 70, the protrusion of the central portion Sc at the leading end of the sheet is reduced in accordance with the movement of both sides Se of the leading end of the sheet. Therefore, the central portion Sc at the front end of the paper gradually becomes easy to sink into the receiving portion 72 of the peeling guide member 70, so that the peeling guide performance of the paper S is sufficiently secured.

Further, in the present embodiment, the sheet guide surface 73 is formed in a substantially mountain shape including the recess 73c, so that the sheet S started to be guided by the peeling guide member 70 is flat on both sides of the sheet S. As a result, the conveyance guide performance of the paper S is further improved. Further, by providing the concave portion 73c, the protrusion of the central portion Sc at the front end of the paper can be easily guided to the paper guide surface 73.
Furthermore, since the release layer is processed on the receiving portion 72 and the paper guide surface 73 of the peeling guide member 70, the frictional resistance between the paper S and the peeling guide member 70 is reduced, and the conveyance guide performance of the paper S is reduced. Will be done smoothly.

  As described above, in the present embodiment, it is possible to realize a small-sized fixing device 40 having a wide fixing nip in which the separation performance of the sheet S and the separation guide performance are sufficiently ensured. It is also possible to realize the fixing device 40 that can perform so-called instant-on (fast rise) without making the elastic layer of the fixing roll 41 unnecessarily thick.

Further, in the present embodiment, as shown in FIG. 3, the embodiment in which the peeling nip member 47 is provided inside the endless belt 43 is shown. However, even when the peeling nip member 47 is not provided, the fixing nip region by the prenip member 46 is used. It goes without saying that the peeling guide member 70 can secure the peeling guide for the paper S delivered from the machine.
Further, the configuration in which the heating source 42 is provided in the fixing roll 41 is shown. However, for example, the heating source 42 is installed in the vicinity of the fixing roll 41 in the vicinity of the upstream of the fixing nip region so as not to interfere with the sheet conveyance. Also good. Further, the endless belt 43 may be configured to be rotatable using, for example, a tension member.

Further, FIGS. 9A to 9D show a modified example of the peeling guide member 70 in the present embodiment, and FIG. 9A shows the peeling guide member 70 in the lateral direction (direction intersecting the paper transport direction). (B) to (d) show cross-sectional views of bb, cc, and dd shown in (a), respectively.
In this example, the receiving portion 72 of the conveyance guide member has a substantially flat shape when viewed from the cross section, and is formed so that the mountain shape of the sheet guide surface 73 increases toward the downstream side in the sheet conveyance direction. Has been.
Therefore, the sheet S guided by the sheet guide surface 73 of the peeling guide member 70 receives an increasing downward force on both sides, so that the center part of the sheet S is expanded sideways, and the protrusion of the center part is further pushed down. It becomes like this. Therefore, even if the peeling guide member 70 has such a shape, the same effect as described above can be obtained.

Embodiment 2
FIG. 10 shows an outline of a fixing device according to a second embodiment used in an image forming apparatus to which the present invention is applied. In the present embodiment, unlike the fixing device of the first embodiment (see, for example, FIG. 3), a pressure roll is provided instead of the endless belt to secure a fixing nip area. Components similar to those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted here.

In the present embodiment, a pressure roll 81 is provided at a position facing the fixing roll 41, and a facing portion between the pressure roll 81 and the fixing roll 41 is a fixing nip region.
The pressure roll 81 includes a cylindrical core 81a made of metal such as aluminum and an elastic layer 81b such as silicone rubber formed on the surface of the core 81a. The material of the core 81a is not particularly limited as long as it has mechanical strength and good thermal conductivity. For example, a metal or an alloy such as aluminum, stainless steel, steel, or brass is used. In addition, the elastic layer 81b is not limited to silicone rubber, and may be, for example, fluorine rubber as long as it has heat resistance. A method of forming the elastic layer 81b on the surface of the core 81a is not particularly limited, An injection molding method or a coating method can be employed. In this embodiment, the elastic layer 81b of the pressure roll 81 is harder than the elastic layer 41b of the fixing roll 41, and it is sufficient that the pressure roll 81 presses the fixing roll 41 in the fixing nip region. A fixing nip area is secured.

  Also in the present embodiment, since the peeling guide member 70 similar to that of the first embodiment is provided at a position facing the fixing roll 41 on the downstream side of the fixing nip region, the sheet S discharged from the fixing nip region is also provided. The peeling guide performance can be secured in the same manner as in the first embodiment.

In this example, the sheet peeling guide performance is evaluated and confirmed by the fixing device having the same configuration as that of the first embodiment.
The fixing roll in this embodiment has the following configuration. A steel cylindrical core having an outer diameter of 30 mm, a length of 360 mm, and a wall thickness of 0.35 mm is used, and the surface is coated with silicone rubber as an elastic layer to a thickness of 500 μm, and further, PFA is used as a release layer on the surface. Dip coat with a thickness of 30 μm. A 600 W halogen lamp was used as a heating source inside the core, and the surface temperature of the fixing roll was controlled to be maintained at 170 ° C.

  On the other hand, the endless belt has a peripheral length of 94 mm, a width (corresponding to the length direction of the fixing roll core) of 320 mm, a wall thickness of 75 μm as a base material, and PFA as a release layer on the outer peripheral surface of 30 μm. A thick coating was used.

In addition, as the peeling nip member, an aluminum member having a width of 5 mm (corresponding to the paper conveying direction), a height of 10 mm, and a length of 320 mm is used. As a curvature shape for forming the peeling nip region, the curvature radius is the center. It was 5 mm at the part and 30 mm at the end part, and it was processed so as to change smoothly in the meantime.
Further, a silicone rubber having a width of 10 mm, a length of 320 m, and a thickness of 5 mm was used as the prenip member, and the surface of this prenip member was a glass fiber base material bonded with PTFE as a low friction sheet.

Further, the peeling guide member is made of stainless steel, and the receiving part on the fixing roll side has an end protruding 5 mm from the central part. Moreover, the recessed part is provided with a rib, and the shape of the receiving part in the recessed part is provided with an inclination of 3 mm from the central part to the end part. Note that the receiving portion and the concave portion of the peeling guide member are coated with a fluororesin so that the frictional resistance with the paper is reduced.
And this peeling guide member is positioned and arrange | positioned by making the both ends of the receiving part contact a fixing roll. Needless to say, this contact position is outside the sheet conveyance area.

In the fixing device having such a configuration, an A4 size ST paper (trade name) manufactured by Fuji Xerox Co., Ltd. was used as the paper, and a solid chart on which 1.6 mg / cm ² toner was placed was used. (Jam) was confirmed.
As a result, no peeling failure occurred in the solid chart until the amount of margin at the front end of the paper reached 2 mm. Also, no paper wrinkles on the paper were confirmed.
The leading edge margin is a non-image area from the leading edge of the paper, and when it is reduced, it tends to be difficult to peel off due to the adhesive force of the toner.

For comparison, evaluation with a conventional configuration was performed as a peeling guide member. Specifically, a stainless steel plate having a thickness of 0.3 mm is coated with a fluorine resin, the gap between the peeling guide member and the fixing roll is 0.5 mm, and the distance from the fixing nip exit to the peeling guide member Was adjusted to 5 mm, and the same evaluation as described above was performed.
As a result, even when the tip margin was 4 mm, a peeling failure occurred.
From the above, the effectiveness of this case was confirmed.

(A) (b) (c) is explanatory drawing which shows the outline | summary of the fixing device based on this invention. 1 is an explanatory diagram showing Embodiment 1 of an image forming apparatus to which the present invention is applied. FIG. 2 is an explanatory diagram illustrating a fixing device according to a first embodiment. FIG. 3 is an explanatory diagram illustrating a nip state of a peeling nip member of the fixing device according to the first embodiment. FIG. 4 is an explanatory view showing a shape of a peeling nip member according to the first embodiment. (A) (b) is explanatory drawing which shows the shape of the peeling guide member of Embodiment 1. FIG. (A) (b) is explanatory drawing which shows an effect | action of the peeling nip member of Embodiment 1. FIG. It is explanatory drawing which shows the effect | action of the peeling guide member of Embodiment 1. FIG. It is explanatory drawing which shows the modification of the peeling guide member of Embodiment 1. FIG. 6 is an explanatory diagram illustrating a fixing device according to a second embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 (1a, 1b) ... Fixing member, 2 ... Recording material, 3 ... Separation guide member, 3a ... Member main body, 3b ... Reception part, 3c ... Recording material guide surface, 4 ... Recording material conveyance path, 5 ... Heat source, N: Contact nip area, T: Unfixed toner image

Claims (13)

A pair of fixing members that roll in contact with each other and heat and pressure-fix an unfixed toner image on the recording material in a contact nip region;
A peeling guide member provided opposite to the downstream side of the contact nip region of at least one of the fixing members, and for peeling and guiding the recording material from the fixing member;
The peeling guide member has a member body extending in the longitudinal direction of the contact nip region,
A receiving portion that continuously protrudes toward the fixing member side from the central portion toward both ends is formed at the fixing member side edge of the member main body, and both longitudinal ends of the member main body are disposed on the recording material conveyance path side of the member main body. Forming a recording material guide surface including a concave portion that is continuously spaced from the recording medium conveyance path toward the central portion ,
A fixing device, wherein the fixing unit is disposed in contact with the fixing member at a portion of the receiving portion where the recording material does not contact . The fixing device according to claim 1.
A fixing device, wherein a release layer for reducing frictional resistance with a recording material is provided on at least a receiving portion of the peeling guide member and a recording material guide surface. The fixing device according to claim 2.
A fixing device characterized in that a member main body of the peeling guide member is provided with a plurality of ribs along a recording material conveyance direction, and a tip locus of these ribs serves as a recording material guide surface. The fixing device according to claim 1.
The fixing device according to claim 1, wherein the peeling guide member has a heating source and is disposed opposite to a fixing member side facing an unfixed toner image surface. The fixing device according to claim 4 .
The other fixing member is an endless belt. The fixing device according to claim 5 .
A fixing device comprising: a peeling pressure member provided in contact with the back surface of the endless belt corresponding to the downstream side of the contact nip region and forming a peeling nip region between the fixing member and the endless belt. The fixing device according to claim 6 .
The contact length of the peeling nip area in the recording material conveyance direction by the peeling pressure member is set wider on the end in the longitudinal direction than the central part in the longitudinal direction of the peeling nip area. The fixing device according to claim 1.
The fixing device, wherein the receiving portion is formed in a smooth curved shape. The fixing device according to claim 1.
The fixing device is characterized in that both ends of the receiving portion are formed in a mountain shape. The fixing device according to claim 1.
The fixing device according to claim 1, wherein the receiving portion has a shape different from an exit shape of the contact nip region. The fixing device according to claim 10 .
The fixing device is characterized in that the exit shape of the contact nip region is such that the length of both end portions in the longitudinal direction is longer than the length of the central portion. An image carrier for carrying a toner image;
A transfer member for transferring the toner image on the image carrier onto a recording material;
An image forming apparatus comprising: a fixing device according to claim 1 for fixing an unfixed toner image transferred onto a recording material.   A peeling guide member used in the fixing device according to claim 1.

Images