JP5526520B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

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

An electrophotographic image forming apparatus includes a fixing device that forms a visible image using toner and fixes the visible image transferred onto a recording medium such as paper to a transfer paper or the like. In this fixing device, a pressure contact portion (nip) is formed by a fixing roller and a fixing belt that are heated and rotated, and a pressure roller and a pressure belt that are pressed and rotated. A recording medium (sheet base material) carrying the developed toner image is passed through the nip, and the toner image on the recording medium is melted and pressed to fix the image on the recording medium. The toner mainly composed of resin is melted and fixed on the recording medium at the press contact portion (nip). The toner melted at the time of fixing is also a cause of sticking to a fixing roller or a fixing belt by exerting adhesive force.
In order to prevent this unnecessary adhesion, a wax component is added to the toner, the surface of the fixing roller or fixing belt is coated with a releasable material, or the surface of the fixing roller or fixing belt is released with silicone oil or the like. By applying an agent or the like, the toner is prevented from adhering to the fixing roller or the fixing belt, or adhesive dust such as a composite of the toner and the recording medium is prevented from adhering to the fixing belt.

Furthermore, in order to prevent sticking to the fixing member, a sheet separation mechanism having a separation claw is attached to the fixing roller and the fixing belt to force the melted toner to wind the paper (recording medium) around the fixing roller and the fixing belt. Separation is also carried out.
In such a separation means using a separation claw, the separation claw and a fixing member such as a fixing belt or a fixing roller rub against each other, and the toner easily stays at a contact portion between the separation claw and the fixing member. There is a problem that the staying toner deviates at a certain time and contaminates the recording medium (sheet base material). Further, since the separation claw and the fixing member (fixing roller or fixing belt) are rubbed, a rubbing trace is generated on the fixing member, causing a decrease in the life of the fixing member, and the rubbing trace is being fixed. There is a problem that an abnormal image is generated by affecting the image. In particular, in recent fixing devices, releasability is imparted to the toner itself, and imparting releasability to the fixing roller and fixing belt of the fixing device tends to be excluded from inconvenience, and the above-mentioned problems Tend to become more prominent.

In order to solve the above-described problem, in the maximum image area (the maximum range in which a toner image can be formed on a transfer portion or a photosensitive member), a fixing member such as a fixing roller or a fixing belt is not used. Inventions relating to separation plates that separate in contact are known.
However, in order to exhibit or maintain the separation performance equivalent to that of the separation claw when the separation plate and the fixing member are not in contact with each other, the gap (gap) between the tip of the separation portion and the fixing member is as small as possible (for example, 0. 0). The gap must be managed while maintaining the distance (about 1 mm). Furthermore, it is necessary to arrange the front end of the separation portion immediately after (near) the nip.
In order to place the separation plate tip at the above position, there is a spatial limitation due to the position of the surface of the rotating body immediately after the nip where the separation plate tip is placed, minute fluctuations during driving, and installation conditions immediately after the nip. is there.

As such an invention, Patent Document 1 discloses an invention of a fixing device, and this publication discloses that a gap between a leading end of a separation guide and a rotating body is formed by an abutting portion outside the maximum image area. (Gazette 2nd page, left column, 6-8 lines, 42-45 line, 50 lines-right column, 6 lines, etc.).
In the configuration disclosed in the present invention, the separation guide is integrally formed of a heat-resistant resin, and this separation guide is easily warped, and a gap (gap) of 0.1 to 0.6 mm over the entire axial direction. ) Is very difficult to maintain. In recent years, in order to improve fixing performance and heat insulation, a foaming elastic layer is used for the fixing roller, and it is difficult to suppress not only the separation guide but also the fixing roller, so that warping and bending are increasingly occurring. It is easy to do.

Patent Document 2 discloses an invention in which a gap (gap) between the tip of the separation plate and the rotating body is managed by a contact member. The abutting member needs to have a thickness of at least 1 mm. In order to place the tip of the separation plate in the space immediately after the narrow nip, the contact position between the contact member and the fixing member (rotating body) and the tip of the separation plate A distance of about 6 mm is required between them.
It is difficult for the front end of the separation plate to respond sensitively to fluctuations on the surface of the rotating body, which is a fixing member adjacent to the front end of the separation plate, and the front end of the separation plate damages the fixing member (rotating body). There is a limit to narrowing the gap (gap) with the rotating body.
In recent years, in order to secure fixing properties in a small space, a sponge material such as foamed silicon is used for the elastic member of the fixing roller, and the amount of biting with the pressure roller is increased to widen the nip width. Further, when a foamed silicon is used as a fixing roller, a fixing device that shortens the rise time and consumes less power is also known. In such an invention, the above-mentioned problems tend to become more prominent.

As described above, in a fixing device in which a fixing roller using a sponge material such as foamed silicon has become mainstream, expectations for extending the life of the fixing roller are increasing. At the same time, the occurrence of the above-mentioned problems has become noticeable.
In order to solve these problems, a mechanism (pressure release mechanism) for releasing the pressure applied to the pressure roller is provided on the fixing roller after the end of the job or when not in use. However, the non-contact separation means disclosed in the above-mentioned document cannot cope with minute fluctuations on the surface of the fixing roller after the pressure is released by the pressure release mechanism. Specifically, when the pressure means such as the pressure roller is depressurized, the fixing roller bite is released and the surface of the rotating body immediately after the nip fluctuates so as to recover to the shape of the surface of the fixing roller before pressing. To do. Such a non-contact separation means cannot cope with a change in the shape state of the surface immediately after the nip, and the tip of the separation means damages the surface of the other rotating body (roller or belt). In order to prevent this from happening, the tip of the separating means is moved away from the position immediately after the nip until the position where the fluctuation (return to the original shape) does not affect, and also away from the surface of the rotating body (roller or belt). There is a need. It can be said that it is extremely difficult to re-set so as to ensure such separation ability.
Japanese Patent No. 2823168 JP 2006-11193 A JP 2008-83515 A

  In view of the above-mentioned problems of the prior art, the present invention is such that the tip of the separation means in a non-contact state reacts to fluctuations on the surface of the rotating body immediately after the nip and can maintain a separation performance equivalent to or exceeding that of a conventional separation claw It is an object of the present invention to provide a fixing device having separation means that can be close to the nip and close to the surface of the rotating body. Another object of the present invention is to provide a fixing device having a separating unit corresponding to a pressure-reducing mechanism for a long life of the fixing member, and to provide an image forming apparatus having such an excellent fixing device.

In order to solve the above problems, the invention of claim 1 is a fixing in which a sheet member having an unfixed toner image carried from the upstream of a nip portion formed by pressure contact between two fixing members is fixed by heating and pressing. In the apparatus, the apparatus further includes a separating unit provided downstream of the nip portion and separated from a surface having a fixing image of the sheet member carried out from the nip portion and one surface of the two fixing members. A separation plate formed uniformly within the maximum image area in the axial direction of the fixing member, a biasing means for biasing the tip of the separation plate, and disposed outside one of the maximum image areas of the fixing member; An abutting member that holds a minute gap between the fixing member and the tip portion, and the tip portion is configured separately from the base on which the abutting member is formed, and is arranged in the axial direction of the base Multiple in the provided groove Are clamped by screws, configured to freely adjust the gap relative to the fixing member in the axial direction by adjusting the plurality of screws, abutment of the abutting member in the rotation axis direction of the fixing member, The front end portion in the maximum image area substantially coincides with a radius of curvature of 0.6 mm or less, and the front end portion in the maximum image area is hemmed by folding a metal plate having a thickness of 0.2 mm or less. It is characterized by that.
According to a second aspect of the present invention, there is provided the fixing device according to the first aspect, wherein the front end portion of the separating means is formed with a fluorine coating layer.

According to a third aspect of the present invention, in the fixing device according to the first or second aspect , a roller that is rotatably supported is provided downstream from the leading end portion, and the sheet extends from the leading end portion to the roller. A guide member that guides the member is provided, and the guide member and the roller are characterized by a fixing device that is integrally installed on the base that constitutes the separating unit.
According to a fourth aspect of the present invention, in the fixing device according to any one of the first to third aspects, the foaming member layer is provided on the surface layer of the fixing member on the side provided with the separating means, and the elastic body. A fixing device having a fixing roller having at least a surface layer thereof, wherein the pressure roller pressed against the fixing roller is switchable between a pressure state and a pressure reduction state with respect to the fixing roller. Features.
According to a fifth aspect of the present invention, an image forming apparatus including the fixing device according to any one of the first to fourth aspects is characterized.

According to the present invention, highly stable separation performance can be ensured. Further, it is possible to prevent the front end portion of the separating means from damaging the fixing member. Furthermore, separation performance can be ensured without causing problems due to the separation claws.

Hereinafter, the invention of the fixing device and the like of the present invention will be described in detail by embodiments with reference to the drawings.
FIG. 1 is an example showing a main part of the fixing device of the present invention. The fixing device shown in FIG. 1 includes a fixing roller 1 and a heating roller 3 in a fixing belt 2. As an example of the configuration, the pressure roller 4 is pressed against the fixing roller 1 via the fixing belt 2 to form the nip portion N. A heat source (halogen heater) 7 is built in the heating roller 3 and the pressure roller 4, and a sheet body (recording medium) such as paper after development on which an unfixed toner image 6 is placed from the right side in the figure. 5) is placed on an endless fixing belt, and is conveyed by the fixing belt from the left side (upstream side) to the formed nip portion, and the sheet body 5 on which this unfixed image is placed is fixed. It is configured so that the developed image is fixed to the sheet member by being sandwiched at the nip portion N together with the belt, pressurized and heated.

The fixing belt 2 has a base layer made of, for example, a polyimide resin having an inner diameter of 75 mm and a thickness of about 90 μm, a silicon rubber layer having a thickness of 200 μm, and a PTFE-PFA (polytetrafluoroethylene having a thickness of about 20 μm as the outermost layer. -Perfluoroalkyl vinyl ether copolymer) layer.
The fixing belt 2 is stretched by, for example, a fixing roller 1 having an outer diameter of about 52 mm and a heating roller 3 made of an aluminum hollow cylinder having an outer diameter of about 35 mm and a thickness of about 0.6 mm. The fixing roller 1 has a heat-resistant / elastic layer made of foamed silicon rubber having an outer shape of about 52 mm and a thickness of about 14 mm, for example.
The pressure roller 4 is, for example, covered with a hollow steel core having a thickness of about 1 mm with silicon rubber having a thickness of about 1.5 mm, and the outermost layer is made of PTFE-PFA (polytetrafluoroethylene-perfluoroalkyl vinyl ether). Polymer) This is a roller having a tube, and its outer shape is about 50 mm.
The pressure roller 4 described above bites into the fixing roller 1 by about 3 mm via the fixing belt 2 to form a nip portion having a width of about 14 mm.
A separation claw 9 for separating the transfer paper (recording medium having a fixed image) 5 from the pressure roller 4 slides in contact with the pressure roller 4 downstream of the nip portion.

In the above-described configuration example of the fixing device according to the present invention, the present invention has been described as a configuration including a fixing roller and a fixing belt as a fixing member and a configuration including a pressure roller as a pressure member. You may employ | adopt or may employ | adopt the structure of a pressure roller and a pressure belt as a pressure member. For example, the pressure belt 2 may not be included as a fixing member, and the pressure roller 4 may be pressed against the fixing roller 1 to form the nip portion N. Both the fixing member and the pressure member may be used. It can also be configured to have a belt. When the fixing member is constituted by a fixing roller, heating means such as a halogen lamp is provided inside the fixing member.
If at least one of the two members (the fixing member and the pressure member) includes a belt, the diameter of the roller for stretching the belt is reduced in the central direction of the central axis of the roller. The portion can be disposed symmetrically with respect to the roller at both ends of the roller. This roller is preferably formed with a groove.

In the present invention, the fixing device is provided with a separating unit 8 for separating the transfer paper 5 from the fixing belt 2 on the side of the fixing belt 2 in contact with the fixing surface of the transfer paper (recording medium) 5 described above.
As shown in FIG. 2, the separating means 8 is configured to be rotatable around a rotation fulcrum 8 a of the separating means, the separating means rotating lever 10 is stretched by a spring 11, and the leading end portion of the separating means 8 is a fixing belt. It is configured to be urged in the direction of 2.
On the downstream side of the nip portion, separation means 8 for separating the paper from the fixing belt 2 is provided on the fixing side. The separating means 8 is supported so as to be swingable about a fulcrum 8a. A spring 11 is stretched between one end of the separating unit 8 and the fixing device frame, and urges the separating unit 8 counterclockwise in the drawing. Thereby, the leading end of the separating plate on the other end side of the separating unit 8 is urged toward the fixing belt 2.
On the downstream side of the nip portion, a sheet member (which may be referred to as a recording paper or a recording medium) 5 separated by the separation means 8 on the fixing member side and the separation means 9 on the pressure member side is a nip portion N (see FIG. 1). ) Is separated from the fixing member and the pressure member by the separation means 8 and the separation claw 57, and then guided to the fixing side guide plate and the pressure side guide plate and conveyed to the paper discharge unit.

FIG. 3 is a perspective view for explaining the configuration of the separation means 8 on the fixing side in more detail. FIG. 5 is an enlarged view of the separating means 8.
As shown in this figure, the separation plate 8c is composed of a base 8d and a tip member 8f. In addition, in a non-sheet passing region on both sides of the tip member 8f, an abutting member 8b which is a separate member is screwed to the base 8d. The leading end portion 8f of the separating means 8 can be disposed in the immediate vicinity of the nip immediately after the nip (near the nip portion and downstream thereof) by the abutting member 8b disposed outside the maximum image area.
FIG. 4 is a detailed enlarged view of a portion A shown in FIG. However, the abutting member 8b on the front side is shown in detail in a removed state.
In order to effectively ensure the separation ability between the fixing member and the sheet member after fixing by the separating means 8 shown in FIGS. 1 to 2, the tip 8f of the separating means shown in FIG. And close to the vicinity of the nip downstream portion side (in FIGS. 1 to 2, the fixing belt 2 is described as a fixing member in direct contact with the sheet member). The front end portion has a curvature shape and has a predetermined thickness, and is a gap management member for managing the distance (gap) between the front end member 8f of the separation plate and the fixing belt as the fixing member.
As can be seen from FIG. 5, the thin and sharp tip 8f and the curvature centers of the curvature shapes of the positioning members 8e on both sides are in the axial direction (the axial direction of the fixing roller 1 = the direction perpendicular to the paper passing direction). The positional relationship is substantially the same.

Specifically, as shown in FIG. 4, a contact member 8b, which is a separate member, is provided in the non-sheet passing region on both sides of the tip member 8f, and the tip of the separation plate 8 is fixed to the fixing belt by a spring 11 (FIG. 2). Even when biased in two directions, the abutting member 8b outside the sheet passing area contacts the surface of the fixing belt 2, and the tip member 8f (located in the sheet passing area) has a predetermined gap G with respect to the fixing belt 2. Can maintain a non-contact state.
In order to ensure separation performance with the non-contact type separation means 8, the tip member 8f of the separation plate 8c must be as close to the fixing belt 2 as possible and close to the vicinity of the downstream portion of the nip as shown in FIG. . The distance r between the nip downstream point and the leading end 8f of the separating means must be equal to or less than the margin W at the leading edge of the transfer paper defined in the product specifications. Further, from the tangent vector n of the nip exit portion, the leading end portion 8f of the separating means must be located on the fixing belt 2 side via the gap G.
Normally, the minimum margin W of the transfer paper 5 is 2 to 5 mm in accordance with the specifications of the image forming apparatus, and is adjusted by adjusting the radius of curvature of the abutting member 8b and the separating plate 8c at both ends outside the maximum image area. The gap G between the fixed end 8f of the separating means and the fixing belt 2 is managed within a range of 0.1 to 0.6 mm. Outside this range, the separation quality (separation performance) deteriorates. In order to satisfy the above configuration, the radius of curvature of the abutting member 8b is set to 0.6 mm or less, and the center of curvature of the abutting member 8b and the front end 8f of the separating means of the separating plate 8c substantially coincide in the axial direction. Placed in position.

With such a configuration, the separation means 8 used in the fixing device of the present invention can ensure separation performance equal to or higher than that of the separation claw (the separation member is in contact with the fixing member) by a non-contact method. Further, since the separating means 8 is not slid on the fixing belt 2 in the maximum image area, no sliding trace is generated, and there is no problem that it occurs in the image.
Similarly, since the fixing member is not slid in the sheet passing area unlike the conventional separation claw, the fixed toner does not collect between the tip member 8 f and the fixing belt 53.
Further, among the members constituting the separating means 8, only the contact member 8b described above is a rotating body (a member that is in sliding contact with the fixing belt 2 and has the shortest life, but the contact member 8b is configured as a separate part. Therefore, it is only necessary to replace the contact member 8b at the time of maintenance, and there is a merit that the running cost can be reduced. In this embodiment, a contact-type separation claw 9 is used for the pressure roller 4 because problems such as occurrence of an abnormal image after sliding hardly occur.

  As shown in FIGS. 3 and 4, the tip of the separation plate 8c is subjected to a hemming process (preferably a hemming process bent 180 degrees) by folding a metallic flat plate having a thickness of 0.2 mm or less, and will be described later. As described above, a coat layer made of a fluororesin is formed. By this processing, an R is formed at the front end portion 8f of the separation plate, and no scratches or the like are caused on the recording medium image peeled off by the separation means 8. Further, even when the leading end 8f of the separation plate 8c touches the fixing belt 2 when there is an abnormality such as a paper jam or the like, the leading end, which is the contact portion, is formed with a layer coated with a fluororesin. Even if they are combined, the fluororesin coat layer of the layer in contact with the tip is an elastomer, has a low surface free energy, and an extremely high melting point, so that no flaws are generated on the fixing belt 2. Thus, the gap G (see FIG. 4) is maintained substantially the same at the tip of the separation plate 8c due to high elasticity by hemming.

Further, as shown in FIG. 3, the separating means 8 has the abutting members 8b arranged at both ends outside the maximum image area, so even if the rubbing rubbing is generated by the abutting member 8b, this is the maximum. It is outside the image area and therefore does not affect the image fixed on the sheet member.
Similarly, the separation plate 8c used in the fixing device of the present invention, such as the separation claw, has a gap between the fixing member and the gap G, and is not directly rubbed. The fixed toner does not stay with the fixing belt 2. Further, since the leading end of the separation plate 8c is formed into an R shape by hemming processing, no damage is generated on the image, and even if it contacts the fixing belt 2 at the time of an abnormality such as a paper jam, there is no damage on the fixing belt 2. Is not generated.
With the above configuration, since the fixing belt 2 and the separating unit 8 are not in contact with each other in the maximum image area, no sliding rubbing is generated on the fixing member, and thus the image is not affected.
In the present invention, as shown in FIG. 4 to FIG. 5, the portion adjacent to the fixing belt 2 and the recording medium (sheet member) 5 of the tip 8 f of the separation plate 8 c obtained by bending a metallic plate of 0.2 mm or less by 180 degrees are provided. A fluorine coating layer 8e using a material such as PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) or PTFE (polytetrafluoroethylene) is formed on the surface layer through the primer layer in the paper passing area. Yes.
The fluorine-based coat layer 8e has good releasability with respect to the toner 6, and the separation plate 8c is not fixed and contaminated by the toner 6. Further, the coating layer is excellent in slidability with the fixing belt 2, and even if the front end 8f of the separation plate and the fixing belt 2 come into contact with each other or rub against each other, the coating layer is an elastomer and an elastic resin. There is an effect that the belt 2 is hardly damaged.

6 shows a cross-sectional view taken along line BB and CC shown in FIG.
As shown in FIG. 6, the separating unit 8 is installed with a roller 8 h rotatably supported at a position corresponding to the downstream side in the conveyance direction of the recording medium P with respect to the nip portion. The rollers 8h assist the conveyance of the recording medium P sent from the nip portion.
A guide member 8g is installed between the separation plate 8c (tip portion 8f) and the roller 8h. The guide member 8g guides the recording medium P delivered from the nip portion toward the roller 8h.
With such a configuration, the recording medium P sent out from the nip portion is conveyed away from the separation plate 8c by the guide member 8g and the roller 8h. Therefore, it is possible to prevent a problem that the image surface of the recording medium P is brought into sliding contact with the separation plate 8c after the separation step and an abnormal image such as a rubbing image is generated. The guide member 8g and the roller 8h are integrally configured and installed with respect to the base 8d. For this reason, the relative position with respect to the front end portion 8f is kept constant, and the transportability of the recording medium P is stabilized.
As described above, the center of curvature of the curvature portion 8e of the contact member 8b is configured to coincide with the front end portion 8f of the separation plate 8c (separation member), or a plurality of separation plates 8c are provided in the width direction. The relative position with respect to the contact member 8b can be adjusted. As a result, wear and damage to the fixing belt 2 (opposing member) and the separation plate 8c are suppressed, and abnormal images such as a stain image after the nail are suppressed, and the separation property with respect to the recording medium P is maintained well. can do.

FIG. 7 is a view of the separating means 8 (with the guide plate removed) shown in FIG. 3 as viewed from below. As shown in FIG. 7, the separation plate 8c is provided with four U-shaped holes in the axial direction, and the U-shaped holes are fitted in grooves 8j provided in the screws 8i.
Then, the screw 8i is fastened to the base 8d integrated with the abutting member 8b by a screw, and the screw 8i is tightened or loosened to prepare the front end 8f of the separation plate.
As shown in FIG. 6, the screw 8 i is tightened to adjust the position of the tip 8 f of the separation plate in the cross section taken along the line BB, and the screw 8 i is loosened in the cross section CC along the tip of the separation plate. The position of 8f is adjusted. And the clearance gap between the fixing belt 2 which is a fixing member and the front-end | tip part 8f of a separation plate is adjusted so that it may become the range of 0.1-0.5 mm as a whole. With the above configuration, the gap (gap) between the front end 8f of the separation plate 8c and the fixing belt 2 as a fixing member can be managed with high accuracy.

8 and 9 are views showing the movement of the pressure release mechanism of the pressure roller 4.
Since the material of the fixing roller 1 on the side provided with the separating means 8 is made of a silicone foam member, the structure is excellent in elasticity, and the pressure roller 4 bites in by about 3 mm to form a nip portion. . For this reason, in this configuration, the countermeasures against the problem of compression set of the fixing roller 1 and the reduction in the service life are taken as follows.
As a countermeasure, in this embodiment, the pressure roller 4 is provided with a pressure reduction switching mechanism for the fixing roller 1.
Specifically, when the recording medium 5 passes, the eccentric cam 13 is in a state as shown in FIG. 8, the pressure lever 12 is pushed up, and the amount of biting of the pressure roller 4 to the fixing roller 1 via the fixing belt 2 is increased. 3 mm. On the other hand, when the recording medium 5 is not transported to the fixing device, such as in the standby state, at the start-up, or in the OFF state, the eccentric cam 13 rotates to the state shown in FIG. 9 and the pressure lever 12 is lowered, and the pressure roller via the fixing belt 2. 4 is provided with a mechanism for reducing or separating the amount of biting into the fixing roller 1.
In order to ensure separation performance with the non-contact type separation means 8, if the position of the separation means tip 8f is arranged in the state shown in FIG. 5, the pressure roller 4 releases the distortion of the fixing roller 1 when the pressure is reduced. As a result, the position of the surface of the fixing belt 2 reaches the position of the leading end 8f of the separating means during pressurization (see FIG. 10).
However, even if the property state of the surface of the fixing belt 2 in the vicinity of the separation means tip 8f changes due to the configuration of the separation means 8, the separation portion tip 8f reacts via the curvature shape 8b at both ends outside the maximum image area. Therefore, it is possible to prevent the surface of the rotating body from being damaged by the separation portion tip 8f.

Next, an image forming apparatus having the fixing device of the present invention will be described with reference to FIG.
FIG. 11 is a schematic diagram showing a configuration example of an image forming apparatus provided with the fixing device of the present invention.
The paper feed unit 31 conveys the paper to the transfer unit.
On the other hand, the writing unit 32 exposes the photosensitive member in the image forming unit 33 by a signal from a scanner or a signal from a printer. The latent image exposed on the photosensitive member is formed on the transfer belt by the image forming unit 33, and the unfixed toner image is transferred to the transferred transfer paper by the transfer unit 34. The unfixed toner image is fixed by the fixing unit 35. Further, at the time of double-sided printing, the recording medium 5 is reversed by the double-sided unit 36 and conveyed again to the transfer unit.
The above configuration ensures separation performance without causing problems due to separation claws, achieves a longer life, and provides an image forming apparatus with improved fixing performance and shorter rise time with a foamed material fixing roller that consumes less power. can do.

Now, a case where copying is performed using the color copying machine configured as described above will be described. First, the document is set on the document table of the automatic document feeder 37. Alternatively, the automatic document feeder 37 is opened to set a document on the contact glass of the scanner, and the automatic document feeder 37 is closed and pressed.
When a start switch (not shown) is pressed, when a document is set on the automatic document feeder 37, the document is transported and moved onto the contact glass, and then the document is set on the other contact glass. Immediately, the scanner is driven and the first traveling body and the second traveling body travel. Then, light is emitted from the light source, reflected light from the document surface is reflected by a mirror, and is input to a reading sensor through an imaging lens to read the content of the document.
When the start switch is pressed, the intermediate transfer belt rotates, and at the same time, the individual image forming units 33 rotate the photoconductors 33-1 so that black, cyan, and magenta are respectively formed on the photoconductors 33-1. A yellow single color image is formed. As the intermediate transfer belt runs, the single color images are sequentially transferred to form a composite color image on the intermediate transfer belt.
Further, by pressing the start switch, the sheet is fed out from one of the sheet feeding cassettes of the sheet feeding unit 31, separated one by one by the separation roller, put into the sheet feeding path, and conveyed by the conveying roller to be copied by the copying machine main body 30. The paper is guided to the inner paper feed path and abutted against the registration roller 34-2 and stopped. Alternatively, when manual feed is selected, the sheets are fed out from the manual feed tray, separated and fed one by one, and abutted against the registration roller 34-2 and stopped.

Then, the registration roller 34-1 is rotated in synchronization with the composite color image on the intermediate transfer belt, and the sheet is fed between the intermediate transfer belt 34-1 and the secondary transfer device 34-3, and the secondary transfer device. A full color image is recorded on the sheet by transferring at 34-3.
The image-transferred sheet is conveyed by the secondary transfer device 34-3 and sent to the fixing device 35. The fixing device 35 applies heat and pressure to fix the transferred image, and then the sheet is discharged outside by the discharge roller. And stacked on the paper discharge tray 38. Alternatively, the sheet is switched by the switching claw and put into the sheet reversing device 39, where it is reversed and guided again to the transfer position, and the image is recorded also on the back surface, and then discharged onto the paper discharge tray 38.
The fixing device 35 includes the separation unit 8 as described above, and the separation unit 8 of this example has a separation performance equal to or higher than that of the contact-type separation claw by a non-contact method. Therefore, an excellent separation performance and a high-quality image can be obtained without causing a sliding trace in the image. In addition, since it is a non-contact type, the fixed toner does not collect at the tip of the separation plate, and it can cope with fluctuations of the fixing member at the time of depressurization, and is excellent in running cost. Since the pressure roller can be depressurized, the life of the fixing device is also long. The fixing device of this embodiment is a belt fixing device that forms a nip with a fixing roller having an elastic layer, and provides a fixing device and an image forming device that have excellent fixing performance, have a short rise time, and consume less power. Can do.
As mentioned above, although this invention was demonstrated by the example of illustration, this invention is not limited to this.

The configuration of the fixing device can be appropriately changed within the scope of the present invention. For example, a fixing roller or a pressure roller having an appropriate configuration can be used, and a tension belt form of the fixing belt is also arbitrary. The present invention can also be applied to a heat roll type fixing device that does not use a fixing belt. The heat source for heating the fixing member is not limited to a heater such as a halogen heater, and induction heating means can also be employed. A configuration using a pressure belt is also possible on the pressure side.
Further, the image forming apparatus is not limited to a full-color apparatus, and may be a monochrome apparatus or a multi-color image forming apparatus. Further, the configuration of the image forming unit and the like of the image forming apparatus is arbitrary. For example, when a color image forming apparatus is used, a configuration in which a plurality of developing devices are arranged around one image carrier can be adopted. Further, a direct transfer method may be adopted. Further, the image forming apparatus is not limited to a copying machine, but may be a printer, a facsimile, or a multifunction machine having a plurality of functions.

It is a figure which shows the operation example of the fixing device of this invention. 1 is a diagram illustrating a configuration of a fixing device of the present invention. FIG. 6 is a diagram for explaining the configuration of the fixing-side separating unit 8 in more detail. FIG. 3 is an enlarged detail view of a separating unit used in the fixing device of the present invention. FIG. 3 is a detailed enlarged view of a portion A shown in FIG. 2 (however, the abutting member 8b on the near side is shown in detail in a removed state). 4 is a cross-sectional view taken along line BB (denoted as (cross section B)) and line CC (denoted as (cross section C)) shown in FIG. 3. It is the figure which looked at the isolation | separation means 8 (state which removed the guide plate) shown in FIG. 3 from the bottom. It is the figure which showed the motion of the depressurization mechanism of a pressure roller (4). It is the figure which showed the motion of the depressurization mechanism of a pressure roller (4). It is the elements on larger scale which show the vicinity of the front-end | tip part of a separation plate. 1 is a schematic diagram illustrating a configuration example of an image forming apparatus provided with a fixing device of the present invention.

Explanation of symbols

  1 fixing roller, 2 fixing belt, 3 heating roller, 4 pressure roller, 5 sheet member (recording medium), 6 toner (toner for development), 7 heater, 8 separating means (fixing member side separating means), 8a Separation unit rotation support shaft, 8b contact member, 8c separation plate, 8d base material, 8e curvature shape portion, 8f separation plate tip, 8g guide member, 8h roller, 8i screw (fixing member), 8j screw groove portion, 9th 2 separation claw (pressure member side separation claw), 10 lever, 11 spring, 12 pressure lever, 13 eccentric cam, 30 image forming device, 31 paper feed unit, 32 writing unit, 33 image forming unit, 33-1 Photosensitive drum, 34 transfer unit, 34-1 intermediate transfer belt, 34-2 registration roller, 34-3 secondary transfer device, 35 fixing unit (fixing device), 3 Duplex unit, 37 an automatic document transport unit, 38 paper discharge tray, 39 sheet reversing device

Claims (5)

In a fixing device that heats and pressurizes a sheet member having an unfixed toner image carried from the upstream of a nip portion formed by pressure contact of two fixing members,
Separating means provided downstream of the nip portion and separated from one surface of the two fixing members and a surface having a fixing image of the sheet member carried out from the nip portion,
The separation unit includes a separation plate that is uniformly formed in a maximum image area in the axial direction of the fixing member, a biasing unit that biases a front end portion of the separation plate, and one maximum image of the fixing member. An abutting member that is disposed outside the region and holds a minute gap between the fixing member and the tip,
The tip is configured separately from the base on which the abutting member is formed, and is sandwiched by a plurality of screws in a groove provided in the axial direction of the base, and by adjusting the plurality of screws The gap with respect to the fixing member in the axial direction is adjustable,
The abutting portion of the abutting member substantially coincides with the tip end portion in the maximum image area in the rotation axis direction of the fixing member, has a radius of curvature of 0.6 mm or less, and is in the maximum image area. A fixing device in which a tip portion is hemmed by folding a metal plate having a thickness of 0.2 mm or less. The fixing device according to claim 1,
A fixing device according to claim 1, wherein a fluorine coating layer is formed at a tip of the separating means. The fixing device according to claim 1 or 2 ,
A roller supported rotatably is provided downstream from the tip,
A guide member for guiding the sheet member from the tip portion to the roller is provided;
The fixing device, wherein the guide member and the roller are integrally installed on the base body constituting the separating means. The fixing device according to any one of claims 1 to 3 ,
The surface of the fixing member on the side provided with the separating means has a foam member layer, and has a fixing roller having an elastic body at least on the surface layer.
The fixing device, wherein the pressure roller pressed against the fixing roller is configured to be switchable between a pressure state and a pressure reduction state with respect to the fixing roller. An image forming apparatus characterized in that it comprises a fixing device according to any one of claims 1 to 4.

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