JP5440356B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device that fixes an image transferred to a recording medium and an image forming apparatus including the fixing device.

  2. Description of the Related Art Image forming apparatuses such as copying machines, printers, and facsimiles are provided with a fixing device that fixes an image transferred as a toner image or the like on a recording medium such as paper by heat and pressure. Conventionally, a belt nip type fixing device using a fixing roller and a fixing belt has been put to practical use as such a fixing device.

  In this type of fixing device, a fixing roller having a heating source, a plurality of rollers around which the fixing belt is wound, and a pressure pad that contacts the fixing belt and urges the fixing belt from the inside to the outside of the belt And a sliding sheet covering the pressing pad. In such a fixing device, a rotary pressing roller and a pressing pad on the downstream side of the plurality of rollers press the fixing belt toward the fixing roller to form a nip region. Therefore, there is an advantage that the nip width can be widened as compared with a fixing device that does not have a fixing belt.

JP 2006-146156 A

As described above, in a conventional fixing device including a plurality of rollers, a fixing belt wound around the rollers, and a pressing pad that urges the fixing belt, the fixing belt, the rotating pressing roller, and the pressing pad include Since the pressure is reduced in the formed wedge-shaped space, the image on the recording medium has a glossy uneven glossiness, which may cause image defects.
More specifically, in the case of paper with low air permeability such as coated paper, there may be a portion where the air present in the unfixed toner layer has a low pressure. For this reason, if there is a portion where the pressing force by the pressing pad is low, a gap is generated at the interface between the fixing roller and the paper, and the toner image that is not completely fixed is disturbed, resulting in an image defect. End up.

  Therefore, by providing a pressing auxiliary member made of a metal rod at the downstream end of the pressing pad, or by forming a crease in the downstream end of the sliding sheet covering the surface of the pressing pad, the fixing belt and the rotating pressing roller An invention has been proposed in which a wedge-shaped space formed by a pressure pad is sufficiently filled with a sliding sheet to prevent a pressure drop at the nip portion (for example, a patent). Reference 1).

However, in the conventional belt nip type fixing device, as shown in FIG. 8A, the front and rear ends of the sliding sheet 56 are sandwiched between the front wall and the rear wall of the fixed pressing member 54 by pressing plates 58c and 58b. It was the structure fixed in the state which gave the space the center part of the moving sheet 56.
For this reason, when the sliding sheet 56 is pressed toward the fixing roller 51, as shown in FIG. 8B, the sheet entrance side of the sliding sheet 56 is deformed into a raised shape. Therefore, even if the solution as in the previous application is applied, the position of the crease provided at the downstream end of the sliding sheet is shifted, so that a desired pressing force cannot be applied, resulting in an image defect. Occurrence cannot be avoided sufficiently.

  Further, if the sliding sheet 56 is fixed in a state where a space is provided, the sliding sheet is loosened on the upstream side of the nip formed by the fixing roller 51 and the fixed pressing member 54, and is fixed. The belt and the paper are pushed up, and the image on the surface of the paper comes into contact with the fixing roller before entering the nip, or the sliding sheet generates undulation along the portion where the nip on the surface of the pressing pad is not formed. It has been found that there is a problem that the paper is pushed up non-uniformly, causing problems such as image distortion and gloss unevenness. The reason for fixing the sliding sheet 56 with a space in the center will be described later.

  The present invention has been made to solve such a conventional problem, and the object of the present invention is to shift the position of a fold provided on the nip downstream side of the sliding sheet or to loosen the sliding sheet. An object of the present invention is to provide a fixing device and an image forming apparatus that can prevent the occurrence of undulations and suppress the occurrence of image defects.

In order to achieve the above object, a fixing device according to claim 1 of the present invention includes:
A heating rotator with a heating source;
An endless belt disposed opposite to the heating rotator,
A plurality of rotating bodies around which the endless belt is wound;
Driving means for rotating the heating rotator or the endless belt;
A fixed pressing member that is disposed inside the endless belt and presses the endless belt toward the heating rotating body;
A sliding sheet covering the fixed pressing member;
A nip area is formed by pressing the endless belt toward the heating rotator by one of the plurality of rotating bodies and the fixed pressing member, and the image-formed paper passes through the nip area. A fixing device for fixing an image on paper,
On the downstream side of the nip region of the fixed pressing member, a protruding portion protruding into a space formed by the heating rotating body and one of the plurality of rotating bodies is provided,
A crease is formed on the downstream side of the nip region of the sliding sheet corresponding to the protruding portion of the fixed pressing member, and an upstream end portion of the nip region of the sliding sheet is formed on the fixed pressing member. It is fixed to a surface facing the heating rotator by a pressing member.

  According to the first aspect of the present invention, since the upstream end portion of the sliding sheet can be fixed to the fixed pressing member without making a crease, the sliding sheet may be loosened or wavy. It is possible to prevent the occurrence of image defects. Further, since the upstream end of the nip region of the sliding sheet is fixed to the surface of the fixed pressing member facing the heating rotator by the pressing member, the position of the crease provided on the downstream side of the sliding sheet nip is shifted during pressing. In the wedge-shaped space formed by the endless belt, one of the rotating bodies, and the fixed pressing member, the pressing force to the heating rotating body is reduced. It is possible to suppress the gaps in the unfixed toner layer at the interface between the heating rotator and the paper from disturbing the toner image and causing image defects.

According to a second aspect of the present invention, in the fixing device according to the first aspect,
The pressing member includes a horizontal piece substantially parallel to a surface of the fixed pressing member facing the heating rotator, and a vertical piece parallel to a front end surface substantially perpendicular to the surface of the fixed pressing member facing the heating rotator. And
A part of the sliding sheet is fixed to the surface of the fixed pressing member facing the heating rotating body by the horizontal piece, and the vertical piece is slid through a spacer between the front end surface of the fixed pressing member. The moving sheet is configured such that the end portion of the moving sheet is sandwiched without a crease.
According to the second aspect of the invention, the front end portion of the sliding sheet can be fixed to the fixed pressing member without a crease by the first pressing member having the horizontal piece and the vertical piece and the spacer, and the sliding sheet Since the front end is fixed to the surface of the first pressing member that faces the heating rotating body of the fixed pressing member, the sliding sheet can be pressed so that it does not shift back and forth during the pressing, thereby sliding during pressing. The sheet shape is stable, and the protruding portion having the fold of the sliding sheet on the downstream side of the nip region can give a stable pressing force toward the heating rotator.

The fixing device according to claim 3 is the fixing device according to claim 1 or 2,
The protruding portion of the fixed pressing member is provided with a pressing auxiliary member that is formed of a material having a rigidity higher than that of the surrounding material and is provided in parallel with the axial direction of the heating rotating body. The sheet is located inside the fold portion on the downstream side of the nip region of the sheet.
According to the third aspect of the present invention, when the fixed pressing member is pressed in the direction of the rotating body, the pressing auxiliary member is pressed against the rotating body via the sliding sheet, so that the endless belt and one In the wedge-shaped space formed by the rotating body and the fixed pressing member, it is possible to suppress a decrease in pressing force acting on the heating rotating body, and voids in the unfixed toner layer are formed at the interface between the rotating body and the paper. It is possible to suppress the occurrence of image defects due to disturbances.

According to a fourth aspect of the present invention, in the fixing device according to the third aspect,
The pressing assisting member is constituted by a bar-shaped member having an arc shape on at least the side facing the sliding sheet.
According to the fourth aspect of the present invention, the pressure distribution of the pressing force acting on the rotating body from the pressing auxiliary member via the sliding sheet is made gentle, and the wear of the sliding sheet is reduced to increase the component life. can do.

According to a fifth aspect of the present invention, in the fixing device according to any one of the first to fourth aspects,
The protruding portion having the crease formed on the downstream side of the nip region of the sliding sheet is set such that the length of the endless belt on the pressing side in the sheet transport direction is longer than the length of the non-pressing side in the sheet transport direction. It is characterized by.
According to the fifth aspect of the present invention, when a bird's beak-like protruding portion is formed on the downstream side of the nip region of the sliding sheet, and the pressing auxiliary member inside the sliding sheet is pushed upward by the fixed pressing member. In addition, since the endless belt can be pushed up at the top of the bird's beak, a larger pressing force can be applied to the fixing belt than when the pressing side and the non-pressing side have the same length.

The image forming apparatus according to claim 6,
An image forming apparatus that forms an image on a sheet by performing charging, image exposure, development, and transfer; and
The fixing device according to any one of claims 1 to 5, wherein an image on a sheet formed by the image forming device is fixed.
It is characterized by providing.

  According to the sixth aspect of the present invention, it is possible to prevent the position of the crease provided on the nip downstream side of the sliding sheet from being displaced, and the sliding sheet from being slackened or wavy, thereby preventing the image. An image forming apparatus capable of suppressing the occurrence of defects can be realized.

  According to the present invention, it is possible to prevent the occurrence of image defects by preventing the position of the crease provided on the nip downstream side of the sliding sheet from being displaced or the sliding sheet from being loosened or wavy. Advantageous fixing device and image forming apparatus can be realized.

1 is a schematic configuration diagram illustrating an image forming apparatus including a fixing device according to an exemplary embodiment. It is explanatory drawing which shows the detail of the shape of the axial direction of a rotation press roller. FIG. 2 is a configuration diagram showing details of a fixing device constituting the image forming apparatus shown in FIG. 1. It is a block diagram which shows the detail of the fixed press member in the fixing device of embodiment. (A) is an enlarged explanatory view showing a fixing method of the nip upstream end of the sliding sheet in the fixed pressing member of the embodiment, and (B) is a fixing method of the nip upstream end of the sliding sheet in the fixed pressing member. An enlarged explanatory view showing another example, (C) is an enlarged explanatory view showing another example of the protruding portion on the nip downstream side of the sliding sheet of the embodiment. 8A is an explanatory diagram showing pressure distribution along the conveyance direction of the nip region in the conventional fixing device of FIG. 8, and FIG. 5B is a conveyance of the nip region in the fixing device to which the embodiment of the present invention shown in FIG. 5 is applied. It is explanatory drawing which shows the pressure distribution along a direction. FIG. 6 is an explanatory diagram showing the relationship between the temperature of the fixing roller and the pressure in the nip region and the occurrence of image disturbance and gloss unevenness in a belt nip type fixing device. (A) is a schematic configuration diagram showing a conventional fixing device, and (B) is an explanatory diagram showing a state of a sliding sheet during pressing in the conventional fixing device.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing an embodiment of an image forming apparatus to which a fixing device according to the present invention is applied.
As shown in FIG. 1, an image forming apparatus 100 according to this embodiment includes a photosensitive drum 40 as an image carrier that carries a toner image, and a toner image carried by the image carrier on a sheet as a recording medium. The image forming apparatus includes a transfer unit 44 for transferring, a fixing device 50 for fixing the image by heating the paper on which the toner image is transferred, and the like.

  The surface of the photosensitive drum 40 as an image carrier is charged to a predetermined potential by a charger 41, and an image is exposed by the exposure means 42 to form an electrostatic latent image on the surface of the photosensitive drum 40. The developing device 43 develops the developer composed of toner and carrier and visualizes the toner image. The obtained toner image is transferred by the transfer means 44 to the paper P conveyed to the photosensitive drum 40. Then, the remaining toner of the transfer remaining on the surface of the photosensitive drum 40 after the transfer of the toner image is removed by the cleaner 45.

On the other hand, the paper P carrying the toner image is sent from the photosensitive drum 40 to the fixing device 50 and heated by a fixing roller 51 incorporating a heating unit, whereby the unfixed toner image on the paper P is fixed and an image is formed. The
The fixing device 50 that fixes the image is provided with a pressing unit 52 that presses the paper P toward the fixing roller 51 while transporting the paper P. The pressing means 52 is swingable in the vertical direction around a point C indicated by an X in FIG. 1 and is usually separated so that a slight gap is generated between the pressing means 52 and the fixing roller 51. When the paper P enters between the fixing roller 51 and the pressing unit 52, the pressing unit 52 is moved toward the fixing roller 51 and pressed.

FIG. 3 is a sectional side view showing details of the fixing device 50 according to the embodiment of the present invention.
As shown in FIG. 3, the fixing device 50 is configured as a belt nip type fixing device using a fixing roller 51 as a rotating body and a fixing belt 53 formed of an endless belt. The fixing belt 53 includes a plurality of fixing belts 53. It is wound around the outer periphery of the rollers 52a to 52d. A fixing pressing member 54 for pressing the fixing belt 53 toward the fixing roller 51 and a stay 55 made of a rigid member (metal) that supports the fixing pressing member 54 are provided inside the fixing belt 53. It has been.

  The stay 55 and the fixed pressing member 54 are pressed in a direction toward the fixing roller 51 by a compression spring (not shown). In this embodiment, the fixing roller 51 and the rotation pressing roller 52c are separately rotated by the rotation driving force transmitted from the driving source, and the fixing belt 53 is transferred by the rotation pressing roller 52c. However, either the fixing roller 51 or the rotation pressing roller 52c may be rotationally driven, and the other and the fixing belt 53 may be configured to rotate with the fixing pressing member 54 being pressed against the fixing roller 51. .

  The fixing roller 51 has a core metal 51a having an outer diameter φ80 and an elastic layer 51b having a thickness of 1.5 mm provided on the outer peripheral surface of the core metal 51a. The elastic layer 51b is made of silicone rubber. In the fixing roller 51, a release layer having a thickness of 50 μm is formed on the elastic layer 51b. This release layer is composed of a PFA (Perfluoroalkoxy) tube. Further, the fixing roller 51 has a halogen heater (heating source) 51c inside.

The fixing belt 53 includes a base made of polyimide having a thickness of 70 μm, an elastic layer made of silicone rubber having a thickness of 180 μm provided on the base, and a release layer made of a PFA tube having a thickness of 50 μm provided on the elastic layer. It is an endless belt.
The plurality of rollers 52a to 52c around which the fixing belt 53 is wound include an inlet roller 52a, a steering roller 52b, a rotation pressing roller 52c, and an auxiliary roller 52d. Among these, the inlet roller 52a is a rotating roller provided on the entrance side of the paper P, and is fixed so as not to change the transport path of the paper P. The steering roller 52b is urged by a spring (not shown) so as to apply a predetermined tension to the fixing belt 53.

  In addition, the inlet roller 52 a located on the paper entry side has a built-in heater and has a function of heating the fixing belt 53. Further, a lubricant supply member 57 that contacts the inlet roller 52a is provided, and the lubricant supply member 57 applies lubricant to the inner peripheral surface of the fixing belt 53 via the inlet roller 52a.

  The lubricant supply member 57 includes an oil impregnated member and an oil regulating film. The oil impregnated member is formed of felt such as aramid fiber, and is surrounded by an oil regulating membrane in which a PTFE porous membrane is formed in a bag shape. A porosity of about 30 to 80% is suitable for the oil regulating membrane. The oil impregnated member is impregnated with a lubricant in advance. The lubricant reservoir stores the lubricant and supplies the lubricant from the porous film of the oil regulating film on the outer peripheral surface. As the lubricant, for example, silicone oil such as dimethyl silicone oil having a viscosity of 100 to 1000 cs or dimethyl phenyl silicone oil having a viscosity of 100 to 1000 cs can be used.

  The steering roller 52b located on the upstream side in the belt conveyance direction of the inlet roller 52a functions so as to correct the shift of the fixing belt 22 by tilting the axis of the steering roller 52b by swinging at least one end thereof. Can be done.

  The rotation pressing roller 52c provided on the discharge side of the paper P is a solid roller made of SUS (Stainless Used Steel) having an outer diameter of φ20, and presses the fixing belt 53 toward the fixing roller at the nip exit. Are arranged as follows. Further, in order to keep the pressure distribution in the axial direction appropriate at the time of pressing, the rotary pressing roller 52c is formed to have a crown shape along the axial direction. Specifically, as shown in Fig. 2, the crown shape is 0.04mm added to the hyperbola with the central part 0.74mm from the center to 80mm on both ends, and the hyperbolic crown shape with the central part 0.74mm on the outside 110mm from the center. And it has a shape that connects them continuously.

  Further, a driving means (not shown) is connected to the rotation pressing roller 52c, and the fixing belt 53 is rotated by rotating the rotation pressing roller 52c. Further, the rotary pressing roller 52c presses the fixing belt 53 toward the fixing roller 51 by a pressing mechanism such as a spring. At this time, the rotation pressing roller 52 c presses the fixing belt 53 so as to bite into the elastic layer 51 of the fixing roller 51. The auxiliary roller 52d is a rotating roller that stretches the fixing belt 53 together with the other rollers 52a to 52c.

  The fixed pressing member 54 includes a pressing pad 54 a made of an elastic material and a support member 54 b made of a rigid material that supports the pressing pad 54 a. The pressing pad 54 a has a curved elastic layer close to the curvature of the fixing roller 51. Formed and pressed in the direction of the fixing roller to form a wide fixing nip. In this embodiment, the nip width is about 20 mm. The pressure pad 54a as an elastic layer is made of SUS with an outer diameter of φ0.8 as a pressing auxiliary member at the tip of the rotating pressing member side downstream of the nip, which is made of silicone rubber having a hardness of JISA1O ° on the upstream side of the nip. The rod 54c is provided. The support member 54b is preferably made of a metal such as stainless steel or aluminum.

  FIG. 4 shows a more detailed configuration of the fixed pressing member 54. As shown in FIG. 4, the fixed pressing member 54 is provided with a sliding sheet 56 that covers the upper portion thereof and reduces the sliding resistance between the fixed pressing member 54 and the fixing belt 53. The sliding sheet 56 is formed of a heat-resistant resin having a thickness of 90 μm, both front and rear ends are fixed to a metal stay 55 that fixes the fixed pressing member 54, and the upstream side of the nip is perpendicular to the sliding surface. The bottom surface of the nip is screwed with a surface along the side surface of the pad.

  Further, the nip downstream end of the sliding sheet 56 covering the surface of the pressing pad 54 a is creased, and a wedge-shaped space formed by the fixing belt 51, the rotating pressing roller 52 c and the pressing pad 54 a is formed on the sliding sheet 56. In this case, the pressure in the nip portion is prevented from being lowered.

  Further, the end of the sliding sheet 56 on the nip upstream side is sandwiched between the spacers 61 and 62, and is sandwiched between the stay 55 by a SUS reverse L-shaped presser plate 58a having a thickness of 0.2 mm. By being sandwiched, the fixed pressing member 54 is attached along the sliding surface. Further, by attaching the spacers 61 and 62 so as to create a space between the upper ends of the spacers 61 and 62 and the presser plate 58a, it is possible to prevent the sliding sheet 56 from being wrinkled by being sandwiched without a crease. Yes. On the other hand, the end on the downstream side of the nip is fixed by being sandwiched between the stay 55 by a flat plate press plate 58b made of SUS having a thickness of 0.2 mm.

  When the end of the sliding sheet 56 on the nip upstream side is fixed to the front wall surface of the fixed pressing member 54, it is also conceivable to crease the sliding sheet 56. However, in the present embodiment, as described above, a crease is formed on the nip downstream side of the sliding sheet 56. For this reason, when a crease is also formed on the nip upstream side of the sliding sheet 56, if the parallelism between the two folds is poor, the sliding sheet 56 is wrinkled, causing image unevenness. However, it is very difficult to process two folds with high parallelism on the sliding sheet 56.

  Therefore, in the present embodiment, as described above, the end of the sliding sheet 56 on the nip upstream side is curved without a crease by the inverted L-shaped presser plate 58a with the spacers 61 and 62 interposed therebetween. By fixing to the stay 55, wrinkles are prevented from occurring on the sliding sheet 56. Further, when the end of the sliding sheet 56 on the upstream side of the nip is pressed and fixed by the horizontal piece on the upper side of the inverted L-shaped pressing plate 58a, the fixed pressing member 54 is pressed to the fixing roller 51 side. In addition, the deformation of the upper portion of the sliding sheet 56 is more stable than in the case of FIG. Accordingly, it is possible to prevent the crease portion provided on the downstream side of the nip of the sliding sheet 56 from moving to the upstream side, and to prevent the pressure from locally changing and greatly decreasing the pressure distribution. it can.

  In short, the point of the present embodiment is that the end of the sliding sheet 56 on the nip upstream side is fixed without a crease and pressed down so as not to move back and forth. Therefore, from this point of view, it is not essential to use the inverted L-shaped presser plate 58a. For example, as shown in FIG. The upper end of the upright wall 55a provided at the front portion of 55 is sandwiched between flat plate-like presser plates 58c, and the end portion of the sliding sheet 56 is fixed to the front wall surface of the stay 55 with an adhesive or another flat plate-like presser. You may make it fix with a plate.

  Furthermore, in the present embodiment, a crease is formed on the nip downstream side of the pressing pad 54a on the upper side of the fixed pressing member 54 so as to protrude into a wedge-shaped space formed by the fixing roller 51 and the rotating pressing roller 52c. A rod 54c as a pressing auxiliary member made of a metal material is provided inside the protruding portion. The rod 54c is formed so as to be integrated with a pressing pad 54a made of silicone rubber by insert molding or the like. The rod 54c may be formed of a hard synthetic resin having heat resistance such as ceramic, PI, PPS, PEEK, or phenol resin.

  Since the fixing device 50 according to the present embodiment has the above-described configuration, the rotary pressing roller 52c and the pressing pad 54a press the fixing belt 53 toward the fixing roller 51 to form a nip region. Then, the fixing device 50 can fix an image made up of a toner image or the like on the paper P by heating when the paper P passes through the nip region.

In the belt nip type fixing device 50 as described above, in particular, the pressing pad 54a has a wedge-shaped protruding portion protruding toward the rotary pressing roller 52c, and, as described above, the sliding sheet 56 Since the crease is provided on the downstream side of the nip, the sliding sheet 56 protrudes into a wedge-shaped gap formed by the fixing roller 51 and the rotary pressing roller 52c, and this space can be filled. Thereby, the pressure drop at the time of the paper P passing between the press pad 54a and the rotation press roller 52c can be suppressed.
In addition, since the pressing pad 54a is provided with a hard rod 54c positioned inside the fold of the sliding sheet 56 at the tip of the wedge-shaped protrusion, the fixing belt 53 is interposed by the rod 54c via the sliding sheet 56. Can be strongly pressed to the fixing roller 51 side, and the pressure drop in the gap between the pressing pad 54a and the rotary pressing roller 52c can be suppressed.

  FIG. 6 shows the results of measuring the pressure distribution when the end of the sliding sheet 56 on the nip upstream side is fixed as shown in FIG. 5 and when the end is fixed as shown in FIG. Among these, FIG. 6A shows the case where the end of the sliding sheet 56 on the nip upstream side is fixed as shown in FIG. 8A, and FIG. 6B shows the case where it is fixed as shown in FIG. Is.

  Comparing FIG. 6 (A) and FIG. 6 (B), the pressure in the vicinity of the conveyance direction position of 20 to 21 mm corresponding to the gap position between the pressing pad 54a and the rotary pressing roller 52c is close to 20 kPa in FIG. 6 (A). 6B, the drop is about 100 kPa, and it can be understood that the pressure drop can be improved by nearly 80 kPa by applying this embodiment.

  By the way, it is known that image disturbance and gloss unevenness on the paper surface generated by the fixing device depend on the temperature of the paper, that is, the temperature of the fixing roller, and image distortion and gloss unevenness are more likely to occur as the temperature increases. However, the temperature of the fixing roller in the copying machine differs considerably between single copying and continuous copying, and even if it is set to 170 ° C. for single copying, it decreases to about 150 ° C. when continuous copying is performed. A single copy and a continuous copy are different in image quality. In addition, image disturbance and gloss unevenness on the paper surface that occur in the fixing device also change depending on the pressure in the nip region.

  FIG. 7 shows the relationship between the temperature of the fixing roller and the pressure in the nip region, and the occurrence of image disturbance and gloss unevenness obtained by experiments conducted by the present inventors. In FIG. 7, “X” indicates that an unacceptable image disturbance or gloss unevenness occurred, “◯” indicates that an image within an allowable range was obtained although there was some image disturbance or gloss unevenness, and “◎” indicates This means that good images without image distortion and uneven gloss were obtained. As shown in FIG. 7, when the fixing device of the above embodiment is used, as described above, the pressure in the nip area does not drop below 100 kPa, so the temperature of the fixing roller decreases to about 150 ° C. in continuous copying. Even if it does, it turns out that a favorable image is obtained.

Next, a modified example of the above embodiment will be described with reference to FIGS.
FIG. 5B shows an upright wall provided on the front portion of the stay 55 with an upper horizontal piece of an inverted L-shaped presser plate 58 a that fixes the end of the sliding sheet 56 on the nip upstream side to the stay 55. It is formed so as to be longer than the width of 55a, and the angle is adjusted so that the tip or the whole of the upper horizontal piece is slightly downward. According to this modification, even if the upper surface of the pressing pad 54a is lower than the upper surface of the upright wall 55a due to manufacturing errors or assembly errors, the sliding sheet 56 is pressed against the pressing pad 54a at the tip of the upper side of the pressing plate 58a. Therefore, there is an advantage that the sliding sheet 56 is prevented from shifting back and forth, and a stable pressing force can be obtained.

  In FIG. 5C, the shape of the protruding portion formed by making a crease downstream of the nip of the sliding sheet 56 is such that the length A of the upper surface is longer than the length B of the lower surface, that is, A> B This is a bird's beak shape. Here, the lengths A and B can be defined as distances from the contacts P1 and P2 between the rod 54c and the sliding sheet 56 to the bird's beak tip P0 of the sliding sheet 56, as shown in FIG.

  By configuring the protruding portion at the tip of the sliding sheet 56 as described above, the waist of the sliding sheet 56 when the rod 54c inside the sliding sheet 56 is pushed upward by the pressing pad 54a. By the action, the fixing belt can be pushed up at the top T of the bird's beak, and a larger pressing force can be applied to the fixing belt than when A = B. And when the fixing method of the sliding sheet 56 demonstrated in the said embodiment is applied to such an devised structure, since the shift | offset | difference of the sliding sheet 56 at the time of a press will decrease, the shape (( It is possible to maintain the shape and position of the bird's beak) almost as they are during pressing, and there is an advantage that a more stable pressing force can be applied to the fixing belt.

  As mentioned above, although this invention was demonstrated based on embodiment, this invention is not limited to this. For example, in the above embodiment, the shape of the rod 54c is a columnar shape, but it may be a semicylindrical shape or a semicircular column shape. In the above-described embodiment, the rod 54c that protrudes into the wedge-shaped space formed by the fixing roller 51 and the rotary pressing roller 52c is provided on the downstream side of the nip of the pressing pad 54a. The present invention can also be applied to a fixing device in which 54a does not have the rod 54c. Further, the fixed pressing member 54 is not limited to the one composed of the pressing pad 54a and the rigid support member 54b.

  Further, in the above-described embodiment, the other rollers 52a, 52b, 52d and the fixing belt 53 are rotated by the rotation of the rotary pressing roller 52c. However, the present invention is not limited to this, and the other rollers 52a, 52b, 52d and the fixing belt 53 itself. The rotation pressing roller 52c and the like may be configured to rotate by the rotation of. Further, the shape, structure, and material of the fixing roller 51, the fixing belt 53, and the fixed pressing member 54 described in the above embodiment can be changed as appropriate.

  As described above, the present invention is applied to a copying machine. However, the fixing device of the present invention is not limited to a copying machine, and for example, fixing that fixes an image transferred to a recording medium such as a printer or a facsimile. The present invention can be widely used for an image forming apparatus including the apparatus.

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 40 Photosensitive drum 41 Charging device 42 Exposure means 43 Developing device 44 Transfer means 45 Cleaner 50 Fixing device 51 Fixing roller (rotating body)
51a Metal core 51b Elastic layer 51c Halogen heater (heating means)
52 pressing means 52c rotating pressing roller (rotating pressing member)
53 Fixing belt (endless belt)
54 fixed pressing member 54a pressing pad (pressing member)
54b Support member (rigid member)
54c Rod (pressing auxiliary member)
55 Stay 56 Sliding sheet 57 Lubricant supply member 58a, 58b Presser plate (presser member)
61, 62 Spacer

Claims (6)

A heating rotator with a heating source;
An endless belt disposed opposite to the heating rotator,
A plurality of rotating bodies around which the endless belt is wound;
Driving means for rotating the heating rotator or the endless belt;
A fixed pressing member that is disposed inside the endless belt and presses the endless belt toward the heating rotating body;
A sliding sheet covering the fixed pressing member;
A nip area is formed by pressing the endless belt toward the heating rotator by one of the plurality of rotating bodies and the fixed pressing member, and the image-formed paper passes through the nip area. A fixing device for fixing an image on paper,
On the downstream side of the nip region of the fixed pressing member, a protruding portion protruding into a space formed by the heating rotating body and one of the plurality of rotating bodies is provided,
A crease is formed on the downstream side of the nip region of the sliding sheet corresponding to the protruding portion of the fixed pressing member, and an upstream end portion of the nip region of the sliding sheet is formed on the fixed pressing member. A fixing device, wherein the fixing device is fixed to a surface facing the heating rotator by a pressing member. The pressing member includes a horizontal piece substantially parallel to a surface of the fixed pressing member facing the heating rotator, and a vertical piece parallel to a front end surface substantially perpendicular to the surface of the fixed pressing member facing the heating rotator. And
A part of the sliding sheet is fixed to the surface of the fixed pressing member facing the heating rotating body by the horizontal piece, and the vertical piece is slid through a spacer between the front end surface of the fixed pressing member. The fixing device according to claim 1, wherein an end portion of the moving sheet is sandwiched without a crease.   The protruding portion of the fixed pressing member is provided with a pressing auxiliary member that is formed of a material having a rigidity higher than that of the surrounding material and is provided in parallel with the axial direction of the heating rotating body. The fixing device according to claim 1, wherein the fixing device is positioned inside a fold portion on the downstream side of the nip region of the sheet.   The fixing device according to claim 3, wherein the pressing auxiliary member is configured by a rod-shaped member having an arc shape on at least a side facing the sliding sheet.   The protruding portion having the crease formed on the downstream side of the nip region of the sliding sheet is set such that the length of the endless belt on the pressing side in the sheet transport direction is longer than the length of the non-pressing side in the sheet transport direction. The fixing device according to claim 1, wherein the fixing device is a fixing device. An image forming apparatus that forms an image on a sheet by performing charging, image exposure, development, and transfer; and
The fixing device according to any one of claims 1 to 5, wherein an image on a sheet formed by the image forming device is fixed.
An image forming apparatus comprising:

Images