JP6928891B2 - Fixing device and image forming device - Google Patents

Description

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

Conventionally, it has a winding member around which an endless fixing belt is wound, a nip forming member that abuts on the winding portion of the fixing belt with respect to the winding member from the outside of the loop to form a fixing nip, and a posture deforming member that deforms the belt posture. Fixing devices are known. The posture deforming member abuts on the portion downstream of the anchoring nip in the belt moving direction and near the exit of the nip from the back surface side of the belt in the entire area in the circumferential direction of the anchoring belt, and the posture deforming member is in contact with the portion and the vicinity thereof. It transforms.

The fixing device described in Patent Document 1 also has such a posture deforming member. Then, after the image is fixed to the recording sheet sandwiched between the fixing nips, the recording sheet is discharged from the fixing nip. At this time, if the recording sheet is thin paper, it may remain wrapped around the belt without being peeled off from the fixing belt, causing jam. Therefore, it is said that by deforming the belt posture in the vicinity of the outlet of the fixing nip by the posture deforming member (pad in Patent Document 1), it is possible to suppress the wrapping of thin paper around the fixing belt as compared with the case where it is not deformed. ..

However, this fixing device has a problem that the fixing belt is damaged by rubbing the recording sheet against the fixing belt in the vicinity of the posture deforming member.

In order to solve the above-mentioned problems, the present invention presents an endless fixing belt, a winding member around which the fixing belt is wound around itself inside the loop of the fixing belt, and a loop outside at a winding portion of the fixing belt with respect to the winding member. From the back side of the belt to the nip forming member that abuts from the fixing nip and the entire area in the circumferential direction of the fixing belt, which is downstream of the fixing nip in the belt moving direction and near the exit of the nip. In a fixing device having a posture deforming member that abuts and deforms the belt posture in the portion and its vicinity and fixes an image on a recording sheet sandwiched between the fixing nips, the fixing belt in the posture deforming member and the fixing belt. The contact portion is surface-moved in the same direction as the fixing belt, and the posture deforming member is formed by a driven rotating body that is carried around the fixing belt, and the entire area in the circumferential direction of the fixing belt is formed. The front surface of the region in which the posture deforming member is in contact is made non-contact with the nip forming member, and the center of the posture deforming member made of the roller-shaped driven rotating body in the direction of the rotation axis. The diameter of the portion is made larger than the diameter of both ends, the nip forming member is formed by a roller-shaped rotating body, and the diameter of the central portion of the nip forming member in the direction of the rotation axis is made smaller than that of both ends. The distance between the ends, which is the distance between the end portion of the deformable member in the rotation axis direction and the portion of the nip forming member facing the end portion, is defined as the central portion of the posture deforming member in the rotation axis direction and the said. The nip forming member is characterized in that it is made larger than the distance between the central portions, which is the distance from the portion facing the central portion.

According to the present invention, there is an excellent effect that scratches on the fixing belt due to rubbing the recording sheet against the fixing belt in the vicinity of the posture deforming member can be suppressed.

The schematic block diagram which shows the printer which concerns on embodiment. The block diagram which shows the fixing device of the printer. An enlarged configuration diagram showing an enlarged posture-changing member of the fixing device and its surroundings. The graph which shows the relationship between the scratch length (the length in the belt movement direction) in the fixing belt which was damaged by the recording sheet by the operation for a long period of time, and the mode of a posture-deforming member. The graph which shows the relationship between the regeneration polishing time of a damaged fixing belt, and the aspect of a posture deforming member. The front view which shows the posture deformation member of the fixing device. The front view which shows the posture change member and a pressure roller of the fixing device. The front view which shows the posture change member and the pressure roller of the fixing device of the printer which concerns on a modification. An enlarged configuration diagram showing an enlarged posture-changing member of a fixing device of a printer according to an embodiment and its surroundings.

Hereinafter, an embodiment of an electrophotographic printer will be described as an image forming apparatus to which the present invention is applied.
First, the basic configuration of the printer according to the embodiment will be described. FIG. 1 is a schematic configuration diagram showing a printer according to an embodiment. In the figure, the printer 100 has a paper feed unit (paper feed table) that supplies a recording sheet housed therein to the paper feed path, and a printer unit mounted on the paper feed unit (paper feed table). The subscripts Y, M, C, and K attached to the end of the symbols in the figure indicate that the members are for yellow, magenta, cyan, and black (black).

Near the center of the printer unit, an endless intermediate transfer belt 10 is provided which is hung around a plurality of support rollers 14, 15, 15', 16, 63 and can move endlessly in the clockwise direction in the drawing. The belt cleaning device 17 is in contact with the cleaning backup roller from the belt front surface side in the entire area of the intermediate transfer belt 10 in the circumferential direction. The belt cleaning device 17 removes the transfer residual toner remaining on the front surface of the intermediate transfer belt 10 after passing through the secondary transfer nip described later.

The region between the drive roller 14 as the support roller and the support roller 15 extends in the substantially horizontal direction in the entire area of the intermediate transfer belt 10 in the circumferential direction. A tandem image forming unit 20 is arranged on the region. The tandem image forming unit 20 has four image-forming units 18Y, 18M, 18C, and 18K for yellow, magenta, cyan, and black arranged along the belt front surface facing the belt front surface. There is.

An optical writing device 21 as a latent image writing means is provided on the tandem image forming unit 20. The image forming units 18Y, 18M, 18C, 18K of the tandem image forming unit 20 are drum-shaped photoconductors 40Y, 40M, 40C as a latent image carrier on which latent images of each color of yellow, magenta, cyan, and black are formed. , 40K. The surface of the photoconductors 40Y, 40M, 40C, 40K is uniformly charged by the charging devices 60Y, 60M, 60C, 60K (for example, -650V), and then the light writing device 21 drives the light source based on the image data. Is lightly scanned by. The light-irradiated portion on the surface of the photoconductors 40Y, 40M, 40C, and 40K generated by this light scanning attenuates the potential (for example, -50V) to form an electrostatic latent image.

The electrostatic latent image formed on the surface of the photoconductors 40Y, 40M, 40C, 40K is developed by the developing apparatus 59Y, 59M, 59C, 59K to become a Y, M, C, K toner image. To the developing devices 59Y, 59M, 59C, 59K, Y, M, C, K toners are supplied from the toner bottles 50Y, 50M, 50C, 50K as needed. In the developing apparatus 59Y, 59M, 59C, 59K, the mixture is stirred as a Y, M, C, K developer in which Y, M, C, K toner and a magnetic carrier are mixed. The Y, M, C, K toners in the Y, M, C, K developer are triboelectrically charged (eg, -30 μC / g). Development rollers for Y, M, C, and K are arranged in the developing devices 59, 59M, 59C, and 59K, respectively. The developing rollers for Y, M, C, and K expose a part of the peripheral surface thereof to the outside through an opening provided in the casing to face the photoconductors 40Y, 40M, 40C, and 40K. The Y, M, C, K developer pumped up by the developing rollers for Y, M, C, and K is conveyed to the developing region facing the photoconductors 40Y, 40M, 40C, and 40K as the rollers rotate. .. In the developing region, negative electrode toner is applied from the roller side to the latent image side between the electrostatic latent image of the photoconductors 40Y, 40M, 40C, 40K and the developing roller to which the development bias (for example, -500V) is applied. The developing potential to move acts. From this development potential, the Y, M, C, K toners on the developing rollers for Y, M, C, K are separated from the magnetic carrier and transferred to the electrostatic latent image of the photoconductors 40Y, 40M, 40C, 40K. .. As a result, the electrostatic latent images of the photoconductors 40Y, 40M, 40C, and 40K are developed by the Y, M, C, and K toners to become Y, M, C, and K toner images.

Primary transfer rollers 62Y, 62M, 62C, 62K are arranged under the photoconductors 40Y, 40M, 40C, 40K, and the intermediate transfer belt 10 is pressed toward the photoconductors 40Y, 40M, 40C, 40K. ing. As a result, primary transfer nip for Y, M, C, K in which the photoconductors 40Y, 40M, 40C, 40K and the intermediate transfer belt 10 come into contact with each other is formed. Around the primary transfer nip for Y, M, C, K, the primary transfer rollers 62Y, 62M, 62C, 62K to which the primary transfer bias is applied, and the electrostatic latent images of the photoconductors 40Y, 40M, 40C, 40K. A primary transfer electric field is formed between the two.

When the printer 100 receives the image data, the drive roller 14 is rotationally driven by the driving means to move the intermediate transfer belt 10 endlessly in the clockwise direction in the drawing. At the same time, the image forming units 18Y, 18M, 18C, 18K are driven to form Y, M, C, K toner images on the photoconductors 40Y, 40M, 40C, 40K. These toner images are primarily transferred by superimposing them on the front surface of the intermediate transfer belt 10 with the primary transfer nips for Y, M, C, and K. As a result, a four-color superimposed toner image is formed on the front surface of the intermediate transfer belt 10.

When forming a black monochromatic image on the intermediate transfer belt 10, the support rollers 15 and 15'other than the drive roller 14 are moved, and the yellow, magenta, and cyan photoconductors 40Y, 40M, and 40C are intermediate. It is also possible to separate it from the transfer belt 10.

On the surface of the photoconductors 40Y, 40M, 40C, 40K after passing through the primary transfer nips for Y, M, C, and K, the transfer residual toner that has not been primarily transferred to the intermediate transfer belt 10 is attached. The transfer residual toner is removed from the surface of the photoconductors 40Y, 40M, 40C, 40K by the drum cleaning devices 61Y, 61M, 61C, 61K, and then transferred to a waste toner bottle.

The surfaces of the photoconductors 40Y, 40M, 40C, 40K after cleaning are uniformly charged again by the charging device 60Y, 60M, 60C, 60K.

The printer 100 selectively rotates one of the paper feed rollers 42 on the paper feed table 200 of the paper feed unit. As a result, the recording sheet is fed out from one of the plurality of paper cassettes 44 provided in multiple stages in the paper bank 43. Then, the recording sheets are separated one by one by the separation roller 45 and sent to the paper feed path 48, and then conveyed by the transfer roller 47 to enter the paper feed path 48 of the printer unit. The recording sheet that has entered the paper feed path 48 of the printer unit abuts on the resist nip of the resist roller vs. 49 and stops.

A secondary transfer device 22 is arranged below the intermediate transfer belt 10. In the secondary transfer device 22, the secondary transfer roller 16'is brought into contact with the portion of the entire area around the intermediate transfer belt 10 in the circumferential direction with respect to the secondary transfer opposing roller 16 as a support roller, and the secondary transfer roller 16'is brought into contact with the secondary transfer roller 16'. Forming a nip.

The resist roller pair 49 starts rotational driving at a timing when the recording sheet can be superimposed on the four-color superimposed toner image on the belt by the secondary transfer nip, and feeds the recording sheet toward the secondary transfer nip. In the secondary transfer nip, the four-color superimposed toner image on the intermediate transfer belt 10 is secondarily transferred to the recording sheet by the action of the secondary transfer electric field and the nip pressure to obtain a full-color image.

The recording sheet that has passed through the secondary transfer nip is sent to the fixing device 25 and a full-color image is fixed on the surface thereof. The recording sheet that has passed through the fixing device 25 is discharged to the outside of the machine via the discharge roller pair 56, and then stacked on the paper discharge tray 57.

In the double-sided printing mode in which an image is formed on both sides of the recording sheet, the recording sheet in which the toner image is fixed only on the first side of both sides passes through the fixing device 25 and then discharges the roller pair 56. Instead, it is sent to the retransmission device 28. Then, the paper is retransmitted to the paper feed path 48 while being inverted by the retransmission device 28. Then, after being sent from the paper feed path 48 to the secondary transfer nip and the four-color superposed toner image is secondarily transferred to the second surface thereof, it is removed from the machine via the fixing device 25 and the discharge roller pair 56. Is discharged to.

The intermediate transfer belt 10 that has passed through the secondary transfer nip enters the primary transfer nip for Y, M, C, and K again after the transfer residual toner adhering to the surface is removed by the belt cleaning device 17. do. The toner contained in the belt cleaning device 17 is collected in a waste toner bottle by a conveying means.

FIG. 2 is a configuration diagram showing the fixing device 25. The fixing device 25 includes a fixing belt 25a, a heating roller 25b, a fixing roller 25c, a pressure roller 25d, a tension roller 25e, a rubbing roller 25f, a lining roller 25g, a separation claw 25h, a posture deforming member 25i, and the like. ..

The endless fixing belt 25a includes a belt substrate made of a material such as nickel, stainless steel, or polyimide, and an elastic layer having a thickness of 300 to 500 [μm] made of silicon rubber laminated on the front surface side of the belt substrate. It is a multi-layered belt having at least. The fixing belt 25a is tension-tensioned while being hung on a heating roller 25b, a fixing roller 25c, and a tension roller 25e arranged inside the loop. Then, as the fixing roller 25c is rotationally driven in the clockwise direction in the figure, it moves endlessly in the clockwise direction in the figure.

The pressure roller 25d as a nip forming member is pressed toward the fixing roller 25c which is a winding member. Then, the fixing nip is formed by contacting the fixing belt 25a with respect to the fixing roller 25c from the outside of the belt loop. At the position of the fixing nip, the fixing belt 25a is sandwiched between the fixing roller 25c inside the belt loop and the pressure roller 25d outside the belt loop.

The fixing roller 25c includes a core metal 25c1 serving as a roller substrate, and an elastic layer 25c2 made of rubber coated on the front surface thereof. Further, the pressure roller 25d also includes a core metal 25d1 serving as a roller substrate and an elastic layer 25d2 made of rubber coated on the front surface thereof.

The elastic layer 25c2 is important for the fixing roller 25c, which also serves as a drive roller for moving the fixing belt 25a endlessly, in order to exert a grip force and suppress the occurrence of belt slip on the peripheral surface thereof. It has a role. On the other hand, with respect to the pressure roller 25d, it is common practice to provide an elastic layer 25d2 having a small thickness and to bite into the elastic layer 25c2 of the fixing roller 25c.

However, when the pressure roller 25d is made to bite into the elastic layer 25c2 of the fixing roller 25c, when a double-structured envelope is used instead of a single-sheet structure paper in the fixing nip, it is caused by the difference in linear velocity between the upper and lower papers. This makes it easier for the envelope to wrinkle.

Therefore, in the printer 100 according to the embodiment, the pressure roller 25d is also provided with the elastic layer 25d2 having a relatively large thickness. Then, in the fixing nip, not only the elastic layer 25c2 of the fixing roller 25c but also the elastic layer 25d2 of the pressure roller 25d is elastically deformed so that neither roller bites into the other as shown in the drawing. Form a anchoring nip. As a result, by eliminating the difference in linear velocity between the upper and lower sheets of the envelope in the fixing nip, it is possible to avoid the occurrence of wrinkles in the envelope due to the difference in linear velocity.

The rubbing roller 25f arranged on the outside of the belt loop sandwiches the fixing belt 25a between the rubbing roller 25f and the backing roller 25g while being urged toward the backing roller 25g arranged on the inside of the belt loop. In this state, the drive means is rotationally driven in the counterclockwise direction in the figure. The rotation direction is a forward direction in which the surface of the rubbing roller 25f is moved in the same direction as the surface of the fixing belt 25a in the contact region between the rubbing roller 25f and the fixing belt 25a. However, the rotational drive speed of the rubbing roller 25f is set so that the surfaces of the two are moved with a linear speed difference in the contact region. Therefore, the rubbing roller 25f rotates while rubbing against the fixing belt 25a. By the rubbing, the surface characteristics of the fixing belt 25a can be maintained at a predetermined value. The surface of the rubbing roller 25f may be rotated in the contact region with the fixing belt 25a so as to move in the direction opposite to the belt surface.

The tubular roller substrate made of metal such as aluminum or iron of the heating roller 25b is heated by the radiant heat of the halogen heater 25b1 in the hollow, and then the heat is transferred to the fixing belt 25a around itself. This heats the fixing belt 25a. Then, the heated fixing belt 25a heats the recording sheet S sent into the nip in the fixing nip. The toner image on the recording sheet S is softened by the heating and fixed on the surface of the recording sheet S.

The recording sheet S that has passed through the fixing nip enhances the adhesive force with the fixing belt 25a due to the viscosity of the softened toner. If it remains wrapped around the fixing belt 25a, jam will occur. The separation claw 25h plays a role of promoting peeling of the recording sheet S from the fixing belt 25a by coming into contact with the surface facing the fixing belt 25a at the tip of the recording sheet S that has passed through the fixing nip.

In the case of a medium-speed machine for general users, it is possible to effectively suppress the occurrence of jam in the fixing device 25 by providing the separation claw 25h. However, in a high-speed machine for commercial use such as the printer 100 according to the embodiment, it is difficult to effectively suppress the occurrence of jam in the fixing device 25 even if the separation claw 25h is provided.

The reason is as follows. That is, in the printer 100 according to the embodiment, in order to secure a sufficient fixing time (fixing nip passing time) for the recording sheet S to be conveyed at high speed, the fixing roller 25c and the pressurizing roller are compared with the medium speed machine. The diameter of 25d is increased to form a wide fixing nip. If the diameter of the fixing roller 25c is relatively large, the curvature of the portion where the fixing belt 25a is hung with respect to the fixing roller 25c becomes relatively small, so that the curvature separability of the recording sheet S from the belt after passing through the fixing nip is improved. It gets relatively bad. As a result, the tip of the recording sheet S immediately after passing through the fixing nip slips between the separation claw 25h and the fixing belt 25a, and jam due to wrapping is likely to occur.

Therefore, in the illustrated fixing device 25, the posture deforming member 25i is provided. The posture deforming member 25i abuts on the portion downstream of the anchoring nip in the belt moving direction and near the exit of the nip from the back surface side of the belt in the entire area of the anchoring belt 25a in the circumferential direction, and the portion and the vicinity thereof. It deforms the belt posture in. Specifically, the belt posture is deformed so that the curvature of the belt posture at the location or the vicinity thereof is higher than the curvature of the belt posture at the fixing nip. More specifically, in the embodiment, as shown in the drawing, the belt posture at or near the contact portion so that the curvature of the contact portion with itself on the fixing belt 25a is higher than the curvature at the fixation nip. Is being transformed. By increasing the curvature of the belt posture in the vicinity of the outlet of the fixing nip, the curvature separation of the recording sheet S from the fixing belt 25a is promoted, and the recording sheet S is satisfactorily peeled from the fixing belt 25a. As a result, it is possible to suppress the occurrence of jam due to the recording sheet S being wound around the fixing belt 25a.

However, in the conventional image forming apparatus, there is a problem that the edge of the recording sheet S rubs against the fixing belt in the vicinity of the posture deforming member and promotes damage to the fixing belt. Specifically, in the conventional image forming apparatus, the fixing belt immediately after exiting the fixing nip rubs the posture deforming member fixed in the loop and receives frictional resistance, thereby reducing the moving speed. On the other hand, the recording sheet S that has exited the fixing nip is given the same linear velocity as the carrying force by the fixing belt and the pressure roller in the fixing nip, so that the moving speed is not lowered. Therefore, on the downstream side of the fixing nip, the moving speed of the fixing belt becomes slower than the moving speed of the recording sheet S, and a linear speed difference occurs between the two. Due to this difference in linear velocity, the edge of the recording sheet S rubs against the front surface of the fixing belt, which promotes scratches on the fixing belt. On the image, the scratches partially reduce the glossiness of the fixed image, and the streaky glossy streaks become apparent.

A conventional device in which the surface of the posture deforming member is covered with a sliding sheet made of a highly slidable material is known for the purpose of reducing the frictional resistance between the fixing belt and the posture deforming member (for example, Japanese Patent Application Laid-Open No. 2016). The fixing device described in Japanese Patent Application Laid-Open No. 095374). However, even if the frictional resistance is reduced by the sliding sheet, the linear speed difference between the fixing belt and the recording sheet S in the vicinity of the posture deforming member is inevitably large in the high-speed machine, and the recording sheet S is used as the fixing belt. The fixing belt will be scratched by rubbing.

Next, a characteristic configuration of the printer 100 according to the embodiment will be described.
In the figure, the posture deforming member 25i moves on the surface in the same direction as the fixing belt 25a in the contact region with the fixing belt 25a. Specifically, the posture deforming member 25i is composed of a driven rotating body that rotates around the fixing belt 25a, and as shown in FIG. 3, the posture deforming member 25i moves its surface in the same direction as the fixing belt 25a at the same speed as shown in FIG. Move with.

In such a configuration, since the posture deforming member 25i is not rubbed by the fixing belt 25a, the speed reduction of the fixing belt 25a due to frictional resistance is avoided, and the fixing belt 25a is substantially the same as the recording sheet S in the vicinity of the posture deforming member 25i. Move at the same speed. As a result, it is possible to prevent the fixing belt 25a from being scratched due to the recording sheet S being rubbed against the fixing belt 25a in the vicinity of the posture deforming member 25i.

The driven rotating body constituting the posture deforming member 25i is a member made of a metal such as stainless steel, a resin that does not deform, or an elastic body such as silicon rubber.

As shown in the figure, the front surface of the region where the back surface of the fixing belt 25a is in contact with the posture deforming member 25i is not in contact with the pressure roller 25d. .. As a result, it is possible to prevent the belt deformation portion due to the posture deformation member 25i from being unnecessarily brought into contact with the pressure roller 25d to widen the fixing nip.

FIG. 4 is a graph showing the relationship between the scratch length (length in the belt moving direction) of the fixing belt 25a damaged by the recording sheet S during long-term operation and the mode of the posture deforming member 25i. In the figure, the conventional mode is a mode in which the posture deforming member 25i is rubbed with the fixing belt 25a without moving the surface as in the conventional device. Further, the embodiment is an embodiment in which the posture deforming member 25i made of a driven rotating body is used as in the printer 100 according to the embodiment. From the figure, it can be seen that the embodiment has a reduced wound length as compared with the conventional embodiment. Even in the embodiment, scratches having a certain length are generated because the fixing belt 25a is damaged by burrs on the edge of the sheet even if the recording sheet S does not rub against the fixing belt 25a.

FIG. 5 shows the relationship between the regeneration polishing time of the damaged fixing belt 25a and the mode of the posture deforming member 25i. In the figure, the regeneration polishing time is the time required for polishing when the surface of the damaged fixing belt 25a is polished to a level at which the scratches are inconspicuous by the polishing machine. Further, the conventional aspect means that the fixing belt 25a damaged by the fixing device of the conventional aspect is polished. Further, the embodiment means that the fixing belt 25a damaged by the fixing device according to the embodiment is polished. From the figure, it can be seen that the embodiment reduces the regeneration polishing time as compared with the conventional embodiment.

FIG. 6 is a front view showing the posture deforming member 25i. As shown in the figure, the posture deforming member 25i has a diameter (φ2) at the center in the direction of the rotation axis larger than the diameter (φ1) at both ends. When there is almost no difference in linear velocity between the recording sheet S and the fixing belt 25a in the vicinity of the posture deforming member 25i, most of the scratches on the fixing belt 25a by the recording sheet S occur at both ends of the recording sheet S in the belt width direction. It is generated when burrs (generated at the time of cutting) come into contact with the fixing belt 25a.

When the diameter (φ2) of the central portion of the posture deforming member 25i in the rotation axis direction is made larger than the diameter of both ends (φ1), the recording sheet S immediately after passing through the fixing nip is peeled off from the belt at both ends in the belt width direction. It is possible to suppress the rubbing between both ends and the belt. Therefore, scratches on the fixing belt 25a due to rubbing the recording sheet S can be further suppressed.

FIG. 7 is a front view showing the posture deforming member 25i and the pressure roller 25d. As shown in the figure, the pressure roller 25d has a diameter (φ4) at the center in the direction of the rotation axis smaller than the diameter (φ3) at both ends. That is, the magnitude relationship between the diameter of the central portion (φ4) and the diameter of both ends (φ3) is opposite to that of the posture deforming member 25i. This is because the pressure roller 25d has a drum-shaped shape in which the diameters at both ends are larger than those at the center, so that the sheet transport speed is faster at both ends than at the center and the occurrence of sheet wrinkles is suppressed. Is. Furthermore, the reverse relationship as described above enables the following. That is, the center of the fixing belt 25a stretched on the posture deforming member 25i having a shape in which the diameters (φ1) of both ends are larger than the diameter of the center portion (φ2) in the belt width direction at the hanging portion with respect to the posture deforming member 25i. It is possible to avoid contact between the portion and the pressure roller 25d.

In the figure, d1 is a distance between ends as a distance between an end portion of the posture deforming member 25i in the direction of the rotation axis and a portion of the pressure roller 25d facing the end portion. Further, d2 is a distance between the central portions as a distance between the central portion of the posture deforming member 25i in the direction of the rotation axis and the portion of the pressure roller 25d facing the central portion. As shown in the figure, the distance between the ends d1 is made larger than the distance d2 between the central parts (d1> d2). In such a configuration, it is possible to suppress the occurrence of scratches on the fixing belt 25a by rubbing the edges of the recording sheet on both ends in the width direction of the fixing belt 25a, as compared with the case where both distances are the same. The difference between the end-to-end distance d1 and the center-to-center distance d2 is in the range of 0.2 to 1.5 [mm].

An example of using a posture deforming member 25i whose length in the rotation axis direction is substantially the same as the length of the pressure roller 25d in the rotation axis direction has been described. However, as the posture deformation member 25i, the pressure roller A plurality of items shorter than 25d may be provided side by side. Specifically, as shown in FIG. 8, one that faces one end of the pressure roller 25d in the direction of the rotation axis, one that faces the other end, and one that faces the center may be provided. Also in this case, as shown in the drawing, the posture deforming member 25i at the center is placed on the pressurizing roller 25d rather than the posture deforming member 25i at both ends so that the distance d1 between the ends is larger than the distance d2 between the centers. It is desirable to arrange them close to each other.

Next, an example in which a more characteristic configuration is added to the printer 100 according to the embodiment will be described. Unless otherwise specified below, the configuration of the printer 100 according to the embodiment is the same as that of the embodiment.

FIG. 9 is an enlarged configuration diagram showing the posture deforming member 25i of the fixing device 25 of the printer 100 according to the embodiment and its surroundings in an enlarged manner. The fixing device 25 is provided with a second posture deforming member 25j that abuts on the back surface of the fixing belt 25a on the downstream side in the moving direction of the fixing belt 25a to deform the posture of the fixing belt 25a. .. The posture deforming member 25i is rotatably held by the second posture deforming member 25j.

In the conventional apparatus, the posture deforming member fixed so as to be rubbed by the fixing belt without moving the surface with the movement of the fixing belt has a relatively large length in the belt moving direction. On the other hand, the length of the posture deforming member 25i in the embodiment and the embodiment in the belt moving direction is relatively small. If the posture deforming member of the conventional device is replaced with the posture deforming member 25i in the embodiment or the embodiment, the tension of the belt is lowered. Therefore, in the printer 100 according to the embodiment, the second posture deforming member 25j is used to prevent the tension of the fixing belt 25a from loosening.

The above description is an example, and the effect peculiar to each of the following aspects is exhibited.
[Aspect A]
Aspect A is an endless fixing belt (for example, a fixing belt 25a), a winding member for winding the fixing belt around itself inside the loop (for example, a fixing roller 25c), and a winding portion of the fixing belt with respect to the winding member from the outside of the loop. A nip forming member (for example, a pressure roller 25d) that comes into contact with each other to form a fixing nip, and a portion of the entire circumferential direction of the fixing belt that is downstream of the fixing nip in the belt moving direction and near the nip outlet. With a posture deforming member (for example, a posture deforming member 25i) that abuts from the back surface side of the belt and deforms the belt posture in or near the portion, with respect to a recording sheet (for example, recording sheet S) sandwiched between the fixing nips. The fixing device (for example, the fixing device 25) for fixing the image is characterized in that the contact portion of the posture deforming member with the fixing belt is surface-moved in the same direction as the fixing belt. ..

In the aspect A, the fixing belt can be prevented from being scratched due to the recording sheet being rubbed against the fixing belt in the vicinity of the nip outlet for the reason described below. That is, in the conventional device, the posture deforming member fixed immovably inside the loop of the fixing belt is rubbed with the fixing belt which is moving endlessly. Then, due to the frictional resistance, the moving speed of the fixing belt in the vicinity of the nip outlet is made lower than the moving speed of the fixing belt in the fixing nip. On the other hand, with respect to the recording sheet, since the conveying force is applied to the recording sheet by the belt moving force at the fixing nip, the moving speed of the recording sheet is hardly reduced. As a result, a speed difference between the fixing belt that reduces the speed and the recording sheet that does not reduce the speed is generated in the vicinity of the posture deforming member, and the recording sheet is rubbed against the fixing belt. This rubbing scratched the fixing belt. Therefore, in the aspect A, by moving the surface of the posture deforming member in the same direction as the fixing belt, the friction between the fixing belt and the posture deforming member due to the movement of the fixing belt is compared with the conventional one in which the surface is not moved. Reduce resistance. As a result, by reducing the speed difference between the fixing belt and the recording sheet in the vicinity of the nip outlet, it is possible to suppress damage to the fixing belt due to rubbing the recording sheet against the fixing belt due to the speed difference.

[Aspect B]
Aspect B is characterized in that, in Aspect A, the curvature of the belt posture is made higher than the curvature of the belt posture at the fixing nip by deforming the belt posture at or in the vicinity thereof by the posture deforming member. It is a thing. In such a configuration, by increasing the curvature of the fixing belt by the posture deforming member, it is possible to promote the separation of the curvature of the recording sheet from the fixing belt and effectively suppress the winding of the recording sheet around the fixing belt.

[Aspect C]
Aspect C is characterized in that, in Aspect A or B, the posture deforming member is formed by a driven rotating body that is carried around the fixing belt. In such a configuration, the friction between the fixing belt and the posture deforming member due to the endless movement of the fixing belt can be substantially eliminated by causing the posture deforming member to rotate around the fixing belt.

[Aspect D]
In aspect D, in aspect C, the front surface of the region in which the posture-deforming member is in contact with the entire area in the circumferential direction of the fixing belt is made non-contact with the nip-forming member. It is characterized by.

[Aspect E]
Aspect E is characterized in that, in Aspect D, the diameter of the central portion of the posture deforming member made of the roller-shaped driven rotating body in the direction of the rotation axis is made larger than the diameter of both end portions. With such a configuration, it is possible to promote peeling of both ends of the recording sheet from the fixing belt in the belt width direction immediately after passing through the fixing nip, and to suppress rubbing between both ends of the recording sheet and the fixing belt. Therefore, scratches on the fixing belt due to rubbing the recording sheet can be further suppressed.

[Aspect F]
Aspect F is characterized in that, in the aspect E, the nip forming member is formed by a roller-shaped rotating body, and the diameter of the central portion of the nip forming member in the rotation axis direction is smaller than that of both end portions. .. In such a configuration, it is possible to prevent the belt posture correction portion by the straightening member from being unnecessarily brought into contact with the nip forming member to widen the fixing nip due to the adoption of the aspect D.

[Aspect G]
Aspect G is an end-to-end distance (for example, an end-to-end distance) which is a distance between an end portion of the posture deforming member in the rotation axis direction and a portion of the nip forming member facing the end portion in the F aspect. d1) is larger than the distance between the central portions (for example, the distance between the central portions d2), which is the distance between the central portion of the posture deforming member in the direction of the rotation axis and the portion of the nip forming member facing the central portion. It is characterized by being enlarged. In such a configuration, it is possible to suppress the occurrence of scratches on the fixing belt due to rubbing the edges of both ends of the recording sheet against both ends in the width direction of the fixing belt, as compared with the case where both distances are the same.

[Aspect H]
Aspect H is a subject posture deforming member in any of aspects A to G, which abuts on the back surface of the fixing belt on the downstream side in the moving direction of the fixing belt to deform the posture of the fixing belt. (For example, the second posture deforming member 25j) is provided. In such a configuration, the conventional fixing belt can be used as it is.

[Aspect I]
Aspect I is characterized in that, in any of aspects A to H, as each of the winding member and the nip forming member, an elastic layer is coated on the surface of the substrate. With such a configuration, it is possible to suppress the occurrence of wrinkles in the envelope due to the difference in linear velocity between the fixing belt and the nip forming member in the fixing nip.

[Aspect J]
Aspect J includes an image forming means for forming an image on a recording sheet (for example, a tandem image forming unit 20, an intermediate transfer belt 10, a primary transfer roller 62, a secondary transfer roller 16', an optical writing device 21, and the like). An image forming apparatus including a fixing means for fixing the image on the recording sheet is characterized in that any of aspects A to I is used as the fixing means.

10: Intermediate transfer belt (part of image forming means)
16': Secondary transfer roller (part of image forming means)
20: Tandem image forming part (part of image forming means)
21: Optical writing device (part of image forming means)
25: Fixing device 25a: Fixing belt 25b: Heating roller 25c: Fixing roller (winding member)
25d: Pressurized roller (nip forming member)
25i: Posture deformation member 25j: Second posture deformation member 61: Primary transfer roller (part of image forming means)
S: Recording sheet d1: Distance between ends d2: Distance between centers

Japanese Unexamined Patent Publication No. 2015-180906

Claims (5)

An endless fixing belt, a winding member around which the fixing belt is wound around the inside of the loop, and a nip forming member that abuts from the outside of the loop at a winding portion of the fixing belt with respect to the winding member to form a fixing nip. , Of the entire area in the circumferential direction of the fixing belt, the belt posture is deformed by contacting a portion downstream of the fixing nip in the belt moving direction and near the exit of the nip from the back surface side of the belt. In a fixing device having a posture-changing member for fixing an image on a recording sheet sandwiched between the fixing nips.
The contact portion of the posture deforming member with the fixing belt is surface-moved in the same direction as the fixing belt .
The posture deforming member is formed by a driven rotating body that is carried around the fixing belt.
Of the entire area in the circumferential direction of the fixing belt, the front surface of the region in contact with the posture deforming member is made non-contact with the nip forming member.
The diameter of the central portion in the direction of the rotation axis of the posture deforming member composed of the roller-shaped driven rotating body is made larger than the diameter of both end portions.
The nip forming member is formed by a roller-shaped rotating body, and the diameter of the central portion of the nip forming member in the rotation axis direction is made smaller than that of both ends.
The distance between the ends, which is the distance between the end portion of the posture deforming member in the rotation axis direction and the portion of the nip forming member facing the end portion, is defined as the central portion of the posture deformation member in the rotation axis direction. , A fixing device characterized in that the distance between the central portions, which is the distance between the nip forming member and the portion facing the central portion, is larger than the distance between the central portions. In the fixing device of claim 1,
A fixing device characterized in that the curvature of the belt posture is made higher than the curvature of the belt posture at the fixing nip by deforming the belt posture at or in the vicinity thereof by the posture deforming member . The fixing device according to請Motomeko 1 or 2,
A fixing device characterized in that a second posture deformation member is provided that abuts on the back surface of the fixing belt on the downstream side in the moving direction of the fixing belt to deform the posture of the fixing belt. In the fixing device according to any one of claims 1 to 3,
A fixing device characterized in that an elastic layer is coated on the surface of a substrate as each of the winding member and the nip forming member. In an image forming apparatus including an image forming means for forming an image on a recording sheet and a fixing means for fixing the image on the recording sheet.
An image forming apparatus according to any one of claims 1 to 4 , wherein the fixing device is used as the fixing means.

Images