JP2021071537A - Fixing device and image forming apparatus - Google Patents

Abstract

To provide a fixing device that can achieve stable contact between a fixing belt and a belt guide in both a circumferential direction and a rotation axis direction of the fixing belt.SOLUTION: A fixing device 40 comprises: an endless fixing belt 41; a pressure roller 42; a nip forming member 44; a belt guide 45; and a frame member 46. The nip forming member 44 is arranged inside the fixing belt 41 while being opposite to the pressure roller 42 with the fixing belt 41 therebetween, and is in contact with an inner peripheral surface of the fixing belt 41 to form a fixing nip part N. The belt guide 45 is in contact with the inner peripheral surface of the fixing belt 41 other than the fixing nip part N to support the fixing belt 41 from the inside. The fixing device is provided with urging members 481 that are arranged at both ends in a rotation axis direction of the fixing belt 41, and urge the belt guide 45 in a direction approaching the fixing belt 41.SELECTED DRAWING: Figure 3

Description

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

In electrophotographic image forming devices such as copiers and printers, the heat fixing method is widely adopted as a method for fixing an unfixed toner image transferred to a recording medium such as paper on paper. As the fixing device, a device including a rotating pressurizing member and an endless fixing belt that rotates in contact with the outer peripheral surface of the pressurizing member is known. An example of such a fixing device is disclosed in Patent Document 1.

The conventional fixing device disclosed in Patent Document 1 includes a pressure roller (pressurizing member), a fixing belt, an exciting coil that heats the fixing belt by electromagnetic induction, and a belt guide arranged inside the fixing belt. , Equipped with. The contact portion of the belt guide with the fixing belt is curved in an arc shape along the inner peripheral surface of the fixing belt, and makes overall contact with the inner peripheral surface of the fixing belt. As a result, the rotation trajectory of the fixing belt can be stabilized, and the distance between the fixing belt and the exciting coil can be kept constant.

Japanese Unexamined Patent Publication No. 2016-20467

The belt guide of the conventional fixing device disclosed in Patent Document 1 is fixed to the support member with a screw on the upstream side of the fixing nip portion in the belt rotation direction, and is attached to and detached from the support member on the downstream side of the fixing nip portion in the belt rotation direction. Engaged as possible. As a result, stable contact between the fixing belt and the belt guide is realized in the circumferential direction. However, in the direction of the rotation axis (paper width direction), the fixing belt and the belt guide may be in an unstable contact state due to the influence of the variation in the shape of the belt guide. As a result, there is a concern that one-sided contact between the fixing belt and the belt guide occurs in the direction of the rotation axis, the temperature distribution of the fixing belt becomes uneven, and abnormal heat generation occurs in a region where the contact pressure between the fixing belts is high.

The present invention has been made in view of the above points, and is a fixing device and an image forming capable of realizing stable contact between the fixing belt and the belt guide in both the circumferential direction and the rotation axis direction of the fixing belt. The purpose is to provide the device.

In order to solve the above problems, the fixing device of the present invention includes an endless fixing belt, a pressure member, a nip forming member, a belt guide, and a frame member. The endless fixing belt can rotate along the transport direction of the recording medium. The pressurizing member contacts the outer peripheral surface of the fixing belt to give a rotational driving force to the fixing belt. The nip forming member is arranged inside the fixing belt so as to face the pressurizing member across the fixing belt, and contacts the inner peripheral surface of the fixing belt to form the fixing nip portion. The belt guide contacts the inner peripheral surface of the fixing belt other than the fixing nip portion and supports the fixing belt from the inside. The frame member holds the nip forming member and the belt guide. Bending members are provided at both ends of the fixing belt in the direction of the rotation axis to urge the belt guides in the direction approaching the fixing belt.

According to the configuration of the present invention, the belt guide is held by the frame member and comes into contact with the inner peripheral surface of the fixing belt other than the fixing nip portion to support the fixing belt from the inside. Further, in the belt guide, both ends of the fixing belt in the rotation axis direction are urged by the urging member in a direction approaching the fixing belt. This makes it possible to realize stable contact between the fixing belt and the belt guide in both the circumferential direction and the rotation axis direction of the fixing belt.

It is a schematic cross-sectional front view which shows the structure of the image forming apparatus of embodiment of this invention. It is sectional drawing front view of the fixing apparatus of 1st Embodiment of this invention. It is a side view of the cut portion end face of the fixing device of 1st Embodiment of this invention. It is a partial side view of the fixing device of the 1st Embodiment of this invention. It is sectional drawing front view of the fixing apparatus of the modification of 1st Embodiment of this invention. It is a partial side view of the fixing device of the 2nd Embodiment of this invention. It is sectional drawing front view of the fixing device of 3rd Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following contents.

FIG. 1 is a schematic cross-sectional view showing the configuration of the image forming apparatus 1 of the embodiment. An example of the image forming apparatus 1 of the present embodiment is a tandem color printer that transfers a toner image onto paper P using an intermediate transfer belt 31. The image forming apparatus 1 may be a so-called multifunction device having functions such as printing (printing), scanning (image reading), and facsimile transmission.

As shown in FIG. 1, the image forming apparatus 1 has a paper feeding unit 3, a paper conveying unit 4, an exposure unit 5, an image forming unit 20, a transfer unit 30, a fixing device 40, a paper discharging unit 7, and a paper discharging unit 7 in the main body 2. The control unit 8 is included.

The paper feeding unit 3 accommodates a plurality of sheets of paper P (recording medium), and separates and sends out the paper P one by one at the time of printing. The paper transport unit 4 conveys the paper P fed from the paper feed unit 3 to the secondary transfer unit 33 and the fixing device 40, and further discharges the fixed paper P from the paper ejection port 4a to the paper ejection unit 7. .. When double-sided printing is performed, the paper transport unit 4 distributes the paper P after fixing on the first side to the reverse transport unit 4c by the branch portion 4b, and the paper P is again transferred to the secondary transfer unit 33 and the fixing device 40. Transport. The exposure unit 5 irradiates the image forming unit 20 with a laser beam controlled based on the image data.

The image forming unit 20 includes an image forming unit 20Y for yellow, an image forming unit 20C for cyan, an image forming unit 20M for magenta, and an image forming unit 20B for black. These four image forming units 20 have the same basic configuration. As a result, in the following description, the identification symbols of "Y", "C", "M", and "B" representing each color may be omitted unless it is particularly necessary to limit them.

The image forming unit 20 includes a photoconductor drum 21 which is an image carrier rotatably supported in a predetermined direction (clockwise in FIG. 1). The image forming unit 20 further includes a charging unit, a developing unit, and a drum cleaning unit around the photoconductor drum 21 along the rotation direction thereof. The primary transfer unit 32 is arranged between the developing unit and the drum cleaning unit.

The charging unit charges the surface of the photoconductor drum 21 to a predetermined potential by, for example, a charging roller. Then, an electrostatic latent image of the original image is formed on the surface of the photoconductor drum 21 by the laser light emitted from the exposure unit 5. The developing unit supplies toner to this electrostatic latent image and develops it to form a toner image. Each of the four image forming units 20 forms toner images of different colors.

The transfer unit 30 includes an intermediate transfer belt 31, a primary transfer unit 32Y, 32C, 32M, 32B, a secondary transfer unit 33, and a belt cleaning unit 34. The intermediate transfer belt 31 is an intermediate transfer body that is rotatably supported in a predetermined direction (counterclockwise in FIG. 1) and in which toner images formed by each of the four image forming portions 20 are sequentially superimposed and primary transferred. .. The four image forming portions 20 are arranged in a so-called tandem system in which the intermediate transfer belt 31 is arranged in a row from the upstream side to the downstream side in the rotation direction.

The primary transfer units 32Y, 32C, 32M, 32B are arranged above the image forming units 20Y, 20C, 20M, 20B of each color. The secondary transfer unit 33 is on the upstream side of the paper transfer unit 4 in the paper transfer direction with respect to the fixing device 40, and is an intermediate transfer belt 31 of the transfer unit 30 with respect to the image forming units 20Y, 20C, 20M, and 20B of each color. It is arranged on the downstream side in the rotation direction of. The belt cleaning unit 34 is arranged on the upstream side in the rotation direction of the intermediate transfer belt 31 with respect to the image forming units 20Y, 20C, 20M, and 20B of each color.

The toner image is first transferred to the surface of the intermediate transfer belt 31 by the primary transfer portions 32Y, 32C, 32M, 32B of each color. Then, as the intermediate transfer belt 31 rotates, the toner images of the image forming portions 20 are continuously superimposed and transferred to the intermediate transfer belt 31 at a predetermined timing, so that the surface of the intermediate transfer belt 31 is covered with yellow, cyan, and cyan. A color toner image is formed by superimposing four color toner images of magenta and black. The drum cleaning unit removes toner and the like remaining on the surface of the photoconductor drum 21 after the primary transfer for cleaning.

The color toner image on the surface of the intermediate transfer belt 31 is transferred to the paper P synchronously sent by the paper transport unit 4 by the secondary transfer nip portion formed in the secondary transfer unit 33. The belt cleaning unit 34 cleans by removing toner and the like remaining on the surface of the intermediate transfer belt 31 after the secondary transfer.

The fixing device 40 heats and pressurizes the paper P on which the toner image is transferred to fix the toner image on the paper P.

The control unit 8 includes a CPU (not shown), an image processing unit, a storage unit, and other electronic circuits (not shown) and electronic components (not shown). The CPU controls the operation of each component provided in the image forming apparatus 1 based on the control program or data stored in the storage unit, and performs processing related to the function of the image forming apparatus 1. Each of the paper feed unit 3, the paper transport unit 4, the exposure unit 5, the image forming unit 20, the transfer unit 30, and the fixing device 40 receives commands individually from the control unit 8 and prints on the paper P in conjunction with each other. The storage unit is composed of a combination of a non-volatile storage device such as a program ROM (Read Only Memory) and a data ROM (not shown) and a volatile storage device such as a RAM (Random Access Memory).

Subsequently, the configuration of the fixing device 40 of the first embodiment will be described with reference to FIGS. 2, 3, 4, and 5. FIG. 2 is a cross-sectional front view of the fixing device 40 of the first embodiment. FIG. 3 is a side view of the end surface of the cut portion of the fixing device 40 of the first embodiment. FIG. 4 is a partial side view of the fixing device 40 of the first embodiment. FIG. 5 is a cross-sectional front view of the fixing device 40 of the modified example of the first embodiment. In FIGS. 2, 3, 4, and 5, for convenience of explanation, the fixing belt 41 is arranged above the fixing nip portion N, and the pressurizing roller 42 (pressurizing member) is arranged below. The composition was drawn. In FIGS. 2 and 5, the left side is the upstream side in the paper transport direction with respect to the fixing device 40, and the right side is the downstream side in the paper transport direction with respect to the fixing device 40.

As shown in FIGS. 2 and 3, the fixing device 40 includes a fixing belt 41, a pressure roller 42 (pressurizing member), a heating unit 43, a nip forming member 44, a belt guide 45, a frame member 46, and a positioning unit 47. Be prepared.

The fixing belt 41 is rotatably supported by the housing portion of the fixing device 40 around a horizontal axis. The fixing belt 41 has an endless shape, for example, has a cylindrical shape with an outer diameter of 20 mm to 50 mm, and has an axial length (length in the width direction of the paper P) substantially the same as that of the pressure roller 42. The fixing belt 41 can rotate along the conveying direction of the paper P, which is a recording medium.

The fixing belt 41 has a laminated structure in which an elastic layer and a release layer are provided on the outer peripheral side of a heat generating layer which is a base material layer. The heat generating layer is composed of, for example, a metal film having a thickness of 30 μm to 50 μm such as nickel, or a polyimide film having a thickness of 50 μm to 100 μm mixed with a metal powder such as copper, silver, or aluminum. The elastic layer is made of, for example, silicon rubber having a thickness of 100 μm to 500 μm. The release layer is composed of a fluorine-based resin such as PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) having a thickness of 30 μm to 50 μm, for example.

The pressurizing roller 42 is rotatably supported by the housing portion of the fixing device 40 around a horizontal axis. The pressure roller 42 has a cylindrical shape and has substantially the same axial length (the width direction length of the paper P) as the fixing belt 41. A predetermined pressure is applied to the pressurizing roller 42 toward the fixing belt 41 by a pressurizing mechanism (not shown). The outer peripheral surface of the pressure roller 42 presses the nip forming member 44 via the fixing belt 41 and comes into contact with the outer peripheral surface of the fixing belt 41 to form the fixing nip portion N.

The pressurizing roller 42 is connected to a drive source including a motor (not shown), receives power from the motor, and rotates clockwise in FIG. The pressure roller 42 comes into contact with the outer peripheral surface of the fixing belt 41 and applies a rotational driving force to the fixing belt 41.

The pressure roller 42 has a laminated structure in which an elastic layer and a release layer are provided on the outer peripheral side of the core metal. The core metal is made of a metal such as aluminum having a diameter of about 20 mm, for example. The elastic layer is made of, for example, silicon rubber having a thickness of about 8 mm. The release layer is made of a fluororesin such as PFA having a thickness of, for example, about 10 μm to 50 μm.

The heating unit 43 is arranged to face the outer peripheral surface of the fixing belt 41 with a predetermined gap in the region opposite to the side where the pressurizing roller 42 is arranged with respect to the fixing belt 41. The heating unit 43 extends slightly longer than the fixing belt 41 along the axial direction (paper width direction) of the fixing belt 41. The heating unit 43 heats the fixing belt 41 by generating heat in the heat generating layer of the fixing belt 41 by induction heating.

The heating unit 43 includes an exciting coil 431, a holding member (not shown), a core, and the like. The exciting coil 431 and the core are held in place by the holding member. The exciting coil 431 is composed of a litz wire in which a plurality of conducting wires are bundled, and is wound so as to extend along the axial direction (paper width direction) of the fixing belt 41. The exciting coil 431 is formed in an arc shape along the outer peripheral surface of the fixing belt 41 in the circumferential direction of the fixing belt 41.

The nip forming member 44 is arranged inside the fixing belt 41 so as to face the pressure roller 42 across the fixing belt 41. The nip forming member 44 comes into contact with the inner peripheral surface of the fixing belt 41, and forms a fixing nip portion N between the fixing belt 41 and the pressure roller 42.

The nip forming member 44 has a substantially rectangular parallelepiped shape extending along the axial direction (paper width direction) of the fixing belt 41 with substantially the same length as the fixing belt 41. The nip forming member 44 has a base material made of a metal such as aluminum or a heat-resistant resin such as a liquid crystal polymer. The nip forming member 44 may have an elastic layer made of, for example, an elastomer, silicon rubber, or the like on the side of the base material facing the fixing belt 41. Further, the nip forming member 44 has a sheet material (release layer) made of a fluororesin such as PFA in a region facing the fixing belt 41. The sheet material comes into contact with the inner peripheral surface of the fixing belt 41 at the fixing nip portion N, and extends to a region on the upstream side and the downstream side of the fixing nip portion N in the rotational direction of the fixing belt 41, which does not contact the fixing belt 41.

The belt guide 45 is arranged inside the fixing belt 41 so as to face the heating portion 43 across the fixing belt 41. The belt guide 45 contacts the inner peripheral surface of the fixing belt 41 other than the fixing nip portion N, and supports the fixing belt 41 from the inside. The belt guide 45 is composed of a sheet metal extending along the axial direction (paper width direction) of the fixing belt 41 with substantially the same length as the fixing belt 41. The belt guide 45 is made of an elastic magnetic metal such as SUS430 having a thickness of 0.1 mm to 0.5 mm, for example. The belt guide 45 includes a contact portion 451 and a connection portion 452.

The contact portion 451 is arranged on the opposite side of the fixing nip portion N with the radial center portion of the fixing belt 41 separated from the contact portion 451. The contact portion 451 is curved in an arc shape along the inner peripheral surface of the fixing belt 41. The contact portion 451 contacts the inner peripheral surface of the fixing belt 41 over almost the entire area. The contact portion 451 faces the exciting coil 431 across the fixing belt 41.

The connecting portion 452 is arranged on each of the upstream side and the downstream side in the rotation direction of the fixing belt 41 of the contact portion 451. The two connecting portions 452 are connected to both end portions in the circumferential direction of the contact portion 451. The connecting portion 452 bends and extends inward in the radial direction of the fixing belt 41 from each of both ends in the circumferential direction of the contact portion 451 and does not come into contact with the fixing belt 41. The connecting portion 452 includes a positioning piece 4521 shown in FIG.

The positioning piece 4521 is arranged at the center of the fixing belt 41 in the axial direction (paper width direction). The positioning piece 4521 is adjacent to the frame member 46 and extends in a direction in which the contact portion 451 approaches and separates from the fixing belt 41.

The frame member 46 is a substantially central portion in the radial direction of the fixing belt 41, and is arranged between the contact portion 451 of the belt guide 45 and the nip forming member 44. The frame member 46 extends slightly longer than the fixing belt 41 along the axial direction (paper width direction) of the fixing belt 41.

The frame member 46 holds the nip forming member 44 and the belt guide 45. The nip forming member 44 is fixed to the nip side wall portion 461 of the frame member 46 facing the fixing nip portion N. The connecting portion 452 of the belt guide 45 is connected to the side wall portions 462 of the frame member 46 on the upstream side and the downstream side of the fixing nip portion N of the fixing belt 41 in the rotational direction.

The positioning portion 47 is located at the center of the fixing belt 41 in the axial direction (paper width direction), and is arranged at the positioning piece 4521 of the connecting portion 452 of the belt guide 45. The positioning unit 47 includes a positioning pin 471 and a positioning hole 472.

The positioning pin 471 is provided on the side wall portion 462 of the frame member 46 as shown in FIGS. 2 and 4. The positioning pin 471 has a cylindrical shape and projects toward the fixing belt 41 in a direction intersecting the rotation axis direction of the fixing belt 41.

As shown in FIG. 4, the positioning hole 472 is provided in the positioning piece 4521 of the belt guide 45. The positioning hole 472 is circular in a plan view and penetrates the positioning piece 4521 in a direction intersecting the rotation axis direction of the fixing belt 41. The positioning hole 472 is a circle having a diameter slightly larger than the diameter of the positioning pin 471, and the positioning pin 471 is inserted into the positioning hole 472.

The belt guide 45 is connected to and held by the frame member 46 by the positioning portion 47 having such a configuration. Since the positioning hole 472 is circular in which the cylindrical positioning pin 471 can be inserted, the position of the belt guide 45 can be stabilized.

The fixing device 40 further includes an urging unit 48. The urging portion 48 is arranged inside the contact portion 451 of the belt guide 45 and in a region facing the inner peripheral surface of the contact portion 451 and the frame member 46. The urging portions 48 are arranged at both ends of the fixing belt 41 in the rotation axis direction (paper width direction). The urging unit 48 includes an urging member 481, an urging base 482, and an urging guide 483.

The urging member 481 is composed of, for example, a single compression coil spring, and is arranged at the central portion in the circumferential direction of the contact portion 451 of the belt guide 45. One end of the urging member 481 in the coil center axis direction is connected to the urging base 482, and the other end is connected to the urging guide 483. The urging member 481 urges the contact portion 451 of the belt guide 45 in a direction approaching the fixing belt 41.

The urging base 482 is fixed to the guide side wall portion 463 of the frame member 46 facing the belt guide 45. The urging base 482 supports one end of the urging member 481 composed of a compression coil spring in the direction of the coil center axis.

The urging guide 483 is arranged adjacent to the inner peripheral surface of the contact portion 451 of the belt guide 45. The urging guide 483 is a band-shaped member that curves in an arc shape along the inner peripheral surface of the contact portion 451 and extends in the circumferential direction of the contact portion 451. The urging guide 483 is attached to one end of the urging member 481 composed of a compression coil spring in the direction of the coil center axis. The urging guide 483 is pressed against the inner peripheral surface of the contact portion 451 by the elastic force (urging force) of the urging member 481.

As shown in FIG. 5, the urging portion 48 may abolish the urging base 482 and provide two urging members 481 composed of compression coil springs. Further, although not shown, the urging portion 48 may be provided with an urging member 481 composed of three or more compression coil springs. Further, the urging member 481 may be composed of another elastic member such as a sponge. Further, the urging unit 48 may have at least one urging member 481, and the urging base 482 and the urging guide 483 may be omitted.

According to the above configuration, the belt guide 45 is held by the frame member 46 and comes into contact with the inner peripheral surface of the fixing belt 41 other than the fixing nip portion N to support the fixing belt 41 from the inside. Further, in the belt guide 45, both ends of the fixing belt 41 in the rotation axis direction are urged by the urging member 481 in a direction approaching the fixing belt 41. This makes it possible to realize stable contact between the fixing belt 41 and the belt guide 45 in both the circumferential direction and the rotation axis direction of the fixing belt 41.

Further, since the belt guide 45 is made of magnetic metal, the magnetic flux leaked to the inside of the fixing belt 41 is absorbed by the contact portion 451 of the belt guide 45, causing the contact portion 451 to generate heat. Then, the contact portion 451 heats the fixing belt 41 from the inside of the fixing belt 41. Therefore, the heating efficiency of the fixing belt 41 can be increased, and the energy saving performance can be improved.

Next, the image forming apparatus 1 of the second embodiment will be described. FIG. 6 is a partial side view of the fixing device 40 of the second embodiment. Since the basic configuration of the second embodiment is the same as that of the first embodiment (see FIGS. 1 to 5) described above, the common components are given the same reference numerals or the same names as before. In some cases, the description thereof may be omitted, and the description of the configuration other than the featured parts may be omitted.

As shown in FIG. 6, the fixing device 40 of the image forming device 1 of the second embodiment includes a positioning unit 47. The positioning portion 47 is arranged at the center of the fixing belt 41 in the rotation axis direction (paper width direction). It includes a positioning pin 471 and a positioning hole 473.

The positioning pin 471 is provided on the side wall portion 462 of the frame member 46. The positioning pin 471 has a cylindrical shape and projects toward the fixing belt 41 in a direction intersecting the rotation axis direction of the fixing belt 41.

The positioning hole 473 is provided in the positioning piece 4521 of the belt guide 45. The positioning hole 473 is composed of an elongated hole extending in a direction in which the contact portion 451 of the belt guide 45 approaches and separates from the fixing belt 41, and penetrates the positioning piece 4521 in a direction intersecting the rotation axis direction of the fixing belt 41. The positioning hole 473 has a width slightly larger than the diameter of the positioning pin 471 (the length in the axial direction (paper width direction) of the fixing belt 41), and the positioning pin 471 is inserted.

The belt guide 45 is movably supported with respect to the frame member 46 by the positioning portion 47 having such a configuration. According to this configuration, the belt guide 45 can move in the direction of approaching and separating from the fixing belt 41 with respect to the frame member 46. That is, it is possible to improve the followability of the belt guide 45 to the displacement and deformation of the fixing belt 41. Thereby, it is possible to improve the stability of the contact state between the fixing belt 41 and the belt guide 45 in both the circumferential direction and the rotation axis direction of the fixing belt 41.

Next, the image forming apparatus 1 of the third embodiment will be described. FIG. 7 is a cross-sectional front view of the fixing device 40 of the third embodiment. Since the basic configuration of the third embodiment is the same as that of the first embodiment (see FIGS. 1 to 5) described above, the common components are given the same reference numerals or the same names as before. In some cases, the description thereof may be omitted, and the description of the configuration other than the featured parts may be omitted.

As shown in FIG. 7, the fixing device 40 of the image forming device 1 of the third embodiment includes an urging unit 48. The urging portions 48 are arranged at both ends of the fixing belt 41 in the rotation axis direction (paper width direction). The urging unit 48 includes an urging member 484.

The urging member 484 is arranged on the belt guide 45 side of the guide side wall portion 463 facing the belt guide 45 of the frame member 46. The urging member 484 is composed of a strip-shaped leaf spring extending in a direction intersecting the axial direction of the fixing belt 41. The urging member 484 extends from the upstream side to the downstream side in the rotational direction of the fixing belt 41 with respect to the fixing nip portion N.

The urging member 484 has elastic portions 4841 at both ends in a direction intersecting the axial direction of the fixing belt 41. Each of the two elastic portions 4841 bends toward the fixing nip portion N side and comes into contact with one surface of the connecting portion 452 of the belt guide 45 on the fixing nip portion N side.

In the urging member 484, each of the two elastic portions 4841 urges the connecting portion 452 toward the contact portion 451 side in the direction in which the contact portion 451 of the belt guide 45 approaches the fixing belt 41. That is, the urging member 484 urges the belt guide 45 in the direction approaching the fixing belt 41 at two positions on the upstream side and the downstream side in the rotation direction of the fixing belt 41 with respect to the fixing nip portion N.

The urging member 484 is composed of, for example, a sheet metal other than a leaf spring, and another elastic member is separately provided between each of the two elastic portions 484 of the urging member 484 and the connecting portion 452 of the belt guide 45. You may.

According to the above configuration, the twist of the fixing belt 41 can be eliminated in the circumferential direction. Therefore, it is possible to further improve the stability of the contact state between the fixing belt 41 and the belt guide 45 in the circumferential direction of the fixing belt 41.

Further, according to the above embodiment, the image forming apparatus 1 includes a fixing device 40 having the above configuration. As a result, in the image forming apparatus 1, both ends of the belt guide 45 in the rotation axis direction of the fixing belt 41 are urged by the urging member 481 in the direction approaching the fixing belt 41. Therefore, in the image forming apparatus 1, stable contact between the fixing belt 41 and the belt guide 45 can be realized in both the circumferential direction and the rotation axis direction of the fixing belt 41.

Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to this, and various modifications can be made without departing from the gist of the invention.

For example, in the above embodiment, the image forming apparatus 1 is a so-called tandem type image forming apparatus for color printing in which images of a plurality of colors are sequentially superimposed, but the image forming apparatus 1 is limited to such a model. Instead, it may be an image forming apparatus for color printing or an image forming apparatus for monochrome printing, which is not a tandem type.

The present invention can be used in fixing devices and image forming devices.

1 Image forming device 40 Fixing device 41 Fixing belt 42 Pressurizing roller (pressurizing member)
43 Heating part 44 Nip forming member 45 Belt guide 46 Frame member 47 Positioning part 48 Biasing part 471 Positioning pin 472, 473 Positioning hole 481, 484 Bending member N Fixing nip part

Claims (5)

An endless fixing belt that can rotate along the transport direction of the recording medium,
A pressure member that comes into contact with the outer peripheral surface of the fixing belt and gives a rotational driving force to the fixing belt.
A nip forming member which is arranged inside the fixing belt so as to face the pressurizing member across the fixing belt and contacts the inner peripheral surface of the fixing belt to form a fixing nip portion.
A belt guide that contacts the inner peripheral surface of the fixing belt other than the fixing nip portion and supports the fixing belt from the inside, and
The nip forming member, the frame member holding the belt guide, and
With
A fixing device provided with urging members arranged at both ends in the direction of the rotation axis of the fixing belt and urging the belt guide in a direction approaching the fixing belt. It is provided at the center of the fixing belt in the direction of the rotation axis, and includes a positioning portion that movably supports the belt guide with respect to the frame member.
The positioning unit is
The positioning pin provided on the frame member and
A positioning hole provided in the belt guide and formed of an elongated hole extending in a direction in which the belt guide approaches and separates from the fixing belt and into which the positioning pin is inserted.
The fixing device according to claim 1, wherein the fixing device has. The fixing according to claim 1 or 2, wherein the urging member urges the belt guide at two positions, an upstream side and a downstream side in the rotation direction of the fixing belt, with respect to the fixing nip portion. apparatus. It is provided with a heating unit which is arranged to face the outer peripheral surface of the fixing belt and heats the fixing belt by electromagnetic induction.
The fixing device according to any one of claims 1 to 3, wherein the belt guide is made of a magnetic metal. An image forming apparatus comprising the fixing apparatus according to any one of claims 1 to 4.

Images