JP7127496B2 - Fixing device and image forming device - Google Patents

Description

The present invention relates to fixing devices and image forming apparatuses.

In recent years, in image forming apparatuses such as copiers, printers, and facsimiles, images are formed by image forming processes such as electrophotographic recording, electrostatic recording, and magnetic recording. (recording material sheet, printing paper, photosensitive paper, electrostatic recording paper, etc., hereinafter also simply referred to as "paper").
A belt-type fixing device is known as an example of a fixing device for fixing an unfixed toner image.

In recent years, belt-type fixing devices require a longer warm-up time (the time required from normal temperature to a predetermined printable temperature (reload temperature), such as when the power is turned on) and first print time (after receiving a print request). There is a demand for shortening the time from the preparation for printing to the completion of the printing operation to the completion of paper discharge.

On the other hand, Patent Document 1 discloses a nip forming member having a sliding surface in sliding contact with the endless belt inside the endless belt, and a backup supporting the nip forming member located on the opposite side of the sliding surface of the nip forming member. A fixing device has been proposed which consists of a member and a heat source, can reduce the heat capacity around the heat source, directly heats the endless belt with the heat source, and forms a nip at that portion, thereby shortening the first printing time. .

On the other hand, when the endless belt is directly heated from the inside, the radiant heat from the heat source also heats the internal components of the endless belt. There is a risk.

On the other hand, in Patent Document 2, a heat transfer member with high thermal conductivity is attached to a nip support member (hereinafter also referred to as a "stay") that is arranged inside the endless belt and supports the nip forming member. A fixing device is disclosed that is tethered to the frame of the body. With such a configuration, the heat applied to the nip forming member and the supporting member is released to the frame of the apparatus main body through the heat transfer member, thereby avoiding overheating of the nip forming member and the nip supporting member. is stated.

In addition, Patent Document 3 discloses a heat source arranged inside an endless belt, a reflecting member arranged inside the endless belt to reflect radiant heat from the heat source, a stay, and a fastening member for fastening the reflecting member to the stay. is disclosed. The reflecting member has a wall portion and a protruding portion protruding from the wall portion toward the stay. It is described that with such a configuration, the reflecting member can be firmly coupled to the stay and the wall portion of the reflecting member is separated from the stay, so that the heat of the reflecting member can be prevented from being transmitted to the stay and becoming high temperature.

However, in the fixing device of Patent Document 2, since separate members with high heat conductivity are arranged, it is necessary to increase the thickness of the members in order to improve the uniformity of heat, which leads to an increase in the size of the device and space saving. There is a problem of difficulty.

In addition, in the fixing device of Patent Document 3, if the contact area between the reflector and the stay is large, it is difficult to prevent the heat of the reflector from being transmitted to the stay, and the stay becomes hot. be. In particular, heat accumulates in the central part of the length of the stay, and the temperature tends to be high, and the heat is transmitted to the surrounding members of the stay, which may exceed the heat-resistant temperature of the surrounding members. , may cause deformation or melting of the member.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a fixing device capable of preventing thermal deformation and melting of internal components while achieving space saving without complicating the component configuration.

In order to achieve such an object, a fixing device according to the present invention includes an endless fixing belt, fixing belt holding members for holding the fixing belt at both ends, and pressure members for contacting the outer peripheral surface of the fixing belt. a nip forming member arranged inside the fixing belt and forming a nip by contacting the pressing member via the fixing belt; a nip supporting member supporting the nip forming member; and an inner side of the fixing belt. a heat source that heats the fixing belt; a reflecting member that reflects the radiant heat of the heat source; a side plate that integrally fixes the fixing belt holding member and the nip support member; a pressurizing mechanism for pressing a pressure member against the nip forming member, wherein the nip supporting member is formed by integrally forming at least two types of members having different thermal conductivities , and openings formed in the side plates. The at least two types of members having different thermal conductivities are fixed at a plurality of contact points that contact the side plate .

According to the present invention, it is possible to provide a fixing device capable of preventing thermal deformation and melting of internal components while achieving space saving without complicating the configuration of components.

1 is a cross-sectional view schematically showing an example of a schematic configuration of a fixing device according to an embodiment of the invention; FIG. 1 is a perspective view showing an example of a schematic configuration of a fixing device according to an embodiment of the invention; FIG. 1 is a top view showing an example of a schematic configuration of a fixing device according to an embodiment of the invention; FIG. FIG. 2 is an explanatory view schematically showing part of the side surface of the fixing device according to the embodiment of the invention; 1 is a cross-sectional view showing an example of an image forming apparatus according to an embodiment; FIG.

A fixing device and an image forming apparatus according to the present invention will be described below with reference to the drawings. In addition, the present invention is not limited to the embodiments shown below, and can be changed within the scope of those skilled in the art, such as other embodiments, additions, modifications, deletions, etc. is also included in the scope of the present invention as long as the functions and effects of the present invention are exhibited.

[Fixing device]
A fixing device according to the present invention will be described with reference to FIGS.
The fixing device according to the present embodiment includes an endless fixing belt 60 , fixing belt holding members 51 that hold the fixing belt 60 at both ends, and a pressure member (hereinafter referred to as “applying member”) that contacts the outer peripheral surface of the fixing belt 60 . 70 (also referred to as “pressure roller”).
Further, a nip forming member 80 which is arranged inside the fixing belt 60 and contacts the pressure member 70 via the fixing belt 60 to form a nip, and a nip supporting member (stay) 90 which supports the nip forming member 80 . , and a heat source 61 arranged inside the fixing belt 60 to heat the fixing belt 60 .
Further, the pressure member 70 is pressed against the nip forming member 80 through the reflecting member 91 that reflects the radiant heat of the heat source 61, the side plate 52 that integrally fixes the fixing belt holding member 51 and the nip supporting member 90, and the fixing belt 60. and a pressurizing mechanism (biasing means) that causes the pressure to rise.

A reflector 54 that reflects the radiant heat from the heat source 61 is arranged between the heat source 61 and the nip support member 90 and fixed to the nip support member 90 with screws. Although this has the effect of preventing the heat of the reflector 54 from being directly transmitted to the nip support member 90, the heat of the reflector 54 is transmitted to the nip support member 90 at the screw fixing contact surface, and the nip support member 90 gradually heats up. Therefore, it is necessary to ensure that the contact portion with the nip forming member 80 does not exceed the heat-resistant temperature.
The fixing device of the present embodiment also includes a temperature sensor (not shown) or the like as temperature detection means for detecting the temperature of the fixing belt 60 .

The fixing belt 60 is composed of a thin flexible endless belt member (including a film). Specifically, the fixing belt 60 has an inner peripheral side base material made of a metal material such as nickel or SUS or a resin material such as polyimide (PI). Furthermore, it is composed of a release layer on the outer peripheral side made of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE), or the like.
An elastic layer made of a rubber material such as silicone rubber, foamed silicone rubber, or fluororubber may be interposed between the substrate and the release layer.

The pressure roller 70 includes a core metal 71, an elastic layer 72 made of foamed silicone rubber, silicone rubber, fluororubber, or the like provided on the surface of the core metal 71, and PFA or PTFE provided on the surface of the elastic layer 72. and the like (not shown).
The pressure roller 70 is biased toward the fixing belt 60 by a pressure mechanism (biasing means) (not shown), and is in contact with the nip forming member 80 via the fixing belt 60 .
At the location where the pressure roller 70 and the fixing belt 60 are pressed against each other, the elastic layer 72 of the pressure roller 70 is crushed, thereby forming a nip (nip portion) N having a predetermined width in the lateral direction of the nip forming member 80 . is formed.

This nip N is continuously formed in the longitudinal direction (perpendicular to the paper surface) of the nip forming member 80 .
Further, the pressure roller 70 is configured to be rotationally driven by a drive source such as a motor (not shown) provided in the body of the image forming apparatus (printer) on which the fixing device according to this embodiment is mounted.
When the pressure roller 70 is rotationally driven, the driving force is transmitted to the fixing belt 60 at the nip N, and the fixing belt 60 is driven to rotate.

The heat from the heat source 61 is reflected by the reflecting member 91, but part of it remains on the reflecting member 91 and is transmitted to the nip supporting member 90. Therefore, the temperature of the nip supporting member 90 may become high due to continuous sheet feeding. If the temperature of the nip support member 90 exceeds the heat resistance temperature of the nip forming member 80, the resin nip forming member 80 may deform or melt.
On the other hand, in the fixing device according to the present invention, the nip support member 90 is integrally formed of at least two types of members having different thermal conductivities.
The members with different thermal conductivities are made of materials with different thermal conductivities, for example.
The nip support member 90 has a member that contacts the nip forming member 80 and a member that does not contact the nip forming member 80. The member that contacts the nip forming member 80 is a member that does not contact the nip forming member 80. higher thermal conductivity than
With such a configuration, the maximum temperature at the contact portion between the nip forming member 80 and the nip supporting member 90 can be made lower than in the conventional configuration. It is possible to suppress the deformation and prevent melting and deformation.

The first embodiment is shown in FIGS. 1 and 2(A), and the second embodiment is shown in FIG. 2(B).
The first mode shown in FIGS. 1 and 2A is an example in which the nip support member 90 is integrally formed of three types of members having different thermal conductivities.
The nip support member 90 is composed of a high thermal conductivity member 90a having a heat equalizing function and high rigidity members 90b and 90c having a function of supporting the nip load, which are integrated by caulking or welding.

A second embodiment shown in FIG. 2B is an example in which the nip support member 90 is integrally formed of two types of members having different thermal conductivities.
The nip support member 90 is composed of a highly thermally conductive member 90a having a heat equalizing function and a highly rigid member 90b having a function of supporting the nip load and formed by bending, which are integrated by caulking or welding. there is

Further, in the fixing device of the present embodiment, as shown in FIGS. 2A and 2B, at least a portion of the nip support member 90 penetrates the side plate 52 and extends to the outside of the side plate 52. , is supported in contact with the side plate 52 at the penetrating portion.
By arranging the high thermal conductivity member 90a outside the side plate 52 and bringing it into contact with the side plate 52, in addition to the heat equalization effect, the effect of lowering the temperature of the member can be obtained. That is, the amount of heat emitted from the side plate 52 can be increased, and by increasing the area of contact with the air layer on the outside of the side plate 52, the amount of heat dissipation at the end portion can be increased. can reduce the maximum value of

Of the at least two types of members with different thermal conductivities that constitute the nip support member 90, the member with the highest thermal conductivity (for example, the high thermal conductivity member 90a) is longer than the other members in the longitudinal direction. It is preferable that the length extending through the side plate 52 to the outside of the side plate 52 is long. The weight and cost of the fixing device can be reduced by increasing the amount of extension of only the member with high thermal conductivity (for example, the high thermal conductivity member 90a) through the side plate 52 to the outside.

The nip support member 90 has a member that contacts the nip forming member 80 and a member that does not contact the nip forming member 80. The member that contacts the nip forming member 80 (for example, the high thermal conductivity member 90a) is The members (for example, high-rigidity members 90b and 90c) that are arranged so that their thickness direction overlaps with the direction in which the pressure member 70 presses the nip forming member 80 and do not come into contact with the nip forming member 80 are the nip forming member 80 It is preferable that the Young's modulus is higher than that of the member that abuts on the nip, and that the width direction of the member is arranged so as to overlap the direction in which the pressure member 70 presses the nip forming member.
The value of the Young's modulus of the member that does not contact the nip forming member 80 is preferably 200 GPa or more.

In this manner, the nip support member 90 is arranged to receive pressure from the high rigidity members 90b and 90c having a backup function via the high thermal conductivity member 90a, thereby preventing deformation of the high thermal conductivity member 90a. can do. That is, even if the strength of the high thermal conductivity member 90a is low, the nip load can be supported by arranging the member 90a to receive pressure in the thickness direction, and the nip width can be accurately formed.

In addition, with the arrangement described above, it is possible to use copper, aluminum, or the like, which are representative of high thermal conductivity materials, as the material of the high thermal conductivity member 90a.
On the other hand, as the material of the high-rigidity members 90b and 90c, a metallic material having high mechanical strength such as stainless steel or iron is preferable in order to satisfy the function of preventing the nip forming member 80 from bending. Moreover, it is desirable that the high-rigidity members 90b and 90c be produced by punching. In addition, by making the member 90 from a steel plate, it is possible to obtain the member 90 at a low cost and with high rigidity.

FIG. 3A is a top view of the fixing device of this embodiment, and FIG. 4 is an explanatory diagram schematically showing a part of the side surface.
As shown in FIG. 3A, the nip forming member 80 is arranged longitudinally along the rotation axis direction of the fixing belt 60 or the rotation axis direction of the pressure roller 70 and is supported by the nip support member 90. there is In FIG. 3A, members disposed inside the fixing belt 60 are indicated by dashed lines.
Both ends of the nip support member 90 are fitted into openings (mounting holes: only one end is shown in FIG. 4) formed in the side plate 52 fixed to the housing (not shown) of the fixing device, It is fixed at contact points Pa, Pb, and Pc.
With such a configuration, it is possible to prevent the nip forming member 80 and the nip supporting member 90 from being displaced due to the pressure from the pressure roller 70 .

As shown in FIG. 3A, left and right side plates 52 are integrally formed with fixing belt holding members 51 protruding toward each other.
Each fixing belt holding member 51 has a notched annular curved convex portion, and each outer peripheral curved surface is in sliding contact with both inner wall surfaces of the annular fixing belt 60, thereby suppressing rotation deviation of the fixing belt 60 in the radial direction and the axial direction. ing.

The heat source 61 may be the halogen heater of the present embodiment, but may also be an IH, a resistance heating element, a carbon heater, or the like. An example in which two halogen heaters constitute the heat source 61 will be described below, but the number of heaters is not limited.

In the fixing device of the present embodiment, two halogen heaters of the heat source 61, a central heater 61a and an end heater 61b, are used in parallel.
In the following description, the central heater 61a and the end heaters 61b are collectively referred to as halogen heaters 61. As shown in FIG.

The central heater 61 a and the end heaters 61 b have different heat generation ranges, and can heat the fixing belt 60 according to the size of the paper passed through the fixing device 50 .
Specifically, both the central heater 61a and the end heater 61b are turned on when a wide sheet of paper such as A3 vertical is passed, and the central heater 61a is turned on when a narrow sheet of paper such as A4 vertical is passed. only lights up. With such a configuration, the power consumption used for heating the fixing belt 60 can be suppressed.

FIG. 3B is a graph showing the temperature distribution in the width direction (longitudinal direction) of the nip support member 90 of the fixing device of this embodiment. The vertical axis indicates the temperature of the nip support member 90, and the horizontal axis indicates the position of the nip support member 90 in the longitudinal direction. Also, the position of the left side plate 52 in the drawing is indicated by S1, and the position of the right side plate 52 is indicated by S2.
The values of the present embodiment are indicated by a solid line, and the values of the conventional example are indicated by a broken line.
In the conventional example (broken line) in which the nip support member 90 is made of only a single high-rigidity material (mainly steel), heat can be dissipated by contacting the side plates 52 at both ends, but the heat is dissipated at the central portion. The heat is not radiated and the temperature rises, exceeding the heat-resistant temperature Tn of the nip support member.
On the other hand, in the example of the present embodiment (solid line), the nip support member 90 is uniformly heated by the high heat conduction member 90a, and the peak temperature at the central portion is suppressed to the heat resistance temperature Tn or less of the nip support member.

Next, the basic operation of the fixing device according to this embodiment will be described.
When the main body of the image forming apparatus (printer) in which the fixing device is mounted is turned on, electric power is supplied to the halogen heater 61 and the pressure roller 70 starts rotating clockwise. As a result, the fixing belt 60 rotates counterclockwise due to the frictional force with the pressure roller 70 .

After that, as shown in FIG. 1, the paper P, which is an image bearing member carrying an unfixed toner image T, is conveyed in the direction of arrow A1 while being guided by a guide plate (not shown), and the fixing belt 60 is in a press-contact state. and the nip N of the pressure roller 70 .
Then, the toner image T is fixed on the surface of the paper P by the heat from the fixing belt 60 heated by the halogen heater 61 and the pressing force between the fixing belt 60 and the pressure roller 70 .

The paper P on which the toner image T is fixed is carried out from the nip N.
At this time, the paper P is separated from the fixing belt 60 by the leading edge of the paper P coming into contact with the leading edge of the separation member 75 supported by the side plate 52 . Thereafter, the separated paper P is discharged outside the machine by the paper discharge rollers and stocked in the paper discharge tray, as described above.

Next, the nip forming member 80 will be described.
The nip forming member 80 is formed of a base portion 80b and a foot portion 80c made of resin, and a fibrous sheet 80a provided on the surface of the base portion. In order to reduce contact resistance with the fixing belt 60, the fibrous sheet 80a is impregnated with silicone oil.
As shown in the cross-sectional views of FIGS. 1 and 4, the nip forming member 80 is in contact with the supporting member 90 at two upper and lower leg portions 80c.

Since the nip forming member 80 is required to have heat insulation and heat resistance, LCP, PAI, or the like is preferable as the material resin, for example.

Next, the nip support member 90 will be described.
The nip support member 90 is a member integrally formed of at least two types of members having different thermal conductivities.
The members with different thermal conductivities are made of materials with different thermal conductivities.
In this embodiment, an example in which the high thermal conductivity member 90a and the high rigidity material 90b, or the high thermal conductivity member 90a and the high rigidity materials 90b and 90c are configured will be described, but the type and number of members are not limited to this. .

The nip support member 90 is required to have high dimensional accuracy in order to suppress variations in the width of the nip N. As shown in FIG. That is, if the nip support member 90 does not have sufficient dimensional accuracy, the nip forming member 80 may be displaced and the width of the nip N may vary. In the fixing operation, if the width of the nip N is too wide or too narrow, the toner T is not heated appropriately, which causes poor fixing.
The nip support member 90 of this embodiment, which provides a uniform width of the nip N in the longitudinal direction of the nip forming member 80, will be described below.

Both ends of the nip support member 90 are engaged with holes formed for mounting the left and right side plates 52, and are integrally fixed. It is configured to support the nip forming member 80 in the longitudinal direction and receive the pressure (load) applied from the pressure roller 70 via the fixing belt 60 as a beam supported on both sides.

For example, the nip support member 90 shown in FIG. 1 is composed of a high thermal conductivity member 90a having an L-shaped cross section, a flat plate-like high rigidity member 90b, and a bent high rigidity member 90c, which are integrally formed by caulking. .

In order to increase the mechanical strength of the nip support member 90, the high-rigidity members 90b and 90c are made of a highly rigid steel material to prevent deformation due to the load from the pressure roller .

As a material of the high thermal conductivity member 90a, a material having a thermal conductivity of 200 W/mK or more is preferable, and examples thereof include copper (398 W/mK) and aluminum (236 W/mK).
With such a configuration, the temperature is dispersed in the longitudinal direction while maintaining the mechanical strength. can be prevented from occurring.

Further, as shown in FIG. 4, in the fixing device of the present embodiment, the pressure D1 received from the pressure roller 70 is transferred from the leg portion 80c of the nip forming member through the high heat conduction member 90a of the nip supporting member to the high rigidity member. Since there is a positional relationship in the thickness direction (D2, D3) of 90b and 90c, shearing force is not applied to the high heat conduction member 90a, and even a material with low rigidity will not deform.

Furthermore, in order to reduce the temperature of the nip support member 90 itself, the high thermal conductivity member 90a abuts on the side plate 52 at the contact points Pa and Pb at the upper and lower plate thickness surfaces to which no load is applied, as shown in FIG. The load (D4) from the pressure roller 70 is received by the high-rigidity members 90b and 90c at the contact point Pc.

The high thermal conductivity member 90a is arranged so as to penetrate the side plate 52 and protrude outside the side plate 52, and the length of its outward extension is longer than the length of the high rigidity members 90b and 90c. preferable.

In addition, the high thermal conductivity member 90a preferably has a large surface area in order to increase the amount of heat dissipation, and preferably has a curved shape such as an L-shaped cross section. As a result, heat is radiated from both ends of the nip support member 90, the temperature is lowered, and the temperature range that does not exceed the heat-resistant temperature of the nip forming member 80 can be maintained.

With the above configuration, the fixing device of the present embodiment can prevent thermal deformation and melting of internal components while achieving space saving without complicating the component configuration.

[Image forming apparatus]
FIG. 5 shows a schematic configuration diagram of a color printer as an image forming apparatus equipped with a fixing device according to the present invention.
The image forming apparatus 10 shown in FIG. 5 includes a fixing device 50 according to the present invention and an electrophotographic image forming section. Means 1a, 1b, 1c and 1d are provided. The first to fourth image forming units 1a, 1b, 1c and 1d have the same configuration, but differ only in the corresponding toner colors. Therefore, in these image forming means, for example, a black toner image, a magenta toner image, a cyan toner image and a yellow toner image are formed.
Since these image forming means have the same configuration except for the difference in the color of the developer (toner), the suffixes a, b, c, and d in the reference numerals are omitted as appropriate in the following description. do.

In the image forming means 1, a drum-shaped photoreceptor 2, which is an electrostatic latent image carrier, is arranged. there is
The photoreceptor 2 can be rotated clockwise, and a charging member 3 is pressed against the surface of the photoreceptor 2 .
The charging member 3 is driven to rotate as the photosensitive member 2 is driven to rotate.
A predetermined bias voltage is applied to the charging member 3 from a high-voltage power source (not shown), so that the surface of the rotating photosensitive member 2 can be uniformly charged.
The charging member 3 shown here employs a roller-shaped member that contacts the photoreceptor 2, but it is also possible to employ a non-contact type that utilizes corona discharge or the like.

Further, in the image forming apparatus 10 shown in FIG. 5, an exposure device 6 is provided diagonally below in parallel with the four image forming means.
The exposure device 6 has appropriately appropriate structural members such as a light source, a polygon mirror, an f-θ lens, and a reflecting mirror.
Then, each photosensitive member 2 charged by the charging member 3 is exposed based on the image information formed according to the image data of each color toner.
It is provided to create an electrostatic latent image on each photoreceptor 2 .
The electrostatic latent image formed on the photoreceptor 2 using the exposure device 6 is developed and visualized by applying toner of each color as the photoreceptor 2 rotates and passes through the developing device 4 . be.

Toner bottles 20 a , 20 b , 20 c and 20 d filled with black, magenta, cyan and yellow toners are arranged above the inside of the image forming apparatus 10 .
A predetermined amount of toner is supplied from the toner bottles 20a, 20b, 20c and 20d to the respective color developing devices 4a, 4b, 4c and 4d via a transport path (not shown).

Further, an endless belt-shaped intermediate transfer belt 7 configured as an intermediate transfer member is disposed facing the photoreceptors 2 of each image forming means, and each photoreceptor 2 is in contact with the surface of the intermediate transfer belt 7 . in contact with
The intermediate transfer belt 7 shown in FIG. 5 is wound around a plurality of support rollers (for example, support rollers 15a and 15b). In the illustrated example, the support roller 15a is connected to a drive motor (not shown) as a drive source.
By driving the drive motor, the intermediate transfer belt 7 rotates counterclockwise in the drawing, and the supporting roller 15b that can be rotated is rotated.

A primary transfer roller 8 is arranged on the back surface of the intermediate transfer belt 7 so as to face the photosensitive member 2 with the belt interposed therebetween.
A primary transfer bias is applied to the primary transfer roller 8 from a high-voltage power supply (not shown), and the toner image on the photosensitive member 2 visualized by the developing device 4 is primarily transferred to the intermediate transfer belt 7 .
The primary transfer residual toner left on the photoreceptor 2 without primary transfer is removed by the intermediate transfer belt cleaning means 19 in preparation for the next image forming operation by the photoreceptor 2, and the toner on the photoreceptor 2 is removed. is completely removed.

Further, in the illustrated image forming apparatus 10 , a secondary transfer roller 18 as a secondary transfer device is provided on the downstream side of the primary transfer roller 8 in the driving direction of the intermediate transfer belt 7 .
The secondary transfer roller 18 faces the support roller 15b with the intermediate transfer belt 7 interposed therebetween.
The secondary transfer roller 18 and the support roller 15b form a secondary transfer nip with the intermediate transfer belt 7 therebetween.

The image forming apparatus 10 also includes a paper feeding cassette 30 and a feeding roller 31 as a recording medium stacking unit, and a registration roller pair (positioning roller pair) 35 and the like.
A fixing device 50 and a pair of discharge rollers 36 are provided downstream of the secondary transfer roller 18 in the conveying direction of the recording medium.

Next, the image forming operation will be described.
In this image forming operation as well, the configuration for forming a toner image on each photoreceptor 2 and transferring the toner image to the intermediate transfer belt 7 is substantially the same except for the color of the toner image. , a, b, c and d subscripts are omitted as necessary.

First, the photoreceptor 2 is rotated clockwise by a drive source (not shown), and at this time, the surface of the photoreceptor is irradiated with light from a neutralizer (not shown) to initialize the surface potential.
The surface of the photosensitive member 2 whose surface potential has been initialized is then uniformly charged to a predetermined polarity by the charging member 3 . The charged surface of the photoreceptor is irradiated with laser light from the exposure device 6, thereby forming an electrostatic latent image on the surface of the photoreceptor.
At this time, the image information exposed to each photosensitive member 2 is monochromatic image information obtained by decomposing a desired full-color image into respective toner color information of yellow, cyan, magenta and black.
The electrostatic latent image formed on the photoreceptor in this manner is given toner (developer) of each color from the developing device 4 when passing through the developing device 4, and is visualized as a visualized toner image. .

Further, the intermediate transfer belt 7 is driven to run counterclockwise in the figure.
A primary transfer voltage having a polarity opposite to the toner charge polarity of the toner image formed on the photosensitive member is applied to the primary transfer roller 8 described above.
Thereby, a transfer electric field is formed between the photoreceptor 2 and the intermediate transfer belt 7 .
Then, the toner image on the photoreceptor 2 is electrostatically primarily transferred onto an intermediate transfer belt 7 which is rotationally driven in synchronism with the photoreceptor 2 .
In this way, the primary-transferred toner images of the respective colors are successively superimposed on the intermediate transfer belt 7 from the upstream side of the intermediate transfer belt 7 in the conveying direction, and a desired full-color image is formed.

On the other hand, the recording medium on which an image is to be formed is separated sheet by sheet from the recording medium stack loaded in the paper feed cassette 30 to the registration roller pair 35 by the action of an appropriately appropriate conveying member such as the feed roller 31 . and fed.
At that time, the leading edge of the conveyed recording medium collides with the nip portion of the registration roller pair 35 which has not yet started to rotate, forming a so-called loop, thereby performing registration of the recording medium. .

After that, the registration roller pair 35 is started to rotate in synchronization with the full-color toner image carried on the intermediate transfer belt 7 .
Then, the recording medium is sent toward a secondary transfer nip portion composed of the support roller 15b and the secondary transfer roller 18 facing the support roller 15b with the intermediate transfer belt 7 interposed therebetween.
In this embodiment, a transfer voltage having a polarity opposite to the toner charge polarity of the toner image on the surface of the intermediate transfer belt is applied to the secondary transfer roller 18 .
Thus, the full-color toner image formed on the surface of the intermediate transfer belt 7 is collectively transferred onto the recording medium.

The recording medium onto which the toner image has been transferred is further conveyed to the fixing device 50 .
Then, when passing through the fixing device 50, heat and pressure are applied to fix the toner image on the recording medium as a permanent image.
The image-fixed recording medium is discharged to a recording medium discharge unit such as the discharge tray 29 via the paper discharge roller pair 36 to complete the image forming operation.
Residual toner remaining on the intermediate transfer belt 7 without being transferred at the secondary transfer nip portion where the secondary transfer roller 18 is arranged is removed and collected by the intermediate transfer belt cleaning means 19 .

10 Image forming apparatus 50 Fixing device 51 Fixing belt holding member 52 Side plate 60 Fixing belt 61 Heat source 70 Pressure member 80 Nip forming member 90 Nip support member 90a High thermal conductivity member 90b High rigidity member 90c High rigidity member 91 Reflective member P Recording medium (Paper)
T toner image

Japanese Patent Application Laid-Open No. 2007-233011 JP 2014-174439 A JP 2017-215434 A

Claims (8)

an endless fixing belt;
a fixing belt holding member that holds the fixing belt at both ends;
a pressing member that contacts the outer peripheral surface of the fixing belt;
a nip forming member that is disposed inside the fixing belt and contacts the pressure member via the fixing belt to form a nip;
a nip support member that supports the nip forming member;
a heat source disposed inside the fixing belt to heat the fixing belt;
a reflecting member that reflects the radiant heat of the heat source;
a side plate for integrally fixing the fixing belt holding member and the nip support member;
a pressurizing mechanism that presses the pressurizing member against the nip forming member via the fixing belt;
The nip support member is formed by integrally forming at least two types of members with different thermal conductivities, and is fitted in openings formed in the side plates, and the at least two types of members with different thermal conductivities are combined. The fixing device is fixed at a plurality of contact points that contact the side plate . 2. The fixing device according to claim 1, wherein the members having different thermal conductivities constituting said nip support member are made of materials having different thermal conductivities. The nip support member has a member that contacts the nip forming member and a member that does not contact the nip forming member,
3. The fixing device according to claim 1, wherein the member contacting the nip forming member has higher thermal conductivity than the member not contacting the nip forming member. 2. A material having a thermal conductivity of 200 W/mK or more is used for the member having the highest thermal conductivity among at least two types of members having different thermal conductivity that constitute the nip support member. 4. The fixing device according to any one of 3 to 3. 5. The nip support member according to any one of claims 1 to 4, wherein at least part of said nip support member penetrates said side plate and extends to the outside of said side plate, and is supported in contact with said side plate at the penetrating portion. A fixing device as described. Of the at least two types of members with different thermal conductivities forming the nip support member, the member with the highest thermal conductivity extends through the side plate to the outside of the side plate more than the other members in the longitudinal direction. 6. The fixing device according to claim 5, wherein the fixing length is long. The nip support member has a member that contacts the nip forming member and a member that does not contact the nip forming member,
The member that contacts the nip forming member is arranged such that its thickness direction overlaps with the direction in which the pressure member applies pressure to the nip forming member,
The member that does not come into contact with the nip forming member has a higher Young's modulus than the member that comes into contact with the nip forming member, and is arranged so that its width direction overlaps the direction in which the pressing member presses the nip forming member. 7. The fixing device according to any one of claims 1 to 6, characterized in that: An image forming apparatus comprising the fixing device according to claim 1 .

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