JP7434940B2 - Fixing device and image forming device - Google Patents

Description

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

In an electrophotographic fixing device, in order to suppress temperature unevenness in the axial direction during paper feeding, a nip forming member made of a thin metal plate material that has both heat capacity and heat uniformity is used to prevent heat transfer to the support member. In order to reduce the contact surface, and to avoid narrowing the center of the nip due to deflection due to pressure from the opposing member, it is supported by a support member that has a certain amount of continuous arcuate convex shape on the cut surface. do.

For example, in Patent Document 1, a flexible endless fixing member, a heat source that heats the fixing member, a pressure member facing the fixing member, and a space between the fixing member and the pressure member In the fixing device, the fixing device includes a nip forming member that forms a nip, and a supporting member that supports the nip forming member, wherein a back surface of the nip forming member that comes into contact with the supporting member has a non-linear shape in the longitudinal direction. Disclosed.

However, when the supporting member of the nip forming member is provided with a convex shape as in Patent Document 1, there is a problem that the nip forming member is deformed due to load concentration when the nip forming member is in the shape of a thin plate.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device that can improve load concentration on a nip forming member.

The fixing device according to the present invention includes a rotatable endless fixing member, a facing member that contacts an outer circumferential surface of the fixing member, a heating element for heating the fixing member, and an inner circumferential side of the fixing member. a nip forming member made of a metal material and abutting against the opposing member to form a nip portion; a support member supporting the nip forming member via a surface pressure dispersing member; and the nip forming member and the supporting member. a surface pressure dispersion member disposed between the nip formation member and made of a material with higher rigidity than the nip formation member , the area of the contact surface between the surface pressure distribution member and the nip formation member being the surface pressure dispersion member. The fixing device is configured as a fixing device characterized in that the area is larger than the area of the contact surface between the member and the support member.

According to the present invention, it is possible to improve load concentration on the nip forming member.

FIG. 1 is a diagram illustrating an example of an image forming apparatus according to the present embodiment. FIG. 2 is a cross-sectional view showing a conventional fixing device. FIG. 2 is a perspective view of a conventional nip forming member and support member. FIG. 2 is a cross-sectional view showing a fixing device in this embodiment. It is a perspective view of a nip formation member and a support member in this embodiment. It is a figure which shows the example of the conventional surface pressure dispersion member. It is a figure which shows the example of the surface pressure dispersion member in this Embodiment. It is a figure which shows the other example of the surface pressure dispersion member in this Embodiment. FIG. 6 is a diagram showing an example of a shape in which the surface pressure dispersion member can have higher rigidity than the nip forming member. It is a figure which shows an example of the support member formed by the convex part whose cut surface is interrupted, and the several surface pressure dispersion member arrange|positioned according to the convex part. FIG. 3 is a diagram illustrating an example of a fixing device including a heat insulating member with low thermal conductivity between a nip forming member and a surface pressure dispersing member. FIG. 3 is a diagram illustrating an example of a fixing device including a heat insulating member with low thermal conductivity between a nip forming member and a surface pressure dispersing member. 11 is a diagram showing a configuration example in which the height of the cut surface of the support member shown in FIG. 10 is made uniform, and the thickness of the surface pressure dispersion members among the plurality of surface pressure distribution members shown in FIG. 10 is made different. FIG. FIG. 7 is a diagram illustrating an example of creating a highly accurate central convex shape while sandwiching a surface pressure reducing member of the same thickness between a support member having support surfaces of the same height and a nip forming member. FIG. 2 is a cross-sectional view schematically showing a fixing device in which a heat generating portion is provided in a nip forming member. FIG. 16 is a diagram showing an example of the configuration of the heat generating section shown in FIG. 15;

Embodiments of the present invention will be described below. In this embodiment, a fixing device used in an image forming apparatus such as a copying machine, a printer, or a facsimile machine, and an image forming apparatus equipped with the fixing device, have a low heat capacity and a low heat capacity to suppress temperature unevenness in the axial direction when paper passes. The nip forming member is made of a thin metal plate material that achieves both heat uniformity and has a small contact surface to reduce heat transfer, and also to avoid narrowing of the center of the nip due to deflection due to pressure from the opposing member. In order to do this, it is supported by a support member provided with a certain amount of continuous arcuate convex shapes on the cut surface. For example, a contact pressure dispersion member that is made of a member or shape that is more rigid than a nip formation member made of aluminum or copper, and whose contact surface with the nip formation member is larger than the area of the cut surface of the support member is used to form the nip. Provided between the member and the support member. As a result, the surface pressure distribution member can transmit the concentrated load from the supporting member to the nip forming member as a load distributed over the entire contact surface with the nip forming member in response to the pressing force of the opposing member. It becomes possible to prevent plastic deformation of the forming member. The features of the present invention described above will be explained in detail using the following drawings.

The image forming apparatus 1 shown in FIG. 1 is a color laser printer, and four image forming sections 4Y, 4M, 4C, and 4K are provided in the center of the apparatus main body. Each of the image forming units 4Y, 4M, 4C, and 4K accommodates developers of different colors, yellow (Y), magenta (M), cyan (C), and black (K), corresponding to the color separation components of a color image. The configuration is the same except for the

Specifically, each of the image forming units 4Y, 4M, 4C, and 4K includes a drum-shaped photoreceptor 5 as a latent image carrier, a charging device 6 that charges the surface of the photoreceptor 5, and a charging device 6 that charges the surface of the photoreceptor 5. It includes a developing device 7 that supplies toner, a cleaning device 8 that cleans the surface of the photoreceptor 5, and the like. In FIG. 1, only the photoreceptor 5, charging device 6, developing device 7, and cleaning device 8 included in the black image forming section 4K are labeled, and the other image forming sections 4Y, 4M, and 4C are designated by reference numerals. The symbol is omitted.

An exposure device 9 for exposing the surface of the photoreceptor 5 is provided below each of the image forming units 4Y, 4M, 4C, and 4K. The exposure device 9 includes a light source, a polygon mirror, an f-θ lens, a reflection mirror, etc., and is configured to irradiate the surface of each photoreceptor 5 with laser light based on image data.

Furthermore, a transfer device 3 is disposed above each image forming section 4Y, 4M, 4C, and 4K. The transfer device 3 includes an intermediate transfer belt 30 as an intermediate transfer body, four primary transfer rollers 31 as primary transfer means, a secondary transfer roller 36 as secondary transfer means, and a secondary transfer backup roller 32. A cleaning backup roller 33, a tension roller 34, and a belt cleaning device 35 are provided.

The intermediate transfer belt 30 is an endless belt, and is stretched by a secondary transfer backup roller 32, a cleaning backup roller 33, and a tension roller 34. Here, by rotationally driving the secondary transfer backup roller 32, the intermediate transfer belt 30 is configured to travel around (rotate) in the direction shown by the arrow in the figure.

The four primary transfer rollers 31 each sandwich the intermediate transfer belt 30 with each photoreceptor 5 to form a primary transfer nip. Further, a power source (not shown) is connected to each primary transfer roller 31, and a predetermined direct current voltage (DC) and/or alternating current voltage (AC) is applied to each primary transfer roller 31.

The secondary transfer roller 36 and the secondary transfer backup roller 32 sandwich the intermediate transfer belt 30 to form a secondary transfer nip. Further, similar to the primary transfer roller 31 described above, a power source (not shown) is also connected to the secondary transfer roller 36, and a predetermined direct current voltage (DC) and/or alternating current voltage (AC) is applied to the secondary transfer roller 36. It is now possible to do so.

The belt cleaning device 35 includes a cleaning brush and a cleaning blade that are arranged to come into contact with the intermediate transfer belt 30. A waste toner transfer hose (not shown) extending from the belt cleaning device 35 is connected to an entrance of a waste toner container (not shown).

A bottle accommodating section 2 is provided at the top of the printer body, and four toner bottles 2Y, 2M, 2C, and 2K for accommodating replenishment toner are removably attached to the bottle accommodating section 2. . A supply path (not shown) is provided between each toner bottle 2Y, 2M, 2C, 2K and each developing device 7. Toner is supplied to the device 7.

On the other hand, at the bottom of the printer body, there are provided a paper feed tray 10 that accommodates paper P as a recording medium, a paper feed roller 11 that carries out paper P from the paper feed tray 10, and the like. In addition to plain paper, recording media include cardboard, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheets, and the like. Further, although not shown, a manual paper feeding mechanism may be provided.

A conveyance path R is disposed within the printer body for discharging the paper P from the paper feed tray 10 through the secondary transfer nip and out of the apparatus. In the conveyance path R, a pair of registration rollers 12 are disposed upstream of the position of the secondary transfer roller 36 in the paper conveyance direction as timing rollers that measure the conveyance timing and convey the paper P to the secondary transfer nip. ing.

Furthermore, a fixing device 20 for fixing the unfixed image transferred to the paper P is disposed downstream of the position of the secondary transfer roller 36 in the paper conveyance direction. Further, a pair of paper ejection rollers 13 for ejecting the paper out of the apparatus is provided downstream of the fixing device 20 in the paper transport direction of the transport path R. Further, a paper discharge tray 14 for storing paper discharged outside the apparatus is provided on the top surface of the printer main body.

Next, the basic operation of the printer according to this embodiment will be explained with reference to FIG. When the image forming operation is started, each photoreceptor 5 in each of the image forming units 4Y, 4M, 4C, and 4K is rotated clockwise in the figure by a drive device (not shown), and the surface of each photoreceptor 5 is charged by a charging device 6. is uniformly charged to a predetermined polarity. The charged surface of each photoreceptor 5 is irradiated with laser light from the exposure device 9, and an electrostatic latent image is formed on the surface of each photoreceptor 5. At this time, the image information exposed to each photoreceptor 5 is monochrome image information obtained by separating a desired full-color image into yellow, magenta, cyan, and black color information. By supplying toner from each developing device 7 to the electrostatic latent image formed on each photoreceptor 5 in this way, the electrostatic latent image is developed (visualized) as a toner image. .

Further, when the image forming operation is started, the secondary transfer backup roller 32 is driven to rotate counterclockwise in the figure, causing the intermediate transfer belt 30 to travel around in the direction indicated by the arrow in the figure. Further, by applying a constant voltage or constant current controlled voltage having a polarity opposite to the charging polarity of the toner to each primary transfer roller 31, a primary transfer nip between each primary transfer roller 31 and each photoconductor 5 is formed. A transfer electric field is formed at.

Thereafter, as each photoreceptor 5 rotates, when the toner image of each color on the photoreceptor 5 reaches the primary transfer nip, the toner image on each photoreceptor 5 is generated by the transfer electric field formed in the primary transfer nip. are transferred onto the intermediate transfer belt 30 in a superimposed manner. In this way, a full-color toner image is carried on the surface of the intermediate transfer belt 30. Furthermore, the toner on each photoreceptor 5 that has not been completely transferred to the intermediate transfer belt 30 is removed by the cleaning device 8 . Then, the surface of each photoreceptor 5 is neutralized by a static eliminating device (not shown), and the surface potential is initialized.

At the bottom of the printer, the paper feed roller 11 starts rotating, and the paper P is sent out from the paper feed tray 10 to the conveyance path R. The conveyance of the paper P sent out to the conveyance path R is temporarily stopped by the registration rollers 12.

Thereafter, rotation of the registration rollers 12 is started at a predetermined timing, and the paper P is conveyed to the secondary transfer nip at the timing when the toner image on the intermediate transfer belt 30 reaches the secondary transfer nip. At this time, a transfer voltage having a polarity opposite to the toner charge polarity of the toner image on the intermediate transfer belt 30 is applied to the secondary transfer roller 36, thereby forming a transfer electric field in the secondary transfer nip. . Then, the toner images on the intermediate transfer belt 30 are transferred onto the paper P all at once by this transfer electric field. At this time, residual toner on the intermediate transfer belt 30 that has not been completely transferred to the paper P is removed by a belt cleaning device 35, and the removed toner is conveyed to a waste toner container (not shown) and collected.

After that, the paper P is conveyed to the fixing device 20, and the toner image on the paper P is fixed to the paper P by the fixing device 20. Then, the paper P is discharged out of the apparatus by the paper discharge roller 13 and is stocked on the paper discharge tray 14.

The above explanation is about the image forming operation when forming a full-color image on paper. It is also possible to use two or three image forming sections to form a two-color or three-color image.

FIG. 2 is a sectional view showing a conventional fixing device, and FIG. 3 is a perspective view of a conventional nip forming member and supporting member. Hereinafter, the configuration of the fixing device 20 will be described based on FIG. 2.

As shown in FIG. 2, the fixing device 20 includes a fixing belt 21 as a fixing member, a pressure roller 22 as an opposing member that contacts the outer peripheral surface of the fixing belt 21, and a heat source that heats the fixing belt 21. A nip forming member 24 that contacts the pressure roller 22 from the inner peripheral side of the fixing belt 21 to form a nip portion N, a support member 25 that supports the nip forming member 24, and a A reflecting member 26 that reflects heat to the fixing belt 21 and a shielding member 27 that partially shields the heat from the halogen heater 23 as necessary or depending on paper passing conditions may be provided. Further, a temperature sensor 28 and the like as temperature detection means for detecting the temperature of the fixing belt 21 is provided.

The fixing belt 21 is composed of a thin and flexible endless belt member (including a film). Specifically, the fixing belt 21 includes an inner base material made of a metal material such as nickel or SUS, or a resin material such as polyimide (PI), and a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA). Alternatively, it is constituted by a release layer on the outer peripheral side made of polytetrafluoroethylene (PTFE) or the like. Furthermore, an elastic layer made of a rubber material such as silicone rubber, foamable silicone rubber, or fluororubber may be interposed between the base material and the release layer.

In addition, when there is no elastic layer, the heat capacity is small and the fixing performance is improved, but when unfixed toner is crushed and fixed, minute irregularities on the belt surface are transferred to the image, causing uneven gloss in the solid areas of the image. may occur. To prevent this, it is desirable to provide an elastic layer with a thickness of 100 μm or more. By providing an elastic layer with a thickness of 100 μm or more, minute irregularities can be absorbed by elastic deformation of the elastic layer, so that uneven gloss can be avoided.

In this embodiment, in order to reduce the heat capacity of the fixing belt 21, the fixing belt 21 is made thin and small in diameter. Specifically, the thickness of each of the base material, elastic layer, and release layer constituting the fixing belt 21 is set in the range of 20 to 50 μm, 100 to 300 μm, and 10 to 50 μm, and the overall thickness is It is set to 1 mm or less. Further, the diameter of the fixing belt 21 is set to 20 to 40 mm. In order to further reduce the heat capacity, the entire thickness of the fixing belt 21 is preferably 0.2 mm or less, and more preferably 0.16 mm or less. Further, it is desirable that the diameter of the fixing belt 21 is 30 mm or less.

The pressure roller 22 includes a core metal 22a, an elastic layer 22b made of foamable silicone rubber, silicone rubber, fluororubber, etc. provided on the surface of the core metal 22a, and a PFA layer provided on the surface of the elastic layer 22b. Alternatively, the release layer 22c is made of PTFE or the like. The pressure roller 22 is pressed toward the fixing belt 21 side by a pressure means (not shown) and comes into contact with the nip forming member 24 via the fixing belt 21 . At a location where the pressure roller 22 and the fixing belt 21 come into pressure contact, the elastic layer 22b of the pressure roller 22 is crushed, thereby forming a nip portion N having a predetermined width. Note that the fixing member and the facing member are not limited to being in pressure contact with each other, but may also be configured in such a manner that they are simply brought into contact without applying pressure.

Further, the pressure roller 22 is configured to be rotationally driven by a drive source such as a motor (not shown) provided in the printer body. When the pressure roller 22 is driven to rotate, the driving force is transmitted to the fixing belt 21 at the nip portion N, and the fixing belt 21 is driven to rotate.

In this embodiment, the pressure roller 22 is a solid roller, but it may be a hollow roller. In that case, a heat source such as a halogen heater may be provided inside the pressure roller 22. Further, the elastic layer 22b may be made of solid rubber, but if there is no heat source inside the pressure roller 22, sponge rubber may be used. Sponge rubber is more desirable because it has better heat insulation and makes it difficult for the fixing belt 21 to lose heat.

The halogen heater 23 is disposed on the inner peripheral side of the fixing belt 21 and on the upstream side of the nip portion N in the paper conveyance direction. The halogen heater 23 is configured to generate heat under output control by a power supply section provided in the printer body, and the output control is performed based on the detection result of the surface temperature of the fixing belt 21 by the temperature sensor 28. be exposed. By controlling the output of the heater 23 in this manner, the temperature of the fixing belt 21 (fixing temperature) can be set to a desired temperature. Note that instead of the temperature sensor 28 that detects the temperature of the fixing belt 21, a temperature sensor (not shown) that detects the temperature of the pressure roller 22 is provided, and the temperature of the fixing belt 21 is determined based on the temperature detected by the temperature sensor. It may also be predicted.

In this embodiment, two halogen heaters 23 are provided, but the number of halogen heaters 23 may be one or three or more depending on the size of paper used in the printer. Furthermore, as a heat source for heating the fixing belt 21, it is also possible to use a resistance heating element, a carbon heater, or the like in addition to the halogen heater.

The nip forming member 24 is adapted to slide directly on the inner surface of the belt. The shape of the nip portion N is determined by receiving the pressure from the pressure roller 22. In this embodiment, the shape of the nip portion N is flat, but it may have a concave shape or other shapes.

The support member 25 supports the nip formation member 24 at its cut surface as shown in FIG. 3, so that the nip formation member 24 and the support member 25 are in line contact, so that heat does not easily flow to the support member 25. Further, by providing an arcuate convex shape on the cut surface of the support member 25, it is possible to cancel the deflection of the stay when a load is applied, thereby providing an effect of preventing a decrease in the central nip.

The reflecting member 26 is fixedly supported by the supporting member 25 so as to face the halogen heater 23 . By reflecting the heat (or light) radiated from the halogen heater 23 to the fixing belt 21 by the reflecting member 26, the transfer of heat to the support member 25 etc. is suppressed, and the fixing belt 21 is efficiently heated. At the same time, we are working to save energy. As the material of the reflective member 26, aluminum, stainless steel, or the like is used. In particular, when an aluminum base material on which silver having a low emissivity (high reflectance) is vapor-deposited is used, it is possible to improve the heating efficiency of the fixing belt 21.

The shielding member 27 is constructed by forming a metal plate with a thickness of 0.1 mm to 1.0 mm into an arcuate cross-sectional shape along the inner peripheral surface of the fixing belt 21. Further, the shielding member 27 is movable in the circumferential direction of the fixing belt 21 as necessary. In this embodiment, in the circumferential region of the fixing belt 21, there is a direct heating region where the halogen heater 23 directly faces and heats the fixing belt 21, and a region other than the shielding member 27 between the halogen heater 23 and the fixing belt 21. Although there is a non-direct heating area in which members (reflection member 26, support member 25, nip forming member 24, etc.) are interposed, if it is necessary to provide heat shielding, the shielding member 27 may be placed at a shielding position on the direct heating area side. Set up On the other hand, when there is no need for heat shielding, the shielding member 27 can be moved to the retracted position on the side of the non-direct heating area, and the shielding member 27 can be retracted to the back side of the reflective member 26 and the support member 25. . In addition, since the shielding member 27 requires heat resistance, it is preferable to use a metal material such as aluminum, iron, stainless steel, or ceramic, as the material thereof.

FIG. 4 is a sectional view showing a fixing device according to an embodiment of claim 1, and FIG. 5 is a perspective view of a nip forming member and a support member according to an embodiment of claim 1.

The fixing device 20 of this embodiment will be explained using FIGS. 4 and 5. The fixing device 20 in this embodiment includes an endless fixing member 21, a facing member 22 that contacts the outer circumferential surface of the fixing member, a heat source 23 that heats the fixing member 21, and a portion facing from the inner circumferential side of the fixing member 21. 22, a support member 25 that supports the nip formation member 24, and a nip formation member that is independently disposed between the nip formation member 24 and the support member 25. The present invention differs from the conventional one in that it includes a surface pressure dispersion member 29 whose contact surface with the supporting member 24 is larger than the area of the contact surface of the support member 25.

In order to suppress temperature unevenness in the axial direction during paper passing, a contact surface with the nip forming member 24 is provided between the nip forming member 24 and the supporting member 25, which are made of a thin metal plate material that has both low heat capacity and heat uniformity. By arranging the surface pressure dispersion member 29 larger than the area of the contact surface of the support member 25, the surface pressure dispersion member 29 can nip the concentrated load from the support member 25 against the pressing force of the opposing member. The load can be transmitted as a distributed load over the entire contact surface with the forming member 24, making it possible to prevent plastic deformation of the nip forming member 24.

By making the surface of the supporting member 25 that supports the nip forming member a cut surface such as the cut surface 25a, which is easy to form a continuous convex shape with high precision due to its excellent workability, the center of the nip is It is possible to prevent plastic deformation of the nip forming member 24 by the surface pressure dispersing member 29 while also obtaining the effect of avoiding the portion from becoming narrow. Further, by supporting the plurality of cut surfaces 25a, it becomes possible to stably support the nip forming member 24 and the surface pressure dispersing member 29.

Next, a fixing device according to an embodiment of claims 4, 5, 6, and 8 will be described. The surface pressure dispersion member 29 will be explained using FIGS. 6 and 7. In the conventional configuration shown in FIG. 6, a nip forming member 24 made of a metal material is supported by a support member 25 made of a steel plate or the like. The metal material of the nip forming member 24 is required to have high (large) thermal conductivity in order to improve heat uniformity, so aluminum or copper, which has high thermal conductivity among metals with excellent workability and production volume, is used. This is desirable. However, since concentrated loads such as f1 and f2 are applied from the supporting member 25 to the nip forming member 24 on a limited contact surface, the nip forming member is made of aluminum or copper, which is less rigid than the steel plate of the supporting member 25. There is a problem that 24 is plastically deformed.

In the present embodiment shown in FIG. 7, the nip forming member 24 is made of a member or shape (work-hardened shape or thicker shape) that has the same or higher rigidity than the nip forming member 24 made of aluminum or copper. By providing a contact pressure dispersing member 29 between the nip forming member 24 and the supporting member 25 whose contact surface with the nip forming member 24 is larger than the area of the cut surface of the supporting member 25, the pressure F of the opposing member 22 can be suppressed. Therefore, the surface pressure dispersing member 29 can transmit the concentrated loads f1 and f2 from the support member 25 to the nip forming member 24 as a load fa that disperses the loads f1 and f2 over the entire contact surface with the nip forming member 5. , it becomes possible to prevent plastic deformation of the nip forming member 24. In addition, the surface pressure dispersion member 29 is made of a material that not only has superior rigidity compared to aluminum or copper, but also has a lower thermal conductivity than aluminum, copper, or steel plate, so that the heat from the nip forming member 24 is It is desirable to use stainless steel material because it also makes it possible to prevent the movement of the material. Further, in the case of a surface pressure dispersion member using a pressed part, it is preferable that the surface that contacts the support surface and the nip forming member is not a cut surface. This is because the cut surfaces of the press work are rough, so it is difficult to ensure contact across the entire surface, and as a result, pressure is concentrated in one part, making it difficult to obtain a surface pressure dispersion effect.

By making the surface pressure dispersion member 29 an independent component, the easy-to-process cut surface of the support member 25 can be used as it is, so that a highly accurate convex shape can be maintained. Further, it is possible to use an elastic member, a resin material, or the like, which is difficult to make the same as the support member 25, as the material. In addition, since the stress applied when processing the support member 25 to be the same as that of the supporting member 25 can be avoided, the heat transfer to the nip forming member 24 can be reduced by making the surface pressure dispersing member 29 thinner and having a lower heat capacity. It becomes possible. Further, as shown in FIG. 8, by providing an opening 80 in the surface pressure dispersing member 29, the heat capacity can be lowered, so that it is possible to reduce heat transfer of the nip forming member 24.

Next, a fixing device according to an embodiment of claim 7 will be described. FIG. 9 shows an example of a shape in which the surface pressure dispersion member 29 can have higher rigidity than the nip forming member 24. As shown in FIG. As shown in FIG. 9, by providing a plurality of uneven shapes 90 on the surface of the surface pressure dispersion member 29, the strength of the surface pressure dispersion member 29 is increased, and deformation of the surface pressure dispersion member 29 itself can be prevented.

Next, a fixing device according to an embodiment of claims 9 and 10 will be described. FIG. 10 shows an example of a support member 25 formed of convex portions 1000 with intermittent cut surfaces, and a plurality of surface pressure dispersion members arranged according to the convex portions 1000. By making the support member 25 into an intermittent convex shape as shown in FIG. 10 and arranging the surface pressure dispersion member 29 partially accordingly, the contact area can be further reduced and heat transfer of the nip forming member 24 can be reduced. becomes possible.

Next, a fixing device according to an embodiment of claim 11 will be described. 11 and 12 show an example of a fixing device that includes a heat insulating member 30 with low thermal conductivity between the nip forming member 24 and the surface pressure dispersing member 29. In FIG. As shown in the figure, by combining not only the surface pressure reducing member 29 that prevents the deformation of the nip forming member 24 but also a plurality of heat insulating members 30 with excellent thermal conductivity, the nip forming member 24 can be formed while reducing heat transfer. It becomes possible to prevent deformation of the member 24 and to strengthen it. The material of the heat insulating member 30 may be, for example, the same material as the surface pressure dispersion member 29, or a material having a lower thermal conductivity than aluminum, copper, or steel plate.

Next, a further example will be described in which a convex shape is not created using a support member that facilitates processing, but a convex shape is created by changing the thickness of a surface pressure dispersion member. In FIG. 13, the height of the cut surface 25a of the support member 25 shown in FIG. 10 is made uniform, and among the plurality of surface pressure dispersion members 29 shown in FIG. Examples of configurations with different thicknesses are shown. In FIG. 13, a member 291 is arranged on the end side in the width direction, and a member 292 is arranged in the center part in the width direction, and the member 292 is arranged so as to be thicker than the member 291, When the surface pressure dispersion member 29 is arranged, the central portion is generally thicker than the end portions.

With this configuration, the nip forming member supporting surfaces 25a of the supporting member are formed at approximately the same height, making shearing easier, and furthermore, the nip forming member supporting surfaces 25a of the supporting member By aligning the support surfaces with the same reference plane (flat practical datum shape) and integrating them (by gluing, welding, etc.), it is possible to create a support member in which the heights of the two stays are aligned with high precision. By sandwiching surface pressure reducing members having different thicknesses between the support member 25 and the nip forming member 24, which have support surfaces of the same height, a highly accurate central convex shape can be created. At this time, in order to obtain a sufficiently convex shape, it is desirable to use a member having higher rigidity than at least the pressure roller as the nip forming member.

In addition, as another embodiment, FIG. 14 shows a method of creating a highly accurate central convex shape while sandwiching a surface pressure reducing member of the same thickness between a support member having a support surface of the same height and a nip forming member. . In FIG. 14, the plurality of surface pressure dispersion members 291 and 292 shown in FIG. 295 (the member 295 is more rigid than the member 294).

In this way, the height of the support surfaces is all the same, and the thickness of the surface pressure dispersion member is also the same, but by increasing the rigidity of the surface pressure dispersion member toward the center and weakening the edges, the pressure can be increased. Sometimes the center can create a convex shape. By doing so, the surface on which the nip forming member is placed during product assembly (without pressure) becomes a flat surface, which also provides the advantage of stable assembly. Furthermore, by using the embodiments shown in FIGS. 13 and 14 in combination, it becomes possible to widely meet demands for more appropriate product functions and product assemblability. Although FIGS. 13 and 14 are diagrams of discontinuous support surfaces, they do not necessarily have to be discontinuous, and may have a shape like the cut surface 25a shown in FIG. 5, for example.
<Modified example>

The nip forming member 24 may be provided with a heat generating portion on one surface thereof. Examples of a nip forming member provided with a heat generating portion are shown in FIGS. 15 and 16. FIG. 15 is a cross-sectional view schematically showing a fixing device in which the nip forming member 24 is provided with a heat generating section. FIG. 16 is a diagram showing an example of the configuration of the heat generating section shown in FIG. 15. As shown in FIGS. 15 and 16, a heat generating mechanism section 1500 having a heat generating body 1501 and a circuit 1502 for causing the heat generating body 1501 to generate heat is provided inside the nip forming member 24. For example, as shown in FIG. 7, this configuration includes a nip forming member 24, a surface pressure dispersion member 29, and a support member 25 supported by a plurality of cut surfaces 25a in the longitudinal direction via the surface pressure dispersion member 29. It can be used in a fixing device equipped with.
As explained above, load concentration can be improved by providing the surface pressure dispersion member between the nip forming member and the support member. In addition, it is possible to maintain the convex shape of the support member in the conventional configuration, reduce heat transfer from the nip forming member to other parts, and prevent plastic deformation of the nip forming member to form a nip portion suitable for image formation. becomes possible.

1 Image forming apparatus 20 Fixing device 21 Fixing member 22 Opposing member 23 Heat source 24 Nip forming member 25 Support member 29 Surface pressure dispersing member 25a Cut surface 80 Opening 90 Uneven shape 30 Heat insulating member 291, 292, 294, 295 Member 1500 Heat generation Mechanism section 1501 Heat generating element 1502 Circuit

Japanese Patent Application Publication No. 2019-159176

Claims (12)

a rotatable endless fixing member;
an opposing member that comes into contact with the outer peripheral surface of the fixing member;
a heating element for heating the fixing member;
a nip forming member made of a metal material and abutting against the opposing member from an inner peripheral side of the fixing member to form a nip portion;
a support member that supports the nip forming member via a surface pressure dispersion member;
a surface pressure dispersion member disposed between the nip forming member and the supporting member and made of a material with higher rigidity than the nip forming member ;
The area of the contact surface between the surface pressure dispersion member and the nip forming member is larger than the area of the contact surface between the surface pressure distribution member and the support member.
A fixing device characterized by: a rotatable endless fixing member;
an opposing member that comes into contact with the outer peripheral surface of the fixing member;
a heating element for heating the fixing member;
a nip forming member made of a metal material and abutting against the opposing member from an inner peripheral side of the fixing member to form a nip portion;
a support member that supports the nip forming member at a cut surface via a surface pressure dispersion member;
a surface pressure dispersion member disposed between the nip forming member and the supporting member and made of a material with higher rigidity than the nip forming member ;
The area of the contact surface between the surface pressure dispersion member and the nip forming member is larger than the area of the cut surface where the surface pressure distribution member and the support member contact.
A fixing device characterized by: a rotatable endless fixing member;
an opposing member that comes into contact with the outer peripheral surface of the fixing member;
a heating element for heating the fixing member;
a nip forming member made of a metal material and abutting against the opposing member from an inner peripheral side of the fixing member to form a nip portion;
a supporting member that supports the nip forming member at a plurality of cut surfaces in the longitudinal direction via a surface pressure dispersing member;
a surface pressure dispersion member disposed between the nip forming member and the supporting member and made of a material with higher rigidity than the nip forming member ;
The area of the contact surface between the surface pressure dispersion member and the nip forming member is larger than the total area of the contact surfaces of the surface pressure dispersion member and the support member.
A fixing device characterized by: the metal material of the nip forming member is aluminum;
The fixing device according to any one of claims 1 to 3, characterized in that: the metal material of the nip forming member is copper;
The fixing device according to any one of claims 1 to 3, characterized in that: The surface pressure dispersing member has a shape with higher rigidity than the nip forming member.
The fixing device according to any one of claims 1 to 5 , characterized in that: The surface pressure dispersion member is made of a material having a lower thermal conductivity than the nip forming member.
The fixing device according to any one of claims 1 to 6 , characterized in that: The cut surface of the support member is composed of intermittent convex portions.
The fixing device according to any one of claims 1 to 7 , characterized in that: Consisting of a plurality of surface pressure dispersion members corresponding to the plurality of cut surfaces or intermittent convex portions of the support member,
The fixing device according to claim 3 or 8 , characterized in that: a heat insulating member having low thermal conductivity is provided between the nip forming member and the surface pressure dispersing member;
The fixing device according to any one of claims 1 to 9 . The fixing device includes the fixing device according to any one of claims 1 to 10 .
An image forming apparatus characterized by: a rotatable endless fixing member;
an opposing member that comes into contact with the outer peripheral surface of the fixing member;
a heating element for heating the fixing member;
a nip forming member having a heating element that comes into contact with the facing member from an inner peripheral side of the fixing member to form a nip portion;
a supporting member that supports the nip forming member at a plurality of cut surfaces via a surface pressure dispersing member;
a surface pressure dispersion member disposed between the nip forming member and the supporting member and made of a material with higher rigidity than the nip forming member ;
The area of the contact surface between the surface pressure dispersion member and the nip forming member is larger than the area of the contact surface between the surface pressure distribution member and the support member.
A fixing device characterized by:

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