JP2023138262A - Nip forming unit and image forming apparatus - Google Patents

Abstract

To prevent the generation of fine particles by preventing lubricant from moving to a belt support member.SOLUTION: A nip forming unit comprises: a rotatable endless belt (fixing belt 21); a heat source (halogen heater 23) that heats an inner peripheral surface of the endless belt; a belt support member (flange member 40) that slidably supports the inner peripheral surface at both ends in an axial direction of the endless belt; a nip forming member 24 that can be in contact with the inner peripheral surface of the endless belt; and a pressure member (pressure roller 22) that is in pressure contact with the nip forming member with the endless belt therebetween to form a nip, and the nip forming unit conveys a body to be conveyed through the nip. A clearance C of 2 mm or more in the longitudinal direction of the nip forming member is formed between both ends in the longitudinal direction of the nip forming member and the belt support member.SELECTED DRAWING: Figure 4

Description

The present invention relates to a nip forming unit in which an endless belt is heated from the inside, and an image forming apparatus using the nip forming unit.

In image forming apparatuses such as copying machines, printers, facsimile machines, or multifunctional devices thereof, belt-type or surf-type fixing devices using a rotatable endless belt are known (for example, Patent Document 1: Japanese Patent Laid-Open No. 2014 -178405). The endless belt is heated from the inside by a heat source such as a halogen heater. The inner circumferential surfaces of both axial ends of the endless belt are slidably supported by belt support members (flange members).

A nip forming member on the inside of the endless belt presses against a pressure member on the outside with the belt in between to form a nip. A conveyed object such as paper passes through this nip. A lubricant is interposed between the endless belt and the nip forming member in order to reduce frictional resistance and suppress generation of abnormal noise.

When the support member (flange member) becomes high temperature due to the heat of the heating source and the lubricant is heated by this, fine particles or ultrafine particles, which are volatile substances, may be generated from the lubricant and leak to the outside. .

In recent years, from the viewpoint of environmental protection, it has been required to suppress the generation of not only volatile organic compounds but also fine particles and ultrafine particles. In particular, ultrafine particles are particles with a diameter of 1 μm or less, and the upper limit of emission is regulated by environmental standards such as Germany's Blue Angel.

Therefore, an object of the present invention is to suppress the generation of ultrafine particles by suppressing the flow of lubricant to the belt support member.

In order to solve the above problems, the nip forming unit of the present invention includes a rotatable endless belt, a heating source that heats the inner circumferential surface of the endless belt, and a slidable inner circumferential surface of both ends in the axial direction of the endless belt. a belt supporting member that supports the endless belt, a nip forming member that can contact the inner circumferential surface of the endless belt, and a pressure member that presses against the nip forming member through the endless belt to form a nip; In the nip forming unit, wherein the conveying body is conveyed through the nip, there is a gap of 2 mm or more in the longitudinal direction of the nip forming member between both longitudinal ends of the nip forming member and the belt support member. It is characterized by the formation of a gap.

According to the present invention, the gap between both longitudinal ends of the nip forming member and the belt support member can suppress the lubricant from flowing into the belt support member, thereby suppressing the generation of ultrafine particles. can.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a cross-sectional view of the fixing device with the shielding member moved to a light-shielding position. FIG. 3 is a cross-sectional view of the fixing device with the shielding member moved to a retracted position. FIG. 3 is a perspective view of a fixing device. (a) is a schematic diagram of a nip forming unit according to the present invention, and (b) is a schematic diagram of a conventional nip forming unit. 3 is a correlation graph between the driving time of the fixing device and the temperature of the inner and outer circumferential surfaces of the flange member. 3 is a correlation graph between the driving time of the fixing device and the rate of generation of fine particles. It is a correlation graph between hot plate temperature and fine particle concentration. FIG. 3 is a schematic diagram of a nip forming unit according to the first embodiment. It is a schematic diagram of the nip formation unit based on 2nd Embodiment. It is a schematic diagram of the nip formation unit based on 3rd Embodiment. It is a schematic diagram of the nip formation unit based on 4th Embodiment. FIG. 3 is a cross-sectional view showing the configuration of another fixing device to which the present invention is applicable. 8 is an exploded perspective view of the fixing device shown in FIG. 7. FIG. FIG. 7 is a sectional view showing the configuration of yet another fixing device to which the present invention is applicable. 10 is an exploded perspective view of the fixing device shown in FIG. 9. FIG. FIG. 7 is a sectional view showing the configuration of yet another fixing device to which the present invention is applicable. 12 is an exploded perspective view of the fixing device shown in FIG. 11. FIG. FIG. 7 is a sectional view showing the configuration of yet another fixing device to which the present invention is applicable. FIG. 14 is a cross-sectional view of the fixing device shown in FIG. 13 taken along the longitudinal direction of the fixing belt. FIG. 7 is a sectional view showing the configuration of yet another fixing device to which the present invention is applicable. 16 is an exploded perspective view of the fixing device shown in FIG. 15. FIG. FIG. 7 is a sectional view showing the configuration of yet another fixing device to which the present invention is applicable. 18 is a sectional view showing a holding structure for the pressure roller shown in FIG. 17. FIG. FIG. 7 is a sectional view showing the configuration of yet another fixing device to which the present invention is applicable. 20 is a perspective view of the fixing device shown in FIG. 19. FIG.

Embodiments of the present invention will be described below based on the accompanying drawings. In each drawing for explaining the embodiments of the present invention, components such as members and components having the same function or shape are given the same reference numerals as much as possible so that they can be easily distinguished. The explanation will be omitted here.

(Image forming device)
A schematic configuration and operation of an image forming apparatus using a fixing device according to an embodiment of the present invention will be described with reference to FIG. 1, and then details of the fixing device will be explained.

An image forming apparatus 1 shown in FIG. 1 is a color laser printer. Four image forming units 4Y, 4M, 4C, and 4K are provided at the center of the main body of the apparatus. Each image forming section 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. The photoreceptor 5 includes a developing device 7 that supplies toner to the photoreceptor 5, 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 symbols are omitted for the other image forming sections 4Y, 4M, and 4C. ing.

An exposure device 9 that exposes 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.

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 and four primary transfer rollers 31 as primary transfer means.

The transfer device 3 also includes a secondary transfer roller 36 and a secondary transfer backup roller 32 as secondary transfer means. The transfer device 3 also includes a cleaning backup roller 33, a tension roller 34, and a belt cleaning device 35.

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 FIG.

The four primary transfer rollers 31 each sandwich the intermediate transfer belt 30 with each photoreceptor 5 to form a primary transfer nip. 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. The secondary transfer roller 36 is also connected to a power source (not shown) in the same way as the primary transfer roller 31, and a predetermined direct current voltage (DC) and/or alternating current voltage (AC) is applied to the secondary transfer roller 36. It looks like this.

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 replenishment path (not shown) is provided between each toner bottle 2Y, 2M, 2C, 2K and each developing device 7, and each toner bottle 2Y, 2M, 2C, 2K is connected to each developing device through this replenishment path. 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 timing rollers 12 are arranged 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. has been done.

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. A paper discharge tray 14 for storing paper discharged outside the apparatus is provided on the upper surface of the printer 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. .

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 rotate in the direction indicated by the arrow in the figure. 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, the toner is transferred in the primary transfer nip between each primary transfer roller 31 and each photoreceptor 5. An electric field is formed.

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.

The toner on each photoreceptor 5 that has not been completely transferred to the intermediate transfer belt 30 is removed by a 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 timing roller pair 12.

Thereafter, the rotation of the timing roller pair 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.

(Fixing device)
2A and 2B are cross-sectional views of the fixing device 20 of this embodiment, which is an example of a nip forming unit. The fixing device 20 includes a fixing belt 21 and a pressure roller 22 as a facing member that comes into contact with the outer peripheral surface of the fixing belt 21.

The fixing device 20 also includes a halogen heater 23 as a heat source that heats the fixing belt 21, and 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 N. The fixing device 20 also includes a stay 25 that supports the nip forming member 24 and a reflecting member 26 that reflects radiant heat from the halogen heater 23 to the fixing belt 21. The fixing device 20 also includes a shielding member 27 that shields radiant heat from the halogen heater 23, a temperature sensor 28 as a temperature detection means that detects the temperature of the fixing belt 21, and the like.

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).

Furthermore, a release layer on the outer peripheral side is formed of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) or polytetrafluoroethylene (PTFE). 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 80 μm or more. By providing an elastic layer with a thickness of 80 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 thicknesses of the base material, elastic layer, and release layer constituting the fixing belt 21 are set in the ranges of 20 to 50 μm, 80 to 300 μm, and 3 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 by a pressure means (not shown) such as a spring, and is in 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 N having a predetermined width.

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 through the nip N, and the fixing belt 21 is driven to rotate. The fixing belt 21 has a flange member 40 as a belt support member inserted at both ends of the fixing belt 21 except for the nip N, as will be described later in FIG. It has become.

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 N in the paper conveyance direction. Specifically, in FIG. 2A, if L is an imaginary straight line passing through the center Q of the nip N in the paper transport direction and the rotation center O of the pressure roller 22, the halogen heater 23 is located upstream of this imaginary straight line L in the paper transport direction. (lower side in FIG. 2A).

The halogen heater 23 is configured to generate heat under output control by a power supply section provided in the printer body. Output control of the power supply section is performed based on the detection result of the surface temperature of the fixing belt 21 by the temperature sensor 28.

By controlling the output of the halogen 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 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 predicted based on the temperature detected by the temperature sensor. You may also do so.

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. However, in consideration of the cost of the halogen heater 23 itself, the space around the inner periphery of the fixing belt 21, etc., it is desirable that the number of halogen heaters 23 be two or less. The heat source for heating the fixing belt 21 uses radiant heat, and in addition to a halogen heater, a resistance heating element, a carbon heater, or the like can also be used.

The nip forming member 24 includes a base pad 24a and a low-friction sliding sheet 24b provided on the surface of the base pad 24a facing the fixing belt 21. The base pad 24a is disposed in a longitudinal direction extending in the axial direction of the fixing belt 21 or in the axial direction of the pressure roller 22.

The sliding sheet 24b is not absolutely necessary. If the surface characteristics of the base pad 24a itself provide good sliding properties with the fixing belt 21, it is also possible to omit the sliding sheet 24b.

The shape of the nip N is determined by the base pad 24a receiving the pressure from the pressure roller 22. In this embodiment, the nip N has a flat shape, but it may have a concave shape or other shapes.

The sliding sheet 24b is provided to reduce sliding friction when the fixing belt 21 rotates. Note that if the base pad 24a itself is formed of a low-friction material, a configuration without the sliding sheet 24b is also possible.

The base pad 24a is made of a heat-resistant member with a heat-resistant temperature of 200° C. or higher, and prevents deformation of the nip forming member 24 due to heat in the toner fixing temperature range, ensures a stable nip N state, and improves output image quality. We are trying to stabilize the situation. Materials for the base pad 24a include polyether sulfone (PES), polyphenylene sulfide (PPS), liquid crystal polymer (LCP), polyether nitrile (PEN), polyamideimide (PAI), polyether ether ketone (PEEK), etc. It is possible to use a general heat-resistant resin.

The base pad 24a is fixedly supported by a stay 25. This prevents the nip forming member 24 from being bent due to the pressure exerted by the pressure roller 22, and allows a uniform nip width to be obtained in the axial direction of the pressure roller 22.

In order to satisfy the function of preventing the nip forming member 24 from deflecting, the stay 25 is desirably made of a metal material with high mechanical strength, such as stainless steel or iron. The base pad 24a is also desirably made of a somewhat hard material to ensure strength. As the material of the base pad 24a, resin such as liquid crystal polymer (LCP), metal, ceramic, or the like can be used.

The reflecting member 26 is fixedly supported by the stay 25 so as to face the halogen heater 23 . By reflecting the radiant heat (or light) emitted from the halogen heater 23 to the fixing belt 21 by the reflecting member 26, the transfer of heat to the stay 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 surface of the reflective member 26 facing the halogen heater 23 is formed to widen toward the inner circumferential surface of the fixing belt 21 . In the reflecting member 26 shown in FIG. 2A, a portion facing below the halogen heater 23 (a portion extending along the circumferential direction of the fixing belt 21) is designed to shield radiant heat at both ends of the halogen heater 23. It is provided. This portion is not provided over the entire longitudinal direction of the reflecting member 26.

The shielding member 27 is formed by forming a heat-resistant metal plate such as stainless steel (SUS) with a thickness of 0.1 mm to 1.0 mm into a cross-sectional shape that follows the inner peripheral surface of the fixing belt 21. . In the illustrated example, the shielding member 27 does not have a circumferentially closed annular shape but has an end-shaped cross-sectional shape. Specifically, the shielding member 27 has a partially arcuate cross-sectional shape.

The shielding member 27 is rotatable around the halogen heater 23, and in this embodiment, is rotatable along the circumferential direction of the fixing belt 21. Specifically, 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. Further, there is a non-direct heating region between the halogen heater 23 and the fixing belt 21 in which members other than the shielding member 27 (reflecting member 26, stay 25, nip forming member 24, etc.) are interposed.

If it is necessary to provide thermal shielding between the halogen heater 23 and the fixing belt 21, as shown in FIG. 2A, the shielding member 27 is disposed at a shielding position directly on the heating area side. If it is not necessary to provide heat shielding between the halogen heater 23 and the fixing belt 21, the shielding member 27 is moved to the retracted position on the side of the non-direct heating area, as shown in FIG. 2B.

That is, the shielding member 27 is retracted to the back side of the reflecting member 26 and the stay 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. 3 is a perspective view of the fixing device 20 of this embodiment. The sliding sheet 24b, stay 25, shielding member 27, etc. are omitted. As shown in FIG. 3, cylindrical portions 40a of flange members 40 are inserted into the inner peripheral surfaces of both ends of the fixing belt 21, respectively.

The fixing belt 21 is rotatably held by the inner circumferential surfaces of both ends of the fixing belt 21 in the axial direction coming into sliding contact with the cylindrical portion 40a of the flange member 40. The left and right flange members 40 in FIG. 3, the halogen heater 23, the nip forming member 24, and the stay 25 in FIGS. 2A and 2B are fixedly supported by a pair of side plates (not shown) of the fixing device 20.

(●Operation of fixing device)
The operation of the fixing device 20 according to this embodiment will be described below with reference to FIGS. 2A and 2B. When the power switch of the printer main body is turned on, power is supplied to the halogen heater 23, and the pressure roller 22 starts rotating clockwise in FIGS. 2A and 2B. As a result, the fixing belt 21 is driven to rotate counterclockwise in FIGS. 2A and 2B due to the frictional force with the pressure roller 22.

Thereafter, the paper P carrying the unfixed toner image T in the image forming process described above is conveyed in the direction of arrow A1 in FIG. 2A while being guided by a guide plate (not shown), and the fixing belt 21 and It is fed into the nip N of the pressure roller 22. Then, the toner image T is fixed on the surface of the paper P by the heat generated by the fixing belt 21 heated by the halogen heater 23 and the pressing force between the fixing belt 21 and the pressure roller 22.

The paper P on which the toner image T has been fixed is carried out from the nip N in the direction of arrow A2 in FIG. 2A. At this time, the leading edge of the paper P comes into contact with the leading edge of a separation member (not shown), so that the paper P is separated from the fixing belt 21 . Thereafter, as described above, the separated sheets P are discharged from the machine by the paper discharge rollers and are stocked on the paper discharge tray.

[Nip formation unit]
The above-described fixing belt 21, halogen heater 23, pressure roller 22, nip forming member 24, and flange member 40 constitute the nip forming unit of this embodiment. This nip forming unit is also called a "fixing unit" in the image forming apparatus.

The nip forming member 24 and the flange member 40 can be made of, for example, a heat-resistant resin such as a liquid crystal polymer. A gap C is formed in the longitudinal direction of the nip forming member 24 between both longitudinal ends of the nip forming member 24 and the cylindrical portion 40a of the flange member 40, as shown in FIG.

The schematic diagram of FIG. 4(a) clearly shows the gap C. The feature of the nip forming unit of this embodiment is that a gap C of a predetermined size is formed between the nip forming member 24 and the cylindrical portion 40a of the flange member 40, as shown in FIG. 4(a). . The size of this gap C is at least 2 mm or more in the longitudinal direction of the nip forming member 24. The reason why the size of the gap C is set to 2 mm or more will be described later.

As the gap C increases, the length of the nip forming member 24 in the longitudinal direction becomes shorter. The upper limit of the gap C is when the length of the nip forming member 24 in the longitudinal direction is the same as that of the pressure roller 22, as shown in FIG. 4(a).

A lubricant G is interposed between the nip forming member 24 and the fixing belt 21. This lubricant G tends to flow outward in the longitudinal direction of the nip forming member 24 due to the pressure acting on the nip N.

In many conventional fixing devices, both longitudinal ends of the nip forming member 24 are in contact with the cylindrical portion 40a of the flange member 40, as shown in FIG. 4(b). In this way, if there is no gap between the nip forming member 24 and the flange member 40, the lubricant G between the nip forming member 24 and the fixing belt 21 will leak onto the inner peripheral surface and outer peripheral surface of the cylindrical portion 40a of the flange member 40. Easy to flow.

In contrast, in the present invention, a gap C is formed between the nip forming member 24 and the cylindrical portion 40a of the flange member 40 as shown in FIG. It is difficult to flow to the inner circumferential surface and outer circumferential surface of the portion 40a. Even if a portion of the lubricant G protrudes into the gap C, the gap C functions as a lubricant reservoir, so that it is retained in the gap C as it is.

(●Generation of ultrafine particles)
In order to confirm the ultrafine particles generated from the fixing device, a 10-minute continuous printing test was conducted using an image forming apparatus having a conventional fixing device as shown in the schematic diagram of FIG. 4(b). As the lubricant G, fluorine grease: 70 [mg] and silicone oil: 35 [mg] were used.

FIG. 5A shows the results of measuring the temperature of the inner circumferential surface and outer circumferential surface of the flange member 40 of the fixing device during this test. Further, FIG. 5B shows the results of measuring the generation rate (pieces/second) of fine particles (FP) and ultrafine particles (UFP) according to the measurement method specified by Blue Angel. The concentration of FP/UFP generated was measured using a particle counter FMPS (Model 3091 Fast Mobility Sizer manufactured by Tokyo Dilec).

From FIG. 5B, it can be seen that fine particles begin to come out all at once about 3 minutes after the start of printing, and continue to come out while gradually increasing until the end of printing. The number of fine particles generated far exceeded the Blue Angel standard value of 3.5 x 10^11 particles.

In FIG. 5B, the timing at which the ultrafine particles rapidly increase is approximately 3 minutes later, and this timing (approximately 3 minutes later) almost coincides with the timing when the inner circumferential surface of the flange reaches 200° C. or higher in FIG. 5A.

On the other hand, FIG. 5C shows the results of heating the lubricant G with a hot plate and measuring the concentration of ultrafine particles generated. From this measurement result, it can be seen that at temperatures above 200°C, ultrafine particles begin to come out all at once.

From this, it is presumed that the inner circumferential surface of the flange is the location where ultrafine particles are generated. The outer circumferential surface of the flange also reaches 200° C. in about 9 minutes, but ultrafine particles have already been generated before then. Therefore, when the nip forming unit of the present invention is used in a fixing device where the temperature of the flange member 40 is 200° C. or higher, the effect of reducing ultrafine particles can be exhibited.

(●Size of gap C)
The reason why the size of the gap C mentioned above is set to 2 mm or more is as follows. That is, in an image forming apparatus having a fixing device shown in the schematic diagram of FIG. Printing test) was conducted.

From the paper passing results, it was found that the lubricant G was significantly attached to the flange member 40 in the fixing unit with C=1.0 mm. In addition, in the fixing unit with C=1.5 mm, slight adhesion of lubricant G to the flange member 40 was observed.

On the other hand, in the fixing unit with C=2.0 mm, no lubricant G adhered to the flange member 40. Further, no occurrence of FP/UFP was observed. Then, after paper passing through the actual machine with C=2.0 mm, the fixing unit was disassembled, the fixing belt 21 was cut open, and the diameter φ of the droplets of lubricant G adhering to the gap C was confirmed, and it was found that φ≒1 mm. Ta.

From this, if the size of the gap C is at least 2 mm or more, in relation to the diameter of the droplet of the lubricant G (φ≒1 mm), it is possible to prevent the lubricant G from adhering to the flange member 40. It has been found that it is possible to prevent the liquid from flowing outward in the longitudinal direction of the nip forming member 24. Further, in order to balance the pressing force to ensure the fixability of the toner to the paper, the upper limit of the gap C is preferably from the flange member 40 to the position facing the end of the pressure roller 22.

The aforementioned FIG. 4(a) shows the basic form of the nip forming unit of the present invention. Various embodiments are possible on the premise that there is a gap C between the nip forming member 24 and the cylindrical portion 40a of the flange member 40.

FIGS. 6A to 6D show four embodiments, first to fourth. These embodiments are illustrative, and it goes without saying that the present invention is not limited to these embodiments.

(●First embodiment)
In the first embodiment shown in FIG. 6A, the lower and side surfaces of the nip forming member 24 are covered with a sliding sheet 124. This sliding sheet 124 has low friction characteristics to reduce friction with the fixing belt 21, and also has a high lubricant retention ability.

The sliding sheet 124 may be formed of an elongated rectangular sheet made of woven resin fibers such as PTFE, and may have an open shape in a vertical section in the longitudinal direction of the sliding sheet 124. Specifically, the sliding sheet 124 has both end regions in the sliding direction bent approximately at right angles to the nip surface (sliding surface), and the sliding sheet 124 has an approximately U-shape ( (cono-shaped). The sliding sheet 124 covers the entire surface of the nip forming member 24 on the nip forming surface side, and the surface of the sliding sheet 124 corresponds to the nip surface.

The sliding sheet 124 may be a PFA sheet or a PTFE sheet with low frictional resistance. Alternatively, the base material may be coated with a coating having physical properties with a low coefficient of friction.

Since the lubricant G is retained in the sliding sheet 124 in an impregnated state, it becomes more difficult to flow toward the outside in the longitudinal direction. Even if a portion of the lubricant G spills out into the gap C, it is retained within the gap C as it is.

(Second embodiment)
In the second embodiment shown in FIG. 6B, in addition to the configuration shown in FIG. 6A, an annular protrusion 21a is formed on the inner circumferential surface of the fixing belt 21 as a flow reducing member that suppresses outward movement of the lubricant G.

Since centrifugal force acts on the lubricant G as the fixing belt 21 rotates, the presence of the annular protrusion 21a can prevent the lubricant G that has protruded into the gap C from flowing further outward.

The flow reducing member is not limited to the shape of the annular projection 21a shown in FIG. 6B. That is, the annular protrusion 21a is not limited to a horizontally long rectangular cross section, but may have a vertically long rectangular cross section, or may have a complicated shape with a large surface area, such as an L-shaped cross section, a T-shaped cross section, a W-shaped cross section, or the like. By increasing the surface area of the flow reducing member in this way, the ability to hold the lubricant G increases, and the lubricant G becomes difficult to flow into the flange member 40.

(Third embodiment)
In the third embodiment shown in FIG. 6C, an accommodation space 224a that can accommodate the lubricant G is provided on the lower surface of the nip forming member 224. This accommodation space 224a can be formed, for example, in the shape of one or more lines in the longitudinal direction of the nip forming member 224. By holding the lubricant G in the accommodation space 224a, movement of the lubricant G to the outside in the axial direction can be suppressed.

(●Fourth embodiment)
The fourth embodiment shown in FIG. 6D has a lubricant absorbing member 50 disposed within the gap C in addition to the configuration shown in FIG. 6A. This lubricant absorbing member 50 can be configured to have the same width as the nip forming member 24 in the direction perpendicular to the paper plane of FIG. 6D. The lubricant absorbing member 50 can be positioned by being connected to an arm extending from the nip forming member 24.

Even if a portion of the lubricant G protrudes into the gap C, it is absorbed and retained by the lubricant absorbing member 50, so that it can be prevented from flowing further to the flange member 40. Moreover, since there is a gap on both sides of the lubricant absorbing member 50, the lubricant G is also held in the gap. Therefore, it becomes even more difficult for the lubricant G to flow to the flange member 40.

(Other configurations of fixing device)
Further, the present invention is applicable not only to the fixing device having the above-described configuration but also to fixing devices having various configurations. Below, some configurations of fixing devices to which the present invention can be applied will be illustrated.

The fixing device 400 shown in FIGS. 7 and 8 includes a fixing belt 410 as a first rotating body, a pressure roller 420 as a second rotating body, a heater 430 as a heat source, and a heat source holding member. It includes a heater holder 440, a pressure stay 450 as a support member, a thermistor 480 as a temperature detection member, and a flange 470 (see FIG. 8) as a rotating body holding member.

The functions and configurations of the fixing belt 410 and the pressure roller 420 shown in FIG. 7 are basically the same as those of the fixing belt 210 and the pressure roller 220 shown in FIG. 2 above.

The heater 430 is a ceramic heater having a plate-like substrate and a resistance heating element provided on the substrate, and generates heat by applying electricity to the resistance heating element. The heater 430 is arranged so as to be in contact with the inner peripheral surface of the fixing belt 410, and when the heater 430 generates heat, the fixing belt 410 is heated from the inside. Further, the heater 430 also functions as a nip forming member that forms a nip portion N with the fixing belt 410 sandwiched between the heater 430 and the pressure roller 420 .

Heater holder 440 is a heat source holding member that holds heater 430. The heater holder 440 is made of, for example, heat-resistant resin. In this case, since the heater holder 440 is formed to have a semicircular arc-shaped cross section along the inner circumferential surface of the fixing belt 410, the rotation trajectory of the fixing belt 410 is regulated by the heater holder 440.

Pressure stay 450 is a support member that supports heater holder 440. Since the pressure stay 450 supports the heater holder 440, the deflection of the heater holder 440 and the heater 430 due to the pressure applied by the pressure roller 420 is suppressed, and a uniform width is maintained between the pressure roller 420 and the fixing belt 410. A nip portion N is formed. The pressurizing stay 450 is preferably made of a metal material such as stainless steel (SUS) in order to ensure rigidity.

Further, the pressurizing stay 450 is provided with a thermistor 480 as a temperature detection member. The thermistor 480 detects the temperature of the fixing belt 410 by facing the inner peripheral surface of the fixing belt 410 in contact or non-contact.

The flanges 470, like the belt holding members 270 described above, are a pair of holding members that hold both ends of the fixing belt 410 in the longitudinal direction. This flange 470 also has a backup part 470a as an insertion part inserted into the fixing belt 410, and a flange part 470b as a regulating part that regulates movement of the fixing belt 410 in the longitudinal direction. In this case, each flange 470 is held inserted into the fixing belt 410 by being urged toward each end of the fixing belt 410 by a biasing member such as a spring.

Even in the fixing device 400 having such a configuration, when the heater 430 generates heat, the temperature of the flange 470 increases, and the temperature of the lubricant adhering to the flange 470 increases, which may cause FP/UFP. Therefore, by applying the present invention to the fixing device 400 shown in FIGS. 7 and 8, it is possible to suppress the temperature rise of the flange 470 and suppress the occurrence of FP/UFP.

Next, a fixing device 500 shown in FIGS. 9 and 10 is a fixing device that includes a ceramic heater (heater 530), like the fixing device 400 shown in FIGS. 7 and 8 above. Specifically, the fixing device 500 shown in FIGS. 9 and 10 includes a fixing belt 510 as a first rotating body, a pressure member 520 as a second rotating body, a heater 530 as a heat source, and a heat source. A heater holder 540 as a holding member, a reinforcing member 550 as a supporting member, a belt holding part 570 as a rotating body holding member (see FIG. 10), a heat sensitive element 580 as a temperature sensing member (see FIG. 10), and a cover. A member 590 (see FIG. 10) is provided.

The functions and configurations of the fixing belt 510, pressure member 520, heater 530, heater holder 540, reinforcing member 550, and belt holding section 570 shown in FIGS. 9 and 10 are the same as those of the fixing belt 510 shown in FIGS. 7 and 8 above. 410, pressure roller 420, heater 430, heater holder 440, pressure stay 450, and flange 470.

The heat sensitive body 580 is provided on the side of the heater holder 540 opposite to the surface that holds the heater 530, and detects the temperature of the heater 530 via the heater holder 540. By controlling the heat generation of the heater 530 based on the detected temperature of the heat sensitive body 580, the fixing belt 510 is maintained at a predetermined fixing temperature.

The cover member 590 is a box-shaped member made of heat-resistant resin. The cover member 590 is disposed within the fixing belt 510 to face the heater holder 540 with the heat sensitive body 580 interposed therebetween, so that the corresponding heat sensitive body 580 is covered by the cover member 590.

In this way, the fixing device to which the present invention is applied may include the heat sensitive body 580 that detects the temperature of the heater 530 and the cover member 590 that covers the heat sensitive body 580.

Next, a fixing device 600 shown in FIGS. 11 and 12 is a fixing device that includes a halogen heater (heater 630) as a heat source, similar to the fixing device 200 shown in FIGS. 2 and 3 above. Specifically, the fixing device 600 shown in FIGS. 11 and 12 includes a fixing belt 610 as a first rotating body, a pressure roller 620 as a second rotating body, a heater 630 as a heat source, and a nip forming device. A member 640, a support part 650 as a support member, a reflection plate 660 as a reflection member, a holding frame 670 as a rotating body holding member (see FIG. 12), and a ring 680 as a sliding member (see FIG. 12). It is equipped with

The functions and configurations of the fixing belt 610, pressure roller 620, heater 630, nip forming member 640, support section 650, reflection plate 660, and holding frame 670 shown in FIGS. 11 and 12 are shown in FIGS. 2 and 3. It is basically the same as the fixing belt 210, pressure roller 220, heater 230, nip forming member 240, stay 250, reflecting member 260, and belt holding member 270 shown. Note that the nip forming member 640 includes a metal base pad 6400 and a fluororesin sliding sheet 6410 interposed between the base pad 6400 and the inner peripheral surface of the fixing belt 610.

The ring 680 is attached to the outer peripheral surface of the cylindrical portion 670a as an insertion portion of the holding frame 670 inserted into the fixing belt 610, and is attached to the longitudinal edge of the fixing belt 610 and the fixing plate as a regulating portion of the holding frame 670. 670b. When the fixing belt 610 rotates, the ring 680 rotates together with the fixing belt 610, or the fixing belt 610 slides against the low-friction ring 680, so that the fixing belt 610 and the holding frame 670 are connected to each other. The sliding resistance that occurs between the two is reduced.

In this way, the fixing device to which the present invention is applied may include the ring 680.

Next, a fixing device 700 shown in FIGS. 13 and 14 is a fixing device that includes a halogen heater 730 as a heat source, similar to the fixing device 200 shown in FIGS. 2 and 3 above. Specifically, the fixing device 700 shown in FIGS. 13 and 14 includes a fixing belt 710 as a first rotating body, a pressure roller 720 as a second rotating body, a halogen heater 730 as a heat source, and a nip. It includes a forming member 740, a reflecting member 760, a belt supporting member 770 (see FIG. 14) as a rotating body holding member, a temperature sensor 780 as a temperature detecting member, and a guide member 790.

The fixing belt 710, pressure roller 720, halogen heater 730, nip forming member 740, reflective member 760, belt support member 770, and temperature sensor 780 shown in FIGS. 13 and 14 are the fixing belt shown in FIGS. 2 and 3. 210, the pressure roller 220, the heater 230, the nip forming member 240, the reflecting member 260, the belt holding member 270, and the temperature sensor 280.

However, the reflecting member 760 shown in FIGS. 13 and 14 mainly reflects the radiant heat (infrared rays) emitted from the halogen heater 730 not to the fixing belt 710 but to the nip forming member 740. The reflective member 760 is formed to have a U-shaped cross section so as to cover the outside of the halogen heater 730, and an inner surface 760a of the reflective member 760 facing the halogen heater 730 is a reflective surface with high reflectance. Therefore, when radiant heat is emitted from the halogen heater 730, the radiant heat is reflected to the nip forming member 740 by the reflective surface 760a of the reflective member 760.

As a result, the nip forming member 740 is heated by the radiant heat emitted from the halogen heater 730 toward the nip forming member 740 and the radiant heat reflected toward the nip forming member 740 by the reflecting member 760. Then, the heat of the nip forming member 740 is transferred to the fixing belt 210 at the nip portion N.

That is, in this case, the nip forming member 740 not only forms the nip portion N but also functions as a heat transfer member that transmits heat to the fixing belt 710 at the nip portion N. For this reason, the nip forming member 740 is made of a metal material such as copper or aluminum that has good thermal conductivity.

Further, the reflecting member 760 also functions as a supporting member (stay) that supports the nip forming member 740. By supporting the nip forming member 740 in the longitudinal direction of the fixing belt 710 by the reflecting member 760, deflection of the nip forming member 740 is suppressed, and a uniform width is formed between the fixing belt 710 and the pressure roller 720. A nip portion N is formed. The reflecting member 760 is preferably made of a highly rigid metal material such as SUS or SECC in order to ensure its function as a supporting member.

The guide member 790 is a member that is disposed inside the fixing belt 710 and guides the rotating fixing belt 710 from the inside. The guide member 790 has a guide surface 790a that curves along the inner peripheral surface of the fixing belt 710, and as the fixing belt 710 is guided along the guide surface 790a, the fixing belt 710 is largely deformed. Rotates smoothly without any movement.

In this way, the fixing device to which the present invention is applied may be configured to heat the fixing belt 710 by transmitting the heat of the halogen heater 730 via the nip forming member 740 having good thermal conductivity.

Next, a fixing device 800 shown in FIGS. 15 and 16 is a fixing device that includes a ceramic heater (heater 830) as a heat source, similar to the fixing device 400 shown in FIGS. 7 and 8 described above. Specifically, the fixing device 800 shown in FIGS. 15 and 16 includes a fixing belt 810 as a first rotating body, a pressure roller 820 as a second rotating body, a heater 830 as a heat source, and a heat source. A holding member 840 as a holding member, a stay 850 as a supporting member, an arcuate guide 870 (see FIG. 16) as a rotating body holding member, a heat diffusion member 880 as a heat transfer member, and a retainer as a heat insulating member. A hot plate 890 is provided.

The fixing belt 810, pressure roller 820, heater 830, holding member 840, stay 850, and arcuate guide 870 shown in FIGS. 15 and 16 are the fixing belt 410, pressure roller 420, and pressure roller 420 shown in FIGS. It basically has the same functions as the heater 430, heater holder 440, pressure stay 450, and flange 470. Note that the holding member 840 holds not only the heater 830 but also a heat diffusion member 880 and a heat retaining plate 890 in a stacked state.

The heat diffusion member 880 is made of a metal material such as stainless steel, aluminum alloy, or iron. The heat diffusion member 880 is arranged so as to be in contact with the inner peripheral surface of the fixing belt 810, and transmits the heat generated from the heater 830 to the fixing belt 810, and also contacts the pressure roller 820 via the fixing belt 810. , forming a nip portion N.

Furthermore, thermally conductive grease is applied between the heater 830 and the heat diffusion member 880 to improve the efficiency of heat transfer from the heater 830 to the heat diffusion member 880. On the other hand, the heat retaining plate 890 is disposed on the side opposite to the surface of the heater 830 on the heat diffusion member 880 side in order to suppress the heat of the heater 830 from being transmitted to the holding member 840 and the stay 850.

When the fixing belt 810 rotates, the fixing belt 810 slides against the heat diffusion member 880, so a lubricant is applied between the fixing belt 810 and the heat diffusion member 880 to improve sliding properties. Further, the sliding surface of the heat diffusion member 880 that contacts the fixing belt 810 is formed with a surface layer such as glass coating or hard chrome plating that has low friction and wear resistance.

Even in such a fixing device, if the temperature of the arcuate guide 870 rises due to the heat generated by the heater 830, the temperature of the lubricant adhering to the arcuate guide 870 may rise, causing FP/UFP. By applying this, it is possible to suppress the occurrence of FP/UFP.

Next, the fixing device 900 shown in FIGS. 17 and 18 includes an endless belt 910 as a first rotating body, a heating roller 960 as a heating member, a heater 930 as a heating source, and a second rotating body. The fixing device includes a pressure roller 920 as a roller, a nip forming member 940, a support member 950, a guide member 980, a lubricant applying member 990 as a lubricant supply member, and a bearing 970 (see FIG. 18). .

As shown in FIG. 17, the belt 910 is wound around a heating roller 960, a nip forming member 940, and a guide member 980. A predetermined tension is applied to the belt 910 by urging the heating roller 960 in a direction away from the nip forming member 940 by a spring or the like. In this state, the pressure roller 920 is rotationally driven, and the belt 910 is driven to rotate.

The nip forming member 940 includes a pressing member 9400 and a low-friction sliding sheet 9410 interposed between the pressing member 9400 and the inner peripheral surface of the belt 910. Since the pressing member 9400 is supported by the supporting member 950, the pressing member 9400 receives the pressing force of the pressing roller 920, and a nip portion N is formed.

The heater 930 is a halogen heater or the like, and is arranged inside the heating roller 960. When the heater 930 generates heat, the heating roller 960 is heated, and the heat of the heating roller 960 is transferred to the belt 910.

The lubricant application member 990 contacts the inner circumferential surface of the belt 910 and supplies a lubricant to the inner circumferential surface of the belt 910 to improve sliding properties. As the belt 910 rotates, the lubricant supplied to the inner peripheral surface of the belt 910 is interposed between the guide member 980 and the belt 910 and between the nip forming member 940 and the belt 910. Allows smooth rotation.

Here, the heating roller 960 is generally supported by a bearing 970 such as a sliding bearing or a ball bearing so as to be rotatable. The bearings 970 as such a rotating body holding member are attached to both axial ends (both longitudinal ends) of the heating roller 960, and the bearings have sliding resistance or rotational torque when the heating roller 960 rotates. A lubricant is applied to reduce the

Therefore, when the heating roller 960 is heated and the bearing 970 is affected by the heat, the temperature of the lubricant adhering to the bearing 970 increases, which may cause FP/UFP. Therefore, it is preferable to apply the present invention to the fixing device shown in FIG. 17 as well.

For example, by arranging the first shielding member 310 and the second shielding member 320 as heat transfer suppressing members as described above inside the heating roller 960, a rotating body holding member that holds the heating roller 960 from the heater 930 can be used. Heat transfer to the member (bearing 970) can be effectively suppressed. This makes it possible to reduce the number of FPs/UFPs generated, as in the above embodiment.

Furthermore, the present invention is also applicable to a fixing device 1100 having a configuration as shown in FIGS. 19 and 20.

The fixing device 1100 shown in FIGS. 19 and 20 includes a fixing belt 1110 as a first rotating body, a fixing roller 1160, a pressure roller 1120 as a second rotating body, a heater 1130 as a heat source, and a nip. A pressure pad 1140 as a forming member, a guide member 1150, a support member 1170, a temperature sensor 1180 as a temperature detection member, a heat transfer member 1190, and a belt holding member 1220 as a rotating body holding member (see FIG. 20) ).

A fixing belt 1110 shown in FIG. 19 is wound around a fixing roller 1160, a pressure pad 1140, a guide member 1150, and a heat transfer member 1190. The fixing roller 1160 rotates as the pressure roller 1120 rotates.

The heater 1130 is a planar or plate-shaped heater such as a ceramic heater, and is provided in the heat transfer member 1190. The heat transfer member 1190 is a member that is interposed between the heater 1130 and the fixing belt 1110 and transfers the heat of the heater 1130 to the fixing belt 1110. Further, the heat transfer member 1190 is urged by a spring 1200 attached to the support member 1170 so as to contact the inner peripheral surface of the fixing belt 1110.

Pressure pad 1140 is urged to contact the inner peripheral surface of fixing belt 1110 by another spring 1210 attached to support member 1170. As a result, the pressure pad 1140 is pressed against the pressure roller 1120 via the fixing belt 1110, and a nip portion N is formed between the fixing belt 1110 and the pressure roller 1120.

Guide member 1150 is attached to and supported by support member 1170. Further, a temperature sensor 1180 is attached to the guide member 1150, and the temperature of the fixing belt 1110 is detected by the temperature sensor 1180.

The fixing device 1100 as shown in FIG. 19 is also provided with a belt holding member 1220 that holds both ends of the fixing belt 1110 in the longitudinal direction. There is a possibility that FP/UFP may occur due to the temperature of the lubricant increasing. Therefore, by applying the present invention to such a fixing device 1100, it is possible to effectively suppress the occurrence of FP/UFP in the same manner as in each of the above embodiments.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various changes can be made without departing from the gist of the present invention. For example, the image forming apparatus is not limited to a printer as shown in FIG. 1, but may also be a copying machine, a facsimile machine, or a combination thereof.

<Additional notes>
Hereinafter, preferred embodiments of the present invention will be additionally described.
<First aspect>
a rotatable endless belt; a heating source that heats an inner circumferential surface of the endless belt; a belt support member that slidably supports inner circumferential surfaces of both axial ends of the endless belt; and an inner circumferential surface of the endless belt. and a pressure member that presses against the nip forming member to form a nip through the endless belt, and the conveyed object is conveyed passing through the nip. A nip forming unit characterized in that a gap of 2 mm or more in the longitudinal direction of the nip forming member is formed between both longitudinal ends of the nip forming member and the belt support member.
<Second aspect>
The nip forming unit according to the first aspect, characterized in that a flow reducing member is disposed in the gap.
<Third aspect>
The nip forming unit according to the first aspect, characterized in that a lubricant absorbing member is disposed in the gap.
<Fourth aspect>
The nip forming unit according to any one of the first to third aspects, wherein a sliding sheet impregnated with a lubricant is disposed between the nip forming member and the endless belt.
<Fifth aspect>
The nip forming unit according to any one of the first to fourth aspects, characterized in that an accommodation space for accommodating a lubricant is formed between the nip forming member and the endless belt.
<Sixth aspect>
An image forming apparatus comprising a nip forming unit according to any one of the first to fifth aspects.

1: Image forming device 2: Bottle housing section
2Y, 2M, 2C, 2K: Toner bottle 3: Transfer device
4Y, 4M, 4C, 4K: Image forming section 5: Photoconductor 6: Charging device 7: Developing device 8: Cleaning device 9: Exposure device 10: Paper feed tray 11: Paper feed roller 12: Timing roller pair 13: Paper ejection Roller 14: Paper discharge tray 20: Fixing device 21: Fixing belt 21a: Annular protrusion 22: Pressure roller 22a: Core metal 22b: Elastic layer 22c: Release layer 23: Halogen heater 23: Halogen heater (heat source)
24: Nip forming member 24a: Base pad 24b: Sliding sheet 25: Stay 26: Reflective member 26: Reflective member 27: Shielding member 28: Temperature sensor 30: Intermediate transfer belt 31: Primary transfer roller 32: Secondary transfer backup roller 33: Cleaning backup roller 34: Tension roller 35: Belt cleaning device 36: Secondary transfer roller 40: Flange member 40a: Cylindrical portion 50: Lubricant absorbing member 124: Sliding sheet 224: Nip forming member 224a: Accommodation space A1, A2: Arrow C: Gap G: Lubricant N: Nip P: Paper R: Conveyance path T: Toner image

Japanese Patent Application Publication No. 2014-178405

Claims (6)

a rotatable endless belt; a heating source that heats an inner circumferential surface of the endless belt; a belt support member that slidably supports inner circumferential surfaces of both axial ends of the endless belt; and an inner circumferential surface of the endless belt. and a pressure member that presses against the nip forming member to form a nip through the endless belt, and the conveyed object is conveyed passing through the nip. In the nip forming unit,
A nip forming unit characterized in that a gap of 2 mm or more is formed in the longitudinal direction of the nip forming member between both longitudinal ends of the nip forming member and the belt support member. 2. The nip forming unit according to claim 1, further comprising a flow reducing member disposed in said gap. 2. The nip forming unit according to claim 1, further comprising a lubricant absorbing member disposed in said gap. 4. The nip forming unit according to claim 1, wherein a sliding sheet impregnated with a lubricant is disposed between the nip forming member and the endless belt. The nip forming unit according to any one of claims 1 to 3, wherein a storage space for storing a lubricant is formed between the nip forming member and the endless belt. An image forming apparatus comprising the nip forming unit according to claim 1.

Images