JP2016031516A - Fixation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem in which, when a backup roller becomes hot due to continuous printing, the backup roller expand to vary the conveyance speed of a recording material in a nip part, in a fixation device including a heating member and the backup roller having a rubber layer and forming the nip part with the heating member.SOLUTION: The fixation device includes a backup roller having a rubber layer made of a sponge formative silicone rubber composition containing an inorganic thickener. The backup roller is driven. A heating member rotates in response to the rotation of the backup roller.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a fixing device used in an image forming apparatus such as an electrophotographic copying machine or printer.

  As a fixing device used in an image forming apparatus such as an electrophotographic copying machine or a printer, a cylindrical film, a heater that contacts the inner surface of the film, a backup roller that forms a nip portion with the heater via the film, Are known. Since this fixing device uses a film having a small heat capacity, it has an advantage of a short warm-up time. Japanese Patent Application Laid-Open No. H10-228561 discloses a technique in which a driving force from a driving source is transmitted to a backup roller to be driven, and a film is rotated by a frictional force received from the backup roller at a nip portion.

JP 2000-315028 A

  However, in the fixing device described in Patent Document 1, the pressure roller is heated as continuous printing is continued, the outer diameter of the pressure roller expands to widen the nip width, and the recording material conveyance speed at the nip portion increases. . That is, there is a problem that the conveyance speed of the recording material in the nip portion is not stable.

  A first preferred embodiment of the present invention for solving the above-mentioned problems includes a heating member, a cored bar, and a rubber layer formed on the outside of the cored bar, and a nip together with the heating member. A fixing roller for fixing the toner image to the recording material by heating while conveying the recording material on which the toner image is formed at the nip portion. It is formed from a sponge-forming silicone rubber composition containing a system thickener, the backup roller is driven, and the heating member is rotated by the rotation of the backup roller.

  A second preferred embodiment of the present invention for solving the above-mentioned problems includes a heating member, a cored bar, and a rubber layer formed on the outside of the cored bar, and a nip together with the heating member. A fixing roller that heats the recording material on which the toner image is formed at the nip portion and heats the recording material to fix the toner image on the recording material. It has a reversible characteristic that the hardness decreases as the rate increases and the hardness increases as the moisture content decreases, and the backup roller is driven and the heating member is rotated by the rotation of the backup roller.

  According to the present invention, there is an effect that the conveyance speed of the recording material in the nip portion of the fixing device is stabilized regardless of the warming state of the backup roller.

Sectional view of the fixing device according to the first embodiment. Sectional drawing of transfer device and fixing device according to Embodiment 1 Sectional view of the fixing device according to the second embodiment. (A) Cross-sectional view of a fixing device having a halogen lamp (modified example of Embodiment 1), (b) Cross-sectional view of a fixing device having a halogen lamp (modified example of Embodiment 2) Sectional view of the image forming apparatus according to the first embodiment. The figure which showed the relationship between the relative humidity which concerns on Example 1, and rubber hardness

Example 1
Hereinafter, an image forming apparatus and a fixing device according to the present embodiment will be described in detail with reference to the drawings.

(Image forming device)
The image forming apparatus 50 according to the present embodiment will be described. FIG. 5 is a cross-sectional view of the image forming apparatus according to the present embodiment. In the image forming apparatus 50 according to the present exemplary embodiment, the peripheral surface of the photosensitive drum 1 that is an image carrier is exposed to the charger 2 and laser light to the photosensitive drum 1 in order along the rotation direction (arrow R1 direction). The apparatus 3, the developing device 5, the transfer roller 10, and the photosensitive drum cleaner 16 are disposed. First, the surface of the photosensitive drum 1 is charged to a negative polarity by the charger 2. Next, an electrostatic latent image is formed on the surface of the charged photosensitive drum 1 by the exposure L of the exposure means 3. The toner of this embodiment is charged with a negative polarity. First, negative toner is attached only to the electrostatic latent image portion on the photosensitive drum 1 by the developing device 5 containing the toner, and the toner image is formed on the photosensitive drum 1. It is formed. When the recording material P is conveyed by the conveying roller 9 to the transfer nip portion formed by the photosensitive drum 1 and the transfer roller 10, the toner image on the photosensitive drum 1 is transferred onto the recording material P at the transfer nip portion. The When the toner image is transferred from the photosensitive drum 1 to the recording material P, a positive transfer bias having a polarity opposite to the polarity of the toner is applied to the transfer roller 10 from a power source (not shown). The transfer residual toner on the surface of the photosensitive drum 1 after the transfer is removed by a photosensitive drum cleaner 16 having an elastic blade. A series of image forming processes of charging, exposing, developing, transferring, and cleaning are performed in the image forming unit 80 to form a toner image on the recording material P. The recording material P carrying the toner image is conveyed to the fixing device 100, where the toner image on the surface is heated and fixed.

(Fixing device)
FIG. 1 is a cross-sectional view of a fixing device 100 in this embodiment. The fixing device 100 includes a cylindrical fixing film 112 as a heating member, a heater 113 that is in contact with the inner surface of the fixing film 112, and a pressure roller as a backup roller that forms a nip portion N 1 together with the heater 113 via the fixing film 112. 110. The fixing device 100 performs a fixing process for fixing the unfixed toner image T to the recording material by heating the recording material on which the unfixed toner image T is formed at the nip portion N1 while conveying the recording material.

  The pressure roller 110 is driven by a driving source (not shown), and the fixing film 112 is rotated by receiving a frictional force from the pressure roller 110 at the nip portion N1. The rotation direction of the pressure roller 110 is the arrow R2 direction in FIG. 1, and the rotation direction of the fixing film 112 is the arrow R1 direction in FIG. The heat of the heater 113 is transmitted from the inner surface of the fixing film 112 to the outer surface, and the surface of the pressure roller 110 is also heated at the nip portion N1. When the recording material P to which the unfixed toner image T has been transferred is conveyed to the nip portion N1 from the direction of the arrow A1 in the figure, the heat of the fixing film 112 is transmitted to the unfixed toner image T and the recording material P, and the toner image T is fixed to the recording material P.

  In the following description, the upstream side in the conveyance direction of the recording material P with respect to the nip portion N1 of the fixing device 100 is defined as upstream, and the downstream side in the conveyance direction of the recording material P with respect to the nip portion N1 is defined as downstream. . Further, the conveyance direction of the recording material P in the nip portion N1 is defined as the short direction, and the direction orthogonal to the conveyance direction of the recording material is defined as the long direction.

  The heater 113 is supported by a heater holder 119, and a fixing film 112 is provided around the heater holder 119. The heater holder 119 is preferably made of a material having a low heat capacity. In this embodiment, a liquid crystal polymer (LCP) which is a heat resistant resin is used. The surface of the heater holder 119 opposite to the surface that supports the heater 113 is supported in the longitudinal direction by a stay 120 that is made of metal and has a U-shaped cross section in order to improve bending rigidity. The stay 120 is pressed by the pressure spring 114 at both ends in the longitudinal direction with a force of 147N in the direction of the arrow A2 in the figure. The pressing force applied to the stay 120 is transmitted to the heater 113 via the heater holder 119, and the heater 113 is pressed against the pressure roller 110 via the fixing film 112 to form a nip portion N1 having a width of 7.5 mm. . In this embodiment, the material of the stay 120 is iron.

(Fixing film)
The fixing film 112 of this embodiment has an inner diameter of φ18 and has a multilayer structure in the thickness direction. The fixing film 112 has a base layer 112b for maintaining the strength of the film and a release layer 112a for reducing adhesion of dirt to the surface. The material of the base layer 112b needs heat resistance because it receives heat from the heater 113, and heat resistant resin such as polyimide, metal (SUS, Ni), or the like may be used. Since resin has a lower specific gravity than metal, there is an advantage that the heat capacity is small and the resin is easily heated. In this embodiment, polyimide resin is used as the material of the base layer 112b of the fixing film 112, and a carbon-based filler is added to improve the thermal conductivity and strength. Although the heat of the heater 113 is more easily transferred to the surface of the fixing film 112 as the thickness of the base layer 112b is thinner, it is preferably about 15 μm to 100 μm because the strength is reduced. In this embodiment, it is set to 60 μm.

  The material of the release layer 112a of the fixing film 112 is preferably a fluororesin such as perfluoroalkoxy resin (PFA), polytetrafluoroethylene resin (PTFE), tetrafluoroethylene-hexafluoropropylene resin (FEP). In this example, among the fluororesins, PFA having excellent releasability and heat resistance was used. The release layer 112a may be either a tube coated or a coating formed with a paint. In this example, a release layer 112a formed by a coat excellent in thin-wall molding was used. The thinner the release layer 112a, the easier it is to transfer the heat of the heater 113 to the surface of the fixing film 112. However, if the release layer 112a is too thin, the durability deteriorates, and is preferably about 5 to 30 μm.

  The fixing film 112 may be displaced in the longitudinal direction, and fixing flanges 130 (regulating members) that restrict the displacement are provided at both ends of the fixing film 112 at the end of the fixing film 112. . The end face of the fixing film abuts against the fixing flange 130 where the deviation occurs and the deviation is regulated.

(heater)
In the heater 113, a heating resistance layer of Ag / Pd (silver palladium) is applied by screen printing to an alumina substrate surface having a width of 6 mm and a thickness of 1 mm by screen printing. The one covered with Sasa Glass was used. A temperature detection element 115 for detecting the temperature of the substrate is disposed on the back surface of the heater 113. In accordance with the detection temperature of the temperature detection element 115, the supply amount of power supplied to the heating resistor layer from an electrode portion (not shown) at the end in the longitudinal direction is appropriately controlled, and the detection temperature of the temperature detection element 115 is the target temperature. I try to reach temperature. The heat of the heater 113 is transmitted from the inner surface of the fixing film 112 to the surface, and heats the surface of the pressure roller 110 via the nip portion N1. When the recording material P to which the unfixed toner image T has been transferred as described above is conveyed to the nip portion N1, the heat of the fixing film 112 and the pressure roller 110 is transferred to the unfixed toner image T and the recording material P. The toner image T is fixed on the recording material P.

(Pressure roller)
The pressure roller 110 according to the present embodiment includes a core metal 117, a rubber layer 110a formed outside the core metal 117, and a release layer 110b formed outside the rubber layer 110a. The outer diameter of the pressure roller 110 of this embodiment is φ18. The surface hardness of the pressure roller 110 was set to Asker-C hardness (4.9 N load) 42 to 48 ° under an environment of 25 ° C. and 50%.

  The core metal 117 is made of iron and has a diameter of 12 mm. The release layer 110b may be a tube coated or coated with a paint. In this example, a perfluoroalkoxy resin (PFA) tube having excellent durability was used. As the material of the release layer 110b, in addition to PFA, a fluororesin such as PTFE or FEP, a fluororubber having good releasability, a silicone rubber, or the like may be used.

  The rubber layer 110a is formed of a silicone rubber sponge having a thickness of 3 mm. The rubber layer 110a is made of a silicone composition manufactured from polyorganosiloxane, an emulsifier, water, a thickener and the like. The thickener is a natural or synthetic inorganic thickener, and can be mixed with water to increase the viscosity of water and facilitate the dispersion of water into the silicone composition. A thickener is mix | blended in order to stabilize the dispersion state of the water in a silicone composition. Water and a thickener are dispersed in polyorganosiloxane to make an emulsion.

  Examples of inorganic thickeners include natural or synthetic smectite clays such as bentonite mainly composed of inorganic clay minerals such as montmorillonite, hectorite, saponite, sauconite, beidellite and nontronite, And hydrophilic composites with anionic polymers such as acrylic acid.

  A cored bar is fixed to the center of the cylinder in a cylindrical roller molding die or the like, and after completely filling the silicone rubber composition, it is heated by being put into a hot air circulating oven or hot water. As a result, the sponge-forming silicone rubber composition is cured (cross-linked) in the mold and integrated with the cored bar to form a roller-shaped silicone rubber sponge. After heating for a predetermined time, the roller mold is cooled as necessary, and the silicone rubber sponge roller is taken out.

  The removed silicone rubber sponge roller is in a water-containing state, so it is dehydrated by heating. On the other hand, many thickeners remain in the cell. Thus, a silicone rubber sponge roller having fine and uniform open cells can be obtained.

  In addition, although the heating temperature at the time of dehydration is arbitrary and natural drying at normal temperature is also possible, the temperature of 100 degreeC or more is preferable for the formation of efficient sponge, and the heating temperature of 120-250 degreeC is more preferable.

  When the pressure roller 110 has a large heat capacity and a high thermal conductivity, the heat of the surface of the pressure roller 110 is easily absorbed into the inside, and the surface temperature of the pressure roller 110 is unlikely to rise. That is, the rubber layer of the pressure roller 110 can reduce the warm-up time of the fixing device 100 by using a material having a heat capacity as low as possible and a low thermal conductivity and a high heat insulating effect. The silicone rubber sponge has a thermal conductivity of 0.8 to 0.16 W / m · K, which is lower than that of solid rubber. The specific gravity related to the heat capacity is about 1.05 to 1.30 for solid rubber, and about 0.5 to 0.85 for silicone rubber sponge, which is also a low heat capacity. Therefore, the silicone rubber sponge contributes to shortening the warm-up time of the fixing device 100.

(Open cell)
The change in the hardness of the silicone rubber sponge in this embodiment is caused by taking atmospheric air into the pressure roller, so that the higher the open cell rate (the rate at which the bubble cells are continuous), the higher the effect. The open cell ratio is preferably 70% or more, more preferably 90% or more. Here, the open cell ratio can be examined by substituting the sponge in water and reducing the pressure to replace the air in the open cell with water. The ratio of the open cells to the total cell in the sponge, that is, the open cell rate is the following formula with the density of water being 1.0 g / cm 3:
[Equation 1]
Open cell ratio (%) = {(mass of absorbed water) / (bubble partial volume)} × 100
Can be obtained. In the above formula, “bubble partial volume” is the following formula:
[Equation 2]
Bubble partial volume (cm3) = {(sponge mass) / (sponge density)}-{(sponge mass) / (rubber density)}
Can be obtained. The “rubber density” in the above formula is a silicone rubber molding obtained by crosslinking and curing a silicone rubber composition prepared in the same manner except that it does not contain the components (C), (D) and (E). It is a value obtained by measuring the density of the product, and represents the density of the sponge bubble wall. In this example, a pressure roller having an open cell ratio of 95% or more was used.

(Mechanism of rubber hardness change)
As described above, an inorganic clay mineral is used as a thickener when forming the silicone rubber sponge of the rubber layer 110a of the pressure roller 110 of this embodiment. The inorganic clay mineral contained in the sponge-forming silicone rubber composition remains in the silicone rubber sponge even when the roller is crosslinked or dehydrated. Inorganic clay minerals have high hydrophilicity and easily absorb moisture in the atmosphere. Inorganic clay minerals vary in hardness depending on the moisture content, and become harder when dried and softer when moisture is absorbed. The hardness of the inorganic clay mineral affects the rubber hardness after formation. That is, the rubber layer 110a of the present embodiment has a reversible characteristic that the hardness increases when dried and the moisture content decreases, and the hardness decreases when moisture is absorbed and the moisture content increases. In particular, when the pressure roller 100 receives heat from the heater 113 during the fixing process, the moisture of the inorganic clay mineral of the pressure roller 110 evaporates and becomes hard, and the rubber hardness of the pressure roller 110 increases. Cheap. Conversely, when the pressure roller is left at room temperature (for example, temperature 25 ° C. and humidity 50%), the inorganic clay mineral absorbs moisture and the rubber hardness decreases. The amount of change in hardness can be adjusted by the content of the thickener, the size of the cell, the size and number of the bubble cells, and the pressure roller 110 of this embodiment has a relative humidity of around 0% and a relative humidity assumed to be room temperature. 50% was adjusted to have a hardness difference of about 3 °. The relative humidity referred to here is the amount of saturated water vapor at a certain air temperature of 100, and the actual measured value of water vapor is expressed as a ratio (percent).

  Next, the effect of the fixing device 100 of this embodiment will be described. First, the relationship between the hardness of the rubber layer 110a of the pressure roller 110 and the recording material conveyance speed in the nip portion N1 will be described. The lower the hardness of the rubber layer 110a of the pressure roller 110, the wider the nip portion N1 and the higher the recording material conveyance speed. Further, as the outer diameter of the pressure roller 110 expands and increases, the width of the nip portion N1 increases and the conveyance speed increases. On the contrary, when the pressure roller hardness is high, the width of the nip portion N1 is narrowed and the recording material conveyance speed is lowered. Further, as the outer diameter of the pressure roller 110 shrinks and becomes smaller, the width of the nip portion N1 becomes narrower and the recording material conveyance speed decreases. As described above, the outer diameter and hardness of the pressure roller 110 affect the width of the nip portion N1, and the width of the nip portion N1 affects the conveyance speed of the recording material.

  FIG. 6 shows the result of comparing the change in rubber hardness by changing the relative humidity between the fixing device 100 of the present embodiment and the fixing device of Comparative Example 1. The fixing device of Comparative Example 1 is a device equipped with a pressure roller having a silicone rubber sponge layer foamed with a resin microballoon without using an inorganic clay mineral. The fixing device 100 of this embodiment is a device on which a pressure roller 110 formed using an inorganic viscosity mineral is mounted. According to FIG. 6, the pressure roller of Comparative Example 1 hardly changes the rubber hardness even when the humidity changes, whereas the hardness of the pressure roller 110 of the present example increases as the relative humidity increases. Rubber hardness is reduced. In other words, the pressure roller of Comparative Example 1 expands to increase the outer diameter when heated during the fixing process, but since the rubber hardness does not change, the width of the nip portion becomes wider and the conveyance speed of the recording material increases. . That is, in Comparative Example 1, the conveyance speed of the recording material at the nip portion is likely to vary. On the other hand, the pressure roller 110 of this embodiment expands the pressure roller 110 during the fixing process to increase the outer diameter, but the rubber hardness increases. Therefore, the nip portion at the end of the pressure roller 110 is increased. Is less wide than Comparative Example 1. Therefore, the conveyance speed of the recording material in the nip portion of this embodiment is less likely to fluctuate than that of Comparative Example 1, and is stable.

  Next, problems as an image forming apparatus will be described. As shown in FIG. 2, the recording material is sandwiched between both the nip portion N2 of the fixing device 100 and the transfer nip portion N3 of the transfer portion 80 on the upstream side of the nip portion N2 in the recording material conveyance direction. Consider a case in which a recording material is conveyed at each nip portion. When the recording material conveyance speed at the nip portion N2 is likely to fluctuate as in the fixing device of the comparative example 1, the following problem occurs. When the conveyance speed of the nip portion N2 of the fixing device 100 is higher than the conveyance speed of the transfer nip portion N3, the unfixed toner image transferred to the recording material in the transfer nip portion N3 is extended, resulting in an image defect. On the contrary, when the conveyance speed of the recording material in the nip portion N2 of the fixing device 100 becomes slower than the conveyance speed in the transfer nip portion N3, the recording material is pushed into the transfer nip portion N3 and transferred to the recording material in the transfer nip portion N3. The toner image is shrunk and the image becomes defective. On the other hand, in the fixing device 100 according to the first exemplary embodiment, the conveyance speed of the nip portion N2 of the fixing device 100 hardly changes, and the difference from the conveyance speed in the transfer nip portion N3 is difficult to increase. There is an effect that image defects are less likely to occur.

(Effect confirmation)
In order to confirm the effect of this embodiment, small-size recording materials were continuously printed by the fixing device 100 equipped with the pressure roller 110 of this embodiment and the fixing device equipped with the pressure roller of Comparative Example 1. Table 1 shows the results of experiments comparing the fluctuations in the conveyance speed of the nip portion.

  As an experimental method, the change in the conveyance speed at the nip portion was evaluated from the sub-scanning magnification of the printing accuracy. The sub-scanning magnification is a grid image in which one grid has a size of 10 mm × 10 mm, and the length of the printed recording material grid in the recording material conveyance direction (sub-scanning direction) is 10 mm. The method of quantifying by the magnification whether it only fluctuates. If the length of the recording material in one grating in the conveyance direction is longer than 10 mm, it means that the conveyance speed at the nip portion of the fixing device is faster than the conveyance speed at the nip portion of the transfer portion. On the other hand, if the length of the recording material of one grating in the conveyance direction is shorter than 10 mm, it means that the conveyance speed at the nip portion of the fixing device is slower than the conveyance speed at the nip portion of the transfer portion.

  Using a paper having a basis weight of 80 g / m 2 and an A4 size (width 210 mm, length 297 mm) in an environment of 23 ° C. and 50%, the fixing device was left in the environment for 30 minutes or more. A sheet was printed. The maximum width recording material that can be used in the fixing device of this embodiment is a letter size (width 216 mm, length 279 mm). The length in the conveyance direction of the recording material of one lattice in one printed material was averaged, and how much the length of one lattice changed from the start to the end of printing was measured. Further, the width of the nip portion at a temperature corresponding to the number of prints of the pressure roller was measured. As a method for measuring the width of the nip portion, the solid black image that has been fixed is conveyed again at the nip portion of the fixing device without forming an image, and the conveyance is stopped in the middle of the conveyance. As the fixed toner in the nip portion melts again, the glossiness of the solid black image region corresponding to the nip portion becomes higher than the solid black image region other than the nip portion. The portion where the glossiness is increased is measured as the width of the nip portion.

  According to Table 1, in Comparative Example 1, the sub-scanning magnification is increased by about 7% between 1 to 200 continuous prints, so that the conveyance speed at the nip portion of the fixing device increases from the initial stage to the latter half of the continuous print. It shows that. In the image forming apparatus of Comparative Example 1, it is considered that measures such as making the rotation speed of the pressure roller variable are necessary to ensure high printing accuracy. On the other hand, in this embodiment, the sub-scan magnification is substantially the same from the initial stage to the latter half of the continuous printing, and it can be seen that there is little variation in the conveyance speed at the nip portion of the fixing device.

  Also in the comparative example 1, the width of the nip portion is 1.3 mm wider between 1 to 200 continuous prints, indicating that the conveyance speed of the nip portion of the fixing / fixing device is increased. On the other hand, in this embodiment, the width of the nip portion in the initial printing and the second half of the printing is almost the same, and it can be seen that the conveyance speed of the nip portion of the fixing device is not easily changed.

  As described above, according to the present embodiment, there is an effect that the conveyance speed of the recording material in the nip portion hardly fluctuates and is stable regardless of the warming condition of the pressure roller 110.

  The fixing device of this embodiment does not supply power to the heater 113 when executing a standby mode (standby mode) in which the rotation of the fixing film 112 is stopped and a print instruction is waited. When power is supplied to the heater 113 and the pressure roller 110 is warmed in the standby mode, the water in the rubber layer 110a evaporates and the hardness is high before the start of printing. This is because even if the pressure roller 110 is warmed by continuous printing, since the water has already evaporated, the hardness is hardly increased and the effect of the present invention is reduced.

(Example 2)
The image forming apparatus 50 and the fixing device 200 according to the second embodiment will be described. Since the configuration of the image forming apparatus 50 of the present embodiment is the same as that of the first embodiment except for the fixing device 200, the description thereof is omitted. 3 includes a fixing roller 210, a heating film 112 serving as a heating member, a heater 113 that contacts the inner surface of the fixing film 112, a pressure film 240 serving as a backup member, and formation of a nip portion. Member 250. The heater 113 forms a heating pressure contact portion N5 together with the fixing roller 200 via the heating film 112. Further, the nip portion forming member 250 forms a nip portion N6 together with the fixing roller 200 via the pressure film 240. The recording material on which the toner image is formed at the nip is heated while being conveyed, and the toner image is fixed on the recording material. The thermistor 115 as a temperature detection member is provided on the surface of the heater 113 opposite to the surface in contact with the heating film 112, and detects the temperature of the heater 113. A controller (not shown) controls the heater 113 based on the temperature detected by the thermistor 115.

(Fixing roller)
The fixing roller 210 includes a cored bar 217, a first rubber layer 210a formed outside the cored bar 217, a second rubber layer 210b formed outside the first rubber layer 210a, and a second rubber layer 210a. And a release layer 210c formed on the outer side of the rubber layer 210b. The cored bar 217 of this embodiment is made of iron and has an outer diameter of φ18. The first rubber layer 210a is a silicone rubber sponge containing an inorganic clay mineral as an inorganic thickener having a thickness of 3 mm manufactured by the same manufacturing method as in Example 1. The second rubber layer 210b is a rubber layer whose main component is alumina rubber having a thickness of 200 μm, and has a higher thermal conductivity than the first rubber layer 210a. The release layer 210c is a layer mainly composed of PTFE, PFA, FEP or the like having a thickness of 10 μm.

(Heating member)
Since it is the same as that of Example 1, detailed description of the configuration is omitted.

(Backup material)
The pressure film 240 has a base layer with an outer diameter of 18 mm and a thickness of 60 μm formed of polyimide or the like, and a 10 μm thick release layer formed of PFA or the like outside the base layer. The material of the nip portion forming member 250 is preferably a metal material such as stainless steel, iron, or aluminum having mechanical strength and high thermal conductivity. The nip portion forming member of this embodiment is a plate-like member made of stainless steel and having a width of 7.5 mm and a thickness of 1 mm. The backup member 260 further includes a holder 251 that supports the nip portion forming member 250 and a support body 252 that supports the holder 251. The holder 251 is a member formed of a liquid crystal polymer. The surface of the holder 251 opposite to the surface that supports the nip forming member 250 is supported by a support body 252 formed of metal over the longitudinal direction. A nip portion forming member 250 is pressed against the fixing roller 210 via the pressure film 240 by a pressure mechanism (not shown), and a nip portion N6 having a predetermined width is formed.

  Further, the heater 221 is pressed against the fixing roller 210 via the heating film 112 by a pressurizing mechanism (not shown) to form a nip portion N5. The backup member 260 is disposed on the side opposite to the heating member with respect to the fixing roller 210.

  The backup member of this embodiment uses the heating film 240, but may be a roller having a rubber layer. In the driving method of the fixing device of this embodiment, the fixing roller 210 is driven by a driving source (not shown), and the heating film 112 and the pressure film 240 are rotated by the rotation of the fixing roller 210.

(Effect confirmation)
In order to confirm the effect of this embodiment, Table 2 shows the result of the same experiment as that of Embodiment 1 using the fixing device of this embodiment and the fixing device of Comparative Example 2. The fixing device of Comparative Example 2 is a device equipped with a fixing roller having a rubber layer of silicone rubber sponge foamed by a resin microballoon without using an inorganic clay mineral. Since the experimental method and conditions are the same as in Example 1, the description is omitted.

  According to Table 2, in Comparative Example 2, the sub-scanning magnification increased by about 8% between 1 to 200 continuous prints, so that the recording material conveyance speed in the nip portion increased from the initial printing to the second half. Is shown. On the other hand, this embodiment shows that the sub-scanning magnification in the initial stage and the latter half is almost the same, and the conveyance speed of the recording material in the nip portion hardly varies from the initial stage of printing to the latter half of printing. As for the width of the nip portion, Comparative Example 2 spreads 1.8 mm between 1 to 200 continuous prints, indicating that the recording material conveyance speed in the nip portion is increased. On the other hand, this embodiment shows that the width of the nip portion in the initial stage and the latter half is almost the same, and the conveying force of the recording material in the nip portion hardly fluctuates from the initial stage to the second half of printing.

  As described above, according to the present exemplary embodiment, there is an effect that the conveyance speed of the recording material at the nip portion is stabilized regardless of the warming condition of the fixing roller 210.

  In addition, although the heating member of Example 1, 2 used the film, it is not limited to this structure. For example, as the heating member, a halogen heater 401 may be included in the fixing film 410 as shown in FIGS. 4A and 4B. The fixing device in FIG. 4A includes a nip portion forming member 420 for forming a nip portion together with the pressure roller 110 via a film 410. 4B includes a nip portion forming member 420 for forming a heating and pressing portion together with the fixing roller 210 via the film 410.

  Note that the fixing device of this embodiment also does not supply power to the heater 113 when executing a standby mode in which the rotation of the fixing roller 210 is stopped and a print instruction is waited for the same reason as in the first embodiment.

DESCRIPTION OF SYMBOLS 100 Fixing device 110 Pressure roller 110a Rubber layer 112 Fixing film 113 Heater 115 Temperature detection element 117 Core metal

Claims (8)

A heating member;
A backup roller having a cored bar and a rubber layer formed outside the cored bar, and forming a nip portion together with the heating member;
A fixing device for fixing the toner image on the recording material by heating while conveying the recording material on which the toner image is formed at the nip portion,
The rubber layer is formed from a sponge-forming silicone rubber composition containing an inorganic thickener,
The fixing device, wherein the backup roller is driven, and the heating member is rotated by the rotation of the backup roller. A heating member;
A backup roller having a cored bar and a rubber layer formed outside the cored bar, and forming a nip portion together with the heating member;
A fixing device for fixing the toner image on the recording material by heating while conveying the recording material on which the toner image is formed at the nip portion,
The rubber layer has a reversible characteristic that the hardness decreases as the moisture content increases and the hardness increases as the moisture content decreases,
The fixing device, wherein the backup roller is driven, and the heating member is rotated by the rotation of the backup roller. A control unit for controlling power supplied to the heating member;
3. The fixing device according to claim 1, wherein the control unit stops supplying power to the heating member in a standby mode waiting for an instruction to start a fixing process.   The fixing device according to claim 1, wherein an open cell ratio of the rubber layer is 70% or more.   The fixing device according to claim 1, wherein the thickening material is an inorganic viscosity mineral.   The fixing device according to claim 5, wherein the viscosity mineral is at least one of montmorillonite, hectorite, saponite, sauconite, beidellite, and nontronite.   The fixing device according to claim 1, wherein the heating member includes a cylindrical film.   The fixing device according to claim 7, wherein the heating member includes a heater that contacts an inner surface of the film.

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