JP5072381B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device of an image forming apparatus in which toner is fixed to a recording medium with a fixing roller, and more specifically to a heat conductive elastic fixing member in which the heat conductivity of the fixing roller is improved. By improving the heat conductivity of the fixing roller, it is possible to shorten the start-up time of the fixing device by the fixing roller, and to enable low-temperature fixing and reduce the energy released from the fixing roller. It is something that can be done.

  As a fixing member for the outer layer of a transfer roller, in an electrophotographic copying machine, a printer, or an apparatus for forming color electrophotography for the purpose of high image quality, in order to ensure flexible adhesion to toner and heat resistance It is common to use a heat resistant rubber material such as silicone rubber. However, heat-resistant rubber materials such as silicone rubber have low thermal conductivity, and serve as a heat resistance layer when transferring heat from a heat source to a recording material (a recording medium such as a paper sheet). In a color image transfer roller, it is important that the fixing member is a particularly soft rubber layer in order to improve image quality. On the other hand, the heat resistant rubber material has a large heat capacity and a high thermal resistance, so that the fixing device takes a long time to start up, and the heat supply is not in time for a high-speed machine. For this reason, attempts have been made to improve the thermal conductivity of the heat-resistant rubber material by mixing a filler.

[Problems of background technology]
As described above, attempts have been made to incorporate a filler having high thermal conductivity in order to increase the thermal conductivity of the heat-resistant rubber material. However, the fixing member has been reduced in density, reduced in heat capacity, and increased in thermal conductivity. (The following “foaming ratio” is obtained by using the volume Vs without bubbles as a denominator and the sum of the bubbles volume Vf and Vs as a numerator. In the description of the invention, it is expressed by the expansion ratio).
There are two reasons for this.
1. When the expansion ratio is increased in order to reduce the density of the heat-resistant rubber material, the thermal conductivity rapidly decreases. This occurs when the thermal conductivity of the original material does not change (see the Eucken equation in the thermophysical handbook Yokendo C.2 p.179).
2. Further, when the expansion ratio is increased, the wall surface of the fixing member becomes relatively thin, so that the strength is lowered.

Due to the above two problems, it has been difficult to develop a member having a low heat capacity (low density) and a high thermal conductivity for a heat-resistant fixing member that is repeatedly deformed in a high temperature environment.
Japanese Patent Laid-Open No. 2004-286084 (Patent Document 1) discloses a conventional technique. This patent document 1 discloses a technique related to a heat insulating material of a fixing device, and includes, for example, a description of pressure dependency of thermal conductivity using sponge silicone. However, in FIG. 9, the variability of the foamed silicone depending on the pressure is shown. In such a case, the bubble portion is crushed and returned only to the original by the pressure. The thermal conductivity is not exceeded and the above problem has not been solved.
JP 2004-286084 A

Based on such a background, the present invention aims to speed up the rise of a fixing device of an image forming apparatus. For a fixing member made of a heat-resistant rubber material, a low heat capacity (low density) and a high heat The technical challenge is to increase the conductivity.
In the description of the detailed description of the present invention, “thermal contact” means “not directly touching, but because the materials are very close to each other, It is considered to be the same as if

  According to the first aspect of the present invention, in the fixing nip portion, when the material is compressed, the thermal conductivity is increased and heat can be efficiently released, and otherwise, the thermal conductivity is decreased to lower the substantially set fixing temperature. The purpose of this is to speed up the start-up of the fixing device and to save energy.

The invention of claim 1 aims to increase the thermal conductivity of the fixing member made of silicone rubber by increasing the contact between the fibers of the carbon fiber, and a material having good adhesiveness with the silicone rubber is placed around the bubbles. Therefore, it is a technical problem to improve the strength of the entire fixing member.

The invention of claim 2 aims at increasing the thermal conductivity of the fixing member made of silicone rubber by increasing the contact between the carbon fiber fibers, and disposing a material having good adhesion to the silicone rubber around the bubbles. Accordingly, a technical problem is to improve the strength of the entire fixing member.

The invention of claim 3 aims to improve the thermal conductivity of the fixing member made of silicone rubber by increasing the contact between the carbon fiber fibers, and a material having good adhesion to the silicone rubber is arranged around the bubbles. Accordingly, a technical problem is to improve the strength of the entire fixing member.

According to a fourth aspect of the present invention, by using a thin core metal having a high strength, it is possible to take advantage of the characteristics of the material having a high thermal conductivity and a low heat capacity to speed up the start-up of the image forming apparatus and save energy. Objective.

Another object of the present invention is to provide a highly durable heat fixing member that can be released even with oilless toner.

The object of the present invention is to improve the releasability with toner and to obtain a fixing member having high durability.

An object of the present invention is to obtain a fixing device having high releasability from toner and high durability of a fixing member.

An object of the present invention is to obtain a fixing device having high releasability from toner and high durability of a fixing member.

The object of the invention of claim 9 is to obtain a fixing device having a good fixing property and to fix the toner with a pressure within the limit of the releasing property of the wax or the releasing agent in order to prevent toner adhesion .

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The invention of claim 10 is intended to high durability, obtained quality, an image forming apparatus having the energy-saving properties.

To develop a fixing member having a low heat capacity (low density) and high thermal conductivity, the following two points are technically problematic.
1. Thermal conductivity decreases rapidly as the expansion ratio is increased.
2. Similarly, as the expansion ratio is increased, the wall surface becomes relatively thin and the strength decreases.
The present invention includes a fixing roller having a heat source built in the center thereof and having an elastic member on the outer periphery of the cored bar, and a rotating member that presses against the fixing roller, and includes the fixing roller and the rotating member. Regarding a fixing device of an image forming apparatus that conveys a recording medium carrying toner to a pressurized nip portion and fixes the toner to the recording medium to form an image.
The fixing roller is an elastic member having bubbles, and carbon fiber (for example, pitch-based carbon fiber) is mixed into the elastic member to form the high thermal conductivity portion by the carbon fiber around the bubbles. Is a solution.
In order to improve the thermal conductivity, it is very important to improve the contact state between the filler, that is, the carbon fibers. In the present invention, the thermal conductivity variability (thermal conductivity during pressure compression) is improved by utilizing the improvement in thermal contact between the high thermal conductivity portion around the bubble and the carbon fiber due to deformation during pressure compression. Changed and become higher).

In addition, by arranging a good heat conductor or the like on the wall surface of the bubble and thereby strengthening the bubble wall surface, it was possible to improve the restoring property and reduce the compression set.
In addition, there exists a tendency for contact efficiency to rise, so that the mixing rate of carbon fiber is high, and for contact efficiency to fall on the other hand. The mixing ratio required to give the heat conductivity necessary for the fixing member varies depending on the material of the fixing member, the difference in firing rate, the type of carbon fiber, the difference in length, and the like. It is appropriately selected within a range of ˜60% by weight.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional configuration diagram illustrating a part of a fixing roller 1 according to the fixing device of the present invention as an enlarged schematic diagram. The fixing roller 1 shown in FIG. 1 is provided with a heat source (not shown). The heat source is provided on the outer periphery of the metal core 10 through a metal core 10 mainly made of a metallic material. The heat is transmitted to the silicone rubber layer 11 used as the fixing member. Further, a fluororesin layer 12 is coated on the outer peripheral surface side of the silicone rubber layer 11 so as to cover the silicone rubber layer 11, and the fluororesin layer 12 is a heat transfer element for transmitting the heat. And an element for improving the peelability from the recording medium.
In FIG. 1, a characteristic place is the configuration of a silicone rubber layer 11 used as a fixing member. The silicone rubber layer 11 functions as an elastic member that is compressed by pressurization, includes a good thermal conductor made of acicular carbon fibers 22 in the matrix phase inside the silicone rubber layer 11, and further includes bubbles 23. It is characterized in that it is contained and a good thermal conductor covers the periphery of the bubble 23.

The structure shown in FIG. 1 shows a case where the silicone rubber layer 11 is in an uncompressed state, and in this uncompressed state, the carbon fiber 22 of a good thermal conductor is dispersed due to the presence of bubbles 23, that is, Since there are few contact locations between the carbon fibers 22, the effect of heat transfer due to the contact between the carbon fibers 22 is low, and the heat transmitted through the cored bar 10 from the heat source (not shown) is transmitted through the silicone rubber layer 11. The surface is not easily transmitted to the fluororesin layer 12 on the surface.
On the other hand, FIG. 2 shows a state in which the silicone rubber layer 11 which is an elastic member is compressed by pressure. In this pressure compression state, the silicone rubber layer 11 that is an elastic member is compressed, so that the bubbles 23 contained in the silicone rubber layer 11 are also compressed. However, since the carbon fiber 22 has very rigid characteristics, the carbon fiber 22 itself does not greatly depend on the deformation of the silicone rubber layer 11 and the carbon fiber 22 itself has a small amount of deformation. And in connection with it, in the pressurization compression state shown in FIG. 2, since the contact location of carbon fibers 22 increases compared with the case of the non-compression state shown in the said FIG. The heat conduction efficiency due to the contact is improved, and the thermal conductivity of the entire portion of the silicone rubber layer 11 is increased.

Here, regarding the high thermal conductivity of the entire portion of the silicone rubber layer 11 in the pressurized and compressed state, it is important that the surface portion constituting the shape of the bubble 23 is covered with a good thermal conductor (not shown). It is.
In the configuration of the present invention, it is important that the thermal conductivity is low in the non-compressed state shown in FIG. 1 and the thermal conductivity is high in the compressed state shown in FIG. only the contact between the thus is significantly that the thermal conductivity of high Kusuru difficult. However, since the surface portion constituting the shape of the bubble 23 is covered with a heat good conductor (not shown), the carbon fiber 22 and the heat good conductor on the surface of the bubble 23 can be brought into contact with each other. Good conductors can be brought into contact with each other, which is advantageous because the thermal conductivity can be increased.

That is, the fixing roller provided with the silicone rubber layer 11 which is the elastic member of the present invention has a higher thermal conductivity in the pressure compression state than in the non-compression state.
In addition, due to this, in the conventional technology, the heat-resistant rubber material has a large heat capacity and a high thermal resistance, so the rise time of the fixing device becomes long, and the heat supply is not in time even in the case of a high-speed machine. The point is solved.

FIG. 3 schematically shows an enlarged cross-sectional structure of the silicone rubber layer 11 on the surface layer portion of the fixing roller 1 of the present invention . In FIG. 3, the main flow of heat is indicated by an arrow 21, and here, heat from a heat source inside the fixing roller 1 (not shown) passes through the metallic cored bar 10 to the surface layer portion of the fixing roller 1. The flow to the fluororesin layer 12 is schematically shown.
Also here, the carbon fiber 22 and the good heat conductor on the surface of the bubble 23 are in contact with each other because the surface portion constituting the shape of the bubble 23 is covered with a good heat conductor (not shown in FIG. 3). It is also possible to make contact between the heat good conductors on the surface of the bubble 23, which is advantageous because the thermal conductivity can be increased.

From the description so far, it is clear from the main flow of heat described above that the high thermal conductivity is obtained because the high thermal conductivity carbon fiber 22 contacts the high thermal conductivity portion around the bubble 23. In addition, it is advantageous in the present invention that the thermal resistance is very small because there are many contact portions between the carbon fibers 22.
The details of each material used in this manner and constituting the present invention will be described in order.
As the carbon fiber 22, pitch type Nippon Graphite Fiber Co., Ltd. product name: carbon fiber milled, product number: XN-100-05M (50 microns), XN-100-15M (150 microns), etc. are optimal. . These have a thermal conductivity of 500 W / mK, whereas the PAN-based thermal conductivity is 50 W / mK at the maximum.

A dispersion of the carbon fiber and the expanded particles on the main component side of a two-pack type addition-type liquid silicone, a PFA tube having an adhesive layer formed on the inner surface in advance, and a core metal having a thickness of 0.4 mm set on the inner side. In between, it injects, mixing with a hardening | curing agent, is foamed by primary heating, and is fixed by secondary heating. As a result, the illustrated fixing roller is manufactured.
The metal core 10 is thin, and as shown in FIG. 6 , annular ribs 10a are provided on the inner surface at regular intervals and reinforced.
The silicone uncrosslinked liquid produced in the same manner can be applied and crosslinked on a roller to form a fluororesin coat layer, or it can be covered with a fluororesin tube.

FIG. 4 shows a fixing device 40 using the fixing roller 1 and the pressure roller 42 according to the present invention, and a heater H for heating is provided at the center of the fixing roller 1.
FIG. 5 shows an image forming apparatus provided with a fixing device according to the present invention. The configuration of this image forming apparatus is conventionally known except for the fixing device.
As the fluororesin used in the present invention, those having good melt film-forming properties by firing and having a relatively low melting point (preferably a melting point of 250 to 300 ° C.) are preferable. Specifically, low molecular weight polytetrafluoroethylene ( PTFE), tetrafluoroethylene - hexafluoropropylene copolymer (FEP), tetrafluoroethylene - fine powder of perfluoroalkyl vinyl ether copolymer (PFA) are suitable.

  As the low molecular weight polytetrafluoroethylene (PTFE) powder, Lubron L-5, L-2 (Daikin Industries), MP1100, 1200, 1300, TLP-10F-1 (Mitsui Dupont Fluorochemical) are known. As the tetrafluoroethylene-hexafluoropropylene copolymer (FEP) powder, 532-8000 (DuPont) is known. As the tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), MP-10 and MP102 (Mitsui DuPont fluorochemical) are known. In particular, MP103, MP300 (Mitsui Dupont Fluorochemical), AC-5600, AC5539 (Daikin Industries) and the like are suitable for the present invention as those having a low MFR (melt flow rate) and low fluidity.

Further, as resin balloons for forming bubbles, there are MFL-100CA, MFL-80CA, F-80DE, etc. of Matsumoto Yuka Pharmaceutical Co., Ltd. Furthermore, the carbon fibers include PAN (poly (polyethylene)) made from synthetic acrylic long fibers. There are pitch-based carbon fibers made from (acrylonitrile) -based carbon fibers, coal tar, and petroleum pitch.
The PAN-based carbon fiber is obtained by carbonizing a PAN precursor (polyacrylonitrile fiber) and has properties of high strength and high elastic modulus. Pitch-based carbon fibers are obtained by carbonizing pitch precursors (pitch fibers obtained using coal tar or heavy petroleum components as raw materials). A wide range of properties with high strength can be obtained.
Ultra-high modulus products have excellent thermal conductivity and conductivity characteristics, as well as high rigidity applications.
The heat-conducting elastic fixing member of the fixing roller in the following examples was measured with the thickness set to 75% of the original thickness except for “Example F”.

[Example A]
An electroless gold-plated F-80DE and XN-100-05M (50 micron) dispersed in an addition-type liquid silicone is prepared, and the powder is dispersed in a hollow cored bar made of aluminum via a primer. A silicone layer (thickness 2 mm) is formed and heated to be primarily cured. Further, the heating temperature is changed and secondarily cured, and a PFA resin tube is adhered to the outside thereof to produce a fixing roller having an outer diameter of 40 mm.
The fixing roller of “Example A” was set in a fixing unit of a copying machine MF4570 manufactured by Ricoh Co., Ltd., and the minimum fixing temperature was measured by a smear method using a 1000 (W) halogen heater.

  Formulation of XN-100-05M (50 microns) into the silicone rubber was performed in parts by weight. Moreover, the foaming ratio by said F-80DE which gave electroless gold plating was converted with the density after shaping | molding. When the PFA resin layer is made of a material having a model number of HPPlus 950HP manufactured by Mitsui DuPont Fluoro Chemical Co., Ltd., the spherulite becomes small and the surface roughness becomes high. The core metal has a rib and a thickness of 0.4 mm.

上記表１における実施例１、実施例２、実施例３ではいずれも３０秒以内で立ち上がっている。
比較例１では、ほとんど密度がソリッドシリコーンに近く、熱容量が大きくなり、長い温度上昇時間（７３秒）を必要としている。
比較例２では、熱伝導性が下がっていると推測される。 Table 1 shows the measurement results of the minimum fixing temperature and the temperature rise time for Examples 1, 2, and 3 and Comparative Examples 1 and 2.
The lower limit fixing temperature was evaluated by the smear method (according to the density on the cloth when a cloth attached to a weight of 8.8 N / φ15 mm was placed on the transfer paper and rubbed 5 times). The minimum fixing temperature was determined based on a standard of a density of 0.3 or less on the cloth. That is, it is larger than 0.3 below the lower limit fixing temperature. Moreover, it is 0.3 or less above the minimum fixing temperature.
Further, the time from room temperature (25 ° C.) to the lower limit fixing temperature is shown as the temperature rise time (sec).

In Example 1, Example 2, and Example 3 in Table 1 above, all rise within 30 seconds.
In Comparative Example 1, the density is almost similar to that of solid silicone, the heat capacity is increased, and a long temperature rise time (73 seconds) is required.
In Comparative Example 2, it is estimated that the thermal conductivity is lowered.

[Example B]
The above MFL-100CA and XN-100-05M (50 microns) dispersed in addition type liquid silicone are prepared. A powder-dispersed silicone layer having a thickness of 2 mm is formed on a hollow metal core made of aluminum with a primer, and this is heated and primarily cured. Furthermore, the heating temperature is changed to perform secondary curing, and a PFA resin tube is bonded to the outside. The fixing roller thus manufactured has an outer diameter of 40 mm. This was set in a fixing unit of a copying machine MF4570 manufactured by Ricoh Co., Ltd., and a fixing lower limit temperature was measured by a smear method using a 1000 (W) halogen heater. The measurement results are shown in Table 2.

  Formulation of XN-100-05M (50 microns) into the silicone rubber was performed in parts by weight. Moreover, the expansion ratio by MFL-100CA was converted by the density after molding. When the PFA resin layer is made of a material having a model number of HPPlus 950HP manufactured by Mitsui / DuPont Fluorochemical Co., Ltd., the spherulite is reduced and the surface roughness is improved. The metal core is provided with ribs (reinforcing ribs) and has a thickness of 0.4 mm.

実施例４、実施例５、実施例６では４０秒以内で立ち上がっている。比較例３では、ほとんど密度がソリッドシリコーンに近く、熱容量が大きくなり、温度上昇時間８２秒を必要としており、また、比較例４では、熱伝導性が下がっていると推測される。 The lower limit fixing temperature was evaluated by the smear method (according to the density on the cloth when a cloth attached to a weight of 8.8 N / φ15 mm was placed on the transfer paper and rubbed 5 times). The minimum fixing temperature was determined based on a standard of a density of 0.3 or less on the cloth. That is, it is larger than 0.3 below the lower limit fixing temperature. Moreover, it is 0.3 or less above the minimum fixing temperature.
Further, the time required to raise the temperature from room temperature (25 ° C.) to the fixing lower limit temperature is shown as temperature rise time (sec). MFL-100CA is obtained by arranging calcium carbonate around the periphery of a resin balloon.

In Example 4, Example 5, and Example 6, it stands up within 40 seconds. In Comparative Example 3, the density is almost similar to that of solid silicone, the heat capacity is increased, and a temperature rise time of 82 seconds is required. In Comparative Example 4, it is presumed that the thermal conductivity is lowered.

実施例５の芯金の厚さは０．４ｍｍであるが、環状のリブがあるので、回転時破壊はなく、温度上昇時間は１６秒であって２０秒以下である。芯金の厚さが０．５ｍｍ以上の例では、温度上昇時間は２２秒以上になっている。 [Example C]
Example C is a modification in which the thickness of the cored bar of the fixing member of Example 5 is variously changed. FIG. 6 shows a cored bar 10 provided with an annular rib on the inner surface, FIG. 6 (a) shows a cross section of the whole cored bar, and FIGS. 6 (b), (c) and (d) show the rib 10a. An example of the cross-sectional shape is shown. The core metal 10 is provided with an annular rib 10a on the inner surface, so that the necessary strength is ensured even if it is thin.
The thickness of the cored bar of Example 5 was changed to be Example 7, Comparative Example 9, Comparative Example 10 to Comparative Example 12, and the temperature rise time was measured. The results are shown in Table 3.

Although the thickness of the cored bar of Example 5 is 0.4 mm, since there is an annular rib, there is no breakage during rotation, and the temperature rise time is 16 seconds and 20 seconds or less. In the example where the thickness of the core metal is 0.5 mm or more, the temperature rise time is 22 seconds or more.

Example D
The fixing roller of Example 5 was mounted on a fixing unit of MF4570 manufactured by Ricoh Co., Ltd., and 10,000 sheets of a black solid image of “Imagio MP C4500” manufactured by Ricoh Co., Ltd. were passed through. The winding was observed. The results are shown in Table 4.
It was confirmed that if the surface roughness (ten-point average roughness: JIS B0601-1994) Rz of the fixing roller is 5 μm or less, there is an effect. When the surface roughness Rz was 7 μm, jamming occurred frequently on 8298 sheets.

Example E
A paper passing test was performed on an unfixed image created with “IPSIO Color 8100” manufactured by Ricoh Co., Ltd. Since the toner of “IPSIO Color 8100” has insufficient releasability, an oil application member impregnated with silicone oil is added to the fixing roller. The fixing roller of Example 5 is used. Through this “IPSIO Color 8100”, 10,000 sheets of solid black images were passed, and the toner adhesion state on the roller surface was observed. There was no noticeable adhesion, and there was no difference from the normal one. When the oil application member was not provided, the toner adhered to the fixing roller on 2500 sheets.

[Example F]
A fixing roller of Example 5 having a surface roughness Rz of 2 μm or less was prepared, and a fixing test machine using a fixing unit of MF4570 was prepared. An unfixed image by “Imagio MP C4500” manufactured by Ricoh Co., Ltd. The (wax-containing toner) was passed through the fixing unit under various pressures. The results are shown in Table 5.
When the applied pressure was 2.9 (N / cm ² ) or less, the fixability was very poor, and when it was 19.6 ( N / cm ² ) or more, toner adhesion to the fixing roller was observed. “Paper wrapping” in Table 5 indicates that the toner adhesion state further deteriorated and wrapping occurred. When the applied pressure is 39.2 ( N / cm ² ) or less, no wrapping of paper is observed. Fixability was determined by the smear method. It should be noted that a level of 0.3 or less having no problem is indicated by “◯”, an allowable level of 0.5 or less is indicated by “Δ”, and a level of 0.51 or more is indicated by “x”.

[Example G]
In the fixing device of an image forming apparatus, the second heat conductor is a metal powder, carbides, oxides, carbonate compound, is made of talc inorganic powder. Examples of the present invention are as follows.
In one example, Examples 4, 5 and 6 in [Example B] are examples of carbonate compounds. Similarly, Matsumoto Yushi Seiyaku's pharmaceuticals are manufactured under the same conditions in place of MFL-100CA in Example 5. 80GTA (talc), also was prepared by the 30STI (titanium oxide), the minimum fixing temperature was similar at 135 ° C.. The rise was 9 seconds. Further, a silver powder having a particle size of 2 microns, similarly SiC powder, was attached to Matsumoto Yushi Seiyaku F-80SD with a hybridizer manufactured by Nara Machinery, and foamed, instead of MFL-100CA of Example 5. Were similarly used under the same conditions. The minimum fixing temperatures are 135 ° C. and 140 ° C., respectively. Also, the rise was 9 seconds and 13 seconds.

In the fixing device of an image forming apparatus, in which the second heat conductor is made of a metal film. Example A is also this example.

〔The invention's effect〕
The silicone rubber layer 11 used as the fixing member of the present invention functions as an elastic member that is compressed by pressurization, and a matrix of thermal good conductors made of acicular carbon fibers 22 inside the silicone rubber layer 11. The bubbles are further included in the phase, and the heat good conductor covers the periphery of the bubbles 23.
As a result, it is in a non-compressed state before the fixing device is started, and from there it is compressed (in the nip state) to achieve high thermal conductivity, and heat from the heater is efficiently transferred to the surface of the fixing roller for fixing. become able to. As a result, the portion other than the nip has a relatively low thermal conductivity, so that the surface temperature of the roller decreases. And since the temperature is set in this part, it becomes possible to fix at a substantially low temperature, so that less energy is released to the surroundings, and since the set temperature is lowered, the heat-up time is shortened accordingly. Has the effect.

Since the good thermal conductor of the present invention contains carbon fiber, it is in an uncompressed state before starting the fixing device, and when it is compressed (in the nip), the rigidity and heat of the carbon fiber are increased. Combined with the flexibility of silicone rubber containing bubbles with good conductors formed on the surface, the contact between carbon fibers and the thermal contact efficiency of bubbles with carbon fibers and heat good conductors formed on the surface are increased, and the heat conduction path Is formed, and the heat conductivity becomes high, so that the heat from the heater can be transferred efficiently.
In addition, since the surface temperature of the roller at the nip portion needs to be higher than a certain temperature for fixing, the roller surface at the nip has a required high temperature, but the portion other than the nip has a relatively low heat. Due to the conductivity, the roller surface temperature decreases. Since the temperature is set in the low temperature portion, a substantially low temperature fixing is possible, which reduces the energy released around. Further, since the set temperature is lowered, the rising time (heat up time) is shortened accordingly.

The effect of the invention of claim 4 By providing releasability with a fluororesin, it is possible to provide an induction heating device having releasability and high durability even with oilless toner, but it is heated from the heater at the center of the roller. Since the core is first a core, this heat capacity is important for shortening the start-up time. If the thickness of the core is 0.4 mm or less, the start-up can be performed in about 10 seconds. On the other hand, the strength of the fixing roller is reduced.
However, the invention of claim 4 can provide a fixing device that can be started up in a short time and has a high-strength fixing roller by reinforcing the inner surface of the cored bar by providing an annular rib.

Effects of the Invention of Claim 5
According to the invention of claim 5 , a layer made of a fluorine-based polymer is provided on the outermost surface of the fixing roller, thereby providing a release property by a fluororesin, so that even an oilless toner has a release property. A durable induction heating device can be provided.

The effect of the invention of claim 6 In the solid image, the toner easily adheres to the unevenness of the surface of the fixing member, but the invention of claim 6 has a fixing roller having a surface roughness and a ten-point average roughness Rz of 5 μm or less. Because the surface is made of a fixing member with a smooth surface, it is difficult for toner to adhere to it, and toner adhesion attracts a paper jam, which damages the roller surface and becomes one of the factors that determine the service life. And the durability of the fixing roller is improved.

Effects of the Invention of Claim 7
According to the seventh aspect of the present invention, since fixing is performed using a wax-containing toner, the wax improves the releasability of the toner and the fixing member in contact with the toner.

Effects of the Invention of Claim 8
Since the invention of claim 8 has means for applying a release agent to the fixing member, the release property of the fixing member in contact with the toner can be improved by the applied release agent.

The effect of the invention of claim 9 In the fixing of many toners, the fixability depends on the applied pressure, but the invention of claim 9 is based on the area S ( cm ² ) of the contact portion in pressure contact with the fixing member. divided by pressure F (N) value, 4.9 N / cm ² or more at which or fixing of al picture image rather high, releasability is ensured since it is 39.2 N / cm ² or less. When this value is 39.2 N / cm ² or more, the release agent such as wax or silicone oil possessed by the toner comes out between the toner resin and the fixing member, and the release property by the release agent cannot be maintained .

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Effects of the Invention of Claim 10
According to the tenth aspect of the present invention, since the toner image is fixed on the recording medium by the fixing device according to the first to ninth aspects, heat transfer is uniform by a roller having good thermal conductivity at the nip portion and low rubber hardness. Thus, a fixing roller with a built-in heat source can be used, and an image forming apparatus with high reliability and energy efficiency can be provided.

FIG. 2 is a partially enlarged sectional view of a fixing roller according to the present invention. FIG. 3 is a partially enlarged cross-sectional view of a fixing roller in a pressurized state according to the present invention. FIG. 3 is a diagram schematically showing a heat transfer state in a silicone rubber layer 11 of the fixing roller in FIG. 2. These are side views of the fixing device using the fixing roller of the present invention. These are side views of an image processing apparatus to which the fixing device according to the present invention is applied. (A) is sectional drawing of the metal core of the fixing roller of this invention, (b) is sectional drawing of a rib, (c) (d) is sectional drawing of the other example of a rib.

1: fixing roller 10: core metal 11: silicone rubber layer 12: fluororesin layer 21: arrow 22 indicating the main flow of heat 22: carbon fiber 23: bubble 40: fixing device 42: pressure roller H: heater

Claims (10)

A fixing roller having a built-in heat source, and a rotating member that presses against the fixing roller, and transports a recording medium carrying toner to a pressurized nip formed by the fixing roller and the rotating member; In a fixing device of an image forming apparatus that forms an image by fixing toner on a recording medium,
The fixing roller has a heat source in the center, a cored bar, and an elastic member, and the elastic member is made of silicone rubber .
Wherein the inside silicone rubber, a first heat conductor consisting of acicular carbon fiber, a bubble, a second heat conductor covering the periphery of the bubbles are contained,
When the elastic member is compressed, the contact state between the first heat good conductors, the contact state between the second heat good conductors, and the contact state between the first heat good conductor and the second heat good conductor are: A fixing device for an image forming apparatus , wherein the elastic member is formed and has a high thermal conductivity . The fixing device for an image forming apparatus according to claim 1, wherein the second good heat conductor is an inorganic powder of metal powder, carbide, oxide, carbonate compound, or talc. apparatus. 2. The fixing device for an image forming apparatus according to claim 1 , wherein the second good heat conductor is a metal film . 4. A fixing device of an image forming apparatus according to claim 1, wherein the core metal of the fixing roller incorporating the heat source has a thickness of 0.4 to 0.5 mm and has a plurality of annular shapes on its inner surface. A fixing device for an image forming apparatus, wherein the ribs are integrally formed . 5. The fixing device of the image forming apparatus according to claim 1, further comprising a fixing roller having a layer made of a fluorine-based polymer on an outermost surface . 6. The fixing device of the image forming apparatus according to claim 1 , further comprising a fixing roller having a surface roughness Rz (10-point average roughness: JIS B0601-1994) of 5 μm or less . Fixing device. 7. The fixing device for an image forming apparatus according to claim 1, wherein the fixing is performed using a wax-containing toner . 8. The fixing device for an image forming apparatus according to claim 1, further comprising means for applying a release agent to the fixing member . 9. A fixing device of an image forming apparatus according to claim 1 , wherein a value obtained by dividing the pressure F (N) applied to the member to be fixed by the area S (cm ² ) of the contact portion in pressure contact with the fixing member is 4.9. A fixing device of an image forming apparatus, wherein the fixing device is 39.2 N / cm ² . An image forming apparatus comprising an image forming unit, wherein the image forming unit forms a toner image on a sheet, and the fixing device according to claim 1 fixes the toner image on a recording medium .

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