JP2002006662A - Heating member for fixing and pressurizing member for fixing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problems of the easy tendency to the occurrence of temperature unevenness in an axial direction and the impairment of the uniformity in fixability and image quality when an image carrying member (transfer paper) of a small size is continuously passed through a belt type fixing device as a fixing belt is thin and is therefore little in heat transfer to an axial direction (transverse and longitudinal directions). SOLUTION: The fixing belt 34 has a fixing belt base material layer 61, a fixing belt anisotropic graphite layer 62 and a fixing belt release layer 63. The thermal conductivity of the fixing belt anisotropic graphite layer 62 is 2 to 10 W/m.K in a thickness direction and 200 to 1,000 W/m.K in a surface direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technology of a low-heat-capacity low-wearing heating member used in an image forming apparatus such as an electrophotographic copying machine or a printer, for example, a fixing belt used in a belt-type fixing device. About the field.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile, a latent image is formed in accordance with an image by irradiating a charged photoconductive material with light corresponding to the image. . The latent image is developed by electrostatically adsorbing toner on the latent image, and the developed toner image is electrostatically transferred and adsorbed on an image carrier such as recording paper.

[0003] When the image carrier to which the toner image is electrostatically adsorbed passes through the fixing device, heat and pressure are usually applied to fix the toner image to the image carrier. The image forming apparatus of the electrophotographic type is roughly as described above. However, since this technique is well known, no further description will be given.

Conventionally, a heat roller system using a halogen heater as a heating source has been predominant in the fixing device. This type of fixing device is composed of a heat fixing roller and a pressure roller pressed against the fixing roller, during which the toner is passed through the image carrier on which the toner is electrostatically attracted,
It is to fix it.

The heat fixing roller radiates and heats the base material from the inside and transfers the heat to the surface layer. Since the heat source is provided inside the heat fixing roller, the heat transfer loss to the heat fixing roller is small, and Since heat is transferred from the fixing roller to the toner that is not heated by contact, the heating efficiency is high. In addition, since the structure is relatively simple, the cost can be kept low and there are few failures.

In this heat roller type fixing device, a thick elastic layer such as a multilayer rubber having a total thickness of several millimeters is provided on the surface of the heat fixing roller. This is because rollers having as large a diameter as possible are pressed against each other at a high pressure to form a nip width (a width for holding the image carrier).
The cylindrical base material (core metal) is made of thick metal to prevent the deflection of the roller.

As described above, since the diameters of the heat fixing roller and the pressure roller are large, the fixing device is large, and the heat capacity of the core metal is inevitably large. It wasn't good.

In order to cope with such a problem, a heating member having a low heat capacity such as that found in a belt-type fixing device has been developed and put into practical use. This belt-type fixing device wraps a thin metal belt between two rollers, opposes and presses a pressure roller with one of the rollers sandwiching the belt,
The fixing nip is formed between the belt and the pressure roller. The heating of the belt is performed by heating the inner surface of the heating roller by radiant heat of a halogen heater or the like provided on a heating roller different from the roller of the nip forming portion, and transferring heat from the heating roller to contact the belt base material. It is like that.

This fixing device has the following features.
In other words, the nip width can be secured without depending on the roller diameter due to the flexibility of the belt, so that a roller having a small diameter can be used. There is a degree of freedom in the configuration of the nip, and there is no need to provide a thick elastic layer on the belt surface because the deformation of the elastic layer (rubber) of the roller is not used to separate the image carrier as in the heat roller method. Since the belt can be made thin, that is, low in heat capacity, the temperature rise of the belt base material is fast, heat transfer from there to the surface is fast, and the heat followability is good as a whole.

Therefore, the entire fixing device can be reduced in size and heat capacity, and the warm-up time can be reduced and the temperature can be reduced during the standby time, so that the energy efficiency is extremely excellent.

The heating member having a low heat capacity, which is found in a belt-type fixing device, has the above-described excellent surface, but also has the following problem.

When the heating member comes into contact with the image carrier (transfer paper), heat moves from the surface of the contact portion with the image carrier toward the image carrier (heat is locally taken away). At this time, heat in the vicinity of the contact portion surrounding the contact portion moves so as to compensate for the transferred heat, but since the heating member is a material having a small heat capacity, the contact member, which is a source of direct heat to the contact portion, is used. The amount of heat near the part is also small. for that reason,
The amount of heat in the vicinity of the contact portion is depleted, and the temperature here decreases, and a sufficient amount of heat is not supplied from the vicinity of the contact portion to the surface of the contact portion.

This means that when a small-sized image carrier (transfer paper) is continuously passed through, a temperature difference, that is, a temperature unevenness occurs between a portion that is in contact with the image carrier and a portion that is not in contact with the image carrier. This causes a problem that the uniformity is deteriorated.

In a belt-type fixing device, since the belt is thin, heat transfer (heat conduction) in the axial direction (width and length directions) is performed.
Therefore, when a small-sized image carrier (transfer paper) is continuously passed through the belt-type fixing device, temperature unevenness in the length and width directions is likely to occur, and the fixability and the uniformity of image quality are impaired. In addition, there is a problem that the paper passage property is easily affected by the difference in thermal expansion of the pressure roller.

Further, since the belt has a low heat capacity, it is easily affected by the temperature of peripheral members such as a pressure roller. There is also a problem unique to a heating member having a low heat capacity.

As described above, in the fixing device, as the heat capacity is smaller, the temperature rises faster (the image forming operation is quickly started). However, when the heat capacity is made smaller, temperature unevenness is likely to occur, and the image quality deteriorates. There is a conflicting problem.

[0017]

SUMMARY OF THE INVENTION The present invention solves a new problem in a fixing device using a heating member having a low heat capacity such as a belt as described above, which is not a problem in a heat roller type fixing device. That is the task.

Further, in a fixing device using a toner heating roller which is heated from the outside, the above-mentioned temperature distribution problem and rising problem occur as in the case of the belt-type fixing device, though the degree thereof varies as described later. Therefore, it is an object to solve this problem.

Still another object of the present invention is to reduce the influence of the difference in thermal expansion of the pressure roller on the paper passing property.

[0020]

According to the first aspect of the present invention, the fixing heating member is heated by contacting a high-temperature portion and has a thermal conductivity of 0.1 when the surface layer contacts the image surface.
A surface layer of W / m · K to 1.0 W / m · K, a thermal conductivity in the thickness direction of 2 W / m · K to 10 W / m · K, and a thermal conductivity in the plane direction of 200 W / m · K And an anisotropic heat conductive layer having an anisotropic heat conductivity of １０００1000 W / m · K. The fixing heating member has a low heat capacity, and may be a fixing belt or an externally heated toner heating roller, as supported by Example 1 or Example 3 described below.

With this configuration, since the thermal conductivity in the surface direction of the heating member for fixing is larger than that in the thickness direction, even if a temperature difference is generated along the surface direction, heat is immediately transferred. Accordingly, even if the surface temperature is affected by the temperature of the peripheral members, the surface temperature is immediately uniformized, so that temperature unevenness in the surface direction is unlikely to occur, and the fixability and the uniformity of image quality are hardly impaired.

The heating member for fixing according to the second aspect of the present invention includes the first heating member.
In the fixing heating member of the second invention, the anisotropic heat conductive layer is made of graphite obtained by heat-treating an organic compound at a high temperature of 1800 ° C. or higher.

A heating member for fixing according to a third aspect of the present invention comprises
Alternatively, in the fixing heating member according to the second invention, the anisotropic heat conductive layer is further formed as a composite with a metal.

The heating member for fixing of the fourth invention is the third heating member.
In the heating member for fixing of the second invention, the metal is nickel.

The heating member for fixing according to a fifth aspect of the present invention includes the first heating member.
In the fixing heating member of the second invention, the anisotropic heat conductive layer is further formed in a composite with polyimide.

In a sixth aspect of the present invention, there is provided a fixing pressure member, wherein a surface layer of the fixing pressure member is brought into contact with and pressed by a fixing heating member which is in contact with an image surface to form a heating nip portion. The component layer of the pressure member has a thermal conductivity in the radial direction of 2 W / m ·
K to 10 W / m · K, thermal conductivity in plane direction is 200 W / m
-An anisotropic heat conductive layer having an anisotropic heat conductivity of K to 1000 W / mK.

With this configuration, the temperature distribution of the fixing pressure member is made uniform, and good paper passing performance without wrinkles or the like can be exhibited.

A fixing belt according to a seventh aspect of the present invention has a base layer made of metal or polyimide, and is supported by the base layer, and has a thermal conductivity of 2 W / m · K to 10 W / m · in the thickness direction.
K, 200W / m · K to 1000W / m · K in the plane direction
Is supported by the anisotropic heat conductive layer,
An elastic layer having a thermal conductivity of 0.1 W / m · K to 1.0 W / m · K.

According to this configuration, since the thermal conductivity in the surface direction of the fixing belt is larger than that in the thickness direction, even if there is a temperature difference along the surface direction, heat is immediately conducted, and Even if the surface temperature is affected by the temperature of the peripheral members, the surface temperature is immediately made uniform, so that temperature unevenness in the surface direction is less likely to occur, and the fixability and the uniformity of image quality are hardly impaired.

The fixing belt according to an eighth aspect is the fixing belt according to the seventh aspect, wherein the anisotropic heat conductive layer is further made of graphite.

The pressure roller of the ninth invention has a base layer made of a metal cylinder and is supported by the base layer, and has a thermal conductivity of 2 W / m · K to 10 W / m · in the radial direction. K, an anisotropic heat conductive layer having a surface direction of 200 W / m · K to 1000 W / m · K, and an elastic layer supported by the anisotropic heat conductive layer and having elasticity.

According to this configuration, since the difference in thermal expansion caused by the distribution of the temperature difference between the pressure rollers is reduced, it is possible to reduce the adverse effect on the paper passing property based on the difference in thermal expansion.

The pressure roller according to the tenth aspect of the present invention is the ninth aspect.
In the pressure roller of the second invention, the anisotropic heat conductive layer is further made of graphite.

[0034]

Embodiment 1 FIG. 1 is a sectional view showing an example of a fixing device 28 using a fixing belt and a pressure roller of the present invention.

The fixing device 28 includes a driving roller 31 provided rotatably in the direction of arrow a and a heating roller 33 having a halogen heater lamp 32 as a heat source.
A fixing belt 34 running across the driving roller 31 and the heating roller 33, and a pressing roller 35 pressing the driving roller 31 through the fixing belt 34.
And an oil application unit 36 that applies a release agent for preventing offset to the outer peripheral surface of the fixing belt 34. As the release agent, for example, silicone oil is used. The fixing belt 34 and the pressure roller 35 will be described later.

The drive roller 31 has a drive gear (not shown) fixed to one end thereof, and is driven to rotate in the direction of arrow a by a drive source such as a motor (not shown) connected to the drive gear. The driving roller 31 contacts the back surface of the fixing belt 34 and moves the fixing belt 34 in the direction of arrow b. In order to surely move the fixing belt 34, the outer peripheral surface of the driving roller 31 is coated with a material having a large coefficient of friction (for example, silicon rubber) so that no slip occurs with the fixing belt 34.

In order to secure a predetermined amount of nip width,
The material for coating the outer peripheral surface of the driving roller 31 is more preferably a material having a relatively low hardness (for example, a silicon sponge).

The heating roller 33 is formed of a hollow metal roller, and the halogen heater lamp 32 is disposed on the center axis. As a heat source, a resistance heating element, an electromagnetic induction heating device, or the like may be used. Further, from the viewpoint of efficiently supplying heat to the fixing belt 34, the heating roller 3
3 is preferably formed from a material having high thermal conductivity such as aluminum or copper.

The pressure roller 35 is a roller in which the outer periphery of a metal pipe is coated with silicon rubber or Teflon (registered trademark), and the spring force of a spring 37 is urged to drive the drive roller 31 via the fixing belt 34. Is pressed against. When the fixing belt 34 moves in the direction of arrow b with the rotation of the driving roller 31, the pressing roller 35
Is driven to rotate in the direction of arrow c due to friction with the fixing belt 34. Drive roller 31 and pressure roller 3
The relationship between the five surface hardnesses is set as “surface hardness of pressure roller 35 ≧ surface hardness of drive roller 31”.

The reason for such a relationship is as follows. That is, in order to smoothly discharge the toner-fixed recording paper S from the nip 38 between the pressure roller 35 and the fixing belt 34, the recording paper S should be sent in a direction away from the peripheral surface of the driving roller 31 or flat. This is because, for this purpose, the pressure roller 35 may be pressed against the drive roller 31 via the fixing belt 34 in such a manner that the pressure roller 35 slightly bites into the drive roller 31.

A guide plate 39 is provided below the fixing belt 34 so as to guide the recording sheet S holding the unfixed toner to the nip 38 without touching the fixing belt 34. A discharge guide 40 is provided downstream of the nip 38.

The oil application unit 36 is disposed above the fixing belt 34 and has an oil application roller 50 that holds oil applied to the fixing belt 34 therein.
And the oil supplied from the oil application roller 50 in contact with the surface of the oil application roller 50 and the fixing belt 3
4, an oil transfer roller 51 applied to the outer peripheral surface, a cleaning roller 52 abutting on the surface of the oil transfer roller 51 and removing paper dust and toner attached to the oil transfer roller 51, and these rollers 50, 51, 52
Is rotatably supported by a holder (not shown).

The oil transfer roller 51 is used for the fixing belt 3
4 presses against the fixing belt 34 in a region where the fixing roller 4 moves from the driving roller 31 toward the heating roller 33, and applies an appropriate tension to the fixing belt 34. Thereby, the traveling of the fixing belt 34 is stabilized, and the oil application from the oil transfer roller 51 to the fixing belt 34 is also stabilized.

The oil application roller 50 has a multilayer structure including an oil holding layer 56 provided on the surface of the cored bar 55 for holding oil, and a surface layer 57 provided on the surface side of the oil holding layer 56. I have.

The oil transfer roller 51 is formed by coating a core metal with silicon rubber having good affinity for silicon oil, and the cleaning roller 52 is formed by coating a core metal with felt or the like. The surface of the oil transfer roller 51 is made rougher than the surface of the fixing belt 34 to adhere dirt from the fixing belt 34, while the surface of the cleaning roller 52 is made to adhere dirt from the oil transfer roller 51. Therefore, the releasability is set lower than the surface of the oil transfer roller 51.

The oil application unit 36 is detachably attached to the frame of the fixing device 28. When the oil held inside the oil application roller 50 is used up, the used oil application unit 36 is removed from the frame. Attach a new oil application unit 36 to the frame.

Note that a cleaning pad may be brought into contact with the surface of the oil transfer roller 51 instead of the cleaning roller 52. Further, the oil application roller 50 may be directly pressed against the fixing belt 34.

The operation of the fixing device 28 will be outlined. When the motor is driven, the drive roller 31 rotates in the direction of arrow a,
The fixing belt 34 runs in the direction of arrow b. Fixing belt 3
With the travel of 4, the heating roller 33 is driven to rotate in the direction of arrow d, and the pressure roller 35 is driven to rotate in the direction of arrow c.

The traveling fixing belt 34 is heated to a predetermined temperature by heat from the halogen heater lamp 32 in a contact area with the heating roller 33 after oil is applied at a position on the upstream side of the heating roller 33. The vehicle further travels above 39 and proceeds to a nip 38 between the pressure roller 35.

On the other hand, the recording paper S holding the unfixed toner 49 on the side contacting the fixing belt 34 is conveyed toward the nip 38 while being guided by the guide plate 39 along the direction of arrow e. At this time, the recording paper S and the unfixed toner 4
9 is heated (preheated) by radiant heat of the fixing belt 34 and a heat transfer from the guide plate 39 facing each other with a predetermined gap therebetween. By this preheating, the unfixed toner 49 on the recording paper S is
Is moderately softened in advance.

The recording paper S is further conveyed to the nip 38
, The recording paper S comes into contact with the fixing belt 3
4 is sufficiently heated by the heat of
While the pressing force between the and the drive roller 31 is applied,
It is conveyed while being pinched by the nip portion 38.

Thus, the unfixed toner 4 on the recording paper S
9 is sufficiently heated and melted, and is further pressurized and fixed on the recording paper S. Transfer of toner to the fixing belt 34, that is, offset, is suppressed by oil applied to the surface of the fixing belt 34.

The recording paper S that has passed through the nip 38 is naturally separated from the fixing belt 34 and is conveyed to the paper discharge tray 29. Further, heat is replenished from the halogen heater lamp 32 to the fixing belt 34 from which heat has been removed by contact with the recording paper S under predetermined temperature control.

FIG. 2 is a sectional view of the fixing belt 34. The fixing belt 34 is a thin and preferably seamless endless belt, which includes a fixing belt base layer 61, a fixing belt anisotropic graphite layer 62, and a fixing belt release layer 6.
3 has a multilayer structure.

The fixing belt base material layer 61 is
5 and the fixing belt anisotropic graphite layer 62
And a metal having a thickness of about 50 μm, such as carbon steel, stainless steel, nickel, or a heat-resistant resin such as a polyimide resin.

The fixing belt anisotropic graphite layer 62 is supported by the belt base material layer 61 and is made of anisotropic graphite having a thickness of about 100 μm. This anisotropic graphite has been commercialized under the trade name PGS graphite. One or more polymer films of polyoxadiazole, aromatic polyamide, and polyparaphenylenevinylene having a thickness of 400 μm or less are treated at 1800 ° C. As described above, it is preferably graphite obtained by heat treatment at a temperature of 2400 ° C. or higher.

This layer has anisotropy in thermal conductivity, has a thermal conductivity in the thickness direction of 2 W / m · K to 10 W / m · K,
Thermal conductivity in the plane direction (direction along the plane) is 200 W / m
It is an anisotropic heat conductive layer having a temperature of K to 1000 W / m · K (unit: W: watt, K: kelvin).

The fixing belt release layer 63 is supported by the fixing belt anisotropic graphite layer 62 and has a good affinity for silicon oil and a thermal conductivity of 0.1 W / m · K.
Silicon rubber or the like of up to 1.0 W / m · K
The elastic layer has a thickness of about 200 μm. This fixing belt release layer 63, that is, the elastic layer
Has good releasability and heat resistance to the toner.

FIG. 3 is a fixing belt temperature transition graph showing the temperature of the fixing belt surface with respect to the number of sheets passed through the fixing device 28. In this graph, the solid line indicates the temperature of the portion where the image carrier (recording paper S) is in contact (paper passing portion), and the dotted line indicates the temperature of the portion where this contact was not made (non-paper passing portion).

The comparative example is obtained by using a fixing belt in which silicon rubber having the same thickness is conventionally used instead of the fixing belt anisotropic graphite layer 62. It is the same place value.

As is clear from this graph, the temperature difference between the sheet passing portion and the non-sheet passing portion is larger in the comparative example, while the temperature difference in the present invention is smaller. I have. Also, this temperature difference tends to open more and more as the number of sheets passed increases, but it can be seen that the degree is low in the present invention.

This is because in the fixing belt anisotropic graphite layer 62 of the present invention, the heat conductivity in the thickness direction is smaller than the heat conductivity in the plane direction, so that heat is hardly transmitted in the thickness direction. On the other hand, since heat is easily transmitted in the plane direction, the temperature distribution in the plane direction is made uniform.

This indicates that the present invention can prevent the fixing property from becoming unstable because the temperature distribution of the transfer belt becomes uniform even when the power is turned on and during continuous copying.

In the fixing device using the fixing belt of this embodiment, the temperature distribution of the fixing belt is uniform even when the small-size paper is continuously passed, and a good image can be obtained even when the large-size paper immediately passes. As a result, thermal deterioration of the fixing belt could be suppressed, and cracking did not occur.

Embodiment 2 In Embodiment 1, the fixing belt 34
Fixing belt anisotropic graphite layer 62
In this example, the temperature distribution in the surface direction of the fixing belt 34 is made uniform.

The pressure roller 35 receives heat from the fixing belt 34 and is heated. A temperature difference occurs on the surface when the power is turned on or when paper is continuously fed. When the temperature difference is large, that is, when the temperature is not uniform, wrinkles may occur on the transfer paper due to the difference in thermal expansion.

In the second embodiment, the occurrence of wrinkles is prevented by making the temperature distribution on the surface of the pressure roller 35 uniform.

FIG. 4 is a sectional view showing a section of the pressure roller 35 of the second embodiment. Fixing device 28 in which this is used
The other configuration is the same as that of the first embodiment, and will not be described again.

However, in the second embodiment, the fixing belt 3
No. 4 may have a configuration having the fixing belt anisotropic graphite layer 62 as in the first embodiment, or may be a layer of silicon rubber as conventionally used.

The pressure roller 35 has a pressure roller base material layer 71, a pressure roller anisotropic heat conductive layer 72, and a pressure roller elastic layer 73.

The pressure roller base material layer 71 is a metal cylinder that supports the upper pressure roller anisotropic heat conductive layer 72.

The pressure roller anisotropic heat conductive layer 72 is, for example, a layer of trade name PGS graphite as described above.
This layer has anisotropy with high thermal conductivity in the plane direction (circumferential direction and axial direction) and low thermal conductivity in the radial direction.

A pressure roller elastic layer 73 made of silicon rubber is supported outside the pressure roller anisotropic heat conductive layer 72.

FIG. 5 is a pressure roller temperature transition graph showing the temperature of the surface of the pressure roller 35 with respect to the number of sheets passed through the fixing device 28. In this graph, the solid line indicates the temperature of the portion where the image carrier (recording paper S) is in contact (paper passing portion), and the dotted line indicates the temperature of the portion where this contact was not made (non-paper passing portion).

The comparative example here is made of a metal in which the pressure roller anisotropic heat conductive layer 72 is eliminated and the thickness of the pressure roller base layer 71 is increased by this thickness. It is an example of a pressure roller having a layer.

In the graph of FIG. 5, the number of passed sheets is "
The left side of the 0 "sheet shows the period of the preliminary rotation for increasing the heating time. When the preliminary rotation is started from 30 ° C., the surface temperature of the pressure roller 35 in this embodiment (the present invention) rises. Further, it can be seen that the temperature difference between the sheet passing portion and the non-sheet passing portion is larger than that of the comparative example. It can be seen that a small value is obtained.

This is because, in the pressure roller anisotropic heat conductive layer 72 of the present invention, the heat conductivity in the radial direction is smaller than the heat conductivity in the plane direction, so that heat is hardly transmitted in the thickness direction. On the other hand, since heat is easily transmitted in the plane direction, heat transmitted from the outside hardly flows to the layer below the pressure roller anisotropic heat conductive layer 72, and the surface temperature rises quickly. This is because the temperature distribution in the plane direction is made uniform.

This means that the temperature of the pressure roller 35 rises quickly when the power is turned on, and the temperature distribution on the surface of the pressure roller 35 becomes uniform even during continuous copying. This indicates that the fixing property can be prevented from becoming unstable, such as generation of wrinkles based on the wrinkles.

Further, since heat is hardly conducted to the radial direction, that is, to the pressure roller base material layer 71, dissipation of heat is prevented, which means that temperature is stabilized and energy loss is small.

In this embodiment, as described above, the temperature rise of the pressure roller at the time of the previous rotation prior to the fixing operation at the time of paper feeding is fast rising, the fixing performance after the start of paper feeding is stabilized, and the small-size paper is fixed. In the continuous paper passing, the temperature distribution of the pressure roller was uniform, and no paper wrinkles or the like were generated even when the large-sized paper was passed immediately, and good paper passing performance was exhibited.

Embodiment 3 In the fixing device of Embodiment 1, the fixing belt 34 is connected to an external heating element, that is, a heating roller 33.
Is heated by. FIG. 6 is a cross-sectional view of a fixing device of a type in which fixing is performed by receiving such external heat, showing a different type of fixing device according to a third embodiment. Here, common members are denoted by the same reference numerals as those in the first embodiment, and have substantially the same functions, so that duplicate description will be omitted.

That is, in the third embodiment, the fixing is performed by the heating roller 33 heating the toner heating roller 81 and the heated toner heating roller 81 heating the recording sheet S on which the toner is adsorbed. As is clear from the above description, since the toner heating roller 81 is of the type that is heated from the outside, the surface temperature of the toner heating roller 81 varies due to the influence of paper passing in relation to its heat capacity.

FIG. 7 is a sectional view of the toner heating roller 81, which has a multilayer structure similar to the pressure roller 35 shown in FIG. The toner heating roller base layer 84, the toner heating roller anisotropic heat conduction layer 82, and the toner heating roller elastic layer 83 are arranged in the thickness direction from the innermost layer.

The heat of the heating roller 33 is transmitted to the toner heating roller 81 once. At this time, heat is transmitted from the toner heating roller elastic layer 83 to the toner heating roller anisotropic conductive layer 82. Since the thermal conductivity of the toner heating roller anisotropic conductive layer 82 is larger in the plane direction (the paper plane direction and the circumferential direction in FIG. 7) than in the radius (thickness) direction, the heat is applied to the recording sheet S. Is reduced by the heat conducted from the plane direction, so that the temperature distribution in the plane direction is flattened.

Further, since the heat conduction to the toner heating roller base material layer 84 is small and the heat lost to the toner heating roller base material layer 84 during startup of the image forming apparatus is small, the toner heating roller 81 The temperature of the surface rises quickly, and the startup time can be reduced.

[0086]

According to the present invention, when a small-sized image carrier (transfer paper) is continuously passed through an image forming apparatus, the heating member having a low heat capacity contacts the image carrier.
The phenomenon in which heat is taken from the surface of the contact portion with the image carrier and the temperature is reduced is suppressed by the anisotropic heat conductive layer, and the occurrence of temperature unevenness in the fixing heating member is prevented. . Thereby, there is an effect that the temperature stability when a heating member having a low heat capacity is used is improved, and a decrease in image quality of the image forming apparatus is prevented.

In a fixing device using a fixing belt,
Since this belt is thin, there is little heat transfer in the axial direction (width, length direction). Therefore, when a small-sized image carrier (transfer paper) is continuously passed through the belt-type fixing device, the length and width are reduced. The problem of the prior art that the temperature unevenness in the direction tends to occur and the fixability and the uniformity of the image quality tend to be impaired is that the thermal conductivity in the present invention is 2 W / m · K to 10 in the thickness direction.
W / m · K, 200W / m · K to 1000W in the plane direction
The problem is solved by using an anisotropic heat-conducting layer that is / m · K.

Further, in the present invention, since the belt has a low heat capacity, it is easily affected by the temperature of peripheral members such as a pressure roller. This has the effect of being less unstable.

The present invention has an effect that in the belt-type fixing device as described above, a new problem which is not a problem in the heat roller-type fixing device is solved.

Further, the present invention has an effect that the influence on the paper passing property due to the difference in thermal expansion of the pressure roller is reduced by providing the anisotropic heat conductive layer.

[Brief description of the drawings]

FIG. 1 shows a fixing device using a fixing belt of the present invention.
FIG. 3 is a cross-sectional view showing one example.

FIG. 2 is a cross-sectional view of the fixing belt 34.

FIG. 3 is a fixing belt temperature transition graph showing the temperature of the fixing belt surface with respect to the number of sheets passed through the fixing device.

FIG. 4 is a cross-sectional view illustrating a cross section of a pressure roller 35 according to a second embodiment.

FIG. 5 is a pressure roller temperature transition graph showing the temperature of the surface of the pressure roller 35 with respect to the number of sheets passed through the fixing device 28.

FIG. 6 is a cross-sectional view of a fixing device that fixes by receiving heat from the outside, which is a type different from that of the first embodiment.

FIG. 7 is a sectional view of a toner heating roller.

[Explanation of symbols]

 28 Fixing Device 29 Discharge Tray 31 Drive Roller 32 Halogen Heater Lamp 33 Heating Roller 34 Fixing Belt 35 Pressure Roller 36 Oil Application Unit 37 Spring 38 Nip 39 Guide Plate 40 Discharge Guide 49 Unfixed Toner 50 Oil Application Roller 51 Oil Transfer Roller 52 Cleaning Roller 55 Core Metal 56 Oil Retaining Layer 61 Fixing Belt Base Layer 62 Fixing Belt Anisotropic Graphite Layer 63 Fixing Belt Release Layer 71 Pressure Roller Base Layer 72 Pressure Roller Anisotropic Heat Conductive Layer 73 Pressure roller elastic layer 81 Toner heating roller 82 Toner heating roller anisotropic heat conductive layer 83 Toner heating roller elastic layer 84 Toner heating roller base layer

Claims (10)

[Claims] 1. A fixing heating member which is heated in contact with a high-temperature portion and whose surface layer is in contact with an image surface has a thermal conductivity of 0.1.
A surface layer of 1 W / m · K to 1.0 W / m · K, and a thermal conductivity in a thickness direction of 2 W / m · K to 10 W / m · K;
Thermal conductivity in the plane direction is 200 W / m · K to 1000 W / m
A fixing heating member having, in this order, an anisotropic heat conductive layer having an anisotropic heat conductivity of K; 2. The fixing member according to claim 1, wherein the anisotropic heat conductive layer is made of graphite obtained by heat-treating an organic compound at a high temperature of 1800 ° C. or higher. Heating member. 3. The fixing heating member according to claim 1, wherein the anisotropic heat conductive layer is further formed in a composite with a metal. 4. The fixing heating member according to claim 3, wherein the metal is nickel. 5. The fixing heating member according to claim 1, wherein the anisotropic heat conductive layer is further formed as a composite with polyimide. 6. A fixing pressure member for forming a heating nip portion, wherein a surface layer is contact-pressed to a fixing heating member in contact with an image surface. An anisotropic heat conductive layer having an anisotropic heat conductivity of a conductivity of 2 W / m · K to 10 W / m · K and a thermal conductivity in a plane direction of 200 W / m · K to 1000 W / m · K is provided. And a pressure member for fixing. 7. A base layer made of metal or polyimide, supported by the base layer, and having a thermal conductivity of 2 in the thickness direction.
W / m · K to 10 W / m · K, 200 W / m in plane direction
An anisotropic heat conductive layer having a thermal conductivity of from 0.1 to 1000 W / m · K, supported by the anisotropic heat conductive layer and having a thermal conductivity of 0.1
A fixing belt for use in a fixing device of an image forming apparatus, comprising: an elastic layer having a W / m · K to 1.0 W / m · K. 8. The fixing belt according to claim 7, wherein the anisotropic heat conductive layer is further made of graphite. 9. A base layer made of a metal cylinder, supported by the base layer, and having a thermal conductivity of 2 in the radial direction.
W / m · K to 10 W / m · K, 200 W / m in plane direction
An anisotropic heat conductive layer having K to 1000 W / mK, an elastic layer supported by the anisotropic heat conductive layer and having elasticity;
A pressure roller for use in a fixing device of an image forming apparatus, comprising: 10. The pressure roller according to claim 9, wherein the anisotropic heat conductive layer is further made of graphite. .