JP2005173289A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress consumption power and shorten a warmup period. <P>SOLUTION: A fixing device 1 includes: an endless fixing belt 5 which is stretched between a fixing roller 2 and a support roller 3 and rotated in the direction of the arrow A; a heat roller 6, as a heat member, which heats the fixing belt 5; a pressure roller 7, as a pressure member, which is in firm contact with the fixing roller 2 via the fixing belt 5. The fixing device 1 fixes an unfixed toner image Tn on a recording material P conveyed into a nip N where the fixing belt 5 and the pressure roller 7 are in contact with each other. In the fixing device 1, the heat roller 6 is disposed upstream of the nip N in the running direction of the fixing belt 5 so as to be in contact with the external circumferential face of the fixing belt 5. Thus, since the heat roller 6 directly heats the external face of the fixing belt 5 upstream of the nip N in the running direction of the belt, the external face of the fixing belt 5 is efficiently heated. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fixing device for fixing an unfixed toner image on a recording material fed into a nip portion where a fixing belt heated by a heating member and a pressure member are in contact with each other.

In an image forming apparatus such as an electrophotographic copying machine or a laser beam printer, a toner image is formed on an image carrier such as a photosensitive drum, the toner image is transferred to a recording material such as paper, and the recording is performed. The toner image on the material is fixed by a fixing device.
As such a fixing device, a structure using a heat roller system is often used because of its simple structure and easy miniaturization. In the heat roller type fixing device, for example, a heating roller as a heating member and a pressure roller are arranged to face each other, and a heating lamp as a heating source is provided inside the heating roller, thereby reducing the overall size. It can be incorporated into a small image forming apparatus.

However, in the case of a fixing device using such a heating roller, there is a problem in that a sufficient amount of heat is required when forming a color image, so that sufficient heating cannot be performed.
In order to solve such a problem, there is a fixing device using a fixing belt as disclosed in Patent Document 1, for example. In this fixing device, an endless fixing belt is stretched between a heating roller and a fixing roller with a built-in heater, and is integrated into a cover to form an integrated unit, which is provided with a pressure roller. Removable with respect to.

Then, the inner surface of the fixing belt is heated by a heater built in the heating roller, and the recording material carrying the unfixed toner image is passed between the outer surface of the fixing belt and the pressure roller, and is fixed by the pressure roller. The toner image is fixed by pressing the belt.
In this fixing device, since a fixing belt having a relatively short service life is integrated in a unit shape, the fixing belt can be easily replaced even when the fixing belt has reached the end of its service life.

Further, as a fixing device using a fixing belt, there is one disclosed in Patent Document 2. In this fixing device, an endless fixing belt is stretched around three rollers including a driving roller, a heater is disposed inside the fixing belt, and the fixing belt is pressed against the driving roller by a pressure roller. Yes. The fixing belt is heated from the inner surface of the belt by a heater provided inside the fixing belt.
JP 2000-66541 A JP-A-8-292669

However, since the fixing device described in Patent Document 1 heats the fixing belt by a heater built in the heating roller, heat from the heater is transferred from the heating roller to the inner surface of the fixing belt, and the heat is transferred to the fixing belt. Therefore, a long time is required until the outer surface of the fixing belt used for fixing the toner image is heated to a desired temperature required for fixing. There was a problem of spending a lot of time warming up.
In the fixing device disclosed in Patent Document 1, since the heat of the fixing belt may escape to the cover through the rotating shaft of the heating roller, the surface of the fixing belt is heated to a desired temperature necessary for fixing. In order to achieve this, a great amount of heat energy is required, which causes a problem that power consumption increases.

Further, the fixing device of Patent Document 2 directly heats the belt by a heater provided inside the fixing belt. Since heat from the heater is transferred from the inside to the outside of the fixing belt, for example, the inner surface of the fixing belt. Because the heat of the belt escapes through the rotating shafts of the three rollers that come into contact with the belt, it takes a lot of time and heat energy to bring the temperature of the outer surface of the fixing belt to the desired temperature required for fixing. There was a problem.
The present invention has been made in view of the above problems, and an object of the present invention is to reduce power consumption and shorten the warm-up time.

  In order to achieve the above object, the present invention provides an endless fixing belt stretched between a fixing roller and a support roller, a heating member for heating the fixing belt, and a pressure contacted to the fixing roller via the fixing belt. In a fixing device for fixing an unfixed toner image on a recording material fed to a nip where the fixing belt and the pressure member are in contact with each other, the heating member is connected to the nip portion on the outer peripheral surface of the fixing belt. In contrast, the fixing belt is disposed in contact with the upstream side in the belt running direction.

The fixing roller is a roller having a rubber layer formed on the outer side of the core metal, the fixing belt has a structure having two layers of a release layer and an elastic layer, the thermal conductivity of the rubber layer is λ1, and the heat of the release layer When the conductivity is λ2, it is preferable to satisfy the relationship of λ1 <λ2.
Alternatively, when the thermal conductivity of the elastic layer of the fixing belt is λ3, the relationship of λ1 <λ3 may be satisfied.
Further, the fixing roller may be a roller in which a rubber layer is formed on the outer side of the metal core, and the thermal conductivity of the rubber layer may be 0.15 W / m ° C. or less.
The heating member may also serve as a tension roller that applies tension to the fixing belt.

  According to the present invention, since the heating roller directly heats the outer peripheral surface of the fixing belt on the upstream side in the belt running direction with respect to the nip portion where the fixing belt and the pressure member are in contact with each other, the toner image is fused and fixed in the nip portion. It is possible to efficiently supply the heat necessary for the operation. Therefore, since high energy efficiency can be obtained, the warm-up time for warming the fixing belt until the temperature required for fixing can be shortened.

The best mode for carrying out the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing an embodiment of a fixing device according to the present invention, FIG. 2 is a side view showing a fixing roller provided in the fixing device, and FIG. 3 is provided in the fixing device of FIG. 2 is a cross-sectional view of a fixing belt. FIG.

A fixing device 1 shown in FIG. 1 includes an endless fixing belt 5 that is stretched between a fixing roller 2 and a support roller 3 and rotates in a direction indicated by an arrow A, and a heating member that heats the fixing belt 5. A heating roller 6 and a pressure roller 7 that is a pressure member that is in pressure contact with the fixing roller 2 via the fixing belt 5 are provided, and the heating roller 6 is fed into a nip portion N where the fixing belt 5 and the pressure roller 7 are in contact with each other. The unfixed toner image Tn on the recording material P is fixed.
The heating roller 6 is disposed in contact with the nip portion N of the outer peripheral surface of the fixing belt 5 on the upstream side in the belt running direction of the fixing belt 5.

The fixing device 1 is provided, for example, in an image forming unit of the image forming apparatus shown in FIG.
The image forming apparatus shows an example of a quadruple tandem full-color printer, and a photosensitive member that is an image carrier that forms toner images of four colors of yellow, magenta, cyan, and black in the image forming unit. The body drums 11Y, 11M, 11C, and 11Bk (hereinafter simply referred to as the photoconductor drums 11 if not specified) and images corresponding to the respective colors of yellow, magenta, cyan, and black on the surfaces of the photoconductor drums 11 Are provided with writing devices 13Y, 13M, 13C and 13Bk (hereinafter simply referred to as writing device 13 if not specified).

  The four photosensitive drums 11Y, 11M, 11C, and 11Bk have substantially the same structure, and only the color of the toner image formed thereon is different. Then, around each photosensitive drum 11, each charging device 12 for charging the drum surface to a predetermined potential, and the charged charging surface is exposed to light based on each color-separated image signal and statically exposed. Each writing device 13 that forms an electrostatic latent image, and each developing device 14 that supplies and develops toner of a color corresponding to each electrostatic latent image (the color of toner handled by four developing devices) Are different from each other).

  Furthermore, each transfer roller 15 (transfer device) for transferring the toner image on each photoconductive drum 11 onto the recording material P conveyed by the conveyance belt 20 in an overlaid state, and after the toner image is transferred Each cleaning device 16 that removes residual toner remaining on the drum surface and a static elimination lamp (not shown) that removes charge remaining on each photosensitive drum 11 are provided.

Below each photosensitive drum 11, a conveying belt 20 that conveys the recording material (paper) P in an electrostatically adsorbed state is provided in contact with each photosensitive drum 11.
A paper feed mechanism 30 including a pair of rollers for feeding the recording material P onto the transport belt 20 is provided on the right side of the transport belt 20 in FIG.
The fixing device 1 is disposed on the left side of the conveyance belt 20 in FIG. Then, the toner image is transferred, and the recording material P conveyed to the left in the figure by the conveying belt 20 is sent to the fixing device 1, and the toner image is heated and applied on the recording material P when passing through the recording material P. As a result, the toner image in which the respective colors are combined is melted and permeated and fixed on the recording material P.
Thereafter, the recording material P on which the toner image has been fixed is discharged to a discharge tray or the like by a discharge roller 9.

Next, the fixing device 1 will be described in detail.
As shown in FIG. 1, the fixing device 1 is configured such that the fixing roller 2 and the pressure roller 7 constituting the fixing device 1 are arranged in a positional relationship so as to sandwich the recording material conveyance path from above and below. One fixing roller 2 is a roller in which a rubber layer 32 is formed on the outside of a metal core 31 as shown in FIG. The rubber layer 32 is formed of heat-resistant sponge rubber.
The pressure roller 7 is urged toward the fixing roller 2 by a spring 23 as shown in FIG. 1, whereby the pressure roller 7 is in contact with the fixing belt 5 with a pressure suitable for fixing the toner image. . Note that the pressure roller may be the fixing roller 2 side.

A rotational driving force is transmitted to the pressure roller 7 via a gear (not shown), and the fixing roller 2 contacting the pressure roller 7 via the fixing belt 5 is an arrow of the pressure roller 7. By the rotation in the direction B, it is driven to rotate in the direction indicated by the arrow C. The driving roller may be the fixing roller 2. Further, the pressure roller 7 and the fixing roller 2 may be engaged with each other by a gear, and both of these rollers may be drive rollers.
Although the pressure roller 7 functions as a pressure member, the pressure member is not limited to the roller type, and may be a belt type pressure belt.

The support roller 3 is a roller in which a heat-resistant sponge rubber layer 34 is formed on the outer periphery of a metal core bar 33. In this embodiment, the fixing belt 5 stretched between the support roller 3 and the fixing roller 2 is provided with two layers of a release layer 24 and an elastic layer 25 as shown in FIG. .
That is, the fixing belt 5 has an elastic layer 25 formed on the outer side of a base film 26 made of a resin material made of polyimide or the like, and a release layer 24 is formed on the outer side of the elastic layer 25. Then, the fixing belt 5 rotates endlessly in the direction of arrow A in FIG. 1, so that the outer surface of the release layer 24 is in contact with the surface of the recording material P (upper surface in FIG. 1).

At that time, the outer peripheral surface of the pressure roller 7 comes into contact with the back surface of the recording material P being conveyed. That is, the recording material P is pressurized when passing through the nip portion N between the outer surface of the fixing belt 5 and the outer peripheral surface of the pressure roller 7.
As described above, the heating roller 6 is disposed in contact with the nip portion N on the upstream side of the outer peripheral surface of the fixing belt 5 in the belt traveling direction. The heating roller 6 is formed of a metal pipe having good heat conductivity, and a halogen lamp (heater) 27 is built in the pipe. The inner peripheral surface of the hollow pipe is coated with heat-resistant black paint in order to efficiently absorb the heat energy radiated from the halogen lamp 27.

The heating roller 6 is pressed leftward in FIG. 1 by the biasing force of the spring 28. Accordingly, tension is applied to the fixing belt 5 by the pressure applied to the outer peripheral surface of the fixing belt 5 by the heating roller 6. In other words, in this embodiment, the heating roller 6 also serves as a tension roller that applies tension to the fixing belt 5.
Thus, since the heating roller 6 is pressed against the outer peripheral surface of the fixing belt 5 by the biasing force of the spring 28, the nip portion Nb with a predetermined width is provided between the heating roller 6 and the outer peripheral surface of the fixing belt 5. Is formed. Therefore, the heat radiated from the halogen lamp 27 is transmitted from the inner surface of the pipe material to the surface of the heating roller 6, and the heat is transmitted to the outer peripheral surface of the fixing belt 5 through the nip Nb.

A first thermistor 41 is provided at a position upstream of the nip portion N between the fixing belt 5 and the pressure roller 7 in the belt traveling direction and downstream of the heating roller 6 in the belt traveling direction, and has elasticity. The detection end is in contact with the outer peripheral surface of the fixing belt 5. Thus, by bringing the first thermistor 41 into contact with the outer peripheral surface of the portion of the fixing belt 5 wound around the fixing roller 2, the contact state of the first thermistor 41 with respect to the fixing belt 5 can be stabilized. Therefore, the variation in the detected temperature on the outer peripheral surface of the fixing belt 5 can be reduced.
Further, the elastic detection end of the second thermistor 42 is also brought into contact with the outer peripheral surface of the heating roller 6 so that the temperature of the outer peripheral surface of the heating roller 6 can be detected by the second thermistor 42.

Next, the operation of the fixing device 1 will be described.
When the power of the printer is turned on, the warm-up operation of the fixing device 1 is started and the halogen lamp 27 in the heating roller 6 is turned on, whereby the heating of the heating roller 6 is started.
Further, the temperature of the outer peripheral surface of the heating roller 6 is monitored by the second thermistor 42, and when the temperature reaches a predetermined set temperature, the pressure roller 7 rotates in the direction indicated by the arrow B in FIG. Thus, the fixing belt 5 starts to rotate in the direction of arrow A.

Further, the temperature of the outer peripheral surface of the fixing belt 5 is monitored by the first thermistor 41, and when it reaches a predetermined set temperature, the warm-up operation is finished. At that time, the outer peripheral surface of the fixing belt 5 has been heated to a set temperature necessary for fixing the toner image.
In this way, the warm-up operation is performed and the outer peripheral surface of the fixing belt 5 is heated to the set temperature. The heat transfer during the warm-up is as follows.

First, the heat generated by the halogen lamp 27 is effectively absorbed by the black paint portion applied to the inner surface of the metal pipe of the heating roller 6, and the heat is transmitted to the outer peripheral surface of the heating roller 6. The heat transferred to the outer peripheral surface is transferred to the outer peripheral surface of the fixing belt 5 at the nip Nb with the fixing belt 5.
The unfixed toner image Tn adsorbed by the electrostatic force on the recording material P conveyed to the nip portion N by the heat transferred to the outer peripheral surface of the fixing belt 5 is recorded while applying pressure. It is fixed on the material P.

  Incidentally, the heat transmitted to the outer peripheral surface of the fixing belt 5 is also transmitted in the thickness direction toward the inner surface of the fixing belt 5. The heat transmitted to the inner surface of the fixing belt 5 is also transmitted to the outer peripheral surface of the fixing roller 2 (specifically, the outer peripheral surface of the rubber layer 32) and the outer peripheral surface of the support roller 3 that are in contact with the inner surface. To go. As a result, the heat escapes to the printer housing through the rotation shafts of the fixing roller 2 and the support roller 3.

The heat transmitted to the outer peripheral surface of the fixing belt 5 is also transmitted to the outer peripheral surface of the pressure roller 7 through the nip N by the rotation of the fixing belt 5, and the heat is rotated by the rotation of the pressure roller 7. Even through the shaft and the spring 23, it escapes to the housing of the printer.
As described above, the heat generated by the halogen lamp 27 is the heat directly related to the fixing of the toner image, which is only the heat transmitted from the outer peripheral surface of the fixing belt 5 to the surface of the recording material P. It becomes useless heat to escape without being used for fixing.

Accordingly, the temperature of the outer peripheral surface of the fixing belt 5 can be raised to a set temperature necessary for fixing the toner image, and the fixing belt 5 and the pressure roller 7 are brought into contact with each other with a constant pressing force. The formation of the nip portion N having a predetermined width is a necessary condition for fixing the unfixed toner image on the recording paper P. Otherwise, fixing failure, cold offset, or the like occurs.
The conditions necessary for fixing the toner image are slightly different depending on the physical properties of the toner used, the material of the recording material (paper) used, the thickness thereof, the conveyance speed of the recording material, and the like.

By the way, in order to shorten the time required for warming up to raise the temperature of the outer peripheral surface of the fixing belt 5 to a set temperature necessary for fixing the toner image, the power consumption required for the temperature rise is suppressed as low as possible. It is important to raise the temperature of the outer peripheral surface of 5 efficiently.
Therefore, in the fixing device 1 according to this embodiment, the heating roller 6 is disposed in contact with the nip portion N on the outer peripheral surface of the fixing belt 5 on the upstream side in the belt running direction of the fixing belt 5 as shown in FIG. Yes.

As a result, the outer peripheral surface of the fixing belt 5 used for fixing the unfixed toner image on the recording material P is directly heated by the heating roller 6 on the upstream side of the nip portion N used for fixing the fixing belt 5. Therefore, the heat that escapes without being used for fixing can be reduced as much as possible.
Therefore, as compared with the conventional fixing devices described in Patent Document 1 and Patent Document 2 described above, the heat generated by the heating roller 6 can be effectively used to fix the unfixed toner image. As a result, the temperature of the fixing belt 5 can be efficiently raised in a short time with a little heat energy, so that the power consumption required for raising the temperature of the fixing belt 5 can be kept low. As a result, the time required for warming up the fixing device 1 can be shortened.

Further, in the fixing device 1 according to this embodiment, the fixing roller 2 is a roller in which the rubber layer 32 is formed outside the metal core 31 as described above in order to reduce the heat escape path. And the heat conductivity of the rubber layer 32 is made low.
That is, as shown in FIG. 2, the fixing roller 2 has a rubber layer 32 made of silicone rubber having a low thermal conductivity of, for example, 12 mm on the outside of a metal core 31 having a diameter of, for example, 6 mm. .

  Further, as described with reference to FIG. 3, the fixing belt 5 is also coated with, for example, a 200 μm-thick silicone rubber on the outside of the base film 26 made of a resin material such as polyimide, and the heat-insulating elastic layer 25 is formed. Then, a release layer 24 made of, for example, a fluororesin is formed outside the elastic layer 25. The base film 26 is basically a part that requires heat resistance and mechanical strength, and may be formed of a metal such as nickel (Ni) or stainless steel (SUS).

The fixing device 1 satisfies the relationship of λ1 <λ2 when the thermal conductivity of the rubber layer 32 of the fixing roller 2 is λ1 and the thermal conductivity of the release layer 24 of the fixing belt 5 is λ2. ing. That is, the thermal conductivity of the rubber layer 32 is set lower than the thermal conductivity of the release layer 24.
By doing so, heat necessary to melt the unfixed toner image at the nip portion (fixing nip) N shown in FIG. 1 can be prevented from escaping to the fixing roller 2 side. Therefore, energy efficiency is increased. Thereby, the warm-up time of the fixing device 1 can be shortened.

  Further, when the thermal conductivity of the elastic layer 25 of the fixing belt 5 is λ3, the relationship of λ1 <λ3 may be satisfied. By doing so, the thermal conductivity λ1 of the rubber layer 32 of the fixing roller 2 becomes lower than the thermal conductivity λ3 of the elastic layer 25 of the fixing belt 5, so that the toner is melted at the nip portion N of the fixing belt 5. It is possible to prevent the generated heat from escaping to the fixing roller 2 side.

Furthermore, regardless of the thermal conductivity of the release layer 24 and the elastic layer 25 of the fixing belt 5, the thermal conductivity of the rubber layer 32 of the fixing roller 2 is 0.15 W / m ° C. or less, preferably 0.1 W / m ° C. The following is recommended. By doing so, it is possible to prevent heat necessary for melting an unfixed toner image at the fixing nip portion N from escaping to the fixing roller 2 side. As a result, heat can be efficiently supplied to the unfixed toner image to increase energy efficiency, so that the warm-up time of the fixing device 1 can be shortened.
The fixing belt 5 melts the toner by the release layer 24 if the release layer 24 on the outer layer side has a high thermal conductivity and the elastic layer 25 on the inner layer side has a lower thermal conductivity than the release layer 24. Therefore, it is possible to efficiently supply the heat necessary for this, and it is possible to prevent the heat supplied by the elastic layer 25 from escaping, so that energy efficiency can be improved. Therefore, the time required for warming up the fixing device 1 can be shortened.

In the fixing device 1 shown in FIG. 1, the heating roller 6 also serves as a tension roller for applying tension to the fixing belt 5 as described above, so that the fixing belt 5 can be used without providing a separate tension roller. It is possible to travel stably without causing uneven speed due to slip or the like.
Further, when a dedicated tension roller is provided, the heat of the fixing belt 5 escapes from the tension roller. However, according to this embodiment, the escape of the heat can be prevented and the energy efficiency can be improved. . Thereby, the time required for warming up the fixing device 1 can be shortened.

Next, a description will be given of experimental results obtained by actually measuring the warm-up time of the fixing device according to the present invention. The warm-up time in this experiment is the time for the fixing belt to rise from room temperature to 160 ° C.
In addition, the different conditions in each experiment are the heating side of the fixing belt on the outer peripheral surface and the inner peripheral surface, the thermal conductivity of the rubber layer of the fixing roller, the thermal conductivity of the release layer of the fixing belt, This is the thermal conductivity of an elastic layer made of silicone rubber.
Then, the foaming amount of the foamed silicone was increased to lower the thermal conductivity of the elastic layer, and silica was added to increase the thermal conductivity. For the release layer of the fixing belt, PFA is used when the thermal conductivity is 0.25 W / m ° C, PTFE is used when the thermal conductivity is 0.19 W / m ° C, and thermal conductivity is 0.30 W. The thing of / m degreeC used what added carbon to PFA.

[Experimental result 1]
The heat conductivity of the rubber layer of the fixing roller is heated to 0.10 W / m ° C.
Thermal conductivity of release layer of fixing belt 0.19 W / m ° C
Thermal conductivity of elastic layer of fixing belt 0.40 W / m ° C
Rise time (until 160 ° C rise) 70 seconds

[Experimental result 2]
The heat conductivity of the rubber layer of the fixing belt is heated on the outer peripheral surface of the fixing roller 0.15 W / m ° C.
Thermal conductivity of release layer of fixing belt 0.19 W / m ° C
Thermal conductivity of elastic layer of fixing belt 0.40 W / m ° C
Rise time (until 160 ° C rise) 75 seconds

[Experimental result 3]
The heat conductivity of the rubber layer of the fixing belt is heated on the outer peripheral surface of the fixing roller 0.28 W / m ° C.
Thermal conductivity of release layer of fixing belt 0.30 W / m ° C
Thermal conductivity of elastic layer of fixing belt 0.25 W / m ° C
Rise time (until 160 ° C rise) 73 seconds

[Experimental result 4]
The heat conductivity of the rubber layer of the fixing belt is heated on the outer peripheral surface of the fixing roller 0.28 W / m ° C.
Thermal conductivity of release layer of fixing belt 0.25 W / m ° C
Thermal conductivity of elastic layer of fixing belt 0.30 W / m ° C
Rise time (until 160 ° C rise) 76 seconds

[Experimental result 5]
The heat conductivity of the rubber layer of the outer peripheral surface heating fixing roller of the fixing belt is 0.30 W / m ° C.
Thermal conductivity of release layer of fixing belt 0.25 W / m ° C
Thermal conductivity of elastic layer of fixing belt 0.30 W / m ° C
Rise time (until 160 ° C rise) 80 seconds

[Experimental result 6, comparative example]
The heat conductivity of the rubber layer of the inner surface heated fixing roller of the fixing belt is 0.30 W / m ° C.
Thermal conductivity of release layer of fixing belt 0.25 W / m ° C
Thermal conductivity of elastic layer of fixing belt 0.30 W / m ° C
Rise time (until 160 ° C rise) 100 seconds

Comparing the experimental result 5 in which the present invention was implemented with the comparative example of the experimental result 6 in which the present invention was not applied, the rise time was different by 20 seconds only on the heating side of the fixing belt on the heating surface side. . Therefore, if the fixing belt is heated from the outer peripheral surface side, the warm-up time can be shortened by 20 seconds.
Further, when the experimental result 4 and the experimental result 5 are compared, the rise time when the thermal conductivity of the rubber layer of the fixing roller and the thermal conductivity of the elastic layer of the fixing belt in the experimental result 5 are the same is 80 seconds. However, when the thermal conductivity of the elastic layer of the fixing belt is made larger than the thermal conductivity of the rubber layer of the fixing roller as in Experiment result 4, the rise time is 76 seconds, which is 4 seconds earlier.

Furthermore, when the experimental result 3 and the experimental result 5 are compared, the rise time is 80 seconds when the thermal conductivity of the release layer of the fixing belt in the experimental result 5 is smaller than the thermal conductivity of the rubber layer of the fixing roller. However, when the thermal conductivity of the release layer of the fixing belt is made larger than the thermal conductivity of the rubber layer of the fixing roller as in Experimental result 3, the rise time is 73 seconds, and the rise is as fast as 7 seconds. It has become.
Further, as is clear from the comparison between the experimental result 2 and the experimental result 5 and the comparison between the experimental result 1 and the experimental result 5, when the thermal conductivity of the rubber layer of the fixing roller is 0.15 or less, the separation of the fixing belt is reduced. Regardless of the thermal conductivity of the mold layer and the elastic layer, the rise time is 5 seconds to 10 seconds earlier.

  The present invention can be widely applied to fixing devices that fix an unfixed toner image formed on a recording material by an electrophotographic method by applying pressure while heating.

1 is a schematic configuration diagram illustrating an embodiment of a fixing device according to the present invention. It is a side view showing a fixing roller similarly provided in the fixing device. FIG. 2 is a cross-sectional view of a fixing belt provided in the fixing device of FIG. 1. FIG. 2 is a schematic configuration diagram illustrating an example of an image forming unit of an image forming apparatus provided with the fixing device.

Explanation of symbols

1: fixing device, 2: fixing roller, 3: support roller, 5: fixing belt, 6: heating roller (heating member), 7: pressure roller (pressure member), 24: release layer, 25: elastic layer , 31: cored bar, 32: rubber layer

Claims (5)

An endless fixing belt stretched between a fixing roller and a support roller; a heating member that heats the fixing belt; and a pressure member that presses against the fixing roller via the fixing belt. In a fixing device for fixing an unfixed toner image on a recording material fed into a nip where the pressure member and the pressure member are in contact with each other,
The fixing device, wherein the heating member is arranged in contact with the nip portion on the outer peripheral surface of the fixing belt on the upstream side in the belt running direction of the fixing belt.   The fixing roller is a roller in which a rubber layer is formed on the outer side of a metal core, and the fixing belt includes two layers of a release layer and an elastic layer, the thermal conductivity of the rubber layer is λ1, and the release layer 2. The fixing device according to claim 1, wherein a relationship of [lambda] 1 <[lambda] 2 is satisfied, where [Lambda] is defined as [lambda] 2.   The fixing roller is a roller in which a rubber layer is formed on the outer side of a core metal, and the fixing belt includes two layers of a release layer and an elastic layer, and the thermal conductivity of the rubber layer is λ1, and the elastic layer 2. The fixing device according to claim 1, wherein a relationship of [lambda] 1 <[lambda] 3 is satisfied when the thermal conductivity is [lambda] 3.   2. The fixing device according to claim 1, wherein the fixing roller is a roller in which a rubber layer is formed on an outer side of a core metal, and the thermal conductivity of the rubber layer is set to 0.15 W / m [deg.] C. or less. The fixing device according to claim 1, wherein the heating member also serves as a tension roller that applies tension to the fixing belt.

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