JP2002189364A - Fixing device - Google Patents

Abstract

[PROBLEMS] To provide a fixing device capable of reducing a temperature distribution generated in a paper passing area and a non-paper passing area such as a fixing belt and a fixing roller without increasing the number of members, and performing stable fixing. The task is to SOLUTION: The configuration of a heat diffusion member (heat pipe) is as follows.
A wick layer (11) in which a fine wire core material is formed in a spiral or mesh shape along the inner wall of a hollow cylindrical tube (70) in which a core metal such as aluminum, stainless steel, or carbon steel is hollow.
And both ends are sealed by a journal (10), and a liquid (8) as a heat transfer medium is sealed therein. A heat pipe roller (7) having a release layer (3) formed as necessary on the surface layer of the heat pipe is used as a pressure roller or a belt transport roller of a belt fixing device or a heat roller fixing device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat fixing device mounted on an image forming apparatus such as a copying machine, a printer, a facsimile and the like.

[0002]

2. Description of the Related Art Conventionally, as a fixing device of an image forming apparatus such as a copying machine, a printer, a facsimile, etc., a heat roller fixing device is generally used. In the heat roller fixing device, for example, when switching to large size paper immediately after small size continuous paper passing, the non-sheet passing area formed when small size paper is passed becomes high in temperature, so that hot offset and wrapping jam are likely to occur. . In addition, since the temperature of the paper edge becomes higher than that of the central part, the gloss of the edge part increases, and gloss unevenness occurs at the paper edge and the central part. From the above, various studies have been made to eliminate the temperature distribution on the fixing roller at the time of fixing and to perform uniform fixing.

For example, in the proposal described in Japanese Patent Application Laid-Open No. HEI 8-190303, in a heat roller fixing device, a cooling mode is set when the difference between the end temperature and the center temperature of the pressure roller becomes large. In the cooling mode, the power supply to the heater is turned off, and the cooling fan is fully opened while the heating roller and the pressure roller are stopped to cool the pressure roller. Thereby, the temperature of the center and the end of the pressure roller is made uniform. Also, in the proposal described in JP-A-8-220932, a heat roller fixing device has a first heater having a light distribution corresponding to small-size paper and a light distribution corresponding to other end portions. A second heater and a third heater having a light distribution corresponding to large-size paper are provided. At the time of small size paper passing, by controlling the temperature with the first heater,
Abnormal temperature rise at the end of the fixing roller is prevented.

[0004] However, the above proposal has the following problems. According to the proposal described in Japanese Patent Application Laid-Open No. 8-190303, the machine stops in the cooling mode, and cannot output an image until the end temperature decreases. In addition, there is a need for a cooling fan installation space and an airflow escape route,
Inability to cope with downsizing of machines. Also, JP-A-8-220
The proposal described in Japanese Patent No. 932 uses three heaters and requires temperature control in each heater, which leads to an increase in cost. Furthermore, at the connection between the light distribution of the heater corresponding to the small size and the light distribution corresponding to the other end, temperature unevenness occurs on the fixing roller, which causes a fixing failure. In particular, the tendency is remarkable in the thin fixing roller used for shortening the rise time.

On the other hand, in order to make the surface temperature of the fixing roller uniform in the paper passing area, Japanese Patent Publication No. 2697731 has a structure having a heat pipe inside the pressure roller. Due to the high thermal fluidity of the heat pipe, the surface temperature of the fixing roller is made uniform, and the power consumption of the heater is reduced. According to the proposal described in JP-A-5-173451, in a heat roller fixing device, a plurality of heat pipes are provided inside a fixing roller, and a core metal of the fixing roller located in a paper passing surface area of a small size paper is provided. A roller material having a low thermal conductivity is used in other non-sheet passing areas. As a result, the temperature distribution in the fixing roller is kept uniform even in the case of continuous passing of small size paper.

[0006]

However, in the above proposal, since a heat pipe is used inside the fixing roller, it takes a long time to start up because the core metal is thick and the thermal response is poor. There are also problems such as an increase in roller diameter and an increase in cost.

In view of the above problems, the present invention reduces the temperature distribution generated in the paper passing area and the non-paper passing area of the fixing belt, the fixing roller, etc. without increasing the number of members, thereby achieving stable fixing. It is an object of the present invention to provide a possible fixing device.

[0008]

Means for Solving the Problems In order to solve the above problems, the invention according to claim 1 comprises at least a fixing roller, a heating roller, an endless fixing device stretched over the fixing roller and the heating roller. In a belt fixing device provided with a pressure roller facing the fixing roller via the fixing belt, the pressure roller has a release layer on a surface layer of a heat diffusion member (heat pipe). The fixing device is a heat pipe roller provided. According to a second aspect of the present invention, there is provided a belt fixing device provided with a fixing roller and a pressure belt formed by pressing the fixing roller to form a nip and being wound by at least two rollers. One of the rollers for winding the pressure belt is a heat pipe roller formed of a heat diffusion member (heat pipe), or a heat pipe formed by providing a release layer on the surface layer of the heat diffusion member (heat pipe). The fixing device is a roller. According to a third aspect of the present invention, there is provided a heat roller fixing device including at least a fixing roller and a pressure roller formed by pressing the fixing roller to form a nip.
The fixing device is a heat pipe roller in which the pressure roller is provided with a release layer on the surface of a heat diffusion member (heat pipe). The invention according to claim 4 is the invention according to claims 1 to 3
In the fixing device according to any one of the above, the pressure roller formed of the heat pipe roller has a roller diameter of 30 mm or more and 50 mm or less, and a thickness of 0.3 mm or more and 1.0 mm or less.
The fixing device is configured as follows.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. The fixing device according to claim 1 will be described. FIG. 1 is a schematic sectional view of a belt fixing device according to the present invention. A fixing roller (1), a heating and tension roller (2), and a pressure roller (7a);
An endless fixing belt (4) is stretched between the fixing roller (1) and the heating and tension roller (2). The recording paper carrying the unfixed image is heated via a fixing belt (4) at a nip portion between a fixing roller (1) and a pressure roller (7a).
Pressure is applied to fix an unfixed image.

As the base of the fixing belt (4), an endless belt-like base made of a heat-resistant resin or metal is used. Examples of the material of the heat-resistant resin include polyimide, polyamideimide, and polyetheretherketone, and examples of the material of the metal belt include nickel, aluminum, and iron. It is desirable that the thickness be as thin as 100 μm or less. Since the surface of the fixing belt (4) comes into pressure contact with the recording paper and the toner, it needs to have a releasing property.
Further, those having excellent heat resistance and durability are preferable. Therefore, the surface layer of the fixing belt (4) is configured to be covered with a heat-resistant release layer made of fluorine resin, high release silicone rubber, or the like. The fluorine-based resin is coated on the surface of the base by spraying or the like, and heat-fused to form a surface release layer. The high release silicone rubber layer has a rubber hardness (JIS A
Hardness tester) 25-65 degrees, thickness 100-300 μm
Is desirable as a condition for obtaining good fixing properties and thermal responsiveness.

The fixing roller (1) has a cored bar, and a heat insulating elastic member made of a soft heat-resistant material, for example, a foamed silicon rubber or the like in order to make the nip width sufficiently large on the outer periphery thereof. Have. Further, the thickness of the fixing roller (1) is sufficiently large.
% Of thickness. The configuration of the heating and tension roller (2) is a thin roller of a hollow metal cylinder made of aluminum, carbon steel, stainless steel, or the like. Further, a heater (5) such as a halogen heater is provided in the heating roller. The thermistor (6) is installed at the center of the width of the fixing belt (4), and detects the temperature of the fixing belt (4). The heater is turned on by a temperature control circuit (not shown).
ON / OFF to maintain the fixing belt (4) at a predetermined temperature.

Further, in the fixing device of the present invention, the pressure roller (7a) is a heat pipe roller in which a release layer is provided on a surface layer of a heat diffusion member (heat pipe). FIG. 2 is a diagram illustrating a structure of a heat pipe roller formed by a heat pipe. The structure of the heat pipe is such that a wick layer (11) is formed on the inner surface of a hollow cylindrical tube (70) having a hollow core made of aluminum, stainless steel or carbon steel, and both ends are sealed with a journal (10). And a liquid (8) as a heat transfer medium. Here, the wick layer (11) is obtained by forming a core material of an extremely fine wire in a spiral or mesh shape along the inner wall of the hollow cylindrical tube (70). When the liquid (8), which is the heat transfer medium, in the hollow cylindrical tube (70) changes state by heat and becomes vapor, the vapor is cooled by capillary action due to the structure of the wick layer (11) and returns to the liquid (8). And return.
Further, since the thermal conductivity of the liquid (8) is several hundred times that of metal, the temperature of the heat pipe roller (7) is instantaneously made uniform by repeating this circulation. The inside of the hollow cylindrical tube (70) is in a vacuum state in order to accelerate the evaporation of the liquid. A heat pipe roller (7) is provided by providing a heat-resistant release layer (3) made of a fluorine resin, a high release silicone rubber or the like on the surface layer of the heat pipe.

The pressure roller (7a) having the above configuration
In the present embodiment, in order to further improve the releasability of the sheet from the fixing belt (4), the hardness is made harder than that of the fixing roller (1), and the nip is formed downward.
The thickness of the release layer (3) of the pressure roller (7a) is less than 7% of the diameter of the pressure roller (7a), and its hardness (JI
SA hardness meter) is 40 Hs or more.

Next, the heat transfer of the fixing belt in the fixing device will be described. FIG. 6 is a diagram showing a temperature distribution of the fixing belt when the small-size paper is continuously fed in the conventional fixing device. As described above, when a large number of small-size sheets are continuously copied, the temperature of the end portion, which is the non-sheet passing area of the fixing belt, increases. As a result, the non-sheet passing area becomes high in temperature, and therefore, when switching to the large size sheet immediately after the continuous passing of the small size sheets, a hot offset or a wrapping jam occurs. In addition, the temperature of the paper edge becomes higher than that of the central part, and the glossiness increases, so that gloss unevenness occurs at the paper edge and the central part. Further, the tensile strength of a resin material such as a nickel metal or a polyimide used for a belt base exceeds an allowable value and becomes brittle. The means for solving these problems will be described below. FIG. 3A is a view of the fixing unit as viewed from above, and is a diagram illustrating a heat transfer of the fixing belt when the small-size paper is continuously fed when the pressure roller is a heat pipe roller. FIG. 3B is a diagram showing the temperature distribution of the fixing belt at this time. If the temperature at the end of the non-fixing belt non-sheet passing area rises during the continuous feeding of the small size paper, the heat at the end of the fixing belt is transmitted to the pressure roller in contact with the fixing belt. The pressure roller instantaneously makes the temperature distribution uniform by the effect of the heat pipe, and transmits the heat to the paper passing portion where the temperature of the fixing belt is low. Some of this heat is absorbed by the paper passing through the nip. That is, the temperature rise at the end of the non-sheet passing area of the fixing belt can be prevented as shown in FIG. 3B by the heat pipe effect of the pressure roller and the heat absorbing effect of the sheet passing through the nip. .

Next, a fixing device according to a second aspect will be described. FIG. 4 is a schematic sectional view of the belt fixing device according to the present invention. Fixing roller (9) and fixing roller (9)
A pressure roller (7b) formed in pressure contact with a belt via a belt, and a pressure belt (12) wound around the pressure roller (7b) and the belt transport roller (7c). It is a belt fixing device. In the present embodiment, one belt transport roller (7c) is provided, but two or more belt transport rollers (7c) may be provided. Here, one of the pressure roller (7b) and the belt transport roller (7c) is a roller formed by a heat pipe shown in FIG. Even if two or more belt transport rollers (7c) are provided, one of the rollers for winding the pressure belt (12) may be a heat pipe roller. In particular, it is desirable to form the belt transport roller (7c) with a heat pipe in terms of roller strength. Further, in this fixing device, since the pressure roller (7b) or the belt transport roller (7c), which is a heat pipe roller, does not directly contact the paper, a release layer is not provided on the surface of the heat pipe. Is also good.

Next, a fixing device according to a third aspect will be described. FIG. 5 is a schematic configuration diagram of the roller fixing device according to the present invention. The fixing roller (16) is a core metal roller (1).
4) A silicon rubber layer or a heat-resistant elastic layer (15) having an elastic effect formed by foaming and molding silicone rubber. The surface layer has a release layer. An external heating roller (17) is pressed against the surface of the fixing roller (16) as a heating means of the fixing roller (16) thus configured. on the other hand,
The pressure roller (7d) is a heat pipe roller having a release layer on the surface of the heat pipe shown in FIG. The feature of such a fixing device is that the start-up time is short because the fixing roller (16) is instantaneously heated by the external heating roller (17). In addition, a pressure roller (7
d) It is possible to prevent a rise in the temperature at the end of the non-sheet passing area during continuous sheet feeding of small-size sheets by the above-described feature of the configuration, and thus eliminate the temperature distribution on the fixing roller (16). it can. In addition, this can be achieved with a simple configuration as compared with a belt fixing device.

When the above heat pipe roller is used as a pressure roller, the roller diameter and the wall thickness are preferably as small as possible in order to reduce the heat capacity and shorten the rise time. On the other hand, it is necessary that the roller diameter and the wall thickness of the roller ensure a strength that does not cause deformation or bending of the roller.
To realize both, preferably, the roller diameter is 30 m
m to 50 mm and thickness 0.3 mm to 1.0
mm or less.

An experimental example suitable for determining the roller diameter and thickness of the heat pipe roller will be described below. (Experimental Example) In the fixing device shown in FIG. 1, fixing was performed under the following fixing conditions using pressure rollers having a roller diameter of 30 mm and 60 mm and a core metal of 0.3 mm and 1.0 mm, respectively. The startup time of the device and the amount of deformation of the pressure roller were measured. The start-up time of the fixing device is preferably 60 seconds or less, and more preferably 30 seconds, from the viewpoint of operability and energy saving. .3 mm or less. <Fixing conditions> Heater capacity: 1200 W Fixing temperature: 160 ° C. Fixing pressure: 15 kg / one side Fixing belt configuration: 3-layer belt (base: polyimide thickness 50 μm, intermediate layer: silicone rubber thickness 150 μm, surface layer:・ Fixing roller: roller diameter 30 mm (silicone foam rubber thickness 6 mm) ・ Heating roller: roller diameter 30 mm (core metal thickness 0.6 m)
m)

The results are shown in Tables 1 and 2.

[Table 1]

[0020]

[Table 2]

From the results shown in Table 1, it can be seen that the smaller the roller diameter and the core thickness, the shorter the start-up time of the fixing device. Roller diameter is 30mm and core thickness is 0.3m
In the pressure roller having a roller diameter of 60 mm and a core metal thickness of 1.0 mm, the rise time is 59 seconds. When the diameter and the core thickness increase, the set-up time exceeds the set start-up time, which is not preferable. Further, from the results in Table 2, it can be seen that the larger the roller diameter and the core metal thickness, the smaller the amount of deformation of the pressure roller. In a pressure roller having a roller diameter of 60 mm and a core metal thickness of 1.0 mm, the deformation amount is 0.
02 mm, which is a preferable value, while a roller having a roller diameter of 30 mm and a core metal thickness of 0.3 mm,
It is 0.3 mm, and if the roller diameter and the core metal thickness are further reduced, the allowable deformation amount exceeds the set allowable deformation amount.

[0022]

As described above, according to the present invention, the pressure roller or the belt transport roller in the belt fixing device and the pressure roller in the heat roller fixing device are formed by a heat diffusion member (heat pipe). The temperature rise in the non-sheet passing area of the fixing belt or the fixing roller can be suppressed, causing hot offset and wrapping jam,
Alternatively, it is possible to provide a fixing device capable of preventing uneven gloss and fixing a stable image.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a belt fixing device according to the first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a structure of a heat pipe roller formed by a heat pipe.

FIG. 3A is a diagram of the fixing unit viewed from above, showing heat transfer of the fixing belt when a small-size sheet is continuously fed when a pressure roller is a heat pipe roller. (B)
FIG. 6 is a diagram illustrating a temperature distribution of the fixing belt at this time. FIG. 9 is a temperature distribution diagram showing an end temperature rise in a non-sheet passing area during small-size continuous sheet passing.

FIG. 4 is a schematic sectional view of the belt fixing device according to the second aspect of the present invention.

FIG. 5 is a schematic configuration diagram of a heat roller fixing device according to the invention of claim 3;

FIG. 6 is a diagram illustrating a temperature distribution of a fixing belt when a small-size sheet is continuously fed in a conventional fixing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixing roller 2 Heating and tension roller 3 Release layer 4 Fixing belt 5 Heater 6 Thermistor 7 Heat pipe roller 70 Hollow cylindrical tube 7a Pressure roller 7b Pressure roller 7c Belt conveyance roller 7d Pressure roller 8 Liquid (heat transfer medium) Reference Signs List 9 fixing roller 10 journal 11 wick layer 12 pressurizing belt 14 core metal roller 15 heat-resistant elastic layer 16 fixing roller 17 external heating roller 18 drive source

Claims (4)

[Claims] An endless fixing belt stretched over the fixing roller and the heating roller; and a pressure roller opposed to the fixing roller via the fixing belt. In the provided belt fixing device, the pressure roller is a heat pipe roller in which a release layer is provided on a surface layer of a heat diffusion member (heat pipe). 2. A belt fixing device comprising: a fixing roller; and a pressure belt formed by pressing the fixing roller to form a nip, the pressure belt being wound by at least two rollers. Either of the rollers for winding
A fixing device comprising a heat pipe roller formed of a heat diffusion member (heat pipe) or a heat pipe roller formed by providing a release layer on a surface layer of the heat diffusion member (heat pipe). 3. A heat roller fixing device including at least a fixing roller and a pressure roller formed by pressing the fixing roller to form a nip, wherein the pressure roller is a surface layer of a heat diffusion member (heat pipe). A heat pipe roller provided with a release layer. 4. The fixing device according to claim 1, wherein the pressure roller formed of the heat pipe roller has a roller diameter of 30 mm or more and 50 mm or less, and a thickness of 0.3 mm or more and 1.0 mm or less. A fixing device having the following configuration.