JP2001201978A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device capable of preventing temperature rise in a paper non-passing area (end part) when the paper of a small size consecutively passes and preventing a faulty fixing and jamming or the like caused by hot offset. SOLUTION: This fixing device is equipped with a fixing roller and a heating roller equipped with a heat source on its inside, an endless fixing belt stretched and laid by both rollers and a pressure roller provided to be opposed to the fixing roller through the fixing belt. The heating roller is equipped with at least the 1st heat source and the 2nd heat source on the inside, the 1st heat source has 1st luminous intensity distribution nearly corresponding to the paper of small size and the 2nd heat source has 2nd luminous intensity distribution nearly corresponding to both ends other than the 1st luminous intensity distribution, and 1st and 2nd temperature detection means are respectively provided on the surface of the fixing belt opposed to the respective luminous intensity distribution areas of the 1st and the 2nd luminous intensity distributions through the heating roller, and the temperature of the fixing belt is controlled to specified temperature based on the temperature detection by the 1st and the 2nd temperature detection means by a temperature control means and an ON/OFF circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device provided in an image forming apparatus such as a copying machine, a printer, a facsimile or the like. The present invention relates to a fixing device capable of preventing a fixing defect, a hot offset, and the like.

[0002]

2. Description of the Related Art In general, a fixing method of a fixing device provided in an image forming apparatus such as a copying machine or a printer is a method in which an unfixed toner image is fixed on transfer paper by heating and pressing. In recent years, a fixing belt type fixing device using a thin (low heat capacity type) fixing belt other than such a heat pressure roller type fixing device has been known. This fixing belt type fixing device will be briefly described with reference to FIG. That is, the fixing device 1 is provided so as to face the fixing roller 2 with the fixing roller 2 and the heating roller 3, an endless fixing belt 4 stretched by the rollers 2 and 3, and the fixing belt 4. And a pressure roller 5. The unfixed image on the transfer paper conveyed to the fixing device 1 is pressed and fixed by a nip formed between the fixing roller 2 and the pressure roller 5 via the heating and fixing belt 4.

Conventionally, as this type of fixing device, (1)
Japanese Unexamined Patent Application Publication No. 8-220930 discloses that a heater having a light distribution substantially corresponding to the width of a small-size sheet is continuously turned on when a small-size sheet is passed, and the heater is turned on when a large-size sheet is passed. Japanese Patent Application Laid-Open No. 8-220932 discloses a fixing device that controls the lighting of the heater so as to compensate for the insufficient fixing with a heater having a light distribution substantially corresponding to the paper width.
Has two fixing heaters, each having a different light distribution,
When large-size paper is passed, the lighting device is controlled by two fixing heaters to maintain the fixing device at a predetermined temperature.
Also, (3) Japanese Patent Application Laid-Open No. 5-173451 discloses a method in which a heat pipe is provided inside a fixing roller, and the heat generated by the heat pipe causes a non-sheet passing area (end portion) generated after continuous passing of small-size sheets. Techniques for preventing a temperature rise are disclosed.

[0004]

Here, the following problems occur during continuous feeding of small-size paper in a conventional fixing device. That is, as shown in FIG. 14, the non-sheet passing area (end) of the fixing belt becomes a high temperature area (about 170 ° C.) as compared with the sheet passing area (central part) due to continuous passing of small-sized sheets. . As described above, when the temperature becomes high, the heat resistance and the hardness of the heat-resistant polymer resin material such as nickel metal or polyester used as the base constituting the fixing belt decrease, and the “tensile strength” is set to an allowable value with the decrease. And the fixing belt itself becomes brittle. In particular, when the end temperature in the width direction of the fixing belt (heating roller) rises, the “glossiness” increases compared to the center portion, which causes so-called “gloss unevenness”. Further, since the temperature of the non-sheet passing area becomes high, if the sheet is switched to the large-sized sheet immediately after the continuous passing of the small-sized sheet, there is a possibility that a fixing failure or a wrapping jam due to hot offset or the like may occur.

This will be specifically described with reference to FIG. FIG. 15 is a correlation diagram between the number of sheets passed and the fixing temperature in continuous sheet feeding. As the conditions of the fixing device, one fixing heater (800 W) and a fixing speed of 180 mm /
s, the copy speed is set to 31 cpm (A4 horizontal size), and the temperature transition when small-size paper is continuously passed (99 sheets) is shown. In the figure, the “solid line” indicates the temperature transition at the center,
The “dashed line” indicates the temperature transition at the end of the sheet, and the “dashed line” indicates the temperature transition at the non-sheet passing section. And this figure
As is clear from Fig. 15, after passing 99 sheets of small size paper continuously, the non-paper passing area (end) has a high temperature of up to 190 ° C, and the temperature of the fixing belt at this time has a sharp nickel hardness. About 200 ° C.

Also, in the case of the techniques described in the above publications (1) to (3), in the case of (1), the temperature distribution in the paper passing area and the temperature distribution in the non-paper passing area are not uniform. Therefore, if, for example, a large-size sheet is immediately passed in this state, a fixing failure may occur. In the case of (2), the lighting control by two fixing heaters is performed. However, the boundary between the light distribution of the fixing heater corresponding to the large-sized paper and the light distribution corresponding to the other end portion is controlled. In this case, fixing failure due to temperature unevenness occurs. In particular, such a problem is caused when a thinner fixing roller is used in order to shorten the rise time,
This tendency is remarkable. In the case of (3), it is necessary to provide a heat pipe inside the fixing roller, so that the thickness of the core metal itself constituting the fixing roller becomes thick and the rise time of the fixing device becomes longer due to an increase in heat capacity. This also increases the cost.

Accordingly, an object of the present invention is to solve the above-mentioned problems of the conventional fixing device, to prevent a temperature rise in a non-sheet-passing area (end portion) during continuous passing of small-size sheets, It is an object of the present invention to provide a fixing device capable of preventing a fixing failure when switching to a large-size sheet immediately after continuous feeding of a small-size sheet and preventing a wrapping jam due to a hot offset.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above objects, the present invention provides a fixing roller, a heating roller having a heat source therein, and an endless roller stretched by these two rollers. Fixing device having a fixing belt, and a pressure roller provided opposite to the fixing roller with the fixing belt interposed therebetween, and carrying out fixing by conveying the toner image on the recording paper between the pressure roller and the fixing belt. , The heating roller has at least a first heat source and a second heat source disposed in the axial direction of the heating roller, and the first heat source among the first and second heat sources is small. The first light distribution has a first light distribution substantially corresponding to the size paper, and the second heat source has a first light distribution.
The surface of the fixing belt has a second light distribution substantially corresponding to both end portions other than the light distribution described above, and faces each light distribution region of the first and second light distributions via a heating roller. In
First and second temperature detecting means for detecting the temperature of the fixing belt are provided, respectively.
The temperature of the fixing belt is controlled to a predetermined temperature by an / OFF circuit.

In the case of the present invention, the first heat source is used when fixing small-sized paper, and the second heat source is used when starting the fixing device and fixing large-sized paper. This prevents a temperature increase in the non-sheet passing area (end portion) during the continuous passing of small-size paper, and also prevents fixing failure when switching to the large-size paper immediately after continuous passing of small-size paper. This is to prevent it.

[0010]

1 to 3 show a first embodiment of the present invention. FIG. 1 is a schematic diagram showing the entire configuration of a fixing device. b) shows an example of the arrangement of the first and second heaters (heat sources) and an overall circuit diagram, and FIG.
2 shows light distributions in two heaters. As shown in FIG. 1, the fixing device 1 includes a fixing roller 2 and a heating roller 3, an endless fixing belt 4 stretched between these two rollers 2, 3, and a fixing roller 2 via the fixing belt 4. And a pressure roller 5 provided opposite thereto. The heating roller 3 is configured as a hollow thin metal roller made of aluminum, carbon steel, stainless steel, or the like. Also,
The fixing roller 2 is configured such that an inner cylindrical portion is a cored bar, and an outer peripheral portion thereof is covered with a heat-insulating elastic member (for example, foamed silicon rubber or the like) which is a soft heat-resistant material in order to make the nip width sufficiently large. And The thickness of the fixing roller 2
It is of sufficient thickness that it is about 15% to 20% of the diameter. On the other hand, the pressure roller 5 has a configuration in which a surface layer of a core metal such as aluminum, stainless steel, or carbon steel is covered with a heat-resistant release layer (such as a fluororesin or a high-release silicone rubber). The pressure roller 5 has a downward nip so as to improve the releasability from the fixing belt 4. The thickness of the release layer of the surface layer of the pressure roller 5 is less than 7% of the diameter of the body of the pressure roller 5, and the hardness thereof is 20 Hs or more (JISA). 8
Denotes an oil application roller 8 which rotates in contact with the fixing belt 4
Thus, the oil applying roller 8 can apply a release agent such as silicone oil on the outer peripheral surface of the fixing belt 4. Reference numeral 9 denotes a hollow roller made of aluminum, carbon steel, stainless steel, or the like which rotates in contact with the outer peripheral surface of the fixing belt 4. The hollow roller 9 functions as a cleaning roller for cleaning the surface of the fixing belt 4. I do. The offset toner and the like attached to the hollow roller 9 can be scraped off by the scraper 10.

Here, a feature of the present invention is to prevent a temperature rise in a non-sheet passing area (end portion) during continuous sheet feeding of small size sheets. For this reason, as shown in FIG. 1, inside the heating roller 3, there are provided first and second heaters 6 and 7 (halogen heaters) arranged in the axial direction.
The first heater 6 among the second heaters 6 and 7 has a first light distribution (FIG. 3) corresponding to a small-size sheet.
Has a second light distribution (FIG. 3) corresponding to an end other than the first light distribution. Further, on the surface of the fixing belt 4 opposed to each light distribution area of the first and second light distributions via the heating roller 5, first and second temperature for detecting the temperature of the fixing belt 4 are provided. Detection means 11 and 12 are provided, respectively. Reference numeral 13 denotes a temperature control unit which controls the temperature of the fixing belt 4 to a predetermined temperature based on the temperatures detected by the first and second temperature detection units 11 and 12 by the temperature control unit 13. An ON / OFF circuit 15 controls ON / OFF timing. Then, the unfixed image on the transfer paper conveyed to the fixing device 1 is heated by the first and second heaters 6 and 7 and by a nip formed between the fixing roller 2 and the pressure roller 5 via the fixing belt 4. It is pressed and fixed. In this case,
Since the temperature distribution in the width direction of the fixing belt 4 is made uniform by the respective temperature controls corresponding to the heaters 6 and 7, the non-sheet passing area (end) Part) is the paper passing area (center part)
There is no higher temperature than.

The fixing belt 4 is preferably an endless belt made of nickel, heat-resistant resin (polyimide or the like), carbon steel, stainless steel, or the like, and having no belt seam by, for example, nickel electroforming. The surface layer of the fixing belt 4 has a heat-resistant release layer (fluororesin,
High release silicone rubber) is coated, and the high release silicone rubber layer is of a 25-65 degree rubber hardness (JISA hardness tester) and thin-walled (with a thickness of 100-300um). Is suitable as a condition for obtaining good fixing properties and thermal responsiveness. In the case of a fixing belt with a seam manufactured by a processing method using a precision butt technology (for example, welding) of an ultra-thin thick plate (less than 100 μm) of stainless steel or an iron-based material, the level difference due to welding is “horizontal”. In order to prevent streaks, etc., the thickness should be 10um or less.

FIG. 4 shows a second embodiment of the present invention. As shown in FIG. 4, the basic configuration and functions of the second embodiment are the same as those of the first embodiment, but the first heater 6 among the first and second heaters 6 and 7 almost corresponds to a small-size sheet. The first heater 7 has a first light distribution (FIG. 5)
Is characterized by having a second light distribution (FIG. 5) corresponding to almost the entire area of large-size paper. The difference from the first embodiment is that both the first and second heaters 6 and 7 are used when fixing small-size paper, and only the second heater 7 is used when fixing large-size paper. 4
The temperature detecting means for detecting the temperature of the first and second heaters 6 and 7 is provided only at the first temperature detecting means 11 provided substantially at the center of the heating roller 5. This is for controlling the temperature. by this,
The lighting rate of the fixing heater (second heater 7) for large-size paper can be reduced to about 50% as compared with the related art, and the temperature detecting means for detecting the temperature of the fixing device is compared with the first embodiment. Cost can be reduced. In this case, it is preferable to select the non-sheet passing area in consideration of a fixing heater capable of maintaining a predetermined fixing temperature (heat generation amount).

FIG. 6 shows a third embodiment of the present invention. In the third embodiment, the first and second heaters 6 and 7 shown in the second embodiment are connected to the inner peripheral surface of the fixing belt 4 and It is characterized in that it is arranged so as to heat the outer peripheral surface. That is, a first heater 6 having a first light distribution substantially corresponding to a small-size sheet and a second heater 7 having a second light distribution substantially corresponding to a large-size sheet are provided. , 2 of the heaters 6 and 7, the first heater 6 is disposed in an axial direction in a hollow roller 9 functioning as a cleaning roller, and the second heater 7 is disposed in an axial direction in a heating roller 3. As a result, the fixing belt 4 is heated from the inside by the second heater 7 and
Heat is also supplied from the outer periphery of the hollow roller 9 via the hollow roller 9 heated by the first heater 6. In the same manner as in the second embodiment, both the first and second heaters 6 and 7 are used when fixing small-sized paper, and only the second heater 7 is used when starting up the fixing device and fixing large-sized paper. Independent temperature control is performed. In this case, the temperature of the first and second heaters 6 and 7 may be controlled simultaneously.

Also in the case of the third embodiment, the temperature distribution in the width direction of the fixing belt 4 is made uniform by the respective temperature controls corresponding to the first and second heaters 6 and 7, so that the small size Immediately after continuous paper passing, the non-paper passing area (end) of the fixing belt does not become hotter than the paper passing area (center). Further, the heating roller 3 is usually provided with a belt deviation preventing means (not shown), and the roller diameter of the shaft end of the heating roller 3 is smaller than the roller diameter of the belt winding portion.
In a configuration in which a plurality of fixing heaters are provided inside the heating roller 3, it is relatively difficult to assemble them. In contrast, in the present embodiment, the first and second heaters 6 and 7 are provided at different locations. Therefore, there is no particular problem in assembling.

FIGS. 7 and 8 show a fourth embodiment of the present invention. In the fourth embodiment, first and second heaters 6 and 7 are used.
Are arranged so as to heat the inner peripheral surface or the outer peripheral surface of the pressure roller 5. That is, as shown in FIG. 7, a hollow hollow roller 17 is provided which is in contact with and rotates on the outer peripheral surface of the pressure roller 5, and inside the hollow roller 17, the first of the first and second heaters 6, 7 is provided. The first temperature detecting means 11 for detecting the temperature of the hollow roller 17 is provided on the surface of the heater 6. On the other hand, FIG. 8 shows that the first heater 6 is disposed inside the pressure roller 5 and the pressure roller 5
1 shows a configuration in which a first temperature detecting means 11 for detecting the temperature of the above is provided. As in the third embodiment, both the first and second heaters 6 and 7 are used at the time of fixing small-sized paper, and the second control is used at the time of starting the fixing device and fixing large-sized paper. Temperature control using only the heater 7 is performed. In the fourth embodiment (FIG. 7), the first heater 6 can heat the paper from the back side, and also expects a preheating effect on the paper transport unit (guide plate) close to the hollow roller 17. be able to. As a result, even if the set temperature is lowered below the predetermined fixing temperature, the fixability is not impaired, and as a result, the temperature rise in the non-sheet passing area during continuous small-size sheet passing can be more effectively suppressed. Also, as in the third embodiment, the first and second heaters 6 and 7 are provided at separate locations, so that there is no problem in assembling.

FIGS. 9 to 12 show a fifth embodiment of the present invention. In the fifth embodiment, a heat pipe 18 as a "heat diffusion member" for heating the fixing belt 4 or the pressure roller 5 is used. It is characterized in that it is configured to provide up to 20. That is, in FIG. 9, a hollow heat pipe 18 that rotates while being in contact with the outer peripheral surface of the pressure roller 5 is provided, and the heat pipe 18 heats the surface of the pressure roller 5. Also figure
Reference numeral 10 denotes a configuration in which a hollow heat pipe 19 is provided which rotates in contact with the outer peripheral surface of the fixing belt 4, and the fixing belt 4 is heated by the heat pipe 19. In this case, the heat pipe 19 functions as a cleaning roller. Is also possible. FIGS. 11 and 12 show a configuration in which the heat pipe 20 is in contact with the inner peripheral surface side of the fixing belt 4. here,
The heat pipes 18 to 20 are hollow cylinders each having a wick layer on its inner surface and sealed at both ends, and a liquid as a heat transfer medium is sealed therein. This liquid evaporates by heating, moves inside the heat pipe, and is returned to the high temperature part of the heat pipes 18 to 20 through the wick layer,
The heat vapor refluxed to the high temperature part becomes liquid in the low temperature part. The temperature of the entire heat pipes 18 to 20 can be made uniform by repeating the “thermal circulation” between the high temperature part and the low temperature part. Where the heat pipe
Since the thermal conductivity of the hot steam in 18 to 20 is several hundred times higher than that of the metal body, the temperature can be made uniform quickly. 9 to 12
Although the heat pipe is provided on one of the fixing belt 4 and the pressure roller 5, the heat pipe may be provided on both. Further, the pressure roller 5 or the heating roller 3 itself may be configured as a heat pipe. The "heat diffusion member" used in the heat pipe may be a member having good thermal conductivity, and for example, a copper member or the like can be employed.

FIG. 13 is a correlation diagram showing heat transfer in the heat pipe when small-size paper is continuously passed when the fifth embodiment is applied. On the other hand, FIG. 14 is a correlation diagram showing heat transfer in a conventional fixing device not using a heat pipe. The paper passing conditions are continuous paper passing of small size paper (99 sheets). Here, the temperature of the non-sheet passing area (end) is about 170 ° C., and the temperature of the fixing belt 4 corresponding to the sheet passing area (small size sheet width) is “140”.
° C ”. Then, as shown in FIG. 13, the heat of the fixing belt 4 heated by the heat pipe is returned to the low-temperature part from the high-temperature part by heat conduction, and heat circulation is again performed by the heat pipe (arrows in the figure). ). For this reason, the temperature distribution of the fixing belt 4 in the sheet passing width direction is substantially flat as compared with the related art. In other words, the temperature of the non-sheet passing area (end) of the small-size sheet does not increase significantly, and the temperature of the non-sheet passing area (end) during continuous sheet feeding of the small-size sheet can be prevented. .

FIG. 15 is a view for explaining a sixth embodiment of the present invention. In the sixth embodiment, when the continuous passage of the small-size sheets exceeds a predetermined number, the small-size sheets are passed. After the paper is completed, the power supply to the fixing heater for heating the fixing belt 4 is stopped for a predetermined time (for about one minute), and the fixing belt 4 is idled.
The configuration of the fixing belt 4 in this embodiment is nickel (thickness, 0.04 mm), and the release layer is silicon rubber (thickness, 0.04 mm).
0.15mm) and adopt a thin-walled low calorific value belt. That is, as shown in FIG. 15, when the power supply to the fixing heater is stopped for 30 seconds after the continuous feeding of the small size paper, the non-paper passing area temperature becomes about 170 ° C., and the power supply stop time is reduced to two minutes. When this happens, the non-sheet passing area temperature can be reduced to about 140 ° C. Therefore, the fixing device 1
The self-cooling speed due to heat radiation is promoted because the fixing belt 4 used for the printing is thin, so that the fixing belt temperature can be returned to the predetermined temperature in a short time, so that the next printing start can be prepared. . The belt heating fixing device of the present application is a system in which the belt is heated via a heating roller. In addition to preventing temperature rise in the non-sheet passing area (end portion) during continuous feeding of small size paper, poor fixing when switching to large size paper immediately after continuous feeding of small size paper, winding jam due to hot offset, etc. Can be prevented. If the continuous paper passing is less than 20 sheets, the non-paper passing area (edge)
Is not more than 20 ° C. In this way, when the temperature of the non-sheet passing area rises, the toner on the sheet is excessively heated, so that there is a problem that hot offset and wrapping jam occur. As a result, it is possible to quickly return to a state close to the predetermined temperature.

[0020]

The present invention is as described above, and the invention according to claim 1 is a fixing roller, a heating roller having a heat source therein, and an endless fixing belt stretched by these two rollers. And a pressure roller provided opposite to the fixing roller via the fixing belt, wherein the fixing device transports the toner image on the recording paper between the pressure roller and the fixing belt and performs fixing. Inside the heating roller, there are at least a first heat source and a second heat source arranged in the axial direction of the heating roller.
The first heat source has a first light distribution substantially corresponding to the small-sized paper, and the second heat source has the second light distribution substantially corresponding to both ends other than the first light distribution. The surface of the fixing belt having a distribution and facing each light distribution area of the first and second light distributions via a heating roller is provided with a first and a second for detecting the temperature of the fixing belt. Temperature detection means are provided, and the temperature of the fixing belt is controlled to a predetermined temperature by the temperature control means and the ON / OFF circuit based on the temperature detection by the first and second temperature detection means. This prevents the temperature in the non-sheet passing area (end portion) from increasing during continuous sheet passing, and prevents jamming due to defective fixing and hot offset.

According to a second aspect of the present invention, there is provided a fixing roller, a heating roller having a heat source therein, an endless fixing belt stretched by both rollers, and a fixing roller opposed to the fixing roller via the fixing belt. And a fixing roller for conveying the toner image on the recording paper between the pressing roller and the fixing belt to fix the toner image on the recording paper. At least a first heat source and a second heat source arranged in the direction, and the first heat source among the first and second heat sources has a first light distribution substantially corresponding to a small size sheet. , The second heat source has a second light distribution substantially corresponding to large size paper,
A temperature detecting means for detecting the temperature of the fixing belt is provided on the surface of the fixing belt facing the first and second light distribution areas via the heating roller. Based on the detection, the temperature of the fixing belt is controlled to a predetermined temperature by a temperature control unit and an ON / OFF circuit, and the first and second fixing belts are fixed at the time of fixing a small-size sheet.
Since the second heat source is used at the time of fixing large-sized paper, the temperature of the non-sheet passing area (end) during continuous paper passing of small-sized paper is prevented, and the fixing failure and the fixing failure are prevented. Jams and the like due to hot offset can be prevented, and there is an effect that cost can be reduced because the temperature detecting means is used alone.

According to a third aspect of the present invention, there is provided a fixing roller, a heating roller having a heat source therein, an endless fixing belt stretched by both rollers, and a fixing roller opposed to the fixing roller via the fixing belt. And a hollow roller that rotates in contact with the outer peripheral surface of the fixing belt, and conveys the toner image on the recording paper between the pressing roller and the fixing belt to perform fixing. In the fixing device,
A first heat source having a first light distribution substantially corresponding to the small-size paper and a second heat source having a second light distribution substantially corresponding to the large-size paper; Wherein the first heat source is disposed axially in the hollow roller, the second heat source is disposed axially in the heating roller, and has a first light distribution substantially corresponding to a small-size sheet. The second heat source has a second light distribution substantially corresponding to the large-size paper, and a first temperature detecting means for contacting the hollow roller to detect the temperature of the first light distribution area;
A second temperature detecting unit which is in contact with the surface of the fixing belt opposed to the fixing belt via the heating roller and detects the temperature of the second light distribution area; The temperature of the fixing belt is controlled to a predetermined temperature by a temperature control means and an ON / OFF circuit based on the temperature. Since the second heat source is used at the time of fixing the paper, it is possible to prevent the temperature of the non-sheet passing area (end portion) from rising when the small size paper is continuously passed, and also to prevent the fixing failure and the jam due to the hot offset. In addition, since the first and second heat sources are provided at different locations, there is an effect that there is no particular problem in assembling.

According to a fourth aspect of the present invention, there is provided a fixing roller, a heating roller having a heat source therein, an endless fixing belt stretched between the two rollers, and a fixing roller opposed to the fixing roller via the fixing belt. And a hollow roller that rotates in contact with the outer peripheral surface of the fixing belt, and conveys the toner image on the recording paper between the pressing roller and the fixing belt to perform fixing. In the fixing device,
A first heat source having a first light distribution substantially corresponding to the small-size paper and a second heat source having a second light distribution substantially corresponding to the large-size paper; The first heat source is disposed in the axial direction so as to heat the inner peripheral surface or the outer peripheral surface of the pressure roller, and the second heat source is disposed in the axial direction in the heat roller, and is disposed on the small-sized paper. The second heat source has a first light distribution substantially corresponding to the first light distribution, and the second heat source has a second light distribution substantially corresponding to the large-size paper, and a second light source for detecting the temperature of the first light distribution region. A first temperature detecting means and a second temperature detecting means for detecting the temperature of the second light distribution area by contacting the surfaces of the fixing belts opposed to each other via the heating roller. Temperature control means and ON / OFF circuit based on temperature detection by temperature detection means More the temperature of the fixing belt is controlled to a predetermined temperature, the first at the time of fixation of small-sized paper,
Since the second heat source is used when the fixing device is started and when the large-size paper is fixed, the temperature rise of the non-sheet passing area (end) when the small-size paper is continuously passed is reduced. In addition to this, there is an effect that it is possible to prevent jamming due to defective fixing and hot offset.

According to a fifth aspect of the present invention, in the first aspect of the present invention, when the continuous passing of the small-sized sheets exceeds a predetermined number, the passing of the small-sized sheets is performed. After the end of the paper, the power supply to the heat source for heating the fixing belt is stopped for a predetermined time, and the fixing belt idles.
Non-sheet passing area (edge) when continuously passing small size paper
This has the effect of preventing a rise in temperature and preventing jamming due to defective fixing and hot offset.

According to a sixth aspect of the present invention, there is provided a fixing roller, a heating roller having a heat source therein, an endless fixing belt stretched by both rollers, and a fixing roller opposed to the fixing roller via the fixing belt. And a heat diffusion member for heating the fixing belt in a fixing device having a pressing roller provided as a fixing member and conveying and fixing the toner image on the recording paper between the pressing roller and the fixing belt. A hollow cylindrical heat pipe is provided, and the heat pipe is in contact with one or both of the inner peripheral surface or the outer peripheral surface of the fixing belt and the pressure roller, so that the small-sized paper can be continuously fed. There is an effect that it is possible to prevent a temperature rise in the non-sheet passing area (edge) and to prevent jamming or the like due to defective fixing and hot offset.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram illustrating a fixing device according to a first embodiment of the present invention.

FIGS. 2A and 2B are schematic circuit diagrams of a fixing device showing arrangements of first and second heaters, respectively.

FIG. 3 is an explanatory diagram showing each light distribution in first and second heaters.

FIG. 4 is an overall configuration diagram illustrating a fixing device according to a second embodiment.

FIG. 5 is an explanatory diagram showing each light distribution in the first and second heaters.

FIG. 6 is an overall configuration diagram illustrating a fixing device according to a third embodiment.

FIG. 7 is an overall configuration diagram of a first example showing a fixing device according to a fourth embodiment.

FIG. 8 is an overall configuration diagram of the second example.

FIG. 9 is an overall configuration diagram of a first example showing a fixing device according to a fifth embodiment.

FIG. 10 is an overall configuration diagram of the second example.

FIG. 11 is an overall configuration diagram of the third example.

FIG. 12 is an overall configuration diagram of the fourth example.

FIG. 13 is a temperature distribution diagram in the fixing device when small size paper is continuously passed.

FIG. 14 is a temperature distribution diagram when small-size paper is continuously passed in the conventional fixing device.

FIG. 15 is a correlation diagram showing a temperature transition between the number of sheets passed and the fixing temperature in continuous sheet feeding.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixing apparatus 2 Fixing roller 3 Heating roller 4 Fixing belt 5 Pressure roller 6 First heater 7 Second heater 8 Oil application roller 9, 17 Hollow roller 10 Scraper 11 First temperature detecting means 12 Second temperature detection Means 13 Temperature control means 15 ON / OFF circuit 18, 19, 20 Heat pipe

Claims (7)

[Claims] An image forming apparatus comprising: a fixing roller; a heating roller having a heat source therein; an endless fixing belt stretched between the fixing roller and a pressure roller provided to face the fixing roller via the fixing belt; And a fixing device that conveys and fixes the toner image on the recording paper between the pressure roller and the fixing belt, the fixing device including at least a first roller disposed inside the heating roller in an axial direction of the heating roller. A first heat source and a second heat source, a first heat source among the first and second heat sources has a first light distribution substantially corresponding to a small-size sheet, and a second heat source is a second heat source. The fixing belt has a second light distribution substantially corresponding to both end portions other than the first light distribution, and faces each light distribution region of the first and second light distributions via a heating roller. On the surface, the temperature of this fixing belt is detected. First and second temperature detectors are provided, respectively, and the temperature of the fixing belt is controlled to a predetermined temperature by a temperature controller and an ON / OFF circuit based on the temperature detection by the first and second temperature detectors. A fixing device. 2. A fixing roller, a heating roller having a heat source inside the fixing roller, an endless fixing belt stretched between the two rollers, and a pressure roller provided to face the fixing roller via the fixing belt. And a fixing device that conveys and fixes the toner image on the recording paper between the pressure roller and the fixing belt, the fixing device including at least a first roller disposed inside the heating roller in an axial direction of the heating roller. A first heat source and a second heat source, of which the first heat source has a first light distribution substantially corresponding to a small-size sheet, and the second heat source has a large light distribution. The temperature of the fixing belt is detected on the surface of the fixing belt having a second light distribution substantially corresponding to the size paper and facing the first and second light distribution areas via a heating roller. Temperature detection means is provided for The temperature of the fixing belt is controlled to a predetermined temperature by the temperature control means and the ON / OFF circuit based on the temperature detection by the temperature detection means, and the first and second heat sources are used at the time of fixing small-size paper. A fixing device characterized by using a second heat source when fixing large-size paper. 3. A fixing roller, a heating roller having a heat source inside the fixing roller, an endless fixing belt stretched by the two rollers, and a pressure roller provided to face the fixing roller via the fixing belt. A fixing device that has a roller and a hollow hollow roller that rotates in contact with the outer peripheral surface of the fixing belt, and that conveys and fixes the toner image on the recording paper between the pressure roller and the fixing belt; And a second heat source having a second light distribution substantially corresponding to the large-sized paper, and a first heat source having a second light distribution substantially corresponding to the large-size paper. The first heat source is disposed axially within the hollow roller, the second heat source is disposed axially within the heating roller, and has a first light distribution substantially corresponding to small-size paper; Heat source for large-size paper A first temperature detecting means having a corresponding second light distribution, and abutting against the hollow roller to detect the temperature of the first light distribution area, and a surface of the fixing belt opposed via the heating roller And a second temperature detecting means for detecting the temperature of the second light distribution area in contact with the first and second light distribution areas. The temperature control means and the ON / OFF circuit based on the temperature detection by the first and second temperature detecting means. The temperature of the fixing belt is controlled to a predetermined temperature, the first and second heat sources are used when fixing small-sized paper, and the second heat source is used when starting the fixing device and fixing large-sized paper. A fixing device characterized by the above-mentioned. 4. A fixing roller and a heating roller having a heat source therein, an endless fixing belt stretched between the two rollers, and a pressure roller provided to face the fixing roller via the fixing belt. A fixing device that has a roller and a hollow hollow roller that rotates in contact with the outer peripheral surface of the fixing belt, and that conveys and fixes the toner image on the recording paper between the pressure roller and the fixing belt; And a second heat source having a second light distribution substantially corresponding to the large-sized paper, and a first heat source having a second light distribution substantially corresponding to the large-size paper. The first heat source is arranged in the axial direction so as to heat the inner peripheral surface or the outer peripheral surface of the pressure roller, and the second heat source is arranged in the axial direction in the heating roller, and substantially corresponds to a small-sized sheet. Has first light distribution The second heat source has a second light distribution substantially corresponding to the large-size paper, and is provided via a first temperature detecting means for detecting a temperature of the first light distribution area and a heating roller. A second temperature detecting means for detecting the temperature of the second light distribution area by contacting the surface of the fixing belt facing the first fixing belt, and controlling the temperature based on the temperature detection by the first and second temperature detecting means. The temperature of the fixing belt is controlled to a predetermined temperature by means and an ON / OFF circuit, and the first and second heat sources are used at the time of fixing small-sized paper, and at the time of starting the fixing device and at the time of fixing large-sized paper. A fixing device using a second heat source. 5. The fixing device according to claim 4, wherein the first heat source is provided in a hollow hollow roller that rotates while contacting the outer peripheral surface of the pressure roller. 6. When the continuous passage of the small-sized paper exceeds a predetermined number, after the completion of the passage of the small-sized paper, the power supply to the heat source for heating the fixing belt is stopped for a predetermined time.
2. The fixing belt according to claim 1, wherein the fixing belt idles.
The fixing device according to claim 4. 7. A fixing roller, a heating roller having a heat source therein, an endless fixing belt stretched between the fixing roller and a pressure roller provided opposite to the fixing roller via the fixing belt. A fixing device that has a roller and conveys the toner image on the recording paper between the pressure roller and the fixing belt to perform fixing. In the fixing device, a hollow cylindrical heat pipe that is a heat diffusion member for heating the fixing belt is provided. Wherein the heat pipe is in contact with one or both of the inner peripheral surface and the outer peripheral surface of the fixing belt and / or the pressure roller.